B7 STUDS | BOLTS

ASTM A193

A193 Grades

B7	Alloy steel, AISI 4140/4142 quenched and tempered
B8	Class 1 Stainless steel, AISI 304, carbide solution treated.
B8M	Class 1 Stainless steel, AISI 316, carbide solution treated.
B8	Class 2 Stainless steel, AISI 304, carbide solution treated, strain hardened
B8M	Class 2 Stainless steel, AISI 316, carbide solution treated, strain hardened

A193 Mechanical Properties

Grade	Size	Tensile ksi, min	Yield, ksi, min	Elong, %, min	RA % min	HBW	HRC
B7	Up to 2-1/2	125	105	16	50	321 max	35 max
	2-5/8 – 4	115	95	16	50
	4-1/8 – 7	100	75	18	50
B8 Class 1	All	75	30	30	50	223 max	35 max
B8M Class 1	All	75	30	30	50	223 max	96 max
B8 Class 2	Up to 3/4	125	100	12	35	321 max	35 max
	7/8 – 1	115	80	15	35
	1-1/8 – 1-1/4	105	65	20	35
	1-3/8 – 1-1/2	100	50	28	45
B8M Class 2	Up to 3/4	110	95	15	45	321 max	35 max
	7/8 – 1	100	80	20	45
	1-1/8 – 1-1/4	95	65	25	45
	1-3/8 – 1-1/2	90	50	30	45

A193 Chemical Properties

Element	B7 (AISI 4140)	B8 (AISI 304)	B8M (AISI 316)
Carbon	0.38 – 0.48%	0.08% max	0.08% max
Manganese	0.75 – 1.00%	2.00% max	2.00% max
Phosphorus, max	0.035%	0.045%	0.045%
Sulfur, max	0.040%	0.030%	0.030%
Silicon	0.15 – 0.35%	1.00% max	1.00% max
Chromium	0.80 – 1.10%	18.0 – 20.0%	16.0 – 18.0%
Nickel		8.0 – 11.0%	10.0 – 14.0%
Molybdenum	0.15 – 0.25%		2.00 – 3.00%

A193 Recommended Hardware

Bolt Grade	Nuts	Washers
B7	A194 Grade 2H	F436
B8 Class 1	A194 Grade 8	SS304
B8M Class 1	A194 Grade 8M	SS316
B8 Class 2	A194 Grade 8	SS304
B8M Class 2	A194 Grade 8M	SS316

ASTM A193 Grade B8 specification covers requirements for 304/304L stainless steel bolting material with high tensile properties, for use in high temperature or high-pressure service and other special purpose applications. It is a fastener material specification defining typical chemical composition, mechanical properties, hardness requirement, preferential heat treatment, product marking, certification and other requirements, suitable for bolting used in pressure vessel service, valves, flanges and fittings. ASTM A193 defines both SI (Metric) and inch-pound units.

ASTM A193 Grade B8 is subdivided into 3 property classes with different tensile strength; Class 1, Class 2 & Class 2B. A193 Gr B8 Class 1 is a carbide solution-treated 304 stainless steel bolting material with minimum tensile strength requirement of 75 ksi (515 Mpa), yield 30 ksi (205 Mpa), and maximum hardness of 223 HBW (96 HRB); A193 Gr B8 Class 2 has a minimum tensile requirement of 125 ksi (860 Mpa), yield of 100 ksi (690 Mpa), and maximum hardness of 321 HBW (35 HRC); A193 Gr B8 Class 2B has a minimum tensile requirement of 95 ksi (655 Mpa), yield of 75 ksi (515 Mpa), and maximum hardness of 321 HBW (35 HRC).