外文翻譯---模具成型軋制(更新版)
【正文】 erial to flow out through a suitable opening, called a die. In this process, only the shapes with constant crosssections (die outlet crosssection) can be produced.Advantages and Disadvantages of Hot and Cold Forming Now that we have covered the various types of metal working operations, it would only be appropriate that we provide an overall evaluation of the hot and cold working processes. Such a discussion will help in choosing the proper working conditions for a given situation. During hot working, a proper control of the grain size is possible since active grain growth takes place in the range of the working temperature. As a result, there is no strain hardening, and therefore there is no need of expensive and timeconsuming intermediate annealing. Of course, strain hardening is advisable during some operations (viz., drawing) to achieve an improved strength。材料的流動應(yīng)力在再結(jié)晶溫度之上或之下全然不同。軋制在這一工藝中，通過一個調(diào)整過的位于兩個動力驅(qū)動的軋輥之間的孔利用摩擦來拉伸工件。金屬薄板被放在磨具上利用一個坯料壓板來避免產(chǎn)品缺陷。在熱加工過程中，因為活躍晶粒在加工溫度范圍內(nèi)會生長，就有可能適當(dāng)控制晶粒尺寸。冷加工的主要優(yōu)點是經(jīng)濟、操作更為迅速、容易，因為無須安排額外的加熱和處理。此外，晶粒流動方向的控制增加了產(chǎn)品的強度特性。當(dāng)然，在一些操作（如拉延）中應(yīng)變硬化是可取的，可以提高強度；在這些情況下，熱加工幾乎沒有優(yōu)勢。這道工藝由一套設(shè)計適當(dāng)?shù)耐鼓：桶寄硗瓿?。這是一種很有用途的工藝，用于生產(chǎn)金屬薄板和各種常用端面，如鐵軌、槽鋼、角鋼和圓鋼。這一點很重要，因為大的冷作硬化會使材料變脆。在此工藝中引起的應(yīng)力大于材料的屈服強度，但小于材料的斷裂強度。此外，一部分輸入的能量在通過應(yīng)變硬化提高產(chǎn)品的強度上得到了卓有成效的利用。此外，熱變形降低了材料的強度，結(jié)果甚至可以使用具有一定容量的機器加工很大尺寸的產(chǎn)品。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。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。此外，對于大多數(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
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