Fracture mechanics investigation of MgO-C bricks for steelmaking by bending and fatigue failure tests along with X-ray CT scan observation

Abstract

Fatigue failure tests were firstly carried out. The material constant derived from S-N curve was evaluated and compared with previous study. The compliance method was subsequently used to evaluate the fracture toughness of MgO-C brick and the relationship between the stress factor and crack growth rate. In order to use this method, the effects of brick carbon content on the crack growth rate and crack growth rate in high temperature were investigated. As a result, it was found that the crack growth rate increased when the carbon content in brick decreased. This result was confirmed by X-ray CT scans, which revealed large cracks in bricks with a lower carbon content, even in the middle of fatigue failure tests. Furthermore, the material constants obtained from fatigue failure test and K-V diagram were compared. A material constant was derived by evaluating the relationship between the crack growth rate and stress intensity factor, and the result was found to agree with the value derived from fatigue failure tests. This result confirms that that material constant derived from fatigue failure tests is the inherent property of the material and corresponds to the variation of crack growth rate with changes in stress factor. The effects of carbon content in MgO-C brick on the crack growth behaviour and fatigue failure mechanism were also investigated.