Home » Square Weld Nuts (DIN 928) - 10B21 Medium-Strength Steel - ISO Class 10 - Bare

Square Weld Nuts (DIN 928) - 10B21 Medium-Strength Steel - ISO Class 10 - Bare

Square Weld Nuts (DIN 928) – 10B21 Medium-Strength Alloy Steel, ISO Class 10, Bare Finish

FULLERKREG DIN 928 square weld nuts in 10B21 boron alloy steel at ISO class 10 represent the highest strength grade available in the DIN 928 weld nut series. With a proof load stress of 1000 MPa, these nuts are engineered for the most demanding structural welding applications — including heavy commercial vehicles, off-highway equipment, structural steel fabrication, and safety-critical load-bearing joints. The 10B21 boron alloy steel achieves class 10 strength through a controlled quench and temper heat treatment process, delivering consistent mechanical properties across production batches. The bare (uncoated) finish ensures optimal electrical conductivity during resistance projection welding and maximum adhesion for subsequent e-coat, powder coat, or paint processes. Four precision weld projections on the bearing face concentrate heat for consistent, high-integrity weld joints. The square body provides excellent anti-rotation resistance in the parent material.

Product Specifications

Standard Type Material Grade Surface Treatment Thread RoHS
DIN 928 Square Weld Nut (Projection Welding) 10B21 Boron Alloy Steel ISO Class 10 Bare / Plain (Uncoated) Metric (M3–M12) Compliant

Dimensional Data

All dimensions in millimeters (mm). Weight per 1000 pcs in kg. Unit weight (g/pc) calculated from standard data. Refer to diagram: A = body width across flats, C = body thickness, D = thread diameter, H = projection height, E = projection diameter, F = projection pitch circle diameter.

Thread (D) Body Width (A) mm Body Thickness (C) mm Projection Height (H) mm Projection Ø (E) mm Proj. PCD (F) mm Weight / 1000 pcs (kg) Unit Weight (g/pc)
M3 9 3 0.8 1.5 5.5 1.38 1.38
M4 11 3.5 0.9 1.8 7 2.57 2.57
M5 13 4 1.0 2.0 8.5 4.15 4.15
M6 16 4.5 1.1 2.3 10.5 7.21 7.21
M8 20 5 1.2 2.8 13.5 14.33 14.33
M10 25 6 1.4 3.2 17 27.68 27.68
M12 30 7 1.6 3.8 20.5 49.42 49.42

Note: Dimensional data per DIN 928 standard. Weights based on 10B21 alloy steel density (7.85 g/cm³). Actual weights may vary slightly by batch.

Mechanical Properties – ISO Class 10 / 10B21

Property Value Standard
Material 10B21 Boron Alloy Steel SAE J403 / GB/T 6478
Proof Load Stress 1000 MPa ISO 898-2
Tensile Strength (min) 1000 MPa ISO 898-2
Hardness (min) 272 HV ISO 898-2
Hardness (max) 353 HV ISO 898-2
Carbon Content 0.18–0.23% SAE J403
Boron Content 0.0005–0.003% SAE J403
Heat Treatment Quench & Temper –
Surface Finish Bare / Plain (no coating) –
Weldability Good – boron addition improves hardenability without sacrificing weldability –

Strength Grade Comparison – DIN 928 Weld Nuts

Property ISO Class 4 (Q195) ISO Class 8 (10B21) ISO Class 10 (10B21)
Proof Load Stress 310 MPa 800 MPa 1000 MPa
Tensile Strength ≈400 MPa ≥800 MPa ≥1000 MPa
Hardness 130–302 HV 250–353 HV 272–353 HV
Material Q195 Low Carbon 10B21 Boron Alloy 10B21 Boron Alloy
Heat Treatment None Quench & Temper Quench & Temper (higher)
Typical Use Light general assembly High-load structural joints Safety-critical & heavy structural

About 10B21 Boron Alloy Steel at Class 10

10B21 boron alloy steel achieves ISO class 10 strength through a more aggressive quench and temper cycle compared to class 8, resulting in higher proof load (1000 MPa vs 800 MPa) while maintaining the same compact DIN 928 geometry. Key advantages of 10B21 at class 10:

  • Maximum proof load in DIN 928 geometry – 1000 MPa without increasing nut body size
  • Consistent batch-to-batch hardness – Boron ensures uniform through-hardening across all sizes
  • Good weldability retained – Low carbon equivalent minimizes HAZ cracking risk vs higher-carbon alloys
  • Weight-optimized design – Achieve class 10 joint strength without upsizing to larger nut format
  • Cost-effective high strength – 10B21 delivers alloy steel performance at competitive material cost

Welding Guide

Parameter Guidance
Welding Method Resistance projection welding (spot welding machine)
Parent Material High-strength low-alloy (HSLA) or structural steel sheet (1.5–5.0 mm)
Projection Function 4 projections concentrate current for consistent high-integrity weld nugget
Electrode Force Higher force required vs class 8; calibrate per sheet thickness and nut size
Weld Energy Increase weld energy vs class 8 to ensure full projection collapse and nugget formation
Post-weld Treatment Apply e-coat, powder coat, or paint promptly; bare steel will surface-rust if exposed to moisture
Thread Protection Use thread protector plug during welding and coating to keep thread clean
Heat-affected Zone Class 10 HAZ may show localized softening; design joint to minimize HAZ stress concentration; post-weld stress relief recommended for critical applications
Storage Store in dry, sealed conditions; bare finish will surface-rust if exposed to moisture before assembly

Selection Guide

Application Scenario Recommended Size Reason
Heavy commercial vehicle chassis M8 – M12 Maximum proof load for safety-critical structural joints
Off-highway & mining equipment M8 – M12 Class 10 withstands extreme dynamic and impact loads
Structural steel fabrication M6 – M12 High-strength weld nut for load-bearing structural panels
Agricultural machinery frames M6 – M12 Heavy sheet metal; class 10 for high-torque fastening points
Crane & lifting equipment M8 – M12 Safety-critical joints requiring maximum proof load
Industrial press & tooling frames M6 – M10 High static load; class 10 prevents thread stripping under sustained load

Standard Reference

DIN 928 specifies square weld nuts with metric threads and four weld projections, issued by the Deutsches Institut für Normung (DIN). The standard defines body dimensions, projection geometry, and thread tolerances for resistance welding applications. FULLERKREG manufactures these class 10 weld nuts in 10B21 boron alloy steel with strict conformance to DIN 928 dimensional tolerances. The bare finish is specified for assemblies where post-weld surface coating is applied as part of the production process. Class 10 is the highest strength grade offered in the FULLERKREG DIN 928 weld nut range.

Product Gallery

DIN 928 Class 10 10B21 Alloy Steel Bare Square Weld Nuts – actual product photos

[Photo 1] [Photo 2] [Photo 3] [Photo 4]

Why Choose FULLERKREG?

🏭 Direct Manufacturer – Factory-direct pricing with full dimensional traceability
📐 DIN Precision – Strict conformance to DIN 928 tolerances, projection geometry verified by QC
💪 ISO Class 10 – Maximum Strength – 1000 MPa proof load, the highest grade in DIN 928 weld nut series
⚡ Weld-Ready Projections – 4 precision projections ensure consistent high-integrity resistance weld
🔬 10B21 Boron Alloy – Superior hardenability, consistent batch strength, good weldability
🎨 Bare Finish – Optimal for post-weld e-coat, powder coat, or paint processes
✅ RoHS Compliant – All products meet EU RoHS environmental directives
📦 Bulk Wholesale Ready – MOQ flexible, available in bags, boxes, or bulk cartons
🌍 Global Shipping – Reliable export logistics to Europe, North America, Southeast Asia
💬 Technical Support – Engineering team available for welding parameters and joint design queries

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