Soft measurement model of ring's dimensions for vertical hot ring rolling process using neural networks optimized by genetic algorithm

Vertical hot ring rolling(VHRR) process has the characteristics of nonlinearity,time-variation and being susceptible to disturbance.Furthermore,the ring's growth is quite fast within a short time,and the rolled ring's position is asymmetrical.All of these cause that the ring's dimensions cannot be measured directly.Through analyzing the relationships among the dimensions of ring blanks,the positions of rolls and the ring's inner and outer diameter,the soft measurement model of ring's dimensions is established based on the radial basis function neural network(RBFNN).A mass of data samples are obtained from VHRR finite element(FE) simulations to train and test the soft measurement NN model,and the model's structure parameters are deduced and optimized by genetic algorithm(GA).Finally,the soft measurement system of ring's dimensions is established and validated by the VHRR experiments.The ring's dimensions were measured artificially and calculated by the soft measurement NN model.The results show that the calculation values of GA-RBFNN model are close to the artificial measurement data.In addition,the calculation accuracy of GA-RBFNN model is higher than that of RBFNN model.The research results suggest that the soft measurement NN model has high precision and flexibility.The research can provide practical methods and theoretical guidance for the accurate measurement of VHRR process.

Edge crack damage analysis of AZ31 magnesium alloy hot-rolled plate improved by vertical roll pre-rolling

In the present study,through vertical roll pre-rolling of AZ31 magnesium alloy hot-rolled plate at room temperature,the effect of different vertical roll pre-rolling reduction on edge crack of the plate during flat rolling was systematically studied.The evolution of microstructure and texture in the edge and middle of the plate after vertical roll pre-rolling,heating and rolling was analyzed by using EBSD technology.The results show that during the vertical roll pre-rolling,{10–12}primary twins and{10–12}-{10–12}secondary twins dominated the edge deformation,while{10–12}primary twins dominated the middle deformation.With the increase of vertical roll pre-rolling reduction,the twin volume fraction of the edge and the middle increased,and the difference between them decreased gradually.After heating,the twin orientation caused by vertical roll pre-rolling was still maintained,and there was a significant difference in grain size between the edge and the middle.When the reduction rate of flat rolling was 30%,cracks have already appeared in the initial plate,while the vertical roll pre-rolled samples showed extremely high rolling performance.When the reduction rate of flat rolling was 50%,the 8PR sample still had no crack initiation.In addition,after flat rolling of 50%,the initial plate showed a strong basal texture,while the maximum pole density of the 8PR plate was small,and the texture distribution was very scattered,showing the characteristics of weak orientation.

Study on Vertical Vibration Characteristics of the 2-DOF Strip Rolling Mill Model with a Single Weak Defect on the Work Roll Bearing Outer Raceway

Considering the influence caused by a early single pit defect on the outer raceway of the work roll bearing,a 2-DOF plate strip rolling mill vertical vibration model with a single point weak fault on the outer raceway was established.With the practical parameters of the roughing mill of the 1780 hot continuous rolling mill,the vertical vibration characteristics of the rolling mill work roll with different rotating speed and different single pit defect area on the bearing outer raceway are analyzed by numerical simulation.It is found that with the change of the rotation speed of the work roll,different nonlinear vibration behaviors occurred,such as superharmonic resonance,main resonance,com-bined resonance and sub-harmonic resonance.Especially the subharmonic resonance of the work roll is more harmful than the main resonance when the work roll speed is twice the rotation speed corresponding to the first and second natural frequency of the rolling mill.This work provides a theoretical basis for further clarifying the effect caused by a early defect of the work roll bearing on the mill vibration.

Preparation of AZ31 magnesium alloy strips using vertical twin-roll caster

A newly developed technology for manufacturing magnesium alloy strip,vertical twin-roll strip casting,has been described.This manufacturing process is easy to be facilitated in an economical way to manufacture wrought magnesium alloy strips. As an example,AZ31 magnesium alloy was used to investigate the appropriate manufacturing conditions for vertical twin-roll strip casting by varying the temperatures of the molten materials and rolling speeds.The effects of manufacturing conditions on forming quality were clarified in terms of roll speeds and casting temperature.In addition,microscopic observation and X-ray diffraction of the as-cast strips were performed.It has been determined that AZ31 alloy strip of 1-3 mm in thickness can be produced at a speed of 30 m/min by a vertical twin-roll caster.The microstructure of as-cast strip only containsα-phase(Mg)and no other phase,and the twin-roll casting process can effectively refine the grain size.The fine equiaxed grain of as-cast strips is beneficial to the plastic deformation of the strips,and it is also suitable for direct cold-rolling with a maximum cold-rolling reduction of 40%.

Modulation Equations for Roll Waves on Vertically Falling Films of a Power-Law Fluid

Waves of finite amplitude on a thin layer of non-Newtonian fluid modelled as a power-law fluid are considered. In the long wave approximation, the system of equations taking into account the viscous and nonlinear effects has the hyper- bolic type. For the two-parameter family of periodic waves in the film flow on a vertical wall the modulation equations for nonlinear wave trains are derived and investigated. The stability criterium for roll waves based on the hyperbolicity of the modulation equations is suggested. It is shown that the evolution of stable roll waves can be described by self-similar solutions of the modulation equations.

Dynamic modeling and analysis on rigid-flexible coupling between vertical chatter and transverse bending vibration in process of cold rolling

Considering the dynamic variation of roll gap and the transverse distribution of dynamic rolling force along the work roll width direction, the movement and deformation of rolls system, influenced by the coupling of vertical chatter and transverse bending vibration, may cause instability and also bring product defect of thickness difference. Therefore, a rigid-flexible coupling vibration model of the rolls system was presented. The influence of dynamic characteristics on the rolling process stability and strip thickness distribution was investigated. Firstly, assuming the symmetry of upper and lower structures of six-high rolling mill, a transverse bending vibration model of three-beam system under simply supported boundary conditions was established, and a semi-analytical solution method was proposed to deal with this model. Then, considering both variation and change rate of the roll gap, a roll vertical chatter model with structure and process coupled was constructed, and the critical rolling speed for self-excited instability was determined by Routh stability criterion. Furthermore, a rigid-flexible coupling vibration model of the rolls system was built by connecting the vertical chatter model and transverse bending vibration model through the distribution of dynamic rolling force, and the dynamic characteristics of rolls system were analyzed. Finally, the strip exit thickness distributions under the stable and unstable rolling process were compared, and the product shape and thickness distribution characteristics were quantitatively evaluated by the crown and maximum longitudinal thickness difference.

Numerical Simulation and Vertical Motion Control of Rolls for Variable Gauge Rolling

The vertical motion control of the roll was studied in order to improve the accuracy in simulation of variable gauge rolling. The discretization was carried out in the transition zone of TRB according to the principle of volume invariance. Based on this assumption, the formula for time step of vertical motion of rolls was proposed and the time-displacement curve of the verti- cal motion of rolls was established. In the preliminary simulation, the time-displacement curve was used as an initial method to control the vertical motion of rolls. Based on the simulation result, the formula for vertical velocity of roll in variable gauge rolling was derived from the common rolling principle. According to the formula, reasonable vertical velocity of rolls in the subsequent simulation was determined. It can accurately control the motion of rolls along the vertical direction. The desired thickness and out- line profile of transition zone were acquired and the formula proved effective by the simulation. Further analysis shows that the di fference of thickness in the thick zone and the thin zone of TRB, length of the transition zone of TRB, radius of work rolls and rota- tion speed of rolls have a significant effect on the vertical velocity of rolls.

Optimization of Preventive Grinding of Backup Roll against Contact Fatigue Cracking

In order to optimize the current grinding procedure of the backup roll of 2050 continuously variable crown (CVC) mills, the behavior of rolling contact fatigue (RCF) cracking was investigated. Two RCF short cracks, including vertical short crack and ratcheting short crack initiated from ratcheting, were observed. The behavior of both RCF cracks was analyzed in detail. Then a modified grinding procedure was proposed according to the behavior of RCF cracks and the preventive grinding strategy.

Application of dynamic vibration absorber for vertical vibration control of corrugated rolling mill

A variable mass tuned particle absorber is designed for the nonlinear vertical vibration control of the corrugated rolling mill in the composite plate rolling process.Considering the nonlinear damping and nonlinear stiffness between the corrugated interface,a three-degree-of-freedom nonlinear vertical vibration mathematical model of corrugated rolling mill based on dynamic vibration absorber control is established.The multi-scale method is used to solve the amplitude–frequency characteristic curve equation of the installed dynamic vibration absorber(DVA)system.The effects of stiffness coefficient and damping coefficient on the amplitude–frequency characteristic curve are analyzed.The expressions of the dynamic developed factor of the corrugated roll are derived,and the influence laws of mass ratio,frequency ratio and damping ratio on the dynamic amplification factor are analyzed.The optimal parameters of the DVA are obtained by adaptive genetic algorithm.The control effect of the DVA on the nonlinear vertical vibration is studied by numerical simulation.The feasibility of the designed dynamic absorber is verified through experiments.The results show that the designed dynamic absorber can effectively suppress the vertical vibration of the corrugated roller.

Vertical Short Crack Initiation in Medium Carbon Bainitic Steel Under Mild Tractive Rolling Contact

To improve the current grinding procedure of the back-up roll of CVC hot rolling mills so that the back-up roll service life can be extended, the crack initiation and propagation behavior of medium carbon bainitic back-up roll steel was investigated, a kind of asperity-scale, surface originated vertical short cracks occurred at 5 × 10^2 -1 × 10^4 cycles. Theoretical analysis indicated that the maximum tensile stress occurring at the back edge of the contact of asperities keeps at above 1 347. 97 MPa, and ratcheting and cyclic plastic deformation take place at such sites within 1 × 10^4 cycles. The early initiation of the vertical short cracks is caused by the asperity contact. According to the crack initiation mechanism, short crack behavior and preventive grinding strategy, steel consumption can be reduced considerably by decreasing the surface roughness and removing the asperity influenced surface thin layer at about 70%-80% of the surface distress life.

Analysis of Crack Tip Stress of Transversal Crack on Slab Corner During Vertical-Horizontal Rolling Process by FEM

Behavior of transversal crack notched on slab corner during vertical-horizontal rolling process was simulated by FEM. The crack tip stress in the whole rolling process was obtained. Influences of the friction coefficient, the initial crack size, the edger roll profile, and the groove fillet radii of grooved edger roll on crack tip stress were analyzed. For vertical rolling, the tension stress appears at crack tip near the slab top surface and the compression stress appears at crack tip near the slab side surface for the flat edger roll; however, the compression stress appears at crack tip near the slab top surface and the tension stress appears at crack tip near the slab side surface in the exit stage for the grooved edger roll. For horizontal rolling, the tension stress appears at crack tip just at the exit stage for the flat edger roll, and the tension stress appears in whole rolling stage; the tension stress value near the slab side surface is much larger than that near the slab top surface for the grooved edger roll.

桨叶分段线性扭转对降低旋翼振动载荷的作用分析

研究了用桨叶分段线性扭转来降低旋翼振动载荷。使用基于弹性梁的旋翼模型用于预测旋翼振动载荷。采用4片桨叶旋翼作为基准旋翼,桨叶形状与UH-60直升机桨叶相似。桨叶被划分为内、中、外3段,讨论了各段扭转对载荷的影响。低速时桨叶每一段的扭转都能减少桨毂四阶垂向力。当以80 km/h前飞时,中段-24°/R的扭转可使其降低99.5%。桨叶内段的扭转不利于降低桨毂四阶滚转和俯仰力矩,另外两段的扭转则可以在大多数前飞速度时控制这2个振动力矩。使用参数扫描以尽可能降低旋翼振动载荷。降低四阶垂向力方面,低速时桨叶所有段都需要扭转,而高速时未扭转的桨叶表现更好。降低四阶滚转和俯仰力矩方面,在低速时需要桨叶外段高度扭转,而在中高速时则需要桨叶中段的扭转。

IF钢边部黑线原因分析及解决措施

针对IF钢边部黑线问题,分析认为板坯边部形状,热轧立辊使用周期、材质及侧压量等是导致边部黑线的主要原因。通过采取倒角结晶器改变板坯边部形状,缩短立辊使用周期,优化立辊材质及减小立辊侧压量等措施,IF钢边部黑线缺陷率由0.57%降至0.39%,每月可节省14万元。

立辊轧机故障解析及维修原理分析

以1台直径为1 750 mm的立辊轧机为例,对其故障原因及维修原理进行了分析。通过对小轮碎裂、球面垫掉落和立辊轧机倾斜等故障原因的深入分析,提出了相应的解决方法和维修原理;通过科学的分析和合理的维修措施,有效解决了设备故障,提高了生产效率,确保了设备的稳定性和可靠性。

立辊轧机轴承机械密封设计及安装维护

立辊轧机轴承机械密封设计及安装维护是保证轧机正常运行和延长轴承寿命的重要环节。针对立辊轧机轴承机械密封的设计原理、安装步骤和维护方法进行了详细介绍。通过合理的设计和正确的安装维护,有效防止润滑油泄漏、杂质进入和密封失效等问题,提高了立辊轧机的工作效率和可靠性。

改进增广最小二乘的轧机垂振系统参数辨识

数字孪生是物理实体的数字化表现,它通过数学模型实时监测和控制物理实体,因此对数学模型的精度要求非常高。针对轧机垂振系统模型精度低的问题,提出了改进增广最小二乘法对轧机垂振系统进行辨识。建立了垂振系统数学模型,并通过系统离散化推导出动力学方程,确定了辨识模型的结构。以现场采集的数据为基础,采用改进最小二乘法对模型参数进行辨识。实验结果表明,实测振幅与机理模型输出振幅的均方根误差为0.82,而与辨识模型输出振幅的均方根误差只有0.62,有效提高了模型的精度。

冷轧双相钢HC340/590DP翘皮缺陷原因分析与工艺优化

针对冷轧双相钢HC340/590DP表面翘皮缺陷,采用显微组织观察、能谱分析等手段,明确了通卷边部点状翘皮、带尾翘皮和通卷边部翘皮三类翘皮缺陷产生的根本原因分别为冷轧轧制线辊剐蹭、热轧粗轧立辊下凸台高度尺寸偏差、炼钢铸坯边裂导致。通过冷轧工序优化双相钢拉矫延伸率和定期更换轧制线辊、热轧工序提高粗轧立辊表面质量和优化立辊压下制度、炼钢工序提高连铸机设备精度及保证二冷水喷淋状态等系列措施,有效解决了冷轧双相钢表面翘皮缺陷。

棒材生产线精轧机组平立转换轧机机列运行稳定性研究与优化改造

新疆昆玉钢铁有限公司轧钢厂棒材生产线精轧机组14HV/16HV/18HV为平立可转换轧机,根据生产品种的不同,轧机进行平立转换,以满足生产工艺要求。但在轧制运行过程中,离合器同轴度随轧制负荷变化而动态变化,常出现旋转框架不对中、离合器温度升高、减速机运转振动大等问题。针对此问题,重点研究制定平立转换轧机机列稳定运行的措施,并对旋转框架定位和离合器同轴度进行优化调整。此研究对平立转换轧机机列稳定运行和车间稳定生产具有重要意义。

水泥立磨终粉磨系统节能降耗改造实践

在立磨研磨水泥工艺中,原料水分波动容易引起立磨震动,一般采用喷水稳定料床,但喷水后容易造成熟料水化降低水泥强度。为了实现不喷水研磨,对磨辊、选粉机、风环等进行改造。结果表明,技改降低了熟料配比2.9%,产量提高19%,单位电耗降低3.3 kWh/t以上,实现了提产降耗节能减碳的目的。

二棒粗轧机组立式轧机固定端轴承箱密封机构的改进

本文通过对二棒粗轧机组轧机立式机架固定端轴承箱密封机构进行分析、研究,对轴承箱密封机构部分备件进行了完善改进,到达解决轴承箱频繁烧损的难题,实现二棒生产线的高效生产的目标。