GUN BARREL TOUGHENERS

CD1963012 E&MP19.010

Electric Furnaces

October 9, 1942

Industrial electric furnaces have a vital role in the war and production of the devices was 16 times greater during the first six months of 1942 than during any pre-war half year, according to C. L. Ipsen, manager of electric sales for General Electric.

"Prior to World War I, electric furnaces were used mainly in laboratories, but they were speedily adapted to war," Mr. Ipsen said. "Today they are playing a leading role in heat treating thousands of different parts and [sic] subassemblies for war materials of all kinds. By plant expansion and by working around the clock, however, makers of electric furnaces are supplying the demand for facilities.

"This increase of electric furnace installations foreshadows an even more extensive application in the post-war period, when carefully controlled heat treatment can be expected to play an important role in the manufacture of enormous quantities of metal products of all types."

One of the most recent wartime applications of electric furnaces is in annealing steel cartridge cases. This use of steel as a substitute for brass, now scarce, has created a new demand for electric annealing furnaces.

Other war materials creating demands for electric furnaces include gun parts and barrels, armor-piercing and other shells, hand grenades, demolition and other bombs, airplane engine parts, propellers, various tank parts, and alloy bar stock widely produced in steel mills for use in all war industries.

Electric furnaces are also widely used in brazing such sub-assemblies as track links for tanks, landing gear, serial cameras, superchargers and thousands of small joints and fixtures for planes, trucks, tanks. In brazing, a copper alloy wire is placed on two metal parts and after heat treatment the copper fuses the parts together in a joint which is often stronger than either of the members.

Nearly all metals require heat treating, either in the raw material state or later in the more nearly finished state, or both. The valuable properties of alloys are developed by the proper application and control of heat. This heat treatment is essential to the uniformity of individual pieces being turned out in great volume.

Thirty years ago, metals were heat treated only in fuel-burning furnaces. Instruments were not generally available, so the adjustment of the furnace depended on the experience of the operator. The parts then required additional processing, such as sand blasting, pickling, machining or grinding, to eliminate oxidation and decarburization which developed during heat treating.

Electric furnaces, small in size, were first used in laboratories to provide careful control under exacting experimental conditions. Production during World War I, however, demanded speedy and accurate heat treatment on an extensive scale.

"It was a bold step from a pigmy-size laboratory furnace to a giant-size furnace big enough to contain huge gun barrels," Mr. Ipsen recalled, "but General Electric engineers accomplishedthe feat.

Before the war was over, the Company installed several cylindrical-shaped pit furnaces into which large gun barrels were lowered for heat treating."

Following the war, as the manufacture of high grade consumer products such as ranges, refrigerators, typewriters and automobiles expanded on a mass production basis, the commercial application of electric furnaces developed steadily. As the years passed, new types of furnaces, adaptable for ever-widening applications, came into being. Today furnaces with time and temperature automatically controlled to insure accuracy and uniformity are in wide use. Certain types have cycle arrangements whereby a complete process can be repeated by an automatic timer.

Such surface changes as oxidation and decarburization are prevented during heat treating processes by gases which provide electric furnaces with atmospheric protection. Such subsequent processes as sand blasting are therefore eliminated, thus affording an important saving in production time, man-hours and materials.

Most electric furnaces used in mass production are of the conveyor type. Others, best suited in most cases for smaller output, include: the elevator type, used in annealing iron; the upright cylinder type, lowered over loads of material to be heat treated; the pit type, and the box-shaped type. 

Original Caption by Science Service
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