Hot ductility and tensile strength are investigated on the synthetic heat-affected-zones (HAZ) simulating weld thermal and reheating cycles in relation to tensile strain rate dependency.
Four commercial steels, three, high strength and one mild steel, are used for testing.
Four programs of weld thermal cycles A, B, C, and D are compared, but the main experiments are conducted on thermal cycle C, which is a tensile test at various strain rates on each holding temperature with subsequent reheating of the first weld thermal cycle of 1400°C peak temperature. The main results are as follows :
(1) Hot ductilities of synthetic HAZ specimens tested at various temperatures generally fall after subsequnt reheating thermal cycle.
(2) Hot ductilities of synthetic HAZ specimens generally decrease at slower strain rates. Especially, in case of 80 kg/mm² high strength steel 8A, the hot ductility of synthetic HAZ specimen falls to almost zero after subseouent reheatine at about 700°C and/or 900°C.
(3) In various hot ductility curves, three distinct temperatures are found, that is, one of maximum ductility Tit and two of minimum TL, and T_L2.
(4) The maximum ductility temperature T_H exists in 700-800°C range, and their hot ductilities are not affected by strain rates.
However, in the other temperature ranges, hot ductilily decreases rapidly with an increasing strain rate.
(5) Hot tensile strength in reheating weld thermal cycle increases straightly with an increase of strain rate on a logarithmic scale.
(6) Fractographic observations of reheating weld HAZ specimens showed that an intergranular fracture mostly occurred in case of testing in T_H temperature range, and was more significant with an increasing strain rate.

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Some experiments to determine the density of austenitic stainless steel castings and weldments carried out. The results may be summarized as follows.
1. The density of an austenitic stainless steel casting appeared lower compared with that of a wrought condition. The difference in the density can be attributed to the porosity in the casting.
2. The density of an austenitic stainless steel weldment, on the other hand, appeared higher compared with that of a wrought condition. The difference may be attributable to the coarse grained structure of the specimen used in this investigation. It is obvious anyway that weldments are much dense than castings.
3. An increase in density of an austenitic stainless steel is observed, provided that the specimen is sensitized. A decreade in density appears, on the contrary, when the specimen is solution treated after sensitized.
4. The density of an 18:8 type stainless steel initially increases followed by a further decrease when the specimen is cold-worked.
5. The density of a 25:20 type stainless steel, however, decreases monotonously when the specimen is cold-worked.

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In the previous paper, theoretical evaluation on the strength of fillet welded joint was presented and compared with the experimental results. Theoretical value agreed well with the test results obtained by using model specimens machined from a homogeneous mild steel sheet. But in the welded joints, mechanical properties of weld metal and heat-affected zone are different from those of base metal. So the mechanical behaviour and the strength of fillet welded joint will be different from those of model specimen.
In this paper the mechanical behaviour and the strength of the front fillet welded joints are explained experimentally and theoretically. Experiments are made with four typical types of front fillet welded joints as follows;
1. Double Tee fillet welded joint.
2. Double strapped fillet welded joint.
3. Double Tee fillet welded joint including soft or hard weld metal.
4. Partial penetration groove welded joint.
The results obtained are as follows.
1. Fracture mode of fillet weld is affected by the strength and work hardening properties of weld metal (cf. Photo 1).
2. The strength of front fillet welded joint can be calculated by using the equation (2), (3), or (4) which are given by theoretical analysis.
3. The strength of front fillet welded joint including soft or hard weld metal can be estimated by using the equivalent weld metal strength σ_we (cf. Fig. 15).
4. The friction between base plate and strapped plate has large influence on the strength of double strapped fillet welded joint (cf. Fig. 11, Fig.12).
5. The equation for evaluation of the strength of partial penetration groove welded joint is given by comparing the test results and the theoretical analysis.

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Pressure butt welding using high frequency induction heating has already been used practically in many fields. However its application is limited to seam welding of pipes or low pressure pipe lines and seldom extended to high pressure lines.
This paper deals with the results of experimental fabrication of carbon steel pipes and low alloy steel pipes (ICr-1/2 Mo) and discusses the investigation on how far the welding conditions affect the mechanical properties of pressure welded parts.
(1) It is necessary to finith the surface condition of pressure butt welded part to ∇∇ in actual work.
(2) The mechanical properties of pressure welded part are not necessarily better when using shielding gas than when not using it.
(3) Upset volume is to be 1.0-1.5t (t: pipe thickness).
(4) Heating temperature is to be kept at more than 1, 300°C on the innerside of pressure butt welded part.

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Experimental study was made on the effect of alloying elements on brittle fracture characteristics of submerged-arc welded joint, empolying 120 mm width tensile specimen.
Steels containing higher amount of manganese, chromium and nickel have better fracture characteristics than steels with lower content.
The important findings in this study are in the fact that small amount of titanium, zirconium and aluminium are effective in improving weld bond fracture characteristics. Suitable content of titanium and zirconium are 0.02 % and 0.05 %, respectively.

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Investigations have been madee on some metallurgical and mechanical behaviors of the feathery crystal which is developed-in TIG arc weld metal of 1 and 2 mm thick 5083 aluminum alloy sheets.
The major conclusions obtained are as . follows:
(1) The solidification structure in the center of the weld metal varies generally from columnar to feathery and an equiaxed crystal as heat input is increased under the same welding speed of less than 500 mm/min. Moreover, the feathery crystal is developed more esaily at low welding speed.
(2) The growth mode of the feathery crystal in the weldcenter is macroscopically in the shape of an unfolded fan with a large curvature. This is due to the phenomenon that each twin plane, in the feathery crystal, microscopically, grows intermittently with a small inclination angle with each other.
(3) According to X-ray analysis the twin plane the feathery crystal developed in the weld metal accords with {111} and the difference in the orientation of adjacent twins is within a few degrees.
(4) When the featherycrystal is developed in the weld metal the elongation of the welded joint decreases considerably, while the tensile strength does not decrease much.

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