What is Seamless Pipe?

A seamless pipe is a pipe without a seam or a weld-joint. A solid round steel billet is heated
t high temperatures to make the  Stainless Steel Seamless Pipes. These billets are pushed or pulled over a form to shape it into a hollow pipe which is then released through a die and mandrel combination to reduce the outside diameter and expand the inner diameter as per the requirements.

The seam or the weld-joint is the weaker part of the pipe in both – Seam and Welded pipes. This attribute limits the strength of the pipe to the strength of the weld-joint whereas in seamless pipes,there are no such joints which ensures uniform structure and strength all over the pipe body. Due to such characteristics, the seamless pipe can withstand higher pressure, higher temperature, higher mechanical stress and corrosive atmosphere. So, it has wide applications in Oil and Gas, Refinery,Petrochemical, Chemical, Fertilizer, Power, Automotive, Bearing, Mechanical and Structural applications.

Advantages of Stainless Steel Seamless Pipes

There are three major advantages of stainless steel seamless pipes:

1. Strength under loads – These pipes have great strengths under loading. Empty pipes can support their own weights easily but when a pipe is filled with material (under load), it must support that weight as well. Failures and leaks in welded pipes usually occur at the welded seam; however, as the seamless pipes don’t have any welded seams it isn’t subject to those failures.
Due to such benefits, the stainless steel seamless pipes are the preferred material in an array of commercial pipe applications including ship building, pipelines, oil rigs, oil field equipment, pressure vessels, machinery parts and offshore rigs. Seamless pipes are also found to perform well in harsh conditions – extremely hot or cold environments.

2. Increased Pressure Ratings – The increased ability to withstand pressure is the greatest advantage of stainless steel seamless pipes whereas the weakest point in a stainless steel welded pipe is the welded seam. As there are no welded joints in a seamless steel pipe, it doesn’t have that seam, making it equally strong around the entire circumference of the pipe. This also makes calculating pressure much easier without being required to take weld quality into consideration.

3. Uniformity of Shape – Welded seam pipe may not be as round as a seamless steel pipe because it is wrapped around another form before being welded and welding adds heat, stress, and other extraneous variables to the forming process. Because of the uniformity in shape, stainless steel seamless pipe is easy to install and to add fittings as it is a continuous extrusion of alloy, meaning that it will have a round cross section that you can count on.

Stainless Steel Pipe Materials

There are many grades of stainless steel pipes available on the market that can be grouped into four major categories:

Austenitic Stainless Steel

Austenitic stainless steel is the most common grade of stainless steel. Their microstructure is obtained with the addition of nickel, manganese, and nitrogen giving weldability and formability properties to the alloy. The corrosion resistance can be improved by augmenting the percentage of chrome, moly, and nitrogen to the base alloy. Austenitic stainless steels are divided into two series categories:

1. Series 200 (chromium-manganese-nickel alloys)
2. Series 300 (chromium-nickel alloys like 304, 309, 316, 321, 347, etc.)

Martensitic Stainless Steel

Martensitic stainless steels and ferritic steels are both similar in characteristics as they both have remarkable chromium content; however, martensitic steels have higher carbon content comparatively (up to 1%). Due to the increased carbon content, martensitic steels can be hardened and tempered as standard carbon and chrome alloy steels. When compared to standard austenitic stainless steels,martensitic grades are magnetic. Common martensitic grades are 410, 420 and 440C

Ferritic Stainless Steel

Ferritic stainless steels have significantly lesser chrome content and low additions on carbon – generally below 0.1%. Like martensitic steels, ferritic stainless steels are magnetic in nature. The most common ferritic grades are the 430 (17% chromium), and the 409 (11% chromium), largely used in the automotive sector.

Duplex and Super Duplex Stainless Steel

Duplex stainless steels are 50% ferritic and 50% austenitic. This microstructure gives them better strength than either ferritic or austenitic steels.

The common grades under this family are:
•Lean duplex: UNS S32101, S32202 (UR2202), S32304, and S32003.
Standard duplex: UNS S31803/S32205
•Super duplex: UNS S32760 (Zeron 100), S32750 (2507), and S32550 (Ferralium 255)
•Hyper duplex: UNS S32707 and S33207

Stainless Steel Pipe Dimensions

Pipe is generally specified by a nominal diameter with a constant outside diameter (OD) and a schedule that defines the thickness.

The European and international designation equivalent to NPS is DN (diameter nominal/nominal diameter/Durchmesser nach Norm), in which sizes are measured in millimeters. The term NB (nominal bore) is also frequently used interchangeably with NPS.

Based on the NPS and schedule of a pipe the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M

https://www.scodatubes.com/portfolio/stainless-steel-seamless-pipes/
Pipe Dimension Table from above links

ASTM A312 Stainless Steel Pipe – Diameter Tolerance

NPSASTM A312/ASME SA312 OD Tolerance
+-
mmInchmmInch
1/8 to 1 1 /21/64(0.015)0.41/32(0.031)0.8
> 1 1 /2 to 41/32(0.031)0.81/32(0.031)0.8
> 4 to 81/16(0.062)1.61/32(0.031)0.8
> 8 to 183/32(0.093)2.41/32(0.031)0.8
> 18 to 261/8(0.125)3.21/32(0.031)0.8
> 26 to 345/32(0.156)41/32(0.031)0.8
> 34 to 483/16(0.187)4.81/32(0.031)0.8

ASTM A312 Stainless Steel Pipe – Wall Thickness Tolerance

NPSASTM A312/ASME SA312 WT Tolerance, %
+-
1/8-2 1 /22012.5
3~18, t/D≤ 5%22.512.5
3~18, t/D> 5%1512.5
≥ 20, welded17.512.5
≥ 20, seamless, t/D≤ 5%22.512.5
≥ 20, seamless, t/D> 5%1512.5

ASTM A312 Stainless Steel Pipe Chemical Compensation

ASTM A312 Mechanical Properties of Stainless Steel Pipe

SS Pipes GradeTensile StrengthYield StrengthElongation
ASTM A312/ASME SA312N/mm2 (min)N/mm2 (min)% (min)
TP30451520535
TP304L48517035
TP31651520535
TP316L48517035
TP321OD < 17,1 mm – 515OD < 17,1 mm – 20535
OD > 17,1 mm – 485OD > 17,1 mm – 170

ASTM VS EUROPEAN Stainless Steel Pipe Materials

Stainless Steel Pipe Grades
Werkstoff/DINEN gradesASTM grades
1.4541X6CrNiTi18-10A 312 Grade TP321
1.4571X6CrNiMoTi17-12-2A 312 Grade TP316Ti
1.4301X5CrNi18-10A 312 Grade TP304
1.4306X2CrNi19-11A 312 Grade TP304L
1.4307X2CrNi18-9A 312 Grade TP304L
1.4401X5CrNiMo17-12-2A 312 Grade TP316
1.4404X2CrNiMo17-13-2A 312 Grade TP316L
1.4462X2CrNiMoN22-5-3UNS S 31803 (Duplex)
1.4529X1NiCrMoCuN25-20-7UNS N 08926
1.4539X1NiCrMoCu25-20-5UNS N 08904 (904L)
1.4547X1CrNiMoCuN20-18-7UNS S 31254

ASTM A312 Pipe (ASME B36.19) – Stainless Steel Pipe Weight Chart

Nominal Pipe SizeOutside DiameterStainless Steel Pipes Dimensions
Sch. 5SSch. 10SSch. 40SSch. 80S
mmInchWT / WEIGHT
mm (in)kg/mmm (in)kg/mmm (in)kg/mmm (in)kg/m
1/810.30.405--1.25 (0.049)0.281.73 (0.068)0.372.42 (0.095)0.47
1/413.70.54--1.66 (0.065)0.492.24 (0.088)0.633.03 (0.119)0.8
3/817.20.675--1.66 (0.065)0.632.32 (0.091)0.853.20 (0.126)1.1
151/221.30.841.650.812.111.022.31.072.77
1/221.30.841.65 (0.065)0.812.11 (0.083)12.77 (0.109)1.273.74 (0.147)1.62
3/426.71.051.65 (0.065)1.022.11 (0.083)1.282.87 (0.113)1.683.92 (0.154)2.2
133.41.3151.65 (0.065)1.32.77 (0.109)2.093.38 (0.133)2.54.55(0.179)3.24
4048.31.91.651.932.773.1133.353.68
1 ¼42.21.661.65 (0.065)1.662.77 (0.109)2.693.56 (0.140)3.394.86 (0.191)4.47
1 ½48.31.91.65 (0.065)1.912.77 (0.109)3.113.69 (0.145)4.065.08 (0.200)5.41
260.32.3751.65 (0.065)2.42.77 (0.109)3.933.92 (0.154)5.455.54 (0.218)7.49
2 ½732.8752.11 (0.083)3.693.05 (0.120)5.265.16 (0.203)8.647.01 (0.276)11.4
388.93.52.11 (0.083)4.523.05 (0.120)6.465.49 (0.216)11.37.62 (0.300)15.3
3 ½101.642.11 (0.083)5.183.05 (0.120)7.415.74 (0.226)13.68.08 (0.318)18.6
2008219.088.6252.7714.83.76206.3533.318.18
4114.34.52.11 (0.083)5.843.05 (0.120)8.376.02 (0.237)16.18.56 (0.337)22.3
5141.35.5632.77 (0.109)9.463.41 (0.134)11.66.56 (0.258)21.89.53 (0.375)31
6168.36.6252.77 (0.109)11.33.41 (0.134)13.97.12 (0.280)28.310.9 (0.432)42.6
8219.18.6252.77 (0.109)14.83.76 (0.148)208.18 (0.322)42.512.7 (0.500)64.6
10273.110.753.41 (0.134)22.74.20 (0.165)27.89.28 (0.365)60.412.7 (0.500)81.5
12323.912.753.97 (0.156)31.34.58 (0.180)36.19.53 (0.375)73.912.7 (0.500)97.4

Stainless Steel Pipe Finishing and Testing

PolishingManufacturers can polish any stainless steel pipe mirror finish.
CuttingsStainless steel pipes can be produced in standard lengths or cut to size (standard lengths are 20′ and 40′ depending on the nominal pipe size).
BevelingManufacturers can bevel the edges of stainless steel pipes to prepare them for welding.
ThreadingStainless steel pipes can be supplied, besides plain and beveled ends, also with threaded ends (generally for NPS below 2 inches)
Pipe Honing & TurningManufacturers can hone SS pipe and tube, using precision abrasion tools and obtain any desired finish or dimensional tolerance.
Heat treating & AnnealingMost stainless steel pipes grades can be heat treated to modify their mechanical properties.
Positive Material Identification (PMI)Manufacturers can perform PMI testing to ascertain the actual content of Nickel, Chrome, and Moly in the pipe.
UT TestingIn some cases, UT testing of the stainless steel plates may be required.

In short, Scoda Tubes Limited is the maker of high quality treated steel pipe, In
stainless steel Seamless pipe production. we are leading for Indian and
international market. Beneficial things for scoda tubes constrained we have a
limit with respect to PIPE Sizes up to 12 NB Sizes. The Stainless Steel
Piping is a market which is constantly expanding, and Scoda is a big player
here to have long race.