US2805150A - Composition for addition to cast iron or steel - Google Patents

Description

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nited Strtes Patent f COMPOSITION FOR ADDITION-T CAST IRON 0R STEEL Jerome Strauss, New York, N. Y., assignor to Vanadium Corporation of America, New. York, N, Y a corporation of Delaware No Drawing. Application Mai-ch11, 1954,

Serial No. 415,680

3 Claims. (Cl. 75125) tion, Serial No. 214,649, filed March 8, 1951, Patent No.

2,676,097, granted April 20, 1954.

The cast iron which is most used commerciallyfor con struction applications is gray iron, which term actually covers a wide range of compositions with correspond inglywidely varying properties which depend to a great extent upon the forms in which the carbon exists and their distribution.

While a part of the carbon present in gray iron may be combined as iron carbide, the greater amount is present in the free or elemental form as graphite. The relative amounts of free carbon and combined carbon, as well as the shape, size and distribution of the particles, are dependent upon such factors as the maximum temperature of the iron in the liquid state, rate of cooling during and after solidification, and types of heat treatment, if any, applied to the solidified casting.

It is known that magnesium and certain other elements introduced into iron which would otherwise cast gray or nearly so, cause the graphite to change from flakes or plates into spheroids or nodules with a simultaneous increase in the strength of the metal and production of some ductility. This ductility may frequently be increased by annealing with relatively small sacrifice in the strength of the metal.

In my copending application, above mentioned, I have described an improved composition for the production of cast iron containing nodular graphite, this composition being preferably in the form of an alloy and containing, in addition to magnesium, silicon, copper and iron within the ranges specified, one or more of the modifying agents calcium, barium, strontium and lithium which make it possible to effect nodulan'zation of cast iron not only by the addition of less magnesium but by the addition of less total magnesium and modifying agent than when magnesium without the modifying agent is employed. The use of the alloy there described results in less loss of magnesium and modifying element and less spitting of metal out of the receptacle in which the addition is made.

I have now discovered that in compositions containing magnesium, lithium, silicon and iron, which compositions are to be used in the production of nodular iron, certain critical relations between the lithium and the magnesium contents are necessary in order to secure the maximum of desired properties in the finished iron and the optimum in economy in use of the addition composition or alloy. I have found that the lithium content should amount to about to 70% and preferably about to 50% of the magnesium content of the alloy. It is most important that the alloy contain a substantial amount of Patented Sept.f 3, 19 57 silicon, not only from the standpoint of rendering fully effective a very small addition of magnesium plus lithium to the molten iron butalso of ease of manufacture of an iron-containing alloy and likewise to facilitate the production of a solid alloy in which the various components of the alloy are distributed throughout the mass in a uniform concentration. Non-uniformity in the alloy is highly objectionablein that such segregation of the alloy components leads. to non-uniformity of addition elements to. successive iron castings, particularly when the size of the lumps of the alloy is large or the size of the iron melt to which the alloy is added is small.

My improved addition alloy containing ratios of lithium to magnesium within the ranges stated may or may not contain copper. Copper may-be present in the alloy of my invention to a degree determined by the character of theraw material used' in its preparation. or copper maybeintentionally' added where itis desired that copper in substantial amountbe present in the finished casting. *Thus, myalloy may containabout' 2 or 3% of copper where it.v is desired to introduce into the finished iron casting-notmore than about 0.20% copper, even after the usual foundry returns are employed inmaking molten iron. On the other hand, my alloy may contain up to 15 %:-or 20% or even up'to 25% of copper where it isidesired to; impart additional strength to the iron casting, as for example in the prodnctiono'f nodular irons having tensile strengths of 100,000 pounds per square inch or higher and a ductility measured by an elongation on the order of 5%.

Alloys according to my invention may have the following composition ranges:

The balance of the alloy is iron, the iron being between 5 and 65% of the alloy.

As above stated, within these ranges, the proportions of lithium and magnesium are such that the lithium constitutes from 15 to 70% and preferably from 20 to 50% of the magnesium in the alloy. The alloy always contains silicon and the other elements within the ranges stated. It is known to add a magnesium-lithium alloy to molten iron to produce nodular graphite in the fin ished iron castings but such alloys have not contained any substantial amount of silicon. substantial amount of silicon, the magnesium loss is exceedingly high when adding the alloy to molten iron but the loss of magnesium is greatly reduced where, as in my alloy, the alloy contains a substantial amount of silicon. Thus, by using my alloy, a desired amount of magnesium and lithium can be incorporated in iron by using a considerably smaller amount of my alloy containing silicon than would be the case if a magnesium-lithium alloy not containing a substantial amount of silicon were employed. For instance, instead of having to add approximately 0.70% magnesium in order to retain in the solidified iron 0.05% magnesium, this result may be achieved by adding not more than 0.25% magnesium.

Economy in the use of the added alloy is of consider able importance in the establishment of commercial practice. Loss of the elements added will vary according to manufacturing conditions, among which the temperature .7

of the molten iron at the time the addition is made and the temperature and total time of the pouring operation In the absence of a.

during which the very volatile magnesium and the less volatile lithium can be lost are very important- The recovery of the added elements in the solidified iron will also be dependent upon the composition of the molten iron and very importantly uponitssulphur con-v tent. --y-r"-f' For example, with an ironof any suitable carbon, silicon and manganese contents andf0.030% sulphurand the addition of an alloy containing'8% magnesium and 2.5% lithium with38%.silicon, it is possibletoaddv as little as 0.08 %.magnesium (thus simultaneously adding 0.025% lithium) and retain in the solidified iron casting about 0.025% magnesium and:about 0.020% lithium, the product containing its graphite practically completely inspheroidalform.' *1

While as muchfas 0.25% magnesium and the corresponding amount of .lithiummay'be added and under conditions of high pouring temperature and relatively high sulphur content in the iron vwill result in the retention of only 0.05 magnesiumyvery much lower additions can be made and are naturally to be desired. By

adding 'from'OLOS 'to' 0.15% magnesium and the corresponding amounts of lithium to irons having low sulphur content either naturally was the result of any suitable desulphurizing means, nodular irons may be produced containing from about 0.015% to'about 0.050% magnesium with lithium fromabout 0.008% to about 0.035%.

In order to produce optimum results in nodulizing iron, not'only must the components of the alloy be within the ranges specified but the lithium and magnesium must be within the proportions herein given.

The invention is not limited to the preferred embodiment but may be otherwise embodied or practiced within the scope of the following claims.

I claim:

1. A composition of matter for addition to cast iron or steel, said composition comprising about 3 to 20% magnesium, about 0.5 to 13% lithium, the lithium amounting to about 15 to 70% of the magnesium, about 10 to 60% silicon and about to 25% copper, the balance being substantially all iron, the iron being in an amount between and 65%.

2. An alloy for addition to cast iron or steel, said alloy comprising about 3 to 20% magnesium, about 0.5 to 13% lithium, the lithium amounting to about 15 to 70% of the magnesium, about to 60% silicon and about 0 to 25% copper, the balance being substantially all iron, the iron being in an amount between 5 and 65%.

3. An alloy for addition to cast iron or steel, saicl alloy comprising about 5 to magnesium, about 1 to 80% lithium, the lithium amounting to about to of the magnesium, about 20 to 45% silicon and about 0 to 25 copper, the balance beingsubstantially all iron',

the iron being in an amount between 5 and References Cited in the file of this patent .UNITED, STATES PATENTS 2,485,760 ,Millis et al.... Oct. 25, 1949 2,625,473 Smalley Ian. 13, 1953 2,690,392 Millis et al Sept. 28, 1954

Claims (1)

1. A COMPOSITION OF MATTER FOR ADDITION TO CAST IRON OR STEEL, SAID COMPOSITION COMPRISING ABOUT 3 TO 20% MAGNESIUM, ABOUT 0.5 TO 13% LITHIUM, THE LITHIUM AMOUNTING TO ABOUT 15 TO 70% OF THE MAGNESIUM, ABOUT 10 TO 60% SILICON AND ABOUT 0 TO 25% COPPER, THE BALLANCE BEING SUBSTANTIALLY ALL IRON BEING IN AN AMOUNT BETWEEN 5 AND 65%