Cold Drawn Rolled Welded Tubes - High Precision

Regarding the production of stainless-steel tubes using the method of cold drawing for welded pipes, their performance and the data from test measurements show that they can fully replace seamless Stainless Steel Tubes.

1. The roundness tolerances the inner and outer diameters of the tubes are higher in precision. This prevents defects seen in Seamless Tubes, where one side is thicker while the other is thinner.
2. The hardness of the tubes can be chosen based on their production process, allowing for flexible adjustments to meet material usage or assembly requirements.
3. Cold-drawn tubes can withstand internal pressure (tested with hydraulic bursting) sufficient to reach or exceed the internal pressure capacity of seamless tubes.
4. It completely eliminates defects in seamless stainless steel tubes, such as air pockets, laminations, peeling, and slag inclusions that may appear in the Raw Materials.
5. The steel strips are sourced from large companies, ensuring the material fully conforms to national/international standards and maintains stability and consistency.

Measurement Data for Cold Drawn and Precision Rolled Tubes

1. Outer diameter tolerance (below 12.0mm): +/- 0.015mm.
2. Inner diameter tolerance (below 11.0mm): +/- 0.02mm.
3. Roundness within a range of 0.02mm.
4. Radial runout within a range of 0.02mm.
5. Straightness tolerance within 1/1000mm.
6. Hardness - can be controlled based on technical requirements, with HV hardness values within a range of +/- 20.
7. Tube withstands internal pressure testing (hydraulic bursting test) exceeding 50Mpa.
8. Weld seam thickness after cold drawing is consistent with tube wall thickness.
9. Weld seam thickness after cold drawing is consistent with point corrosion testing and salt spray testing of the tube material.
10. The tube's Mechanical properties after cold drawing complies with various international material standards.

Drawing and Precision Rolling Stainless Steel Pipe Production Process

1. Use laser to weld the steel strips into pipes. The requirement for the internal weld seam of the welded pipe is to have a height more significant than the thickness of the original steel strip by a range of 0.05+/-0.01mm. Increasing the weld seam thickness enhances its mechanical strength.
2. The melting point temperature of stainless steel (SUS304) is 1650 degrees, while the maximum temperature used in laser welding is 8500 degrees (based on international laser welding standards). Thus, using laser welding as the processing method, the temperature is sufficient to transform the ends of the steel strip from solid to liquid and then back to stable after cooling.
3. The key to precision pipe production lies in treating the weld seam. After multiple cycles of extrusion and solution annealing of the weld seam, the performance in the weld seam region can be made consistent with that of the steel strip. During the welding process, the height and saturation of the weld seam are controlled to achieve high weld strength. The weld seam height is within the range of 0.05+/-0.01mm, and the internal weld seam width is ensured to be on the same uniform line. The internal leveling treatment of the weld seam is performed without oxidation of the inner and outer weld seams. The weld seam height is reduced by 0.02 to 0.03mm compared to the thickness of the steel strip through internal leveling and extrusion. Note: In actual welding of pipes, for four series ferritic welded pipes/3 series austenitic thick pipes (with a thickness greater than 0.8mm)/8 series high-nickel alloy pipes, laser welding yields better weld strength performance compared to argon arc welded pipes.
4. The cold drawing method for pipes involves a cold extrusion process that simultaneously reduces the outer and inner diameters of the pipes. The outer die is used to decrease the outer diameter, transitioning from larger to smaller sizes. The mandrel inside the pipe is used to thin the thickness of the pipe, simultaneously reducing the thickness of the weld seam to match that of the pipe, transitioning from thick to thin. The pipe's outer diameter, thickness, and mechanical properties are consistent through repeated cycles of cold drawing processing, annealing treatment, cold drawing, and annealing treatment (note: laser-welded pipes can reduce the number of cold drawing processing steps).
5. The hardness of the pipes can be adjusted through the production process of cold drawing and annealing treatment.