Polyamide Pipe Infrared Welding for Uniform Crystallinity
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Solution Overview
Problem
Infrared welding methods for joining crystalline resin tubular members often result in a joined body with a relatively low tensile strength due to uneven crystallinity and temperature distribution, leading to breakage at a low tensile force when subjected to a low-temperature tensile test.
Innovation Solution
A welding joining method that controls the characteristics of infrared emission to maintain a uniform crystallinity distribution near the joined portion by using a combination of low-output and high-output infrared, adjusting the power supply and wavelength to ensure uniform heat input and distribution, thereby preventing sudden changes in crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If infrared welding method is used to join crystalline resin tubular members, then the joining process is efficient and automated, but the tensile strength of the joined body is low due to uneven crystallinity distribution
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate of the molten resin after infrared welding. Specifically, the cooling rate is adjusted to prevent sudden crystallization, thereby achieving uniform crystallinity distribution and improving tensile strength while maintaining the efficiency of infrared welding
Solution Approach 2:
The patent utilizes phase transitions by controlling the crystallization process of the resin during cooling. By managing the transition from molten state to crystalline state at controlled rates, uniform crystallinity is achieved, preventing weak points and improving overall tensile strength
2Speed
If high-output infrared is used to quickly melt the end surfaces, then the welding speed is high, but the temperature distribution becomes uneven causing sudden crystallinity changes
Solution Approach 1:
The patent applies periodic action by using a two-stage infrared heating process. First, low-output infrared is applied for a predetermined time to achieve uniform preliminary heating, then high-output infrared is applied to complete the melting. This periodic application of different heating intensities ensures both speed and crystallinity uniformity
Solution Approach 2:
The patent applies preliminary action by performing low-output infrared heating before high-output infrared heating. This preliminary heating stage creates a uniform temperature distribution that prevents sudden crystallinity changes during the subsequent high-intensity heating and cooling process
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
The method achieves a high tensile strength in the welding joined body by maintaining a uniform crystallinity distribution, reducing the likelihood of breakage at the joined portion even under low-temperature tensile testing.
Implementation Method 1
heating and melting the end portions of the tubular members by emitting infrared from the infrared emission unit
Implementation Method 2
cooling down the molten end portions of the tubular members in a state where the end portions are bonded to each other by pressure
Data Source
AI summary
Provided is a welding joining method for joining end portions of first and second pipes made of polyamide resin by bonding the end portions to each other by pressure in a molten state. The welding joining method includes: a placing step of placing an infrared radiation lamp between the first and second pipes placed to face each other at an interval; a heating and melting step of heating and melting the end portions of the first and second pipes by emitting infrared; and a pressure bonding step of cooling down the molten end portions in a state where the molten end portions are bonded to each other by pressure.