JPS5831066A - Punch for cold working - Google Patents

Abstract

PURPOSE:To obtain a punch for cold working with superior wear resistance, galling resistance and seizing resistance by forming a nitrided coat layer on the surface of the body of a punch of a high alloy steel having a specified composition by nitriding at a low temp. and by coating the nitrided coat layer with a hardened layer by vapor deposition. CONSTITUTION:A punch 1 is formed with a high alloy steel consisting of 0.35- 0.70% C, <0.1% Si, <1.0% Mn, 1.0-5.0% Cr, 0.1-7.0% Mo, 0.1-4.0% V and the balance Fe. The surface of the body 2 of the punch 1 is nitrided at about 550 deg.C which is lower than the tempering temp. to form a nitrided coat layer 3. A hardened surface layer 4 of TiN or the like may be further formed by ion plating or other method. The resulting punch satisfies required characteristics such as superior wear resistance, galling resistance, seizing resistance and toughness.

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technology belongs to the field of mold materials for molds used in cold working such as cold forging and processing technology thereof.

Therefore, the invention of this application forms the mold body from high-grade tool steel having strength and compressive deformation resistance similar to 5KH9, etc., and furthermore, the mold body is made of a nitrided material having wear resistance, galling resistance, and seizure resistance on the surface. This relates to a mold for cold working such as cold forging which is provided with a treated coating layer, and in particular, the high-grade tool steel is made of C: 0.35 to 07%, Si: <1.0%, Mn :<1
．． 0%, Cr: 1.0-5.0q6, Mo: 0
．． High alloy steel with a composition of 1 to 7.0 q6, V: 0.1 to 4.0% balance Fe, quenched and tempered using standard heat treatment, and then nitrided at a softening temperature and a low transfer temperature. For cold processing, a nitrided coating layer is formed by processing, resulting in less processing distortion and minimal post-processing, and a surface hardening layer such as TiN is formed by low-temperature physical vapor deposition such as ion blasting. This relates to molds.

As is well known, cold working is widely used in cold forging, sintering forming, glace forming, etc.
The molding die is selected and used depending on the processing conditions, and the mold materials such as punches are also rated according to JIS standards, such as 5KDII, depending on the usage load.
(cold die steel), 5KH9, 5KH57 (high speed steel), and even ultra-high alloys.

Incidentally, the usage load is selected above in order to have a long life in relation to durability, but the forms of wear and tear on the mold that affect the life include large cracks in the mold due to lack of strength and toughness, and cracks due to lack of strength and toughness. There is also partial chipping, etc., wear, galling, and seizure of the mold surface due to insufficient wear resistance, galling resistance, and seizure resistance, and deformation of the mold mainly due to insufficient strength (compressive yield strength). It can be seen that there is a deep correlation between the mold material properties and the composition of the mold material related to such mold wear.

That is, the mold material changes from 5KD11 to 5KH9, 5KH9
It has been found that as the composition moves from 5KH57 to higher grade compositions, the toughness properties definitely decrease.

On the other hand, when considering the lifespan of the mold, as the required level of mold deformability, wear resistance, galling resistance, and seizure resistance increases, from 5KD11 to 5KH9, and further to 5K
There is a tendency to upgrade from H9 to 5KH57 and from 5KH57 to cemented carbide.

In some cases, a hard carbide or nitride coating is formed as a measure against surface hardening of the mold material.

As mentioned above, as mold materials become more sophisticated, their toughness deteriorates, and the disadvantages of chipping and the like are unavoidable.

To deal with this, some steel materials have recently been developed to improve toughness, but this is limited to improving the material itself, so although toughness is improved, hardness and wear resistance are A contradiction has arisen in that

Therefore, as a completely different method, materials such as IC86 and IC322, which are special low carbon steels that are quenched and then carburized, have been devised as toughness improving materials. It is only used for forming, etc., and therefore, when subjected to high stress compression such as in cold forging, it deforms into a so-called cylindrical shape, making it unusable for practical use.

Since the carburizing temperature is higher than the tempering temperature, processing distortions such as deformation and dimensional changes are unavoidable, and post-processing such as mold finishing is required after the carburizing process, which requires a large number of man-hours and the work is performed at the top of the furnace. There were disadvantages that led to high costs.

The purpose of the invention of this application is to solve the problems of mold materials and processing of cold working molds based on the above-mentioned prior art, and to
, Mn, Cr, Mo, and V by selecting a high-alloy steel shape material with a predetermined ratio of Fe to Fe.
It can maintain strength and compressive deformation resistance comparable to high-grade tool steels such as KH9, 5KH57, etc., and has significantly superior toughness.The mold surface is also nitrided at a temperature lower than the tempering temperature, resulting in excellent wear resistance. It is an object of the present invention to provide a cold working mold which has good properties such as hardness, galling resistance, and seizure resistance, and which requires as little post-processing as possible.

The structure of the invention of this application in accordance with the above-mentioned purpose is that the mold material forming the mold body contains C: 0.35 to 0.7%, Si: <1°0, Mn: <1.0%, and Cr: 1.0. ~5.0%, M
o: 0. ．． 1-7.0%, V: 0.1-4. O%
, the balance is made of high-alloy steel with a blend composition of Fe, and is subjected to standard heat treatment to provide quenching properties that provide uniform hardness of about HRC 58 to 60 over the entire mold body, and the strength and compression deformation resistance are It is the same as conventional high-grade tool steel and has excellent heat treatment and toughness properties, and is nitrided at a temperature lower than the firing temperature of 550℃ or higher to coat the surface of the mold body with a sufficiently deep hardened layer. In addition, depending on the design, a hardened layer of TiN or the like is further coated by low-temperature physical vapor deposition means such as ion blasting.

Next, embodiments of the invention of this application will be described below with reference to the drawings.

The mold/mold 1 that constitutes the gist of the invention of this application is a punch for cold forging, and the mold body 2 has a carbon content of 0.35 to 0.7%.
, Si:<1.0%, Mn:g], 00%Cr:1, O
~5.0. %, Mo: 0.1-7.0%, V: 0.
It is a high alloy steel with a distribution composition consisting of 1 to 4.0% balance Fe.

For example, in the case of special applications such as severe cold forging molds that require nitriding treatment, W: 4. , -20chi, Co
10Ni: 1~12%, At: 0.2~2.0
%, N: 0.2% or less may be contained.

The above distribution composition is determined for the following reasons: C functions to impart strength and compression resistance to the mold body, and C does not function at all below 0.35%;
When it exceeds 0.7 inch, the formation of carbides and nitrides increases,
Decreases toughness.

Although Si is an effective element in contributing to toughness, 1.
If it exceeds 0%, toughness will deteriorate.

Furthermore, Mn is useful for increasing the hardenability of the mold material, but if it exceeds 10 inches, inclusions increase and the toughness is impaired.

Cr also increases hardenability, but it also acts effectively to increase the depth of the hardened layer during nitriding, but this effect starts to take effect at 1.01 or more, but at 5.0% Exceeding this is undesirable because it promotes the formation of carbides and nitrides and impairs toughness.

Furthermore, like Cr, Mo contributes to hardenability and increase in hardened layer, but it does not work effectively below o, i qb.
If it exceeds 0%, carbides and nitrides will increase and toughness will deteriorate.

Finally, V increases the surface hardness and hardening depth associated with nitriding, but if it is less than 0.1%, it has no effect, and if it exceeds 4.0%, it also supports the formation of carbides and nitrides. However, both Wl and Co+Ni work effectively by increasing the heat resistance, tempering, and softening resistance of the molded material, but the former is less than 4% and the latter is less than 4%. Less than 1 inch has no effect, 20%
, 12q6, carbides and nitrides increase and the toughness is not improved.

In addition, for At, the hardening depth of nitriding treatment can be quickly and
Although it works effectively to increase the size, it is not effective when it is less than 0.02 inch, and when it exceeds 2.0 inch, it also causes an increase in carbides and nitrides, which is not favorable for toughness.

Regarding N, it is effective for strength and compression resistance, and 0
．． If it exceeds 2 inches, it will contribute to the formation of carbides and nitrides, and will not improve the toughness.

After forming the mold body 2 using the above-mentioned high alloy steel in a prescribed manner, uniform hardness was ensured and maintained throughout through standard heat treatment, and then ion nitriding, gas nitriding, salt bath nitriding, and solid state were performed at a temperature of 550°C, lower than the resetting temperature. A nitriding treatment is performed using an appropriate means such as nitriding to form a nitriding coating layer 3 on the surface of the mold body 20 with a sufficient depth to improve the wear resistance, galling resistance, and seizure resistance of the surface. There is no distortion due to high temperatures such as carburizing, and no post-finishing is required.

Then, depending on the design, a physical vapor deposition treatment at a low temperature is performed by means such as ion blasting, and a hardened layer 4 of nitride or carbide such as TiN with a hardness of approximately HRC 60 or more is applied.
Of course, the strength and compression resistance of the mold body 20 are not impaired in any way by the above-mentioned nitriding treatment and physical vapor deposition, and in this way, the high toughness of the mold body 2 and the wear resistance and galling resistance on the surface are improved. It is possible to differentiate between the properties of heat and burn-in.

Next, an experimental example based on the above-mentioned embodiment will be shown below.

For the mold body 2, high alloy steel is made of C: 0.55q6, Si
: 0.3%, Mn: 0.4%, Cr: 4.1
%% MO: 5.1 inches, W: 6.6%, V: 1.
The high alloy steel was made into a composition of 96'% and the balance was
Quench at 200℃ salt and temper at 56"0℃.

In this state, the hardness is HcR60 and the Charpy impact value is 7.
3 kV/cni (10R notch) and bending strength of 300 stains/- could be secured.

After that, the mold body 2 is subjected to gas nitriding treatment for 550 ml.
℃ x 20 hours, and as a result, a nitride coating layer 3 was obtained, the surface hardness of which was HV 1200 or more, and the hardened layer depth was 0.3 tta.
It was found that the depth was greater than n, and compared to mold body 2, the wear resistance, rudder resistance, and seizure resistance were significantly improved.

Finally, a TiN surface hardening layer 4 was obtained by ion silating, and its thickness was 0.5 to 20 microns.

It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments, and various embodiments such as press molding, sintering molds, etc. can be adopted in addition to cold forging.

As mentioned above, according to the invention of this application, the physical and mechanical functions are basically divided between the mold body and the hardened surface layer, so that the mold body has the wear resistance required for the hardened layer. ,
There is no need to consider stiffness and seizure resistance that much, and
Therefore, the hardenability, which can be uniformly obtained by standard heat treatment, the strength that can be maintained even after nitriding treatment, physical vapor deposition treatment, and toughness such as compression resistance are obtained, but on the other hand, the hardened layer has poor wear resistance and toughness. Excellent effects can be achieved in improving galling and seizing properties.

Therefore, instead of having to make contradictory choices between wear resistance, galling resistance, seizure resistance, and toughness as in the past, it is now possible to obtain an excellent mold that can satisfy the required characteristics of both. be.

Therefore, after the heat treatment of the mold body, nitriding can be performed at a temperature lower than the tempering temperature, and a hardened layer of the nitrided coating layer can be obtained. As a result, there is no thermal distortion or size change, and there is no need for post-processing finishing, reducing man-hours and
There is also the advantage of cost reduction.

In addition, by applying physical vapor deposition such as ion routing to the nitrided coating layer to obtain a final surface hardening layer, the carbides and nitrides have the same or higher wear resistance than conventional CVD and TD treatments. It has the effect of imparting properties such as hardness, galling resistance, and seizure resistance, providing excellent surface properties, and further improving the double-cured layer.

As for the toughness of the mold body, by using the high-alloy steel composition, there is an effect that the mold body, which does not share the function of the hardened layer, is effective due to mutual tension. be.

[Brief explanation of drawings]

The drawings are explanatory diagrams of one embodiment of the invention of this application, and are a model of a cold forging punch, in which FIG. 1 is a schematic explanatory view of the bottom surface thereof, and FIG. 2 is a partially longitudinal sectional side explanatory view thereof.

Claims (2)

[Claims] (1) In a cold working mold having a mold body made of high-grade tool steel and a nitrided coating layer on the surface of the mold body, C:
0.35-0.7%, Si:<1. OtslMn:
<1.0%, Cr: 1.0-5. O%', Mo
: 0.1~7.0'16, V: 0.1~4.0
H. A mold for cold working, characterized in that a nitrided coating layer formed at a treatment temperature lower than the tempering temperature is provided on the surface of the mold body made of high-alloy steel with a balance of Fe. (2) In a cold working mold having a mold body made of high-grade tool steel and a nitrided coating layer on the surface of the mold body, C:
0.35-0.7%, Si:<0.1%, Mn:<1
．． 0%, Cr: 1.0-5.0%, Mo: 0
．． 1-7.0%, V: 0.1-4.0ch, remainder F
A nitrided coating layer formed at a treatment temperature lower than the tempering temperature is provided on the surface of the high alloy steel mold body of e, and a hardened layer formed by physical vapor deposition is further coated thereon.7. Mold for cold working.