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Research on Refractories for Sliding Nozzle Slides

The sliding water inlet is widely used to control the steel flow in the linked casting. Due to the strong erosion effect of sliding water in the water mouth, it is required to have high corrosion resistance and heat shock resistance. As the refractory material of the skateboard, Al2O3-C material is usually used. However, when casting special brand steel steel, AIO3-C quality material was strongly eroded.

We believe that due to the effect of adding some special additives in steel water during smelting, the skateboard material can be eroded. CAO, MNO, and Feo are particularly easy to react with Al203. As a result, a molten compound is formed, which quickly erodes the ALO3-C mass material.

Therefore, when casting a special brand steel containing the above components, the ALO3-C skateboard is strongly eroded. If the damage of ALO3-C is so serious, it is unreasonable to use it. Other materials should be used (eg, MG0-spinel, ZR02, MG0-C and other materials). But in terms of physical properties, there are differences between them. Therefore, it is necessary to pay attention to the chemical performance and physical properties of substitute materials.

Experiments

Sample

We have prepared 4 samples: MG0-spinel stone, ZR02, MGO-C, and Al2O3-C mass test sample for test comparison. Its performance is shown in Table 1. The above performance value is the value before the material was not impregnated with the coal tar.

Table 1 Properties of samples
 Al2O3-CMgO-SpinelZrO2MgO-C
Al2O37710
MgO88392
ZrO21194
C74
Open porosity/%19.812.517.310.9
Bulk density/g.cm-33.253.044.663.02

Anti -corrosion assessment

The corrosion test was performed in the rotary 坩埚 in 1650, and the erosion was evaluated. Figure 2 shows the test of the test device. The four test samples (80mmx60mmx30mm) are arranged to form a rectangular container, and the scum is injected into the container. Use the gas oxygen burner to implement heating.

Research on Refractories for Sliding Nozzle Slides

Table 2 lists the composition of the scum. The scum is synthesized in advance and sent into the pupa. The amount of additional people per hour is 200g.

To study the impact of corrosive composition of furnace slag. Use three different ingredients:

1. High A-CA0 content in furnace slag;

2. High content in the furnace slag B one MnO-SIO2;

3. High content in the furnace slag C, a high content.

The oxides selected for the research institute are components of corrosive skateboard materials.

Table 2 Chemical composition of slag
 Slag ASlag BSlag C
CaO35
MnO3520
Al2O335
FeO303070
SiO23510

Evaluate anti -erosiveness by determining the maximum depth of erosion in the sample cross section.

Anti -heat shock assessment

The method of heating to about 1800C is used to evaluate the heat shock resistance. Figure 3 shows the schematic diagram of the heat shock test. Heat the upper surface of the sample, and evaluate the number and width of the cracks on the cross section of the sample. The anti -folding strength was determined at 1400.

Research on Refractories for Sliding Nozzle Slides

The sample with a size of 150mmx25mmx25mm was used to determine the high -temperature resistance strength at the inert gas (N2) atmosphere in the atmosphere of 1400c in the atmosphere of the inert gas (N2) atmosphere, and the distance between the fulcrum was 125mm.

Results and discussion

Anti -corrosion assessment

Results of slag A (CaO-Al03-FeO system)

Fig. 4 shows the results of an erosion test of slag A having a high CaO content. The test results show that the slag resistance of Mg0-spinel, Zr02 and MgO-C materials to the slag is greater than that of AlO3-C materials. Presumably, its reason is: Mg0 or Zr02 and CaO do not produce low melting point phase when reacting. Due to the reaction with CaO, the Al2O3-C material is strongly damaged. In order to improve the corrosion resistance, Mg0-spinel, Zr02 and Mg0 materials should be used.

Research on Refractories for Sliding Nozzle Slides
Results of slag B (MnO-SiOz-FeO system)

Fig. 5 shows the results of the slag resistance test on the slag B with high MnO and SiO2 contents. Obviously, the slag resistance of AlO3-C and Mg0-spinel materials is lower than that of Zr0z and Mg0-C materials. Although the MgO content in MgO-C-based materials is similar to that in MgO-spinel-based materials, the corrosion resistance of MgO-C-based materials is significantly higher than that of Mg0-spinel-based materials. The reason is as follows: the carbon in the MgO-C material can prevent the slag from invading into the refractory matrix. Therefore, the reaction of the MgO-C material with the slag is limited to the surface.

Research on Refractories for Sliding Nozzle Slides

Mg0-spinel material does not contain carbon, but contains 10% ALO3. Al2O3 reacts easily with Mg0-SiOz components. Therefore, the slag is easy to invade the matrix of the Mg0-spinel sliding plate. The vitrified bond of the slide is damaged by the invading slag, and undamaged particles are released from the refractory structure. Therefore, the intrusion of slag leads to strong damage to the structure of the product. Impregnation with coal tar pitch is effective to improve the performance of Mg0-spinel materials, and this process can limit the intrusion of slag. The corrosion resistance of Zr02-based products is higher than that of Al03-C-based materials. However, MgO-C material has the best corrosion resistance to slag with high MnO-SiOz content.

Results of slag C (FeO-MnO-SiO2 system)

Fig. 6 shows the test results of slag C having a high FeO content. The corrosion resistance of MgO-C based materials is higher than other materials. The ZrO2-based material has good corrosion resistance to slags A and B, but it has poor corrosion resistance to slag C. It appears that the melting point of the phase produced when Zr0z-like material reacts with FeO-rich slag drops from 2000°C to 1400°C.

Research on Refractories for Sliding Nozzle Slides

Thermal Shock Resistance

Fig. 7 shows a cross-sectional view of the sample after the thermal shock resistance test. Few cracks were found in the AlO3-C material, and other samples also had cracks. However, AlO3-C samples suffered less damage.

Research on Refractories for Sliding Nozzle Slides

MgO-C based materials have wider cracks. Figure 8 shows the thermal expansion of the samples. It appears that the thermal expansion rate of the MgO-C material is large due to its low thermal shock resistance.

Research on Refractories for Sliding Nozzle Slides

The cracks of ZrO2 samples are narrower than those of MgO-C samples. Therefore, we speculate that its damage probability is less than that of MgO-C materials.

MgO-spinel material has less cracks and good thermal shock resistance. Since the Mg0-spinel material system is composed of periclase sand and spinel (Mg0.AlO3), the thermal expansion rate difference between periclase sand and spinel leads to the formation of microscopic cracks during the production stage. These microscopic cracks lead to a decrease in the modulus of elasticity and prevent cracks from appearing during application. For this reason, Mg0-spinel materials have good thermal shock resistance.

Flexural strength at 1400°C

The test results of the flexural strength at 1400° C. are shown in FIG. 9 . This parameter is smaller for the Mg0-spinel material than for the other three samples. It appears that the aforementioned microscopic cracks lead to a decrease in the high temperature flexural strength of these specimens. The values of this parameter for the other samples were quite high and the difference was not significant.

Research on Refractories for Sliding Nozzle Slides

Discussion about experiments

Fig. 10 shows the test results of slag resistance.

Research on Refractories for Sliding Nozzle Slides

MgO-spinel materials have good corrosion resistance to slags containing CaO, but poor corrosion resistance to slags with high MnO-SiO2 content and high FeO content. Zr02-based materials are severely damaged by slags with high Fe0 content.

Therefore, Mg0-spinel and Zr0z materials are not omnipotent in use, especially when casting special grades of steel. Therefore, it is necessary to find out which component has the strongest erosive effect when selecting materials for skateboards.

MgO-C materials have good corrosion resistance to all slags (including slags with high CaO content, high MnO-SiO2 content and high FeO content).

when subjected to thermal shock. Therefore, attention should be paid to the balance between slag resistance and thermal shock resistance when selecting materials for sliding gate slides.

In the case of MgO-spinel-based materials or Zr0z-based materials with higher thermal shock resistance than MgO-C-based materials, in order to improve erosion resistance, such materials can be used, although their erosion resistance is not high enough, but These materials can still be used in severe heat conditions.

In solving the problem of what material to use for the slide plate, service conditions, erosion resistance and thermal shock resistance (that is, aggressive components, casting hole diameter, turnover rate of the ladle, etc.) play an important role.

In order to improve materials for skateboards, MgO-C materials need to be improved in thermal shock resistance, and Mg0-spinel and Zr02 materials need to be improved in erosion resistance.

In addition, since the flexural strength at 1400 °C affects the erosion resistance and wear resistance, Mg0-spinel materials need to improve this index.

Conclusion

We evaluated the erosion resistance, thermal shock resistance and 1400 flexural strength of certain types of materials for skateboards:

●MgO-spinel material has good thermal shock resistance, but it only has good corrosion resistance to slag with high CaO content. The low flexural strength at 1400°C is due to the formation of microscopic cracks.

●Zr02 material has good corrosion resistance to slag with high CaO content and high MnO-SiO2 content, but its thermal shock resistance is lower than that of Mg0-spinel material. The high-temperature flexural strength of Zr0z material is higher than that of Mg0-spinel material, and its resistance to mechanical action is also higher than that of Mg0-spinel material.

MgO-C based materials have good erosion resistance to some aggressive components, but their thermal shock resistance is low. Therefore, Mg0-C materials are only used in occasions where the amount of thermal shock is minimal.

When selecting suitable materials for specific conditions of use, it is extremely important to evaluate the properties of skateboard materials.

Therefore, in order to improve the performance of materials used in slides, Mg0-spinel materials need to improve their erosion resistance and high temperature flexural strength; Zr02 materials should improve their erosion resistance and thermal shock resistance; Mg0-C materials should Improve its thermal shock resistance. For solving the above-mentioned problems, it is very important to prolong the service life of the sliding nozzle slide plate.

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As professional one-stop solution provider, LIAONING MINERAL & METALLURGY GROUP CO., LTD(LMM GROUP) Established in 2007, and focus on engineering research & design, production & delivery, technology transfer, installation & commissioning, construction & building, operation & management for iron, steel & metallurgical industries globally. 

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As professional one-stop solution provider, LIAONING MINERAL & METALLURGY GROUP CO., LTD(LMM GROUP) Established in 2007, and focus on engineering research & design, production & delivery, technology transfer, installation & commissioning, construction & building, operation & management for iron, steel & metallurgical industries globally. 

Our product  have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time.

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