Prodn. of steel profiles esp. for ski edges - involves nitriding of steel followed by cold working to produce austenitic steel having high strength, toughened and corrosion resistance

摘要

Process is used for prodn. of profiles made of austenitic steel in which a perform in wire form is nitrided at 800-1700 deg.C in an atmosphere contg. nitrogen, ammonia and hydrogen prior to subjecting to several cold working stages. The atmosphere may also contain an inert gas. The partial pressure of the nitrogen during nitriding is 100-200 kPa. The nitriding time is given as at least one-fifth of the quotient of (surface/volume)2 over diffusion coefficient of material at the chosen temp. The nitrided steel is solution annealed, followed by quenching. It is then cold worked in several stages with intermediate annealing. The nitriding process must be sufficient to produce a uniformly nitrided cross-section contg. at least 0.3 wt% N or a uniform surface content of nitrogen of 0.3 wt%. This ensures that no deformation martensite is produced during cold working. The starting steel may contain special metal elements which precipitate at as nitrides during annealing, so as to leave a residual nitrogen content in the steel structure of at least 0.3 wt%. USE/ADVANTAGE - Prodn. of ski edges. The prod. has the strength, toughness and wear and corrosion resistance of austenitic steel.