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ASTM A350 Low Temperature Carbon Steel Flanges

LTCS forged flanges in A350 LF2, LF3, LF6 and other grades, from stock in Mumbai, India.

ASTM A350 / ASME SA350 LTCS Flanges for Sub-Zero Service

ASTM A350 low temperature carbon steel flanges

Dinesh Tube India supplies ASTM A350 low temperature carbon steel (LTCS) flanges from Mumbai to LPG, ammonia, gas processing, refinery and cold-storage projects in India and abroad. Every A350 flange is Charpy impact tested at the temperature required by its grade, and supplied with an EN 10204 3.1 certificate showing the impact results.

We supply weld neck, slip-on, blind, socket weld, threaded and RTJ flanges from 1/2" to 48", Class 150 to 2500, mainly in A350 LF2 Class 1, with LF3, LF6 and other grades on request.

This page compares all A350 grades. For full data on the most common grade, see our A350 LF2 flanges page. For ambient and high-temperature service, see ASTM A105 flanges.

Table of Contents


What Are LTCS Flanges?

ASTM A350 is the standard specification for carbon and low-alloy steel forgings requiring notch toughness testing for piping components. Flanges made to it are called low temperature carbon steel (LTCS) flanges. Ordinary carbon steel such as A105 becomes brittle in the cold; A350 forgings are heat treated by normalising, normalising and tempering, or quenching and tempering, and then Charpy V-notch impact tested to prove they stay tough at their rated temperature.

The grade sets the test temperature: LF2 Class 1 is tested at −46 °C (−50 °F) and is the standard LTCS flange, while nickel-bearing grades such as LF3 go down to −101 °C. A350 is a carbon or low-alloy steel, not a corrosion-resistant alloy. ASME adopts it as SA350.

ASTM A350 Flange Specification

Material

ASTM A350 / ASME SA350

Grades

LF2 Class 1 & 2; LF1, LF3, LF6, LF9 on request

Size

1/2" – 24" (B16.5); 26" – 48" (B16.47 Series A / B)

Pressure Class

Class 150, 300, 600, 900, 1500, 2500; PN 6 – PN 64

Dimensions

ASME B16.5, B16.47, B16.48, EN 1092-1, BS 4504

Types

WN, SO, blind, SW, threaded, lap joint, long weld neck, spectacle blind

Face

Raised face (RF), flat face (FF), ring type joint (RTJ)

Heat Treatment

Normalised, normalised and tempered, or quenched and tempered

Testing

Charpy impact, tensile, hardness; UT, MPI, PMI on request

Certification

EN 10204 3.1 with impact results; 3.2 / TPI; NACE MR0175 on request
ASTM A350 LTCS flange specification

ASTM A350 Grades and Impact Test Temperatures

GradeTypeStandard Impact Test TemperatureCharpy Energy, Avg / Single (min)
LF1Carbon steel−29 °C (−20 °F)18 J / 14 J
LF2 Class 1Carbon steel−46 °C (−50 °F)20 J / 16 J
LF2 Class 2Carbon steel−18 °C (0 °F)27 J / 20 J
LF3 Class 13.5% nickel steel−101 °C (−150 °F)20 J / 16 J
LF6 Class 1Carbon-manganese-vanadium steel−51 °C (−60 °F)20 J / 16 J
LF9Nickel-copper steel−73 °C (−100 °F)20 J / 16 J

Full-size specimens. Grades LF5 and LF787 and other classes are also covered by A350. The purchaser may specify a lower test temperature.

ASTM A350 Chemical Composition

GradeC maxMnSiNiOther
LF10.300.60 – 1.350.15 – 0.300.40 maxV 0.08 max
LF20.300.60 – 1.350.15 – 0.300.40 maxV 0.08 max
LF30.200.90 max0.20 – 0.353.3 – 3.7V 0.03 max
LF60.221.15 – 1.500.15 – 0.300.40 maxV 0.04 – 0.11, N 0.01 – 0.030
LF90.200.40 – 1.06—1.60 – 2.24Cu 0.75 – 1.25

Weight %. All grades: P 0.035 max, S 0.040 max, with limits on Cr, Mo, Cu and Nb. Check the current edition of A350 for complete limits.

ASTM A350 Mechanical Properties

GradeTensile Strength, MPaYield Strength, min, MPaElongation, min
LF1415 – 58520525%
LF2 Class 1 / 2485 – 65525022%
LF3 Class 1 / 2485 – 65526022%
LF6 Class 1455 – 63036022%
LF9435 – 60531525%

Elongation in 2 in. (50 mm). LF2 hardness is limited to 197 HBW maximum.

Choosing an A350 Grade

Minimum Design TemperatureUsual Flange GradeMatching Pipe
Down to −29 °CA105 (per design code) or LF2A106 Gr B
Down to −46 °CA350 LF2 Class 1A333 Gr 6
Down to −51 °C, higher strengthA350 LF6 Class 1A333 Gr 6 / per design
Down to −101 °CA350 LF3A333 Gr 3
Below −101 °C (LNG, cryogenic)Stainless steel A182 F304L / F316LA312 TP304L / 316L

Complete the LTCS system with A420 WPL6 butt-weld fittings. See also our LTCS pipe guide.

Need LTCS flanges? Send your A350 grade, flange type, size, class, face, bore schedule and minimum design temperature to kamlesh@dineshtube-india.com or call +91 83559 10913. You can also send an enquiry.

Types of A350 LTCS Flanges

ASTM A350 LTCS weld neck flange

A350 Weld Neck Flange

The preferred type for cold, high-pressure and cyclic service.
ASTM A350 LTCS slip-on flange

A350 Slip-On Flange

Fillet welded; for lower-pressure cold lines where the code allows.
ASTM A350 LTCS blind flange

A350 Blind Flange

Closes line ends and nozzles in low-temperature systems.
ASTM A350 LTCS socket weld flange

A350 Socket Weld Flange

For small-bore LTCS lines, usually 2" and below.
ASTM A350 LTCS threaded flange

A350 Threaded Flange

NPT threaded, for small non-critical lines without welding.
ASTM A350 LTCS RTJ flange

A350 RTJ Flange

Metal ring gasket groove for high-pressure gas and LPG service.

ASTM A350 Flange Applications

  •   LPG, propane and butane storage and transfer
  •   Ammonia and fertiliser plants
  •   Gas processing, compression and pressure let-down lines
  •   Refrigeration and cold-storage plants
  •   Refinery and petrochemical cold service
  •   Plants in cold climates and offshore
Industries using ASTM A350 LTCS flanges

Packing: wooden cases or pallets with face protectors. See all carbon steel flanges.

ASTM A350 LTCS Flanges: FAQs

What is ASTM A350?

ASTM A350 is the standard specification for carbon and low-alloy steel forgings that require notch toughness (Charpy impact) testing, used for flanges, fittings and other piping components in low-temperature service. ASME adopts it as SA350. Flanges made to A350 are commonly called LTCS (low temperature carbon steel) flanges.

What are the grades of ASTM A350?

The main grades are LF1, LF2 (Class 1 and 2), LF3, LF5, LF6, LF9 and LF787. LF2 Class 1 is by far the most common and is impact tested at −46 °C. LF3 contains about 3.5% nickel and is tested at −101 °C, while LF6 is a higher-strength vanadium grade tested at −51 °C.

What is the difference between A350 LF2 Class 1 and Class 2?

Both have the same chemistry and strength. Class 1 is impact tested at −46 °C (−50 °F) with a lower energy requirement, while Class 2 is tested at −18 °C (0 °F) with a higher energy requirement. Class 1 is the usual choice for low-temperature piping.

What is the difference between A105 and A350 LF2 flanges?

Both are forged carbon steel with similar strength. A105 is for ambient and high-temperature service and is not impact tested. A350 LF2 is heat treated and Charpy impact tested at −46 °C, so it can be used for low-temperature service. LF2 flanges are often dual certified to A105.

What pipe and fittings are used with A350 LF2 flanges?

A350 LF2 Class 1 flanges are normally used with ASTM A333 Grade 6 seamless pipe and ASTM A420 WPL6 butt-weld fittings, all impact tested at around −45 °C, to form a complete LTCS piping system.

Are A350 flanges corrosion resistant?

No. A350 grades are carbon and low-alloy steels chosen for toughness at low temperature, not for corrosion resistance. They are supplied oiled or painted, and need coating or a corrosion allowance like other carbon steel flanges. For corrosive or cryogenic service, stainless steel flanges such as A182 F316L are used.

Export Destinations for A350 Flanges

We export ASTM A350 LTCS flanges to the Middle East (UAE, Saudi Arabia, Qatar, Kuwait, Oman, Bahrain, Iraq), Africa (Nigeria, Egypt, South Africa, Kenya, Ghana, Tanzania), Asia (Bangladesh, Sri Lanka, Nepal, Indonesia, Malaysia, Thailand, Vietnam, Philippines), Europe and the Americas on request.