Flange Materials Specification

Dimensions from carbon steel and stainless steel flanges are defined in the ASME B16.5 standard. The material qualities for these flanges are defined in the ASTM standards.
These ASTM standards, define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by "Grade".

Large size bland flange	Stainless blind flange

For example, a carbon steel flange can be identified with Grade F9 or F11, a stainless-steel flange with Grade F316 or Grade F321 etc..
Below you will find as an example a table with chemical requirements for fittings ASTM A403 Grade WP304, WP304L, WP316L and a table with frequent Grades, arranged on pipe and pipe-components, which belong together as a group. As you may be have noted, in the table below, ASTM A105 has no Grade. Sometimes ASTM A105N is described;
"N" stands not for Grade, but for normalized. Normalizing is a type of heat treatment, applicable to ferrous metals only. The purpose of normalizing is to remove the internal stresses induced by heat treating, casting, forming etc.

Carbon Steel Flange

ASTM A105, ASTM A350 LF1, LF2 CL1/CL2, LF3 CL1/CL2

ASTM A694 F42, F46, F48, F50, F52, F56, F60, F65, F70

Stainless Steel Flange

ASTM A182 F304/304L, F316/316L, F316H, F310, F321, F44 (UNS S31254)

Alloy Steel Flange

ASTM A182 F1, F5a, F9, F11, F12, F22, F91

Chemical Requirements (Composition, %, max)

Material Symbol	C	Mn	P	S	Si	Ni	Cr	Mo	Cu	N	V	Co
ASTM A105	0.35	0.60-1.05	0.035	0.040	0.10-0.35	0.40	0.30	0.12	0.40	_	0.08	_
ASTM A350 LF2	0.30	0.60-1.35	0.035	0.040	0.15-0.30	0.40	0.30	0.12	0.40	_	0.08	0.02
ASTM A182 F304	0.08	2.00	0.045	0.030	1.00	8.0-11.0	18.0-20.0	_	_	_	_	_
ASTM A182 F304L	0.03	2.00	0.045	0.030	1.00	8.0-13.0	18.0-20.0	_	_	_	_	_
ASTM A182 F316	0.08	2.00	0.045	0.030	1.00	10.0-14.0	16.0-18.0	2.00-3.00	_	_	_	_
ASTM A182 F316L	0.03	2.00	0.045	0.030	1.00	10.0-15.0	16.0-18.0	2.00-3.00	_	_	_	_
ASTM A182 F321	0.08	2.00	0.045	0.030	1.00	9.0-12.0	17.0-19.0	_	_	_	_	_
EN 10025 S235JR	0.20	1.40	0.045	0.045	_	_	_	_	_	0.009	_	_
20Mn	0.17-0.23	0.70-1.00	0.035	0.035	0.17-0.37	0.30	0.25		0.25
20	0.17-0.23	0.60-1.00	0.030	0.020	0.17-0.37	0.25	0.25		0.25
16Mn	0.13-0.19	1.20-1.60	0.030	0.020	0.20-0.60	0.30	0.30		0.25

Mechanical Requirements

Material Symbol	Tensile Strength, min, MPa	Yield point, min, Mpa	Elongation, min, %	Reduction of area, min, %	Hardness, max, HB	Min. Impact Average, J	Test Temperature, °C
ASTM A105	485	250	22	30	187
ASTM A350 LF2	485-655	250	22	30		20	-46
ASTM A182 F304	515	205	30	50
ASTM A182 F304L	485	170	30	50
ASTM A182 F316	515	205	30	50
ASTM A182 F316L	485	170	30	50
ASTM A182 F321	515	205	30	50
20Mn	450	275	24	50	197
20	410	245	25	55	156