A simple method-to avoide the welding crack of cast iron is described here.
Before welding, shallow glooves were made on the surface of mother metal adjascent to the V-groove as shown in Fig. 6. Cast iron was repaired by nickel electrode or mild steel electrode with standard welding procedure of cast iron which contains low welding current, intermittent welding and peening of the deposit etc. The occurence of welding crack was diminished remarkably by the effect of these shollow grooves.
As the reasons, geometrical surface ductility and ductility accompanied by the instantenous high temperature caused by the gloove at the surface adjascent to the weld may be taken into account. Table 1 shows the maximum temperature which can be measured and the apparent elongation measured at the gloove.

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Following five Testing Methods which were slected out of about twently Weldability Tests being made during past several years, are utilized for Low Alloy High Strength Ni-Cr-Mo Steel on this Study.
Slit Typie Crack Senstivity Test.
C.T.S. Crack Sensitivity Test.
Maximum Hardness Test of Heat Affected Zone.
Single-Bead Bending Test.
V-Notch Charpy impact Test.
Utilized Rolled Steel Plates which have 10, 16 and 37 mm thickness respectively and 50 mm Casted Steel Plates were given by ten Japanese steel manufacturers.
The nature of Coated Electrode NCM-T was reported in the Report (I) and the Report (II) already.
The Result on this Study is suinmerized as follows.
(1) Slit Type Test is quite Effective to resurch the Crack Sensitivity of Low Alloy High Strength Steel.
(2) Serious relation is seen between Crack Sensitivity Ratio in Slit Type Test and Maximum Hardnes in the heat affected zone.
(3) Certain relation is seen between V-Notch Charpy Value and Crack Sensitivity Ratio in Slit Type Test.
(4) Crack Sensitivity Ratio in Single-Bead Bending Test or Slit Type Test has certain relation with the Maximum Hardness in the heat effected zone.
(5) C.T.S. Test can be effective for the Crack Sensitivity Test in the case of austenitic welding of Low Alloy High Strength Steel.

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In order to make the behaviors of the consumption-rates of anode and cathode clear, experiments have been performed chiefly in nitrogen and chlorine arc in the range of amperage 8 to 180A.
The results are summarized as follows ;
1. Below 40 and 15A, as the current decreases, the consumption-rates of anode and cathode increase respectively.
2. The consumption-rate of anode is hardly influenced by the surrounding gases, and the diameters of electrodes used, but it is almost constant above 50A.
3. The consumption-rate of cathode of the smaller diameter is higher than that of the larger diameter, depends upon the gases surrounding arc, and it is maximum in chlorine and higher in nitrogen than in argon.

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The object of this research is to clarify a relation between porosity of weld and volume percentage of nitrogen in the mixed gas supplied for shielding of arc and its neighborhood. Three kinds of mixed gas ; C0₂-N₂, A-N₂ and 0₂-N₂, were supplied.
The results of experiments showed the following facts
1. In the case of CO₂-N₂ arc welding, the weld metal becomes very porous regardless of content of deoxidizers in the base metal, when the volume percentage of nitrogen in supplied gas is over the limit value, 4.5%.
2. Also in the case of A-N2 arc welding this limit value is nearly the same. But the weld metal by A-N₂ arc welding has generally higher content of total nitrogen, including nitride, than that by C0₂-N₂ arc welding with the same mixed percentage of nitrogen.
3. The true partial pressure of nitrogen in arc atmosphere is deduced to be over about 0.1 atm., when a weld metal becomes porous.
And the difference between the above "true" value, about 10%, and the "supplied" value, 4.5%, was discussed.

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Coated electrodes were laid down along weld seams, over which granular flux was heaped, and arc welding was performed automatically. Coated electrodes used are of the types D4301 (ilmenite), D4312 (rutile), D4313 (rutile), D4316 (lime basic) and D4320 (iron oxide). Two types of granular flux were used.
External appearance and radiograph of a weld bead was examined and compared with each other. D4316electrodes gave most beautiful bead free from any type of weld defects.
Burn-off rates of electrodes, consumption of granular flux and penetration depth of weld beads were measured. Tensile tests of cross fillet-welded specimens were carried out.

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In the previous paper, authors described on the advisable conditions of plastic welding. In this paper, authors reported mainly on the heat effects of plastic welding investigated by the optical method and the mechanical test.
Polyvinylchloride specimens as recieved and annealed were previously observed by the photoelasticity test in advance to the charnv impact test at the room temnerature.
The above mentioned tests were also applied to the heat affected zone of welded plastics. According to the results of the experiments, stress relief heat treatment taken place under the sui-table period of time and temperature for polyvinylchloride was effective to relief the weldingstress and the initial stress. Nevertheless, because of the dissolution in the structure ofpolyvinylchloride, the stress reliefed specimens have been shown brittlenees.

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