【摘要】 45钢零件盐浴加热淬火常出现黑班软点。本文通过试验及光学和电子金相分析发现黑斑表层有深度0.3毫米左右的贝氏体组织,其余部分是马氏体组织,所以黑斑处硬度低。试验证实黑斑不是腐蚀痕。笔者认为黑斑软点是淬火加热时零件出炉瞬间盐浴中某些粘稠悬浮物附着在零件表面,使淬火冷却时冷速降低而形成“逆淬”现象。黑班是附着痕更多还原

【Abstract】 The dark,soft spots on the surface of parts made of steel NO 45 often occur when heating in the salt bath furnace and quenching.By testing and optical and electronic metallographyanalysis,we’re found that the surface of the dark spots is composed of bainite with a depth of about 0.3 mm,the other area martensite,so the dark Spots have low hardness.The test proves that the dark,soft spots are not corrosion spots.The authors consider that the dark spots are the adhering spots.Because some viscous suspensions in salt bath adhere to the surface of the parts at the time just before quenching and decrease the cooling speed of the adhering spots when quenching,the dark,soft spots come out onto the surface of the parts.The“reverse quenching”phenomenon is formed.更多还原