含Ca、Ba合金和Al基合金的复合脱氧实验研究

通过250kg底吹气非真空感应炉，对FeSiAl、SiAlBaCaSr和SiAlBaCa三种合金及SiCaBa、SiCa包芯线进行了组合对比脱氧实验，实验表明三种合金的脱氧效果相当，SiAlBaCa合金的脱氧产物具有明显的聚集长大上浮现象，处理结束时夹杂物的总面积和数量均为最低，脱氧产物为复合型夹杂，形状多为球状。通过与喂丝处理的比较，SiAlBaCa合金脱氧可以起到喂丝处理效果。     

Bend testing of wrought wire removable partial denture alloys

The flexibility of the wrought wire clasp is related to a number of factors, including the type and gauge of the alloy. The purpose of this study was to compare the bend behavior of five wrought wire alloys used in removable partial dentures. The alloys and their gauge diameters (in millimeters) were Ticonium (18, 19, 20), platinum-gold-palladium (18, 19), Wironium (18, 20), Jelenko Standard (18, 19, 20), and Denture Clasp (18, 19, 20). A total of 12 to 15 samples of each dental alloy were tested. Three-point bending was performed on a servohydraulic testing system controlled by a computer at 1.00 mm/sec until fracture or actuator contact occurred. Maximum stress and elastic modulus in bending were determined for each gauge diameter. Analysis of variance and post hoc Scheffe statistical analyses revealed significant maximum stress and elastic modulus in bending differences for different alloys of the same gauge and for different gauges of the same alloy. The choice of material and the gauge diameter significantly influenced the mechanical property of bending for wrought wire removable partial denture alloys. The Ticonium alloy had the greatest elastic modulus (stiffest) at all levels and the Denture Clasp and the Jelenko Standard alloys had the lowest elastic modulus (most flexible). These data indicate that knowledge of the bending properties of an alloy is equally as important as the gauge size when selecting a wire clasp.     

Preparation of Hard Alloy WC and WC – Co Mixtures with Reduction and Carbidizing Treatment of Oxidized Tungsten Containing Scrap

A method of single-stage reduction and carbidizing treatment of oxidized tungsten containing scrap (hard alloys of the VK type and tungsten wire) is proposed. Procedures are suggested for preparing very fine tungsten carbide of stoichiometric composition without adding carbon black by reduction and carbidizing treatment of oxidized tungsten wire scrap and also with introduction of solid carbon (carbon black) during reduction and carbidizing treatment of oxidized hard alloy scrap.     

铝及铝合金焊丝的研究与发展现状

随着铝合金焊接结构的广泛应用及铝合金焊接技术的发展,铝合金焊丝愈加受到人们的关注.本文主要介绍铝合金焊丝的化学成分、产品性能及选择原则,阐述其生产工艺的发展现状,指出我国焊丝生产存在的问题,展望铝合金焊丝的发展趋势.     

Global and Local Mechanical Properties and Microstructure of Friction Stir Welds with Dissimilar Materials and/or Thicknesses

This article studies the properties of a wide range of friction-stir-welded joints with dissimilar aluminum alloys or thicknesses. Two aluminum alloys, namely, 2024-T3 and 7075-T6, are selected for the study and are welded in ten different combinations of alloys and thicknesses. The welding parameters are optimized for each configuration, and a systematic study of the effects of material and thickness combinations on the microstructural features, global and local mechanical properties, and fracture mechanisms of the welds is carried out. It is shown that dissimilar alloys are extruded into each other, the texture is heterogeneous in the weld zone, and that there is no significant diffusion of alloying elements between the alloys. For most configurations, the local and global mechanical properties decrease as the thickness ratio increases. The local yield strength and plasticity parameters substantially vary next to the weld centerline, hence requiring their implementation in finite element method (FEM) models. Machining to obtain a constant thickness significantly influences the mechanical properties of the welds. The fracture mechanism is found to be a mixture of ductile and brittle fractures and to qualify as “quasi-cleavage.”     

增材制造TiAl基合金的研究进展

TiAl基合金具有优异的高温性能,是一种极具竞争力的新型轻质高温结构材料,在汽车、军工、航空航天等领域具有广阔的发展潜力和应用前景.然而,TiAl基合金室温脆性较大,成形困难,是阻碍其发展与应用的主要瓶颈之一.增材制造基于"离散+堆积"的成形思想,以激光、电子束、电弧等作为高能热源,通过熔化丝材或者粉末,逐层堆积实现零...     

中性点不接地系统单相接地保护的分析

阐述了中性点不接地系统中单相接地时的参数变化,并对相关的保护形式和新型TY系列单相接地选线与定位保护的原理进行了分析和探讨。     

中性点不接地系统单相接地保护的分析

阐述了中性点不接地系统中单相接地时的参数变化，并对相关的保护形式和新型TY系列单相接地选线与定位保护的原理进行了分析和探讨。     

Detection of K-ras mutations in stools of patients with colorectal cancer by mutant-enriched PCR

This study determined the effect of various durations of induction melting of a cobalt-chromium alloy on resistance to deflection fatigue. Commercial cobalt-chromium alloy was melted by high-frequency induction for various lengths of time before it was cast into the shape of a denture clasp. The test method used was a constant-deflection fatigue test. The fatigue fracture surface of the clasp was examined with a scanning electron microscope, and the surface hardness (Vickers hardness) of the clasps was measured. In clasps with greater fatigue resistance scanning electron microscope photomicrographs revealed a coarse grain structure. The surface hardness of the alloy was least in the group with the lowest fatigue resistance and was higher in groups with greater fatigue resistance. This study suggests that, although some porosities are formed in the middle of the clasps after the alloy is overheated, the fatigue resistance of cobalt-chromium alloy denture clasps can be increased by lengthening the induction melting period of the alloy.     

电弧喷涂高性能防腐耐磨涂层

垃圾焚烧厂工件表面通常暴露在含HCl/KCl的高温气氛中,这些高腐蚀性高温气氛是造成焚烧厂高额维护费用的主要原因。使用热喷涂技术对部件表面进行涂层防护可明显提高传统钢材的表面耐腐蚀性能。电弧喷涂由于其易于操作性和低成本,已成为最为成熟的技术之一。要得到可观的腐蚀防护能力,涂层必须有很高的致密度。因此,电弧喷涂必须做出适当调整以适应垃圾焚烧厂的特殊需求。虽然镍基合金和钴基合金代表了当今腐蚀防护的技术水平,但是这些合金非常昂贵。属于同一系列的铁基合金将成为一种经济效益更为可观的防腐蚀材料。最近的研究表明,与铁铬基合金和镍铬基合金相比,铁基合金中加入硅后其耐腐蚀性能得到显著提高。鉴于这一原因,本文开展了对不同成分的铁-铬-硅系合金的研究,重点讨论了该合金的最新研究结果。     

Cr20Ni80电热合金盘圆轧制孔型应用研究

镍铬类电热合金是重要的电热工程材料，盘圆轧制是这类线材生产的重要工序。本文研究了采用横列式轧机轧制Cr20Ni80电热合金盘圆的孔型设计，对易产生的轧制缺陷进行了分析，提出了孔型优化方案。     

Selected Applications of Aeropropulsion Actuation and Shape Control Devices Using HTSMAs

Recent research has contributed to the relatively rapid development of high-temperature shape memory alloys (HTSMAs), materials that combine useful work output with transition temperatures well in excess of the range of typical binary NiTi SMAs. This article describes recent demonstration applications of HTSMAs in devices representative of mechanisms useful for a variety of aeropropulsion applications requiring high transition temperatures. Work to date has chiefly featured application of Pt-doped NiTi alloys in wire form, although some data on the use of Hf-doped alloys has also been generated. The results presented describe benchtop and wind tunnel experiments of demonstration devices employing HTSMA wire actuators. The test results validate operation at 573+?K (300+?°C) and document the force and strain capability of the new alloys. Ongoing and projected work in pertinent areas is also described.     

Structure and Properties of Carbon Steel Wire in Drawing

A method of continuous deformational nanostructuring of wire is described. In the method, a continuously moving wire is subjected simultaneously to tensile deformation in drawing, flexural deformation on passing through a roller system, and torsional deformation. This combination permits wide variation in its mechanical properties, ensuring both high strength and plasticity. The benefits of such deformation are the use of a tool already employed in the production of metal components; compatibility with the speeds of coarse and moderate wire drawing; and simplicity of the equipment. Laboratory apparatus for this method is described. Carbon steel 50 wire is selected for investigation, since it in great demand. The chemical composition and mechanical properties of the wire in the initial state are described. Experiments are conducted to investigate the effectiveness of the proposed differential nanostructuring in producing ultrafine-grain structure in the wire. The deformation conditions of the wire are described, as well as the drawing process. The transverse and longitudinal microstructure of the carbon steel 50 wire at the surface and in the center after different types of deformational treatment is investigated. In the experiments, the influence of the type of deformational treatment on the microstructure of the steel and its anisotropy over the wire cross section is established. The compliance of the wire’s mechanical properties with current standards is verified. After all types of treatment, its mechanical properties are consistent with State Standard GOST 17305–91. Metallographic data and mechanical test results after combined deformational treatment indicate that such combinations of deformation provide a promising approach to creating ultrafine-grain structure in carbon wire.     

Laser wire casting

Abstract

A new technique has been developed for the production of solid wire or rods from powder by laser melting. Three techniques have been developed to ensure that the molten powder solidifies as a rod or wire rather than a series of droplets. The straight rods or wires produced in this way have near-circular cross-section, are several millimetres in diameter and can be pore free. The techniques can be used to produce welding rods, tensile test samples and other solid pieces from a wide range of powder mixes. The rapid thermal cycle involved means that it is now possible to produce hitherto difficult mixtures and alloys in the solid form in seconds.     

高速线材P/F运输线工艺设计

针对高速线材生产线中普遍应用的P/F运输线的工艺布置、C形钩数量选择、C形钩表面质量等参数进行了探讨,对相关设计人员有一定的参考作用.     

Cold-Drawn Bioabsorbable Ferrous and Ferrous Composite Wires: An Evaluation of Mechanical Strength and Fatigue Durability

Yield strengths exceeding 1 GPa with elastic strains exceeding 1 pct were measured in novel bioabsorbable wire materials comprising high-purity iron (Fe), manganese (Mn), magnesium (Mn), and zinc (Zn), which may enable the development of self-expandable, bioabsorbable, wire-based endovascular stents. The high strength of these materials is attributed to the fine microstructure and fiber textures achieved through cold drawing techniques. Bioabsorbable vascular stents comprising nutrient metal compositions may provide a means to overcome the limitations of polymer-based bioabsorbable stents such as excessive strut thickness and poor degradation rate control. Thin, 125-μm wires comprising combinations of ferrous alloys surrounding a relatively anodic nonferrous core were manufactured and tested using monotonic and cyclic techniques. The strength and durability properties are tested in air and in body temperature phosphate-buffered saline, and then they were compared with cold-drawn 316L stainless steel wire. The antiferromagnetic Fe35Mn-Mg composite wire exhibited more than 7 pct greater elasticity (1.12 pct vs 1.04 pct engineering strain), similar fatigue strength in air, an ultimate strength of more than 1.4 GPa, and a toughness exceeding 35 mJ/mm³ compared with 30 mJ/mm³ for 316L.     

Production of continuous-cast blanks for rod and wire drawing at KUZOTsM

KUZOTsM has developed a highly profitable process for production of wire from many alloys; this process includes production of a continuous-cast blank of small cross section, which provides for a significant reduction in the production cycle and reduces metal loss through avoidance of hot working processes (rolling or extrusion). Implementation of this trend will lead to a substantial improvement in product yield and other production performance indicators, while maintaining quality of the end product at an appropriate level.     

含钡合金对冷镦钢脱氧的试验研究

在250kg感应炉上对冷镦钢进行了含钡合金脱氧的试验研究。试验中钡系合金主要选取SiAlBaCa和SiAlBaCaSr及用于钙处理的SiCa、SiCaBa包芯线。选用FeSiAl作为对比脱氧剂，考察了钡系合金脱氧的全氧含量，脱氧产物的分布、尺寸和形貌，探讨了钡系合金脱氧和对夹杂物的变质作用的机理。试验中发现，含钡合金用于钢液脱氧，可获得较低的氧含量，其脱氧产物易于上浮且速度很快，钢中的夹杂物形态发生改善呈球形，而且均匀分布于钢中。     

A study of fracture in high purity 7075 aluminum alloys

Ten different alloys based on the 7075 composition were used to study the effect of purity level, dispersoid type, and heat treatment on fracture toughness. Five purity levels ranging from 0.03 to 0.30 wt pct Fe + Si and two dispersoid types were investigated. Each alloy was given two heat treatments: the standard T651 heat treatment or a special thermomechanical treatment (TMT). Fracture toughness was measured using notched round tensile specimens taken from both the longitudinal and long-transverse directions. The notched round tensile test was modified to give the “plastic energy per unit area”. This fracture toughness parameter gave the same ranking for corresponding alloy/heat treatment combinations as the total energy per unit area measured on precracked Charpy specimens. The fracture toughness ranking for the ten alloys was the same in the longitudinal and long-transverse directions. This suggests the elongated distribution of constituent particles in the rolling direction does not change the failure mechanism. Fractographic evidence showed a bimodal distribution of ductile dimple size in all ten alloys. The number of large ductile dimples decreased with increasing purity level while the number of small ductile dimples increased. This is interpreted to mean that the smaller dispersoid and hardening particles become increasingly important in controlling the fracture toughness as the large intermetallic particles are eliminated by increasing the purity of these aluminum alloys. Since thermomechanical processing controls the amount and type of these smaller particles, it is a useful means for increasing fracture toughness in high purity aluminum alloys.     

提高轧机导卫辊寿命的研究

在分析棒、线材轧机使用的Gx铸造合金导卫轶失效形式的基础上，对不同热处理状态的GJH-2合金和Gx铸造合金，在不同温度下的高温磨损特性进行了对比试验，并将GJH-2合金制成导卫辊在轧机上进行了装机试验，试验结果表明，用GJH-2合金代替Gx铸造合金制作导卫辊可以大幅度提高导卫辊的使用寿命和经济效益，GJH-2合金导卫辊的使用寿命是Gx铸造合金辊的16.5倍。