ASTM A193
Alloy and stainless steel bolting for high-temperature or high-pressure service
Covers alloy and stainless steel bolting for high-temperature or high-pressure service — stud bolts and bolts in grades B7, B8, B8M, B16 and others.
- Bolting
- ASME SA-193
- 5 grades supplied to it
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is ASTM A193?
ASTM A193 is the specification for alloy and stainless steel bolting for high-temperature or high-pressure service — bolting material (bars, bolts, screws, studs and stud bolts) for flanges, valves and pressure vessels; for threaded rod, confirm the required product form and grade in the purchase specification. The most common grades are B7 (quenched and tempered chromium-molybdenum steel), B7M (reduced hardness for sour service), B8 (304) and B8M (316). Matching nuts are ordered to ASTM A194.
ASTM A193 at a glance
| Products | Bolting material — bars, bolts, screws, studs and stud bolts for pressure equipment |
|---|---|
| Material families | Cr-Mo alloy steel and austenitic stainless |
| Key grades | B7, B7M, B16, B8 / B8M (class 1 and class 2) |
| Matching nuts | ASTM A194 — 2H with B7, 2HM with B7M, 8 / 8M with B8 / B8M |
| Low temperature | Not covered — use ASTM A320 (e.g. L7) |
| ASME designation | SA-193 |
ASTM A193 B7 minimum properties by diameter
B7 strength requirements step down as the diameter increases. Current standard verification pending. Numerical specification requirements are published only after the applicable current standard edition has been verified.
| Diameter | Tensile, min | Yield, min |
|---|---|---|
| Up to 2½" | Pending current standard text | Pending current standard text |
| Over 2½" to 4" | Pending current standard text | Pending current standard text |
| Over 4" to 7" | Pending current standard text | Pending current standard text |
A193 grades and their nuts
| Stud grade | Material | Nut (A194) | Typical use |
|---|---|---|---|
| B7 | Cr-Mo steel, quenched and tempered | 2H | General flanged joints, carbon and alloy piping |
| B7M | B7 with hardness limited for sour service | 2HM | H₂S service per NACE MR0175 |
| B8 class 1 / 2 | 304 stainless (class 2 strain hardened) | 8 | Corrosive service, moderate loads |
| B8M class 1 / 2 | 316 stainless (class 2 strain hardened) | 8M | Chlorides and marine exposure |
| ASTM A320 L7 | Cr-Mo steel, impact tested | 4 / 7 (with S3 marking 7L where impact tested) | Low-temperature service |
How to write ASTM A193 on a purchase order
Name the product, size, material specification and grade, the dimensional standard and the certificate. An example line:
Illustrative only — sizes, tests, inspection level and any project values come from your purchase specification.
ASTM A193 edition and verification status
Which edition we have confirmed, and what is still being checked before any numerical requirement is published here.
| Current edition (publisher listing) | A193/A193M-26 — checked 7 October 2026 |
|---|---|
| Full-text verification | In progress — numerical requirements are published here only after the current text has been reviewed |
| Edition on your order | The edition named in your purchase order or design code governs — confirm it with your enquiry |
What to know before ordering to ASTM A193
The points that decide whether material to ASTM A193 is accepted at inspection.
- B7 is chrome-moly alloy steel; B8 is 304 and B8M is 316 stainless.
- Class 1 is solution-treated; Class 2 is strain-hardened for higher strength.
- Nuts are ordered separately to ASTM A194.
How ASTM A193 fits into an order
A purchase order line is only complete when it names the material standard, the dimensional standard and the inspection document. Miss one and the mill, the inspector and the buyer can each read the order differently.
Standards used with ASTM A193
Same family
ASTM A193 — questions buyers ask
What is ASTM A193?
ASTM A193 is the specification for alloy and stainless steel bolting for high-temperature or high-pressure service — bolting material (bars, bolts, screws, studs and stud bolts) for flanges, valves and pressure vessels; for threaded rod, confirm the required product form and grade in the purchase specification. The most common grades are B7 (quenched and tempered chromium-molybdenum steel), B7M (reduced hardness for sour service), B8 (304) and B8M (316). Matching nuts are ordered to ASTM A194.
Which nut goes with an ASTM A193 B7 stud?
ASTM A194 grade 2H heavy hex nuts. For B7M studs in sour service use 2HM.
What is the difference between B8 class 1 and class 2?
Class 1 is solution treated (carbide solution treated). Class 2 is solution treated and then strain hardened, which raises strength — useful when stainless studs must carry higher bolt loads.
What is the difference between B8 and B8M?
B8 is 304 stainless; B8M is 316 stainless with molybdenum for better chloride resistance.
Can B7 be used at low temperature?
Not where impact properties are required. Use ASTM A320 L7, which is impact tested.
Which grades do you supply to ASTM A193?
SS 304, SS 304L, SS 316 / 316L, SS 321, SS 347 — see the table on this page for the exact product and designation.
What is the current edition of ASTM A193?
The publisher's listing checked on 7 October 2026 shows A193/A193M-26 as the current edition. The edition that governs an order is the one named in the purchase order or design code. Full-text review of the current edition is in progress, so numerical requirements are not published on this page yet.
Do you supply certificates to this standard?
Yes. Material is supplied with mill test certificates to EN 10204 3.1 showing the standard, grade and heat number; 3.2 with third-party inspection on request.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026