Welding Processes Gautam singh (M.E 4th yr) 10030104014

WELDING Welding is a materials joining process which produces coalescence of materials by heating them to suitable temperatures with or without the application of pressure or by the application of pressure alone, and with or without the use of filler material. Welding is used for making permanent joints. It is used in the manufacture of automobile bodies, aircraft frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, general repair work and ship building.

Types of Welding Fusion Welding Pressure Welding Friction Welding Homogeneous Heterogeneous Brazing Soldering Gas Welding Electroslag MIG TIG High Energy Beam Shielded Metal Arc – “Stick” Electric Arc

Fusion Welding Principles Base metal is melted Filler metal may be added Heat is supplied by various means Oxyacetylene gas Electric Arc Plasma Arc Laser

Fusion Welding ELECTRODE COATING CORE WIRE WELDING ATMOSPHERE ARC STREAM ARC POOL SOLIDIFIED SLAG PENETRATION DEPTH WELD BASE METAL

Weld Fluxes Typical fluxes SiO2, TiO2, FeO, MgO, Al2O3 Produces a gaseous shield to prevent contamination Act as scavengers to reduce oxides Add alloying elements to the weld Influence shape of weld bead during solidification

Inert Gases Argon, helium, nitrogen, and carbon dioxide Form a protective envelope around the weld area Used in MIG TIG Shield Metal Arc

Types of Fusion Welding Oxyacetylene Cutting/Welding Shielded Metal Arc (“Stick”) Metal Inert Gas (MIG) Tungsten Inert Gas (TIG)

Oxyacetylene Welding Flame formed by burning a mix of acetylene (C2H2) and oxygen Fusion of metal is achieved by passing the inner cone of the flame over the metal Oxyacetylene can also be used for cutting metals TORCH TIP 2300 deg F Inner Cone: 5000-6300 deg F Combustion Envelope 3800 deg F

Gas Welding (Oxy-acetylene) A number of welding processes use a flame produced by burning a mixture of fuel gas and oxygen. The gas usually used is Acetylene but other gases are also used. Separate cylinders and a hose pipe from each cylinder transports the gases to a torch. Gas and fuel mix in the torch burns @ 3100°C.

Metal Inert Gas (MIG) Uses a consumable electrode (filler wire made of the base metal) Inert gas is typically Argon DRIVE WHEELS CONSUMABLE ELECTRODE POWER SOURCE SHIELDING GAS ARC COLUMN BASE METAL PUDDLE

Tungsten Inert Gas (MIG) Tungsten electrode acts as a cathode A plasma is produced between the tungsten cathode and the base metal which heats the base metal to its melting point Filler metal can be added to the weld pool TUNGSTEN ELECTRODE (CATHODE) POWER SOURCE TUNGSTEN ELECTRODE + + + + - - - SHIELDING GAS ARC COLUMN BASE METAL PUDDLE BASE METAL (ANODE)

Submerged Arc Welding (SAW) Similar to MIG welding, SAW involves formation of an arc between a continuously-fed bare wire electrode and the workpiece Applications SAW welding taking place in the flat position. Ideal for heavy workpieces Carbon-manganese steels,low alloy steels and stainless steels

Welding Positions FLAT HORIZONTAL OVERHEAD VERTICAL INCREASING DIFFICULTY FLAT HORIZONTAL OVERHEAD VERTICAL

Weld Symbols (Butt Joints) Backing

Weld Symbol (Fillet Joints)

Weld Symbol (Corner Joints)