Showing papers in "Quarterly Journal of The Japan Welding Society in 1985"
TL;DR: In this article, the maximum arc pressure at a base metal was investigated in GTA welding and it was shown that the pressure increases with a decrease in a vertex angle of an electrode and then the pressure decreases with the decrease in the angle less than 45°.
Abstract: Effects of an electrode geometry on the maximum arc pressure at a base metal were investigated in GTA welding.Results obtained are as follows;(1) The pressure increases with a decrease in a vertex angle of an electrode. But at the vertex angle of 45° the pressure has a peak value and then the pressure decreases with the decrease in the angle less than 45°.(2) When a shape of an electrode tip is treated a frustum of a cone, the pressure decreases and a vertex angle is not effective on the pressure. This fact suggests that the pressure is dependent on temperature distribution near an electrode tip.(3) Arc is more concentrative at the tip by such an arc characteristic that arc generates along the shortest path between an electrode and a base metal.On the other hand, temperature at an electrode tip becomes high and arc disperses to an upper part of the electrode from the tip. As these results, the pressure has a peak value about the angle of 45°.(4) When a diameter of an electrode increases, the pressure increases usually and such tendency is remarkable at the angle of 45°.This fact is understood that a rise of temperature near the tip is prevented and arc concentrates at the tip according to increasing the diameter.
19 citations
TL;DR: In this paper, the microstructure distribution in weld heat affected zone (HAZ) of multi-pass welded 60 kgf/mm2 class high strength steel was investigated.
Abstract: The characteristic of toughness in weld heat affected zone (HAZ) of multi-pass welded high strength steel was investigated in this study. In multi-pass HAZ, some kinds of microstructure are distributed and toughness can be affected by this microstructure distribution. Therefore, in this report, the distribution of microstructure in HAZ of multi-pass welded 60 kgf/mm2 class high strength steel was investigated.The main results obtained were as follows.(1) It was confirmed that HAZ was heated above the reverse transformation temperature once, twice or three times by weld thermal cycles. But it was found that the microstructure in HAZ could be almost simulated by single or double thermal cycles.(2) Peak temperature of weld thermal cycle could be divided into three regions according to its effect on microstructure. That is, (I) α-γ dual phase region, (II) low hardenability region and (III) hardenability recovered region.(3) Microstructure was relatively uniform in the outer and the intermediate part of HAZ. But, in the inner part (that is, near the fusion line), three kinds of microstructures were ditsributed.
17 citations
TL;DR: In this paper, the role of assist gas in CO2 laser welding has been discussed, and the optimum gas-assisting parameters have been determined to suppress plasma formation, and a role of the assist gas has been analized in CO 2 laser welding.
Abstract: Optimum gas-assisting parameters have been determined to suppress plasma formation, and the role of the assist gas has been analized in CO2 laser welding. Results obtained are summarized as follows:(1) When the assist-gas pressure p is higher than pp, which is slightly higher than vapor pressure or surface tension pressure the plasma formation is suppressed by forcing the vapor stream going up along the laser beam axis to eject along the rear wall of the cavity, providing increased penetration depth without weld defects. The value pp decreases with increasing laser power and decreasing welding speed. The fluctuation of the penetration depth tends to increase with increasing p, since the cavity diameter is enlarged by the vapor pressure which exeeds the value for the surface tension pressure to keep the cavity stable.(2) When p is too high, a lot of molten metal flowed out of the cavity closes the cavity entrance on re-entering into the cavity due to its large mass motion, providing humping bead containing large porosities.(3) The plasma formation is also suppressed effectively at vacuum pressure range 10-20 torr, providing deeper penetration depth without fluctuation of the penetration.
16 citations
TL;DR: In this article, a two-dimensional model for solid state bonding process is proposed, where the bonding process was achieved by four fundamental mechanisms: plastic deformation, creep deformations, interface diffusion and volume diffusion.
Abstract: A two-dimensional model for solid state bonding process is proposed. The bonding process is assumed to be achieved by four fundamental mechanisms: plastic deformation, creep deformation, interface diffusion and volume diffusion. The numerical analysis based on this model makes it possible to understand quantitatively the effects of temperature, pressure, bonding time, asperity of faying surface on the bonding process. Besides, it is possible to estimate the relative contributions of the four bonding mechanisms to the percent bonded area. It is found from the analysis that the deformation mechanisms tend to be dominant with increasing temperature. The tendency is striking under high pressures.
14 citations
12 citations
TL;DR: In this paper, the effect of the welding condition on the oxygen content and microstructure of weld metal has been investigated in the gas shield arc welding with SUS304 austenitic stainless steel base metal and JISY308L type electrod.
Abstract: In the gas shield arc welding with SUS304 austenitic stainless steel base metal and, JISY308L type electrod, the effect of the welding condition on the oxygen content and microstructure of weld metal has been investigated. Next, the effect of the oxygen on the mechanical properties, mainly on the fracture toughness, were studied. The main results are summarized as follows;1) The oxygen content of weld metal is increased with dicreasing the welding current (from 200A to 400A) and with increasing the arc voltage (from 20V to 30V). At the constant welding atmosphere, there is a linear correlation between the oxygen content and a parameter of A/V which is established by the authors, where A is welding current and V is arc voltage. The oxygen content decreases with increasing the parametre A/V.2) The most of the oxygen exists in the γ region as the spherical oxide of Mn-Silicate. The number of oxide per unit volumu is related to the welding heat input. The number decreases with increasing the heat input.3) Charpy impact values and Jin values decrease with increasing the oxide volume fraction.4) The relationship between Charpy impact value and oxide volume fraction is represented by linear line on the log-log cordinate. At the constant oxide voulme fraction, the distribution (number and size) of oxide has little effect to Charpy impact value.
12 citations
TL;DR: In this article, the effects of helium gas on the maximum arc pressure and on the critical travel speed to melt a base metal were investigated in GTA welding and it was shown that mixed He gas has a great influence on arc phenomena in a front of electrode tip, but it has little influence on an arc column.
Abstract: Effects of helium gas on the maximum arc pressure and on the critical travel speed to melt a base metal were investigated in GTA welding.Results were obtained as follows;(1) The critical speed in helium (He) gas arc is much higher than in argon (Ar) gas arc. Heat input per bead length at the critical speed in He gas arc is lower than in Ar gas arc. This fact is understood because distribution of a heat source in He gas arc is more concentrative than in Ar gas arc.(2) Electrode geometry is effective on the critical speed and especially the critical speed has a maximum value at a vertex angle of 45°, when a diameter of electrode is held constant.(3) The pressure in He gas arc is much lower than in Ar gas arc and is not sensitive to electrode geometry. This fact is understood because a spreading angle of arc current in a front of an electrode tip in He gas arc is smaller than in Ar gas arc.(4) When He gas is mixed into Ar shielding gas, generally the pressure decreases, but the critical speed is held constant. This fact shows that mixed He gas has a great influence on arc phenomena in a front of electrode tip, but it has little influence on an arc column.(5) When a few litter per minute of He gas is added to an upper part of an electrode tip through a nozzle in Ar shielding gas, the pressure effectively decreases to the degree of the pressure measured in He shielding gas.
12 citations
TL;DR: In this paper, the behavior of oxide film on void surface of the diffusion-welded interface has been investigated with Auger electron spectroscopy, SEM and EPMA.
Abstract: Behavior of oxide film on void surface of the diffusion-welded interface has been investigated with Auger electron spectroscopy, SEM and EPMA. Results obtained are summarized as follows.1.The oxide film of aluminum on the void surface did not disappear during welding. However, the oxide film of copper, iron and SUS 304 stainless steel disappeared, forming lumps of oxide on the void surface owing to spheroidizing of the oxide film, wheres the lumps of oxide was not observed on the free surface heated in a vacuum. On the other hand, the oxide film of titanium disappeared without forming lumps of oxide.2. Disappearance of the oxide film of copper, iron, SUS 304 stainless steel and titanium was owing to diffusion of the oxide film into the base metal.
10 citations
TL;DR: In this article, the surface composition and thickness of the welding surface of diffusion welds were investigated with Auger electron spectroscopy, and the relation between change of surface composition by diffusion welding and tensile strength of welded joints was investigated.
Abstract: The surface film of weld parts is a very important factor affecting the weld characteristics of diffusion welds. It is desirable to clarify the behavior of the surface film on the diffusion welded interface. In this study, the surfaces before and after diffusion welding were observed with Auger electron spectroscopy. Composition and thickness of the welding surface, and the relation between change of surface composition by diffusion welding and tensile strength of welded joints are investigated. The following results were obtained.1) The films of the welding surface of aluminum, copper, iron and SUS 304 stainless steel are composed of oxygen, carbon and base metal.2) Composition and thickness of the surface films of various materials do not so much depend on the surface treatment such as the degreasing with acetone and the annealing in a vacuum.3) The surface film along the welded interface of aluminum does not change during diffusion welding, but those of copper, iron and SUS 304 stainless steel disappear.4) When the surface film disappears during diffusion welding, metallic bonding is formed at intimate contact area along the welded interface. The stability of the surface film has an influence on tensile strength of welded joints.5) The segregation of sulfur is observed on no-contact surface along the welded interfaces of copper, iron and SUS 304 stainless steel, but it does not have much effect on tensile strength of welded joints.
9 citations
9 citations
TL;DR: In this paper, the two-dimensional model of bonding process proposed in our previous report (Part 1) was experimentally verified, using an oxygen-free copper as material for bonding tests.
Abstract: The two-dimensional model of bonding process proposed in our previous report (Part 1) was experimentally verified, using an oxygen-free copper as material for bonding tests. The boundary conditions in the bonding tests were settled in accordance with the two-dimensional model. The ranges of test conditions (bonding time, pressure and temperature) were determined by the numerical calculations. The experimental results are in good agreement with the calculated results. It is also found that the bonded interface (bond-line) does not migrate during bonding even if the percent bonded area roughly attains to 100%. It is, therefore, considered that the two-dimensional model proposed in Part 1 can be appropriate to actual solid state bonding process.
TL;DR: In this article, the authors used magnetic stirring in TIG welding of an Al-Mg-Mn alloy (5083) and SUS316, and studied the effects of magnetic field intensity and frequency and welding conditions on the solidification structures, hot cracking and blowholes in the welds.
Abstract: Aluminum alloys and stainless steels are used in the construction of many types of industrial equipment, but the welds in these materials are subject to micro-cracking and blowholes.In order to reduce such welding defects, the authors used magnetic stirring in TIG welding of an Al-Mg-Mn alloy (5083) and SUS316, and studied the effects of magnetic field intensity and frequency and welding conditions on the solidification structures, hot cracking and blowholes in the welds.The test results are summarized as follows:1) When aluminum alloys had a field intensity between 100 and 300 gausses and field frequency between 5 and 10 Hz and stainless steels had field intensity between 200 and 300 gausses and field frequency between 1 and 5 Hz, the magnetic stirring reduces the grain size. The combined effects using the pulse arc were also observed.2) Under the conditions in 1), the columnar structure disappeared. This contributed to the reduction of hot cracking.3) The magnetic stirring released gas from the molten metal, and as a result, reduced the occurrence of blowholes.
TL;DR: In this article, the effects of welding conditions and the nitrogen partial pressure on the nitrogen content of stainless steel weld metal were systematically studied. 20Cr-10Ni stainless steel was welded in N2 and N2-Ar atmospheres at 1-30 atm pressures.
Abstract: 20Cr-10Ni stainless steel was welded in N2 and N2-Ar atmospheres at 1-30 atm pressures. Effects of welding conditions and the nitrogen partial pressure on the nitrogen content of stainless steel weld metal were systematically studied. The results are summarized as follows:(1) In the nitrogen welding atmosphere, the nitrogen content of the weld metal decreased with increasing the welding current and increasing the travel speed, and with decreasing the arc voltage.(2) In the nitrogen welding atmosphere, the nitrogen content of the weld metal increased with the nitrogen pressure, but the nitrogen absorption of the weld metal does not obey the Sieverts' law.(3) In N2-Ar welding atmosphere, the nitrogen content of the weld metal was lower in high atmospheric pressure than in low pressure at the same nitrogen partial pressure.(4) Using thermodynamic data obtained by equilibrium study, the nitrogen absorption into the stainless steel weld metal in the nitrogen atmosphere of high pressure was discussed.(5) All stainless steel weld metals had no porosity.
TL;DR: In this article, the effects of the morphology and composition of nickel-base interlayers on the transient liquid phase diffusion weldability of superalloy Inconel 713C have been investigated by microscopy, electron probe microanalysis and high temperature strength tests of the joints.
Abstract: Effects of the morphology and composition of nickel-base interlayers on the transient liquid phase diffusion weldability of superalloy Inconel 713C have been investigated by microscopy, electron probe microanalysis and high temperature strength tests of the joints.Proper composition adjustment, powder refinement and homogenization of the interlayers were indicated to be both important for the improvement of the weldability. Especially in amorphous interlayers made by the rapid quenching liquid metal method, the composition homogeneity which contributes to easy homogenization of the joints was fairly improved without segregation of molybdenum and hafnium. Additionally, in case of using amorphous interlayers, the thickness of liquid layer formed at the joint interface during welding was revealed to become thinner compared with the case of using powdered interlayers, so that the isothermal solidification of the liquid phase could occur more rapidly. These phenomena were demonstrated to result in increasing the joint strength, and some of the joints showed 100 percent joint efficiency in stress-rupture tests.
TL;DR: In this paper, the effects of welding parameters and wire compositions on the droplet transfer of CO2 arc welding by flux-cored wire, have been examined by means of photograph by a high speed camera.
Abstract: The effects of welding parameters and wire compositions on the droplet transfer of CO2 arc welding by flux-cored wire, have been examined by means of photograph by a high speed camera.As the welding current and the argon content in CO2 shielding gas are increased, the droplet transfer becomes more preferable; the average droplet diameter decreases and the transfer frequency increases.The wire cross-sectional shape has almost no influence on the droplet transfer. Increase of flux percentage in wire is effective in the improvement of the droplet transfer.As the increase of TiO2, Fe-Si and Al2O3 or the decrease of CaF2 content in flux, the droplets become smaller and transfer more frequently. The effect of iron powder and Fe-Mn content is almost none. These variations of droplet transfer can be mainly explained by the repulsive force of slag vaporization in the droplet suspended at the tip of the wire.
TL;DR: In this paper, the theory of thermal elastic analysis based on the finite element method has been used for diffusion bonding between dissimilar materials which have the marked difference in coefficients of thermal expansion, diffusion bonding of WC-Co hardmetal to steel has been carried out.
Abstract: As a basic research of diffusion bonding between dissimilar materials which have the marked difference in coefficients of thermal expansion, diffusion bonding of WC-Co hardmetal to steel has been carried out.Thermal stresses generated as a result of the difference in the coefficients of thermal expansion of the hardmetal and the steel during the cooling of bonded parts have been estimated by. the theory of thermal elastic analysis based on the finite element method. Tensile strengths of the bonded joints have been also discussed on the effects of thermal stress, interlayer thickness and cooling rate after bonding.It is found from the result of the calculation that a maximum tensile stress is generated on the surface of the bonded hardmetal. Therefore, the bonding strength seems to be lowered by the thermal stress.The use of an interlayer affected the bonding strength. The bonding strength increased through a maximum at 0.25 mm thickness of the interlayer then decreased with increasing the thickness. The improvement of the bonding strength is due to the decrease of the thermal stress.The bonding strengths were improved at faster cooling rates than 13°C/min. The improvement of the bonding strength was interpreted by the decrease of the thermal stress whihc is due to the expansion of the bonded steel caused as the result of the martensite transformation during cooling.
TL;DR: In this paper, the effect of yield ratio of material used on structural performance and the possiblity of making low-yield-ratio HT80-class steel was investigated.
Abstract: The objectives of the present paper is to clarify the effect of yield ratio of material used on structural performance and to consider the possiblity of making low-yield-ratio HT80-class steel. Mechanical analyses on deformations of typical structural elements have been conducted to determine the appropriate condition of yield ratio of materials. Based on the analysis of plastic deformation of dual-phased structure steel, consideration has been carried out of the making process of low yield ratio HT80 by using the same kind of steel as the conventional QT-HT80.The decrease of yield ratio is effective procedure for increasing deformability of structural element. In HT80 steel, controlled rolling and on line accelerated cooling process followed by quenching from α+ γ phases is a proper treatment for obtaining low-yield-ratio steel with dual-phased structure in which martensite structure includes a certain fraction of lower strength ferrite.
TL;DR: In this paper, the side-groove Charpy tests were used to evaluate fracture transition temperature vTS of weld metal/HAZ of EB-welds and the absorbed energy vE versus temperature T relations of welds were arranged uniquely by using the relative temperature parameter (T-vTS).
Abstract: The purpose of the present study is to conduct the consideration on V-notch Charpy characteristics of HT80 electron beam welds which have remarkable hcterogeneity, by using side-groove Charpy tests developed in this study. Two kinds of 800 MPa class high tensile steels were used and three kinds of heatinput conditions of electron beam welding were selected. Both standard V-notch Charpy specimen and Charpy specimen with deep-both-side groove, 3 mm deep, were used.The fracture path of electron beam welds which have considerable heterogeneity does not necessarily select the net section of standard V-notch Charpy specmien. For that case, the evaluation method proposed newly in the present paper is effective to evaluate fracture transition temperature vTS of weld metal/HAZ of EB-welds.The absorbed energy vE versus temperature T relations of welds should be arranged uniquely by using the relative-temperature parameter (T-vTS). Although the evaluation of absorbed energy of HT80 EB-welds by standard V-notch Charpy tests is impassible due to remarkable heterogeneity in strength, the evaluation method using side groove Charily tests and the absorbed energy vE versus (T-vTS) curve proposed newly gives the reasonable results from the engineering sense.
TL;DR: In this article, a joining of plain carbon steel (SS41) to alumina or mullite using copper filler metal was made in a slightly oxidizing atmosphere, and the joining strength was determined by fracture shear loading.
Abstract: Joining of plain carbon steel (SS41) to alumina or mullite using copper filler metal was made in a slightly oxidizing atmosphere. Joining strength was determined by fracture shear loading. The liquid copper wetted both alumina and steel during joining, and a strong joining was formed after cooling down. The strong bond is attributable to the formation of hercynite (FeAl2O4) at the interface between copper and α-alumina. The use of this joining provides various type of joints such as alumina/steel tee joint and alumina butt joint strapped with steel.
Journal Article•
TL;DR: In this article, the effect of welding factors on the critical stress for LME-cracking of steel was examined and the behavior of thermal stress and residual stress during dipping in the molten zinc that cause the crack in steel structure was analyzed.
Abstract: In previous report, the effect of welding factors on the critical stress for LME-cracking of steel was examined. In addition, because of preventing the crack, it is necessary to study the behavior of thermal stress and residual stress during dipping in the molten zinc that cause the crack in steel structure.In this report, the distribution of temperature and thermal stress during dipping simple plate and pipe in the molten zinc were analyzed. The results are as follows.(1) Maximum tensile thermal stress, (σt)max occurred at the lower side of plate and pipe, and causedLME-cracking at this position.(2) (σt)max increased as plate width is large and plate thickness is small. And (σt)max increased as pipe diameter is large.(3) For the plate and pipe, (σt)max increased as dipping velocity is small.
TL;DR: In this article, a back bead width control system has been proposed to stabilize the process of one side FCB SAW in which a stationary copper backing plate covered with a flux layer of several milimeter thickness is used as backing.
Abstract: A possibility of a back bead width control system have been proposed to stabilize the process of one side FCB SAW in which a stationary copper backing plate covered with a flux layer of several milimeter thickness is used as backing.When a stable welding process is maintained under an adequate welding condition, a signal voltage between the backing copper plate and the plate being welded have beeen detected. The polarity and phase of the detected voltage having a few volt level is well corresponding to those of the arc voltage in case of AC current welding.In a stable FCB SAW process, the back side bead is mostly formed by a key-hole action of the arc. It is assumed for the reason that the arc penetrates through' the welding groove and the flux layer, then it contacts the copper plate and is reflected to the welding plate. The correlation between the detected voltage level and the back side bead width is recognized.The similar phenomenon is observed in a key-hole welding by using a transfer type plasma arc welding.In order to maintain the back bead width constant the detecting voltage is compared with a reference voltage, and then the welding current is controlled by the difference of the above voltages.
TL;DR: In this article, the processes of ductile fracture of Type 304 stainless steel weld metal specimens, which are cut from weldments produced by using four types of welding condition, are observed.
Abstract: The processes of ductile fracture of Type 304 stainless steel weld metal specimens, which are cut from weldments produced by using four types of welding condition, are observed. Although quite few large voids are observed at a relatively low strain level, they have no important role in fracture processes. As soon as micro-voids nucleate at some strain level, which is the stage just before final fracture, they rapidly grow and coalesce. The volume fraction of micro-inclusions which are nuclei of micro-voids, seems to control true fracture strain of weld metal specimens.
TL;DR: In this article, the authors applied FEM analyses to calculate deformation behaviors under tension of two kinds of cracked plates: L-type specimen in which crack is perpendicular to the joining surface and P-type sample in which cracks are parallel to the ioinine surface.
Abstract: Considerations have been conducted fundamentally on stresses·strains controlling parameter of cracked plate joined with two dissimilar materials, especially of which yield strengths are different each other, that is σIY, σIY. Attention mainly is paid to the joined plate with a crack of which tip, exists in the vicinity of joining surface of dissimilar materials. FEM analyses are applied for calculation of deformation behaviours under tension of two kinds of cracked plates: L-type specimen in which crack is perpendicular to the joining surface and P-type specimen in which crack is parallel to the ioinine surface.Mechanical heterogeneity remarkably influences on stresses.strains in the vicinity of the crack tip when plastic deformation spreads beyond the joining surface. On the analogy of linear elastic fracture mechanics theory, the parameter, F, which controls stresses. strains in the vicinity of the crack tip has been proposed. By using two parameters; strength ratio of two materials, Sr(=σIIY/σIY, and F[=σG/σIY)·√c/d], characteristics of stress.strain distributions of two kinds of cracked plates can be classified.