本文選題：貝氏體鋼軌鋼 + 強韌性��； 參考：《北京交通大學(xué)》2017年博士論文

【摘要】：本文以20Mn2SiCrMo貝氏體鋼軌鋼為對象,進行了"成分-工藝-組織-性能"的系統(tǒng)研究,基于動態(tài)/靜態(tài)CCT曲線和TTT曲線,結(jié)合模擬計算和實驗檢測,探究了成分、關(guān)鍵工藝參數(shù)與組織性能間的關(guān)系;針對貝氏體鋼軌大生產(chǎn)時軋后空冷過程中出現(xiàn)的類等溫平臺現(xiàn)象,揭示了不同等溫溫度對相變、組織及性能的影響規(guī)律;研究了回火過程中殘余奧氏體形態(tài)、含量及穩(wěn)定性等對強韌性的影響規(guī)律;就深冷處理對貝氏體鋼軌鋼的影響進行了初步探索,并就調(diào)整后的貝氏體鋼軌與珠光體鋼軌的磨損與接觸疲勞性能進行了對比研究,獲得結(jié)果如下:1.元素Mn、Mo、Ni強化鋼淬透性的作用明顯,在現(xiàn)有貝氏體鋼軌成分體系基礎(chǔ)上,當(dāng)Mn含量大于1.9wt.%左右時,能避免60kg/m重載鋼軌軋后空冷過程中先共析鐵素體的形成。模擬計算和試驗檢測吻合度較高,獲得了—整套"模擬計算預(yù)測—實測—組織表征—關(guān)鍵部位仿真計算—反饋"的科學(xué)研究方案。2.在跟蹤貝氏體鋼軌實際生產(chǎn)時發(fā)現(xiàn),軋后空冷到室溫的過程中,在中溫區(qū)某一溫度附近鋼軌將經(jīng)歷一定時長的類等溫平臺,該平臺溫度對鋼軌的相變行為、顯微組織及綜合性能等有重要影響。隨等溫溫度升高,粒狀貝氏體含量逐步增加,板條貝氏體含量降低,馬奧島尺寸逐漸增大。通過調(diào)整等溫平臺溫度可達到組織細化和性能優(yōu)化的效果。當(dāng)?shù)葴販囟葹?25℃時,抗拉強度、斷后伸長率及室溫U型沖擊韌性分別為1391 MPa、15%、142 J,比350℃等溫時的沖擊韌性高出約46%。以本研究結(jié)果為基礎(chǔ),后續(xù)通過進一步探究等溫平臺參數(shù)(溫度、時間等)與相變行為的內(nèi)在聯(lián)系,從而可根據(jù)該等溫平臺的參數(shù)來感知鋼中相變行為,并對鋼軌的組織和性能進行預(yù)測與調(diào)控。3.回火處理后組織中殘余奧氏體的含量、形態(tài)及穩(wěn)定性對鋼軌性能具有重要影響。隨回火溫度升高,馬奧島分解程度增加,殘余奧氏體數(shù)量減少,鋼軌鋼韌性出現(xiàn)先升高后降低的趨勢�；鼗鹛幚砜商岣邿彳垜B(tài)鋼軌中殘余奧氏體的穩(wěn)定性,經(jīng)280℃回火后,殘余奧氏體的穩(wěn)定性較高,可獲得最佳的強韌性匹配。與鋼軌軋態(tài)、250℃回火狀態(tài)相比,280℃回火處理后貝氏體鋼軌室溫沖擊韌性分別相應(yīng)提高約90%和10%。4.深冷處理可作為貝氏體鋼軌鋼性能優(yōu)化和延長鋼軌服役壽命的一種潛在工藝。鋼軌鋼經(jīng)深冷處理后,除殘余奧氏體穩(wěn)定性得到進一步提高外,其強度、延伸率及硬度等均獲得不同程度提高。5.在滑動磨損和沖擊磨損過程中,鋼軌的相對耐磨性與實驗所采用的載荷大小緊密相關(guān)。較大實驗載荷下,貝氏體鋼軌鋼的耐磨性優(yōu)于珠光體鋼軌鋼;較低實驗載荷下,珠光體鋼軌鋼的耐磨性相對較好。在滾動接觸疲勞過程中,珠光體組織比貝氏體組織更易形成表面硬化層,該硬化層與基體組織的界面是潛在的裂紋擴展路徑。6.貝氏體鋼軌服役過程中的失效分析表明,膜狀馬奧島對于裂紋擴展具有抑制作用。
[Abstract]:In this paper, a systematic study of 20Mn2SiCrMo bainite rail steel was carried out. Based on the dynamic / static CCT curve and the TTT curve, the relationship between the components, the key process parameters and the microstructure and properties was investigated by the combination of the dynamic / static CCT curves and the TTT curves. The effect of different isothermal temperature on the phase transition, microstructure and properties of different isothermal temperatures is revealed, and the influence of the retained austenite shape, content and stability on the strength and toughness during the process of tempering is studied, and the influence of the cryogenic treatment on bainite rail steel is first explored, and the adjusted bainite rail and pearlite are made. The wear and contact fatigue performance of the body rail are compared. The results are as follows: 1. elements Mn, Mo and Ni strengthen the hardenability of steel obviously. On the basis of the existing bainite rail composition system, when the content of Mn is more than 1.9wt.%, the formation of the eutectoid ferrite in the cold process of heavy rail after 60kg/m heavy load can be avoided. A scientific research program of "simulated calculation, measurement, measurement, organization characterization, key position simulation calculation feedback" is obtained from the test test, and.2. is found in the actual production of bainite rail. It is found that in the process of air cooling to room temperature after rolling, the rail will undergo a certain length of class in the middle temperature zone near a temperature. Temperature platform, the temperature of the platform has an important influence on the phase transformation, microstructure and comprehensive properties of the rail. With the increase of temperature, the content of granular bainite increases gradually, the content of bainite decreases, and the size of Ma o Island increases gradually. The effect of microstructure refinement and performance optimization can be achieved by adjusting the temperature of the isothermal platform. At 325 C, the tensile strength, the elongation at the end and the U type impact toughness at room temperature are 1391 MPa, 15%, 142 J respectively, and the impact toughness is about 46%. higher than that of 350 C, based on the results of this study, and further explore the internal relations between the isothermal platform parameters (temperature, time, etc.) and the phase variation behavior, which can be based on the parameters of the isothermal platform. The phase transformation behavior in steel is perceived and the microstructure and properties of the rail are predicted and the content, morphology and stability of the retained austenite in the.3. tempering process have important influence on the rail performance. With the increase of tempering temperature, the decomposition degree of the Mao Island increases, the amount of the retained austenite decreases, and the toughness of the rail steel increases first. The tempering treatment can improve the stability of retained austenite in the hot rolled rail. After tempering at 280 C, the stability of the retained austenite is higher and the best strength and toughness can be obtained. Compared with the rail rolling state and the tempering state at 250 C, the impact toughness of the bainitic steel rail at 280 C after tempering is about 90% and 10%.4., respectively. Cryogenic treatment can be used as a potential process for optimizing the performance of bainite rail steel and prolonging the service life of rail. After cryogenic treatment of rail steel, the strength, elongation and hardness of the retained austenite are further improved, and the relative resistance of rail to.5. in the process of sliding wear and impact wear is improved in varying degrees. The wear resistance of the bainite rail steel is better than the pearlite rail steel under the larger experimental load. The wear resistance of the pearlite rail steel is better under the lower experimental load. In the rolling contact fatigue process, the pearlite structure is more prone to form the surface hardening layer than the bainite structure, and the hardened layer is more easily formed. The interface between the matrix and the matrix is the potential crack propagation path.6. bainite rail service failure analysis shows that the membrane like maro island has an inhibitory effect on the crack growth.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：U213.4

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