NiMn20-6 (Material No. 1.3932) Forged Bar, Billet and Ring
Technical data sheet published by Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory, Jiangyin, Jiangsu, China. Reviewed 3 October 2026.
NiMn20-6 is a nickel-iron-manganese alloy with specified thermal expansion, carrying material number 1.3932. It is listed in DIN 17745:2025-09, the current edition superseding DIN 17745:2002-09, and in the older SEW 385:1991-07, where it is described as a ferrous alloy with special thermal expansion. The alloy is bought for how it moves with temperature, not for corrosion resistance. It serves as the active, high-expansion layer of thermostatic bimetals under DIN 1715, and its expansion-temperature curve has no break point. Typical composition is roughly 19 to 21 percent nickel and 5.5 to 6.5 percent manganese, balance iron, with no chromium.
A note on where this grade is filed
This page sits in our stainless steel directory for historical reasons. NiMn20-6 is not a stainless steel. No published composition for 1.3932 contains chromium, and the governing standards cover controlled-expansion nickel-iron alloys. The VDA 231-106 classification is group 1.1.2. If you need a corrosion-resistant grade, see Sanicro 28 or A182-F51 duplex instead.
1. Chemical composition
| C | Si | Mn | P | S | Ni | Fe |
|---|---|---|---|---|---|---|
| ≤ 0.05 | 0.15–0.30 | 5.5–6.5 | ≤ 0.02 | ≤ 0.02 | 19.0–21.0 | Balance |
VDM Metals lists the same material number, 1.3932, under its expansion alloy range as VDM Alloy 20-6 with a typical composition of Ni 20, Fe 73, Mn 6. The nickel and manganese figures agree with the table above.
On tolerances. Some trading data sheets circulate a wider specification for this grade, with C up to 0.20, Si up to 1.00 and Mn 6.00 to 7.00. The nickel window of 19.0 to 21.0 is consistent across every source we have checked. Carbon, silicon and manganese are not. The authoritative limits are those in DIN 17745:2025-09. We melt to whichever limits your purchase specification calls out and state the actual heat analysis on the certificate.
2. Physical properties
This alloy is normally characterised as one half of a bimetal couple rather than as a bar on its own, because that is how it does its job. The figures below are published for the Ni20Mn6 and Ni36 thermostatic bimetal, in which Ni20Mn6 is the active high-expansion layer and Ni36, an Invar-type 36 percent nickel alloy, is the passive low-expansion layer.
| Density | 8.1 g/cm³ |
|---|---|
| Electrical resistivity at 20 °C | 0.8 ± 5 % Ω·mm²/m |
| Thermal conductivity | 12 W/(m·°C) |
| Modulus of elasticity | 147–177 GPa |
| Specific curvature K, 20–135 °C | 15 × 10−6 /°C |
| Flexivity F, 20–130 °C | 28.5 × 10−6 /°C, ± 5 % |
| Allowable operating temperature | −70 to +350 °C |
| Linear response range | −20 to +180 °C |
Tensile strength, 0.2 percent proof strength, elongation and hardness for monolithic 1.3932 are held inside DIN 17745 and commercial material databases. We report measured values per heat on the test certificate rather than quote nominal numbers we cannot attribute.
3. Designations, suppliers and trade names
| Designation | Standard or source | Country, supplier |
|---|---|---|
| NiMn20-6 | DIN 17745:2025-09 | Germany |
| NiMn20-6 | SEW 385:1991-07 | Germany |
| 1.3932 | Material number | Germany |
| Ni20Mn6 | Bimetal active-layer designation | China |
| Dilaton 206 | Trade name | Deutsche Nickel GmbH, Schwerte |
| VDM Alloy 20-6 | Trade name, expansion alloys | VDM Metals GmbH |
| NiMn20-6 | Supplier designation | Schmidt + Clemens, Edelstahlwerk Kaiserau, Lindlar |
| NiMn20-6 | Supplier designation | pauly STAHLHANDEL, Essen |
Alloys listed as similar materials to 1.3932 are Ni36 (1.3910), Ni30 (1.3903), Ni38 (1.3913) and RNi24. Of these, Ni36 matters most in practice, because it is the usual low-expansion partner when NiMn20-6 forms the high-expansion side.
4. Where NiMn20-6 is actually used
The alloy expands strongly and predictably as it heats. Bond it to a low-expansion partner and the pair bends by a calibrated amount, and that deflection is then used to switch, limit or indicate. Published applications for the Ni20Mn6 and Ni36 couple cover thermostats and temperature controllers, temperature relays, automatic protection switches, exhaust gas temperature gauges, pressurisers, diaphragm meters, current-limiting elements, and temperature compensation elements inside instruments and control systems.
The absence of a break point in the expansion curve is the commercially useful detail. A designer can treat deflection as effectively linear across the working range rather than calibrate around a discontinuity.
5. Product forms we forge in NiMn20-6
Most end users receive this alloy as thin strip. Bimetal is commonly rolled down to around 0.1 mm thickness in widths of roughly 5 to 120 mm. Our work sits upstream of that. We supply the forged and hot-worked semi-finished shapes that strip, machined components and tooling are made from.
| Form | Typical use |
|---|---|
| Forged round bar | Machined thermal-response components, test coupons, redraw stock |
| Forged square and flat billet | Feedstock for hot and cold rolling to bimetal strip |
| Forged slab and plate blank | Cladding and roll-bonding feedstock |
| Seamless rolled ring | Thermally actuated rings and sleeves |
| Forged disc, sleeve, bushing | Expansion-matched spacers and compensation parts |
We do not list NiMn20-6 flanges, crankshafts, valve seat rings or gears, and we will not quote them. A chromium-free expansion alloy is the wrong choice for pressure-containing and wear-duty parts. For those, ask us about A182-F51, Inconel 625 or Monel 400.
6. Melting, testing and certification
Our melting route for this grade is EAF plus VOD plus ESR: electric arc furnace, vacuum oxygen decarburisation, then electroslag remelting. The reason for the remelt step here is compositional uniformity. Expansion behaviour tracks chemistry closely, so segregation across a forged section shows up as scatter in deflection.
On ultrasonic examination, read the standard carefully. EN 10228-3 covers ferritic and martensitic forgings and does not suit this alloy, which has an austenitic, non-magnetic structure. EN 10228-4:2016 covers ultrasonic testing of austenitic and austenitic-ferritic stainless steel forgings, so its techniques fit the structure, although NiMn20-6 falls outside that standard's stainless scope. ASTM A388 is a general practice for ultrasonic examination of steel forgings and is not grade-restricted, which makes it the cleaner reference to name on an order for this material. SEP 1921 acceptance classes can be applied on request.
Inspection documents are issued under EN 10204. Specify 3.1, issued by our own independent inspection department, or 3.2, countersigned by an agreed third party such as SGS, BV or TÜV, at enquiry stage rather than after production.
7. Request a quotation
Send a drawing or the finished dimensions, the quantity, the standard you must certify to, and any required expansion, flexivity or deflection values. We come back with forged weight, machining allowance, delivery condition and lead time.
Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factoryNo.1 Chengxiqiao Road, Zhouzhuang Town,
Jiangyin City, Jiangsu Province, China
Telephone, WhatsApp and WeChat: +86-189-2135-9659
Email: sales@steelforgepieces.com Email a drawing for quotation
8. Frequently asked questions
What is NiMn20-6?
A nickel-iron-manganese alloy with specified thermal expansion, material number 1.3932, listed in DIN 17745:2025-09 and in SEW 385:1991-07. Around 19 to 21 percent nickel, 5.5 to 6.5 percent manganese, balance iron, no chromium. High coefficient of thermal expansion, with no break point in the expansion-temperature curve.
Is NiMn20-6 a stainless steel?
No. It contains no chromium and is not corrosion resistant in the stainless sense. It is a controlled-expansion nickel-iron alloy, selected for dimensional response to temperature.
Is NiMn20-6 magnetic?
The alloy has an austenitic structure and is supplied non-magnetic. As with other austenitic nickel-iron-manganese alloys, permeability can rise after heavy cold work, so state any magnetic permeability limit on the order and we will verify it before despatch.
What is NiMn20-6 used for?
As the active, high-expansion layer of thermostatic bimetals under DIN 1715, usually bonded to Ni36. The finished bimetal drives thermostats, temperature relays, automatic protection switches, exhaust temperature gauges, pressurisers, diaphragm meters and temperature compensation elements.
What is the material number of NiMn20-6?
1.3932.
What are the trade names for 1.3932?
Dilaton 206 from Deutsche Nickel GmbH in Schwerte, VDM Alloy 20-6 from VDM Metals, and NiMn20-6 as supplied by Schmidt + Clemens at Edelstahlwerk Kaiserau and by pauly STAHLHANDEL in Essen.
Can I buy NiMn20-6 as forgings rather than strip?
Yes. We supply forged bar, billet, slab, discs, sleeves and seamless rolled rings in NiMn20-6 to drawing, melted EAF plus VOD plus ESR, with EN 10204 3.1 or 3.2 documentation. Telephone +86-189-2135-9659 or email sales@steelforgepieces.com.
Which alloys are similar to NiMn20-6?
Ni30 (1.3903), Ni36 (1.3910), Ni38 (1.3913) and RNi24 are listed as similar materials. Ni36 is the standard low-expansion partner layer.
9. Standards referenced
- DIN 17745:2025-09, wrought nickel-iron alloys, chemical composition. Current edition, supersedes DIN 17745:2002-09, which specified the chemical composition of wrought nickel-iron alloys with specific magnetic properties and thermal behaviour for semi-finished products.
- SEW 385:1991-07, Eisenlegierungen mit besonderer Wärmeausdehnung, iron alloys with special thermal expansion.
- DIN 1715, thermostatic bimetals. NiMn20-6 is used for the active component.
- VDA 231-106, material classification. NiMn20-6 falls in group 1.1.2.
- EN 10228-4:2016, non-destructive testing of steel forgings, part 4, ultrasonic testing of austenitic and austenitic-ferritic stainless steel forgings.
- ASTM A388, standard practice for ultrasonic examination of steel forgings.
- EN 10204, metallic products, types of inspection documents.
Data on this page is compiled from published standards listings and supplier data sheets for comparison purposes. It is not a design allowable. Verify against the current standard and the heat-specific certificate before release to manufacture.