大圆坯连铸带液芯矫直过程的应力、应变有限元模拟

应用Marc有限元软件对圆坯连铸的连续矫直变形过程进行模拟.以马鞍山钢铁公司大圆坯连铸机为原型,考虑铸坯与辊子的接触状态,建立了圆坯矫直变形模型;模拟分析了大圆坯连铸带液芯矫直过程中坯壳的应力、应变,得到了铸坯在矫直过程中的变形规律,可为铸机矫直工艺及设备设计提供参考依据,从而进一步优化铸坯的矫直变形,以提高圆坯的内部质量和表面质量.     

微合金碳氮化物在铁素体中沉淀析出的PTT曲线的理论计算

根据经典形核长大动力学理论,分析解决了包括相变化学自由能、界面能、形核沉淀方式等一系列相关参量的理论计算或理论处理问题,由此提出了微合金钢中微合金碳氮化物在铁素体基体中沉淀析出的PTT曲线(沉淀量-温度-时间曲线)的相对定量理论计算方法.     

Q235钢的热变形特性

通过热模拟压缩试验,研究了Q235钢热变形时的动态再结晶行为,确定了其热变形激活能,建立了峰值应力、峰值应变、晶粒尺寸与Zener-Hollomon参数之间的关系模型.结果表明:Q235钢的动态再结晶主要发生在形变温度≥900℃、应变速率≤5 s-1(即lnZ≤37.77)的条件下.     

中间包控制汇流旋涡的水模研究

 为了减小中间包汇流旋涡所造成的卷渣对钢质量的危害，就某钢厂现有中间包的各工艺参数对汇流旋涡形成的影响进行了水模实验研究，结果表明：小塞棒高度、小拉速和小中间包水口口径对防止汇流旋涡有利，渣在一定程度上可以抑制旋涡的产生和发展，但渣层的厚度对旋涡没有明显影响；塞棒高度为60 mm、拉速为068 m/min、中间包水口内径为56 mm和有渣是本实验所得的该钢厂实际中间包最佳防止汇流旋涡工艺条件。     

Influence of Simulated Outside-Reactor Irradiation on Anticorrosion Property of Austenitic Stainless Steel

The influence of γ-ray irradiation on the properties of inside-reactor stainless steel structures was studied by simulating the working condition of pressurized water reactor （PWR） first circuit and the outside-reactor y-ray irradiation. The result shows that the simulated outside-reactor irradiation （irradiation dose 4. 4 ）〈 104 Gy） has no influence on anticorrosion properties of solutionized SUS304 austenitic stainless steel, including intergranular corrosion （IC） and stress corrosion cracking （SCC）. Anticorrosion properties （IC, SCC） of sensitized SUS304 austenitic stainless steel are reduced by simulated outside-reactor irradiation. The longer the sensitized time is, the more obvious the influence is.     

Giant magnetoimpedance in nanocrystalline Fe90.3−xZr7B2.7Cux (0.5 ≤ x ≤ 1.5) as-spun ribbons

The nanocrystalline ribbons Fe_90.3−xZr₇B_2.7Cu_x with low Cu contents can be directly obtained through melt-spinning technique with an appropriate low quenching speed such as 22 m/s. Sizes of bcc-Fe grains precipitated in Fe_90.3−xZr₇B_2.7Cu_x as-spun ribbons were 17 nm for x = 0.75, 15 nm for x = 1 and 12 nm for x = 1.25. The addition of Cu reduces grain size of bcc-Fe in as-spun nanocrystalline Fe_90.3−xZr₇B_2.7Cu_x ribbons. Among the investigated samples (0.5 ≤ x ≤ 1.5), the largest magnetoimpedance can be obtained in the nanocrystalline Fe_80.3Zr₇B_2.7Cu₁ as-spun ribbon with x = 1. The value of magnetoimpedance (Z(H) − Z(0)) / Z(0) under H = 90 Oe for Fe_80.3Zr₇B_2.7Cu₁ as-spun ribbon reaches − 28.2% at a frequency of 1 MHz.     

碳、铌对ASME S30432奥氏体耐热钢晶间腐蚀性能的影响

研究了碳、铌含量对ASME S30432钢晶间腐蚀性能的影响.结果表明:当碳含量在0.058%～0.110%变化时,随碳含量增加该钢的晶间腐蚀敏感性增加,易发生晶界腐蚀;铌含量由0.30%增加到0.70%对抗晶间腐蚀性能有改善,含碳量对晶间腐蚀的影响比铌明显;铌含量与碳含量的比值至少在5.8以上才可能对晶间腐蚀有抑制作用.     

Structures and Electrochemical Performances of As-spun RE-Mg-Ni-Mn-based Alloys Applied to Ni-MH Battery

The La-Mg-Ni-Mn-based AB₂-type La_1-xCe_xMgNi_3.5Mn_0.5 (x = 0, 0.1, 0.2, 0.3, and 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content on the structures and electrochemical hydrogen storage performances of the alloys were studied systematically. The XRD and SEM analyses proved that the experimental alloys consist of a major phase LaMgNi₄ and a secondary phase LaNi₅. The variation of Ce content causes an obvious change in the phase abundance of the alloys without changing the phase composition. Namely, with the increase of Ce content, the LaMgNi₄ phase augments and the LaNi₅ phase declines. The lattice constants and cell volumes of the alloys clearly shrink with increasing Ce content. Moreover, the Ce substitution for La results in the grains of the alloys clearly refined. The electrochemical tests showed that the substitution of Ce for La obviously improves the cycle stability of the as-spun alloys. The analyses on the capacity degradation mechanism demonstrate that the improvement can be attributed to the ameliorated anti-corrosion and anti-oxidation ability originating from substituting partial La with Ce. The as-spun alloys exhibit excellent activation capability, reaching the maximum discharge capacities just at the first cycling without any activation treatment. The substitution of Ce for La evidently improves the discharge potential characteristics of the as-spun alloys. The discharge capacity of the alloys first increases and then decreases with growing Ce content. Furthermore, a similar trend also exists in the electrochemical kinetics of the alloys, including the high rate discharge ability (HRD), hydrogen diffusion coefficient (D), limiting current density (I_L) and charge transfer rate.     

Application of fluidization technology in productions of cemented carbides

The fluidization technique has advantages in rapid and high-efficiency heat transfer. Application of fluidization technology can significantly improve the productivity and product performance in the cemented carbide industries. This technique has become an attractive research topic within the issue of green and low-carbon technologies. Aiming at better understanding the principles of fluidization, in the present paper we demonstrate three typical cases of liquid–solid fluidized crystallization, bubbling bed combustion synthesis and reduction carbonization production. From these samples, we study the factors which play an important role in the fluid dynamics, fluidized state of materials and reaction thermodynamics during the process of cemented carbide production. The solutions and mechanisms of the practical problems such as the fluidized state of ultrafine particles, critical opening percentage of the distribution plate and adherent effect in multilayer bubbling bed are proposed. Moreover, the potential applications and prospects of the fluidization technology in the field of cemented carbides are presented.     

Investigations on hydrogen storage performances and mechanisms of as-cast TiFe0.8-mNi0.2Com (m=0, 0.03, 0.05 and 0.1) alloys

In order to improve the hydrogen storage performances of TiFe-based alloys, a new type of TiFe_0.8-mNi_0.2Co_m (m = 0, 0.03, 0.05 and 0.1) alloys were prepared through vacuum medium-frequency induction melting. XPS results showed that the composition of surface oxide film contains TiO₂, FeO and NiO for the cobalt-free alloy, and it also includes CoO and Co₃O₄ besides the above oxides for the cobalt-containing alloys. The activation temperature is 523, 403, 383 and 373 K for the TiFe_0.8-mNi_0.2Co_m (m = 0, 0.03, 0.05 and 0.1) alloys, respectively. The changes of the composition and microstructure of the surface oxide film are the root causes of the reduction of the activation temperature. XRD and SEM analyses showed that all the alloys are composed of the majority phase of TiFe phase and non-hydrogenated phase of Ti₂Fe phase. Adding appropriate amount of cobalt is beneficial to inhibiting the generation of Ti₂Fe phase and increasing the cell volume of TiFe phase. The hydrogenation capacity is proportional to the content of TiFe phase, which is 1.11, 1.48, 1.54 and 1.29 wt% for the TiFe_0.8-mNi_0.2Co_m (m = 0, 0.03, 0.05 and 0.1) alloys at 313 K, respectively. The hydrogenation plateau performance also is improved correspondingly.