高温合金617B管材热挤压特征及工艺优化控制

Hot extrusion characteristics and technique optimization for superalloy 617B tube

基于高温合金617B的组织演变模型,采用DEFORM-2D有限元软件构建了617B合金管材的热挤压模拟计算过程,对高温合金617B的热挤压特征进行了分析,并实现了管坯温度、晶粒尺寸等的定量预测.在结合生产实际的基础上,提出了包括温度准则、载荷准则、组织精确控制准则等在内的组织可控的可挤出性准则,对准则的控制原理和实施过程进行了阐述,并采用该类准则对617B合金的热挤压工艺参数范围进行优化,顺利得到了轴向形状尺寸均匀,表面质量较好的高温合金617B管材.该方法的提出和验证,为镍基高温合金无缝管材的生产提供了工艺优化的理论依据和研究方法.

Nickel-base superalloy 617 B is one of the most promising candidates for superheater and reheater pipes of advanced ultra-supercritical(AUSC)power plants.Hot extrusion is a key process during the manufacturing of superalloy 617 B pipes.However,the high content of alloying elements in superalloy 617 B makes microstructure control difficult during the hot extrusion process.Furthermore,to date,no systematical theoretical investigation has been conducted in the hot extrusion process control of superalloy 617 B.Hence,in this work,the hot extrusion process of superalloy 617 B tube was studied by finite element simulation using DEFORM-2 D finite element software.The microstructure evolution during hot extrusion was considered by combining the microstructure evolution model of superalloy 617 B and finite element simulation software.The microstructure evolution model was programmed using FORTRAN language and was developed using the finite element simulation software.The hot extrusion characteristics of superalloy 617 B were systematically analyzed by the simulation.As a result,the evolution of temperature,grain size,and loading could be predicted quantitatively.At the same time,to optimize the hot extrusion parameters,microstructure-based hot extrusion control principles,including temperature principle,loading principle,precise microstructure control principle,were proposed considering practical hot extrusion process.Moreover,the control mechanism and application process of these principles were elaborated in detail in this paper.The hot extrusion parameters of superalloy 617 B tube were optimized based on the proposed microstructure-based hot extrusion control principles.Under the guidance of the microstructure-based hot extrusion control principles,superalloy 617 B tube with uniform axial dimension and good surface quality was extruded successfully in the factory.The practical extrusion result agrees well with the simulated one.Therefore,the establishment and validation of the simulation method and microstructure-based hot extrusion control principles can provide theoretical guidance for the hot extrusion process optimization of nickel-base superalloy tube in practical applications.