JPH06328155A - Press forming method for magnesium sheet - Google Patents

Abstract

PURPOSE:To make possible a press forming at a high temperature by making a die temperature a specific temperature or below from the room temperature, and performing a press forming by laying 'Teflon(R)' sheets as a heat insulating material on the upper and the lower surfaces of a sheet metal in working a magnesium sheet metal heated in a specific temperature range. CONSTITUTION:The temperature controller 5 of a punch 1, a thermocouple detecting the temperature of the shoulder part of the punch, a thermocouple 9 detecting the temperature of a flange part, a temperature controller 8 of the flange part, and insert heater 7, 10, are provided. When performing a press forming of a magnesium sheet metal 4 heated to a temperature between >=200 deg.C and <=500 deg.C, a die temperature is increased to <=180 deg.C from the room temperature, and 'Teflon(R)' sheets 12 as a heat insulating material, are laid on the upper and the lower surfaces of this sheet metal 4 to perform a press forming. Consequently, a press forming is performed at a high temperature actually necessary for working the magnesium sheet metal, and it enables the aptitude confirmation investigation of the die for a trial manufacture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forming method for performing press forming such as deep drawing forming, bending forming, or stretch forming of a magnesium thin plate, and in particular, performs full-scale mass production by press forming of a magnesium thin plate. Prior to the above, the present invention relates to a trial press-molding method in which a low-melting metal is usually used to perform trial press-molding using an inexpensive and simple trial-production die.

[0002]

2. Description of the Related Art Parts used for electric appliances, furniture, automobiles and the like are manufactured by press forming thin steel sheets. However, reducing the emission of carbon dioxide has become an important issue due to global environmental problems in recent years, and the need to reduce the weight of automobiles has been particularly emphasized. There is a debate about how to achieve stepwise. From the viewpoint of achieving such a significant reduction in the weight of automobiles, in addition to the use of steel materials, the application of light metal materials such as aluminum and magnesium is becoming more active.

In the production of automobile parts, these light metal materials are mainly cast products, and forged products have been used in part. However, in order to use light metal materials for further weight reduction, it is necessary to change press-formed products such as automobile outer panels and interior parts from the conventional steel products of thin steel plates to the use of light metal materials. become. For example, with respect to aluminum, considerable consideration is being made, such as the publication of a number of papers on "Aluminum materials for automobile weight reduction and their processing technology" at the 137th Plastic Working Symposium (September 1991).

The inventors of the present invention have heretofore investigated the molding technique utilizing temperature and its effect. That is, the present invention relates to press forming of a material mainly composed of a thin steel plate, but in Japanese Patent Application No. 62-230548, as a method for forming a laminated plate of a synthetic resin and a metal, the elongation of the synthetic resin exceeds the elongation of the metal. The molding at a temperature of -30 ° C to 0 ° C is described. Further, in Japanese Patent Application No. 1-292279, as a deep drawing method for cooling a part of the punch, in a deep drawing in a transfer press, a method of cooling a punch head from which the punch head is easily broken from the inside of the punch is formed. Is disclosed.

On the other hand, regarding the press forming of a magnesium thin plate, there is almost no thin plate production activity itself in Japan, and a basic study centered on the United States is accepted. Conventionally, in press forming of a magnesium thin plate,
It is known that the temperature of the plate is usually required to be about 220 ° C. or higher, and in full-scale production by press molding, the mold temperature is raised by embedding an electric heater in the inside, etc. It is considered necessary to heat the thin plate for implementation. Generally, for press forming of thin steel sheet, when industrially mass producing, a low melting point metal (for example, Al 3.9%,
Cu 1.0%, Mg 0.04%, balance Zn, etc.) is used to make an inexpensive and simple prototype die and press-mold it on a trial basis. It is necessary to repeat the trial manufacture test to confirm that

Therefore, regarding the press forming of a magnesium thin plate which has not been well known in the past, in the case of industrial mass production, a trial mold is prepared in the same manner as the press forming of a thin steel plate. Perform press molding on a trial basis,
It is necessary to repeat the trial test to confirm whether the product shape is the exact size as intended. However, in the trial press molding using the above-mentioned low melting point metal trial mold, since the melting point of the mold is as low as about 250 to 400 ° C., the strength of the mold at high temperature is low, and the mold itself is It was not possible to perform press molding with heating and applying a large force.

For this reason, conventionally, although it is a test mold, an expensive steel mold is prepared, and the mold temperature is raised by the method as described above to raise the temperature of the magnesium thin plate to 220. We have adopted the method of press-forming as a trial production at a temperature above ℃. In such a case, since a trial production is repeated, an expensive trial production cost is required, and a large amount of expense is required until an industrial condition for mass production is found.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, the temperature of a magnesium thin plate is set to 220 ° C. or higher when performing the trial press forming of a magnesium thin plate by using an inexpensive and simple prototype die made of a metal having a low melting point. It is also an object of the present invention to provide a method for performing press molding while keeping the temperature of the mold at a low temperature of about room temperature.

[0009]

The gist of the present invention is 200
When press-forming a magnesium thin plate heated to a temperature range of ℃ or more and 500 ° C or less, the temperature of the punch and the flange is heated from room temperature to 180 ° C or less,
A press forming method for a magnesium thin plate, characterized in that a Teflon sheet as a heat insulating material is installed on the upper and lower surfaces of the magnesium thin plate and press forming is performed.

The present invention will be described in detail below. First, the rectangular tube deep-drawing forming, which is the basic shape of press forming, will be described. In FIG. 1, 1 is a punch, 2 is a die, 3 is a blank holder, 4 is a material to be molded with Teflon film 12 as an insulating material on the upper and lower surfaces, 5 is a temperature control device for the punch, and 6 is the surface of the punch shoulder. A thermocouple for detecting the temperature in the vicinity, 7 is an insert heater installed inside the punch,
8 is a temperature control device for the flange portion, 9 is a thermocouple for detecting the temperature in the vicinity of the die shoulder as a representative temperature of the flange portion, 10
Is an insert heater installed inside the die and the blank holder, and 11 is a heat insulating material. 5, 7, 8 and 1
If the temperature controller and insert heater of 0 are not used, it is the same as molding at room temperature in a normal press (hereinafter referred to as room temperature molding). Was broken and could not be molded. Generally, in the press forming of a magnesium thin plate, for example, it is necessary to put the thin plate in a state where the mold is heated in advance and heat the plate by bringing it into contact with the mold to perform press forming at a high temperature. Yes,
As described above, the temperature at which press molding is possible is 220 ° C.
That is all.

According to the apparatus shown in FIG. 1, the mold can be heated and high-temperature press molding of a magnesium thin plate can be performed. However, the object of the present invention is to "make a prototype mold using a metal having a low melting point". In “test press molding”, since the melting point of the mold is as low as about 250 to 400 ° C., the strength of the mold at high temperature is low, and it is not possible to heat the mold itself and perform press molding with a large force. Absent. Therefore, the mold temperature is preferably room temperature, and it is necessary to keep the temperature at most 180 ° C. even when heated.

For this reason, the present inventors installed a Teflon sheet as a heat insulating material on both sides of the punch and die such that the upper and lower surfaces of the magnesium thin plate were sandwiched by the Teflon sheet during press molding. After insulating the punch and die from the upper and lower surfaces of the magnesium thin plate,
Using a furnace that heats the plate, heat the magnesium sheet,
By carrying out all the steps of taking out the thin plate from the heating furnace and placing it on a die and press-molding with a punch in a short time of about several seconds to 7 seconds, a warm press of a magnesium thin plate is performed without heating the punch and the die. Depending on the method used, high temperature press molding of the thin plate is possible. The Teflon sheet is normally disposable. The Teflon sheet may have a thickness of about 0.5 to several mm, two or three sheets may be used depending on the case, and it may be experimentally examined and used. Generally, it is said that most of automobile parts can be molded if the limit drawing ratio is 2.0 or more, and it is possible to sufficiently check the suitability of the prototype mold by the above method. The purpose is achieved.

Here, the reason why the magnesium thin plate is set to 220 ° C. or higher is to enable press forming.
The reason why the temperature is 0 ° C. or lower is that the thin plate may be ignited. The reason for setting the temperature of the punch and the flange to a temperature of 180 ° C. or lower by heating from normal temperature to 180 ° C. is that the prototype die is usually made of a low melting point alloy and cannot be heated to a high temperature. is there.

[0014]

EXAMPLES Next, the present invention will be specifically described based on examples. Table 1 shows the chemical composition, the plate thickness, and the mechanical properties at room temperature of the material subjected to deep drawing of the rectangular tube by the apparatus shown in FIG. Table 2 shows the test results of the press formability of Examples and Comparative Examples. The shape and dimensions of the mold used in this test are as follows. That is,
Punch 75 mm square, punch shoulder radius 5 mm die 80 mm square, die shoulder radius 5 mm corner radius 8 mm.

[0015]

[Table 1]

[0016]

[Table 2]

Example 1 Using a Zn alloy mold, press molding was carried out at a mold temperature of 28 ° C. The magnesium thin plate was heated to 250 ° C., inserted into a mold equipped with a Teflon sheet within 3 seconds, and press-molded. As a result, the limit aperture ratio is
It was 1.5.

Example 2 Using a Zn alloy mold, press molding was carried out at a mold temperature of 28 ° C. Magnesium sheet at 300 ℃
It was heated to, and inserted into a mold equipped with a Teflon sheet within 3 seconds to perform press molding. As a result, the limiting aperture ratio was 1.8.

Example 3 Using a Zn alloy mold, press molding was carried out at a mold temperature of 28 ° C. 350 ° C for magnesium sheet
It was heated to, and inserted into a mold equipped with a Teflon sheet within 3 seconds to perform press molding. As a result, the limiting aperture ratio was 2.2.

Example 4 Using a Zn alloy mold, press molding was carried out by heating the mold temperature to 150 ° C. 35 sheets of magnesium sheet
It was heated to 0 ° C., inserted into a mold equipped with a Teflon sheet within 3 seconds, and press-molded. As a result, the limiting aperture ratio was 2.4.

Comparative Example 1 Using a steel mold, press molding was carried out at a mold temperature of 28 ° C. 28 without heating magnesium sheet
It was inserted into a mold without a Teflon sheet at 0 ° C. and press-molded. As a result, even if the blank size was reduced, the plate was broken from the punch corner portion, and press molding could not be performed. The limit aperture ratio is 1.4
It was below.

Comparative Example 2 Using a Zn alloy mold, press molding was carried out at a mold temperature of 28 ° C. The magnesium thin plate was inserted into a mold equipped with a Teflon sheet at 28 ° C. without heating and press-molded. As a result, even if the blank size was reduced, the plate was broken from the punch corner portion, and press molding could not be performed. The limit aperture ratio is 1.4
It was below.

Comparative Example 3 Using a steel mold, press molding was carried out at a mold temperature of 250 ° C. The magnesium thin plate was sandwiched in a mold without heating and without a Teflon sheet, and the thin plate was heated by contact with the mold to perform press molding. As a result, the limit drawing ratio was 2.2, and press molding was sufficiently possible, but the target mold temperature was 18
Below 0 ° C has not been achieved.

Comparative Example 4 Using a steel mold, press molding was carried out at a mold temperature of 100 ° C. The magnesium thin plate was sandwiched in a mold without heating and without a Teflon sheet, and the thin plate was heated by contact with the mold to perform press molding. As a result, the limit drawing ratio was 1.4 or less, and the plate was broken from the punch corner portion, and press molding could not be performed.

The Teflon sheet used in this test had a thickness of 1.5 mm, and two sheets were stacked and placed on the entire die, and two sheets were stacked to cover the entire punch. As a result, heat insulation is achieved in the press for a few seconds. With this heat insulation, the temperature during press molding of the magnesium thin plate was secured at 180 ° C. or higher, and press molding became possible.

[0026]

As described above, according to the present invention, in the press forming of a magnesium thin plate in which the thin plate temperature is required to be a high temperature of 220 ° C. or more, the die is formed by a trial press forming using a trial die. Use a Teflon sheet for heat insulation in the case of a low melting point mold having a melting point of about 250 to 400 ° C., and when the mold itself cannot be heated to perform press molding with a large force. By doing so, it is possible to actually perform press forming at a high temperature necessary for a magnesium thin plate, and it becomes possible to conduct a suitability confirmation investigation of a prototype die.

[Brief description of drawings]

FIG. 1 is a sectional pattern diagram of a mold used in an example of the present invention.

[Explanation of symbols]

1 punch 2 die 3 blank holder 4 material to be molded 5 temperature control device for punch 6 thermocouple for detecting temperature near surface of shoulder of punch 7 insert heater installed inside punch 8 temperature control device for flange 9 die Thermocouple for detecting temperature near shoulders 10 Insert heater installed inside die and blank holder 11 Insulation material 12 Magnesium thin plate 13 Thermocouple

Continuation of front page (72) Inventor Tomohisa Katayama 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (1)

[Claims] 1. When press-molding a magnesium thin plate heated to a temperature of 200 ° C. or more and 500 ° C. or less, the temperature of the punch and the flange is heated from room temperature to 180 ° C. or less, and a Teflon sheet is used as a heat insulating material. A press forming method for a magnesium thin plate, characterized by being installed on the upper and lower surfaces of the thin plate and performing press forming.