JP4137517B2 - Method for producing stainless steel sheet having good surface properties - Google Patents
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Description
【0001】
【発明の属する技術分野】
本発明は、ステンレス鋼の冷間圧延鋼帯を製造する場合に、最終製品表面にマクロ模様のない鋼帯を製造する方法に関する技術である。
【0002】
【従来の技術】
ステンレス鋼の冷延鋼帯の製造に関しては、熱間圧延後のホットコイルの酸化スケールをデスケールした後に冷間圧延し、焼鈍し、酸洗して製品として製造される。このような鋼板は様々な機器の表面に用いられる場合が多く、仕上表面が美麗であることが求められる。
【0003】
この冷延鋼帯の製造法の製品前に実施される酸洗に関して、特開昭61−276999号公報では、Cr含有鋼板を、特定濃度の硫酸水溶液にフルオロケイ酸塩又はフルオロホウ酸塩、及び硝酸塩又は硫酸塩を添加した溶液で電解酸洗することにより、仕上表面の美麗な鋼板を得る方法が示されている。
【0004】
また、この冷延鋼帯の製造法の製品前に実施される焼鈍と酸洗に関して、特開平3−90600号公報では、Cr含有冷延鋼板について露点を−15〜−40℃弱酸化性雰囲気でかつ鋼板の再結晶開始温度〜再結晶完了温度+50℃の範囲で焼鈍し、フルオロケイ酸塩等を添加した硫酸水溶液で電解酸洗することで、外観の平滑な鋼板を高速大量生産する方法が示されている。
【0005】
【発明が解決しようとする課題】
この製造法に関し、更に詳細な検討を行った結果、以下のことが判明した。
特開昭61−276999号公報及び特開平3−90600号公報に示された方法で冷延鋼帯を製造した場合、冷延し焼鈍し酸洗した後の鋼板表面にL方向に巾0.5〜2mm程度で長さ30〜70mm程度の筋状の模様が多数発生する場合があることがわかった。
本発明は、従来技術では達成できなかった最終製品表面にマクロ模様のない鋼帯を製造することを目的とする。
【0006】
【課題を解決するための手段】
この課題を解決するために、本発明は以下の構成を要旨とする。
(1) 質量で、
C :0.12%以下、 Si:1.00%以下、
Mn:1.00%以下、 P :0.1%以下、
S :0.030%以下、 Cr:10〜20%、
Ni:0.75%以下、 Cu:0.005〜0.20%、
Ti:0.001〜0.30%、 Al:0.001〜0.30%、
N :0.06%以下
を含有し、残部がFe及び不可避的不純物であり、下式(1)に示す組成にコントロールした熱延鋼帯を製造し、熱延後の熱処理として、熱延後にコイルを冷却した後に焼鈍する際に焼鈍温度を700〜880℃、焼鈍温度を1〜6時間として行い、メカニカルデスケーリングし、酸洗し、冷間圧延し、露点−15〜−40℃、水素濃度1〜20%の弱酸化性雰囲気中で鋼板の再結晶開始温度〜再結晶完了温度+60℃の温度範囲で焼鈍した後、20〜400g/L硫酸水溶液中に、フルオロケイ酸塩もしくはフルオロホウ酸塩の1種又は2種を硫酸水溶液1L(リットル)あたり1〜50g添加し、更に硝酸塩、硫酸塩の1種又は2種を硫酸水溶液1Lあたり50〜400g混合した酸洗溶液で、電流密度20〜60A/Dm 2 で電解酸洗して製造することを特徴とする表面性状の良好なステンレス鋼板の製造方法。
γp(%)=420* [C]+470*[N]+23*[Ni]+9*[Cu]+7*[Mn]-11.5*[Cr]-11.5*[Si]-12*
[Mo]-23*[V]-47*[Nb]-49*[Ti]-52*[Al]+189 ≧30・・・・式(1)
(2)熱延後の熱処理として、熱延終了後の鋼帯巻き取り温度を700℃以上で保定し、コイル冷却後に焼鈍することを特徴とする前記(1)記載の表面性状の良好なステンレス鋼板の製造方法。
【0007】
【発明の実施の形態】
本発明者らは、課題解決のため種々の詳細な検討を行った結果、最終製品表面にマクロ模様のない鋼帯を製造する方法として、γpを一定値以上になるように成分コントロールした熱延鋼帯を製造し、焼鈍しメカニカルデスケーリングし、酸洗し、冷間圧延し、弱酸化性雰囲気中で焼鈍し、電解酸洗して製造することが最も有効であることを見出した。以下、実験結果に従い説明する。
【0008】
前述のように、特開昭61−276999号公報及び特開平3−90600号公報に示された方法で冷延鋼帯を製造した場合、冷延し焼鈍し酸洗した後の鋼板表面にL方向に巾0.5〜2mm程度で長さ30〜70mm程度の筋状の模様が多数発生する場合があることがわかった。
【0009】
そこで本発明者らは、このような模様の発生を低減できる熱延後熱処理処理条件を、以下のような実験により検討した。
SUS430の熱延鋼帯3〜5mm厚のものを用いて、巻取り温度600℃で焼鈍を省略するか700〜880℃で2時間焼鈍し、メカニカルデスケーリングし、酸洗し、0.6〜1.2mm厚に冷間圧延し、窒素中に水素を8%含有させた露点−20℃の弱酸化性雰囲気中で880℃で20sec 間焼鈍し、100g/L(リットル)硫酸水溶液中に、20g/L Na2 SiF6 、50g/L NaNO3 、50g/L Na2 SO4 を混合した水溶液で40A/Dm2 の電流密度、80℃で10sec 間電解酸洗した。
【0010】
このようにして製造した筋状の模様の発生状況を、成分条件をγpとして計算により表わしたγpと、熱延鋼帯の熱処理有無との関係について纏めた結果を図1に示す。
図1から明らかなように、熱延鋼帯の熱処理を省略した場合には、筋状の模様が多く発生し、γpの増加とともに若干良好になる。さらに、700〜880℃で2Hrの焼鈍を行った場合には大きな改善が認められ、γpが30%以上で筋状の模様は皆無になる。
【0011】
このように、γpの増加と焼鈍を付与することが有効である理由は、γpが小さく熱延鋼帯にγ相の生成が少ない場合と、熱延鋼帯の焼鈍が充分に行われなかった場合には、冷延中に圧延L方向に沿った微小凹凸が生じやすい。この凹部と凸部で、弱酸化性雰囲気中で焼鈍した際に酸化スケールの生成のしかたに違いが生じ、電解酸洗後に模様化するためである。このため、冷延後の微小凹凸を軽減するγpを大きくすることと焼鈍することが有効に作用しているものと考えられる。
【0012】
次に本発明の限定理由について説明する。
成分の限定理由は以下のとおりである。なお単位は質量%である。
Cは、耐孔食性や耐食性の点から低い方がよいが、製造性を考慮して上限を0.12%とした。
【0013】
Siは、脱酸作用を持った有用な成分であるが、1.00%を超えて含有させると熱間加工性が劣化して、熱間圧延時の表面疵を多発するようになることから1.00%以下とした。
【0014】
Mnは、機械的強度維持および脱酸に有効に寄与するが、1.00%を超えると靭性劣化の不利を招き、熱間圧延での表面疵を多発するようになるので、1.00%以下とする必要がある。
【0015】
Pは、P固溶度の低下に伴い粒界に濃化し粒界偏析を生じ、硫酸との組み合わせで粒界腐食溝を生じる有害元素であり、低いほど望ましいが、製鋼時の経済性を考えて0.1%以下とする。
Sは、耐食性向上のためできるだけ低い方が望ましく、0.030%以下とする。
【0016】
Crは、耐食性および耐酸化性を向上させるステンレス鋼としての重要な元素であるが、そのためには少なくとも10%が必要であり、一方、20%を超えると靭性の劣化を招くので、10〜20%の範囲に限定した。
【0017】
Niは、優れた耐食性、耐酸性を付与する作用があり、耐孔食性ならびに耐隙間腐食性を向上させる作用もある。ただし、0.75%を超えて添加することは経済性を損なうので、0.75%以下とした。
【0018】
Cuは、耐食性向上および機械的強度向上のために有用な元素であるが、0.005%未満では所望の効果が得られず、一方、0.20%を超えると熱間加工性低下の点で好ましくないので、0.005〜0.20%の範囲に限定した。
【0019】
Tiは、耐食性向上および機械的性質向上のために有用な元素であるが、0.001%未満では所望の効果が得られず、一方、0.30%を超えると熱間加工性低下の点で好ましくないので、0.001〜0.30%の範囲に限定した。
【0020】
Alは、脱酸作用を持ち材質にも有用な成分であるが、0.001%未満では所望の効果が得られず、0.30%を超えて含有させると熱間加工性が劣化して、熱間圧延時の表面疵を多発するようになることから、0.30%以下とした。
【0021】
Nは、耐食性向上および機械的強度向上のために有用な元素であるが、0.06%を超えると熱間加工性低下の点で好ましくないので、0.06%以下の範囲に限定した。
【0022】
これらの成分は前記式(1)、即ち、γp(%)=420*〔C〕+470*〔N〕+23*〔Ni〕+9*〔Cu〕+7*〔Mn〕−11.5*〔Cr〕−11.5*〔Si〕−12*〔Mo〕−23*〔V〕−47*〔Nb〕−49*〔Ti〕−52*〔Al〕+189≧30で示される組成にコントロールする必要がある。
γpが30%以上では熱延鋼帯の焼鈍との組み合わせで筋状の模様はなくなる。一方30%未満では焼鈍と組み合わせても改善は難しいためである。
【0023】
熱延後の鋼帯の熱処理は、コイルを冷却した後に焼鈍する際に焼鈍温度を700〜880℃とすることが筋状の模様の軽減に有効である。加熱温度は700℃未満では効果がなく、700℃以上で、さらに高温にするほど効果がある。しかし、880℃を超えてγ相がでるようになると、冷延時に耳割れが生じたり圧延荷重が大きくなるので、880℃以下とした。
【0024】
熱延後の鋼帯の熱処理は、熱延終了後の鋼帯巻き取りを700℃以上の温度で保定することによっても有効に作用する。700℃未満では効果がなく、700℃以上で効果がある。
【0025】
これら熱処理後の鋼帯を、メカニカルデスケーリングし、酸洗し酸化スケールを完全に除去した後、冷間圧延し、弱酸化性雰囲気中で焼鈍する。冷延鋼帯の焼鈍条件については、露点を−15〜−40℃の弱酸化性雰囲気中とする。−15〜−40℃の範囲では電解酸洗しやすい酸化スケールが生成する。一方、−15℃より高温では電解酸洗で除去できない厚さの酸化スケールが生成するためであり、露点は低いほど良いが、−40℃より低温の露点を得るには設備費が増大してしまうためである。
【0026】
この弱酸化性雰囲気は窒素中に水素を1〜20%加えることによって得られる。水素濃度が1%未満であれば酸化スケールの厚みは著しく厚くなり、後で行われる酸洗作業が煩雑になる。また水素濃度が20%を超すと、供給するガスのコストがかさみ、操業面での安全管理にも問題をきたす。
【0027】
また、製品鋼帯を加工しやすい柔らかな鋼帯とするため、鋼板の再結晶開始温度〜再結晶完了温度+60℃の範囲で焼鈍する。再結晶完了温度+20℃未満では軟質化が安定しないが、+20℃以上では安定する。+60℃を超えると粒成長しやすく組織を一定化できないためである。
【0028】
電解酸洗溶液として、20〜400g/L(リットル)硫酸水溶液中に、Na2 SiF6 等のフルオロケイ酸塩、もしくはNaBF4 等のフルオロホウ酸塩を添加し、更にNaNO3 、Na2 SO4 等の硝酸塩、硫酸塩の1種又は2種を混合した酸洗溶液を用いる。20〜400g/L 硫酸で安定した電解酸洗が可能で、20g/L 未満では酸洗能力が極端に小さくなり、400g/L を超えると酸洗能力を制御することが難しくなる。
【0029】
Na2 SiF6 等のフルオロケイ酸塩、もしくはNaBF4 等のフルオロホウ酸塩は、酸化スケールの除去速度を大幅に向上させるために添加する。その添加量としては、硫酸水溶液1L(リットル)あたり1〜50g が好ましい。硫酸水溶液1L あたり1g 未満では効果がほとんど見られず、一方50g を超えても効果は飽和する。
【0030】
NaNO3 等の硝酸塩は、電解酸洗時に鋼帯が陰極化するときに素地の溶解を促進させるために、Na2 SO4 等の硫酸塩は、電解酸洗における過酸洗を抑制するために添加する。その添加量は硫酸水溶液1L あたり50〜400g 添加するのが好ましい。硫酸水溶液1L あたり50g 未満では効果がほとんど見られず、一方400g を超えても効果は飽和する。
電解酸洗は、酸洗浴中を通板する鋼帯の両面に対向して2枚1組の陽極板、陰極板を設け間接通電酸洗する。
【0031】
【実施例】
表1に示す、SUS430鋼でγpを30%以上の熱延鋼帯とし、表2に示す700〜880℃の焼鈍を施すか、熱延終了後の鋼帯巻取り温度を700℃以上とし、メカニカルデスケーリングし、酸洗し、40〜90%の冷間圧延し、表3の条件で焼鈍し、表4の条件で電解酸洗した。この条件で製造した最終製品鋼帯には、表2に示す様に筋状の模様はなかった。一方、これ以外の条件で製造した鋼帯には筋状の模様がはっきりと認められた。
【0032】
【表1】
【0033】
【表2】
【0034】
【表3】
【0035】
【表4】
【0036】
【発明の効果】
本発明によって、従来技術では達成できなかった、最終製品表面にマクロ模様のない鋼帯を製造することが出来る。
【図面の簡単な説明】
【図1】成分の異なる熱延鋼帯を製造し、熱延後の熱処理を付与したり省略して、メカニカルデスケーリングし、酸洗し、冷間圧延し、弱酸化性雰囲気中で焼鈍し、電解酸洗した場合に、成分条件をγpとして纏め、このγpと、熱延鋼帯の熱処理有無と、筋状の模様との関係を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique related to a method of manufacturing a steel strip having no macro pattern on the surface of a final product when manufacturing a cold rolled steel strip of stainless steel.
[0002]
[Prior art]
Regarding the production of a stainless steel cold-rolled steel strip, a hot coil after hot rolling is descaled and then cold-rolled, annealed, pickled, and manufactured as a product. Such a steel plate is often used on the surface of various devices, and the finished surface is required to be beautiful.
[0003]
Regarding the pickling performed before the product of the manufacturing method of this cold-rolled steel strip, JP-A-61-276999 discloses a Cr-containing steel plate in a sulfuric acid aqueous solution having a specific concentration, fluorosilicate or fluoroborate, and A method of obtaining a steel sheet having a beautiful finish surface by electrolytic pickling with a solution to which nitrate or sulfate is added is shown.
[0004]
Moreover, regarding annealing and pickling performed before the product of the manufacturing method of this cold-rolled steel strip, in JP-A-3-90600, the dew point of the Cr-containing cold-rolled steel sheet is −15 to −40 ° C. in a slightly oxidizing atmosphere. And high-speed mass production of steel plates with smooth appearance by annealing in the range of the recrystallization start temperature of the steel plate to the recrystallization completion temperature + 50 ° C. and electrolytic pickling with an aqueous sulfuric acid solution containing fluorosilicate or the like It is shown.
[0005]
[Problems to be solved by the invention]
As a result of further detailed studies on this production method, the following was found.
When a cold-rolled steel strip is manufactured by the method disclosed in Japanese Patent Application Laid-Open Nos. 61-276999 and 3-90600, a width of 0. 0 in the L direction is formed on the surface of the steel sheet after cold rolling, annealing and pickling. It was found that many streak patterns with a length of about 5 to 2 mm and a length of about 30 to 70 mm may occur.
An object of the present invention is to produce a steel strip without a macro pattern on the surface of a final product that cannot be achieved by the prior art.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the gist of the present invention is as follows.
(1) By mass
C: 0.12% or less, Si: 1.00% or less,
Mn: 1.00% or less, P: 0.1% or less,
S: 0.030% or less, Cr: 10-20%,
Ni: 0.75% or less, Cu: 0.005 to 0.20%,
Ti: 0.001 to 0.30 %, Al: 0.001 to 0.30 %,
N: 0.06% or less, the balance being Fe and inevitable impurities, producing a hot-rolled steel strip controlled to the composition shown in the following formula (1), and as a heat treatment after hot-rolling, after hot-rolling When annealing after cooling the coil, the annealing temperature is 700 to 880 ° C. , the annealing temperature is 1 to 6 hours , mechanical descaling, pickling, cold rolling, dew point −15 to −40 ° C., hydrogen After annealing in a temperature range from the recrystallization start temperature of the steel sheet to the recrystallization completion temperature + 60 ° C. in a weakly oxidizing atmosphere with a concentration of 1 to 20% , a fluorosilicate or fluoroboric acid is added in a 20 to 400 g / L sulfuric acid aqueous solution. one or two of salt added 1~50g per sulfate aqueous solution 1L (liter), further nitrate, in pickling solution mixed 50~400g per aqueous sulfuric 1L one or sulfates,
γp (%) = 420 * [C] + 470 * [N] + 23 * [Ni] + 9 * [Cu] + 7 * [Mn] -11.5 * [Cr] -11.5 * [Si] -12 *
[Mo] -23 * [V] -47 * [Nb] -49 * [Ti] -52 * [Al] +189 ≧ 30 ・ ・ ・ ・ Formula (1)
(2) As a heat treatment after hot rolling, the steel strip winding temperature after hot rolling is kept at 700 ° C. or higher, and annealing is performed after coil cooling, and the stainless steel with good surface properties according to (1) above A method of manufacturing a steel sheet .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
As a result of various detailed studies for solving the problems, the present inventors, as a method for producing a steel strip having no macro pattern on the surface of the final product, have performed hot rolling in which components are controlled so that γp becomes a certain value or more. It has been found that it is most effective to produce a steel strip, annealed, mechanically descaled, pickled, cold-rolled, annealed in a weakly oxidizing atmosphere, and electrolytically pickled. Hereinafter, it demonstrates according to an experimental result.
[0008]
As described above, when a cold-rolled steel strip is manufactured by the method disclosed in JP-A-61-276999 and JP-A-3-90600, L is applied to the steel plate surface after cold-rolling, annealing and pickling. It was found that a large number of streak patterns having a width of about 0.5 to 2 mm and a length of about 30 to 70 mm may occur in the direction.
[0009]
Therefore, the present inventors examined the heat treatment conditions after hot rolling that can reduce the occurrence of such patterns by the following experiments.
Using a SUS430 hot rolled steel strip 3-5 mm thick, annealing is omitted at a coiling temperature of 600 ° C. or annealing at 700-880 ° C. for 2 hours, mechanical descaling, pickling, 0.6- Cold rolled to a thickness of 1.2 mm, annealed at 880 ° C. for 20 seconds in a weakly oxidizing atmosphere with a dew point of −20 ° C. containing 8% hydrogen in nitrogen, and in a 100 g / L (liter) sulfuric acid aqueous solution, Electrolytic pickling was performed for 10 seconds at 80 ° C. at a current density of 40 A / Dm 2 with an aqueous solution in which 20 g / L Na 2 SiF 6 , 50 g / L NaNO 3 and 50 g / L Na 2 SO 4 were mixed.
[0010]
FIG. 1 shows the results of summarizing the relationship between the occurrence of the streak pattern produced in this manner and the calculation of the component condition γp and the presence or absence of heat treatment of the hot-rolled steel strip.
As is apparent from FIG. 1, when the heat treatment of the hot-rolled steel strip is omitted, a lot of streak patterns are generated and become slightly better as γp increases. Further, when annealing is performed at 700 to 880 ° C. for 2 hours, a great improvement is observed, and when γp is 30% or more, there are no streak patterns.
[0011]
As described above, the reason why it is effective to increase γp and to provide annealing is that the γp is small and the generation of γ phase in the hot-rolled steel strip is small, and the hot-rolled steel strip is not sufficiently annealed. In some cases, micro unevenness along the rolling L direction is likely to occur during cold rolling. This is because when the recesses and the projections are annealed in a weakly oxidizing atmosphere, a difference occurs in the generation of oxide scale, and a pattern is formed after electrolytic pickling. For this reason, it is considered that increasing γp for reducing minute irregularities after cold rolling and annealing are effective.
[0012]
Next, the reason for limiting the present invention will be described.
The reasons for limiting the components are as follows. The unit is mass%.
C is preferably lower in terms of pitting corrosion resistance and corrosion resistance, but the upper limit is set to 0.12% in consideration of manufacturability.
[0013]
Si is a useful component having a deoxidizing action, but if it exceeds 1.00%, hot workability deteriorates, and surface flaws during hot rolling frequently occur. It was 1.00% or less.
[0014]
Mn contributes effectively to the maintenance of mechanical strength and deoxidation, but if it exceeds 1.00%, it causes a disadvantage of toughness deterioration, and surface flaws occur frequently in hot rolling, so 1.00% It is necessary to do the following.
[0015]
P is a harmful element that concentrates at the grain boundaries as the solid solubility of P decreases and causes segregation at the grain boundaries, and creates intergranular corrosion grooves when combined with sulfuric acid. The lower the value, the better. And 0.1% or less.
S is desirably as low as possible for improving corrosion resistance, and is 0.030% or less.
[0016]
Cr is an important element as stainless steel for improving corrosion resistance and oxidation resistance. For this purpose, at least 10% is necessary. On the other hand, if it exceeds 20%, toughness is deteriorated. % Range.
[0017]
Ni has an effect of imparting excellent corrosion resistance and acid resistance, and also has an effect of improving pitting corrosion resistance and crevice corrosion resistance. However, since addition exceeding 0.75% impairs economic efficiency, it was made 0.75% or less.
[0018]
Cu is an element useful for improving corrosion resistance and mechanical strength. However, if it is less than 0.005%, a desired effect cannot be obtained. On the other hand, if it exceeds 0.20%, hot workability decreases. Therefore, the content is limited to 0.005 to 0.20%.
[0019]
Ti is an element useful for improving corrosion resistance and mechanical properties. However, if it is less than 0.001%, a desired effect cannot be obtained. On the other hand, if it exceeds 0.30%, hot workability decreases. Therefore, the content is limited to 0.001 to 0.30%.
[0020]
Al is a component that has a deoxidizing action and is useful for the material, but if less than 0.001%, the desired effect cannot be obtained, and if it exceeds 0.30%, hot workability deteriorates. Since surface flaws frequently occur during hot rolling, the content is set to 0.30% or less.
[0021]
N is an element useful for improving corrosion resistance and mechanical strength. However, if it exceeds 0.06%, it is not preferable in terms of a decrease in hot workability, so it is limited to a range of 0.06% or less.
[0022]
These components are represented by the above formula (1), that is, γp (%) = 420 * [C] + 470 * [N] + 23 * [Ni] + 9 * [Cu] + 7 * [Mn] -11.5 * [Cr] −11.5 * [Si] −12 * [Mo] −23 * [V] −47 * [Nb] −49 * [Ti] −52 * [Al] + 189 ≧ 30 is there.
When γp is 30% or more, the streak pattern disappears in combination with annealing of the hot-rolled steel strip. On the other hand, if less than 30%, improvement is difficult even when combined with annealing.
[0023]
In the heat treatment of the steel strip after hot rolling, it is effective to reduce the streak pattern by setting the annealing temperature to 700 to 880 ° C. when annealing after cooling the coil. If the heating temperature is less than 700 ° C., there is no effect, and if the heating temperature is 700 ° C. or higher, the effect is further increased. However, if a γ phase appears above 880 ° C., ear cracks occur during cold rolling and the rolling load increases, so the temperature was set to 880 ° C. or lower.
[0024]
The heat treatment of the steel strip after hot rolling also works effectively by maintaining the winding of the steel strip after the hot rolling at a temperature of 700 ° C. or higher. Below 700 ° C. there is no effect and above 700 ° C. there is an effect .
[0025]
These steel strips after heat treatment are mechanically descaled and pickled to completely remove the oxide scale, and then cold-rolled and annealed in a weakly oxidizing atmosphere. About the annealing conditions of a cold-rolled steel strip, let a dew point be in -15--40 degreeC weakly oxidizing atmosphere. In the range of −15 to −40 ° C., an oxide scale that is easy to electrolytically pickle is formed. On the other hand, an oxide scale having a thickness that cannot be removed by electrolytic pickling at temperatures higher than −15 ° C. is generated. The lower the dew point, the better, but the equipment cost increases to obtain a dew point lower than −40 ° C. It is because it ends.
[0026]
This weakly oxidizing atmosphere is obtained by adding 1-20% of hydrogen in nitrogen. If the hydrogen concentration is less than 1%, the thickness of the oxide scale becomes extremely thick, and the pickling operation to be performed later becomes complicated. Further, if the hydrogen concentration exceeds 20%, the cost of the gas to be supplied increases, which causes problems in safety management in terms of operation.
[0027]
Moreover, in order to make a product steel strip into a soft steel strip which is easy to process, it anneals in the range of the recrystallization start temperature of a steel plate-recrystallization completion temperature +60 degreeC. Softening is not stable at a recrystallization completion temperature of less than + 20 ° C., but is stable at + 20 ° C. or higher. This is because if the temperature exceeds + 60 ° C., the grains are likely to grow and the structure cannot be made constant.
[0028]
As an electrolytic pickling solution, a fluorosilicate such as Na 2 SiF 6 or a fluoroborate such as NaBF 4 is added to a 20 to 400 g / L (liter) sulfuric acid aqueous solution, and NaNO 3 and Na 2 SO 4 are added. A pickling solution in which one or two of nitrate and sulfate are mixed. 20 to 400 g / L is in enabling stable electrolytic pickling sulfate, pickling ability is extremely small at less than 20 g / L, it is hardly properly controlling the pickling capacity exceeds 400 g / L.
[0029]
A fluorosilicate such as Na 2 SiF 6 or a fluoroborate such as NaBF 4 is added to greatly improve the removal rate of the oxide scale. The amount added is preferably 1 to 50 g per liter (liter) of aqueous sulfuric acid solution. When the amount is less than 1 g per liter of sulfuric acid aqueous solution, the effect is hardly observed, while when the amount exceeds 50 g, the effect is saturated.
[0030]
Nitrate such as NaNO 3 promotes dissolution of the base when the steel strip becomes a cathode during electrolytic pickling, and sulfate such as Na 2 SO 4 suppresses over pickling in electrolytic pickling. Added. The amount added is preferably 50 to 400 g per liter of sulfuric acid aqueous solution. When the amount is less than 50 g per liter of sulfuric acid aqueous solution, the effect is hardly observed, while when the amount exceeds 400 g, the effect is saturated.
In the electrolytic pickling, indirect energization pickling is performed by providing a set of two anode plates and a cathode plate facing both surfaces of a steel strip passing through a pickling bath.
[0031]
【Example】
As shown in Table 1, SUS430 steel is a hot rolled steel strip having a γp of 30% or more, and annealing at 700 to 880 ° C. shown in Table 2 is performed, or the steel strip winding temperature after hot rolling is 700 ° C. or higher, Mechanical descaling, pickling, 40-90% cold rolling, annealing under the conditions in Table 3, and electrolytic pickling under the conditions in Table 4. The final product steel strip manufactured under these conditions did not have a streak pattern as shown in Table 2. On the other hand, streaky patterns were clearly observed in the steel strips manufactured under other conditions.
[0032]
[Table 1]
[0033]
[Table 2]
[0034]
[Table 3]
[0035]
[Table 4]
[0036]
【The invention's effect】
According to the present invention, it is possible to produce a steel strip having no macro pattern on the surface of the final product, which can not be achieved by the prior art.
[Brief description of the drawings]
[Fig. 1] Manufacturing hot-rolled steel strips with different components, applying or omitting heat treatment after hot rolling, mechanical descaling, pickling, cold rolling, annealing in a weakly oxidizing atmosphere The figure which summarizes component conditions as (gamma) p when electrolytically pickling, and shows the relationship between this (gamma) p, the heat processing presence or absence of a hot-rolled steel strip, and a streaky pattern.
Claims (2)
C :0.12%以下、
Si:1.00%以下、
Mn:1.00%以下、
P :0.1%以下、
S :0.030%以下、
Cr:10〜20%、
Ni:0.75%以下、
Cu:0.005〜0.20%、
Ti:0.001〜0.30%、
Al:0.001〜0.30%、
N :0.06%以下
を含有し、残部がFe及び不可避的不純物であり、下式(1)に示す組成にコントロールした熱延鋼帯を製造し、熱延後の熱処理として、熱延後にコイルを冷却した後に焼鈍する際に焼鈍温度を700〜880℃、焼鈍温度を1〜6時間として行い、メカニカルデスケーリングし、酸洗し、冷間圧延し、露点−15〜−40℃、水素濃度1〜20%の弱酸化性雰囲気中で鋼板の再結晶開始温度〜再結晶完了温度+60℃の温度範囲で焼鈍した後、20〜400g/L硫酸水溶液中に、フルオロケイ酸塩もしくはフルオロホウ酸塩の1種又は2種を硫酸水溶液1L(リットル)あたり1〜50g添加し、更に硝酸塩、硫酸塩の1種又は2種を硫酸水溶液1Lあたり50〜400g混合した酸洗溶液で、電流密度20〜60A/Dm 2 で電解酸洗して製造することを特徴とする表面性状の良好なステンレス鋼板の製造方法。
γp(%)=420* [C]+470*[N]+23*[Ni]+9*[Cu]+7*[Mn]-11.5*[Cr]-11.5*[Si]-12*
[Mo]-23*[V]-47*[Nb]-49*[Ti]-52*[Al]+189 ≧30・・・・式(1)By mass
C: 0.12% or less,
Si: 1.00% or less,
Mn: 1.00% or less,
P: 0.1% or less,
S: 0.030% or less,
Cr: 10 to 20%,
Ni: 0.75% or less,
Cu: 0.005 to 0.20%,
Ti: 0.001 to 0.30%,
Al: 0.001 to 0.30%,
N: 0.06% or less, the balance being Fe and inevitable impurities, producing a hot-rolled steel strip controlled to the composition shown in the following formula (1), and as a heat treatment after hot-rolling, after hot-rolling When the coil is cooled and then annealed, the annealing temperature is 700 to 880 ° C , the annealing temperature is 1 to 6 hours , mechanical descaling, pickling, cold rolling, dew point -15 to -40 ° C, hydrogen After annealing in a temperature range from the recrystallization start temperature of the steel sheet to the recrystallization completion temperature + 60 ° C. in a weakly oxidizing atmosphere having a concentration of 1 to 20% , a fluorosilicate or fluoroboric acid is added in a 20 to 400 g / L sulfuric acid aqueous solution. one or two of salt added 1~50g per sulfate aqueous solution 1L (liter), further nitrate, in pickling solution mixed 50~400g per aqueous sulfuric 1L one or sulfates, current density 20 ~ 60 Method for producing a good stainless steel surface texture, characterized in that to produce electrolytically pickled / Dm 2.
γp (%) = 420 * [C] + 470 * [N] + 23 * [Ni] + 9 * [Cu] + 7 * [Mn] -11.5 * [Cr] -11.5 * [Si] -12 *
[Mo] -23 * [V] -47 * [Nb] -49 * [Ti] -52 * [Al] +189 ≧ 30 ・ ・ ・ ・ Formula (1)
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