热挤压工艺对690合金组织的影响及控制

The Influence of Hot Extrusion Process on Microstructure and Control for 690 Alloy

摘要:

利用Gleeble热压缩实验,构建了690合金的挤压工艺的再结晶图,探讨了完全动态再结晶的临界挤压工艺,将合金的热变形组织演变模型带入deform-2D有限元软件,并针对挤压中合金的组织演变过程对有限元软件进行了二次开发,进而模拟计算了挤压比、坯料温度以及挤压速率对690合金挤压管组织的影响规律,依据挤压机设备能力以及组织要求提出了挤压工艺的控制方法,并进一步根据有限元计算结果进行实际挤压验证。结果表明：挤压管的晶粒尺寸随着挤压比的增大呈现出先降低后增加的趋势；690合金挤压管的晶粒尺寸随坯料温度和挤压速度的降低而减小；当坯料温度在1200℃,挤压比为15.3,挤压速率200 mm/s时,挤压管的晶粒尺寸可以控制在62.7 μm以下；模拟计算结果与挤压管的相对误差仅为4.5%。

Abstract:

The critical extrusion process of the fully dynamic recrystallization of the 690 alloy was analyzed by the Gleeble thermal compression experiment. The microstructure evolution model of 690 alloy was taken into the finite element (FE) software DEFORM-2D, and the secondary development of the FE software was carried based on the microstructure evolution during extrusion process. Then the influence of extrusion ratio, billet temperature and extrusion speed on the microstructure of 690 alloy were studied. The extrusion process control method for the microstructure o f 690 pipe according to the capacity of the extruder and the microstructure requirement. And further performing actual extrusion vertification based on the FE results. The results show that the grian size of the extrusion pipe decreases firstly and then increases with the increasing of extrusion ratio. The grain size of 690 extrusion pipe derceases with the decrease of billet temperature and extrusion speed. The grain size of the extruded pipe can bu controlled bellow 62.7μm when the billet temperature is 1200 ℃ and extrusion ratio is 15.3. The relative error between the simulation results and the extruded pipe is only 4.5%.