Effect of Online-Cooling on Microstructure and Mechanical Properties of Hot-Rolled L360 Steel Pipe

doi:10.12068/j.issn.1005-3026.2018.11.014

Abstract

Abstract: In the view of the hot-rolled seamless steel pipe problems which lacks the way to control microstructure and mechanical properties， depends on the addition of alloying element excessively and uses an off-line heat treatment， an online cooling after rolling treatment is used to replace off-line treatment by means of the plate rolling instead of tube rolling. The effects of different cooling strategy on the microstructure and mechanical properties of a typical hot-rolled L360 steel pipe is studied. The results show that compared with air cooling treatment which easily causes a coarse Widmanstatten structure in L360 steel， the cooling after rolling treatment can promote the precipitation of microalloying elements， refine Widmanstatten structure and improve mechanical properties of the steel. When cooling temperature is controlled at 650℃， the formation of Widmansatten structure is reduced effectively and the balance of strength， toughness and plasticity of L360 steel can be achieved with the yield strength of 478MPa， the tensile strength of 641MPa， the elongation of 25.3%， the yield ratio of 0.74 and the impact energy at 0℃ of 164J， respectively， which meet the requirements of the standard of API SPEC 5L—2012.

Key words: hot-rolled L360 steel pipe, Widmanstatten structure, microstructure, mechanical property

CLC Number:

TG142.2

LI Zhen-lei， CHEN Dong， KANG Jian， YUAN Guo. Effect of Online-Cooling on Microstructure and Mechanical Properties of Hot-Rolled L360 Steel Pipe[J]. Journal of Northeastern University Natural Science, 2018, 39(11): 1588-1592.

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