In many cases an isothermal treatment of throughhardening bearing grades in the lower bainitic range allows to adjust the mechanical properties of machine components to the later application, similar to those of marte...In many cases an isothermal treatment of throughhardening bearing grades in the lower bainitic range allows to adjust the mechanical properties of machine components to the later application, similar to those of martensitic hardening. The achieved microstructure contains only a negligible amount of retained austenite, so a dimensional change of components during application can be reduced. One disadvantage of the isothermal bainitic treatment in salt bath is that the duration of the treatment is much longer than that of the martensitic hardening and this causes higher costs. Therefore it would be desirable to be able to shorten the transformation duration in the lower bainitic range. The aim of the present work is to determine the parameters, by which the process could be greatly shortened in comparison with the conventional transformation process in the lower bainitic range. Therefore the bainitic transformation behavior of the steel 100 Cr6 (SAE 52100) and the relevant influence factors were investigated by means of dilatometry, in which the heat treatments were carried out with different process variants including pre-quenching or post-quenching. The amount of retained austenite in the microstructure and the hardness of the steel after the shortened heat treatments were measured. Finally the possibility to use these processes in industrial production is discussed.展开更多
Possibilities of means of dilatometry in connection with production of multiphase (DP- and TRIP-) steels were examined in detail. These steels are characterized by an excellent combination of high strength and good pr...Possibilities of means of dilatometry in connection with production of multiphase (DP- and TRIP-) steels were examined in detail. These steels are characterized by an excellent combination of high strength and good press formability, which are essentially important in the automotive industry. Transformation processes, cooling rates, holding temperatures, composition and technological parameters play a very important role in formation of applicable microstructure of multiphase steels. Dilatometrical experiments were carried out to study the processes of intercritical annealing and hot rolling of several DP- and TRIP-steels.展开更多
The isochronal y—m transformation of Fe-ISi alloy was measured by high-resolution dilatometry. According to the variation of the ferrite formation rate, an abnormal y—>a phase transformation was recognized, while...The isochronal y—m transformation of Fe-ISi alloy was measured by high-resolution dilatometry. According to the variation of the ferrite formation rate, an abnormal y—>a phase transformation was recognized, while normal reaction, i.e. one peak continuous reaction, was also detected. The occurrence the one or the other type of y—?a transformation strongly depends on the grain size: the transformation type changes from abnormal to normal with decreasing grain size. In the abnormal transformation process the first stage of the transformation corresponds to the first peaks in the transformation rate, which are not thermally activated.展开更多
Effects of Zn/P ratio on the structures and properties of glasses with the general composition of （80-x）ZnO-20Fe2O3-xP2O5 （x=40, 45, 50, 55, 60） （molar fraction, %） were investigated. Glass structure was measure...Effects of Zn/P ratio on the structures and properties of glasses with the general composition of （80-x）ZnO-20Fe2O3-xP2O5 （x=40, 45, 50, 55, 60） （molar fraction, %） were investigated. Glass structure was measured by infrared absorption spectrum. Glass density （/9） was measured by the Archimedes method. Coefficients of thermal expansion （a） and characterization temperature were obtained by a dilatometer. Water durability of each glass was estimated from the dissolution rate （DR）in water at 90 ℃ for 24 h. With increasing Zn/P ratio, water durability of zinc-iron phosphate glasses increases dramatically without large increase in the characterization temperature. （80-x）ZnO-20Fe2O3-xP2O5 glasses with 0.3≤Zn/P≤0.5 are suit for low-to-mid temperature sealing application for substrates with a〈8.0× 10^-6℃^-1.展开更多
文摘In many cases an isothermal treatment of throughhardening bearing grades in the lower bainitic range allows to adjust the mechanical properties of machine components to the later application, similar to those of martensitic hardening. The achieved microstructure contains only a negligible amount of retained austenite, so a dimensional change of components during application can be reduced. One disadvantage of the isothermal bainitic treatment in salt bath is that the duration of the treatment is much longer than that of the martensitic hardening and this causes higher costs. Therefore it would be desirable to be able to shorten the transformation duration in the lower bainitic range. The aim of the present work is to determine the parameters, by which the process could be greatly shortened in comparison with the conventional transformation process in the lower bainitic range. Therefore the bainitic transformation behavior of the steel 100 Cr6 (SAE 52100) and the relevant influence factors were investigated by means of dilatometry, in which the heat treatments were carried out with different process variants including pre-quenching or post-quenching. The amount of retained austenite in the microstructure and the hardness of the steel after the shortened heat treatments were measured. Finally the possibility to use these processes in industrial production is discussed.
文摘Possibilities of means of dilatometry in connection with production of multiphase (DP- and TRIP-) steels were examined in detail. These steels are characterized by an excellent combination of high strength and good press formability, which are essentially important in the automotive industry. Transformation processes, cooling rates, holding temperatures, composition and technological parameters play a very important role in formation of applicable microstructure of multiphase steels. Dilatometrical experiments were carried out to study the processes of intercritical annealing and hot rolling of several DP- and TRIP-steels.
文摘The isochronal y—m transformation of Fe-ISi alloy was measured by high-resolution dilatometry. According to the variation of the ferrite formation rate, an abnormal y—>a phase transformation was recognized, while normal reaction, i.e. one peak continuous reaction, was also detected. The occurrence the one or the other type of y—?a transformation strongly depends on the grain size: the transformation type changes from abnormal to normal with decreasing grain size. In the abnormal transformation process the first stage of the transformation corresponds to the first peaks in the transformation rate, which are not thermally activated.
基金Project(7602110340) supported by the Postdoctoral Science Foundation of Central South University, ChinaProject(721500277)supported by the Fundamental Research Funds for the Central Universities of China
文摘Effects of Zn/P ratio on the structures and properties of glasses with the general composition of （80-x）ZnO-20Fe2O3-xP2O5 （x=40, 45, 50, 55, 60） （molar fraction, %） were investigated. Glass structure was measured by infrared absorption spectrum. Glass density （/9） was measured by the Archimedes method. Coefficients of thermal expansion （a） and characterization temperature were obtained by a dilatometer. Water durability of each glass was estimated from the dissolution rate （DR）in water at 90 ℃ for 24 h. With increasing Zn/P ratio, water durability of zinc-iron phosphate glasses increases dramatically without large increase in the characterization temperature. （80-x）ZnO-20Fe2O3-xP2O5 glasses with 0.3≤Zn/P≤0.5 are suit for low-to-mid temperature sealing application for substrates with a〈8.0× 10^-6℃^-1.
