KR100899578B1 - Method for surface hardening by high temperature nitriding in vacuum - Google Patents

Method for surface hardening by high temperature nitriding in vacuum Download PDF

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KR100899578B1
KR100899578B1 KR1020070098774A KR20070098774A KR100899578B1 KR 100899578 B1 KR100899578 B1 KR 100899578B1 KR 1020070098774 A KR1020070098774 A KR 1020070098774A KR 20070098774 A KR20070098774 A KR 20070098774A KR 100899578 B1 KR100899578 B1 KR 100899578B1
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oil
workpiece
heating chamber
cooling
temperature
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KR20090033638A (en
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김성완
김상권
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한국생산기술연구원
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—After-treatment

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
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Abstract

본 발명은 저급 소재를 활용하면서도 내마모성과 표면경도를 극대화시킴과 아울러 변형량을 최소화시키고, 질소 흡착율을 향상시켜 제품 생산속도를 향상시킬 수 있도록 한 고온 진공 질화법에 의한 경화처리 방법에 관한 것이다.The present invention relates to a hardening treatment method using a high temperature vacuum nitriding method to maximize the wear resistance and surface hardness while minimizing the deformation amount, improving the nitrogen adsorption rate, and improving the product production rate while utilizing a low-grade material.

이를 위해, 가열실 내부를 350~500℃의 온도로 가열하여 피처리물을 가열하고, 가열실 내부에 산소를 투입하여 피처리물 표면을 산화 활성화시키며, 가열실 내부의 온도를 700℃ 이상으로 승온시키고, 내부에 암모니아 가스를 투입하여 피처리물을 질화 처리하고, 피처리물을 냉각실로 이동시켜 오일소입조 내에서 오일로 균일 냉각하며, 오일소입조 내에서 냉각된 피처리물을 들어올려 오일 분위기에서 가스로 균일 냉각하는 것을 특징으로 한다.To this end, the interior of the heating chamber is heated to a temperature of 350 to 500 ° C. to heat the workpiece, and oxygen is added to the interior of the heating chamber to oxidize and activate the surface of the workpiece. The temperature is increased, ammonia gas is injected into the inside of the object, and the object is nitrided. The object is moved to a cooling chamber to be uniformly cooled with oil in an oil simmering tank, and the object is cooled in the oil sintering tank. It is characterized by uniformly cooling with gas in an oil atmosphere.

상기한 구성에 따라, 내부는 인성 및 충격강도가 좋은 재질로 남아 있고, 표면만 대략 800HV 정도의 고경도를 갖도록 경화처리하여, 내마모성과 내구성이 필요한 제품에 사용이 적합하고, 저급 소재에 적용 가능하여 제품의 단가를 절감할 수 있으며, 표면 활성화를 통해 질소의 흡착률과 흡착속도를 향상시켜 제품의 생산성을 극대화시킬 수 있는 효과가 있다.According to the above configuration, the inside remains of a material with good toughness and impact strength, and the surface is hardened to have a high hardness of about 800 HV, so it is suitable for use in products requiring wear resistance and durability, and can be applied to low-grade materials. The cost of the product can be reduced, and the surface activation has the effect of maximizing the productivity of the product by improving the adsorption rate and adsorption rate of nitrogen.

침탄, 질화, 표면경화, 표면 활성화, 암모니아가스, 저탄소 합금강. Carburization, Nitriding, Surface Hardening, Surface Activation, Ammonia Gas, Low Carbon Alloy Steel.

Description

고온 진공 질화법에 의한 경화처리 방법{Method for surface hardening by high temperature nitriding in vacuum}Hardening treatment method by high temperature vacuum nitriding method {Method for surface hardening by high temperature nitriding in vacuum}

본 발명은 경화처리 방법에 관한 것으로, 보다 상세하게는 저급 소재를 활용하면서도 내마모성과 표면경도를 극대화시킴과 아울러 변형량을 최소화시키고, 질소 흡착율을 향상시켜 제품 생산속도를 향상시킬 수 있도록 한 고온 진공 질화법에 의한 경화처리 방법에 관한 것이다.The present invention relates to a hardening treatment method, and more particularly, a high temperature vacuum quality that maximizes abrasion resistance and surface hardness while minimizing deformation amount and improving nitrogen adsorption rate to improve product production rate while utilizing low-grade materials. It relates to a curing treatment method by the chemical method.

일반적으로, 표면경화처리는 철강의 열처리에서, 표면의 내마모성, 내피로성을 증가하기 위해 철강의 표면층만을 경화하여 내부에는 인성(靷性)을 보존하는 방법으로, 열처리, 침탄, 침탄질화, 질화(연질화, 염욕질화 등), 고주파 등이 사용되고 있다.In general, the surface hardening treatment is a method of hardening only the surface layer of steel in order to increase the wear resistance and fatigue resistance of the steel in order to preserve the toughness therein. Soft nitriding, salt bath nitriding, etc.), and high frequency.

이 중, 침탄은 침탄제의 종류에 따라 고체, 액체, 가스 침탄법으로 분류가 되는데, 탄소량을 매우 낮게 만들어 놓은 저탄소강(低炭素鋼)의 표면으로부터 탄소를 스며들게 하여, 표면 가까이에만 탄소량을 높이고 그 후 담금질, 템퍼링의 처리를 함으로써 표면을 경화시키는 방법이다.Among these, carburization is classified into solid, liquid, and gas carburizing method according to the type of carburizing agent. Carbon carbide is infiltrated from the surface of the low carbon steel which has made the carbon amount very low, and the amount of carbon only near the surface. It is a method of hardening a surface by raising and then hardening and tempering.

이러한, 침탄공정은 내마모성이나 피로저항이 커지는 특성으로 인해 자동차 부품의 경화처리에 주로 사용되고는 있으나, 상기 침탄공정은 냉각시 변형이 심하여 얇은 판재 부품에 적용하기 어려워 표면만을 경화하고자 하는 경우에는 질화처리를 대체하여 실시한다.The carburizing process is mainly used for hardening of automotive parts due to the characteristics of wear resistance and fatigue resistance. However, the carburizing process is hard to be applied to thin plate parts due to severe deformation during cooling. Replace with

이와 같은 질화처리는 경화처리하고자 하는 제품의 내마모성을 향상시키고, 변형을 줄일 수 있는 효과가 있으나, 저온에서 실시되는 공정 특성상 침탄과 동일한 깊이로 질소를 침투시키기 위해서는 경화처리에 상당한 시간이 소요되고, 경화처리한 제품의 단가가 상승하여 가격경쟁력이 떨어지는 문제가 있으며, 또한 질화처리 중 제품 표면에 화합물층을 형성하여 제품의 표면을 거칠게 하는 문제도 발생하였다.Such nitriding treatment has the effect of improving the wear resistance of the product to be cured and reducing the deformation. However, in order to penetrate nitrogen to the same depth as carburizing due to the process characteristics performed at low temperature, it takes a considerable time for the curing treatment. There is a problem in that the price competitiveness of the cured product is increased and the price competitiveness is lowered. In addition, the compound layer is formed on the surface of the product during nitriding to roughen the surface of the product.

이에, 상기한 문제점을 해결하기 위해 1990년대 일본에서는 질소를 첨가하여 제품을 경화처리하는 L-Tec라는 방법을 제시하였다. 즉, 680~800℃의 온도 구간에서 탄소, 즉 이산화탄소, 메탄, 에탄 등의 가스나 메탄올, 에탄올, 이소프로필알콜 등을 첨가함으로써, 반응시 제품 표면에 약간의 침탄반응이 일어나도록 함과 동시에 질소를 첨가하는 것이다.Thus, in order to solve the above problems, Japan in the 1990s proposed a method called L-Tec to cure the product by adding nitrogen. That is, by adding carbon such as carbon dioxide, methane, ethane, methanol, ethanol, isopropyl alcohol, etc. in the temperature range of 680-800 ° C., nitrogen may be slightly carburized on the surface of the product during the reaction. Is to add.

또한, 최근에는 일본의 니혼테크노사에서 초기 활성도를 증가시키기 위해 진공을 만들고 다시 대기압력으로 올려 CO2 가스와 암모니아의 함량을 조절하면서 강종별로 질소마르텐사이트를 만드는 N-Quenching이라는 공정이 개발되었다.In recent years, Nihon Techno Co., Ltd. has developed a process called N-Quenching, which makes nitrogen martensite by steel type while adjusting the contents of CO 2 gas and ammonia by making a vacuum and increasing it to atmospheric pressure to increase the initial activity.

즉, 철의 일반적인 표면에서는 질소를 넣기가 매우 어렵기 때문에, 위의 N-Quenching 공정에서는 질소를 넣기 위해 CO2 가스를 활용하여 표면을 활성하면서 산화와 침탄 질화를 동시에 실시하는 것이다. 즉, 연질화를 고온에서 실시하는 방법을 취한다.That is, since it is very difficult to put nitrogen on the general surface of iron, in the above N-Quenching process, the oxidation and carburization and nitriding are simultaneously performed while activating the surface by using CO 2 gas for nitrogen. That is, the method of carrying out soft nitriding at high temperature is taken.

그러나, 상기한 N-Quenching 공정의 경우 소재의 탄소량이나 가공정도 등에 따라 불균일이 심하고, 특히 암모니아 가스 조절과 더불어 함유 가스로서 혼합가스를 사용하여 제어를 하는데 공정이 복잡하며, 현재 실용화 하는데 균일성 문제가 남아 아직 실용화 되지 못했다.However, in the case of the N-Quenching process, the non-uniformity is severe depending on the amount of carbon and the degree of processing of the material, and in particular, the process is complicated to control by using a mixed gas as a gas containing ammonia gas, and uniformity for the practical use. The problem remains and it has not been put to practical use yet.

본 발명은 전술한 바와 같은 종래의 문제점을 해결하기 위하여 안출한 것으로, 저급 소재를 활용하면서도 내마모성과 표면경도를 극대화시킴과 아울러 변형량을 최소화시키고, 질소 흡착율을 향상시켜 제품 생산속도를 향상시킬 수 있도록 한 고온 진공 질화법에 의한 경화처리 방법을 제공하는 데 있다. The present invention has been made to solve the conventional problems as described above, while maximizing the wear resistance and surface hardness while using a low-quality material to minimize the amount of deformation, improve the nitrogen adsorption rate to improve the product production rate The present invention provides a hardening method by a high temperature vacuum nitriding method.

상기와 같은 목적을 달성하기 위한 본 발명의 구성은, 피처리물의 표면을 경화처리하기 위한 방법에 있어서, 가열실 내부를 350~500℃의 온도로 가열하여 피처리물을 가열하는 공정과; 상기 가열실 내부에 산소를 투입하여 피처리물 표면을 산화 활성화시키는 공정과; 상기 가열실 내부의 온도를 700℃ 이상으로 승온시키고, 내부에 암모니아 가스를 투입하여 피처리물을 질화 처리하는 공정과; 질화처리한 피처리물을 냉각실로 이동시키되, 냉각실의 압력과 교반속도를 제어하여 피처리물을 오일소입조 내에서 오일로 균일 냉각하는 공정과; 상기 오일소입조 내에서 냉각된 피처리물을 들어올려 오일 분위기에서 가스로 균일 냉각하는 공정을 포함한다.A structure of the present invention for achieving the above object is a method for curing the surface of the workpiece, the step of heating the interior of the heating chamber by heating to a temperature of 350 ~ 500 ℃; Injecting oxygen into the heating chamber to oxidatively activate the surface of the workpiece; Raising the temperature inside the heating chamber to 700 ° C. or higher, and injecting ammonia gas into the nitriding treatment of the object; Moving the nitrided object to a cooling chamber to control the pressure and agitation speed of the cooling chamber to uniformly cool the object with oil in an oil sintering tank; And lifting the cooled object in the oil sintering tank to uniformly cool the gas in an oil atmosphere.

상기한 과제 해결수단을 통해 본 발명은, 내부는 인성 및 충격강도가 좋은 재질로 남아 있고, 표면만 대략 800HV 정도의 고경도를 갖도록 경화처리하여, 내마모성과 내구성이 필요한 구조물 및 구동부품 등에 사용이 가능한 효과가 있고, 또한 저탄소 소재(강)와, 저탄소 합금강 등의 판재에 적용 가능하여 제품의 단가를 획기적으로 절감할 수 있는 효과도 있다.The present invention through the above-described problem solving means, the inside remains of a material with good toughness and impact strength, and the surface is hardened to have a high hardness of about 800 HV, it is easy to use for structures and driving parts that require wear resistance and durability There is a possible effect, and also can be applied to low carbon materials (steel), plate materials such as low carbon alloy steel, there is also an effect that can significantly reduce the unit cost of the product.

더욱이, 질화공정 이전에 표면을 산화 활성화시켜 질소의 흡착률과 흡착속도를 증가시키고, 질소를 빠른 시간 내에 피처리물 내부로 확산시켜, 경화처리 속도를 향상시킴과 아울러 제품의 생산성을 극대화시킬 수 있는 효과도 있다.Moreover, by oxidizing and activating the surface prior to the nitriding process, the adsorption rate and adsorption rate of nitrogen can be increased, and the nitrogen can be diffused into the workpiece quickly, thereby improving the curing rate and maximizing the productivity of the product. There is also an effect.

게다가, 변형량이 침탄에 비해 매우 적고, 질화보다 처리온도가 높아 피처리물 표면에 확산층을 생성하므로, 생산효율 증대 및 저가의 내구성이 필요한 구동부품이나 기능성 구조물 제조에 탁월한 효과도 있다.In addition, since the amount of deformation is much smaller than that of carburizing and the treatment temperature is higher than that of nitriding, a diffusion layer is formed on the surface of the workpiece, and thus, it is also excellent in manufacturing a driving component or a functional structure that requires increased production efficiency and low-cost durability.

본 발명의 바람직한 실시예를 첨부된 도면에 의하여 상세히 설명하면 다음과 같다.When described in detail with reference to the accompanying drawings a preferred embodiment of the present invention.

도 1 내지 도 9는 본 발명의 고온 진공 질화법에 의한 경화처리 방법에 대한 것으로, 크게 가열공정(P10)과, 활성화공정(P20)과, 질화공정(P30)과, 오일 냉각공정(P40)과, 가스 냉각공정(P50)을 포함한다.1 to 9 illustrate a hardening treatment method according to the high temperature vacuum nitriding method of the present invention, and are largely a heating step (P10), an activation step (P20), a nitriding step (P30), and an oil cooling step (P40). And a gas cooling step (P50).

도 1 내지 도 3을 통해 설명하면, 먼저 가열공정(P10)은 가열실(10) 내부를 가열하여 피처리물을 가열하는 공정으로써, 진공 분위기에서 가열실(10) 내부의 온도를 피처리물의 소재에 따라 약 350~500℃의 다양한 온도로 가열하여 피처리물을 가열한다.Referring to FIGS. 1 to 3, first, the heating step P10 is a step of heating the inside of the heating chamber 10 to heat the target object. The workpiece is heated by heating to a variety of temperatures of about 350 ~ 500 ℃ depending on the material.

활성화공정(P20)은 상기 가열실(10) 내부에 산소를 투입하여 피처리물 표면을 산화 활성화시키는 공정으로써, 가열실(10) 내부에 약 10~60분 동안 산소를 투입하여 피처리물 표면을 산화시킨다.The activation step (P20) is a step of oxidizing and activating the surface of the workpiece by injecting oxygen into the heating chamber 10, and injecting oxygen into the heating chamber 10 for about 10 to 60 minutes to surface the workpiece. Is oxidized.

질화공정(P30)은 상기 가열실(10) 내부의 온도를 승온시키고, 내부에 암모니아 가스를 투입하여 피처리물을 질화 처리하는 공정으로써, 가열실(10) 내부의 온도를 약 700~850℃로 승온 유지시키고, 상기 가열실(10)에 암모니아가스를 약 8~30ℓ/min 투입하면서, 피처리물을 약 60~180분 동안 질화처리한다.The nitriding step P30 is a step of raising the temperature inside the heating chamber 10 and injecting ammonia gas into the nitriding treatment of the object to be processed, and adjusting the temperature inside the heating chamber 10 to about 700 to 850 ° C. The temperature is maintained in the furnace, and the ammonia gas is introduced into the heating chamber 10 in an amount of about 8 to 30 l / min, and the object to be treated is nitrided for about 60 to 180 minutes.

오일 냉각공정(P40)은 질화처리한 피처리물을 냉각실(20)로 이동시키되, 냉각실(20)의 압력을 약 100~700mbar로 제어하고, 오일소입조(25) 내의 오일 교반속도를 약 5~15Hz로 제어하면서, 피처리물을 오일소입조(25) 내에 침지시켜 오일로 균일 냉각한다. 여기서, 냉각실(20)의 압력이 가열실(10)의 압력보다 높은 경우에는 상기 피처리물의 이동을 제한하고, 냉각실(20)의 압력이 가열실(10)의 압력과 동일해지는 경우, 상기 피처리물의 이동을 허가하게 된다.The oil cooling process (P40) is to move the nitrided to be processed to the cooling chamber 20, to control the pressure of the cooling chamber 20 to about 100 ~ 700 mbar, the oil stirring speed in the oil sintering tank 25 While controlling at about 5 to 15 Hz, the object is immersed in the oil sintering tank 25 and uniformly cooled with oil. Here, when the pressure of the cooling chamber 20 is higher than the pressure of the heating chamber 10, the movement of the object is restricted, and when the pressure of the cooling chamber 20 is equal to the pressure of the heating chamber 10, The movement of the object is allowed.

그 이유는, 냉각실(20)의 압력이 가열실(10)의 압력보다 현저히 높은 경우에 가열실(10)과 냉각실(20) 사이를 개방하면 냉각실(20)의 높은 압력에 의해 냉각실(20) 내부에 구비된 오일소입조(25) 내의 냉각매질(오일)이 가열실(10)로 넘어가게 되어, 사고 발생의 위험이 있기 때문이다. 또한, 오일소입조(25) 내의 냉각매질은 전열을 발생시켜 가열함으로써, 상기 오일소입조(25) 내에서 순환 유동시켜 염도 및 온도가 균일하게 되도록 한다.The reason for this is that when the pressure in the cooling chamber 20 is significantly higher than the pressure in the heating chamber 10, if the pressure is opened between the heating chamber 10 and the cooling chamber 20, it is cooled by the high pressure of the cooling chamber 20. This is because the cooling medium (oil) in the oil sintering tank 25 provided in the chamber 20 is transferred to the heating chamber 10, which may cause an accident. In addition, the cooling medium in the oil sintering tank 25 generates heat to heat, thereby circulating and flowing in the oil sintering tank 25 so that salinity and temperature are uniform.

가스 냉각공정(P50)는 상기 오일소입조(25)에서 냉각된 피처리물을 들어올려 기화된 오일의 가스 분위기에서 균일 냉각한다.The gas cooling step P50 lifts the object to be cooled in the oil sintering tank 25 and uniformly cools it in the gas atmosphere of the vaporized oil.

이와 같이 구성된 본 발명의 작용 및 효과를 상세하게 설명하면 다음과 같다.Referring to the operation and effect of the present invention configured as described in detail as follows.

본 발명의 고온 진공 질화법에 의해 피처리물을 경화처리 하기 위해서는 먼저 가열실(10) 내부에 경화처리하고자 하는 피처리물을 장입하게 되는데, 상기 피처리물은 저탄소 소재(강)나 저탄소 합금강 등으로써, 판재 혹은 제품의 표면만을 경화시키고자 하는 구동제품이고, 그 재질로 적절하게는 SPCC, S20C, SS440, SCM415 등을 들 수 있다.In order to cure the object by the high temperature vacuum nitriding method of the present invention, first, the object to be cured is loaded into the heating chamber 10. The object is a low carbon material (steel) or a low carbon alloy steel. For example, it is a drive product which wants to harden only the surface of a board | plate material or a product, and SPCC, S20C, SS440, SCM415 etc. are mentioned suitably as the material.

가열실(10) 내부에 상기한 피처리물을 장입한 상태에서, 진공분위기에서 가열실(10) 내부를 350~500℃의 온도로 가열하여 피처리물을 가열한다. 이와 동시에, 상기 가열실(10) 내부에 산소를 투입하여 10~60분 정도 피처리물 표면을 산화처리한다. 즉, 상기 산화작용을 통해 피처리물 표면이 활성화되면서 에칭이 일어나게 되고, 피처리물의 표면에 형성되어 있던 오염층과 가공층이 사라지게 된다.In the state where the said to-be-processed object was charged in the heating chamber 10, the inside of the heating chamber 10 is heated to the temperature of 350-500 degreeC in a vacuum atmosphere, and a to-be-processed object is heated. At the same time, oxygen is introduced into the heating chamber 10 to oxidize the surface of the workpiece about 10 to 60 minutes. That is, etching occurs while the surface of the workpiece is activated through the oxidation, and the contamination layer and the processed layer formed on the surface of the workpiece disappear.

도 4a, 4b는 상기한 표면 활성화공정(P20)을 거친 피처리물의 표면 사진을 각각 나타낸 것으로, 도 4a에서는 S20C를 400℃에서 40분간 산화한 경우, 표면이 에칭되어 나타남을 확인할 수 있고, 도 4b에서는 SCM415를 400℃에서 40분간 산화한 경우, 표면이 에칭되어 표면에 결정립이 관찰됨을 확인할 수 있다.4A and 4B respectively show surface photographs of the workpieces subjected to the surface activation step (P20). In FIG. 4A, when the S20C is oxidized at 400 ° C. for 40 minutes, the surface is etched. In 4b, when SCM415 is oxidized at 400 ° C. for 40 minutes, it can be confirmed that the surface is etched and crystal grains are observed on the surface.

이처럼, 피처리물의 표면을 활성화시킨 이 후, 상기 가열실(10) 내부의 온도를 700~850℃로 승온시키고, 가열실(10) 내부에 암모니아 가스를 투입하여 피처리물을 질화 처리한다. 이때, 상기 피처리물 표면에는 FeO, Fe3O4층이 형성되어, 질소의 흡착률과 흡착속도를 증가시키고, 질소를 빠른 시간 내에 표면 반응을 유발시켜 피처리물 내부로 확산이 되도록 하며, 이에 따라 피처리물의 경화처리 속도 향상에 의해 제품 생산성을 향상시킬 수 있게 된다.As such, after activating the surface of the workpiece, the temperature inside the heating chamber 10 is raised to 700 to 850 ° C, and ammonia gas is introduced into the heating chamber 10 to nitrate the workpiece. At this time, the FeO, Fe3O4 layer is formed on the surface of the workpiece to increase the adsorption rate and adsorption rate of nitrogen, causing the surface reaction within a short time to diffuse into the workpiece, thereby Product productivity can be improved by the hardening process rate of a processed material.

여기서, 질화 처리 이전에 산화를 시키지 않고 암모니아가스를 첨가하는 경우에는, 전혀 질화가 이루어지지 않거나, 불균일하게 일부만 질소마르텐사이트가 형성되는 데 반해, 본 발명과 같이 질화처리 이전에 산화를 시키게 되면, 피처리물 전체에 걸쳐 매우 균일하게 질화처리가 이루어질 수 있게 된다.Here, in the case where ammonia gas is added without oxidation before nitriding treatment, nitriding is not performed at all, or only part of nitrogen martensite is formed unevenly. When oxidation is performed before nitriding treatment as in the present invention, Nitriding can be performed very uniformly throughout the workpiece.

이와 같이 피처리물의 질화처리가 완료되면, 가열실(10)과 냉각실(20)의 압력이 동일하게 되도록 조절한 후, 상기 가열실(10)과 냉각실(20) 사이를 개방하여 가열된 피처리물을 냉각실(20)로 이동시키고, 상기 가열실(10)과 냉각실(20) 사이를 차단한다.When the nitriding treatment of the workpiece is completed as described above, the pressure in the heating chamber 10 and the cooling chamber 20 is adjusted to be the same, and then the heating chamber 10 is opened between the cooling chamber 20 and heated. The object to be processed is moved to the cooling chamber 20, and the heating chamber 10 and the cooling chamber 20 are blocked.

그리고, 이동된 피처리물은 냉각실(20) 하부에 조성된 오일소입조(25)에 침지시켜 냉각시키게 되는데, 이때 상기 피처리물의 특성에 따른 연속냉각곡선을 감안하여 상기 냉각실(20)의 압력을 변화 및 제어하게 된다.In addition, the moved object is cooled by immersing it in an oil sintering tank 25 formed under the cooling chamber 20. In this case, the cooling chamber 20 takes into account the continuous cooling curve according to the characteristic of the object. To change and control the pressure.

이와 같이, 상기 냉각실(20)의 압력을 변화시켜 피처리물을 냉각시키면, 피처리물의 분압과 점도가 바뀌게 되고, 그에 따라 증기막 단계와 대류단계 개시 온도가 바뀌게 된다. 이에 따라, 피처리물 내, 외부의 냉각 시작온도를 제어하여 피처리물의 냉각 성능을 높일 수 있게 된다.As such, when the pressure of the cooling chamber 20 is changed to cool the workpiece, the partial pressure and viscosity of the workpiece are changed, thereby changing the vapor membrane stage and the convection stage start temperature. Accordingly, it is possible to increase the cooling performance of the workpiece by controlling the start temperature of cooling inside and outside the workpiece.

즉, 일반적으로 피처리물을 오일에 침지하는 경우 오일에 처음 닿게 되는 위치와 늦게 닿게 되는 위치가 서로 다르게 됨으로써, 피처리물 내, 외부의 냉각 시작시간이 서로 다르게 되고, 그에 따라 피처리물의 변형이 발생하게 된다. 따라서, 냉각실(20)의 압력 조절을 통해 피처리물 내, 외부의 냉각 시작시간을 서로 동일하게 제어함으로써, 상기한 변형 발생을 최소화시키고자 하는 것이다.
이에, 상기한 냉각실 압력 제어작용에 대하여 부가하여 설명하면, 소입되는 오일의 특성에 따라 냉각실(20) 압력을 조절하는 경우, 냉각실(20) 내의 오일 분위기에서 기화되는 가스가 피처리물의 표면에 적게 붙게 됨으로써, 오일 내에서 형성되는 기포발생량이 작아지게 되고, 이로 인해 피처리물 표면에서 증기막이 깨지는 시간이 바뀌게 된다. 이와 함께, 피처리물 내부의 활동도가 달라져 전체적인 피처리물 냉각속도를 지연시키고, 오일 내에서 형성되는 기포발생량을 부위별로 차이가 없이 만들어 피처리물 내, 외부에 균일한 냉각을 실시하게 됨으로써, 피처리물의 열처리 중 발생하는 변형 및 크랙 등을 방지할 수 있게 된다.That is, in general, when the object to be immersed in oil is different from the position where the first contact with the oil and the late contact position, the start time of the cooling inside and outside the processing is different, thereby deforming the processing object This will occur. Therefore, by controlling the cooling start time of the inside and the outside of the workpiece through the same pressure control of the cooling chamber 20, it is intended to minimize the above-mentioned deformation.
Therefore, the cooling chamber pressure control action described above is further described. When the pressure of the cooling chamber 20 is adjusted according to the characteristics of the quenched oil, the gas vaporized in the oil atmosphere in the cooling chamber 20 is controlled. By less sticking to the surface, the amount of bubbles generated in the oil is reduced, thereby changing the time the steam film breaks on the surface of the workpiece. In addition, the activity inside the workpiece is changed to delay the overall cooling rate of the workpiece, and the amount of bubbles generated in the oil is made without difference for each part to uniformly cool the workpiece. It is possible to prevent deformation, cracks, and the like, which occur during the heat treatment of the workpiece.

아울러, 상기와 같이 피처리물의 열 변형을 최소화함으로써, 열 변형에 따른 후처리공정절감 및 이로 인한 금형제작 및 제반 비용을 절감할 수도 있고, 또한 상기 후처리 가공 및 연마에 따라 발생되는 폐기물을 절감할 수 있으며, 그에 따른 환경오염인자를 감소 및 개선시킬 수 있는 것이다.In addition, by minimizing the thermal deformation of the workpiece as described above, it is possible to reduce the post-treatment process according to the thermal deformation, thereby reducing the mold production and overall costs, and also reduce the waste generated by the post-processing and polishing It is possible to reduce and improve the environmental pollution factor accordingly.

상기와 같이 오일소입조(25)에서 냉각을 마친 후에는 상기 피처리물을 들어올려 냉각실(20) 상부 공간의 오일 분위기에서 가스 냉각을 시행하여 피처리물의 경화처리 과정을 완료하게 된다. 이때, 상기 가스 냉각공정(P60) 이 후에 피처리물의 크기가 큰 경우에는 다시 오일소입조(25) 내부에 침지시켜 재냉각시킬 수도 있다.After the cooling is completed in the oil sintering tank 25 as described above, the object is lifted to perform gas cooling in the oil atmosphere of the upper space of the cooling chamber 20 to complete the hardening process of the object. At this time, if the size of the workpiece after the gas cooling step (P60) is large, the oil immersion tank 25 may be immersed again to cool again.

부가하여 설명하면, 도 9에 도시한 바와 같이 탄소강 상태도의 경우, BCC→FCC로 바뀌는 오스테나이징 온도가 723℃로 높은 반면, 질소의 경우 오스테나이징 온도가 약 590℃정도로 낮다. 즉, 탄소강에서는 아직 변태온도가 아니기 때문에 마르텐사이트를 형성할 수 없는 온도이나, 질소가 들어간 층의 경우에는 오스테나이징이 되므로 냉각을 하게 되면 마르텐사이트 조직을 가질 수 있는 것이다.In addition, as shown in FIG. 9, in the case of the carbon steel state diagram, the austenizing temperature of changing from BCC to FCC is high at 723 ° C, while in nitrogen, the austenizing temperature is low at about 590 ° C. That is, in carbon steel, since it is not yet transformation temperature, martensite cannot be formed, or in the case of a layer containing nitrogen, since it is austenized, it can have martensite structure when cooled.

이와 같이, 본 발명은 저탄소 소재(강)와, 저탄소 합금강 등의 판재의 경우에도, 탄소에 비해 낮은 온도에서 형성되는 마르텐사이트 조직을 표면만 얻을 수 있으므로, 내부는 기존의 펄라이트와 페라이트의 인성 및 충격강도가 좋은 재질로 남아 있고, 표면만 800HV 정도의 고경도를 갖도록 경화처리 함으로써, 내마모성과 내구성이 필요한 구조물 및 구동부품 등에 사용이 가능하고, 또한 제품의 단가를 획기적으로 절감할 수 있게 된다.As described above, the present invention can obtain only martensite structure formed at a lower temperature than carbon even in the case of a low carbon material (steel) and a plate such as low carbon alloy steel. The impact strength remains as a good material, and the surface is hardened to have a high hardness of about 800 HV, so that it can be used for structures and driving parts that require wear resistance and durability, and also greatly reduce the unit cost of the product.

즉, 도 5a는 S20C강종에 적용된 질소마르텐사이트의 2시간 경화처리공정에서 확보된 단면조직과 그 확대 사진이고, 도 5b는 도 5a의 경화처리시 얻어진 경도 프로필로써, 표면의 경도가 820HV인 것을 확인할 수 있다.That is, Figure 5a is a cross-sectional structure obtained in the two-hour curing process of nitrogen martensite applied to S20C steel grades and an enlarged picture thereof, Figure 5b is a hardness profile obtained during the curing treatment of Figure 5a, the surface hardness is 820HV You can check it.

또한, 도 6a는 SPCC강종에 적용된 질소마르텐사이트의 2시간 경화처리공정에서 확보된 단면조직과 그 확대 사진이고, 도 6b는 도 6a의 경화처리시 얻어진 경도 프로필로써, 표면의 경도가 800HV인 것을 확인할 수 있다.In addition, Figure 6a is a cross-sectional structure obtained in the two-hour curing process of nitrogen martensite applied to the SPCC steel grade and an enlarged picture thereof, Figure 6b is a hardness profile obtained during the curing treatment of Figure 6a, the surface hardness is 800HV You can check it.

또, 도 7은 S45C강종에 적용된 질소마르텐사이트의 2시간 경화처리공정에서 확보된 단면조직과 그 확대 사진이고, 또한 도 8은 SCM415강종에 적용된 질소마르텐사이트의 2시간 경화처리공정에서 얻어진 경도 프로필로써, 표면의 경도가 820HV인 것을 확인할 수 있다.FIG. 7 is a cross-sectional structure obtained in a two-hour hardening process of nitrogen martensite applied to S45C steel and an enlarged photograph thereof. FIG. 8 is a hardness profile obtained from a two-hour hardening treatment of nitrogen martensite applied to SCM415 steel. As a result, it can be confirmed that the hardness of the surface is 820HV.

더욱이, 침탄을 하게 되면 변형이 크기 때문에 얇은 제품의 변형량 예측이 어려우나, 본 발명은 변태점을 지나지 않기 때문에 변형량이 침탄에 비해 매우 적고, 질화보다 온도가 높아 화합물층 대신 확산층만 생성하므로, 후 연마가 불필요하며, 이로 인해 생산효율 증대 및 저가의 내구성이 필요한 구동부품이나 기능성 구조물 제조에 탁월한 효과가 있는 것이다.Moreover, when carburizing, the deformation is large, so it is difficult to predict the amount of deformation of the thin product. However, the present invention does not pass the transformation point, so the amount of deformation is very small compared to carburizing, and the temperature is higher than that of nitriding. This is an excellent effect for the production of driving parts or functional structures that require increased production efficiency and low-cost durability.

한편, 본 발명은 상기한 구체적인 예에 대해서만 상세히 설명되었지만 본 발명의 기술사상 범위 내에서 다양한 변형 및 수정이 가능함은 당업자에게 있어서 명백한 것이며, 이러한 변형 및 수정이 첨부된 특허청구범위에 속함은 당연한 것이다.On the other hand, the present invention has been described in detail only with respect to the specific examples described above it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, it is natural that such variations and modifications belong to the appended claims. .

도 1은 본 발명에 의한 경화처리 방법을 순차적으로 나열한 블럭도,1 is a block diagram sequentially listing the curing treatment method according to the present invention,

도 2는 본 발명에 의한 경화처리 방법의 공정을 나타낸 그래프선도,2 is a graph showing a step of the curing treatment method according to the present invention;

도 3은 본 발명에 의한 경화처리 장치를 나타낸 개략도,3 is a schematic view showing a coin processing device according to the present invention;

도 4a, 4b는 본 발명에 의한 활성화공정 이 후에 각각 다른 강종의 피처리물 표면을 나타낸 사진,Figure 4a, 4b is a photograph showing the surface of the workpieces of different steel grades after the activation process according to the present invention,

도 5a, 5b는 본 발명에 의한 경화처리를 통해 확보된 S20C강종의 단면조직 사진 및 경도 프로필,Figure 5a, 5b is a cross-sectional structure photograph and hardness profile of the S20C steel species secured through the curing process according to the present invention,

도 6a, 6b는 본 발명에 의한 경화처리를 통해 확보된 SPCC강종의 단면조직 사진 및 경도 프로필,Figure 6a, 6b is a cross-sectional structure photograph and hardness profile of the SPCC steel secured through the curing treatment according to the present invention,

도 7은 본 발명에 의한 경화처리를 통해 확보된 S45C강종의 단면조직 사진,7 is a cross-sectional structure photograph of the S45C steel species secured through the curing treatment according to the present invention,

도 8은 본 발명에 의한 경화처리를 통해 확보된 SCM415강종의 경도 프로필,8 is a hardness profile of the SCM415 steel species secured through the curing treatment according to the present invention,

도 9는 본 발명의 경화처리작용을 부가하여 설명하기 위한 Fe-C계 상태도 및 Fe-N계 상태도.9 is a Fe-C-based state diagram and a Fe-N-based state diagram for adding and explaining the hardening treatment action of the present invention.

*도면중 주요 부호에 대한 설명** Description of Major Symbols in Drawings *

10 : 가열실 20 : 냉각실10: heating chamber 20: cooling chamber

25 : 오일소입조 P10 : 가열공정25: oil quenching tank P10: heating process

P20 : 활성화공정 P30 : 질화공정P20: Activation Process P30: Nitriding Process

P40 : 오일 냉각공정 P50 : 가스 냉각공정P40: oil cooling process P50: gas cooling process

Claims (6)

피처리물의 표면을 경화처리하기 위한 방법에 있어서,In the method for hardening the surface of the workpiece, 진공 분위기에서 가열실(10) 내부를 350~500℃의 온도로 가열하여 피처리물을 가열하는 공정(P10)과;Heating the workpiece by heating the interior of the heating chamber 10 to a temperature of 350 to 500 ° C. in a vacuum atmosphere (P10); 상기 가열실(10) 내부에 산소를 투입하여 피처리물 표면을 산화 활성화시키는 공정(P20)과;Injecting oxygen into the heating chamber (10) to oxidatively activate the surface of the workpiece (P20); 상기 가열실(10) 내부의 온도를 700~850℃로 승온 유지시키고, 내부에 암모니아가스를 8~30ℓ/min 투입하면서, 피처리물을 60~180분 동안 질화 처리하는 공정(P30)과;Maintaining the temperature inside the heating chamber 10 at 700 to 850 ° C., nitrifying the object for 60 to 180 minutes while injecting ammonia gas to the interior at 8 to 30 l / min (P30); 질화처리한 피처리물을 냉각실(20)로 이동시키되, 냉각실(20)의 압력을 제어하고 오일소입조(25) 내부의 오일 교반속도를 제어하여, 피처리물을 오일소입조(25) 내에서 오일로 균일 냉각하는 공정(P40)과;The nitrided object is moved to the cooling chamber 20, and the pressure of the cooling chamber 20 is controlled and the oil agitation speed inside the oil sintering tank 25 is controlled to convert the object to be sintered. Step (P40) to uniformly cool with oil in the); 상기 오일소입조(25) 내에서 냉각된 피처리물을 들어올려 기화된 오일의 가스 분위기에서 균일 냉각하는 공정(P50)을 포함하는 것을 특징으로 하는 고온 진공 질화법에 의한 경화처리 방법.And a step (P50) of lifting the object to be cooled in the oil sintering tank (25) and uniformly cooling it in a gas atmosphere of vaporized oil. 삭제delete 삭제delete 제 1항에 있어서, 상기 피처리물은 저탄소 소재(강)나 저탄소 합금강을 사용하는 것을 특징으로 하는 고온 진공 질화법에 의한 경화처리 방법.The hardening treatment method by the high temperature vacuum nitriding method of Claim 1 in which the to-be-processed object uses a low carbon material (steel) or a low carbon alloy steel. 제 4항에 있어서, 상기 피처리물은 SPCC, S20C, SS440, SCM415 중 어느 하나를 사용하는 것을 특징으로 하는 고온 진공 질화법에 의한 경화처리 방법.The method of claim 4, wherein the workpiece is any one of SPCC, S20C, SS440, and SCM415. 삭제delete
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