【摘要】：超超臨界汽輪機高中壓轉(zhuǎn)子作為典型的大型鍛件產(chǎn)品,其生產(chǎn)制造流程中大型鋼錠的鑄錠是最關(guān)鍵環(huán)節(jié),大型鑄錠質(zhì)量是決定鍛件產(chǎn)品質(zhì)量的重要基礎(chǔ)。而鑄錠質(zhì)量主要與凝固過程控制相關(guān),因此,有必要對鑄錠凝固過程進行系統(tǒng)深入研究。另一方面,高中壓轉(zhuǎn)子在長期服役過程中,涉及高溫和應(yīng)力作用下微觀組織演變等組織穩(wěn)定性理論問題,需要全面系統(tǒng)地了解高中壓轉(zhuǎn)子材料在高溫/力作用下微觀組織亞結(jié)構(gòu)演變規(guī)律。這是超超臨界汽輪機高中壓轉(zhuǎn)子產(chǎn)品開發(fā)和使用中面臨的兩個核心理論問題,必須深入開展理論研究,為制造工程提供科學(xué)支撐。針對上述兩個核心問題,以高中壓轉(zhuǎn)子用材X12CrMoWVNbN10-1-1為例,開展了系統(tǒng)探究,主要的研究內(nèi)容與研究結(jié)果如下:1.運用ProCast軟件對大型鑄錠凝固過程中溫度場、流場進行模擬計算。并根據(jù)改進型Niyama判據(jù)對鑄錠中心疏松分布進行預(yù)測。結(jié)果表明,中心疏松缺陷呈細長條帶分布。建立了表征中心疏松區(qū)域尺度的判據(jù)函數(shù)N=H_(porosity)/H_(ingot),其中H_(porosity)為疏松帶長度,H_(ingot)為鑄錠高度,結(jié)果表明,錠身高徑比從1.0增加至1.5,判據(jù)函數(shù)N值基本按二次多項式規(guī)律增加,其數(shù)值由0.274增加至0.509;而錠身錐度由6%增加至12%,N值基本按線性規(guī)律遞減,其數(shù)值由0.378減小到0.309。2.采用CAFE(元胞有限元)法對鑄錠宏觀組織進行模擬計算,通過低倍組織檢驗對數(shù)值模擬準確性進行驗證。并基于此CAFE模型,研究形核密度以及過熱度對柱狀晶和等軸晶分布、芯部等軸晶晶粒尺寸等幾方面的影響規(guī)律。3.為縮小冒口尺寸,開發(fā)了冒口感應(yīng)加熱專利技術(shù)。通過數(shù)值模擬定量描述了感應(yīng)加熱過程中溫度場及流場分布,研究了電參數(shù)(輸入功率、頻率)及線圈設(shè)計(熔體與線圈間距、線圈高度)對感應(yīng)加熱過程的影響。結(jié)果表明:冒口感應(yīng)加熱技術(shù)可以控制鑄錠冒口的凝固過程,影響冒口區(qū)域流場分布,并且隨著加熱功率提高,縮孔形態(tài)由窄而深的“V字型”轉(zhuǎn)變?yōu)闇\而平的“碗狀”,縮孔深度大大減少。以200 kg中間試驗鑄錠為例,通過冒口感應(yīng)加熱使得縮孔深度相對減小了40%。4.650℃時效結(jié)果表明,時效750 h后,開始有Laves相析出。時效10000 h后,基體α相和Laves相存在的位向關(guān)系為:{011}α∥{0001}Laves、{411}α∥{0001}Laves、{111}α∥{0001}Laves、{011}α∥{2110}Laves、{211}α∥{1101}Laves。5.650℃/300 h蠕變試驗結(jié)果表明,蠕變應(yīng)力促進了馬氏體板條寬化程度,蠕變應(yīng)力從0增至170 MPa,馬氏體板條寬度由330 nm增至465 nm。M23C6尺寸由97 nm增加至130 nm,數(shù)量密度由2.55個/μm~2減少至2.08個/μm~2;而MX型析出相尺寸和數(shù)量密度相對穩(wěn)定,分別為80 nm和2.8個/μm~2,蠕變應(yīng)力沒有對其產(chǎn)生明顯影響。初生Laves大多沿50-60°大角度晶界析出,蠕變應(yīng)力會促進Laves相沿晶界和板條界的形核長大。通過EBSD、TEM、XRD等先進手段針對高中壓轉(zhuǎn)子服役過程中熱作用下的Laves與基體相位向關(guān)系、熱-應(yīng)力綜合作用下組織演變理論問題所進行的深入剖析,豐富和拓展了我國超超臨界高中壓轉(zhuǎn)子材料服役條件下的組織性能穩(wěn)定性研究理論體系。高中壓轉(zhuǎn)子材料鑄錠凝固過程的數(shù)值模擬計算研究結(jié)果深化了凝固過程所涉及的溫度場、縮孔及中心疏松缺陷分布、凝固宏觀組織分布等理論問題的認識,可對我國高中壓轉(zhuǎn)子用大型鑄錠生產(chǎn)中鋼錠模設(shè)計優(yōu)化提供理論依據(jù)與技術(shù)指導(dǎo),具有顯著的工程實踐意義。
[Abstract]:As a typical large-scale forging product, the super-supercritical steam turbine high-pressure rotor is the most critical step in the production and manufacturing process of large-scale ingot, and the quality of large-scale ingot is an important basis for determining the product quality of the forging. The quality of the ingot is mainly related to the control of the solidification process. Therefore, it is necessary to deeply study the solidification process of the ingot. On the other hand, in the process of long-term service, the high-and high-pressure rotor relates to the theory of microstructure evolution such as microstructure evolution under high temperature and stress. It is necessary to comprehensively and systematically understand the microstructure evolution of the high-and high-pressure rotor material under the action of high temperature/ force. This is the two core theoretical problems faced in the product development and use of the super-supercritical steam turbine high-pressure rotor, and the theoretical research must be carried out to provide scientific support for manufacturing engineering. In view of the above two core problems, the system inquiry is carried out with the material X12CrMoWVNbN10-1-1 for high-school pressure rotor, and the main research contents and the research results are as follows: 1. The temperature field and flow field in the solidification process of large-scale ingot were simulated by using ProCast software. and the loose distribution of the ingot center is predicted according to the modified Niyama criterion. The results show that the central loose defect is in the form of an elongated strip. The criterion function N = H _ (porsoity)/ H _ (ingot) for the scale of the central loose zone is established, where H _ (porsoity) is the length of the loose strip, and the H _ (ingot) is the height of the ingot. The results show that the height-diameter ratio of the ingot is increased from 1.0 to 1.5, and the N value of the criterion function is basically increased by the law of the quadratic polynomial, and its value is increased from 0.274 to 0.509; and the taper of the spindle body is increased from 6% to 12%, and the N value is gradually decreased by the linear rule, and the numerical value is reduced from 0.378 to 0.309. 2. In this paper, the CAFE method is used to calculate the macrostructure of the ingot, and the accuracy of the numerical simulation is verified by the low-time tissue test. Based on the CAFE model, the influence of the shape core density and the degree of superheat on the crystal grain size of the equiaxed grain and the equiaxed grain, the core part and the like is studied. In order to reduce the size of the riser, the technology of riser induction heating is developed. The influence of the electric parameters (input power, frequency) and coil design (the distance between the melt and the coil and the height of the coil) on the induction heating process is studied by means of numerical simulation. The results show that the riser induction heating technology can control the solidification process of the riser and influence the distribution of the flow field in the riser region, and the shrinkage cavity form is changed from the narrow and deep 鈥淰-type鈥，

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