ASTM A350 is the standard specification covering carbon and low-alloy steel forged or ring-rolled flanges, forged fittings and valves intended primarily for low-temperature service and requiring notch toughness testing. They are manufactured to corresponding ASME or API dimensional standards. The forgings may be made from ingots, blooms, billets, slabs or bars through hot-forging process. The steel shall be fully killed and fine-grain. ASTM A350 covers several grades and classes: Grade LF1, Grade LF2, Grade LF3, Grade LF5, Grade LF6, Grade LF9, Grade LF787; and Class 1, Class 2, Class 3. All the forgings supplied by Metals-Piping will be ultrasonically tested.

1. ASTM A350 Chemical Composition Requirements

Element	Composition, w.t % Grades
	LF1	LF2	LF3	LF5	LF6	LF9	LF787
C	≤0.30	≤0.30	≤0.20	≤0.30	≤0.22	≤0.20	≤0.07
Mn	0.60-1.35	0.60-1.35	≤0.90	0.60-1.35	1.15–1.50	0.40–1.06	0.40–0.70
P	≤0.035	≤0.035	≤0.035	≤0.035	≤0.025	≤0.035	≤0.025
S	≤0.040	≤0.040	≤0.040	≤0.040	≤0.025	≤0.040	≤0.025
Si	0.15-0.30	0.15-0.30	0.20-0.35	0.20-0.35	0.15-0.30	...	≤0.40
Ni	≤0.40	≤0.40	3.30-3.70	1.00-2.00	≤0.40	1.60-2.24	0.70–1.00
Cr	≤0.30	≤0.30	≤0.30	≤0.30	≤0.30	≤0.30	0.60–0.90
Mo	≤0.12	≤0.12	≤0.12	≤0.12	≤0.12	≤0.12	0.15-0.25
Cu	≤0.40	≤0.40	≤0.40	≤0.40	≤0.40	0.75–1.25	1.00-1.30
Cb	≤0.02	≤0.02	≤0.02	≤0.02	≤0.02	≤0.02	≥0.02
V	≤0.08	≤0.08	≤0.03	≤0.03	0.04-0.11	≤0.03	≤0.03
N	...	...	...	...	0.01–0.030	...	...

*1. When vacuum carbon-deoxidation is required, the silicon content shall be 0.12% maximum.
*2. For grades LF1, LF2 & LF6, the sum of Cu, Ni, Cr, V and Mo shall not exceed 1.00 % on heat analysis.
*3. For all grades except grade LF787, the sum of Cr and Mo shall not exceed 0.32 % on heat analysis.
*4. For grades LF1 & LF2, the limit for Cb may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
*5. The carbon equivalent C.E = [C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15] shall not exceed 0.45%.

2. ASTM A350 Mechanical Properties

Grade/Class	Tensile Strength		Yield Strength, min.		Elongation, min.	Hardness, max.
	ksi	MPa	ksi	MPa	%	HBW
LF1 CL1	60-85	415–585	30	205	25	197
LF5 CL1	60-85	415–585	30	205	25	197
LF2 CL1	70–95	485–655	36	250	22	197
LF2 CL2	70–95	485–655	36	250	22	197
LF3 CL1	70–95	485–655	37.5	260	22	197
LF3 CL2	70–95	485–655	37.5	260	22	197
LF5 CL2	70–95	485–655	37.5	260	22	197
LF6 CL1	66–91	455–630	52	360	22	197
LF6 CL2	75–100	515–690	60	415	20	197
LF6 CL3	75–100	515–690	60	415	20	197
LF9	63–88	435–605	46	315	25	197
LF787 CL2	65-85	450-585	55	380	20	197
LF787 CL3	75-95	515-655	65	450	20	197

*1. The elongation values are on the basis of standard round specimen, or small proportional specimen, min % in 4D gauge length.
*2. The yield strength shall be determined by either the 0.2 % offset method or the 0.5 % extension under load method.

3. ASTM A350 Charpy V-Notch Impact Properties

Charpy V-Notch Energy Requirements for 10x10 mm Specimens
Grade/ Class	*A		*B
	ft*lbf	J	ft*lbf	J
LF1 and LF9	13	18	10	14
LF2 CL1	15	20	12	16
LF3 CL1	15	20	12	16
LF5 CL1 & CL2	15	20	12	16
LF787 CL2 & CL3	15	20	12	16
LF6 CL1	15	20	12	16
LF2 CL2	20	27	15	20
LF3 CL2	20	27	15	20
LF6 CL2 & CL3	20	27	15	20

*A denotes minimum impact energy required for average of each set of three specimens.
*B denotes minimum impact energy permitted for one specimen only of a set.

Standard Impact Test Temperature for 10x10 mm Specimens
Grade/ Class	Test Temperature
	°F	°C
LF1	-20	-29
LF2 CL1	-50	-46
LF2 CL2	-0	-18
LF3 CL1 & CL2	-150	-101
LF5 CL1 & CL2	-75	-59
LF6 CL1 & CL2	-60	-51
LF6 CL3	-0	-18
LF9	-100	-73
LF787 CL2	-75	-59
LF787 CL3	-100	-73

* Applicable for specimens representing forging material with thickness ≥ 10 mm.

Minimum Equivalent Absorbed Energy for Various Specimen Sizes. ft·lbf [J]
Standard Size	3/4 Size	2/3 Size	1/2 Size	1/3 Size	1/4 Size
10x10 mm	10x7.5 mm	10x6.6 mm	10x5 mm	10x3.3 mm	10x2.5 mm
15 [20]	12 [16]	10 [14]	8 [11]	5 [7]	4 [6]
13 [18]	10 [14]	9 [12]	7 [10]	5 [7]	4 [6]
12 [16]	10 [14]	9 [12]	7 [10]	4 [6]	3 [5]
10 [14]	8 [11]	7 [10]	5 [7]	3 [5]	3 [5]

* Straight-line interpolation for intermediate values is permitted.

4. Heat Treatment & Welding Process

As specified by ASTM A350, after hot working and before reheating for heat treatment, the forging shall be allowed to cool substantially below the transformation range. Forgings of grades other than Grade LF787 shall be furnished in the normalized, or normalized and tempered, or quenched and tempered condition. All quenched forgings shall be then tempered at 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.  Grade LF787 forgings shall be furnished in either the normalized-and-precipitation heat treated condition or in the quenched-and-precipitation heat treated condition.

For Grade LF1 and LF2 forgings, the weld metal shall be deposited using carbon steel electrodes E 7015, E 7016, or E 7018, complying with AWS A 5.1. For Grade LF2 forgings, the weld metal shall be deposited using low-alloy steel electrodes E 7015-A1; E 7016-A1, or E 7018-A1 complying with AWS 5.5; for Grade LF3 forgings, the weld metal shall be deposited using low-alloy steel electrodes E 8016-C2 or E 8018-C2 complying with AWS A 5.5; for Grades LF5, LF9, and LF787 forgings, the weld metal shall be deposited using low-alloy steel electrodes E 8016-C1 or E 8018-C1 complying withAWS A 5.5. For Grade LF6, the electrodes shall be low-hydrogen, E-XX15, E-XX16, or E-XX18 complying with AWS A 5.1 or A 5.5, as applicable.

5. Product Forms & Dimensional Standards

The Dimensional Standards for ASTM A350 Forgings
ASME B16.5	Steel Pipe Flanges and Flanged Fittings
ASME B16.9	Factory-MadeWroughtSteelButt-WeldingFittings
ASME B16.11	Forged Steel Fittings, Socket-Welding and Threaded4
ASME B16.34	Valves-Flanged, Threaded, and Welding End
ASME B16.47	Large Diameter Steel Flanges
API 600	Steel Gate Valves with Flanged or Butt-Welding Ends
API 602	Compact Design Carbon Steel Gate Valves for Refinery Use
API 605	Large Diameter Carbon Steel Flanges

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