What is welded pipe?

Welded steel pipe refers to a steel pipe with seams on the surface that is welded after bending and deforming a steel strip or steel plate into a circular, square, etc. shape. The blank used for the welded steel pipe is steel plate or strip steel. With the rapid development of continuous rolling production of high-quality strip steel and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the varieties and specifications of welded steel pipes have increased day by day, and seamless pipes have been replaced in more and more fields. Welded steel pipes have lower cost and higher production efficiency than seamless steel pipes. So what are the points that need to be paid attention to during the installation process of welded steel pipes?

Precautions when installing welded pipes:

1) Before the welded pipe is installed, trenches should be excavated according to the drawings. The masonry of the tube well has been completed, and all kinds of welded steel pipes required have been handed over, the quality is intact, and they have passed the inspection. The required construction equipment including welding machines, cutting machines, electric motors, hammers, grinders, etc. are ready, and only a series of preparatory work can start the installation.

2) When installing the bayonet groove and steel groove, its position and size must be accurate, and no misalignment and skewing can occur.

3) The size and shape of the wooden strips for fixing the grooves must be accurate and the wood must meet the design requirements. The size of the wooden strips is accurate, which can ensure that the cooperation between the wooden strips and the steel channel is moderately tight. There is no need to use strong knocking during installation to avoid damage to the surface of the steel channel, and to ensure that the surface of the steel channel is consistent with the surface of the cylinder without unevenness. The shape of the wooden strip is accurate, which can make the glued surface uniform after the steel channel is embedded in the wooden strip, ensure firm bonding, and prevent the sideways phenomenon of the groove surface.

4) According to the drawing design, prefabricated the prefabricated pipe frame according to the site conditions, then cut according to the design and site, then polished the groove with a polishing machine, and then welded. During the welding process, the steel strip will be sent to the pipe welding unit, and in the multi-pass rolling process, the steel strip will be rolled up gradually to form a circular tube blank with an open gap. Adjust the pressing amount of the kneading roller, control the welding seam gap in the range of 1 to 3mm, and make the two ends of the welding seam level. If the gap is too large, the proximity effect will reduce the lack of eddy heat and poor intergranular connection of the weld, resulting in non-fusion or cracking. If the gap is too small, the proximity effect will increase, and the welding heat will be too large, causing the weld to burn, otherwise the weld will form deep pits after kneading and rolling.

Quality inspection of welded pipes after installation

1) The branch pipe shall not be welded at the weld seam, and the elbow shall avoid welding.

2) The error of vertical equipment is less than 3mm per meter, and the error of horizontal equipment is less than 1mm per meter.

3) The surface quality of longitudinally welded steel pipes should be lubricated, and defects such as folding, cracking, delamination, and lap joints are not allowed. Slight defects on the surface of welded steel pipes (such as scratches, nicks, misalignment of welds, burns, scars, etc.) should not exceed the negative error of wall thickness.