201 stainless steel external hexagonal head screws, GB30 hexagonal full thread b

Release time：2020-01-16 18:44 Browse：

1. Material Composition & Properties

• Alloy Structure: Constructed from 201 stainless steel (composition: ~17% chromium, 4.5% nickel, 6-8% manganese, 0.15% carbon), a nitrogen-strengthened austenitic alloy.

• Mechanical Traits:

• Tensile strength: ~520 MPa (comparable to mild steel).

• Magnetic permeability: Ferromagnetic due to manganese content (unlike non-magnetic 304).

• Moderate ductility for cold forming but less corrosion-resistant than 304/316 grades.

• Corrosion Resistance:

• Suitable for dry indoor environments (e.g., workshops, offices) or low-humidity areas.

• Prone to rust in marine, coastal, or high-chloride conditions; not recommended for outdoor/long-term exposure without additional coatings.

2. Design Standards & Geometry

• GB30 Compliance: Follows Chinese National Standard GB/T 5782 (equivalent to ISO 4014 for hex bolts), specifying:

• Hex head dimensions (width across flats, height).

• Full-thread configuration (threads run the entire length of the shank).

• Metric coarse threads (pitch: M4×0.7, M5×0.8, up to M20×2.5).

• Head Features:

• External hexagonal head with 120° included angle for wrench/socket compatibility (6-point engagement reduces slippage).

• Chamfered edges on head and threads for easy alignment during installation.

3. Size Range & Thread Specifications

• Nominal Sizes:

• M4, M5, M6, M8, M10, M12, M16, M20 (common metric diameters).

• Lengths: 10–200 mm (standard), with custom lengths available for bulk orders.

• Thread Precision:

• Conforms to ISO 68-1 (metric threads) with 6g tolerance for external threads, ensuring tight fit with 6H nuts.

• Full-thread design maximizes clamping force in through-hole applications (e.g., thin plates, flanges).

4. Surface Finishes & Coatings

• As-Machined Finish:

• Natural mill finish (bright or dull) with slight tool marks; cost-effective for non-aesthetic uses.

• Optional Treatments:

• Passivation: Chemically treated to remove free iron and enhance corrosion resistance (suitable for food-contact applications).

• Zinc Plating: Available for improved rust protection in mildly corrosive environments (e.g., outdoor fixtures).

• Black Oxide: Provides a decorative matte finish with minimal corrosion resistance (ideal for interior design projects).

5. Applications & Use Cases

• General Industry:

• Fastening in HVAC systems, ventilation ducts, and agricultural equipment.

• Assembly of metal furniture, shelving units, and conveyor belts.

• Low-Corrosion Environments:

• Indoor machinery (e.g., motors, pumps), electrical enclosures, and control panels.

• Temporary outdoor structures (e.g., scaffolding, signage) with limited exposure to moisture.

• Cost-Sensitive Projects:

• Ideal for applications where 304/316 stainless steel is unnecessary, offering a 20–30% cost savings.

6. Limitations & Alternatives

• Not Recommended For:

• Marine, coastal, or saltwater environments.

• High-temperature applications (>300°C) or chemical processing.

• Upgrade Paths:

• Switch to 304 stainless steel (GB/T 5783) for superior corrosion resistance.

• Use grade 8.8 carbon steel (zinc-plated) for higher tensile strength in non-corrosive settings.

7. Quality Control & Compliance

• Testing Protocols:

• Thread accuracy verified via Go/No-Go gauges.

• Head hardness tested (Rockwell B scale: ~85 HRB).

• Batch sampling for tensile strength and coating thickness (when plated).

• Certifications:

• RoHS compliant for use in EU markets.

• CE marking available upon request for structural applications.

8. Installation Tips

• Tooling: Use hex wrenches, socket sets, or impact drivers (avoid over-torque to prevent stripping).

• Lubrication: Apply anti-seize compound (e.g., copper grease) for dissimilar metal connections (e.g., stainless steel to aluminum).

• Torque Guidelines:

• M8 bolt: ~20–25 Nm (dry thread, no lubricant).

• M12 bolt: ~70–80 Nm (follow GB30 torque tables for precision).

9. Packaging & Logistics

• Standard Packaging:

• Bulk: 500–1,000 pieces per carton with moisture-resistant paper.

• Retail: 50–100 pieces per poly bag with size-labeled headers.

• Lead Times:

• Stock sizes: 1–3 days for orders <5,000 pieces.

• Custom sizes: 2–4 weeks for production and plating.

10. Environmental Considerations

• Recyclability: 201 stainless steel is 100% recyclable, reducing environmental impact.

• Plating Waste: Zinc plating processes adhere to EPA standards for wastewater treatment.