JPH04308035A - Production of steel plate for structural use excellent in toughness at low temperature - Google Patents
Production of steel plate for structural use excellent in toughness at low temperatureInfo
- Publication number
- JPH04308035A JPH04308035A JP7338791A JP7338791A JPH04308035A JP H04308035 A JPH04308035 A JP H04308035A JP 7338791 A JP7338791 A JP 7338791A JP 7338791 A JP7338791 A JP 7338791A JP H04308035 A JPH04308035 A JP H04308035A
- Authority
- JP
- Japan
- Prior art keywords
- rolling
- toughness
- cooling
- temperature
- steel
- 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
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 44
- 239000010959 steel Substances 0.000 title claims abstract description 44
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 14
- 238000005096 rolling process Methods 0.000 claims abstract description 53
- 238000001816 cooling Methods 0.000 claims abstract description 52
- 229910000746 Structural steel Inorganic materials 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 15
- 238000007711 solidification Methods 0.000 claims abstract description 8
- 230000008023 solidification Effects 0.000 claims abstract description 8
- 238000001953 recrystallisation Methods 0.000 claims description 9
- 238000010791 quenching Methods 0.000 claims description 7
- 230000000171 quenching effect Effects 0.000 claims description 7
- 238000005496 tempering Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 abstract description 27
- 238000010438 heat treatment Methods 0.000 abstract description 19
- 238000003303 reheating Methods 0.000 abstract description 7
- 230000007423 decrease Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 238000005204 segregation Methods 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 239000010953 base metal Substances 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 238000005275 alloying Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 206010038743 Restlessness Diseases 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- -1 steam Substances 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【0001】0001
【産業上の利用分野】本発明は、母材及び溶接熱影響部
(以下HAZと稱す)が共に低温靭性に優れた構造用鋼
板を生産性良く経済的に製造する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 highly productive and economical method for producing structural steel plates in which both the base metal and the weld heat affected zone (hereinafter referred to as HAZ) have excellent low-temperature toughness.
【0002】0002
【従来の技術】海洋構造物、船舶、貯蔵タンク等の大型
構造物に使用される溶接構造用鋼板については、構造物
の破壊がもたらす被害の大きさ及び社会不安の大きさか
ら、当業分野における材質特性の改善は目覚ましく、特
に鋼材の母材靭性及びHAZ靭性の改善努力は留まると
ころがない。しかも該構造物の大型化に伴い、その構築
材である溶接構造用鋼板を安価に提供される事が望まれ
ている。[Prior Art] Welded structural steel plates used for large structures such as offshore structures, ships, and storage tanks are not well known in the art due to the magnitude of damage and social unrest caused by the destruction of the structures. Improvements in material properties have been remarkable, and efforts to improve the base material toughness and HAZ toughness of steel materials in particular are continuing. Moreover, as the structures become larger, it is desired that welded structural steel plates, which are the construction materials, be provided at low cost.
【0003】母材の低温靭性を向上させる方法としては
多数の提案がある。例えば、特開昭59−47323号
公報の提案、特開昭58−19431号公報の提案、特
公昭60−169516号公報の提案、これらの方法を
改善するとする特願平01−14668号による提案等
がある。There are many proposals for improving the low-temperature toughness of the base material. For example, the proposal of JP-A-59-47323, the proposal of JP-A-58-19431, the proposal of JP-A-60-169516, and the proposal of Japanese Patent Application No. 01-14668 which purports to improve these methods. etc.
【0004】0004
【発明が解決しようとする課題】しかしながら、前記し
た提案は何れも実用時に問題を内在しており、それぞれ
に改善が待たれている。特開昭59−47323号公報
の提案は低温で加熱し、未再結晶域で大きな加工を加え
、制御冷却を行って圧延を終了後急冷して微細なフェラ
イト及びマルテンサイトを生成して母材靭性を向上する
方法であるが、この方法は他のスラブの加熱温度と対象
のスラブの加熱温度が異なるため両者間の加熱炉操業条
件を調整する時間が必要となり、加熱効率の大幅な低下
が避けられず、更に未再結晶域での加工量を大きくする
ため、制御圧延時の温度待ち時間が極めて長くなり、圧
延効率の低下及び再加熱に伴うコスト上昇を招き、生産
性の低下が著しい。[Problems to be Solved by the Invention] However, all of the above-mentioned proposals have inherent problems in practical use, and improvements are awaited in each of them. The proposal in JP-A No. 59-47323 is to heat at a low temperature, apply large processing in the non-recrystallized region, perform controlled cooling, and after finishing rolling, rapidly cool to generate fine ferrite and martensite to form the base material. This method improves toughness, but since the heating temperature of the target slab is different from that of other slabs, it requires time to adjust the operating conditions of the heating furnace between the two, resulting in a significant decrease in heating efficiency. Unavoidably, the amount of processing in the non-recrystallized area is increased, so the temperature waiting time during controlled rolling becomes extremely long, leading to a decrease in rolling efficiency and an increase in costs due to reheating, resulting in a significant decrease in productivity. .
【0005】また、特開昭58−19431号公報に開
示されているアレスト特性に優れた高張力鋼は、Ni及
びNbの使用に加えて、圧延後再加熱して完全にオ−ス
テナイト化して母材靭性を向上しており、この再加熱に
よるコスト上昇と生産性の低下は避けられない。[0005] Furthermore, the high tensile strength steel with excellent arrestability disclosed in JP-A No. 58-19431 uses Ni and Nb and is completely austenitized by reheating after rolling. The toughness of the base material has been improved, and this reheating inevitably increases costs and reduces productivity.
【0006】また、特公昭60−169516号公報に
開示された方法は、母材とHAZ共に望ましい靭性を確
保するために高温での加熱処理に加え、再加熱後800
℃以下での圧下を必須としており、この再加熱圧延によ
る生産性の低下とコストの上昇は著しい。[0006] Furthermore, the method disclosed in Japanese Patent Publication No. 169516/1980 requires heat treatment at a high temperature to ensure the desired toughness of both the base material and the HAZ, and a heat treatment of 800°C after reheating.
It is essential to perform rolling at a temperature below 0.degree. C., and this reheating and rolling significantly reduces productivity and increases costs.
【0007】また、これ等の改善を目的とした特願平0
1−14668号の方法は、HAZ靭性を確保する偏析
拡散のために、1250℃以上の温度に加熱後、再結晶
終了温度からAr3 点温度迄に圧下量50%以上の未
再結晶域での圧延により母材靭性を向上しているため、
所定の温度域に冷却するまでの温度待ち時間及び温度低
下による圧延t/hrの低下による経済性の低下が避け
られず、生産性、経済性の悪化を免れない。[0007] In addition, a patent application for the purpose of improving these
The method of No. 1-14668 is to heat to a temperature of 1,250°C or higher and then apply a reduction of 50% or more from the recrystallization end temperature to the Ar3 point temperature in the non-recrystallized region in order to achieve segregation and diffusion to ensure HAZ toughness. Because the base material toughness is improved by rolling,
A reduction in economic efficiency due to the temperature waiting time until cooling to a predetermined temperature range and a reduction in rolling t/hr due to the temperature drop is unavoidable, and productivity and economic efficiency are inevitably deteriorated.
【0008】本発明はこれらの問題点を伴わずに、優れ
た母材靭性及びHAZ靭性を有する鋼板を生産性良く、
経済的に効率よく製造する方法を提供することを課題と
するものである。[0008] The present invention does not involve these problems and can produce steel sheets having excellent base material toughness and HAZ toughness with good productivity.
The objective is to provide an economically efficient manufacturing method.
【0009】[0009]
【課題を解決するための手段】本発明は上記課題を達成
するために、凝固完了の後、1200℃以上に加熱した
構造用鋼の鋳片をAr3 点温度以上で終了する圧延に
おいて、該鋳片の圧延開始から再結晶を終了する迄の間
、鋳片厚t(mm)と冷却速度V(℃/秒)がV>(1
8/t)0.5 の関係を満足する冷却を行う事を特徴
とする低温靭性の優れた鋼板の製造方法を第1の手段と
し、[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for rolling a structural steel slab heated to 1200°C or higher after completion of solidification to a temperature higher than the Ar3 point. From the start of slab rolling to the end of recrystallization, the slab thickness t (mm) and cooling rate V (°C/sec) are V > (1
As a first means, a method for producing a steel plate with excellent low-temperature toughness is characterized by performing cooling that satisfies the relationship of 8/t)0.5,
【0010】凝固完了の後、1200℃以上に加熱
した構造用鋼の鋳片をAr3 点温度以上で終了する圧
延において、該鋳片の再結晶後から該圧延を終了する迄
の間、鋳片厚t(mm)と冷却速度V(℃/秒)がV>
(18/t)0.5 の関係を満足する冷却を行う事を
特徴とする低温靭性の優れた鋼板の製造方法を第2の手
段とし、[0010] In rolling of a structural steel slab heated to 1200° C. or higher after completion of solidification and completed at an Ar3 point temperature or higher, the slab is Thickness t (mm) and cooling rate V (°C/sec) are V>
As a second means, a method for manufacturing a steel plate with excellent low-temperature toughness, which is characterized by performing cooling that satisfies the relationship of (18/t)0.5,
【0011】凝固完了の後、1200℃以上に
加熱した構造用鋼の鋳片をAr3 点温度以上で終了す
る圧延において、該鋳片の圧延開始から該圧延を終了す
る迄の間、鋳片厚t(mm)と冷却速度V(℃/秒)が
V>(18/t)0.5 の関係を満足する冷却を行う
事を特徴とする低温靭性の優れた鋼板の製造方法を第3
の手段とし、[0011] In rolling a structural steel slab heated to 1200° C. or higher after completion of solidification to a temperature higher than the Ar3 point, the thickness of the slab changes from the start of rolling to the end of rolling. A third method for producing a steel plate with excellent low-temperature toughness is characterized in that cooling is performed such that the relationship between t (mm) and cooling rate V (°C/sec) is V>(18/t)0.5.
as a means of
【0012】圧延終了後、冷却速度5℃/
秒以上、冷却停止温度650℃以下の加速冷却を行う事
を特徴とする第1の手段を第4の手段とし、After rolling, the cooling rate is 5°C/
The first means is characterized by performing accelerated cooling at a cooling stop temperature of 650° C. or less for at least 2 seconds as the fourth means;
【0013】圧延終了後、冷却速度5℃/秒以上、冷却
停止温度650℃以下の加速冷却を行う事を特徴とする
第2の手段を第5の手段とし、[0013] After completion of rolling, the second means is characterized in that accelerated cooling is performed at a cooling rate of 5° C./sec or more and a cooling stop temperature of 650° C. or less;
【0014】圧延終了後、冷却速度5℃/秒以上、冷却
停止温度650℃以下の加速冷却を行う事を特徴とする
第3の手段を第6の手段とし、[0014] After the rolling, the third means is characterized in that accelerated cooling is performed at a cooling rate of 5° C./sec or more and a cooling stop temperature of 650° C. or less;
【0015】圧延終了後、引き続き焼入れ焼戻し処理を
行う事を特徴とする第1の手段を第7の手段とし、[0015] The first means is characterized in that a quenching and tempering treatment is subsequently performed after the rolling is completed, and the seventh means is
【0
016】圧延終了後、引き続き焼入れ焼戻し処理を行う
事を特徴とする第2の手段を第8の手段とし、0
[016] The second means is characterized in that a quenching and tempering treatment is subsequently performed after the rolling is completed, and the eighth means is
【001
7】圧延終了後、引き続き焼入れ焼戻し処理を行う事を
特徴とする第3の手段を第9の手段としている。001
7) The third means is characterized in that a quenching and tempering treatment is subsequently performed after the rolling is completed, and the ninth means is the third means.
【0018】本発明が対象とする構造用鋼は、例えば、
特公昭58−14849号公報に記載され、次記するよ
うに、通常の溶接構造用鋼が所要の材質を得るために、
従来から当業分野での活用で確認されている作用・効果
の関係を基に定めている添加元素の種類と量を同様に使
用して同等の作用と効果が得られる。従ってこれ等を含
む構造用鋼を本発明は対象鋼とするものである。以下に
これ等の各成分元素につきその添加理由と量を示す。Structural steels to which the present invention is directed include, for example,
As described in Japanese Patent Publication No. 58-14849, as described below, in order to obtain the required material quality of ordinary welded structural steel,
Equivalent actions and effects can be obtained by using the types and amounts of additive elements that have been determined based on the action-effect relationship that has been conventionally confirmed in the field of art. Therefore, the present invention targets structural steels containing these materials. The reason for addition and amount of each of these component elements will be shown below.
【0019】Cは鋼の強度を向上する有効な成分として
添加するものであるが、0.20%を超える過剰な含有
量では、HAZに島状マルテンサイトを析出し、HAZ
靭性を著しく劣化させるので0.20%以下に規制する
。。C is added as an effective component to improve the strength of steel, but if the content exceeds 0.20%, island martensite will precipitate in the HAZ and the HAZ
Since it significantly deteriorates toughness, it is restricted to 0.20% or less. .
【0020】Siは溶鋼の脱酸元素と強度増加元素とし
て添加するが、0.01%未満では脱酸効果が不十分で
あり、1.0%を超えて添加すると、鋼の加工性が低下
し、HAZの靭性が低下するため、添加量は0.01〜
1.0%に規制する。[0020]Si is added as a deoxidizing element and a strength increasing element for molten steel, but if it is less than 0.01%, the deoxidizing effect is insufficient, and if it is added in excess of 1.0%, the workability of the steel decreases. However, since the toughness of HAZ decreases, the amount added is 0.01~
It will be regulated at 1.0%.
【0021】Mnも脱酸成分元素として必要であり、0
.3%未満では鋼の清浄度を低下して加工性を害する。
また鋼材の強度を向上する成分として0.3%以上の添
加が必要である。しかし、Mnの過剰な添加は溶接性を
劣化させるので2.0%を上限とする。Mn is also necessary as a deoxidizing component element, and 0
.. If it is less than 3%, the cleanliness of the steel decreases and the workability is impaired. Further, it is necessary to add 0.3% or more of C as a component to improve the strength of steel materials. However, excessive addition of Mn deteriorates weldability, so the upper limit is set at 2.0%.
【0022】Al及びNはAl窒化物により鋼の結晶粒
径が微細化出来るので必要である。しかし添加量が少な
いとその効果がなく、過剰の場合には鋼の靭性が劣化す
るので、Alの添加量は0.001〜0.20%に規制
し、不可避的に含有されるNは0.020%以下に限定
する。[0022] Al and N are necessary because the crystal grain size of steel can be made finer by means of Al nitride. However, if the amount of Al added is small, it will not be effective, and if it is excessive, the toughness of the steel will deteriorate. .020% or less.
【0023】本発明が対象とする構造用鋼の基本成分は
以上である。これを基本に母材強度の上昇或いは、継手
靭性の向上を目的として、要求される性質に応じて合金
元素を添加するが、添加量が過ぎると溶接性の確保が困
難になる。そこで合金の添加量としては、Ni、Cr、
Mo、Cu、W,P,Co、V、Nb、Ti、Zr、T
a、Hf、希土類元素、Y、Ca、Mg、Te、Se、
Bの1種類以上を合計で4.5%以内に規制している。The basic components of the structural steel to which the present invention is directed are as described above. Based on this, alloying elements are added depending on the required properties with the aim of increasing base metal strength or joint toughness, but if the amount added is too large, it becomes difficult to ensure weldability. Therefore, the amount of alloy added is Ni, Cr,
Mo, Cu, W, P, Co, V, Nb, Ti, Zr, T
a, Hf, rare earth elements, Y, Ca, Mg, Te, Se,
One or more types of B are regulated within 4.5% in total.
【0024】また、上記した構造用鋼の鋳片を圧延する
には、先ず鋳片が凝固完了後に中心迄1200℃に加熱
して偏析を拡散する。また、圧延の終了温度は、鋼板で
最も低温となる鋼板の表面が、Ar3 点温度未満にな
るとオーステナイト粒が粗大化して表面靭性が劣化する
ので、本発明における圧延終了温度のAr3 点温度以
上は表面温度を含んでいる。[0024] Furthermore, in order to roll the above-mentioned structural steel slab, first, after the slab has solidified, it is heated to 1200° C. to the center to diffuse segregation. In addition, when the surface of the steel sheet, which is the lowest temperature in the steel sheet, becomes less than the Ar3 point temperature, the austenite grains become coarse and the surface toughness deteriorates. Includes surface temperature.
【0025】また、本発明の実施に当たって、鋳片の1
200℃以上への加熱の上限は、圧延電力原単位と加熱
燃料原単位のバランスと鋳片のハンドリング条件から決
定すれば良く、通常は1350℃以下とするのが望まし
い。[0025] In carrying out the present invention, one of the slabs is
The upper limit of heating to 200° C. or higher may be determined from the balance between rolling power consumption and heating fuel consumption and the handling conditions of the slab, and it is usually desirable to set it to 1350° C. or lower.
【0026】[0026]
【作用】本発明者等は、前記従来技術が有する問題を解
決すると共に、本発明の課題を達成するため、一般的な
構造用鋼を代表する供試鋼として実施例の表1に示す鋼
種2を用いて種々実験検討を繰り返した。[Operation] In order to solve the problems of the prior art as well as achieve the objects of the present invention, the present inventors have developed the steel types shown in Table 1 of Examples as test steels representative of general structural steels. We repeated various experimental studies using 2.
【0027】連続鋳造方法で製造した鋳片から得た構造
用鋼板にあっては、板厚中心部のCやMn濃度の偏析は
加熱温度に応じて拡散し、HAZ靭性を向上する事が理
論的かつ実験的に確かめられている。本発明者等は上記
構造用鋼鋳片の加熱温度を種々変えて上記構造用鋼にお
ける加熱温度とHAZ靭性の関係を調査した結果、図1
に示す通り、鋳片の中心温度が1200℃以上の領域に
なるとHAZ1mmの靭性は良好な値が得られる事を確
認した。一方、この構造用鋼板のオーステナイト粒径は
加熱温度により変化する事が知られている。本発明者等
は上記構造用鋼鋳片の加熱温度を種々変えて上記構造用
鋼における加熱温度と結晶粒の粒径の関係を調査した結
果、図2に示す様に鋳片の中心温度が1100℃を超え
ると結晶粒は粗大化し、上記したHAZ靭性の向上とは
逆に母材靭性の劣化が避けられない事を確認した。In structural steel sheets obtained from slabs produced by continuous casting, it is theoretically possible that the segregation of C and Mn concentrations at the center of the sheet thickness will diffuse in accordance with the heating temperature, improving HAZ toughness. It has been confirmed experimentally. The present inventors investigated the relationship between the heating temperature and HAZ toughness of the structural steel by varying the heating temperature of the structural steel slab, and found that FIG.
As shown in Figure 2, it was confirmed that when the center temperature of the slab was in the region of 1200°C or higher, a good value for the toughness of HAZ 1mm was obtained. On the other hand, it is known that the austenite grain size of this structural steel sheet changes depending on the heating temperature. The present inventors investigated the relationship between the heating temperature and grain size of the structural steel by varying the heating temperature of the structural steel slab, and found that the center temperature of the slab was as shown in Figure 2. It was confirmed that when the temperature exceeds 1100°C, the crystal grains become coarser and, contrary to the above-mentioned improvement in HAZ toughness, deterioration in base material toughness is unavoidable.
【0028】本発明者等は、上記C及びMn偏析を改善
してHAZ靭性を向上しつつ、生産性良く、経済的に母
材靭性を向上する方法を探索するため、圧延中の冷却速
度が0.4〜0.5℃/秒と認識されている通常の圧延
における鋳片厚みと冷却速度の関係を調査した。この時
に使用した鋳片は、凝固完了後1200℃以上に加熱し
て中心偏析を拡散した鋳片である。その結果、従来の圧
延技術では全く活用されていない被圧延材の厚みに対応
した冷却速度の実態が判明した。その実態を図3に曲線
Aで示す。[0028] In order to search for a method of improving the HAZ toughness by improving the above-mentioned C and Mn segregation while also improving the base metal toughness with good productivity and economically, the present inventors decided to increase the cooling rate during rolling. The relationship between slab thickness and cooling rate during normal rolling, which is recognized to be 0.4 to 0.5°C/sec, was investigated. The slab used at this time was a slab that had been heated to 1200°C or higher to diffuse center segregation after solidification. As a result, the actual state of the cooling rate that corresponds to the thickness of the rolled material, which has not been utilized at all with conventional rolling technology, was revealed. The actual situation is shown by curve A in FIG.
【0029】本発明者等は、この実態を活用し、従来技
術に共通する生産性の低下と経済性の悪化の要因となっ
ている鋳片の極端な低温加熱、及び圧延温度調整のため
の滞留・待機、更には低温域での再加熱圧延等を用いる
事なく、従来技術で得られていたと同等またはそれ以上
の母材靭性及びHAZ靭性を有する鋼板の製造方法を確
立するため、次の3点から実験検討を重ねた。[0029] The present inventors took advantage of this fact to solve the problem of extremely low-temperature heating of slabs and rolling temperature adjustment, which are common causes of productivity decline and deterioration of economic efficiency in the prior art. In order to establish a method for manufacturing steel sheets that has base metal toughness and HAZ toughness equivalent to or better than those obtained with conventional technology without using holding, waiting, or reheating rolling at low temperatures, the following steps were taken. Experimental studies were conducted from three points.
【0030】■ 圧延中の鋳片を再結晶終了温度迄の
高温域で冷却する事による鋳片滞留時間の減少及び再結
晶終了温度の高温化と、粒成長の抑制及び鋼板の結晶粒
の微細化の関係。
■ 鋳片を再結晶終了後の圧延中に冷却する事による
フェライト変態前のオーステナイト結晶粒への歪みの蓄
積と変態後の鋼板のフェライト粒径の関係。
■ ■と■の組み合わせと、母材靭性の関係。
図3の上部にこの3つの適用範囲を示す。この適用範囲
の■と■の境界となる再結晶終了温度は、良く知られて
いる様に被加工鋼材の履歴温度と履歴加工量の関係から
一定しない。従って図示した再結晶終了温度及びこれに
対応する圧延材の板厚は一例の位置を示す。■ By cooling the slab during rolling in a high temperature range up to the recrystallization completion temperature, the residence time of the slab is reduced, the recrystallization completion temperature is increased, grain growth is suppressed, and the crystal grains of the steel sheet are made finer. relationship. ■ Relationship between the accumulation of strain in the austenite grains before ferrite transformation due to cooling of the slab during rolling after completion of recrystallization and the ferrite grain size of the steel sheet after transformation. ■ Relationship between the combination of ■ and ■ and base material toughness. These three applicable ranges are shown in the upper part of Figure 3. As is well known, the recrystallization end temperature, which is the boundary between (1) and (2) in this applicable range, is not constant due to the relationship between the hysteresis temperature of the steel to be processed and the hysteresis processing amount. Therefore, the illustrated recrystallization end temperature and the corresponding plate thickness of the rolled material indicate an example position.
【0031】この実験検討で、母材靭性としてシャルピ
ー衝撃試験でのvTrsが−89℃を示した■、−85
℃を示した■、−100℃を示した■の各厚み別冷却速
度を図3に曲線Bで示す。この曲線は鋳片の厚みをtと
すると、(18/t)0.5 で近似出来る事が判明し
た。
これにより圧延中に被圧延材が圧延により厚みが変化し
ても、冷却速度V(℃/秒)が(18/t)0.5 以
上を満足すると本発明の課題が達成出来る事が判明した
。図4に冷却条件t×V2 〔mm・(℃/秒)2 〕
と圧延後の鋼板の1/2t母材靭性の関係を示す。[0031] In this experimental study, the vTrs in the Charpy impact test was -89°C as the base material toughness.■, -85
Curve B in FIG. 3 shows the cooling rate for each thickness in ■, which indicates ℃, and -100℃. It was found that this curve can be approximated by (18/t)0.5, where t is the thickness of the slab. As a result, it was found that even if the thickness of the rolled material changes during rolling, the objects of the present invention can be achieved as long as the cooling rate V (°C/sec) satisfies (18/t) 0.5 or more. . Figure 4 shows the cooling conditions t×V2 [mm・(℃/sec)2]
The relationship between and the 1/2t base material toughness of the steel plate after rolling is shown.
【0032】また、以上により得た構造用鋼板の強度を
加速冷却により向上するには、圧延終了後、水、水蒸気
、気水混合体等の何れかの冷却剤を用いて冷却速度5℃
/秒以上、冷却停止温度650℃以下の加速冷却を行え
ば良く、また、以上により得た本発明の構造用鋼板を上
記圧延後、焼入れ焼戻しを行うと本発明の効果を損なう
事なく強度、靭性を向上できる事が判明した。本発明は
以上の知見を基になされたものである。Further, in order to improve the strength of the structural steel plate obtained as described above by accelerated cooling, after the rolling is completed, a cooling rate of 5° C. is applied using any coolant such as water, steam, or a mixture of steam and water.
It is sufficient to carry out accelerated cooling at a cooling stop temperature of 650° C. or more for at least 650° C., and if the structural steel sheet of the present invention obtained as described above is subjected to quenching and tempering after rolling, the strength and strength can be improved without impairing the effects of the present invention. It has been found that toughness can be improved. The present invention has been made based on the above knowledge.
【0033】[0033]
【実施例】本発明の供試鋼の成分は、前記した一般的な
構造用鋼の元素と添加量であれば何れの組合せでも良い
が、強度レベルが異なる代表的な構造用鋼として本実施
例に用いた鋼の化学成分を表1に示す。また、本例の製
造条件を表2に、その時使用した圧延パススケジュール
と圧延中の冷却条件を表3、表4に、得られた材質を表
5に従来例を併記して示す。[Example] The composition of the test steel of the present invention may be any combination of the elements and addition amounts of the general structural steels mentioned above, but this test was carried out as a typical structural steel with different strength levels. Table 1 shows the chemical composition of the steel used in the example. Further, the manufacturing conditions of this example are shown in Table 2, the rolling pass schedule used at that time and the cooling conditions during rolling are shown in Tables 3 and 4, and the obtained material is shown in Table 5 along with the conventional example.
【0034】[0034]
【表1】[Table 1]
【0035】[0035]
【表2】[Table 2]
【0036】[0036]
【表3】[Table 3]
【0037】[0037]
【表4】[Table 4]
【0038】[0038]
【表5】[Table 5]
【0039】表1に示す供試鋼の鋼番1〜3は40キロ
級鋼、鋼番4〜7は50キロ級鋼、鋼番8〜10は60
キロ級鋼である。それぞれには必要に応じ合金元素を添
加している。表2に示す通り、No.A1−1〜A10
−3の本発明例は、指定パス冷却とゾーン冷却の何れも
従来技術の母材靭性及びHAZ靭性と同等またはそれ以
上を有する鋼板を生産性、経済性良く製造する事が出来
た。[0039] Of the test steels shown in Table 1, steel numbers 1 to 3 are 40 kg class steel, steel numbers 4 to 7 are 50 kg class steel, and steel numbers 8 to 10 are 60 kg class steel.
It is kilo class steel. Alloying elements are added to each as necessary. As shown in Table 2, No. A1-1 to A10
Example -3 of the present invention was able to produce a steel plate with good productivity and economy, with both designated pass cooling and zone cooling having the same or higher base material toughness and HAZ toughness than those of the prior art.
【0040】これに対し、No.B1〜B10の従来例
は何れも圧延中に温度待ち等を行ったにもかかわらず、
図3の曲線Aの冷却速度を用いたので表示した母材靭性
及びHAZ靭性しか得られなかった。表2に示すFLは
固液境界線を示し、HAZ1mmは該FLから1mm離
れた位置、以下HAZ3mm、HAZ5mmはそれぞれ
3mm、5mm離れた位置を示す。On the other hand, No. In all of the conventional examples B1 to B10, although temperature waiting was performed during rolling,
Since the cooling rate of curve A in FIG. 3 was used, only the indicated base material toughness and HAZ toughness could be obtained. FL shown in Table 2 indicates a solid-liquid boundary line, and HAZ1mm indicates a position 1mm away from the FL, hereinafter HAZ3mm and HAZ5mm indicate positions 3mm and 5mm away, respectively.
【0041】加熱温度が1200℃未満のNo.B3、
B5〜B10の従来例は、各試験温度におけるFLとH
AZ1mmの靭性が、2.1〜7.8kgf・mと同じ
加熱温度を用いた本発明例に比べて吸収エネルギーは低
かった。[0041] No. 1 with a heating temperature of less than 1200°C. B3,
Conventional examples of B5 to B10 have FL and H at each test temperature.
The toughness of AZ1 mm was 2.1 to 7.8 kgf·m, and the absorbed energy was lower than that of the present invention example using the same heating temperature.
【0042】また、鋳片中心も1200℃以上の加熱を
行ったB1,B2,B4,B9は、FL、HAZ1mm
のHAZ靭性は、11.7〜23.1kgf・mと良好
な吸収エネルギーを示したが、HAZ3mm、HAZ5
mmは低い母材靭性に影響されて、5.9〜7.7kg
f・mと吸収エネルギーは低かった。[0042] In addition, B1, B2, B4, and B9, in which the center of the slab was also heated to 1200°C or higher, have a FL and HAZ of 1 mm.
The HAZ toughness of 11.7 to 23.1 kgf・m showed good absorption energy, but
mm is 5.9 to 7.7 kg due to the low base material toughness.
f・m and absorbed energy were low.
【0043】[0043]
【発明の効果】本発明は以上の説明から明らかな通り、
前記の手段により発生する前記の作用を活用する事によ
り、母材及びHAZの低温靭性が共に優れた構造用鋼板
を高い生産性のもとに円滑に安定して経済的に製造する
技術を確立したもので、本発明の利用分野にもたらす効
果、及び関係する分野への波及効果は極めて大きい。[Effects of the Invention] As is clear from the above description, the present invention has the following features:
By utilizing the above-mentioned effects generated by the above-mentioned means, we have established a technology to smoothly, stably, and economically manufacture structural steel plates with excellent low-temperature toughness in both the base material and the HAZ with high productivity. Therefore, the effect brought about in the field of application of the present invention and the ripple effect on related fields are extremely large.
【図1】構造用鋼鋳片の加熱温度と鋼板のHAZ1mm
の靭性の関係を示す。[Figure 1] Heating temperature of structural steel slab and HAZ1mm of steel plate
shows the relationship between toughness.
【図2】構造用鋼鋳片の加熱温度とオーステナイト粒径
の関係を示す。FIG. 2 shows the relationship between heating temperature and austenite grain size of structural steel slabs.
【図3】圧延中の鋳片厚みと該厚みにおける板厚方向の
平均冷却速度の関係を示す。FIG. 3 shows the relationship between the thickness of a slab during rolling and the average cooling rate in the thickness direction at that thickness.
【図4】本発明の冷却条件と1/2厚の母材靭性の関係
を示す。FIG. 4 shows the relationship between cooling conditions of the present invention and base material toughness of 1/2 thickness.
Claims (9)
した構造用鋼の鋳片をAr3 点温度以上で終了する圧
延において、該鋳片の圧延開始から再結晶を終了する迄
の間、鋳片厚t(mm)と冷却速度V(℃/秒)がV>
(18/t)0.5 の関係を満足する冷却を行う事を
特徴とする低温靭性の優れた鋼板の製造方法。Claim 1: After completion of solidification, rolling of a structural steel slab heated to 1200° C. or higher is completed at an Ar3 point temperature or higher, from the start of rolling to the end of recrystallization. The thickness t (mm) and the cooling rate V (°C/sec) are V>
A method for producing a steel plate with excellent low-temperature toughness, characterized by performing cooling that satisfies the relationship of (18/t)0.5.
した構造用鋼の鋳片をAr3 点温度以上で終了する圧
延において、該鋳片の再結晶後から該圧延を終了する迄
の間、鋳片厚t(mm)と冷却速度V(℃/秒)がV>
(18/t)0.5 の関係を満足する冷却を行う事を
特徴とする低温靭性の優れた鋼板の製造方法。[Claim 2] In rolling a structural steel slab heated to 1200° C. or higher after completion of solidification at an Ar3 point temperature or higher, from the time after recrystallization of the slab until the end of the rolling, The slab thickness t (mm) and the cooling rate V (°C/sec) are V>
A method for producing a steel plate with excellent low-temperature toughness, characterized by performing cooling that satisfies the relationship of (18/t)0.5.
した構造用鋼の鋳片をAr3 点温度以上で終了する圧
延において、該鋳片の圧延開始から該圧延を終了する迄
の間、鋳片厚t(mm)と冷却速度V(℃/秒)がV>
(18/t)0.5 の関係を満足する冷却を行う事を
特徴とする低温靭性の優れた鋼板の製造方法。3. After completion of solidification, rolling of a structural steel slab heated to 1200° C. or higher is completed at an Ar3 point temperature or higher, from the start of rolling of the slab to the end of rolling. The thickness t (mm) and the cooling rate V (°C/sec) are V>
A method for producing a steel plate with excellent low-temperature toughness, characterized by performing cooling that satisfies the relationship of (18/t)0.5.
冷却停止温度650℃以下の加速冷却を行う事を特徴と
する請求項1に記載の方法。[Claim 4] After finishing rolling, the cooling rate is 5°C/sec or more,
The method according to claim 1, characterized in that accelerated cooling is performed at a cooling stop temperature of 650° C. or lower.
冷却停止温度650℃以下の加速冷却を行う事を特徴と
する請求項2に記載の方法。[Claim 5] After finishing rolling, the cooling rate is 5°C/sec or more,
The method according to claim 2, characterized in that accelerated cooling is performed at a cooling stop temperature of 650° C. or lower.
冷却停止温度650℃以下の加速冷却を行う事を特徴と
する請求項3に記載の方法。[Claim 6] After finishing rolling, the cooling rate is 5°C/sec or more,
The method according to claim 3, characterized in that accelerated cooling is performed at a cooling stop temperature of 650° C. or lower.
理を行う事を特徴とする請求項1に記載の方法。7. The method according to claim 1, further comprising performing quenching and tempering treatment after the rolling is completed.
理を行う事を特徴とする請求項2に記載の方法。8. The method according to claim 2, further comprising performing quenching and tempering treatment after the rolling is completed.
理を行う事を特徴とする請求項3に記載の方法。9. The method according to claim 3, further comprising performing quenching and tempering treatment after the rolling is completed.
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Cited By (2)
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---|---|---|---|---|
WO2014201877A1 (en) | 2013-06-19 | 2014-12-24 | 宝山钢铁股份有限公司 | Zinc-induced-crack resistant steel plate and manufacturing method therefor |
CN112746218A (en) * | 2019-12-30 | 2021-05-04 | 宝钢湛江钢铁有限公司 | Low-cost, high-crack-resistance and high-heat-input-welding YP 420-grade steel plate and manufacturing method thereof |
-
1991
- 1991-04-06 JP JP3073387A patent/JP3009750B2/en not_active Expired - Fee Related
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2014201877A1 (en) | 2013-06-19 | 2014-12-24 | 宝山钢铁股份有限公司 | Zinc-induced-crack resistant steel plate and manufacturing method therefor |
CN112746218A (en) * | 2019-12-30 | 2021-05-04 | 宝钢湛江钢铁有限公司 | Low-cost, high-crack-resistance and high-heat-input-welding YP 420-grade steel plate and manufacturing method thereof |
CN112746218B (en) * | 2019-12-30 | 2021-11-16 | 宝钢湛江钢铁有限公司 | Low-cost, high-crack-resistance and high-heat-input-welding YP 420-grade steel plate and manufacturing method thereof |
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