本文選題：核電主管道 + 熱鍛　； 參考：《北京科技大學(xué)》2015年博士論文

【摘要】：超低碳控氮316LN奧氏體不銹鋼,因其具有良好的加工性能、較好的力學(xué)性能和耐晶間應(yīng)力腐蝕性能,在第三代壓水堆AP1000核電站中作為一回路主管道材料,是核一級(jí)關(guān)鍵裝備材料。然而,AP1000主管道設(shè)計(jì)由二代、二代加的不銹鋼分段鑄件焊接改為不銹鋼整體鍛造,制造難度堪稱目前世界核電主管道之最。主管道冷段與熱段作為超大型鍛件,其工藝要同時(shí)滿足成形與組織控制的目標(biāo),其中晶粒度控制是重點(diǎn)。因而,對(duì)316LN奧氏體不銹鋼在熱變形過程中的微觀組織演變行為進(jìn)行較系統(tǒng)的研究,對(duì)晶粒變化規(guī)律進(jìn)行模擬,掌握工藝-組織關(guān)系規(guī)律,可預(yù)測(cè)實(shí)際鍛造過程中的晶粒變化,并且為主管道制備工藝的優(yōu)化提供依據(jù),對(duì)微觀組織調(diào)控技術(shù)的發(fā)展有著重要的意義。 本文采用Gleeble熱模擬實(shí)驗(yàn)和物理冶金模型計(jì)算相結(jié)合的方法,系統(tǒng)研究了316LN在鍛造過程中的晶粒演變規(guī)律以及組織模擬技術(shù)。 在Gleeble3500熱力模擬試驗(yàn)機(jī)上,采用單道次軸向熱壓縮實(shí)驗(yàn)研究了316LN不銹鋼的高溫流變行為,用以模擬其高溫鍛造過程�；趯�(shí)驗(yàn)數(shù)據(jù),引入Zener-Hollomon參數(shù),建立了Arrhenius型唯象本構(gòu)方程,用以描述316LN奧氏體不銹鋼熱變形過程中應(yīng)變速率、形變溫度與應(yīng)力應(yīng)變關(guān)系。在此基礎(chǔ)上,獲得了316LN動(dòng)態(tài)再結(jié)晶晶粒尺寸演變的經(jīng)驗(yàn)公式,可以預(yù)測(cè)一定工藝條件下的鍛造組織的晶粒度。 通過對(duì)熱模擬試樣高溫淬火后顯微組織的研究分析,觀察了不同形變參數(shù)下樣品的微觀組織,結(jié)果表明在關(guān)鍵性的最后一火次鍛造時(shí),在316LN奧氏體不銹鋼的鍛造工藝條件允許的情況下,應(yīng)盡可能使用較大的壓下量,使其充分發(fā)生動(dòng)態(tài)再結(jié)晶,以獲得細(xì)化的奧氏體組織。鍛造溫度在1273K-1423K之間,應(yīng)變速率在0.1s-1數(shù)量級(jí),可以獲得完全動(dòng)態(tài)再結(jié)晶組織,晶粒尺寸在10μm～15μm范圍,遠(yuǎn)小于AP1000核電主管道所要求的二級(jí)晶粒度的尺寸。本文還探討了316LN奧氏體不銹鋼的形變、動(dòng)態(tài)回復(fù)、動(dòng)態(tài)再結(jié)晶的相互作用,研究了動(dòng)態(tài)再結(jié)晶的形核機(jī)制,為建立基于物理冶金原理的模型提供了理論依據(jù)。 由于Arrhenius型唯象型本構(gòu)方程作為經(jīng)驗(yàn)?zāi)Ｐ?普適度欠佳,為了更好地預(yù)測(cè)316LN奧氏體不銹鋼的晶粒變化,建立了以物理冶金原理為基礎(chǔ),綜合化學(xué)成分、形變和再結(jié)晶微觀組織演變的熱變形奧氏體再結(jié)晶模型。模型包括關(guān)鍵的計(jì)算模塊包括位錯(cuò)密度模塊、形核模塊、再結(jié)晶和析出模塊,以及工藝輸入模塊,常量模塊及合金成分輸入模塊等輔助部分。通過對(duì)模型參數(shù)的調(diào)整,預(yù)測(cè)316LN奧氏體不銹鋼熱鍛在不同形變條件下的流變應(yīng)力行為和再結(jié)晶行為,并將模擬所得的晶粒尺寸結(jié)果與Gleeble熱模擬試驗(yàn)所得的晶粒尺寸結(jié)果進(jìn)行對(duì)比,兩者吻合較好,從而驗(yàn)證了所建微觀組織模型的可靠性。 此外,利用該物理冶金模型還對(duì)具有碳氮化物析出的含Nb微合金鋼的熱變形行為進(jìn)行了預(yù)測(cè),通過輸入不同鋼的成分、本征常量以及變形工藝,進(jìn)行調(diào)試,同Gleeble熱模擬試驗(yàn)的結(jié)果進(jìn)行對(duì)比驗(yàn)證,模擬結(jié)果與實(shí)驗(yàn)值符合較好,表明該模型可以運(yùn)用于不同的鋼種,具有較好的普適性。
[Abstract]:The ultra - low carbon nitrogen - controlled 316LN austenitic stainless steel is a key equipment material at the nuclear level because of its good processing performance , good mechanical property and intergranular stress corrosion resistance . However , the design of the main pipeline in the third generation PWR AP1000 nuclear power plant is the primary key equipment material . However , the design of the main pipeline in the third generation PWR AP1000 nuclear power plant is the primary key equipment material . However , the main pipeline cooling section and the hot section of the 316LN austenitic stainless steel are used as the super - large forgings . The grain size control is the key point . Therefore , it is important for the development of the microstructure control technology to provide the basis for the optimization of the preparation process of 316LN austenitic stainless steel .

In this paper , Gleeble heat simulation experiment and physical metallurgy model are used to calculate the grain evolution law and tissue simulation technology of 316LN in forging process .

The high temperature rheological behavior of 316LN stainless steel is studied by single - pass axial thermal compression test on Gleeble 3500 thermal simulation testing machine . Based on the experimental data , the Zener - Holden parameter is introduced to describe the relationship between strain rate , deformation temperature and stress strain in 316LN austenitic stainless steel thermal deformation process . Based on the experimental data , the empirical formula of the size evolution of 316LN dynamic recrystallization grain is obtained , and the grain size of forged tissue under certain process conditions can be predicted .

The microstructure of specimens under different deformation parameters is studied by the study of microstructure of hot - simulated specimens after high temperature quenching . The results show that , under the condition that the forging process conditions of 316LN austenitic stainless steel are permitted under the condition of forging process conditions of 316LN austenitic stainless steel , it is possible to obtain complete dynamic recrystallization structure with grain size of 10 渭m ~ 15 渭m , which is far less than the secondary grain size required by AP1000 nuclear power main pipeline . The nucleation mechanism of dynamic recrystallization is studied , which provides the theoretical basis for the establishment of the model based on the principle of physical metallurgy .

The model includes dislocation density module , nucleation module , recrystallization and precipitation module , process input module , constant module and alloy component input module . The model includes the key calculation module including dislocation density module , nucleation module , recrystallization and precipitation module , process input module , constant module and alloy component input module .

In addition , the thermal deformation behavior of Nb - containing microalloy steel with carbon nitride precipitation is predicted by using the physical metallurgy model . By inputting the composition , the intrinsic constant and the deformation process of different steels , the simulation results are compared with the results of the Gleeble thermal simulation test , and the simulation results are in good agreement with the experimental values , indicating that the model can be applied to different steel types , and has good universality .
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG142.71

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本文編號(hào)：1918350