Shielded Metal Arc Welding Joints and Passes Butt joint, Corner joint, Lap joint Tee joint, Root pass, Hot pass, Filler pass, Cover pass

Shielded Metal Arc Shielded Metal Arc Welding Joints and Welding Joints and

PassesPasses

Butt joint, Corner joint, Lap joint Tee joint, Root pass, Hot pass, Filler pass, Cover pass

PREP FOR 1PREP FOR 1STST PROJECT! PROJECT!

The know how behind how to do your first project!

Joints , Welds, And Passes

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Tack WeldsTack Welds

Short welds spaced at intervals to join parts to whole in process of assembly before welding

Must be strong◦Hold part in position◦Able to resist stress when expansion and

contraction occur during weldingNumber and size of tack welds depend

upon thickness of plate, length of seam, and amount of cold working to be done

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Use more heat for tack welding than for major welding

Must have good fusion and good root penetration

Flat and smooth

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

American Welding Society

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Position is important as metal heats and cools it expands and contracts

Example from P.D Session



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Stringer BeadStringer Bead

Weld made by moving weld pool along intended path in straight line

Fast cooling rates because of faster travel speed◦Can impact grain structure and affect distortion

level


American Welding Society, Welding Inspection Technology, 4th ed.,p. 4-27, Fig. 4.32, 2000.

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PorosityPorosity

Cavity-type discontinuities (pores) formed by gas entrapment during solidification

Discontinuities are spherical and may be elongated

Usually caused by contamination of filler metal or base metal or impropergas shielding

Not considered as severeconcern as cracks or incomplete fusion


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Four Weld TypesFour Weld Types

Bead (surface) weld

Fillet weld

• Groove weld

• Plug (slot) weld


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Bead WeldsBead Welds

Also called surface weldsSingle-pass deposits of weld metalUsed to build up pad of metal and to

replace metal on worn surfaces


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Fillet WeldsFillet Welds

Consist of one or more beads deposited in right angle formed by two plates

Take triangular cross section due to location placed in weld joint

Used for lap joints, T-joints, and open corner joints

Weld symbol takes same triangular shape as weld


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Fillet WeldFillet Weld


American Welding Society, Welding Inspection Technology, 4th ed., p. 4-24, Fig. 4.22, 2000

Important aspect is its profile

KNOW TERMS**

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Fillet WeldsFillet WeldsMost common weld used in industryAs strong or stronger than base metal if weld

correct size and proper welding techniques used

Contour is shape of face of weld◦Flat◦Convex◦Concave


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Under WeldedUnder Welded

Remember: A weld or weld joint is no stronger than its weakest point.


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Weld LengthWeld Length

Fillet and groove welds usually made along full length of joint◦Sometimes full strength can be achieved by

welding a portion of jointEffective length of fillet weld measured as

overall length of full-size fillet weld◦Start and stop of weld must be allowed for

Not square, so allowance made when measuring Space between welds determined by

center-to-center distance of weld which is called pitch

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Weld Area Weld Area and Stressand Stress

Easily calculatedImportant to determine how much stress

joint can take

area = weld length x weld size

area weld

load stress

Safety margins are built in to ensure the weld is able to withstand the load.

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Groove WeldsGroove Welds


Consist of one or more beads deposited in groove

Used for butt joints◦Unprepared with square edges◦Prepared with bevel or J-groove

If both members prepared same, take shape of V or U and named V-groove or U-groove butt joint

Weld applicable on both plate and pipe

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Groove WeldsGroove Welds



ActivityActivityForm joints with pieces of wood or metal

and draw

Square Butt JointSquare Butt Joint

Made by tack welding two flat pieces of plate together

Root Opening/Gap – Space between the plates

Edge WeldEdge Weld

Made by placing edges of the weld evenly

Metal held together by clamp with no openings

Weld should equal the thickness of the plate, have build up

Weld bead equal to thickness of joint (usually tack first)

Edge WeldEdge Weld

Outside Corner JointOutside Corner Joint

Placing plates at 90˚ to each other with edges forming V-Groove

May or may not have slight root opening left between plate edges

Weld bead should completely fill V-Groove formed by the plates and may be slightly convexted



Lap Joint (Project #2) Lap Joint (Project #2)

Made by overlapping the edges of two plates

Can be welded on one or both sides of joint with fillet welds

Build up of weld should equal the thickness of the plate


Penetration on lap joints does not improve strength

Complete fusion is required – root must be melted for fusion


Very important to use tack welds to hold in place and clean slag after welds



Tee Joint Tee Joint

Tack welding one piece of metal to another piece of metal at a right angle

Important to place tack welds correctly ◦PD EXAMPLE

◦Remove slag from tack welds

Tee Joint Tee Joint

Watch heat and strength

Root PassRoot Pass

First weld bead of a multi pass weld

Fuses two parts of metal together and establishes depth of weld metal penetration

Essential for a good weld

Root PassRoot Pass

May or may not use backing strip

Root PassRoot Pass

Terms to know for project

Root PassRoot Pass

Ideal root pass

Root PassRoot Pass

Our project (except backing plate)

Hot PassHot PassSurface of root pass may be irregular,

have undercut, overlap, slag inclusions or other defects

A way to clean out trapped slag and make the root pass more uniform

Hot PassHot PassUses a higher-than-normal amperage

setting and a fast travel rate to reshape the bead and burn out the trapped slag.

Can be made after chipping away slag and cleaning with wire brush

Filler PassFiller PassUsed after root pass in completed and has

been cleaned

Groove is filled up with beads = Filler passes

“Fills up” Area to be welded

Filler PassFiller PassUse stringer beads

Beads must overlap each other enough so the finished bead is smooth

Must clean bead before doing next pass

****** VERY IMPORTANT FOR****** PROJECT #1

Filler PassFiller Pass

WILL BE DOING THIS ON PROJECT

Cover PassCover Pass

Last bead on a multi-pass weld = Cover Pass

Important to keep it clean and neat looking because most welds have visual inspection

Should be free from defects (undercut, overlap, porosity, slag inclusions)

Cover PassCover Pass

No more than 1/8th the groove opening

Project #1Project #1



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Shielded Metal Arc Welding Joints and Passes Butt joint, Corner joint, Lap joint Tee joint, Root pass, Hot pass, Filler pass, Cover pass