Ferro-silicon

The powder has black gray metallic lustre. This is reactive with alkali solution and dissolves in it, generating hydrogen gas. Stable against ordinary acids. 

Ferro-silicon is used for red thermit as an ignition composition. 

The more the silicon is present, the more the heat of combustion increases. 

Quality. JIS standard G2302 shows that the first class material has 88-93% silicon content and it is used for explosives(carlit) or generating hydrogen gas in combination with sodium hydroxide. From the second to the fifth class, the silicon contents are defined as 75-80%, 43-47%, 

25-30%, 20-25% respectively, and these classes are used as the deoxidation against in iron manufacture or the silicon supply for manufacturing silicon steel plate etc. The sixth class has 15-19% silicon content and is used for acid-proof iron vessels. For firework use(for the red thermit) the first class is recommended. 

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Both silicon and aluminium are added to zinc to control the adverse effects of iron. The former forms a ferro-silicon dross (which may be removed during casting). Aluminium forms an intermetallic compound which is less active as a cathode than FeZn,] . Similarly in aluminium and magnesium alloys, manganese is added to control the iron . Thus in aluminium alloys for example, the cathodic activity of, FeAl, is avoided by transformation of FeAlj to (Fe, Mn)Al/. This material is believed to have a corrosion potential close to that of the matrix and is, therefore, unable to produce significant cathodic activity . 

Imatra Also called the Solid Lime Process. A method for desulfurizing steel made by an electric arc process. Additions are made of burnt lime (calcium oxide), fluorspar (mineral calcium fluoride), and ferro-silicon. 

Other markets for char include iron, steel, and sili-con/ferro-silicon industries. Char can be used as a reducing agent in direct reduction of iron. Ferro-silicon and metallurgical-grade silicon metal are produced carbothermally in electric furnaces. Silica is mixed with coke, either iron ore or scrap steel (in the case of ferro-silicon), and sawdust or charcoal in order to form a charge. The charge is then processed by the furnace to create the desired product. Char can be substituted for the coke as a source of reducing carbon for this process. Some plants in Norway are known to have used coal-char in the production of silicon-based metal products as late as mid-1990.5 The use of char in this industry is not practiced due to lack of char supply. 

Preparation. For the carbo-thermal production of silicon and ferro-silicon, arc furnaces are used. Another method starts with SiF4. After purification and fractional distillation SiF4 can be reduced to silicon with Na. Alternatively the following reaction can be used ... 

The first experiment performed was the heating of the ferro-silicon (92 per cent Si) in a flask with boiling water the resulting steam was condensed, but there was no residual gas. Therefore it was concluded that at the temperature of boiling water no reaction between ferro-silicon and water took place. 

Remembering that the temperature of the caustic soda solution used in the silicol process is above 100" C., frequently rising to 120° C., it was thought that a higher temperature might perhaps produce the suspected reaction ferro-silicon was accordingly heated in an atmosphere of steam in an electric resistance furnace to a temperature of 300° C., but still no hydrogen was produced. Consequently it was concluded that the explanation of the smaller consumption of caustic soda than would be anticipated from theoretical considerations must be explained on some basis other than the reaction of silicon with water. 

The next experiment attempted was the heating of ferro-silicon with sodium silicate, i.e. with a pure form of the product of the usual equation. When ferro-silicon was heated with an aqueous solution of pure sodium mono-silicate, considerable quantities of hydrogen were... 

The ferro-silicon employed was of French manufacture. I have since found that some high-grade Canadian ferro-silicons give traces of hydrogen with water under the conditions cited in the expenments... 

The Silicon Content of the Perro SiIicon.— The grade of ferro-silicon used in this process is very important, as low-grade material does not yield anything like the theoretical quantity of hydrogen which should be obtained from the silicol present. This arises to a slight extent from the protective action of the impurities, which enclose particles of silicon and therefore prevent the caustic soda from attacking it. 

The curve (Fig. 4), obtained experimentally, shows that to get even moderate efficiency ferro-silicon of over 80 per cent silicon content should be used. 

The degree of subdivision of the ferro-silicon is also important, not so much because of its effect on the total yield of hydrogen, but because of its influence on the rapidity of generation. 

The following laboratory experiments with ferro-silicon containing 92 per cent silicon and caustic soda containing 98 per cent, of sodium hydroxide illustrate the effect of soda solutions of varying strengfth, and also the effect of varying ratios of pure silicon to pure sodium hydroxide. From these it will be seen that the most economical results are obtained when a 40 per cent solution of caustic soda is employed and the ratio of silicon to sodium hydroxide is approximately i to i 6. 

The experiments already described indicate that to obtain hydrogen from ferro-silicon a base must be used to react with it. It therefore occurred to the author that the cost of the operation of the process might be reduced by the substitution of slaked lime for caustic soda. 

Laboratory experiments, using ferro-silicon containing 92 per cent, silicon and pure slaked lime, were made to see if the following reaction took place —... 

The following experiments, using a mixture of slaked lime and caustic soda, appear to indicate that the surmise was partly or wholly correct, for with approximately only half as much caustic soda as ferro-silicon a yield of almost 16 cubic feet of hydrogen per lb. of ferro-... 

The commercial caustic soda employed always contains a certain amount of carbonate of soda, which takes no part in the reaction and is found unaltered in the sludge. The same remark applies to the iron contained in the ferro-silicon. 

The following analysis gives the chemical composition of the sludge produced when 1414 lb. of ferro-silicon, containing 84 per cent, of silicon, and 2688 lb. 

That the temperature produced is exceedingly high can be well illustrated by putting, say, half an ounce of an intimate dry mixture of ferro-silicon and red lead, in which the proportions of the active principals are as indicated in the above equation, on a sheet of thin aluminium, say of an inch thick. On putting a match to this mixture it will be found a hole is melted in the aluminium sheet. ... 

An intimate mixture of ferro-silicon and powdered caustic soda or lime is packed in strong cylinders communicating with a high pressure storage. By means of a fuse the temperature is locally raised so that chemical reaction takes place, with the production of hydrogen and sodium and calcium silicates. 

Echos or Escho. Accdg to Molina (Ref 1, p 342), Esplosivo Echos — AN 75, Si (95% pure) 16, Al pdr 2 dried horse dung (called Ippo-sino ) 7% — was used by the Italians for military purposes. Silicon can be replaced by ferro-silicon. Belgrano (Ref 31) lists it as Echo on p 316 but erroneously gives AN content as 25 instead of 75%... 

Clark La Motta (Ref 7) showed that LOX made with gas black or lamp black are more sensitive to impact than the standard Bureau of Mines 40% straight Dynamite. Impact sensitivity increased when small amounts of iron oxides, aluminum dust or ferro-silicon were added to the LOX. Impact sensitivity also increased as absorbent particle size was reduced. As the oxygen evapd, impact sensitivity, as expected, decreased... 

The following metals have been suggested for this purpose magnesium, aluminium, zinc and also silicon sometimes ferro-silicon, alumino-silicon and calcium silicide are also employed. Deissler [54] was the first (1897) to recommend aluminium as a component of explosives. He was followed by Goldschmidt [55], Escales [56], von Dahmen [57] and Roth [58], In later years Kast [59] investigated military explosives which contained aluminium. 

During World War II the Japanese employed mixtures with aluminium or ferro-silicon. Some examples of these are tabulated below (Table 58). 

In addition to aluminium, calcium silicide or ferro-silicon, the use of silicon was also recommended. The comparative figures illustrating the effect of the addition of these compounds on the strength of the explosive have been given by Sar-torius [70] (Table 59). The power is expressed in terms of expansion in the lead block (taking picric acid as 100). 

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