Crucibles Overview

All crucibles, alumina, magnesia and zirconia to name a few, are manufactured in Capital's own modern purpose-built facility in the Czech Republic where we press, cast and fire various materials into crucibles.

Product Range

Isopressed

Capital Refractories is able to supply a full range of isostatically pressed crucibles from 2 kg capacity to 75 kg, in different grades and qualities. We use a state-of-the-art semi-automated cold isostatic press. Cold isostatic pressing applies pressure to the workpiece in all directions producing products of uniform density. 

The advantages of Isostatically Pressed Crucibles are:

  • Wide range of qualities
  • Wide range of crucibles sizes
  • Smooth internal surface giving a reduction of inclusions
  • Consistent material properties throughout crucible
  • Defect free- no casting bubbles etc
  • Uniform density throughout the product improving its resistance to thermal stress

Vibrocast

Crucibles are produced by vibration casting (vibrocast) when the required size or shape is uneconomical or impractical by the isopressing production method.

Capital Refractories can offer a range of vibration cast crucibles, including T-Pot Ladles:

Benefits
Complex shapes, e.g. internal pouring siphon

To complement our range of crucibles we also offer numerous ancillary products and materials used within the investment and related foundry industries.

Description

Quality Description
Alumina: General purpose crucible with good resistance to acidic and basic slags. Used for a wide range of alloys and stainless steels.
.....AL97I .....Superior erosion resistance
.....AL88I .....Improved thermal shock resistance
.....AL90C .....General purpose with good strength and thermal shock resistance.
.....AL97C .....Improved resistance to slag.
Chrome Alumina High resistance to slags; preferred to alumina in more arduous applications.
.....CA93I .....Superior erosion resistance
.....CA84I .....Improved thermal shock resistance
.....CA91I .....Superior thermal shock resistance
Magnesia High resistance to basic slags.
.....MG88I .....Used for a variety of alloys.
.....MG95I .....Higher resitance to more exotic alloys.

Chemistry

Quality Al₂O₃ SiO₂ MgO CaO Fe₂O₃ Cr₂O₃ ZrO₂ + HfO₂
Alumina AL91I 97.5 1.6 - 0.1 <0.1 - -
Alumina AL88I 88.5 9.4 - 0.1 0.2 - -
Alumina AL90C 90.7 8.7 <0.1 0.1 0.1 0.2 -
Alumina AL97C 96.6 2.5 <0.1 0.1 0.1 0.2 -
Chrome Alumina CA93I 93.4 2.2 - 0.1 <0.1 3.6 -
Chrome Alumina CA84I 84.3 9.0 - 0.1 0.2 4.8 -
Chrome Alumina CA91 91.5 2.2 - 0.1 <0.1 5.3 -
Magnesia MG88I 3.5 3.8 88.0 3.8 0.2 - -
Magnesia MG95I 0.5 0.8 95.0 2.5 0.1 - -

Properties

Quality Bulk Density ( g / cm³) Apparent Porosity (%) Thermal Expansion (x10-6 / K) Thermal Conductivity (W / m K) Maximum Service Temperature (°C)
Alumina AL97I 2.95 23.8 8.0 4.2 1700
Alumina AL88I 2.59 23.8 8.0 4.2 1700
Alumina AL90C 2.9 18.0 7.7 4.0 1750
Alumina AL97C 3.1 19.6 8.0 4.1 1800
Chrome Alumina CA93I 3.05 23.0 8.2 3.4 1800
Chrome Alumina CA84I 2.85 20.0 7.6 3.4 1730
Chrome Alumina CA91I 3.10 21.5 8.2 3.4 1800
Magnesia MG88I 2.83 17.0 14.5 2.4 1700
Magnesia MG95I 2.95 15.0 13.0 2.5 1750

Crucibles suffixed I are isopressed, those sufficed C are cast.

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