Alloyed Hot-Dip Galvanized Steel Sheet Surface Uniformity
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Solution Overview
Problem
Conventional alloyed hot-dip galvanized steel sheets face issues with non-uniform surface properties, poor plating wettability, formation of plating streaks, sticking to dies during press working, and secondary work embrittlement, which affect their appearance and productivity.
Innovation Solution
An alloyed hot-dip galvanized steel sheet with a specific chemical composition and microstructure, including a base steel sheet with controlled elements and grain diameter, and a plating layer composition that enhances wettability and alloying speed, reducing streak formation and embrittlement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alloyed hot-dip galvanized steel sheet is used, then basic plating function is achieved, but surface uniformity is poor and plating streaks form
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the base steel sheet (C: 0.0005-0.0100%, Si: 0.01-0.50%, Mn: 0.01-1.30% or 1.70-2.00%, P: 0.100% or less, S: 0.010% or less, Ti: 0.040-0.180%, Nb: 0-0.100%, B: 0.0005-0.0100%) and the microstructure parameter (average grain diameter ≤7.5 μm) to eliminate plating streaks and improve surface uniformity. The specific compositional ranges and grain size control create optimal conditions for uniform plating deposition.
Solution Approach 2:
The patent applies local quality by creating a specific microstructure with controlled grain distribution and composition uniformity throughout the base steel sheet. The average grain diameter of 7.5 μm or less ensures consistent local properties across the material, which promotes uniform plating penetration and prevents localized streak formation.
2Reliability
If conventional alloyed hot-dip galvanized steel sheet is used, then plating is formed, but wettability of plating to base steel sheet is insufficient
Solution Approach 1:
The patent improves plating wettability by optimizing the chemical composition parameters of the base steel sheet, particularly the controlled ranges of Mn (0.01-1.30% or 1.70-2.00%), Si (0.01-0.50%), and P (0.100% or less), along with the average grain diameter of 7.5 μm or less. These parameter optimizations create a base steel sheet surface that promotes better wetting and adhesion of the plating layer, eliminating plating defects.
3Ease of manufacture
If alloyed hot-dip galvanized steel sheet is press-formed, then shaping is achieved, but nonalloyed plating sticks to dies
Solution Approach 1:
The patent prevents sticking to dies during press-forming by controlling the chemical composition parameters of the base steel sheet (C: 0.0005-0.0100%, Si: 0.01-0.50%, Mn: 0.01-1.30% or 1.70-2.00%, P: 0.100% or less, S: 0.010% or less, Ti: 0.040-0.180%, Nb: 0-0.100%, B: 0.0005-0.0100%) and microstructure (average grain diameter ≤7.5 μm). These controlled parameters ensure that the plating layer maintains appropriate alloying characteristics that prevent excessive adhesion to die surfaces during forming operations.
4Ease of manufacture
If alloyed hot-dip galvanized steel sheet is press-formed, then shaping is achieved, but secondary work embrittlement occurs
Solution Approach 1:
The patent suppresses secondary work embrittlement by precisely controlling the chemical composition parameters of the base steel sheet, particularly the ranges of C (0.0005-0.0100%), Si (0.01-0.50%), Mn (0.01-1.30% or 1.70-2.00%), S (0.010% or less), Ti (0.040-0.180%), Nb (0-0.100%), and B (0.0005-0.0100%), along with maintaining an average grain diameter of 7.5 μm or less. This controlled composition and microstructure prevent excessive embrittlement during press-forming operations, maintaining both shapeability and mechanical integrity.
Data Source
AI summary
An alloyed hot-dip galvanized steel sheet excellent in appearance and press-formability is disclosed. The alloyed hot-dip galvanized steel sheet of the present disclosure has a base steel sheet having a predetermined chemical composition. If the base steel sheet has a chemical composition containing, by mass %, Mn: 0.01 to 1.30%, the predetermined relationships of formulas (1) and (3) are satisfied and if the base steel sheet has a chemical composition containing, by mass %, Mn: 1.70 to 2.00%, the predetermined relationships of formulas (2) and (3) are satisfied. The amounts of Mn, P, S, Ti, and Nb detected in the extraction residue of the base steel sheet satisfy the predetermined relationship of formula (4). The average grain diameter of the base steel sheet is 7.5 μm or less.