JPH09174227A - Formation of spheroidal graphite cast iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the heat load applied to a mold and prevent the deformation of graphite. SOLUTION: This forming method is constituted of a melting process for heating and fusing a raw material consisting of spheroidal graphite cast iron within the temp. range of 1150-1300 deg.C and a forming process for forming the fused spheroidal graphite cast iron 1 in the period remaining the sphroidal graphite. The forming process includes a mold-forming sucking the fused iron the mold, an extrusion-forming extruding it while being passed through a die and a roll-forming rolling it while being passed through gap between pair of rollers, etc., in addition to a mold-forming pressurizing it while being pushed into a mold 4, also.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forming method such as die forming, rolling, forging, extrusion or the like, which utilizes good fluidity without deteriorating the spheroidization rate of spheroidal graphite in spheroidal graphite cast iron. .

[0002]

2. Description of the Related Art As a method for obtaining spheroidal graphite cast iron, a method is generally used in which a molten cast iron having a composition adjusted in a molten state is subjected to a graphite spheroidizing treatment and then cast. According to this method,
Very high melting or casting temperature (usually 1400
Since the heat load is large on the mold, the life of the mold is significantly reduced. Further, shrinkage during solidification may cause cavities, and it is necessary to cast at a temperature as low as possible. However, there is a problem that the graphite spheroidizing action disappears with time, and there is no time margin to lower the temperature. On the other hand, there is a method in which spheroidal graphite cast iron is heated to a solid phase temperature range, for example, 1000 ° C, and is molded by forging, rolling and the like. According to this method, since the solid phase molding is used, it is necessary to increase the molding load, and there is a problem that the graphite, which should be spherical, is deformed by the plastic flow of the solid phase. Deformation of graphite leads to deterioration of the original toughness of spheroidal graphite cast iron.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce the heat load on a mold and prevent the graphite from being deformed, which is spheroidal graphite cast iron. The present invention is to provide a molding method.

[0004]

The present invention has excellent fluidity in a state where spheroidal graphite cast iron is heated and melted,
Moreover, it was completed by discovering that there is a temperature range in which the spheroidization rate of spheroidal graphite does not deteriorate. That is, the means of the present invention uses a material made of spheroidal graphite cast iron at 1150 ° C.
It is characterized by including a process of heating and melting within a temperature range of 1 to 1300 ° C and a process of molding the melted spheroidal graphite cast iron during the period in which the spheroidal graphite remains. The molding process, using a mold, normal mold casting, pressurizing pressure casting, suction casting, mold forging, also, rolling by a roll to process the longitudinal cross-sectional shape is uniform, or extruded through a die, Etc.

In the above means, the reason for limiting the temperature range as described above is that if the temperature is less than 1150 ° C., there is a large amount of undissolved solid phase, so that the fluidity cannot be secured and it is difficult to mold it into a desired shape. This is because the lower the temperature, the higher the possibility of cracking. When the temperature exceeds 1300 ° C, the effect of spheroidizing the graphite disappears, that is, as the temperature increases, the spheroidal graphite dissolves into the tissue and becomes non-spherical, and the spheroidizing rate decreases. This is because a structure containing spherical graphite cannot be obtained. The state where the raw material spheroidal graphite cast iron is heated in the range of 1150 ° C. to 1300 ° C. is a semi-molten state exhibiting fluidity, and the spheroidal graphite exists as it is. The results of basic experiments show that spheroidal graphite cast iron containing 3.5 wt% C and 3.2 wt% Si with a spheroidization rate of graphite of 86.8% is used as a material, and this material is housed in a crucible and heated to 1200 ° C. Then, after maintaining at this temperature for 5 minutes, it was left to cool in the air to be solidified, and the spheroidization ratio of the graphite was examined. As a result, it was 87.4% (experimental result 1). Also, the same material as above was heated to 1240 ° C. and held for 5 minutes, then cooled and solidified in the same manner, and the graphite spheroidization rate was examined. As a result, it was 82.6% (experimental result 2). 5 (a) is a material, FIG. 5 (b) is a microstructure photograph of cast iron of experimental result 1, and FIG.
It can be seen that the spherical graphites of (b) and (c) are almost unchanged from the spherical graphite of (a). In subsequent experiments, it was confirmed that the spheroidization ratio of graphite hardly changed even when the graphite was solidified after being kept at a predetermined temperature within the above range for 20 minutes. Therefore, if the molding is completed within the period in which the spherical shape of the spheroidal graphite is maintained, it is possible to obtain a high quality spheroidal graphite cast iron molded product corresponding to the original material. The time of 20 minutes is a time period which is substantially satisfactory as the time required for molding.

Further, the maximum value of the temperature range is 130.
Even at 0 ° C, the casting temperature of ordinary spheroidal graphite cast iron is 1
Since it is 100 ° C lower than 400 ° C, the heat load on the mold and the die is reduced accordingly, and the strength of the mold and the die can be easily secured. Therefore, suction casting and indentation pressure casting are possible. In addition, the die life is extended. The lowest value of the temperature range, 1150 ° C., is higher than that of conventional forging and rolling of spheroidal graphite cast iron, that is, forging and rolling by heating in the solid phase temperature range (1000 ° C.). Graphite is a solid phase, but most of the other is a liquid phase, and spherical graphite is not deformed even when a forming process corresponding to die forging or roll rolling is performed. Therefore, it becomes possible to obtain a molded product of spheroidal graphite cast iron of a quality corresponding to the original material, and when the material is pressed in the molding process, the structure becomes dense but has fluidity, so There is no deformation and the quality is improved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment is die molding by pressurization. As shown in the schematic view of FIG. 1, the raw material of spheroidal graphite cast iron is in the range of 1150 ° C to 1300 ° C. The melt 1 melted by heating to a predetermined temperature is housed in a container 2, and is pushed into the mold space of the mold 4 by advancing the ram 3 downward, solidified and taken out as a molded product.
Reference numeral 5 in the figure is a heating means composed of a high-frequency heating coil or a resistance heating element, which is used as necessary. The time within the above temperature range from the melting of the material to the start of solidification during molding is preferably 20 minutes or less. Further, in the apparatus used in this embodiment, in addition to the above method of use, a method of containing unmelted material in the container 2 and melting it by the heating means 5 from the beginning is possible. Good. The obtained molded product is a spheroidal graphite cast iron that is almost the same as the material,
Since it is pressure-molded, the structure is more compact.

The second embodiment is suction casting, and as shown in the schematic view of FIG.
The melt 6 melted by heating to a predetermined temperature within the range of 150 ° C. to 1300 ° C. is sucked into the mold space of the mold 7, solidified, and taken out as a molded product. In the figure, 8 is a holding furnace, 9 is heating means consisting of a high frequency heating coil or a resistance heating element, 1
Reference numeral 0 is a suction nozzle, and 11 is a suction pipe. The time within the above temperature range from the melting of the material to the start of solidification during molding is preferably 20 minutes or less. The obtained molded product is spheroidal graphite cast iron that is almost the same as the raw material, and since it is suction-molded, it is degassed during suction and the quality is improved.

The third embodiment is extrusion molding, and as shown in the schematic view of FIG. 3, the raw material spheroidal graphite cast iron is heated to a predetermined temperature within a range of 1150 ° C. to 1300 ° C. and melted. A predetermined amount of the melted substance 12 is added to the container 1
The ram 14 is housed in the mold 3 and is pushed forward through the die 15 to form a molded product 16 having a predetermined cross-sectional shape. In this case, immediately after exiting the die 15, the vicinity of the surface is solidified, but the central portion is still in a molten state and easily deformed. Therefore, it is preferable to guide the molded article in a straight line. If necessary, the container 13 is provided with a heating means as shown in FIG. The time within the above temperature range from the melting of the material to the start of solidification during molding is preferably 20 minutes or less. Further, also in the apparatus used in this embodiment, when the heating means is provided, the unmelted material from the beginning may be accommodated in the container 13 and melted. The obtained molded product is spheroidal graphite cast iron that is substantially the same as the material.

The fourth embodiment is forming corresponding to rolling using a roller, and as shown in the schematic view of FIG. 4, the material spheroidal graphite cast iron is 1150 ° C. to 1300 ° C.
Melt 17 melted by heating to a predetermined temperature in the range of ° C 17
Is supplied between the pair of rotating rollers 18 and 19 equipped with a cooling means so that a substantially constant amount is accumulated on the roller portion, and the outer surface is solidified and comes out from between the rollers 18 and 19. Obtained as a continuous molded product 20 having a predetermined cross-sectional shape. The time within the above temperature range from the melting of the material to the start of solidification during molding is preferably 20 minutes or less. The obtained molded product is spheroidal graphite cast iron that is substantially the same as the material. Third,
The molded products 16 and 20 of the fourth embodiment have a uniform cross-sectional shape, for example, the cross-sectional shape 2 shown in FIGS. 4B and 4C.
1, 22 and so on. Incidentally, in connection with the third embodiment, it is possible to form a tube made of spheroidal graphite cast iron, particularly a tube having an irregular cross section, by using an apparatus configured to use a mandrel.

[0011]

EXAMPLE In the first embodiment, as the raw material spheroidal graphite cast iron, C containing 3.5 wt%, Si containing 3.2 wt% and a graphite spheroidizing rate of 86.8% are used. 11
What was heated to 80 ° C was designated as melt 1, and the outer diameter was 50 m.
m, an inner diameter 44 mm, and a height 75 mm. A microstructure photograph of the peripheral wall of the molded product at an intermediate height position is shown in FIG. The spheroidization rate of graphite of the molded product was 87.4% as an average value at several points. From this result, it can be determined that the spheroidization rate of graphite is substantially the same for the material and the molded product. In addition,
It is generally recognized that if the graphite spheroidization rate of spheroidal graphite cast iron is 70% or more, no defect in strength occurs. Therefore, it can be said that this molded product is a sufficiently good spheroidal graphite cast iron product.

[0012]

According to the invention described in claim 1, it is possible to obtain a molded article of spheroidal graphite cast iron having a quality corresponding to the original material, and the spheroidal graphite cast iron of the material is reheated within a predetermined temperature range. Since it is formed by molding, it is possible to melt as many materials as necessary and support the production of small lots of spheroidal graphite cast iron molded products.By stocking the materials, it is possible to quickly produce small orders. Play. In addition, since the melting temperature range is lower than the casting temperature of conventional spheroidal graphite cast iron, the occurrence of cavities is reduced, and the heat load on the mold and die used in molding is reduced, so the effect of extending its life is obtained. Play. Since the invention described in claim 2 is pressure molding,
It is possible to obtain a high quality spheroidal graphite cast iron molded product having a complicated shape. Since the invention described in claim 3 is casting by suction, there is an effect that degassing is performed and a good quality spheroidal graphite cast iron molded product is obtained. Since the invention according to claim 4 is extrusion molding, there is an effect that it is possible to cope with different spheroidal graphite cast iron molded products only by changing the die. Since the invention described in claim 5 is roll-forming by rollers, it has an effect that the structure becomes dense and a good quality spheroidal graphite cast iron molded product is obtained.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional front view schematically showing a first embodiment of the present invention together with a pressure casting device to be used.

FIG. 2 is a vertical sectional front view schematically showing a second embodiment of the present invention together with a suction casting device to be used.

FIG. 3 is a vertical sectional front view schematically showing a third embodiment of the present invention together with an extrusion molding apparatus used.

FIG. 4 (a) is a vertical cross-sectional front view schematically showing the fourth embodiment of the present invention together with a rolling apparatus to be used,
(B) And (c) is sectional drawing which shows the example of the molded article obtained by 3rd and 4th embodiment.

FIG. 5 (a) is a microstructure photograph of spheroidal graphite cast iron as a material, and (b) and (c) are microstructure photographs of spheroidal graphite cast iron obtained by heating and melting the material and holding it for a predetermined time to solidify it.
(D) is a microstructure photograph of the spheroidal graphite cast iron of the example.

[Explanation of symbols] 1 melted material 2 container 3 plunger 4 type 5 heating device 6 melted material 7 type 8 holding furnace 9 heating device 10 suction nozzle 11 suction pipe 12 melted material 13 container 14 plunger 15 die 16 molded product 17 Molten material 18 Roller 19 Roller 20 Molded product

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Kiuchi 2-12-21 Shinjuku, Zushi City, Kanagawa Prefecture

Claims (5)

[Claims] 1. A material made of spheroidal graphite cast iron is 1150 °
Spherical graphite characterized by including a melting process of heating and melting within a temperature range of C to 1300 ° C., and a forming process of molding the melted spheroidal graphite cast iron during a period in which spheroidal graphite remains. Cast iron forming method. 2. The spheroidal graphite cast iron forming method according to claim 1, wherein the forming step is a die forming in which the molten spheroidal graphite cast iron is pressed into a mold and pressed. Molding method. 3. The molding method of spheroidal graphite cast iron according to claim 1, wherein the molding step is a mold molding for sucking the molten spheroidal graphite cast iron into a mold. Method. 4. The method for molding spheroidal graphite cast iron according to claim 1, wherein the molding step is extrusion molding in which the molten spheroidal graphite cast iron is extruded through a die. 5. The spheroidal graphite cast iron forming method according to claim 1, wherein the forming step is roll forming in which the molten spheroidal graphite cast iron is rolled between a pair of rollers. Molding method for graphite cast iron.