JPH05345919A - Production of high strength hot rolled steel plate - Google Patents
Production of high strength hot rolled steel plateInfo
- Publication number
- JPH05345919A JPH05345919A JP4153938A JP15393892A JPH05345919A JP H05345919 A JPH05345919 A JP H05345919A JP 4153938 A JP4153938 A JP 4153938A JP 15393892 A JP15393892 A JP 15393892A JP H05345919 A JPH05345919 A JP H05345919A
- Authority
- JP
- Japan
- Prior art keywords
- heating
- temperature
- steel
- steel sheet
- temp
- 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.)
- Granted
Links
Landscapes
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は近年の電縫管，建材、車
両等の高強度化に好適な靱性の優れた高強度熱延鋼板の
製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength hot-rolled steel sheet having excellent toughness, which is suitable for increasing the strength of electric resistance welded pipes, building materials, vehicles and the like in recent years.
【０００２】[0002]
【従来の技術】強度と靱性の優れた熱延鋼板として近年
Ｎｂを添加して制御圧延・制御冷却を組み合わせる非調
質鋼板が著しく進歩しており、その鋼板の製造法として
例えば特公昭４９−１４６０９号公報，特公昭５８−７
３２号公報がある。特公昭４９−１４６０９号公報はＮ
ｂ添加炭素鋼を用いスラブの加熱温度をＮｂ炭窒化物の
溶体化温度以上の１２３０℃以上にし、その後スラブを
冷却して１１００℃で圧延する制御圧延を行い、結晶粒
を微細化した高靱性鋼を製造する方法である。この方法
では通常厚み２００〜３００ｍｍのスラブをガスまたは
重油を燃焼する加熱炉を用いて中心部までＮｂ炭窒化物
の溶体化温度以上に加熱するため高温で長時間の加熱が
行われる。そのため、加熱後のスラブのオーステナイト
結晶粒径は著しく大きくなり、引き続いて行われる制御
圧延により鋼板のフェライト結晶粒を微細化している。
しかし、この方法では結晶粒微細化に限界があり、従っ
て、靱性改善にも限界がある。2. Description of the Related Art In recent years, as a hot rolled steel sheet having excellent strength and toughness, a non-heat treated steel sheet in which Nb is added and controlled rolling and controlled cooling are combined has made remarkable progress. No. 14609, Japanese Patent Publication No. 58-7
There is No. 32 publication. Japanese Patent Publication No. Sho 49-14609 is N
Controlled rolling was performed by using b-added carbon steel to raise the heating temperature of the slab to 1230 ° C. or higher, which is higher than the solutionizing temperature of Nb carbonitride, and then cooling the slab and rolling it at 1100 ° C. It is a method of manufacturing steel. In this method, a slab having a thickness of 200 to 300 mm is usually heated to a central portion at a solution temperature of Nb carbonitride or higher by using a heating furnace that burns gas or heavy oil, and thus heating is performed at high temperature for a long time. Therefore, the austenite crystal grain size of the slab after heating becomes remarkably large, and the ferrite crystal grains of the steel sheet are refined by the subsequent controlled rolling.
However, this method has a limit in refining the crystal grains, and therefore has a limit in improving the toughness.
【０００３】特公昭５８−７３２号公報はＮｂ添加炭素
鋼を用いスラブの加熱温度をＮｂ炭窒化物の溶体化温度
以上にし、１０００〜１１５０℃の温度範囲で熱間圧延
し、オーステナイト粒を再結晶により細粒にした後、さ
らに９００℃以下で圧延する方法である。この方法は、
特公昭４９−１４６０９号公報に比べて粗圧延によりオ
ーステナイト粒を細かくする優れた方法であるが、粗圧
延時にＮｂが加工誘起析出することによる強度向上への
寄与が減少される欠点がある。Japanese Patent Publication No. 58-732 discloses that Nb-added carbon steel is used and the heating temperature of the slab is set to a solutionizing temperature of Nb carbonitride or higher and hot rolling is performed in a temperature range of 1000 to 1150 ° C. to regenerate austenite grains. This is a method in which the grains are made into fine particles and then rolled at 900 ° C. or lower. This method
This is an excellent method of making austenite grains finer by rough rolling, as compared with JP-B-49-14609, but has a drawback that work-induced precipitation of Nb during rough rolling reduces the contribution to strength improvement.
【０００４】[0004]
【発明が解決しようとする課題】本発明は、Ｎｂを添加
した非調質高強度熱延鋼板の結晶粒を微細化する新しい
製造方法を提供することを目的とし、この方法により強
度と靱性の優れた電縫管用，建材用，車両用等の熱延鋼
板を提供するものである。SUMMARY OF THE INVENTION It is an object of the present invention to provide a new manufacturing method for refining the crystal grains of a non-heat treated high strength hot rolled steel sheet containing Nb. It provides excellent hot-rolled steel sheets for electric resistance welded pipes, building materials, and vehicles.
【０００５】[0005]
【課題を解決するための手段】本発明の要旨とするとこ
ろは次のとおりである。 Ｃ：０．０５〜０．２０％，Ｓｉ：≦０．６０％，Ｍ
ｎ：０．２０〜２．５０％，Ａｌ：０．００４〜０．１
０％，Ｎｂ：０．０１〜０．１０％，Ｎ：０．００２〜
０．００８％，残部Ｆｅおよび不可避不純物からなる連
続鋳造スラブを加熱するに際して、少なくとも１１００
℃からＮｂ（Ｃ，Ｎ）の溶体化温度以上１４００℃以下
の加熱温度までの温度領域を毎時１５０℃以上の昇温速
度で加熱し、加熱温度での保定時間を５分以上３０分以
内とし、その後熱間圧延することを特徴とする高強度熱
延鋼板の製造方法。The gist of the present invention is as follows. C: 0.05 to 0.20%, Si: ≤ 0.60%, M
n: 0.20 to 2.50%, Al: 0.004 to 0.1
0%, Nb: 0.01 to 0.10%, N: 0.002
When heating a continuously cast slab consisting of 0.008%, balance Fe and unavoidable impurities, at least 1100
The temperature range from the solution temperature of Nb (C, N) to the heating temperature of 1400 ° C or less is heated at a heating rate of 150 ° C or more per hour, and the holding time at the heating temperature is set to 5 minutes or more and 30 minutes or less. A method for producing a high-strength hot-rolled steel sheet, characterized by comprising hot rolling thereafter.
【０００６】以下、本発明の詳細について説明する。強
度と靱性の優れたＮｂを添加した非調質高強度熱延鋼板
を製造するためには、微量のＮｂを析出硬化元素として
利用して、且つ加熱・熱延・冷却の工程をとる熱間圧延
工程で結晶粒の微細化を行うことが必要である。通常、
目的の成分に調整された鋼は連続鋳造されＡｒ3 変態点
以下に冷却されるが、鋳片の厚みが２００〜３００ｍｍ
あるためその冷却速度は遅い。そのため鋳片にはＮｂ
（Ｃ，Ｎ）の０．０５ミクロン以上の大きな析出物が析
出している。熱間圧延による結晶粒の微細化に効果的な
析出物は溶体化していて加工時に加工誘起析出するもの
であると言われている。まだ、強度向上に寄与するＮｂ
も整合析出している極めて微細なＮｂ（Ｃ，Ｎ）である
と言われている。従って、鋳片に析出しているＮｂ
（Ｃ，Ｎ）が熱間圧延前の加熱段階で溶体化している必
要がある。The details of the present invention will be described below. In order to produce a non-heat treated high strength hot rolled steel sheet to which Nb having excellent strength and toughness is added, a small amount of Nb is used as a precipitation hardening element, and the steps of heating, hot rolling and cooling are performed. It is necessary to refine the crystal grains in the rolling process. Normal,
The steel adjusted to the desired composition is continuously cast and cooled to below the Ar 3 transformation point, but the thickness of the slab is 200 to 300 mm.
Therefore, the cooling rate is slow. Therefore, the slab is Nb
Large deposits of (C, N) of 0.05 micron or more are deposited. It is said that the precipitate effective for refining the crystal grains by hot rolling is a solution and is a work-induced precipitate during working. Nb still contributing to strength improvement
Is also said to be extremely fine Nb (C, N) which is coherently precipitated. Therefore, the Nb deposited on the slab
It is necessary that (C, N) be solutionized at the heating stage before hot rolling.
【０００７】溶体化のための加熱温度は、以下に示す析
出物の溶解度積と温度（Ｔ：°Ｋ）との関係の温度Ｔ°
Ｋ以上必要である。 ｌｏｇ10〔％Ｎｂ〕・〔％Ｃ＋％０．８６Ｎ〕 ＝２．２６−６，７７０／Ｔ・・・(1) しかし、この温度で加熱したスラブのオーステナイト結
晶粒は粗大化しているため、鋼板のフェライト結晶粒微
細化のためその後の熱延・冷却工程で種々の工夫がされ
る。すなわち、熱延工程では低温で大圧下圧延を行う等
の種々の工夫がなされている。冷却工程では変態域での
冷却速度を速くするなどの工夫がなされている。The heating temperature for solution treatment is the temperature T ° which is the relationship between the solubility product of the precipitate and the temperature (T: ° K) shown below.
K or more is required. log 10 [% Nb] · [% C +% 0.86N] = 2.26-6,770 / T (1) However, since the austenite crystal grains of the slab heated at this temperature are coarsened, Various refinements are made in the subsequent hot rolling / cooling process to refine the ferrite crystal grains of the steel sheet. That is, in the hot rolling process, various ideas such as large reduction rolling at low temperature have been made. In the cooling process, various measures are taken such as increasing the cooling rate in the transformation region.
【０００８】ところで、熱延・冷却工程での工夫だけで
なく、加熱工程を工夫して熱間圧延前のオーステナイト
結晶粒を細かくできれば熱延後の鋼板のフェライト結晶
粒を更に細かくでき、靱性改善に極めて有効である。本
発明者等は、種々の実験の結果、少なくとも１１００℃
からＮｂ（Ｃ，Ｎ）の溶体化温度以上１４００℃以下の
加熱温度までの温度領域を毎時１５０℃以上の昇温速度
で加熱し、加熱温度での保定時間を５分以上３０分以下
と限定することによってオーステナイト結晶粒の粗大化
を防止しつつ析出物を溶体化させ得ることを新たに知見
したものである。By the way, if the austenite crystal grains before hot rolling can be made finer by devising not only the hot rolling / cooling step but also the heating step, the ferrite crystal grains of the steel sheet after hot rolling can be made finer and the toughness can be improved. It is extremely effective for As a result of various experiments, the present inventors have found that at least 1100 ° C.
To a solution temperature of Nb (C, N) to a heating temperature of 1400 ° C or lower at a heating rate of 150 ° C or more per hour, and the holding time at the heating temperature is limited to 5 minutes to 30 minutes. This is a new finding that the precipitates can be solutionized while preventing the austenite crystal grains from coarsening.
【０００９】図１は０．１５％Ｃ−０．３０％Ｓｉ−
１．２０％Ｍｎ−０．０４０％Ｎｂ−０．０２０％Ａｌ
−０．００４０％Ｎ鋼の２５０ｍｍスラブを加熱条件を
変えて加熱し、その温度に１５分保持後、圧延を開始
し、仕上げ入り側板厚４０ｍｍ、熱延仕上げ温度８００
℃で板厚６ｍｍに熱延後、圧延後の冷却速度１５℃／ｓ
ｅｃ、巻取り温度５８０℃で熱間圧延した鋼板の引張強
さを示す。このときのスラブを加熱条件はスラブ断面平
均の加熱温度と加熱昇温速度を変えて実験を行った。こ
れによると、引張強さは加熱温度が１１００℃から１２
５０℃まで高くなるにつれて高くなり、１２５０℃以上
では殆ど変化がない。また、加熱昇温速度の影響は各加
熱温度とも殆どみられない。即ち、この鋼のＮｂ（Ｃ，
Ｎ）の計算溶体化温度が１２４０℃であることから、Ｎ
ｂ（Ｃ，Ｎ）が溶体化している１２５０℃以上で引張強
さは殆ど変わらないことを示しており、Ｎｂ（Ｃ，Ｎ）
の溶体化に加熱昇温速度の影響は殆どないことを示して
いる。FIG. 1 shows 0.15% C-0.30% Si-
1.20% Mn-0.040% Nb-0.020% Al
-A 250 mm slab of 0.0040% N steel is heated under different heating conditions, kept at that temperature for 15 minutes, and then rolled, and the side plate thickness with finish is 40 mm and the hot rolling finish temperature is 800.
Cooling rate after rolling after hot rolling at 6 ℃ to a plate thickness of 6mm 15 ℃ / s
ec, the tensile strength of the steel sheet hot rolled at a coiling temperature of 580 ° C. The slab heating conditions at this time were varied by changing the slab cross-section average heating temperature and heating rate. According to this, the tensile strength of the heating temperature from 1100 ℃ to 12
It becomes higher as the temperature rises to 50 ° C, and there is almost no change at 1250 ° C or higher. Moreover, the effect of the heating rate is hardly seen at each heating temperature. That is, Nb (C,
Since the calculated solution temperature of N) is 1240 ° C., N
It shows that the tensile strength hardly changes at 1250 ° C or higher when b (C, N) is solutionized, and Nb (C, N)
It is shown that there is almost no effect of the heating rate on the solution heat treatment of.
【００１０】図２は図１と同じ条件で熱延した鋼板のシ
ャルピー試験破面遷移温度（ｖＴｒｓ）に及ぼす加熱温
度および加熱昇温速度の影響を示す。これによると、加
熱昇温速度を７０℃／ｈｒの場合、加熱温度が高くなる
につれて破面遷移温度は高くなり（靱性が劣化する）、
１２５０℃以上で引張強さが同じであるにもかかわら
ず、破面遷移温度は急激に高くなっている。これは、１
２５０℃以上の加熱でＮｂ（Ｃ，Ｎ）が溶体化後、オー
ステナイト結晶粒が急激に大きくなり、圧延後も鋼板の
フェライト結晶粒が大きく、従って破面遷移温度が高く
なっている。一方、加熱昇温速度を１５０℃／ｈｒ以上
の場合、加熱温度１２５０℃までは加熱温度が高くなる
につれて破面遷移温度は高くなるが、加熱温度１２５０
℃から１３５０℃までは殆ど変わらない。これは、加熱
温度１２５０℃までの鋼板は引張強さが高くなるにつれ
て破面遷移温度は高くなったものであり、それより高い
温度では引張強さは変わらず、しかも急速加熱のため結
晶粒も大きくならず、従ってこの条件で加熱した鋼板の
破面遷移温度も高くならない。FIG. 2 shows the effects of heating temperature and heating rate on the Charpy test fracture surface transition temperature (vTrs) of a steel sheet hot-rolled under the same conditions as in FIG. According to this, when the heating temperature rising rate is 70 ° C./hr, the fracture surface transition temperature becomes higher as the heating temperature becomes higher (the toughness deteriorates),
Despite the same tensile strength above 1250 ° C, the fracture surface transition temperature rises sharply. This is 1
After heating Nb (C, N) into solution by heating at 250 ° C. or more, the austenite crystal grains rapidly increase, the ferrite crystal grains of the steel sheet are large even after rolling, and the fracture surface transition temperature is therefore high. On the other hand, when the heating temperature rising rate is 150 ° C./hr or more, the fracture surface transition temperature increases as the heating temperature increases up to the heating temperature 1250 ° C., but the heating temperature 1250
There is almost no change from ℃ to 1350 ℃. This is because the fracture surface transition temperature becomes higher as the tensile strength becomes higher in the steel sheet up to the heating temperature of 1250 ° C, and the tensile strength does not change at higher temperatures, and the crystal grains also grow due to rapid heating. It does not increase, and therefore the fracture surface transition temperature of the steel sheet heated under these conditions does not increase.
【００１１】図３は鋼板の破面遷移温度に及ぼす加熱昇
温速度の影響を示す。これは加熱昇温速度が１５０℃／
ｈｒ未満では破面遷移温度も高くならないことを示す。
これらのことは、加熱昇温速度を１５０℃／ｈｒ以上に
することは引張強さが高く、しかも破面遷移温度が低い
（靱性が良好な）鋼板を製造する有効な方法であること
を示している。FIG. 3 shows the effect of the heating rate on the fracture surface transition temperature of the steel sheet. The heating rate is 150 ° C /
If it is less than hr, the fracture surface transition temperature does not increase.
These show that setting the heating rate to 150 ° C./hr or more is an effective method for producing a steel sheet having high tensile strength and low fracture surface transition temperature (good toughness). ing.
【００１２】本発明における上記鋼成分の限定理由は次
の如くである。 Ｃ：Ｃは高い引張り強さを得るために最も効果的な元素
であって、この目的のために少なくとも０．０５％の添
加が必要である。しかし、Ｃの増加と共に加工性、靱性
および溶接性が低下するので、その上限を０．２０％と
限定した。 Ｓｉ：Ｓｉは強化元素として有用であるが、鋼を経済的
に製造するために０．６０％を上限として添加すること
とした。 Ｍｎ：Ｍｎも強度の向上には効果的な元素であって、こ
の目的のために少なくとも０．２０％の添加が必要であ
る。しかし、２．５０％を越すと溶鋼製造上困難になる
ので上限を２．５０％とした。The reasons for limiting the above steel components in the present invention are as follows. C: C is the most effective element for obtaining high tensile strength, and addition of at least 0.05% is necessary for this purpose. However, since the workability, toughness, and weldability decrease with the increase of C, the upper limit was set to 0.20%. Si: Si is useful as a strengthening element, but in order to economically produce steel, 0.60% is added as the upper limit. Mn: Mn is also an effective element for improving strength, and at least 0.20% must be added for this purpose. However, if it exceeds 2.50%, it becomes difficult in molten steel production, so the upper limit was made 2.50%.
【００１３】Ａｌ：Ａｌは脱酸上０．００４％以上必要
であるが、０．１０％を越すと結晶粒の粗大化を来たし
強度を劣化させるので０．１０％以下に限定した。 Ｎｂ：Ｎｂは少量の添加によってＣおよびＮと結合して
Ｎｂ（Ｃ，Ｎ）を形成し鋼を強化するので少なくとも
０．０１％を必要とする。しかし、過剰に添加してもそ
の強度向上効果は飽和するのでその上限を０．１０％と
し、０．０１〜０．１０％の範囲に限定した。 Ｎ：Ｎは現状では鋼中に不可避的に含まれており、Ｎｂ
が添加されているとＮｂ（Ｃ，Ｎ）を形成し鋼を強化す
るが、そのために特に添加する必要はない。製鋼上のＮ
を０．００２％未満にするのは困難なので下限を０．０
０２％とした。また、Ｎが０．００８％を越えて含まれ
ると鋼板の低温靱性が低下するので、上限を０．００８
％とした。Al: Al is required to be 0.004% or more for deoxidation, but if it exceeds 0.10%, the crystal grains become coarse and the strength is deteriorated, so it is limited to 0.10% or less. Nb: Nb requires at least 0.01% as it combines with C and N with a small amount of addition to form Nb (C, N) and strengthens the steel. However, even if added excessively, the strength improving effect is saturated, so the upper limit was made 0.10% and was limited to the range of 0.01 to 0.10%. N: N is currently unavoidably contained in steel, and Nb
Is added, it forms Nb (C, N) and strengthens the steel, but it is not necessary to add it for this purpose. N on steelmaking
Is less than 0.002%, so the lower limit is 0.0
It was set to 02%. Further, when N exceeds 0.008%, the low temperature toughness of the steel sheet decreases, so the upper limit is 0.008.
%.
【００１４】次に加熱条件の限定理由は次の如くであ
る。鋼板の靱性を改善するためには鋼板の結晶粒を細か
くすることが必要であり、加熱時のスラブのオーステナ
イト結晶粒を細かくすることにより、鋼板のフェライト
結晶粒も細かくできる。スラブのオーステナイト結晶粒
径は、保持される温度と時間および結晶粒の成長をとめ
る析出物の有無に影響される。したがって、加熱時の昇
温速度は保持される温度と時間に影響し、昇温速度１５
０℃／ｈｒ未満では加熱後スラブのオーステナイト結晶
粒が大きくなり、その結果、鋼板のフェライト結晶粒も
大きくなり靱性が劣化する。そのため、昇温速度１５０
℃／ｈｒ以上に限定した。また、昇温速度１５０℃／ｈ
ｒ以上にする加熱温度範囲を１１００℃以上と限定した
のはそれ以下の温度では、昇温速度が低くても結晶粒の
成長が比較的少ないためである。Next, the reason for limiting the heating conditions is as follows. In order to improve the toughness of the steel sheet, it is necessary to make the crystal grains of the steel sheet fine, and by making the austenite crystal grains of the slab during heating fine, the ferrite crystal grains of the steel sheet can also be made fine. The austenite grain size of the slab is affected by the temperature and time of holding and the presence or absence of precipitates that stop the grain growth. Therefore, the rate of temperature rise during heating affects the temperature and time to be maintained, and the rate of temperature rise 15
If it is less than 0 ° C / hr, the austenite crystal grains of the slab after heating become large, and as a result, the ferrite crystal grains of the steel sheet also become large and the toughness deteriorates. Therefore, the temperature rising rate is 150
C / hr or higher. Also, the heating rate is 150 ° C / h
The reason why the heating temperature range to be r or higher is limited to 1100 ° C. or higher is that at the temperature lower than that, the growth of crystal grains is relatively small even if the heating rate is low.
【００１５】加熱温度をＮｂ（Ｃ，Ｎ）の溶体化温度以
上としたのは、スラブの鋳造時の徐冷により析出した粗
大なＮｂ（Ｃ，Ｎ）を溶体化して熱延後の冷却時に微細
析出させ鋼板の強度を得るためであり、上限を１４００
℃としたのは、それを超える温度では表面スケールの溶
融がおこり鋼板の表面性状を劣化させるためである。加
熱温度での保定時間を５分以上３０分以下としたのは、
５分未満ではＮｂ（Ｃ，Ｎ）の溶体化が不十分であり、
３０分超では保定時間中にオーステナイト結晶粒が大き
くなってしまうためである。なお、本発明におけるスラ
ブの加熱昇温速度を１５０℃／ｈｒ以上に速くする加熱
方法には、誘導加熱を使う方法、直接通電による方法等
あるが、とくに限定するものではない。また、１１００
℃までの温度域は燃料加熱による炉加熱を行い、それよ
り高い温度のみを誘導加熱または直接通電による方法を
利用しても良い。また、鋼板の製造方法として、ホット
ストリップミルで製造しても、仕上げ圧延もリバース圧
延が行われる厚板圧延機を用いるいずれの方法でも良
い。The heating temperature is set to the solutionizing temperature of Nb (C, N) or higher because the coarse Nb (C, N) precipitated by slow cooling during casting of the slab is solutionized and cooled after hot rolling. This is for fine precipitation to obtain the strength of the steel sheet, and the upper limit is 1400.
The reason for setting the temperature to ° C is that melting of the surface scale occurs at a temperature higher than that and the surface quality of the steel sheet deteriorates. The holding time at the heating temperature is set to 5 minutes or more and 30 minutes or less,
If it is less than 5 minutes, solution treatment of Nb (C, N) is insufficient,
This is because if it exceeds 30 minutes, the austenite crystal grains become large during the retention time. The heating method for increasing the heating rate of the slab in the present invention to 150 ° C./hr or more includes, but is not particularly limited to, a method of using induction heating and a method of directly energizing. Also, 1100
In the temperature range up to ° C, the furnace may be heated by heating the fuel, and only the higher temperature may be used by induction heating or direct energization. Further, as a method for manufacturing a steel plate, any method using a thick plate rolling machine which is manufactured by a hot strip mill or finish rolling and reverse rolling may be used.
【００１６】[0016]
【実施例】表１に示される化学成分を持った鋼を転炉で
溶製し、連続鋳造により厚み２５０ｍｍの鋳片とした。
化学成分についてみると、Ａ，Ｂ鋼はＮｂ添加鋼で本発
明の成分条件を満足するものである。表２にスラブの加
熱条件とホットストリップミルで熱延した鋼板の材質試
験結果を示す。加熱方法としては、加熱法Ｉ：１１００
℃までガス加熱で１１００℃以上を誘導加熱で１５０℃
／ｈｒの昇温速度を行う方法、加熱法II：室温から目的
の温度まで誘導加熱で１５０℃／ｈｒの昇温速度を行う
方法、加熱法 III：室温から目的の温度までガス加熱で
１１００℃以上では７０℃／ｈｒの昇温速度を行う方法
の３つを比較した。熱延条件は熱延仕上げ温度を８５０
℃とし、巻取り温度をＮｂ添加鋼は５８０℃とし、同一
鋼種では熱延条件が同じで加熱条件だけ違うようにし
た。Example Steels having the chemical compositions shown in Table 1 were melted in a converter and continuously cast into slabs having a thickness of 250 mm.
Regarding the chemical composition, the A and B steels are Nb-added steels and satisfy the compositional conditions of the present invention. Table 2 shows the heating conditions of the slab and the material test results of the steel sheet hot rolled by the hot strip mill. As a heating method, heating method I: 1100
Gas heating up to ℃ 1100 ℃ or more by induction heating 150 ℃
Heating method II: heating method II: induction heating from room temperature to a target temperature of 150 ° C / hour heating method III: heating method from room temperature to a target temperature of 1100 ° C by gas heating In the above, three methods of increasing the temperature rising rate of 70 ° C./hr are compared. The hot rolling condition is a hot rolling finishing temperature of 850.
C., the winding temperature was 580.degree. C. for Nb-added steel, and the same steel type had the same hot rolling conditions but different heating conditions.
【００１７】[0017]
【表１】 [Table 1]
【００１８】[0018]
【表２】 [Table 2]
【００１９】これによると、鋼板Ａ−１，Ａ−２，Ａ−
３，Ａ−４，Ａ−５，Ａ−６は鋼種Ａを用いた本発明の
製造条件を満足するものである。しかし、鋼板Ａ−７は
鋼種Ａを用いているが加熱時の保持時間が短く、Ｎｂ
（Ｃ，Ｎ）の溶体化が不十分で目的の強度を得ていな
い。鋼板Ａ−８は鋼種Ａを用いているが昇温速度が７０
℃／ｈｒと遅く、鋼板Ａ−１に比べてｖＴｒｓが高い比
較例である。鋼板Ａ−９は鋼種Ａを用いているが昇温速
度が１５０℃／ｈｒの昇温速度で加熱したが、加熱温度
での保定時間が鋼板Ａ−１に比べて４０分と長く、従っ
てｖＴｒｓが高い比較例である。鋼板Ｂ−１は鋼種Ｂを
用いた本発明の製造条件を満足するものである。しか
し、鋼板Ｂ−２は昇温速度が７０℃／ｈｒと遅く、鋼板
Ｂ−１に比べてｖＴｒｓが高い比較例である。According to this, the steel plates A-1, A-2, A-
3, A-4, A-5 and A-6 satisfy the manufacturing conditions of the present invention using the steel type A. However, although the steel plate A-7 uses the steel type A, the holding time during heating is short, and Nb
The solution strength of (C, N) is insufficient and the desired strength is not obtained. Steel plate A-8 uses steel type A but has a temperature rising rate of 70.
This is a comparative example, which is as slow as C / hr and has a higher vTrs than the steel plate A-1. Steel plate A-9 uses steel type A, but was heated at a temperature rising rate of 150 ° C./hr, but the holding time at the heating temperature was 40 minutes longer than that of steel plate A-1, and therefore vTrs Is a high comparative example. Steel plate B-1 satisfies the manufacturing conditions of the present invention using steel type B. However, Steel Plate B-2 is a comparative example in which the temperature rising rate is as slow as 70 ° C./hr and vTrs is higher than Steel Plate B-1.
【００２０】[0020]
【発明の効果】以上説明したような、本発明によるとき
は同じ鋼種および同一熱延条件でも強度および靱性の優
れた熱延鋼板の製造が可能になり工業的にその効果は大
きい。As described above, according to the present invention, a hot-rolled steel sheet having excellent strength and toughness can be manufactured even under the same steel type and the same hot-rolling condition, and the effect is industrially great.
【図１】０．１５％Ｃ−０．３０％Ｓｉ−１．２０％Ｍ
ｎ−０．０４０％Ｎｂ−０．０２０％Ａｌ−０．００４
０％Ｎ鋼を用いた鋼板の引張強さに及ぼす加熱温度およ
び加熱昇温速度の影響を示した図、FIG. 1 0.15% C-0.30% Si-1.20% M
n-0.040% Nb-0.020% Al-0.004
A diagram showing the effects of heating temperature and heating rate on the tensile strength of a steel sheet using 0% N steel,
【図２】シャルピー試験破面遷移温度（ｖＴｒｓ）に及
ぼす加熱温度および加熱昇温速度の影響を示した図、FIG. 2 is a diagram showing the effects of heating temperature and heating rate on the Charpy test fracture transition temperature (vTrs).
【図３】シャルピー試験破面遷移温度（ｖＴｒｓ）に及
ぼす加熱昇温速度の影響を示した図である。FIG. 3 is a diagram showing the effect of the heating rate on the Charpy test fracture transition temperature (vTrs).
Claims (1)
加熱するに際して、少なくとも１１００℃からＮｂ
（Ｃ，Ｎ）の溶体化温度以上１４００℃以下の加熱温度
までの温度領域を毎時１５０℃以上の昇温速度で加熱
し、加熱温度での保定時間を５分以上３０分以内とし、
その後熱間圧延することを特徴とする高強度熱延鋼板の
製造方法。1. C: 0.05 to 0.20% Si: ≤ 0.60% Mn: 0.20 to 2.50% Al: 0.004 to 0.10% Nb: 0.01 to 0. 10% N: 0.002-0.008% When heating a continuous casting slab consisting of the balance Fe and inevitable impurities, at least 1100 ° C. to Nb
The temperature range from the solutionizing temperature of (C, N) to the heating temperature of 1400 ° C. or less is heated at a heating rate of 150 ° C. or more per hour, and the holding time at the heating temperature is set to 5 minutes or more and 30 minutes or less,
A method for producing a high-strength hot-rolled steel sheet, which comprises hot rolling thereafter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4153938A JP3043519B2 (en) | 1992-06-15 | 1992-06-15 | Manufacturing method of high strength hot rolled steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4153938A JP3043519B2 (en) | 1992-06-15 | 1992-06-15 | Manufacturing method of high strength hot rolled steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05345919A true JPH05345919A (en) | 1993-12-27 |
| JP3043519B2 JP3043519B2 (en) | 2000-05-22 |
Family
ID=15573366
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4153938A Expired - Fee Related JP3043519B2 (en) | 1992-06-15 | 1992-06-15 | Manufacturing method of high strength hot rolled steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3043519B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010265537A (en) * | 2009-05-18 | 2010-11-25 | Nippon Steel Corp | Steel heating method, heating controller, and program |
| CN102650016A (en) * | 2012-05-24 | 2012-08-29 | 宝山钢铁股份有限公司 | Manufacturing method for high-magnetic induction low-cost 250 MPa cold-rolled magnetic pole steel |
| JP2020204066A (en) * | 2019-06-14 | 2020-12-24 | 日本製鉄株式会社 | Slab management method |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6583491B1 (en) | 2018-07-02 | 2019-10-02 | 横浜ゴム株式会社 | Pneumatic tire |
-
1992
- 1992-06-15 JP JP4153938A patent/JP3043519B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010265537A (en) * | 2009-05-18 | 2010-11-25 | Nippon Steel Corp | Steel heating method, heating controller, and program |
| CN102650016A (en) * | 2012-05-24 | 2012-08-29 | 宝山钢铁股份有限公司 | Manufacturing method for high-magnetic induction low-cost 250 MPa cold-rolled magnetic pole steel |
| JP2020204066A (en) * | 2019-06-14 | 2020-12-24 | 日本製鉄株式会社 | Slab management method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3043519B2 (en) | 2000-05-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPH11140582A (en) | High toughness thick steel plate excellent in toughness in weld heat-affected zone, and its production | |
| JPS6366368B2 (en) | ||
| JP2004269924A (en) | High efficient producing method of steel sheet excellent in strength and toughness | |
| JPH05195058A (en) | Production of thick steel plate having high toughness and high tensile strength | |
| JP3043519B2 (en) | Manufacturing method of high strength hot rolled steel sheet | |
| JP3043517B2 (en) | Manufacturing method of high strength hot rolled steel sheet | |
| JP3635803B2 (en) | Method for producing high-tensile steel with excellent toughness | |
| JP2556411B2 (en) | Method for producing high-strength hot-rolled steel sheet with good workability and weldability | |
| JP3806958B2 (en) | Manufacturing method of high-tensile hot-rolled steel sheet | |
| JP2003034825A (en) | Method for manufacturing high strength cold-rolled steel sheet | |
| JP3043518B2 (en) | Manufacturing method of high strength hot rolled steel sheet | |
| JPH01184227A (en) | Production of alloyed and galvanized steel sheet for drawing | |
| JPS6367524B2 (en) | ||
| JPS6410565B2 (en) | ||
| JPH05271770A (en) | Manufacture of fine-grained thick steel plate | |
| JPS601928B2 (en) | Manufacturing method for hot-rolled high-strength steel sheets with excellent workability | |
| JP2001089816A (en) | Method of manufacturing high strength hot rolled steel plate | |
| KR100276295B1 (en) | The manufacturing method for high work used cold rolling steel sheet with excellent resirtance weldability | |
| KR20240075040A (en) | Hot rolled steel sheet and method of manufacturing the same | |
| KR100415663B1 (en) | A method for manufacturing hot rolled steel sheet having good high temperature strength | |
| JPH05331538A (en) | Manufacture of thick high toughness and high tensile strength steel plate excellent in toughness on central part of plate thickness | |
| JPH08302427A (en) | Production of thick steel plate excellent in toughness | |
| JPH08283844A (en) | Production of thick four resistant steel plate excellent in toughness | |
| JPH1088277A (en) | Non-heat treated high tensile strength thick steel material and its production | |
| JPH0619109B2 (en) | Method for producing straight-rolled thick steel plate having excellent characteristics at low pressure reduction ratio |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20000229 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080310 Year of fee payment: 8 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090310 Year of fee payment: 9 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20090310 Year of fee payment: 9 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100310 Year of fee payment: 10 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110310 Year of fee payment: 11 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120310 Year of fee payment: 12 |
|
| LAPS | Cancellation because of no payment of annual fees |