JPH05115930A - Treatment of metallic molds - Google Patents

Abstract

PURPOSE:To prevent the generation of 'galling' between a material to be treated and metallic molds for plastic working at the time of plastic working and to obtain a high reduction ratio and a well worked surface condition by forming a surface treatment layer having sufficient hardness and adequate lubricity and high adhesive strength on the surface of the metallic molds. CONSTITUTION:The surfaces of the metallic molds are directly plated with tin or after the surfaces of the metallic molds are plated with copper or nickel, the surfaces are subjected to tin plating or tin-zinc alloy plating, then to a heat treatment, by which intermetallic compd. layers are formed on the surfaces of the metallic molds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to surface treatment of a metal mold 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, in order to extend the life of a mold, surface treatment such as hardened chromium plating, carbide coating such as vanadium carbide, or titanium nitride coating has been performed.

However, in the above technique, although the hardness is extremely high, it has the following drawbacks because it has no lubricity. (1) Depending on the material of the material to be processed, a "galling" (also referred to as "seizure") state may occur with the mold, so that the degree of processing cannot be increased. (2) Since the "galling" phenomenon occurs, the product surface after processing is easily scratched.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a surface treatment layer having sufficient hardness and proper lubricity and having a strong adhesion strength is formed on the surface of a metal mold for plastic working, so that the plastic working die The purpose is to prevent the occurrence of "galling" between the material to be treated and the mold, and to obtain a high degree of processing and a good processed surface state.

[0005]

In order to solve the above problems, the present invention has been made based on the finding that intermetallic compounds have unique properties for preventing the "galling" phenomenon.

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

A second aspect of the invention is that after the surface of a steel mold is copper-plated or nickel-plated, it is tin-plated or tin-plated.
The present invention provides a die treatment method for plastic working of a titanium material, which comprises forming an intermetallic compound layer on the die surface by applying zinc alloy plating and then heat treating.

More specifically, the surface of the metal mold for metal working is plated with tin or tin-zinc alloy, and then 200-600.
A mold treatment method for forming a strong intermetallic compound layer on the mold surface by causing a mutual diffusion reaction between the mold base metal and the plating metal by performing heat treatment at a temperature of ℃, A) In order to improve the adhesion in the plating process, copper undercoat is preliminarily applied. B) In order to improve the adhesion in the plating process, nickel undercoat is preliminarily applied. C) In the plating process, In order to improve the adhesiveness of the above, it is a mold treatment method characterized in that nickel undercoating and copper plating are applied in advance.

That is, according to the present invention, after the surface of a metal mold for plastic working is plated, heat treatment is carried out to cause a diffusion reaction between the plated metal and the metal in the metal mold, and the surface of the metal mold is hardened. By forming an intermetallic compound layer that has high lubricity and very high adhesion strength, it reduces the "galling" state during plastic working, improving the working degree and good working surface. It is to get the state.

Next, the present invention will be described in detail. Tin or tin-zinc alloy plating is applied to a plastic working die 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 plated layer is formed. At this time, in order to improve the adhesion of the plated layer, copper undercoat may be plated in advance.

A sulfuric acid bath is used for tin plating, a tin-zinc-cyan bath is used for tin-zinc alloy plating, and a tin-zinc alloy is used as an anode.
The bath composition is adjusted so that it becomes%.

The metal mold plated as described above is charged into a heat treatment furnace, and the temperature is 200 to 600 ° C., preferably 250 to 40.
A thermal diffusion process 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 is partially melted and flows to form a so-called "drip", and the desired predetermined surface characteristics cannot be obtained.

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

By the above treatment, in the case of tin plating, an intermetallic compound layer mainly composed of Fe-Sn is formed on the surface of the mold with a depth of about 1.5 times the plating thickness. Further, in the case of tin-zinc alloy plating, Fe- which forms a solid solution with the third element
A layer made of an intermetallic compound mainly containing Sn, Fe-Zn is formed.

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

[0016]

【Example】

Example 1 Cylindrical deep drawing die (drawing diameter: 32 mmφ, material: SCM
435) was tin-plated to a thickness of 7 μm on the surface of the mold by a usual treatment, and then heat-treated at 400 ° C. for 6 hours in a hot air circulation type furnace.

A cylindrical deep drawing test of a pure titanium material (1 mm thickness, JIS TP28C) was carried out using this heat-treated mold, and a drawing ratio: D / d (D: blank diameter before drawing, d: Aperture diameter) 2.4 was obtained.

Next, repeated drawing was carried out at a drawing ratio of 1.8. The surface of the processed product was smooth even after 30 times, and
No scratches due to "galling" were observed, and the maximum drawing force remained almost unchanged from the beginning.

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

1 and 2, the tool steel mold (SK
The case according to D11) is shown with a ●, the case with a hard chrome-plated mold is shown with a ◎, and the case with a plating heat diffusion treatment mold according to the method of the present invention is shown with a ○. The results of this graph show the following.

In the case of the plating heat diffusion treatment 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 significantly increased from the second time. In the case of the treated die, the drawing force does not change even after the 30th time, and in the case of the former two dies, the scratches that are considered to be caused by "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 scratch was found on the outer surface of the processed product and it remained smooth.

[0023]

As described above, according to the present invention,
Plastic processing, especially with difficult processing materials such as titanium,
Moreover, it can be processed in a good surface condition. As a result, there is an advantage that the plastic working process can be shortened and the post-processing can be rationalized.

[Brief description of 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).

Claims (2)

[Claims] 1. A metal for plastic working, comprising forming a tin-containing layer on the surface of a die made of an iron-based material and then heat treating it to form an intermetallic compound layer on the surface of the die. Mold processing method. 2. A steel mold surface is plated with copper or nickel, then tin plated or tin-zinc alloy plated, and then heat treated to form an intermetallic compound layer on the mold surface. A method for processing a die for plastic working of titanium material.