Home » DIN 128A Lock Washer Spring – 70# Steel Black

DIN 128A Lock Washer Spring – 70# Steel Black

DIN 128A Curved Spring Lock Washer — 70# Spring Steel, Black Oxide

FULLERKREG DIN 128A curved spring lock washers are manufactured to DIN 128 Type A standard in 70# high-carbon spring steel (Grade 70, per GB/T 699) with a black oxide surface treatment. DIN 128 Type A is a curved (single-coil) spring washer that generates axial spring force through its curved profile, providing anti-loosening performance with smooth, even load distribution and no surface marking. The 70# spring steel achieves 40–50 HRC hardness after quench and temper. Black oxide is the preferred surface treatment for high-hardness spring steel — a chemical conversion coating (Fe₃O₄) with no acid pickling, no electrical current, and no hydrogen embrittlement risk.

Product Highlights

  • Standard: DIN 128 Type A (Curved Spring Lock Washer)
  • Material: 70# Spring Steel (Grade 70, GB/T 699)
  • Surface Treatment: Black Oxide (Chemical Blackening / Fe₃O₄)
  • Appearance: Uniform matte black, non-reflective finish
  • Hardness: 40–50 HRC (392–513 HV) after quench & temper
  • Size Range: M2 – M36
  • Profile: Type A — Curved single-coil (not helical split, not wavy)
  • No hydrogen embrittlement risk — safe for high-hardness spring steel
  • Coating thickness 1–3 um — negligible dimensional impact
  • RoHS & REACH Compliant

Dimensional Specifications — DIN 128 Type A (Curved), 70# Steel Black

All dimensions in millimeters (mm). Per DIN 128 Type A.

Nominal Size For Bolt d1 min d2 max h min h max s (thickness) b (width)
2 M2 2.1 4.4 0.70 1.10 0.6 0.9
2.3 M2.3 2.4 4.9 0.90 1.10 0.6 0.9
2.5 M2.5 2.6 5.1 0.90 1.10 0.6 1.0
2.6 M2.6 2.7 5.2 0.90 1.10 0.6 1.0
3 M3 3.1 6.2 1.10 1.30 0.7 1.3
3.5 M3.5 3.6 6.7 1.20 1.30 0.7 1.3
4 M4 4.1 7.6 1.20 1.40 0.8 1.5
5 M5 5.1 9.2 1.50 1.70 1.0 1.8
6 M6 6.1 11.8 2.00 2.20 1.3 2.5
8 M8 8.1 14.8 2.45 2.75 1.6 3.0
10 M10 10.2 18.1 2.85 3.35 1.8 3.5
12 M12 12.2 21.1 3.35 3.65 2.1 4.0
14 M14 14.2 24.1 3.90 4.30 2.4 4.5
16 M16 16.2 27.4 4.50 5.10 2.8 5.0
18 M18 18.2 26.4 4.50 5.10 2.8 5.0
20 M20 20.2 33.6 5.10 5.90 3.2 6.0
22 M22 22.5 35.9 5.10 5.90 3.2 6.0
24 M24 24.5 40.0 6.50 7.50 4.0 7.0
27 M27 27.5 43.0 6.50 7.50 4.0 7.0
30 M30 30.5 48.2 9.50 10.50 5.0 8.0
36 M36 36.5 58.2 10.30 11.30 6.0 10.0

All dimensions in mm per DIN 128 Type A. s = material thickness; b = ring width; h = free height. Black oxide coating 1–3 um — negligible dimensional impact.

Material Properties — 70# Spring Steel (GB/T 699)

Property Value
Material Grade 70# Spring Steel (Grade 70)
GB Standard GB/T 699, GB/T 4354
C Content 0.67 – 0.75%
Mn Content 0.50 – 0.80%
Heat Treatment Quench & Temper
Hardness 40 – 50 HRC (392 – 513 HV)
Tensile Strength 1275 MPa min.
Surface Treatment Black Oxide (Chemical Blackening / Fe₃O₄)
Coating Thickness 1 – 3 um (conversion coating, negligible dimensional impact)
Operating Temperature -40°C to +120°C
RoHS / REACH Compliant

Chemical Composition — 70# Spring Steel (GB/T 699)

Element C Mn Si P max S max Cr max Ni max
Content % 0.67–0.75 0.50–0.80 0.17–0.37 0.035 0.035 0.25 0.25

Black Oxide vs. Zinc — Surface Treatment Comparison

Property Black Oxide Zinc (Mechanical)
Coating thickness 1–3 um 8–25 um
Corrosion resistance Basic — indoor / dry Good — light outdoor & humid
H2 embrittlement risk None None (mechanical process)
Appearance Matte black Bright silver-grey
Dimensional impact Negligible 8–25 um added
Best for Indoor, dry, precision assemblies Outdoor, humid, general industrial

Application Scenarios

  • Cheese head screw assemblies (DIN 84) — curved profile optimized for cheese head applications, matte black finish
  • Pan head screw assemblies (DIN 7985) — smooth curved profile, no surface marking
  • Electrical enclosures & control panels — matte black, non-reflective, professional appearance
  • Precision mechanical assemblies — 1–3 um coating preserves dimensional tolerances
  • Heavy machinery — indoor or dry environments — high spring force without corrosion exposure
  • Automotive manufacturing — engine and drivetrain assemblies in dry environments
  • Soft material assemblies — curved profile distributes load without sharp edge marking

Product Photo Gallery

FULLERKREG DIN 128A Curved Spring Lock Washer, 70# Spring Steel, Black Oxide:

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

Why Choose FULLERKREG?

  • 🏭 Direct manufacturer — factory in China, no middlemen
  • 📐 Strict DIN dimensional control — 100% inspection on critical dimensions and hardness
  • 🌍 Global export experience — serving distributors in Europe, North America, Southeast Asia
  • 📦 Flexible MOQ — small trial orders and large bulk shipments both welcome
  • 📋 Full documentation — material certs, hardness reports, RoHS declarations available
  • ⚡ Fast lead times — standard sizes in stock, ready to ship

Frequently Asked Questions

Q: What is DIN 128 Type A?
A: DIN 128 Type A is a curved spring lock washer. The ring is formed into a single curved arc. When compressed under bolt load, it acts as a spring maintaining axial clamping force and resisting loosening. Unlike DIN 127B (helical split with sharp edges), it has no sharp edges and does not mark bearing surfaces.

Q: Why black oxide for 70# spring steel?
A: At 40–50 HRC, electroplating introduces hydrogen embrittlement risk. Black oxide is a chemical conversion coating (Fe₃O₄) applied without acid pickling or electrical current, eliminating this risk. Preferred for high-hardness spring steel in indoor/dry environments.

Q: Black oxide vs. zinc — which to choose?
A: Black oxide (1–3 um) is ideal for indoor, dry, or precision applications. Choose zinc plating (8–25 um) for outdoor or humid environments requiring better corrosion protection.

Q: DIN 128A vs. DIN 128B — which to choose?
A: DIN 128A (curved) is designed for cheese head and pan head screws with a single smooth arc. DIN 128B (wavy) provides multi-point contact for general assemblies. Both share the same dimensions.

Q: Do you provide material test certificates?
A: Yes. Mill certificates, hardness reports, chemical composition reports, and RoHS declarations available upon request.

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