为了解决传统U型钢拉杆存在的生产工艺落后、加工周期长、材料利用率低等问题，提出一体式钢拉杆成形工艺。以35型钢拉杆U型头预制坯的成形为研究对象，设计了3道次加热镦粗方法，采用DEFORM-3D有限元软件分析了不同工艺条件下镦粗后温度场、应力场的模拟结果，探讨了成形效果较佳的热成形工艺参数，并通过实验验证成形的可行性。结果表明，各道次较佳的热成形工艺参数如下：第1道次始锻温度为1 150 ℃、冲头速度为20 mm/s，第2道次始锻温度为1 150 ℃、冲头速度为30 mm/s，第3道次始锻温度为1 100 ℃、冲头速度为20 mm/s；在该热成形工艺参数下，各道次的成形力分别为1 520，2 090，5 290 kN，各道次的胀模力分别为5 870，6 710，8 830 kN；镦粗后金属流线分布合理，没有出现交叉、折叠等现象，成形效果较好。采用3道次热镦粗方法制备预制坯，制件内部的等效应力分布都比较均匀，可以形成质量良好的制件，研究结果可为35型钢拉杆U型头预制坯的镦粗聚料工艺设计以及设备选择提供参考。
In order to solve the problems of backward production technology, long processing cycle and low material utilization rate in traditional U-shaped steel tie rods, an integrated steel tie rod forming process was proposed. Taking the preform forming of 35 steel tie rod U-shaped head as the research object, a three-pass heating upsetting method was designed. The DEFORM-3D finite element software was used to analyze the simulation results of the temperature field and stress field after upsetting under different process conditions. The hot forming process parameters with better forming effect were discussed, and the feasibility of forming was verified through experiments. The results show that the optimum hot forming process parameters of each pass are as follows: the initial forging temperature of the first pass is 1 150 ℃, while the punch speed is 20 mm/s; the initial forging temperature of the second pass is 1 150 ℃, while the punch speed is 30 mm /s; the initial forging temperature of the third pass is 1 100 ℃, while the punch speed is 20 mm/s. Under the hot forming process parameters, the forming forces of each pass are 1 520, 2 090, 5 290 kN, and the expansion forces of each pass are 5 870, 6 710, 8 830 kN, respectively. After upsetting, the metal streamline distribution is reasonable, there is no crossover and folding phenomenon, and the forming effect is good. The equivalent stress distribution inside the part is relatively uniform while preparing the preform in the three-pass hot upsetting method, which can form a good quality part. It provides a certain reference for the upsetting aggregate process design and equipment selection of the U-shaped head perform of 35 steel tie rod.