690合金传热管内外壁“细晶”组织的成因及控制

Contributing Factors and Control of Formation of Fine-grain Microstructure in Inner and Outer Surfaces of 690 Alloy Tube for Heat Transfer Service

分析了冷轧变形量、脱脂质量、热处理保护气氛、中间品原始组织等对690合金传热管光亮固溶热处理组织的影响。分析认为:内外壁再结晶形核率的差异是导致690合金传热管内外壁出现异常"细晶"组织的根本原因;通过改变热处理气氛、增大冷轧变形量、改善脱脂质量等手段,可有效消除光亮固溶热处理后690合金传热管内外壁的"细晶"组织。

Analyzed are the factors affecting the l^right solid solution heat treatment microstructure of the 690 alloy pipe for heat transfer service, including the cold-rolling deformation rate, degreasing quality control, heat- treatment protective atmosphere and original microstructure of the semi-product. The analysis reveals that the difference between the re-crystallization nucleation rate of the inner surface and that of the outer surface acts as the root cause for development of the abnormal fine-grain microstructure on the inner and outer surfaces of the pipe. Accordingly, such fine-grain microstructure of the saie 690 alloy pipe as occurred after bright solid solution heat treatment is expected to be eliminated by means of improving the heat treatment atmosphere, increasing the deformation rate and improving degreasing quality, etc.