TWI509077B - Refractory coating for blast furnace castings for cooling pipes - Google Patents

Description

Refractory coating slurry for blast furnace cast wall cooling pipe

The present invention relates to a coating slurry for pipe fittings, and more particularly to a refractory coating slurry for a blast furnace cast wall cooling pipe.

The Stave cooler used in blast furnace furnaces is traditionally made of cast iron (graphite spheroidized) block embedded cooling iron pipes, which are carried away by the cooling water that passes through the cooling iron pipes. The cooling iron pipe shall have a coating resistant to high-temperature molten iron corrosion when pouring high-temperature cast iron liquid to prevent the cooling iron pipe from sticking to the graphite cast iron block or causing corrosion and breakage, when the cooling iron pipe is bonded to the cast iron block, The iron pipe will be stressed and ruptured due to the thermal expansion and contraction effect, and the water leakage will damage the furnace body.

Conventional cast type (unshaped) refractory materials are formulated with calcium aluminate cement (CAC) as a binder, although the hydrated phase of the cement to provide a low temperature bond of the refractory material. However, when the cement-containing refractory coating heats up (or encounters high-temperature molten iron), the calcium aluminate cement is hydrated into various constituent phases, and it is difficult to remove water during the rapid heating process. Therefore, in the process of removing moisture The coating will create voids, and the water that is not discharged in time will vaporize at high temperatures and cause the coating to disintegrate.

Therefore, it is necessary to provide an innovative and progressive refractory coating slurry for a blast furnace wall cooling pipe to solve the above problems.

The invention provides an innovative and progressive refractory coating slurry for a blast furnace wall cooling pipe, and the technical problem to be solved is to improve the high temperature corrosion resistance and thermal shock resistance of the refractory coating of the blast furnace cast wall cooling pipe.

The technical problem solved by the present invention can be achieved by the following technical solutions. A refractory coating slurry for a blast furnace cast-wall cooling pipe according to the present invention, comprising: 35 to 60% by weight of zircon sand having a particle diameter of 0.2 to 80 μm; 8 to 20% by weight of alumina, The mature clay having a particle diameter of from 0.2 to 10 μm; from 8 to 20% by weight, having a particle diameter of from 0.3 to 40 μm; from 7 to 7.5% by weight of the cerium sol binder; and from 16.85 to 17.35 wt% of water.

The above description is only an overview of the technical solutions of the present invention, and the technical means of the present invention can be more clearly understood, and the objects, features, and advantages of the present invention can be more clearly understood. The preferred embodiment will be described in detail with reference to the accompanying drawings.

The composition of the refractory coating slurry for the blast furnace cast-wall cooling pipe of the present invention comprises 35 to 60% by weight of zircon sand, 8 to 20% by weight of alumina, 8 to 20% by weight of mature clay, and 7 to 7.5% by weight of cerium sol. The binder and 16.85 to 17.35 wt% water. In the present embodiment, the total weight of the powders such as zircon sand, alumina and mature clay is between 75 and 76% by weight, and zircon sand, alumina and mature clay of different particle sizes are used for preparation, and the particle size distribution of the raw materials is as follows. Figure 1 shows. Among them, the particle size of zircon sand-A is between 0.15 and 11 micrometers, which is a finer particle size, and the particle size of zircon sand-B is between 0.2 and 80 micrometers, which is a relatively coarse raw material and a particle size of alumina-A. The particle size of the clay-A is between 0.2 and 80 microns, the particle size of the mature clay-A is between 0.25 and 11 microns, and the particle size of the mature clay-B is between 0.3 and 40 microns. In this embodiment, the zircon sand has good thermal insulation performance and low thermal expansion coefficient, and has better thermal shock resistance; the alumina has the function of resisting high temperature corrosion; the alumina contains alumina and cerium oxide at high temperature. The formation of low thermal expansion coefficient of mullite (also known as mullite, Mullite) slows the expansion stress and increases the thermal shock resistance, and the clay can increase the plasticity of the slurry.

Figure 2 shows a sprayed implementation of the coating slurry of the present invention. In order to verify the high temperature corrosion resistance and thermal shock resistance of the refractory coating slurry for the blast furnace cast-wall cooling pipe, the coating slurry was sprayed on the blast furnace cast-wall cooling pipe at room temperature with a 2.5 mm diameter spray gun. In this embodiment, the coating slurry is fed by a gravity type, the volume of the cup is 400 c.c., and the slurry is transported with air of a pressure of 3.0 to 3.5 kg/cm ² , and the implementation thereof is as shown in FIG. 2 . Shown.

The refractory coating slurry is sprayed on the blasted steel sheet and dried at room temperature. There are two kinds of steel sheets in the embodiment: one is carbon steel and the size is 300×80×0.3 mm. The coating on the steel sheet is mainly evaluated for uniformity, thickness and 90 degree bending adhesion, and the coating bending adhesion is evaluated. It is to consider the adhesion of the coating on the rounded surface of the cooled iron pipe after drying; the other is a stainless steel piece with a size of 25×25×8 mm. The coating on the steel sheet is mainly subjected to a temperature of 30 °C for 30 minutes, and then taken out of the air. The thermal shock resistance was evaluated to observe the cracking and peeling of the coating.

Examples and comparative examples:

3 shows the appearance of the coatings of Comparative Examples 1 to 4 and Example 1 after drying; and FIG. 4 shows the appearance of the coatings of Example 1 and Comparative Example 4 after bending. Comparative Examples 1 to 4 of Table 1 show that the sprayed slurry does not use calcium aluminate cement (CAC) as a binder, and the combination of zircon sand-A, alumina and clay-A is used as a binder for the conventional refractory materials. When the material is used, the slurry has relatively more water content, good fluidity and uniform coating, but the coating is dried and cracked, as shown in Fig. 3.

The binder of spray refractory slurry has the function of medium temperature combined with refractory material, the binder aluminum sulfate has the function of high temperature combined with refractory material, and the binding agent polyvinyl alcohol has room temperature and low temperature combined with refractory material. The function, the binder sol (Colloidal silica, SiO ₂ content about 30%) has a combination of room temperature to high temperature, the solvent is water (H ₂ O), the dispersant polycarboxylic acid is also known as a debonding agent or a water reducing agent. It can increase the fluidity of the slurry and reduce the water consumption of the refractory slurry.

Comparative Example 1 shows that the low-temperature binder polyvinyl alcohol is not added, and only the medium and high-temperature binder is added. The powder in the coating is condensed and bonded by the capillary action, and the bond between the powder disappears when the water evaporates. , causing the coating to rupture. However, after changing the clay-A in the formulation to the mature clay-A, Comparative Example 3 showed no low-temperature bonding agent, and the coating only produced micro-cracks, but the chips were peeled off after bending, and the coating adhesion was still poor. . Example 1 is composed of a formulation similar to that of Comparative Example 3, and different amounts of 2, 1.5, and 0.5% by weight of polyvinyl alcohol are added. Only the coating of Example 1 has no peeling after bending, and the bending adhesion is good, as shown in the figure. 4 is shown. The slurry formulation of Example 1 was 9 wt% zircon sand-A, 9 wt% alumina, 21 wt% mature clay-A, 58.5 wt% water, and 0.5 wt% binder polyvinyl alcohol. When the binder polyvinyl alcohol is added in an appropriate amount, and the amount of the water solvent is decreased, and the amount of the powder is increased, the coagulation between the particles in the coating will be combined with the capillary phenomenon of the water instead of the polyvinyl alcohol bond to avoid evaporation of water. Loss of capillary action and break. In addition, the proportion of the powder in the slurry is increased from 41% to 45%, the amount of water is reduced from 57% to about 52%, and the ratio of zircon sand-A, alumina-A and mature clay-A and polyvinyl alcohol are changed. In the amount used, the coating exhibits large cracks and peeling.

Table 1. Composition and coating characteristics of spray coatings of Comparative Examples 1 to 4 and Example 1.

The increase of the amount of powder and the decrease of water content have not improved the cracking property after the coating is dried. It should be fine powder of 0.2 to 11 μm with cobalt sand-A, alumina-A and mature clay-A. According to the material, due to the fine powder formula, the capillary phenomenon absorbs more water. After the water in the drying process evaporates, the ability of the binder to replace the bonding with polyvinyl alcohol is insufficient, and the addition of the medium-high temperature bonding agent is unfavorable to the coating cracking property, so The mature clay-A is changed to a mature clay-B having a coarser particle diameter of 0.3 to 40 μm, and the coating is not cracked after drying. When the slurry formulation composition is 15% by weight of zircon sand-A, 15% by weight of alumina, 35% by weight of mature clay-B, the total amount of powder is increased to 65% by weight, the water content is reduced to 34% by weight, and the combination When the polyvinyl alcohol is 1% by weight, the coating has no cracking property, but for the slurry formulation of the room temperature bonding agent polyvinyl alcohol, the plasticity of the polyvinyl alcohol is not good at room temperature, and the coating is bent and deformed. It is easy to produce elastic rupture.

Figure 5 shows the appearance of the coatings of Examples 2 to 10 after drying; Figure 6 shows the appearance of the coatings of Examples 9 to 12 after bending. The slurry of the room temperature binder polyvinyl alcohol is very sensitive to the formulation composition and particle size selection, the reproducibility is not easy to control, and the coating has poor bending adhesion. Therefore, another type of room temperature binder 矽 sol is used instead of polyvinyl alcohol, and the slurry using ruthenium sol can be made at a lower water content by the repulsive force of a hydroxyl group (Si-OH). The slurry has good dispersibility and fluidity, and the mesh SiO ₂ particles formed by the dehydration process combine with the powder particles of other formulations to prevent cracking after drying. Examples 2 to 10 of Table 2 show formulations in which the powder content is increased to 66 to 80% by weight, and the fine powders of the previous particle size range of 0.15 to 11 μm, zircon sand-A, alumina-A, and mature clay-A are formulated. The mature clay-A in the composition is changed to mature clay-B (particle size range 0.3 to 40 μm), as in Examples 2, 3, 4, 5, 6 and 10, and the pulp is mixed with different ratios of bismuth sol binder. After spraying, the fluidity of the coating is different, but the coating will not crack after drying at room temperature, as shown in Fig. 5, in addition, even if the formula of the cooked clay-A is used, the coatings of Examples 7 and 9 are also Does not crack after drying. The coatings of Examples 2 to 10 exhibited good bending adhesion and no peeling, and the appearance of the coatings of Examples 9 and 10 after bending was shown in Fig. 6. The coating thicknesses of Examples 2 to 10 range from 0.15 to 0.4 mm, and the coating thickness is related to the powder solid content and the amount of the binder sol. For example, Examples 2 and 3 have a solid content of 66% by weight and a cerium sol content of 10, respectively. The weight % and 77% by weight, and the cerium sol content of 8% by weight, the coating adhesion thickness was doubled due to the different fluidity of the slurry, and was 154 and 310 μm, respectively.

Table 2. Spray paste composition and coating characteristics of Examples 2-10

Example 4 used 23% by weight of zircon sand-A, alumina-A and cooked clay-B, a powder content of 69% by weight and 10% by weight of cerium sol and 20% by weight of water to prepare a slurry, coating uniformity The thickness is up to 329 microns, the coating is not cracked and bent at 90 degrees without peeling and no micro-cracking. If the relative proportion of zircon sand-A, alumina-A and mature clay-B is changed, the content of mature clay-B is From 23% by weight to 33, 41% by weight. As in Examples 5 and 6, the coating thickness became thinner due to the increased fluidity of the slurry. The thickness of the coating was reduced from 329 to 280, 257 microns. The mature clay-B of the group increases the fluidity of the slurry. If the mature clay-B in the slurry is maintained at 28% and the total amount of the powder is increased to 80% as in Example 10, the coating thickness can be increased to 405 μm, and the coating is not peeled but slightly cracked after being bent. If the composition of the fine powders of zircon sand-A, alumina-A and mature clay-A is maintained, the amount of cooked clay-A is reduced to 12 to 16.5% by weight, and the sol-gel ingredients are used as in Examples 7 and 9, Then the coating does not crack after drying, but the bending is fine, although there is no peeling. If the amount of mature clay-A is too much, and the amount of mature clay-A is 31 and 23% by weight, the coating peels off when bent, such as reducing the amount of cooked clay-A to 7.5% by weight, then cracking after drying but bending There are still small pieces peeling off.

Therefore, the slurry is made of bismuth sol as a binder. When the size of the mature clay material used in the formulation composition is fine, such as cooked clay-A (0.2 to 10 μm), the amount used should be controlled between 12 and 16.5 wt% (if implemented) In Examples 7 and 9), the total amount of powder is between 61 and 71%, so that the coating can be dried without cracking, bending and peeling, which limits the amount of mature clay-A. On the other hand, if a general clay-A having a particle diameter of 0.2 to 80 μm is used, the amount is 11 to 25% by weight, the total amount of the powder is 66 to 74% by weight, and the coarse clay-A powder is finely mixed (0.2 to 10). The micron) powder zircon sand-A, alumina-A, has a wide particle size distribution, and the slurry dispersibility is better, but the coating is uniform, but the bending adhesion is poor.

Table 3 shows the spray paste composition and coating characteristics of Examples 11-18. When the alumina-A content is as high as 50 to 60% by weight and the coarse-grained clay-A ratio is relatively less than about 7 to 12% by weight, as in Examples 11 and 12, the coating does not peel after bending. As shown in Figure 6, but the coating is not thick enough to only 0.15 to 0.23 mm. The slurry is prepared by using a bismuth sol-binding agent. If the water content of the slurry is too much >24% by weight, and the particle size ratio of the powder raw material is improper, and the content of the easily-absorbed clay-A raw material is excessive, the coating ruptures after drying. The advantage of using the bismuth sol-binding agent is that the slurry can have good fluidity, dispersibility and sprayability under the condition of low water consumption, and the polyvinyl alcohol binder requires a larger amount of water to prepare the fluidity. Slurry, so the coating is prone to cracking after drying.

Figure 7 shows the appearance of the coatings of Examples 13-18 after bending. In order to increase the thickness of the coating, change the clay-A to mature clay-B, and control the content of zircon sand-A, alumina-A and mature clay-B (particle size 0.3 to 40 μm) to 16.5 to 31, respectively. % by weight, the total weight of the powder is 67 to 68.5% by weight, the amount of the cerium sol binder is 9.5 to 10% by weight, the viscosity of the slurry is about 1000 to 2000 cps, as in Examples 13, 14 and 15, and carbon black and SiC are added. As in Examples 16 and 17, the coating thickness was increased to 0.2 to 0.35 mm, and the coating did not peel off after bending, as shown in FIG. In order to increase the thickness of the coating, the first coating is dried for about 4 hours, and then the second coating is sprayed to increase the coating thickness. As in Example 18, the formulation of Example 14 is used. The slurry is sprayed twice to obtain a coating having a thickness of about 0.62 mm. The coating is only slightly cracked but not peeled after being bent; however, the slurry of SiC is added to obtain a thickness of about 0.67 mm by spraying twice. The coating, after the coating is bent, the second coating is cracked and peeled off, but the first coating does not crack and does not peel off.

Table 3. Composition and coating characteristics of spray pastes of Examples 11-18

In order to improve the bending adhesion of the thick coating, the powder is selected from the powder and the particle size level, and a small amount of a dispersing agent such as a polycarboxylic acid is added, in addition to reducing the water consumption and maintaining the proper fluidity of the slurry. Formulation composition of Example 19 of Table 4: 20% by weight of zircon sand-B, 35% by weight of alumina-A and 20% by weight of mature clay-B, in addition to using 7.5% by weight of cerium sol binder, an additional 0.15 weight was added. % of the polycarboxylic acid dispersant, when the coating thickness is 0.5 mm, there is no crack after peeling and no peeling. The use of a relatively coarse particle size of zircon sand-B, together with the use of a dispersing agent, can reduce the water consumption of the slurry, that is, have good fluidity, and when the thickness of the coating increases, it does not break and peel after bending.

Figure 8 shows the appearance of the coatings of Examples 19-26 (coating thickness ~ 0.5 mm) after bending; Figure 9 shows the appearance of the coating after thermal shock of Examples 19-26 (coating thickness ~ 0.5 mm); Figure 10 shows Examples 19-26 (coating thickness > 0.7 mm) Appearance of the coating after thermal shock. Table 4 shows that the spray paste formulations of Examples 19 to 26 have a composition of 35 to 60% by weight of zircon sand-B (particle size 0.2 to 80 μm) and 8 to 20% by weight of alumina-A (particle size 0.2 to 10). (micron) and 8 to 20% by weight of cooked clay-B (particle size 0.3 to 40 microns), total powder weight of 75 to 76% by weight and 7 to 7.5% by weight of cerium sol binder, 0.15% by weight of carboxy Acid dispersant and 16.85 to 17.35 wt% water, slurry viscosity of 1000 to 1500 cps, when the coating thickness is about 0.2 to 0.5 mm, there is no crack after peeling, no peeling, as shown in Figure 8, and the thermal shock test also shows No cracking and no peeling, as shown in Fig. 9, when the coating thickness is more than 0.7 mm, the coating is cracked but not peeled after the thermal shock test, as shown in Fig. 10, the coatings of Examples 25 and 26, when the coating When the thickness is more than 0.7 mm, only partial microcracking and no peeling after the thermal shock test is the best slurry of the present invention. In Example 25, a relatively large amount of 60% by weight of zirconium sand-B (compared to 50% by weight of Examples 21, 22, and 23) was preferred, and thermal shock resistance was preferred. In Example 26, only 35 % by weight was used. Zircon sand-B, but adding 5% by weight of niobium carbide powder (particle size <200 μm), and using 15% by weight of fine-grained alumina-A, when the coating thickness is greater than 0.7 mm, only after thermal shock test The local microcracks did not peel off, and showed better thermal shock resistance than Example 20.

Table 4. Composition and coating characteristics of spray pastes of Examples 19-26

Thermal shock resistance: After cooling at 1000 ° C for 30 minutes, take out air cooling.

Figure 11 shows the process and results of the high temperature molten steel ablation and thermal shock test of the coating of Example A and the coating of Comparative Example A. Example A shown in Figure 11 (i.e., Example 21 formulation slurry Al ₂ O ₃ -ZrSiO ₄ -Ripe Clay) coated steel bar and Comparative Example A (Al ₂ O ₃ -SiC-C based formulation slurry) The coated steel bar, when the coating thickness is about 0.5 mm, is immersed in the molten steel temperature at 1380 ° C for 30 seconds, and then taken out and cooled. The result shows that the coating of Example A has no crack and no peeling, and has better high temperature resistant steel liquid. Corrosive and thermal shock resistance, molten steel adhered to the coating, but the coating of Comparative Example A was ablated and resistant to thermal shock, but still retained a coating of about 0.2 mm. The results show that the present invention uses 50% by weight of zircon sand-B, 13% by weight of alumina-A and 13% by weight of mature clay-B, and the slurry prepared by the cerium sol can obtain high temperature resistance (>1350 ° C). Corrosion of molten steel and coating against thermal shock at 1350 °C.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the scope of the present invention. The scope of the invention should be as set forth in the appended claims.

1 shows a particle size distribution diagram of various raw materials used in the present invention; FIG. 2 shows a sprayed implementation view of the coating slurry of the present invention; and FIG. 3 shows the appearance of the dried coatings of Comparative Examples 1 to 4 and Example 1; 4 shows the appearance of the coatings of Example 1 and Comparative Example 4 after bending; FIG. 5 shows the appearance of the coatings of Examples 2 to 10 after drying; FIG. 6 shows the appearance of the coatings of Examples 9 to 12 after bending; FIG. The appearance of the coatings of Examples 13 to 18 after bending; Figure 8 shows the bending of the coatings of Examples 19 to 26 (coating thickness ~ 0.5 mm) Appearance; Figure 9 shows the appearance of the coating after thermal shock of Examples 19-26 (coating thickness ~ 0.5 mm); Figure 10 shows the appearance of the coating after thermal shock of Examples 19-26 (coating thickness > 0.7 mm); Figure 11 shows the process and results of the high temperature molten steel ablation and thermal shock test of the coating of Example A and the coating of Comparative Example A.

(no component symbol description)

Claims (7)

A refractory coating slurry for a blast furnace cast-wall cooling pipe, comprising: 35 to 60% by weight of zircon sand having a particle diameter of 0.2 to 80 μm; 8 to 20% by weight of alumina having a particle diameter of 0.2 Up to 10 microns; 8 to 20% by weight of mature clay having a particle size of from 0.3 to 40 microns; from 7 to 7.5% by weight of cerium sol binder; and from 16.85 to 17.35 weight percent of water. The refractory coating slurry for the blast furnace cast wall cooling pipe of claim 1, wherein the total weight of the powder such as zircon sand, alumina and mature clay is between 75 and 76% by weight. A refractory coating slurry for a blast furnace cast wall cooling pipe of claim 1 further comprising a polycarboxylic acid dispersant. A refractory coating slurry for a blast furnace cast wall cooling pipe according to claim 3, wherein the polycarboxylic acid dispersing agent is used in an amount of 0.15% by weight. The refractory coating slurry for the blast furnace cast wall cooling pipe of claim 1 further comprises a cerium carbide powder. A refractory coating slurry for a blast furnace cast wall cooling pipe according to claim 5, wherein the cerium carbide powder is used in an amount of 5% by weight. The refractory coating slurry for the blast furnace cast wall cooling pipe of claim 1 has a viscosity of 1000 to 1500 cps.