JPS5852952B2 - Thermoradiant ceramic coating composition and method of use thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heat-radiating ceramic composition and a coating material for the interior of an industrial heating furnace (i.e., the refractory wall of the furnace and the metal structure inside the furnace) having heat-radiating properties. Regarding the method used as

BACKGROUND ART Heat-resistant paints for coating metal surfaces and compositions for coating refractory materials on furnace inner walls that utilize heat radiation have been known.

Furthermore, when indirect heat treatment is performed using metal structures inside the furnace, the absorption and re-radiation of the refractory material inside the furnace are improved, and the thermal conductivity absorption and re-radiation of the metal structures inside the furnace on the heat-receiving surface are improved. It is a well-known fact that we must also increase the

However, conventional coatings with heat radiation properties cause poor adhesion and peel off even when coated on metal structures inside the furnace.

Therefore, only the inner wall of the heating furnace can be coated, and as a result, the thermal energy absorbed from the surface of the furnace internal structure, conducted through the structure wall, and re-radiated onto the heated object placed inside the structure can be sufficiently absorbed. can't get it.

Therefore, the object of the present invention is to find a heat-radiating ceramic composition that not only has good thermal conductivity, heat resistance, and heat-radiating properties, but also has good adhesion that follows the expansion and contraction of metal due to heating and cooling. That's true.

As a result of research, this problem could be solved by the following composition: a) 40-750-75 parts by weight of silicon carbide, b) 15-405-40 parts by weight silicon 3-20 parts by weight, 5 parts by weight of phosphate. -20 parts by weight, 2-10 parts by weight of chromium oxide, 2-10 parts by weight of tantalum carbide and 5-20 parts by weight of aluminum powder, and c) 10-350-35 parts by weight of aluminum 1-10 Parts by weight, glass powder 3-15
3 to 15 parts by weight of zirconium oxide, 1 to 10 parts by weight of silicon dioxide, 1 to 10 parts by weight of magnesium oxide, and 1 to 10 parts by weight of iron oxide. and a thermally emissive ceramic coating composition, characterized in that the sum of components a) jb) and C) is 10,000 parts by weight.

Silicon carbide as a heat radiating material of component a) has a particularly high emissivity (total emissivity of 0.92 at a temperature of 20 to 300°C).
, the amount used is component a)>b) and c) (hereinafter abbreviated as all components).

) should be 40 to 750 to 75 parts by weight in total.

If this amount exceeds 755 parts by weight, when the composition is used as a coating, it becomes difficult to follow the coefficient of thermal expansion of metal, which causes the coating to peel off.

If the amount is less than 400 parts by weight, the thermal radiation properties and thermal conductivity of the coating will be significantly inferior, making it impossible to obtain the desired radiant energy.

Component b) acts as a heat radiation aid and a binder,
It is necessary to use 15 to 405 to 40 parts by weight based on the total of all components.

b) How many compounds make up the component and their mutual proportions: 3-20 parts by weight of silicon nitride, 5-20 parts by weight of phosphate, 2-10 parts by weight of chromium oxide, 2-10 parts by weight of tantalum carbide and aluminum. The powder is 5 to 20 parts by weight.

If the ratio of each compound constituting component b) exceeds the above range, desired heat radiation characteristics cannot be obtained.

If the amount of silicon nitride is less than 3 parts by weight, the airtightness of the coating will be impaired and the life of the heat radiation properties will be significantly reduced.

If the phosphate content is less than 5 parts by weight, the adhesive strength to the coating substrate will decrease.

If the amount of chromium oxide is less than 2 parts by weight, the amount of tantalum carbide is less than 2 parts by weight, and the amount of aluminum powder is less than 5 parts by weight, the desired heat conduction properties cannot be obtained and the adhesion strength to the object to be coated is poor.

Next, component C) must be in an amount of 10 to 350 to 35 parts by weight of the total of all components, and the individual compounds that make up component C) include 5 parts by weight of magnesium oxide, aluminum oxide, iron oxide, and silicon dioxide. 10 parts by weight each, zirconium oxide and glass powder should not exceed 15 parts by weight each.

If the amount of each of these components exceeds a predetermined range, a highly airtight fired coating layer of the heat radiator cannot be obtained.

If the amount of aluminum oxide, magnesium oxide, iron oxide and silicon dioxide is less than 1 part by weight each, and the amount of zirconium oxide and glass powder is less than 3 parts by weight, a stable composition with high adhesive strength cannot be obtained.

The coating amount of the coating composition of the present invention on the inner wall of the furnace is about 1.5 to 2.
．． OKp/@'', and the optimum amount of coating on the metal structures in the furnace is about 0.5 to 1.OKp/m.

The present invention further provides the method of applying the above-described thermally emissive ceramic coating composition onto a substrate, from a starting temperature of room temperature to 400°C to 500°C.
Heating for several hours (3-5 hours) with stepwise or continuous heating up to a temperature of 550-800°C
It also relates to a method of using the thermally emissive ceramic coating composition, characterized in that it is heated and fired at a temperature of from 1 to 3 hours.

Furthermore, when applying the composition of the present invention onto a substrate, if approximately 10 to 15 weight (based on the total amount of the composition) of water is additionally mixed into the composition, the coating process may be difficult. It was found that the performance improved.

If scale is observed on the metal furnace internals as a pre-coating treatment, it is necessary to remove it with a wire brush or the like.

One particularly advantageous embodiment of providing heat-resistant coatings to furnace wall refractories and internal furnace metal structures using the coating compositions of the present invention includes the use of coating compositions containing water in the proportions indicated above. After coating, there is a method in which the temperature is increased by 100° C. every hour to 400° C., and then further heated at 600° C. for 2 hours to bake the adhesive.

When the coating composition of the present invention is made into a coating in this way, it has heat resistance of 1850° C. or higher.

Furthermore, the coating achieves high thermal emissivity and saves thermal energy when applied to furnace inner wall refractories as well as to furnace metal fabrication structures.

For example, by applying the coating composition of the present invention to an indirect heating furnace, the heating time of the metal structure in the furnace on the heat receiving surface is 41.6
% and the thermal energy at that time was saved by 20%.

Next, one embodiment of using the thermal radiation ceramic coating composition of the present invention for coating an indirect heating furnace will be explained with reference to the accompanying drawings: Figure 1 is a schematic diagram of an indirect heating furnace, and 1 is a heating furnace using refractory and insulating bricks. , 2 is a resistance heating element, 3 is a metal structure inside the furnace, and 4 is a container containing heat medium oil.

FIG. 2 is a cross section of the refractory material for the inner wall of the heating furnace, and 5 shows the inner side of the furnace coated with the heat radiation ceramic coating composition of the present invention.

FIG. 3 is a cross-sectional view of a metal structure in a furnace (boiler tube) coated with the thermal radiation ceramic coating composition of the present invention.

In such an indirect heating furnace, when an electric current is passed through the resistance heating element 2, heat is generated inside the furnace 1, which raises the temperature of the metal structure (boiler tube) inside the furnace 3. The heat medium oil is heated and circulates with the heat medium oil in the container 4, and the temperature of the heat medium oil in the container rises.

Figure 4 is a graph of the atmospheric temperature inside the heating furnace, comparing the case where the refractory inner wall of the heating furnace and the metal structure inside the furnace are coated with the heat-emitting ceramic composition of the present invention (solid line) and when they are not coated (dashed line). This is a graph showing.

FIG. 5 is a comparison graph showing the rate of increase in surface temperature of the metal structure inside the heating furnace.

FIG. 6 is a comparison graph showing the rate of increase in internal temperature of the metal structure in the heating furnace.

FIG. 7 is a comparison graph showing the rate of temperature rise of heat transfer oil.

As is clear from the comparison of these figures 4 to 7, when the heat emitting ceramic coating composition of the present invention is coated on the refractory wall of the furnace and the metal structure inside the furnace, the rate of increase in the atmospheric temperature is This results in a time reduction of 33.3%, and a time reduction of 41.6% in terms of the temperature rise rate on the surface of the metal structure in the furnace.

The internal temperature rise rate of the metal structure inside the furnace was also 33.3.
%, and the temperature rise rate of the heat medium oil, which is the final heated material, is reduced by 25%.

As is clear from the comparison before and after coating in the same heating furnace, the thermal radiation ceramic coating composition of the present invention produces good results when coated on the refractory material on the inner wall of the heating furnace and on the metal structures inside the furnace. It was confirmed that

Next, the present invention will be explained in more detail with reference to the following examples.

Example 1 45.0 parts by weight of silicon carbide, 3.0 parts by weight of silicon nitride, 12.0 parts by weight of aluminum phosphate, 3.0 parts by weight of chromium oxide, 5.0 parts by weight of tantalum carbide, 6.0 parts by weight of aluminum powder.
0 parts by weight, 7.0 parts by weight of aluminum oxide, 2.0 parts by weight of magnesium oxide, 4.0 parts by weight of iron oxide, 5 parts by weight of glass powder
．． 0 parts by weight, 6.0 parts by weight of zircon oxide, 2 parts by weight of silicon dioxide
．． 0 parts by weight of the composition and additionally added 15 parts of water.
Approximately 0.8 parts by weight and sprayed onto the refractory material on the inner wall of the heating furnace.
0 coating, and use a brush to coat the metal structures inside the furnace with approximately 0.0 coating.
3 m/m coating coating.

It is heated to 100°C every hour and then baked at 600°C for 2 hours to harden the adhesive.

For comparison purposes, tests were conducted before and after coating the thermally emissive ceramic coating composition.

The rate of temperature increase in the furnace atmosphere was reduced by 35% of the time, and the rate of temperature increase of the heating medium oil of the object to be heated was reduced by 25.5%.

At this time, thermal energy was saved by 20%.

Example 2 65 parts by weight of silicon carbide, 5 parts by weight of silicon nitride, 5 parts by weight of aluminum phosphate, 2 parts by weight of chromium oxide, 3 parts by weight of tantalum carbide
parts by weight, 8 parts by weight of aluminum powder, 1 part by weight of aluminum oxide, 1 part by weight of magnesium oxide, 3 parts by weight of iron oxide, 3 parts by weight of glass powder, 3 parts by weight of zirconium oxide, and 1 part by weight of silicon dioxide. The method of Example 1 was repeated using

The rate of increase in ambient temperature was reduced by 39 hours, and the rate of increase in temperature of heat transfer oil of the object to be heated was reduced by 27 hours.

At this time, thermal energy was saved by 22 tons.

Example 3 The method of Example 1 was repeated using mixtures of various compositions.

Good results were confirmed for all of these.

Table 1 shows the raw material composition and effects.

[Brief explanation of drawings]

FIG. 1 is a sketch of an indirect heating furnace, and FIGS. 2 and 3 are cross-sectional views of the furnace inner wall refractory material and the furnace metal side structure coated with the heat radiation ceramic coating composition of the present invention. Figures 4 to 7 show a comparison between the presence and absence of the coating composition of the present invention. Figure 4 shows the atmospheric temperature in the heating furnace, Figure 5 shows the surface temperature of metal objects in the furnace, and Figure 6 shows the metal objects in the furnace. Structure internal temperature,
FIG. 7 is a graph showing the relationship between each temperature rise time and heating time of heat transfer oil. The symbols in Figures 1 to 3 mean the following: 1. Curved refractory insulating brick, 2. Resistance heating element, 3. Metal structure inside the bending furnace, 4.・Container containing heating medium oil, 5...
Intercoating composition.

Claims (1)

[Scope of Claims] 1a) 40-750-75 parts by weight Silicon carbide as a member, b) 15-405-40 parts by weight Silicon 3-20 parts by weight, phosphate 5-20 parts by weight, chromium oxide 2-10 parts by weight c) 10 to 350 to 35 parts by weight of aluminum, 1 to 10 parts by weight of aluminum, and 3 to 15 parts of glass powder.
3 to 15 parts by weight of zirconium oxide, 1 to 10 parts by weight of silicon dioxide, 1 to 10 parts by weight of magnesium oxide, and 1 to 10 parts by weight of iron oxide. and the sum of components aLb) and C) is 100
A thermally emissive ceramic coating composition characterized in that the weight φ. 2a) 40-750-75 parts by weight Silicon carbide as a member, b) 15-405-40 parts by weight Silicon 3-20 parts by weight, phosphate 5-20 parts by weight, chromium oxide 2-10 parts by weight, tantalum carbide 2-2 parts by weight c) 10 to 350 to 35 parts by weight of aluminum, 1 to 10 parts by weight of aluminum, and 3 to 15 parts by weight of glass powder;
It consists of additives that improve adhesion and intercoating bond strength, consisting of 3 to 15 parts by weight of zirconium oxide, 1 to 10 parts by weight of silicon dioxide, 1 to 10 parts by weight of magnesium oxide, and 1 to 10 parts by weight of iron oxide. and the sum of components a) yb) and C) is 10
A thermally emissive ceramic coating composition having a weight φ of 0 wt. A method for using the heat emitting ceramic coating composition described above, which further comprises heating and baking at a temperature of 550°C to 800°C for 1 to 3 hours. 3. The method of claim 2, wherein the thermally emissive ceramic coating composition is coated on the substrate with about 10 to 15 parts by weight of water added to the composition. 4. The method according to claim 2 or 3, wherein the base material is a refractory material for the inner wall of an industrial heating furnace or a metal structure inside the furnace.