What is straight seam steel pipe?
Straight seam steel pipe refers to a steel pipe in which the weld seam is parallel to the longitudinal direction of the steel pipe.
The production process of straight seam welded pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW steel pipes) and submerged arc welded straight seam steel pipes (LSAW steel pipes) according to the production process. Submerged arc welded straight seam steel pipes are divided into UOE, RBE, JCOE steel pipes, etc. according to their different forming methods.
High frequency welding process:
The high-frequency welding process refers to the local heating of the steel at the edge of the weld to a molten state based on the principle of electromagnetic induction and the skin effect, proximity effect and eddy current thermal effect of AC charges in the conductor. After being squeezed by the roller, the butt weld is made Realize inter-crystal bonding to achieve the purpose of welding. High-frequency welding is a kind of induction welding (or pressure contact welding). It does not require weld fillers, has no welding spatter, has a narrow welding heat affected zone, beautiful welding shapes, and good welding mechanical properties. Therefore, it is widely used in the production of steel pipes.
Submerged arc welding process:
The welding process used in submerged arc welded straight seam steel pipes is submerged arc welding technology, using filler welding and particle protected flux submerged arc. The diameter of production can reach 1500mm. LSAW is the English abbreviation of submerged arc welded straight seam steel pipe. The production process of submerged arc welded straight seam steel pipe includes JCOE forming technology and roll forming submerged arc welding technology. When the diameter is large, two steel plates may be used for rolling, which will form a double weld (DSAW Pipe) phenomenon.
Acceptance methods and steps for ERW and LSAW straight seam steel pipes:
1) Preparation work
Before accepting steel pipe products, the materials need to be classified, packaged, and labeled, and the invoices, contracts, inspection certificates and other documents of the goods need to be checked. Only when all preparatory work is in place can the acceptance of the steel begin.
2) Appearance inspection
Appearance inspection is the first step in the acceptance of straight seam steel pipes. Its purpose is to determine whether there are obvious quality problems on the surface of the steel, such as rust, surface unevenness, scratches, pits, etc. Appearance inspection mainly needs to check the following aspects:
1. The surface of the steel should be flat and smooth, without obvious unevenness, peeling, pitting, folds, scratches or prefabricated defects.
2. Observe the steel section for defects, cracks, pores, inclusions, etc.
3. Check whether there is dirt, rust, etc. on the surface. If there is any, use steel brushes, steel balls, etc. to remove it.
4. Check whether the surface engraving is clear and whether the steel number is consistent with the acceptance document.
3) Inspection of weld quality
The quality of welds is crucial to the effectiveness and safety of
welded pipes. During the acceptance process of straight seam welded pipes, the appearance and internal quality of the welds need to be inspected. For appearance quality, you should pay attention to whether the welds are rusty, cracked, loose, etc.; for internal quality, you should check whether the welds are uniform, have pores, and precipitate. If defects exist, they need to be rectified promptly.
4) Inspection of pipe straightness
The straightness of the pipe is one of the important factors affecting the use effect. When accepting straight seam welded pipes, it is necessary to check whether the straightness of the pipe meets the specified standards. The straightness of the pipe can be checked in the following ways:
1. Conduct a tensile test on both ends of the pipe to test whether its stretch is within the specified range.
2. Use tools such as rulers or calipers to measure the straightness of the pipe and check whether the deviation exceeds the standard.
5) Inspection of dimensional deviation
Dimensional measurement is one of the important aspects of steel acceptance. Dimensional deviation refers to whether the length, diameter, wall thickness and other dimensional parameters of the pipe meet the specified standards. During the acceptance process, it is necessary to check whether the dimensional deviation of the pipe meets the standards. Specifically, it can be checked from the following aspects:
1. Whether the pipe length meets the standard size. By measuring the actual length of the pipe, check whether it matches the standard length.
2. Whether the pipe diameter meets the standard size. By measuring the actual diameter of the pipe, check whether it matches the standard diameter.
3. Whether the wall thickness of the pipe meets the standard size. By measuring the actual wall thickness of the pipe, check whether it matches the standard wall thickness.
6) Chemical composition inspection
The chemical composition of steel is one of the important factors in judging its performance. Chemical composition inspection can understand whether the content of various elements in the steel meets the requirements, thereby determining whether the steel meets specific standards. Chemical composition inspection mainly requires the following aspects:
1. Sampling: According to the inspection standards, a certain number of steel samples are intercepted at designated locations and marked according to the required standards.
2. Sample preparation: Cut and grind the sample to ensure the flatness of its surface and make it into a sample suitable for inspection.
3. Chemical analysis: Use chemical analysis instruments to measure the prepared samples, and process and judge the data in strict accordance with the test standards.
4. Inspection results: Measure the chemical composition according to the inspection standards to evaluate whether the chemical composition of the steel meets the requirements of the standard data.
7) Mechanical performance test
The mechanical properties of straight seam steel pipes are one of its important quality indicators, including strength, plasticity, toughness, hardness and other indicators. Mechanical property testing refers to conducting mechanical property tests and experiments on straight seam steel pipes such as tension, impact, hardness, etc., and evaluating whether the mechanical properties of the steel meet the corresponding standards by detecting numerical data.
Conclusion:
For the methods and steps for the acceptance of straight seam steel pipes, we need to conduct a comprehensive evaluation in terms of appearance inspection, weld quality inspection, pipe straightness inspection, dimensional deviation inspection, chemical composition inspection, and mechanical performance testing. Comprehensive steel acceptance work can effectively ensure safe production in construction, manufacturing and other industrial fields, while also ensuring the stable quality and performance of straight seam steel pipes.
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