US1829118A - Process for making steel insensible to the action of hot gases and vapors - Google Patents

Description

Patented Oct. 27, 1931 UNITED STATES PATENT OFFICE BEN'NO STRAUSS, OF ISSEN, GERMANY, ASSIGNOR TO FRIED. KRUPP AKTIENGESEL L- SGHAFT, F ESSENON-THE-RUHR, GERMANY PROCESS FOR MAKING STEEL INSENSIBLE TO THE ACTION OF HOT GASES AND VAPOBS Ho Drawing. Application filed November 18, 1926,

Steel when exposed to the action of hot gases and vapors generally becomes brittle, this brittleness, in its turn, causing cracking of the steel. for instance with steam boilers and high pressure receptacles. The tendency to crack is greater, the higher the pressure to which the articles are exposed dur' ing operation. The change in the texture taking place due to the action of hot gases and vapors consists in an enlargementof the grain boundaries which are in a. yieldingly tensioned condition, and in phenomena arising in the grain boundaries which have not been explored hitherto. Probably these phenomena consist in the reaction of certain constituents of the steel with the gases. In steam boilers, for instance, the products of dissociation of the water, hydrogen and oxygen, cause such a reaction, the oxygen in particular tending to enlarge the grain boundarie's, when in nascent state. For, the grain boundaries which are to be considered the seat of the oxides enveloping the individual grains as closed pellicles so to speak, form ways for the entrance of gases and vapors, the penetrating gases and vapors. in their turn, cause a noxious alteration of the cohe'rence prevailing between the individual crystal grains and thus generate a successively increasing brittleness which may be denoted as aging of the material.

Now my invention has for its object to provide a proces which will prevent the hot gases and vapors from exerting a noxious effect on the steel or the articles made thereof. This object is obtained according to my invention by subjecting the steel or the articles made thereof to a heat treatment by which the grains and the oxide particles lying between them are refined to such an extent that grain boundaries can no longer be detected.

In carrying out the process forming the subject-matter of my invention, preferably a steel is made use of containing for instance about to 4 per cent of nickel, to 2 per cent of chromium and 0.1 to 0.39 per cent of carbon, thisbeing a steel in which a formation of martensite takes place when quickly I. cooled from above the pointof recalescence,

Serial No. 149,282, and in Germany April 1, 1926.

A03, in the present example from 900 C., and in which by a subsequent reheating, in the present example up to about 600 to 650 C., the desired properties of strength are obtaincd, without grain boundaries being formed again or an alteration of the distribution of the oxides arising otherwise.

When a steel of this nature is treated in the indicated manner, grain boundaries can no longer be detected by an etching test. The steel has thus been brought into a condition of highest tenacity in which a penetration of hot gases and vapors is excluded and which does not undergo any subsequent alteration.

Besides chromium and nickel, silicon vanadium and tungsten come into consideration as additions, the percentage of the additions depending on the cross sections of the articles to be manufactured of the steel.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is

1. The process of treatin steel containing about A,, to 4 per cent 0 nickel, to 2 per cent of chromium and 0.1 to 0.39 per cent of carbon to render the same insensible to the action of hot gases and Vapors, which consists in refining the grains and the oxide particles lying between them by heating the steel above the point of recalescence, AC3, quickly cooling it from above this point and reheating it up to about 600 to 650 C.

2. The process of treating steel containing about V; to 4 per cent of nickel, to 2 per cent of chromium, 0.1 to 0.39 per cent of carbon, and to render the same insensible to the action of hot gases and vapors, which consists in refining the grains and the oxide particles lying between them by heating the steel above the point of recalescence, A03, quickly cooling it from above this paint and reheating it up to about 600 to 650 w 3. The process of treating steel containing about to 4 per cent of nickel, to 2 per cent of chromium and 0.1 to 0.3 per cent of carbon to render the same insensihle to the action of hot gases and vapors, which consists in refining thegrains and the oxide 100 particles lying between them by heating the steel above the point of recalescence A03, quickly cooling it from above this point and reheating it up to about 600 to 650 C.

4. An iron alloy containing to 4% of nickel, A), to'2% of chromium, and 0.1 to 0.39% of carbon and heat treated according to the process described in claim 1, said alloy having high tenacity and resistance to corrosion by hot gases and vapors and having a structure which appears in an etched section as a continuous mass unbroken by grain boundaries.

5. An iron alloy containing to 4% of nickel, to 2% of chromium, 0.1 to 0.39%

of carbon, and tungsten, and heat treated according to the process described in claim 2,

said alloy having high tenacity and resistance to corrosion by hot gases and vapors and having a structure which appears in an etched section as a continuous mass unbroken by grain boundaries.

The foregoing specification signed at Colggne, Germany, this 26th day of October,

BENNO STRAUSS.

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