JPH04367362A - Complex molten metal forging method - Google Patents

Abstract

PURPOSE:To provide molten metal forging method, by which service life of metallic mold is drastically improved without damaging formability to parts having complicated shape and further, pouring operation of the molten metal is saved and formation of the product having different materials in outer face and inner part is easily executed. CONSTITUTION:In order to prevent direct contact between the molten metal and the metallic mold, a metal body 3 having m.p. of >=500 deg.C and the lower limit temp. of below 50 deg.C from m.p. of steel material for hollow body, is beforehand charged into the hollow body 1 formed simpler shape than product shape and these are heated with a high frequency heating coil 2 at the lower limit temp. of m.p. of the metal body for 1-5 min. These are charged into the metallic mold 4 preheated at >=300 deg.C with a heating device 7 and the metal body is pressurize-formed in the metallic mold with a punch 5 during molten or semi- molten state. At this time, thickness/the most outer diameter ratio of the hollow body is made to be <=0.15.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal forging method, and more particularly to a processing method for mass production such as the manufacture of parts for automobiles, industrial machinery, etc.

0002

BACKGROUND OF THE INVENTION Molten metal forging is a technology for directly manufacturing mechanical parts from molten metal, and its use is expanding primarily to the production of automobile parts. Compared to conventional casting methods, this technique has advantages such as superior mechanical performance due to the finer microstructure, no internal voids, and high accuracy in outer diameter. Currently, it is being applied to automobile foot parts.

0003

[Problems to be Solved by the Invention] However, in the molten metal forging method, molten metal is directly injected into the mold, which causes fusion in the mold, causing problems in product release and metal life. In order to solve this problem, Japanese Patent Application Laid-Open No. 53-13022
No. 9 discloses a method in which molten metal is injected into a hollow metal body and then pressure-formed. However, this invention had the problem that since the metal hollow body remains cold, formability during processing is poor and it is difficult to form parts with complex shapes, which is an advantage of molten metal forging. This is especially noticeable when using hollow bodies made of steel.
Applicable part shapes were limited. In addition, since the molten metal is injected into the hollow body, it is difficult to control the amount of molten metal injected, resulting in large variations in the weight of the product, and the molten metal injection nozzle becomes clogged, requiring frequent replacement. Ta.

0004

[Means for Solving the Problems] The present invention has been made in view of the current situation, and its gist is to use a steel material containing less than 2% carbon to form a shape in advance that is simpler than the product shape. After inserting a metal body with a melting point of 500°C or higher and an upper limit of 50°C below the melting point of the steel material of the hollow body into a formed hollow body whose wall thickness / outermost diameter ratio is within 0.15, is heated with high frequency for 1 to 5 minutes with the melting point of the metal body as the lower limit, and the inserted metal body is heated in a mold that has a product shape while it is molten or semi-molten and has been preheated to 300°C or higher. It is a composite molten metal forging method characterized by pressing, forming and solidifying.

[0005]

[Operation] FIG. 1 shows one embodiment of the molten metal forging method according to the present invention. In the same figure (a), the hollow body 1 is made of a steel material containing less than 2% carbon and is formed into a shape simpler than the product shape, and the wall thickness/outermost diameter ratio is within 0.15. A metal body 3 whose upper limit is 50° C. below the melting point of the hollow steel material is inserted in advance and heated within the high-frequency heating coil 2 . As a result, only the inserted metal body is melted, and the hollow body can maintain its shape. After the heating is completed, the hollow body and the molten metal body therein are inserted into the mold 4 which has been preheated to 300° C. or higher by the heating device 7, as shown in FIG. 4(b). Thereafter, by performing pressure forming using the punch 5, the hollow body and the molten metal body fill the cavity 6 and solidify, thereby completing the product 8 shown in FIG. 2(c).

In the present invention, since the molten metal is not directly injected into the mold, there is no fusion between the molten metal and the mold, and the hollow body itself is also heated. Compared to other methods, it is possible to mold parts with more complex shapes. Furthermore, there is no step of injecting molten metal, and instead a metal body with a lower melting point than the hollow body is inserted, which not only makes it easier to control the weight of the product, but also eliminates maintenance such as nozzle replacement.

The reason why the carbon content of the steel material used for the hollow body is set to less than 2% is that steel materials with a carbon content higher than this have low ductility, and the hollow body will break during pressure forming and the molten metal body will flow out. It is from. Also, the wall thickness/maximum diameter ratio of the hollow body is 0.
．． The reason for setting it within 15 is that a hollow body having a wall thickness/outermost diameter ratio exceeding this value will not easily fill the void 6 in the mold during subsequent pressure molding, and will not be able to be molded into a product shape. The reason why the melting point of the metal body inserted into the hollow body is set to 500°C or higher is that the method of the present invention requires heating the hollow body to 500°C or higher because it is necessary to soften the hollow body. This is because the hollow body does not soften much due to heating. The reason why the upper limit of the melting point of the metal body to be inserted is set to 50°C lower than the melting point of the steel material of the hollow body is because metal bodies with a higher melting point than this may melt when the hollow body is heated to a predetermined temperature. Because I don't like it. The reason why the heating temperature is set above the melting point of the metal body is that the metal body will not melt at a temperature lower than this. High-frequency heating is used to reduce skin roughness due to oxidation during heating, and at this time, heating time of 1 minute or more is required to soak the hollow body. It should be avoided from the standpoint of efficiency and prevention of oxidized scale. Note that heating in an inert gas atmosphere such as argon or nitrogen is also possible in order to prevent oxide scale. Furthermore, the reason why pressure forming is performed while the injected metal body is in a molten or semi-molten state is that once the metal body solidifies, the fluidity of the metal body deteriorates and the voids are no longer filled with the metal body. .

[0008] Also, the purpose of preheating the mold to 300°C or higher is to prevent the fluidity of the hollow body from decreasing due to the temperature drop of the hollow body during pressure molding, and the effect is low at temperatures lower than this. It is from.

[0009]

[Example] As an example of the method of the present invention, molding was carried out according to the steps shown in FIG. A hollow body 1 in the shape of a cylindrical container (outer diameter φ40 mm, height 50 mm) is formed from a plate material (thickness 2 mm) of carbon steel S10C for mechanical structures having the components shown in Table 1, and the hollow body 1 is filled with the components shown in Table 1. Hard steel wire rod SWRH8 with
After inserting the metal body 2 of 2A, high frequency heating was performed to 1500°C at a temperature increase rate of 10°C/s. The thickness/outermost diameter ratio of the hollow body at this time was 0.05, and the heating was performed in an inert gas atmosphere using argon gas. Thereafter, these were inserted into the mold 11 for 1.5 seconds, and the molten S
The shape of the mold 4, which was pressure-formed by WRH82AC at 1480°C with the punch 5, is a spur gear shape with a module of 2 mm, number of teeth: 24, pitch circle diameter of 48 mm, and tip circle diameter of 52 mm, and is preheated to 400 °C by high frequency. I kept it.

As a conventional method, hard steel wire rod SWR shown in Table 1 is used.
Conventional method 1 was defined as a case in which H82A was heated and melted at 1500°C in a high frequency furnace, poured into the mold 4 as it was without using a hollow body, and then pressure-molded at 1480°C. Japanese Patent Publication No. 53-130
Following the description in Publication No. 229, a cylindrical container-shaped hollow body of S10C, which is the same as the method of the present invention, was inserted into the mold 4 without heating, and the components shown in Table 1 were heated and melted at 1500°C in a high frequency furnace. After injecting the hard steel wire rod SWRH82A with
Pressure molding was carried out at 480°C. This is referred to as conventional method 2. In both methods, pressure molding was performed at a set load of 350 tons, and in Conventional Method 1 and Conventional Method 2, no mold preheating was performed.

Table 2 shows the product shape as the residual porosity, which is the value obtained by dividing the void between the mold and the product after molding by the void between the mold and the product before molding, and conventional method 1, conventional method 2, and the present method. The invention method was shown. The table also shows the number of products manufactured with one mold as the mold life. As shown in the same table, the residual porosity was as high as 29% in conventional method 2, and it was not possible to form the gear into the desired gear shape. Therefore, the mold life was 0. The residual porosity was 0.3% and 0.6% in the conventional method 1 and the method of the present invention, respectively, and it was possible to form the gear into the predetermined gear shape. However, while conventional method 1 had a mold life of 52 molds, the method of the present invention had a mold life of 1265, an improvement of more than 20 times.

0012

[Table 1]

[0013]

[Table 2]

[0014]

[Effect of the invention] By using the present invention, the life of the mold can be dramatically improved without impairing the formability of complex-shaped parts, which is a feature of molten metal forging, and the molding of products with different materials on the outside and inside can be made. can be easily carried out.

[Brief explanation of drawings]

FIG. 1 is a diagram showing aspects of the present invention and a molten metal forging method used in examples of the present invention.

[Explanation of symbols]

1 Hollow body 2 High frequency heating coil 3 Metal body 4 Mold 5 Punch 6 Void area before pressure molding 7 Mold heating device 8. Product

Claims (1)

[Claims] [Claim 1] Pre-formed into a simpler shape than the product shape using a steel material containing less than 2% carbon content,
and inside the hollow body whose wall thickness/outermost diameter ratio is within 0.15,
After inserting a metal body with a melting point of 500℃ or higher and an upper limit of 50℃ lower than the melting point of the hollow steel material, these are heated with high frequency for 1 to 5 minutes with the melting point of the metal body as the lower limit, and the inserted metal body is melted. Alternatively, a composite molten metal forging method is characterized in that it has a product shape in a semi-molten state and is pressurized in a mold preheated to 300° C. or higher to form an integral part and solidify.