Melted alumina-zirconia ceramic grains, abrasive tools and refractory parts produced from said grains
View Patent ↗A process for producing fused alumina-zirconia grits includes mixing raw materials suitable to produce grits with the following chemical composition, in % by weight: ZrO 2 +HfO 2 : 10–60%, Al 2 O 3 : 38–90%, SiO 2 : <0.8%, and Impurities: <1.2%. The process also includes adding carbon and aluminum metal to the mixture of raw materials to obtain a charged batch containing, in % by weight,: Carbon: 0.4–1% Aluminum metal: 0.5–2.5%. The process further includes melting the charged batch in an electric arc furnace with a voltage of 175–205 V and a delivered specific electrical energy of 2.5 to 4 kWh per kg of charge.
1. A process for producing fused alumina-zirconia grits comprising the steps of:
a) mixing raw materials to produce grits with the following chemical composition, in % by weight:
ZrO 2 + HfO 2 :
10–60%
Al 2 O 3 :
38–90%
SiO 2 :
<0.8%
Impurities:
<1.2%
b) adding carbon and aluminum metal to the mixture of raw materials to obtain a charged batch containing, in % by weight,:
Carbon:
0.4–1%
Aluminum metal:
0.5–2.5%
c) melting said charged batch in an electric arc furnace with a voltage of 175–205 V and a delivered specific electrical energy of 2.5 to 4 kWh per kg of charge.
2. A process for producing fused alumina-zirconia grits according to claim 1 , wherein said delivered specific electrical energy is 2.7–3.3 kWh per kg of charge.
3. A process for producing fused alumina-zirconia grits according to claim 1 , wherein said carbon is coke, pet coke, coal, or a mixture of these materials.
4. A process for producing fused alumina-zirconia grits according to claim 1 , wherein said carbon content is 0.7–0.9%.
5. A process for producing fused alumina-zirconia grits according to claim 1 , wherein said aluminum metal content is 2.4–2.5%.
6. A process for producing fused alumina-zirconia grits according to claim 1 , further comprising the following step d) after step c):
d) quenching said melted charged batch of step c).
7. A process for producing fused alumina-zirconia grits according to claim 6 , further comprising the following steps e) and f) after step d):
e) milling said quenched charged batch of step d) into grits,
f) calcining said grits at a temperature between 800° C. and 1100° C. for a time between 2 to 8 hours.
8. A process for producing fused alumina-zirconia grits according to claim 7 , wherein said calcining is operated at 850–950° C., for 3–5 hours.
9. A process for producing fused alumina-zirconia grits according to claim 7 , wherein, before step f), said grits are screened and grits of grit numbers from F12 to F120 (FEPA “F” standard) are selected.
10. A process for producing fused alumina-zirconia grits according to claim 1 , wherein, at step a), said mixture of raw materials produces grits further containing up to 10% by weight of at least one of the following oxides: yttrium oxide, titanium oxide and magnesium oxide, the content of Al 2 O 3 being reduced accordingly.
11. A process for producing fused alumina-zirconia grits according to claim 1 , wherein, at step a), said mixture of raw materials produces grits further containing up to 3% by weight of at least one of the following oxides: yttrium oxide, titanium oxide and magnesium oxide, the content of Al 2 O 3 being reduced accordingly.
12. A process for producing fused alumina-zirconia grits according to claim 1 , wherein, at step a), ZrO 2 +HfO 2 represent from 35 to 50% by weight and Al 2 O 3 represents from 48 to 65% by weight.
13. A process for producing fused alumina-zirconia grits according to claim 1 , wherein, at step a), ZrO 2 +HfO 2 represent 38–45% by weight.
14. A process for producing fused alumina-zirconia grits according to claim 1 , wherein, at step a), SiO 2 represents <0.4% by weight.
15. A process for producing fused alumina-zirconia grits according to claim 1 , wherein, at step a), said mixture of raw materials produces grits further containing at least one of yttrium oxide in an amount from 0.3 to 2% by weight and titanium oxide in an amount from 1 to 3% by weight and magnesium oxide in an amount from 1 to 2% by weight, the content of Al 2 O 3 being reduced accordingly.
16. A process for producing abrasive tools comprising the production of fused alumina-zirconia grits according to a process according to claim 1 and further comprising one of the steps of bonding the grits by a binder; and depositing the grits as a layer on a flexible support and then retaining the grits by a binder.
17. A process according to claim 16 , wherein said abrasive tools are formed into wheels, and said binder is a vitreous mineral binder.
18. A process for producing refractory components comprising
a) the production of fused alumina-zirconia grits according to a process according to claim 1 and
b) the incorporation of said grits into a matrix.
19. A process for producing refractory components according to claim 18 , wherein said matrix is an oxide-based matrix.