Square tubes are a type of steel commonly used in fields such as structures, machinery and construction. During its production, it is necessary to pay attention to multiple processes and quality control links. In order to ensure the performance and quality of square tubes, the precautions in the production process are very important. The following are the main precautions for the production of square tubes:
square and rectangular tubes
1. Selection and inspection of raw materials
Steel quality: The main raw material of square tubes is hot-rolled strip steel or cold-rolled strip steel. High-quality steel that meets national standards or industry standards must be selected to ensure that it has good mechanical properties and ductility. The chemical composition, tensile strength and yield strength of the raw materials need to be strictly inspected.
Surface quality inspection: There should be no obvious defects on the surface of the steel strip, such as cracks, bubbles, rust, etc. The surface quality of the raw materials directly affects the effect of subsequent processes such as welding and coating.
2. Cold bending process
Bending radius control: In the production of square tubes, cold bending is a key step. The steel strip must be bent into a square or rectangular cross-section under a certain forming pressure. The bending radius needs to be controlled during bending to avoid excessive deformation, which may cause cracks or dents in the tube wall.
Rolling accuracy: During the rolling process, the rolling accuracy must be ensured to ensure the dimensional stability and uniform shape of the square tube. Excessive deviation may make the square tube difficult to assemble in subsequent processing, or even unable to be used normally.
Hollow section pipe
3. Welding process and control
Welding method selection: High-frequency welding or automatic gas shielded welding (MAG welding) is generally used in the production of square tubes. During the welding process, the control of welding temperature and current is crucial. Too high temperature may cause the material to overheat, deform or burn through, while too low temperature may cause the welding to be unstable.
Welding quality control: During the welding process, the width, depth and welding speed of the weld should be controlled to ensure that the weld joint is firm. The weld of the square tube after welding needs to be inspected. Common inspection methods include visual inspection, ultrasonic inspection and X-ray inspection.
Release of welding stress: Thermal stress will be generated during the welding process, which may easily cause the square tube to deform. Therefore, heat treatment or straightening is required after welding to reduce internal stress and ensure the stability of the geometric dimensions of the pipe.
4. Straightening and shaping
Straightening process: The square tube after welding may be warped or deformed, so it needs to be straightened by a straightener. The straightening process requires careful control of the straightening force to avoid excessive bending or deformation.
Shaping accuracy: During the straightening process, the angle, straightness and edge flatness of the square tube should be ensured to meet the design requirements. Excessive deformation will affect the load-bearing capacity and appearance of the square tube.
5. Dimension and wall thickness control
Dimension accuracy: The length, width and height of the square tube need to be precisely controlled. Any dimensional deviation may affect the assembly or installation of the square tube. During the production process, the dimensions should be measured and verified regularly to ensure that the square tube meets the design specifications.
Wall thickness uniformity: The wall thickness of the square tube should be kept uniform during the production process. Excessive wall thickness deviation may affect the strength and load-bearing capacity of the pipe, especially in structural applications with high loads. Wall thickness testing is usually required before leaving the factory to ensure compliance with standards.
6. Surface treatment and anti-corrosion
Surface cleaning: After the square tube is produced, the surface of the pipe needs to be cleaned to remove residual welding slag, oil stains, rust, etc. A clean surface is helpful for subsequent coating and anti-corrosion treatment.
Anti-corrosion coating: If the square tube is used outdoors or in harsh environments, anti-corrosion treatment is required. Common treatment methods include hot-dip galvanizing and spraying anti-corrosion coatings. Galvanizing can effectively prevent corrosion and increase the service life of square tubes.
Surface quality inspection: After the surface treatment is completed, surface defects such as cracks, dents, rust, etc. should be inspected. If defects appear on the surface, it may affect the appearance and subsequent use.
7. Heat treatment and cooling
Annealing: For some high-strength steels, annealing may be required to reduce the hardness of the material, improve its plasticity, and avoid brittle fracture of the pipe due to excessive hardness of the material.
Cooling control: The cooling process of the square tube requires precise control of the cooling rate to prevent internal stress concentration and deformation caused by rapid cooling or uneven cooling.
8. Quality inspection and testing
Dimension and tolerance inspection: The outer dimensions of the square tube need to be checked regularly during the production process to ensure that they meet the design requirements, including length, width, height, wall thickness, etc.
Mechanical properties test: The mechanical properties of the square tube are tested through tensile tests, bending tests, etc. to ensure that its strength, toughness and plasticity meet the standard requirements.
Surface defect detection: The surface of the square tube should be free of obvious defects such as cracks, bubbles, and dents. Visual inspection or ultrasonic testing methods are often used to ensure that the surface quality of the tube meets the standards.
Packaging and transportation
Packaging requirements: After production, the square tube needs to be properly packaged to prevent damage during transportation. Anti-rust oil packaging, cartons or wooden pallets are usually used for packaging.
Transportation conditions: During transportation, avoid collision or compression between the square tube and other items, and avoid scratches, deformation and other problems on the surface of the tube. Avoid long-term exposure to humid environments during transportation to prevent corrosion.
Post time: Mar-06-2025
