冷軋高強(qiáng)鋼板淬火過程板形瓢曲缺陷演變規(guī)律研究冷軋高強(qiáng)鋼板淬火過程板形瓢曲缺陷演變規(guī)律研究FLATNESS DEFECT EVOLUTION OF COLD-ROLLED HIGH STRENGTH STEEL STRIP DURING QUENCHING PROCESS 針對已有板形瓢曲浪形缺陷冷軋高強(qiáng)鋼板的淬火過程，應(yīng)用ABAQUS有限元分析平臺及其UMAT二次開發(fā)功能，建立淬火過程溫度-組織-應(yīng)力應(yīng)變多場耦合的有限元仿真模型，研究淬火過程高強(qiáng)鋼板的彈塑性變形行為及其對初始板形瓢曲缺陷的改變。通過熱模擬實(shí)驗(yàn)結(jié)果對該有限元仿真模型進(jìn)行了驗(yàn)證，模擬再現(xiàn)了已瓢曲高強(qiáng)鋼板的淬火過程及彈塑性變形，獲得了板形瓢曲浪形在淬火過程中的演變規(guī)律，指出鋼板寬度方向上的溫度梯度以及依先后順序相變所引起的鋼板縱向延伸變形沿寬度方向上分布不均勻，導(dǎo)致原有板形瓢曲浪形發(fā)生改變，甚至可以生成新的瓢曲浪形。定義了描述板形瓢曲浪形改變程度的指標(biāo)，如浪高變化率、浪寬變化率、浪距變化率，定量揭示橫向溫差、張力等工藝參數(shù)對冷軋高強(qiáng)鋼板淬火過程板形變化的影響規(guī)律。搭建實(shí)驗(yàn)室冷軋鋼板淬火實(shí)驗(yàn)研究系統(tǒng)，開展具有單邊浪板形瓢曲缺陷鋼板的淬火實(shí)驗(yàn)，實(shí)驗(yàn)結(jié)果與仿真計算結(jié)果取得定性一致。本工作的數(shù)值模擬方法建立了冷軋高強(qiáng)鋼淬火過程工藝參數(shù)和板形缺陷變化之間的聯(lián)系，為實(shí)際熱處理過程提供了支撐。 Quenching is a key process in cold-rolled high strength steel manufacturing for the improvement of the material strength and plasticity. The quenching, however, may bring initial flatness defects of the steel strips, which causes problems for subsequent production process. It is thus necessary to study the flatness defects evolution during the quenching process. Using the secondary development of ABAQUS subroutine UMAT, this work establishes a temperature-microstructure-stress coupling Finite Element Modeling (FEM) model to simulate the quenching process of the high strength steel with initial buckling defects. Thermal simulation experiments are further conducted to verify the present FEM model. Then, the elastic-plastic deformation behavior of the steel plates and its effects on flatness buckling during the quenching process is investigated using the FEM model. As a consequence, the buckling defect evolution mechanism in heat treatment process is obtained for the cold-rolled high strength steel. The flatness change or the forming of new flatness defect is mainly caused by the longitudinal extension arising from temperature gradient and the sequential phase transformation different in width and transverse directions. Change rates of the wave height, width, and length are used to describe the flatness change degree, quantifying the influence of the tension and initial transverse temperature difference on flatness change. The simulation shows that the tension has a positive correlation with the improvement of initial bucking defects. The initial edge waves become more severe after quenching along with the appearance of the new quarter waves, when the initial temperature of strip center is higher than that of the edge. On the contrary, the initial central waves become more serious when the initial temperature of strip center is lower. Meanwhile, joint impact of the tension and the initial transverse temperature difference on wave height is revealed for the application of industrial practice. Furthermore, quenching experiments of the high strength steel plates with initial single edge wave buckling defects are carried out using the experiment system in lab. Different sides of the plates quench into the water tank to reproduce the sequence of the phase change. The simulation and experiments produce consistent results qualitatively. This work makes connections between technological parameters and flatness change during quenching process, which can provide support to industrial heat treatment of high strength steel.
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