Carbon Steel
Fasteners
Manufacturer India
Grade Selector — ISO 898 · DIN · ASTM Strength Classes
Carbon steel fastener strength is defined by property class (ISO/DIN system) or ASTM grade designation. Select by required minimum tensile strength and the applicable design code. Bar charts show UTS relative to Grade 4.6 baseline.
Grade 4.6
Grade 8.8
Grade 10.9
Grade 12.9
ASTM A193 B7
ASTM A307
How to Read Property Class Numbers — ISO 898 Marking Explained
The ISO 898 / DIN property class system uses a two-digit code separated by a decimal point to encode both UTS and yield ratio in a single number. Grade 8.8: First digit (8) × 100 = 800 MPa minimum UTS. Second digit (8) × 10% × first digit (800 MPa) = 640 MPa minimum yield strength. The ratio 640/800 = 0.80 — confirming 80% yield-to-tensile ratio. Grade 10.9: 10 × 100 = 1000 MPa UTS. 9 × 10% × 1000 = 900 MPa YS (actual standard specifies ≥940 MPa — the rule is approximate).
This property class system applies to ISO 898 hex bolts, set screws, and studs in metric thread M1.6–M100. It does not apply to nuts — nuts use a different marking system (property class 8, 10, 12 without the decimal) defined by proof load. The ASTM system uses entirely different designations (A193 B7, A307, A325) with separate material and mechanical property specifications.
Grade 12.9 and hydrogen embrittlement: High-strength fasteners (≥1040 MPa / Grade 10.9 and above) are susceptible to hydrogen embrittlement during electroplating — the reason Grade 12.9 is never hot-dip galvanised and must not be electroplated with zinc without a low-hydrogen baking procedure after plating. For Grade 12.9 in corrosive environments, specify a mechanical zinc coating (Geomet, Delta-Protekt) or stainless steel fasteners.
| Property | A193 B7 | Grade 8.8 |
|---|---|---|
| Steel Type | Cr-Mo (4140) | Med. Carbon Q&T |
| Min UTS | ≥862 MPa | ≥800 MPa |
| Min YS | ≥724 MPa | ≥640 MPa |
| Hardness | ≤HRC 35 | HRB 84–HRC 34 |
| Application | ASME B16.5 flanges | DIN structural |
| Nut Pairing | ASTM A194 2H | DIN 934 Gr.8 |
| NACE Sour ver. | B7M (≤235 HB) | — |
Carbon Steel Fastener Types — Full Range
Black self-colour, HDG, and zinc-plated options across all grades. ASTM A193 B7 stud bolts for ASME B16.5 service. DIN Grade 8.8 and 10.9 for structural and mechanical applications. M4–M100.
A193 B7 Stud Bolts
Cr-Mo alloy steel (AISI 4140) fully threaded stud bolts for ASME B16.5 pressure flanges — the most widely specified stud bolt in global refinery, petrochemical, and power generation ASME bolted connections. Class 150–2500, NPS ½”–24″, M12–M100, lengths to 3,000mm. Matching ASTM A194 2H heavy hex nuts. NABL hardness and tensile on every lot.
Structural Hex Bolts
Grade 8.8 and 10.9 hex bolts (DIN 931 partial thread, DIN 933 full thread) for steel structures, industrial equipment frames, bridge construction (Grade 10.9 per EN 14399), wind turbine towers, machinery mounting, and all structural applications requiring calculable bolt preload from a defined property class. M4–M100, black and HDG (8.8 only).
Hex Nuts
ASTM A194 Grade 2H (B7 matching nut, carbon steel), 2HM (NACE sour service ≤235 HB), DIN 934 Grade 8 (8.8 matching nut), Grade 10 (10.9 matching), Grade 12 (12.9 matching). Standard hex and heavy hex (ASME B18.2.2). M4–M100. NABL hardness testing confirming property class and NACE hardness limits for 2HM lots.
Washers
ASTM F436 hardened structural washers for A325/A490 structural bolt assemblies. DIN 125 plain flat washers in Grade 8.8 and carbon steel. HDG washers to ASTM A153. Spring washers DIN 127. Large OD structural washers DIN 9021. IS 1363 washers for Indian standard construction. M4–M100.
Anchor Bolts / Foundation Bolts
ASTM A307 Grade A/B anchor bolts, J-bolts, L-bolts, and double-end bolts in carbon steel for equipment and structural foundation anchoring. IS 5624 foundation bolts for Indian civil projects. Plain and HDG (ASTM A153). M16–M100, custom lengths to 3,000mm. Machine, equipment, tower, and civil structure foundation anchor bolt sets.
U-Bolts
Round bend U-bolts, square bend U-bolts, and pipe clamp U-bolts in carbon steel Grade 4.6 and Grade 8.8. M8–M36. For pipe supports, conduit clamps, rack saddles, cable tray supports, and structural attachment applications. Available in black, zinc plated, and HDG ASTM A153. Custom bend radius to drawing.
Threaded Rods
Carbon steel threaded rods in Grade 4.6, 8.8, and ASTM A193 B7 material. Full thread, metric and inch UNC. M4–M100, lengths to 6,000mm. Hanger rods for suspended ceilings and pipework, structural tie-rods, sag rods, and all applications requiring long threaded rod in carbon steel. HDG available in Grade 4.6 and 8.8.
Custom Carbon Steel
Non-standard dimensions, inch UNC/UNF thread in metric drawings, A307 anchor bolt bespoke bends, coupling nuts, turnbuckles, and all drawing-specific carbon steel fastener configurations. Contact sales@akbarfasteners.in with grade, dimensions, surface finish, and quantity.
Carbon Steel Surface Finishes & Coatings
Carbon steel corrodes without protection. Surface finish selection governs service life in the installation environment. Grade 12.9 must never be hot-dip galvanised — specify mechanical zinc or change alloy.
Carbon Steel Application Areas
From general structural construction (Grade 8.8 HDG) through ASME pressure vessel stud bolts (A193 B7), high-strength structural (Grade 10.9), anchor bolts (A307), and NACE sour service (B7M).
Structural Construction
A325/F3125 structural
Refinery / Petrochemical
pressure vessel stud bolts
Oil & Gas NACE
NACE MR0175 sets
Power Generation
turbine structural bolts
Civil & Infrastructure
HDG foundation bolts
Wind Energy
EN 14399 structural
Heavy Equipment
10.9 flange connections
Chemical Processing
ASME VIII vessel bolts
Carbon Steel Standards Coverage
Same ISO 9001:2015 quality system across all grades. NABL-accredited tensile and hardness testing on every lot — the critical quality gate for confirming Grade 8.8, 10.9, 12.9, and A193 B7 compliance.
Complete Documentation Package
Grade / ASTM Stated
Tensile · Hardness
NACE B7M ≤235 HB
Conformance
TÜV · BV · Lloyds
Related Higher-Alloy Fastener Grades
Carbon steel for strength at low cost. SS 316L for corrosion resistance. A193 B7 (alloy steel) for ASME pressure service. Exotic alloys for aggressive chemistry.
SS 316L Fasteners
When corrosion protection is required beyond coating capability — SS 316L (2% Mo, PRE≈24) is the first stainless upgrade from carbon steel for chemical, pharmaceutical, food, and marine atmospheric service where HDG or zinc plating would fail.
View SS 316L →SS 304 Fasteners
The most widely used stainless steel — SS 304 (A2-70) provides atmospheric and mild corrosion resistance superior to carbon steel + coating at comparable cost in smaller fastener sizes. For food equipment, clean-room, architectural, and indoor corrosive atmosphere bolting.
View SS Range →Hastelloy C276 Fasteners
When the process environment contains HCl, mixed acids, or concentrated chlorides — carbon steel B7 stud bolts fail immediately; SS 316L fails by pitting. Hastelloy C276’s PRE≈66 handles the aggressive environments that make all carbon and stainless steel grades unsuitable.
View C276 →Full Bolt Range
Complete bolt manufacturing capability at Akbar Fasteners — carbon steel through exotic alloy, M4–M100, all head forms, all finishes. ASTM, DIN, ISO, IS, and custom. One source for the complete fastener schedule of any industrial project.
View Bolt Range →Need Carbon Steel
Fasteners?
Grade · form · size · surface finish · standard · quantity. Akbar Fasteners Pvt. Ltd. responds within 24 hours with pricing and full NABL documentation list.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in