【摘要】：大鍛件制造是綜合大型鋼錠冶煉、鍛造與熱處理一體化復(fù)雜工藝過(guò)程,鍛造和熱處理是大鍛件制造過(guò)程中非常重要的兩個(gè)環(huán)節(jié)。晶粒度不均勻和變形不均勻在很大程度上影響大鍛件產(chǎn)品的質(zhì)量,嚴(yán)重時(shí)直接導(dǎo)致產(chǎn)品報(bào)廢。大鍛件成形過(guò)程鋼錠內(nèi)部發(fā)生復(fù)雜的微觀組織演變,產(chǎn)品最終的晶粒度和均勻性受變形溫度、壓下量和變形均勻性等多種因素控制,如果處理不恰當(dāng),都將會(huì)給后續(xù)熱處理帶來(lái)非常大的麻煩。因此,研究成形過(guò)程組織均勻性、鍛件內(nèi)部組織演變和晶粒大小分布對(duì)于獲得優(yōu)質(zhì)大鍛件具有非常重要的意義。本文以核電大型轉(zhuǎn)子材料12%Cr超超臨界轉(zhuǎn)子用鋼為對(duì)象,主要研究了奧氏體晶粒長(zhǎng)大規(guī)律和拔長(zhǎng)過(guò)程微觀組織演變。首先,通過(guò)箱式電阻爐研究了此鋼在不同保溫時(shí)間和不同加熱溫度內(nèi)奧氏體晶粒長(zhǎng)大規(guī)律。再利用非線性回歸分析方法和Arrhenius晶粒長(zhǎng)大模型,得到了此鋼奧氏體晶粒長(zhǎng)大動(dòng)力學(xué)方程。接著,運(yùn)用DEFORM-3D數(shù)值模擬技術(shù)和縮比試驗(yàn)相結(jié)合的方法,研究了不同鍛比上平砧下V型砧拔長(zhǎng)工藝對(duì)12%Cr超超臨界轉(zhuǎn)子鋼微觀組織演變的影響,分析了鍛件不同鍛比不同截面特征點(diǎn)晶粒大小分布和變形均勻性等,對(duì)比分析了試驗(yàn)結(jié)果和數(shù)值模擬結(jié)果。由此得出:當(dāng)鍛比從1.1逐漸增大到1.3過(guò)程中,鍛件的變形不均勻性隨之增加,但平均晶粒尺寸有減小的趨勢(shì),鍛件組織不均勻性也能得到一定改善。最后,再次運(yùn)用DEFORM-3D數(shù)值模擬軟件分析了12%Cr超超臨界轉(zhuǎn)子用鋼在上下平砧(FM拔長(zhǎng)法)、上平砧下梯型砧和上下梯型砧三種不同砧型下各自的成形過(guò)程和變形特點(diǎn),與上平砧下V型砧拔長(zhǎng)的效果進(jìn)行對(duì)比。并從等效應(yīng)變、等效應(yīng)力、溫度場(chǎng)和動(dòng)態(tài)再結(jié)晶百分?jǐn)?shù)分布等方面,詳細(xì)對(duì)比分析了四種砧型拔長(zhǎng)工藝的優(yōu)劣。最終結(jié)果表明:上平砧下V型砧拔長(zhǎng)與上平砧下梯型砧拔長(zhǎng)效果較好。
[Abstract]:The manufacturing of large forgings is a complex process of integrated smelting, forging and heat treatment of large ingots. Forging and heat treatment are two very important links in the manufacturing process of large forgings. Grain size inhomogeneity and deformation inhomogeneity affect the quality of large forgings to a great extent and lead to product scrapping directly when serious. During the forming process of large forgings, complex microstructure evolves inside the ingot, and the final grain size and uniformity of the product are controlled by many factors, such as deformation temperature, reduction amount and deformation uniformity, etc., if the treatment is not appropriate, Will bring great trouble to the follow-up heat treatment. Therefore, it is very important to study the microstructure homogeneity, microstructure evolution and grain size distribution in forging for obtaining high quality forgings. In this paper, the austenitic grain growth law and microstructure evolution during pull-out process of 12%Cr ultra-supercritical rotor steel for nuclear power large rotor material are studied. First, the austenite grain growth law of this steel at different holding time and different heating temperature was studied by box resistance furnace. The dynamic equation of austenite grain growth in this steel is obtained by using nonlinear regression analysis and Arrhenius grain growth model. Then, the effect of V-shaped anvil drawing process under different forging ratios on the microstructure evolution of 12%Cr ultra-supercritical rotor steel was studied by using DEFORM-3D numerical simulation technique and shrinkage test. The grain size distribution and deformation uniformity at different forging ratios and cross section characteristic points of forgings are analyzed, and the experimental results and numerical simulation results are compared and analyzed. It is concluded that when the forging ratio increases from 1.1 to 1.3, the deformation inhomogeneity increases, but the average grain size decreases, and the microstructure inhomogeneity of the forging can be improved to some extent. Finally, DEFORM-3D numerical simulation software is used to analyze the forming process and deformation characteristics of 12%Cr ultra-supercritical rotors under three different anvil types: upper and lower trapezoidal anvil (FM), upper and lower trapezoidal anvil and upper and lower trapezoidal anvil. The results were compared with that of V type anvil under upper flat anvil. From the aspects of equivalent strain, equivalent stress, temperature field and dynamic recrystallization percentage distribution, the advantages and disadvantages of four anvil drawing processes are compared and analyzed in detail. The final results showed that the drawing length of V type anvil under upper flat anvil and trapezoidal anvil under upper flat anvil was better than that of trapezoidal anvil under upper flat anvil.
【學(xué)位授予單位】：太原科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG142.1;TG316.12

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本文編號(hào)：2412267