高能脉冲电流作用下高强度耐磨不锈钢/碳钢轧制复合机理研究

A high strength and wear-resisting stainless steel strip and a carbon steel strip could not be bonded together by cold rolling because oxide layers of the to-be bonded surfaces can’t be broken by insufficient plastic deformation there. The critical plastic deformation is big while the bonding strength is low. High energy pulse current is creatively supplied to the to-be bonded surfaces during this traditional cold cladding rolling to make the stainless steel strip and the carbon steel strip bond together with much smaller critical deformation and much higher bonding strength, taking advantage of the skin effect and the proximity effect of the high energy pulse current. The Joule heating effect can decrease plastic deformation resistance of the metal materials around the to-be bonded surfaces while the non-heat effect of the currency can activate metallurgical behaviors. This high energy pulse current aided bonding process could be treated as a healing process of a complicated edge crack under plain strain condition. Field variables around the crack tip zone can be determined by finite element method. Displacement criterion for the crack healing can be established basing on the bowling out mechanism of a grain boundary in the to-be bonded surfaces. And the energy criterion for the crack healing can be established with the aid of the J parameter from the Elastic Plastic Fracture Mechanics. The thermodynamics model and the kinetics model for the metallurgical behaviors around the crack tip zone can be established on the basis of characterization and evaluation of the metallurgical behaviors. The bonding mechanism for high energy pulse current aided cladding rolling of the stainless steel strip and the carbon steel strip can be clarified basing on the crack healing criterion and the metallurgical behavior models. As a result, basic theories and new technologies for rolling bonding of high strength and wear-resisting metals with high efficiency, low energy consumption and high bonding quality can be provided by this study.

高强度耐磨双金属冷轧复合过程中待复合表面很难获得足够的塑性变形，无法通过待复合表面硬化层破裂实现复合，存在着临界压下量大、复合界面强度低的问题。本项目创新性地利用高能脉冲电流的趋肤效应和邻近效应，将其准确地添加到高强度耐磨不锈钢/碳钢轧制复合表面区域。其热效应能高效降低待复合区域金属的变形抗力，其非热效应能有效激活复合界面金属的冶金行为，实现电-热-力耦合作用下的轧制复合。复合过程实质为平面应变条件下“半无限大平板”复合型边裂纹的愈合过程。解析脉冲电流作用下轧制复合界面裂纹尖端区域的场量，基于界面复合的晶界弓出机制，建立裂纹愈合的位移判据。引入弹塑性断裂力学J积分参量，建立裂纹愈合的能量判据。表征裂纹尖端区域的冶金行为，建立其热力学模型和动力学模型。据此，阐明高能脉冲电流作用下不锈钢/碳钢轧制复合机理。为实现高强度耐磨双金属高效、低能耗、高质量轧制复合提供新的理论基础和技术支持。

项目以解决高强度耐磨双金属冷轧固相复合技术中存在的临界道次压下量大、界面复合质量不高、难以实现高强度耐磨金属材料有效复合的问题，利用高频脉冲电流的趋肤效应和邻近效应，将高频脉冲电流直接添加至不锈钢/碳钢轧制复合界面及其附近区域，实现了电-热-力耦合作用下不锈钢/碳钢轧制/压下复合。项目组完成了不锈钢和碳钢不同温度、压下速率条件下的单道次压缩实验，回归得到了基于Zener-Hollomon参数的流变应力模型、回复再结晶动力学模型，不锈钢再结晶激活能为356.4 kJ/mol，普碳钢再结晶激活能为273.41kJ/mol。在商用有限元软件平台上建立了高频脉冲电流辅助不锈钢/碳钢轧制/压下复合过程电-热-力耦合有限元模型，并通过二次开发将不锈钢和碳钢回复再结晶模型耦合到上述有限元模型中，实现了脉冲电流辅助不锈钢/碳钢轧制/压下复合过程电-热-力-组织耦合有限元法解析。在自制脉冲电流辅助双金属准静态压下复合实验设备上开展了系列高频脉冲电流辅助下不锈钢/碳钢压下复合实验研究。建立了平面应变条件下半无限大裂纹愈合的能量判据。研究结果表明，在居里温度以下增加脉冲电流频率强化脉冲电流在钢带中的临近效应，增加不锈钢带和碳钢带厚度方向的温度梯度，且不锈钢复合面上温度和温度梯度均大于碳钢侧的温度和温度梯度，温度梯度有利于压下过程中增加不锈钢和碳钢待复合表面的变形量，高频脉冲电流作用下不锈钢/碳钢压下复合界面发生再结晶，界面实现冶金结合。项目研究成果为开发临界道次压下量小、界面复合质量好、分层厚度精度高的高效、节能的不锈钢/碳钢轧制复合新技术奠定了坚实理论和实验基础。