JP3165896B2 - Mold processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the surface treatment of metal molds for metal plastic working, and more particularly to the field of metal plastic working and metal surface processing.

[0002]

2. Description of the Related Art Conventionally, surface treatments such as hardened chromium plating, carbide coating such as vanadium carbide, or titanium nitride coating have been performed to extend the life of a mold.

[0003] However, in the above-mentioned technique, although the hardness is very high, there is the following disadvantage because of lack of lubricity. (1) Depending on the material of the workpiece, a "galling" (also referred to as "seizure") state may occur with the mold, so that the degree of processing cannot be increased. (2) The product surface after processing is apt to be damaged due to the occurrence of the "galling" phenomenon.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a surface treatment layer having sufficient hardness and appropriate lubricity on a surface of a metal mold for plastic working and having a strong adhesion strength. An object of the present invention is to prevent occurrence of "galling" between a material to be processed and a mold, and to obtain a high degree of processing and a good processing surface state.

[0005]

In order to solve the above-mentioned problems, the present invention has been made based on the finding that an intermetallic compound has a property peculiar to the prevention of the "galling" phenomenon.

The first invention of the present invention is characterized in that after a tin-containing layer is formed on the surface of a mold made of an iron-based material, heat treatment is performed to form an intermetallic compound layer on the surface of the mold. This is a mold processing method for metal plastic working.

[0007] In the second invention, a steel mold surface is plated with copper or nickel and then tin-plated or tin-plated.
An object of the present invention is to provide a mold processing method for plastic working of a titanium material, characterized in that an intermetallic compound layer is formed on the surface of the mold by applying a zinc alloy plating and then performing a heat treatment.

More specifically, after the surface of a metal plastic working mold is plated with tin or a tin-zinc alloy, 200 to 600
C. by performing a heat treatment at a temperature of ℃, causes a mutual diffusion reaction between the mold base metal and the plating metal, a mold processing method for forming a strong intermetallic compound layer on the mold surface, A) Preliminary copper plating to improve adhesion in the above plating step; b) Preliminary nickel plating to improve adhesion in the above plating step; c) In the above plating step The method is a mold processing method characterized in that a base nickel and further copper plating are preliminarily applied in order to improve the adhesion of the mold.

That is, according to the present invention, after the surface of a plastic working mold is plated, heat treatment is performed to cause a diffusion reaction between the plated metal and the metal in the mold, and the surface of the mold has a hardness. By forming an intermetallic compound layer with high lubricity and excellent adhesion strength, it reduces the "galling" state during plastic working, improves the workability and improves the work surface This is to get the status.

Next, the present invention will be described in detail. Tin or tin-zinc alloy plating is applied to a plastic working mold made of an iron-based material such as tool steel or die steel (for example, SKD, SCM, etc.), and 1 to 20 μm, preferably 5 to 10 μm.
A μm plating layer is formed. At this time, in order to improve the adhesion of the plating layer, a base copper plating may be applied in advance.

In the case of tin plating, a sulfuric acid bath is used. In the case of tin-zinc alloy plating, a tin-zinc alloy is used as an anode in a tin-zinc-cyanide bath.
% To adjust the bath composition.

The metal mold plated as described above is placed in a heat treatment furnace, and is heated at 200 to 600 ° C., preferably 250 to 40 ° C.
A thermal diffusion treatment is performed at a temperature of 0 ° C. At this time, the heat treatment furnace used is preferably a hot-air circulation type furnace in order to prevent local heating. When the plating metal is locally heated by radiant heat or the like, the plated metal partially melts and flows to form a so-called “drip”, and a desired predetermined surface characteristic cannot be obtained.

The heating time varies depending on the size of the mold and the thickness of the plating, but it is 2 to 20 hours at a predetermined temperature, preferably 5 to 20 hours.
It is necessary to hold for 10 to 10 hours. After the heating is completed, it is naturally cooled, and is taken out of the furnace when the temperature becomes 150 ° C. or less.

By the above-mentioned processing, in the case of tin plating, an intermetallic compound layer mainly composed of Fe-Sn is formed on the surface of the mold at a depth of about 1.5 times the plating thickness. Further, in the case of tin-zinc alloy plating, Fe-
A layer made of an intermetallic compound mainly composed of Sn and Fe-Zn is formed.

In any case, the outermost surface of the treatment layer is almost an intermetallic compound, and the ratio of the mold material phase gradually increases toward the inside of the mold, and finally the compound layer disappears with a temporary decrease. Because it has a so-called inclined structure,
The film strength is very high. Next, the present invention will be described with reference to examples.

[0016]

【Example】

Example 1 A cylindrical deep drawing die (drawing diameter: 32 mmφ, material: SCM
435) was subjected to a 7 μm-thick tin plating on the surface of the mold by a usual treatment, followed by a heat treatment at 400 ° C. for 6 hours in a hot-air circulation furnace.

Using the heat-treated mold, a cylindrical deep drawing test of a pure titanium material (1 mm thick, JIS TP28C) was performed. The drawing ratio was D / d (D: blank diameter before drawing, d: (Diaphragm diameter) of 2.4 was obtained.

Next, repeated drawing was performed at a drawing ratio of 1.8. Even after 30 times, the surface of the processed product was smooth.
No scratches due to "galling" or the like were observed at all, and the maximum drawing force hardly changed from the beginning.

Example 2 A pure titanium plate was used as a workpiece, tool steel (SKD11) was used as a mold material, hard chrome plating was applied to the tool steel, and plating heat diffusion treatment was applied to SCM435 (the method of the present invention).
A comparative test was carried out by cylindrical deep drawing using three types of dies with those subjected to the above. The results are shown in FIG. 1 (a graph showing the relationship between the drawing ratio (D / d) and the maximum drawing force in deep drawing of a titanium plate) and FIG. 2 (showing the change in the maximum drawing force in continuous drawing of a titanium plate). Graph).

In FIG. 1 and FIG. 2, a tool steel mold (SK
The case of D11) is indicated by a mark, the case of a hard chrome plating mold is indicated by a mark, and the case of a plating heat diffusion treatment mold according to the present invention is indicated by a mark. The following can be seen from the results of this graph.

In the case of the plating heat diffusion mold according to the present invention, the maximum drawing ratio is about 1.3 times that of the tool steel mold and about 1.2 times that of the hard chrome plating mold.

Further, in the continuous drawing test, as shown in FIG. 2, when the tool steel mold and the hard chrome plating mold were used, the drawing force was greatly increased from the second time. In the case of using the processing mold, the drawing force does not change even at the 30th time, and in the case of the former two molds, the scratches that are attributed to "galling" are clearly recognized over the entire outer peripheral surface of the processed product. On the other hand, in the case of the mold according to the present invention, no damage was seen on the outer surface of the processed product, and the processed product remained smooth.

[0023]

As described above, according to the present invention,
Plastic working, especially difficult-to-machine materials such as titanium
Moreover, it can be processed with a good surface condition. Thereby, there is an advantage that rationalization such as shortening of the plastic working step and omitting post-working can be achieved.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a drawing ratio (D / d) and a maximum drawing force in deep drawing of a pure titanium material (JIS TP28C).

FIG. 2 is a graph showing a change in maximum drawing force in continuous drawing of a pure titanium material (JIS TP28C).

Continuation of front page (56) References JP-A-4-235292 (JP, A) JP-A-51-122632 (JP, A) JP-A-63-203221 (JP, A) JP-A-63-203792 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21D 37/20 B21D 37/01 C25D 5/26 C25D 5/50 C25D 7/00

Claims (2)

(57) [Claims] 1. A metal for metal plastic working, wherein an intermetallic compound layer is formed on the surface of a mold after forming a layer containing tin on the surface of a mold made of an iron-based material and then performing a heat treatment. Type processing method. 2. A method of forming an intermetallic compound layer on the surface of a steel mold by subjecting the surface of the steel mold to copper plating or nickel plating, applying tin plating or tin-zinc alloy plating, and then performing heat treatment. A mold processing method for plastic working of titanium material, characterized by the following.