Research and Development of 600MPa Grade High Strength Thin-walled TRIP Steel Tube for Tube Hydro-forming

摘要

The transformation induced plasticity (TRIP) steels, of which the strength and plasticity are improved by inducing transformation of retained austenite to martensite, have been widely applied in manufacturing automobile components and parts, e.g. underframe. However, till now there has been no detailed report on the research and development for tube steel by adopting TRIP effect. In this paper, we developed a Si-Mn TRIP steel and used it as raw material, a φ43×1.5mm multi-phase seamless steel tube has been successfully trial-produced by forging, piercing, cold-drawing and heat treatment. To confirm the chemical composition designed whether it adapted to produce TRIP steel, the hot rolled was carried out before manufacturing tube, as for the production process of the TRIP steel tube is complicated and production cycle is long. This tube steel behaves TRIP effect during cold deformation and can be used in tube hydro-forming (THF), which possess a tensile strength of over 650 MPa and elongation to failure of over 33% and has a retained austenite content of about 5 vol.%. An analysis has been mainly made on the effect of thermo-mechanical controlled processing on deformation induced transformation of the experimental steel. The results can provide a valid evaluation of the formability in tube hydro-forming.