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| EFFECT OF HOT WORKING CONDITIONS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CARBON STEELS |
| CHANG TSO-MEI;LI CHIEN-HWA Institute of Mechanical Engineering; Academia Sinica |
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Cite this article:
CHANG TSO-MEI;LI CHIEN-HWA Institute of Mechanical Engineering; Academia Sinica. EFFECT OF HOT WORKING CONDITIONS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CARBON STEELS. Acta Metall Sin, 1959, 4(2): 143-154.
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Abstract A study has been made on the effects of hot working conditions on the austenitic grainsize and mechanical properties of carbon steels. At the same time, the cumulative effect ofsuccessive reductions and the effect of austenitic grain size on such hot working characteristics asplasticity, resistance to deformation and the impact values have also been investigated. Thefollowing are the results obtained. Specimens having coarse austenitic grain size, besides the general tendency of giving greatergrain size with the increase in cooling speed, also give nonuniform long grains, banded structuresand widmanstatten structures. Specimens having higher carbon contents (0.66％C) give sorbitic,pearlitic and ferritic structures with different cooling speeds. With the increase in the austenitic grain size, there is a notable lowering in the yield pointand the impact values at—20℃. Tensile tests with specimens having the same austenitic grainsize show that the cooling speed after rolling has little effect on the reduction in area, but withthe increase in cooling speed there is a raise in the yield point, the ultimate strength and theimpact values at room temperature and at—20℃. When steels with different carbon contents are rolled at 1050℃, there appears a criticalreduction range between 0 and 10％, in which the austenitic grains become coarse. However,under the same hot working conditions and within the same critical reduction range, there is alarge difference in the largest grain size obtained with different carbon steels. The soaking timehas also different effects on different steels. In all steels investigated, there is a marked cumulative effect of reduction, but the reductionin the last hot working operation has the greatest effect on the austenitic grain size. Hence it isimportant to avoid critical reduction in the last rolling pass. Specimens from carbon steels having No. 0 and No. 8 grain sizes respectively show littledifference in their hot working characteristics: at 900℃, the difference in impact values betweenthese two specimens amounts only to 8％, the difference in the resistance to deformation to 3％and the difference in the critical reduction in height at fracture in the impact compression testamounts only to 2％.
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Received: 18 February 1959
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[1] 张作梅、李建华,钢三中板机械性能的研究。金属学报,第1卷第1期,1956,87--126页.
[2] 张作梅、徐有容、高子明、郭胜泉,球墨铸跌的可塑性的研究,金属学报,第1卷第2期,1956,165--188页.F |
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