JP4464804B2 - Thermal spraying material for industrial kiln repair - Google Patents

Description

  The present invention relates to a thermal spray material used in a thermal spraying method using combustion heat of metal powder in repairing the lining of an industrial kiln furnace.

  As a furnace wall repair for industrial kilns, there is a thermal spraying method of refractory raw material powder. Flame spraying, plasma spraying, and laser spraying are known as thermal spraying methods, but all of these require a large apparatus, have high equipment costs, and are complicated in operation.

  On the other hand, there is a method in which a thermal spray material containing refractory raw material powder and metal powder as a main material is sprayed onto a work surface with a carrier gas using oxygen, and the refractory raw material is melted and adhered using the heat generated by combustion of the metal powder. This method has a relatively simple apparatus structure and is easy to operate. In addition, it can be applied with larger capacity than plasma spraying and laser spraying, and is suitable for furnace wall repair.

In this thermal spraying method using the combustion heat generation of metal powder, the general materials of the thermal spray material used for it are mainly refractory raw material powder made of silica powder and metal Si powder of the heat generating material. In addition, the use of Al—Mg alloy or Ca—Si alloy is known as the heat generating material.
JP 2000-159579 A JP-A-5-330931 Japanese Patent Laid-Open No. 5-17237

  In the thermal spraying method using the heat generated by combustion of the metal powder, the thermal spray material is ignited by burning the metal powder in the thermal spray material mixture with a seed flame or residual heat from the furnace wall at the start of spraying. Next, the heat generated by this combustion becomes a fire type, and the sprayed material sprayed sequentially burns continuously, and a melt-adhered construction body is formed.

  However, the conventional thermal spray material does not continuously burn even if the surface to be worked is ignited at a room temperature or a location where the residual temperature is low, such as a furnace port, and the construction efficiency is poor. In addition, adhesion, adhesion, and strength are inferior due to insufficient melting of the obtained construction body.

  When a metal powder such as a highly exothermic Al—Mg alloy or Ca—Si alloy is used as the heat generating material, although the adhesiveness and adhesion are improved, the effect is not exceptional. This is because the thermal spray material itself has a limited heat receiving area, and since the metal powder is in a dispersed state in the refractory raw material powder, even if the metal powder is highly exothermic, the amount of heat generated by the heat generation is small. This is because it is not sufficiently propagated throughout the sprayed material structure.

  In addition, the use of highly exothermic metal powder is concerned about spontaneous ignition and requires strict management. As a result, the cost and cost of the thermal spray material are increased due to the necessity of equipment and handling with consideration for work safety.

  By increasing the amount of addition of the metal Si powder in the usage example, stable continuous combustion is exhibited even when the temperature of the workpiece is low. However, when the amount of the metal powder is increased, the dust generation of the metal powder is remarkable at the time of construction, and the working environment is deteriorated. In addition, due to the generation of a large amount of gas accompanying the oxidation of the metal powder, the construction body has a reduced strength due to the porous structure.

  It is an object of the present invention to provide a thermal spray material that solves the above-mentioned conventional problems. The features are as follows.

(1) A thermal spraying material containing a refractory raw material powder and a metal Si powder as a main material, spraying oxygen on a work surface as a carrier gas, and melting and adhering to the work surface by combustion heat generation of the metal Si powder. Thermal spraying material for repairing industrial kilns containing 2 to 25% by weight of calcia powder having a CaO content of more than 75% by weight, 5 to 30% by weight of metal Si powder, and 50 to 90% by weight of siliceous powder.

(2) Industrial kiln repair as described in (1) above, wherein the calcia powder has a particle size of 0.5 mm or less and the siliceous powder has a particle size of 2 mm or less and a ratio of 0.3 mm or less is 0 to 15% by mass. Thermal spray material.

(3) The thermal spraying material for industrial kiln repair according to (1) or (2) above, wherein the calcia powder is one or more selected from calcia powder and magnesia-calcia powder.

In the present invention, a specific amount of calcia powder is combined with a thermal spray material mainly composed of metal Si powder and refractory raw material powder. During construction, after generating the SiO ₂ component metal Si powder reacts with the oxygen of the carrier gas, further reaction of the SiO ₂ component and calcia protein powder _{(3CaO + SiO 2 → 3CaO ·} SiO 2, 2CaO + SiO 2 → 2CaO · SiO ₂₎ fused siliceous powder is promoted by the adhesion and adhesion are improved. In addition, a dense and high-strength construction structure is formed by the CaO.SiO ₂ refractory bond structure produced by the reaction.

In general, the denser the thermal sprayed body, the easier it is to crack when subjected to thermal shock. On the other hand, the thermal spray material according to the present invention exhibits an excellent effect in thermal shock resistance. This is considered that the CaO · SiO ₂ structure produced by the thermal spray material of the present invention has a smaller thermal expansion than, for example, a structure such as CaO, MgO, MgO · SiO ₂ .

In the conventional thermal spray material using only siliceous powder as a refractory raw material powder, the component of the construction body is SiO ₂ . On the other hand, CaO.SiO _{2 which} is a construction body component formed of the material of the present invention has much higher heat storage than SiO ₂ . The thermal spray material of the present invention is stably sprayed by being sequentially sprayed onto the construction body of CaO · SiO ₂ with high heat storage during construction, and misfires even in construction on a repaired surface at room temperature or relatively low temperature. Without burning continuously.

  In addition, the heat generating material used in the present invention is a metal Si powder, and there is no fear of spontaneous ignition or the like seen with the use of a highly exothermic metal powder, and it is excellent in work safety.

Regarding the thermal spray material of the present invention, the particle size of the calcia powder is preferably 0.5 mm or less. This is because when the particle size is 0.5 mm or less, it easily reacts with the SiO ₂ component and siliceous powder generated from the metal Si powder, and the amount of CaO · SiO ₂ liquid phase generated increases, and the compacted body becomes dense. It is for improving. Moreover, since the particle size is 0.5 mm or less, the rebound loss at the time of spraying calcia powder is reduced, which is preferable for adhesion.

  The particle size of the siliceous powder is preferably 2 mm or less and the proportion of 0.3 mm or less is preferably 0 to 15% by mass. This is because, unlike calcia powder, siliceous powder with a particle size of 0.3 mm or less tends to adhere to the metal Si powder, and when the proportion of siliceous powder with a particle size of 0.3 mm or less increases, the contact area between the metal Si powder and oxygen Is reduced. As a result, it is difficult to ignite at the start of construction, and continuous combustion is difficult to occur if the powder supply amount is increased even if ignited.

  The thermal spray material of the present invention exhibits an excellent effect in adhesion and adhesiveness in a thermal spraying method using combustion heat generation of metal powder. In addition, the obtained construction body is dense and high in strength and excellent in thermal shock resistance. Further, since the heat storage property of the construction body is remarkably high, stable construction is possible without misfire even in thermal spraying on a relatively low temperature repaired surface.

  The specific example of the calcia raw material powder used as a refractory raw material for the thermal spray material of the present invention is one or more selected from calcia powder, magnesia-calcia powder and the like. These may be either sintered products or electromelted products.

The CaO content of the calcia raw material powder is more than 75% by mass. If the CaO content is less than this, the reactivity between the calcia raw material powder and SiO ₂ is poor, and since the amount of CaO · SiO ₂ produced is small, the heat storage property of the construction body is insufficient, and the remarkable continuous combustion property according to the present invention. I cannot get a fever.

  A more preferable range of the CaO content of the calcia raw material powder is 88% by mass or more. When it is 88% by mass or more, the thermal shock resistance is particularly remarkable.

The particle size of the calcia raw material powder is preferably 0.5 mm or less in order to sufficiently react with the SiO ₂ component. More preferably, it is 0.3 mm or less. In addition, the description of a particle size including the following description of each raw material composition is based on JIS standard sieve opening.

  The proportion of calcia powder used is 2 to 25% by mass. If it is less than 2% by mass, the continuous combustion is not stable when the temperature of the workpiece is low, and the adhesion and adhesion are poor. If it exceeds 25% by mass, the amount of metal Si powder or siliceous powder is reduced by that amount, and the characteristics of metal Si powder and siliceous powder are impaired.

  When the amount of metal Si powder used is less than 5% by mass, the heat generated by combustion is inferior, and the adhesion, adhesiveness, and construction strength are inferior. If it exceeds 30% by mass, the dust generation of the metal powder is remarkable at the time of construction, which not only causes the working environment to deteriorate, but also causes the generation of gas accompanying the oxidation of the metal powder, thereby making the construction body porous. The particle size of the metal Si powder is preferably 75 μm or less, more preferably 45 μm or less in terms of average particle size in order to obtain sufficient reactivity.

  The main material of the refractory raw material powder is siliceous powder. Specific examples of the siliceous powder include quartzite powder, quartz sand, natural quartz powder, fused silica powder, or refractory powder mainly composed of these components. If the use ratio is less than 50% by mass, the volume stability of the thermal sprayed body is inferior and the adhesiveness is lowered. When it exceeds 90 mass%, the rebound loss at the time of spraying will become large, and adhesiveness will fall.

  The particle size of the siliceous powder is preferably 2 mm or less in terms of meltability. As long as the particle size is in the range of 2 mm or less, there is no great difference in melting even if the particle size is limited to 1.5 mm or less or 1 mm or less.

  Moreover, it is preferable that a siliceous powder adjusts 0.3 mm or less particle size to 0-15 mass%. That is, in the ceramic industry operation, the particle size of the refractory raw material is adjusted with a sieve after pulverization, so that a certain amount of fine particles are naturally present under the sieve. For example, a sieve having a particle size of 2 mm usually contains 20 to 30% by mass of particles having a particle size of 0.3 mm or less. Here, the amount of the particle size of 0.3 mm or less under the sieve is regulated.

  Here, the siliceous powder has a particle size of 0.3 mm or less and a limitation of 0 to 15% by mass, even when particles having a particle size of 0.5 mm or less or 0.1 mm or less are removed in the particle size adjustment operation. It means that particles having a particle size of 0.3 mm or less in the whole powder are 0 to 15% by mass.

  Moreover, it is preferable that the ratio of the CaO component which the thermal spray material of this invention occupies for the whole thermal spray material with a chemical component value shall be 2-25 mass%. The CaO component is also contained in natural siliceous raw materials such as siliceous, but its content is very small. The CaO component source in the present invention is substantially supplied from calcia powder.

  If the CaO component occupying the entire thermal spray material is less than 2% by mass, the effect of sustaining ignition to the repaired portion having a small heat source is insufficient, and stable construction such as misfire or poor adhesion tends to be difficult. Since the CaO component has a large coefficient of thermal expansion, if the proportion exceeds 25% by mass, there is a concern about the occurrence of cracks in the furnace wall lining, which is the surface of the workpiece, due to the difference in thermal expansion with the workpiece.

  Examples of metal powders other than metal Si powder include Al powder and Al-Mg alloy powder. These metal powders are preferably not used from the viewpoint of work safety because of their high heat generation properties. However, even if they are used, it is necessary to keep them at less than 5% by weight, preferably 3% by weight or less from the viewpoint of work safety. Moreover, the usage-amount needs that the total amount of metal powder including metal Si powder does not exceed 30 mass%.

  The thermal spray material according to the present invention is used for repairing furnace walls of various steel industry furnaces such as coke ovens, non-ferrous metal industry furnaces, glass furnaces, steel industry furnace furnaces and the like.

Examples of the present invention and comparative examples are shown below. Table 1 shows chemical component values of the refractory raw materials used in each example, Table 2 shows examples of the present invention, and Table 3 shows comparative examples. Tables 2 and 3 also show the test results of each example.

  In order to prepare for the risk of combustion of the thermal spray material in the material tank due to flashback from the nozzle tip, etc., the thermal spraying device used in the construction of the thermal spray material in each example is provided with nitrogen gas, which is an inert gas, in the material tank. Introduced. The thermal spray material was cut out with a table feeder provided at the bottom of the tank and transported with oxygen. At that time, the inert gas from the inside of the material tank is mixed in oxygen, but the amount thereof is small and there is no problem in the combustion and ignition of the thermal spray material.

  In each example, 3 kg of the thermal spray material was sprayed onto the workpiece with a powder supply rate of 50 kg / h and a distance between the workpiece and the nozzle tip of 50 to 70 mm. The work body was made of chamotte bricks assuming the repair of the furnace refractories of the coke oven.

  It sprayed and evaluated on each conditions of normal temperature and hot (surface temperature of a to-be-processed body 500 degreeC). In normal temperature construction, the sprayed material was ignited with a pilot burner. In each of the hot constructions, the thermal spray material was burned by the heat of the work piece without using a pilot burner.

  Continuous ignitability: In thermal spraying, the nozzle is moved along the work surface in order to expand the construction area. The continuous ignitability at that time was tested. ◎… Even if the nozzle was moved faster on the work surface in order to increase the construction efficiency, there was no sign of misfire, indicating extremely stable combustion. Δ: If the nozzle movement on the work surface is fast, combustion is intermittent and unstable. ×… If the nozzle is moved quickly, it will quickly misfire and will not ignite continuously.

  Adhesiveness: The adhesion rate was determined from the amount of sprayed material sprayed from the nozzle and bounce loss at room temperature.

  Adhesiveness: The degree of adhesion of the thermal sprayed body was also measured during spraying at room temperature. ○: Adhesiveness is good both hot and after cooling, Δ: Adhesive when hot, but peeled off when cooled, ×: Already peeled when hot.

  Denseness: Apparent porosity was measured for the sample cut out from the thermal sprayed construction.

  Strength: Compressive strength was measured for a sample cut out from the thermal sprayed body.

  Thermal shock resistance: The state of occurrence of cracks in the thermal sprayed body after cooling was confirmed visually. A: No crack, B: Small crack, B: Small crack, X: Large crack. Cracks cause peeling of the construction body and cause a decrease in durability.

  As shown in the test results shown in Table 2, each of the thermal spray materials of the examples of the present invention is excellent in adhesion and adhesiveness, and forms a dense and high-strength construction body. In addition, stable continuous combustion is exhibited in thermal spraying on the repaired surface at room temperature.

  Examples 1 to 6 and Examples 9 and 10 use calcia powder having a CaO content of 96.97% by mass and high CaO purity, and the effect of improving thermal shock resistance is remarkable.

  On the other hand, Comparative Example 1 is a material mainly composed of magnesia-calcia powder. In Comparative Example 2, the particle size of the magnesia-calcia powder in the thermal spray material of Comparative Example 1 is reduced to 0.5 mm or less. Comparative Example 3 is a combination material of magnesia-calcia powder and siliceous powder. In Comparative Example 4, the particle size of the magnesia-calcia powder in the material of Comparative Example 3 is reduced to 0.5 mm or less. In either case, the construction body structure is porous, and thus has excellent thermal shock resistance. However, both adhesion and strength are inferior due to the porosity.

  Comparative Example 5 is a material in which the amount of calcia powder added is greater than the limited range of the present invention. In Comparative Example 6, the amount of calcia powder added is further increased in the material of Comparative Example 5. These are all inferior in thermal shock resistance. In addition, there is a concern that a furnace wall lining crack, which is the surface of the workpiece, may be generated due to a difference in thermal expansion from the workpiece. Moreover, all of Comparative Examples 1-6 are inferior to adhesiveness.

  In the examples of the present invention, for example, the particle size of the calcia powder is 1 mm or less, or 0.5 mm or less. However, even when the particle size is 0.1 mm or less, the effect of the present invention is obtained.

Claims (3)

  It is a thermal spray material that uses refractory raw material powder and metal Si powder as the main materials, sprays oxygen on the work surface as a carrier gas, and melts and adheres to the work surface by the combustion heat of the metal Si powder. A thermal spray material for repairing industrial kiln furnaces containing 2 to 25% by mass of calcia powder having a content of more than 75% by mass, 5 to 30% by mass of metal Si powder and 50 to 90% by mass of siliceous powder.   The thermal spray material for industrial kiln repair according to claim 1, wherein the calcia powder has a particle size of 0.5 mm or less and the siliceous powder has a particle size of 2 mm or less and a ratio of 0.3 mm or less is 0 to 15 mass%.   The thermal spray material for industrial furnace furnace repair according to claim 1 or 2, wherein the calcia powder is one or more selected from calcia powder and magnesia-calcia powder.