Search

One of the main trends in the development of materials for the body and other parts of automobiles is the greater use of high-strength steels, this being done in order to make the vehicle safer and lighter. The need for this change stems from the continual tightening of standards on tailpipe emissions. The largest metallurgical companies that presently make automobile sheet have been working with the main Russian automobile manufacturers to develop steels with improved commercial properties. This article presents results from studies conducted to optimize the technology used to make rolled products of high-strength, ultralow-carbon steels 01YuTB an 01YuPTB for the automotive industry. The optimized technology includes heat treatment in a continuous annealing furnace. Emphasis should be given to developing technical recommendations on how to optimally combine strength, stampability, and a guaranteed level of the BH-effect (BH2 ≥ 30–40 N/mm2) in the production of automobile sheet of strength class K180, as well as BH steels of strength class K220 or higher.

1. Achieving total reductions of 40–80% for steel 01 YuT ensures high mechanical properties (σy=151–176 N/mm2,σB=294–318 N/mm2, δ4=42–47%) and high values of the strain-hardening index (n=0.233–0.251), regardless of the annealing variant (continuous annealing furnace, bell-type furnaces). 2. Increasing the reductions made during the cold reduction of steel 01YuT to values within the range 75–84% increases the number of grains with the {111} orientation and decreases the number of grains with the {110} orientation. Both of these orientation changes improve the stampability of the steel and result in high values for the coefficient of normal plastic anisotropy and the ductility coefficient (Kdc=11.1–19.0;R=1.96–2.08). 3. The annealing of steel 01YuT with small reductions (40.5, 52.4%) results in a deterioration of the texture of the metal and a decrease in the coefficient of normal plastic anisotropy (Kdc=4.3–7.1;R=1.20–1.45).