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Volume 51, Issue 3
Displaying 1-9 of 9 articles from this issue
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Yoshikazu Moriwaki, Shinpei Denoh, Masaaki Murao1982 Volume 51 Issue 3 Pages 264-271
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSDownload PDF (532K) -
Fundamental Study of the Early Process of Diffusion Welding by Means of Electric Resistance Measurement (Report 1)Toshio Enjo, Kenji Ikeuchi, Naofumi Akikawa1982 Volume 51 Issue 3 Pages 272-279
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe early process of diffusion welding for several kinds of commercially pure metals (aluminum, titanium, iron, copper and silver) has been investigated by means of electric resistance measurement with particular reference to oxide film on faying surfaces. A couple of base metals were placed in vacuo with their faying surfaces in contact at a constant welding pressure and the couple was heated at a constant rate from room temperature to a temperature below melting point. The electric resistance across bond interface ρ was measured during the heating process and analyzed on the basis of the theory of convergence resistance. Results obtained are summarized as follows.
(1) The electric resistance across bond interface ρ for each metal was higher than that of the base metal in the early process of heating and approached that of the base metal as the bond interface was heated. The temperature at which the value of p became to be nearly equal to the resistivity of the base metal was different among the base metals; the temperature was 630°C for aluminum, 900°C for titanium, 850°C for iron, 600°C for copper and 500°C for silver.
(2) The ratios of the initial electric resistance across bond interface (before heating) to the resistivity of the base metals except for silver were rather higher than the value (≈6) estimated from convergence-resist-ance theory on the assumption that the faying surfaces were perfectly clean metallic surfaces. In particular those of the aluminum and titanium which had tenacious oxide film on the faying surface were much higher (102-105). This fact suggests that the faying surfaces of metals except for silver are not clean metallic surfaces but have a factor which prevents true metal-to-metal contact at the bonding interface.
(3) The electric resistance across bond interface of aluminum, titanium and copper increased largely, as the thickness of oxide film on the faying surfaces increased (the faying surfaces were subjected to hightemperature oxidation before welding). And the temperatures at which the value of p approached the resistivity of the base metal became higher with increasing the thickness of oxide film.
These results described above indicate that the oxide film is one of the most important factors which prevents true metal-to-metal contact at the bonding interface.View full abstractDownload PDF (589K) -
Wataru Shimada, Susumu Hoshinouchi1982 Volume 51 Issue 3 Pages 280-286
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSLow pressure TIG arc has remarkable characteristics as a welding heat source such as low arc pressure and high temperature cathode zone. Bead formation by low pressure TIG arc in high speed condition is studied in comparison with those by atmospheric TIG arc. Mechanism of under-cut bead formation and a method of prevention of under-cut bead are also studied in the report. The results obtained are as follows;
(1) Bead shapes by low pressure TIG arc change with both arc current and welding speed similarly to those by atmospheric TIG arc. Welding condition ranges for bead mode are basically divided into three parts by Front Gouging Line, where gouging region occupies the front part of the molten pool, and Bottom Vacant Line, where vacant parts remain at the bottom part of the penetration.
(2) In low pressure condition, both Front Gouging Line and Bottom Vacant Line shift remarkably to higher current-higher speed side compared with those in atomospheric condition because of lower arc pressure. So, the suitable welding region, limited by the appearance of improper bead such as. under-cut bead, is enlarged much to high current-high speed side.
(3) Once gouging region appears in front of the molten pool under transition condition, a wide and shallow normal bead changes rapidly to a narrow and deep bead corresponding to the shape of cathode zone. Under-cut bead is formed when the gouging region occupies maximum bead width, because side part of the gouging region solidifies rapidly after detached from the cathode zone. (4) On the surface of the gouging region in under-cut bead, thin molten metal of several ten microns thickness flows uniformly toward backside, and it satisfies the condition of supercritical flow in fluid dynam-ics. Under such a condition, gravity head of molten pool is balanced with arc pressure, surface tension of molten metal and hydraulic jump effect of supercritical flow.
(5) For the prevention of under-cut bead formation in high speed condition, prevention of gouging formation by forward metal flow under forward torch angle in low arc pressure condition is an effective method. Uneven bead in the current region up to Bottom Vacant Line can be basically changed to the normal bead using the above method.View full abstractDownload PDF (1730K) -
Effect of Focal Position on Humping Bead FormotionSusumu Tsukamoto, Hirosada Irie, Tatsuya Hashmoto, Michio Inagaki1982 Volume 51 Issue 3 Pages 286-291
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe mechanism of humping bead formation in electron beam welding was investigated. In the first part, the process of humping bead formation was clarified by high-speed cine-camera. In the second, the effect of focal position was discussed. The obtained results were as follows.
1) Humping bead was apt to be formed when the focal point was just on or slightly below the weld surface.
2) The reduction of surface bead width was apt to form the humping bead and reduce the pitch of humping bead formation.
3) The formation of nailhead-shaped welds at the focal position above the weld surface prevented to form the humping bead.
4) Nailhead-shaped welds were due to the melting by molten metal flow around the side walls, and to the melting or pre-heating effects by peripheral regions of gaussian distribution type electron beam.
5) The instability of capillary molten metal at the weld surface formed the humping bead.View full abstractDownload PDF (3177K) -
Kenji Seo, Junichi Masaki1982 Volume 51 Issue 3 Pages 291-297
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe present study was carried out to clarify the physical interpretation for the upper shelf energy of weld zone in Charpy impact test. Standard Charpy impact test were conducted on the structural high tension steel with bead welding by electron beam weld.
The results obtained were as follows:
1) The upper shelf energy of weld zone in Charpy impact test was affected not only by the toughness of material under the notch root but also by the mechanical properties of base metal in the vicinity of weld zone.
2) It became clear that a large fraction of the upper shelf energy was associated with the plastic strain energy consumed to deform a specimen.View full abstractDownload PDF (4802K) -
Junichi Kinugawa, Sadao Fukushima1982 Volume 51 Issue 3 Pages 297-303
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe influence of chemical composition of steels on the proportions of martensite, hardnesses and critical rupture stresses of implant cracking tests (specified in WES 1104, Specimen: Type 1B) at coarse-grained regions in underwater wet welding was investigated by substituting the "equivalent carbon contents" Ceq (JIS G 3106 and WES-3001) or the "chemical composition for weld cracking susceptibility" Paz (WES-3002) for the chemical composition of the steels.
JIS-SM and some equivalent steels were employed as the materials to be tested. The test, welds ("autogenous welds" in the flat position) were deposited at a depth of 20 cm in fresh water, using a plasma arc as a source of heat.
The results summarized in empirical equations are as follows:
1) For cooling time from 800 to 500°C S(800-500°C) (s) ranging between some 3 and 11 s, the proportions of martensite M (%) in coarse-grained regions is given by;
M=(270×logS(800-500°C)-24.6)× Ceq-163×logS(800-500°C)+ 115.
2) For S(800-500°C) not exceeding 4s, the Vickers' hardness Hv with a load of 10 kgf is; Hv=563×POM-123×logS(800-500°C)+315
while for S(800-500°C) from 4 to 11s;
Hv=(885×logS(800-500-°C)-117) ×Ceq-449×logS(800-500°C)+483
3) Under the conditions. that the weld contains diffusible hydrogen of the level of 20-30 ml/"100 g of weld metal" (Collecting medium: Mercury), the critical rupture stress (σcr) imp (MPa), below which cracking does not lead to complete rupture of the implant, is;
(σcr)imp={(1.72×logS(800-500°C)-2.42)×Ceq-0.239×logS(800-500C)+0.956}×103or,
(σcr)imp={(1.72×logS(P-100°C)-4.04)×Ceq-0.239×logS(P-100°C)+1.18}×103
where S(P-100°C) is cooling time from peak temperature to 100°C (s) and ranges from about 20 to 100s.
In case (σcr)imp's calculated by the above-cited equations drop below 230 MPa, they can be estimated to be on the fixed level of 230 MPa.View full abstractDownload PDF (3672K) -
Study on Penetration Control of Weld (Report 1)Yuzo Kozono, Satoshi Kokura, Ryoichi Kajiwara, Akira Onuma1982 Volume 51 Issue 3 Pages 304-309
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSSurface temperature near the end part of the molten pool in TIG arc welding for 2.3 mm thick mild steel plates was measured with a Silicon monochromatic optical pyrometer. Relationships between the surface temperature and the reverse side bead width were investigated under various conditions.
Results of this experiment are summarized as follows.
(1) The effect of TIG arc on the temperature measurement disappeared at the position about 10 mm away from the center of the arc.
(2) It was concluded from the results of measurements that the mutual relation existed between the surface temperature near the rear end part of the molten pool and the reverse side bead width.View full abstractDownload PDF (456K) -
Direct Observation of Crack Propagation and Metallographic Examination of CracksTakehiko Watanabe, Isao Okane1982 Volume 51 Issue 3 Pages 309-314
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSHydrogen-assisted crack propagation and cracking in as-received HY80 steel were directly observed. Metallographic examination of cracks was performed using the etchant of picric acid with wetting agent. Direct observation of crack propagation shows that before microcracks start to grow localized yielding occurs in advance of crack tip and subsequently evolution of hydrogen occurs, and then microcracks grew into macrocracks, accompanying thus periodic process.
Metallographic examinations of cracks exhibited that the incidence of cracking was predominantly high at bands and the presence of bands seemed to play very important roles in hydrogen-assisted cracking in HAZ.View full abstractDownload PDF (7752K) -
Studies on Friction Welding of SUS 304 (Report 4)Kozo Okita, Masatoshi Aritoshi, Waichiro Kishimoto1982 Volume 51 Issue 3 Pages 314-319
Published: March 05, 1982
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThis paper concerns with the measurement of the friction temperature at friction surface under steady state done with two-colours pyrometer.
By using the measurement results thus obtained, the relations among the surface temperature, friction welding conditions and friction welding characteristics are discussed in detail.
Major conclusions obtained are as follows:
(1) It was revealed that the peak surface temperature at friction interface measured with two-colours pyrometer was well correlated to the mean temperature at friction interface measured with the directthermocouple method.
Thus, it seems to be possible to evaluated the mean temperature at the friction interface by measuring the circumferential temperature with the method used in this study with only a little correction.
(2) In the range of this experiment, it was observed that the temperature at the friction welding interface became lower with the increase in the friction pressure, and that it did higher with the increase in the friction speed.
But, the temperature became to take almost constant value in disregard of the friction speed when further increase in the friction pressure was given.
(3) The value of the friction interface temperature can be estimated with the amount of the total energy consumed in the unit volume of the material at the welding interface.View full abstractDownload PDF (394K)
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