KR101873512B1

KR101873512B1 - Method for surface treatment of parts

Info

Publication number: KR101873512B1
Application number: KR1020170024147A
Authority: KR
Inventors: 정수진; 정원기; 강지영
Original assignee: 동우에이치에스티 주식회사
Priority date: 2017-02-23
Filing date: 2017-02-23
Publication date: 2018-07-02

Abstract

The present invention relates to a method for surface treatment of a sintered product after degreasing the sintered product by vacuum and then subjecting the sintered product to a heat treatment. In the method for surface treatment of the component, a sintered product is charged into a chamber of a vacuum degreasing apparatus, A degreasing step of degreasing the degreased product, and a heat treatment step of charging the degreased product into the heat treatment furnace and performing heat treatment. With this method, oil can be completely removed from the product sintered by vacuum degreasing, thereby preventing occurrence of vapor during heat treatment of the product.

Description

{METHOD FOR SURFACE TREATMENT OF PARTS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a component surface treatment method, and more particularly, to a component surface treatment method of degreasing a sintered product by vacuum and then performing heat treatment.

Generally, sintered products are heat treated for surface hardening. As a method of heat treatment for surface hardening of the product, there is a nitriding and carburizing heat treatment process. Here, plasma nitridation, gas nitridation, and low-pressure nitridation processes are used for the nitriding heat treatment process, and gas carburization, vacuum carburization, and plasma carburization processes are used for the carburization heat treatment process.

In the sintered product, since the internal density is low and the gas easily enters the interior, it is difficult to obtain a nitrogen compound having a high nitrogen concentration at the outermost surface through the gas nitriding process during the heat treatment process.

Thus, the sintered product forms a high-hardness nitrogen compound layer on the surface of the product through the plasma nitridation process. At this time, it is necessary to clean and degrease the product in order to optimize the process.

However, in the case of the sintered product, the oil component remains inside, which is not completely removed by the cleaning and the atmospheric pressure degreasing process.

Accordingly, plasma is unstable due to the oil vapor generated by the oil remaining in the sintered product in the plasma nitridation process, and the plasma nitriding process becomes longer.

In addition, there is a problem that it takes a lot of time and cost to contaminate the plasma nitrification facility and the vacuum facility due to the vapor, and to maintain and repair the same.

It is an object of the present invention to provide a method for surface treatment of a part which is developed to solve the above-mentioned problems, and which performs degreasing the sintered product in a vacuum to completely remove the oil remaining in the product and then subjecting it to heat treatment.

According to another aspect of the present invention, there is provided a surface treating method for a component, comprising: charging a sintered product into a chamber of a vacuum degreasing apparatus, heating the product to a predetermined temperature range, step; And a heat treatment step of charging the vacuum degreased product into a heat treatment furnace and performing heat treatment.

The vacuum degreasing step may include: charging a sintered product into a chamber of the vacuum degreasing apparatus; A gas introducing step of introducing a nitrogen gas into the chamber; A heating step of operating the heating unit provided in the chamber to heat the chamber; And a vacuum cooling step of turning off the heating part and activating the vacuum pump to bring the chamber into a vacuum state when the chamber reaches a certain temperature range.

The heating step may include a vapor exhaust line opening step of opening a vapor discharge line valve provided in a pipe connecting the vapor storage tank and the dust collection unit, in which the vapor discharged from the chamber is stored; A pump line closing step of closing a pump line valve provided in a pipe connecting the vapor storage tank and a vapor cooling unit for cooling the vapor discharged from the vapor storage tank; And operating the heating unit such that the temperature inside the chamber is raised to a predetermined temperature for a predetermined period of time.

Here, the operation of the heating unit may operate the heating unit such that the temperature inside the chamber is raised to the recrystallization temperature of the product.

The vacuum cooling step may include closing the vapor exhaust line closing the vapor discharge line valve; A pump line opening step of opening the pump line valve; And operating the vacuum pump such that the pressure inside the chamber is lowered to a predetermined pressure for a predetermined period of time.

Further, the vacuum cooling step may further include a chamber cooling unit operation step of operating a chamber cooling unit provided outside the chamber so that the temperature inside the chamber is cooled to a predetermined temperature.

The heat treatment may be carried out by any one of gas carburization, vacuum carburization, and plasma carburization.

Alternatively, the heat treatment may be a nitridation process of plasma nitridation, gas nitridation, or low pressure nitridation.

Wherein the heat treatment comprises a plasma nitridation process in a nitriding process, and the heat treatment process includes a product charging step of charging a vacuum degreased product into a heat treatment furnace; A gas introducing step of introducing an atmospheric gas into the heat treatment furnace; A nitriding preparation step for heating the heat treatment furnace to a vacuum state while heating it to a predetermined temperature range; And a nitriding treatment step of plasma nitriding treatment for a predetermined period of time.

Here, in the nitriding preparation step, the inside of the heat treatment furnace may be heated to 500 to 600 ° C for 3 to 4 hours.

The nitriding step may be a plasma nitriding process for 2 to 5 hours in a temperature range of 500 to 600 占 폚 inside the heat treatment furnace.

According to the component surface treatment method of the present invention, oil can be completely removed from the sintered product through vacuum degreasing, thereby preventing occurrence of vapor during heat treatment of the product.

According to the present invention, the degreasing process time and the heat treatment process time can be saved through vacuum degreasing.

Also, according to the present invention, oil can be completely removed from a sintered product through vacuum degreasing, thereby improving the heat treatment effect and improving the quality of the product.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart schematically showing a method for surface treatment of parts according to an embodiment of the present invention;
FIG. 2 is a schematic view illustrating a vacuum degreasing apparatus used in a vacuum degreasing step in a component surface treatment method according to an embodiment of the present invention; FIG.
3 is a block diagram schematically showing the configuration of a vacuum degreasing apparatus used in a vacuum degreasing step in the method of surface treatment of a component according to an embodiment of the present invention.
4 is a flowchart schematically showing a vacuum degreasing step in the component surface treatment method according to the embodiment of the present invention,
5 is a graph and a table schematically showing a vacuum degreasing process through a vacuum degreasing step in the method of surface treatment of parts according to an embodiment of the present invention,
6 (a) is a graph schematically showing a plasma nitriding process of a conventional cleaning and atmospheric pressure degreased product,
6B is a graph schematically showing a plasma nitridation process of the component surface treatment method according to the embodiment of the present invention for forming the same thickness as the nitride compound layer formed by the plasma nitridation process according to FIG.
FIG. 7A is a photograph schematically showing a nitride compound layer formed by the plasma nitridation process according to FIG. 6A,
7B is a schematic view showing a nitrided compound layer formed by the plasma nitridation process after vacuum degreasing by the component surface treatment method according to the embodiment of the present invention at the same process time as the plasma nitridation process according to FIG. It is a photograph.

In order to facilitate understanding of the features of the present invention, a vacuum degreasing apparatus and a control method thereof according to an embodiment of the present invention will be described in detail.

It should be noted that, in order to facilitate understanding of the embodiments described below, reference numerals are added to the components of the accompanying drawings, so that the same components are denoted by the same reference numerals even though they are shown in different drawings . In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, a specific embodiment of the present invention will be described with reference to the accompanying drawings.

Fig. 1 is a flowchart schematically showing a component surface treatment method according to an embodiment of the present invention.

Referring to FIG. 1, the method for surface treatment of parts according to an embodiment of the present invention includes a vacuum degreasing step (S10) of charging a sintered product into a chamber of a vacuum degreasing apparatus, heating the product to a predetermined temperature range, , And a heat treatment step (S20) of charging the vacuum degreased product into the heat treatment furnace and performing heat treatment.

In the heat treatment step, a nitriding and carburizing heat treatment process may be performed. More specifically, the carburizing step can be carried out by any one of gas carburizing, vacuum carburizing, and plasma carburizing. As the nitriding process, any one of plasma nitridation, gas nitridation, and low pressure nitridation can be performed.

Hereinafter, the plasma nitridation process during the heat treatment process will be described as an example.

The heat treatment step S20 includes a product charging step S21 for charging the degreased product into the heat treatment furnace, a gas charging step S22 for introducing the atmospheric gas into the heat treatment furnace, A nitriding preparation step (S23) for making a vacuum state while heating, and a nitriding treatment step (S24) for plasma nitriding treatment for a predetermined time.

For example, in the nitriding preparation step (S23), the inside of the heat treatment furnace may be heated to 500 to 600 ° C for 3 to 4 hours, and the nitriding treatment step (S24) To 600 ° C for 2 to 5 hours.

Of course, the temperature and time conditions of the nitriding preparation step (S23) and the nitriding treatment step (S24) are examples and can be changed by the size of the product, the material, the thickness of the target nitrogen compound layer, and the like.

Hereinafter, the vacuum degreasing apparatus used in the vacuum degreasing step (S10) and the vacuum degreasing step will be described in more detail below with reference to FIGS. 2 and 3. FIG.

FIG. 2 is a view schematically showing a vacuum degreasing apparatus used in the degreasing step in the component surface treatment method. FIG. 3 schematically shows the structure of a vacuum degreasing apparatus used in the vacuum degreasing step in the component surface treatment method A block diagram is shown.

2 and 3, the vacuum degreasing apparatus 100 includes a chamber 200 having a door 210 that opens and closes an opened upper portion and into which a product P is charged, A vacuum pump 400 installed in the chamber 200 for heating the chamber 200 and a vacuum pump 400 for sucking the gas in the chamber 200 to make the inside of the chamber 200 vacuum; Trapping means 300 disposed between the vacuum pump 400 and the vacuum pump 400 for filtering the oil O from the vapor discharged from the chamber 200 and the product P charged in the chamber 200, And a control unit 500 for sequentially operating the heating unit 220 and the vacuum pump 400 to degas.

The chamber 200 is formed to have a double space, the sintered product P is loaded in the inner space, and the heating unit 220 is disposed in the outer space to heat the inner space.

The chamber 200 may further include a chamber cooling unit 280 for cooling the inner space. The chamber cooling unit 280 may be provided in any form capable of cooling the heated chamber 200 by a blower or the like.

The chamber 200 may be provided with a heater heat exhaust line 250 that is provided as a pipe and communicates with the outside space and the outside and a heater heat exhaust line valve 260 that opens and closes the heater heat exhaust line 250 have.

This is because when the chamber cooling unit 280 is operated to cool the chamber 200, the heater heat exhaust line 250 is opened to discharge the warm air inside the chamber 200 to the outside, It is for this reason.

The door 210 for opening and closing the upper portion of the chamber 200 may include a gas inlet 230 connected to the gas supply unit 240 to supply nitrogen gas to the chamber 200 . This is to turn the inside of the chamber 200 into a nitrogen gas atmosphere during the vacuum degreasing process of the product.

The door 210 of the chamber 200 may be provided with a temperature sensor 270 for measuring the temperature inside the chamber 200. This is to measure the inside of the chamber 200 to control the heating unit 220 so that the inside of the chamber 200 satisfies an appropriate temperature range during the vacuum degreasing process of the product P. [

The trap means 300 is disposed between the chamber 200 and the vacuum pump 400 and is provided to filter the oil from the vapor discharged from the chamber 200. That is, when the chamber 200 is heated, the oil remaining in the product P is heated to generate vapor. The trap means 300 filters the oil so that the generated vapor does not flow into the vacuum pump 400.

More specifically, the trap means 300 includes a vapor storage tank 310 in which the vapor discharged from the chamber 200 is stored, and a discharge port 310 connected to the vapor storage tank 310 and discharged from the vapor storage tank 310 And a vapor cooling unit 350 connected to the vapor storage tank 310 and cooling the vapor discharged from the vapor storage tank 310 to filter oil from the vaporized vapor in the vapor storage tank 310 . The vacuum pump 400 further includes a filter unit 360 disposed between the vapor cooling unit 350 and the vacuum pump 400 to filter foreign substances from the gas introduced into the vacuum pump 400.

The vapor storage tank 310 is connected to the chamber 200 by piping, and the vapor generated in the chamber 200 is stored first. Since the temperature of the vapor stored in the vapor storage tank 310 is lowered, a part of the vapor is condensed and stored in the vapor storage tank 310 as the liquid.

The vapor storage tank 310 may include a discharge unit 311 and a valve 312 to discharge the liquid oil to the outside when the liquid oil is filled in the vapor storage tank 310 by a predetermined amount or more.

The dust collecting unit 330 is connected to the vapor discharge line 320 provided in the vapor storage tank 310 and is provided to filter the oil from the vapor discharged from the vapor storage tank 310. Of course, the dust collecting part 330 may be provided to filter oil as well as foreign matter from the oil vapor. In addition, the dust collecting unit 330 may be configured to discharge the steam filtered by the oil to the outside.

The dust collecting part 330 may be provided in any form as long as it is capable of filtering oil and foreign substances contained in the gas.

The vapor cooling unit 350 is connected to a pump line 340 provided in the vapor storage tank 310 and a pipe line. The vaporized vapor discharged from the vapor storage tank 310 is cooled and condensed into liquid oil, Lt; / RTI >

The vapor cooling unit 350 includes a cooling tank 351 connected to the vapor storage tank 310 and through which the vapor discharged from the vapor storage tank 310 flows, A cooling line 352 for cooling and condensing the vapor, and a cooling water supply 353 for circulating the cooling water to the cooling line 352. Here, the cooling line 352 is arranged in the cooling tank 351 in a zigzag form.

With this configuration, when the vapor is introduced into the cooling tank 351, the vapor is cooled and condensed while passing through the cooling line 352, and the condensed oil is collected in the lower portion of the cooling tank 351.

When the condensed liquid oil in the cooling tank 351 is filled to a certain level or more, the cooling tank 351 may include a discharge portion 354 and a valve 355 to discharge the liquid to the outside.

The filter unit 360 is disposed in front of the vacuum pump 400 to filter the vapor and foreign substances that may remain in the gas flowing into the vacuum pump 400.

The filter unit 360 may be provided in any form as long as it is capable of filtering oil and foreign substances contained in the gas.

The trap means 300 further includes a vapor discharge line valve 321 and a pump line valve 341.

The vapor discharge line valve 321 is installed in the vapor discharge line 320 which is a pipe connecting the vapor storage tank 310 and the dust collection unit 330 to open and close the vapor discharge line 320 .

The pump line valve 341 is installed in a pump line 340 that connects the vapor storage tank 310 and the vapor cooling unit 350 and opens and closes the pump line 340.

The control unit 500 controls the heating unit 220 and the vacuum pump 400 to sequentially operate so as to degrade the products loaded in the chamber 200. [

More specifically, the control unit 500 operates the heating unit 220 so that the inside of the chamber 200 is heated to a predetermined temperature for a predetermined time, and when the temperature reaches a predetermined temperature, the heating unit 220 is turned off, The vacuum pump 400 is operated so that the inside of the vacuum chamber 200 is lowered to a predetermined pressure for a predetermined time.

At this time, when the heating unit 220 is operated, the control unit 500 opens the vapor discharge line valve 321 and closes the pump line valve so that the vapor discharged from the chamber 200 flows into the vapor storage tank And then flows into the dust collecting unit 330 through the vapor exhaust line 320 to completely filter the oil from the vapor and then to the outside.

When the vacuum pump 400 is operated, the control unit 500 closes the vapor discharge line valve 321 and opens the pump line valve 341 so that the vacuum pump 400 can be operated in the chamber 200 ) Make the inside of the vacuum state. At this time, the remaining vapor in the chamber 200 is condensed while passing through the vapor cooling unit 350, and is filtered with liquid oil, and is further filtered while passing through the filter unit 360.

The discharge unit of the vacuum pump 400 may be connected to the dust collecting unit 330 through an exhaust line 410 so that the gas sucked through the vacuum pump 400 may be discharged to the dust collecting unit 330 .

Hereinafter, a method of vacuum degreasing a sintered product in a vacuum degreasing method will be described as an example. Therefore, the process temperature and the treatment time are not limited thereto, but may be changed depending on the condition of the degreasing product, the process environment, and the like.

FIG. 4 is a flowchart schematically showing a vacuum degreasing step using the vacuum degreasing apparatus in the component surface treatment method, and FIG. 5 is a graph and a table schematically showing a vacuum degreasing step through the vacuum degreasing step.

4 and 5, the vacuum degreasing step includes the steps of charging a sintered product into the chamber and closing the door (S100), introducing a nitrogen gas into the chamber through a gas inlet provided in the door A heating step (S300) of operating the heating unit provided in the chamber to heat the chamber; and a step of turning off the heating unit and operating the vacuum pump when the chamber reaches a predetermined temperature, And a vacuum cooling step (S400) for making the vacuum state.

Here, the heating step S300 may include opening a vapor exhaust line (S310) for opening a vapor exhaust line valve provided in a pipe connecting the vapor storage tank and the dust collection unit to store the vapor discharged from the chamber, A pump line closing step S310 for closing a pump line valve provided in a pipe connecting a tank and a vapor cooling unit for cooling the vapor discharged from the vapor storage tank, And operating the heating unit to raise the temperature to 450 DEG C (S330).

The vacuum cooling step S400 may include closing a vapor exhaust line S410 for closing the vapor line valve, opening a pump line for opening the pump line valve S410, And operating the vacuum pump so that the pressure inside the chamber is lowered to 0.01 to 0.1 torr (S420, S430).

Further, in the vacuum cooling step S400, the chamber cooling unit provided outside the chamber is operated so that the temperature inside the chamber is cooled to 150 to 250 DEG C for 2 to 4 hours together with the vacuum pump operating step (S420) And a chamber cooling section operation step (S440, S450).

If the sintered product is degreased through the vacuum degreasing apparatus and its control method, the oil in the product can be removed more effectively with a degreasing process time of about 20 to 30% of the time required for the conventional cleaning and atmospheric pressure degreasing process . For example, if it takes 24 hours to degrease the same quantity of products, the vacuum degreasing process can provide an excellent oil removal effect even if the degreasing process is performed for 5 to 7 hours.

Through this, it is possible to completely remove the oil remaining in the sintered product to prevent occurrence of vapor in the plasma nitriding process, which is a surface hardening process of the product, thereby shortening the nitriding process time and improving the product quality, The failure of the nitriding process equipment can be prevented in advance.

Hereinafter, referring to the accompanying drawings, a description will be given of a specific example in which the degreased product is degreased by the conventional degreasing process and the degreased product is degreased by the degreasing process of the present invention.

6 (a) is a graph schematically showing a plasma nitridation process of a conventional cleaning and atmospheric pressure degreased product, and FIG. 6 (b) is a graph showing the same plasma nitridation process as that of the nitride nitriding process FIG. 2 is a graph schematically showing a plasma nitridation process of a component surface treatment method according to an embodiment of the present invention for forming a thickness. FIG.

That is, the graph of the plasma nitridation process shown in FIG. 6 shows the process conditions for forming the nitrogen compound layer to a thickness of 3.4 탆 on the surface of the degreased product.

Referring to FIG. 6A, the degreased product in the conventional degreasing process is vacuum-quenched by heating the interior of the product by nitriding for 4 hours, and then subjected to a plasma nitriding process at 560 ° C. for 7 hours to form a nitrogen compound layer Can be formed to a thickness of 3.4 mu m. In the conventional degreasing process, the vapor is generated in the process of heating the inside of the nitride, and the generated vapor makes the plasma unstable, and the plasma nitriding process time becomes long.

6 (b), the degreased product in the vacuum degreasing process according to the embodiment of the present invention is heated by nitriding for 4 hours while keeping the inside thereof in a vacuum state, and is heated at 560 ° C. for 2 hours The nitrogen compound layer can be formed on the surface of the product to a thickness of 3.4 탆. That is, the time for the plasma nitriding process for 5 hours can be shortened to form the nitrogen compound layer having the thickness of 3.4 탆.

Therefore, the oil can be completely removed from the product through the vacuum degreasing process, so that even when the inside of the furnace is heated, the vaporization is hardly generated, so that the plasma nitriding process can be stably performed. can do.

7 (a) is a photograph schematically showing a nitride compound layer formed by the plasma nitridation process in FIG. 6 (a), and FIG. 7 (b) is a view similar to the plasma nitridation process in FIG. 6 Is a photograph schematically showing a nitride compound layer formed by a plasma nitridation process after vacuum degreasing by a component surface treatment method according to an embodiment of the present invention.

As shown in FIG. 7 (a), when the degreased product is subjected to plasma nitriding at 560 ° C. for 7 hours through a conventional degreasing process, a nitrogen compound layer having a thickness of 3.4 μm is formed on the surface of the product.

7 (b), when the degreased product is plasma-nitrided at 560 ° C. for 7 hours through the vacuum degreasing process according to the embodiment of the present invention, a product having a thickness of 5.38 μm The nitrogen compound layer is formed. Therefore, even when the same plasma nitriding process time is invested, the effect of increasing the thickness by about 50% or more can be obtained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that various changes and modifications may be made without departing from the scope of the appended claims.

O: Oil P: Product
100: vacuum degreasing apparatus 200: chamber
210: Door 220: Heating part
230: gas inflow part 240: gas supply part
250: heater heat exhaust line 260: heater heat exhaust line valve
270: Temperature sensor 280: Chamber cooling section
300: trap means 310: vapor storage tank
320: Vapor exhaust line 321: Vapor exhaust line valve
330: dust collector 340: pump line
341: Pump line valve 350: Vapor cooling unit
351: Cooling tank 352: Cooling line
353: Cooling water supply part 360: Filter part
400: Vacuum pump 500: Control unit

Claims

A vacuum degreasing step of charging a sintered product into a chamber of a vacuum degreasing apparatus, heating the product to a predetermined temperature range, vacuum-cooling the product, and degreasing the product; And
And a heat treatment step of charging the vacuum degreased product into the heat treatment furnace and performing heat treatment,
In the vacuum degreasing step,
A product charging step of charging the sintered product into the chamber of the vacuum degassing apparatus;
A gas introducing step of introducing a nitrogen gas into the chamber;
A heating step of operating the heating unit provided in the chamber to heat the chamber;
A vacuum cooling step of turning off the heating part and operating the vacuum pump to bring the chamber into a vacuum state when the chamber reaches a certain temperature range; And
Operating the chamber cooling unit to operate the chamber cooling unit provided outside the chamber so that the temperature inside the chamber is cooled to a predetermined temperature together with the vacuum cooling step;
Wherein the component surface treatment method comprises the steps of:

delete

The method according to claim 1,
In the heating step,
Opening a vapor exhaust line valve provided in a pipe connecting the vapor storage tank and the dust collection unit, the vapor discharge line valve storing the vapor discharged from the chamber;
A pump line closing step of closing a pump line valve provided in a pipe connecting the vapor storage tank and a vapor cooling unit for cooling the vapor discharged from the vapor storage tank; And
Operating the heating unit such that the temperature inside the chamber is raised to a predetermined temperature for a predetermined time;
Wherein the component surface treatment method comprises the steps of:

The method of claim 3,
The heating unit operation step includes:
And operating the heating unit such that the temperature inside the chamber is raised to the recrystallization temperature of the product.

The method of claim 3,
The vacuum cooling step may include:
Closing the vapor exhaust line valve closing the vapor exhaust line valve;
A pump line opening step of opening the pump line valve; And
Operating the vacuum pump so that the pressure inside the chamber is lowered to a predetermined pressure for a predetermined time;
Wherein the component surface treatment method comprises the steps of:

delete

The method according to claim 1,
Wherein the heat treatment is carried out by any one of carburizing, vacuum carburizing, and plasma carburizing.

The method according to claim 1,
Wherein the heat treatment is a nitriding process of any one of plasma nitridation, gas nitridation, and low pressure nitriding.

9. The method of claim 8,
Wherein the heat treatment includes a plasma nitridation process in a nitriding process,
The heat treatment step may include:
A step of charging a product into a heat treatment furnace by vacuum degreasing;
A gas introducing step of introducing an atmospheric gas into the heat treatment furnace;
A nitriding preparation step for heating the heat treatment furnace to a vacuum state while heating it to a predetermined temperature range; And
A nitriding treatment step for plasma nitriding treatment for a predetermined time;
Wherein the component surface treatment method comprises the steps of:

10. The method of claim 9,
In the nitriding preparation step,
And heating the inside of the heat treatment furnace to raise the temperature to 500 to 600 占 폚 for 3 to 4 hours.

11. The method of claim 10,
In the nitriding process,
Wherein the plasma nitriding treatment is performed for 2 to 5 hours at a temperature of 500 to 600 占 폚 inside the heat treatment furnace.