Dissimilar Metal Stack Welding With Thermal-Conduction Laser Heating

Solution Overview

Problem

The existing method for stack-welding dissimilar metal members, such as aluminum and copper, faces challenges in controlling the intermetallic compound ratio and preventing early-stage cracking due to the stirring of the molten pool during key-hole welding, which affects the strength and conductivity of the welded part.

Innovation Solution

A method where a metal member with a higher melting point is placed on top of a metal member with a lower melting point, and a laser beam is applied for thermal-conduction welding from above the higher melting point member, forming a molten pool that only melts the higher melting point member, preventing the pool from being stirred and thus reducing intermetallic compound generation and early-stage cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If key-hole welding is performed by applying a laser beam from above the aluminum plate, then the copper plate can be welded through the aluminum plate, but the molten pool becomes stirred and intermetallic compound ratio becomes difficult to control

Engineering Contradiction:

Improvewelding reliabilityVSAvoidintermetallic compound ratio control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional welding approach by reversing the positions of aluminum and copper plates. Instead of placing aluminum on copper and welding from above aluminum, the patent places copper on aluminum and applies the laser beam from above the copper plate. This inversion prevents the laser beam from directly heating the aluminum plate, thereby avoiding excessive melting and stirring of the molten pool, and enables better control of the intermetallic compound ratio in the welded joint.

Inventive Principle:

Principle #13The other way round (Inversion)

2Strength

If key-hole welding is performed with stirring of the molten pool, then welding can be achieved, but early-stage cracking occurs due to accelerated intermetallic compound generation

Engineering Contradiction:

Improvewelded part strengthVSAvoidearly-stage cracking

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the conventional welding approach by reversing the positions of aluminum and copper plates. Instead of placing aluminum on copper and welding from above aluminum, the patent places copper on aluminum and applies the laser beam from above the copper plate. This inversion prevents the laser beam from directly heating the aluminum plate, thereby avoiding excessive melting and stirring of the molten pool, and enables better control of the intermetallic compound ratio in the welded joint.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the welding parameters by switching from key-hole welding to thermal conduction welding. This parameter change is achieved by adjusting the laser beam application method and position, which results in reduced molten pool stirring and controlled intermetallic compound formation, thereby preventing early-stage cracking while maintaining welding strength.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the laser beam is applied from above the aluminum plate, then welding can be performed, but the intermetallic compound reaches the surface of the molten pool causing cracking

Engineering Contradiction:

Improvewelding process simplicityVSAvoidcracking in welded part

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the conventional welding approach by reversing the positions of aluminum and copper plates. Instead of placing aluminum on copper and welding from above aluminum, the patent places copper on aluminum and applies the laser beam from above the copper plate. This inversion prevents the laser beam from directly heating the aluminum plate, thereby avoiding excessive melting and stirring of the molten pool, and enables better control of the intermetallic compound ratio in the welded joint.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the welding parameters by switching from key-hole welding to thermal conduction welding. This parameter change is achieved by adjusting the laser beam application method and position, which results in reduced molten pool stirring and controlled intermetallic compound formation, thereby preventing early-stage cracking while maintaining welding strength.

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 effectively prevents the molten pool from being stirred, reducing intermetallic compound formation and subsequent cracking, thereby enhancing the strength and conductivity of the welded joint.

Implementation Method 1

applying a laser beam for thermal-conduction welding from above the second metal member, in which after the molten pool comes into contact with the first metal member

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

performing laser welding by placing a first metal member and a second metal member having a melting point higher than that of the first metal member on top of one another

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 3

the molten pool solidifies, so that the first and second metal members are welded together

Methodology Applied

Scientific EffectSolidification: Freezing

Data Source

PatentUS11413706B2Method for stack-welding dissimilar metal members

Publication Date: 2022.08.16 TOYOTA JIDOSHA KK

AI summary

A method for stack-welding dissimilar metal members by placing a first metal member and a second metal member having a melting point higher than that of the first metal member on top of one another and performing laser welding is provided. The second metal member is placed on the first metal member, and a molten pool in which only the second metal member is melted is formed by applying a laser beam for thermal-conduction welding from above the second metal member. After the molten pool comes into contact with the first metal member and hence the first metal member melts in the molten pool, the molten pool solidifies, so that the first and second metal members and are welded together.