关键词: 航空齿轮材料, 16Cr3NiWMoVNbE钢, 边缘粗晶, 正火处理, 锻造温度

Abstract: Effect of normalizing treatment (940/1000 ℃×120 min, air cooling) on the coarse grains at the edge of high-strength 16Cr3NiWMoVNbE steel bars were investigated by means of OM and SEM. The results show that normalizing at 1000 ℃ has a significant refinement effect on the coarse grains at the edge of the steel bars, with the grains refining to grade 7. Normalizing at 940 ℃ has a certain improvement effect on the coarse grains at the edge of the steel bars, but the coarse grain area cannot be completely eliminated. The reason is that a large amount of M(C, N) type carbides near the original austenite grain boundaries and in the matrix cannot be completely dissolved, which hinders static recrystallization. In addition, the reason for the formation of coarse grains is that the surface layer of the steel bars cools down faster during the last forging pass, and thermodynamically it cannot meet the requirements of grain migration and growth, which affects the recrystallization process. The edge of the steel bars is in a critical condition of two-phase zone hot deformation, resulting in a small amount of ferrite forming blocky structures along the grain boundaries, which is displayed as coarse grains on the inspection specimens.

Key words: aviation gear material, 16Cr3NiWMoVNbE steel, coarse crystal at the edge, normalizing treatment, forging temperature