JP4793054B2 - Method for producing converter slag component adjustment material - Google Patents

Description

  The present invention relates to a method for producing a converter slag component adjusting material, and in particular, increases the MgO content of slag used for slag coating of converter lining refractories, and makes the liquid phase ratio of the slag 40% or less. It is related to effective technology.

  Furnace used in steel refining, such as converters, protects the inside of the iron shell with a refractory, but it reacts with slag at high temperatures during refining, wear due to hot metal flow or molten steel flow, or thermal shock Due to spalling, the lining refractory wears out. Therefore, so-called “slag coating” has been performed as one of the techniques for extending the life of the lining refractory. It is possible to leave the slag in the furnace after the molten steel that has been refined is finished, tilt the furnace, or blow the slag into a splash with gas, and cover the surface of the lining refractory with the slag, It protects lining refractories.

  In actually carrying out such “slag coating”, it is necessary to adjust the composition of the slag remaining in the furnace in advance. This is because it is desirable that the coated slag is not peeled off as much as possible during the subsequent refining. For example, in order to adjust this slag composition, the technique which adds a slag solidification material in a converter is disclosed so that the liquid phase volume fraction of the coated slag may be 40% or less (refer patent document 1). . There is also a technique for measuring the slag composition at the end of refining, determining the amount of auxiliary material to be added for slag reforming based on the measurement result, and introducing the auxiliary material into the furnace before the end of refining. (See Patent Document 2). In recent converters, MgO-C system is widely used for lining refractories. Therefore, raw dolomite, light-burned dolomite and the like are often used for the solidified material and the secondary material.

  By the way, when the converter is dismantled, a large amount of refractory waste is generated. From the viewpoint of effective use of resources, these refractory wastes are also used for the solidified material and the secondary material. For example, MgO briquette has already been proposed as a slag concentration adjusting material using the refractory waste (see Patent Document 3). It is a used refractory mainly composed of MgO pulverized to 5 mm or less and formed into a briquette by adding and kneading a binder and water. Moreover, in this briquette, the tar pitch is 5-10 mass% in external number, and 5-11 mass% in external number is added as a binder. And by using such briquettes for the composition adjustment of the coating slag, such as poor solubility that occurs when using a material with a large particle size, pulverization by handling before charging the converter, reduction of input yield, etc. Not only was the problem eliminated, but the entire amount of refractory debris could be recycled, greatly contributing to the reduction of steelmaking costs.

However, although the said briquette employ | adopts tar pitch as a binder, this tar pitch generally has much sulfur (symbol: S) content as 6-10 mass%. Further, since the addition amount as a binder is as large as 5 to 10% by mass, when the briquette is added to the slag, the sulfur (symbol: S) content of the slag layer coated with the lining refractory also increases. Therefore, there exists a problem that the molten steel melted | melted by subsequent refining is contaminated with this sulfur, and raises the sulfur concentration of this molten steel. This is inconsistent with the recent circumstances for high-grade steel. Further, tar pitch is a flaky solid, and if the addition amount is large, the amount of briquette production raw material increases, which also contributes to a reduction in productivity. Furthermore, since a relatively large amount of water is also added, there is a problem that the manufactured briquette cannot be used unless it is separately dried.
JP-A-7-258717 Japanese Patent Laid-Open No. 11-229020 Japanese Patent Laid-Open No. 10-317040

  In view of such circumstances, the present invention aims to provide a method for producing a converter slag component adjusting material that not only has a risk of contaminating molten steel with sulfur, but also can reduce the cost of a slag adjusting material as compared with the prior art. Yes.

  In order to achieve the above-mentioned object, the inventor has conducted intensive studies focusing on the binder, and has realized the results in the present invention.

  That is, the present invention provides a component adjustment material for converter slag that is added to the slag previously left in the converter and used to adjust the components when coating the refractory surface of the converter lining. In addition, asphalt as a binder was added to converter-lined refractory scraps crushed to 2 mm or less and kneaded at a temperature of 70 to 90 ° C., and then the kneaded product was engraved with many hole molds on the outer peripheral surface. It is a method for producing a converter slag component adjusting material, which is formed into briquettes with a molding machine equipped with a roll.

  In this case, it is preferable that the amount of the asphalt added is 0.5 to 5.0% by mass of the kneaded product, or the converter lining refractory waste is MgO-C based. The briquette shape may be any of a Macek type, a center concave type, a stamp type, and an egg type.

  According to the present invention, not only there is no fear of contaminating the molten steel with sulfur, but the amount of briquettes made of refractory waste is increased accordingly, so the cost of the slag adjusting material can be reduced. That is, effective use of the entire amount of refractory waste is achieved as a substitute for lightly baked dolomite, fired dolomite, and the like.

  Hereinafter, the best embodiment of the present invention will be described based on the background of the invention.

  First, the inventor examined alternative materials for the binder in order to correct the disadvantage of tar pitch, which is a relatively high sulfur content. As a result, it was found that the sulfur content was as low as 3 to 5% by mass in the case of asphalt made from petroleum. In addition, asphalt liquefies at a low temperature, it was considered that there was no need to add water as in tar pitch, and the present invention was completed.

  That is, the main matter is to use the refractory lining of the converter lining pulverized to 2 mm or less as a main raw material, and add asphalt as a binder instead of tar pitch. And these kneading | mixing was performed at the temperature of 70-90 degreeC. As a result, asphalt was liquefied, and when the kneaded material was briquetted, it showed a crushing strength comparable to that of tar pitch. In other words, it was found that there was no problem of scattering or difficulty in handling when it was put into the converter.

  In the present invention, the heating means during the kneading is not particularly limited. However, in consideration of economy, it is preferable to spray cheap steam generated in the steelworks as an energy saving measure. Further, the heating temperature is set to 70 to 90 ° C., if the temperature is less than 70 ° C., the asphalt is not sufficiently liquefied and the dispersion to the powdered refractory waste is poor, and if it exceeds 90 ° C., the amount of heat is wasted. It is.

  The amount of the asphalt added may be significantly smaller than that of the tar pitch, and it is sufficient if the upper limit is 5.0% by mass of the entire kneaded product. However, when the amount was less than 0.5% by mass, the effect of the binder was not found. Therefore, in the present invention, 0.5 to 5.0% by mass of the kneaded product was determined as a preferable range.

  The particle size of the refractory waste is preferably 2 mm or less. If it is too large, dissolution in the slag will be delayed, and the effect of addition will not be substantially exhibited. If it is 2 mm or less, even if there is no explosion as in the case of tar pitch, it is sufficiently dissolved by addition to slag.

  Next, as shown in FIG. 2, the briquette is manufactured by a molding machine (also known as a briquette machine 4) having a pair of rolls 2 in which a large number of perforations 1 are engraved on the outer peripheral surface and raw material charging means 3. I decided to use it. This is because if such a roll 2 is used, the kneaded material can be compressed simply by adjusting the interval between the rolls 2 and a large number of briquettes can be manufactured quickly without performing special pressurization. Further, the shape of the briquette (converter slag component adjusting material) 5 is a Macek type, a middle concave type, a stamping type and an egg type as shown in FIGS. 3 (a), (b), (c) and (d). Either of these is preferable. This is because it is easy to engrave a hole mold on the roll 2 and it is easy to handle the obtained briquette.

  In addition, the example of a process used for implementation of the manufacturing method of the converter slag component adjustment material which concerns on this invention described above is shown in FIG. In FIG. 1, refractory waste as a main raw material and asphalt as a binder are each pulverized to a predetermined size by a pulverizer 6. The pulverized product is conveyed and charged into a known kneader 8 by a belt conveyor 7. The types of the pulverizer 6 and the kneader 8 are not particularly limited in the present invention. In FIG. 1, two types, a so-called “kneader” method and a method having a stirring blade, are arranged in parallel. Further, as the binder, the binder storage tank 9 is also shown so that liquefied asphalt can be used. The manufactured briquette 5 is simply stored in the product tank 10 without being dried, and then used.

  In the process shown in FIG. 1, the converter slag component adjusting material according to the present invention was manufactured. The main raw material refractory scrap is a dismantled refractory lining of a bottom-blown converter for melting molten steel, and is a MgO-C system. The main raw material and the asphalt of the binder were each pulverized to 2 mm or less by the pulverizer 6 and then sent to the kneader 8. The asphalt is adjusted to 3.5% by mass of the kneading amount. Further, the liquid asphalt shown in FIG. 1 is not used in this example.

  Next, the kneading is performed by maintaining the atmosphere in the kneading machine 8 at 80 ° C. with water vapor, and the kneaded material is continuously continuously supplied to the briquette machine 4 (trade name 35 / H briquette machine manufactured by Keihan Co., Ltd.). Thus, a briquette having a size of 40 m × width 40 mm × height 26 mm was manufactured, and the obtained product was stored in the product tank 10. The product is simply allowed to cool to the atmosphere and is not dried.

  When the crushing strength of the briquette cooled to room temperature was measured by the method specified in JIS M 8713 and the drop strength was defined in JIS M 8711 (according to sintered ore), the crushing strength was 140 to 160 kgf, and the drop strength index was 90-95. These values are comparable to those of conventional briquettes using tar pitch as a binder, and have no inferiority. Moreover, sulfur content was very low compared with 0.11-0.15 mass% and the conventional thing (sulfur content: 0.6-1.0 mass%) which used tar pitch as the binder.

Therefore, I tried to use this briquette for slag coating in a converter in operation. The operation is performed in a 230-ton pure oxygen bottom blow converter, and the steel output temperature is 1580 to 1650 ° C. This briquette was introduced into the converter with the goal of increasing MgO in the slag remaining in the furnace by approximately 2% by mass (approximately 300 kg in terms of briquettes). As a result, the average result of 20 charges was an increase of 1.98% by mass. Further, when the sulfur content of the molten steel produced by this operation was investigated, the average increase was only about 1 ppm or less compared to the case where slag coating was not performed. In other words, it became clear that there was almost no sulfur contamination of molten steel by slag used for slag coating.
In other words, it was confirmed that this briquette can be used in a large amount as a substitute for lightly baked dolomite, baked dolomite, etc., as a slag composition adjusting material during slag coating.

  On the other hand, as a comparative example, a conventional briquette (sulfur content: 0.8% by mass) using tar pitch as a binder was put into the converter so that MgO in the slag increased by about 2% by mass. The input amount was 330 kg in terms of briquettes. With an average of 20 charges, MgO in the slag was 1.97% by mass, which was the same as the example of the present invention, but the increase in the sulfur content of the molten steel was extremely low sulfur steel ( In the case of a sulfur content of 30 ppm or less, serious component defects were caused.

It is a flowchart which shows the process example used for implementation of the manufacturing method of the converter slag component adjustment material which concerns on this invention. It is a cross-sectional view showing an example of a briquette machine provided with a pair of rolls engraved with many hole molds and raw material charging means. It is the figure which showed the shape of the briquette obtained with the manufacturing method of the converter slag component adjustment material which concerns on this invention by the plane and the side, (a) is a Macek type, (b) is a center concave type, (c) is The seal type and (d) are egg type.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hole type 2 Roll 3 Raw material charging means 4 Briquette machine 5 Briquette 6 Crusher 7 Belt conveyor 8 Kneading machine 9 Binder storage tank 10 Product tank

Claims (4)

When slag coating the lining refractory surface of the converter, it is added to the slag previously left in the converter, and in manufacturing the component adjustment material of the converter slag used to adjust the component,
Molding provided with a roll in which asphalt as a binder is added to converter refractory waste crushed to 2 mm or less and kneaded at a temperature of 70 to 90 ° C. A method for producing a converter slag component adjusting material, which is formed into briquettes by a machine.   The method for producing a converter slag component adjusting material according to claim 1, wherein an amount of the asphalt added is 0.5 to 5.0 mass% of the kneaded product. The method for producing a converter slag component adjusting material according to claim 1 or 2, wherein the converter lining refractory waste is MgO-C.   The method for producing a converter slag component adjusting material according to any one of claims 1 to 3, wherein the briquette has any one of a Macek type, a center concave type, a stamping type, and an egg type.

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