Copper to copper lap joint was made by the resistance heating, applying pressure simultaneously. The copper plate was pre-soldered and the alloyed layer was pre-formed by using Pb-50Sn solder and then joint mechanism of press-soldered joints was analyzed. The reason of enhancing strength and heat resistance heated by applying voltage in press-soldered joints is summarized as follows. (1) Solder composition turns to Cu-Sn alloy composition. (2) Joint layer with higher melting point was formed in which Cu increases and Sn decreases. (3) In terms of the crystal structure, Cu3Sn, Cu6Sn5 and Cu(α) phases turns to Cu41Tn11 and Cu(α) phases which have high heat resistance.
This study has been conducted to obtain more improved high manganese steel than A-T and B-T which were investigated in the previous paper. Then, tensile and impact properties at cryogenic temperature of three kinds of high manganese steel, AS (17Mn-12Cr-4.5Si), BV (21Mn-6.3Cr-3.4Si-0.19N) and CT (25Mn-6.5Cr-4.5Si), and their electron beam welded joints were examined by using tensile and instrumented Charpy impact testing apparatus. From the view points of ultimate tensile strength, elongation and total absorbed energy at cryogenic temperature, CT is far better than A-T and B-T, and can be considered as an improved high manganese steel.
Generally, in TIG arc welding method, the ratio of penetration depth (D) to bead width (W) is small and the deep penetration cannot be obtained comparatively. But in the case of using the stationary TIG arc when the welding conditions were set to the suitable range, the value of D/W is closer to unity and the penetration depth becomes deep. Paying attention to the above mentioned phenomenon, the authors have made researches into the practical application of the stationary TIG arc. In this paper, the welding conditions which we obtained from the above mentioned penetration forms were investigated using SUS304. It was found out that when suffer (S) content of the base metal is more than 0.005 mass%, both the method of using the electrode with at vertex angle above 60° or with in argon shielding gas and the method of using helium to shielding gas are successful to increase the penetration depth. In the case of using the base metal which contains sulfer about 0.001 mass%, the method of using the tip-cutting electrode in argon shielding gas is more effective for same purpose.
In this study, the effects of the bonding conditions and the postheat treatment on the bondability of the joints of molybdenum to titanium have been investigated. Results obtained are summarized as follows; 1) In case of the joint of molybdenum to titanium, the diffusion layers formed on bonded zone were both a phase and α+β phase. Kirkendall effect was observed at the bond interface between molybdenum and titanium, and the voids were formed in diffusion layer. 2) The joint strength of the joint of molybdenum to titanium depended on the bonding temperature and the maximum joint strength of 440 MPa was obtained at 850°C for the bonding time of 1 ks and 1.8 ks, and tension fracture occurred in titanium base metal. However, the joint strength decreased as the bonding temperature became higher. 3) When joints having the maximum joint strength were heated at 700°C, the joint strength was not affected by the heating time up to 72 ks. However, it decreased with the increase of holding time at 900°C and 1000°C. 4) Rotating bending fatigue limits of the joints of Mo/Ti, TZM/Ti, Mo/Ti-6Al-4V and TZM/Ti-6Al-4V were the value of 40%-50% of each joint strength.
Recently, ductile nickel base brazing foil has been prepared by a rapid solidification technology. So that it seemed that the brazing, which used the ductile nickel base brazing foil, is more effective method for joining having a large joining area than the brazing which used the powder form nickel base brazing filler metal. Therefore it has seemed that the brazing, which used the nickel base brazing foil, has been effective method for producing of the clad materials. In this study, the clad material which have been brazed the nickel base heat resistant alloy; Inconel 600 on the mild steel; SM400B has been tried producing by the brazing using the four types of nickel base brazing foils. The brazeability was estimated by the mechanical properties, microstructures and the distributions of the elements which were investigated with a SEM and a EPMA examination. The sound joint was obtained for all of brazing conditions in this study. The shear strength of the specimen was increased by increasing brazing time and temperature. About 310 MPa was obtained as the maximum shear strength for every brazing foil. The shear strength was influenced by the cross-sectional microstructures at the brazed joint. According to the cross-sectional microstructures and the elemental distributions, when the eutectic structure concentrating Cr and B was formed in the brazed joint, the shear strength was increased by decreasing this eutectic structure.
Considerable papers which experimentally examined the effect of residual stress on the brittle fracture strength of weldment have been published. The effect of stress-relieving on the brittle fracture strength has been experimentally examined too. In those papers, the residual stress distributions were measured by the stress-relaxation method, assumed as a simple curve and represented by a simple function. There have been, however, few analytical works concerned with stress and strain near a crack in the residual weld stress field. In the present study, an as-welded plate and a welded plate stress-relieved mechanically are dealt with. Each of them has a through-thickness center crack perpendicular to the welding bead. The crack initiates after welding or after stress-relieving. The residual stresses due to welding and those after stress-relieving by the uniform pre-straining are measured by means of the ultrasonic technique, because, from a practical point of view, the residual stress should be measured nondestructively. A uniform tensile load perpendicular to the crack is applied to the plate. Stress, strain, plastic zone near a crack and crack opening displacement are examined by elasto-plastic finite element analysis as well as experiment. Considering the residual stresses distributed after pre-cracking, the deformation near the tip of a crack in a plane stress field are analyzed. The effect of residual stresses and that of stress-relieving on the deformation near a crack are revealed. The tensile residual stress around a crack tip contributes to the increase of stress, strain, plastic zone size near the crack and crack opening displacement. The stress-relieving contributes to the increase of fracture strength of welded plate.
In order to investigate the corrosion properties of Ni alloys after nitriding treatment, tentative Ni binary alloys of Ni-7 wt%Ti, -15 wt%V, -10 wt%Nb, -20 wt%Cr and -30 wt%Cr and Ni ternary alloys of Ni-7 wt%Ti-2 wt% (V, Nb, Ta, Cr, Mo or Al) and Ni-20 wt%Cr-2 wt% (Ti, V, Nb, Ta, Mo or Al) were nitrided by means of PIN process under the condition of 873 K (823 K at Ni-30 wt%Cr), 10.8 ks, N2+H2 mixed gas atmosphere of 800 Pa. Corrosion properties of tentative Ni alloys were determined in an acid solution (30°C, 5%H2SO4) by means of potentiodynamic polarization methode. Pure nickel and austenitic stainless steel; SUS304 were also used as reference materials. Tentative Ni alloys showed better corrosion resistance then pure nickel before PIN treatment. PIN treatment resulted in a slight deterioration of corrosion resistance of tentative Ni alloys. Comparison of corrosion resistance of Ni alloys and SUS304 after PIN treatment, deterioration of corrosion resistance of Ni alloys were slighter than SUS304. Pitting and intergranular corrosion were observed in nitrided Ni binary alloys excepted Ni-Cr alloys and Ni-7 wt%Ti-X ternary alloys. Separation of nitrided layer occured in nitrided Ni-Cr binary alloys. Taking into consideration of corrosion properties of each tentative Ni binary and ternary alloys after PIN treatment and hardening behavior of their alloys by PIN treatment, it seemed that Ni-7 wt% Ti binary alloys and Ni-7 wt%-X and Ni-20 wt%Cr-X ternary alloys were most benefitial Ni alloys for using after PIN treatment.
In an oxidizing gas welding atmosphere of Ar-O2, Ar-CO2 or CO2-O2 gas mixture, oxygen absorption behavior by steel weld metal has been investigated metallurgically, using a popular Fe-Si-Mn electrode wire and two types of base metal, that is, pure iron and rolled steel for welded structure. As an addition of oxygen to argon-based mixture, the oxygen content in steel weld metal extremely increases and the losses of alloying elements such as silicon and manganese steadily increase. As an addition of carbon-dioxide to argon-based mixture, the oxygen content in steel weld metal increases somewhat and limited amount of alloying elements losses. As an addition of oxygen to carbon-dioxide-based mixture, only a little amount of oxygen is absorbed into the steel weld metal. Despite the active gas of CO2 instead of Ar adds into the welding atmosphere, unexpectedly, the oxygen content of steel weld metal under CO2-O2 is lower than that of the weld metal under Ar-O2 for the same oxygen partial pressure over the range of 0.01 MPa. The losses of alloying elements are not so significant in this atmosphere.
In an oxidizing gas welding atmosphere of Ar-CO2-O2 gas mixture, oxygen absorption behavior by steel weld metal has been investigated metallurgically, using a popular Fe-Si-Mn electrode wire and two types of base metal, that is, pure iron and rolled steel for welded structure. The oxygen content in steel weld metal is controlled by the partial pressure of oxygen, and the partial pressure of carbon-dioxide has the both different effects of gain and decrease of the oxygen content. The silicon and manganese contents in steel weld metal depend on the degree of deoxidation reaction. Thus, the more the oxygen in steel weld metal, the less the silicon and manganese content. The carbon content in steel weld metal decreases as the result of the deoxidation reaction and increases depending on the absorption of carbon from the CO2 in welding atmosphere. Finally, the diagram of oxygen, silicon, manganese and carbon cuntent of steel weld metal have been produced as the function of the ternary welding atmosphere of Ar-CO2-O2.
Pure iron plates were welded using Fe-Cr alloy electrode wires in a controlled arc atmosphere. The effect of chromium on the oxygen content and non-metallic inclusion in the weld metals were investigated under various welding conditions in Ar-O2 welding atmosphere. The oxygen content of Fe-Cr weld metal increases with increasing the partial pressure of oxygen and decreases with increasing chromium content in the weld metal. The non-metallic inclusions are mainly chromium oxide. The composition of the non-metallic inclusion in the Fe-Cr weld metal takes various form of FeCr2O4, Cr3O4, CrO2 and CrO depending on decreasing oxygen content and increasing chromium content of the weld metal. The behavior of the oxygen absorption by Fe-Cr weld metal is discussed using thermodynamic data.
Fe-Cr-Ni alloys were arc-melted and GTA-welded at a nitrogen gas atmosphere with various conditions, in order to study effects of chromium and nickel on the nitrogen absorption of ternary iron alloy during arc-welding. The nitrogen content of arc-melted alloy decreased with an increase of arc-current, and the tendency was marked in high chromium and low nickel alloys. Nitrogen content diagrams in the ternary system of Fe-Cr-Ni where each alloy content is less than 30% were obtained by arc-melting and GTA-welding. The nitrogen absorption of Fe-Cr-Ni alloy during arc-welding was thermodynamically discussed comparing with arc-melting and equilibrium data at equivalent tempera-tures.
Crack Tip Opening Displacement (CTOD) properties in HAZ of 490 N/mm2 class steels were investigated from viewpoint of Al content in steel. The C-Mn microalloyed steels with Al content of 0.015 and less than 0.001 mass% were selected in this study. The critical CTOD property in HAZ of low Al content steel was more excellent than that in HAZ of conventional Al content steel. The microstructure in HAZ of low Al content steel mainly consisted of fine ferrite. On the other hand, the microstructure in HAZ of conventional Al content steel consisted of upper bainite with M-A constituent. Ferrite formation in low Al content steel was easier than that in conventional Al content steel at usual cooling rate during welding, because the region of ferrite formation was shifted to a higher cooling rate at low Al content. In HAZ of conventional Al content steel, M-A constituent formation is easy due to the suppression of ferrite formation because of the decrease in interfacial energy between γ and α. This is base on condencing the carbon atoms in γ side of γ/α interface due to delaying the diffusion rate of carbon atoms in γ region. From these results, the effects of low Al content on the improvement of the critical CTOD property in HAZ are affecting the transformation behaviour through promoting the diffusion of carbon atoms, resulting in fine ferrite microstructures without M-A constituent.
In an oxidizing gas welding atmosphere of Ar-O2, Ar-CO2 or CO2-O2 gas mixture, mechanical properties of steel weld metal such as ultimate tensile strength and Charpy impact property have been investigated, using a popular Fe-Si-Mn electrode wire (YGW 12) and rolled steel for welded structure (SM 400B). As an addition of oxygen to argon-based mixture, both the tensile strength and toughness tend to decrease. As an addition of carbon-dioxide to argon-based mixture, the tensile strength decreases and then improves, and impact property reveals complex behavior. As an addition of oxygen to carbon-dioxide-based mixture, changes in atmospheric gas composition have a minor effect on the mechanical properties of steel weld metal.
In an oxidizing gas welding atmosphere of Ar-CO2-O2 gas mixture, mechanical properties of steel weld metal such as ultimate tensile strength and Charpy impact property have been investigated, using a popular Fe-Si-Mn electrode wire (YGW 12) and rolled steel for welded structure (SM 400B). The diagrams of ultimate tensile strength and impact property of steel weld metal have been produced as the function of the ternary welding atmosphere of Ar-CO2-O2. The ultimate tensile strength is high at the argon and carbon-dioxide rich gas mixture, and decreases as the partial pressure of oxygen increases. The ultimate tensile strength is governed principally by alloying content. The impact property improves at the optimum gas compositions of a little amount of oxygen and carbon-dioxide addition to argon. The impact property is controlled by a number of factors such as microstructure and non-metallic inclusion etc.
In this study J-integral of interfacial crack in the bonded joint which was composed of the materials with different mechanical properties was studied by finite element method. J-values of two types of bonded joints under the uniformly tensile stress and the three-point bending load were studied. One type was the bimaterials joint, in which the material B was bonded directly to the material A, and the other type was the trimaterials joint, in which the material B was bonded to the material A by using the insert material C. The obtained results were as follows; (1) It was clarified that the normalized J-values of bimaterials joint, J/JA=B, were able to be determined only by the ratio of Young's modulus of both materials, EA/EB, and J-values were hardly affected by Poisson's ratio. JA=B was the J-value of same material joint. (2) J-values of trimaterials joint were affected by the thickness of insert materials, d, and the ratio of Young's modulus of each materials, EA/EB and EC/EB. The equation for calculating J-values of trimaterials joint under any loading condition was derived as shown as the next equation. (J/Ja) -1/(Jc/Ja) -1=(d/d0)0.5 where Ja: J-integral value of bimaterial (material A and material B) Jb: J-integral value of bimaterial (material C and material B) d0: Ligament length d: Thickness of insert material
In recent years, the orthotropic steel deck bridges have been constructed at many places due to numerous merits. And the automatic fabrication of them have been forwarded. However, a noticeable increase in recent heavy through traffic has accelerated the fatigue damages at the connections between longitudinal and crossing member due to the existense of slits. In order to improve the fatigue strength of them considering automatic welding, F.E.M. analysis and large scale fatigue testing were carried out. As the results of this study shows, the details of the slit can be improved considering automatic welding and improvement of fatigue strength. (1) The upper width of slit is narrower than ordinary shape. (2) The upper scallop can be removed. (3) Boxing weld between upper flange and web can be removed. (4) The fillet weld between longitudinal rib and web plate is stopped about 20 mm before the web edge. (5) The fillet welds between longitudinal rib and upper flange should precede the other welds.
In CO2 laser cutting Si3N4 and A12O3 ceramics, temperature distribution was measured at various cutting speeds, assist gas pressures and laser powers, and cutting mechanism was discussed. Results obtained are summarized as follows; (a) At given cutting speed, the temperature at cutting front was constant from top to bottom surface. The temperature increased with increasing cutting speed, and was independent of laser power and assist gas pressure. (b) From the slope of an Arrhenius plot, an activation energy was found to agree well with bond energy of Si-N and Al-O for Si3N4 and Al2O3, respectively, which shows that cutting speed is dominated by thermal decomposition rate of ceramics. (c) High pressure N2 gas due to decomposition of Si3N4 blew the liquid Si layer off.