The porosity in welding is a common problem encountered in the semi-automatic welding process of self-protected flux-cored wire. For this reason, we analyze the cause of semi-automatic welding hole of self-protected flux-cored wire, and put forward the corresponding control measures.
Causes of welding porosity
(1) The effect of cooling speed during welding
In the vertical welding section, due to the gravity of the liquid metal itself, the welding speed is faster, and the penetration depth of the weld is shallow, which speeds up the cooling rate of the liquid metal in the weld and reduces the chance of gas escape, resulting in more pores in the weld passage.
(2) The effect of splashing during welding
The self-protected flux-cored wire used at present has a large metal oxidation splash during welding. When the front end of the conductive nozzle adheres to a certain amount of metal oxide splash, it enters the weld pool with the moving wire. This phenomenon is more serious with the increase of metal filling in the pass, resulting in the formation of pores in the pass.
(3) The influence of weld joints
When the welder is welding, due to the limitation of space position, the arc is stopped during welding. Therefore, the weld joints of the hot welding layer, the filling layer and the cover layer are easily superimposed, which increases the chance of dense porosity in the weld pass.
(4) The influence of natural environment
When the construction is in a high humidity environment, the remaining welding wire is placed in the open environment at the end of the work, and the welding wire is not properly kept, resulting in moisture. In addition, when the wind speed of the construction environment is greater than 8m/s, if no corresponding windproof measures are taken, it is also an important factor leading to the formation of pores in the weld passage.
(5) The influence of welding process parameters
The adjustment range of welding process parameters is narrow, the general arc voltage is 18~22V, and the wire feed speed is 2000~2300mm/min. Therefore, these two parameters must be adjusted well. Otherwise, the high voltage is easy to cause the slag protection effect of the weld surface is not good, easy to produce pores.
Control measure
(1) When welding, pay attention to the Angle of the welding torch.
Before the welding of the cover layer, when the filling layer of the vertical welding section is too low or too high, it should be trimmed to reach the height of the welding seam of the filling layer is about 0.5~1.0mm lower than the base material, before the welding of the next process can be carried out.
(2) Control the extension length of the welding wire as much as possible during the welding process.
When the JENT self-protected flux-cored wire is used as the surfacing material, the length of the wire is 15~20mm, too short will cause the metal oxide at the front end of the conductive nozzle to splash and accumulate too fast; Too long will reduce the arc voltage and affect the welding quality. In addition, pay attention to check and clean the conductive nozzle before welding.
(3) The weld joints between each pass layer should be arranged reasonably.
Before welding, the welder first squatts down to determine the position of the overhead welding, and then stands up and does not move his feet to weld.
(4) In the case of large wind speed welding, windproof measures should be taken.
The remaining welding wire should be properly kept at the end of work every day to prevent moisture. The wire feeder is more troublesome to disassemble, so it should be covered with a rainproof protective cover.
(5) Before welding, carefully adjust the arc voltage and wire feed speed.
After long-term use of welding equipment in field construction, ammeter and voltmeter are not very accurate and can only be used as a reference. It is best to test welding on the steel plate to determine the reasonable process parameters.
