Showing papers in "Transactions of JWRI in 1986"

Effects of Ultrasonic Vibration on Diffusion Welding of Aluminum(Materials, Metallurgy & Weldability)

Abstract: The ultrasonic vibration has been applied in the diffusion welding of aluminum in an attempt to break up the superficial oxide film of the bond interface. The ultrasonic vibration and subsequent welding have been carried out in a vacuum of 10-2 Pa at 875 K to 893 K under a welding pressure of 1 to 3 MPa. The bond strength increased with the increase in the input power to the transducer and working time of ultrasonic vibration. The increase in pressure to the bond interface during the vibration, however, lowered the bond strength. TEM observation and electric resistance measurement of the bond interface revealed that the application of ultrasonic vibration had the effect of breaking up and dispersing the oxide film, which was closely related to the increase in bond strength. On the fractured surface of joint, dimple patterns, increased with the rise of bond strength. These portions may be regarded as places where the application of ultrasonic vibration promotes breaking up and dispersing the oxide film.

Influence of Nitrogen on the Structure and Low Temperature Impact Properties of 304 Type Austenitic Stainless Steel Weld Metals by SMAW Process(Materials, Metallurgy & Weldability)

Abstract: Experimental covered electrodes(lime-titania type)were made by selective additions of Mn-nitride or Cr-nitride to the electrode covering. 304LN stainless steel base plates(t=12mm)whose edge preparation was machined to single sided V, 60°included angle were clamped in a jig and were welded together bymulti-pass shielded metal arc welding process.Nitrogen content of wcld metals was adjusted by changing the content of Mn-nltride or Cr-nitride in the electrode covering.Effect of nitrogenon the microstructure of weldmetal, δ-ferrite content, mean grain width, hardness and δ-ferrite secondary arm spacing were studied. Impact test for as welded specimen and solution treated specimen have been carried out at temperature range from 77K to room temperature.Influence of nitrogen on the impact value of wcld metals was mainly discusxsed.Results obtained are summarized as follows:(1)δ-ferrite content in the weld metals is influenced largely by the nitrogen content.(2)Impact value of weld metals increases with increasing of the nitrogen content of the weld metals up to about 1700 ppm after then the impact value falls as the nitrogen further increased.(3)The strengthening mechanism of weld metals due to addition of nitrogen is estimated that the effect of austenitic structure stabilized and inetrstitial solution hardening. Micro fissuring and precipitation of cluster(nitride)in excess of nitrogen containing weld metals decrease the impact value of weld metals.(4)Nitrogen content up to about 1700 ppm of weld metal which is introduced by SMAW process gives a good influence on the impact properties at low test temperature under condition of this study.