Non-magnetizable steel · SEW 390 family
X40MnCrN19Material number 1.3813 — open-die forgings, seamless rolled rings, flanges, bars and shafts
X40MnCrN19, material number 1.3813, is a non-magnetizable steel alloyed with 17 to 19 % manganese, 3 to 5 % chromium and 0.08 to 0.12 % nitrogen. It is rust and acid resistant, and is most often supplied hot-cold-worked, where it reaches 830 to 1030 N/mm² tensile strength and at least 390 N/mm² yield strength at room temperature.
The grade earns its place where a loaded component must not become magnetic. Manganese and nitrogen hold the austenite stable, so permeability stays near 1.01 G/Oe even after hot work, instead of climbing as it would in a conventional austenitic stainless steel.
- Designation
- X40MnCrN19
- Material no.
- 1.3813
- Character
- Non-magnetizable, rust and acid resistant
- Mn / Cr / N
- 17–19 % / 3–5 % / 0.08–0.12 %
- Rm
- 830–1030 N/mm² hot-cold-worked
- Rp0.2
- min. 390 N/mm² hot-cold-worked
- Permeability
- max. 1.01 G/Oe hot worked
- Melt route
- EF + LF + VOD, ESR where specified
- Certification
- EN 10204 3.1, 3.2 on request
Chemical composition
Nitrogen is the element that does the work here. At 0.08 to 0.12 % it strengthens the austenite in solid solution and, with 17 to 19 % manganese behind it, keeps the structure austenitic down to room temperature without the nickel that a 300-series stainless steel would need.
| C | Si | Mn | P | S | Cr | N |
|---|---|---|---|---|---|---|
| 0.30–0.50 | max. 0.80 | 17.00–19.00 | max. 0.100 | max. 0.030 | 3.00–5.00 | 0.080–0.120 |
Manganese, chromium and nitrogen are quoted identically across the datasheets consulted. Carbon is not: Basedo Steel gives 0.30 to 0.50 %, while Longhai Steel gives 0.03 to 0.50 % and silicon as max. 0.87 %. The tighter range is shown above. If your drawing or approval calls up a specific range, state it on the enquiry and the heat will be aimed at that window rather than at the broader one.
Mechanical properties
Delivery condition changes yield strength by more than 60 %, from 295 N/mm² solution annealed to 490 N/mm² cold-worked. This grade work hardens strongly and is not quench-and-temper hardenable, so the condition stated on the order is what sets the properties on the certificate.
| Condition | Rp0.2 | Rm | Elongation A | Impact energy |
|---|---|---|---|---|
| Quenched / solution annealed | min. 295 N/mm² | 740–930 N/mm² | min. 45 % | min. 124 J |
| Cold-worked | min. 490 N/mm² | 830–1030 N/mm² | min. 35 % | min. 103 J |
| Hot-cold-worked | min. 390 N/mm² | 830–1030 N/mm² | min. 40 % | min. 124 J |
Hot-cold-working is the usual compromise: it buys roughly 100 N/mm² of yield over the annealed condition while keeping elongation at 40 % and impact energy at the full 124 J, where fully cold-worked material gives up both. For a part that will be machined heavily after delivery, the annealed condition cuts tool wear and distortion, at the cost of strength.
Physical and magnetic properties
Permeability is the property most buyers are actually specifying against, so it is worth reading the three figures separately. Cold work raises permeability in this grade, as it does in any austenitic steel, but only from 1.01 to 1.03 G/Oe.
| Property | Value | Condition |
|---|---|---|
| Magnetic permeability | max. 1.01 G/Oe | Quenched |
| Magnetic permeability | max. 1.01 G/Oe | Hot worked |
| Magnetic permeability | max. 1.03 G/Oe | Cold worked |
| Modulus of elasticity | approx. 191 000 MPa | 20 °C |
| Density | approx. 7.9 kg/dm³ | — |
| Electrical resistivity | approx. 0.70 Ω·mm²/m | 20 °C |
| Mean thermal expansion | 17.1 × 10⁻⁶ K⁻¹ | to 200 °C |
| Mean thermal expansion | 17.9 × 10⁻⁶ K⁻¹ | to 300 °C |
| Mean thermal expansion | 18.7 × 10⁻⁶ K⁻¹ | to 400 °C |
Expansion is high, close to 18 × 10⁻⁶ K⁻¹ by 400 °C. Where 1.3813 is bolted to a ferritic or martensitic component that expands at roughly 12, differential growth across a heated joint needs checking at the design stage rather than at assembly.
Forging and heat treatment
| Operation | Temperature | Cooling |
|---|---|---|
| Hot forming / open-die forging | approx. 850–1050 °C | — |
| Solution annealing | approx. 1000–1050 °C | Water or air |
The forging window is narrow by carbon steel standards, and high manganese makes the steel stiff under the press, so reheats are more frequent than a buyer used to 42CrMo4 might expect. Finishing too cold risks edge cracking; finishing too hot coarsens the grain. On a 6,300 t press with car-bottom furnaces alongside, the practical answer is more passes and a disciplined reheat schedule, which is one reason non-magnetic grades carry a higher forging cost per tonne than alloy steel.
Nitrogen is also a loss risk at temperature. Melting through the electric arc furnace with vacuum oxygen decarburisation, or through electroslag remelting under protective atmosphere where the order calls for it, keeps nitrogen inside the 0.08 to 0.12 % band instead of chasing it back after the fact.
Designations and neighbouring grades
| Designation | Remark |
|---|---|
| X40MnCrN19 | DIN / EN name |
| 1.3813 | European material number |
| X40MnCrN18 | Closely related designation |
| SEW 390 | Steel-iron material sheet covering non-magnetizable steels |
| 1.3817 / 1.3952 / 1.3964 | Other non-magnetizable grades listed alongside 1.3813 |
X40MnCrN19 sits at 18Mn–4Cr. Generator retaining rings in service today are forged from the 18Mn–18Cr nitrogen-strengthened family, which the power industry moved to because the earlier lower-chromium rings proved vulnerable to stress corrosion cracking in moist environments, with the higher-chromium alloy offering high strength together with better cracking resistance.
If the enquiry is for a retaining ring, say so and the 18Mn–18Cr grade will be quoted instead. Supplying 1.3813 against a retaining ring drawing because the words "non-magnetic ring" appear on it is a mistake worth avoiding at the enquiry stage rather than at commissioning.
Where the grade is used
Published descriptions of 1.3813 are consistent and narrow: an amagnetic steel for mechanically and thermally stressed components. The documented application areas are these.
- Mechanically and thermally stressed non-magnetic components in general machine building, which is the description the material databases use for the grade.
- Connecting parts, bolts and nuts that must stay amagnetic in assembly, with high-voltage electrical apparatus named as a typical application for non-magnetizable steels of this family.
- Aerospace components, where 1.3813 appears listed as a non-magnetizable special steel.
- Instrument, sensor and measuring equipment housings where stray permeability would disturb the measurement.
With 3 to 5 % chromium and no molybdenum, 1.3813 is not a corrosion alloy. For sour service, oxidising acids, chlorides or seawater, look instead at A182-F55 super duplex, 904L or Hastelloy C-276. For a non-magnetic grade with genuine corrosion resistance and galling resistance, Nitronic 60 and Nitronic 50 are the usual alternatives. Quoting the wrong alloy into corrosive service costs more in failure than the order was worth.
Forms supplied, testing and certification
Steel is melted, forged, heat treated, machined and tested on one site, so traceability on a 1.3813 order runs from the melt number to the shipped part rather than stopping at a purchased billet certificate.
| Form | Typical use | Size limit |
|---|---|---|
| Seamless rolled rings | Housings, races, non-magnetic ring components | to OD 6,000 mm |
| Forged rings | Sections outside the ring-mill envelope | from OD 50 mm |
| Forged flanges | Non-magnetic piping and vessel connections | to drawing |
| Round bars and blocks | Machining stock for bolts, nuts, fittings | to drawing |
| Forged shafts and spindles | Drives in magnetically sensitive equipment | to 14,000 mm turned length |
| Discs, blanks, tube sheets | Covers, end plates, exchanger components | to 5,000 mm machined dia. |
| Sleeves, bushings, hollow bars | Liners, spacers, guide bushings | bored to 1,600 × 10,000 mm |
Testing and documents
- Melting. Electric arc furnace with ladle refining and vacuum oxygen decarburisation; protective-atmosphere electroslag remelting where the order calls for it. Maximum heat size 60 t, maximum single forging 30 t.
- Non-destructive examination. Ultrasonic testing to ASTM A388 or EN 10228-3 and magnetic particle testing to ASTM E709, to the acceptance class nominated on the order.
- Mechanical testing. Tensile to ASTM A370 or ISO 6892 and Charpy V-notch down to −60 °C, carried out in the on-site laboratory.
- Composition. Optical emission spectrometry to ASTM E415 and infrared carbon and sulphur analysis to ASTM E1019, with portable alloy verification available on the finished part.
- Permeability verification. Arranged on request, since the figure is normally the reason the grade was chosen.
- Certification. EN 10204 3.1 as standard; EN 10204 3.2 witnessed by BV, DNV, LR, SGS, TUV or your own inspector on request. The works holds CCS, BV, DNV, LR and NK approvals.
Frequently asked questions
What is X40MnCrN19 steel?
X40MnCrN19, material number 1.3813, is a non-magnetizable steel alloyed with 17 to 19 % manganese, 3 to 5 % chromium and 0.08 to 0.12 % nitrogen. It is rust and acid resistant and is normally supplied in the hot-cold-worked condition, where it reaches 830 to 1030 N/mm² tensile strength and at least 390 N/mm² yield strength at room temperature.
What is the material number for X40MnCrN19?
1.3813. A closely related designation is X40MnCrN18, and the grade belongs to the SEW 390 group of non-magnetizable steels. Grades 1.3817, 1.3952 and 1.3964 are listed alongside it.
Is X40MnCrN19 magnetic?
No. Relative permeability is quoted as max. 1.01 G/Oe quenched, max. 1.01 G/Oe hot worked and max. 1.03 G/Oe cold worked. Cold work raises the figure slightly, as in any austenitic steel, but not enough to make the part magnetic in service.
At what temperature is X40MnCrN19 forged?
Hot forming runs at approximately 850 to 1050 °C, with solution annealing at approximately 1000 to 1050 °C followed by water or air cooling. The window is narrow and the steel is stiff under the press, so expect more reheats than an equivalent alloy steel forging.
Can X40MnCrN19 be hardened by quenching and tempering?
No. The structure is austenitic and stays austenitic, so strength comes from nitrogen in solid solution and from work hardening, not from a martensitic transformation. Yield strength is therefore set by the delivery condition: 295 N/mm² solution annealed, 390 N/mm² hot-cold-worked, 490 N/mm² cold-worked.
Is X40MnCrN19 a generator retaining ring steel?
Not the grade used today. X40MnCrN19 is an 18Mn–4Cr steel, while current non-magnetic retaining rings are forged from 18Mn–18Cr alloys, adopted for their combination of high strength, fracture toughness and resistance to stress corrosion cracking. State the application on the enquiry and the correct grade will be quoted.
Is X40MnCrN19 corrosion resistant?
It is described as rust and acid resistant, but with 3 to 5 % chromium and no molybdenum it does not belong in chloride, sour or strongly oxidising service. For those conditions use a duplex, super-austenitic or nickel alloy instead. The reason to specify 1.3813 is permeability, not corrosion.
What is the minimum order for X40MnCrN19 forgings?
10 kg, with no minimum piece count. A single part is quotable. Small parts are grouped into a batch to share furnace and setup time, so quantity still affects unit price even though it does not decide whether the job can be taken. Normal lead time is 20 to 60 days.
Request a quotation
Send a drawing or the finished dimensions. Quotations normally come back within two working days. Minimum order 10 kg, no minimum piece count, lead time 20 to 60 days.
State the grade
X40MnCrN19 or 1.3813, plus any governing specification or approval.
State the condition
Solution annealed, cold-worked or hot-cold-worked. This sets the certificate values.
State the testing
UT class, impact temperature, permeability check, EN 10204 3.1 or 3.2.
State the destination
Port and any witnessed inspection, so it is scheduled before shipment.