Steel Sheet Yield Strength Slab Corner Cracking
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Solution Overview
Problem
High-strength steel sheets with high C and N contents are prone to cracking at slab corners during continuous casting due to poor high-temperature ductility, leading to increased costs and reduced yield from necessary surface grinding.
Innovation Solution
A steel sheet composition with reduced S and Al contents, combined with solid-solution strengthening using C and N, and grain refinement strengthening using P and Mn, along with controlled processing to prevent cracking at slab corners during continuous casting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high C and N contents are used for solid-solution strengthening to achieve high yield strength, then the yield strength increases, but the steel becomes prone to cracking at slab corners during continuous casting due to poor high-temperature ductility
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling S content to 0.005% or less and Al content to 0.030% or less, while maintaining high C (0.03-0.10%) and N (0.005-0.012%) contents. This parameter optimization prevents MnS and AlN precipitates at grain boundaries, resolving the contradiction between achieving high yield strength through solid-solution strengthening and preventing cracking during continuous casting.
2Strength
If high C and N contents are used to achieve yield strength of 450 MPa or more, then the strength requirement is met, but surface grinding becomes necessary due to slab corner cracking, reducing productivity and increasing cost
Solution Approach 1:
By optimizing the chemical composition parameters (C: 0.03-0.10%, N: 0.005-0.012%, S: 0.005% or less, Al: 0.030% or less, Mn: 0.50-1.50%), the invention achieves yield strength of 450 MPa or more while completely preventing slab corner cracking during continuous casting. This eliminates the need for surface grinding operations, thereby maintaining high production yield and reducing manufacturing costs.
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 steel sheet achieves a yield strength of 450 to 470 MPa without cracking at slab corners, maintaining strength while preventing embrittlement and ensuring ductility within the specified temperature range.
Implementation Method 1
high C and N contents, which function as solid-solution strengthening elements
Implementation Method 2
grain refinement strengthening using P and Mn
Data Source
AI summary
There is provided a steel sheet for a can, the steel sheet having a yield strength of 450 MPa or more, and the occurrence of cracking at a slab corner being prevented in a continuous casting process. A method for manufacturing the steel sheet is also provided. The steel sheet contains 0.03%-0.10% C, 0.01%-0.5% Si, 0.001%-0.100% P, 0.001%-0.020% S, 0.01%-0.10% Al, 0.005%-0.012% N, and the balance being Fe and incidental impurities, in which when Mnf = Mn [% by mass] - 1.71 x S [% by mass], Mnf is in the range of 0.3 to 0.6. The steel sheet has microstructures that do not contain a pearlite microstructure. Preferably, the S content is in the range of 0.001% to 0.005%, and/or the Al content is in the range of 0.01% to 0.04%. Solid-solution strengthening using solid-solution strengthening elements such as C and N and solid-solution strengthening and grain refinement strengthening using P and Mn result in a yield strength of 450 to 470 MPa. Furthermore, a reduction in S and/or Al content prevents cracking at a slab corner.