Stainless Steel 17-4PH, UNS S17400, DIN 1.4542 Bars

Product Description

Stainless Steel 17-4PH (designated as UNS S17400 and DIN 1.4542 / X5CrNiCuNb17-4) is the cornerstone of the precipitation-hardening martensitic stainless steel family.

Because you have previously looked at its global equivalent designations (Alloy 630, AFNOR Z6CNU17-04, and cast SCS 24), this standard 17-4PH / DIN 1.4542 iteration represents the most common commercial raw-material format you will source globally for high-strength machining and forging applications.

Technical Specifications & Standards Matrix

Depending on the geographic origin of your material test reports (MTRs), 17-4PH round, square, or hex bars are certified under several dominant international frameworks:

Chemical Profile: W.Nr. 1.4542 vs. ASTM A564

The chemical composition between the European DIN standard and the American ASTM specification is virtually identical, ensuring seamless interchangeability in 99% of engineering applications:

• Chromium (Cr): 15.00 – 17.00% (DIN/EN restricts the upper cap slightly more tightly to 17.00% compared to ASTM's 17.50%)

• Nickel (Ni): 3.00 – 5.00%

• Copper (Cu): 3.00 – 5.00% (The primary aging element that precipitates out to lock the crystal lattice)

• Niobium (Nb) / Columbium: $5 \times \text{C min}$ to $0.45\%\text{ max}$ (DIN) or $0.15\text{--}0.45\%$ (ASTM)

• Carbon (C): ≤ 0.07%

Heat Treatment Mapping: US "H" vs. European EN Conditions

When transitioning a design from US specifications to European manufacturing yards, the thermal processing nomenclature changes. The mechanical properties remain bound to the same metallurgical transformations:

1. Lösungsgeglüht (Solution Annealed / Condition A)

• EN Designation: +A

• Microstructure: Untempered, low-carbon martensite.

• Characteristics: Highly machinable, but not optimized for service. Hardness typically sits around 360 HBW max.

2. Ausgelagert (Precipitation Hardened / Aged)

• EN Designation: +P followed by the minimum tensile strength limit (e.g., +P930, +P1070).

• US Equivalent Mapping:

 [ Heat Treatment Correlation ] US Aging Condition EU Delivery Condition Typical Hardness Range ──────────────────── ─────────────────────── ──────────────────────── H900 +P1200 40 – 47 HRC H1025 +P1070 35 – 42 HRC H1150 +P930 28 – 37 HRC

Technical Engineering Watchouts for 17-4PH / 1.4542 Bars

• Low-Temperature Embrittlement: Like most martensitic steels, 17-4PH undergoes a ductile-to-brittle transition. It should not be used in cryogenic or sub-zero structural applications where ambient temperatures consistently drop below -29°C (-20°F).

• Hydrogen Embrittlement / NACE Compliance: When peak hardness is triggered (Condition H900), the material is highly susceptible to hydrogen-induced stress cracking. For subsea oil & gas applications or sour environments governed by NACE MR0175, the bars must be double-overaged to the H1150-M condition (requiring a dual-stage post-solution bake at $760^\circ\text{C}$ then $620^\circ\text{C}$) to drastically lower hardness below 28 HRC.

• Galvanic Corrosion: While 17-4PH acts similarly to 304 stainless steel in uniform corrosion tests, it behaves as a more noble metal if coupled with carbon steel or aluminum hardware. Always isolate connections if moisture or salt spray is present.