摘要
部分表面渗锌双头螺栓在安装过程中断裂。通过对断裂螺栓、同批螺栓及调质处理后待加工的同批棒料进行理化检验,发现断裂螺栓所用材料为45Cr钢,而非规定的40Cr钢;材料中硅酸盐夹杂多且呈块状集中分布;在螺栓纵、横面有多处显微缩孔,显微组织出现半网状铁素体和针状铁素体,同时材料强度和硬度值偏高,而塑性和韧性值偏低;断裂螺栓断口及高倍金相检查均发现有明显腐蚀产物及腐蚀特征。分析认为,腐蚀造成组织间结合力降低是螺栓断裂的主要原因,调质处理工艺不当,材料冶金缺陷是造成螺栓断裂的次要原因。提出了相应的改进及预防建议。
The full-scale physical testing and chemical analysis was done in details on the fracture bolt, the thread of bolts, and the thread of bars which need be manufactured after quenching and tempering treatment. The results show that the material of the bolts is made of 45Cr steel, but not of 40Cr steel that is planned; and it includes a lot of silicate inclusion in block-concentric distribution. The examination on the bolts′surface from vertical to horizontal found that there are some microholes, while the microstructure has azimuth tempering sorbite, and half-reticulated ferrite is precipitated in some grain boundaries of surface layer′s structure, even some needle-like ferrite is in the central structure. Strength, hardness increased slightly, whereas the plasticity decreased slightly. It is found that there are a lot of corrosion products by microstructure examination. It is thought that corrosion is the main reson of bolt fracture that cause the strength of microstructure boundary decreased. Unperfect quenching and tempering were the most important reason to cause fracture, and also the metallurgical defects. So some improvement and suggestion were also proposed in this paper.
出处
《理化检验（物理分册）》
CAS
2003年第9期481-484,共4页
Physical Testing and Chemical Analysis(Part A:Physical Testing)
