High-silicon stainless

Abstract

A high-Si stainless steel excellent in various characteristics, inclusive of strength, corrosion resistance, workability and castability, consists of, on the mass % basis, Si: 2 to 5%, Cr: 8 to 25%, Ni: 4 to 16%, Mn: not more than 5%, Cu: not more than 4%, Co: not more than 8%, Mo: not more than 4%, Nb: not more than 3%, Ta: not more than 3%, Ti: not more than 3%, W: not more than 4%, V: not more than 4%, B: not more than 0.01%, Mg: not more than 0.01%, Ca: not more than 0.01%, rare earth elements: not more than 0.01%, the balance being Fe. Impurities in this steel are as follows: C: not more than 0.04%, P: not more than 0.03%, S: not more than 0.02%, Al: not more than 0.03%, N (nitrogen): not more than 0.05%, O (oxygen): not more than 0.005%, and H (hydrogen): not more than 0.0003%.

Description

[0001] The present invention relates to a high-silicon stainless steel having excellent corrosion resistance and high strength as fundamental characteristics and, in addition, having various characteristics such as fatigue resistance, heat resistance, castability and workability.[0002] Typical metallic materials excellent in corrosion resistance are stainless steels. The field of application of stainless steels covers a wide range and, in recent years, stainless steels are used for not only corrosion resistance material but also various materials that should have characteristics such as mentioned below.[0003] (1) Fatigue Resistance Characteristics[0004] The uses requiring fatigue resistance are, for example, springs, gears, driving shafts, and the like. A special use is core wires of inter-tooth brush.[0005] (2) Heat Resistance[0006] High Cr steels, such as stainless steels, are generally excellent in heat resistance. In addition to such general heat resistance, the resistance again...

AI Technical Summary

Benefits of technology

[0027] The above-mentioned high-silicon stainless steel is a steel having a dual phase structure mainly composed of austenite and ferrite. Owing to its high Si content as compared with ordinary stainless steels, this steel has both corrosion resistance and high strength and shows good fluidity on the occasion of casting. Furthermore, as mentioned above, it can be provided with age hardenability through adjustment of the alloy composition, so that it is also possible to work that steel in a low-strength solid solution state and then causing the same to have high strength by the subsequent aging treatment. The products hardly deform upon aging treatment.

[0030] The present inventor confirmed that the above object could be accomplished by increasing the index of cleanliness of the high-silicon stainless steel. Generally, the index cleanliness of steel means the amount of inclusions, mainly oxides and sulfides. A steel wherein these inclusions are reduced is referred to as a steel with a high index of cleanliness.

[0075] For improving the age hardenability, it is desirable that the steel contain at least one of the four components, namely 0.5 to 4% of Cu, 0.1 to 1.5% each of Nb, Ta and Ti, in addition to the above constituents. Further, residues of the Mg, Ca and rare earth elements used as refining agents may remain each at a level not exceeding 0.01%.

Problems solved by technology

This is because the material cost accounts for a great proportion of the total cost in the production of large-sized or mass-produced instruments and apparatus.

However, very few materials can meet all of such requirements.

These are quench-hardenable stainless steels and are excellent in hardness, strength and wear resistance but are not satisfactory in corrosion resistance.

Their hardness can be increased by quenching but strains are readily caused on the occasion of that heat treatment, whereby subsequent finishing works become difficult.

However, even the above-mentioned high-silicon stainless steel cannot yet fully satisfy such various requirements as mentioned above.

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