Product Summary

Longze High-Precision Square Weld Nuts (DIN 928 / ISO 21670) are specialized heavy-duty fasteners designed to be permanently fused to metal sheets via resistance welding.

Manufactured in Yongnian, China, our weld nuts feature four precision-engineered corner projections that ensure uniform heat distribution and a high-strength fusion bond.

Whether for automotive chassis components, industrial electrical enclosures, or steel furniture, Longze square weld nuts provide a permanent threaded anchor that eliminates the risk of spinning or loosening under high-torque assembly.

• ✔ Balanced Projection Heights: Our advanced cold-heading process ensures all four welding bosses are identical in height within ±0.05mm, ensuring 100% contact and a balanced weld pool.

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• ✔ Optimized Weldability: Produced from low-carbon steel (C1008/C1010) or stabilized stainless steel, our nuts minimize the heat-affected zone (HAZ) and prevent brittle weld joints.

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• ✔ Pilot Diameter Precision: The central pilot (centering ring) is precision-machined to fit perfectly into pre-punched holes, ensuring the nut remains perfectly concentric during robotic welding.

• Standards: DIN 928, ISO 21670, ASME B18.2.2 (Weld Series).

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• Thread Range: M4 to M16 | #8 to 5/8".

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• Material Grade: Low Carbon Steel (Weldable) | Stainless Steel 304 (A2) & 316 (A4).

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• Projection Type: 4 Corner Projections (Standard).

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• Surface Finish: Plain/Lightly Oiled (Required for welding), Stainless Steel Passivated.

Mechanical Properties & Material Standards

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

• Material Type	Carbon Content	Tensile Strength	Weldability Rating	Environmental Suitability
  Weldable Steel	0.08 - 0.13%	350 - 450 MPa	Excellent	General Sheet Metal
  Stainless 304	≤ 0.08%	500 - 700 MPa	Good (Inert Gas)	Food / Medical
  Stainless 316	≤ 0.08%	550 - 750 MPa	Good	Marine / Chemical

Standard Cross Arm Dimensions

• Common configurations for standard robotic sheet metal welding lines.

• Thread Size (D)	Nut Width (s)	Total Height (m)	Pilot Dia (d2)	Projection Height (h)
  M6	10 mm	5.0 mm	7.5 mm	0.80 mm
  M8	13 mm	6.5 mm	9.5 mm	1.00 mm
  M10	16 mm	8.0 mm	11.5 mm	1.20 mm
  M12	19 mm	10.0 mm	14.5 mm	1.40 mm

Surface Treatment & Weld Integrity

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

• Finish Type	Process	Weld Compatibility	Resistenza alla corrosione	Best Application
  Plain (Oiled)	Cold Forged	100% (Standard)	Low (Post-Paint)	Automotive OEM
  Stainless 316	Machined	High (Clean)	Extreme	Offshore Cabinets
  Zinc Plated	Electrolytic	NOT RECOMMENDED	Moderate	(Plating post-weld only)

Avoid Pitfalls:

• Welding Through Plating: Never attempt to weld zinc-plated nuts. The zinc vaporizes, causing "porosity" in the weld and toxic fumes. Longze provides Plain/Oiled nuts specifically for welding, which are then painted or E-coated with the final assembly.

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• Excessive Welding Pressure: If the robotic welder applies too much pressure before the current flows, the projections can collapse, leading to a weak surface-bond. Our projections are engineered with a specific "aspect ratio" to resist premature collapse.

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• Thread Distortion (Heat): Excessive heat can warp internal threads. We recommend using copper-alloy electrodes and optimized timing to ensure the threads remain within 6H tolerance after cooling.

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Perfect Fit Assembly:

• Automated Feeding: Longze DIN 928 nuts are precision-sorted to ensure zero "deformed" parts, making them perfect for high-speed vibratory bowl feeders and robotic pick-and-place systems.

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• Pilot Hole Sizing: For the best results, ensure your sheet metal pilot hole is 0.2mm - 0.5mm larger than the nut's pilot diameter (d2) to allow for thermal expansion and easy positioning.

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Quality Control & Logistics:

• ISO 9001 Certified: 5-step QC including "Push-out" and "Torque-out" destructive testing on sample welds, thread gauge verification, and material chemical analysis.

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• Sea-Worthy Packaging: Packed in 25kg heavy-duty bags or cartons, plastic-lined to prevent flash rust during maritime transit, and palletized for export from our Yongnian facility.

• Q: Why use a square nut instead of a hex weld nut? A: Square nuts (DIN 928) provide a larger surface area and are easier for robotic grippers to orient and hold during the welding cycle compared to hex nuts (DIN 929).

• Q: Do you offer these in Imperial (UNC) threads? A: Yes, we manufacture 1/4", 5/16", and 3/8" square weld nuts for North American automotive and appliance maintenance projects.