It is our aim to investigate the behaviors of consumptions of cathodes and anodes of arc, which are influenced by oxygen surrounding them. Iron, copper, aluminum and nickel bars of various diameters were used as a cathode or an anode in experiments. These consumption-rates in argon have been measured under the conditions that arc current is 90-180 A and argon flow 7-15 1/min. Summarizing the results as follows ; 1. The characteristic curves of consumptions of cathodes are particular to used materials. 2. Its orientation along oxygen including-rate translates to the direction of more oxygen including-rate, if arc current is made larger, smaller electrode is used, and electrode is better cleaned. 3. The consumption characteristics of anode are hardly influenced by oxygen including-rate, having particular values to used metals, but slightly in nickel.
From the analogy of the C.S. arc welding process, which depends on the effects of CO2 shielding and deoxidizers in electrode wire, and the arc welding with low hydrogen type electrode, it was deduced and confirmed by experiments that causes of porosity in a weld metal obtained by a low hydrogen type electrode can be ascribed to unsufficient protective action of this type coating or the produced slag and gas shield or unsufficient action of deoxidizer. On the low hydrogen type electrodes in market, the former is considered to be a main cause of the porosity. It is a simple method to prevent the porosity that CO2 gas is fed from a cylinder to the neighbourhood of the arc and molten pool.
We have compared with welding workability, mechanical properties and crack sencitivity of deposited metals, for trial production and market austenitic electrodes. The results are as follows : 1. Titania type coated austenitic electrodes has good welding workability compared with lime type. 2. Low ratio of silicon content to manganese content, low ratio of sulphur content to manganese content and low phosphorous content in deposited metals is desirable to prevent the weld metal hot cracking. 3. Trial production fully austenitic Ni-Cr-Mn (12-20-8) electrode has good welding workability, mechanical properties and crack free welds. 4. Trial production austenitic. Mn-Cr-Ni (17-17-5) electrode has good weldability too. 5. Tezuka type slit test has excellent characters for the crack test of welding electrodes.
Based on the results obtained in Report 1 and 2, an effect of chemical composition on the absorbed energies by non-notch impact bend at 0°C and the bend angles by non-notch-impact and slow bend, of the two mild steels and the five high tensile steels, were considered. In order to gain higher velues of the absorbed energy and bend angle of a steel cooled in short time from A3 point to 500°C, it is necessary; 1. to hold the carbon content in a lower range as possible, 2. to hold the manganese and silicon contents in higher range, corresponding to the ultimate tensile strength required. In this case, it is desirable that the point showing the composition of steel exists in the field II of Fig. 2.
As a part of the study of hot cracking with FISCO Tester, the following investigations were performed, (1) On the reproducibility of FISCO test result (2) On the effect of chromium contents and nickel contents in modified type D310 weld metal (3) The estimation of hot cracking temperature and the following results were obtained. (1) By testing the hot crack sensitivity of austenitic stainless steel weld metal with FISCO Tester were obtained the results in accordance with the experiences in the past. The maximum confidence limits in population mean of crack sensitivity were as follows. (Confidence 95%) f4(%)=16.7±1.4 on type D347, 4 mmφ with SUS7, A.C. 140 amp. f3(%)=25.2±3.3 on type D310, 3.2mmφ with SUS12, D.C.R. 100 amp. (2) As nickel contents were increased in modified type D310 weld metal, to both SUS7-SM41W and SUS12-SUS12 butt welding, the crack sensitivity had the tendency to be increased. As chromium contents were increased in the same type weld metal, to both butt welding, the crack sensitivity was reduced. (3) On the basis of the coloring tendency of various stainless steel materials at high temperature, hot cracking temperature was observed. It was estimated for D316L and D347 weld metal that hot cracking at above 1000°C (1832°F) was limited to very small portion on the upper part in crater zone and cracking at 400°C (752°F) to 700°C (1292°F) occured for the most part. For D310 weld metal, hot cracking at above 1000°C occured on all upper part in crater zone. Hot cracking at above 1000°C in started zone occured on the lower limitted portion, on another portion at 400°C to 700°C. Cracking in middle zone occured only at 400°C to 700°C.
For many applications, titanium may be used because of its excellent corrosion resistance rather than its good mechanical properties. We therefore investigated the corrosion resistance of the welded commercial pure titanium in sea water compared with those of the welded practical corrosion resisting alloys (corrosion resisting aluminium alloy, 18-8 stainless steel and mild steel). Additionally, we tested the welds of these alloys in alkali and acid. We used two kinds of corrosion test; extents of corrosion were determined with weight loss or increase of the electrical resistance respectively. The results of these tests showed that the commercial pure titanium was the most excellent among the tested materials, but the heat affected zone was inferior to the parent metal and the weld.
Contact angle is an important factor which influences wettability of brazing alloy to base metal. Relation between wettability and contact angle was examined in this paper. Brazing alloys were set upon the horizontal base metal plates in vacuum as the first method. After brazing alloys were melted, the shapes of alloys spreading over base metals were photographed in phorizontal direction. Alloys which have eutectic point in their diagrams, such as Sn-Pb and Sn-Bi, have minimum contact angle to Cu at the composition a little nearer to Sn than eutectic. Alloys having nonmetalic element such as P, As have very small contact angles. Contact angle also decreases when alloy have small amount of base metal element. As second method, following experiment was done. Slitts, composed of parallel base metal plates, were preheated in soldering flux. After holding them several miniutes at test temperature, the slitts were inserted vertically into molton brazing alloy under flux. Rights of the capillary rises and contact angles wera measured from X-ray radiographs. Contact angles and their decreases with temperature rise were very small in flux compared to in vacuum. It was obtained from the shape of sessile drop that surface tension of Sn in ZnCl2 at 300°C was smaller than in vacuum about 30%. Hight of capillary rise increases with test temperature increasing. Though this phenomenon is considered largely due to decrease of contact angle, authers could not determine it with X-ray radiographs.