Experimental Analysis of Strain of Blast Furnaces Shell During the Start up to

Circumferential BF hearth shell stress was measured during the two blast furnaces blow-in periods. BF1 had the hearth with not developed salamander. It was blew down after reline and few days of full tuyeres operation. BF3 hearth had fully developed salamander after 12 years of operation. Before start up both BF hearths were identical cleaned up 1 m bellow the tap hole elevation. Blow in line on BF1 also BF3 salamander were circumferential trenched out up to the hearth bottom elevation down. Maximal measured BF1 hearth shell tension level reached 100 MPa. 160 MPa was the detected maximal BF3 hearth shell tension. Tension level 100 MPa was detected 6 days after start up on both furnaces, This level stayed identical on BF1 for the next four days but on BF3 tension rose during the next two days period up to level 160 MPa. Maximal pressure started relieve on both furnaces 8 days after start up. Hearth shell stress stabilized on both furnaces on range 30 – 50 MPa when hearth thermocouples readings started stabilize. Data shows significant contribution of hearth refractory to hearth shell stress creation. Melting rate, tuyeres opening strategy, casting schedule can contribute to BF hearth shell stress control during the blow in period.