In high-pressure valves, flanges and process equipment where a 12-13% chromium martensitic stainless bolting grade is specified, ASTM A193 Grade B6 provides a high-strength Type 410 option. B6 is quenched and tempered and, for diameters through 4 inches in the ASTM mechanical table, carries minimum tensile and yield strengths of 110 ksi and 85 ksi.
Unifit Fastener manufactures ASTM A193 Grade B6 bolts, stud bolts and threaded bolting in India for pressure vessels, valve assemblies, process piping, refinery equipment and other elevated-temperature or high-pressure applications where B6 is specified. For the complete A193 grade family, see ASTM A193 grades and specifications. If the project calls for the lower-strength, controlled-hardness variant, compare ASTM A193 Grade B6X fasteners.
Request a Quote | Send ASTM A193 B6 RequirementASTM A193 Grade B6 is a chromium stainless bolting grade based on Type 410 / UNS S41000 chemistry. It belongs to the heat-treated ferritic/martensitic group within ASTM A193 and is supplied in the quenched-and-tempered condition to meet the grade's mechanical requirements.
The ASTM designation controls the bolting material, heat treatment and mechanical properties. It does not replace the product dimensional standard, thread requirement, matching nut specification or project inspection plan. A purchase order should therefore state B6 together with the bolt/stud geometry, dimensions, thread and documentation requirements.
For the wider material family, see stainless steel fasteners. Keep generic stainless material browsing on that page; this URL should remain focused on ASTM A193 B6.
B6 uses Type 410 / UNS S41000 chemistry with approximately 12-13% chromium. The values below are the public B6 composition limits used for engineering reference; verify the project-specified ASTM edition before purchase.
| Element | Minimum % | Maximum % |
|---|---|---|
| Carbon (C) | 0.08 | 0.15 |
| Manganese (Mn) | - | 1.00 |
| Phosphorus (P) | - | 0.040 |
| Sulfur (S) | - | 0.030 |
| Silicon (Si) | - | 1.00 |
| Chromium (Cr) | 11.50 | 13.50 |
B6 bolting is quenched and tempered. In the public ASTM A193 mechanical table, B6 for diameters up to 4 inches has a minimum tempering temperature of 1100°F (593°C). The finished bolting must then meet the required tensile, yield, elongation and reduction-of-area values.
| Diameter | Min tempering | Min tensile | Min yield | Elongation | RA | Hardness |
|---|---|---|---|---|---|---|
| Up to 4 in., inclusive | 1100°F / 593°C | 110 ksi / 760 MPa | 85 ksi / 585 MPa | 15% | 50% | No maximum shown in public table |
Do not publish a fixed hardening temperature as an ASTM requirement unless it is specifically supported by the applicable manufacturing procedure. For SEO and buyer clarity, the page should focus on the grade's required final condition and verified mechanical properties.
The most relevant B6 product forms for pressure-service procurement are stud bolts, headed bolts and threaded studs. The project should specify the product geometry separately from the B6 material grade.
| Product form | Typical use | What to specify |
|---|---|---|
| Stud bolts | Flanges, valves, pressure vessels and process-equipment joints | Diameter, overall length, thread series/pitch, full/double-end/tap-end form, nut quantity |
| Heavy hex / hex bolts | Pressure equipment and assemblies requiring a headed bolt | Diameter, length, dimensional standard, thread, head form |
| Threaded studs / rods | Custom-length threaded bolting | Diameter, length, thread, end configuration, cut/rolled thread if specified |
| Special / drawing-based bolting | Project-specific geometry or tolerances | Latest drawing, grade, dimensions, tolerances, finish and inspection scope |
Related product pages: industrial bolts | stud bolts
ASTM A193 B6 bolting is commonly paired with ASTM A194 Grade 6 heavy hex nuts. The final nut dimensions, thread, finish and project requirements should be confirmed as part of the complete assembly.
See ASTM A194 Grade 6 hex nuts for the dedicated nut specification page.
B6 and B6X use the same Type 410 / UNS S41000 chemistry. Their key difference is mechanical condition. B6 carries higher minimum strength; B6X lowers the strength requirement and adds a 26 HRC maximum hardness limit.
| Grade | Material | Tensile min | Yield min | Elong. min | Hardness | Page ownership |
|---|---|---|---|---|---|---|
| B6 | Type 410 / UNS S41000 | 110 ksi | 85 ksi | 15% | No max shown in public table | Standard higher-strength B6 intent |
| B6X | Type 410 / UNS S41000 | 90 ksi | 70 ksi | 16% | 26 HRC max | Controlled-hardness B6-family intent |
Open the dedicated ASTM A193 Grade B6X fasteners page when the purchase specification calls for B6X or a 26 HRC maximum. Do not substitute B6 and B6X without purchaser/engineering approval.
| RFQ field | What to send |
|---|---|
| Grade | ASTM A193 Grade B6; include required ASTM edition when project-controlled |
| Product form | Stud bolt, heavy hex/hex bolt, threaded stud/rod or drawing-based part |
| Diameter / length | Metric or inch; overall length and any plain-shank length |
| Thread | UNC, UNF, 8UN or metric; pitch/TPI and class/fit |
| Dimensional standard | ASME/ANSI, ISO, DIN or project drawing |
| Matching components | ASTM A194 Grade 6 nut requirement and washers if specified |
| Finish / surface | Plain, passivated or project-specific surface condition where applicable |
| Quantity / delivery | Quantity, destination and required schedule |
| Inspection / documents | MTC, PMI, mechanical/hardness testing, TPI, marking and project documentation |
The chromium content in Type 410 gives B6 better oxidation and general corrosion resistance than plain carbon or low-alloy steel, but B6 should not be treated as equivalent to austenitic Type 304 or 316 grades in aggressive chloride environments. If corrosion resistance is the dominant design requirement, the engineer may need to compare B6 with B8, B8M or a higher-alloy grade.
B6 is also not the low-temperature route within the ASTM bolting family. ASTM A320 is the specification normally associated with low-temperature bolting. The final grade should follow the service temperature, pressure, corrosion environment, joint design and governing project specification.
Related stainless grades: ASTM A193 Grade B8 fasteners | ASTM A193 Grade B8M fasteners.
B6 is used where the design or project specification calls for high-strength Type 410 stainless bolting under ASTM A193. Typical applications include:
The application list is not a substitute for material selection. B6 should be used because the project specification calls for its chemistry and properties, not simply because an industry appears in a supplier catalogue.
For critical pressure-service bolting, the RFQ should define traceability and inspection before production or dispatch. B6 parts should be identified to the applicable ASTM marking requirements and linked to the material heat/lot records.
ASTM A193 Grade B6 is a Type 410 / UNS S41000 chromium stainless bolting grade for high-temperature, high-pressure and other special-purpose A193 service. It is supplied in the quenched-and-tempered condition and, for diameters through 4 inches in the public ASTM table, has minimum tensile and yield strengths of 110 ksi and 85 ksi.
B6 and B6X share the same Type 410 / UNS S41000 chemistry. B6 has higher minimum strength at 110 ksi tensile and 85 ksi yield. B6X is 90 ksi tensile and 70 ksi yield and adds a 26 HRC maximum hardness limit. They are separate grade conditions and should not be substituted without approval.
Yes. B6 is based on Type 410 / UNS S41000 martensitic stainless steel. However, its corrosion behaviour is not the same as austenitic Type 304 or 316 grades, so the service environment must still be reviewed.
The public ASTM A193 mechanical table lists a minimum tempering temperature of 1100°F (593°C) for B6 in the stated size range. The final heat treatment and compliance should be verified against the ASTM edition specified on the order.
ASTM A194 Grade 6 heavy hex nuts are a common compatible nut specification for ASTM A193 B6 bolting. The nut dimensions, thread, finish and project requirements should be confirmed as part of the full assembly.
Do not assume this from the stainless-steel designation. B6 uses Type 410 chemistry and does not provide the chloride pitting resistance associated with 316-based or higher-alloy stainless grades. The project corrosion assessment should determine the material.
Send the B6 grade, product form, diameter, length, thread, dimensional standard or drawing, matching nut/washer requirement, surface condition, quantity, delivery location and any MTC, PMI, testing, third-party inspection or marking requirement.