431 Stainless Steel Round Bar
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1.4057 – martensitic steel with nickel
1.4057 (AISI 431), X17CrNi16-2, is a martensitic stainless steel with about 16% chromium and 2% nickel. Nickel and higher chromium set it apart from 13% chromium grades such as 1.4021 and 1.4034: 431 offers better corrosion resistance and much higher impact toughness, and after quenching and tempering it reaches a tensile strength of approx. 800–1,050 MPa. It is magnetic. More on this group of steels in the article Martensitic stainless steel: properties and applications.
Chemical composition of 1.4057 / 431
| Grade | C | Cr | Ni |
|---|---|---|---|
| 1.4057 / 431 | 0.12–0.22 | 15.0–17.0 | 1.50–2.50 |
| 1.4034 / 420C (for comparison) | 0.43–0.50 | 12.5–14.5 | – |
Values in wt. % per EN 10088-3. Equivalents: 1.4057 = X17CrNi16-2 = AISI 431 = UNS S43100. The heat chemistry is confirmed by the 3.1 certificate.
Delivery condition and properties
1.4057 bar is usually supplied quenched and tempered: +QT800 (tensile strength approx. 800–950 MPa) or +QT900 (approx. 900–1,050 MPa), in which the material already has its final strength and can be machined without further heat treatment. The condition of each heat is stated on the certificate. Weldability is limited – the steel needs preheating and post-weld tempering, so 431 parts are usually joined mechanically.
Diameters Ø 10–125 mm and applications
We stock bar in diameters of 10, 12, 16, 20, 25, 30, 40, 50, 75, 80, 120 and 125 mm, in lengths from 10 cm to 3 m or cut to length. 1.4057 is used for pump and mixer shafts, boat propeller shafts, valve stems, pins, high-strength bolts and nuts, axles and parts for food and paper machinery. Diameter tolerances are described on the round bar tolerances page.
431 or another grade?
Where higher hardness and wear resistance are needed – blades, knives, mandrels – 420 / 420C round bar (1.4021 / 1.4034) is the better choice. In seawater and chlorides, pump shafts are increasingly made from duplex 1.4462 round bar, and where strength is not critical, from 316L round bar. Other grades are in the Round bars category.