Hot-Rolled Steel Processing for Strength and Low-Temperature Toughness
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Solution Overview
Problem
Producing steel with both high yield strength and high impact toughness is challenging, as enhancing one property often diminishes the other, making it difficult to achieve both simultaneously.
Innovation Solution
A method involving continuous casting and hot-rolling of steel with specific composition and temperature control to produce a steel slab with a yield strength greater than 550 MPa and impact toughness of at least 27 J, eliminating unnecessary processing steps like cooling and reheating, which reduces the number of stations and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional steel production methods are used to enhance yield strength, then strength increases, but impact toughness decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling chemical composition parameters (carbon content 0.15-0.40%, silicon content 0.01-2.00%, manganese content 0.01-2.00%, etc.) and processing parameters (slab temperature 800-1000°C, rolling temperature 800-1000°C, cooling rate 5-50°C/s) to achieve both ultra-high yield strength (>550 MPa) and high impact toughness (≥27 J) simultaneously, resolving the traditional trade-off between strength and toughness
Solution Approach 2:
The patent creates a composite microstructure consisting of ferrite and martensite phases through controlled composition and thermomechanical processing. The specific alloying elements (C, Si, Mn, Ti, Nb, V, B) work synergistically to form a dual-phase microstructure that combines the ductility of ferrite with the strength of martensite, achieving both high strength and high impact toughness
2Use of energy by stationary object
If multiple processing steps (cooling and reheating) are eliminated to reduce energy consumption, then energy efficiency improves, but manufacturing precision may deteriorate
Solution Approach 1:
The patent applies preliminary action by performing alloying and inclusion control during the initial steelmaking and continuous casting stages. The chemical composition is optimized in advance to enable direct hot-rolling without intermediate cooling and reheating, while still achieving the desired microstructure and properties through controlled cooling during rolling
Solution Approach 2:
The patent maintains manufacturing precision by implementing precise parameter control during the simplified process: chemical composition parameters are tightly controlled, slab temperature is maintained at 800-1000°C, rolling temperature is controlled at 800-1000°C, and cooling rate is regulated at 5-50°C/s. These controlled parameter changes ensure consistent ultra-high strength and high impact toughness properties even without intermediate cooling and reheating steps
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
Results in ultra-high strength and high impact toughness with improved formability, weldability, and reduced carbon equivalence, achieving a smaller footprint and lower energy consumption while maintaining high strength and toughness.
Implementation Method 1
The steel slab is heated to maintain a predetermined temperature
Implementation Method 2
The melted steel is poured into a mold. The metal steel is continuously cast into a steel slab
Data Source
AI summary
A method is used to fabricate a hot-rolled steel having a yield strength greater than 550 MPa and an impact toughness of at least 27 J at a temperature of -40° F. In one embodiment, the yield strength is greater than 690 MPa. The method includes melting steel to create melted steel. The melted steel is poured into a mold. The metal steel is continuously cast into a steel slab. The steel slab is heated to maintain a predetermined temperature. The steel slab is rolled to reduce the thickness to a predetermined thickness to create a hot-rolled steel sheet.