Science: Weld It!

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Machine tools. Casting is being nudged aside too by arc welding, notably in the machine-tool industry. Welding allows the frames of huge presses, drills, saws, etc., to be built of smaller pieces rather than cast in large chunks which then have to be cut, shaped and finished. Welding can cut by 25% (average) the time and cost of manufacturing the $450,000,000 worth of machine tools required yearly by the arming U.S.

Resistance welding in its several forms, like arc welding, has made notable contributions to defense production. Commonest form is spot welding: two pieces of thin metal are fused together by the heat generated, due to their electrical resistance when an electric current passes through them. Unlike arc welding, melting of the current-feeding electrode is avoided by: 1) making the electrode partly of copper, whose resistance is very low; 2) mixing the copper, through powder-metal techniques (TIME, Sept. 29), with compounds whose melting point is far higher than steel's; 3) cooling the electrode with water.

Widely used in auto-building, spot welding is today spreading through the aviation industry now that the problems of welding aluminum have been outwitted.— Engineer Paul H. Merriman of Glenn L. Martin Co. estimates that when spot welding has captured the entire aircraft industry—with perhaps 60 welds applied in one movement of a machine—U.S. plane output will increase by 30%.

Shotwelding is a refinement of spot welding designed for stainless steel (usual formula: 18% chromium, 8% nickel), whose great tensile strength—four times that of ordinary carbon steel—is lost when it is heated to 1,100° to 1,600°. The Shotwelding electrodes stab the metal for 1/10 th 1/20 th of a second, heating it so instantaneously through its danger zone to its 2,700° fusing point that the alloy's unique strength is not affected. Invented by Budd Manufacturing Co. (and used for making stainless steel railroad coaches), Shotwelding may well make steel planes lighter than even welded aluminum planes.

Detroit's William B. Stout, an aeronautical engineer whose visions have often come to pass, observed last week:

"Aluminum weighs one-third as much as steel, but [stainless] steel is more than four times as strong as aluminum in pull and tension. Recent developments in structure mathematics now enable us, even in small planes, to build trusses of thin stainless steel of equal weight to duralumin [an alloy containing 95% aluminum, 4% copper, ½ % manganese and ½ % magnesium while in larger ships there is a greater advantage to the steel construction.

"The art of building a featherweight, superstrength, welded steel structure is growing at a tremendous rate. It is my prediction that all future commercial planes and most military planes will be made of welded steel."

— The chief problems: 1) aluminum has a low melting point (1220° F.); 2) it oxidizes ("rusts") easily when hot.

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