高强度紧固件法兰外圈开裂研究分析

Research and Analysis on Cracking of High-Strength Fastener Flange Outer Rings

摘要

航空、能源、轨道交通领域广泛使用高强度结构连接件，行业对紧固件成形质量、尺寸精度及加工稳定性标准持续提升。国内高强度紧固件产业规模稳步扩张，但高端产品在原料纯净度、热处理均匀性、表面处理及全流程质控方面仍存在明显不足。某厂采用退火拉拔 ML40Cr 钢生产 10.9 级冷镦紧固件时，工件法兰部位近乎全部出现密集斜向 X 形交叉裂纹。通过化学成分、宏观断口与金相组织对比检测分析，证实法兰开裂根源为钢材表层增碳形成球链状珠光体；该组织塑性与冷变形性能较差，冷镦镦粗区域变形量大，应力集中后最终引发批量交叉开裂缺陷。

Abstract

High-strength structural fasteners are widely used in aviation, energy, and rail transportation sectors, with industry standards for fastener forming quality, dimensional accuracy, and processing stability continuously being elevated. Although China’s high-strength fastener industry has experienced steady growth, premium products still exhibit significant shortcomings in raw material purity, heat treatment uniformity, surface treatment, and comprehensive quality control throughout the production process. During the manufacturing of Grade 10.9 cold heading fasteners from annealed drawn ML40Cr steel at a facility, nearly all flange sections developed dense oblique X-shaped cross-cracks. Comparative analysis of chemical composition, macroscopic fracture surfaces, and metallographic structures confirmed that the root cause was carbon-induced pearlitic structure formation with spherical chains on the steel surface; this microstructure exhibits poor plasticity and cold deformation performance, leading to substantial deformation in the cold heading zone and subsequent stress concentration that ultimately resulted in batch-wide cross-cracking defects.

关键词

高强度紧固件 / 法兰开裂 / 增碳

Key words

high-strength fasteners / flange cracking / carbonization

参考文献

[1] 柯炜, 崔贵博, 李建开, 等. 含硼冷镦钢10B33冷镦开裂原因分析[J]. 金属制品, 2024, 50(03):48-51+55.

[2] 王小忠, 朱文凯, 安鹏达, 等. ML40Cr冷镦螺栓法兰外圈表面开裂原因分析[J]. 四川冶金, 2022, 44(02):44-47.

[3] 李为龙, 袁桥军, 周国子. 冷镦螺母横裂纹成因分析[J]. 金属材料与冶金工程, 2021, 49(6):3-7.