材料期刊网

滚压加工螺纹可以获得更高的螺纹强度、精度,其在加工效率和环保性方面的优越性不容忽视.同时,滚压加工可以解决某些工艺方法不能解决的问题,如对特大型缸体的加工,可以达到减少机床和夹具、提高工件加工精度、缩短加工周期和节约作业面积的效果.为此,本文采用一种四滚丝轮车床滚压加工得到了304不锈钢管圆锥外螺纹.通过金相分析、扫描电镜、显微硬度计和万能试验机等手段,研究了304不锈钢管滚压成形圆锥外螺纹的组织及性能,并与传统的套丝管螺纹进行对比.研究结果表明,套丝加工的管螺纹,齿表层出现孔洞、金属组织被切断,其内部显微组织仍是原有的等轴晶,齿形不完整;而滚压加工使得螺纹表层组织细化,形成了沿螺纹齿形连续分布的纤维组织.套丝加工后304钢管螺纹硬度有所提高,但幅度不大;与套丝加工相比,滚压加工后304钢管螺纹的抗剪拉力和硬度均有大幅提高.

Rolling processing is effective to get higher strength and precision of thread, which shows superiorities in processing efficiency and environmental protection. Besides, rolling processing can handle the oversize cylinder which cannot be processed by the traditional technology, and the rolling processing possesses outstanding advantages in reducing machine and fixture tools, improving the machining accuracy of workpieces, shorting machining period and saving operating area. In this work, the tapered external thread was obtained by rolling 304 stainless steel tube using a four-wheel rolling lathe. By metallographic analysis, scanning electron microscopy ( SEM) , micro-hardness tester and universal testing machine, the microstructures and properties of external taper screw thread of 304 stainless steel tube were investigated, and the thread obtained by traditional cutting thread was also studied for comparison. The results show that, for the pipe thread obtained by cutting process, the holes appear on the surface of the pipe thread's tooth accompanying with the destruction of metal microstructure, and the original isometric crystal is still remained as well as the incomplete tooth shape for the thread. However, for the pipe thread obtained by the rolling process, continuous distributing fibrous tissue along the screw thread teeth, which is related to the refined surface microstructures, can be observed. The hardness of 304 steel pipe threads is improved after cutting process with a very small increase. Compared with the thread obtained by cutting process, the shear strain and hardness of 304 steel pipe thread has been increased significantly after rolling process.