Thermite welding process

At high temperatures, aluminum reduces many oxygen-containing compounds, particularly metal oxides. These reactions, of the type shown in equation 6, are used in the manufacture of certain metals and alloys, as well as in the thermite welding process. ... 

An intimately powdered mixture, usually ignited by magnesium ribbon as a high-temperature fuse, reacts with an intense exotherm to produce molten iron and was used formerly (before the advent of gas or arc welding) in the commercial thermite welding process. Incendive particles have been produced by this reaction on impact between aluminium and rusty iron. (The term thermite reaction has now been extended to include many combinations of reducing metals and metal oxides) [1], Some accidents in demonstrating the thermite reaction are described [2],... 

This is done to ensure ease of algebraic addition and subtraction of the chemical equations. Stated differently, we can conclude that the lines lying lower in the diagram denote a more stable oxide. An element, e.g., Al, capable of giving a more stable oxide can reduce a relatively less stable oxide (e.g., FeO). The reaction between Al and FeO is the basis of the Thermit Welding Process. 

Thermit-bom be, /. thermite bomb, -brand-bombe, /. thermite incendiary bomb, -fiil-iung, /. thermite filling or charge, -ladung, /. thermite charge, -schweissung,/. thermite weld(ing). -verfahren, n. thermite process. 

Thermite welding is used for joining iron rails and also for liberating elements such as W and V from their oxides. The welding process involves heating a mixture of aluminium powder and hematite (thermite) the vigorous reaction which results produces AI2O3 and iron, i. e. 

The common practice of thermite welding is another application of the Goldschmidt process. Iron rails are often welded together by this procedure. The ends to be welded together are surrounded by a packing of sand and clay. Molten iron is produced by the reaction... 

In the field of rail welding, the thermite process supplements and sometimes replaces flash or gas-pressure welding. The latter methods require very costly factory installations. They furnish rails about one-quarter of a mile long, which are hauled to the point of field installation. Here one can resort to the old-fashioned mechanical join-Ing (a source of most maintenance on a railroad) or use field welds. The best of these is the thermite weld. It may be used exclusively with specialty items such as crossings, for haulage tracks in coal mines, and for crane rails. ... 

GOLDSCHMIDT REDUCTION PROCESS. Reaction of oxide), of various metals with aluminum lo yield aluminum oxide and the free metal. This inaction has been used to produce certain metals, e g. chromium and zirconium, from oxide ores and it is also used in welding (iron oxide plus aluminum giving metallic iron and aluminum oxide, plus considerable heat). (Thermite process. ... 

The thermite process is of historical interest as a method of welding iron ... 

The thermite process (see Fig. 12.11) is used for welding railway track together. In this reaction, aluminum reduces iron(III) oxide to metallic iron ... 

Before arc welding was developed, a displacement reaction involving aluminum and iron(III) oxide was commonly used to produce molten iron (the thermite process). This reaction was used, for example, to connect sections of iron railroad track. Calculate the mass of molten iron produced when 1.00 kg of aluminum reacts with 2.00 mol of iron(III) oxide. 

Thermite is used in incendiary bombs and for welding steel. See also Goldschmidt process. 

While other methods of reparing machine parts, such as electroslag and submerged-arc welding, have become popular, the thermite process has remained competitive because it requires no capital investment and is easily performed as a one-at-a-time operation. Normally, a certain amount of preheating is desirable, but recently a Self-Preheat process has dispensed with this. ... 

A1 + Fe203 —> AI2O3 + 2Fe The reaction is highly exothermic and the increase in temperature is sutBcient to melt the iron produced, it has been used for localized welding of steel objects (e.g. railway lines) in the Thermit process. Thermite is also used in incendiary bombs. 

The Thermit or aluminothermic process for constructing railways by welding the rails in place A powder mixture of FeO and A1 is ignited by Ba02- The heat of reaction is sufficient to let the iron as the reaction product liquefy and flow into the welding gap. 

AI2O3 and aluminothermic welding, thermit process 3Fe304 + 8A1 9Fe -b 4AI2O3). 

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