Control principle of the automatic air adjusting system of medium and small blast furnaces and realization method of control mode were presented,and the technical difficulties and countermeasures in implementation were also described.

Control principle of the automatic air adjusting system of medium and small blast furnaces and realization method of con-trol mode were presented, The automation system has been used successfully for the blast furnace air supply system.

In this paper,author analyses the medium blast furnace and point out its advantage is easy of intensificatlon,but the shortcoming is lower of labor capacity.

In this paper,contacting the actual production in Hengsteel EAF,technological standard of middle and small EAF has been analyzed in detail,the proposal about developing middle and small EAF has been put forward.

At present,if mini-medium BOF plants in our country adopt automatic steelmaking technology by using sublance system,there are still some restricted conditions,such as small mouth and high cost.