Core Mechanism of New-Generation TMCP and UFC Technology

TheNew generation TMCP (NG-TMCP) core of TMCPThermo-mechanical control process (TMCP) technology lies in the matching control of controlled rollingControlled rolling and controlled coolingControlled cooling. Firstly, the hardening state of austenite is controlled by the controlled rolling process, i.e., a large amount of energy is accumulated in austenite through rolling deformation, and the hardened austenite with a large number of deformation bands, dislocations, twins and other “defects” is obtained during rolling, laying the foundation for grain refinement in the subsequent phase transformation process. Then, the transformation process of hardened austenite is controlled by the controlled coolingControlled cooling process to further refine ferrite grains and obtain bainite and other strengthening phases through transformation strengtheningTransformation strengthening, so as to improve the comprehensive properties of the material. Because the “defects” in hardened austenite are the core of ferrite nucleation during phase transformation, the more “defects” the hardened austenite has, the higher the ferrite nucleation rate is, and the finer the ferrite grains are. Under the condition of relatively low cooling intensity of traditional controlled coolingControlled cooling, in order to obtain sufficient hardened austenite, the basic measures adopted are “low temperature high reduction” and adding micro-alloying elements. “Low temperature” is to inhibit the recrystallization of austenite and maintain its hardened state. “High reductionReduction” is to increase the deformation energy stored in hardened austenite. Adding micro-alloying elements such as Nb can increase the recrystallization temperature of austenite, and make austenite in the non-recrystallization zone maintain a relatively high temperature, which is convenient to realize the hardening state of austenite by conventional rolling system. It should be pointed out that the adoption of the “low temperature high reductionReduction” process runs counter to the long-standing concept of “strike the iron while it is hot”, and is bound to be limited by the equipmentEquipment capacity. In order to achieve the “low temperature high reductionReduction”, the rolling equipment capacity has to be greatly improved under the traditional TMCPThermo-mechanical control process (TMCP) conditions for a long time, and a lot of capital, manpower and resources have been invested.