Stainless pipes & tubes

Stainless steel is a versatile material comprised of a steel alloy and a small percentage of chromium — the addition of chromium adds to the material’s corrosion resistance, a trait that earned stainless steel its name. Because stainless steel is also low-maintenance, oxidation resistant, and doesn’t affect other metals it comes in contact with, it is frequently used in a large array of applications, especially in piping and tubing manufacturing.

Based on the end use of the pipe, stainless steel piping is broken down into several categories.

Material stainless steel grades

Also known as "marine grade" stainless steel due to its increased ability to resist saltwater corrosion compared to type 304. SS316 is often used for building nuclear reprocessing plants.

304/304L Stainless Steel

304 Stainless is a low carbon (0.08% max) version of basic 18-8 also known as 302.

316/316L Stainless Steel

Type 316 is more resistant to atmospheric and other mild environments than Type 304.

310S Stainless Steel

310S Stainless Steel has excellent resistance to oxidation under constant temperatures to 2000°F.

317L Stainless Steel

317L is a molybdenum bearing austenitic chromium nickel steel similar to type 316, except the alloy content in 317L is somewhat higher.

321/321H Stainless Steel

Type 321 is basic type 304 modified by adding titanium in an amount at least 5 times the carbon plus nitrogen contents.

410 Stainless Steel

Type 410 is a martensitic stainless steel which is magnetic, resists corrosion in mild environents and has fairly good ductility.

Duplex 2205 (UNS S31803)

Duplex 2205 (UNS S31803), or Avesta Sheffield 2205 is a ferritic-austenitic stainless steel.

Duplex 2507 (UNS S32750)

Duplex 2507 (UNS S32750) is a super duplex stainless steel with 25% chromium, 4% molybdenum..


UNS S32760 is described as a super duplex stainless with a microstructure of 50:50 austenite and ferrite.

SA 269

ASTM A269 / A269M Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service

SA 249 Stainless Steel

ASME SA 249 Standard Specification for Welded Austenitic Steel Boiler,
Superheater, Heat-Exchanger, and Condenser Tubes.

904L Stainless steel

904L stainless steel consists of chromium, nickel, molybdenum and copper contents, these elements give type 904L stainless steel excellent properties

Duplex pipes

What is Duplex Stainless Steel?

Duplex Stainless Steel is a type of steel containing the high amount of chromium and minimum amount of nickel. It provides great strength and resistance to corrosive environments.

Duplex 2205 (UNS S31803)

Duplex 2205 (UNS S31803), or Avesta Sheffield 2205 is a ferritic-austenitic stainless steel.

Duplex 2507 (UNS S32750)

Duplex 2507 (UNS S32750) is a super duplex stainless steel with 25% chromium, 4% molybdenum, and 7% nickel designed.

Super duplex UNS S32760

UNS S32760 is described as a super duplex stainless with a microstructure of 50:50 austenite and ferrite.

Dual phase steel

Dual-phase steel (DPS) is a high-strength steel that has a ferrite and martensitic microstructure.

Comparison table of stainless steel brands of various countries

In order to solve the cumbersome and difficult to remember stainless steel grades, improve the practicability of the brand representation, and the contrast with the international standard grades, China has formulated the "Universal Code System for Steel and Alloy Grades", such as 06Cr19Ni10, corresponding to 304. Different grades of stainless steel have different ingredients, but they all have a national standard. The standards of each country are also different.

The specific standards of each country are as follows:

NoChina,GBJapanAmericanKoreaEURIndaiAustraliaTai Wan
Austenitic stainless steel
21Cr18Mn8Ni5N12Cr18Mn9Ni5NSUS202202S20200STS2021.4373 -202
130Cr18Ni12Mo3Ti06Cr17Ni12Mo2TiSUS316Ti 316TiS31635-1.457104Cr17Ni12MoTi20316Ti 316Ti
Austenitic ferritic stainless steel (duplex stainless steel)
0Cr18Ni10Ti Iron type stainless steel
Martensitic stainless steel
353Cr1330Cr13SUS420J2--STS420J21.402830 Cr13420J2420J2

Stainless Steel Tube & Pipe Tolerance

Outside diameter (OD), wall thickness and length are three basic parameters in the process of manufacture and distribution for stainless steel tube & pipe, and these parameters have been standardized.

Outer diameter and wall thickness are particularly important, they are not only the basic support for meeting the design requirements of various types of applications such as strength, stiffness and fluid delivery, but also have a decisive influence on the subsequent processing, therefore, standards for stainless steel tube & pipe diameter and wall thickness of the manufacturing accuracy (tolerance) should been standardized.

European Standard

European stainless steel tube & pipe standards specify 4 classes outer diameter and wall thickness in percentage or absolute value on the basis of nominal dimension.

Generally, larger diameter or heavy wall thickness stainless steel pipe use percentage, small diameter or thin wall thickness stainless steel tube use absolute value.

Standard Manufacturing Process & Type Outer Diameter Tolerance Wall Thickness Tolerance Others
OD (Mm) Class
EN10216-5 Hot Finished Seamless Tube 219.1-610 D1 +22.5%T,-15%T T/D≤0.05
T1 T/D≤0.09
T2 T/D>0.09
30-219.1 D2 T1
Cold Finished Seamless Tubes ≤219.1 D3 T3
D4 T4 Agreement
EN10297-2 Hot Finished Seamless Tube D1 T1
D2 T2 Agreement
Cold Finished Seamless Tubes D3 T3
D4 T4 Agreement
EN10217-7 Welded Tubes >168.3 D2 T3
≤168.3 D3 T3
D4 T3 Agreement
EN10296-2 Welded Tubes >168.3 D2 T3
≤168.3 D3 T3
≤114.3 D4 T3 Agreement
EN10312 Welded Tubes Series 1 D4 T3 T=0.6-2 Mm
Series 2 D3 – D4 T3 – T4 T=1-3 Mm

From D1 to D4 class for outer diameter, and T1 to T4 for wall thickness tolerance comply to DIN EN ISO 1127 standard, stainless steel tubes – Dimensions, tolerances and conventional masses per unit length.

Outside Diameter Wall Thickness
Class Tolerance Class Tolerance
D1 ±1.5%, Or ±0.75 Mm Min. T1 ±15%, Or ±0.6 Mm Min.
D2 ±1.0%, Or ±0.5 Mm Min. T2 ±12.5%, Or ±0.4 Mm Min.
D3 ±0.75%, Or. ±0.3 Mm Min. T3 ±10%, Or ±0.2 Mm Min.
D4 ±0.50%, Or ±0.1 Mm Min. T4 ±7.5%, Or ±0.15 Mm Min.
T5 +/- 5.0 %, Or +/- 0.10 Mm Min.

The tolerances on outside diameter and thickness from above table, greater value shall be selected.

EN 10312 has specific values in table series 1 and series 2.

America Standard

America standard has two standard rules to specify outside diameter and thickness, ASTM A999 / A999M and A1016 / A1016M.

ASTM A999 ASTM A1016
  • ASTM A312 / A12M
  • A358 / A358M
  • A376 / A376M
  • A409 / A409M
  • A778
  • A790 / A790M
  • A813 / A813M
  • A814 / A814M
  • A928 / A928M
  • A213 / A213M
  • A249 / A249M
  • A268 / A268M
  • A269
  • A270
  • A688 / A688M
  • A789 / A789M
  • A803 / A803M

But A511 for seamless stainless steel mechanical tubing and A554 welded stainless steel mechanical tubing not conform to above standards, they have separate outside diameter and thickness tolerances.

Standard Manufacturing & delivery condition Outside Diameter
OD / mm
OD tolerance mm Thickness
T / mm
T tolerance mm
Minimum Average
ASTM A1016
Hot drawn seamless tubes <=100 +0.4, -0.8 <=2.4 +0.4t, 0
100 – 200 +0.4, -1.2 2.4 – 3.8 +0.35t, 0
200 – 225 +0.4, -1.6 3.8 – 4.6 +0.33t, 0
>=4.6 +0.28t, 0
Cold drawn seamless tubes <25 +0.1, -0.11 +0.20t, 0 +/-0.10t
25 – 40
40 – 50 +/-0.2 +0.22t, 0 +/-0.10t
50 – 65 +/-0.25
65 – 75 +/-0.3
75 – 100 +/-0.38
100 – 200 +/-0.38, -0.04
200 – 250 +/-0.38, -1.14
Welded tubes 40 – 50 +/-0.2 +0.18t, 0 +/-0.10t
50 – 65 +/-0.25
65 – 75 +/-0.3
75 – 100 +/-0.38
100 – 200 +/-0.38, -0.04
200 – 250 +/-0.38, -1.14
ASTM A999 / M Seamless tubes and welded tubes <48.3 +0.4, -0.8 -0.125t
ASTM A312 / M Seamless tubes and welded tubes 48.3-114.3 +/-0.8 OD=10.3-73 +0.20 t, -125t
168.3-219.1 +1.6, -0.8 t/OD<=5% OD=88.9-457.2 +0.225 t, -125t
219.1-457.2 +2.4, -0.8 t/OD>5% OD=88.9-457.2 +0.15 t, -125t
Welded tubes 508-660 +3.2, -0.8 OD>=508 +0.175 t,-0.125 t
711-864 +4.0, -0.8 t/OD<=5%, OD>=508 +0.225 t,-0.125 t
Seamless tubes 914-1209 +4.8, -0.8 t/OD>5%, OD>=508 +0.15 t, -125t
ASTM A409 / M Welded tubes +/-0.2% T<4.8
+/-0.4% t>=4.8
ASTM A358 / M Welded tubes   +/-0.50%
ASTM A511 Seamless tubing <=12.7 +/-0.1 +/-0.15t
12.7-38.1 +/-0.2 +/-0.10t
38.1-88.9 +/-0.3
88.9-139.7 +/-0.4
139.7-203.1 +/-0.8
203.1-220 +/-1.1
220-325 +/-1.6

American standard outside diameter tolerance mainly used to represent the absolute value, over and below tolerances are often asymmetric, SS tube and pipe in American standard average tolerance can reach even higher than D4 class in EN ISO 1127 standard.

Wall thickness tolerance should be +/-10%t or better, and average thickness tolerance should be ( +/-20 – 22%t, 0 ), pipeline pipe has a larger tolerance, hot finished seamless pipe largest.

China Standards

China has more quantity standards compared to European standards, but less than american standards, SS tube and pipe standards are similar with EU standards in system, and absorb favorable experience in USA specifications.

Specification Manufacturing O.D(Mm) O.D Tolerance W.T(Mm) W.T Tolerance
GB13296 Cold Rolled Seamless Pipe 6~30 ±0.15/-0.2 1~3 +20% -0%
>30~50 ±0.3 >3 +22% -0%
>50 ±0.75% Also Average Wall
GB/T14976 Cold Rolled Seamless Tube 6~10 ±0.15 1~3 +12.5% -12.5%
10~30 ±0.2 >3 +12.5% -10%
30~50 ±0.3 Average Wall, +22%
>50 ±0.8%
Standard Comparison

Stainless steel tube & pipe wall thickness tolerance are the same as the general accuracy of American ASTM / ASME and EU standards, but slightly lower than the high requirements of the EU standards.

Stainless steel tube & pipe outer diameter tolerances are mostly lower than American standards, and approaching the EU standards. it is more reasonable that the American standard specify the OD tolerance is tight, compared to thickness tolerance.

China GB standards and EU standard have no weight tolerance specified, seamless tube & pipe in GB standard delivery goods as actual weight or theoretical weight, welded tube & pipe as theoretical weight or actual weight.

Out Of Roundness

Out of roundness, sometimes referred to as ovality is tube or pipe on the same cross-section of the outer diameter, roundness or ovality is difference between the maximum and minimum dimensions of outside diameter, is carefully measured the high and low points at any one section of the tube or pipe.


Concentricity or eccentricity refers to tube & pipe wall thickness variations, if need a high precision in tube tolerance, or fit into other tube or parts, which need a good concentricity.



Concentricity be contained wall thickness tolerance specified in EU standard, and just specified in ASTM A1016/M OD≥50 mm and t≥5.6 mm thick wall stainless steel tube the same cross section thickness varieties.

For seamless tube,

WTmax – WTmin ≤ ±10% (WTmax + WTmin) / 2

For welded tube,

WTmax – WTmin ≤ 5% (WTmax + WTmin) / 2


Standard pipes and tubes are supplied straightened to the eye: for special applications the permissible deviation from the straight line may be agreed between purchaser and tube manufacturer; the maximum permissible deviation from the straight line related to the length of measurement L is to be indicated, e.g. 1mm/1000mm.

For example:

OD Mm ≤ OD Inches ≤ Wall Straightness Commercial FT Achievable Mm
15.9 0.625 All Sizes 1 In 600 1 In 2000
25.4 1.00 2% Of OD Or Heavier 1 In 600 1 In 1500
25.4 1.00 Less Than 2% Of OD 1 In 400 1 In 1000

Stainless Steel Density

Stainless steel density refers to substance mass per unit volume, it is one of typical property of stainless steel, commonly, density of stainless steel range from 7600 kg/m3 to 8000 kg/m3.

Stainless steel is a wide used material, containing at least 10.5% of Chromium, and other elements added to form stainless steel structure, these elements have Carbon, Silicon, Manganese, Phosphorus, Sulfur, Nickel, Molybdenum, Titanium and Copper, it is noted as high strength and excellent corrosion resistance.

Densities change depending on these alloy elements changing, different alloy content have different density value, even it is the same grade, it is difficult to calculate accurate density values, theoretic density value is given below for reference.

Stainless Steel Density Table Chart
Grade Density ( G / Cm3 ) Density ( Kg / M3 )
7.93 7930
7.98 7980
904L 7.98 7980
7.80 7800
S32750 7.85 7850
7.75 7750
440A 7.74 7740
440C 7.62 7620
420 7.73 7730
7.70 7700
434 7.74 7740
444 7.75 7750
405 7.72 7720

*These densities given at standard conditions for temperature and pressure condition.

304 And 316 Stainless Steel Densities

304 and 316 are the most used stainless steel grades, their densities are not the same, this decide by chemical composition and content, stainless steel 304 density is 7930 kg / m3, 316 density is 7980 kg / m3, so when calculating stainless steel weight, it is different between 304 and 316 stainless steel.

Stainless Steel Density Conversion, Kg/M3, G/Cm3 And Lbs/In3
Density of stainless steel calculated by dividing the mass by the volume, usually measured in g/cm3, kg/m3, and lbs/in3, each unit can be converted to other units.

Conversion: 1 kg/m3 = 0.001 g/cm3 = 1000 g/m3 = 0.000036127292 lbs/in3.

Density Relations With Temperature And Pressure

Densities of stainless steel vary by changing either the temperature or the pressure, in general, increasing the temperature decreases the density, increasing the pressure always increases the density.

Difference Between Seamless And Welded Tube & Pipe

Seamless and welded are mainly two types stainless steel tube & stainless steel pipe, there is a debate whether seamless is better than welded for a long time.

Although with improved metallurgy and welding processes in welded tubes, the arguments typically focus on structural integrity and corrosion resistance in weld area.

Obviously, seamless and welded tubes & pipes difference is manufacturing process.

There are some cases where paying extra for a different, higher-performing alloy is necessary.

Welded Tube Manufacturing Process

Depending on the outer dimension, wall thickness and final application, there are different ways of manufacturing welded tubes and pipes, and different manufacturing method.

Strip Welded Tubes & Pipes

Welded tube start from stainless steel strip and coil that is passed through grooved rollers till the shape is formed and the free edges are properly shaped for welding, cold forming is performed step by step from flat strip into a round profile, the edges are welded together as they approach the welding rolls.

Typical welding method for strip welded tubes is traditionally autogenous tungsten inert gas (TIG), TIG welding method have some advantages that can effectively protect weld seam.

After welding outside and inside grinding of the weld seam, solution annealing or stress relieving may be necessary by application requirements.

TIG Welding Stainless Steel Tubing

TIG Welding Stainless Steel Tubing

  • Coil
  • Inspection and analysis
  • Slitting
  • Auto-welding
  • Seam-grinding
  • Solution treatment
  • Cut to length
  • Straightening
  • Picking
  • End-facing
  • Eddy current test
  • Hydrostatic test
  • Final inspection
  • Marking
  • Packing
  • Shipping

Today, most of the modern welding lines are equipped with inline induction annealing, then straitening and calibration to control dimension of tube & pipe, cut to standard or special lengths, de-burred, NPD & DT testing and inspection should be carried out as standard or requirement.

Heavy Wall Tubes & Pipes

When large outside diameter or heavy wall or both welded tubes & pipes required, there is a different welding method and process, for large diameter and heavy wall pipes, EFW, ERW and other welding methods can be used.

Starting from stainless steel plate or sheet, the forming is done in a roller bending machine or in a hydraulic press, then some steps are same with strip welded tubes.

  • Plate
  • Inspection
  • Plasma-cutting
  • Edging
  • Bending
  • Seam cleaning
  • Forming
  • Auto- welding
  • Degreasing
  • Anneaspanng
  • Roundness caspanbrating
  • End-facing
  • Eddy current test
  • Hydrostatic test
  • Final inspection
  • Marking
  • Packing
  • Shipping

For testing and inspection, large diameter sizes, radiography test (RT) and hydrostatic test (HT) are often required.

For large diameter welded pipes, double welding method can be accepted.

Seamless Tube Manufacturing Process

Seamless tubes are generally made in complex steps starting with the drilled hollows from billets, by cold drawing and cold rolling manufacturing process with cold drawing & cold rolling machines.

To control outside diameter and wall thickness, seamless type dimension is difficult to control compared to welded tube, cold work improves the mechanical properties and tolerances.

Cold pilgering is the preferred production process since this technique provides a high forming rate, narrow tolerances and good productivity yields, but cold drawing gives narrower tolerance ranges and better surface quality.

  • Round bar
  • Inspection and analysis
  • Cut to length
  • Centering
  • Peel
  • Heating
  • Perforation
  • Inspection of size
  • Pickspanng
  • Inspection of surface
  • Lubricating
  • Cold drawing / cold rolspanng
  • Degreasing
  • Anneaspanng
  • Straightening
  • Cut
  • Picking / passivating
  • Final inspection
  • Marking
  • Packing
  • Shipping

Solution annealing should be made through offline annealing furnace, then straightening and pickling, these are important steps in manufacturing seamless stainless steel pipe and tubes.

Advantages Of Welded Tubes & Pipes

  • Lower cost compared to the equivalent seamless alternative.
  • Short lead time.
  • Better surface finishing of outside and inside, the internal material surface for welded tubes can be checked prior to manufacture.
  • Thinner wall thickness, and more uniform.
  • Tighter tolerance.

Advantages Of Seamless Tubes & Pipes

  • Heavy and thick wall thickness.
  • No weld seam. generally be considered as better properties and corrosion resistance
  • Seamless pipes have better ovality, or roundness

How To Choose Tubes & Pipes, Welded Or Seamless?

Despite many advantages with welded tubes, seamless tube is still treated better than welded type, especially used in rough environment, considered as higher strength, higher pressure, and better corrosion resistance.

Delivery requirment:

Capped end stainless steel tube

  • Package: knitting strip bundle, wooden box or steel box
  • Mill test certificate: according to EN 10204 3.2
  • Inspection: Third party inspection, or by clints
Capped end stainless steel tube
Tubes putted in wooden boxes

Tubes putted in wooden boxes

  • Marking: SunnySteel, material grade, standard, specification, heat no.

The wooden boxes packing for stainless products

  • Surface Treatment: Bright annealed, polished outside and inside surface.
Stainless Steel Seamless Pipes
Stainless Steel Seamless Pipes


Pipe size range:

  • Outside diameter: range from 6mm to 530mm.
  • Wall thickness: SCH5S, SCH10S, SCH40S, SCH80S, SCH 120S
  • Legnth: unbending length or fix length

Range applications of Stainless pipes & tubes

Stainless steel pipe (tube) has excellent characteristics of corrosion resistance and smooth finishing. Stainless steel pipe (tube) is commonly used in demanding equipment like automobiles, food processing, water treatment facilities, oil and gas processing, refinery and petrochemicals, breweries and energy industries.

The stainless steel tubing that is supplied by SunnySteel can used in a variety of industries, including:

Considering the importance of outside and inside surface of stainless steel tubes for fluid power industry, Our mills are providing tubes that are free from scale, rust, seams, laps.



Our team are highly trained and experienced in servicing and producing all types of steel supplies. Whether you've got a large construction project, or need parts for industrial machinery, our team of steel fabrication consultants will ensure that your project is provided with the parts you need, when you need them.

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