Resistance Spot Weld Interface Member for Reduced Embrittlement

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Solution Overview

Problem

Current resistance spot welding methods often cause undesirable tension and mechanical stress, leading to surface cracks and liquid metal embrittlement in metal workpieces, which weaken the joints and can cause them to pull apart.

Innovation Solution

A method and system that uses an interface member with a hollow peripheral wall between metal workpieces, where the peripheral wall is heated to create a weld joint with an inner void, reducing embrittlement and enhancing weld strength by concentrating current density and minimizing the heat-affected zone.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional resistance spot welding is used to join metal workpieces, then the workpieces are joined together, but undesirable tension and mechanical stress are created causing surface cracks and liquid metal embrittlement

Engineering Contradiction:

Improvejoint strengthVSAvoidliquid metal embrittlement and surface cracks

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

A filler material is introduced as an intermediary substance between the two metal workpieces during resistance spot welding. This filler material absorbs the harmful tension and mechanical stress that would otherwise cause liquid metal embrittlement and surface cracks in the base metals, while still enabling the workpieces to be joined together. The filler material acts as a buffer that protects the workpieces from direct exposure to the harmful welding stresses.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If conventional resistance spot welding is used to join metal workpieces, then the workpieces are joined together, but large operational heat-affected zone is created

Engineering Contradiction:

Improvejoint strengthVSAvoidheat-affected zone

Core Design Contradiction:

StrengthVSArea of stationary object

Solution Approach 1:

The filler material is placed locally at the weld interface between the two workpieces, concentrating the beneficial effects to the specific area where it is needed. This local placement allows the heat-affected zone to be minimized while still protecting the critical weld region from liquid metal embrittlement. The filler material creates a localized protective environment at the faying surface without requiring large areas of the workpieces to be affected.

Inventive Principle:

Principle #3Local quality

3Productivity

If conventional resistance spot welding is used with high current density, then welding speed is improved, but embrittlement and mechanical stress increase

Engineering Contradiction:

Improvewelding speedVSAvoidliquid metal embrittlement

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The filler material converts the harmful high current density and associated mechanical stress into a beneficial effect by providing a protective barrier. The filler material has properties that allow it to withstand the high current density and mechanical stress conditions, transforming what would be harmful conditions into a controlled welding process that still achieves rapid welding speeds while preventing liquid metal embrittlement of the base metals.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach results in increased joint strength and reduced embrittlement of metal workpieces, minimizing the risk of surface cracks and liquid metal embrittlement while using relatively less current density and force.

Implementation Method 1

The peripheral wall is heated at the first weld portion to join the first metal workpiece with the first open end and at the second weld portion to join the second metal workpiece to the second open end

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The step of heating comprises melting the peripheral wall to join the first metal workpiece with the first open end and to join the second metal workpiece with the second open end

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS11794270B2System and method of manufacturing a resistance spot weld of workpieces

Publication Date: 2023.10.24 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A system for increasing joint strength and reducing embrittlement in a resistance spot weld of metal workpieces is disclosed. The system comprises a stackup of first and second metal workpieces, and an interface member disposed between the first and second metal workpieces. The interface member comprises a peripheral wall defining a hollow inner portion. The peripheral wall has a first open end extending to a second open end. The first open end is in contact with the first metal workpiece defining a first weld portion thereon. The second open end is in contact with the second metal workpiece defining a second weld portion thereon. The system further comprises a first electrode configured to contact the first metal workpiece to heat the peripheral wall at the first weld portion and join the first metal workpiece with the first open end of the peripheral wall. The system further comprises a second electrode configured to contact the second metal workpiece to heat the peripheral wall at the second weld portion and join the second metal workpiece with the second open end of the peripheral wall to define a weld joint. The system further comprises a power source configured to power the first and second electrodes and a controller configured to control the power to the first and second electrodes to heat the peripheral wall.