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棒料剪切工艺是多工位冷镦机的第1步工序,坯料的断面质量对后续挤压工序有着重要影响。研究径向不夹紧条件下的棒料剪切工艺,将棒料剪切分为4个过程:初始阶段、棒料倾斜、弹塑性变形和裂纹产生及扩展,分析了每个过程的特点。以20Cr为试验材料,在剪切速度分别为200,400,600和800 mm·s~(-1)的条件下进行棒料剪切试验。定性分析各剪切速度条件下的坯料端断面和棒料端断面的断面形貌,发现随着剪切速度的增大,坯料端光亮带比例逐渐减小,棒料端断面不平度明显减小;定量比较各剪切速度条件下的坯料端断面和棒料端断面的椭圆度与断面倾角,发现随着剪切速度的增大,断面椭圆度逐渐减小,棒料端断面倾角基本不变。
Bar cutting process is a multi-station cold heading machine step 1 process, the blank section of the quality of the follow-up extrusion process has an important impact. In this paper, we study the bar shear process under the condition of radial non-clamping, and divide the bar shear into four processes: the initial stage, the slab inclination, elastoplastic deformation and the generation and propagation of cracks, and analyze the characteristics of each process. Using 20Cr as the test material, the shear tests of the bar were carried out under the shear velocities of 200, 400, 600 and 800 mm · s ~ (-1) respectively. Qualitative analysis of the billet end and billet cross-section profiles at each shear rate found that with the increase of the shear rate, the proportion of bright bands on the billet side gradually decreased and the unevenness of the bar end decreased significantly The ellipticity and cross-section inclination of the billet end and the bar end are quantitatively compared under different shear rates. It is found that the ellipticity decreases with the increase of the shear rate, .