US1732915A - Alloy of aluminum, silicon, and iron - Google Patents

Description

Patented Oct, 22, 1929 NITED STATES PATENTI JQFFI' E BYRAMJI ID. SAKLAYTWALLA, or CRAFT-0N, P uNsYLvsNIA', assmNoarovAivAmum CORPORATION or AMERICA, or BRIDGEVIIJLE, PENNSYLVANIA, vacom'oaarrou or DELAWARE No Drawing.

Thisinvention'relates to an alloy containing aluminum, silicon, andiron, and especiallyto an alloy suitable for addition to molten steel for the purpose of obtaining sound,

dense ingots when such steel solidifies.

The use of metallic aluminum for the purpose of scavenglng molten steel 1s very well known and is more or less universally used in steel manufacturing practice. Its use, however, is combined with very marked 'de ficiencies so that, while the aluminum frees the molten steel .of impurities, such asiron oxide, by chemically reacting with .it, the

product formed from-such reaction, namely,-

alumina, remains entrapped in the steel, thus imparting to it several obj ectionable'qualit ies. Moreover, the amount of alumina'remalnmg entrapped inthe steel is not always the same and consequently ingots are-obtained which have varying physical qualities, such as ductility, although of the same chemical composition. The presence of alumina in alumi num treated steel can be always detected by means of the microscope and it is well recog- F ni'zed that the aluminum content found -in such steel is notin the form of metallic aluminum but chemically combined with oxygen as alumina. If any metallic aluminum were residually present, itwou'ld be very helpful in ,densifying the steel and its presence would be a full assurance of the perfect scavenging action of the balance of the aluminum added; Metallic aluminum for the, purcertain characteristic deficiencies'of the prod ucts heretofore made. The term alloys thus. produced -contain appreciable quantities of carbon from approximately .50% to about 1.7 This carbon content is'present in these alloys in the form of carbides, either a siliconhasbeen prevented; 1

ALLOY or ALUMINUM, snixcou, {Ann Application filed February 2, 1928. Serial 1t6. 25i,4es. Q

carbide, or aluminum-carbidepor mixed carbides of silicon and alum num, 01 0f; silicon,

aluminum andiron'." As'is well known inthe' caseof the, ferroesilicon aIloys,-"the presence of impurities such as; carbides, tends. to dis- I integrate-such alloys, makingithemf unfit for addition to moltenisteel. J The presence of these carbides-"in the 'ferro-aluminum for" j sequent disintegrationis" one of: the 7 reasons ferro-alumin'um silicon alloys andtheir con-- i that their commercial use inthe steelindustry The improved composition of present.

mum amount of carbon so as to be substantial invention consists of an alloy with a mini ly'carbide'free' and contains aluminum from 5 ,to30 preferablyfrom'1Q%" to'25'%, and silicon'from 60% to 90%,,preferablybetween 60%, and the remainder beingprincipallyiron, although usualimpurities', or perhaps-small quantities of otheralloying metals, may be present. The carbon shouldbe kept to a minimum not over'.4=% and preferably less than.1 5%.' The alloy may" be made by the addition of, metallic aluminum into a 1' bath'ofiferro silicon of. the suitable com posi'tlon 1n the'ordinary electric furnace used c for themanufacture' of ferro silicon, The

conditions underwhich a bath ofmolten ferro silicon exists in such'a furnace are such as.

to avoid contamination of the alloy produced by carbon."

Because of the relatively higher siliconjcontentas compared with the aluminum content,

a'certain percentage of the silicon can be much less quantity off-aluminum than would be the case ofan addition alloy having a especial advantage in .the manufacture of lower silicon-to-aluminum ratio. This is of steels which call for a relatively high percentage of silicon in the finished material.

This alloy,;which' is substantially free from carbides, canbe'obtai-ned and-kept in solid non-disintegrating lumps or masses suitable for addition to molten steel. This alloyhas- .aspecific gravity much greater than that of,

as Iretained in-the steel with the retention of a.

- other impurities present in the steel in such 7 3 the ferro-silicon-aluminum andthe molten' lower meltin an instantaneous and violent manner as does metalic aluminum, but descends into the molten steel andinteracts gradually, allowing the non-metallic impurities formed by the reac tion to'rise to the-surface of the steel. Further, the product formed b the oxidation of the aluminum and silicon a loy together is an aluminum silicate, which has a very much point than aluminum, and therefore by t e exothermic reaction between steel, finds sufiicient temperature to melt and .riseto the surface through the body .of the molten steel. Also, this alloy does not have the objectionable feature of introducing-carbides into the steel,to thereby raise its carbon content, as would be the case with the carbide containing ferro-aluminum-silicon a ll y s heretofore used. This allo further has the,

advantage that by its ad ition to steel its aluminum content acts more effectually on the body of steel, owing to its gradual and more positive action',' not burning up quickly with the oxidation reaction-as would. be the 7 case b the addition of metallic aluminum.

While I have described my alloy in its preferr'ed composition, it is to be understood that the inventmn isnot. so limited but ma be otherwiselembodiedwithin the scope o the T followng claims. 7

Iclaim:

1.' A steel'densifying and scavengingalloy, containing aluminum from to 30%; sili con about 60% to. 90%; the remainder bein principally iron, and containingv not over.

about 4% carbon. v 2.; A steel densifying and scavenging alloy,

containing aluminum about 10% to silicon' about to the remainderbeing principally iron, 'and containing not over a about 15% carbon.

In testimony whereof I have hereunto set