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Volume 42, Issue 5
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1973 Volume 42 Issue 5 Pages 395-467
Published: May 25, 1973
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSDownload PDF (27013K) -
Effects of Roughness on Torsional Strength of Brazed JointYoshifumi Suezawa1973 Volume 42 Issue 5 Pages 468-476
Published: May 25, 1973
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSThe study of relation between the base metal roughness and its torsional strength of mild steel brazed joint has been investigated in this experiment. To obtain some experimental data, some specimens (16φ×105mm) of mild steel rods (SS 41) and BAg-8 filler metal were prepared.
The surface of each specimen was identically polished by various emery papers (No 60, 240 and 600 esh), and other specimens were machined by milling cutter or ground by WA 60, WA 80 grinding wheels. These specimens were brazed with BAg-8 filler metal (wt=0.1g) using the 35KW resistance furnace operated in hydrogen atmosphere, and machined according to the scheme of Fig 1. The torsional strength test of these sepcimens was carried out by a 50Kg-m torsional strength testing machine shown in Photo. 1. The torsional test of these specimens gave the results as follows:
1) The torsional strength of specimen polished by No. 600 mesh emery paper (Rmax=0.6 micron) was very high, its value being 34.1 kg/mm2 at the joint clearance 0.12 mm, but that of the specimen polished by No. 60 mesh emery paper (Rmax = 15 micron) was lower, its value being 30.9 kg/mm2 at the joint clearance 0.15mm.
2) The torsional strength of specimen ground by WA80 grinding wheel (Rmax=0.8micron) was excellent, its value being 35.5Kg/mm2 at the joint clearance 0.18mm, but that of the specimen ground by WA60 grinding wheel (Rmax=1.6 micron) was poor, it value bieng.32.2Kg/mm2 at the joint clearance 0.11mm.
3) In general, the torsional strength of brazed joint with a smooth surface was greater than that of one with a coarse brazing surface due to the effect of residual stress of filler metal at the brazed joint.
4) As regards the relation between torsional strength and joint clearance, the torsional strength of specimen with 0.12-0.3mm joint clearance was very high among the specimens polished by emery papers and those of specimens with other joint clearance were lower, and also, that of a specimen with 0.15-0.25mm joint clearance was high among the specimens machined or ground.View full abstractDownload PDF (7244K) -
Some considerations on the sources of hydrogen in shielded metal-arc weldingJunichiro Tsuboi, Yukio Hirai, Toshiharu Hiro1973 Volume 42 Issue 5 Pages 477-488
Published: May 25, 1973
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSStudies are made to determine the sources of hydrogen in shielded metal arc weld metal.
First, by assuming that dissolution of hydrogen in molten metal obeys Sieverts'law, an equation is theoretically derived which is able to distinguish between the effects of humidity in the ambient atmosphere and those of moisture from the electrode coating.
Next, the coefficients involved in the equation are determined experimentally.
Finally, a formula which can predict the diffusible hydrogen content in the weld metal of HT50-HT100 steels is proposed.
The results are summarized as follows:
1) Evaporation of water from coating flux of low hydrogen type electrode occurs in two stages; one is the evaporation of moisture up to about 200°C and the other is that of bound water with a peak temperature at 750°C.
2) The effects of slag covering and its basicity in weld puddle on the diffusible hydrogen content are negligible in the case of low hydrogen type electrode.
3) Moisture evaporated from the coating of electrode at elevated temperatures contributes as the cause of the diffusible hydrogen in weld metal much more than that evaporated at relatively low temperatures.
4) The diffusible hydrogen content [H]D in weld metal in ml/100g is given by
[H]D=(A+12a+0.64b)1/2-1.8,
where A is a material constant of electrode which depends mainly on the evaporation of moisture at elvated temperatures in ml/100g, a being moisture content in the coating in wt.% and b the partial pressure of vapour in the ambient atmosphere in mmHg.
5) The above equation gives the practical information to control the diffusible hydrogen content in weld metal.View full abstractDownload PDF (766K) -
The mechanism of grain-boundary liquation cracking of Type 347 and Type 321 steelsHiroshi Tamura, Takehiko Watanabe1973 Volume 42 Issue 5 Pages 489-499
Published: May 25, 1973
Released on J-STAGE: August 05, 2011
JOURNAL FREE ACCESSA series of experiments on stainaless steels have been conducted in order to understand the phenomenon and mechanism of weld hot cracking, especially due to grain-boundary liquation, in heat-affected zone of some steel weldments.
In previous report (the lst report), some new knowledge of liquation cracking was obtained for Type 310 and Type 304 austenitic stainless steels.
In this report, some experiments on Type 347 and Type 321 stabilized austenitic stainless steels were conducted with a high temperature microscope and an electron probe X-ray microanalyser to obtain a more detail understanding of grain-boundary liquation cracking in the weld heat-affected zone.
The main results obtained in this study are as follows:
1) In Type 347 stainless steel, the appearance of liquid phase occurred at temperature lower by about 70°C than the solidus in both cases of rapid and slow heating.
This phenomenon is probably attributed to eutectic reaction between niobium carbide and r-iron.
2) Grain-boundary liquation was observed in the heat-affected zone of Type 347 stainless steel. The mechanism causing grain-boundary liquation is presumed to be as follows:
Grain-boundary migration accompanying rapid heating occurs and these migrating grain boundaries are pinned by niobium precipitates which remain indissolved in spite of heating at high temperature above 1300°C. Continuously, with an increasing temperature NbC-r-iron eutectic reaction occurs and then eutectic liquid produced in close vicinity of niobium precipitates penetrates into the grain boundaries which have been pinned and fixed here.
3) Narrow ferrites extended in the rolling direction of the base metal were liable to promote liquation hot cracking in HAZ.
4) It was presumed that Type 321 stabilized steel has less tendency to grain-boundary liquation than Type 347 stabilized steel and then has less susceptibility to hot cracking in HAZ.View full abstractDownload PDF (12715K)
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