Originally approved in 1936, this specification is heavily utilized in petroleum and chemical construction applications. The ASTM standard covers alloy steel and stainless steel bolting materials for high temperature or high-pressure service. This specification includes fasteners intended for use in pressure vessels, valves, flanges, and fittings. Although, this material is often available in national coarse (UNC) thread pitches, if being used in traditional applications, threads are specified 8 threads per inch (tpi) for diameters above one inch.
Below is a basic summary of a few of the common grades. ASTM A193 covers a number of other standard specifications not covered in this description including B5, B6, and B16.
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 |
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 |
| 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 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
