The purpose of this study, it is that achieve high performance and high function of the industrial product under the low cost. The fatigue test of SUS304/S35C and SUS304/S55C friction welded joints with flash was investigated by rotating bending fatigue test. The experimental results as follows; 1) The broken part of friction welded joints of SUS304/S35C and SUS304/S55C was changed by amplitude stress, its part was toe of flash of S35C and S55C when amplitude stress was low. And, in the case of the high amplitude, it was specimen parallel part of SUS304. 2) The stress concentration factor of toe of flash of S35C and S55C was increased with increase of upset pressure. This tendency was slightly in the case of SUS304, And in the case of carbon steel, it was increased remarkably with increase of carbon. 3) When amplitude stress was low, broken part of S35C and S55C joints was toe of flash, these fatigue strength was decreased remarkably with increase of upset pressure. This main reason was increased of the stress concentration factor. 4) When amplitude stress was high, broken part of SUS304 was parallel part and this reason was by red-hot. These reason occurred heat by internal friction and low thermal conductivity. But, this red-hot was prevented completely with dropping of water of 50ml/min. 5) When parallel part length of SUS304 was less than 25mm, amplitude stress of broken by red-hot was increased with decrease of parallel part length.
The problem of high-temperature corrosion caused by wood fuel ash produced by the wood biomass combustion apparatus, has arisen from the expanded usage of wood biomass energy in recent years. The purpose of this study is to develop chromium-free composite coating that provides high durability and corrosion resistance against wood fuel ash with cold spray technology. In this study, fabrication of NiAl intermetallic compound coatings by cold spraying using compressed air is examined. Particle velocity and deposition efficiency were measured to attempt a comparison between compressed air and helium gas. The coating characteristics such as microstructure, micro Vickers hardness and corrosion resistance were evaluated. As a result, a dense NiAl intermetallic compound coating was formed with compressed air by using the powder prepared by that blending Ni-Al mechanically milled powder and Al2O3 powder. Moreover, the coating showed excellent corrosion resistance in the polarization measurements and high temperature corrosion tests.
This study evaluated both the joint strength of copper wire on a copper substrate with tin plating and the joint reliability of copper wire bonding after heat treatment. The suitable tin thickness and bonding conditions, which are stage temperature, wire bonding power and bonding time, were chosen by the peel test after copper wire bonding. Tin thickness of 10 microns showed a high bonding rate under the conditions of stage temperature 373 K, bonding power 500 to 700 mW and bonding time 30 to 50 ms. Before heat treatment, the peel strength of the copper wire on the copper substrate with tin plating conditions was weaker than that of gold wire on a gold substrate. After heat treatment for more than 70 hours at 298 K, the peel strength of the copper wire became higher than that of the gold wire and twice as high as the initial bonding strength. The tin layer remained between the copper wire and copper substrate before heat treatment. When the samples were held at 298 K, tin reacted with copper and turned into a Cu-Sn intermetallic compound. Upon completion of this reaction at 298 K for over 70 hours, the soft tin layer between the copper wire and copper substrate disappeared. Therefore, the peel strength of copper wire after heat treatment increased. These results were observed by SEM images of the interface between the copper wire and copper substrate before and after heat treatment.
In order to clarify fume formation mechanism in arc welding, quantitative investigation based on understanding of interaction among the electrode, arc and weld pool is indispensable. A fume formation model consisting of a heterogeneous condensation model, a homogeneous nucleation model and a coagulation model has been developed and coupled with a TIG welding model. A series of processes from setting arc operation conditions to generation of metal vapor and fume formation from the metal vapor is totally investigated by employing this simulation model. This paper aims to visualize the fume formation process and clarify the fume formation mechanism theoretically through numerical analysis. Furthermore, the reliability of the simulation model was also evaluated through comparison of the simulation result with experimental result. As a result, it was found that the size of the secondary particle consisting of small particles with size of several nm which range like a chain reaches 300nm at maximum in helium TIG welding.
To minimize the volume of argon required for on-site TIG welding of titanium plate, we investigated the behavior of argon flow in a trailing-shielding box by means of computational fluid dynamics (CFD) simulations. In this study, we designed a model of a solid rectangular shielding box consisting of 9.5×105 tetrahedral elements. Then, argon flow was simulated for various shielding parameters, namely, the gap between the box and floor and the argon supply rate. In an experiment using dry ice mist to visualize the flow of argon, we investigated the flow from a shielding box model consisting of acrylic plates for various shielding parameters. In this manner, we studied the relation between the oxygen content in the shielding box and the shielding parameters. Then, a conventional shielding box and a prototype shielding box were evaluated experimentally. We confirmed the relation between the oxygen content in the shielding boxes and the degree of oxidation on the bead surface in TIG arc melt-run welding of titanium plate. The experimental results show that the simulation model used in the CFD simulations allowed the behavior of argon to be predicted. We conclude that the simulation model is useful for improving the structure of the shielding box.
The experiments under the static loads were carried out in order to investigate the possibility of repair/reinforcement by welding. Preventing the influence on the experimental devices due to the welding current by isolating between the jigs and the experimental devices, the stable experiments could be carried out. For the cruciform joints and I-shape joints, semi-auto CO2 gas welding was carried out under compressive static loads on the assumption of the dead load. As the experimental results, any cracks were not found. In the cruciform joints with multi-pass welding, there was a tendency that the longer weld length became, the larger the magnitude of out-of-plane displacement became. In the actual construction, it was verified that repair welding under static loads could be performed without welding defects by confirming repair weld length, heat input and inter-pass temperature and so on.
Fatigue tests of Al-Mg alloy and low carbon steel joints by means of the spot friction stir welding, were carried out to investigate the basic fatigue properties. The influences of joining conditions on the fatigue behavior was also studied by using the joints which were joined under the different plunge depth conditions. From the experimental results, it was found that the fatigue life and strength were slightly different with difference in the plunge depth in case of tests under the higher applied load levels. There were three types of fatigue fracture modes which depend on both of plunge depth and applied cyclic load level. They were shearing type fracture due to detaching of the joining interface, fatigue fracture type in the aluminum alloy due to fatigue crack growth in perpendicular to the loading direction and the plug type fracture due to crack growth along the spot FSW region. Under the applied load which was the border level between two types of fracture mode, both fracture process propagated concurrently and the final fracture occurred when either process attained to the critical stage.
This study was carried out to develop cadmium-free silver brazing alloys that meet the following requirements. First, these alloys have the melting point lower than that of the BAg-1 brazing alloy, of which the melting point is the lowest in the conventional brazing alloys. Second, they have not only good wetting characteristics and the ability to produce a sound joint with excellent mechanical properties but also the plastic formability. Using the calculated phase diagrams on Ag-Cu-Zn-Sn quaternary alloys, the authors selected several alloys with the possibility for meeting the above requirements. The melting point and other properties such as hardness and brazeability of the selected alloys were evaluated. As a result, the authors successfully developed the silver-based brazing alloys that had the low melting point below about 600°C and met the above requirements by adding a small amount of indium as an alloying element into the Ag-Cu-Zn-Sn quaternary alloys. The newly developed brazing alloys were slightly inferior in wetting characteristics to BAg-1; however, the brazing alloy that contained about 3mass% indium showed the wetting characteristics comparable to BAg-1. Furthermore, the new brazing alloys could produce the joints with high tensile strength equivalent to about 83% of that of the joint brazed using BAg-1.
The formation of stable back beads in the root pass weld during one side multi-layer welding is important to achieve high quality welded metal joints in MAG welding. The authors employed the switch back welding method for V groove joints without backing plates. In this switch back welding method, the torch moves forward and backward with the weaving of 2.5Hz. In order to achieve this welding, the personal computers control the conventional welding robot, the power source characteristic and the wire feeder unit. During the forward, the torch is weaving on the V groove gap without the weld pool. If the weaving width becomes wider than proper width, the tip of the wire becomes high and a good back bead cannot be obtained. The weaving width is adjusted so as to get the proper width in the switch back welding. The suitability of the welding conditions for each root gap was verified by observation of the arc, the weld pool and the external appearance of back beads. A good back bead was obtained under V groove welding in 2mm gap to 4mm gap.
Drilling is an important aspect of materials processing in industry. Conventional drilling methods cannot completely meet production needs. As a result, the emergence of many new processing methods has become a prominent trend in recent years. However, few reports have been published on drilling processes using plasma arc technology. Plasma arc technology has been applied in various engineering fields including welding, thermal cutting, and heat treatment. This study proposes the use of plasma arc technology as a drilling method. A plasma arc drilling system was set up and a number of experiments were carried out. The geometrical characteristics and quality of holes generated using a plasma arc were analyzed. Various hole shapes were obtained by plasma arc drilling; namely, a conical blind hole, a taper hole, a cylinder hole, and a reverse taper hole. Variations in the volume of removed material and the material removal rate (MRR) of plasma arc drilling were investigated. The experimental results have verified that plasma arc drilling is an effective and high-speed drilling method.
Drilling is widely applied in materials processing. Novel drilling methods, including electrical discharge machining, laser drilling, and plasma arc drilling, have emerged in recent years to overcome such problems as tool wear and low efficiency in the drilling of thick plates or difficult-to-machine materials. Plasma arc drilling is an effective method for the drilling of thick plates, and the quality of the drilled holes is also high. However, the drilling performance of the plasma arc drilling method has not yet been fully elucidated. Since drilling performance is an important criterion in practical processing, we conducted a number of experiments to investigate the drilling performance of this method in terms of penetration ability, electrical energy consumption, and material removal rate. The results obtained for the drilling of mild steel plate of 12 mm in thickness were a penetration time of about 0.75 s, a minimum specific energy of about 30 J/mm3, and a maximum material removal rate of about 300 mm3/s.
The heat input parameters, the local heat transfer coefficient, α, and the gas temperature right on the plate, TG, are nearly unchanged with time during preheating for Oxyfuel gas cutting. A genetic algorithms (GA)-based identification technique for α and TG is proposed. The validity of the proposed technique and the accuracy of the identified parameters are examined by comparing the measured and calculated plate back face temperatures during spot heating tests. Hydrogen-LP mixed gas and LPG are used as preheating gases in these tests. It is considered that the plate temperatures during preheating for piercing can be calculated by using α and TG identified in spot heating tests. The minimum piercing time is estimated by calculating the time until the plate heating face temperature reaches the kindling temperature. The validity of the above assumption is examined by comparing the estimated and measured minimum piercing times for Hydrogen-LP mixed gas and LPG. As a result, the followings are found. 1) The plate temperatures during spot heating tests calculated by using the identified heat input parameters agree well with the ones measured. This demonstrates the accuracy of the identified parameters and the validity of the proposed heat transfer simulation technique. 2) The heat flux of Hydrogen-LP mixed gas flame around the preheating gas ejection hole is 40% larger than that of LPG flame while the total calorific value of Hydrogen-LP mixed gas is 25% smaller than that of LPG. This result shows that it is not appropriate to evaluate the thermal effect of preheat flame only from the total calorific value alone. 3) The calculated time until the plate face temperature to exceed the steel's kindling temperature almost agrees with the minimum piercing time observed in piercing tests. It becomes possible to anticipate the piercing time by numerical simulation for the first time.
In welded structures, it is thought that the crack in welds may be related to collapse of structure. So, the investigation on the relation between weld crack and acting loads in repair/reinforcement work by welding are performed. There are three kinds of load conditions in welding of the site: no loads, static loads and fluctuated loads. In the previous paper, welding under static loads were carried out, it was confirmed that weld crack was not generated. In this case, installation of bents and traffic control were required. So, concerning to the social and economical situation, welding under fluctuated loads without traffic control was desirable. In this paper, performing CO2 arc welding under cyclic loads on the assumption that fluctuated loads, examinations for detection of the crack were carried out. The hot cracks were observed at I-type joints. From the results of fractography, projections of cellular dendrite and striations were observed. And it was known that the magnitude of root gap opening displacement (Δδ) and heat input (Q) were induced the hot crack in the weld metal.