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534539645铁虫 (正式写手)
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[求助]
求大神翻译这一小段，有关超高强度刚热冲压件淬取方面的
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For the reduction in weight and improvement of crash safety for automobiles, hot stamping of quenchable steel sheets is increasingly employed for production ofultra-high strength steel parts. By heating the steel sheets, the forming load is remarkably reduced, the springback is prevented and the formability is improved [1,2]. In addition, the stamped parts are hardened by quenching with dies, and thus the ultra-high strength steel parts having a tensile strength of approximately 1.5 GPa are obtained under a low forming load [3]. In hot stamping, dies are held at the bottom dead centre of a press for about 10 s to harden stamped parts, and thus the productivity of hot stamping is considerably low, 2 and 3 shots per minute (see Fig. 1 ). The martensite transformation does not occur for insufficient holding, i.e. no hardening. The cooling speed of die quenching is lower than that of water quenching due to low heat transfer. In addition, the stamped parts have a non-uniform distribution of thickness, and thus are locally in contact with the dies during holding as shown in Fig. 2. Local thinning tends to occur due to a temperature distribution induced by local contact with dies during stamping [4]. Since the cooling speed of die quenching is influenced by the die pressure [5], large holding force is required to increase the cooling speed during die quenching. It is desirable in forming industry to reduce the holding time at the bottom dead centre because of productivity improvement. In the present study, the productivity and formability in hot stamping of ultra-high strength steel parts were improved by water and die quenching. In addition, blankholding was delayed to improve hardening of a flange portion in hot stamping with water and die quenching |
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2楼2016-06-28 16:33:29