1.4057 (X17CrNi16-2) Stainless Steel: Material Equivalents and Heat-Treated Properties
What 1.4057 Covers
1.4057 is the EN material number for X17CrNi16-2, a martensitic stainless steel that the US system knows as Type 431 and UNS S43100. The grade combines about 16 % chromium with roughly 2 % nickel, which raises hardenability and toughness compared with the plain 12 % chromium martensitic grades and gives better corrosion resistance than Type 420 while still allowing high strength through quenching and tempering. Typical uses are pump shafts, valve stems, studs and fasteners, marine hardware and aircraft components.
Cross-Standard Equivalents
| System | Standard | Designation |
|---|---|---|
| Europe (EN) | EN 10088-1, EN 10088-2, EN 10088-3 | X17CrNi16-2 (1.4057) |
| United States | ASTM A276, ASTM A240, ASTM A959 | Type 431 / UNS S43100 |
| ISO | ISO 15510 | X17CrNi16-2 (4057-431-00-X) |
| China | GB/T 1220, GB/T 3280 | 17Cr16Ni2 (S43120) |
| Japan | JIS G4303, JIS G4304 | SUS431 |
Product form coverage differs, so an equivalent grade is not automatically an equivalent purchase. Bar stock is normally ordered to ASTM A276 or EN 10088-3, plate and sheet to ASTM A240 or EN 10088-2, and custom forgings to a drawing specification agreed between purchaser and mill, with the acceptance criteria written into the order rather than assumed from the grade name.
Chemical Composition
| Element, % | EN 10088-3 | ASTM A276 |
|---|---|---|
| C | 0.12-0.22 | 0.20 max |
| Si | 1.00 max | 1.00 max |
| Mn | 1.50 max | 1.00 max |
| P | 0.040 max | 0.040 max |
| S | 0.030 max | 0.030 max |
| Cr | 15.0-17.0 | 15.0-17.0 |
| Ni | 1.50-2.50 | 1.25-2.50 |
The EN grade sets a minimum carbon of 0.12 % to guarantee response to hardening, while the ASTM grade only caps carbon at 0.20 %. A heat at the low end of the EN range tempers to a lower hardness than a heat at 0.22 %, so where a hardness window is contractual the carbon range should be tightened by agreement rather than left to the mill.
Heat Treatment Window
Soft annealing is carried out in the 680 to 800 degrees C band with slow cooling, producing a machinable structure at a hardness at or below about 295 HBW. Hardening is carried out by austenitising between 950 and 1050 degrees C and quenching in oil or air depending on section size, followed by tempering. Tempering in the 650 to 750 degrees C band produces the 800 MPa strength class; tempering at 600 to 650 degrees C produces the 900 MPa class.
Tempering between roughly 400 and 600 degrees C should be avoided. Chromium carbides precipitate at the boundaries in that window and both corrosion resistance and impact toughness fall sharply. If corrosion resistance matters more than peak strength, the higher tempering temperature is the correct choice even though the yield strength is lower.
Mechanical Properties
| Condition | 0.2 % proof strength | Tensile strength |
|---|---|---|
| Soft annealed | Not specified | About 950 MPa maximum |
| Quenched and tempered, 800 MPa class | 600 MPa minimum | 800-950 MPa |
| Quenched and tempered, 900 MPa class | 700 MPa minimum | 900-1050 MPa |
The grade is ferromagnetic in every condition, with a density near 7.7 g/cm3 and an elastic modulus of about 215 GPa at 20 degrees C. Mean thermal expansion is close to 10 x 10-6 per K between 20 and 100 degrees C, similar to carbon steel, which keeps mixed-material assemblies predictable. The higher strength class has lower elongation and impact energy than the 800 MPa class, so thin sections and stress concentrations need attention in design.
Where It Works and Where It Does Not
| Application | Suitability |
|---|---|
| Shafts, spindles, pump and valve stems | Good, in the quenched and tempered condition |
| Studs, bolts and general fasteners | Good where moderate chloride exposure is expected |
| Marine hardware and propeller shafting | Acceptable for intermittent exposure, not for permanent immersion |
| Chloride-rich chemical process equipment | Not recommended; a duplex or molybdenum-bearing austenitic grade performs better |
In chloride-bearing environments 1.4057 clearly outperforms Type 410 and Type 420 but stays well below a duplex stainless steel. Where chloride pitting or stress corrosion cracking is expected, selecting a duplex grade at the design stage is normally cheaper than replacing 431 after a few years of service.
Frequently Asked Questions
Q: What is 1.4057 equivalent to in the US system?
A: Type 431, UNS S43100, listed in ASTM A276 for bars and ASTM A240 for plate, sheet and strip.
Q: Can 1.4057 be welded?
A: It can, but martensitic grades need preheat and controlled cooling, and matching-strength welds require post-weld heat treatment. Many fabrications use an austenitic filler instead and accept the property mismatch.
Q: Why is a minimum carbon specified in EN 10088-3?
A: Carbon controls the hardness response to quenching. Without a minimum, a low-carbon heat would not reach the hardness that the +QT800 and +QT900 conditions imply.
Q: Is 1.4057 magnetic?
A: Yes, it is ferromagnetic in the annealed and in the hardened and tempered conditions, which matters in instrument and sensor applications.
Q: Which tempering temperature should be avoided?
A: The 400 to 600 degrees C range, where chromium carbide precipitation reduces both corrosion resistance and toughness. Temper either above or below that window and state the requirement on the drawing.
Q: How should the material be certified?
A: With an EN 10204 3.1 inspection certificate quoting heat number, chemical analysis, heat treatment condition and mechanical results, plus ultrasonic or dye penetrant testing for critical shaft and stem applications.
