ADVANCED WELDING TECHNOLOGY

By:-HEMANT KUMAR

SYLLABUS

Unit-I1. Introduction: Importance and application of welding classification of welding process. Selection of welding process.2. Brief review of conventional welding process: Gas welding Arc welding MIG & TIG welding Resistance welding Electroslag welding Friction welding.3. Welding of Steel, CI, Al, Stainless steel4. Maurer/ Schaefflar Diagram. 5. Soldering & Brazing.

Welding Definition & ClassificationWelding Definition & Classification Process of permanent joining two materials (usually metals) through Process of permanent joining two materials (usually metals) through

localised coalescence of heat or force.localised coalescence of heat or force.

Selection of the welding processSelection of the welding process Nature of jointNature of jointMaterials to be weldedMaterials to be weldedGeometry of componentGeometry of componentQualityQualityStrength & mechanical propertiesStrength & mechanical propertiesTime factorTime factorCostCostWelding EnvironmentWelding EnvironmentSource of energySource of energy

Gas WeldingGas Welding 2C2C22HH2 +2 + 2O 2O2 2 ----- 4CO + 2H----- 4CO + 2H2 + 2 + HeatHeat

4CO + 2H4CO + 2H22 + 3O + 3O2 ---- 2 ---- 4CO4CO22 + 2H + 2H22O + HeatO + Heat

Types of FlamesTypes of Flames

Comparison b/w FlamesS. No. Neutral Flame Oxidizing flame Reducing Flame

Temperature

Materials

O2:C2H2

3200

CI, MS, SS Cu, Al

1:1

3300

Cu or Zinc alloys

1.2:1

3100

Lead ,HSS

1:1.2

Oxy- Fuel Welding Oxygen is used with other fuel gas to

produce flame & coalescence of heat.

1. Hydrogen2. Propane3. Butane4. Natural gas

Advantage

Most versatile. Considerable control over temp. by varying supply of gases. Deposition rate is controlled Low cost & versatile equipment Portable & low maintenance

Disadvantage Not for heavy sections Lower temp of flame limits its use. Flux used causes irritating smoke. Refractory metals & reactive metals cannot be welded Long heat up time Larger HAZ More safety & handling problem with gases.

APPLICATION

Joining up to thickness 8 mm. Materials having harmful effect of rapid heating &

cooling. Materials like- CI, SS, LCS, HCS, Cu,

Zn, Ni, Mg etc. In automobile & aircraft industry for sheet-metal

applications.

Arc Welding

PRINCIPLE Heat is generated from arc struck between

an electrode & work piece. Temp.= 5500 Celsius Stand off dis.= 1 - 5 mm. Arc length = 0.6 - 0.8 of electrode dia. Current =150 – 1000 Amp. Voltage = 40 - 45 volts (DC) 50 -60 volts (AC)

ARC GENERATION

Supply is on, voltage is applied, electrode & w/p are stuck together and hence current flow starts; then the electrode is kept 2-5mm and due to current flow electron jumps gap & ionization of gap takes place and arc is initiated.

Methods to initiate arc:1. TOUCH METHOD2. PASS-AWAY METHOD

Varients

1. Carbon Arc Welding.2. Shielded Metal Arc Welding. 3. Submerged Arc Welding.4. TIG (or GTAW) Welding. 5. MIG (or GMAW) Welding. 6. Electroslag Welding. 7. Electro gas Welding. 8. Plasma Arc Welding. 9. Arc Spot Welding. 10. Stud (Arc) Welding.

Tungsten Inert Gas ARC WELDING

(TIG/GTAW) • Heat is generated by electric arc struck

between a tungsten electrode and the job.• A shielding gas (argon helium, nitrogen,

etc.) is used to avoid atmospheric contamination of the molten weld pool.

• A filler metal may be added, if required.

SPECIFICATION 0f TIG• Temp. = 5500 Celsius• Welding torch angle= 70- 80 degrees• Filler rod angle= 10-20 degree• Current= 100-500 Amp• Electrode diameter = 2-5 mm• Filler rod diameter = 2-6 mm• Flow rate of gases = 7-11 lit/minutes• Electrode material = W, W alloys,

Thoriated W, Zerconiated W.• Shielding gases = Ar, Ne, He etc

ADVANTAGE

Applicable to wide range of materials (ferrous & non-ferrous).

Good for welding thin sections (0.125mm) and delicate work pieces

high quality and appearance of weld. Clear visibility No flux entrapment risk

DISADVANTAGE Restricted to flat or horizontal welding. W in weld pool causes seviour problem Filler rod end causes contamination of

weldment Costly.

APPLICATION

Al, Mg, Cu, Ni, and their alloys. Carbon alloys, SS, High temp &

hard surfacing alloys like Zr, Ti. Welding thinner sections. Welding of expansion bellows,

transistor cases, instrument diaphragm & sealing joints

Rocker motor chamber fabrication in launch vehicles.

METAL INHERT GAS ARC WELDING

(MIG)• Heat is generated by electric arc struck between a

consumable metal electrode and the job.• A shielding gas (argon helium, nitrogen, etc.) is

used to avoid atmospheric contamination of the molten weld pool.

• It needs Wire Electrode feed mechanism.

Process of MIG

ADVANTAGE Versatility - readily applied to a variety

of applications and a wide choice of electrodes

Relative simplicity and portability of equipment

Low cost Adaptable to confined spaces and

remote locations Suitable for out-of-position welding

DISADVANTAGE Not as productive as continuous wire

processes Likely to be more costly to deposit a given

quantity of metal Frequent stop/starts to change electrode Relatively high metal wastage (electrode

stubs) Current limits are lower than for continuous or

automatic processes (reduces deposition rate)

RESISTANCE WELDING• Heat generated at interface due to

resistance offered. H= I*I*R*T• Autogenous Weld (no filler needed)

Variants

Spot welding Seam welding Projection welding Upset/Butt welding Flash Butt welding Percussion welding

Electrode Material

0.99Cu 0.1Cd- LCS, Al & Mg alloy. 0.992Cu 0.8Cr- SS, Ni alloy, Ni plated

steel 0.05Be 0.1Ni 0.1Co 0.975Cu- Low

electrical & high thermal conducting materials.

SPOT WELDING

Welding steps SQUEEZE TIME- Both workpices are

squeezed together, by app of pressure by electrodes.

CURRENT SUPPPLY- Now welding current is applied for short time.

HOLD TIME- Current is off but the forces remains applied for proper weld.

OFF TIME- the forces on the work is removed.

PARAMETERS & USES Voltage= 5-25 volts Current= 100-5000 Amp Time= 0.06-3 sec Materials welded Ferrous- Hardanable steel, HSS, SS,

Coated Steels etc. Non-Ferrous- Al, Al-Mg alloys, Al-Mn alloys,

Cu, Cu-Al alloys, Ni, Ni alloy, Monal (Ni-Cu) alloys etc.

ADVANTAGE

Low cost High welding speed Less skilled labor. Elimination of wrapping/distortion of

parts High uniformity & quality of products Easy automation No need of edge preparation

APPLICATION

Spot weld up to 12.5mm thickness Attachment of braces, brackets,

pods, clips of box, container & trays are welded

Automobile & aircraft industry. Joining sheet metals

SEAM WELDING

ADVANTAGEADVANTAGE Gas & liquid tight Gas & liquid tight

welds.welds. Overlap may be less Overlap may be less

than spot weldingthan spot welding Single seam weld or Single seam weld or

parallel welds can parallel welds can be producedbe produced

DISADVANTAGEDISADVANTAGE ONLY STRAIGHT OR ONLY STRAIGHT OR

UNIFORM CURVE CAN UNIFORM CURVE CAN BE WELDEDBE WELDED

DIFFICULT TO WELD DIFFICULT TO WELD THICKNESS MORE THICKNESS MORE THAN 3MMTHAN 3MM

SPECIAL DESIGNE OF SPECIAL DESIGNE OF WELD ROLLSWELD ROLLS

APPLICATION•ROUND, SQUARE, RECTANGULAR WELDS•EXPECT Cu & HIGH Cu ALLOYS ALL OTHER MATERIALS ARE WELDED•CAN BE USED FOR LAP, BUTT JOINTS

PROJECTION WELDINGPROJECTION WELDING

PRINCIPLEPRINCIPLE

Current flow is concentrated at Current flow is concentrated at the contact surface by an the contact surface by an embossed projection.embossed projection.

Projection effectively localizes the Projection effectively localizes the currentcurrent

ADVANTAGE

No of simultaneous weld Thick joints Less interference by rust, oil & work

coating Long electrode life Can be used for complicated shapes Better heat balance Lower current & pressure

DISADVANTAGE

Limited to metals which can be embossed

For proper weld all projection must have equal height.

APPLICATON

Various automobile parts Small fasteners & nuts can be

welded Refrigerator condenser Cross wire welding Grating of boilers Household grills.

FRICTION WELDING

• solid-state welding• Heat through mechanical friction

b/w a moving work piece & a stationary component .

• Technically, because no melt occurs, so its a forging technique .

Friction Welding Process

Process Parameters

Process Specification

Peripheral velocity= 50-200 m/min Axial pressure= 30-200 N/mm2 Material Welded- Al, Ti, Ni, Cu and

their alloys, Brass, Bronze, Mg, Carbon steel, SS, Tantalum etc..

Dissimilar material welds- Alloy steel to carbon steel, super alloys to carbon steel, SS to carbon steel

ELECTROSLAG WELDING

• Highly productive, single pass process (thickness 25-300 mm) in a vertical position

• Arc is initially struck by wire fed into the weld location & then flux is added.

• Additional flux is added until the molten slag extinguishes the arc.

• The wire is then continually fed and the filler metal are then melted using the electrical resistance of the molten slag to cause coalescence.

Processes

Points to ConsiderADVANTAGE Butt & T joint square

face Large thickness upto

600mm Alloy steel are welded Extremely high

deposition rates Residual stress &

distortion is low Low flux consumption No spattering & flashing

occurs.

DISADVANTAGE More costly for

section below 60mm Hot cracking Tends to produce

larger grain size Limited to vertical &

uphill position Tendency to notch

sensitivity in HAZ

APPLICATION

Heavy casting, forging plates (butt weld)

Welding of thick LCS & MCS. High strength structure steel Large cross-section of flyovers,

structures, marine ships etc.

WELDING of CAST IRONWELDING of CAST IRON Good fluidity & high solidification shrinkage. SMAW, GMAW, Oxy-fuel, flux coated arc, Termite

welding processes are applicableGrey CI: Certain precaution like preheating & low cooling rates.White CI: Considered as un weldable.Malleable CI: Post weld heat treatment Very low cooling rates to prevent it to change to

White CI.Nodular CI: Proper flux is needed to prevent losing of Mg which is

responsible for ductility.

WELDING of ALUMINIUMWELDING of ALUMINIUMHigher heat input needed (Reverse DC

polarity)Thick sections needs preheatingHigh reflective hence no red colour is

appered during heatingGMAW, GTAW, Resistance welding is

common. PAW, EBM are specially usedSMAW & oxy fuel welding are used

when strength is not essential

WELDING of STEELWELDING of STEEL

LCS(0.13-0.3 %C): arc welding is preferredMCS(0.3-0.5 %C): Pre weld heat treatment is common Post weld heat treatment is sometimes necessary for

thin sectionsHCS(0.5-1.5%C): Pre & Post weld eat treatment is essential Low H, S welding process Should be welded in annealed conditionHIGH STRENGTH LOW ALLOY STEELS: SMAW, TIG/MIG, Flux coated ,Submerged arc welding

are applicable. Low Hydrogen welding Resistance welding can be applied

SOLDERINGSOLDERING• Two or more metal items are joined

together by melting and flowing a filler metal into the joint

• The filler metal having a relatively low melting point

• Soldering is characterized by the melting point of the filler metal, is below 400 °C

• The filler metal used in the process is called SOLDER

• It is distinguished from welding by the base metals not being melted during the joining

Process- SolderingProcess- Soldering

ApplicationApplication

Assembling electronic components to printed circuit boards

Permanent but reversible connections between copper pipes in Plumbing systems

Jewelry components are assembled and repaired by soldering

Solders Solders

tin-lead (general purpose) tin-zinc for joining aluminum lead-silver for strength at higher than

room temperature cadmium-silver for strength at high

temperatures zinc-aluminum for aluminum and

corrosion resistance tin-silver and tin-bismuth for

electronics

Typical Soldering Example