Welding Seminar - Terminology, Symbol & Metallurgy

8/8/2019 Welding Seminar - Terminology, Symbol & Metallurgy

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As with most industrial processes, welding has its own terms that are not

otherwise used in everyday communication; and, in instances where

everyday words are used, they often have a special meaning with referenceto welding. To provide common understanding, these terms have been

defined and standardized. Thus, the engineer can provide instructions to the

shop with the assurance that they will be clearly understood. The inspector,

when employing standard nomenclature, can be assured that his ideas areproperly understood.

Standard terminology is defined in AWS A3.0, Welding Terms and

Definitions. Additional terms and definitions of a special nature not

common to all welding are very often contained in a specific code orpublication to which they are related, such as AWS D1.1, Structural

Welding Code. A list of definitions for discontinuities & many of which are

taken from AWS A3.0

Definitions of Welding TermsDefinitions of Welding Terms


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e ng erms

Definitions

arc seam weld - a seam weld made by an arc welding process

arc spot weld - a spot weld made by an arc welding process

arc strike - any inadvertent discontinuity resulting from an

arc, consisting of any localized remelted metal,heat-affected metal, or change in the surface profileof any metal object. The arc may be caused by arcwelding electrodes, magnetic inspection prods, orfrayed electrical cable.

arc welding - a group of welding processes wherein coalescenceis produced by heating with an arc or arcs, with orwithout the application of pressure, and with orwithout the use of filler metal

as-brazed - adj. pertaining to the condition of brazements afterbrazing, prior to any subsequent thermal,

mechanical, or chemical treatments as-welded - adj. pertaining to the condition of weld metal,

welded joints, and weldments after welding butprior to any subsequent thermal, mechanical, orchemical treatments


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backgouging - the removal of weld metal and base metal fromthe weld root side of a welded joint to facilitatecomplete fusion and complete joint penetrationupon subsequent welding from that side

backhand welding - a welding technique in which the welding torch orgun is directed opposite to the progress of welding

backing - a material placed at the root of a weld joint for thepurpose of supporting molten weld metal so as tofacilitate complete joint penetration. The material

may or may not fuse into the joint. See retainer. backing gas -a gas, such as argon, helium, nitrogen, or reactive

gas, which is employed to exclude oxygen from theroot side (opposite from the welding side) of weld

joints

base metal - the metal or alloy that is welded, brazed, or cut Braze - a joint produced by heating an assembly to suitable

temperatures and by using a filler metal having aliquidus above 840F and below the solidus of thebase materials. The filler metal is distributedbetween the closely fitted surfaces of the joint bycapillary action.

Welding Terms & Definitions


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brazer - one who performs a manual or semiautomaticbrazing operation

Brazing - a group of metal joining processes which

produces coalescence of materials by heatingthem to a suitable temperature, and by using afiller metal having a liquidus above 840F andbelow the solidus of the base materials. The fillermetal is distributed between the closely fittedsurfaces of the joint by capillary action.

brazing, automatic - brazing with equipment which performs thebrazing operation without constant observationand adjustment by a brazing operator. Theequipment may or may not perform the loadingand unloading of the work.

Buttering - the addition of material, by welding, on one orboth faces of a joint, prior to the preparation ofthe joint for final welding, for the purpose ofproviding a suitable transition weld deposit forthe subsequent completion of the joint



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Coalescence - the growing together or growth into one body ofthe materials being joined

complete fusion - fusion which has occurred over the entire basematerial surfaces intended for welding, andbetween all layers and beads

Composite - a material consisting of two or more discretematerials with each material retaining its physical

identity consumable insert - filler metal that is placed at the joint root before

welding, and is intended to be completely fusedinto the root to become part of the weld

contact tube -a device which transfers current to a continuous

electrode corner joint - a joint between two members locatedapproximately at right angles to each other in theform of an L



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Crack - a fracture-type discontinuity characterized by a sharp tipand high ratio of length and width to openingdisplacement

defect - a discontinuity or discontinuities that by nature or

accumulated effect (for example, total crack length) rendera part or product unable to meet minimum applicableacceptance standards or specifications. This termdesignates rejectability. See also discontinuity and flaw.

direct current electrode negative (DCEN)the arrangement of direct current arc welding leads in

which the electrode is the negative pole and theworkpiece is the positive pole of the welding arc

direct current electrode positive (DCEP)

the arrangement of direct current arc welding leads inwhich the electrode is the positive pole and theworkpiece is the negative pole of the welding arc



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discontinuity - an interruption of the typical structure of amaterial, such as a lack of homogeneity in itsmechanical, metallurgical, or physical

characteristics. A discontinuity is not necessarily adefect. See also defect and flaw.

double-welded joint - a joint that is welded from both sides

double-welded lap joint- a lap joint in which the overlapped edges of the

members to be joined are welded along the edgesof both members

dwell - the time during which the energy source pausesat any point in each oscillation

electrode, arc welding - a component of the welding circuit through

which current is conducted electrode, bare - a filler metal electrode that has been produced as

a wire, strip, or bar with no coating or coveringother than that incidental to its manufacture orpreservation



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electrode, carbon - a non filler material electrode used in arc weldingand cutting, consisting of a carbon or graphite rod,which may be coated with copper or other materials

electrode, composite - a generic term of multi component filler metalelectrodes in various physical forms, such asstranded wires, tubes, and covered electrodes

electrode, covered -a composite filler metal electrode consisting of acore of a bare electrode or metal-cored electrode towhich a covering sufficient to provide a slag layer onthe weld metal has been applied. The covering maycontain materials providing such functions asshielding from the atmosphere, deoxidation, and arcstabilization, and can serve as a source of metallic

additions to the weld.

electrode, electroslag welding - a filler metal component of the weldingcircuit through which current is conducted betweenthe electrode guiding member and the molten slag



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filler metal - the metal or alloy to be added in making a welded,brazed, or soldered joint

filler meta4 brazing -the metal or alloy used as a filler metal in brazing,

which has a liquidus above 450C (840F) andbelow the solidus of the base metal

filler metal, powder - filler metal in particle form

filler metal, supplemental - in electroslag welding or in a welding process

in which there is an arc between one or moreconsumable electrodes and the workpiece. apowder, solid, or composite material that isintroduced into the weld other than the consumableelectrode(s) fillet weld a weld of approximatelytriangular cross section joining two surfacesapproximately at right angles to each other in a lap

joint, tee joint, or corner joint

flaw - an undesirable discontinuity. See also defect.



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forehand welding - a welding technique in which the weldingtorch or gun is directed toward the progress ofwelding

frequency - the completed number of cycles which theoscillating head makes in I mm or otherspecified time increment

fusion (fusion welding) - the melting together of filler metal and base

metal, or of base metal only, to produce a weld

fusion face - a surface of the base metal that will bemelted during welding

fusion line - a non-standard term for weld interface gas

backing see backing gas

globular transfer (arc welding) - a type of metal transfer in whichmolten filler metal is transferred across the arcin large droplets



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groove weld - a weld made in a groove formed within a single memberor in the groove between two members to be joined. Thestandard types of groove weld are as follows:

square groove weld

single-Vee groove weld single-bevel groove weld single-Ugroove weld

single-J groove weld

single-flare-bevel groove weld

single-flare-Vee groove weld double-Vee groove weld

double-bevel groove weld double-U groove weld

double-J groove weld

double-flare-bevel groove weld double-flare-Vee grooveweld



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heat-affected zone - that portion of the base metal which has notbeen melted, but whose mechanical properties ormicrostructures have been altered by the heat ofwelding or cutting

interpass temperature - the highest temperature in the weld jointimmediately prior to welding, or in the case ofmultiple pass welds, the highest temperature inthe section of the previously deposited weldmetal, immediately before the next pass isstarted

Joint -the junction of members or the edges ofmembers which are to be joined or have been

joined

joint penetration - the distance the weld metal extends from theweld face into a joint, exclusive of weldreinforcement



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keyhole welding - a technique in which a concentrated heat sourcepenetrates partially or completely though a workpiece, forming a hole (keyhole) at the leading edgeof the weld pool. As the heat source progresses, themolten metal fills in behind the hole to form the

weld bead.

lap or overlap - the distance measured between the edges of twoplates when overlapping to form the joint

lap joint - a joint between two overlapping members inparallel planes

lower transformation temperature - the temperature at which austenitebegins to form during heating

melt-in - a technique of welding in which the intensity of aconcentrated heat source is so adjusted that a weldpass can be produced from filler metal added to theleading edge of the molten weld metal



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Oscillation - for a machine or automatic process, analternating motion relative to the direction oftravel of

overlay, corrosion-resistant weld metal - deposition of one or more layersof weld metal to the surface of a base material inan effort to improve the corrosion resistanceproperties of the surface. This would be applied ata level above the minimum design thickness as a

non structural component of the overall wallthickness.

overlay, hard-facing weld metal - deposition of one or more layers ofweld metal to the surface of a material in an effort

to improve the wear resistance properties of thesurface. This would be applied at a level above theminimum design thickness as a non structuralcomponent of the overall wall thickness.



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pass - a single progression of a welding or surfacingoperation along a joint, weld deposit, or substrate. Theresult of a pass is a weld bead or layer.

pass, cover - a final or cap pass(es) on the face of a weld pass, wash - pass to correct minor surface aberrations and/or

prepare the surface for non-destructive testing

peel test - a destructive method of testing that mechanicallyseparates a lap joint by peeling

peening - the mechanical working of metals using impact blows

plug weld - a weld made in a circular, or other geometricallyshaped hole (like a slot weld) in one member of a lap ortee joint, joining that member to the other. The walls ofthe hole may or may not be parallel, and the hole maybe partially or completely filled with weld metal. (Afillet-welded hole or spot weld should not be construedas conforming to this definition.)



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polarity, reverse - the arrangement of direct current arc weldingleads with the work as the negative pole and theelectrode as the positive pole of the welding arc;a synonym for direct current electrode positive

polarity, straight - the arrangement of direct current arc welingleads in which the work is the positive pole andthe electrode is the negative pole of the weldingarc; a synonym for direct current electrode

negative preheat temperature - the minimum temperature in the weld joint

preparation immediately prior to the welding; orin the case of multiple pass welds, the minimumtemperature in the section of the previously

deposited weld metal, immediately prior towelding

preheating - the application of heat to the base metalimmediately before a welding or cuttingoperation to achieve a specified minimumpreheat temperature



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seal weld - any weld designed primarily to provide a specific degreeof tightness against leakage

seam weld - a continuous weld made between or upon overlappingmembers in which coalescence may start and occur on the

faying surfaces, or may have proceeded from the surfaceof one member. The continuous weld may consist of asingle weld bead or a series of overlapping spot welds.

single-welded joint - a joint welded from one side only single-welded

lap joint - a lap joint in which the overlapped edges of themembers to be joined are welded along the edge of onemember only

slag inclusion - non-metallic solid material entrapped in weld metal orbetween weld metal and base metal

spot weld - a weld made between or upon overlapping members inwhich coalescence may start and occur on the fayingsurfaces or may proceed from the outer surface of onemember. The weld cross section (plan view) isapproximately circular.



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stringer bead - a weld bead formed without appreciable weaving

surfacing - the application by welding, brazing, or thermal spraying ofa layer(s) of material to a surface to obtain desired propertiesor dimensions, as opposed to making a joint

thermal cutting (TC) - a group of cutting processes that severs or removesmetal by localized melting, burning, or vaporizing of theworkpieces

throat, actual (of fillet) - the shortest distance from the root of a fillet weld toits face

throat, effective (of fillet) - the minimum distance from the fillet face, minusany convexity, to the weld root. Jn the case of fillet weldscombined with a groove weld, the weld root of the grooveweld shall be used.

throat, theoretical (of fillet) - the distance from the beginning of the jointroot perpendicular to the hypotenuse of the largest righttriangle that can be inscribed within the cross-section of afillet weld. This dimension is based on the assumption thatthe root opening is equal to zero.



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Undercut - a groove melted into the base metal adjacent to the weldtoe or weld root and left unfilled by weld metal

upper transformation temperature - the temperature at whichtransformation of the ferrite to austenite is completed duringheating

weave bead - for a manual or semiautomatic process, a weld beadformed using weaving.

weaving - a welding technique in which the energy source is

oscillated transversely as it progresses along the weld path

weld - a localized coalescence of metals or nonmetals producedeither by heating the materials to the welding temperature,with or without the application of pressure, or by the

application of pressure alone and with or without the use offiller material

weld, auto genous - a fusion weld made without filler metal

weld bead - a weld deposit resulting from a pass. See stringer bead and

weave bead.



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weld face - the exposed surface of a weld on the side from whichwelding was done

weld interface - the interface between the weld metal and base metal in afusion weld

weld metal - metal in a fusion weld consisting of that portion of the basemetal and filler metal melted during welding

weld reinforcement - weld metal on the face or root of a groove weld inexcess of the metal necessary for the specified weld size

weld size: groove welds - the depth of chamfering plus any penetrationbeyond the chamfering, resulting in the strength carryingdimension of the weld

weld size: for equal leg fillet welds - the leg lengths of the largest isoscelesright triangle which can be inscribed within the fillet weldcross section

weld size: for unequal leg fillet welds - the leg lengths of the largest righttriangle which can be inscribed within the fillet weld crosssection

welder - one who performs manual or semiautomatic welding



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weldment - an assembly whose constituent parts arejoined by welding, or parts which contain weldmetal overlay

welding, electro gas (EGW) - an arc welding process that usesan arc between a continuous filler metal electrodeand the weld pool, employing approximately

vertical welding progression with retainers toconfine the weld metal. The process is used with orwithout an externally supplied shielding gas andwithout the application of pressure. Shielding for

use with solid or metal-cored electrodes is obtainedfrom a gas or gas mixture. Shielding for use withflux-cored electrodes may or may not be obtainedfrom an extemally supplied gas or gas mixture



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welding, electron beam (EBW)

a welding process that produces coalescence with a concentratedbeam composed primarily of high velocity electrons, impinging on

the joint. The process is used without shielding gas and without theapplication of pressure.

welding, electroslag (ESW)

a welding process producing coalescence of metals with moltenslag which melts the filler metal and the surfaces of the work to bewelded. The molten weld pool is shielded by this slag which movesalong the full cross section of the joint as welding progresses. Theprocess is initiated by an arc which heats the slag. The arc is thenextinguished and the conductive slag is maintained in a molten

condition by its resistance to electric current passing between theelectrode and the work. See electroslag welding electrode andconsumable guide electroslag welding.



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welding, flux-cored arc (FCAW) - a gas metal-arc welding process thatuses an arc between a continuous filler metal electrode and theweld pool. The process is used with shielding gas from a fluxcontained within the tubular electrode, with or without additionalshielding from an extemally supplied gas, and without theapplication of pressure.

welding, gas metal-arc (GMAW) - an arc welding process that uses anarc between a continuous filler metal electrode and the weld pool.The process is used with shielding from an externally supplied gasand without the application of pressure.

welding, gas metal-arc, pulsed arc (QMAW-P) - a variation of the gasmetal-arc welding process in which the current is pulsed. See alsopulsed power welding.

welding, gas metal-arc, short-circuiting arc (OMAWS) - a variation ofthe gas metal-arc welding process in which the consumableelectrode is deposited during repeated short circuits. See alsoshort-circuiting transfer



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welding, gas tungsten-arc (GTAW) - an arc welding process whichproduces coalescence of metals by heating them with anarc between a tungsten (non consumable) electrode andthe work. Shielding is obtained from a gas or gas mixture.

Pressure may or may not be used and filler metal may ormay not be used. (This process has sometimes been calledTIG welding, a non preferred term.)

welding, gas tungsten-arc, pulsed arc (QTAW-P) - a variation of the gas

tungsten-arc welding process in which the current ispulsed.

welding, induction (LW) - a welding process that produces coalescenceof metals by the heat obtained from resistance of the

workpieces to the flow of induced high frequencywelding current with or without the application ofpressure. The effect of the high-frequency weldingcurrent is to concentrate the welding heat at the desiredlocation.



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welding, laser beam (LBW) - a welding process which producescoalescence of materials with the heat obtained from theapplication of a concentrated coherent light beam impinging uponthe members to be joined

welding, oxyjliel gas (OFW) - a group of welding processes whichproduces coalescence by heating materials with an oxyfuel gasflame or flames, with or without the application of pressure, andwith or without the use of filler metal

welding, plasma-arc (PAW) - an arc welding process which producescoalescence of metals by heating them with a constricted arcbetween an electrode and the workpiece (transferred arc), or theelectrode and the constricting nozzle (nontransferred arc). Shieldingis obtained from the hot, ionized gas issuing from the torch orifice

which may be supplemented by an auxiliary source of shielding gas.Shielding gas may be an inert gas or a mixture of gases. Pressuremay or may not be used, and filler metal may or may not besupplied.



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welding, resistance (RW) a group of welding processes that producescoalescence of the faying surfaces with the heat obtained fromresistance of the workpieces to the flow of the welding current in acircuit of which the workpieces are a part, and by the application ofpressure

welding, resistance seam (RSEW) a resistance welding process thatproduces a weld at the faying surfaces of overlapped partsprogressively along a length of a joint. The weld may be made withoverlapping weld nuggets, a continuous weld nugget, or by forgingthe joint as it is heated to the welding temperature by resistance to the

flow of the welding current. welding, resistance spot (RSW) a resistance welding process that

produces a weld at the faying surfaces of a joint by the heat obtainedfrom resistance to the flow of welding current through the workpiecesfrom electrodes that serve to concentrate the welding current and

pressure at the weld area welding, resistance stud a resistance welding process wherein

coalescence is produced by the heat obtained from resistance toelectric current at the interface between the stud and the workpiece.until the surfaces to be joined are properly heated, when they arebrought together under pressure



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welding, semiautomatic arc - arc welding with equipment which controlsonly the filler metal feed. The advance of the welding is manuallycontrolled.

welding, shielded metal-arc (SMAW) - an arc welding process with an

arc between a covered electrode and the weld pool. The process isused with shielding from the decomposition of the electrodecovering, without the application of pressure, and with filler metalfrom the electrode

welding, stud - a general term for the joining of a metal stud or similar

part to a workpiece. Welding may be accomplished by arc,resistance, friction, or other suitable process with or withoutexternal gas shielding.

welding, submerged-arc (SAW) - an arc welding process that uses an arcor arcs between a bare metal electrode or electrodes and the weldpool. The arc and molten metal are shielded by a blanket of granular

flux on the workpieces. The process is used without pressure andwith filler metal from the electrode and sometimes from asupplemental source (welding rod, flux, or metal granules).



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Master Chart of Welding, Allied Processes, and Thermal Cutting

Inspection personnel involved in the inspection of welds or weld related

products must be familiar with the welding and allied processes within the

scope of their work. A welding or allied process is the basic classification of

the operation to be performed, subdivided into the more specific processes.

In the hierarchy of welding, the welding process stands first. Each welding

process definition is complete so that it will stand alone, Processes are defined

for prescribed elements of operation rather than for other characteristics such

as metallurgy, source of energy, etc. This method of organization is the basisfor the Master Chart of the welding and allied processes shown in the figure.

The chart is a visual display of a hierarchy of welding and allied processes; the

highest generic levels (least specific) are in the center, and the most specific

are in boxes around the perimeter. The chart is intended to be ccmprehensive

and includes not only widely used production processes, but also some that areof limited use because they have been replaced by other processes ,have only

recently been introduced, or have limited applications


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Basic W elding Sym bol


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Location of Elements of a Welding Symbol


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Basic Joints Identification of arrow side & other side of joint


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Basic Joints Identification of arrow side & other side of joint

Typical Welding Symbol


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Typical Welding Symbol


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NDT - Symbol


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Basic Testing Symbol


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Basic Testing Symbol

Ethical & Requirements for the Welding


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Ethical & Requirements for the Welding

Inspector

There are many different kinds of welding inspectors, depending uponthe applicable technical requirements for the particular fabricationprocess or processes. Today is an age of specialization and the

complexities of the hardware being built are awesome, There aredestructive testing specialists, non-destructive testing specialists, codeinspectors, military (govermnent) inspectors, owners representativeinspectors, and on and on. All of these individuals may, at one time oranother consider themselves welding inspectors, for they do, in fact,

inspect welds. There are three basic work function categories into which most ofthese inspectors may fall:

(1) Overseer

(2) Specialist

(3) Combination of overseer and specialist

Categories of Inspector


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Overseer - An overseer can be one individual (for example, a code

inspector) or many individuals whose degrees and ranges ofskill and expertise vary such that any amount or type ofworkmanship may be inspected, from the contractorsquality assurance program down to the last nut and bolt

of the welding operations. Economics and technicalrequirements will determine the extent to which these typesof inspectors will group themselves and specialize in thevarious areas of expertise.


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A specialist is an individual, who may or may notperform independently of an overseer, who performssome refined aspect of one or more inspectionprocesses. An example of specialist is the non-destructive testing radiographer, whose responsibilityis to accept or reject the results of the radiography,which in turn determines certain aspects of theweldment. A specialist could also be diversified toperform all types of NDT, etc. The specialist has onlylimited responsibilities in the weld inspection process.

Specialist -


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In some industries it is quite common to combine theoverseer and the specialist inspector concept as follows :All welding inspectors are employed as overseers and areassigned to a given section of the shop or to a given

geographic area. In addition, each inspector is trained as aspecialist in one specific field, such as radiography,welder qualification, or aluminum welding. This enablesan overseer inspector to obtain in-house assistance fromanother overseer inspector with the speciality needed toresolve a particular problem.

Com bination of Overseer &Specialist -


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Ethical Requirem ents :

In order to safeguard the publics health and well-being and to maintain integrity and high standardsof skills, practice, and conduct in the occupation ofwelding inspection, the welding inspector must be aspecial kind of individual who must sometimes

walk a two-way street. He or she must renderdecisions promptly while remaining impartial andtolerant of the opinions of others. The following areconsidered ethical features or desirable qualities ofa welding inspector.


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Integrity -

Welding inspectors hold positions ofresponsibility and should conductthemselves as responsible persons with goodcharacter, ability, and common sense. Aboveall, welding inspectors must be honest, notreadily influenced by prejudiced opinions,

gifts, or special services.

espons ty to t e

P bli


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Public -

The welding inspector is obligated to preserve the health and well-being of the public by performing the duties required of weldinspection in a conscientious and impartial manner to the full extent ofhis or her moral and civic responsibilities and qualifications.Accordingly, the welding inspector shall :

(1) Undertake and perform assignments only when qualified bytraining, experience and capability.

(2) Be completely objective, thorough, and factual in any written

report, statement, or testimony of the work and include allrelevant or pertinent information, in such communiques ortestimonials.

(3) Sign only for work that he or she ha inspected, or for work over

which he or she has personal knowledge through direct technicalcontrol.

(4) Neither associate with nor knowingly participate in a fraudulentor dishonest venture.


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Public Statem ents-

The welding inspector will issue no statements, criticisms, or

arguments on weld inspection matters: connected with publicpolicy that are inspired or paid for by an interested party, orparties, without first identifying the party, the speaker, anddisclosing any possible pecuniary interest. The welding

inspector will publicly express no opinion: on a weldinspection subject unless it is founded upon adequateknowledge of the facts in issue, upon a background oftechnical competence pertinent to the subject, and uponhonest conviction of the accuracy and propriety of thestatement.

Conflict of Interest


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Conflict of Interest

- The welding inspector shall conscientiously avoid conflict ofinterest with the employer or client and will disclose any businessassociation, interests, or circumstances that might be so considered.

The welding inspector shall not accept compensation, financial orotherwise, from more than one party for services on the sameproject, or for services pertaining to the same project, unless thecircumstances are fully disclosed and agreed to by - all interestedparties or their authorized agents.

The welding inspector shall not solicit or accept gratuities, directlyor indirectly, from any party or parties dealing with the client oremployer in connection with the welding inspectors work.

The welding inspector shall neither inspect, review, nor approve anywork on behalf of another party or parties while serving in thecapacity of an elected, retained, or employed public official.


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Solicitation of Employment-

The welding inspector shall neither pay, solicit, nor offer

directly or indirectly any bribe or commission forprofessional employment with the exception of the usual

commission required from licensed employment agencies.

The welding inspector shall neither falsify, exaggerate, nor

indulge in the misrepresentation of personal academic and

professional qualifications, past assignments,

accomplishments, and responsibilities, or those of his or herassociates.


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Essential Requirementsof a Welding Inspector

Physical Condition - An inspectors physical condition must be sufficiently good to

permit him to fulfill his duties. Some inspection processesrequire climbing around large fixtures and assemblies, andconditions are often difficult since the work is positioned

primarily for the welders or welding operators convenience.Good vision (the AWS certification requirement is 20/40natural or corrected distance acuity) is vital to an inspector,who must look closely at welds and inspection test results.Some inspection processes may make it desirable for theinspector to have good color vision. Any necessary correctiveaids, such as eye - glasses, must be used during the inspectionprocess.


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Attitude - The importance of the attitude adopted by inspectors cannot be

over-emphasized. It determines the degree of their success orfailure. To be successful, they are very much dependent upon

the cooperation of their associates in all departments, and theymust command the respect of those associates in order to obtainit. Attitude plays an important role in this. Since many decisionsmay involve marginal material, all decisions must beconsidered, impartial, and consistent. A definite policy ofinspection procedure and standards should be adopted andfollowed faithfully. Inspectors can be neither stubborn noreasily swayed. Under no circumstances can they seek favor orincur obligation through their decisions. The most difficultperiod for all inspectors is those first few weeks on any newlocation. During that time, those with whom they must deal willbe testing them for weakness in policy. If they are informed,fair, and consistent, and if they follow the intent of the contractspecifications, they will earn respect and cooperation.


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Know ledge of W elding -

Inspectors must have sufficient knowledge ofwelding processes to know what defects are mostlikely to occur and where to look for them. Theyshould be familiar with all the procedure

specifications that apply to their area ofresponsibility. In particular, each inspector shouldknow the variables of the particular welding processand should monitor these variables during theoperation.


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Knowledge of Drawings, Specifications, andProcedures -

Most welding inspection requires at least some

fundamental - knowledge (and, in many instances, detailedspecific knowledge) of the drawings and specificationrequirements. Therefore, the welding inspector shouldmost assuredly have the ability to read blueprints anddrawings and have a good understanding of basic

specification requirements. In particular, a workingknowledge of welding and non-destructive testing symbolsis essential. In almost all cases, the welding inspectorshould be thoroughly familiar with working proceduresused for both inspection and fabrication processes. Vital

materials should be carried to the job site by the inspector,readily available for reference at all times, without relianceon memory. In this way, the inspectors knowledge of the

job should become comprehensive.


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Knowledge of Testing

Methods - Numerous weld testing methods are available to the inspector.

It would be highly desirable, regardless of the particularresponsibilities of the individual inspector, to have a good

fundamental knowledge of each of the common methods. Somemay require more than just familiarity ; i.e., they may requirepersonal expertise in a particular method. However, sincealmost all testing methods (including destructive and non-destructive tests) have advantages and limitations, the welding

inspector would be well advised to learn some basics in each.Some weldments may require extended evaluations in manydifferent methods, or some weldments may requirecombinations of engineering judgment with a particular testmethod. Still other weldments may reveal a particular condition

requiring referral to a specialized test method for morecomplete evaluation. The successful welding inspectormaintains a diversified knowledge of testing methods.


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Records - An inspector should be able to maintain adequate records.

Inspectors must be able to write clear and concise reports

so that superiors will have no difficulty understandingtheir meaning. Also, they must be able to recall thereasons for past decisions if these must be reviewed later.Inspection reports should be concise, yet complete enough

to be clear to a reader unfamiliar with the productinspected. In preparing the records, the most basic factsmust be included even though they are well known andunderstood at the time of writing, since they may not beremembered so clearly later. Thus, good records not onlyprotect the inspectors who wrote them, they also help inadhering to a policy of uniform standards.

Education and Training


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Education and Training

- As with almost any discipline, education and training are

essential to welding inspectors. How much education andtraining and how they receive them will depend upon the

individuals and the requirements of the particular job. Asmentioned previously, some requirements will be morestringent than others and thus require advanced knowledge.In some instances, education can supplement extensivetraining; i.e., the amount of training required can by offset

by previous skill acquired by the inspector who was welleducated. Usually the mote diversified the education andtraining are, the more diversified the welding inspector willbe. The weld inspector who has fundamental knowledge ofengineering and metallurgical principles, in addition to

other essentials mentioned herein, will be exceedinglydiversified regardless of whether such knowledge wasobtained through education or experience.


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Welding Experience -

Actual experience as a welder or weldingoperator is valuable to welding inspectors. Iteffectively broadens their welding knowledgeand gives their opinions more authority if they

are requested to offer constructive criticismwhen rejecting poor work.


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Inspection Experience -

The attitude and point of view ofgood inspectors are acquired onlythrough inspection-experience. Anysuch experience will be extremely

helpful in the inspection of welding,since good inspectors developdistinct ways of thinking and

working. Those without such

experience should observe howexperienced inspectors performtheir duties.

C tifi ti f Q lifi ti


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Certification of Qualification -

Education, training, and experience provide some desirable characteristics with regard toqualification essentials of the welding inspector. A potential welding inspector should beaware that the increasing variety of welding processes, materials, codes, and standardsapplied to todays product technologies makes it correspondingly more difficult to properlyfullfill the inspection function and to enforce or meet design requirements. This simply

means that welding inspectors have an increasingly important job and that this job mustbe done in a more uniform manner throughout the United States. At this writing, theAmerican Welding Society is working to help all concerned meet this challenge byoffering a qualification and certification service that will assist in standardizing this job.Certification of any qualification will be made in accordance with the AWS QCI, Standardfor Qualification and Certification of Welding Inspectors, latest edition.

Nationwide examinations for welding inspector certification will normally be offeredseveral times each year in various locations throughout the United States by AWS. Theminimum levels of experience, educational training, and vision requirements set forth bythe AWS Committee on Qualification and Certification must be met to qualify for theexam. If all the requirements are met and the exam is successfully completed, AWS will

certify, register, and document the qualification with a certificate and wallet card.Recertification would normally be required every three years. More complete information,including updated examination schedules and locations on this certification service, isavailable from AWS.


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Welding Metallurgy Mild Carbon Steel

Mild carbon steels contain iron plus small quantities of other

elements. The five most common and their quantitative limits in arepresentative grade, AISI/SAE 1020 steel, are:

Carbon (C) 0.18-0.23%

Manganese (Mn) 0.30-0.60%

Silicon (Si) 0.30% max Phosphorous (P) 0.040% max

Sulfur (S) 0.050% max

When such a steel is slowly cooled and subsequently viewed under ametallurgical microscope, a network of light-colored grains will bevisible (refer to Figure 7.1). The grains are outlined by much darkergrain boundaries and can contain islands of darker materials.


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Mild Carbon Steel


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Mild Carbon Steel

When this material is viewed at 100x magnification,grain size can be measured. While ASTM provides

comparison charts (ASTM Specification E112) for

such measurements, an approximation can be made

by determining the average number of grains per

linear inch at this l00x magnification. On this basis,

seven grains per inch approximates ASTM grain size

7.


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Mild Carbon Steel


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The light part of the grain is called ferrite. It is nearly pureiron since it can only absorb a maximum of 0.025% C. The

dark grain boundaries are predominantly iron carbide(Fe3C). This iron-carbon phase is called cementite. Thedarker islands are mixtures of ferrite and Cementite thatform thin layers called pearlite (Fig. 7.2). The amount ofcementite and pearlite is proportional to the carbon content.

Due to the large quantity of ferrite in weldable grades ofcarbon steel, such steels are referred to as ferritic steels.

Further magnification of this steel would reveal a crystalline

structure within each grain. This structure contains therelative orientation of the iron atoms as shown in Fig. 7.3.Ferrite and cementite have the body-centered cubic

Mild Carbon Steel


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Crystal Structures in Steel


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Body Centered Cubic -BCC (BCC) structure as shown in Fig. 7.3A, while the

orientation of some other phases (such as austenite

which will be discussed subsequently) is face-centeredcubic (FCC) as shown in Fig. 7.3B. Most of the atomsthat make up these crystals are iron, but if alloys areadded, some of these iron atoms are replaced by the

alloying elements. At other times the alloy atoms aresqueezed into the space between the normal crystalpattern. These changes in crystal structure or phasesgive ferritic steels the somewhat unique characteristic ofbeing able to change their mechanical properties bydifferent heat treating cycles.


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Slowly cooled mild carbon steels have a uniformmicrostructure with the lowest tensile strength and the

highest ductility. These can be changed by heat

treating, mechanical working, alloy or carbon

additions, or combinations thereof. The effect ofheating and cooling is of particular interest to welding,

since part of the metal is heated to the melting point in

most welding processes.

Body Centered Cubic -BCC


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When mild carbon steel is heated during

welding or heat treating, the first important

change, a predominantly mechanical one,

starts at about 950F (500 C). The change

lowers the yield strength of the steel; some ofthe residual stresses caused by cold working

or weld shrinkage are relieved, and the

material is softened.

Body Centered Cubic -BCC


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Face Centered Cubic - FCC

A major metallurgical change occurs when ferritic

steel is heated above its lower transformationtemperature, often referred to as the A, temperature.For all carbon steels this temperature is 1333 F(720 C). When heated above A1, both of the body-centered cubic (BCC) phases (ferrite and cementite)

begin to transform into a face-centered cubic (FCC)phase called austenite. The temperature that must bereached to complete this transformation, which isreferred to as upper transformation temperature orA3, depends upon the specific chemical compositionof the steel. For a mild carbon steel (e.g., AISI1020), A3 is at about 1560F (850 C).


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This austenite is retained until melting starts at

2535 F (13900 C). However, in the austeniticrange grains can increase in size. The higher the

temperature and the longer the holding time, the

larger the grain size. Since some of these grains

retain their size after cooling, the largest grains in

a weldment are located in the base metal

immediately adjacent to the fusion line of the

weld.

Face Centered Cubic - FCC


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Heat Affected Zone - HAZ It is important to note that thesemetallurgical changes occurevery time a weld bead is

deposited. Figure 7.4 showsthat a temperature range existsduring welding that permitsferrite, cementite, austenite, andliquid metal to exist in close

proximity. The base metaladjacent to the weld, which hasnot become molten but hasgone through some

metallurgical changes, isreferred to as the heat-affectedzone or the HAZ.

Two Events during cooling of welding


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As the welding arc travels along the weld seam or is extinguishedto change electrodes, or upon completion of the weld, the heatedareas are free to cool. Two major events occur during this coolingoperation:

(1) Residual stresses and distortions are caused by localweld area shrinkage during solidification and cooling. Thisis called mechanical process.

(2) The metallurgical process described earlier will bereversed as the steel cools through the transformationrange. If slow cooling can be obtained, the transformation

cycle upon cooling will be the reverse of the transformationcycle upon heating although grain size may be changed asshown on Fig. 7.5, the HAZ will contain a combination offerrite, pearlite, and cementite and thus will be similar tothe original soft base metal.

Crystal Structure of Cold Rolled


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Crystal Structure of Cold Rolled

Steel

Martensite & Bainite


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While a certain amount of martensite andbainite is normally unavoidable, their amountand their effect can be minimized by properbase metal and electrode selection, weldingtechnique, and preheating and interpasstemperatures. The need for such actionsbecomes more important as material thicknessor carbon content, or both, increase. Thickerbase metal removes heat in less time from theweld area and thus increases the rate ofcooling. A unit called carbon equivalent(CE) is often employed to predict the

combined effect of carbon and manganeseupon the tendency to form martensite. Formild carbon steel, the carbon equivalent ismost commonly expressed as:

CE = %C +%Mn/4 or

CE = %C +%Mn/6

The higher the CE and the thicker thematerial, the greater the need for preheating.

Low Alloy Steels


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To increase strength, notch ductility, corrosion resistance,and other specific properties, alloys are often added to mildcarbon steels. The welding engineer must select electrodescapable of matching the mechanical properties and thechemical composition of these alloy base metals in order toachieve a uniform structure.

Although the addition of such elements as chromium,nickel, molybdenum, copper, and vanadium cansignificantly change the properties of the steel, the basicmetallurgical concepts are similar to those that apply to

mild carbon steel. A combination of ferrite and alloy-iron-carbon phases can produce weldable materials withadequate ductility


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Softening will start between 1000 F (540 C) and

1250 F (680 C), depending upon the specificcomposition. For alloy steels, the lowertransformation temperature is higher than the 133 3F (720 C) that applies to carbon steel. For many (butnot for all) alloy steels, the safe maximum PWHTtemperature below the transformation range is 1475F (800C). Since this temperature varies some foreach low alloy steel classification, optimum PWHTtemperatures should be established and documented

for each. For several alloy steels, it is not uncommonto anneal the welded component at much highertemperatures.

Low Alloy Steels ..

Low Alloy Steels


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During welding, part of the alloy steel will passthrough the lower and the upper transformationtemperatures and thus will be fully austenitic. In thisrespect, there is little difference between mild carbonand low alloy steel. Also, the cooling rate for lowalloy steels is the same as the rate for mild carbonsteels. However, the alloy material is more susceptibleto hardening, to embrittling, and subsequently tocracking, since martensite can form at slower coolingrates. The ability of the alloy steel to form such

martensite can again be expressed as a carbonequivalent (CE) for which there are many similarformulas that include many elements in addition tocarbon and manganese.

..

Carbon Equivalent


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q

Formula

Low Alloy Steels ..


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With a high CE, even a relatively slow

cooling of the weldment will producelarge quantities of martensite and bainite.Preheating, while essential for nearly all

alloy steel welds, often fails to retard thecooling rate sufficiently; however, it canprevent cracking during fabrication.

Thus, PWHT is mandatory for manyalloy steels to restore sufficient ductilityprior to exposing the assemblies to

service conditions.

y


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Hydrogen and Steel Carbon and low alloy steels can absorb considerable quantities

of hydrogen at elevated temperatures. However, as the steelcools, it can retain less and less hydrogen in solution; thus, itejects the excess hydrogen.

When steel is held at elevated temperatures and during slowcooling, the small hydrogen atoms can escape by diffusion tothe atmosphere. However, rapid cooling, often associated with

welding, tends to trap the atoms, which will then collect insmall voids. As more hydrogen enters these voids, the pressurewill build up. If the material is ductile, the void can growslightly and thereby reduce the pressure. In a brittle materialand in materials with high residual stresses, the growth of voids

can easily propagate into cracks. This phenomenon is known bysuch terms as hydrogen cracking, underbead cracking, ordelayed cracking. Steels with higher strengths and higher alloycontents are more susceptible to hydrogen-related cracking.


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Hydrogen can enter the weld metal by release from moisture ororganic matter on the material surface, in the weldingatmosphere, or within the welding consumables (e.g., electrodes,

fluxes, and gases). In fact, coatings of some electrodes (such asE6010) contain hydrogen- rich cellulose; some of this hydrogencan and will enter the steel during welding.

Thin walled, mild carbon steel weldments are practicallyimmune to underbead cracking and thus permit the use ofcellulose coated electrodes. However, carbon and alloyadditions to steel increase strength and, therefore, the probabilityof hydrogen-related defects. This can be minimized byestablishing and enforcing welding procedures that preventhydrogen from entering the weld area and by taking steps thatpermit hydrogen to escape.

Hydrogen and Steel ..

Hydrogen and Steel


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Typical methods to achieve these aims include:

Thorough cleaning and drying of the base metal

Pre-heating and maintaining minimum interpass

temperatures

Exclusive use of low hydrogen electrodes or hydrogen-freewelding processes

Proper drying and storing of welding electrodes, fluxes,

and gases and proper maintenance of equipment such as

wire feeders

Postweld heat treatment

..


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Austenitic Stainless Steel

The most common austenitic stainless steels

contain between 18 and 25 percentchromium and between 8 and 20 percentnickel as primary alloying elements. Inproduct forms such as plates, forgings, and

electrodes, they are classified by a three-digit numbering system and can be easilyrecognized since the first digit is a 3; thedetailed chemical composition is governed

by the last two digits. In view of these twofacts, these materials are often referred to asaustenitic chromium-nickel steels or 300-series steels.



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The 300-series steels have many chemical and

metallurgical characteristics that clearly

distinguish them from ferritic steels such as

mild carbon or low alloy steels. Specifically,

the 300-series steels:

Are more corrosion resistant in most environments

Have higher tensile and creep strength at elevated

temperatures

Are not magnetic or only slightly magnetic

Cannot be hardened by heat treatment

.



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. Austenitic stainless steels do not undergo the normal phase

changes that apply to ferritic steels. While mild carbon steelis austenitic and non-magnetic at elevated temperatures, it

will transform into ferrite, pearlite, martensite, and otherphases as it is cooled through the transformation range.

However, when austenitic stainless steel is cooled, all ornearly all of the material is retained as austenite at roomtemperature, Without phase changes, no hardening willoccur. Thus, hard areas are not found in the heat affectedzone (HAZ) of 300-series stainless steels. This reduces the

need for preheating and postweld heat treating.


.Wh h i l ld d (2) ifi i


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When these materials are welded, two (2) specific itemsmust be considered:

(1) carbide precipitation or sensitization,

(2) microfissuring, ferrite content, and sigma formation.

The corrosion resistance of the 300-series stainless steelsdepends upon the addition of various alloys of whichchromium is of primary importance. If the alloy is heated tothe so- called sensitization range of 800-1600 F (425-870 C), some of the chromium can combine with anycarbon that is available and form a chromium-rich

precipitate. Whenever this occurs, as it can during welding,less chromium is available to resist corrosion. This isespecially serious if the corrodent is an acid (for example,see Fig. 7.7).


.

Thi i i i b b f h


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This sensitization can be overcome by any one of thefollowing actions:

Heat the steel after welding to about 1900 F (1050 C) to dissolvethe carbides and cool rapidly through the sensitization range. This iscalled solution annealing. It is practiced in steel and pipe mills, butit is not easily adapted to shop assemblies and field erection.

Employ 300-series steel with low carbon content. By limiting the

percent carbon to a maximum of 0.03 or 0.04, these so-called Lgrades (e.g., 308L, 3l6L, etc.) also limit the amount of carbides thatcan form and thus the amount of chromium that can be depleted.

Stabilize the material by adding scavengers in sufficient quantity.Elements like columbium and titanium will combine preferentially

with the carbon. This will retain the chromium for corrosionprotection even when reaching the sensitization range during weldingor other operations.

Austenitic Stainless Steel .


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Laminations


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and Lamellar Tearing

While the terms lamination and lamellar tearing soundquite similar, occur primarily in the same places, and are

likely to produce similar failures, they represent twodistinctly different phenomena.

Laminations are inclusions or separations that exist in the

material as the result of impurities (such as sulfates orsilicates) that segregate during ingot solidification and aresubsequently flattened during rolling or hot workingapplications. Thus, they are most likely to occur at or nearthe center of plates as indicated on Fig. 7.9. The probabilityof plates containing laminations increases with the thicknessof the plate and decreases with increased cleanliness of thesteel. Laminations are seldom, if ever, found in castings.

Laminations



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Laminations



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Lamellar tearing occurs during a weldingoperation and is not a pre-existing condition.

For most steel plates, the percent elongation

is approximately the same in the direction of

rolling and in the transverse direction (A

and B in Fig. 7.10).


Laminations



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Other Metallurgical

C id ti


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Considerations The soundness of a weld during fabrication and during its service life is

influenced by many metallurgical considerations. While most are beyondthe scope of this book and the activities of an inspector, a few concepts

have been highlighted below. Metallurgical Inclusions: Many elements are added to steel or other basemetals to produce certain desirable properties. However, certain elementsmay severely deteriorate the base and weld metal properties by penetratinginto the molten weld metal. These include the

Following elements that may be in contact with a metal during weldingrelated operations: Copper (in the form of contact tips and magnetic particle testing prods)

Lead (in the form of caulking or lining)

Sulfur (in the form of molecular sulfur that has been deposited while theequipment was in service)

Zinc when welding austenitic stainless steel and carbon steels (in the form ofgalvanized components or cathodic protection equipment)

Fatigue


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FatigueFatigue cracking occurs inservice and not when theweld is made. However, the

manner in which the weld ismade may influence fatiguelife of the product. Sinceany irregularity in shape or

any notch (such as a roll-over or undercut) may beundesirable, special grindingor machining of welds is,

sometimes specified by thedesigner to improve thefatigue life of hiscomponent.

ELECTRODES & FILLER

WIRES


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WIRES

MAXIMUM STORAGE TIME :

Shelf life is practically unlimited when electrodes

are kept in their original packaging and are stored

at a temperature at least equal to room

temperature, in stores with relative humiditybelow 60%.

ELECTRODES & FILLER

WIRES


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Low hydrogen and low hydrogen-rutile electrodes

Coatings of. this type are more hygroscopic. This is why their

water content is carefully checked in the factory before packing.Nevertheless, for assemblies which require excellent density.and very good mechanical characteristics, and to limit as far aspossible the risk of cold cracking, very dry electrodes must beused. This is particularly applicable when welding non-alloyed

or low alloy steels with high hardenability when introduction ofhydrogen has to be limited as much as possible. Dryingtemperatures and temperature stabilization times for these typesof electrodes vary with grades.

Drying should be carried out when the electrodes are taken from

their package. They should preferably be arranged in thin layers on trays in a

drying oven.

WIRES

CONDITIONS FOR PRESERVATION AFTER DRYING

ELECTRODES & FILLER

WIRES


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CONDITIONS FOR PRESERVATION AFTER DRYINGANI BEFORE USE

After drying, low hydrogen and low hydrogen-rutile

electrodes must be kept at a temperature between 70C and120C, protected from moisture. These conditions can beobtained using portable drying ovens and storage cabinets.

Jf a storage cabinet is not used, the welder must use theelectrode within half an hour of its removal from the dryingoven (AWS D- 1-1-81 recommendation).

However, it is recommended not to exceed three dryingoperations.

WIRES


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GUIDING PRINCIPLES IN MANUAL ARC

WELDING


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WELDING

The mechanics of Welding with an Electric Arc

When the arc is struck, the heat of the arc melts theposition of the base metal under it and the tip of thecore wire, forming droplets of molten metal that aretransferred to the work along the path of the arc. The

electrode coating also melts but at slower rate than thecore wire. A molten pool of metal thus forms beneaththe arc, partially covered by the molten slag from thecoating, which, being lighter than the metal, floats tothe top. When the arc moves on, the molten mixturesolidifies immediately. The weld metal thereforeconsist of a mixture of a filler metal and the fusedportion of the work piece.

D i th d l t f t l


WELDING


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During the process droplets of metaland molten pool are protected fromthe atmosphere by a shield of gases(mainly CO2 which are given off bythe coating when burned. Other

ingredients are present in the coatingwhich help to refine the weld metal,to replace alloying elements lost inthe heat of the arc (or increase theircontent to give desired properties tothe deposit) and in the case of iron

powder types, increase the percentagedeposition.

The heat of the arc must be sufficientto maintain the molten pool at alltimes so that there will be notendency for the electrode to stick or

freeze to the work and in order thatthe slag and gases mixed with theliquid metal can rise to the surfaceinstead of being entrapped in thesolidified weld

Current Requirements


WELDING


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The heat liberated to the arc is directly proportional to the arcvoltage and the intensity of the current. Since the arc voltageunder ordinary conditions depends on the arc length, which ideally

should be held constant, the current or amperage used is thereforethe main factor in determining the heat input, which in turn affectsthe condition of the weldment.

At high current values the hotter arc will cause a larger area tomelt faster, giving deeper penetration and faster welding speed.

However, too high current will cause harmful overheating of thebase metal with undercutting or possibility of burn-through forthin work pieces. The pool will be large and irregular, giving a flatwide bead. There will be much spattering and the electrode maybecome red-hot and soften.

On the other hand, if the current is too low, there is not enoughheat to melt the base metal and there will be little or nopenetration. Beads will pile up (exhibit overlaps), look irregular andthe electrode tends to stick or freeze to the work.

The amperage to be used depends on :


WELDING


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The amperage to be used depends on :

a) Kind of Electrode - some electrode coating require more orless current than others for good weldability.

b) Size of Electrode - The greater the diameter of the corewire, the greater the current required to producesufficient heat to melt the metal at the desired rate

c) Thickness of Plates - More current is required for thick andheavy pieces than for light, thin sections.

d) Welding Position - In general, less current for vertical andoverhead positions (than for flat position) to preventexcessive run-down of the molten metal.

A L h


WELDING


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Arc Length

Besides the current, the arc length is an essential factor in

producing a sound weld. Too long an arc dissipates the arc

force resulting in less concentration of heat in the work.

The arc tends to be wobbly and is difficult to maintain

with consequently excessive spattering. The danger of

porosity becomes greater, as the longer arc permits longerexposure of the droplets of molten metal to the harmful

effects of the nitrogen and oxygen in the air. If the arc is

too short, a high uneven bead results with poor fusion and

the possibility of entrapping slag and the formation of thesurface gas holes becomes greater.


WELDING


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Travel Speed

Assuming that one maintains the correct current, the speed at

which one moves the electrode will now determine thesoundness and appearance of the weld bead. Too high speed willresult in incomplete fusion (not enough time is provided to meltthe base metal) with slag inclusions and gas holes, specially infillet welds, as there is not enough puddling time to allow

these impurities to escape to the surface. The slag maybe leftbehind and slag coverage will be incomplete. Too slow a speedis a waste of time and electrode-the metal piles up-and the slagmay crowd the arc and smother it.

In general the rate of travels is correct if the length of thedeposited bead is 3/4 or about equal to that or the consumedelectrode.


WELDING


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Size of Electrode

For economical reasons, it is best to use the largest size electrodeapplicable. The use of small electrodes requires more passes and is

of no advantage except in welding special alloy or castings (i.e.,cast iron, stainless steel ) where low heat input is desirable.

However, small size electrode may be necessary for the first pass

or stringer bead to assure complete fusion at the roots of joints.

In overhead or horizontal welding, electrodes smaller by one sizethan those used for flat position are recommended to minimizemetal run-down. Electrodes more than 5.0mm in diameter are not

recommended for overhead welding.


WELDING


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Documents

Welding Seminar - Terminology, Symbol & Metallurgy