JP2002167658A - Method of vacuum carburizing for steel parts - Google Patents
Method of vacuum carburizing for steel partsInfo
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- JP2002167658A JP2002167658A JP2000364847A JP2000364847A JP2002167658A JP 2002167658 A JP2002167658 A JP 2002167658A JP 2000364847 A JP2000364847 A JP 2000364847A JP 2000364847 A JP2000364847 A JP 2000364847A JP 2002167658 A JP2002167658 A JP 2002167658A
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- carburizing
- set value
- kpa
- gas
- limit pressure
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は鋼材部品の真空浸炭
方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vacuum carburizing steel parts.
【０００２】[0002]
【従来の技術】従来、鋼材表面の耐摩耗性その他の機械
的性質を向上させる表面処理法として真空浸炭処理が行
われている。この真空浸炭処理は、鋼材部品を真空中で
８７０〜１０００℃の浸炭温度まで加熱し、均熱状態に
達した時点で、浸炭性ガスを加熱室内に供給すると共
に、雰囲気温度を前記浸炭温度に維持しながら１０〜７
０ＫＰａの減圧下で所定時間保持することにより鋼材部
品の表面に浸炭性ガスの熱分解によって生じた炭素を侵
入拡散させるものである。2. Description of the Related Art Conventionally, vacuum carburizing has been performed as a surface treatment method for improving the wear resistance and other mechanical properties of a steel material surface. In this vacuum carburizing treatment, the steel part is heated in a vacuum to a carburizing temperature of 870 to 1000 ° C., and when the steel reaches a soaking state, a carburizing gas is supplied into the heating chamber, and the atmospheric temperature is reduced to the carburizing temperature. 10-7 while maintaining
By maintaining the pressure for a predetermined time under a reduced pressure of 0 KPa, carbon generated by the thermal decomposition of the carburizing gas penetrates and diffuses into the surface of the steel component.
【０００３】前記真空浸炭処理においては、鋼材部品の
全表面に均一に浸炭層を形成するためには浸炭初期に鋼
材部品の全表面が浸炭ガスに均一に、かつ、十分に晒さ
れることが必要であるが、通常、浸炭性ガスとして使用
されているプロパン、プロピレン、エチレンなどでは比
較的安定性が高いため熱分解するためには、加熱室内を
高温に維持し、かつ、多量に供給しなければならず、必
然的に浸炭性ガスの消費量が多くなるだけでなく多量の
煤を発生するため、設備の保守管理に多大のコストを要
するという問題がある。In the vacuum carburizing treatment, in order to form a carburized layer uniformly on the entire surface of a steel part, it is necessary that the entire surface of the steel part be uniformly and sufficiently exposed to a carburizing gas at an early stage of carburizing. However, propane, propylene, ethylene, etc., which are usually used as carburizing gases, have relatively high stability, so in order to thermally decompose, the heating chamber must be maintained at a high temperature and supplied in large quantities. In addition, there is a problem that not only the consumption of carburizing gas is inevitably increased but also a large amount of soot is generated.
【０００４】これらの問題を解決するため、特許第２９
６３８６９号公報にて、浸炭性ガスとしてアセチレン系
ガスを使用し、１ＫＰａ以下の減圧下で鋼材部品を真空
浸炭する方法が提案されている。具体的には、浸炭期に
アセチレンガスを連続的に供給する一方、連続的に排気
することで炉内圧力を１ＫＰａ以下、望ましくは０.３
ＫＰａ以下、さらに望ましくは０.１ＫＰａ以下の一定
値に保持して浸炭処理するものである。[0004] In order to solve these problems, Patent No. 29
JP-A-63869 proposes a method in which an acetylene-based gas is used as a carburizing gas, and a steel component is vacuum carburized under a reduced pressure of 1 KPa or less. Specifically, while the acetylene gas is continuously supplied during the carburization period, the pressure inside the furnace is reduced to 1 KPa or less, preferably 0.3 KPa, by continuously exhausting the gas.
Carburizing treatment is carried out while maintaining the pressure at a constant value of not more than KPa, more preferably not more than 0.1 KPa.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、前述の
如く鋼材部品の全表面に均一で、かつ、短時間で浸炭層
を形成するには、浸炭初期に鋼材部品の全表面が浸炭性
ガス（アセチレンガス）に均一に、かつ、十分に晒され
ることが必要であるが、前記方法では、浸炭期における
炉内圧を１ＫＰａ以下の一定値である高真空度に保持す
るため、浸炭期の煤発生は回避できるものの、浸炭層の
均―性が十分でなく、また、浸炭性ガス（アセチレン）
の消費量が多くなるという問題がある。特に、処理量が
多く、多量の浸炭性ガスの供給が必要な場合には顕著と
なる。However, in order to form a carburized layer uniformly and in a short time on the entire surface of a steel part as described above, the entire surface of the steel part must be made of a carburizing gas (acetylene) in the early stage of carburizing. Gas), it is necessary to uniformly and sufficiently expose the gas to the gas). However, in the above-described method, since the furnace pressure during the carburization period is maintained at a high degree of vacuum of 1 KPa or less, soot generation during the carburization period Although it can be avoided, the uniformity of the carburized layer is not sufficient, and carburizing gas (acetylene)
However, there is a problem that the consumption amount of the material increases. In particular, when the amount of treatment is large and a large amount of carburizing gas needs to be supplied, this becomes remarkable.
【０００６】従って、本発明は、処理材に煤の付着する
ことを回避して浸炭層の均一な形成とアセチレンガスの
消費量の低減を図ることを課題とするものである。SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent the soot from adhering to the treatment material and to form a carburized layer uniformly and reduce the consumption of acetylene gas.
【０００７】[0007]
【課題を解決するための手段】本発明は、前記課題を解
決するための手段として、鋼材部品を減圧下で浸炭処理
する真空浸炭方法において、浸炭期に所定量のアセチレ
ンガスを連続的に供給する一方、上限圧力設定値で排気
を開始し、下限圧力設定値で排気を停止することからな
る排気を行うとともに、前記浸炭期におけるアセチレン
ガスの連続供給を浸炭開始後の所定時間以降において漸
減させ、かつ、上限圧力設定値及び下限圧力設定値を
１.１ＫＰａ〜３.５ＫＰａとし、前記上限圧力設定値を
前記下限圧力設定値の１.５倍以上にするようにしたも
のである。According to the present invention, there is provided a vacuum carburizing method for carburizing steel parts under reduced pressure, wherein a predetermined amount of acetylene gas is continuously supplied during the carburizing period. On the other hand, the exhaust is started by starting the exhaust at the upper limit pressure set value and stopping the exhaust at the lower limit pressure set value, and the continuous supply of the acetylene gas in the carburizing period is gradually reduced after a predetermined time after the start of the carburizing. The upper limit pressure set value and the lower limit pressure set value are set to 1.1 KPa to 3.5 KPa, and the upper limit pressure set value is set to be 1.5 times or more of the lower limit pressure set value.
【０００８】本発明の実施態様においては、前記上限圧
力設定値は１．７〜３.５ＫＰａ、好ましくは、２.０〜
３.０ＫＰａの範囲内の値に、また、前記下限圧力設定
値は１.１〜１.６５ＫＰａ、好ましくは、１.１〜１.３
ＫＰａの範囲内の値にそれぞれ設定される。[0008] In an embodiment of the present invention, the upper limit pressure set value is 1.7 to 3.5 KPa, preferably 2.0 to 3.5 KPa.
To a value within a range of 3.0 KPa, and the lower limit pressure set value is 1.1 to 1.65 KPa, preferably 1.1 to 1.3.
It is set to a value within the range of KPa.
【０００９】浸炭期の上限圧力設定値及び下限圧力設定
値を１.１ＫＰａ〜３.５ＫＰａの範囲内に設定したの
は、次の理由による。即ち、浸炭期の上限圧力設定値の
最高値が３.５ＫＰａ以下では加熱室内でアセチレンガ
スの熱分解を生じても、処理材表面に煤が付着すること
を回避できるが、３.５ＫＰａを超えると、加熱室内で
アセチレンガスの熱分解によって生じた煤が処理材表面
に煤が付着するのを回避するのが困難となるためであ
る。また、前記下限圧力設定値の最低値を１.１ＫＰａ
としたのは、１.１ＫＰａ未満では均一な浸炭層を得る
のに重要な要素である浸炭初期時におけるアセチレンガ
スの供給量を確実に確保することができなくなるからで
ある。The reason why the upper limit pressure set value and the lower limit pressure set value in the carburizing period are set within the range of 1.1 KPa to 3.5 KPa is as follows. That is, when the maximum value of the upper limit pressure set value in the carburizing period is 3.5 KPa or less, soot can be prevented from adhering to the surface of the processing material even if thermal decomposition of acetylene gas occurs in the heating chamber, but exceeds 3.5 KPa. This is because it becomes difficult to prevent soot generated by thermal decomposition of acetylene gas in the heating chamber from adhering to the surface of the processing material. Further, the minimum value of the lower limit pressure set value is 1.1 KPa.
The reason is that if the pressure is less than 1.1 KPa, the supply of acetylene gas at the initial stage of carburization, which is an important factor for obtaining a uniform carburized layer, cannot be ensured.
【００１０】さらに、前記浸炭期における加熱室内の上
限圧力設定値を下限圧力設定値の１.５倍以上、即ち、
間欠排気時における下限圧力設定値に対する上限圧力設
定値の比（上限圧力設定値／下限圧力設定値）を１.５
倍以上にしたのは、連続送入されるアセチレンガス（新
鮮な浸炭性ガス）を確実に処理材表面に接触させること
ができるためであり、１.５未満では浸炭ムラを生じや
すくなるからである。Further, the upper limit pressure set value in the heating chamber during the carburizing period is 1.5 times or more the lower limit pressure set value, that is,
The ratio of the upper limit pressure set value to the lower limit pressure set value during intermittent exhaust (upper limit pressure set value / lower limit pressure set value) is 1.5.
The reason for the double or more is that the continuously fed acetylene gas (fresh carburizing gas) can be reliably brought into contact with the surface of the treated material, and if it is less than 1.5, carburizing unevenness is likely to occur. is there.
【００１１】また、本発明の他の実施態様においては、
浸炭性ガスとして、アセチレンガスに加えて水素ガスを
供給することが行われる。即ち、アセチレンの熱分解反
応は、Ｃ２Ｈ２＝２Ｃ↓＋Ｈ２で表されるが、アセチレ
ンはプロパン等に比べて低い温度で熱分解し易いため、
アセチレンガスのみでは排気系の制御遅れにより多量に
煤が発生するのを避けられなくなる場合がある。ところ
が、アセチレンガスと共に水素ガス（Ｈ２）を加熱室内
に供給すると、加熱室内の水素ガス分圧が増加するため
前記反応式における反応が右に進みにくくなる。そのた
めアセチレンの分解速度が遅くなり、加熱室内の圧力を
高くして（即ち、加熱室内滞留時間を長くして）も、ア
セチレンの分解に伴う煤の発生は少なくなり処理材へ付
着をも防止できる。In another embodiment of the present invention,
As a carburizing gas, a hydrogen gas is supplied in addition to an acetylene gas. That is, the thermal decomposition reaction of acetylene is represented by C2H2 = 2C ↓ + H2. Since acetylene is easily thermally decomposed at a lower temperature than propane or the like,
With only acetylene gas, a large amount of soot may be unavoidable due to control delay of the exhaust system. However, when hydrogen gas (H2) is supplied into the heating chamber together with the acetylene gas, the partial pressure of the hydrogen gas in the heating chamber increases, so that the reaction in the above reaction formula does not easily proceed to the right. Therefore, even if the decomposition speed of acetylene is reduced and the pressure in the heating chamber is increased (that is, the residence time in the heating chamber is increased), the generation of soot due to the decomposition of acetylene is reduced and the adhesion to the processing material can be prevented. .
【００１２】従って、他の観点から見れば、本発明は、
鋼材部品を減圧下で浸炭処理する真空浸炭方法におい
て、浸炭期に、所定量のアセチレンガスと水素ガスとを
連続的に供給する一方、上限圧力設定値で排気を開始
し、その下限圧力設定値で排気を停止することからなる
排気を行うとともに、前記浸炭期におけるアセチレンガ
スと水素ガスとの連続供給を浸炭開始後の所定時間以降
において漸減させ、かつ、上限圧力設定値及び下限圧力
設定値を１.１ＫＰａ〜８.０ＫＰａとし、前記上限圧力
設定値を前記圧力下限設定値の１.５倍以上とする鋼材
部品の真空浸炭処理法を提供するものである。Therefore, from another viewpoint, the present invention provides:
In the vacuum carburizing method of carburizing steel parts under reduced pressure, during the carburizing period, a predetermined amount of acetylene gas and hydrogen gas are continuously supplied, while the exhaust is started at the upper limit pressure set value and the lower limit pressure set value is started. While performing the exhaust consisting of stopping the exhaust at, the continuous supply of acetylene gas and hydrogen gas in the carburizing period is gradually reduced after a predetermined time after the start of carburizing, and the upper limit pressure set value and the lower limit pressure set value are reduced. An object of the present invention is to provide a vacuum carburizing method for a steel component in which the upper limit pressure set value is set to 1.1 KPa to 8.0 KPa and the upper limit pressure set value is 1.5 times or more of the lower limit pressure set value.
【００１３】好ましい実施態様においては、前記上限圧
力設定値は２.０〜８.０ＫＰａ、好ましくは、２.５〜
７.０ＫＰａの範囲内の値に、また、前記下限圧力設定
値は１.１〜４.０ＫＰａ、好ましくは１.１〜２.０ＫＰ
ａの範囲内の値にそれぞれ設定される。[0013] In a preferred embodiment, the upper limit pressure set value is 2.0 to 8.0 KPa, preferably 2.5 to 8.0 KPa.
To a value within a range of 7.0 KPa, and the lower limit pressure set value is 1.1 to 4.0 KPa, preferably 1.1 to 2.0 KP.
It is set to a value within the range of a.
【００１４】また、好ましい実施態様においては、水素
ガスの量はアセチレンガス量の１〜３倍、通常、約２倍
程度に設定される。In a preferred embodiment, the amount of hydrogen gas is set to 1 to 3 times, usually about 2 times, the amount of acetylene gas.
【００１５】[0015]
【発明の実施の形態】本発明に係る鋼材の真空浸炭処理
方法は、バッチ式真空浸炭炉や連続式真空浸炭炉など任
意の形態でも実施できるが、ここでは図４に示す二室型
真空浸炭炉を用いて実施する場合を例に挙げて説明す
る。BEST MODE FOR CARRYING OUT THE INVENTION The vacuum carburizing method for steel materials according to the present invention can be carried out in any form such as a batch vacuum carburizing furnace and a continuous vacuum carburizing furnace. The case of using a furnace will be described as an example.
【００１６】図示の二室型真空浸炭炉は、装入室１と加
熱室１１とからなり、前記装入室１は、油焼入槽を有す
るとともにガス供給ライン２及びバルブ３ａを介して窒
素供給源４に接続される一方、第１排気系ライン５ａ及
び第１排気弁６ａを介して真空排気系及び排ガス処理系
に接続され、装入室１の一端側には装入ドア７が配設さ
れている。他方、前記加熱室１１は、前記装入室１の他
端側に中間ドア８を介在させて接続されると共に、ガス
供給ライン２ｂ、２ｃ及びバルブ３ｂ、３ｃを介してア
セチレンガス供給源９、水素ガス供給源１０に、また、
第２排気系ライン５ｂ及び第２排気弁６ｂを介して真空
排気系及び排ガス処理系にそれぞれ接続されている。な
お、前記加熱室１１には加熱手段が配設されると共に、
前記装入室１と同様に被処理材を移行させる移送手段が
配設されているが、これらは公知のものと同じ構成であ
るので省略する。The illustrated two-chamber vacuum carburizing furnace comprises a charging chamber 1 and a heating chamber 11. The charging chamber 1 has an oil quenching tank and nitrogen gas via a gas supply line 2 and a valve 3a. While being connected to the supply source 4, it is connected to a vacuum exhaust system and an exhaust gas treatment system via a first exhaust system line 5 a and a first exhaust valve 6 a, and a charging door 7 is provided at one end of the charging chamber 1. Has been established. On the other hand, the heating chamber 11 is connected to the other end of the charging chamber 1 with an intermediate door 8 interposed therebetween, and is connected to an acetylene gas supply source 9 via gas supply lines 2b, 2c and valves 3b, 3c. To the hydrogen gas supply source 10,
They are connected to a vacuum exhaust system and an exhaust gas treatment system via a second exhaust system line 5b and a second exhaust valve 6b, respectively. In addition, while the heating means is provided in the heating chamber 11,
Transfer means for transferring the material to be treated are provided in the same manner as in the charging chamber 1, but these are omitted since they have the same configuration as that of the known one.
【００１７】前記二室型真空浸炭炉を用いて被処理材で
ある鋼材部品を真空浸炭処理する場合、まず、被処理材
を積載したトレイを装入室１に装入し、第１及び第２排
気系ライン５ａ、５ｂを介して装入室１及び加熱室１１
内をそれぞれ真空排気して所定の真空度（約０.０２Ｋ
Ｐａ）にまで減圧した後、装入室１内のトレイに積載さ
れた処理材を減圧下の加熱室１１内に位置させる。次い
で、窒素供給源４からガス供給ライン２ｂを介して窒素
ガスを加熱室１１内に導入し、炉内圧力を所定圧（８
６.５〜１００ＫＰａ）まで上昇させ、窒素雰囲気下で
浸炭処理温度（８７０〜１０００℃）に昇温させる。When vacuum-carburizing a steel part as a material to be processed using the two-chamber vacuum carburizing furnace, first, a tray on which a material to be processed is loaded is loaded into the loading chamber 1, and first and second trays are loaded. 2 The charging chamber 1 and the heating chamber 11 via the exhaust system lines 5a and 5b
The inside of each chamber is evacuated to a predetermined degree of vacuum (about 0.02K
After the pressure is reduced to Pa), the processing material loaded on the tray in the charging chamber 1 is positioned in the heating chamber 11 under reduced pressure. Next, nitrogen gas is introduced into the heating chamber 11 from the nitrogen supply source 4 via the gas supply line 2b, and the furnace pressure is set to a predetermined pressure (8
6.5 to 100 KPa) and then to a carburizing temperature (870 to 1000 ° C.) in a nitrogen atmosphere.
【００１８】昇温が完了すると、この浸炭温度で所定時
間保持して均熱処理する。この際、均熱処理完了の約２
０分前の時点で加熱室１１内を真空排気（約０.０２Ｋ
Ｐａ）して、真空下で均熱を行う。均熱が完了すると、
ガス供給ライン２ｂを介して加熱室１１内にアセチレン
ガス（浸炭性ガス）を連続的に送入し、所定時間浸炭
後、加熱室１１内を真空排気（約０.０２ＫＰａ）して
拡散処理する。When the temperature rise is completed, the carburizing temperature is maintained for a predetermined time to perform a soaking process. At this time, about 2
At 0 minutes before, the inside of the heating chamber 11 is evacuated (about 0.02K).
Pa), and soaking under vacuum. When soaking is complete,
Acetylene gas (carburizing gas) is continuously fed into the heating chamber 11 through the gas supply line 2b, and after a predetermined time of carburizing, the heating chamber 11 is evacuated (about 0.02 KPa) to perform diffusion processing. .
【００１９】この浸炭期には、アセチレンガスは浸炭初
期の導入量を浸炭後期の導入量より多く連続的に送入す
る。一方、加熱室１１の排気は、間欠排気（パルス排
気）される。すなわち、加熱室１０内の圧力が上限圧力
設定値（最高設定値：３.５ＫＰａ）に達すると、第２
排気弁６ｂを開とする一方、下限圧力設定値（最低設定
値：１.１ＫＰａ）に達すると、第２排気弁６ｂを閉と
する（パルス操業）。この浸炭・拡散処理が完了する
と、窒素ガス（Ｎ２）を所定圧（８６.５〜１００ＫＰ
ａ）まで送入して窒素雰囲気下で焼入れ温度（約８１０
〜９００℃）に保持する。その後、装入室１で焼入れ処
理する。In the carburizing period, the acetylene gas is continuously supplied in a larger amount at the initial stage of carburizing than at the latter stage. On the other hand, the exhaust of the heating chamber 11 is intermittently exhausted (pulsed exhaust). That is, when the pressure in the heating chamber 10 reaches the upper limit pressure set value (maximum set value: 3.5 KPa), the second
While the exhaust valve 6b is opened, when the lower limit pressure set value (minimum set value: 1.1 KPa) is reached, the second exhaust valve 6b is closed (pulse operation). When the carburizing / diffusion treatment is completed, the nitrogen gas (N2) is set to a predetermined pressure (86.5-100 KP).
a) and a quenching temperature (about 810) under a nitrogen atmosphere.
９００900 ° C.). Thereafter, a quenching process is performed in the charging room 1.
【００２０】前記実施態様は、浸炭ガスとしてアセチレ
ンガスのみを使用した場合であるが、浸炭性ガスとして
アセチレンガスと水素ガスとの混合ガスを使用する場
合、次の様に操業される。即ち、前記の態様と同様にし
て真空下で均熱化処理を行い、均熱が完了すると、加熱
室１１内にアセチレンガスと水素がス（浸炭性ガス）を
連続的に送入し、所定時間浸炭後、加熱室１１内を真空
排気（約０.０２ＫＰａ）して拡散処理する。なお、水
素ガスはアセチレンガスの約２倍程度とする。この浸炭
期には、加熱室１１内の圧力が上限圧力設定値（最高設
定値：８ＫＰａ）に達すると、第２排気弁６ｂを開とす
る一方、下限圧力設定値（最低設定値：１.１ＫＰａ）
に達すると、第２排気弁６ｂを閉とするパルス操業を行
う。The above embodiment is a case where only acetylene gas is used as the carburizing gas. However, when a mixed gas of acetylene gas and hydrogen gas is used as the carburizing gas, the operation is performed as follows. That is, a soaking process is performed under vacuum in the same manner as in the above-described embodiment, and when the soaking is completed, acetylene gas and hydrogen are continuously fed into the heating chamber 11 through a gas (carburizing gas). After carburizing for a time, the inside of the heating chamber 11 is evacuated (about 0.02 KPa) to perform diffusion treatment. The hydrogen gas is about twice as large as the acetylene gas. In this carburizing period, when the pressure in the heating chamber 11 reaches the upper limit pressure set value (highest set value: 8 KPa), the second exhaust valve 6b is opened, and the lower limit pressure set value (minimum set value: 1.KPa). 1KPa)
, The pulse operation of closing the second exhaust valve 6b is performed.
【００２１】[0021]
【実施例１】ＳＣｒ４２０Ｈ製トランスミッションギヤ
（φ１８０mm）を処理材とし、これをトレイ上に１２０
枚積載（全表面積８.５m2）し、目標有効浸炭深さ０．
６mmとして図４に示す下記の仕様の２室型真空浸炭炉を
用いて図１に示す真空浸炭ヒートサイクルで真空浸炭焼
入れ処理を行った。 炉型式： ２室型（焼入れ：油） 加熱室容積： ７.８m3（有効寸法：１２２０mm長さ×
７６０mm巾×７１０mm高さ） 真空ポンプ： 油回転ポンプ（４５０m3/時） メカニカルブースタ（２５０m3/時） 即ち、多数の処理材を搭載したトレイを加熱室１１内に
配置させた後、８６．５〜１００ＫＰａの窒素雰囲気
中、加熱室内温度を浸炭温度９５０℃にまで昇温させ、
均熱化する。均熱処理完了の約２０分前の時点で真空排
気し、０．０２ＫＰａの真空下で均熱処理を更に約２０
分間行う。均熱処理完了後、加熱室１１内に浸炭性ガス
としてアセチレンガスを連続的に供給して浸炭処理を行
う。浸炭期には、アセチレンガスを浸炭開始から５分ま
では４０Ｌ／分、５〜１０分の間は１５Ｌ／分、１０〜
２５分の間は９Ｌ／分と徐々に減少させながら連続的に
供給し、その間、加熱室１１内の圧力が上限圧力設定値
の２.０ＫＰａに達すると第２排気弁６ｂを開いて真空
排気し、加熱室１１内の圧力が下限圧力設定値の１.１
ＫＰａに達すると第２排気弁６ｂを閉じることからなる
間欠排気を行って加熱室１１内の圧力制御を行う。次い
で、加熱室１１内を０.０２ＫＰａの真空度に真空排気
し、同真空度を維持しながら約１.３時間加熱して拡散
処理を行う。拡散処理後、加熱室１１内に窒素ガスを導
入して略大気圧のＮ2雰囲気とし、同雰囲気中で焼入温
度の８５０℃までに降温させ、同温度で１時間保持す
る。その後、装入室内に窒素ガスを導入して略大気圧の
Ｎ２雰囲気とし、トレイを装入室１に移行させて、１２
０℃の温度の油に入れて油焼入れを行う。Embodiment 1 A transmission gear (φ180 mm) made of SCr420H was used as a processing material, and was placed on a tray for 120 minutes.
Loaded (total surface area 8.5 m 2 ), target effective carburization depth 0.
Vacuum carburizing and quenching treatment was performed by a vacuum carburizing heat cycle shown in FIG. 1 using a two-chamber vacuum carburizing furnace having the following specifications shown in FIG. Furnace model: 2-chamber type (quenching: oil) Heating chamber volume: 7.8 m 3 (Effective dimensions: 1220 mm length x
Vacuum pump: Oil rotary pump (450 m 3 / hour) Mechanical booster (250 m 3 / hour) That is, after a tray on which a large number of processing materials are mounted is placed in the heating chamber 11, 86. In a nitrogen atmosphere of 5 to 100 KPa, the temperature of the heating chamber is raised to a carburizing temperature of 950 ° C.,
Soak. About 20 minutes before the completion of the soaking, evacuation was performed, and the soaking was further performed under a vacuum of 0.02 KPa for about 20 minutes.
Do for a minute. After the completion of the soaking treatment, acetylene gas is continuously supplied as a carburizing gas into the heating chamber 11 to perform carburizing treatment. In the carburizing period, acetylene gas is supplied at 40 L / min for 5 minutes from the start of carburization, 15 L / min for 5 to 10 minutes, and 10 to 10 minutes.
During 25 minutes, the supply is continuously performed while gradually decreasing the rate to 9 L / min. During that time, when the pressure in the heating chamber 11 reaches the upper limit pressure set value of 2.0 KPa, the second exhaust valve 6b is opened to evacuate. The pressure in the heating chamber 11 is set to the lower limit pressure set value of 1.1.
When the pressure reaches KPa, the pressure in the heating chamber 11 is controlled by performing intermittent exhaust including closing the second exhaust valve 6b. Next, the inside of the heating chamber 11 is evacuated to a vacuum degree of 0.02 KPa, and the diffusion processing is performed by heating for about 1.3 hours while maintaining the vacuum degree. After the diffusion treatment, a nitrogen gas is introduced into the heating chamber 11 to form an N2 atmosphere at substantially atmospheric pressure, the temperature is lowered to a quenching temperature of 850 ° C. in the atmosphere, and the temperature is maintained for 1 hour. Thereafter, nitrogen gas was introduced into the charging chamber to make it a N2 atmosphere at substantially atmospheric pressure, and the tray was moved to the charging chamber 1 to be charged in the charging chamber 1.
Oil quenching is performed in oil at a temperature of 0 ° C.
【００２２】真空浸炭焼入れ後、処理材を観察したとこ
ろ、有効浸炭深さは０.５９〜０.６１mmで表面に煤の付
着や浸炭ムラは認められず、良好な結果が得られた。な
お、真空浸炭処理に於ける浸炭時間と鋼材中の炭素濃度
プロファイルは図２に示す通りであり、また、単位時間
毎の鋼材中への炭素侵入割合（即ち、浸炭後の全侵入炭
素量に対する一定時間浸炭後の侵入炭素量の割合）は図
３に示す通りである。図３に示す結果から、浸炭温度９
５０℃、有効浸炭深さ０．６mmの条件下では、浸炭開始
後５分間で全侵入炭素量の４６％が侵入し、５分後から
１０分後の５分間で全侵入炭素量の１８％が侵入するこ
とが分かる。このため、前述のように、浸炭初期におけ
る浸炭性ガスの供給量を多くし、侵入炭素量の減少に対
応して、浸炭性ガスの供給量を減少させるものである。When the treated material was observed after vacuum carburizing and quenching, the effective carburizing depth was 0.59 to 0.61 mm, and no adhesion of soot or uneven carburization was observed on the surface, and good results were obtained. The carburizing time and the carbon concentration profile in the steel material in the vacuum carburizing treatment are as shown in FIG. 2, and the ratio of carbon intrusion into the steel material per unit time (that is, with respect to the total amount of carbon infiltrated after carburizing). The ratio of the amount of invading carbon after carburizing for a certain period of time) is as shown in FIG. From the results shown in FIG.
Under the conditions of 50 ° C. and an effective carburization depth of 0.6 mm, 46% of the total invading carbon amount penetrated in 5 minutes after the start of carburizing, and 18% of the total invading carbon amount in 5 minutes after 5 minutes to 10 minutes. Can be seen invading. Therefore, as described above, the supply amount of the carburizing gas is increased in the early stage of carburization, and the supply amount of the carburizing gas is reduced in response to the decrease in the amount of invading carbon.
【００２３】[0023]
【実施例２】ＳＣｒ４２０Ｈ製ピニオンギヤ（φ３０m
m）を処理材とし、これをトレイ上に５０００個積載
（全表面積：２６ｍ2）し、目標有効浸炭深さ０．６mm
として実施例１と同様にして下記条件下で真空浸炭焼入
れ処理を行った。 真空浸炭焼入れ後、処理材を観察したところ、有効浸炭
深さは０.５６〜０.６１mmで表面に煤の付着や浸炭ムラ
は認められず、良好な結果が得られた。Embodiment 2 Pinion gear made of SCr420H (φ30m
m) as a treatment material, and 5,000 of them are loaded on a tray (total surface area: 26 m 2 ), and the target effective carburization depth is 0.6 mm.
In the same manner as in Example 1, vacuum carburizing and quenching treatment was performed under the following conditions. When the treated material was observed after vacuum carburizing and quenching, the effective carburizing depth was 0.56 to 0.61 mm, and no adhesion of soot or uneven carburization was observed on the surface, and good results were obtained.
【００２４】[0024]
【実施例３】ＳＣＭ４２０Ｈドライブシャフト（約２５
０mm長）を処理材とし、これをトレイ上に２５６個積載
（全表面積：８ｍ2）し、目標有効浸炭深さ１．０mmと
して実施例１と同様にして下記条件下で真空浸炭焼入れ
処理を行った。 真空浸炭焼入れ後、処理材を観察したところ、表面に煤
の付着や浸炭ムラは認められず、有効浸炭深さは０.５
６〜０.６１mmと良好な結果が得られた。Embodiment 3 SCM420H drive shaft (about 25
(0 mm length) as a treatment material, 256 pieces are loaded on a tray (total surface area: 8 m 2 ), and a target effective carburization depth of 1.0 mm is subjected to vacuum carburizing and quenching treatment under the following conditions in the same manner as in Example 1. went. Observation of the treated material after vacuum carburizing and quenching showed no adhesion of soot and uneven carburization on the surface, and the effective carburizing depth was 0.5.
Good results of 6 to 0.61 mm were obtained.
【００２５】[0025]
【実施例４】ＳＣｒ４２０Ｈ製ピニオンギヤ（φ３０m
m）を処理材とし、これをトレイ上に５０００個積載
（全表面積：２６ｍ2）し、目標有効浸炭深さ０．６mm
として実施例１と同様にして下記条件下で真空浸炭焼入
れ処理を行った。 真空浸炭焼入れ条件 浸炭温度：９５０℃ 浸炭ガス：アセチレンガス＋水素ガス ガス供給量：０〜５分‥アセチレン（１００Ｌ／分）＋水素（２００Ｌ／分） ５〜１０分‥アセチレン（３５Ｌ／分）＋水素（７０Ｌ／分） １０〜２５分‥アセチレン（２０Ｌ／分）＋水素（４０Ｌ/分） 加熱室内圧力： 上限圧力設定値‥７.０ＫＰａ 下限圧力設定値‥１.５ＫＰａ 焼入れ温度：８４０℃ 焼入れ：油焼入れ（温度：１２０℃） 真空浸炭焼入れ後、処理材を観察したところ、表面に煤
の付着や浸炭ムラは認められず、有効浸炭深さは０.５
９〜０.６２mmと良好な結果が得られた。Embodiment 4 Pinion gear made of SCr420H (φ30m
m) as a treatment material, and 5,000 of them are loaded on a tray (total surface area: 26 m 2 ), and the target effective carburization depth is 0.6 mm.
In the same manner as in Example 1, vacuum carburizing and quenching treatment was performed under the following conditions. Vacuum carburizing and quenching conditions Carburizing temperature: 950 ° C Carburizing gas: acetylene gas + hydrogen gas Gas supply amount: 0 to 5 minutes ‥ acetylene (100 L / min) + hydrogen (200 L / min) 5 to 10 minutes ‥ acetylene (35 L / min) + Hydrogen (70 L / min) 10 to 25 minutes２５Acetylene (20 L / min) + Hydrogen (40 L / min) Heating chamber pressure: Upper limit pressure set value ‥ 7.0 KPa Lower limit pressure set value ‥ 1.5 KPa Hardening temperature: 840 ° C. Quenching: oil quenching (Temperature: 120 ° C) After vacuum carburizing and quenching, the treated material was observed. No adhesion of soot or uneven carburization was observed on the surface, and the effective carburizing depth was 0.5.
Good results of 9 to 0.62 mm were obtained.
【００２６】[0026]
【比較例１】ＳＣｒ４２０Ｈピニオンギヤ（φ３０mm）
を処理材とし、これをトレイ上に５０００個積載（全表
面積：２６ｍ2）し、目標有効浸炭深さ０．６mmとして
実施例１と同様にして下記条件下で真空浸炭焼入れ処理
を行った。 焼入れ温度：８４０℃ 焼入れ：油焼入れ（温度：１２０℃） 真空浸炭焼入れ後、処理材を観察したところ、処理材表
面に煤が付着し、有効浸炭深さは０.４８〜０.６１mmと
ムラがあった。これは、浸炭期における加熱室内の上限
圧力設定値が適切でないためと思われる。[Comparative Example 1] SCr420H pinion gear (φ30 mm)
5,000 were loaded on a tray (total surface area: 26 m 2 ), and vacuum carburizing and quenching treatment was performed under the following conditions in the same manner as in Example 1 with a target effective carburizing depth of 0.6 mm. Quenching temperature: 840 ° C Quenching: oil quenching (Temperature: 120 ° C) After vacuum carburizing and quenching, when the treated material was observed, soot adhered to the treated material surface and the effective carburizing depth was 0.48 to 0.61 mm, which was uneven. was there. This seems to be because the upper limit pressure set value in the heating chamber during the carburizing period is not appropriate.
【００２７】[0027]
【比較例２】ＳＣｒ４２０Ｈ製ピニオンギヤ（φ３０m
m）を処理材とし、これをトレイ上に５０００個積載
（全表面積：２６ｍ2）し、目標有効浸炭深さ０．６mm
として実施例１と同様にして下記条件下で真空浸炭焼入
れ処理を行った。 真空浸炭焼入れ条件 浸炭温度：９５０℃ 浸炭ガス：アセチレンガス＋水素ガス ガス供給量：０〜５分‥アセチレン（１２０Ｌ／分）＋水素（８０Ｌ／分） ５〜１０分‥アセチレン（３５Ｌ／分）＋水素（５０Ｌ／分） １０〜２５分‥アセチレン（２０Ｌ／分）＋水素（３０Ｌ／分） 加熱室内圧力： 上限圧力設定値‥１０.０ＫＰａ 下限圧力設定値‥１.５ＫＰａ 焼入れ温度：８４０℃ 焼入れ： 油焼入れ（温度：１２０℃） 真空浸炭焼入れ後、処理材を観察したところ、処理材表
面に煤が付着し、有効浸炭深さは０.４０〜０.６２mmと
ムラが多く実用不可能であった。これは、浸炭期におけ
る加熱室内の圧力の上限圧力設定値および水素添加量が
適切でないためと思われる。[Comparative Example 2] Pinion gear made of SCr420H (φ30m
m) as a treatment material, and 5,000 of them are loaded on a tray (total surface area: 26 m 2 ), and the target effective carburization depth is 0.6 mm.
In the same manner as in Example 1, vacuum carburizing and quenching treatment was performed under the following conditions. Vacuum carburizing and quenching conditions Carburizing temperature: 950 ° C Carburizing gas: acetylene gas + hydrogen gas Gas supply amount: 0 to 5 minutes ‥ acetylene (120 L / min) + hydrogen (80 L / min) 5 to 10 minutes ‥ acetylene (35 L / min) + Hydrogen (50 L / min) 10-25 min ‥ Acetylene (20 L / min) + Hydrogen (30 L / min) Heating chamber pressure: Upper limit pressure set value ‥ 10.0 KPa Lower limit pressure set value 1.5 KPa Hardening temperature: 840 ° C. Quenching: Oil quenching (Temperature: 120 ° C) After vacuum carburizing and quenching, when the treated material was observed, soot adhered to the treated material surface, and the effective carburized depth was 0.40 to 0.62 mm, which was so uneven that it was not practical. Met. This is presumably because the upper limit pressure set value of the pressure in the heating chamber and the amount of hydrogen added during the carburizing period are not appropriate.
【００２８】[0028]
【発明の効果】以上の説明から明らかなように、本発明
は、浸炭期には、所定量のアセチレンガスを連続的に供
給する一方、上限圧力設定値で排気を開始し、下限圧力
設定値で排気を停止することからなる排気（パルス排
気）を行うため、連続送入されるアセチレンガス（新鮮
な浸炭性ガス）を確実に処理材表面に接触させることが
できる。また、浸炭初期の加熱室の圧力が１.１ＫＰａ
から３.５ＫＰａとなるため、均一な浸炭層を得るのに
重要な要素である浸炭初期時におけるアセチレンガスの
供給量を確実に確保することができる。さらに、前記浸
炭期におけるアセチレンガスの連続供給を浸炭開始後の
所定時間以降において漸減するため、過剰なアセチレン
ガスの送入することなく、アセチレンガスの消費量を軽
減できる。しかも、本発明によれば、前記効果の相乗作
用により、処理材表面に煤が付着することを回避して、
均一な浸炭層を形成することができる。また、浸炭期
に、アセチレンガスと水素ガスとを供給するため、煤の
発生が抑制されるとともに、処理材表面への煤の付着を
回避でき、均一な浸炭層を形成し得る加熱室内の圧力を
高くすることができ、真空排気装置の小型化をも図るこ
とができる。As is apparent from the above description, in the present invention, in the carburizing period, while a predetermined amount of acetylene gas is continuously supplied, the exhaust is started at the upper limit pressure set value and the lower limit pressure set value is started. (Pulse evacuation) is performed to stop the evacuation, so that the continuously fed acetylene gas (fresh carburizing gas) can be reliably brought into contact with the surface of the processing material. In addition, the pressure of the heating chamber at the initial stage of carburizing is 1.1 KPa.
From 3.5 KPa, the supply amount of acetylene gas at the initial stage of carburization, which is an important factor for obtaining a uniform carburized layer, can be reliably ensured. Furthermore, since the continuous supply of acetylene gas during the carburization period is gradually reduced after a predetermined time after the start of carburization, the consumption of acetylene gas can be reduced without sending in excess acetylene gas. Moreover, according to the present invention, by the synergistic effect of the above effects, soot is prevented from adhering to the surface of the processing material,
A uniform carburized layer can be formed. In addition, since acetylene gas and hydrogen gas are supplied during the carburizing period, generation of soot is suppressed, soot can be prevented from adhering to the surface of the processing material, and the pressure in the heating chamber can form a uniform carburized layer. And the size of the vacuum exhaust device can be reduced.
【図１】 本発明方法における真空浸炭ヒートサイクル
の一例を示す図FIG. 1 is a diagram showing an example of a vacuum carburizing heat cycle in the method of the present invention.
【図２】 浸炭時間と鋼材中の炭素濃度プロファイルを
示すグラフFIG. 2 is a graph showing a carburizing time and a carbon concentration profile in a steel material.
【図３】 単位時間毎の鋼材中への炭素侵入割合を示す
グラフFIG. 3 is a graph showing the ratio of carbon intrusion into steel material per unit time.
【図４】 本発明に使用する真空浸炭炉のブロック図FIG. 4 is a block diagram of a vacuum carburizing furnace used in the present invention.
１…装入室 ２…ガス供給ライ
ン ３…バルブ ４…窒素供給源 ５…第１排気系ライン ６ａ、６ｂ…排気
弁 ７…装入ドア ８…中間ドア ９…アセチレンガス供給源 １０…水素ガス供
給源 １１…加熱室DESCRIPTION OF SYMBOLS 1 ... Loading room 2 ... Gas supply line 3 ... Valve 4 ... Nitrogen supply source 5 ... 1st exhaust system line 6a, 6b ... Exhaust valve 7 ... Loading door 8 ... Intermediate door 9 ... Acetylene gas supply source 10 ... Hydrogen gas Supply source 11: heating chamber
─────────────────────────────────────────────────────
────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成１３年２月９日（２００１．２．９）[Submission date] February 9, 2001 (2001.2.9)
【手続補正１】[Procedure amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】発明の詳細な説明[Correction target item name] Detailed description of the invention
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【０００１】[0001]
【発明の属する技術分野】本発明は鋼材部品の真空浸炭
方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vacuum carburizing steel parts.
【０００２】[0002]
【従来の技術】従来、鋼材表面の耐摩耗性その他の機械
的性質を向上させる表面処理法として真空浸炭処理が行
われている。この真空浸炭処理は、鋼材部品を真空中で
８７０〜１０００℃の浸炭温度まで加熱し、均熱状態に
達した時点で、浸炭性ガスを加熱室内に供給すると共
に、雰囲気温度を前記浸炭温度に維持しながら１０〜７
０ＫＰａの減圧下で所定時間保持することにより鋼材部
品の表面に浸炭性ガスの熱分解によって生じた炭素を侵
入拡散させるものである。2. Description of the Related Art Conventionally, vacuum carburizing has been performed as a surface treatment method for improving the wear resistance and other mechanical properties of a steel material surface. In this vacuum carburizing treatment, the steel part is heated in a vacuum to a carburizing temperature of 870 to 1000 ° C., and when the steel reaches a soaking state, a carburizing gas is supplied into the heating chamber, and the atmospheric temperature is reduced to the carburizing temperature. 10-7 while maintaining
By maintaining the pressure for a predetermined time under a reduced pressure of 0 KPa, carbon generated by the thermal decomposition of the carburizing gas penetrates and diffuses into the surface of the steel component.
【０００３】前記真空浸炭処理においては、鋼材部品の
全表面に均一に浸炭層を形成するためには浸炭初期に鋼
材部品の全表面が浸炭ガスに均一に、かつ、十分に晒さ
れることが必要であるが、通常、浸炭性ガスとして使用
されているプロパン、プロピレン、エチレンなどでは比
較的安定性が高いため熱分解するためには、加熱室内を
高温に維持し、かつ、多量に供給しなければならず、必
然的に浸炭性ガスの消費量が多くなるだけでなく多量の
煤を発生するため、設備の保守管理に多大のコストを要
するという問題がある。In the vacuum carburizing treatment, in order to form a carburized layer uniformly on the entire surface of a steel part, it is necessary that the entire surface of the steel part be uniformly and sufficiently exposed to a carburizing gas at an early stage of carburizing. However, propane, propylene, ethylene, etc., which are usually used as carburizing gases, have relatively high stability, so in order to thermally decompose, the heating chamber must be maintained at a high temperature and supplied in large quantities. In addition, there is a problem that not only the consumption of carburizing gas is inevitably increased but also a large amount of soot is generated.
【０００４】これらの問題を解決するため、特許第２９
６３８６９号公報にて、浸炭性ガスとしてアセチレン系
ガスを使用し、１ＫＰａ以下の減圧下で鋼材部品を真空
浸炭する方法が提案されている。具体的には、浸炭期に
アセチレンガスを連続的に供給する一方、連続的に排気
することで炉内圧力を１ＫＰａ以下、望ましくは０.３
ＫＰａ以下、さらに望ましくは０.１ＫＰａ以下の一定
値に保持して浸炭処理するものである。[0004] In order to solve these problems, Patent No. 29
JP-A-63869 proposes a method in which an acetylene-based gas is used as a carburizing gas, and a steel component is vacuum carburized under a reduced pressure of 1 KPa or less. Specifically, while the acetylene gas is continuously supplied during the carburization period, the pressure inside the furnace is reduced to 1 KPa or less, preferably 0.3 KPa, by continuously exhausting the gas.
Carburizing treatment is carried out while maintaining the pressure at a constant value of not more than KPa, more preferably not more than 0.1 KPa.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、前述の
如く鋼材部品の全表面に均一で、かつ、短時間で浸炭層
を形成するには、浸炭初期に鋼材部品の全表面が浸炭性
ガス（アセチレンガス）に均一に、かつ、十分に晒され
ることが必要であるが、前記方法では、浸炭期における
炉内圧を１ＫＰａ以下の一定値である高真空度に保持す
るため、浸炭期の煤発生は回避できるものの、浸炭層の
均―性が十分でなく、また、浸炭性ガス（アセチレン）
の消費量が多くなるという問題がある。特に、処理量が
多く、多量の浸炭性ガスの供給が必要な場合には顕著と
なる。However, in order to form a carburized layer uniformly and in a short time on the entire surface of a steel part as described above, the entire surface of the steel part must be made of a carburizing gas (acetylene) in the early stage of carburizing. Gas), it is necessary to uniformly and sufficiently expose the gas to the gas). However, in the above-described method, since the furnace pressure during the carburization period is maintained at a high degree of vacuum of 1 KPa or less, soot generation during the carburization period Although it can be avoided, the uniformity of the carburized layer is not sufficient, and carburizing gas (acetylene)
However, there is a problem that the consumption amount of the material increases. In particular, when the amount of treatment is large and a large amount of carburizing gas needs to be supplied, this becomes remarkable.
【０００６】従って、本発明は、処理材に煤の付着する
ことを回避して浸炭層の均一な形成とアセチレンガスの
消費量の低減を図ることを課題とするものである。SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent the soot from adhering to the treatment material and to form a carburized layer uniformly and reduce the consumption of acetylene gas.
【０００７】[0007]
【課題を解決するための手段】本発明は、前記課題を解
決するための手段として、鋼材部品を減圧下で浸炭処理
する真空浸炭方法において、浸炭期に所定量のアセチレ
ンガスを連続的に供給する一方、上限圧力設定値で排気
を開始し、下限圧力設定値で排気を停止することからな
る排気を行うとともに、前記浸炭期におけるアセチレン
ガスの連続供給を浸炭開始後の所定時間以降において漸
減させ、かつ、上限圧力設定値及び下限圧力設定値を
１.１ＫＰａ〜３.５ＫＰａとし、前記上限圧力設定値を
前記下限圧力設定値の１.５倍以上にするようにしたも
のである。According to the present invention, there is provided a vacuum carburizing method for carburizing steel parts under reduced pressure, wherein a predetermined amount of acetylene gas is continuously supplied during the carburizing period. On the other hand, the exhaust is started by starting the exhaust at the upper limit pressure set value and stopping the exhaust at the lower limit pressure set value, and the continuous supply of the acetylene gas in the carburizing period is gradually reduced after a predetermined time after the start of the carburizing. The upper limit pressure set value and the lower limit pressure set value are set to 1.1 KPa to 3.5 KPa, and the upper limit pressure set value is set to be 1.5 times or more of the lower limit pressure set value.
【０００８】本発明の実施態様においては、前記上限圧
力設定値は１．７〜３.５ＫＰａ、好ましくは、２.０〜
３.０ＫＰａの範囲内の値に、また、前記下限圧力設定
値は１.１〜１.６５ＫＰａ、好ましくは、１.１〜１.３
ＫＰａの範囲内の値にそれぞれ設定される。[0008] In an embodiment of the present invention, the upper limit pressure set value is 1.7 to 3.5 KPa, preferably 2.0 to 3.5 KPa.
To a value within a range of 3.0 KPa, and the lower limit pressure set value is 1.1 to 1.65 KPa, preferably 1.1 to 1.3.
It is set to a value within the range of KPa.
【０００９】浸炭期の上限圧力設定値及び下限圧力設定
値を１.１ＫＰａ〜３.５ＫＰａの範囲内に設定したの
は、次の理由による。即ち、浸炭期の上限圧力設定値の
最高値が３.５ＫＰａ以下では加熱室内でアセチレンガ
スの熱分解を生じても、処理材表面に煤が付着すること
を回避できるが、３.５ＫＰａを超えると、加熱室内で
アセチレンガスの熱分解によって生じた煤が処理材表面
に付着するのを回避するのが困難となるためである。ま
た、前記下限圧力設定値の最低値を１.１ＫＰａとした
のは、１.１ＫＰａ未満では均一な浸炭層を得るのに重
要な要素である浸炭初期時におけるアセチレンガスの供
給量を確実に確保することができなくなるからである。The reason why the upper limit pressure set value and the lower limit pressure set value in the carburizing period are set within the range of 1.1 KPa to 3.5 KPa is as follows. That is, when the maximum value of the upper limit pressure set value in the carburizing period is 3.5 KPa or less, soot can be prevented from adhering to the surface of the processing material even if thermal decomposition of acetylene gas occurs in the heating chamber, but exceeds 3.5 KPa. And the soot generated by the thermal decomposition of acetylene gas in the heating chamber
This is because it is difficult to avoid adhesion to the surface . The reason why the minimum value of the lower limit pressure set value is 1.1 KPa is that if the pressure is less than 1.1 KPa, the supply amount of acetylene gas at the initial stage of carburizing, which is an important factor for obtaining a uniform carburized layer, is ensured. Because they can no longer do it.
【００１０】さらに、前記浸炭期における加熱室内の上
限圧力設定値を下限圧力設定値の１.５倍以上、即ち、
間欠排気時における下限圧力設定値に対する上限圧力設
定値の比（上限圧力設定値／下限圧力設定値）を１.５
倍以上にしたのは、連続送入されるアセチレンガス（新
鮮な浸炭性ガス）を確実に処理材表面に接触させること
ができるためであり、１.５倍未満では浸炭ムラを生じ
やすくなるからである。Further, the upper limit pressure set value in the heating chamber during the carburizing period is 1.5 times or more the lower limit pressure set value, that is,
The ratio of the upper limit pressure set value to the lower limit pressure set value during intermittent exhaust (upper limit pressure set value / lower limit pressure set value) is 1.5.
The reason for increasing the value twice or more is that acetylene gas (fresh carburizing gas) continuously fed can be reliably brought into contact with the surface of the treated material, and if it is less than 1.5 times , carburizing unevenness easily occurs. It is.
【００１１】また、本発明の他の実施態様においては、
浸炭性ガスとして、アセチレンガスに加えて水素ガスを
供給することが行われる。即ち、アセチレンの熱分解反
応は、Ｃ２Ｈ２＝２Ｃ↓＋Ｈ２で表されるが、アセチレ
ンはプロパン等に比べて低い温度で熱分解し易いため、
アセチレンガスのみでは排気系の制御遅れにより多量に
煤が発生するのを避けられなくなる場合がある。ところ
が、アセチレンガスと共に水素ガス（Ｈ２）を加熱室内
に供給すると、加熱室内の水素ガス分圧が増加するため
前記反応式における反応が右に進みにくくなる。そのた
めアセチレンの分解速度が遅くなり、加熱室内の圧力を
高くして（即ち、加熱室内滞留時間を長くして）も、ア
セチレンの分解に伴う煤の発生は少なくなり処理材へ付
着をも防止できる。In another embodiment of the present invention,
As a carburizing gas, a hydrogen gas is supplied in addition to an acetylene gas. That is, the thermal decomposition reaction of acetylene is represented by C2H2 = 2C ↓ + H2. Since acetylene is easily thermally decomposed at a lower temperature than propane or the like,
With only acetylene gas, a large amount of soot may be unavoidable due to control delay of the exhaust system. However, when hydrogen gas (H2) is supplied into the heating chamber together with the acetylene gas, the partial pressure of the hydrogen gas in the heating chamber increases, so that the reaction in the above reaction formula does not easily proceed to the right. Therefore, even if the decomposition speed of acetylene is reduced and the pressure in the heating chamber is increased (that is, the residence time in the heating chamber is increased), the generation of soot due to the decomposition of acetylene is reduced and the adhesion to the processing material can be prevented. .
【００１２】従って、他の観点から見れば、本発明は、
鋼材部品を減圧下で浸炭処理する真空浸炭方法におい
て、浸炭期に、所定量のアセチレンガスと水素ガスとを
連続的に供給する一方、上限圧力設定値で排気を開始
し、その下限圧力設定値で排気を停止することからなる
排気を行うとともに、前記浸炭期におけるアセチレンガ
スと水素ガスとの連続供給を浸炭開始後の所定時間以降
において漸減させ、かつ、上限圧力設定値及び下限圧力
設定値を１.１ＫＰａ〜８.０ＫＰａとし、前記上限圧力
設定値を前記圧力下限設定値の１.５倍以上とする鋼材
部品の真空浸炭処理法を提供するものである。Therefore, from another viewpoint, the present invention provides:
In the vacuum carburizing method of carburizing steel parts under reduced pressure, during the carburizing period, a predetermined amount of acetylene gas and hydrogen gas are continuously supplied, while the exhaust is started at the upper limit pressure set value and the lower limit pressure set value is started. While performing the exhaust consisting of stopping the exhaust at, the continuous supply of acetylene gas and hydrogen gas in the carburizing period is gradually reduced after a predetermined time after the start of carburizing, and the upper limit pressure set value and the lower limit pressure set value are reduced. An object of the present invention is to provide a vacuum carburizing method for a steel component in which the upper limit pressure set value is set to 1.1 KPa to 8.0 KPa and the upper limit pressure set value is 1.5 times or more of the lower limit pressure set value.
【００１３】好ましい実施態様においては、前記上限圧
力設定値は２.０〜８.０ＫＰａ、好ましくは、２.５〜
７.０ＫＰａの範囲内の値に、また、前記下限圧力設定
値は１.１〜４.０ＫＰａ、好ましくは１.１〜２.０ＫＰ
ａの範囲内の値にそれぞれ設定される。[0013] In a preferred embodiment, the upper limit pressure set value is 2.0 to 8.0 KPa, preferably 2.5 to 8.0 KPa.
To a value within a range of 7.0 KPa, and the lower limit pressure set value is 1.1 to 4.0 KPa, preferably 1.1 to 2.0 KP.
It is set to a value within the range of a.
【００１４】また、好ましい実施態様においては、水素
ガスの量はアセチレンガス量の１〜３倍、通常、約２倍
程度に設定される。In a preferred embodiment, the amount of hydrogen gas is set to 1 to 3 times, usually about 2 times, the amount of acetylene gas.
【００１５】[0015]
【発明の実施の形態】本発明に係る鋼材の真空浸炭処理
方法は、バッチ式真空浸炭炉や連続式真空浸炭炉など任
意の形態でも実施できるが、ここでは図４に示す二室型
真空浸炭炉を用いて実施する場合を例に挙げて説明す
る。BEST MODE FOR CARRYING OUT THE INVENTION The vacuum carburizing method for steel materials according to the present invention can be carried out in any form such as a batch vacuum carburizing furnace and a continuous vacuum carburizing furnace. The case of using a furnace will be described as an example.
【００１６】図示の二室型真空浸炭炉は、装入室１と加
熱室１１とからなり、前記装入室１は、油焼入槽を有す
るとともにガス供給ライン２及びバルブ３ａを介して窒
素供給源４に接続される一方、第１排気系ライン５ａ及
び第１排気弁６ａを介して真空排気系及び排ガス処理系
に接続され、装入室１の一端側には装入ドア７が配設さ
れている。他方、前記加熱室１１は、前記装入室１の他
端側に中間ドア８を介在させて接続されると共に、ガス
供給ライン２ｂ、２ｃ及びバルブ３ｂ、３ｃを介してア
セチレンガス供給源９、水素ガス供給源１０に、また、
第２排気系ライン５ｂ及び第２排気弁６ｂを介して真空
排気系及び排ガス処理系にそれぞれ接続されている。な
お、前記加熱室１１には加熱手段が配設されると共に、
前記装入室１と同様に被処理材を移行させる移送手段が
配設されているが、これらは公知のものと同じ構成であ
るので省略する。The illustrated two-chamber vacuum carburizing furnace comprises a charging chamber 1 and a heating chamber 11. The charging chamber 1 has an oil quenching tank and nitrogen gas via a gas supply line 2 and a valve 3a. While being connected to the supply source 4, it is connected to a vacuum exhaust system and an exhaust gas treatment system via a first exhaust system line 5 a and a first exhaust valve 6 a, and a charging door 7 is provided at one end of the charging chamber 1. Has been established. On the other hand, the heating chamber 11 is connected to the other end of the charging chamber 1 with an intermediate door 8 interposed therebetween, and is connected to an acetylene gas supply source 9 via gas supply lines 2b, 2c and valves 3b, 3c. To the hydrogen gas supply source 10,
They are connected to a vacuum exhaust system and an exhaust gas treatment system via a second exhaust system line 5b and a second exhaust valve 6b, respectively. In addition, while the heating means is provided in the heating chamber 11,
Transfer means for transferring the material to be treated are provided in the same manner as in the charging chamber 1, but these are omitted since they have the same configuration as that of the known one.
【００１７】前記二室型真空浸炭炉を用いて被処理材で
ある鋼材部品を真空浸炭処理する場合、まず、被処理材
を積載したトレイを装入室１に装入し、第１及び第２排
気系ライン５ａ、５ｂを介して装入室１及び加熱室１１
内をそれぞれ真空排気して所定の真空度（約０.０２Ｋ
Ｐａ）にまで減圧した後、装入室１内のトレイに積載さ
れた処理材を減圧下の加熱室１１内に位置させる。次い
で、窒素供給源４からガス供給ライン２ｂを介して窒素
ガスを加熱室１１内に導入し、炉内圧力を所定圧（８
６.５〜１００ＫＰａ）まで上昇させ、窒素雰囲気下で
浸炭処理温度（８７０〜１０００℃）に昇温させる。When vacuum-carburizing a steel part as a material to be processed using the two-chamber vacuum carburizing furnace, first, a tray on which a material to be processed is loaded is loaded into the loading chamber 1, and first and second trays are loaded. 2 The charging chamber 1 and the heating chamber 11 via the exhaust system lines 5a and 5b
The inside of each chamber is evacuated to a predetermined degree of vacuum (about 0.02K
After the pressure is reduced to Pa), the processing material loaded on the tray in the charging chamber 1 is positioned in the heating chamber 11 under reduced pressure. Next, nitrogen gas is introduced into the heating chamber 11 from the nitrogen supply source 4 via the gas supply line 2b, and the furnace pressure is set to a predetermined pressure (8
6.5 to 100 KPa) and then to a carburizing temperature (870 to 1000 ° C.) in a nitrogen atmosphere.
【００１８】昇温が完了すると、この浸炭温度で所定時
間保持して均熱処理する。この際、均熱処理完了の約２
０分前の時点で加熱室１１内を真空排気（約０.０２Ｋ
Ｐａ）して、真空下で均熱を行う。均熱が完了すると、
ガス供給ライン２ｂを介して加熱室１１内にアセチレン
ガス（浸炭性ガス）を連続的に送入し、所定時間浸炭
後、加熱室１１内を真空排気（約０.０２ＫＰａ）して
拡散処理する。When the temperature rise is completed, the carburizing temperature is maintained for a predetermined time to perform a soaking process. At this time, about 2
At 0 minutes before, the inside of the heating chamber 11 is evacuated (about 0.02K).
Pa), and soaking under vacuum. When soaking is complete,
Acetylene gas (carburizing gas) is continuously fed into the heating chamber 11 through the gas supply line 2b, and after a predetermined time of carburizing, the heating chamber 11 is evacuated (about 0.02 KPa) to perform diffusion processing. .
【００１９】この浸炭期には、アセチレンガスは浸炭初
期の導入量を浸炭後期の導入量より多く連続的に送入す
る。一方、加熱室１１の排気は、間欠排気（パルス排
気）される。すなわち、加熱室１０内の圧力が上限圧力
設定値（最高設定値：３.５ＫＰａ）に達すると、第２
排気弁６ｂを開とする一方、下限圧力設定値（最低設定
値：１.１ＫＰａ）に達すると、第２排気弁６ｂを閉と
する（パルス操業）。この浸炭・拡散処理が完了する
と、窒素ガス（Ｎ２）を所定圧（８６.５〜１００ＫＰ
ａ）まで送入して窒素雰囲気下で焼入れ温度（約８１０
〜９００℃）に保持する。その後、装入室１で焼入れ処
理する。In the carburizing period, the acetylene gas is continuously supplied in a larger amount at the initial stage of carburizing than at the latter stage. On the other hand, the exhaust of the heating chamber 11 is intermittently exhausted (pulsed exhaust). That is, when the pressure in the heating chamber 10 reaches the upper limit pressure set value (maximum set value: 3.5 KPa), the second
While the exhaust valve 6b is opened, when the lower limit pressure set value (minimum set value: 1.1 KPa) is reached, the second exhaust valve 6b is closed (pulse operation). When the carburizing / diffusion treatment is completed, the nitrogen gas (N2) is set to a predetermined pressure (86.5-100 KP).
a) and a quenching temperature (about 810) under a nitrogen atmosphere.
９００900 ° C.). Thereafter, a quenching process is performed in the charging room 1.
【００２０】前記実施態様は、浸炭ガスとしてアセチレ
ンガスのみを使用した場合であるが、浸炭性ガスとして
アセチレンガスと水素ガスとの混合ガスを使用する場
合、次の様に操業される。即ち、前記の態様と同様にし
て真空下で均熱化処理を行い、均熱が完了すると、加熱
室１１内にアセチレンガスと水素がス（浸炭性ガス）を
連続的に送入し、所定時間浸炭後、加熱室１１内を真空
排気（約０.０２ＫＰａ）して拡散処理する。なお、水
素ガスはアセチレンガスの約２倍程度とする。この浸炭
期には、加熱室１１内の圧力が上限圧力設定値（最高設
定値：８ＫＰａ）に達すると、第２排気弁６ｂを開とす
る一方、下限圧力設定値（最低設定値：１.１ＫＰａ）
に達すると、第２排気弁６ｂを閉とするパルス操業を行
う。The above embodiment is a case where only acetylene gas is used as the carburizing gas. However, when a mixed gas of acetylene gas and hydrogen gas is used as the carburizing gas, the operation is performed as follows. That is, a soaking process is performed under vacuum in the same manner as in the above-described embodiment, and when the soaking is completed, acetylene gas and hydrogen are continuously fed into the heating chamber 11 through a gas (carburizing gas). After carburizing for a time, the inside of the heating chamber 11 is evacuated (about 0.02 KPa) to perform diffusion treatment. The hydrogen gas is about twice as large as the acetylene gas. In this carburizing period, when the pressure in the heating chamber 11 reaches the upper limit pressure set value (highest set value: 8 KPa), the second exhaust valve 6b is opened, and the lower limit pressure set value (minimum set value: 1.KPa). 1KPa)
, The pulse operation of closing the second exhaust valve 6b is performed.
【００２１】[0021]
【実施例１】ＳＣｒ４２０Ｈ製トランスミッションギヤ
（φ１８０mm）を処理材とし、これをトレイ上に１２０
枚積載（全表面積８.５m2）し、目標有効浸炭深さ０．
６mmとして図４に示す下記の仕様の２室型真空浸炭炉を
用いて図１に示す真空浸炭ヒートサイクルで真空浸炭焼
入れ処理を行った。 炉型式： ２室型（焼入れ：油） 加熱室容積： ７.８m3（有効寸法：１２２０mm長さ×
７６０mm巾×７１０mm高さ） 真空ポンプ： 油回転ポンプ（４５０m3/時） メカニカルブースタ（２５０m3/時） 即ち、多数の処理材を搭載したトレイを加熱室１１内に
配置させた後、８６．５〜１００ＫＰａの窒素雰囲気
中、加熱室内温度を浸炭温度９５０℃にまで昇温させ、
均熱化する。均熱処理完了の約２０分前の時点で真空排
気し、０．０２ＫＰａの真空下で均熱処理を更に約２０
分間行う。均熱処理完了後、加熱室１１内に浸炭性ガス
としてアセチレンガスを連続的に供給して浸炭処理を行
う。浸炭期には、アセチレンガスを浸炭開始から５分ま
では４０Ｌ／分、５〜１０分の間は１５Ｌ／分、１０〜
２５分の間は９Ｌ／分と徐々に減少させながら連続的に
供給し、その間、加熱室１１内の圧力が上限圧力設定値
の２.０ＫＰａに達すると第２排気弁６ｂを開いて真空
排気し、加熱室１１内の圧力が下限圧力設定値の１.１
ＫＰａに達すると第２排気弁６ｂを閉じることからなる
間欠排気を行って加熱室１１内の圧力制御を行う。次い
で、加熱室１１内を０.０２ＫＰａの真空度に真空排気
し、同真空度を維持しながら約１.３時間加熱して拡散
処理を行う。拡散処理後、加熱室１１内に窒素ガスを導
入して略大気圧のＮ2雰囲気とし、同雰囲気中で焼入温
度の８５０℃までに降温させ、同温度で１時間保持す
る。その後、装入室内に窒素ガスを導入して略大気圧の
Ｎ２雰囲気とし、トレイを装入室１に移行させて、１２
０℃の温度の油に入れて油焼入れを行う。Embodiment 1 A transmission gear (φ180 mm) made of SCr420H was used as a processing material, and was placed on a tray for 120 minutes.
Loaded (total surface area 8.5 m 2 ), target effective carburization depth 0.
Vacuum carburizing and quenching treatment was performed by a vacuum carburizing heat cycle shown in FIG. 1 using a two-chamber vacuum carburizing furnace having the following specifications shown in FIG. Furnace model: 2-chamber type (quenching: oil) Heating chamber volume: 7.8 m 3 (Effective dimensions: 1220 mm length x
Vacuum pump: Oil rotary pump (450 m 3 / hour) Mechanical booster (250 m 3 / hour) That is, after placing a tray on which a large number of processing materials are mounted in the heating chamber 11, 86. In a nitrogen atmosphere of 5 to 100 KPa, the temperature of the heating chamber is raised to a carburizing temperature of 950 ° C.,
Soak. About 20 minutes before the completion of the soaking, evacuation was performed, and the soaking was further performed under a vacuum of 0.02 KPa for about 20 minutes.
Do for a minute. After the completion of the soaking treatment, acetylene gas is continuously supplied as a carburizing gas into the heating chamber 11 to perform carburizing treatment. In the carburizing period, acetylene gas is supplied at 40 L / min for 5 minutes from the start of carburization, 15 L / min for 5 to 10 minutes, and 10 to 10 minutes.
During 25 minutes, the supply is continuously performed while gradually decreasing the rate to 9 L / min. During that time, when the pressure in the heating chamber 11 reaches the upper limit pressure set value of 2.0 KPa, the second exhaust valve 6b is opened to evacuate. The pressure in the heating chamber 11 is set to the lower limit pressure set value of 1.1.
When the pressure reaches KPa, the pressure in the heating chamber 11 is controlled by performing intermittent exhaust including closing the second exhaust valve 6b. Next, the inside of the heating chamber 11 is evacuated to a vacuum degree of 0.02 KPa, and the diffusion processing is performed by heating for about 1.3 hours while maintaining the vacuum degree. After the diffusion treatment, a nitrogen gas is introduced into the heating chamber 11 to form an N2 atmosphere at substantially atmospheric pressure, the temperature is lowered to a quenching temperature of 850 ° C. in the atmosphere, and the temperature is maintained for 1 hour. Thereafter, nitrogen gas was introduced into the charging chamber to make it a N2 atmosphere at substantially atmospheric pressure, and the tray was moved to the charging chamber 1 to be charged in the charging chamber 1.
Oil quenching is performed in oil at a temperature of 0 ° C.
【００２２】真空浸炭焼入れ後、処理材を観察したとこ
ろ、有効浸炭深さは０.５９〜０.６１mmで表面に煤の付
着や浸炭ムラは認められず、良好な結果が得られた。な
お、真空浸炭処理に於ける浸炭時間と鋼材中の炭素濃度
プロファイルは図２に示す通りであり、また、単位時間
毎の鋼材中への炭素侵入割合（即ち、浸炭後の全侵入炭
素量に対する一定時間浸炭後の侵入炭素量の割合）は図
３に示す通りである。図３に示す結果から、浸炭温度９
５０℃、有効浸炭深さ０．６mmの条件下では、浸炭開始
後５分間で全侵入炭素量の４６％が侵入し、５分後から
１０分後の５分間で全侵入炭素量の１８％が侵入するこ
とが分かる。このため、前述のように、浸炭初期におけ
る浸炭性ガスの供給量を多くし、侵入炭素量の減少に対
応して、浸炭性ガスの供給量を減少させるものである。When the treated material was observed after vacuum carburizing and quenching, the effective carburizing depth was 0.59 to 0.61 mm, and no adhesion of soot or uneven carburization was observed on the surface, and good results were obtained. The carburizing time and the carbon concentration profile in the steel material in the vacuum carburizing treatment are as shown in FIG. 2, and the ratio of carbon intrusion into the steel material per unit time (that is, with respect to the total amount of carbon infiltrated after carburizing). The ratio of the amount of invading carbon after carburizing for a certain period of time) is as shown in FIG. From the results shown in FIG.
Under the conditions of 50 ° C. and an effective carburization depth of 0.6 mm, 46% of the total invading carbon amount penetrated in 5 minutes after the start of carburizing, and 18% of the total invading carbon amount in 5 minutes after 5 minutes to 10 minutes. Can be seen invading. Therefore, as described above, the supply amount of the carburizing gas is increased in the early stage of carburization, and the supply amount of the carburizing gas is reduced in response to the decrease in the amount of invading carbon.
【００２３】[0023]
【実施例２】ＳＣｒ４２０Ｈ製ピニオンギヤ（φ３０m
m）を処理材とし、これをトレイ上に５０００個積載
（全表面積：２６ｍ2）し、目標有効浸炭深さ０．６mm
として実施例１と同様にして下記条件下で真空浸炭焼入
れ処理を行った。 焼入れ温度：８４０℃ 焼入れ：油焼入れ（温度：１２０℃） 真空浸炭焼入れ後、処理材を観察したところ、有効浸炭
深さは０.５６〜０.６１mmで表面に煤の付着や浸炭ムラ
は認められず、良好な結果が得られた。Embodiment 2 Pinion gear made of SCr420H (φ30m
m) as a treatment material, and 5,000 of them are loaded on a tray (total surface area: 26 m 2 ), and the target effective carburization depth is 0.6 mm.
In the same manner as in Example 1, vacuum carburizing and quenching treatment was performed under the following conditions. Quenching temperature: 840 ° C Quenching: Oil quenching (Temperature: 120 ° C) After vacuum carburizing and quenching, the treated material was observed. The effective carburizing depth was 0.56 to 0.61mm, and soot adhesion and carburizing unevenness were observed on the surface. No good results were obtained.
【００２４】 [0024]
【実施例３】 ＳＣｒ４２０Ｈ製ピニオンギヤ（φ３０m
m）を処理材とし、これをトレイ上に５０００個積載
（全表面積：２６ｍ2）し、目標有効浸炭深さ０．６mm
として実施例１と同様にして下記条件下で真空浸炭焼入
れ処理を行った。 真空浸炭焼入れ条件 浸炭温度：９５０℃ 浸炭ガス：アセチレンガス＋水素ガス ガス供給量：０〜５分‥アセチレン（１００Ｌ／分）＋水素（２００Ｌ／分） ５〜１０分‥アセチレン（３５Ｌ／分）＋水素（７０Ｌ／分） １０〜２５分‥アセチレン（２０Ｌ／分）＋水素（４０Ｌ/分） 加熱室内圧力： 上限圧力設定値‥７.０ＫＰａ 下限圧力設定値‥１.５ＫＰａ 焼入れ温度：８４０℃ 焼入れ：油焼入れ（温度：１２０℃） 真空浸炭焼入れ後、処理材を観察したところ、表面に煤
の付着や浸炭ムラは認められず、有効浸炭深さは０.５
９〜０.６２mmと良好な結果が得られた。 Embodiment 3 Pinion gear made of SCr420H (φ30m
m) as a treatment material, and 5,000 of them are loaded on a tray (total surface area: 26 m 2), and the target effective carburization depth is 0.6 mm.
In the same manner as in Example 1, vacuum carburizing and quenching treatment was performed under the following conditions. Vacuum carburizing and quenching conditions Carburizing temperature: 950 ° C Carburizing gas: acetylene gas + hydrogen gas Gas supply amount: 0 to 5 minutes {acetylene (100 L / min) + hydrogen (200 L / min) 5 to 10 minutes} acetylene (35 L / min) + Hydrogen (70 L / min) 10-25 min ‥ Acetylene (20 L / min) + Hydrogen (40 L / min) Heating chamber pressure: Upper limit pressure set value 下限 7.0 KPa Lower limit pressure set value 温度 1.5 KPa Hardening temperature: 840 ° C. Quenching: oil quenching (Temperature: 120 ° C) After vacuum carburizing and quenching, the treated material was observed. No adhesion of soot or uneven carburization was observed on the surface, and the effective carburizing depth was 0.5.
Good results of 9 to 0.62 mm were obtained.
【００２５】[0025]
【比較例１】ＳＣｒ４２０Ｈピニオンギヤ（φ３０mm）
を処理材とし、これをトレイ上に５０００個積載（全表
面積：２６ｍ2）し、目標有効浸炭深さ０．６mmとして
実施例１と同様にして下記条件下で真空浸炭焼入れ処理
を行った。 真空浸炭焼入れ後、処理材を観察したところ、処理材表
面に煤が付着し、有効浸炭深さは０.４８〜０.６１mmと
ムラがあった。これは、浸炭期における加熱室内の上限
圧力設定値が適切でないためと思われる。[Comparative Example 1] SCr420H pinion gear (φ30 mm)
5,000 were loaded on a tray (total surface area: 26 m 2 ), and vacuum carburizing and quenching treatment was performed under the following conditions in the same manner as in Example 1 with a target effective carburizing depth of 0.6 mm. After vacuum carburizing and quenching, when the treated material was observed, soot adhered to the treated material surface, and the effective carburized depth was 0.48 to 0.61 mm, which was uneven. This seems to be because the upper limit pressure set value in the heating chamber during the carburizing period is not appropriate.
【００２６】[0026]
【比較例２】ＳＣｒ４２０Ｈ製ピニオンギヤ（φ３０m
m）を処理材とし、これをトレイ上に５０００個積載
（全表面積：２６ｍ2）し、目標有効浸炭深さ０．６mm
として実施例１と同様にして下記条件下で真空浸炭焼入
れ処理を行った。 真空浸炭焼入れ条件 浸炭温度：９５０℃ 浸炭ガス：アセチレンガス＋水素ガス ガス供給量：０〜５分‥アセチレン（１２０Ｌ／分）＋水素（８０Ｌ／分） ５〜１０分‥アセチレン（３５Ｌ／分）＋水素（５０Ｌ／分） １０〜２５分‥アセチレン（２０Ｌ／分）＋水素（３０Ｌ／分） 加熱室内圧力： 上限圧力設定値‥１０.０ＫＰａ 下限圧力設定値‥１.５ＫＰａ 焼入れ温度：８４０℃ 焼入れ： 油焼入れ（温度：１２０℃） 真空浸炭焼入れ後、処理材を観察したところ、処理材表
面に煤が付着し、有効浸炭深さは０.４０〜０.６２mmと
ムラが多く実用不可能であった。これは、浸炭期におけ
る加熱室内の圧力の上限圧力設定値および水素添加量が
適切でないためと思われる。[Comparative Example 2] Pinion gear made of SCr420H (φ30m
m) as a treatment material, and 5,000 of them are loaded on a tray (total surface area: 26 m 2 ), and the target effective carburization depth is 0.6 mm.
In the same manner as in Example 1, vacuum carburizing and quenching treatment was performed under the following conditions. Vacuum carburizing and quenching conditions Carburizing temperature: 950 ° C Carburizing gas: acetylene gas + hydrogen gas Gas supply amount: 0 to 5 minutes セ acetylene (120 L / min) + hydrogen (80 L / min) 5 to 10 minutes ‥ acetylene (35 L / min) + Hydrogen (50 L / min) 10-25 min ‥ Acetylene (20 L / min) + Hydrogen (30 L / min) Heating chamber pressure: Upper limit pressure set value ‥ 10.0 KPa Lower limit pressure set value 1.5 KPa Hardening temperature: 840 ° C. Quenching: Oil quenching (Temperature: 120 ° C) After vacuum carburizing and quenching, when the treated material was observed, soot adhered to the treated material surface, and the effective carburized depth was 0.40 to 0.62 mm, which was so uneven that it was not practical. Met. This is presumably because the upper limit pressure set value of the pressure in the heating chamber and the amount of hydrogen added during the carburizing period are not appropriate.
【００２７】[0027]
【発明の効果】以上の説明から明らかなように、本発明
は、浸炭期には、所定量のアセチレンガスを連続的に供
給する一方、上限圧力設定値で排気を開始し、下限圧力
設定値で排気を停止することからなる排気（パルス排
気）を行うため、連続送入されるアセチレンガス（新鮮
な浸炭性ガス）を確実に処理材表面に接触させることが
できる。また、浸炭初期の加熱室の圧力が１.１ＫＰａ
から３.５ＫＰａとなるため、均一な浸炭層を得るのに
重要な要素である浸炭初期時におけるアセチレンガスの
供給量を確実に確保することができる。さらに、前記浸
炭期におけるアセチレンガスの連続供給を浸炭開始後の
所定時間以降において漸減するため、過剰なアセチレン
ガスの送入することなく、アセチレンガスの消費量を軽
減できる。しかも、本発明によれば、前記効果の相乗作
用により、処理材表面に煤が付着することを回避して、
均一な浸炭層を形成することができる。また、浸炭期
に、アセチレンガスと水素ガスとを供給するため、煤の
発生が抑制されるとともに、処理材表面への煤の付着を
回避でき、均一な浸炭層を形成し得る加熱室内の圧力を
高くすることができ、真空排気装置の小型化をも図るこ
とができる。As is apparent from the above description, in the present invention, in the carburizing period, while a predetermined amount of acetylene gas is continuously supplied, the exhaust is started at the upper limit pressure set value and the lower limit pressure set value is started. (Pulse evacuation) is performed to stop the evacuation, so that the continuously fed acetylene gas (fresh carburizing gas) can be reliably brought into contact with the surface of the processing material. In addition, the pressure of the heating chamber at the initial stage of carburizing is 1.1 KPa.
From 3.5 KPa, the supply amount of acetylene gas at the initial stage of carburization, which is an important factor for obtaining a uniform carburized layer, can be reliably ensured. Furthermore, since the continuous supply of acetylene gas during the carburization period is gradually reduced after a predetermined time after the start of carburization, the consumption of acetylene gas can be reduced without sending in excess acetylene gas. Moreover, according to the present invention, by the synergistic effect of the above effects, soot is prevented from adhering to the surface of the processing material,
A uniform carburized layer can be formed. In addition, since acetylene gas and hydrogen gas are supplied during the carburizing period, generation of soot is suppressed, soot can be prevented from adhering to the surface of the processing material, and the pressure in the heating chamber can form a uniform carburized layer. And the size of the vacuum exhaust device can be reduced.
【手続補正２】[Procedure amendment 2]
【補正対象書類名】図面[Document name to be amended] Drawing
【補正対象項目名】図３[Correction target item name] Figure 3
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【図３】 FIG. 3
Claims (2)
炭方法において、浸炭期に、所定量のアセチレンガスを
連続的に供給する一方、上限圧力設定値で排気を開始
し、下限圧力設定値で排気を停止することからなる排気
を行うとともに、前記浸炭期におけるアセチレンガスの
連続供給を浸炭開始後の所定時間以降において漸減さ
せ、かつ、上限圧力設定値及び下限圧力設定値を１.１
ＫＰａ〜３.５ＫＰａとし、前記上限圧力設定値を前記
下限圧力設定値の１.５倍以上とすることを特徴とする
鋼材部品の真空浸炭方法。In a vacuum carburizing method for carburizing a steel part under reduced pressure, a predetermined amount of acetylene gas is continuously supplied during a carburizing period, while exhaustion is started at an upper limit pressure set value, and a lower limit pressure set value is set. And the continuous supply of acetylene gas during the carburizing period is gradually reduced after a predetermined time after the start of carburizing, and the upper limit pressure set value and the lower limit pressure set value are set to 1.1.
A vacuum carburizing method for steel parts, wherein the pressure is set to KPa to 3.5 KPa, and the upper limit pressure set value is set to 1.5 times or more of the lower limit pressure set value.
炭方法において、浸炭期に、所定量のアセチレンガスと
水素ガスとを連続的に供給する一方、上限圧力設定値で
排気を開始し、その下限圧力設定値で排気を停止するこ
とからなる排気を行うとともに、前記浸炭期におけるア
セチレンガスと水素ガスとの連続供給を浸炭開始後の所
定時間以降において漸減させ、かつ、上限圧力設定値及
び下限圧力設定値を１.１ＫＰａ〜８.０ＫＰａとし、前
記上限圧力設定値を前記下限圧力設定値の１.５倍以上
とすることを特徴とする鋼材部品の真空浸炭方法。2. A vacuum carburizing method for carburizing a steel part under reduced pressure, wherein a predetermined amount of acetylene gas and hydrogen gas are continuously supplied during a carburizing period, and exhaust is started at an upper limit pressure set value, While performing the exhaust consisting of stopping the exhaust at the lower limit pressure set value, the continuous supply of acetylene gas and hydrogen gas in the carburizing period is gradually reduced after a predetermined time after the start of carburizing, and the upper limit pressure set value and A vacuum carburizing method for steel parts, wherein a lower limit pressure set value is set to 1.1 KPa to 8.0 KPa, and the upper limit pressure set value is set to 1.5 times or more of the lower limit pressure set value.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2005220390A (en) * | 2004-02-04 | 2005-08-18 | Nachi Fujikoshi Corp | Vacuum carburizing method and vacuum carburizing device |
| JP2005350729A (en) * | 2004-06-10 | 2005-12-22 | Ishikawajima Harima Heavy Ind Co Ltd | Vacuum carburization method |
| CN100406610C (en) * | 2006-05-11 | 2008-07-30 | 上海交通大学 | Carburizing process with pre-vacuumizing, protecting nitrogen-base atmosphere and no inner oxidation |
| WO2012144283A1 (en) * | 2011-04-22 | 2012-10-26 | アイシン・エィ・ダブリュ株式会社 | Complex steel component and production method therefor |
| JP2013501852A (en) * | 2009-08-07 | 2013-01-17 | スウエイジロク・カンパニー | Low temperature carburization under low vacuum |
| JP2016148091A (en) * | 2015-02-13 | 2016-08-18 | ジヤトコ株式会社 | Vacuum carburization method and vacuum carburization device |
| WO2018216615A1 (en) * | 2017-05-26 | 2018-11-29 | 中外炉工業株式会社 | Carburizing apparatus and carburizing method |
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