Submerged arc welding process: single-sided welding of butt joints

In butt submerged arc welding, the weldment can be opened V-shaped, U-shaped or I-shaped groove, which is not only to ensure the penetration, but also to control the fusion ratio and forming. Under normal circumstances, the I-shaped groove of submerged arc welding can weld the weldment less than 20 mm at a time, and the gap needs to be left at this time. Generally, when the thickness of the plate is more than 14 ~ 16 mm and the penetration is required, the V-shaped, U-shaped and other grooves need to be opened, The common methods of single side welding are as follows:

Single side submerged arc welding with root sealing or root backing

Due to the limitation of welding structure, it is not easy to adopt double-sided welding process. Therefore, the root can be sealed by shielded metal arc welding, and then welded by submerged arc welding, so as to ensure that the weld can be welded thoroughly. The groove can be made on the weldment, and the backing layer can be welded by shielded metal arc welding or manual argon tungsten arc welding, and then the filler layer and cover layer can be welded by submerged arc welding.

Submerged arc welding single side welding double side forming

That is to say, a strong welding current is used to weld the weldment thoroughly at one time, and then the metal is melted and solidified on the inner lining, so as to achieve the purpose of back forming. This method can increase productivity and improve working conditions. In order to weld the weld thoroughly at one time and form on both sides, it is necessary to use a gasket to support the liquid metal in the molten pool, so as to prevent the molten metal from burning through under its own weight To ensure the weld quality, the backing should have the following properties: it can maintain its own shape under the high temperature of the molten pool, prevent burning through, and have a close contact with the weldment, prevent the loss of liquid metal from the gap, and control the width and reinforcement uniformity of the back weld. The backing used at present can be divided into copper backing, flux backing and ceramic backing.

Copper pad uses pure copper as the backing, because of its good thermal conductivity, it is an ideal backing material. The copper pad is a forming groove with the same shape as the back of the weld on the pure copper plate. When welding with this method, the flux is spread in the groove of the copper pad, which plays the role of flux pad in the welding process, and at the same time, it protects the copper pad from the direct effect of the arc The process is not sensitive to the assembly quality of the weldment and the flux supporting force on the backing plate. According to the size of the copper pad and the sticking method, the copper pad can be divided into fixed type and mobile type.

The length of the fixed copper pad is slightly longer than that of the weld, and the copper pad is fixed in the welding process. In order to make the copper pad close to the weldment, the electromagnetic platform can be used to fix it. However, due to the limitation of the length of the copper pad, the weld can not be too long. The length of the mobile copper pad is only slightly larger than the length of the welding pool. In the welding process, the copper pad closely follows the welding head and slides at the bottom of the weld, so it is also called copper slide The copper slider is attached to the back of the weld by the tension spring on the welding head through the root gap of the weldment.

Using copper slider, the welding length is not limited by the length of the slider, but because the length of the copper slider is too small, the heat dissipation performance is poor, and it is easy to be heated and oxidized, so it needs to be cooled by water. The copper slider can be tightened through the weld gap, the weld groove should have enough gap, and there should be a specially designed welding head. The flux pad uses the self weight of the weldment or the flux pad backed by the inflatable rubber hose to weld The quality of seam forming mainly depends on the size and uniformity of the supporting force of the flux pad and the uniformity of the root gap.

The flux pad can prevent the loss of metal in the molten pool. The flux pad should use fine particles of flux as far as possible. The particle size of flux is uneven, which is difficult to ensure the uniformity of the supporting force. Therefore, the back weld formation is not uniform, and the serious welding defects will appear. The thicker the weldment is, the greater the welding current is. The more serious this situation is, the weldment is easy to deform when welding the thin plate, and the pressure frame can be used for electromagnetic leveling To ensure the tightness of the weldment and the gasket.