ASTM F436 is the ASTM standard that specifies chemical, mechanical, and dimensional requirements for hardened steel washers used in structural bolting. It covers inch-series washers from 1/4 in. through 4 in. nominal thread diameter. The companion specification F436M covers the metric series from M12 through M100. Two types are defined: Type 1 (carbon steel, through-hardened 38-45 HRC) and Type 3 (weathering steel with a Corrosion Resistance Index of 6.0 or higher, used where atmospheric corrosion resistance is required).

What is the hardness requirement for ASTM F436 washers?

ASTM F436 through-hardened washers must have a hardness of 38 to 45 HRC. When zinc-coated by the hot-dip process, the hardness range is reduced to 26 to 45 HRC. Carburized washers (used for sizes above 1.5 in. or M36) require a surface hardness of 69 to 73 HRA (or 79 to 83 HR15N) and a minimum core hardness of 30 HRC. Hot-dip galvanized carburized washers must meet 63 to 73 HRA or 73 to 83 HR15N surface hardness.

What is the difference between ASTM F436 Type 1 and Type 3?

Type 1 washers are carbon steel, through-hardened 38-45 HRC, used for general structural connections. Type 3 washers are weathering steel, required to have a Corrosion Resistance Index (CRI) of 6.0 or higher per ASTM Guide G101 using the Legault-Leckie formula, or to be manufactured from steels listed in A588/A588M or F3125 Table 2. Type 3 is used with A325 Type 3 and A490 Type 3 bolts on exposed structures such as bridges and towers where the steel is intended to develop a protective oxide patina in lieu of paint.

What is the difference between F436 and F436M?

F436 is the inch-series standard covering washers for fasteners with nominal thread diameters from 1/4 in. to 4 in. F436M is the metric-series companion covering washers from M12 to M100. The mechanical and hardness requirements are identical between the two. The dimensional tables differ to match inch versus metric thread sizes. Both Type 1 and Type 3 grades are available in both series.

Can ASTM F436 washers be used with A325 and A490 bolts?

Yes. ASTM F436 washers are the standard companion washer for A325 and A490 structural bolts per RCSC specifications. Type 1 F436 washers are used with Type 1 and Type 2 A325 bolts. Type 3 F436 washers are required when using Type 3 A325 or A490 bolts on weathering-steel structures to maintain atmospheric corrosion resistance across the full joint assembly. Extra-thick F436 washers (per RCSC Table 2.1) are required for oversized or short-slotted holes perpendicular to load direction.

What finishes are available for ASTM F436 washers?

Standard finishes include as-fabricated (plain), hot-dip galvanized (zinc coating per ASTM A153 which reduces through-hardened hardness ceiling to HRC 26-45), and mechanically galvanized. Specialty coatings supplied on request include Geomet (321, 500, 720), Xylan (1070, 1014, 1400, 1424), Xylar (2, 101), and SermaGard 1105/1280. EN 10204 Type 3.1 and Type 3.2 (with third-party inspection) certifications are available.

ASTM F436 Washer Specifications — F436/F436M Hardened Steel Washer

ASTM F436/F436M Hardened Steel Washers from TorqBolt. We manufacture the full inch series (1/4 through 4 in.) and metric series (M12 through M100) of F436 hardened washers in both Type 1 carbon steel and Type 3 weathering steel. Type 1 covers general structural connections; Type 3 is the atmospheric-corrosion-resistant grade used with A325 Type 3 and A490 Type 3 bolts on weathering-steel structures, bridges and towers where the protective oxide patina is intended to develop.

All four geometric forms (circular, beveled with a 1:6 square taper, clipped for clearance against fillet welds, and extra thick for slotted-hole and over-size applications) are supplied to the same chemical, mechanical and hardness requirements (HRC 38–45 through-hardened; HRA 69–73 surface-hardened on carburized variants). Standard finishes: as-fabricated, hot-dip galvanized (zinc coating reduces hardness ceiling to HRC 26–45), mechanically galvanized, and Geomet/Xylan coatings on request.

Quick reference: full F436 washer specifications (chemistry, mechanical, marking), F436 washer dimensions (flatness, concentricity, burr tolerances by nominal size), and the F436M metric series (M12 through M100).

Scope

ASTM F436/F436M specification covers the chemical, mechanical, and dimensional requirements for Metric and Imperial(Inch) Series Hardened Steel Washers for structural use with fasteners having nominal thread diameters of 1/4 through 4 in. and M12 through M100. These washers are intended for general-purpose mechanical and structural use with bolts, nuts, studs, and other internally and externally threaded fasteners. These washers are suitable for use with fasteners covered in Specifications A354, A449, A563, A563M, F959/F959M, and F3125. Steel used in the manufacture of washers shall be produced by the open-hearth, basic-oxygen, or electric-furnace process. Washers up to and including 11/2 in. for inch fasteners and M36 for metric fasteners, shall be through hardened. Washers over 11/2 in. for inch fasteners and M36 for metric fasteners, may be either through hardened or carburized at the option of the manufacturer. Unless otherwise specified, washers shall be furnished "plain" with the "as-fabricated" surface finish without protective coatings.

ASTM F436/F436M Mechanical Properties

ASTM F436/F436M Through hardened washers shall have a hardness of 38 to 45 HRC, except when zinc-coated by the hot-dip process, in which case they shall have a hardness of 26 to 45 HRC. Carburized washers shall be carburized to a minimum depth of 0.015 in. (inch series) or 0.38 mm (metric series) and shall have a surface hardness of 69 to 73 HRA or 79 to 83 HR15N, except when zinc-coated by the hot-dip process, in which case they shall have a hardness of 63 to 73 HRA or 73 to 83 HR15N.
Carburized and hardened washers shall have a minimum core hardness of 30 HRC or 65 HRA.

Dimensional Characteristics	<1 in. Nominal Size	1 through 1¹/₂ in. Nominal Size	>1¹/₂ through 3 in. Nominal Size	>3 in. Nominal Size
Flatness: max deviation from straightedge placed on cut side shall not exceed (in.)	0.010	0.015	0.020	0.032
Concentricity, in.: center of hole to outside diameter	0.030 FIR^A	0.060 FIR^A	0.090 FIR^A	0.250 FIR^A
Burr shall not project above immediately adjacent washer surface more than (in.)	0.010	0.015	0.020	0.025
(A) Full indicator reading.

Dimensional Characteristics	12mm through 16 mm Nominal Size	>16 mm Nominal Size
Flatness: max deviation from straightedge placed on cut side shall not exceed	^B	^B
Concentricity, in.: center of hole to outside diameter	0.6 mm FIR^A	0.9 mm FIR^A
Burr shall not project above immediately adjacent washer surface more than (mm)	0.25 mm	0.25 mm
(A) Full indicator runout. (B) Flat within 0.01mm/mm of Outside Diameter

Type	Marking
ASTM F436/F436M Type 1	TB F436 1
ASTM F436/F436M Type 3	TB F436 3

ASTM F436 Hardened Steel Washer — F436/F436M Specifications

Scope

ASTM F436/F436M Mechanical Properties

ASTM F436 Washer Dimensional Tolerances (Inch washers)

ASTM F436M Washer Dimensional Tolerances (Metric Washers)

ASTM F436 Washer Marking

Related Specifications

Surface Treatments

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