Pulsed Resistance Welding Joint Hardness Control
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Solution Overview
Problem
When joining carburized materials, the quenched carburized layer becomes extremely hard and brittle, and existing tempering methods using a capacitor-type resistance welding machine require high electric currents, risking re-quenching of the joint portion.
Innovation Solution
A method involving pulsed welding electric currents for joining, followed by controlled tempering steps with progressively smaller currents to achieve appropriate hardness in the joint portion, including a first tempering step for the central portion and a second tempering step for the end portions, with optional additional tempering steps to ensure uniform hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large electric current is used for tempering the joint portion to achieve appropriate hardness, then the hardness of the joint portion is improved, but the risk of re-quenching and brittleness increases
Solution Approach 1:
The tempering process is divided into multiple stages with decreasing current values. The first tempering uses a larger current to address the central portion, followed by a second tempering with a smaller current to treat end portions without re-quenching. This segmentation allows different current levels to be applied to different regions and stages of the tempering process.
Solution Approach 2:
Different current values are applied to different portions of the joint. The end portions receive a smaller current (A3) compared to the central portion (A2), matching the local hardness requirements and avoiding excessive heating that would cause re-quenching in brittle end regions.
2Stability of the object's composition
If tempering is performed to reduce hardness and brittleness of the joint portion, then the ductility is improved, but additional processing time is required
Solution Approach 1:
The joining and tempering operations are merged into a single continuous process using the same resistance welding machine. The tempering currents are applied immediately after joining without removing the workpiece, combining two heat treatment operations into one processing sequence.
Solution Approach 2:
The tempering process uses periodic pulsed electric currents with specific duty cycles. The currents are applied in controlled pulses rather than continuously, allowing heat to distribute evenly and achieve tempering效果 without excessive processing time.
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 ensures a joined member with a joint portion having appropriate hardness, reducing the risk of brittleness and cracking while maintaining the required mechanical properties.
Implementation Method 1
joining step S2 of joining the first member D and the second member E by passing a pulsed welding electric current A1 for joining through the joint target portions J of the first member D and the second member E
Implementation Method 2
first tempering step S3 of tempering a joint portion F by passing a first tempering electric current A2 through the joint portion F
Data Source
AI summary
A method for manufacturing a joined member and a joined member manufacturing apparatus which can manufacture a joined member with a joint portion having an appropriate hardness. A method for manufacturing a joined member C by joining a first member D formed of a metal material having a possibility of undergoing quenching and a second member E formed of a metal material, the method includes a contact-placing step S1 of placing the first and second members D and E with joint target portions of the first and second members D and E respectively being in contact with each other; a joining step S2 of joining the first and second members D and E by passing a pulsed welding electric current A1 for joining through the joint target portions J of the first and second members D and E; a first tempering step S3 of tempering a joint portion F, where the first and second members D and E are joined, by passing a first tempering electric current A2 through the joint portion F; and a second tempering step S4 of tempering the joint portion F by passing a second tempering electric current A3 smaller than the first tempering electric current A2 through the joint portion F.