CN1092163C

CN1092163C - Heterogeneous zirconia-mullite refractory material with sintered bound phase and its preparation

Info

Publication number: CN1092163C
Application number: CN00125277A
Authority: CN
Inventors: 赵世柯; 黄校先; 郭景坤
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2000-09-19
Filing date: 2000-09-19
Publication date: 2002-10-09
Anticipated expiration: 2020-09-19
Also published as: CN1284487A

Abstract

The present invention relates to ZrO2-mullite complex phase fire-resistant material which takes reaction sintering products as a coupling phase and preparing technology, which belongs to the field of advanced fire-resistant material. The present invention is characterized in that superfine ZrSiO4 powder and Al2O3 powder are used as raw material; reaction sintering technology is adopted, the reaction sintering products of the superfine ZrSiO4 powder and the Al2O3 powder are used as the coupling phase of the fire-resistant material, and coarse-grain mullite and PSZ particles are used as aggregate; thus, the high performance ZrO2-mullite complex phase fire-resistant material is prepared by means of a phase composition and grain grading design and technologic process optimization. The preparing technology has the advantages of low price of the raw material and simple technologic process, and the ZrO2-mullite complex phase fire-resistant material has the characteristics of favorable combination performance and good repeatability.

Description

Zirconia-mullitemultiphase refractory material taking reaction sintering product as binder phase and preparation method thereof

The invention relates to a zirconium oxide (ZrO) with a reaction sintering product as a binding phase₂) The mullite composite refractory is prepared with coarse and medium mullite and partially stabilized ZrO₂(PSZ) isAggregate of ZrSiO₄And α -Al₂O₃The product of the reaction is the combined phase. Belongs to the field of advanced refractory materials.

Mullite (3 Al) is well known₂O₃·2SiO₂) Has a series of excellent thermal and mechanical properties (such as lower thermal conductivity and thermal expansion coefficient, excellent high-temperature creep resistance and thermal shock resistance, and good chemical stability and high-temperature strength), and is an ideal refractory material. Addition of ZrO to mullite matrices₂The strength, the erosion resistance and the thermal shock resistance of the material can be further improved. ZrO (ZrO)₂The mullite complex phase refractory material has wide application in the fields of glass melting, steel, metallurgy and the like, and has more and more paid more attention in the steel continuous casting process in recent years. Although this material has been developed for a long time and is widely studied, the continuous and rapid development of high temperature technology, especially steel and metallurgical technology, puts forward more and more rigorous requirements on the performance of refractory materials, which usually requires the material to have excellent mechanical properties, erosion resistance and thermal shock resistance, and the dependence of these properties on the compactness of the material is usually contradictory. Conventional refractory processes have not been able to meet this requirement, and thus ZrO of good overall properties has to be obtained₂The mullite complex phase refractory material has to break through the traditional refractory material organizational structure design and the traditional production process, and needs to introduce new ideas and technologies.

From the late 70 s of the 20 th century, people looked at ZrO₂Extensive and intensive research has been carried out on mullite multiphase materials. With ZrSiO₄And α -Al₂O₃Preparing ZrO by using a reaction sintering process as a raw material₂The mullite multiphase material is a low-cost route, and the prepared material has unique properties. However, since the mullite reaction during sintering adversely affects the densification, it is difficult to obtain a dense sintered body. In 1980, Claussen adopts an optimized reaction sintering process to obtain ZrO with excellent mechanical properties₂Mullite multiphase materials, since then, many scholars phase from different anglesPreparing ZrO by adopting reaction sintering process₂Mullite materials were studied, including the reactive sintering process, the microstructure and mechanical properties of the material and the influence of the addition of sintering aids. Later, this sintering process was introduced into the refractoryIn the preparation of the material, good effects cannot be achieved because the phase composition and the process are not optimized. Whether or not ZrSiO is allowed₄And α -Al₂O₃Reaction-sintered product of (1) -fine-grained dense ZrO₂The mullite multiphase ceramic material is a combined phase, and the ZrO with excellent performance is prepared by adopting a process of combining an advanced ceramic process with a traditional refractory material process₂Mullite complex phase refractories have been the goal of the materials workers to derive the concept of the present invention and have made beneficial attempts.

The invention aims to provide a method for preparing ZrO by combining an advanced ceramic process with a traditional refractory material process and taking a reaction sintering product as a binding phase₂-mullite complex phase refractory material and a preparation method thereof.

The invention is implemented by the following technical processes:

with industrial superfine ZrSiO₄And α -Al₂O₃The powder is used as raw material, a reaction sintering process is adopted, the fine-grained compact reaction sintering products of the powder and the reaction sintering product are used as a binding phase of the refractory material, and coarse-grain mullite, medium-grain mullite and partially stabilized ZrO are used₂The particles are aggregate, and ZrO with special tissue structure is prepared by phase composition, particle grading design and process optimization₂-mullite complex phase refractory.

The specific preparation process comprises the following steps:

(1) the used raw material is industrial superfine ZrSiO₄Powder:

ZrO₂the content is more than 65 percent, and the granularity is 0.2-5 mu m;

industrial superfine α -Al₂O₃Powder: the granularity is 0.1-3 mu m;

commercially available sintered synthetic mullite grains: close to stoichiometric composition, with a particle size of 1-3 mm;

electrofused partially stabilized ZrO2 particles: the mesh size is 40 mesh and 200 mesh.

(2) Adopting multi-stage particle composition, coarse particles: and (3) medium particle: the fine particles are 3-6: 1-2: 4-6 (volume ratio), and each particle fraction has a sub-grade gradation. Wherein the coarse, medium and fine particles of each gradation are ZrO₂And mullite composition, differing only in grain size and origin.

ZrO in coarse and medium grains₂Calcium oxide or yttrium oxide derived from the above (1) for partially stabilizing ZrO₂(PSZ) such as Ca-PSZ, Y-PSZ and the like; the coarse and medium-grade mullite grains are from the sintered and synthesized mullite in the step (1).

The coarse mullite is prepared by ball-milling sintered mullite of 1-3mm with WC balls for 45 min (ball: material is 4: 1), sieving with a 20-mesh sieve to remove large particles, and sieving with a 40-mesh sieve to remove fine particles, thereby obtaining mullite particles with particle size of 0.5-1 mm.

The medium-grain mullite refers to mullite grains with the median grain diameter of 19.7 mu m, which are obtained after coarse-grain mullite grains are ball-milled for 2 hours by WC balls and sieved by a 40-mesh sieve.

And fine-grained mullite and ZrO₂ZrSiO derived from the above (1)₄And Al₂O₃The ultrafine powder is a reaction product obtained by the following reaction:

fine crystalline ZrO formed by the above reaction₂And mullite as a bonding phase of coarse and medium particle aggregates to form ZrO with a special structure₂-mullite complex phase refractory. Meanwhile, the coarse and medium-grain mullite can play a role of seed crystals, and the defect that the green body is difficult to sinter is overcome to a certain extent.

In the coarse grain and medium grain compositions, the weight ratio of ZrO2 to mullite in the sub-level composition is equal to 36.6: 63.4, and the weight ratio of ZrO2 to mullite generated after the ZrSiO4/Al2O3 mixed powder is completely reacted is equal to that of the ZrO2 and the mullite generated after the ZrO 4 and the mullite are completely reacted.

(3) The concrete preparation process is characterized by that it uses multistage grain composition and mixture formed according to a certain proportion, uses distilled water as medium and uses ZrO₂Ball milling and mixing for 24 hours, drying and sieving with a 20-mesh sieve. Then adding 5 wt% PVA solution as binder, stirring and microwave drying, sieving, forming by dry pressing, isostatic pressing or dry pressing first and isostatic pressing second common advanced ceramic forming process, and sintering at 1600-1700 deg.C in air to obtain ZrSiO₄And Al₂O₃The reaction sintering of the fine powder and the sintering of the green body are carried out simultaneously to obtain ZrO with the reaction sintered product as a binding phase₂-mullite complex phase refractory.

The invention is characterized in that the invention adopts the process of combining the advanced ceramic and the traditional preparation method of refractory materials, and the ZrO with special structure is obtained by combining fine-grained compact ceramic with coarse-grained aggregate₂-mullite complex phase refractory. Coarse grain mullite and ZrO₂The material is embedded in a fine particle matrix, the fine particle area is uniform and compact, the coarse particles and the fine particles are well combined, but an obvious interface can be observed, and the structure ensures that the material has high mechanical property and good thermal shock resistance. In addition, the density of the material is higher, which is beneficial to improving the erosion resistance.

Table 1 lists the basic properties of several materials described in the examples.

TABLE 1ZrO₂Basic properties of mullite multiphase refractories

^*σ_f: bending strength; R.T.: at room temperature

As can be seen from Table 1, compared with the traditional refractory material, the material prepared by the process provided by the invention has outstanding mechanical properties and good thermal shock resistance, and the adopted raw materials are low in price, simple in process and good in industrialization prospect.

FIG. 1 is an SEM photograph of a fracture of specimen No. C.

It can be clearly seen from the figure that the coarse particles are embedded in the fine particle matrix, and some air holes are distributed on the interface of the coarse particles and the matrix, but the combination is still relatively tight. The fine particle region is uniform and dense, and is essentially all transgranular fracture. As mentioned above, the microstructure ensures that the material has high mechanical property and good thermal shock resistance.

The substantial features and the remarkable improvements of the present invention are further illustrated by the following specific examples, which are by no means limiting.

Example 1

Coarse mullite (average particle size of about 0.5-1mm) and Ca-PSZ (40 mesh) were used as aggregates in a weight ratio of 63.4: 36.6, and the medium particles were also composed of mullite (median particle size of 19.7 μm) and Ca-PSZ (200 mesh) in the same weight ratio as above. The fine particles are formed by industrial superfine ZrSiO₄And Al₂O₃The powder composition is as follows:

and (4) batching. The volume ratio of the coarse particles, the medium particles and the fine particles after the reaction is completed is 5: 1: 4. The sample is subjected to dry pressing and then isostatic pressing (200MPa), and then is sintered in the air at the temperature of 1640 ℃ for 3 h. The properties of the resulting material are shown in Table 1 (numbered A).

Example 2

Mullite having an average particle size of about 1mm was used as the coarse particles, mullite having a median particle size of 19.7 μm was used as the medium particles, and the composition of the fine particles was the same as in example 1. The volume ratio of the coarse particles, the medium particles and the fine particles was determined to be 4: 1: 5 in terms of complete reaction. The sample is subjected to dry pressing and then isostatic pressing (200MPa), and then is sintered in air at 1680 ℃/3 h. The properties of the resulting material are shown in Table 1 (numbered C), and the microstructure of the material is shown in FIG. 1. The thermal shock sample prepared by the material is repeatedly quenched (water quenching test) for 20 times at the temperature delta T of 1100 ℃, the sample is intact, and the surface of the sample has no obvious cracking and peeling phenomena. The rest is the same as example 1.

Example 3

The volume ratio of the coarse particles, the medium particles and the fine particles is determined to be 3: 1: 6 according to the complete calculation of the reaction. The sample is subjected to dry pressing and then isostatic pressing (200MPa), and then is sintered in air at 1680 ℃/3 h. The properties of the resulting material are shown in Table 1 (numbered D).

Claims

1. ZrO (ZrO)₂-mullite multiphase refractory material from ZrO₂And a mullite phase, characterized in that:

(1) with industrial superfine ZrSiO₄And Al₂O₃Reaction sintered product of powder-fine grain compact ZrO₂Mullite multiphase ceramic is a binding phase, and the grain sizes of the two kinds of powder are 0.2-5 μm and 0.1-3 μm respectively;

(2) coarse and medium grained mullite and ZrO₂The aggregate is embedded in the reaction sintering product matrix;

(3) the volume ratio of the coarse particles, the medium particles and the fine particles formed by reactive sintering is 3-6: 1-2: 4-6 calculated according to complete reaction;

(4) the average grain diameter of the coarse grains of the mullite grains is 0.5-1mm, and the median grain diameter of the medium grain diameter is 19.7 mu m; ZrO (ZrO)₂The particle diameter of the coarse particles is 40 meshes, and the particle diameter of the medium particles is 200 meshes.

2. The composite refractory of claim 1, wherein the coarse-grained, medium-grained composition comprises ZrO in a sub-level composition₂The weight ratio of mullite and ZrSiO is equal, and the weight ratios of mullite and ZrSiO are 36.6: 63.4₄/Al₂O₃ZrO produced after complete reaction of the mixed fine powder₂And the weight ratio of the mullite is equal to that of the mullite.

3. A process for preparing a complex-phase refractory according to claim 1, wherein the green body is shaped by isostatic pressing or dry pressing followed by isostatic pressing, ZrSiO₄And Al₂O₃And the reaction sintering of the fine powder and the sintering of the green body are carried out simultaneously, and the sintering temperature is 1600-1700 ℃.

4. The method of preparing a material according to claim 3, whichCharacterized in that said ZrO₂ZrO particles partially stabilized with calcium oxide or yttrium oxide₂(ii) a The mullite grains are sintered mullite sold in the market.