【摘要】：高強度鋼在建筑、交通、橋梁、船舶、工程機械、輸油氣管道、大型塔架結構以及國防裝備等眾多領域具有廣泛應用前景。冷軋高強鋼板帶熱處理過程的板形問題是制約其進一步提高質量的主要生產技術難題。因此,本文依托國家自然科學基金面上項目“超高強度鋼板平整與矯直加工過程殘余應力控制的基礎研究”,對有初始板形缺陷冷軋高強鋼板帶熱處理過程的板形變化規(guī)律進行研究,揭示熱處理過程板形演變機理,獲得熱處理過程的板形變化規(guī)律,提出高強鋼板帶熱處理過程板形控制策略,為冷軋高強鋼板帶熱處理生產工藝優(yōu)化提供理論支持。本文的主要內容和研究成果如下。 (1)對DP780鋼和22MnB5鋼進行了等溫拉伸實驗,建立了一種耦合應變硬化效應和溫度軟化效應的改進Johnson-Cook本構模型,將該本構模型進行數(shù)值實現(xiàn)并基于ABAQUS軟件進行了數(shù)值模擬,對典型拉伸實驗過程進行建模及仿真再現(xiàn),模擬結果與實驗結果吻合較好。 (2)建立以上兩種高強鋼考慮應力影響的相變動力學及相變塑性模型和考慮相變及溫度影響的彈塑性本構模型,并通過對ABAQUS軟件二次開發(fā),實現(xiàn)了針對以上兩種高強鋼熱處理過程的溫度場與組織場及應力應變場多場耦合的數(shù)值模擬,通過22MnB5鋼淬火、DP780退火的熱模擬實驗,驗證了兩種熱處理過程多場耦合有限元模型。 (3)針對已瓢曲22MnB5板帶,仿真研究了板形瓢曲缺陷在熱處理過程中的演變機理,發(fā)現(xiàn)帶鋼寬度方向上的溫度梯度和依先后順序相變引起了帶鋼寬度方向的縱向延伸不均進而導致了板形瓢曲的改變,獲得張力、初始橫向溫差等工藝參數(shù)對其板形變化的影響規(guī)律,提出了相應板形控制策略。 (4)針對已翹曲22MnB5板帶,仿真研究了板形翹曲缺陷在熱處理過程中的演變機理,發(fā)現(xiàn)帶鋼厚度方向上的溫度梯度和依先后順序相變引起了帶鋼厚度方向的縱向延伸不均進而導致了板形翹曲的改變,獲得張力、初始厚向溫差等工藝參數(shù)對其板形變化的影響規(guī)律,提出了相應板形控制策略。 (5)在實驗室條件下,設計搭建了淬火實驗系統(tǒng),分別對有瓢曲和有翹曲22MnB5鋼板進行了淬火實驗,研究了淬火對瓢曲和翹曲的影響,實驗較好驗證了仿真模型及結果。
[Abstract]:High strength steel is widely used in many fields, such as construction, transportation, bridge, ship, construction machinery, oil and gas pipeline, large tower structure and national defense equipment. The flatness of cold rolled high strength steel strip during heat treatment is the main technical problem restricting the further improvement of its quality. Therefore, this paper relies on the project of National Natural Science Foundation of China, "basic research on residual stress control in the process of leveling and straightening of ultra-high strength steel plate". In this paper, the shape changing law of cold rolled high strength steel strip with initial shape defect is studied, and the shape evolution mechanism of heat treatment process is revealed, and the shape change law of heat treatment process is obtained. The flatness control strategy during heat treatment of high strength steel sheet and strip is put forward, which provides theoretical support for optimization of heat treatment process of cold rolled high strength steel sheet and strip. The main contents and results of this paper are as follows: (1) the isothermal tensile tests of DP780 and 22MnB5 steels are carried out, and an improved Johnson-Cook constitutive model coupled with strain-hardening effect and temperature-softening effect is established. The constitutive model is numerically realized and simulated based on ABAQUS software. The typical tensile experiment process is modeled and simulated. The simulation results are in good agreement with the experimental results. (2) the transformation kinetics and transformation plasticity model of the two kinds of high strength steels are established, and the elastoplastic constitutive model considering the effect of phase transition and temperature is established. Through the secondary development of ABAQUS software, the numerical simulation of the coupling of temperature field, microstructure field and stress-strain field in the heat treatment process of the two kinds of high strength steels is realized, and the thermal simulation experiment of 22MnB5 steel quenched with DP780 annealing is carried out. The multi-field coupling finite element models of two kinds of heat treatment processes are verified. (3) the evolution mechanism of plate shape curling defects in heat treatment process is simulated and studied for the 22MnB5 plate and strip that have been curled. It is found that the temperature gradient in the width direction and the phase transformation in sequence lead to the uneven longitudinal extension in the width direction of the strip, which leads to the change of the shape of the strip, and the tension is obtained. The influence of process parameters such as initial transverse temperature difference on the shape of the strip is studied, and the corresponding shape control strategy is proposed. (4) the evolution mechanism of the shape warping defect in the heat treatment process is studied by simulation for the 22MnB5 strip. It is found that the temperature gradient in the direction of strip thickness and the phase transformation in sequence lead to the uneven longitudinal extension in the direction of strip thickness, which leads to the change of the shape warpage of the strip, and the tension is obtained. The influence of the process parameters such as initial thickness temperature difference on the shape change of the plate is presented. (5) the quenching experiment system is designed and built under the laboratory conditions. The effects of quenching on the bending and warping of 22MnB5 steel plate were studied, and the simulation model and results were verified.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG162.8;TG335.5

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