The effects of not only degree of cold work but also strain at heating on recrystallization of metals were investigated. First, by comparing the behaviours of secondary recrystallization of Armco iron specimens which were heated freely with those heated under the compressive stress, it was recognized that the secondary recrystallization temperature of Armco iron was reduced by the compressive stress at elevated temperatures. By the hot stage microscopy of the vacuum melted copper specimens compressed to various degrees at room temperature, it was also recognized that the secondary recrystallization temperature was reduced by cold work.
Next, the effects of degree of coldw ork on the recrystallization at weld heat-affected zone received the thermal cycle which had characteristics of rapid heating and cooling, were studied after welding actually some kinds of metal specimens cold worked to various degrees.
The results obtained were as follows:
1) The larger the degree of cold work in aluminum specimens was, the smaller was the size of recrystallized grain at heat-affected zone, except 5% degree of cold work.
2) The size of recrystallized grain at coarse grain part of heat-affected zone in stainless steel specimens cold worked to any degree, was always larger than that of 0% degree of cold work. However, the size of recrystallized grain at fine grain part in specimens cold worked to any degree, was always smaller than that of 0% degree of cold work, except 5% degree of cold work.
3) On the contrary, the difference of size of recrystallized grain in the various degrees of cold work in mild steel specimens which underwent α-γ transformation, was not recognized.
4) The larger the degree of cold work in aluminum and stainless steel specimens was, the larger the width of recrystallized zone at heat-affected zone became.
5) However, any change of the width of recrystallized zone at heat-affected zone in mild steel specimens cold worked more than 15% was hardly recognized.

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In case of the butt joint, previous report indicated that good welds were obtained by using the water curtain type CO₂ arc welding method.
This paper presents the results of experimental investigation of the horizontal fillet welding used by th, said method, and following conclusions were reached.
1) The water curtain type CO₂ arc welding method was also effectively available for underwater horizontal fillet joint.
2) Good welds without blowholes and cracks were obtained by selection of optimum welding conditions.
3) Welding speed used with flux cored wire faster about twice than that of used with solid wire. 4) From the results of studies on effect of O₂ mixing in Ar and CO₂ shileding gas, the hardness of welds decreased with the increace of oxygen content in case of solid wire.
5) The joint with root gap up to 2-3 mm did not affect the welding result.

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This paper deals with residual stresses of high tensile steel member caused during the welding process.
The characteristics of the residual stress distributions in I section members and welded plates of 80 Kg/mm² high tensile steels (HT80) and 50 Kg/mm² high tensile steels (SM50) are discussed by the experiment, the simple model (a connected bar-spring model) and numerical analysis using thermo-elasto-plastic theory.
The following results are obtained.
1) The ratio of average compressive residual stress of HT80 to yield stress is less than that of SM50. This is due to the narrow tensile stress zone of HT80 and its small ratio of tensile residual stress to yield stress.
2) The tensile stress zone of HT80 is narrower than that of SM50 by reason that the maximum heating temperature of HT80 which is necessary for the tensile residual stress appearance is higher than that of SM50.
3) Preheating operation for welding of HT80 is effective to reduce the residual stress.
But, for welding of SM.50, preheating is not effective.

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In the previous paper the author described the effect of coating materials of electrodes on the maximum arc length, the variation of the arc length under various windy conditions, i.e. the different velocities and the directions of wind, and the change of the arc voltage and the current at the experiment. Then the correlation between the set angle of electrode and the winds' condition became evident and it was assumed that the decrease of the maximum arc length was caused by the disturbing actions which affected the ionization of vaporized materials and gasses maintaining the growth of the arc.
In the present paper the author deal with more detailed experimental conditions based upon the previous process of the researches and extend the investigation about some factors concerning the decrease of the maximum arc length under windy conditions while analizing the phenomena of wind disturbance on the arc column.
Results of the experiments are summarized as follows:
(1) The decrease of the maximum arc length of coated electrode, bare electrode or tungsten electrode shows a slight different tendency respectively and this means that the wind may disturb each ionic material of the rods differently. The variation of the maximum arc length shows a similar tendency with alternating or direct current, but it is recognized that the decrease of the arc length with direct current does not change scatteringly and this shows exact stability of the direct current arc.
(2) The decreased length of the arc is not proportional to the increase of wind velocity and for example, the calculated mean value of the decrease percent within the range of the wind velocity of Om/s and 4m/s(L₄/ //LO) is not proportional to that of 4m/s and 9m/s(L₉/L₄).
(3) By the observation of photographs of the arc under the windy condition, the phenomenon of flowing of the arc which differs from the so-called arc blow or other abnormal behavior by the electrical disturbance. It can be considered that the feeding source of ionic materials, i.e. the coating materials, the electrode metals and other atomospheric gasses, seems to be disturbed and floated by the wind blowing.
(4) The analysis of the correlation between the maximum arc length and the set angle of electrode proves that the interaction between the angle and the wind blowing affects the maximum arc length and the angle of:1/4π is effective to maintain the longest arc length.

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Behaviour of sulphide and solidification crack susceptibility in TIG-arc weld metals of Fe-S-Mn-Niand Fe-S-Mn-C quarternary alloys have been investigated. In these alloys the sulphur contents were purposefully somewhat higher than those encountered in commercial steels. Main conclusions obtained are as follows:
1) The addition of 2-..7% nickel or 0.2% carbon to the weld metals containing 1% manganese and 0.0480.086% sulphur not only causes the formation of filmlike sulphides (MnS) at the columnar grain boundaries, but also lowers the eutectic temperature at which the sulphides are formed. The increase in manganese content up to 2-..3%, however, prevents the formation of filmlike sulphides, and raise the eutectic temperature.
2) The solidification crack susceptibility, which is evaluated with Trans-Varestraint test, is increased at 1 % manganese level with the increase in nickel or carbon content. The increase in manganese content up to 3%, however, lowers the susceptibility to the same degree as that of Fe-S-Mn ternary alloy whose Mn3/S is larger than 6.7.
3)The general relationship between manganese and sulphur contents to prevent the detrimental effect of sulphur in Fe-S-Mn-NiandFc.S-Mn-Calloys is expected.
That is, the relationship in which the solidification crack susceptibility is comparatively lowered is given as follows;
Mn5/S>310-560
Moreover, the relationship in which the susceptibility is lowered to the same degree as that of Fe-S-Mnalloy whose Mn³/Sis larger than6.7 is given as follows;
Mn5/S=2500-3600

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As the result of the application of micro-fractography to the investigation of the weld cracking of mild steel, the following fact was clarified: that many of fan-like patterns, which were the evidence of hydrogen embrittlement cracking, and the micro-void coalescence (the dimple pattern) between them were observed on the fracture surface of cold cracking of the deposit metal and the heat affected zone, and that the evidence of the cracking along the dendritic boundaries was observed on the fracture surface of the crater cracking.

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The weldability of dispersion hardening alloys must be made clear in order to use them in various industries. Especially, on the point of practical use, it is very important to increase the joint efficiency.
So, in this report, the disappearance of voids and the behavior of ThO₂ particles at the bonding interface were discussed as the first step of applying the solid state bonding to the dispersion hardening alloys.
The main results obtained are summarized as follows;
(1) The disappearance of voids is mainly accelerated by the local creep deformation. The mechanical deformation at the bonding interface is an important process for the solid state bonding.
(2) The disappearance phenomena of voids and the behavior of ThO₂ particles at the bonding interface were metallurgically investigated. The authors indicated the temperature-time region which was useful to etermine the solid state bonding conditions of TD nickel.

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It is known that the apparent diffusion coefficient and the occlusible amount of hydrogen in steels show anomaly under the temperature of 200°C, depending upon the amount of the plastic strain. If the hydrogen diffusion in steels is influenced by the plastic strain fields, steels cannot be uniform mecdia for hydrogen diffusion. The hydrogen diffusion, therefore, does not follow the Fick's second law but does the general law of mass transfer. in which a driving force for the diffusion is exerted by the chemical potential gradient.
The diffusion and local accumuration of hydrogen in steels were quantitatively analized the finite difference method under the condition holding the law of mass transfer. The analysis was made for steels with distributed hydrogen trapping sites which are assumed to be plastically strained regions. As a-result of the numerical analysis, the apparent diffusion coefficient in steels plastically strained corresponding to 0.1% void volume below 150°C was found to be 0.12 exp (-7800/RT) which coincides with the experimental result by Johnson and Hill.
This analytical method was attempted to solve quantitatively the hydrogen diffusion and accumulation in the weld fusion boundary of a bead on a plate. Findings in this analysis are as follows:
1. The hydrogen concentation at the weld fusion boundary attains to several times the initial concentration 4 days after the completion of welding;
2. The preheat and postheat treatment are effective to prevent the hydrogen accumulation in the weld fusion boundary and the hydrogen concentration never exceeds the initial level when applying 150°C postheat treatment.

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6mmおよび12mm厚さの2 1/4Cr-1Mo鋼(ASTMF 22)とオーステナイト系ステンレス鋼(AISI 316)の異材継手および炭素鋼(SM 41A)の同材継手について,インサート型電子ビーム溶接による適正裏波溶接条件選定を目的とした諸試験を行なった結果,次の結論を得た.
1)最大溶込み深さ部近傍における溶接部の諸特性のうち,スパイク現象については,最大スパイク長さが1.5mm以下のものが全体の約80%を占め,それを越える長さのスパイクの発生頻度は急激に減少する.また,ペネトロパラメータP_pが約6以上になると,1.5mmをこえる長さのスパイクが発生し易い.なお,ビード断面形状については,溶込み部先端が極端に細いクサビ(Wedge)型ビードを形成する.
いっぽう,最大溶込み深さ部以外における溶接部の諸特性のうち,スパイク現象については,1.5mmをこえる長さのスパイクが発生し始めるP_p,sはa_b>0.90のときP_p,s>6,a_b≈0.90でP_p,s≈6,a_b<0.90はでP_p,s<6になり,a_bの減少とともに小さくなる.また,ビード断面形状については,同一条件(同じ電子ビーム)で,同一溶込み深さの得られるa_bは2個存在し,a_b>0.90の場合はビード断面形状は井戸(Well)型に近く,ab≦0.90の場合はクサビ(Wedge)型に近い.
2)インサート型電子ビーム溶接法による裏波溶接においては,インサートメタルの幅以上の断面ビード幅を有し,スパイク現象の発生が少なく,表面および裏面部のビード幅がほぼ等しいような井戸型ビード断面形状の得られる溶接条件を選定しなければならない.このような条件を満足するa_bはほぼ1.20前後である.また継手形状としては,ルートスペースを有する継手形状を採用することにより,裏波溶接が容易になる.また,良好な表面および裏波ビードを得るためには,ビード断面形状および余盛高さの観点より,インサートメタルの高さを継手部の厚さにほぼ等しくなるように選定することが望ましい。
3)ルートスペースを有する継手形状を採用することにより,適正溶接条件範囲が広くなり,板厚が増大するにつれてその有効性は著しくなる.その場合の裏波ビード形成機構は対流型に近づく.また,管の溶接の場合において問題となるスパッタについても,ルートスペースを付すことにより,著しく減少し,実用的価値が高い.
4)脱酸不十分な炭素鋼の同材継手において,インサートメタルを使用しない場合には欠陥の発生は著しい.しかし,強脱酸性を有するアルミキルド鋼のインサートメタルを使用した場合にはインサートキャップ高さ(またはインサートメタル高さ)または断面積が増大するに従って溶接部に発生する欠陥は減少する。

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