JPH03138315A - Heat treatment for ferritic stainless steel - Google Patents
Heat treatment for ferritic stainless steelInfo
- Publication number
- JPH03138315A JPH03138315A JP27548289A JP27548289A JPH03138315A JP H03138315 A JPH03138315 A JP H03138315A JP 27548289 A JP27548289 A JP 27548289A JP 27548289 A JP27548289 A JP 27548289A JP H03138315 A JPH03138315 A JP H03138315A
- Authority
- JP
- Japan
- Prior art keywords
- heat treatment
- steel
- ferritic stainless
- stainless steel
- cooling
- 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.)
- Pending
Links
- 238000010438 heat treatment Methods 0.000 title claims abstract description 23
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 11
- 238000001816 cooling Methods 0.000 claims abstract description 25
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 22
- 239000010959 steel Substances 0.000 claims abstract description 22
- 238000005098 hot rolling Methods 0.000 claims abstract description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 5
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 13
- 238000010583 slow cooling Methods 0.000 abstract description 4
- 239000000203 mixture Substances 0.000 abstract description 2
- 238000002791 soaking Methods 0.000 abstract description 2
- 238000005336 cracking Methods 0.000 description 10
- 238000010586 diagram Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 230000008646 thermal stress Effects 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、フェライト系ステンレス鋼におけるを熱間圧
延後における熱処理方法に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for heat treating ferritic stainless steel after hot rolling.
耐熱性フェライト系ステンレス鋼は、極低炭素かつ極低
窒素の高純度フェライト系ステンレス鋼が用いられてい
る。ところがこの材料は割れ感受性が高く、冷塊、冷片
化過程で比較的容易に熱応力割れを招く。この割れはい
わゆる４７５℃脆化域において長時間加熱すると発生す
るものと考えられる。そこで、従来、この割れを防止す
るため熱間圧延後の鋼片を約５００℃以上の温度域で熱
処理炉に装入していた。As the heat-resistant ferritic stainless steel, high-purity ferritic stainless steel with extremely low carbon and extremely low nitrogen content is used. However, this material is highly susceptible to cracking and relatively easily causes thermal stress cracking during the cold lumping and cold flaking process. It is thought that this cracking occurs when heated for a long time in the so-called 475°C embrittlement region. Therefore, conventionally, in order to prevent this cracking, hot-rolled steel slabs were charged into a heat treatment furnace at a temperature of about 500° C. or higher.
しかし、熱処理炉に熱間圧延後の鋼片を５００℃以上の
温度域で熱処理炉に装入する際は、当該熱処理炉が圧延
ミルの近くにあって、圧延後の材料を迅速にその炉まで
運搬できる設備があればよいが、そのような設備への投
資に多大の費用がかかる。他方で、熱処理炉と圧延ミル
との間にかなりの距離がある場合には、材料が冷えない
ように加熱しながら運搬する必要があり、例えば運搬中
の冷却を防止するため、保温剤でビレットを包むとか、
保温剤を内面に張りつけたカバー内に鋼片を入れて運搬
する等の必要があり、上記割れ防止のための保温対策を
特別に採る必要があり、コスト高の原因となっていた。However, when charging hot-rolled steel slabs into a heat treatment furnace at temperatures above 500°C, the heat treatment furnace is located near the rolling mill, and the rolled material can be quickly transferred to the furnace. It would be nice if there was equipment that could transport the materials up to that point, but investing in such equipment would require a large amount of money. On the other hand, if there is a considerable distance between the heat treatment furnace and the rolling mill, it is necessary to transport the material while heating it to prevent it from cooling down. For example, to prevent cooling during transport, billet Wrapping or
It is necessary to transport the steel pieces in a cover with a heat insulating agent applied to the inner surface, and it is necessary to take special heat insulation measures to prevent the above-mentioned cracking, which causes high costs.
そこで本発明の主目的は、熱処理炉と圧延ミルとがかな
り離れているような場合であっても、特別に保温対策を
採ることなく、割れの発生を確実に防止できるフェライ
ト系ステンレス鋼の熱処理方法を提供することにある。Therefore, the main purpose of the present invention is to provide a heat treatment method for ferritic stainless steel that can reliably prevent the occurrence of cracks without taking special heat insulation measures even when the heat treatment furnace and rolling mill are far apart. The purpose is to provide a method.
上記課題は、Ｃｒ：１８〜２５％、ｃ ： ｏ、 ｏ
ｉ％、Ｎ ： ０． Ｏ１％以下、Ｍｎ： １．０％以
下、Ｓｉ：１．２〜１．５％、Ａｆ：１．２〜１．７％
、必要に応じてＭｏ：２〜３％を含むフェライト系ステ
ンレス鋼を熱間圧延後、得られる８００℃〜１０００℃
の鋼片を互いに密着させることなく間隔を置いた状態で
、４５℃／ｈｒ以上の冷却速度で、１００６Ｃ〜３００
℃まで冷却してから、９００℃〜１２００℃の範囲内の
温度に４〜８時間均熱し、その後３０℃／ｈｒ以下の冷
却速度で徐冷することで解決される。The above problem is Cr: 18-25%, c: o, o
i%, N: 0. O 1% or less, Mn: 1.0% or less, Si: 1.2 to 1.5%, Af: 1.2 to 1.7%
, 800°C to 1000°C obtained after hot rolling a ferritic stainless steel containing 2 to 3% Mo as necessary.
1006C to 300C at a cooling rate of 45℃/hr or more with the steel pieces spaced apart without being brought into close contact with each other.
The problem can be solved by cooling to a temperature of 900°C to 1200°C, soaking for 4 to 8 hours, and then gradually cooling at a cooling rate of 30°C/hr or less.
本発明者は、そもそも熱間圧延後の冷却過程で生ずる割
れの原因は何かということを検討した。The present inventor investigated what is the cause of cracks that occur during the cooling process after hot rolling.
その結果、割れの原因は次の３つであることが判明した
。As a result, it was found that the following three causes caused the cracks.
（１） 鋼片の密着による鋼片の天地面と他の鋼片と
の接触面との温度差に起因する熱応力割れ。(1) Thermal stress cracking caused by the temperature difference between the top and bottom of a steel piece and the contact surface with other steel pieces due to close contact between the steel pieces.
（２１４７５℃脆化域を通る冷却過程に由来する割れ。(Cracks originating from the cooling process that passes through the 21475°C embrittlement zone.
（３）冷片になった時の延性低下による割れ。(3) Cracking due to decreased ductility when turning into cold pieces.
本発明は上記各別れ原因に対処すべ（なされたもので、
まず、鋼片同士を接触させないで冷却することにより、
（１）の割れに対処できる。例えば第３図に示すように
、冷却の際、鋼片１、■・・・の間に、所定間隔をおい
てストッパ２を介在させて、鋼片１．１同士が密着する
ことがないようにする。The present invention has been made to deal with each of the above-mentioned causes of separation. First, by cooling the steel pieces without making them contact each other,
It can deal with cracks in (1). For example, as shown in Fig. 3, during cooling, a stopper 2 is interposed at a predetermined interval between the steel slabs 1, 1, . . . to prevent the steel slabs 1. Make it.
また４７５℃脆化域を避けて冷却するように、８００〜
１２００℃の鋼片を、１００℃〜４５℃／ｈｒの冷却速
度で１００〜３００℃まで冷却することにより、（２）
の割れを防止できる。Also, in order to avoid the 475°C embrittlement region,
(2) By cooling a 1200°C steel billet to 100-300°C at a cooling rate of 100°C to 45°C/hr.
can prevent cracking.
さらに、この冷却鋼片をそのまま１００℃未満にまで冷
却せずに、９００〜ｂ
時間の熱処理を施した後、３０℃／ｈｒ以下の冷却速度
で徐冷することにより（３）の割れを防止できる。Furthermore, without directly cooling this cooled steel piece to below 100°C, the cracking in (3) is prevented by subjecting it to heat treatment for 900 to 1000 hr, followed by slow cooling at a cooling rate of 30°C/hr or less. can.
以上の熱処理により、本発明においては従来法のような
保温対策を採る必要がなく、割れを確実に回避できる。Due to the heat treatment described above, in the present invention, there is no need to take heat retention measures as in the conventional method, and cracking can be reliably avoided.
本発明において、熱間圧延後の鋼片の冷却速度として、
４５℃／ ｈ ｒとしたのは、前述のように、４７５℃
脆化域を避けて冷却するためである。また、１００℃／
ｈｒを超えると、水冷等の急冷が必要となり、温度差に
よる熱応力による割れが発生するため好ましくない。さ
らに、徐冷後の温度が１００℃未満となると、硬度上昇
のためミクロ的な割れが発生し、工程上長時間要するの
で好ましくない。In the present invention, as the cooling rate of the steel billet after hot rolling,
45℃/hr was set at 475℃ as mentioned above.
This is for cooling while avoiding the embrittlement area. Also, 100℃/
If it exceeds hr, rapid cooling such as water cooling will be required, and cracks will occur due to thermal stress due to temperature difference, which is not preferable. Furthermore, if the temperature after slow cooling is less than 100°C, microscopic cracks will occur due to increased hardness, which is undesirable since it will take a long time in the process.
一方、徐冷後、鋼片に対して９００〜１２００’ＣＸ４
〜８時間の熱処理が行われる。９００℃未満では、ラー
ベス（脆化相）が出てくるため割れが発生し易いため好
ましくない。他方、１２００℃を超えると、高温のため
スケールが厚くなり、燃料が無駄となるため好ましくな
い。On the other hand, after slow cooling, 900~1200'CX4
A heat treatment of ~8 hours is performed. If the temperature is less than 900°C, cracks are likely to occur due to the appearance of laves (brittle phase), which is not preferable. On the other hand, if the temperature exceeds 1200°C, the scale will become thick due to the high temperature and fuel will be wasted, which is not preferable.
さらに、熱処理時間として、４時間未満では、加工歪除
去のための再結晶時間が確保できないため、熱処理効果
が得られない。また、８時間を超えると、熱処理の必要
がなく、工程上エネルギー消費上無駄となるため好まし
くない。Further, if the heat treatment time is less than 4 hours, the recrystallization time for removing processing strain cannot be secured, so that the heat treatment effect cannot be obtained. Moreover, if it exceeds 8 hours, there is no need for heat treatment, which is undesirable because energy consumption in the process is wasted.
一方、熱処理後の冷却速度が、３０℃／ｈｒを超える速
度であると、熱応力による割れが発生するため好ましく
ない。On the other hand, if the cooling rate after heat treatment exceeds 30° C./hr, cracks may occur due to thermal stress, which is not preferable.
〔実施例〕 次に実施例により本発明の効果を明らかにする。〔Example〕 Next, the effects of the present invention will be clarified through examples.
第２図に従来法における熱間圧延後のヒートパターンと
、本発明法でのヒートパターンとを比較して示す。なお
、本発明に用いた鋼の組成を第１表に示す。FIG. 2 shows a comparison between the heat pattern after hot rolling in the conventional method and the heat pattern in the method of the present invention. The composition of the steel used in the present invention is shown in Table 1.
第 １ 表（単位：ｗ【％）
一ン図、第３図は熱処理時の鋼片の配置状況を示す図で
ある。Table 1 (Unit: w [%)] Figure 1 and Figure 3 are diagrams showing the arrangement of steel slabs during heat treatment.
１・・・鋼片、２・・・ストッパ。1... Steel piece, 2... Stopper.
本発明では、熱間圧延用ミルと熱処理炉が遠く離れてい
るような場合であっても、許容される時間的余裕が十分
あるので、運搬時間等の自由度が大きく、ハンドリング
が非常に容易になった。In the present invention, even if the hot rolling mill and the heat treatment furnace are far apart, there is sufficient time allowance, so there is a large degree of freedom in terms of transportation time, etc., and handling is very easy. Became.
また第３図に本発明で製造した鋼片のマクロ・ミクロ組
織を示すが、本発明にかかる鋼片では、微細な割れもな
く、健全な組織であった。Further, FIG. 3 shows the macro-microstructure of the steel slab produced according to the present invention, and the steel slab according to the present invention had a sound structure without minute cracks.
以上の通り、本発明法によれば、熱処理炉と圧延ミルと
がかなり離れているような場合であっても、特別に保温
対策を採ることなく、割れの発生を確実に防止できる。As described above, according to the method of the present invention, even if the heat treatment furnace and the rolling mill are far apart, it is possible to reliably prevent the occurrence of cracks without taking any special heat insulation measures.
第１図は熱間圧延後の冷却速度と４７５℃脆化域との関
係を説明するための図、第２図は本発明での熱処理法を
従来法と比較して示すヒートパタ第
図
第
図
第
図
熱関正痩淡め峰逍葡デ（ｈｒｌ
手続補正書
（自発）
ｌ。
事件の表示
平成
１年
特許願
第２７５４８２号
２゜
発明の名称
フェライト系ステンレス鋼の熱処理方法３゜
補正をする者
事件との関係Fig. 1 is a diagram for explaining the relationship between the cooling rate after hot rolling and the 475°C embrittlement region, and Fig. 2 is a heat patter diagram showing a comparison of the heat treatment method of the present invention with the conventional method. Diagram: Heat treatment method for heat treatment of ferritic stainless steel 3゜Amendments Relationship with the incident
Claims (1)
０１％以下、Ｍｎ：１．０％以下、Ｓｉ：１．２〜１．
５％、Ａｌ：１．２〜１．７％、必要に応じてＭｏ：２
〜３％を含むフェライト系ステンレス鋼を熱間圧延後、
得られる８００℃〜１０００℃の鋼片を互いに密着させ
ることなく間隔を置いた状態で、４５℃／ｈｒ以上の冷
却速度で、１００℃〜３００℃まで冷却してから、９０
０℃〜１２００℃の範囲内の温度に４〜８時間均熱し、
その後３０℃／ｈｒ以下の冷却速度で徐冷することを特
徴とするフェライト系ステンレス鋼の熱処理方法。(1) Cr: 18-25%, C: 0.01%, N: 0.
01% or less, Mn: 1.0% or less, Si: 1.2-1.
5%, Al: 1.2-1.7%, Mo: 2 as necessary
After hot rolling ferritic stainless steel containing ~3%,
The obtained steel slabs at 800°C to 1000°C were cooled to 100°C to 300°C at a cooling rate of 45°C/hr or more, with the pieces spaced apart without being brought into close contact with each other, and then cooled to 90°C.
Soak at a temperature within the range of 0°C to 1200°C for 4 to 8 hours,
A method for heat treatment of ferritic stainless steel, which is then slowly cooled at a cooling rate of 30° C./hr or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27548289A JPH03138315A (en) | 1989-10-23 | 1989-10-23 | Heat treatment for ferritic stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27548289A JPH03138315A (en) | 1989-10-23 | 1989-10-23 | Heat treatment for ferritic stainless steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH03138315A true JPH03138315A (en) | 1991-06-12 |
Family
ID=17556142
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27548289A Pending JPH03138315A (en) | 1989-10-23 | 1989-10-23 | Heat treatment for ferritic stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH03138315A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54104424A (en) * | 1978-02-06 | 1979-08-16 | Showa Denko Kk | Heat treating method for high chromium ferritic stainless steel |
| JPS54128464A (en) * | 1978-03-30 | 1979-10-05 | Sumitomo Metal Ind Ltd | Preventing method for transverse crack of continuously cast billet of ferrite stainless steel |
| JPS644458A (en) * | 1987-06-26 | 1989-01-09 | Nippon Yakin Kogyo Co Ltd | Ferrite stainless steel quenched thin strip having excellent toughness |
-
1989
- 1989-10-23 JP JP27548289A patent/JPH03138315A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54104424A (en) * | 1978-02-06 | 1979-08-16 | Showa Denko Kk | Heat treating method for high chromium ferritic stainless steel |
| JPS54128464A (en) * | 1978-03-30 | 1979-10-05 | Sumitomo Metal Ind Ltd | Preventing method for transverse crack of continuously cast billet of ferrite stainless steel |
| JPS644458A (en) * | 1987-06-26 | 1989-01-09 | Nippon Yakin Kogyo Co Ltd | Ferrite stainless steel quenched thin strip having excellent toughness |
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