ASTM A193

First introduced in 1936, ASTM A193 is a widely used specification in petroleum, chemical, and power generation industries. It covers alloy steel and stainless steel bolting materials designed for high-temperature or high-pressure applications.

Typical uses include:

Pressure vessels

Valves

Flanges

Fittings

While ASTM A193 fasteners are often available in national coarse (UNC) threads, for traditional applications the standard specifies 8 threads per inch (TPI) for bolt diameters above 1 inch.

Common Grades in ASTM A193

ASTM A193 includes multiple grades of fasteners, each designed for specific operating conditions. Some popular grades are:

B7 – Chromium-molybdenum alloy steel, heat-treated for strength, ideal for high-pressure applications.

B7M - Similar to Grade B7 but tempered to lower hardness, providing improved ductility and reducing the risk of hydrogen embrittlement in sour-gas or high-temperature environments.

B8 – Stainless steel for corrosion resistance and moderate strength.

B8M – Molybdenum-bearing stainless steel for superior corrosion resistance.

(Note: Other grades like B5, B6, and B16 are also covered under ASTM A193 but are not detailed here.)

Grade	Description
B7	Alloy steel, AISI 4140/4142, quenched and tempered for high strength.
B7M	Alloy-Steel and Stainless-Steel Bolting Materials for High Temperature or High Pressure Service and Other Special Purpose Applications
B8 Class 1	Stainless steel, AISI 304, carbide solution treated for corrosion resistance.
B8M Class 1	Stainless steel, AISI 316, carbide solution treated for enhanced corrosion resistance.
B8 Class 2	Stainless steel, AISI 304, carbide solution treated and strain hardened for added strength.
B8M Class 2	Stainless steel, AISI 316, carbide solution treated and strain hardened for added strength and corrosion resistance.

A193 Mechanical Properties Inch Products:

Grade	Size	Tensile ksi, min	Yield, ksi, min	Elong, %, min	RA % min	HBW	Rockwell
B7	Up to 2-1/2	125	105	16	50	321 max	35 HRC max
	2-5/8 - 4	115	95	16	50
	4-1/8 - 7	100	75	18	50
B7M	4 and under	100	80	18	50	235 max	99 HRB max
B7M	over 4 to 7	100	75	18	50	235 max	99 HRB max
B8 Class 1	All	75	30	30	50	223 max	96 HRB max
B8M Class 1	All	75	30	30	50	223 max	96 HRB max
B8 Class 2	Up to 3/4	125	100	12	35	321 max	35 HRC 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 HRC 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 Mechanical Properties Metric Products:

Grade	Size	Tensile ksi, min	Yield, ksi, min	Elong, %, min	RA % min	HBW	Rockwell
B7	M64 and under	860	720	16	50	321 max	35 HRC max
	over M64 TO M100	795	655	16	50
	over M100 to M180	690	515	18	50
B7M	M100 and under	690	550	18	50	235 max	99 HRB max
B7M	over M100 to M180	690	515	18	50	235 max	99 HRB max
B16	M64 and under	860	725	18	50	321 max	35 HRC max
	over M64 TO M100	760	655	17	45
	over M100 to M200	690	585	16	45

A193 Chemical Properties:

Element	B7/B7M (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%