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 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 |
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 |
0.37 - 0.49% |
0.08% max |
0.08% max |
| Manganese |
0.65 - 1.10% |
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 |
0.75 - 1.20% |
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% |
