Stainless Steel BS S144 Round Bars / BS S144 Rods / BS S144 Rings

Product Description

BS S144 Stainless Steel (Aerospace Series)

BS S144 is the solution-treated (annealed) version of the chromium-nickel-copper-niobium precipitation-hardening steel family in the British Aerospace Series. It shares the same chemical composition as BS S143 and BS S145, but it is supplied in its softest, most ductile state.

This condition is specifically designed to allow for complex machining, cold forming, or heading before the final "aging" heat treatment is applied to reach the desired strength levels of S143 or S145.

Technical Specifications & Designations

BS S144 is the starting point for most high-strength 17-4 PH aerospace components manufactured under British standards.

Mechanical Properties (Solution Treated)

In the S144 condition, the material is relatively soft. The focus is on formability and machinability rather than ultimate strength.

• Tensile Strength ($R_m$): Typically 750–950 MPa (Referenced for information)

• Hardness:$\le$ 331 HBW

• Structure: Untempered martensite (highly receptive to subsequent hardening).

Why Specify BS S144?

The primary reason to procure material as BS S144 rather than the pre-hardened versions is to facilitate the manufacturing process:

1. Extended Tool Life: Machining S144 is significantly easier on cutting tools than machining the hardened S145 variant.

2. Cold Working: If the component requires cold drawing or slight forming, S144 provides the necessary ductility.

3. Dimensional Control: By machining in the S144 state and then hardening, manufacturers can manage the slight dimensional changes that occur during the low-temperature aging process (typically a predictable contraction of about 0.04% to 0.06%).

Product Forms

1. Round Bars & Rods

Often supplied as "Black Bar" (hot rolled) or "Bright Bar" (peeled/ground). These are the primary raw materials for CNC machining aerospace fasteners and fittings.

2. Rings & Forgings

Rings supplied to BS S144 are usually rough-machined. Because the material is in the solution-treated state, it is more forgiving during the initial roughing stages of large-diameter ring production.

The Transformation Process

BS S144 acts as the "base" material that is transformed into other standards via heat treatment:

• S144 + Precipitation Treatment (approx. 500°C - 600°C) $\rightarrow$ BS S143 (Moderate Strength)

• S144 + Precipitation Treatment (approx. 480°C) $\rightarrow$ BS S145 (Highest Strength)

Key Applications

• Semi-finished Components: Parts that require significant metal removal before being hardened for flight.

• Aerospace Fasteners: Bolts and rivets produced via cold heading.

• Custom Forgings: Components where the final mechanical properties will be verified only after the final heat treatment stage of the finished part.

Fabrication Notes

• Corrosion Resistance: In the solution-treated (S144) condition, the material's corrosion resistance is lower than in the hardened states. It should not be used in service as S144; it is intended only as an intermediate manufacturing condition.

• Welding: S144 is highly weldable. It is the preferred condition for welding, as it minimizes the risk of cracking. Post-weld heat treatment (aging) is then used to homogenize the properties across the weld and the base metal.