Carbon Steel Pipe A53/A106 Gr. B, A333 Gr. 6

Learn about the 3 most common specifications for carbon pipes: ASTM A53 (black and galvanized steel pipes, seamless and welded), ASTM A106 (seamless CS tubular for high pressure and high-temperature applications up to 750 degrees F), and ASTM A333 (low-temperature service). The article gives you an overview of these three specifications in terms of typical uses, mechanical and chemical properties, and compares the differences between A53 vs. A106 pipes.


Pipes ASTM A53 black steelA53 pipes convey fluids at low/medium pressures and are also used for mechanical applications. An A53 pipe can be welded, flanged and shaped as necessary, is available in three main types (“F”, i.e. continuous welding/longitudinal furnace butt welded not suited for flanging, “S” seamless hot rolled and cold finished, and “E” ERW).

ASTM A53/ASME SA 53 carbon pipes are available in the size range 1/4 to 30 inches and schedules 10 to 160, both in seamless and welded execution, black and hot-dip galvanized (HDG).


The ASME B36.10 specification covers A53 pipe dimensions (and weights per meter, in kg. and pounds).


There are two ASTM A53 pipes grades, i.e. grade A and B. The two grades feature slight differences in terms of chemical composition (mainly Carbon and Manganese content) and mechanical properties – as shown in the pipe grades charts below:

Maximum values in % Type S
Type E
Type F
(Furnace Weld)
A53 Pipe Grade–> Grade A Grade B Grade A Grade B Grade A
Carbon 0.25 0.3 0.25 0.3 0.3
Manganese 0.95 1.2 0.95 1.2 1.2
Phosphorous 0.05 0.05 0.05 0.05 0.05
Sulfur 0.045 0.045 0.045 0.045 0.045
Copper 0.4 0.4 0.4 0.4 0.4
Nickel 0.4 0.4 0.4 0.4 0.4
Chromium 0.4 0.4 0.4 0.4 0.4
Molybdenum 0.15 0.15 0.15 0.15 0.15
Vanadium 0.08 0.08 0.08 0.08 0.08


Seamless and ERW A53 Grade A A53 Grade B
Tensile Strength, min, psi 48,000 60,000
Yield Strength 30,000 35,000


Density at 20 °C
Modulus of elasticity kN/mm² at Thermal conductivity at 20 
W/m K
Spec. thermal capacity at 20 
J/kg K
Spec. electrical resistivity at 20 °C
Ω mm²/m
20  300 C° 400  450 
7,85 210 192 184 179 51 461 0,20


Hot forming Heat treatment
Temperature °C Type of cooling Normalizing 1) Stress relieving anneal 2) Type of cooling
1100 – 950 Air 890 – 950 °C 600 – 650 °C Air

1)   Normalizing: Holding time 1 minute per mm plate thickness, minimum 30 minutes
2)   Stress relieving anneal: Holding time 1-2 minutes per mm plate thickness, minimum 30 minutes


The tolerances for ASTM A53 – ASME SA53 pipes are:

  • wall thickness: the thickess of the pipe (“WT”) shall be, at any point, not less than the nominal pipe size minus 12.5% (a wt of NPS -13% would not be, for instance, acceptable)
  • weight per foot: + / – 10%


Below are the required physical strength requirements under ASTM A53 Type E for grades A and B.

Test ASTM A53 Grade A ASTM A53  Grade B
Yield  30,000 psi 35,000 psi
Tensile 48,000 psi 60,000 psi
Elongation Determined by formula Determined by formula

In addition to the chemical and physical analysis, the following tests are required under ASTM A53:

Test Test ASTM A53 – ASME SA53
Flattening   Bend Test (Less than or equal to 2.375″ OD) *
Hydrostatic Transverse Weld Tension (Equal to or greater than 8.625″ OD)


  • Pipe schedule below 0.500 inches and schedule STD / XS pipes: plain or beveled ends
  • Pipe schedule above 0.500 inches and schedule XXS: Squared cut plain ends

If pipes are supplied with threaded ends, protection for threads is mandatory for pipes above 4 inches.


Each length of pipe (or bundle for smaller diameters) shall have the following markings applied:

  • Manufacturer name
  • A53 type (S, E, F)
  • Diameter and schedule (from 10 to 160 and XXS)
  • Designation “ASTM A53”
  • Pipe length
  • Heat number

It is frequent to find pipes on the market pipes that comply, at the same time, with multiple standards: A53, A106, API 5L Gr. B. Such compliance is shown as a mark on the pipe itself.


What means galvanized pipe?

Galvanized pipes are steel pipes that have been hot-dipped in a protective zinc coating to prevent corrosion and rust (the process is called “hot dip galvanization”). Galvanized pipes were introduced in the sixties as an alternative to lead pipes for water transmission and distribution. After that, they have been used also for sewerage applications, firefighting, and general plumbing systems.

During the galvanization process, the zinc coating applies both to the outside and the inside of the pipe. The standard zinc coating is between 1.6 and 1.8 oz per square foot.

Galvanized pipes show long-lasting durability, improved resistance to corrosion compared to standard black steel, and are available at a relatively cheap price (and good toughness) compared to alternative metals (the price of galvanized pipe vs copper may be, to give a general indication, 6 times lower per metric ton).

As a rule of thumb, the galvanized price is between 40 and 50% higher than the price of black carbon pipes (the application of a zinc coating requires the transportation of the bare pipe to the galvanization plant, the application of zinc raw material on the pipe and other finishing activities).

On the other side, galvanized pipes are heavy, difficult to repair and tend to develop blockages over the course of time (the internal part of the pipe is subject to corrosion, and it’s not infrequent to find completely rusted galvanized pipes few years after their installation).

ASTM A123, ASTM A153, and ASTM A53

First and foremost, there is a difference between ASTM A53 and ASTM A153. Companies specialized in pipes galvanization are familiar with the ASTM A153 specification (“Standard Specification for Zinc Coating Hot-Dip) on Iron and Steel Hardware”.

The section 17 of the more general ASTM A53 specification, sets requirements for galvanized pipe, i.e. it requires the pipe to be hot-dip galvanized with a zinc grade in accordance with the B6 specification (Standard Specification for Zinc ) and specify the minimum weight per unit area of the coating.
The ASTM A53 specification does not set requirements related to the finishing, the appearance, or the adherence of the galvanized coating that is instead well defined in the ASTM A123 specification (Standard Specification for Zinc, Hot-Dip Galvanized, Coatings on Iron and Steel Product).

Further, the weight per unit area of the coating defined in the ASTM A53 specification corresponds to the minimum coating thickness requirements of ASTM A123. Therefore, the ASTM A123 specification is a more stringent than ASTM A53 with reference to the galvanized coating and whenever a pipe is galvanized according to ASTM A123, it meets the requirements of section 17 of ASTM A53 as well.

Conclusion: when a buyer requires galvanized pipes according to A53, a galvanization process in line with ASTM A123 meets the looser galvanization requirements set by ASTM A53.A


ASTM A106/SA106 pipes are available in size range from 1/2 to 28 inches, and in pipe schedules from 10 to 160 (as per the ASME B36.10 specification). These pipes are available in single random length (17′ – 24′) and in double random length (36′ – 44′).

The ASME B36.10 specification covers the ASTM A106 grade B pipe dimensions (and weights per meter, in kg. and pounds).

ASTM A106 seamless pipe


ASTM A106 pipes are manufactured in grades A, B, and C.

NPS 1-1/2″ and below are available in the hot finished or by cold-drawn type. Pipes of NPS 2 inch and above are generally are hot rolled. ASTM A106 pipes are produced out of killed steel and are suited for high-temperature service (for low temperatures, ASTM A333 pipes should be used instead).

The chemical composition of the three grades of ASTM A106 is shown in the following table:

ASTM A106 – ASME SA106 seamless carbon steel pipe – chemical composition, %
Element C
Mn P
max (3)
max (3)
max (3)
max (3)
max (3)
ASTM A106 Grade A 0.25 (1) 0.27-0.93 0.035 0.035 0.10 0.40 0.40 0.15 0.40 0.08
ASTM A106 Grade B 0.30 (2) 0.29-1.06 0.035 0.035 0.10 0.40 0.40 0.15 0.40 0.08
ASTM A106 Grade C 0.35 (2) 0.29-1.06 0.035 0.035 0.10 0.40 0.40 0.15 0.40 0.08

Download icon
Carbon steel pipe A106 specification.pdf


The manufacturing tolerances of ASTM A106 pipes are shown in the table below:

  • Diameter: see table
  • Wall thickness: the minimum WT of the pipe shall not be, at any point, below the nominal pipe size minus 12.5%
  • Weight: the allowed tolerance in weight shall be within -3.5% and +10% vs. specification. The weight test can be executed on lots for smaller nominal pipe sized (below 4 inches) but must be executed pipe by pipe for higher diameters (6 inch and above).
ASTM A106 Grade B Over Under
inch. mm. inch. mm.
1/8 to 1-1/2 [6 to 40], incl 1/64 (0.015) 0.4 1/64 (0.015) 0.4
Over 1-1/2 to 4 [40 to 100], incl 1/32 (0.031) 0.8 1/32 (0.031) 0.8
Over 4 to 8 [100 to 200], incl 1/16 (0.062) 1.6 1/32 (0.031) 0.8
Over 8 to 18 [200 to 450], incl 3/32 (0.093) 2.4 1/32 (0.031) 0.8
Over 18 to 26 [450 to 650], incl 1/8 (0.125) 3.2 1/32 (0.031) 0.8
Over 26 to 34 [650 to 859], incl 5/32 (0.156) 4 1/32 (0.031) 0.8
Over 34 to 48 [850 to 1200], incl 3/16 (0.187) 4.8 1/32 (0.031) 0.8


ASTM A106 pipe A106 Grade A A106 Grade B A106 Grade C
Tensile Strength, min., psi 48,000 60,000 70,000
Yield Strength, min., psi 30,000 35,000 40,000


NPS On One Length from Each Lot of
Tensile Test 5 and smaller <= 400
6 and larger <= 200
Bending Test 2 and smaller <= 400
Flattening Test 2 through 5 <= 400
6 and over <= 200


The hydro test shall apply a pressure equal to 60% of the minimum yield strength for at least 5 seconds at atmospheric conditions.

The maximum pressure shall not exceed 2500 psi for pipes up to 3 inches, and 2800 for larger sizes. If additional, non-standard, tests are executed, the pipe shall bear an “S” mark on each length or pipe bundle.


Each length of pipe (or bundle for smaller diameters) shall have the following markings applied:

  • Manufacturer name
  • ASTM A106 Grade B (or A, C)
  • Diameter and ANSI schedule (from 10 to 160 and XXS)
  • Pipe length
  • Heat number
  • Hydrostatic test pressure or NDE
  • Weight/foot

We recommend purchasing the ASTM A106 specification from the ASTM website or the IHS store to get a complete understanding of this topic.

A53 PIPE vs. A106

In few words, the main difference between A53 vs. A106 pipes is that A53 pipes are used for low/medium temperature and pressure applications, whereas ASTM A106 pipes are used for higher temperatures-pressures and when seamless execution is mandatory. 

ASTM A53 and A106 pipes are very close in terms of chemical composition and mechanical properties: indeed, it is possible to find pipes on the market that comply with both standards simultaneously (and also with API 5L Grade B).

The key differences between ASTM A53 and A106 pipes are related to the following aspects:

  • Manufacturing process: ASTM A106 steel pipes are available only in seamless execution, whereas ASTM A53 steel pipes are either welded or seamless
  • Covered pressure/temperature range: ASTM A106 pipes withstand higher pressure and temperature ranges than ASTM A53
  • Chemical composition (differences are really minimal).


The chart compares the chemical composition of A53 vs. A106 pipes (grade B). The few differences are related to the chemical elements Mn, P, S, and Si (in red). In particular, Silicon is absent in A53 pipes, whereas it is present in ASTM A106 pipes (silicon gives to the steel alloy better resistance to high temperatures).

Standard Grade Chemical Composition %
C Mn P S Si Cr Cu Ni Mo
ASTM A106 B ≤0.30 0.29-1.06 ≤0.035 ≤0.035 >0.10 ≤0.40 ≤0.40 ≤0.40 ≤0.15 ≤0.08