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虫号: 3591830
注册: 2014-12-12
性别: GG
专业: 金属功能材料

[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

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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