Date of Award

8-1-2021

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Manufacturing structural automotive components, Hot stamping advanced high strength steel sheets, Tailored mechanical properties, Reduce vehicle weight, Improve crashworthiness, Press-hardenable steels, Quenching rates

Supervisor

D. Green

Supervisor

S. Das

Rights

info:eu-repo/semantics/openAccess

Abstract

Manufacturing structural automotive components by hot stamping advanced high strength steel sheets with tailored mechanical properties helps to reduce vehicle weight and improve crashworthiness. The purpose of this research work is to establish a relationship between the die temperature in hot stamping, the corresponding as-quenched microstructural features and mechanical properties. A series of experiments were carried out in which 1.4 mm 22MnB5 and 1.4 mm 37MnB4 steel sheet specimens were austenitized to 930°C and quenched between dies preheated to different temperatures. The mechanical properties were determined from tensile tests and hardness measurements and the corresponding microstructures were analyzed. It was found that when the quenching die temperature changed from 500 °C to 250 °C the tensile strength varied from 650 to 1300 MPa for 22MnB5, whereas it varied from 1075 to 1930 MPa for 37MnB4. There is no doubt that the 1900 MPa strength of fully martensitic 37MnB4 steel is ideal for automotive structures since it will allow for greater light-weighting of existing structural parts while maintaining vehicle safety. Moreover, this work has also shown that 37MnB4 is suitable for producing tailored automotive structures since a quench-die temperature of 500°C can generate a soft zone that has a tensile strength that is only 55% of that of the ultra-high strength zone. And although the tensile strength in the soft zone is relatively high (> 1000 MPa), it contains about 85% bainite and 15% ferrite, has a total elongation of about 11% and exhibits a mixture of brittle and ductile fracture.

Download

Share

COinS