The Ageing Process for Extruded Aluminum Profiles
28
The Ageing Process for Extruded Aluminum Profiles By Al Kennedy Kennedy Eurotech Inc.
description
The Ageing Process for Extruded Aluminum Profiles. By Al Kennedy Kennedy Eurotech Inc. 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 - PowerPoint PPT Presentation
Transcript of The Ageing Process for Extruded Aluminum Profiles
The Ageing Process for Extruded Aluminum Profiles
By
Al KennedyKennedy Eurotech Inc.
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
The Ageing Process
• Natural ageing occurs with time, but requires too much time and floor space in the plant
The Ageing Process
• Natural Ageing
The Ageing Process
•Plants use artificial ageing in ovens to achieve maximum properties with efficient use of time and floor space
The Ageing Process
• Artificial Ageing
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 185oC
(365oF) for 4 to 5 hours.• Most problems that occur are caused by non-uniformity
of temperatures throughout the oven and throughout the load.
The Ageing Process
•Most important to uniform ageing is how the oven is loaded.• Following are examples of incorrect
loading practices:
The Ageing Process
• Loading the Oven
The Ageing Process
• Loading the Oven
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
The Ageing Process
• Loading the Oven
The Ageing Process
• Loading the Oven
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
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
The Ageing Process
• Surveying The Oven
The Ageing Process
•What oven design is best? •Most age ovens in North America are end-
flow type
The Ageing Process
• End-Flow Ovens
The Ageing Process
End-Flow OvensAdvantages:• better thermal efficiency• more open area within the load for air flow• not affected by short profile loads• Requires less floor space• Cheaper to buildDisadvantages:• less temperature uniformity end-to-end
The Ageing Process
• Cross-Flow Oven
The Ageing Process
• Cross-Flow OvensAdvantages:• better temperature uniformityDisadvantages:• 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
The Ageing Process
• Oven Loading: Cross-Flow or End-Flow?
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?
The Ageing Process
•Quality control for ageing
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
The Ageing Process
The Ageing Process
• 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
The Ageing Process
¿Preguntas?Al Kennedy
www.alkennedy.netwww.pressmaintmanual.com
