Azmat Ali Khan 12mt34Usman Nazir 12mt35Naveed Imran 12mt28Haseeb Ahmad 12mt32Muhammad Farhan 12mt13Qamar Zia 12mt10Mazhar Hussain 12mt33

What is WELDING

in engineering, any process in which two or more pieces of metal are joined together by the application of heat, pressure, or a combination of both.

Master chart of Arc Welding and Related Methods

Common Welding Types

Arc Welding (AW)

Oxyfuel Gas Welding(OFW)

Resistance Welding

Types of Arc Welding

Consumable Electrodes Arc Welding Non Consumable electrodes Arc

welding

Types of Consumable Electrode AW Processes Shielded Metal Arc Welding

(SMAW) Submerged Arc Welding (SAW) Flux Cored Arc Welding (FCAW) Metal Arc Welding (GMAW or

MIG)

Types of Non consumable Electrodes AW Processes

Gas Tungsten Arc Welding (GTAW)

Plasma Arc Welding (PAW)Carbon Arc Welding (CAW)

Shielded Metal Arc Welding

Sheilded Metal Arc Welding

It is performed by striking an arc between a coated-metal electrode and the base metal.

Flux- the coating of the metal electrode will form as shield to the molten metal.

SMAW OPERATION

Arc Welding MAchines

Electrode and Holder

Advantages of SMAW High quality welds are made rapidly

at a low cost. Can be used easily even to thick and

wide work piece to be joined. Can be used from thinner to thicker

materials.

Disadvantages SMAW

Consumes bigger electric current Dirty work finish Root pass is lower than TIG and MIG Prone to slag inclusions Weld deposits is prone to blue holes

SAW (Submerged Arc Welding)

SUBMERGED ARC WELDING (SAW)

Is a process in which welding is done by an automatic electrode feeding machine wherein the tip of the electrode is submerged into a granular flux which shields the arc and the molten metal.

SUBMERGED ARC WELDING

SAW Welding Machine

SAW block diagram

SAW APPLICATIONS widely used in heavy steel plate

fabrication work. welding of structural shapes. longitudinal seam of larger diameter pipe. manufacture of machine components for

all types of heavy industry. manufacture of vessels. pressure and storage tanks.

Advantages of SAW high quality of the weld metal. extremely high deposition rate and speed. smooth, uniform finished weld with no spatter. little or no smoke. no arc flash, thus minimal need for protective

clothing. high utilization of electrode wire. easy automation for high-operator factor. normally, no involvement of manipulative skills.

Disadvantages of SAW used only to weld mild and low-alloy high-

strength steels. Unseen arc and puddle can cause poor

penetration. high-heat input, slow-cooling cycle can be

a problem when welding quenched and tempered steels.

limited-position welding process only flat and horizontal

FLUXED CORED ARC WELDING

Flux Cored Arc Welding (FCAW)

is an automatic or semi-automatic electric arc welding process that uses an arc between a continuously fed flux-filled electrode and the weld pool. The process is used with shielded gas from a flux contained within the tubular electrode with or without additional shielding from an externally supplied gas.

FCAW flux filled electrode and torch

NO shielding gas (FCAW)

With Shielding Gas (FCAW)

Two Types of FCAW

no shielding gas - using flux core in the tubular consumable

electrode

uses a shielding gas - gas that must be supplied by an external

supply. This is known informally as "dual shield" welding.

Uses of FCAW

Mild and low alloy steelsStainless steelsSome high nickel alloysSome wear facing/surfacing

alloys

Advantages of FCAW FCAW may be an "all-position" process with the right

filler metals (the consumable electrode) No shielding gas needed making it suitable for outdoor

welding and/or windy conditions A high-deposition rate process (speed at which the filler

metal is applied) in the 1G/1F/2F Some "high-speed" (e.g., automotive applications) Less pre cleaning of metal required Metallurgical benefits from the flux such as the weld

metal being protected initially from external factors until the flux is chipped away

Disadvantages of FCAW

Melted Contact Tip – happens when the electrode actually contacts the base metal, thereby fusing the two metals.

Irregular wire feed – typically a mechanical problem Porosity – the gases (specifically those from the flux-core)

don’t escape the welded area before the metal hardens, leaving holes in the welded metal

More costly filler material/wire as compared to GMAW Less suitable for applications that require painting, such as

automotive body works. Cannot be used in a rugged environment limited to shop

use only.

FCAW Equipment set up

METAL INERT GAS WELDING

GMAW or MIG is an electric arc welding process which

joins metals by heating them with an arc established between a continuous filler metal (consumable) electrode and the work.

Shielding of the arc and molten weld pool is obtained entirely from an externally supplied gas or gas mixture both inert and reactive gases.

GMAW Welding Operations

MIG Machine with Spool feeder

GUN used in GMAW

MIG Torch

GMAW Weld Diagram

Advantages of GMAW

Produced High quality welds & much faster than with SMAW and TIG welding.

No flux is used no slag entrapment in the weld metal.

Very little loss of alloying elements as the metal transfers across the arc.

Minor weld spatter is produced, and it is easily removed.

Advantages of GMAW

Versatile and can be used with a wide variety of metals and alloys, such as Aluminum, Copper, Magnesium,

Nickel, Iron and many of their alloys. The process can be operated in several ways,

including semi- and fully automatic.

MIG welding is widely used by many industries for welding a broad variety of materials, parts, and structures.

Disadvantages of GMAW

IT cannot be used in the vertical or overhead welding positions due to the high heat input and the fluidity of the weld puddle.

Has complex equipment compared to equipment used for the shielded metal-arc welding process.

NON CONSUMABLE ELECTRODES

Gas Tungsten Arc Welding

Gas tungsten arc welding (GTAW) is an AW process that

uses a nonconsumable tungsten electrode and an inert gas for arc shielding. The term TIG

welding (tungsten inert gas welding) is often applied to this process (in Europe, WIG

welding is the term—the chemical symbol for tungsten is W, for Wolfram).

Temperature and shelding gases Tungsten is a good electrode

material due to its high melting point of 3410C (6170F).

Typical shielding gases include argon, helium, or a mixture of these gas elements.

APPLICATION

GTAWisapplicable tonearly allmetals in a wide range of stock thicknesses.

It can also be used for joining various combinations of dissimilar metals.

Its most common applications are for aluminum and stainless steel.

LIMITATIONS

Cast irons, wrought irons, and of course tungsten aredifficult to weld by GTAW.

In steel welding applications, GTAW is generally slower and more costly than the consumable electrode AW processes, except when thin sections are involved and very-high-quality welds are require.

ADVANTAGES

Advantages of GTAW in the applications to which it is suited

include high-quality welds, no weld spatter because no filler metal is transferred across the arc, and little or no post weld cleaning because no flux is used.

PLASMA ARC WELDING

Plasma Arc Welding

Plasma arc welding (PAW) is a special form of gas (TAW) in which a constricted plasma arc is directed at the weld area.

In PAW, a tungsten electrode is contained in a specially designed nozzle that focuses a high-velocity stream of inert gas (e.g., argon or argon–hydrogen mixtures) into the region of the arc to form a highvelocity,intensely hot plasma arc stream

TEMPERATURES

Temperatures in plasma arc welding reach 17,000C (30,000F) or greater, hot enough to melt any known metal.

The reason why temperatures are so high in PAW (significantly) higher than those in GTAW) derives from the constriction of the arc.

ADVANTAGES

its advantages in these applications include good arc stability,better penetration control than most other AW processes, high travel speeds, and excellent weld quality.

The process can be used to weld almost any metal, including tungsten.

LIMITATIONS

Difficult-to-weld metals with PAWinclude bronze, cast irons, lead, and magnesium.

Other limitations include high equipment cost and larger torch size than other AW operations,which tends to restrict access in some joint configurations.

Carbon arc welding

Carbon arc welding (CAW) is an arc-welding process in which a non consumable carbon (graphite) electrode is used.

It has historical importance because it was the first arc-welding process to be developed, but its commercial importance today is practically nil.

APPLICATIONS

The carbon arc process is used as a heat source for brazing and for repairing iron castings.

It can also be used in some applications for depositing wear-resistant materials on surfaces.

Graphite electrodes for welding have been largely superseded by tungsten(in GTAW and PAW).

GAS WELDING AND ITS TYPES

Oxygen Fuel Gas Welding (OFW)

is a group of welding processes which join metals by heating with a fuel gas flame or flares with or without the application of pressure and with or without the use of filler metal.

Types of Oxy-fuel Gas Welding Oxy-Acetylene or Oxygen- Acetylene

Gas Welding Oxy-Hydrogen or Oxygen- Hydrogen

Gas Welding Methylacetone-Propadiene Gas

Welding Pressure Gas Welding.

Advantages of Oxy-fuel Gas Welding

Easy to use both welding and cutting

Controlled heat input

Controlled bead size

Convenient to use in welding thin sheets, tubes and small diameter pipes

Disadvantages of Oxy-Fuel Gas Weldinmoo

Cannot be use to weld on thick work piece.

Expensive gas

Oxy-Acetylene Diagram

Welding Equipment

Complete Oxy-Acetylene Welding Equipment

Resistance Welding  is a process in which the fusing temperature is generated

at the joint by the resistance to the flow of an electrical current.

is  accomplished  by  clamping  two  or  more  sheets  of metal  between  copper  electrodes  and  then  passing  an electrical  current  through  them.  When  the  metals  are heated to a melting temperature, forging pressure is applied through either a manual or automatic means to weld  the  pieces  together.

Two common types are Spot  and Seam  welding

2 Types of Resistance Welding

SPOT WELDING

SEAM WELDING

SPOT WELDING

The metal to be joined is placed between two electrodes and pressure is applied.

A charge of electricity is sent from one electrode through the material to the other electrode.

SEAM Welding

is like spot welding

except that the spots overlap each other, making a continuous weld seam.