JP2009270132A - Method for producing steelmaking slag with high swelling stability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the refining temperature of steel in an electric furnace or ladle refining furnace, promote f-CaO hatching in slag, suppress crystallization of f-CaO, and perform aging treatment The present invention also provides a method for producing a slag having sufficiently low expansion characteristics.
In a steel refining method, a steelmaking material containing CaO is finally put into slag during reduction refining such as ladle refining, and then the refining temperature is raised to 1600 ° C. or higher, and the slag is reduced to 1600 By maintaining the steelmaking slag composition within a specific range by holding it for a certain time or more in a temperature range of ℃ or higher, that is, approximately 15 minutes or more, the composition of the slag is limited to a composition in which CaO does not crystallize. A steelmaking slag having a high expansion stability is produced without performing an aging treatment by a method for producing a low expansion steelmaking slag having a high expansion stability.
[Selection] Figure 1

Description

  The present invention relates to a method for producing slag during reductive refining in order to eliminate the expansion characteristics caused by unmelted CaO-based slag in steelmaking slag and to make the slag effective as a recycled material such as a road material and a civil engineering material. About.

  Non-metallic soot that is produced at the same time during steel production is generally called “steel slag”. Steel slag is classified into `` blast furnace slag '' that is by-produced when producing pig iron in the blast furnace and `` steel slag '' that is produced at the same time when steel is manufactured by refining molten metal, scrap, etc. Depending on the type of refining furnace, it is classified into converter slag and electric furnace slag.

  Steelmaking slag contains metal oxides, so it has high specific gravity and high strength, so it is solidified into a mineral state by slow solidification, then crushed and adjusted in particle size, road materials such as roadbed materials and asphalt aggregates, It is effectively used as a recycling material for civil engineering materials such as backfill materials and foundation works.

Steelmaking slag is made of CaO, SiO ₂ , Al ₂ O _3, and metal oxides such as iron and manganese incorporated as oxides from molten steel into the slag. By these are slow cooling and solidifying at slag processing yard, 2CaO · SiO ₂ (Dicalcium silicate) and, 3CaO · SiO ₂ (tricalcium silicate) _{and, 2CaO · Al 2 O 3 ·} SiO 2 ( gehlenite) etc. It is known that some of the CaO and MgO remain in an unmelted state due to lack of the refining temperature and refining time, which causes expansion of the steelmaking slag.

Unmelted CaO remaining in the steelmaking slag (hereinafter referred to as “f-CaO”) is in contact with water, so that CaO + H ₂ O → Ca (OH) ₂ (volume change rate: 1.95 times). A hydration reaction accompanied by volume change occurs (for example, see Non-Patent Document 1).

Further, even if f-CaO is not sufficiently melted, the composition of the slag, if they contain 3CaO · SiO _2, the decomposition reaction of _{3CaO · SiO 2 → 2CaO · SiO} 2 + CaO, crystallized during 2CaO · SiO ₂ phases It is known that the released CaO phase becomes a cause of expansion (for example, see Non-Patent Document 2).

  When steelmaking slag containing f-CaO is used for road materials such as roadbed materials, it reacts with rainwater and the like to cause an expansion reaction after paving, leading to deterioration of road surface properties called flowering phenomenon. For this reason, when manufacturing a steelmaking slag product, the volume stabilization process called aging is normally performed.

  As means for ensuring the expansion stability of the above-mentioned slag in the prior art, an aging treatment for terminating the hydration reaction of f-CaO and a method for modifying the f-CaO phase into a composition that hardly causes a hydration reaction, or Examples thereof include a method for producing slag in which the f-CaO phase does not crystallize.

  Here, the process of terminating the hydration reaction of f-CaO in steelmaking slag and ensuring the expansion stability of the slag product is referred to as aging as described above, and is the most widely used technology at present. Aging promotes shortening of the aging period by stacking under an open air for about 3 to 6 months and reacting with rain water, etc., and reacting with steam, pressurized steam, or hot water Broadly divided into aging. Among these, atmospheric aging has a long treatment period and requires a vast aging yard, and therefore accelerated aging is widely used in the production of slag products. Regarding the aging technique, many patented techniques have been established for various processing methods and their applications.

  Patents related to hot water aging include slag crushing and aging treatment methods (for example, see Patent Document 1) and steelmaking slag treatment methods (for example, see Patent Document 2).

  In steam aging-related patents, aging pits of steam aging equipment (for example, see Patent Document 3), slag steam aging devices (for example, see Patent Document 4), steelmaking slag aging treatment devices and methods (for example, patents) There are aging methods for steelmaking slag (for example, see Patent Document 6) and slag roadbed material manufacturing methods (for example, see Patent Document 7).

  Patents related to pressurized steam aging include a steelmaking slag aging method and apparatus (for example, see Patent Document 8) and a steelmaking slag aging method (for example, see Patent Document 9).

  As a method for suppressing expansion of slag other than aging, a method for suppressing the hydration reaction of CaO by adding a metal oxide to the CaO phase, which is an expansion factor, has been proposed. These include converter slag reforming (see, for example, Patent Document 10), converter slag excellent in expansion resistance and collapse resistance, and a method for manufacturing the same (for example, see Patent Document 11). In addition, there are a method of hydrating a CaO phase with a silica-containing substance that is latent hydraulic or pozzolanic, a method of suppressing expansion of steelmaking slag, and a method of manufacturing recycled resources (for example, see Patent Document 12). Furthermore, various methods such as a method of obtaining a slag having low expansion characteristics by controlling the slag composition have been studied, and a steelmaking slag reforming method (for example, see Patent Document 13) or (for example, Patent Document). 14), a method for producing low-expansion steelmaking slag (for example, see Patent Document 15), a method for producing a steelmaking slag product, a steelmaking slag product (for example, see Patent Document 16), and a method for melt reforming steelmaking slag. (For example, refer to Patent Document 1).

Tomibo, Matsunaga, Kumagaya, Taguchi, “Reduction and generation of steelmaking slag,” Final report on basic and applied research on steelmaking slag, 1997, p157. Hideaki Mizuwata, Yuichi Yokomaku, Yumiko Hayashida, Aichi Takahashi, Steel Association “Iron and Steel” Vol. 63, 1977, p. 2316. Japanese Patent No. 3241161 Japanese Patent No. 3267737 Japanese Patent No. 3222698 Japanese Patent No. 2871517 Japanese Patent No. 3230412 Japanese Patent No. 3320540 Japanese Patent No. 2927150 Japanese Patent No. 2173178 Japanese Patent No. 2667799 Japanese Patent No. 2636641 Japanese Patent No. 3575160 Japanese Patent No. 3541667 Japanese Patent No. 4000724 JP 2007-254899 A JP 2002-212621 A JP 2003-183717 A JP 2004-331449 A

  The problem to be solved by the present invention is to promote the hatching of f-CaO in slag and to limit the composition of slag by controlling the refining temperature of steel in an electric furnace or ladle refining furnace. Is to suppress the crystallization of f-CaO and to provide a method for producing a slag having sufficiently low expansion characteristics without performing an aging treatment.

  The means of the present invention for solving the above-mentioned problems is that, in the invention of claim 1, in the steel refining method in the refining furnace, the slag material containing CaO is finally contained in the slag during reduction refining such as ladle refining. After the charging, the refining temperature is raised to 1600 ° C. or higher, and the slag is maintained in a temperature range of 1600 ° C. or higher for a certain period of time, that is, 15 minutes or longer, thereby promoting the hatching of CaO. It is a manufacturing method of the low expansion steelmaking slag with high expansion stability. That is, the means of claim 1 is a method for producing a slag having high expansion stability without performing an aging treatment.

The invention according to claim 2 is characterized in that the main mineral layer of the steelmaking slag is held in 2CaO · SiO ₂ or 2CaO · Al ₂ O ₃ · SiO ₂ so that the composition of the slag is limited to a composition in which CaO does not crystallize. It is a manufacturing method of the low expansion steelmaking slag with high expansion stability of Claim 1 to do.

  Since the present invention can be implemented by adding energy necessary for f-CaO hatching to the energy related to refining by using the above-mentioned means, the temperature of the slag whose temperature has been lowered after refining is increased. Therefore, it is not necessary to install a new process because it is energy efficient and can be performed simultaneously with refining. In addition, slag that pulverizes immediately after solidification or slag that pulverizes during the aging process is clogged between slag grains in the aging process, and uneven penetration of steam or rainwater can occur. It is difficult to ensure the reliability of expansion characteristics such as non-uniformity. However, in the present invention, slag having low expansibility can be obtained without aging treatment, and therefore, it is possible to secure the expansion stability of the slag to be pulverized, and there are excellent effects as compared with the conventional method.

The best mode for carrying out the present invention will be described below with reference to the tables and drawings. In the refining process after reductive refining using a large amount of the CaO-based slagging material, the components were adjusted so that the main mineral layer of slag became 2CaO · SiO ₂ or 2CaO · Al ₂ O ₃ · SiO ₂ . Specifically, the slag composition is a value obtained by converting the sum of the contents of CaO, MgO, SiO ₂ , and Al ₂ O ₃ to 100% by mass, and 45.0% ≦ CaO + MgO ≦ 76. MgO content when 0%, 4.0% ≦ SiO ₂ ≦ 35.0%, 5.0% ≦ Al ₂ O ₃ ≦ 35.0%, and the entire steelmaking slag is 100% by mass It has been confirmed that the main mineral layer of slag is 2CaO · SiO ₂ or 2CaO · Al ₂ O ₃ · SiO _{2 in the} component range where the rate is less than 12% by mass, and this component range is satisfied. It is desirable to adjust the components so as to. Here, when the CaO content rate is high beyond the vapor component range, the slag mineral layer becomes a CaO layer or 3CaO · SiO ₂ , and f-CaO crystallizes even when hatching is promoted by the method of the present invention. The expansion suppressing effect cannot be obtained.

  As shown in Table 1, the refining conditions were a refining temperature of 1511 ° C. to 1635 ° C., and after reaching each refining temperature, the temperature was held in the range of ± 5 ° C. for 6 minutes to 37 minutes. Subsequently, after completion of the refining, the slag cooled and solidified in the slow cooling yard was sampled, and the expansion characteristics were measured by the water immersion expansion test method for steel slag as defined in Annex 2 of “Steel Slag for Roads” of JIS A5015. Table 1 shows the refining temperature and holding time in the refining and the water immersion expansion rate of the obtained slag. Furthermore, the graph of FIG. 1 shows the relationship between the water immersion expansion rate of the obtained slag and the treatment temperature.

  From the graph of FIG. 1, it can be seen that the expansion characteristic of slag has a high correlation with the refining temperature. In the case of slag processed in a temperature range exceeding 1600 ° C., that is, four samples of sample names: slag-14, slag-15, slag-16, slag-17, and slag-18, the water expansion coefficient is 0. It was an extremely low value of 05% or less. From this result, it is suggested by the present invention that unmelted CaO (f-CaO) in the slag sufficiently hatches and there is no recrystallization. Therefore, the steelmaking slag by the method of the present invention has high reliability as road materials such as roadbed materials and asphalt aggregates, backfill materials, and civil engineering materials for foundation work during recycling.

It is a graph which shows the relationship between the processing temperature of steelmaking slag, and a water immersion expansion coefficient.

Claims (2)

  In a steel refining method in a refining furnace, after the final addition of a slagging material containing CaO into a slag being refined, the refining temperature is raised to 1600 ° C or higher and the slag is heated in a temperature range of 1600 ° C or higher for a certain time. The manufacturing method of the low expansion steelmaking slag with high expansion stability characterized by promoting the hatching of CaO by hold | maintaining above. The method for producing a low-expansion steelmaking slag having high expansion stability according to claim 1, wherein the main mineral layer of the steelmaking slag is 2CaO · SiO ₂ or 2CaO · Al ₂ O ₃ · SiO ₂ .

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