Sankei Hori

Study of scattering behaviour and temperature of spatter generated during CO2 gas shielded arc welding

Spatter generated from the welding point is scattered over the welding environment in the state of hightemperature particles. Spatter mostly adheres to the base metal surface and impairs the quality of welded products. It is therefore necessary to remove adhering spatter. The recent trend towards automation of welding operations by robots has implied sensors and welding fixtures being generally provided to ensure surveillance of welding states. If spatter adheres to such peripheral equipment, this may cause spurious operation of robots, raise the problems of seizure of welding fixtures and poor weld quality, and even disrupt the progression of welding operations altogether. However, spatter as a molten metal is scattered while at the same time sustaining radiation of heat into the atmosphere and evolution of heat due to oxidation, with the bulk of the spatter generated changing from a molten state into a solidified state. When spatter reaches the base metal surface or peripheral equipment, there is a strong possibility of it adhering when in a molten state and not adhering when in a solidified state. Whether or not spatter adhesion takes place is governed by the cooling state of the spatter scattered through the air, i.e. the spatter temperature. Spatter is also susceptible to the effects of the scattering path and velocity. To solve problems associated with the adhesion of spatter generated during arc welding, it is therefore important to clarify the scattering behaviour of spatter through the air. This article uses photographs of the scattering trajectory of spatter generated during CO 2 gas shielded arc welding to investigate the scattering behaviour and temperature of spatter. More specifically, the scattering trajectory is photographed, the scattering velocity and acceleration of the spatter are determined from this trajectory, and the drag sustained by the spatter during scattering is also ascertained. The temperature of spatter scattered through the air is further determined on the assumption of the spatter being cooled by coercive convective heat transfer and radiant heat transfer, and the relationship between the Reynolds number and drag coefficient of the scattering spatter is determined. On the basis of these results, the scattering trajectory of the spatter is calculated and compared with corresponding measurement results.

Forces acting to remove spatter by wire brushing and its limits. Study of finishing of welding base metal surfaces (Report 2)

Spatter scattered over welding base metal surfaces by molten metal during the welding process seriously impairs the quality of welding products when deposited at the bead periphery. Manufacturers are therefore routinely constrained to remove such spatter. Particularly for welding products attaching importance to safety or impeccable appearance through the immediacy of eye contact, it is imperative to ensure complete removal of spatter. The spatter generated during welding, however, has different adhesion ranges from the bead depending on welding conditions, and the adhesive forces of individual spatters also considerably differ. Finishing of welding base metal surfaces is generally performed by wire brushing with air or electrically operated tools. This is due to the fact that, through the wire brush being an elastic tool, its action during wire brushing can be accommodated to complex joint shapes, and brushing work can be performed without any undue harm to welding base metal surfaces. During wire brushing of welding base metal surfaces, finishing methods and processing conditions often rely on experience, and no fundamental data whatever are currently available to support automation or the establishment of processing conditions ensuring efficient removal of spatter. To establish optimum processing conditions during wire brushing, this study clarifies the relationship between finishing surface shapes and processing conditions during wire brushing of welding base metal surfaces with adhered spatters. The previous paper in this series describes an investigation of the relationship between the brushing forces acting on steel plates and the brushing marks left on the surface when the brush holding angle and pushing force of the brush on the steel plates were varied during application of bevel type and cup type wire brushes affording different brush shapes. The properties of spatters adhering to welding base metal surfaces have also been previously reported. Using model spatters, this study experimentally determines the brush forces received by spatters during wire brushing of base metal with adhered spatters and establishes the relationship with the processing conditions. The paper further examines the adhesive forces and shapes of spatters unable to be removed by wire brushing of welding base metal surfaces with adhered spatters, establishes the relationship with the adhesion site temperature of the base metal surface, and considers the limits of spatter removal by wire brushing.

Research on the path and velocity of spatter in manual metal arc welding

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 ve...

Factors affecting adhesion of spatter: Study of spatter occurring during arc welding (2nd Report)

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 m...

Acting Force at Removing Spatter by Wire Brush and Its Limit. Study on the Finishing of Weld Metal Surface. Report 2.

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.

Measuring the force required to remove spatter from base metal: Research on spatter caused by arc welding (Report 1)

Summary This study deals with shielded metal arc (manual metal arc, MMA) welding and CO2 gas shielded arc welding, measuring the force required to remove adhering spatter from the surface of base metal by using different filler metals and by changing the conditions of the surface of the base metal. Rolled steel for general structural use (SS400) was used as base metal. A high titanium oxide type electrode and a low hydrogen type electrode were used for shielded metal arc welding, a solid wire and a flux‐cored wire were used as filler metal for CO2 gas shielded arc welding respectively. In order to examine the relationship between the condition of the surface of the base metal and the force required to remove spatter, a base metal whose surface was ground by an electric grinder, one which was not ground by an electric grinder, and another which was coated with an anti‐spatter compound were used for the experiments. Whichever filler metal was used, the spatter which adhered to the surface of the base metal ...

Fluidic Conveying of Chips with Through a Horizontal Pipe

In order to accomplish the automation of machining process completely, chips must be continuously conveyed from machine tools to the disposal system by mechanical and fluidic methods. The latter method is more suitable for conveying chips produced under wet condition than with the former, but the mechanism of conveying chips through a horizontal pipe has not yet been clarified. Therefore, in this study the mechanism of hydraulic conveying of chips has been experimentally analyzed. From the results, it was found that the drag coefficient of conveying chips estimated with the representative area, obtained from the number of chips per unit volume, and maximum relative velocity is nearly constant within a range of Reynolds numbers from 20 to 10000. In addition, it was revealed that the maximum velocity for conveying chips through the pipe can be approximately estimated by using the void ratio and the number of chips per unit volume.

Thermal Deformation of Machinetool-workpiece System Caused by Accumulating Chips : 1st Reaort; Thermal Conductivity of Accumulating Chips

One of the causes of the thermal deformation of a machinetool-workpiece system is the heat of chips piled on it. The amount of the thermal deformation due to this cause, however, is hardly yet known. Because, the values of thermal conductivity of accumulating chips and thermal contact resistance between accumulating chips and the surface of the system are hardly clarified. In this paper, the thermal properties mentioned above have been experimentally investigated by using accumulating chips made of different kinds of material and under different cutting conditions and moreover a theoretical investigation has also been carried out considering a model of accumulating ideal chips. From above results, it has been made clear that the value of the thermal conductivity of accumulating chips can be estimated by using the values of the thermal conductivity of the material, the void ratio and the number of chips per unit volume and that the value of thermal contact resistance can be approximately estimated by using the same factors mentioned above.