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2.9 反向挤压尽管正向挤压机目前仍然是最常用的设备,而近来发现反向挤压有一些特殊用途,对于挤压硬铝合金和大批量生产的易切削黄铜合金,反向挤压是比较受欢迎的。反向挤压的部分优点是挤压时需要加的载荷较小,金属流动比较均匀,因为铸锭和挤压筒之间不存在相对运动——没有因摩擦而产生的热量。其主要优点是: (a)与正向挤压相比较,挤压力减少25～30％。 (b)利用现有的较大挤压力时,可以挤压较小截面的制品或者可以降低坯锭的挤压温度,允许使用较高的挤压速度。 (c)挤压力不是坯锭长度的函数。因为
2.9 Reverse Extrusion Although forward extrusion presses are still the most commonly used equipment and reverse-extrusion has recently been found to have some special uses, for extruded hard-alloy and ready-to-cut brass alloys in mass production, the reverse Extrusion is more popular. Part of the advantages of reverse extrusion is the need to add a smaller extrusion load, metal flow is more uniform, because there is no relative movement between the ingot and extrusion cylinder - there is no heat generated due to friction. The main advantages are: (a) The squeezing force is reduced by 25 to 30% compared to the normal extrusion. (b) With the existing large pressing force, it is possible to extrude the product of a smaller cross-section or to lower the extrusion temperature of the billet, allowing the use of a higher extrusion speed. (c) The pressing force is not a function of the length of the billet. because