The inherent defect for the conventional mechanically controlled slow down devices is the frequent breakdown of the timer components caused by the dirts in the air or oil. To eliminate the above defect, new electronically controlled devices are developed. Moreover, how to protect the control circuit against vibration and high temperature due to engine is shown. As rotary solenoid and semiconductor components were employed to adjust the governor of engine, the devices could have many advantages such as higher reliability, longer maintenance-free life, smaller size and lighter weight. Measurement of noise level and gasoline consumption showed that when compared with the case without slow down device, the slow down device could decrease noise level by ten phons and gasoline consumption by more than half.
In this paper the mcehanical properties of five series of cast specimens, simulated to weld metal in cooling rate, were examined to investigate suitable chemical compositions of weld metals of enough strength and ductility by Subzero welding process. These cast specimens of high alloy Ni-Cr steels with unstable austenitic microstructure were tested as cast, refrigerated at -72°C in collant of methylalcohol and liquid nitrodgen or aged at 45°C after refrigeration. The results were as follows; 1. In Cr-Ni-2 %Mo(0.05%C)series, 0.2%proof stress of cast specimens were increased by refrigeration, but elongations of them were decreased. However both 0.2%proof stress and elongation were increased by aging. 2. In l4%Cr-Ni-2%Mo-(3_9%)Mn (0.04%C)series, by increasing manganese content instead of nickel content elongations and Charpy impact values of cast specimens were increased, but incre-ments of strength of them by refrigeration were decreased comparably. 3. In 14%Cr-9%Ni-(Mo, Cu, Co, or Ti) series, 0.2%proof stress of cast specimens were increased by adding alloying elements, Elongations of them by refrigeration were larger than that of other series cast specimens.
At the present time, accurate theoretical values of viscosities are not available. Therefore, in this paper we have proposed an approach to viscosity calculations of molten iron and its dilute binary alloys. Using the expression for pure liquid totals which have been drived by S. Takeuchi and T. lida, the calculated value of viscosity for molten iron at 1600°C is 4.7cP. From the expression and experimental data, we have presented an attempt to calculate viscosities of dilute binary alloys on simple parameters. That is, viscosities of dilute iron based binary alloys are proportional to the square root of the product of atomic weight and melting point, (MTm)1/2, of alloying elements. Viscosities of molten iron due to one atomic percent of various elements at 1600°C are expressed as follows: ηFe⋅dil=ηFe+K[(MT)1/2B-(MTm)1/2Fe] where, K≈3×10-5 (from experimental data) We have obtained same relation for liquid mercury ant its dilute amalgams as well. Consequently, if we obtain experimentally the value K, the approximate values for viscosities of dilute allosy can be calculated.
Twin electrode that made of two coated electrodes used for series arc welding in new process designed for mild steel with heavy rust. In the case of series arc welding with this electrode, arcs are blown outside and make two beads by the cause of electromagnetic force, because current flow reverse direction two coated electrode each other. Arc is ignitioned initially among cores as the result of current flow, and heary rust on the mother metal are melted away for this arc energy afterward series arc initiated between core-mother matel-core. This phenomena has shown ability to welding of automatic non-touch arc starting. The following conculsions could be drown from the observation carried out during this study that prevent arc blow outside and make a bead. 1) A single bead was made by setting copper block at eaeh side of the twin electrode. 2) High quality bead was obtained by proper core distance of a twin electrode and by selection of welding current.
In order to clarify the effect of the peritectic reaction in Fe-C system on the hot cracking in steel weld metal, the hot cracking tendency of the solidified steel specimens, of which carbon content were in the range of 0.01-0.54%, were investigated by means of the simple cast tear tests. The microsegregations in the cast steeel specimens were also examind by the electron-probe microanalyser. It was found that the hot cracking tendency of the solidified steel specimen with more than 0.1% of carbon content increases remarkably, because the sulphur is more segregated during solidification. This could be explained as follows; Through the peritectic reaction the crystallized δ iron has the surface skin of r iron, of which sulphur solubility is much lower than that of δ iron, and the solidification may terminate while the sulphur-enriched melt is sorrounded by r phase. Therefore it is important for the prevention of the hot cracking in steel weld metal to keep the carbon content under 0.1% as well as to reduce the sulphur content.
On the Lay Down Welding Process (Fire-Cracker Welding), using the conventional A.C. Welde, we carried out a systematic research on the direction of the arc blow, making the following 7 factors as changeable factors: kind of the covering, the covering composition, the eccentricity ratio of electrode, arc current, the groove angle of base metal welding position, and the gap between electrode and base metal. The characteristic phenomena are summerized as follows; (1) The arc blow of length direction decrease by following (a)-(g), respectively. (a) Changing the coverings from acidic type to basic type. (b) Increasing iron powder in the coverings and decreasing gas materials. (c) Increasing the eccentricity ratio of electrode. (d) Decreasing the arc current. (e) Decreasing the groove angle of base metal. (f) Changing the welding position from horizontal to flat. (g) Decreasing the gap between electrode and base metal. (2) The arc blow of side direction decreases by following (a)-(f), respectively. (a) Changing the coverings from acidic type to basic type. (b) Increasing the eccentricity ratio of electrode. (c) Increasing the arc current (d) Increasing the groove angle of base metal. (e) Changing the welding position from horizontal to flat. (f) Decreasing the gapbetween electrode and base metal. Above-mentioned arc blows are clearly explained due to geometrical arrangement of welding parts and characteristic of electrode, mentioned above.
The preventive of the cracking occurring in the partially penetrated corner-weld joint of HT-80 steels has become an interesting object for the last years, since the joint has both elements of the butt weld joint and the fillet one. In order to make clear the influences of welding procedure, strength of weld metals and the diffusible hydrogen in weld metals on the cracking, both the restraint corner-weld cracking test and the no-restraint weld cracking test have been performed in this investigation. It is shown that the combination of the highly basic agglomerated flux which generates plenty of CO2 gas in welding and the wire which contains an adequate amount of alloying element can make the crack-free corner-weld metal. The main results obtained are as follows; 1) In 60 Kg/mm2 corner-weld metal the main cause of the root cracks is plastic deformation at the weld root region which is derived from the constriction of weld mead, and the effect of hydrogen on the crack is supplementary. 2) In 60Kg/mm2 corner-weld metal, the root crack propagates in the unmixed zone without relation to the grain boundaries of weld mead. 3) In the case of the submerged arc welding by using the fused flux, the hydrogen induced root crack and transverse crack occur in 80Kg/mm2 weld metal, and these cracks propagate along the austenite grain boundaries of weld metal. 4) The transverse crack observed in the corner-weld metal may occur by the same mechanism as those observed in the butt weld metal and in the fillet one. 5) Such defects are apt to occur in MIG -arc corner-weld joint with a root gap of greater than 2.8mm as a lack of fusion, hot cracking and burn through. 6) As far as partially penetrated corner-weld joint of HT-80 setels, the weld metal should have such characters as low hydrogen content, small thermal constriction and strength higher than that of the base plate and it should be deposited as much as possible per one pass.
To know the effect of ambient pressure on the nitrogen content of weld metal, mild steel specimens were welded using an iron electrode wire in air, N2, Ar-N2, and N2-O2 atmospheres at pressures between 1 atm and 9 atm. The changes in the shape of penetration and the arc phenomena due to the ambient pressure were also investigated. The main results obtained by this study are summarized as follows; 1) In nitrogen welding atmosphere, the nitrogen content of weld metal increased gradually with the increase of the ambient pressure. The absorption of nitrogen does not obey the Sieverts' law. 2) In air welding atmopshere, the nitrogen content of weld metal does not increase continuously with the ambient pressure, but it drops rather at pressures between 4 and 6 atm. 3) In Ar-N2 welding atmosphere, the nitrogen content of weld metal increased with the partial pressure of nitrogen in the atmosphere of 1 to 6 atm pressure. The nitrogen content of weld metal made in the atmosphere of higher pressure is lower as compared with the one in the atmosphere of lower pressure at same partial pressure of nitrogen. 4) In N2-O2 welding atmosphere, the enhancement of nitrogen absorption by steel welds due to the coexistence of oxygen is observed at higher pressures of welding atmosphere too. The oxygen precent of N2-O2 atmospheres, in which the maximum nitrogen content is to be expected, is lower at higher pressures of welding atmosphere.