Keiji Ueda

Influence of Matrix Structure and Hard Carbide on Abrasive Resistance of Steel Plates

The microstructure of abrasion resistant steel plate usually consists of as quenched martensite, because harder matrix structure improves abrasion resistance of a steel plate. However hard martensitic material has lower formability, which is the important material property for fabricating machine parts. In this paper, a new type of abrasion resistant technique for steel plate is introduced. The steel provides good combination of high abrasion resistance and excellent formability without increasing hardness. The key technology to balance abrasion resistance and formability is the microstructural control of the ferritic matrix structure with dispersed extremely hard carbide particles. Basic research of abrasion mechanism revealed that abrasion resistance is strongly affected by the kind of carbides and the dispersed condition.

Development of 780MPa Grade Steel Plate by Microstructural Control Containing M-A through the On-Line Heating Process

High strength steel plates with 780MPa in tensile strength, suitable for building construction use, have been developed. The steel plates provide excellent combination of high strength, toughness, deformability and weldability. The key technology to obtain the excellent combination in mechanical properties of the steel is the microstructural control of M-A (martensite-austenite constituent) and the bainitic ferrite dual-phase structure, through the on-line heat treatment immediately after the accelerated cooling in Thermo-mechanical control process (TMCP). The developed steel plates have microstructure of fine M-A dispersed in the bainitic ferrite matrix. Basic metallurgical research revealed that the transformation behavior and microstructural morphologies were varied with the cooling stop temperature before the on-line heating, and the on-line heating temperature itself. Trial production of the developed 780MPa grade steel plates was also carried out with the plate mill. The obtained plates showed the satisfactory combination of high strength, low yield ratio, toughness.