Papers by Keyword: Tempered

Abstract: The effect of trace cerium on microstructures and mechanical properties of 690MPa steel plates used for engineering machinery was researched by the comparative analysis of the microstructures, inclusions, and comprehensive mechanical properties of the steel plates after rolled, quenched and tempered. The result shows that trace cerium can improve the yield strength, tensile strength of rolled and quenched steel plates, and low temperature impact toughness of the tempered steel plate significantly, but has little effect on the yield strength and tensile strength of the tempered steel plates. The cerium-bearing steel has finer grain size, less inclusion contents and more spheroidal than that of cerium-free steel. The yield strength of 10 megapascal, the tensile strength of 20 megapascal for rolled plates and the yield strength of 130 megapascal, the tensile strength of 100 megapascal for quenched plates was improved by the addition of cerium. In spite of this, the cerium has little effect on the yield and tensile strength but improved about 50 Joule impact energy values under-40 centigrade degree temperature after the plate was tempered at the temperature of 620 centigrade degree. It has the same rules of the plates tempered at the temperature of 580 centigrade degree.

Abstract: The influence of tempering temperature on the microstructure and mechanical properties of low carbon low alloy steel was investigated. The results show that tempering temperature has considerable influence on both yield strength and tensile strength. With the increase in tempering temperature, the yield strength increases first and then decreases after it reaches the highest point at 600°C with a strength of 843MPa, while the tensile strength decreases fastly from 550°C to 650°C and keeps stable after increasing drastically at 720°C. The yield ratio is about 0.60 except at 600°C and 650°C with a high yield ratio of 0.90, while the total elongation has little change. It is concluded that the major change of mechanical properties after tempering has a connection with the decomposition of M/A(martensite/austenite) islands, the recovery of dislocations and the precipitation of alloy elements.

Abstract: To improve the toughness and weldability, the carbon content of the steels has to be deduced, and more and more attention has been attracted to the low carbon and ultra-low carbon steels. To strengthen the microstructure Cu and Nb-bearing steels are developed. However, the knowledge on influence of combined addition of Cu and Nb is still in lack. The microstructure and mechanical properties are studied in the 6-mm thick as-rolled and tempered ultra-low carbon steel plates with varied copper and niobium content. The microstructure and mechanical properties are studied in the 6-mm thick as-rolled and tempered ultra-low carbon steel plates with varied copper and niobium content. The experimental results show that if niobium is added without copper, the increase of niobium addition does not have a significant influence on the phase transformation and mechanical properties before tempering. The strength and toughness of those copper-free niobium steels do not vary significantly after tempered at different temperatures, while the strength of niobium steels with 1.8% copper added increases after tempered in the range of 450-650°C and reaches a peak at 500-550°C. If combined with 1.8% copper, the increase of niobium addition from 0.08% to 0.16% improves the hardenabililty and strength significantly, and the strength peak after tempering moves to a lower temperature. The strength of air-cooled niobium steels with 1.8% copper added is usually higher than those water-cooled, while after tempered at a proper temperature, the strength of the latter becomes higher than the former.