UNS S21600 (XM-17) Austenitic Stainless Steel Plate & Coil
UNS S21600 (XM-17) Austenitic Stainless Steel Plate & Coil - High Nitrogen, High Strength Alloy
Complete material analysis of UNS S21600 (XM-17) austenitic stainless steel plate and coil per ASTM A240, including chemical composition, mechanical & physical properties, equivalents, and application guidance.
Hot rolling, cold rolling, annealing, pickling, cutting, forming, welding, machining
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UNS S21600 Austenitic Stainless Steel Plate & Coil Introduction
UNS S21600, designated as XM-17, is a nitrogen-strengthened austenitic stainless steel offering a unique combination of high strength, good ductility, and excellent corrosion resistance. The deliberate addition of nitrogen significantly increases the yield strength above that of conventional 300-series stainless steels while maintaining toughness and weldability. Under ASTM A240/A240M, it is typically supplied in the solution-annealed condition for plate and coil products. This alloy exhibits superior resistance to pitting and crevice corrosion in chloride-containing environments, making it suitable for demanding applications in marine, chemical, and aerospace industries. Its high work-hardening rate also allows further strengthening through cold working, expanding its utility in high-strength fasteners and shafts.
UNS S21600 Austenitic Stainless Steel Plate & Coil Chemical Composition per ASTM A240 for UNS S21600
The chemical composition of XM-17 is tightly controlled to maximize the benefits of nitrogen strengthening. High levels of manganese and nitrogen substitute for a portion of the nickel, improving strength while maintaining an austenitic structure. Molybdenum further enhances pitting resistance. The balance is iron, with residual elements limited as shown below.
| Element | Requirement (wt.%) | Remarks |
|---|---|---|
| Carbon (C) | 0.08 max | |
| Manganese (Mn) | 7.50 - 9.00 | Austenite stabilizer, contributes to nitrogen solubility |
| Phosphorus (P) | 0.060 max | Residual element, limited for toughness |
| Sulfur (S) | 0.030 max | Residual element, controlled for machinability and corrosion |
| Silicon (Si) | 0.75 max | Residual element, acts as deoxidizer |
| Chromium (Cr) | 17.50 - 20.00 | Primary element for corrosion resistance |
| Nickel (Ni) | 5.00 - 7.00 | Austenite former, provides ductility |
| Molybdenum (Mo) | 2.00 - 3.00 | Improves pitting and crevice corrosion resistance |
| Nitrogen (N) | 0.25 - 0.50 | Key strengthening element, forms interstitial solid solution |
| Iron (Fe) | Balance |
UNS S21600 Austenitic Stainless Steel Plate & Coil Typical Physical Properties
These properties are representative for UNS S21600 in the annealed condition and are based on published data. Actual values may vary slightly depending on specific heat treatment and product form. Thermal expansion is comparable to other austenitic stainless steels, while thermal conductivity is relatively low, as expected for the austenitic structure.
| Property | Typical Value (metric / imperial) | Unit | Condition / Notes |
|---|---|---|---|
| Density | 7.89 / 0.285 | g/cm³ / lb/in³ | Room temperature |
| Modulus of Elasticity (Tension) | 193 / 28.0 x 10⁶ | GPa / psi | Room temperature |
| Shear Modulus | 76 / 11.0 x 10⁶ | GPa / psi | Estimated from E and Poisson's ratio |
| Poisson's Ratio | 0.31 | – | Room temperature, typical for austenitics |
| Mean Coefficient of Thermal Expansion (20–100°C) | 16.8 / 9.36 x 10⁻⁶ | µm/m·°C / in/in/°F | Recommended for design |
| Thermal Conductivity (at 100°C) | 16.3 / 9.4 | W/m·K / Btu/ft·h·°F | Typical at elevated temperature |
| Specific Heat Capacity | 500 / 0.12 | J/kg·K / Btu/lb·°F | Approximate room temperature value |
| Electrical Resistivity | 0.79 | µΩ·m | Typical at room temperature |
UNS S21600 Austenitic Stainless Steel Plate & Coil Minimum Mechanical Properties per ASTM A240
The following mechanical properties are applicable to plate and coil products in the solution-annealed condition. The high yield and tensile strengths result from nitrogen solid-solution strengthening. Elongation requirements vary with product thickness; the values listed are the minimums typically applied. Hardness is controlled to ensure adequate ductility and formability.
| Property | Minimum Value (metric / imperial) | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (0.2% offset) | 415 / 60 | MPa / ksi | Room temperature, annealed plate |
| Tensile Strength | 690 / 100 | MPa / ksi | Room temperature, annealed plate |
| Elongation in 2 in. (50 mm) | 40 | % | Thickness ≤ 0.1875 in. (4.76 mm) |
| Elongation in 2 in. (50 mm) | 30 | % | Thickness > 0.1875 in. (4.76 mm) |
| Hardness, Brinell (HBW) | 250 max | HBW | Typical maximum for annealed condition |
| Hardness, Rockwell B (HRBW) | 100 max | HRBW | Alternative maximum hardness |
UNS S21600 Austenitic Stainless Steel Plate & Coil Direct Equivalent Standards and Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A240/A240M | UNS S21600 (XM-17) | Original specification for chromium and chromium-nickel stainless steel plate, sheet, and strip for pressure vessels and general applications. No recognized EN or ISO direct equivalent. |
UNS S21600 Austenitic Stainless Steel Plate & Coil Application Introduction
UNS S21600 excels in environments where both high mechanical strength and resistance to chloride pitting are required. It is widely specified for shafts, fasteners, and components exposed to seawater or corrosive chemicals. The alloy can be readily machined, formed, and welded, although its high work-hardening rate necessitates proper tooling and slower speeds. Common application areas and specific product examples are listed below.
Product Applications: Propeller shafts and rudder stocks, Chemical reactor vessels and agitators, High-strength corrosion-resistant fasteners, Pump shafts and sleeves, Valve stems, balls, and seats, Heat exchanger components and tube sheets
Processed into products: Bearing rings and wear plates, Bolt and nut assemblies for high-temperature/pressure service, Welded internals for pressure vessels, Motion control linkages, Wire forms and springs requiring combined strength and corrosion resistance, Flanges and forgings for critical piping systems
Application industries: Marine and Offshore Engineering, Chemical and Petrochemical Processing, Aerospace and Defense, Power Generation (including nuclear), Pulp and Paper Industry, Food and Beverage Processing Equipment
UNS S21600 Austenitic Stainless Steel Plate & Coil Similar/Alternative Materials for Consideration
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A240 | UNS S20910 (XM-19) | High-nitrogen, high-strength austenitic stainless. Slightly lower yield strength (min 380 MPa) but higher nickel and similar corrosion resistance. Often considered a direct competitor. |
| USA | ASTM A240 | UNS S30400 / S30403 | Standard 18-8 stainless. Much lower strength but widely available and cost-effective for less demanding environments. Not recommended for high chloride service. |
| USA | ASTM A240 | UNS S31600 / S31603 | Molybdenum-bearing austenitic. Offers improved pitting resistance over 304/304L but at lower strength. Useful when strength is not primary concern but corrosion is. |
Notes:
Welding should be performed using filler metals such as AWS ER209 or ERNiCrMo-3 to preserve corrosion resistance and strength. Post-weld annealing may be required to restore optimum properties in heavily cold-worked regions. For cold forming, the high work-hardening rate can be managed with intermediate annealing. This material is non-magnetic in the annealed condition but may become slightly magnetic after severe cold working. Always consult the latest edition of ASTM A240/A240M for the most current requirements.
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