Operational technology and safety features of submerged arc welding

Submerged arc welding operation technology

1.Butt straight weld welding technology

There are two basic types of welding methods for butt straight welds: single-sided welding and double-sided welding. According to the thickness of steel plate, it is divided into single-layer welding, multi-layer welding, backing method and non backing method.

1) The flux pad method is used for submerged arc automatic welding. When welding butt welds, the flux pad is used as the welding pad to prevent the leakage of slag and molten pool metal. The flux of the flux pad is the same as that used for welding. The flux shall be close to the back of the weldment and can bear a certain uniform support force. It is necessary to select a larger welding specification to make the workpiece penetrate, so as to realize double-sided forming.

2) Manual welding back sealing automatic submerged arc welding. For welds that cannot use backing, manual welding back sealing can be used first, and then submerged arc welding can be used.

3) Suspended welding is used for butt welding without groove and gap. No pad is required. 40% ~ 50% penetration is required for front welding and 60% ~ 70% penetration is required for back welding to ensure workpiece penetration. In practice, it is generally difficult to measure the penetration depth, which is often judged by observing the color of the back of the molten pool during welding, and certain experience is required.

4) For multi-layer submerged arc welding, multi-layer welding can be used for thick steel plates that cannot be welded at one time. During the first layer of welding, the specification should not be too large to ensure penetration and avoid defects such as cracks. The joints of each layer of welds shall be staggered and shall not overlap.

2.Butt girth welding technology

The rolling tyre with speed regulating device shall be adopted. If double-sided welding is adopted, the flux pad shall be placed at the weld on the outer wall of the shell for the first time, the welding trolley shall be extended to the lower flat welding position of the cylinder, and the welding wire shall be shifted from the center line to the downhill welding position. During the second front welding, the welding shall be carried out at the upper flat welding position outside the cylinder.

3.Fillet weld welding technology

The fillet weld of automatic submerged arc welding mainly appears in T-joints and lap joints. Generally, ship welding and bevel welding can be used.

4.Submerged arc semi-automatic welding

It is mainly hose automatic welding. The welding wire with thinner diameter is sent to the molten pool through the curved hose. The movement of arc is completed manually, while the conveying of welding wire is automatic. Semi-automatic welding can replace automatic welding to weld some curved welds, which are used for butt welds and fillet welds.

Safe operation technology of submerged arc welding

1.The trolley wheels and wires of automatic submerged arc welding machine shall be insulated, and the wires shall be straightened to prevent torsion and burning by slag.

2.The control box and welding machine shell shall be grounded to prevent electric leakage, and the wiring board shell shall be covered.

3.The welding handle of semi-automatic submerged arc welding shall have a fixed position to prevent short circuit.

4.The flux composition of automatic submerged arc welding contains manganese oxide and other harmful substances. Although no visible smoke is generated during welding, it will produce certain harmful gases. Therefore, there should be exhaust ventilation equipment in the working place.