An ultra-low carbon steel composition, the process of production of an ULC BH steel product and the product obtained

摘要

The present invention describes an ultralow carbon bake hardenable galvanised or galvannealed steel product, having a higher yield strength at the temperature of the molten zinc bath while maintaining a low yield strength and excellent bake hardening properties in a skinpassed condition, BH0 being higher than 35MPa and BH2 higher than 40MPa (GI) and BH0 > 20MPa and BH2 > 30MPa (GA), as well as having a superior paint appearance after stamping and painting. The content in the steel composition of the Ti is comprised between 3,42 N and 3,42 N + 60 ppm for a fixed nitrogen content (N), and the Nb-content, comprised between 50 ppm and 100 ppm, is fixed so that no substantial precipitation of niobium carbides will occur during the process.