High-alumina inserts for continuous steel casting

Conclusions High-alumina inserts provide adequate service in the continuous casting of steel and killed carbon steel deoxidized by calcium silicon.In the continuous casting of transformer and killed carbon steel deoxidized by aluminum, the high-alumina inserts did not prove superior to regular chamotte nozzles. Chamotte nozzles with magnesite inserts are unsuitable for continuous steel casting.     

A new approach to protect and extend longevity of the thermal barrier coating by an impermeable layer of silicon nitride

A sample representation of a gas turbine engine blade, consisting of a nickel superalloy substrate with a deposited thermal barrier coating (TBC), was covered with silicon nitride, Si₃N₄, as an impermeable layer using plasma enhanced chemical vapor deposition (PECVD). The silicon nitride layer was used to seal the topcoat of yttria-stabilized zirconia (YSZ) surface of the TBC to mitigate calcium–magnesium–aluminum–silicon oxide (CMAS) attack. CMAS testing was carried out on the covered and uncovered surfaces by melting a ratio of 25 mg/cm² of CMAS powder onto the surface of each sample in a furnace at 1100°C for 1 h. The conformal surface reaction of the sealed layer confirmed no cracking or delamination at high temperatures. Scanning electron microscopy (SEM) micrographs confirmed that the surface of YSZ was successfully sealed. The new coating of silicon nitride was shown to be a viable solution and technique to significantly block CMAS infiltration in porous thermal barrier coatings.     

碳电热还原法熔炼一次铝硅合金的反应过程

以Al2O3尾矿和烟煤为原料,在碳管炉内进行了一次铝硅合金熔炼,采用X射线衍射光谱对不同温度不同加碳量反应后的产物进行物相分析,探讨了由尾矿生产一次铝硅合金的反应过程并获得了合格的一次铝硅合金产品. 结果表明,尾矿加烟煤在碳管炉内还原时,在较低温度(<1600℃)下,尾矿中的SiO2与C反应生成SiC,当温度上升到1700~1800℃时,尾矿中的Al2O3开始与C反应生成铝氧碳化物,当温度继续升高到1800℃以上时,在较低温度生成的铝氧碳化物被SiC分解,生成铝和硅,成为一次铝硅合金,最终获得的一次铝硅合金含铝量达40%以上.     

正交法研究钢渣中提取Ca^2＋的可行性

用甲酸对钢渣进行处理以提取钢渣中的钙,溶出的钙和剩余的高铁钢渣可以分别加以利用。试验采用正交法进行。试验结果表明,甲酸浓度对钙离子溶出率的影响最大,酸、渣比例的影响次之,反应时间的影响最小;而对于铁离子的溶出率来说,酸、渣比例的影响最大,酸浓度的影响次之,反应时间的影响最小。当酸、渣比例为1：2,反应时问1d,酸浓度为15％时,钢渣中钙离子溶出量相对较多,铁离子的溶出量较少,即效果最好。此时,钙离子溶出率为43．33％,铁离子的溶出率为0。     

助溶剂对铝合金表面硅烷化预处理的影响

为了了解3-缩水甘油醚丙基三甲氧基硅烷(γ-GPTMS)溶液中助溶剂对水解的γ-GPTMS在铝合金表面的沉积特性的影响,用X射线光电子衍射(XPS)测定了不同助溶剂含量,不同γ-GPTMS浓度的溶液沉积在铝合金表面的硅含量,同时用反射吸收红外光谱(RAIRS)对铝合金表面膜层进行了表征,结果表明,助溶剂对γ-GPTMS在铝合金表面沉积有显著影晌,γ-GPTMS的纯水溶液在铝合金表面所形成硅烷化膜层的硅元素量最高,沉积量随溶液中γ-GPTMS浓度的增加而增加。另外,膜层与氧化的铝合金表面之间形成铝硅氧烷(Al-O-Si)共价键,而且γ-GPTMS分子中的烷氧乙基分布在膜层的外表面,具有较大的反应活性。     

Service of zircon-containing nozzles for use in continuous steel casting plant

Summary During service in the casting of killed steel, zirconium containing nozzles took on a zonal structure. The least changed zone of the nozzles is scarcely distinguishable from the refractories before service. The working zones during service are saturated with oxides of iron, manganese, aluminum, silicon and titanium, and their amount is strictly related to the compositon and quantity of deoxidant.Highly refractory nozzles of ZrO₂ and made of a mixture of ZrO₂ and zircon, possessing a higher apparent porosity, acquire a larger working zone than nozzles made of zircon with clay additions.The dense working zone is more rapidly formed in nozzles made of zircon and clay. The oxides adsorbed in the pores of the refractory contribute to the tightening up of the aperture of the nozzles.Zircon nozzles with clay additions used at the Donets Steel Mill proved to have excellent wear resistance and the lowest tendency to closing up when casting low-carbon killed steels and can be recommended for permanent use in continuous steel casting plants.     

金属铝对氧化锆制品的去稳定化行为

采用物质吉布斯自南能函数法对金属铝造成氧化锆制品的去稳定化行为进行了热力学分析,并结合扫描电子显微镜(SEM)进行了试验验证.结果表明:(1)含锆质制品中,金属铝易与氧化锆的稳定剂氧化钙发生反应,生成层片状六铝酸钙,造成氧化锆中稳定剂脱溶,体积失稳;(2)金属铝易与氧化锆的稳定剂氧化镁进行反应,生成正八面体的镁铝尖晶石,造成氧化锆中稳定剂脱溶,体积失稳;(3)金属铝对氧化锆制品的去稳定化行为,可界定为原始层、脱溶过渡层和反应层三层.     

Rapid fabrication of Al4SiC4 using a self-propagating high-temperature synthesis method

As a promising high-temperature ceramic, aluminum silicon carbide (Al₄SiC₄) has attracted much attention. Al₄SiC₄ is usually synthesized at high temperatures with a long reaction time in an electric furnace. Self-propagating high-temperature synthesis (SHS) is a promising technique for rapid synthesis. In this study, Al₄SiC₄ was prepared by the SHS method from a mixture of silicon, aluminum and carbon black with the addition of poly(tetrafluoroethylene) (PTFE) as an exothermic promoter. The experimental results showed that the use of a high-pressure Ar atmosphere could retain the gaseous materials in the pellet mixture, and the PTFE additive promoted the formation of silicon carbide. In addition, the oxide layer present on the surface of silicon particles inhibited the reaction between silicon and carbon. As a result, high-purity Al₄SiC₄ could be synthesized from aluminum, silicon, and carbon black with 15 wt% PTFE under 1.0 MPa Ar atmosphere in several seconds by the SHS method.     

Improvement of Protective Properties of Borosilicate Melt by Introducing Deoxidizers

The possibilities of improving the protective properties of borosilicate melts by adding deoxidizers are considered. The dependence of the rate of oxidation of steel 30KhGSA on Fe₂O₃ content in the melt is experimentally established. The rate of oxidation of steel 30KhGSA in a melt deoxidized by silicon carbide, silicon nitride, and by a boron-bearing product are determined.     

包覆型铝粉颜料在水性涂料中的应用

以正硅酸乙酯(TEOS)和乙烯基三乙氧基硅烷(VTES)为前驱物,通过溶胶-凝胶反应在铝颜料表面形成了一层致密的包覆层,再通过甲基丙烯酸甲酯(MMA)和丙烯酸(AA)的自由基聚合反应对铝颜料进行第二层包覆,制备了含亲水基团的包覆型铝粉颜料,以此包覆的铝颜料配制了水性铝粉涂料.研究了铝粉及交联剂的用量、涂料黏度和烘烤温度...     

影响玻璃化学钢化盐浴活性因素的研究

研究了盐浴的失活与复活.分别选择不锈钢、银、铝和铜作为反应容器的材料,发现不锈钢和铜质容器容易受到硝酸钾和亚硝酸钾熔液的腐蚀,而银和铝则相对稳定.经过硝酸钾和亚硝酸钾钢化处理后的玻璃表面应力层厚度有很大差别.硝酸钾熔液在使用初期会暂时失去活性,失活的熔液在经过时效处理后能够复活;而使用亚硝酸钾的过程中却没有发现失去活性的现象.分析了失活机理并根据这一机理选择了活化剂.     

Dense zircon insert-batchers for intermediate ladles on continuous steel casting plant

Conclusions A technology was developed for making dense zircon insert-batchers with an open porosity of up to 10%. The insert wear is less than 1 mm during the hot time. They satisfy the property requirements for continuous casting of killed carbon steel deoxidized with aluminum in amounts of up to 300 g/ton.Translated from Ogneupory, No. 3, pp. 11–13, March. 1973.     

锌(铝)防护层与桥梁钢结构的防护

锌(铝)防护层自上世纪开发应用以来,很快被引入桥梁钢结构防护,现在的桥梁钢结构基本上是热喷锌和富锌涂料作为底层防护。通过比较热镀锌、热喷锌、富锌涂料、锌加等锌基涂料在钢结构防护应用中的特点,探讨锌(铝)防护层在桥梁钢结构长效防护和维修防护中的应用。     

Effect of Silica Surface Dopants on the Formation of Alumina/Aluminum Composites by the Directed Metal Oxidation of an Aluminum Alloy

This study focused on clarifying the effect of SiO₂ surface dopants on the formation of Al₂O₃/aluminum composites, especially on oxidation phenomena during the incubation period. The present results showed that a surface dopant decreased the incubation period of an Al-Mg-Si alloy, as well as that of an Al-Mg alloy, and that addition of an external surface dopant decreased the incubation period more effectively than did an internal alloying of silicon. A two-step oxidation process was also conducted. In the first step of the process, an aluminum alloy was oxidized without a surface dopant and cooled to room temperature during the incubation stage. In the second step, the same specimen was surface-doped with SiO₂ powder and reoxidized. The incubation time for the specimen subjected to the two-step oxidation process was the same as that for the single-step specimen oxidized with a surface dopant. The substantial decrease in the incubation period, especially for the Al-Mg alloy, is ascribed to interaction between the SiO₂ surface dopant and the MgO layer. This interaction made the MgO layer thinner and increased the number of magnesium vacancies in the MgO layer, thus providing an appropriate microstructure in the MgO layer for bulk-growth initiation.     

AlN and intermetallic compound layers formed between aluminum and austenitic stainless steel using barrel nitriding

Recently, a new nitriding process was proposed to produce the aluminum nitride on an aluminum surface using a barrel. After barrel nitriding, AlN nitride layer is formed on the aluminum surface and the surface hardness can be improved remarkably. In this study, barrel nitriding was performed to investigate the interface between aluminum substrate, with SUS304 austenitic stainless steel used for a physical catalyst. The barrel nitriding was carried out at 893 K for 18 ks, 25.2 ks and 36 ks, respectively with aluminum and aluminum–magnesium alloy powder. After barrel nitriding, aluminum nitride layer and Fe–Al intermetallic compound layers were formed at the interface between pure aluminum and austenitic stainless steel at the same time. The thickness of the aluminum nitride layer and intermetallic layer was increased by increasing the treatment time.     

氧化钙添加剂对碳酸钠活化粉煤灰的影响及机理

碳酸钠焙烧粉煤灰是一种反应温度低、氧化铝溶出率高,且可同步实现铝、硅高效分离的活化方式,然而该活化过程中所需助剂耗量较大,成为其大规模产业化应用的瓶颈.借鉴高温(1200~1300 ℃)碱石灰烧结活化粉煤灰工艺,在中温(600~1000 ℃)条件下,采用正交实验和单因素实验方法,分别研究了氧化钙添加对碳酸钠焙烧活化粉煤灰后氧化铝溶出率的影响.结果表明,在中温条件下可通过添加一定比例的氧化钙来部分替代碳酸钠,当m(CFA:Na2CO3:CaO)=1:0.6:0.2时,即可使粉煤灰中的氧化铝溶出率达90%以上.通过傅里叶变换红外光谱(FT-IR)、X射线衍射分析(XRD)进一步研究发现,氧化钙之所以可以部分替代碳酸钠,主要是由于低聚合度的硅酸钙形成所导致的.     

锅炉软化与除氧同步式装置的中试试验研究

试验研制成功的锅炉给水同步式软化除氧装置,改变了传统的软化与除氧的过程分别设置、分别进行的模式。通过试验研究了影响除氧效果的主要因素,确定了在不同进水条件下的最佳运行参数及除氧剂Na2SO3的最小投量。即:当进水总硬度≤6 mmol/L时,无需投加催化剂,Na2SO3最小投加比kmin=1.3,最佳流速25～30 m/h;当进水总硬度>6 mmol/L时,需额外投加催化剂CoCl21 mg/L,而最佳流速为20～30 m/h。出水硬度和溶解氧含量均可满足《工业锅炉水质》(GB 1576-2001)标准的规定,为工业化应用奠定了基础。     

Structure of composite materials based on aluminum and coreless silicon carbide fibres

The kinetics of the reaction on the matrix—fibre interface in composite materials based on aluminum and silicon carbide fibres was investigated at temperatures of 700, 800, and 900°C. It was found that the fibres treated at high temperature have important stability in aluminum melt due to the reduced concentration of free carbon in them and the formation of a barrier layer of β-SiC on the surface of the fibres. However, because of their poor mechanical properties, it is not expedient to use them for reinforcement of aluminum. The fibres treated at low temperature are totally suitable for strengthening aluminum but require the minimum contact time with the melt or protective coatings. Moscow State Institute of Steel and Alloys (Engineering University); All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated fromKhimicheskie Volokna, No. 6, pp. 42–46, November–December, 1999.     

Anti-icing and anticontamination properties of coatings induced by surface structure

The development of the first model coatings with innovative surface structures, anti-icing, and anticontamination properties could be implemented in the EU-project CleanSky. A porous aluminum alloy structure created by anodization was filled with fluid silicon oil polydimethylsiloxane. At the surface, the silicon oil was modified with vacuum ultraviolet-light to form a thin and solid hydrophobic layer. For further investigations, laser-structured metal surfaces were copied and reproduced with a coating and afterward filled with fluoro-modified oils. Additionally, aluminum alloy AA2024 samples were pickled and treated with hot water to create micro- and nanostructures at the surface. These samples were also filled with different fluoro-modified and nonmodified oils. After application, the surface properties were analyzed with special tests for functionality regarding anti-ice and anticontamination properties.     

Novel Ti2O3–Al2O3 raw materials with controllable Ti2O3 content from the aluminothermic reduction of ilmenite

Titanium-containing refractories have excellent performance, but the high cost limits their application. A series of Ti₂O₃–Al₂O₃ raw materials with different Ti₂O₃ contents were prepared by aluminothermic reduction of ilmenite, while the generated ferrotitanium alloy can be used as raw materials for special steels. Regulating the amount of aluminum added in the system regulates the degree of titanium reduction, and the formed ferrotitanium alloy can achieve separation from the oxides. With decreasing aluminum content of, the Ti₂O₃ content increased, and the continuous distribution of the corundum area decreased, resulting in a continuously distributed Ti₂O₃ area. Our results indicated that the molar ratio of aluminum to ilmenite should be higher than 1.4 to achieve slag iron separation. The reaction model for the aluminothermic reduction was established, and the formation mechanism of Al₂O₃ and Ti₂O₃ in the system was discussed.