US2821474A

US2821474A - Hard ductile alloy

Info

Publication number: US2821474A
Application number: US422081A
Authority: US
Inventors: Marvin L Steinbuch
Original assignee: Lunkenheimer Co
Current assignee: Lunkenheimer Co
Priority date: 1954-04-09
Filing date: 1954-04-09
Publication date: 1958-01-28
Anticipated expiration: 1975-01-28

Description

Filed April 9', 1954 INVENTOR. I

ATTORNEYS.

United States PateiitO 2,821,474 HARD'DUCTILE AhllbY Marvin L. Steinbuch, Cincinnati, Ohio, assignor to The Lunkenheimer Company, Cincinnati, Ohio, a corporation of Ohio Application April 9, 1954, Serial No. 422,081 4 Claims. (Cl. 75--171) type of alloy is disclosed in United States Patent No.

2,245,566, issued June 17, 1941, for Welding Rod; it comprises substantially 6 to 12% silicon, 9 to 30% chromium and the balance nickel.

Castings made from such an alloy are too hard to be machined by turning or boring in the usual manner, and therefore, they must be formed to shape by grinding. Because of its extreme hardness and wear resistance, such an alloy is potentially useful where such characteristics are desirable, as in the seats of valves which are required to withstand the abrasion incidental to the flow of fluids sometimes under high velocity and pressure. However, if valve seats in the form of castings are made from such an alloy and are brazed in position in the valve structure. the heat of brazing causes, or may cause, slight warpage, cupping or distortion of the seat elements to occur, there by defeating the precision with which the seat element initially may have been fabricated. The alloy of the identified patent is not sufliciently flexible, or it is too lacking in ductility, to be distorted sufliciently to overcome the warpage, and the pressure exerted on a distorted alloy metal seat by the valve closing means is apt to cause it to fracture or break. Thus, although the total amount of distortion caused by the heating incidental to the brazing of the piece may actually be very small, still the brittleness of the alloy is high and it cannot reliably survive the small deflection which is requisite to physically distort the cast element to its original state.

I have discovered that nickel-chromium-silicon alloys having a hardness and wear resistance desirable for valve seats can be made sufficiently ductile to permit any warpage incidental to the brazing operation to be overcome by physical force, incorporating therein a minor percentage of copper which does not exceed substantially by weight of the alloy. Although the silicon content of the alloy shown in the aforesaid patent is relatively high, the addition of the copper does not cause silicion precipitation as would normally be expected. Most significantly, the incorporation of copper in the alloy does not impair hardness, but does increase ductility, the increase in ductility being roughly proportional to the amount of copper utilized.

A typical example of the use of the alloy in a valve structure is disclosed in the accompanying drawing, although it is to be understood that the alloy may be used for any purpose where hardness and ductility are both desired.

The figure of the drawing is a sectional view of an otherwise conventional globe valve structure. In the drawing, 10 indicates the body casting. Within the casting is the seat diaphragm 11 separating the two ends of the valve, in which is located aperture 13. An apertured valve seat element 14 is mounted in a seat recess in the diaphragm portion .15 and is secured in position bya braze 16, conventionally silver. Mounted over the valve seat 14;?is bonnet 17 and stem 18 .on the outer end of which is the valve ,handle 19. .Swiveled to'the lower end of the stem is the movable valve element 20 on which a valve seat element 21 is mounted and secured by a "braze 22.

Valve seats

14 and 21 are fabricated from the alloy herein described.

The valve seat elements are fabricated from the alloy by casting thereof, after which they are ground to shape and then brazed in position, as by silver soldering. The seat elements may be of any desired shape; for example, they may be in the form of thin annular rings having ground or ground and lapped facial surfaces, which are engageable with one another.

If these discs become distorted or cupped as a result of the heat to which they are subjected when being brazed in place in the valve body, then, when the valve handle is operated to close the valve, the seats will not initially engage one another over their entire facial areas as intended. However, by exerting somewhat greater closing force on the valve handle either one or both of the disc elements will flex sufliciently, without breaking, to permit them to be brought into complete facial engagement. In this manner the valve may be closed completely due to the inherent ductility of the nickel-chromium-siliconcopper alloy.

In general, the alloy should comprise from one-half percent to 5% copper, 6 to 12% silicon, 9 to 30% chromium and the balance nickel. For valve seat castings the preferred alloy comprises 4 /2 to 5% copper by weight, 7 to 10% silicon, 15 to 20% chromium and the balance nickel.

A comparison of typical alloys disclosed in United States Patent No. 2,245,566 and the alloys of the present invention indicates the degree to which ductility may be attained without sacrifice of hardness.

Deflection, as given in this table, is the deflection of a A inch diameter cast round rod of alloy held firmly at one end, the deflection being measured at a point 6 inches from the point at which the rod is held.

Like the composition shown in the aforesaid United States Patent No. 2,245,566, the alloys of the present invention are adapted for use in welding, but unlike the previous compositions, the alloys of the present invention provide improved ductility in weld deposits as well as extreme hardness and resistance to abrasion. The invention, therefore, contemplates alloys which are made in the form of welding rods, and weldments fabricated therefrom, as well as castings for valve seats and other uses where ductility is required in combination with hardness and abrasion resistance.

Having described my invention, I desire to be limited only by the following claims:

1. A valve seat comprising a casting of an alloy consisting essentially of /2 to 5% copper, 6 to 12% silicon, 9 to 30% chromium, and the balance nickel.

2. A valve seat comprising a casting of an alloy consisting essentially of 4 /2 to 5% copper, 7 to 10% silicon, 15 to 20% chromium, and the balance nickel.

3. A valve seat thermally bonded to a seat support, said valve seat being formed of a hard ductile alloy consisting essentially of xi to 5% copper, 6 to 12% silicon, 9 to 30% chromium, and the balance nickel.

4. A valve seat thermally bonded to a seat support, said valve seat being formed of a hard ductile alloy consisting essentially of 4 /2 to 5% copper, 7 to 10% silicon, 5 15 to 20% chromium, and the balance nickel.

1,115,239 Parr Feb. 27, 1914 10 Brix Oct. 31, 1916 Spitzley et a1 June 8, 1926 Spitzley et al June 8, 1926 Spitzley et al June 8, 1926 Egeberg Feb. 15, 1938 Bolton June 17, 1941 Norton Sept. 3, 1946 Wissler Sept. 5, 1950

Claims

1. A VALVE SEAT COMPRISING A CASTING OF AN ALLOY CONSISTING ESSENTIALLY OF 1/2 TO 5% COPER, 6 TO 12% SILICON, 9 TO 30% CHROMIUM, AND THE BALANCE NICKEL.