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A lately established melting-refining-casting process for special steel and their qualities are described in this paper. The process consists of electric arc furnace melting, ladle furnace refining, vacuum degassing and continuous casting in this order. Such a complicated process has been put in the practice for the first time to manufacture particularly automobile steels. One of the advantages of this process is the reduction of impurities such as oxygen and sulfur Oxygen is evacuated during vacuum degassing treatment and sulfur is controlled through ladle furnace refining. As a consequence, cold formability is improved significantly. Mechanical reliability can be increased as well, and especially, it should be noteworthy that stress corrosion cracking of high strength fastners is able to be prevented by the reduction of sulfur. Consistent quality is an another major advantage of the process.

ABS sensor rings for automotive use are becoming smaller and thinner because of the demand for low cost and light weight. Such small thin parts are easier to break as they must withstand the same severe conditions as larger heavier parts. Superior elongation properties, after corrosion testing, are necessary for avoiding breakage and to obtain superior corrosion resistance. We have, therefore, developed such high performance P/M stainless steel with superior elongation and corrosion resistance. Conventional stainless steel has uniform pores on its inner surface which makes allows water penetration thus making corrosion worse and decreasing elongation. It is possible to increase corrosion resistance by changing pore structure (e.g. decrease continual pores) through the addition of special alloys that accelerate the sintering process.

Extremely high quality is required for special steels employed for automobile components. Therefore careful consideration was given to maintain high purity, homogeneity and sufficient reduction ratio prior to introducing a continuous casting machine. With this machine it became possible not only to produce steels with outstanding cold forgeability and fatigue strength but also to produce steels with highly homogeneous hardenability, machinability and distortion. Furthermore, estimation tests were carried out for automobile components and it was confirmed that continuous cast steels were performing as well as those of ingot cast steels.