JPH09111395A - Production of integral die for press forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the press forming die having a blade part which is excellent in hardness and toughness by forming the base of the blade edge part, etc., of a fine pearlite structure at the time of producing the press die for steel sheets for automobiles integrated with a main body and the cutting edge part or bending part of spheroidal graphite consisting of a specific compsn. SOLUTION: Molten cast iron contg., by weight %, 3.6 to 4.0 C, 1.4 to 3.0% Si, 0.1 to 2.0% Mn, 0.03 to 0.2% Mg or further contg. 0.1 to 0.5% Mo, 0.1 to 2.0% Ni and 0.1 to 2.0% Cu is cast into a casting mold 1 embedded into the molding sand in a casting flask 5 and is formed by a full-mold method at the time of producing the press die used for forming, cutting and blanking of the steel sheets for forming the bodies of the automobiles. This casting mold is provided with suction holes 4 along the cutting edge constituting part 2 of the casting mold and the other end thereof is opened to a suction pipe 3 connected to a fan 6. Only the cutting edge constituting part 2 is air cooled and hardened by this fan 6 simultaneously with casting of the molten iron. The die having the blade part 2 of which the die base is formed of the fine pearlite structure and which has the excellent toughness and hardness is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a metal mold used for obtaining an iron plate used for an automobile body or the like by press molding. When obtaining a die integrated with a blade portion or a bending blade portion, by making the cutting blade portion or bending blade portion base in the as-cast state of the die a fine pearlite structure, surface hardening and quenching of this base, especially The present invention relates to a method for manufacturing an integral die for press molding which facilitates flame quenching and thereby can form a tough and hard blade portion.

[0002]

2. Description of the Related Art Conventionally, a press die has been used for forming, cutting and punching an iron plate used for an automobile body or the like. This press die is made of cast iron for the main body of the die in terms of hardness and durability, and the cutting edge or bending edge is manufactured separately from cast steel. Alternatively, it is obtained by integrally attaching the bending blade portion to the mold body with a bolt or the like.

[0003]

However, in the conventional die in which the die body and the cutting blade portion or the bending blade portion as described above are separately manufactured and are integrally attached with bolts or the like, the blade material is The manufacturing process of, the processing of the blade material mounting part at the time of manufacturing the die body, the mounting processing of the blade material to the die body, etc.
There was also a problem in terms of cost accordingly.

Further, there has been proposed a steel for a pre-hardened / frame-hardening mold, which is formed by forming an integral mold of a press mold and flame hardening the cutting edge portion thereof (Japanese Patent Laid-Open No. 63-25 / 1988).
No. 9057), which uses carbon steel as a raw material, and in which the cutting edge is flame-hardened after being subjected to quenching and tempering treatment, and spheroidal graphite cast iron having a specified composition is used.
Moreover, at the time of casting, it promotes cooling to facilitate blade formation by flame quenching of the cutting edge or bending blade in the as-cast state, and a press metal mold in which the main body and the cutting edge or bending blade are integrated. The present invention, which aims at obtaining a mold, is different in idea and technical means.

The present invention has been studied in order to solve the above-mentioned problems of the conventional press-molding die, and as a result, the flame-hardenability is better than that of the cast iron material conventionally used for manufacturing the die body. And when casting the entire die including the cutting edge or bending edge using spheroidal graphite cast iron with an alloy composition that provides high hardness and toughness, take measures to cool only the cutting edge or bending edge. Then, then, by flame quenching the cutting edge portion or the bending blade portion in the as-cast state of this casting mold, it was found that a blade portion excellent in toughness can be obtained, and this invention has led to the invention. is there.

[0006]

According to a first aspect of the present invention, the surface of the cutting edge portion or the bending edge portion of the sand mold is molded so that the cutting edge portion or the bending edge portion can be integrally cast with the main body. C3 in a weight ratio in a mold having a configuration in which cooling means is arranged on the side so as to correspond to the cutting blade portion or the bending blade portion.
0-4.0%, Si 1.4-3.0%, Mn 0.1
.About.2.0%, Mg 0.03 to 0.1%, the balance being Fe, and Mo 0.1 to 0.5%, Ni
0.1-2.0% and / or Cu 0.1-2.0
% When casting a molten metal of spheroidal graphite cast iron of the added component to promote cooling of the portion corresponding to the cutting edge portion or bending blade portion of the above-mentioned mold, the mold base of the portion is finely divided. A method for manufacturing an integral mold for press molding, which comprises forming a blade portion by surface hardening and quenching the portion in the as-cast state after forming the pearlite structure.

According to a second aspect of the present invention, in the first aspect of the invention, the cooling means has a suction pipe having a plurality of suction holes having a required diameter bored at a required interval. It is arranged so as to correspond to the blade portion, and has a configuration in which one end of the suction pipe pulled out to the outside of the casting frame is connected to a blower, which promotes cooling of the portion corresponding to the cutting blade portion or the bending blade portion of the mold. At the same time that the molten metal is cast, suction cooling is performed by a blower.

According to a third aspect of the present invention, also in the first aspect of the invention, the surface hardening quenching performed in the as-cast state after suction cooling of the portion corresponding to the cutting edge portion or the bending blade portion of the mold is flame quenching. Further, the invention according to claim 4 is, in the invention according to claim 1, in an as-cast state by suction cooling of a portion corresponding to the cutting blade portion or the bending blade portion of the mold. The mold base of the cutting edge portion or the bending edge portion is made to have a fine pearlite structure with a pearlite area ratio of 85 to 95% and a ferrite area ratio of 5 to 15%.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Since the cutting edge or bending edge of a press-molding die is subjected to a large amount of friction and impact, it is necessary to have high hardness and toughness. Therefore, a uniform and dense quenched structure is obtained. There is a need. However, in general, cast iron differs from steel in that the amount of Si, which is a strong graphitization-promoting element, is high, so the austenitizing temperature is high, and it is difficult for carbon to form a solid solution in austenite, making it difficult to obtain a uniform quenched structure. Is said.

Further, although the hardened structure has high hardness, it tends to lack in toughness, and it is said that it is greatly affected by the amounts of chemical components, particularly alloy elements.

As described above, the present invention provides a molten spheroidal graphite cast iron material having a composition obtained by adding an alloying element of Mo and Ni and / or Cu to the extent that the conventional spheroidal graphite cast iron material composition does not deteriorate in toughness by quenching. , When the mold is cast by casting in a sand mold in which the cutting edge part or the bending edge part is integrally molded, by cooling only the part of the mold base of the cutting edge part or the bending edge part, The pearlite area ratio 85 in which the compound carbon is evenly distributed in the as-cast matrix structure
A fine pearlite structure of 95% and a ferrite area ratio of 5 to 15% is used to make it easy to obtain a hardened structure by surface hardening and quenching, especially by flame quenching. In addition to saving costs and the like, it is possible to form a blade portion excellent in toughness and hardness by saving time and labor.

As for the amount of the alloying elements of Mo, Ni and / or Cu added to the conventional spheroidal graphite cast iron material in the present invention, Mo is 0.1 to 0.5% by weight and Ni and Cu are 0.1%. 1 to 2.0%, but 2 of Mo and Ni or Cu
When adding seeds, the preferable amount of Mo is 0.2 to 0.
At 4%, Ni or Cu is 0.4 to 0.8%, and when 3 kinds of Mo and Ni and Cu are added, M is added.
o is 0.3 to 0.5%, Ni is 0.4 to 0.8%, Cu
Is particularly preferably 0.2 to 0.4%.

As described above, the amount of the additional alloying element is limited by the fact that when the addition amount of each is less than the lower limit amount, the blade portion is flame-quenched to form the blade portion. As a result, a sufficiently hardened structure up to the required hardness cannot be obtained,
On the other hand, if the amount used is more than the upper limit, the toughness may decrease and the blade may cause spillage during use of the die.

Next, an example of the method for manufacturing a mold of the present invention will be described with reference to FIG. 1. In the figure, reference numeral 1 is a casting mold, which is made of expanded polystyrene in a required shape by a full molding method. Reference numeral 2 is a portion that constitutes a cutting blade portion or a bending blade portion of the mold 1 (hereinafter, this is referred to as a cutting blade portion), and 3 is a suction tube. The suction tube 3 is arranged along the cutting edge portion constituting portion 2 of the mold 1, and the suction hole 4 of about 2 to 3 mmφ is provided on the surface corresponding to the cutting blade portion constituting portion 2 in an amount of about 50.
A plurality of holes are drilled at mm intervals. The other end of the suction pipe 3 is drawn out of the casting frame 5 and connected to the blower 6. 7 is foundry sand.

As shown in this figure, the present invention is directed to a casting flask 5
A suction hole 4 is bored on the side of the suction pipe 3 arranged along the cutting edge forming portion 2 of the mold 1 corresponding to the cutting blade forming portion 2, and the other end is connected to the blower 6 outside the casting frame 5. By configuring the cooling means as described above, when the molten metal of the spheroidal graphite cast iron material having the above-described chemical composition is cast into the mold 1,
At the same time, air suction from the blower sucks heat at the time of casting only in the portion corresponding to the cutting blade portion constituting portion 2 to promote cooling of the portion, and the metal structure at the time of as-casting of the cast die is cut into the cutting blade portion. It is possible to form a fine pearlite structure having a pearlite area ratio of 85 to 95% and a ferrite area ratio of 5 to 15% only in the base of (3), which enables sufficient flame hardening of the cutting edge portion and has a tough blade portion. Can be formed.

In the above, the pearlite area ratio is 85 to 95% and the ferrite area ratio is 5 to 15% in order to obtain a fine pearlite structure in the as-cast structure of the cutting edge base of the cast mold. When the pearlite area ratio is large, the hardness is large, but the toughness is poor, and when the ferrite area ratio is out of the above range, the hardness is poor, so that the toughness and hardness are balanced as a cutting edge base.

The cooling means using the suction pipe connected to the blower may be a water cooling pipe system or a cooling system.

[0018]

Next, the present invention will be described in detail with reference to examples. Spheroidal graphite cast iron materials A to C having the respective chemical compositions shown in Table 1 below were used as samples. Samples A and B are cast iron material compositions used in the present invention, and sample C is a conventional cast iron material composition.

Samples A and B in Table 1 were melted in a 500 kg high-frequency induction electric furnace, and then corresponded to the constituent parts of the cutting blade along the constituent parts of the cutting mold formed by the full molding method. The molten metal is cast at 1300 to 1400 ° C. into the mold having the configuration shown in FIG. 1 in which a suction hole is provided on the side where the suction hole is provided and the suction pipe connected to the blower at the other end is connected to the blower. Casting was performed while sucking heat at the time of pouring only in the vicinity of the cutting edge portion constituent portion by suction. Then, after leaving it for 24 hours, the frame is removed, sand is removed by shot blasting, etc., and 500 mm × 500 mm × 2
A 00 mm t-shaped test material was obtained.

For sample C in Table 1, a sand mold according to a normal full molding method without a suction tube as shown in FIG. 1 was used, and 500 mm × 500 mm × 20 mm was obtained in the same manner.
A 0 mm square-shaped test material was obtained.

[0021]

[Table 1]

500 mm × 500 mm × 20 obtained above
The following test was performed using a 0 mmt box-shaped test material.

(1) Microscopic test: 2-3% nitric acid alcohol solution was dropped onto the mirror-finished surface of a test piece of the required size, which was cut out from each of the as-cast sample materials obtained from samples A and C. After corroding the surface to be mirrored, washing with water and drying was used as a microscopic test piece, and the metal structure of each test piece was observed with a metal microscope at a resolution of 100 times.

As a result, in addition to the addition of Mo and Ni as the spheroidal graphite cast iron material composition, the test piece A of the present invention is fine in size because it accelerates the cooling of the portion corresponding to the cutting edge portion during casting. Dense pearlite structure (perlite area ratio 9
2%), the fine pearlite structure surrounds the periphery of the spherical graphite particles, as is apparent from the metal structure of the micrograph of FIG. 2, showing that it is easy to obtain a quenched structure by flame quenching. There is.

On the other hand, the test piece C made of the conventional spheroidal graphite cast iron material to which Mo, Ni, etc. are not added is shown in FIG.
As is clear from the metallographic structure of the micrograph, the ferrite structure (white part) surrounds the spherical graphite particles,
Since the pearlite structure exists on the outside, it is difficult to obtain a uniform hardened structure even if flame hardening is performed due to the ferrite structure around the spheroidal graphite, and therefore it is easy to cause uneven hardness. There is.

(2) Flame quenching test: Using the as-cast sample materials A, B, and C obtained above, the peripheral edges of the upper surfaces of the test materials were 950 to 1000 ° C. × 2 to 950 ° C. with an oxygen-acetylene burner.
Flame quenching was performed in which the material was rapidly heated for 3 minutes and immediately air-cooled. After that, the hardness of this hardened portion was measured at a plurality of locations with an echo tip hardness tester (an improved version of the D type Shore hardness tester). The measurement results are shown in Table 2 after converting the maximum value, the minimum value and the average value into Rockwell C hardness by a hardness conversion reference table. For comparison, the hardness of each sample in the as-cast state before flame quenching is also shown in Table 2.
Further, the states of the metal structures of the test materials A and C after flame quenching are shown in FIGS.

[0027]

[Table 2]

As shown in Table 2, the samples A and B of this example had a small maximum and minimum width at several points, and the flame-hardened portion was almost uniform and had a good hardness. In contrast, the sample of Conventional Example C had a large variation in hardness.

Further, the test materials A and C after flame quenching
Looking at the metallographic structure of Sample A, the test material A according to this example has a specific chemical composition of Mo, Ni and / or Cu added to the conventional chemical composition as spheroidal graphite cast iron, and the vicinity of the cutting edge portion during casting. It was confirmed that the pearlite around the spheroidal graphite was changed to martensite as shown in Fig. 4 by promoting the cooling of No. 1 to make the structure of the cutting edge portion into a fine pearlite structure, and flame quenching was sufficient. Shows that it was done to.

On the other hand, in the case of the test material C, as shown in FIG.
As described above, the ferrite structure and the pearlite structure are mixedly distributed around the spheroidal graphite, indicating that the flame quenching is not sufficient.

[0031]

As described above, according to the present invention, a spheroidal graphite cast iron material having a specified chemical component is used to form a cutting edge portion or a bending edge portion in a sand mold that can be integrally cast with the main body. When integrally casting a die including a cutting blade portion or a bending blade portion, a plurality of suction holes having a required diameter are formed at required intervals on the surface of the cutting blade portion or the bending blade portion of the sand mold as described in claim. The perforated suction pipe is arranged so that the suction hole corresponds to the cutting blade portion or the bending blade portion, and the suction pipe is provided with a cooling means having a structure in which one end of the suction pipe drawn out is connected to a blower. When casting the molten metal of the above materials into the mold, when the molten metal is cast, the heat of the part corresponding to the cutting edge part or the bending blade part of the mold is quickly absorbed by the suction of the blower at the same time as the casting of the molten metal. To accelerate the cooling of the part and reduce the mold base of the part. By having a pearlite structure, it is possible to sufficiently flame quench the cutting edge portion or the bending blade portion in the as-cast state of the obtained cast product, and it is possible to make the blade portion excellent in toughness and hardness, Since it is possible to obtain a pressing die in which a blade part is integrally provided on the die body, as in the case of a conventional pressing die, the die body and the cutting edge part are made separately and attached with bolts or the like. It is possible to significantly reduce the man-hours and labor required for the integration into a single unit, which greatly contributes to cost reduction.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a configuration of a mold used for mold casting of the present invention.

FIG. 2 is a micrograph showing an as-cast metal structure of a sample cast by the method of the present invention.

FIG. 3 is a micrograph showing an as-cast metal structure of a sample cast by a conventional method.

FIG. 4 is a micrograph showing a metal structure of a sample cast by the method of the present invention after flame quenching in an as-cast state.

FIG. 5 is a micrograph showing a metal structure of a sample cast by a conventional method after flame quenching in an as-cast state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Components of cutting edge of mold 3 Suction tube 4 Suction hole 5 Casting frame 6 Blower 7 Foundry sand

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Takashima 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Eiji Nakade 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Hisao Wake 3-12 Kanbei-cho, Otsu-ku, Himeji-shi, Hyogo Nijigi Co., Ltd. Himeji Higashi Plant (72) Inventor Tomonori Matsumoto 3-12 Kanbei-cho, Otsu-ku, Himeji-shi, Hyogo Nijigi Co., Ltd. Inside the Himeji East Factory (72) Inventor Keiji Shirayama 3-12 Kanbei-cho, Otsu-ku, Himeji City, Hyogo Prefecture Inside the Himeji East Factory

Claims (4)

[Claims] 1. The cutting blade portion or the bending blade portion is provided on the surface side of the cutting blade portion or the bending blade portion of a sand mold that is molded so that the cutting blade portion or the bending blade portion can be integrally cast with the main body. In a mold having a cooling means arranged in the
3.0-4.0%, Si 1.4-3.0%, Mn
0.1-2.0%, Mg 0.03-0.1%, the balance Fe, and Mo 0.1-0.5%,
Ni 0.1-2.0% and / or Cu 0.1-
When casting a die by pouring a spheroidal graphite cast iron melt having a component added at 2.0%, the cooling of the portion corresponding to the cutting edge portion or the bending blade portion of the above-mentioned mold is promoted, and the die base of the portion is formed. A method for manufacturing an integral die for press molding, comprising forming a fine pearlite structure, and then subjecting the portion to surface hardening and quenching in the as-cast state to form a blade portion. 2. In the die casting, the cooling means arranges a suction pipe having a plurality of suction holes of a required diameter perforated at a required interval so that the suction holes correspond to the cutting edge portion or the bending blade portion. , A structure in which one end of the suction pipe pulled out to the outside of the casting frame is connected to a blower to promote cooling of the portion corresponding to the cutting blade portion or the bending blade portion of the mold, and suction by the blower at the same time as casting the molten metal. The method for manufacturing an integral mold for press molding according to claim 1, which is performed by cooling. 3. The press-molding integrated body according to claim 1, wherein the surface hardening quenching performed in the as-cast state after suction cooling on the portion corresponding to the cutting edge portion or the bending blade portion of the mold is flame quenching. Mold manufacturing method. 4. A pearlite area ratio of 85 to 95 is obtained by sucking and cooling a portion of the mold corresponding to the cutting blade portion or the bending blade portion to form a die base of the cutting blade portion or the bending blade portion in an as-cast state.
%, And a fine pearlite structure having a ferrite area ratio of 5 to 15%. 2. The method for manufacturing an integral mold for press molding according to claim 1, wherein