KR100650153B1 - Treatment method of austemperring - Google Patents

Treatment method of austemperring Download PDF

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KR100650153B1
KR100650153B1 KR1020050049991A KR20050049991A KR100650153B1 KR 100650153 B1 KR100650153 B1 KR 100650153B1 KR 1020050049991 A KR1020050049991 A KR 1020050049991A KR 20050049991 A KR20050049991 A KR 20050049991A KR 100650153 B1 KR100650153 B1 KR 100650153B1
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South Korea
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workpiece
salt bath
cooling
isothermal
isothermally
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KR1020050049991A
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Korean (ko)
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선철곤
김한군
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선철곤
김한군
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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
    • C21D1/18—Hardening; Quenching with or without subsequent 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
    • C21D1/34—Methods of heating
    • C21D1/44—Methods of heating in heat-treatment baths
    • C21D1/46—Salt baths
    • 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
    • C21D5/00—Heat treatments of cast-iron
    • 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
    • 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
    • C21D2211/002—Bainite

Abstract

An austempering hardening method which improves mechanical properties of the workpiece by isothermally maintaining the workpiece in a water mixed salt bath furnace in a process of isothermally maintaining the quenched workpiece after quenching an austenitized workpiece, and improves structural properties of the workpiece by isothermally maintaining the workpiece for a predetermined time after furnace-cooling the workpiece before quenching an austenitized workpiece, is provided. An austempering hardening method comprises: a step(S100) of preheating a workpiece; an isothermal treatment step(S200) of heating the preheated workpiece and isothermally maintaining the heated workpiece to austenitize the workpiece; a quenching step(S300) of cooling the isothermal treated workpiece to form the isothermal treated workpiece into a bainitic structure; a tempering step(S400) of isothermally maintaining the quenched workpiece in a water mixed salt bath furnace; and an air-cooling step(S500) of cooling the tempered workpiece in the air, wherein the tempering step is performed by containing at least 0.005 wt.% or more of water in the chloride based on the weight of a chloride presenting in the salt bath furnace.

Description

오스템퍼링 경화 방법{Treatment method of Austemperring}Austempering curing method {Treatment method of Austemperring}

도 1은 본 발명에 의한 오스템퍼링 경화 방법의 공정도.1 is a process chart of an ostempering curing method according to the present invention.

도 2는 본 발명에 사용되는 물혼합장치의 구성도.2 is a block diagram of a water mixing device used in the present invention.

도 3은 본 발명의 비교예에 의한 공정그래프.3 is a process graph according to a comparative example of the present invention.

도 4a,4b,4c는 도 3에 의한 비교예의 전자현미경 사진.4A, 4B and 4C are electron micrographs of the comparative example according to FIG. 3.

도 5는 본 발명의 실시예에 의한 공정그래프.5 is a process graph according to an embodiment of the present invention.

도 5a,5b,5c,5d,5e는 도 5에 의한 비교예의 전자현미경 사진.5A, 5B, 5C, 5D, and 5E are electron micrographs of the comparative example according to FIG. 5.

도 7a 내지 도 7b는 본 발명의 실시예와 비교예의 기계적 특성 측정결과 그래프.7a to 7b are graphs of the measurement results of mechanical properties of Examples and Comparative Examples of the present invention.

본 발명은 오스템퍼링 경화 방법에 관한 것으로, 보다 상세하게는 오스테나이트화한 소재를 베이나이트화하는 과정에서 염욕로에 물을 혼합한 상태로 등온유지하는 공정을 실시하여 기계적 특성을 향상시키도록 한 오스템퍼링 경화 방법에 관한 것이다.The present invention relates to an ostempering curing method, and more particularly, to improve mechanical properties by performing an isothermal holding process in which water is mixed in a salt bath in the process of bainizing an austenitized material. It relates to an ostempering curing method.

일반적으로 오스템퍼링 연강(Austempered Ductile Iron;이하 'ADI'라 칭함) 소재는 구상흑연주철을 오스템퍼링 열처리하여 얻어진다. ADI는 인장강도와 연신율이 높고 무게가 가벼우며 마찰저항이 우수한 특징을 갖는다. 따라서 ADI 소재는 내마모성과 강도와 인성이 동시에 요구되는 기어류나 엔진의 부품에 많이 사용되고 있으며, 최근들어 건설업, 광업, 군수, 철도 분야 등 그 사용범위가 확대되고 있는 실정이다.In general, an Austempered Ductile Iron (hereinafter referred to as 'ADI') material is obtained by an ostempering heat treatment of nodular cast iron. ADI is characterized by high tensile strength and elongation, light weight and excellent frictional resistance. Therefore, ADI materials are widely used in gears and engine parts that require abrasion resistance, strength, and toughness at the same time. Recently, the scope of use of ADI materials has been expanded in the construction, mining, military, and railway fields.

이와 같은 ADI 소재의 오스템퍼링 열처리방법을 간단하게 설명하면 다음과 같다. 먼저, 구상흑연주철로 이루어진 소재를 Ac3 변태점 이상으로 가열한 다음 이를 등온 열처리하여 기지조직을 오스테나이트로 변태시킨다. 그리고 오스테나이트화된 소재를 염욕(salt bath)처리하여 펄라이트 생성온도와 마르텐사이트 생성온도사이에서 급냉시키고, 급냉된 처리물을 다시 염욕에서 등온으로 유지하여 오스테나이트 조직을 베이나이트로 변태시킨다. 그리고 마지막으로 베이나이트화 된 소재를 공기중에서 서냉시킨다.A brief description of the method of heat treatment of the ADI material as follows. First, a material made of nodular cast iron is heated above the Ac3 transformation point and then isothermally treated to transform the matrix into austenite. The austenitic material is treated in a salt bath to quench between the pearlite and martensite production temperatures, and the quenched treatment is maintained at isothermal temperature in the salt bath to transform the austenite structure to bainite. Finally, the bainited material is slowly cooled in air.

이처럼 통상적으로 오스템퍼링의 열처리시 오스테나이트화된 소재를 급냉시키거나, 급냉된 처리물을 등온으로 유지하여 베이나이트화하는 과정에서 염욕로(salt bath furnace)에서 염욕처리하고 있다. 이는 염욕로가 가열물의 산화 및 탈탄이 방지되고, 온도 조절이 용이하며, 가열이 균일하게 이루어져 변형이나 균열의 발생가능성이 적고, 전도에 의한 가열이 실시되어 대류 및 복사 보다 현저하게 빠른 가열 성능을 나타내며, 노의 설비비가 저렴하다는 이점을 갖기 때문이다.As described above, the austenitized material is quenched during the heat treatment of ostempering, or the salt bath is treated in a salt bath furnace in the process of baitizing by maintaining the quenched material at an isothermal temperature. The salt bath prevents oxidization and decarburization of the heating material, easy temperature control, uniform heating, so that there is little possibility of deformation or cracking, and heating is conducted by conduction so that heating performance is significantly faster than convection and radiation. It is because it has the advantage that the installation cost of a furnace is cheap.

이와 같이 종래에는 오스테나이트화된 소재를 곧바로 급냉시키고, 급냉된 처리물을 순수한 염욕에서 등온유지하고 있으나, 소재의 조직이 치밀하지 못하여 기 계적 특성을 만족할 만한 수준으로 향상시키지 못하는 문제가 있다.As described above, the austenitic material is quenched immediately, and the quenched processed material is isothermally maintained in a pure salt bath, but there is a problem in that the structure of the material is not dense and the mechanical properties are not improved to a satisfactory level.

이와 같은 문제점을 해결하기 위한 본 발명의 목적은 오스테나이트화된 소재를 급냉처리한 후에 등온유지하는 과정에서 염욕로에 물은 혼합하여 등온유지함으로써 소재의 기계적 특성을 향상시키도록 하려는 것이다.An object of the present invention for solving this problem is to improve the mechanical properties of the material by mixing isothermally by mixing water in the salt bath in the process of isothermally holding the austenitized material after quenching.

본 발명의 다른 목적은 오스테나이트화된 소재를 급냉시키기 전 상태에서 일정온도까지 노냉시킨 후에 소정 시간동안 등온유지하여 소재의 조직 특성을 향상시키도록 하려는 것이다.Another object of the present invention is to improve the tissue properties of the material by isothermalizing for a predetermined time after the austenitized material is quenched to a predetermined temperature in the state before quenching.

상기한 바와 같은 목적을 달성하기 위한 본 발명은 구상흑연주철로 이루어진 소재를 예열하는 단계(S100)를 포함한다.The present invention for achieving the object as described above includes a step (S100) for preheating the material made of nodular graphite iron.

상기 예열 단계(S100)는 소재를 예열함으로써 이후에 가해지는 고온의 열충격을 사전에 완화시키고, 동시에 표면조직의 오스테나이트화에 걸리는 시간을 단축시키기 위함이다. 이때 예열 온도는 대략 500℃ 내지 600℃의 범위로 한다.The preheating step (S100) is to pre-relieve the high temperature thermal shock applied after the preheating of the material, and at the same time to shorten the time taken to austenitize the surface tissue. At this time, the preheating temperature is in the range of approximately 500 ° C to 600 ° C.

그리고 예열된 소재는 가열한 후에, 등온처리하여 소재의 조직을 오스테나이트화하는 등온열처리 단계(S200)를 포함한다.And the preheated material includes an isothermal heat treatment step (S200) of austenitizing the tissue of the material by isothermalizing after heating.

상기 등온열처리 단계(S200)는 예열된 소재에 Ac3 변태점 이상의 고열을 일정하게 가하여 기지조직을 오스테나이트 조직으로 변태시키는 단계이다. 850℃ 내지 930℃ 범위의 온도로 급가열한 후에 900℃의 온도로 2시간 동안 등온상태로 유지시킨다.The isothermal heat treatment step (S200) is a step of transforming the matrix into austenite tissue by constantly applying a high temperature of Ac3 transformation point or more to the preheated material. After rapid heating to a temperature in the range of 850 ° C. to 930 ° C., the temperature is maintained at 900 ° C. for 2 hours.

그리고 노내에서 소재를 800℃의 온도까지 냉각시킨다(S220).And the material is cooled to a temperature of 800 ℃ in the furnace (S220).

냉각된 소재를 800℃ 온도에서 20분 동안 등온상태로 유지시킨다(S240).The cooled material is maintained in an isothermal state for 20 minutes at 800 ℃ (S240).

그 다음에 800℃ 온도의 상기 소재를 냉각시켜 베이나이트화하는 퀀칭 단계(S300)를 포함한다.It then includes a quenching step (S300) of cooling the material at 800 ° C. to bainitize.

상기 퀀칭 단계(S300)는 오스테나이트화한 소재를 급격히 냉각시켜 베이나이트화시키는 단계이다. 이때의 냉각온도는 펄라이트의 생성온도와 마르텐사이트의 생성온도의 중간 온도인 230℃ 내지 400℃ 범위로 한다.The quenching step (S300) is a step of rapidly nitriding the austenitized material by cooling. The cooling temperature at this time is in the range of 230 ° C. to 400 ° C., which is an intermediate temperature between the production temperature of pearlite and the production temperature of martensite.

상기 퀀칭 단계(S300) 이후에는 상기 소재를 염욕로의 내부에서 등온상태로 유지한다. 이때 상기 염욕로의 염화물에 물(H2O)을 혼합하여 등온유지하는 템퍼링 단계(S400)를 포함한다.After the quenching step (S300) to maintain the material isothermally inside the salt bath. At this time, it comprises a tempering step (S400) of isothermal maintenance by mixing water (H 2 O) to the chloride in the salt bath.

상기 템퍼링 단계(S400)는 퀀칭 단계(S300)에서 형성된 베이나이트 조직을 변태 또는 석출시켜 안정적으로 만들어주는 단계로서, 퀀칭 단계의 온도인 230℃ 내지 400℃을 그대로 1시간 가량 등온유지한다. The tempering step (S400) is a step of transforming or depositing the bainite tissue formed in the quenching step (S300) to make it stable, and isothermally maintaining the temperature of the quenching step at 230 ° C. to 400 ° C. for about 1 hour.

여기서 본 발명은 염욕로에 사용되는 염욕 즉, 염화물에 물을 포함한다. 이러한 물의 양은 염욕로에 존재하는 염화물과 중량대비 적어도 0.005％ 이상을 포함한다.The present invention includes water in a salt bath, ie chloride, used in a salt bath. This amount of water comprises at least 0.005% or more by weight of chloride present in the salt bath.

이와 같이 염욕로에 물을 혼합하는 장치로서 도 2에 도시한 바와 같이, 시편이 담구어지는 염욕로의 개구된 상단 중앙에 물이 수납된 물수납실린더(10)가 물공급튜브(12)에 의해 염욕로(20)와 연통되게 설치되고, 염욕로의 중앙에는 하단에 혼 합팬(32)이 구비된 회전샤프트(34)가 설치되며, 상기 회전샤프트를 구동시키기 위한 모터(30)가 염욕로의 상단 일측에 설치된다. 상기 물공급튜브(12)에는 공급되는 물의 양을 조절하기 위한 컨트롤 밸브(14)가 설치되고, 상기 염욕로의 내주벽에는 염욕로의 온도를 측정하기 위한 서모메터(Thermometer)(40)가 설치된다. 부호 S는 시편이다.As shown in FIG. 2 as a device for mixing water in the salt bath as described above, a water storage cylinder 10 in which water is stored in the center of the opened upper end of the salt bath in which the specimen is immersed by the water supply tube 12 is provided. Is installed in communication with the salt bath 20, a rotary shaft 34 having a mixing fan 32 is provided at the bottom of the salt bath, the motor 30 for driving the rotary shaft is installed in the salt bath It is installed on one side of the top. The water supply tube 12 is provided with a control valve 14 for adjusting the amount of water supplied, and the thermometer (40) for measuring the temperature of the salt bath in the inner circumferential wall of the salt bath do. Symbol S is the specimen.

이러한 물 혼합장치를 이용하여 염욕로에 물을 공급하는 경우에 적어도 100℃ 미만의 온도 범위에서 물을 공급한 상태에서 염욕로 내부의 온도를 상승시키는 것이 바람직하다. When water is supplied to the salt bath using such a water mixing device, it is preferable to raise the temperature inside the salt bath in a state in which water is supplied in a temperature range of at least 100 ° C.

상기 염욕로의 내부에서 염욕과 혼합된 상태의 물은 온도가 상승되더라도 기화하지 않고 염욕과 혼합된 상태를 유지하면서 템퍼링 단계를 수행한다.The water mixed with the salt bath in the inside of the salt bath is tempered while maintaining the mixed state with the salt bath without vaporizing even if the temperature is increased.

템퍼링 단계(S400)가 완료되면, 최종적으로 베이나이트화된 소재를 공기중에서 냉각시킨다.(S500)When the tempering step (S400) is completed, the final bainized material is cooled in the air (S500).

다음은 본 발명의 구체적인 실시예 및 비교예에 의한 실험 결과를 설명한다.The following describes the experimental results by specific examples and comparative examples of the present invention.

시편(specimen)의 조성은 C:3.890 Si:2.800, Mn:0.290, P:0.040, S:0.010, Cr:0.020, Cu:0.030, Ti:0.030, Mo:0.001, V:0.003, Ni:0.002, Mg:0.010, Mg:0.010, 나머지 Fe (단위 wt％)이다.The composition of the specimens was C: 3.890 Si: 2.800, Mn: 0.290, P: 0.040, S: 0.010, Cr: 0.020, Cu: 0.030, Ti: 0.030, Mo: 0.001, V: 0.003, Ni: 0.002, Mg: 0.010, Mg: 0.010, remaining Fe (unit wt%).

(비교예 1,2,3)(Comparative Examples 1,2,3)

도 3에 도시한 열처리 사이클 그래프를 참조하여 설명하면, 시편를 예열한 후에 상기 시편을 900℃ 온도로 가열하고 2시간 동안 등온처리하였고, 시편을 800 ℃로 냉각시킨 후에 냉각된 시편을 800℃ 온도에서 20분 유지하였으며, 다시 시편을 230℃, 280℃, 330℃로 각각 급속냉각시켰고, 냉각된 시편은 염욕로에서 1시간동안 등온유지한 후에 공기중에서 서냉시켰다.Referring to the heat treatment cycle graph shown in FIG. 3, after preheating the specimen, the specimen was heated to 900 ° C. and isothermalized for 2 hours, and after cooling the specimen to 800 ° C., the cooled specimen was cooled at 800 ° C. After 20 minutes, the specimens were rapidly cooled to 230 ° C., 280 ° C., and 330 ° C., respectively. The cooled specimens were kept isothermally for 1 hour in a salt bath and then cooled slowly in air.

이와 같이 열처리된 시편의 전자현미경 사진은 도 4a (비교예 1: 230℃ 냉각), 도 4b (비교예 2: 280℃ 냉각), 도 4c (비교예 3: 330℃ 냉각)와 같다.Electron micrographs of the specimens thus heat treated are shown in FIG. 4A (Comparative Example 1: 230 ° C. cooling), FIG. 4B (Comparative Example 2: 280 ° C. cooling), and FIG. 4C (Comparative Example 3: 330 ° C. cooling).

(실시예 1,2,3,4,5)(Examples 1,2,3,4,5)

도 5를 참조하여 설명하면, 시편를 예열한 후에 상기 시편을 900℃ 온도로 가열하고 2시간 동안 등온처리하였고, 시편을 800℃로 냉각시킨 후에 냉각된 시편을 800℃ 온도에서 20분 유지하였으며, 시편을 230℃, 280℃, 330℃,350℃,400℃로 각각 급속냉각시켰고, 냉각된 시편은 염욕로에서 1시간동안 등온유지한 후에 공기중에서 서냉시켰다. 이때, 염욕로에는 0.005wt%의 물이 포함된 상태이다.Referring to FIG. 5, after preheating the specimen, the specimen was heated to 900 ° C. and isothermalized for 2 hours. After cooling the specimen to 800 ° C., the cooled specimen was kept at 800 ° C. for 20 minutes. Were rapidly cooled to 230 ° C., 280 ° C., 330 ° C., 350 ° C., and 400 ° C., respectively. The cooled specimens were isothermally maintained in a salt bath for 1 hour and then slowly cooled in air. At this time, the salt bath is a state containing 0.005wt% water.

이와 같이 열처리된 시편의 전자현미경 사진은 도 6a (실시예 1: 230℃ 냉각), 도 6b (실시예 2: 280℃ 냉각), 도 6c (실시예 3: 330℃ 냉각), 도 6d (실시예 4: 350℃ 냉각), 도 6e (실시예 5: 400℃ 냉각)와 같다.Electron micrographs of the specimens thus heat treated are shown in FIG. 6A (Example 1: 230 ° C. cooling), FIG. 6B (Example 2: 280 ° C. cooling), FIG. 6C (Example 3: 330 ° C. cooling), and FIG. 6D (Example Example 4: 350 ° C. cooling), FIG. 6E (Example 5: 400 ° C. cooling).

이와 같이 열처리된 구상흑연주철 소재로 한 시편의 기계적인 특성중 인장 강도(Tensile strength)는 도 7a에서 보는 바와 같이, 실시예 2가 830MPa로 가장 우수한 특성을 나타내었고, 항복 강도(Yield strenght)는 도 7b에서 실시예 2가 690Mpa로 가장 우수하였으며, 연신율(Elongation)은 실시예 3의 시편이 3.4％로 높 았다. 또한, 내충격도(Impact Value)는 도 7d에서 보는 바와 같이, 실시예 2가 2.85Kg·m/cm2로 가장 우수한 특성을 나타내어 전반적으로 염욕로에 물을 포함하여 템퍼링 공정을 수행한 실시예 1,2,3이 염욕로에 물을 포함하지 않고 템퍼링 공정을 수행한 비교예 1,2,3과 비교하여 기계적 특성이 우수함을 알 수 있었다.Tensile strength of the mechanical properties of the specimens made of the heat-treated spheroidal graphite cast iron as shown in Figure 7a, Example 2 exhibited the most excellent properties of 830MPa, yield strength (Yield strenght) is In FIG. 7B, Example 2 was the best at 690 Mpa, and the elongation of the specimen of Example 3 was 3.4%. In addition, the impact value (Impact Value), as shown in Figure 7d, Example 2 exhibited the most excellent characteristics of 2.85Kg · m / cm 2 , the overall Example 1 performing a tempering process including water in the salt bath It was found that 2,3 was superior in mechanical properties compared to Comparative Examples 1, 2 and 3 in which the tempering process was performed without including water in the salt bath.

상술한 바의 설명에서 본 발명의 비교예 1,2,3의 기술 즉, 시편을 예열한 후에 900℃ 온도로 가열하여 2시간 동안 등온처리하고, 등온처리된 시편을 800℃로 냉각시킨 후에 냉각된 시편을 800℃ 온도에서 20분 유지하며, 다시 시편을 230℃, 280℃, 330℃로 각각 급속냉각하여 냉각된 시편을 염욕로에서 1시간동안 등온유지한 후에 공기중에서 서냉시키는 기술이 종래 기술인 것으로서 설명되었으나, 종래 일반적인 오스템퍼링 열처리 방법인 시편을 900℃ 온도로 가열하고 2시간 동안 등온처리한 후에 곧바로 시편을 230℃, 280℃, 330℃로 각각 급속냉각하는 기술과 비교하여 시편의 조직을 미세화하는 효과를 발휘하게 됨은 의심의 여지가 없으며, 이는 본 발명의 청구범위에 기재하지는 않았으나 종래 기술과 비교하여 현저한 효과를 갖는 기술이라 할 것이다.In the above description, the technique of Comparative Examples 1, 2 and 3 of the present invention, that is, after preheating the specimen, is heated to 900 ° C and isothermalized for 2 hours, and cooled after cooling the isothermalized specimen to 800 ° C. 20 minutes at 800 ℃ temperature, and then rapidly cooled the specimens to 230 ℃, 280 ℃, 330 ℃, respectively, isothermally maintained in the salt bath for 1 hour and then slowly cooled in air technology Although described as a conventional method, the structure of the specimen is compared with a technique of rapidly cooling the specimen at 230 ° C., 280 ° C., and 330 ° C., respectively, after heating the specimen to 900 ° C. and isothermalizing for 2 hours. There is no doubt that the effect of miniaturization is exerted, which is not described in the claims of the present invention, but will be referred to as a technique having remarkable effects compared to the prior art.

이상에서 설명한 바와 같이, 본 발명에 의한 오스템퍼링 경화 방법은 소재를 냉각시켜 베이나이트화하는 퀀칭 단계 이후에 염욕로에서 등온유지하는 템퍼링 단계에서 염욕로에 물을 혼합함으로써 소재의 기계적 특성을 현저하게 향상시키는 효과가 있다.As described above, the ostempering curing method according to the present invention remarkably improves the mechanical properties of the material by mixing water in the salt bath in the tempering step of isothermally maintaining in the salt bath after the quenching step of cooling and bainizing the material. It is effective to improve.

또한, 등온열처리 단계 이후에 소재를 800℃로 냉각시키는 노냉 단계와, 상기 냉각된 소재를 800℃ 온도에서 20분 유지하는 등온유지단계를 더 실시함으로써 소재의 조직이 치밀해져 소재의 기계적 특성이 보다 향상되는 효과가 있다.In addition, after the isothermal heat treatment step, by further performing a furnace cooling step of cooling the material to 800 ° C and an isothermal holding step of maintaining the cooled material at 800 ° C for 20 minutes, the structure of the material is dense, resulting in more mechanical properties of the material. There is an effect to be improved.

Claims (3)

삭제delete 소재를 예열하는 단계와;Preheating the material; 상기 예열된 소재를 가열하고 등온처리하여 오스테나이트화하는 등온열처리 단계와;An isothermal heat treatment step of heating and isothermalizing the preheated material to austenite; 상기 등온열처리된 소재를 냉각시켜 베이나이트화하는 퀀칭 단계와;A quenching step of bainizing the cooled isothermally treated material; 상기 퀀칭된 소재를 물을 혼합한 염욕로에서 등온유지하는 템퍼링 단계 및;A tempering step of isothermally maintaining the quenched material in a salt bath in which water is mixed; 상기 템퍼링된 소재를 공기중에서 냉각시키는 공냉 단계를 포함하되, An air cooling step of cooling the tempered material in the air, 상기 템퍼링 단계에서 상기 염욕로에 혼합되는 물은 상기 염욕로에 존재하는 염화물에 적어도 0.005wt％ 이상을 포함하여 템퍼링을 실시하는 것을 특징으로 하는 오스템퍼링 경화 방법.The water mixed in the salt bath in the tempering step comprises at least 0.005wt% or more of the chloride present in the salt bath to temper the process of tempering. 제 2 항에 있어서,The method of claim 2, 상기 등온열처리 단계와 상기 퀀칭 단계 사이에 소재를 800℃로 냉각시키는 노냉 단계와, 상기 냉각된 소재를 800℃ 온도에서 20분 유지하는 등온유지단계를 더 실시하는 것을 특징으로 하는 오스템퍼링 경화 방법.And an isothermal step of cooling the material to 800 ° C. between the isothermal heat treatment step and the quenching step, and an isothermal holding step of maintaining the cooled material at 800 ° C. for 20 minutes.
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