Failure mode and hot ductility of Ti-bearing steel in the brittle zone

Metallurgical and Ecological Engineering school, University of Science and Technology Beijing, Beijing, P.R. China
e-mail: zengyanann@126.com

Received: 18 May 2013
Accepted: 27 September 2013

Abstract

The hot ductility of Ti-bearing steel was studied by theoretical calculation and a thermal simulation experiment. Meanwhile, microsegregation and precipitates were analyzed. The results showed that the S, P and O elements were enriched at the grain boundaries, while the hot ductility was deteriorated by inclusions of (Fe, Mn, Si, Al)(S,O) in the interdendritic region. At a temperature of 1300 °C, large TiN particles have little effect on the hot ductility. In the temperature range from 1000 °C to 900 °C, the Reduction of Area (R.A) declined rapidly from 81.77% to 31.77%, with the size of particles decreasing from 5 to 20 nm and quantity increasing from 1.2 inds/μm² to 354 inds/μm², respectively. In the temperature range from 900 °C to 850 °C, R.A decreased from 31.77% to 30.12% with the ferric films gradually thickening. The critical stress, 63.58 MPa, was equal to tensile strength at 912 °C. Intergranular fracture occurred easily with higher critical stress below 912 °C.