Effects Of Joining Conditions Research Articles

固相スタッド接合したSS400鋼スタッドと5052アルミニウム合金板の接合界面組織と温度履歴

SS400 steel studs were joined to 5052 aluminum alloy plates by solid-state stud welding at charged voltages of 300 to 475 V. Effects of joining conditions on the interfacial microstructures and tensile fracture load of the joints were evaluated. Thin intermediate layers (Al5Fe2 and Al3Fe) approximately 1 µm thick in total were observed along the joint interface at a distance of 150 µm from both ends of the interface respectively. The tensile fracture surfaces on the stud after tensile test were covered with dimpled structures, indicating ductile fracture, with the exception of the stud tip. This indicates that the stud and plate were joined strongly enough for the base material to partially fracture during the tensile test. The fracture load increased with charged voltage up to 450 V but decreased gradually thereafter. The maximum temperature reached during joining could be also estimated by the presence of martensite near the joint interface.

Effect of joining conditions on microstructure and flexural strength of long silicon nitride pipes fabricated by local heat-joining technique

The microstructure and flexural strength of long silicon nitride pipes joined by a local heat-joining technique at different mechanical pressures, temperatures, and holding times were examined. Silicon nitride pipes sintered with Y2O3 and Al2O3 additives were used as the parent material, and a powder slurry of a Si3N4–Y2O3–Al2O3–SiO2 mixture was brush-coated on the rough or uneven end faces of the pipes. The flexural strength gradually decreased with decreasing mechanical pressure from 5 to 1.4 MPa at 1600 °C for 1 h. A large number of small voids measuring less than 1 μm were present in the joint layers of the samples joined with mechanical pressures of 1.4 and 3 MPa at 1600 °C for 1 h, although there were very few voids formed at 5 MPa. When the joining temperature was increased to 1700 °C for 1 h, some voids were observed in both the joint layer and the parent silicon nitride, and the flexural strength decreased to 529 MPa. Furthermore, some voids were formed in the parent silicon nitride when the holding time was increased from 1 to 4 h at 1600 °C and 5 MPa, which indicated slight degradation of the strength from 677 to 644 MPa.

Effects of joining conditions on the structures and properties of joints of REBCO coated conductors

We investigated the joining of two REBCO (REBa2Cu3O7−X, RE=Y, Gd) coated conductors using the diffusion joint process. REBCO coated conductors with stabilizing silver layer were joined by various joining conditions. Two pieces of the silver layer of tapes were overlapped in a face to face manner. Then, the pieces were pressurized and heat-treated at about 623–673K under a pressure using some weights in oxygen atmosphere. Finally, the joint resistivity was obtained as low as about 10nΩcm2 by 10MPa for YBCO tape. The joint resistivity of the GdBCO tape was 50–60nΩcm2, which was higher than YBCO, but improved to 37nΩcm2 at 10MPa by improving the joining conditions. Influences of joining conditions such as pressure and evenness of specimens and holders were investigated on joint adhesion and resistivity.

Effects of Joining Conditions on Joint Strength of Cu/Cu Joint Using Cu Nanoparticle Paste

High-temperature bonding, or joining, is a key technology for electronic component assembly and other high- temperature applications. Recently, focusing on the sintering behavior of nanoparticles, the joining process using a nanoparticle paste has been proposed as an alternative to soldering for high-temperature applications. In this study, Cu nanoparticle paste was used to join two Cu discs, and the effect of joining conditions on the joint strength of the Cu-to-Cu joint was investigated. Joining using Cu nanoparticle paste was successfully achieved, but the effect of joining conditions such as heating temperature and joining atmosphere on joint strength of the Cu-to-Cu joint was significant.

Properties of as welded and heat treated pure titanium–7075 Al–Zn–Mg alloy friction weld joints

The effects of joining conditions and an age hardening post­weld heat treatment (PWHT) at 120°C for 24 h on the tensile strength and metallurgical properties of dissimilar friction joints between pure titanium and age strengthened 7075 Al–Zn–Mg alloy were investigated. Highest strength was achieved using intermediate friction pressure (150 MPa), short friction time (0.5 s), and high upsetting (forging) pressure (400 MPa). The joint tensile strength decreased when the joint diameter was increased from 8 to 16 mm. The joint tensile strength of as welded (AW) dissimilar joints was similar to that of PWHT joints with diameters of 8, 12, and 16 mm. Detailed TEM confirmed that there was a negligible difference in the thickness of the intermetallic layer formed at the dissimilar joint interface for AW and PWHT joints. While the intermetallic phases formed at the joint interface comprised Al3Ti, τ (Ti2Mg3Al18), and Al in AW joints, they consisted of Al+τ or Mg2Al3+τ+Al in PWHT joints. Softened regions were generated in 7075 base material immediately next to the interface in AW joints. Post­weld heat treatment increased the hardness of the softened region almost to that of as received 7075–T6 base material in 12 and 16 mm diameter joints. In contrast, the hardness of the softened region in 8 mm diameter joints could not be recovered to that of the as received material. This was a result of overaging and coarse precipitates in the softened region produced during the friction welding operation.

溶射皮膜をインサート材としたステンレス鋼と炭素鋼の接合 フレーム溶射に関する研究（第５報）

The joining between stainless steel (SUS304) and carbon steel (SS400) was carried out using thermal spray coating of nickel based self-fluxing alloy under atmospheric conditions for basic data. The size of joining specimen is 50 mm in length and 10 mm in diameter. After the each edged surface of SUS304 and SS400 specimens were blasted by used steel grid material sized No. 70, those were sprayed with self-fluxing alloy (S.F.A.) at the each surface of both specimens coated about 100μm in thickness.The effects of joining conditions on the structure and strength of joining were studied.The results are summarized as follows:(1) The maximum tensile strength at the joint part using R notch specimen was about 579 MPa under condition of 30 sec raising time and 60 sec holding time at 1373 K temperature.(2) The hardness gradient was not observed near the joining zone in the Vickers hardness distribution of the both materials. Furthermore, the Vickers hardness distribution near the joining zone of SUS304 was about Hv120, that was lower than base metal because of the annealing effect.(3) The microstructure near the joining zone did not indicate the martensitic structure, the carburized and the decarburized layer because of its lower cooling rate. The structure near the joining zone of SUS304 was indicated in the annealed twin at the transgranular.(4) By the EPMA line analysis across the joining zone, Cr, Ni, and B were not observed because the inserted material S.F.A. was very little diffused and the most of it was discharged out of the joining part. The elementary analysis of Fe was indicated sligthly concentrated gradient.

フレーム溶射に関する研究 （第４報） 溶射皮膜をインサート材とした鋳鉄と炭素鋼の固相接合

The solid phase joining of ductile cast iron (FCD 600) and carbon steel (SS 400) was carried out using thermal spray coating of nickel based self-fluxing alloy under atmospheric conditions for basic data. The size of joining specimen is 50 mm in length and 10 mm in diameter. After the each edged surface of FCD600 and SS400 specimens were blasted by used steel grid material sized No. 100, those were sprayed with self-fluxing alloy (S.F.A.) at the each surface of both specimens coated about 100 μm in thickness.The effects of joining conditions on the structure and strength of joints were studied. The joints with excellent metallographic structures were obtaind at the joining temperature near the melting point of the spray material.The results are as follows :(1) The maximum tensile strength at the joint part was more than 500 MPa under conditions of 50 sec raising time and 40 sec holding time at 1223 K temperature.(2) The Vickers hardness distribution near the joining zone of FCD 600 was between Hv250 and Hv340. That was a little bit higher than base metal.(3) The microstructure near the joining zone of FCD 600 did not indicate transformation to white pig iron because of its lower cooling rate. The structure around graphite was ferrite and the base metal was pearlite structure.(4) By the EPMA line analysis across the joining zone of FCD 600, Cr, Ni and B were not observed because the inserted material S.F.A. was a very little diffused and the most of it was discharged out of the jointed part.

超音波接合に関する研究(第1報)

The contact face of materials to be joined recieves compression and shearing force under ultrasonic vibration, with becomes hot by friction, and then both the metallic faces are exposed, metallic atoms appreaching mutually; in this way ultrasonic welding is done through mutual attactive force and diffusion of metallic atoms.In this joining method, the joined state sometimes becomes crescent-or ring-shaped, but in order to get perfect (the whole area) joining, it is necessary for to chose the conditions so as to give enough compression and shearing force.There are many factors that influence heat generation at the contact face of materials to be joined, of which particularly effective conditions are described below.1. Ultrasonic power: The greater it is, the higher is temperature rise.2. Tip pressure: The lower it is, the higher becomes temperature rise. But under the same ultraso nic power, tip pressure for the highest temperature at the contact face of materials has some limit, which increases with increase of ultrasonic power.3. Joining time: Temperature immediately rises within 1 to 2 sec., but thereafter becomes almost constant.4. Materials to be joined and sheet thickness: The harder the material is (of cource enough compression and shearing force must be given) and the thinner the sheet is, the higher is temperature rise.5. As the contact face of differently thick materials, the temperature is higher under the condition when a thinner sheet is placed on the tip side than when a thicker sheet is done, and the thinner is the sheet on the tip side, the higher is the temperature rise.Therefors joinability (workability) by ultrasonic welding is almost dependent on materials and their sheet thickness to be placed on the tip side.In this study, we observed a temperature rise over 700°C.The relationship between joining strength and conditions is proportional to the relationship between temperature rise at the contact face of materials to be joined and ultrasonic vibrating conditions which elevate the temperature, and All of 0.08 mm titanium, aluminum and copper were fractured in the base metal around nugget of joining part. The effects of joining conditions on joining properties are as follows:1. Ultrasonic power: The greater it is, the higher is joining strength. But tip or anvil and material to be ioined are often ioined.2. Joining time: Within the limits in which the material to be joined is not joined with tip or anvil, the longer the better.3. Tip pressure: When the joining strength is proportional to the joining area, tip pressure had better be high to the effect that nugget diameter is enlarged.4. Surface condition of the material to be joined: The cleaner the surface, the higher is the joining strength, especially electrolytically polished material is excellent.In joining titanium to titanium or titanium to stainless steel, tip pressure (50 to 60%), ultrasonic power (40 to 70%) and joining time (over 100%) should be increased in comparison with the joining condition of same thickness aluminum sheet. And using of convex anvil is efficient.Joinability (workability) and joining strength by ultrasonic welding were improved by means of electrolytically polishing the material to be joined and using suitably insert.