How to prevent welding spatter
(1) Correct selection of process parameters
1. Welding current and voltage In the CO2 arc, there is a certain rule between the spatter rate and welding current for each diameter of the welding wire. The splash rate is small in the low current area (short circuit excessive area), and also small in the high current area (fine particle excessive area). The splash rate is the largest in the middle area, and the splash rate is small when the current is less than 150A or more than 300A, and the splash rate is large between the two.
When selecting welding current, the current area with high spatter rate should be avoided as far as possible. After the current is determined, the appropriate voltage is matched to ensure the minimum splash rate,
2. When the torch is vertical, the spatter is the smallest, and the inclination Angle is the largest, the more the spatter is. It is best not to tilt the torch forward or backward more than 20 degrees.
3. The stretching length of the welding wire also has an effect on the spatter. The length of welding wire is as short as possible.
(two) choose the appropriate welding wire material to protect the gas composition. Such as:
Choose steel welding wire with low welding carbon as far as possible to reduce the CO gas generated in the welding process. The practice shows that the spatter can be greatly reduced when the amount of carbon in the welding wire is reduced to 0.04%.
2. Use tubular wire for welding. Because the tube welding wire contains deoxidizer arc stabilizer and other gas - slag joint protection, so that the welding process is very stable, spatter can be significantly reduced;
(1) in the long arc welding using CO2 mixture as the protective gas.
Although the splash rate can be reduced by reasonable selection of standard parameters and submersible arc method, the splash amount is still large. Adding a certain amount of Ar gas into CO2 gas is the most effective way to reduce excessive metal splashing of particles.
After adding Ar gas to CO2 gas, the above physical and chemical properties of pure carbon dioxide gas are changed. As the proportion of AR gas increases, the splashing decreases gradually. CO2+Ar mixture can not only overcome the spatter, but also improve the weld forming, and have an effect on the weld depth, weld height and residual height.
When the content is 60%, the size of the transition droplet can be obviously reduced, and even a jet transition can be obtained, which improves the transition characteristics of the droplet and reduces the metal splash.
(2) limit the breaking energy of the liquid metal bridge in the case of excessive short-circuit welding
Excessive short-circuit welding will cause metal splashing. In the final stage of short-circuit excessive welding, due to the sharp increase of short-circuit current, the bridge liquid metal will be heated rapidly, resulting in the condensation of heat, and finally lead to the bridge burst and spatter.
The method to reduce this kind of spatter: in the short circuit transition welding, reasonable selection of welding power supply characteristics and match the appropriate adjustable current, so that when the welding wire with different diameters can be adjusted to the appropriate short circuit current growth rate .The use of low spatter rate welding wire
1. For solid cored wire, under the premise of ensuring the mechanical properties, the carbon content should be reduced as far as possible, and add an appropriate amount of titanium, aluminum and other alloy elements. The splashing caused by gases such as CO2 can be significantly reduced by over particle welding or short circuit welding.
2. Use CS2CO3, K2CO3 and other substances activated treated welding wire, positive polarity welding.
3. Flux cored wire is used. The metal spatter rate of flux-cored wire is 1/3 of that of solid wire.
In the process of CO2 gas shielded welding, the metal splash loss accounts for about 10% of the welding wire molten metal, and the serious loss can be up to 30~40%. Under the best condition, the splash loss can be controlled within the range of 2~4%.
The increase of splash loss will reduce the deposition coefficient of welding wire, thus increasing the consumption of welding wire and electric energy, and reducing welding productivity and welding cost.
The splashing metal will stick to the end face of the conductive nozzle and the inner wall of the nozzle, which will make the wire feeding not smooth and affect the stability of the arc, reduce the protective effect of the protective gas, and deteriorate the quality of the weld forming. In addition, the splashed metal that sticks to the conductive nozzles, nozzles, welds and weldment surfaces still needs to be cleaned up after welding, which increases the auxiliary welding hours.
