Zinc-Coated Steel Sheet Surface Conditioning for Better Phosphatability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing surface-treated sheet steels with zinc-based coatings face challenges in achieving improved phosphatability, formability, and paint finish due to the limitations of existing skin-pass rolling processes.
Innovation Solution
Perform skin-pass rolling with a degree of skin-pass greater than 1%, specifically greater than 1.2% or 1.4%, to alter the dimensions of zinc grains in embossed regions, causing microfractures and enhancing the surface area, thereby improving phosphatability, formability, and paint finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If skin-pass rolling is performed with conventional degree of skin-pass (≤1%), then the surface structure is formed, but the zinc grains are not sufficiently altered and microfractures are not generated
Solution Approach 1:
The patent applies parameter changes by increasing the degree of skin-pass from conventional values (≤1%) to greater than 1% (specifically 1.2-2.0%). This parameter change causes the zinc grains in the embossed regions to be altered in dimension and generates microfractures, thereby improving phosphatability while maintaining surface structure formation
Solution Approach 2:
The skin-pass rolling process is performed as a preliminary action before phosphating to pre-alter the zinc grain structure and create microfractures in the embossed regions. This preliminary modification of the surface structure enhances subsequent phosphating performance by providing increased surface area and improved chemical reactivity
2Reliability
If skin-pass rolling is performed with high degree of skin-pass (>1.4%), then microfractures and surface area increase are achieved, but the forming process requires higher mechanical force
Solution Approach 1:
The patent applies local quality by creating microfractures and altering zinc grains specifically in the embossed regions while leaving the unembossed regions relatively unchanged. This localized modification concentrates the surface area increase and chemical reactivity enhancement where needed, without requiring uniform high force across the entire sheet during forming
3Ease of manufacture
If conventional skin-pass rolling is used, then the process is simple, but the chemical reactivity and surface area are insufficient for improved phosphatability
Solution Approach 1:
The patent modifies the conventional skin-pass rolling process by changing the degree of skin-pass parameter to greater than 1%. This simple parameter adjustment transforms the process outcome to generate microfractures and increase surface area, thereby enhancing chemical reactivity for improved phosphatability while maintaining process simplicity
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 process results in better phosphatability, formability, and paint finish by generating targeted microfractures in the zinc grains, increasing surface area and chemical reactivity, and ensuring homogeneous phosphate layer formation.
Implementation Method 1
due to the force exerted by the skin-pass rolling the zinc grains in the embossed region are altered in dimension relative to the zinc grains in the unembossed region
Implementation Method 2
The resulting 'microfractures' in the intermetallic phase can ensure lower coefficients of friction and thus lower-wear forming
Implementation Method 3
making it possible to alter the zinc grains in the embossed region, wherein the especially 'targeted' effect, for example destroying or damaging the zinc grains in the embossed region, makes it possible to generate advantageous further 'microfractures' on the surface of the coating additional to those already formed in the intermetallic phase which can preferably enhance chemical reactivity by increasing the surface area within the embossed regions
Implementation Method 4
The eutectic mixture or the intermetallic phase present in the eutectic mixture formed in the zinc-based coating comprising Mg in the hot-dip coating process is (markedly) harder than the surrounding matrix (coating) and fractures under the mechanical force exerted in the context of the skin-pass rolling and/or forming process
Implementation Method 5
The resulting 'microfractures' in the intermetallic phase can ensure lower coefficients of friction and thus lower-wear forming
Data Source
AI summary
The present disclosure relates to a process for producing a surface-treated and surface-finished sheet steel. A sheet steel having a zinc-based coating is provided, wherein zinc grains are distributed within the coating. The surface-treated sheet steel are skin-pass rolled to form embossed regions and unembossed regions on the surface of the sheet steel provided with a zinc-based coating. Skin-pass rolling is performed with a degree of skin-pass greater than 1% in such a way that due to the force exerted by the skin-pass rolling the zinc grains in the embossed region are altered in dimension relative to the zinc grains in the unembossed region.