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Stainless Steel 347/347H Bolts are engineered fasteners designed for high-temperature service environments where resistance to intergranular corrosion and oxidation is critical. These bolts are manufactured using niobium-stabilized austenitic stainless steel, making them particularly suitable for applications governed by standards such as ASTM A193 B8C, DIN 1.4550, and ISO metric specifications. Industries including petrochemical processing, power generation, and heat exchangers rely on these bolts for structural integrity under sustained thermal exposure.
The primary advantage of Stainless Steel 347/347H Bolts lies in their ability to resist carbide precipitation during welding and high-temperature operation, ensuring long-term durability. KK Fasteners supplies these bolts with full traceability and compliance to international standards, supporting projects across global markets where material reliability and certification are non-negotiable.
| Parameter | Details |
|---|---|
| Material | Stainless Steel 347, 347H (Nb stabilized) |
| Grade | ASTM A193 B8C, B8C Class 2, UNS S34700 / S34709 |
| Size Range | M6 to M64 / 1/4" to 2.5" |
| Thread Type | Metric (ISO), UNC, UNF, BSW, BSF |
| Standards | ASTM, DIN, ISO, BS, ASME |
| Surface Finish | Plain, Passivated, PTFE Coated, Hot Dip Galvanized |
| Types | Hex Bolts, Heavy Hex Bolts, Stud Bolts, Anchor Bolts |
| Tensile Strength | 515 – 690 MPa (347), up to 750 MPa (347H) |
| Hardness | Max 201 HB |
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | N | |
| 347/347H | min. | – | – | – | – | – | 17.0 | 2.00 | 9.0 | – |
| max. | 0.08 | 2.0 | 1.00 | 0.045 | 0.030 | 20.0 | 3.00 | 13.0 | – | |
| Grade | Tensile Strength (MPa) min | Yield Strength 0.2% Proof (MPa) min | Elongation (% in 50mm) min | Hardness | |
| Rockwell B (HR B) max | Brinell (HB) max | ||||
| 347/347H | 515 | 205 | 40 | 95 | 201 |
| Grade | UNS No | Old British | Euronorm | Swedish SS | Japanese JIS | ||
| BS | En | No | Name | ||||
| 347/347H | S34700 | – | X6CrNiNb18-10 | 1.4550 | – | – | – |
All measurements in millimeters
| NOMINAL SIZE (D) | BODY DIAMETER | HEAD THICKNEASTM A193 | ACROASTM A193 THE FLATS | ACROASTM A193 CORNERS | ||||
|---|---|---|---|---|---|---|---|---|
| D (MAX) | D (MIN) | H (MAX) | H (MIN) | F (MAX) | F (MIN) | C (MAX) | C (MIN) | |
| m10 | 10.00 | 9.78 | 6.63 | 6.17 | 17.00 | 15.73 | 18.48 | 17.77 |
| m12 | 12.00 | 11.73 | 7.76 | 4.24 | 19.00 | 17.73 | 20.78 | 20.03 |
| m14 | 14.00 | 13.73 | 9.09 | 8.51 | 22.00 | 20.67 | 24.25 | 23.35 |
| m16 | 16.00 | 15.73 | 10.32 | 9.68 | 24.00 | 23.67 | 27.71 | 26.75 |
| m20 | 20.00 | 19.67 | 12.88 | 12.12 | 30.00 | 29.16 | 34.64 | 32.95 |
| m24 | 24.00 | 23.67 | 15.44 | 14.56 | 36.00 | 35.00 | 41.57 | 39.55 |
| m30 | 30.00 | 29.67 | 19.48 | 17.92 | 46.00 | 45.00 | 53.12 | 50.85 |
| m36 | 36.00 | 35.61 | 23.38 | 21.63 | 55.00 | 53.80 | 63.51 | 60.79 |
| m42 | 42.00 | 41.38 | 26.97 | 25.03 | 65.00 | 62.90 | 75.06 | 71.71 |
| m48 | 48.00 | 47.38 | 31.07 | 28.93 | 75.00 | 72.60 | 86.60 | 82.76 |
| m56 | 56.00 | 55.26 | 36.2 | 33.80 | 85.00 | 82.20 | 98.15 | 93.71 |
| m64 | 64.00 | 63.26 | 41.32 | 38.68 | 95.00 | 91.80 | 109.70 | 104.65 |
| m72 | 72.00 | 71.26 | 46.45 | 43.55 | 105.00 | 101.40 | 121.24 | 115.60 |
| m80 | 80.00 | 79.26 | 51.58 | 48.42 | 115.00 | 111.00 | 132.72 | 126.54 |
| m90 | 90.00 | 89.13 | 57.74 | 54.26 | 130.00 | 125.50 | 150.11 | 143.07 |
| m100 | 90.00 | 99.13 | 63.9 | 60.10 | 145.00 | 140.00 | 167.43 | 159.60 |
Stainless Steel 347/347H Bolts are used in high-temperature and corrosion-sensitive environments where standard stainless steel fasteners may fail due to carbide precipitation or thermal stress.
These bolts are typically produced through hot forging or cold forming, followed by precision CNC threading to meet dimensional tolerances. Heat treatment processes ensure optimal mechanical properties, especially for high-temperature performance.
KK Fasteners follows a strict quality protocol that includes dimensional inspection, tensile testing, hardness verification, and surface finish evaluation. Each batch is traceable to raw material heat numbers, ensuring compliance with ISO 9001 quality systems. Additional certifications such as RoHS and REACH are available based on project requirements, supporting global compliance needs.
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Stainless Steel 347/347H bolts are high-temperature fasteners made from niobium-stabilized austenitic stainless steel. They are designed to resist intergranular corrosion and oxidation in elevated temperature environments such as boilers, heat exchangers, and pressure vessels. These bolts maintain strength and stability under continuous thermal exposure.
The main difference is carbon content. Grade 347H contains higher carbon, which improves creep strength and mechanical performance at temperatures above 500°C. Grade 347 is better suited for general corrosion resistance and welded structures, while 347H is preferred for long-duration high-heat service applications.
These bolts are manufactured according to ASTM A193 B8C, DIN 1.4550, ISO metric standards, and ASME specifications. These standards ensure controlled chemical composition, mechanical strength, dimensional accuracy, and suitability for high-pressure and high-temperature industrial environments.
Selection depends on operating temperature, load conditions, and environmental exposure. Use 347 for moderate temperature corrosion resistance and general fabrication, while 347H is recommended for high-temperature applications requiring creep resistance and long-term structural stability.
Choose suppliers with certified quality systems, material traceability, and compliance with international standards like ASTM and ISO. A reliable manufacturer should also provide test certificates, consistent supply capability, and export experience across global markets. KK Fasteners follows these requirements with documented quality assurance and international supply support.
For projects requiring high-temperature stability and certified material performance, Stainless Steel 347/347H Bolts provide a proven solution. KK Fasteners supports global procurement teams with traceable materials, tested performance, and consistent supply. Reach out to request a technical datasheet or submit your RFQ for project-specific requirements.
