JP2005272859A - Method for operating electric furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for blending materials by which as steelmaking raw material for electric furnace, Cu content as harmful element to the steel is guaranteed to <0.20% and cheap waste car pressed scraps are used as much as possible. <P>SOLUTION: In the method for realizing the cheap scrap blending, the waste car-pressed scrap is used as much as possible in the scrap-blending combined based on the influence on the Cu value when the blended scrap in one heat melted with the electric furnace is tapped off from the electric furnace, in the range satisfying formula (1); 0.20>0.000A+0.083B-0.066C+1.469D-0.066E+0.083F+0.017G+0.12. In formula (1), respective weights of A to F are expressed by ton unit. wherein A: returned scrap in the work, B: purchased scrap, C: new shearing scrap, D: waste car pressed scrap, E: waste pig iron, F: machining chip and G: pressed can scrap. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for blending scraps of steelmaking raw materials in electric furnace operation.

  In electric furnace operation in steelmaking, waste car press products that press scrap cars as scrap for steelmaking raw materials are inexpensive scraps, so we want to use them as much as possible. However, in order to press without removing many of the copper plates and copper wires used in automobiles, waste car press products contain a large amount of Cu. In addition, there is variation in the amount of Cu contained.

  By the way, as for steel for machine structure, as the Cu content in the steel increases, the rate of occurrence of defects during hot rolling or forging increases, and in particular, as shown in FIG. When the content is 0.20% or more, wrinkling during rolling becomes significant. Therefore, in blending steelmaking raw materials for electric furnaces, it is necessary to ensure that the Cu content is stable to less than 0.20%. However, as described above, waste car press products contain a large amount of Cu, and the amount of variation is large. For this reason, it was not possible to use a large amount of waste automobile press products as materials for electric furnaces.

  On the other hand, there is known a method of charging a collected product of a vending machine as scrap and charging it as a steelmaking raw material for an electric furnace or a converter (see, for example, Patent Document 1 or Patent Document 2). However, this method pays attention to the scraps of the collected goods of the vending machine. However, in the electric furnace operation in steelmaking, various scraps are charged at the most suitable blending ratio as a steelmaking raw material. Therefore, there is a demand for blend ratios of various scraps suitable for such actual operation.

  In general operation of such materials as steelmaking raw materials for electric furnaces, in actual operation, materials are mixed according to the stock of scrap, the target chemical composition of the steel type to be melted, and the operation method. In general, the amount of each of A's in-house reduced waste, C's new rose, E's source, and F's dariko is first determined for this material formulation. Next, in consideration of Cu and Sn components, the usage amounts of the waste car press product of D and the cam press product of G are determined, and finally the purchased scraps of B are used until the specified total scrap amount is reached.

  Here, the characteristics of each scrap will be described. The in-house reduced waste A is generated by scrapping or the like in the in-house manufacturing process. Since it is not a purchased item, the amount of generation is limited. On the other hand, depending on the steel type, there may be a large amount of in-house reducing waste such as SNCM steel. We want to use as much as possible in terms of material composition, but the amount used is limited because the amount generated is limited and the solubility is worse than purchased waste. However, since it is in-house reduced scrap, the effect on the value of Cu in the steel output component is small. When this in-house reducing waste is used, generally in an electric furnace having a furnace capacity of about 60 t or more, it is often used as 10 to 50 t per melting (hereinafter referred to as “/ ch”).

  Purchase waste of B is scrap purchased from outside the company, and is one of the most expensive iron sources that can be used. Therefore, after determining the amount of other types of scrap as described above, it is often used up to a specified total amount. When using this purchase waste, generally it is often used 50t / ch or more.

  C new roses are scraps purchased from outside as well, and are one of the most expensive iron sources that can be used, and the bulk of the material is relatively large. . By the way, this new rose is originally a high-quality iron source with little Cu. Therefore, it is usually used as 20 to 40 t / ch because it is used for the bottom of a scrap charging bucket.

  The waste car press product of D is a product that has been pressed after removing valuable metals from the waste car. Therefore, since many copper plates and copper wires remain without being removed, when used in large quantities, the Cu value of the steel output component becomes high, so the amount of use is limited. Furthermore, since the tin plate is used in scrap cars, the Sn value when steel is extracted from the electric furnace may increase. In consideration of these, generally, when melting steel for machine structure, it is usually used as 2 to 4 t / ch. Here, regarding the Sn value when steel is discharged from the electric furnace, the rate of occurrence of defects during hot rolling or forging increases as the content in the steel increases, as does the Cu value.

  The iron source of E is pig iron scrap generated during handling of hot metal in an iron mill made of iron ore. Since this uses iron ore as a raw material, there are few impurities, such as Cu and Sn, but since slag adheres, there exists a possibility that the P and S of the molten steel which came out may become high. Moreover, since slag adheres, solubility is also bad. Since it is slightly cheaper than the above-mentioned purchased waste, it is desired to use more if there is no problem in operation. However, because of the above-mentioned problem, the amount of use is limited, and it is generally used as less than 10 t / ch.

  F Daraiko is a general term for chips generated when machining a lathe or the like. This is bulky and contains a lot of impurities, but it is a little cheaper than the purchased waste. Therefore, although it is desired to use a large amount, there is a problem that a chemical component such as Cr is contained or there is a problem in material charging due to its high bulk, and the amount of use is limited. Therefore, it is generally used as 10 to 30 t / ch.

  The G stamped product is a scrap product obtained by press-molding a collected empty can. This is a relatively inexpensive iron source, but since tin cans are included, there is a risk that the Sn value at the time of steel removal from an electric furnace may be high, so the amount of use is limited. Therefore, generally, the amount used is about 0 to 4 t / ch.

JP 2002-241827 A JP 2002-241828 A

  The problem to be solved by the present invention is as a steelmaking raw material for an electric furnace, a content of Cu that is harmful to steel is guaranteed to be less than 0.20%, and an inexpensive waste car press product is used as much as possible. Is to provide a method.

  The means of the present invention for solving the above-mentioned problem is a combination of scraps having a combination of effects on the Cu value when steel is produced from each electric furnace of each charge of one charge melted in an electric furnace according to the following formula ( This is a method that is implemented based on 1) and realizes inexpensive material blending by incorporating materials using the waste automobile press products to the maximum extent within the range satisfying the formula (1).

  0.20> 0.000A + 0.083B-0.066C + 1.469D-0.066E + 0.083F + 0.017G + 0.12 (1)

  In formula (1), A is in-house reduced waste, B is purchased waste, C is a new rose, D is a scrap car press product, E is a source of waste, F is a dariko, and G is a press product. Indicates.

  As described in the above-mentioned prior art, the conventional material composition determines the amount of A internal reduction waste, C new rose, E source, F Daraico, and then D waste car press The amount of use of the product and the G-compressed product was determined, and the materials were blended in the order of using the purchased waste of B until the final scrap total amount was reached. However, since the Cu content varies from material to material, the amount of waste automobile press products used must be fairly conservative in view of the Cu value when steel is produced from an electric furnace. It was.

  In the present invention, first, as in the conventional case, the usage amounts of A internal reduction waste, C new rose, E source, and F Daraico are determined. The amount of in-house reduced waste A is determined in consideration of the amount of its stock and the degree of deterioration in solubility of the electric furnace when a large amount of in-house reduced waste is used. In many cases, a new cut rose of C is used in an appropriate amount (about 5 to 20 tons per scrap charging) as the bottom cover of the scrap-incorporating bucket at the time of scrap charging. The amount of E source used is often determined mainly by the value of the P standard of the steel type to be melted. The amount of F Dalaico used is as much as possible within the range where the bulk of the scrap is allowed, and is often determined based on the value of the Cr standard when melting the carbon steel for machine structure. Subsequently, the usage amount of the G pressed product is determined based on the Sn standard and application of the steel type to be melted. Subsequently, based on the formula (1), the Cu value when steeling out from the electric furnace is predicted, and the usage amount of the purchased waste of B and the waste automobile press product of D is determined. Thus, by using the formula (1), it was decided that a large number of waste automobile press products could be used without fear of undesired steel component Cu more than necessary.

The above formula (1) is based on in-house operation data, calculated the effect of each material composition on the Cu value in the steel output components, and calculated the coefficient considering the variation with a standard deviation of 1 sigma. It is. The value calculated by this equation (1) is almost always higher than the value obtained by actual operation, as seen in the following examples, but this is due to the variation of Cu in the material as described above. This is because of consideration. Conversely, if the material composition satisfies the formula (1), a molten steel having a Cu component value of less than 0.20% can be obtained stably.
In order to make maximum use of the waste automobile press product of D, the amount of D is large so that the value of formula (1) is 0.16 or more, preferably 0.18 or more and less than 0.20. Just do it.

  The present invention is made of a material composition consisting of scrap that does not cause the Cu content in the steel component to be 0.20% or more, which is a factor that causes a rapid increase in rolling defects when machine structural steel is hot-rolled. Thus, there is an excellent effect that the cost reduction of the melting of the steel by the electric furnace can be realized.

The best mode for carrying out the present invention will be described through examples. In the material blends of Examples 1 to 3 and Comparative Examples 1 and 2 shown in Table 1 below, 165 t of the total amount of each of A to G scraps was charged into a 150 t electric furnace and melted, and steel for machine structure Was melted.
In addition, the steel for machine structure referred to in the present invention includes various carbon steels for machine structure (SC) and alloy steels for machine structure (SMn, SCr, SCM, SNC, SNCM) and various steels based on these JIS standard steels. This is steel that has been improved by adding elements.

  In Table 1, the calculated value is a calculated value based on the formula (1), and the actually measured value indicates the actually measured content of the Cu value when steel is extracted from the electric furnace. In addition, the pan lower value is an analysis value of a sample collected when casting molten steel, and is a representative component value of the heat.

  The steel for machine structural use obtained by each of these Examples and Comparative Examples was hot and rolled, and the number of surface defects generated on the obtained billet surface was investigated, and the Cu content in the steel The ratio of the occurrence of wrinkles is indicated by an index, which is shown in the graph of FIG. From the graph of FIG. 1, when the Cu content in the steel exceeds 0.20%, the rate of occurrence of soot exponentially increases. However, in the examples of the present invention, since the formula (1) is satisfied, The index is 1 or less.

It is a graph which shows the Cu content rate in steel, and the ratio of flaw generation | occurrence | production with an index | exponent.

Claims (3)

In the steel melting method using an electric furnace using scrap as a steelmaking raw material, the following scrap composition is combined with the effect on the Cu value when steel is produced from each electric furnace of each charge that is melted in the electric furnace. A method for operating an electric furnace, which is carried out based on the formula (1) and blends materials by using a waste automobile press product to the maximum extent within a range satisfying the formula (1).
0.20> 0.000A + 0.083B-0.066C + 1.469D-0.066E + 0.083F + 0.017G + 0.12 (1)
In the formula (1), A is in-house reduced waste, B is purchased waste, C is a new rose, D is a scrap car press, E is a source, F is a dariko, and G is a tonnage of a press. Is a value obtained by dividing by the total amount of scrap (ratio of each scrap in the total scrap).   After determining the usage amount of the internal reduction scrap of A, the new rose of C, the source of E source, and the Dalico of F, the usage amount of the Campless product of G is determined, and then the formula (1) The electric power according to claim 1, comprising predicting the value of the amount of Cu when the steel is discharged from the electric furnace based on the determination of the used amount of the waste car press product of D and the purchased waste of B. How to operate the furnace.   The maximum use of the scrap car press product is to use the scrap car press product by determining the weight of D such that the right side of the formula (1) is 0.16 or more and less than 0.20. Item 3. An electric furnace operating method according to Item 1 or 2.

Images