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利用DICTRA软件及金相法对GCr15轴承钢连铸坯中的液析碳化物在加热工艺中的溶解与扩散机理进行研究,并针对常规加热工艺存在的问题,提出加热工艺的设计思路:第一阶段在液析严重区域连铸坯的固相线温度以下进行加热,加热过程中仅发生液析碳化物的溶解,令C元素快速扩散,同时该区域固相线温度逐渐升高;第二阶段在1200~1280℃的高温区进行加热,由于第一阶段中液析严重区域连铸坯的固相线温度升高,此时很难再有液相增加,可保证Cr元素快速扩散,最终令液析碳化物快速溶解扩散。根据DICTRA软件对加热工艺的模拟计算结果,设计加热工艺为“1100℃加热1 h后1250℃加热1 h”。以该工艺对试样进行加热试验,液析碳化物级别由4.0级降低至0.5级,结果证明了该加热工艺的可行性。
DICTRA software and metallographic method were used to study the dissolution and diffusion mechanism of liquid-phase carbides in GCr15 bearing steel billets in heating process. Aiming at the existing problems of conventional heating process, the design idea of heating process was put forward. In the first stage, In the severe liquid region of slab, the solidus temperature of the slab is heated, and only the dissolution of the hydrometallurgy occurs during the heating process, causing the rapid diffusion of C element while the solidus temperature in the region gradually increases. In the second phase, ~ 1280 ℃ high temperature heating, due to the first phase of severe liquid area billet solidus temperature increases, then it is difficult to increase the liquid phase, to ensure the rapid diffusion of Cr elements, and finally make liquid analysis Rapid dissolution of carbide diffusion. According to the DICTRA software simulation results of the heating process, the design heating process is “heating at 1100 ° C for 1 h and heating at 1250 ° C for 1 h”. The heating test of the sample was carried out with this process, and the level of liquid-phase carbide was reduced from 4.0 to 0.5. The result proves the feasibility of the heating process.