The spatter is cooled during scattering by the air. So, many spatters change from the melt state to the solidification state. Spatter does not adhere to the base metal and peripheral equipment in the solidification state. But, the possibility of adhering to them rises, when the spatter melts. In other words, the adhesion of the spatter is influenced by its cooling condition, that is, the scattering route and velocity of the spatter. Therefore, in order to clarify its adhesion behavior, it is very important to estimate its scattering behavior. Then, is this study, the scattering behavior of the spatter is CO2 gas shielded arc welding is measured and the scattering behavior and terperature of the spatter are simulated. As the results of examining 300 spatters, it is indicated that the initial velocity of the spatter which arise from welding point is about 10 m/s or less and the initial angle of elevation is 70 degree or less. In addition, it is indicated that the Reynolds number of scattering spatter is 7 from 2 and the drag coefficient is 30 from 10. Moreover, when scattering locus of the spatter are simulated by substituting the relationship between drag coefficient and Reynolds number into the momentum equation of the spatter, the results agree well with the experimental results.
In this paper we studied the loci and the velocities of scattering spatters in shielded metal arc welding with high titanium oxide type electrode. We examined only spatters that flew off in the right-angle direction to the weld line and passed through the slit of 4 mm by 75 mm. The loci of the spatters were photographed when they scattered in the air, and their velocities were calculated using their times of photographing. And we simulated the loci and velocities of the spatters. The experimental data and calculated values were compared.In the experiment we examined 110 spatters, and their particle diameters range from 0.1 to 1 mm. The spatters flew around on the surface of base metal within a 500 mm radius circle. They flew in the air for less than about 0.5 seconds. And the highest velocity was 6 m/sec. The Reynolds numbers of the spatters were less than 7. They were given by Re=d×V/ν (d is the diameter of a spatter, V is the velocity of the spatter, ν is coefficient of kinematic velocity). And the coefficient of kinematic viscosity of the air was calculated using the temperature. The temperature was determined by the arithmetic mean of the temperature of spatters (given they were 1637 K) and the temperature of the air (293 K). To simulate the loci and the velocities of the spatters, the equation of motion was set up under a certain condition. The condition is that the temperatures of the scattering spatters are constant and their drag coefficients (Cd) are given by the Stokes equation for a sphere (Cd=24/Re). The calculated value by this equation matches well the experimental results, though the former was a little larger than the latter in almost all the cases.
In the CO2 gas shielded arc welding, spatters are scattered around and bonded to the surface of base metal, and it is still unclear what are the main factors of the difference of their bonding force.In this paper we examined the bonding force of spatters, which were bonded on the surface of base metal (SS400) in different conditions and temperatures in the CO2 gas shielded arc welding (using the solid wire of 1.2 mm in diameter).The conditions of the surface of base metal were as follows:(1) The surface has scale, (2) The scale of the surface was removed with the surface grinder (Rmax=0.6μm), (3) The ground surface was fumed, and(4) The scale of the surface was removed with the disc grinder (Rmax=7-16μm).The temperature of base metal was raised by the ceramic heating unit of 14 mm in diameter, which was set up at the back of base metal. The bonding force was measured through the shear force of the spatter. 400 spatters were examined on each surface. Most of the dimeters of the spatters were 0.4 to 1.4 mm.When the temperature of base metal was below about 450 K, spatters on the surface with scale was not hot enough to melt the base metal and could not bond there by melting the surface of base metal. Most of their shear stresses were below about 40 MPa, but as the temperature raised, the shear stress was increased up to nearly (300) MPa.The fume on the surface or the roughness of the surface did not affect the bonding force as directly as the scale on the surface. The temperature, however, affected the bonding force. When the temperature of base metal was below 450 K, the bonding force became a little smaller.When the spatter bonded on the surface, because of the heat transfer, the change of the microstructure and correspondingly hardening was found to occur. When the spatter and the heat-affected zones of base metal were examined, their Vickers hardnesses indicated a little higher value (some spatters had the value of 470 (Hv)) than the hardness of base metal (156-165 (Hv)), although it depended on the conditions of the surface and the temperature.
Summary In CO2 gas-shielded arc welding, spatter is scattered and adheres to the base metal surface. The main factors affecting any difference in the bonding force remain obscure. This paper examines the bonding force of spatter adhering to the surface of SS400 base metal (rolled steel sheets) under different temperature conditions in CO2 gas-shielded arc welding using 1.2 mm dia. solid wire. The following four types of base metal surface condition were adopted: Type 1: As-received surface covered with an oxide film; Type 2: Ground surface machined with a plain grinder (Rmax = 0.6 μm); Type 3: Surface with fume adhering to the ground surface; Type 4: Free-ground surface machined with a disc grinder (Rmax = 7–16 μm). The base metal was heated by a 14 mm dia. x 600 mm ceramic heater arranged on the back of the base metal. The bonding force was measured as the shearing force of the spatter. Some 400 spatter particles on each surface were examined. The particles mostly have diameters ranging between 0.4–1.4 mm. At a base metal temperature below around 450 K, the spatter on the scaled surface is insufficiently hot to melt the base metal and cannot adhere by melting the base metal surface. The shear stress is mostly below around 40 MPa. Despite a rising base metal temperature, however, spatter removal is still possible at less than 300 MPa. Fume on the surface or the surface roughness do not affect the bonding force as directly as scale on the surface. The temperature, however, affects the bonding force. At a base metal temperature below around 450 K, the bonding force is slightly smaller. When spatter adheres to the surface, heat causes the microstructure to change with corresponding hardening. The spatter and HAZ of the base metal here show a slightly higher Vickers hardness value (some spatter particles having HV470) than the base metal hardness (HV156–165), although this depends on the surface conditions and temperature.
In the arc welding, spatters attached around the bead of base metal. The adhered spatters lower the surface quality of the welding product. Therefore, it is very important to remove the spatters from the welding product. In general, wire brushes of bevel type or cup type have been used to remove the spatters. However, the adherent force of spatters on base metal is not constant. Then, the removal force, which is needed to remove the adhered spatters, is not also constant. Moreover, spatters are scattered on the base metal. Therefore, in order to remove the spatters by the brush, it is very important to clear the relationship between brushing conditions and the removal behavior of spatters.In this study, the removal forces of the adhered spatters are measured by using the removal tool to which strain gages attached. The shapes of the adhered spatters are also measured. Moreover, the force that is applied to the spatter in the brushing has been measured by using a model spatter. The shape of the model spatter is very similar to that of the adhered spatter. A steel plate with scale is used as a base metal. In brushing the metal, the pushing force of the brush is 29.4 N and the holding angle, that is the angle between the brush and base metal, is 15, 20, 25, or 30 degrees.As the result, it is indicated that the applied force to the model spatter in the brushing increases with the height of model spatter proportionally. The holding angle of the wire brush has little influence on the applied force to the model spatter. When the temperature of base metal is less than about 450 K, most of the removal shear forces of spatters are less than about 50 N. In this case, all of the attached spatters can be removed by the brushing. However, when the temperature of the base metal become high, the removal shear force become large and it become hard to remove all of the adhered spatter.
Summary In this paper we studied the loci (paths) and the velocities of scattering spatter in shielded metal arc (MMA) welding with high titanium oxide type electrodes. We examined only spatter that flew off at a right angle to the weld line and passed through a slit of 4 mm by 75 mm. The loci of the spatter were photographed when they scattered in the air and their velocities were calculated from the camera shutter speed. We also simulated the loci and velocities of the spatter and the experimental data and the calculated values were compared. In the experiment we examined 110 spatter particles whose diameters ranged from 0.1 to 1 mm. The spatter particles flew around on the surface of the base metal within a 500 mm radius circle. They flew in the air for less than about 0.5 seconds. And the highest velocity was 6 m/see. The Reynolds numbers of the spatter were less than 7. They were given by Re = d × V/1 (d is the diameter of spatter. V is the velocity of the spatter v is the coefficient of kinematic velocity). And the coefficient of kinematic viscosity of the air was calculated using the temperature. The temperature was determined by the arithmetic mean of the temperature of spatter particles (given they were 1637 K) and the temperature of the air (293 K). To simulate the loci and the velocities of the spatter, the equation of motion is set up under a certain condition. The condition is that the temperatures of the scattering spatter are constant and their drag coefficients (Cd) are given by the Stokes equation for a sphere (Cd = 24/Re). The calculated value by this equation matches well the experimental results, though the former were a little larger than the latter in almost all cases.
In the arc welding, spatters are frequently bonded to the surface of base metal. Therefore, to keep the quality of the weld products, the weld metal surfaces were usually brushed with bevel type or cup type wire brushes. Since the spatters cannot be removed completely under a certain brushing condition, it is very important how to finish the surface of base metal.This study tries to show the brushing conditions under which spatters can be removed completely. As the first step to find the proper condition, we made a brushing apparatus that can control the pushing force of the wire brush, and measured the force (we call it the brushing force) in the steel plate. The brushing force is determined by the two forces. One (Fy) is from the direction of brushing and the other (Fx) is perpendicular to the brush.In brushing the metal, the pushing force was set at 9.8 N, 19.6 N, or 29.4 N and the angle of the brush and workpiece was 15, 20, 25 or 30 degrees. The metals we used were two types of SS400. One had the scale and the other had no scale, which had been removed by the surface grinder.When the steel plate is brushed, various kinds of brushed traces appeared on its surface. The brushed traces were examined through a metallographical microscope and we showed the relations between the brushed traces and the brushing conditions. We also examined the brushing force when a tiny part of the surface (8.04 mm2 in size) was brushed (we call it the local brushing force), so that we could show the relations between the brushed traces and local brushing forces.
