Custom 455 is a titanium-, copper- and niobium-bearing martensitic age-hardenable (precipitation-hardening) stainless steel. This datasheet presents the material within the American (ASTM / ASME / AMS / UNS) standard system.
With about 12% chromium, 9% nickel, 2% copper, titanium and niobium, Custom 455 develops exceptionally high yield strength — roughly three times that of type 304 — after a single low-temperature ageing treatment, while retaining good ductility, toughness and moderate corrosion resistance. It is relatively soft and formable in the solution-treated (annealed) condition (~30–35 HRC) and has a very low work-hardening rate, permitting extensive cold forming. The dimensional change on hardening is only about −0.001 in/in, allowing close-tolerance finish machining in the annealed state.
Typical applications include aerospace structural components, shafting, valve and pump parts, fasteners, springs, and high-strength corrosion-resistant hardware.
Typical values, H1000 condition.
| Property | Value | Unit |
|---|---|---|
| Density | 7.76 | g/cm³ |
| Melting range | 1400–1440 | °C |
| Elastic modulus | 200 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 10.2 | µm/m·°C |
| Thermal conductivity (20 °C) | 17.0 | W/m·K |
| Specific heat (20 °C) | 460 | J/kg·K |
| Structure | Martensitic (precipitation-hardening) | — |
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 11.0 | 12.5 | Corrosion resistance; martensite former |
| Nickel | Ni | 7.5 | 9.5 | Toughness; martensite stability |
| Copper | Cu | 1.5 | 2.5 | Precipitation-hardening phase |
| Titanium | Ti | 0.80 | 1.40 | Precipitation-hardening phase |
| Niobium | Nb | 0.10 | 0.50 | Carbide stabiliser; precipitation |
| Manganese | Mn | — | 0.50 | Deoxidiser |
| Silicon | Si | — | 0.50 | Deoxidiser |
| Carbon | C | — | 0.05 | Low (toughness) |
| Phosphorus | P | — | 0.040 | Residual impurity |
| Sulphur | S | — | 0.030 | Residual impurity |
Typical values by ageing (H) condition, per ASTM A564 / AMS 5617 for UNS S45500.
| Condition | Tensile strength | 0.2% Yield | Hardness |
|---|---|---|---|
| H900 | ≥1655 MPa (240 ksi) | ≥1585 MPa (230 ksi) | ~49 HRC |
| H950 | ≥1620 MPa (235 ksi) | ≥1520 MPa (220 ksi) | ~48 HRC |
| H1000 | ≥1520 MPa (220 ksi) | ≥1410 MPa (205 ksi) | ~44 HRC |
| Annealed (Condition A) | ~1000 MPa (145 ksi) | ~795 MPa (115 ksi) | ~30–35 HRC |
Confirm against the mill test report. Elongation typically ≥8–12% in hardened conditions.
| Environment | Performance | Notes |
|---|---|---|
| Atmospheric / general | Moderate to Good | Between 17-4PH and martensitic 400-series |
| Mild acids | Moderate | At low concentrations |
| Chloride pitting | Moderate | Lower than austenitic grades |
| Stress-corrosion cracking | Moderate | Improved at higher ageing |
| Seawater | Limited | Not recommended for prolonged exposure |
Corrosion resistance is moderate — adequate for many structural applications but below the higher-chromium PH grades; the alloy is selected primarily for its ultra-high strength.
A martensitic precipitation-hardening alloy; supplied in the annealed (solution-treated) condition and hardened by a single low-temperature ageing treatment.
Solution Treatment (Condition A) Approximately 830 °C, hold, then cool to room temperature to form a soft martensitic structure (~30–35 HRC). Generally supplied solution-annealed.
Precipitation Hardening (Ageing) A single ageing treatment develops ultra-high strength: H900 (~482 °C) gives maximum strength; higher temperatures (H950, H1000) progressively lower strength while increasing toughness. Cold work prior to ageing further raises strength. Air cool after ageing; dimensional change is only about −0.001 in/in.
Weldable in much the same manner as other precipitation-hardenable stainless steels; matching filler is used. A post-weld heat treatment restores full properties.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good | Matching Custom 455-type filler |
| GMAW / MIG | Good | Matching filler |
| SMAW / stick | Good | Matching electrode |
Weld in the annealed condition; re-age after welding to restore strength.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Preferred condition | Annealed (machinable in Condition A; close-tolerance possible) |
| Work hardening | Very low rate — allows extensive cold forming |
| Tooling | Carbide tooling; rigid setup |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Extensive cold forming, cold drawing, cold-heading (very low work-hardening rate) |
| Hot forming | ~1150–950 °C; solution treat + age afterward |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Aerospace | Structural fittings, shafts, actuators | Ultra-high strength + fabricability |
| Defence | High-strength structural components | Strength + toughness |
| Sporting goods | High-strength shafts (golf, etc.) | Strength-to-weight |
| General industrial | High-strength fasteners, springs | Hardness + cold formability |
| Product Form | ASTM Standard | ASME / AMS |
|---|---|---|
| Bar and forgings | ASTM A564 grade XM-16 | ASME SA-564 / AMS 5617 |
| Wire | ASTM A580 (XM-16) | AMS 5672 |
| Plate, sheet and strip | ASTM A693 grade XM-16 | AMS 5860 |
| Welded tubing | — | AMS 5578 |
Titanium-, copper- and niobium-bearing martensitic precipitation-hardening stainless steel. UNS S45500.
| Grade | Cr % | Ni % | Cu % | Other | Best Used For |
|---|---|---|---|---|---|
| Custom 455 | 11–12.5 | 7.5–9.5 | 1.5–2.5 | Ti, Nb | Ultra-high-strength PH; fabricable |
| Custom 450 | 14–16 | 5–7 | 1.25–1.75 | Mo, Nb | PH with 304-like corrosion resistance |
| 17-4PH | 15–17.5 | 3–5 | 3–5 | Nb | General-purpose martensitic PH |
| 13-8 Mo | 12.25–13.25 | 7.5–8.5 | — | Mo, Al | Highest-toughness PH; aerospace |
| Type 410 | 11.5–13.5 | — | — | — | Martensitic, lower strength |




