JP3939307B2 - Graphite spheroidizing method - Google Patents

Description

  The present invention relates to a graphite spheroidizing method in which iron-coated Mg wire in which metal Mg or Mg alloy is coated with a steel plate or steel pipe is added to molten cast iron melted in a melting furnace or the like to spheroidize graphite. .

  Ductile casts such as ductile cast iron pipes have the same tensile strength as steel materials, their mechanical test values such as elongation and toughness are more than ten times that of regular cast iron, and have excellent corrosion resistance equivalent to regular cast iron. Therefore, it is widely used in various piping materials under more severe environments such as underground pipes that require these characteristics.

  This ductile casting is obtained by adding an Mg alloy such as metal Mg or Fe—Si—Mg alloy as a graphite spheronizing agent to molten cast iron melted by cupola or an electric furnace using iron scrap as a main iron source material, and C: 3 Molten cast iron for ductile castings containing -4 mass% (hereinafter referred to as "%"), Si: 2-3%, Mn: 0.2-0.5%, Mg: 0.01-0.06% It is manufactured by melting and casting it with a casting facility such as a centrifugal casting machine (see, for example, Patent Document 1).

  Since Mg has a low boiling point (1110 ° C.) and a high vapor pressure in the temperature range of molten cast iron, it is difficult to dissolve in molten cast iron. Various additions such as the pouring method, the ladle addition method with a lid, the plunger method, the pressure addition method, the wire feeder method, etc. as a method for adding metal Mg or Mg alloy having such properties to molten cast iron with a high addition yield The method is implemented (for example, refer nonpatent literature 1). All of these are addition methods that increase the pressure of the atmosphere in which the metal Mg or Mg alloy dissolves and reduce the loss of Mg gas.

  Among these, in the wire feeder method of supplying iron-coated Mg wire coated with metal Mg or Mg alloy with steel plate or steel pipe at high speed into molten cast iron, the length of the supplied iron-coated Mg wire must be managed. It is possible to control the amount of metal Mg or Mg alloy added, and the length of the supplied iron-coated Mg wire is automatically measured by a pinch roll or a measure roll that supplies the iron-coated Mg wire. There is an advantage that the workload is greatly reduced as compared with the other addition methods described above. In other words, by applying the wire feeder method, it becomes possible to unmanned the graphite spheroidization process very easily.

  However, conventionally, when melting molten iron for ductile castings, there is an example using the wire feeder method (see, for example, Patent Document 2), but there is no example of suggesting a specific method for adding iron-coated Mg wire. . Moreover, the mass of Mg contained per unit length of the iron-coated Mg wire is small, and there is an optimum range for the wire feeding speed of the iron-coated Mg wire, and the wire feeding speed cannot be increased excessively. In the graphite spheroidizing process that requires the addition of a large amount of Mg, it is necessary to simultaneously feed two or more iron-coated Mg wires in order to shorten the processing time.

  Usually, since the wire feeder device has a function of feeding only one iron-coated Mg wire, in order to feed two or more iron-coated Mg wires at the same time, It is necessary to install the same number of wire feeder devices. When using two or more wire feeder devices to simultaneously feed iron-coated Mg wires from each wire feeder device, due to wire breakage of the iron-coated Mg wire or troubles in the motor for driving the pinch roll, etc. In some cases, however, there have been no reports of proposals of an optimal charging method for simultaneously charging two or more iron-coated Mg wires.

Japanese Unexamined Patent Publication No. 6-24415 Japan Foundry Association, "Revised 4th Edition Casting Handbook" January 20, 1986, p.560-565 JP-A-56-150111

  The present invention has been made in view of the above circumstances, and its object is to use two or more wire feeder devices to add iron-coated Mg wire from each wire feeder device to molten cast iron for ductile castings. In the method of spheroidizing graphite for melting molten cast iron, even if iron-coated Mg wire cannot be supplied from one or more wire feeder devices, iron-coated Mg wire from at least one wire feeder device Provided is a graphite spheroidizing treatment method capable of automatically feeding a predetermined amount of iron-coated Mg wire, including the amount to be thrown into the wire feeder device that can no longer be fed. That is.

  The graphite spheroidizing treatment method according to the first invention for solving the above-mentioned problems uses two or more wire feeder devices, and iron-coated Mg wires are introduced from each wire feeder device into the molten cast iron in the processing vessel. This is a graphite spheroidizing method that melts molten cast iron for ductile castings, calculates the required input amount of iron-coated Mg wire based on the operating conditions, divides the required input amount and inputs each wire feeder device After dispensing as an amount, start feeding iron-coated Mg wire by each wire feeder device, while feeding iron-coated Mg wire, continuously measure the integrated amount of iron-coated Mg wire in each wire feeder device, If each wire feeder device is operating normally, each wire feeder device will dispense If the wire feeder device that can not be put in the iron-coated Mg wire is generated until the iron-coated Mg wire is completely charged, the amount of input in the wire feeder device that cannot be put in. The shortage is distributed to other wire feeder devices, and the required amount of iron-coated Mg wire is completely charged.

  In the graphite spheroidizing treatment method according to the second invention, in the first invention, the required input amount of the iron-coated Mg wire is set such that the mass of the molten cast iron, the S concentration in the molten cast iron before the treatment, and in the molten cast iron after the treatment. It is obtained based on the target value of Mg concentration and the yield of Mg addition.

  According to the present invention, since the integrated amount of iron-coated Mg wire is fed back in real time, for example, even if a wire feeder device in which iron-coated Mg wire cannot be input due to a failure of an electric motor or the like occurs, at least 1 If the base wire feeder device is operating normally, a predetermined amount of iron-coated Mg wire, including the amount to be inserted by the wire feeder device that has become impossible to input, is operating normally. It becomes possible to perform the graphite spheroidizing treatment by automatically feeding in. As a result, it is possible to unmanned the graphite spheroidizing process in the melting process of the molten cast iron for ductile castings, and it is possible to achieve industrially advantageous effects such as achieving a significant reduction in manufacturing costs.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a process chart in the method of spheroidizing graphite according to the present invention. FIG. 1 shows an example in which two wire feeder devices are arranged.

  Molten cast iron (hereinafter referred to as “hot metal”) that is melted in a melting furnace such as a cupola or electric furnace, and then desulfurized as necessary, using iron sources such as iron scrap and carbon materials such as coke as raw materials. ) Pour hot water into a processing container such as a ladle. During or after the pouring, as shown in FIG. 1, the mass of the hot metal poured into the processing container is weighed by the weighing device 4. The measured value is transmitted to the control device 6 and stored in the control device 6. Further, the S concentration of the molten iron poured into the processing container is input to the operation panel 5 (the operation panel 5 also serves as a display panel). The input S concentration is transmitted to the control device 6 and stored. The S concentration of the hot metal may be analyzed for each hot metal poured into the processing vessel. When the hot metal is once held in a holding furnace, the S concentration of the hot metal in the holding furnace is analyzed. You may represent by an analytical value. The reason for grasping the S concentration in the hot metal during the spheroidizing process of hot metal is that S in the hot metal reacts with Mg added in the graphite spheroidizing process, and the amount of Mg added to dissolve in the hot metal decreases. Therefore, it is for grasping | ascertaining the Mg content lost by this desulfurization reaction. As is well known, Mg functions as an extremely excellent desulfurizing agent for hot metal.

  Next, the processing container containing the hot metal is transported to a graphite spheroidizing treatment facility by appropriate transporting means such as a crane and a transport cart, and the graphite spheroidizing process is performed. FIG. 2 shows a schematic diagram of a graphite spheroidizing treatment facility used in carrying out the graphite spheroidizing method according to the present invention. This graphite spheroidizing treatment facility 1 is a treatment facility provided with wire feeder devices 3 and 3A for putting the iron-coated Mg wire 15 into the hot metal 16. That is, as shown in FIG. 2, two wire feeder devices 3 and 3 </ b> A for supplying the iron-coated Mg wire 15 to the hot metal 16 are installed above the ladle type processing container 2 containing the hot metal 16. ing.

  The wire feeder device 3 is bent in a substantially vertical direction at the center thereof, one tip is directed vertically with respect to the bath surface of the hot metal 16 accommodated in the processing vessel 2, and the other tip is directed horizontally. A pair of pinch rolls 11 that sandwich the iron-coated Mg wire 15 between the guide pipe 10 and the opposite roll and rotate to supply the iron-coated Mg wire 15 toward the guide pipe 10, and the iron coating that has passed It is composed of a measure roll 12 that continuously measures the length of the Mg wire 15, a plurality of guide rolls 13 that guide the iron-coated Mg wire 15, and a drum 14 on which the iron-coated Mg wire 15 is wound in a coil shape. ing. The drum 14 is rotatable about its axis.

  That is, the iron-coated Mg wire 15 wound on the drum 14 is unwound between the pinch rolls 11 opposed to each other, and the input amount is continuously measured by the measure roll 12 while passing through the guide pipe 10. Thus, the hot metal 16 accommodated in the processing container 2 is supplied. The wire feeder device 3 </ b> A has the same configuration as the wire feeder device 3. In FIG. 2, 10A is a guide pipe of the wire feeder apparatus 3A, and the drum of the wire feeder apparatus 3A is omitted. The iron-coated Mg wire 15 is a clad wire in which an Mg alloy such as metal Mg or Fe—Si—Mg alloy is used as a core, and the core is covered with a thin steel plate or a thin steel pipe.

  Before starting the spheroidizing process of the hot metal 16, the target value of Mg concentration in the hot metal after the process and the yield setting value of the iron-coated Mg wire 15 are input to the operation panel 5, and these data are transmitted to the control device 6. And memorize it. When changing the specifications of the iron-coated Mg wire 15 and the wire transmission speed of the iron-coated Mg wire 15, these data are also input to the operation panel 5 and transmitted to the control device 6 for storage. Here, the specification of the iron-coated Mg wire 15 is, for example, the mass of Mg contained per 1 m of the iron-coated Mg wire 15.

  The calculation unit 7 of the control device 6 to which these data are input is based on the iron mass, the S concentration in the hot metal before the treatment, the target value of the Mg concentration in the hot metal after the treatment, and the Mg addition yield setting value. The required input amount of the coated Mg wire 15 is calculated as the length of the iron-coated Mg wire 15. The calculated required input amount is input to the input instruction unit 8 of the control device 6. Here, if the specification of the iron-coated Mg wire 15 changes, the required length of the iron-coated Mg wire 15 changes even if the required input amount is the same.

  The input instruction unit 8 to which the required input amount has been input divides the required input amount into two and distributes it to the two wire feeder devices 3 and 3A. Usually, since the wire feeding capabilities of the two wire feeder apparatuses 3 and 3A are equal, the required input amount is equally divided into two and equally distributed to the respective wire feeder apparatuses 3 and 3A. When there is a difference in the line transmission capability between the two wire feeder devices 3 and 3A, the input amount is distributed according to the line transmission capability so that the respective input times are equal. Then, when the input instruction unit 8 distributes the input amount to each of the wire feeder devices 3 and 3A, the input instruction unit 8 outputs an instruction signal for starting to input the iron-coated Mg wire 15 to the wire feeder devices 3 and 3A. By this instruction signal, the pinch rolls 11 of the two wire feeder devices 3 and 3A are driven, and the iron-coated Mg wire 15 is supplied to the hot metal 16.

  While the iron-coated Mg wire 15 is being charged, the charging length continuously measured by the measure roll 12 is input to the charging amount monitoring unit 9 of the control device 6, and the charging totals charged by the respective wire feeder devices 3 and 3A. Converted as a quantity. Then, the insertion integrated amount in each of the wire feeder devices 3 and 3A is continuously fed back to the input instruction unit 8 described above. That is, when the insertion of the iron-coated Mg wire 15 is stopped and the rotation of the major roll 12 is stopped, the input amount monitoring unit 9 immediately outputs the integrated input amount up to that point to the input instruction unit 8. It has become.

  The input instruction unit 8 to which the input integrated amount is input from the input amount monitoring unit 9 compares the input amount distributed to the respective wire feeder devices 3 and 3A with the input integrated amount, and each wire feeder device 3 and 3A is normal. In the case where the wire feeder devices 3 and 3A are in operation, the respective wire feeder devices 3 and 3A are continuously charged until the predetermined loading amount initially distributed by the respective wire feeder devices 3 and 3A is completed. On the other hand, if one of the wire feeder devices has stopped, calculate the shortage of input in the stopped wire feeder device, and distribute the shortage to the first of the wire feeder devices that are operating normally In addition to the amount, the wire feeder device that is operating normally is continued until the added amount is equal to the integrated amount.

  And when both are operating normally, when each wire feeder device 3, 3A reaches a predetermined amount of integrated amount, and when one of the wire feeder devices stops. The pinch roll 11 is automatically stopped at the point of time when the charged integrated amount of the wire feeder device that is operating normally becomes the corrected charged amount, and the graphite spheroidizing process step ends. The hot metal 16 in the processing vessel 2 is subjected to graphite spheroidization treatment with the added Mg, and the hot metal 16 has, for example, C: 3-4%, Si: 2-3%, Mn: 0.2-0. It is melted in molten cast iron for ductile castings containing 5% and Mg: 0.01 to 0.06%. When the graphite spheroidizing process is completed, the processing vessel 2 containing the molten cast iron for ductile casting is transported to a casting facility such as a centrifugal casting machine in the next process using an appropriate transporting means such as a crane or a transport carriage.

  By performing the graphite spheroidizing treatment of the hot metal 16 in this way, the charging of the iron-coated Mg wire 15 is automated, and simultaneously the integrated amount of the iron-coated Mg wire 15 is fed back in real time. Even if a wire feeder device in which the iron-coated Mg wire 15 cannot be inserted due to a failure of the electric motor or the like occurs, if at least one wire feeder device is operating normally, the wire feeder can no longer be inserted. A predetermined amount of iron-coated Mg wire 15 including the amount to be charged by the apparatus can be automatically charged to perform the spheroidizing treatment.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the calculation unit 7 and the input instruction unit 8 in the control device 6 may be separately installed as individual devices, or conversely, these may be collected. Moreover, although there are two wire feeder devices, it may be three or more. Even when there are three or more wire feeder devices, the present invention can be carried out in accordance with the above.

  The present invention was implemented based on the processing steps shown in FIG. 1 using the graphite spheroidization processing equipment shown in FIG. The hot metal used was obtained by melting iron scrap, pig iron, coke, etc. with a cupola. At the time of extraction from the cupola, the hot metal was desulfurized with quick lime powder containing alumina. The representative components of the hot metal after the desulfurization treatment were C: 3-4%, Si: 1.5-2.0%, Mn: 0.3%, P: 0.03%, S: 0.006%. It was. This hot metal was stored in a holding furnace, divided into a ladle-type treatment container having a capacity of 3 tons, and used as hot metal for a ductile casting. The mass of the hot metal in the processing vessel was measured by a load cell arranged at a position where hot metal was discharged from the holding furnace into the processing vessel. The measured value of the hot metal mass is automatically input to the control device. The S concentration of the hot metal before the treatment was analyzed by collecting a sample during pouring from the holding furnace and inputting the data to the controller.

  In setting the amount of Mg added, it is assumed that Mg equivalent to S contained in the hot metal before the treatment is used for the desulfurization reaction of S in the hot metal, and the target Mg concentration after the treatment The required amount of iron-coated Mg wire was determined by setting the value to 0.025% and the Mg addition yield to 35%. And the required input amount of the defined iron-coated Mg wire was divided into two equal parts, and each wire feeder device was charged into the hot metal at a wire feed speed of 20.0 m / min. During the charging of the iron-coated Mg wire, the charging speed was measured with a major roll, and the result was fed back to the control device to monitor the charging amount.

  In the graphite spheroidization process performed in this way, there was a situation in which it was impossible to send the wire of one wire feeder device. Even in such a case, the input amount of the other wire feeder device was automatically As a result, the required amount of iron-coated Mg wire could be introduced without delay. That is, it has been achieved that the graphite spheroidizing treatment step is stably performed by a remote operation which is substantially unmanned.

It is a process-process figure in the graphite spheroidization processing method which concerns on this invention. It is the schematic of the graphite spheroidization processing equipment used when implementing this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Graphite spheroidization processing equipment 2 Processing container 3 Wire feeder apparatus 3A Wire feeder apparatus 4 Weighing instrument 5 Operation panel 6 Control apparatus 7 Calculation part 8 Input instruction | indication part 9 Input amount monitoring part 10 Guide pipe 11 Pinch roll 12 Major roll 13 Guide roll 14 drum 15 iron-coated Mg wire 16 hot metal

Claims (2)

  A graphite spheroidizing method in which two or more wire feeders are used, and iron-coated Mg wires are introduced from each wire feeder into molten cast iron in a processing vessel to melt molten cast iron for ductile casting. After determining the required input amount of iron-coated Mg wire based on the conditions, dividing the calculated required input amount and distributing it as the input amount of each wire feeder device, start the input of iron-coated Mg wire by each wire feeder device When the iron-coated Mg wire is being charged, the integrated amount of iron-coated Mg wire in each wire feeder device is continuously measured, and when each wire feeder device is operating normally, each wire feeder device However, the charging is continued until the distribution of the distributed amount of iron-coated Mg wire is completed. When a wire feeder device that has made it impossible to insert a wire occurs, the shortage of the input amount in the wire feeder device that has become impossible to input is distributed to other wire feeder devices, and the required input amount of iron is distributed. A graphite spheroidizing method characterized by completing the introduction of a coated Mg wire.   The required input amount of the iron-coated Mg wire is obtained based on the mass of molten cast iron, the S concentration in the molten cast iron before the treatment, the target value of the Mg concentration in the molten cast iron after the treatment, and the addition yield of Mg. The graphite spheroidizing method according to claim 1.

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