US2141389A

US2141389A - Alloy steel

Info

Publication number: US2141389A
Application number: US194880A
Authority: US
Inventors: Hatfield William Herbert
Original assignee: Thos Firth & John Brown Ltd
Current assignee: Thos Firth & John Brown Ltd; THOS FIRTH and JOHN BROWN Ltd
Priority date: 1937-04-19
Filing date: 1938-03-09
Publication date: 1938-12-27
Anticipated expiration: 1955-12-27

Description

Patented Dec. 27, 1938 UNITED STATES PATENT OFFICE 2,141,389 ALLOY STEEL William Herbert signor to Thos. Firth Hatfield, Sheflield, England, as-

& John Brown Limited,

Sheffield, England, a British company 3 Claims.

This invention comprises improvements in or relating to alloy steels exhibiting good mechanical properties at elevated temperatures.

Numerous alloy combinations have been proposed for obtaining improved properties of constructional materials for use at elevated temperatures.

It is generally recognized that, as regards steels, the richer alloys of the austenitic type, containing sufficient proportions of chromium, nickel and other elements to render them for practical purposes stable in the austenitic or austenito-martensitic condition, show superior properties to ordinary alloy steels when tested in the range of temperature round about 500 C. and upwards. In this connection, the addition of tungsten for improving high temperature performance of chromium-nickel steels is well establlshed.

The present invention provides an austenitic nickel-chromium alloy steel suitable in particular as a constructional material for use at elevated temperatures, and characterized in that it contains as essential constituents a small proportion of titanium and a relatively higher proportion of cobalt.

More specifically the invention comprises an alloy containing 20-40% nickel, 6-20% chromium, 10-30% cobalt, 1-5% titanium, up to 0.6% carbon and the remainder iron.

The improved alloy may also embody small proportions of other elements such as manganese and silicon normally used in alloy steel production. It is also within the invention to replace part of the nickel up to say by manganese, and to replace part of the chromium up to say 3% by silicon. The following is an example of an alloy composition according to the invention and of the properties possessed thereby:-

Analysis Per cent 0.1 0.36 1.14 30.05 9.66 20.43 '1 2.08 Fe Remainder.

Treatment:

Air cooled 1050" C. and reheated to 650 C.

Tests at ordinary temperatures:

Yield point 32 tons/sq. in. Maximum stress 59 tons/sq. in. Elongation 31%.

Reduction of area 41%.

Tests at 600 0.-

Short time test:

(Rate of pull 0.12" per minute.) Ultimate strength 35-tons/sq. in. Long time test:

(Hatfield time-yield test) time-yield value 15.5 tons/sq. in.

I claim:

1. An austenitic nickel-chromium alloy-steel suitable in particular as a constructional material for use at elevated temperatures and comprising 20-40% nickel, 6-20'% chromium, in excess of 10% and up to 30% cobalt, 1-5% titanium, a material amount not exceeding 0.6% carbon, and the remainder iron with a minimum of 20%.

2. An austenitic nickel-chromium alloy steel suitable in particular as a constructional material for use at elevated temperatures and comprising about 30% nickel, 10% chromium, 20% cobalt, 2% titanium, 0.1% carbon and the remainder iron. v

3. A constructional aterial for use at elevated temperatures comprising an austenitic nickel-chromium alloy steel containing about 30% nickel, 10% chromium, 20% cobalt, 2% titanium, 0.1%carbon and the remainder iron, the steel being in the condition which results from heat treatment by air cooling at about 1050 C. and reheating to about 650 C., and having a yield point of about 32 tons per square inch, a maximum stress of about 60 tons per square inch and a percentage elongation of about 31.

WILLIAM HERBERT HATFIELD.