How Microstructure Affects Creep in Refractories

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How Microstructure Affects Creep in Refractories

• Creep and Microstructure in Refractory Materials
• V. Jokanovic, G. Djurkovic, R. Curcic
• Institute for Technology of Nuclear and Other
  Mineral Raw Materials, Belgrade, Yugoslavia
• ACERS Bulletin, Vol. 77, no. 7, pp 61-65, 1998

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Background

• Creep depends on load intensity and duration as
  well as on material parameters grain size,
  porosity, point-and-line defects, vacancy
  clusters, and the distribution of any glassy
  phase in a refractory
• Intergrain bonds are weakened by glassy phase
  components penetrating into the grain boundary
• Refractory solids are weakened when a glassy
  phase completely wets grains, and become prone to
  creep as a result

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Experimental Details

• Materials to be tested
• High alumina (HACh and HAD)
• Tar-bonded magnesite
• Dolomite (TMR and TDD)
• Silicate-bonded chrome-magnesite (CHMM)
• Sample Shape
• Equilateral cylinders
• 50mm diameter

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Experimental Details (2)

• Sample Preparation
• Brick surface was one base of the cylinder
• Other base of cylinder was made by grinding
• Testing procedure
• Pressure 0.2 MPa
• Heating rate 15ºC/min up to 1000ºC then 8ºC/min
  up to 1400ºC or 1500ºC
• Hold time 24 hours, except one high alumina
  sample which was 8 hours

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Results

• High sensitivity to creep deformation was found
  in high-alumina materials (HAD) and tar-bonded
  materials
• Primary creep characteristics rearrangement with
  larger pores
• Secondary creep characteristics plastic-viscous
  yielding
• Plastic-viscous yielding is caused by low-melting
  phases (glassy phases) located along the grain
  boundaries