Measures to control the residual height of the weld

1. Wall thickness of larger steel pipes should be beveled

For wall thickness greater than 14.3mm steel pipe, should open an X-shaped bevel and pre-welding. If the pre-welding conditions are not mature, it should be welded with gas planing after root clearing, or grinding wheel automatic grinding root clearing, or milling root clearing and other methods, will be welded outside the weld in the unwelded before the processing into a U-shaped groove and then welded.

2. Adjustment of welding line energy

To check whether the welding line energy is appropriate, generally use the acid etching sample of the welded joint to check. One is to check the degree of overlap between the internal and external weld, and the second is to check the width of the waist of the weld channel. The provisions of the amount of overlap are generally greater than 1.5mm, but the author believes that the amount of overlap between the internal and external weld to 1.3 ~ 3.0mm is more appropriate, if more than 3.0mm shows that the line energy is large.

Line energy is large, not only is the depth of fusion large, but the weld height is also large, such as no open bevel or U-shaped groove, the weld height is even larger. This is because the greater the welding line energy, the melting of the wire per unit of time is bound to increase. For high-strength steel, welding line energy should be strictly controlled. Welding of high-strength steel, to reduce the line energy of each layer, generally using multi-channel welding (more than 2), should make the shape of the weld coefficient in 1.3 ~ 2.0 mm.

3. Multi-wire welding is appropriate to use a thinner front wire

Take more wire welding, such as the original diameter of the three wire welding match is 4mm +3.2mm +3.2mm (DC-AC-AC), the front wire to Ф3.2mm better. Because in the case of the same current, the use of Ф3.2mm wire than the use of Ф4mm wire depth of fusion. That is to say, before the wire with Ф3.2mm wire, even if you reduce some of the line energy, you can also use Ф4mm with the same effect of the depth of fusion, which is due to the fine wire as the current density of the thick wire.

Experience has shown that in other conditions remain unchanged, the use of Ф3.2mm of the front of the wire than Ф4 mm of the front of the wire depth of fusion of about 20%. This is not in the weld bevel or not planing groove to reduce the outer weld height effect is more obvious.

However, when the welding wall thickness is greater than 14.3mm pipe and the need for front wire current in 1000A or so, should be used Ф4 mm front wire, otherwise it may affect the arc of the stable combustion.

4. Spiral welding must adjust the position of the internal and external welding head

Spiral submerged arc welded pipe welding should be adjusted within the position of the head to minimize or eliminate the “saddle-shaped” internal weld; outside the weld, should also be adjusted to the position of the welding head of the space to minimize or eliminate the “fish spine back-shaped” external weld, which is mainly by the external welding joints The off-center value of the adjustment to achieve. Spiral welded pipe of different calibers, the off-center value of the outer weld is different.

In practical application, it can be selected according to the specific project requirements.

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