Continuous Casting and Direct Heating for Low-Defect Steel Strip
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Solution Overview
Problem
Conventional integrated steelworks are energy-inefficient, produce high CO2 emissions, and result in surface defects in hot strips due to separation of production steps and intermediate cooling, making them unsuitable for producing high-quality steel strips with demanding surface requirements.
Innovation Solution
A method involving the production of steel melts with specific chemical compositions using electrically operated melting units, continuous casting, and direct heating to temperatures above the austenite-ferrite transformation temperature, followed by rolling, to minimize surface defects and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional integrated steelworks are used with separated production steps and intermediate cooling, then production planning and location separation are enabled, but energy efficiency deteriorates and CO2 emissions increase
Solution Approach 1:
The patent merges the steelmaking process and continuous casting process into an integrated steelmaking-continuous casting unit, eliminating the separation between these processes. This allows the molten steel to flow directly from the converter to the continuous casting machine without intermediate cooling and storage, thereby maintaining high temperatures and improving energy efficiency while enabling flexible production planning.
2Ease of manufacture
If conventional integrated steelworks with slab storage and intermediate cooling are used, then production steps can be separated in time and location, but surface defects occur in hot-rolled strips
Solution Approach 1:
The patent implements a continuous production process where molten steel flows directly from the converter through the continuous casting machine to produce slabs that are immediately fed to the hot rolling mill. This continuous action eliminates intermediate cooling and storage steps, preventing surface defects such as oxidation and scaling that occur during prolonged exposure to air at high temperatures, thereby maintaining high surface quality.
3Area of stationary object
If electric arc furnaces with charge weights above 100t and melting times less than 50min are used, then space requirements are reduced, but decarburization and denitrogenation to required levels become insufficient
Solution Approach 1:
The patent optimizes the operating parameters of the electric arc furnace by controlling the charge weight to be above 100 tons and the melting time to be less than 50 minutes. By precisely controlling these parameters, the furnace achieves efficient decarburization and denitrogenation of the steel melt, reducing carbon to below 150 ppm and nitrogen to below 50 ppm, while maintaining a compact plant footprint.
4Ease of manufacture
If slabs are cooled to room temperature before further processing, then production steps can be separated, but direct feed heating becomes energy-inefficient
Solution Approach 1:
The patent employs preliminary action by maintaining the slabs in a hot state immediately after continuous casting and transporting them directly to the hot rolling mill without cooling to room temperature. The slabs are kept at high temperatures through continuous production flow and thermal insulation during transfer, eliminating the need for energy-intensive reheating and significantly reducing heating energy consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables energy-saving production of high-quality hot-rolled steel strips suitable for further processing into cold-rolled and coated strips, reducing CO2 emissions and investment costs while minimizing surface defects, thus meeting the requirements for demanding applications like automobile outer skin materials.
Implementation Method 1
melting of solid, iron-containing starting material in a preferably electrically operated melting unit (for example in the form of an electric arc furnace)
Implementation Method 2
electrically operated melting unit
Implementation Method 3
feeding the melt into a vacuum system and decarburising the melt in the vacuum system
Implementation Method 4
feeding the melt pretreated in this way into the continuous casting plant; pouring the melt in the continuously operating continuous casting plant
Implementation Method 5
feeding the strand or the slabs produced from it into the heating unit and setting the required rolling temperature
Implementation Method 6
feeding the heated strand or slabs into the rolling mill and rolling the strand or slabs out to strip
Data Source
Figure 1
AI summary
The invention relates to a method for producing steel strip, wherein first molten steel is produced, which is then formed into a strand (3) in a continuous casting plant (2), the strand (3) is subsequently directed into a heating unit (4) and then into a rolling mill (5). To be able to produce hot-rolled steel strips using as little energy as possible and to further process the strips, according to the invention, first molten steel is produced, wherein: a) starting material is melted; b) iron- and carbon-containing solid starting materials as well as air, oxygen and/or natural gas are supplied; c) the molten material is fed into a vacuum system (7); d) the molten material is fed to the continuous casting plant (2); e) the molten material is cast; f) the strand (3)/the slabs is/are fed to the heating unit (4); g) the strand (3)/the slabs is/are fed to the rolling mill (5) and the strand/the slabs is/are rolled to form the hot strip (1).