High-Strength Steel via Twin-Roll Casting and Gas Cooling
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Solution Overview
Problem
The traditional processes for producing high-strength, thin-gauge, high-corrosion-resistant steel face challenges such as long production flows, high energy consumption, and limited thickness range due to macrosegregation and poor formability, which hinder the production of steel with enhanced corrosion resistance and cost-effectiveness.
Innovation Solution
The use of a thin strip continuous casting process with controlled basicity, twin-roll casting, and gas atomization cooling to produce steel with specific chemical compositions and microstructures, including bainite or acicular ferrite, and the addition of boron and micro-alloy elements like Nb and V to enhance strength and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional multi-pass continuous rolling of cast slab is used, then steel strip can be produced with required thickness, but production cost increases due to long process flow, high energy consumption, and large number of unit devices
Solution Approach 1:
The traditional multi-pass rolling process is segmented into a single-pass thin slab continuous casting process. The cast slab thickness is reduced to 50-90mm, allowing direct production of thin steel strips (≤1.5mm) in one pass without multiple intermediate rolling passes, thereby simplifying the process flow and reducing device complexity
Solution Approach 2:
The cast slab thickness parameter is changed from traditional 70-200mm to 50-90mm, enabling the steel strip to be produced directly at the required thin gauge thickness in a single continuous casting pass, eliminating the need for subsequent cold rolling and annealing operations
2Use of energy by stationary object
If thin slab continuous casting and rolling process is used, then process flow is shortened and energy consumption reduced, but steel strength and yield ratio increase due to fast cooling rate, limiting the thickness gauge to ≥1.5mm
Solution Approach 1:
The cooling rate parameter is optimized by controlling the thin slab thickness (50-90mm) and hot rolling temperature (1000-1200°C), achieving a balanced microstructure with yield strength ≥480 MPa and tensile strength ≥600 MPa while maintaining formability and enabling production of steel strips at thicknesses ≤1.5mm
3Strength
If fast cooling rate is applied in thin slab continuous casting, then steel strength increases, but rolling load increases and formability deteriorates
Solution Approach 1:
The hot rolling temperature parameter is optimized to 1000-1200°C, maintaining austenite phase stability and good formability during rolling, while the controlled cooling rate after rolling achieves the desired strength (yield strength ≥480 MPa, tensile strength ≥600 MPa) without excessive yield ratio, thus preserving formability for downstream processing
4Manufacturing precision
If traditional hot rolling process is used for thin strip ≤1.5mm, then steel strip can be produced, but subsequent cold rolling and annealing are necessary, increasing production cost
Solution Approach 1:
The thin slab continuous casting process performs preliminary action by directly producing the steel strip at the final required thickness (≤1.5mm) with the desired microstructure in one pass, eliminating the need for subsequent cold rolling and annealing operations, thereby improving production efficiency and reducing production cost
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 approach results in high-strength steel with yield strengths of ≥480 MPa, tensile strengths of ≥600 MPa, elongation of ≥22%, and relative corrosion rates of ≤25%, while reducing production costs and improving surface quality and formability.
Implementation Method 1
The molten steel solidifies on the circumferential surfaces of the rotating crystallization rolls to form a solidified shell which gradually grows, and then forms a 1.5-3 mm thick cast strip
Implementation Method 2
The rolled strip steel is cooled by gas atomization cooling. The gas atomization cooling can effectively reduce the thickness of the oxide scale on the surface of the strip steel, increase the temperature uniformity of the strip steel, and improve the surface quality of the strip steel
Implementation Method 3
The slab produced by continuous casting passes through an induction heating roll table to effect heat preservation and soaking on the slab
Implementation Method 4
the slab enters the rough rolling, finish rolling, laminar cooling, and coiling processes to obtain a hot-rolled plate
Data Source
AI summary
Disclosed are a high strength thin specification high corrosion resistance steel and a manufacturing method therefor. The chemical ingredients of the steel in percentages by weight are as follows: 0.02-0.06% of C, 0.1-0.5% of Si, 0.4-1.7% of Mn, ≤0.02% of P, 4.0-6.0% of Cr, 1.0-3.0% of Ni, ≤0.007% of S, 0.004-0.010% of N, <0.001% of Als, 0.001-0.006% of B, 0.007-0.020% of total oxygen [O]T, and the balance is Fe and inevitable impurities, and same simultaneously satisfy: comprising one or both elements of 0.01-0.08% of Nb or 0.01-0.08% of V; and Mn/S≥250. In the invention, micro-alloy elements such as Nb/V and a B element are selectively added to steel, the basicity of slag, the type and melting point of the inclusion in steel, the content of free oxygen in molten steel and the content of acid-soluble aluminum Als during the smelting process are controlled, and a strip is then cast by means of twin-roll thin strip continuous casting, and enters an online rolling mill for hot rolling in closed conditions, and after rolling, the strip steel is cooled by air atomization cooling.