Experimental investigation of the failure of conical picks under thermal and abrasive effects.

• Hard rock cutting hastens heat accumulation on pick body and metal softening; • Wear of cutter in hard rock cutting with and without coolant conditions is analyzed; • Thermal effect is taken into consideration during measurement of rock abrasiveness. Conical picks are widely used in fields such as tunnel excavation, and high temperatures often occur on the surfaces of conical picks during the hard rock cutting process. To explore the influence of temperature on the wear of conical picks, a rotary cutting test was arranged. The cutting head torque, heat distribution and wear on the conical pick at different rotating speeds and cutting depths were explored. Moreover, the working process with and without cooling liquid was taken into consideration, and the mass losses of the conical pick under those conditions were analyzed. The experimental results showed that under cooling liquid conditions, the maximum temperature on the conical pick decreased by 230°C, and the mean mass loss of the conical pick decreased by 15.8 g. Therefore, high temperature could not be ignored in hard rock cutting. On the basis of these findings, a method for the measurement of rock abrasiveness was proposed in this paper, and different from previous research, the thermal effect was taken into consideration. A test bed for rock abrasiveness measurement was assembled in which a sintered WC-Co rod was used for rotary grinding on the rock sample, and the mass loss of the grinding rod was determined to evaluate the rock abrasiveness. The loading force between the grinding rod and rock sample was considered in the measurement of rock abrasiveness. The results showed that the mass losses of sintered WC-Co rods increased with the loading force. In addition, the characteristics of oxygen found from scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) showed that peeling and cracking could be found at distances of 5 mm and 10 mm from the end face of the grinding rod, and the increased oxygen content suggested obvious oxidization at those regions as well. [ABSTRACT FROM AUTHOR]