中空六角钢表面螺旋裂纹的成因

FORMATION OF SCREWY SURFACE CRACKS ON HOLLOW HEXAGONAL DRILL BAR

本文介绍了通过各种试验方法,找出了用“热穿孔—减径—拉轧”工艺生产的中空六角钢表面螺旋裂纹的产生原因。试验结果表明,穿管坯料上存在的原始缺陷是产生螺旋裂纹的内在因素。而减径变形中的扭转变形不但使原始缺陷形成螺旋状,同时还进一步扩展了裂纹。针对上述原因,采取了相应的措施,基本上消除了这种裂纹缺陷。

This palter describes the formation of screwy surface cracks on hollow hexagonal drill steel bar produced by "hot piercing-reduction diameter-drawing-rolling" proce'ss. The study shows that the primary defects on the round billet used for piercing are the sources of screwy surface cracks. The distortion deformation during diameter reduction not only changes the primary defects (such as hair-line seams) into screwy form, but also enlarges the primary cracks. Aiming at the cause mentioned above, some appropriats measures have been adopted and this kind of defects can be basically prevented.