JPH0534438B2 - - Google Patents
Info
- Publication number
- JPH0534438B2 JPH0534438B2 JP62252335A JP25233587A JPH0534438B2 JP H0534438 B2 JPH0534438 B2 JP H0534438B2 JP 62252335 A JP62252335 A JP 62252335A JP 25233587 A JP25233587 A JP 25233587A JP H0534438 B2 JPH0534438 B2 JP H0534438B2
- Authority
- JP
- Japan
- Prior art keywords
- descaling
- electrolysis
- aqueous solution
- salt aqueous
- reaction
- 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
Links
- 238000006243 chemical reaction Methods 0.000 claims description 44
- 150000003839 salts Chemical class 0.000 claims description 44
- 238000005868 electrolysis reaction Methods 0.000 claims description 43
- 230000007935 neutral effect Effects 0.000 claims description 39
- 239000007864 aqueous solution Substances 0.000 claims description 36
- 229910001220 stainless steel Inorganic materials 0.000 claims description 18
- 239000010935 stainless steel Substances 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 11
- 229910000831 Steel Inorganic materials 0.000 claims description 8
- 239000010959 steel Substances 0.000 claims description 8
- 238000010349 cathodic reaction Methods 0.000 claims description 4
- 150000002500 ions Chemical class 0.000 description 19
- 239000000243 solution Substances 0.000 description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 11
- 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
- 230000000694 effects Effects 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
- 229910052804 chromium Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 229910021645 metal ion Inorganic materials 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 229960002050 hydrofluoric acid Drugs 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000002244 precipitate Substances 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
- 239000010960 cold rolled steel Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000010438 heat treatment Methods 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
- 229910001105 martensitic stainless steel Inorganic materials 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
- 238000002203 pretreatment Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000011160 research Methods 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
- 230000001629 suppression Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Landscapes
- 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
カリ塩への浸清処理（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図の模式図に示すように、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、
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とを電解槽５内に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。ステンレス鋼帯は陰電極間を通
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法のために必
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、特定の電解順序と中性塩水溶液中の６価
のCrイオン量の限定および中性塩水溶液のPH値
の限定とを組合わせることにより、カソード反応
における脱スケール阻害反応を大幅に軽減させ得
ることを見い出した。
本発明は前途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
ンレス冷延鋼帯のスケール処理を行うに当り、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、かつ中性塩水溶液中の６価Crイオン濃度を
８ｇ／以下とし、中性塩水溶液のPH値を２以上
６以下とする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である。
〔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態で
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
状の物質が析出付着した場合は、次のアノード
反応で比較的容易に酸化スケールと共に除去さ
れる。
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、対象攻鋼種、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、電解
槽５内で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。
中性塩水溶液４中の６価のCrイオン濃度を８
ｇ／以下に限定したのは８ｇ／を越えると本
発明の電解順序を採用してもカトード反応におけ
るスケール状物質の析出が過大となること、およ
びアノード反応における脱スケール反応が抑制さ
れることにより、第３図に示すごとく、脱スケー
ル能力が大幅に低下するためである。
第３図は後述の実施例第２表のNo.７の条件の
内、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る。縦軸の脱スケー
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
スケールを表わす指数である。
中性塩水溶液中のCr以外のFe、Ni、Mn等の
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Crイオンに比べ影響は
軽微であるので特に限定はしない。
中性塩水溶液のPH値上限を６としたのは６を越
えると６価Cr6+イオン濃度が８ｇ／を越えた場
合と同様な理由で第４図に示すように脱スケール
能力が大幅に低下するためである。
第４図は後述の実施例第２表のNo.７の条件の
内、溶液の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。またPH値の下限を２とし
たのは２以下になると特にフエライト系およびマ
ルテンサイト系のステンレス表面の平滑度が悪く
なり脱スケール後の表面の美麗さが失われるため
である。
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Crイオン還元し沈
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。
中性塩水溶液中での電解処理において、上記の
電解順序、水溶液中の６価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、表面の仕上りの点から硫酸
ナトリウムの使用が適してる。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。
第２図の電極配列を用いた従来のNo.１は電解時
間総合計36秒、電気量144クーロン／ｄm2の中性
塩水溶液電解の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。
また本発明と同一の電解時間総合計と電気量の
条件で上記従来法で処理したNo.２（比較例）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. In response, pretreatment methods to facilitate pickling include immersion treatment in molten alkali salts (salt treatment) and electrolytic treatment in a neutral salt aqueous solution as shown in Japanese Patent Publication No. 38-12162. and has been 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 shown in the schematic diagram of Fig. 2, electrolysis of cold rolled stainless steel strip in 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 electrolytic cell 5 in the direction of steel strip movement, sandwiching the stainless steel strip 3 from above and below, and a DC voltage is applied between the two electrodes. When the stainless steel strip passes between the negative electrodes, an anodic reaction occurs on the surface of the steel strip, and when it passes between the positive electrodes, a cathodic reaction occurs on the surface of the steel strip, and descaling occurs while undergoing both reactions alternately. Processing is being done. 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 occurs inevitably 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 methods to reduce the descaling inhibition reaction in the cathode reaction, and found that the specific electrolysis order, the limitation of the amount of hexavalent Cr ions in the neutral salt aqueous solution, and the PH value of the neutral salt aqueous solution. It has been found that by combining this with limitation, the descaling inhibition reaction in the cathode reaction can be significantly reduced. The present invention is constructed based on newly obtained knowledge in the future. That is, when scaling a cold-rolled stainless steel strip by indirect electrolysis in a neutral salt aqueous solution, first a cathodic reaction occurs once or multiple times on the surface of the steel strip, and then an anodic reaction occurs on the surface of the steel strip. The method is characterized by adopting an electrolytic sequence that produces only one or more times, the concentration of hexavalent Cr ions in the neutral salt aqueous solution is 8 g / or less, and the pH value of the neutral salt aqueous solution is 2 or more and 6 or less. This is a method for descaling cold-rolled stainless steel strip. [Function] The reason why the electrolysis order is set as in the present invention is that the cathode reaction occurs with the surface covered with a dense oxide scale, metal ions mainly consisting of Cr are reduced, and a scale-like structure is formed on top of the oxide scale. If such substances precipitate and adhere, they are relatively easily removed together with the oxide scale in the next anode reaction. A large amount of the oxide scale is removed through the anodic reaction, and when a part of the base iron under the oxide scale is exposed, it undergoes the cathode reaction and scale-like substances are precipitated and adhered to the surface of the base iron, which will be removed in the next anode reaction. becomes extremely difficult. This is based on new knowledge. 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 should be set appropriately by considering the production scale of the descaling equipment, the target steel type, the threading speed, the electrolytic circuit resistance, etc. In short, it is important to first cause a cathode reaction in the electrolytic cell 5 on the stainless steel strip 3 with oxide scale, then cause an anode reaction to occur, and not to cause a cathode reaction after the anode reaction. The concentration of hexavalent Cr ions in neutral salt aqueous solution 4 is 8
The reason why it is limited to less than 8 g/g is because if it exceeds 8 g/, even if the electrolysis sequence of the present invention is adopted, the precipitation of scale-like substances in the cathode reaction becomes excessive, and the descaling reaction in the anode reaction is suppressed. This is because, as shown in FIG. 3, the descaling ability is significantly reduced. FIG. 3 shows the descaling situation when the hexavalent Cr ion concentration was changed under the conditions No. 7 in Table 2 of Examples described later. Descaling indices 1, 2, 3, and 4 on the vertical axis are indices representing large remaining scale, medium remaining scale, small remaining scale, and complete descaling, respectively. 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 also small, the effect is minor compared to hexavalent Cr ions, so there are no particular restrictions. do not. The reason why the upper limit of the pH value of the neutral salt aqueous solution was set at 6 is that when the pH value exceeds 6, the descaling ability is significantly reduced, as shown in Figure 4, for the same reason as when the hexavalent Cr 6+ ion concentration exceeds 8 g/. This is because it decreases. FIG. 4 shows the descaling situation when the pH value of the solution was changed under the conditions of No. 7 in Table 2 of Examples described below. The lower limit of the pH value is set to 2 because if it is less than 2, the smoothness of the surface of ferritic and martensitic stainless steel in particular deteriorates and the beauty of the surface after descaling is lost. 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, by discharging a part of the solution in which the amount of hexavalent Cr ions has become high due to an increase in the amount of descaling. A method of introducing a new solution or a method of introducing a reducing agent to reduce trivalent Cr ions and remove precipitates can be applied. In addition, in conventional electrolysis in a neutral salt aqueous solution, the influence of the amount of hexavalent Cr ions in the solution was not known, so there is no known value, but according to measurements by the present inventors, in a steady state The value was approximately 10g/or more. Further, it is preferable to adjust the pH value of the solution using sulfuric acid or sodium hydroxide. In electrolytic treatment in a neutral salt aqueous solution, by limiting the electrolysis order, hexavalent Cr ion concentration in the aqueous solution, and pH value of the solution, the descaling suppression effect in the cathode reaction can be significantly reduced, and the descaling effect in the anode reaction can be significantly reduced. The effect of promoting the scale reaction is exhibited, and the descaling ability is greatly improved. 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 using the electrode arrangement shown in FIG. 2 was able to be descaled by nitric acid immersion treatment in neutral salt aqueous solution electrolysis for a total electrolysis time of 36 seconds and an electrical quantity of 144 coulombs/dm 2 . On the other hand, Example No. 3 whose hexavalent Cr ion concentration and solution PH value are within the range of the present invention according to the electrolysis sequence of the present invention has a total electrolysis time of 12 seconds and a neutral electricity quantity of 48 coulombs/ dm2. Descaling was possible using only salt aqueous electrolysis without the need for pickling. Further, in No. 2 (comparative example), which was treated by the above-mentioned conventional method under the same total electrolysis time and electricity amount conditions as in the present invention, a considerable amount of scale remained.
【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。
それに対し実施例の電解順序で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は電解時間総合計
16.8秒以内、電気量67.2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.６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.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 scope of the present invention in the electrolysis order of the example, the total electrolysis time was
Descaling was possible within 16.8 seconds with neutral salt aqueous electrolysis and nitric acid immersion treatment within 67.2 coulombs/dm 2 of electricity. On the other hand, in Comparative Example No. 5, which was processed by the conventional method under the same total electrolysis time and electricity amount conditions as Example No. 6, 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、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 could be descaled by electrolysis in a neutral salt aqueous solution with a total electrolysis time of 28.8 seconds and an amount of electricity of 115.2 coulombs/dm 2 and immersion in nitric-fluoric acid. On the other hand, in Example No. 12, in which the hexavalent Cr ion concentration and the pH value of the solution were within the range of the present invention using the electrolysis sequence of the present invention, the total electrolysis time was 12 seconds, and the amount of electricity was 48 coulombs/dm 2 . Descaling was possible by salt aqueous electrolysis and nitrofluoric 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.
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図は本発明の電解順序を使用
して脱スケールを行つた場合の中性塩水溶液中の
６価のCrイオン濃度の影響を示したグラフであ
り、第４図は中性塩水溶液のPH値の影響を示した
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. Figure 3 is a graph showing the influence of the hexavalent Cr ion concentration in a neutral salt aqueous solution when descaling is performed using the electrolysis sequence of the present invention, and Figure 4 is a graph showing the influence of the concentration of hexavalent Cr ions in a neutral salt aqueous solution. It is a graph showing the influence of the PH value of a salt aqueous solution. 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に当り、該電解にお
ける鋼帯表面の反応を最初にカソード反応、次い
でアノード反応で終結させるとともに、該中性塩
水溶液の６価Crイオン濃度を８ｇ／以下、PH
値を２〜６とする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 cold rolled stainless steel strip by indirect electrolysis in a neutral salt aqueous solution, the reaction on the surface of the steel strip during the electrolysis is first terminated by a cathodic reaction, then an anode reaction, and the neutral salt aqueous solution is Hexavalent Cr ion concentration of 8g/or less, PH
A method for descaling a cold rolled stainless steel strip, characterized in that the value is 2 to 6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25233587A JPH0196398A (en) | 1987-10-08 | 1987-10-08 | Method for electrolytically descaling cold rolled stainless steel strip with neutral salt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25233587A JPH0196398A (en) | 1987-10-08 | 1987-10-08 | Method for electrolytically descaling cold rolled stainless steel strip with neutral salt |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0196398A JPH0196398A (en) | 1989-04-14 |
| JPH0534438B2 true JPH0534438B2 (en) | 1993-05-24 |
Family
ID=17235836
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25233587A Granted JPH0196398A (en) | 1987-10-08 | 1987-10-08 | Method for electrolytically descaling cold rolled stainless steel strip with neutral salt |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0196398A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW401471B (en) * | 1994-07-28 | 2000-08-11 | Hitachi Ltd | Treatment of neutral salt electrolyte, and treating device therefor, descaling of stanless steel and device therefor |
| KR101908800B1 (en) * | 2016-12-16 | 2018-10-16 | 주식회사 포스코 | Method for acid pickling lean duplex stainless steel |
Citations (2)
| 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 |
-
1987
- 1987-10-08 JP JP25233587A patent/JPH0196398A/en active Granted
Patent Citations (2)
| 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 |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0196398A (en) | 1989-04-14 |
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