US1988153A

US1988153A - Alloy and method of making same

Info

Publication number: US1988153A
Application number: US696162A
Authority: US
Inventors: Bolton John Ward
Original assignee: Lunkenheimer Co
Current assignee: Lunkenheimer Co
Priority date: 1933-11-01
Filing date: 1933-11-01
Publication date: 1935-01-15
Anticipated expiration: 1952-01-15

Description

Jan. 15, 1935.

J w. BOLTON ALLOY AND METHOD OF MAKING SAME Filed Nov. 1. 1933 w/ r .1 a

M/I/EA/TOI? JOHN W. 80L 7'04.

JN A. 1 @Z ATTORNEY-5 Patented Jan. 15, 1935 PATENT OFFICE ALLOY AND METHOD OF MAKING SAME John Ward Bolton, Cincinnati, Ohio, assignor to The Lunkenheimer Company, CincinnatiNOhio,

a corporation of Ohio Application November 1, 1933, Serial No. 696,162

- 3 Claims.

It is the object of this invention to provide an alloy and a method of making it, which results in an increase in fluidity and a decrease in shrinkage or contraction cavity formation tendency in 5 copper and nickel base alloys.

It is a further object to provide a modification of grain structure, especially in the elimination of loose coarse grain or excessive dendritism in copper or nickel base alloys.

- A further object is the prevention of brittleness and the reduction of the liability of cracking during heat treatments of such alloys.

The object of this invention is to add calcium or certain compounds or alloys thereof to various alloys of copper and nickel and of copper, nickel and silicon for the accomplishment of the foregoing objects.

In particular, it is the object of this invention to permit of a nickel, copper, or nickel, copper and silicon alloy to be cast with high initial hardness and then softened for machining purposes by heating to a high temperature and then quickly quenching. Thereafter, the original hardness is restored by heating or aging at a temperature somewhat below the quenching temperature.

If fsuificientlydrastic quenching to get maxi.- mum machinability is employed, it has been found thatcracking will likely result so that the'manufacturer is unable to safely employ quenching treatments to get maximum machinability.

While such alloysare machinable within a o'ertain range, yet the present invention, by the addition of calcium or certain compounds or alloys including it permits the castings to be quenched to produce greater softness and better machinability with the result that ordinary machine operations through a wide range can be performed upon this alloy and there has opened up a large number of manufacturing operations and consequent uses for this alloy which were not hitherto open to it.

The addition of calcium minimizes the tendency towards cracking and permits of the economic production of parts made from such agehardened copper, nickel and silicon alloys, together with a grain refinement which is very marked.

It is a further object to provide for the addition of a small percentage of calcium within the alloy so that the range of retained calcium for ordinary purposes is 0.2 to 0.5 percent, and for this purpose 0.1 to 1.0 percent of calcium is added to the alloy initially in the mix.

To illustrate the beneficial effects of calcium I have run three heats having the following analysis:

(a) It increases the fluidity in copper base;- copper-nickel base, and copper nickel base alloys to which silicon has been added. The following indicates the results obtained with the use of retained calcium. For example, this action appears in alloys of 90% copper and 10% nickel and alloys of 62% copper, 4% tin, 34% nickel which alloys do not have much age-hardening possibilities. It also increases the fluidity of the coppernickel silicon age-hardening alloys. The fluidity increase is not due to a deoxidation effect; as it increases the fluidity of already carefully deoxidized alloys. The advantages of increased fluidity for successful pouring of intricate castings is well known. It is beneficial in elimination of v shrinkage or contraction cavities formation.

(b) It refines the grain size of various alloys within the above classification. This claim is not confined to alloys of copper-nickel and silicon, although it cannot be fairly said to hold in all alloys of copper base nickel base, and copper nickel base.

It minimizes the tendency toward red shortness of various alloys of the above types. This benefit is not necessarily confined to agehardening alloys. Forexample, the red short tendencies of Monel metal (65% nickel, 35% copper) are well known and the calcium addition will benefit this-because the heat treating troubles of non-calcium modified copper-nickel-silicon alloys are due to the same causea red short range. Grain refinement and prevention of red shortness in these alloys enables me to employ more drastic quenching media, and hence to obtain a softer more machinable alloy after this treatment. It is probable that similar benefit would be obtained in any other age-hardening alloys which have tendency toward cracking. In none of the alloys does calcium in itselfappear to increase hardness.

Any equivalent analysis might be used within the scope of this invention, but I have used this as typical for illustrative purposes.

Referring to the drawing:

Figure 1 illustrates the grain size as cast without calcium. This drawing is based upon a macrograph etched and magnified five diameters with oblique illumination employed; the cross section shown in the drawing is based upon the. macrograph so photographed.

Figure 2 is a similar view showing the use of calcium. The drawing is based upon a macrograph showing the grain size as cast using the same etchant, a bar of the same size as in Figure 1 with the same magnification and the same oblique illumination; it will be noted that the general grain size of Figure 1 is about twice that of Figure 2 and illustrates the beneficial effect of calcium on the grain size of (as cast) alloys.

Figure 3 is an illustration of a cross section of the specimen of Figure 1 which has been oilquenched. The same etchant and illumination were utilized as in Figure 1 but with a magnification of 7 diameters. The grain structure of this composition without calcium is apparent.

Figure 4 is a similar view of the specimen shown in Figure 2 using calcium and treated in the same manner as the specimen in Figure 3.

Figure 5 is a reproduction of a photograph of a macrograph showing the composition of the specimen shown in Figure 1 which has been wa ter-quenched. The magnification is six diameters and a Silverman illuminator was used for the detection of the intercrystalline crystal cracks, one of which is very apparent and the cross grain size also is apparent. The grain boundaries are located where the orientation of the small primary dendrites change.

Figure 6 is a similar view of the same specimen in which the grain boundaries are more clearly defined for the purpose of illustration with black ink lines.

Figure 7 shows the structure of Figure 2 that has been water-quenched and photographed in the same way as that of Figure 5. The fine uniform grain size and freedom from cracks are quite apparent.

Figure 8 is a similar view of the composition of a specimen of Monel metal (65% nickel and copper) with the addition of calcium.

It will be understood that this drawing is based upon actual macrographs and photographs of the etched specimens and is as near as it is'possible to reproduce such photographs in a. drawing.

The alloy of this invention may be produced with high resistance to wear, high hardness, resistance to galling or seizing, high strength and a marked resistance to corrosion under conditions of high temperature, high pressure water, and high steam or air pressures. In the presence of corrosive materials, such as dilute sulphuric acid, and the presence of various alkaline substances, such as sodium hydroxide, it is practically immune to attack.

This alloy is one that may be cast and heattreated so that it will have a relatively low hardness for machining or forming purposes and thereafter by heat-aging can be made to give a resulting high hardness.

The alloy has a further characteristic that after a second or aging treatment to increase its hardness, it produces no scaling, no pronounced distortion and slight shrinkage without cracking and can be used with very little or no re-machining after the second treatment.

The base of this alloy may either be copper or nickel or both or a combination of copper. nickel and silicon. To this combination of copper and nickel, or copper, nickel and silicon is added calcium in amounts ranging from 0.1 to 1.0 percent. By "calcium is meant metallic calcium. alloys of calcium with copper, nickel, manganese, magnesium, beryllium, zirconium, or other metals, compounds of calcium, such as silicides and carbide, or other commonly used materials containing calcium, suchas calcium-manganese-silicon or calcium-ferro-silicon. In short, it is of no importance how the calcium is added so long as the requisite amount is added.

The addition of calcium improves the properties of the alloy, modifies the grain structure and improves the ability to heat treat the alloy in order to get the most economic use of the machine.

As a typical alloy, there may be selected an alloy consisting of from 1.75 to 3.25 percent silicon, the balance being copper and nickel in varying ratios but approximately equal ratios preferably.

To this alloy is added from 0.1 to 1.0 percent of calcium.

After casting this alloy, it is softened by quenching in any suitable medium, such as air, water or oil, from a temperature approximately 1350 to 1600 degrees Fahrenheit. We hold such a temperature for about forty-five minutes or more according to the requirements of heat penetration and the time necessary for partial resolution of the silicon rich component. This varies somewhat with the specific composition and the nature of the casting or the part being treated. Upon being suitably quenched, as in oil, the alloy is ready for machining. The hardness is not affected by the addition of calcium and ranges from 150 to 190 Brinell. About 170 Brinell is preferred and it is possible by the addition of the calcium to get a Brinell as low as this in order to give the most satisfactory machinability for work in the shop.

After the machine work has been performed, the parts that have been machined are subjected to an aging treatment at from 900 to 1200 degrees Fahrenheit for approximately eight hours. The parts are then cooled in the air or in the furnace as desired.

The result of this aging treatment is to recover or increase the initial hardness. The grain refinement is very marked as a result of the addition of the calcium. The calcium does not disappear in the ultimate alloy but remains substantially in the proportion of from 0.2 to 0.5 percent.

It will be understood that this effect is also secured in a somewhat different manner and degree with the use of nickel and copper alloys without the addition of silicon but the silicon, nickel and copper alloy has been selected purely as illustrative because of the practical experience with this combination on an extensive scale and because of the marked change in this alloy upon the addition of calcium.

The result of the aging treatment is to increase the hardness from 250 to 350 Brinell while at the same time retain an appreciable ductility in the alloy.

The exact properties desired can be secured by the use of this composition of alloy, first casting it, then heat treating it. to increase ductility and obtain reduction of hardness, machining it and then recovering or increasing hardness by age-hardening it without affecting the machine work and without pronounced distortion, shrinkage or cracking. In short. the resulting product is ready for use, with possibly a slight finish which sometimes is desired.

It will be understood that the resulting alloy such as described herein has the light silver or white color of alloys containing large percentages of nickel and is only slightly darkened by the final heat treatment.

Under conditions which are extremely severe, as encountered by valve seats, disks and like structures, the alloy develops unique mechanical properties of resistance to galling or seizing, and

high strength. It is produced at a much lower cost than any material such as stainless steel of equivalent hardness and can be handled in a machine shop without difiiculty due to its controllable hardness.

It does not lose its hardness at working temperature as in valves of 500 degrees, whereas such products as stainless steel will lose as much as 50 points hardness under similar circumstances.

It will be understood that the reduction of hardness after the first heat treatment of this cast alloy enables rapid machining on automatic or semi-automatic machine tools with accompanying economies of production.

A modification of the alloy by the addition of calcium results in the improvement of the casting properties, the grain structure and the ability to heat treat to get the most economical machining. The entire appearance of the alloy is changed from one that has a rather large rough grain structure to one that has a very fine smooth and uniform grain structure when calcium is added. In addition, cracking of the alloy is avoided with consequent perfection in the resulting product. It will be understood that it is desired to comprehend within this invention and the scope of the claims thereof such equivalent materials and proportions as may be found necessary to adapt this invention to the varying conditions met in actual practice and this invention is not limited to these specific materials and proportions.

The silicon confers age-hardening properties and the calcium the properties of improving casting, refining grain structure, prevention of cracking and fissures, and increasing the ability to heat treat to. get the most economical machining properties. By caicium" I include any means or method of incorporating calcium in the mix. It will be further understood that calcium, silicon and calcium copper have proved convenient materials for the purpose of this invention but there is no intention to limit the invention to these materials. The amounts of 0.1 to 1.0 percent indlcate the practical boundaries of the percentage of calcium but it will be understood that a variation from those amounts may be had without completely destroying the merits of the invention but simply reducing the maximum success of.-the invention. For instance, calcium over 1 percent tends to reduce the ductility of the alloy w ch, for most purposes, is undesirable.

I- will be understood-that this effect is secured in a somewhat different manner and dezree in other alloys whose mador components are copper or nickel or copper and nickeL' I have described specifically the effect of calcium addition to age-hardening alloys of copper nickel and silicon because in these alloys all the eil'ects described in this description are combined with great advantage to the casting properties of such casting properties, and minimizes tendency toward red shortness (brittleness at elevated temperatures) sometimes noticed in conditions of manufacture and service.

In short, the addition of calcium in such manner that metallic calcium is retained within the structure of the alloys described in the following claims results in the benefits described.

The addition of calcium as above specified, does not materially change the hardness or ultimate strength of such alloys, but improves their castability, their grain size, and their ductility at elevated temperatures.

Calcium addition dissipated by oxidation effects does not produce these results. The calcium must be retained in the structure of the final alloy. .For this reason full benefit is atthis purpose.

Age hardening alloys are particularly susceptible to the phenomenon of intergranular precipitation, resulting in an undesirable structural condition. The presence of brittle intergranular constituents impair the ductility of the alloy, and increase the dangers of cracking during processes of manufacture. The alloy hereinafter described minimizes or eliminates the tendency toward intergranular precipitation, resulting in a structurally satisfactory material of excellent mechanical properties.

It will be understood that I desire to comprehend within my invention such modifications as .may be necessary to adapt it to varying conditions and uses. I

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

1. In a new article of manufacture for use as an age hardening alloy consisting substantially of nickel, copper, an age hardening elementsillcon in a percentage ranging from 1.75 to 3.25 percent to cause age hardening, and retained calcium in the amount of 0.1 to 1.0 percent.

2. In a new article of manufacture for use as an age hardening alloy consisting substantially of nickel and copper in approximate equal ratios, an age hardening element silicon in a percentage 1.75 to 3.25 percent to cause age hardening, and retained calcium in the amount of 0.1 to 1.0 percent.

3. An age hardened article of manufacture that is machinable and substantially free of cracks, consisting substantially entirely of nickel and copper, and containing an'age hardening element in an'amount to cause age hardening and from .1 to 1. percent of retained calcium.

JOHN wsnn non'mn. I

tamed only by addition to-fully deoxidized alloys