Making a steel profile with outer corrosion protection - by heat treating, scaling, applying zinc coating and heat treating thus improving productivity

摘要

A method of giving a high hardness, tough steel profile an outer corrosion protection comprises the following steps: 1) heat treatment, 2) scaling, 3) application of a Zn coating, and 4) heat treatment of the Zn treated part. More specifically, a steel profile made by hot rolling (opt. cold rolling, followed by heat treatment) was scaled and subsequently annealed under a protective gas atmos. (in complete absence of O), then heat treated in a Zn bath. After the annealing the profile needs to undergo rapid cooling under a protecting gas blanket. Cooling agents can be oil, water or liquid N, if the latter is used it evaporates and becomes the protective gas. The annealing stage in the Zn bath is carried out at temps. in the range 480-500 deg.C, and needs to be held at this temp. for at least 3 minutes. This process is suitable for making tube-form steel profiles used for reinforcing motor car doors. USE/ADVANTAGE - Simpler and cheaper method than conventional Zn corrosion protecting techniques, fewer stages.