Study On The Structure Evolution Rule Of27SiMn Hydraulic Bracket Tube

27SiMn steel is a kind of low-carbon and low-alloy steel with strong toughness which is developed in accordance with China’s specific national conditions. It has been widely used in the manufacture of single hydraulic prop’s cylinder block and plunger tube, as well as other important parts because it has a better weldability and lower price compared with Nickel-chromium steel.This paper takes the27SiMn hydraulic bracket tube which is produced by Baogang as the object of study, and aims at the existing practical problems in the production process of hydraulic bracket tube, and takes advantage of Gleeble-1500D type to thermal simulate experimental machine and its rolling process, so as to get the true stress-true strain curve. And it studies the effects of different heat treatment processes after rolling on the performance of27SiMn steel. It provides a very important theory evidence for the optimization of the production process of27SiMn hydraulic bracket tube, including the improvement of product quality and decline of costs from the deformation process parameters on its austenite grain size, microstructure evolution rule and the effects of different heat treatment process on its toughness.According to the production process of27SiMn hydraulic bracket tube, it studies the evolution rule of austenite grain size in the rolling process of hydraulic bracket tube. And the study indicates that: the initial austenitic grain size of27SiMn steel used in this experiment is68.52um; while the austenite grain size is137.42um after growing up. The austenite grain size is81.82um after the simulation of the first pass of rolling and piercing, and the austenite grain size is54.39um after the simulation of the second pass of rolling and rolled tube, and the austenite grain size is50.21um after the simulation of the third pass of rolling and the development of reducing.It takes the advantage of thermal simulator to carry out single-pass thermal compression test to get the true stress under different temperatures and deformation rates-true strain curve, establishing the dynamic recrystallization mathematical model of27SiMn steel. Meanwhile, we can obtain its dynamic recrystallization activation energy is24.634KJ/mol by calculation, the expression of the thermal deformation equation isZ exp24.6341038.314T, it provides the theoretical basis for the optimization of the production process.In order to further optimize the heat treatment process of27SiMn hydraulic bracket tube after rolling, it studies the effects of process parameters, such as quenching temperature, tempering temperature and process parameters on the hardness and impact toughness. The study result shows that the variation regularity of hardness value is not significant when the temperatures of quenching from850℃up to980℃. With the combination of hardness and impact energy, it finally selects930℃with the thermal insulation of50minutes water quenching plus430℃with the thermal insulation of30minutes tempering cooled water process to carry out heat treatment, its comprehensive mechanical performance is the best.