多参数耦合下高氮低镍热轧不锈钢高次浪形生成机理与在线数值模拟

Strong rolling force and serious roll bending are the two problems in hot rolling of high nitrogen and low nickel stainless steel. And the combined effect of the equipment parameters, severely uneven distribution of material lateral temperature, the rolling process parameters, leads to high-order wave shape defect. Although this defect can be resolved through designing a special roll shape curve, but because lacking of researching on generation mechanism and numerical methods of the high-order wave, that leads to the uncertainty of control. This project intends to establish an online numerical simulation model and research on generation mechanism for high-order wave of high nitrogen and low nickel stainless steel. The model includes the following aspects. Through the creation of three-dimensional transient temperature field based on alternating differential rolling process, gets the temperature distribution of stainless steel width and thickness direction. Establishment of deformation resistance model based on the deformation resistance experimental data of stainless steel, and thus can quantitatively get the horizontal distribution of stainless steel deformation resistance on each stand of finish rolling. Establishment of the rapid rolls deformation model and material three-dimensional plastic deformation model based on the finite volume method, and thus can calculate internal stress distribution after rolling. Establishment of strip buckling critical threshold and instability path model under high temperature, and thus can get the generation mechanism of higher-order wave. By establishing above models, this project can quantitatively analyze the influence law of device parameters, material properties and rolling process parameters to high nitrogen and low nickel wave shape, and also can improve the shape control theory of stainless steel.

热轧高氮低镍不锈钢轧制压力大，轧辊挠曲严重，且在设备参数、材料横向温度分布严重不均、轧制工艺参数共同作用下，产生高次浪形缺陷。虽然通过特殊辊形曲线设计可以解决这一缺陷，但由于缺乏对高次浪生成机理和数值模拟研究，导致控制上存在未知性。本项目拟进行高氮低镍不锈钢高次浪形生成机理的研究和在线数值模拟，包括以下内容：通过建立基于交替差分的轧制流程三维瞬态温度场模型，得到不锈钢的宽度和厚度方向的温度分布情况；结合实验得到的不锈钢变形抗力数据，建立回归模型，进而可以得到精轧各机架出口和入口的变形抗力横向分布情况；建立快速辊系变形模型和基于有限体积法求解的材料三维塑性变形模型，求解轧后内应力分布；建立高温下板带屈曲失稳临界阈值及失稳路径模型，得到高次浪形的生成机理。通过以上模型，可以定量分析设备参数、材料特性和轧制工艺参数对高次浪形的影响规律，完善不锈钢板形控制理论。

相比于常规的铬镍奥氏体不锈钢，高氮低镍奥氏体不锈钢具有对人体危害小、价格低的优势。但是与常规铬镍不锈钢、普碳钢相比，高氮低镍奥氏体不锈钢有特殊板形缺陷，即四分之一高次浪形，不仅影响表面质量，同时也制约宽薄极限规格不锈钢生产。.为了研究其生成机理并消除高次浪形，本课题建立了高次浪形的在线数值模型，包括：基于有限差分法的轧制流程三维瞬态温度模型；利用Gleeble3500热模拟压缩实验，采用数值回归方法建立的高氮低镍不锈钢的变形抗力模型，用于确定带钢横向变形抗力分布；快速辊形变形模型和基于有限体积法的轧件三维变形模型，二者耦合计算得到带钢出口的的断面形状和横向内应力的分布；基于能量法的板带屈曲失稳的解析模型。利用建立的高次浪形在线预报模型，对高次浪形影响因素进行了综合评判，作为工艺参数和辊形优化的基础。.本课题考虑了高氮低镍不锈钢横向的变形抗力分布，弥补了现有板形模型在这一部分的缺陷。建立了高次浪形的在线预报模型，可以分析设备参数、材料特性和工艺参数对高次浪形的影响规律以及固定设备下浪形生成的临界条件，完善高次低镍不锈钢板形控制理论，做到高氮低镍不锈钢高次浪形控制手段从定性化转到定量化，具有重要的科学意义。并且在工业轧机上进行了模型验证：研究成果已在四家热连轧不锈钢生产企业得到应用，通过减少横向温差、优化倒角工艺、优化负荷、采用MVC辊形技术，有效控制了高氮低镍不锈钢的四分之一浪形，带来显著技术进步与经济效益，一定程度上突破了长期困扰不锈钢产品的质量瓶颈，积极推动了我国不锈钢技术进步。