Alloy 20 Washers

Alloy 20 Washers — Specifications & Dimensions

Alloy 20 washers distribute clamp load over a wider bearing area. TorqBolt manufactures Alloy 20 washers per ASME B18.21.1 / B18.22.1, DIN 125 / 126 / 127 / 9021, and ISO 7089 / 7090 / 7093 / 7094, in metric (M3–M100) and imperial (#4–4") sizes.

Plain Washer Dimensions

Alloy 20 plain washers are characterized by ID (clearance), OD (load distribution area), and thickness. Standard tolerances h13 on OD, H13 on ID per ISO 286-2; flatness and parallelism 0.05 mm/100 mm verified per lot.

Form Variants

Hardness & Surface

Alloy 20 washers are hardness-controlled to balance load-distribution stiffness against surface damage. Typical Vickers HV: plain 140–180; spring 380–440; Belleville 460–540. Surface finish Ra 1.6 µm or better. EN 10204 3.1 / 3.2 certs standard; NACE MR0175 on request.

High-Mo Super-Austenitic Stainless (254 SMO, 904L, Alloy 20)

Super-austenitic stainless steels are high-Mo (≥6%), high-N austenitic alloys with chloride-pitting resistance approaching duplex grades while retaining austenitic formability.

254 SMO (S31254) is the benchmark with PREN ~43. 904L (N08904) is the original 4.5% Mo super-austenitic for sulfuric-acid plants. Alloy 20 (N08020) is Cu-bearing for hot sulfuric acid. AL-6XN (N08367) extends pitting resistance with 6.5%+ Mo.

Super-austenitic fasteners ship per ASTM A276 / A479 with ASTM G48 Method A pitting testing. Welding requires Ni-base filler (alloy 625 / C-276) to avoid Mo segregation.

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