The equipment of a state-of-the-art high-performance hot strip mill includes heat insulation hoods. They are positioned between roughingst and finishing mill to prevent temperature loss of the transfer bar in order to keep strip temperature at an optimum level for processing in the finishing mill. Heat insulation hoods must be resistant to high temperature fluctuations. These are due to the fact that the hot strip underneath the insulation hoods is running discontinuously as a consequence of the respective process. The temperature variations caused by radiation are enormous and expose the equipment to high stress by thermal tension. Conventional heat insulation hoods are susceptible to wear reducing the insulating efficiency. To keep operation safe despite the adverse conditions, maintenance and servicing require labor-intensive effort, which has a detrimental impact on operating costs. SMS group has dedicated to the challenge, developed and already tried and tested a new, efficient system
Heat loss reduced by 50 percent
The new HIBOX heat insulation hood system of SMS group is installed above the connecting roller table between roughing stand and finishing mill and cuts the heat loss over the entire transfer bar length between strip head and tail by up to 50 percent depending on the boundary conditions, which clearly reduces temperature speed-up in the finishing mill. In addition, the rolling process is more stable and the product mix can be expanded towards smaller final- thickness products and/or higher-strength grades. The HIBOX system hence boosts the productive efficiency of the hot strip mill. HIBOX hoods are arranged above the feed roller table as hinged elements. They are mounted on an assembly plate and allow for individual replacement in case of damage. Each HIBOX hood consists of several HIBOX modules. This design permits individual HIBOX modules to be replaced within the scope of maintenance and greatly simplifies module inspection and maintenance. A single HIBOX module is composed of several steel plate boxes (HIBOX) of manageable size, each thereof filled with insulating material. The HIBOX gave its name to the system and is the basic component thereof. The completely modular design concept offers the benefit of greater resistance to load and wear occurring in the process. The HIBOX system can be integrated in every hot strip mill. Being the smallest unit of this system, the HIBOX can be installed respectively retrofitted in all existing heat insulation hood setups. This means the new HIBOX system developed by SMS group will increase the efficiency and life cycle of existing heat insulation hoods, too.
In the meantime, several tests have provided evidence of the HIBOX system attaining a manifold longer service life than conventional heat insulation hoods do. This additionally opens up the opportunity to provide the HIBOX with thinner membrane plates than used for conventional heat insulation hoods thus ensuing targeted optimization of the insulating efficiency. Experience from the HIBOX pilot installation showed a lifetime triple that of the installed conventional heat insulation hoods. The HIBOX cassette can be recycled or reused a second time after turning. Pilot tests of the HIBOX system performed by SMS group in numerous hot strip mills of different capacities revealed remarkable results. The first high-performance hot strip mill to be completely equipped with HIBOX-system heat insulation hoods is the new hot strip mill at PT Krakatau Steel in Indonesia, which is being established by SMS group. This new hot strip mill is designed for a maximum strip width of 1,650millimeters and an annual capacity of 1.5 million tons in the first construction stage with the option to later increase production to four million tons. In addition to other innovative rolling technologies from SMS group, it is the efficient HIBOX heat insulation hood system in particular that will make the hot strip mill of PT Krakatau Steel rank among the most advanced plants of this kind in the world