Thermal Behaviors of Work Roll in Finishing Trains of Hot Rolling

In order to analyze the thermal field and thermal contour of work roll in finishing trains of hot rolling in rolling process, a quasi two-dimension implicit finite difference model is developed. To improve the calculating speed and precision, some special solutions are introduced, including the development of this model, the simplification of boundary conditions and the computation of heat transfer coefficients. The results show that these solutions of thermal behaviors of work roll are very much efficient and the model can be used as an on-line profile and fatness control model of large industrial mills.

Improvement of prediction model for work roll thermal contour in hot strip mill

Though high accuracy of the thermal contour was obtained while adopting finite element method,it could not meet the real-time requirement.One-dimensional finite difference method could realize real-time control in the case of neglecting both the circumferential and radical heat exchange,but the over-simplified modes resulted in poor accuracy.And two-dimensional full explicit difference was also limited in practical application since its time step was restricted to keep the model stable.Consequently,a new method of alternating direction finite difference was introduced and discussed in the model's stability,calculating speed and precision.Specific work roll after one real rolling unit was researched,The result shows that error of temperature on work roll surface between measured and calculated values is within 5 ℃.The influence of rolling rhythm and strip width on thermal crown was also studied.The conclusion is verified theoretically and practically that it can maintain absolutely stable and meet the online requirement.

Roll shifting strategy with varying stroke and step in hot strip mill

A new roll shifting strategy with varying stroke and varying step was investigated,Two characteristic parameters including cat ear height and gap contour smoothness were introduced to assess the effect of shifting strategy on roll wear,and the relation between characteristic parameters and shifting strategy was established.Both varying stroke and varying step can reduce cat ear height and gap contour smoothness,so the shifting strategy with varying stroke and varying step is better than the one with either varying stroke or varying step,Based on the effect of shifting control parameters on characteristic parameters of roll wear,the selection principle of these shifting control parameters was gained.A case study was conducted to validate the proposed roll shifting strategy,reducing uncontrollable quartic loading gap contour,improving strip profile and extending rolling length of a rolling campaign.

Thermal Crown Model and Shifting Effect Analysis of Work Roll in Hot Strip Mills

Considering the effect of work roll shifting on roll temperature field,a finite difference method of PR format for roll temperature field was presented,which can meet the requirements of accuracy and speed of online calculation.The step-by-step accumulation method was used to simulate the roll temperature field and thermal crown,and the evolution of roll thermal crown in a rolling campaign was studied.And then,the effects of strip width,rolling rhythm and work roll shifting on roll thermal crown were analyzed.It is found that work roll shifting can disperse the thermal expansion of the roll body especially the edge to make roll thermal contour uniform.The effect of work roll shifting on roll thermal crown is mainly concentrated in regions around twice of roll shifting stroke,and the change range of roll thermal crown is±30μm or so in the same roll body location.

Optimization of Roll Shifting Strategy of Alternately Rolling in Hot Strip Mill

An optimization solution to roll shifting strategy for alternately rolling campaign is presented. All the strips in a rolling campaign are divided into narrow strips and wide ones, and shifting position of narrow strips is obtained by the recursive method, and then shifting position of wide strips is optimized by NSGA-II which is a multiobjective genetic algorithm. For wide strips, a multi-objective optimization model of roll shifting strategy is pro posed, which takes 3 wear contour factors including edge smoothness, body smoothness and edge drop as optimization objectives. The Pareto optimal front of roll shifting strategy can be gained quickly by NSGA-II, which suggests a series of alternative solutions to roll shifting strategy. Analysis shows that the conflict exists among the 3 objectives. The final optimal solution is selected from the Pareto optimal solutions by the weighted-sum decision-making method. Industrial production proves the validity of the solution, and it can improve strip profile of alternately rolling, reduce strip edge wave, and extend the rolling miles of rolling campaigns.

板带热轧过程工作辊磨损预测研究

为实现轧辊磨损的精准预测,建立了基于Archard公式和轧制基本理论的工作辊磨损预测模型,使用ABAQUS建立了轧制过程中轧辊-工件热力耦合模型,在此基础上,系统分析了压下率、轧制速度、轧件宽度及支撑辊对工作辊接触应力和磨损的影响规律,并使用现场实测数据验证了模型的有效性。结果表明,随着压下率的增加,接触应力和磨损显著增大。轧制速度的增加基本不改变接触应力的分布情况,但会引起相对滑动速度增大,导致工作辊磨损增加。工件宽度影响磨损的轴向分布,随着轧件宽度的增加,接触应力和磨损减小。轧辊与轧件产生的磨损为辊间磨损的30倍以上。通过与某厂1580 mm产线实际数据对比,计算磨损值与实测数据吻合良好,模型平均预测误差为3.85%,实现了轧制过程工作辊磨损的高精度预测。

热镀锌线中轴套衬瓦的锌腐蚀-磨损交互行为研究

目的明确轴套、衬瓦间锌腐蚀-磨损的交互作用机制对合理选材、有效控制磨损的重要意义。方法使用陶瓷纤维马弗炉将纯锌粒加热到460℃后,对轴套、衬瓦试样进行液锌浸蚀试验,利用Ansys模拟出三辊轴套、衬瓦间的接触应力,采用多功能磨损试验机测出试样的摩擦系数以及磨损量,使用三维视频显微镜观察试样的三维形貌,使用扫描电镜对试样进行表面形貌观察和微观组织分析。结果当316L不锈钢试样浸入高温锌液1 h后,可以看到基体外表面出现多个合金层,总厚度达600~800μm。在带钢张力20 kN,矫正辊插入量10 mm的常见工况下,沉没辊轴套、衬瓦间接触应力可达65.14 MPa,稳定辊轴套、衬瓦间接触应力可达17.79 MPa,矫正辊轴套、衬瓦间接触应力可达26.69 MPa。无渗锌处理,垂直施加载荷为81 N时,在900 s以后摩擦系数稳定到0.03;当载荷为154.5 N时,摩擦系数维持在较低水平。渗锌处理时,无论载荷是81 N还是154.5 N,摩擦系数均在0.1上下波动。渗锌处理并加入硬质锌渣时,摩擦系数进一步的升高,波动幅度更大。无论施加的垂直施加载荷是81 N还是154.5 N,磨损量在无渗锌处理、渗锌处理、渗锌处理并加入硬质锌渣3种工况下依次递增。结论316L不锈钢经高温渗锌腐蚀形成的渗锌层、硬质锌渣显著提升了轴套、衬瓦间的摩擦系数以及磨损量,使表面低硬度合金层快速磨损。磨损磨去合金层,使新鲜基体持续暴露,促进了高温锌腐蚀的持续进行,不断形成新的腐蚀层,又不断被磨损掉,两者间的交互协同使得不锈钢轴套磨损速率提高而迅速失效。

700 MPa级热轧薄规格高强钢加工开裂行为分析

薄规格高强钢以其强度高、轻量化的优势一直受到了汽车市场的广泛关注,但其加工过程易受载荷、环境温度的影响而发生断裂失效。针对热轧700 MPa级别薄规格高强钢材料在制管剪切过程中出现的开裂问题进行了全流程系统剖析。对其冶金缺陷、晶粒及晶界缺陷、夹杂物控制、金相组织缺陷、元素偏析、零件加工缺陷、冷加工缺陷及脆性显微组织缺陷等可能的成因进行了逐项分析,最终认为材料在冷加工中产生的端部毛刺是高强钢开裂的根本原因。建议用户定期更换剪刃,尤其在钢管端部出现毛刺等缺陷时需尽快更换。

Effect of Cooling Rates in Coiling Process on Microstructures and Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel

In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation- induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9-11% at cooling rates of 0.05-1 ℃/s and 4-6% at cooling rates of 5-10 ℃/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05℃/s and 0.5 ℃/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 ℃/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5℃/s remained stable.

基于模糊PID的钢铁厂热连轧机主传动控制系统

针对钢铁厂热连轧机工作中普遍存在负载扰动等问题,本文设计了一种基于模糊PID的钢铁厂热连轧机主传动控制系统。主传动控制系统的硬件选择交-交变频同步电机作为动力装置,选择三相交-交变频器作为变频装置。主传动控制系统的软件引入盲源分离技术处理热连轧机产生的复杂且不明确的振动信号,引入模糊PID控制技术实现热连轧机的主传动控制。实例分析结果表明,本文设计的系统可以在一定时间内将热连轧机控制在稳定运行状态,具有响应快、自适应性强等优势。

热轧工作辊磨损模型的遗传算法

热轧精轧机组工作辊磨损非常严重,是板形控制中主要的干扰因素,也是板形研究的难点。分析了工作辊的磨损机理及其影响因素,建立了轧辊磨损模型,并采用遗传算法对模型参数进行估计。验证结果表明该模型实用可靠,可用于工作辊磨损在线预报。

LVC工作辊辊型的板形控制性能研究

提出一种新型线性变凸度工作辊辊型即LVC辊型,这种辊型实现了辊缝凸度调节与板宽成线性化。用承载辊缝调节域和承载辊缝横向刚度这两个基本板形控制性能来验证LVC工作辊的板形调节能力,并将LVC工作辊应用到实际生产中,经过计算和比较可以看出LVC工作辊辊型具有较好的实用性。在工作辊辊型的研究上具有一定的新颖性。

宽带钢热连轧机板形控制系统的开发

轧机的机型选择与配置、支持辊及工作辊辊型的配置与设计、弯辊 /窜辊工艺制度的设定以及控制模型的建立 ,是决定宽带钢热连轧机板形控制系统工作性能和板形质量的要素。武钢 170 0热连轧机进行了“VCR变接触支持辊”和“ASR非对称自补偿工作辊”的自主开发和生产应用 ,在提高板形质量、增强薄规格品种轧制能力以及有效改善支持辊磨损性能。

宽带钢热连轧工作辊热辊形模型

实现工作辊热辊形的在线预报是板形控制的难题之一.采用一维有限差分方法建立了工作辊热辊形在线计算模型,并利用该模型计算了热轧过程中和下机后任意时刻工作辊温度场及其热辊形.仿真和在线应用结果表明,此在线模型计算速度快,精度高,能满足板形在线过程控制的需要.

兼顾热轧工艺润滑的工作辊磨损预报模型

通过对某1700热连轧厂润滑轧制中轧辊磨损主要影响因素的研究,提出了包含润滑项的工作辊磨损预报模型,并采用模拟退火遗传算法估算模型主要参数。现场运用结果表明,该工作辊磨损模型结构及其模型参数能够兼顾热轧润滑和非润滑工况,提高了工作辊磨损的预报精度,满足在线运用需求。

热连轧机轧制力和轧制力矩模型研究

研究了一种适用于热连轧机的新型高精度轧制力和轧制力矩模型,建立了一个轧制力功系数和轧制力矩功系数的新型指数公式,将两个系数的表达式统一起来,仅含"压下率"和"压扁半径与出口厚度之比"两个影响因子,形式简洁,物理意义明显.给出了新型指数公式中待定参数的确定方法,求得的待定参数值对不同钢种和不同精轧机架具有通用性.预测实践表明,新型轧制力和轧制力矩模型提高了热连轧过程中轧制力和轧制力矩的预报精度,可用于热轧板带生产线精轧机架的在线控制.

工作辊弯辊力对热轧带钢凸度的影响

为了建立高精度的热轧带钢凸度计算数学模型,采用影响函数法开发了四辊轧机热轧带钢凸度影响率计算软件;系统地研究了工作辊弯辊力对带钢凸度的影响规律,得出了工作辊弯辊力影响率基本值和工作辊直径、单位宽度轧制力、压下量对弯辊力影响率修正指数的6次项拟合系数,建立了高精度工作辊弯辊力影响率的计算模型,为优化板形控制参数提供了理论依据。

热带钢轧机线性变凸度工作辊的研制及应用

为改善轧机的板形调控性能,在分析连续变凸度(Continuously variable crown,CVC)辊形技术的板形控制特性的基础上,开发出用于热带钢轧机的线性变凸度(Linearly variable crown,LVC)工作辊辊形技术及其相应的板形控制模型。LVC技术的板形调节能力与窜辊量成线性关系,同时与带钢宽度成近似线性关系。在满足宽带钢板形控制要求的同时,提高轧机对窄带钢的板形控制能力,使轧制各种规格带钢时所需弯辊力处于合理的的幅值。在1 700 mm热带钢轧机上一年多的工业应用表明,采用LVC工作辊后,板形控制精度提高30%以上,尤其是轧制高强度钢种时,凸度下降显著,轧制公里数一般都大于55 km,磨损辊形和轧辊消耗与常规工作辊基本一致。

带钢热连轧机工作辊瞬态温度场的有限元仿真

提出了一种二维的瞬态仿真模型，并利用有限元的数值方法对其瞬态温度场进行了仿真，仿真结果与实测值和三维大型有限元仿真值相符．

LVC工作辊在超宽带钢热轧机的应用

分析了超宽带钢轧机的板形控制特性,指出其在板形控制方面的不足。为增加超宽带钢热轧机的板形调节能力,开发了线性变凸度(LVC)工作辊,实现板形调节与带钢宽度成线性关系,其板形控制性能优于CVC技术。建立了LVC工作辊的板形控制策略模型,在超宽带钢热轧机上实现了长期稳定应用。生产实绩表明,LVC工作辊可显著提高带钢的凸度控制精度,对凸度控制要求严的供冷轧料和凸度难控制的高强度管线钢,其凸度控制在50±18mm的比例可达96%以上。