Model Software Package Development for Laminar Cooling Process in Hot Mill

The use of computer simulation techniques in the control system design of the laminar cooling process in a hot mil! can significantly reduce the development cost while ensuring maximum production safety. The case-based modelling strategy was proposed and implemented in a software package. The functional structure of the software package was discussed in detail. The interfaces and functions of the software package were introduced. The results of industrial experiments can be directly visualized in the software package,allowing accurate and instant comparison of the model predictions with real measurements. The software package provides the simulation platform for research into advanced modelling and control strategies of the laminar cooling process in a hot rolling mill.     

Modelling of Stress State,Centre Consolidation and Roll Force in Billet Rolling

Roll pressure models have been derived from theoretical studies, FEM simulations and experimental investigations. A model developed from slip line field theory has been shown to fit well to the experimental results. The Finite Element simulations overestimated the pressure function. This is a common problem in hot rolling experiments, since the problem of measuring the correct rolling temperature makes the estimation of the yield strength very difficult. The difference between the FE calculations and the experimental measurements is a measure for the error in the experimental temperature measurements rather than for the accuracy of the Finite Element Method. Traditional modelling has not been an appropriate tool to evaluate the material flow in the centre of the billet. In spite of the fact that the entire stress state can be modelled by slip line field theory, the slip lines which determine the stress state in the centre coincide for actual geometries only in one single point. Thus the strain increments are known only in that single point. Since a material element passes that point instantaneously, it is not possible to find any finite strains in the centre by integrating any incremental function. By FEM, strain modelling is simple and the possibility to consolidate a porous bloom or ingot core can be determined. FE modelling requires an entirely new approach to the modelling problem. It is not reasonable to use FEM to evaluate only the temperature distribution for the use in roll force models from the previous century. Instead, a fully thermomechanically coupled FE model is suggested. However, the calculation time is still far too long to be used for on‐line control purposes. For this application hybrid modelling can be a solution, where off‐line FE models are combined with empirical modelling, and simplified models can be used for the process control.     

冷轧轧辊磨损数学模型研究

针对我国某厂1420mm冷轧生产线，研究了轧辊磨损的数学模型。结合实测磨损数据，用轮廓曲线对比法修正模型并进行了模拟计算。计算结果与实测值十分吻合，显著提高了模型的计算精度。     

Roll Wear Evaluation of HSS,HiCr and IC Work Rolls in Hot Strip Mill

While it is acknowledged that roll wear is one of the most challenges to hot strip mills (HSM), very few studies which detail an exact prediction model have been published. The aim of this work is to evaluate and compare two prediction models with measured roll wear. The first prediction model, model 1, developed for a plate mill, was modified to use in strip rolling process. The second prediction model, model 2, is a simplified on‐line model. Data of two hot strip mills were used to investigate the influence of different rolling schedules. The rolls and strip properties were described and the rolling conditions were detailed. The influence of hot rolling factors, such as strip strength, roll grades, rolling temperature, rolling force, reduction and contact length, were also studied. When rolling with different work roll materials and strip grades, the modified prediction model has better prediction accuracy than the simplified model. The accuracy of both models becomes better at higher roll wear > 150 μm. HSS work rolls were confirmed to exhibit improvement of roll wear in comparison with HiCr rolls, the wear resistance was 3 to 4 times better. The influence of strip grade on roll wear was shown to be significant, with higher accuracy of the regression statistics for rolling with similar strip grades and lower regressed accuracy for rolling with mixed strip grades. The roll wear was evaluated at the centre of the barrel.     

Analytical and Numerical Approaches in Studying Immersed De‐carbonization in RH‐plants

In this paper the de‐carbonization rate of RH plants is studied by means of analytical and numerical approaches. In the first case the RH‐plant is recognized as a one‐dimensional looping reactor. The corresponding mathematical modelling provides a system of ordinary differential equations (ODE's). In the second case the flow pattern inside the RH‐plant is modelled by means of a three‐dimensional numerical simulation. In both cases emphasis is placed on the coupling between the immersed gas bubbles, the local de‐carbonization reaction and the recirculation rate. Furthermore, the influence of gas expansion on the gas hold‐up and thus on the recirculation and reaction rate is addressed. After a general presentation of the modelling concepts the individual strengths and weak‐points of both approaches are discussed.     

Optimum Temper Rolling Degree: Pre‐Set and Influencing Effects of Bending Deformations

The present article describes a research project concerning the influence of bending deformations on strip mechanical properties imparted by temper rolling and a strategy for mill pre‐set to achieve the selected temper rolling degree in as short a time as possible. Research results show that, during strip temper rolling, rolls involved in the process, for example deflector rolls and anti‐sticking rolls, introduce plastic bending deformations into the strip which can amount to more than 30% of the temper rolling reduction, depending on the effective bending radii. Bending tests involving strips made of low‐carbon steel in a tension roller system with an integrated bending unit demonstrate that bending deformations influence the mechanical properties of the strip in a manner similar to the temper rolling process itself. It appears necessary to take account of the bending effects when selecting the optimum temper rolling degree. The most accurate roll force pre‐calculation possible and its application at the mill stand are of major importance for pre‐setting the required temper rolling degree. Existing analytical methods have been unable to yield the necessary calculation accuracy. Combination of an optimised analytical approach with a data‐based model to create a hybrid model has led to significant improvements. The accuracy achieved in the pre‐calculation of the required roll force has helped to improve mill pre‐set of the investigated temper mill and to reduce strip head‐end scrap on average by around 6 m per strip. Based on the annual outputs stated by the plant operator, this makes it possible to achieve a cost saving of more than 200,000 € per year.     

2050热连轧精轧机组PFC磨损预报与实测的对比分析

介绍了宝钢２０５０ＣＶＣ热带钢连同精轧机组轧辊磨损的实测结果及分析，并结合实测结果对现有ＰＦＣ磨损模型作出评价，磨损实测结果对轧机板形、板凸度控制具有重要意义。     

Inclusion Growth and Removal in Gas‐Stirred Ladles

A static modelling approach was used to study the growth and removal of inclusions during gas stirring in a ladle. A mathematical model of a gas‐stirred ladle was used to predict the data necessary to calculate growth and removal of inclusions. Results indicated that inclusion growth resulting from laminar shear collisions is negligible in comparison with growth from turbulent and Stokes collisions. Furthermore, the need for a model describing inclusion flotation by spherical‐cap bubbles was identified. Since the existing models presented in the literature are only valid for spherical bubbles, a model for the removal of inclusions by spherical‐cap bubbles was developed. Inclusion removal to the slag, refractory and by bubble flotation was compared. The mechanism determined to be responsible for the removal of the majority of inclusions larger than 25 μm was Stokes flotation and for the majority of the smaller inclusions, bubble flotation by spherical‐cap bubbles (assuming plane contact between the inclusion and the bubble).     

Numerical Cooling Strategy Design for Hot Rolled Dual Phase Steel

In this article, a Mo‐Mn dual phase steel and its process parameters in hot rolling are discussed. The process window was derived by combining the experimental work in a hot deformation dilatometer and numerical calculation of the process parameters using rate law models for ferrite and martensite transformation. The ferrite formation model is based on the Leblond and Devaux approach while martensite formation is based on the Koistinen‐Marburger (K‐M) formula. The carbon enrichment during ferrite formation is taken into account for the following martensite formation. After completing the parameter identification for the rate law model, the evolution of phases in this steel can be addressed. Particularly, the simulations allow the prediction of preferable degree of retained strain and holding temperature on the run out table (ROT) for the required ferrite fraction.     

Application of Thermodynamic Model for Inclusion Control in Steelmaking to Improve the Machinability of Low Carbon Free Cutting Steels

Oxide inclusions formed during steelmaking processes influence the machinability of steel products. At moderate and high cutting speeds, the tool life is dominated by chemical wear. However this wear can be suppressed by engineering exogenous and indigenous glassy oxide inclusions in steel. The present work demonstrates a method to engineer glassy oxide inclusions in a low carbon free cutting steel applying a new thermodynamic model for deoxidation control of steel based on slag‐melt as well as melt‐oxide inclusion equilibration. The model is used online in an industrial production line for the controlled production of glassy inclusions. These inclusions are shown to improve machinability by lubricating the tool‐chip interface during machining of the steel at high cutting speeds. Using an inclusion engineered work piece, the crater wear of an uncoated P10 tool is significantly improved and the tool life is tripled at cutting speeds in the range between 200 and 400 m/min. The industrial results show that thermodynamic modelling is a powerful tool to produce free cutting steels with consistently good machinability behaviour.     

Finite Element Analysis of Flange Spread Behavior in H‐beam Universal Rolling

Flange spread is one of the most important factors in the production of H‐beams with the universal rolling mill. Although some prediction models for flange spread have been proposed, the constants in the model equations should be determined for each product size, which requires much experimental work. In this research, finite element analysis was carried out in various rolling conditions and a technique for deciding the model constants by the analysis was investigated. First, rolling experiments using pure lead were carried out to confirm the correctness of the flange spread model. Finite element analyses were then executed for rolling conditions corresponding to the experiments. The flange spread in the numerical analyses showed very good agreement with the experimental results, confirming the accuracy of the numerical simulation. At the same time, the possibility of determining the model constants by numerical analysis was demonstrated. Other related properties of universal rolling were also investigated with the data from the finite element analysis. Changes in the web and flange thicknesses after exiting the roll gap were quantitatively simulated. The cross‐flow behavior between the web and flange was investigated, and the effect of rolling conditions on the cross‐flow ratio was obtained. This research demonstrates that finite element simulation is a powerful tool for investigating and modeling deformation in H‐beam universal rolling.     

Computer Modelling of Deformation of Steel Samples with Mushy Zone

The integrated casting and rolling of steel plates in processes such as Inline Strip Production or Arvedi Steel Technology is the latest and very efficient way of hot strip production. The numerical modelling is very helpful in developing a “know how” theory for the mentioned processes. One of the most important relationships having crucial influence on the metal flow path is the strain‐stress curve. The inverse method, which is usually the only method of calculating a real strain‐stress relationship, needs a good mathematical model describing the plastic behaviour of the material. The model presented in the current paper fills the gap in modelling of plastic deformation of semi‐solid materials. On the other hand, the mathematical modelling should be closely related to experiments. The well known machine allowing tests in the discussed temperature range is the GLEEBLE thermo‐mechanical simulator. However, carrying out experiments with steel deformation in the semi‐solid state using this machine is very expensive. Therefore, application of a dedicated computer simulation system is strictly required. Inverse analysis and appropriate modelling of the testing procedure makes tests possible, first of all, but it also results in lowering testing cost. The newest version of the Def_Semi_Solid is a unique FEM system supporting tests at extra high temperature.     

Ф530轧机孔型优化

通过对φ530轧机孔型的修改,减小了由于φ530轧机孔型磨损不均造成的折叠,对提高钢材热顶锻合格率起到了良好作用。     

The Development of Ring Rolling Technology

A thorough survey of work on ring rolling published in the English and German languages by 2004 is presented. The process is briefly introduced and a set of ideals are stated, as the target for all developments in the area. The main challenges which inhibit attainment of these ideals are given, and the process is compared with alternatives. The main body of the review is organised in four parts: the evolution of the design of ring rolling equipment is described, including detailed discussion of the design and manufacture of preforms; the methods used to investigate the process are reviewed, separated into experimental and theoretical categories; the insights gained from these investigations are organised according to the challenges identified at the outset; developments in the control and operation of the process are described. Having given a set of ideal targets for the process, the state of current knowledge about ring rolling is assessed in order to predict likely developments: process modelling capability is nearly able to predict rolling behaviour for a complete cycle with sufficient accuracy to allow effective use of models for design of rolling schedules and preforms; analysis of material behaviour is relatively mature for steel rings, but has scope for significant extension for titanium and aluminium alloys and composites; design choices that seek to extend the flexibility of the process have had some exploration, but could be extended. Finally, the seminal contribution of Professor Kopp is briefly described.     

我国Mn13轧制耐磨钢板的开发生产与应用

Mn13钢种在受到强烈的冲击或较大挤压载荷作用下,表面会瞬时产生加工硬化。随着这种硬化效果的快速积累,钢板表面的硬度迅速升高,而钢的基板始终保持奥氏体钢良好的冲击性能。目前Mn13广泛应用于我国机械设备制造中,是用途最广、用量最大的耐磨钢品种。Mn13轧制钢板现在尚处于推广发展的阶段,正逐步成为替代高锰钢铸件等品种的新一代材料。重点阐述了Mn13轧制钢板的生产工艺、产品用途和生产应用的建议。     

3D‐FE Modelling and Simulation of Multi‐way Loading Process for Multi‐ported Valves

Multi‐ported valves are widely used in the marine, sanitary, petrochemical and power industry. Multi‐way loading forming technology provides an efficient approach for integral forming of high strength multi‐ported valves, such as tee pipe coupling, high‐pressure cross valves, large‐scale complex valves, and so on. Since the multi‐way loading process is a very complicated plastic forming process due to the complexity of loading path, finite element numerical simulation is adopted to investigate the multi‐way loading process in order to predict and control the multi‐ported valve forming process. A reasonable model of the process is developed under DFEORM‐3D environment based on the coupled thermo‐mechanical finite element method. Then the reliability of the model is validated with respect to geometry development and forming defects. Numerical simulations of multi‐way loading forming for a tee valve and a cross valve have been carried out via using the developed model. Further, the forming processes of tee valve and cross valve have been compared. Moreover, the modelling method is also suitable for multi‐way loading processes of other complex components.     

焦罐车旋转机构支承辊轮运行状态的探析

对焦罐车旋转机构支承辊轮的运行状态进行了分析。探讨了焦罐车旋转机构支承辊轮的三种型式：圆柱辊轮、腰鼓形辊轮及圆台形辊轮在运行状态下的滚动、磨损、效率。总结出支承辊轮的理想运行状态。     

On the Mechanism of Natural Convection and Equiaxed Structure during Dendritic Solidification Processes

A new technique has been developed to generate dendritic‐equiaxed structures in aluminium alloy casting processes, not only to improve the mechanical properties but also to study the effect of crystal structure on the chemical and physical properties of alloys to be cast. The investigation combined laboratory experimental work, metallographic examination and mathematic modelling. The laboratory experimental work involved different superheats for Al‐4.5%Cu alloy in cast ingots. Measurements of temperature distributions were conducted to verify the solidification model. A metallographic study combined macro and micro structural evolution of cast ingot samples. Two‐dimensional mathematical models of fluid flow and heat transfer were developed to characterise the natural convection streams and thermal fields. The model predictions were compared to temperature and isotherms measurements where a good agreement was found. The formation of cast structure and columnar, equiaxed transition (CET) and macro segregation phenomena were studied and discussed, based not only on the theories of nucleation but also on the thermal effects in the mushy and liquid zones.     

热轧板孔洞缺陷成因分析及治理

对热轧板孔洞缺陷形成的原因进行了分析,指出连铸过程操作参数控制不合理是产生该种缺陷的主要因素;利用水模试验研究了水口插入深度、拉速、吹氩量等因素对结晶器内气泡分布的影响,在此基础上提出了治理热轧板孔洞缺陷的措施,取得了较好的效果.