【摘要】：核電站管道材料在使用和加工制造過程中會處于高溫環(huán)境,此高溫環(huán)境會導(dǎo)致材料發(fā)生熱老化效應(yīng),使奧氏體在晶界處產(chǎn)生析出物,即“敏化”。這種熱老化效應(yīng)對材料的力學(xué)性能有明顯影響。核電站壓水堆一回路輔助管道在運(yùn)行期間,會承受內(nèi)壓、振動等復(fù)雜載荷工況,導(dǎo)致材料發(fā)生棘輪效應(yīng),縮減材料或結(jié)構(gòu)的疲勞壽命,影響管道的安全可靠性。為了保障核電站壓力管道的安全運(yùn)行,本文針對壓水堆一回路輔助管道用材Z2CND18.12N奧氏體不銹鋼,從材料熱老化效應(yīng)、棘輪效應(yīng)、棘輪疲勞壽命、微觀機(jī)理以及本構(gòu)模型等方面進(jìn)行了系統(tǒng)的研究。本研究對核電站壓力管道的設(shè)計(jì)及運(yùn)行具有重要的指導(dǎo)意義。利用電液伺服疲勞實(shí)驗(yàn)機(jī)對Z2CND18.12N奧氏體不銹鋼管材進(jìn)行了單軸拉伸試驗(yàn)及單軸棘輪試驗(yàn),得到材料在室溫條件下基本的力學(xué)性能。在單軸棘輪試驗(yàn)中,棘輪應(yīng)變隨加載率的增加而降低,隨平均應(yīng)力的增加而增加,隨應(yīng)力幅值的增加而增加。加載歷史與應(yīng)力比對棘輪應(yīng)變也有明顯的影響。對Z2CND18.12N奧氏體不銹鋼進(jìn)行高溫老化,分別在500℃和700℃下將管材老化1小時、10小時、50小時、100小時和500小時。利用疲勞實(shí)驗(yàn)機(jī)對老化后的管材進(jìn)行了室溫下的單軸拉伸試驗(yàn)及單軸棘輪試驗(yàn)。在單軸拉伸試驗(yàn)中,老化后的材料與原始材料相比,楊氏模量與屈服應(yīng)力有小幅度的降低。拉伸強(qiáng)度與延伸率沒有明顯變化。在單軸棘輪試驗(yàn)中,承受同一載荷條件下,棘輪應(yīng)變隨老化溫度的升高而增加,隨老化時間的增長而增加。棘輪疲勞壽命隨老化溫度的升高而減少,隨老化時間的增長而減少。提出了老化損傷的概念,并對老化材料的棘輪疲勞壽命進(jìn)行預(yù)測,取得了較好的預(yù)測結(jié)果。對老化后的試樣進(jìn)行了SEM與EDS微觀觀測與分析。通過SEM的觀測結(jié)果得出材料熱老化過程的析出行為隨老化溫度、老化時間的規(guī)律。利用EDS對析出物進(jìn)行了成分分析,確定了析出物的類型隨老化條件的改變而改變,包括M_(23)C_6,η,x等。利用OW II模型結(jié)合各向同性強(qiáng)化準(zhǔn)則,對原始材料的棘輪行為進(jìn)行預(yù)測,并將OW II模型中的強(qiáng)化律指數(shù)m修正為與老化時間相關(guān)的指數(shù)形式,并對老化后材料的棘輪應(yīng)變進(jìn)行預(yù)測,得到了較好的預(yù)測結(jié)果。
[Abstract]:Nuclear power plant pipeline materials will be in a high temperature environment in the process of using and processing. This high temperature environment will lead to the thermal aging effect of the materials, which makes austenite produce precipitates at grain boundaries, that is, "sensitization". This effect of thermal aging has a significant effect on the mechanical properties of the material. The auxiliary pipeline of primary circuit of PWR in nuclear power station will bear complex load conditions such as internal pressure and vibration during operation, which will lead to ratchet effect of material, reduce the fatigue life of material or structure, and affect the safety and reliability of pipeline. In order to ensure the safe operation of nuclear power plant pressure pipeline, the Z2CND18.12N austenitic stainless steel, which is used in the primary circuit auxiliary pipeline of PWR, is studied in this paper from the effect of material thermal aging and ratchet fatigue life. The microscopic mechanism and constitutive model are systematically studied. This study has important guiding significance for the design and operation of nuclear power plant pressure pipeline. Uniaxial tensile tests and uniaxial ratchet tests were carried out on Z2CND18.12N austenitic stainless steel pipes by electro-hydraulic servo fatigue test machine. The basic mechanical properties of the materials were obtained at room temperature. In uniaxial ratchet test, ratchet strain decreases with the increase of loading rate, increases with the increase of average stress and increases with the increase of stress amplitude. The loading history and stress ratio also have obvious influence on ratchet strain. The Z2CND18.12N austenitic stainless steel was aged at 500 鈩，

本文編號：2373999