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Brazeability test for CAB materials - comparision with flux spreading test
2004 (English)Independent thesis Advanced level (degree of Master (One Year))Student thesis
Abstract [en]

The market for aluminium heat exchangers has seen a massive growth the past decades, mostly since the demand for lightweight materials in vehicles has arisen (in order to save energy). Aluminium heat exchangers are preferably joined by brazing. One of the most common brazing methods is controlled atmosphere brazing (CAB). For proper joining to occur, the joint surfaces must be free from oxides. In CAB, a fluoride-based flux is used to dissolve the oxide layer on the aluminium surface. Different brazing results are achieved with different aluminium alloys, and there is no simple and effective method to determine the actual brazeability for CAB materials. The purpose of this project was to investigate new test methods for evaluating brazeability in CAB and to find a possible correlation between brazeability and flux spreading in CAB. A method to examine flux spreading has been developed by the Swedish Institute of Metal Research (SIMR) in collaboration with Sapa Technology (ST) and has been used to measure the ability of the flux to dissolve the oxide layer on an aluminium surface. The three brazeability test methods that were examined along with the flux spreading test, were Angled T-joint test, Gradient of flux, and Angle on coupon. The results from these methods did not show any regular differences between alloys or surface preparations. However, interesting results from the Gradient of flux samples were collected, and these results could be connected to the flux spreading test which proved the correlation between brazeability and flux spreading. The most important conclusions drawn from this project are: ß The great irregularities in the CAB batch furnace at ST, makes it unsuitable to detect small differences in brazeability. ß There is a correlation between brazeability and flux spreading. ß The flux spreading test can be used for evaluating brazeability of CAB materials. ß The method can indicate small differences between substrates, and it can be used to evaluate influence of different alloys, surface preparations, storage parameters, etc. ß The flux spreading results from this project are similar to those of SIMR, which indicates that the flux spreading test is a repeatable method. The flux spreading test has proven to be a powerful tool when evaluating Al surfaces. The method has great potential and is a simple and quick method for deciding brazeability. However, since the melt area is manually measured and calculated, caution must be taken when comparing results from different operators.

Place, publisher, year, edition, pages
2004. , 55 p.
Identifiers
URN: urn:nbn:se:kau:diva-57207Local ID: MTK D-2OAI: oai:DiVA.org:kau-57207DiVA: diva2:1121810
Subject / course
Mechanical Engineering
Available from: 2017-07-12 Created: 2017-07-12

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  • apa
  • harvard1
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  • vancouver
  • Other style
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  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
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  • text
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