Hot-Pressed Steel Sheet Surface Control for Coating Clarity
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Solution Overview
Problem
Existing hot-pressed steel sheets with increased strength face challenges in achieving both post-coating image clarity and corrosion resistance, particularly in automotive applications where complex shapes are required.
Innovation Solution
The surface of the hot-pressed members and steel sheets for hot pressing are configured with specific geometric parameters such as filtered centerline waviness (Wca) and line roughness (Ra) to enhance post-coating image clarity, and a plated layer of Al, Zn, or Fe is applied to improve corrosion resistance, with coating layers added for further enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel sheet strength is increased, then corrosion resistance and formability are improved, but surface roughness correction becomes difficult and post-coating image clarity deteriorates
Solution Approach 1:
The patent applies preliminary action by controlling the surface geometry parameters (filtered centerline waviness Wca ≤ 1.5 μm and line roughness Ra ≤ 2.0 μm) of the steel sheet before hot pressing and coating. This pre-control of surface characteristics ensures that even after hot pressing and coating processes, the final surface maintains excellent image clarity without requiring post-processing correction.
2Strength
If steel sheet strength is increased, then formability is improved, but post-coating image clarity deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling surface geometry parameters (filtered centerline waviness Wca and line roughness Ra) within specific ranges. By changing and optimizing these surface parameters before hot pressing, the invention achieves both high strength and excellent post-coating image clarity, resolving the contradiction between strength and surface quality.
3Manufacturing precision
If a panel member with low strength and excellent appearance is disposed on the outer surface, then appearance quality is improved, but device complexity increases
Solution Approach 1:
The patent applies the taking out principle by extracting the appearance quality function from a separate panel member and integrating it directly into the hot-pressed member itself. Through precise control of surface geometry parameters and application of plated layers, the hot-pressed member achieves both high strength and excellent appearance quality, eliminating the need for an additional panel member and reducing structural complexity.
4Reliability
If plated layer is applied to improve corrosion resistance, then corrosion resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies merging by combining the corrosion protection function with the surface geometry control in a single integrated process. The plated layer (containing Al, Zn, or Fe) is applied to the hot-pressed member with controlled surface parameters, achieving both corrosion resistance and excellent post-coating image clarity without requiring separate manufacturing steps for each function.
Data Source
AI summary
A hot-pressed member is disclosed including at least one surface that has a filtered centerline waviness Wca of less than or equal to 1.5 μm.