Three layers-and two layers-laminated plates were made by electro-slag welding. The effect of heat treatment, reduction in thickness by forging-rolling, and relative thickness of core steel weld metal were examined in relation to the notch toughness and static mechanical properties. These properties were compared with those of the rolled laminated plates which were previously reported. The results obtained were as follows: (1) In the case of mild steel-2% Nickel steel weld metal-mild steel laminated plate, the largest impact value was obtained by homogenizing annealing at 1100°C followed by quenching and tempering. This value corresponded to that of the laminated plate which was made by rolling. (2) In the case of mild steel-Si-Mn steel weld metal-mild steel laminated plate, a refined microstructure accompanying a remarkable increase of impact value was obtained by the forging and rolling with a larger reduction in thickness than 80%. (3) The impact value of stainless steel weld metal-mild steel laminated plate increased with the increase of stainless steel thickness, as similar tendency as the laminated plate made by rolling.
Shape and distribution of sulphides formed in TIG-arc weld metals of Fe-S binary alloys have been investigated. In these alloys the sulphur contents were purposefully much higher than those encountered in commercial steels to make the observation of sulphides easy. Main conclusions obtained are as follows: 1) Two types of iron sulphides, that is, filmlike and globular sulphides are formed in weld metal. 2) Amount of sulphides does not vary from the fusion boundary to the weld center. 3) Filmlike sulphide is generally formed at columnar grain boundary. On the other hand globular sulphide is formed at cell boundary or cellular dendrite boundary. 4) In general sulphides at columnar grain boundary was observed to be more in quantity than at cell boundary or cellular dendrite boundary. 5) Solidification crack occurs along the filmlike sulphide at columnar grain boundary. No crack is observed along the globular sulphide. 6) It was considered to be due to the difference between the grain boundary energies that the shape of sulphide at columnar grain boundary was different from that at cell boundary or cellular dendrite boundary.
Occurring and developing mechanism of longitudinal hot cracking due to rotational deformation of specimen of thin aluminum plate is studied experimentally based on the results in previous report.Fursthermore, a new method of assessment of hot cracking susceptibility is suggested basedon the above experimental results and modification of Houldcroft hot cracking test. It is observed that in welding a rectangular specimen starting rom edge, longitudinal cracking occurs in weld bead and when the width of specimen is increased, the cracking ratio changes abruptly from 100% to 0% at a certain width of specimen-critical width-in high speed welding, but at low welding speed, the cracking ratio decreases gradually from 100% and drops to 0%. In these cases, it is observed that the cracking occurs in the brittle area behind the molten pool in the start part of weld bead and it develops from A to B in Fig. 2 with the molten pool. The above mentioned results may be understood from the existence of minimum deformation -l for thecracking (which is described in 1st report) and the actual deformation. The latter is affected bythe rigidity of the plate and the temperature distribution in the width direction. From above results, it is concluded that the factor which stops the cracking in Houldcroft type cracking test is uniformity of temperature distribution in the width direction due to the decrease of effective width by a slit inserted. On the other hand, there is another tendency of the development of cracking being accelerated by the decrease of rigidity due to the slit. Accordingly, it is understood that Houldcroft type cracking test is an obscure one with an inconsistent factor in stopping mechanism of cracking. From above results, a new improved hot cracking test is suggested.
Studies were conducted to investigate the effects of compositions and any other factors on the HAZcracking of 75Ni-15Cr-Fe alloy and to perform the prevention of it. In the 1th report, the characteristics of the 75Ni-15Cr-Fe alloy and the HAZ cracking of the alloy were described. The contents described in this report are as follows: 1. Eutectic structure (Ni2Mg+Ni), which is substituted partially by Cr and Fe in a portion of Ni, crystalizes in 75Ni-15Cr-Fe alloy containing Mg 2. Grain boundary weld cracking is occured in the HAZ of 75Ni-15Cr-Fe alloy 3. HAZ cracking of 75Ni-15Cr-Fe alloy is affected rather by the chemical composition than by welding method, type of welding joint and thickness of plate
CO2 arc welding which is employed in the wet underwater welding has the following advantages. (1) The process is simple to operate. (2) In the safety aspects, the lower open voltage characteristics of arc welder is particulary helpful to avoid electric shock. (3) Welds can be made in all positions. But, in conventional wet underwater CO2 arc welding, nozzle-base metal distance was not more than 4 mm, therefore the welding operation was very difficult. We studied the following system that was called curtain water type underwater CO2 arc welding aimed to improve this problem. In the dual flow system which we used, curtain water was introduced from the outer nozzle. By this system we could take nozzle-base metal distance about two times longer than that for conventional shielding system. As the results of radiographic examination, no difficulty was found to obtain the welds without blowholes. At the first step to develop this process, we report experimental results of down hand position butt welding for mild steel.