What temperatures do TB RT, RDT, TIT, FDT and CT respectively represent in hot continuous rolling?
TB (Billet Temperature
Representing the temperature of the billet, it refers to the temperature of the slab before it enters the heating furnace. This temperature mainly depends on the source of the billet and the previous processing conditions. For instance, the billet coming out of the continuous casting machine may have a relatively high temperature, but after a certain period of cooling, storage and transportation, the temperature will drop. In some hot continuous rolling production lines, the temperature of the billet may approach room temperature.
RT (Reheating Temperature
It is the reheating temperature of the heating furnace, that is, the temperature to which the slab is heated in the heating furnace before entering the roughing mill. This temperature is crucial for ensuring that the slab has good plastic deformation capacity. Different steel grades and slab sizes have different requirements for RT. For instance, for common carbon steel, RT is generally around 1100-1250℃. For alloy steels containing a relatively high amount of alloying elements, since alloying elements can affect the thermal properties of the steel, RT may be higher to ensure the uniform distribution of alloying elements in the steel and good hot working performance.
RDT (Roughing Delivery Temperature
It indicates the final rolling temperature of rough rolling, which is the temperature of the strip steel at the exit of the last rough rolling mill in the rough rolling stage. This temperature will have a significant impact on the process conditions of the subsequent finishing rolling stage and the final performance of the steel. If the RDT is too high, the grains of steel are prone to grow during rough rolling, which affects the strength and toughness of the final product. If the RDT is too low, it will increase the rolling force for subsequent finishing rolling, which may lead to problems such as equipment overload. Generally speaking, the final rolling temperature of rough rolling may be around 1000-1100 ℃ depending on the steel type and rolling process.
TIT (Transfer Bar Intermediate Temperature)
It is the intermediate billet transfer temperature, that is, the temperature of the intermediate billet after rough rolling before it is conveyed to the finishing mill. During the conveying process, the intermediate billet will experience a temperature drop due to factors such as thermal radiation and convection. Reasonable control of TIT has a certain correlation with the temperature control in the finishing rolling process and the quality of the final product. For instance, in some efficient hot continuous rolling production lines, by optimizing the conveying speed of intermediate billets and insulation measures, etc., TIT can be controlled at around 900-1000 ℃, providing favorable initial conditions for the finishing rolling process.
FDT (Finishing Delivery Temperature)
It refers to the final rolling temperature of finishing rolling, which is the temperature of the strip steel at the exit of the last rolling mill in the finishing stage of hot continuous rolling. It has an extremely important influence on the final properties of steel, including grain size, microstructure and morphology, etc. For instance, when manufacturing some high-strength automotive steels, to refine the grain structure, FDT is usually controlled at around 800-900 ℃, which enables a better balance between the strength and toughness of the steel.
CT (Coiling Temperature
It represents the coiling temperature, that is, the temperature at which the hot-rolled strip steel leaves the finishing mill and enters the coiling machine for coiling operation. The coiling temperature has a significant impact on the microstructure and properties of steel, especially on its phase transformation behavior. For instance, when manufacturing some low-carbon steels with good deep drawing performance, by controlling the coiling temperature at around 600-700 ℃, the steel can obtain a microstructure conducive to deep drawing, such as fine-grained ferrite and an appropriate amount of pearlite structure.
Other temperature abbreviations
T0 (Initial Temperature) : It can represent the initial temperature. In the hot continuous rolling process, it may refer to the initial temperature after the heating furnace is taken out of the furnace or the temperature at the beginning of a certain process stage.
TR (Roughing Temperature) : Roughing temperature, which can sometimes be further divided into roughing inlet temperature and roughing outlet temperature, etc. Generally, the roughing outlet temperature is abbreviated as TR2.
TCT (Coiling Temperature) : Synonymous with CT, it is another way of writing to indicate the coiling temperature.
TD (Delivery Temperature) : Delivery temperature, that is, the temperature at which the product is delivered. However, strictly speaking, it is not the temperature control stage in the hot continuous rolling process, but it is sometimes mentioned.
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