Ni-Plated Steel Welded Member for Corrosion-Resistant Joining
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Solution Overview
Problem
The challenge is to create a welded member using a steel sheet that is less expensive than pure Ni sheet while maintaining excellent corrosion resistance, especially in high temperature and alkaline environments.
Innovation Solution
The solution involves welding a Ni plated steel sheet with a Fe—Ni diffusion alloy layer using a pure Ni-based welding wire, ensuring a specific state of the Ni plating layer to enhance corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a Ni plated steel sheet is used to reduce cost, then material cost is reduced, but pinholes are formed in the Ni plating layer during welding causing deterioration in corrosion resistance
Solution Approach 1:
The patent applies preliminary action by performing annealing treatment on the Ni plated steel sheet before welding. This pre-treatment forms a Fe-Ni diffusion alloy layer and reduces hydrogen content in the Ni plating layer, preventing pinhole formation during subsequent welding operations and maintaining corrosion resistance while using cost-effective Ni plated steel sheet
Solution Approach 2:
The patent applies parameter changes by controlling specific parameters of the Ni plated steel sheet: Ni plating layer thickness (5-20 μm), Fe-Ni diffusion alloy layer thickness (0.5-2.0 μm), and hydrogen content in Ni plating layer (0.5-5.0 wt ppm). By optimizing these parameters, the material achieves both cost reduction and maintained corrosion resistance after welding
2Ease of manufacture
If a Ni plated steel sheet is welded, then a welded member is produced, but Fe thermally diffuses to the surface layer of the Ni plating layer decreasing Ni concentration and causing deterioration in corrosion resistance
Solution Approach 1:
The patent applies preliminary action by performing annealing treatment before welding to pre-form the Fe-Ni diffusion alloy layer with controlled thickness (0.5-2.0 μm). This pre-formed barrier layer limits excessive Fe diffusion during welding, maintaining Ni concentration (≥70 mass%) in the surface layer and preserving corrosion resistance
Solution Approach 2:
The patent applies parameter changes by controlling the annealing temperature (500-850°C) and time (1-60 minutes) to achieve the desired Fe-Ni diffusion alloy layer thickness. By optimizing these parameters, Fe diffusion during welding is controlled to maintain surface Ni concentration above 70 mass%, ensuring corrosion resistance
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 allows for the production of a welded member that is cost-effective and exhibits superior corrosion resistance, even when using a Ni plated steel sheet as the raw material.
Implementation Method 1
Fe derived from the steel sheet thermally diffuses during the welding to reach the surface layer of the Ni plating layer
Implementation Method 2
a Ni plated steel sheet obtained by performing annealing after electrolytic Ni plating to form a Fe—Ni diffusion alloy layer
Data Source
AI summary
To obtain a welded member using a steel sheet less expensive than a pure Ni sheet as a raw material and excellent in corrosion resistance. A welded member according to the present invention is made by connecting a Ni plated steel sheet having a Ni plating layer and a Fe—Ni diffusion alloy layer and another steel sheet via a welded part, wherein: a Ni concentration is 70 mass % or more and a Fe concentration is 30 mass % or less in a surface layer of each of a toe, a toe near area, and the welded part; and a thickness of the Fe—Ni diffusion alloy layer is 0.5 to 1.5 μm and a total thickness of the Ni plating layer and the Fe—Ni diffusion alloy layer is 2.7 to 14.0 μm at a non-welded part, and a total concentration of S and C in the Ni plating layer at the non-welded part is less than 20 ppm.