Water-calorimetric measurements of absorption efficiencies in CO2 laser beam welding of mild steel plates were made. In this study, the same measurement method was used to measure absorption efficiencies of heat in TIG-DCEN arc welding, electron beam welding in a high vacuum and CO2 laser beam welding. Improvements were applied to the welding jig and the measurement system used in the previous report No. 1. The absorption efficiencies for TIG arc welding and EB welding agreed with reported values in the literature. The values of absorption efficiency for CO2 laser beam welding of mild steel specimen in bead-on-plate welding are changeable with welding conditions but generally in the range of 72-87%.
In this study we have tried to produce TiNi intermetallic compound spray coating on aluminium substrate using a composite wire of titanium wire (φ300μm) and nickel wire (φ300μm). The composite wire was melted by using CO2 laser in an atmosphere of argon gas and atomized and coated on the aluminium substrate by a high pressure argon gas. Effects of spray conditions on porosity of coating layer were investigated. Wear resistance of the coating was also evaluated by using an Ohgoshi wear tester. It was possible to produce TiNi intermetallic compound layer using a composite wire by a laser reactive spraying method. 100% TiNi intermetallic compound was found from the X-ray diffraction analysis of coating layer. As the spray distance increased from 50 mm to 200 mm and the atomize gas pressure decreased from 392 kPa to 196 kPa, the porosity of coating layer decreaced. A porosity of 5% was obtained at the spray distance of 200 mm and the atomize gas pressure of 196 kPa. The wear resistance of the coating increased by about ten times than that of aluminiun substrate.
Recently, the concept of "Manufacturing System" is strongly paid to attention in various kinds of industries. This concept is that all the design and manufacturing elements should be considered as one system to produce the products more efficiently. By such a change in industries, new development is demanded to the welding. That is, to promote the systematization and the computerization of the welding. In this paper, two kinds of models are introduced to achieve the systematization and the computerization of the welding. One is "Welding Operation Model". "Welding Operation Model" is an information model by which information to execute the welding operation is expressed statically. By the data conversion of "Welding Operation Model", various information for welding facilities can be offered. Another is "Process Model for Welding Operation Growth". In this model, the relations between various design/manufacturing information and welding information are regularized, and the flow and the mechanism to generate welding information are described. By the use of these two models, welding information can be generated efficiently in manufacturing system. Moreover, based on these considerations, prototype system for generating welding information is developed. This system is shown at the end of this paper.
The diffusion-bondability of A6061 aluminum alloy to SUS316 stainless steel was improved by using Ag insert metal. Diffusion bonding of A6061/SUS316 was carried out at 758-848 K for 0.3-12.0 ks applying 9.8 MPa in vacuum. Ag insert metal was electroplated on SUS316 stainless steel following the uderplating of Ni prior to diffusion bonding. The thickness of Ag insert metal was varied between 0.5 and 3μm. The contour maps of joint strength were obtained through the mathematical calculation by using interpolation method. The maximum joint strength of 130 MPa was presumed when the thickness of Ag insert metal was 1μm and the bonding condition was 795 K×1.0 ks. The safety margins of bonding conditions where the sound joint strength was maintained were clearly enlarged by using Ag insert metal compared with direct-diffusion bonding, although the maximum value of joint strength became slightly below that in direct-bonding. Microstructural analyses revealed that the reaction layer consisted of Al-Ni and/or Fe-Al intermetallic compounds were formed at the A6061/SUS316 interface, and that Ag insert metal mostly diffused away into A6061 base metal at the optimum bonding condition.
The formation of chromium depleted zone due to the precipitation of chromium carbides along grain boundaries in weld metal of Type 308 stainless steels with δ-γ duplex structure was theoretically analyzed in this study. The kinetics theory of grain boundary precipitation, which was developed by modifying the nucleation and growth theory proposed by Johnson, was applied to the theoretical analysis to predict precipitation of chromium carbides at grain boundaries. Profiles of chromium concentration adjacent to grain boundaries were analyzed by using a two-dimensional finite difference method which included the impinging effect of the chromium profile along grain boundaries. Calculation of nucleation time showed that precipitation of chromium carbides in δ/γ boundary occurred faster than that in γ/γ boundary. Numerical analysis for the chromium distribution around chromium carbides revealed that chromium depleted zone in t grain side of δ/γ boundary increased much faster than in γ grain side. It was also indicated that the continuous network of chromium depleted zone along δ/γ boundaries formed in shorter time than in γ/γ boundary. Thus provided that the δ/γ boundary was linked continuously in weld metal, serious intergranular corrosion and intergranular stress corrosion crack may take place in weld metal in much shorter time.
The purpose of the present study was to investigate the effect of grain size on HAZ cracking susceptibility of cast alloy 718. Three kinds of base metals with three different levels of grain size were used. HAZ cracking susceptibility has been evaluated by using Spot-Varestraint test at four different strain levels. It was found that HAZ cracking susceptibility was dependent on the grain size. The length of HAZ cracking decreased with decreasing the grain size. According to Isothermal Liqaution test, smaller grain size reduced the ratio of grain boundary liquation. Microscopic observation revealed that the percentage of Laves cluster on the grain boundary was decreased with decreasing the grain size. On the basis of these results, the improvement of HAZ cracking susceptibility by smaller grain size was considered to be attributed to the reduction of Laves cluster on grain boundary.
The purpose of this study is to clarify the effect of homogenization heat treatment on HAZ cracking susceptibility of cast alloy 718. Homogenization heat treatment was conducted at 1368 K and 1378 K with varying holding time. HAZ cracking susceptibility was evaluated using Longitudinal -Varestraint test at three different strain levels. The test results showed that the number and length of cracks decreased by homogenization heat treatment. HAZ cracking susceptibility was found to be most improved at the heat treatment condition of 1378 K×10.8 ks. According to the isothermal liqaution test, grain boundary liquation was suppressed in heat treated samples. Microscopic observation indicated that the number and size of Laves cluster on the grain boundary decreased by homogenization heat treatment. On the basis of these results, the improvement of HAZ cracking susceptibility by homogenization heat treatment was considered to be attributed to mainly the reduction of Laves cluster on the grain boundary.
The static and fatigue strengths of ultrahigh-strength steel sheets and ultrahigh-strength steel sheet and lower-strength steel sheet joined by spot welding were investigated. The tensile shear strength of the joint of ultrahigh-strength sheets was lower than the estimated value calculated by estimate equations with the increase in the tensile strength of the base steel, because of the existence of the heat affected zone strength of which was relatively lower than that of the base steel. The tensile shear strength of the joint of ultrahigh-strength sheet and lower-strength sheet depended on the tensile strength of the lower-strength steel. The fatigue strength of the tensile shear mode did not depend on the tensile strength of the base steel. It showed almost a constant value with a change of tensile strength of the base steel. The fatigue strength of the cross tension mode is showed the same tendency as the case of the tensile shear mode. The fatigue strength of the bending mode also showed the same tendency. The fatigue strength did not change with the change of tensile strength of base the steel. But the appearance of fractures were different from each other. Cracks propagated into the ultrahigh-strength side in the case of the tensile shear mode and cross tension mode, but in the case of the bending mode they propagated into the lower strength side.
In The Great Hanshin-Awaji Earthquake Disaster, brittle fractures with plastic strain were observed in beam-column connections of steel building frames. It is considered that the mechanical properties of weld metal, especially the ductility of weld metal, have a substantial effect on the fracture. In this paper we describe bi-axial loading test results using cruciform butt specimens under monotonic loading. The specimens are modeled on a cruciform joint by taking out the part of the beam-flange to column-flange connection and welded by two types of welding consumable. So we use two series of specimen that have different ductility. The purpose of this paper is to examine the effect of the ductility of weld metal on fractures under monotonic loading at room temperature and -40°C The high strain rates during the earthquake are substituted for static tests at -40°C. The main results under monotonic loading are summarized as follows. 1) The fracture-surface appearance mainly depends on the specimen temperature and hardly depends on the ductility of the weld metal. 2) In the case of the ductile weld metal specimen, it presented a brittle fracture-surface at -40°C, but the elongation is almost equal to that at room temperature which presented a ductile fracture-surface. 3) In the case of the brittle weld metal specimen, the elongation at -40°C fell to less than 1/2 of that at room temperature, mainly because the brittle fracture occurred after the plastic deformation. 4) In the case of the brittle weld metal specimen, the elongation in the bi-axial tests tends to become large with specimen temperature rising. 5) In the range of this experiment, only the absolute values of reduction of area in tensile test correspond to the elongation capacity in the bi-axial loading test using cruciform butt specimens.
(Al, Ti) N films were grown on silica and silicon substrates by aluminum and titanium vapor deposition and simultaneous nitrogen ion implantation under the conditions of the nitrogen ion energy of 2.0 keV and the atomic transport ratios of (Ti+ Al)/N of 0.5-1.5 and of Ti/(Ti+Al) of 0-1.0. The crystalline structure of the films depends on the atomic transport ratio of Ti/(Ti+Al). A single phase with Wurtzite or NaCl structure exists at Ti/(Ti+Al)≤0.17 or ≥0.25, and two phases with Wurtzite and NaCl structures at Ti/(Ti+Al)≈0.20. The surface morphology of the films is largely affected by titanium content. With an increase of Ti/(Ti+Al), the surface becomes fine. The microhardness of the films was found to have a maximum value in those films with two phases. The chemical bonds of Al-N and Si-N were identified in the interface between a (Al, Ti) N film and a silicon substrate by means of AES analysis. The metallic aluminum was not found in the interface of such films prepared at the atomic transport ratio of (Ti+Al)/N≤1.0.
The time dependence of bond strength between Au wire and Au film produced by the room temperature bonding was investigated. The bonding tests were carried out under an ultra high vacuum condition (1.0×10-8 Pa). The bonding surfaces of the specimens were cleaned by Ar+ ion sputter system (Ar+ irradiation : 2 kV×30 min) before bonding. The bonding pressure σB was from 5 to 20 MPa and the bonding time tB was 1 min. The peel strength increased with time after bonding. It was found that the bonded area did not increase with time by SEM observation. Therefore, it was suggested that the stress situation on the bond interface could be changed with time. Bonding process was also analyzed using a two-dimensional numerical model. Calculated results suggested that the stress distribution on the bond-interface was changed with time even at room temperature. It follows that the time dependence of the bond strength is caused by the relaxation of residual stress on the bond-interface.