Steel Section Rolling with Selective Cooling for Uniform Toughness
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Solution Overview
Problem
Existing steel section manufacturing methods struggle to achieve uniform physical properties and low-temperature impact toughness, particularly in medium or small-sized sections, due to temperature differences and deformation during cooling, especially in three-dimensional shapes with thickness variations.
Innovation Solution
A method involving reheating steel with specific alloy compositions and controlling the rolling process using a selective cooling device to manage cooling rates and temperatures, ensuring a microstructure with ferrite and pearlite, and grain sizes of 10 µm or less, with controlled yield strength differences between flange parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If TMCP is applied to hot rolling to achieve grain refinement effect, then low-temperature impact toughness is improved, but temperature differences and deformation occur during cooling due to three-dimensional shape and thickness differences
Solution Approach 1:
The patent applies selective cooling to different regions of the steel section based on their specific thermal characteristics. The cooling device sprays cooling water selectively on the flange portions rather than uniformly across the entire section, addressing the thickness differences between flange and web to achieve uniform microstructure and physical properties throughout the section.
Solution Approach 2:
The patent controls the cooling process by adjusting the temperature parameters during rolling. The rolling temperature is maintained within a specific range (900-1100°C) and the cooling rate is controlled to achieve the desired microstructure (ferrite and pearlite) while minimizing temperature differences between different parts of the section.
2Strength
If TMCP is used in manufacturing medium or small-sized steel sections, then high-strength impact toughness is achieved, but cooling proceeds too quickly and the cooling rate cannot be precisely controlled
Solution Approach 1:
The patent introduces a selective cooling device as an intermediary between the rolling process and the final product. This device allows precise control of the cooling rate by selectively applying cooling water to specific regions, mediating between the rapid cooling tendency and the desired controlled cooling rate for medium and small-sized sections.
Solution Approach 2:
The cooling process is made dynamic and adjustable rather than fixed. The selective cooling device can adapt its cooling intensity and distribution based on the specific requirements of different section sizes and shapes, allowing precise control of the cooling rate throughout the manufacturing process.
3Ease of manufacture
If conventional hot rolling is used, then manufacturing simplicity is maintained, but uniform physical properties and low-temperature impact toughness cannot be achieved
Solution Approach 1:
The patent prepares the steel for optimal performance by controlling the microstructure formation during the rolling process. By maintaining the rolling temperature within a specific range and applying selective cooling, the desired ferrite and pearlite microstructure is formed in advance, ensuring low-temperature impact toughness is achieved during the manufacturing process itself rather than requiring subsequent treatments.
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
The method produces high-performance steel sections with uniform physical properties, achieving yield strengths of 420 MPa or more, low-temperature impact toughness of 50 J or more, and minimal yield strength differences between flange parts, enhancing stability and weldability.
Implementation Method 1
the rolling intermediate temperature is controlled by spraying cooling water from a selective cooling (S/C) device
Implementation Method 2
reheating steel to a temperature of 1150 to 1300 °C
Data Source
Figure 1
Figure 2~3a
Figure 3b
AI summary
A method for manufacturing a steel section, according to an embodiment of the present invention, comprises the steps of: (a) reheating steel to 1150-1300 °C, the steel comprising 0.04-0.14 wt% of carbon (C), 0.10-0.55 wt% of silicon (Si), 0.90-1.65 wt% of manganese (Mn), 0.020 wt% or less of phosphorus (P), 0.007 wt% or less of sulfur (S), 0.015-0.055 wt% of aluminum (Al), 0.010-0.080 wt% of vanadium (V), 0.005-0.025 wt% of titanium (Ti), 0.010-0.050 wt% of niobium (Nb), and the remainder of iron (Fe) and other inevitable impurities; and (b) rolling the steel, wherein the rolling start temperature is 900-1100 °C, the rolling medium temperature is 850-1000 °C, and the rolling end temperature is 800-900 °C. Accordingly, it is possible to realize a high-performance steel section which achieves uniform physical properties while securing low-temperature impact toughness and a method for manufacturing the steel section.