JP5565826B2 - Abrasive for blasting and method for producing the same - Google Patents

Description

  The present invention relates to an abrasive used for blasting performed as a pre-coating process for steel, for example, and a method for manufacturing the same.

  Conventionally, products and structures made of materials that easily cause rust such as ordinary steel have been painted to protect the surface and increase the corrosion resistance life. As one of the pretreatments performed before painting on ordinary steel or the like, there is a blast treatment in which an abrasive is sprayed on the surface of the steel material. The purpose of the blast treatment is to remove the oxide layer, surface contaminants, old paint film layer, etc. on the surface of the steel material, which is the material to be treated, to form a clean surface and improve paint adhesion.

  Abrasive materials used for blasting include silica sand, steel shot, and glass beads. However, silica sand is easily crushed by the impact of spraying and generates a lot of dust, and since it is a natural product, its quality is not stable. Recently, silica has become unusable due to pneumoconiosis problems. Steel shots are not easily crushed and generate little dust and have excellent grinding ability. However, they are extremely rusty, and there is a problem that the particles cannot be used because they adhere to each other with rust. Glass beads are brittle and easily crushed, so there is a problem that the amount of dust generated is large and the durability life is short. As a prior art for solving such a blast processing abrasive, an abrasive using slag discharged from an electric furnace or converter used for melting steel products has been proposed (see Patent Document 1). In addition, a grinding material made of slag produced when high carbon ferrochrome is produced and refined in an electric furnace has been proposed (see Patent Document 2).

  In patent document 1, the slag discharged | emitted from an electric furnace or a converter is water-cooled, it is made to quench-harden, and this slag hardened | cured material is used as an abrasive. Such a slag cured product has a high hardness, and thus has an excellent grinding force and is difficult to be crushed, and thus has an advantage of generating less dust. Moreover, in patent document 2, the high carbon ferrochrome refining slag which was rapidly solidified by the air crushing process or the water crushing process is crushed, and it is set as an abrasive. Grinding material made of such refined slag particles is hard to break even when it collides with the material to be treated, has an internal structure that does not generate dust even if it breaks, and has excellent grinding power, so it can be blasted in a short time. Has the advantage of being able to.

Japanese Patent No. 3720622 Japanese Patent No. 4049848

  However, the abrasives disclosed in Patent Document 1 and Patent Document 2 are both manufactured by subjecting slag to water or air crushing with a water cooling device or a forced air cooling device. A large amount of slag is generated in the refining process of steel and the like, and an apparatus having a large cooling capacity is required to rapidly cool a large amount of slag. An apparatus having a large cooling capacity occupies a large installation area in the factory, so that there is a problem that the work space is narrowed and the capital investment burden is increased due to the high cost.

  The objective of this invention is providing the grinding material for blasting processing which uses steel-making slag as a raw material, and its manufacturing method, without water cooling or forced air cooling.

The present invention is a steelmaking slag produced in the steelmaking process of stainless steel , scraped into a noropot and slowly cooled, produced through a wet crushing process,
The composition of the main component _{CaO: 30~43wt%, MgO: 6~15wt} %, Al 2 O 3: 5~17wt%, SiO 2: the 20～35Wt% of steelmaking slag as the raw material,
Mohs hardness is 7-9,
A blasting abrasive having a particle size of 0.1 to 3.0 mm.

In addition, the present invention, steelmaking slag produced in the steelmaking process of stainless steel , scraped into a Noropot and gradually cooled,
The steelmaking slag after slow cooling is crushed with a constant crushing load in the wet crushing process ,
A method for producing an abrasive for blasting, characterized by classifying into sandy slag having a Mohs hardness of 7 to 9 and a particle size of 0.1 to 3.0 mm.

According to the present invention, steelmaking slag produced in the steelmaking process of stainless steel is scraped into a noropot and gradually cooled. The steelmaking slag after slow cooling is used as a raw material, and the Mohs hardness and grain size are limited to a specific range through a wet crushing process, whereby a blasting abrasive can be obtained. That is, the steelmaking slag that is gradually cooled can be used as the abrasive without the need for water cooling equipment or forced air cooling equipment. As a result, it is possible to prevent the work space in the factory from being narrowed and the capital investment to be increased, and it is possible to provide a versatile blasting abrasive that reflects cost reduction.

Moreover, according to this invention, the steelmaking slag produced | generated at the steelmaking process of stainless steel is scraped out into a noropot, and is cooled slowly . Steelmaking slag after slow cooling is a wet crushing process, and sand slag with a specific range of Mohs hardness is collected with a constant crushing load and classified to a specific range of particle size to produce blasting abrasives To do. In this way, water-cooling equipment and forced air-cooling equipment are not required, so that grinding materials for blasting can be manufactured using steelmaking slag as a raw material without causing problems such as narrowing the work space in the factory and increasing capital investment. can do.

It is a figure which simplifies and shows the process of manufacturing the abrasive for blasting which is embodiment of this invention. It is a figure which shows the process which separates the ingot and the steelmaking slag in the beneficiation process 3.

  FIG. 1 shows a simplified process for manufacturing a blasting abrasive according to an embodiment of the present invention. The process of producing a blasting abrasive (hereinafter simply referred to as an abrasive) includes a steelmaking process 1 in which a steelmaking slag as a raw material is generated, a steelmaking slag cooling process 2, and a metal is recovered from the steelmaking slag. It includes a beneficiation process 3 and an abrasive production process 4 for producing an abrasive by wet crushing and classifying the massive steelmaking slag after the recovery of the metal.

In the steelmaking process 1, stainless steel is melted and steelmaking slag is generated as a byproduct. As steelmaking slag produced during melting of stainless steel, secondary smelting of slag produced in the desulfurization process of stainless steel melted in an electric furnace and vacuum degassing of the desulfurized stainless steel is performed. There is slag generated in the process. Of these slags, CaO in the composition of the main _{component: 30~43wt%, MgO: 6~15wt%} , Al 2 O 3: 5~17wt%, SiO 2: 20~35wt% of steel slag is used as a material The

  The reason for setting such a component range is as follows.

The range of CaO is determined as a value added as a necessary component in refining during steelmaking, rather than being determined as a value suitable for manufacturing a blasting abrasive. That is, as a refining reaction, a range required for a desulfurization reaction or a reduction reaction is 30 to 43 wt%. If it is less than 30 wt%, sufficient desulfurization reaction or reduction reaction cannot be achieved. Therefore, the component is adjusted by adding a flux such as lime (CaO). Conversely, if it exceeds 43 wt%, the fluidity of the slag deteriorates in the range of SiO ₂ described below, which hinders the removal work. Or the remaining charge in the furnace will interfere with the melting of the next charge.

This is because SiO ₂ needs a certain concentration to obtain the hardness required as a grinding material for blast treatment. A minimum of 20 wt% is necessary, and at a concentration higher than this, hardness as a blasting abrasive can be obtained while securing the slag fluidity. The higher the SiO ₂ concentration is, the higher the hardness is. However, when it exceeds 35 wt%, so-called basicity decreases too much due to the balance with CaO, which hinders the refining reaction. Thus, SiO ₂ as the optimum range for satisfying both the hardness of the slag as a refining reaction and blast processing abrasive is adjusted to 20~35wt%.

Although some MgO enters from steelmaking raw materials, most of the origin comes to be contained as a slag component by refractory materials such as bricks being melted. Since the melting point of the slag changes depending on the ratio of CaO / SiO ₂ , as a result, the degree of refractory melting is determined. If CaO is 30 to 43 wt% and SiO2 is in the range of ₂₀ to 35 wt%, MgO is generally in the range of 6 to 15 wt%.

A higher Al ₂ O ₃ component is suitable for obtaining hardness, but requires a flux for increasing the Al ₂ O ₃ component, which is disadvantageous in terms of cost. The origin of Al ₂ O ₃ is the same as that of MgO, and some of it comes from steelmaking raw materials, but most of the origin is in the concentration range determined by the refractory such as bricks being melted. Some prior patents, references, and the like try to obtain slag hardness by excessively adding Al ₂ O ₃ , but in the present invention, the concentration of Al ₂ O ₃ mixed in a natural body is not added intentionally. The hardness is adjusted by the balance between CaO and SiO ₂ and the slag crushing load.

  Steelmaking slag produced in an electric furnace or a secondary refining furnace is scraped out into a noropot before the molten steel is produced and cooled in the cooling step 2. In the cooling step 2, natural cooling, so-called gradual cooling, is performed in the atmosphere without forced water cooling or forced air cooling. Or it is gradually cooled to the degree of watering. Therefore, forced water cooling equipment and forced air cooling equipment are not required for cooling the steelmaking slag used as the material of the abrasive. Slowly-cooled steel slag is crystalline, and its hardness is slightly lower on average as compared to granulated or air-crushed slag containing amorphous slag. However, steelmaking slag produced by slow cooling with one charge melting is mixed with various hardnesses, and many have a hardness range suitable for abrasives.

In the beneficiation process 3, it is preferable to perform a wet crushing process in order to increase hardness. The slag contains free CaO and MgO, and the portion containing this has low hardness. By crushing in water (wet), free CaO and MgO undergo hydration reaction,
(CaO + H ₂ O → Ca (OH) ₂ , MgO + H ₂ O → Mg (OH) ₂ )
It becomes easy to be crushed during the crushing process, and as a result, only a hard part remains, and a sand (slag grain) having a high hardness suitable for blasting can be produced. Further, if free CaO or MgO remains, this soft part may remain white in a state of being rubbed against the grinding surface during the blasting process, which is not preferable because an extra work to remove it is necessary. . Therefore, it is necessary to pass the wet crushing process in order to produce the abrasive for blast treatment.

  FIG. 2 shows a process of separating the bullion and the steelmaking slag in the beneficiation process 3. Steelmaking slag contains a relatively large amount of useful metal components. Then, in the beneficiation process 3, in order to reuse as a molten auxiliary material, the metal which is a metal component contained in the steelmaking slag is recovered. The steelmaking slag is crushed to a rough size in the rod mill crushing step 31. The crushed steelmaking slag is sorted into those having a predetermined size or less in the sieving classification process 32, and sent to a wet bullion recovery process. The steelmaking slag that has not passed through the sieve in the sieve classification process 32 is returned to the rod mill crushing process 31 again. The classified steelmaking slag is again crushed in a wet crushing process, and only the metal 5 is beneficiated and collected through a specific gravity beneficiation process 33 and a magnetic beneficiation process 34. The steelmaking slag after the mineral metal 5 is beneficiated is the thickener 35, and the powdery steelmaking slag 6 is collected. The sandy steel slag 7 is recovered in the Akins classification step 36 as the sandy steel slag 7 having a particle size of about 5 mm. Sandy steel slag 7 is used as the material for the abrasive. In the particle size adjustment step, the air classifier 41 and the sieve classifier 42 perform classification so that the particle size is 0.1 to 3.0 mm. Moreover, it may be classified into a finer range as necessary.

When crushing sandy steelmaking slag in the wet crushing step, sandy slag having a Mohs hardness of 7 to 9 can be obtained by adjusting the crushing load (P / T). The adjustment of the size of the crushing load (P / T) that makes the Mohs hardness of the crushed steelmaking slag 7-9 is to crush the crushing power (kW) by varying the various slag material throughput (T), This is done by measuring the Mohs hardness of the steelmaking slag after crushing. The relationship between the magnitude of the crushing load (P / T) and the Mohs hardness of the steelmaking slag crushed with the crushing load (P / T) is obtained in advance, and the Mohs hardness of the steelmaking slag after crushing is 7-9. The crushing load (P / T) is set so that For the present invention, CaO is the composition of the aforementioned main _{components: 30~43wt%, MgO: 6~15wt%} , Al 2 O 3: 5~17wt%, SiO 2: a 20~35wt%, gradually cooled steel If slag is used as a raw material and the crushing load (P / T) is set at (12 to 25 kWh / T), an abrasive having a particle size of 0.1 to 3.0 mm and a Mohs hardness of 7 to 9 can be obtained. By using such a crushing load (P / T), soft steelmaking slag having a Mohs hardness of less than 7 is crushed into fine sand 9 having a particle size of less than 0.1 mm, and a hard steelmaking slag having a Mohs hardness of more than 9 is obtained. Circulates in the system without being crushed, and is crushed until the particle size becomes less than 3.0 mm.

  The air classifier 41 adjusts the pressure and flow rate of air acting on the crushed steelmaking slag in the slag containing box, removes the steelmaking slag crushed into fine powder from the slag containing box, and collects it through the discharge pipe. Discharge to the trash can. Finally, the steelmaking slag remaining in the slag storage box is classified by the sieve classifier 42. The sieve classifier 42 includes a sieve having a mesh of 3.0 mm and a sieve of 0.1 mm, and classifies the steelmaking slag so that the particle size is in a range of 0.1 to 3.0 mm. A steelmaking slag having a particle size after classification of 0.1 to 3.0 mm and a Mohs hardness of 7 to 9 is defined as an abrasive 8. Steelmaking slag that has passed through a 0.1 mm sieve is used as a fine-grained sand 9 for applications such as roadbed improvement materials.

  Hereinafter, the reasons for limiting the range of the grain size and the Mohs hardness of an abrasive made of slowly cooled steel slag will be described.

Particle size: 0.1-3.0mm
When the particle size is less than 0.1 mm, the mass of each particle of the abrasive is small, and the grinding force during blasting is not sufficiently exhibited. When the thickness exceeds 3.0 mm, the abrasive is easily broken, and there is a problem that dust increases due to pulverization. In addition, nozzles are likely to be clogged during grinding. Therefore, the particle size is 0.1 to 3.0 mm. A more preferable range of the particle size is 0.5 to 2.5 mm. Moreover, you may classify | categorize into a finer particle size range according to a user's request | requirement and the grinding objective as needed.

Mohs hardness: 7-9
If the Mohs hardness is less than 7, since it is soft, it is easily crushed by collision with the material to be processed, and the amount of dust generated increases. When the Mohs hardness exceeds 9, since it is hard, the grinding force is excellent, but the wear of the blasting apparatus is accelerated, and the surface of the treated material after blasting becomes rough, which is not preferable from the viewpoint of paint adhesion. Therefore, the Mohs hardness is 7-9.

  Examples of the present invention will be described below. Here, a blast treatment test was performed on the material to be treated using the grinding material of the example using the slow-cooled steel slag as a raw material and the three types of grinding materials of the comparative example, and the performance was evaluated. As the abrasive of the examples, those manufactured by the method shown in FIG. 1 were used. Table 1 shows an outline of the composition of steelmaking slag, which is a material of the abrasive material of the example.

  The abrasive materials used as comparative examples are silica sand, copper smelting slag, and ferronickel slag, which are referred to as Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. Here, ferronickel slag is slag produced when refining ferronickel used as an auxiliary material for steelmaking. In both Examples and Comparative Examples 1 to 3, the particle size of the abrasive was adjusted to 1.2 to 2.5 mm. Table 2 shows the Mohs hardness of the abrasives of Examples and Comparative Examples 1 to 3.

  A blasting test using the abrasives of Examples and Comparative Examples 1 to 3 was performed as follows. As the material to be treated, a normal steel plate having a width of 110 mm having an old coating layer having a thickness of 300 to 350 μm was used. The injection pressure of the compressor that injects the abrasive material of the blast treatment device is 0.7 MPa, the spraying distance to the material to be treated is 400 to 800 mm, and the target for the surface finish of the material to be treated is Japanese Industrial Standard (JIS) Z0313 The specified Sa2.0. In both Examples and Comparative Examples 1 to 3, 25 kg of abrasive material is used, and the material to be treated is blasted until the abrasive material is completely jetted under the above conditions, construction efficiency, finished surface roughness, dust generation The performance of the abrasive was evaluated by quantity and other indicators and comprehensive evaluation of these indicators.

  Hereinafter, each evaluation index will be described.

  Construction efficiency: The total length of the material to be treated that was able to finish the surface of the material to be treated to the target surface finish Sa2.0 was determined. Based on the length that could be finished with the grinding material of the copper smelting slag of Comparative Example 2, the ratio of the length that could be finished with each grinding material to the reference length was obtained and relatively evaluated. Therefore, the construction efficiency of Comparative Example 2 is 1.0. Construction efficiency was calculated | required about each grinding | polishing material of an Example and a comparative example, and if it was 0.8 or more, it was evaluated that it was favorable if less than 0.8.

  Finished surface roughness: Ra specified by JIS-B0601 (1994) was measured with a surface roughness meter (model name, manufacturer name) on the surface of the treated material after blasting. From the viewpoint of paint adhesion when the treated material after blasting was painted again, it was evaluated that the surface roughness was in the range of 50 to 100 μm.

  Dust generation amount: A photograph was taken against the white wall through the dust during blasting. The photograph taken was visually observed and judged by a sensory test based on the degree to which the white wall of the photograph was cloudy. The case where there was no clouding and the white wall was clearly visible was evaluated as very good (◎), the case where there was a slight cloudiness but the white wall appeared sufficiently white was evaluated as good (◯), and the case where the white wall appeared cloudy was evaluated as poor (×).

  Other indicators: After the blast treatment test, the inner surface of the hose that transports the abrasive to the injection nozzle of the blast treatment apparatus was visually observed to evaluate the degree of wear. A case in which hose wear was hardly observed was evaluated as good, a case in which hose wear was slightly recognized, a case in which hose wear was recognized remarkably, or a case in which hose damage due to sharp abrasives was observed was evaluated as poor. Further, the degree to which the grinding material that collided with the material to be treated penetrated into the protective equipment worn by the operator (hereinafter referred to as protective equipment intrusion for convenience) was evaluated based on the operator's sense. The case where the protective device intrusion was not recognized was evaluated as good, the case where the protective device intrusion was slightly recognized was normal, and the case where the protective device intrusion was slightly high was evaluated as defective. Other indicators were combined with hose wear and protective device intrusion. The evaluation is good when both hose wear and protective device penetration are good (○), when both hose wear and protective device penetration are normal, or when either one is good and the other is bad (△), a case where both hose wear and protective device intrusion were defective or one of them was normal and the other was defective was evaluated as defective (x).

  Comprehensive evaluation: The above four indicators are evaluated in a comprehensive manner. A case where all the indicators were good was evaluated as good (◯), a case where normal or defective was included (normal), and a case where two or more defects were included as poor (×).

  Table 3 shows the evaluation results of each index for Examples and Comparative Examples 1 to 3. The abrasives made from the steelmaking slag of the example were good for all the indicators, and the overall evaluation was good. Although the grinding material made from silica sand of Comparative Example 1 had good finished surface roughness, the construction efficiency and the amount of dust generation were poor, and the overall evaluation was poor. The grinding material made from the copper smelting slag of Comparative Example 2 had good construction efficiency and finished surface roughness, and extremely good dust generation, but other indicators were poor and the overall evaluation was normal. It was. The grinding material made of ferronickel slag of Comparative Example 3 had good construction efficiency, finished surface roughness and dust generation, but other indicators were normal and overall evaluation was normal. As mentioned above, it turns out that the grinding material of the Example which consists of steelmaking slag expresses the most outstanding performance.

DESCRIPTION OF SYMBOLS 1 Steelmaking process 2 Cooling process 3 Mineral processing process 4 Abrasive material manufacturing process 7 Sandy steelmaking slag 8 Abrasive material 41 Air classifier 42 Sieve classifier

Claims (2)

The steelmaking slag generated in the steel making process of the stainless steel, and gradually cooled scrape the Noropotto, it is generated by passing the wet crushing process,
The composition of the main component _{CaO: 30~43wt%, MgO: 6~15wt} %, Al 2 O 3: 5~17wt%, SiO 2: 20~3 a 5 wt% of the steelmaking slag as raw material,
Mohs hardness is 7-9,
A blasting abrasive having a particle size of 0.1 to 3.0 mm. Steelmaking slag produced in the steelmaking process of stainless steel is scraped into a noropot and gradually cooled.
The steelmaking slag after slow cooling is crushed with a constant crushing load in the wet crushing process ,
A method for producing an abrasive for blasting, characterized by classifying sandy slag having a Mohs hardness of 7 to 9 and a particle size of 0.1 to 3.0 mm.

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