Tempering Behavior of 420 MPa Grade Steel with Cu Alloying

Nodes made from steel are widely applicable to the structure of pipe racks. In this paper, the Cu content and tempering temperature of 420 MPa grade (yield strength grade) steel alloyed with Cu were studied for their effect on strength and toughness. The precipitation behavior of different Cu contents during the normalizing cooling and tempering process of the steel, and the corresponding strength and toughness levels, were clarified. The research results showed that an experimental steel with ferrite as the matrix was prepared by the normalizing and tempering method. A strengthening method mainly based on Cu precipitation was proposed, which effectively promoted the steel to have a good toughness reserve while meeting the strength requirements. With the increase in Cu content, the contribution of Cu particle precipitation to strength gradually slowed down, mainly due to the weakening of the contribution of Cu particle growth and coarsening to precipitation strengthening.