Alloy Steel Socket Weld Flanges | A182 F5, F11, F22, F91

Alloy steel socket welds flanges are forged flanges featuring a counterbore socket to receive the pipe end. The pipe is welded to a single fillet weld and is against an inbuilt shoulder. They are manufactured from ASTM A182 grades F5, F9, F11, F12, F22 and F91 and used on small bore lines in steam, refinery and power services at high pressure and high temperature. The dimensions are in accordance with ASME B16.5. Solitaire Overseas provides the flanges with EN 10204 3.1 certificates and test material traceability for domestic and export orders

Technical Data

Specifications Chemical Composition Mechanical Properties Pressure Class Sizes and Facings Alloy Grades

Specifications of Alloy Steel Socket Weld Flanges

Parameter	Technical Details & Standard Options
Product	Alloy Steel Socket Weld Flanges, raised face (SWRF)
Material Specifications	ASTM A182 / ASME SA182 grades F5, F9, F11, F12, F22, F91
Dimensional Standard	ASME B16.5
Pressure Classes	Class 150, Class 300, Class 600, Class 900, Class 1500 (Class 400 available on stock check)
Size Range	NPS 1/2 to 3 in Class 150, 300, and 600; NPS 1/2 to 2 1/2 in Class 900 and 1500
Custom Engineered Items	Class 2500 and sizes above NPS 3 (supplied to client drawings and labeled as custom)
Flange Facing	Raised Face (RF) as standard; Ring-Type Joint (RTJ) available on request
Socket Bore	Precision-machined to match the pipe outside diameter and specified schedule
Heat Treatment	Normalized and tempered, or annealed, per ASTM A182 grade requirements
Documentation	EN 10204 3.1 Mill Test Certificate (MTC); 3.2 third-party inspection available on request

Chemical Compositions of Alloy Steel Socket Weld Flanges

Element	A182 F5 (%)	A182 F9 (%)	A182 F11 Cl. 2 (%)	A182 F12 Cl. 2 (%)	A182 F22 Cl. 3 (%)	A182 F91 (%)
Carbon (C)	0.15 max	0.15 max	0.10 to 0.20	0.10 to 0.20	0.05 to 0.15	0.08 to 0.12
Manganese (Mn)	0.30 to 0.60	0.30 to 0.60	0.30 to 0.80	0.30 to 0.80	0.30 to 0.60	0.30 to 0.60
Phosphorus (P)	0.030 max	0.030 max	0.040 max	0.040 max	0.040 max	0.020 max
Sulfur (S)	0.030 max	0.030 max	0.040 max	0.040 max	0.040 max	0.010 max
Silicon (Si)	0.50 max	0.50 to 1.00	0.50 to 1.00	0.10 to 0.60	0.50 max	0.20 to 0.50
Chromium (Cr)	4.00 to 6.00	8.00 to 10.00	1.00 to 1.50	0.80 to 1.25	2.00 to 2.50	8.00 to 9.50
Molybdenum (Mo)	0.44 to 0.65	0.90 to 1.10	0.44 to 0.65	0.44 to 0.65	0.87 to 1.13	0.85 to 1.05
Nickel (Ni)	0.50 max	0.50 max	Not specified	Not specified	Not specified	0.40 max
Vanadium (V)	Not specified	Not specified	Not specified	Not specified	Not specified	0.18 to 0.25
Niobium (Nb)	Not specified	Not specified	Not specified	Not specified	Not specified	0.06 to 0.10
Nitrogen (N)	Not specified	Not specified	Not specified	Not specified	Not specified	0.030 to 0.070
Aluminum (Al)	Not specified	Not specified	Not specified	Not specified	Not specified	0.02 max
Titanium (Ti)	Not specified	Not specified	Not specified	Not specified	Not specified	0.01 max
Zirconium (Zr)	Not specified	Not specified	Not specified	Not specified	Not specified	0.01 max

Mechanical Properties of Alloy Steel Socket Weld Flanges

Grade & Class	Tensile Strength, Min (MPa)	Yield Strength, Min (MPa)	Elongation in 2 in., Min (%)	Reduction of Area, Min (%)	Brinell Hardness Range (HBW)
ASTM A182 F5	485	275	20	35	143 to 217
ASTM A182 F9	585	380	20	40	179 to 217
ASTM A182 F11 Class 2	485	275	20	30	143 to 207
ASTM A182 F11 Class 3	515	310	20	30	156 to 207
ASTM A182 F12 Class 2	485	275	20	30	143 to 207
ASTM A182 F22 Class 3	515	310	20	30	156 to 207
ASTM A182 F91	585	415	20	40	190 to 248

Pressure Class Reference of Alloy Steel Socket Weld Flanges

Pressure Class	Working Pressure at Ambient (psig)	Working Pressure at Ambient (bar)
Class 150	~290	~20
Class 300	~750	~51
Class 600	~1500	~103
Class 900	~2250	~155
Class 1500	~3750	~258

Sizes, Pressure Classes, and Facings of Alloy Steel Socket Weld Flanges

Pressure Class	NPS Range (ASME B16.5)	Standard Availability	Notes
Class 150, 300, 600	NPS 1/2" to NPS 3	Standard Production	Small-bore piping systems
Class 900, 1500	NPS 1/2" to NPS 2-1/2	Standard Production	High-pressure small-bore lines
Class 2500	N/A	Custom / Non-Standard	Not covered under ASME B16.5 for Socket Weld; supplied per engineering drawing
Above NPS 3"	N/A	Custom / Non-Standard	Not covered under ASME B16.5; custom engineering required

Alloy Grades for Socket Weld Flanges

Grade	Nominal Alloy	Cr %	Mo %	Typical Use
A182 F5	5Cr 0.5Mo	4.0 to 6.0	0.44 to 0.65	Refinery lines needing sulfidation and oxidation resistance
A182 F9	9Cr 1Mo	8.0 to 10.0	0.90 to 1.10	Higher temperature refinery and power lines
A182 F11	1.25Cr 0.5Mo	1.00 to 1.50	0.44 to 0.65	Steam, boiler and general chrome moly service
A182 F12	1Cr 0.5Mo	0.80 to 1.25	0.44 to 0.65	Steam and process lines at moderate temperature
A182 F22	2.25Cr 1Mo	2.00 to 2.50	0.87 to 1.13	High temperature steam and hydrogen service
A182 F91	9Cr 1Mo V Nb N	8.0 to 9.5	0.85 to 1.05	Ultra supercritical steam lines

Applications and Industrial Uses of Alloy Steel Socket Weld Flanges

Power Generation Plants
Oil and Gas Industry
Petrochemical Plants
Oil Refineries
Boiler Systems
Chemical Processing Plants
Fertilizer Manufacturing Plants
Industrial Heat Exchangers

Frequently Asked Questions

1. What are alloy steel socket weld flanges?

Forged flanges in ASTM A182 chrome moly grades with a counterbored socket. The pipe slides in and is joined by one fillet weld, mainly for small bore high pressure lines.

2. Why is a 1/16 inch gap left before welding?

The pipe is pulled back approximately 1.6 mm from the internal shoulder. This gap accommodates weld shrinkage and thermal expansion while reducing the risk of cracking.

3. Which sizes and pressure classes are available?

ASME B16.5 socket weld flanges cover NPS 1/2 to 3 in the lower classes and up to NPS 2 1/2 in Class 900 and 1500. Larger sizes are custom.

4. Which alloy grade should I choose?

F11 and F22 suit most steam and refinery service. F91 is chosen for higher design temperatures. The design code and operating temperature decide the grade.

5. Is PWHT required for alloy steel socket weld joints?

Usually, depending on grade, thickness and code. Preheat and PWHT follow the approved welding procedure. F91 needs tight control of PWHT temperature.

6. How does a socket weld flange compare with a weld neck flange?

Weld neck gives a full penetration weld that can be radiographed and suits cyclic service. Socket weld fits faster on small bore lines but leaves a crevice at the gap.

7. Can alloy steel socket weld flanges be used in corrosive service?

Avoid them where crevice corrosion is a concern, because the gap can trap fluid. Choose a weld neck flange or a corrosion resistant alloy instead.

8. What details are needed to order?

Give NPS, class, grade and class of grade, face type, pipe schedule, standard, quantity and the certificates needed, such as EN 10204 3.1.

Alloy Steel Socket Weld Flanges Manufacturer and Supplier in India