HR3C钢中σ相析出动力学研究
发布时间：2018-10-26 19:06
【摘要】：HR3C钢作为一种新型奥氏体耐热钢具有较高的蠕变强度,特别是良好的抗高温氧化腐蚀性能,因而广泛应用于超超临界机组的过热器和再热器上。由于超超临界电站寿命要求达到30～40年,对设备用钢的稳定性也有较高的要求,高温高压条件致使部件用钢的组织结构随着服役时间增加不断老化,机组运行安全性和可靠性下降,甚至发生早期失效。因而对服役过程中HR3C钢显微组织稳定性、力学性能变化及可靠性的研究具有重要意义。目前,就HR3C钢在服役过程中NbCrN、M23C6、Nb(C, N)等相的析出及其对性能影响已有大量的研究,而只有很少的研究者就HR3C钢中σ相的析出问题给出报道。HR3C钢从成分设计上抑制σ相的析出,但国内外近期的研究工作发现服役后HR3C钢管出现脆性问题,我们的前期工作对700℃～800℃时效的住友HR3C钢进行研究发现有a相的析出。一般认为,a相的析出会显著降低材料的力学性能和蠕变性能,因而,对于HR3C钢中σ相的析出行为及对材料性能的影响需要进行更多、更细致的研究。本研究通过金相显微镜、X射线衍射分析仪、扫描电子显微镜等对HR3C钢高温时效过程中σ相的析出进行确认,主要借助显色腐蚀半定量方法,结合Avrami方程对a相析出动力学行为进行分析,并研究了时效过程中HR3C钢性能的变化,同时初步探究了推迟a相析出的热处理工艺。研究结果表明,HR3C钢在650～800℃时效足够时间后,都会有σ脆性相在晶界析出；根据显色腐蚀半定量方法结合Avrami公式得到HR3C钢中a相析出的动力学曲线,C曲线的鼻尖温度在750℃附近,并且根据预测,在接近实际服役温度的650℃时效,σ相的转变量达到5%只需约10500h；同样时效条件下,国产HR3C钢比住友HR3C钢更容易析出。相；将HR3C钢在1200℃预固溶处理1h可以有效推迟后续时效过程中σ相的析出时间；对700℃时效下不同状态HR3C钢的硬度、冲击韧性及蠕变持久性能研究发现,初始态试样直接时效至2000h,硬度增加,冲击韧性大幅下降,持久寿命明显降低；1200℃预固溶处理后再时效,冲击韧性并没有改善,但持久寿命较之前明显提高。
[Abstract]:As a new austenitic heat-resistant steel, HR3C steel has high creep strength, especially good oxidation corrosion resistance at high temperature, so it is widely used in superheaters and reheaters of ultra-supercritical units. Since the service life of ultra supercritical power station is 30 ~ 40 years and the stability of equipment steel is also required, the structure of steel for components is aging with the service time increasing under high temperature and high pressure conditions. The operation safety and reliability of the unit decreased, and even the early failure occurred. Therefore, it is of great significance to study the microstructure stability, mechanical properties and reliability of HR3C steel during service. At present, a lot of studies have been done on the precipitation of NbCrN,M23C6,Nb (C, N) and other phases and its influence on the properties of HR3C steel during its service. However, only a few researchers report the problem of 蟽 phase precipitation in HR3C steel. The composition design of HR3C steel inhibits 蟽 phase precipitation, but recent researches at home and abroad have found that there is a brittle problem in HR3C steel tubes after service. In our earlier work, the precipitation of a phase was found in Sumitomo HR3C steel aged at 700 鈩，
本文编号：2296677
[Abstract]:As a new austenitic heat-resistant steel, HR3C steel has high creep strength, especially good oxidation corrosion resistance at high temperature, so it is widely used in superheaters and reheaters of ultra-supercritical units. Since the service life of ultra supercritical power station is 30 ~ 40 years and the stability of equipment steel is also required, the structure of steel for components is aging with the service time increasing under high temperature and high pressure conditions. The operation safety and reliability of the unit decreased, and even the early failure occurred. Therefore, it is of great significance to study the microstructure stability, mechanical properties and reliability of HR3C steel during service. At present, a lot of studies have been done on the precipitation of NbCrN,M23C6,Nb (C, N) and other phases and its influence on the properties of HR3C steel during its service. However, only a few researchers report the problem of 蟽 phase precipitation in HR3C steel. The composition design of HR3C steel inhibits 蟽 phase precipitation, but recent researches at home and abroad have found that there is a brittle problem in HR3C steel tubes after service. In our earlier work, the precipitation of a phase was found in Sumitomo HR3C steel aged at 700 鈩，
本文编号：2296677
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