Heat treatment facilities for the future.

EBNER® has been designing, manufacturing and installing heat treatment facilities for electrical steel for more than 50 years. In total, more than five decades of experience flow into each project, while at the same time taking into account future market developments and product features, as well as customer requirements. Thanks to the equilibrium of tradition and innovation, EBNER® has risen to become today's international market leader in the heat treatment facilities sector.

The heat treatment facilities developed by EBNER® are characterized by pure furnace atmospheres, ideal temperature uniformity, highest manufacturing quality and low maintenance requirements.

EBNER® quality electrical steel

A wide variety of next-generation electrical steel grades are produced reliably and with perfect flatness.

  • NGO fully-processed grades such M210-35A, M230-50A, NO30-15
  • NGO semi-processed grades such as M290-50K, 47D165
  • GO grades such as highly permeable HGO (e.g. M85-23P) or conventiona CGO (e.g. M110-23S)

Advantages

  • High heating rates, slow and uniform cooling
  • Consistent magnetic and mechanical properties over strip width and length
  • Resource-saving and tailor-made facilities designed to minimize utility & operating costs
  • Process simulation before heat treatment makes it possible to identify suitable annealing programs to reduce scrap and achieve optimized magnetic and mechanical properties

HICON/H2® HORIZONTAL RADIANT TUBE-HEATED CONTINUOUS FURNACE with hydrogen process atmosphere

Material. Non grain-oriented electrical steel.

Non grain-oriented electrical steel (NGO) has very similar magnetic properties across the width and along the length of the strip because the distribution of the grains is almost random (see fig. 2). This is known as isotropic material properties. Due to these properties, these materials are particularly well suited for use in rotating applications with magnetic fluxes in undefined spatial directions, such as electric motors (fig. 4) and generators (fig. 3).

Production workflow

The production of NGO electrical steel requires one- or two-stage heat treatment, depending on the magnetic properties that need to be achieved. EBNER® has the know-how to enable precise temperature control during heat treatment. There are two types of EBNER® heat treatment facility used here:

» HICON/H2® bell annealer facility (BAF)
» HICON/H2® annealing and coating line (ACL)

Microstructure of non grain-oriented electrical steel

Almost random orientation of the grains to the direction of rolling

Generators for wind turbines

Electric motor for drives in electric vehicles

Production workflow for NGO

EBNER® technology for NGO electrical steel. HICON/H2® annealing and coating line (ACL)

After cold rolling, the highly worked non-grain-oriented electrical steel is recrystallized in a horizontal continuous annealing furnace and the grain size is adjusted by secondary recrystallization.

A thin layer of insulating lacquer is then applied in-line using a roller coater in order to reduce eddy current losses in the electrical motor and counteract corrosion.

Advantages

✔ Lowest dewpoints
due to an excellent furnace sealing concept and up to 100% hydrogen process atmosphere to avoid surface oxidation, especially for the highest quality electrical steel grades (> 2.5% Si) at annealing temperatures > 1000 °C (1832 °F)

✔ Homogeneous slow cooling
over the strip width in the cooling zone for optimum flatness; produces good punching and laser cutting properties of the electrical steel.

✔ Material temperature > 1100 °C (2012 °F) feasible
especially for highly efficient power plant grades such as M230-50A (> 3% Si)

✔ Resource-saving and tailor-made furnace design
to minimize investment and the cost of wear parts and utilities

✔ Saves hydrogen by up to 50%
thanks to the hydrogen regeneration system

✔ The very latest burner/radiant tube technology and rapid heating systems
for high heating gradients to achieve efficient decarburization and improved texture (crystalline orientation)

✔ Process simulation before heat treatment
makes it possible to identify suitable annealing programs to achieve the specified magnetic and mechanical properties

Schematic presentation of a HICON/H2® annealing and coating line (ACL)

  1. Multi-stage strip cleaning
  2. Rapid strip heating in the heating up section of the continuous
    furnace (optionally with rapid heating systems up to 500 K/s)
  3. Option: decarburization to prevent magnetic aging
  4. Annealing for recrystallisation and discontinuous
    grain growth in process atmosphere
  5. Controlled cooling in the slow cooling zone and final cooling zone
  6. Coating by roller coater and drying in a floater furnace

Technology for NGO electrical steel. HICON/H2® bell annealer facility (BAF)

EBNER® patented HICON/H2® technology has revolutionized heat treatment in bell annealers worldwide. Also for electrical steel, in the form of hot- and cold-rolled strip, efficient and high quality anneals can be carried out at material temperatures between 650 (1202) and 900 °C (1652 °F).

To improve the magnetic properties of the electrical steel, the texture (crystalline orientation) of the hot-rolled strip is controlled during an anneal at a temperature between 750 (1382) and 900 °C (1652 °F).

After cold rolling, semi-processed electrical steel is recrystallized at a temperature of 650 (1202) to 750 °C (1382 °F). The subsequent skin pass of the semi-processed strip is to activate the material prior to the final anneal performed by the end user or stamper.

Advantages

✔ Lowest dewpoints and up to 100% hydrogen process atmosphere
for lowest surface oxidation and best rolling/skin pass results

✔ Shortest heating and cooling times
achieved with a combination of high convection (HICON®) and 100% hydrogen process atmosphere to ensure the highest productivity

✔ 100% load-bearing surface for the first coil and optimized convector plates
to protect the edges of the strip. This reduces the probability of cracks and prevents scrap entering the downstream process

✔ Low energy consumption and low maintenance requirement
due to refined design and high-quality manufacturing

Technology for NGO electrical steel. HICON/H2® bell annealer facility (BAF)

EBNER® patented HICON/H2® technology has revolutionized heat treatment in bell annealers worldwide. Also for electrical steel, in the form of hot- and cold-rolled strip, efficient and high quality anneals can be carried out at material temperatures between 650 (1202) and 900 °C (1652 °F).

To improve the magnetic properties of the electrical steel, the texture (crystalline orientation) of the hot-rolled strip is controlled during an anneal at a temperature between 750 (1382) and 900 °C (1652 °F).

After cold rolling, semi-processed electrical steel is recrystallized at a temperature of 650 (1202) to 750 °C (1382 °F). The subsequent skin pass of the semi-processed strip is to activate the material prior to the final anneal performed by the end user or stamper.

Advantages

✔ Lowest dewpoints and up to 100% hydrogen process atmosphere
for lowest surface oxidation and best rolling/skin pass results

✔ Shortest heating and cooling times
achieved with a combination of high convection (HICON®) and 100% hydrogen process atmosphere to ensure the highest productivity

✔ 100% load-bearing surface for the first coil and optimized convector plates
to protect the edges of the strip. This reduces the probability of cracks and prevents scrap entering the downstream process

✔ Low energy consumption and low maintenance requirement
due to refined design and high-quality manufacturing

Material. Grain-oriented electrical steel.

Grain-oriented (GO) electrical steel has excellent magnetic properties in the rolling direction due to a preferential orientation of the grains (see figure 2). The strict orientation of the easily magnetizable Goss-oriented grains makes the magnetization processes in the direction of rolling energetically very favorable. These materials are therefore particularly well suited in static applications with magnetic fluxes in defined directions, such as power and distribution transformers (figure 3).

Production workflow

Compared to NGO electrical steel, the production of GO electrical steel requires a highly complex, multi-stage heat treatment process. It is very important that the individual heat treatment steps are perfectly matched with the alloying system in order to achieve the best magnetic properties.  EBNER® offers the following facilities.

» HICON/H2® decarburizing and coating line (DCL)
» HITT high temperature bell annealer facility (HBAF)
» HICON® final annealing and coating line (FCL)