目前,大多数锻造、模锻水压机都采用三梁四柱式结构。四根立柱分别用大螺帽与上、下横梁固定在一起,组成一个封闭框架。为了使其具有较大的刚性,大螺帽必须进行预紧。立柱螺旧的预紧对于水压机的正常工作十分重要。在一般情况下,实际预紧应力应当大于工作应力。这样,水压机工作时螺帽和横梁之间始终存在着一定的压力,使框架保持为一个整体。如果预紧应力小于工作应力,锻压时 At present, most forging, forging hydraulic presses are used three-beam four-column structure. Four studs, respectively, with a large nut and the upper and lower beams fixed together to form a closed frame. In order to make it more rigid, large nuts must be preloaded. The pre-tensioning of the studs is very important for the normal operation of the hydraulic press. Under normal circumstances, the actual pre-stress should be greater than the working stress. In this way, there is always a certain pressure between the nut and the beam when the hydraulic press is working, and the frame is maintained as a whole. If the pre-stress is less than the working stress, when forging