Pre-deposited Alloy Control Layer for Steel Strip Coating
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Solution Overview
Problem
The ZINCALUME process for coating steel substrates with zinc/aluminium alloys faces issues due to the presence of silicon in the bath, which leads to brittle coatings, corrosion pathways, and incompatibility with additives like magnesium, resulting in a less ductile and more brittle coating layer.
Innovation Solution
A method involving vapor or electro-deposition of an alloy control material onto the substrate before passing it through a molten coating bath, allowing for a controlled alloying process without silicon, thereby forming a more ductile coating layer and enabling the use of magnesium for enhanced corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If silicon is added to the molten coating bath to prevent excessive alloying, then alloying control is improved, but coating brittleness increases and corrosion resistance deteriorates
Solution Approach 1:
The patent applies preliminary action by depositing a thin alloy control material layer (such as silicon, aluminum, or zinc) onto the steel substrate before hot dipping. This pre-deposited layer controls the alloying reaction during subsequent immersion in the molten coating bath, preventing excessive alloying without requiring high silicon content in the bath, thereby avoiding coating brittleness while maintaining alloying control.
Solution Approach 2:
The patent changes the parameter of where alloy control material is introduced - shifting from adding silicon to the molten bath (traditional approach) to depositing alloy control material directly onto the substrate surface. This parameter change allows precise control of alloying at the substrate-coating interface without the harmful effects of bulk silicon in the coating layer.
2Stability of the object's composition
If silicon is present in the coating bath, then alloying control is improved, but magnesium additive compatibility deteriorates
Solution Approach 1:
By pre-depositing the alloy control material layer on the substrate before hot dipping, the patent enables magnesium to be added to the molten coating bath without direct contact between magnesium and the substrate. The pre-deposited layer acts as a barrier, preventing magnesium from reacting with the substrate while still allowing controlled alloying, thus enabling magnesium additive compatibility.
Solution Approach 2:
The pre-deposited alloy control material layer serves as an intermediary between the substrate and the molten coating bath containing magnesium. This intermediate layer prevents direct interaction between magnesium and the substrate, avoiding harmful reactions while still permitting beneficial alloying control, thereby enabling the use of magnesium additive.
3Stability of the object's composition
If silicon needles precipitate during coating solidification, then alloying control is achieved, but coating quality deteriorates due to corrosion pathways
Solution Approach 1:
The patent applies preliminary action by controlling the alloying reaction before solidification occurs. The pre-deposited alloy control material layer regulates the alloying during the molten state, preventing the formation of silicon needles during solidification. This approach achieves alloying control without creating the corrosion pathways associated with silicon needle precipitation.
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 method achieves a similar or enhanced alloying effect with less material, reduces brittleness, and allows for the introduction of magnesium, resulting in a more ductile and corrosion-resistant coating layer.
Implementation Method 1
vapour or electro-depositing an alloy control material onto the substrate
Implementation Method 2
vapour or electro-depositing an alloy control material onto the substrate
Implementation Method 3
controls the degree of alloying between the metal of the metal substrate and one of more components of the coating material
Data Source
AI summary
A method for coating a metal substrate, such as a steel strip, is disclosed. The method comprises vapor or electro-depositing an alloy control material, as described herein, onto the substrate and passing the substrate through a bath of molten coating material and forming a coating of the coating material onto the deposited alloy control material.