ASTM A350 / A350M Grade LF6 Class 1

ASTM A350 Grade LF6 Class 1 is a standard material specification for carbon and low alloy steel forgings, requiring notch toughness testing for piping components. This includes forged flanges, fittings, valves and similar forged and machined parts. This specification covers requirements such as chemical composition, mechanical properties and impact test for notch toughness. Ferrobend stocks, manufactures and supplies forgings, flanges, pipe fittings, valves and similar piping components in ASTM A350 Grade LF6 Class 1 specification.

Chemical Composition

Element	Composition
Carbon, max	0.22
Manganese	1.15–1.50
Phosphorus, max	0.025
Sulfur, max	0.025
Silicon [Note A]	0.15–0.30
Nickel	0.40 max [Note B]
Chromium	0.30 max [Note B,C]
Molybdenum	0.12 max [Note B,C]
Copper	0.40 max [Note B]
Columbium	0.02 max
Vanadium	0.04–0.11
Nitrogen	0.01–0.030

Note:
A: When vacuum carbon-deoxidation is required by Supplementary Requirement S4, the silicon content shall be 0.12 % maximum.
B:The sum of copper, nickel, chromium, vanadium and molybdenum shall not exceed 1.00 % on heat analysis.
C:The sum of chromium and molybdenum shall not exceed 0.32 % on heat analysis.
D:By agreement, the limit for columbium may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.

Heat Treatment

1: After hot working and before reheating for heat treatment, the forging shall be allowed to cool substantially below the transformation range.
2:Forgings of grades other than Grade LF787 shall be furnished in the normalized, or in the normalized and tempered, or in the quenched and tempered condition described by the following procedures:
2.1:Normalize—Heat to a temperature that produces an austenitic structure, holding sufficient time to attain uniform temperature throughout. Cool uniformly in still air.
2.2:Normalize and Temper—Subsequent to normalize,reheat to 1100 °F [590 °C] minimum, holding at temperature a minimum of 30 min/in. [30 min/25 mm] of maximum thickness, but in no case less than 30 min. Cool in still air.
2.3:Quench and Temper—The procedure for quenching shall consist of either (1) fully austenitizing the forgings followed by quenching in a suitable liquid medium or (2) using a multiple stage procedure whereby the forging is first fully austenitized and rapidly cooled, then reheated to partially reaustenitize, followed by quenching in a suitable liquid medium. All quenched forgings shall be tempered by reheating to a temperature between 1100 °F [590 °C] and the lower transformation temperature, holding at temperature a minimum of 30 min/in. [30 min/25 mm] of maximum thickness but in no case less than 30 min.

Mechanical Properties [Note A]

Tensile Strength, ksi [MPa]	Yield Strength, min, ksi [MPa] [Note B, C]	Elongation		Reduction of Area, min, %
		Round Specimen in 4D, min, %	Strip Specimen in 2 Inch [50mm], min, %
66–91 [455–630]	52 [360]	22	30	40

Notes:
A: See 7.3 for hardness tests.
B: Determined by either the 0.2 % offset method or the 0.5 % extension under load method.
C: For round specimens only.

Charpy V-Notch Energy Requirements [10mm by 10mm]

Minimum Impact Energy Required for Average of Each Set of Three Specimens, ft.lbf [J]	Minimum Impact Energy Permitted for One Specimen only of a Set, ft.lbf [J]	Testing Temperature, °F [°C]
15 [20]	12 [16]	−60 [−51]

Associate Standards