What is Controlled Rolling and Controlled Cooling?

Within the industry, there are two ways to interpret controlled rolling and controlled cooling.

The first is the split approach, which separates the process into controlled rolling (CR) and controlled cooling (AC/ACC, controlled cooling/accelerate cooling).

This view treats rolling and post-rolling cooling as two independent processes that can be used individually or combined, and early steel production lines mostly employed either CR or AC alone.

The second is the integrated concept, corresponding to the English term TMCP (thermal-mechanical control processing), which can be literally translated as thermal-mechanical rolling or thermal treatment, but a more fitting translation for the original meaning is 'comprehensive control of temperature and forming.' In China’s rolling field, it’s commonly referred to as controlled rolling and controlled cooling.

TMCP treats the entire hot rolling production line as a complete system, coordinating the temperature and deformation throughout the process, without separating rolling and cooling stages anymore.

Both approaches share the same core goal—regulating the microstructure and properties of steel—but differ in perspective: CR and AC focus on two separate process units, while TMCP emphasizes integrated process coordination.

Chinese literature often mixes the terms 'controlled rolling and controlled cooling,' 'controlled rolling,' and 'controlled cooling,' whereas English literature mainly uses TMCP. When publishing English papers, Chinese researchers consistently use TMCP as the standard term.

The full definition of controlled rolling and controlled cooling can be summarized as: a hot-rolling production process that online controls the deformation, temperature, and time of the rolled product to achieve the desired microstructure and mechanical properties.

Here, 'online' has a specific boundary, referring to the entire main hot-rolling process from when the steel billet comes out of the furnace to the completion of post-rolling cooling. Any secondary processing or offline heat treatment performed after the steel has fully cooled to room temperature is not part of controlled rolling and controlled cooling.

Controlled rolling and controlled cooling rely on the hot-rolling line to achieve online microstructure toughening. By coordinating deformation, temperature, time, and cooling rate, high-strength, high-toughness hot-rolled steel can be produced without subsequent offline heat treatment.

Compared with processes that control only rolling or only post-rolling cooling, the integrated TMCP approach can fully tap steel’s performance potential, simplify production steps, and reduce manufacturing costs, making it an indispensable core process for modern high-end hot-rolled steel production.