Effect of Ni content on continuous cooling transformation curves of EQ70 steel for marine engineering

doi:10.13251/j.issn.0254-6051.2022.01.017

Abstract

Abstract: Thermal expansion curves of EQ70 steel for marine engineering with Ni content of 1.53%, 1.72%, 1.81% and 2.06% were measured by DIL805A thermal dilatometer at different cooling rates. Combined with microstructure and Vickers hardness, continuous cooling transformation curves of the steel were obtained. The results show that microstructure of the tested steels is all bainite when the cooling rate is below 0.5 ℃/s, while microstructure is all transformed into martensite as the cooling rate is above 2 ℃/s. With the increase of Ni content, Ac₃ of the tested steel changes little, Ac₁ and Ms decrease, the temperature range of bainite transformation decreases, the cooling rate range of bainite transformation expands, and the morphology of bainite also changes, but the morphology of martensite is almost unchanged.

Key words: Ni content, continuous cooling transformation, marine engineering steel, microstructure, hardness

CLC Number:

TG113.12

Tao Sufen, Wu Hao, Sun Guilin, Chen Long, Chen Bo. Effect of Ni content on continuous cooling transformation curves of EQ70 steel for marine engineering[J]. Heat Treatment of Metals, 2022, 47(1): 100-105.

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