Tailored Blank Joining for Uniform Formability Across Strength Grades
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Solution Overview
Problem
Conventional welding methods for manufacturing tailored blank materials result in welded portions with mechanical properties different from the base material, leading to embrittlement, hardening, and difficulty in achieving uniform formability, especially when joining metal materials with different strengths.
Innovation Solution
The use of linear friction-joining to connect metal members with a tensile strength difference of 150 MPa or more, where the joining temperature is controlled to within 100°C of the members' tensile strengths, and burrs are discharged to form a narrow, homogeneous joint, minimizing contamination and phase transformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional welding methods are used to join metal sheets, then the joined portions are formed, but the welded portions exhibit embrittlement, hardening, and non-uniform mechanical properties different from the base material
Solution Approach 1:
The invention changes the fundamental parameters of the joining process by using friction-based solid-phase joining instead of fusion welding. This involves controlling friction temperature to remain below the melting point of the base materials, preventing martensite formation and heat-affected zone softening. The friction temperature and pressure parameters are carefully controlled to achieve homogeneous mechanical properties throughout the joined portion that match the base material.
Solution Approach 2:
The invention replaces the thermal-field-based fusion welding process with a mechanics-based friction joining process. Instead of using high heat to melt and fuse materials, the invention uses mechanical friction to generate localized heat that softens materials just enough for bonding while remaining in the solid phase, thereby avoiding the embrittlement and hardening associated with conventional welding.
2Ease of manufacture
If fusion welding is used to join metal materials with different strengths, then the joined portions are formed, but the temperature inevitably exceeds the melting point causing softening of the heat-affected zone
Solution Approach 1:
The invention fundamentally changes the temperature parameter regime by maintaining friction temperature below the melting point of the base materials throughout the joining process. This prevents the formation of a heat-affected zone with softened properties. The friction temperature is controlled through adjustment of friction speed, pressure, and duration to achieve bonding without excessive heating.
3Productivity
If conventional welding techniques are used, then joined portions are created, but hardening and softening occur making it impossible to provide the same level of formability as the base metal
Solution Approach 1:
The invention changes the joining mechanism from thermal fusion to friction-based solid-phase bonding, controlling parameters such as friction speed, pressure, and duration to achieve uniform mechanical properties throughout the joined portion. This eliminates the hardening and softening zones characteristic of conventional welding while maintaining efficient joining capability.
Solution Approach 2:
The invention replaces the thermal-field process of conventional welding with a mechanics-based friction process. This substitution eliminates the temperature excursions that cause hardening and softening, resulting in uniform mechanical properties throughout the joined portion that match the base material, while maintaining productive joining speeds.
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 produces a tailored blank material with excellent formability and isotropic mechanical properties, suitable for high-tensile steel sheets, reducing the influence of the joint on formability and ensuring a smooth, corrosion-resistant interface.
Implementation Method 1
linear friction-joining
Implementation Method 2
friction heat generated by linear relative motion
Implementation Method 3
progress cooling of a remelting zone
Implementation Method 4
cooling progresses at a rapid rate
Data Source
AI summary
Provided are: a tailored blank material that comprises a joining section with excellent formability and that is formed from metal materials of different strengths; and a method for manufacturing the tailored blank material simply and efficiently. Also provided is a press-molded article for which this tailored blank material is used. This method for manufacturing a tailored blank material is characterized in that one member and another member are joined by linear friction welding and in that the difference between the tensile strengths of the one member and the other member is at least 150 MPa. When the welding pressure applied during the linear friction welding is P, the temperature at which the tensile strength of the one member reaches P is T1 (° C.), and the temperature at which the tensile strength of the other member reaches P is Y2 (° C.), it is preferable for P to be set so that the difference between T1 and T2 is 100° C. or less.