KR100681505B1 - Method for austempering heat treatment by controlling surfaces pressure of salt - Google Patents

Method for austempering heat treatment by controlling surfaces pressure of salt Download PDF

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KR100681505B1
KR100681505B1 KR1020050094539A KR20050094539A KR100681505B1 KR 100681505 B1 KR100681505 B1 KR 100681505B1 KR 1020050094539 A KR1020050094539 A KR 1020050094539A KR 20050094539 A KR20050094539 A KR 20050094539A KR 100681505 B1 KR100681505 B1 KR 100681505B1
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cooling
heating
salt bath
workpiece
heat treatment
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KR1020050094539A
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Korean (ko)
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김성완
김상권
문경일
조용기
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한국생산기술연구원
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    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • 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
    • C23C8/20—Carburising
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)

Abstract

An austempering heat treatment method for controlling surface pressure is provided to prevent deformation of a treatment object due to a cooling rate difference between inner and outer parts of the treatment object by controlling pressure of a cooling chamber for cooling the treatment object. An austempering heat treatment method for controlling surface pressure comprises: a heating preparation step(S10) of maintaining a vacuum state in a heating chamber by a vacuum pump, and determining a heating temperature and a heating time of the treatment object according to the material and the size of a treatment object; a heating step(S20) of creating a carburizing atmosphere in the vacuumed heating chamber to heat the treatment object; a treatment object moving step(S30) of moving the heated treatment object to a cooling chamber; a cooling preparation step(S40) of determining a continuous cooling curved line corresponding to required heat treatment characteristics in accordance with the material and the size of the treatment object; a salt bath cooling step(S50) of controlling pressure and stirring rate of the cooling chamber according to characteristics of the continuous cooling curved line to uniformly cool the treatment object within a salt bath; and a gas cooling step(S60) of lifting up the treatment object cooled in the salt bath to uniformly cool the treatment object using a gas in a salt bath atmosphere.

Description

면압 제어 오스템퍼링 열처리 방법{Method for austempering heat treatment by controlling Surfaces Pressure of salt}Method for austempering heat treatment by controlling Surfaces Pressure of salt}

도 1은 본 발명에 따른 면압 제어 오스템퍼링 열처리 방법을 순차적으로 나타낸 블록도,1 is a block diagram sequentially showing a surface pressure control ostempering heat treatment method according to the present invention,

도 2는 본 발명에 따른 열처리 장치를 나타낸 개략도,2 is a schematic view showing a heat treatment apparatus according to the present invention,

도 3은 본 발명의 열처리 방법에 적용된 열처리공정도,3 is a heat treatment process diagram applied to the heat treatment method of the present invention,

도 4는 본 발명의 열처리 방법에 적용된 50CrV4의 열처리 연속냉각곡선,4 is a heat treatment continuous cooling curve of 50CrV4 applied to the heat treatment method of the present invention,

도 5는 본 발명의 열처리 방법에 의해 제작된 샘플의 조직사진.5 is a tissue photograph of a sample produced by the heat treatment method 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 : 염욕조 S10 : 가열 준비단계25: salt bath S10: heating preparation step

S20 : 가열단계 S30 : 피처리물 이동단계S20: heating step S30: moving object to be processed

S40 : 냉각 준비단계 S50 : 염욕 냉각단계S40: cooling preparation step S50: salt bath cooling step

S60 : 가스 냉각단계 S50' : 염욕 재냉각단계S60: gas cooling step S50 ': salt bath recooling step

P : 진공펌프P: vacuum pump

본 발명은 면압 제어 오스템퍼링 열처리 방법에 관한 것으로, 보다 상세하게는 냉각실의 압력을 조절하여 피처리물 내, 외부의 냉각 속도 차이에 의한 피처리물의 변형을 방지할 수 있도록 한 면압 제어 오스템퍼링 열처리 방법에 관한 것이다.The present invention relates to a surface pressure control ostempering heat treatment method, and more particularly, to control the surface pressure control ostempering to prevent deformation of the processing object by the difference in the cooling rate of the inside and the outside of the object by adjusting the pressure of the cooling chamber. It relates to a heat treatment method.

일반적으로, 오스템퍼링 열처리에 사용되는 강재는 하부베이나이트를 형성시킴으로써 내구성과 내마모성 및 내마멸성 등이 확보되어야 하고, 강성이나 인성 등도 커야할 뿐만 아니라, 충격력에 의해 쉽게 깨지지도 말아야 하기 때문에 주로 고탄소강이나 고장력강을 사용하여 제조하게 된다.In general, steel used in the heat treatment of austempering should be secured for durability, abrasion resistance, and abrasion resistance by forming lower bainite, and should not only be large due to stiffness or toughness, but also should not be easily broken by impact force. It is manufactured using high strength steel.

이 중에서, 고탄소강(high-carbon steel)을 간략하게 설명하면, 탄소 함유량이 0.6%이상인 것으로, 절삭공구나 스프링 그리고 동력전달장치나 자동변속기 등에 쓰이는 구동판 등과 같이 아주 높은 강도와 경도, 내마모성 등이 필요한 제품에 일반적으로 이용되며, 탄소함유량이 많은 철강일수록 열처리 후에도 경도, 강도, 내마모성 등이 좋아지므로 대게는 형상 가공된 후에 제품을 열처리하여 물리적성질 및 기계적성질을 더욱 좋게 한다.Among these, high-carbon steel is briefly described, having a carbon content of more than 0.6%, such as cutting tools, springs, and driving plates used in power transmission devices or automatic transmissions. It is generally used for this necessary product, and the steel with higher carbon content improves hardness, strength, and abrasion resistance even after heat treatment, so that the product is generally heat treated after shape processing to improve physical and mechanical properties.

그리고, 고장력강(high tensile steel)은 일반적으로 0.2% 정도의 탄소를 함유한 탄소강에 규소·망간·니켈·크롬·구리 등을 첨가하여 인장강도가 50kg/㎟이상인 고성능 강으로, 항장력(抗張力)에 따라 60킬로 하이텐 또는 80킬로 하이텐, 그리고 열처리에 의해서 성능이 더 향상된 80~100킬로 하이텐의 고장력강 등으로 분류될 수 있다.High tensile steel is a high-performance steel having a tensile strength of 50 kg / mm 2 or more by adding silicon, manganese, nickel, chromium, copper, etc. to carbon steel generally containing about 0.2% of carbon. Therefore, it can be classified into high strength steel of 60 to 80 kilo high or 80 kilo high ten, and 80 to 100 kilo high ten, which is further improved by heat treatment.

이러한, 강을 이용한 오스템퍼링은, 내, 외부 온도가 거의 균일하게 된 후에 공냉하는 마아템퍼링과는 달리, 강에 점성과 강성을 동시에 부여되게 함으로써, 높은 내구성과 내마모성 및 내마멸성, 인성, 내충격성 등이 요구되는 제품에는 상기 오스템퍼링 열처리가 필수적인 것이다.Unlike the tempering which is air-cooled after the internal and external temperature becomes almost uniform, the ostempering using steel is provided with high viscosity and rigidity at the same time, thereby providing high durability, abrasion resistance, abrasion resistance, toughness, impact resistance, and the like. The ostempering heat treatment is essential for this required product.

그러나, 오스템퍼링 열처리 특성상 강재의 냉각온도를 250~400℃ 범위 내로 급속히 이동시켜야 하므로, 강재의 변형이 불가피하게 발생하는 문제가 있다.However, since the cooling temperature of the steel must be rapidly moved within the range of 250 to 400 ° C. due to the osmosis heat treatment characteristic, there is a problem inevitably causing deformation of the steel.

더욱이, 대형제품의 경우는 제품의 급냉시 내, 외부의 열응력차이로 인해 제품에 변형이 발생하게 되고, 이것이 심하면 제품의 형상에 따라 크랙이 발생하는 경우도 있고, 외부에 방치하면서도 갑자기 파괴가 일어나는 경우도 발생하는 문제도 있다.In addition, in the case of large products, deformation occurs in the product due to the difference in thermal stress between the inside and outside of the product, and if this is severe, cracks may occur depending on the shape of the product. There are also problems that arise.

또한, 염에 상압에서 담금질하게 되는 경우 제품의 담금질성능은 좋아지지만, 제품 표면에서의 냉각 속도가 빠르기 때문에 내부와의 냉각 속도 차이가 심하여 제품의 부피가 크거나 형성이 복잡할 경우 상압에서 냉각 속도를 조절하기가 어려워 오히려 제품 불량의 요인으로 작용할 수 있는 폐단이 있었다.In addition, when the salt is quenched at normal pressure, the quenching performance of the product is improved, but the cooling rate at the surface of the product is fast, so the difference in cooling rate from the inside is severe. It was difficult to control the rather it was a defect that could act as a factor of product defects.

본 발명은 전술한 바와 같은 종래의 문제점을 해결하기 위하여 안출한 것으로, 피처리물이 냉각되는 냉각실의 압력을 조절하여, 피처리물 내, 외부의 냉각 속도 차이에 의한 피처리물의 변형을 방지할 수 있도록 한 면압 제어 오스템퍼링 열처리 방법을 제공하는 데 있다.The present invention has been made to solve the conventional problems as described above, by adjusting the pressure of the cooling chamber in which the workpiece is cooled, to prevent deformation of the workpiece by the difference in the cooling rate of the inside and outside of the workpiece. The present invention provides a method of controlling a surface pressure control tempering process.

상기와 같은 목적을 달성하기 위한 본 발명의 열처리 방법은, 강종으로 이루어진 피처리물을 오스테나이트의 상태로 가열하고 급냉한 이 후에 그 온도에서 변태 및 냉각시켜 필요한 조직을 얻는 오스템퍼링 열처리 방법에 있어서, 피처리물의 소재 및 크기에 따라 가열온도 및 가열시간을 결정하는 가열준비단계와; 진공의 가열실 내부에 침탄성분위기를 조성하여 상기 피처리물을 가열하는 가열단계와; 상기 가열된 피처리물을 냉각실로 이동시키는 피처리물 이동단계와; 상기 피처리물의 소재 및 크기에 따라 열처리 요구 특성에 맞는 연속냉각곡선을 결정하는 냉각 준비단계와; 상기 연속냉각곡선의 특성에 따라 냉각실의 압력과 교반속도를 제어하여 상기 피처리물을 염욕조 내에서 균일 냉각하는 염욕 냉각단계와; 상기 염욕조에서 냉각된 피처리물을 들어 올려 염욕 분위기에서 가스로 균일냉각하는 가스 냉각단계를 포함하는 것을 특징으로 한다.In the heat treatment method of the present invention for achieving the above object, in the austempering heat treatment method of heating a workpiece made of steel grade in the state of austenite and quenching and then transforming and cooling at the temperature to obtain the required structure A heating preparation step of determining a heating temperature and a heating time according to the material and the size of the workpiece; A heating step of heating a workpiece by forming a carburizing component atmosphere in a vacuum heating chamber; A to-be-processed object moving step of moving the heated to-be-processed object into a cooling chamber; A cooling preparation step of determining a continuous cooling curve according to heat treatment requirements according to the material and the size of the workpiece; A salt bath cooling step of uniformly cooling the to-be-processed object in a salt bath by controlling the pressure and the stirring speed of the cooling chamber according to the characteristics of the continuous cooling curve; Lifting the object to be cooled in the salt bath characterized in that it comprises a gas cooling step of uniform cooling with a gas in a salt bath atmosphere.

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 1과 도 2는 본 발명의 면압 제어 오스템퍼링 열처리 방법에 대한 것으로, 크게 가열 준비단계(S10)와, 가열단계(S20)와, 피처리물 이동단계(S30)와, 냉각 준비단계(S40)와, 염욕 냉각단계(S50)와, 가스 냉각단계(S60)를 구성요소로 한다.1 and 2 are directed to the surface pressure control ostempering heat treatment method of the present invention, the heating preparation step (S10), the heating step (S20), the workpiece processing step (S30), the cooling preparation step (S40) ), A salt bath cooling step (S50), and a gas cooling step (S60) as components.

이하 설명하면, 먼저 가열 준비단계(S10)에서는 진공펌프(P)를 이용하여 가열실 내부를 진공상태로 유지시키고, 피처리물의 소재 및 크기에 따라 가열온도 및 가열시간을 결정하는 것으로, 피처리물의 소재에 따라 가열온도를 설정하고, 그 피처리물의 크기에 따라 가열시간을 선정하되, 가공량을 고려하여 승온시간 및 가열 의 구배를 결정하게 된다.In the following description, first, in the heating preparation step (S10), the inside of the heating chamber is maintained in a vacuum state using a vacuum pump (P), and the heating temperature and the heating time are determined according to the material and the size of the workpiece. The heating temperature is set according to the material of the water, and the heating time is selected according to the size of the object to be treated, and the temperature rising time and the gradient of heating are determined in consideration of the processing amount.

계속해서, 가열단계(S20)에서는 피처리물을 가열실(10) 내부에 투입하고, 진공의 가열실(10) 내부에 침탄성분위기를 조성하여 피처리물을 가열하는 것으로, 상기 피처리물이 50CrV4인 경우, 상기 가열실(10)을 300~650℃로 승온시켜 약 1시간 30분 유지시킨 후, 약 850~880℃까지 승온시켜 약 30~50분동안 피처리물을 가열한다.Subsequently, in the heating step (S20), the object to be treated is introduced into the heating chamber 10, and a carburizing component crisis is formed inside the vacuum heating chamber 10 to heat the object. In the case of 50CrV4, the heating chamber 10 is heated to 300 to 650 ° C, held for about 1 hour and 30 minutes, and then heated to about 850 to 880 ° C to heat the workpiece for about 30 to 50 minutes.

이 때, 상기 침탄성분위기로는 엔도가스(Rx gas) 또는 아세틸렌(C2H2), 프로판(C3H8)등이 사용되는데, 여기서 상기 엔도가스는 대개 수소(H2) 30Wt%이상, 메탄(CH4) 3~30Wt%, 이산화탄소(CO2) 0.5Wt%이상, 잔량의 질소(N2)로 구성되며, 수분(H20)은 0.5Wt%이하여야 한다.At this time, as the carburizing component endo gas (Rx gas) or acetylene (C 2 H 2 ), propane (C 3 H 8 ), etc. are used, where the endose is usually hydrogen (H 2 ) 30Wt% or more , Methane (CH 4 ) 3 ~ 30Wt%, carbon dioxide (CO 2 ) more than 0.5Wt%, the balance of nitrogen (N 2 ), moisture (H 2 0) should be less than 0.5Wt%.

계속해서, 피처리물 이동단계(S30)에서는 상기 가열된 피처리물을 냉각실(20)로 이동시키는 것으로, 냉각실(20)의 압력이 가열실(10)의 압력보다 높은 경우에는 상기 피처리물의 이동을 제한하고, 냉각실(20)의 압력이 가열실(10)의 압력과 동일해 지는 경우, 상기 피처리물의 이동을 허가하게 된다. Subsequently, in the moving object to be processed (S30), the heated object is moved to the cooling chamber 20. When the pressure of the cooling chamber 20 is higher than the pressure of the heating chamber 10, If the movement of the processing object is restricted and the pressure of the cooling chamber 20 becomes equal to the pressure of the heating chamber 10, the movement of the processing 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) 내부의 염이 가열실(10)로 넘어가게 되어, 사고 발생의 위험이 있기 때문이다. 이에 따른, 피처리물이 이동되는 경우의 가열실(10)과 냉각실(20)의 최소 압력은 각각 25~50mbar가 되도록 조절하는 것이 적절하다.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 salt inside the chamber 20 is transferred to the heating chamber 10, which may cause an accident. Accordingly, it is appropriate to adjust the minimum pressure of the heating chamber 10 and the cooling chamber 20 when the object to be moved is 25 to 50 mbar, respectively.

다음으로, 냉각 준비단계(S40)에서는 상기 피처리물의 소재 및 크기에 따라 열처리 요구 특성에 맞는 연속냉각곡선을 결정하는 것으로, 첨부도면 도 4는 본 발명에 사용되는 50CrV4의 연속냉각곡선(CCT곡선:Continuous Cooling Transformation Diagram)을 나타낸 것인데, 상기와 같은 연속냉각곡선은 피처리물의 소재별로 서로 상이하게 나타난다.Next, in the cooling preparation step (S40) to determine the continuous cooling curve according to the heat treatment required characteristics according to the material and size of the workpiece, the accompanying drawings Figure 4 is a continuous cooling curve (CCT curve) of 50CrV4 used in the present invention : Continuous Cooling Transformation Diagram), the above-mentioned continuous cooling curve is different from each other by the material of the workpiece.

계속해서, 염욕 냉각단계(S50)에서는 상기 연속냉각곡선의 특성에 따라 냉각실(20)의 압력과 교반속도를 제어하여, 상기 피처리물을 염욕조(25)에 침지시켜 냉각하게 된다.Subsequently, in the salt bath cooling step (S50), the pressure and stirring speed of the cooling chamber 20 are controlled according to the characteristics of the continuous cooling curve, and the object to be treated is cooled by immersing in the salt bath 25.

이러한, 상기 염욕 냉각단계(S50)에서는 피처리물의 소재가 50CrV4인 경우, 냉각실(20)의 압력을 100~700mbar로 제어하고, 염욕조(25) 내부의 온도를 250~400℃로 제어하며, 염욕조(25) 내의 교반속도를 5~15Hz로 제어하여 상기 피처리물을 약 15분간 냉각한다. 그리고, 상기 냉각실(20) 상부의 진공펌프(P)를 이용하여 냉각실(20)의 진공 상태를 유지시키게 된다.In the salt bath cooling step (S50), when the material to be treated is 50CrV4, the pressure of the cooling chamber 20 is controlled to 100 to 700 mbar, and the temperature inside the salt bath 25 is controlled to 250 to 400 ° C. , By controlling the stirring speed in the salt bath 25 to 5 ~ 15Hz to cool the object to be treated for about 15 minutes. Then, the vacuum state of the cooling chamber 20 is maintained by using the vacuum pump P above the cooling chamber 20.

이 때, 상기 피처리물의 크기가 100㎤이상이고 그 형상이 복잡한 경우에는, 기포발생단계의 시간이 지연되는 압력으로 조절하여야 함으로써, 냉각실(20)의 압력을 100~500mbar 사이로 낮게 조절하여 피처리물을 냉각하게 된다.At this time, when the size of the workpiece is 100 cm 3 or more and its shape is complicated, the bubble generation step should be adjusted to a pressure that delays the time of the bubble generation step, so that the pressure in the cooling chamber 20 is adjusted to be low between 100 and 500 mbar. Cool the treatment.

여기서, 상기 염욕조(25)에 사용되는 냉각매질은 질산나트륨(NaNO3) 또는 아질산나트륨(NaNO2) 및 질산칼륨(KNO3) 등을 사용하고, 수산화나트륨(NaOH), 수산화칼륨(KOH), 염화주석(SnCl2), 염화구리(CuCl) 등을 첨가제로 혼합하여 사용한다.Here, the cooling medium used in the salt bath 25 is sodium nitrate (NaNO 3 ) or sodium nitrite (NaNO 2 ) and potassium nitrate (KNO 3 ) and the like, sodium hydroxide (NaOH), potassium hydroxide (KOH) , Tin chloride (SnCl 2 ), copper chloride (CuCl) and the like are used as an additive.

그리고, 상기 냉각매질은 전열을 발생시켜 가열함으로써, 오스템퍼링시의 냉각온도로 유지시킬 수 있게 하고, 상기 염욕조(25) 내에서 냉각매질을 순환 유동시켜 염도 및 온도가 균일하게 되도록 한다.In addition, the cooling medium generates heat and heats it to be maintained at the cooling temperature at the time of ostampering, and circulates the cooling medium in the salt bath 25 so that salinity and temperature are uniform.

계속해서, 가스 냉각단계(S60)에서는 상기 염욕조(25)에서 냉각된 피처리물을 들어올려 약 700mbar 압력의 염욕 분위기에서 냉각하는 것으로, 가스 냉각이 완료되면 냉각실(20)을 개방하여 피처리물을 인출하게 된다.Subsequently, in the gas cooling step (S60), the object to be cooled in the salt bath 25 is lifted and cooled in a salt bath atmosphere at a pressure of about 700 mbar. When the gas cooling is completed, the cooling chamber 20 is opened to be avoided. The processed material is withdrawn.

여기서, 상기 피처리물의 크기 및 부피가 큰 경우, 즉 100㎤ 이상이고 상기 피처리물의 형상이 복잡할 때에는 가스 냉각단계(S60) 이후에 냉각실(20)을 개방하지 않고 상기 피처리물을 다시 염욕조(25)에 침지시켜 냉각시키는 염욕 재냉각단계(S50')를 더 실시하게 된다.In this case, when the size and volume of the workpiece are large, that is, 100 cm 3 or more and the shape of the workpiece is complicated, the workpiece is reopened without opening the cooling chamber 20 after the gas cooling step S60. The salt bath recooling step (S50 ') of immersing and cooling the salt bath 25 is further performed.

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.

먼저, 도 1 내지 도 3과 같이 소정 제품으로 가공된 피처리물을 가열실(10) 내부에 장입시켜 상기 피처리물을 침탄성분위기 하에서 가열한다. 즉, 상기 피처리물을 가열실(10) 내부의 엔도가스 또는 아세틸렌, 프로판 등의 분위기에서 가열 유지하게 됨으로써, 피처리물을 침탄 분위기에서 가열할 수 있는 것이다.First, as shown in Figs. 1 to 3, the workpiece processed into a predetermined product is charged into the heating chamber 10 to heat the workpiece under a carburizing component crisis. That is, the to-be-processed object can be heated in carburizing atmosphere by maintaining and heating the said to-be-processed object in the atmosphere of the endo gas, acetylene, propane, etc. in the inside of the heating chamber 10.

이 중에서, 엔도가스 분위기에서의 가열은 "2CH4+O2 → 2CO+4H2"의 반응식으로 나타낼 수 있는 흡열반응(Endothermic reaction)이 이루어지게 되는데, 이 때 가스에 의한 강한 환원성 분위기가 조성되고, 피처리물 표면에 탄화물(Fe3C)층이 형 성됨으로써, 피처리물로부터의 탈탄이 방지될 수 있게 된다.Among them, the heating in the endo gas atmosphere is an endothermic reaction, which can be represented by a reaction formula of "2CH 4 + O 2 → 2CO + 4H 2 ", at this time a strong reducing atmosphere by the gas is formed By forming a carbide (Fe 3 C) layer on the surface of the workpiece, decarburization from the workpiece can be prevented.

그리고, 상기 가열실(10)은 폐쇄된 상태에서 가열 작용이 이루어지므로 내부에 열을 균일하게 분포 작용시킬 수 있게 되고, 이로써 상기 피처리물을 열편차없이 고르게 가열시킬 수 있게 된다.In addition, since the heating operation is performed in a closed state, the heating chamber 10 can uniformly distribute heat therein, thereby allowing the object to be heated evenly without thermal deviation.

한편, 상기한 바와 같이 피처리물의 가열이 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.On the other hand, when the heating of the workpiece is completed as described above, after adjusting the pressure of the heating chamber 10 and the cooling chamber 20 to be the same, opening between the heating chamber 10 and the cooling chamber 20. Thereby moving the heated object to the cooling chamber 20, and blocking the heating chamber 10 from the cooling chamber 20.

이처럼, 이동된 피처리물은 냉각실(20) 하부에 조성된 염욕조(25)에 침지시켜 냉각시키게 되는데, 이 때 상기 피처리물의 특성에 따른 연속냉각곡선을 감안하여 상기 냉각실(20)의 압력을 변화 및 제어하게 된다.As such, the moved object is cooled by immersing it in a salt bath 25 formed in the lower part of the cooling chamber 20. At this time, 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, 다시 설명하면 상기 냉각실(20)의 압력 변화에 의해, 염욕조(25)의 기체분자량이 줄어들게 되고, 피처리물 내부에 전달되는 냉각속도가 차이가 나게 되며, 액체의 기화 속도가 빨라지게 된다. 따라서, 피처리물 내부의 활동도가 달라져 전체적인 피처리물 냉각속도를 지연시키고, 염내에서 형성되는 기포발생단계를 부위별로 차이가 없이 만들어 균일냉각을 시킴으로써, 상기 피처리물의 열처리 중 발생 되는 변형 및 크랙 등을 방지할 수 있는 것이다.That is, the gas molecular weight of the salt bath 25 is reduced by the pressure change of the cooling chamber 20, the cooling rate delivered to the inside of the object is different, and the vaporization rate of the liquid is faster. You lose. Therefore, the activity inside the workpiece is changed to delay the overall cooling rate of the workpiece, and by uniformly cooling the bubble generation step formed in the salt without making a difference for each part, deformation and heat generated during the heat treatment of the workpiece Cracks can be prevented.

아울러, 상기와 같이 피처리물의 열 변형을 최소화함으로써, 열 변형에 따른 후처리공정절감 및 이로 인한 금형제작 및 제반 비용을 절감할 수도 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 and thereby reduce the mold production and overall costs.

한편, 상기와 같이 염욕조(25)에서 냉각을 마친 후에는 상기 피처리물을 들어올려 냉각실(20) 상부 공간의 염욕 분위기에서 가스 냉각을 시행하여 열처리 과정을 완료하게 된다. 이 때, 상기 가스 냉각단계(S60) 이 후에 피처리물의 크기가 큰 경우에는 다시 염욕조(25) 내부에 침지시켜 재냉각시킬 수도 있게 된다.On the other hand, after the cooling in the salt bath 25 as described above to lift the workpiece to perform gas cooling in the salt bath atmosphere of the upper space of the cooling chamber 20 to complete the heat treatment process. At this time, if the size of the workpiece after the gas cooling step (S60) is large, it can be immersed again in the salt bath 25 to be cooled again.

도 5는 상기와 같이 열처리된 50CrV4강종의 내, 외부 조직 및 경도를 나타낸 것으로, 조직의 관찰 결과 미세한 카바이드가 제품의 내, 외부에 고르게 분포됨을 알 수 있고, 이로 인해 인성이 우수한 열처리조직을 만들고 있음을 알 수 있는 것이다.Figure 5 shows the internal and external structure and hardness of the 50CrV4 steel species heat-treated as described above, it can be seen that the fine carbide is distributed evenly in and out of the product, as a result of the observation of the tissue, thereby making excellent heat treatment structure You can see that.

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. .

즉, 본 발명에서는 피처리물의 소재를 50CrV4강종을 적용한 일예만을 설명 및 도시하였으나, 오스템퍼링 열처리가 적용 가능한 다른 강종(SK5 등)의 열처리 방법 역시 본 발명의 구성에 포함된다.That is, in the present invention, only one example in which 50CrV4 steel is applied to the material to be treated is described and illustrated. However, the heat treatment method of other steel grades (SK5, etc.) to which an ostempering heat treatment is applicable is also included in the configuration of the present invention.

이상에서와 같이 본 발명은 피처리물의 냉각 작용시 냉각실의 압력 변화에 의해 전체적인 피처리물 냉각속도를 지연시키고, 염내에서 형성되는 기포발생단계를 부위별로 차이가 없이 만들어 균일냉각을 시키므로, 열처리 중 피처리물에 발생되는 변형 및 크랙 등을 방지할 수 있는 효과가 있고, 또한 상기와 같이 피처리물의 열 변형을 최소화함으로써, 열 변형에 따른 후처리공정절감 및 이로 인한 금형제작 및 제반 비용을 절감하는 효과가 있다.As described above, the present invention delays the overall cooling rate of the workpiece by the change of pressure in the cooling chamber during the cooling action of the workpiece, and makes uniform cooling by making the bubble generation step formed in the salt without any difference for each part. There is an effect that can prevent deformation and cracks generated in the workpiece, and by minimizing the thermal deformation of the workpiece as described above, to reduce the post-treatment process according to the thermal deformation, and thereby mold and overall costs There is a saving effect.

더욱이, 상기와 같이 냉각실의 압력을 제어하여 대류가 일찍 일어나도록 함으로써 마르텐사이트 변태온도에 보다 빨리 도달되어 피처리물의 경도를 높게 하는 한편, 열처리를 통해 분포되는 미세한 카바이드에 의해 인성이 우수한 열처리조직을 생산할 수 있는 효과도 있는 것이다.Furthermore, by controlling the pressure in the cooling chamber as described above, convection occurs early to reach the martensite transformation temperature faster, thereby increasing the hardness of the workpiece, and the heat treatment structure having excellent toughness due to fine carbide distributed through heat treatment. There is also an effect that can produce.

Claims (7)

강종으로 이루어진 피처리물을 오스테나이트의 상태로 가열하고 급냉한 이 후에 그 온도에서 변태 및 냉각시켜 필요한 조직을 얻는 오스템퍼링 열처리 방법에 있어서,In the ostempering heat treatment method in which a workpiece made of steel is heated in the state of austenite and quenched and then transformed and cooled at the temperature to obtain a required structure, 진공펌프(P)에 의해 가열실(10)을 진공상태로 유지하고, 피처리물의 소재 및 크기에 따라 가열온도 및 가열시간을 결정하는 가열준비단계(S10)와;A heating preparation step (S10) for maintaining the heating chamber 10 in a vacuum state by the vacuum pump P and determining a heating temperature and a heating time according to the material and the size of the workpiece; 진공의 가열실(10) 내부에 침탄성분위기를 조성하여 상기 피처리물을 가열하는 가열단계(S20)와;A heating step (S20) of heating a workpiece by forming a carburizing component crisis in a vacuum heating chamber 10; 상기 가열된 피처리물을 냉각실(20)로 이동시키는 피처리물 이동단계(S30)와;A to-be-processed object moving step (S30) for moving the heated to-be-processed object to the cooling chamber 20; 상기 피처리물의 소재 및 크기에 따라 열처리 요구 특성에 맞는 연속냉각곡선을 결정하는 냉각 준비단계(S40)와;Cooling preparation step (S40) for determining a continuous cooling curve according to the heat treatment requirements according to the material and size of the workpiece; 상기 연속냉각곡선의 특성에 따라 냉각실(20)의 압력과 교반속도를 제어하여 상기 피처리물을 염욕조(25) 내에서 균일 냉각하는 염욕 냉각단계(S50)와;A salt bath cooling step (S50) of uniformly cooling the object in the salt bath 25 by controlling the pressure and the stirring speed of the cooling chamber 20 according to the characteristics of the continuous cooling curve; 상기 염욕조(25)에서 냉각된 피처리물을 들어 올려 염욕 분위기에서 가스로 균일 냉각하는 가스 냉각단계(S60)를 포함하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.And a gas cooling step (S60) of lifting the object to be cooled in the salt bath (25) and uniformly cooling the gas in a salt bath atmosphere (S60). 제 1항에 있어서, 상기 피처리물의 크기 및 형상에 따라 가스 냉각단계(S60) 이후에 상기 피처리물을 다시 염욕조(25)에 침지시켜 냉각시키는 염욕 재냉각단계(S50')를 더 포함하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.The method of claim 1, further comprising a salt bath re-cooling step (S50 ') for immersing the object again in the salt bath 25 after the gas cooling step (S60) according to the size and shape of the object. A surface pressure control oscillating heat treatment method, characterized in that. 제 1항에 있어서, 상기 가열단계(S20)에서의 피처리물의 소재가 50CrV4인 경우, 가열실(10)의 온도를 300~650℃로 승온시켜 1시간 30분 유지시킨 후, 850~880℃까지 승온시켜 30~50분 동안 가열하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.The method of claim 1, wherein when the material to be processed in the heating step (S20) is 50CrV4, the temperature of the heating chamber 10 to 300 ~ 650 ℃ to maintain for 1 hour 30 minutes, 850 ~ 880 ℃ Surface temperature control osmosis heat treatment method characterized in that for heating up to 30 to 50 minutes to raise the temperature. 제 1항에 있어서, 상기 피처리물 이동단계(S30)에서,According to claim 1, In the processing object moving step (S30), 냉각실(20)의 압력이 가열실(10)의 압력보다 높은 경우 상기 피처리물의 이동을 제한하고, 냉각실(20)의 압력이 가열실(10)의 압력과 동일한 경우 상기 피처리물의 이동을 허가하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.When the pressure of the cooling chamber 20 is higher than the pressure of the heating chamber 10, the movement of the workpiece is restricted, and when the pressure of the cooling chamber 20 is the same as the pressure of the heating chamber 10, the movement of the workpiece Surface pressure control oscillating heat treatment method characterized in that to permit. 제 4항에 있어서, 상기 피처리물 이동단계(S30)에서 피처리물이 이동되는 경우 가열실(10)과 냉각실(20)의 압력은 각각 25~50mbar가 되도록 조절하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.The surface pressure of claim 4, wherein the pressures of the heating chamber 10 and the cooling chamber 20 are adjusted to be 25 to 50 mbar, respectively, when the workpiece is moved in the movement of the workpiece S30. Controlled austempering heat treatment method. 제 1항에 있어서, 상기 염욕 냉각단계(S50)에서 피처리물의 소재가 50CrV4인 경우, 냉각실(20)의 압력을 100~700mbar로 제어하고, 염욕조(25) 내부의 온도를 250~400℃℃ 제어하며, 염욕조(25) 내의 교반속도를 5~15Hz로 제어하여 냉각하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.According to claim 1, If the material to be treated in the salt bath cooling step (S50) is 50CrV4, the pressure of the cooling chamber 20 is controlled to 100 ~ 700 mbar, the temperature inside the salt bath 25 250 ~ 400 A surface pressure controlled osmampling heat treatment method characterized by controlling the ℃, and cooling by controlling the stirring speed in the salt bath (25) to 5 ~ 15Hz. 제 1항에 있어서, 상기 염욕 냉각단계(S50)에서 피처리물의 크기가 100㎤이상이고 그 형상이 복잡한 경우에, 냉각실(20)의 압력을 100~500mbar 사이로 낮게 조절하여 피처리물을 냉각하는 것을 특징으로 하는 면압 제어 오스템퍼링 열처리 방법.The method of claim 1, wherein in the salt bath cooling step (S50), when the size of the workpiece is 100 cm 3 or more and its shape is complicated, the pressure of the cooling chamber 20 is adjusted to be low between 100 and 500 mbar to cool the workpiece. A surface pressure control oscillating heat treatment method, characterized in that.
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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN112280950A (en) * 2020-11-23 2021-01-29 昆山市福玛精密钣金有限公司 Steel hardening and tempering equipment and efficient vacuum isothermal treatment process thereof

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JPH0372029A (en) * 1989-08-14 1991-03-27 Topy Ind Ltd Austempering treatment for fastener product
JPH03253512A (en) * 1990-03-02 1991-11-12 Komatsu Ltd Austemper treatment by cooling high-temperature and high-pressure gas
KR19990056686A (en) * 1997-12-29 1999-07-15 정몽규 Method for carburising-austempering steel
KR20050119995A (en) * 2004-06-17 2005-12-22 유신정밀공업 주식회사 A great quantity austempering method

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Publication number Priority date Publication date Assignee Title
JPH0372029A (en) * 1989-08-14 1991-03-27 Topy Ind Ltd Austempering treatment for fastener product
JPH03253512A (en) * 1990-03-02 1991-11-12 Komatsu Ltd Austemper treatment by cooling high-temperature and high-pressure gas
KR19990056686A (en) * 1997-12-29 1999-07-15 정몽규 Method for carburising-austempering steel
KR20050119995A (en) * 2004-06-17 2005-12-22 유신정밀공업 주식회사 A great quantity austempering method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112280950A (en) * 2020-11-23 2021-01-29 昆山市福玛精密钣金有限公司 Steel hardening and tempering equipment and efficient vacuum isothermal treatment process thereof

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