US2167301A - Alloy cast iron - Google Patents

Description

Patented July 25, 1939 PATENT OFFICE "ALLOY CAST nioN Edwin A. Jones, Jacksomand Arthur H. v

Ohio, assisnors to Globe Iron Com Columbus,

Dierker,

pany, Jackson, Ohio, a corporation No Drawing. Application March 23, 1938, Serial No. 197,726

4 Claims.

Our present invention relates to an improvement in alloy cast iron, in which silicon and chromium are the principal alloying agents, and in which the silicon, in the various proportions in 5 which it may be used with reference to the chromium, is always in substantial excess of the chromium content.

We have'found that alloys prepared in accordance with our invention, have high wear and heat-resisting properties, and exhibit unusual vated temperatures. 4

We have further found that such alloy cast irons are machinable at- Brinell hardness far in excess of that at which cast irons or steels are considered to be unmachinable.

Further, our alloy cast iron can be produced from low cost materials, 'in furnaces of "the cupola type, which are recognized as, being the lowest cost type of furnace in common use today, and by labor which does not require to be highly skilled.

Cast iron is generally considered to contain the following materials substantially within the ranges indicated, namelyresistance to scaling.,warping and growth at ele- Per cent Total carbon 2.50 to 3.70

. sn'im'n .80 to 3.00 Manganese .40 to 1.20 Sulphur Under 0.20 Phosphorus Under 1.00

Where any of the elements exceed the maximum amounts indicated, the excess of the 3:; amount of such element usually required to produce an iron of normal properties, is considered an alloying element.

In the alloy cast iron of our invention, weuse silicon in excess of theamount required to pro- 40 duce a good quality of cast iron, as an alloying agent to secure properties not found in unalloyed irons, and we also use chromium as an alloying agent, but in the compositions of our alloy we maintain the silicon content always in excess of the chromium content by a substantial amount. Despite its hardness, our'alloy contains as cast free carbon in the form of graphite flakes or nodules, and is thus definitely not a steel, and should not be confused with steels containing silicon and chromium.

With the foregoing explanation in-mind-, one of the principal objects. of our invention is to provide an alloy cast iron havin h W and heat resisting properties and unusual, resistance to scaling, warping and growth at elevated tem-t 5 Deratures. 1 a

A further object is to provide an alloy cast iron of great hardness, which is machinable at unusually high Brinell hardness, and without the use of lubricants.

A further object is to provide an alloy cast iron comprising silicon and chromium as the principal alloying agents. with the silicon in excess of the. chromium, and having .free graphite, the alloy being characterized by high resistance to wear, 15 and to scalingpwarpingand growthlat elevated temperatures, and being machinable at hardnesses far beyond those of cast-irons.

Still another object of .our invention is to provide an alloy cast iron of thecharacteristics set 20 forth above, and having a relatively low melting point and .low shrinkage characteristics, such that good castings of intricate and thin sections can be produced with ordinary foundry facilities.

A further object is to provide an alloy cast iron having the various qualities and characteristics referred to, which is capable of production in cupola furnaces at relatively low cost, and without requiring labor of anything more than ordinary skill. I I

In producing our alloy cast iron, we prefer that it contain constituents within the following table, ,namely-- I While the percentages of the various materials within the ranges indicated may vary, in all cases we keep the silicon content in excess of the chro- 4 5 mium by a substantial amount. The presence of the relatively high silicon content with regard to the chromium in our alloy, we believe, lowers the, solubility of the carbon in the iron at room temperatures, andhence, as the iron cools ,from

' tributed substantially uniformly the molten condition, carbon is precipitated from solution in the form of graphite, which is disthroughout the body. of the metal in the form of small flakes or nodules.

The alloy can be produced from relatively low cost raw materials and in simple and economical types of melting units, by workmen of no more than ordinary skill. As illustrative, alloy steels require for their production, the use of the-electric furnace, the open hearthfurnace, or the crucible furnace. All of these types of furnaces are expensive to build, maintain and operate. Our alloy, on the other hand, can be produced in the cupola type furnace which, as recognized in the industry, is the type of furnace which is the cheapest per unit of capacity, in common use. It is not only less expensive in initial cost, than the other types of furnaces referred to, but is also cheaper to maintain and operate.

Examples of a number of compositions of our alloy are given in the tables which follow, in which tables various specimens have been tested against other cast irons.

We give below some results of wear tests, as well as tests of other physical properties, and .a few compositions of the alloy of our invention. The wear tests were made by holding the specimen under a weight of 1380 grams on they table of a Dorry machine, a. constant stream of washed silica sand being fed to test. At the end of 6000 revolutions, the specimen was moved and weighed, and the weight loss due to wear was noted. The physical properties were determined by standard A. F. A. methods.

Specimen No 7i 2352 i 2395 2423 2423 Analysis:

'I. C 3.30 3.10 2. 52 3.17 2. 21 Heat Si 2.40 1.73 4. 23 3.05 5.30 treated Mn .65 .94 .60 .50 .63 P. .18 .16 .11 .056 .084 S .11 13 .065 .065 .052 Or 2.20 .96 2. 98 Brinell hardness Noun 179 217 255 255 341 388 Transverse strength pounds 2, 560 3, 230 2,950 3,290 2,120 Deflection inches 292 270 190 282 137 Tensile strength lbs. per sq. in. 29, 200 43, 000 34, 700 42, 800 32, 000 43,000 Wear s grams.. 5.19 3.85 1.931 2.07 1.67

is of the same composition as the specimen of that same number in the table, but not designated as heat-treated. The heat treatment consisted of normalizing at 1800 deg. F. and drawing at 1300 deg. F.

The above data shows that the alloy iron, despite its high hardness, has strength and toughness comparable to a good grade of high test iron.

A remarkable feature of our alloy is that it can be machined at unusually high Brinell hardness. Cast iron is ordinarily considered unmachinable when it has a Brinell hardness of more than 280. All of the given examples of our al- 10y, however, even though they tested up to 388 Brinell, were readily machinable, and indeed, we havemachined specimens of our alloy having a Brinall hardness of 415.

The superior resistance of our alloy to growth the table during the tance,

Specimen No 1343 219-6 'l. 2.80 3.44 Si 2.30 2.25 Mn .37 .53 .56 P .05 .27 .43 S .02 .08 .06 CL. 4.16 Scale loss .percent. 2.00 8.87 10.70 Growth percent 07 1. 74 5. 82

In this table, specimen 1343 isan alloy of our invention, while specimen 219-6 is a high strength cast iron, and specimen 116-1 is a soft cast iron. The scale loss. and the growth of our alloy are both remarkably low, as indicated in the table.

In addition to the qualities of unusual high hardness, and high wear and heat-resistance, our alloy exhibits the further quality of relatively small shrinkage during solidfication of the metal I from the molten state, and in addition, has a melting point very much lower than alloy steels. Hence the alloy possesses excellent casting properties, such indeed, that with ordinary foundry facilities, sound castings of intricate and thin sections can be made.

We areawarethat steels containing silicon and chromium are known in the art, but our alloy possesses characteristics which distinctly differentiate it from such steels, such for inas its low production cost; its machinability; its silicon content in excess of the chromium; and its brittleness as compared to workability of steel; also ease of casting to shape as compared to steel. i

On the other hand, the ability of our alloy to be machined at Brinell hardness far greater than that of cast irons, and its unusually high heat resistance and wear resistance, give it qualities unpossessed by cast irons heretofore known in the art with which we are acquainted.

It will be understood that our alloy may be heat-treated subsequent to casting by one of the accepted methods for ferrous alloys; i. e., annealing, either at a temperature above or below the critical; normalizing from -a temperature above or below the critical; quenching from a temperature above the-critical and drawing at some suitable temperature below the critical.

While the foregoing description sets out a number of specific embodiments of our invention, it will be understood that various changes in proportions of the elements constituting our alloy may be made within the scope of the appended claims. It will further be understood that the foregoing for purposes of'illustration of our invention,and that no undue limitations should be deduced therefrom, but that the claims should be broadly construed within the limitations of the prior art.

Having thus described our invention what we claim as new and desire to secure by United States Letters Patent is:

1. An alloy cast iron, having silicon in proportions greater than chromium, and in which a substantial part of the carbon is in the form description has been given 1 about .11%; sulphur of free graphite, said alloy containing silicon 4.23% to 10.00%; chromium 0.6% to 8.00%; manganese 0.20% to 3.00%; phosphorus under 0.30%; sulphur under 0.20%; carbon 1.80% to 3.20%, and the balance iron.

2. An alloy cast iron containing silicon about 4.23%; manganese about 50%; phosphorus about .065%; chromium about 2.20%, total carbon about 2.50%, and the balance iron, said alloy being characterized by high wear and heat resistance.

3. An alloy cast iron containing silicon about 5.30%; manganese about .63%; phosphorus 5.73% manganese about 084%; sulphur about .o52%-; chromium about 2.98%, total carbon about 2.20%, and the balance iron, said alloy being characterized by high wear and heat resistance.

4. An alloy cast iron containing silicon about about .37 phosphorus about 0.05%; sulphur about .02%; chromium about 4.16%,total carbon about 2.13%, and the balance iron, said alloy being characterized by high wear and heat resistance.

EDWIN A. JONES. A. H. DIERKER.