在考慮鍛造工藝時(shí)特別是后一火的鍛造時(shí)，應(yīng)盡量避免在臨界變形程度下進(jìn)行，以免得到粗大晶粒組織。具體來說，高溫下金屬塑性好，變形抗力小，應(yīng)采用遠(yuǎn)大于臨界變形程度的較大變形量鍛造；低溫修正時(shí)采用低于臨界變形程度的小變形量進(jìn)行局部修整。

When the forging process is cidered, especially when the last fire is forged, the critical deformation should be avoided as far as , so as to avoid coarse grain structure. Concretely speaking, high temperature metal has good plasticity and small deformation resistance. We should adopt large deformation amount forging far greater than critical deformation degree. When low temperature correction is used, small deformation below critical deformation degree should be used for local trimming.

碾環(huán)是指通過專用設(shè)備碾環(huán)機(jī)生產(chǎn)不同直徑的環(huán)形零件，主要用來生產(chǎn)汽車輪轂、火車車輪等輪形零件。特種鍛造包括輥鍛、楔橫軋、徑向鍛造、液態(tài)模鍛等鍛造方式，這些方式都比較適用于生產(chǎn)特殊形狀的零件。

Roller ring refers to the production of circular parts with different diameters through the roller ring machine of special equipment, which is mainly used to produce wheel hub, train wheel and other wheel shaped parts. Special forgings include roll forging, cross wedge rolling, radial forging, liquid forging and so on. These methods are suitable for producing parts with special shape.

隨著電動(dòng)機(jī)的發(fā)明，十九世紀(jì)末出現(xiàn)了以電為動(dòng)力的機(jī)械壓力機(jī)和空氣錘，并獲得迅速發(fā)展。生產(chǎn)中使用的鍛錘有空氣錘和蒸汽-空氣錘，有些廠還使用結(jié)構(gòu)簡單，投資少的彈簧錘、夾板錘、杠桿錘和鋼絲錘等。第二次以來，七十五萬千牛的模鍛水壓機(jī)、一千五百千焦的對(duì)六萬千牛的板料沖壓壓力機(jī)、十六萬千牛的熱模鍛壓力機(jī)等重型鍛壓機(jī)械，和一些自動(dòng)冷鐓機(jī)相繼問世，形成了門類齊全的鍛造機(jī)械體系。

With the invention of motor, the mechanical press and air hammer powered by electricity appeared at the end of nineteenth Century, and developed rapidly. Since the Second World War, the forging water press, one thousand and five hundred thousand char, the punching press of Liu Wanqian cattle, the hot forging press of sixteen thousand thousand cattle, and some automatic cold heading machines have come out in succession, forming a complete system of forging machinery.