​

Stainless Hollow Section is a kind of high-performance structural material widely used in construction, machinery, chemical and other fields, mainly made of stainless steel, with a hollow cross-section.

Stainless steel hollow profiles can be divided into the following categories according to the section shape:
• Square Tube: square section, often used in architectural frames, decorative structures, etc.
• Round Tube: circular section, suitable for fluid transport, mechanical shaft parts, etc.
• Rectangular Tube: rectangular section, mostly used for load-bearing structures and industrial equipment.
• Seamless Tube: continuous hollow profiles without welds, suitable for high pressure or high precision scenarios (such as heat exchanger pipes).
• Custom Tube: non-standard cross sections customized according to demand, such as ellipses, hexagons, etc.

The manufacturing process of stainless steel hollow profiles is mainly divided into two categories:
• Welding molding: Through the cold-rolled or hot-rolled stainless steel plate after crimping welding into a tube, low cost, suitable for common use.
• Seamless forming: Using hot piercing or cold drawing technology to avoid weld defects, suitable for high pressure or corrosion resistant environments (such as chemical pipelines).
• Surface treatment: including polishing, sandblasting, acid etching, etc., to meet the aesthetic or functional needs of different scenes.

The core advantage of stainless steel hollow profiles lies in their material characteristics:
• Corrosion resistance: Austenitic stainless steel (such as 304, 316L) performs well in wet, acid and alkali environments and is suitable for Marine engineering and chemical plants.
• High strength and lightweight: Hollow structures have higher bending and torsional properties than solid materials under the same weight, suitable for long-span buildings and Bridges.
• Hygiene: The surface is smooth and non-porous, which meets the cleanliness standards of the food and pharmaceutical industry (such as thin-walled drinking water pipes).
• High temperature resistance: Partially duplex stainless steel is stable at high temperatures for boilers and heat exchangers.

Stainless steel hollow profiles are widely used in the following fields because of their comprehensive properties:
• Buildings and Bridges: such as unit curtain wall support structures, ultra-thin bridge cantilevers (case: stainless steel trusses used in Tintagel Castle Bridge, UK).
• Mechanical manufacturing: As a hydraulic system pipeline, robot skeleton, etc., need to withstand high loads and dynamic stresses.
• Energy and chemicals: heat exchange tubes, reaction vessel linings, etc., depend on corrosion resistance and high temperature resistance.
• Medical and food: Sanitary stainless steel tubes are used to transport sterile fluids or food ingredients.
• Environmental engineering: large-diameter sewage pipes and seawater desalination systems, resistant to corrosive media.

1. ASTM A511/A511M-21a
• Scope of application: seamless stainless steel mechanical pipe and hollow bar, suitable for high temperature, corrosion resistance scenarios (such as chemical equipment, mechanical parts).
• Core requirements:
• The grade of the material must meet the chemical composition requirements in Table 1-3 (such as 304, 316L, etc.);
• Outer diameter ≤325mm, shape including round, square, rectangular and special custom profile;
• Optional supplementary requirements (such as non-destructive testing, flaring tests, etc.) shall be specified in the contract.

2. BS/EN series standards
• BS 4-2:1969: Structural performance requirements for hot rolled hollow profiles;
• BS 6633:1983: Technical specification for welded cold formed hollow steel structures;
• EN 10219: European standard for cold formed welded hollow profiles, covering dimensional tolerances and mechanical properties.

3. AS 1163 (Australian Standard)
• Suitable for structural steel hollow profiles, requiring material strength, ductility and welding process to meet building load-bearing requirements.

1. Material performance test
• Chemical composition analysis: verify the content of Cr, Ni, Mo and other elements (such as SUS304 to meet Cr 17-19%, Ni 8-11%);
• Mechanical properties test: including tensile strength, yield strength, elongation (such as elongation ≥40% as required by ASTM);
• Hardness test: Vickers hardness (HV≥200) or Rockwell hardness (HRB≥90).

2. Size and surface inspection
• Section size deviation: according to the tolerance table (such as length ±1.0mm, wall thickness ±0.1mm);
• Surface quality: visual inspection of cracks, bubbles, scratches, polishing surface roughness ≤Ra 0.8μm;
• Weld inspection: X-ray or ultrasonic inspection to ensure no open welding, dislocation defects.

3. Functional testing
• Corrosion resistance: salt spray test ≥500 hours (as required by JG/T 115-2018);
• High temperature resistance: high temperature stability test (suitable for duplex stainless steel);
Residual stress analysis: Evaluation of machining stress by X-ray diffraction.

4. Additional tests in special scenarios
• Hygienic testing: FDA or ISO 2037 standards (surface cleanliness, no porosity) for food/medical applications;
• Fire resistance: Fire resistance test of fire resistant coating (such as BS 476 standard).

​