小方坯连铸结晶器电磁搅拌磁场和流场的耦合分析

借助有限元方法,对小方坯结晶器电磁搅拌过程进行了磁场和流场耦合数值分析,得出了不同频率下钢液内部磁感应强度和电磁体积力及搅拌速度的分布规律.结果表明,在结晶器电磁搅拌时,随着频率的增加,钢液内部磁感应强度降低,电磁体积力在钢液内部分布不均匀;在电流频率为3 Hz时,钢液搅拌速度最大.在现场对结晶器电磁搅拌器的磁场强度进行了冷态测试,实验值和模拟值基本相符.     

摆动磁场条件下的焊接接头组织研究

为了优化不锈钢焊接工艺,提高焊接质量,进行了外加电磁场条件下的304不锈钢钨极氩弧焊(TIG),磁场施加方式分别为横向磁场和旋转磁场.焊后采用电子显微镜对焊接接头进行显微组织观察,研究了不同外加磁场类型和不同焊接速度对不锈钢焊接接头组织的作用规律.试验结果表明,外加磁场改变了熔池的流动形态,使金属液由四周向中心流动并伴有搅拌,也使焊缝熔深增大的同时,抑制柱状晶的形成,细化组织.     

Preparation and characterization of stainless steel/TiC nanocomposite particles by ball-milling method

A stainless steel/10wt%TiC nanocomposite particles were prepared by high-energy ball-milling method using stainless steel, carbon and titanium as raw materials. The evolution of phase composition, microstructure and specific surface area of the stainless steel/TiC nanocomposite particles with increasing ball-milling time in the range of 0–100 h were investigated by XRD, SEM, TEM and BET techniques. The results showed that the stainless steel/TiC nanocomposite particles were fabricated when the ball-milling time was longer than 20 h. However, the nanocomposite particles were soldered and agglomerated again when the ball-milling time was longer than 60 h. The microstructure of the composite particles transformed from lamellar structure to nanostructure during the repeated process of the cold welding and cracking. TEM image reveals clearly that the in-situ TiC nanoparticles with grain size of 3–8 nm are in the interior of the stainless steel/TiC nanocomposite particles obtained by ball-milling 100 h. Funded by the Natural Science Foundation of Hubei Province (No. 2006ABA304)     

CSP结晶器内钢液流动及凝固的数值模拟

应用数值模拟方法,建立CSP漏斗型结晶器内钢液流动及凝固传热耦合模型。针对结晶器内铸坯角部受到强冷的特点,对结晶器内热流密度采用修正方程进行计算,分析热流密度修正系数对铸坯凝固坯壳表面温度计算精度的影响。通过比较不同拉坯速率下结晶器内钢液凝固的特点,研究凝固坯壳对结晶器内钢液流动行为的影响。结果表明,采用热流密度修正系数后,铸坯凝固坯壳角部温度的计算值与实际情况更相符;提高拉坯速率可使铸坯凝固坯壳厚度减小;拉坯速率较大时凝固坯壳厚度随铸坯距弯月面距离的增大基本呈线性增长,拉坯速率为3m/min时,凝固坯壳在生长过程中厚度的增长有短暂的停滞现象;凝固坯壳对钢液流动的影响较大,主要是由钢液有效流动区域减少及两相区额外动量阻损造成的。     

浸入式水口电磁搅拌对钢液传热凝固的影响

在圆坯连铸浸入式水口上施加电磁力,对水口内钢水产生电磁搅拌作用,对水口出流成螺旋状态的液体的传热凝固过程进行数值模拟,结果表明：旋流出流使得铸坯内温度场明显均匀化,加快钢液热量的释放,气隙厚度减小。温度的均匀化,使得固液相温度梯度减小,改善凝固组织、提高铸坯质量。     

不锈钢高速连铸中结晶器的热流计算

在高效连铸过程中,结晶器的传热效率起着至关重要的作用。在进行加拿大国家自然科学基金资助的高速连铸的战略性研究项目时,在Ａｔｌａｓ Ｓｔｅｅｌ钢铁公司的方坯连铸机上进行了１次工业试验,目的是研究高速连铸不锈钢时结晶器的热流变化。试验中,结晶器４壁共安装了４２个热电偶。不同工艺条件下的温度信号以１０Ｈｚ的频率记录在计算机中,根据每点的平均温度,针对ＩＨＣＰ（Ｉｎｖｅｒｓｅ Ｈｅａｔ Ｃｏｎｄｕｃｔｉｏ     

Technology of black coloring for stainless steel by electrochemical method

The technology of black coloring for stainless steel by electrochemical method was studied. The optimum bath compositions and operating conditions were obtained as follows. 40 - 50 g/L K2Cr2O7, 15 - 20 g/L MnSO4, 15 -20 g/L （NH4）2SO4, 20 -40 g/L H3BO3, 20 -30 g/L additive A, 2 g/L （NH4）6Mo7O24 ; time 9 -20 min; temperature 15 - 30 ℃ ; potential 3 V and current density 1 - 2 mA/cm^2. The effects of the compositions of the bath on the quality of black colored film were discussed. The influences of passivation process on the black coloring velocity and performances of black colored film layer were investigated. The results show that the passivation process can improve the corrosion resistance and the stability to bear color-change; （NH4）2 SO4 can control the black coloring velocity and prolong black coloring bath life remarkably; and additive A can improve the evenness and compactness of black colored film layer. The results of scanning electron microscopy and energy dispersive spectra show that the microstructure is of cylindrical lump, the filling process can decrease the crackles, and the main elements of black colored film are Fe, Cr, Mn and Ni.     

Thermal deformation behavior and microstructure of nuclear austenitic stainless steel

Gleeble-1500D thermal simulation tester was employed in the hot-compression investigation of as-cast nuclear 304 austenitic stainless steel under conditions: deformation temperature 950―1200℃; deformations 30% and 50%; deformation rates 0.01 and 0.1 s?1. The results show that the flow stress decreases with temperature rise under the same strain rate and deformation, that the flow stress increases with deformation under the same temperature and strain rate, and that the flow stress increases with strain rate...     

Effect of Aluminum Tri-polyphosphate on Corrosion Behavior of Reinforcing Steel in Seawater Prepared Coral Concrete

Atri-polyphosphate was used as a corrosion inhibitor in the seawater prepared coral concrete, and its influence on the corrosion behavior of carbon steel, 304 austenitic stainless steel, and 2205 duplex stainless steel was studied by the open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization, respectively. The results reveal that the corrosion potential and impedance of the reinforcing steel increase, while the corrosion current density decreases with the content of aluminum tripolyphosphate in the coral concrete. A low content of the corrosion inhibitor significantly retards the corrosion of the two stainless steels, but it cannot effectively inhibit the corrosion of the carbon steel in the coral concrete.In general, the carbon steel is unsuitable for the coral concrete for its poor corrosion resistance. In contrast,the stainless steels, especially the 2205 duplex stainless steel, shows an excellent anti-corrosion property in the seawater prepared coral concrete containing a certain amount of inhibitor, which is one of the satisfactory candidate methods to build the long-life coral concrete constructions.     

Thermo-analytical study on stainless steelmaking dust

1　INTRODUCTIONStainlesssteelmakingdustisaby productwastegeneratedfromsteelmakingindustry .Itcontainssig nificantamountsofiron ,lead ,nickel,chromium ,etc .Heavymetalmaybeleachedintotheenviron mentbyrainorundergroundwater ,soitisclassifiedashazardouswastesandbannedbeingdisposedinreg ularlandfill[1] .Thevaluablemetalsinthedustcanberecoveredinthewayofdirectrecycling[2 6 ] andtheworthlessdustshouldbetreatedinthewayofvitrifi cation[7] .But,itisnecessarytocommandthether malbehaviorofthedustbe…     

Influence of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy

1 INTRODUCTION In recent years, magnesium alloys have been used in the automobile industry to save fuel and lower emission levels, and about 60 different types of components of magnesium alloys have been applied in automobile parts, in which AZ91magnesium alloy (Mg-Al system) approximately accounts for 90%[1?4]. It is well known that grain size has very important effect on material properties. According to Hall-Petch equation, when grain size decreases, the mechanical properties such as…     

Influence of alkyl group of imidazolinyl-quaternary-ammonium-salt on corrosion inhibition efficiency

The action between imidazolinyl-quaternary-ammonium-salt（IQAS） molecule and Fe atom was studied, and the influence of the alkyl group connected with N atom of imidazoline ring on corrosion inhibition efficiency was explored. Quantum chemical methods, HF/6 - 31 G and HF/Lan L2 dz, were applied successively to calculate the parameters such as front molecular orbit energy of IQAS Ⅰ-Ⅳ and chemical adsorption for IQAS Ⅰ-Ⅳ and Fe atom. The corrosion inhibition efficiency was measured with the weight loss method of carbon steel samples in acidic solution and oil field sewage. Based on the theoretical analyses and experimental results, it is concluded that N-Fe coordination bond is formed between IQAS molecule and Fe atom, corrosion inhibition efficiency is decreased in the following order（from large to small） ： IQAS Ⅳ, IQAS Ⅲ, IQAS Ⅱ , IQAS Ⅰ.     

Semi-solid slurry preparation and rolling of 1Cr18Ni9Ti stainless steel

The preparation and rolling of the semi-solid slurry 1Cr18Ni9Ti stainless steel were researched. The experimental results show that when stirred for 2-3 min under the given test condition, the semi-solid slurry with about 50%-60% (volume fraction) solid and the spherical primary austenitic grains in the size of 100-200μm can be obtained, and it is easy to be discharged from the bottom little hole of the stirring chamber. The semi-solid slurry of 1Cr18Ni9Ti stainless steel can be rolled into the given plate successfully. However, the solid phase and liquid phase are easily separated in the rolling process, so that the solid primary austenitic grains are concentrated in the center and the liquid phase is near the edge of the rolled plate. The strengths of the plate rolled in the semi-solid state are higher than that of the traditionally repeated hot-rolled plate of 1Cr18Ni9Ti stainless steel.     

Refinement of austenite grain using uniform experiment design for AISI H13

The uniform experiment design is an effective way of optimizing technology scheme for refining the grain size during multistage deformation. In this paper, it is adopted to evaluate the effect of each technology parameter on final grain size of AISI H13 hot-work tool steel during multistage deformation. It has been verified that the technology scheme for refining the final grain size can be determined rapidly and efficiently with the aid of the uniform design. The results show that the deformation parameters and the intermission time after deformation of the first stage affect the final grain size remarkably. For AISI H13 hot-work tool steel, the final grain size can be refined notably when deformation parameters for the first stage are set as follows: a deformation temperature range of 1 025-1 085 ℃; a true strain of above 0.26 and the interpass time between the first and the second stage of deformation less than 10 s.     

奥氏体不锈钢活性屏低温离子渗碳工艺研究

利用活性屏离子热处理技术对奥氏体不锈钢进行低温离子渗碳（ASPC）处理,可以在不锈钢表面形成一层无碳化铬析出的碳的过饱和固溶体（Sc相）。ASPC可以在不降低奥氏体不锈钢耐蚀性能的前提下大幅度提高其表面硬度,并解决了不锈钢直流离子渗碳温度均匀性差、工件存在边缘效应等问题,渗碳试样表面基本可以保持不锈钢原色。通过对活性屏上溅射下来的纳米粒子进行显微分析表明,这些粒子是Fe3C、Fe2C5中性粒子,其在ASPC中起到渗碳载体的作用,ASPC是一个溅射-吸附-脱附的过程。     

长期热老化对铸造奥氏体不锈钢断裂韧性的影响

为了研究热老化对铸造奥氏体不锈钢断裂韧性的影响及其微观机理,按照ASTME1820-05a等实验标准,采用标准C（T）试样对Z3CN20.09M铸造奥氏体不锈钢进行了热老化断裂韧性测量.结果表明：Z3CN20.09M铸造奥氏体不锈钢的断裂韧性随热老化时间的增加呈现下降趋势;通过SEM观察断口发现,断裂机制由原始态的微孔聚集型断裂转变为解理断裂和微孔聚集断裂的混合断裂;断裂韧性J值与热老化时间t满足幂指数关系.对该材料制造的主管道的热老化断裂韧性做出外推预测.     

Kinetics of nickel leaching from roasting-dissolving residue of spent catalyst with sulfuric acid

Sulfuric acid leaching process was applied to extract nickel from roasting-dissolving residue of a spent catalyst, the effect of different parameters on nickel extraction was investigated by leaching experiments, and the leaching kinetics of nickel was analyzed. The experimental results indicate that the effects of particle size and sulfuric acid concentration on the nickel extraction are remarkable; the effect of reaction temperature is mild; while the effect of stirring speed in the range of 400–1 200 r/min is negligible. Decreasing particle size or increasing sulfuric acid concentration and reaction temperature, the nickel extraction efficiency is improved. 93.5% of nickel in residue is extracted under suitable leaching conditions, including particle size (0.074–0.100) mm, sulfuric acid concentration 30% (mass fraction), temperature 80 °C, reaction time 180 min, mass ratio of liquid to solid 10 and stirring speed 800 r/min. The leaching kinetics analyses shows that the reaction rate of leaching process is controlled by diffusion through the product layer, and the calculated activation energy of 15.8 kJ/mol is characteristic for a diffusion controlled process. Foundation item: Project (50574101) supported by the National Natural Science Foundation of China; Project (2003UDBEA00C020) supported by the Collaborative Project of School and Province of Yunnan Province, China     

AISI 304奥氏体不锈钢活性屏离子渗碳

利用活性屏离子热处理技术对AISI 304奥氏体不锈钢进行低温离子渗碳(AS-PC)处理,可以在不锈钢表面形成一层无碳化铬析出的碳的过饱和固溶体(Sc相)。处理后的奥氏体不锈钢可以在不降低耐蚀性能的基础上大幅度提高不锈钢表面的硬度,并解决了不锈钢直流离子渗碳温度均匀性差,工件存在边缘效应等问题,ASPC渗碳试样表面基本可以保持原色。     

Biocompatibility of MIM 316L stainless steel

To evaluate the biocompatibility of MIM 316L stainless steel, the percentage of S-period cells were detected by flow cytometry after L929 incubated with extraction of MIM 316L stainless steel, using titanium implant materials of clinical application as the contrast. Both materials were implanted in animal and the histopathological evaluations were carried out. The statistical analyses show that there are no significant differences between two groups (P>0.05), which demonstrates that MIM 316L stainless steel has a good biocompatibility. Foundation item: Project (2003AA302210) supported by the National Hi-tech Research Program of China     

不锈钢纤维/铜基摩擦材料的研究

以磁悬浮列车的制动材料为研究对象,探讨了奥氏体不锈钢纤维对不锈钢纤维/铜基复合材料摩擦磨损性能的影响.研究结果表明:加入不锈钢纤维后,材料的硬度明显增加,最大值为94HRF,摩擦系数略有增加,摩擦失重减小.材料的磨损机制主要为磨粒磨损与疲劳磨损,同时伴有粘着磨损.材料的断裂方式为韧性断裂.该制动材料的制动性能可以满足磁悬浮列车的制动要求.