BS CS40 Alloy Steel Bar CS40 Round Bars CS40 Rods

Product Description

BS CS40 is a medium-carbon steel grade specified under the British Standard BS 1449 (though often associated with the older BS 970 framework). It is essentially a "Conditioned Surface" or specialized carbon steel with approximately 0.40% carbon.

It is widely used in the UK and Commonwealth engineering sectors for components that require more "backbone" than mild steel but must remain easy to machine.

1. Chemical Composition

As a medium-carbon non-alloy steel, its properties are driven primarily by the Carbon and Manganese content.

2. Mechanical Properties

CS40 is versatile and its strength profile changes significantly depending on its "condition" (e.g., Normalized or hardened).

3. Key Technical Characteristics

• Surface Hardening: CS40 is an excellent candidate for induction or flame hardening. You can achieve a surface hardness of 50–55 HRC, which is perfect for parts that face high-friction wear.

• Machinability: Very good. In its normalized or cold-drawn state, it chips cleanly, making it a favorite for high-speed automated lathe work.

• Weldability: Limited. Like most 0.40% carbon steels, it has a risk of cracking. Pre-heating to 150°C–250°C is highly recommended if welding is required.

• Toughness: It offers a solid compromise between the ductility of lower carbon steels (like CS15) and the higher strength of CS50.

4. Global Equivalents

If you are sourcing materials globally or looking for a modern alternative, CS40 aligns with these standards:

5. Common Applications

BS CS40 round bars and rods are typically used for "stressed" mechanical parts:

• Power Transmission: Transmission shafts, keyed shafts, and spindles.

• Automotive: Steering joints, connecting rods, and crankshafts.

• Fasteners: High-tensile studs and bolts (Property Class 8.8).

• General Machinery: Gears, racks, and pinions (often surface-hardened).

Available Stock & Finishes

• Round Bars: Available from 6mm to 300mm+ diameters.

• Precision Rods: Frequently supplied as Bright Drawn (h9 or h11 tolerance) for a smooth finish and tight dimensional control.

• Delivery Condition: Usually stocked in Normalized or As Rolled condition, but can be supplied Hardened and Tempered (Condition R or S) upon request.