Low-Temperature Metal Joining for Strength-Preserving Weld Interfaces
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Solution Overview
Problem
Conventional friction stir welding methods fail to effectively suppress the deterioration of mechanical properties at joint portions and heat-affected zones, particularly for high-tensile steels and heat-treatment aluminum alloys, and require additional coolant and equipment.
Innovation Solution
A low-temperature joining method that reduces the recrystallization temperature at the joint interface by introducing a strong strain and controlling the joining temperature below the recrystallization temperature of the metal materials, using a rotation tool with a peripheral velocity of 51 mm/s or less to form fine equiaxed recrystallized grains, thereby maintaining the mechanical properties of the parent material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional friction stir welding is used to join high-tensile steel or heat-treatment type aluminum alloy, then the joint can be formed, but the mechanical properties at the joint portion and heat-affected zone deteriorate significantly
Solution Approach 1:
The invention changes the temperature parameter by conducting joining at low temperature (below recrystallization temperature) and alters the strain parameter by introducing strong strain through specific tool rotation speeds (51 mm/s or less), thereby preventing the deterioration of mechanical properties at the joint portion and heat-affected zone while still achieving sound joints in high-tensile steels and heat-treatment type aluminum alloys
2Strength
If friction stir welding is used to suppress strength reduction at joint portion, then ductility improves, but additional coolant supply mechanism and equipment are required
Solution Approach 1:
The invention extracts and eliminates the coolant supply mechanism from the joining process by achieving effective joining through low temperature (below recrystallization temperature) and strong strain conditions alone, thereby maintaining joint strength without requiring additional coolant equipment
Solution Approach 2:
The joining process utilizes the inherent properties of the metal materials under low temperature and strong strain conditions to achieve self-regulation of the joining process without external coolant intervention, allowing the system to serve itself by controlling temperature and strain parameters directly
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 method effectively suppresses the reduction in strength at joint portions and heat-affected zones, achieving a joint structure with hardness equal to or higher than the parent material, and can be applied to various high-tensile steels and aluminum alloys without the need for coolant or specialized equipment.
Implementation Method 1
the peripheral velocity of the outermost periphery of the rotation tool is set to 51 mm/s or less, thereby a recrystallization temperature inherent to the metal materials is reduced by introducing a large strain to the joint portion
Implementation Method 2
recrystallized grains are generated at the joint interface by setting the joining temperature to less than the recrystallization temperature inherent to the metal materials
Implementation Method 3
a low-temperature joining method of metal materials by forming a joint interface in which two metal materials face each other at a joint portion and plunging a rotation tool caused to rotate at a prescribed speed into the joint portion
Implementation Method 4
introducing a large strain to the joint portion
Data Source
AI summary
A low-temperature joining method effectively suppresses reductions in the mechanical properties of a junction of various types of high-tensile steel or aluminum, and of a heat-affected zone; and produces a joint structure. A method for joining two metal materials by forming a joint interface in which the two metal materials face each other at a joint portion and plunge a rotation tool caused to rotate at a prescribed speed into the joint, the method for low-temperature joining of metal materials characterized in that the peripheral velocity of the outermost periphery of the rotation tool is set to 51 mm/s or less, whereby the recrystallization temperature inherent to the metal materials is reduced by introducing a large strain to the joint, and recrystallized grains are generated at the joint interface by setting the joining temperature to less than the recrystallization temperature inherent to the metal materials.