What precision alloys are needed for the manufacture of electric heaters

Precision alloys have the necessary physical and mechanical characteristics to achieve optimal performance and reliability of electric heaters.

In order for certain alloys to be used in the production of electric heaters, they must have a number of specific properties. Such as:

• high heat resistance — electric heaters operate at high temperatures, so alloys must be resistant to oxidation under extreme operating conditions;
• high electrical resistance — this makes it possible to effectively concentrate thermal power in a limited amount;
• sufficient creep resistance — alloys must retain their geometry and structure during long-term operation at high temperatures;
• satisfactory plasticity in the cold state — this allows manufacturers to create elements of the desired geometry without the need to heat the material.

Among various groups precision alloys Two are most widely used: iron-chromium-aluminum steels and nichromes. These materials have the above qualities and are effectively used in electric heaters.

Features of production and quality control of alloys

Alloys for heaters are mainly produced in the form of cold-rolled strip and wire. The heat resistance of these materials is controlled by the survivability test method, that is, the service life of the samples is determined during cyclic heating and cooling.

The physical and mechanical properties of steels change when held in certain temperature ranges. For example, Fe-Cr and Fe-Cr-Al alloys become stronger but less ductile after holding at a certain temperature.

Iron-chromium-based alloys acquire so-called 475-degree brittleness when held at 475°C. However, the embrittlement process is reversible: it is possible to restore the required characteristics of the material by quenching it in an aqueous medium at 750-860°C.

Fe-Cr-Al alloys and other ferritic metals have low creep resistance at high temperatures (above 1100-1200°C), which can lead to sagging heaters during operation. To prevent this, it is recommended to use additional supports along the entire length of the heaters. In addition, iron-chromium-aluminum materials react with a number of metals and oxides. This does not allow them to be used in combination with any ceramics without an additional insulating layer in places where ceramic elements come into contact with electric heaters.

Applications and operating temperatures of precision alloys

Eight grades of precision alloys are used in electric heaters, each of which has its own purpose and operating temperature range.

1. X13U4 — will be used in the manufacture of rheostats and heating elements for household appliances. The maximum allowable temperature is 1000°C, the optimum temperature is 900°C.
2. X15N60 — the scope of application is similar to the previous steel grade. The optimum operating temperature is 950°C, the maximum is 1000°C
3. X15N60-N — precision alloy for industrial and laboratory furnaces, as well as various household appliances with heating elements. It can operate at temperatures up to 1100°C, but 1050°C is recommended.
4. X20N80 — the material is used in the manufacture of small-sized resistances, rheostats and household appliances. The optimum operating temperature is 1050°C, the maximum temperature is 1100°C.
5. X20N80-N — used in industrial and laboratory furnaces and household appliances. It can be used at temperatures up to 1200°C, the optimal operating conditions are 1050°C.
6. X23U5 — used in glow plugs, industrial and laboratory furnaces. The optimum operating temperature is 1150°C, the maximum is 1200°C.
7. X23U5A — The scope of application is similar to the previous material, but this steel grade can be used in devices with a longer service life. The maximum allowable temperature is 1200°C, the optimum temperature is 1175°C.
8. X27U5A — is considered the most suitable metal for heating elements of high-temperature laboratory and industrial furnaces. It can be used at temperatures up to 1300°C; 1250°C is considered optimal.

Alloys for electric heaters with the letters A and H at the end of the marking are of high quality. The required physical and mechanical characteristics are achieved by adding rare earth and alloying metals, which have a significant effect on oxidative processes at high temperatures.

Precision alloys produced by the PZPS plant

St. Petersburg Precision Alloy Plant produces steels for the production of electric heaters of brands X15N60-N, X20N80-N et X23U5 in the form of cold rolled strip with a thickness of 0.005 to 4.0 mm and a width of 3 to 250 mm in accordance with GOST 12766.2. The availability of a modern laboratory complex and modernized production equipment also makes it possible to produce materials according to individual customer specifications. To learn more about the company's capabilities and clarify the details of cooperation, leave a request or call the specified phone number.

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