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QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY
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PRINT ISSN: 0288-4771

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY Vol. 12 (1994), No. 4

  • A Study on Residual Stresses of Dissimilar Welding Joints

    Bahaa ZAGHLOUL, Abdel-Monem EL-BATAHGY, Alber SADEK, Mohamed EL-SHENAWY

    pp. 459-467

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    DOI:10.2207/qjjws.12.459

    Abstract

    This research work focused on different types of dissimilar weld joints commonly used in refineries and chemical industries to investigate the magnitude, type and distribution of welding residual stresses in weld metal and HAZ at both face and root sides. These joints were combined from mild steel, stainless steel types 304 and 316, and Incoloy 800. For comparison, similar weld joints for each material were also studied. Stress relaxation or sectioning technique was used for welding residual elastic strain measurements using electrical strain gauges.
    The results of this study have shown that measured elastic strains of both face and root sides were different and this difference increased with the increase in plate thickness. Welding residual stresses of HAZ did not depend on joint type, it depended only on properties of base metal.
    A considerable difference in the value of welding residual stresses between similar and dissimilar pipe weld joints was obtained. However, both have shown almost similar trend of stress distributions.

  • Automatic Simultaneous Control of Bead Height and Back Bead Shape Utilizing Arc Sensor in One Side Welding with Backing Plate

    Yuji Sugitani, Wenjie Mao

    pp. 468-476

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    DOI:10.2207/qjjws.12.468

    Abstract

    An automatic welding system that can simultaneously control the bead height and the back bead shape in one side MAG welding process with backing plate has been introduced in this paper. In the system, a high speed rotating arc welding method is used and the seam tracking and the torch height control are realized by utilizing arc sensing technique.
    On the other hand, the variations of groove shape is also detected by the arc sensing technique. The detecting mechanism is in detail discussed in the paper.
    Moreover, the system uses a new welding parameters control method that is developed by authors in which only wire feeding rate and welding voltage are adaptively regulated and the other welding conditions are all holded. The new method is able to keep the bead height constant and hold the back bead shape in the case of groove shape changing.
    The primary welding experimental results have proved that the system is effective and satisfactory for controlling the weld bead shape in one side GMAW process with backing plate.

  • Phenomena of micro-discharge across the gap of sub-micrometer

    Hiroshi Maruo, Yoshinori Hirata, Kimihiro Ozaki

    pp. 477-484

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    DOI:10.2207/qjjws.12.477

    Abstract

    Micro-discharge phenomena is experimentally investigated in vacuum environment. The experimental setup based on a STM (Scanning Tunneling Microscope), which is consisted of electric circuit for micro-discharge and nanometer controlled actuators for adjusting gap length, was constructed. In order to carry out the in-situ observation of micro-discharge phenomena it was installed in a SEM (Scanning Electron Microscope) chamber fitted with a photomultiplier. Applying several hundereds voltages to the gap between the electrode and the specimen at a distance of several hundreds nanometers, the electrical breakdown followed by micro-discharge occurs. Light emission was simultaneously detected with photomultiplier. It was found that the micro-discharge voltage falls with increasing current.

  • Behavior of Cadmium on Brazing

    Takanori Nishida, Kazushi Kimura, Michio Inagaki

    pp. 485-494

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    DOI:10.2207/qjjws.12.485

    Abstract

    This experiment, the behavior of Cadmium (Cd) during brazing, reports the cases of fumes, flux and filler metal in case of using BAg-1 BAg-3. And at the same time the authors observed the floating fumes during brazing by EPMA, farthermore they examind number frequency (%) about particle size of fumes, and were made clear particle size (μm) distribution of fumes.
    This experiment was conducted to clarify the behavior of Cd on brazing more correctly and completely so as to obtain a guideline for executing more proper brazing and for finding the safety measures.
    As a result, the following conclusion was obtained :
    (1) The amount of Cd content in flux (slag), compared with that in fumes, was approx. 300 up the 700 times when brazing was done at the optimum heating temperature, it was reduced to approx. 3 up to 30 times, due to increasing movement of Cd content to fumes, when the optimum temperature was exceeded. The result suggests the necessity of an effective consideration to be given to flux cleaning.
    (2) Of fumes, flux and filler metal, filler metal is the largest in terms of Cd percentage by weight. It was clarified however that flux contained 10-1 or so of Cd even at the optimum heating temperature and that both fumes and flux contained 10-1 up the 1 of Cd when the optimum heating temperature was exceeded.
    (3) Particle size of fumes signify same tendency regardless of heating temperature. Number fre-quency is the most highest below fume size 0.43, um, and this phenomenon means that these fume size are generally very fine. Also, up about 95% are below 7.07, um fume size which are absorbed fumes, and so we must be careful of the fumes which are produced in case of using filler metals containing Cd.

  • Brazing of Al-Mg alloy and Al-Mg-Si alloy with Al-Ge based filler metals

    Takashi Kayamoto, Jong-Hoon Kim, Shinji Saito, Tadao Onzawa

    pp. 495-501

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    DOI:10.2207/qjjws.12.495

    Abstract

    Vacuum brazing of A5000 (Al-Mg) series and A6000 (Al-Mg-Si) series aluminum alloys are considerably difficult because of their rather high magnesium contents. For the purpose of sound and high strength brazing of these materials, a series of Al-Ge-Si-Mg system based filler metales was developed by the authors. Evaluations of brazed joint strength of A5052 and A6061 base alloys with these filler metals were performed and the relationship between the joint strength and the brazing conditions was investigated.
    In A6061 base alloy, the brazed joints provided sufficient joint strength which were equal to that of the base alloy. In A5052 alloy, on the other hand, the joint strength was considerably low which was as low as one half of that of the base alloy.
    The examination of brittle intermetallic compound Mg2Ge through the reaction between Mg in the base alloys and Ge in the filler metals occured at the interfaces of the brazed joints. Accordingly the formation of this intermetallic compound lead the decrease in the joint strength of A5052 alloy, which contains much Mg.

  • Brazing of titanium with Ag-based filler metals in the air

    Takehiko Watanabe, Yutaka Higo, Takayuki Miki, Atushi Yanagisawa

    pp. 502-508

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    DOI:10.2207/qjjws.12.502

    Abstract

    In this study, we developed Ag-based filler metals and new fluxes in order to braze commercially pure titanium in the air.
    The fluxes consisting of AgCI or CuCl added with small content of LiF can provide good wetting of the Ag-based filler metals on the titanium surface. In particular, the flux with the composition of 90%AgCI-10%LiF is the most effective from the viewpoint of the wetting and the joint strength. The joint brazed with 70%Ag-30%Zn filler metal through the metallizing process shows higher tensile strength than that of the joint brazed with the conventional filler metal.
    The adequate addition of copper to 70Ag-30Zn filler metal increases the strength of the brazed joint, but the addition of nickel to the Ag-Zn-Cu system filler metal is harmful to the strength of the joint.

  • Solidification Phenomena and Bonding Strength at the Interface of Diamond and Active-Metal-Brazing-Filler

    Akio Suzumura, Takahisa Yamazaki, Kunio Takahashi, Tadao Onzawa

    pp. 509-514

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    DOI:10.2207/qjjws.12.509

    Abstract

    Natural diamond has been brazed to Fe-42Ni alloy sheet using Ag-Cu eutectic filler including active metal of 4.5 wt% Ti, in order to investigate on the relation between the segregation behavior of the active metal to the brazed interface and the joint strength.
    The examination of the effects of brazing thermal cycles on the reaction products and titanium segregation behavior at the diamond-filler interface showed that the microstructures at the interface were dendrite and cell structure in case of cooling rate of 12 K/sec and 1.5 K/sec respectively, and that the active metal (Ti) was not detected by EDS in the both structures. This suggests that titanium segregation at the joint interface and the grain boundaries occurs as a result of exclusion of titanium out of Ag-Cu eutectic crystals accompanied by the crystal growth.
    The joints were fractured at the interface between diamond and brazing filler using a developed tensile shear test method to get the joint strength and the fractured surfaces at the interface. The strength of the joint made by the cooling rate of 1.5 K/sec was higher than that made by the rate of 15 K/sec. The disregistry values were also calculated from the mismatch of surface orientations and lattice constants at the bonded interface. The results showed that the disregistry of diamond and TiC to Ti were remarkably larger than those to Cu and Ag, which corresponded to the joint strengths and the fracture paths.

  • The effects of Chemistry and microstructure of the base metal on preferential corrosion properties of line pipe welded joint

    Shigeru Endo, Moriyasu Nagae, Sakae Fujita, Takashi Wada

    pp. 515-520

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    DOI:10.2207/qjjws.12.515

    Abstract

    In order to get rid of the preferential corrosion problems occurring in the welded joint of line pipes transporting oil and gas containing CO2, the effects of the chemical composition of heat affected zone (HAZ) and weld metals on the preferential corrosion property in CO2 containing environment were investigated. Electrochemical polarization and galvanic current density measurements were carried out to examine the preferential corrosion of welded joint in synthetic sea water saturated with 0.1 MPa CO2. The effect of base metal chemistry, seam and girth weld metal chemistry of line pipes on the preferential corrosion of HAZ and weld metals was investigated. The effect of base metal and HAZ microstructures on HAZ preferential corrosion property was also investigated.
    HAZ preferential corrosion is not likely to occur in Cu and Ni bearing steel whose microstructure consists of bainite. The chemical composition of weld metal and base metal affect the preferential corrosion behavior of the welded joint and the addition of Ni and/or Mo to the weld metals is effective to prevent the preferential corrosion of the weld metals regardless of welding methods.

  • Toughness Recovery for weld HAZ by Post weld Heat Treatment

    Hitoshi Okada, Fukuhisa Matsuda, Kenji Ikeuchi, Zhonglin Li

    pp. 521-527

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    DOI:10.2207/qjjws.12.521

    Abstract

    In order to determine optimum parameters of PWHT (Post Weld Heat Treatment) for improving the toughness of HAZ of 780 and 980 MPa class HSLA steels welded with high heat inputs, the effect of PWHT on the toughness of simulated weld HAZ of the steels has been systematically investigated in relation to the decomposition of the M-A (Martensite-Austenite) constituent.
    The optimum PWHT time and temperature proposed by considering the practical workability are 8 hr's and 623 K for the weld CGHAZ (Coarse Grain HAZ) and ICCGHAZ (Intercritically Reheated CGHAZ) of the employed steels of 780 and 980 MPa classes.
    The optimum PWHT parameters have been tested on specimens actually welded with a heat input twice as high as the conventional. The toughness of the actually welded specimen, estimated from CTOD value, is also improved significantly by PWHT under the proposed conditions, and satisfies demands for practical application. The tensile strength of the actually specimen welded with a heat input twice as high as the conventional, estimated from wide tensile test pieces, has been presumed to satisfy the specification of weld joint using 780 MPa class HSLA steel.
    The tensile strength of the actually welded joint, although it includes the HAZ softening zone, is calculated to be a value satisfying the specification of 780 MPa class steels, provided that the width of the test specimen is more than 5 times as large as the thickness.

  • Effect of Heat Treatment on Bond Characteristics of Aluminum Clad Steel

    Shizuo Mukae, Kazumasa Nishio, Mitsuaki Katoh, Toshiaki Inoue, Kenji Sumitomo

    pp. 528-533

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    DOI:10.2207/qjjws.12.528

    Abstract

    An aluminum clad steel was produced using the vacuum roll bonding. The clad steel was heated at 560 to 650°C for 0 to 20 s to study formation of intermetallic phases and bond shear strength in the bond interface between the aluminum and the steel of the aluminum clad steel given weld thermal cycles. Main results obtained are as follows ; (1) Although the clad steel was heated at 650°C without holding, an intermetallic phase was not formed in the bond interface. (2) However, when the clad steel was heated for a certain time, intermetallic phases of FeAl3 and Fe2Al5 were formed in the bond interface and the activation energy for formation of the phases was 41 kcal/mot. (3) When the thickness of the phases was more than around 1.5μm, the bond shear strength of the clad metal was abruptly decreased in comparison with that of the clad steel in as-produced condition.

  • Intergranular Corrosion Resistance of Stainless Steel Diffusion Bonding Joint with Amorphus Insert Metal Containing Boron

    Kazuhiro Ogawa, Shigeki Azuma

    pp. 534-538

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    DOI:10.2207/qjjws.12.534

    Abstract

    The intergranular corrosion resistance in the bonded joint of austenitic stainless steel by diffusion bonding with an amorphus insert metal containing 1.5 mass% boron was investigated to clarifiy the optimum bonding condition on which austenintic stainless steel pipes are joined using a high speed diffusion bonding system. The copper-copper sulfuric acid test was conducted to evaluate the intergranular corrosion of bonded joints to be caused by the chromium depleted zone. The joints bonded on lower bonding pressure and shorter bonding time conditions were more sensitive to intergranular corrosion. The precipitats of the chromium boride and chronium carbo-boride, which cause the selective corrosion, were observed at the bonding layer on such bonding conditions. On the contrary, the joints bonded on higher bonding pressure and sufficient bonding time condition had no intergranular corrosion or had scarcely precipitates at the bonding layer. The optimum bonding condition to prevent the intergranular corrosion was obtained as the bonding temperature at 1473 K, the bonding pressure higher than 9.8 MPa and the bonding time longer than 180 s.

  • Development of Insert Metal for Liquid Diffusion Bonding of Alloy 800

    Yoshikuni Nakao, Kazutoshi Nishimoto, Yosuyuki Fujiya

    pp. 539-546

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    DOI:10.2207/qjjws.12.539

    Abstract

    This report presents a new alloy-designing technique to develop the insert metal for liquid diffusion bonding. A mathematical programming method was developed by modifying the method in two dimensions proposed by I.P. Schagen into multi dimensions. The main procedure of this method is to obtain the optimum point to maximize some index of an objective performance by calculation from the limited experimental data using interpolation. An interpolating function which yields a curved surface passing on all the specified data points was determined assuming the values of data were normally distributed. If the curved surface is once obtained, its general view will give suggestions for further searches and the optimum point can be efficiently searched. This method has been applied for developing the insert metal for liquid diffusion bonding of Alloy 800. As for the candidate insert metals, alloys which had similar composition to that of Alloy 800, but contained some amounts of silicon, boron and carbon as the depressant elements were chosen. The objective function which was introduced as an index of the performance of insert metals involves the melting point, the strength (hardness) and formability of brittle phases in the bonding interlayer as the evaluating factors. Through calculation based on twenty three experimental date, a composition of Fe-20Cr-30Ni-1.5B-0.75C-4Si which optimized the objective function was determined. Scanning electron microscopic analysis revealed that the joint bonded with the newly developed insert metal (Fe-20Cr-30Ni-1.5B-0.75C-4Si) had a sound microstructure without forming brittle phases in the bonding interlayer. This joint also exhibited good tensile properties, that is, its strength and ductility were comparable to those of the base alloy.

  • Simple Measuring Methods of 3 Dimensional Residual Stresses in Bead-on-plate Welds

    Yukio Ueda, Ning Xu Ma

    pp. 547-553

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    DOI:10.2207/qjjws.12.547

    Abstract

    In this paper, very simple measuring methods of 3-dimensional residual stresses are proposed with the aid of distribution functions of inherent strains. In the simple measuring methods, inherent strain zones are predicted by newly proposed formulas based on the results of thermal elastic plastic FEM analysis, and a few of coefficients involved in distribution functions of inherent strains are estimated using measured elastic strains at some points. In the actual measurements, when a specimen T perpendicular to weld line is sliced from a welded plate, the method is called as simple T method. When measurements are done only on the surface of a welded plate, the method is called as simple surface method.
    With comparing residual stresses obtained both by thermal elastic plastic FEM analysis and by simple T method and simple surface method, the validity of proposed simple measuring methods is demonstrated.

  • Fucntion Expression for Inherent Strains in Fillet Welds and Its Accuracy

    Yukio Ueda, Ning Xu Ma

    pp. 554-560

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    DOI:10.2207/qjjws.12.554

    Abstract

    In this paper, three dimensional residual stresses due to single pass and multipass fillet welding are analysed by thermal elastic-plastic Finite Element Method. Then, inherent strain distributions produced in fillet welds are expressed by series function with good accuracy. Based on the results of series function, a very simple distribution pattern of inherent strains is proposed and described as functions which only has a few unknown parameters. To determine these parameters by experiments, required measurements will be greatly reduced.

  • Study on Production Mechanism of Welding Residual Stress at the Juncture of a Pipe Penetrating a Thick Plate

    Masahito Mochizuki, Kunio Enomoto, Noriaki Okamoto, Hideyo Saitoh, Eisaku Hayashi

    pp. 561-567

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    DOI:10.2207/qjjws.12.561

    Abstract

    This paper studies welding residual stresses at the intersection of a small diameter pipe penetrating a thick plate. The pipe is welded to the plate, and Tungsten Innert Gas (TIG) cladding is melted on the inner surface of the pipe to protect it from stress corrosion cracking due to long operation in nuclear power plants.
    Stresses are calculated by heat conduction analysis and thermal elasto-plastic analysis, and also measured by strain gauges. Welding residual stresses are shown to have no corrosive influence on the inner pipe surface, and the stresses are compressed enough to protect the pipe against stress corrosion cracking on the outer surface.
    It was also studied to make clear the production mechanism of the residual stresses which were generated by welding processes at the pipe.

  • Fracture Toughness Evaluation of Multipass Weld HAZ with Focus on Mechanical Mis-Matching Effect

    Fumiyoshi Minami, Yoshifumi Nakano, Shuichi Suzuki, Toyoaki Shiwaku, Yutaka Moriya, Yukito Hagiwara, Masao Toyoda

    pp. 568-574

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    DOI:10.2207/qjjws.12.568

    Abstract

    HAZ-notched CTOD tests have been conducted for multipass welds of high strength steels with SMYS 420 to 460 MPa for offshore structural use. The weld metal strength overmatch brings about different fracture behaviors depending upon the actual CGHAZ toughness. In the case that the CGHAZ is completely embrittled, the weld metal overmatch leads to lower bound critical CTOD value. This is due to the elevation of the local stress in the CGHAZ caused by the constraint effect by the overmatch weld metal. The fracture surface is generally flat and brittle fracture originates from the CGHAZ sampled by the fatigue crack front. Larger fraction of the CGHAZ along the crack front gives smaller critical CTOD value. On the other hand, in the case that the CGHAZ has moderate toughness, the weld metal overmatch can produce a higher critical CTOD value at brittle fracture initiation. This is attributed to the crack path deviation toward the base metal. The plastic strain accumulates preferably to a larger extent in the softer base metal side, before the critical stress condition for brittle fracture is attained at the CGHAZ. This asymmetrical plastic deformation promotes the deviation of ductile crack growth from the crack tip CGHAZ. In such a case, the critical CTOD value does not always reflect the CGHAZ toughness itself.
    Notch tip location much closer to weld metal sometimes causes fracture initiation at the weld metal even if the fatigue crack tip samples the CGHAZ. Such test data can not tell the real CGHAZ toughness.
    The meaning of critical CTOD value obtained in the test must be identified in the fracture toughness eveluation of the weld CGHAZ. This paper presents an evaluation procedure for CTOD test results of HAZ-notched welds taking the mis-matching effect into account.

  • Reduction of Thermal Stress in Tungsten/Copper Graded Composites

    Masashi Takahashi, Yoshiyasu Itoh, Masao Toyoda

    pp. 575-581

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    DOI:10.2207/qjjws.12.575

    Abstract

    A tungsten (W) /copper (Cu) graded material has been developed as a new material against high heat flux, for example, plasma, ion beam, electron beam and so on. The combination of these materials is based on high thermal resistance property of W and good thermal conductivity of Cu, and the reduction of thermal stress is performed in graded structure between W and Cu. A sintering and infiltration technique is proposed for fabricating the W/Cu graded composites. On the other hand, an establishment of material design technique is also very important to enhance a heat sink ability of the W/Cu graded composite. In this paper, temperature distribution and thermal stress properties of the W/Cu graded composite are examined, when it is used as a beam target against a high heat flux. Especially, the effect of W/Cu graded structure on the temperature distribution and thermal stress properties is discussed by analyzing a multi-layer structure model. It is shown that a maximum thermal stress is the smallest when the n-value, which is a index number in the equation {W(z)=W1(1-z/t)n, W (z) : W content in thickness z, W1: W content in surface, t : thickness of W/Cu graded zone}, is 0.5.

  • Relation between Ni Plating Condition and Joints Quality

    Hideaki Sasaki, Shinichi Kazui, Tatsumi Shibata, Ryosuke Morinari

    pp. 582-587

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    DOI:10.2207/qjjws.12.582

    Abstract

    Plarallel gap resistance welding of Ag plated 0.18mm diameter oxygen free copper wires to Au+ Ni plated of Printed circuit boards (P/B) was investigated (Concerning Ni Plating). The results are summarized as follows.
    (1) Fracture for watt's bath Ni plating circuit board after tensile strength test is Ductile fracture surface.
    (2) Fracture for Sulfamate Ni plating Circuit board is Brittle fracture surface.
    (3) Sulfamate Ni plating cause to Brittle fracture surface, by the reason of heating 500°C [773 K] (Tensil strength and Elongatio value decrease).
    (4) The origin of Brittle fracture is Sulfur (After heating 500°C [773 K] Sulfur of fine precipitates growth in grain boundary).
    (5) When Sulfamate Ni plating of electrical parts is used in heating process, we must take care of use.

  • Relation between Impurities (Au Plating) and Joints Quality

    Hideaki Sasaki, Shinichi Kazui, Tatsumi Shibata, Ryosuke Morinari

    pp. 588-590

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    DOI:10.2207/qjjws.12.588

    Abstract

    Parallel gap resistance welding of Ag plated 0.18 mm diameter oxygen free copper wires to Au+ Ni plated of Printed circuit boards (P/B) was investigated (concerning Au plating). The results are summarized as follows.
    (1) Au plating bath for Good Micro Welding is composed Cobaltion 0.35-3 gf/l [5.9-51 mol/m3] and Nickelion 0.02-0.5 gf/l [0.34-8.5 mol/m3], after Au plate it's composition of Co 0.2-3% and Ni 0.4-2% except Au :
    (2) Cobalt content and Nickel content beyond the allowable limit are Bad Welding for Au plating, they cause Blow hole in the weld fillet and decrease weld strength.

  • Reliability of Parallel Gap Micro Joints of Fine Wire to Solder Plated Printed Circuit Board

    Hideaki Sasaki, Shinichi Kazui, Tatumi Shibata

    pp. 591-599

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    DOI:10.2207/qjjws.12.591

    Abstract

    Parallel gap resistance welding of Ag plated 0.18 mm, 0.26 mm diameter oxygen free copper wires to solder plated printed circuit boards (Edge card for computer tape cable) was investigated.
    The Results are summarized as follows
    (1) Optimum welding condition was estabilished (gap of electrode, electrode wear and weld voltage).
    (2) Computer's tape cables have been produced by Automatic tape cable assemble line was producted computer's tape calbe.
    (3) Developed welding method gave sataisfactory results (5×108 weld points for 20 years were no trouble).
    (4) Quality control of parallel gap was estabilished (Purchasing parts Inspection, manufacturing quality control, improvent activites, shipment quality).
  • © 1994 JAPAN WELDING SOCIETY

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