Press-Hardened Steel Sheet Composition for Isotropic Bending
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Challenging to produce very high strength steels with uniform resistance to crack formation under bending and isotropic bending behavior, which affects the crash worthiness and design of automotive parts.
Innovation Solution
A steel sheet with controlled chemical composition and microstructure, including specific ranges of elements like carbon, manganese, silicon, and inclusions, combined with a refining process to manage inclusion population, resulting in a press hardened steel part with high tensile strength and low bending anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If very high strength steel is produced to achieve high tensile strength above 1300 MPa, then mechanical strength is improved, but bending resistance deteriorates and crack formation occurs early under bending load
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (carbon content 0.23-0.37%, manganese 1.00-2.00%, silicon 0.10-0.50%) and inclusion characteristics (clustering index ≤ 300 μm/mm²) to achieve a balance between high tensile strength and improved bending resistance, transforming the material properties to resolve the contradiction
Solution Approach 2:
The patent creates a composite microstructure consisting of martensite as the primary phase with controlled inclusion distribution, where the specific combination of alloying elements and inclusion characteristics produces a composite material system that simultaneously achieves high strength and improved bending performance
2Ease of manufacture
If conventional steel sheet is used, then manufacturing is simple, but bending behavior is anisotropic with better performance in rolling direction than transverse direction
Solution Approach 1:
The patent applies homogeneity by controlling the inclusion distribution and microstructure to be uniform throughout the steel sheet, eliminating the directional differences in bending behavior. The clustering index control ensures homogeneous distribution of inclusions, making the bending performance isotropic across different directions while maintaining conventional manufacturing processes
Data Source
AI summary
A steel sheet has a chemical composition including in wt % C: 0.2-0.4%, Mn: 0.8-2.0%, Si: 0.1-0.5%, Al: 0.01-0.1%, Ti: 0.01-0.1%, B: 0.0005-0.005%, P≤0.040%, Ca≤0.01%, S≤0.006%, N≤0.01%. The steel sheet includes from the bulk to the surface of the coated steel sheet a bulk and a skin layer occupying the outermost 10% of the thickness on either side of the bulk. The bulk includes an inclusion population in which the sum of clustering indexes of MnS and TiN/Ti(C,N) inclusions is less than or equal to 300 μm/mm2. This allows to manufacture hot pressed parts having a tensile strength equal to or greater than 1300 MPa and a bending anisotropy equal to or lower than 7°.