An accurate prediction for the thermal crown of the continuously variable crown (CVC) work roll is a key to improve the accuracy of the computer on-line control model. In this paper, the authors have developed a finite difference model to simulate the thermal deformation of the CVC work rolls in hot strip rolling. The effects of the heat generation produced by the strip deformation and friction, heat conduction and convection on the thermal crown are introduced in the simulation. A comparison of the calculating roll temperature and measured values shows that they are in good agreement. Result shows that a model of calculating the thermal crown of the CVC rolls can be obtained based on the finite difference method. The modelling of the thermal crown of CVC rolls in hot strip rolling can improve the accuracy of on-line control model.

In order to solve the problem of strip surface pores generated by the combination of the tertiary scale on strip surface with black oxide layers produced on the roll surface, the mechanism of strip scale pores formation was analyzed using several instruments such as the SEM, the AHM-2-HL optical microscope and the Oxford ISIS EDAX energy spectrometer. Amethod of control is advanced to reduce strip scale pores, which is effective and clearly beneficial for enhancing the strip surface quality in practice.

The thermal wear ratio of a high speed steel roll was investigated experimentally in hot strip rolling with a DTW-166 thermal wear testing machine developed by the authors. It is clear that the wear ratio increased with number of cycles. Some of the increase in wear was because of the black oxide layer generated on the roll surface at the beginning. The wear ratio also increased as slippage ratio and loads increased. Loads played a more important role than slippage ratio for thermal wear. The appearance of the roll surface was observed by SEM under different conditions. The mechanism of thermal wear was composed of adhesive, microploughing, mirocutting, oxidation, and plastic slippage wear.

Using a Gleeble 1500 hot simulator, the dynamic recrystallization (DRX) behavior and changes of DRXgrain size of a Mn-Cr type gear steel have been investigated at deformation temperatures of 900-1150℃, strain rates of 0.1-1 s−1, and initial austenite grain sizes of 70-150m. The experimental results show that the Mn-Cr gear steel exhibits a typical DRX behavior under higher deformation temperatures, lower strain rates and smaller initial austenite grain sizes. The DRX takes place under the conditions with Zener-Hollomon parameter (Z) less than a critical value Zc. The DXR grains are formed by the bulging mechanism. By regression analysis, activation energy and stress exponent were determined to be 378.6kJ/mol and 5.8, respectively. The complete DRX grain size is a power law function of Z with an exponent of-0.25. The reason why Z parameter determines uniquely the DRX grain size was analyzed.

采用Gleeble1500热模拟试验机研究了一种新型Mn-Cr系齿轮钢在变形量为70%，变形速率为0.1～1s-1，变形温度为850～1150℃，原始奥氏体晶粒尺寸为70～150μm条件下的动态再结晶行为及再结晶后奥氏体晶粒尺寸的变化规律•研究结果表明：在一定的变形量下，变形速率、变形温度、奥氏体晶粒尺寸是影响再结晶的3个因素，只有变形条件Z小于上临界值Zc时才会发生动态再结晶•再结晶后奥氏体晶粒尺寸D是由变形条件Z惟一地决定而与原始奥氏体晶粒大小无关，Z 增加，D减小，二者符合关系式Z=AD-3.91。

针对宝山钢铁（集团）公司2050热连轧层流冷却系统，采用神经网络与数学模型相结合的方法，给出优化的层流冷却对流换热系数，以实现准确地预报卷取温度的目的。结果表明，采用神经网络计算出的对流换热系数后，卷取温度的计算值与实测值的标准差降低了22184%，效果显著。

High-speed steel M2 strip has been experimentally produced by using a twin roll strip castor. The microstructure of the strip and the eutectic carbide in the cast-rolled strip were examined in detail. The spheroidizing procedure of the eutectic carbide in the twin roll cast M2 high-speed steel strip was investigated with the method of annealing, quenching and tempering. The results show that the eutectic carbide was gradually spheroidized with the increase of heating temperature and holding time through coarsening and accumulation of eutectic carbide, dissolving and breaking up of net work eutectic carbide, and precipitating and coarsening of secondary carbide. The kinetics analysis of coarsening and accumulating of eutectic carbide, and coarsening of secondary carbide in the high-speed steel strip were made based on the experimental results, and the growing transient velocity equations of carbide were deduced. The mechanism of cast-rolling enhancing the spheroidizing of eutectic carbide in M2 steel was discussed.

Two quenching methods were applied in the experiments carried out on Gleeble 1500 thermomechanical simulator: (1) spurting water; (2) making the samples drop into water, and the cooling rate distributed un-uniformly in the samples quenched by the former and uniformly by the latter. The critical cooling rate of preventing ferrite precipitation was determined, and the microstructure observation position in which the microstructure could be frozen to room temperature in the samples quenched by spurting water was also determined and using this method the Ad3 was determined to be about 830℃ for tested materials. Using second quenching method, single-pass deformation experiments at different temperatures were carried out, and the microstructure analysis indicates that, as the deformation temperature decreased, the ferrite morphology changed from Widmanstätten and allotriomorphs to equiaxed at about 800℃. Combining the dilation-temperature curves measured during cooling process after deformation at different temperatures, the Ad3 was determined to be also about 830℃ for tested materials.

In this paper, the influence of Nb, Vand Ti on the peak strain of deformed austenite in Mo-based micro-alloyed steels has been studied. Four steels, identified as Mo, Mo+V, Mo+N b and Mo+Ti, respectively, were heated to 1200℃ and held for 10min and then the temperature was rapidly reduced to test temperatures and maintained for 40s. The test temperatures were 950, 1000, 1050, 1100, 1150 and 1200℃ at the strain rates of 0.05, 0.1, 0.5, 1 and 5s 1, respectively. Results indicate that the presence of Nb, Ti, and Vaffects significantly the value of peak strain (ep), especially Nb which has a significant effect on the start of the dynamic recrystallisation. For all the steels studied, the peak strainep was modelled as a function of the Zener–Hollomon parameter and the austenite grain size.

在热模拟机上测试了16MnCr5钢经1200℃加热的未变形奥氏体、在860℃经50%压缩变形奥氏体的CCT曲线和维氏硬度，研究了其相变组织。结果表明：未变形奥氏体以0.025℃/s连续冷却时和在860℃变形的未再结晶奥氏体以012℃ös连续冷却时及1100℃变形的再结晶奥氏体分别以0.05℃/s连续冷却和快冷至660℃等温退火时均得到多边形铁素体+珠光体组织。