【作者】 王存宇；

【导师】 付瑞东；

【作者基本信息】 燕山大学 ， 材料学， 2006， 硕士

【摘要】 2.25Cr -1Mo-0.25V钢主要用来制造热壁加氢反应器,具有强度高、抗高温蠕变、氢蚀、氢脆、回火脆化性能好等特点。然而对该钢的应用基础研究一直滞后于实际生产,进而影响对热加工工艺的进一步优化。为此,在Gleeble-3500热模拟试验机上,采用热压缩方法及应力松弛方法对2.25Cr -1Mo-0.25V钢的热变形行为和热变形后驰豫过程中第二相粒子的溶解与析出规律进行了研究。研究结果表明:2.25Cr -1Mo-0.25V钢的应力-应变曲线有动态回复型和动态再结晶型两种。由应力-应变曲线计算出的热变形激活能Q =474.82kJ/mol,拟和出的热变形方程可表达为:ε|-= 3 .03e³⁴ [s inh（0 .0329σ）]^1.309exp（-474820/RT）通过对显微组织观察以及建立应变速率为0.01s-1的再结晶图可知,应变速率越低,变形温度越高,越容易发生动态再结晶;而参数Z越大（变形温度越低或变形速率越大）动态再结晶越困难。2.25Cr -1Mo-0.25V钢热变形后驰豫过程中发生应变诱导析出现象,其应力松弛曲线呈现多个析出平台的特征,第二相粒子的孕育、析出和长大等几个过程相互交替进行。900℃析出孕育期最短,由于800℃发生γ→α相变,使PTT曲线不成典型的“C”形。驰豫过程中应变诱导析出主要发生于位错,其形状由小尺寸的球形向大尺寸的方形过渡,淬火过程中产生短棒状析出物;固溶处理过程中未溶解的第二相粒子对应力松弛没有明显的抑制作用;通过控制驰豫时间可以得到最小的平均晶粒尺寸,对组织有一定的细化效果。更多还原

【Abstract】 The 2.25Cr-1Mo-0.25V steel had been widely used in manufacturing hotwall hydrogen reactor for its higher intensity and stronger resistance to the hightemperature creeping, and hydrogen corrosion and brittleness temperedbrittleness. However, the investigations of essential character lag behindpractical manufacture, furthermore, the further optimization of hot workingprocess were firmly retarded.Therefore the hot deformation behaviors and precipitation during holdingprocess in 2.25Cr -1Mo-0.25V steel were investigated by using of Gleeble-3500thermal simulator.The results show that the stress vs. strain curves of this steel can beclassified into two types: dynamic recover and dynamic recrystallization, Hotdeformation activation energy which was calculated based on stress vs. straincurves is 474.82kJ/mol and the hot deformation formation was fitted asfollowing:ε|-= 3 .03e³⁴ [sinh（0 .0329σ）]^1.309exp（-474820/RT）From the microstructure and the map of dynamic recrystallization state withstrain rate of 0.01s-1, we can credibly conclude that the lower strain rate orhigher deformation temperature is, the more easily dynamic recrystallization canoccur. Otherwise, the larger the Z parameter is, i.e. lower deformationtemperature or higher strain rate, the more difficultly dynamic recrystallizationcan occur. Strain induced precipitation took place during holding process after hotdeformation, strain relaxation curves exhibit several short plateaus which arerelated to the inoculation, precipitation and growth process of the second phaseparticles. The inoculation time at 900 ℃ is the shortest, and the PTT（Precipitation-Time-Temperature） curves do not exhibit typical “C” shape. Theshape of the second phase particles transformed from small-scale spherical tolarge-scale quadrate. The short virgulate precipitates were observed in waterquenched samples;The second phase particles did not dissolve duringhomogenized treatment can not retard stress relaxation effectively. The finegrains can be obtained by controlling the holding time.更多还原