What Are The Factors That Affect The Quality of Steel Pipes in The ERW High Speed Tube Mill Production Line?

First of all, the welded pipe process is an important link in the ERW High Speed Tube Mill production line, which can directly affect the quality of the products produced. The production process depends on the product variety. From raw materials to finished products, a series of processes are required. Completing these processes requires corresponding various mechanical equipment and welding, electrical control, and testing devices. These equipment and devices have different requirements according to different process flows. A reasonable arrangement, the typical process flow of a high-frequency welded pipe production line: uncoiling - strip leveling - head and tail shearing - strip butt welding - loop storage - forming - welding - burrs - sizing - flaw detection - flying cutting - primary Inspection - steel pipe straightening - pipe section processing - hydraulic test - flaw detection - printing and coating - finished product. Among them, there are many aspects that affect product quality, and attention should be paid to the work of all aspects of the high-frequency welded pipe production line.

1.Raw materials are the main factors that affect the quality of steel pipe welding in the high-frequency welded pipe production line. There are three main aspects: unstable mechanical properties of the steel strip, surface defects of the steel strip, and large geometric deviations. Therefore, key controls should be carried out from these three aspects.

1) The impact of the mechanical properties of steel strips on the quality of steel pipes

The commonly used steel type for welded steel pipes is carbon structural steel. If the yield point and tensile strength of the steel strip are too high, it will cause difficulties in the forming process of the steel strip in the high-frequency welded pipe production line. Especially when the pipe wall is thick, the material's resilience is large, and the steel pipe will undergo large deformation during welding. Stress, welds are prone to cracks. When the tensile strength of the steel strip exceeds 635MPa and the elongation is less than 10%, the weld seam of the steel strip is prone to cracking during the welding process. When the tensile strength is lower than 300MPa, the surface of the steel strip is prone to wrinkles due to its soft material during the forming process. It can be seen that the mechanical properties of the material have a great influence on the quality of the steel pipe. Therefore, attention should be paid to this source link of the high-frequency welded pipe production line to effectively control the quality of the steel pipe in terms of material strength.

2) The impact of surface defects of steel strips on the quality of steel pipes

Common surface defects of steel strips include sickle bends, wavy shapes, slitting edges, etc. Sickle bends and wavy shapes generally appear during the rolling process of cold-rolled steel strips and are caused by improper control of the reduction amount. During the steel pipe forming process, sickle bends and wavy shapes will cause the strip to deflect or turn over, which can easily cause lap welding of the steel pipe welds and affect the quality of the steel pipe. The edge of the steel strip (that is, the edge of the steel strip is jagged and uneven) generally appears on the slitting belt. The reason is that the disc blade of the slitting machine is blunt or not sharp. Due to the gnawing of the edge of the steel strip, local flesh shortages often occur, which makes the steel strip prone to cracks and cracks during welding and affects the stability of the weld quality.

3) The influence of steel strip geometric dimensions on steel pipe quality

When the width of the steel strip is less than the allowable deviation, the extrusion force when welding the steel pipe is reduced, causing the welding of the steel pipe weld to be unstable, cracks or open pipes appearing; when the width of the steel strip is greater than the allowable deviation, the welding force of the steel pipe is reduced. As the extrusion force increases, welding defects such as sharp lips, lap welds or burrs will appear at the steel pipe welds. Therefore, the fluctuation of the steel strip width not only affects the accuracy of the outer diameter of the steel pipe, but also seriously affects the surface quality of the steel pipe.

2. High-frequency welding also has an impact on the quality of steel pipes. In the high-frequency welding process of the high-frequency welded pipe production line, the control of the welding process and process parameters, the placement of the induction coil and the resistor position, etc., have a great impact on the welding quality of the steel pipe weld.

3. The impact of roll adjustment on the quality of steel pipes in high-frequency welded pipe production lines cannot be ignored. Roll adjustment is an operating process for steel pipes. During the production process, when the rolls are damaged or severely worn, part of the rolls need to be replaced on the unit, or if a certain variety is continuously produced in sufficient quantity, the entire set of rolls needs to be replaced. At this time, the rollers should be adjusted to obtain good steel pipe quality. If the rollers are not adjusted properly, defects such as twisting of the steel pipe seams, lap welding, edge waves, bulging, indentations or scratches on the surface of the pipe body, large ovality of the steel pipe, etc. should be mastered when changing the rollers. Skill.