Transactions of Materials and Heat Treatment

Title：Effect of trace elements on fatigue strength of connecting rods for large marine diesel engine

Authors： Sun Changfen Xu Jiuhai Yuan Zhiqiang

Unit： Hudong Heavy Machinery Co Ltd

KeyWords： trace element connecting rod of diesel engine S30Mn steel fatigue strength CCT diagram

ClassificationCode：TG316.2

year,vol(issue):pagenumber：2020,45(12):203-206

Abstract：

The problems of uneven grain size and low fatigue strength in the center of heavy forgings were solved, and the internal quality of forgings met the design requirements by adjusting the trace elements of Cr, Ni，Si etc., reducing the final forging temperature and increasing the center deformation. To determine the material parameters accurately, the S30Mn steels with different chemical compositions were compared by Gleeble thermal simulator, the critical transition temperature under the heating condition and the phase transition temperature under different cooling rates were measured, and the CCT diagram was drawn. The strengthening mechanism of the trace element in S30Mn steel was studied, the trace elements of Cr, Ni, Si could be solid soluted in the matrix-structure more effectively to delay the transforming temperature of γ phase to pearlite by 40 ℃, the γ phase could still transform to pearlite effectively at a low cooling speed of 005 ℃·s-1, the lamella distances of pearlite turned thin, and the grain size refined more. The results show that after adjusting the trace elements and optimizing forging process, the mechanical properties, core grain size and fatigue strength of products are improved significantly.

Funds：

工信部船用低速柴油机原理样机研制资助（CDGC01-KT0103）

孙常奋（1965-），男，工程硕士，高级工程师 E-mail：dt_SUN@126com

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