Characteristics of Fluid Flows in a Novel Self-Stirring Reactor

Fluid flow characteristics in a novel self-stirring reactor have been studied by numerical simulation method and particle image velocity (PIV) in this article. The novel self-stirring reactor is furnished with a driving turbine that can make impellers agitate under high-pressure energy of fluid. It is found that areas of dead zone decrease with an increase of the liquid level in range of 60–200 mm for the driving turbine and impeller types used in this study. The dead zone almost disappears with the liquid level 200 mm. Some minor-cycle flows that appear in the axial direction promote the mixing and exchange of fluid, which is beneficial to the process of dissolution reaction. Free-fall of liquid becomes more distinct and more energy losses occur as the situation gets further from the inlet. The pressure energy of fluid is converted into kinetic energy, and the velocity near the driving turbine is greater. While rotation drag is smaller at liquid level of 180 mm, the effect of circulation is obvious. The flow field recorded by PIV is consistent with the result achieved by simulation. Agitation leads to the level fluctuation. The velocity direction is away from the stirring shaft and outward toward the wall of the reactor.     

Microstructure and Mechanical Properties of AA5005/AA6061 Laminated Composite Processed by Accumulative Roll Bonding

The AA5005/AA6061 laminated composite has been fabricated by the accumulative roll bonding (ARB) using commercial AA5005 and AA6061. In the ARB process, one piece of AA5005 sheet and one piece of AA6061 sheet were stacked together and rolled with a 50 pct reduction without any lubrication. The materials were heated at 473 K (200 °C) for 10 minutes before each rolling process and were deformed up to four cycles to accumulate an equivalent strain of 3.2 and form an AA5005/AA6061 laminated composite. Mechanical properties and microstructure of the laminated composites were tested. The hardness and tensile strength increased, and the grain size reduced with the number of ARB cycles. Ultrafine grains elongated along the rolling direction were developed during the ARB process. The thicknesses of the grains of both the AA5005 and AA6061 layers were less than 200 nm after the fourth cycle. The uniform elongation decreased drastically after the first cycle ARB and stayed almost unchanged after further ARB process. The hardness of the AA5005 layer was slightly lower than that of the AA6061 layer. The microstructures from optical microscope and transmission microscope showed that in the AA6061 layer large precipitates in the micron scale and small particles less than 100 nm were present, whereas in the AA5005 layer there were large scale precipitates, but no small-sized particles.     

新一代轧后冷却装置供水系统的优化设计

针对新一代TMCP工艺轧后冷却装置对配套水系统提出的工艺要求,在分析传统的工频泵增压供水、高位水塔供水和变频泵供水的优缺点和水泵变频调速节能效率的基础上,提出了一种优化的高压变频泵供水系统,并对系统中关键设备进行了分析和设计。系统投入运行后,变频工作范围、带载调节速度比传统的供水系统有了很大的提高,满足了新一代轧后冷却系统的大流量范围和大压力变化范围及连续柔性化快速调节的供水工艺要求,取得了很好的节能增效的效果。     

中厚板特殊钢热处理线的新发展和新技术

从加热、冷却、矫直、酸洗、电控这几个方面分析和总结了进几年国内外中厚板特殊钢连续热处理线的新发展和新技术.加热方面,通过采用耐火石棉纤维炉辊替换耐热合金炉辊有效解决了钢板的表面压入缺陷问题,采用高速脉冲烧嘴和新型复合脉冲燃烧控制技术,使加热更均匀和更节能;采用国内研究开发的辊式淬火机及空冷室设备和技术,使冷却的钢板厚度范围大,极限规格薄,钢板平直度高;矫直方面,通过采用全液压动态凸度补偿系统及机架高强度和高刚度,并配置合理的辊系,使矫直具备冷、热矫直功能和矫直的厚度范围大;通过采用立式酸洗和新的酸洗工艺,使设备占地空间小、酸洗质量好;电控系统方面,通过先进齐全的仪表配置、完善的4级控制系统、加热、淬火、矫直、酸洗模型在线应用等,使生产过程高产、优质、稳定和自动化.对中厚板热处理线的建设和研究具有一定的参考意义.     

经济型铁素体/贝氏体高扩孔钢的组织与性能

 通过TMCP工艺实验,研究了Si、Mn含量对低碳Si Mn钢显微组织、力学及成形性能的影响,探讨了铁素体/贝氏体双相钢(FB钢)在扩孔过程中的裂纹形成及扩展行为。研究结果表明,增加Si含量,实验钢中等轴铁素体的体积分数增加,扩孔性能得到改善;而增加Mn含量,实验钢的强度和韧性显著提高,但塑性和扩孔性能有所下降。FB钢中的裂纹扩展主要是以微孔聚集机制进行,当遇到贝氏体时,裂纹通过铁素体 贝氏体相界面并剪断铁素体进行扩展。合理选择Si、Mn含量和TMCP工艺参数,可以获得690 MPa级的经济型热轧FB高扩孔钢,扩孔率达到了95%,综合性能较好。     

Q550D钒氮钢特厚板组织性能与表面质量

研究了控轧控冷工艺对工业试生产的50 mm厚V-N微合金钢中厚板组织与性能的影响,利用光学显微镜、扫描电镜、透射电镜、拉伸试验机等对试验钢微观组织、力学性能及钢板表面质量进行了观察及分析.结果表明:试验钢在终冷温度为630℃时,显微组织由针状铁素体、多边形铁素体和少量粒状贝氏体组成,可观察到V(C,N)析出粒子.试验钢...     

喷水冷却对400MPa级超细晶粒钢焊接接头组织和性能的影响

采用手工电弧焊焊接400MPa级超细晶粒钢，并对不同冷却条件下的焊接接头显微组织及力学性能进行分析。结果表明，400MPa级超细晶粒钢手工焊焊接接头热影响区存在着严重的晶粒长大和强度下降现象；焊接过程中采用喷水冷却可明显提高焊接接头强度，实际生产中可以应用手工电弧焊水冷处理方法焊接400MPa级超细晶粒钢。     

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.