Welding steel pipe slag is a residue left inside the weld.In theoretical analysis, the main reasons for the automatic welding seams of buried arcs are mainly the following 3 points: ① There are many miscellaneous objects in raw materials (including mother material, welding wires, and welds);③ The selected welding process parameters are improper, which is not conducive to the emergence of the slag.
Based on the production characteristics of the straight joints buried arc welded steel pipes, the reason can be ruled out to clean up the seams to produce slag when the layer is not cleaned when the layer is not clean.
For raw materials, there are many miscellaneous objects and the welded seams produce residue. After the pre -welding test of the mother material, the new welding wire and welding, etc.Things are not the main causes of slag.
Therefore, the main reason for the melting wire clamping of the thick wall in straight wall buried arc welding is the improper welding process parameters selected.The welding process parameters of the thick wall stitches buried arc welded pipes are mainly: line energy, welding current, welding voltage, welding speed, welding wire spacing, slope size, etc.
In -depth analysis from the aspect of welding metallurgical, we can see that the cause of the welding seam fusion line produces residue clamps is that the melting line temperature is too low, so that the liquid slag is too late to be precipitated.Low or cooling speed.
The method of seeing the long -sewing steel pipe of the cutting straight seam is qi cutting. Qi cutting is the use of the heat generated by oxygen and acetylene combustion to make the cut metal melted at the iron scum produced at high temperature.The straight seam steel pipe is cut off.
The efficiency of the straight seam steel pipes with gas cutting is high, and the operation of the incision is relatively neat, but a layer of oxide film will be attached to the surface of the incision.Need to be removed before welding.During the installation of straight steel pipe pipes, various straight steel pipes, steel plates, and profiles with larger diameter of air cutting pipes are often used.
The air cutting tool of cutting straight steel pipes is divided into two types: shooting and suction type and other pressure types according to the different pressure of acetylene.The oxygen for gas cutting is supplied by the oxygen cylinder, and acetylene is supplied by acetylene gas cylinder or acetylene generator.
Due to the danger of qi cutting, it is necessary to strictly implement the operating regulations when cutting the stitched steel pipe with gas cutting methods:
1. Regardless of whether the straight steel pipe rotates or fixes the mouth, it should be kept vertically on the surface of the straight seam steel pipe. After cutting, the mouth is gradually tilted forward to the cut line of the cut point at a 70 ° -80 ° angle.
2. When the gas cutting fixing straight seam steel pipes generally start with the lower part of the straight steel pipe.
3. The selection of cutting mouth and oxygen pressure is related to the thickness of straight steel tubes, which can be selected according to the actual situation.
4. The distance between the surface of the mouth and the straight steel pipe should be determined according to the length of the preheating flame and the thickness of the straight seam steel pipe. Generally, it is advisable to be 3--5mm at the end of the flame heart.
5. After the straight seam steel pipe is cut off, the oxidative iron residue at the incision of the knife or the hand sand wheel is applied to make it smooth and clean.
6. The end of gas cutting should quickly close the cutting oxygen valve and acetylene valve preheating oxygen valve.
