Product Summary

Longze High-Strength Stud Bolts (DIN 976-1 / ASME B18.31.2) are premium fully-threaded or double-ended fasteners designed for high-pressure piping, structural steel

connections, and heavy-duty machinery anchoring. Manufactured in Yongnian, China, our stud bolts are cold-rolled to ensure grain flow continuity and superior thread fatigue life.

Whether for a subsea oil manifold requiring SS316 (A4-80) or a wind turbine foundation demanding Class 12.9 alloy steel, Longze delivers the precise mechanical performance and dimensional accuracy required for critical engineering specifications.

• ✔ Cold-Rolled Thread Integrity: Every stud is produced via cold-rolling, which work-hardens the threads, making them 20% stronger and significantly smoother than cut threads, reducing the risk of galling.

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• ✔ Exceptional Straightness: We implement a dedicated straightening stage for all rods, ensuring a straightness tolerance of ±0.2mm/m—critical for seamless installation in long-distance pipe flanges.

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• ✔ Precise Form A Chamfering: Our studs feature a standard 45° end chamfer (DIN 976 Form A) that removes sharp burrs, ensuring jam-free nut engagement even in high-speed automated assembly.

• Standards: DIN 976-1 (Metric), ASME B18.31.2 (Continuous Thread), ISO 898-1.

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• Diameter Range: M6 to M100 | 1/4" to 4".

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• Length Range: 20 mm to 6000 mm (Custom cut-to-length available).

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• Property Class: Class 8.8, 10.9, 12.9 | B7, B7M, L7 | Stainless Steel 304 (A2) & 316 (A4).

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• Surface Finish: Hot Dip Galvanized (HDG), Zinc Plated, PTFE (Teflon), Black Oxide, Plain.

Mechanical Properties & Material Standards

• Matching the steel grade to the structural requirements of the transmission line.

• Property Class	Malzeme	Tensile Strength (min)	Yield Strength (min)	Hardness Range
  Class 8.8	Medium Carbon Steel	800 MPa	640 MPa	22 - 32 HRC
  Class 10.9	Alloy Steel (SCM435)	1040 MPa	940 MPa	32 - 39 HRC
  Class 12.9	Alloy Steel (SCM440)	1220 MPa	1100 MPa	39 - 44 HRC
  ASTM A193 B7	Chromium-Moly Steel	860 MPa	720 MPa	35 HRC Max

Standard Cross Arm Dimensions

• Common configurations for standard robotic sheet metal welding lines.

• Thread Size (D)	Pitch (Metric)	Sectional Area (mm²)	Proof Load (10.9)	Max Torque (12.9)
  M16	2.0 mm	157 mm²	147 kN	280 Nm
  M20	2.5 mm	245 mm²	230 kN	540 Nm
  M24	3.0 mm	353 mm²	332 kN	930 Nm
  M30	3.5 mm	561 mm²	527 kN	1900 Nm

Galvanizing & Corrosion Resistance

• Ensuring 30+ years of service life in corrosive environments.

• Surface Treatment	Process	Salt Spray Test	Service Life	Best Environment
  Zinc Plated	Electrolytic	72 - 144 Hours	High	Indoor / Dry
  Hot Dip Galv.	Thermal Bath	500 - 800 Hours	Maximum	Solar / Infrastructure
  PTFE (Teflon)	Fluoropolymer	1000 - 2000 Hours	Extreme	Offshore / Petrochem
  SS316 Polished	N/A	1000+ Hours	Lifetime	Marine / Chemical

Avoid Pitfalls:

• Hydrogen Embrittlement (12.9 Grade): For high-tensile 12.9 studs that are electro-galvanized, we implement a strict 8-hour de-embrittlement bake to prevent sudden brittle fracture under high clamping loads.

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• Nut Seizing on HDG: For hot-dip galvanized studs, we ensure the threads are rolled to 6g/6h tolerances and recommend using Longze 6AZ (Oversized) Nuts to ensure smooth assembly over the thick zinc coating.

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• Inconsistent Thread Length: For double-ended studs (DIN 938/939), the "metal-end" length is critical. Longze utilizes digital calipers to ensure every batch meets the exact $1d$ veya $1.25d$ engagement depth required.

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Perfect Fit Assembly:

• Heavy Hex Nut Pairing: For ASME B18.31.2 (B7/B8) studs, we recommend pairing with Longze ASTM A194 2H or Grade 8 Heavy Hex Nuts for a certified pressure-vessel connection.

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• Lubrication Consistency: To achieve accurate pre-load, we suggest using Moly-based lubricants. Longze provides friction coefficient data for all our PTFE-coated Ve Ova stud bolts.

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Quality Control & Logistics:

• ISO 9001 Certified: 5-step QC including Ultrasonic flaw detection (for M36+), thread pitch gauge verification, and full material spectrometer analysis.

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• Sea-Worthy Packaging: Studs are bundled with steel strapping, wrapped in moisture-proof plastic, and secured in reinforced wooden crates to prevent bending or thread damage during export from our Yongnian hub.

• Q: Can you provide PTFE-coated stud bolts in specific colors? A: Yes, we offer Blue, Green, and Red Teflon coatings which provide low friction and extreme chemical resistance for subsea and oilfield applications.

• Q: What is the difference between DIN 975 and DIN 976-1? A: DIN 975 refers to 1-meter, 2-meter, or 3-meter threaded rods. DIN 976-1 refers to shorter, cut-to-length stud bolts with specific end chamfers. We supply both.