Fittings Materials: A234, A403, B366

Quick Reference

BW fittings materials: A234 WPB/WPC (high-temp CS, match A106/A53), A420 WPL6 (low-temp CS, match A333), A860 WPHY (high-yield, match API 5L X-grades), A234 WP5/11/22/91 (alloy, match A335), A403 WP304/316 (SS, match A312), A815 S31803/S32750 (duplex/super duplex), B366 (nickel alloys). Always match fitting and pipe grades.

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Need fitting dimension charts? Download the ASME B16.9 Fitting Dimensions or ASME B16.11 Forged Fittings charts.

Buttweld Fittings Materials

What Are BW Fittings Material Specifications

BW fittings material specifications must match or exceed the performance requirements of the piping system. The fitting grade controls how the component handles operating pressure, temperature, and chemical exposure in service.

Carbon steel buttweld fittings dominate pipeline and process piping in oil and gas, power generation, and general industrial service. Stainless steel and higher-grade alloys come into play when the system demands greater temperature resistance, higher pressure capability, or protection against corrosive media (typical of desalination, pharmaceutical, and food-processing applications).

ASTM/ASME Specifications for BW Fittings

The following sections cover the common ASTM/ASME material specifications for buttweld fittings, organized by alloy family and service condition.

Carbon Steel for High-Temperature Service

ASTM A234 WPB and WPC covers wrought carbon steel and alloy steel fittings of seamless and welded construction. These grades serve moderate and high-temperature service conditions. WPB is the workhorse grade for standard carbon steel fittings; WPC carries a higher tensile requirement with tighter chemistry controls.

Carbon Steel for Low-Temperature Service

ASTM A420 WPL6 covers wrought carbon steel and alloy steel fittings of seamless and welded construction for low-temperature service. The WPL6 grade provides reliable toughness at temperatures down to -46 degrees C, backed by mandatory Charpy impact testing.

High Yield Carbon Steel

ASTM A860/MSS SP-75 WPHY 42, WPHY 52, WPHY 60, WPHY 65, and WPHY 70

ASTM A860 (A860M), Standard Specification for Wrought High-Strength Ferritic Steel Butt-Welding Fittings, covers wrought high-strength low-alloy steel butt-welding fittings of seamless and electric fusion-welded construction for high-pressure gas and oil transmission and distribution systems. It includes several grades with minimum yield strengths ranging from 42,000 psi (290 MPa) to 80,000 psi (550 MPa).

Common grades include WPHY 42, WPHY 52, WPHY 60, WPHY 65, and WPHY 70. The “WPHY” prefix stands for “Wrought Pipe High-Yield,” and the number indicates the material’s minimum yield strength in ksi.

MSS-SP:

These Manufacturers Standardization Society (MSS) specifications cover high-strength, wrought, high-yield carbon steel buttwelding fittings. The WPHY prefix stands for “Wrought Pipe High-Yield,” followed by a number indicating the minimum yield strength (in thousands of psi) of the material.

Alloy Steel

ASTM A234 WP1, WP5, WP9, WP11, WP22, and WP91 covers alloy steel fittings for high-temperature service. Each WP grade corresponds to a different alloy composition, providing varying levels of strength, corrosion resistance, and temperature capability.

Stainless Steel

ASTM A403 WP304/L and WP316/L covers wrought austenitic stainless steel fittings for pressure piping applications. The WP304/L grade applies to fittings made from 304 stainless steel, with “L” indicating low carbon content for improved weldability. WP316/L follows the same convention for 316 stainless steel.

Duplex Stainless

ASTM A815 is the primary specification for wrought ferritic, ferritic/austenitic, and martensitic stainless steel piping fittings, including buttweld fittings. Key duplex grades under this specification:

• S31803 (2205): standard duplex grade with a roughly 50/50 austenite-ferrite microstructure. Strong resistance to pitting and crevice corrosion, high mechanical strength, and good weldability.
• S32205: a modified version of S31803 with higher nitrogen content, which improves both corrosion resistance and strength.

Super Duplex Stainless Steel

ASTM A815 also covers super duplex stainless steel buttweld fittings. Common grades:

• S32750 (2507): offers exceptional strength and corrosion resistance through high molybdenum, chromium, and nitrogen content. Suitable for aggressive chloride environments.
• S32760: another super duplex grade with excellent corrosion resistance and toughness, incorporating tungsten and copper for enhanced performance in severe service.

Nickel Alloys

ASTM B366 covers nickel alloy fittings for corrosive environments across a range of temperatures and pressures. Common alloy families include Inconel, Monel, Hastelloy, and Nickel 200/201, each selected where resistance to specific corrosive media and elevated temperatures is the controlling factor.

The key specifications are reviewed in detail (chemical composition and mechanical properties) in the sections below.

European Specifications for BW Fittings

European standards for buttweld fittings set the requirements for dimensions, material grades, mechanical properties, and testing. They align with European manufacturing practices and differ from the ASTM/ASME system used predominantly in North America.

EN (European Norm) Standards for BW Fittings

• EN 10253-1 and EN 10253-2 are the primary European standards for buttweld fittings. EN 10253-1 covers buttwelding pipe fittings made of carbon steel without specific inspection requirements, while EN 10253-2 specifies fittings made of non-alloy and ferritic alloy steels with specific inspection requirements. This standard includes details on type A (reduced load factor) and type B (full load factor) fittings, material grades, mechanical properties, dimensions, and tolerances.
• EN 10253-3 and EN 10253-4 specify the requirements for austenitic and austenitic-ferritic (duplex) stainless steel fittings. EN 10253-3 covers fittings without specific inspection requirements; EN 10253-4 covers fittings with specific inspection requirements.

Material Grades

European standards designate material grades by chemical composition and mechanical properties. Common examples:

• P235GH and P265GH: carbon steel grades for moderate to high-temperature applications.
• 16Mo3, 13CrMo4-5, 10CrMo9-10: alloy steels for higher temperature and pressure service.
• 1.4307, 1.4404 (equivalent to SS 304L and 316L): stainless steels for corrosion-resistant applications.
• 1.4462 (equivalent to S31803/S32205): duplex stainless steel for applications requiring high strength and corrosion resistance.

Dimensions and Tolerances

EN standards provide detailed dimensions and tolerances for buttweld fittings, ensuring compatibility and interchangeability across European-manufactured piping components. These specifications span a range of sizes and pressure ratings.

Testing and Certification

European specifications require buttweld fittings to undergo dimensional checks, mechanical testing, and non-destructive testing (NDT). Fittings used in pressure service must also meet the Pressure Equipment Directive (PED), which imposes additional testing and certification requirements.

European standards for buttweld fittings harmonize manufacturing, testing, and application of piping components across the EU, maintaining consistent quality, reliability, and safety in industrial piping systems.

Match Pipe & BW Fittings Materials

It’s key to understand that the material composition of both the pipe and the buttweld fitting must be compatible; for instance, an ASTM A106 Gr. B pipe should be coupled with an ASTM A234 WPB buttweld fitting, while an ASTM A312 T304 pipe needs to be joined to an ASTM A403 WP304 fitting, etc.

Mixing materials between pipes and buttweld fittings is neither allowed nor safe. Similarly, the size of the buttweld fitting must correspond exactly to the size of the pipe it connects to.

Pro Tip

When ordering fittings to match API 5L X-grade pipe, specify ASTM A860 WPHY fittings - not A234 WPB. Standard A234 WPB has lower yield strength than X52 or higher pipe grades, creating a weak point at every fitting. The “Y” in WPHY means it’s yield-matched to the pipe.

This basic rule applies to both ASTM/ASME BW pipe fittings and their EN (European) equivalents.

In the piping materials compatibility table, also called the “piping materials matching table”, we present the precise correlation in material grades between pipes, fittings, flanges, and other components used in piping systems.

BW Fittings Material Selection

Selecting the right BW fitting material requires evaluating three factors together:

Factor	What to Verify
Temperature and pressure ratings	The material must handle the full range of operating and design pressures and temperatures without creep or embrittlement.
Corrosion resistance	The alloy must resist the specific corrosive agents in the process fluid and the external environment.
Material compatibility	Fitting and pipe grades must match to prevent galvanic corrosion and maintain a mechanically sound joint.

Meeting these material specifications keeps buttweld fittings performing reliably through the full service life of the piping system.

Chemical and Mechanical Properties of ASTM/ASME Fittings

High-Temp Carbon/Alloy Steel BW Fittings (ASTM A234)

ASTM A234 carbon steel buttweld fittings serve moderate and high-temperature pressure piping systems. This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction, primarily used in industrial pipelines carrying oil, gas, steam, water, and air under elevated temperature and pressure conditions.

The ASTM A234 specification covers carbon steel and alloy steel pipe fittings (butt weld) for high-temperature service (carbon steel and alloy steel):

• ASTM A234 WPA, WPC and, WPC fittings match ASTM A53, ASTM A106 and, API 5L Gr. B pipes.
• ASTM A234 WP1 to WP91 specifies butt weld fittings for ASTM A335 chrome-moly pipes (low-alloy steel).
• ASTM A420 WPL covers low-temperature carbon steel butt weld fittings to match ASTM A333 Gr.3 and ASTM A333 Gr. 6 pipes.
• ASTM A860 specification (WPHY42, WPHY52, WPHY56, WPHY60) covers high-yield wrought carbon steel fittings that match high-yield API 5L Gr. X42, X52, X56, X60 pipes.

ASTM A234 Chemical Composition

Chemical composition of ASTM A234 Carbon and Alloy Steel Fittings

Grade	C	Mn	P max	S max	Si	Cr	Mo	Ni	Cu	Others
WPB(1,2,3,4,5)	0.30max	0.29-1.06	0.050	0.058	0.10min	0.40max	0.15max	0.40max	0.40max	V 0.08max
WPC(2,3,4,5)	0.35max	0.29-1.06	0.050	0.058	0.10min	0.40max	0.15max	0.40max	0.40max	V 0.08max
WP1	0.28max	0.30-0.90	0.045	0.045	0.10-0.50		0.44-0.65
WP12 CL1	0.05-0.20	0.30-0.80	0.045	0.045	0.60max	0.80-1.25	0.44-0.65
WP12 CL2	0.05-0.20	0.30-0.80	0.045	0.045	0.60max	0.80-1.25	0.44-0.65
WP11 CL1	0.05-0.15	0.30-0.60	0.030	0.030	0.50-1.00	1.00-1.50	0.44-0.65
WP11 CL2	0.05-0.20	0.30-0.80	0.040	0.040	0.50-1.00	1.00-1.50	0.44-0.65
WP11 CL3	0.05-0.20	0.30-0.80	0.040	0.040	0.50-1.00	1.00-1.50	0.44-0.65
WP22 CL1	0.05-0.15	0.30-0.60	0.040	0.040	0.50max	1.90-2.60	0.87-1.13
WP22 CL3	0.05-0.15	0.30-0.60	0.040	0.040	0.50max	1.90-2.60	0.87-1.13
WP5 CL1	0.15max	0.30-0.60	0.040	0.030	0.50max	4.0-6.0	0.44-0.65
WP5 CL3	0.15max	0.30-0.60	0.040	0.030	0.50max	4.0-6.0	0.44-0.65
WP9 CL1	0.15max	0.30-0.60	0.030	0.030	1.00max	8.0-10.0	0.90-1.10
WP9 CL3	0.15max	0.30-0.60	0.030	0.030	1.00max	8.0-10.0	0.90-1.10
WPR	0.20max	0.40-1.06	0.045	0.050				1.60-2.24	0.75-1.25
WP91	0.08-0.12	0.30-0.60	0.020	0.010	0.20-0.50	8.0-9.5	0.85-1.05	0.40max		V 0.18- 0.25Nb 0.06-0.10N 0.03-0.07Al 0.02 max(6)Ti 0.01 max(6)Zr 0.01 max(6)
WP911	0.09-0.13	0.30-0.60	0.020	0.010	0.10-0.50	8.0-9.5	0.90-1.10	0.40max		V 0.18-0.25Nb 0.060-0.10N 0.04-0.09Al 0.02 max(6)B 0.0003-0.006W 0.90-1.10Ti 0.01 max(6)Zr 0.01 max(6)

Notes:

• Fittings from bar or plate 0.35 max carbon.
• Fittings from forgings 0.35 max Carbon and 0.35 max Silicon with no minimum.
• For each reduction of 0.01% below the specified Carbon maximum, an increase of 0.06% Manganese above the specified maximum is permitted, up to a maximum of 1.35%.
• The sum of Cu, Ni, Niobium, and Moly shall not exceed 1.00%.
• The sum of Niobium and Moly shall not exceed 0.32%.
• This applies to heat and product analyses

ASTM A234 Mechanical Properties

Tensile and Yield Strength ASTM A234 for Carbon and Alloy Steel Fittings

Property	WPB	WPC, WP11-CL2	WP11-CL1, WP22-CL1, WP5-CL1, WP9-CL1	WP11-CL3, WP22-CL3, WP5-CL3, WP9-CL3	WP91
Tensile strength, minimum unless a range is given ksi (MPa)	60 (415)	70 (485)	60 (415)	75 (520)	90 (620)
Yield strength, min ksi (MPa) (0.2% offset or 0.5% extension under-load)	35 (240)	40 (275)	30 (205)	45 (310)	60 (415)

Elongation ASTM A234 for Carbon and Alloy Steel Fittings

Specimen Type	WPB, WPC, WP11, WP22 Longitud.	WPB, WPC, WP11, WP22 Transverse	WP91 Longitud.	WP91 Transverse
Standard round specimen, or small proportional specimen, min % in 4 D	22	14	20	13
Rectangular specimen for wall thickness 5/16″ and over, and for all small sizes tested in full section; min % in 2 in.	30	20	-	-
Rectangular specimen for wall thickness less than 5/16″; min % in 2 in (1/2″ wide specimen)	see note	-	-	-

Note: For each 0.79 mm decrease in wall thickness below 7.94 mm, a deduction of 1.5 % for longitudinal and 1.0 % for transverse from standard values is permitted

Low-Temp Carbon/Alloy Steel BW Fittings (ASTM A420)

ASTM A420 covers wrought carbon steel and alloy steel buttweld fittings of seamless and welded construction for low-temperature pressure piping and pressure vessel service. These fittings must demonstrate adequate toughness and fracture resistance at sub-zero operating temperatures, verified through mandatory Charpy V-notch impact testing.

ASTM A420 Chemical Composition

Chemical Composition of ASTM A420

Elements	WPL6, %	WPL9, %	WPL3, %	WPL8, %
Carbon [C]	≤0.30	≤0.20	≤0.20	≤0.13
Manganese [Mn]	0.50-1.35	0.40-1.06	0.31-0.64	≤0.90
Phosphorus [P]	≤0.035	≤0.030	≤0.05	≤0.030
Sulfur [S]	≤0.040	≤0.030	≤0.05	≤0.030
Silicon [Si]	0.15-0.40	…	0.13-0.37	0.13-0.37
Nickel [Ni]	≤0.40	1.60-2.24	3.2-3.8	8.4-9.6
Chromium [Cr]	≤0.30	…	…	…
Molybdenum [Mo]	≤0.12	…	…	…
Copper [Cu]	≤0.40	0.75-1.25	…	…
Columbium [Cb]	≤0.02	…	…	…
Vanadium[V]	≤0.08	…	…	…

ASTM A420 Mechanical Properties

Grade	Tensile Strength ksi	Tensile Strength MPa	Yield Strength ksi	Yield Strength MPa	Elongation Longitudinal %	Elongation Transverse %
WPL6	65-95	415-655	35	240	22	12
WPL9	63-88	435-610	46	315	20	-
WPL3	65-90	450-620	35	240	22	14
WPL8	100-125	690-865	75	515	16	-

ASTM A420 Impact Test Properties

Charpy Impact Requirements for WPL6, WPL9, and WPL3

Size of Specimen (mm)	A* ft·lbf	A* J	B* ft·lbf	B* J
10 by 10.0	13	17.6	10	13.6
10 by 7.5	10	13.6	8	10.8
10 by 5.0	7	9.5	5	7.0
10 by 2.5	4	5.4	3	4.1

A* Charpy V-Notch Impact Value Required for Acceptance (Average of Three Specimens) B* Minimum Charpy V-Notch Impact Value Without Requiring Retest (One Specimen Only of a Set)

Charpy Impact Requirements for WPL8

Size of Specimen (mm)	A* ft·lbf	A* J	B* ft·lbf	B* J
10 by 10.0	25.0	33.9	20.0	27.1
10 by 7.5	21.0	28.5	17.0	23.1
10 by 5.0	17.0	23.1	14.0	19.0
10 by 2.5	8.0	10.8	6.0	8.1

A* Charpy V-Notch Impact Value Required for Acceptance (Average of Three Specimens) B* Minimum Charpy V-Notch Impact Value Without Requiring Retest (One Specimen Only of a Set)

Impact Test Temperature

Grade	°F [°C]
WPL6	−50 [−45]
WPL9	−100 [−75]
WPL3	−150 [−100]
WPL8	−320 [−195]

High-Yield Carbon/Alloy Steel BW Fittings (ASTM A860)

ASTM A860 covers wrought high-strength ferritic steel butt-welding fittings of seamless and electric fusion-welded construction. These fittings are purpose-built for high-pressure gas and oil transmission and distribution pipelines, where the pipe grade demands yield-matched fittings.

When selecting ASTM A860 fittings, three factors govern the specification:

Factor	Requirement
Matching pipe material	The fitting grade must be compatible with the high-strength pipe grade to handle the full range of design pressures and loads.
Charpy V-notch impact testing	A860 fittings undergo mandatory impact testing to verify toughness, which is critical for low-temperature environments or sour service.
Chemical compatibility	The fitting alloy must be compatible with the transported fluid to prevent corrosion or degradation that could compromise pipeline integrity.

ASTM A860 Chemical Composition

The Chemical Composition of ASTM A860, %

Element	Value
Carbon	≤0.20*A
Manganese	1.00-1.45
Phosphorus	≤0.030
Sulfur	≤0.010
Silicon	0.15-0.40*B
Nickel	≤0.50*C
Chromium	≤0.30*C
Molybdenum	≤0.25*C
Copper	≤0.35*C
Titanium	≤0.05
Vanadium	≤0.10
Columbium	≤0.04
Vanadium plus Columbium	≤0.12
Aluminum	≤0.06

*A The carbon equivalent C.E.=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 shall not exceed 0.42%. *B If vacuum carbon deoxidation is used, silicon shall not exceed 0.10% by heat analysis and 0.12% by-product analysis. *C The sum of Ni+Cr+Mo+Cu shall not exceed 1.0%.

ASTM A860 Mechanical Properties

Grade	Yield Strength ksi	Yield Strength MPa	Tensile Strength ksi	Tensile Strength MPa	Elongation %	Cv ft*lbs (avg/min)	Cv J (avg/min)
WPHY 42	42	290	60-85	415-585	25	30/25	40/34
WPHY 46	46	315	63-88	435-605	25	30/25	40/34
WPHY 52	52	360	66-91	455-625	25	30/25	40/34
WPHY 60	60	415	75-100	515-690	20	30/25	40/34
WPHY 65	65	450	77-102	530-705	20	30/25	40/34
WPHY 70	70	485	80-105	550-725	20	30/25	40/34

*1. The actual yield strength shall not exceed the specified minimum by more than 15 ksi [105 MPa]. *2. The elongation values shall be measured based on the standard round specimens, or small-size proportional specimens, in 4D. *3. The size of Charpy V-notch specimens shall be 10×10 mm while the impact-test temperature shall be −50°F[−46°C]. *4. All fittings of ASTM A860 shall have a maximum hardness of 22 HRC(235 HBW).

Stainless Steel BW Fittings (ASTM A403)

ASTM A403 covers wrought austenitic stainless steel buttweld fittings of seamless and welded construction for pressure piping. These fittings handle moderate and high-temperature service where corrosion resistance is a primary requirement.

The ASTM A403 specification covers austenitic stainless steel butt weld fittings to match ASTM A312 TP304, TP316, TP321, etc., pipes.

ASTM A403 Chemical Composition

Grade	UNS	C	Mn	P	S	Si	Ni	Cr	Mo	Ti	N	Others
WPXM-19	S20910	0.06	4.0-6.0	0.045	0.03	1	11.5-13.5	20.5-23.5	1.50-3.0		0.20-0.40
WP304	S30400	0.08	2	0.045	0.03	1	8.0-11.0	18.0-20.0
WP304L	S30403	0.030(4)	2	0.045	0.03	1	8.0-12.0	18.0-20.0
WP304H	S30409	0.04-0.10	2	0.045	0.03	1	8.0-11.0	18.0-20.0
WP304N	S30451	0.08	2	0.045	0.03	1	8.0-11.0	18.0-20.0			0.10-0.16
WP304LN	S30453	0.03	2	0.045	0.03	1	8.0-11.0	18.0-20.0			0.10-0.16
WP309	S30900	0.2	2	0.045	0.03	1	12.0-15.0	22.0-24.0
WP310S	S31008	0.08	2	0.045	0.03	1	19.0-22.0	24.0-26.0
WPS31254	S31254	0.02	1	0.03	0.01	0.8	17.5-18.5	19.5-20.5	6.0-6.5		0.18-0.22	Cu 0.50-1.0
WP316	S31600	0.08	2	0.045	0.03	1	10.0-14.0	16.0-18.0	2.0-3.0
WP316L	S31603	0.030(4)(5)	2	0.045	0.03	1	10.0-14.0	16.0-18.0	2.0-3.0
WP316H	S31609	0.04-0.10	2	0.045	0.03	1	10.0-14.0	16.0-18.0	2.0-3.0		0.10-0.16
WP316N	S31651	0.08	2	0.045	0.03	1	10.0-13.0	16.0-18.0	2.0-3.0		0.10-0.16
WP316LN	S31653	0.03	2	0.045	0.03	1	10.0-13.0	16.0-18.0	2.0-3.0		0.10-0.16
WP317	S31700	0.08	2	0.045	0.03	1	11.0-15.0	18.0-20.0	3.0-4.0
WP317L	S31703	0.03	2	0.045	0.03	1	11.0-15.0	18.0-20.0	3.0-4.0
WPS31725	S31725	0.03	2	0.045	0.03	1	13.5-17.5	18.0-20.0	4.0-5.0		0.2
WPS31726	S31726	0.03	2	0.045	0.03	1	13.5-17.5	17.0-20.0	4.0-5.0		0.10-0.20
WPS31727	S31727	0.03	1	0.03	0.03	1	14.5-16.5	17.5-19.0	3.8-4.5		0.15-0.21	Cu 2.8-4.0
WPS32053	S32053	0.03	1	0.03	0.01	1	24.0-26.0	22.0-24.0	5.0-6.0		0.17-0.22
WP321	S32100	0.08	2	0.045	0.03	1	9.0-12.0	17.0-19.0		(6)
WP321H	S32109	0.04-0.10	2	0.045	0.03	1	9.0-12.0	17.0-19.0		(7)
WPS33228	S33228	0.04-0.08	1	0.02	0.015	0.3	31.0-33.0	26.0-28.0				Ce 0.05-0.10, Al 0.025, Nb 0.6-0.10
WPS34565	S34565	0.03	5.0-7.0	0.03	0.01	1	16.0-18.0	23.0-25.0	4.0-5.0		0.40-0.60	Nb 0.10
WP347	S34700	0.08	2	0.045	0.03	1	9.0-12.0	17.0-19.0
WP347H	S34709	0.04-0.10	2	0.045	0.03	1	9.0-12.0	17.0-19.0
WP348	S34800	0.08	2	0.045	0.03	1	9.0-12.0	17.0-19.0				Nb+Ta 10x(C)-1.10, Ta 0.10, Co 0.20
WP348H	S34809	0.04-0.10	2	0.045	0.03	1	9.0-12.0	17.0-19.0				Nb+Ta 8x(C)-1.10, Ta 0.10, Co 0.20
WPS38815	S38815	0.03	2	0.04	0.02	5.5-6.5	13.0-17.0	13.0-15.0	0.75-1.50			Cu 0.75-1.50, Al 0.30

Notes:

• Maximum, if not otherwise indicated.
• The method of analysis for Nitrogen is agreed between the purchaser and manufacturer.
• Niobium 0.10-0.30%; Vanadium, 0.10-0.30%.
• For small diameter or thin walls, a Carbon maximum of 0.040% is mandatory in grades TP304L and TP316L. Small outside diameter tubes are those less than 0.50 in. [12.7 mm] 5) in outside diameter and light wall tubes as those less than 0.049 in. [1.24 mm] in average wall thickness.
• On pierced tubing, the Nickel may be 11.0-16.0%.
• 5 X (C+N2)-0.70.
• 4 X (C+N2) -0.70.
• The Niobium % shall be ten times above the Carbon content and not more than 1.10%.
• The Niobium % shall be eight times above the Carbon content and not more than 1.10%.

ASTM A403 Mechanical Properties

Tensile and Elongation Requirements ASTM A403

Property	WP304, WP316	WP304L, WP316L
Yield Strength, min, ksi [MPa]	30 [205]	25 [170]
Tensile Strength, min, ksi [MPa]	75 [515]	70 [485]
Elongation Longitudinal (%)	28	28
Elongation Transverse (%)	20	20

Duplex/ Super Duplex BW Fittings (ASTM A815)

ASTM A815 duplex steel buttweld fittings combine the properties of austenitic (300 series) and ferritic (400 series) stainless steels. The result is a material with high resistance to pitting and crevice corrosion, plus greater tensile and yield strength than standard austenitic stainless steel.

The ASTM A815 specification covers duplex and super duplex butt weld fittings to match ASTM A790 and ASTM A928 pipes. These grades serve chemical processing, piping, oilfield systems, heat exchangers, and flue gas desulfurization.

Duplex stainless steel has the following advantages over Series 300 standard SS: **

• Good general corrosion resistance and high strength
• Higher resistance to chloride stress corrosion cracking
• Resistance to chloride pitting and crevice corrosion
• Good sulfide stress corrosion resistance
• Easy to weld and conform

UNS S31803, UNS S32205 Chemical Composition (Duplex)

Grade	C	Mn	Si	P	S	Cr	Mo	Ni	N	Fe
S31803	0.030 max	2.00 max	1.00 max	0.030 max	0.020 max	22.0 - 23.0	3.0 - 3.5	4.50 - 6.50	0.14 - 0.20	63.72 min
S32205	0.030 max	2.00 max	1.00 max	0.030 max	0.020 max	21.0 - 23.0	2.50 - 3.50	4.50 - 6.50	0.8 - 0.20	63.54 min

UNS S31803, UNS S32205 Mechanical Properties (Duplex)

Grades	Density (g/cm 3)	Density (lb/in 3)	Melting Point (°C)	Melting Point (°F)
S31803 / S32205	7.805	0.285	1420 - 1465	2588 - 2669

UNS S32750, UNS S32760 Chemical Composition (Super Duplex)

Grade	C	Mn	Si	P	S	Cr	Mo	Ni	N	Fe
S 32750	0.030 max	1.20 max	0.80 max	0.035 max	0.020 max	24.00 - 26.00	3.00 - 5.00	6.00 - 8.00	0.24 - 0.32	58.095 min
S 32760	0.05 max	1.00 max	1.00 max	0.030 max	0.010 max	24.00 - 26.00	3.00 - 4.00	6.00 - 8.00	0.20 - 0.30	57.61 min

UNS S32750, UNS S32760 Mechanical Properties (Super Duplex)

Grades	Density (g/cm 3)	Density (lb/in 3)	Melting Point (°C)	Melting Point (°F)
S32750 / S32760	7.8	0.281	1350	2460

Nickel Alloy BW Fittings (ASTM B366)

ASTM B366 nickel alloy buttweld fittings serve applications that demand high corrosion resistance, strength at elevated temperatures, and in some cases, specific magnetic or thermal expansion characteristics. These fittings handle the most severe operational environments across oil and gas, chemical processing, and power generation.

The ASTM B366/SB 366 specification covers high-alloy (super-alloy) buttweld fittings including Inconel, Incoloy, Hastelloy, Monel, and others listed in the grades table. The MSS-SP 43 specification covers the dimensions and tolerances of nickel alloy buttweld fittings.

Nickel-Alloy Buttweld Fittings Grades

Name	UNS	DIN	Matching Pipe Grade	Equivalent Forged Grade
904L	N08904	1.4539	B677/B673	B649
Alloy 020	N08020	2.466	B729/B464	B462
Alloy 230	N06230	-	B622/B619	B564
Alloy 400 (Monel)	N04400	2.436	B165/B725	B564
Alloy 59	N06059	2.4605	B622/B619	B564
Alloy 600 (Inconel)	N06600	2.4816	B167/B517	B564
Alloy 625 (Inconel)	N06625	2.4856	B444/B705	B564
Alloy 800 (Incoloy)	N08800	1.4558	B407/B514	B564
Alloy 800H (Incoloy)	N08810	1.4958	B407/B514	B564
Alloy 800HT (Incoloy)	N08811	1.4959	B407	B564
Alloy 825 (Incoloy)	N08825	2.4858	B423/B705	B564
Alloy B	N10001	-	B622/B619	-
Alloy B2 (Hastelloy)	N10665	2.4617	B622/B619	-
Alloy B3 (Hastelloy)	N10675	-	B622/B619	B564
Alloy C22 (Hastelloy)	N06022	2.4602	B622/B619	B564
Alloy C276 (Hastelloy)	N10276	2.4819	B622/B619	B564
Alloy C4	N06455	2.461	B622/B619	-
Alloy G-3	N06985	2.4619	B622/B619	-
Alloy G30	N06030	-	B622/B619	-
Alloy K500 (Monel)	N05500	2.4375	-	B865
Nickel 200	N02200	2.4066	B161/B725	B564
Nickel 201	N02201	2.4068	B161/B725	-

Nickel-Alloy Buttweld Fittings Chemical Composition

Grade	Fe	C	Ni	Cr	Mo	Co	Cu	Mn	S	Si	W	V	P	Al	Ti
Nickel 200	.40 max	.15 max	99.0 min				.25 max	.35 max	.01 max	.35 max
Nickel 201	.40 max	.02 max	99.0 min				.25 max	.35 max	.01 max	.35 max
Hastelloy C276	4.0-7.0	.01 max	Remainder	14.5-16.5	15.0-17.0	2.5 max		1.0 max	.03 max	.08 max	3.0-4.5	.35 max	.04 max
Inconel 600	6.0-10.0	.15 max	72.0 min*	14.0-17.0			.50 max	1.00 max	.015 max	.50 max
Inconel 601	14	0.05	61.5	22.5				0.3		0.2				1.4
Inconel 625	5.0 max	.10 max	Remainder	20.00-30.00	8.0-10.0	1.0 max**		.50 max	.015 max	.50 max			.015 max	.40 max	.40 max
Inconel 718	Remainder	.08 max	50.00-55.00	17.00-21.00	2.80-3.30	1.00 max	.30 max	.35 max	.015 max	.35 max			.015 max	.20-.80	.65-1.15
Incoloy 800	39.5 min	.10 max	30.0-35.0	19.0-23.0										.15-.60	.15-.60
Incoloy 800H	39.5 min	.05-.10	30.0-35.0	19.0-23.0										.15-.60	.15-.60
Incoloy 800HT	39.5 min	.06-.10	30.0-35.0	19.0-23.0										.25-.60	.25-.60
Incoloy 825	22.0 min	0.05 max	38.0-46.0	19.5-23.5			1.5-3.0	1.0 max	0.03 max	0.5 max				0.2 max	.6-1.2
Alloy 20	Balance	.07max	32.00-38.00	19.0-21.0	2.0-3.0		3.0-4.0	2.0max	.035max	1.0max			.045max
Monel K500	2.0 max	.25 max	63.0-70.0				Remainder	1.5 max	.01 max	.50 max				2.30-3.15	.35-.85

Typical Applications for Nickel Alloy Materials (Oil & Gas)

Nickel Alloy	Typical Application Area in Oil & Gas Engineering
Nickel 200/201	Marine and offshore engineering; Caustic handling equipment; Manufacture and handling of sodium hydroxide; Reactors and vessels where fluorine reacts with hydrocarbons
Hastelloy C-276	Pollution control stack liners, ducts, dampers, scrubbers, stack-gas reheaters, fans, and fan housings; Flue gas desulfurization systems; Chemical processing components like heat exchangers, reaction vessels, evaporators, and transfer piping; Sour gas wells
Monel K500	Sour-gas service applications; Oil and gas production safety lifts and valves; Oil well tools and instruments like drill collars; Oil well industry; Chains, cables, springs, valve trim, fasteners for marine service
Monel 400	Marine engineering; Chemical and hydrocarbon processing equipment; Gasoline and freshwater tanks; Crude petroleum stills; De-aerating heaters; Boiler feed water heaters and other heat exchangers; Valves, pumps, shafts, fittings, and fasteners; Industrial heat exchangers; Chlorinated solvents; Crude oil distillation towers
Incoloy 800H/HT	Ethylene furnace quench boilers; Hydrocarbon cracking; Valves, fittings, and other components exposed to corrosive attack from 1100-1800° F; Industrial furnaces; Heat-treating equipment; Chemical and petrochemical processing; Super-heaters and re-heaters in power plants; Pressure vessels; Heat exchangers
Incoloy 825	Chemical Processing; Pollution-control; Oil and gas well piping; Nuclear fuel reprocessing; Components in Pickling equipment like heating coils, tanks, baskets, and chains; Acid production
Inconel 600	Chemical industry; Heat treating industry; Nuclear Engineering; Gas turbine components
Inconel 601	Chemical Processing; Aerospace; Heat treating industry; Power generation; Heat-treating muffles and retorts; Radiant tubes; Catalyst support grids in nitric acid production; Steam superheater tube supports
Inconel 625	Specialized seawater equipment; Chemical process equipment
Inconel 718	Chemical processing; Pollution-control equipment; Nuclear reactors; Cryogenic storage tanks; Valves, fasteners, springs, mandrels, tubing hangers; Wellhead completion equipment and blow out preventers (BOPS)

Coated, Lined and Clad BW Fittings

Coated, lined, and clad buttweld (BW) fittings extend the life of piping systems by adding corrosion-resistant barriers to standard carbon steel fitting bodies. Each approach addresses a different set of service conditions, and the right choice depends on the medium being transported, the operating environment, and the required design life.

Coated Buttweld Fittings

Coated fittings have a protective layer applied to their exterior and/or interior surfaces. Common coatings include epoxy, zinc, and polyethylene. The coating prevents corrosion from soil contact, atmospheric exposure, or mildly aggressive process fluids. Coated fittings are typical in buried pipelines, water transmission systems, and applications where external protection is the primary concern.

Lined Buttweld Fittings

Lined fittings have an inner lining of a chemically resistant material (typically PTFE, PFA, or rubber) bonded inside the metal shell. The lining acts as a barrier between the process fluid and the carbon steel body. These fittings are common in chemical processing, pharmaceutical manufacturing, and food processing where the fluid would rapidly attack unprotected steel.

Clad Buttweld Fittings (CRA)

Clad fittings bond a layer of corrosion-resistant alloy (CRA) to a carbon steel base metal through welding or metallurgical bonding. This construction delivers the mechanical strength of carbon steel with the full corrosion resistance of the cladding material (typically stainless steel, Inconel, or Hastelloy). Clad fittings serve severe corrosive environments such as offshore oil and gas production, petrochemical plants, and desalination facilities where the entire wetted surface must resist aggressive media.

Considerations

Consideration	Details
Selection criteria	The choice between coated, lined, or clad fittings depends on the transported medium, environmental conditions, and the target service life.
Cost-effectiveness	Higher upfront cost compared to bare fittings, but the extended lifespan and reduced maintenance make these options more economical over the full project life cycle.
Compatibility	The coating, lining, or cladding material must be chemically compatible with the process fluid to prevent degradation and maintain system integrity.

Coated, lined, and clad buttweld fittings provide targeted protection against corrosion, abrasion, and chemical attack, extending the durability and reliability of piping systems in demanding service conditions.

European Vs. ASTM/ASME BW Fittings

The table shows the equivalent ASTM and European pipe fittings materials grades.

Carbon Steel Fittings Materials

Werkstoff Number	European Grade	ASTM Grade
1.0254 St 37.0	S235	-
1.0305 St 35.8/I	P235GH (1.0345)	A 234 Grade WPA
1.0305 St 35.8/III	P235GH (1.0345)	-
1.0405 St 45.8/I	P265GH (1.0425)	A 234 Grade WPB
1.0405 St 45.8/III	P265GH (1.0425)	-

Alloy Steel Fittings Materials

Werkstoff Number	European Grade	ASTM Grade
1.5415 15 Mo 3	16Mo3	A 234 Grade WP1
1.7335 13 CrMo 4 4	13CrMo4-5	A 234 Grade WP11, WP12
1.7380 10 CrMo 9 10	10CrMo9-10	A 234 Grade WP22
1.7362 12 CrMo 19 5	X11CrMo5	A 234 Grade WP5
-	-	A 234 Grade WP9
1.4903	X10CrMoVNb9-1	A 234 Grade WP91

Low-Temperature Carbon Steel Fittings Materials

Werkstoff Number	European Grade	ASTM Grade
1.5637 10 Ni 14	12Ni14	A 420 Grade WPL3
1.0356 TTSt 35 N	P215NL (1.0451)	-
1.0356 TTSt 35 V	-	-
-	-	A 420 Grade WPL6

High-Yield Carbon Steel Fittings Materials

Werkstoff Number	European Grade	ASTM Grade
1.0486 StE 285	-	A860 Grade WPHY42
1.0562 StE 355	P355N	A860 Grade WPHY52
1.8902 StE 420	-	A860 Grade WPHY60
1.8905 StE 460	-	A860 Grade WPHY70
1.0457 StE 240.7	-	-
1.0484 StE 290.7	L290NB	A860 Grade WPHY42
1.0582 StE 360.7	L360NB	A860 Grade WPHY52
1.8972 StE 415.7	L415NB	A860 Grade WPHY60

Stainless Steel Fittings Materials

Werkstoff Number	European Grade	ASTM Grade
1.4541 X 6 CrNiTi 18 10	X6CrNiTi18-10	A 403 Grade WP321
1.4571 X 6 CrNiMoTi 17 12 2	X6CrNiMoTi17-12-2	A 403 Grade WP316Ti
1.4301 X 5 CrNi 18 10	X5CrNi18-10	A 403 Grade WP304
1.4306 X 2 CrNi 19 11	X2CrNi19-11	A 403 Grade WP304L
1.4307	X2CrNi18-9	A 403 Grade WP304L
1.4401 X 5 CrNiMo 17 12 2	X5CrNiMo17-12-2	A 403 Grade WP316
1.4404 X 2 CrNiMo 17 13 2	X2CrNiMo17-12-2	A 403 Grade WP316L
1.4462 X 2 CrNiMoN 22 5 3	X2CrNiMoN22-5-3	UNS S 31803 (Duplex)
1.4529 X 1 NiCrMoCuN 25 20 6	X1NiCrMoCuN25-20-7	UNS N 08926
1.4539 X 1 NiCrMoCuN 25 20 5	X1NiCrMoCu25-20-5	UNS N 08904 (904L)
1.4547	X1CrNiMoCuN20-18-7	UNS S 31254

Common Mistake

Specifying A234 WPB fittings for low-temperature service (below -29°C/-20°F). Standard WPB has no impact test requirement and can become brittle at low temperatures. For cryogenic or cold-climate applications, specify A420 WPL6 fittings which are impact tested at -46°C.

Field Note

When receiving stainless steel fittings, verify the heat number on each piece matches the MTC - especially for 304L vs 304H or 316L vs 316H. The “L” (low carbon) and “H” (high carbon) grades look identical but have different welding requirements and service limitations. A mixed batch can cause sensitization failures in service.

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