Method of fabrication of a piece of structural steel, and the steel fabricated thereby

Abstract

The invention relates to a method for fabricating a piece of structural steel that includes thermal or thermomechanical treatment steps that could ordinarily lower the fatigue strength and shock and impact resistance of the steel piece. In the method of the invention a workpiece of microalloy steel is fabricated containing the following elements in the mounts indicated and having a bainitic structure: ______________________________________ C 0.05-0.5 wt. % Mo 0-0.5 wt. % Mn 1-2 wt. % V 0-0.30 wt. % Si 0.05-1.5 wt. % B 0-0.010 wt. % Cr 0.1-1 wt. % Ti 0-0.030 wt. % Nb 0-0.1 wt. % ______________________________________ The workpiece is then subjected to a treatment that includes a heating stage wherein at least a part of said piece is subjected to a temperature in the range 500.degree.-900.degree. C., followed by a cooling stage in which at least the part of the piece is subjected to cooling at a rate greater than 500.degree. C./hr. The composition and bainitic structure of the workpiece prevents its fatigue strength and shock and impact resistance from lowering in the part heated within the 500.degree.-900.degree. C. range. The invention further encompasses the structural steel fabricated by the aforementioned method.

Dependencies are inferred from the claim text.