热轧HP295带钢中魏氏体组织成因及控制

以HP295为对象,研究了魏氏体组织对热轧带钢横向组织与性能均匀性的影响。通过对加热、轧制和冷却过程数据分析,认为板坯加热温度低、在炉时间短,造成板坯加热后温度均匀性差,影响带钢后续轧制及冷却过程,最终导致基体出现较严重的魏氏体组织。优化热轧工艺后,带钢魏氏体组织大幅减轻,产品质量明显提升。     

控制层流冷却过程对热轧带钢性能的影响

本文阐述了层流冷却情况下,热轧带钢急冷开始温度、终了温度及冷却速度对其性能的影响。在生产试验的基础上提出了三种新的控制冷却方式,通过模拟试验和金相分析,作者探讨了不同冷却方式影响带钢强度的机理;提出了形成魏氏组织的必要条件;阐述了针状铁素体对带钢性能的影响。这些工作完善了原来的热连轧层流冷却控制模型。     

带钢层流冷却过程数值模拟及卷取温度预测分析

结合宝钢2050热连轧层流冷却生产线,建立了带钢层流冷却过程传热数学模型,同时考虑相变潜热对带钢温度的贡献。采用实测的卷取温度,修正了带钢表面换热系数模型,模拟研究了冷却模式、速度、厚度等对卷取温度的影响。结果表明:卷取温度计算值与实测值的标准差小于14℃;相变潜热对卷取温度的贡献为28℃;冷却模式、速度、厚度是影响卷取温度的重要因素;该模型能够满足宝钢2050热连轧层流冷却卷取温度的预报精度,对实际生产具有较好的指导性作用。     

热轧带钢层流冷却过程温度场研究

 建立了热轧带钢层流冷却过程中温度场的三维有限元模型,对3 mm厚带钢轧后冷却过程带钢温度场进行模拟计算,得出卷取温度比现场测量值低9.5 ℃,相对误差为1.42%,验证了模型和假设的合理性。研究了上喷嘴直径对带钢温度的影响,带钢上表面宽度方向上存在2种不同的冷却区域：位于喷嘴正下方层流冷却过程中交替经过冲击区和平流区的区域和位于两喷嘴之间层流冷却过程中只经过平流区的区域,这造成带钢宽度方向上温度分布不均匀。计算结果表明,喷水量保持不变的情况下,存在一个最佳喷嘴直径,使带钢宽度方向上温度分布更均匀。喷水速度保持不变,增加喷嘴的直径有利于带钢宽度上方温度均匀,但增加了喷水量,降低了带钢的卷取温度。     

热连轧机带钢卷取温度影响因素仿真分析

针对带钢冷却特点,建立了带钢瞬态热传导仿真模型,采用有限差分法对1800mm热连轧机带钢终轧速度、带钢终轧温度、冷却水温度等因素对带钢层流冷却后温度的影响进行了仿真分析。得到的结果对于认识热轧带钢卷取温度的变化规律具有一定的应用价值。     

热轧中碳宽带钢冷却过程横向弯曲变化规律的数值模拟

 针对目前困扰热轧中碳高强度宽带钢生产的横向弯曲缺陷,使用有限元软件ABAQUS结合FORTRAN语言编写子程序,建立热轧带钢轧后冷却有限元模型。通过模型计算,分析带钢轧后冷却过程中上下表面的冷却不均以及带钢厚度对带钢横向弯曲的影响。研究结果表明,相同厚度情况下,带钢上下表面冷却不均程度越大,带钢横向弯曲程度越严重,上下表面相同冷却效率比的情况下,带钢越厚,带钢横向弯曲越严重。冷却过程中,受温度变化和相变的综合影响,带钢弯曲方向和大小会发生较大变化,且冷却过程中带钢弯曲量最大值远远大于冷却结束后横向弯曲量。     

一套新型带钢冷却模型

冷却速度严重地影响热轧带钢的质量 ,因为用来控制产品质量的时间—温度曲线对金属的机械特性有举足轻重的影响。为了使产品质量均匀 ,即使带钢通过轧机的速度有所改变 ,带钢冷却时也需要尽可能各部分均匀冷却。传统的带钢冷却模型只考虑卷取机的温度 ,但这是不够的。在冷却时带钢需经过随温度而变化的相变过程。如果带钢速度变化 ,带钢的不同部分经常出现不同的物理特性。西门子公司已经建立了一套新型带钢冷却模型 ,据称它提出了一种解决方法 ,使热轧机的操作人员能够通过沿着整个带钢长度方向温度—时间曲线控制冷却过程 ,作为整个闭环冷…     

立式连续退火炉中带钢气体射流冷却数值模拟及温度场计算

气体射流冷却是立式连退炉内带钢快速冷却的主要方式,计算冷却过程中带钢温度场分布,对改善带钢连续退火工艺有着重要的指导意义。利用CFD模拟软件对冷却过程进行数值模拟,获得带钢表面换热系数分布规律。运用有限差分法,对带钢温度场分布进行数值仿真计算。研究了初始带钢温度对冷却过程中带钢温度场分布规律的影响。     

基于Ansys有限元的带钢层流冷却工艺的确定

采用Ansys对不同厚度带钢的层流冷却过程进行瞬态有限元模拟。得到了不同时刻带钢的温度变化和带钢宽度方向的位移变化;分析了在不同冷却工艺下带钢的温度场和应力分布;以某钢厂的层流冷却设备参数为例,来探讨不同厚度带钢的层流冷却工艺,为现场生产提供参考依据。     

带钢层流冷却过程中冲击穿透深度的数值模拟

带钢在层流冷却过程中距表面较近的区域温度存在反复升降的现象,造成厚度方向上组织和性能的差异。结合酒钢CSP热轧带钢生产数据,建立一维热轧带钢有限元模型,计算层流冷却过程中带钢的温度场。提出了冷却过程中带钢冲击穿透深度的概念,并初步探究其影响因素。厚度为3和4mm的带钢计算得出的卷取温度比实测温度分别高3和8℃,相对误差分别为0.44%和1.16%,验证了模型和假设的合理性。结果表明,冷却过程中冲击穿透深度受带钢的导热系数、平流区的对流换热系数、带钢表面温度和喷嘴分布的影响;带钢上表面喷嘴分布较少,冲击穿透深度随对流换热系数的增大而增加,下表面喷嘴分布密集起主导作用,增加对流换热系数,冲击穿透深度几乎不受影响。     

热轧奥氏体不锈钢带钢的退火工艺机理

总结分析了热轧奥氏体不锈钢带钢的退火工艺机理,研究结果可知：热轧奥氏体不锈钢带钢退火时,在500~870℃之间需快速加热,加热速度为10~31℃/s,以防止碳化物和σ相析出、δ- 铁素体分解,并且在1020℃以上保温一段时间,时间大于11s,以使组织充分再结晶软化,碳化物、σ相充分固溶,δ- 铁素体质量分数降到最低,然后在870~500℃之间需快速冷却,冷却速度为38~100℃/s,以防止已经固溶了的碳化物、σ相重新析出。     

590 MPa含锰钢带罩式炉退火氧化色分析与控制

针对罩式炉工业化生产590 MPa含锰低合金冷轧钢带表面氧化色缺陷,分析了表面氧化色的主要组成。实验室采用马弗炉模拟了罩式炉退火工艺,验证了金属锰薄片对钢带表面氧化色的抑制作用。结果表明,金属锰薄片可以通过消耗炉内氧化性气氛,保护试样表面在退火过程中不被氧化。罩式炉工业化退火采用冷点温度620 ℃、热点温度630 ℃、保温时间25 h及全过程40 m3/h氢气流量吹扫制度,同时退火过程中在每个对流板中心处装入125 kg纯金属锰薄片,可避免工业化生产590 MPa含锰低合金冷轧钢带边部出现氧化色缺陷,同时力学性能满足要求。     

Study on strip running deviation at exit of heat section in continuous annealing furnace for cold rolling

In order to solve strip reciprocating and quick- moving running deviation at the exit of heat section for vertical continuous annealing furnace, the thermal crown of furnace roller was analyzed quantitatively and regression method was used to determine the impact of roller crown on strip running deviation. And then the alarm program for strip running deviation was established, which can give early warning of strip running deviation and adjust the model parameter and the heating and cooling temperature rate simultaneously. With the application of this system on a continuous annealing machine for cold rolling in Shougang Jingtang Company, the strip running deviation which caused by thermal crown of furnace roller can be solved.     

Mathematical model of metallurgical thermal processes and application

There are lots of physical changes and chemical reactions in the processes of iron and steel making, these processes are quite complex in the aspect of heat transfer.The processes of iron and steel making can be approximately divided into three kinds.The first kinds are the processes of fusion metallurgy which involve enormous chemical reactions,such as blast furnace,converter,electric furnace and coke oven.The second kinds are the processes of heating and cooling which are mainly the physical changes,such as walking-beam reheating furnace,annular heating furnace and car-type furnace.The third kinds are the processes of heat treatment which mainly adjust metallurgical structure of metal,such as roller hearth heat treatment furnace, strip continuous heat treatment vertical/horizontal furnace and HPH bell-type annealing furnace.Every process can only be finished in particular thermal equipment.And all the physical and chemical processes mentioned above must obey first principles of engineering thermodynamics,heat & mass transfer,hydromechanics, combustion,metallurgy physical chemistry etc,and which can be summarized as principle of heat transfer,mass transfer,momentum transfer and chemistry reaction.In this paper,based on first principle of heat and mass transfer in iron and steel making processes,a series of mathematical models of thermal equipments and processes are presented.Such as the model of hot-blast stoves,coke oven,CDQ-boiler system,sintering, reheating furnace,soaking furnace,annular heating furnace,roller hearth heat treatment furnace,strip continuous heat treatment vertical/horizontal furnace,HPH bell-type annealing furnace,control cooling of medium plate,burner,heat exchanger and regenerative burner etc.The on-line application of the model is based on experimental certification of the mathematical model.And finally the computer optimization system of metallurgical thermal process is obtained.     

Thermal performance of annealing line heating furnace

Abstract

In the present study, a stepwise model based on the enclosure concept has been applied to an annealing line heating furnace. The model has been satisfactorily tested using three industrial manufacturing data sets. As temperature measurement inside the furnace is difficult, the model could be used to improve control and to obtain the outlet temperature of the steel strip, the heat transfer rate loss and the strip heat transfer rate throughout the length of the furnace. Variations in the thermodynamic properties included in the model and in the operational conditions, which cannot be accurately known, have been tested to ascertain their effects on the evolution of the strip temperature. It is found that precise knowledge of the heat capacity and heating power introduced in the furnace are important to obtain good results in application of the model.     

镀锌机组带钢C翘缺陷综合治理技术的开发

 为了研究带钢热镀产品C翘板形缺陷导致其镀层不均匀性严重问题,优化热镀锌机组连退工艺过程,开发带钢C翘缺陷综合治理技术。首先考虑热镀锌连退过程的设备与其工艺特点,分析C翘板形发生机理,明火烧嘴状态、辐射管状态、风机状态、带钢重力、上游工艺段遗传板形等影响因素,使得带钢表面各处存温度差异性较大,致使带钢横向残留塑性变形在其厚度方向分布均匀,当其超过其临界失稳条件而发生C翘。然后,从系统学的观点出发建立兼顾C翘缺陷影响因素的连退炉系统函数,考虑到连退炉多变量耦合、复杂非线性特点,以工艺段为单位将连退过程划分子系统,以各工艺段板形翘曲最小为目标,基于带钢C翘预报模型分别建立加热段温度优化目标函数、均热段温度优化目标函数、冷却段冷却风机状态优化目标函数,并以各工艺段目标函数相叠加的形式建立系统函数。得出了连退过程各工艺段工艺参数综合优化方法,制定其工艺优化流程,并形成加热段温度优化设定技术、均热段温度优化设定技术、冷却段冷却风机状态优化设定技术等关键技术。最后,将该综合治理技术应用于国内型钢铁机组取得良好效果。结果表明,典型规格带钢在连退过程各工艺参数优化前后对比,其最大翘曲量由17.0 mm降至5.9 mm;该类型带钢的镀层厚度生产统计数据显示,带钢C翘板形改善后,带钢上下表面平均镀层厚度降至用户要求的范围内。     

Modeling of Strip Temperature in Rapid Cooling Section of Vertical Continuous Annealing Furnace

 The strip temperature is affected by many factors in rapid cooling section (RCS) of the vertical continuous annealing furnace (VCAF). They can be divided into four types: the physical properties of cooling gas, the geometry characteristics of configuration of cooling equipment, the heat transfer between the strip and the cooling gas, and the conductivity of the strip. It aims to model the strip temperature in the cooling section based on the fundamental heat transfer theory and the four aspects factors. The model for transient Nusselt number is obtained by considering Reynolds number, Prandtl number and geometry characteristics of RCS. Then cooling model of the strip transient temperature is built by Nusselt number, heat transfer coefficient and heat conductivity of the strip. The results are compared with the data from production line. The comparisons indicate that the model can well predict cooling temperature of the strip. It is hoped that the proposed model can be used for design and control of the vertical continuous annealing furnace.     

Modeling of Strip Heating Process in Vertical Continuous Annealing Furnace

 The mechanism for heat transfer of radiation is usually adopted to heat strip in vertical continuous annealing furnace. The rate of heat transfer among strip and other objects can be hugely affected by the parameters of strip speed, geometry factors and radiating characteristic of surfaces of strip, radiating tubes and walls of furnace. A model including all parameters is proposed for calculating the heat transfer coefficient, predicting the strip temperature and boundary temperature of strip through analyzing these parameters. The boundary temperature is a important datum and different from average arithmetic value of temperature of strip and temperature in furnace. Also, the model can be used to analyze the relation for temperature of strip and heat transfer coefficient, total heat transfer quantity and heating time. The model is built by using the radiating heat transfer rate, the Newton′s law of cooling, and lumped system analysis. The results of calculation are compared to the data from production line. The comparisons indicate that the model can well predict the heating process. The model is already applied for process control in production line. Also, this research will provide a new method for analyzing the radiation heat transfer.     

立式连退炉快冷段氢气含量对带钢温度的影响

立式连续热处理炉快冷段混合气的氢气含量,对换热系数和带钢温度有很大的影响,体现了冷却气体物理性质与换热系数和带钢温度之间的关系。在其他条件相同而氢气含量不同的条件下,对带钢传热状态进行分析,利用冷却设备几何结构、努塞尔数与换热系数的关系,得到带钢瞬时冷却温度计算公式,为生产及工程设计提供了一定的依据。