带钢表面在线检测与质量控制技术分析

冷轧酸轧线轧制带钢经常由于没有发现带钢表面的孔洞、翘皮以及其他缺陷导致带钢进入轧机时出现断带,严重影响了带钢生产质量,在轧机自动生产过程中带钢跑线速度快,人的肉眼不能及时发现这些带钢表面存在的缺陷,出现这种情况就要耗费大量的人力去处理废料带钢,对企业效益产生不良影响,因此,利用带钢表面在线检测技术能有效解决上述问题,在轧钢机组自动运行时能够及时发现带钢表面缺陷,减少带钢断带次数。对此,该文首先分析了带钢在线检测技术的主要原理,并结合笔者实际工作经验,提出了带钢表面在线检测与质量控制的具体实施方案,希望为轧钢质量控制提供一些有益的参考。     

首钢京唐热轧2250mm短行程控制的研究

短行程控制是热轧粗轧宽度调整过程中改善带钢端部形状，减少成材率损失的主要方法。首钢京唐热轧2250mm短行程控制是按照压下量、成品带钢宽度和入口厚度层别分类进行控制，为提高热轧带钢短行程控制精度，本文引入钢种、SsP是否使用，轧制策略等因素对短行程控制的影响，实际使用后提高了轧线成材率。     

连续退火炉炉内带钢纠偏系统分析与建模

本文结合攀钢2030连退退火炉机组，对炉内带钢纠偏系统控制原理和系统组成进行了分析，并对其各组成部分建立了相关的数学模型，为后续对带钢在炉内的高精度的跑偏控制提供了实用理论和模型方法。     

基于AMEsim的带钢卷取机纠偏控制系统建模仿真研究

卷取机是带钢生产线上的关键设备，要求有很高的卷取控制性能，包括快的响应速度和高的控制精度。本文在分析了带钢卷取机纠偏控制系统工作原理的基础上，用AMESim软件对该液压系统进行了仿真，仿真结果表明该系统满足控制性能。     

带钢表面黑斑缺陷分析

采用扫描电镜及能谱等手段对热轧带钢和冷轧带钢表面产生黑斑的原因进行了分析。结果表明:酸洗热轧带钢表面黑斑主要是氧化铁,冷轧带钢表面黑斑主要是热轧带钢氧化铁经退火后被还原产生的还原铁。     

热轧带钢层流冷却过程的温度预测模型

通过焓法模型和相变热力学和相变动力学模型来研究分析热轧带钢在层流冷却过程中的能量变化,利用层流冷却过程中带钢的温度场和热焓场的计算结果来预测带钢冷却后的温度,并验证热轧带钢层流冷却过程并非带钢温度下降的过程,而是带钢能量传递给了周围的环境。     

正交各向异性带钢瓢曲变形行为样条有限元研究

带钢在轧制过程由于晶粒的择优取向而产生各向异性,为了研究这种各向异性对带钢板形瓢曲行为的影响规律,针对生产中常见的板形瓢曲缺陷,根据正交各向异性薄板小挠度理论和屈曲问题的驻值势能原理,建立了带钢在纵向延伸塑性应变(初应变)作用下以样条函数为基础的前屈曲样条有限元计算模型,获得了屈曲临界塑性应变、临界波长与带钢各向异性程度的关系;根据大挠度理论和虚功原理,应用样条有限元获得了正交各向异性带钢后屈曲路径。计算分析了带钢正交各向异性程度对中浪、边浪、四分之一浪、边中复合浪屈曲变形前屈曲临界条件及后屈曲变形过程的影响规律。     

SPHC带钢表面氧化皮结构及色差分析

针对SPHC带钢开卷后中部和边部颜色差异的问题,通过对现场取样分析,利用扫描电镜(SEM)对存在表面色差的SPHC热轧带钢表面的氧化皮形貌、厚度、微观结构进行分析,测量了氧化皮平均厚度和共析组织比例,对比不同卷取温度对氧化皮的影响,分析了热轧带钢色差形成主要原因。结果表明:热轧带钢横向不同位置的表面粗糙度不同;卷取温度560和670 ℃时,带钢宽度方向上的氧化皮厚度相近,说明色差与氧化皮厚度没有直接关系;带钢宽度方向氧化铁皮的Fe₃O₄厚度和氧化皮粗糙度差异导致光的漫反射不同,造成其视觉上颜色差异。生产中,提高层流冷却过程中带钢横向温度均匀性,适当增大卷取张力以减小钢卷层间缝隙,有效改善了带钢表面氧化铁皮颜色差异现象。     

莱钢平整机自动辊缝控制系统分析

平整机是确保冷轧带钢成品质量的一道关键工序,对提高产品质量、板形控制、满足用户要求起着至关重要的作用。辊缝控制合理有效的实施是改善带钢板形、提高带钢表面质量和精度的必由之路。本文通过对莱钢平整机的辊缝系统进行研究与分析,为退火卷板型质量的提升与控制提供了良好的参考。     

平整加工对高强钢抗畸变能力的影响及优化

为解决高强带钢在生产加工过程中产生的板形缺陷和畸变,本文采用裂纹柔度法测量单下辊传动平整加工前后620JJ带钢内部残余应力,并依据残余应力在厚度或板宽方向分布不均将导致带钢发生畸变,定义带钢应力不平衡度为畸变评价指标,分析了平整工艺对带钢内部残余应力分布和畸变的影响,并利用ABAQUS有限元模拟探究了工艺优化方案。结果表明：裂纹柔度法能够准确表征带钢内部残余应力;应力不平衡度可以直观地表征带钢产生畸变的可能性;平整加工对带钢的主要影响是应力的均衡化和降低整体残余应力水平,平整前后各测点弹性应变能极值与平均值差值从169.25 MPa·mm降至141.86 MPa·mm,带钢内部残余应力的最大值由463.26 MPa降至363.6 MPa;将平整工艺改为双辊传动、增加摩擦力、增加张力、增加轧制力等方式均可有效改善应力不平衡度。     

Calculation of an integral arising in dry flat grinding for a general heat flux profile. Application to maximum temperature evaluation

We study the surface temperature expression in flat dry grinding for a general heat flux profile entering into a workpiece within the friction strip due to contact between wheel and workpiece. This expression involves a non-tabulated integral that we proceed to calculate. Since the maximum temperature is reached at the workpiece surface in the stationary regime, the advantage of this calculation is that the maximum temperature can be computed very rapidly, so it can be applied in on-line monitoring of the grinding process in order to avoid thermal damage.     

金属浴石油产品铜片腐蚀检测仪器的研制

为解决传统液体浴腐蚀仪器试验恒温时间长、控温误差大的问题,设计了一种基于金属浴温控技术的石油产品铜片腐蚀测定器。该仪器主要用于测定部分石油产品在特定温度下,对金属铜的腐蚀程度。试验结果表明该仪器温场波动小、加热均匀、工作效率高,可在石油产品铜片腐蚀试验中广泛应用。     

On the transient heat transfer in liquid helium in narrow horizontal channels

The results of an experimental investigation into transient heat transfer from a horizontal flat copper strip surface both to an opened volume of liquid helium and to different crosssection cooling channels placed below the heated surface are given. The copper strip of 0.2 mm thickness is heated by passing the electrical current through it. The temperature in the centre of the strip is measured by a copper-iron versus copper thermocouple. The thermocouple junction to be measured is placed into the vacuum.     

Thermoelastic analysis of a partially insulated crack in a strip under thermal impact loading using the hyperbolic heat conduction theory

In this paper, the transient temperature and thermal stresses around a partially insulated crack in a thermoelastic strip under a temperature impact are obtained using the hyperbolic heat conduction theory. Fourier and Laplace transforms are applied and the thermal and mechanical problems are reduced to solving singular integral equations. Numerical results show that the hyperbolic heat conduction parameters, the thermal conductivity of crack faces, and the geometric size of the strip have significant influence on the dynamic temperature and stress field. The results based on hyperbolic heat conduction show much higher temperature and much more dynamic thermal stress concentrations in the very early stage of impact loading comparing to the Fourier heat conduction model. It is suggested that to design materials and structures against fracture under transient thermal loading, the hyperbolic model is more appropriate than the Fourier heat conduction model.     

乳化炸药钢带凉药工艺的改进

分析了乳化炸药钢带凉药机的工作原理,针对钢带凉药机冷却能力低、与装药机能力不匹配的问题,提出了解决方案:将自然对流改为强制对流,提高对流换热系数;安装风冷循环系统,提高基质与冷风的温差等。经试验证明,该方案能实现钢带凉药机与装药机的产能匹配。     

Modelling thermal and microstructural evolution on runout table of hot strip mill

Abstract

A mathematical model has been developed to predict the thermal and phase transformation response of a 0·34 and a 0·05 wt-%C steel during cooling on the runout table of a hot strip mill. The model incorporates the cooling characteristics of laminar water bar sprays, the austenite–ferrite plus pearlite phase transformation kinetics as a function of the austenite grain size, and the heat of transformation. Overall heat transfer coefficients for the laminar water banks were determined from data obtained from in-plant trials carried out at the Stelco Lake Erie Works (LEW) hot strip mill. Isothermal and continuous cooling diametral dilatometer tests were performed on a Gleeble 1500 thermomechanical simulator at temperatures and cooling rates that simulate LEW hot strip mill conditions. The isothermal data were used to establish the phase transformation kinetics as afunction of austenite grain size and temperature. The continuous cooling results were used to obtain the relationship between cooling rate, transformation start temperature, and fraction of ferrite formed. The model was tested and validated by simulating the LEW cooling conditions while monitoring the phase transformation behaviour and by comparison of predicted and measured microstructural detail.

MST/1331     

A New Pulse Hot Strip Sensor for Measuring Thermal Conductivity and Thermal Diffusivity of Solids

The pulse hot strip method is a newly developed dynamic method to measure the thermal conductivity and thermal diffusivity of solids. It is based on monitoring the temperature response of a sample to a very short heat pulse liberated by a strip heat source. The instrument's uncertainty is estimated to be less than 3% for both quantities.     

薄规格带材气垫式连续热处理新技术研究

利用开发的新型带材气垫式加热-淬火装置,实验研究了新型气垫式射流喷嘴喷射压力、风速、风温及带材张力等参数对漂浮高度、漂浮稳定性和换热均匀性的影响规律,借助有限元模拟及数学建模等方法开发出动态漂浮技术和层级串联淬火技术,解决了传统气垫式热处理炉、淬火装备漂浮稳定性可控性不强,换热效率不高,换热均匀性差等难题.研究表明,采用新型装置和技术实现漂浮托举力增加近1倍,换热均匀性提高近1倍,淬火后带材平直度≤25I.     

Analysis of boundary layer control by heat transfer strips using an asymptotic approach to the PSE

The effect of heating strips on the stability of boundary layer flow over a flat plate is investigated. Heating strips alter the flow stability through the temperature dependence of the fluid properties. A stability study is carried out using the parabolized stability equations (PSE) that calculates the effects of temperature dependent fluid properties in terms of asymptotic expansions based on the total heat input. The leading order influence is obtained as a general result and, for the particular Prandtl number taken, is independent of any special set of property laws. In a fluid for which the intrinsic viscosity increases with temperature and the density decreases with temperature (such as air) the results show that the optimal location for a heating strip to stabilise the flow is upstream of the neutral point. The optimal location moves further upstream as the total heat input level is increased. For a given heat input widening the heating strip further stabilises the flow. Finally, the potential of the asymptotic method as a tool for further analysis of the flow is discussed.     

Temperatureinfluss auf den Adhäsionsverschleiß beim Umformen von Aluminiumblechen

Influence of temperature on adhesive wear at deep drawing of aluminium alloys Deep drawing processes, used to manufacture aluminium components, are often sensitive to adhesive wear. Thus, the process stability as well as the quality of the formed parts may not fulfil the required specifications. Approaches, developed to reduce this wear phenomenon, still neglect the influence of temperature inside the forming area. Hence, this parameter is analysed by numerical and experimental tests. The tests are conducted by using a strip drawing device, enabling the experimenter to accomplish parameter variations. Subsequently analysis with tempered tools were done to show correlation between adhesion and temperature. The temperature supplied to the model tool corresponds to the temperature occurring in real forming process. In contrast to strip drawing test without external heat source, during the experiments with tempered tools adhesive wear could be shown. Thus, approaches to reduce adhesion wear should account for the influence of temperature.