Variations of the melting rates of stainless steel (308) wires with three different diameters, 0.035″, 0.045″ and 1/16″, were measured when MIG welding was carried out with them under varied conditions of gun setting (Fig. 4), i, e., when these wires had the length of their current-passing portion varied. Figures 5 and 6 give the results of measurements, which can be represented by the experimental formula S=α+βI+γIIn (dotted line of Fig. 5). Fairly good agreement was established between this formula and the theoretical one (Eq. 6) which was derived separately through analysis of these results. As in the case of the previous report on aluminium, the dripping frequency, size of drop, practical minimum current were studied by means of arc pictures, oscillograms, and observations of bead grains. The authors believe that the obtained results will be useful as reference to the welding of mild steel, the consumable electrode arc melting of other metals as well as to practical MIG welding of stainless steel.
Directionality of crystal grain of high Ni-Cr weld metals, i.e. inconel(70 Ni-15 Cr and 70 Ni-20 Cr), comparing with 25 Cr-20 Ni and 18 Cr-8Ni steel, was studied by investigating tensile property, impactvalue and microstructure. The results are summarized as follows: (1) Mechanical properties of inconel weld deposits vary considerably with the direction observed:theywere worst in progressive weld direction and best in piling up direction along which the crystal grainsgrew. (2)With increasing nickel content in weld metals, the length of columner grain increases and thegrains themselves tend to become coarse, making the directional variation of the mechanical propertiesmore remarkable. (3) Preheating of the base metal before welding makes the grain of inconel weld metal more coarse, and deteriorates the mechanical properties, but these can be remedied by rapid cooling after welding. (4) Precipitation of columbium nitrides or carbides around the grain boundaries is the main cause ofcrack forming and deterioration of the mechanical properties. The addition of manganese to inconelweld metal prevents this precipitation, in spite of causing some degree of grain growth. Thus preparedweld metal shows no cracking and possesses superior mechanical properties.
This is a report on the effects of welding variables in mash seam welding of cold rolled and annealed low carbon rimmed steel sheets of lmm thickness on joint thickness, Erichsen value and tensile elongation along the weld line. Throughout the investigation, welding current and electrode force were varied in the wide range, while the rest of the condition were kept constant as follows: Welding speed 1m/min, weld time and cool time 4 _??_ and 2 _??_, and jointoverlap 1.5mm. The results obtained are as follows:- 1. When the welding condition is properly chosen, the Erichsen value of over 10.0 and the tensile elongation of 30% along the weld line are obtained. 2. In the range of the condition investigated. The electrode force of 600-700Kg and the welding current of 9000A may be recommended to obtain the best ductility of the weld. 3. Ductility of weld decreases with the increase of welding current, and the lower becomes the electrode force, the higher is the decrease rate, but too low current results in the incomplete bond and very poor ductility. 4. Joint thickness decreases with the increase of welding current and electrode force, but the effect of electrode force is not so distinct as that of current. 5. The microstructure of the weld section at the time when ductility is the best presents recrystalized ferrite grains and small islands of bainite and martensite surrounding cementite, and there is no regions of fine ferrite and pearlite or columnar dendritic nugget which show the temperature has risen above the critical or melting limits.
We studied the shape of bead-i.e. penetration, width, hight of reinforcement, reinforced area, penetrated area and fused area-obtained by C. S. arc welding process. And this process was compared with various welding processes, i.e. argon arc, submerged arc and manual arc with two types of coated electrodes, about the items mentioned above and penetration ratio : penetration/width of bead. Moreover the electric energy needed to deposit unit length of bead was calculated, and the ratios of penetration, width of bead and fused area to the energy were compared. Next authors investigated the effects of oxygen added in the supplied gas in case of C. S. arc welding on the porosity of weld metal and the shape of bead. The results obtained are as follows. i) Penetration in case of C. S. arc welding is largest compared with those by other welding processes. It is 1.7 times of that by argon arc welding, 1.6 times of that by submerged arc welding and 2.2-3.8 times of those by manual arc weldings. ii) Penetration ratio in case of C. S. arc welding is largest among others, too. iii) In spite of the same proceeding rate of bead, width of bead by submerged arc welding is largest compared with C. S. and argon arc welding processes. iv) The electric energy needed to make the same length and penetration of bead is smallest in case of C. S. arc welding compared with others. v) With increase of oxygen content of supplied gas in case of C. S. arc welding, the penetration increases and width of bead decreases. vi) The limit of permissible addition of oxygen in supplied gas, below which the blow hole does not occur in bead, depends upon the degree of deoxidation of base metal and contents of deoxidizers of filler wire.