US2376869A - Alloys - Google Patents

Description

Patented May 29, 1945 UNITED STATE s PATENT OFFICE} ALLOYS No Drawing. Application September 1, 1943, Serial No. 500,842

'7 Claims.

Our invention relates to the preparation of alloys which are particularly resistant to the action of sulphur-containing gases but have other utilitie as well, including resistance to scaling at high temperatures such as up to about 1600 degrees F. l

The alloys to which our invention relates contain from about 3% to about 12% aluminum,- from about.45% to about 75% iron, from a fraction of 1%, for example, 0.15%, up to about 10% of chromium, balance substantially all manganese, the manganese constituting at least 20% of the alloy. A preferred embodiment of our invention encompasses alloys containing from about 5% to about aluminum, from about 2% to about 10% chromium, from about 20% to about 50% manganese, balance substantially all iron. We have found that when these alloys are made from manganese of high purity, particularly electrolytic manganese, preferably at least 99.0%

pure and especially at least 99.9% pure, and commercially pure forms of aluminum, chromium and iron, their ductility tends to be enhanced and many of them, particularly those in which the chromium content does not substantially exceed about 2%, may be rolled and drawn into wire. With increasing percentages of chromium the ductility of the alloys is progressively lessened.

The following examples are illustrative of the preparation of alloys pursuant to our present invention. It will be understood that these alloys and their mode of preparation are merely illustrative of the preparation of alloys in accordance with the present invention and are not to be construed as in any manner liinitative of the full scope of ourinvention, the latter being set out in the claims.

Example I Percent Iron 72 Manganese 20 Aluminum 6 Chromium 2 In the preparation of this alloy, a low carbon ingot iron is first melted with the required amount of metallic manganese. A we have pointed out above, we prefer particularly to use electrolytic manganese having a purity of the order of at least 99.0%, but other manganese of high purity may be used. We then add the aluminum and finally the chromium. The chromium is preferably added in the form of a low carbon ferro-chro- Example III Percent Manganese -25 Aluminum .5 Chromium l 1 Iron 69 Example IV Per cent Manganese 22 Aluminum 8 Chromium 2 Iron Example-V Per cent Manganese 30 Aluminum 6 Chromium", 3

cold rolled or otherwise worked. When heated to temperatures of the order of 1400 degrees F. to 1600 degrees F., it forms a thin surface coating but does not scale even after long hours of heat- Example II Percent Iron 64 Manganese 20 Chromium 10 Aluminum 6 This alloy may be made in the manner de scribed in Example I. It is advantageous, however, from the standpoint of cost, and also from the standpoint of producing better ductility in the resulting alloy, to utilize an alumino-thermic reduction procedure. This is accomplished by mixing iron oxide of high purity, such as mill scale, with manganese, dioxide of high purity, together with chromite concentrates of high purity. This mixture, properly proportioned. based on it analysis, is mixed with an amount of powdered aluminum so calculated that the correct amount of residual aluminum will be present in the final alloy. The mixture is then ignited and the resulting molten alloy cast into the desired shape. Since the amount of aluminum which remains in the alloy is somewhat determined by the specific conditions under which the reduction reaction takes place, preliminary tests or experimentsshould be carried out in connection with any given reduction procedure utilized in thepreparation of the alloy. The reduction of residual aluminum increases the ductility of this alloy with only slight loss of scale-resistant properties if the aluminum is not reduced below 3%.

Examples of other alloys which may be made in accordance with our invention are as follows.

Iron 61 I: trolyte.

acids better than stainless steel.

7 As we have pointed out in the Example I, the

carbon content of the alloys should be kept at a minimum and in no case should exceed 0.15%.j

The alloys may contain up to about 2% of silicon in the form of the element or, in other words, 'el'e-i mentary silicon, as distinguished from silicon oxides.' It is important, if the ductility and other characteristics of our alloys are not to be im paired, that oxides of silicon, which are frequent-I ,filed October 20, 1941, now Patent 5.

part of our prior application, SerialjNo. 415,769,

issued September 14,1943. 7 V r 7 'What we claim as new and desire'to'protect by Letters Patent of the United States is:

'from 45% to 75% iron, balance substantially all 1y present in silicon-reducedjmanganese and .chrornium,.,, and aluminum-reduced manganese:

and chromium, benot present in our alloys or, if present, the amounts thereof should be exceeda ingly' small,not over approximately 0.2% and preferably less or totally absent.

'The alloys of our present invention have, in}

T general, low linear coefficients of expansion whichf renderthem useful in connection with production of bi-m'etal strips or other expansion elements or units; The electrical resistance of the alloys of our present invention is, in "general, quite high and said'alloys are, therefore, of utility for the; manufacture of heating elements operating at moderately'high temperatures.

Weihave also found that the alloys of our present invention may be anodized to provide them with acoating of a continuous film of alu-fl 7' minum oxide. This film .or coating may be placed manganese, the manganese constituting at least 20% of the alloy. 7

2. Alloys containing from 5 to 10% .alu-

minum, from 0.15% to about 10% chromium,

from 20% to mangan'ese;'balance SllbStfiIl.

tially all iron, the alloy being made with aluminum, manganese, and iron of high purity.

3. Alloys containing. from 5% to 10% ;alu-

minum, from 0.15% toabout 10% chromium,

from 20% to 50% electrolytic manganese'having a purityof at least 99.0%, balance substantially all iron, the iron constituting from 45% to of the alloy.- 7

4. Alloys containing minum, from 0.15% to about 2% of chromium, from 45% to 75% iron, balance substantially all 'manganesqthe manganese. constituting at least 20% of the alloy.

upon the alloys by the w'ell-known'so-called 'ano dizing process, that'is, by making the alloy the anode of an electrical :circuitin a suitable elec- Such anodized alloys, in certain in-'' stances, appear to withstand the action of dilute 5. An alloy' containing about 72% iron, about 20% manganese, about 6% aluminum, and about 2% chromium.

s 6. An alloy containing 3% to 12%aluminum," I 2% to l0%wchromium,45% to 75% iron, balance 7 substantially all manganesathe manganeseconstituting at least 20% of the alloy. 7 r ,7 7. An alloy containing about 64% iron, about 20% manganese, about 10% chromium, and about 6% aluminum.

REGINALD S.DEAN.- V CLARENCE T. ANDERSON.

Our present application is-a continuation-in No. 2,329,186, r

1. Alloys containing from 3% to 12%aluminum', from 0.15% to about 10% chromium,

from 3% to 12% alu-