43B17钢带状组织对渗碳淬火组织的影响及其消除方法探讨

Effect of Banded Structure on Carburizing and Quenching Structure of 43B17 Steel and Elimination Method

针对43B17钢齿轮热处理加工过程中经常出现比较严重的带状组织,而导致金属材料各向异性、金属组织和硬度不符合要求以及金属工艺下降低等问题,通过分析43B17钢制齿坯锻造后的退火金相发现,带状组织会对渗碳组织产生影响,具体分析43B17钢带状组织形成条件后,寻找出了消除带状组织以及其对渗碳层组织影响的方法,即通过在齿坯的锻造过程中延长加热保温时间,使扩散充分进行,并在后续的预备热处理工艺中采用940℃的高温正火的热处理工艺,得出43B17钢直接淬火后的金相组织为弥散分布的针状马氏体。以该方法得到的金相组织带状组织评定为1级,有效控制了带状组织的形成,同时其渗碳层深度和硬度也达到了设计要求,硬度不在呈现锯齿状,从表面到心部硬度逐渐下降,大幅提高了金属的热处理工艺性能。

The serious banded structure often appears in the heat treatment process of 43B17 steel gear,which leads to the anisotropy of metal materials,the metal structure and hardness do not meet the requirements,and the metal process is reduced.In this paper,through the metallographic analysis of annealing after forging of 43B17 steel gear blank,the influence of banded structure on carburized structure is found,and the formation conditions of banded structure of 43b17 steel are analyzed in detail,so as to find a method to eliminate the banded structure and its influence on carburized layer structure.Through the test,during the forging process of gear blank,the heating and holding time is extended to allow full diffusion.In the subsequent preparatory heat treatment process,the heat treatment process of high temperature normalizing at 940℃is adopted.It is concluded that the metallographic structure of 43B17 steel after direct quenching is dispersed acicular martensite,and the banded structure is evaluated as grade 1,which controls the formation of banded structure,At the same time,the carburized layer depth and hardness also meet the design requirements.The hardness is no longer serrated,and the hardness gradually decreases from the surface to the heart,so as to greatly improve the heat treatment process performance of the metal.