Impeller Brazing Thermal Cycle Control
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Solution Overview
Problem
The existing brazing method for impeller manufacturing can result in gaps between the disk and blades due to temperature differences during the heat treatment process, leading to brazing defects and requiring rework.
Innovation Solution
A modified thermal cycle with controlled temperature increasing and decreasing rates, including intermediate retentions, and the use of a heating setup that heats the impeller from the inner circumferential side to reduce temperature distribution and prevent expansion at the bond interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional brazing thermal cycle is used to bond the disk and blades, then the bonding strength is improved, but temperature distribution during heating causes gap formation at the bond interface
Solution Approach 1:
The patent applies preliminary action by heating the inner circumferential side of the assembly body before completing the overall heating process. This preliminary localized heating compensates for the temperature lag in the inner regions, ensuring uniform temperature distribution across the entire assembly before brazing begins, thereby preventing gap formation at the bond interface while maintaining strong bonding.
2Reliability
If the thermal cycle duration is extended to ensure complete heating and bonding, then bonding quality is improved, but manufacturing time increases
Solution Approach 1:
By performing preliminary heating of the inner circumferential side, the patent reduces the overall thermal cycle time. This preliminary action ensures that the inner regions reach the required temperature earlier, allowing the brazing process to be completed more quickly without compromising bonding quality or creating temperature-related defects.
Solution Approach 2:
The patent changes the heating parameters by applying localized heating to the inner circumferential side at a higher rate than conventional uniform heating. This parameter modification optimizes the thermal cycle, achieving complete and uniform heating faster than traditional methods, thus reducing manufacturing time while maintaining or improving brazing quality.
3Productivity
If rapid heating is applied to reduce manufacturing time, then productivity is improved, but temperature distribution becomes uneven causing distortion
Solution Approach 1:
The patent applies local quality by differentiating the heating approach for different regions of the assembly body. The inner circumferential side receives accelerated localized heating, while other regions follow the conventional heating rate. This localized quality control ensures rapid overall heating without causing excessive temperature gradients that would lead to distortion, thereby maintaining dimensional accuracy while improving productivity.
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 inhibits the occurrence of gaps and defects at the brazing interface, ensuring a strong bond and reducing manufacturing costs by shortening the brazing thermal cycle while maintaining the dimensional accuracy and strength of the impeller.
Implementation Method 1
a heating setup that heats the impeller from the inner circumferential side to reduce temperature distribution
Implementation Method 2
Bonding by brazing has a thermal cycle in which, with a brazing material made of, for example, an Au—Ni alloy, being interposed between members to be bonded
Implementation Method 3
a gap may occur between the disk 11 and the blades 13, which are supposed to have been bonded via the brazing material, due to a difference in generation temperature during a heat treatment
Data Source
AI summary
The present invention relates to an impeller manufacturing method in which a thermal cycle is performed on an assembly body with a brazing material formed of a Ni-containing Au alloy being placed at a bond portion of at least two impeller constituent members. The thermal cycle includes a temperature increasing process with a temperature increasing rate of 20° C./hr. to 100° C./hr., the process including a first intermediate retention and a second intermediate retention each keeping the temperature, the first intermediate retention performed in a temperature range of 500° C. to 850° C. and the second intermediate retention performed in a temperature range of 850° C. to 950° C. (but not including 850° C.). In the thermal cycle, the temperature is increased in a temperature range exceeding 950° C. after the second intermediate retention at a rate lower than that before the second intermediate retention.