KR20160009504A

KR20160009504A - Surface treating method of extrusion die, Extrusion die and Extrude process system

Info

Publication number: KR20160009504A
Application number: KR1020150099375A
Authority: KR
Inventors: 양비룡; 최비공; 김현
Original assignee: 금오공과대학교 산학협력단; 주식회사대영금속
Priority date: 2014-07-15
Filing date: 2015-07-13
Publication date: 2016-01-26

Abstract

The present invention relates to a method of surface treatment of an extrusion die and an extrusion die manufactured using the same, and is superior in mechanical properties and can eliminate the step of preheating an extrusion die before an extrusion process.

Description

TECHNICAL FIELD [0001] The present invention relates to a surface treatment method of an extrusion die, an extrusion die and an extrusion process system,

The present invention relates to a method of surface-treating an extruded mold, an extruded mold surface-treated by the method, and an extrusion process system that does not perform a pretreatment process of pre-heating an extruded mold before the extrusion process using the surface-treated extruded mold.

In general, various kinds of mechanical parts often require strength against impact and high hardness of the surface, such as gears, cams, and clutches, depending on the purpose of use. In such a case, a method of improving the surface hardness, abrasion resistance, heat resistance and other properties of the surface of the material and increasing the resistance to impact by imparting appropriate strength to the interior is referred to as surface hardening method.

As one of the surface hardening methods, a nitriding method is a method in which a nitriding steel is heated in an ammonia stream or a salt bath to diffuse and penetrate nitrogen, and the nitriding steel is nitrided to form nitrided iron FeN) layer, i.e., a nitride layer. These nitrification methods include gas nitridation, liquid nitrification (or salt bath nitridation), softening, and ion nitridation. Among these methods, the liquid nitriding method or the salt bath nitriding method is a method of nitriding at about 570 ° C. using a molten salt bath comprising KCN, KCNO, and Na ₂ CO ₃ as a main component. Since toxic chemicals must be used, Is difficult.

In addition, the softening method does not primarily aim at hardness improvement but mainly improves other properties. When the carbon steel is made soft, the surface hardness is hardly increased, but the friction coefficient is decreased, the abrasion resistance is increased, And fatigue is improved.

In the ion nitridation method, two electrodes, a cathode and an anode, are placed in a sealed vacuum container, the pressure in the vessel is reduced to several millibars (mbar), and a DC voltage of several hundreds to several thousand volts is applied. a method of nitriding a metal surface using a nitrogen ion plasma generated by a glow discharge is also referred to as a plasma nitriding method.

On the other hand, the gas nitriding method is a method in which activated nitrogen produced by heating and decomposing ammonia gas is reacted with a metal surface to obtain a nitrided layer having a high hardness, which requires a long process time of about 50 to 100 hours, Since the ammonia gas (NH ₃ ) used in the gas nitriding process is a compound of nitrogen and oxygen and is a toxic gas harmful to human body, there is a problem that the gas nitriding process is insufficient in stability against a gas leakage accident that may occur in an industrial field. Further, in the gas nitriding method, nitrogen produced by the thermal decomposition reaction of ammonia is diffused and adsorbed on the surface of the material to be treated, and a nitrided layer is formed through a chemical reaction, so that nitrogen is uniformly controlled to diffuse to the surface of the material It is difficult to uniformly control the thickness and composition of the nitride layer. In addition, since the interfacial bonding property with the material to be treated is low, the peeling phenomenon easily occurs, so that the production period is shortened during the extrusion process and the production efficiency is lowered.

In the prior art of the nitriding method described above, a voltage of 540 V is supplied to a vacuum furnace, the temperature of the material to be treated is set to 530 ?, and H ₂ - N ₂ -CH ₄ mixed gas is introduced to generate a plasma to nitridize the aluminum extrusion die.

However, atmospheric gas nitriding has been recognized as a representative process mainly for steel components, but it is difficult to control the composition of the surface compound layer, and it is difficult to control the composition of the surface compound layer at the entire process time of 12 to 20 hours, It has been pointed out that the nitriding reaction can not be completely performed in a small hole portion.

Further, in the case of gas nitriding, there is a problem that nitriding needles are formed along the grain boundaries together with the nitrogen compound formed on the surface, so that the surface nitrided layer is peeled off from the base material during the extrusion or the nitriding process.

Further, in the case of the salt bath nitriding method, there is an advantage that a porous compound layer can be obtained on the surface and the processing cost is low, but harmful components are generated in the process, and the use thereof is gradually decreased. There is a limit to improve the abrasion resistance characteristics through the use of the abrasive.

Further, the extrusion die subjected to nitriding by the conventional method must be subjected to a separate preheating process before the extrusion process, resulting in a problem of low energy consumption and low productivity.

Korean Patent Laid-Open Publication No. 2001-0027622 (published on April 4, 2001) Korean Patent Publication No. 10-2010-0107874 (published on June 10, 2010)

The surface of the extruded mold is subject to wear and heat due to the friction between the slurry and the mold during extrusion molding, which reduces the mold replacement cycle and thus reduces the production efficiency and degrades the quality of the extruded product In addition, the extruded mold surface is coated with a coating to improve the mechanical properties. However, as described above, the conventional coating treatment method has a problem that it takes a long time to process, which leads to poor productivity and non-environmental problems. As a result of studies to solve this problem, plasma ion nitriding treatment under certain conditions showed excellent physical properties It is possible to provide an extrusion die having a plurality That is, the present invention provides a surface treatment method of an extrusion die and an extrusion die produced by the above method.

In order to solve the above-described problems, the present invention relates to a method of surface treatment of an extrusion die, comprising the steps of: (1) injecting an extrusion die into a chamber and then forming a chamber in a vacuum atmosphere; A second step of injecting gas containing nitrogen (N ₂ ) and hydrogen (H ₂ ) at a ratio of 1: 0.8 to 1.2; Performing a plasma ion nitriding process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to produce an extrusion die having a nitrided layer on its surface; A chamber containing a gas containing nitrogen (N ₂ ), hydrogen (H ₂ ), and a mixed gas of nitrogen and carbon dioxide (CO ₂ ) at a ratio of 1: 0.9 to 1.2: 2.5 to 3.5 by volume, A fourth step of injecting the formed extrusion die; And performing a plasma ion nitridation process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to form a nitrided layer on the surface of the extruded mold having the nitrided layer formed thereon, The third and fourth steps may be performed intermittently.

The present invention also provides a method for surface treatment of an extrusion die, comprising the steps of: injecting an extrusion die into a chamber, and then forming a chamber in a vacuum atmosphere; A second step of injecting gas containing nitrogen (N ₂ ) and hydrogen (H ₂ ) at a ratio of 1: 0.8 to 1.2; Performing a plasma ion nitriding process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to produce an extrusion die having a nitrided layer on its surface; A gas containing nitrogen (N ₂ ), hydrogen (H ₂ ), and a mixed gas of nitrogen and carbon dioxide (CO ₂ ) at a ratio of 1: 0.9 to 1.2: 2.5 to 3.5 Step 4; And performing a plasma ion nitridation process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to form a nitrided layer on the surface of the extruded mold having the nitrided layer formed thereon, The third and fourth steps may be performed continuously.

As a preferred embodiment of the present invention, in the method of surface treatment of an extrusion die of the present invention, the plasma ion nitridation treatment in the above three stages may be performed for 5 to 15 hours, The plasma ion nitridation process is performed for 10 to 15 hours.

As a preferred embodiment of the present invention, in the method of surface-treating an extrusion die of the present invention, the nitrided layer in the three stages may have an average thickness of 50 탆 to 150 탆, Wherein the quality carbonized layer has an average thickness of 100 mu m to 300 mu m.

As a preferred embodiment of the present invention, in the method of surface treatment of an extrusion die according to the present invention, the extrusion die is made of SUS (Steel Use Stainless), SACM (Steel Aluminum Chromium Molybdenum), SCM (Steel Chromium Molybdenum) Steel Aluminum Tool Dise) or SNCM (Steel Nichel Chromium Molybdenum).

In one preferred embodiment of the present invention, the extrusion dies may be SUS440C, SUS304, SACM645, SCM415, SCM430, SCM435, SCM440, SKD1, SKD2, SKD6, SKD11, SKD12, SKD61, SNCM8 or SNCM21 .

The present invention also relates to an extrusion die, characterized in that a nitrided layer and a nitrided layer are sequentially formed on the surface of the coating layer.

In a preferred embodiment of the present invention, the nitrided layer of the extrusion die has an average thickness of 50 탆 to 150 탆 in average thickness and an average thickness of 100 탆 to 300 탆 in the quality carbonization layer have.

According to a preferred embodiment of the present invention, when the extrusion die is SKD61, the hardness of the inner portion of the extruded mold is 0.01 mm to 0.12 mm and the hardness of the curb is 820 HV0 3 to 1,300 HV0.3.

Further, as a preferred embodiment of the present invention, when the extrusion die is SKD61, the hardness of the extruded mold is measured from the surface of the extruded mold to the inner depth of 0.15 mm to 0.24 mm at the time of measuring the Rockwell hardness according to KS B 0811: 2003 400 HV0.3 to 960 HV0.3.

As a preferred embodiment of the present invention, when the extrusion mold is SKD61, the hardness of the extruded mold is measured from the surface of the extruded mold according to KS B 0811: 2003 to a depth of 0.25 mm to 0.30 mm 185 HV0.3 to 500 HV0.3.

Further, as a preferred embodiment of the present invention, the extrusion die has an average surface roughness (R _t ) of 1.2000 mu m to 2.6000 mu m.

The present invention also relates to an extrusion process system, which is characterized in that an extrusion process is performed with an extrusion die, but a pre-process for preheating the extrusion die before the extrusion process is not performed.

The present invention can shorten the nitriding process time without requiring a preheating process, unlike the conventional nitriding process which has been carried out after the nitriding process, and has an excellent mechanical property It is an invention that can provide an extrusion mold with an environmentally friendly method which can provide not only high productivity but also toxic gas leakage problem harmful to human body.

Fig. 1 is a photograph of the extrusion die produced in Example 1. Fig.
Fig. 2 is a schematic view of a plasma ion machine used for surface treatment of an extrusion die in the embodiment. Fig.

Hereinafter, the present invention will be described in more detail.

The present invention relates to an extrusion die in which a nitrided layer and a nitrided layer are sequentially laminated on a surface, wherein the nitrided layer may include Fe, Cr, N and the like, and the nitrided layer includes Fe, Cr, N But also the carbon atoms (C) are included to form a coating layer for improving the mechanical properties of the extrusion die.

The extrusion mold is an alloy tool steel which may include SUS, SACM, SCM, SKD or SNCM and preferably SUS440C, SUS304, SACM645, SCM415, SCM430, SCM435, SCM440, SKD1, SKD2, SKD6, SKD11, SKD12, SKD61, SNCM8 or SNCM21, and more preferably SKD11, SKD12 or SKD61.

The average thickness of the nitride layer may be 50 탆 to 150 탆, preferably 70 탆 to 130 탆, and more preferably 80 탆 to 120 탆. The average thickness of the nitrided carbon layer may be 100 μm to 300 μm, preferably 120 μm to 260 μm, and more preferably 140 μm to 220 μm.

At this time, if the average thickness of the nitride layer is less than 50 탆, there is a problem that the adhesive force between the nitride layer and the carbonaceous layer deteriorates and mechanical properties may be reduced. If the average thickness of the nitride layer is less than 150 탆, . If the average thickness of the carbon nitride layer is less than 100 占 퐉, the thickness thereof is too thin, and sufficient mechanical properties such as hardness and abrasion resistance may not be secured. On the other hand, The time is too long, and there is little further improvement in physical properties in proportion to the thickness.

The extrusion mold in which the nitrided layer and / or the nitrided layer of the present invention is formed on the surface has an inner depth of 0.01 mm to 0.12 mm from the surface of the extruded mold at the time of measuring the Rockwell hardness according to KS B 0811: The hardness may be 820 HV 0.3 to 1300 HV 0.3, preferably 830 HV 0.3 to 1200 HV 0.3, more preferably 900 HV 0.3 to 1200 HV 0.3, and KS B 0811: 2003, the hardness of the burrs is from 400 HV0.3 to 960 HV0.3, preferably from 420 HV0.3 to 950 HV0.3 to the inner depth of 0.15 mm to 0.24 mm from the surface of the extruded mold at the time of measuring the Rockwell hardness. 3, and more preferably 430 HV0.3 to 950 HV0.3.

Then, when measured by the same method, the hardness of the burses is 185 HV 0.3 to 500 HV 0.3, preferably 190 HV 0.3 to 480 HV 0.3, and furthermore, from 0.25 mm to 0.30 mm from the surface of the extruding mold And preferably 190 HV0.3 to 450 HV0.3.

The extrusion mold of the present invention was manufactured by using an alpha-step IQ, which is a thin film thickness measuring instrument, with a scan range of 1,000 mu m, a scan speed of 50 mu m / sec, (R _t ) is 1.2000 탆 to 2.6000 탆, preferably 1.8000 탆 to 2.5000 탆, more preferably 1.9000 탆 to 2.3500 탆, under the condition of a cut-off of 100 탆 can do.

In the extrusion mold of the present invention, the nitriding layer and the nitriding layer are sequentially laminated by plasma ion nitriding treatment. At this time, the nitriding layer and the plasma ion nitriding process for forming the nitriding layer may be performed intermittently or continuously You can do it. This will be described in detail as follows.

The method for manufacturing an extrusion mold (method 1) of the present invention comprises the steps of: 1) putting an extrusion die into a chamber, and then forming a chamber in a vacuum atmosphere; A step of introducing a gas containing nitrogen (N ₂ ) and hydrogen (H ₂ ) in a ratio of 1: 0.8 to 1.2 by volume; Performing a plasma ion nitriding process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to produce an extrusion die having a nitrided layer on its surface; A chamber containing a gas containing nitrogen (N ₂ ), hydrogen (H ₂ ), and a mixed gas of nitrogen and carbon dioxide (CO ₂ ) at a ratio of 1: 0.9 to 1.2: 2.5 to 3.5 by volume, A fourth step of injecting the formed extrusion die; A step of performing plasma ion nitridation processing at 450 ° C. to 600 ° C. and 1 × 10 ^-2 to 1 × 10 ^-6 Torr to form a nitrided layer on the surface of the extruded mold having the nitrided layer formed thereon, Steps 3 and 4 can be performed intermittently.

Further, the extrusion die manufacturing method (method 2) of the present invention comprises the steps of: (1) injecting an extrusion die into a chamber, and then forming the interior of the chamber in a vacuum atmosphere; A second step of injecting gas containing nitrogen (N ₂ ) and hydrogen (H ₂ ) at a ratio of 1: 0.8 to 1.2; Performing a plasma ion nitriding process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to produce an extrusion die having a nitrided layer on its surface; A gas containing nitrogen (N ₂ ), hydrogen (H ₂ ), and a mixed gas of nitrogen and carbon dioxide (CO ₂ ) at a ratio of 1: 0.9 to 1.2: 2.5 to 3.5 Step 4; A step of performing plasma ion nitridation processing at 450 ° C. to 600 ° C. and 1 × 10 ^-2 to 1 × 10 ^-6 Torr to form a nitrided layer on the surface of the extruded mold having the nitrided layer formed thereon, Steps 3 and 4 can be performed continuously.

In the two steps of the method 1 and the method 2, the nitrogen and hydrogen are preferably added in a ratio of 1: 0.8 to 1.2, preferably 1: 0.9 to 1.1, more preferably 1: 1, If the amount of hydrogen supplied is less than 0.8 volume ratio with respect to nitrogen, there may be a problem of generation of a nitrided layer having a nonuniform composition. If the amount of hydrogen supplied exceeds 1.2 volume ratio, there may be a problem with uneven thickness and stability. .

The plasma ion nitridation process in the three steps of the method 1 and the method 2 can be performed for 5 to 15 hours, preferably 5 to 12 hours. When the plasma ion nitridation process is performed for less than 5 hours, The thickness of the nitrided layer may be excessively thick. If the thickness of the nitrided layer exceeds 15 hours, the thickness of the nitrided layer may be 50 to 150 占 퐉, preferably 70 to 130 占 퐉, It is preferable to perform the plasma ion nitridation process for the above-mentioned time to secure 80 占 퐉 to 120 占 퐉. The plasma ion nitridation process in the third step is performed at 450 to 600 ° C and 1 × 0 ^-2 to 1 × 0 ^-6 Torr by applying an RF voltage or a DC voltage, And 5 × 0 ^-2 to 5 × 0 ^-5 Torr, more preferably 520 ° C. to 600 ° C. and 1 × 0 ^-3 to 1 × 0 ^-5 Torr. If the temperature is less than 450 ° C, the nitrided layer may not be uniformly formed on the surface of the extruded mold, and the inside of the nitrided layer may not be dense. If the temperature exceeds 600 ° C, there is a problem of lattice distortion and composition change due to diffusion . If the pressure exceeds 1 × 0 ^-2 , it may be difficult to precisely control the nitrided layer thickness.

The nitrogen, hydrogen and the mixed gas are used in a volume ratio of 1: 0.9 to 1.2: 2.5 to 3.5, preferably 1: 0.9 to 1.1: 2.7 to 3.2, more preferably 1: If the amount of hydrogen input is less than 0.9 volume ratio with respect to nitrogen, there may be a problem of generation of a nitrided layer having an uneven composition. When the amount of hydrogen input exceeds 1.1 volume ratio, There is a problem in thickness and stability, so it is preferable to inject nitrogen and hydrogen in the volume ratio. In addition, when the mixed gas is added to the nitrogen at a rate of less than 2.5 volume ratio, the amount of carbon is small, so there may be a problem of forming a uniform compound layer, and when it exceeds 3.5 volume ratio, unstable crystal phase formation and characteristics may change.

The mixed gas is preferably a mixed gas of nitrogen (N ₂ ) and carbon (C) in an amount of 2.5 to 3.5 parts by volume of carbon relative to one part by volume of nitrogen.

The plasma ion nitridation process of the above-mentioned method 1 and the above-mentioned step 5 may be performed for 10 to 15 hours, preferably for 11 to 14 hours. When the plasma ion nitridation process is performed for less than 10 hours, The carbonized layer may be too thin to ensure sufficient mechanical properties. If it exceeds 15 hours, the quality carbonized layer may become too thick. The average thickness of the optimum quality carbonized layer may be in the range of 100 to 300 탆, Preferably 120 占 퐉 to 260 占 퐉, and more preferably 140 占 퐉 to 240 占 퐉. The plasma ion nitridation process in the fifth step is preferably performed at 450 to 600 ° C and 1 × 0 ^-2 to 1 × 0 ^-6 Torr by applying an RF voltage or a DC voltage, More preferably at a temperature of 520 ° C to 600 ° C and at a temperature of 1 × 0 ^-3 to 1 × 0 ^-5 Torr, more preferably at 5 × 0 ^-2 to 5 × 0 ^-5 Torr. If the temperature is less than 450 ° C, the nitrided layer may not be uniformly formed on the surface of the extruded mold and the nitrided layer may not be dense. If the temperature exceeds 600 ° C, the problem of lattice distortion and composition change . If the pressure exceeds 1 × 0 ^-2 , it may be difficult to precisely control the nitrided layer thickness.

As described above, the extrusion die may be made of SUS, SACM, SCM, SKD or SNCM as the alloy tool steel, and preferably SUS440C, SUS304, SACM645, SCM415, SCM430, SCM435, SCM440, SKD1, SKD2, SKD6, SKD11, SKD12, SKD61, SNCM8 or SNCM21, and more preferably SKD11, SKD12 or SKD61.

Unlike the conventional extrusion process, when the extrusion process is performed with the extrusion die of the present invention, the pre-process for preheating the extrusion die before the extrusion process is not required.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to the examples, and the following examples are intended to facilitate understanding of the present invention.

[ Example ]

Example One

An SKD 61 extrusion die was charged into a chamber of a plasma ion appliance having the same structure as the schematic view shown in Fig. Mechanical pumping and diffusion pumping were then performed to evacuate the interior of the chamber.

Next, a mixed gas of nitrogen and hydrogen in a volume ratio of 1: 1 was introduced into the chamber. Next, a DC voltage was applied, the temperature in the chamber was raised to 570 캜, and the plasma ion nitridation process was performed at the above temperature and 1 × 10 ^-6 Torr for 10 hours. Then, immediately (continuously), a gas was introduced into the chamber so that nitrogen, hydrogen, and mixed gas in the chamber were in a 1: 1: 3 volume ratio. At this time, the mixed gas is a mixture of nitrogen and carbon dioxide at a ratio of 1: 0.25 by volume.

Next, a DC voltage was applied to raise the temperature in the chamber to 590 占 폚, and the plasma ion nitridation process was performed for 13 hours at the above-mentioned temperature and 1 占^10-6 Torr. Finally, A 70 mu m thick nitride layer and an average thickness 205 mu m to 215 mu m quality carbonized layer were laminated in this order, and a photograph thereof is shown in Fig.

Example 2

Next, a mixed gas of nitrogen and hydrogen in a volume ratio of 1: 1 was introduced into the chamber. Next, a DC voltage was applied, the temperature in the chamber was raised to 570 占 폚, and the plasma ion nitridation process was performed at the temperature and 1 占^10-6 Torr for 10 hours to form an average thickness of 65 占 퐉 to 70 占 퐉 To prepare an extrusion die having a nitrided layer.

After the extrusion die having the nitride layer formed thereon was taken out, the chamber was again evacuated, and then the extrusion die having the nitride layer formed thereon was inserted again. Next, nitrogen, hydrogen, and mixed gas in the chamber were introduced into the chamber in a ratio of 1: 1: 3 by volume. At this time, the mixed gas is a mixture of nitrogen and carbon dioxide at a ratio of 1: 0.25 by volume.

Next, a DC voltage was applied to raise the temperature in the chamber to 590 DEG C, and plasma ion nitridation process was performed for 13 hours at the temperature and 1 x 10 < ^-6 > Torr for an average thickness of 190 mu m to 195 mu m An extrusion die having a carbonized layer was produced, and a photograph thereof is shown in Fig.

Example 3

The surface of the extruded metal mold was prepared in the same manner as in Example 1 except that nitrogen, hydrogen, and the mixed gas were introduced into the chamber at a volume ratio of 1: 1: 2.8 at the time of forming the nitrided layer, To produce an extrusion die in which a nitrided layer having an average thickness of 67 to 69 mu m and a nitrided layer having an average thickness of 203 mu m to 212 mu m were stacked in this order.

Example 4

A plasma ion nitriding process was performed by introducing nitrogen, hydrogen, and the mixed gas into the chamber at a ratio of 1: 1: 3.2 at the time of forming the nitrided layer by the same method as in Example 1, To prepare an extrusion die in which a nitrided layer having an average thickness of 66 to 68 占 퐉 and a nitrided layer having an average thickness of 212 占 퐉 to 218 占 퐉 were laminated in order.

Example 5

The surface of the extruded metal mold was prepared in the same manner as in Example 1 except that nitrogen, hydrogen, and the mixed gas were introduced into the chamber at a volume ratio of 1: 1: 3.5 during the formation of the carbon nitride layer, To prepare an extrusion die in which a nitride layer having an average thickness of 66 to 68 占 퐉 and a nitride layer having an average thickness of 216 占 퐉 to 224 占 퐉 were laminated in order.

Example 6

A plasma nitriding process was performed at 520 ° C. and 1 × 10 ^-6 Torr to form a nitrided layer having an average thickness of 66 to 68 μm, Layer and a quality carbonized layer having an average thickness of 205 탆 to 213 탆 were laminated in this order.

Comparative Example One

The same SKD 61 extrusion mold as in Example 1 was charged into the chamber of the plasma ionizer of Example 1. Next, mechanical pumping and diffusion pumping were made into a vacuum inside the chamber. Next, a mixed gas of nitrogen, hydrogen, and a mixed gas in a volume ratio of 1: 1: 3 was introduced into the chamber. At this time, the mixed gas is a mixture of nitrogen and carbon dioxide at a ratio of 1: 0.25 by volume.

Next, a DC voltage was applied to raise the temperature in the chamber to 580 占 폚, and a plasma ion nitridation process was performed at the temperature and 1 占^10-6 Torr for 26 hours to form a layer having an average thickness of 270 占 퐉 to 275 占 퐉 An extrusion die having a carbonized layer was produced.

Comparative Example 2

The surface of the extruded metal mold was prepared in the same manner as in Example 1 except that nitrogen, hydrogen, and the mixed gas were introduced into the chamber at a volume ratio of 1: 1: 2.2 at the time of forming the nitrided layer, To prepare an extrusion die in which a nitrided layer having an average thickness of 66 to 68 占 퐉 and a nitrided layer having an average thickness of 180 占 퐉 to 188 占 퐉 were laminated in order.

Comparative Example 3

A plasma ion nitriding process was performed by introducing nitrogen, hydrogen, and the mixed gas into the chamber at a ratio of 1: 1: 3.8 volume ratio at the time of forming the nitrided layer by the same method as in Example 1, To produce an extrusion die in which a nitrided layer having an average thickness of 66 to 68 占 퐉 and a nitrided layer having an average thickness of 225 占 퐉 to 234 占 퐉 were laminated in order.

Comparative Example 4

A plasma nitriding process was performed under the conditions of 430 ° C. and 1 × 10 ^-6 Torr to form a nitrided layer having an average thickness of 66 to 68 μm, Layer and a carbon nitride layer having an average thickness of 189 탆 to 195 탆 were laminated in this order.

Comparative Example 5

A plasma nitriding process was performed under the conditions of 650 ° C. and 1 × 10 ^-6 Torr to form a nitrided layer having an average thickness of 66 to 68 μm, Layer and a carbonized layer having an average thickness of 209 탆 to 217 탆 were laminated in this order.

Experimental Example One : Surface roughness measurement experiment

The surface roughnesses of the extruded molds prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were measured. At this time, the surface roughness measurement experiment was carried out using a thin film thickness measuring instrument Alpha-Step IQ, and a scan range of 1,000 탆, a scan speed of 50 탆 / sec, a cut- -off) of 100 ㎛ and 23 ℃ ~ 25 ℃ and relative humidity of 30% ~ 40%, and the surface roughness (R _t , ㎛) was measured at three arbitrary points in each of the extruded mold specimens , And the results are shown in Table 1 below.

division Branch 1 Branch 2 Branch 3 Average surface roughness
(R _t , 탆) Example 1 2.0286 탆 2.1890 탆 2.5261 탆 2.2497 탆 Example 2 1.8552 탆 2.2417 탆 2.0628 탆 2.0532 탆 Example 3 1.9573 탆 2.1630 탆 2.2085 μm 2.1096 탆 Example 4 1.9087 탆 1.9925 탆 1.9234 탆 1.9415 탆 Example 5 1.9238 탆 2.0589 탆 1.9540 탆 1.9789 탆 Example 6 2.2006 탆 2.3233 탆 2.4392 탆 2.3210 탆 Comparative Example 1 1.3896 탆 2.1586 탆 2.4363 탆 1.9948 탆 Comparative Example 2 1.9097 탆 2.1113 탆 2.1840 탆 2.0683 탆 Comparative Example 3 1.9275 탆 2.1174 탆 2.1954 탆 2.0801 탆 Comparative Example 4 2.7021 탆 2.6457 탆 2.4936 탆 2.6138 탆 Comparative Example 5 1.8745 탆 1.9248 탆 1.9170 탆 1.9054 탆

The results of Table 1 show that Examples 1 to 6 have an average surface roughness in the range of 1.9400 μm to 2.3500 μm. Comparative Examples 1 to 3 and Comparative Example 5 In addition, Good average surface roughness results were obtained. However, in Comparative Example 4, the average surface roughness was 2.6000 mu m or more, which was not good.

Experimental Example 2: Hardness measurement experiment

The extrusion molds prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were subjected to Rockwell hardness measurement at 18 ° C to 22 ° C and 45% to 55% relative humidity according to KS B 0811: 2003 The results are shown in Tables 2 to 3 below.

Observation Location
(Distance from surface) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Surface (0 mm) 1112 HV0.3 1203 HV0.3 1093 HV0.3 1168 HV0.3 1174 HV0.3 1090 HV0.3 0.03 mm 1015 HV0.3 1023 HV0.3 1005 HV0.3 1103 HV0.3 1127 HV0.3 1001 HV0.3 0.06 mm 925 HV0.3 1015 HV0.3 902 HV0.3 1008 HV0.3 1059 HV0.3 898 HV0.3 0.09 mm 875 HV0.3 996 HV0.3 864 HV0.3 913 HV0.3 962 HV0.3 857 HV0.3 0.12 mm 850 HV0.3 965 HV0.3 839 HV0.3 909 HV0.3 938 HV0.3 835 HV0.3 0.15 mm 832 HV0.3 950 HV0.3 825 HV0.3 886 HV0.3 925 HV0.3 811 HV0.3 0.18 mm 782 HV0.3 882 HV0.3 768 HV0.3 851 HV0.3 865 HV0.3 760 HV0.3 0.21 mm 764 HV0.3 797 HV0.3 758 HV0.3 778 HV0.3 782 HV0.3 746 HV0.3 0.24 mm 432 HV0.3 642 HV0.3 430 HV0.3 497 HV0.3 521 HV0.3 428 HV0.3 0.27 mm 320 HV0.3 425 HV0.3 317 HV0.3 382 HV0.3 423 HV0.3 313 HV0.3 0.30 mm 195 HV0.3 250 HV0.3 191 HV0.3 225 HV0.3 244 HV0.3 190 HV0.3

Observation Location
(Distance from surface) Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Surface (0 mm) 1058 HV0.1 1021 HV0.3 1212 HV0.3 976 HV0.3 1152 HV0.3 0.03 mm 982 HV0.3 950 HV0.3 1184 HV0.3 913 HV0.3 1038 HV0.3 0.06 mm 1005 HV0.3 873 HV0.3 1109 HV0.3 814 HV0.3 1014 HV0.3 0.09 mm 998 HV0.3 792 HV0.3 1034 HV0.3 739 HV0.3 975 HV0.3 0.12 mm 982 HV0.3 721 HV0.3 997 HV0.3 676 HV0.3 939 HV0.3 0.15 mm 946 HV0.3 685 HV0.3 968 HV0.3 679 HV0.3 917 HV0.3 0.18 mm 661 HV0.3 573 HV0.3 921 HV0.3 634 HV0.3 866 HV0.3 0.21 mm 280 HV0.3 386 HV0.3 842 HV0.3 459 HV0.3 714 HV0.3 0.24 mm 212 HV0.3 304 HV0.3 576 HV0.3 381 HV0.3 402 HV0.3 0.27 mm 195 HV0.3 199 HV0.3 493 HV0.3 287 HV0.3 225 HV0.3 0.30 mm 193 HV0.3 183 HV0.3 312 HV0.3 192 HV0.3 161 HV0.3

The results of measurement of the hardness of Examples 1 to 6 and Comparative Example 1 are shown in Table 2 and Table 3. As a result, And the hardness was relatively good. In addition, Example 2 showed a slightly better value than Example 1.

However, in the case of Comparative Example 2 in which the nitrogen and the mixed gas in the nitrogen, the hydrogen and the mixed gas were mixed at a ratio of 1: 2.2 volume ratio of less than 1: 2.5 volume ratio, the hardness was lowered in comparison with Example 1, This is because the amount of carbon in the carbonized layer is so small that the texture is insufficient. In the case of Comparative Example 3 in which nitrogen and a mixed gas of nitrogen, hydrogen, and a mixed gas were mixed at a ratio of 1: 3.8 by volume exceeding 1: 3.5 by volume, the hardness was generally excellent, but some cracks were generated .

Also, in the case of Comparative Example 4 in which the plasma ion nitriding treatment was performed at 430 占 폚, which is lower than 450 占 폚, the hardness from the surface to the inner depth of 0.12 mm was significantly reduced as compared with Example 1. The plasma ion nitriding treatment is excellent in hardness from the surface of Comparative Example 5 at 640 占 폚 exceeding 600 占 폚 up to the inner depth of 0.12 mm. However, as compared with Example 1, the hardness is suddenly increased from the inner depth of 0.21 mm , Which seems to be due to increased lattice distortion due to diffusion.

Experimental Example 3: Abrasion , Friction coefficient measurement experiment

The extrusion molds prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were submitted to the Research Institute of Automotive Parts and their friction coefficient and abrasion resistance were measured with a TE77 instrument (manufactured by PLINT partners Co. Ltd.) 4, and the results are shown in Table 5.

Exam conditions weight 50 N speed 4 Hz Stroke 10.8 mm Temperature Room temperature (25 ℃ ~ 28 ℃) time 60 minutes (steady state) Lubrication condition deflation Data acquisition 1/1 sec sample water 3 EA

division Average coefficient of friction Average wear (g) Example 1 Average 0.45 0.0018 (average 0.0030% reduction) Example 2 Average 0.48 0.0020 (average 0.0036% reduction) Comparative Example 1 Average 0.51 0.0023 (average 0.0038% reduction)

The results of the measurement of Table 5 show that the abrasion resistance of Examples 1 and 2 having a nitrided layer and a nitrided layer were superior to those of Comparative Example 1 in which surface treatment was performed only with a nitrided layer, Example 1 in which a nitrided layer and a carbonized layer were formed through a continuous process rather than that in Example 2 in which the intermetallic compound was formed through an intermittent process was relatively excellent in abrasion resistance, This is because it is excellent.

Through the above Examples and Experimental Examples, the extrusion dies produced by the surface treatment method of the present invention can have mechanical properties such as excellent surface roughness, hardness, abrasion resistance, etc., Unlike the case where the extrusion mold was preheated before, it was confirmed that the preheating process was not required.

Claims

A step of injecting an extrusion mold into a chamber, and then forming a chamber in a vacuum atmosphere;
A second step of injecting gas containing nitrogen (N ₂ ) and hydrogen (H ₂ ) at a ratio of 1: 0.8 to 1.2;
Performing a plasma ion nitriding process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to produce an extrusion die having a nitrided layer on its surface;
A chamber containing a gas containing nitrogen (N ₂ ), hydrogen (H ₂ ), and a mixed gas of nitrogen and carbon dioxide (CO ₂ ) at a ratio of 1: 0.9 to 1.2: 2.5 to 3.5 by volume, A fourth step of injecting the formed extrusion die;
A step of performing a plasma ion nitridation process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to form a nitrided layer on the surface of the extruded mold having the nitrided layer formed thereon,
Wherein the steps 3 and 4 are intermittently performed.

A step of injecting an extrusion mold into a chamber, and then forming a chamber in a vacuum atmosphere;
A second step of injecting gas containing nitrogen (N ₂ ) and hydrogen (H ₂ ) at a ratio of 1: 0.8 to 1.2;
Performing a plasma ion nitriding process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to produce an extrusion die having a nitrided layer on its surface;
A gas containing nitrogen (N ₂ ), hydrogen (H ₂ ), and a mixed gas of nitrogen and carbon dioxide (CO ₂ ) at a ratio of 1: 0.9 to 1.2: 2.5 to 3.5 Step 4;
A step of performing a plasma ion nitridation process at 450 占 폚 to 600 占 폚 and 1 占^10-2 to 1 占^10-6 Torr to form a nitrided layer on the surface of the extruded mold having the nitrided layer formed thereon,
Wherein the step 3 and the step 4 are continuously performed.

The method of claim 1 or 2, wherein the plasma ion nitridation process in the third step is performed for 5 to 15 hours.

The method according to claim 1 or 2, wherein the plasma ion nitridation process in the fifth step is performed for 10 to 15 hours.

The surface treatment method of an extrusion die according to any one of claims 1 to 3, wherein the nitrided layer in the third step has an average thickness of 50 탆 to 150 탆.

The surface treatment method of an extrusion die according to claim 1 or 2, wherein the nitrided carbonaceous layer in the fifth step has an average thickness of 100 mu m to 300 mu m.

The method according to claim 1 or 2, wherein the extrusion die is an alloy tool steel including SACM, SCM, SKD or SNCM.

The method according to claim 7, wherein the extrusion die
Wherein the surface of the extrusion die is selected from the group consisting of SUS440C, SUS304, SACM645, SCM415, SCM430, SCM435, SCM440, SKD1, SKD2, SKD6, SKD11, SKD12, SKD61, SNCM8 or SNCM21.

Wherein a coating layer on which a nitride layer and a carbon nitride layer are sequentially formed is formed on a surface of the extrusion die.

The extrusion die according to claim 9, wherein the nitrided layer has an average thickness of 50 탆 to 150 탆, and the nitrided layer has an average thickness of 100 탆 to 300 탆.

10. The method of claim 9,
The extrusion die is SKD61,
Wherein the hardness of the bushing is from 820 HV0.3 to 1300 HV0.3 from the surface of the extruded mold to the inner depth of 0.01 mm to 0.12 mm when measuring the Rockwell hardness based on KS B 0811: 2003.

The method according to claim 9, wherein the hardness of the bushes is from 400 HV 0.3 to 960 HV 0.3 from the surface of the extruded mold to the inner depth of 0.15 mm to 0.24 mm when measuring the Rockwell hardness according to KS B 0811: 2003 Extrusion mold.

The extrusion die according to claim 9, wherein an average surface roughness (R _t ) of the extrusion die is 1.2000 탆 to 2.6000 탆.

10. The method of claim 9, wherein the extrusion die comprises at least one member selected from the group consisting of SUS (Steel Use Stainless), SACM (Steel Aluminum Chromium Molybdenum), SCM (Steel Chromium Molybdenum), SKD (Steel Aluminum Tool Dise), or SNCM (Steel Nichel Chromium Molybdenum) Alloy tool steel. &Lt; RTI ID = 0.0 > 11. < / RTI >

An extrusion die produced by the surface treatment method of claim 1.

An extrusion die produced by the surface treatment method of claim 2.

The extrusion process system according to claim 15 or 16, wherein an extrusion process is performed with the extrusion die, wherein a pre-process for preheating the extrusion die before the extrusion process is not performed.