JPH0987736A - Method for spheroidizing annealing low alloy steel - Google Patents
Method for spheroidizing annealing low alloy steelInfo
- Publication number
- JPH0987736A JPH0987736A JP24624895A JP24624895A JPH0987736A JP H0987736 A JPH0987736 A JP H0987736A JP 24624895 A JP24624895 A JP 24624895A JP 24624895 A JP24624895 A JP 24624895A JP H0987736 A JPH0987736 A JP H0987736A
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- Prior art keywords
- point
- alloy steel
- low alloy
- spheroidizing
- temperature
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、鋼材の熱処理方法
に関し、詳しくは、塑性加工、切削加工を容易にし、さ
らに機械的性質をも改善する目的で鋼中の炭化物を球状
化する熱処理技術に係わる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for steel materials, and more particularly to a heat treatment technology for spheroidizing carbides in steel for the purpose of facilitating plastic working and cutting, and further improving mechanical properties. Involve
【０００２】[0002]
【従来の技術】自動車および産業機械等に用いられる機
械部品には、従来から炭素鋼または合金鋼が素材として
汎用されている。これら機械部品は、通常、棒鋼線材を
球状化焼なまし、切断、冷間鍛造、最後に切削等の加工
を行うことによって製造されている。その際、冷間鍛造
は、製品の加工精度、量産性及びコストの点で優れてい
るので多用されるが、球状化焼なましは、鋼中炭化物を
球状化し、鋼材の変形抵抗を低下させて冷間鍛造性を向
上させる目的で施されるのである。2. Description of the Related Art Conventionally, carbon steel or alloy steel has been widely used as a raw material for machine parts used in automobiles and industrial machines. These mechanical parts are usually manufactured by subjecting a steel bar wire rod to spheroidizing annealing, cutting, cold forging, and finally cutting. At that time, cold forging is often used because it is excellent in processing accuracy, mass productivity and cost of products, but spheroidizing annealing reduces the deformation resistance of steel materials by spheroidizing carbides in steel. It is applied for the purpose of improving cold forgeability.
【０００３】ところで、その球状化焼なまし方法は、鋼
材に高温且つ長時間の加熱を施すため、熱処理費用がか
さみ、従来から問題視されていた。そこで、解決策とし
て、例えば特公平６−２８９８号公報は、高炭素クロム
軸受鋼の短時間球状化熱処理方法を開示し、具体的には
図２に示すヒートパターンで鋼材を処理することを提案
した。また、特開平４−３６２１２３号公報は、軸受用
鋼素材の製造方法として、図３に示すヒートパターンの
採用を提案している。By the way, in the spheroidizing annealing method, since the steel material is heated at a high temperature for a long time, the heat treatment cost is high and has been regarded as a problem from the past. Therefore, as a solution, for example, Japanese Examined Patent Publication No. 6-2898 discloses a short-time spheroidizing heat treatment method for high carbon chromium bearing steel, and specifically proposes to treat the steel material with the heat pattern shown in FIG. did. Further, Japanese Patent Laid-Open No. 4-362123 proposes the use of the heat pattern shown in FIG. 3 as a method for manufacturing a steel material for bearings.
【０００４】しかしながら、特公平６−２８９８号公報
記載の方法は、従来２０時間かかっていたものを１０時
間にした効果はあっても、依然として長時間で、且つ数
回の繰り返し熱サイクルを加えるものであり、エネルギ
ーコスト及び温度制御の点では上記問題が残されたまま
である。また、特開平４−３６２１２３号公報記載の方
法は、エネルギーコストの点では改善されているもの
の、本来重視すべき炭化物の球状化という点が不十分で
あった。However, the method described in Japanese Examined Patent Publication No. 6-2898 has the effect of changing from the conventional 20 hours to 10 hours to 10 hours, but is still a long time and the heat cycle is repeated several times. In terms of energy cost and temperature control, the above problems still remain. Further, the method described in Japanese Patent Laid-Open No. 4-362123 has been improved in terms of energy cost, but the point of spheroidizing the carbide, which should be emphasized originally, was insufficient.
【０００５】[0005]
【発明が解決しようとする課題】本発明は、かかる事情
を鑑み、エネルギーコストを低減し、安価な熱処理費用
で炭化物の球状化に優れた低合金鋼の球状化焼きなまし
方法を提供することを目的としている。SUMMARY OF THE INVENTION In view of the above circumstances, the present invention aims to provide a spheroidizing annealing method for a low alloy steel which is excellent in spheroidizing of carbides at a low heat treatment cost while reducing energy costs. I am trying.
【０００６】[0006]
【課題を解決するための手段】本発明者は、上記目的を
達成するため、クロムを含む低合金鋼の球状化焼なまし
条件に関して鋭意調査研究を重ね、鋼中炭化物の球状化
には炭化物中に含まれるクロムが大きな影響を及ぼして
いることを見いだし、さらに、球状化焼なましの最高加
熱温度保持前の炭化物中に含まれるクロム量が球状化に
大きく影響していることを確認できた。すなわち、炭化
物中に含まれるクロム量が多いほど、その後の冷却中に
成長する炭化物の核が多く残留し、球状化程度は向上す
ることが明らかとなった。その理由は、最高加熱温度に
おいて炭化物中に含まれるクロム量が多いほど炭化物が
溶解しにくく、特に小さな炭化物の核が残留しやすく、
これらの核がその後の冷却中に成長して球状化するため
である。そして、発明者は、この検討結果を具現化する
ための球状化焼なまし条件を検討し、本発明を創案する
に至った。In order to achieve the above-mentioned object, the present inventor has conducted extensive research into the spheroidizing annealing conditions of a low alloy steel containing chromium, and the spheroidizing of carbides in steel is carried out by spheroidizing carbides. It was found that the chromium contained in the spheroid had a great effect, and it was confirmed that the amount of chromium contained in the carbide before holding the maximum heating temperature during spheroidization had a great influence on the spheroidization. It was That is, it has been clarified that the greater the amount of chromium contained in the carbide, the more the carbide nuclei that grow during the subsequent cooling remain, and the degree of spheroidization is improved. The reason is that as the amount of chromium contained in the carbide increases at the maximum heating temperature, the carbide is more difficult to dissolve, and particularly small nuclei of carbide tend to remain,
This is because these nuclei grow and spheroidize during the subsequent cooling. Then, the inventor studied the spheroidizing annealing conditions for embodying the results of this study, and came up with the present invention.
【０００７】すなわち、本発明は、炭素：０．１５〜
１．５０重量％、クロム：０．１０〜２．５０重量％を
含有する低合金鋼を加熱、冷却して球状化焼なましを行
うにあたり、上記低合金鋼を（Ａ1 点−３０）〜（Ａ1
点−５）℃ の範囲の温度に昇温してその温度に一定時
間保持し、さらに（Ａ1 点＋３０）〜（Ａ1 点＋５０）
℃の範囲の最高温度に昇温、保持してから、Ａ1 点以下
の温度まで１５℃／時間以下の速度で冷却することを特
徴とする低合金鋼の球状化焼なまし方法である。また、
本発明は、上記一定時間を０．５ 〜２．０時間の範囲
でクロム含有量に応じて定めることを特徴とする低合金
鋼の球状化焼なまし方法である。That is, according to the present invention, carbon: 0.15 to
In heating and cooling a low alloy steel containing 1.50% by weight and chromium: 0.10 to 2.50% by weight, the above low alloy steel was subjected to spheroidizing annealing (A 1 point -30). ~ (A 1
Point-5) The temperature is raised to a temperature in the range of ℃, held at that temperature for a certain period of time, and (A 1 point +30) to (A 1 point +50).
A method for spheroidizing and annealing a low alloy steel, which comprises heating and holding at a maximum temperature in the range of ° C and holding it at a temperature of A 1 point or lower at a rate of 15 ° C / hour or less. Also,
The present invention is a spheroidizing annealing method for a low alloy steel, characterized in that the above-mentioned fixed time is determined within a range of 0.5 to 2.0 hours depending on the chromium content.
【０００８】本発明を鋼材の熱処理に採用することで、
鋼材を高温にさらす時間を従来に比べ大幅に短縮できる
ようになり、球状化に要するエネルギーコストを低減で
き、さらには球状化程度も従来より一層促進できるよう
になる。By applying the present invention to the heat treatment of steel,
The time required for exposing the steel material to high temperatures can be greatly shortened as compared with the conventional method, the energy cost required for spheroidizing can be reduced, and the degree of spheroidizing can be further promoted as compared with the conventional method.
【０００９】[0009]
【発明の実施の形態】本発明に係る低合金鋼の球状化焼
なましは、図１のヒートパターンで鋼材を熱処理するこ
とである。そして、本発明で、このヒートパターンを採
用した理由は、以下の通りである。 （１）（Ａ1 変態点−３０）〜（Ａ1 変態点−５）℃に
昇温し、一定時間保持すること、本発明では、鋼材の最
高加熱温度にする前に炭化物中にクロムをできるだけ濃
化させる必要がある。種々の温度で鋼材を保持した後の
炭化物中のクロム量を調査したところ、現実的な保持時
間を考慮した場合Ａ1 変態点直下が最もクロム量が多く
なり、Ａ1 変態点以上では鋼中の炭化物が基地に固溶を
始めるため、Ａ1変態点（以下、単にＡ1 点）より低い
温度が濃化に最も好ましいことがわかった。以上より、
本発明では、鋼材を最高温度に昇温する前に、上記温度
範囲に一定時間保持するようにしたのである。その保持
時間は、０．５ 〜２．０時間の範囲程度で十分であっ
た。その理由は、クロム含有量が多い程、保持時間は少
なくて良いが、０．５時間未満ではその効果がなく、ク
ロム含有量が最小の０．１重量％でも２時間を超える
と、その効果が飽和するためである。 （２）さらに、（Ａ1 点＋３０）〜（Ａ1 点＋５０）℃
に昇温し、保持すること、鋼材の最高加熱温度をこの範
囲に限定した理由は、この温度範囲外では、高すぎても
低過ぎても球状化は不十分となったためである。その理
由は、温度が高すぎると、炭化物の殆どが鋼材中に固溶
してしまい、球状炭化物の各生成サイトの密度が減少
し、結果として冷却時に再生パーライト組織が生じるた
めであり、また温度が低過ぎると、層状パーライトが固
溶せず鋼中に残存するからである。BEST MODE FOR CARRYING OUT THE INVENTION The spheroidizing annealing of a low alloy steel according to the present invention is to heat treat a steel material in the heat pattern shown in FIG. The reason for adopting this heat pattern in the present invention is as follows. (1) To raise the temperature to (A 1 transformation point −30) to (A 1 transformation point −5) ° C. and hold it for a certain period of time. In the present invention, chromium is added to the carbide before reaching the maximum heating temperature of the steel material. It needs to be concentrated as much as possible. When checking the chromium content in the carbide after holding the steel material at various temperatures, realistic case holding considering time becomes large most chromium content is just below the A 1 transformation point, in steel at A 1 transformation point or more It was found that the temperature lower than the A 1 transformation point (hereinafter, simply referred to as A 1 point) is the most preferable for the concentration because the carbide of No. 3 starts to form a solid solution in the matrix. From the above,
In the present invention, the steel material is kept in the above temperature range for a certain period of time before being heated to the maximum temperature. The holding time was sufficient in the range of 0.5 to 2.0 hours. The reason is that the higher the chromium content, the shorter the holding time may be, but the effect is not obtained when the content is less than 0.5 hours, and when the chromium content is 0.1% by weight, which is the minimum, exceeds the effect. Is saturated. (2) Furthermore, (A 1 point +30) to (A 1 point +50) ° C
The reason why the temperature was raised to and maintained at, and the maximum heating temperature of the steel material was limited to this range was that spheroidization was insufficient outside this temperature range, either too high or too low. The reason for this is that if the temperature is too high, most of the carbides form a solid solution in the steel material, the density of each site for the formation of spherical carbides decreases, and as a result, a regenerated pearlite structure occurs during cooling. If is too low, layered pearlite does not form a solid solution and remains in the steel.
【００１０】また、この温度範囲での保持時間は、１．
０ 〜３．０時間程度であれば良い。その理由は、球状
化の程度を低める層状パーライトを溶解するには、１．
０時間未満では不十分であり、３時間を超えると、その
後の冷却中に成長する炭化物の核が基地に固溶して炭化
物の数が減少するからである。 （３）Ａｌ点以下の温度間で１５℃／時間以下の速度で
冷却すること、炭化物の球状化を促進するためには、冷
却中にパーライト組織ではなく球状炭化物を成長させる
必要があり、そのためには、冷却速度、冷却停止温度の
選定が重要である。冷却速度、冷却停止温度を種々変化
させて球状化の程度を調べたところ、安定的に球状化し
た炭化物を得るには、Ａ1 点以下の温度まで１５℃／時
間以下の速度で冷却することが必要であることがわかっ
た。それ以上に冷却速度が速いと、あるいは冷却停止温
度があまりに低過ぎると、炭化物の球状化程度、温度制
御、及び生産性が落ちるので、上記範囲に冷却速度を限
定した。The holding time in this temperature range is 1.
It may be about 0 to 3.0 hours. The reason is that in order to dissolve the layered perlite that reduces the degree of spheroidization, 1.
This is because if it is less than 0 hour, it is insufficient, and if it exceeds 3 hours, the nuclei of carbides growing during the subsequent cooling are solid-dissolved in the matrix and the number of carbides is reduced. (3) Cooling at a rate of 15 ° C./hour or less between temperatures below the Al point, and in order to promote spheroidization of carbides, it is necessary to grow spherical carbides instead of pearlite structure during cooling. For this reason, it is important to select the cooling rate and the cooling stop temperature. When the degree of spheroidization was investigated by variously changing the cooling rate and the cooling stop temperature, in order to obtain a stable spheroidized carbide, cooling to a temperature of A 1 point or less at a rate of 15 ° C./hour or less I found it necessary. If the cooling rate is faster than that, or if the cooling stop temperature is too low, the degree of spheroidization of the carbide, the temperature control, and the productivity decrease, so the cooling rate was limited to the above range.
【００１１】次に、本発明において、低合金鋼の化学組
成を限定した理由及び作用を述べる。 Ｃ：炭素は、鋼中に固溶して基地を強化し、機械部品と
しての十分な強度、耐摩耗性を向上させる有用元素であ
るが、含有量が０．１５重量％未満ではその効果が少な
く、一方１．５０重量％を超えると母材の靭性が著しく
低下するため、Ｃ量は０．１５〜１．５０重量％の範囲
に限定した。Next, the reason and action of limiting the chemical composition of the low alloy steel in the present invention will be described. C: Carbon is a useful element that forms a solid solution in steel to strengthen the matrix and improve sufficient strength and wear resistance as mechanical parts, but if the content is less than 0.15% by weight, its effect is On the other hand, if it exceeds 1.50% by weight, the toughness of the base material remarkably decreases, so the C content is limited to the range of 0.15 to 1.50% by weight.
【００１２】Ｃｒ：クロムは、鋼材の焼入性改善と炭化
物の球状化のために有効に寄与するが、含有量が０．１
０重量％以下ではその効果が小さく、一方２．５０重量
％を超えると炭化物が粗大化することによる切削性の低
下及び化学組成からみてコストアップとなるので、Ｃｒ
量は０．１０〜２．５０重量％の範囲で添加するものと
した。Cr: Chromium effectively contributes to the improvement of hardenability of steel and spheroidization of carbides, but its content is 0.1.
If the amount is less than 0% by weight, the effect is small. On the other hand, if the amount exceeds 2.50% by weight, the carbides are coarsened to lower the machinability and increase the cost in view of the chemical composition.
The amount was 0.10 to 2.50% by weight.
【００１３】[0013]
【実施例】本発明の実施例を以下に説明する。表１に示
す種々の化学組成の鋼を、転炉で溶製し、連続鋳造法で
鋼片とした後、５５ｍｍφの棒鋼に圧延した。この棒鋼
に種々のヒートパターンで球状化焼なましを施した。そ
して、各素材からミクロサンプルを切り出し、顕微鏡を
用いて５０００倍で１０視野ずつ炭化物の形状を観察
し、炭化物の球状化の程度を調べた。その結果を表２に
一括して示す。EXAMPLES Examples of the present invention will be described below. Steels having various chemical compositions shown in Table 1 were melted in a converter, formed into steel pieces by a continuous casting method, and then rolled into 55 mmφ steel bars. This steel bar was subjected to spheroidizing annealing with various heat patterns. Then, a micro sample was cut out from each material, and the shape of the carbide was observed with a microscope at a magnification of 5000 times in 10 fields of view to examine the degree of spheroidization of the carbide. The results are collectively shown in Table 2.
【００１４】表２から明らかなように、本発明に係るヒ
ートパターンで球状化焼なましを実施した場合は、長径
／短径の比が２以下の炭化物量が１００％に近く、加工
性の良いことを示す球状化組織が得られている。これに
対して、比較例Ｎｏ．１１〜２０は、球状化焼なまし条
件が本発明の条件よりはずれているため、いずれも、長
径／短径の比が２以下の炭化物の割合が少なく、不十分
な球状化組織となっていた。As is clear from Table 2, when the spheroidizing annealing is carried out by the heat pattern according to the present invention, the amount of carbide having a major axis / minor axis ratio of 2 or less is close to 100%, and the workability is improved. A spheroidized structure showing good results has been obtained. On the other hand, Comparative Example No. In Nos. 11 to 20, the spheroidizing annealing conditions deviate from the conditions of the present invention, and thus the proportion of carbides having a major axis / minor axis ratio of 2 or less is small, resulting in an insufficient spheroidized structure. It was
【００１５】[0015]
【表１】 [Table 1]
【００１６】[0016]
【表２】 [Table 2]
【００１７】従って、本発明により低合金鋼素材の球状
化焼なましを行うと、最高到達温度や、その前のクロム
濃化処理温度での保持時間が短くても、球状化が十分に
達成できることがわかった。つまり、エネルギーコスト
は、従来に比べて低減でき、安価な球状化処理が可能と
なった。Therefore, when the low alloy steel material is spheroidized and annealed according to the present invention, the spheroidization is sufficiently achieved even if the maximum reaching temperature and the holding time at the previous chromium concentration treatment temperature are short. I knew I could do it. That is, the energy cost can be reduced as compared with the conventional one, and the inexpensive spheroidizing treatment can be performed.
【００１８】[0018]
【発明の効果】以上述べたように、本発明により、安価
で且つ球状化程度に優れた炭化物を有する低合金鋼の製
造ができるようになり、産業上極めて有用な効果がもた
らされた。As described above, according to the present invention, it becomes possible to manufacture a low alloy steel having a carbide which is inexpensive and has an excellent degree of spheroidization, and brings about an extremely useful effect industrially.
【図１】本発明に係る低合金鋼の球状化焼なまし方法を
示す温度パターンの一例を示す図である。FIG. 1 is a diagram showing an example of a temperature pattern showing a spheroidizing annealing method for a low alloy steel according to the present invention.
【図２】特公平６−２８９８号公報記載の温度パターン
を示す図である。FIG. 2 is a diagram showing a temperature pattern described in JP-B-6-2898.
【図３】特開平４−３６２１２３号公報記載の温度パタ
ーンを示す図である。FIG. 3 is a diagram showing a temperature pattern described in JP-A-4-362123.
Claims (2)
ム：０．１０〜２．５０重量％を含有する低合金鋼を加
熱、冷却して球状化焼なましを行うにあたり、 上記低合金鋼を（Ａ1 点−３０）〜（Ａ1 点−５）℃
の範囲の温度に昇温してその温度に一定時間保持し、さ
らに（Ａ1 点＋３０）〜（Ａ1 点＋５０）℃の範囲の最
高温度に昇温、保持してから、Ａ1 点以下の温度まで１
５℃／時間以下の速度で冷却することを特徴とする低合
金鋼の球状化焼なまし方法。1. When heating and cooling a low alloy steel containing carbon: 0.15 to 1.50% by weight and chromium: 0.10 to 2.50% by weight, the spheroidizing annealing is performed as described above. Low alloy steel (A 1 point −30) to (A 1 point −5) ° C.
And heated to a range of temperature was kept constant time that temperature, further (A 1 point + 30) - heated to a maximum temperature in the range of (A 1 point +50) ° C., and held there, following point A Up to 1
A spheroidizing annealing method for low alloy steel, which comprises cooling at a rate of 5 ° C / hour or less.
範囲内でクロム含有量に応じて定めることを特徴とする
請求項１記載の低合金鋼の球状化焼なまし方法。2. The method for spheroidizing and annealing a low alloy steel according to claim 1, wherein the certain period of time is set within a range of 0.5 to 2.0 hours according to the chromium content.
Priority Applications (1)
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|---|---|---|---|
| JP24624895A JP3915128B2 (en) | 1995-09-25 | 1995-09-25 | Method of spheroidizing annealing of low alloy steel |
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| JP24624895A JP3915128B2 (en) | 1995-09-25 | 1995-09-25 | Method of spheroidizing annealing of low alloy steel |
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| JPH0987736A true JPH0987736A (en) | 1997-03-31 |
| JP3915128B2 JP3915128B2 (en) | 2007-05-16 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005078297A1 (en) * | 2004-02-12 | 2005-08-25 | Ntn Corporation | Shell type needle roller bearing, support structure of compressor spindle, and support structure of piston pump drive part |
| JP2008088448A (en) * | 2006-09-29 | 2008-04-17 | Sanyo Special Steel Co Ltd | Method for annealing low-carbon steel containing cr |
| CN103572013A (en) * | 2013-11-19 | 2014-02-12 | 东北大学 | Spheroidizing annealing method of 40Cr steel |
| JP2014201813A (en) * | 2013-04-08 | 2014-10-27 | 株式会社神戸製鋼所 | Method for manufacturing cold forging steel material |
| CN104451048A (en) * | 2014-10-23 | 2015-03-25 | 杭州嘉诺德金属冷拉有限公司 | Anti-cracking boron steel isothermal spheroidizing annealing method |
| CN106521107A (en) * | 2016-10-17 | 2017-03-22 | 江阴兴澄特种钢铁有限公司 | Novel spheroidizing annealing method for low-carbon bainite steel |
-
1995
- 1995-09-25 JP JP24624895A patent/JP3915128B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005078297A1 (en) * | 2004-02-12 | 2005-08-25 | Ntn Corporation | Shell type needle roller bearing, support structure of compressor spindle, and support structure of piston pump drive part |
| JP2008088448A (en) * | 2006-09-29 | 2008-04-17 | Sanyo Special Steel Co Ltd | Method for annealing low-carbon steel containing cr |
| JP2014201813A (en) * | 2013-04-08 | 2014-10-27 | 株式会社神戸製鋼所 | Method for manufacturing cold forging steel material |
| CN103572013A (en) * | 2013-11-19 | 2014-02-12 | 东北大学 | Spheroidizing annealing method of 40Cr steel |
| CN104451048A (en) * | 2014-10-23 | 2015-03-25 | 杭州嘉诺德金属冷拉有限公司 | Anti-cracking boron steel isothermal spheroidizing annealing method |
| CN106521107A (en) * | 2016-10-17 | 2017-03-22 | 江阴兴澄特种钢铁有限公司 | Novel spheroidizing annealing method for low-carbon bainite steel |
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| JP3915128B2 (en) | 2007-05-16 |
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