Ni Preplating for Hot-Dip Galvanizing Steel Sheets
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Solution Overview
Problem
Existing hot-dip galvanization methods often result in nonplating defects across various types of plating sheets, which limits their application in industries requiring high appearance quality and weldability, such as automobiles and household appliances.
Innovation Solution
A Ni preplating technique is employed, where the amount of Ni preplating is adjusted based on the type of plating sheet to prevent nonplating defects, involving surface cleaning, rapid heating in a nonoxidizing atmosphere, and subsequent hot-dip galvanization in a bath with specific alloy compositions to ensure defect-free plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hot-dip galvanization methods are used, then the process is simple and cost-effective, but nonplating defects occur on various types of plating sheets
Solution Approach 1:
The patent applies preliminary action by introducing a Ni preplating step before hot-dip galvanization. This preplating creates a foundation layer that prevents nonplating defects during subsequent galvanization. The Ni layer is deposited in advance to ensure proper plating adhesion and prevent defects that would otherwise occur on various plating sheet types.
Solution Approach 2:
The patent applies parameter changes by optimizing multiple process parameters including Ni preplating amount (0.05-5.0 g/m²), preplating bath temperature (40-80°C), heating temperature (400-550°C), and heating rate (10-100°C/s). These parameter adjustments enable defect-free plating across different plating sheet types while maintaining process control.
2Reliability
If the amount of Ni preplating is increased to prevent nonplating defects, then plating quality improves, but production cost increases
Solution Approach 1:
The patent optimizes the Ni preplating amount parameter within the range of 0.05-5.0 g/m², with preferred ranges of 0.1-2.0 g/m² for cold-rolled sheets and 0.2-3.0 g/m² for hot-rolled sheets. This parameter optimization ensures sufficient defect prevention while minimizing excessive Ni consumption and associated costs.
Solution Approach 2:
The patent applies local quality by adjusting Ni preplating amounts based on specific plating sheet types and their Si content. Different plating sheets receive different Ni preplating amounts tailored to their specific characteristics, ensuring optimal plating quality without uniformly increasing Ni usage across all sheet types.
3Reliability
If rapid heating is applied to prevent nonplating defects, then plating adhesion improves, but energy consumption increases
Solution Approach 1:
The patent optimizes heating parameters including heating temperature (400-550°C), heating rate (10-100°C/s), and heating atmosphere (5-95% inert gas). This parameter optimization achieves rapid heating that improves plating adhesion while controlling energy consumption through efficient heat transfer and appropriate temperature selection.
Solution Approach 2:
The patent uses an inert or reducing atmosphere (5-95% inert gas such as N2 or Ar) during rapid heating to prevent oxide formation on the plating sheet surface. This atmosphere control ensures proper plating adhesion without requiring excessive heating temperatures, thereby reducing energy consumption.
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 effectively prevents nonplating defects in hot-rolled and cold-rolled steel sheets, enabling their use in diverse applications by optimizing plating conditions and maintaining superior corrosion resistance and adhesion.
Implementation Method 1
rapidly heating it in a nonoxidizing or reducing atmosphere to a sheet temperature between about 430 and about 500° C. at a temperature rise rate of about 20° C./sec or more
Implementation Method 2
cleaning the surface of a plating sheet
Implementation Method 3
preplating it with Ni
Implementation Method 4
hot-dip plating it in a galvanization bath
Data Source
AI summary
Exemplary embodiments of the present invention can provide a galvanization method for hot-rolled steel sheet, cold-rolled steel sheet, or plating sheet of various compositions, which can avoid nonplating defects by using an Ni preplating procedure. For example, an exemplary galvanization method can be provided for pickled hot-rolled steel sheet or annealed cold-rolled steel sheet which is free from non-plating defects which includes cleaning the surface of the plating sheet, preplating it with Ni, rapidly heating the sheet in a nonoxidizing or reducing atmosphere to a sheet temperature of about 430 to 500° C. at a heating a rate of about 20° C./sec or more, and then hot dip plating the sheet in a galvanization bath. The exemplary amount of Ni preplating can be determined based on the plate type and amount of Si in the sheet steel to produce a hot dip galvanization that is free from non-plating defects.