Thermo Mechanical Control Processing in Rolling Mills Jul07

Thermo Mechanical Control Processing in Rolling Mills...

Thermo Mechanical Control Processing in Rolling Mills Thermo mechanical controlled processing (TMCP) is a technique designed to improve the mechanical properties of materials by controlling the hot-deformation process in a rolling mill. This was originally designed to produce the required external shape of the product. Controlled rolling, controlled-cooling and direct-quenching are typical examples of thermo mechanical controlled processing. Such processing saves energy in the manufacture of steel by minimizing or even eliminating the heat treatment after hot-deformation, thus increasing the productivity for high grade steels. It normally requires a change in alloy design and often reduces the productivity of the hot deformation process itself, but at the same time makes it possible to reduce the total amount of alloying additions and to improve weldability, whilst sometimes producing new and beneficial characteristics in the steel. TMCP process has several advantages that can help overcome issues related to the addition of major alloying elements and conventional heat treatments. TMCP steels with added micro alloys have been developed to manage the conflicting requirements of strength, toughness and weldability through grain refinement. TMCP effectively enables a reduction of the preheating temperature, thus lowering the rolling cost. As TMCP steels afford good weldability, they are highly valued in industries such as shipbuilding, offshore structures, pipelines and building construction. TMCP is the sophisticated combination of well-defined deformation operations and well-defined heat treatment in a single production stage to control the microstructure of the steel being rolled. TMCP produces steels with the desired external qualities (dimensions, shape and surface quality) and acceptable mechanical properties. TMCP is normally considered as the final stage in the production of steels. TMCP is generally associated with hot rolling operations in hot strip mills, plate mills and bar and rod mills. For example, in case of...

TMCP Steels

TMCP Steels TMCP stands for Thermo Mechanical Control Process and TMCP steels are those steels which are produced by this process. TMCP is a microstructural control technique combining controlled rolling (thermo mechanical rolling) and controlled cooling (accelerated cooling). These steels are sometimes microalloyed. Thermo mechanical control process is normally used to obtain excellent properties for steel plates such as high strength, excellent toughness along with excellent weldability through maximizing of grain refinement. These steels have almost same formability and weldability compared with mild steels. The superior mechanical properties introduced to the steel through this processing route are virtually equivalent to those obtained by heat treating conventionally rolled or forged steel and hence Thermo mechanical control process is used as a substitute for heat treatments that require additional material handling and furnace facilities. TMCP technology was developed early in 1980s and major Japanese plate rolling mills have started to produce TMCP steels by middle of 1980s. TMCP steels production When TMCP is chosen as the process route, the input material (i.e. the slab) is heated to a temperature regularly used for hot rolling operations (around 1200 deg C). The roughing operation during rolling in the rolling mill is carried out in a normal way, but the finish rolling is carried out at a lower temperature (around 750 deg C to 800 deg C) than the temperatures used in a normal rolling process. Plastic deformation at this lower temperature promotes fine grain sizes and retards precipitation. The final hot working may continue down to temperatures below the critical temperature of transformation from austenite to ferrite. This requires heavy rolling equipment capable of deforming the steel at low hot working temperatures. The optimum precipitate size and dispersion is obtained when the finish rolling temperature is around 775...