722M24 Nitriding Alloy Steel Round Bars

Product Description

722M24 (famously known under its legacy designation EN40B) is a premier British Standard (BS 970) 3% Chromium-Molybdenum nitriding steel.

Supplied primarily as bright round bars in the hardened and tempered "T" condition (722M24T), it is specifically designed for high-stress dynamic components requiring a tough, shock-resistant core combined with an extremely hard, wear-resistant surface layer after gas or plasma nitriding.

1. Chemical Composition (BS 970 Mass %)

2. Mechanical Properties by Supply Condition

722M24 round bars are supplied pre-heat-treated so parts can be machined to final shape without needing additional core hardening:

3. Global Standard Equivalents

4. Processing & Nitriding Workflow

1. Procurement: Source bars in 722M24T condition.

2. Rough Machining: Machine parts leaving $\sim 0.5\text{--}1.0\text{ mm}$ finishing stock.

3. Stress Relieving: Heat to 550°C – 580°C for 2+ hours and slow cool. (Must be at least 30°C higher than the planned nitriding hold to prevent core softening).

4. Finish Machining / Grinding: Machine to final pre-nitriding tolerances.

5. Nitriding: Hold at 500°C – 530°C in a gas or plasma nitriding furnace for 20 to 80 hours depending on specified case depth ($0.20\text{--}0.60\text{ mm}$).

5. Primary Applications

• Automotive & Motorsport: Race engine crankshafts, camshafts, output shafts, timing pinions, and wrist pins.

• Plastics Machinery: Injection molding feed screws, extruding barrels, and tie bars.

• General Engineering: High-pressure pump shafts, heavy-duty gear pinions, valve rods, and precision spindles.