Effect of intercritical heat treatment process on the microstructure and mechanical properties of low alloy structural steels with residual element tin

ABSTRACT

The intercritical heat treatment process is considered a novel technology to solve the mismatch of strength and toughness of low alloy steel containing residual elements. In the present study, the effects of initial microstructure and intercritical quenching temperature on microstructural morphology, mechanical properties and fracture appearance of the experimental tin-bearing steel have been investigated. The results show that, under the same intercritical quenching and tempering (IQ-T) heat treatment parameters, the initial microstructures of bainite and ferrite (B-F) and complete martensite (M) yield different ferrite morphologies, block and strip-like ferrite, respectively. It is found that after IQ-T process, the tensile strength of the steel containing 0.09% tin with B-F as initial microstructure is 1061 MPa, but the impact energy value is only 26 J; while the steel with M has achieved the combined properties of high strength and excellent toughness, and the optimal intercritical quenching temperature is 770°C.

KEYWORDS:

• Residual element tin
• ductility
• toughness
• heat treatment
• initial microstructure
• intercritical quenching
• ferrite-martensite
• fracture
• austenite nucleation

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 51974017].