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一、磨削烧伤的本质磨削烧伤是淬火处理后的钢材在磨削加工中一种常见的缺陷。磨削烧伤可分为三种类型:裂纹、二次淬火烧伤及回火烧伤。其中尤以回火烧伤为常见。众所周知,钢材磨削时,磨削接触区的温度是很高的,例如磨削区表层最高温度可达1000℃。由于温度升高,必然引起钢材表层组织的变化。当温度超过相变温度时,珠光体向奥氏体转变,随后就被钢材心部较冷的基体淬硬,得到淬火马氏体,这就形成钢材表层的二次淬火烧伤。即使温度在相变温度以下,也会使回火马氏体向屈氏体或者索氏体转变,使表层软化,就形成回火烧伤。必须指出,磨削区内瞬间高温是形成变质层(指发生组织变化的表层)的主要条件,但是,它不同于一般热处理加热,除服从一般钢材的加热组织变化规律外,有其自身的特点。首先,它需要更大的过热温度,其次,它的组织转变是不充分的。
First, the essence of grinding burns Burning is quenched steel after grinding in a common defect. Grinding burns can be divided into three types: cracks, secondary quenching and tempering burns. Among them, tempering burns are common. As we all know, grinding steel, grinding contact zone temperature is high, for example, the highest surface grinding zone up to 1000 ℃. As the temperature rises, inevitably lead to changes in the surface of the steel tissue. When the temperature exceeds the phase transition temperature, the pearlite changes to austenite, and then hardened by the colder substrate of the steel core to obtain quenched martensite, which forms a secondary quench burn on the steel surface. Even if the temperature is below the phase transition temperature, the tempered martensite will also transform into troostite or sorbite, softening the surface and forming a tempering burn. It must be pointed out that the instantaneous high temperature in the grinding zone is the main condition for the formation of the metamorphic layer (referring to the surface layer where the microstructure changes). However, it is different from the normal heat treatment and has its own characteristics . First, it requires a greater overheating temperature, and secondly, its organizational transformation is not sufficient.