JP6812494B2 - Metal spring manufacturing method and manufacturing equipment - Google Patents
Metal spring manufacturing method and manufacturing equipment Download PDFInfo
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- JP6812494B2 JP6812494B2 JP2019091076A JP2019091076A JP6812494B2 JP 6812494 B2 JP6812494 B2 JP 6812494B2 JP 2019091076 A JP2019091076 A JP 2019091076A JP 2019091076 A JP2019091076 A JP 2019091076A JP 6812494 B2 JP6812494 B2 JP 6812494B2
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- 239000002184 metal Substances 0.000 title claims description 66
- 229910052751 metal Inorganic materials 0.000 title claims description 66
- 238000004519 manufacturing process Methods 0.000 title claims description 34
- 238000005121 nitriding Methods 0.000 claims description 183
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 90
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 41
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 39
- 150000001875 compounds Chemical class 0.000 claims description 29
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 28
- 238000010438 heat treatment Methods 0.000 claims description 17
- 150000004767 nitrides Chemical class 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 14
- 230000015572 biosynthetic process Effects 0.000 claims description 12
- 239000000725 suspension Substances 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 29
- 239000001257 hydrogen Substances 0.000 description 15
- 229910052739 hydrogen Inorganic materials 0.000 description 15
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- 229910021529 ammonia Inorganic materials 0.000 description 11
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000001569 carbon dioxide Substances 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 5
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 4
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 229910001337 iron nitride Inorganic materials 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000010587 phase diagram Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005422 blasting Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003682 fluorination reaction Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000002506 iron compounds Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 238000005480 shot peening Methods 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
Description
本発明は、窒化層が形成された弁ばね等の金属製ばねの製造方法及び製造装置に関する。 The present invention relates to a method and an apparatus for manufacturing a metal spring such as a valve spring on which a nitride layer is formed.
鋼材等の金属体の機械的強度を向上させる方法として、処理対象金属体に対して窒化処理を行うことが広く利用されている。 As a method for improving the mechanical strength of a metal body such as a steel material, nitriding the metal body to be treated is widely used.
この窒化処理においては、処理対象金属体の表面に窒化層を形成しつつ化合物層の発生を防止乃至は低減することが重要となる。 In this nitriding treatment, it is important to prevent or reduce the generation of the compound layer while forming the nitriding layer on the surface of the metal body to be treated.
即ち、処理対象金属体の表面に化合物層が生成されてしまうと、前記金属体表面近傍の粒界に窒化物や炭窒化物が生じことになる。 That is, when a compound layer is formed on the surface of the metal body to be treated, nitrides and carbonitrides are generated at the grain boundaries near the surface of the metal body.
従って、一旦、窒化処理によって化合物層が生成されると、たとえ化合物層を除去したとしても、粒界に生じた窒化物や炭窒化物は残ったままとなり、処理対象金属体の機械的強度を十分には向上できない。
特に、弁ばね等の繰り返し荷重を受ける部材が処理対象金属体とされる場合には、耐久性の観点で問題となる。
Therefore, once the compound layer is formed by the nitriding treatment, even if the compound layer is removed, the nitrides and carbonitrides generated at the grain boundaries remain, and the mechanical strength of the metal body to be treated is increased. It cannot be improved sufficiently.
In particular, when a member such as a valve spring that receives a repetitive load is a metal body to be processed, there is a problem from the viewpoint of durability.
この点に関し、下記特許文献１には、弁ばねの製造方法として、第１の濃度範囲の窒化ガス雰囲気で窒化処理を施し、その後、それよりも低濃度である第２の濃度範囲の窒化ガス雰囲気で窒化処理を施す方法が開示されている。 Regarding this point, in Patent Document 1 below, as a method for manufacturing a valve spring, nitriding treatment is performed in a nitriding gas atmosphere in the first concentration range, and then the nitriding gas in the second concentration range having a lower concentration is performed. A method of performing nitriding treatment in an atmosphere is disclosed.
詳しくは、前記特許文献１には、窒化ガスの濃度が高い（窒化ポテンシャルが高い）場合には、弁ばね表面の窒素濃度が高まり、弁ばね表面に窒化鉄の化合物層が形成され、一旦、このように表面に窒化鉄の化合物層が形成された後に、窒化ガスの濃度を低濃度とすると、弁ばねの表面においては新規な窒化鉄の化合物層の形成が抑制されると共に、既存の窒化鉄の化合物層が溶解して窒素が弁ばねの内部に拡散する旨の説明がなされている。 Specifically, in Patent Document 1, when the concentration of nitriding gas is high (the nitriding potential is high), the nitrogen concentration on the surface of the valve spring increases, and a compound layer of iron nitride is formed on the surface of the valve spring. If the concentration of the nitriding gas is lowered after the iron nitride compound layer is formed on the surface in this way, the formation of a new iron nitride compound layer is suppressed on the surface of the valve spring, and the existing nitriding is suppressed. It is explained that the iron compound layer dissolves and nitrogen diffuses into the valve spring.
しかしながら、実際の窒化処理において、一旦、弁ばね表面に窒化鉄の化合物層が形成された後に、この化合物層を低濃度の窒化ガス雰囲気での窒化処理によって溶解させることは困難である。 However, in the actual nitriding treatment, once a compound layer of iron nitride is formed on the surface of the valve spring, it is difficult to dissolve the compound layer by the nitriding treatment in a low concentration nitriding gas atmosphere.
また、下記特許文献２には、窒化処理の前に、処理対象金属体に対してフッ化処理を行うことにより、窒化処理時に化合物層が生成されることを防止乃至は低減する方法が開示されている。 Further, Patent Document 2 below discloses a method for preventing or reducing the formation of a compound layer during the nitriding treatment by performing a fluorination treatment on the metal body to be treated before the nitriding treatment. ing.
しかしながら、この方法では、窒化処理とは別にフッ化処理が必要であり、処理コストの高騰を招くと共に、処理に相当な時間を要するという問題がある。 However, this method requires a fluorination treatment separately from the nitriding treatment, which causes a problem that the treatment cost rises and the treatment takes a considerable amount of time.
本発明は、斯かる従来技術に鑑みなされたものであり、化合物層の発生を有効に防止しつつ、深い窒化層が形成された金属製ばねを製造する為の製造方法及び製造装置の提供を目的とする。 The present invention has been made in view of such prior art, and provides a manufacturing method and a manufacturing apparatus for manufacturing a metal spring in which a deep nitrided layer is formed while effectively preventing the generation of a compound layer. The purpose.
本発明は、前記目的を達成するために、表面に窒化層が形成された金属製ばねの製造方法であって、所定のばね形状に形成された金属製ばね本体を気密性雰囲気炉内に配置させた状態で炉内温度を所定窒化処理温度まで上昇させる昇温工程と、炉内温度を前記所定窒化処理温度に保持しつつ、前記炉内の窒化ポテンシャルが所定の高レベル値となるようにアンモニアガスを供給する第１窒化工程と、炉内温度を前記所定窒化処理温度に保持しつつ、前記炉内へのアンモニアガスの供給を停止し且つ前記炉内に水素ガス及び窒素ガスを３：１の割合で供給して、前記炉内の窒化ポテンシャルを前記金属製ばね本体に化合物層が生成しない低レベル値まで低下させる窒化ポテンシャル低下工程と、炉内温度を前記所定窒化処理温度に保持し且つ前記炉内の窒化ポテンシャルを前記低レベル値に保持する第２窒化工程とを含み、前記第１窒化工程における窒化ポテンシャルの前記高レベル値は、当該第１窒化工程を所定時間以上に亘って継続すると前記金属製ばね本体に化合物層の生成を招く濃度とされており、前記第１窒化工程の処理時間は前記所定時間より短い時間とされている金属製ばねの製造方法を提供する。 The present invention is a method for manufacturing a metal spring having a nitride layer formed on its surface in order to achieve the above object, and a metal spring body formed in a predetermined spring shape is arranged in an airtight atmosphere furnace. A temperature raising step of raising the temperature inside the furnace to a predetermined nitriding treatment temperature in the state of being nitrided, and a predetermined high level value of the nitriding potential in the furnace while maintaining the temperature inside the furnace at the predetermined nitriding treatment temperature. In the first nitriding step of supplying ammonia gas, while maintaining the temperature inside the furnace at the predetermined nitriding treatment temperature, the supply of ammonia gas into the furnace is stopped, and hydrogen gas and nitrogen gas are supplied into the furnace. A nitriding potential lowering step of supplying at a ratio of 1 to lower the nitriding potential in the furnace to a low level value at which no compound layer is formed on the metal spring body, and maintaining the nitriding potential in the furnace at the predetermined nitriding treatment temperature. Moreover, the high level value of the nitriding potential in the first nitriding step includes the second nitriding step of maintaining the nitriding potential in the furnace at the low level value, and the first nitriding step is carried out for a predetermined time or more. Provided is a method for producing a metal spring, which has a concentration that causes the formation of a compound layer in the metal spring body when continued, and the processing time of the first nitriding step is shorter than the predetermined time.
また、本発明は、気密性雰囲気炉と、前記雰囲気炉内を加熱する加熱手段と、前記雰囲気炉へのアンモニアガスの供給及び供給停止を切り換えることができ、さらに供給時には供給量を調整可能なアンモニアガス供給手段と、前記雰囲気炉への水素ガスの供給及び供給停止を切り換えることができ、さらに供給時には供給量を調整可能な水素ガス供給手段と、前記雰囲気炉への窒素ガスの供給及び供給停止を切り換えることができ、さらに供給時には供給量を調整可能な窒素ガス供給手段と、前記雰囲気炉内の窒化ポテンシャルを検出する窒化ポテンシャルセンサと、前記雰囲気炉内の温度を検出する温度センサと、制御装置とを備えた金属製ばねの製造装置を提供する。 Further, in the present invention, it is possible to switch between an airtight atmosphere furnace, a heating means for heating the inside of the atmosphere furnace, and supply and stop of supply of ammonia gas to the atmosphere furnace, and further, the supply amount can be adjusted at the time of supply. Ammonia gas supply means, hydrogen gas supply means that can switch between supply and suspension of hydrogen gas to the atmosphere furnace, and the supply amount can be adjusted at the time of supply, and supply and supply of nitrogen gas to the atmosphere furnace. A nitrogen gas supply means that can switch the stop and adjust the supply amount at the time of supply, a nitride potential sensor that detects the nitride potential in the atmosphere furnace, and a temperature sensor that detects the temperature in the atmosphere furnace. Provided is a metal spring manufacturing device equipped with a control device.
本発明に係る前記製造装置において、前記制御装置には、事前試験に基づき予め設定された制御モードが記憶される。
前記制御モードは、被処理体である金属製ばね本体が前記炉内に配置された状態で前記温度センサによって検出される炉内温度が事前試験に応じて予め設定された所定窒化処理温度まで上昇するように前記加熱手段を制御する昇温工程と、前記温度センサによって検出される炉内温度が前記所定窒化処理温度に保持されるように前記加熱手段を制御しつつ、前記窒化ポテンシャルセンサに基づく前記炉内の窒化ポテンシャルが事前試験に応じて予め設定された所定の高レベル値となるように前記アンモニアガス供給手段を制御する第１窒化工程と、前記温度センサによって検出される炉内温度が前記所定窒化処理温度に保持されるように前記加熱手段を制御しつつ、前記窒化ポテンシャルセンサに基づく前記炉内の窒化ポテンシャルが事前試験に応じて予め設定された所定の低レベル値まで低下するように、前記アンモニアガス供給手段を停止制御させて前記炉内へのアンモニアガスの供給を停止させ且つ前記水素ガス供給手段及び前記窒素ガス供給手段を供給制御させて前記炉内に水素ガス及び窒素ガスを３：１の割合で供給させる窒化ポテンシャル低下工程と、前記温度センサによって検出される炉内温度が前記所定窒化処理温度に保持されるように前記加熱手段を制御しつつ、前記窒化ポテンシャルセンサに基づく前記炉内の窒化ポテンシャルが前記低レベル値に保持されるように、前記アンモニアガス供給手段、前記水素ガス供給手段及び前記窒素ガス供給手段の作動制御を行う第２窒化工程とを含むものとされる。
In the manufacturing apparatus according to the present invention, the control apparatus stores a control mode preset based on a preliminary test.
In the control mode, the temperature inside the furnace detected by the temperature sensor rises to a predetermined nitriding treatment temperature set in advance according to the preliminary test in a state where the metal spring body to be processed is arranged in the furnace. Based on the nitriding potential sensor while controlling the heating means so that the heating means is controlled so that the temperature inside the furnace detected by the temperature sensor is maintained at the predetermined nitriding treatment temperature. The first nitriding step of controlling the ammonia gas supply means so that the nitriding potential in the furnace becomes a predetermined high level value preset according to the preliminary test, and the temperature in the furnace detected by the temperature sensor are While controlling the heating means so as to be maintained at the predetermined nitriding treatment temperature, the nitriding potential in the furnace based on the nitriding potential sensor is reduced to a predetermined low level value set in advance according to the preliminary test. To stop and control the ammonia gas supply means to stop the supply of ammonia gas into the furnace, and to control the supply of the hydrogen gas supply means and the nitrogen gas supply means to the inside of the furnace with hydrogen gas and nitrogen gas. To the nitriding potential sensor while controlling the heating means so that the temperature inside the furnace detected by the temperature sensor is maintained at the predetermined nitriding treatment temperature and the nitriding potential lowering step of supplying the nitriding potential at a ratio of 3: 1. It includes a second nitriding step for controlling the operation of the ammonia gas supply means, the hydrogen gas supply means, and the nitrogen gas supply means so that the nitriding potential in the furnace is maintained at the low level value. Will be done.
ここで、窒化ポテンシャルの前記高レベル値は、前記所定窒化処理温度での窒化処理を所定時間以上に亘って継続すると前記金属製ばね本体に化合物層の生成を招く濃度とされ、前記第１窒化工程の処理時間は前記所定時間より短い時間とされ、窒化ポテンシャルの前記低レベル値は、前記所定窒化処理温度での窒化処理を行っても前記金属製ばね本体に化合物層を生成させない濃度とされる。 Here, the high level value of the nitriding potential is a concentration that causes the formation of a compound layer in the metal spring body when the nitriding treatment at the predetermined nitriding treatment temperature is continued for a predetermined time or longer, and the first nitriding is performed. The processing time of the step is shorter than the predetermined time, and the low level value of the nitriding potential is a concentration that does not form a compound layer in the metal spring body even if the nitriding treatment is performed at the predetermined nitriding treatment temperature. To.
本発明に係る金属製ばねの製造方法及び製造装置によれば、所定時間以上に亘って継続して窒化処理を行うと金属製ばね本体に化合物層の生成を招く高レベル値の窒化ポテンシャルで窒化処理を行っているので深い窒化層を金属製ばね本体の表面全体に可及的に均一に形成することができ、さらに、高レベル値の窒化ポテンシャルでの前記窒化処理を前記所定時間より短い時間に制限しているので金属製ばね本体に化合物層が生成することを確実に防止することができる。 According to the method and apparatus for manufacturing a metal spring according to the present invention, nitriding with a high level value nitriding potential that causes the formation of a compound layer in the metal spring body when the nitriding treatment is continuously performed for a predetermined time or longer. Since the treatment is performed, a deep nitriding layer can be formed as uniformly as possible on the entire surface of the metal spring body, and the nitriding treatment at a high level value nitriding potential can be performed for a time shorter than the predetermined time. Since it is limited to, it is possible to surely prevent the formation of a compound layer on the metal spring body.
以下、本発明に係る金属製ばねの製造方法の一実施の形態について、添付図面を参照しつつ説明する。 Hereinafter, an embodiment of the method for manufacturing a metal spring according to the present invention will be described with reference to the accompanying drawings.
まず、本実施の形態に係る金属製ばねの製造方法を実施する際に用いられる製造装置の一例１００について説明する。
図１に、前記製造装置１００の模式図を示す。
First, an example 100 of a manufacturing apparatus used when carrying out the method for manufacturing a metal spring according to the present embodiment will be described.
FIG. 1 shows a schematic view of the manufacturing apparatus 100.
図１に示すように、前記製造装置１００は、気密性雰囲気炉１０と、前記炉１０内を加熱するヒーター等の加熱手段２０と、前記炉１０へのアンモニアガスの供給及び供給停止を切り換えることができ、さらに供給時には供給量を調整可能なアンモニアガス供給手段３０と、前記炉１０への水素ガスの供給及び供給停止を切り換えることができ、さらに供給時には供給量を調整可能な水素ガス供給手段４０と、前記炉１０への窒素ガスの供給及び供給停止を切り換えることができ、さらに供給時には供給量を調整可能な窒素ガス供給手段５０と、前記炉１０内の窒化ポテンシャルＫｎを検出する窒化ポテンシャルセンサ６０と、前記炉１０内の温度を検出する温度センサ６１と、制御装置９０とを備えている。 As shown in FIG. 1, the manufacturing apparatus 100 switches between an airtight atmosphere furnace 10, a heating means 20 such as a heater that heats the inside of the furnace 10, and supply and suspension of supply of ammonia gas to the furnace 10. Ammonia gas supply means 30 whose supply amount can be adjusted at the time of supply, and a hydrogen gas supply means which can switch between supply and stop of hydrogen gas to the furnace 10 and can adjust the supply amount at the time of supply. 40, a nitrogen gas supply means 50 capable of switching between supply and stop of supply of nitrogen gas to the furnace 10 and adjusting the supply amount at the time of supply, and a nitride potential for detecting the nitride potential Kn in the furnace 10. It includes a sensor 60, a temperature sensor 61 that detects the temperature inside the furnace 10, and a control device 90.
図１に示すように、本実施の形態においては、前記アンモニアガス供給手段３０は、前記炉１０にアンモニアガスを供給するアンモニアガス供給ライン３１と、前記アンモニアガス供給ライン３１に介挿されたアンモニアガス制御手段３５とを有している。 As shown in FIG. 1, in the present embodiment, the ammonia gas supply means 30 has an ammonia gas supply line 31 for supplying ammonia gas to the furnace 10 and ammonia inserted in the ammonia gas supply line 31. It has a gas control means 35.
本実施の形態においては、図１に示すように、前記アンモニアガス供給ライン３１は、大流量のアンモニアガスが供給される第１アンモニアガス供給ライン３１ａ及び小流量のアンモニアガスが供給される第２アンモニアガス供給ライン３１ｂを含んでおり、前記アンモニアガス制御手段３５は、前記第１及び第２アンモニアガス供給ライン３１ａ、３１ｂをそれぞれＯＮ／ＯＦＦする第１及び第２アンモニアガス電磁弁３５ａ、３５ｂを含んでいる。
当然ながら、前記アンモニアガス供給ライン３１が流量の異なる３本以上のアンモニアガス供給ラインを有するように構成することも可能である。
In the present embodiment, as shown in FIG. 1, the ammonia gas supply line 31 includes a first ammonia gas supply line 31a to which a large flow of ammonia gas is supplied and a second ammonia gas supply line 31a to which a small flow of ammonia gas is supplied. The ammonia gas supply line 31b is included, and the ammonia gas control means 35 includes first and second ammonia gas electromagnetic valves 35a and 35b for turning on / off the first and second ammonia gas supply lines 31a and 31b, respectively. Includes.
As a matter of course, it is also possible to configure the ammonia gas supply line 31 to have three or more ammonia gas supply lines having different flow rates.
また、前記アンモニアガス制御手段３５として、前記電磁弁３５ａ、３５ｂに代えて、弁開度を連続的に且つ自由に調整可能な電動弁（図示せず）を採用することも可能である。
この場合には、前記アンモニアガス供給手段３０は、大流量のアンモニアガスが供給される単一のアンモニアガス供給ラインと、前記アンモニアガス供給ラインに介挿されるアンモニアガス電動弁とを有するものとなる。
Further, as the ammonia gas control means 35, instead of the solenoid valves 35a and 35b, an electric valve (not shown) capable of continuously and freely adjusting the valve opening degree can be adopted.
In this case, the ammonia gas supply means 30 has a single ammonia gas supply line to which a large flow rate of ammonia gas is supplied, and an ammonia gas electric valve inserted in the ammonia gas supply line. ..
図１に示すように、本実施の形態においては、前記水素ガス供給手段４０は、前記炉１０に水素ガスを供給する水素ガス供給ライン４１と、前記水素ガス供給ライン４１に介挿された電磁弁又は電動弁等の水素ガス制御手段４５とを有している。 As shown in FIG. 1, in the present embodiment, the hydrogen gas supply means 40 has a hydrogen gas supply line 41 for supplying hydrogen gas to the furnace 10 and an electromagnetic valve inserted in the hydrogen gas supply line 41. It has a hydrogen gas control means 45 such as a valve or an electric valve.
図１に示すように、本実施の形態においては、前記窒素ガス供給手段５０は、前記炉１０に窒素ガスを供給する窒素ガス供給ライン５１と、前記窒素ガス供給ライン５１に介挿された電磁弁又は電動弁等の窒素ガス制御手段５５とを有している。 As shown in FIG. 1, in the present embodiment, the nitrogen gas supply means 50 has a nitrogen gas supply line 51 for supplying nitrogen gas to the furnace 10 and an electromagnetic valve inserted in the nitrogen gas supply line 51. It has a nitrogen gas control means 55 such as a valve or an electric valve.
前記制御装置９０は、前記各種センサ等から入力される信号に基づいて演算処理を実行する制御演算手段を含む演算部と、制御プログラム及び制御条件を記憶すると共に、前記演算部による演算中に生成されるデータを一時的に保持する記憶部とを備えている。 The control device 90 stores a calculation unit including a control calculation means that executes calculation processing based on signals input from the various sensors and the like, a control program, and control conditions, and is generated during the calculation by the calculation unit. It is provided with a storage unit that temporarily holds the data to be stored.
本実施の形態においては、前記制御装置９０は、前記各種センサからの入力信号及び前記制御プログラムに基づき、前記アンモニアガス供給手段（前記アンモニアガス制御手段３５）、前記水素ガス供給手段（前記水素ガス制御手段４５）、前記窒素ガス供給手段（前記窒素ガス制御手段５５）及び前記加熱手段２０の作動制御を司る。 In the present embodiment, the control device 90 has the ammonia gas supply means (the ammonia gas control means 35) and the hydrogen gas supply means (the hydrogen gas) based on the input signals from the various sensors and the control program. It controls the operation of the control means 45), the nitrogen gas supply means (the nitrogen gas control means 55), and the heating means 20.
ここで、窒化ポテンシャルＫｎについて説明する。
窒化ポテンシャルＫｎとは、炉内雰囲気の窒化力を示す指標であって、次式によって表される。
Ｋｎ＝ＰＮＨ３／ＰＨ２ ３／２
（式中のＰＮＨ３ はアンモニア（ＮＨ３）の分圧、ＰＨ２は水素（Ｈ２）の分圧を示す）
Here, the nitriding potential Kn will be described.
The nitriding potential Kn is an index showing the nitriding power of the atmosphere in the furnace, and is expressed by the following equation.
Kn = P NH3 / PH2 3/2
(P NH 3 in the formula indicates the partial pressure of ammonia (NH 3 ), and PH 2 indicates the partial pressure of hydrogen (H 2 ))
この窒化ポテンシャルＫｎは水素濃度を検出することによって算出され得る。
即ち、炉内に供給されたアンモニアガス（ＮＨ３）は次式に基づいて、窒素（Ｎ２）と水素（Ｈ２）とに熱分解する。
ＮＨ３ → （１／２）Ｎ２ ＋ （３／２）Ｈ２
This nitriding potential Kn can be calculated by detecting the hydrogen concentration.
That is, the ammonia gas (NH 3 ) supplied into the furnace is thermally decomposed into nitrogen (N 2 ) and hydrogen (H 2 ) based on the following equation.
NH 3 → (1/2) N 2 + (3/2) H 2
ここで、アンモニアガスの単位量が炉内に導入された際の当該アンモニアガスの分解率をαとすれば、未分解アンモニア量は１−α、発生窒素量はα／２、発生水素量は３α／２となり、これらガスの総量は１＋αとなる。 Here, assuming that the decomposition rate of the ammonia gas when the unit amount of ammonia gas is introduced into the furnace is α, the amount of undecomposed ammonia is 1-α, the amount of generated nitrogen is α / 2, and the amount of generated hydrogen is It becomes 3α / 2, and the total amount of these gases becomes 1 + α.
従って、アンモニア分圧ＰＮＨ３、窒素分圧ＰＮ２、水素分圧ＰＨ２は、次式によって表される。
ＰＮＨ３＝（１−α）／（１＋α） ・・・ （１）
ＰＮ２ ＝（α／２）／（１＋α） ・・・ （２）
ＰＨ２ ＝（３α／２）／（１＋α） ・・・ （３）
Therefore, the ammonia partial pressure P NH3 , the nitrogen partial pressure P N2 , and the hydrogen partial pressure PH 2 are expressed by the following equations.
P NH3 = (1-α) / (1 + α) ・ ・ ・ (1)
P N2 = (α / 2) / (1 + α) ・ ・ ・ (2)
PH2 = (3α / 2) / (1 + α) ・ ・ ・ (3)
前記式（１）〜（３）から、ＰＮＨ３及びＰＮ２は、それぞれ、
ＰＮＨ３＝（３−４ＰＨ２）／３
ＰＮ２ ＝ＰＨ２／３
となり、前述の窒化ポテンシャルＫｎは、
Ｋｎ＝ＰＮＨ３／ＰＨ２ ３／２
＝（３−４ＰＨ２）／３ＰＨ２ ３／２
＝（１−４ＰＨ２／３）／ＰＨ２ ３／２
となる。
From the above formulas (1) to (3), PNH3 and PN2 are respectively.
P NH3 = (3-4P H2 ) / 3
P N2 = PH2 / 3
The above-mentioned nitriding potential Kn is
Kn = P NH3 / PH2 3/2
= (3-4P H2 ) / 3P H2 3/2
= (1-4P H2 / 3) / P H2 3/2
Will be.
従って、前記雰囲気炉内の水素分圧ＰＨ２を検出すれば、炉内雰囲気の窒化ポテンシャルＫｎを求めることができる。 Therefore, by detecting the hydrogen partial pressure P H2 of the atmosphere furnace, it is possible to obtain the nitride potential Kn in the furnace atmosphere.
この点から、前記窒化ポテンシャルセンサ６０として、水素センサを好適に用いることができる。
前記水素センサとしては、例えば、水素分子透過性を備えた測定管によるもの（例えば、独Ｉｐｓｏｎ社製：ＨｙｄｒｏＮｉｔ−ｓｏｎｄｅ）を用いることができるが、炉体に直接装着することができ、炉内の水素濃度を連続的に測定できる点から、熱伝導式センサー（例えば、独Ｓｔａｎｇｅ社製：ＳＥ−Ｈ２）が好適に利用され得る。
From this point, a hydrogen sensor can be preferably used as the nitriding potential sensor 60.
As the hydrogen sensor, for example, one using a measuring tube having hydrogen molecule permeability (for example, HydroNit-sone manufactured by Ipson, Germany) can be used, but it can be directly mounted on the furnace body and inside the furnace. A heat conduction type sensor (for example, manufactured by Stage, Germany: SE-H2) can be preferably used because the hydrogen concentration of the hydrogen can be continuously measured.
参考として、図２及び図３に、前記関係式に基づき得られる、窒化ポテンシャルＫｎと水素濃度、アンモニア濃度及び窒素濃度との関係を示す。
所望の窒化層を形成するために必要な窒化ポテンシャルＫｎが定まれば、前記関係式又は図２及び図３に示す表から、前記雰囲気炉内において制御目標値とすべき水素分圧ＰＨ２を求めることができる。
For reference, FIGS. 2 and 3 show the relationship between the nitriding potential Kn and the hydrogen concentration, the ammonia concentration, and the nitrogen concentration obtained based on the above relational expression.
Once the nitriding potential Kn required to form the desired nitriding layer is determined, the hydrogen partial pressure PH2 to be the control target value in the atmosphere furnace can be determined from the relational expression or the tables shown in FIGS. 2 and 3. Can be sought.
なお、本発明において、前記アンモニアガス供給ライン３１を介して前記炉１０内にアンモニアガスを供給する構成には、アンモニアガスだけを供給する態様に加えて、所謂、ガス軟窒化処理の態様も含まれる。前記ガス軟窒化処理には、アンモニアガスに炭酸ガスを加えたアンモニア・炭酸混合ガスを供給する態様や、アンモニアガスにアセチレンガスを加えたアンモニア・アセチレン混合ガスを供給する態様が含まれる。 In the present invention, the configuration of supplying ammonia gas into the furnace 10 via the ammonia gas supply line 31 includes a so-called gas nitrocarburizing treatment mode in addition to the mode of supplying only ammonia gas. Is done. The gas nitrocarburizing treatment includes a mode of supplying an ammonia / carbon dioxide mixed gas obtained by adding carbon dioxide gas to ammonia gas, and a mode of supplying an ammonia / acetylene mixed gas obtained by adding acetylene gas to ammonia gas.
アンモニア・炭酸混合ガスを供給する態様においても、炭酸ガスの量はアンモニアガスに比して３〜５％程度であるため、前記炭酸ガスの存在を無視して、前記関係式（図２及び図３の関係表）を利用することができる。同様に、アンモニア・アセチレン混合ガスを供給する態様においても、前記関係式（図２及び図３の関係表）を利用することができる。 Even in the mode of supplying the mixed gas of ammonia and carbon dioxide, the amount of carbon dioxide gas is about 3 to 5% as compared with that of ammonia gas, so the presence of the carbon dioxide gas is ignored and the relational expression (FIGS. 2 and FIG. 3 relationship table) can be used. Similarly, the above relational expression (relationship table of FIGS. 2 and 3) can be used in the mode of supplying the mixed gas of ammonia and acetylene.
好ましくは、図１に示すように、前記製造装置１００には、前記炉１０内のガスの排出及び排出停止を切り換えるガス排出手段７０と、前記炉１０内の圧力を検出する圧力センサ６２とが備えられる。 Preferably, as shown in FIG. 1, the manufacturing apparatus 100 includes a gas discharge means 70 for switching between discharge and stop of gas discharge in the furnace 10 and a pressure sensor 62 for detecting the pressure in the furnace 10. Be prepared.
この場合、前記制御装置９０は、前記圧力センサ６２の検出信号に基づき前記炉１０内の圧力が負圧とならないように前記ガス排出手段７０の作動制御を行う。 In this case, the control device 90 controls the operation of the gas discharge means 70 based on the detection signal of the pressure sensor 62 so that the pressure in the furnace 10 does not become a negative pressure.
本実施の形態においては、図１に示すように、前記ガス排出手段７０は、前記炉１０内のガスを排出させる排出ライン７１と、前記排出ライン７１に介挿された排出電磁弁７５とを有しており、前記排出電磁弁７５が前記制御装置９０によって作動制御される。 In the present embodiment, as shown in FIG. 1, the gas discharge means 70 has a discharge line 71 for discharging gas in the furnace 10 and a discharge solenoid valve 75 inserted in the discharge line 71. The discharge solenoid valve 75 is operated and controlled by the control device 90.
本実施の形態においては、図１に示すように、前記製造装置１００は、さらに、前記排出ライン７１の下流端に接続された分解炉８０を有しており、前記炉１０内での窒化処理での残余のアンモニアが前記分解炉８０によって分解され、排出ガス中の可燃性ガス成分と共に燃焼炉８５で燃焼された上で、大気に放出される。 In the present embodiment, as shown in FIG. 1, the manufacturing apparatus 100 further has a decomposition furnace 80 connected to the downstream end of the exhaust line 71, and a nitriding process in the furnace 10 is performed. The residual ammonia in the above is decomposed by the decomposition furnace 80, burned in the combustion furnace 85 together with the combustible gas component in the exhaust gas, and then released to the atmosphere.
ここで、本実施の形態に係る金属製ばね製造方法について説明する。
図４に、本実施の形態に係る金属製ばね製造方法における炉内雰囲気制御のタイムチャートを示す。
Here, a metal spring manufacturing method according to the present embodiment will be described.
FIG. 4 shows a time chart of the atmosphere control in the furnace in the metal spring manufacturing method according to the present embodiment.
図１に示すように、本実施の形態に係る金属製ばね製造方法は、昇温工程と、第１窒化工程と、窒化ポテンシャル低下工程と、第２窒化工程とを含んでいる。 As shown in FIG. 1, the metal spring manufacturing method according to the present embodiment includes a temperature raising step, a first nitriding step, a nitriding potential lowering step, and a second nitriding step.
前記昇温工程は、小量のアンモニアガス及び窒素ガスを供給しつつ、炉内温度を所定の窒化処理温度（例えば４５０℃）まで上昇させるものであり、これにより、炉内及び被処理体である金属製ばね本体の酸化を防止する。
なお、後続する前記第１窒化工程、前記窒化ポテンシャル低下工程及び前記第２窒化工程では炉内温度は前記所定窒化処理温度に維持される。
In the temperature raising step, the temperature inside the furnace is raised to a predetermined nitriding treatment temperature (for example, 450 ° C.) while supplying a small amount of ammonia gas and nitrogen gas, whereby in the furnace and the object to be treated. Prevents oxidation of certain metal spring bodies.
In the subsequent first nitriding step, the nitriding potential lowering step, and the second nitriding step, the temperature inside the furnace is maintained at the predetermined nitriding treatment temperature.
前記第１窒化工程は、前記炉１０内の窒化ポテンシャルＫｎが前記金属製ばね本体の表面に化合物層の生成を招く高レベル値となるように、アンモニアガスを供給する。 In the first nitriding step, ammonia gas is supplied so that the nitriding potential Kn in the furnace 10 becomes a high level value that causes the formation of a compound layer on the surface of the metal spring body.
ここで、所定窒化処理温度及び窒化ポテンシャルの高レベル値は、図５に示すレーラー状態図を利用して予め設定され、前記制御装置９０に制御条件として記憶される。 Here, the predetermined nitriding treatment temperature and the high level value of the nitriding potential are preset by using the railer phase diagram shown in FIG. 5, and are stored in the control device 90 as control conditions.
即ち、図５に示すレーラー状態図は、窒化生成相に及ぼす窒化ポテンシャルＫｎと処理温度の関係を示しており、鋼部品にガス窒化処理（あるいは軟窒化処理）を施す際に、目的とする相組成の窒化層を形成するために必要な窒化ポテンシャルＫｎを求めるのに利用することができる。 That is, the Lehrer state diagram shown in FIG. 5 shows the relationship between the nitriding potential Kn on the nitriding phase and the processing temperature, and is the target phase when gas nitriding treatment (or soft nitriding treatment) is performed on a steel part. It can be used to determine the nitriding potential Kn required to form a nitriding layer of composition.
なお、図５に示すレーラー状態図は、純鉄から成るワーク表面の窒化ポテンシャルＫｎと炉内雰囲気の窒化ポテンシャルＫｎとが一致する平衡状態をベースに作成されているので、現実の処理状況の非平衡状態、及び／又は、被処理体である金属製ばね本体の材質（鋼種）によっては、多少の誤差が生じることが考えられる。 The Lehrer phase diagram shown in FIG. 5 is created based on an equilibrium state in which the nitriding potential Kn on the surface of the work made of pure iron and the nitriding potential Kn in the atmosphere inside the furnace match. Some errors may occur depending on the equilibrium state and / or the material (steel type) of the metal spring body to be treated.
したがって、現実の処理状態、金属製ばね本体の材質、及び／又は、軟窒化処理時における炭酸ガス又はアセチレンガスの添加量が比較的多い場合などには、必要に応じて、事前試験によって補正し、予め必要な窒化ポテンシャルＫｎ及び窒化処理温度を求めておくことが望ましい。 Therefore, in the actual processing state, the material of the metal spring body, and / or when the amount of carbon dioxide gas or acetylene gas added during the soft nitriding treatment is relatively large, it is corrected by a preliminary test as necessary. It is desirable to obtain the required nitriding potential Kn and nitriding treatment temperature in advance.
前記第１窒化工程の処理時間は、事前試験によって得られるデータに基づいて予め以下のように設定され、前記制御装置９０に制御条件として記憶される。
即ち、前記第１窒化工程における窒化条件、つまり、窒化ポテンシャルＫｎが前記高レベル値で且つ炉内温度が前記窒化処理温度とされた窒化条件での窒化処理において、前記金属製ばね本体の表面に化合物層が生じ始める所定時間を、予め、事前試験によって確認する。
The processing time of the first nitriding step is set in advance as follows based on the data obtained by the preliminary test, and is stored in the control device 90 as a control condition.
That is, in the nitriding condition in the first nitriding step, that is, in the nitriding condition in which the nitriding potential Kn is the high level value and the temperature inside the furnace is the nitriding treatment temperature, the surface of the metal spring body The predetermined time at which the compound layer begins to form is confirmed in advance by a preliminary test.
その上で、前記第１窒化工程の処理時間を前記所定時間より短い時間に設定し、前記制御装置９０に記憶する。
好ましくは、前記第１窒化工程の処理時間は、前記所定時間の６０％以上、より好ましくは前記所定時間の８０％以上とされる。
Then, the processing time of the first nitriding step is set to a time shorter than the predetermined time and stored in the control device 90.
Preferably, the processing time of the first nitriding step is 60% or more of the predetermined time, more preferably 80% or more of the predetermined time.
前記窒化ポテンシャル低下工程は、炉内温度を前記所定窒化処理温度に維持しつつ、前記炉１０内へのアンモニアガスの供給を停止し且つ前記炉１０内に水素ガス及び窒素ガスを３：１の割合で供給して、前記炉１０内の窒化ポテンシャルＫｎを前記金属製ばね本体に化合物層が生成しない低レベル値まで低下させる。 In the nitriding potential lowering step, while maintaining the temperature inside the furnace at the predetermined nitriding treatment temperature, the supply of ammonia gas into the furnace 10 is stopped, and hydrogen gas and nitrogen gas are supplied into the furnace 10 at a ratio of 3: 1. The nitriding potential Kn in the furnace 10 is reduced to a low level value at which a compound layer is not formed in the metal spring body.
詳しくは、前記窒化ポテンシャルＫｎの前記低レベル値は、前記レーラー状態図、及び／又は、事前試験に基づいて、予め設定され、前記制御装置９０に制御条件として記憶される。 Specifically, the low level value of the nitriding potential Kn is preset based on the railer phase diagram and / or a preliminary test, and is stored in the control device 90 as a control condition.
前記制御装置９０は、前記温度センサ６１に基づいて得られる炉内温度が前記所定窒化処理温度に維持されるように前記加熱手段２０を作動させつつ、前記窒化ポテンシャルセンサ６０からの信号に基づいて得られる前記炉１０内の窒化ポテンシャルＫｎが前記低レベル値まで低下するように前記水素ガス電磁弁４５及び前記窒素ガス電磁弁５５の作動制御を行う。 The control device 90 operates the heating means 20 so that the temperature inside the furnace obtained based on the temperature sensor 61 is maintained at the predetermined nitriding treatment temperature, and based on the signal from the nitriding potential sensor 60. The operation of the hydrogen gas electromagnetic valve 45 and the nitrogen gas electromagnetic valve 55 is controlled so that the nitriding potential Kn in the obtained furnace 10 is lowered to the low level value.
前記第２窒化工程は、炉内温度を前記所定窒化処理温度に保持し且つ前記炉１０内の窒化ポテンシャルＫｎを前記低レベル値に保持した状態を所定時間維持する。 In the second nitriding step, a state in which the temperature inside the furnace is maintained at the predetermined nitriding treatment temperature and the nitriding potential Kn in the furnace 10 is maintained at the low level value is maintained for a predetermined time.
即ち、前記制御装置９０は、前記温度センサ６１に基づいて得られる炉内温度が前記所定窒化処理温度に維持されるように前記加熱手段２０を作動させつつ、前記窒化ポテンシャルセンサ６０からの信号に基づいて得られる前記炉１０内の窒化ポテンシャルＫｎが前記低レベル値に維持されるように前記アンモニアガス制御手段３５、前記水素ガス制御手段４５及び前記窒素ガス制御手段５５の作動制御を行う。 That is, the control device 90 receives a signal from the nitriding potential sensor 60 while operating the heating means 20 so that the temperature inside the furnace obtained based on the temperature sensor 61 is maintained at the predetermined nitriding treatment temperature. The operation of the ammonia gas control means 35, the hydrogen gas control means 45, and the nitrogen gas control means 55 is controlled so that the nitriding potential Kn in the furnace 10 obtained based on the above is maintained at the low level value.
なお、前記炉１０内の窒化ポテンシャルＫｎの前記低レベル値の維持は、前記アンモニアガス制御手段３５のＯＮ／ＯＦＦ制御によって行うこともできるし、アンモニアガスの供給による窒化ポテンシャルの上昇制御と窒素ガス及び水素ガスの供給（水素ガス及び窒素ガスの３：１の割合での供給）による窒化ポテンシャルの下降制御との組み合わせによって行うことも可能である。 The low level value of the nitride potential Kn in the furnace 10 can be maintained by ON / OFF control of the ammonia gas control means 35, or the increase control of the nitride potential by the supply of ammonia gas and nitrogen gas. It is also possible to carry out this in combination with the lowering control of the nitride potential by supplying hydrogen gas (supplying hydrogen gas and nitrogen gas at a ratio of 3: 1).
前記第２窒化工程の処理時間も予め設定されており、前記制御装置９０は、制御条件として記憶されている処理時間に亘って前記第２窒化工程を実行する。 The processing time of the second nitriding step is also set in advance, and the control device 90 executes the second nitriding step for the processing time stored as a control condition.
かかる構成の金属製ばね製造方法によれば、以下の効果を得ることができる。
即ち、窒化処理前の金属製ばね本体の表面は、汚れ状態や酸化状態に関し均一とは言えない。
従って、このような状態の処理対象物（金属製ばね本体）に対して低濃度の窒化ポテンシャルで窒化処理を行うと、金属製ばね本体の表面に窒化のばらつきが生じ、結果として、金属製ばねの耐久性を十分には向上できない。
According to the metal spring manufacturing method having such a configuration, the following effects can be obtained.
That is, the surface of the metal spring body before the nitriding treatment cannot be said to be uniform in terms of the dirty state and the oxidized state.
Therefore, when the object to be processed (metal spring body) in such a state is subjected to nitriding treatment with a low concentration nitriding potential, nitriding varies on the surface of the metal spring body, and as a result, the metal spring Durability cannot be improved sufficiently.
これに対し、本実施の形態に係る前記製造方法によれば、金属製ばね本体に対する最初の窒化処理（前記第１窒化工程）は、前記金属製ばね本体の表面に化合物層の生成を招くような高レベル値の窒化ポテンシャルで行われている。 On the other hand, according to the manufacturing method according to the present embodiment, the first nitriding treatment (the first nitriding step) on the metal spring body causes the formation of a compound layer on the surface of the metal spring body. It is performed with a high level value of nitriding potential.
従って、窒化処理前の状態において金属製ばね本体の表面が汚れ状態や酸化状態に関し均一では無かったとしても、金属製ばね本体への窒化を可及的に均一且つ深く行うことができる。 Therefore, even if the surface of the metal spring body is not uniform in terms of the dirty state and the oxidized state in the state before the nitriding treatment, the nitriding of the metal spring body can be performed as uniformly and deeply as possible.
さらに、前記第１窒化工程においては、処理時間を制御することによって、処理対象物である金属製ばね本体の表面に化合物層が生成することを防止している。
従って、高レベル値の窒化ポテンシャルで窒化処理を行うことによって金属製ばね本体に深い窒化層を有効に形成しつつ、金属製ばね本体に化合物層が生成することを、簡単な制御で且つ確実に防止することができる。
Further, in the first nitriding step, the treatment time is controlled to prevent the compound layer from being formed on the surface of the metal spring body which is the object to be treated.
Therefore, by performing the nitriding treatment with a high level value nitriding potential, a deep nitrided layer is effectively formed in the metal spring body, and a compound layer is formed in the metal spring body with simple control and surely. Can be prevented.
即ち、理論上においては、窒化ポテンシャルＫｎの濃度の増減制御を繰り返し行うことによっても、金属製ばね本体の表面に深い窒化層を得ることが可能である。 That is, in theory, it is possible to obtain a deep nitriding layer on the surface of the metal spring body by repeatedly controlling the increase / decrease in the concentration of the nitriding potential Kn.
しかしながら、窒化ポテンシャルＫｎの濃度の増減制御を応答性良く且つ正確に行うことは、現実的には非常に困難である。 However, it is practically very difficult to control the increase / decrease of the nitriding potential Kn concentration with good responsiveness and accuracy.
これに対し、本実施の形態においては、前記第１窒化工程における窒化ポテンシャルＫｎ及び炉内温度は一定とされており、窒化処理処理時間を制御することによって、高濃度の窒化ポテンシャルで窒化処理を行いつつ化合物層の生成を防止している。
従って、高レベル値の窒化ポテンシャルで窒化処理を行うことによって深い窒化層を形成しつつ、化合物層の生成を簡単な制御で確実に防止することができる。
On the other hand, in the present embodiment, the nitriding potential Kn and the temperature inside the furnace in the first nitriding step are constant, and by controlling the nitriding treatment time, the nitriding treatment can be performed with a high concentration of nitriding potential. While doing so, the formation of a compound layer is prevented.
Therefore, it is possible to reliably prevent the formation of a compound layer with simple control while forming a deep nitriding layer by performing the nitriding treatment with a high level value nitriding potential.
好ましくは、前記昇温工程においても、前記高レベル値を目標値として前記炉１０内に対するアンモニアガスの供給制御を行うことができる。
斯かる構成によれば、第１窒化工程の処理時間を可及的に短縮化させることができる。
Preferably, even in the temperature raising step, the supply of ammonia gas to the inside of the furnace 10 can be controlled with the high level value as a target value.
According to such a configuration, the processing time of the first nitriding step can be shortened as much as possible.
本実施の形態に係る製造方法は、図４に示すように、前記昇温工程の前に、アイドリング工程（待機工程）を有している。
アイドリング工程は、前記金属製ばね本体を炉内の雰囲気に慣らす為の処理である。
As shown in FIG. 4, the manufacturing method according to the present embodiment includes an idling step (standby step) before the temperature raising step.
The idling step is a process for acclimatizing the metal spring body to the atmosphere inside the furnace.
前記金属製ばね製造方法は、好ましくは、前記昇温工程の前に、前記金属製ばね本体に対してショットブラストを行う前処理工程を含むことができる。
前記前処理工程を備えることにより、後続する前記第１及び第２窒化工程での窒化処理の安定化を図ることができる。
The metal spring manufacturing method preferably includes a pretreatment step of performing shot blasting on the metal spring body before the temperature raising step.
By providing the pretreatment step, it is possible to stabilize the nitriding treatment in the subsequent first and second nitriding steps.
また、前記金属製ばね製造方法は、好ましくは、前記第２窒化工程の後に、前記金属製ばね本体に対してショットブラスト又はショットピーニングを行う後処理工程を含むことができる。
前記後処理工程を備えることにより、金属製ばねの耐久性を向上させることができる。
In addition, the metal spring manufacturing method can preferably include a post-treatment step of performing shot blasting or shot peening on the metal spring body after the second nitriding step.
By providing the post-treatment step, the durability of the metal spring can be improved.
１０ 気密性雰囲気炉
２０ 加熱手段
３０ アンモニアガス供給手段
４０ 水素ガス供給手段
５０ 窒素ガス供給手段
６０ 窒化ポテンシャルセンサ
６１ 温度センサ
６２ 圧力センサ
７０ ガス排出手段
９０ 制御装置
１００ 金属製ばね製造装置
10 Airtight atmosphere furnace 20 Heating means 30 Ammonia gas supply means 40 Hydrogen gas supply means 50 Nitrogen gas supply means 60 Nitride potential sensor 61 Temperature sensor 62 Pressure sensor 70 Gas discharge means 90 Control device 100 Metal spring manufacturing device
Claims (2)
所定のばね形状に形成された金属製ばね本体を気密性雰囲気炉内に配置させた状態で炉内温度を所定窒化処理温度まで上昇させる昇温工程と、
炉内温度を前記所定窒化処理温度に保持しつつ、前記炉内の窒化ポテンシャルが所定の高レベル値となるようにアンモニアガスを供給する第１窒化工程と、
炉内温度を前記所定窒化処理温度に保持しつつ、前記炉内へのアンモニアガスの供給を停止し且つ前記炉内に水素ガス及び窒素ガスを３：１の割合で供給して、前記炉内の窒化ポテンシャルを前記金属製ばね本体に化合物層が生成しない低レベル値まで低下させる窒化ポテンシャル低下工程と、
炉内温度を前記所定窒化処理温度に保持し且つ前記炉内の窒化ポテンシャルを前記低レベル値に保持する第２窒化工程とを含み、
前記第１窒化工程における窒化ポテンシャルの前記高レベル値は、当該第１窒化工程を所定時間以上に亘って継続すると前記金属製ばね本体に化合物層の生成を招く濃度とされており、前記第１窒化工程の処理時間は前記所定時間より短い時間とされていることを特徴とする金属製ばねの製造方法。 A method for manufacturing a metal spring having a nitride layer formed on its surface.
A temperature raising step of raising the temperature inside the furnace to a predetermined nitriding treatment temperature while the metal spring body formed in a predetermined spring shape is arranged in the airtight atmosphere furnace.
The first nitriding step of supplying ammonia gas so that the nitriding potential in the furnace becomes a predetermined high level value while maintaining the temperature in the furnace at the predetermined nitriding treatment temperature.
While maintaining the temperature inside the furnace at the predetermined nitriding treatment temperature, the supply of ammonia gas into the furnace is stopped, and hydrogen gas and nitrogen gas are supplied into the furnace at a ratio of 3: 1 to provide the inside of the furnace. The nitriding potential lowering step of lowering the nitriding potential of the above to a low level value at which no compound layer is formed on the metal spring body, and
It includes a second nitriding step of maintaining the temperature in the furnace at the predetermined nitriding treatment temperature and the nitriding potential in the furnace at the low level value.
The high level value of the nitriding potential in the first nitriding step is a concentration that causes the formation of a compound layer in the metal spring body when the first nitriding step is continued for a predetermined time or longer. A method for manufacturing a metal spring, characterized in that the processing time of the nitriding step is shorter than the predetermined time.
前記制御装置には、事前試験に基づき予め設定された制御モードが記憶されており、
前記制御モードは、被処理体である金属製ばね本体が前記炉内に配置された状態で前記温度センサによって検出される炉内温度が事前試験に応じて予め設定された所定窒化処理温度まで上昇するように前記加熱手段を制御する昇温工程と、前記温度センサによって検出される炉内温度が前記所定窒化処理温度に保持されるように前記加熱手段を制御しつつ、前記窒化ポテンシャルセンサに基づく前記炉内の窒化ポテンシャルが事前試験に応じて予め設定された所定の高レベル値となるように前記アンモニアガス供給手段を制御する第１窒化工程と、前記温度センサによって検出される炉内温度が前記所定窒化処理温度に保持されるように前記加熱手段を制御しつつ、前記窒化ポテンシャルセンサに基づく前記炉内の窒化ポテンシャルが事前試験に応じて予め設定された所定の低レベル値まで低下するように、前記アンモニアガス供給手段を停止制御させて前記炉内へのアンモニアガスの供給を停止させ且つ前記水素ガス供給手段及び前記窒素ガス供給手段を供給制御させて前記炉内に水素ガス及び窒素ガスを３：１の割合で供給させる窒化ポテンシャル低下工程と、前記温度センサによって検出される炉内温度が前記所定窒化処理温度に保持されるように前記加熱手段を制御しつつ、前記窒化ポテンシャルセンサに基づく前記炉内の窒化ポテンシャルが前記低レベル値に保持されるように、前記アンモニアガス供給手段、前記水素ガス供給手段及び前記窒素ガス供給手段の作動制御を行う第２窒化工程とを含み、
窒化ポテンシャルの前記高レベル値は、前記所定窒化処理温度での窒化処理を所定時間以上に亘って継続すると前記金属製ばね本体に化合物層の生成を招くものとされており、
前記第１窒化工程の処理時間は前記所定時間より短い時間とされ、
窒化ポテンシャルの前記低レベル値は、前記所定窒化処理温度での窒化処理を行っても前記金属製ばね本体に化合物層を生成させないものとされていることを特徴とする金属製ばねの製造装置。 An airtight atmosphere furnace, a heating means for heating the inside of the atmosphere furnace, and an ammonia gas supply means capable of switching between supply and stop of supply of ammonia gas to the atmosphere furnace and adjusting the supply amount at the time of supply. The supply and suspension of hydrogen gas to the atmosphere furnace can be switched, and the supply and suspension of nitrogen gas to the atmosphere furnace can be switched between the hydrogen gas supply means whose supply amount can be adjusted at the time of supply. Further, a nitrogen gas supply means whose supply amount can be adjusted at the time of supply, a nitride potential sensor for detecting the nitride potential in the atmosphere furnace, a temperature sensor for detecting the temperature in the atmosphere furnace, and a control device are provided.
The control device stores a control mode preset based on a preliminary test.
In the control mode, the temperature inside the furnace detected by the temperature sensor rises to a predetermined nitriding treatment temperature set in advance according to the preliminary test in a state where the metal spring body to be processed is arranged in the furnace. Based on the nitriding potential sensor while controlling the heating means so that the heating means is controlled so that the temperature inside the furnace detected by the temperature sensor is maintained at the predetermined nitriding treatment temperature. The first nitriding step of controlling the ammonia gas supply means so that the nitriding potential in the furnace becomes a predetermined high level value preset according to the preliminary test, and the temperature in the furnace detected by the temperature sensor are While controlling the heating means so as to be maintained at the predetermined nitriding treatment temperature, the nitriding potential in the furnace based on the nitriding potential sensor is reduced to a predetermined low level value set in advance according to the preliminary test. To stop and control the ammonia gas supply means to stop the supply of ammonia gas into the furnace, and to control the supply of the hydrogen gas supply means and the nitrogen gas supply means to the inside of the furnace with hydrogen gas and nitrogen gas. To the nitriding potential sensor while controlling the heating means so that the temperature inside the furnace detected by the temperature sensor is maintained at the predetermined nitriding treatment temperature and the nitriding potential lowering step of supplying the nitriding potential at a ratio of 3: 1. A second nitriding step for controlling the operation of the ammonia gas supply means, the hydrogen gas supply means, and the nitrogen gas supply means so that the nitriding potential in the furnace based on the nitriding potential is maintained at the low level value is included.
The high level value of the nitriding potential is said to cause the formation of a compound layer in the metal spring body when the nitriding treatment at the predetermined nitriding treatment temperature is continued for a predetermined time or longer.
The processing time of the first nitriding step is shorter than the predetermined time.
An apparatus for manufacturing a metal spring, wherein the low level value of the nitriding potential is such that a compound layer is not formed on the metal spring body even if the nitriding treatment is performed at the predetermined nitriding treatment temperature.
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