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某机器上有个形机匣,在两侧壁上有两个方孔,中间压配6×6×60毫米的一个销钉,部件在总装前要经发兰处理,生产中发现大部分销钉在发兰后出现裂纹,有的稍加负载便脆断,不符合设计要求。 该销钉系用30CrMnMoTiA钢方条,机加工后经860℃淬火,220℃回火处理,磨成6×6毫米断面及一定公差要求,装配时紧配压入形机匣方孔,然后整个部件经200℃半小时去应力退火,再发兰,清洗总装。 销钉在未装配前都经检验无裂纹,在发兰后总装过程中观察到有的出现裂纹,裂纹都在销钉一侧,靠近销钉中间部位出现1～3条,深浅不一,裂纹走向弯曲,但趋向与销钉长轴垂直,最深的几道贯通销钉整个断面。
There is a machine on a machine casing, two square holes on both sides of the wall, the middle pressure with a 6 × 6 × 60 mm pin, the assembly before the hair to deal with the assembly, the production found most of the pin Crack after the hair blue, some brittle load will be broken, does not meet the design requirements. The pin is 30CrMnMoTiA steel bar, after machining by 860 ℃ quenching, 220 ℃ tempering, ground into 6 × 6 mm section and some tolerance requirements, the assembly tight-fitting press-shaped casing square hole, and then the entire component After 200 ℃ to half an hour to stress annealing, then hair blue, cleaning assembly. The pins were tested without cracks before assembly. Cracks were observed in the assembly process after the hair extensions were made. One or three cracks appeared on the side of the pins near the middle of the pins, varying in depth. The cracks tended to bend, But the trend and the long axis perpendicular to the pin, the deepest of the pin through the entire cross-section.