US2469887A - Forgeable high-temperature alloys - Google Patents

Description

Patented May 10, 1949 2,469,887 FORGEABLE HIGH-TEMPERATURE ALLOYS Eugene L. Olcott, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York No Drawing. Application October 2, 1945, Serial No. 619,899

3 Claims.

The present invention is a "heat treated alloy which is particularly adapted for use at temperatures in the neighborhood of 900 to 1100 F.

It is one of the objects of the invention to provide a heat treatable alloy which can be forged, cast, and welded which has satisfactory room temperature as well as high temperature properties and which is relatively cheap to manufacture.

In carrying out the invention, I employ an iron base alloy containing to 14% chromium, .06 to .13% carbon, .2 to 6% columbium, .2 to 1% manganese, .15 to .45% silicon, .1 to .8% nickel with the balance iron. The most satisfactory results are obtained when the ratio of columbium to carbon has a value of 3 to '5 and the chrome content of the alloy is about 12%. The alloy can be welded under stress conditions with 150 C. preheat. With stainless electrodes it can be welded without preheat.

In order to obtain the desired properties in the alloy, it is heat treated at about 1100 C. until uniformly heated throughout the mass and then cooled in air. It is then drawn at a temperature of about 650 C. for about two hours. After such a heat treatment an alloy consisting of 13.42% chromium, .07% carbon, .32% columbium, .77% nickel, .42% manganese, .42% silicon, balance iron, had a tensile strength of 137,900 pounds per square inch, an elastic limit of 95,900 pounds per square inch, an elongation of 16.5%, a 49% reduction of area, a Rockwell B hardness of 106, and a charpy impact of 26 foot pounds.

My improved alloy also has high rupture and creep strengths. For example, at 1000 F. it has a 1000 hour rupture strength of 44,000 pounds per square inch, a 10,000 hour rupture strength of 37,000 and a 100,000 hour rupture strength of 32,000 pounds per square inch. Another heat containing 12.72% chromium, .09% carbon, 32% columbium, 30% manganese, 36% silicon with the remainer iron showed a 1000 F. rupture strength of 58,000 pounds per square inch for 1000 hours, 49,000 pounds per square inch for 10,000 hours, and 42,000 pounds per square inch for 100,000 hours. The 1% per 100,000 hour creep rate for the two heats was 19,000 and 23,000 pounds per square inch.

I have found that the small quantity of nickel employed in the alloy tends to eliminate free chrome ferrite. The manganese and silicon additions are employed for deoxidation purposes. The columbium when present in the correct amount promotes high temperature strength while the chromium provides oxidation resistance.

My improved alloy is particularly desirable for use as nozzle partitions, bolting material in turbine construction, and also as turbine wheels and buckets where the temperatures encountered in operation of the turbine do not materially exceed 1025 F. The high damping capacity of the alloy makes it particularly suitable for buckets.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A heat treated and heat-resistant alloy containing 10 to 14% chromium, .06 to .13% carbon, .2 to .6% columbium, .2 to 1% manganese, .15 to .45% silicon, .1 to .8% nickel with the balance iron, the ratio of columbium to carbon varying from about 3 up to 5:1.

2. A heat treated, heat-resistant and Weldable alloy containing about 13% chromium, 07% carbon, .32% columbium, .77% nickel, .42% manganese, 42% silicon with the balance substantially all iron.

3. A heat treated, heat-resistant and corrosion-resistant iron base alloy containing 10 to 14% chromium, .06 to .13% carbon, .2 to .6% columbium, .2 to 1% manganese, .15 to .45% silicon, .1 to .8% nickel and the balance iron, the ratio of columbium to carbon varying from about 3 up to 5:1, said alloy characterized by a rupture strength of 44,000 p. s. i. after 1000 hours at a temperature of 1000 F.

EUGENE L. OLCOTT.

REFERENCES CITED The following references are of record in the file of this patent: I UNITED STATES PATENTS Number Name Date 2,174,025 Wise et a1 Sept. 26, 1939 2,381,416 Wyche et al Aug. 7, 1945 FOREIGN PATENTS Number Country Date 374,541 Great Britain June 16, 1932 OTHER REFERENCES Metals Handbook, 1939 edition, page 616.

Certificate of Correction Patent No. 2,469,887 May 10, 1949.

EUGENE L. OLCOTT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 12, for .2 to 6% columbium read .2 to .6'% columbium;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 18th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents.