1. Multi-stack Bell-type Annealing Furnaces (MBAF) for Silicon Steel Strip

Multi-stack Bell-type Annealing Furnaces (MBAF) for Silicon Steel Strip

Tenova LOI Thermprocess, with its predecessors Matthias Ludwig and Nassheuer, has been building bell-type annealing plants for more than 60 years. Throughout the world, more than 500 LOI multi-stack annealing bases have been installed. The world-wide market share during the past 10 years is virtually 100%.

In the production of grain-oriented electrical strip, the material is annealed at about 1,200 °C following decarburizing and coating to obtain defined grain growth and a specified surface layer on the electrical strip.

In contrast to their widespread use for carbon steel and stainless steel, single-stack bell-type annealing furnaces have not become as established solution for the annealing of grain-oriented electrical steel sheet. Most of the new plants constructed for these applications over the past 20 years have therefore been multi-stack bell-type annealing furnaces (MBAF).

Normally three or four individual charge stations are installed in a row under the heating hood. Small coils (usually ≤ 12 t) are often charged in two layers. In other words, two coils may be stacked on each other on self-supporting plates.

Larger coils (usually ≥ 12 t) are charged in one layer on a charge plate manufactured from a high-temperature-resistant alloy or positioned directly on the base.Throughout the world, it has become normal practice to install electrically heated MBAF-plants. Multi-stack plants for two-layer operation have already been constructed with gas firing system with significant lower operating costs.

  • Value for Money

    Value for Money

    • Solid annealing equipment design
    • Low operational costs
  • Efficiency


    • Excellent temperature uniformity
    • Very uniform mechanical and magnetic properties of the electrical sheet
    • High heat transfer mainly by radiation
    • High efficient electrical heating or low NOx gas-fired burners
    • Individual coolers
  • Safety


    • TÜV proven safety strategy
    • Sophisticated process control
    • O2 concentration monitoring
  • Service


    • Long service life
    • Sturdy base support design
  • Reference


    • > 60 years of experience in Bell-type Annealing
    • > 500 multi-stack annealing bases worldwide
    • World-wide market share during the past 10 years virtually 100%
  • Environment


    • Selection of alternative heating systems (electrical and gas-fired heating)
    • Low NOx burners in case of gas-fired heating
  • Digitalization


    • Fully automated control system
    • Various software modules for optimization
  • Technical Excellence

    Technical Excellence

    • World's first gas-fired MBAF plant
    • Flameless combustion technology
    • Possibility to produce HiB-grades
  • ContactContact PersonPositionLegal EntityDepartmentPhoneFaxE-mailAddress
    LOI Thermprocess GmbH
    +49 201 1891-1
    +49 201 1891-321

    Am Lichtbogen 29

    45141 Essen


Silicon Steel