JP2016094664A - Steel slag grain, steel slag, and method for producing steel slag grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel slag grain easy in handling and storage at a yard or the like using equipment such as a belt conveyor and a track, in which hydration expansion is hard to occur, and being suitably usable as a fine aggregate, steel slag containing the steel slag grain, and a method for producing the same.SOLUTION: Provided is a steel slag grain having a surface shape in which a part of a closed curved surface is made into a fracture face, and 10 to 90% of the surface area is composed of curved face.SELECTED DRAWING: None

Description

  The present invention relates to steelmaking slag particles, steelmaking slag, and a method for producing steelmaking slag particles.

  Slag is produced as a by-product in the steelmaking, steelmaking processes, specifically blast furnaces, kneading vehicles (preliminary treatment processes, etc., hereinafter also referred to simply as “pretreatment processes”), converters, and electric furnaces. Will occur. Among these, slag in a steelmaking process such as a pretreatment process, a converter, and an electric furnace is referred to as steelmaking slag. Steelmaking slag is used for civil engineering and building materials, ground improvement materials, fertilizers and soil improvement materials. When it is used as a cement raw material or an aggregate for civil engineering and building materials, steelmaking slag containing a large amount of lime that is added as an auxiliary raw material in the steelmaking process does not completely dissolve, but free lime (f Since it remains as -CaO), when it comes into contact with water, the problem arises that free lime hydrates and expands. There are several treatment methods as means for suppressing the hydrated expansion caused by the free lime, and one of them is a crushing treatment as described in Patent Document 1.

  The air crushing process is a process in which a gas such as air is blown onto a molten slag to be cooled and solidified. The steelmaking slag that has been subjected to the air-crushing treatment becomes spherical particles having an average particle diameter of several mm or less, which is called air-crushing slag. As a use of such a spherical crushed slag, it is used as a fine aggregate used for concrete, asphalt, etc., based on the feature of not expanding and an average particle size of several mm or less.

JP 2004-238234 A

  However, a spherical steelmaking slag such as a pulverized slag has a small angle of repose (hereinafter simply referred to as “repose angle”) when transporting and storing it, and the shape of the pile cannot be maintained. It is difficult to handle and store using existing equipment. Therefore, in order to use it as a fine aggregate, new facilities and methods are required for handling and storage. In addition, it is possible to increase the angle of repose by grinding spherical steel-making slag, but in that case, the particle size becomes too fine to be used as a fine aggregate. Therefore, the present invention increases the angle of repose, is easy to handle using equipment such as a belt conveyor and a truck, and is stored in a yard, and is not easily hydrated and expanded, and is preferably used as a fine aggregate. It is an object to provide steelmaking slag particles that can be manufactured together with the production method.

  In order to achieve the above-mentioned object, the present inventors have conducted intensive research on a steelmaking slag treatment method, the shape of steelmaking slag particles, and the like. As a result, the steelmaking slag is shaped like a particle having a curved surface and a fracture surface, and 10 to 90% of the surface area is composed of a curved surface, thereby achieving a repose angle greater than that of a spherical steelmaking slag such as crushed slag. In addition, the present inventors have found that handling using facilities such as a belt conveyor and a truck and storage in a yard are easy and can be suitably used as a fine aggregate. The present invention has been completed based on this finding.

That is, the gist configuration of the present invention is as follows.
1. Steelmaking slag particles characterized in that a part of a closed curved surface has a surface shape that becomes a fractured surface, and 10 to 90% of the surface area is constituted by a curved surface.

2. 2. The steelmaking slag particles as described in 1 above, wherein the average particle diameter is 0.1 to 5 mm.

3. The steelmaking slag particles according to 1 or 2, wherein a gas is blown onto a molten slag generated during steelmaking to form a spherical slag, and the spherical slag is mechanically crushed.

4). The steelmaking slag particles according to 3 above, wherein the steelmaking slag particles having a passage mass of 50% have an average mass in the range of 0.1 to 0.5 of the average mass of the spherical slag having a passage mass of 50%.

5. A steelmaking slag comprising the steelmaking slag particles according to any one of 1 to 4 above.

6). A process of obtaining a spherical slag by blowing a gas to the molten slag generated in the steelmaking process;
Mechanically crushing the spherical slag;
The method for producing steelmaking slag particles according to any one of 1 to 4 above.

7). The manufacturing method according to 6 above, wherein the spherical slag is mechanically crushed using a rod mill.

  According to the present invention, the angle of repose is large, handling using equipment such as a belt conveyor and a truck, and storage in a yard are easy, and it does not expand even when contacted with water, and is suitable as a fine aggregate. The steelmaking slag particle which can be used, the steelmaking slag containing the said steelmaking slag particle, and the manufacturing method of the said steelmaking slag particle can be provided.

[Steel making slag particles]
Hereinafter, the steelmaking slag particles of the present invention will be specifically described.
The steelmaking slag particles of the present invention have a surface shape in which a part of a closed curved surface becomes a fractured surface, and 10 to 90% of the surface area is constituted by a curved surface. Here, “closed curved surface” means a curved surface that is closed like a spherical surface. When a part of the closed curved surface becomes a fractured surface, the steelmaking slag particle surface is composed of one or more curved surfaces and one or more fractured surfaces. Here, the “curved surface” means a continuously curved convex surface formed by moving a curved line and not broken by a mechanical force. Such a curved surface is glossy, smooth and has no corners. The curvature of the curved surface is not particularly limited, and may be smaller or larger than the curvature of the spherical surface. In addition, the “fracture surface” is a spherical steel-making slag having a surface shape composed of a closed curved surface (referred to as “spherical slag” in this specification), which is broken by receiving mechanical force such as crushing. Means a newly generated cross-section along any surface of the spherical slag. The arbitrary surface may or may not pass through the center of the spherical slag having the closed curved surface. Such a fracture surface does not have gloss and is not necessarily smooth, and one or more convex surfaces and / or concave surfaces or corners may exist on one fracture surface. The steelmaking slag particles of the present invention have one or more such fracture surfaces.

  The fact that the steelmaking slag particles have a surface shape in which a part of the closed curved surface becomes a fractured surface is composed of one or more curved surfaces and one or more fractured surfaces by visual observation or using a magnifying glass or an optical microscope. It can be confirmed by observing that it is present. The curved surface is observed as a glossy, smooth curved surface having no corners, while the fractured surface is observed as a brownish surface without gloss.

  In the steelmaking slag particles of the present invention, it is preferable that 10 to 90% of the surface area is constituted by a curved surface, and 15 to 80% of the surface area is constituted by a curved surface of spherical slag before crushing. “10 to 90% of the surface area is composed of a curved surface” means that the surface area of the steelmaking slag particles, that is, the total area of one or more curved surfaces and the total area of one or more fractured surfaces It means to occupy 10 to 90% as the total area of the one or more curved surfaces. The ratio of the total area of the one or more curved surfaces to the surface area, that is, the curved surface area ratio, can be determined by measuring or estimating by a known method. Specifically, several hundred grams of steelmaking slag particles are collected, shredded to several tens of grams with a reducer, and a picture is taken from above with the steelmaking slag particles arranged in one layer. Then, lattice lines in which the length of one side of the square is equal to or less than the steelmaking slag particle diameter are evenly written on the photographed photograph. It is visually determined whether the surface of the steelmaking slag particles that overlap the point (intersection point) at which the lattice lines intersect is a glossy curved surface or a non-glossy fracture surface. By counting the number of intersections of the one that overlaps the curved surface, the one that overlaps the fracture surface, and the number of each intersection, the ratio (%) of the total area of one or more curved surfaces of the steelmaking slag after crushing and the total area of one or more fracture surfaces Can be calculated.

  The steelmaking slag particles of the present invention have a surface shape in which a part of a closed curved surface becomes a fractured surface, and 10 to 90% of the surface area is constituted by a curved surface, and thus has a large angle of repose compared to a spherical slag. Therefore, even when the steelmaking slag particles are stacked and transported on a plane having an inclination such as a conveyor belt, the steelmaking slag particles do not roll and fall down. Therefore, handling using equipment such as a belt conveyor and transport means such as a truck and storage in a yard can be facilitated. Moreover, since 10 to 90% of the surface area is composed of a curved surface, it can maintain a constant particle size and average particle size, and can be suitably used as a fine aggregate in concrete or asphalt.

  The steelmaking slag particles of the present invention preferably have an average particle size of 0.1 to 5 mm. Here, the “average particle size” is a particle size at which the mass fraction determined by this is determined as a mass fraction passing through each sieve in accordance with JIS A 1102, and the mass fraction determined thereby is 50%. means. This is because by setting the average particle size to 0.1 to 5 mm, particles having a particle size smaller or larger than necessary do not exist and can be suitably used as a fine aggregate in concrete or asphalt. The average particle diameter of the steelmaking slag particles of the present invention is determined in accordance with JIS A 1102 by determining the mass fraction through which each steelmaking slag particle passes each sieve, and the mass fraction determined thereby is 50%. Can be determined by specifying.

  Although the steelmaking slag particles of the present invention are not particularly limited, it is preferable to form spherical slag by blowing a gas to molten slag generated in the steelmaking process and mechanically crush the spherical slag. The slag that can be used as the molten slag generated in the steelmaking process may be by-produced from any of the pretreatment process, the converter, and the electric furnace, and is not particularly limited by the composition. When the molten slag generated in the steelmaking process flows out of the container, for example, from the vertical direction to the horizontal direction and is blown with gas, surface tension acts on the molten slag and is cooled and solidified to form spherical slag. it can. The gas blown onto the molten slag is not particularly limited, and examples thereof include air, oxygen, carbon dioxide, and water vapor. Although the flow rate of the gas to blow is not specifically limited, 80-150 m / s is preferable.

  The process which blows the gas concerning the molten slag generated in the process of steelmaking, and makes it spherical slag is also called a crushing process. When air crushing is performed, iron and FeO in the molten slag are oxidized with air to form a ferrite phase, and calcium ferrite is generated by the ferrite phase and CaO. A spherical slag can be obtained. Alternatively, an aqueous solution containing carbon dioxide, carbonate ions, hydrogen carbonate ions, or the like as the gas may be sprayed together with air, oxygen, carbon dioxide, water vapor, or the like to form a carbonate coating on the spherical slag surface. The monooxide film can make hydration expansion more difficult to occur.

  Spherical slag obtained by the above-mentioned crushing treatment (fractured slag) is not particularly limited, but steelmaking slag particles that can be suitably used as fine aggregates in concrete and asphalt can be obtained. It preferably has an average particle size.

  The steelmaking slag particles of the present invention are preferably formed by mechanically crushing spherical slag (winded slag) obtained by performing the above-described air crushing treatment. In the present invention, crushing means applying force to the particles to be crushed and crushing them roughly to obtain relatively large particles having a particle size of 0.1 to 5 mm. Here, “particle diameter” means the major axis diameter of each particle, and “major axis diameter” is the largest parallel interval when the contour of the particle is sandwiched between two parallel lines in contact therewith. Means.

  The force applied to the particles to be crushed when crushing is not particularly limited, and examples thereof include pressure, impact force, shear force, friction force, bending force, and centrifugal force. Only one type of force may be applied for crushing, or two or more types of force may be applied in combination for crushing. Examples of the crushing means that can apply these forces mechanically include various crushers, crushers, and mills. More specifically, a rod mill, a jet mill, a ball mill, etc. are mentioned, for example. Depending on the composition of steelmaking slag, the hardness, the average particle size desired for the steelmaking slag particles, the type of force to be applied, and other crushing conditions can be appropriately selected.

  As described above, the curved surface of the steel-making slag particles of the present invention formed by mechanical crushing is the curved surface constituting the surface of the spherical slag before crushing. The curved surface area ratio of the steel-manufactured slag particles of the present invention mechanically crushed is adjusted as appropriate by conditions such as crushing means, crushing conditions, composition of the spherical slag to be crushed and hardness used in the production method described below. Can be controlled.

  Moreover, the steelmaking slag particles of the present invention mechanically crushed as described above have an average mass of particles having a passage mass of 50% before the particles having a passage mass of 50% are mechanically crushed. It is preferable to have an average mass in the range of 0.1 to 0.5. In the present specification, “average mass of particles having a passing mass of 50%” means the average mass of particles having the average particle diameter. “Mechanically crushed steelmaking slag particles having a mass passing through 50% have an average mass in the range of 0.1 to 0.5 of the average mass of the spherical steelmaking slag passing mass 50%. "Means that the steelmaking slag particles that are crushed are about one-tenth to about one-half that of the spherical slag before crushing. In other words, it means that one spherical slag was crushed to about 2 to about 10. This is because it can have a large angle of repose compared to a spherical slag, can maintain a relatively narrow particle size distribution and average particle size, and can be suitably used as a fine aggregate in concrete and asphalt. The average mass of particles with a passing mass of 50% can be estimated by multiplying the volume by the particle density, assuming a true sphere of average particle size.

[Steel making slag]
The steelmaking slag of this invention is characterized by including the steelmaking slag particle | grains mentioned above. The steelmaking slag of this invention should just contain the 1 or more steelmaking slag particle | grains mentioned above, and may be comprised only from the 1 or more steelmaking slag particle | grains mentioned above.

[Method for producing steel slag particles]
Steelmaking slag particles characterized in that a part of the closed curved surface has a surface shape that becomes a fractured surface and 10 to 90% of the surface area is constituted by a curved surface is a gas in the molten slag generated in the steelmaking process. It is preferable to manufacture by the manufacturing method which comprises the process of spraying and obtaining the spherical slag and the process of crushing the spherical slag mechanically.

  In the step of obtaining spherical slag by blowing gas to the molten slag generated in the steelmaking process, the slag that can be used as the molten slag generated in the steelmaking process is a pretreatment process, converter, electric furnace It may be a by-product of any of the above. When the molten slag is discharged from the container in the horizontal direction, for example, from the vertical direction and blown with gas, surface tension acts on the molten slag and is cooled and solidified to form spherical slag. The gas blown onto the molten slag is not particularly limited, and examples thereof include air, oxygen, carbon dioxide, and water vapor. Although the flow rate of the gas to blow is not specifically limited, 80-150 m / s is preferable.

  The production method of the present invention includes a step of mechanically crushing a spherical slag obtained by blowing a gas to a molten slag generated in the steelmaking process. The force applied to the spherical slag to be crushed and the crushing means when crushing are as described above. By mechanically crushing the spherical slag, the spherical slag can be made into two or more steelmaking slag particles each having one or more fractured surfaces in addition to a curved surface derived from the surface of the spherical slag. .

  Among the crushing means, the spherical slag has an average particle diameter of 0.1 to 5 mm which can be suitably used as a fine aggregate by crushing not only a part of the amount to be treated but also the whole amount to be treated. Since it can be set as a steelmaking slag particle, a rod mill is preferable. In the rod mill, force is applied to the spherical slag by the falling of the rod or the collision between the rod and the slag in the rotating mill. The rotational speed of the rod mill is not particularly limited, but is preferably 100 to 200 rpm.

  The steelmaking slag particles obtained after the crushing step may be subjected to sieving, classification and the like as necessary. Since the steelmaking slag particles of the present invention have a large stability angle, handling using equipment such as a belt conveyor and a truck and storage in a yard are easy. When the crushing process is performed in the production process, hydration and expansion are difficult. Moreover, since the fixed particle size is hold | maintained, it can be used conveniently as a fine aggregate in concrete or asphalt.

  Hereinafter, the present invention will be described more specifically with reference to invention examples and comparative examples, but these do not limit the scope of the present invention.

  The decarburized converter slag was used as a molten slag generated in the steelmaking process. After this converter decarburization slag is melted at 1550 ° C or higher, the container containing the molten slag is tilted, the slag is discharged, and air that is faster than the nozzle installed in the lower part of the slag is dropped. It was sprayed and scattered. The flow rate of the sprayed air was 100 to 150 m / s, and the cross section of the nozzle used was 50 mm × 3 mm. The spherical slag thus obtained had a closed curved surface close to a glossy sphere, and the average particle size was 1.0 mm. The spherical slag was collected and subjected to crushing treatment by mechanically applying force using any one of crushing means of a rod mill, a ball mill, and a rotary mill using neither a rod nor a ball.

  Table 1 shows configurations and results of Examples and Comparative Examples. The results were evaluated based on (1) crushing condition, (2) angle of repose evaluation (conveyance of belt conveyor), (3) curved surface area ratio, and (4) mass after crushing / mass before crushing. The evaluation methods (1) to (4) are as follows.

(1) Crushing status The crushing status was evaluated based on the state of steelmaking slag particles after crushing treatment. When the steelmaking slag particles after the crushing treatment are mainly those having a surface shape in which a part of the closed curved surface becomes a fractured surface, and have an average particle diameter in the range of 0.1 to 1.0 mm, The crushing situation was evaluated as good. On the other hand, when the steelmaking slag particles after the crushing treatment are mainly those that do not have a surface shape in which a part of the closed curved surface becomes a fractured surface, or when the average particle size is less than 0.1 mm (100 μm) The crushing situation was evaluated as poor. The surface shape was evaluated by magnifying the surface shape using a microscope. The average particle size was measured according to JIS A 1102.

(2) Angle of repose evaluation Steelmaking slag particles obtained after the crushing treatment in each example and comparative example were placed on a horizontal conveyor belt having a width of 600 mm, transported 100 m at a speed of 180 m / min, It was observed whether or not particle rolling was observed. When rolling of the steelmaking slag particles was not recognized, it was evaluated as “good”, and when rolling of the steelmaking slag particles was observed, it was evaluated as “bad”. When the evaluation is good, the steelmaking slag particles obtained after the crushing treatment have a large stability angle and have a surface shape that is good or sufficient for use. On the other hand, when evaluation is unsatisfactory, the stability angle of the steelmaking slag particles obtained after the crushing treatment is small, which is equivalent to the angle of repose of the spherical slag before the crushing treatment.

(3) Curved area ratio 100 g of steelmaking slag particles after crushing were sampled and shrunk to 10 g with a reducer, and a photograph was taken from above with the steelmaking slag particles arranged in one layer. The photographed image was enlarged, and grid lines having a square side length equal to or smaller than the particle diameter of the steelmaking slag particles were evenly written thereon. It was visually judged whether the surface of the steelmaking slag particles overlapping the intersections of the grid lines was a glossy curved surface or a non-glossy fracture surface. By counting the number of intersections that overlap the curved surface and the number of intersections that overlap the fracture surface, the ratio of the curved surface to the fracture surface in the surface area of the steelmaking slag particles after crushing is calculated, and the area ratio (%) of the curved surface is calculated. did.

(4) Mass after crushing / mass before crushing The average mass of particles with a passing mass of 50% of spherical slag was determined before crushing treatment. Similarly, in each Example and Comparative Example, the average mass of particles with a passing mass of 50% of steelmaking slag particles obtained after crushing treatment was obtained, and this was the average of particles with a passing mass of 50% of spherical slag before crushing treatment. Values obtained by dividing by mass are shown in Table 1.

  In the invention example using the rod mill, the spherical slag was crushed, and the steelmaking slag particles of the present invention were obtained. The steel-making slag particles obtained in the inventive examples were composed of a glossy curved surface and a glossless fracture surface, and the total area of the glossy curved surface occupied 10 to 90% of the entire surface area. That is, the steelmaking slag particles obtained in the inventive examples were composed of curved surfaces in which 10 to 90% of the surface area was derived from spherical slag before crushing. Further, the steelmaking slag particles having a passing mass of 50% have an average mass within the range of 0.1 to 0.5 of the average mass of the spherical slag before the crushing treatment, and are crushed small to an average particle size of less than 100 μm. There was nothing happened. Moreover, it had a large angle of repose, no rolling on the conveyor belt was observed, and the angle of repose evaluation (conveyance condition of the belt conveyor) was also good.

  On the other hand, in the case of a rotating mill in which only balls and rods are not inserted into the mill and only the slag is rotated, the spherical steel slag particles are slightly chipped even after the mill is rotated for 30 minutes. More than 90% of the material was composed of curved surfaces, and almost retained the spherical shape as it was when it was charged. In addition, in the case of a ball mill in which 10 balls with a diameter of 5 mm are put and rotated, the steelmaking slag particles obtained after rotating the mill for 60 minutes are composed of curved surfaces with more than 90% of the surface area. Almost retained the spherical shape as it was. Steelmaking slag particles in which more than 90% of the surface area is composed of a curved surface had a small angle of repose, so that rolling on the conveyor belt was recognized, and the angle of repose evaluation (conveyance condition of the belt conveyor) was poor.

  In addition, when crushing under severe conditions such as increasing the number of rods or balls, increasing the rotational speed (rpm) of the mill to increase the rotational speed, the resulting steelmaking slag particles are curved surfaces. The area ratio was less than 10%, and it was pulverized to an average particle size of less than 0.1 mm (100 μm), so that it was not suitable for use as a fine aggregate.

  As is clear from the above results, the steelmaking slag particles of the inventive example have a large angle of repose and can be suitably used as a fine aggregate.

  The steelmaking slag particles of the present invention and the steelmaking slag containing the steelmaking slag particles can be suitably used as fine aggregates used in concrete and asphalt. Moreover, the manufacturing method of this invention can be utilized for reuse of the slag generated in the steelmaking process as a manufacturing method of the steelmaking slag particle | grains which can be utilized suitably as a fine aggregate for concrete and asphalt.

Claims (7)

  Steelmaking slag particles characterized in that a part of a closed curved surface has a surface shape that becomes a fractured surface, and 10 to 90% of the surface area is constituted by a curved surface.   The steelmaking slag particles according to claim 1, wherein the average particle diameter is 0.1 to 5 mm.   The steelmaking slag particles according to claim 1 or 2, wherein a gas is blown onto a molten slag generated during steelmaking to form a spherical slag, and the spherical slag is mechanically crushed.   The steelmaking according to claim 3, wherein the steelmaking slag particles having a passing mass of 50% have an average mass in the range of 0.1 to 0.5 of the average mass of the spherical slag having a passing mass of 50%. Slag particles.   Steelmaking slag containing the steelmaking slag particle of any one of Claims 1-4. A process of obtaining a spherical slag by blowing a gas to the molten slag generated in the steelmaking process;
Mechanically crushing the spherical slag;
The manufacturing method of the steel-making slag particle | grains of any one of Claims 1-4 characterized by the above-mentioned.   The method of producing steelmaking slag particles according to claim 6, wherein the spherical slag is mechanically crushed using a rod mill.