JPH09209025A - Production of hic resistant steel excellent in low temperature toughness in welded part - Google Patents
Production of hic resistant steel excellent in low temperature toughness in welded partInfo
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- JPH09209025A JPH09209025A JP1984896A JP1984896A JPH09209025A JP H09209025 A JPH09209025 A JP H09209025A JP 1984896 A JP1984896 A JP 1984896A JP 1984896 A JP1984896 A JP 1984896A JP H09209025 A JPH09209025 A JP H09209025A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は耐ＨＩＣ性および溶
接部の低温靱性に優れた鋼の溶製方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting steel having excellent HIC resistance and low temperature toughness of a welded portion.
【０００２】[0002]
【従来の技術】低温かつ腐食性環境で用いられるライン
パイプ材では、母材および溶接部の両方での高い耐サワ
−性と溶接部の優れた低温靱性とが要求される。2. Description of the Related Art A line pipe material used in a low temperature and corrosive environment is required to have a high saw resistance in both a base material and a welded portion and excellent low temperature toughness in the welded portion.
【０００３】ラインパイプなどで発生する水素誘起割れ
（以下、ＨＩＣと記す）は、圧延時に線状に破砕された
Al2O3 クラスターや線状に伸延されたMnS を起点に発生
することが知られている。したがって従来、溶鋼にＣａ
含有物質を添加することによりAl2O3 クラスターをＨＩ
Ｃの起点とならない球状介在物に形態制御するととも
に、Ｃａと溶鋼中の硫黄〔Ｓ〕とを反応させ、CaO-Al2O
3-CaS 系介在物として脱硫することによりMnS の生成を
抑止する技術がある。[0003] Hydrogen-induced cracking (hereinafter referred to as HIC) generated in a line pipe or the like is crushed linearly during rolling.
It is known to originate from Al 2 O 3 clusters and linearly elongated MnS. Therefore, conventionally, Ca
HI was added to the Al 2 O 3 clusters by adding the contained substances.
In addition to controlling the morphology of spherical inclusions that do not become the starting point of C, Ca reacts with sulfur [S] in the molten steel to produce CaO-Al 2 O
There is a technology that suppresses the formation of MnS by desulfurizing as 3- CaS inclusions.
【０００４】一方、ラインパイプなどの電縫溶接管で
は、溶接部およびその近傍に存在する介在物が電縫溶接
するときに変形し、溶接部の低温靱性が低下することが
知られている。従って、介在物形態を変形しない組成に
制御し、溶接部の低温靱性を向上させる技術が知られて
いる。On the other hand, in an ERW pipe such as a line pipe, it is known that a weld portion and an inclusion existing in the vicinity thereof are deformed during ERW welding, and the low-temperature toughness of the weld portion is reduced. Therefore, a technique is known in which the inclusion morphology is controlled to a composition that does not deform to improve the low temperature toughness of the weld.
【０００５】一般に、ラインパイプなどの耐ＨＩＣ鋼は
以下の方法によって製造される。転炉出鋼後の溶鋼をＡ
ｌなどで脱酸した後、ＲＨ真空脱ガス装置などを用いて
溶鋼中の窒素および水素を除去する。この後、溶鋼脱硫
処理を施す場合もある。このように脱酸および脱ガス処
理した後、溶鋼にＣａ含有物質を添加する。一般に添加
するＣａ含有物質としては、Ｃａを約３０wt％含んだＣ
ａ−ＳｉおよびＣａ−ＡｌなどのＣａ合金が用いられ
る。Ｃａ含有物質の添加方法としては、溶鋼に浸漬した
ランスから不活性ガスとともにＣａ含有物質を溶鋼中に
吹き込むインジェクション方法と、Ｃａ含有物質粉を鉄
で被覆し線状となしたものを溶鋼に送り込むワイヤーフ
ィーダー法とが用いられている。Generally, HIC resistant steel such as line pipe is manufactured by the following method. Molten steel after converter tapping is A
After deoxidizing with 1, etc., nitrogen and hydrogen in the molten steel are removed using an RH vacuum degassing device or the like. After this, molten steel desulfurization treatment may be performed. After deoxidation and degassing in this way, a Ca-containing substance is added to the molten steel. As a Ca-containing substance generally added, C containing about 30 wt% of Ca
Ca alloys such as a-Si and Ca-Al are used. As a method of adding the Ca-containing substance, an injection method in which the Ca-containing substance is blown into the molten steel together with an inert gas from a lance immersed in the molten steel, and a wire-like one in which the powder of the Ca-containing substance is coated with iron and fed into the molten steel is sent. The wire feeder method is used.
【０００６】しかし、そのＣａ処理方法が不適切である
とAl2O3 クラスターの球状化が不十分となり、または添
加Ｃａと溶鋼中〔Ｓ〕との反応により生成したCaS クラ
スターや凝固時に生成するMnS により、耐ＨＩＣ性が著
しく悪化する。さらに、電縫溶接時に変形しやすい介在
物が多量に生成し、溶接部の低温靱性が悪化する。However, if the Ca treatment method is inappropriate, the spheroidization of Al 2 O 3 clusters becomes insufficient, or CaS clusters formed by the reaction between added Ca and molten steel [S] or during solidification are formed. MnS significantly deteriorates the HIC resistance. Furthermore, a large amount of inclusions that are easily deformed during electric resistance welding are generated, and the low temperature toughness of the welded portion deteriorates.
【０００７】このような問題を解決するため、従来、耐
ＨＩＣ性あるいは低温靱性の向上を図るいくつかの方法
が提案されてきた。In order to solve such a problem, several methods for improving the HIC resistance or the low temperature toughness have been conventionally proposed.
【０００８】母材の耐ＨＩＣ性向上を図る方法として
は、以下のような方法がある。As a method for improving the HIC resistance of the base material, there are the following methods.
【０００９】特開昭57-9822 号公報は、CaS クラスター
介在物の少ない清浄度の優れたラインパイプ用鋼材を製
造するために「溶鋼中のＳ含有量を２０ppm 以下に低減
するとともに、７０ppm 以下のＣａを添加する工程など
を有する製造方法」を提案している。この方法における
上記限定は、「Ｓは溶鋼へのＣａの添加によりCaS とし
て固定されるが、CaS クラスター介在物の発生に非常に
鋭敏な効果を有するため、ＣａおよびＳの濃度積を低く
するため」である。Japanese Unexamined Patent Publication (Kokai) No. 57-9822 discloses that in order to produce a steel material for a line pipe having a low cleanliness of CaS cluster inclusions, the content of S in molten steel is reduced to 20 ppm or less and 70 ppm or less. Manufacturing method including a step of adding Ca, etc. The above-mentioned limitation in this method is that "S is fixed as CaS by the addition of Ca to the molten steel, but since it has a very sensitive effect on the generation of CaS cluster inclusions, it reduces the concentration product of Ca and S. It is.
【００１０】特開昭63-7322 号公報は、Ｃａ添加量が不
足することによりAl2O3 系介在物が十分にCaO-Al2O3 系
介在物へ変化しないこと、およびＣａ添加量の過剰によ
りCaS 系介在物が生成することなどの問題点を解決する
ために「溶鋼をＣａ処理するに当たり、下式を満足する
ようにＣａを添加して操業を行う方法」を提案してい
る。Japanese Unexamined Patent Publication No. 63-7322 discloses that Al 2 O 3 -based inclusions are not sufficiently converted to CaO-Al 2 O 3 -based inclusions due to insufficient Ca addition amount, and In order to solve the problems such as the formation of CaS-based inclusions due to excess, "a method for adding Ca so that the following formula is satisfied when performing Ca treatment on molten steel" is proposed.
【００１１】 0.7-14〔Ｓ〕＜〔Ｃａ〕／〔Ｏ〕＜1.1-14〔Ｓ〕 ただし、 〔Ｃａ〕：溶鋼中のＣａ濃度(ppm) 〔Ｓ〕：溶鋼中のＳ濃度（wt％） 〔Ｏ〕：溶鋼中の酸素濃度(ppm) 特開平3-79713 号公報は、Ｃａ添加量を制御するために
上記とは異なる下式を用いる方法を提案している。0.7-14 [S] <[Ca] / [O] <1.1-14 [S] where [Ca]: Ca concentration in molten steel (ppm) [S]: S concentration in molten steel (wt% [O]: Oxygen concentration in molten steel (ppm) Japanese Patent Laid-Open No. 3-79713 proposes a method of using the following formula different from the above to control the amount of Ca added.
【００１２】0.50≦〔Ｃａ〕／〔Ｏ〕T ≦1.00 〔Ｃａ〕≦40 〔Ｏ〕T ≦40 ただし、〔Ｏ〕T ：溶鋼中の全酸素濃度(ppm) ここで、〔Ｃａ〕／〔Ｏ〕T を0.50以上にするのはCaO-
Al2O3 系介在物を融点の低い組成にし、一方1.00以下に
するのはCaS 生成を防止するためである。[0012] 0.50 ≦ [Ca] / [O] T ≦ 1.00 [Ca] ≦ 40 [O] T ≦ 40 provided that [O] T: wherein all the oxygen concentration in the molten steel (ppm), [Ca] / [ O] T is 0.50 or more is CaO-
The composition of the Al 2 O 3 -based inclusions has a low melting point, while 1.00 or less is to prevent CaS formation.
【００１３】特開平3-183721号公報は、Ｃａ添加速度Ｖ
を下式のように制御し、Al2O3 介在物を十分にCaO-Al2O
3 系介在物に改質するとともに、CaS の生成を抑止する
方法を提案している。Japanese Unexamined Patent Publication No. 3-183721 discloses a Ca addition rate V
Is controlled according to the following formula, and the Al 2 O 3 inclusions are sufficiently CaO-Al 2 O
We have proposed a method to suppress the formation of CaS while reforming it to a three- system inclusion.
【００１４】Ｖ≦−25×〔Ｃ〕＋35 ただし、Ｖ ：Ｃａ添加速度〔g/(min・ton ・steel)〕 〔Ｃ〕：溶鋼中のＣ含有量（wt％） 一方、耐ＨＩＣ性と溶接部の低温靱性との向上を図る方
法としては、以下のようなものがある。V ≦ −25 × [C] +35 where V: Ca addition rate [g / (min.ton.steel)] [C]: C content in molten steel (wt%) There are the following methods for improving the low temperature toughness of the welded portion.
【００１５】特開昭63-137144 号公報では、鋼中にＺｒ
を添加し、介在物をZrO2・Al2O3 に改質することにより
介在物の融点を上げ、電縫溶接時に介在物を変形・延伸
させない方法が提案されている。In Japanese Patent Laid-Open No. 63-137144, Zr is contained in steel.
Has been proposed to improve the melting point of inclusions by modifying the inclusions into ZrO 2 · Al 2 O 3 so that the inclusions are not deformed or stretched during electric resistance welding.
【００１６】特開平6-41684 号公報では、Ｓ、Ｏおよび
Ｃａの含有量を特定式を満足するように制御した上で、
介在物を (CaO)m ・ (Al2O3)n 系とし、その分子構成比
（ｍ／ｎ）を１未満とする方法が提案されている。In JP-A-6-41684, the contents of S, O and Ca are controlled so as to satisfy a specific expression ,
A method has been proposed in which the inclusion is a (CaO) m · (Al 2 O 3 ) n system and the molecular constitution ratio (m / n) is less than 1.
【００１７】[0017]
【発明が解決しようとする課題】従来、Ｃａ添加により
ＨＩＣの起点となるMnS あるいはAl2O3 クラスターを耐
ＨＩＣ性に無害とされるCaO-Al2O3-CaS 系球状介在物に
改質し、かつＣａ添加時に生成するCaS を抑止すれば、
実用上十分な鋼材の耐ＨＩＣ性が得られると考えられて
きた。Conventionally, MnS or Al 2 O 3 clusters, which are the starting points of HIC by adding Ca, are modified into CaO-Al 2 O 3 -CaS-based spherical inclusions which are harmless to HIC resistance. And suppress CaS generated when Ca is added,
It has been considered that practically sufficient HIC resistance of steel can be obtained.
【００１８】しかし、Ｃａ添加によりＨＩＣの起点とな
る有害介在物を球状CaO-Al2O3-CaS介在物に無害化改質
し、かつCaS 介在物を抑止してもＨＩＣ発生を十分に抑
えることはできない。そこで、本発明者がＣａ添加を施
した鋼材を耐ＨＩＣ評価試験で評価し、電子線マイクロ
アナライザ−（以下、ＥＰＭＡと記す）を用いてＨＩＣ
が発生した鋼材中の介在物形態の観察および組成分析を
行った結果、以下が明らかとなった。However, by adding Ca, the harmful inclusions which are the starting point of HIC are detoxified and modified into spherical CaO-Al 2 O 3 -CaS inclusions, and even if the CaS inclusions are suppressed, HIC generation is sufficiently suppressed. It is not possible. Therefore, the present inventor evaluated the steel material added with Ca by the HIC resistance evaluation test, and HIC was measured using an electron beam microanalyzer (hereinafter referred to as EPMA).
As a result of observing the morphology of inclusions in the steel material in which the occurrence of the phenomenon and analyzing the composition, the following became clear.
【００１９】スラブ中に存在した介在物は全て球状であ
り、その組成はＣａ−Ａｌ−Ｏ−Ｓからなっていた。こ
のスラブを圧延し、この圧延後の鋼中介在物を調査した
ところ、介在物の一部は球状であるものの、多くは線状
に破砕されていた。さらに、この圧延材をＨＩＣ評価試
験にて評価したところ、この線状に破砕された介在物を
起点としてＨＩＣが発生していた。The inclusions present in the slab were all spherical and had a composition of Ca-Al-OS. When this slab was rolled and the inclusions in the steel after this rolling were investigated, some of the inclusions were spherical, but most were crushed into linear shapes. Furthermore, when this rolled material was evaluated by the HIC evaluation test, HIC was generated starting from the linearly crushed inclusions.
【００２０】そこで、圧延した後、線状に破砕された介
在物と球状のままだった介在物の組成を詳細に調査した
ところ、以下が明らかとなった。線状に破砕された介在
物の組成はCaS ＞１０wt％なるCaO-Al2O3-CaS 系介在物
か、あるいはCaO ＜３５wt％およびAl2O3 ＞６５wt％な
る介在物であった。一方、圧延した後も球状であった介
在物は、３５wt％≦CaO ≦９０wt％、CaS ≦１０wt％お
よび残部はAl2O3 からなる組成のものであった。したが
って、介在物組成が不適当であると、溶鋼中およびスラ
ブ中で球状であっても圧延時に破砕し、ＨＩＣの起点と
なるのである。Then, after rolling, the composition of the linearly crushed inclusions and the inclusions that remained spherical were examined in detail, and the following became clear. The composition of the inclusions is crushed linearly was CaS> comprising 10wt% CaO-Al 2 O 3 or -CaS inclusions, or CaO <35 wt% and Al 2 O 3> 65wt% comprising inclusions. On the other hand, the inclusions that were spherical even after rolling had a composition of 35 wt% ≤ CaO ≤ 90 wt%, CaS ≤ 10 wt% and the balance Al 2 O 3 . Therefore, if the composition of inclusions is improper, even if it is spherical in the molten steel and the slab, it is crushed during rolling and becomes the starting point of HIC.
【００２１】また、CaO-Al2O3 系介在物中CaO 濃度が３
５wt％未満、つまり介在物中のCaO／Al2O3(分子構成比)
が0.98未満では、介在物の鋼中〔Ｓ〕吸収能力が低
く、十分に鋼中〔Ｓ〕を低下させることができないため
凝固時の中心偏析によりMnS 介在物が生成する。Further, the CaO concentration in the CaO-Al 2 O 3 -based inclusion is 3
Less than 5 wt%, that is, CaO / Al 2 O 3 in inclusions (molecular composition ratio)
Is less than 0.98, the [S] absorption capacity of the inclusions in the steel is low and the [S] content in the steel cannot be sufficiently lowered, so MnS inclusions are generated due to center segregation during solidification.
【００２２】さらに、溶鋼中のＳ濃度と介在物中のCaS
濃度との相関関係について調査したところ、Ｃａ処理前
において溶鋼中のＳ濃度が７ppm を超えると凝固過程で
介在物中のCaS 濃度が上昇し、最終的に介在物中のCaS
濃度が１０wt％を超えることが判明した。Further, S concentration in molten steel and CaS in inclusions
When the correlation with the concentration was investigated, the CaS concentration in the inclusions increased during the solidification process when the S concentration in the molten steel exceeded 7 ppm before Ca treatment, and finally the CaS concentration in the inclusions increased.
It was found that the concentration exceeded 10 wt%.
【００２３】したがって、鋼材の耐ＨＩＣ性を十分に向
上させるには、MnS およびCaS 単体介在物生成の抑止お
よび介在物の完全球状化に加えて、下記およびを達
成しなければならないのである。Therefore, in order to sufficiently improve the HIC resistance of the steel material, in addition to suppressing the formation of MnS and CaS simple inclusions and completely spheroidizing the inclusions, the following must be achieved.
【００２４】介在物中において、CaS 濃度≦１０wt
％、３５wt％≦CaO 濃度≦９０wt％および残部Al2O3 と
する。In inclusions, CaS concentration ≦ 10 wt
%, 35 wt% ≤ CaO concentration ≤ 90 wt% and the balance Al 2 O 3 .
【００２５】Ｃａ処理前において溶鋼中のＳ濃度を７
ppm 以下とする。Before the Ca treatment, the S concentration in the molten steel was adjusted to 7
It should be below ppm.
【００２６】さらに、本発明者らが溶接部の低温靭性を
悪化させる介在物の形態・組成を特定するために、Ｃａ
添加鋼の低温靭性不良材および良好材の電縫溶接部をＥ
ＰＭＡを用いて詳細に調査した結果、以下が判明した。Further, in order for the present inventors to specify the morphology and composition of inclusions that deteriorate the low temperature toughness of the welded portion, Ca
E for welded parts of low temperature toughness of additive steel and good low temperature toughness
As a result of detailed investigation using PMA, the following was found.
【００２７】低温靱性不良材の溶接部で観察された介在
物形態は球状ではなく、板状に変形したものであった。
その成分はCaO-Al2O3 系であり、組成は３５wt％≦CaO
＜６０wt％、１０wt％＜CaS および残部Al2O3 である。The inclusion morphology observed in the weld of the low temperature toughness poor material was not spherical but deformed into a plate shape.
Its component is CaO-Al 2 O 3 system, composition is 35 wt% ≦ CaO
<60 wt%, 10 wt% <CaS and the balance Al 2 O 3 .
【００２８】一方、低温靱性良好材の溶接部で観察され
た介在物形態は球状であり、変形していなかった。その
成分はCaO-Al2O3 系であり、組成はCaO ≧６０wt％、Ca
S ≦１０wt％および残部Al2O3 であった。この介在物組
成における融点は１６００℃以上であり、介在物の融点
が高いために上記組成の介在物は電縫溶接時に変形しな
かったと考えられる。On the other hand, the morphology of inclusions observed in the welded portion of the low temperature toughness material was spherical and was not deformed. Its component is CaO-Al 2 O 3 system, the composition is CaO ≧ 60 wt%, Ca
S ≦ 10 wt% and the balance Al 2 O 3 . The melting point of this inclusion composition is 1600 ° C. or higher, and it is considered that the inclusion of the above composition did not deform during electric resistance welding because of the high melting point of the inclusion.
【００２９】このことから、Ｃａ添加鋼において電縫溶
接時の介在物変形を阻止し、溶接部の低温靱性を向上さ
せるには、鋼中の介在物組成をCaO 濃度が６０wt％以上
となるように制御すればよいという新たな知見を得た。From the above, in order to prevent the inclusion deformation during the electric resistance welding and improve the low temperature toughness of the welded portion in the Ca-added steel, the inclusion composition in the steel should be such that the CaO concentration is 60 wt% or more. We gained new knowledge that it should be controlled.
【００３０】すなわち、鋼材の耐ＨＩＣ性と溶接部の低
温靱性とを同時に確保するには、鋼中の介在物組成が下
記ａ〜ｃの条件を同時に満たすように制御しなければな
らない。That is, in order to simultaneously secure the HIC resistance of the steel material and the low temperature toughness of the welded portion, the composition of the inclusions in the steel must be controlled so as to simultaneously satisfy the following conditions a to c.
【００３１】ａ．介在物中のCaO 濃度が６０wt％以上９
０wt％以下 ｂ．介在物中のCaS 濃度が１０wt％以下 ｃ．残部がAl2O3 しかし、前記従来の特開昭57-9822 、特開昭63-7322 、
特開平3-79713 および特開平3-183721の各号公報では、
介在物をCaO-Al2O3 系介在物または低融点CaO-Al2O3 系
介在物に制御し、CaS 単体介在物の生成を抑止する方法
を提案しているにすぎず、CaO-Al2O3 系球状介在物の破
砕抑止による耐ＨＩＣ性の向上および電縫溶接時の介在
物変形防止による溶接部の低温靱性向上を十分に達成す
ることができない。A. CaO concentration in inclusions is 60 wt% or more 9
0 wt% or less b. CaS concentration in inclusions is 10 wt% or less c. The balance is Al 2 O 3, however, the above-mentioned conventional JP-A-57-9822, JP-A-63-7322,
In JP-A-3-79713 and JP-A-3-183721,
It only proposes a method of controlling the inclusions to be CaO-Al 2 O 3 -based inclusions or low-melting CaO-Al 2 O 3 -based inclusions to suppress the formation of CaS simple inclusions. It is impossible to sufficiently improve the HIC resistance by suppressing the crushing of 2 O 3 type spherical inclusions and the low temperature toughness improvement of the welded part by preventing the deformation of inclusions during electric resistance welding.
【００３２】特開昭63-137144 号公報の方法では、介在
物をZrO2・Al2O3 に改質することで介在物融点を上昇さ
せ、溶接部の低温靱性を向上させることはできるが、介
在物球状化並びにCaS およびMnS などの硫化物系介在物
の形態制御が不十分であり、実用上十分な耐ＨＩＣ性を
得ることが困難である。In the method disclosed in Japanese Patent Laid-Open No. 63-137144, the melting point of inclusions can be increased by reforming the inclusions into ZrO 2 .Al 2 O 3 to improve the low temperature toughness of the weld. However, spheroidization of inclusions and morphology control of sulfide inclusions such as CaS and MnS are insufficient, and it is difficult to obtain practically sufficient HIC resistance.
【００３３】一方、特開平6-4684号公報の方法では、Ca
O-Al2O3 介在物中のAl2O3 濃度上昇、つまりCaO 濃度の
低下により、介在物融点を上昇させて低温靱性を確保
し、かつこの高融点のCaO-Al2O3 系介在物により耐ＨＩ
Ｃ性が得られるとしている。しかし、高Al2O3 濃度のCa
O-Al2O3 系介在物ではMnS 生成抑止が不十分であり、ま
たは本発明者等が見いだしたように球状介在物の破砕抑
止が困難であり、実用上十分な耐ＨＩＣ性が得られな
い。さらに、高Al2O3 濃度のCaO-Al2O3 系介在物に制御
する具体的手段が示されていない。すなわち、Ｃａ添加
量低減のみで介在物中のAl2O3 濃度を上昇させようとす
ると、介在物の融点を１６００℃（通常の製鋼処理温
度）以下とすることができず、結果として介在物が球状
化されず、耐ＨＩＣ性に致命的なクラスタ−介在物とな
ってしまう。On the other hand, according to the method disclosed in JP-A-6-4684, Ca
By increasing the Al 2 O 3 concentration in the O-Al 2 O 3 inclusions, that is, decreasing the CaO concentration, the melting point of the inclusions is increased to secure low temperature toughness, and this high melting point CaO-Al 2 O 3 inclusion HI resistant depending on the product
It is said that C property can be obtained. However, high Al 2 O 3 concentration of Ca
O-Al 2 O 3 -based inclusions do not sufficiently suppress the formation of MnS, or, as found by the present inventors, it is difficult to suppress the crushing of spherical inclusions, and practically sufficient HIC resistance is obtained. Absent. Furthermore, there is no specific means for controlling CaO-Al 2 O 3 -based inclusions with a high Al 2 O 3 concentration. That is, if an attempt is made to increase the Al 2 O 3 concentration in the inclusions only by reducing the amount of Ca added, the melting point of the inclusions cannot be reduced to 1600 ° C. (normal steelmaking treatment temperature) or less, resulting in inclusions. Are not spheroidized and become cluster inclusions that are fatal to HIC resistance.
【００３４】以上のように従来の技術では、耐ＨＩＣ性
と溶接部の低温靱性とを十分に向上させることができな
かった。As described above, the conventional techniques could not sufficiently improve the HIC resistance and the low temperature toughness of the welded portion.
【００３５】本発明の目的は、上記課題を解決して耐Ｈ
ＩＣ性および溶接部の低温靱性に優れた鋼を製造するこ
とが可能な方法を提供することにある。The object of the present invention is to solve the above problems and to prevent H
An object of the present invention is to provide a method capable of producing a steel excellent in IC property and low temperature toughness of a welded portion.
【００３６】[0036]
【課題を解決するための手段】本発明の要旨は次の耐Ｈ
ＩＣ鋼の製造方法にある。The gist of the present invention is as follows.
It is in the method of manufacturing IC steel.
【００３７】予め脱酸処理された溶鋼中のＳ濃度を脱硫
処理により７ppm 以下とした後、この溶鋼をＣａ処理す
るにあたり、溶鋼中のＣａ濃度と酸素濃度との比〔Ｃ
ａ〕／〔Ｏ〕が下記(1) 式を、かつＣａ純分の添加速度
Ｖが下記(2) 式をそれぞれ満たすように制御することを
特徴とする溶接部の低温靱性に優れた耐ＨＩＣ鋼の製造
方法。After the S concentration in the molten steel which has been deoxidized beforehand is reduced to 7 ppm or less by the desulfurization treatment, when this molten steel is treated with Ca, the ratio of the Ca concentration in the molten steel and the oxygen concentration [C
a] / [O] is controlled so as to satisfy the following equation (1) and the Ca addition rate V for the Ca content is controlled so as to satisfy the following equation (2). Steel manufacturing method.
【００３８】 1.19＜（〔Ｃａ〕／〔Ｏ〕）＜2.11 ・・(1) 0.023 ＜Ｖ＜0.7 ・・・・・・・・・・(2) ただし、〔Ｃａ〕：溶鋼中のＣａ濃度（wt％） 〔Ｏ〕：溶鋼中の酸素濃度（wt％） Ｖ：Ｃａ純分の添加速度〔kg／(t・min)〕 鋼材の耐ＨＩＣ性および溶接部の低温靱性の向上を同時
に達成するには、前述のように、Ｃａ添加により、鋼中
の介在物組成が下記ａ〜ｃの条件を同時に満たすように
制御する必要がある。1.19 <([Ca] / [O]) <2.11 (1) 0.023 <V <0.7 (2) where [Ca]: Ca concentration in molten steel (Wt%) [O]: Oxygen concentration in molten steel (wt%) V: Addition rate of Ca pure component [kg / (t · min)] At the same time, improved HIC resistance of steel and low temperature toughness of weld In order to do so, it is necessary to control the composition of inclusions in the steel so as to simultaneously satisfy the following conditions a to c by adding Ca as described above.
【００３９】ａ．介在物中のCaO 濃度が６０wt％以上９
０wt％以下 ｂ．介在物中のCaS 濃度が１０wt％以下 ｃ．残部がAl2O3 Ｃａ添加前の溶鋼中のＳ濃度、添加後のＣａ濃度と酸素
濃度との比およびＣａ純分の添加速度を同時に適切に制
御することにより、同一のＣａ純分の添加量および溶鋼
中のＳ濃度であっても、上記ａ〜ｃの条件を同時に満足
させることができる。上記方法における脱硫およびＣａ
処理は取鍋で行うのが望ましい。A. CaO concentration in inclusions is 60 wt% or more 9
0 wt% or less b. CaS concentration in inclusions is 10 wt% or less c. The balance is the addition of the same Ca content by appropriately controlling the S concentration in the molten steel before the addition of Al 2 O 3 Ca, the ratio between the Ca concentration and the oxygen concentration after the addition, and the Ca content addition rate at the same time. Even with the amount and the S concentration in the molten steel, the above conditions a to c can be simultaneously satisfied. Desulfurization and Ca in the above method
Treatment is preferably done in a ladle.
【００４０】[0040]
【発明の実施の形態】本発明方法を実施するには、転炉
または電気炉などの脱炭精錬炉ならびに取鍋または炉な
どの脱硫およびＣａ処理の容器を用いる。以下、本発明
方法を脱炭精錬炉および取鍋を用いる場合を例にとって
説明する。BEST MODE FOR CARRYING OUT THE INVENTION To carry out the method of the present invention, a decarburizing and refining furnace such as a converter or an electric furnace and a desulfurization and Ca treatment vessel such as a ladle or a furnace are used. Hereinafter, the method of the present invention will be described with reference to a case where a decarburizing refining furnace and a ladle are used.
【００４１】まず、脱炭処理された溶鋼を、次の脱硫お
よびＣａ処理のために通常の方法を用いて予め脱酸す
る。First, the decarburized molten steel is pre-deoxidized by the usual method for the subsequent desulfurization and Ca treatment.
【００４２】次いで、溶鋼にＣａ添加するに先立ち、取
鍋脱硫処理にて溶鋼中のＳ濃度を７ppm 以下まで低減す
る。この理由は次のとおりである。Next, before adding Ca to the molten steel, the S concentration in the molten steel is reduced to 7 ppm or less by ladle desulfurization treatment. The reason is as follows.
【００４３】Ｃａは極めて活性でＳとも親和性の高い物
質である。そのため溶鋼中のＳ濃度が７ppm を超えて高
くなると、Ｃａをいかなる方法で添加しても介在物中の
CaS濃度は１０wt％よりも高くなる。また、溶鋼中のＣ
ａ添加位置近傍ではＣａ濃度が著しく高い領域が形成さ
れてしまうため、CaS 単体の介在物が生成する。これを
図１により説明する。Ca is a substance that is extremely active and has a high affinity with S. Therefore, if the S concentration in the molten steel becomes higher than 7 ppm, no matter how Ca is added, the inclusions in the inclusions
The CaS concentration becomes higher than 10 wt%. In addition, C in molten steel
A region having a significantly high Ca concentration is formed in the vicinity of the a-addition position, so that CaS simple substance inclusions are generated. This will be described with reference to FIG.
【００４４】図１は、溶鋼中のＳ濃度〔Ｓ〕を変化させ
た場合のＣａ処理中の介在物組成の変化を示す図であ
る。ただし、Ｃａ添加前の介在物はAl2O3 である。
〔Ｓ〕が高いと介在物中のCaO は容易にCaS に変化する
ため、介在物中に生成したCaO は速やかにCaS に変化す
る。このため、図１中に曲線Ａ、ＢおよびＣで示すよう
に、介在物中のCaO 濃度は上昇せずに、CaS 濃度が著し
く増加する。しかし、〔Ｓ〕が７ppm 以下であると介在
物中のCaO は安定し、CaS に変化しにくいため、図１中
に曲線Ｄ、ＥおよびＦで示すように、低CaS 濃度のまま
高CaO 濃度の介在物となる。したがって、Ｃａ添加に先
立ち、予め溶鋼中のＳ濃度を７ppm 以下まで低減する必
要がある。FIG. 1 is a diagram showing changes in the composition of inclusions during Ca treatment when the S concentration [S] in the molten steel is changed. However, the inclusions before addition of Ca are Al 2 O 3 .
When [S] is high, CaO in the inclusions easily changes to CaS, so CaO formed in the inclusions quickly changes to CaS. Therefore, as shown by curves A, B, and C in FIG. 1, the CaO concentration in the inclusions does not increase, but the CaS concentration significantly increases. However, if [S] is 7 ppm or less, CaO in the inclusions is stable and is unlikely to change to CaS. Therefore, as shown by curves D, E and F in Fig. 1, the high CaO concentration remains at the low CaS concentration. It becomes the inclusion of. Therefore, it is necessary to reduce the S concentration in molten steel to 7 ppm or less in advance before adding Ca.
【００４５】次に、溶鋼中のＣａ濃度と酸素濃度との比
〔Ｃａ〕／〔Ｏ〕を下記(1) 式に従い制御する。Next, the ratio [Ca] / [O] between the Ca concentration and the oxygen concentration in the molten steel is controlled according to the following equation (1).
【００４６】 1.19＜（〔Ｃａ〕／〔Ｏ〕）＜2.11 ・・(1) ただし、〔Ｃａ〕：溶鋼中のＣａ濃度（wt％） 〔Ｏ〕：溶鋼中の酸素濃度（wt％） この理由を図２により説明する。1.19 <([Ca] / [O]) <2.11 (1) where [Ca]: Ca concentration in molten steel (wt%) [O]: Oxygen concentration in molten steel (wt%) The reason will be described with reference to FIG.
【００４７】図２は、〔Ｃａ〕／〔Ｏ〕とCaO-Al2O3 系
介在物中のCaO 濃度との関係を示す図である。溶鋼中の
Ｃａ濃度と酸素濃度との比〔Ｃａ〕／〔Ｏ〕が1.19以下
になると、図２に示すように介在物中のCaO 濃度は６０
wt％未満になる。逆に2.11以上になると、介在物中のCa
O 濃度が９０wt％を超えて高くなる。そのため、Ｃａ添
加後の〔Ｃａ〕／〔Ｏ〕は、上記(1) 式を満足するよう
に制御しなければならない。FIG. 2 is a diagram showing the relationship between [Ca] / [O] and the CaO concentration in CaO--Al 2 O 3 inclusions. When the ratio [Ca] / [O] between the Ca concentration and the oxygen concentration in the molten steel becomes 1.19 or less, the CaO concentration in the inclusions becomes 60 as shown in FIG.
It becomes less than wt%. On the other hand, if it exceeds 2.11, Ca in inclusions
The O 2 concentration exceeds 90 wt% and becomes high. Therefore, [Ca] / [O] after addition of Ca must be controlled so as to satisfy the above formula (1).
【００４８】操業上、(1) 式を満足するようにＣａ添加
量を決定する方法は、操業後に得られたスラブを分析し
て実績から決定してもよいし、操業中のＣａ添加前に溶
鋼サンプルを分析し、酸素濃度を求めてこの値を基に決
定してもよい。In terms of operation, the method of determining the amount of addition of Ca so as to satisfy the formula (1) may be determined from the actual results by analyzing the slab obtained after the operation, or before the addition of Ca during operation. The molten steel sample may be analyzed to obtain the oxygen concentration, and the oxygen concentration may be determined based on this value.
【００４９】しかし、上記のように溶鋼中のＳ濃度を低
減し、かつ上記(1) 式を満足させるだけでは、目標とす
る前記ａ〜ｃの条件を同時に満たす介在物組成に制御す
ることはできない。単純にＣａ添加量のみを制御してそ
の量を増加させると、溶鋼中のＣａ活量の急激な増大を
招き、結果として介在物中のCaS 濃度の増加や、場合に
よってはCaS 単体介在物の生成を引き起こすからであ
る。However, by merely reducing the S concentration in the molten steel as described above and satisfying the above expression (1), it is possible to control the inclusion composition to simultaneously satisfy the target conditions a to c. Can not. Simply controlling only the amount of Ca added to increase the Ca content causes a rapid increase in the Ca activity in the molten steel, resulting in an increase in the CaS concentration in the inclusions and, in some cases, CaS simple inclusions. This is because it causes generation.
【００５０】このため、本発明方法ではさらに、下記
(2) 式の条件を満たしてＣａ純分の添加速度 を制御す
るＣａ処理を行うことにより、前記ａ〜ｃの三条件を同
時に満足する目標介在物の組成に制御する。Therefore, in the method of the present invention,
By performing the Ca treatment that satisfies the condition of the equation (2) and controls the addition rate of the pure Ca component, the composition of the target inclusions that simultaneously satisfy the above three conditions a to c is controlled.
【００５１】 0.023 ＜Ｖ＜0.7 ・・・・・・・・・・(2) ただし、Ｖ：Ｃａ純分の添加速度〔kg／(t・min)〕 次に、Ｃａ純分の添加速度Ｖを上記(2) 式に従い制御す
る理由について、図３により説明する。0.023 <V <0.7 (2) However, V: Ca pure component addition rate [kg / (t · min)] Next, Ca pure component addition rate V The reason why control is performed according to the above equation (2) will be described with reference to FIG.
【００５２】図３は、溶鋼中の介在物中におけるCaO お
よびCaS 濃度とＣａ純分の添加速度Ｖとの関係を示す図
である。Ｃａ純分の添加速度Ｖが0.7 kg／(t・min)以上
になると、溶鋼中のＣａ濃度が一時的に急激に高くなる
ため介在物中のCaO 濃度は高くなるが、適正濃度範囲の
上限は超えない。しかしこの場合、溶鋼中のＳ濃度が低
くても、介在物中のCaS 濃度も著しく増大して高CaS 濃
度の介在物となり、その適正濃度上限を超える。また、
介在物組成のばらつきが大きく、介在物組成の制御性も
悪化する。一方、Ｃａ純分の添加速度Ｖが0.023 kg／(t
・min)以下になると、溶鋼中のＣａ濃度の一時的かつ急
激な増加は抑制でき、もちろん介在物中のCaS 濃度が増
加することもない。しかし、逆にＣａ蒸発速度が添加速
度よりも早くなるため溶鋼中のＣａ濃度が十分に増加せ
ず、したがってＣａとAl2O3 介在物との反応が進行せ
ず、図３に示すように、介在物中のCaO 濃度が低下し、
その適正濃度の下限未満となる。FIG. 3 is a diagram showing the relationship between the CaO and CaS concentrations in the inclusions in the molten steel and the addition rate V of the Ca pure component. If the addition rate V of pure Ca is 0.7 kg / (t · min) or more, the Ca concentration in the molten steel rises temporarily temporarily and the CaO concentration in the inclusions increases, but the upper limit of the proper concentration range is reached. Does not exceed However, in this case, even if the S concentration in the molten steel is low, the CaS concentration in the inclusions also significantly increases to become inclusions with a high CaS concentration, exceeding the upper limit of the appropriate concentration. Also,
The variation in the composition of inclusions is large, and the controllability of the composition of inclusions is also deteriorated. On the other hand, the Ca addition rate V of Ca is 0.023 kg / (t
・ If it is less than min), the temporary and rapid increase of Ca concentration in molten steel can be suppressed, and of course, CaS concentration in inclusions will not increase. However, on the contrary, since the Ca evaporation rate becomes faster than the addition rate, the Ca concentration in the molten steel does not increase sufficiently, and therefore the reaction between Ca and Al 2 O 3 inclusions does not proceed, and as shown in FIG. , The CaO concentration in the inclusions decreases,
It becomes less than the lower limit of the proper concentration.
【００５３】溶鋼の脱硫方法は、ＣａＯ含有フラックス
およびＭｇ含有フラックスなどの脱硫能の高いフラック
スを窒素および不活性ガスなどのキャリヤーガスととも
に溶鋼に吹き込む方法など、いかなる方法でもよい。し
かし、清浄度向上のため溶鋼表面にCaO-Al2O3 系スラグ
などの脱硫能の高いスラグを添加し、不活性ガスなどを
溶鋼に吹き込んで溶鋼を撹拌するバブリング脱硫法が望
ましい。The desulfurization method of molten steel may be any method such as a method of blowing flux having a high desulfurization ability such as CaO-containing flux and Mg-containing flux into molten steel together with a carrier gas such as nitrogen and an inert gas. However, a bubbling desulfurization method in which a slag having a high desulfurization ability such as CaO-Al 2 O 3 slag is added to the surface of molten steel to improve cleanliness and an inert gas is blown into the molten steel to stir the molten steel is desirable.
【００５４】Ｃａ含有物質としては、Ｃａが含有されて
いればよく、Ｃａ−Ｓｉ、Ｆｅ−Ｃａ、Ｃａ−Ａｌなど
の合金を用いればよい。Ｃａを含有する金属粉体とその
他の金属粉とを混合したもの、あるいは混合した後、圧
力成形したものを用いてもよい。また、介在物組成の範
囲を狭く制御することを目的として、これらＣａ含有物
質に、CaO 、Al2O3 、CaF2、CaO-Al2O3 、CaO-CaF2およ
びCaO-Al2O3-CaF2などのフラックスを混合して用いても
よい。As the Ca-containing substance, Ca may be contained, and an alloy such as Ca-Si, Fe-Ca or Ca-Al may be used. You may use what mixed the metal powder containing Ca and other metal powder, or what mixed and then pressure-molded. In addition, for the purpose of controlling the range of the composition of inclusions to be narrow, CaO, Al 2 O 3 , CaF 2 , CaO-Al 2 O 3 , CaO-CaF 2 and CaO-Al 2 O 3 are added to these Ca-containing substances. -A flux such as CaF 2 may be mixed and used.
【００５５】添加するＣａ含有物質中のＣａ純度は５０
wt％以下が望ましく、さらに望ましい範囲は４０wt％以
下５wt％以上である。Ｃａは反応性が高いために、純度
が高すぎると添加時の反応が激しくなり、スプラッシュ
発生が問題となる。逆に純度が低すぎるとＣａ以外の金
属成分が多くなり、必要なＣａ純分を添加する際に必要
となるＣａ含有物質の原単位が大きくなりすぎる。The purity of Ca in the added Ca-containing substance is 50.
Wt% or less is desirable, and a more desirable range is 40 wt% or less and 5 wt% or more. Since Ca is highly reactive, if the purity is too high, the reaction at the time of addition becomes vigorous, causing a problem of splash generation. On the other hand, if the purity is too low, the amount of metal components other than Ca increases, and the basic unit of the Ca-containing substance required when adding the required amount of pure Ca becomes too large.
【００５６】Ｃａ添加量あるいはＣａ原単位（いずれも
Ｃａ純分換算）は、0.4 kg/t以下が望ましい。その理由
は、Ｃａ添加量が過剰になると、Ｃａ添加速度を低減し
ても反応すべきAl2O3 系介在物が減少あるいは消失し、
CaO-Al2O3 系介在物中のCaS濃度が高くなりすぎるから
である。It is desirable that the amount of added Ca or the basic unit of Ca (both calculated as pure Ca) be 0.4 kg / t or less. The reason is that if the Ca addition amount becomes excessive, the Al 2 O 3 -based inclusions that should react will decrease or disappear even if the Ca addition rate is reduced,
This is because the CaS concentration in the CaO-Al 2 O 3 -based inclusions becomes too high.
【００５７】また、Ｃａ添加量あるいはＣａ原単位（い
ずれも、Ｃａ純分換算）は0.05kg/t以上であることが必
要である。その理由は、Ｃａ添加量が低すぎると、Al2O
3 系介在物が十分にCaO-Al2O3 系介在物になりきらず
に、アルミナクラスター系の介在物が残留するからであ
る。さらに、Ｃａ添加量が低すぎると、鋳造中の中心偏
析によりＭｎの濃化した領域で耐ＨＩＣ性能に悪影響の
あるMnS が生成するからである。Further, it is necessary that the added amount of Ca or the basic unit of Ca (both in terms of pure Ca) is 0.05 kg / t or more. The reason is that when the amount of Ca added is too low, Al 2 O
This is because the CaO-Al 2 O 3 -based inclusions are not fully converted to the 3 -based inclusions, and the alumina cluster-based inclusions remain. Furthermore, if the amount of Ca added is too low, MnS, which adversely affects the HIC resistance, is generated in the region where Mn is concentrated due to center segregation during casting.
【００５８】Ｃａ添加方法としては、粉体のＣａ含有物
質を不活性ガスであるＡｒガスをキャリアーガスとして
浸漬ランスを用いて行うのが通例である。この時、粉体
ホッパーにはロードセルを設け、単位時間当たりの粉体
供給量を狭い幅に管理することが望ましい。また、同様
に、Ｃａ含有物質を内包した鉄被覆ワイヤーを溶鋼上面
から溶鋼中へ添加してもよい。ワイヤーの添加では、そ
の駆動装置により単位時間当たりの送り出し長さが正確
に決定できる。したがって、ワイヤーの単位長さあたり
の重量から容易にＣａ添加速度を算出することができ
る。また、可能であれば溶融状態のＣａ含有物質を添加
してもよい。As a method of adding Ca, it is customary to carry out the powdery Ca-containing substance by using an immersion lance using Ar gas which is an inert gas as a carrier gas. At this time, it is desirable to provide a load cell in the powder hopper and control the powder supply amount per unit time within a narrow width. Similarly, an iron-coated wire containing a Ca-containing substance may be added into the molten steel from the upper surface of the molten steel. With the addition of wire, the delivery length per unit time can be accurately determined by the driving device. Therefore, the Ca addition rate can be easily calculated from the weight per unit length of the wire. If possible, a Ca-containing substance in a molten state may be added.
【００５９】さらに、合金ホッパーからＣａ含有物質を
添加してもよいが、通例では添加速度を狭い範囲に制御
するのが困難であるため、連続切り出し装置などを備え
て添加速度の制御をすることが望ましい。Further, the Ca-containing substance may be added from the alloy hopper, but since it is usually difficult to control the addition rate within a narrow range, a continuous cutting device or the like should be provided to control the addition rate. Is desirable.
【００６０】本発明方法では、Ｃａ含有物質の添加前に
真空脱ガス法（ＲＨ法、タンク脱ガス法等）により溶鋼
脱水素処理を行なうことが望ましい。これは、鋼中の水
素濃度を低下させることにより、ＨＩＣを防止するため
である。連続鋳造法を適用する場合には、鋳造後にスラ
ブ徐冷および圧延後に成品徐冷などを行うことにより鋼
の水素濃度を低下させることができるならば、この溶鋼
脱水素処理を省略あるいは溶鋼脱水素処理の軽減化を図
ることが可能である。ただし、スラブ徐冷および成品徐
冷の場合には水素濃度低下に時間がかかるため、成品納
期短縮の面からは不利である。In the method of the present invention, it is desirable to carry out molten steel dehydrogenation treatment by a vacuum degassing method (RH method, tank degassing method, etc.) before adding the Ca-containing substance. This is to prevent HIC by reducing the hydrogen concentration in the steel. When the continuous casting method is applied, if the hydrogen concentration of the steel can be lowered by performing slab gradual cooling after casting and product gradual cooling after rolling, this molten steel dehydrogenation treatment is omitted or molten steel dehydrogenation is performed. It is possible to reduce the processing. However, in the case of slab gradual cooling and product gradual cooling, it takes time to reduce the hydrogen concentration, which is disadvantageous in terms of shortening the delivery time of the product.
【００６１】また、脱硫処理後にＣａ含有物質を添加
し、そこで生成したCaO-Al2O3 系介在物を真空脱ガス法
（ＲＨ法、タンク脱ガス法等）で浮上分離し、その後、
さらにＣａ含有物質を添加してもよい。真空脱ガス法は
介在物の分離に適しているが、真空処理を行うために溶
鋼中に溶解するＣａが気化しやすいためである。After the desulfurization treatment, a Ca-containing substance is added, and the CaO-Al 2 O 3 -based inclusions produced there are float-separated by a vacuum degassing method (RH method, tank degassing method, etc.), and thereafter,
Further, a Ca-containing substance may be added. The vacuum degassing method is suitable for separating inclusions, but it is because Ca dissolved in molten steel is easily vaporized because vacuum treatment is performed.
【００６２】転炉出鋼後、取鍋にて脱硫処理する前ある
いは後に、酸素供給による溶鋼昇熱や電気加熱によって
取鍋内溶鋼温度を補償してもよい。一般に、脱硫処理に
おいては処理時間がかかることや処理中の放熱量が大き
いことから出鋼温度の上昇を招くため、このように出鋼
後に昇熱工程を入れることにより出鋼温度低下を計って
もよい。The temperature of molten steel in the ladle may be compensated by raising the temperature of the molten steel by supplying oxygen or by electric heating after the steel is discharged from the converter and before or after the desulfurization treatment in the ladle. Generally, in desulfurization treatment, it takes a long processing time and the amount of heat released during the treatment is large, which causes a rise in the tapping temperature.Therefore, by including the heating step after tapping in this way, the tapping temperature decrease can be measured. Good.
【００６３】[0063]
【実施例】転炉から取鍋に出鋼した溶鋼250tonに脱酸を
施し、表１に示すような化学組成に調整した。[Example] 250 tons of molten steel, which was tapped from a converter to a ladle, was deoxidized to adjust the chemical composition as shown in Table 1.
【００６４】[0064]
【表１】 [Table 1]
【００６５】取鍋内の溶鋼に浸漬したランスを用いてＡ
ｒガスで溶鋼を攪拌し、脱硫した後、ＲＨ真空脱ガス装
置を用いてＡｒガス撹拌時間９分および環流処理時間１
０分の処理を施し、その後Ｃａを添加した。Ｃａ添加に
は、組成が３０wt％Ｃａ−７０wt％ＳｉのＣａ−Ｓｉ合
金およびワイヤーフィーダー法を用いた。表２に各処理
条件を示す。Using a lance immersed in molten steel in the ladle, A
After stirring the molten steel with r gas and desulfurizing, using an RH vacuum degassing device, stirring time for Ar gas was 9 minutes and reflux treatment time was 1
A treatment of 0 minutes was performed, and then Ca was added. A Ca-Si alloy having a composition of 30 wt% Ca-70 wt% Si and a wire feeder method were used for Ca addition. Table 2 shows each processing condition.
【００６６】[0066]
【表２】 [Table 2]
【００６７】表２に示す各条件に従い処理した溶鋼を、
連続鋳造機により厚さ235 mmのスラブとし、これらを圧
延して厚さ26.5mmの厚板とした。次いでサンプルを切り
出し、検鏡法により介在物形態を観察するとともにＮＡ
ＣＥ条件にしたがい耐ＨＩＣ評価試験に供した。表２に
ＨＩＣ評価試験結果を併せて示す。表中○印はＨＩＣが
全く発生しなかったことを、×印はＨＩＣが発生したこ
とをそれぞれ示す。The molten steel treated according to the conditions shown in Table 2 was
A slab having a thickness of 235 mm was made by a continuous casting machine, and these were rolled into a thick plate having a thickness of 26.5 mm. Then, the sample is cut out, and the morphology of inclusions is observed by a microscopic method and the NA is determined.
It was subjected to a HIC resistance evaluation test according to CE conditions. Table 2 also shows the HIC evaluation test results. In the table, ◯ indicates that HIC did not occur at all, and X indicates that HIC occurred.
【００６８】次に、上記厚板から電縫鋼管を製造し、溶
接部靱性の試験を行った。溶接部靱性の評価は、ＪＩＳ
Ｚ２２０２に規定の４号試験片あるいはサブサイズ４号
試験片を各電縫鋼管のＣ方向から採取し、衝合部にＶノ
ッチを入れたものを使用し、ＪＩＳＺ２２４２に規定の
シャルピ−衝撃試験に準じて測定した溶接部における破
面遷移温度 vＴrsで実施した。表２に、上記結果を併せ
て示す。Next, an electric resistance welded steel pipe was produced from the above thick plate, and a weld toughness test was conducted. Weld toughness is evaluated according to JIS
Z2202 specified No. 4 test piece or subsize No. 4 test piece was taken from the direction C of each ERW steel pipe, and the one with a V notch at the abutting part was used for the Charpy impact test specified in JIS Z2242. The fracture surface transition temperature vTrs in the welded portion was measured according to the above. Table 2 also shows the above results.
【００６９】表２に示すとおり、本発明方法で定める条
件に従って処理した場合、ＨＩＣは全く発生せず、溶接
部靱性も良好である。しかし、処理条件中に本発明方法
に従わないものがある場合、耐ＨＩＣ性および低温靱性
が同時に良好なものは得られなかった。As shown in Table 2, when treated according to the conditions defined by the method of the present invention, HIC does not occur at all and the toughness of the welded portion is good. However, when some of the treatment conditions did not comply with the method of the present invention, the HIC resistance and the low temperature toughness were not simultaneously excellent.
【００７０】[0070]
【発明の効果】本発明方法によれば、効果的に介在物の
組成および形態制御を行い、耐ＨＩＣ性および溶接部の
低温靱性に極めて優れた鋼材を製造することができる。According to the method of the present invention, the composition and morphology of inclusions can be effectively controlled, and a steel material having excellent HIC resistance and low-temperature toughness of a welded portion can be manufactured.
【図１】溶鋼中のＳ濃度を変化させた場合のＣａ処理中
の介在物組成の変化を示す図である。ただし、Ｃａ添加
前の介在物はAl2O3 である。FIG. 1 is a diagram showing changes in the composition of inclusions during Ca treatment when the S concentration in molten steel is changed. However, the inclusions before addition of Ca are Al 2 O 3 .
【図２】〔Ｃａ〕／〔Ｏ〕とCaO-Al2O3 系介在物中のCa
O 濃度の関係を示す図である。[Fig. 2] Ca in [Ca] / [O] and CaO-Al 2 O 3 inclusions
It is a figure which shows the relationship of O 2 concentration.
【図３】溶鋼中の介在物中におけるCaO およびCaS 濃度
とＣａ純分の添加速度との関係を示す図である。FIG. 3 is a diagram showing a relationship between CaO and CaS concentrations in inclusions in molten steel and the addition rate of Ca pure content.
Claims (1)
処理により７ppm 以下とした後、この溶鋼をＣａ処理す
るにあたり、溶鋼中のＣａ濃度と酸素濃度との比〔Ｃ
ａ〕／〔Ｏ〕が下記(1) 式を、かつＣａ純分の添加速度
Ｖが下記(2) 式をそれぞれ満たすように制御することを
特徴とする溶接部の低温靱性に優れた耐ＨＩＣ鋼の製造
方法。 1.19＜（〔Ｃａ〕／〔Ｏ〕）＜2.11 ・・(1) 0.023 ＜Ｖ＜0.7 ・・・・・・・・・・(2) ただし、〔Ｃａ〕：溶鋼中のＣａ濃度（wt％） 〔Ｏ〕：溶鋼中の酸素濃度（wt％） Ｖ：Ｃａ純分の添加速度〔kg／(t・min)〕1. The S concentration in molten steel that has been previously deoxidized is reduced to 7 ppm or less by desulfurization, and when this molten steel is treated with Ca, the ratio of the Ca concentration in the molten steel to the oxygen concentration [C
a] / [O] is controlled so as to satisfy the following formula (1), and the addition rate V of Ca pure content is controlled so as to satisfy the following formula (2). Steel manufacturing method. 1.19 <([Ca] / [O]) <2.11 ・ ・ (1) 0.023 <V <0.7 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2) However, [Ca]: Ca concentration in molten steel (wt% ) [O]: Oxygen concentration in molten steel (wt%) V: Addition rate of Ca pure content [kg / (t · min)]
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1984896A JPH09209025A (en) | 1996-02-06 | 1996-02-06 | Production of hic resistant steel excellent in low temperature toughness in welded part |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1984896A JPH09209025A (en) | 1996-02-06 | 1996-02-06 | Production of hic resistant steel excellent in low temperature toughness in welded part |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09209025A true JPH09209025A (en) | 1997-08-12 |
Family
ID=12010680
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1984896A Pending JPH09209025A (en) | 1996-02-06 | 1996-02-06 | Production of hic resistant steel excellent in low temperature toughness in welded part |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09209025A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009063660A1 (en) * | 2007-11-14 | 2009-05-22 | Sumitomo Metal Industries, Ltd. | Steel for steel pipes excellent in sour resistance and process for manufacturing the same |
| WO2015022899A1 (en) | 2013-08-16 | 2015-02-19 | 新日鐵住金株式会社 | Electric-resistance-welded steel pipe with excellent weld quality and method for producing same |
| CN104451346A (en) * | 2014-11-29 | 2015-03-25 | 首钢总公司 | Smelting method of yield 345MPa grade hydrogen cracking-resistant container steel |
-
1996
- 1996-02-06 JP JP1984896A patent/JPH09209025A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009063660A1 (en) * | 2007-11-14 | 2009-05-22 | Sumitomo Metal Industries, Ltd. | Steel for steel pipes excellent in sour resistance and process for manufacturing the same |
| US7959709B2 (en) | 2007-11-14 | 2011-06-14 | Sumitomo Metal Industries, Ltd. | Method of producing steel for steel pipe excellent in sour-resistance performance |
| US8262767B2 (en) | 2007-11-14 | 2012-09-11 | Sumitomo Metal Industries, Ltd. | Method of producing steel for steel pipe excellent in sour-resistance performance |
| WO2015022899A1 (en) | 2013-08-16 | 2015-02-19 | 新日鐵住金株式会社 | Electric-resistance-welded steel pipe with excellent weld quality and method for producing same |
| KR20150140826A (en) | 2013-08-16 | 2015-12-16 | 신닛테츠스미킨 카부시키카이샤 | Electric-resistance-welded steel pipe with excellent weld quality and method for producing same |
| US10081042B2 (en) | 2013-08-16 | 2018-09-25 | Nippon Steel & Sumitomo Metal Corporation | Electric resistance welded steel pipe excellent in weld zone and method of production of same |
| CN104451346A (en) * | 2014-11-29 | 2015-03-25 | 首钢总公司 | Smelting method of yield 345MPa grade hydrogen cracking-resistant container steel |
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