JP6031313B2 - Carburizing method - Google Patents

Carburizing method Download PDF

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JP6031313B2
JP6031313B2 JP2012218347A JP2012218347A JP6031313B2 JP 6031313 B2 JP6031313 B2 JP 6031313B2 JP 2012218347 A JP2012218347 A JP 2012218347A JP 2012218347 A JP2012218347 A JP 2012218347A JP 6031313 B2 JP6031313 B2 JP 6031313B2
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carburizing
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furnace
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JP2014070254A (en
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桂太 吉富
桂太 吉富
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Dowa Thermotech Co Ltd
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本発明は、鋼材の浸炭処理方法に関するものである。   The present invention relates to a steel carburizing method.

鋼材の浸炭処理方法として、一酸化炭素ガス(CO)を含む吸熱式変成ガスを雰囲気ガスとし、さらに所定のカーボンポテンシャル(CP)を得るためのエンリッチガスとして炭化水素系ガスを浸炭処理室内に供給して浸炭処理するガス浸炭処理方法が、広く普及している。このガス浸炭処理方法では、浸炭処理室内雰囲気を構成するガス成分の濃度もしくは分圧を測定することにより、その測定値からカーボンポテンシャルを算出し、その結果を元にエンリッチガスの供給量を調節することにより浸炭の制御を行っている。   As a carburizing method for steel, an endothermic modified gas containing carbon monoxide gas (CO) is used as an atmospheric gas, and a hydrocarbon gas is supplied into the carburizing chamber as an enriched gas for obtaining a predetermined carbon potential (CP). A gas carburizing method for carburizing is widely used. In this gas carburizing method, the carbon potential is calculated from the measured value by measuring the concentration or partial pressure of the gas component constituting the atmosphere of the carburizing chamber, and the supply amount of the enriched gas is adjusted based on the result. Therefore, carburization is controlled.

鋼材の浸炭処理に関し、例えば特許文献1には、連続炉において、炉内CPを安定させるために、変成ガスおよびエンリッチガスの供給流量を調整する熱処理方法が記載されている。   Regarding the carburizing treatment of steel materials, for example, Patent Document 1 describes a heat treatment method for adjusting the supply flow rates of a metamorphic gas and an enriched gas in a continuous furnace in order to stabilize the in-furnace CP.

一方、バッチ式の浸炭処理炉では、従来、炉内が負圧になるのを防止するために、常時、同量の処理ガスを供給している。すなわち、図5に示すように、
(1)炉内に被処理体が無い空炉時
(2)被処理体の炉内への搬入時に炉の入口扉を開閉し、一旦温度が下がった後昇温する間
(3)浸炭処理温度の930℃で浸炭処理している間
(4)浸炭処理が終了し降温する間
(5)2次設定温度の850℃で2次加熱する間
(6)被処理体を油槽へ搬出する際に炉の出口扉を開閉して被処理体を焼入する間
の工程(1)〜(6)において、変成ガスを、常時、例えば置換回数5回/hr〜15回/hrで供給している。
On the other hand, in a batch type carburizing furnace, the same amount of processing gas is conventionally supplied to prevent the inside of the furnace from becoming negative pressure. That is, as shown in FIG.
(1) When the furnace has no workpiece in the furnace (2) While the furnace door is opened and closed when the workpiece is carried into the furnace, the temperature is once lowered and then the temperature is raised (3) Carburizing treatment While carburizing at a temperature of 930 ° C. (4) While carburizing is completed and the temperature is lowered (5) During secondary heating at a secondary set temperature of 850 ° C. (6) When the workpiece is carried out to the oil tank In steps (1) to (6) during which the exit door of the furnace is opened and closed and the object to be treated is quenched, the metamorphic gas is constantly supplied, for example, at a replacement frequency of 5 times / hr to 15 times / hr. Yes.

ところが、浸炭処理時に炉内に供給される変成ガスに含まれるCOの多くは、未反応のまま燃焼され、COとなって炉外に排出される。そのため、無駄なコストを要するうえ、多くのCOを排出するという問題があった。 However, most of the CO contained in the metamorphic gas supplied into the furnace during the carburizing process is burned unreacted and becomes CO 2 and discharged outside the furnace. Therefore, there is a problem that wasteful cost is required and a large amount of CO 2 is discharged.

そこで、特許文献2に、所望の品質を付与しつつ、浸炭処理または浸炭窒化処理における変成ガスの流量を低減することによりCOの排出量を抑制することを可能とする鋼の熱処理方法が記載されている。 Therefore, Patent Document 2 describes a steel heat treatment method capable of suppressing CO 2 emission by reducing the flow rate of metamorphic gas in carburizing or carbonitriding while providing desired quality. Has been.

特開2011−42878号公報JP 2011-42878 A 特開2010−285642号公報JP 2010-285642 A

しかしながら、特許文献1に記載されている連続炉では、処理室毎に扉の開閉が頻繁に行われるため、CPを保つためには、処理ガスの量を減らすことが困難である。また、特許文献2に記載された方法は、処理ガスの供給量が極めて少なく、現在のCP(Oセンサ)とCO制御では、種々の製品について浸炭処理をばらつきなく行うことは厳しいと考えられる。 However, in the continuous furnace described in Patent Document 1, since the door is frequently opened and closed for each processing chamber, it is difficult to reduce the amount of processing gas in order to maintain the CP. In addition, the method described in Patent Document 2 has a very small supply amount of processing gas, and it is considered that it is difficult to perform carburization processing for various products without variation with the current CP (O 2 sensor) and CO 2 control. It is done.

本発明の目的は、バッチ式の処理炉において、変成ガスの供給量を削減しつつ、炉内のCPを安定させることができる浸炭処理方法を提供することにある。   An object of the present invention is to provide a carburizing treatment method capable of stabilizing CP in a furnace while reducing the supply amount of metamorphic gas in a batch type treatment furnace.

上記問題を解決するため、本発明は、バッチ式の処理炉(加熱室)に変成ガスおよびエンリッチガスを供給し、前記処理炉内に搬入した被処理体を浸炭処理する浸炭処理方法であって、昇温工程、浸炭工程、降温工程、2次加熱工程、焼き入れ工程からなり、前記昇温工程、前記浸炭工程、前記降温工程において、前記処理炉内に前記被処理体が収容され前記処理炉が閉じた状態で800℃以上を保持している間は、前記処理炉内に供給される前記変成ガスの置換回数を1.0回/hr〜4.0回/hrとすることを特徴とする、浸炭処理方法を提供する。 In order to solve the above problems, the present invention is a carburizing method for supplying a metamorphic gas and an enriched gas to a batch-type processing furnace (heating chamber) and carburizing a workpiece to be carried into the processing furnace. A temperature raising step, a carburizing step, a temperature lowering step, a secondary heating step, and a quenching step. In the temperature raising step, the carburizing step, and the temperature lowering step, the object to be processed is accommodated in the processing furnace and the treatment is performed. While maintaining the furnace at 800 ° C. or higher with the furnace closed, the number of replacements of the modified gas supplied into the processing furnace is 1.0 times / hr to 4.0 times / hr. A carburizing method is provided.

なお、変成ガスの置換回数とは、バッチ式の処理炉において、1時間当たりに供給した変成ガス量を、浸炭処理を行う加熱室の容積と比べて表した数値であり、例えば1時間あたり加熱室の容積の4倍の量(体積)の変成ガスを供給したときは4.0回/hrとなる。   The number of times of substitution of the modification gas is a numerical value representing the amount of modification gas supplied per hour in a batch type processing furnace compared to the volume of the heating chamber in which the carburizing process is performed. When the metamorphic gas is supplied in an amount (volume) that is four times the volume of the chamber, the rate is 4.0 times / hr.

本発明によれば、扉の開閉や温度低下により負圧が発生するとき以外は、変成ガスの供給量を低減することにより、CO削減およびコストを低減して、浸炭処理を行うことができる。 According to the present invention, except when negative pressure is generated due to opening / closing of a door or a temperature drop, carburizing treatment can be performed by reducing the supply amount of metamorphic gas, thereby reducing CO 2 and cost. .

熱処理装置の概略を示す構成図である。It is a block diagram which shows the outline of a heat processing apparatus. 本発明の浸炭処理方法の説明図である。It is explanatory drawing of the carburizing method of this invention. ガス置換回数毎の、浸炭処理開始からの経過時間とCO濃度との関係を示すグラフである。For each gas replacement number is a graph showing the relationship between the elapsed time and the CO 2 concentration from carburization start. ガス置換回数毎の、浸炭処理開始からの経過時間とCO濃度との関係を示すグラフである。It is a graph which shows the relationship between the elapsed time from the carburizing process start, and CO density | concentration for every gas replacement frequency. 従来の浸炭処理方法の説明図である。It is explanatory drawing of the conventional carburizing process method. 実施例における鋼材サンプルの測定(処理)位置を示す説明図である。It is explanatory drawing which shows the measurement (process) position of the steel material sample in an Example.

以下、本発明の実施の形態を、図を参照して説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

図1は、本発明にかかる鋼材の浸炭焼き入れ処理を行う熱処理装置の例を示す。熱処理装置1は、搬入部10、浸炭処理炉としての加熱室11、冷却室12、搬出コンベア13を有している。搬入部10に置かれたケース20内には、被処理体としての鋼材が収納される。加熱室11の入口側(図1において左側)には、開閉自在な扉21を備えた入口フード22が取り付けられている。   FIG. 1 shows an example of a heat treatment apparatus for performing a carburizing and quenching treatment of a steel material according to the present invention. The heat treatment apparatus 1 includes a carry-in unit 10, a heating chamber 11 as a carburizing furnace, a cooling chamber 12, and a carry-out conveyor 13. In the case 20 placed in the carry-in unit 10, a steel material as an object to be processed is stored. An inlet hood 22 having an openable / closable door 21 is attached to the inlet side of the heating chamber 11 (left side in FIG. 1).

加熱室11内には、ヒータ25が設けられている。加熱室11内には、雰囲気ガスを構成する変成ガスとカーボンポテンシャルを調整するためのエンリッチガスが供給され、加熱室11内に供給されたこれらの処理ガスがヒータ25で所定の温度に加熱されて、加熱室11内に搬入された鋼材の浸炭処理が行われる。加熱室11の天井には、加熱室11内の処理ガスを攪拌し、鋼材の加熱温度を均一化させ、また鋼材に当たる処理ガスの風速を制御するファン26が設けられている。加熱室11の出口側(図1において右側)には、開閉自在な中間扉27が取り付けられている。   A heater 25 is provided in the heating chamber 11. In the heating chamber 11, a metamorphic gas constituting the atmospheric gas and an enrich gas for adjusting the carbon potential are supplied, and these processing gases supplied in the heating chamber 11 are heated to a predetermined temperature by the heater 25. Thus, the carburizing process of the steel material carried into the heating chamber 11 is performed. A fan 26 is provided on the ceiling of the heating chamber 11 to stir the processing gas in the heating chamber 11 to equalize the heating temperature of the steel material and to control the wind speed of the processing gas striking the steel material. An openable / closable intermediate door 27 is attached to the outlet side of the heating chamber 11 (right side in FIG. 1).

冷却室12には、鋼材が収納されたケース20を昇降させるエレベータ30が設けられている。冷却室12の下部には、冷却用の油31を溜めた油槽32が設けられている。冷却室12の出口側(図1において右側)には、開閉自在な扉35を備えた出口フード36が取り付けられている。   The cooling chamber 12 is provided with an elevator 30 that raises and lowers the case 20 in which the steel material is stored. An oil tank 32 in which cooling oil 31 is stored is provided at the lower portion of the cooling chamber 12. An outlet hood 36 having an openable / closable door 35 is attached to the outlet side (right side in FIG. 1) of the cooling chamber 12.

かかる熱処理装置1において、鋼材が収納されたケース20が、プッシャー等により、搬入部10から加熱室11内に搬入される。その後、加熱室11内に処理ガスが供給される。さらに、加熱室11内に供給された処理ガスがヒータ25で所定の温度にされて、ファン26で攪拌しながら、加熱室11内に搬入された鋼材の浸炭処理が行われる。次いで、降温、2次加熱処理を加熱室11内で施した後、焼き入れの行われる冷却室12に鋼材が収納されたケース20を移動し、焼き入れ処理が行われる。   In the heat treatment apparatus 1, the case 20 in which the steel material is stored is carried into the heating chamber 11 from the carry-in unit 10 by a pusher or the like. Thereafter, the processing gas is supplied into the heating chamber 11. Further, the processing gas supplied into the heating chamber 11 is heated to a predetermined temperature by the heater 25, and the carburizing process of the steel material carried into the heating chamber 11 is performed while stirring with the fan 26. Next, after the temperature lowering and the secondary heat treatment are performed in the heating chamber 11, the case 20 in which the steel material is stored is moved to the cooling chamber 12 where the quenching is performed, and the quenching treatment is performed.

以上のように、本発明にかかる浸炭処理は、バッチ炉である加熱室11を用いて行われる。図2は、本発明の熱処理方法の実施形態の一例を示す模式図であり、縦軸は加熱室11内の温度変化、横軸は処理工程(時間軸)を表す。   As mentioned above, the carburizing process concerning this invention is performed using the heating chamber 11 which is a batch furnace. FIG. 2 is a schematic diagram showing an example of an embodiment of the heat treatment method of the present invention, where the vertical axis represents a temperature change in the heating chamber 11 and the horizontal axis represents a processing step (time axis).

本発明では、浸炭処理炉(加熱室11)の扉の開閉時や負圧が発生するときを除いた期間、すなわち、図2の工程において、雰囲気温度が所定温度以上を保つ昇温時〜浸炭処理時〜降温時の雰囲気温度が所定温度に下がるまでの間における変成ガスの供給量を、扉の開閉時や負圧が発生する期間よりも低減させるのが好ましく、ガス置換回数1.0回/hr〜4.0回/hrとする。所定温度は、例えば800℃以上浸炭処理温度以下、好ましくは850℃以上浸炭処理温度以下とし、図2の例では850℃である。低減時の変成ガスの供給量は、置換回数4.0回/hrを超えると、CO排出量やコストを低減する効果が低く、1.0回/hrを下回ると、CO、COが不足し、浸炭処理後の被処理体の品質が低下する。1.5回/hr〜3.0回/hrであることが、より好ましい。 In the present invention, in a period excluding when the door of the carburizing furnace (heating chamber 11) is opened and closed and when negative pressure is generated, that is, in the process of FIG. It is preferable to reduce the supply amount of the metamorphic gas from the time of treatment to the time when the ambient temperature is lowered to a predetermined temperature, compared to the time when the door is opened and closed and the period during which negative pressure is generated. / Hr to 4.0 times / hr. The predetermined temperature is, for example, 800 ° C. or more and the carburizing temperature or less, preferably 850 ° C. or more and the carburizing temperature or less, and is 850 ° C. in the example of FIG. When the amount of metamorphic gas supplied during reduction exceeds 4.0 times / hr, the effect of reducing CO 2 emissions and costs is low, and when it is below 1.0 times / hr, CO and CO 2 are reduced. Insufficient and the quality of the to-be-processed object after a carburizing process falls. It is more preferable that it is 1.5 times / hr to 3.0 times / hr.

本発明者は、昇温工程、浸炭処理工程および降温工程において、所定の温度以上を保っていれば、ガス置換回数を上記の範囲としても被処理体の浸炭品質は従来と同等であり、且つ、浸炭処理中に浸炭雰囲気の特別な制御や制御機器は不要であることを見出し、本発明の完成に至った。なお、図2の被処理体を加熱室に搬入する前の空炉時においても、焼入れ処理の影響での雰囲気の乱れから加熱室の雰囲気が回復・安定していれば、ガス置換回数を上記の範囲に減らしてもよい。   The inventor has the same carburizing quality as the conventional object even if the number of gas replacements is within the above range as long as a predetermined temperature or higher is maintained in the temperature raising step, the carburizing treatment step, and the temperature lowering step, and The present inventors have found that special control and control equipment for the carburizing atmosphere are not required during the carburizing process, and the present invention has been completed. In addition, even in the case of the empty furnace before carrying the object to be processed in FIG. 2, if the atmosphere in the heating chamber is recovered and stabilized from the disturbance of the atmosphere due to the influence of the quenching process, the number of times of gas replacement is set as above. You may reduce to the range.

以下、図2にしたがって、本発明の熱処理方法の手順の一例を説明する。   Hereinafter, an example of the procedure of the heat treatment method of the present invention will be described with reference to FIG.

(1)空炉
雰囲気温度が850℃に加熱された加熱室11内に被処理体が搬送される前の空炉の状態では、変成ガスは、置換回数1.5回/hrで加熱室11内に供給される。また、加熱室11内のCOの濃度を所定の範囲とするために、CO制御が行われる。
(1) Empty furnace In the state of the empty furnace before the object to be processed is transferred into the heating chamber 11 heated to an ambient temperature of 850 ° C., the transformed gas is heated at the number of replacements of 1.5 times / hr. Supplied in. Further, CO 2 control is performed in order to set the concentration of CO 2 in the heating chamber 11 within a predetermined range.

(2)昇温工程
加熱室11に被処理体を搬入する際、加熱室11の入口である扉21を開けると、加熱室11の雰囲気温度が下がり、加熱室11内に負圧が発生する。そのため、扉21を開けるときに、変成ガスの供給量を、置換回数5回/hrに増やす。その後扉21を閉じてから、ヒータ25で浸炭処理温度の930℃まで加熱する途中、加熱室11の雰囲気温度が850℃(所定温度)に戻るまでの間、この置換回数5回/hrの供給量を維持する。なお、扉21を開けるとき、扉21を閉じて所定温度に戻るまでの変成ガスの供給量は炉内が大気圧より負圧にならなければよく、負圧にならないのであれば変成ガスの置換回数は5回/hrより少なくてもよい。850℃を超えると、変成ガスの供給量を置換回数1.5回/hrに低減する。扉21を開けてから浸炭処理温度になるまでの間、CO制御は切っておく。
(2) Temperature raising process When the object to be processed is carried into the heating chamber 11, if the door 21 that is the inlet of the heating chamber 11 is opened, the atmospheric temperature of the heating chamber 11 is lowered and a negative pressure is generated in the heating chamber 11. . Therefore, when the door 21 is opened, the supply amount of the metamorphic gas is increased to 5 replacements / hr. Thereafter, after the door 21 is closed, the heater 25 is heated to the carburizing temperature of 930 ° C., and the atmosphere temperature in the heating chamber 11 returns to 850 ° C. (predetermined temperature). Maintain quantity. When the door 21 is opened, the supply amount of the modified gas until the door 21 is closed and returned to the predetermined temperature does not have to be a negative pressure from the atmospheric pressure in the furnace. The number of times may be less than 5 times / hr. When the temperature exceeds 850 ° C., the supply amount of the metamorphic gas is reduced to 1.5 replacements / hr. The CO 2 control is turned off until the carburizing temperature is reached after the door 21 is opened.

(3)浸炭処理工程
浸炭処理温度である930℃で被処理体を浸炭処理する間、変成ガスの供給量を置換回数1.5回/hrに維持するとともに、CO制御、また、エンリッチガスの供給量を調整することなどによりCP制御を行う。
(3) Carburizing treatment step While carburizing the workpiece at 930 ° C, which is the carburizing treatment temperature, the supply amount of the metamorphic gas is maintained at 1.5 substitutions / hr, CO 2 control, and enrichment gas CP control is performed by adjusting the supply amount of the liquid.

(4)降温工程
被処理体の浸炭処理が終了すると、加熱室11内の雰囲気温度が850℃まで降温される。この間も、変成ガスの供給量を置換回数1.5回/hrとし、CO制御、CP制御が行われる。
(4) Temperature lowering step When the carburizing process of the object to be processed is completed, the atmospheric temperature in the heating chamber 11 is decreased to 850 ° C. During this time, the supply amount of the metamorphic gas is set to the number of substitutions of 1.5 times / hr, and CO 2 control and CP control are performed.

(5)2次加熱工程
加熱室11内の雰囲気温度が、2次設定温度の850℃に達すると、変成ガスの供給量を置換回数5回/hrに増やし、CO制御、CP制御を継続する。850℃で所定時間の2次加熱を行った後、加熱室11の出口である中間扉27を開く。
(5) Secondary heating process When the atmospheric temperature in the heating chamber 11 reaches the secondary set temperature of 850 ° C., the supply amount of the metamorphic gas is increased to 5 replacements / hr, and CO 2 control and CP control are continued. To do. After performing secondary heating for a predetermined time at 850 ° C., the intermediate door 27 that is the outlet of the heating chamber 11 is opened.

(6)焼き入れ工程
被処理体が収納されたケース20が加熱室11から冷却室12に搬送され、冷却室12では、エレベータ30によりケース20が油槽32に沈められて、被処理体の冷却(焼き入れ)が例えば15分間行われる。焼き入れ工程が終了すると、被処理体が収納されたケース20が搬出コンベア13で搬出される。こうして、熱処理装置1における一連の処理が終了する。焼き入れ工程の間、加熱室11の雰囲気温度が下がって負圧が発生するので、加熱室11に供給される変成ガスは、置換回数5回/hrを保持し、CO制御が行われる。なお、焼き入れ工程における冷却方法は、油冷である必要はなく、空冷、ガス冷、水冷などの方法で行ってもよい。
(6) Quenching process The case 20 in which the object to be processed is stored is transported from the heating chamber 11 to the cooling chamber 12, and in the cooling chamber 12, the case 20 is submerged in the oil tank 32 by the elevator 30 to cool the object to be processed. (Quenching) is performed for 15 minutes, for example. When the quenching process is completed, the case 20 in which the object to be processed is stored is carried out by the carry-out conveyor 13. Thus, a series of processes in the heat treatment apparatus 1 is completed. During the quenching process, the atmospheric temperature in the heating chamber 11 decreases and a negative pressure is generated. Therefore, the modified gas supplied to the heating chamber 11 maintains the number of replacements 5 times / hr, and CO 2 control is performed. The cooling method in the quenching step does not need to be oil cooling, and may be performed by a method such as air cooling, gas cooling, or water cooling.

従来は、浸炭処理中に常時一定量、例えば置換回数5回〜10回/hr程度で変成ガスを流していたが、本発明の実施形態の例として、上記のように、空炉時、及び、850℃以上の昇温時〜浸炭処理時〜850℃までの降温時の間の変成ガスの供給量を、置換回数1.5回/hrに低減した。これにより、加熱室11の炉内容積が1.6mの場合、表1に示すように、変成ガス量を約70%低減することができる。すなわち、本発明によれば、浸炭処理において、扉の開閉や温度低下によって負圧が発生するときを除いて、変成ガスの供給量を低減することで、CO排出量を削減するとともに、コストを低減することができる。 Conventionally, the metamorphic gas was always flowed at a constant amount during the carburizing process, for example, about 5 to 10 times per replacement, but as an example of an embodiment of the present invention, as described above, The supply amount of the metamorphic gas during the temperature increase from 850 ° C. or more to the carburization treatment to the temperature decrease to 850 ° C. was reduced to 1.5 replacements / hr. Thereby, when the furnace volume of the heating chamber 11 is 1.6 m 3 , as shown in Table 1, the amount of the metamorphic gas can be reduced by about 70%. In other words, according to the present invention, in the carburizing process, except when a negative pressure is generated due to opening / closing of the door or a temperature drop, the supply amount of the metamorphic gas is reduced, thereby reducing the CO 2 emission amount and the cost. Can be reduced.

Figure 0006031313
Figure 0006031313

なお、本発明の方法によりCO制御を行う浸炭〜降温〜2次加熱の工程において、CO制御開始の浸炭工程より、浸炭処理炉に備えられている一般的な赤外分析計を用いてCOおよびCOのガス分析を行い、推移確認を実施したところ、従来と差異ないことが確認された。 In the carburizing to temperature lowering to secondary heating process in which CO 2 control is performed according to the method of the present invention, a general infrared analyzer provided in the carburizing treatment furnace is used from the carburizing process at the start of CO 2 control. When CO and CO 2 gas analysis was performed and transition confirmation was performed, it was confirmed that there was no difference from the conventional one.

以上、本発明の好適な実施形態について説明したが、本発明はかかる例に限定されない。当業者であれば、特許請求の範囲に記載された技術的思想の範疇内において、各種の変更例または修正例に想到しうることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。   As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

図2に示す工程のうち、850℃以上の昇温時〜930℃保持時(浸炭処理、2時間保持)〜850℃までの降温時の間において、エンリッチガスを適宜供給することによりCO制御、CP制御を行いながら、供給する変成ガスの置換回数を変化させ、雰囲気中のCOおよびCO濃度を測定した。加熱室に相当するバッチ炉の容積は1.6mであり、850℃以上の間の変成ガスの置換回数を、1回/hr(1.6m/hr)、2回/hr(3.2m/hr)、5回/hr(8.0m/hr)、8回/hr(12.8m/hr)の4通りとし、それぞれの条件で被処理体を浸炭処理した。なお、850℃よりも低い温度域では、変成ガスの供給量を、本試験における浸炭処理(昇温工程〜焼き入れ工程)において加熱室が大気圧よりも負圧にならなかった6m/hr(置換回数3.75回/hr)とした。また、いずれも、エンリッチガスを最大で1L/min供給した。 In the process shown in FIG. 2, CO 2 control, CP by appropriately supplying an enriched gas during a temperature increase from 850 ° C. or higher to a temperature maintained from 930 ° C. (carburization treatment, 2 hours) to a temperature decrease from 850 ° C. While performing the control, the number of substitutions of the supplied modified gas was changed, and the CO 2 and CO concentrations in the atmosphere were measured. The volume of the batch furnace corresponding to the heating chamber is 1.6 m 3 , and the number of replacements of the metamorphic gas between 850 ° C. and higher is 1 time / hr (1.6 m 3 / hr), 2 times / hr (3. 2m 3 / hr), 5 times /hr(8.0m 3 / hr), and four kinds of /hr(12.8m 3 / hr) 8 times to carburizing an object to be processed at each condition. In the temperature range lower than 850 ° C., the supply amount of the metamorphic gas is 6 m 3 / hr in which the heating chamber did not become a negative pressure from the atmospheric pressure in the carburizing process (temperature raising process to quenching process) in this test. The number of substitutions was 3.75 / hr. In either case, the enriched gas was supplied at a maximum of 1 L / min.

このときの加熱室内のCO濃度とCO濃度を測定した。図3は、浸炭処理開始からの経過時間と炉内(加熱室)のCO濃度との関係を示し、図4は、浸炭処理開始からの経過時間と炉内のCO濃度との関係を示す。また、それぞれの置換回数について、初期(0分後)と120分後のCOおよびCO濃度を表2に示す。 The CO 2 concentration and CO concentration in the heating chamber at this time were measured. FIG. 3 shows the relationship between the elapsed time from the start of the carburizing process and the CO 2 concentration in the furnace (heating chamber), and FIG. 4 shows the relationship between the elapsed time from the start of the carburizing process and the CO concentration in the furnace. . Table 2 shows the CO 2 and CO concentrations at the initial stage (after 0 minutes) and after 120 minutes for each number of substitutions.

Figure 0006031313
Figure 0006031313

浸炭処理開始時(0分)では、置換回数の少ない方がCO濃度が高いが、50分経過した頃からCO濃度は置換回数によらずほぼ同等になり、置換回数に関係なくCO濃度の設定値(約0.25vol%)に到達する時間は120分経過後であり、同等であった。また、CO濃度については、置換回数により最大で1vol%程度の差があるが、これは、許容されるばらつきの範囲であり、いずれもほぼ同等であった。 The carburizing start (0 minute), although lesser of substitution number of high CO 2 concentration, CO 2 concentration since I have passed 50 minutes becomes substantially equal regardless of the substitution number, regardless of the substitution count CO 2 The time to reach the set value of concentration (about 0.25 vol%) was after 120 minutes and was equivalent. Regarding the CO concentration, there is a difference of about 1 vol% at the maximum depending on the number of substitutions, but this is a permissible range of variation, and they are almost the same.

図3、図4において120分よりも後は、図2の(4)〜(5)の工程である850℃までの降温および2時加熱(焼き入れ前の均熱、拡散処理)であり、この間は浸炭処理に比べるとCP値の制御は精密でなくてもよく、CO、CO濃度ともに、十分な範囲で制御できている。 After 120 minutes in FIG. 3 and FIG. 4, the steps of (4) to (5) in FIG. 2 are the temperature drop to 850 ° C. and 2 o'clock heating (soaking before quenching, diffusion treatment), During this time, the CP value may not be precisely controlled as compared with the carburizing treatment, and both the CO 2 and CO concentrations can be controlled within a sufficient range.

また、上記と同様に850℃以上の間の変成ガスの置換回数を、1回/hr(1.6m/hr)、2回/hr(3.2m/hr)、5回/hr(8。0m/hr)、8回/hr(12.8m/hr)の4通りとし、且つケース20の図6に示されるそれぞれの位置にSCM420材からなる被処理体を配置して浸炭処理した鋼材サンプルを切断し、断面(深さ)方向のビッカース硬さHVを測定した。そして、表面から深さ方向にビッカース硬さHVを測定したとき、HVが513のときの表面からの深さを有効硬化深さ(浸炭深さ:mm)とし、この有効硬化深さのガス置換回数による影響を比較した。ビッカース硬さの試験荷重は300gとした。鋼材サンプルの測定(処理)位置を図6に示し、有効硬化深さの測定結果を表3に示す。 Similarly, the number of substitutions of the metamorphic gas between 850 ° C. and above is set to 1 time / hr (1.6 m 3 / hr), 2 times / hr (3.2 m 3 / hr), 5 times / hr ( 8.0m 3 / hr), by placing eight times /hr(12.8m 3 / and are four in hr), and consists of SCM420 material to each position shown in FIG. 6 of the case 20 workpiece carburized The treated steel material sample was cut, and the Vickers hardness HV in the cross section (depth) direction was measured. When the Vickers hardness HV is measured in the depth direction from the surface, the depth from the surface when the HV is 513 is defined as an effective hardening depth (carburization depth: mm), and gas replacement of this effective hardening depth is performed. We compared the influence of the number of times. The test load for Vickers hardness was 300 g. The measurement (processing) position of the steel sample is shown in FIG. 6, and the measurement result of the effective hardening depth is shown in Table 3.

Figure 0006031313
Figure 0006031313

表3に示すように、ガス置換回数によって有効硬化深さに違いは認められないことが確認された。   As shown in Table 3, it was confirmed that there was no difference in effective curing depth depending on the number of gas replacements.

本発明は、COを含む吸熱式変成ガスを雰囲気ガスとする熱処理に適用できる。   The present invention can be applied to heat treatment using an endothermic modified gas containing CO as an atmospheric gas.

1 熱処理装置
10 搬入部
11 加熱室
12 冷却室
13 搬出コンベア
20 ケース
21 扉
22 入口フード
25 ヒータ
26 ファン
27 中間扉
30 エレベータ
31 油
32 油槽
35 扉
36 出口フード
DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 10 Carry-in part 11 Heating chamber 12 Cooling chamber 13 Unloading conveyor 20 Case 21 Door 22 Inlet hood 25 Heater 26 Fan 27 Intermediate door 30 Elevator 31 Oil 32 Oil tank 35 Door 36 Outlet hood

Claims (1)

バッチ式の処理炉に変成ガスおよびエンリッチガスを供給し、前記処理炉内に搬入した被処理体を浸炭処理する浸炭処理方法であって、
昇温工程、浸炭工程、降温工程、2次加熱工程、焼き入れ工程からなり、
前記昇温工程、前記浸炭工程、前記降温工程において、前記処理炉内に前記被処理体が収容され前記処理炉が閉じた状態で800℃以上を保持している間は、前記処理炉内に供給される前記変成ガスの置換回数を1.0回/hr〜4.0回/hrとすることを特徴とする、浸炭処理方法。
A carburizing method for supplying a metamorphic gas and an enriched gas to a batch type processing furnace, and carburizing the object to be processed carried into the processing furnace,
It consists of a heating process, carburizing process, cooling process, secondary heating process, quenching process,
In the temperature raising step, the carburizing step, and the temperature lowering step, while the object to be processed is accommodated in the processing furnace and the processing furnace is closed and kept at 800 ° C. or higher, the processing furnace A carburizing method, wherein the number of substitutions of the supplied metamorphic gas is 1.0 times / hr to 4.0 times / hr.
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