JPH09314251A - Press die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press die free from corrosion of the die caused by the working oil and capable of stable working for a long time by using the WC-Co corrosion resistant cemented carbide of the chromium concentration ratio in the prescribed range in a punch and a die of the press die. SOLUTION: In a press die, a work is inserted in a clearance (a) between a die plate 2 and a stopper plate 1, and an upper die is lowered until a blade tip of a punch 7 of the upper die passes a blade tip of the die plate 2 of a lower die to shear the work. The punch 7 and the die plate 2 of the press die to perform the plastic working including shearing, bending and drawing of the metal and the non-metal are formed of WC-Co corrosion resistant cemented carbide of 0.005-0.2 in chromium concentration ratio which is the mole ratio of chromium to the mole number of cobalt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press die for plastic working, in particular, a die having improved punch and die materials used in the die.

[0002]

2. Description of the Related Art Conventionally, as a press working die of this type, for example, "New Press Working Data Book" (1993-5-25) edited by New Press Working Data Book Editing Committee.
There is one disclosed in Nikkan Kogyo Shimbun P84. FIG. 1 is a cross-sectional view of the main part thereof, in which 1 is a stopper plate, 2 is a die plate, 3 is a die holder, 4 is a die post, 5 is a guide bush, 6 is a punch holder, 7 is a punch, and 8 is a punch plate. , 9 are backing plates, a combination of 1, 2, 3, 4 is called a lower mold, and a combination of 5, 6, 7, 8, 9 is called an upper mold.

Next, the operation of this mold will be described. First, a workpiece (not shown) is passed through the space a between the die plate 2 and the stopper plate 1, and the upper die is lowered until the blade edge of the upper die punch 7 exceeds the blade edge of the lower die plate 2 and The processed material is sheared. Next, although the upper die enters the ascending process, since the side surface of the punch 7 is pressed against the shear surface of the work piece, the work piece is supported by the stopper plate 1 and the side surface of the punch 7 and the work piece. Punch 7 while causing friction with the shear surface of the material
Is removed from the work piece. At this time, generally, in order to reduce the wear of the cutting edge of the die plate 2 and the wear of the cutting edge of the punch 7, processing oil (not shown) is dropped on the upper surface of the work material, and the wear of each cutting edge is increased by the lubricating action. However, in such a mold, the die plate 2
It is well known that wear is caused on the cutting edge of the punch 7 and the cutting edge of the punch 7, and it is also well known that this wear causes a defect such as burrs on the workpiece.
The fact that the forms of wear include abrasive wear, adhesive wear, fatigue wear, etc. is based on the fact that Seiji Kataoka, "Lubrication Technology for Press Work" (sho 63-7-20), Kaibundo P8-15 and the Japan Society for Plastic Processing. "Shearing" (1992-7-10) is disclosed in Corona P40 and the like.

Further, as a method for reducing these abrasions and improving the abrasion resistance, a cemented carbide is used for punches and dies against abrasive abrasion [particles of tungsten carbide (WC) which is extremely hard with cemented carbide]. Is retained by cobalt (Co) as a binder], and chlorine-based compounds, sulfur-based compounds, phosphorus-based compounds, etc. are added as extreme pressure additives to the processing oil for cohesive wear. Then, the compound is decomposed by the processing heat generated at the time of processing and reacts with the metal of the punch and die to form a chemical conversion film with weak mechanical strength on the surface of the punch and die. A method of reducing or preventing adhesive wear is disclosed.

Further, regarding corrosive wear, the extreme pressure additive contains a component [eg, chlorine (Cl)] that causes corrosion when decomposed by processing heat, which is the content of cemented carbide (WC-Co). To selectively dissolve cobalt (Co), which is a binder, tungsten carbide (W
The holding power of the particles of C) becomes weak, and tungsten carbide (W
The particles of C) fall off and cause corrosion wear of the cemented carbide. Therefore, it is disclosed that it is necessary to add a large amount of the extreme pressure additive or to prevent the reactivity from becoming too high.

Further, regarding fatigue wear, a punch,
In order to prevent the metal, which is the material of the die, from having high fatigue strength and to prevent defects (for example, pores) that are sources of stress concentration inside the material, H. I. P processing (HOT ISOSTA
TIC PRESS) and the like are disclosed. However, it is also well known that extreme pressure additives added to processing oils for the purpose of reducing cohesive wear, on the other hand, have the contradictory property of promoting corrosive wear.

[0007]

However, even in such punches and dies made of cemented carbide, a very small amount of the extreme pressure additive contained in the working oil causes remarkable corrosive wear to the cutting edges of the punches and dies. As a result, there is a problem in that burrs are generated on the workpiece and stable processing cannot be performed for a long time.

An object of the present invention is to provide a press die that can prevent corrosive wear of the punch and die of the cemented carbide and can be stably processed for a long period of time.

[0009]

Means for Solving the Problems In order to solve the above problems, the present invention provides a cemented carbide for punches and dies in which the ratio of the number of moles of chromium to the number of moles of cobalt (hereinafter referred to as the chromium concentration ratio) is It is formed of 0.005-0.2 WC-Co based corrosion resistant cemented carbide. The chromium concentration ratio is such that the cobalt component of the cemented carbide is m% by weight, the chromium component is n% by weight, the atomic weight of cobalt is M, and the atomic weight of chromium is N.
Then, it is as follows. First, the weight of cobalt in the cemented carbide of W (g) is Therefore, the number of moles of cobalt at this time is Indicated by Similarly, the number of moles of chromium is Becomes As described above, the chromium concentration ratio is the ratio of the number of moles of chromium to the number of moles of cobalt. Therefore, from the above equations (2) and (3), Indicated by (Same in the following description)

In the present invention, the chromium concentration ratio is less than 0.
Since the WC-Co type corrosion resistant cemented carbide of 005 to 0.2 was used, it is possible to prevent the die from being corroded by the working oil without significantly lowering its mechanical strength.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to test results. First, the corrosion of tungsten carbide (WC) -cobalt (Co) based cemented carbide by working oil was investigated. Corrosion of cemented carbide is caused by the decomposition of the extreme pressure additive added to the processing oil by the processing heat as described above, but since model experiments are difficult, it is actually incorporated in the mold. Data was collected.

As a work piece, SUS304 CP
The plate thickness t = 1 mm, and the average grain size of tungsten carbide (WC) as a material for the punch and die is φ = 0.6 μm.
Of the ultrafine-particle type cemented carbide, cobalt (Co) was set to 8% by weight, 14% by weight, and 17% by weight. Mold is φ = 10m
A round hole of m was punched, and the clearance was 0.06 mm, which was 6% of the plate thickness of the workpiece. Further, the processing oil is 58% by weight of mineral oil, 25% by weight of oiliness agent, and chlorine compound 1.
0% by weight, 5% by weight of sulfur compounds, 2% by weight of rust inhibitor,
The viscosity was 105 cst (40 ° C.), and a very general punching oil was used. Further, it is well known that the wear of the cutting edges of punches and dies and the size of the burr generated on the workpiece have a close relationship, and therefore the burr height is evaluated as a substitute characteristic of the wear of the cutting edge. It was to be. The height of the burr was measured by a tool microscope as a non-contact measuring method. The allowable height of the burr is 5% of the plate thickness of the work piece, which is 5%.
0 μm was provisionally determined as the life value in this test. Here, the processing speed by pressing was 60 SPM. FIG. 2 shows the test results.

In FIG. 2, the horizontal axis represents the number of punches under the above conditions, and the vertical axis represents the height of the burr (unit: μm). In the figure, the symbol Δ shows the case where cobalt in the cemented carbide was contained by 8% by weight, the symbol ◯ shows 14% by weight, and the symbol □ shows the case by which 17% by weight was contained. According to the figure, the smaller the cobalt content, the better the corrosion resistance.
This shows that there is no great difference, and it was found that the working oil of the WC-Co based cemented carbide must have improved corrosion resistance. Therefore, the inventor of the present invention is "Powder and Powder Metallurgy" 31 [2] P56 and Japanese Examined Patent Publication No. 5-2866 edited by Japan Society of Powder and Powder Metallurgy
Attention was paid to improving the corrosion resistance of the WC-Co based cemented carbide shown in No. 6 by adding a chromium component.

FIG. 3 shows WC-Co containing chromium (Cr).
A punch and a die were formed using a system cemented carbide, and under the above conditions, the chromium concentration ratio and the number of punches until the burr height of the work piece when the work piece was punched was 50 μm. It shows the relationship of. In the figure, the horizontal axis represents the chromium concentration ratio and the vertical axis represents the number of blanks. Further, the symbols Δ, ○ and □ in the figure show the cases where cobalt is contained in the cemented carbide at 8% by weight, 14% by weight and 17% by weight, respectively. According to the results shown in the figure, when the chromium concentration ratio exceeds 0.005, the wear amount decreases, that is, the number of punches increases, as the concentration increases. That is, in order to improve the corrosion resistance to the press working oil, the chromium concentration ratio should be 0.005 or more.

Next, the mechanical strength, which is an important characteristic for a die, particularly a punch and a die, will be described. Usually, in cemented carbide, mechanical strength is expressed by transverse rupture strength. FIG. 4 shows the relationship between the chromium concentration ratio and the transverse rupture strength ratio. In the figure, the horizontal axis shows the chrome concentration ratio and the vertical axis shows the transverse rupture strength ratio. The value of transverse rupture strength when chromium is added is divided by the value of transverse rupture strength when chromium is not added. The closer the ratio is to 1, the less decrease in transverse rupture strength due to addition of chromium. Means According to the figure, the decrease in transverse rupture strength is very small until the chromium concentration ratio reaches approximately 0.15, and
Even at a chromium concentration ratio of 0.2, it still maintains a suitable value,
It was found that the transverse rupture strength decreased remarkably as the concentration increased further. That is, in order to maintain a constant level value of the transverse rupture strength ratio, the upper limit of the chromium concentration ratio is set to 0.2.
It is necessary to Specifically, even if the transverse rupture strength ratio of cemented carbide is 0.6 (chromium concentration ratio 0.2), there is no problem with a press die designed to maintain sufficient mechanical strength. It was possible to perform stable press working over a long period of time without causing corrosion, and it was remarkably suitable for corrosion resistance.

From the above results, in order not to significantly deteriorate the transverse rupture strength of the cemented carbide and to improve its corrosion resistance, chromium may be added in a chromium concentration ratio of 0.005 to 0.2.

Next, chromium carbide (Cr3C2) is added in place of the above chromium (Cr), and chromium component (C
r) The values converted into the concentration ratio are shown in FIGS. Figure 5,
The results shown in FIG. 6 show that even when chromium carbide (Cr3C2) is added, both the transverse rupture strength and the corrosion resistance show the same tendency as chromium, and as a result, the chromium component (Cr) concentration ratio is 0.005 to 0.005.
It is sufficient to add 0.2.

[0018]

As described in detail above, according to the press die of the present invention, the punch and the die have a chromium concentration ratio of 0.
By using the WC-Co type corrosion resistant cemented carbide of 005 to 0.2, since it has sufficient mechanical strength and corrosion resistance, it becomes possible to perform stable processing for a long period of time.

In addition to the punching die, the bending die,
It goes without saying that similar effects can be obtained when using a processing oil containing an extreme pressure additive such as a drawing die, a header die, a cold forging die, and rolling soybean.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a press die.

FIG. 2 is a diagram showing the relationship between the number of punches and the burr height according to the present invention.

FIG. 3 is a diagram showing the relationship between the chromium concentration ratio and the number of blanks according to the present invention.

FIG. 4 is a diagram showing a relationship between a chromium concentration ratio and a transverse rupture strength ratio according to the present invention.

FIG. 5 is a diagram showing the relationship between the chromium concentration ratio and the number of blanks when the chromium carbide according to the present invention is used.

FIG. 6 is a diagram showing the relationship between the chromium concentration ratio and the transverse rupture strength ratio when the chromium carbide according to the present invention is used.

[Explanation of symbols]

 1 Stopper plate 2 Die plate 3 Die holder 6 Punch holder 7 Punch 8 Punch plate 9 Backing plate

Claims (1)

[Claims] 1. A press die having a punch and a die for performing plastic working such as metal, non-metal punching, bending, and drawing, wherein the punch and die have a ratio of the number of moles of chromium to the number of moles of cobalt. A certain chromium concentration ratio is 0.005
A press die formed of 0.2 WC-Co type corrosion resistant cemented carbide.