日日狠狠久久偷偷色综合0_亚洲日本一线产区和二线_久久久久久精品免费无码无_伊人色综合九久久天天蜜桃

From Germany to introduce an electron beam welder. The elastic properties of spring steel and good cutting ability of the high-speed steel by electron beam welded together. Electron beam welding in a vacuum, the chemical composition of the weld stable and pure, high joint strength, high weld quality.