采煤机螺母开裂的失效分析

Failure analysis of shearer nut cracking

利用扫描电镜、直读光谱仪和光学显微镜研究了采煤机螺母的断口形貌、化学成分和微观组织。结果表明:螺母的化学成分对应于40Cr钢,硬度和显微组织均符合相关国家标准的技术要求。裂纹起源处有颗粒状的非金属夹杂物,微观形貌是沿晶断裂和韧性断裂,由于夹杂物在受到外力时候破坏金属基体的连续性,且镀锌过程中螺母吸附了大量氢原子,这些氢原子在晶界处聚集,弱化了晶界之间的结合力,在外力的诱发作用下,形成早期的脆性断裂。针对失效原因进行工艺改进,首先选用特钢材料,其次增加除氢工序;经实际生产验证,采取的改进措施取得满意效果。

Fracture morphology,chemical composition and microstructure of nut were analyzed by SEM,OES and metallographic microscope.The results show that the chemical composition of the nut corresponds to the 40 Cr steel,the hardness and the microstructure match the technical requirements of relerant national standards.The crack originates from granular non-metallic inclusions,and the micro-morphology is intergranular fracture and ductile fracture.Because the inclusions destroy the continuity of the metal matrix when subjected to external force,and a large number of hydrogen atoms are adsorbed on the nut during galvanizing process,which aggregate at the grain boundary,weaken the bonding force between the grain boundaries,and form early brittle fracture under the induction of external force.In view of the causes of failure,process improvement is carried out,firstly,the selection of special steel materials,and secondly,the addition of dehydrogenation process.The actual production verifies that the improvement measures adopted have achieved satisfactory results.