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In order to solve the delayed fracture phenomenon of the wear resistant steel plate, the chamber electric furnace was used to carry out the tempering test; and the influence of tempering temperature and tempering time on the hardness, tensile strength and-20 impact energy of the wear resistant steel is analyzed. The statistical results shows that the comprehensive performance of wear resistant steel is more excellent when the tempering temperature is 450℃ and the tempering time is 2.5H.

Abstract-R&D of the DL05 cable steel are briefly introduced, then, the influence of element Mn and S on the electrical conductivity of DL05 cable steel are presented in details. some Key thermal properties and controlled manganese-sulphurratio in steel of the DL05 cable steel have been researched by using the mathematical including liquid, solidus temperature, the MnS precipitation temperature under different sulfur content, δ-Fe and γ-Fe allotrope transformation point temperature etc, which can provide references for the large-scale industrial production of the steel.

Abstract. To the problem of delayed cracking of the high strength low alloy abrasion-resistant steel plate NM360, the fracture, surface cracks and microstructure were investigated by optical microscopy, electron scanning microscopy and energy spectroscopy, and the residual stress was tested by X ray. The main results were as follows: The fracture source was in the center of the thickness of the steel plate and there were obvious central segregation in the mid-depth of the plate. Microstructure was not uniform in the surface, 1/4 depth and mid-depth of the steel, changed form lath martensite to martensite+granular bainite+ferrite. The steel showed the characteristics of the typical stress crack, there were different degree of resiual stree from edge to center, the impact of various residual stresses generating during heat treatment and the flame cutting on the defective areas was the main reason for the formation of the delayed crack.