Study On Z-direction Properties And Evaluation Of Medium Plate

The test method on the through-thickness property of medium plate nowadays is very simple in our country, and there is only one standard that is Steel plate with through-thickness characteristics(GB5313-85). In order to solve it, the research method which is the shearing method to measure the through-thickness property of medium plate is proposed.The test data illustrate that through-thickness property of medium plate is not homogeneous and shear strength in the centre of the steel plate is lower than that on the surface. The thicker the steel plate is, the more evident the difference is. According to the metallographic observation of the samples, it can be found the crystal grain of ordinary sample Q345B is coarsest, and the gap in the centre and on surface is also the greatest. The crystal grain of Q345B sample produced by TMCP technology is thinning evidently, whose differences are shortened distinctly. However, the crystal grain of Q345B sample by normalizing treatment of 870℃is the slightest, whose organization is also the most homogeneous. The experiment states that TMCP technology can improve the through-thickness property of medium plate in certain points. But if to improve it further, the proper heat treating is still an effective method.The correlation can be found through comparing the experiment data gained from the method of shearing and tension. The shearing strength is relatively higher if the Z direction percentage reduction of area of the steel plate is better. That is to say the shearing method to measure the through-thickness property of medium plate is scientific and practical.The experiment of acid dipping and the analysis of tensile fracture and metallographic had been made for the medium plate samples taken from Tangsteel, it can be found that the main elements which influence the through-thickness property of medium plate produced in Tangsteel are centre porosity, sulphide inclusion, Si and Mn oxide inclusion.