S106 Nitriding Steel S106D Alloy Steel Round Bars

Product Description

BS S106 (commonly designated in supply standards as S106 or S106D) is a premier British Aerospace Standard 3% Chromium-Molybdenum (Cr-Mo) nitriding alloy steel.

The suffix "D" in S106D specifically denotes the supply condition: bars that have been hardened, tempered, stress-relieved, and bright-finished (peeled, turned, or precision ground). This pre-treated state allows precision components to be machined and nitrided at low temperatures ($500^\circ\text{C}\text{--}540^\circ\text{C}$) with virtually zero dimensional distortion or core softening.

1. Chemical Composition (BS S106 Mass %)

2. Mechanical Properties (Supply Condition S106D vs. Post-Nitrided)

3. Global Standard Equivalents

4. Fabrication & Nitriding Workflow

To preserve fine tolerances during aerospace and motorsport manufacturing:

1. Procurement State: Source as S106D / 4S106D bright round bars.

2. Rough Machining: Machine component leaving $0.5\text{--}1.0\text{ mm}$ allowance for stress-relief movement.

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

4. Finish Machining / Grinding: Finish grind or turn to pre-nitride final dimensions.

5. Nitriding: Hold at 500°C – 530°C in gas or plasma (ion) nitriding atmosphere for 20 to 80 hours depending on specified effective case depth.

5. Primary Engineering Applications

• Aerospace & Defense: Gas turbine main shafts, actuator power screws, turbine fasteners, high-load fuel pump shafts, and gear pinions.

• Motorsport & Performance Automotive: Formula 1 / Supercar crankshafts, camshafts, output shafts, wrist pins, and transmission gears.

• Industrial Equipment: Plastics extrusion feed screws, high-pressure barrels, precision guide rods, and heavy-duty tie bars.