Development of Electrical Steels

Objectives

The primary objective of the project was to develop an indigenous technology for (Cold rolled grain oriented) CRGO steels. It was planned to achieve it through optimization of chemistry and processing parameters for hot band preparation. Annealing of cold rolled sheet were investigated to obtain the required microstructure of electrical steels.

Technical Details

Laboratory scale experiments have been done to produce hot-band for CRGO steels. Laboratory scale cold-rolling and annealing have been done to produce large Goss grains. Several compositions were casted at NML. Hot-rolling was done to make 2 mm thick strip. Hot-rolling was done through novel processing routes. The rolling passes and temperatures were studied to obtain proper final microstructure. The strips were annealed and prepared for cold rolling. After cold rolling the thin sheets were annealed in several steps to obtain large Goss grains. Decarburization of the cold rolled sheets was done in a controlled atmosphere. The formation of inhibitor was studied in details. They were formed to pin the other grains during final secondary recrystallization so that Goss grains can only grow.

Achievement (Output/outcome)

New compositions and processing routes were obtained from this project. An efficient method is invented to produce an acquired inhibitor. By controlling the chemistry of the steel and hot-rolling at a lower temperature a new direction for hot-rolling of this steel is proposed which is generally prescribed to be rolled in austenite+ferrite region in the literature. Four patents were filed from this project. 

Impact

This project was to develop indigenous processing route for production of CRGO in India. Trials were made upto the maximum possible limits within the laboratory scale to obtain the required microstructure of CRGO steels. Casting, rolling and annealing were investigated and suitable processing windows were identified. In terms of scientific impact the development of texture during hot-rolling and abnormal growth of Goss grains was investigated in this project. The nucleation mechanism of Goss grains was investigated.

Secondary recrystallized Goss grain obtained from selection of suitable processing parameters