Description
Controlled-hardness Cr-Mo alloy steel
ASTM A193 B7M Threaded Rod
Heat-treated alloy steel all-thread for pressure bolting where the design requires B7M mechanical properties, hardness control and project-specific sour-service qualification.
Product overview
ASTM A193 Grade B7M threaded rod is a chromium-molybdenum alloy-steel bolting material with mechanical-property and maximum-hardness controls that differ from standard B7. It is frequently specified for sour hydrocarbon service and other applications where controlled hardness is part of the materials strategy.
B7M marking alone does not automatically establish compliance with every NACE MR0175 / ISO 15156 or project sour-service requirement. The purchase order must identify the environmental standard, heat-treatment sequence, hardness testing, supplementary tests and documentation required for the finished threaded rod.
ASTM A193 B7M threaded rod specifications
| Bolting standard | ASTM A193/A193M, ordered edition |
|---|---|
| Grade / material | Grade B7M, chromium-molybdenum alloy steel |
| Condition | Heat treated to B7M mechanical-property and hardness requirements |
| Thread systems | ASME B1.1 UNC, UNF or 8UN; metric threads when ordered |
| Size range | 1/4–4 in and M6–M100 typical; exact range subject to testing and availability |
| Compatible nuts | ASTM A194 Grade 2HM commonly specified, subject to project requirements |
| Sour-service option | NACE MR0175 / ISO 15156 and purchaser supplements only when explicitly ordered |
| Finish options | Plain, black or qualified project coating; coating and lubricant reviewed together |
Final dimensions, tolerances, heat treatment, coating, testing and acceptance criteria follow the confirmed purchase order and the applicable standard edition. Availability depends on diameter, length, thread form and production quantity.
Why specify this material?
B7M is considered when the materials engineer needs an established Cr-Mo bolting grade with controlled hardness. It is not simply a lower-cost alternative to corrosion-resistant alloy bolting; environment, stress, cathodic protection and service temperature still govern selection.
Engineering note
Cutting, thread production and heat treatment must follow the ordered standard and project sequence. Confirm whether hardness testing is required on each piece, each end or by lot, and whether testing must occur after all manufacturing operations.
Typical applications
Quality, inspection and documentation
Procurement should define hardness frequency, mechanical testing, heat-treatment traceability and any sour-service supplements. A complete B7M package commonly includes MTC, hardness results, thread inspection and coating records.
- EN 10204 3.1 material test certificate
- Heat-number and batch traceability
- Chemical composition and mechanical properties
- Dimensional inspection and thread gauging
- PMI for stainless and nickel alloys when ordered
- Coating thickness or surface inspection when applicable
- Third-party inspection and additional testing by agreement
- Export marking and seaworthy packing
Information required for quotation
- Material grade, governing material/bolting standard and required edition
- Diameter, thread series, pitch and thread class or tolerance
- Overall length, cut-end requirements and quantity
- Heat treatment, surface finish or coating system
- Matching nuts and washers, including anti-galling requirements
- Inspection plan, MTC, PMI, NDE and third-party witness requirements
- Delivery destination, packaging and required schedule
Frequently asked questions
Is ASTM A193 B7M automatically NACE compliant?
No. B7M provides grade-specific hardness and mechanical requirements, but NACE MR0175 / ISO 15156 suitability depends on the exact environment, product form, heat treatment and project requirements.
What nut grade is commonly used with B7M?
ASTM A194 Grade 2HM nuts are commonly specified. The engineer must confirm nut grade, hardness, coating and thread compatibility.
How does B7M differ from B7?
B7M has lower strength and controlled maximum hardness requirements compared with B7, together with grade-specific manufacturing and testing provisions.
Can B7M threaded rod be fluoropolymer coated?
Yes when permitted by the design and qualified purchase specification. Coating thickness, cure temperature, thread fit, lubricant and installation torque require coordinated control.
Related threaded rod products
Request a technical quotation
Send your bill of materials, drawing or project specification. SASA FLANGE will review the grade, thread, dimensions, documentation and delivery requirements before quotation.
