锌系统沉铁渣综合回收工艺优化研究

对侧吹烟化炉中处理锌系统沉铁渣时粉煤用量、Fe₂O₃/SiO₂比、CaO/SiO₂比、反应温度、反应时间对熔炼过程的影响进行了研究, 确定了最优工艺技术参数。结果表明, 在m_粉煤/m_渣样=1/2.8, CaO/SiO₂=0.75, Fe₂O₃/SiO₂>1, 烟化温度1 250 ℃, 烟化时间1 h条件下获得铅锌挥发率均大于96%。     

Corner crack mechanism of boron-containing LCAK steel slabs

At Baoshan Iron Steel Co., Ltd., corner cracks of boron containing LCAK steel slabs had caused remarkable quality loss and mass flow disorder. With the help of fractography and thermodynamics analysis,the embrittlement mechanism of this steel grade was studied and the results are as follows: ① The transformation from γ to α starts at the austenite grain boundaries and a layer of thin ferrite film gradually forms around the austenite grains. Strain concentration will preferentially start inside the ferrite phase when the stress accumulates to a certain level.② The coarse BN particles acceleratedly precipitated at the γ/α interfaces further deteriorate the ductility of the ferrite film,and brittleness results in strain concentration and microvoid coalescence inside the ferrite film.Therefore the austenite grain boundaries are prone to intergranular failure.③ The stoichiometry among Al,N and B is a very important factor influencing the hot ductility of this steel grade.By controling the B-to-N atomic ratio to above 1,all N can be fixed by B instead of Al.Thus coarse-grained steel is available and fewer grain boundaries and higher ductility can reduce the risk of corner cracks.④ By adjusting the B-to-N atomic ratio,Baoshan Iron Steel Co. ,Ltd.successfully reduced the number of cracks to nearly one tenth of that in the past and the hot tensile tests confirmed remarkable improvement in the hot ductility of this steel.     

Creep rupture behaviour of modified 9Cr-1Mo heat-resistant steel strengthened with different mechanisms

The creep rupture behaviours and microstructural changes of a modified 9Cr-1Mo heat-resistant steel were investigated at 853 K. Analysis of creep results suggests that dislocation climb is the dominant deformation mechanism with true stress exponent of 5 under the present conditions. Based on the microstructural analysis, strengthening contributions from M₂₃C₆ carbides and MX carbonitrides were clarified. The M₂₃C₆ carbides can promote grain boundary strengthening by exerting Zener pinning forces, whereas MX carbonitrides can enhance the creep strength by interacting with mobile dislocations to induce threshold stress. Besides, softening of the steel is related not only to the decrease of dislocations, but also the coarsening of precipitates and substructures. The value of creep damage tolerance factor is close to 6.6, which further confirms that the creep damage is mainly attributed to the microstructural degradations, such as the coarsening of precipitates and substructures and decrease of dislocations.     

Precipitation of second phases in aged Ni rich NiTiRe shape memory alloy

Abstract

This study investigated the effect of aging on the structure and precipitation of second phases of Ni₅₂Ti_47·7Re_0·3 shape memory alloys. The alloy was solutionised at 1000°C for 24 h before aging at various temperatures ranging from 300 to 600°C for 3 h. The matrix phase in both solutionised and aged specimens was martensite. Ti₂Ni phase was also present in the microstructure of both solutionised and aged specimens and its volume fraction decreased as the aging temperature increased. Ni₄Ti₃ phase began in appearance by increasing aging temperature to 400°C. Ni₄Ti₃ precipitates had lenticular and non-geometry shapes. Aging at 600°C led to precipitation of Ni₃Ti phase in the microstructure. This precipitated phase formed in white blocky shapes. Ti/Ni ratio increased and/or Ni content decreased in the matrix with increasing in aging temperature.     

Nb和Cu在低碳微合金钢回火过程中的析出行为

利用金相技术、硬度测量及透射电子显微术,研究了Nb钢及Nb-Cu钢在525℃回火过程中的析出行为.结果表明:两种实验钢在850℃奥氏体化淬火后,组织类型类似,525℃回火20h后,显微组织没有发生明显变化.Nb-Cu钢在回火的初始阶段硬度下降迅速,15min后硬度上升,90min左右到达峰值,Cu的析出快于Nb;而在随后的回火过程中因为Nb的析出导致硬度变化平缓.通过对比Nb钢的硬度曲线及透射电镜观察,认定ε-Cu的析出和NbC的析出是独立进行的,采用相同工艺回火的C-Mn钢硬度变化曲线进一步证实了这一点     

7050-T7452锻件模拟高温服役环境下组织性能的演化

通过拉伸试验和微观组织观察等方法对经过不同温度和时间模拟高温服役环境热暴露处理后7050-T7452锻件的室温拉伸性能以及合金金相组织、析出相的变化情况进行系统研究。结果表明：7050-T7452锻件在100~175℃下热暴露处理后,合金的强度随热暴露温度的提高和时间的延长而降低,伸长率随之增加;当热暴露温度超过125℃后,变化更为明显;随热暴露温度和时间的变化,合金的晶粒尺寸以及再结晶程度没有明显改变;当热暴露温度≤125℃时,合金晶粒内部析出相的尺寸和种类没有明显变化;随热暴露时间的增加,晶界无析出带的宽度略有增宽;当热暴露温度超过125℃时,合金晶内的析出相随温度以及热暴露时间的增加而迅速粗化,η相的体积分数增加,晶界无析出带加宽,合金的强度明显下降。     

Recrystallization kinetics and grain growth studies in twin-roll cast strips of commercial purity aluminium (1050) and aluminium-magnesium alloy (5005)

Recrystallization kinetics and grain size distribution have been studied in commercial purity aluminium (1050) and Al-Mg alloy (5005) which had been previously twin-roll cast to thicknesses of 1.5 mm and 3 mm. The samples were annealed at 300 °C for different times up to 20 hours. The index of recrystallization was found to be 3.2 ± 0.2 for each type of material, which implied a three-dimensional nature of recrystallization. The 1.5 mm thick samples had higher nucleation rates and, therefore, a smaller final average recrystallized grain size. The grain size distribution was more stabilised in the 1050 samples than in the 5005 samples, and this may be due to the drag effect of the FeAl₃ particles on the grain boundaries in the commercial aluminium samples. The degree of spread in the distribution of the grain sizes was bigger in samples rolled to 3 mm than those rolled to 1.5 mm. Anisotropy in the microstructure was observed in the 1050 sheets of thickness 3 mm, in that, the average grain size in the rolling direction (RD) was larger than that in the transverse direction (TD). However, during annealing at 500 °C, the 1.5 mm-thick samples of the 1050 sheet preceded the 3.0 mm-thick samples in achieving an equiaxed grain structure.     

Technique for recovering uranium from sludge-like uranium-bearing wastes using hydrochloric acid

Sludge-like uranium-bearing wastes generated from uranium refining and conversion R&D facilities are stored at the Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency. So far, approximately 1500 t of uranium wastes with radioactivity levels exceeding 10,000 Bq/g have been generated. We have proposed an environmentally benign aqueous process for recovering uranium from wastes using hydrochloric acid (HCl). This makes it possible to dispose of the wastes easily, and to reclaim uranium as a resource. In this process, first, the uranium content in the calcium fluoride (CaF₂) sludge along with the entire sludge is dissolved almost completely in aqueous solutions containing HCl and aluminum chloride. The uranium species are then recovered as peroxide from the CaF₂ sludge solution. Their characteristics are similar to those specified for uranium ore concentrate. After recovering the uranium content, the uranium concentration in the solution is reduced to below 0.01 mg/L using an iminodiacetic chelating resin. Also, the uranium concentration of the precipitate generated by the neutralization of the barren solution falls below 1 Bq/g.     

Role of Intermetallic Precipitates in Hydrogen Uptake of Zircaloy-2

The hydrogen uptake behavior of two types of Zircaloy-2 specimens containing either fine intermetallic precipitates or coarse ones was studied at 623–723 Kin the pre-transition period of oxidation to clarify the role of the precipitates in the hydrogen transport through the oxide film. In the former case, the amount of hydrogen taken up was small and did not show the oxidation temperature dependence. In the latter case, the amount of hydrogen taken up was large and dependent markedly upon the oxidation temperature; it increased with decreasing oxidation temperature. These results were successfully explained with the model that the intermetallic precipitates remaining in a metallic state in the oxide film act as the fast transport route of hydrogen.     

Inconel 740H主要强化元素对热力学平衡相析出行为的影响

对700℃等级超超临界电站过热器/再热器管材所用镍基高温合金Inconel 740H进行热力学相计算并研究了主要析出强化元素对其平衡析出相析出行为的影响.结果表明:合金中γ′相和M23C6碳化物稳定温度范围较宽;Al、Ti和Nb 3种元素对γ′相、η相和σ相的析出行为影响较大,而Co元素对其影响不大,其中Al对γ′相和σ相的析出和稳定有促进作用,对η相却有抑制作用,Ti和Nb对γ′相、η相和σ相均有促进作用;C对M23C6碳化物析出量的影响显著,而Cr对M23C6的析出温度影响显著.将Al、Ti、Nb、C和Cr的质量分数控制在一定范围内并适当减小Co的质量分数,可以使Inconel 740H合金的成分范围得到一定的优化.