Submerged arc welding technology

Submerged arc welding is a welding method to bury the strong welding arc light. Naturally, the arc light can not be seen in the welding process, and most of the welding is automatic, and the working conditions are greatly improved. With the development of industrial production, more and higher requirements are put forward for welding technology. Today we will talk about the welding process of submerged arc welding. The selection of process parameters compared with welding rod arc welding, submerged arc welding technology parameters of the need to control is more, the welding quality and the greater influence on the weld process parameters are: welding current, arc voltage, welding speed, welding wire diameter and length, wire Angle, assembling clearance and the size of the groove, and flux layer thickness and size also have an impact on the quality of weld. Their effects on weld quality and forming are described below respectively. 1. Welding current With the increase of welding current, the weld depth and weld height increase significantly, while the weld width changes little. This is because when the welding current increases, the heat generated by the arc also increases, and the heat transferred to the welding part also increases, and the force of the arc on the molten pool also increases correspondingly, so the penetration depth increases accordingly. At the same time, with the increase of welding current, the melting amount of welding wire also increases correspondingly, which makes the weld excess height increase. Otherwise, both the depth and the residual height decrease. However, when the welding current is too large, the heat affected zone will be too large and the weld will be burned through due to the deep penetration and little change of weld width. It also makes it difficult for the gas and inclusions in the molten pool to rise and escape, and the weld is easy to produce defects such as porosity, slag inclusion and crack. When the current is too small, the depth of penetration is insufficient, easy to produce bad fusion, no penetration and slag inclusion and other defects. Therefore, in order to improve the welding quality, the arc voltage must be increased correspondingly when the welding current is increased to ensure the corresponding weld width. 2. Arc voltage When other parameters remain unchanged, with the increase of arc voltage, the welding width increases obviously, while the penetration depth and weld height decrease. This is because the arc voltage is proportional to the arc length, and the increase of the arc voltage, that is, the increase of the arc length, so the area of the weldment heated by the arc also increases, resulting in the increase of the width of the weld. At the same time, the increase of arc length will make more heat used to melt the flux, while the melting amount of the welding wire does not increase, and the melted welding wire should be distributed over a larger area, so the residual height of the weld will be reduced. In addition, with the increase of arc length, the arc swing will be intensified, and the force of arc on the molten pool will be relatively weakened, so that the weld penetration depth becomes smaller. In submerged arc welding, the arc voltage is adjusted according to the welding current, that is, only a certain arc length of welding current can ensure the stable combustion of welding arc, so the range of arc voltage variation is limited. However, when the arc voltage is too high, not only the penetration depth becomes smaller, but also poor weld formation, difficult slag removal, and even bite defects. Therefore, while increasing arc voltage, welding current should also be increased appropriately. 3. Welding speed When other welding parameters remain unchanged and welding speed increases, welding heat input decreases correspondingly, so the weld penetration depth decreases. At the same time, the melting amount of welding wire within the unit length of the weld is reduced, so the width and residual height of the weld are correspondingly reduced. When the welding speed is too large, the amount of molten metal is insufficient, which is easy to produce defects such as edge bite and incomplete penetration. In order to ensure the welding quality, a certain amount of welding heat input must be guaranteed, that is, the welding current and arc voltage should be increased simultaneously with the welding speed to improve the productivity, so as to ensure the welding quality. 4. Wire diameter and extended length 4.1 Wire diameter When the welding current, arc voltage and welding speed are constant, the weld shape will change with the different wire diameter. Other conditions unchanged, penetration and the relationship between is inversely proportional to the diameter of wire, but the relationship is weakened along with the increase of current density, this is because with the increase of current density, increasing amount of molten metal molten pool, increase slow penetration, and with the increase of amount of molten metal, more than the high increase weld deformation is poor, so an increase in submerged arc welding welding current at the same time to increase the arc voltage, To ensure the weld forming quality. 4.2 Extended length of welding wire When the other welding parameters remain the same and the length of the welding wire increases, the resistance will also increase, the preheating effect of the extended part of the welding wire will increase, the melting speed of the welding wire will accelerate, the result is that the depth of penetration will become shallow, and the weld residual height will increase. If the wire is extended too long, the wire under the conductive nozzle will become red. Therefore, it is necessary to control the length of the welding wire, not too long. 5. Angle of welding wire The tilt direction of the welding wire is divided into forward tilt and backward tilt. The force and heat effect of arc on weld pool are different with the different direction and size of inclination Angle, which affects weld forming. When the welding wire is tilted back at a certain Angle, because the arc points to the welding direction, the weldment in front of the molten pool is preheated, and the discharge effect of the arc on the liquid metal in the molten pool is weakened, resulting in the width of the weld and the shallow depth of penetration. On the contrary, the weld width is small and the penetration depth is large, but it is easy to cause the weld edge unfusion and edge bite, and make the weld deformation is poor. 6. Other 6.1 Groove shape When other welding parameters remain unchanged, when the depth and width of groove are increased, the weld penetration depth increases, the weld residual height and fusion ratio decrease significantly, but the weld thickness remains roughly unchanged. 6.2 Root clearance In the butt weld, the penetration depth increases with the increase of the root gap. 6.3 Weldment thickness and heat dissipation conditions When the weld thickness is thicker and the heat dissipation condition is better, the weld width will decrease and the residual height will increase. 6.4 When the flux layer is too thin, welding arc is easy to be exposed, and the arc protection is not good, which is easy to produce pores or cracks; When the flux layer is too thick, the weld seam becomes narrow and the forming coefficient decreases. 6.5 In general, the flux size has little effect on the weld formation, but when small diameter welding wire is used to weld thin plates, the flux size has an effect on the weld formation. If the flux size is too large, the arc is unstable, and the weld surface is coarse.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods