Mechanical properties of Q690E/Q960E high-strength steels at low and ultra-low temperatures: Tests and full-range constitutive models

Abstract

Mechanical properties of high-strength steels (HSSs) at varying temperatures are fundamental information for the design and numerical analysis of cold-region structures and LNG containers using HSSs. Tensile tests on 14 HSS Q690E and 17 Q960E tensile coupons were firstly carried out at six low temperatures of 20, −30, −60, −80, −120 and −165 °C. The required low-temperature environment for the tensile tests was achieved through an insulation chamber with injecting liquid nitrogen (LN) gas. Their results showed that decreasing the low temperature from 20 to −165 °C slightly affected the elastic modulus of both HSS Q690E and Q960E materials, but significantly increased their yield and ultimate strengths. In addition, ductile failure occurred to all the HSS coupons at low temperatures, and the ductility of HSS was not compromised. Finally, this paper developed full-range constitutive models to describe stress–strain laws of HSS Q690E and Q960E at a low-temperature range of −165 ∼ 20 °C. Validations against the reported test results showed that the proposed full-range constitutive model reasonably estimated the stress–strain behaviours of Q690E and Q960E HSSs at low temperatures.