Investigation of Failure of 15Cr2Ni3MoW Steel Piercing Plug and Modification

Described in the paper are the main types of failures of the 15Cr2Ni3MoW steel piercing plug encountered with during piercing the 27SiMn steel billet. A comparison of the metallographic structure and micro-hardness of the unused plug and the faulty plug is made. Another comparison of the deformation resistance of the 27SiMn steel with that of the 20# steel at the piercing temperature is also conducted by means of the Gleeble-1500 thermal simulator. Moreover, the oxide film on the unused plug is analyzed with the scanning electron microscope and the energy spectrometer. As a result, it is concluded that the said failures of the piercing plug are mainly caused by such elements like rather large deformation resistance of the 27SiMn steel at piercing temperature, high Si content of the steel, high operating temperature of the plug, porous structure of the plug surface oxide film as well a layer of crude ferrite soft area formed under the said oxide film. Accordingly, measures aiming at a longer service span of the plug are proposed.