JPH0687029A - Forming method excellent in deep drawing performance - Google Patents

Abstract

PURPOSE:To provide a forming method excellent in deep drawing performance for manufacturing a deep drawn article easily and stably when a deep drawn part used in an automobile, a furniture, an electrical appliance, etc., are formed by a press. CONSTITUTION:The temperature of the punch shoulder part of a press die is set at >=-10 deg.C <=20 deg.C, the temperature of one of the die or the blank holder is raised up so as to be 20 deg.C higher than the temperature of the shoulder part of the punch and when the highest temperatures of the die and the blank holder part are <=40 deg.C and <=100mum nonmetallic material is stuck on lubricant coated on the surface of a cold rolled steel plate, deep drawing can be performed easily and stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for press-molding deep-drawn parts used in automobiles, furniture, home appliances and the like.

[0002]

2. Description of the Related Art Conventionally, in forming deep drawing parts such as oil pans for automobiles, bathtubs and sinks for furniture, and cartridge tanks for petroleum stoves for home appliances,
It is known that as the amount of processing increases, the temperature of the deep-drawing parts rises due to the heat generation of the processing, and the temperature of the press die also rises due to the propagation of the heat generation of the processing.

From the viewpoint of moldability, this temperature rise is
Conventionally, even if a hydraulic press is mainly used and a mechanical press is used, the number of moldings per unit time is relatively small, and the problem in molding due to the rise of the mold temperature has been rarely noticed.

However, since the transfer press has become widespread in recent years and has come to be applied to the molding of such deep-drawn parts as well, the rise of the mold temperature becomes extremely large and the problem of the deterioration of the moldability begins to become apparent. . Therefore, various measures have been taken against deterioration of formability due to an increase in mold temperature.

For example, a method of applying a water-soluble cooling oil to the entire mold is effective for moldability, but there is a problem that the cooling oil is scattered around at the time of pressing and the working environment is deteriorated, and the extreme pressure additive is used. Although the use of the lubricant containing is effective for moldability,
The cost of degreasing after molding increases, and the method of increasing the number of drawing steps to reduce deformation heat generation is effective for moldability, but there are problems such as increase in manufacturing cost due to increase in the number of molds. However, the reality is that the measures are not necessarily satisfactory.

As a prior art related to the present invention, there is Japanese Patent Laid-Open No. 3-155420, which cools a punch die in order to improve drawability, and when the forming speed is high. Cooling the punch die alone is not sufficient, and the effect of improving deep drawability is small.

[0007]

In the conventional forming method, when a deep-drawn part is formed, the temperature of the part and the die rises due to the heat generated during processing, and the rise in temperature causes a decrease in the proof stress of the steel sheet and a deterioration in the performance of the lubricant. As a result, there is a big problem that defective molding occurs.

It is an object of the present invention to provide a forming method excellent in deep drawability for stably forming a deep drawn part by a hydraulic press, a tandem type mechanical press and a transfer press.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is +20 at a punch shoulder temperature of -10 ° C. or higher in press molding.
Within the range of ℃ or less, the temperature of either one of the die part and the plate pressing part is higher than the punch shoulder temperature by 20 ° C or more, and the maximum temperature of the die part and the plate pressing part is within 40 ° C. A forming method with excellent deep drawability, characterized in that a rust preventive oil or a press oil is applied to one surface or both surfaces of a steel sheet, and a nonmetallic substance having a thickness of 100 μm or less is applied onto the one surface or both surfaces. .

[0010]

The details of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a situation where an oil pan is molded according to the present invention. Fig. 2 shows a dangerous part 1 where breakage is likely to occur during the molding of an automobile oil pan, which is a typical drawing component.
Is shown. In the oil pan shown in FIG.
Consider the occurrence of breakage risk area 1.

Generally, the conditions for forming by deep drawing are as follows:
The fracture strength of the material in the fracture risk area 1 in FIG.
This is the case when it exceeds the diaphragm resistance of. However, as the number of moldings increases, the molding state at the initial stage of molding changes, which causes the breakage risk region 1.

The first cause is that, when the number of moldings increases, the mold temperature rises, the performance of the lubricant deteriorates, the friction resistance of the flange portion increases, the drawing resistance increases, and the drawing resistance breaks. Since the breaking strength of the material of the dangerous portion 1 approaches, the breaking dangerous portion 1 occurs.

The second factor is that the temperature of the material at the risk of breakage area 1 rises as the mold temperature rises, and the tensile strength of the material decreases, so the fracture strength of the danger of fracture area 1 itself. As a result, the fracture risk part 1 is generated.

As a countermeasure against these state changes, as described in the prior art, for example, an extreme pressure additive is used for a lubricant to prevent an increase in friction resistance, and a decrease in tensile strength may result in a risk of fracture. Cooling the mold in contact with the part 1 to prevent the tensile strength from decreasing, and so on.

However, in the situation where transfer presses have become widespread in recent years and at the same time the molding speed has increased, the measures taken so far have been ineffective and insufficient. The most remarkable one is cooling of the mold in contact with the fracture risk region 1, and the effect is reduced as the molding speed and the number of moldings are increased.

The present invention focuses on this method of preventing an increase in frictional resistance, and as shown in FIG. 1, in order to eliminate the occurrence of the fracture risk part 1 even if the forming speed and the forming quantity are increased, the steel sheet is By sticking a non-metallic substance on the surface rust-preventing oil or press oil, the lubrication effect of rust-preventing oil or press oil is maintained, and the non-metallic substance reduces the metal contact between the press die and the steel plate. From the effect, it is intended to provide a molding method excellent in deep drawability in which the frictional resistance of the flange portion is reduced.

The outline of the present invention has been described above. Next, the reasons for defining the molding method of the present invention will be described.

The punch shoulder temperature is set to -10 ° C. or higher because if the temperature is lower than that, dew condensation on the die is increased, the dew condensation produces a lubricating effect, and the material of the fracture risk part 1 is easily deformed. This is because the decrease occurs and the breakage easily occurs, and the reason why the temperature is set to 20 ° C. or lower is that the tensile strength of the material at the risk of breakage area 1 is decreased, and the breakage resistance is decreased to cause the breakage. This is because it becomes easier.

The reason why the temperature of the die part and the plate pressing part is made higher than the punch shoulder part temperature by 20 ° C. or more is that if the temperature is lower than that, the effect of reducing the drawing resistance of the flange part is small and the deep drawability is impaired. The reason why the temperature is 40 ° C. or lower is that if the temperature exceeds 40 ° C., the increase in frictional resistance becomes larger than the decrease in drawing resistance, impairing the deep drawability.

The non-metallic substance is in the form of a sheet, such as polyethylene, nylon, vinyl or paper, which is not particularly limited and may be a commercially available substance.
The reason why it is set to m or less is that wrinkles are generated in the flange portion at the time of molding and the deep drawability is impaired if it exceeds m.

The types of materials that can be molded by the present invention are currently J
Either a soft steel plate or a high-strength steel plate by hot and cold rolling specified by IS may be used. Further, the plate thickness of the steel plate is preferably 0.5 to 3.0 mm considering the intended use.

[0022]

EXAMPLE FIG. 2 shows an outline of a molded part in the first step of an oil pan for an automobile molded according to the present invention. FIG. 1 shows a vertical cross section during deep drawing by the forming method of the present invention.
And a polyethylene sheet 8 is further applied. As shown in Table 1, the test material used was an ultra-low carbon titanium-added steel cold-rolled steel sheet having a thickness of 1.2 mm. 3 is a punch shoulder portion of the press die, 4 is a die of the press die, and 5 is a plate pressing portion of the press die.

[0023]

[Table 1]

The forming speed is 15 pieces / minute, the punch shoulder temperature and the die part temperature and the plate pressing temperature are changed, and the plate pressing force is set to a constant condition of 350 kN. The molding height was set to 180 mm, and the number of moldings until the breakage occurred when 150 pieces were molded under the above conditions was evaluated, and the results are shown in Table 2.

[0025]

[Table 2]

Examples of the molding method of the present invention (test material 1
Nos. 17 to 17 show excellent deep drawability as compared with Comparative Examples (test materials 18 to 23).

In addition, the test materials 18 and 19 of the comparative examples are not satisfactory in drawability due to an increase in frictional resistance due to metal contact. Further, in the test materials 20 and 21 of the comparative example, the drawing resistance of the flange portion decreased due to the rise of the die temperature, but the friction resistance due to metal contact increased, and the effect of deep drawing performance was small.

Since the test materials 22 and 23 of the comparative example have a thick polyethylene sheet, they break due to wrinkles, and the deep drawability cannot be satisfied.

[0029]

EFFECTS OF THE INVENTION According to the present invention, it is possible to easily secure the molding for the drawn parts by the hydraulic press, the mechanical press and the transfer press for automobiles, furniture and home electric appliances, and it is particularly difficult to perform the molding. It is extremely effective for various deep-drawn parts, has a wide range of applications in automobiles, furniture, and home electric appliances, and has great industrial utility value.

[Brief description of drawings]

FIG. 1 is a schematic view showing a molding method of the present invention.

FIG. 2 is a schematic view of the shape of an oil pan for automobiles.

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[Procedure amendment]

[Submission date] January 25, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

[0023]

[Table 1]

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Claims (1)

[Claims] 1. In press molding, the temperature of the punch shoulder is within the range of -10 ° C. to + 20 ° C., and the temperature of either the die portion or the plate pressing portion is 2 from the punch shoulder temperature.
Raise the temperature by 0 ° C or more, and the maximum temperature of the die and the plate pressing part is within 40 ° C. Apply rust preventive oil or press oil to one or both sides of the steel plate surface, and then apply one or both sides to it. A molding method with excellent deep drawability, characterized in that a non-metallic substance having a thickness of 100 μm or less is attached to.