US2074604A - Alloy - Google Patents

Description

Patented Mar. 23, 1937 STATES PATENT Columbus,

Ohio, assignors to The Lunkenheimer Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Application December 28, 1934, Serial No. 759,536

1 Claim.

It is the object of our invention to provide a copper base alloy and a method of making it. In particular it is our object to provide an alloy, as cast or as wrought, of particular utility 5 in structures subjected to elevated temperatures.

Such alloys of this invention are especially useful in the construction of pressure-containing parts in valves and fittings which are used at elevated temperatures. His a further object of our invention to provide a copper base alloy which provides good resistance to "creep" (that is, ability to sustain loads continuously at elevated temperatures with- .out dangerous continued distortion), high impact strength, and economical manufacture.

It is our object to provide an alloy that is strong, ductile and tough at room temperaturesand which is characterized by fine grain size,

fluidity insuring ready castability, easy machinabiiity and good corrosion resistance in combination with structural and mechanical stability.

Our alloy accomplishes these things to a degree not heretofore known in the art, and constitutes a marked advance in meeting the conditions of elevated temperatures while at the same time providing the characteristics heretofore enumerated.

It is a further object to provide an alloy which may be either used as cast or plus a stabilizing treatment, which is sometimes desirable, or which may be either cold or hot worked; as desired.

By "as cast" we-refer to using the alloy as a finished rough casting or as a machined casting,

and by "as hot or cold worked we refer to such operations as forging, rolling, drawing, Stamping,

etc., which operations can be conducted at various temperatures.

It is the particular object of this invention to provide an alloy with a copper content of 80 per cent. or above, a nickel content of from 6 to 15 per cent. approximately, and other elements such as iron or manganese or both to insure strength, ductility, toughness and a dendritic structure that has marked strength and stability at elevated temperatures. This alloy possesses a reddish color. To the alloy there may be added metals of the sixth group of the periodic table (including metals of high melting point such as molyb- 50 denum, chromium and tungsten), either singly or in combination. In the production of most nonferrous alloys the use of deoxidizers is desirable. We have found desirable the use of materials such as aluminum, barium, calcium, magnesium, sili- 55 con or sodium, or any of their equivalents; and

we have also found that. lithium, phosphorus and zinc are useful.

It is a further object of our invention to provide for a stabilizing treatment of our alloy in order that uniformity of hardness to secure the 5 best machinability and maintenance of dimensions when the structure is subjected to elevated temperatures may be obtained. We also desire structural stability. For this purpose we have found it helpful under some circumstances, when 10 the alloy is not to be used above 750 degrees F., to subject the alloy to a normalizing treatment of approximately one hour or more at 1000 degrees F. or for longer periods at lower temperatures. These temperatures and times are approx- 15 imate and are adjusted according to the ultimate temperatures to which the alloy is to be subjected. While metallurgists have only realized the fact within a comparatively recent period, most alloys are subject to precipitation hardening and 20 change their properties in service at elevated temperatures. For our purposes, where constancy of properties at elevated temperatures is required, such a phenomenon is not desired.

Some excess of deoxidizing element or elements 25 over that required for deoxidation has to be used in any deoxidation operation in order to get commercially uniform deoxidation, and in general,

" more than one deoxidizing agent may be used.

If too great an excess of deoxidizing elements is 30 present, some precipitation hardening effect may occur, and since the range of usable deoxidizing elements is large and the mutual eiiect upon precipitation hardening of the excess of each agent that is left in the alloy can scarcely be predicted 5 without special experiment; hence, we aim to keep the excess of deoxidizers as low as is practical andto use, in the composition of the alloy itself, iron and/or manganese in quantity suf-. ficient to restrainthe possible precipitation har- 40 dening propensities of the deoxidizers. In order to control any such propensity that may remain, We introduce the stabilizing treatment. As the best combination of deoxidizing elements is not determined by the composition of the alloy being dealt with as much as it is by the melting method and the atmosphere over the melt, which vary in different foundries, the stabilizing treatment should be selected to meet the particular foundry conditions.

There are three classes of alloys for use in pressure-containing parts at elevated temperatures of 450 degrees F. or above. These are (a) cast irons, (b) bronzes and. (c) steels. Among known alloys which conceivably might be so employed are (d) aluminum bronzes and (e) high nickel alloys, such as Monel metal.

(a) Cast irons are limited to 450 degrees F. and 250 lbs. gauge pressure. Our alloy possesses ductility, toughness and freedom from growth,

, permitting its use at temperatures and pressures above those permitted cast irons.

(b) Bronzes are limited to temperatures not in excess of 500 degrees F. (by bronzes we refer to alloys 88 copper, 10 tin, 2 zinc; 88 copper, 6 tin, 4 zinc, 2 lead; copper, 5 tin, 5 zinc, 5 lead and related compositions). The best of these alloys is 88 copper, 6 tin, 4 zinc, 2 lead (ASTM- 3-61 valve bronze), which possesses a creep strength (0.1 per cent. elongation, 10,000 hours basis) of about 8000 p. s. i. at 500 degrees F. and a room temperature Charpy notched bar impact of about 15 foot pounds. The alloy of our invention possesses creep strength at temperatures of 650 degrees F. (or above) in excess of that of 3-61 bronze at 500 degrees F. and has far higher impact value. Its machinability lies within the range of machinability of the above described bronzes.

(c) Steels (both carbon and alloy) possess higher room temperature and creep strengths (per unit cross section) than the alloy of our invention.

mums of certain permitted classes of steels.

In general the advantages of our alloy over steel lie in (1) its much lower cost of production in cast shapes and (2) its better corrosion resistance.

(d) The difllculties of producing sound pressure containing parts of aluminum bronzes and of machining them are notorious. The alloy of our invention is superior in creep resistance to 7 /2 per cent. aluminum die casting bronze at 560 degrees F.

(e) The higher nickel alloys, while in many cases stronger at elevated temperatures require more costly raw materials and are more difflcult to cast and to machine.

It is thus seen that the alloy of our invention possesses either (1) better elevated temperature properties at equivalent cost or (2) suiflcient high temperature strength, better corrosion resistance and far greater economy in manufacture.

It will be understood that the addition of metals of the sixth group (molybdenum, chromium and tungsten, singly or in combination) up to or slightly above their limits of solid solubility to the four elements mentioned modify in degree the room temperature properties of the alloy. Molybdenum-in particular effects marked grain refinement. The incorporation of percentages of these high melting point metals is of advantage in alloys for elevated temperature service.

- The above may be used together with less than 0.5 per cent of aluminum and less than 0.3 per cent each of any one or more of the following The minimum impact values of our alloy and the minimum ductility exceed the mini- V elements: barium, calcium, lithium, magnesium, phosphorus,- silicon and sodium.

Deoxidizers, aluminum not to exceed 0.5 per cent; silicon, calcium, magnesium, barium, lithium or phosphorus not to exceed 0.2 per cent in the final alloy.

We do'not limit ourselves to this composition, inasmuch as certain elements, such as cobalt, which donot injure high temperature properties, or deoxidizers such as beryllium, may be added without detriment, but the advantages to be gained do not generally warrant their inclusion in the basic alloy composition.

The use of excess deoxidizer should be avoided as appreciable residual precentages, as of barium, for example, is detrimental to the strength of the alloy.

Efiect of additions To illustrate the effect of the additions, a base alloy containing 10.2 per cent, Ni, 0.10 per cent Si and 0.31 per cent iron was made up and had the following properties: tensile strength 32,700 lbs. per sq. in., yield point 9,900 lbs. per sq. in. When iron was increased to 1.85 per cent in this alloy (silicon and nickel content maintained) we found a tensile strength of 50,600 lbs. per sq. in., a yield strength of 28,400 lbs. per sq. in., and elongation of 25.3 per cent and a dendritlc (as compared to a polygonal structure), all of which features are highly desirable.

It is especially desired to avoid excessive age hardening reactions since these lower the ductility of the alloy and impair its utility for the purpose intended. We have found that the use of iron and to a somewhat less degree the use of manganese, tend to delay or nullify possible precipitation hardening effect of residual deoxidizer.

Example 3 As illustrative of a composition including an element of the sixth group, with 12.62 per cent. nickel, .78 per cent. manganese, .62 per cent. iron, .18 per cent. silicon and .40 per cent.molybdenum, balance copper, the following properties were obtained on the cast alloy-tensile strength 54,600 lbs, per sq. in., yield strength 33,100 lbs. per sq. in., elongation 22.7 per cent., Charpy notched impact of 32 ft. lbs. at room temperature and 19 ft. lbs. tested at 650 degrees F., together with extremely fine grain and cupped fracture.

Example 4 As a further illustration, with 1.80 per cent. iron, 0.97 per cent. manganese, 0.24 per cent. molybdenum, 12.67 per cent. nickel, balance copper, to which 0.2 per cent. of a sodium-zinc alloy was added, the following properties were obtained on the cast alloy. Tensile strength 49,800 lbs. per

sq. in., yield strength 24,800 lbs. per sq. in., elongation 27.5 per cent, together with a fine and uniform grain structure.

Example 5 The addition of aluminum, in addition to effecting deoxidation, increases somewhat the duotility of the alloy for a .given'yield strength. As illustrative, with nickel 11.28 per cent., manganese 2.58 per cent., iron 1.63 per cent., aluminum .47 per cent., balance copper, tensile strength was 50,700 lbs, per sq. in., yield strength 22,300 lbs. per sq. in. and elongation 34.4 per cent.

We have added molybdenum to 1.19 per cent., tungsten to 0.81 per cent., and chromium to over 2 per cent. Complete solid solubilities of these elements in the alloy are less than the above percentages, but the presence of excess solute isin some cases advantageous in promotion of desired heterogeneous structure. v

It has been ourexperience that the use of a larger percentage of iron than of manganese is desirable. The sum of these elements should preferably be 1 per cent. or above. Chromium possesses the highest solid solubility of the elements molybdenum, chromium and tungsten, but molybdenum has the most grain refining action.

Rolling and forming operations-Hot or cold worked As illustrative of the adaptability of our alloy to forming and working operations, we have been able to reduce the thickness of bars of the alloy, which had previously been broken in the tensile test, approximately 50 per cent. in thickness by cold forging without cracking or other deleterious eilects.

In order to summarize the presentation" of our various examples, we point out that our alloy falls in the following primary classifications:

l. A copper-nickel alloy as described, with the sum of iron and manganese ranging from 1.0 to 5.5 per cent.

2. A copper-nickel-iron-manganese' alloy with 40 one or more or the high melting point elements.

' not exceeding 0.3 per such as molybdenum, chromium and tungsten.

3. A copper-nickel-iron-manganese alloy with one or more of the high melting point elements, such as molybdenum, chromium. and tungsten with the addition of a deoxidizer as described.

It will be understood that we desire to comprehend within our invention variations of our alloy in elements, temperatures and proportions in order to adapt it to varying conditions and uses; and we have made no attempt to be inclusive in the statement of all oi. the equivalent elements that might be employed to secure equivalent results. We desire to reserve for additional applications as companion applications to this application or as divisions, extensions or continuations thereof the subject-matter is not specifically claimed.

Wherea deoxidizer such as barium, calcium,

lithium, magnesium, phosphorus, silicon or sodium is mentioned in the claim, it will be understood that the mention of any one of these elements means that any one of the other oi! the elements recited in this sentence can be substituted there-.

for and is the equivalent thereof in an amount cent. Aluminum'is a deoxidizer which should not be used in excess of 0.5 per cent.

Having thus fully described our invention, what we claim as new and desire to secure'by Letters Patent, is: I

In a heat resisting, permanently ductile alloy embrittlement, having the following elements only: copper ranging from 80 to 92 per cent: nickel from 5 to per cent; iron from 1 to 3 per cent; and manganese from V. to 3 per cent, the total content of the iron and manganese in the alloy being not less than 1% per cent nor more than approximately 5.5 per cent.

- JOHN W. BOLTON.

disclosed herein that-