Why use a hardened washer with high-strength steel?

Why use a hardened washer with high-strength steel?

• A. to prevent galling the steel during tightening
• B. to prevent rust
• C. to reduce weight
• D. to improve conductivity

Answer: (A)

When tightening high-strength steel joints, metal-to-metal contact can seize or gall under high clamping forces, causing sticking or loss of preload. A hardened washer provides a very hard, smooth bearing surface between the bolt head (or nut) and the joint, reducing friction and the tendency for adhesion and cold-welding at the interface. It also spreads the load over a larger area, lowering peak contact stress and protecting the softer base material from embedding under the fastener. This combination preserves the intended clamp force and makes tightening more reliable. The other options don’t address the frictional seizing issue during tightening.

When tightening high-strength steel joints, metal-to-metal contact can seize or gall under high clamping forces, causing sticking or loss of preload. A hardened washer provides a very hard, smooth bearing surface between the bolt head (or nut) and the joint, reducing friction and the tendency for adhesion and cold-welding at the interface. It also spreads the load over a larger area, lowering peak contact stress and protecting the softer base material from embedding under the fastener. This combination preserves the intended clamp force and makes tightening more reliable. The other options don’t address the frictional seizing issue during tightening.