1. The Ageing Process for Extruded Aluminum Profiles By Al Kennedy Kennedy Eurotech Inc.

2. The Ageing Process Extrusions in Al-Mg-Si family are aged to improve properties Called “age hardening” but goal is not hardness, but increased ultimate tensile strength and yield strength The precipitation process is quite complex and involves the solubility of inter-metallic clusters that precipitate within the alloy

3. The Ageing Process Natural ageing occurs with time, but requires too much time and floor space in the plant

4. The Ageing Process Natural Ageing

5. The Ageing Process Plants use artificial ageing in ovens to achieve maximum properties with efficient use of time and floor space

6. The Ageing Process Artificial Ageing

7. The Ageing Process These charts from the paper Precipitation Aging by R.W. Hains show that maximum properties are achieved quickly under controlled temperatures and time. From these and similar references the ideal process parameters of time and temperature can be defined for ageing profiles of different alloys. A common process for ageing alloy 6063 is at 185 o C (365 o F) for 4 to 5 hours. Most problems that occur are caused by non-uniformity of temperatures throughout the oven and throughout the load.

8. The Ageing Process Most important to uniform ageing is how the oven is loaded. Following are examples of incorrect loading practices:

9. The Ageing Process Loading the Oven

10. The Ageing Process Loading the Oven

11. The Ageing Process Most important principle: hot air must pass through the load, with maximum contact with the extrusions If hot air can by-pass the load, over the top or around the sides, ageing will not be uniform and the heating cycle will be much longer

12. The Ageing Process Loading the Oven

13. The Ageing Process Loading the Oven

14. The Ageing Process The age cycle has two parts: Heat-up, or time for the entire load to reach temperature, and Time at correct temperature for ageing or precipitation Must assure that the entire load is at the correct temperature for the specified time

15. The Ageing Process Conduct frequent surveys of oven temperature, to assure uniform temperatures Locate thermocouples throughout the oven to check for hot and cold places Make surveys every 3 months to 1 year

16. The Ageing Process Surveying The Oven

17. The Ageing Process What oven design is best? Most age ovens in North America are end- flow type

18. The Ageing Process End-Flow Ovens

19. The Ageing Process End-Flow Ovens Advantages: better thermal efficiency more open area within the load for air flow not affected by short profile loads Requires less floor space Cheaper to build Disadvantages: less temperature uniformity end-to-end

20. The Ageing Process Cross-Flow Oven

21. The Ageing Process Cross-Flow Ovens Advantages: better temperature uniformity Disadvantages: less thermal efficiency less open area for air flow adverse effect for short profile loads (air can by-pass the load) More expensive and more floor space required

22. The Ageing Process Oven Loading: Cross-Flow or End-Flow?

23. The Ageing Process Decision: Cross-Flow or End-Flow? Consider the mix of profiles to be aged: how are they stacked? Is there space between the layers? what is the maximum open space for air flow? does the length of loads allow by-passing? can air by-passing be avoided?

24. The Ageing Process Quality control for ageing

25. The Ageing Process A study by Mr. Bob Werner was presented at ET 84 Seminar He concluded that Webster hardness testing is not reliable enough for testing the properties of ageing. He recommended full tensile and yield testing as first choice Barcol is second choice Rockwell E is the third choice

26. The Ageing Process

27. Ageing cycle is determined by alloy Good properties require uniform temperatures and uniform time-at- temperature Uniform temperature depends on how the oven is loaded Prevent hot air from by-passing the load Take temperature surveys to assure quality

28. The Ageing Process ¿Preguntas? Al Kennedy www.alkennedy.net www.pressmaintmanual.com alkennedy@usa.net