This research was aimed at surveying the differences of welding residual stresses due to the differences of welding conditions in connection with the research on welding cracks conducted by the author. The variations of welding conditions prefered were those for the kinds of electrodecore-rods, the diameter of core-rods, the kinds of base metals and the local heat-treatment after welding.
Single beads were deposited on the surfaces of many rectangular. specimens of mild steel and ducol steel.
These specimens were subdivided into strips perpendicular or parallel to the bead line after depositing.
The differences of the distances between two point-marks before and after subdividing, namely residual strains, were measured.
The distributions of residual welding, stresses were determined from these measurements by an approximate calculation formula of elasticity.
The main points of the results obtained are as follows:
1) The residual stresses perpendicular-to weld lines are in compression at both edge-portions and in tension at the central portion of the plate.
2) The. residual stresses parallel to weld, lines are in compression at. both sides and in tension in the. vicinity of weld lines.
3) These is no great variation in the residual stress distributions between mild steel and ducol steel.
4) The amounts of residual stresses are changed considerably by the differences of electrodes. And even if the core rods are equally mild steel, there are pretty large differences in residual stresses between the cases for 5mm and 3.2mm diameter core rods. Namely, the maximum tensile stress perpendicular to the bead line by the former is greater than. the latter, and the maximum tensile stress parallel to the bead line by the former is smaller than the latter.
When the amounts of residual stresses by Cr-Mo. steel electrodes, mild steel electrodes and 18-8 atstenitic steel electrodes are compared, the maximum values of tensile stresses for both directions are arranged from large to small in order of this description. Therefore, it is understood that onefactor for the suitability of austlnitic steel type electrodes for the welding of alloy steel, especially high tensile alloy steel, is a small amount of residual stresses.
5) There is no great change in the distribution of mean residual stresses in the macroscopic field even when the weld line is locally post-heated by gas-flames.
However, the maximum tensile stress parallel to the weld line of ducol steel plates is increased considerably by local postheating. This phenomenon is considered to be due to the tempering of hardened zones.
6) Local heating at the center line of steel plates, which seemed to have no initial stress, gives much the same distribution of residual stresses as in the case of welding.
The author examined the relation between the results obtained and the types and prevention of welding cracks.

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In the hardness distribution of welding beads in the direction of the welding, the highest values are found at both ends of the beads. These facts giay be discussed by the theory of cooling rates in the unstable state which we treated in the preceding paper and the quenching diagram of welded metals.

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In order to stabilize the arc in the automatic metallic arc welding, we manufactured a new apparatus to control the arc length.
In this paper we report the function of this apparatus and some results obtained from its application to practice.

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In this research, the authors designed and manufactured a special apparrtus for statical bendingbreak tests of plates, and statically broke unaffected plates made of alloy steels and plates deposited with a single bead using the apparatus. And they measured the energies necessary for the statical bending-break, and compared the numerical value of the former with that of the latter. In this manner, the following results were obtained.
(1) The energy necessary for the statical bending-break of a rectangular alloy steel plate deposited with a single bead is very smoller than that of the unaffected plate having the same composition and heat-treated in the same manner without weld-deposition. That is, the effect, of a bead deposited with arc on the necessary energy is very large.
(2) The energy necessary for the statical bending-break of alloy steel is variable with the kind of alloy steel considerably. Namely, if we assume that the toughness of a steel plate can be expressed in sgch a numerical value, the toughness varies with the kind of alloy steel in a marked degree.
(3) The authors called the numerical value, which is obtained with dividing necessary energy for the unaffected plate by that for the plate deposited with a single bead, in the term of the sensibility value for weld-deposition. Then they proposed to express the sensibility for weld deposition in such a numerical value. That is, this property varies remarkably with the kind of alloy steiel. And the authors considered that the phenomenerr of (1) is closely bound up with the formation of the hardened. zone adjacent to the bead deposited.

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In this research, the authors confirmed the effect of the local post-heating on the energies necessary for statical bending break of alloy steel plates deposited with a single bead, and, clarified the main cause of the lowering of the necessary energy for plates which were deposited and not postheated locally.
Namely, after Mn-Cr-Mo alloy steel plate wds arc-deposited with a single bead, if the suitable local post-heating is carried on. and the heat affected and hardened zone by deposition is softened, that is, the enrgy maximum hardnests is lowered, the energy necessary for the statical bending break of a long rectangular plate deposited with a longitudinal single Lead, is very larger than that of plates without the' post-heating.
In othen words, the following matter can be understood. The main cause of the lowering of the energy necessary for statical. bending break of alloy steel plates deposited with a single bead, is the existence of the hardenedl zone adjacent to the weld, and the post-heating being able to soften such a hardened zone gives a good effect on the increase of. the energy necessary for the break.

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