S. J. Chen
,
S. Y. Yin
,
L. Feng and L. Y. Li( 1) School of Materials Science and Engineering
,
Beijing Polytechnic University
,
Beijing 100022
,
China 2)National Key Laboratory of Advanced Welding Production Technology
,
HIT
,
Harbin 150001
,
China)
金属学报(英文版)
Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.
关键词:
arc welding inverter
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null
,
null
R. P. Liu
,
Z. J. Dong and Y. H. Wei( 1)Harbin Research Institute of Welding
,
Harbin 150080
,
China 2)National Key Laboratory of Advanced Welding Production Technology
,
HIT
,
Harbin 150001
,
China)
金属学报(英文版)
This paper has analyzed the influences of the heat input of welding arc, the latent heat of solidifica- tion,fluid flow of liquid metal on the heat conductivity pertaining to welding solidification crack of stainless steels. As a result,two - dimensional heat conduction models with prescribed heat flux mov- ing along the the have been developed that can simulate welding arc, convection and radiation heat loss from top and bottom surfaces of the workpiece. Finally, the finite element model was used to ana- lyze and calculate the temperature field.
关键词:
stainless steel
,
null
,
null
,
null
LIANG Yong LI Ruiguo Institute of Metal Research
,
Academia Sinica
,
Shenyang 110015
,
ChinaInstitute of Corrosion and Protection of Metals
,
Aademia Sinica
,
Shenyang
,
110015
,
China
材料科学技术（英）
Recent advances in laser coating technology including laser cladding,laser surface alloying and laser vapour deposition in China are reviewed in this paper.
关键词:
laser
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null
,
null
,
null
,
null
Daihua HE
,
Zhengyi FU
,
Qingjie ZHANG
材料科学技术（英）
Combustion reaction welding, one promising method to weld ceramics and metals, was used to weld TiB¬2 and Mo. The results showed that the reacted products through combustion reaction were TiB¬2 and MoB when the Mo contents in reactants were 20 wt pct and 40 wt pct while there was Mo besides MoB and TiB¬2 when there were 60 wt pct and 80 wt pct Mo in reactants. Diffusion of elements occurred at the interfaces of the two substrates. The interfaces between the reacted and the two substrates were indistinct after being welded. The welding temperature strongly affected properties of the samples. The value of bending strength of the sample with 80 wt pct Mo in reactant welded at 1500℃ was the highest, 368.52 MPa. The highest value of shear strength among all the samples was that of the one with 40 wt pct Mo in reactant welded at 1500℃, 50.97 MPa.
关键词:
Combustion reaction welding
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null
,
null
,
null
C.G.Shi
,
Y.H.Wang
,
L.G.Cai
,
C.H.Zhou
金属学报(英文版)
There are four new achievements of this work on the theory and technology of explosive welding.(1) It has been found and defined three kinds of bonding interfaces: big wavy, small wavy and micro wavy, and the micro wavy interface is the best. In a cladding plate,it is for the first time to find that the form of interface presents regular distribution.(2) Although the interface has the features of melt, diffusion and pressure welding in the mean time, the seam and "hole" brought by the melt weaken the bonding strength of interface greatly, and the effect of melt on interface must be eliminated in explosive welding, so explosive welding is not a melt weld. The diffusion welding is a kind of form of pressure welding, and the diffusion is not the reason of the bonding of interface but the result of interface high pressure. So the diffusion welding cannot also explain the bonding mechanism of it. The experiment and theory make clear that explosive welding is a special pressure one.(3) To get good interface of no melt, explosive charge must be selected on the low limit of welding windows. In explosive welding, the drive plate should be treated as the viscous and plastoelastic body, not incompressible fluid. The bending moment under the explosive welding loading must be greater than that under dynamic limit of drive plate. According to the condition, the lower limit of explosive welding is obtained. It is about 20 1.019373e-312ss than that obtained by tradition calculation, and suitable for engineering application.(3) It is for the first time to test and study on soil anvil characteristics and change regularity under explosive welding impact loading. Through soil anvil parameter optimization analysis, it is the best for explosive welding with sandy soil of water content 17.00and density 1.74g/cm^3.
关键词:
explosive welding
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null
,
null
Zhihua LIU
,
Qing ZHAO
,
Deqing LI
材料科学技术（英）
In this paper, technology margin experiment of hollow cathode fusion are welding (FAW) and penetrating are welding (PAW) is presented in detail. The advantages of PAW, compared with FAW, are better weld formation, narrower welds, as well as a larger welding technology margin. Technological experiment and hydraulic test for the Ti alloy pressure vessels with PAW are described. Also, the weld formation control on Ti alloys is preliminarily analyzed. Finally, conclusions are addressed.
关键词:
WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate
,
Lawrence Livermore National Laboratory
,
Livermore
,
CA 94551)
金属学报(英文版)
The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.
关键词:
: U.S. Materials Science. U.S. National Laboratories and Facilities
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null
Y. P. Kathuria (Laser X Co. Ltd. Chick - shi Aichi - ken 472
,
Japan)
金属学报(英文版)
With the established technique of laser in science and industry, its applications hare become diversified in the automotive welding.Two potential lasers CO2 and Nd - YAG operating in the i. r. region hare been applied in various demains covering different spectrum of welding,ranging from dissimilar matal to aluminium alloy welding.These lasers considered as thermal processing tools offers an advantage of the keyhole welding offered by the electron beam where the energy is transferred from the surface by the keyhole formation. with the incorporation of these lasers as a flexible thermal processing tool,it has become essential to use them optimally through feedback with planning and constructional rules.Based upon the modulation and duty cycle variation,a simulation technique is demonstrated which enable us to estimate the processing results and determine the characterisitcs of the fabricated part. From the giv- en provess parameters such as haer power, focus radius,processing speed /interaction time and materi- al characteristics, one can optimize the welding condition etc. through the simulation process. In the present work the laser simulation process in welding were carried out with Al- alloy A 5052 of various thickness by using a multiwave high power Nd - YAC lasers.The simulated weld conditions resulted in better utility of the lasers with increased efficiency and better quality. The use of simuation method helped in the designing and prediction of welding technology, which reduced the rejection rate as well as the cost of production.
关键词:
easer beam welding
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null
,
null
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null
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
A new type of tungsten inert gas (TIG) welding has been developed, in which an ultra-deep penetration is obtained. In order to control the Marangoni convection induced by the surface tension gradient on the molten pool, He gas containing a small amount of oxidizing gas was used. The effect of the concentration Of O-2 and CO2 in the shielding gas on the weld shape was studied for the bead-on-plate TIG welding of SUS304 stainless under He-O-2 and He-CO2 mixed shielding gases. Because oxygen is a surface active element for stainless steel, the addition of oxygen to the molten pool can control the Marangoni convection from the outward to inward direction on the liquid pool surface. When the oxygen content in the liquid pool is over a critical value, around 70ppm, the weld shape suddenly changes from a wide shallow shape to a deep narrow shape due to the change in the direction of the Marangoni convection. Also, for He-based shielding gas, a high welding current will strengthen both the inward Marangoni convection on the pool surface and the inward electromagnetic convection in the liquid pool. Accordingly, at a welding speed of 0.75 mm/s, the welding current of 160 A and the electrode gap of I mm under the He-0.4%O-2 shielding, the depth/width ratio reaches 1.8, which is much larger for Ar-O-2 shielding gas (0.7). The effects of the welding parameters, such as welding speed and welding current were also systematically investigated. In addition. a double shielding gas method has been developed to prevent any consumption of the tungsten electrode. (c) 2008 Elsevier B.V. All rights reserved.
关键词:
Weld shape;Oxygen;Helium;Marangoni convection;Electromagnetic;convection;Double shielding gas;gas tungsten arc;shape variations;oxide fluxes;penetration;parameters
