Introduction to GB/T 3098.3-2016 Standard
This article provides a detailed overview of the GB/T 3098.3-2016 standard, which specifies the mechanical properties of set screws as part of the fasteners series. It covers essential aspects such as chemical composition and mechanical performance requirements, ensuring compliance for manufacturing and application in mechanical engineering. Understanding these specifications is crucial for selecting appropriate materials and heat treatments to achieve desired strength and durability in fastening systems.
Table of Contents
- Chemical Composition
- Mechanical Properties
- Perguntas frequentes (FAQ)
Chemical Composition
The chemical composition of materials used for set screws under GB/T 3098.3-2016 is critical for ensuring the required mechanical properties after heat treatment. This section outlines the permissible limits for carbon, phosphorus, sulfur, and other elements across different hardness grades. Proper material selection based on these compositions helps prevent issues like brittleness or insufficient hardenability. For instance, higher carbon content in higher hardness grades supports quenching and tempering processes to achieve superior strength.
| Hardness Grade | Vickers Hardness HV min | Material | Heat Treatment¹ | C%, max² | C%, min² | P%, max² | S%, max² | |
|---|---|---|---|---|---|---|---|---|
| 14H | 140 | Carbon steelc | / | 0.5 | / | 0.11 | 0.15 | |
| 22H | 220 | Carbon steeld | Quenched and tempered | 0.5 | 0.19 | 0.05 | 0.05 | |
| 33H | 330 | Carbon steeld | Quenched and tempered | 0.5 | 0.19 | 0.05 | 0.05 | |
| – | 45H | 450 | Carbon steeld,e | Quenched and tempered | 0.5 | 0.45 | 0.05 | 0.05 |
| – | 450 | Carbon steel with added elementsd (boron, manganese or chromium, etc.) | Quenched and tempered | 0.5 | 0.28 | 0.05 | 0.05 | |
| – | 450 | Alloy steeld,f | Quenched and tempered | 0.5 | 0.3 | 0.05 | 0.05 | |
- No surface hardening is permitted.
- In case of dispute, product analysis shall be carried out.
- Free-cutting steel may be used, with maximum contents of lead 0.35%, phosphorus 0.11%, sulfur 0.34%.
- Steel with a maximum lead content of 0.35% may be used.
- Applicable only for d ≤ M16.
- These alloy steels shall contain at least one of the following elements with minimum contents: chromium 0.30%, nickel 0.30%, molybdenum 0.20%, vanadium 0.10%. When two, three, or four alloying elements are present, the total content shall not be less than 70% of the sum of the individual minimum contents.
These guidelines ensure that set screws maintain integrity under load. Engineers should verify compositions through certified testing to comply with industry standards, particularly in high-stress applications like machinery assembly.
Mechanical Properties
The mechanical properties defined in GB/T 3098.3-2016 include hardness values measured by Vickers, Brinell, and Rockwell methods, along with decarburization and surface hardness limits. These properties are essential for evaluating the suitability of set screws in various environments, ensuring they resist deformation and failure. For example, higher hardness grades like 45H are ideal for demanding conditions, but require careful control of decarburization to preserve thread strength.
| Hardness Grade | Vickers Hardness HV10 max | Brinell Hardness HBW F=30D² min | Brinell Hardness HBW F=30D² max | Rockwell Hardness HRB min | Rockwell Hardness HRB max | Rockwell Hardness HRC min | Rockwell Hardness HRC max | Thread Non-Decarburized Layer Height E/mm min | Thread Full Decarburization Layer Height G/mm max | Surface Hardness HV0.3 max | No Carburization HV0.3 max |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 14H | 290 | 133 | 276 | 75 | 105 | – | – | – | – | – | – |
| 22H | 300 | 209 | 285 | 95 | um | um | 30 | 1/2 H1 | 0.015 | 320 | c |
| 33H | 440 | 314 | 418 | – | – | 33 | 44 | 2/3 H1 | 0.015 | 450 | c |
| 45H | 560 | 428 | 532 | – | – | 45 | 53 | 3/4 H1 | b | 580 | c |
- For 22H grade, when Rockwell hardness test is performed, use HRB minimum and HRC maximum values.
- For 45H, no full decarburization layer is allowed.
- When measuring surface and core hardness with HV0.3, the surface hardness shall not exceed the core hardness by more than 30 HV units.
Adhering to these mechanical properties is vital for quality control. Regular testing using standardized methods can guide manufacturers in optimizing production processes, such as heat treatment cycles, to meet performance expectations in real-world applications.
Perguntas frequentes (FAQ)
- What is the purpose of GB/T 3098.3-2016?
- This standard specifies the mechanical properties of set screws, ensuring they meet requirements for hardness, material composition, and surface integrity in fastening applications. It guides manufacturers in producing reliable components for mechanical systems.
- How to select the appropriate hardness grade for set screws?
- Choose based on application demands: 14H for low-stress uses, 22H or 33H for moderate loads, and 45H for high-strength needs. Consider factors like load-bearing capacity and environmental conditions to match the grade’s mechanical properties.
- What are the key alloying elements allowed in 45H grade alloy steel?
- Alloy steels must include at least one of chromium (min 0.30%), nickel (min 0.30%), molybdenum (min 0.20%), or vanadium (min 0.10%). For multiple elements, the total content should be at least 70% of the sum of individual minima.
- What are the decarburization limits and why are they important?
- Limits include minimum non-decarburized layer heights (e.g., 3/4 H1 for 45H) and maximum full decarburization (0.015 mm for 22H and 33H). These prevent weakening of threads, ensuring torque retention and fatigue resistance in service.
- What is the difference between carbon steel and alloy steel in this standard?
- Carbon steel relies on carbon content for hardenability, while alloy steel incorporates elements like Cr, Ni for enhanced properties. Alloy options in 45H provide better toughness and corrosion resistance for demanding environments.
- How should disputes in chemical composition be resolved?
- In case of controversy, perform product analysis as per the standard’s guidelines to verify compliance with specified limits for elements like C, P, and S.
