低塑性拔長(zhǎng)時(shí)，應(yīng)注意選擇合適的送進(jìn)比，送進(jìn)比太小時(shí)，變形集中在上下部，中心都鍛不透，并沿軸向產(chǎn)生拉鍛造應(yīng)關(guān)于鍛件的一些基本知識(shí)力，導(dǎo)致內(nèi)部橫向裂紋產(chǎn)生。拔長(zhǎng)拔長(zhǎng)是使坯料的長(zhǎng)度增加，截面減小的鍛造工序，通常用來(lái)生產(chǎn)軸類件毛坯，如車床主軸、連桿等。在鐓粗時(shí)，常用軟襯墊鐓粗或疊鐓（用于鍛薄餅形零件），以改善變形的不均勻性，防止產(chǎn)生表面裂紋。

When low plasticity is pulled out, attention should be paid to selecting suitable delivery ratio, sending too much time, deformation  on the upper and lower parts, and the center can not be built, and forging along the axial direction should be related to some basic knowledge of forging, resulting in the occurrence of internal transverse cracks. In the upsetting, commonly used soft liner (for upsetting or folding upsetting forging thin pancake, uneven parts) to improve the deformation, prevent the generation of cracks on the surface.

機(jī)器鍛造是自由鍛造的主要方法，可鍛造質(zhì)量達(dá)到幾百噸的大型鍛件，這使得自由鍛在重型機(jī)械制造中具有特別重要的作用。在現(xiàn)代工業(yè)生產(chǎn)中，機(jī)器自由鍛已成為鍛造生產(chǎn)的主要方法，在重型機(jī)械制造中，它具有特別重要的作用。例如，水輪機(jī)主軸、多拐曲軸、大型連桿、重要的齒輪零件，在工作時(shí)都承受很大的載荷，常采用自由鍛造方法生產(chǎn)毛坯，使其具有很高的力學(xué)性能.滿足使用要求。

Machine forging is the main method of free forging. It can forge large forgings with a quality of hundreds of t, which makes free forging play a very role in heavy machinery manufacturing. For example, the main shaft of a hydraulic turbine, a multi crank crankshaft, a large connecting rod, and important gear parts are subjected to heavy loads when they are working. Free forging is often used to produce blanks, so that they have high mechanical properties.

二十世紀(jì)60年代以后，鍛造機(jī)械改變了從19世紀(jì)開始的，向重型和大型方向發(fā)展的趨勢(shì)，轉(zhuǎn)而向高速、、自動(dòng)、精密、專用、多品種生產(chǎn)等方向發(fā)展。

After 60s twentieth Century, forging machinery changed the trend from nineteenth Century to heavy and large direction, and turned to high speed, high efficiency, automatic, precision, special, multi variety production.

鐓粗主要有以下形式：

完全鐓粗。完全鐓粗是將坯料豎直放在砧面上， 在上砧的錘擊下， 使坯料產(chǎn)生高度減小，橫截面積增大的塑性變形。

Upsetting mainly includes the following forms:

Full upsetting. Complete upsetting is to place the blank vertically on the anvil surface, hammering on the anvil, so that the height of the blank decreases, the cross-sectional area increases plastic deformation.