Precautions for box column welding

(1) In order to ensure the stability of the electroslag welding process and the quality of the welding, the five key links including installation and equipment adjustment, arc slag production, normal welding and welding seam closing should be completed continuously, and try not to stop in the middle.

(2) Before assembling the box beams (columns), scribe and drill the fusion nozzle holes (φ30mm), and it is required that the top and bottom must be aligned vertically.

(3) Nozzle length = welding mouth length + about 150mm.

(4) During welding, pay attention to check whether the molten pool is fully melted and whether the slag amount and depth are appropriate. If the slag pool is too deep, the melting width will be reduced, causing the temperature of the slag pool to drop, which will easily lead to insufficient heating of the welding edge, resulting in defects such as unfusion or poor fusion; if the slag pool is too shallow, even if the welding current increases, electroslag welding will fail. The process is also unstable, and the welding wire easily contacts the metal molten pool and causes a short circuit, which increases spatter and causes welding interruption. Therefore, the depth of the slag pool is very important, and it is appropriate to control the depth of the slag pool at 30 to 40 mm. The depth of the slag pool can also be judged by hearing. The sound produced by a moderately deep slag pool is like cooking porridge, with a "gurgling" sound. The internal fusion situation can also be judged by observing the red color and width of the contact surface of the outer steel plate of the welding joint. The outer steel plate with good fusion can also be judged by hearing. The red color is uniform, slightly wider than the welding joint, and the width is more uniform.

When flux needs to be added, avoid adding too much at one time and add it slowly and in small amounts. If too much is added at one time, it may easily cause defects such as poor weld fusion.

(5) The heat of electroslag welding mainly depends on the current. If the current is too large, the molten pool will boil severely and the weld will not be formed well, which may easily cause defects such as poor fusion. If the current is small, the electroslag process will be unstable and it is easy to cause unintended consequences. Defects such as fusion and slag inclusions. After arc ignition, the welding current should be relatively small at the beginning of welding, and then gradually increase to the normal value.

(6) Electroslag welding is a resistive load. Generally speaking, the welding voltage directly affects the molten width of the weld (for electroslag welding, it refers to the area of the molten pool and the slag pool). The higher the voltage, the greater the melting width. The wider it is, the smaller it is on the contrary. Therefore, the welding voltage should be slightly higher than the normal welding voltage when starting welding, generally 3 to 5V higher is appropriate.

(7) The alignment center of the melting nozzle in the welding joint and the condition of the slag pool during welding can be observed with the help of a small mercury glass mirror.