外文翻譯---模具成型軋制-預(yù)覽頁
【正文】 also be worked upon by the hot working operation. It should, however, be remembered that there are certain materials (viz., steels containing sulphur ) which bee more brittle at elevated temperatures. When a very accurate dimensional control is required, hot working is not advised because of shrinkage and loss of surface metal due to scaling. Moreover, surface finish is poor due to oxide formation and scaling. The major advantages of cold working are that it is economical, quicker, and easier to handle because here no extra arrangements for heating and handling are necessary. Further, the mechanical properties normally get improved during the process due to strain hardening. What is more, the control of grain flow directions adds to the strength characteristics of the product. However, apart from other limitations of cold working (viz., difficulty with high strength and brittle materials and large product sizes), the inability of the process to prevent the significant reduction brought about in corrosion resistance is an undesirable feature. 成形成形可以定義為一種通過材料的塑性變形獲得所需尺寸和形狀的工藝。此外，一部分輸入的能量在通過應(yīng)變硬化提高產(chǎn)品的強(qiáng)度上得到了卓有成效的利用。在熱加工過程中，可以產(chǎn)生大的塑性變形而無大的冷作硬化。此外，熱變形降低了材料的強(qiáng)度，結(jié)果甚至可以使用具有一定容量的機(jī)器加工很大尺寸的產(chǎn)品。產(chǎn)品的形狀和尺寸由軋輥及其輪廓之間的間隙來決定。拉延在這一工藝中，金屬絲的截面或者是條鋼或鋼管的 截面由于工件被拉過磨具的錐形孔而減小。彎曲如其名所示，這是一道塑性彎曲一塊金屬薄板以獲得所需形狀的工藝。在這一工藝中，只有具有固定截面（磨具出口截面）的形狀可以制造。于是沒有冷作硬化，因此無須昂貴耗時(shí)的中間退火。此外，對(duì)于大多數(shù)材料來說，延展性隨溫度而增大，因此易碎的材料也可采用熱加工工序來加工。另外，在加工過程中由于冷作硬化，機(jī)械特性通常
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