Seamless cold drawn steel tube to GOST, ASTM and JIS standards for hydraulic, mechanical and low-temperature applications. No weld seam, tight wall tolerance and a bore that can be honed or machined.
The tube is pierced from a solid billet and then cold drawn, so there is no weld to inspect and no heat-affected zone running down the length. Buyers who write seamless steel pipe, SMLS pipe or carbon steel seamless pipe are asking for this product: one piece of steel, no seam, a wall that can be held close to nominal and a bore that machines true.
Seamless steel pipe or seamless steel tube?
Both names describe the same mill product. Pipe is sized and sold by nominal bore and schedule for flow, tube by outside diameter and wall for structure and precision. A refinery orders a seamless pipe in schedule 40; a machine shop orders a seamless tube in 25.4 x 2 mm. The difference is the sizing convention on the drawing, not the steel.
| Term on the enquiry | Who writes it | What it means |
|---|---|---|
| seamless steel pipe / seamless pipe | Process, boiler and oil and gas buyers | Sized by nominal bore and schedule |
| SMLS pipe / SMLS steel pipe | Purchase orders, shipping documents | The abbreviation of seamless, same product |
| seamless steel tube / seamless tube | Machine builders, hydraulic shops | Sized by OD and wall |
| carbon steel seamless pipe | ASTM A106 and A53 buyers | Carbon grade for pressure service |
| cold drawn seamless, CDS | UK and European drawings | Drawn after piercing, tighter tolerance |
| seamless mechanical tubing | A519 and JIS G3445 buyers | Tube intended to be machined |
If the enquiry arrives as a schedule number we convert it to OD and wall before quoting, because a schedule 40 wall and a drawn wall are not the same measurement and the price moves with the wall, not with the name.
Standards we work to
| Standard | Scope | Grades we supply | Where it goes |
|---|---|---|---|
| GOST 8734-75 | Seamless cold and warm formed pipe | 10, 20, 09G2S | Russia, CIS, low-temperature service |
| GOST 9567-75 | Seamless high precision tube | 10, 20, 09G2S | Precision parts, CIS drawings |
| ASTM A519 | Seamless carbon and alloy mechanical tubing | 1010, 1018, 1020, 1026, 4130, 4140 | Machined parts, chromoly work |
| JIS G3445 | Carbon steel tube for machine structures | STKM 11A to 13C | Automotive, machinery, Japan drawings |
| DIN 2391 / EN 10305-1 | Seamless precision tube | St35, St45, St52 / E235, E355 | Hydraulic cylinders, Europe |
| SAE J524 / J525 | Seamless low carbon tubing | 1008, 1010 | Automotive lines and fittings |
Products in this group
GOST 8734-75 Seamless Cold Formed Steel PipeGOST 8734-75 · steel 10 / 20 / 09G2SView tube →
09G2S Seamless Pipe GOST 8734-75GOST 8734-75 · 09G2S · low temperature serviceView tube →
ASTM A519 Seamless Mechanical TubingASTM A519 · 1020 / 1045 / 4130View tube →
JIS G3445 STKM Carbon Steel TubeJIS G3445 · STKM 11A–13CView tube →How a seamless tube is made
A round billet is heated and pierced over a mandrel to make a hollow shell, and from that point the tube has no seam anywhere in its length. The shell is then cold drawn over a plug or a mandrel, which sets the wall, the concentricity and the surface finish. Between draws the tube is annealed so that the steel can be deformed again without cracking, and the last draw decides the tolerance the customer sees.
That is why cold drawing costs more than rolling and why it is worth the money on a hydraulic part: the wall can be held to a few hundredths of a millimetre, the bore comes out round, and the surface is good enough to hone or to plate without a machining allowance. A hot finished seamless pipe is cheaper per tonne but its wall varies far more, and no amount of inspection fixes a wall that was never drawn.
Carbon steel grades across standards
The same steel is written differently in every market, and a quotation that lists only one name looks unfamiliar to a buyer from another country. The table crosses the grades we draw most often.
| Grade | Equivalent names | Typical use |
|---|---|---|
| 20# | S20C, AISI 1020, C22 | General mechanical parts, low-pressure lines |
| 45# | S45C, AISI 1045 | Shafts, pins, parts machined after drawing |
| E235 | St35, St37.4 | Hydraulic lines, general precision tube |
| E355 | St52, 1.0580 | Cylinder barrels, structural parts |
| 09G2S | 09G2S only, GOST grade | Low-temperature service, down to -40 C and below |
| 4130 | 25CrMo4, 1.7218 | Chromoly parts where strength per kilo matters |
| STKM 11A to 13C | JIS G3445 series | Automotive and machinery tube |
Sizes and tolerances
| Item | Range | Note |
|---|---|---|
| Outside diameter | 4-80 mm | Outside this range quoted as a special draw |
| Wall thickness | 0.6-10 mm | Wall to drawing where the OD allows |
| OD tolerance | +-0.05 to +-0.10 mm | Cold drawn, tighter on the last draw |
| Wall tolerance | +-10 percent | Closer on request, especially for honed bores |
| Length | 4-7 m random, or fixed | Cut to length with deburred ends on request |
| Delivery condition | Cold drawn, annealed, normalised, stress relieved | Condition chosen for the next operation |
Tubes ordered for honing or skiving are drawn with a bore allowance and a wall that stays concentric, because an eccentric wall shows up as an uneven layer after plating and as a weak side in a pressure part. Where the drawing gives an ID rather than an OD, the draw schedule is set from the bore.
Seamless or welded?
Seamless is the safe answer wherever the wall is thin, the pressure is high or the bore is machined after cutting, because there is no seam to open. Welded and cold drawn tube, such as DIN 2393 and EN 10305-2, does the same job at a lower price for shock absorber bodies, bushes and general mechanical parts where the wall is heavier. Both routes are drawn in the same workshop, so the choice can be made on the part rather than on availability.
See DIN 2393 welded precision tube for the welded side of the comparison.
FAQ
What does SMLS mean in a pipe specification?
SMLS is the abbreviation of seamless. An SMLS pipe has no weld anywhere in its length, which is why it is specified for pressure, for low temperature and for anything that will be machined after cutting.
Is seamless steel pipe the same as seamless steel tube?
The product is the same. Pipe is ordered by nominal bore and schedule, tube by outside diameter and wall, so the two names describe different ways of sizing one mill product.
Which is stronger, seamless or welded tube?
For the same wall and grade, seamless has no weld to be the weak point, so it is preferred for pressure and fatigue. A cold drawn welded tube is strong enough for most mechanical parts, and its weld has been drawn out and annealed, but the seam is still there in the metallurgy.
What is cold drawn seamless tube used for?
Hydraulic cylinder barrels, shock absorber parts, bushings, shafts, spindles and machined components, plus low-temperature lines where 09G2S or a fine grain grade is required.
What sizes do you draw?
Outside diameter 4-80 mm with wall 0.6-10 mm, cold drawn, annealed or normalised. Special sizes are drawn to order rather than cut from stock, so the size is not a limit but the lead time is longer.
Do you supply to GOST as well as ASTM?
Yes. GOST 8734-75 and GOST 9567-75 are regular production for Russia and the CIS, with certificates and marking in Russian, and the same workshop draws ASTM A519 and JIS G3445 to the same equipment.
What to send with an enquiry
Standard, OD, wall, length, steel grade and quantity. We reply with price, tolerance and lead time within one working day.