Ferritic Stainless Steel Plating Bath Component
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Solution Overview
Problem
In hot-dip Al—Zn plating baths with high Al content, the reaction of Fe from steel strips or components with Al or Zn leads to the formation of dross, causing defects on steel strips and reducing the lifespan of bath components, particularly in Al—Zn baths with 50% or more Al content.
Innovation Solution
A component for hot-dip metal plating baths featuring a ferritic stainless steel base material with specific composition and microstructure, coated with a thermal spray coating of ceramic or cermet materials, which reduces dross attachment and enhances wear resistance, allowing for longer bath component lifespan and ease of recoating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional bathtub materials for hot-dip Zn plating are used in hot-dip Al-Zn baths with high Al content, then the components have good initial corrosion resistance, but they suffer significant erosion and shortened lifespan
Solution Approach 1:
The invention uses composite materials consisting of a ferritic stainless steel base material combined with a thermal spray coating layer. This composite structure provides both the mechanical strength of the steel base and the erosion/corrosion resistance of the ceramic or cermet coating, enabling the component to withstand the harsh environment of high-Al content hot-dip plating baths while extending service life.
Solution Approach 2:
The invention changes the chemical composition parameters of the base material by specifying a ferritic stainless steel with controlled ranges of Cr (15-30%), Si (0.01-4%), Mn (0.1-3%), and C (0.1-0.5%), along with specific carbide-forming elements. These parameter changes optimize the material's resistance to erosion and corrosion in high-Al plating baths while preventing excessive dross generation.
2Strength
If Fe-containing components are used in hot-dip Al-Zn plating baths, then the components provide structural integrity, but Fe reacts with Al or Zn to generate dross that causes defects on steel strips
Solution Approach 1:
The invention applies local quality by providing a thermal spray coating on the surface of the ferritic stainless steel component. This coating creates a localized barrier between the Fe-containing base material and the molten Al-Zn bath, preventing Fe-Al-Zn reaction at the surface while maintaining the structural integrity of the Fe-based substrate. The coating selectively protects the surface without compromising the bulk material properties.
Solution Approach 2:
The thermal spray coating acts as an intermediary layer between the Fe-containing base material and the molten Al-Zn plating bath. This intermediate coating prevents direct contact and reaction between Fe and the bath metals, thereby eliminating dross generation while allowing the component to maintain its structural function. The coating serves as a protective mediator that reconciles the need for Fe-based structural integrity with the need to prevent harmful reactions.
3Reliability
If thermal spray coating is applied to reduce dross attachment, then the coating protects the base material, but the coating may crack or peel under thermal stress
Solution Approach 1:
The invention changes the thermal and mechanical parameters of the base material by selecting ferritic stainless steel with specific composition ranges. This material has appropriate thermal expansion coefficients and mechanical properties that match the thermal spray coating materials, reducing thermal stress and preventing coating cracking or peeling during repeated heating and cooling cycles in the plating bath.
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 solution significantly reduces dross formation and wear on components, extends their operational life, and prevents cracking or peeling of the thermal spray coating, making them suitable for high-temperature Al—Zn baths with minimal reactivity with the plating bath.
Implementation Method 1
a thermal spray coating disposed to cover at least part of a surface of the base material
Data Source
AI summary
A component for a hot-dip metal plating bath includes a base material and a thermal spray coating disposed to cover a surface of the base material. The base material includes ferritic stainless steel that contains: C: 0.10% to 0.50% by mass; Si: 0.01% to 4.00% by mass; Mn: 0.10% by mass to 3.00% by mass; Cr: 15.0% to 30.0% by mass; a total of Nb, V, Ti, and Ta: 0.9% by mass to 5.0% by mass; and a balance of Fe and unavoidable impurities. The ferritic stainless steel includes a microstructure that includes a ferrite phase as a main phase and a crystallized carbide, an area fraction of a Nb carbide, a Ti carbide, a V carbide, a Ta carbide, and a composite carbide thereof to the crystallized carbide of 30% or more. The hot-dip metal plating bath contains 50% by mass or more of Al.