Mechanical Properties and Machinability of a High Strength Medium Carbon, Microalloyed Steel
Abstract:
The development of a high-strength (tensile strength beyond 900 N/mm2), medium-carbon, vanadium microalloyed steel for hot-forged automotive components has been reviewed in the paper.
The influence of different alloying elements was investigated. The most effective elements to increase the strength were chromium and manganese. In TEM investigation, it was found that, in comparison with the lower-strength melt, chromium plus manganese alloyed steel showed a high density of small V(C, N) precipitates. Mechanical properties were studied in tensile, impact, fatigue, and fracture mechanics tests. Most mechanical properties of the microalloyed and quenched and tempered steel were essentially equal. Exceptions were the lower impact strength and higher fatigue strength of the microalloyed steel. Possibilities to improve the impact strength of the microalloyed steel are being considered. Machinability was tested in different operations. Generally, the machinability of the high-strength microalloyed steel was comparable with quenched and tempered steels. However, a different behavior was found in deephole drilling. The use of calcium treatment to improve the machinability is discussed.
The high-strength microalloyed grade developed can substitute for alloyed quenched and tempered steels in most components. When weight saving is desired, the possibility of substituting the high-strength grade for lower-strength microalloyed steels is considered.
Keywords:
vanadium, microalloyed, medium carbon steel.
Author:
V. Ollilainen, H. Hurmola, H. Pontinen
Affiiation
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Source:
Vanadium Structural Steels - Reprint of papers on vanadium steel from the proceedings of “ASM HSLA Steels Technology and Applications Conference, Philadelphia, USA, Oct., 1983, pp.199-212
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