ASTM F436 Hardened Steel Washer | Structural Flat Washer for A325 A490 Bolts

Size: 1/4"– 4"/ M12 – M100 | Type: Type 1 Carbon Steel / Type 3 Weathering Steel | Material: Carbon Steel Q&T / Weathering Steel Q&T

ASTM F436/F436M hardened steel washer — through-hardened carbon steel (Type 1) or weathering steel (Type 3) flat washer with controlled hardness of HRC 38–45 (plain) or HRC 26–45 (hot-dip galvanized), designed for structural bolted connections with ASTM A325,A490, and F3125 heavy hex bolts. Circular, beveled, and clipped configurations available. Hardness tested per batch per ASTM F436 Section 6. EN 10204 3.1 certificate available.

What Is an ASTM F436 Hardened Washer?

AnASTM F436 hardened washer is a heat-treated steel washer manufactured to the dimensional and mechanical requirements of ASTM F436/F436M. Unlike general-purpose flat washers (ASTM F844), F436 washers undergo quenching and tempering to achieve a through-hardened microstructure with a specified hardness range of 38–45 HRC (plain finish) or 26–45 HRC (hot-dip galvanized finish). This controlled hardness prevents the washer from embedding into the connected steel plate under the high contact pressures developed by tensioned structural bolts.

F436 washers are available in four configurations: Circular (standard round), Beveled (square/rectangular with 1:6 tapered surface for use on sloped flanges of S-shapes and C-channels), Clipped (circular or beveled with one edge truncated to clear adjacent fillet welds), and Extra Thick (nominal 5/16"thickness for oversized hole applications). Type 1 is carbon steel for general structural use; Type 3 is weathering steel with atmospheric corrosion resistance matching A588/A709W grade steel members.

Washer placement per AISC/RCSC: For turn-of-nut and calibrated wrench tensioning with standard holes, the F436 washer is placed under the turned element (typically the nut). For oversized or slotted holes, F436 washers are required at both ends of the bolt assembly.

Marine Applications

Note: The applications listed below are based on typical industry practice for ASTM F436 hardened washers in marine and offshore environments. Specific application suitability should be confirmed against the vessel design specifications and applicable classification society rules.

F436 vs F844: Which Washer to Specify

The most common specification question in structural bolting: when to use F436 hardened washersversusF844 general-purpose flat washers. The answer is simple — F436 is mandatory wherever high-strength structural bolts (A325/A490/F3125) are tensioned to specified preload. F844 is for non-structural, low-stress applications only.

Critical: Specifying F844 where F436 is required is a common field error. An unhardened F844 washer will dent into the beam flange under tensioned structural bolt loads, causing the bolt to lose pretension and the connection to loosen. Per AISC and RCSC specifications, F436 is mandatory for all tensioned structural bolted connections.

Specifications & Materials

Why Choose sinofastener for ASTM F436 Washers?

Standards Reference

• ASTM F436/F436M-19 — Standard Specification for Hardened Steel Washers, Inch and Metric Dimensions
• ASTM F3125/F3125M — Standard Specification for High Strength Structural Bolts and Assemblies (consolidates former A325/A490)
• ASTM F844-19 — Standard Specification for Washers, Steel, Plain (Flat), Unhardened for General Use
• ASTM A354 — Standard Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded Fasteners
• ASTM F2329/F2329M — Standard Specification for Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, and Nuts
• RCSC Specification — Research Council on Structural Connections: Specification for Structural Bolted Joints (washer placement requirements)
• AISC 360 — Specification for Structural Steel Buildings (bolted connection design and installation)

FAQ

Why does ASTM F436 specify different hardness for plain vs. HDG washers?

Per ASTM F436 Section 6.1, through-hardened washers in plain (uncoated) condition must achieve 38–45 HRC. When the same washers are hot-dip galvanized, the hardness range is lowered to 26–45 HRC. This accounts for the hydrogen embrittlement relief baking required after hot-dip galvanizing (per ASTM F1470/F2329), which can slightly reduce the achieved hardness. The 26 HRC minimum for HDG washers still provides adequate resistance to embedment under structural bolt loads.

When are F436 washers required at both ends of the bolt?

Per AISC and RCSC specifications, F436 hardened washers are required at both ends of the bolt assembly when the connection uses oversized or slotted holes. For standard round holes with turn-of-nut or calibrated wrench tensioning, the washer is placed under the turned element only (typically the nut). When a direct tension indicator (DTI, ASTM F959) is used, an F436 washer is placed between the DTI and the turned element.

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

Type 1 is carbon steel, quenched and tempered — the standard choice for general structural and marine applications. Type 3 is weathering steel with specific chemical composition limits (Cr 0.45–0.65%, Cu 0.25–0.45%, Ni 0.25–0.45% per heat analysis) that provides atmospheric corrosion resistance. Type 3 develops a dark oxide patina over time, matching the appearance of weathering steel structural members (ASTM A588, A709 Grade 50W). Type 3 is specified for exposed atmospheric applications where painting is not desired.

Can ASTM F436 washers be used with metric bolts?

Yes. ASTM F436M is the metric counterpart of F436, covering hardened washers for metric fasteners M12 through M100. F436M washers are dimensioned for metric bolt sizes with the same hardness requirements (38–45 HRC plain / 26–45 HRC HDG). F436M washers are suitable for use with ISO 4014/4017 metric hex bolts and EN 14399 structural bolt assemblies.