the ageing process for extruded aluminum profiles
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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

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the ageing process for extruded aluminum profiles

The Ageing Process for Extruded Aluminum Profiles

By

Al Kennedy

Kennedy Eurotech Inc.

the ageing process
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
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The Ageing Process
  • Natural ageing occurs with time, but requires too much time and floor space in the plant
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The Ageing Process
  • Natural Ageing
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The Ageing Process
  • Plants use artificial ageing in ovens to achieve maximum properties with efficient use of time and floor space
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The Ageing Process
  • Artificial Ageing
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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.
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The Ageing Process
  • Most important to uniform ageing is how the oven is loaded.
  • Following are examples of incorrect loading practices:
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The Ageing Process
  • Loading the Oven
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The Ageing Process
  • Loading the Oven
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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
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The Ageing Process
  • Loading the Oven
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The Ageing Process
  • Loading the Oven
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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
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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
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The Ageing Process
  • Surveying The Oven
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The Ageing Process
  • What oven design is best?
  • Most age ovens in North America are end-flow type
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The Ageing Process
  • End-Flow Ovens
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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
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The Ageing Process
  • Cross-Flow Oven
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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
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The Ageing Process
  • Oven Loading: Cross-Flow or End-Flow?
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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?
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The Ageing Process
  • Quality control for ageing
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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
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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
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The Ageing Process

¿Preguntas?

Al Kennedy

www.alkennedy.net

www.pressmaintmanual.com

[email protected]

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