A350 LF3 Flanges | ASTM A350 | UNS K32025

ASTM A350 LF3 flanges are forged carbon steel flanges built for low-temperature service. This nickel-bearing low-alloy grade, often called 3.5% nickel steel, keeps its notch toughness and impact resistance at sub-zero temperatures down to -101°C (-150°F). The specification covers forged or ring-rolled flanges, fittings, and valves for pressure systems where resistance to brittle fracture is critical. We produce LF3 flanges to ASME B16.5 and other international standards, in weld neck, slip-on, blind, socket weld, threaded, and lap joint types. PM Industries manufactures, supplies, and stocks them in a full range of sizes and pressure classes.

The chemistry is controlled for cold service: maximum 0.20% carbon, 3.3-3.7% nickel, manganese up to 0.90%, and low phosphorus and sulfur. That nickel content is what raises toughness and ductility at cryogenic temperatures. On the mechanical side, LF3 offers tensile strength from 485 to 655 MPa, minimum yield around 260 MPa, and elongation of at least 21%, with mandatory Charpy V-notch impact testing to confirm performance at the specified low temperatures. The flanges are normalized and tempered to reach those properties.

You will find A350 LF3 flanges wherever cryogenic fluids are handled, including LNG plants, natural gas processing, petrochemical facilities, offshore platforms, and refrigeration systems. They go into pipelines, storage tanks, pressure vessels, and equipment exposed to extreme cold, such as Arctic or subsea installations. The low-temperature toughness is what prevents brittle failure, which is why LF3 is chosen over standard carbon steels like A105 in this kind of service.

A350 LF3 flanges hold reliable sealing and structural integrity across pressure classes from 150 to 2500, depending on design and temperature. They weld well, so they integrate cleanly into piping systems, and good machinability supports precise manufacturing. We supply them with full traceability, material test certificates, and hydrostatic testing to meet strict quality and safety requirements.

For demanding low-temperature environments, A350 LF3 flanges are a specialized solution where material performance ties directly to operational safety. Their mix of strength, toughness, and code compliance supports long service life in cryogenic and sub-zero conditions. Proper selection, installation, and maintenance get the most out of them. PM Industries holds stock ready to ship, with certification and impact-test documentation on every order. Tell us your flange type, size, class, and face, and we will quote it.

Specification A350 LF3 Flanges

Standards	ANSI/ASME B16.5, B16.48, ANSI Flanges, GOST Flanges, DIN Flanges, EN-1092, B16.47 Series A & B, ASME Flanges, EN Flanges, AWWA Flanges, BS Flanges.
JIS Standard	5K, 10 K, 16 K 20 K, 30 K, 40 K, 63 K
DIN FLANGES	DIN 2527, 2627, 2631, 2656, 2576, 2673, 2629, 2628, 2566, 2641, 2637, 2655, 2634, 2636, 2632, 2633, 2638, 2642, 2573, 2635.
Pressure Rating	Class 150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS
Types	Threaded, Plate, Screwed, Forged.
Supporting material	Gasket, Ring Joint, Flange Bolts
Size range	1/2" (15 NB) to 48" (1200NB) DN10~DN5000
Production technique	Forged, machined and Heat treated
Available Flange Type	Weld Neck Flanges, RTJ Flanges, Slip On Flanges, Spectacle Blind Flanges, Flanges Gaskets, Square Flanges, Standard Insert Flanges, High Hub Blinds Flanges, Flat Flanges, forged flanges, Weldo / Nipo Flanges, Jacket Insert Flanges, Tongue groove Flanges, Blind Flanges, Socket Weld Flanges, Large diameter Flanges, Long Weld Neck Flanges, Spacer Blinds, SWRF Flanges, SORF Flanges, Angle Face Rings Flanges, Spades Ring Spacers Flanges, WNRF Flanges, Screwed Flanges, Insert Flanges, flanges bolts, cf flange, Lap Joint Flanges, ASME B16.36 Orifice Flanges, Plate Flange, Expander Flanges, Ring Type Joint Flanges, Loose Flanges, Reducing Flanges, puddle flange, Threaded Flanges, blank flange, vacuum flange.
Connect Type/ Flange Face Type	Ring Type Joint (RTJ), Flat Face (FF), Tongue & Groove, Small Male-Female (SMF), Lap-Joint Face (LJF), Raised Face (RF), Large Male-Female (LMF), Small Tongue.
Custom design	As per your drawing
Test	Direct-reading Spectrograph, X-ray detector, UItrasonic flaw detector, Magnetic particle detector, Hydrostatic testing machine.
Origin	Indian / USA / Korean / West Europe / Japan
Pressure Class	PN 6 TO PN 100
Thickness	Normal Pipe Size ≤ 18
Bore Diameter	Normal Pipe ≤ 10
High Temperature	Above 200°C (400°F) For Class 150 Or Above 400°C (750°F)
Low Temperature	Above -29 Degree C (−20°F)
Coating/Surface Treatment:	Zinc Plated, Anti-rust Paint, Oil Black Paint, Yellow Transparent, Cold and Hot Dip Galvanized.
European/African/Russian Standard Flanges	Available
Gaskets Types	Full Face, Metallic Ring, Flat Ring Gasket
Marking Standard	Name of Manufacturer
	Schedule
	Type of Flange Facing
	Pressure Class
	Nominal Pipe Size, etc
Test Certificates	EN 10204/3.1B, NACE MR0103, NACE MR0175
	Raw Materials Certificate
	100% Radiography Test Report
	Third Party Inspection Report, etc

Flange Type Available

Chemical Properties

Element	Composition
Carbon, maximum	0.20 maximum
Manganese	0.90 maximum
Phosphorus, maximum	0.035 maximum
Sulfur, maximum	0.040 maximum
Silicon [Note A]	0.20–0.35
Nickel	3.3–3.7
Chromium	0.30 maximum [Note C]
Molybdenum	0.12 maximum [Note C]
Copper	0.40 maximum
Columbium	0.02 maximum
Vanadium	0.03 maximum

Mechanical Properties

Tensile Strength, minimum:	70,000 psi (485 MPa]
Minimum. Yield Point:	36,000 psi [250 MPa]
Reduction of area, minimum:	30% minimum
Hardness, HB, maximum	187

Carbon Steel LF3 Flanges Thickness Chart

ASTM A350 LF3 Flanges Wall Thickness
NPS (Normal Pipe Sizes)	Outside Daimeter (O.D.)	Schedule 10	Schedule 20	Schedule 30	STD Wall	Schedule 40	Schedule 60	EXT Hvy	Schedule 80	Schedule 100	Schedule 120	Schedule 140	Schedule 160	XX Hvy
½	0.84	0.083	...	...	0.109	0.109	...	0.147	0.147	...	...	...	0.188	0.294
¾	1.05	0.083	...	...	0.113	0.113	...	0.154	0.154	...	...	...	0.219	0.308
1	1.315	0.109	...	...	0.133	0.133	...	0.179	0.179	...	...	...	0.25	0.358
1 ¼	1.66	0.109	...	...	0.14	0.14	...	0.191	0.191	...	...	...	0.25	0.382
1 ½	1.9	0.109	...	...	0.145	0.145	...	0.2	0.2	...	...	...	0.281	0.4
2	2.375	0.109	...	...	0.154	0.154	...	0.218	0.218	...	...	...	0.344	0.436
2 ½	2.875	0.12	...	...	0.203	0.203	...	0.276	0.276	...	...	...	0.375	0.552
3	3.5	0.12	...	...	0.216	0.216	...	0.3	0.3	...	...	...	0.438	0.6
3 ½	4	0.12	...	...	0.226	0.226	...	0.318	0.318	...	...	...	...	0.636
4	4.5	0.12	...	...	0.237	0.237	...	0.337	0.337	...	0.438	...	0.531	0.674
5	5.563	0.134	...	...	0.258	0.258	...	0.375	0.375	...	0.5	...	0.625	0.75
6	6.625	0.134	...	...	0.28	0.28	...	0.432	0.432	...	0.562	...	0.719	0.864
8	8.625	0.148	0.25	0.277	0.322	0.322	0.406	0.5	0.5	0.594	0.719	0.812	0.906	0.875
10	10.75	0.165	0.25	0.307	0.365	0.365	0.5	0.5	0.594	0.719	0.844	1	1.125	1
12	12.75	0.18	0.25	0.33	0.375	0.406	0.562	0.5	0.688	0.844	1	1.125	1.312	1
14	14	0.25	0.312	0.375	0.375	0.438	0.594	0.5	0.75	0.938	1.094	1.25	1.406	...
16	16	0.25	0.312	0.375	0.375	0.5	0.656	0.5	0.844	1.031	1.219	1.438	1.594	...
18	18	0.25	0.312	0.438	0.375	0.562	0.75	0.5	0.938	1.156	1.375	1.562	1.781	...
20	20	0.25	0.375	0.5	0.375	0.594	0.812	0.5	1.031	1.281	1.5	1.75	1.969	...
22	22	0.25	...	...	0.375	...	...	0.5	...	...	....	....	....	....
24	24	0.25	0.375	0.562	0.375	0.688	0.969	0.5	1.219	1.531	1.812	2.062	2.344	....
26	26	....	....	....	0.375	....	....	0.5	....	....	....	....	....	....
30	30	0.312	0.5	0.625	0.375	....	....	0.5	....	....	....	....	....	....
36	36	0.312	0.5	0.625	0.375	0.75	....	0.5	....	....	....	....	....	....
40	40	....	....	....	0.375	....	....	0.5	....	....	....	....	....	....
42	42	……..	……..	……..	0.375	……..	……..	0.5	……..	……..	……..	……..	……..	……..
48	48	……..	……..	……..	0.375	……..	……..	0.5	……..	……..	……..	……..	……..	……..

LTCS LF3 Flanges Bolts And Nuts

	Class 150 Flanges				Class 300 Flanges				Class 600 Flanges
NPS	# Bolts And Studs	Diameter of Bolts And Studs	Stud Length		# Bolts And Studs	Diameter of Bolts And Studs	Stud Length		# Bolts And Studs	Diameter of Bolts And Studs	Stud Length
			1/16 RF	RTJ			1/16 RF	RTJ			1/4 RF	RTJ
1/2	4	0.50	2-1/4	–	4	0.50	2-1/2	3	4	0.50	3	3
3/4	4	0.50	2-1/2	–	4	0.63	3	3-1/2	4	0.63	3-1/2	3-1/2
1	4	0.50	2-1/2	3	4	0.63	3	3-1/2	4	0.63	3-1/2	3-1/2
1-1/4	4	0.50	2-3/4	3-1/4	4	0.63	3-1/4	3-3/4	4	0.63	3-3/4	3-3/4
1-1/2	4	0.50	2-3/4	3-1/4	4	0.75	3-1/2	4	4	0.75	4-1/4	4-1/4
2	4	0.63	3-1/4	3-3/4	8	0.63	3-1/2	4	8	0.63	4-1/4	4-1/4
2-1/2	4	0.63	3-1/2	4	8	0.75	4	4-1/2	8	0.75	4-3/4	4-3/4
3	4	0.63	3-1/2	4	8	0.75	4-1/4	4-3/4	8	0.75	5	5
3-1/2	8	0.63	3-1/2	4	8	0.75	4-1/4	5	8	0.88	5-1/2	5-1/2
4	8	0.63	3-1/2	4	8	0.75	4-1/2	5	8	0.88	5-3/4	5-3/4
5	8	0.75	3-3/4	4-1/4	8	0.75	4-3/4	5-1/4	8	1.00	6-1/2	6-1/2
6	8	0.75	4	4-1/2	12	0.75	4-3/4	5-1/2	12	1.00	6-3/4	6-3/4
8	8	0.75	4-1/4	4-3/4	12	0.88	5-1/2	6	12	1.13	7-1/2	7-3/4
10	12	0.88	4-1/2	5	16	1.00	6-1/4	6-3/4	16	1.25	8-1/2	8-1/2
12	12	0.88	4-3/4	5-1/4	16	1.13	6-3/4	7-1/4	20	1.25	8-3/4	8-3/4
14	12	1.00	5-1/4	5-3/4	20	1.13	7	7-1/2	20	1.38	9-1/4	9-1/4
16	16	1.00	5-1/4	5-3/4	20	1.25	7-1/2	8	20	1.50	10	10
18	16	1.13	5-3/4	6-1/4	24	1.25	7-3/4	8-1/4	20	1.63	10-3/4	10-3/4
20	20	1.13	6-1/4	6-3/4	24	1.25	8	8-3/4	24	1.63	11-1/4	11-1/2
24	20	1.25	6-3/4	7-1/4	24	1.50	9	10	24	1.88	13	13-1/4

Pressure Class/ Rating

ASME/ANSI B 16.5	Lap Joint Flange, Ring Type Joint Flange, Threaded Flange, Blind Flange, High Hub Blind Flange, Socket Weld Flange, Slip on Flange, Welding Neck Flange.
PRESSURE CLASS	150, 300, 400, 600, 900, 1500, 2500
ASME/ANSI B 16.47	Blind Flange [Series A & B], Welding Neck Flange.
PRESSURE CLASS	75, 150, 300, 400, 600, 900
ASME/ANSI B 16.36	Slip on Flange, Threaded Flange, Welding Neck Flange.
PRESSURE CLASS	300, 400, 600, 900, 1500, 2500
BS 4504 SEC 3.1	Plate Flange, Welding Neck Flange, Hubbed Slip on Flange, Lapped Pipe End Flange, Loose Plate With Weld Neck Flange, Hubbed Threaded Flange, Blank Flange, Loose Plate Flange.
PRESSURE CLASS	PN 2.5 TO PN 40
BS 4504[PART 1]	Blank Flange, Loose Plate With Weld On Plate Collar, Welding Neck Flange, Plate Flange, Hubbed Slip-On Hubbed Threaded.
PRESSURE CLASS	PN 2.5 TO PN 400
BS 1560 BOSS	Blind Flange, Screwed Boss Flange, Welding Neck Flange,Slip-On Flange, Lapped Flange, Socket Welding Flange.
PRESSURE CLASS	150, 300, 400, 600, 900, 1500, 2500
BS10	Screwed Boss Flange, Plate Slip-On Flange, Slip-On Boss Flange, Blind Flange, Welding Neck Flange.
TABLE	D, E, F, H
DIN FLANGES	DIN 2527, 2632, 2635, 2673, 2566, 2655, 2631, 2627, 2634, 2576, 2636, 2629, 2633, 2573, 2656, 2638, 2637, 2642, 2641, 2628
PRESSURE CLASS	PN 6 TO PN 100

ASME/ANSI B16.5 A350 Lf3 Flanges Dimensions Class-400

Nominal Pipe Size NPS (inches)	Class 400
	Diameter of Flange (inches)	No. of Bolts	Diameter of Bolts (inches)	Diameter of Bolt Holes (inches)	Bolt Circle (inches)
1/4	3-3/8	4	1/2	0.62	2-1/4
1/2	3-3/4	4	1/2	0.62	2-5/8
3/4	4-5/8	4	5/8	0.75	3-1/4
1	4-7/8	4	5/8	0.75	3-1/2
1-1/4	5-1/4	4	5/8	0.75	3-7/8
1-1/2	6-1/8	4	3/4	0.88	4-1/2
2	6-1/2	8	5/8	0.75	5
2-1/2	7-1/2	8	3/4	0.88	5-7/8
3	8-1/4	8	3/4	0.88	6-5/8
3-1/2	9	8	7/8	1	7-1/4
4	10	8	7/8	1	7-7/8
5	11	8	7/8	1	9-1/4
6	12-1/2	12	7/8	1	10-5/8
8	15	12	1	1.12	13
10	17-1/2	16	1-1/8	1.25	15-1/4
12	20-1/2	16	1-1/4	1.38	17-3/4
14	23	20	1-1/4	1.38	20-1/4
16	25-1/2	20	1-3/8	1.5	22-1/2
18	28	24	1-3/8	1.5	24-3/4
20	30-1/2	24	1-1/2	1.62	27
24	36	24	1-3/4	1.88	32

SA350 LF3 Weight Chart According to ASME B16.5

Nominal Pipe Sizes (NPS)	Slip On (SORF)	Threaded (NPT)	Socket Weld (SWRF)	Lap Joint (Loose)	Blind (BLRF)	Weld Neck (WRNR)
½	1	1	2	1	2	2
¾	2	2	2	2	2	2
1	2	2	2	2	2	3
1¼	3	3	3	3	3	3
1½	3	3	3	3	4	4
2	5	5	5	5	5	6
2½	8	8	8	8	7	10
3	9	9	9	9	9	11.5
3½	11	12	11	11	13	12
4	13	13	13	13	17	16.5
5	15	15	15	15	20	21
6	19	19	19	19	27	26
8	30	30	30	30	47	42
10	43	43	43	43	70	54
12	64	64	64	64	123	88
14	90	90	90	105	140	114
16	106	98	98	140	180	140
18	130	130	130	160	220	165
20	165	165	165	195	285	197
22	185	185	185	245	355	225
24	220	220	220	275	430	268