SMO 254 Weld Neck Flange Order From China

On February 11, 2025, an old customer of our company sent us an inquiry for SMO 254 weld neck flange. After the quotation was completed, the customer placed an order with us on the same day.

ZIZI is a company specializing in the production and processing of pipes and fittings. The pipes and pipe fittings we produce are mainly used in chemical, petroleum, natural gas, water conservancy, electric power, marine engineering and other fields. The products mainly include seamless pipes, welded pipes, butt-welding pipe fittings, high-pressure forged pipe fittings and flanges of various sizes. The materials include carbon steel, stainless steel, alloy steel, low-temperature steel, duplex steel, base alloy, etc.

Inspection of SMO254 Weld Neck Flange

1. Material Verification

Chemical composition (should have high molybdenum (~6%) and nitrogen content).

Mechanical properties: tensile strength, yield strength, elongation, hardness.

PMI (Positive Material Identification):

Handheld XRF gun or optical emission spectrometer to verify alloy composition.

2. Dimensional Inspection

Based on ASME B16.5 or project drawing:

Outer and inner diameters

Flange thickness

Raised face height

Bolt hole size, number, and pitch circle diameter (PCD)

Neck bore and length

Bevel preparation (weld prep)

 

SMO254 Weld Neck Flange Specification

A SMO 254 weld neck flange is a high-performance flange made from SMO 254 (UNS S31254)—a super austenitic stainless steel known for its exceptional corrosion resistance, especially in chloride-rich and marine environments.

SMO 254 stainless steel (also known as Alloy 254 SMO) is a highly corrosion-resistant, super-austenitic stainless steel designed for use in aggressive environments. It is known for its excellent resistance to pitting, crevice corrosion, and stress corrosion cracking, particularly in environments with chlorides and other corrosive substances.

Dimensions	ANSI/ASME B16.5
Standard	ANSI Flanges, ASME Flanges,
Size	1/8″ NB TO 24″ NB
Class / Pressure	150#, 300#, 600#, 900#, 1500#, 2500#, PN6, PN10, PN16, PN25, PN40, PN64 etc.
Flange Face Type	Flate Face (FF), Raised Face (RF), Ring Type Joint (RTJ)
Grade	ASTM A182 Gr F44 UNS S31254

✅ Key Properties of SMO 254 (UNS S31254):

Very high molybdenum (6%) and nitrogen content

PREN (Pitting Resistance Equivalent Number) > 42 (excellent resistance to pitting & crevice corrosion)

High mechanical strength

Excellent resistance to chloride stress corrosion cracking (SCC)

Designed for aggressive environments where 316L or duplex steel would fail

 

ASTM A182 Duplex F44 UNS S31254 Flanges Chemical Composition

 

Grade	Ni	C	Mo	Mn	Si	F	Cu	S	P	Cr
SMO 254	17.5 – 18.5	0.02 max	6 – 6.5	1 max	0.8 max	–	0.5 – 1	0.01 max	0.03 max	19.5 – 20.5

 

ASTM A182 F44 UNS S31254 Flanges Mechanical Properties

 

Element	Density	Melting Point	Yield Strength (0.2%Offset	Tensile Strength	Elongation
SMO 254	8.0 g/cm3	1320-1390 ℃	300	650	35%

 

Equivalent Standards for SMO 254

 

Standard	Equivalent Grade
UNS (Unified Numbering System)	S31254
EN (European Standard, DIN)	1.4547
ASTM	A182, A240, A312, A479, A813, A814
ASME	SA-182, SA-240, SA-312, SA-479
JIS (Japanese Standard)	JIS G 4304 SUS 312L
AFNOR (French Standard)	Z1 CNDU 20.18.06Az
BS (British Standard)	F44

 

SMO 254 Weld Neck Flange Pressure Rating

 

Table Il-2-2.8 Pressure-Temperature Ratings for Group 2.8 Materials
Nominal Designation		Forgings		Castings		Plates
20Cr-18Ni-6Mo		A182 Gr.F44		A351 Gr.CK3MCuN		A240 Gr.S31254
Working Pressures by Classes,psig
Class
Temp.,F	150	300	400	600	900	1500	2500
-20 to 100	290	750	1000	1500	2250	3750	6250
200	260	745	990	1490	2230	3720	6200
300	230	665	890	1335	2000	3335	5560
400	200	615	820	1230	1845	3070	5120
500	170	580	775	1160	1740	2905	4840
600	140	555	740	1115	1670	2785	4640
650	125	545	730	1095	1640	2735	4560
700	110	540	725	1085	1625	2710	4520
750	95	530	710	1065	1595	2660	4430

 

Applications

 

Offshore and marine systems

Desalination plants

Heat exchangers and pressure vessels

Pulp and paper industry

Chemical processing