Zn-Al-Mg Plated Hot-Press Steel With Controlled Oxide Layer
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Solution Overview
Problem
High-strength steel used in hot press forming is prone to corrosion and decarburization during high-temperature processing, leading to reduced corrosion resistance and processing challenges due to excessive zinc oxidation in zinc-based plated steel materials, limiting the effectiveness of magnesium additions.
Innovation Solution
A Zn-Al-Mg-based plated steel material with specific composition and processing conditions, including a controlled Al/Mg ratio in the oxide layer, is used to form a hot press product with enhanced corrosion resistance, involving a base iron composition and a Zn-Al-Mg-based plating layer with optimized Mg and Al content, and a controlled heating process to suppress Mg oxidation and promote Al2O3 formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a zinc-based plated steel material is used for hot press forming, then corrosion protection during high-temperature processing is improved, but zinc is excessively oxidized leading to decreased effective thickness and deteriorated corrosion resistance after forming
Solution Approach 1:
The invention changes the chemical composition parameters of the plating layer by adding magnesium (0.03-5 mass%) to the zinc-based plating, creating a Zn-Mg-based plating layer that forms a protective oxide barrier during hot press forming, thereby reducing zinc oxidation loss while maintaining corrosion protection
Solution Approach 2:
The invention creates a composite plating layer structure consisting of multiple phases including zinc-rich phases, magnesium-rich phases, and oxide phases (particularly MgO and ZnO), where the composite structure provides both corrosion protection during heating and reduced zinc oxidation
2Object-affected harmful factors
If magnesium is added to the zinc-based plating layer to improve corrosion resistance, then a dense magnesium-based corrosion product is formed below the corrosive environment, but magnesium is rapidly oxidized at high temperature greatly damaging the plating layer
Solution Approach 1:
The invention uses aluminum oxide (Al2O3) as an intermediary protective layer that forms on the surface during hot press forming, acting as a barrier that prevents direct oxidation of magnesium while allowing the magnesium to form protective corrosion products in the underlying plating layer
Solution Approach 2:
The invention creates different functional zones within the plating layer: an outer oxide-rich layer (primarily Al2O3 and ZnO) that protects against oxidation during heating, and an inner magnesium-rich zone that provides corrosion protection, where each zone has optimized local composition for its specific function
3Strength
If high-strength steel is processed at room temperature, then material strength is maintained, but the steel is easily abraded or fractured and precise dimension processing is difficult due to spring back
Solution Approach 1:
The invention changes the temperature parameter during processing by performing hot press forming at elevated temperatures (typically 700-950°C), where the steel exhibits improved ductility and reduced spring back, enabling complex shape formation while maintaining final strength through controlled cooling and martensitic transformation
4Manufacturing precision
If high-strength steel is processed by hot press forming, then complicated shapes with precise dimensions are achieved, but corrosion and decarburization occur on the steel surface during heating
Solution Approach 1:
The invention applies a multi-phase composite plating layer (Zn-Mg-based with Al addition) on the steel surface that forms a protective oxide barrier during hot press forming, preventing both corrosion and decarburization while allowing the underlying steel to achieve precise dimensional control through hot forming
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 approach results in a hot press formed product with excellent corrosion resistance and improved weldability, as demonstrated by reduced maximum corrosion depth and maintained weldable current range, effectively addressing the limitations of existing zinc-based plated steel materials.
Implementation Method 1
there may be corrosion or decarburization on the surface of the steel material... zinc may be excessively oxidized during heating for hot press forming... a controlled Al/Mg ratio in the oxide layer
Implementation Method 2
steel is subjected to processing, simultaneously with quenching in the state of being heated equal to or higher than the austenite region to transform the structure of steel to martensite
Implementation Method 3
a magnesium-based corrosion product is densely formed below the corrosive environment to decrease a corrosion rate
Data Source
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AI summary
Disclosed is a hot press formed product, which is prepared by means of hot press forming a Zn-Al-Mg plated steel material comprising base iron and a Zn-Al-Mg plated layer, and a method for preparing same, the hot press formed product comprising an oxide layer formed on the surface thereof, wherein the content ratio of Al to Mg (Al/Mg) in the oxide layer is 0.8 or higher.