There are stomach defects inside or surface on the weld.
(1) Harm
The pores reduce the effective cross -sectional area of the weld, loosen the weld, thereby reducing the intensity of the joints, forming penetration with other welding defects, and destroying the density of the weld;
In the weld, the continuous pores will reduce the weld bearing capacity and damage the welding structure.
(2) Cause analysis
The formation of the pores is that during the solidification process of the molten pond, there are a lot of gas to be relieved from the metal. When the solidification speed is greater than the gas out of the gas, the pores are formed;
The main reason for the pores is that the mother material or filling metal surface is rust, oil pollution, etc.
The dishes of the beakers and welds will increase the amount of pores, because the water in rust, oil and stains and electrodes, and the water in the welds, and the water in the welds decompose into a gas at high temperature, which increases the content of the gas in the high temperature metal;
The cooling speed of the melting pond is not conducive to gas renewal; insufficient seam metal dehydration will also increase oxygen pores.
(3) Control measures
Clear oil, rust, moisture and debris on the welding wire, pipeline slopes and the surface near its surface;
Use alkaline stripes and welds, and completely dry;
Use the appropriate welding polarity, and use short arcs to weld;
Preheat before welding to slow down the cooling speed;
Select the appropriate way of transport.
