To clarify the types of cracking and their causes in weld zone of 50kg/mm2 class high tensile steels, R.T.R.I. (Railway Technical Research Institute) type slit cracking tests were carried out with 46-57kg/mm2 high tensile steels and several kinds of electrodes for mild and high tensile steels. Crack appearances, hardness distribution, microstructure and notch profile at root etc. in weld zone were investigated. Diffusible and residual hydrogen content in weld metals was measured. Three types of cracking appeared in the transverse section of weld zone. From experimental results, authors confirmed that considerably intimate relation exists between the types of cracking and the above-mentioned factors.
Using a constant potential type rectifier, many beads were deposited on plates by CO2-O2 arc welding, varying polarity, open voltage and feeding rate. And the deposition efficiency were measured. For the purpose of comparison, the same experiments were carried out with argon arc and manual arc welding with a coated electrode. The experimental results are as follows : 1. At a constant feeding rate, the deoposition efficiency increased with the increment of open voltage. 2. At a constant open voltage, the deposition efficiency increased with the decrease of arc voltage and the increment of welding current. 3. In the case of CO2-O2 arc welding the deposition efficiency reaches 99% under an optimum condition. 4. The deposition efficiency with the straight polarity is not so good as with the reverse polarity. With straight polarity, the maximum efficiency did not over 90%. 5. Argon arc welding showed the same tendency as the CO2-O2 arc welding. 6. In the case of the manual arc welding with a coated electrode, the maximum deposition efficiency was 88%.
In this report, the oxidize ability of oxy-acetylene flame was defined as follow, (total oxygen quantity in flame)-(oxygen quantity that is eauivalent oxidize ability=to acetylene in flame)/total quantity of combustion product Authors have introduced the new idea what is called the atomic rate in order to calculate the oxidize ability. The relations among the oxidize ability [O]/[S] and the mixed ratio O2/C2H2 of flame, the di-stance from outlet of tip were shown in Fig. 6. The oxidize ability [O]/[S] shown in Fig. 6 was calculated from analytical result of combustion gas shown in Table 1.
Argon-Hydrogen Gas shield tungsten-arc cutting found to produce excellent quality cuts in aluminum, stainless steel, Copper and Brass. It can be used mechanically or manually in any position. Constricted tungsten arc cutting is a new high speed process and it is used in conjunction with a mixture of argon and hydrgen gas, and can cut alumimum up to 1 1/2 in thick. In this paper discussion centers on the equipment requirements, the cutting conditions and the metallurgical effects of cutting.
Eight kinds of Si-Mn steel electrodes and high-Al steel electrodes were manufactured for testing. High-Al and high-Si-Mn electrodes produced sound welds on semi-killed steel plates using carbon dioxide gas. Oxygen content of all weld metals obtained from high-Al electrodes were lower than that obtained from Si-Mn electrods. The mechanical properties of all weld metals were as follows. Tensile strength: 55.9-62.5 kg/mm2, Yield strength: 44.6-51.1 kg/mm2, Elongation: 23.8-32.0%, Tr15:<-60--40°C By using two kinds of high-Al electrodes, it was possible to make quality welds on 12 mm semi-killed steel plate with three kinds of joint preparation.
Although stresses exist in welded specimen both during and after welding, only those remai. ning after specimen has conpletely cooled have much discussed. As a preliminary experiment for investigation on the generation mechanism of residual stress by welding, Authors inquired into process of arise of welding strain in this experiment, and have taken the following results. Transverse strain indicates expansion in high temperature above starting temperature of Ar' transformation, but it changes to contraction when temperature of deposited metal falls below Ar' point. As a whole, remarkable amount of contraction is produced by the time deposited metal cools to room temperature. The state of these contraction agreed to result analysed by heat conduction theory (see Fig. 8) Angular distortion is mostly produced in high temperature range above Ar' transformation.