JPH06154991A - Method for squeezing molten complex metal - Google Patents

Abstract

PURPOSE:To enable high precise formation by inserting a metal body having shorter height than a hollow body in the hollow body beforehand formed into simpler shape than a product shape, heating the hollow body after drawing the hollow part and pressurize-forming in the die. CONSTITUTION:In the hollow body 1 having <=0.2 ratio of thickness/outermost diameter, the metal body 2 having the m.p. lower than m.p. of the steel material of the hollow body by 50 deg.C as the upper limit and the height shorter than the hollow body, is inserted. The part 3 of the hollow body is drawn. Successively, these materials are heated by high frequency induction in non-oxidizing atmosphere in the high frequency induction heating coil 4 to the higher temp. either of the liquidus temp. -45 deg.C of the metal body or 500 deg.C as the lower limit, and only the inserted metal body is semi-melted or melted and the hollow body is kept to the shape. Successively, by using a die 5 and punch 6 preheated to >=300 deg.C by heating device 7, the pressurize-forming is executed. By this the formation of the product having different materials between the outer surface and the inner part can easily be executed with high die service life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal forging method, and more particularly to a working method for mass production such as manufacturing parts for automobiles, industrial machines and the like.

[0002]

2. Description of the Related Art The molten metal forging method is a technique for producing mechanical parts directly from molten metal, and its application is expanding mainly to the production of automobile parts. This technique has advantages in that the microscopic structure is finer than that in the conventional method, so that the mechanical performance is excellent, voids are not formed inside, and the outer diameter accuracy is high. At present, it is mainly applied to the parts of the undercarriage such as wheels of automobile parts, and also to pistons as described in Kobe Steel Technical Report Vol. 21, No. 3, 57. However, in the molten metal forging method, since molten metal is directly injected into the mold, it causes fusion to the mold, resulting in problems of product release and mold life. To solve this, JP-A-53-13
Japanese Patent No. 0229 discloses a method of injecting a molten metal into a hollow metal body and thereafter performing pressure molding. In addition, the present inventors in Japanese Patent Application No. 03-140275,
We proposed a method for forging a molten metal in which a metal body having a melting point lower than that of the hollow body is inserted into a hollow body made of steel, and these are heated to melt only the metal body.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method disclosed in Japanese Patent No. 29 has a problem that since the metal hollow body remains cold, the formability during processing is poor and it is difficult to form a complex-shaped part, which is an advantage of molten metal forging. . This is particularly noticeable when a hollow body made of steel is used, and the applicable component shapes are limited. Further, since the molten metal is injected into the hollow body, there is a problem that it is difficult to control the amount of the molten metal to be injected and the weight variation of the product is large, and the molten metal injection nozzle needs to be replaced frequently. . Japanese Patent Application No. 03-1402
According to the method described in Japanese Patent No. 75, the hollow body is also heated, so that the deformation resistance can be reduced, and it becomes possible to mold a part having a complicated shape as compared with the method disclosed in Japanese Patent Laid-Open No. 53-130229. Further, since the metal body is not poured as a molten metal, there is little variation in weight and the problem with the injection nozzle is solved.

However, in both the inventions described in Japanese Patent Application Laid-Open No. 53-130229 and Japanese Patent Application No. 03-140275, the metal body is not covered with the hollow body on the punch side, which is a metal mold, and is melted in the punch. Since the metal body is welded, product detachment and punch life are problems. Further, in these inventions, it is impossible to process a product which requires covering the entire surface of the metal body with a hollow body.

In order to solve the above-mentioned problems, the present invention is capable of forming a highly precise part having a good formability during processing and having a complicated shape, and a metal body having a high moldability without being welded to the mold. Provided is a composite molten metal forging method that realizes die life and punch life.

[0006]

In order to solve the above problems, the present invention uses a hollow body having a height higher than that of a metal body, and draws a hollow body portion not filled with the metal body. As a result, the metal body is covered with the hollow body portion that has been drawn during the pressure molding, and the molding of a complex shaped part is realized without melting the metal body in the punch. That is, the gist of the present invention is 0.1% or more by weight%,
Using a steel material containing less than 1% of carbon, a hollow body that is previously formed into a simpler shape than the product shape and has a wall thickness / outermost diameter ratio of 0.2 or less and a melting point of 500 ° C or more. After the upper limit is 50 ° C. below the melting point of the steel material of the hollow body, the height of the metal body is lower than that of the hollow body, and the hollow body portion not filled with the metal body is subjected to forging such as drawing. A liquidus temperature of -45 ° C in an equilibrium diagram of the metal body at an average heating rate of the hollow body of 5 ° C / sec or more and 20 ° C / sec or less in a non-oxidizing atmosphere. It is heated by high frequency with 500 ℃ whichever is higher as the lower limit, and while the inserted metal body is in a molten or semi-molten state, it is pressurized in a mold preheated to 300 ℃ or more in advance and integrated with molding. This is a composite molten metal forging method.

Here, the melting point refers to the liquidus temperature in the equilibrium diagram for both metal and hollow steel materials.

[0008]

FIG. 1 shows one embodiment of the molten metal forging method according to the present invention. As shown in FIG. 1 (a), a hollow body 1 made of a steel material formed into a shape simpler than the product shape and having a wall thickness / outermost diameter ratio within 0.2 has a melting point of a hollow steel body. The metal body 2 whose upper limit is 50 ° C. below the melting point and whose height is lower than that of the hollow body is inserted in advance. Then, as shown in FIG. 1B, the hollow body portion 3 not filled with the metal body is drawn. At this time, a part of the metal may be processed if it does not affect the subsequent forging. In addition, after drawing,
As shown in (b '), compression processing may be applied until the hollow body portion 3 comes into contact with the upper end surface of the metal body, which results in a product in which the entire metal body is covered with the hollow body material in the molding of cup-shaped parts. Molding becomes possible. After that, as shown in FIG. 1 (c), these are inserted in the high-frequency heating coil 4 by heating them with the liquidus temperature in the equilibrium diagram of the metal body being −45 ° C. or 500 ° C., whichever is higher, as the lower limit. Only the formed metal body is semi-melted or melted and the hollow body can retain its shape. After heating, as shown in FIG.
A product can be obtained by press-molding these using the die 5 and the punch 6 preheated to 300 ° C. or more by the heating device 7.

In the present invention, compared with the invention of Japanese Patent Application No. 03-140275, since the metal body is covered with the hollow body on the punch side as well, welding of the metal body to the punch can be avoided. Further, it becomes possible to form a composite product in which the entire surface of the metal body is covered with a hollow body. When the carbon content of the steel material used for the hollow body is 0.1% or more and less than 1% by weight, it is 0.1
If it is less than 1%, the cold deformation resistance is low, so there is no effect of heating the hollow body to reduce the deformation resistance, and if it is 1% or more, the toughness becomes low and it cannot be applied to important parts such as automobiles. is there. In addition, the wall thickness / maximum diameter ratio of the hollow body is set to be within 0.2, in the case of a hollow body having a wall thickness / outermost diameter ratio exceeding this, the hollow body fills the mold during the subsequent pressure molding. This is because it is difficult and cannot be molded into a product shape. The melting point of the metal body to be inserted into the hollow body is 500 ° C. or higher because the method of the present invention requires the steel material of the hollow body to be softened, and thus the hollow body needs to be heated to 500 ° C. or higher, which is lower than this. This is because the softening of the hollow body due to heating does not occur so much at temperature. The upper limit of the melting point of the metal body to be inserted is 50 ° C. below the melting point of the steel material of the hollow body. With a metal body having a melting point higher than this, the hollow body also melts down when the metal body is semi-melted or melted, This is because the metal body may flow out. Any type of metal body may be used as long as it satisfies the condition that the melting point is 500 ° C. or higher and the melting point of the hollow steel material is −50 ° C. or lower, and examples thereof include aluminum alloy, titanium alloy, copper alloy, and steel.

The lower limit of the heating temperature of the hollow body is the liquidus temperature of −45 ° C. or 500 ° C. in the equilibrium diagram of the metal body, whichever is higher. The fluidity of the hollow body deteriorates,
This is because the moldability is reduced. At that time, the average heating rate of the hollow body is set to 5 ° C./sec or more and 20 ° C./sec or less by using a rapid heating method such as high frequency heating in a non-oxidizing atmosphere such as argon or nitrogen. This is to improve the accuracy by suppressing the oxide film formation during heating as much as possible. This is because if the average heating rate is less than 5 ° C./second, suppression of oxide film formation cannot be expected, and if the average heating rate exceeds 20 ° C./second, the internal temperature of the hollow body becomes uneven and melts down locally. Because. Further, the reason why the pressure molding is performed while the injected metal body is in a molten or semi-molten state is that if the metal body is solidified, the fluidity of the metal body deteriorates and the moldability deteriorates.
The reason why the mold is preheated to 300 ° C. or more in advance is to prevent the flowability of the hollow body from being lowered due to the temperature drop of the hollow body that comes into contact with the mold during pressure molding. Is low.

[0011]

EXAMPLES As an example of the method of the present invention, molding was carried out by the steps shown in FIG. Steel type A having the components shown in Table 1
(Thickness 2 mm, 6 mm, 8 mm, 15 mm) was used to form a cylindrical container-shaped (inner diameter φ40 mm, height 78 mm and 60 mm) hollow body, in which the metal body of steel type B having the components shown in Table 1 (outer (Diameter 39.8 mm, height 60 mm) was inserted. The hollow body portion not filled with the metal body was cold drawn and drawn at a die half angle of 20 °, and then heated to a predetermined temperature by a high frequency at a heating rate of 1 to 20 ° C / sec. Immediately after heating, these were compression-molded with a punch and a die preheated at 100 to 350 ° C. to a maximum of 20 tonf as shown in FIG.

[0012]

[Table 1]

Table 2 shows the enlargement ratio (α) of the cross-sectional area in the direction perpendicular to the material axis, the welding state of the metal body to the punch, and the oxide film thickness on the product surface after forging in the product obtained after molding. The measurement result of is shown. The area enlargement ratio and the oxide film thickness are average values of 20 forged products under each condition. The setting of the average heating rate shown in Table 2 is performed by using a sample in which a thermocouple is embedded in the surface of the hollow body and the center of the hollow body, and the average temperature of the two is set as the temperature of the hollow body, and the average heating rate of the hollow body is a predetermined value. The high frequency heating conditions were determined so that the above condition was satisfied, and heating was performed based on the conditions in the examples. The distribution of the heating temperature in the metal was within the set temperature + 10 ° C.

[0014]

[Table 2]

From Table 2, the area enlargement ratio α representing the workability is 4.0 or more in all of the methods 1 to 8 of the present invention.
In Comparative method 1 in which the wall thickness of the hollow body is large, Comparative method 3 and Comparative method 7 in which the heating temperature is low, and Comparative method 4 in which the mold preheating temperature is low, α is 3.1 or less, and the method of the present invention is used. It can be seen that higher workability can be imparted by Further, as a result of investigating whether or not the metal body was welded to the punch, the metal body was melted in the cases of Comparative methods 5 and 6 in which the height of the hollow body was the same as that of the metal body. As a result, the comparison methods 5, 6
With the method (2), the punch cannot be formed into a predetermined shape, and the punch life has been reached. Further, the oxide film thickness after forging is less than 40 μm in each of the methods of the present invention, and is 124 μm in Comparative method 2 in which the heating rate is slow,
200 μm in Comparative Method 8 in which the heating atmosphere was air.
It was over m.

According to the method 9 of the present invention in Table 2, after the hollow body was drawn in the method 6 of the present invention, the hollow body was subjected to compression processing to flatten the upper surface of the sample as shown in FIG. 1 (b ').
This is the case when heating and forging are performed thereafter. Also in this case, it was found that the area expansion ratio, the welding of the metal body to the punch, and the thickness of the oxide film of the product can be formed in the same manner as in the methods 1 to 8 of the present invention.

[0017]

EFFECTS OF THE INVENTION According to the present invention, it is possible to perform the molding of a complex-shaped part, which is a feature of molten metal forging, with high accuracy without impairing the mold forging, and to have a long mold life without the metal body welding to the mold. In addition to being processed, it becomes possible to easily form a product having different materials on the outer surface and the inner portion.

[Brief description of drawings]

FIG. 1 is a diagram showing an aspect of the present invention and a molten metal forging method used in Examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hollow body 2 ... Metal body 3 ... Drawing process part 4 ... High frequency heating coil 5 ... Mold 6 ... Punch 7 ... Mold heating device

Claims (1)

[Claims] 1. A steel material containing a carbon content of 0.1% or more and less than 1% in weight% is previously formed into a shape simpler than the product shape, and the wall thickness / outermost diameter ratio is 0. .2
A hollow body in which a metal body having a melting point of 500 ° C. or more and 50 ° C. or less below the melting point of the steel material of the hollow body, the height of which is lower than that of the hollow body, is not filled in the hollow body After performing a forging process such as drawing, the hollow body in which the metal body is inserted is heated in an non-oxidizing atmosphere at an average heating rate of 5 ° C./sec or more and 20 ° C./sec or less. The liquidus temperature in the equilibrium diagram was heated by high frequency with the higher one of -45 ° C and 500 ° C as the lower limit, and the inserted metal body was preheated to 300 ° C or higher in the molten or semi-molten state. A composite molten metal forging method characterized by pressurizing in a mold to integrally mold.