1. Advantages of submerged arc welding
1. High production efficiency
This is because, on the one hand, the conductive length of the welding wire is shortened, and the current and current density are increased, so the penetration depth of the arc and the deposition efficiency of the welding wire are greatly improved. (Generally, the single-sided penetration can reach 20mm without grooves.) On the other hand, due to the thermal insulation effect of the flux and slag, there is basically no heat radiation loss on the arc, and there is little spatter, although the heat loss for melting the flux is increased, but the overall thermal efficiency is still greatly increased.
2. High quality of welding seam
The slag has a good protection effect against air, and the welding parameters can be kept stable through automatic adjustment, which requires the technical level of the welder Not high, the weld composition is stable, and the mechanical properties are better.
3. Good working conditions
In addition to reducing the labor intensity of manual welding operations, it has no arc radiation, which is a unique advantage of submerged arc welding.
Second, submerged arc welding process parameters
1. Welding current Under normal welding conditions, the weld penetration is proportional to the welding current. With the increase of welding current, the penetration depth and the weld height increased significantly, while the weld width did not change much. At the same time, the melting amount of the welding wire also increases accordingly, which increases the excess height of the weld. As the welding current decreases, both the penetration and the overhang decrease.
2. With the increase of arc voltage, the welding width increases obviously, while the penetration depth and the weld height decrease. However, when the arc voltage is too large, it will not only reduce the penetration depth, resulting in incomplete penetration, but also lead to poor weld formation, difficulty in slag removal, and even defects such as undercut. Therefore, while increasing the arc voltage, the welding current should also be appropriately increased.
3. Welding speed When other welding parameters remain unchanged and the welding speed increases, the welding heat input decreases accordingly, so that the penetration depth of the weld also decreases. Too high welding speed will cause defects such as 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 correspondingly increased while the welding speed is increased in order to increase the productivity.
4. Welding wire diameter and extension length When other welding parameters remain unchanged and the welding wire diameter increases, the diameter of the arc column increases, that is, the current density decreases, which will cause the weld width to increase and the penetration depth to decrease. Small. On the contrary, the penetration depth increases and the weld width decreases. When other welding parameters remain unchanged and the length of the welding wire increases, the resistance also increases, the preheating effect of the extending part of the welding wire increases, and the melting speed of the welding wire increases, resulting in a shallower penetration depth and an increase in the weld height. The extension length of the welding wire must be controlled, and it should not be too long.
5. Wire inclination The inclination direction of the wire is divided into forward inclination and backward inclination. The direction and size of the inclination angle are different, and the force and heat effect of the arc on the molten pool are also different, thus affecting the weld formation. When the welding wire is tilted back at a certain angle, since 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 a wide weld and shallow penetration. On the contrary, the width of the weld is small and the penetration is large, but it is easy to cause unfusion and undercut at the edge of the weld, and the weld formation is deteriorated.
6. Others. a. Groove shape b, root gap c, weldment thickness and weldment heat dissipation conditions.
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