【摘要】：HR3C鋼作為一種新型奧氏體耐熱鋼具有較高的蠕變強(qiáng)度,特別是良好的抗高溫氧化腐蝕性能,因而廣泛應(yīng)用于超超臨界機(jī)組的過(guò)熱器和再熱器上。由于超超臨界電站壽命要求達(dá)到30～40年,對(duì)設(shè)備用鋼的穩(wěn)定性也有較高的要求,高溫高壓條件致使部件用鋼的組織結(jié)構(gòu)隨著服役時(shí)間增加不斷老化,機(jī)組運(yùn)行安全性和可靠性下降,甚至發(fā)生早期失效。因而對(duì)服役過(guò)程中HR3C鋼顯微組織穩(wěn)定性、力學(xué)性能變化及可靠性的研究具有重要意義。目前,就HR3C鋼在服役過(guò)程中NbCrN、M23C6、Nb(C, N)等相的析出及其對(duì)性能影響已有大量的研究,而只有很少的研究者就HR3C鋼中σ相的析出問(wèn)題給出報(bào)道。HR3C鋼從成分設(shè)計(jì)上抑制σ相的析出,但國(guó)內(nèi)外近期的研究工作發(fā)現(xiàn)服役后HR3C鋼管出現(xiàn)脆性問(wèn)題,我們的前期工作對(duì)700℃～800℃時(shí)效的住友HR3C鋼進(jìn)行研究發(fā)現(xiàn)有a相的析出。一般認(rèn)為,a相的析出會(huì)顯著降低材料的力學(xué)性能和蠕變性能,因而,對(duì)于HR3C鋼中σ相的析出行為及對(duì)材料性能的影響需要進(jìn)行更多、更細(xì)致的研究。本研究通過(guò)金相顯微鏡、X射線衍射分析儀、掃描電子顯微鏡等對(duì)HR3C鋼高溫時(shí)效過(guò)程中σ相的析出進(jìn)行確認(rèn),主要借助顯色腐蝕半定量方法,結(jié)合Avrami方程對(duì)a相析出動(dòng)力學(xué)行為進(jìn)行分析,并研究了時(shí)效過(guò)程中HR3C鋼性能的變化,同時(shí)初步探究了推遲a相析出的熱處理工藝。研究結(jié)果表明,HR3C鋼在650～800℃時(shí)效足夠時(shí)間后,都會(huì)有σ脆性相在晶界析出；根據(jù)顯色腐蝕半定量方法結(jié)合Avrami公式得到HR3C鋼中a相析出的動(dòng)力學(xué)曲線,C曲線的鼻尖溫度在750℃附近,并且根據(jù)預(yù)測(cè),在接近實(shí)際服役溫度的650℃時(shí)效,σ相的轉(zhuǎn)變量達(dá)到5%只需約10500h；同樣時(shí)效條件下,國(guó)產(chǎn)HR3C鋼比住友HR3C鋼更容易析出。相；將HR3C鋼在1200℃預(yù)固溶處理1h可以有效推遲后續(xù)時(shí)效過(guò)程中σ相的析出時(shí)間；對(duì)700℃時(shí)效下不同狀態(tài)HR3C鋼的硬度、沖擊韌性及蠕變持久性能研究發(fā)現(xiàn),初始態(tài)試樣直接時(shí)效至2000h,硬度增加,沖擊韌性大幅下降,持久壽命明顯降低；1200℃預(yù)固溶處理后再時(shí)效,沖擊韌性并沒(méi)有改善,但持久壽命較之前明顯提高。
[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，

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