Differential heat treatment of rails by means of rolling heat

Differential heat treatment of rails by air on the basis of the rolling heat is considered. The research is conducted at AO EVRAZ ZSMK during the reconstruction of rail production. The influence of the chemical composition of the steel and the conditions of plastic deformation and heat treatment on the onset of polymorphic transition is studied. Thermokinetic diagrams are plotted for steels of experimental chemical composition. The cooling rate over the cross section of the rail head is investigated as a function of the heat-treatment parameters. The optimal chemical composition and heat-treatment conditions are determined. The heat treatment of rail samples directly after rolling is experimentally studied. Recommendations for the industrial introduction of differential quenching are developed on the basis of the theoretical and laboratory results. Industrial tests show that the rails produced are of high quality and comply with standard requirements.     

A method for the diagnosis and treatment of diseases using high-temperature short-term heat impulses

The comparative study of the immunogenic and protective properties of V. cholerae, grown in vivo and in vitro, and cell walls and lysates obtained from these organisms. In the mouse protection test the efficacy of preparations obtained from vibrios grown in vivo did not exceed that of the preparations obtained from V. cholerae agar cultures.     

轧后余热处理钢筋与常规轧制钢筋抗震性能对比

在钢筋轧制中,利用轧后余热处理,可以大幅度提高产品性能,减少合金的加入量,降低生产成本,所以越来越受到各大钢铁企业的青睐。对轧后余热处理钢筋与常规轧制钢筋（即非轧后余热处理钢筋）抗震性能进行对比分析。     

Casting and rolling in one heat

In regard of the reduction of energy consumption during the production of steel slabs and strips different charging procedures are of high economic interest. Especially hot and direct charging procedures are used in modern ways of strip production like CSP and strip casting. For simulation of these procedures and their related effects on the microstructure and the mechanical properties of the material, the complete process chain of melting, casting and hot rolling in one heat has been realised in a pilot scale. In this concept process parameters such as temperature over time are controlled during the complete process. By variation of the thermomechanical process parameters the microstructure and the mechanical properties gained in different processing routes can effectively be simulated. This new set‐up allows the simulation of the casting and rolling processes not only in a laboratory scale by using conventional compression, tensile and quench tests but now also in a pilot scale. The results will be used as input parameters for FEM simulation. In this paper the set‐up of the laboratory facility is described with the measured and controlled parameters.     

面心纯铝轧制织构的晶体塑性有限元模拟

基于率相关晶体塑性本构模型,分别将Taylor模型和有限单元模型两种多晶模型嵌入大型有限元程序ABAQUS,实现了晶体塑性学有限元模拟.直接将电子背散射衍射(EBSD)获取的晶粒初始取向输入晶体塑性有限元模型,预测了两种不同应变情况下面心1050纯铝轧制织构的演化.模拟结果与EBSD实验测得的织构演化结果有较好的一致性,随着变形程度的增加,预测织构与实测织构变得更加锋锐.经过比较,Taylor型模型预测出了{4411}〈11118〉的Dillamore取向,而有限单元模型预测出了铜型织构取向,比Taylor模型预测结果更接近实验验证结果.两种模型并不能预测出{011}〈211〉黄铜取向、{123}〈523〉S取向、{011}〈100〉Goss取向及其他理想取向.     

Microstructural analysis of multilayered titanium aluminide sheets fabricated by hot rolling and heat treatment

This study is concerned with the microstructural analysis of multilayered or bulk Ti aluminide sheets fabricated by the self-propagating high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. Multilayered Ti/Al sheets were prepared by stacking thin Ti and Al sheets alternately, and a good Ti/Al interfacial bonding was achieved after rolling at 500 °C. When these sheets were held at 1000 °C, spheroidal TiAl₃ phases were formed by the SHS reaction at Ti/Al interfaces and inside Al layers. Microstructural analysis on the hot-rolled, multilayered Ti/TiAl₃ sheets revealed that intermetallic phases such as TiAl₂, TiAl, and Ti₃Al were formed at Ti/TiAl₃ interfaces due to interaction between Ti and TiAl₃ and that pores formed in the TiAl₃ layer were significantly reduced during hot rolling. When multilayered Ti/Ti aluminide sheets were heat treated at 1000 °C, Ti₃Al, TiAl, and TiAl₂ were grown as Ti and TiAl₃ were consumed. As the heat treatment proceeded, TiAl grew further, eventually leading to the fabrication of multilayered sheets composed of Ti₃Al and TiAl. Bulk Ti aluminide sheets, having a lamellar structure of Ti₃Al and TiAl, instead of multilayered sheets, were also fabricated successfully by heat treatment at 1400 °C. This fabrication method of the bulk sheets had several advantages over the method by hot forging or rolling of conventional cast Ti aluminides. From these findings, an idea to fabricate multilayered or bulk Ti aluminide sheets by hot rolling and heat treatment is suggested as an economical and continuous fabrication method, and the formation and growth mechanisms of interfacial phases are elucidated in this study.     

智能算法在双辊铸轧过程铸轧力计算中的应用

在双辊铸轧过程中,铸轧力的控制是铸轧过程稳定进行和提高薄带质量的关键.为了控制铸轧力,必须建立铸轧力计算数学模型,本文采用了一种基于贝叶斯方法的前向神经网络训练算法以提高网络的泛化能力,在网络的目标函数中引入了表示网络结构复杂性的惩罚项,融入"奥克姆剪刀"理论,避免了网络训练的过拟合.将上述网络应用于铸轧过程的铸轧力计算,具有很高的计算精度,同时在收敛速度、稳定性和泛化能力方面都优于传统的BP神经网络.     

Hot rolling and heat treatment of Ni−Cu−Cb(Nb) steel

Copper-containing steels can be susceptible to hot shortness and the properties of columbium (Nb) grain-refined steels are sensitive to processing conditions. Ni?Cu?Cb steel embodies both copper age-hardening and columbium grain refining; therefore, the effect of nickel on hot shortness and the effects of hot rolling and heat treatment on mechanical properties were examined with the 0.85 pct Ni-1.2 pct Cu-0.03 pct Cb, age hardenable steel. The nickel level of 0.7 to 1.0 pct in Ni?Cu?Cb steel is sufficient to prevent hot shortness due to copper. A suitable aging treatment is 1 hr at 1050°F while comparable properties can be obtained by aging for 4 hr at 975°F. Laboratory processing has shown that lower hot rolling finishing temperatures and greater reductions at the finishing temperature improve laboratory-made heats of this steel by lowering the ductile-to-brittle transition temperature and raising the yield strength. Lower soaking temperatures also result in lower impact transition temperatures but have no effect on strength.     

Computational-and-experimental evaluation of the implementation condition of combined rolling–pressing using the power balance method

The results of solving the problem of determining the implementation of combined rolling–pressing (CRP) are presented. Components of the total power for the process under study are written in the analytical form, they are calculated with the help of the computer program, and the influence of separate factors on the CRP implementation is analyzed. The possibility of implementing the process for CRP conditions of aluminum alloys with the use of a pilot installation of the combined treatment is evaluated quantitatively using the capacity reserve coefficient as the main criterion.     

Fundamental phenomena governing heat transfer during rolling

To quantify the effect of roll chilling on the thermal history of a slab during hot rolling, tests were conducted at the Canada Center for Mineral and Energy Technology (CANMET) and at the University of British Columbia (UBC). In these tests, the surface and the interior temperatures of specimens were recorded during rolling using a data acquisition system. The corresponding heat-transfer coefficients in the roll bite were back-calculated by a trial-and-error method using a heat-transfer model. The heat-transfer coefficient was found to increase along the arc of contact and reach a maximum, followed by a decrease, until the exit of the roll bite. Its value was influenced by rolling parameters, such as percent reduction, rolling speed, rolling temperature, material type,etc. It was shown that the heat-transfer coefficient in the roll gap was strongly dependent on the roll pressure, and the effect of different variables on the interfacial heat-transfer coefficient can be related to their influence on pressure. At low mean roll pressure, such as in the case of rolling plain carbon steels at elevated temperature, the maximum heat-transfer coefficient in the roll bite was in the 25 to 35 kW/m² °C range. As the roll pressure increased with lower rolling temperature and higher deformation resistance of stainless steel and microalloyed grades, the maximum heat-transfer coefficient reached a value of 620 kW/m² °C. Obviously, the high pressure improved the contact between the roll and the slab surface, thereby reducing the resistance to heat flow. The mean roll-gap heat-transfer coefficient at the interface was shown to be linearly related to mean roll pressure. This finding is important because it permitted a determination of heat-transfer coefficients applicable to industrial rolling from pilot mill data. Thus, the thermal history of a slab during rough rolling was computed using a model in which the mean heat-transfer coefficient between the roll and the slab was determined from an estimate of the rolling load. It was found that the heat loss of a slab to the roll was 33 pet of the total, which emphasizes the importance of accurately characterizing the heat-transfer coefficient in the roll bite during hot rolling.     

一种新的静态轧制过程有限元模拟方法

提出了一种将欧拉法与拉格朗日法结合起来的静态轧制过程有限元模拟新方法.其主要内容包括:在轧制件纵向上用欧拉坐标, 厚度和宽度方向上用拉格朗日坐标,时间变量是独立的,计算轧制件厚度和宽度方向上的实际位移时采用的流线形积分改用沿纵向的欧拉坐标一元积分.     

轧钢加热炉余热利用技术

国内轧钢加热炉,过去大多数是以燃煤方式加热钢坯,由于环保等原因,逐渐为燃气、燃油方式加热所替代,在燃气或燃油的轧钢加热炉上装置列管式日交换器,再配上完善的水、汽、电控制装置,即可组合成简单实用的加热炉余热生产蒸汽系统,能为企业生产和生活供应充足的蒸汽。     

金属非晶态-过冷液态转变的比热容研究

利用DSC热分析法研究了Zr基及78Fe-9Si-13B非晶合金的比热容随温度的变化规律,发现Zr基非晶的比热容温度曲线与二级相变热容变化的规律十分相似,因此从热力学上证明了玻璃态与过冷液态之间的转变属于二级相变.78Fe-9Si-13B非晶合金的比热容温度曲线上仅存在一个λ形峰值,这显示居里温度与玻璃转变温度几乎相等,结构有序性与磁矩有序性的变化发生了重叠.     

A method for the calculation of temperature during hot rolling of bars and rod

A semi-analytical finite element method is presented which enables the calculation of temperature distribution over the cross-section of the rolling stock as it passes through the individual stands and cooling zones of a wire rod mill. Conformal mapping techniques have been used to subdivide the numerous cross-sectional areas that occur during rolling into suitable macro-elements. The system of ordinary differential equations resulting from the application of Galerkin's method to the diffusion-convection equation is solved by means of the eigenvalue method. The accuracy of the developed mathematical method was checked by means of comparison with numerical results obtained from the conventional finite element method. The method is an integral part of a complete process model predicting the temperature distribution of wire rod and bars during hot rolling to be dealt with later.