JPH0534440B2 - - Google Patents
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- Publication number
- JPH0534440B2 JPH0534440B2 JP62252337A JP25233787A JPH0534440B2 JP H0534440 B2 JPH0534440 B2 JP H0534440B2 JP 62252337 A JP62252337 A JP 62252337A JP 25233787 A JP25233787 A JP 25233787A JP H0534440 B2 JPH0534440 B2 JP H0534440B2
- Authority
- JP
- Japan
- Prior art keywords
- descaling
- solution
- reaction
- electrolysis
- neutral salt
- 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 - Fee Related
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- 238000006243 chemical reaction Methods 0.000 claims description 57
- 238000005868 electrolysis reaction Methods 0.000 claims description 41
- 150000003839 salts Chemical class 0.000 claims description 38
- 239000000243 solution Substances 0.000 claims description 38
- 230000007935 neutral effect Effects 0.000 claims description 35
- 239000007864 aqueous solution Substances 0.000 claims description 31
- 229910001220 stainless steel Inorganic materials 0.000 claims description 17
- 239000010935 stainless steel Substances 0.000 claims description 14
- 229910000831 Steel Inorganic materials 0.000 claims description 13
- 239000010959 steel Substances 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 11
- 239000010960 cold rolled steel Substances 0.000 claims description 2
- 150000002500 ions Chemical class 0.000 description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 9
- 238000007654 immersion Methods 0.000 description 9
- 229910017604 nitric acid Inorganic materials 0.000 description 9
- 230000005611 electricity Effects 0.000 description 8
- 229910052742 iron Inorganic materials 0.000 description 8
- 238000007796 conventional method Methods 0.000 description 7
- 238000005554 pickling Methods 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 229910021645 metal ion Inorganic materials 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 239000012295 chemical reaction liquid Substances 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 229960002050 hydrofluoric acid Drugs 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 238000010349 cathodic reaction Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000004904 shortening Methods 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 150000001447 alkali salts Chemical class 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000003796 beauty Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 230000002980 postoperative effect Effects 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- RPACBEVZENYWOL-XFULWGLBSA-M sodium;(2r)-2-[6-(4-chlorophenoxy)hexyl]oxirane-2-carboxylate Chemical compound [Na+].C=1C=C(Cl)C=CC=1OCCCCCC[C@]1(C(=O)[O-])CO1 RPACBEVZENYWOL-XFULWGLBSA-M 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Landscapes
- Electrolytic Production Of Metals (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Description
〔産業上の利用分野〕
本発明はステンレス冷延鋼帯表面の酸化スケー
ルを連続的に除去するための効率のよい脱スケー
ル方法に関するものである。
〔従来の技術〕
一般にステンレス冷延鋼帯は酸化性雰囲気で焼
鈍や焼入れなどの熱処理を行うと鋼帯表面に酸化
スケールが形成されるため酸化スケールを除去す
るための脱スケール処理が行われる。
脱スケール処理には硫酸、塩酸、硝弗酸（硝酸
と弗酸の混合酸）などを用いた酸洗が一般に用い
られているが、ステンレス冷延鋼帯に形成される
酸化スケールは緻密で強固であるので完全に脱ス
ケールするのは仲々困難である。これに対し酸洗
を容易にするための前処理法として、溶融アルカ
リ塩への浸漬処理（ソルト処理）あるいは特公昭
38−12162に示される中性塩水溶液中での電解処
理などが開発され実用化されている。
〔発明が解決しようとする問題点〕
中性塩水溶液中での電解処理はソルト処理に比
べ美麗な表面性状を得やすいこと、溶液が中性の
ため作業環境が優れていることなどの長所があ
る。しかしながら、脱スケール能力が優れている
ソルト処理と同等の効果を得るためには、電解に
多量の電気エネルギーを必要とすること、また長
時間の電解を要することから長大な電解槽を必要
とすることなどの欠点がある。
本発明は中性塩水溶液中での電解処理につい
て、その長所を損なうことなく、脱スケール効率
を上げて所要電気エネルギーを減少させ、かつ電
解時間を短縮させることを目的になされたもので
ある。
〔問題点を解決するための手段〕
一般に第２図に模式的に示すように、ステンレ
ス冷延鋼帯の中性塩水溶液４中における電解は、
電解槽５中のステンレス鋼帯３を上下から挟む形
で陽電極１と陰電極２とを鋼帯進行方向に配列
し、両極間に直流電圧を付加する間接電解方式が
採用されている。ステンレス鋼帯３は陰電極２間
を通過する際、鋼帯表面ではアノード反応が生
じ、陽電極１間を通過する際、鋼帯表面ではカソ
ード反応が生じ、この両者の反応を交互に受けな
がら、脱スケール処理がなされている。
アノード反応では酸化スケールを構成している
主な金属元素であるCrおよびFeがそれぞれ６価
のCrイオンと３価のFeイオンに酸化され溶液中
に溶出することにより脱スケールが進行する。
一方、カソード反応は間接電解方式のために必
然的に生じるものであるが、従来は水素ガスの発
生反応のみが生じ、水素ガス気泡による酸化スケ
ール除去作用が僅かながら期待できるものの、脱
スケールには殆ど寄与しないものと考えられてい
た。
本発明者らは工業的に中性塩水溶液中での電解
を行つた場合のカソード反応に着目し、その反応
挙動を詳細に調査研究した結果、従来実施してい
る電解処理条件のもとではカソード反応が脱スケ
ールを大きく阻害しているという重大な発見をな
すに至つた。
すなわち工業的に脱スケール処理を行つている
中性塩水溶液中にはアノード反応で溶出したCr、
Feなどの金属イオンが含まれており、このよう
な溶液中におけるカソード反応では水素ガス発生
反応以外にCr、Feなどの金属イオンが還元され、
鋼帯表面に析出し、スケール状の物質（Cr、Fe
などの酸化物あるいは水和酸化物と思われる）が
付着する反応が生じていることを見い出した。
従つて、従来の方法ではアノード反応における
脱スケール反応と、カソード反応におけるスケー
ル状の物質の析出付着反応が交互に生じているた
め、脱スケールに要する電気エネルギーが多大と
なり、かつ電解時間も長時間を要していたと言え
る。
また、カソード反応におけるCr、Feなどの金
属イオンの還元析出はそのほどんどがCrイオン
によつて生じていることも明らかとなつた。
そこで本発明者らはカソード反応における脱ス
ケール阻害反応を軽減させる方法について研究し
た結果、特定の電解順序とし鋼帯がアノード反応
を生ずる個所の中性塩水溶液とカソード反応を生
ずる個所の溶液とを分割し、またさらにそれぞれ
の溶液の６価のCrイオン濃度とPH値を特定範囲
に限定することにより、大幅に脱スケール能力が
向上することを見い出した。
本発明は前述の新たに得られた知見に基づいて
構成されたものである。
即ち、中性塩水溶液中での間接電解によりステ
ンレス冷延鋼帯の脱スケール処理を行うに当り、
カソード反応液とアノード反応液とを分割した
上、最初に鋼帯表面にカソード反応のみを１回ま
たは複数回生じさせ、次いで鋼帯表面にアノード
反応のみを１回または複数回生じさせる電解順序
をとり、かつ鋼帯表面にカソード反応を生じさせ
る個所の中性塩水溶液（カソード反応液）を下記
のＡの条件を満足する溶液とし、鋼帯表面にアノ
ード反応を生じさせる個所の中性塩水溶液（アノ
ード反応液）を下記のＢの条件を満足する溶液と
するステンレス冷延鋼帯の脱スケール方法であ
る。
Ａ：溶液中の６価のCrイオン濃度８ｇ／以下、
溶液のPH値１以上６以下
Ｂ：溶液中の６価のCrイオン濃度10ｇ／以下、
溶液のPH値２以上６以下
〔作用〕
電解順序を本発明のようにした理由は、表面が
緻密な酸化スケールで覆われた状体でカソード反
応を受け、Crを主体とした金属イオンが還元さ
れ酸化スケールの上にスケールの上にスケール状
の物質が析出付着したば場合は次のアノード反応
で比較的容易に酸化スケールとともに除去される
が、アノード反応を受けて酸化スケールがかなり
除去され、酸化スケール下の地鉄の一部が露出し
た状態でカソード反応を受け、地鉄表面にスケー
ル状の物質が析出付着した場合は次のアノード反
応で除去が非常に困難になるという新しい知見に
よるものである。
すなわち一旦アノード反応を受けた後にはカソ
ード反応を受けさせないことが本発明の重要なポ
イントである。本発明の電解順序を実現する電極
配列の一例を模式的に第１図に示す。
陰電極２および陽電極１の寸法、本数は本発明
では特に限定しない。それらは脱スケール設備の
生産規模、対象鋼種、通板速度、電解回路抵抗な
どを考慮して適切に設定すれば良い。要は酸化ス
ケールの付いたステンレス鋼帯３に対し、まずカ
ソード反応を生じさせ、次いでアノード反応を生
じさせ、アノード反応の後にはカソード反応を生
じさせないことが重要である。
鋼帯表面にカソード反応を生じる個所の中性塩
溶液中の６価のCrイオン濃度を８ｇ／以下に
したのは８ｇ／を越えるとスケール状の物質の
析出が過大となつて、次のアノード反応での除去
が困難となり、第３図のように脱スケール能力が
急激に低下するためである。また溶液のPH値を１
以上６以下に限定したのは６を越えるとスケール
状ぼ物質の析出が過大となり、第４図のように脱
スケール能力が急激に低下し、１以下になると均
一な脱スケールが困難となるためである。
第３図は後述の実施例第２表No.７の条件の内、
カソード反応液中の６価Crイオン濃度を変化さ
せた場合の脱スケール状況を示したものであり、
脱スケール指数１、２、３、４はそれぞれスケー
ル残り大、スケール残り中、スケール残り小、完
全に脱スケールを表わしている。
また第４図は後術の実施例第２表No.７の条件の
内カソード反応液のPH値を変化させた場合の脱ス
ケール状況を示したものである。
鋼帯表面にアノード反応を生じさせる個所の中
性塩水溶液中の６価Crイオンを10ｇ／以下に
したのは10ｇ／を越えると第５図のように脱ス
ケール能力が大幅に低下するためである。また溶
液PHを２以上６以下に限定したのは６を越えると
第６図のように脱スケール能力が大幅に低下し、
２以下になると脱スケール後の表面の美麗さが損
れるためである。
第５図は後述の実施例第２表のNo.７の条件の内
のアノード反応液中の６価Crイオン濃度を変化
させた場合の脱スケール状況を表わしたものであ
り、第６図は同じく実施例第２表No.７の条件の内
アノード反応液のPH値を変化させた場合の脱スケ
ール状況を示したものである。
アノード反応溶液とカソード反応溶液を分割す
る理由は上述の如く脱スケール能力を大幅に向上
させるためのそれぞれの溶液条件が異るため、両
者を分割しない場合は、両者を満足する範囲、す
なわち６価Crイオン濃度８ｇ／以下、PH値２
〜６と許容範囲が狭くなるためである。
なお、溶液中の６価Crイオン濃度を本発明の
上限値以下に調節する方法は自由であるが、例え
ば脱スケール処理量の増加により６価Crイオン
量の高くなつた溶液の一部を排出して新液を投入
する方法や、還元剤を投入して３価のCrイオン
に還元し沈殿物を除去する方法などを適用するこ
とができる。なお従来の中性塩水溶液中での電解
においては溶液中の６価のCrイオン量の影響が
知られていなかつたため公知の値はないが、本発
明者らが測定した所、定常状態ではほぼ10ｇ／
以上の値を示していた。
また溶液のPH値の調節は硫酸または水酸化ナト
リウムを用いて行うのが好ましい。
中性塩水溶液中のCr以外のFe、Ni、Mnなど
の金属イオン濃度も低いに越したことはないが溶
解量も少ないため６価のCrイオンに比べ影響が
軽微であるので特に限定はしない。
中性塩水溶液中での電解処理において上記の電
解順序、水溶液中の６価のCrイオン濃度、溶液
のPH値の限定により、カソード反応における脱ス
ケール抑制作用を大幅に軽減させ、アノード反応
における脱スケール反応を促進させる効果が発揮
され脱スケール能力が大きく向上する。
中性塩の種類、中性塩水溶液の濃度と温度、電
流密度などの他の諸条件は従来の条件が本発明に
も適用される。中性塩は硫酸、硝酸、塩酸などの
Na塩、Ｋ塩を単独または複合して使用すること
ができるが、経済性、表面仕上りの点から硫酸ナ
トリウムの使用が適している。中性塩水溶液の濃
度と温度はそれぞれ100〜300ｇ／、70〜90℃が
適正である。
電流密度はアノード反応電流密度、カソード反
応電流密度ともに２〜15A／ｄm2が適正である。
比較的脱スケール性の良いステンレス鋼の場合
は、中性塩水溶液中での電解だけで脱スケールが
可能であるが、不十分な場合は引続いて酸洗処理
を行うことにより完全に脱スケールすることが可
能となる。
中性塩水溶液中の電解処理後の酸洗は従来と同
様の処理、すなわちフエライト系、マルテンサイ
ト系のステンレスに対しては主として硝酸浸漬ま
たは硝酸電解が適用され、オーステナイト系ステ
ンレスに対しては主として硝弗酸浸漬が適用され
る。
〔実施例〕
酸化性雰囲気で焼鈍を行つた板厚0.8mmの
SUS410、SUS430およびSUS304について、種々
の条件の中性塩水溶液中の電解とそれに引続いた
酸洗処理を脱スケール実験装置を用いて行い、脱
スケール状況の観察を行つた。
なお、SUS410については酸洗処理を省略した
場合も調査した。
中性塩水溶液中での電解順序は、従来例につい
ては第２図の電極配列とし、実施例および比較例
については第１図の電極配列を想定してそれぞれ
実施した。カソード反応電流密度は全て12A／ｄ
m2、アノード反応電流密度は全て6A／ｄm2一定
とした。
中性塩水溶液としてはNa2SO4の水溶液を使用
し、中性塩の濃度は約200ｇ／、溶液温度は85
℃一定とし、PHの調整にはH2SO4およびNaOH
を使用した。
実施例 １
SUS410について得られた結果を第１表に示
す。
従来例のNo.１は電解時間総合計36秒、電気量
144クーロン／ｄm2の中性塩水溶液電解と硝酸浸
漬処理で脱スケールが可能であつた。それに対し
本発明の電解順序で６価Crイオン濃度と溶液の
PH値を本発明の範囲内にある実施例のNo.３は電解
時間総合計12秒、電気量48クーロン／ｄm2の中性
塩水溶液電解のみで酸洗を必要とすることもなく
脱スケールが可能であつた。
また本発明法と同一の電解時間総合計と電気量
の条件で従来法で処理した比較例No.２はかなりの
スケール残りが発生した。
[Industrial Application Field] The present invention relates to an efficient descaling method for continuously removing oxidized scale from the surface of a cold-rolled stainless steel strip. [Prior Art] In general, when a cold rolled stainless steel strip is subjected to heat treatment such as annealing or quenching in an oxidizing atmosphere, oxide scale is formed on the surface of the steel strip, so a descaling treatment is performed to remove the oxide scale. Pickling using sulfuric acid, hydrochloric acid, nitric-fluoric acid (a mixed acid of nitric acid and hydrofluoric acid), etc. is generally used for descaling, but the oxide scale that forms on cold-rolled stainless steel strips is dense and strong. Therefore, it is difficult to completely descale. On the other hand, as a pretreatment method to facilitate pickling, immersion treatment in molten alkali salt (salt treatment) or
Electrolytic treatment in a neutral salt aqueous solution as shown in No. 38-12162 has been developed and put into practical use. [Problems to be solved by the invention] Electrolytic treatment in a neutral salt aqueous solution has the advantages of being easier to obtain a beautiful surface texture than salt treatment, and because the solution is neutral, the working environment is excellent. be. However, in order to obtain the same effect as salt treatment, which has excellent descaling ability, electrolysis requires a large amount of electrical energy and a long electrolysis time, so a long electrolytic cell is required. There are drawbacks such as: The present invention is aimed at increasing the descaling efficiency, reducing the required electrical energy, and shortening the electrolysis time without sacrificing the advantages of electrolytic treatment in a neutral salt aqueous solution. [Means for solving the problem] Generally, as schematically shown in FIG. 2, electrolysis of a cold rolled stainless steel strip in a neutral salt aqueous solution 4 is as follows.
An indirect electrolysis method is adopted in which an anode 1 and a cathode 2 are arranged in the direction of steel strip movement so as to sandwich the stainless steel strip 3 in the electrolytic cell 5 from above and below, and a DC voltage is applied between the two electrodes. When the stainless steel strip 3 passes between the negative electrodes 2, an anode reaction occurs on the surface of the steel strip, and when it passes between the anode electrodes 1, a cathode reaction occurs on the surface of the steel strip. , has been descaled. In the anodic reaction, Cr and Fe, which are the main metal elements constituting the oxide scale, are oxidized to hexavalent Cr ions and trivalent Fe ions, respectively, and are eluted into the solution, thereby progressing descaling. On the other hand, the cathode reaction inevitably occurs due to the indirect electrolysis method, but conventionally only the hydrogen gas generation reaction occurs, and although a slight oxidized scale removal effect by hydrogen gas bubbles can be expected, it is not effective for descaling. It was thought that it would make little contribution. The present inventors focused on the cathode reaction when electrolysis is carried out industrially in a neutral salt aqueous solution, and as a result of detailed investigation and research into the reaction behavior, we found that under the conventional electrolytic treatment conditions, An important discovery was made that the cathode reaction greatly inhibits descaling. In other words, in the neutral salt aqueous solution that is being industrially descaled, Cr, eluted by the anode reaction,
Contains metal ions such as Fe, and in the cathode reaction in such a solution, in addition to the hydrogen gas generation reaction, metal ions such as Cr and Fe are reduced.
Precipitated on the steel strip surface, scale-like substances (Cr, Fe
It was discovered that a reaction occurs in which oxides such as oxides or hydrated oxides are attached. Therefore, in the conventional method, the descaling reaction in the anode reaction and the precipitation and adhesion reaction of scale-like substances in the cathode reaction occur alternately, so the electrical energy required for descaling is large and the electrolysis time is also long. It can be said that it required It was also revealed that most of the reduction and precipitation of metal ions such as Cr and Fe during the cathode reaction was caused by Cr ions. Therefore, the present inventors researched a method to reduce the descaling inhibition reaction in the cathode reaction, and found that a specific electrolysis order was used, and a neutral salt aqueous solution was used in the part where the steel strip would undergo the anodic reaction, and a solution in the part where the cathode reaction would occur. It has been found that the descaling ability can be greatly improved by dividing the solution and further limiting the hexavalent Cr ion concentration and PH value of each solution to a specific range. The present invention is constructed based on the above-mentioned newly obtained knowledge. That is, when descaling a cold rolled stainless steel strip by indirect electrolysis in a neutral salt aqueous solution,
After dividing the cathode reaction liquid and the anode reaction liquid, the electrolysis sequence is such that first only the cathode reaction occurs on the steel strip surface once or multiple times, and then only the anodic reaction occurs on the steel strip surface once or multiple times. A neutral salt aqueous solution (cathode reaction liquid) at a location where a cathode reaction is caused to occur on the steel strip surface is a solution that satisfies the condition A below, and a neutral salt aqueous solution at a location where an anodic reaction is caused on the steel strip surface This is a method for descaling cold-rolled stainless steel strip in which (anode reaction solution) is a solution that satisfies condition B below. A: Hexavalent Cr ion concentration in the solution 8 g/or less,
PH value of solution 1 or more and 6 or less B: Hexavalent Cr ion concentration in the solution 10g/or less,
PH value of the solution is 2 or more and 6 or less [Function] The reason why the electrolysis order is as in the present invention is that the surface is covered with a dense oxide scale and undergoes a cathodic reaction, and metal ions mainly composed of Cr are reduced. If a scale-like substance precipitates and adheres to the oxide scale, it is relatively easily removed along with the oxide scale in the next anode reaction, but a large amount of the oxide scale is removed by the anode reaction. This is based on new knowledge that if a part of the bare iron under the oxide scale undergoes a cathodic reaction while exposed, and scale-like substances precipitate and adhere to the surface of the bare iron, it will be extremely difficult to remove it in the next anode reaction. It is. That is, an important point of the present invention is not to allow the cathodic reaction to occur once the anode reaction has been carried out. An example of an electrode arrangement realizing the electrolysis sequence of the present invention is schematically shown in FIG. The dimensions and number of the negative electrode 2 and the positive electrode 1 are not particularly limited in the present invention. They can be set appropriately by taking into account the production scale of the descaling equipment, target steel type, threading speed, electrolytic circuit resistance, etc. In short, it is important to first cause a cathode reaction and then an anodic reaction to occur on the stainless steel strip 3 with oxide scale, and not to cause a cathode reaction after the anodic reaction. The reason why the concentration of hexavalent Cr ions in the neutral salt solution at the point where the cathode reaction occurs on the surface of the steel strip was set to 8 g/or less is because if it exceeds 8 g/, the precipitation of scale-like substances becomes excessive and the next anode is removed. This is because it becomes difficult to remove by reaction, and the descaling ability decreases rapidly as shown in FIG. Also, the PH value of the solution is 1
The reason for limiting the value to 6 or less is that if the value exceeds 6, the precipitation of scale-like substances will be excessive and the descaling ability will decrease rapidly as shown in Figure 4, and if the value is less than 1, uniform descaling will become difficult. It is. Figure 3 shows the conditions of Example Table 2 No. 7 described below.
This shows the descaling situation when changing the concentration of hexavalent Cr ions in the cathode reaction solution.
Descaling indices 1, 2, 3, and 4 represent large scale remaining, medium scale remaining, small scale remaining, and complete descaling, respectively. Moreover, FIG. 4 shows the descaling situation when the PH value of the cathode reaction liquid was changed under the conditions of No. 7 in Table 2 of the post-operative examples. The reason why the amount of hexavalent Cr ions in the neutral salt aqueous solution at the point where the anodic reaction occurs on the steel strip surface was set to 10 g/or less is because if it exceeds 10 g/, the descaling ability will be significantly reduced as shown in Figure 5. be. In addition, the reason why the solution pH was limited to 2 or more and 6 or less is that if it exceeds 6, the descaling ability will decrease significantly as shown in Figure 6.
This is because if it is less than 2, the beauty of the surface after descaling will be impaired. Figure 5 shows the descaling situation when the concentration of hexavalent Cr ions in the anode reaction solution was changed under the conditions No. 7 in Table 2 of Examples described below, and Figure 6 shows This figure also shows the descaling situation when the PH value of the anode reaction solution was changed under the conditions shown in Example Table 2 No. 7. The reason for dividing the anode reaction solution and the cathode reaction solution is that, as mentioned above, the solution conditions for each are different in order to significantly improve the descaling ability. Cr ion concentration 8g/or less, PH value 2
This is because the permissible range is narrower to 6. Note that there is no limit to the method of adjusting the concentration of hexavalent Cr ions in the solution to below the upper limit of the present invention, but for example, it is possible to adjust the concentration of hexavalent Cr ions in the solution to below the upper limit of the present invention. A method in which a new solution is added, a method in which a reducing agent is added to reduce the amount to trivalent Cr ions, and the precipitate is removed can be applied. In addition, in conventional electrolysis in a neutral salt aqueous solution, there is no known value because the influence of the amount of hexavalent Cr ions in the solution was not known, but according to measurements by the present inventors, in a steady state it is approximately 10g/
It showed the above value. Further, it is preferable to adjust the pH value of the solution using sulfuric acid or sodium hydroxide. It is better to have a low concentration of metal ions other than Cr such as Fe, Ni, Mn, etc. in the neutral salt aqueous solution, but since the dissolved amount is small, the effect is less than that of hexavalent Cr ions, so there is no particular limitation. . In the electrolytic treatment in a neutral salt aqueous solution, by limiting the above electrolysis order, the concentration of hexavalent Cr ions in the aqueous solution, and the pH value of the solution, the descaling suppressing effect in the cathode reaction can be significantly reduced, and the descaling effect in the anode reaction can be significantly reduced. It has the effect of accelerating the scale reaction and greatly improves the descaling ability. Regarding other conditions such as the type of neutral salt, the concentration and temperature of the neutral salt aqueous solution, and the current density, conventional conditions are also applied to the present invention. Neutral salts include sulfuric acid, nitric acid, hydrochloric acid, etc.
Although Na salt and K salt can be used alone or in combination, sodium sulfate is suitable from the viewpoint of economy and surface finish. The appropriate concentration and temperature of the neutral salt aqueous solution are 100 to 300 g/70 to 90°C, respectively. The appropriate current density is 2 to 15 A/dm 2 for both the anode reaction current density and the cathode reaction current density. In the case of stainless steel, which has relatively good descaling properties, it is possible to descale it simply by electrolysis in a neutral salt aqueous solution, but if this is not sufficient, it can be completely descaled by subsequent pickling treatment. It becomes possible to do so. Pickling after electrolytic treatment in a neutral salt aqueous solution is carried out in the same way as conventional methods; nitric acid immersion or nitric acid electrolysis is mainly applied to ferritic and martensitic stainless steels, and nitric acid immersion or nitric acid electrolysis is mainly applied to austenitic stainless steels. Nitrofluoric acid immersion is applied. [Example] A plate with a thickness of 0.8 mm annealed in an oxidizing atmosphere
SUS410, SUS430, and SUS304 were subjected to electrolysis in a neutral salt aqueous solution under various conditions and subsequent pickling treatment using a descaling experimental device, and the descaling status was observed. Regarding SUS410, we also investigated the case where the pickling treatment was omitted. Regarding the order of electrolysis in a neutral salt aqueous solution, the electrode arrangement shown in FIG. 2 was used for the conventional example, and the electrode arrangement shown in FIG. 1 was used for the examples and comparative examples. All cathode reaction current densities are 12A/d
m 2 and anode reaction current density were all constant at 6 A/dm 2 . An aqueous solution of Na 2 SO 4 was used as the neutral salt aqueous solution, the concentration of the neutral salt was approximately 200 g/, and the solution temperature was 85
℃ constant, pH adjustment using H 2 SO 4 and NaOH
It was used. Example 1 Table 1 shows the results obtained for SUS410. Conventional No. 1 has a total electrolysis time of 36 seconds and an amount of electricity.
Descaling was possible by electrolysis in a neutral salt aqueous solution at 144 coulombs/dm 2 and nitric acid immersion treatment. On the other hand, in the electrolysis sequence of the present invention, the hexavalent Cr ion concentration and the solution
In Example No. 3, whose PH value is within the range of the present invention, the total electrolysis time was 12 seconds, and the amount of electricity was 48 coulombs/dm 2. Descaling was achieved without the need for pickling using only neutral salt aqueous solution electrolysis. was possible. Further, in Comparative Example No. 2, which was processed by the conventional method under the same total electrolysis time and electricity amount conditions as the method of the present invention, a considerable amount of scale remained.
【表】【table】
【表】
実施例 ２
SUS430について得られた結果を第２表に示
す。
従来例のNo.４は電解時間総合計43.2秒、電気量
172.8クーロン／ｄm2の中性塩水溶液電解と硝酸
浸漬処理で脱スケールが可能であつた。
それに対し本発明の電解順序で６価のCrイオ
ン濃度と溶液のPH値を本発明の範囲内で種々変化
させた実施例No.６、No.７、No.８はいずれも電解時
間総合計14.4秒以内、電気量57.6クーロン／ｄm2
以内の中性塩水溶液電解と硝酸浸漬処理で脱スケ
ールが可能であつた。
一方、実施例No.８と同一の電解時間総合計と電
気量の条件で従来法で処理した比較例のNo.５はか
なりのスケール残りが発生した。
また溶液のPH値が本発明の下限を下回つた比較
例No.９はスケール残りは発生しなかつたが脱スケ
ール後の表面光沢が本発明法、従来法に比べて劣
つていた。[Table] Example 2 The results obtained for SUS430 are shown in Table 2. Conventional example No. 4 has a total electrolysis time of 43.2 seconds and an amount of electricity.
Descaling was possible by electrolysis in a neutral salt aqueous solution at 172.8 coulombs/dm 2 and nitric acid immersion treatment. On the other hand, in Examples No. 6, No. 7, and No. 8, in which the concentration of hexavalent Cr ions and the pH value of the solution were variously changed within the range of the present invention in the electrolysis order of the present invention, the total electrolysis time was Within 14.4 seconds, electricity amount 57.6 coulombs/dm 2
Descaling was possible through neutral salt aqueous electrolysis and nitric acid immersion treatment. On the other hand, in Comparative Example No. 5, which was treated by the conventional method under the same total electrolysis time and electricity amount conditions as Example No. 8, a considerable amount of scale remained. In Comparative Example No. 9, in which the pH value of the solution was below the lower limit of the present invention, no scale remained, but the surface gloss after descaling was inferior to that of the method of the present invention and the conventional method.
【表】【table】
【表】
実施例 ３
SUS304について得られた結果を第３表に示
す。
従来例のNo.10はいずれも電解時間総合計28.8
秒、電気量115.2クーロン／ｄm2の中性塩水溶液
電解と硝弗酸浸漬で脱スケールが可能であつた。
それに対し本発明の電解順序で６価のCrイオ
ン濃度と溶液のPH値を本発明の範囲内とした実施
例のNo.12は電解時間総合計12秒、電気量48クーロ
ン／ｄm2の中性塩水溶液電解と硝弗酸浸漬で脱ス
ケールが可能であつた。
また本発明と同一の電解総時間と電気量の条件
で従来法で処理した比較例のNo.11はスケール残り
が発生した。[Table] Example 3 Table 3 shows the results obtained for SUS304. Conventional example No. 10 has a total electrolysis time of 28.8
Descaling was possible by electrolysis in a neutral salt aqueous solution and immersion in nitric-fluoric acid with an electrical energy of 115.2 coulombs/dm 2 per second. On the other hand, in Example No. 12, in which the concentration of hexavalent Cr ions and the pH value of the solution were within the range of the present invention in the electrolysis sequence of the present invention, the total electrolysis time was 12 seconds and the amount of electricity was 48 coulombs/ dm2. Descaling was possible by aqueous salt electrolysis and nitric-fluoric acid immersion. Further, in Comparative Example No. 11, which was treated by the conventional method under the same conditions of total electrolysis time and amount of electricity as those of the present invention, scale remained.
【表】【table】
本発明のスレンレス冷延鋼帯の脱スケール方法
を適用することにより、従来よりも脱スケール処
理時間の大幅な短縮による生産性の大幅な向上と
使用電気エネルギーの大幅な低減による経済効果
を得ることが可能となる。
また本発明の脱スケール方法はフエライト系、
マルテンサイト系、オーステナイト系、２相系の
いずれのステンレス鋼にも適用することができる
という汎用性も備えている。
By applying the descaling method for stainless steel cold rolled steel strip of the present invention, it is possible to obtain economic effects by significantly improving productivity by significantly shortening the descaling treatment time and significantly reducing the electrical energy used compared to the conventional method. becomes possible. In addition, the descaling method of the present invention uses ferrite-based,
It also has the versatility of being applicable to any of martensitic, austenitic, and two-phase stainless steels.
第１図は本発明の中性塩水溶液電解方法を具現
する装置の例を模式的に示した図、第２図は従来
の中性塩水溶液電解処理装置の代表的な例を模式
的に示した図、第３図および第４図は本発明の電
解順序でカソード反応液の６価のCrイオン濃度、
PH値を変化させた場合の脱スケールに対する影響
を示したグラフ、第５図および第６図はアノード
反応液の６価のCrイオン濃度とPH値を変化させ
た場合の脱スケールに対する影響を示したグラフ
である。
１……陽電極、２……陰電極、３……ステンレ
ス冷延鋼帯、４……中性塩水溶液、５……電解
槽。
Fig. 1 is a diagram schematically showing an example of an apparatus embodying the neutral salt aqueous solution electrolysis method of the present invention, and Fig. 2 is a diagram schematically showing a typical example of a conventional neutral salt aqueous solution electrolysis treatment apparatus. Figures 3 and 4 show the hexavalent Cr ion concentration of the cathode reaction solution,
Graphs showing the effects on descaling when changing the PH value, Figures 5 and 6 show the effects on descaling when changing the hexavalent Cr ion concentration and PH value of the anode reaction solution. This is a graph. 1... Positive electrode, 2... Negative electrode, 3... Cold rolled stainless steel strip, 4... Neutral salt aqueous solution, 5... Electrolytic cell.
Claims (1)
ス冷延鋼帯を脱スケールする際に、該電解の反応
液を６価Crイオン濃度を８ｇ／以下、PH値１
〜６のカソード反応液と、６価Crイオン濃度10
ｇ／以下、PH値２〜６のアノード反応液とに分
割し、鋼帯表面での反応をカソード反応、次いで
アノード反応の順に行うことを特徴とするステン
レス冷延鋼帯の脱スケール方法。1 When descaling a stainless steel cold rolled steel strip by indirect electrolysis in a neutral salt aqueous solution, the electrolytic reaction solution has a hexavalent Cr ion concentration of 8 g/or less and a pH value of 1.
~6 cathode reaction solution and hexavalent Cr ion concentration 10
1. A method for descaling a cold rolled stainless steel strip, which comprises dividing the solution into an anode reaction solution having a pH value of 2 to 6 and carrying out reactions on the surface of the steel strip in the order of a cathode reaction and then an anode reaction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25233787A JPH0196400A (en) | 1987-10-08 | 1987-10-08 | Method for descaling cold-rolled band stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25233787A JPH0196400A (en) | 1987-10-08 | 1987-10-08 | Method for descaling cold-rolled band stainless steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0196400A JPH0196400A (en) | 1989-04-14 |
| JPH0534440B2 true JPH0534440B2 (en) | 1993-05-24 |
Family
ID=17235867
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25233787A Granted JPH0196400A (en) | 1987-10-08 | 1987-10-08 | Method for descaling cold-rolled band stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0196400A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5347336A (en) * | 1976-10-12 | 1978-04-27 | Kogyo Gijutsuin | Method descaling band steel by electrolysis |
| JPS5710200A (en) * | 1980-06-20 | 1982-01-19 | Matsushita Electric Ind Co Ltd | Voice synthesizer |
| JPS62167900A (en) * | 1986-01-17 | 1987-07-24 | Agency Of Ind Science & Technol | Descaling method for hot rolled sus304 steel |
-
1987
- 1987-10-08 JP JP25233787A patent/JPH0196400A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5347336A (en) * | 1976-10-12 | 1978-04-27 | Kogyo Gijutsuin | Method descaling band steel by electrolysis |
| JPS5710200A (en) * | 1980-06-20 | 1982-01-19 | Matsushita Electric Ind Co Ltd | Voice synthesizer |
| JPS62167900A (en) * | 1986-01-17 | 1987-07-24 | Agency Of Ind Science & Technol | Descaling method for hot rolled sus304 steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0196400A (en) | 1989-04-14 |
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