Square 304 Stainless Steel Welded Pipe Laser Cutting Processing
304 stainless steel welded pipe is manufactured by roll-forming stainless steel coil or plate into a tubular shape followed by longitudinal welding. As an austenitic stainless steel grade, it offers excellent corrosion resistance, high dimensional accuracy, and a bright surface finish. The production process is efficient, cost-effective, and available in a wide range of sizes and specifications. Products are available as longitudinally welded pipe or spiral welded pipe.
304 stainless steel is the most widely used stainless and heat-resistant steel. It provides better corrosion resistance than 200-series stainless steel and performs well at high temperatures, withstanding up to 1000–1200°C. In recent years, with the rapid development of continuous rolling of high-quality stainless steel strip and advances in welding and inspection technology, weld quality has continuously improved. As a result, 304 stainless steel welded pipe has replaced seamless pipe in many applications — particularly heat exchanger tubes, decorative tubes, and low-to-medium pressure fluid pipes.
Key Features at a Glance:
- High corrosion resistance – 18–20% chromium content forms a dense chromium oxide passive film, resisting various acids and alkalis
- Good workability – High ductility, easy to form by hot or cold working, custom lengths available
- Bright surface – Smooth inner and outer surface finish, attractive appearance
- Cost-effective – Higher production efficiency, lower cost than seamless pipe, excellent value
- Hygienic & safe – Non-toxic, odorless, smooth surface inhibits bacterial growth
Product Details
Applicable Standards
304 stainless steel welded pipe is manufactured and supplied according to the following standards:
| Standard | Scope |
|---|---|
| ASTM A312 | Austenitic stainless steel welded pipe for pressure, high-temperature, and corrosive service |
| ASTM A358 | Electric-fusion-welded pipe for high-temperature service |
| ASTM A778 | Welded pipe for general corrosive service |
| GB/T 12771 | Welded stainless steel pipe for fluid handling (Chinese standard) |
| GB/T 12770 | Welded stainless steel pipe for mechanical structures (Chinese standard) |
| JIS G3459 | Stainless steel pipe (Japanese standard) |
Manufacturing Process
Raw Material – Stainless steel coil or plate conforming to ASTM A240, grade 304/304L austenitic stainless steel
Forming & Welding – The steel strip is continuously roll-formed into a tubular shape, and the longitudinal seam is welded using automated methods. Common welding processes include TIG (GTAW), plasma arc welding (PAW), high-frequency welding (HFW), and laser welding. Welding is performed under protective atmosphere to prevent oxidation of the weld metal.
Post-Weld Treatment – Solution annealing (1050–1150°C) to relieve internal stresses, homogenize the metallurgical structure, and achieve mechanical properties close to seamless pipe. Inner and outer weld beads are removed to create a smooth inner surface and reduce flow resistance. Surface finishing options include pickling and polishing (#4, #6, #8 mirror finish) as required.
Inspection & Testing – Chemical composition analysis, mechanical property testing, hydrostatic testing or non-destructive testing (eddy current / ultrasonic), dimensional inspection.
Product Classification
| Classification | Description |
|---|---|
| By application | Fluid handling pipe, mechanical structural pipe, decorative pipe, heat exchanger tube |
| By shape | Round pipe, square pipe, rectangular pipe |
| By surface finish | Mill finish, brushed finish, polished (6K/8K mirror), shot-blasted |
Specification Table
General Specifications
| Parameter | Details |
|---|---|
| Product Name | 304 Stainless Steel Welded Pipe / 304L Stainless Steel Welded Pipe |
| Applicable Standards | ASTM A312, GB/T 12771, JIS G3459 |
| Material Grade | 304, 304L (UNS S30400 / S30403) |
| Manufacturing Type | Welded pipe (longitudinally welded) |
| OD Range | 12.0mm – 3000mm (custom available) |
| Wall Thickness Range | 0.5mm – 30.0mm (custom available) |
| Length | 6m fixed length, or cut to size (5.8M, 6M, 11.8M, 12M, etc.) |
| Surface Finish | Mill finish, pickled, annealed, brushed, polished (6K/8K mirror) |
| End Finish | Plain ends, beveled ends, threaded, grooved |
Common Dimensions Table (Round Pipe)
Common dimensions for 304 stainless steel welded pipe are as follows:
| Nominal Bore DN | OD (mm) | Wall Thickness (mm) Range | Common WT (mm) |
|---|---|---|---|
| DN15 | 21.3 | 0.8-2.5 | 1.5, 2.0 |
| DN20 | 26.7 | 0.8-2.5 | 1.5, 2.0 |
| DN25 | 33.4 | 1.0-3.0 | 1.5, 2.0, 2.5 |
| DN32 | 42.2 | 1.0-3.0 | 1.5, 2.0, 2.5 |
| DN40 | 48.3 | 1.0-3.5 | 1.5, 2.0, 2.5 |
| DN50 | 60.3 | 1.2-4.0 | 1.5, 2.0, 2.5, 3.0 |
| DN65 | 76.1 | 1.5-4.0 | 2.0, 2.5, 3.0 |
| DN80 | 88.9 | 1.5-5.0 | 2.0, 2.5, 3.0, 4.0 |
| DN100 | 101.6 | 1.5-5.0 | 2.0, 2.5, 3.0, 4.0 |
| DN125 | 133.0 | 2.0-6.0 | 2.5, 3.0, 4.0, 5.0 |
| DN150 | 159.0 | 2.0-6.0 | 2.5, 3.0, 4.0, 5.0 |
| DN200 | 219.0 | 2.5-8.0 | 3.0, 4.0, 5.0, 6.0 |
| DN250 | 273.0 | 3.0-10.0 | 4.0, 5.0, 6.0, 8.0 |
| DN300 | 325.0 | 3.0-12.0 | 4.0, 5.0, 6.0, 8.0, 10.0 |
Note: The above are common dimensions. Custom sizes are available upon request. Maximum OD up to 3000mm, maximum wall thickness up to 30mm.
Square / Rectangular Tube Dimensions
| Dimension (mm) | Wall Thickness (mm) | Grade |
|---|---|---|
| 10×10 – 20×20 | 0.5-1.0 | 304 |
| 25×25 – 40×40 | 0.8-1.5 | 304 |
| 50×50 – 80×80 | 1.0-2.5 | 304 |
| 100×100 – 150×150 | 1.5-4.0 | 304 |
Square and rectangular tubes are manufactured to ASTM A554.
Applications
304 stainless steel welded pipe is widely used across the following industries due to its excellent combination of properties and cost-effectiveness:
| Industry | Typical Applications |
|---|---|
| Fluid Handling Systems | Petrochemical piping, water treatment equipment, HVAC, low-to-medium pressure fluid transfer |
| Food & Beverage | Food processing pipelines, juice/milk/beer transfer lines, CIP lines |
| Pharmaceutical & Biotech | Purified water systems, clean piping, medical device components |
| Machinery Manufacturing | Hydraulic system piping, boiler heat exchangers, mechanical structural parts |
| Construction & Decoration | Water supply systems, handrails and guardrails, curtain walls, hotel/hospitality decoration |
| Environmental Engineering | Flue gas desulfurization (FGD), wastewater treatment equipment, desalination systems |
| Marine & Offshore | Marine piping, dock construction, ship repair |
| Automotive Industry | Automotive exhaust systems, structural components |
Selection Guide
304 vs 304L – How to Choose?
| Comparison | 304 | 304L |
|---|---|---|
| Carbon content | ≤0.08% | ≤0.03% (lower) |
| Intergranular corrosion resistance | Moderate | Excellent (more stable after welding) |
| Strength | Slightly higher | Slightly lower |
| Recommended applications | General corrosive environments, minimal or no welding | Piping systems requiring welding, chloride-containing environments |
Recommendation: If your piping system requires significant welding or will be exposed to conditions that risk intergranular corrosion, 304L is the preferred choice.
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