ASTM A193 Grade B7 / B8 / B8M
A193 covers alloy and stainless bolting for high-temperature and pressure service: flanges, valves and process equipment. B7 chromium-molybdenum steel is the most common grade.
| Marking | Grade on the stud end plus maker ID |
|---|---|
| Nuts | ASTM A194 2H for B7; 2HM for B7M; 8 / 8M for B8 / B8M |
Common grades
| Grade | Material | Size | Tensile (min) | Yield (min) |
|---|---|---|---|---|
| B7 | Cr-Mo alloy, Q&T | to 2-1/2 in | 125 ksi | 105 ksi |
| B7 | over 2-1/2 to 4 in | 115 ksi | 95 ksi | |
| B7 | over 4 to 7 in | 100 ksi | 75 ksi | |
| B7M | Cr-Mo, hardness-controlled | to 4 in | 100 ksi | 80 ksi |
| B8 / B8M Class 1 | 304 / 316, solution treated | all | 75 ksi | 30 ksi |
| B8 / B8M Class 2 | 304 / 316, strain hardened | to 3/4 in | 125 / 110 ksi | 100 / 95 ksi |
Class 2 strength falls with diameter; values shown for the smallest size range. Verify the full size table in A193.
These tables carry the same figures as the printed sheet below.
The printed sheet
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Text version of this sheet
ASTM A193 / A193M · high-temperature and pressure bolting
What it is
FIELD IDENTIFICATION
A193 covers alloy and stainless bolting for high-temperature and pressure service: flanges, valves and
process equipment. B7 chromium-molybdenum steel is the most common grade.
B7
Marking
Grade on the stud end plus maker ID
Nuts
ASTM A194 2H for B7; 2HM for B7M; 8 / 8M for B8 / B8M
Stud bolt with heavy hex nuts; grade marked
on stud end
Common grades
Grade
Material
Size
Tensile (min)
Yield (min)
B7
Cr-Mo alloy, Q&T
to 2-1/2 in
125 ksi
105 ksi
over 2-1/2 to 4 in
115 ksi
95 ksi
B7
B7
over 4 to 7 in
100 ksi
75 ksi
B7M
Cr-Mo, hardness-controlled
to 4 in
100 ksi
80 ksi
B8 / B8M Class 1
304 / 316, solution treated
all
75 ksi
30 ksi
B8 / B8M Class 2
304 / 316, strain hardened
to 3/4 in
125 / 110 ksi
100 / 95 ksi
Class 2 strength falls with diameter; values shown for the smallest size range. Verify the full size table in A193.
Key points
B7M is hardness-limited for sour (H2S) service.
Governing standards: ASTM A193/A193M-24; ASTM A194/A194M-24. Editions shown are the latest confirmed as of September 2026. The drawing and the governing standard
always take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-15424C · thefastenerapp.com/fastener-guide/technical-reference/astm-a193-grade-b7-b8-b8m · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
