Review
Many interested pairs of eyes focus on the two flames aimed towards the aluminium parts. The brazing alloy begins to melt, the flames recoil and the two aluminium parts are joined together. Practically experienced knowledge is better understood than mere hypothesis. Over 20 participants of the EABS in Hannover in early October enjoyed a lively two-day seminar with many practical demonstrations on the fundamentals of aluminium brazing.
The seminar participants learned about metallurgy, flame brazing, furnace brazing, material science and much more. “A fast-paced seminar – the lessons were interesting and comprehensible. I particularly liked the subsequent implementation from theory into practise,” said Antonella di Parigi from Solvay in Italy
In September 2012 the aluminium industry met in Shanghai for a two-day seminar. SAPA, namesake and host, organized the conference to the complete satisfaction of the more than 350 participants, who mainly came from the Asian region. Numerous lectures and discussions were held on the three thematic areas automotive, HVAC/R and EV (electro vehicles) were held in parallel.
The latest material trends in the aluminium sector and the processing thereof were among the highlights of the event. “Above all, the well-attended lectures with the main focus on HVAC/R showed that brazed aluminium heat exchangers are well established in the market,” said Dr. Hans-Walter Swidersky, NOCOLOK Technical Marketing.
In September the NOCOLOK Team shared the booth at Chillventa with the refrigerants colleagues from Solvay Special Chemicals. The exhibition for refrigeration and air-conditioning technology, held annually in Nuremberg, was extremely well attended during the three days with 29,000 trade visitors.
The NOCOLOK Team were also delighted with the numerous customer contacts from the air-conditioning sector. Brazed heat exchangers indicate an upward trend in the European markets. The technique is now well established and is applied by many manufacturers.
The 5th International Trade Fair Joining Cutting Surfacing was an extremely large event, with plenty of presentations and over 6,000 visitors from October 30th to November 1st in Mumbai, India. Apart from lectures, there were hundreds of different exhibitions booths.
Dr. Leszek Orman from the NOCOLOK Team made a presentation about aluminum brazing with more than 30 visitors showing particular interest. Discussions with customers from India made the show a great success for Dr. Orman.
Outlook
Visit us at the AHR EXPO 2013 Solvay Special Chemicals is taking part at the AHR EXPO 2013 from January 28 to 30. Solvay Special Chemicals will show two main topics for the HVAC/R industry at the show: NOCOLOK Pioneered Flux Technology‚ Connected Thinking.
SOLKANE Refrigerants‚ High Performance Refrigerants Visit us and talk to our experts at the AHR EXPO 2013, 28‚ 30 January 2013, Dallas Convention Center, 650 S Griffin St., Dallas, Texas 75202, Stand 2587
Expansion of NOCOLOK capacity at the
August 2012 saw the start of the new facility for the processing of potassium hydroxide in the Solvay plant Onsan in South Korea. In an exact defined process, the flux for aluminium brazing, NOCOLOK, is manufactured from the delivered potassium hydroxide. Thus, the annual production of NOCOLOK in Onsan can be increased by 30%.
The demand for NOCOLOK has grown steadily in recent years in Southeast Asia. With the capacity expansion, Solvay Special Chemicals is following the growing markets in Asia, especially China and Thailand. “Not only the automotive industry requires large amounts of flux, but also the HVAC/R industry now manufactures more heat exchangers from aluminium, which are applied in air-conditioning and refrigeration systems,” says Werner Schmitt, Global sales & Marketing Manager at Solvay Special Chemicals.
The Solvay plant in Onsan started the production of fluorine products in 2007. In addition to NOCOLOK, sulphur hexafluoride, iodine pentafluoride and F1EC are also produced. The plant employs approximately 100 people and is part of the global Solvay business unit Special Chemicals.
Connected global thinking and local support
In this issue we would like to introduce Dr. Ferdinand Hardinghaus, who is engaged in the Fluorine Research Center in Hannover.
Dr. Hardinghaus is chemist and wrote his doctoral thesis on the subject of inorganic chemistry in 1989. He has worked at Solvay since 1990 and has headed various laboratories at the Hoenningen plant. In 1995 he headed the research laboratory and was deputy production manager in Bad Hoenningen. His areas of expertise include nano materials and the scale-up process of the research facility in industrial production.
Since April 2011 Dr. Hardinghaus is coordinator of the inorganic application technology in Hannover and responsible for various Solvay Fluor and NOCOLOK products. The NOCOLOK Team benefits from his multifaceted perspectives in various challenges and his experience in the global business unit Solvay Special Chemicals’ research projects, where he conducts research with his colleagues across locations. His life centres around Bad Honnef, near Bad Hoenningen, where his family lives.
In his spare time, the enthusiastic rower still competes in races when he is not underway on his bike or motorcycle to search for interesting photo motives.
NOCOLOK Online Survey
First we would like to thank all those who participated in our online customer satisfaction survey. Your opinion is important and helps us to continuously improve our service. We are therefore happy about each completed online questionnaire. Those who have not yet participated should do so before 31st December to secure the last chance of winning an iPad 4.
For among all the participants in 2012, who expressed their opinion in our online survey, we will be raffling one of the ultimate Apple tablets in January 2013. Additionally, among all the participants of the 4th quarter we are raffling a 6th generation silver iPod Nano. Nadja Oehmigen from Hannover was "Lady Luck" and drew the winner's name of the 3rd quarter out of the box. Nadja supports the NOCOLOK Team in the back office area. The winner will receive his iPod at the end of November.
Click here for the survey
Selective Pre-Fluxing with Adhesives - Fashion or Progress
Editor: Dr. Leszek Orman and Dr. Hans W. Swidersky
Summary
Over the last 15 years, selective pre-fluxing - also called paint fluxing or binder-based fluxing - has evolved as an alternative method for applying flux powder in aluminium brazing industry. There are many activities to define process parameters of fluxing with adhesives.
The first part of this paper outlines key features of pre-fluxing. The methodology for measurements of physical characteristics of binders and paint flux mixtures are described. General rules for behaviour of flux paints in brazing process are discussed together with some examples of flux paint features.
In the second part a case study is shown to illustrate common challenges when brazing with flux paint. The last part of this paper provides a cost comparison as guidance for choosing the right fluxing method for two different cases, one being extremely negative and the second as a positive case.
3. Overview of Binders
Group | Adhesion providing components | Co-solvents / dispersion agents (examples only) | Carriers / solvents |
1 |
Polyurethane (aqueous polyurethane dispersion) |
N-Methyl-2-pyrrolidon |
water |
2 |
Water-based acrylic |
3-Methoxy-3-methyl-1-butanol |
water |
3 |
Solvent-based acrylic |
1-Methoxy-2-propyl acetate and others |
Preferably non-explosive and non-flammable organic solvents (e.g. esters of dicarboxylic acids) |
Table 1: Main groups of flux binders / flux paints.
One of the most important characteristic of a binder is the kinetics of binder removal. This property is measured by a method called Differential Thermal Analysis [DTA]. The specimen (binder or flux paint) is placed in a small crucible and heated with a preset rate. The device measures the change of weight of the specimen and heat emitted or absorbed by the sample. The test can be done in air or at a chosen gas atmosphere.
An example of the curves obtained in such device is shown in Fig. 1
Fig. 1: DTA curves obtained from liquid flux paint sample. Test performed in air.
The upper curve represents lost of weight upon heating, and the lower curve represents thermal effects appearing in the heated sample. The endothermic effect is associated with evaporation of the sample and the exothermic effect is usually connected with burning of the sample.
It should be observed that the above curves represent a sample of liquid flux paint. The removal of the liquid phase (carrier evaporation) takes place during curing of the painted part. This process is always done before putting the parts into the brazing line.
For flux paints made with water as a carrier it is simple evaporation. Removal of the solid phase (cured binder) which takes place at much higher temperature then evaporation of the carrier and on real parts is done after assembling and most commonly in the brazing line. Kinetics of the solid phase removal is shown in Fig. 2. In this case the analyzed sample is prepared by painting a metal surface, curing the paint and careful scratching off the solid paint, which is then analyzed in DTA device.
Fig. 2: DTA curves obtained from solid flux paint sample. Test performed in air.
As can be seen the end of the binder removal is in the temperature range of 450oC.
Binder Type |
Tested in Air |
Tested in Nitrogen |
Middle temp. [°C] |
End Temp. [°C] |
Weight loss [%] |
Middle temp. [°C] |
End Temp. [°C] |
Weight loss [%] |
Polyurethane Binder A |
355 |
530 |
99.7 |
370 |
460 |
99.6 |
Polyurethane Binder B |
360 |
550 |
98.5 |
370 |
460 |
97.5 |
Acrylic Binder C (water soluble) |
317, 382 |
450 |
87.2 |
220, 387 |
430 |
85.2 |
Acrylic Binder D (high adhesion) |
267 |
420 |
Not measured* |
385 |
Not measured* |
27.5 |
Acrylic resin Binder E |
275 |
400 |
86.9** |
370 |
450 |
89.3** |
* DTA performed only on ready mixtures **Lower values due to some flux residue (sample obtained from ready mixture) |
Table 2: Examples of debinding temperatures for different types of binders.
To simulate this condition, a dry flux paint sample was analyzed by DTA with a hold for 10 minutes at 300oC. As can be seen from Fig. 3, holding at constant temperature for a prolonged time does not lead to full removal of the binder. In the given case only about 36% of the binder was removed.
Fig. 3: DTA curves with holding time 10min. at 300oC Test performed in air.
Different furnace design and different size of the brazed parts are responsible for different heating kinetics in the brazing lines. An influence of different heating rates on kinetics of binder removal is shown in Fig. 4.
Fig. 4: DTA curves with different heating rates Test performed in air.
The curves presented in Fig. 4 were obtained from analyzing a polyurethane binder heated in nitrogen atmosphere. It can be seen that only the middle temperature is moved to higher values with increased heating rate. The beginning and end of the debinding process do not depend on the heating rate.
Several examples of debinding temperatures for different type of binders are presented in table 2.
Will be continued in the next issue of the NOCOLOK News.
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