WELDING

Welding is a process of permanent joint production by formation of interatomic bonds origination between the parts being joined.

Friction welding

Welding methods

Welding by fusion

– Gas welding

– Cold welding– Electric arc welding

– Friction welding

Welding by pressure

– Plasma welding – Ultrasonic welding

Plasma welding

а b

U, V

WELDING

Electric arc welding

The welding arc is a powerful stable electric discharge burning between electrodes in the atmosphere of ionised gases and vaporised metals.

Scheme of direct currentwelding arc: 1 – electrode; 2 – base metal;

3 – bath of liquid metal; 4 – arc column

Static volt-ampere arc characteristic (а);external characteristics of current sources for welding (b)

WELDING:

Diameter of electrode d is chosen depending on welded metal thickness: where s is the thickness of welded metal, mm.

Manual metal-arc welding circuit diagram:

1 – A.C. mains supply;2 – neutral;3 – live;4 – fused switch; 5 – primary cables;6 – current control; 7 – welding set; 8 – welding cable; 9 – electrode holder; 10 – electrode;11 – work-piece; 12 – work support; 13 – return current cable; 14 and 15 – earth

Electric arc welding

WELDING

Automatic submerged arc welding (SAW):1 – sliding conductor ; 2 – feeder; 3 – welding wire; 4 – liquid slag; 5 –layer of flux; 6

– slag crust; 7 – welded seam; 8 – basic metal; 9 – pool of liquid metal; 10 – arc zone

Advantages of the process:– the most productive way of welding;– high quality of a seam;– low production cost of 1 m of seam;– welding metal up to 20 mm thickness for one pass without cutting of edges.Application: in serial and mass production, such as manufacturing of boilers, tanks, ship hulls, bridge beams, welded pipes with a direct and a spiral seam, wheels.

Electric arc welding

2 –

WELDING

Resistance butt welding (RW):

1 – current supply clips; 2 – billets; 3 – motionless plate; 4 – mobile plate; 5 –

guide; 6 – welding transformer; 7 – flexible busesAdvantages of the process:

– cleaning of surfaces is not necessary;– welding parts of a complex section and with the different shape of the section;– dissimilar metals can be welded.Application: welding of rings, wheels, the end tool (drills, mills, taps), rods, rails, reinforcement, pipes.

Resistance welding

Flash welding (FW)