JP6460169B2 - Manufacturing method of steelmaking slag roadbed material - Google Patents

Description

  The present invention relates to a method for producing a steelmaking slag roadbed material produced by pressurized steam aging of steelmaking slag.

  In the steelmaking slag, some of the lime source and magnesia source added by refining remain unmelted or free without forming a compound with other components. When such free CaO or free MgO hydrates with water, the volume expands more than twice and destroys surrounding structures. Therefore, before using steelmaking slag as a stone or roadbed material, It is necessary to promote hydration and calm down at this stage.

  In order to rapidly react free CaO and free MgO in steelmaking slag with moisture, reaction promotion (steam aging) with steam that simultaneously raises temperature and supplies moisture is generally performed. Among them, pressurized steam aging using high-temperature and high-pressure steam can be processed at high speed. Conventionally, several proposals have been made on apparatuses and aging patterns for performing this pressurized steam aging.

Patent Document 1 shows a transition pattern of temperature-pressure at the time of pressurized steam aging, and shows a method of processing by lowering the steam pressure for a short time during pressurizing and holding the pressure again to a high pressure. ing.
Further, in Patent Document 2, steam is blown from the inside of the slag filling section through the steam pipe into the slag storage container in order to perform the pressurized steam aging in a short time even in the case of slag that is fine and does not easily enter the steam. The method is shown.

Japanese Patent No. 2873178 Japanese Patent No. 4972609

When steam aging steelmaking slag, some of the slag particles collapse due to expansion reaction, so the particle size distribution changes to the fine side. If the time of pressurized steam aging is lengthened or the temperature or pressure is increased in an attempt to suppress the expansion, finer particles will progress, but the expansion stability will slow down. Thus, the productivity of the aging process for producing a stable roadbed material that satisfies the expansion standard of the roadbed material product is lowered.
The method of Patent Document 1 is intended to stabilize the particles by proceeding with the collapse of the particles due to the pressure change during pressurized steam aging. However, since the new expansion source of the particles is continuously exposed, the state in which the expansion reaction further proceeds. There arises a problem in that fine graining is inefficiently progressed for stabilization. In the method of Patent Document 2, steam enters fine particles and the temperature rises. However, if the original is fine particles, the finer particles become finer and the stabilization of the expansion rate becomes slower.

  Accordingly, an object of the present invention is to provide a production method capable of producing a steelmaking slag roadbed material having extremely low expansibility with high productivity in a method of producing a steelmaking slag roadbed material by pressurized steam aging of the steelmaking slag. There is.

The gist of the present invention for solving the above problems is as follows.
[1] Steelmaking slag (a) crushed to a particle size with a particle size of 40 mm or less being 80 mass% or more, by increasing or decreasing the fine particles / fine powder content under the following conditions (i) or (ii) When the particle size distribution of the slag (a) is approximated by Andreazen's curve formula, after adjusting the particle size distribution of the steelmaking slag (a) so that the Fuller index is 0.4 to 0.6, pressurized steam aging is performed. The manufacturing method of the steel-making slag roadbed material characterized by performing.
(I) A part of the steelmaking slag (a) is classified with a sieve (x) having a sieve mesh of 10 mm or less to reduce fine particles and fine powder, and then mixed with the remainder of the steelmaking slag (a).
(Ii) Fine particles and fine powder obtained by classifying steelmaking slag previously crushed to a particle size with a particle size of 40 mm or less being 80 mass% or more with a sieve (x) having a sieve mesh of 10 mm or less Is added to the steelmaking slag (a) and mixed.

[2] In the production method of [1] above, the steelmaking slag (a) is decarburized slag generated in the same refining equipment on the same day, and a sieve having a mesh size of 10 mm or less for a part of the steelmaking slag (a) ( After reducing the fine particles and fine powder by classifying in x), mixing with the remainder of the steelmaking slag (a) reduces the fine particles and fine powder of the steelmaking slag (a) and adjusts the particle size distribution. A method for producing a steelmaking slag roadbed material.
[3] In the manufacturing method of [1], the steelmaking slag (a) is composed of two or more types of steelmaking slag, and the mesh size of all or part of one type of steelmaking slag (a1) is 10 mm or less. After reducing the fines and fines by classifying with a sieve (x), the remaining one or more types of steelmaking slag (a2) and the remainder of the steelmaking slag (a1) (however, all of the steelmaking slag (a1) A method for producing a steelmaking slag roadbed material characterized by adjusting the particle size distribution by reducing the fine and fine particles of the steelmaking slag (a) by mixing with the above.

[4] In the production method of [3] above, the steelmaking slag (a1) is decarburized slag generated in the same refining equipment on the same day, and the steelmaking slag (a2) is steelmaking slag other than decarburized slag. A method for producing steelmaking slag roadbed material.
[5] A method for producing a steel-making slag roadbed material, wherein the sieve (x) has a mesh size of 5 mm (however, nominal diameter) in the production method of any one of [1] to [4] above.
[6] In the manufacturing method according to any one of the above [1] to [5], in the pressurized steam aging, the steelmaking slag roadbed material is maintained at a steam pressure of 0.20 to 1.96 MPa for 1 to 5 hours. Manufacturing method.
[7] In the production method according to any one of [1] to [6] above, the particle size range of steelmaking slag after pressurized steam aging is CS-40, CS whose particle size range is defined in JIS A5015 (2013). A method for producing a steelmaking slag roadbed material satisfying any particle size range of -30, CS-20, MS-25, and HMS-25.

  ADVANTAGE OF THE INVENTION According to this invention, the steel-making slag roadbed material which reduced the expansibility to the lowest level which can be reached | attained on the applied aging conditions can be manufactured with high productivity. For this reason, even when expandable steelmaking slag is subjected to pressurized steam aging under the same aging conditions and steam intensity as in the past, more expansion rate acceptable products (roadbed material products) can be obtained. Moreover, the steel-making slag roadbed material manufactured by the method of the present invention has not only extremely low expansibility but also excellent compactability because of its high density.

Each tamping of steelmaking slag was performed by changing the standard 92 times / layer × 3 layers tamping to 46 times / layer × 3 layers, 92 times / layers × 3 layers, and 184 times / layers × 3 layers. Graph showing the dry density of the specimen FIG. 1 is a graph showing the transition of the expansion coefficient in a water immersion test immersed in a water tank maintained at 80 ° C. for each specimen shown in FIG. A graph showing the particle size distribution of a sample collected at the time when only one layer was tamped in the tamping of the three layers from which the specimens of FIGS. 1 and 2 were obtained. The graph which shows the relationship between the dry density of the test body (steel-making slag) which gave the pressurization steam aging at 158 degreeC (steam pressure 0.5MPa), and a water immersion expansion coefficient The graph which shows the relationship between the dry density of a test piece (steel-making slag) which gave pressurized steam aging at 173-183 degreeC (steam pressure 0.75-1.0MPa), and a water immersion expansion coefficient. Graph showing Andreasen's curve (cumulative distribution) Fuller index q in the case of approximating the particle size distribution of various steelmaking slag samples subjected to pressurized steam aging by Andreasen's curve formula, and the dry density at the time of compaction of each sample (E defined in JIS A1210 (2009)) -Dry density obtained by performing tamping of 92 times / layer × 3 layers in accordance with the method of -b) The graph which shows the relationship between the water immersion expansion coefficient (expansion coefficient after 4 days at 80 degreeC constant holding | maintenance) and the Fuller index | exponent q of the steel-making slag which performed pressurized steam aging at 158 degreeC (steam pressure 0.5MPa). The graph which shows an example of the result of having calculated the Fuller index | exponent q about the steelmaking slag before pressurized steam aging in an Example by approximating the particle size distribution by Andreazen's curve type | formula

The inventor conducted the following experiment.
In the tamping test used for the expansibility evaluation of the roadbed material, the number of tamping is determined depending on the conditions. In the E-b method defined in JIS A1210 (2009), a 4.5 kg rammer is dropped 92 times into a cylindrical container (CBR test form) with an inner diameter of 150 mm, and this is thrust into three layers. To a height of 125mm. If the mass of the solidified specimen is known, the specimen mass and density at the time of drying can be determined based on the moisture content adjusted in advance.

  The standard 92 times / layer x 3 layers tamping is changed to 46 times / layers x 3 layers, 92 times / layers x 3 layers, 184 times / layers x 3 layers, and the steelmaking slag is tamped and tamped. The dry density of each specimen was measured. The results are shown in FIG. 1, and the dry density increases as the number of tamping increases. On the other hand, the tamped specimen was immersed in a water tank maintained at 80 ° C., and the transition of expansion was measured. FIG. 2 shows the transition of the expansion coefficient of each specimen in this water immersion test. The expansion coefficient increases in the order of decreasing density. That is, the expansion coefficient is 46 times / layer> 92 times / layer> 184 times / layer. In the tamping of the three layers, a sample at the time of tamping only one layer was collected, and the result of the particle size distribution measurement is shown in FIG. 3, and it can be seen that the coarse particles slightly collapsed when the number of tamping times was 184.

The above results show that the expansion is smaller when the particles are packed so as to have a higher density even if the particles are broken to some extent and broken to some extent.
Others So far, the water vapor expansion test has been conducted under various conditions where the pressurized steam aging temperature is 158 ° C. to 183 ° C. (vapor pressure 0.5 MPa to 0.95 MPa) and the holding time is changed from 2 hours to 12 hours. As a result of examining the dry density and the water immersion expansion rate (in this case, compared with the expansion rate after 4 days at a constant temperature of 80 ° C.) for the test piece (steel slag), the test sample with a lower dry density tended to have a higher expandability. It was.

  FIG. 4 shows the relationship between the dry density of the specimen (steel slag) subjected to pressurized steam aging at 158 ° C. (steam pressure: 0.5 MPa, holding time: 3 ± 1 hour) and the water immersion expansion rate. Is a dry density (JIS A1210 (2009)) of a specimen (steel slag) subjected to pressurized steam aging at 173 to 183 ° C. (steam pressure: 0.75 to 1.0 MPa, holding time: 3 ± 1 hour) The dry density obtained by tamping the standard 92 times / layer × 3 layers according to the method of Eb) and the water immersion expansion rate are shown respectively. The same tendency can be seen even if the values are different.

  When focusing on one slag particle, if the filling property is high and the constraint from surrounding particles is large, the expansion source in the crack of the particle reacts and expands, and even if it tries to expand the particle itself, it is restrained. The reaction does not proceed freely. If the particle is further destroyed by the expansion reaction and the crack is advanced, the space in which moisture reaches the expansion source during the reaction and the unreacted expansion source at the advanced crack tip is expanded. However, if the constraint around the particles is strong, the space for supplying moisture to the expansion source cannot be easily expanded, and as a result, the expansion reaction is suppressed.

  In order to increase the density of the steelmaking slag, it is desirable to arrange the coarse particles densely, fill the voids formed between the coarse particles with fine particles, and further fill the voids where fine powder remains between the fine particles. However, if there are more fine particles or fine powder than necessary to fill the voids, the fine particles come into contact with each other to form a large number of small voids. Even if the pressurized steam aging is lengthened, if the fine particles increase more than necessary, the packing of the slag particles is deteriorated and the reduction of the expansion rate is hindered.

When the particle size distribution of various steelmaking slags subjected to pressurized steam aging was examined, it was found that there was a considerable difference in the particle size distribution.
There is Andreasen's curve formula for the expression of the continuous particle size distribution, and the passing mass fraction at each intermediate diameter (Dp) with respect to the maximum particle diameter (Dpmax) is expressed as the following formula (1) using the Fuller index q. .
U (Dp) = (Dp / Dpmax) ^q (1)
Here, Dp is the particle size, Dpmax is the maximum particle size, and U (Dp) is the passing mass fraction up to the particle size Dp. (Source: For example, “Shigeo Miwa, Powder Engineering, Nikkan Kogyo Shimbun, 1981, p. 42”)
This Andreasen curve has an integrated distribution as shown in FIG. 6, and the smaller the number of fine particles, the smaller the Fuller index q. Experimentally, q = 1/2 for sparse filling and q = 1/3 for dense filling, and the density is highest.

  Using the maximum particle size Dpmax and the Fuller index q as variables, the particle size distribution of various steelmaking slag samples subjected to pressurized steam aging was approximated by Andreasen's curve formula. The dry density at the time of tamping each sample (dry density obtained by tamping of 92 times / layer × 3 layers in accordance with the method of Eb defined in JIS A1210 (2009)) and the Fuller index q The relationship is shown in FIG. According to FIG. 7, the dry density becomes maximum when q is 0.4 to 0.6, and tends to be small before and after that. When fine particles and fine powder increase, q falls below 0.4 and the dry density decreases. On the other hand, q exceeds 0.6 at a level where the fine particles and fine powder were experimentally reduced, but the dry density is still small. This means that q has an optimum range for filling, and is consistent with the tendency of Andreasen's curve formula.

In an actual crushing plant for steelmaking slag, products that have undergone crushing process and re-crushing coarse particles that have been classified should have less fines and fines than necessary in light of the JIS standard for steel slag roadbed materials (JIS A5015). There are not so many, and it is thought that there are many cases where it is crushed finely.
In the above-mentioned FIG. 7, the level at which the dry density is small and the expansion is large is that q is less than 0.4. Incidentally, the relationship between the water immersion expansion rate (expansion rate after 4 days at a constant hold of 80 ° C.) and the Fuller index q of steelmaking slag subjected to pressurized steam aging at 158 ° C. (steam pressure 0.5 MPa) is shown in FIG. As shown in FIG. 6, the water expansion coefficient decreases toward q = 0.5.

  When the Fuller index q is larger than 0.6, the frequency with which the coarse particles come into contact with each other increases, and the fine particles that fill the gaps between the coarse particles are insufficient, thereby reducing the filling property. Also in this case, the constraint between the particles becomes low, and an environment in which expansion and collapse can be promoted more freely. Furthermore, in the case of only coarse particles, the probability that the coarse particles are directly subjected to the impact of the Ranma increases when the sample particles are solidified in the mold by the water immersion expansion test specified in JIS A5015. Since there are few particles in contact with the filler, the stress cannot be dispersed to the surroundings, and the impacted coarse particles are frequently broken down. As a result, an unreacted expansion source appears on the new fracture surface, so that despite the aging of pressurized steam, many unreacted expansion sources are likely to react before the water immersion expansion test. Will increase the rate. Therefore, it is not necessary to simply coarsen the particle size.

  From the above, the present inventor found that the water immersion expansion of steelmaking slag subjected to pressurized steam aging is also affected by the particle size distribution, and the particle size distribution is inadequate, so the slag particle filling ability is reduced. Then, it discovered that water immersion expansion was increasing. Therefore, even if the desired pressurized steam aging is performed, it is considered that a considerable number of cases where the expansibility is judged to be rejected due to an inappropriate particle size distribution. In particular, in pressurized steam aging, the expansion reaction is accelerated at high temperatures in a short time and the expansion source capable of reacting is intended to react as much as possible. Tends to be inappropriate.

  As a result of further investigation based on the above knowledge, the present inventor has determined that the minimum achievable under the applied aging conditions if the steam aging is applied to the steelmaking slag whose fine particles and fines have been increased or decreased in advance under the predetermined conditions. It was found that a roadbed material having an expansion rate can be obtained. Specifically, it has been found desirable to adjust the particle size distribution so that the Fuller index q is 0.4 to 0.6. According to this method, it is only necessary to increase / decrease the fine particles / fine powder content of the steelmaking slag before pressurized steam aging, so it is possible to produce a steelmaking slag roadbed material with extremely low expansibility with high productivity, The manufactured steelmaking slag roadbed material is excellent in compaction because of its high density.

Therefore, in the present invention, the steelmaking slag (hereinafter referred to as “steelmaking slag a” for convenience of description) crushed to a particle size in which the ratio of the particle size of 40 mm or less is 80 mass% or more is the following condition (i) or (ii) The particle size distribution of the steelmaking slag a is adjusted so that the Fuller index is 0.4 to 0.6 when the particle size distribution of the steelmaking slag a is approximated by Andreazen's curve formula by increasing or decreasing the fine grain / fine powder content. After adjustment, pressurized steam aging is performed. The particle size of 40 mm or less is a particle size that passes through a sieve having a sieve mesh of 40 mm (nominal diameter).
(I) A part of the steelmaking slag a is classified by a sieve having a sieve mesh of 10 mm or less (hereinafter referred to as “sieve x” for convenience of explanation) to reduce fine particles and fine powder, and then the remainder of the steelmaking slag a ( Mix with solid grain steelmaking slag a).
(Ii) Fine particles and fine powder obtained by classifying steelmaking slag previously crushed into a particle size with a particle size of 40 mm or less being 80 mass% or more with a sieve x having a mesh size of 10 mm or less, In addition to steelmaking slag a (steelmaking slag a having a solid particle size), it is mixed.
The “previously obtained fine particles / fine powder” in (ii) above refers to the fine particles / fine particles obtained and classified in the previous classification.
Steelmaking slag is slag generated in the steelmaking process of the steel production process, including decarburization slag (converter decarburization slag), hot metal pretreatment slag (desiliconization slag, dephosphorization slag, etc.), ingot slag, smelting reduction slag There are electric furnace slags, and one or more of these can be used.

In the present invention, regarding steelmaking slag a before adjusting the particle size distribution by increasing / decreasing fine particles / fine powder, the maximum particle size of slag occupying 80 mass% or more is set to 40 mm. This is because the number of expansion sources to be increased increases, and even when pressurized steam aging is performed, the variation in the water immersion expansion rate increases, and the expandability is not stabilized.
It is considered that the curve under the integrated sieve greatly changes in Andreazen's curve formula in a region where the particle size is 20% or less of the maximum particle size in the region where the Fuller index q is smaller than 1. If the particle size distribution passes 80 mass% or more at a mesh size of 40 mm, the particle size of 20% of the maximum particle size is substantially 10 mm, and it is desirable to adjust the amount of fine particles and fine powder below that. For this reason, in the present invention, as in (i) and (ii) above, the fine particle / fine powder content is increased / decreased through classification with a sieve x having a sieve mesh of 10 mm or less, and the particle size distribution is adjusted.

In addition, the portion where the change is large in the vicinity of the desired Fuller index q1 / 2 is a portion of 10% or less (about 5 mm or less) of the maximum particle size, and directly increasing or decreasing the particle size of 5 mm or less manipulates the particle size distribution. Cheap. Therefore, in the present invention, the sieve x of the sieves (i) and (ii) is set to 5 mm (nominal diameter), and the fine and fine particles having a particle diameter of 5 mm or less that pass through the sieve can be increased or decreased. (In the following description, “particle size of 5 mm or less” and “−5 mm” are particle sizes that pass through a mesh size of 5 mm (nominal diameter)). That is, when reducing the fine particles and fines as in (i) above, for example, only a part of the target steelmaking slag a pile (steeling slag generated in the same refining equipment on the same day) has a mesh size of 5 mm. Particles with a particle size of 5 mm or less are separated by classification with (nominal diameter) sieve x, and the remaining mountain parts (the remainder of the steelmaking slag a) are left as they are without classification, and classified steelmaking slag. a and steelmaking slag a which is not classified and which has a solid particle size are mixed. In this case, by changing the ratio of the steelmaking slag a classified by the sieve x having a sieve mesh of 5 mm, the ratio of fine particles / fine powder having a particle diameter of 5 mm or less as a whole can be adjusted. On the other hand, when there are insufficient particles of 5 mm or less and the amount of fine particles and fines to be insufficient is increased as in (ii) above, -5 mm of the stock screened by the previous classification (ratio of particle size of 40 mm or less) Is added to the steelmaking slag crushed to a particle size of 80 mass% or more with a sieve x having a mesh size of 5 mm (nominal diameter) as much as necessary, and mixed. Then, by adjusting the particle size distribution as described above, the Fuller index q is set to 0.4 to 0.6.
Among steelmaking slag, decarburized slag has a relatively high basicity (CaO / SiO ₂ ) and a high content of free CaO. Therefore, slag particles having a particle size of 5 mm or less are used for, for example, sintering raw materials and refining. Since it can be recycled for use as a firewood, it also has the advantage of being actively classified and extracted.

Two or more kinds of steelmaking slag can be mixed and used for the steelmaking slag roadbed material. Thus, when the steelmaking slag a consists of two or more types of steelmaking slag, a sieve x having a sieve size of 10 mm or less (for example, the sieve mesh is the nominal diameter) of all or a part of one type of the steelmaking slag a1. After the fine particles and fines are reduced by classification with a 5 mm sieve x), the remaining one or more types of steelmaking slag a2 and the remainder of the steelmaking slag a1 remain in the solid particle size not classified (however, the steelmaking slag a1 The particle size distribution may be adjusted by mixing with the above). In this case, (1) changing the ratio of the steelmaking slag a1 classified by a sieve x having a sieve mesh of 10 mm or less (for example, a sieve x having a nominal diameter of 5 mm), (2) the steelmaking slag a1 and the steelmaking slag a2 The ratio of fine particles / fine powder having a particle size of 5 mm or less as a whole can be adjusted by either or both of changing the quantitative ratio. Then, by adjusting the particle size distribution as described above, the Fuller index q is set to 0.4 to 0.6.
A typical example of using two or more types of steelmaking slag mixed with steelmaking slag roadbed material as described above is decarburization slag generated in the same refining equipment on the same day, and steelmaking slag a2 is decarburized. This is the case of steelmaking slag other than slag.

  In the present invention, it is the steelmaking slag a before pressurized steam aging that adjusts the particle size distribution so that the Fuller index q is 0.4 to 0.6. The grain size of steelmaking slag a increases with fine steam and fine powder when subjected to pressurized steam aging, but at the same time, the reduction of coarse grains reduces the maximum grain size in Andreasen's curve formula, so the shape of the grain size distribution changes greatly. do not do. For this reason, the Fuller index q of the steelmaking slag a (roadbed material product) after being subjected to pressurized steam aging is also generally maintained in the range of 0.4 to 0.6. However, the fuller index may increase due to a decrease in the maximum particle diameter despite the fact that the whole is fined by pressurized steam aging. For this reason, it is more preferable to perform pressurized steam aging after adjusting the particle size distribution so that the Fuller index q is approximately 0.5 (0.5 ± 0.05).

  Mixing of the slag mentioned above, that is, mixing of the classified steelmaking slag a and the unclassified steelmaking slag a, and mixing of the steelmaking slag a1 and the steelmaking slag a2 must be performed before pressurized steam aging. . When trying to mix slag particles uniformly using heavy machinery or a mixer after pressurized steam aging, mechanical stress acts on the slag particles, causing them to collapse again, scratching or scraping the particle surface after the expansion reaction has ended. Or unreacted expansion sources appear. As a result, the water immersion expansion rate increases, the variation increases, and the proportion of products that are rejected increases.

  The pressure of pressurized steam aging can be adjusted according to the amount of free CaO and free MgO in the steelmaking slag. The larger the amount, the faster it is necessary to react free CaO or free MgO in a reactive state, and it is advantageous to raise the temperature and raise the saturated vapor pressure. If the saturated vapor pressure is set to a level exceeding 1.96 MPa, the steam supply equipment and the pressure vessel become larger than the processing amount, which is uneconomical. On the other hand, when the saturated vapor pressure is less than 0.20 MPa, the saturated vapor pressure temperature is low, and the reaction promoting effect on the vapor at 100 ° C. that is balanced under atmospheric pressure is small. For this reason, the vapor pressure is preferably 0.20 to 1.96 MPa.

  The treatment time (holding time) for pressurized steam aging is suitably about 1 to 5 hours. The desirable upper limit of the treatment time (holding time) is set to 5 hours. If the treatment time is too long, the productivity is lowered, and the advantage of promoting the reaction by pressurized steam is lost. This is because it becomes the same level as aging. For this reason, it is desirable to shorten the holding time by raising the steam temperature. Further, the reason why the desirable lower limit of the processing time (holding time) is set to 1 hour is that at least 1 hour is required for the slag in the pressure vessel to uniformly raise the temperature and promote the reaction.

The particle size of steelmaking slag after pressurized steam aging in the method of the present invention is that of CS-40, CS-30, CS-20, MS-25, HMS-25 whose particle size ranges are defined in JIS A5015 (2013). It is preferable to satisfy any particle size range. These stipulate the physical properties including the grain size of steel slag for roads, and the numbers in the standard names indicate the approximate maximum grain size. In practice, those satisfying this granularity are used for road paving work, so it is necessary to pass this standard to sell roadbed materials.
The steelmaking slag roadbed material manufactured by the method of the present invention as described above preferably has a particle size distribution with a Fuller index of 0.4 to 0.6 when the particle size distribution is approximated by an Andreazen curve formula.
The steelmaking slag roadbed material manufactured according to the present invention may be used (constructed) alone, or used (constructed) by mixing with other roadbed materials (for example, other slag roadbed materials and crushed stones). Also good.

Steelmaking slag used as a raw material is decarburized slag and ingot slag, both of which are crushed to a particle size of 40 mm or less (passed through a sieve having a sieve size of 40 mm (nominal diameter)). The free CaO content was 4.9 to 5.2 mass% for decarburized slag and 1.3 mass% for ingot slag. In Example 1 and Example 2, as decarburized slag, slag A (particle size 5-40 mm) in which particles of -5 mm are classified and eliminated with a sieve having a mesh size of 5 mm (nominal diameter), and the same day as this slag A Decarburized slag generated in the same refining equipment was used, and slag B (particle size 0-40 mm) having a solid particle size containing -5 mm particles as they were without classification. In Example 2, slag C having a solid particle size (particle size of 0 to 40 mm) containing -5 mm particles as they were without classification was used as the ingot slag. Moreover, in Example 3, as the decarburized slag, the solid particle size slag D (particle size 0-40 mm) that has not been classified and the decarburized slag previously crushed to a particle size of 40 mm or less have a mesh size of 5 mm ( The slag E (particle size 0-5 mm) that was under-sieved when classified with a sieve having a nominal diameter) was used. The slag D has a particle size of 0 to 40 mm, but is a slag having a particle size distribution with a coarse particle size overall and a small fine particle content.
When mixing two slags out of the slags A to E, a heavy machine such as a wheel loader was used to mix the slags, and the mixing was made uniform by repeating the turnover several times.

37.5 mm (nominal diameter 40 mm), 31.5 mm, 26.5 mm, 19.0 mm, 13.0 mm, 9.5 mm (nominal diameter 10 mm), to measure the passing mass fraction (particle size distribution) of slag, The sieves of 4.75 mm (nominal diameter 5 mm), 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, 0.15 mm and 0.075 mm were used. This sieve series is a compromise between the sieve series for measuring the aggregate particle size and the sieve series for measuring the particle size of the slag roadbed material. This is in order to precisely measure the distribution on the finer grain side than the slag roadbed material sieve series. JIS A5015 (2013) The steel slag for roads has a water immersion expansion rate of 1.5% or less, but in actual operation, it is stabilized to a smaller expansion rate in consideration of variations in the product. It is often done. In this example, the standard was to reduce the water immersion expansion rate to 0.7% or less with a simple slag after pressurized steam aging.
Pressurized steam aging was carried out in a horizontal autoclave where the temperature was increased and increased by blowing steam under the condition that the steam pressure was maintained at 0.98 MPa for 3 hours.

[Example 1]
Except for Comparative Example 1, slag A (particle size 5-40 mm) in which fine particles of -5 mm were classified / excluded and slag B (solid size 0-) in which -5 mm fine particles were not classified / excluded 40 mm) was mixed to obtain a slag (sample) having a predetermined particle size distribution. In addition, the comparative example 1 was made into the slag (sample) which consists only of slag B (granularity 0-40mm) of solid particle size. For the slag before pressurized steam aging, the Fuller index q in Andreasen's curve equation was determined using the regression function of the graph software. An example is shown in FIG. At that time, the passing mass fraction of 100 mass%, that is, the passing mass fraction of the entire mesh was not used as data, and only the passing mass fraction of the mesh with a passing mass fraction of less than 100 mass% was approximated as data.
After subjecting each slag to pressurized steam aging, the particle size distribution measurement and the calculation of the Fuller index q were performed again. Moreover, the water immersion expansion test defined in JIS A5015 (2013) Annex 2 was performed on the slag after pressurized steam aging, and the dry density and the water expansion coefficient of each specimen were measured.

The results are shown in Tables 1 and 2. The maximum particle size Dpmax described in Tables 1 and 2 is the maximum particle size of slag obtained from the fitted curve when the particle size distribution of each slag is approximated by Andreazen's curve formula (the slag is all through). (Sieving in calculation). The same applies to the maximum particle size Dpmax described in Tables 3 to 6.
According to Table 1 and Table 2, Invention Examples 1-3 in which the Fuller index q is in the range of 0.4 to 0.6 have a high dry density of the water immersion expansion specimen, and the water expansion coefficient is in the comparative example. Low compared. On the other hand, in Comparative Examples 1 and 2 in which the Fuller index q is less than 0.4 and in Comparative Examples 3 and 4 in which the Fuller index q is greater than 0.6, even if the slag is the same as that of the inventive example, The expansion rate is high.

[Example 2]
A slag having a predetermined particle size distribution by mixing slag A (particle size 5-40 mm) or slag B (particle size 0-40 mm) as decarburized slag and slag C (particle size 0-40 mm) as ingot slag. ). With respect to the slag before pressurized steam aging, the Fuller index q was determined in the same manner as in Example 1. In addition, after subjecting each slag to pressurized steam aging, the particle size distribution measurement and fuller index q are calculated in the same manner as in Example 1, and the dry density and water expansion coefficient of each specimen are measured. did.
For comparison, slag A, slag B, and slag C are each subjected to simple pressurized steam aging, and similarly, the particle size distribution after aging treatment and the calculation of the fuller index q are calculated, and each specimen is dried. The density and water expansion coefficient were measured.

  The results are shown in Tables 3 and 4. According to this, slag B (granularity 0-40 mm) and solid slag C (granularity 0-40 mm) having a fine particle size of -5 mm not classified / excluded were mixed at 70:30 (mass ratio). In Comparative Example 5, the Fuller index q is less than 0.4. On the other hand, Invention Example 4 in which slag A (particle size 5-40 mm) and slag C (particle size 0-40 mm) obtained by classifying and eliminating a fine particle portion of -5 mm was mixed at 50:50 (mass ratio) had a Fuller index q of 0. Within the range of 4-0.6. Here, when slags A, B, and C are used in a simple manner, since slag C has little free CaO, expansion stabilization occurs quickly, and the water immersion expansion rate after pressurized steam aging is As low as 0.23%. On the other hand, slag A and slag B, which are decarburized slags, originally have more free CaO than slag C, and the Fuller index q is both out of the range of 0.4 to 0.6, and the dry density of the specimen is Low, the water expansion coefficient is higher than 0.7%. In the case of Invention Example 4, the dry density of the specimen is high, the water expansion coefficient is lower than the average water expansion coefficient of slag B and slag C, and the effect of adjusting the particle size distribution appears.

[Example 3]
Any of the decarburized slag is a slag (sample) having a predetermined particle size distribution by mixing solid slag D (particle size 0-40 mm) and slag E (particle size 0-5 mm) under a sieve size of 5 mm. did. With respect to the slag before pressurized steam aging, the Fuller index q was determined in the same manner as in Example 1. Moreover, after performing pressurized steam aging with respect to slag, while performing the particle size distribution measurement and the calculation of Fuller index | exponent q by the method similar to Example 1, the dry density and water immersion expansion coefficient of the test body were measured.
For comparison, the Fuller index q was determined for the slag D plain by the same method as in Example 1. Furthermore, pressurized steam aging was performed with the slag D alone, and the particle size distribution measurement after the aging treatment and the calculation of the Fuller index q were similarly performed, and the dry density and the water immersion expansion rate were measured.

  The results are shown in Tables 5 and 6. According to this, the fuller index q is larger than 0.6 for the slug D (grain size 0-40 mm) having a solid particle size with a little fine particle content. On the other hand, Invention Example 5 in which fine slag E (particle size 0-5 mm) is mixed at 85:15 (mass ratio) with solid slag D has a Fuller index q of 0.4 to 0.6. It is in the range. Even in the particle size distribution after pressurized steam aging, the slag D has a Fuller index q greater than 0.6, but Inventive Example 5 has a Fuller index q in the range of 0.4 to 0.6. In addition, Invention Example 5 has a higher dry density than the slag D, and the water immersion expansion rate is less than 0.7%.

Claims (7)

For steelmaking slag (a) crushed to a particle size with a particle size of 40 mm or less at 80 mass% or more, steelmaking slag (a) is increased or decreased under the following conditions (i) or (ii). When the particle size distribution of the steelmaking slag (a) is adjusted so that the Fuller index becomes 0.4 to 0.6 when the particle size distribution of) is approximated by Andreazen's curve formula, pressurized steam aging is performed. A method for producing a steelmaking slag roadbed material.
(I) A part of the steelmaking slag (a) is classified with a sieve (x) having a sieve mesh of 10 mm or less to reduce fine particles and fine powder, and then mixed with the remainder of the steelmaking slag (a).
(Ii) Fine particles and fine powder obtained by classifying steelmaking slag previously crushed to a particle size with a particle size of 40 mm or less being 80 mass% or more with a sieve (x) having a sieve mesh of 10 mm or less Is added to the steelmaking slag (a) and mixed.   Steelmaking slag (a) is decarburized slag generated in the same refining equipment on the same day, and a part of the steelmaking slag (a) is classified with a sieve (x) having a sieve mesh of 10 mm or less, so that fine particles and fine powder content Steelmaking slag according to claim 1, wherein the particle size distribution is adjusted by reducing the fine and fine content of steelmaking slag (a) by mixing with the remainder of steelmaking slag (a) after reducing Manufacturing method of slag roadbed material.   Steelmaking slag (a) is composed of two or more types of steelmaking slag, and all or part of one type of steelmaking slag (a1) is classified with a sieve (x) having a mesh size of 10 mm or less. After reducing the fine powder content, it is mixed with the remaining one or more types of steelmaking slag (a2) and the remainder of the steelmaking slag (a1) (except when all of the steelmaking slag (a1) is classified above). The method for producing a steelmaking slag roadbed material according to claim 1, wherein the particle size distribution is adjusted by reducing the fine particles and fines of the steelmaking slag (a).   The steelmaking slag roadbed material according to claim 3, wherein the steelmaking slag (a1) is decarburized slag generated in the same refining equipment on the same day, and the steelmaking slag (a2) is steelmaking slag other than decarburized slag. Manufacturing method.   The method for producing a steelmaking slag roadbed material according to any one of claims 1 to 4, wherein the sieve (x) has a mesh size of 5 mm (however, nominal diameter).   The method for producing a steelmaking slag roadbed material according to any one of claims 1 to 5, wherein the pressurized steam aging is performed at a steam pressure of 0.20 to 1.96 MPa for 1 to 5 hours.   The particle size of steelmaking slag after pressurized steam aging is any particle size of CS-40, CS-30, CS-20, MS-25, and HMS-25 whose particle size range is defined in JIS A5015 (2013). The method for producing a steelmaking slag roadbed material according to any one of claims 1 to 6, wherein the range is satisfied.

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