US1988154A - Alloy - Google Patents

Description

1935- J. w. BOLTON ET AL 1,988,154

ALLOY Filed May 11, 1935 til Patented Jan. 15, 1935 UNlTED STATES PATENT OFFICE ALLOY corporation of Ohio Application May 11, 1933, Serial No. 670,516

2 Claims.

Our invention relates to alloys and in particular to an alloy of silicon, nickel and copper, and to a method of treating such an alloy in order to permit of its machining while maintaining its ultimate hardness beyond the limit of economic machining practice.

It is our object to provide an alloy which has 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, steam or air, and in the presence of corrosive materials such as dilute sulphuric acid, as well as in the presence of various alkaline substances, such as sodium hydroxide and sodium carbonate. 7

It is our object to provide such an alloy that has a good resistance to corrosion of a wide variety of solutions.

It is a further object to provide an alloy that can be cast and heat treated 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.

It is our object particularly to provide an alloy that after the second or aging treatment to increase itshardness, produces no scaling, no pronounced distortion and very slight shrinkage and therefore can be immediately used with very little or no re-machining after the second treatment.

It is our object to provide an alloy particularly useful in valves for application to valve seats and disks and other structures wherein physical characteristics embodied in this alloy may be employed with obvious advantage.

Referring to the drawing, Figure lillustrates a microphotograph of this alloy of our invention prior to the first heat treatment.

Figure 2 represents a microphotograph subsequent to the first treatment.

Figure 3 is a microphotograph after the second heat treatment. I

Figure 1 shows the cast structure enlarged 50 diameters after having been etched with nitricacetic acid plus a crystal of chromic acid. The black structure (marked 1) is the harder component rich in silicon while the softer background in white (marked 2) consists largely of the copper-nickel solid solution.

Referring to Figure 2, it will be noted that as a resultof the first heat treatment, there is a small amount of the black hard component 1 with a marked. uniformity of structure which results in the workable characteristics hereinafter described. The magnification and the etching destroy the uniformity of the structure.

fluid are the same as that used in connection with Figure 1.

Referring to Figure 3, which has been treated with the same etching fluid and has the same magnification as the other views, the effect of aging at 1000 degrees on the structure in No. 2 is evident. There is a marked increase in hardness due to the increase in the hard black component 1, but this second heat treatment does not Thus the hardness is increased, but the other qualities of the alloy are maintained.

We have found that this alloy should consist of from 1.75 to 3.25 percent silicon, the balance being copper and nickel in approximately equal ratios.

We have found alloys of 1.75 to 2.75 percent silicon and the balance in nickel and copper in approximately equal ratios, or 2 to 3.25 percent silicon and the balance in-copper and nickel in approximately equal ratios, to be excellent alloys for our purpose.

Small percentages of lead and phosphorus do not materially affect the properties of our alloy and may be added to facilitate foundry and shop production.

Heretofore in the art the regular cupro-nickel alloy having copper and nickel of approximately equal amounts possesses the following approximate physical properties in the cast condition:

Tensile strength 50,000-60,000' Elongation 20-35% Brinell hardness -120 We have found, however, that our alloy of silicon, nickel and copper possesses the following physical properties in cast condition:

Tensile strength 90,000-125,000 Elongation 245% Brinell hardness 250-325 After casting this alloy, we first soften the alloy by quenching in any suitable medium such as air, water or oil from a temperature of approximately 1350 degrees to 1600 degrees Fahrenheit. We hold such a temperature for 45 minutes or more according to the requirements of heat penetration and time necessary for partial re-sothat gives the most satisfactory hardness for machine work in the shop.

After the parts are machined, they are then subjected to an aging treatment process at from 900 to 1200 degrees Fahrenheit for approximate- 17 8 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. Such recovered or increased hardness ranges from 275 Brinell up to as high as 360 Brinell. We also retain appreciable ductility as a result of these treatments.

The exact properties desired can be secured by the use of this compcsition of alloy, first cast- 1 ing 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.

Other characteristics of the alloy of our invention are developed by the addition of any one of the following to the alloy:

. Per cent (a) Manganese to (b) Iron 0 to 10 (c) Aluminum 0 to 5 (d) Tin 0 to 5 (e) Zinc 0 to 5 (I) Phosphorus 0 to 1 (0) Lead 0 to 2 (h) Molybdenum 0 to 4 (i) Chrom O to 4 (i) Cobalt 0 to 4 (k) Vana 0 to 2 (l) Tungsten 0 to 3 (m) Tita 0 to 3 The addition of manganese toughens the alloy and lowers the quenching temperature. In some instances it lowers it about 200 degrees. This is desirable in certain types of castings because the lower the quenching temperature, the less the possibility of undue strain and possible cracking and also the finer the grain and the greater the ductility.

The addition of aluminum lowers the strength somewhat but the hardness remains'at approximately 320 Brinell.

The addition of iron within the percentage specified does not change the physical properties. The addition of tin does not change the strength of the alloy but lowers the Brinell to about 286. The addition of zinc likewise lowers the Brinell about 50 points.

The use of lead improves the machinability of the alloy.

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 difilculty 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.

We find that the addition of the unusual amount of silicon as indicated within the ranges indicated gives us the properties we desire and as we depart from these ranges, the properties we desire begin to disappear.

It will be understood that we desire to comprehend within our invention and the scope of the claims thereof such equivalent materials and I proportions as may be found necessary to adapt this invention to the varying conditions met in actual practice and we do not limit ourselves to these specific materials and proportions.

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

l. A new article of manufacture for use as an alloy which is ductile and which may be softened and machined without hot rolling after being heat treated comprising the combination of 1.75 to 2.75 percent silicon, the balance being nickel and copper in approximately equal ratios.

2. A new article of manufacture comprising an alloy which is ductile and which may be softened and machined without hot rolling after being heat'treated consisting of approximately 1.75 to 3.25 percent silicon with nickel and copper in approximately equal ratios.

JOHN W. BOLTON. SYLVESTER A. WEIGAND.

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