Stainless Steel BS S145 Round Bars / BS S145 Rods / BS S145 Rings

Product Description

BS S145 Stainless Steel (Aerospace Series)

BS S145 is a high-strength, corrosion-resisting precipitation-hardening steel within the British Aerospace Series. It is essentially the higher-strength counterpart to BS S143, achieving its enhanced mechanical properties through a specific heat treatment process (typically the H950 or H1025 condition).

Like its sibling alloys, S145 is a chromium-nickel-copper-niobium steel, often technically categorized as a 17-4 PH variant tailored for high-integrity aerospace components.

Technical Specifications & Designations

BS S145 is designed for applications where the tensile strength requirements exceed those of BS S143.

Mechanical Properties (Typical for S145)

The primary distinction of BS S145 is its elevated strength profile. While S143 typically targets a tensile strength around 1000 MPa, S145 is pushed further.

• Tensile Strength ($R_m$): 1270–1470 MPa

• 0.2% Proof Stress ($R_{p0.2}$):$\ge$ 1050 MPa

• Elongation ($A$):$\ge$ 8%

• Hardness: 375–444 HBW (Approx. 40–47 HRC)

Product Forms

1. Round Bars & Rods

Supplied in various finishes, including hot rolled, peeled, or centerless ground. Due to the high hardness of S145, these rods are often used for precision-machined shafts that must resist deflection under extreme loads.

2. Rings & Forged Blanks

Produced via mandrelling or rolled ring forging to ensure a circumferential grain flow. This is critical for aerospace rings that undergo high centrifugal stress or internal pressure.

Comparison: S143 vs. S145

It is common to see these two standards mentioned together, as they share the same base chemistry but differ in their final heat-treated state:

Key Applications

BS S145 is reserved for structural parts where weight-to-strength ratios are a priority:

• Aerospace Structures: Load-bearing airframe components and wing attachment fittings.

• Engine Components: Compressor blades, high-strength fasteners, and turbine supports.

• Defense: Missile components and high-pressure hydraulic blocks.

• Oil & Gas: High-performance valve trim and pump shafts operating in mildly corrosive environments.

Fabrication & Machining

• Machinability: BS S145 is more challenging to machine than S143 due to its higher hardness. It is highly recommended to perform heavy metal removal in the solution-annealed state (BS S144) before final hardening, leaving only a small margin for finish grinding.

• Corrosion Resistance: Offers excellent resistance to atmospheric corrosion and is superior to standard 400-series martensitic steels. However, like all 17-4 PH variants, it may be susceptible to stress corrosion cracking (SCC) when used at its highest strength levels (S145) in certain chloride-rich environments.