Introduction to GB/T 3098.8 Standard
This standard outlines mechanical properties, materials, inspection, identification, and marking for bolted connection parts operating in extreme temperatures from -200°C to +700°C. It ensures reliability in applications such as pressure vessels, boilers, and high-temperature machinery, supplementing standards like GB/T 3098.1, GB/T 3098.6, and DIN EN 10269.
范围
GB/T 3098.8-2010 specifies requirements for fasteners made of austenitic steels for low temperatures down to -200°C and steels/nickel alloys for high temperatures up to +700°C. It covers mechanical performance grades, testing methods, and material matching to guarantee structural integrity under thermal stresses. This is crucial for industries requiring resistance to creep, relaxation, and brittle failure.
- Applies to bolts, screws, studs, and nuts in bolted connections.
- Focuses on full load-bearing capacity for safe operation in extreme environments.
- References related standards for comprehensive compliance.
Materials and Mechanical Properties
Materials are selected based on temperature ranges to maintain mechanical integrity. For low temperatures, austenitic steels provide ductility; for high temperatures, steels and nickel alloys offer strength and creep resistance. Properties must meet specified hardness, tensile strength, and proof loads.
Low-Temperature Materials
Table 1 lists austenitic steel groups for minimum working temperatures to -200°C, with properties per GB/T 3098.6 and GB/T 3098.15. Copper content ≤1%. Higher temperatures have no impact; lower require performance tests per conditions.
| Minimum Continuous Working Temperature (Approximate) | Steel Group一个 | 表现等级 | |
|---|---|---|---|
| 螺栓 | Nut | ||
| -60°Cb | A2L | 50 | 50 |
| A2 | |||
| A3 | 70 | ||
| -200°Cc | A4L | 70 | |
| A4 | 80 | ||
| A5 | |||
一个 Copper content ≤1% (per GB/T 3098.6 and GB/T 3098.15).
b Headed bolts.
c Studs.
High-Temperature Materials
Table 2 specifies steels and nickel alloys for up to +700°C, with properties per DIN EN 10269 Table 4 for heat treatment. Reference data for yield strength, creep strength, and relaxation from DIN EN 10269 Tables 5, C.1, D.1. Related to AD 2000-W2, W7, W10, and VdTUV sheets.
| Working Temperature Range per DIN EN 10269 | 材料 | Bolt and/or Nut Hardness/HV | ||||||
|---|---|---|---|---|---|---|---|---|
| 最小 | Short-term一个 最大限度 | Long-termb 最大限度 | Abbreviation | 数字 | Grade | Condition | 最小 | 最大限度 |
| -120°C | / | / | KB | 1.568 | X12Ni5 | +NT | 157 | 203 |
| +QT | 173 | 235 | ||||||
| / | 400°C | 500°C | Yd | 1.1181 | C35E | +N | 150 | 200 |
| / | 400°C | 500°C | YK | 1.1181 | C35E | +QT | 165 | 210 |
| / | 400°C | / | YB | 1.5511 | 35B2克 | +QT | 165 | 210 |
| -60°C | 500°C | 550°C | KG | 1.7218 | 25CrMo4 | +QT | 195 | 240 |
| -100°C | 500°C | / | GC | 1.7225 | 42CrMo4 | +QT | 275 | 337 |
| / | 500°C | 550°C | GA | 1.7709 | 21CrMoV5-7 | +QT | 225 | 272 |
| / | 600°C | 550°C | GB | 1.7711 | 40CrMoV46 | +QT | 272 | 320 |
| / | 550°C | 600°C | Ve | 1.4923 | X22CrMoV12-1 | +QT 1e | 256 | 303 |
| / | 550°C | 600°C | VHf | 1.4923 | X22CrMoV12-1 | +QT 2f | 287 | 367 |
| / | 600°C | 600°C | VW | 1.4913 | X19CrMoNbVN11-1 | +QT | 287 | 367 |
| / | 650°C | 670°C | S | 1.4986 | X7CrNiMoBNb16-16 | +WW+P | 210 | 272 |
| -196°C | 650°C | 650°C | SD | 1.498 | X6NiCrTiMoVB25-15-2 | +AT+P | 287 | 367 |
| -196°C | 650°C | 800°C | SB | 2.4952 | NiCr20TiAl | +AT+P | 320 | 417 |
一个 Temperature limit for yield and tensile strength.
b Temperature limit for creep and rupture strength.
c Conditions per DIN EN 10269 Table 4: +N (normalized), +NT (normalized and tempered), +QT (quenched and tempered), +WW (warm worked), +AT (solution annealed), +P (precipitation hardened).
d For nuts only.
e V per DIN EN 10269, Rp0.2 ≥600 N/mm² (+QT1).
f VH per DIN EN 10269, Rp0.2 ≥600 N/mm² (+QT2).
克 See VdTUV WB 490.
Load Capacities
Load values ensure fasteners withstand operational stresses. Use for design verification.
Minimum Tensile Loads for Coarse Thread Bolts
Table 4a: As,nom × Rm,min /kN
| 螺纹尺寸 d | Stress Area As,nom /mm² | Austenitic Stainless Steel Grade | Steel and Nickel Alloys | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 50 | 70 | KB | YK | KG | GA | GB | GC | V | VH | S | SD | SB | ||
| YB | VW | |||||||||||||
| M3 | 5.03 | 2.52 | 3.52 | 2.67 | 2.52 | 3.02 | 3.52 | 4.28 | 4.33 | 4.02 | 4.53 | 3.27 | 4.53 | 5.03 |
| M3.5 | 6.78 | 3.39 | 4.75 | 3.59 | 3.39 | 4.07 | 4.75 | 5.76 | 5.83 | 5.42 | 6.1 | 4.41 | 6.1 | 6.78 |
| M4 | 8.78 | 4.39 | 6.15 | 4.65 | 4.39 | 5.27 | 6.15 | 7.46 | 7.55 | 7.02 | 7.9 | 5.71 | 7.9 | 8.78 |
| M5 | 14.2 | 7.1 | 9.94 | 7.53 | 7.1 | 8.52 | 9.94 | 12.1 | 12.2 | 11.4 | 12.8 | 9.23 | 12.8 | 14.2 |
| M6 | 20.1 | 10.1 | 14.1 | 10.7 | 10.1 | 12.1 | 14.1 | 17.1 | 17.3 | 16.1 | 18.1 | 13.1 | 18.1 | 20.1 |
| M7 | 28.9 | 14.5 | 20.2 | 15.3 | 14.5 | 17.3 | 20.2 | 24.6 | 24.9 | 23.1 | 26 | 18.8 | 26 | 28.9 |
| M8 | 36.6 | 18.3 | 25.6 | 19.4 | 18.3 | 22 | 25.6 | 31.1 | 31.5 | 29.3 | 32.9 | 23.8 | 32.9 | 36.6 |
| M10 | 58 | 29 | 40.6 | 30.7 | 29 | 34.8 | 40.6 | 49.3 | 49.9 | 46.4 | 52.2 | 37.7 | 52.2 | 58 |
| M12 | 84.3 | 42.2 | 59 | 44.7 | 42.2 | 50.6 | 59 | 71.7 | 72.5 | 67.4 | 75.9 | 54.8 | 75.9 | 84.3 |
| M14 | 115 | 57.5 | 80.5 | 61 | 57.5 | 69 | 80.5 | 97.8 | 98.9 | 92 | 104 | 74.8 | 104 | 115 |
| M16 | 157 | 78.5 | 110 | 83.2 | 78.5 | 94.2 | 110 | 133 | 135 | 126 | 141 | 102 | 141 | 157 |
| M18 | 192 | 96 | 134 | 102 | 96 | 115 | 134 | 163 | 165 | 154 | 173 | 125 | 173 | 192 |
| M20 | 245 | 123 | 172 | 130 | 123 | 147 | 172 | 208 | 211 | 196 | 221 | 159 | 221 | 245 |
| M22 | 303 | 152 | 212 | 161 | 152 | 182 | 212 | 258 | 261 | 242 | 273 | 197 | 273 | 303 |
| M24 | 353 | 177 | 247 | 187 | 177 | 212 | 247 | 300 | 304 | 282 | 318 | 229 | 318 | 353 |
| M27 | 459 | 230 | / | 243 | 230 | 275 | 321 | 390 | 395 | 367 | 413 | 298 | 413 | 459 |
| M30 | 561 | 281 | / | 297 | 281 | 337 | 393 | 477 | 482 | 449 | 505 | 365 | 505 | 561 |
| M33 | 694 | 347 | / | 368 | 347 | 416 | 486 | 590 | 597 | 555 | 625 | 451 | 625 | 694 |
| M36 | 817 | 409 | / | 433 | 409 | 490 | 572 | 694 | 703 | 654 | 735 | 531 | 735 | 817 |
| M39 | 976 | 488 | / | 517 | 488 | 586 | 683 | 830 | 839 | 781 | 878 | 634 | 878 | 976 |
Bearing Capacity of Bolt Connections
For full capacity: Matching full-capacity bolts and nuts with appropriate heights (Type 1 for coarse, Type 2 for fine), thread tolerances, and strength ratios. Fracture in tensile tests must occur in unthreaded sections per GB/T 3098.1 or 3098.6. Waisted studs per GB/T 13807.2/3 with tolerances per GB/T 3103.4.
- Perform tensile tests to verify minimum loads.
- Ensure nut height meets type requirements for load distribution.
- Match materials to avoid weak links in the assembly.
常问问题
What materials are suitable for -200°C applications?
Austenitic steels like A4L, A4, A5 with grade 70 or 80, ensuring ductility and toughness per Table 1.
How to select matching bolts and nuts for high temperatures?
Use Table 3 for rational pairings, ensuring nut strength >70% of bolt and proper thread tolerances for full capacity.
What if operating temperature exceeds +700°C?
The standard limits to +700°C; for higher, conduct specific creep and relaxation tests per DIN EN 10269 guidelines.
Why higher proof stress for austenitic nuts?
To account for manufacturing variations in small batches, ensuring reliability when matched with softer bolts (see Table 3 note b).
How to test for full load-bearing capacity?
Conduct tensile tests per GB/T 3098.1 or 3098.6, verifying fracture location and minimum loads from Tables 4a/5a.
Are there restrictions on copper content?
Yes, ≤1% for austenitic steels to prevent embrittlement in low-temperature service.
