Spot-Welded Metallic Assembly for Oxide-Coated Hardened Steel
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Solution Overview
Problem
There is no sufficient method developed to weld specific coated press hardened parts with aluminum or zinc-based coatings, which are difficult due to the hardness and thickness of their native oxide layers.
Innovation Solution
An assembly of at least two metallic substrates is spot welded using a specific alloyed coating comprising 0.1 to 11.0% zinc, 0.1 to 20% silicon, and optionally magnesium, topped with a native oxide layer of ZnO and MgO. A spot welding cycle with pulsation and welding currents is applied, breaking the native oxide layer and allowing effective welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aluminum or zinc-based coatings are applied to hardened steel parts, then corrosion resistance and thermal properties are improved, but welding becomes very difficult due to the hardness and thickness of the native oxide layer
Solution Approach 1:
The patent changes the chemical composition parameters of the coating by introducing silicon (5-20 wt%) and zinc (2-15 wt%) to aluminum-based coatings, which fundamentally alters the properties of the native oxide layer formed on the coating surface. This composition modification reduces the oxide layer's thickness and hardness, making it weldable while preserving corrosion resistance
Solution Approach 2:
The patent creates a composite coating system consisting of an aluminum-based matrix with silicon and zinc additions. This composite structure produces a native oxide layer with optimized properties - sufficiently protective for corrosion resistance but sufficiently removable during welding to allow proper weld penetration and bonding
2Reliability
If the native oxide layer on coated hardened parts is made thicker and harder for better corrosion resistance, then protection is improved, but welding quality deteriorates due to inability to break through the oxide barrier
Solution Approach 1:
The patent modifies the oxide layer parameters by changing the coating composition to include silicon and zinc, which transforms the oxide layer from thick and hard (non-weldable) to thinner and softer (weldable), while maintaining adequate corrosion protection through the aluminum-based matrix
3Ease of manufacture
If high current is applied to break the native oxide layer during welding, then weldability is improved, but splashing on the assembly surface increases
Solution Approach 1:
The patent changes the material parameters of the coating (adding silicon and zinc to aluminum) which softens the native oxide layer, allowing it to be broken at lower welding currents. This reduces the intensity of the welding process while achieving proper oxide removal, thereby minimizing splashing
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 achieves a welding range equal or above 1 kA and reduces splashing on the assembly surface, improving welding quality by breaking the native oxide barrier layer and allowing current flow through the coated hardened steel parts.
Implementation Method 1
A spot welding cycle with pulsation and welding currents is applied, breaking the native oxide layer and allowing effective welding
Implementation Method 2
said spot welded joint comprising a nugget
Data Source
AI summary
An assembly of at least two metallic substrates spot welded together through at least one spot welded joint is provided, a method for the manufacture of the assembly is also provided, such method including two steps and the use of this assembly for the manufacture of automotive vehicle.