变步长数值转换法在热连轧负荷分配中的应用

针对Newton-Raphson迭代法存在难以实现轧制力和轧制功率负荷分配模式在线应用的缺陷,提出了一种变步长数值转换方法.模拟计算结果表明,该方法可满足计算要求,能实现上述2种负荷分配模式的在线应用.     

Simulated Calculations of Strain Induced Precipitation Behaviorin a Nb-Ti-V Steel

On the basis of regular solution sublattice model and classical nucleation and growth theory Strain induced precipitation kinetics in Nb-Ti-V combined treated microalloying Steels has been calcu lated. The calculated precipitation-time-temperature (PTT) diagram is in reasonable agreement with experimental results obtained from isothermal Stress relaxation method.     

A fuzzy algorithm for flatness control in hot strip mill

Based on BP neural network, a flatness prediction model in hot strip mill was developed, in which the same location point data were adopted for training and testing to avoid the influence of time-delay. Two fuzzy flatness control algorithms in hot strip mill were developed, and the simulations were carried out by using the flatness prediction model as controlled objective. Conventional fuzzy control algorithm replacing PID linear control system entirely can reduce flatness error significantly. However, the control quality is not good in steady state. The coupled fuzzy-PID control algorithm reduces flatness error significantly as well as produces the desired flatness with small steady-state error and good stability. The coupled fuzzy-PID control algorithm is found to be suitable for rolling the desired flatness in hot strip mill.     

Microstructure characterization of austenitic Fe–25Mn–22Cr–2Si–0.7N alloy processed by twin roll strip casting

Near net shape casting of austenitic stainless steel containing high Mn and N was explored by using a twin roll strip caster. Microstructural observation and analysis of the as-cast strip by XRD, SEM, and TEM demonstrated that the formation of δ-ferrite and carbides had been prohibited due to the high solidification cooling rate of more than 14,000 K/s during strip casting. Tensile tests indicated that the as-cast strip possessed reasonably good mechanical properties, with a yield strength of 500 MPa and elongation of about 15%. The elastic modulus of the as-cast strip was higher than that of solution treated steel by about one order of magnitude. From the TEM observations, it was found that the as-cast strip contained more dislocations and numerous interstitial elements (N and C) dissolved in grains than the solution treated material, in which dislocations were scarcely observed and precipitates were formed along grain boundaries. Fracture morphology indicates that the as-cast strip has undergone ductile rupture during tensile testing. Deformation twins were observed in the deformed region of the sample by the in-situ tensile test under SEM and TEM observations. The formation of deformation twins were believed to be responsible for high plasticity of the as-cast strip.     

20MnSi Ⅲ级热轧螺纹钢筋的开发

采用控轧控冷的方法生产400 MPa级的Ⅲ级钢筋,可以降低成本.用热模拟试验机测定了20MnSi钢的动态CCT曲线,确定了开发20MnSi Ⅲ级钢筋的生产试验方案,所生产的螺纹钢筋的性能指标达到了Ⅲ级钢筋的标准要求.     

CSP热轧过程中氧化铁皮结构和厚度演变规律研究

介绍了CSP热轧生产过程中表面氧化铁皮的结构和厚度演变规律,建立了氧化动力学模型,对汽车大梁钢（510L）在CSP过程中氧化铁皮的厚度变化进行了数值模拟,模拟结果与现场实际吻合较好。降低开轧温度、合理控制终轧温度、卷取温度是控制氧化铁皮厚度和结构的有效手段。在此基础上进行现场工业试轧,试轧结果氧化铁皮以Fe3O4为主,其含量超过75%,氧化铁皮厚度11-14μm。冷弯实验表明氧化铁皮与钢板粘附性好,弯曲面铁皮呈细粉末状。     

仿晶界型铁素体/贝氏体低碳锰钢的组织和力学性能

对一种低碳锰钢进行了终轧温度高于Ar3卷取温度的不同控轧控冷处理．扫描电镜和透射电镜观察表明,终轧变形在奥氏体再结晶区进行时,有利于获得均匀分布的铁素体和一定含量的贝氏体组织．终轧温度降低到800℃,实验钢产生了形变诱导铁素体相变．当冷速增加到60℃／s且卷取温度为400℃左右时,铁素体主要沿原奥氏体晶界分布,晶粒得到细化,贝氏体体积分数增加,强度有较大的提高,但延伸率较低,屈强比较高．通过控制终轧温度为800-850℃、冷速为40℃／s左右以及卷取温度为550℃左右时,低碳锰钢可以获得仿晶界型铁素体／贝氏体的复相组织,其中铁素体晶粒尺寸为8-8．5μm,贝氏体体积分数在30％左右,综合性能较好．     

初始组织对20CrMnTi钢伪渗碳过程中奥氏体化相变与晶粒长大行为的影响

研究了20CrMnTi钢球化退火过程中的渗碳体析出行为及其与铁素体回复和再结晶的相互作用,着重分析了热轧态、淬火态和球化态3种初始组织在伪渗碳过程中的奥氏体化相变与晶粒长大行为。结果表明,热轧态和淬火态试样分别具有均匀粗大的“铁素体+珠光体”组织和均匀细化的马氏体板条组织;在球化态试样中,由于球化时碳化物析出与马氏体基体回复、再结晶的相互作用,基体组织与碳化物均存在微观非均匀现象。经伪渗碳后,奥氏体平均晶粒尺寸按热轧态、淬火态和球化态次序依次减小,但不均匀性因子按该次序依次增大;与初始组织相关的奥氏体形核密度与形核均匀性是控制渗碳过程中奥氏体晶粒长大行为的关键因素之一。     

Thermodynamic Calculation of Carbide Precipitate in Niobium Microalloyed Steels

Microalloyed elements such as Nb, Ti and Vinhigh strength low alloyed steels play an extremelyi mportant roleini mprovement of mechanical proper-ties ,due to the formation of fine precipitates duringhot working process . Quantitatively thermodynamiccalculations of precipitates are the basis of precipita-tion model . On the basis of regular solution sublat-tice model , a thermodynamic model was developedto predict the austenite/carbide equilibrium in Fe-Nb-Csystem.1 Thermodynamic Model1·1 D…