轴箱拉杆紧固螺栓(见图1)是电力机车上紧固轴箱用的重要零件,工作时承受较大的拉力和振动,故要求零件有较高的强度和韧性,零件按GB30—76要求,机械性能为GB38—76的5.9级(见表1)。此螺栓原采用外购标准件,是用冷拔钢镦头滚丝成形的,能满足性能要求,经试验螺栓的最大拉力为16.8T。现我厂自制此种螺栓,采用20钢热锻、机械加工后滚丝。由于强度不够,在用风板机紧固装配时,螺栓丝扣断裂滑扣不能使用。对自制螺栓试验其最大拉力仅12.87T(平均值),低于外购标准件。为了提高材料的强度,我们对螺栓采用了低碳马氏体强韧化工艺,取得了较好的效果。试验材料为20钢,含碳量为0.18％,淬 Axle box tie rod fastening bolts (see Figure 1) is an important part of electric locomotive fastening axle box, work to withstand greater tension and vibration, it requires parts with higher strength and toughness, the parts according to GB30-76 Requirements, the mechanical properties of GB38-76 of 5.9 (see Table 1). The original bolt purchased standard parts, is the use of cold-drawn steel heading roll forming, to meet the performance requirements, the maximum tensile force of the test bolt is 16.8T. I plant this kind of self-made bolts, using 20 steel hot forging, rolling after machining. As the strength is not enough, when the wind plate machine fastening assembly, the bolt threaded rupture slider can not be used. For the self-made bolt test, the maximum pulling force is only 12.87T (average value), lower than purchased standard parts. In order to improve the strength of the material, we adopted a low-carbon martensite toughening process for bolts, and achieved good results. The test material is 20 steel, carbon content of 0.18%, quenching