JP2012161807A - Casting procedure and device of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a casting product which is excellent in quality, in which various characteristics are substantially equivalent regardless of regions.SOLUTION: An inoculation agent 26 is inoculated through a measurement hopper 18 with respect to a molten metal 14 flowing from a first ladle 12 to a second ladle 16 in the middle of moving the molten metal 14 accumulated in the first ladle 12 to the second ladle 16 when performing a casting operation using a casting device 10. Thus, the molten metal 14 to which the inoculation agent 26 is inoculated is received by the second ladle 16. Further, after the molten metal 14 inoculated in the second ladle 16 becomes the predetermined amount, the molten metal 14 is poured in a molding 20. The molten metal 14 is cooled and solidified in the cavity 36, obtaining the casting product.

Description

  The present invention relates to a casting method and apparatus for obtaining a casting by pouring molten metal inoculated with an inoculum into a mold.

  When a cast product is obtained from a molten cast iron, it is generally performed to inoculate the molten metal with an inoculum. For example, in the case of gray cast iron, it is possible to obtain a cast product in which the grain size of graphite grains in the structure is small by inoculating the inoculum. Such a cast product is excellent in strength.

  For example, the inoculum is inoculated against the molten metal stored in the ladle. In this case, if a long time elapses after inoculating the inoculum and pouring the molten metal into the mold, the inoculation effect becomes effective. It causes so-called fading to be reduced. In order to prevent this, the inoculum is inoculated against the flowing molten metal (hereinafter also referred to as molten metal flow) that is being poured from the ladle into the mold, so-called hot water flow inoculation, or inoculation in the cavity. When the molten metal is poured into the mold after being stored in advance, so-called inoculation in the mold, in which the molten metal is inoculated into the molten metal in the cavity, may be performed.

  Furthermore, the inoculation method described in Patent Document 1 is known. In this case, the molten metal is first transferred from the large ladle to the small ladle, and then the inoculum is inoculated to the molten metal stored in the small ladle. Thereafter, molten metal is poured from the small ladle into the mold.

Japanese Patent Laid-Open No. 9-174229

  When the inoculum is inoculated to the molten metal in the small ladle as described in Patent Document 1, impurities such as noro and oxide are generated in the small ladle. These slags or oxides tend to adhere and accumulate on the inner wall surface of the small ladle. When the casting operation is continued without removing the deposit, the inside of the small ladle is narrowed by the deposit. In other words, the internal shape of the small ladle changes.

  When such a situation occurs, the pouring speed changes, causing a difference between the molten metal temperature at the start of the pouring and the molten metal temperature at the end of the pouring or causing a disturbance in the flow of the molten metal. . As a result, casting defects such as shrinkage nests, hot water boundaries, and foreign object bites are easily generated, and the quality of the cast product is deteriorated.

  Moreover, when inoculating with respect to the molten metal in a small ladle, dispersion | fluctuation is recognized by the particle size of the graphite grain in a structure | tissue according to the site | part of a casting. Various characteristics are also different between portions where the particle size of the graphite grains is different. As can be understood from this, in this case, there is a problem that it is not easy to obtain a cast product having various characteristics substantially the same throughout. This reason is presumed to be because the inoculum inoculated into the molten metal in the small ladle is not evenly dispersed in the molten metal.

  The present invention has been made to solve the above-described problems, and can reduce the occurrence of casting defects and can provide a cast product having various characteristics substantially equivalent throughout, and an apparatus therefor. The purpose is to provide.

In order to achieve the above object, the present invention provides a casting method for pouring molten metal inoculated with an inoculum into a mold to obtain a cast product,
Transferring the molten metal stored in the first ladle to the second ladle and inoculating the molten metal flowing from the first ladle toward the second ladle;
Receiving the molten metal inoculated with the inoculum until a predetermined amount is reached in the second ladle;
Pouring a predetermined amount of the molten metal received in the second ladle into a mold to obtain a cast product;
It is characterized by having. Needless to say, the “predetermined amount” is more than the amount required for pouring.

  In this invention, while using two ladles, inoculation is performed with respect to the molten metal in the middle of liquid transfer between ladles. This inoculated molten metal is sequentially introduced into the second ladle. Accordingly, convection occurs in the molten metal in the second ladle. This is because the molten metal previously introduced into the second ladle is pressed by the molten metal flowing down later and once flows downward, then further pressed and flows upward.

  The inoculum moves along with the convection molten metal. As a result, the inoculum diffuses substantially evenly in the molten metal. For this reason, it is avoided that the site | part where the density | concentration of the inoculant became locally large and the site | part which became small are formed in molten metal.

  As a result of the inoculum being dispersed substantially uniformly in the molten metal in this way, in the case of gray cast iron, the particle sizes of the graphite grains in the metal structure are substantially uniform. That is, it is avoided that the particle size of the graphite grains differs depending on the part. Therefore, it is possible to obtain a casting having substantially the same characteristics throughout. In addition, the occurrence of shrinkage nests is suppressed.

  Moreover, even if noro or oxides are generated in the molten metal in the second ladle, these noro or oxides are also moved by the convective molten metal. Therefore, it is possible to avoid the occurrence of deposits and deposits on the inner wall of the second ladle.

  For this reason, it can prevent that the pouring speed | rate from a 2nd ladle to a metal mold | die changes. As a result, it is possible to prevent the temperature difference between the melts from increasing at the start and end of pouring, and the flow of the melt from being disturbed. Therefore, the occurrence of shrinkage nests, hot water boundaries, foreign object bites, and the like are suppressed, and eventually a high-quality cast product can be obtained.

  When carrying out the casting operation as described above, it is preferable that the amount of molten metal transferred from the first ladle to the second ladle is only an amount for performing one pouring. In this case, since all of the inoculated molten metal received in the second ladle is poured into the mold, it is possible to avoid the remaining molten metal in which fading has occurred. Therefore, it is not necessary to re-inoculate to obtain the inoculation effect again, and resource saving can be achieved.

Further, the present invention is a casting apparatus for pouring molten metal inoculated with an inoculum into a mold to obtain a cast product,
A first ladle for storing molten metal;
A second ladle that receives the molten metal derived from the first ladle;
An inoculum inoculating means for inoculating the molten metal flowing from the first ladle toward the second ladle;
A mold for pouring the molten metal received in the second ladle after the inoculum is inoculated;
It is characterized by having.

  By comprising in this way, the above-mentioned casting method can be implemented. Therefore, casting defects can be reduced, and a cast product having substantially the same characteristics throughout can be obtained.

According to the present invention, the first ladle and the second ladle are used, and the inoculum is inoculated to the molten metal being transferred from the first ladle to the second ladle. So
Convection occurs in the molten metal in the second ladle, so that the inoculum diffuses substantially evenly in the molten metal, and it is avoided that deposits and deposits are generated on the inner wall of the second ladle. As a result, it is possible to obtain a high-quality cast product that has substantially the same characteristics because a substantially equivalent metal structure is formed over the entire surface, and that has suppressed the occurrence of casting defects.

It is a schematic side partial sectional view of a casting apparatus for carrying out a casting method according to an embodiment of the present invention. It is a schematic longitudinal cross-sectional view which shows typically that the convection has arisen in the molten metal in the 2nd ladle which comprises the casting apparatus of FIG. It is an evaluation result of the casting obtained by the Example and the casting obtained by Comparative Examples 1-4.

  Hereinafter, a preferred embodiment of the casting method according to the present invention will be described in detail in relation to a casting apparatus for carrying out the casting method, with reference to the accompanying drawings. In this embodiment, a case where a camshaft is created using a molten cast iron is illustrated.

  FIG. 1 is a schematic side sectional view of a casting apparatus 10 according to the present embodiment. The casting apparatus 10 includes a first ladle 12, a second ladle 16 that receives a molten iron 14 derived from the first ladle 12, and the first ladle 12 and the second ladle 16. A weighing hopper 18 (inoculum inoculation means) disposed between them and a mold 20 into which the molten metal 14 led out from the second ladle 16 is poured.

  The first ladle 12 is supported by the first pedestal 21. The first pedestal 21 is supported on the second pedestal 23 in a freely tiltable manner via a first tilting mechanism 22 made of, for example, a pinion gear. The second pedestal 23 can be displaced in the direction of a total of three axes including a vertical direction and two axes orthogonal to each other under the action of a displacement mechanism (not shown). Are moved to any position together with the first pedestal 21 and the first tilting mechanism 22.

  Of course, the first tilting mechanism 22 can tilt and stop the first ladle 12 to an arbitrary angle. As the first ladle 12 is tilted under the action of the first tilting mechanism 22 in this way, the molten metal 14 stored in the first ladle 12 flows down toward the second ladle 16. That is, the molten metal 14 is transferred to the second ladle 16.

  The weighing hopper 18 is for inoculating the molten metal 14 transferred from the first ladle 12 to the second ladle 16 as described above, and a valve 24 is provided at the outlet pipe. Intervened. For example, a known inoculum 26 such as an Fe-Si alloy is accommodated in the weighing hopper 18 in advance.

  The second ladle 16 is supported by a third pedestal 27, and the third pedestal 27 is, like the first pedestal 21, a fourth pedestal 29 via a second tilting mechanism 28 made of, for example, a pinion gear. It is supported so that it can tilt freely. Similar to the second pedestal 23, the fourth pedestal 29 can be displaced in the direction of a total of three axes including the vertical direction and the two axes orthogonal to each other under the action of a displacement mechanism (not shown). Due to this displacement, the second ladle 16 is moved to any position together with the third pedestal 27 and the second tilting mechanism 28.

  Further, the second ladle 16 is tilted and stopped to an arbitrary angle under the action of the second tilting mechanism 28. With this tilting, the molten metal 14 received by the second ladle 16 is poured into the mold 20.

  In this case, the mold 20 is for simultaneously obtaining a plurality of camshafts constituting the internal combustion engine. Accordingly, a runner 34 communicating with the hot water chamber 32 is formed in the mold 20 on the downstream side of the pouring port 30 and branched from the runner 34, and each shape has a cavity 36 corresponding to the shape of the camshaft. Are formed. The molten metal 14 introduced from the pouring port 30 is distributed from the runner 34 and introduced into the cavities 36 after passing through the hot water chamber 32. A filter 35 is disposed in the hot water chamber 32.

  In the present embodiment, the mold 20 has a substantially rectangular parallelepiped shape, and in other words, the fixed mold 38 installed so as to lie down so that its axial direction extends along a substantially horizontal direction. A movable mold 40 is provided. The lower fixed mold 38 is positioned and fixed, while the upper movable mold 40 can be displaced along a substantially vertical direction under the action of a lifting mechanism (not shown). With this displacement, the movable mold 40 approaches or separates from the fixed mold 38.

  The casting apparatus 10 according to the present embodiment is basically configured as described above. Next, the function and effect will be described in relation to the casting method according to the present embodiment.

  When producing a camshaft with the mold 20, first, the molten metal 14 is generated in a melting furnace (not shown). This molten metal 14 is stored in the first ladle 12. The first ladle 12 has an amount corresponding to the sum of the total volume of the plurality of cavities 36 and the volume from the pouring port 30 to the runner 34, that is, an amount corresponding to one pouring amount. However, it is possible to store more molten metal 14 than that.

  Next, by energizing the first tilting mechanism 22, the first ladle 12 is tilted as shown in FIG. By this tilting, the molten metal 14 starts to flow toward the second ladle 16 at a predetermined speed. That is, a molten metal flow is formed. Of course, the first ladle 12 and the second ladle 16 are displaced by the displacement of the first pedestal 21 and the third pedestal 27 under the action of the displacement mechanism before the molten metal flow is formed. The first pedestal 21, the second pedestal 23, the third pedestal 27, and the fourth pedestal 29 are moved to a predetermined appropriate position.

  Simultaneously with or slightly after the start of the flow, the valve 24 is released. Therefore, the inoculum 26 previously stored in the weighing hopper 18 flows down by its own weight, is led out from the outlet pipe, and is inoculated into the molten metal stream. That is, in the present embodiment, the inoculum 26 is inoculated to the molten metal 14 being transferred from the first ladle 12 to the second ladle 16.

  The molten metal 14 inoculated with the inoculum 26 is received by the second ladle 16. As schematically shown in FIG. 2, the molten metal 14 previously introduced into the second ladle 16 is once pressed downward by the molten metal 14 flowing down later, and then flows so as to rise. As a result, convection occurs in the molten metal 14 in the second ladle 16 as indicated by arrows in FIG. The inoculum 26 moves in the molten metal 14 accompanied by the convective molten metal 14. Thereby, the inoculant 26 can be diffused substantially uniformly in the molten metal 14.

  Moreover, even if impurities such as slag and oxide are generated in the molten metal 14, these slags or oxides are entrained in the second ladle 16 by being accompanied by the convective molten metal 14, similarly to the inoculum 26. Moving. For this reason, it is possible to prevent deposits, oxides, or the like from adhering to or depositing on the inner wall of the second ladle 16. As a result, it is avoided that the inside of the second ladle 16 is narrowed by the deposit.

  The inoculation end timing of the inoculant 26 is preferably just before or almost at the same time as the molten metal 14 in an amount corresponding to one pouring amount flows down from the first ladle 12. Thus, when inoculating the inoculum 26 from the start to the end of the flow of the molten metal 14 from the first ladle 12 to the second ladle 16, the concentration of the inoculum 26 is locally increased. This is because it can be easily avoided. In other words, it is easy to disperse the inoculum 26 in the molten metal 14 substantially evenly.

  Note that the inoculation of the inoculum 26 is terminated when the valve 24 (see FIG. 1) is closed or when the entire amount of the inoculum 26 previously stored in the measuring hopper 18 flows down.

  As described above, the inoculated molten metal 14 is received by the second ladle 16. Here, it is preferable that the amount of the inoculated molten metal 14 received by the second ladle 16 is an amount corresponding to a single pouring amount. In this case, since all the inoculated molten metal 14 is subjected to casting work, there is no residue stored in the second ladle 16 for a long time. For this reason, the fading described above can be avoided.

  In addition, the amount of the molten metal 14 received in the second ladle 16 is set once by setting the amount of the molten metal 14 stored in the first ladle 12 to an amount corresponding to a single pouring amount. It becomes easy to set it as the amount equivalent to the amount of pouring of. In this case, the total amount of the molten metal 14 stored in the first ladle 12 may be transferred to the second ladle 16, and the amount of the molten metal 14 remaining in the first ladle 12 can be calculated. This is because it is not necessary to control the tilt angle of the first ladle so that the amount can remain.

  In order to avoid fading from occurring after the predetermined amount of molten metal 14 is received in the second ladle 16, preferably an amount corresponding to the amount of pouring once, the second tilting mechanism 28 is moved as quickly as possible. Be energized. Therefore, the residence time of the molten metal 14 in the second ladle 16 is relatively short and is about 40 to 45 seconds.

  As the second ladle 16 tilts, the molten metal 14 starts to flow toward the pouring port 30 of the mold 20 at a predetermined speed. That is, pouring of the molten metal 14 into the mold 20 is started.

  The molten metal 14 flowing from the pouring port 30 to the hot water chamber 32 is pressed by the molten metal 14 introduced into the hot water chamber 32 later and flows toward the runner 34. During this time, when passing through the filter 35, various foreign matters such as noro and oxide generated in the molten metal 14 are removed. The molten metal 14 is further distributed from the runner 34 and introduced into each of the plurality of cavities 36.

  Thus, the pouring speed is kept substantially constant from the start of pouring until all the cavities 36 are filled with the molten metal 14. This is because it is avoided that the inside of the second ladle 16 is narrowed because it is difficult for deposits to adhere to the inner wall of the second ladle 16 as described above. Therefore, it is avoided that the difference between the molten metal temperature at the start of pouring and the molten metal temperature at the end of the molten metal is increased, and that the flow of the molten metal 14 is disturbed.

  After all the cavities 36 are filled with the molten metal 14, the molten metal 14 is cooled and solidified as a predetermined time elapses. Thereby, a cam shaft is formed. Next, the camshaft is exposed by moving the movable mold 40 away from the fixed mold 38, in other words, by performing so-called mold opening.

  When the metal structure of the camshaft is observed with a scanning electron microscope or the like, it is recognized that relatively fine graphite grains having a substantially uniform particle size are dispersed substantially uniformly. Further, the number of graphite grains per unit area is substantially the same regardless of the part. This reason is presumed to be because the inoculum 26 is inoculated into the molten metal 14 (molten metal flow) that is flowing down from the first ladle 12 to the second ladle 16 as described above. That is, when the molten metal flow is introduced into the second ladle 16, the inoculated molten metal 14 causes convection in the second ladle 16, so that the inoculum 26 is dispersed substantially evenly in the molten metal 14. It is thought that.

  In addition, as described above, the pouring speed from the start to the end of pouring is kept substantially constant, so that the camshaft hardly shows casting defects such as shrinkage nests, hot water boundaries, and foreign object bites.

  And in the camshaft in which the particle size of the graphite grains in the metal structure is substantially the same, various characteristics are almost the same regardless of the part. In addition, since the occurrence of casting defects such as shrinkage cavities is avoided, the appearance quality is excellent and the formation of locally low strength parts is avoided. After all, according to the present embodiment, it is possible to obtain a camshaft having various characteristics that are substantially the same throughout and having good appearance quality.

  In the above-described embodiment, the case where the camshaft is obtained as a cast product is illustrated, but it goes without saying that the cast product is not particularly limited to this. Of course, the mold is not particularly limited to the mold 20 described above.

  Of course, a spheroidizing agent or the like may be further added to the molten metal 14.

  Then, when the inoculant 26 is derived from the weighing hopper 18, the inoculant 26 may be moved downward little by little using rotation or vibration of a screw.

  When casting using the casting apparatus 10 shown in FIG. 1, the inoculum 26 was inoculated against the molten metal flow from the first ladle 12 to the second ladle 16. That is, molten metal flow inoculation was performed. Further, the inoculated molten metal 14 was poured from the second ladle 16 into the mold 20 to produce a camshaft. This is an example.

  In addition, as the molten metal 14 and the inoculant 26, FCD400 equivalent material and SF silicon (Fe-Si alloy manufactured by Osaka Special Alloy Co., Ltd.) were selected. Further, JMM-N3 (3% Mg alloy manufactured by Toyo Denka Kogyo Co., Ltd.) as a spheroidizing agent was added to the molten metal 14. The same applies to Comparative Examples 1 to 4 described below. Here, “FCD400” is a standard for ductile cast iron defined in JIS.

  For comparison, the inoculum 26 is inoculated while stirring the molten metal 14 in the first ladle 12 with a stirring means, and then poured directly from the first ladle 12 to the mold 20 without using the second ladle 16. Hot water was applied to make a camshaft. This is referred to as Comparative Example 1. In the following, this inoculation method is referred to as “stirring”.

  In addition, the second ladle 16 was not used, and hot water was poured directly from the first ladle 12 into the mold 20, and an inoculum 26 was inoculated into the molten metal flow to produce a camshaft. This is referred to as Comparative Example 2.

  Further, the inoculum 26 is placed in advance on the bottom wall of the second ladle 16, and then the molten metal 14 is transferred from the first ladle 12 to the second ladle 16 so that the molten metal 14 and the inoculum 26 are transferred. After mixing, pouring was performed to produce a camshaft. During the transfer, inoculum 26 was not inoculated against the molten metal stream. This is referred to as Comparative Example 3. In the following, this inoculation method is referred to as “placed pouring”.

  Furthermore, after the molten metal 14 is transferred from the first ladle 12 to the second ladle 16 without inoculating the inoculum 26 against the molten metal flow, the molten metal 14 in the second ladle 16 is stirred by the stirring means. While inoculating the inoculum 26, a camshaft was prepared using the inoculated molten metal 14. This is referred to as Comparative Example 4.

  About the camshaft of the above Example and Comparative Examples 1-4, the generation | occurrence | production condition of a foreign material bite and a shrinkage nest was evaluated. In addition, about the foreign substance bite, 100 places or more were selected at random on the surface of the camshaft, and the ratio was obtained based on the number of places where the foreign substance bite was recognized.

  Further, for shrinkage nests, the number of graphite grains per unit area existing in the metal structure of the camshaft was measured at 100 or more locations, and the distribution width of the number of graphite grains was determined. The smaller the distribution width of the number, the more uniform the distribution of the graphite grains, which means that shrinkage cavities are generated and various characteristics are equivalent. On the contrary, the larger the distribution width of the number, the more shrinkage nests are generated and the various characteristics are recognized.

  The evaluation results are also shown in FIG. From FIG. 3, in the examples using the first ladle 12 and the second ladle 16 and the comparative examples 3 and 4, as compared with the comparative examples 1 and 2 using only the first ladle 12, the foreign object bite. It can be seen that the rate of occurrence can be significantly reduced.

  Furthermore, the 1st ladle 12 and the 2nd ladle are understood so that the Example which performs the molten metal flow inoculation, the comparative example 3 which inoculates by pouring, and the comparative example 4 which inoculates by stirring may be compared. In combination with the use of No. 16 and the molten metal flow inoculation, it is possible to obtain a camshaft that suppresses the occurrence of shrinkage and has substantially the same characteristics regardless of the part. The reason for this is presumed that in the case of molten metal flow inoculation, it is easier to disperse the inoculant 26 in the molten metal 14 more uniformly than inoculation by pouring or stirring. This inference is supported by the difference in the occurrence of shrinkage cavities in Comparative Example 1 and Comparative Example 2.

  From the above, in the embodiment in which the first ladle 12 and the second ladle 16 are used, and the molten metal 14 flowing from the first ladle 12 toward the second ladle 16 is inoculated. According to this, it is clear that the occurrence of foreign matter bites and shrinkage can be suppressed.

DESCRIPTION OF SYMBOLS 10 ... Casting apparatus 12 ... 1st ladle 14 ... Molten metal 16 ... 2nd ladle 18 ... Measuring hopper 20 ... Mold 22 ... 1st tilting mechanism 26 ... Inoculum 28 ... 2nd tilting mechanism 36 ... Cavity 38 ... Fixed mold 40 ... Moveable type

Claims (3)

In a casting method of pouring molten metal inoculated with an inoculum into a mold to obtain a cast product,
Transferring the molten metal stored in the first ladle to the second ladle and inoculating the molten metal flowing from the first ladle toward the second ladle;
Receiving the molten metal inoculated with the inoculum until a predetermined amount is reached in the second ladle;
Pouring a predetermined amount of the molten metal received in the second ladle into a mold to obtain a cast product;
A casting method characterized by comprising:   The casting method according to claim 1, wherein the amount of the molten metal transferred from the first ladle to the second ladle is limited to a single pouring amount. In a casting apparatus for pouring molten metal inoculated with an inoculum into a mold to obtain a cast product,
A first ladle for storing molten metal;
A second ladle that receives the molten metal derived from the first ladle;
An inoculum inoculating means for inoculating the molten metal flowing from the first ladle toward the second ladle;
A mold for pouring the molten metal received in the second ladle after the inoculum is inoculated;
The casting apparatus characterized by having.

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