# NiMn20-6 (Material No. 1.3932) Forged Bar, Billet and Ring

Source: https://steelforgepieces.com/Stainless-Steel/NiMn20-6.html
Supplier: Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
Address: No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Telephone: +86-189-2135-9659
Email: sales@steelforgepieces.com
Reviewed: 2026-10-03

## Summary

NiMn20-6 is a nickel-iron-manganese alloy with specified thermal expansion, 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. It is used as the active, high-expansion layer of
thermostatic bimetals under DIN 1715, and its expansion-temperature curve has no break
point. Typical composition is 19 to 21 percent nickel and 5.5 to 6.5 percent manganese,
balance iron, with no chromium. VDA 231-106 classification is group 1.1.2.

NiMn20-6 is not a stainless steel. It contains no chromium and is not corrosion
resistant in the stainless sense.

## Chemical composition

Limits published for Ni20Mn6, the high-expansion bimetal layer, weight percent.

| 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 material number 1.3932 in its expansion alloy range as VDM Alloy 20-6
with a typical composition of Ni 20, Fe 73, Mn 6.

Tolerance note: some trading data sheets circulate a wider specification, 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 sources; carbon, silicon and manganese are not. DIN 17745:2025-09 holds the
authoritative limits.

## Physical properties

Published for the Ni20Mn6 and Ni36 thermostatic bimetal, where Ni20Mn6 is the active
high-expansion layer and Ni36 is the passive low-expansion layer.

| Property | Value |
|----------|-------|
| Density | 8.1 g/cm3 |
| Electrical resistivity at 20 C | 0.8 +/- 5 % ohm.mm2/m |
| Thermal conductivity | 12 W/(m.C) |
| Modulus of elasticity | 147-177 GPa |
| Specific curvature K, 20-135 C | 15 x 10^-6 /C |
| Flexivity F, 20-130 C | 28.5 x 10^-6 /C, +/- 5 % |
| Allowable operating temperature | -70 to +350 C |
| Linear response range | -20 to +180 C |

Mechanical values for monolithic 1.3932 are held inside DIN 17745 and commercial
databases. Measured values are reported per heat on the test certificate.

## 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 |

Similar materials: Ni36 (1.3910), Ni30 (1.3903), Ni38 (1.3913), RNi24. Ni36 is the usual
low-expansion partner layer.

## Applications

The alloy expands strongly and predictably with temperature. Bonded to a low-expansion
partner, the pair bends by a calibrated amount, and that deflection switches, limits or
indicates. Published applications for the Ni20Mn6 and Ni36 couple: thermostats and
temperature controllers, temperature relays, automatic protection switches, exhaust gas
temperature gauges, pressurisers, diaphragm meters, current-limiting elements, and
temperature compensation elements in instruments and control systems.

The absence of a break point in the expansion curve lets a designer treat deflection as
effectively linear across the working range.

## Forged product forms

Most end users receive this alloy as thin strip, commonly rolled to around 0.1 mm
thickness in widths of 5 to 120 mm. Jiangyin Jiangnan Metal supplies the forged and
hot-worked semi-finished shapes upstream of that.

| 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 |

Not offered in this grade: flanges, crankshafts, valve seat rings, gears. A chromium-free
expansion alloy is the wrong material for pressure-containing and wear-duty parts.

## Melting, testing and certification

Melting route: EAF plus VOD plus ESR. Electroslag remelting is used here for
compositional uniformity, because expansion behaviour tracks chemistry closely and
segregation shows up as scatter in deflection.

Ultrasonic examination: EN 10228-3 covers ferritic and martensitic forgings and does not
suit this austenitic, non-magnetic alloy. EN 10228-4:2016 covers austenitic and
austenitic-ferritic stainless steel forgings, so its techniques fit the structure, though
NiMn20-6 is outside that standard's stainless scope. ASTM A388 is a general practice for
ultrasonic examination of steel forgings and is not grade-restricted, making it the
cleaner reference for this material. SEP 1921 acceptance classes available on request.

Inspection documents under EN 10204, type 3.1 or 3.2. Specify at enquiry stage.

## Commercial terms

Pricing is by quotation against drawing, tonnage and certification level. Send a drawing
or finished dimensions, quantity, the standard to certify to, and any required expansion,
flexivity or deflection values. Reply includes forged weight, machining allowance,
delivery condition and lead time.

## FAQ

**What is NiMn20-6?**
A nickel-iron-manganese alloy with specified thermal expansion, material number 1.3932,
listed in DIN 17745:2025-09 and 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,
no break point in the expansion-temperature curve.

**Is NiMn20-6 a stainless steel?**
No. No chromium, not corrosion resistant in the stainless sense. It is a
controlled-expansion nickel-iron alloy.

**Is NiMn20-6 magnetic?**
Austenitic structure, supplied non-magnetic. Permeability can rise after heavy cold work,
so state any permeability limit on the order.

**What is NiMn20-6 used for?**
The active, high-expansion layer of thermostatic bimetals under DIN 1715, usually bonded
to Ni36. The 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 (Deutsche Nickel GmbH, Schwerte), VDM Alloy 20-6 (VDM Metals), and NiMn20-6
as supplied by Schmidt + Clemens at Edelstahlwerk Kaiserau and pauly STAHLHANDEL, Essen.

**Can NiMn20-6 be supplied as forgings rather than strip?**
Yes. Jiangyin Jiangnan Metal Co., Ltd. supplies NiMn20-6 forged bar, billet, slab, discs,
sleeves and seamless rolled rings to drawing, melted EAF plus VOD plus ESR, with EN 10204
3.1 or 3.2 documentation. Telephone +86-189-2135-9659, email sales@steelforgepieces.com.

**Who supplies NiMn20-6 forgings in China?**
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road,
Zhouzhuang Town, Jiangyin City, Jiangsu Province, China.

**Which alloys are similar to NiMn20-6?**
Ni30 (1.3903), Ni36 (1.3910), Ni38 (1.3913), RNi24.

## Standards referenced

- DIN 17745:2025-09, wrought nickel-iron alloys, chemical composition. Supersedes
  DIN 17745:2002-09, which specified the composition of wrought nickel-iron alloys with
  specific magnetic properties and thermal behaviour for semi-finished products.
- SEW 385:1991-07, Eisenlegierungen mit besonderer Waermeausdehnung.
- DIN 1715, thermostatic bimetals. NiMn20-6 used for the active component.
- VDA 231-106, material classification, group 1.1.2.
- EN 10228-4:2016, ultrasonic testing of austenitic and austenitic-ferritic stainless
  steel forgings.
- ASTM A388, ultrasonic examination of steel forgings.
- EN 10204, types of inspection documents.

Technical data is given for comparison only, not as a design allowable. Verify against
the current standard and the heat-specific certificate before release to manufacture.