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研究了一种用水平连铸技术生产的球墨铸铁型材的扭转强度和缺口扭转强度。实验发现光滑扭转试样是沿４５°方向开裂，开裂面是最大拉应力面，表现为典型的脆性断裂。缺口试样的断裂模式分两种情况：当为钝缺口时（即（ρ≥０．７５ｍｍ，Ｋｔ≤１．６），其断裂特征与光滑试件相同；而当为尖锐缺口时（即ρ＜０．３７５ｍｍ，Ｋｔ＞２．１）的开裂出现在缺口根部，并且开裂面垂直于轴线方向，是剪应力作用。实验结果还表现出扭转缺口强度与应力集中系数的关系，即应力集中系数越大，扭转缺口强度反而越高。该球墨铸铁的缺口敏感性（ＮＳＲ）大于１，故缺口完全不敏感。
The torsional strength and notched torsion strength of a nodular cast iron profile produced by horizontal continuous casting were investigated. It was found that the smooth and torsion specimen was cracked in the direction of 45 ° and the crack surface was the maximum tensile stress surface, showing the typical brittle fracture. The fracture mode of the notched specimen is divided into two cases: when it is a blunt notch (ie, (ρ≥0.75mm, Kt≤1.6), the fracture characteristics of the notched specimen are the same as that of a smooth specimen; and when it is a sharp notch <0.375mm, Kt> 2.1) appears in the notch root, and the cracking plane is perpendicular to the axial direction, which is the effect of shear stress.The experimental results also show the relationship between the strength of the torsional notch and the stress concentration factor, that is, the stress concentration factor The larger the torsional notch strength, the higher the notch sensitivity (NSR) of the ductile iron is greater than 1, so the notch is completely insensitive.