JP3878241B2 - Highly efficient and uniform steel heat treatment method - Google Patents
Highly efficient and uniform steel heat treatment method Download PDFInfo
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- JP3878241B2 JP3878241B2 JP06842196A JP6842196A JP3878241B2 JP 3878241 B2 JP3878241 B2 JP 3878241B2 JP 06842196 A JP06842196 A JP 06842196A JP 6842196 A JP6842196 A JP 6842196A JP 3878241 B2 JP3878241 B2 JP 3878241B2
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- temperature
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- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は厚鋼板、形鋼などの鋼材の熱処理方法に関するものである。
【０００２】
【従来の技術】
一般的に、鋼材の熱処理は加熱炉に鋼材を挿入することにより行われる場合が多い。通常は所定の温度以上に鋼材の温度が上昇することを避けるために、目的とする鋼材の熱処理温度とほぼ同等の温度に炉内の雰囲気温度を設定する。このため、鋼材の昇温速度は極めて遅く、炉加熱による熱処理の生産性は一般に低い。
【０００３】
線材のように体積あるいは重量の小さい場合は、通電加熱や高周波誘導加熱などを用いることができるが、体積あるいは重量の大きい厚板、形鋼などの鋼材の熱処理には不適である。熱処理の生産性を高めるためには、炉の設定温度を高めて炉内雰囲気温度と被加熱鋼材の温度差を大きくすると良いが、この方法では、鋼材の周囲が過度に加熱されて鋼材内部の温度分布が不均一になり、材質変動の原因となる。このため、効率的で且つ鋼材を均一な温度に加熱できる熱処理法が強く求められてきた。
【０００４】
【発明が解決しようとする課題】
本発明は、高効率で且つ均一性の良い鋼材の熱処理方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、上記のような従来の炉加熱による熱処理法の欠点を有利に排除しうる、現行の熱処理炉の設定温度を制御して高効率で且つ均一性良く鋼材を熱処理する方法であり、その要旨は次の通りである。
（１）直火式のバーナー方式、ラジアントチューブ方式、電気炉方式のいずれかの方式の加熱炉において、当該炉の入り側を目的とする熱処理温度である４５０〜６７０℃より２００℃以上高く設定し、炉の出側に向かって段階的に設定炉温を低下させ、炉の出口前での炉の設定温度を前記目的とする熱処理温度±２０℃以内とすることを特徴とする高効率で且つ均一性の良い厚鋼板あるいは形鋼の熱処理方法。
【０００６】
【発明の実施の形態】
以下本発明について詳細に説明する。本発明の根幹をなす技術思想は以下のとおりである。
一般に、炉内雰囲気温度と被加熱鋼材の温度差が大きくなると、鋼材の昇温速度は大きくなるため、熱処理の効率をあげるためには炉内雰囲気温度と被加熱鋼材の温度差を大きくすることが望ましい。しかし炉内では、鋼材は表面から加熱されるため表層部の温度は内部より高くなる。炉の雰囲気温度まで鋼材温度が上昇すれば、鋼材内部の温度分布は解消される方向に向かうが、炉の雰囲気温度と鋼材温度に差が有る限り温度差は解消されない。
【０００７】
よって、炉の雰囲気温度を目的とする鋼材の熱処理温度より高く設定すると、必然的に鋼材内部の温度差が増加し材質変動をもたらすことになる。このような温度差や材質変動を防止するためには、炉内雰囲気温度を低く設定して、鋼材表層部あるいは外周部が過度に加熱されるのを防ぐしかなった。
【０００８】
しかるに本発明者らは、炉内で鋼材を連続的に搬送して熱処理する場合において、炉の内部の雰囲気温度に傾斜をつけ、炉の入り側を高温に、出側を低温に設定することを特徴とする高効率で且つ均一性の良い熱処理方法を見出した。すなわち、炉の入り側を高温に設定することにより、炉内雰囲気温度と被加熱鋼材の温度差を大きくし、鋼材の昇温速度を高めことが可能である。しかる後に、被加熱鋼材は低温に設定した炉の出側を通過するために鋼材内部の温度差は収斂し、均一な熱処理が可能となる。
【０００９】
効率を最も高めるためには、炉の入り側を目的とする熱処理温度より２００℃以上高く設定することが効果的である。２００℃を切ると効率が低下し、効果が小さくなる。また均一性を高めるためには、炉の出側に向かって徐々に設定炉温を低下させ、炉の出口前での炉の設定温度を目的とする熱処理温度±２０℃以内とすることが有効である。これ以上炉の設定温度と目的とする熱処理温度の差が大きくなると、鋼材内部の温度のばらつきが増加し、材質も不安定になる。
【００１０】
また熱処理炉は、被熱処理材の通過に伴う炉温の低下を保証しうる温度制御機能を備えたものが望ましい。加熱方法は直火式のバーナー、ラジアントチューブなどいずれでも良く、特に定める必要はない。熱処理後は放冷しても良いし、可及的すみやかに水冷しても本発明の特徴を損なうことはない。本発明はあらゆる寸法および化学成分の鋼材の熱処理に対して有効であるため、とくにその寸法や化学成分を定める必要はない。
【００１１】
【実施例】
次に、本発明を実施例に基づいて詳細に説明する。
まず表１（熱処理材の寸法）に示す寸法の厚板および形鋼について、表２（熱処理炉▲１▼の仕様一覧表）および表３（熱処理炉▲２▼の仕様一覧表）に示す熱処理炉を用いて、表４（熱処理炉条件）に示す本発明方法および比較方法の熱処理を適用した。
【００１２】
図１は、熱処理される厚板の寸法および測温位置を示した図である。測温は図中の位置ａ，ｂ，ｃ，ｄに熱電対を板厚中心部まで埋め込んで行った。図２は、熱処理される形鋼の寸法および測温位置を示した図である。測温は図中の位置ａ，ｂ，ｃ，ｄに熱電対を板厚中心部まで埋め込んで行った。
【００１３】
その結果、表５（熱処理時間および鋼材内温度分布）に示したような熱処理時間と鋼材内部の温度分布が得られ、明らかに本発明により熱処理時間が短縮され、さらに鋼材内部の温度分布も低減しており、本発明は有効である。
【００１４】
【表１】
【表２】
【表３】
【表４】
【表５】
表５によると、同じサイズの鋼材で熱処理時間を比較した場合、本発明の炉内雰囲気温度を段階的に低下させて設定した熱処理法で要する熱処理時間は、炉温を低温の一定温度に設定した従来の熱処理法（No．２，４，１２，１４）で要する熱処理時間より明らかに短い。この効果は炉の規模の大小、鋼材の大小を問わずに発揮される。
【００２０】
さらに、本発明の熱処理を施した鋼材内部の温度差は極めて均一であり、炉温を低温の一定温度に設定した従来の熱処理法の場合と遜色ない。また、炉温を高温の一定温度に設定した熱処理法の場合（No．６）と比較すると、明らかに温度差は小さくなっていることがわかる。
【００２１】
炉の入り側温度を目的とする熱処理温度より１００℃高く設定した場合（No．８）は、熱処理に要する時間が従来法とあまり変わらず効率の面で問題がある。炉の出側温度を目的とする熱処理温度より３０℃高く設定した場合（No．１０）は、鋼材内部の温度分布が大きく実用に適さない。
【００２２】
【発明の効果】
本発明によれば、高効率で且つ均一性の良い鋼材が得られ、産業上の寄与は多大である。
【図面の簡単な説明】
【図１】熱処理される厚板の寸法および測温位置を示した図である。
【図２】熱処理される形鋼の寸法および測温位置を示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment method for steel materials such as thick steel plates and section steels.
[0002]
[Prior art]
In general, heat treatment of steel is often performed by inserting the steel into a heating furnace. Usually, in order to prevent the temperature of the steel material from rising above a predetermined temperature, the atmospheric temperature in the furnace is set to a temperature substantially equal to the heat treatment temperature of the target steel material. For this reason, the rate of temperature rise of steel materials is extremely slow, and the productivity of heat treatment by furnace heating is generally low.
[0003]
When the volume or weight is small, such as a wire, electric heating or high-frequency induction heating can be used, but it is unsuitable for heat treatment of a steel material such as a thick plate or shape steel having a large volume or weight. In order to increase the productivity of heat treatment, it is better to increase the set temperature of the furnace to increase the temperature difference between the furnace atmosphere temperature and the steel material to be heated. The temperature distribution becomes non-uniform, causing material fluctuations. For this reason, there has been a strong demand for a heat treatment method that is efficient and can heat a steel material to a uniform temperature.
[0004]
[Problems to be solved by the invention]
An object of this invention is to provide the heat processing method of steel materials with high efficiency and favorable uniformity.
[0005]
[Means for Solving the Problems]
The present invention is a method for heat-treating a steel material with high efficiency and uniformity by controlling the set temperature of the current heat treatment furnace, which can advantageously eliminate the disadvantages of the conventional heat treatment method by furnace heating as described above, The summary is as follows.
(1) In a heating furnace of any one of a direct-fired burner system, a radiant tube system, and an electric furnace system, it is set to 200 ° C. or more higher than 450 to 670 ° C. which is a heat treatment temperature for the entrance side of the furnace. and, set stepwise furnace temperature was lowered to towards the exit side of the furnace, the set temperature of the furnace in front outlet of the furnace at a high efficiency, characterized in that within the heat treatment temperature ± 20 ° C. to the object And heat treatment method for thick steel plate or section steel with good uniformity.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below. The technical idea forming the basis of the present invention is as follows.
In general, when the temperature difference between the furnace atmosphere temperature and the steel material to be heated increases, the temperature rise rate of the steel material increases. Therefore, to increase the efficiency of heat treatment, the temperature difference between the furnace atmosphere temperature and the steel material to be heated should be increased. Is desirable. However, since the steel material is heated from the surface in the furnace, the temperature of the surface layer portion is higher than that inside. If the steel material temperature rises to the furnace ambient temperature, the temperature distribution inside the steel material tends to be eliminated, but the temperature difference is not eliminated as long as there is a difference between the furnace atmosphere temperature and the steel material temperature.
[0007]
Therefore, if the furnace atmosphere temperature is set higher than the intended heat treatment temperature of the steel material, the temperature difference inside the steel material inevitably increases, resulting in material fluctuations. In order to prevent such temperature difference and material fluctuation, the furnace atmosphere temperature must be set low to prevent the steel surface layer portion or the outer peripheral portion from being excessively heated.
[0008]
However, in the case where the steel material is continuously conveyed and heat-treated in the furnace, the present inventors set the inclination of the atmosphere temperature inside the furnace, and set the entrance side of the furnace to a high temperature and the exit side to a low temperature. The present inventors have found a highly efficient and uniform heat treatment method characterized by That is, by setting the entrance side of the furnace to a high temperature, it is possible to increase the temperature difference between the furnace atmosphere temperature and the steel material to be heated, and increase the temperature rise rate of the steel material. After that, since the steel material to be heated passes through the exit side of the furnace set at a low temperature, the temperature difference inside the steel material is converged, and a uniform heat treatment becomes possible.
[0009]
In order to maximize the efficiency, it is effective to set the temperature higher by 200 ° C. than the intended heat treatment temperature on the furnace entrance side. When the temperature is lower than 200 ° C., the efficiency is lowered and the effect is reduced. In order to improve the uniformity, it is effective to gradually lower the set furnace temperature toward the exit side of the furnace, and to set the set temperature of the furnace in front of the furnace outlet to within the intended heat treatment temperature ± 20 ° C. It is. If the difference between the set temperature of the furnace and the target heat treatment temperature becomes larger than this, the temperature variation in the steel material increases and the material becomes unstable.
[0010]
Further, it is desirable that the heat treatment furnace has a temperature control function capable of guaranteeing a decrease in the furnace temperature accompanying the passage of the material to be heat treated. The heating method may be any of a direct-fired burner, a radiant tube, etc., and does not need to be specifically defined. After the heat treatment, it may be allowed to cool, or even as quickly as possible with water, the characteristics of the present invention will not be impaired. Since the present invention is effective for heat treatment of steel materials having any size and chemical composition, it is not necessary to define the dimensions and chemical composition.
[0011]
【Example】
Next, the present invention will be described in detail based on examples.
First of all, the heat treatment shown in Table 2 (specification list of heat treatment furnace (1)) and Table 3 (specification table of heat treatment furnace (2)) for thick plates and sections with the dimensions shown in Table 1 (dimensions of heat treatment material) Using the furnace, the heat treatment of the method of the present invention and the comparative method shown in Table 4 (heat treatment furnace conditions) were applied.
[0012]
FIG. 1 is a diagram showing dimensions and temperature measuring positions of a thick plate to be heat-treated. The temperature measurement was performed by embedding a thermocouple up to the center of the plate thickness at positions a, b, c, and d in the figure. FIG. 2 is a diagram showing dimensions and temperature measuring positions of the shape steel to be heat-treated. The temperature measurement was performed by embedding a thermocouple up to the center of the plate thickness at positions a, b, c, and d in the figure.
[0013]
As a result, the heat treatment time and the temperature distribution inside the steel as shown in Table 5 (heat treatment time and steel temperature distribution) are obtained. The heat treatment time is obviously shortened by the present invention, and the temperature distribution inside the steel is also reduced. Therefore, the present invention is effective.
[0014]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
[Table 5]
According to Table 5, when the heat treatment times of steel materials of the same size are compared, the heat treatment time required for the heat treatment method set by gradually reducing the furnace atmosphere temperature of the present invention sets the furnace temperature to a constant low temperature. It is clearly shorter than the heat treatment time required for the conventional heat treatment method (No. 2, 4, 12, 14). This effect is exhibited regardless of the size of the furnace and the size of the steel material.
[0020]
Furthermore, the temperature difference inside the steel material subjected to the heat treatment of the present invention is extremely uniform, which is comparable to the conventional heat treatment method in which the furnace temperature is set to a constant low temperature. In addition, it can be seen that the temperature difference is clearly smaller when compared with the case of the heat treatment method in which the furnace temperature is set to a high constant temperature (No. 6).
[0021]
When the furnace entry side temperature is set to 100 ° C. higher than the intended heat treatment temperature (No. 8), the time required for the heat treatment is not much different from the conventional method and there is a problem in terms of efficiency. When the outlet temperature of the furnace is set 30 ° C. higher than the target heat treatment temperature (No. 10), the temperature distribution inside the steel material is large and not suitable for practical use.
[0022]
【The invention's effect】
According to the present invention, a steel material with high efficiency and good uniformity can be obtained, and the industrial contribution is great.
[Brief description of the drawings]
FIG. 1 is a diagram showing dimensions and temperature measurement positions of a thick plate to be heat-treated.
FIG. 2 is a diagram showing dimensions and temperature measuring positions of a shape steel to be heat-treated.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06842196A JP3878241B2 (en) | 1996-03-25 | 1996-03-25 | Highly efficient and uniform steel heat treatment method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP06842196A JP3878241B2 (en) | 1996-03-25 | 1996-03-25 | Highly efficient and uniform steel heat treatment method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09256053A JPH09256053A (en) | 1997-09-30 |
| JP3878241B2 true JP3878241B2 (en) | 2007-02-07 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP06842196A Expired - Fee Related JP3878241B2 (en) | 1996-03-25 | 1996-03-25 | Highly efficient and uniform steel heat treatment method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3878241B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7857919B2 (en) | 2003-06-16 | 2010-12-28 | Jfe Steel Corporation | Process for producing steel product and production facility therefor |
| JP5482539B2 (en) * | 2010-07-26 | 2014-05-07 | 新日鐵住金株式会社 | Determination of furnace temperature of continuous heat treatment furnace |
-
1996
- 1996-03-25 JP JP06842196A patent/JP3878241B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
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| JPH09256053A (en) | 1997-09-30 |
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