WELDING Harkness career center What is MIG Metal

WELDING Harkness career center

What is MIG? § Metal Inert Gas (MIG) § MIG is an arc welding process that uses a continuous solid wire electrode for the filler metal and a shielding gas to protect the weld zone. § The molten puddle is shielded by an external shielding gas – ARGON/CO 2 MIX – CO 2

Welding Safety - Leather gloves Sleeves Full face helmet Welding shade 9 -14 Arc weld can be 8 times brighter than the sun! “ welders flash”

MIG welder setup -The cart- secures all the components -The tank- filled with an inert gas 2 k to 3 k psi -The regulator- controls tank pressure 15 to 20 psi -The welder - converts AC voltage to DC voltage - controls the wire speed and heat

Welder schematic

Regulator -The regulator reduces tank pressure -The gauge closest to the tank reads tank pressure -The gauge closest to the hose outlet reads working pressure -Working pressure should be 15 to 20 psi -The adjuster screw should backed off when not in use

Ground clamp -Supplies the welded metal a ground -The surface must be clean and rust free -Should be as close to the weld as possible

Welding gun 1. Gun housing 2. Electrical insulator 3. Positive electrode and gas discharge 4. Contact tube 5. Fill wire “electrode”

MIG gun and weld area

Welding process

MIG PROCESS

GUN MOVEMENTS

Welding Flaws Kalpakjian

-Welding Flaws at the Underside of the weld -Incomplete Penetration (not enough heat input) www. mig-welding. co. uk www. ndt-ed. org/Education. Resources

Distortion from Welding Processes • Non-uniform shrinkage of weld bead • Difficult to maintain alignments • Solution: Rigid fixtures, pre-compensate for warping, loose tolerances Kalpakjian

Types of Joints Kalpakjian

Weld bead profile: Convex or Concave? • Solidification of molten bead leads to shrinkage • Shrinkage of a concave bead leads to tension on surface tends to crack • Shrinkage of a convex bead leads to compression on surface does not crack • Generally, slightly convex beads are preferred. Lincoln Electric

WELDING WITHOUT GAS

Wire Welder MAKE SURE TO TURN ON FLOW GAGES!! § Millermatic 35 § Blue Hobart – Set heat 1— 6 (Turn & Pull) – Set wire speed § Usually around 50 – Adjust heat and speed as needed. – Determine type of metal and position – Lift cover and determine welder preset selection for heat and speed. – Adjust machine – Fine adjustment wire speed and heat to individual needs.

Wire Welder Problems § 1. Make sure your turn on the flow gages. – Setting to around 25— 30 § § § 2. Make sure your hoses are straight 3. Popping Noise—Adjust wire speed down. 4. Check wire tips 5. Dip wire tips into nozzle lubricant 6. Make sure you have good penetration. Internet Site: http: //www. lincolnelectric. com/knowledge/articles/c ontent/gmaw. asp