Recent proposal of utilisation of impurities in steel requires preservation of phosphorus in molten steel during its refining process. To know the phosphorus absorbing ability of deoxidation by-product slag having CaO, the phosphorus partition has been investigated between the MnO-SiO2-FetO-CaO-MgO-P2O5 slag and molten iron in this study. The phosphate capacities (CPO4 3-) for the present slag having CaO content from 4.73 to 19.6 mass% have been determined to be from 2.22×10 15 to 1.25×10 17 at temperatures from 1 843 to 1 923 K. Focused on the slag basicity, a thermodynamic discussion gives the capacity as functions of optical basicity (Λ) and temperature (T) as follows; logCPO4 3-= (11 300Λ + 54 560)/T + 18.30Λ-27.43 Estimated values of phosphorus distribution ratio ranges from 0.0003 to 0.008 between the present slags and molten iron in practical operations according to empirical phosphate capacities. CaO is useful to improve phosphate capacity of this system to some extent.
A simple method to evaluate the strength of corona bond of resistance spot welding is proposed and verified by removing the nugget of welded specimen before conducting a cross tension test. The strength of the corona bond is evaluated using thin steel sheets of different strengths. The result indicates that the higher the strength of the steel sheet, the higher the strength of the corona bond. A tensile test of the corona bond part is conducted using the small tensile test technique to verify the corona bond strength. A comparison of the stress value at the same strain (1%) indicates that the stress of the small tensile test is in the order of the strength of the steel sheet.
The present paper describes the characteristics of the arc sensor, focusing on the sensitivity of the change in welding voltage and current to the torch oscillation frequency, in the low current and high speed torch oscillation metal active gas (MAG) process. First, a mathematical model of the short circuiting transfer welding is proposed, based on a previously reported model of spray transfer welding. Then, the relationship between the oscillation frequency and the rate of short circuiting was investigated using the proposed model. Numerical calculation results revealed that short circuiting regularly occurs at both oscillating edges at oscillation frequencies close to half the rate of short circuiting obtained under non-oscillating conditions. This finding agrees satisfactorily with the experimental results. Fast Fourier transformation analyses of the signals of welding voltage and current showed that the sensitivity of the change in the voltage and current is maximised at a frequency equal to about half the short circuiting rate obtained under nonoscillating conditions. It is considered that accurate seam tracking by arc sensors in short circuiting MAG welding can be achieved by setting the torch oscillation frequency to the above value.A arc heating coefficient of wire melting5 0 . 22 mm s 21 A 21 B Joule heating coefficient of wire melting5 6 . 3610 25 s 21 A 22 E a electric field intensity in arc column5 0 . 7 V mm 21 I welding current, A J z Joule heating weight at location z of wire extension, A 2 s K s slope of U-I characteristic of power source5 0 . 02 V[w5 L a arc length, mm L e wire extension length, mm L s inductance of circuit52 . 5610 24 H L t torch height (L e zL a ), mm P t ,P v ,P i peak strength at frequency of 2f for torch height, voltage, and current signals respectively R a electric resistance of arc column50 . 03 V R c resistance of welding power cable556 10 23 V R e resistance of wire extension, V r(J z ) resistance of unit length of wire extension as function of J z , r(J z )59610 28 J z z3 . 56 10 24 V mm 21 U a arc voltage, V U ao constant component of arc voltage516 V U e voltage drop across wire extension, V U s equivalent output voltage of power source in state when I50, V U t welding voltage (U a zU e ), V V f wire feeding rate, mm s 21 V m wire melting rate, mm s 21 z location of wire extension t time, s Symbols for short circuiting transfer condition B 1 Joule heating coefficient of wire melting at short circuiting53 . 8610 3 mm s 21 A 22 V 21 L em droplet length, mm L es wire extension length of unmelted part, mm N s rate of short circuiting with oscillation, s 21 N s0 rate of short circuiting without oscillation, s 21 R m radius of droplet having assumed spherical shape, mm S cross-sectional area of wire, mm 2 t ia time at start of droplet growth, s t is time at start of short circuiting, s a coefficient of droplet length53 b coefficient of short circuiting time5200
If resistance spot welding (RSW) is conducted when there is a gap between a steel sheet and an unmovable electrode, the steel sheets are bended by a movable electrode, and the quality of RSW is influenced. Therefore, it is necessary to understand the effect of the gap on RSW. In this study, two high-tensile strength steel sheets were welded with the gap. In addition, cross-section observations and cross tension tests were conducted to verify the effect of the gap on weldability and joint strength. Consequently, two notable results were obtained. First, the observation indicated that deformation around the corona-bond was varied depending on the gap. Second, the cross tension tests showed that the gap decreased the joint strength even though the nugget was large enough. These result indicated that controlling the gap is important to ensure the quality of RSW.
This study shows the time variation of temperature distribution and concentration distribution of metal vapor during gas tungsten arc welding. In this study, stationary gas tungsten arc welding of pure iron was conducted in helium as shielding gas. We investigated the influence of iron vapor on arc plasma and mechanism of iron vapor transportation from the weld pool into the arc plasma. We observed the arc plasma two-dimensionally with spectrometric method. We captured three different monochromatic images simultaneously by three monochromators with high speed video cameras. Thus, two inherence spectra of iron and also one inherence spectrum of helium in arc plasma were obtained. Using these spectra, plasma temperature distribution was obtained. In addition, concentration distribution of iron vapor was obtained by measuring electron density. It was concluded that plasma temperature decreased with increase of iron vapor concentration. Especially, the metal vapor concentration indicated the highest value near the base metal and the temperature around the weld pool decreased rapidly.
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