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Submerged arc welding process

The welding method of spiral steel pipe is submerged arc welding; forming process, front swing type intermittent production; unit speed, 0.5--3m/min; welding speed, 0.5--3m/min. The unit consists of an unwinder, a straightening machine, a centering device, a hydraulic shear, a milling machine, a disc cutter, a milling machine, a panel cleaning device, a conveyor, a plate edge pre-bending device, a molding machine, an internal welding, an external welding, Flashing, dialing, pouring slag, repair welding, flat head chamfering, water pressure inspection, finished product inspection, degreasing collection. The whole process of submerged arc welding of spiral steel pipe is as follows:

The principle of spiral steel pipe-submerged arc welding: submerged arc welding is performed by arc heat energy. Unlike manual electrode arc welding, the submerged arc welding wire is bare and there is no coating on it. Submerged arc welding is indeed pre-plated. At the place to be welded, the submerged arc welding wire extends into the flux, and the arc is burned under the flux. When the welding wire is in contact with the workpiece, when the pressing button is pressed, the welding wire and the workpiece are energized, the welding wire is pumped back, the arc is ignited, the welding trolley is advanced, and the welding wire is continuously conveyed downward to maintain the arc burning under the flux layer under the arc. Form a weld pool. Around the arc, the flux melts to form a void. This void and molten pool continue to advance, and the metal behind the molten pool solidifies to form a continuous weld. This process is carried out under the flux, so we can't see it with the naked eye. It can be seen by means of X-ray photography.

Because the spiral steel pipe adopts the welding technology of submerged arc automatic welding, the production efficiency is high except that the production auxiliary time is small, the time for changing the welding rod is saved, the welding condition is clean and no splash, the cleaning time is saved, and the weld quality is high. It also provides the necessary conditions for the delivery of the spiral steel pipe plant, so that the production time of the large spiral steel pipe is guaranteed, so it is still widely used.

 

 

The spiral submerged arc welded steel pipe is formed by spirally bending the strip steel and welding the inner joint and the outer joint by submerged arc automatic welding to form a spiral seam steel pipe. It can be widely used in the production of large diameter steel pipes for the following reasons:

1) As long as the forming angle is changed, it is possible to produce steel pipes of various calibers with strips of the same width;

2) Because the continuous bending is formed, the length of the steel pipe is not limited;

3) The weld spiral is evenly distributed on the circumference of the whole steel pipe, so the steel pipe has high dimensional accuracy and high strength;

4) The equipment is cheap and easy to change the size, and is suitable for the production of small batch and multi-type steel pipes.

Weld type

 

 

 

Weld type of large diameter spiral steel pipe

Butt weld: It is a ring weld formed by joining two steel pipes together.

Steel belt butt weld: It is the weld of the steel plate or steel strip on the spiral seam steel pipe.

Positioning Weld: It is the weld used to fix the butt edge before final welding.

Large-diameter spiral steel pipe weld surface requirements

The shape of the weld of large-diameter spiral steel pipe shall be evenly regularized, and the transition shall be gentle. The surface of the weld shall not have defects such as arc breaking, burn through, crack, crusting, folding and crater.

 

 

Cause of wrong side

Reasons for the wrong side of large diameter spiral steel pipe:

Large-diameter spiral steel pipes are produced at the time of production, and there are many influencing factors. In the production practice, the steel pipe is often downgraded by the dry and wrong side. Therefore, it is necessary to analyze the causes of the wrong side of large-diameter spiral steel pipe and its preventive measures.

1. The sickle bend of the steel strip is the most important factor causing the wrong side of the steel pipe. In the spiral welded pipe forming, the boring of the steel strip will continuously change the forming angle, resulting in a change in the weld gap, resulting in a slit, a wrong side or even a lap. Seriously affect the quality of the steel pipe, so observe the bending of the steel drum after the unwinding of the coil, by controlling the vertical roller to cut the part of the boring tool and the continuous control and correction of the forming angle is to reduce the steel belt boring in the production process An effective way to create a wrong side.

2. Due to the poor shape and dimensional accuracy of the uncut edge steel strip, it is easy to cause the steel strip to bend hard and cause the wrong side.

3. When the residual height of the butt weld of the steel strip is large, it may cause a large misalignment if it is improperly handled during overmolding.

4. The poor condition of the edge of the steel strip is another important cause of the wrong side.