JPH0757885B2 - Manufacturing method of steel plate with excellent low temperature toughness - Google Patents
Manufacturing method of steel plate with excellent low temperature toughnessInfo
- Publication number
- JPH0757885B2 JPH0757885B2 JP9165688A JP9165688A JPH0757885B2 JP H0757885 B2 JPH0757885 B2 JP H0757885B2 JP 9165688 A JP9165688 A JP 9165688A JP 9165688 A JP9165688 A JP 9165688A JP H0757885 B2 JPH0757885 B2 JP H0757885B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- steel
- rolling
- temperature toughness
- low temperature
- 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.)
- Expired - Lifetime
Links
- 229910000831 Steel Inorganic materials 0.000 title claims description 52
- 239000010959 steel Substances 0.000 title claims description 52
- 238000004519 manufacturing process Methods 0.000 title claims description 19
- 238000005096 rolling process Methods 0.000 claims description 33
- 238000001816 cooling Methods 0.000 claims description 24
- 229910052758 niobium Inorganic materials 0.000 claims description 17
- 229910052759 nickel Inorganic materials 0.000 claims description 15
- 229910000859 α-Fe Inorganic materials 0.000 claims description 15
- 229910052719 titanium Inorganic materials 0.000 claims description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 229910052796 boron Inorganic materials 0.000 claims description 11
- 229910052720 vanadium Inorganic materials 0.000 claims description 10
- 229910052710 silicon Inorganic materials 0.000 claims description 9
- 238000007711 solidification Methods 0.000 claims description 9
- 230000008023 solidification Effects 0.000 claims description 9
- 229910052791 calcium Inorganic materials 0.000 claims description 8
- 229910052748 manganese Inorganic materials 0.000 claims description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 239000002244 precipitate Substances 0.000 claims description 5
- 239000000047 product Substances 0.000 claims description 5
- 229910052726 zirconium Inorganic materials 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims 9
- 238000000034 method Methods 0.000 description 20
- 239000000463 material Substances 0.000 description 11
- 230000009466 transformation Effects 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 7
- 238000007670 refining Methods 0.000 description 5
- 238000005266 casting Methods 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 238000003303 reheating Methods 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229910001562 pearlite Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、均質かつ方向性のない強靭鋼板を鋳造後再加
熱することなしに鋳造まま或いは小圧減比の圧延によっ
て製造する方法に関する。Description: TECHNICAL FIELD The present invention relates to a method for producing a homogeneous and non-oriented tough steel sheet by casting as-cast or by rolling with a small reduction ratio without reheating after casting.
［従来の技術］ 熱間圧延鋼板の製造技術においては、製造コストの低減
のため工程の簡略化や省略をすることが近年強く指向さ
れてきている。鋳造と熱間圧延との中間工程である再加
熱工程の省略ないしは簡略化を目的とした直送圧延指向
もその一つの表われである。[Prior Art] In the manufacturing technology of hot-rolled steel sheet, it has been strongly aimed in recent years to simplify or omit the process in order to reduce the manufacturing cost. One of the manifestations is direct-flow rolling for the purpose of omitting or simplifying the reheating step, which is an intermediate step between casting and hot rolling.
しかしながら、このような直送圧延技術の開発は主とし
て従来の圧延による結晶粒の微細化技術に立脚したもの
が殆どであり、圧延工程の省略ないしは簡略化の実現に
までは至っていない。However, most of the developments of such a direct-feed rolling technique are based on the conventional technique of refining crystal grains by rolling, and the omission or simplification of the rolling process has not been realized.
厚鋼至を直送圧延することは、鋼板の低温靭性がそれほ
ど厳しくは要求されない軟鋼や一般の普通鋼分野では、
冶金学的には実施できることがよく知られている。しか
しながら、低温用鋼や低温靭性の要求される高張力鋼な
どについては、直送圧延すると従来の製造法によるもの
に比べて低温靭性が劣る。Direct rolling of thick steel is necessary for mild steel and general ordinary steel fields where low temperature toughness of steel sheet is not required so severely.
It is well known that it can be carried out metallurgically. However, for low-temperature steels and high-strength steels that require low-temperature toughness, low-temperature toughness is inferior when they are directly fed and rolled as compared with those produced by conventional manufacturing methods.
その主たる原因は、直送圧延においては圧延前の初期オ
ーステナイト粒が極めて大きく、圧延による組織微細化
が困難であることによる。これを補う手段として、例え
ば特開昭57−131320号公報に開示されているように、強
度の制御圧延を制御冷却に先行させる方法が提案されて
いる。The main reason for this is that in direct rolling, the initial austenite grains before rolling are extremely large, and it is difficult to make the structure fine by rolling. As a means for compensating for this, for example, as disclosed in JP-A-57-131320, a method has been proposed in which strength controlled rolling precedes controlled cooling.
しかしながら、このような方法は圧延中の時間−温度管
理制約が大きく、圧延工程の生産性を著しく阻害するこ
とになる。However, such a method has a large time-temperature control constraint during rolling, and significantly impairs the productivity of the rolling process.
このような圧延による組織微細化技術の直送圧延への適
用の限界を補う手段として、例えば特開昭61−213322号
公報に開示されているように、TiO,Ti2O3のいずれか１
種または２種の複合した結晶相を含む酸化物系介在物を
変態核として利用した組織微細化の方法が提案されてい
る。しかしながら、このような方法はTi量による材質の
変動が大きく、またTi量を精錬段階で精度良く制御する
ことが困難であるという欠点がある。As a means for compensating for the limitation of the application of the structure refining technique by rolling to direct rolling, for example, as disclosed in JP-A-61-213322, either TiO or Ti 2 O 3 is used.
There has been proposed a method of refining a structure using an oxide-based inclusion containing one or two composite crystal phases as a transformation nucleus. However, such a method has the drawbacks that the material changes greatly depending on the Ti content and that it is difficult to control the Ti content with high precision in the refining stage.
［発明が解決しようとする課題］ Ti系の介在物を変態核として利用して組織の微細化を計
る方法については、溶接金属あるいは溶接熱影響部の高
靭化技術として既知であり、直送圧延時の鋼板の製造に
関しても前述の特開昭61−213322号公報に開示してあ
る。[Problems to be Solved by the Invention] A method of using a Ti-based inclusion as a transformation nucleus to refine the structure is known as a technique for toughening a weld metal or a heat-affected zone of a weld, and direct rolling The production of a steel sheet at that time is also disclosed in the above-mentioned JP-A-61-213322.
直送圧延時の鋼板の製造においてTi酸化物系析出物を利
用するためには、Ti酸化物を微細に分散析出させる必要
があるが、その際Tiを過剰に添加すると、残存した固溶
Tiによる析出硬化によって、特に溶接熱影響部等におけ
る靭性の劣化が生じる。そのため精錬段階においてTi量
を正確に制御する必要があるが、これは容易ではなく安
定的かつ効率的な生産が困難であるという欠点がある。In order to utilize Ti oxide-based precipitates in the production of steel sheets during direct rolling, it is necessary to finely disperse and precipitate Ti oxides.
Precipitation hardening due to Ti causes deterioration in toughness, particularly in the weld heat affected zone. Therefore, it is necessary to accurately control the Ti content in the refining stage, but this is not easy and there is a drawback that stable and efficient production is difficult.
本発明はTi系の介在物を使用することなく、より安定的
かつ効率的な直送圧延プロセスによる鋼板の製造を可能
にすることを目的とする。An object of the present invention is to enable the production of a steel sheet by a more direct and efficient direct rolling process without using Ti-based inclusions.
［課題を解決するための手段］ 本発明は、上記の目的を達成するために、以下の手段を
採用した。[Means for Solving the Problems] The present invention adopts the following means in order to achieve the above object.
すなわち、重量％でC:0.001〜0.300％、Si:0.8％以下、
Mn:0.4〜2.0％、Al:0.007％以下、O:0.0010〜0.0100
％、を基本成分とし、必要によりCu:1.5％以下、Ni:10
％以下、Cr:1％以下、Mo:1％以下、Nb:0.2％以下、V:0.
5％以下、Ti:0.005％以下、Zr:0.015％以下、B:0.0025
％以下、REM:0.010％以下、Ca:0.005％以下のいずれか
１種または２種以上を含み、残部鉄および不純物を含む
溶鋼を、液相線〜固相線間の冷却速度が10℃／分以上に
て冷却して、（Mn,Si）Ｏを含む酸化物系介在物を分散
析出し、かつその凝固後の冷却途上において800℃以上
の温度から鋳造ままなしは圧減比1.5以下で圧延したの
ち、800℃から600℃以下までの間を２℃／秒以上50℃／
秒以下の冷却速度で冷却することを特徴とするアシキュ
ラーフェライト組織を有する鋼板の製造法である。That is, C: 0.001 to 0.300% by weight, Si: 0.8% or less,
Mn: 0.4-2.0%, Al: 0.007% or less, O: 0.0010-0.0100
% As a basic component, if necessary Cu: 1.5% or less, Ni: 10
% Or less, Cr: 1% or less, Mo: 1% or less, Nb: 0.2% or less, V: 0.
5% or less, Ti: 0.005% or less, Zr: 0.015% or less, B: 0.0025
% Or less, REM: 0.010% or less, Ca: 0.005% or less, and a molten steel containing any one or two or more and the balance iron and impurities, and the cooling rate between the liquidus and solidus lines is 10 ° C / After the solidification, the oxide-based inclusions containing (Mn, Si) O are dispersed and precipitated, and during solidification, cooling is performed at a temperature of 800 ° C or higher at an as-cast temperature of 1.5 or less. After rolling, the temperature between 800 ° C and 600 ° C is 2 ° C / sec or more and 50 ° C / sec.
It is a method for producing a steel sheet having an acicular ferrite structure, characterized by cooling at a cooling rate of not more than a second.
以下に、まず、本発明に関わる鋼材の成分組成を限定す
る理由について述べる。First, the reasons for limiting the composition of the steel material according to the present invention will be described below.
C,Si,Mnは鋼材の強度を高める一方HAZ組織の硬化を促す
ので適量が必要であるが、高すぎないようにしなければ
ならない。本発明法の適用が意図される鋼材では、この
ような観点からＣについては0.001から0.300％、Siにつ
いては0.8％以下、Mnについては0.4％から2.0％の範囲
とした。C, Si, Mn increase the strength of the steel material while promoting the hardening of the HAZ structure, so an appropriate amount is required, but it must be kept not too high. In the steel material to which the method of the present invention is intended, from such a viewpoint, 0.001 to 0.300% for C, 0.8% or less for Si, and 0.4% to 2.0% for Mn.
Alは一般に脱酸を目的として添加されるが、Alが0.007
％より高いと微細なアシキュラーフェライト組織の生成
核としての（Mn,Si）Ｏを含む酸化物系介在物の生成が
阻害される。したがって、Alについては0.007％以下と
した。また、Ｏについては上記酸化物系介在物を充分に
確保し、かつ過度のＯによる材質の劣化を避けるために
0.0010％から0.0100％の範囲とした。Al is generally added for the purpose of deoxidation, but Al is 0.007
%, The formation of oxide inclusions containing (Mn, Si) O as formation nuclei of a fine acicular ferrite structure is inhibited. Therefore, Al is set to 0.007% or less. Regarding O, in order to sufficiently secure the above oxide-based inclusions and to avoid deterioration of the material due to excessive O
The range was 0.0010% to 0.0100%.
Cuは鋼材の耐食性と強度の向上に有効であるが、多過ぎ
ると溶接金属の熱間割れを起こすので1.5％以下とし
た。Cu is effective for improving the corrosion resistance and strength of steel, but if it is too much, it causes hot cracking of the weld metal, so it was made 1.5% or less.
Niは鋼材の強度と低温靭性を同時に高めるので、そのよ
うな目的には添加する程好ましいが、Niが10％を超える
鋼では本発明による経済的効果が得にくい。したがっ
て、10％以下とした。Since Ni enhances the strength and low temperature toughness of the steel material at the same time, it is preferable to add Ni for such purpose, but it is difficult to obtain the economical effect according to the present invention with the steel containing more than 10% Ni. Therefore, it is set to 10% or less.
Cr,Mo,Bは鋼の焼き入れ性を高め、本発明によるプロセ
スではアシキュラーフェライト組織の安定化に有効であ
る。しかしながら、多過ぎるとγ相からの変態過程で熱
間割れを生ずる。したがって、CrとMoについてはそれぞ
れ１％以下、Ｂについては0.0025％以下とした。Cr, Mo and B enhance the hardenability of steel and are effective in stabilizing the acicular ferrite structure in the process of the present invention. However, if too much, hot cracking occurs during the transformation process from the γ phase. Therefore, Cr and Mo are each set to 1% or less, and B is set to 0.0025% or less.
Nb,Vは、本発明法においては圧延後の冷却過程におい
て、微細な炭窒化物としては析出して鋼の強度を高める
が、多過ぎると鋼材の低温靭性を損なう。したがって、
Nbは0.2％以下、Ｖは0.5％以下とした。In the method of the present invention, Nb and V precipitate as fine carbonitrides in the cooling process after rolling to enhance the strength of the steel, but if they are too large, they impair the low temperature toughness of the steel material. Therefore,
Nb was 0.2% or less and V was 0.5% or less.
Tiは本発明においてはTi系の介在物を用いないことか
ら、その上限を0.005％とした。In the present invention, Ti does not use Ti-based inclusions, so the upper limit was made 0.005%.
Zr,Ca,REMは鋼中のＳを固定し、鋼材の延性や切欠靭性
に有害なMnSを低減する働きがあるので、そのような用
途に対して添加される。ただし、多過ぎると鋼の清浄度
を低下させ、鋼板の内部欠陥の原因になる。またZr,Ca,
REMの過剰な添加は酸化物系介在物中の（Mn,Si）Ｏの析
出量を著しく低下させることから、Zrについては上限を
0.015％、Caについては0.005％、REMについては0.010％
とした。Zr, Ca, and REM have the function of fixing S in steel and reducing MnS, which is harmful to the ductility and notch toughness of steel, and are therefore added for such applications. However, if the amount is too large, the cleanliness of the steel is lowered, which causes internal defects in the steel sheet. Also Zr, Ca,
Since excessive addition of REM significantly reduces the amount of (Mn, Si) O precipitation in oxide inclusions, the upper limit of Zr is set.
0.015%, 0.005% for Ca, 0.010% for REM
And
なお、P,SおよびＮについては本発明法における技術的
要件に対しては第一義的に重要な意味はないが、溶接継
手部（熱影響:HAZ、および溶接金属部）の靭性にとって
好ましくないので低い程好ましく、P,Sについては0.025
％以下、Ｎについては0.0050％以下であることが望まし
い。It should be noted that P, S, and N have no primary meaning to the technical requirements in the method of the present invention, but are preferable for the toughness of the welded joint (heat effect: HAZ, and weld metal). Since it is not present, the lower the better, and 0.025 for P and S.
%, And N is preferably 0.0050% or less.
つぎに、本発明法の圧延方法と圧延後の冷却条件につい
て限定する理由を述べる。Next, the reasons for limiting the rolling method of the present invention and the cooling conditions after rolling will be described.
本発明においては、以上述べたような成分条件を満たし
た溶鋼を、液相線〜固相線間の冷却速度を10℃／分以上
にて冷却して、（Mn,Si）Ｏを含む酸化物系介在物を分
散析出し、かつその凝固後の冷却途上において800℃以
上の温度から鋳造ままないしは鋳片厚み（または鋼塊厚
み）／製品厚みで定義する圧減比1.5以下で圧延したの
ち、800℃から600℃までの間を２℃／秒から50℃／秒以
下の冷却速度で冷却しなければならない。In the present invention, a molten steel satisfying the above-described compositional conditions is cooled at a cooling rate between the liquidus and solidus lines of 10 ° C./min or more to perform oxidation including (Mn, Si) O. After the solid inclusions are dispersed and precipitated, and after solidification, they are rolled from a temperature of 800 ° C or higher in the as-cast state or at a reduction ratio of 1.5 or less defined by the thickness of the ingot (or the thickness of the ingot) / the product thickness. , Between 800 ° C and 600 ° C must be cooled at a cooling rate of 2 ° C / sec to 50 ° C / sec or less.
本発明法においては、酸化物系介在物を変態核としたア
シキュラーフェライト組織を活用するが、そのためには
変態核となる（Mn,Si）Ｏを含む酸化物系介在物を二次
脱酸生成物として微細に分散析出させることが必要であ
る。In the method of the present invention, an acicular ferrite structure having an oxide-based inclusion as a transformation nucleus is utilized. For that purpose, the oxide-based inclusion containing (Mn, Si) O that serves as a transformation nucleus is secondarily deoxidized. It is necessary to finely disperse and precipitate the product.
二次脱酸生成物の生成は凝固冷速と密接な関係にあり、
凝固冷速が遅くなればなるほど二次脱酸生成物は粗大化
し、その個数も減少して10℃／分未満の冷速では充分な
個数の変態核が確保し得なくなる。したがって、凝固冷
速（液相線〜固相線間の冷却速度）を10℃／分以上とす
ることが必要である。800℃未満の温度における圧延は
γ相に圧延加工組織を残存させ、アシキュラーフェライ
ト組織の形成に有害である。The formation of the secondary deoxidation product is closely related to the solidification cooling rate,
The slower the solidification cooling rate, the coarser the secondary deoxidation product becomes, and the number thereof also decreases, so that a sufficient number of transformation nuclei cannot be secured at a cooling rate of less than 10 ° C / min. Therefore, it is necessary to set the solidification cooling rate (cooling rate between the liquidus line and the solidus line) to 10 ° C./min or more. Rolling at a temperature lower than 800 ° C. leaves a rolling work structure in the γ phase and is harmful to the formation of an acicular ferrite structure.
また、圧減比1.5超の圧延を施すと、γ粒が細粒化して
粒界からの変態が支配的になり、アシキュラーフェライ
ト組織の形成を阻害する。したがって、圧延は実施しな
いか（すなわち鋳造まま）、あるいは実施するとしても
800以上で、かつ圧減比1.5以下としなければならない。Further, if the reduction ratio exceeds 1.5, the γ grains become finer and the transformation from the grain boundaries becomes dominant, which impedes the formation of the acicular ferrite structure. Therefore, rolling is not carried out (that is, as cast), or if it is carried out,
It must be 800 or more and a reduction ratio of 1.5 or less.
また、800℃未満の冷却速度は、大きすぎると組織が粗
大ベーナイト化あるいはマルテンサイト化し、また小さ
すぎるとフェライト−パーライト化するため、本発明の
目的とするアシキュラーフェライト組織が得られない。
このため、800℃から600℃以下までの間を２℃／秒以上
50℃／秒以下の冷却速度で冷却することが必要である。On the other hand, if the cooling rate is lower than 800 ° C., if it is too large, the structure becomes coarse bainite or martensite, and if it is too small, it becomes ferrite-pearlite, so that the acicular ferrite structure intended by the present invention cannot be obtained.
Therefore, between 800 ℃ and 600 ℃ or less, 2 ℃ / sec or more
It is necessary to cool at a cooling rate of 50 ° C./second or less.
すなわち本発明は主として厚鋼板の製造において、その
製造工程のうちの再加熱工程のみならず圧延工程をも合
わせて省略・簡略化して鋳造−圧延工程の直結化・一体
化を実現するものである。That is, the present invention mainly realizes the direct connection / integration of the casting-rolling process by omitting / simplifying not only the reheating process but also the rolling process in the manufacturing process of the thick steel plate. .
［実 施 例］ 第１表は真空溶解にて製造した鋳片から厚鋼板を製造し
た際の供試鋼の化学成分を示す。[Examples] Table 1 shows the chemical composition of the sample steel when a thick steel plate was produced from a slab produced by vacuum melting.
第２表には製造条件を、第３表には厚鋼板の材質特性を
示す。Table 2 shows the manufacturing conditions, and Table 3 shows the material properties of the thick steel plate.
本発明法で製造した鋼はいずれも従来法で製造した鋼に
比べて低温靭性に優れる。All of the steels produced by the method of the present invention are superior in low temperature toughness to the steels produced by the conventional method.
Ａ成分の鋼Ａ−３は圧減比が2.0と大きく、γ粒の再結
晶がある程度まで進行したためアシキュラーフェライト
組織が得られず靭性が悪い。Ａ−４は、圧延温度が800
℃以下と低く圧延加工組織が発達したため、微細アシキ
ュラーフェライト組織の生成を阻害し靭性が劣化してい
る。Steel A-3, which is an A component, has a large reduction ratio of 2.0, and the recrystallization of γ grains has progressed to a certain degree, so that an acicular ferrite structure cannot be obtained and the toughness is poor. A-4 has a rolling temperature of 800
Since the rolling work structure developed as low as ℃ or less, the formation of the fine acicular ferrite structure was hindered and the toughness deteriorated.
Ａ−５は、800〜500℃の変態域冷速が遅く、組織が粗大
なフェライト−パーライトとなったため極めて靭性が悪
い。Ａ−６は、逆に変態域冷速が早過ぎて組織が粗大な
上部ベーナイト化したため靭性に劣る。Ａ−７は、凝固
冷速が10℃／分未満の部位（最終凝固位置）があり、変
態核となる酸化物の生成が不充分となったため靭性が悪
い。A-5 has a very low toughness because it has a slow cooling rate in the transformation range of 800 to 500 ° C. and has a coarse structure of ferrite-pearlite. On the contrary, A-6 is inferior in toughness because the transformation region cold speed is too fast and the structure becomes coarse upper bainite. A-7 has a portion (final solidification position) where the solidification cooling rate is less than 10 ° C./min, and the toughness is poor because the formation of oxides that serve as transformation nuclei is insufficient.
Ｂ成分の鋼Ｂ−１およびＢ−２は、Al量が0.025％と多
く、Al2O3主体の酸化物が生成したため、（Mn,Si）Ｏ系
の酸化物が生成が不充分となり靭性が劣化したものであ
る。In the B component steels B-1 and B-2, the amount of Al was as large as 0.025%, and the oxide mainly composed of Al 2 O 3 was generated, so that the (Mn, Si) O-based oxide was insufficiently generated and the toughness was increased. Is deteriorated.
また、本発明鋼の実施例をさらに、第４表〜第６表に示
す。第４表には化学成分を、第５表には、製造条件、第
６表には厚鋼板の材質特性を示す。Further, Examples of the steel of the present invention are further shown in Tables 4 to 6. Table 4 shows chemical components, Table 5 shows manufacturing conditions, and Table 6 shows material properties of thick steel plates.
［発明の効果］ ラインパイプ、低温用各種貯蔵・圧力容器、造船・海
溝、その他常温域あるいはそれ以下の温度域で使用され
る各種の鋼構造物に使われる鋼を、鋳造ままあるいは鋳
造後直ちに小圧減比での圧延を施したのち、その冷却過
程で加速冷却によって、酸化物系介在物を核として放射
状に発達する微細なアシキュラーフェライト組織を得る
ことにより、従来の再加熱圧延材、直送圧延材あるいは
それを焼き入れ焼き戻し、焼鈍、さらには圧延後直ちに
加速冷却法によって製造される鋼板と同等ないしはそれ
以上の強度と靭性を付与するとともに、従来法に比較し
て圧延省略あるいは極めて軽微な圧延にて、高品質な鋼
板の製造が可能になることから、飛躍的な生産性の向上
と設備コストの低減を可能にするものである。 [Effects of the Invention] Steel used for various kinds of steel structures used in line pipes, various low temperature storage / pressure vessels, shipbuilding / sea trenches, and other normal temperature regions or lower temperature regions, as-cast or immediately after casting. After performing rolling with a small reduction ratio, by accelerated cooling in the cooling process, to obtain a fine acicular ferrite structure that develops radially with oxide inclusions as nuclei, conventional reheated rolled material, Directly rolled material or quenching and tempering of it, annealing, and immediately after rolling, it imparts strength and toughness equivalent to or better than that of steel sheet manufactured by accelerated cooling method, and omits or extremely reduces rolling compared to conventional methods. Since it is possible to manufacture high-quality steel sheets with slight rolling, it is possible to dramatically improve productivity and reduce equipment costs.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭61−113715（ＪＰ，Ａ) 特開 昭55−113861（ＪＰ，Ａ) 特開 昭59−35629（ＪＰ，Ａ) ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-113715 (JP, A) JP 55-113861 (JP, A) JP 59-35629 (JP, A)
Claims (5)
冷却速度が10℃／分以上にて冷却して、（Mn,Si）Ｏを
含む酸化物系介在物を分散析出し、かつその凝固後の冷
却途上において800℃以上の温度から鋳造ままないしは
鋳片厚み（または鋼塊厚み）／製品厚みで定義する圧減
比1.5以下で圧延したのち、800℃から600℃以下までの
間を２℃／秒以上50℃／秒以下の冷却速度で冷却するこ
とを特徴とするアシキュラーフェライト組織を有する低
温靭性の優れた鋼板の製造法。Claims 1. In weight%, C: 0.001 to 0.300% Si: 0.8% or less Mn: 0.4 to 2.0% Al: 0.007% or less O: 0.0010 to 0.0100% as a basic component, molten steel containing the balance iron and impurities, Cooling is performed at a cooling rate between the liquidus and solidus lines of 10 ° C./min or more to disperse and precipitate oxide inclusions containing (Mn, Si) O, and 800 during cooling after solidification. From the temperature of ℃ or more, as-cast or after rolling at a reduction ratio of 1.5 or less defined by the thickness of the slab (or the thickness of the ingot) / the product thickness, then 2 ℃ / sec or more and 50 ℃ or more between 800 ℃ and 600 ℃ or less A method for producing a steel sheet having an acicular ferrite structure and excellent in low-temperature toughness, characterized in that the steel sheet is cooled at a cooling rate of not more than 1 second.
を含む溶鋼を用いる請求項１に記載するアシキュラーフ
ェライト組織を有する低温靭性の優れた鋼板の製造法。[2] The basic components include Cu: 1.5% or less, Ni: 10% or less, Cr: 1% or less, Mo: 1% or less, Nb: 0.2% or less, V: 0.5% or less, Ti: 0.005% or less, B: 0.0025% or less, REM. : 0.010% or less Ca: 0.005% or less Zr: 0.15% or less Any one or two of the following is used, and a molten steel containing the balance iron and impurities is used, and excellent low temperature toughness having an acicular ferrite structure according to claim 1. Steel plate manufacturing method.
を用いる請求項１に記載するアシキュラーフェライト組
織を有する低温靭性の優れた鋼板の製造法。3. A basic component containing Cu: 1.5% or less, Ni: 10% or less, Mo: 1% or less, Nb: 0.2% or less, V: 0.5% or less, Ti: 0.005% or less, B: 0.0025% or less, Ca: 0.005% or less, Zr. : 0.015% or less (I) Ti, Cu, Ni (II) B, Cu, Ni (III) Nb, Ti, Ca (IV) NB, Ti, V (V) Nb, Ti, B (VI) Ti 2. A molten steel containing 3 kinds of Ca, Zr (VII) Nb, B, V (VIII) Nb, Ni, Mo (IX) Nb, Cu, Ni and the balance iron and impurities is used. A method for producing a steel sheet having an acicular ferrite structure and excellent in low temperature toughness.
を用いる請求項１に記載するアシキュラーフェライト組
織を有する低温靭性の優れた鋼板の製造法。(4) Of the basic components, Cu: 1.5% or less Ni: 10% or less Nb: 0.2% or less V: 0.5% or less Ti: 0.005% or less B: 0.0025% or less Ca: 0.005% or less (I) Nb , Ti, Ca, B (II) Nb, Ti, B, V (III) Nb, Ti, Cu, Ni (IV) Nb, B, Ni, V including 4 types, including the balance iron and impurities The method for producing a steel sheet having an acicular ferrite structure and excellent low temperature toughness according to claim 1, wherein molten steel is used.
を用いる請求項１に記載するアシキュラーフェライト組
織を有する低温靭性の優れた鋼板の製造法。5. A basic component containing Cu: 1.5% or less Ni: 10% or less Cr: 1% or less Mo: 1% or less Nb: 0.2% or less V: 0.5% or less Ti: 0.005% or less B: 0.0025% or less Ca : 0.005% or less (I) Nb, Ti, Cu, Ni, Cr (II) Nb, Ti, Ca, Cu, Ni (III) Nb, Ti, Cu, Ni, V (IV) Nb, Ti, B , Cu, Ni (V) Cu, Ni, Cr, Mo, V containing 5 kinds, and using molten steel containing the balance iron and impurities, the low temperature toughness having an acicular ferrite structure according to claim 1 is excellent. Steel plate manufacturing method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9165688A JPH0757885B2 (en) | 1987-04-24 | 1988-04-15 | Manufacturing method of steel plate with excellent low temperature toughness |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9968587 | 1987-04-24 | ||
| JP62-99685 | 1987-04-24 | ||
| JP9165688A JPH0757885B2 (en) | 1987-04-24 | 1988-04-15 | Manufacturing method of steel plate with excellent low temperature toughness |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6425917A JPS6425917A (en) | 1989-01-27 |
| JPH0757885B2 true JPH0757885B2 (en) | 1995-06-21 |
Family
ID=26433095
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9165688A Expired - Lifetime JPH0757885B2 (en) | 1987-04-24 | 1988-04-15 | Manufacturing method of steel plate with excellent low temperature toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0757885B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5167628B2 (en) * | 2006-11-17 | 2013-03-21 | 新日鐵住金株式会社 | Steel slab with fine solidification structure |
| JP5459166B2 (en) * | 2010-09-28 | 2014-04-02 | 新日鐵住金株式会社 | Steel plate for ice sea structure |
| JP5612532B2 (en) * | 2011-04-26 | 2014-10-22 | 株式会社神戸製鋼所 | Steel sheet excellent in low temperature toughness and weld joint fracture toughness and method for producing the same |
-
1988
- 1988-04-15 JP JP9165688A patent/JPH0757885B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6425917A (en) | 1989-01-27 |
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