Technical Requirements for Production of H-Finned Tubes (Square Finned Tubes)
1 Welding strength and stability
1.1 Tensile force test: greater than 200MPa or partial tearing of steel pipe
1.2 Weld Width: Greater than fin thickness or welding rate >99%
1.3 Stability of welding strength: The first sample of each class is to meet the requirements of 2.1 or 2.2 for welding samples.
1.4 Weld seam bending resistance test: The fins bend left and right by 20 degrees and bend left and right twice. There is no crack in the welds.
1.5 Hammer test: Strike the upper part of the fins parallel to the steel pipe until the fins fall off the fins themselves must not break
1.6 Annealing must be enabled if the test fails
2 heat affected zone
Measuring with Microscope and Micro Hardness Tester
Depth of heat affected zone of steel pipe is less than 0.5mm
3 Product Size Accuracy
3.1 Full length of the fin segment -1mm ~ +1mm Segmental movement accuracy -0.5mm ~ +0.5mm
3.2 Pitch -0.2mm ~ +0.2mm
3.3 Verticality of fins and steel pipes -1 degree~ +1 degree
3.4 Except the height difference caused by the thickness tolerance of the fins of the same group of the welding fins -0.2mm ~ +0.2mm
3.5 Difference in height of butt welding fins of the same group -0.2mm ~ +0.2mm except height difference caused by dimensional tolerance of fins themselves
3.6 Double tube center distance tolerance -0.5mm ~ +0.5mm
3.7 In the same steel tube material, the same sheet distance and the number of sheets, the length change after welding of different finned tubes is consistent
4 welding speed
Base pipe outer diameter 25~51 Fin thickness 2mm Each pair welding time is less than 3 seconds (not including loading and unloading time and annealing time)
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