拟定下图所示轴的加工工艺路线。已知毛坯为45钢f38×126，大批量生产。<br /> <img src="https://nimg.ppkao.com/2018-08/wenxueying/2018082911422550675.jpg?sign=191c7a2717942f845a3283a91a47af96&t=62d50367" />