Elbow Welding
Customized according to drawings and quantities
Technical characteristics and material selection
Material compatibility: Commonly used are 304/316L stainless steel (corrosion-resistant), carbon steel (economical), alloy steel (high strength), and titanium alloy (biocompatible). Surface treatment includes anodizing, electroplating or coating (such as Teflon anti-corrosion), adapting to different media (such as acidic/alkaline environments) and industry requirements.
Structural features: Elbow pipes are usually composed of multiple pipe sections welded together. For instance, the tail water elbow pipe of a hydropower station is divided into a diffuser section and a elbow section, and sealing is achieved through longitudinal and circumferential seam welding. The design should take into account the radius of curvature (usually 4 to 6 times the pipe diameter), the uniformity of wall thickness (deviation ≤-20%), and roundness (within -5% of the outer diameter of the reference).
Process flow and key technologies
Blanking and forming: Blanking is carried out using CNC cutting machines or semi-automatic cutting machines to ensure dimensional accuracy (for example, the Longtan Hydropower Station requires that the flatness of the pipe opening be ≤12mm and the circumference deviation be ≤10mm). The tile rolling process uses a three-roll plate rolling machine. The arc is controlled by the plain line method, and the deviation of the arc detected by the sample is ≤3mm.
Assembly and welding: It is vertically assembled onto a steel platform. The gap of the butt joint (1-4mm) and the misalignment (≤2mm) are adjusted by using a tensioner and a code. Welding methods include:
Manual arc welding: Suitable for longitudinal seam welding, using CHE507 electrodes, multi-pass welding in layers and sections, and controlling the temperature and current between layers (140-180A).
CO₂ gas shielded welding: It is used for reinforcing fillet welds, featuring high deposition efficiency and aesthetically pleasing weld seams.
Laser welding: In high-end scenarios (such as aerospace), it achieves narrow weld seams, low heat input, and reduces deformation.
Deformation control: Reduce welding deformation through symmetrical welding, adding internal supports, reserving shrinkage amounts (such as reserving "rice" shaped supports for circumferential seam waiving), and post-weld heat treatment (such as annealing).
Quality control and standards
Inspection method: After 100% visual inspection of the weld seam is completed, non-destructive testing is carried out (ultrasonic testing ≥50% longitudinal seam, magnetic particle/penetrant testing for weld quality). Dimensional inspection includes the flatness of the pipe opening, circumference deviation, perpendicularity (measured at multiple points), and ellipticity.
Standard system: Complies with standards such as ASTM, ISO 15614, and GB/T 10969. Medical-grade products must pass ISO 13483 certification to ensure biocompatibility and aseptic sealing.
Installation specifications: For the installation of elbow pipes in hydropower stations, the elevation and center offset (≤4mm) need to be controlled, and the dimensional stability should be verified through remeasurement after the second concrete pouring.
Application scenarios and cases
Hydropower project: The tailwater elbow pipe of Longtan Hydropower Station is welded in sections. Through CNC cutting, plate rolling forming and symmetrical welding, the deviation of the circumference of a single pipe section is ≤10mm, and the non-destructive testing pass rate of the weld seam is 100%. The elbow pipe manufacturing of the Liyuan Hydropower Station in Yunnan Province adopts sample control for arc, and 100% magnetic particle flaw detection is carried out after longitudinal seam welding to ensure smooth weld seams on the flow surface.
Petrochemical industry: The elbow pipe of the pipeline needs to withstand high pressure and corrosive media. It is made of 316L stainless steel and Teflon coating, and is compatible with IP68/IP69K protection grades.
Aerospace: The elbow pipe connecting the engine turbine blades is made of titanium alloy by laser welding, meeting the requirements of high temperature and high pressure (above 300℃) as well as lightweight.
Medical equipment: Biocompatible elbow tubes are used for surgical robot joints and have passed ISO 10993 certification to ensure they are non-toxic and harmless.
Customized solutions
Special design: Customized dimensions (such as segmented welding of super-long elbow pipes), connection methods (flanges, threads), and sealing materials (oxygen-free copper gaskets, silver-plated gaskets) according to application scenarios.
Process optimization: By optimizing the welding sequence (such as segmented symmetrical step-back welding), designing internal supports and conducting post-weld heat treatment, deformation is controlled and structural rigidity is enhanced.
Industry adaptation: For instance, the cooling system of new energy battery packs adopts thin-walled stainless steel elbow tubes, which achieve high-precision sealing through laser welding. The food processing equipment adopts 316L stainless steel elbow pipes, meeting the FDA hygiene standards.
