LOI Thermprocess: Products

Non-grain-oriented strip is annealed in a radiant tube furnace using a continuous process after cold rolling to ensure recrystallization and controlled grain growth. Top-quality steel requires strip temperatures above 1100°C and a very dry atmosphere with a high hydrogen content. This is followed by controlled cooling to obtain an extremely flat strip.

The hot rolled strips (NGO and GO) are initially annealed in a continuous process to eliminate brittleness prior to cold rolling and to modify the microstructure. The annealing process is followed by a controlled cooling stage with a cooling rate which may range from 5 to 80 K/s depending on the steel grade required.

Tenova, with its over 40 years of experience, has the competence and knowledge of the thermal process which is required for the production of stainless steel strip.

Cold rolled GO Si steel strip is annealed in a continuous process line for primary recrystallization and decarburization. After the steel strip has passed through the DCL furnace, it is coated with magnesium oxide and then dried.

For the final heat treatment process the transformer strip is coated with insulating varnish in an in-line process and then dried in an indirectly heated furnace. The steel strip is heated further in a radiant tube furnace with a controlled atmosphere and then straightened using the integrated hot stretching equipment. This stage is followed by a slow cooling process.

Semi-finished electrical steel requires an annealing process with recrystallizing, decarburizing and blueing. The punched laminations are continuously annealed in a roller hearth furnace or for smaller capacity in a pusher type furnace.