JPS599245B2 - Manufacturing method for extruded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an extruded article, in which an extruded article having a mirror-like smooth inner surface is obtained by backward perforation extrusion.

As shown in Figs. 1 and 2, the backward perforation extrusion method involves forming a product with a hollow cross section from a cylindrical material such as steel, aluminum, or copper by backward extrusion.
Insert the blank) into the die hole 2 and move the punch 3 forward.
In this method, pressure is applied in one direction to extrude the material from the gap 5 between the punch 3 and the die 4 to obtain a product 6 with a long and thin hollow cross section.

In this method, when performing cold extrusion processing, a very large surface pressure is applied from the punch to the blank, resulting in seizure between the punch and the blank, which has been considered a major drawback of this method.

Therefore, in the past, the lubrication performance of steel or aluminum blanks was improved by applying a phosphate coating to the contact surface with the punch to prevent seizure during cold extrusion processing.

However, it is not always easy to apply a phosphate coating to the contact surface of the blank each time with the punch in the mass production process, and even if extrusion processing is performed with lubrication treatment, Even so, surface roughness due to the presence of the phosphate film remains on the processed surface, making it impossible to obtain a smooth surface.

Therefore, the inventors of the present invention have found that even when performing backward drilling extrusion processing using a blank whose contact surface with the punch is not lubricated (hereinafter referred to as a non-lubricated blank), seizure does not occur and the inside of the extruded product remains unchanged. The present invention was completed through research aimed at providing a manufacturing method capable of producing an extruded product having a mirror-like smooth extruded surface.

Note that a mirror-like smooth surface is defined by a surface roughness of R.
max −= 0. Refers to those with a diameter of 1 μm or less.

That is, the present invention involves a step of performing cold backward perforation extrusion on a blank with no lubrication on the contact surface with the punch using a punch with a carbide coating layer formed on the surface, and then extruding the extruded product and the punch. This is a method for producing an extruded product, which is characterized by comprising a step of taking out the extruded product as one body from a die, and finally a step of separating the extruded product and the punch.

The materials of the blank to which the method for manufacturing an extruded product of the present invention can be applied are metals such as steel, aluminum, and copper that can be subjected to cold backward punching and extrusion processing.

However, it is particularly effective when applied to blanks made of steel or aluminum, where the occurrence of seizure during cold backward drilling extrusion is considered to be a serious problem.

The contact surface 7 of the blank shown in FIG. 1 with the punch may be in an unlubricated state.

However, if the contact surface 8 of the blank with the die is lubricated, the frictional force between the blank and the die will be smaller than the frictional force between the blank and the punch, and the punch will be pulled out as shown in Figure 3. This is preferable because it can eliminate the phenomenon in which the blank sometimes rises together with the punch (this is called blank up).

A carbide coating layer 9 is provided on the surface of the punch.

Hereinafter, the punch thus obtained will be referred to as a carbide-coated punch.

Since the carbide layer not only has excellent seizure resistance but also excellent wear resistance, it is possible to improve the seizure resistance and wear resistance of the punch at the same time.

Note that a nitride layer, boride layer, or oxide layer may also be considered as a coating layer that can improve seizure resistance.
From a practical standpoint, it is not as effective as a carbide layer.

As the carbide layer, specifically, a carbide layer that can generally exist as a carbide, such as a titanium carbide layer, a niobium carbide layer, a vanadium carbide layer, a chromium carbide layer, etc., can be used.

However, if the base material is iron, a vanadium carbide layer is preferable, and if the base material is aluminum, a titanium carbide layer or a niobium carbide layer is preferable for seizure resistance.

The method for forming the carbide layer may be any commonly used known method.

The thickness of the carbide layer is preferably in the range of 5 to 10 μm.

If it is thicker than this, it tends to cause peeling of the coating layer, and if it is thinner than this, it is not useful for improving the seizure resistance of the punch and blank.

The surface of the carbide layer should be smooth like a mirror, that is, the surface roughness should be Rmax = 0. It is desirable to keep the thickness to 1 μm or less.

If the hole becomes rougher than this, depending on the depth of the hole, during extrusion molding,
In particular, when the punch is pulled out, scratch marks tend to occur on the inner surface of the extruded product, making it difficult to always obtain a mirror-like inner surface.

The base material of the punch must be strong enough to withstand the high pressure applied during extrusion.

Therefore, the base material is die steel, which does not have sufficient strength.
High speed steel is preferred.

Using the carbide-coated punch described above, a non-lubricated blank is subjected to cold backward drilling extrusion processing.

Note that the backward perforation extrusion process of the present invention includes front and rear extrusion processes in which front extrusion process is performed simultaneously with the rear perforation extrusion process.

After completing the hole extrusion process on the blank, the extruded product and the punch are then taken out from the die as a unit.

As shown in Figure 3, there is a method for taking out the extruded product and the punch as one body from the die by blanking up, in which the blank rises together with the punch when the punch is pulled out from the die. be.

Also, push the extruded product from below with knockout 10 and die 4
There is a method of forcibly taking out the punch 3 and the extruded product 6, and a method of moving the die 4 pressing the extruded product from side to side to remove the extruded product from the restraint of the die and separate it.

The extrudate and punch are then separated.

As an example of a method for separating, as shown in FIG. 3, there is a method in which a stripper 11 is provided on the upper part of the die.

The extruded product 6 and the punch 3 that have come out of the die 4 are the extruded product 6.
When the punch 3 hits the stripper 11, the punch 3 and the extruded product 6 are separated.

In this way, when the extruded product is in the die and under high surface pressure, the punch and the extruded product do not slide, and the punch only comes out of the extruded product when the die is no longer constrained and the surface pressure becomes low. ing.

In this way, the inner surface of the extruded product can be prevented from being damaged when the punch is pulled out, and a mirror-like smooth inner surface can be obtained.

Hereinafter, the present invention will be explained in more detail based on Examples.

EXAMPLE As shown in FIG. 1, a blank 1, which is a material to be extruded, was inserted into a die hole 2 formed by a die 4 and a knockout 10, and placed on the knockout 10.

Then, a punch 3 having a carbide coating layer 9 formed on its surface and having a punch nose portion 31 forming a bulge at the tip was inserted into the die hole as shown in FIG. 2, and the blank 7 was subjected to backward perforation extrusion processing.

Thereafter, the extruded product 6 formed as shown in FIG. 3 and the punch 3 were taken out from the die 4 as a unit.

Next, when the extruded product 6 and the punch 3 come out of the die hole, the extruded product 6 is removed from the stripper 11 fixed on both sides.
was removed from the punch 3.

The extruded product 6 thus obtained had an inner diameter of 21.2 mm and an outer diameter of 301 nm.

High speed steel (JIS SKH9) was used as the material of the punch.

In forming the carbide coating layer on the surface of the punch, borax is used as the main ingredient, vanadium oxide (■205) and boron carbide (
The punch was immersed in a molten salt bath containing B 4 C) at 1000° C. for 5 hours to form a vanadium carbide (VC) layer with a thickness of about 7 μm on the punch surface.

Hereinafter, this punch will be referred to as a VC coated punch. After that, quenching and tempering is performed in vacuum to achieve a specific base material strength (HRC6
3).

Note that the punch nose portion 31 was lapped with diamond paste to give a surface roughness of 0.1 μm or less.

The blank, which is the material to be extruded, is made of a spheroidized annealed material (H.v~120) manufactured by JISSIOC.

The contact surface of the blank with the punch was degreased with acetone and was not lubricated, but the other surfaces of the blank were treated with a phosphorus salt coating.

The main extrusion process is a knuckle joint press (250t)
It was done using

The processing speed at that time was 150 to 200 mu/3.

Further, the cross-sectional reduction rate of the blank was 50%.

Furthermore, the surface roughness of the punch nose part is Rm
ax = 0.1 μm, 1 μm, 3 μm
, 6 μm, and the drilling depth was changed from 5 to 377 μm.
The perforation extrusion process of the present invention was performed by varying the diameter up to n1l.

Then, the properties of the inner surface of the obtained extruded product were observed.

The results are shown in Table 1.

In addition, "push" in the "extrusion process" column in the table refers to the time when the blank is pushed in, and "pull" refers to the time when the punch is pulled out from the blank. ``No burning or scratching marks'', △ mark means ``little burning or scratching marks'', X mark means ``many burning marks'', and ku mark means ``many scratching marks''.

Also, the O mark indicates that the blank also rose all at once when it was pulled out.
In other words, this indicates the occurrence of blanking.

At the same time, in order to compare the effects of the present invention, a punch (HRC~63) made of JIS SKI-{9 quenched and tempered material having the same shape as the VC coated punch was prepared. on the other hand, a non-lubricated blank made of JISSIOC spherical annealed material (Hv ~ 120),
Two types of blanks were prepared using the same material treated with a phosphate coating.

Then, using the above-mentioned quenched and tempered punch, under the same conditions as in the present invention, both the above-mentioned non-lubricated blank and the blank subjected to phosphate coating treatment were subjected to backward perforation extrusion processing. Ta.

The properties of the inner surfaces of the resulting extrudates are shown in Table 1.

In addition, the surface roughness of the punch nose is Rmax20.1μm.
The extruded product obtained by punching and extruding was cut vertically using a punch to observe the surface properties, and the results of measuring the surface roughness of the surface are shown in FIGS. 4 to 7.

The vertical direction in the figure indicates the radial unevenness of the inner surface of the extruded product, and the horizontal direction indicates the position of the inner surface of the extruded product in the axial direction.

When a non-lubricated blank is extruded using a quenching and tempering punch, as shown in Table 1, all the parts where the punch has slid are seized.

In addition, when measuring the roughness of that part, as shown in Figure 4, 10
Roughness of ~30 μm was recorded.

On the other hand, when a non-lubricated blank is extruded using the VC coated punch according to the method of the present invention and blank up occurs when the punch is pulled out, no seizure occurs as shown in Figure 5 and Table 1. The inner surface of the extruded product is very smooth, like a mirror with a metallic luster (Rmax ~ 0.1 μm)
) surface condition.

Incidentally, even when the surface of a hardened and tempered punch or a VC coated punch was subjected to a phosphate coating treatment, no seizure occurred as shown in Table 1 (Table 1).

However, FIGS. 6 and 7 show the surface roughness of the inner surface of each extruded product obtained by extruding a phosphate-coated blank using a quenching and tempering punch and a VC-coated punch, respectively. As is clear from a comparison between Figure 5 and Figure 5, an extremely smooth surface with metallic luster is obtained when the non-lubricated blank is extruded using a VC coated punch.

As shown in Table 1, even when extruding a non-lubricated blank with a VC-coated punch, as the surface roughness of the punch nose increases or the depth of the hole increases, the number of scratch marks increases. The surface condition has deteriorated.

However, even in this case, by performing a blank-up during punch drawing, which is the method of the present invention, it was possible to obtain an extruded product with a good surface condition with no or few scratch marks.

In summary, the method for producing an extruded product of the present invention uses a punch having a carbide coating layer with excellent seizure resistance to perform backward perforation extrusion on a non-lubricated blank, thereby preventing the occurrence of seizure between the punch and the blank. Furthermore, by separating the punch and extruded product when the die is no longer constrained and the surface pressure is low, damage to the inner surface of the extruded product can be prevented and a mirror-smooth inner surface can be achieved. This made it possible to mass produce extruded products with

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing the mold and extrusion process of an embodiment of the present invention, where Figure 1 is before extrusion, Figure 2 is during extrusion molding, and Figure 3 is when the extruded product is extracted. Diagram showing the time,
4 to 7 are diagrams showing the surface roughness of the inner surface of the extruded product cut vertically. 1...Blank, 2...Die hole, 3
...Punch, 4...Dice, 5...
...Gap between punch and die, 6...Extruded product,
7...Contact surface with blank punch, 8...
... Contact surface with blank die, 9 ... Carbide layer coating layer, 10 ... Knockout, 11.
·····stripper.

Claims (1)

[Claims] 1. Using a punch with a carbide coating layer formed on the surface, the blank is subjected to cold backward drilling extrusion processing with no lubrication on the contact surface with the punch, and then the extruded product and the punch are removed from the die as a unit. A method for producing an extruded product, comprising a step of taking it out and, finally, a step of separating the extruded product from a punch.