ASTM A350 Flange Material Specification

ASTM A350 covers various grades of carbon and low-alloy steels, forged or ring-rolled flanges, forged fittings and valves primarily intended for use at lower temperatures and requiring impact testing.

They are manufactured according to the corresponding dimensional standards of ASME or API. The forgings can be manufactured from ingots, blooms, billets, slabs or bars by hot forging process. The steel should be completely killed and fine-grained.

ASTM A350 includes different grades and classes such as Grade‎‏ LF1, Grade LF2, Grade LF3, Grade LF5, Grade LF6, Grade LF9, Grade LF787, and Class 1, Class 2, Class 3.

Chemical Composition

Element	Composition, w.t % Grades
	LF1	LF2	LF3	LF5	LF6	LF9	LF787
Carbon max	0.30	0.30	0.20	0.30	0.22	0.20	0.07
Manganese	0.60-1.35	0.60-1.35	0.90 max	0.60-1.35	1.15-1.50	0.40-1.06	0.40-0.70
Phosphorus max	0.035	0.035	0.035	0.035	0.025	0.035	0.025
Sulfur max	0.040	0.040	0.040	0.040	0.025	0.040	0.025
Silicon(a)	0.15-0.30	0.15-0.30	0.20-0.35	0.20-0.35	0.15-0.30	...	0.40 max
Nickel	0.40 max(b)	0.40 max(b)	3.30-3.70 max	1.00-2.00 max	0.40 max(b)	1.60-2.24	0.70-1.00
Chromium	0.30 max(b)(c)	0.30 max(b)(c)	0.30 max(c)	0.30 max(c)	0.30 max(b)(c)	0.30 max(c)	0.60-0.90
Molybdenum	0.12 max(b)(c)	0.12 max(b)(c)	0.12 max(c)	0.12 max(c)	0.12 max(b)(c)	0.12 max(c)	0.15-0.25
Copper	0.40 max(b)	0.40 max(b)	0.40 max	0.40 max	0.40 max(b)	0.75-1.25	1.00-1.30
Niobium(e)	0.02 max(d)	0.02 max(d)	0.02 max	0.02 max	0.02 max	0.02 max	-0.02 min
Vanadium	0.08 max	0.08 max	0.03 max	0.03 max	0.04-0.11	0.03 max	0.03 max
Nitrogen	...	...	...	...	0.01-0.030	...	...

• (a) When vacuum carbon-deoxidation is required, 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 niobium (columbium) may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
• (e) Niobium and columbium are interchangeable names for the same element and both names are acceptable for use in A01.22 specifications.

Mechanical Requirements

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
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 CL1	60-85	415-585	30	205	25	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

Elongation values are based on a standard round specimen, or a small proportional specimen, minus % in 4D length‎‏ gauge. Yield‎‏ strength should be determined using the 0.2%‎‏ offset method or the 0.5%‎‏ extension under load method.

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 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 Minimum impact energy required for average of each set of three specimens, ft·lbf (J)
B Minimum Impact Energy Permitted for One Specimen nly of a Set, ft·lbf (J)

Heat Treatment

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.

ASTM Grade LF787 forgings shall be furnished in either the normalized-and-precipitation heat treated condition or in the quenched-and-precipitation heat treated condition.

Referenced Documents

ASTM Standards

• A788 Specification for Steel Forgings, General Requirements
• A961 Specification for Common Requirements for Steel Flanges, Forged Fittings, Valves, and Parts forPiping Applications

ASME Standards

B16.5 Steel Pipe Flanges and Flanged Fittings

B16.9 Factory-MadeWrought Steel Butt-Welding Fittings

B16.10 Face-to-Face and End-to-End Dimensions of Ferrous Valves

B16.11 Forged Steel Fittings, Socket-Welding and Threaded

B16.30 Unfired Pressure Vessel Flange Dimensions

B16.34 Valves-Flanged, Threaded, and Welding End

B16.47 Large Diameter Steel Flanges

ASME Boiler and Pressure Vessel Code

• Section IX2

API Standards

• 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

Frequently used ASTM Grades

Material	Pipes	Fittings	Flanges	Valves	Bolts & Nuts
Carbon Steel	A106 Gr A	A234 Gr WPA	A105	A216 Gr WCB	A193 Gr B7 A194 Gr 2H
	A106 Gr B	A234 Gr WPB	A105	A216 Gr WCB
	A106 Gr C	A234 Gr WPC	A105	A216 Gr WCB
Carbon Steel Alloy High-Temp	A335 Gr P1	A234 Gr WP1	A182 Gr F1	A217 Gr WC1	A193 Gr B7 A194 Gr 2H
	A335 Gr P11	A234 Gr WP11	A182 Gr F11	A217 Gr WC6
	A335 Gr P12	A234 Gr WP12	A182 Gr F12	A217 Gr WC6
	A335 Gr P22	A234 Gr WP22	A182 Gr F22	A217 Gr WC9
	A335 Gr P5	A234 Gr WP5	A182 Gr F5	A217 Gr C5
	A335 Gr P9	A234 Gr WP9	A182 Gr F9	A217 Gr C12
Carbon Steel Alloy Low-Temp	A333 Gr 6	A420 Gr WPL6	A350 Gr LF2	A352 Gr LCB	A320 Gr L7 A194 Gr 7
	A333 Gr 3	A420 Gr WPL3	A350 Gr LF3	A352 Gr LC3
Austenitic Stainless Steel	A312 Gr TP304	A403 Gr WP304	A182 Gr F304	A182 Gr F304	A193 Gr B8 A194 Gr 8
	A312 Gr TP316	A403 Gr WP316	A182 Gr F316	A182 Gr F316
	A312 Gr TP321	A403 Gr WP321	A182 Gr F321	A182 Gr F321
	A312 Gr TP347	A403 Gr WP347	A182 Gr F347	A182 Gr F347

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