Transactions of Materials and Heat Treatment

Title：Study on delayed cracking mechanism for ultra-high strength steel of 1000 MPa grade

Authors： Wang Rongchun1 2 Fu Liming2 Wang Xueshuang3 Cao Baoshan4 Gong Xun5

Unit： 1. Materials Engineering Department Bohai Shipbuilding Vocational College 2. School of Materials Science and Engineering Shanghai Jiao Tong University 3. China FAW Group Corporation 4. Liaoning Shunda Machinery Manufacturing (Group) Co. Ltd. 5. People′s Government of Longgang District Huludao City

KeyWords： ultra-high strength steel delayed cracking hydrogen permeation threshold stress hydrogen concentration

ClassificationCode：TG111.91

year,vol(issue):pagenumber：2023,48(8):238-242

Abstract：

The hydrogen-induced delayed cracking properties for three kinds of ultra-high strength steels of 1000 MPa grade were studied by U-shaped bending test, dynamic hydrogen filling and constant load test and hydrogen permeation test. The results of U-shaped bending test and dynamic hydrogen filling and constant load test show that the hydrogen-induced delayed cracking sensitivity of the three test steels from high to low is B steel > A steel > C steel, respectively. The results of hydrogen permeation test show that the hydrogen apparent diffusion coefficients of the three test steels from low to high is B steel > A steel > C steel, respectively. The delayed cracking mechanism of the three ultra-high strength steels of 1000 MPa grade is as follows: with the increasing of steel strength, the hydrogen trap concentration in the steel increases, and the hydrogen apparent diffusion coefficient of the steel decreases. At the same time, with the change of hydrogen concentration in the environment, the hydrogen concentration in the steel is bound to increase. Once the hydrogen concentration reaches the critical hydrogen concentration C0 for delayed cracking, the hydrogen-induced delayed cracking appears in the test steel. Two important factors affecting the delayed cracking of ultra-high strength steel are the hydrogen trap concentration in the steel and the hydrogen concentration in the environment.

Funds：

辽宁省教育厅2021年度科学研究经费项目（LJKZ1277）

作者简介：万荣春（1981-），男，博士，教授,E-mail：springs111@163.com

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