【摘要】：P91耐熱鋼由于突出的抗蠕變性能、良好的抗腐蝕性和高溫抗氧化能力,成為火電、核電廠管道部件的主選或更新?lián)Q代材料。工程上,將管道材料的持久蠕變壽命定義為在使用時(shí)間為105h時(shí),形變量不超過(guò)2%。此時(shí)低應(yīng)力下蠕變的應(yīng)變率將會(huì)低于10-10ms-1,傳統(tǒng)的單軸蠕變?cè)囼?yàn)由于應(yīng)變率低,不能滿足此應(yīng)變速率下蠕變性能研究的需求;另一面,P91耐熱鋼在服役過(guò)程中會(huì)產(chǎn)生組織退化,組織退化對(duì)高溫低應(yīng)力下的蠕變性能的影響仍未知。本研究的目的:采用具有高應(yīng)變率的“螺旋彈簧蠕變?cè)囼?yàn)法”調(diào)查不同條件的熱時(shí)效處理后P91耐熱鋼在高溫低應(yīng)力下的蠕變性能,揭示了P91耐熱鋼高溫低應(yīng)力下的“組織退化因子”。通過(guò)ANSYS有限元仿真軟件,對(duì)不同螺距的P91螺旋彈簧試樣的力學(xué)場(chǎng)進(jìn)行了分析,得到結(jié)論:當(dāng)螺距的長(zhǎng)度是螺旋段橫截面長(zhǎng)度的1-3倍時(shí),“螺旋彈簧蠕變?cè)囼?yàn)法”滿足純扭轉(zhuǎn)變形。對(duì)不同熱時(shí)效處理時(shí)間的試樣分別進(jìn)行X-rd和SEM微觀組織分析,結(jié)果顯示:1)析出相有M23C6、Laves相和MX相。2)MX相在熱處理之后達(dá)到飽和狀態(tài),主要彌散析出在馬氏體板條晶粒的內(nèi)部。3)M23C6相沿馬氏體板條晶界處和原奧氏體晶界析出,在時(shí)效700h達(dá)到飽和狀態(tài),之后發(fā)生粗化。4)Laves相在時(shí)效2100h沿馬氏體板條邊界和亞晶邊界析出,且極易長(zhǎng)大。對(duì)P91耐熱鋼在高溫低應(yīng)力下蠕變性能進(jìn)行了研究,得出結(jié)論:1)“螺旋彈簧蠕變?cè)囼?yàn)法”有效。2)Blackburn’s equation能夠最好的描述實(shí)測(cè)蠕變數(shù)據(jù)。3)單軸蠕變?cè)囼?yàn)法會(huì)過(guò)大的評(píng)測(cè)使用材料的剩余壽命。4)Laves相是影響P91耐熱鋼高溫低應(yīng)力下的蠕變性能的“組織退化因子”。本文從有限元分析、微觀組織觀察和高溫低應(yīng)力下的蠕變性能三個(gè)方面對(duì)P91耐熱鋼進(jìn)行了研究,研究結(jié)果對(duì)下一步開(kāi)展耐熱鋼改性提供了理論支持,高溫、低應(yīng)力下的蠕變數(shù)據(jù)為開(kāi)展高鉻耐熱鋼的服役安全性評(píng)價(jià)提供了數(shù)據(jù)支持。
[Abstract]:Due to its outstanding creep resistance, good corrosion resistance and high temperature oxidation resistance, P91 heat resistant steel has become the main selection or replacement material for pipeline components of thermal power plants and nuclear power plants. In engineering, the creep life of pipeline material is defined as that when the service time is 105 h, the shape variable is not more than 2. Under low stress, the strain rate of creep will be lower than 10-10ms-1. the traditional uniaxial creep test can not meet the need of creep property research at this strain rate because of its low strain rate, on the other hand, the microstructure of P91 heat-resistant steel will degenerate during service. The effect of microstructure degradation on creep properties at high temperature and low stress is still unknown. The purpose of this study is to investigate the creep properties of P91 heat-resistant steel under high temperature and low stress by means of "helical spring creep test method" with high strain rate. The microstructure degradation factor of P 91 heat resistant steel under high temperature and low stress was revealed. The mechanical field of P91 helical spring specimens with different pitch is analyzed by ANSYS finite element simulation software. It is concluded that when the length of pitch is 1-3 times of the length of cross section of spiral segment, The helical spring creep test method satisfies the pure torsional deformation. X-rd and SEM microstructures of samples with different thermal aging time were analyzed. The results showed that: 1) the precipitated phases were M23C6 Laves phase and MX phase. 2) the MX phase reached saturation state after heat treatment. The main dispersion precipitation occurs in the interior of martensite lath grain. 3) the M23C6 phase precipitates along the martensite lath grain boundary and the original austenite grain boundary, and reaches saturation state at 700h, then coarsens. 4) the Laves phase precipitates along martensite lath boundary and subcrystalline boundary at 2100h. And easy to grow up. The creep behavior of P91 heat resistant steel under high temperature and low stress was studied. The conclusions are as follows: 1) "helical spring creep test method" is effective. 2) Blackburn's equation can best describe the measured creep data. 3) uniaxial creep test method can evaluate the remaining life of used materials too large. 4) Laves phase affects the high temperature and low temperature of P91 heat-resistant steel. The "microstructure degradation factor" of creep properties under stress. In this paper, P91 heat resistant steel is studied from three aspects: finite element analysis, microstructure observation and creep property under high temperature and low stress. The results provide theoretical support for further modification of heat resistant steel at high temperature. The creep data under low stress provide data support for evaluating the service safety of high chromium heat resistant steel.
【學(xué)位授予單位】：天津理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TG142.73

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本文編號(hào)：2290538