Fe-Plated Hot Press Steel Sheet for Oxide-Controlled Plating
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Solution Overview
Problem
Existing hot-dip plated steel sheets for hot press forming suffer from non-plating and plating peeling issues due to surface oxides formed by alloying elements like Mn and Si, leading to poor plating quality and potential linear defects.
Innovation Solution
A steel sheet composition with controlled Mn and Si concentration profiles, combined with an Fe plating layer containing 5 to 50 wt% oxygen, is annealed in a controlled atmosphere to suppress surface diffusion of these elements, forming a GDS profile with a difference in converted concentrations of at least 10% between maximum and minimum points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If alloying elements (Mn, Si, Al, Cr, B) are added to improve hardenability, then the steel sheet achieves excellent hardenability and mechanical properties, but surface oxides form during annealing causing non-plating and plating quality deterioration
Solution Approach 1:
The patent applies preliminary action by performing internal oxidation during the annealing process before hot-dip plating. Alloying elements (Mn, Si, Al) are oxidized internally to form oxides at a controlled depth from the surface, preventing their diffusion to the surface and subsequent oxide formation that would cause non-plating. This preliminary internal oxidation eliminates the harmful surface oxides before the plating process begins.
Solution Approach 2:
The patent uses an intermediary approach by introducing a zinc-based plating layer as a barrier. The zinc plating serves as an intermediary that prevents oxygen from reaching and oxidizing the alloying elements on the surface during annealing. This intermediary zinc layer blocks the harmful oxidation pathway, allowing the steel to achieve both hardenability and good plating quality.
2Strength
If elements with high oxidation tendency (Mn, Si, Al) are added to improve hardenability, then the steel sheet achieves desired mechanical properties, but these elements diffuse to the surface during annealing forming oxides that reduce surface reactivity and cause non-plating
Solution Approach 1:
The patent performs preliminary internal oxidation during annealing, where alloying elements are oxidized at a controlled depth from the surface before the hot-dip plating process. This prevents the elements from diffusing to the surface and forming harmful oxides that would cause non-plating, while still allowing the steel to achieve its desired mechanical properties.
Solution Approach 2:
The patent applies parameter changes by controlling the annealing temperature, time, and atmosphere to precisely manage the oxidation process. By adjusting these parameters, the patent ensures that alloying elements are oxidized internally at the correct depth, preventing surface diffusion while maintaining the steel's mechanical properties and plating quality.
3Object-generated harmful factors
If surface oxides are formed during annealing to prevent non-plating, then wettability is improved, but plating adhesion deteriorates due to insufficient alloying inhibition layer formation
Solution Approach 1:
The patent uses a zinc-based plating layer as an intermediary that prevents oxygen from reaching the steel surface during annealing. This intermediary zinc layer blocks the formation of harmful surface oxides while allowing the necessary alloying inhibition layer to form properly, ensuring both non-plating prevention and good plating adhesion.
Solution Approach 2:
The patent creates an inert environment by using a zinc-based plating layer that prevents oxygen access to the steel surface during annealing. This inert barrier allows the steel to be annealed without forming harmful surface oxides, while still enabling proper alloying inhibition layer formation for good plating adhesion.
4Object-generated harmful factors
If Fe plating layer is formed by electroplating to suppress surface diffusion, then non-plating is prevented, but the plating layer contains oxygen that may affect subsequent annealing and plating quality
Solution Approach 1:
The patent applies parameter changes by controlling the electroplating conditions to achieve the desired oxygen content (5-50 wt%) in the Fe plating layer. This controlled oxygen content is sufficient to suppress surface diffusion of alloying elements during annealing while not excessively high to cause harmful effects in subsequent plating processes.
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
This approach prevents non-plating and plating peeling, ensuring excellent adhesion and surface quality, even after alloying heat treatments, by effectively managing the distribution of Mn and Si oxides.
Implementation Method 1
a surface condition of an annealed steel sheet immediately before plating, and plating properties may deteriorate due to the formation of surface oxides during annealing caused by elements such as Mn, Si, Al, Cr, and B added to secure physical properties of the steel sheet. That is, during the annealing process, the elements may diffuse to surfaces thereof and react with a trace amount of oxygen or water vapor present in an annealing furnace to form single or complex oxides of the elements on the surface of the steel sheet
Implementation Method 2
oxidizing the steel sheet in a direct flame furnace in an oxidizing atmosphere to form an iron oxide including Si, Mn or Al alone or complex oxides to a certain depth inside the steel sheet
Implementation Method 3
Hot press forming is a processing method for obtaining high-strength parts by forming and cooling a steel sheet at high temperatures substantially simultaneously
Implementation Method 4
during the annealing process, the elements may diffuse to surfaces thereof and react with a trace amount of oxygen or water vapor present in an annealing furnace
Data Source
AI summary
The steel sheet for plating according to an aspect of the present invention has a GDS profile of an Mn element and a GDS profile of an Si element, which are observed from the surface to the depth, sequentially including a maximum point and a minimum point, wherein a difference of converted concentration of Mn is 10% or more, and a difference of converted concentration of Si is 10% or more.