Laser Welded Joint Interface Layer for Higher Tensile Shear Strength

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Solution Overview

Problem

Existing laser welding methods for automotive applications face challenges in increasing tensile shear strength without extending welding time or using expensive remote laser heads, as they often require multiple passes and are limited by the width of the weld zone.

Innovation Solution

A method involving the formation of a metal or metal compound layer, such as zinc oxide, on one surface of the metal sheets to be welded, which is then overlaid and welded using a laser beam from the overlaid direction, expanding the width of the weld metal at the joined interface to improve tensile shear strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If multiple passes are used to increase tensile shear strength, then joint strength is improved, but welding time increases

Engineering Contradiction:

Improvetensile shear strengthVSAvoidwelding time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The invention changes the physical-chemical parameters of the welding interface by introducing a metal or metal compound layer. This layer modifies the welding dynamics, enabling single-pass welding to achieve the same joint strength that previously required multiple passes, thereby reducing welding time while maintaining tensile shear strength

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

A metal or metal compound layer is introduced as an intermediary substance at the welding interface. This intermediary layer facilitates better weld penetration and bonding, allowing single-pass welding to achieve sufficient joint strength without requiring multiple welding passes

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If remote laser head is used to form preliminary weld bead, then tensile shear strength is improved, but production cost increases

Engineering Contradiction:

Improvetensile shear strengthVSAvoidproduction cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

Instead of using expensive remote laser heads, the invention employs a disposable or consumable metal or metal compound layer at the welding interface. This inexpensive material layer provides the necessary welding enhancement without requiring costly equipment modifications

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention changes the chemical composition and physical properties at the welding interface by introducing a metal or metal compound layer. This parameter change enables conventional laser heads to achieve improved tensile shear strength without requiring expensive remote laser head equipment

Inventive Principle:

Principle #35Parameter changes

3Strength

If weld zone width is increased to improve tensile shear strength, then joint strength is improved, but heat deformation increases

Engineering Contradiction:

Improvetensile shear strengthVSAvoidheat deformation

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The invention changes the thermal and chemical parameters at the welding interface through the metal or metal compound layer. This enables better heat distribution and control, allowing increased weld zone width for improved strength while maintaining manufacturing precision by reducing unwanted heat deformation

Inventive Principle:

Principle #35Parameter changes

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 enhances tensile shear strength without increasing welding time or requiring an expensive remote laser head, using conventional laser welding equipment, and maintains precision by preventing heat deformation.

Implementation Method 1

The heat source in laser beam welding is a focused laser beam. A laser beam is comprised of light of a single wavelength and no phase differences, so can be focused on an extremely small point by an optical lens to obtain high density energy.

Methodology Applied

Scientific EffectLaser beam: Laser

Implementation Method 2

A laser beam is comprised of light of a single wavelength and no phase differences, so can be focused on an extremely small point by an optical lens to obtain high density energy.

Methodology Applied

Scientific EffectFocused high energy density heat source: Focusing

Implementation Method 3

forming a layer of a metal or metal compound with a boiling point higher than a melting point of the metal sheets at a scheduled welding location on one surface of a metal sheet

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS11174883B2Laser welded joint and method of production of same

Publication Date: 2021.11.16 NIPPON STEEL CORPORATION

AI summary

A laser welded joint improving the tensile shear strength without causing an increase in the welding time and without using an expensive remote laser head, that is, a laser welded joint obtained by arranging metal sheets overlaid and welding them by a laser beam from the overlaid direction, wherein when a total thickness of the metal sheets welded overlaid is “t” (mm), the width of the weld metal at the joined interface is 0.6t1/3+0.14 (mm) or more.