Research Of H-beam Steel After Ultra Fast Cooling

As a kind of environmental protectial steel, H-beam steel is attached importance in recent years. Becauce of more and more strict demands on H-beam steel in all sectors, it have a practical application prospect to manufacture the H-beam which incorporate favorable integrated,uniform mechanical properties over their cross-section and high strength.Ultra fast cooling technology is a high cooling rate method, which developed in recent years, It is mainly used in thermal processing of steel in the process of rapid cooling after rolling, to improve the comprehensive mechanical properties of steel, the use of performance and productivity, in the hot-rolled steel plate and rods production line has gradually become a mature technology, while in the H-beam production line, there didn't form a mature cooling theory and technology.This thesis takes Q235 H-beam steel, and the Q235, Q345 and Q450 plate steel of different thickness as research object, using for ultra fast cooling technology research. In laboratory conditions, it experiment and simulating the rolling and cooling process of H-beam. The cooling process was explored according to using different parameters; the strengthening principle was studied by analysis the microstructure and the comparison comprehensive properties, and using ANSYS FEM analysis software to simulate the cooling process. The main works and results involved are as follows:(1) Cooling water pressure, water flow and cooling time were considered for the effect on H-beam ultra fast cooling. By changing the process parameters, reducing the surface temperature of H-beam in a short time could be achieved, and complete the strengthening process. The total water pressure controlled on about 0.7MPa as the best, it has a 300℃-500℃temperature dropping in 2-3 seconds, the cooling rate reached 150℃per second, and the various parts of steel is temperature uniformity, non-deformation after cooling.(2) By studying the cooling process, the strengthening principle of the H-beam steel ultra fast cooling was analysed, because the steel which is above the austenite temperature, have a wide-range of temperature dropping in a short period of time, austenite in a larger degree of supercooling, occurred bainite transformation, formed the higher strength and hardness bainite grains, thus to strengthen of steel. After ultra fast cooling, the H-beam steel grains were refinable, mechanical properties have a general increase(3) The temperature fields of H-beam section during different cooling conditions were accurate simulated by using ANSYS FEM software. To gain uniform section temperature after cooling, heat transfer coefficients at different parts of the section were optimized, the results of the optimization indicated that, the heat transfer coefficient of inner and outer R-section should be larger and the flange and web should be smaller. The thesis provides a theoretical basis for the production of H-beam steel.