Shielded Metal Arc Welding by Hobart Institute

Author:Hobart Institute [Hobart Institute]
Language: eng
Format: epub
Published: 0101-01-01T00:00:00+00:00

irons do not have the brittleness that the gray cast irons

have because of the shape of the graphite. Nickel-base

covered electrodes are also used for the welding of mal-

leable and nodular cast irons. After these cast irons have

been welded, they should be annealed to obtain opti-

mum ductility.

Copper and Copper Alloys

Shielded metal arc welding is mainly used for minor repair

jobs, difficult to reach fillets, or dissimilar metals when it

is used to weld copper and copper alloys. Shielded metal

arc welding does not do as good a job as the gas metal

arc welding or the gas tungsten arc welding process. The

filler metal that is used for the welding of the copper and

copper alloys contains deoxidizers. Shielded metal arc

welding of these metals is generally restricted to the flat

position. Out of position welding can only be performed

satisfactorily on phosphor bronzes and copper nickels.

Shielded metal arc welding is usually not recommended

for the welding of many of the copper alloys because

it produces poor mechanical properties and many un-

sound welds. The coppers and brasses are generally not

welded using this process.

Nickel and Nickel Alloys

The shielded metal arc welding process can be used

to weld nickel and nickel alloys in thicknesses ranging

down to about .050” (1.3mm). The covered electrodes

used have chemical compositions similar to the base

metals being welded. Elements such as manganese, co-

lumbium and titanium are contained by the electrodes

and act as deoxidizers and prevent weld metal crack-

ing. Direct current electrode positive welding current is

used when welding nickel and nickel alloys. Flat position

welding is used whenever possible because it produces

a better quality weld. Molten nickel alloy weld metal does

not flow as well as molten steel weld metal so the nickel

alloy weld metal must be deposited where it is needed.

Oscillating or weaving techniques are usually needed be-

cause of this. The heat of the welding arc usually does

not have a bad effect on the nickel-base metals. Preheat

is usually not required for welding these metals but the

base metal should be warmed to at least 70°F (21°C) to

avoid the condensation of moisture which could produce

porosity in the weld metal.

– 33 –

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