Normalizing heat treatment is an important technology to improve the toughness of steel plate. Its characteristic is to heat the steel plate to 30 ℃ ~ 50 ℃ or higher above the upper critical point of ferrite austenite transformation, so that the steel can be austenitized and cooled in free atmosphere after homogenization of heat preservation.
In the conventional normalizing heat treatment process, after normalizing and air cooling, ferrite grains will still grow, resulting in low strength of steel plate. If the controlled cooling rate is adopted after normalizing, the transformation temperature can be reduced, the transformation type can be controlled, the transformation structure can be refined, and the growth of carbonitride of microalloyed elements can be inhibited, so that it can disperse and precipitate at low temperature, so as to improve the strength of steel and keep the toughness of steel unchanged.
From the point of view of composition design, under the condition of ensuring the same mechanical properties, the content of carbon or alloy elements in steel can be reduced, so as to improve the weldability of steel. For this reason, the relevant researchers or manufacturers have carried out exploratory research and development on the normalized cooling equipment and process, and achieved some results.
After normalizing furnace control cooling system (NCC - N ORM a lizing contro LLE cooling). The NCC system is set after the roller hearth normalizing furnace, after the medium and thick steel plates are heated out of the furnace, they are controlled and cooled by the NCC system, the steel plates are rapidly cooled to the phase change temperature, and then cooled in the cooling bed. Some are equipped with straighteners after NCC equipment.
On 2018-08-08 11:45:46
