Recently, the Shanxi Provincial Quality Supervision Bureau issued the results of the quality supervision and inspection of high-strength bolts. This time, a total of 15 batches produced by one company in the province and 14 batches produced by the provincial enterprises distributed in the Taiyuan market, totaled 15 The quality of the high-strength bolts of the batches was supervised and spot-checked, and 13 batches were qualified. The detection rate of unqualified products was 13.3%.
It is understood that the main quality problems found in this spot check are the wedge load test of individual products, the large diameter of the thread and the hardness do not meet the standard requirements. Wedge load is a key item to evaluate the mechanical properties of the product under tensile load. It is especially important for high-strength fasteners. If this indicator does not meet the requirements, plastic deformation may occur due to pre-tightening force and working load. Thereby reducing the pre-tightening force and loosening the connection; the hardness is also an important indicator for evaluating the mechanical properties of the fastener. The materials used for the products of different performance grades are different, and the mechanical performance grade is an important basis when the fastener is selected. And in use, the working load and installation torque should be determined according to the performance level. For a specific material, the hardness should be controlled at a reasonable level. If the hardness is not up to standard, the quality of the fastener will be affected. If the large diameter of the thread is unqualified, it will affect the component. Assembly use.
In this spot check, the M16×70-8.8S XRN brand high-strength bolt produced by the Ningbo Yinzhou Sanduo Fastener Co., Ltd., which is distributed by Xuyuan Hardware Operation Department of Xinghualing District, Taiyuan City, has a wedge load test. Does not meet the standard requirements. M20×90-10.9S S brand high-strength bolt produced by Ningbo Zhenhai High-strength Fastener Industrial Co., Ltd., which is distributed by Xindayu Standard Parts Processing Department of Xinghualing District, Taiyuan City. Its thread diameter, hardness and wedge The load test did not meet the standard requirements.
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