钻杆环缝数控自动焊机

研制的钻杆环缝数控自动机焊为全自动的数控焊机。用于钻杆与两端法兰的内外共4条环缝的焊接。工件的上料、定位、夹紧、内外焊枪的到位、内外焊枪的焊接、自动排列焊道各层各道的焊接工艺参数的改变等均能自动进行。不同管径和不同壁厚采用的各种焊接参数都可在人机界面上预置。采用富氩混合气体保护焊工艺方法，焊缝美观，性能优良，几乎没有飞溅。经大量的生产实践证明该钻杆环缝数控自动焊机焊接质量好，生产效率高。     

Copper-nickel superalloys as inert alloy anodes for aluminum electrolysis

The superalloys Cu-Ni-Al, Cu-Ni-Fe, and Cu-Ni-Cr were studied as anodes for aluminum electrolysis. The alloys were tested for corrosion in acidic electrolyte molten salt and for oxidation in both air and oxygen. The results showed that the Cu-Ni-Al anodes possess excellent resistance to oxidation and corrosion, and the oxidation rates of Cu-Ni-Fe and Cu-Ni-Al anodes were slower than those of pure copper or nickel. During electrolysis, the cell voltage of the Cu-Ni-Al anode was affected most by the concentration of alumina in cryolite molten salt. The Cu-Ni-Fe anode exhibited corrosion resistance in electrolyte molten salt. Comparatively, the Cu-Ni-Cr anode showed poor resistance to oxidation and corrosion. The testing found that further study is warranted on the use of Cu-Ni-Al and Cu-Ni-Fe as inert alloy anodes. For more information, contact Zhongning Shi, Northeastern University, School of Materials and Metallurgy, WenhuiRoad No. 3, Shenynag, Liaoning 110004 China; e-mail znshi@163.com     

Properties of Induction Plasma Sprayed Iron Based Nanostructured Alloy Coatings for Metal Based Thermal Barrier Coatings

Metal-based thermal barrier coatings (MBTBCs) have been produced using high frequency induction plasma spraying (IPS) of iron-based nanostructured alloy powders. The study of MBTBCs has been initiated to challenge issues associated with current TBC materials such as difficult prediction of their “in-service” lifetime. Reliability of TBCs is an important aspect besides the economical consideration. Therefore, the study of MBTBCs, which should posses higher toughness than the current TBC materials, has been initiated to challenge the mechanical problems of ceramic-based TBCs (CBTBCs) to create a new generation of TBCs. The thermal diffusivity (TD) (α) properties of the MBTBCs were measured using a laser flash method, and density (ρ) and specific heat (C _p) of the MBTBCs were also measured for their thermal conductivity (k) calculation (k = αρ C _p).     

Advances in fabricating superplastically formed and diffusion bonded components for aerospace structures

Superplastic forming and diffusion bonding (SPF/DB) production hardware is being fabricated today for aerospace applications. Metal tooling is being used to bring the titanium sheets into contact so diffusion bonding can occur. However, due to material sheet and tooling tolerances, good bond quality is difficult to achieve over large areas. A better method for achieving DB is to use “stop-off” inside sealed sheets of titanium, which constitutes a pack, and then the pack is bonded using external gas pressure. A good method for heating the pack for this process is to use induction heating. Components using “stop-off” that were diffusion bonded first and then superplastically formed have shown much better bond quality than components that were produced using matched metal tooling. This type of tooling has been successful at bonding small areas as long as the exerted pressure is concentrated on the area where bonding is required. Finite element modeling is providing weight effect solutions for titanium SPF/DB aerospace structures. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

利用Ca（NO3）2-P2O5乙醇溶液体系制备纳米羟基磷灰石

使用Ca（NO3）2-P2O5乙醇溶液体系制备纳米羟基磷灰石，研究了在该体系中水浴温度、煅烧温度、陈化时间等因素对粉体的相成分，粒度和结晶度的影响。结果表明：水浴温度低，合成的粉体粒度小（约20nm），颗粒均匀且具有良好的分散性，但是结晶度较低；陈化后导致粉体粒度变大，结晶度增加；随着煅烧温度的升高，粉体的结晶度增加，600℃时可以得到结晶高的单一的羟基磷灰石粉体。在800℃煅烧时，羟基磷灰石发生部分分解。     

Improvement of wear resistance of plasma-sprayed molybdenum blend coatings

The wear resistance of plasma sprayed molybdenum blend coatings applicable to synchronizer rings or piston rings was investigated in this study. Four spray powders, one of which was pure molybdenum and the others blended powders of bronze and aluminum-silicon alloy powders mixed with molybdenum powders, were sprayed on a low-carbon steel substrate by atmospheric plasma spraying. Microstructural analysis of the coatings showed that the phases formed during spraying were relatively homogeneously distributed in the molybdenum matrix. The wear test results revealed that the wear rate of all the coatings increased with increasing wear load and that the blended coatings exhibited better wear resistance than the pure molybdenum coating, although the hardness was lower. In the pure molybdenum coatings, splats were readily fractured, or cracks were initiated between splats under high wear loads, thereby leading to the decrease in wear resistance. On the other hand, the molybdenum coating blended with bronze and aluminum-silicon alloy powders exhibited excellent wear resistance because hard phases such as CuAl₂ and Cu₉Al₄ formed inside the coating.     

A computational fluid dynamic analysis of gas and particle flow in flame spraying

The flame spraying process, which is a common industrial thermal spraying application, has been analyzed by means of three-dimensional computational fluid dynamics (CFD) simulations. The process used at the Volvo Aero Corporation for the coating of fan and compressor housings has been modeled. The process uses the Metco 6P torch (Metco, Westbury, NY), which ejects a mixture of acetylene and oxygen at high speed through a ring of 16 orifices to form the flame. A stream of argon gas flowing through an orifice in the center of the ring carries a powder of nickel-covered bentonite through the flame to the spray substrate. The torch is cooled by a flow of air through an outer ring of 9 orifices. The simulation emulated reality closely by including the individual inlets for fuel, cooling air, and injected particles. The gas combustion was simulated as a turbulent, multicomponent chemically reacting flow. The standard, two-equation k-ε turbulence model was used. The chemical reaction rates appeared as source terms in the species transport equations. They were computed from the contributions of the Arrhenius rate expressions and the Magnussen and Hjertager eddy dissipation model. The first simulations included several intermediate chemical substances whose predicted concentration agreed favorably with measurements. Later, more simplified simulations incorporated only the global chemical reaction involving the initial and the final products, with corrections to the thermal properties being made to account for the missing intermediaries. The gas velocity and temperature fields predicted by the later simulations compared satisfactorily to those predicted by the earlier, more elaborate, ones. Therefore, the final simulations, which incorporated injected particles, were conducted employing the simplified model with only the global reaction. An in-house finite difference code was developed to calculate particle properties. Allowance was made for elliptical shapes, phase changes, and internal heat transfer with regard to the composite material. The particle velocities and temperatures predicted by the final simulations compared fairly well with experimental results obtained with the optical DPV2000 system.     

Influence of the post-deformation annealing heat treatment on the low-cycle fatigue of NiTi shape memory alloys

Shape memory alloys (SMA) suffer from the same impairing mechanisms experienced during cycling loading by classic alloys. Moreover, SMA fatigue behavior is greatly influenced by thermomechanical cycling through the zone of thermoelastic phase transformation, which is the basis of shape memory and superelasticity effects. Since the fatigue resistance of any material can be improved by an appropriate thermomechanical treatment, in the present work combined differential scanning calorimetry and microhardness testing were used to determine an optimum annealing temperature for the cold-worked Ni-50.1%Ti alloy. The optimization is based on the assumption that latent heat of transformation is proportional to the mechanical work generated by SMA upon heating, while material hardness is related to the yield stress of the material. It is supposed that an optimum trade-off in these two properties guarantees the best dimensional and functional stability of SMA devices. The level and stability of the mechanical work generated by the material during low-cycle fatigue testing are considered criteria for the material performance and thus of the validity of the proposed optimization procedure.     

渗硼层脆性判据K的物理本质

从实验和理论上对显微硬度压痕结合声发射测量渗硼层脆性的合理性及其脆性判据Ｋ的物理意义进行了讨论。Ｋ值可以反映渗硼层显微压痕裂纹长度随负荷增加的变化率，因而可以表征渗硼层的脆性。根据断裂力学可以导出入与Ｇ＿（ＩＣ）之间存在如下关系：Ｋ＝β（Ｇ＿Ｉ－Ｇ＿（ＩＣ））。Ｋ值间接反映了渗硼层的断裂韧性，可以作为定量评价渗硼层本质脆性的力学参量。     

Elevated temperature Mg-Al-Sr: Creep resistance,mechanical properties,and microstructure

Mg-Al-Sr-based alloys (AJ alloys) have shown superior creep performance and tensile strength at temperatures as high as 175° with stresses up to 70 MPa. Mg-6Al-2.4Sr (AJ62x) exhibits an optimum combination of creep resistance and excellent castability, while AJ62Lx (strontium <2.1) has better ductility than other AJ formulations. The AJ alloy microstructure is characterized by the Al₄Sr-α(Mg) lamellar phase that forms at the interdendritic/grain boundary region of the primary magne sium matrix. Mg-5Al-2Sr (AJ52x) contains a ternary phase that was tentatively named Al₃Mg₁₃Sr. When the strontium level is low in AJ62x, the volume fraction of Al₄Sr is reduced, the aluminum supersaturation of the magnesium primary phase increases, and Mg₁₇Al₁₂ forms. In this article, a mechanism is proposed whereby the creep resistance decreases with the strontium level but the tensile strength and ductility increase. For more information, contact Eric Baril, Noranda, Noranda Technologies Centre, 240 Hymus Pointe-Claire (Montréal), Québec, H9R 1G5 Canada; (514) 630-9347; fax (514) 630-9379; e-mail eric.baril@ntc.noranda.com.