Seamless Stainless Steel Pipe & Tube
We supply seamless stainless steel pipe and seamless stainless steel tubing from 6 to 660 mm OD, with walls of 1–12 mm. Pipe is made to ASTM A312; tube to A213 and A269. Grades are 304, 316L, 321, 347, 310S, 2205 and 2507.
Lengths 4–12 m: 6 m standard, also 5, 8, 9, 10 or 12 m
Sch 40S and Sch 80S pipe, and tube walls up to 12 mm
100% hydro or eddy current tested; UT on request
Laser cut to length in our own plant, backed by 3,000 tons of stainless pipe & tube in stock (out of 80,000 tons in total)
Why Order SS SMLS Pipe & Tube From MTS
01
Seven Grades, 6 to 660 mm OD
Seamless pipe & tube come in 304, 316L, 321, 347, 310S, 2205 and 2507. 304, 316L, 321, 310S and 2205 run 6–660 mm OD; 347 runs to 610 mm OD.
02
Cut to Length in Our Plant
Standard length is 6 m, and we also supply 5, 8, 9, 10 and 12 m. Our tube laser cuts lengths, holes and slots up to 350 mm OD, 10 mm wall and 9 m long.
03
Extra NDT on Request
Ultrasonic testing, intergranular corrosion tests and third-party witness can be added to your order.
04
Walls Up to 12 mm
Seamless walls run from 1 to 12 mm. That covers Sch 40S up to NPS 24" and Sch 80S up to NPS 6". Heavier walls are quoted per order.
05
Processing Capacity, Stock and Delivery
We process up to 100,000 tons a month and keep 3,000 tons of stainless pipe & tube in stock in 60,000 m² of warehouse space in Wuxi. Our own cranes load each container for Shanghai, Qingdao or Tianjin.
No Weld Seam, No Weak Line
Seamless pipe & tube start as a solid round billet. It is pierced, then rolled or drawn to size. There is no weld anywhere along the length.
That matters for high pressure, cyclic loads and heavy walls. Many design codes give seamless full strength without a weld factor. For high pressure, high temperature or hazardous service, seamless stainless steel is often the safest choice.
Seamless Pipe & Tube Range
SS 304 Seamless Pipe & Tube
304 seamless runs 6–660 mm OD with walls of 1–12 mm, in sizes such as 57 × 3, 89 × 4, 108 × 4, 159 × 4.5 and 219 × 6 mm. Seamless 304 stainless steel tubing and stainless steel 304 seamless pipe serve pressure water, steam and process lines.
SS 316 Seamless Pipe & Tube
316L seamless from 6 to 660 mm OD for chemical and coastal plants. See 316 Stainless Steel Pipe & Tube for grade details.
Sch 40S Seamless Pipe
The standard wall for threaded and medium-pressure lines. Also ordered as Sch40S or 40S pipe.
Sch 80S Seamless Pipe
Heavy wall for high pressure, threading and socket welding. Common in 1/2" to 2".
Heavy Wall Seamless Tubing
Thick wall stainless steel pipe & tube by OD × wall, with walls up to 12 mm, for hydraulic cylinders, shafts and high-pressure parts.
Boiler and Heat Exchanger Tube to A213
Seamless tube for boilers, superheaters and heat exchangers, in 304, 316L, 321, 347 and 310S.
High-Temperature Seamless Pipe to A376
TP304H and TP316H for power plant headers. TP321H and TP347H are quoted on request.
Specifications
| Item | Range |
|---|---|
| Grades | TP304, TP304H, TP316L, TP316H, 316Ti, TP321, TP347, TP310S, 904L, 2205, 2507 |
| Process | Hot extruded or hot rolled; cold drawn or cold pilgered |
| Pipe | OD 6–660 mm (to NPS 26″); Sch 10S and 40S; Sch 80S to NPS 6″; wall 1–12 mm |
| Tube | OD 6–660 mm, wall 1–12 mm (TP347: OD 6–610 mm, wall 1–10 mm) |
| Length | 4–12 m; 6 m standard; 5, 8, 9, 10 or 12 m |
| Standards | Pipe: ASTM A312 / SA312, A376 / SA376, A790. Tube: ASTM A213 / SA213, A269, A789. General: A999, A1016. EN 10216-5 |
| Tests | Hydro or ET, flattening, flaring; UT and IGC (A262) on request |
Buying Seamless Stainless Steel Pipe & Tube: What to Check
How Seamless Pipe & Tube Are Made
A round billet is heated and pierced, or hot extruded, into a hollow shell. The shell is rolled to size. This gives hot finished pipe & tube.
For smaller sizes, the hollow is then cold drawn or cold pilgered. Each pass reduces OD and wall. The product is annealed and pickled at the end. Cold drawn material has tighter tolerances and a smoother bore.
Both routes produce “SMLS” pipe & tube. When your spec only says seamless, either is accepted. If you need a smooth bore or tight OD, write “cold finished” on the order.
Wall Tolerance and Eccentricity
Seamless pipe & tube can have uneven wall, thicker on one side. ASTM A312 allows the wall to be 12.5% under nominal at any point. A213 tube is often ordered to minimum wall instead.
That is why seamless may weigh slightly differently from welded. If your design uses minimum wall, check that 87.5% of nominal is still enough. If not, order a heavier wall or a tighter tolerance.
Sch 40S, Sch 80S and When "S" Matters
Schedule applies to pipe only. Sch 40 ss pipe is used for threaded joints and moderate pressure. Sch 80S is used for higher pressure and socket welds.
Many searches say “sch 40s pipe.” From NPS 1/2″ to 10″, Sch 40S and Sch 40 have the same wall. A 2″ Sch 40 stainless steel pipe and a 2″ Sch 40S pipe are both 3.91 mm. Above 10″, they differ, so write the “S” for stainless walls.
The same applies to 2″ Sch 80 pipe in stainless: Sch 80S at 2″ is 5.54 mm. Carbon steel buyers search the same words, so add the grade on your request.
Heavy Wall Tube
Thick wall stainless steel tube is sold by OD × wall. Our seamless range goes up to 12 mm wall. It goes into hydraulic parts, bushings, shafts and high-pressure lines. Heavy wall stainless steel tubing is almost always seamless, since welding thick walls is slow and costly.
When Seamless Is Worth the Extra Cost
Seamless usually costs more than welded in the same size. It is worth it when:
- Pressure or temperature is high, and your code derates welded material.
- Your spec bans welded pipe & tube in hazardous, sour or cyclic service.
- You need heavy walls such as Sch 80S, 160, XXS or thick wall tube.
- You will thread, flare or bend tightly.
For low and medium pressure lines, welded and annealed material works well and costs less. See Stainless Steel Welded Pipe & Tube.
A312, A213 or A376?
The standard depends on pipe or tube, so they stay separate here.
ASTM A312 covers seamless and welded pipe. Most seamless pipe orders use it.
ASTM A213 / ASME SA213 covers seamless tube for boilers, superheaters and heat exchangers. If your list says “A213 tubing” or “ASTM A213 tubing,” it means exact OD × wall, tested to tighter rules.
ASTM A376 covers seamless pipe for high-temperature power plant service, mainly H grades. Order it only when your power plant spec calls for it.
All of them call up general requirement standards, A999 for pipe and A1016 for tube. These set the shared rules on tolerance, marking and certificates.
Frequently Asked Questions
What does SMLS mean on stainless pipe & tube?
SMLS is short for seamless. You will see it stenciled on the material and printed on certificates. An "SS SMLS pipe" order means seamless pipe with no weld seam. Welded material is marked "WLD" or "WELDED."
How can I tell seamless from welded pipe & tube?
Look at the bore. Welded material often shows a faint seam line, even after bead removal. Seamless has none. The stencil and certificate also state the process. For critical lines, ask for a macro-etch on a sample.
Do you stock SS 304 seamless pipe & tube?
Yes. We supply SS 304 seamless pipe & tube from 6 to 660 mm OD, with walls of 1–12 mm, in lengths of 4–12 m. Send your size list and we will confirm availability and quote within 2–4 working hours.
What is ASTM A999?
ASTM A999 / A999M sets general requirements for alloy and stainless steel pipe. It covers tolerances, testing, marking and certification. You don't order to A999 alone. It applies through A312, A376 and other pipe standards.
Do you work with seamless stainless steel tubing suppliers and distributors?
Yes. We supply stockists with mixed sizes of seamless tubing and pipe in one container. Ask for our current size list.
Is seamless always stronger than welded?
The base metal is the same. Under A312, both have the same minimum strength. The difference lies in design codes, which may derate welded material with a joint factor. Seamless also avoids any risk of weld defects.
Request a Quote
We reply within 2–4 working hours with a price per ton, valid for 3 days.