JP2803108B2 - Heat treatment method for steel - Google Patents
Heat treatment method for steelInfo
- Publication number
- JP2803108B2 JP2803108B2 JP63277680A JP27768088A JP2803108B2 JP 2803108 B2 JP2803108 B2 JP 2803108B2 JP 63277680 A JP63277680 A JP 63277680A JP 27768088 A JP27768088 A JP 27768088A JP 2803108 B2 JP2803108 B2 JP 2803108B2
- Authority
- JP
- Japan
- Prior art keywords
- heat treatment
- furnace
- gas
- steel
- dew point
- 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 - Fee Related
Links
Description
【発明の詳細な説明】 〔産業上の利用分野〕 この発明は鋼の熱処理方法に関し、さらに詳しくは鋼
を無脱炭無浸炭状態で熱処理できる熱処理方法に関す
る。Description: TECHNICAL FIELD The present invention relates to a heat treatment method for steel, and more particularly to a heat treatment method capable of heat treating steel in a non-decarburized and non-carburized state.
従来無脱炭無浸炭状態で鋼の熱処理をおこなう方法と
しては、熱処理炉内にRXガスやNXガスを供給してカーボ
ンポテンシヤルを制御する方法が一般的であるが、ガス
発生装置が必要で設置スペースがかさみ保守に手間がか
かるとともに、大量のガス使用のため運転費がかさみ、
使用ガスによつては爆発のおそれがあり、さらに鋼種や
熱処理温度の変更に伴う雰囲気の切換にも時間がかかる
という多くの欠点がある。Conventionally, as a method of heat-treating steel without decarburization and no carburization, a method of supplying RX gas or NX gas into a heat treatment furnace to control the carbon potential is generally used, but a gas generator is required and installed Space is bulky, maintenance is troublesome, and operating costs increase due to the large amount of gas used.
Depending on the gas used, there is a risk of explosion, and there are many disadvantages in that it takes time to switch the atmosphere due to changes in the steel type and heat treatment temperature.
そこで気密性の高い熱処理炉内にN2ガスのみを送入
し、N2ガス雰囲気中で熱処理をおこなうことも試みられ
ている。Therefore, it has been attempted to carry out heat treatment in an N 2 gas atmosphere by feeding only N 2 gas into a highly airtight heat treatment furnace.
ところがこの熱処理法の場合は、市販のN2ガス中には
微量ではあるがたとえば５〜10ppm程度のO2ガスが混入
しており、また炉の気密性を上げてもシール部から空気
が炉内に侵入することは避けることができないため、こ
れらによるO2ガスが鋼の脱炭あるいは酸化をひきおこす
という問題がある。このためO2ガスを全く含まない高純
度のN2ガスを使用し、かつ熱処理炉の気密性を極度に高
めて炉内を超微量O2分圧に維持しない限り、高品質の熱
処理は困難であり、実用炉において経済的にN2ガスのみ
により熱処理をおこなうことは困難視されていた。However, in the case of this heat treatment method, a small amount of, for example, about 5 to 10 ppm of O 2 gas is mixed in the commercially available N 2 gas. Since it is unavoidable to infiltrate the inside of the steel, there is a problem that the O 2 gas by these causes decarburization or oxidation of the steel. For this reason, high-quality heat treatment is difficult unless high-purity N 2 gas containing no O 2 gas is used and the airtightness of the heat treatment furnace is extremely increased to maintain a very small O 2 partial pressure inside the furnace. Therefore, it has been considered difficult to economically perform heat treatment using only N 2 gas in a practical furnace.
この発明は上記従来の問題点を解決するもので、N2ガ
ス雰囲気中における熱処理を経済的に実施できる鋼の熱
処理方法を提供しようとするものである。The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for heat-treating steel in which a heat treatment in an N 2 gas atmosphere can be economically performed.
上記問題点を解決すべく発明者はN2ガス雰囲気中での
熱処理方法について鋭意研究を重ねた結果、炉内へ微量
のCOガスを供給することにより炉内のO2ガスを還元さ
せ、脱炭を確実に防止できることを見出してこの発明を
完成するに至つた。In order to solve the above problems, the inventor conducted intensive research on a heat treatment method in an N 2 gas atmosphere.As a result, a small amount of CO gas was supplied to the furnace to reduce the O 2 gas in the furnace and to remove the gas. The inventors have found that charcoal can be reliably prevented, and have completed the present invention.
すなわちこの発明の方法は、熱処理炉内へN2ガスのみ
を供給してN2ガス雰囲気中で熱処理をおこなう鋼の熱処
理方法において、前記熱処理炉内へCOガスを供給して炉
内のCO濃度を500〜15000ppmに維持するとともに、炉内
雰囲気の露点を−40℃以下に維持しつつ、鋼の熱処理を
おこなうことを特徴とする鋼の熱処理方法である。That is, the method of the present invention is a heat treatment method for steel in which only N 2 gas is supplied into a heat treatment furnace and heat treatment is performed in an N 2 gas atmosphere. Is a heat treatment method for steel while maintaining the dew point of the furnace atmosphere at −40 ° C. or lower while maintaining the temperature at 500 to 15000 ppm.
この発明の対象となる鋼は、脱炭あるいは酸化を抑え
る必要のある機械構造用炭素鋼および合金鋼などであ
る。The steels to which the present invention is applied include carbon steels for machine structural use and alloy steels for which decarburization or oxidation needs to be suppressed.
この発明においては、熱処理炉内へ供給されたN2ガス
に混入しているO2、および熱処理炉のシール部から炉内
へ侵入する空気中のO2は、熱処理炉内へ供給されたCOガ
スと反応して還元し、鋼の脱炭が防止される。CO In the present invention, O 2 in the air entering from the sealing portion of the O 2, and the heat treatment furnace mixed in N 2 gas supplied to the heat treatment furnace into the furnace is supplied to the heat treatment furnace It reacts with the gas to reduce it, preventing the decarburization of steel.
熱処理炉内のCO濃度を500〜15000ppmとしたのは、こ
の条件で鋼の脱炭および浸炭がともに僅少量に抑制され
るからであり、CO濃度が500ppm未満では鋼の脱炭が、CO
濃度が15000ppmを越えると鋼の浸炭が、それぞれ進行す
るので好ましくない。The reason for setting the CO concentration in the heat treatment furnace to 500 to 15000 ppm is that under these conditions, both decarburization and carburization of steel are suppressed to a very small amount.
If the concentration exceeds 15000 ppm, carburization of the steel proceeds, which is not preferable.
また炉内雰囲気の露点を−40℃以下（低湿度）とした
のは、上記露点が−40℃を越える（高湿度になる）と、
鋼の脱炭および酸化が進行し好ましくないからである。
この炉内雰囲気の露点は、炉内に供給されるN2ガスの露
点と熱処理炉の気密性により影響を受けるものである
が、市販のN2ガスの露点は−70℃前後で限界があるた
め、熱処理炉の気密性が大きく関係する。すなわち熱処
理炉の気密性が劣る場合は、COガスの供給量を多くすれ
ば、炉内のCO濃度を前記規定値内に維持することはでき
るが、多量に炉内に侵入する空気とCOガスとの反応によ
りCO2およびH2Oが増加し、炉内雰囲気の露点が−40℃以
上となつてしまう。従つて炉内雰囲気の露点を−40℃以
下に維持するためには、炉の気密性を向上させる必要が
あり、これによつてCOガスの炉内への供給量は少量で済
むことになり、運転コストは安価なものとなる。なお発
明者の実験によると上記の露点維持のための炉の気密性
は、通常の真空熱処理炉程度の気密性を有すればよい。The reason why the dew point of the furnace atmosphere is -40 ° C or lower (low humidity) is that when the dew point exceeds -40 ° C (high humidity),
This is because the decarburization and oxidation of the steel proceed, which is not preferable.
The dew point of the atmosphere in the furnace is affected by the dew point of the N 2 gas supplied into the furnace and the airtightness of the heat treatment furnace, but the dew point of a commercially available N 2 gas has a limit at around −70 ° C. Therefore, the airtightness of the heat treatment furnace is significantly related. In other words, when the airtightness of the heat treatment furnace is poor, if the supply amount of CO gas is increased, the CO concentration in the furnace can be maintained within the above specified value, but a large amount of air and CO gas entering the furnace can be maintained. The reaction with increases CO 2 and H 2 O, and the dew point of the furnace atmosphere becomes −40 ° C. or higher. Therefore, in order to maintain the dew point of the furnace atmosphere at −40 ° C. or lower, it is necessary to improve the airtightness of the furnace, which requires a small amount of CO gas to be supplied into the furnace. In addition, the operating cost is low. According to the experiment of the inventor, the airtightness of the furnace for maintaining the dew point described above may be as high as that of a normal vacuum heat treatment furnace.
以下この発明の実施例を説明する。 Hereinafter, embodiments of the present invention will be described.
試料としてS45C材の短尺丸棒材（直径28mm、長さ50m
m）を用い、バツチ式熱処理炉により焼鈍処理を第１図
の温度（炉温）線図に従つておこなつた。N2ガスとして
は純度99.99％、露点−75℃のものを用い、炉内へのN2
ガス送気量は毎時4m3Nとした。一方COガスは、ガスボン
ベから熱処理中一定送気量で炉内へ供給し、この送気量
を２/H〜60/Hに変えることにより炉内のCO濃度を５
段階にわたつて変化させ、それぞれ前記熱処理をおこな
つた。第１図の炉内露点、炉内CO量、およびCO送気量
は、試験No.4の試料についての実測データを示す。また
比較例として、炉内のCO濃度を100ppmおよび20000ppmと
した場合についても、前記実施例と同条件で熱処理をお
こなつた。S45C short round bar (diameter 28mm, length 50m)
m), an annealing treatment was carried out by a batch type heat treatment furnace according to the temperature (furnace temperature) diagram of FIG. N used as a purity of 99.99%, dew point -75 ° C. as 2 gas, N 2 into the furnace
The gas supply rate was 4 m 3 N / h. On the other hand, CO gas is supplied from the gas cylinder into the furnace at a constant gas supply during the heat treatment, and the gas supply is changed from 2 / H to 60 / H to reduce the CO concentration in the furnace to 5 / H.
The heat treatment was performed in each step. The in-furnace dew point, the in-furnace CO amount, and the CO gas supply amount in FIG. 1 show the actually measured data of the sample of Test No. 4. Further, as a comparative example, when the CO concentration in the furnace was set to 100 ppm and 20000 ppm, the heat treatment was performed under the same conditions as those in the above example.
このようにして得た各試料について、脱炭層深さおよ
び浸炭層深さを測定したところ、第１表に示す結果を得
た。なお炉内雰囲気の露点は試験No.1〜７では−40℃以
下に維持されていた。炉内のCO濃度は熱処理の進行によ
り多少変動するので第１表にはその最大値を示してあ
る。When the depth of the decarburized layer and the depth of the carburized layer of each sample thus obtained were measured, the results shown in Table 1 were obtained. The dew point of the furnace atmosphere was maintained at -40 ° C or lower in Test Nos. 1 to 7. Since the CO concentration in the furnace fluctuates somewhat with the progress of the heat treatment, Table 1 shows its maximum value.
上記表に示されるように、COガス濃度および炉内雰囲
気露点がこの発明の限定値範囲内にある実施例の方法に
よれば、上記限定値範囲外の条件で試験をおこなつた比
較例のものに比べて、脱炭および浸炭量が０〜微量であ
るすぐれた熱処理品を得ることができた。 As shown in the above table, according to the method of the embodiment in which the CO gas concentration and the furnace dew point are within the limited value range of the present invention, the comparative example in which the test was performed under the conditions outside the limited value range was performed. An excellent heat-treated product in which the amount of decarburization and carburization was 0 to a small amount as compared with that of the product was obtained.
以上説明したようにこの発明によれば、少量のCOガス
を炉内へ供給することにより、炉内のO2による脱炭およ
び浸炭を防止でき、N2ガス雰囲気中における無脱炭無浸
炭状態での熱処理を経済的に実施できる。またCOガスは
供給量の複雑な制御を必要としないので、設備費および
運転費は安価ですみ、爆発の危険性も少なく安全に熱処
理をおこなうことができる。As described above, according to the present invention, by supplying a small amount of CO gas into the furnace, decarburization and carburization due to O 2 in the furnace can be prevented, and the decarburized and uncarburized state in the N 2 gas atmosphere can be prevented. Can be economically performed. In addition, since the supply of CO gas does not require complicated control, equipment costs and operating costs are low, and there is little risk of explosion, and heat treatment can be performed safely.
第１図はこの発明の実施例を示すタイムチヤートであ
る。FIG. 1 is a time chart showing an embodiment of the present invention.
Claims (1)
雰囲気中で熱処理をおこなう鋼の熱処理方法において、
前記熱処理炉内へCOガスを供給して炉内のCO濃度を500
〜15000ppmに維持するとともに、炉内雰囲気の露点を−
40℃以下に維持しつつ、鋼の熱処理をおこなうことを特
徴とする鋼の熱処理方法。1. A method for heat treating steel in which only N 2 gas is supplied into a heat treatment furnace and heat treatment is performed in an N 2 gas atmosphere.
Supply CO gas into the heat treatment furnace to reduce the CO concentration in the furnace to 500.
~ 15000 ppm, and the dew point of the furnace atmosphere
A heat treatment method for steel, wherein the heat treatment is performed on the steel while maintaining the temperature at 40 ° C or lower.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63277680A JP2803108B2 (en) | 1988-11-02 | 1988-11-02 | Heat treatment method for steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63277680A JP2803108B2 (en) | 1988-11-02 | 1988-11-02 | Heat treatment method for steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02125810A JPH02125810A (en) | 1990-05-14 |
| JP2803108B2 true JP2803108B2 (en) | 1998-09-24 |
Family
ID=17586809
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63277680A Expired - Fee Related JP2803108B2 (en) | 1988-11-02 | 1988-11-02 | Heat treatment method for steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2803108B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6620262B1 (en) | 1997-12-26 | 2003-09-16 | Nsk Ltd. | Method of manufacturing inner and outer races of deep groove ball bearing in continuous annealing furnace |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5582729A (en) * | 1978-12-14 | 1980-06-21 | Kobe Steel Ltd | Heat treating method for steel material |
| JPS5980713A (en) * | 1982-10-29 | 1984-05-10 | Oriental Eng Kk | Heat treatment of steel product accompanied by no decarburization |
-
1988
- 1988-11-02 JP JP63277680A patent/JP2803108B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02125810A (en) | 1990-05-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |