Zn-Al-Mg Plated Steel Surface Hardness
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Solution Overview
Problem
Existing plated steel materials lack sufficient friction resistance and white rust resistance, particularly in worsening corrosive environments, despite advancements in zinc alloy-based coatings.
Innovation Solution
A method for preparing a plated steel material with a Zn-Al-Mg based plating layer, where the magnesium content is concentrated near the surface, achieving a specific distribution ratio to enhance surface hardness and corrosion resistance, involving a plating bath composition of 0.5 to 14% Al and 0.5 to 5% Mg, and a cooling process that includes primary and secondary cooling stages with controlled rates and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mg is added to Zn-Al plating composition to improve corrosion resistance, then white rust resistance is improved, but Mg-oxide dross formation increases and friction resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform Mg distribution within the plating layer. The surface region contains lower Mg content (0.1-3 wt%) to prevent dross formation and maintain friction resistance, while the inner region contains higher Mg content (1-10 wt%) to provide corrosion protection. This spatial variation in composition resolves the contradiction between corrosion resistance and surface quality.
Solution Approach 2:
The patent transitions from considering only bulk plating composition to considering the depth-dependent composition profile. By controlling Mg distribution through the plating layer thickness using specific cooling rates and temperatures, the invention exploits the dimensional aspect of composition gradients to simultaneously achieve good surface properties and corrosion resistance.
2Reliability
If Mg content in plating layer is increased to improve corrosion resistance, then white rust resistance is improved, but friction resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform Mg distribution within the plating layer. The surface region contains lower Mg content (0.1-3 wt%) to prevent dross formation and maintain friction resistance, while the inner region contains higher Mg content (1-10 wt%) to provide corrosion protection. This spatial variation in composition resolves the contradiction between corrosion resistance and surface quality.
3Reliability
If uniform Mg distribution in plating layer is created, then corrosion resistance is improved, but surface hardness and friction resistance deteriorate
Solution Approach 1:
The patent applies local quality by creating a non-uniform Mg distribution within the plating layer. The surface region contains lower Mg content (0.1-3 wt%) to prevent dross formation and maintain friction resistance, while the inner region contains higher Mg content (1-10 wt%) to provide corrosion protection. This spatial variation in composition resolves the contradiction between corrosion resistance and surface quality.
4Manufacturing precision
If plating bath temperature is maintained high to ensure proper plating, then plating quality is improved, but energy consumption increases and cooling control difficulty increases
Solution Approach 1:
The patent applies periodic action by implementing a two-stage cooling process with distinct temperature ranges and rates. The first stage uses rapid cooling (10-100°C/s) from plating temperature to intermediate temperature to control Mg distribution, then the second stage uses slower cooling to room temperature. This time-dependent temperature control achieves desired plating quality while reducing total energy consumption compared to prolonged high-temperature maintenance.
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 method results in a plated steel material with improved friction resistance and white rust resistance, as evidenced by surface concentration of magnesium and the formation of stable corrosion products, while maintaining bending-workability and preventing Mg-oxide dross formation.
Implementation Method 1
zinc in a plated layer forms a dense corrosion product on a surface of the steel material while being oxidized, to block the steel material from an oxidizing atmosphere
Implementation Method 2
a cooling process that includes primary and secondary cooling stages with controlled rates and temperatures
Implementation Method 3
obtained by dipping a steel material in molten zinc to form a plating layer
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An embodiment of the present invention provides a plated steel material having a plated layer comprising, by weight, 0.5-14% of Al, 0.5-5% of Mg, and the balance of Zn and inevitable impurities, wherein the plated steel material satisfies expression 1 below. MgS−Mg1/2/Mg1/2≥0.3 (where, [Mg]S means the Mg content (wt%) in a surface of the plated layer, and [Mg]1/2 means the Mg content (wt%) at 1/2t (t represents the thickness of the plated layer, hereinafter the same) in a thickness direction from a surface of the plated layer.