JPS641547B2 - - Google Patents
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- Publication number
- JPS641547B2 JPS641547B2 JP8757680A JP8757680A JPS641547B2 JP S641547 B2 JPS641547 B2 JP S641547B2 JP 8757680 A JP8757680 A JP 8757680A JP 8757680 A JP8757680 A JP 8757680A JP S641547 B2 JPS641547 B2 JP S641547B2
- Authority
- JP
- Japan
- Prior art keywords
- gas
- furnace
- amount
- carburizing
- carbon concentration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007789 gas Substances 0.000 claims description 84
- 238000000034 method Methods 0.000 claims description 40
- 238000005255 carburizing Methods 0.000 claims description 34
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 33
- 229910052799 carbon Inorganic materials 0.000 claims description 33
- 238000004458 analytical method Methods 0.000 claims description 14
- 229910000831 Steel Inorganic materials 0.000 claims description 13
- 239000010959 steel Substances 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 7
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 6
- 229930195733 hydrocarbon Natural products 0.000 description 11
- 150000002430 hydrocarbons Chemical class 0.000 description 11
- 239000004215 Carbon black (E152) Substances 0.000 description 10
- 238000004364 calculation method Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 8
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical class O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 5
- 239000012159 carrier gas Substances 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000010926 purge Methods 0.000 description 2
- 229910017112 Fe—C Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
Description
この発明は、ガス浸炭処理方法に関し、特に、
窒素を雰囲気ガスの主成分とする方法であつて、
処理品を設置した密閉熱処理炉内を減圧し、その
後窒素ガスを該炉内に導入して一定圧まで回復さ
せ、しかる後有機液剤を滴注し、炉内に生じる
CO，CO2の濃度を測定し、これによつて目標
CO2量を演算して設定し、それとCO2量の分析値
との偏差に基づいて炉内に供給されるエンリツチ
ガス量を制御し、雰囲気ガス中のCO量が変動し
ても浸炭雰囲気の平衡炭素濃度を所望値に保持さ
せ且つ炭化水素の使用量を著るしく節約し、且つ
適確な浸炭結果を得る。
一般に行なわれているガス浸炭処理方法には、
吸熱型変成ガスによる変成炉方式と、有機溶剤を
直接炉内に滴注する滴注方式とがある。
変成炉方式では、炭化水素ガスと空気とを一定
割合で混合し、1050℃に加熱された変成炉内の触
媒を通過させると次の如く反応が起る。
ａ・CxHy＋ｂ・（O2＋3.76N2）→ｃ・H2＋
ｄ・CO＋3.76×ｂ・N2
この変成されたガスをキヤリヤガスとして浸炭
炉に送り、浸炭濃度を高めるためのエンリツチ剤
として、同様の炭化水素CxHyを送入し、以つて
炉内を所定の雰囲気に調整して目標の浸炭を行な
う。この際に送入されるガス量は、その処理品の
表面積によつて若干異なるが、ほぼ炉内の容積の
６〜10倍のガスを必要とし、そしてこの使用済み
のガスは、公害や危険防止の観点から炉の近くで
燃焼廃棄されるものである。したがつて、使用ガ
スの実質効率はきわめて低く不経済である。ま
た、滴注方式の浸炭方法では、浸炭温度に加熱さ
れた浸炭炉に有機液剤を直接滴注すると、
CxHyOz→ａ・Co＋ｂ・H2
のように分解する。
この分解してなるガスは、変成炉方式のキヤリ
ヤガスに相当するものであり、これに、炭化水素
CxHyを添加したり、遊離炭素を発生する有機液
剤を事前混合したりして、これを同時滴注させて
エンリツチ作用をもたせ浸炭雰囲気を形成する。
この場合も、炉内に滴注する有機液剤量は、処理
品の表面積により若干異なるが、炉内の容積の
2.5〜４倍のガス量を生成するだけ必要とし、そ
してこの使用済みのガスは、変成炉方式同様の観
点から、炉の近くで燃焼廃棄されるものである。
このような方法に対して、炉内に炭化水素ガス
と空気とを送入し、浸炭に必要なガスを炉内で変
成させパージ用のガスとして窒素ガスを使用する
いわゆるN2ベース浸炭方法が提供されている。
しかし、この方法も、前述二方式の方法と同様
に、使用する設備は開放式であり、多量のガスを
消費する。また、雰囲気の安定性を得るために、
酸化性のガスと炭化水素ガスとを用い、これらを
炉内で混合し変成させるが、ガス効換率が高くつ
まりガス流速が大であるため、十分なガス変成が
なされず、したがつて、未分解ガスによる浸炭も
生じ、信頼できる安定浸炭雰囲気を得ることは困
難である。
また一般に、鋼材を浸炭雰囲気中で熱処理する
場合の浸炭機構は、次の反応式によつて与えられ
る。
2CO〔Ｃ〕＋CO2 ……(1)
上式から浸炭雰囲気の炭素濃度は、雰囲気ガス
成分の中のCO2の分圧を測定することによつて制
御する方法が、従来から行なわれている。しかし
ながら、この制御方法はCO量が一定であること
を前提とするものであるため、必ずしも精密な制
御を望み得ないという難点がある。すなわち、前
記変成炉方式による雰囲気ガスでは、変成に用い
られる炭化水素ガスの種類および炭化水素ガスと
空気との混合比によつて、それぞれガス組成が変
動し、また、省資源を目的として、真空炉のよう
な完全密閉容器に被処理鋼材とともに雰囲気ガス
をパツクして行なう浸炭方式では、エンリツチガ
スの供給量に応じてガス組成が変動するため、こ
れによるCOの分圧の変動を免れず、したがつて、
CO2のみを測定して行なう従来の制御方法では、
鋼材表面の炭素濃度を所望値に制御するのは、き
わめて困難なこととされていた。
そこで、このような難点を排除する技術として
CO2以外の組成ガスを計測する方法も提案される
に至り、たとえば、特開昭51−149135号および特
開昭51−149136号各公報では、CO，CO2，CH4
およびH2を、特開昭52−14539号および特開昭52
−14540号各公報では、CO，H2およびH2Oをそ
れぞれ計測し、これらの分析値で算出した雰囲気
中の炭素濃度を所望の平衡炭素濃度設定値と比較
して、その偏差に応じてエンリツチガスの添加量
を制御するようにしている。これらの方法は従来
よりも高精度の制御が可能となる点において効果
を有するものの、分析される組成ガスが少くとも
３種類を必要とするため、却つて分析装置や演算
装置の構造と配置が大型かつ複雑となり、その管
理も容易ではないという難点がある。
この発明は、従来の浸炭方法のかかる問題を解
決するものであり、その目的は、用いるガスない
しその原料を無駄にしない経済的なガス浸炭方法
を提供するにありまたこの発明の目的は、CO2と
COの２種類の組成ガスを測定することによつて
浸炭雰囲気の炭素濃度を簡易に、かつ精密に制御
し得る方法を提供することにあり、また、この発
明の目的は、雰囲気ガスの組成とくにCOの変動
や炉内温度の変化に応じて所望の平衡炭素濃度に
相応するCO2量を修正することによつて浸炭雰囲
気の平衡炭素濃度を一定に制御する方法を提供す
ることにあり、さらに、この発明の目的は、鋼材
の品質を均一かつ高精度にすることにあり、さら
にこの発明の別の目的は、危険の少ないガス浸炭
方法を提供するにあり、さらにまたこの発明の目
的は、実施装置が簡単で操作も容易なガス浸炭方
法を提供するにある。
すなわち、この発明は、図示する実施例の如
く、鋼材の処理品Ｗを設置した熱処理炉１内を密
閉状態で真空ポンプＰで減圧し、その後窒素ガス
を炉内に導入して一定圧まで回復させ、しかる後
有機液剤を滴注して炉内で分解し、その雰囲気組
成ガスからCO2量とCO量とを分析し、CO量の分
析値と炉内温度と処理品Ｗ表面の目標炭素濃度と
により雰囲気ガスの平衡炭素濃度に相応する目標
CO2量を演算して設定し、目標CO2量と雰囲気ガ
ス中のCO2量の分析値との偏差に基づいて炉内に
供給されるCxHyのエンリツチガス量を制御する
ことを特徴とする密閉式ガス浸炭処理方法に係
る。詳細には、炉内ガス置換を早めるために密閉
した熱処理炉１を用い、この中に処理品Ｗを設置
し、真空ポンプＰにより一定まで真空引きし、そ
の後窒素ガスを送入し昇温して安定時間をとり、
然る後に、分解性のよい有機液剤CH3OHを初期
段階にて５〜15％のCO濃度になるように滴注す
る。滴注された有機液剤は直ちに次のように分解
する。
CH3OH→CO＋2H2 ……(2)
（33.3％）（66.6％）
炉内ガスを赤外線分析計にて測定し、予め設し
た炭素分圧値に応じて次に炭化水素ガスCxHy
（エンリツチガスとなる）を添加し雰囲気を制御
する。
上記(1)式の反応は、炉を密閉してあるので、未
分解ガスの影響を受け難くCO，H2は安定して得
られる。
エンリツチ剤としての炭化水素ガスとして
C3H8を使用した場合、炉内H2OおよびCO2と次
のように反応する。
3H2O＋C3H8→3CO＋7H2 ……(3)
3CO2＋C3H8→6CO＋4H2 ……(4)
この生成されたCOは、(1)式のCOガスと同様に
次式の浸炭作用をする。
〔Fe〕〓＋2CO→〔Fe―Ｃ〕〓＋CO2 ……(5)
炉内に送込まれたガスの排気は一定圧に調整さ
れた微圧調整弁にて炉外に排出されるが、そのガ
ス量はきめわてわずかである。また、含有する危
険なガスのCO，H2もわずかなので燃焼もしくは
そのまま外気排出される。
この発明の制御方法は、次に述べる演算式を用
いて行なわれる。すなわち、前掲の浸炭機構の反
応式(1)における平衡恒数をＫとすると、次の平衡
式が成立する。
Ｋ＝Pco2／ac・Pco2 ……(6)
ここに、ac；飽和度
Pco，Pco2；それぞれCO，CO2の分圧
ac＝平衡炭素濃度CPeq／飽和炭酸濃度CPsat ……(7)
いま、式(7)を式(6)に代入して変形すると、
Pco2＝Ｓ×Pco2／CPeq ……(8)
ここに、Ｓ＝CPsat／Ｋ
Ｓは処理温度によつて定まる定数（温度係数）
である。
式(8)から、Pcoの変化分で目標とするPco2を修
正すればよいことが判る。
以下、この発明の制御方法を図示した実施例に
ついて説明する。第１図は、この発明に用いる制
御装置の実施例を示すブロツク図であり、一定の
処理温度に保持されている熱処理炉１には、モー
タＭを載置し炉内にフアンＦを臨ませた炉蓋を有
し、炉内にヒータＨを設置し、さらに真空ポンプ
Ｐを連通してある。この熱処理炉１内に鋼材Ｗを
装入して浸炭処理を行なう。この熱処理炉１内に
は、窒素および浸炭ガスを発生させる滴注剤を図
示しない供給源から管路２によつて供給し、また
同様にエンリツチガスを図示しない供給源から制
御弁４を介して管路３によつて供給して所定の平
衡炭素濃度の雰囲気ガスを生成させるようになつ
ている。この雰囲気ガスは管路５から該管路５に
接続されたCO分析計６に送られる。該CO分析計
６によつて分析されたCO量はCO分析信号として
演算装置１０に入力する。また、炉内温度を、熱
電対７により測定して温度信号とするか、あるい
は炉内温度に相当する信号をあらかじめ設定して
おいて、同様に演算装置１０に入力する。一方、
所望する鋼材の表面炭素濃度を炭素濃度設定器８
に設定して、これを目標炭素濃度設定信号として
同様に演算装置１０に入力する。
演算装置１０には、前掲式(8)の演算回路が組み
込まれており、これに入力されたCO分析信号、
温度信号および目標炭素濃度設定信号による演算
を行なつて、雰囲気ガスの平衡炭素濃度に相当す
る目標CO2量を算出する。この目標CO2量はCO2
調節計９の設定値として入力する。
また、炉内の雰囲気ガスは管路５に接続された
CO2分析計１１によつてCO2量が分析され、CO2
分析信号としてCO2調節計９にフイードバツクさ
れる。CO2調節計９は前記演算装置１０から設定
値として入力された目標CO2量の信号とCO2分析
計１１から測定値として入力されたCO2分析信号
とを比較して、これにより生じた偏差信号で管路
３に接続された制御弁４を作動させ、偏差信号の
大小に応じて該制御弁４の開度を調節する。かく
して、熱処理炉１内に供給されるエンリツチガス
量が増減して、炉内の雰囲気ガスの平衡炭素濃度
は所望に保持される。
前記実施例における雰囲気ガス中のCO2量およ
びCO量の分析方法としては、たとえば赤外線吸
収法またはガスクロマトグラフ法その他適宜の方
法を採用するものとする。またCO2調節計として
は、サーボ設定形式のものが好適である。演算装
置はアナログ式とデジタル式の何れでも採用する
ことができる。第２図は、第１図の実施例におい
てアナログ式演算装置を用いた場合の演算工程を
示すブロツク図である。CO分析計６（第１図）
からのCO分析信号Pcoは２乗演算器１２に入力
されて２乗演算が施され、Pco2として次の乗算
器１３に送られる。一方、熱電対７からの温度信
号は、関数発生器１４により炉内温度に対応した
温度係数Ｓ（＝CPsat／Ｋ）に変換されて乗算器１３
に送られる。乗算器１３では、Pco2とＳとの信
号の乗算が行なわれ、Pco2・Ｓとして次の除算
器１５に入力される。除算器１５はこのPco2・
Ｓを炭素濃度設定器８からの目標炭素濃度設定信
号CPeqで除して、Pco2・Ｓ／CPeqとしてCO2調節計９
に出力する。このようにして、CO2調節計９には
雰囲気ガスの平衡炭素濃度に相当する目標CO2量
が設定値として入力される。
この発明の制御方法を用いて、浸炭処理を行な
つて得た被処理鋼材の表面炭素濃度の分析結果を
従来の赤外線式CO2分析法による分析結果と対比
してみると第３図に示すとおりである。同図の浸
炭時間は、炉内が浸炭温度（930℃）に達し、雰
囲気制御を開始してから後の経過時間である。同
図におけるこの発明の方法を用いた浸炭処理は、
次の工程にしたがつて行なつたものである。ま
ず、被処理鋼材を炉内に装入したのち、真空ポン
プにて炉内を0.1〜1.0torrまで真空排気する。そ
の後、大気圧付近までキヤリアガスを封入して密
閉する。次いで昇温し炉内温度が回復したころ
で、この発明の制御方法によつてエンリツチガス
を供給し、雰囲気ガスの平衡炭素濃度を所定値に
保持しながら所定時間浸炭処理を行なう。
この発明は、前述したとおり雰囲気ガス中の
CO量と炉内温度と鋼材表面の目標炭素濃度とか
ら所望の平衡炭素濃度に相応する目標CO2量を設
定し、この設定値と雰囲気ガス中のCO2量との偏
差に基づいてエンリツチガスの供給量を制御する
ように構成したものである。したがつて、この発
明によれば雰囲気ガス中のCO量がどのように変
動しても雰囲気ガスの平衡炭素濃度を一定に制御
することが可能となる。しかも、雰囲気ガスのう
ち、CO量とCO2量の２種類の組成ガスを分析し
て、目標CO2量をCO量の変動に応じて修正する
ものであるから、きわめて簡易な手段によつて雰
囲気ガスの精密制御が可能となるだけでなく、均
一かつ高精度のすぐれた品質の鋼材を得ることが
できる。また、この発明によれば、エンリツチガ
スはもちろん、キヤリアガスの大幅な節減が可能
となり、省資源化の要請に充分応えることができ
る。この処理のときのガス組成分析値の一例を次
表に示す。
The present invention relates to a gas carburizing method, and in particular,
A method using nitrogen as the main component of the atmospheric gas,
The pressure inside the closed heat treatment furnace in which the treated product is installed is reduced, and then nitrogen gas is introduced into the furnace to restore the pressure to a constant level, and then the organic liquid is injected dropwise to reduce the pressure generated inside the furnace.
Measure the concentration of CO, CO 2 and use this to set the target.
The amount of CO 2 is calculated and set, and the amount of enrichment gas supplied to the furnace is controlled based on the deviation between it and the analysis value of the amount of CO 2. Even if the amount of CO in the atmosphere gas fluctuates, the carburizing atmosphere remains balanced. The carbon concentration is maintained at the desired value and the amount of hydrocarbon used is significantly saved, and a proper carburizing result is obtained. Commonly used gas carburizing methods include:
There are two types: a conversion furnace method using endothermic conversion gas, and a dripping method in which an organic solvent is directly injected into the furnace. In the shift furnace system, when hydrocarbon gas and air are mixed at a fixed ratio and passed through a catalyst in a shift furnace heated to 1050°C, the following reaction occurs. a・CxHy+b・(O 2 +3.76N 2 )→c・H 2 +
d・CO＋3.76×b・N 2 This metamorphosed gas is sent to the carburizing furnace as a carrier gas, and a similar hydrocarbon CxHy is fed as an enrichment agent to increase the carburizing concentration, and the inside of the furnace is heated to a specified level. Adjust the atmosphere and perform the targeted carburization. The amount of gas sent in at this time varies slightly depending on the surface area of the product being processed, but it requires approximately 6 to 10 times the volume of the furnace, and this used gas is a source of pollution and danger. From the standpoint of prevention, these are burned and disposed of near the furnace. Therefore, the actual efficiency of the gas used is extremely low and uneconomical. In addition, in the dripping carburizing method, when an organic liquid is directly dripped into a carburizing furnace heated to the carburizing temperature, it decomposes as CxHyOz→a・Co+b・H 2 . The gas produced by this decomposition corresponds to the carrier gas of the shift furnace system, and it also contains hydrocarbons.
CxHy is added or an organic liquid that generates free carbon is premixed, and these are simultaneously added dropwise to provide an enriching effect and form a carburizing atmosphere.
In this case as well, the amount of organic liquid to be dripped into the furnace varies slightly depending on the surface area of the product to be treated, but it depends on the volume of the furnace.
It is necessary to generate 2.5 to 4 times the amount of gas, and this used gas is burned and disposed of near the furnace, from the same viewpoint as the shift furnace system. In contrast to this method, there is a so-called N2- based carburizing method, in which hydrocarbon gas and air are introduced into the furnace, the gas necessary for carburizing is transformed in the furnace, and nitrogen gas is used as a purge gas. provided.
However, like the above two methods, this method uses open equipment and consumes a large amount of gas. In addition, in order to obtain stability of the atmosphere,
Oxidizing gas and hydrocarbon gas are used to mix and transform them in a furnace, but because the gas efficiency is high, that is, the gas flow rate is high, sufficient gas transformation is not achieved. Carburization due to undecomposed gas also occurs, making it difficult to obtain a reliable and stable carburizing atmosphere. Generally, the carburizing mechanism when steel is heat treated in a carburizing atmosphere is given by the following reaction equation. 2CO[C]+CO 2 ...(1) From the above equation, the carbon concentration in the carburizing atmosphere has traditionally been controlled by measuring the partial pressure of CO 2 in the atmospheric gas components. . However, since this control method is based on the premise that the amount of CO is constant, there is a drawback that precise control cannot necessarily be expected. In other words, the gas composition of the atmospheric gas produced by the above-mentioned shift furnace system varies depending on the type of hydrocarbon gas used for shift conversion and the mixing ratio of hydrocarbon gas and air. In the carburizing method, in which atmospheric gas is packed together with the steel to be treated in a completely sealed container such as a furnace, the gas composition changes depending on the amount of enrichment gas supplied, so the partial pressure of CO changes due to this. Got tired,
With conventional control methods that measure only CO 2 ,
It has been considered extremely difficult to control the carbon concentration on the surface of steel to a desired value. Therefore, as a technology to eliminate such difficulties,
Methods for measuring compositional gases other than CO 2 have also been proposed; for example, in JP-A-51-149135 and JP-A-51-149136, CO, CO 2 , CH 4
and H 2 , JP-A-52-14539 and JP-A-52
-14540 Each publication measures CO, H 2 and H 2 O, compares the carbon concentration in the atmosphere calculated from these analytical values with the desired equilibrium carbon concentration set value, and calculates the value according to the deviation. The amount of enrichment gas added is controlled. Although these methods are effective in that they enable more precise control than conventional methods, they require at least three types of gas composition to be analyzed, which means that the structure and arrangement of the analysis equipment and calculation equipment are more difficult. It has the disadvantage that it is large and complex, and its management is not easy. This invention solves the problems of conventional carburizing methods, and its purpose is to provide an economical gas carburizing method that does not waste the gas or its raw materials. 2 and
It is an object of the present invention to provide a method for easily and precisely controlling the carbon concentration in a carburizing atmosphere by measuring two types of composition gases, including CO. The object of the present invention is to provide a method for controlling the equilibrium carbon concentration of a carburizing atmosphere to a constant level by modifying the amount of CO 2 corresponding to a desired equilibrium carbon concentration in accordance with fluctuations in CO and changes in furnace temperature; The purpose of this invention is to make the quality of steel materials uniform and highly accurate, and another purpose of this invention is to provide a less dangerous gas carburizing method. It is an object of the present invention to provide a gas carburizing method that has a simple implementation device and is easy to operate. That is, the present invention, as in the illustrated embodiment, reduces the pressure in a heat treatment furnace 1 in which a steel product W is installed in a sealed state with a vacuum pump P, and then introduces nitrogen gas into the furnace to restore the pressure to a constant level. After that, the organic liquid is dropped and decomposed in the furnace, and the amount of CO 2 and the amount of CO are analyzed from the atmospheric composition gas, and the analyzed value of the amount of CO, the temperature inside the furnace, and the target carbon on the surface of the treated product concentration and target corresponding to the equilibrium carbon concentration of the atmospheric gas.
A closed system characterized by calculating and setting the amount of CO 2 and controlling the amount of CxHy enrichment gas supplied into the furnace based on the deviation between the target amount of CO 2 and the analysis value of the amount of CO 2 in the atmosphere gas. This relates to a gas carburizing treatment method. In detail, a sealed heat treatment furnace 1 is used to speed up the gas replacement in the furnace, the processed product W is placed inside the furnace, the vacuum is evacuated to a certain level using a vacuum pump P, and then nitrogen gas is introduced to raise the temperature. and take a stabilization time,
Thereafter, a highly decomposable organic liquid, CH 3 OH, is added dropwise to give a CO concentration of 5 to 15% at the initial stage. The injected organic liquid immediately decomposes as follows. CH 3 OH → CO + 2H 2 ...(2) (33.3%) (66.6%) The gas in the furnace is measured with an infrared analyzer, and then hydrocarbon gas CxHy is measured according to the preset carbon partial pressure value.
(becomes an enrichment gas) and control the atmosphere. In the reaction of equation (1) above, since the furnace is sealed, it is not easily affected by undecomposed gas, and CO and H 2 can be stably obtained. As a hydrocarbon gas as an enrichment agent
When C 3 H 8 is used, it reacts with H 2 O and CO 2 in the furnace as follows. 3H 2 O＋C 3 H 8 →3CO＋7H 2 ...(3) 3CO 2 +C 3 H 8 →6CO+4H 2 ...(4) This generated CO, like the CO gas in equation (1), undergoes the carburizing effect of the following equation. do. [Fe]〓+2CO→[Fe-C]〓+CO 2 ...(5) The exhaust gas sent into the furnace is discharged outside the furnace by a fine pressure regulating valve that is adjusted to a constant pressure. The amount of gas is extremely small. In addition, since the dangerous gases CO and H 2 it contain are small, they are either burned or exhausted into the outside air. The control method of the present invention is performed using the following arithmetic expression. That is, if K is the equilibrium constant in the reaction equation (1) of the carburizing mechanism described above, the following equilibrium equation holds true. K=Pco 2 /ac・Pco 2 ...(6) where, ac: saturation degree Pco, Pco 2 ; partial pressure of CO and CO 2 , respectively ac=equilibrium carbon concentration CPeq/saturated carbon dioxide concentration CPsat ...(7) Now , by substituting equation (7) into equation (6) and transforming it, we get Pco 2 = S temperature coefficient)
It is. From equation (8), it can be seen that the target Pco 2 should be corrected by the change in Pco. Embodiments illustrating the control method of the present invention will be described below. FIG. 1 is a block diagram showing an embodiment of the control device used in the present invention. A heat treatment furnace 1 maintained at a constant processing temperature is equipped with a motor M and a fan F facing into the furnace. A heater H is installed inside the furnace, and a vacuum pump P is connected to the furnace. A steel material W is charged into this heat treatment furnace 1 and carburized. Inside this heat treatment furnace 1, a dropping agent for generating nitrogen and carburizing gas is supplied from a supply source (not shown) through a pipe line 2, and enrichment gas is similarly supplied from a supply source (not shown) through a pipe line 2 through a control valve 4. The atmosphere gas is supplied through line 3 to generate an atmospheric gas having a predetermined equilibrium carbon concentration. This atmospheric gas is sent from the pipe 5 to a CO analyzer 6 connected to the pipe 5. The amount of CO analyzed by the CO analyzer 6 is input to the calculation device 10 as a CO analysis signal. Further, the temperature inside the furnace is measured by the thermocouple 7 and used as a temperature signal, or a signal corresponding to the temperature inside the furnace is set in advance and similarly inputted to the calculation device 10. on the other hand,
Carbon concentration setter 8 sets the desired surface carbon concentration of the steel material.
This is similarly input to the calculation device 10 as the target carbon concentration setting signal. The arithmetic device 10 has a built-in arithmetic circuit of the above formula (8), and the CO analysis signal input thereto,
A calculation is performed using the temperature signal and the target carbon concentration setting signal to calculate the target amount of CO 2 corresponding to the equilibrium carbon concentration of the atmospheric gas. This target CO2 amount is CO2
Input as the setting value of the controller 9. In addition, the atmospheric gas in the furnace is connected to pipe 5.
The CO 2 amount is analyzed by the CO 2 analyzer 11, and the CO 2
It is fed back to the CO 2 controller 9 as an analysis signal. The CO 2 controller 9 compares the target CO 2 amount signal input as a set value from the arithmetic unit 10 with the CO 2 analysis signal input as a measured value from the CO 2 analyzer 11, and calculates the amount of CO 2 generated thereby. A control valve 4 connected to the pipe line 3 is actuated by the deviation signal, and the opening degree of the control valve 4 is adjusted depending on the magnitude of the deviation signal. In this way, the amount of enrichment gas supplied into the heat treatment furnace 1 is increased or decreased, and the equilibrium carbon concentration of the atmospheric gas within the furnace is maintained at a desired level. As a method for analyzing the amount of CO 2 and the amount of CO in the atmospheric gas in the above embodiments, for example, an infrared absorption method, a gas chromatography method, or other appropriate method is employed. Also, as the CO 2 controller, a servo setting type is suitable. As the arithmetic unit, either an analog type or a digital type can be employed. FIG. 2 is a block diagram showing the calculation process when an analog calculation device is used in the embodiment shown in FIG. CO analyzer 6 (Figure 1)
The CO analysis signal Pco from is input to a square calculator 12, subjected to a square calculation, and sent to the next multiplier 13 as Pco 2 . On the other hand, the temperature signal from the thermocouple 7 is converted by the function generator 14 into a temperature coefficient S (=CPsat/K) corresponding to the temperature inside the furnace, and sent to the multiplier 13. The multiplier 13 multiplies the signals Pco 2 and S, and inputs the signal as Pco 2 ·S to the next divider 15. The divider 15 calculates this Pco 2・
S is divided by the target carbon concentration setting signal CPeq from the carbon concentration setting device 8 and outputted to the CO 2 controller 9 as Pco 2 ·S/CPeq. In this way, the target CO 2 amount corresponding to the equilibrium carbon concentration of the atmospheric gas is input to the CO 2 controller 9 as a set value. Figure 3 shows a comparison of the analysis results of the surface carbon concentration of the treated steel material obtained by carburizing using the control method of this invention with the analysis results using the conventional infrared CO 2 analysis method. That's right. The carburizing time in the figure is the elapsed time after the inside of the furnace reached the carburizing temperature (930°C) and atmospheric control was started. The carburizing treatment using the method of this invention in the same figure is as follows:
This was done according to the following steps. First, the steel material to be treated is charged into the furnace, and then the inside of the furnace is evacuated to 0.1 to 1.0 torr using a vacuum pump. After that, carrier gas is filled to near atmospheric pressure and the chamber is sealed. Next, the temperature is raised and when the furnace temperature has recovered, enrichment gas is supplied according to the control method of the present invention, and carburization is carried out for a predetermined time while maintaining the equilibrium carbon concentration of the atmospheric gas at a predetermined value. As mentioned above, this invention
A target CO 2 amount corresponding to the desired equilibrium carbon concentration is set from the CO amount, furnace temperature, and target carbon concentration on the surface of the steel material, and the enrichment gas is adjusted based on the deviation between this set value and the CO 2 amount in the atmospheric gas. It is configured to control the supply amount. Therefore, according to the present invention, it is possible to control the equilibrium carbon concentration of the atmospheric gas to be constant no matter how the amount of CO in the atmospheric gas changes. Moreover, the method analyzes two types of composition gases, the amount of CO and the amount of CO 2 in the atmospheric gas, and corrects the target amount of CO 2 according to the fluctuations in the amount of CO, so it is an extremely simple method. Not only is it possible to precisely control the atmospheric gas, but it is also possible to obtain uniform, highly accurate, and excellent quality steel products. Further, according to the present invention, not only enrichment gas but also carrier gas can be significantly reduced, and the demand for resource saving can be fully met. An example of gas composition analysis values obtained during this treatment is shown in the following table.
【表】
この方法で使用されるガス量は最初の真空引き
後のパージに用いられる窒素ガスと、５〜15％の
CO濃度にするための有機液剤CH3OHが最も多
く、これはその後の雰囲気調整に用いられる炭化
水素（エンリツチガス）の添加量程度であり、き
わめて少ない。
同じ容積の熱処理炉を用いて従来の開放式で浸
炭を行なつた場合とこの発明の場合とを比較する
と、変成炉方式に対して16分の１、滴注式に対し
て７分の１のキヤリヤガスで行なうことができる
好結果を得た。そして、浸炭の深さ、表面炭素濃
度などは何ら従来と変りない結果を得た。[Table] The amount of gas used in this method is the nitrogen gas used for purging after the first vacuum, and the 5 to 15%
The organic liquid agent CH 3 OH used to adjust the CO concentration is the most common, and this amount is about the same as the amount of hydrocarbon (enrichment gas) used for subsequent atmosphere adjustment, which is extremely small. Comparing the conventional open carburizing method using a heat treatment furnace with the same volume, the carburization of this invention is 1/16th of the conversion furnace method and 1/7th of the dripping method. Good results were obtained by using a carrier gas. The depth of carburization, surface carbon concentration, etc. were no different from conventional results.
第１図は、この発明に用いる制御装置の実施例
を示すブロツク図、第２図は演算工程の実施例を
示すブロツク図、第３図は被処理鋼材の表面炭素
濃度と浸炭時間との関係を示す線図である。
図中、１は熱処理炉、４は制御弁、６はCO分
析計、８は炭素濃度設定器、９はCO2調節計、１
０は演算装置、１１はCO2分析計である。
Fig. 1 is a block diagram showing an embodiment of the control device used in the present invention, Fig. 2 is a block diagram showing an embodiment of the calculation process, and Fig. 3 is the relationship between the surface carbon concentration of the steel to be treated and the carburizing time. FIG. In the figure, 1 is a heat treatment furnace, 4 is a control valve, 6 is a CO analyzer, 8 is a carbon concentration setting device, 9 is a CO 2 controller, 1
0 is a calculation device, and 11 is a CO 2 analyzer.
Claims (1)
空ポンプで減圧し、その後窒素ガスを炉内に導入
して一定圧まで回復させ、しかる後有機液剤を滴
注して炉内で分解し、その雰囲気組成ガスから
CO2量とCO量とを分析し、CO量の分析値と炉内
温度と鋼材表面の目標炭素濃度とにより雰囲気ガ
スの平衡炭素濃度に相応する目標CO2量を演算し
て設定し、目標CO2量と雰囲気ガス中のCO2量の
分析値との偏差に基づいて炉内に供給される
CxHyのエンリツチガス量を制御することを特徴
とする密閉式ガス浸炭処理方法。1. The inside of the heat treatment furnace in which the treated product is installed is sealed and the pressure is reduced using a vacuum pump, and then nitrogen gas is introduced into the furnace to restore it to a constant pressure. After that, an organic liquid is injected dropwise and decomposed in the furnace, From the atmosphere composition gas
The amount of CO 2 and the amount of CO are analyzed, and the target amount of CO 2 corresponding to the equilibrium carbon concentration of the atmospheric gas is calculated and set based on the analysis value of the amount of CO, the temperature inside the furnace, and the target carbon concentration on the surface of the steel material. Supplied into the furnace based on the deviation between the amount of CO 2 and the analysis value of the amount of CO 2 in the atmospheric gas
A closed gas carburizing method characterized by controlling the amount of CxHy enrichment gas.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8757680A JPS5713170A (en) | 1980-06-27 | 1980-06-27 | Gas carburizing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8757680A JPS5713170A (en) | 1980-06-27 | 1980-06-27 | Gas carburizing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5713170A JPS5713170A (en) | 1982-01-23 |
| JPS641547B2 true JPS641547B2 (en) | 1989-01-11 |
Family
ID=13918823
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8757680A Granted JPS5713170A (en) | 1980-06-27 | 1980-06-27 | Gas carburizing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5713170A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04101655U (en) * | 1991-02-08 | 1992-09-02 | 天龍工業株式会社 | seat with armrests |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4386973A (en) * | 1981-05-08 | 1983-06-07 | General Signal Corporation | Vacuum carburizing steel |
| DE10235131A1 (en) * | 2002-08-01 | 2004-02-19 | Ipsen International Gmbh | Method and device for blackening components |
-
1980
- 1980-06-27 JP JP8757680A patent/JPS5713170A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04101655U (en) * | 1991-02-08 | 1992-09-02 | 天龍工業株式会社 | seat with armrests |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5713170A (en) | 1982-01-23 |
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