Chromium-Base Alloy and a Production Process Therefor

Abstract

A chromium-base alloy characterized by containing titanium within a range from 0.002 t0 1.5 mass %, with the balance comprising chromium and inevitable impurities, and being produced by melting or casting only. A chromium-base alloy that can be obtained by melting only, has room temperature ductility and a good workability, and has excellent high temperature strength and oxidation resistance even at a high temperature of about 1300° C., as well as a production process therefor are provided.

Description

TECHNICAL FIELD[0001]The invention of the application concerns a chromium-base alloy and a production process therefore. More specifically, the invention of the application concerns a chromium-base alloy obtained only by melting, having room temperature ductility and a good workability, and having excellent high temperature strength and oxidation resistance even at a high temperature of about 1300° C.BACKGROUND ART[0002]It is said that the usable temperature of nickel-base heat resistance alloys used for rotors and stators in gas turbines is limited to 1100° C. by their melting points, even when countermeasures by coating and air cooling are used in combination. In view of the above, chromium which has a high melting point (1863° C.) as well as a good oxidation resistance and a relatively low density or a chromium-base alloy has been desired as an alternative alloy for nickel-base heat resistant alloys.[0003]However, since chromium and chromium-base alloy have the drawback of lackin...

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Benefits of technology

[0012]According to the invention of the application, a light-weight chromium-base alloy that can be produced only by melting and having a room temperature ductility and a good workability is provided. The chromium-base alloy can exhibit excellent oxidation resistance and high temperature strength even when the total amount of impurity elements about 1000 mass ppm. Further, these properties can be maintained during repetitive use at a high temperature up to about 1300° C. Further, since the chromium-base alloy of the invention of the application can be cast to form products, it can be utilized for rotors and stators blades in gas turbines, as well as various types of heat resistant components such as blades, intake and exhaust valves, and rocker arms of aircraft jet engines and industrial gas turbines and, further, connecting rods and heat resistant wheels of motorcycle and automobile engines. Particularly, a high chromium-base alloy containing 70 mass % or more of chromium can be used, for example, in stator blades of gas turbines, blades of compressors and the like.

Problems solved by technology

However, the Patent Document 1 describes that the ductile-brittle transition temperature of the obtained chromium alloy is from 200 to 700° C., and this indicates that in the case of adding Al, Ti, Zr, Hf, Y or the like to chromium, the tensile ductility at a temperature lower than the transition temperature thereof, for example, at room temperature cannot be improved.

Further, since it is essential that the alloys comprising chromium need adjustment of alloy structure by 70% rolling reduction or higher, they involve a drawback that they cannot be utilized, for example, as cast products such as rotors and stators blades of gas turbines.

Further, it is necessary to use a material of high purity as the starting material, reducing the amount of impurities of four kinds of C+N+O+S to be much lower than in usual alloy materials, to 170 mass ppm or less, requiring an increased cost to make the products expensive.

Furthermore, this material is not intended at all to have high temperature properties, particularly mechanical properties at about 1300° C. which have been required in recent years, and they are not utilized at all as heat resistant structural alloys.

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