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| Preparation and properties of large-size ZrO2 delivery tube for vacuum induction melting gas atomization |
| WANG Laiwen1，YU Jianbin1，SHUI Guoyan2，GUO Xinli2，WANG Gang1，DU Penghui1 |
| （1. Sinosteel Luoyang institute of Refractories Research CO., Ltd, State Key Laboratory of Advanced Refractories,
Luoyang 471039,China; 2. Shenyang Research Institute of Foundry, Shenyang 110022,China） |
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Abstract Ceramic delivery tube was the key functional component of vacuum induction melting gas atomization
method(VIGA). With the enlargement of equipment, the size of ceramic delivery tube was also gradually larger.
The BN delivery tube had good thermal shock resistance, but it was prone to oxidation and erosion in practical
application. It was one of the main factors affecting the production and alloy powder quality. ZrO2 had high temper‐
ature resistance, wear resistance, chemical resistance, low specific heat and thermal conductivity, so it was the ideal
material to replace the BN delivery tube. The thermal shock resistance of ZrO2 became worse with its larger size
and more complex structure. Large size delivery tube with complex structure and heavy wall( 20 mm thickest ) re‐
quired higher fluidity of hot injection moulding. The effects of paraffin addition amount and sintering temperature
on the performance of large-size ZrO2 delivery tube were studied. On account of phase transition, the thermal shock
resistance of m-ZrO
2 was poor. Stabilizers were usually introduced to make m-ZrO2 become partially stabilized
ZrO
2. MgO, CaO and Y2O3 were the commonly used stabilizers. MgO stabilized ZrO2 had the best thermal shock re‐
sistance. The Large-size ZrO2 delivery tube was prepared by hot injection moulding with MgO stabilized ZrO2 and
monoclinic ZrO
2 as the main materials, MgCO3 as the stabilizer, the paraffin wax addition amount of 9.5%, 10%
and 10.5% respectively. After degreasing, the bodies were sintered at 1 650, 1 700 and 1 750 ℃ for 7 h, respectively. The results shows that the density and room temperature flexural strength of the samples are gradually increased
with the increase of sintering temperature. The density, room temperature flexural strength and thermal expansion
coefficient of the samples are decreased with the increase of paraffin wax addition amount. The density and thermal
expansion coefficient of imported large-size ZrO2 delivery tube are lower than that of the experimental samples,
and the thermal shock resistance at 1 100 ℃ is equivalent to that of the experimental samples sintered at 1 700 ℃
with the paraffin wax addition content of 10%. Through this study, the technical bottleneck that hot injection
moulding cannot prepare thick-wall products has been broken, and the technical parameter for preparing thickwalled products by hot injection moulding is determined. The delivery tube sintered at 1 700 ℃ with the paraffin
wax addition content of 10% has the best comprehensive performance and meets the requirements of one-time
on-line service. Improving the cold shock resistance of delivery tube is beneficial to its reuse.
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Received: 24 February 2022
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2022, Vol. 32 
