AGRICULTURAL ENGINEERING NEWS LETTER AGRICULTURAL EXTENSION DIVISION UNIVERSITY OF MINNESOTA UNIVERSITY FARM, ST. PAUL-AUGUST 15, 1936--NO. 53

WELDING FARM EQUIPMENT J. G. DENT

Welding methods are classified into a new casting with possible delay result­ is used extensively in farm equipment as two groups, "cohesion caused by pressing ing, while now a good welder will make well as for pipe fittings, harness hard­ and hammering metals while in a plastic it as strong and as good as new, quickly ware, etc. A broken malleable casting or fusion state" and "cohesion of metals and usually at a fraction of the cost of a has a somewhat smoother appearance in a fusion or vapor state." Forge weld­ new part. Cast iron may be either weld­ than ordinary cast iron and bends before ing is included in the former and oxy­ ed (melting or fusing the parts together), breaking. acetylene and electric arc welding in the or brazed (similar to "soldering," using Wrought Iron is practically carbon­ latter. brass or bronze). free containing about .OS per cent car­ Forge Welding Brazing bon, is tough, can be bent and twisted, The welding of iron in the forge is an Many welders prefer to braze a casting and is easily welded by any process. It ancient art. Historians tell us that the because it requires only a red heat, while is sometimes used for well casings and pipe, but because of its high cost has been process of welding was developed by the in welding the c;ist iron must be heated Greeks about 600 B. C. At the beginning entirely replaced by mild steel in farm to its melting point. Brazing causes less machinery. of the present century forge welding was expansion and contraction and less dan­ the only process known and it was pos­ ger of cracking. Although bronze weld­ Mild Steel carbon content ranges up­ sible to weld only relatively small pieces ing rods cost about twice as much as cast ward from 0.2 per cent. It is exten­ of wrought iron and steel. However, iron rods, less gas is used in brazing. sively used in farm equipment in the within its obvious limitations forge weld­ Therefore, on a small job the cost is form of rods, bars, channels, and angle ing was developed to the point where, about the same. A brazed job has some iron, as well as for wire, nails, screws, in the hands of a competent blacksmith, advantages over a welded one in cast and sheets. It is tough, strong, and easily a weld could be produced which was iron because it will bend before breaking, welded by any process. as strong and as good as the original while the cast iron will not. A good Tool Steel for ordinary tools such as piece. It is not possible to weld cast welded or brazed cast iron job will be drills, taps and dies, axes, knives, and iron by the forge method. Within the equally satisfactory and will not break chisels contains from .80 to 1.10 per cent last few years the old time blacksmith in the repaired part if made slightly carbon. It is much more difficult to weld has largely disappeared and in his place larger than the original piece. Mild steel satisfactorily than mild steel. The high­ have come the oxy-acetylene and electric may also be brazed, and because bring­ er the carbon content the more difficult welders. ing malleable iron to a molten state ruins to weld. Oxy-Acetylene Welding its structure it should always be brazed. Hard Overlays The oxy-acetylene method of welding Electric Arc Welding Hard overlays are used on plowshares, came as a result of the discovery in 1892 Practically anything that can be weld­ drag teeth, and road machinery. In many of calcium carbide by Morehead and ed with the oxy-acetylene torch can be communities the soil is of such nature Willson of Spray, North Carolina. welded by the electric arc method, and that plowshares and other machine parts These men were experimenting with in most cases the results are equally are so rapidly worn away as to make it an electric furnace trying to produce good. As yet electric outfits are not worth while to have a hard overlay put aluminum by fusing coal tar and lime. generally used in repair shops but be­ on all parts where wear takes place. Instead of aluminum the result was a cause of their low cost of operation they These hard overlays are applied in a hard crystalline substance which we now are becoming more popular. thin layer, rarely over ~ inch in thick­ know as calcium carbide. The acetylene ness. Those with an iron base are weld­ gas resulting from this substance being Kinds of Iron ed or fused to the surface to be protected dissolved in water was first used for light Cast Iron contains about 3.5 per cent and the other type, which contains no and heat. carbon, is brittle, will not bend, and can iron, is applied to the surface similar to In 1908 the first commercial oxygen not be worked or shaped while red hot as brazing. plant began operation making possible can steel. Although it can not be welded Welding White Metal welding by the oxy-acetylene method. in the forge, it is easily welded or brazed Die cast zinc and aluminum alloys are Since 1908 oxy-acetylene welding has de­ with the oxy-acetylene or electric arc used in many automobile parts, such as veloped rapidly and to a great extent has method. A broken casting may be iden­ door handles and radiator ornaments. replaced the forge method. While the tified by the clean cut break showing no They are also used in making tools, toys, forge man is limited to the welding of bending and usually by a rough outsiue novelties, and electrical appliances. Until comparatively small parts of wrought appearance showing marks of the mold. recently it has been impossible to weld iron and steel, the oxy-acetylene welder It is often used in farm equipment. or solder these. Now they may be easily works in copper, brass, bronze, cast iron, Malleable Iron contains from 1.5 to repaired with the oxy-acetylene torch stainless steel, aluminum, white metal, 2.0 per cent carbon and is cast iron that using a new type white metal rod. hard overlays and many others. has received a heat treatment for a week The oxy-acetylene flame is approxi­ or more, which changes the form of the Selecting a Welder mately 6300 degrees Fahrenheit while the carbon, making it tough and capable of Many welders guarantee their work and forge produces about 2500 degrees Fah­ withstanding considerable twisting and although their charges are usually some­ renheit. bending. It can not be welded success­ what higher, it is one way to pick the Previous to the oxy-acetylene welding, fully, but is easily and satisfactorily better workman and is generally worth a broken cast iron part meant ordering brazed with the oxy-acetylene torch. It the extra cost.

Published in furtherance of Agricultural Extension Acts of May 8 and June 30, 1914, F. W . Peck, Director, Agricultural Extension Division. Department of Agriculture, University of Minnesota, cooperating with U. S. Department of Agriculture