GB/T 3098.2-2015 specifies the mechanical properties of coarse thread nuts made from carbon steel and alloy steel, applicable for general engineering purposes. This standard aligns closely with international norms such as ISO 898-2, ensuring compatibility in fastener systems. It covers performance grades from 4 to 12, focusing on proof load, chemical composition, hardness, and compatibility with bolts, screws, or studs. Below, key aspects are detailed with data extracted from the standard for precise reference.
Proof Load Values for Coarse Thread Nuts
The proof load represents the maximum load a nut can withstand without permanent deformation, essentially the minimum tensile strength it must endure. Units are in Newtons (N). The following table provides proof load values for various thread sizes and performance grades.
| Faden | Tonhöhe | Grade 04 (N) | Grade 05 (N) | Grade 5 (N) | Grade 6 (N) | Grade 8 (N) | Grade 10 (N) | Grade 12 (N) |
|---|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 5400 | 7100 | 8250 | 9500 | 12140 | 14800 | 16300 |
| M6 | 1 | 7640 | 10000 | 11700 | 13500 | 17200 | 20900 | 23100 |
| M7 | 1 | 11000 | 14500 | 16800 | 19400 | 24700 | 30100 | 33200 |
| M8 | 1.25 | 13900 | 18300 | 21600 | 24900 | 31800 | 38100 | 42500 |
| M10 | 1.5 | 22000 | 29000 | 34200 | 39400 | 50500 | 60300 | 67300 |
| M12 | 1.75 | 32000 | 42200 | 51400 | 59000 | 74200 | 88500 | 100300 |
| M14 | 2 | 43700 | 57500 | 70200 | 80500 | 101200 | 120800 | 136900 |
| M16 | 2 | 59700 | 78500 | 95800 | 109900 | 138200 | 164900 | 186800 |
| M18 | 2.5 | 73000 | 96000 | 121000 | 138200 | 176600 | 203500 | 230400 |
| M20 | 2.5 | 93100 | 122500 | 154400 | 176400 | 225400 | 259700 | 294000 |
| M22 | 2.5 | 115100 | 151500 | 190900 | 218200 | 278800 | 321200 | 363600 |
| M24 | 3 | 134100 | 176500 | 222400 | 254200 | 324800 | 374200 | 423600 |
| M27 | 3 | 174400 | 229500 | 289200 | 330500 | 422300 | 486500 | 550800 |
| M30 | 3.5 | 213200 | 280500 | 353400 | 403900 | 516100 | 594700 | 673200 |
| M33 | 3.5 | 263700 | 347000 | 437200 | 499700 | 638500 | 735600 | 832800 |
| M36 | 4 | 310500 | 408500 | 514700 | 588200 | 751600 | 866000 | 980400 |
| M39 | 4 | 370900 | 488000 | 614900 | 702700 | 897900 | 1035000 | 1171000 |
These values are critical for selecting nuts in applications where load-bearing capacity is paramount, such as in structural assemblies or machinery.
Chemical Composition Requirements
The standard specifies chemical limits for carbon steel nuts to ensure proper heat treatment and performance. Maximum values for carbon (C), phosphorus (P), and sulfur (S), along with minimum manganese (Mn), are outlined below. Heat treatment types include optional quenching and tempering for lower grades and mandatory for higher ones.
| Leistungsnote | Material | Wärmebehandlung | C (%) max | Mn (%) min | P (%) max | S (%) max | |
|---|---|---|---|---|---|---|---|
| 4 | Carbon steel | Optional | 0.58 | 0.25 | 0.060 | 0.150 | |
| 5 | Carbon steel | Quenched and tempered | 0.58 | 0.30 | 0.048 | 0.058 | |
| 5 | Carbon steel | Optional | 0.58 | – | 0.060 | 0.150 | |
| 6 | Carbon steel | Optional | 0.58 | – | 0.060 | 0.150 | |
| 8 | Tall nut (Style 2) | Optional | 0.58 | 0.25 | 0.060 | 0.150 | |
| 8 | Standard nut (Style 1) D ≤ M16 | Optional | 0.58 | 0.25 | 0.060 | 0.150 | |
| 8 | Standard nut (Style 1) D > M16 | Quenched and tempered | 0.58 | 0.30 | 0.048 | 0.058 | |
| 10 | Carbon steel | Quenched and tempered | 0.58 | 0.30 | 0.048 | 0.058 | |
| 12 | Carbon steel | Quenched and tempered | 0.58 | 0.45 | 0.048 | 0.058 | |
Note: For grades requiring quenching and tempering, materials must exhibit sufficient hardenability to achieve approximately 90% martensite in the thread section before tempering. Chemical composition evaluations should follow relevant standards.
Hardness Requirements
Hardness is measured in Vickers (HV), Brinell (HB), and Rockwell C (HRC) scales, with ranges varying by nut size and grade. These ensure the nut’s resistance to deformation under load.
| Gewindegröße | Grade 04 | Grade 05 | Grade 5 | Grade 6 | Grade 8 | Grade 10 | Grade 12 | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Scale | Min | Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | Max | Min | Max | |
| M5 ≤ D ≤ M16 | HV | 188 | 302 | 272 | 353 | 130 | 302 | 150 | 302 | 200 | 302 | 272 | 353 | 295 | 353 |
| M16 < D ≤ M39 | HV | 188 | 302 | 272 | 353 | 146 | 302 | 170 | 302 | 233 | 353 | 272 | 353 | 272 | 353 |
| M5 ≤ D ≤ M16 | HB | 179 | 287 | 259 | 336 | 124 | 287 | 143 | 287 | 190 | 287 | 259 | 336 | 280 | 336 |
| M16 < D ≤ M39 | HB | 179 | 287 | 259 | 336 | 139 | 287 | 162 | 287 | 221 | 336 | 259 | 336 | 259 | 336 |
| M5 ≤ D ≤ M16 | HRC | – | 30 | 26 | 36 | – | 30 | – | 30 | – | 30 | 26 | 36 | 29 | 36 |
| M16 < D ≤ M39 | HRC | – | 30 | 26 | 36 | – | 30 | – | 30 | – | 36 | 26 | 36 | 26 | 36 |
Footnotes: For tall nuts (Style 2) in Grade 8, minimum hardness is 180 HV (171 HB). For Grade 8 tall nuts, maximum is 302 HV (287 HB, 30 HRC). For Grade 12 tall nuts, minimum is 272 HV (259 HB, 26 HRC).
Compatibility with Bolts, Screws, or Studs
Nuts must match bolt grades to ensure joint integrity. The table below shows nut styles, nominal diameters, and compatible bolt grades.
| Nut Style | Grade 04 | Grade 05 | Grade 5 | Grade 6 | Grade 8 | Grade 10 | Grade 12 |
|---|---|---|---|---|---|---|---|
| Standard (Style 1) | – | – | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M39x3 | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M39x3 | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M39x3 | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M16x1.5 | M5 ≤ D ≤ M16 |
| Tall (Style 2) | – | – | – | – | M16 ≤ D ≤ M39 / M8x1 ≤ D ≤ M16x1.5 | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M39x3 | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M16x1.5 |
| Thin (Style 0) | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M39x3 | M5 ≤ D ≤ M39 / M8x1 ≤ D ≤ M39x3 | – | – | – | – | – |
| Compatible Bolt Grade (Max) | – | – | 5.8 | 6.8 | 8.8 | 10.9 | 12.9 |
This compatibility ensures that the nut does not fail before the bolt in tension, maintaining assembly safety.
Torque Considerations
GB/T 3098.2-2015 does not specify failure torque for nuts, as torque values are influenced by friction, lubrication, and assembly conditions. Instead, focus on proof load and preload for design. In practice, torque applied to nuts converts partially to clamping force, often around 20% efficiency depending on factors like surface finish. For reference, consult matching bolt torque values from standards like GB/T 3098.1, but always verify through testing for specific applications.
Häufig gestellte Fragen (FAQ)
- 1. What is the proof load in GB/T 3098.2-2015?
- The proof load is the axial tensile force that the nut must withstand without permanent deformation, serving as a measure of its load-bearing capacity.
- 2. How does heat treatment affect nut performance?
- Quenching and tempering are required for higher grades (e.g., 8 for D > M16, 10, 12) to achieve necessary hardness and strength, ensuring at least 90% martensite structure before tempering.
- 3. Can Grade 8 nuts be used with Grade 10.9 bolts?
- Yes, Grade 8 nuts are compatible with up to Grade 8.8 bolts, but for Grade 10.9, use Grade 10 nuts to match strength and avoid nut failure.
- 4. Why are phosphorus and sulfur limits stricter for higher grades?
- Lower P and S content (e.g., 0.048% max for P in Grade 10) reduces embrittlement risks, improving toughness and reliability in high-stress applications.
- 5. How should hardness be tested for nuts?
- Hardness is typically measured on the nut’s bearing surface or cross-section using HV, HB, or HRC methods, with values varying by size (e.g., higher minimum for smaller diameters in some grades).
- 6. What if a nut exceeds maximum hardness?
- Excessive hardness can lead to brittleness; nuts must stay within specified ranges (e.g., max 353 HV for Grade 10) to balance strength and ductility.
