采用外观和金相检验等方法对牙钳表面裂纹进行了分析。结果表明,该批牙钳的坯料在非控温的油炉中加热时间过长且加热温度又过高,在坯料表面出现了严重过烧及在其内部出现了严重过热。当锻件退火后进行鳃孔扩口和柄部弧形弯曲时,过热和过烧的缺陷引起表面浅层裂纹和龟裂。

Surface crack on teethclamp was studied by means of macroscopic and metallographic examination. The results showed the teethclamp was forged in oilfurnace,heating temperature was not controlled and heating-time was too long,forging-temperature was too high,so the surface had appeared over-burnt and the inside of teethclamp was severely over-heating. When gillhole was enlarged and handlearc was formed after annealed,the surface shallow crack and chap appeared.