Stainless Steel, Austenitic
S20910 (XM-19) Bar & Sheet
A highly alloyed austenitic stainless steel with good mechanical strength and high corrosion resistance.
XM-19 is a nitrogen-strengthened austenitic stainless steel that is available in an annealed or high strength condition.
XM-19 can be used in a wide variety of industries including chemical, marine, nuclear, food processing, petrochemical, sour well service, cryogenic, textile and pulp & paper.
UNS S20910/XM-19 stainless steel provides outstanding resistance to general corrosion – Superior to Types 316/316L and 317/317L in many media.
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Range
| Product Form | Size Range |
| Round Bar Peeled K12 | 35mm - 70mm |
PLEASE NOTE
If you do not see what you are looking for, please contact your local service centre with your specific requirements.
S20910 (XM-19) Stainless Steel Related Specifications
| System / Standard | Country / Region | Grade / Designation |
| UNS | International | S20910 |
| AISI / ASTM | USA | XM-19 (Nitrogen-strengthened austenitic) |
| Trade name | USA | Nitronic 50 (ARMCO / AK Steel) |
| EN / W.Nr. | Europe | 1.3964 |
| EN Name | Europe | X2CrNiMnMoNNb21-16-5-3 |
| ASTM A240 | USA | S20910 (plate, sheet, strip) |
| ASTM A276 / A479 | USA | XM-19 / S20910 (bars, shapes) |
| ASTM A182 | USA | Grade FXM-19 (forgings, flanges, fittings) |
Properties
Chemical Composition
| Chemical Element | % Present |
| Carbon (C) | 0.00 - 0.03 |
| Chromium (Cr) | 20.50 - 23.50 |
| Nickel (Ni) | 11.50 - 13.50 |
| Manganese (Mn) | 4.00 - 6.00 |
| Phosphorous (P) | 0.00 - 0.04 |
| Sulphur (S) | 0.00 - 0.01 |
| Silicon (Si) | 0.20 - 0.60 |
| Molybdenum (Mo) | 1.50 - 3.00 |
| Nitrogen (N) | 0.20 - 0.40 |
| Vanadium (V) | 0.10 - 0.30 |
| Niobium (Columbium) (Nb) | 0.10 - 0.30 |
| Iron (Fe) | Balance |
Mechanical Properties
| Mechanical Property | Value |
| 0.2% Proof Stress | 380 N/mm2 |
| Tensile Strength | 690 N/mm2 |
| Hardness Brinell | 293 max HB |
General Physical Properties
| Physical Property | Value |
| Density | 7.8 g/cm³ |
| Thermal Conductivity | 13.3 W/m.K |
Applications of S20910 (XM-19) Stainless Steel
S20910 (XM-19), commonly known as Nitronic 50, is a high-strength austenitic stainless steel alloyed with nitrogen, manganese, chromium and molybdenum. It offers roughly twice the yield strength of 316/317, with excellent pitting and crevice corrosion resistance in seawater and is essentially non-magnetic in the annealed condition, making it popular in demanding marine and process environments.
1. Marine and Seawater Equipment
Seawater piping, manifolds and headers on ships and offshore platforms
Seawater-cooled heat exchangers, coolers and condensers
Shipboard and offshore structural hardware exposed to splash and tidal zones
Shafts, pins, clevises and hardware for marine cranes, winches and handling gear
Why XM-19?
High strength and very good resistance to pitting, crevice attack and chloride stress-corrosion cracking in seawater, with better performance than 316L and standard 300-series grades.
2. Pump, Valve and Shaft Components
Pump shafts for seawater, brine and chemical service
Valve stems, bodies, seats and internals in corrosive media
Mixer and agitator shafts in tanks containing chlorides or mildly acidic/alkaline solutions
Centrifugal pump bowls, casings and impellers where erosion–corrosion is an issue
Why XM-19?
Combines high strength, good galling resistance and superior corrosion resistance, allowing smaller shaft diameters and longer service life compared with 316/317.
3. Petrochemical, Chemical and Process Industry
Process piping, fittings and flanges in chloride-bearing chemical streams
Equipment in fertilizer, organic chemical and refinery units where 316/317 are marginal
Heat-exchanger tubes, tube sheets and shells handling seawater or aggressive cooling water
Components in mixed chloride + oxidizing environments where both strength and corrosion margin are needed
Why XM-19?
Provides a strong upgrade over 316L/317L in terms of strength and pitting resistance, without going to duplex or nickel alloys, and remains fully austenitic (non-magnetic).
4. Fasteners, Springs and Mechanical Parts
High-strength bolts, studs, nuts and washers for marine, offshore and chemical plants
Springs and spring washers requiring high strength and good corrosion resistance
Chains, shackles, couplings and rigging components operating in seawater or coastal atmospheres
Wear-resistant pins, bushings and guides in corrosive environments
Why XM-19?
High yield strength allows compact, high-load fasteners and mechanical parts, while corrosion resistance is significantly better than standard 300-series stainless fasteners.
5. Offshore, Subsea and Structural Uses
Structural members and brackets on offshore platforms and coastal installations
Components for subsea equipment where non-magnetic behaviour is beneficial (e.g. near instrumentation)
Tie-rods, hangers and tension members exposed to seawater or splash zones
Hardware in riser systems, clamps and supports where both load capacity and corrosion life matter
Why XM-19?
Non-magnetic austenitic structure, high strength and excellent seawater resistance make it attractive where duplex steels may not be desired (e.g. for magnetic or fabrication reasons).
6. Pulp & Paper, Food and General Industrial Applications
Pulp and paper equipment in chloride-containing bleaching and washing stages
Components in food and beverage plants where strong cleaners or brines are used
Industrial washers, cleaners, and equipment exposed to detergents and chlorinated waters
General plant items (tanks, frames, guides) that need more strength and corrosion resistance than 304/316
Why XM-19?
Good cleanability, stainless behaviour and corrosion resistance, combined with higher strength, reduce section thickness and extend service life in aggressive wash and process environments.
Summary
S20910 (XM-19 / Nitronic 50) stainless steel is widely used in marine and seawater systems, pump and valve components, petrochemical and process equipment, high-strength fasteners and springs, offshore/structural hardware, and aggressive industrial service, wherever designers need a non-magnetic, high-strength austenitic stainless steel with significantly better pitting, crevice and chloride stress-corrosion resistance than 316/317, without stepping up to duplex or nickel-based alloys.
Characteristics of S20910 (XM-19) Stainless Steel
S20910 (XM-19), commonly known as Nitronic 50, is a high-strength austenitic stainless steel with nitrogen strengthening, excellent seawater corrosion resistance and essentially non-magnetic behaviour in the annealed condition, making it a special variant within the 300-series family.
1. High-Strength Austenitic Stainless Steel
Fully austenitic stainless steel, not duplex or martensitic.
Nitrogen and manganese additions give roughly twice the yield strength of 316/317 in the annealed state.
Allows use of smaller cross-sections and lighter components compared with standard 300-series grades while carrying the same load.
2. Enhanced Corrosion Resistance (Especially in Seawater)
Corrosion resistance is better than 316/317 in many chloride-bearing environments.
Very good pitting and crevice corrosion resistance in natural and brackish seawater.
Suitable for marine, offshore and cooling-water systems where 316 can pit or crevice-corrode prematurely.
3. Non-Magnetic (or Very Low Magnetic Permeability)
Essentially non-magnetic in the annealed condition, even at high strength levels.
Remains very low magnetic permeability compared with cold-worked 304/316, even after some forming or light cold work.
Attractive for equipment near magnetic instruments, sensors and actuators, and for marine applications where magnetic signature is important.
4. Good Toughness and Ductility Over a Wide Temperature Range
Maintains good impact toughness from cryogenic temperatures up to typical service temperatures.
Ductility is good despite higher strength, so it can withstand shock, vibration and dynamic loading in shafts, fasteners and structural parts.
More resistant to brittle fracture than high-strength martensitic or duplex grades in many conditions.
5. Galling, Wear and Erosion–Corrosion Resistance
Better galling resistance than many standard austenitic grades, useful for:
Fasteners
Sliding and bearing components
Pump and valve internals
High strength plus good corrosion resistance gives good erosion–corrosion performance in high-velocity seawater and process fluids.
6. Work-Hardening, Forming and Machining Behaviour
As an austenitic steel, XM-19 work hardens during cold deformation.
Formability is generally good, but forming loads are higher than for 304/316 because of its higher yield strength.
Machinability is more demanding than 316, requiring:
Rigid setups
Sharp carbide tooling
Correct speeds/feeds and abundant coolant
to manage work hardening and tough chip formation.
7. Weldability and Fabrication Considerations
Generally weldable with appropriate austenitic or matching fillers.
Heat input and interpass temperature should be controlled to avoid excessive grain growth and to maintain corrosion resistance.
Welds and HAZ should be properly cleaned and, where needed, pickled/passivated to restore full pitting resistance in seawater or chloride service.
Summary
S20910 (XM-19) stainless steel is a high-strength, nitrogen-strengthened austenitic stainless with yield strength about twice that of 316/317, excellent pitting and crevice resistance in seawater, very low magnetic permeability, good toughness, improved galling resistance and reasonable weldability and formability, making it a go-to material for demanding marine, pump/valve, fastener and process applications where standard 300-series grades are not strong or corrosion-resistant enough.
Additional Information
Weldability
Weldability of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is generally weldable, but as a high-strength, nitrogen-alloyed austenitic stainless steel it needs good procedure control to avoid hot cracking, loss of corrosion resistance and reduced strength in the weld and HAZ.
1. General Weldability Characteristics
Austenitic structure → no preheat normally required and good basic weldability.
Higher strength and nitrogen content make it less forgiving than 304/316 if procedures are poor.
Main risks with bad practice:
Hot cracking (solidification cracking)
Loss of nitrogen and chromium at the weld, reducing pitting resistance
Excessive distortion due to high heat input
2. Suitable Welding Processes
Commonly used processes:
GTAW (TIG) – preferred for root passes and thin material, with excellent control and shielding.
GMAW (MIG/MAG) – for production welding of pipe, tube and plate.
SMAW (MMA) – for site work, repairs and thicker sections with appropriate electrodes.
FCAW – possible with suitable stainless flux-cored wires in shop fabrication.
Autogenous (no-filler) welding is only recommended for very thin sections; for most joints, filler is needed to control composition and cracking resistance.
3. Filler Metal Selection
Use matching or slightly over-alloyed austenitic stainless fillers recommended for XM-19 service.
Objectives for filler metal:
Maintain strength appropriate to the design (often close to or above 316L levels).
Provide pitting and crevice corrosion resistance at least equal to the base metal in seawater / chloride service.
Offer good crack resistance and weldability.
In particularly aggressive environments, more highly alloyed austenitic fillers may be used to give the weld metal extra corrosion margin.
4. Heat Input, Interpass Temperature and Cooling
Use moderate heat input – not too low, not excessive:
Too low → risk of lack of fusion or poor bead shape.
Too high → wider HAZ, higher distortion and more nitrogen/chromium loss at the surface.
Keep interpass temperature controlled (moderate, not excessively hot) to limit grain growth and distortion.
Allow welds to cool in still air; no rapid quenching is needed or desirable.
5. Weld Microstructure, Properties and Corrosion Behaviour
Proper procedures produce welds with:
Austenitic weld metal and HAZ with adequate toughness.
High strength, often comparable to or slightly below base-metal yield strength.
Corrosion resistance suitable for marine and chemical service when surfaces are cleaned and finished correctly.
Poor practice (high heat input, poor shielding, incorrect filler, contaminated joint surfaces) can:
Reduce pitting and crevice resistance near welds.
Increase risk of hot cracking.
Leave welds and HAZ more susceptible to corrosion in seawater or aggressive media.
6. Shielding, Root Quality and Post-Weld Cleaning
Shielding gas quality is important:
Use appropriate inert (or inert-rich) shielding to prevent oxidation and nitrogen loss.
For pipe and tank roots, use back purging to keep the root oxide-free and corrosion-resistant.
After welding:
Remove slag, spatter, heat tint and oxidation by grinding, brushing or blasting.
Use pickling and/or passivation where required to restore a clean, chromium-rich passive film.
Smooth, well-finished welds perform much better in seawater and chloride service than rough or heat-tinted ones.
7. Optional Post-Weld Heat Treatment
For most fabrication, XM-19 is used in the as-welded condition with no post-weld heat treatment.
For very heavily restrained or highly stressed components in severe environments, a solution anneal + rapid cool after welding may be specified to:
Restore optimum toughness and corrosion resistance
Homogenise microstructure in the weld/HAZ
Whether this is needed depends on code, application and section size.
Summary
S20910 (XM-19) stainless steel has good weldability for a high-strength austenitic grade, provided you use suitable austenitic fillers, moderate heat input and interpass temperatures, good shielding and back purging, and thorough post-weld cleaning and passivation; with these measures, welds retain the high strength and excellent seawater corrosion resistance that make XM-19 attractive for marine, pump/valve and process applications.
Fabrication
Fabrication of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is a high-strength austenitic stainless steel. It fabricates broadly like 316/317, but with higher forming loads, tougher machining and a bit more care in welding because of its strength and nitrogen content.
1. General Fabrication Approach
Usually supplied solution-annealed and pickled (plate, bar, pipe, forgings).
Most forming, machining and welding should be done in this condition.
Compared with 304/316, expect:
Higher forming and cutting forces
Somewhat tougher machining
Slightly tighter weld procedure window
2. Forming and Cold Working
Cold formability is good, but yield strength is much higher than 316 → more press/roll capacity needed.
Good practice:
Use slightly larger bend radii than with 304/316 to avoid cracking on thicker sections.
Form in gradual steps with smooth tools and good lubrication to reduce galling.
Allow for more spring-back than standard 300-series grades.
As an austenitic alloy, XM-19 work hardens, so very heavy cold reduction can significantly increase hardness and forming difficulty; very severe cold work may be followed by solution annealing if top toughness and corrosion resistance are critical.
3. Hot Working and Heat Treatment in the Route
Hot working (forging, hot bending) follows typical austenitic stainless practice:
Heat thoroughly and work in the recommended high-temperature range.
Use substantial reductions, not light tapping, to refine structure.
After significant hot work, a solution anneal + rapid cooling is normally used to:
Restore a uniform austenitic structure
Recover toughness and corrosion resistance
Final components for demanding service are typically used in the solution-annealed condition, then welded and finished.
4. Machining
Machinability is more demanding than 316 due to higher strength and work hardening.
Recommendations:
Use carbide tooling and rigid setups.
Run moderate speeds with enough feed and depth to cut beneath any work-hardened layer.
Apply plenty of coolant and chip-breaking geometries (XM-19 forms tough chips).
A sensible route is:
Rough machine in the solution-annealed condition → weld/form → finish machine / grind to final size and surface finish.
5. Welding within Fabrication
XM-19 is weldable, but needs good procedure control (see Weldability section):
Use suitable austenitic or matching fillers with adequate corrosion resistance.
Keep heat input moderate and control interpass temperature.
Use good shielding and back purging on pipe/tank roots.
Normally no PWHT is required; components are used in the as-welded, solution-annealed condition, with quality controlled by procedure rather than tempering.
6. Surface Cleaning, Pickling and Passivation
To achieve full corrosion performance (especially in seawater):
Remove slag, spatter, heat tint and oxide from welds and HAZ.
Use appropriate pickling and/or passivation (or high-quality mechanical cleaning) to restore a clean, chromium-rich passive film.
Aim for smooth, defect-free finishes on wetted or crevice-prone surfaces.
7. Distortion and Dimensional Control
Austenitic structure gives relatively high thermal expansion, so welding can still cause distortion.
Higher strength means:
Stronger residual stresses where heavily welded or cold worked.
Practical measures:
Use balanced welding sequences and proper fixturing.
Avoid excessive local cold straightening in critical areas.
For precision parts, plan:
Form → Weld → Light straighten (if needed) → Finish machine / grind.
Summary
S20910 (XM-19) fabricates much like a “stronger, tougher 316”: it can be cold and hot formed, machined and welded with standard stainless shop practices, provided you allow for higher forming/machining loads, use suitable austenitic fillers and controlled welding procedures, and always finish with thorough cleaning and passivation to preserve its high-strength, seawater-resistant performance.
Hot Working
Hot Working of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is an austenitic stainless steel that can be hot worked using procedures similar to 316/317, but its higher strength and nitrogen content mean temperature control and subsequent solution annealing are very important.
1. Recommended Hot Working Temperature Range
XM-19 is typically hot worked in a high-temperature austenitic range (conceptually in the same band as other high-alloy austenitic stainless steels).
Practical guidelines:
Start hot working at a high enough temperature to ensure good plasticity.
Do not continue working when the material has cooled too far (toward the lower austenitic limit), as ductility drops and cracking risk increases.
Exact start/finish temperatures and soaking times should always follow the mill datasheet for the specific product (plate, bar, forging stock).
2. Heating and Forging Practice
Heat the workpiece uniformly through the full section before applying heavy reductions.
Use substantial reductions per pass rather than light tapping to refine the grain structure.
Reheat as needed when temperature falls toward the lower working limit; do not keep working it “too cold”.
Avoid excessive or prolonged overheating at the top of the range to limit:
Grain growth
Scale formation
Unnecessary surface damage
3. Cooling and Subsequent Solution Annealing
After hot working, allow parts to cool in still air down to a safe handling temperature.
For demanding applications (marine, chemical, high-load service), a full solution anneal + rapid cooling after hot working is strongly recommended to:
Restore a homogeneous austenitic microstructure
Recover toughness and corrosion resistance
Remove any adverse effects of non-uniform deformation or partial phase changes
Typical practice:
Solution anneal in the appropriate high-temperature range specified for XM-19.
Hold long enough for full through-heating.
Rapidly cool (usually water quench or very fast air for thin sections).
4. Surface Scale, Machining Allowance and Cleaning
At hot-working temperatures, XM-19 will develop oxide scale and slight surface roughness.
Leave sufficient machining or grinding allowance to remove:
Scale
Any decarburised or mechanically damaged surface layer
After hot working and solution annealing, clean surfaces by:
Mechanical methods (grinding, brushing, blasting) and/or
Pickling and passivation
to restore a clean, chromium-rich passive film for maximum corrosion resistance (especially in seawater).
5. Effect on Microstructure and Properties
Correct hot working followed by solution annealing yields:
A fine-grained, uniform austenitic structure.
High yield strength (for an austenitic grade) with good toughness.
Reliable pitting and crevice corrosion resistance in marine and process environments.
Poor practice (working too cold, severe local deformation without subsequent solution anneal) can result in:
Localised hard, heavily worked regions
Reduced toughness and more difficult machining
Non-uniform properties through the section
6. Design, Distortion and Cracking Control
Design preforms and forgings with:
Smooth transitions and generous radii
Avoidance of sharp corners and abrupt thickness changes that concentrate stress during forging and cooling
For long shafts, rings or complex shapes:
Use proper support and handling during hot work and cooling to minimise bending and distortion.
Inspect forgings for surface cracks, laps and folds before investing in final heat treatment and machining.
Summary
Hot working of S20910 (XM-19) should be carried out in an appropriate high-temperature austenitic range with uniform heating and substantial reductions, followed by air cooling and—where high performance is required—a solution anneal with rapid cooling and proper cleaning; this route preserves a fine austenitic structure, high strength, good toughness and the excellent seawater and process-corrosion resistance that XM-19 is chosen for.
Heat Resistance
Heat Resistance of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is a high-strength austenitic stainless steel intended mainly for ambient to moderately elevated temperatures in corrosive, especially seawater, environments. It is not a dedicated high-temperature / creep-resistant alloy.
1. Recommended Service Temperature Range
Typically used from sub-zero temperatures up to about 250–300°C in continuous service.
Within this range it maintains:
High yield strength (well above 316/317)
Good toughness and ductility
Very good pitting and crevice corrosion resistance in seawater and process waters
For long-term service significantly above this range, both mechanical properties and corrosion behaviour may degrade and other heat-resistant alloys are usually preferred.
2. Strength and Toughness at Elevated Temperatures
As temperature rises:
Yield and tensile strength decrease, as with all steels, but XM-19 still stays stronger than 316/317 at the same temperature.
Fatigue strength also drops with increasing temperature and cyclic loading.
XM-19 retains good impact toughness over its normal working range, making it suitable for dynamically loaded shafts, fasteners and structural parts in warm environments.
3. Corrosion Behaviour in Hot Seawater and Process Fluids
XM-19 is designed for hot, chloride-containing environments such as seawater and aggressive cooling water:
Better pitting and crevice corrosion resistance than 316/317, even at elevated temperatures.
Good resistance to chloride stress-corrosion cracking compared with standard austenitic grades, though not as SCC-resistant as duplex/super duplex steels.
In hot chemical and process streams, it offers a useful combination of corrosion margin + strength, as long as temperature and chemistry stay within typical XM-19 limits.
4. Microstructural Stability and Sensitization
As an austenitic grade it does not form sigma phase the way duplex/super duplex steels do, but it can still suffer:
Sensitization (chromium carbide formation at grain boundaries) if held for long times in the traditional “sensitization” band; this can reduce resistance to intergranular corrosion in some media.
Correct solution annealing and reasonable fabrication heat cycles minimise these effects and keep the microstructure stable for normal service temperatures.
5. Design Considerations for Elevated-Temperature Service
Treat XM-19 as a high-strength, corrosion-resistant austenitic stainless for moderate temperatures, not as a primary high-temperature or creep-resistant alloy.
In design you should:
Use temperature-dependent allowable stresses that reflect strength loss with temperature.
Avoid configurations that create local hot spots or long-term exposure near sensitization ranges if intergranular attack is a concern.
Combine good material choice with proper surface finish, welding procedures and post-weld cleaning for hot seawater and process service.
Summary
S20910 (XM-19) stainless steel offers reliable heat resistance and high strength in corrosive, especially seawater, environments up to roughly 250–300°C, retaining good toughness and superior pitting/crevice resistance compared with 316/317; however, it is not intended for long-term high-temperature or creep-critical service, where dedicated heat-resistant stainless or nickel alloys are more appropriate.
Machinability
Machinability of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is a high-strength austenitic stainless steel with noticeably more difficult machinability than 304/316. It can still be machined very successfully, but only with rigid setups, correct tooling and well-chosen cutting data.
1. General Machining Behaviour
Higher yield strength than 316/317 → higher cutting forces and tool loads.
Strong work hardening if feeds are too low or tools rub instead of cutting.
Produces tough, stringy chips unless chip-breaking is well controlled.
Overall machinability: significantly worse than 304/316, but manageable with a good machining strategy.
2. Preferred Condition for Machining
Best machined in the solution-annealed, pickled condition as supplied.
Avoid heavy cold work on surfaces immediately before finish machining, as it:
Increases surface hardness
Reduces tool life
Makes dimensional control more difficult
For precision parts, a good route is:
Rough machine → weld/form (if needed) → light straighten → finish machine / grind.
3. Tooling and Cutting Parameters
Use carbide tooling designed for stainless / austenitic materials.
Key setup points:
Rigid machines, fixturing and toolholders to minimise chatter.
Positive or mildly positive rake inserts to reduce cutting forces.
Cutting data (conceptually):
Moderate speeds – lower than for 304/316.
Adequate feed and depth of cut so the tool cuts beneath any work-hardened skin.
Avoid very light “polishing” cuts that just rub and harden the surface.
4. Coolant and Chip Control
XM-19 generates substantial heat → coolant is essential:
Use abundant, well-directed cutting fluid/emulsion at the cutting zone.
For deep holes, ensure coolant reaches the drill tip and flushes chips.
Chips tend to be long and tough:
Use inserts with effective chip breaker geometries.
Adjust feed and depth to encourage chip breaking and avoid bird-nesting.
Good chip control improves tool life, surface finish and CNC reliability.
5. Drilling, Tapping and Threading
Drilling
Use carbide or high-quality cobalt HSS drills.
Apply steady feed; avoid dwelling at the bottom of the hole.
Use peck cycles for deep holes to clear chips and limit work hardening.
Tapping / Threading
Use strong, high-performance taps with plenty of lubricant and modest speed.
Expect higher torque than with 316.
For critical or larger threads, thread milling is often safer and gives better control over fit and size.
6. Surface Finish and Dimensional Accuracy
With proper tooling and parameters, XM-19 can achieve excellent turned, milled and ground finishes for seal and bearing surfaces.
For accurate dimensions:
Use balanced machining (symmetrical material removal) where possible.
Avoid local overheating from aggressive grinding or very heavy cuts.
On slender shafts and long parts, use multiple controlled passes instead of one very heavy cut to maintain straightness.
Summary
S20910 (XM-19) stainless steel has demanding but manageable machinability: treat it as a stronger, more work-hardening version of 316—use rigid setups, stainless-rated carbide tools, moderate speeds with solid feeds, abundant coolant and good chip-breaking strategies, plus a sensible roughing–finishing route, to achieve good tool life, accurate dimensions and high-quality surfaces on marine, pump/valve and structural components.
Corrosion Resistance
Corrosion Resistance of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is a high-strength austenitic stainless steel with significantly better corrosion resistance than 316/317, especially in seawater and chloride-bearing environments, while remaining essentially non-magnetic in the annealed condition.
1. General Corrosion Behaviour
Excellent resistance to uniform (general) corrosion in many industrial, marine and chemical environments.
Clearly superior to 304/316 in most chloride-containing waters and many process streams.
Well suited to long-term service in seawater, brackish water, cooling water and many chemical plant environments.
2. Pitting and Crevice Corrosion in Chloride Media
Alloyed with Cr, Mo, N and Mn to provide enhanced pitting and crevice resistance over 316/317.
Performs very well in:
Natural and warm seawater
Brackish and chlorinated cooling waters
Many chloride-bearing process fluids
As with all stainless steels, tight crevices, deposits and stagnant zones can still become attack sites, so good design and clean surfaces remain important.
3. Chloride Stress-Corrosion Cracking (SCC)
XM-19 shows better SCC resistance than standard austenitics such as 304/316, especially in warm chlorides.
However, it is still an austenitic grade and not as SCC-resistant as duplex/super duplex stainless steels in the most severe hot-chloride conditions.
For many marine and cooling-water applications, it offers a good balance of strength + SCC resistance without moving to duplex metallurgy.
4. Behaviour in Chemical and Process Environments
Good performance in many mild to moderately aggressive acids, alkalis and salt solutions, especially where chlorides are present.
Frequently used where 316/317 are at the limit but full duplex or nickel alloys are not yet required.
For very strong mineral acids, highly reducing media or extreme temperature–concentration combinations, more highly alloyed stainless or nickel alloys may still be necessary.
5. Intergranular Corrosion and Welded Joints
With proper solution annealing and reasonable control of thermal exposure, XM-19 has good resistance to intergranular corrosion.
Poor practice (long holds in sensitization temperature ranges, inadequate solution anneal, or highly overheated welds) can:
Cause chromium carbide precipitation at grain boundaries.
Reduce resistance to intergranular attack in certain media.
Correct welding, followed by good cleaning and, where needed, pickling/passivation, helps maintain weld corrosion resistance close to the base metal.
6. Influence of Surface Finish, Cleaning and Design
As with all stainless steels, corrosion resistance depends strongly on surface condition:
Smooth, clean, ground or brushed finishes resist pitting and fouling better than rough or damaged surfaces.
Weld scale, heat tint and contamination should be removed by mechanical cleaning and/or pickling plus passivation.
Good design practice includes:
Minimising crevices, dead legs and dirt traps.
Providing drainage and access for inspection and cleaning.
Avoiding unfavourable galvanic couples with more active alloys in wet service.
Summary
S20910 (XM-19) stainless steel offers markedly better pitting, crevice and general corrosion resistance than 316/317 in seawater and chloride-bearing environments, with improved SCC resistance for austenitic steel, provided it is correctly solution-annealed, welded with suitable procedures, and finished with clean, well-designed surfaces—making it a strong choice for demanding marine, cooling-water, pump/valve and process applications where standard 300-series grades are not durable enough.
Heat Treatment
Heat Treatment of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is a high-strength austenitic stainless steel. It is not hardened by quenching like martensitic steels; instead, its strength comes from composition (N, Mn, Mo) and any cold work, with heat treatment mainly used to obtain or restore the correct austenitic structure and corrosion resistance.
1. General Heat-Treatment Behaviour
Fully austenitic in the solution-annealed condition.
Cannot be precipitation-hardened like 17-4PH / 15-5PH, and does not form martensite on quenching.
Main functions of heat treatment are to:
Restore a uniform austenitic microstructure after hot or heavy cold work.
Recover toughness and corrosion resistance.
Reduce or redistribute residual stresses where necessary.
2. Solution Annealing (Primary Heat Treatment)
Purpose
Dissolve carbides and any unwanted phases.
Re-homogenise and refine the austenitic structure.
Recover the best pitting, crevice and general corrosion resistance, especially for seawater service.
Typical practice (conceptually)
Heat into a high-temperature solution-annealing range specified for XM-19.
Hold long enough for full through-heating of the section.
Rapidly cool – usually water quench (or very fast air for thin products) – to freeze in a clean, single-phase austenitic structure.
After proper solution annealing and rapid cooling, XM-19 has:
High yield strength for an austenitic stainless steel.
Good toughness over a wide temperature range.
Maximum available corrosion resistance for this grade.
3. Stress Relief and Post-Fabrication Heat Treatment
In many applications, components are used in the as-welded, solution-annealed condition without extra stress relief.
Austenitic steels like XM-19 do not require carbon-steel-style stress-relief cycles for most service, and excessive intermediate-temperature exposure can:
Promote sensitization (chromium carbide at grain boundaries).
Slightly reduce resistance to intergranular corrosion in some media.
Where a code or design demands stress reduction:
Any stress-relief treatment must follow XM-19-specific guidance from the mill or standard.
Temperature and time should be chosen to minimise sensitization while achieving the required stress reduction.
4. Interaction with Cold Work and Mechanical Properties
XM-19 can be strengthened by cold working (drawing, rolling, forming):
Cold work increases yield and tensile strength.
It also raises hardness and residual stress.
A subsequent solution anneal will:
Remove the extra strength gained from heavy cold work.
Restore maximum toughness and corrosion resistance.
For critical seawater or fatigue applications, designers must decide whether to:
Use cold-worked, higher-strength material with more residual stress, or
Use solution-annealed material with slightly lower strength but maximum corrosion resistance and toughness.
5. Effect of Improper Heat Exposure
Long or repeated exposure in the traditional sensitization temperature range can:
Lead to chromium carbide precipitation at grain boundaries.
Reduce resistance to intergranular corrosion in certain environments.
Overheating or prolonged holds outside the recommended bands are unnecessary and can:
Cause grain growth and minor loss of toughness.
Degrade surface condition, requiring more extensive finishing to regain corrosion resistance.
6. Practical Heat-Treatment Route in Fabrication
Typical route for demanding marine / process parts:
Supply from mill in solution-annealed and pickled condition.
Hot work / heavy forming, if needed → followed by solution anneal + rapid cool.
Cold forming, machining and welding using good austenitic procedures.
Normally no PWHT after welding, just:
Correct welding parameters and filler selection.
Thorough post-weld cleaning, pickling and passivation to restore a clean passive surface.
Summary
For S20910 (XM-19) stainless steel, heat treatment is centred on high-temperature solution annealing followed by rapid cooling, used to obtain or restore a clean, homogeneous austenitic structure with high toughness and excellent corrosion resistance; it is not quench-hardened like martensitic steels, and any stress-relief or additional heat treatment must be carefully controlled to avoid sensitization and preserve its seawater-resistant performance.
Cold Working
Cold Working of S20910 (XM-19) Stainless Steel
S20910 (XM-19 / Nitronic 50) is a high-strength austenitic stainless steel with good ductility but strong work hardening. It can be cold worked successfully, but requires higher forming loads and good control of strain levels, tooling and lubrication.
1. General Cold Workability
Fully austenitic → good ductility, suitable for bending, rolling, drawing and shaping.
Yield strength is much higher than 304/316 → significantly higher forming forces are needed.
Strong work hardening:
Strength and hardness rise quickly with strain.
Residual stresses can become high in heavily worked areas.
2. Bending, Rolling and Forming Practice
Suitable for:
Rolling of plate and sections
Forming shells, cones, flanges and general profiles
Moderate deep drawing or stretch forming with correct tooling
Good practice:
Use slightly larger minimum bend radii than for 304/316, especially on thicker sections.
Form in gradual, controlled steps rather than one very heavy hit.
Use smooth, polished tools and good lubrication to reduce friction and galling.
Allow for more spring-back than standard 300-series grades.
3. Work Hardening and Residual Stresses
XM-19 work hardens strongly under cold deformation:
Increases local strength and hardness.
Reduces ductility in heavily strained zones.
Introduces residual stresses, affecting:
Distortion during/after welding
Fatigue and corrosion-fatigue behaviour
Very heavy local cold work can:
Make subsequent machining noticeably more difficult.
Increase risk of distortion and stress-related issues in service.
4. Heavy Cold Work and Solution Annealing
For light to moderate cold work (typical bends, rolling, general forming):
Parts are often used as cold formed, especially where extra strength is beneficial.
For severe cold work, such as:
Tight-radius bends on thick plate
Large-area deep drawing or heavy cold reduction
Highly strained regions in critical components
a solution anneal + rapid cooling is recommended to:Restore a uniform austenitic microstructure
Recover maximum toughness and corrosion resistance
Reduce residual stress and excessive hardness
5. Interaction with Welding and Machining
Cold-worked areas:
Are more prone to distortion when welded due to stored strain energy.
May be harder to machine because of increased surface hardness.
For precision or critical parts, a good overall route is:
Form → Weld (with suitable austenitic procedures) → Light straighten if needed → Finish machine / grind.
6. Design Recommendations for Cold-Worked XM-19 Components
Assume high forming forces and size presses/rolls accordingly.
Avoid:
Very sharp corners or extremely tight radii in highly stressed / corrosive regions.
Severe local thinning (necking) where fatigue or corrosion is critical.
For demanding marine or process-service parts:
Keep cold strain moderate and well distributed.
Use solution annealing after extreme forming if top-level toughness and corrosion resistance are required.
Summary
S20910 (XM-19) stainless steel has good cold formability but strong work hardening: it can be bent, rolled and formed effectively when you allow for higher forming loads, use generous radii, smooth tools and good lubrication, control strain levels and spring-back, and apply solution annealing after very heavy cold work where maximum toughness, corrosion resistance and dimensional stability are required for critical service.
Precipitation Hardening Steels
Precipitation Hardening Steels
Precipitation hardening (PH) steels are alloys that achieve very high strength and hardness through a two-step heat treatment: solution treatment followed by aging. Fine, controlled precipitates form in a relatively tough matrix (often martensitic or austenitic), giving much higher strength than conventional quenched-and-tempered steels at similar or better levels of toughness and corrosion resistance.
1. Basic Principle and Strengthening Mechanism
Steels are first solution treated at high temperature to dissolve alloying elements and create a uniform microstructure.
After cooling, they are aged at a moderate temperature, where:
Fine, nanoscale precipitates (Cu-rich, Ni-Al, Ni-Ti, etc.) form.
These particles block dislocation motion, greatly increasing yield strength and hardness.
The matrix (often martensitic or austenitic) provides:
Reasonable toughness and ductility
A base level of corrosion resistance, especially in stainless PH grades
2. Main Groups of Precipitation Hardening Steels
Martensitic PH Stainless Steels
Examples: 17-4PH (630), 15-5PH, 13-8PH, 15-7PH.
High Cr for stainless behaviour, Cu and other elements for precipitation hardening.
Used widely in aerospace, energy, marine, pump/valve and structural components.
Semi-Austenitic and Austenitic PH Stainless Steels
Some grades are austenitic as-supplied and transform/age during heat treatment.
Offer good toughness and corrosion resistance with medium–high strength.
Maraging and High-Alloy PH Steels (Non-Stainless)
Very low carbon, Ni-rich or Co-rich alloys strengthened by intermetallic precipitates.
Ultra-high strength with good toughness, used in tooling, aerospace and specialty mechanical parts.
3. Typical Heat-Treatment Route
Solution Treatment (Condition A / Solution Annealed)
High-temperature treatment dissolves alloying elements and sets the base microstructure.
Followed by air cooling or quenching depending on the grade.
Aging (H-Conditions, e.g. H900, H1025, H1150)
Reheat to a moderate temperature for a set time, then cool.
Lower aging temperature → higher strength, higher hardness, lower toughness.
Higher aging temperature → lower strength, higher toughness, better stress-corrosion performance.
4. Advantages Over Conventional Quenched-and-Tempered Steels
Very high strength with a relatively simple heat-treatment cycle.
Good dimensional stability during aging (little distortion compared with quenching).
Stainless PH grades combine:
High mechanical strength
Stainless corrosion resistance
Reduced need for coatings or heavy corrosion protection systems.
Aging temperature can be chosen to tailor properties for different components (e.g. H900 vs H1150).
5. Key Limitations and Design Considerations
Strength and toughness are sensitive to the exact aging condition; wrong temperature or time can:
Undershoot strength
Over-age and reduce toughness/corrosion resistance
Some PH steels are not as corrosion-resistant as fully austenitic stainless grades (e.g. 316) in the most aggressive environments.
Welds usually need:
Qualified procedures
Attention to heat input and possible re-aging after welding for best properties.
Summary
Precipitation hardening steels are a family of alloys—especially martensitic PH stainless steels like 17-4PH and 15-5PH—that achieve high to ultra-high strength through solution treatment plus aging, using fine precipitates to strengthen a relatively tough matrix; by selecting suitable aging conditions, engineers can tune the balance of strength, toughness and corrosion resistance to meet demanding aerospace, marine, energy and mechanical application requirements.
