Stainless Steel Pipe

With more than 20 years of industrial metals supply experience, Shaanxi Shangyou Stainless Steel Co., Ltd. supplies stainless steel pipe and tube for distributors, engineering contractors, equipment manufacturers, fabricators and project procurement teams. Orders can be reviewed against the required material grade, product standard, manufacturing route, outside diameter, wall thickness, length, surface, end preparation, testing and inspection documents.

Stainless steel pipe and tube are used to transport fluids, contain pressure, transfer heat, protect instruments, form mechanical structures and create hygienic or decorative assemblies. These products may look similar, but they are not interchangeable by appearance alone. A process pipe ordered by nominal pipe size and schedule has different dimensional, testing and acceptance requirements from a heat-exchanger tube ordered by actual outside diameter and wall thickness.

The correct purchase specification should define both the material and the intended service. Grade selection addresses corrosion, strength, temperature and fabrication behavior; the product standard controls manufacturing route, dimensions, heat treatment, testing and certification. Critical orders may also need a piping or pressure design code, project specification, corrosion test, weld procedure, NDE plan or third-party inspection.

Seamless pipe is produced without a longitudinal weld seam. It is selected when the project standard, pressure design, temperature, corrosion conditions or customer specification requires a seamless manufacturing route. Seamless construction does not remove the need to verify heat treatment, dimensions, surface condition, mechanical properties, hydrostatic or nondestructive testing and material traceability.

Key page targets: ASTM A312 304L Seamless Pipe · ASTM A312 316L Seamless Pipe · ASTM A376 High-Temperature Seamless Pipe · EN 10216-5 Seamless Stainless Steel Tube · JIS G3459 Stainless Steel Pipe

Welded pipe is formed from stainless steel strip, coil or plate and joined by a continuous longitudinal weld seam running along the pipe length. It should not be illustrated as a pipe made from short sections joined by repeated circumferential welds. The weld process, heat treatment, weld-bead condition, radiography or other NDE, filler metal and acceptance requirements depend on the governing product standard and purchase specification.

Welded construction is widely used for process piping, sanitary tube, heat-exchanger tube, mechanical tubing and large-diameter EFW pipe. It can offer efficient dimensional availability, especially at larger diameters, but welded and seamless products should never be substituted without engineering and specification approval.

Key page targets: ASTM A312 Welded Pipe · ASTM A358 EFW Stainless Steel Pipe · ASTM A409 Large-Diameter Welded Pipe · ASTM A778 Welded Tubular Products · EN 10217-7 Welded Stainless Steel Tube

ASTM A790 pipe and ASTM A928 EFW pipe cover ferritic-austenitic stainless steel grades for applicable orders. Common duplex selections include 2205, while 2507 is considered for more severe chloride service. Duplex material requires control of heat treatment, phase balance, welding heat input, filler selection, interpass temperature and any specified corrosion testing.

Key page targets: ASTM A790 S32205 Duplex Pipe · ASTM A790 S32750 Super Duplex Pipe · ASTM A928 S32205 EFW Pipe · ASTM A928 S32750 EFW Pipe

Sanitary tubing is purchased by actual outside diameter, wall thickness, surface condition and cleanliness requirement. ASTM A270 is commonly specified for sanitary tube; higher-purity pharmaceutical or biotechnology projects may add ASME BPE dimensional, surface, material and documentation requirements. The RFQ should state internal surface roughness, weld-bead condition, heat treatment, end preparation, cleaning, packaging and inspection requirements.

Key page targets: ASTM A270 304L Sanitary Tube · ASTM A270 316L Hygienic Tube · Electropolished Stainless Steel Tube

Heat-transfer tubing may be seamless or welded. ASTM A213 is used for applicable seamless boiler, superheater and heat-exchanger tubes; ASTM A249 covers applicable welded boiler, superheater, heat-exchanger and condenser tubes. ASTM A268 and A789 cover ferritic/martensitic or duplex tube families for applicable service. Diameter, wall tolerance, length, heat treatment, grain structure, surface, straightness, tube-end condition and testing should match the exchanger design and tube-sheet fabrication method.

Key page targets: ASTM A213 Stainless Steel Tube · ASTM A249 TP304 Welded Tube · ASTM A249 TP316L Condenser Tube · ASTM A789 S32205 Duplex Tube

Round, square, rectangular and oval stainless steel tubes are used for frames, railings, equipment, furniture, architectural trim and mechanical parts. ASTM A554 is commonly specified for welded mechanical tubing, while ASTM A511 covers applicable seamless mechanical tubing. Mechanical and decorative tubing should not be represented as pressure pipe unless it separately meets the required pressure-product standard and design code.

Key page targets: ASTM A554 Round Tube · ASTM A554 Square Tube · Polished Stainless Steel Tube · Hairline Stainless Steel Tube

The words "pipe" and "tube" are sometimes used interchangeably in commercial searches, but the purchase order must use the terminology and dimensional system required by the governing standard.

Neither route is universally "better." Select the manufacturing process required by the product standard, design code, service conditions, diameter, wall, inspection plan and project approval list.

The following table is a quotation framework, not a universal guaranteed range. Final availability depends on grade, standard, manufacturing route, outside diameter, wall thickness, length, test level and order quantity.

1. Product standard and grade/UNS designation
2. Seamless, welded, EFW or another required manufacturing route
3. NPS/DN and schedule, or actual OD * wall thickness
4. Dimensional standard and required tolerances
5. Length type and quantity
6. End condition and fabrication details
7. Surface condition and roughness where relevant
8. Test, inspection and document requirements
9. Packing, destination and unloading restrictions

• Chlorides: 316L usually offers a higher pitting-resistance margin than 304, but neither grade is universally suitable for warm, stagnant or concentrated chloride service.
• Crevices and deposits: Gaskets, threaded joints, supports and stagnant zones can create local corrosion conditions that bulk-fluid data do not reveal.
• High temperature: Select 309S, 310S, 321, 347 or another grade only after reviewing temperature, atmosphere, thermal cycling, load and code limits.
• Sour service: NACE MR0175/ISO 15156 applicability depends on material condition, hardness, environment and product form. Do not claim compliance from the grade name alone.
• Sanitary or pharmaceutical service: Material grade is only one part of the requirement; surface roughness, weld quality, drainability, cleaning, passivation and documentation may control acceptance.
• Duplex service: Welding and heat treatment must preserve acceptable microstructure and corrosion performance. Project specifications may require additional ferrite, impact or corrosion testing.

NPS and DN are nominal size designations. They do not always equal the measured outside diameter. The purchase order should cite the applicable dimensional standard and pipe size rather than relying on a nominal number alone.

For stainless steel pipe, ASME B36.19M commonly uses the "S" schedule designations such as 5S, 10S, 40S and 80S. Other schedule designations may be ordered under the applicable dimensional and product requirements. "Schedule 40" or "Schedule 40S" is incomplete without the NPS because the actual wall thickness changes with pipe size.

Sanitary, instrumentation, heat-exchanger and mechanical tubes are normally ordered by actual outside diameter and wall thickness. State tolerances for OD, wall, ovality, straightness and length. Heat-exchanger orders may also require tight control of tube ends for rolling or welding into the tube sheet.

For preliminary logistics planning:

Theoretical mass (kg/m) = π * (OD - t) * t * density ÷ 1,000

Where OD and wall thickness t are in millimetres and density is in g/cm³. Use the density of the specified grade. The formula gives a theoretical value; commercial shipment weight should use actual measured mass and the order's permitted dimensional variation.

• Annealed and pickled
• Descaled or blasted when permitted by specification
• Bright annealed for applicable tube products
• Mill finish for further fabrication
• OD polished where appearance or cleanability requires it

• Mechanically polished ID and/or OD
• No.4 or directional satin finish
• Hairline finish for architectural tube
• Mirror-type finish for decorative applications
• Electropolishing by project specification

Finish names alone do not guarantee a particular roughness. For hygienic or appearance-critical orders, define the measured roughness parameter and limit, sampling method, polishing direction, weld-bead condition and approved comparison sample.

Solution heat treatment, annealing, quenching or another delivery condition must follow the selected grade and product standard. Duplex grades require particular control to develop the intended ferritic-austenitic structure.

When post-fabrication heat treatment is required, the purchaser should confirm furnace capacity, temperature uniformity, atmosphere, quench method, cleanliness and documentation.

• Plain ends
• Beveled ends to an agreed angle and root face
• Threaded and coupled ends when size, wall and specification permit
• Grooved ends for applicable piping systems
• Orbital-weld preparation for hygienic or high-purity tubing
• Custom machined ends to drawing

Specify end caps, cleanliness protection and whether bevels require coating-free or contamination-controlled handling.

Pipe and tube can be supplied in random, double-random or fixed lengths, or cut to the buyer's bill of materials. State length tolerance, squareness, burr removal, traceability transfer and bundle identification.

Bevel angle, root face, end squareness, internal taper and dimensional acceptance should match the welding procedure or fabrication drawing. Heavy-wall and corrosion-resistant grades may need specific machining controls.

When bending is required, provide the centerline radius, straight-leg lengths, angle, orientation, ovality limit, wall-thinning limit and post-bend inspection. Weld-seam orientation should be controlled for welded tube where it affects the qualified process.

Define whether the requirement is visual polishing, measured roughness, chemical cleaning, pickling or passivation. These processes have different purposes and should not be treated as interchangeable. The procedure, acceptance criteria and post-process packaging should be agreed before production.

Drilling, slotting, flaring, expanding, threading, grooving or welded spool fabrication may be discussed against drawings and applicable procedures. Pressure-retaining fabrication requires qualified procedures, personnel, inspection and documentation appropriate to the project code.

A stainless steel pipe order should be verified against the complete purchase specification, not only by surface appearance or a handheld magnet.

1. Specification review: grade, standard edition, manufacturing route, size, wall, length, ends and supplementary requirements
2. Material traceability: heat/lot numbers, markings and correspondence with the material certificate
3. Chemical and mechanical review: heat analysis, tensile properties, hardness and other standard-required results
4. Dimensional checks: OD, wall, length, ovality, straightness, end preparation and shape dimensions
5. Surface and weld review: visual condition, longitudinal weld seam, weld bead, polish and internal cleanliness where applicable
6. Pressure or NDE verification: hydrostatic, eddy-current, ultrasonic, radiographic or another method as required by the product standard and order
7. Special tests: flattening, flaring, bend, intergranular corrosion, ferrite, impact or corrosion testing when specified
8. Final document and packing check: markings, MTC, test reports, end protection, bundle list and shipping marks

• EN 10204 Type 3.1 material test certificate
• Dimensional and visual inspection report when required
• Positive material identification by agreement
• Hydrostatic or nondestructive electric testing as required by standard/order
• Radiographic examination for applicable EFW classes or project requirements
• Eddy-current or ultrasonic examination for applicable tube products
• Surface-roughness report for sanitary tube when specified
• Third-party inspection or witnessing by agreement
• Packing photographs and mark verification when requested

Optional tests must appear in the RFQ and purchase order so that sampling, acceptance criteria, hold points, cost and schedule can be agreed before manufacture or dispatch.

ASTM A312 or ASTM A790 pipe may be considered for process lines, utilities and corrosion-resistant systems. The final specification must align with the piping design code, fluid composition, pressure, temperature, corrosion allowance, welding procedure, NDE and sour-service requirements where applicable.

304L, 316L, 904L, 2205 and 2507 may be used in different chemical environments. Material selection should account for all constituents, concentration, temperature, aeration, flow, cleaning chemicals, shutdown conditions, crevices and contamination.

ASTM A270 tubing and project-specific hygienic requirements are used for product-contact and clean-utility systems. Buyers should define surface roughness, weld condition, drainability, cleaning, passivation, packaging and documentation rather than purchasing by grade alone.

ASTM A213, A249, A268 or A789 tubes may be selected according to construction route, alloy family and service. Tube-to-tube-sheet joining, thermal expansion, erosion, fouling, chloride level and inspection access affect the specification.

Stainless and duplex pipes are used in selected filtration, brackish-water, desalination and water-distribution systems. Chloride concentration, temperature, disinfection chemistry, flow, stagnation and crevice design must be evaluated.

ASTM A554 and related mechanical tubes are fabricated into handrails, frames, equipment, vehicle parts and decorative structures. Shape, finish, weld condition, bendability and dimensional tolerances generally matter more than pressure-pipe tests.

ASTM A269 and other application-specific tube standards are used for small-bore fluid and instrumentation lines. Tube OD, wall, hardness, surface, cleanliness, fitting compatibility, pressure design and testing should be reviewed as one system.

Packing should protect pipe ends, machined bevels, polished surfaces and traceability markings while remaining compatible with the buyer's lifting and unloading method.

• Plastic or metal end caps for cleanliness and impact protection
• Bundles with separators and reinforced straps
• Protective wrapping for polished or sanitary tube
• Wooden boxes or crates for small-diameter, thin-wall or precision tubing
• Steel skids or frames for large-diameter or heavy-wall pipe
• Waterproof protection and desiccant when the route and product require it
• Piece, bundle, heat and package identification linked to the packing list
• Shipping marks, lifting points and center-of-gravity information where required

Marking content should follow the product standard and purchase order. Tell us the destination, transport mode, package-weight limit, unloading equipment and any port or site restrictions before packing is finalized.

• Broad pipe and tube coverage: seamless, welded, EFW, sanitary, heat-exchanger, duplex and mechanical products
• Standard-based review: grade, product standard, manufacturing route, dimensions, ends, tests and documents assessed together
• Custom processing: cutting, beveling, threading, polishing and drawing-based processing options
• Inspection support: MTC 3.1, traceability, dimensional inspection, PMI and optional third-party inspection
• Export packing: bundles, boxes, skids or frames selected for geometry, surface and handling method
• Practical material guidance: corrosion exposure, pressure design, fabrication and acceptance requirements clarified before quotation

We do not recommend replacing seamless with welded pipe, changing a material grade or accepting a nominal "equivalent" standard solely to reduce price. Critical substitutions require documented technical approval.

Send the grade, standard, manufacturing route, NPS or OD, schedule or wall thickness, length, ends, surface, quantity, tests, documents and destination. Attach the project specification or drawing when pressure, corrosion, hygiene, tolerance or fabrication is critical.

1. What is the difference between stainless steel pipe and stainless steel tube?

   Pipe is commonly ordered by NPS/DN and schedule for fluid or pressure service. Tube is usually ordered by actual OD * wall thickness for heat transfer, instrumentation, sanitary, mechanical or precision use. The governing product standard determines the exact dimensions, tolerances and tests.

2. Is seamless stainless steel pipe always better than welded pipe?

   No. Each manufacturing route serves different standards, sizes and project requirements. Seamless pipe has no longitudinal weld seam; welded pipe can offer efficient availability and large-diameter capability. Select the route required by the design code, product standard and approved material specification.

3. What does a correct welded stainless steel pipe seam look like?

   A straight-seam welded pipe has one continuous longitudinal weld line running along the pipe length. Circumferential welds normally join separate pipe sections during fabrication and should not be confused with the mill seam of a straight-seam welded pipe.

4. What is the difference between ASTM A312 and ASTM A358?

   ASTM A312 covers seamless, welded and heavily cold-worked austenitic stainless steel pipe. ASTM A358 covers electric-fusion-welded austenitic chromium-nickel stainless steel pipe and includes class-related manufacturing, heat-treatment and examination requirements. The project specification determines which standard and class are acceptable.

5. What is the difference between 304L and 316L stainless steel pipe?

   316L contains molybdenum and generally provides better resistance than 304L to pitting in many chloride-containing environments. It is not corrosion-proof. Fluid chemistry, chloride level, temperature, crevices, cleaning and shutdown conditions should guide selection.

6. When should I consider 2205 duplex pipe instead of 316L?

   2205 offers higher strength and improved resistance to chloride stress-corrosion cracking in many environments. It also requires different forming, welding and heat-treatment controls. Compare corrosion conditions, design code, wall calculation, fabrication qualification and lifecycle cost before changing grades.

7. What is the difference between Schedule 40 and Schedule 40S?

   The "S" suffix is used in the stainless-pipe schedule series of ASME B36.19M. Wall thickness must be checked for the exact NPS and dimensional standard; the schedule designation alone does not define pressure rating or wall thickness for every size.

8. Can you supply custom OD and wall thickness?

   Custom or non-schedule dimensions may be available depending on the grade, product standard, seamless or welded route, tooling and order quantity. Send the exact OD, wall, tolerance, length and application for a feasibility review.

9. Which ends are available?

   Plain, beveled, threaded/coupled, grooved and drawing-specific machined ends may be discussed. Availability depends on size, wall, standard and service. Bevel geometry and end tolerance should match the purchaser's welding or joining procedure.

10. Can the inside and outside surfaces be polished?

    Yes, for applicable tubing. State whether the requirement applies to ID, OD or both, and define the finish, roughness limit, weld-bead condition, polishing direction, cleaning and protective packaging. A finish name without measurable acceptance criteria may be insufficient for hygienic service.

11. Can you provide an EN 10204 3.1 material certificate?

    An EN 10204 Type 3.1 material test certificate can be supplied for applicable orders. Additional PMI, NDE, corrosion tests, roughness records or third-party witnessing should be specified before ordering.

12. What tests are used for stainless steel pipe and tube?

    Requirements vary by standard and may include chemistry, tensile, hardness, flattening, flaring, hydrostatic testing, eddy current, ultrasonic testing, radiography, intergranular corrosion or duplex corrosion/ferrite testing. The order must state any tests beyond the governing standard.

13. Is magnetic testing a reliable way to identify stainless steel grade?

    No. Ferritic and martensitic grades are magnetic, while cold working or welding can increase the magnetic response of austenitic grades. Grade verification should use traceable documents and, when required, suitable analytical testing such as PMI.

14. What affects the price of stainless steel pipe?

    Price depends on grade and alloy surcharge, seamless or welded route, OD, wall, schedule, length, quantity, heat treatment, surface, ends, testing, inspection, packing, freight and Incoterm. A complete specification produces a more dependable quotation than a request based only on grade and nominal diameter.

15. What information do you need for a quotation?

    Provide the product standard, grade, manufacturing route, NPS/DN or OD, schedule or wall, length, ends, surface, quantity, tests, inspection documents, packing, destination and required delivery window. Add the fluid, pressure, temperature or drawing when technical review is needed.

16. Can ASTM, EN and JIS grades be treated as direct equivalents?

    Not automatically. Compare chemistry, mechanical properties, heat treatment, dimensions, tolerances, manufacturing route, tests and design-code acceptance. Any substitution should be documented and approved by the responsible purchaser or engineer.

Shaanxi Shangyou Stainless Steel Co., Ltd.