GB/T 3098.16: Stainless Steel Set Screws Properties

This standard specifies the mechanical properties of stainless steel set screws and similar non-tensile fasteners, focusing on austenitic grades. It ensures reliability in corrosive environments, such as marine or chemical applications, by defining chemical compositions and performance criteria. Compliance with GB/T 3098.16-2014 guarantees fasteners withstand operational stresses without failure.

Engineers should reference this for selecting materials that balance corrosion resistance and mechanical strength, preventing issues like intergranular corrosion through appropriate alloy choices.

The chemical composition for austenitic stainless steel groups used in set screws is outlined in Table 2, consistent with GB/T 3098.6-2014. Manufacturers select within specified ranges unless otherwise agreed. For intergranular corrosion-prone applications, test per GB/T 4334 and prefer stabilized A3/A5 or low-carbon (≤0.03%) A2/A4 groups.

• Compositions maximize corrosion resistance while maintaining formability.
• Adjustments like sulfur substitution with selenium enhance machinability in A1 group.
• Stabilization with titanium or niobium prevents carbide precipitation.

^ए Maximum values unless stated otherwise.

^बी Sulfur may be replaced by selenium.

^c If nickel content is below 8%, minimum manganese content shall be 5%.

^डी If nickel content exceeds 8%, no minimum copper content is specified.

^e Molybdenum content may be added at manufacturer’s discretion; specify limits if needed.

^एफ If chromium content is below 17%, minimum nickel content shall be 12%.

^जी For stainless steel with maximum carbon 0.03%, nitrogen may reach 0.22%.

^h For stabilization, titanium ≥ (5×C%) to 0.8%, or niobium/tantalum ≥ (10×C%) to 1.0%.

^मैं For larger diameters, carbon may increase to 0.12% to achieve properties.

General Requirements

Set screws must meet values in Tables 3 and 4 for acceptance. These properties ensure durability under torque and hardness demands in assembly applications.

1. Verify via specified tests for consistent performance.
2. Applicable to hardness classes 12H and 21H.

Guaranteed Torque for Socket Set Screws

Socket set screws comply with minimum torque in Table 3, tested at specified lengths to simulate real-world use.

^ए Minimum length corresponds to at least one full socket depth as per product standards.

Hardness Requirements

Set screws must achieve hardness levels in Table 4, critical for wear resistance and load-bearing capacity.

Hardness Testing

Conduct tests per GB/T 231.1 (HB), GB/T 230.1 (HRB), or GB/T 4340.1 (HV). In disputes, use Vickers as basis. Follow procedures from GB/T 3098.3 for accuracy.

• Ensure surface preparation avoids altering results.
• Test multiple points for uniformity in production batches.

Appendix B: Austenitic Stainless Steel Compositions (from ISO 683-13:1986)

This informative appendix provides detailed compositions for austenitic steels, aiding in material selection for specific environments.

Notes from appendix: Type numbers are provisional; no additions of unlisted elements without agreement; prevent scrap contamination.

Appendix C: Austenitic Stainless Steels for Cold Heading and Extruding (from ISO 4954:1993)

This appendix lists compositions optimized for cold forming processes, ensuring workability without compromising strength.

Notes: Designations include sequential numbers and ISO names; no unlisted element additions; prevent contamination for optimal properties.

Appendix E: Relative Magnetic Permeability of Austenitic Stainless Steels

For magnetic-sensitive applications, consult metallurgists. Austenitic steels are non-magnetic in solution-annealed state but may become magnetic after cold working. Relative permeability μ_r measures magnetization; values near 1 indicate low permeability.

• Example: A2: μ_r ≈1.8
• A4: μ_r ≈1.015
• A4L: μ_r ≈1.005
• F1: μ_r ≈5

Use in electronics or medical devices where low magnetism is essential.