"Welded stainless" covers four different products on a purchase order, and the difference between them is not the seam but what happened after it: whether the pipe was solution annealed, how much of the weld was radiographed, and whether the product is rated for pressure at all. Those answers change both price and design wall thickness. Our stainless steel welded pipes and tubes cover ASTM A312 and A358 pipe, A249 and A269 tube, and A778 unannealed pipe for non-pressure service. Welded construction is what makes large-diameter stainless affordable at plants across Oman. Seamless options sit on the stainless steel pipes and tubes hub.
Four Standards, Four Products
Standard | Product | Heat treatment | Typical use |
|---|---|---|---|
ASTM A312 welded | Austenitic pipe in standard sizes | Solution annealed after welding | Pressure piping alongside seamless A312 |
ASTM A358 | EFW pipe supplied in classes, mainly larger diameters | Class-dependent, with defined radiography | Large-diameter pressure piping at high temperature or corrosive service |
ASTM A249 | Welded boiler, superheater and exchanger tube | Heat treated after welding | Tube bundles and heat transfer service |
ASTM A778 | Unannealed welded pipe | None after welding | Non-pressure corrosion service, tanks, vents, drains |
A778 deserves particular attention on a receiving dock: it looks like A312 welded pipe, costs less and is not for pressure service. Keeping the two apart in stores and on the certificate check avoids an expensive mistake.
Sour and Chloride Service
Under NACE MR0175 / ISO 15156-3, austenitic grades are acceptable in sour service only within defined limits of H2S, chloride, temperature and pH. In hot chloride service, chloride stress corrosion cracking limits austenitic grades regardless of whether the pipe is welded or seamless, and duplex or ferritic grades may suit better. State your service conditions in the RFQ; requirements are confirmed at quotation.
Price Factors for Welded Stainless
- Grade and alloy surcharges
- Standard and class, particularly A358
- Diameter, wall and length
- Finish, including polishing
- Radiography, corrosion testing and PMI
- Quantity and stock availability versus a mill order
- Certification (EN 10204 3.1 or 3.2) and third-party inspection
- Incoterm and destination port
Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.
What to send for a quotation:
grade, standard and class, NPS or OD, schedule or wall, length, quantity, finish, testing, certification, inspection, destination port and required date.
Certificates and Inspection
Welded stainless pipe and tube are supplied with EN 10204 3.1 certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. Check that the certificate names the correct standard and class, records solution annealing and shows the radiographic and pressure test results. See the MTC and EN 10204 certification guide.
Storage and Handling
Lead time is confirmed at quotation. Material ships capped and, where the finish requires, wrapped. Keep welded stainless off carbon steel racks and away from carbon steel grinding dust, and store A778 pipe separately from pressure-rated A312 and A358 pipe so the two cannot be confused during fabrication.
Fittings and Related Products
- Stainless steel fittings and flanges hub
- Stainless steel seamless pipes and tubes
- Stainless steel instrumentation tubing
Welded stainless is used across desalination and water treatment, refinery and petrochemical and fertilizer plants.
Welded Stainless Pipe FAQ
Is welded stainless pipe suitable for pressure service?
Yes, when supplied to A312 or A358 and designed with the correct weld joint efficiency. A778 pipe is unannealed and is not for pressure service.
What is the difference between A312 welded and A358 pipe?
A312 covers standard welded pipe sizes; A358 covers EFW pipe in classes, mainly in larger diameters, with defined radiography and heat treatment.
Why does the A358 class matter?
It sets the joint efficiency used in pressure design, which changes the required wall thickness.
Does the mill seam corrode faster than the pipe body?
In solution annealed pipe, not materially. Site welds and heat tint are the greater risk.
Which grades are available welded?
All the common austenitic grades, including 304L, 316L, 321, 347, 310S and the high-alloy grades.
What should I send for a quotation?
Send the grade, standard and class, size, schedule or wall, length, quantity, finish, testing, certification, inspection and destination port.
Request a Quote for Welded Stainless Pipes and Tubes
Send the grade, standard, class where applicable, size and quantity. Every enquiry is checked against the governing standard before the offer is prepared, so unannealed pipe is never offered against a pressure requirement.