In this study, it was carried out to investigate in detail the one dimensional diffusion phenomenon of carbon in steel, in austenitic temperature range, in the case of both time and temperature varying at the same time such as weld thermal cycles. According to the experimental results and phenomenological considerations, it was made clear that the one dimensional diffusion phenomenon of carbon in steel in austenitic temperature range during weld thermal cycles could be explained phenomenologically by Fick's second law in which diffusion coefficient, D was made to be a function of time.
In previous papers, on aniline hydrochloride flux action of soldering, it has been shown that molten aniline hydrochloride reacts with copper to give CuCl2 and copper complex, which react with molten solder to give metallic copper. Successively, this copper dissolves into the molten solder and a thin Cu-rich layer is formed on the surface of molten solder. The wetting of the solder on copper plate is improved through the reaction and the dissolution of Cu into molten solder. In this report, the flux action of various inorganic metal salts (chloride, sulfate and nitrate) on soldering was studied in the relation between the reaction of flux with Sn and wettability of Sn solder on Cu plate. The results of flux action of various inorganic metal salts are summarized as follows: 1) The reaction of molten Sn with metal salt and the effect of metal salt on spreading are dependent mainly on an electrochemical series. 2) The improvement of spreading by inorganic metal salts may be ascribed to the reaction of molten Sn with metal salt and the dissolution of the metal into molten Sn from the flux. 3) The difference in effect on spreading by inorganic metal salts is acknowledged to some degree.
This study is investigated on weldability of TD nickel, especially on the behavior of dispersed particles in welded zone at the first step of the study on weldability of dispersion hardening alloys. In previous report, the following results was obtained. In case of fusion welding of TD nickel, fusion zone is micrographically separated into three different regions. Even if melting-solidification time is about 1/6 sec, its separation is occured. So, in this report it was confirmed by the transmission electron microstructures of various fusion welded zone that the previous three regions were separated by distribution of ThO2 particles. And it was investigated the propriety of fusion welding for dispersion hardening alloys. The results obtained from this study are summarized as follows. (1) By transmission electron microstructures of various fusion welded zone, it became evident that the previous three regions are separated by distribution of ThO2 particles. Namely, in Region I, ThO2 particles make agglomeration and growth to some degree and form the honeycomb structure. In Region II, ThO2 particles make agglomeration and growth larger than in Region I. In Region III, ThO2 particles are excluded when matrix nickel is melted and solidified, and so it has the solidified structure of pure nickel. (2) At the point of view of wettability of metal-oxide system and work of adhesion, it is considered about the phenomena based on the behavior of ThO2 particles. And its propriety on consideration of exclusion of ThO2 particles is confirmed by the experiment of melting of SAP. (3) The tensile properties of TIG welded and EBW joints, having the previous three regions in fusion zone, are lower than those of base metal. (4) As the results of consideration for the propriety of fusion welding to welding of dispersion hardening alloys, it is concluded that it is impossible to obtain the dispersion hardening effect at the joint by existing fusion welding.
Six types of plain carbon steels were electron beam welded using a 150kV high vacuum type machine. In the preliminary testing, a set of welding parameters was selected which produced the largest amount of blow-holes and voids at 20 mm penetration. Using this condition, effects of beam oscillation (X, Y, circle) of various frequencies and double welding on defect-formation were investigated. It was found that 100 to 1000 Hz X(in line of welding) beam oscillation and double pass welding were effective to prevent above mentioned defects, and (C) × (O) showed the best coincidence with the tendency of defect-occurrence. These findings suggest that formation of CO gas during welding is the main cause of blow-holes and voids, however (Mn) contents showed the same degree of coincidence which suggest another mechanism of defect-formation as proposed by Arata et al. Conclusions are left to further studies. Spikes did not change appreciably among six materials, and this fact seems to support the theory proposed by Tong. From metallurgical investigations, the anthers propose to adopt qp=EI/vp (J/cm2, where E: accerelating voltage kV, I: beam current mA, v; welding speed cm/sec, p: depth of penetration cm) parameter for metallurgical as well as deformation and stress analysis.
The present paper gives a survey on shrinkage and distortion of groove welds of an explosive austentic stainless clad steel plate, paying attention to the effect of the clad metal of stainless steel with considerably different thermal and mechanical properties from those of the base metal of mild steel. The welding is performed by depositing a multi-pass bead in the groove of mild steel side by covered arc or submerged arc welding and subsequent back run of two passs with stainless steel covered electrodes. The interesting facts revealed are as follows: 1) The thermal cycles observed separately in clad and base metals at the same distance from the weld line are not so different during any pass welding as estimated approximately from the thermal conductivity of the two metals. 2) The formation of shrinkage and distortion of welds is, for the most part, due to the welding process of mild steel, and the effect of the back run is small. 3) By the submerged arc welding in mild steel groove, fan-like distortion of halves of weld on either side of weld line occurs so widely that the transverse shrinkage takes place in an arched curve along the weld line and the longitudinal shrinkage dose in a chevron in the transverse direction just as expansion occurs in the weld zone. 4) The angular distortion makes a general profile of welds saddle-backed with the stainless steel face concave along the weld line and convex in the transverse direction. 5) In the final state of welds, both the longitudinal remaining plastic contraction of weld zone and the longitudinal elastic strain corresponding to the residual stress distribute in conventional forms.
In the submerged arc welding, the diffusible hydrogen in the weld metal is remarkably influenced by the basicity of slag, CO2 gas generated from the flux and fluorine content in it. In order to make clear the hydrogen dissolution into submerged arc weld metal, it is necessary to study the hydrogen absorption in arc weld slag. In this paper, an investigation was performed on the hydrogen absorption in arc melted slag of lime-silica-iron oxide system. The slag was melted by using a tungsten electrode in a copper crucible under Ar- H2O or Ar- H2 atmosphere and the hydrogen content in the slag was determined by a vacuum fusion technique. The main results obtained are summarized as follows; (1) The hydrogen absorption in the slag achieves equilibrium within about 30 seconds of arc melting. (2) The amount of hydrogen absorbed by the arc melted slag is increased in proportion to the square root of water vapour pressure in the arc atmosphere. (3) The effect of the basicity of slag on the hydrogen absorption is remarkable, and the neutral slag has the minimum value of hydrogen content. (4) In the case of arc melting, the hydrogen in the slag can be absorbed not only by the water vapour but also by the hydrogen has in the arc atmosphere. (5) The hydrogen absorbed by the arc melted slag is decreased with addition of CO2 or O2 to the atmosphere. (6) The solubility of hydrogen in a molten slag may be estimated using a rigid sphere model in liquid state.
It is supposed that the grain boundary precipitation behaviour of chromium carbide and the decrease of corrosion resistance of the welded parts in austenitic stainless steel, with both thermal and strain cycles are different from those in the parts with only thermal cycle. The effects of stress at elevated temperatures on corrosion resistance in stressd and unstressed specimens (SUS 304) at sensistization temperatures were investigated for different keeping times. The results obtained are as follows: (1) It was recognized that the decrease of corrsoion resistance was promoted by the keeping stress at elevated temperatures (500°-800°C). (2) The longer the heating time, the more distinctive was the difference in decrease of corrosion resistance between the stressed and unstreassed specimens at 700°-800°C; it also became more distinctive as the stress was larger or the thermal and strain cycles were longer. (3) It was also recognized that the corrosionof the restrained parts of weldments were more serious than that of the unstrained parts.
Some basic problems in the application of supplementary heat to a weld joint before or after welding have been investigated using a mild steel, medium carbon steels, 50 to 100 kg/mm2 high tensile steels and low alloy steels. The results indicate that (1) cold cracking can not occur at temperatures above the critical point, which is 80°C in the case of HT-80 steel joint, (2) the activation energy determined by the incubation time is 11000 cal/mol at temperatures over-30°C and 2300 cal/mol below -30°C, (3) the activation energy determined by the effect of post-heating on cracking is 13000 cal/mol independently of steel grade, and (4) the preheat temperature may be reduced by using post-heating, but thermal stress cracking may occur under certain conditions under which blue brittleness or precipitation brittleness takes place.
Copper alloy clad steels have been used for vessels and other structures, e.q. heat exchanger, condenser, evaporator, particle accelerator, etc. 9/1 cupro-nickel clad steel has been often used for evaporator of sea water. Results of formability and weldability tests on clad steel hot-rolled with insert of nickel are described in the present report. The following are the results obtained from the examination. The clad steel exhibited a bond strength higher than the cladding after high temperature heating and severe deformation. No cracks were shown in bend test when welded by the TIG process with or without a buffer of monel or alminum bronze. Two kind of grain boundary infiltration were observed as reported by Matthews and Savage when these copper alloys except monel were deposited on steel. Peel out of the cladding and "dig" of base metal are often performed to prepare the weld groove, but a "dig depth" under 10% of base metal thickness did not result in reduction of joint strength.
An experimental study on thin-walled hybrid plate girders subjected to repeated loading is described. Six large-sized hybrid plate girders which were fabricated of HT-80 (quenched and tempered high strength steel) at a tension flange, SM-58 at a compression flange and SS-41 at a web were tested under repeated bending. Parameters investigated in this study were maximum stress, stress range, web slenderness ratio and rigidity ratio of longitudinal stiffener. Test results were discussed on the observed fatigue crack patterns according to the classification proposed by Toprac, and S-N curves for hybrid girders were plotted and compared with several past research data. Consequently, it has been proved that the stress range is one of the most significant parameters that affect the fatigue strength of hybrid girders, and the fatigue failure can be evaluated well from the crack at the transverse stiffener-to-web fillet weld below the neutral axis (Type 2 crack). A good correlation was observed in the fatigue test results between model specimens with transverse fillet welded attachments and largesized girder specimens, and comparisons with several fatigue data on steel plates with transverse fillet welded attachments showed that SS-41 web is the most economical.