What are the main production methods of Q215 steel pipe?
Hot rolling is the most commonly used production method. It can be quickly formed through high-temperature rolling and is suitable for mass production. The steel pipe produced by the cold drawing process has high dimensional accuracy and good surface finish, but the production cost is relatively high. The high-frequency resistance welding (ERW) method is suitable for the production of welded steel pipes, with high production efficiency and low cost. The spiral welding process is mainly used to produce large-diameter pipelines and is widely used in the field of oil and gas transportation. The choice of different production processes mainly depends on factors such as product use, quality requirements and cost budget.
What is the performance difference between hot-rolled and cold-drawn Q215 steel pipes?
Hot-rolled steel pipes have a coarse grain structure and obvious anisotropy of mechanical properties, but high production efficiency. After cold working, the grains of cold-drawn steel pipes are finer, the strength can be increased by 10-15%, and the dimensional accuracy is higher. There is oxide scale on the surface of hot-rolled pipes, which usually requires subsequent treatment before use, while the surface of cold-drawn pipes is smooth. In terms of elongation, hot-rolled pipes are better than cold-drawn pipes and are more suitable for subsequent bending and forming. From a cost perspective, hot-rolled tubes are more suitable for large-volume general products, while cold-drawn tubes are used for precision parts.
What should be paid attention to when welding Q215 steel pipes?
Before welding, ensure that the area to be welded is clean, remove impurities such as oil and rust, and ensure the welding quality. It is recommended to use E43 series welding rods, whose strength matches the parent material and can obtain good welded joints. During welding, the heat input should be controlled to avoid overheating and coarse grains that affect performance. For thick-walled pipe welding, it is recommended to use multi-layer multi-pass welding and control the interlayer temperature not to exceed 200℃. No special heat treatment is required after welding, but appearance inspection and necessary non-destructive testing should be carried out.
How to reduce residual stress in Q215 steel pipe production?
Hot-rolled steel pipes can eliminate most of the bending stress and improve dimensional accuracy through the straightening process. Cold-drawn steel pipes need to be stress-relieved annealed, usually at 500-600℃ and then slowly cooled. Vibration aging technology is a method widely used in recent years, which redistributes residual stress through mechanical vibration. Reasonable rolling process parameter design can reduce stress generation from the source, such as controlling the final rolling temperature. For particularly important components, the thermomechanical control process (TMCP) can be used to optimize the stress state.
What are the production standards for Q215 steel pipes?
GB/T 8162 is the main standard for seamless steel pipes for structures, which specifies the chemical composition and mechanical properties. GB/T 3091 is applicable to welded steel pipes for low-pressure fluid transportation, including galvanized and non-galvanized. ASTM A53 is the American Society for Testing and Materials standard, which is often used for export products. EN 10219 is a European standard with more stringent performance requirements for welded steel pipes. API 5L is a special standard for oil and gas transmission pipes, and Q215 steel pipes are usually only suitable for low-pressure branch pipelines.
