Arc spraying condition is related to the maximum adhesion strength of sprayed coatings of aluminium and stainless steel. The suitable condition of arc spraying is obtained through arc stability test, measurement of the adhesion strength and observation of fused particle with high speed camera.
Main results of the study are summarized as follows;
(1) Three different areas on arc stability of spraying are recognized dependent on negative and positive wire feed speed, that is stable, self-regulation and unstable arc area.
(2) The maximum adhesion strength of sprayed coatings is obtained at the spraying condition of boundary between stable and self-regulation arc area.
(3) The adhesion strength increases with increasing, the size of fused particles on stainless steel arc spraying.
The fused particles are sphere of various diameater.
The fused particles are cooled within 1/8000 second after clashing on the substrate.

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It is well known that electron beam welding is superior in high efficiency, precision, and economy of cost, because of obtaining deep penetration with a single pass. Then it is eagerly awaited to apply electron beam welding for nuclear power plant components.
On the other hand, austenitic stainless steel widely used for nuclear power plant components. In this case, it is desirable to lower welding heat input as low as possible.
In response to this demand, the authors have been studied the welding conditions and the chemical compositions of base metal to prevent weld defect of austenitic stainless steel. The results obtained are summarized as follows:
(1) Electron beam welding is applicable for austenitic stainless steel up to 80 mm thickness.
(2) To prevent hot cracking, (P+S) contents of base metal should be controlled under 0.045%.
(3) To prevent porosity, nitrogen contents and oxygen contents should be controlled under a certain value according to the thickness.

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Undercutting occurs when molten metal is displaced more than a solidification ponit along a toe of weld pool. Therefore, it seems likely that the occurrence of undercutting can be suppressed by means of delaying solidification of weld pool and preventing the displacement of molten metal. Based on these results obtained in report 1 of this study, this investigation aimed to develop a new submerged arc welding technic which allows higher welding speed without undercutting than that of the conventional submerged arc welding.
The results were as follows,
(1) Oblate ratio of arc heat source to the welding direction affects the solidification pattern greatly. The higher oblate ratio becomes, the more the solidification of weld pool is delayed.
(2) The effect of heat source shape (electrode shape) on the solidification pattern is observed in welds which are performed with strip electrodes. But the application of strip electrode for high speed welding is not suitable because of an instability of its arc.
(3) Deformed arc heat source with a group of fine electrodes lined up along the welding direction allows higher welding speed without undercutting than that of the conventional submerged arc welding, as a result of delay of solidification and smaller displacement of molten metal.

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It had been shown that hot tensile strength and thermal embrittlement were improved by a small addition of vanadium about electroslag weld metals of heavy section 2 1/4Cr-1Mo steels which were usually used for high temperature and pressure vessels such as direct desulfurizing processes.
Effects of vanadium on the properties of the weld metals were more precisely discussed in this study. The main conclusions are as follows:
(1) Reheat cracking susceptibilities were not changed in the electroslag weld metals even if the vanadium was addde up to 0.12%.
(2) Tneisle strength at room temperature and at 435°C were linearly increased with vanadium content up to 0.07% and up to 0.03%, respectively. More addition of vanadium up to 0.12%, however, did not changed both tensile strength and kept them constant. Factured elongation was gradually decreased with vanadium addition at first, and then became constant or a little increasing.
(3) Thermal embrittlement of the weld metal was drastically improved with vanadium addition and the weld metal with 0.12% V was judged practically immune from thermal embrittlement.
(4) Favorable effect of vanadium on thermal embrittlement was mainly attributed to prevention of precipitation of P and Mn on grain boundaries.

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Thermal embrittlement of 2 1/4Cr-1Mo electroslag weld metals in high temperature operation was studied in this report, with particular emphasis on grain boundary segregation of solute elements proved by Auger spectrum analysis.
The main conclusions obtained in the study were as follows:
(1) The embrittlement were mainly caused by grain boundary segregation of phosphorus.
(2) Silicon and manganese acted as promote the segregation of phosphorus, and also manganese itself did embrittled grain boundaries by segregation like copper and some carbides.
(3) Small precipitates on grain boundaries, which were supposed chromium and/or molybdenum carbides, gave favorable site for segregation of phosphorus.
(4) Sulphur in weld metals occupied grain boundaries after welding and postweld heat treatment, being in contrast with no occupation in base metals. This might be main reason why weld metals were much less tough, compared with base metals when fracture occurred in grain boundaries such as thermal embrittlement.
(5) Segregation of phosphorus and other solute elements increased with holding time in isothermal treatment and reached to a saturated value. Degree of segregation was larger for phosphorus than for carbon, chromium and molybdenum.
(6) Progress of segregation of solute elements was more rapid than that of embrittling.
(7) Correlation of embrittlement between step cooling and isothermal treatment was not definite and changed depending on chemistry and thermal history of weld metals.
(8) C-curves of isothermal embrittlement of 2 1/4Cr-1Mo welds had an intermediate mode between that of Ni-Cr steel by Jaffe and that of Cr steel by Vidal.

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Influences of V and Ti on the reheat cracking sensitivity of Cr-Mo steels were investigated using 13 synthetic 0.06%V-bearing and 9 synthetic 0.07%Ti-bearing Cr-Mo steels, which contained 0 to 2%Cr and 0.25 to 0.8% Mo. Cracking sensitivity was evaluated in term of the critical restraint stress; σAW-crit obtained by the implnat type reheat cracking test. The results are summarized as follows. (1) 0.06%V addition increases the cracking sensitivity especially in the content region of low Mo. (2) 0.07%Ti addition increases the cracking sensitivity especially in the content region of low Cr and high Mo. (3) Two important factors which dominate the critical rsetraint stress are the stress relaxation; R and the grain boundary strength at the time of crack initiation; σpw-crit. V and Ti remarkably decrease R but they hardly decrease σpw-crit. (4) The decrease of the stress relaxation was mainly associated with the strengthening of matrix which was brought by the precipitation of V₄C₃ and TiC during reheating.

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Consideration has been conducted on the quantitative evaluation of the residual stresses and deformations due to longitudinal welds of a pipe. In the present study, the trapezoid-inherent strain model based on the Green function in a non-stationary thermoelastic problem of a thin cylindrical shell, was newly proposed to estimate the stresses/deformations. The stresses and deformations calculated from the analytical model proposed newly agree well with those measured in the practical longitudinal welds. The parameters controlling the properties of the residual stresses and deformations could be derived analytically by using the above analytical model. The controlling parameters, which it is confirmed experimentally to be successful for evaluating stresses and deformations, are (Tav)x{=Q/2cρπah} and β_z{=√a/h·a/l}, where Q, c and ρ are net heat input per unit weld length, specific heat and density, and a, h and l are the mean radius, thickness and length of a cylindrical shell respectively. When the value of the parameter β_x is considerably small, both of the residual stresses and deformations are determined by the only parameter (T_av)_x.

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Recent welding sequences are studied on the erection butt joint of ship-hull-block, in which plates and stiffeners are tack-welded at the same time.
Restraint intensity and residual stress are measured with block butt joints fabricated by the recent welding sequences and compared with the value of calculation by F.E.M., calculation of elastic dynamic, and measurement on actual ship by other researchers.
The conclusions are as follows:
(1) No cold cracks due to restraint occur under the maximum restraint condition of block butt joint which has a tack welding at the weld deferment.
(2) The residual stress distribution of welded joint of ship-hull-block shows no remarkable differences due to the welding sequences.

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The standard conditions for stress relief annealing (SR-treatment) of welded structures such as pressure vessels are indicated by JIS or ASME code. However, application of these conditions to high quality thick plates seems to be unreasonable, since they require for such plates to simply keep higher temperature for longer time than actually needed. This is partially due to the lack of sufficient knowledge on the effect of SR-treatment over the reduction of welding residual stresses, especially for thick plates. On the other hand, the theory of thermal elastic-plastic creep analysis based on the finite element method has been well developed. Although the SR-treatments of welded joints of very thick plates have been analyzed by this method, its application. is not easy but requires a great deal of computation. Accordingly, it is necessary to develop some simple calculation method to accurately estimate residual stresses remained in a very thick plate after SR-treatment.
In this fundamental study, using the various relations between stresses and strains during SR-treatment, estimating equations are formulated in order to simply calculate residual stresses after SR-treatment as in a uniaxial stress state. As a demonstration, approximate equations are developed for the relaxation test both at a constant and changing temperatures because of its similar stress relaxation phenomenon to that of SR-treatment. The results are compared with the highly accurate analytical result based on the finite element method. The both results show such a good coincidence that the appropriateness of the adopted method is confirmed.
In the next report, this method will be developed and applied to SR-treatment of welded structures with more general stress state and boundary condition in order to obtain the change of residual stresses in a welded joint of a very thick plate.

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The weldability of Inconel 713C casted alloy and Inconel 718 forged alloy for high tmeperature components was investigated as a dissimilar metal joint by electron beam welding. As a result, fine Equation cracks in HAZ of the joint were detected by microscopic examination. This type of crack was very difficult to be prevented only by changing EB welding parameters. Then, it was experimentally found that hot isostatic pressing as a thermomechanical process could completely healed such fine cracks. And tensile strength at elevated temperature and creep rupture stress of HIPed joints after EB welding were not less than those of Inocnel 718 alloy.

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Relation between electric constants of coils and the result of electromagnetic welding was examined on the specimens consisted of the couple of tube and core bars. Electric constants of apparatus and coils were obtained from the current waves under each condition. The result of welding was estimated for each coil by the acceptable limit of clearance between tube and core bar.
As a result, accumulating rate of magnetic energy of coil which was defined as the time differential of magnetic energy was confirmed to be the most important electromagnetic factor. Welded joint became more successful according as the coil with larger accumulating rate was used for welding. The largest accumulating rate was obtained by the coil inductance of 3.3 μH for the apparatus of Ro=7.3 mΩ, L_o= 2.38 μH and C_o=912 μF.

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An effective method to investigate the causality model in heat processing is discussed. The computer processing system in this method consists of the data base and several peripheral modules.
The hardness estimation of CO₂ laser surface hardening is carried out in this report as the concrete application of this system. Several hardness estimation models are implemented by composing and utilizing small and simple program modules. These modules are evaluated in this system which utilizes data base and corrected by steps. This process is very effectively executed in this system. The most suitable model that has been evaluated by the above method can be applied to the hardness estimation in the wide range of condition.
For the verification, automatic condition setting is done. The estimated results closely correspond to the experimental results (hardness distribution) under the setting conditions.

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The effects of silicon and oxygen content on the toughness of 9%Ni steel weld metal were investigated using ferritic welding wires. (1) The toughness behavior against heat treatment temperatures is similar to that of 9%Ni steel plate, showing a peak value by tempering at 590°C regardless of the content of the two elements. (2) Reducing oxygen content improves the peak value when the silicon is low (0.10wt%), but it works adversely when the silicon is high (0.45%). At a medium silicon (0.27%), the toughness reaches a peak when the oxygen content is about 230ppm. The absolute value of vE-196, however, tends to decrease with an increase in silicon content. To use a low silicon wire in a pure argon shield is the best measure for furnishing sufficient toughness to the weld metal. (3) The temper-softening is retarded by increasing silicon content, and non-metallic inclusions are multiplied by increasing oxygen content. The toughness behavior against oxygen contents is determined by the balance between the content of silicon in solid solution and the amount of non-metallic inclusions. (4) At the optimum tempreing temperature of 590°C, the amount of retained austenite shows a peak value as well. However, the retained austenite alone is not considered the major factor influencing the toughness of ferritic weld metal.

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The notch toughness of weld-HAZs deteriorates with the increase in welding heat input. The degradation of notch toughness is caused by the austenite grain growth and heterogeneous transformation products. 60 kg/mm² grade high tensile strength steel's weld-HAZ has a stronger tendency to increase the unfabourable transformation products, for example M-A constituent, than 50 kg/mm² grade steel's weld-HAZ, because of its higher hardnability. So it was concluded that 60 kg/mm² grade steel's weld-HAZ showed lower notch toughness than 50 kg/mm² grade steel's weld-HAZ, when the high heat input welding processes were used.
This investigation was carried out to clarify the factors which govern the HAZ toughness and to develop the 60 kg/mm² grade steel suitable for high heat input welding. The results were summalized as follows.
(1) 60 kg/mm² grade steel's weldment made by the electrogas are welding technique showed low notch toughness at the weld-HAZ. These deterioration could be recognized not only at the coarse grained region but also at the fine grained region in HAZ.
(2) When the welding heat input was higher than 60 kJ/cm, HAZ toughness was improved with decreasing the heat input. On the other hand, HAZ toughness became to deteriorate with decreasing the heat input, when the welding heat input was lower than 60 kJ/cm.
(3) Welding heat input dependency on HAZ toughness mentioned above could not be explained by metallurgical point of view. But it could be interpreted by correlation between notch position and hardness distribution. That is, when the discontinuity of strength existed near the notch, the brittle crack initiated at the notch root deviated and propagated towards weaker region. And obtained values were govrened by the characteristics of weaker region.
(4) The experiment was conducted to improve the HAZ toughness. As a result, HAZ toughness of 60 kg/mm² grade steel's weld-HAZ toughness was improved by reduction of carbonequivalent. This improvement was resulted from reduction of M-A constituent and formation of pearlite.
(5) The tensile strength of low carbon equivalent type 60 kg/mm² grade steel's weld-HAZ had a tendency to decrease at the inverse of heat input. In practice, however it was concluded that lowering the carbon equivalent in a range investigated in this study got no trouble.

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In the previous paper, the authors conducted the coil-spring loading 3-point bending COD test and the large sacle tests on the 9% nickel steel weldments and determined that the weld-HAZ itself had satisfactorily high toughness to avoid the initiation of brittle fracture at cryogenic temperatures down to -196°C.
This paper describes further studies conducted on the 9% nickel steels including the extra low impurities one to bear out the superior weld-HAZ toughness from the metallurgical view points. Fracture toughness expressed in terms of CTOD and Charpy-V energy value was revealed to be significantly improved with the decreasing of phosphorous content in the region below 0.005%.
The relation of fracture toughness and the microstructures which form the weld-HAZ structure were evaluated qualitatively by paying special attention to the reverse martensitic transformation mode during heating. As a result, it was evidenced that the superior weld-HAZ toughness depended on mainly its matrix structure, as low carbon Ni contained cellular martensite. The island-like martensite observed in microstructure of specimens subjected to heating to the temperatures, 700 to 900°C was identified as high carbon twinned martensite by the electron diffraction pattern analysis. The microstructure of specimens subjected to heating to 1350°C contains a little upper bainite.

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The present study was carried out to clarify the effect of neighboring mechanical heterogeneity on the ductile-to-brittle transition behavior of steel in the Charpy impact test. Specimens were manufactured from a high tension structural steel with bead welding by electron beam weld. Instrumented Charpy test was carried out in the transition temperature range. The resuts of the Charpy test were shown to be dependent not only on the toughness of weld metal but also the mechanical properties of base metal in the vicinity of weld metal. The mechanical heterogeneity existing in the neighborhood of the notch root decreased the upper shelf energy and raised the transition temperature in the Charpy test of specimens with weld bead.
In addition, the elasto-plastic analyses on stress and strain in the Charpy specimen with weld bead were conducted by using finite element method. The analyses showed why the upper shelf energy and the transition temperature were affected not only by the toughness of weld metal under the the notch root but also the mechanical properties of base metal in the vicinity of weld metal.

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Concentrations of stress/strain at the notch tip of notched-wide plate specimens of undermatching and evenmatching welded joints are investigated by elasto-plastic FEM analyses. In the undermatching weld specimen in which notch is located at weld fusion line, magnitude of stresses/plastic strains in an area of heat-affected zone side adjacent to the notch tip is released by plastic deformations of weld metal of which yield strength is lower than base metal, and as the results the stress/strain concentration is quite smaller than those in evenmatching weld specimen. This leads us to the conclusion that 9% Ni steel weldments of undermatching austenitic 70%Ni-alloy weld metal will be much insensitive to brittle crack initiation at HAZs than those of evenmatching ferritic weld metal. The local COD δBep values which should control stresses/strains at embrittled HAZs are also considerably smaller in undermatching specimens than in evenmatching specimen. Based on expected joint strength of 9%Ni steel weldments, discussions are made on fracture toughness requirement for both undermatching and evenmatching weld HAZs. Carck path observed in notched-wide plate tension tests at LNG temperatures that brittle crack initiated from the pre-existing notch at HAZ goes into austenitic weld metal and is often arrested is understood by the change of principal stress directions resulted from the difference in Young's modulus between weld metal and base metal.

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This paper deals with the effect of welding conditions on the residual stress distribution produced in solid and hollow cylinders by use of finite difference method for obtaining the thermal elastoplastic stresses. The important parameters of residual stress distribution were derived with the similar law of heat flow theory. The figure representing the relation between the parameter and the residual stress distribution was obtained. It appears that the temperature dependence of Young's modulus and the coefficient of linear expansion had no influence on the residual stress distribution. The water cooling conditions exerted the influence on the residual stress of the weld metal.

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In order to correlate the temperature dependence of critical COD, δ_c, with Charpy-V transition temperature, FATT, the statistical analysis was attempted on the available data of notch toughness.
About 1300 data on the notch toughness in the base metal and welded joint of mild steel and high strength steel were compiled from published and unpublished literatures.
Firstly, the statistical hypothesis that there exists the linear relationship between logarithm of δ_c, and reciprocal of absolute temperature was tested. As a result, the hypothesis was found to be significant. The coefficient of the linearity decreases with increasing strength and doesnot depend on FAIT.
Secondly, the correlationship between temperature at δ_c=0.16 mm and FATT was examined.
Finally, taking into account the uncertainties included in the estimation of δ_c. from FATT, the following equation was established with the aid of maximum likelihood method:
Inδ_c=In0.16-4328/√σY0(1/TK-1/TK0.16)+|0.86+14.0(1/TK-1/TK0.16)|z
whereTK=Tsv-6√B+303(K), TK0.16=γTS+σY0+153(K),
f(z)=1/√2πexp(-z²/2)(standard normal probability density function),
vTs: FATT (°C), Tsv: service temperature (°C),
σY0: yield stress at room temperature (kg/mm²), B: thickness of COD test specimen (mm).

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The welding distortion of electron beam welding is smaller than conventional arc welding processes and the behavior of the welding distortion by the multipass welding is different from the arc welding because of its deep penetration characteristics.
We report the results of some measurements on transverse shrinkage and angular distortion and discuss them in this paper.
The results obtained in this study are as follows;
1) The transverse shrinkage of the partial penetration was smaller than the full penetration.
2) The transverse shrinkage of electron beam welding was in proportion to the welding heat input per unit.joint area.
3) The angular distortion of electron beam welding was inversely as the plate thickness.
4) The transverse shrinkage of the mutipass welding was proportinal to the number of passes.
5) The volume of reinforcement by electron beam welding was closely connected with the transverse shrinkage.

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High-nitrogen bearing austenitic stainless steel weld metals were obtained by using type 304 electrode wire (1.6 mm) and N₂-Ar mixture shielding gas.
Tensile and impact tests on deposited weld metals were carried out at test temperatures from 0°C to -196°C.
The results can be summarized as follows:
Nitrogen content of weld metals increased considerably with N₂-volume percent in shielding gas, and at 100% N₂ shielding gas, the nitrogen content of weld metal showed about 0.2wt%.
A cast structure which contained δ-ferrite was observed in the weld metal in as-welded condition, but the content of δ-ferrite decreased with increasing nitrogen content of weld metals. There is no δ ferrite in the weld metals which contained about 0.18wt% nitrogen. The 0.2% proof stress increased with nitrogen content of weld metals. This tendency was clearly observed as the test temperature decreased and this behavior was discussed in relation to the strain-induced martensitic transformation in the weld metal at low temperature.
The tensile strength of weld metals increased as the test temperature decreases but was not changed by nitrogen content of specimens.
At impact test, the absorbed energy of weld metals slightly increased with increasing of nitrogen content of weld metals.
The effect of nitrogen on the absorbed energy of high-nitrogen bearing weld meatl can be changed by welding methods and source of nitrogen to weld metals.
High-nitrogen bearing type 304 austenitic stainless steel weld metals can secure a high proof stress without decreasing of the toughness at low temperature.

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Spatter generation in CO₂ arc welding was investigated, using 1.2 mm solid wires with various chemical compositions. Correlation between the amount of spatter, measured by collection on a copper plate with a diameter of 1, 200 mm, and the number of short circuit longer than 1 msec were investigated. Increase of manganese, silicon, selenium and titanium in wire decrease the amount of spatter, while carbon, aluminum and REM increase the amount of spatter. However, an excess of selenium increase the amount of spatter. Spatter generating process was classified into five groups, and it was concluded that the spatter in CO₂ welding was mainly caused by the explosive enengy of the arc.

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The feasibility of wet welding process in underwater with covered electrode is investigated. Welding experiments are done with HT 60 steel plate and D5003 covered electrode.
The following results are obtained:
(1) The hardness of heat-affected zone seems to be relatively low in case of two pass welding.
(2) In underwater welding, weld metal seldom has blowholes, and no cracks are observed on the weld metal in X-ray inspection.
(3) In underwater welding the oxygen absorption of weld metal is about 1.7 times of that in-air welding, the nitrogen absorption has about 0.25 times.
(4) The quantity of diffusible hydrogen collected in mercury reaches to a constant volume in about 2.4 × 10⁴ min. (408 hr).: In air welding, it is about 30 cc/100 g in case of one pass welding and about 25 cc/100 g in case of two pass welding; in underwater, it is about 70 cc/100 g in case of one pass welding and about 55 cc/ 100 g in case of two pass welding.
(5) On two pass welding, the quantity of diffusible hydrogen is about 20% less than one pass welding.

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The flashing phenomena in flash welding have been investigated using the steel sheets of 1.2 mm thickness in previous studies. In this study, the effects of the flashing variables on the absorbed thermal energy and the situation of the specimen to be welded are discussed. The absorbed thermal energy of the specimen in flashing operation is calculated from the temperature rises of the copper blocks fixed the specimen. The following results are obtained.
1. There is a critical value of secondary no load voltage for flashing that changes remarkably the absorbed thermal energy in specimen to be welded. The decreasing voltage from the critical vlaue results in increasing absorbed thermal energy because of joule's heat in the bridge phase.
2. The critical voltage is about 6 volt under the welding conditions in this study, and also has influence upon the heat affected zone and the quantities of fusion metal on the edges of specimen.
3. It is possible to control the absorbed thermal energy in specimen using the new processes such as voltage waveform control, mechanical or electrical platen control.

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In this paper we describe the permissible time of arc sound exposure from standpoint of conservation of hearing acuity.
The permissible time of arc sound exposure was revealed in accordance with the standard of ACGIH (American Conference of Governmental Industrial Hygienists) in various welding methods and conditions.
The particular attention should be paid to high current arc welding, pulsed arc welding, plasma jet or the like: in this case, ear plug and ear muffler have the effects of conservation of hearing acuity.
The standard of ACGIH is different from that of JCGIH (Japan Conference of Governmental Industrial Hygienists) in terms of the permissible arc sound exposure. It is shorter in JCGIH than in AC-GIH in most cases.

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