Stainless steel pipes fall into two main categories: Seamless Pipe and Welded Pipe (ERW). They are manufactured in accordance with Chinese national standards GB/T, American standards ASTM A312/A269, ASME B36.19M. EN and JIS standards are commonly used for foreign trade. The universal format for specifying dimensions is Outside Diameter (OD) × Wall Thickness (WT) in mm. In piping engineering, nominal diameter DN and SCH wall thickness schedules are also adopted. The price is primarily determined by material grade, wall thickness, manufacturing process, surface finish, tolerance, order quantity, and the futures price of nickel/molybdenum raw materials. It is a bulk commodity with daily price fluctuations.

1. Material Grades (Mainstream in Industry)

1. 201 (1Cr17Mn6Ni5N)：200 series, manganese replaces nickel. Poor corrosion resistance. Used for indoor decoration and guardrails. Lowest price, prone to rust in humid environments.
2. 304 / 304L (06Cr19Ni10 / 022Cr19Ni10)：Standard 304; 304L is low-carbon grade with resistance to intergranular corrosion, preferred for welded applications. Widely used in general industry, water supply & drainage, food equipment, highest market consumption.
3. 316 / 316L (06Cr17Ni12Mo2 / 022Cr17Ni12Mo2)：Molybdenum (Mo) added for chloride corrosion resistance (seawater, chemical industry, coastal areas). 316L low-carbon grade is the first choice for chemical pipelines. Price is noticeably higher than 304.
4. Special Grades: 321 (titanium-stabilized for high temperature), 310S (high temperature resistance up to 1100℃, furnace tube), 904L (super austenitic for heavy corrosion), duplex steel 2205/2507 (high strength + pitting resistance) with substantial price premium.

400 series ferritic/martensitic grades (430, 410) are magnetic, mostly for mechanical structures, rarely for fluid transportation.

2. Specification System

2.1 Classified by Manufacturing Process

• Seamless Stainless Steel Pipe: Produced by piercing billet + hot rolling / cold rolling / cold drawing. No weld seam, high pressure bearing capacity, suitable for high pressure, high temperature and corrosive media. OD range: φ6～φ630mm; Wall thickness 0.5～50mm. Seamless pipe is preferred for heavy wall and small bore precision tubes. Disadvantages: high cost, limited fixed length options.
• ERW Straight Welded Pipe: Stainless steel coil formed and high-frequency welded, weld seam solution treated. Advantages for large OD & thin wall, used for low-pressure fluid piping and decoration. OD φ9.5~φ1200mm. For the same OD & WT, welded pipe is 20%~40% cheaper than seamless pipe. Polished welded pipe is widely adopted for sanitary food pipelines.
• Spiral Welded Pipe: Extra large diameter, for municipal engineering and large-flow low-pressure fluid. Low market share for industrial stainless steel spiral pipe.

2.2 Dimension Expression Rules

1. Round pipe: OD × WT, e.g. Φ108×4 → Outside Diameter 108mm, Wall Thickness 4mm;
2. SCH schedule (wall thickness for pressure piping in American standard): SCH10/SCH40/SCH80. Larger SCH number means thicker wall under same OD;
3. Square / Rectangular pipe: Side length × wall thickness, mostly for structural decoration, seldom for fluid transmission;
4. Length: Standard fixed length 6 meters, custom cutting available (cutting fee charged separately, surcharge for small batches).

2.3 Tolerance Grade (Key for Foreign Trade & Inspection)

• Normal grade: OD ±0.5~±1%, WT ±10%;
• Precision grade (instrument & heat exchanger tube ASTM A269): OD ±0.1mm, strict negative wall tolerance. Precision tolerance brings obvious price premium.

2.4 Surface Finish

• Pickled white finish (industrial pipe, standard stock);
• 2B, brushed, mirror polishing (Sanitary pipe: internal & external BA / EP electropolishing for food & pharmaceutical industry, high premium).

3. Pricing Logic & Spot Reference 2026 (Wuxi market, VAT included, bulk price per ton, for industry reference only, not formal quotation)

Core principle: 304 price links to nickel price; 316L links to nickel + molybdenum price. The thinner the wall, the higher unit price per ton (due to high production loss). Slicing, polishing, NDT inspection and mill certificates all incur extra charges.

Spot price range for mainstream grades (conventional industrial pipe, reference size Φ108×4)

1. 201 welded pipe: CNY 10,000 ~ 12,000 / MT
2. 304 straight welded pipe: CNY 14,500 ~ 16,000 / MT
3. 304 seamless pipe: CNY 16,300 ~ 18,500 / MT
4. 316L seamless pipe: CNY 31,000 ~ 32,500 / MT
5. 310S, 904L, 2205 duplex steel: Starting from CNY 40,000 / MT, fluctuating greatly with raw materials.

Extra Charges Frequently Seen in Foreign Trade Inquiries

1. Negative wall tolerance: Traders normally deliver with minus tolerance. If full actual wall thickness required: +CNY 800~1,500 / MT;
2. NDT Non-Destructive Testing: Eddy current test, hydrostatic test, mandatory for chemical pressure vessel orders;
3. Export Documentation: MTC material test certificate, EN10204 3.1 / 3.2 certification. Extra cost for 3.2 third-party certificate;
4. Surface polishing: Internal & external polished sanitary 304 welded pipe: +CNY 3,000~8,000 / MT; EP electropolishing has higher premium;
5. MOQ: Bulk tonnage price for full container. Cut-to-length & small orders of dozens of kg: 20%~50% unit price increase;
6. Yield loss: Thin-wall small bore pipe & large OD heavy wall pipe have high production scrap rate, unit price much higher than standard sizes.

4. Selection & Procurement Recommendations

1. Low-pressure fluid, water supply & drainage: 304 welded pipe, best cost performance;
2. Chemical high pressure, high temperature, chloride environment: 316L seamless pipe;
3. Food & pharmaceutical: Sanitary grade internal & external polished welded pipe, requiring weld solution treatment and no black spots;
4. Inquiry checklist: Must specify material grade, standard, OD × actual WT, seamless / welded, surface finish, NDT requirement, certificate, fixed length, delivery location, order weight. You cannot get accurate quotation by simply asking "price of 304 stainless steel pipe per ton".
5. Risk reminder: Plenty of 201 disguised as 304, excessive wall minus tolerance, welded pipe without weld solution treatment in market. Spectral re-inspection is required for import & export projects.

5. Theoretical Weight Formula for Round Stainless Pipe

Density: 7.93 g/cm³ for 304/316L Weight per meter (kg/m) = (OD mm − WT mm) × WT mm × 0.02491

Example: Φ108×4 (108−4)40.02491 = 104 ×4 ×0.02491 = 10.36 kg/m