55MnCrNb钢的脱碳行为

Decarburization behavior of 55MnCrNb steel

以含Nb高碳钢为研究对象,研究了钢的表面脱碳层深度及奥氏体晶粒大小随温度变化规律。结果表明：试验钢在800℃保温20 min,钢的表面有一层致密的氧化铁皮,脱碳现象不明显。温度从900℃升高到950℃,钢表面氧化铁皮开始开裂并与基体间形成缝隙,脱碳现象明显,在1180℃时总脱碳层深度为269μm。随温度从900℃升高到1180℃,奥氏体晶粒尺寸长大明显,900℃奥氏体晶粒平均尺寸16.8μm,当温度升高到1180℃时,奥氏体晶粒平均尺寸达到132μm。随温度升高,未固溶Nb C量降低及奥氏体晶粒长大,使C原子扩散阻力降低,脱碳层深度随温度升高而增大。

The depth of decarburized layer and the grain size of autenite for high carbon Nb bearing steel with the increasing of temperature were researched.The results show that there are compact iron scale and the decarburization phenomenon is not distinct on the surface of the steel.The decarburization behavior occur when the iron scale cracking with the temperature increased from 900 ℃ to 950 ℃.The total depth of decarburized layer is 269 μm at 1180 ℃.The grain size of autenite increases from 16.8 μm to 132 μm with the temperature increased from 900 ℃ to 1180 ℃.The insoluble Nb C content decrease and the austnite size increases which decreases the diffuse resistance of carbon and leads to the increase of the depth of decarburized layer with the temperature increasing.