本文關(guān)鍵詞：釉化用鋼熱軋和熱處理過程奧氏體—鐵素體轉(zhuǎn)變的數(shù)值模擬　出處：《東南大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 釉化用鋼 數(shù)值模擬 元胞自動(dòng)機(jī) 奧氏體-鐵素體相變 屈服強(qiáng)度

【摘要】：本文采用模擬和實(shí)驗(yàn)相結(jié)合的方法,對(duì)釉化用鋼熱軋和熱處理過程中顯微組織和C濃度分布的演化進(jìn)行研究。在實(shí)驗(yàn)基礎(chǔ)上,建立耦合熱力學(xué)數(shù)據(jù)庫(kù)以及有限元模擬的溫度場(chǎng)和應(yīng)力場(chǎng)的二維元胞自動(dòng)機(jī)(cellular automaton,CA)模型。該模型包含了奧氏體(Y)和鐵素體(α)的連續(xù)形核、由C濃度場(chǎng)、應(yīng)變能和界面遷移率所控制的相變、溶質(zhì)C在γ/α界面處的再分配以及在αα和γ中的擴(kuò)散。應(yīng)用該CA模型模擬了形變誘導(dǎo)鐵素體相變(dynamic strain induced transformation,DSIT)熱軋和連續(xù)熱軋過程、在αα-Y兩相區(qū)的保溫、以不同冷卻速度的連續(xù)冷卻、以及不同溫度下回火的熱處理過程中的顯微組織與C濃度場(chǎng)的演化,在此基礎(chǔ)上分析工藝-組織-力學(xué)性能之間的關(guān)系。此外,采用實(shí)驗(yàn)方法研究了不同保溫時(shí)間對(duì)冷、熱軋釉化用鋼在不同溫度保溫冷卻后的組織和性能的影響。熱軋過程的CA模擬結(jié)果表明,DSIT過程中第四道次軋前降溫過程,隨溫度降低,αα相分?jǐn)?shù)增長(zhǎng)速率先慢后快再逐漸減小。軋制過程中溫度迅速升高且有應(yīng)力作用,但由于持續(xù)時(shí)間較短,顯微組織無明顯變化,α/γ相界面周圍出現(xiàn)貧C區(qū)。在軋后降溫過程中,發(fā)生α→γ逆轉(zhuǎn)變,隨后開始γ→α相變。因此,αα相分?jǐn)?shù)先降低后升高,室溫時(shí)顯微組織主要為晶粒尺寸較細(xì)小的α相和沿晶界分布的富C塊狀相。在連軋第七道次降溫過程中發(fā)生γ→α轉(zhuǎn)變,α相分?jǐn)?shù)增長(zhǎng)速率先慢后快再逐漸減小。室溫時(shí)顯微組織主要為晶粒尺寸較粗大的α相和晶界處尺寸較大的富C塊狀相。熱處理過程的CA模擬結(jié)果表明,在α-γ兩相區(qū)的815℃保溫過程中α→γγ相變由界面控制逐漸轉(zhuǎn)變?yōu)閿U(kuò)散控制,呈現(xiàn)出混合控制模式,保溫300 s后αα相與γ相中的C濃度均達(dá)到各自的平衡值。在隨后的連續(xù)冷卻過程發(fā)生γ→α相變,以1.5℃/s冷速冷卻至室溫后的C濃度場(chǎng)比5.0℃/s時(shí)的C濃度場(chǎng)更均勻。以5.0℃/s冷卻至室溫后的試樣在300℃和500℃溫度下回火5 min,C分布均勻性隨回火溫度升高而提高。模擬結(jié)果可合理解釋相關(guān)實(shí)驗(yàn)現(xiàn)象的機(jī)理。保溫不同時(shí)間的熱處理實(shí)驗(yàn)結(jié)果表明,C、Mn、Si含量較低的2#冷軋鋼板經(jīng)不同溫度保溫空冷后,與軋制態(tài)相比,屈服強(qiáng)度降低,并隨保溫溫度升高而下降,不同保溫時(shí)間對(duì)屈服強(qiáng)度影響不大。C、Mn、Si較高的18#冷軋鋼板經(jīng)700～870℃保溫砂冷后,屈服強(qiáng)度高于空冷及軋制態(tài)的屈服強(qiáng)度,在760℃和840℃保溫10 min砂冷的屈服強(qiáng)度比保溫5 min砂冷的屈服強(qiáng)度分別提高46 MPa和27 MPa;在760～870℃溫度范圍內(nèi)保溫10 min空冷的屈服強(qiáng)度比保溫5 min空冷的屈服強(qiáng)度提高約15 MPa。與18#成分相同的17#熱軋鋼板在不同溫度保溫空冷后,在700～815℃區(qū)間,延長(zhǎng)保溫時(shí)間對(duì)屈服強(qiáng)度影響不大;在840℃和870℃時(shí),延長(zhǎng)保溫時(shí)間能提高屈服強(qiáng)度約25 MPa。
[Abstract]:This paper uses the method of combination of simulation and experiment, the glaze and microstructure evolution of C steel hot rolling and heat treatment process of concentration distribution is studied. On the basis of experiment, a coupled thermodynamic database and finite element simulation of temperature field and stress field of two-dimensional cellular automata (cellular, automaton, CA) model. The model consists of austenite and ferrite (Y) (a) of the continuous nucleation, C concentration field, strain energy and interface mobility under the control of the phase transition, the solute C in gamma / alpha at the interface and redistribution in the alpha alpha and gamma diffusion in the application of the CA model. The deformation induced ferrite transformation (dynamic strain induced transformation, DSIT) and continuous hot rolling process, thermal insulation in the alpha alpha -Y two-phase region, with continuous cooling with different cooling rate, microstructure and heat treatment under different temperature tempering process of fabric and C concentration field of play Analysis of the relationship between technology and organization of mechanical properties on this basis. In addition, an experimental study of different cold preservation time on the effect of hot rolling, glaze microstructure and properties of steel at different temperature after cooling the hot rolling process. The simulation results show that CA, DSIT in the process of fourth times before rolling the cooling process, with the decrease of temperature, the alpha alpha phase fraction the growth rate of the first slow fast and then decreased gradually. In the process of rolling temperature increased rapidly and the stress, but due to short duration, no significant changes in microstructure, alpha / gamma phase interface around the C area. In the poor cooling after rolling process. To have alpha gamma gamma inverse transformation, then began to alpha transformation. Therefore, alpha alpha phase fraction increased firstly and then decreased, the microstructure at room temperature is mainly a phase and grain size smaller distributed along the grain boundaries of C rich phase, alpha gamma. Block occurred in the rolling seventh cooling process Change, phase fraction growth rate soon after the first slow then decreases. When the room temperature microstructure of C rich massive large phase and grain boundary grain size coarse phase. The heat treatment process of CA simulation results show that the insulation in the alpha gamma phase region 815 DEG C during alpha to gamma gamma phase from the interface control gradually transformed into diffusion control, presents a hybrid control mode, after holding for 300 s and alpha alpha gamma phase C concentration reached their equilibrium values. And phase change in continuous gamma alpha cooling to 1.5 DEG C, C concentration field /s cooling rate and cooling to room temperature than the concentration of C 5 C /s is more uniform. The sample /s 5 degrees of cooling to room temperature after tempering for 5 min at 300 DEG C and at a temperature of 500 DEG C, C distribution uniformity with the tempering temperature increases. The simulation results can explain the mechanism of the experimental phenomena. The experiments of heat treatment for different holding time. The results show that C, Mn, 2# cold rolled steel plate with low content of Si with different temperature after air cooling, compared with rolling, the yield strength decreased, and decreased along with temperature, different holding time has little influence on the yield strength of.C, Mn, 18# cold rolled steel Si higher by 700 ~ 870 DEG C sand cold, yield strength is higher than that of air cooling and rolling, the yield strength in the yield strength of 760 degrees and 840 degrees heat 10 min sand cold insulation cold sand than 5 min were increased by 46 MPa and 27 MPa; in 760 ~ 870 degrees Celsius temperature range 10 min insulation cooling yield strength more than 5 min air cooling insulation yield strength is increased by about 15 MPa. with the same 18# components of 17# hot rolled steel at different temperature after air cooling, in 700 ~ 815 degrees interval, time has little influence on the yield strength; at 840 DEG and 870 DEG C, holding time can improve the yield strength of about 25 MPa.

【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG142.1;TG335.11;TG161

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