In case of the rising or constant potential type power source for CO2-O2 arc welding, the open voltage is variable, unlike the case of drooping type power source, which has ordinaly a constant open voltage. This experiments were carried out in order to get enough knowledge about effects of open voltage on the arc-state and to select the optimum welding conditions for CO2-O2 arc welding. Using a constant potential type rectifier and a rising type motor generator on the market, many oscillograms of welding arc were taken under various welding conditions. Arc times, numbers of momentary short circuit per unit time and times to start arc were measured on the oscillograms. The experimental results are as follows : 1. The arc time reaches 100% when open voltage of C.P.R. is over 32V and that of R.M.G. over 16V, or when arc voltage is over 22V in the cases of both power sources. 2. The number of momentary short circuit decreases remarkably with the increment of open voltage. And the number reaches zero at about 32V of arc voltage. 3. The higher open voltage, the more easily an arc starts. The starting of arc with the used R.M.G. is not as good as the C.P.R..
This paper describes about the experimental study on the shear fatigue strength of the fillet weld of welded beams, such as connecting web and flange. Though these problems, in our opinion are important in practice as well as in design, we could not find any papers which clarified these problems. The object of this experiment is, at first, in comparision of shear fatigue strength of fillet welds, automatic and manual. Next, it is in clarifying the fatigue strength of fillet weld, which is simply under pure shearing stress or combined stresses, shearing and tensile or compressive. Moreover, shear fatigue strength of fillet welds were compared with I section specimen and box section specimen. Fatigue test was made with 4 type specimens whose moments of inertia were nearly equal and nominal throat of fillet welds were, also, nearly equal ; 6mm. The plates used were SM41 & SM41W. The Results obtained are as follows ; (1) We succeed at obtaining fatigue fracture by pure shear with special specimen whose she-aring stress distribution along the welding direction was uniform. (2) The, fatigue strength of fillet joint welded by automatic method was almost the same as that of manual weld referred to the nominal throat stress. However, referred to the actual throat stress, manual weld was about 30% stronger than the automatic weld. (3) It was found that the axial stress did not at all affect the shear fatigue strength when the fillet joint under combined stresses. But it must be considered that there is stress concentra-tion as to the shearing stress on the throat section by the gap in the root part, but no stress con-centration as to the axial stress. (4) I section specimen was about 30 % stronger than box section in fatigue strength at N= 2×106 cycles as to the nominal stress.
The CO2 gas shielded arc welding in welding of the steel is, recentry, being put to practical use. This welding method has some merits and demerits, compared with the other. A demerit of this method is the fact that it tend to produce large amounts of spatter. We observed the process of metal transference by the high speed motion pictures, and studied on the causes of spatter, then we investigated the ways to eliminate spatter. The results obtained are as follows:- (1) The substantial large liquidity of DS-1 electrode wire is a cause for pormoting the spatter. (2) The metal transference is globular type due to the high pressure of gas generated where the carbon dioxide dissociates in the arc colum or its surroundings in the high temperature. At that time, the small particles are apt to be ejected either from the transfering globule or from the molten parts of the electrode tip at the instant when the molten droplet of metal detaches the electrode tip. (3) If the arc is maintained so short that the electrede tip is inserted into the crater of molten pool of the work but it does not touch the work, the amount of spatter is minimized. (4) The current density of the electrode should be large then the spatter will be decreased be-cause the molten droplet of metal cannot remain long at the electrode tip by the strong electro-magnetic pinch force and it cannot grow large.
The sensitivities of the stress corrosion cracking of types 304, 304L and 347 weldments were discussed with the specimens cutting from the base metals, heat affected zones and deposited metals of the weldments and tested in the boiling solution of 42 per-cents Mg Cl2 under tensile loads. Under these conditions, the sensitivities of the stress corrosion cracking are affected with the yielding points rather than with the constructions and the compositions of the materials. Also, in the case of plastic working, the higher the order of. deformation is, the lower the sensitivity of stress corrosion cracking is. Moreover, the stress corrosion tests of welded plates were carried out in the same corrosive solution as above. It become clear that the stress corrosion cracking occured by the residual stress is coincide with the results of the above tensile tests.
Steel pipe may be welded to steel plate at right angle by using the electrolytic capacitor type spot welder. Maximum storing energy of this welder is about 15 k joules, and total capacitance of the electrolytic capacitors is 125, 000μF. Mechanical force to the tip electrode is variable from 850 kg to 3000 kg. For the steel pipe 19.8 mm in diameter, 1.2 mm in thickness, 40 mm in length, weld time should be selected as short as about 3 m sec, and welding energy as large as about 4.8 k joules to obtain a good weld. By observing oscillograms of current and voltage during this welding, it is found that weld starts at about 8×104 sec after the switchin and finishes at about 102 sec.
For the purpose of spot welding of aluminum plate of appreciable thickness, we have made a powerful spot welder using huge electrolytic capacitors (125, 000μF, 500 volts dc.). This welder being 40 KVA in capacity, a constant charging current system with thyratron control is used to minimize the loss due to charging resistor and to shorten the period of charging large capcitance. Spot welding is carried out in a cycle per two seconds and welding current continues about 0.1 seconds. About 150 KA are used to get sound welds of 4.0 mm, 2S aluminum sheets.