CN115103933A - Descaling liquid for stainless steel and descaling method for stainless steel - Google Patents
Descaling liquid for stainless steel and descaling method for stainless steel Download PDFInfo
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- CN115103933A CN115103933A CN202180014868.5A CN202180014868A CN115103933A CN 115103933 A CN115103933 A CN 115103933A CN 202180014868 A CN202180014868 A CN 202180014868A CN 115103933 A CN115103933 A CN 115103933A
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- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 67
- 239000010935 stainless steel Substances 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims description 28
- 239000007788 liquid Substances 0.000 title claims description 22
- 238000011282 treatment Methods 0.000 claims abstract description 91
- 239000000243 solution Substances 0.000 claims abstract description 60
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims abstract description 54
- MGFYIUFZLHCRTH-UHFFFAOYSA-N nitrilotriacetic acid Chemical compound OC(=O)CN(CC(O)=O)CC(O)=O MGFYIUFZLHCRTH-UHFFFAOYSA-N 0.000 claims abstract description 48
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000002738 chelating agent Substances 0.000 claims abstract description 21
- 230000007935 neutral effect Effects 0.000 claims abstract description 17
- 239000003792 electrolyte Substances 0.000 claims abstract description 14
- 239000012266 salt solution Substances 0.000 claims abstract description 13
- 239000007864 aqueous solution Substances 0.000 claims abstract description 11
- 150000004677 hydrates Chemical class 0.000 claims abstract description 11
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 9
- 229960001484 edetic acid Drugs 0.000 claims description 17
- 238000007654 immersion Methods 0.000 claims description 12
- 239000011260 aqueous acid Substances 0.000 claims description 5
- 238000005868 electrolysis reaction Methods 0.000 claims description 5
- 239000012530 fluid Substances 0.000 claims 1
- 235000011149 sulphuric acid Nutrition 0.000 claims 1
- 239000001117 sulphuric acid Substances 0.000 claims 1
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 abstract description 12
- -1 ethylenediaminetetraacetic acid compound Chemical class 0.000 abstract description 6
- 229940071106 ethylenediaminetetraacetate Drugs 0.000 abstract description 2
- 239000011651 chromium Substances 0.000 description 35
- 150000002500 ions Chemical class 0.000 description 15
- 238000000137 annealing Methods 0.000 description 13
- 239000007789 gas Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 12
- 239000002253 acid Substances 0.000 description 10
- 239000012298 atmosphere Substances 0.000 description 9
- 239000011734 sodium Substances 0.000 description 9
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 8
- 150000004683 dihydrates Chemical class 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 6
- 239000000523 sample Substances 0.000 description 6
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 5
- 229910000831 Steel Inorganic materials 0.000 description 5
- 229910052938 sodium sulfate Inorganic materials 0.000 description 5
- 235000011152 sodium sulphate Nutrition 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000003638 chemical reducing agent Substances 0.000 description 4
- 238000007598 dipping method Methods 0.000 description 4
- 239000008151 electrolyte solution Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000013522 chelant Substances 0.000 description 3
- 239000000571 coke Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 206010040844 Skin exfoliation Diseases 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000035618 desquamation Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000010985 leather Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 150000004689 octahydrates Chemical class 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- KSPIHGBHKVISFI-UHFFFAOYSA-N Diphenylcarbazide Chemical compound C=1C=CC=CC=1NNC(=O)NNC1=CC=CC=C1 KSPIHGBHKVISFI-UHFFFAOYSA-N 0.000 description 1
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 description 1
- QZKRHPLGUJDVAR-UHFFFAOYSA-K EDTA trisodium salt Chemical compound [Na+].[Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O QZKRHPLGUJDVAR-UHFFFAOYSA-K 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- 230000009920 chelation Effects 0.000 description 1
- 239000003818 cinder Substances 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 description 1
- RHPXYIKALIRNFA-UHFFFAOYSA-L disodium;2-[carboxylatomethyl(carboxymethyl)amino]acetate Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CC([O-])=O RHPXYIKALIRNFA-UHFFFAOYSA-L 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000004255 ion exchange chromatography Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000155 iron(II) phosphate Inorganic materials 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- SDEKDNPYZOERBP-UHFFFAOYSA-H iron(ii) phosphate Chemical compound [Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O SDEKDNPYZOERBP-UHFFFAOYSA-H 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- JRKICGRDRMAZLK-UHFFFAOYSA-N peroxydisulfuric acid Chemical compound OS(=O)(=O)OOS(O)(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-N 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- DZCAZXAJPZCSCU-UHFFFAOYSA-K sodium nitrilotriacetate Chemical compound [Na+].[Na+].[Na+].[O-]C(=O)CN(CC([O-])=O)CC([O-])=O DZCAZXAJPZCSCU-UHFFFAOYSA-K 0.000 description 1
- ZAWGLAXBGYSUHN-UHFFFAOYSA-M sodium;2-[bis(carboxymethyl)amino]acetate Chemical compound [Na+].OC(=O)CN(CC(O)=O)CC([O-])=O ZAWGLAXBGYSUHN-UHFFFAOYSA-M 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- ISIJQEHRDSCQIU-UHFFFAOYSA-N tert-butyl 2,7-diazaspiro[4.5]decane-7-carboxylate Chemical compound C1N(C(=O)OC(C)(C)C)CCCC11CNCC1 ISIJQEHRDSCQIU-UHFFFAOYSA-N 0.000 description 1
- UEUXEKPTXMALOB-UHFFFAOYSA-J tetrasodium;2-[2-[bis(carboxylatomethyl)amino]ethyl-(carboxylatomethyl)amino]acetate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]C(=O)CN(CC([O-])=O)CCN(CC([O-])=O)CC([O-])=O UEUXEKPTXMALOB-UHFFFAOYSA-J 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/08—Iron or steel
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
- C25F1/02—Pickling; Descaling
- C25F1/04—Pickling; Descaling in solution
- C25F1/06—Iron or steel
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
The invention provides a descaling solution which does not leave hexavalent chromium after electrolytic descaling treatment. The descaling solution is an aqueous solution for electrolytic descaling treatment of stainless steel, and contains an electrolyte and a chelating agent, wherein the electrolyte is at least one selected from neutral salt solutions, dilute sulfuric acid and nitric acid, and the chelating agent is at least one selected from ethylenediaminetetraacetic acid and nitrilotriacetic acid. The above-mentioned ethylenediaminetetraacetic acid compound is at least one selected from the group consisting of ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, and a hydrate thereof. The nitrilotriacetic acid is at least one selected from the group consisting of nitrilotriacetic acid, nitrilotriacetic acid salts, and hydrates thereof.
Description
Technical Field
The present invention relates to a descaling liquid for stainless steel and a descaling method for stainless steel using the descaling liquid.
Background
Stainless steel is annealed after cold rolling in order to ensure workability and corrosion resistance.
As a method of annealing stainless steel, there are mainly two methods, a method of annealing stainless steel in a reducing gas atmosphere containing hydrogen, nitrogen, or the like, and a method of annealing stainless steel in a combustible gas atmosphere containing oxygen at about several percent (for example, a gas atmosphere obtained by burning coke oven gas, a gas atmosphere obtained by burning natural gas, an atmospheric atmosphere obtained by raising the temperature by electric power or the like).
In the former method, no oxide film (hereinafter referred to as "scale") is formed on the surface of the stainless steel.
However, in the latter method, during annealing, Fe, Cr, Si, Mn, and the like contained in stainless steel are oxidized to generate scale. Stainless steel with scale formed may have problems in terms of surface gloss, corrosion resistance, workability, and the like.
Therefore, in general, when stainless steel is annealed in a combustible gas atmosphere, descaling treatment using a descaling solution is performed after the annealing to remove scale.
Examples of the descaling treatment include a treatment in which stainless steel is immersed in a molten salt at a high temperature of 450 to 500 ℃ and an electrolytic descaling treatment.
Specifically, electrolytic descaling treatment is performed by subjecting stainless steel to electrolytic treatment in a descaling solution which is an electrolyte solution such as a neutral salt solution (patent document 1).
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 5768141
Disclosure of Invention
Problems to be solved by the invention
The scale cinder of the stainless steel mainly consists of Cr 2 O 3 、Fe 2 O 3 And (4) forming.
When electrolytic descaling treatment is performed on stainless steel having such scale in a descaling solution such as a neutral salt solution, Cr in the scale is hexavalent chromium (Cr) 6+ ) The form of (2) is dissolved into a scale removing solution. This causes minute defects in the scale, and the scale is peeled off from the stainless steel and removed due to the defects.
In this case, hexavalent chromium eluted into the descaling solution may remain in the descaling solution. From the viewpoint of environmental aspects, it is preferable to suppress the residue of hexavalent chromium.
Accordingly, an object of the present invention is to provide a descaling solution for stainless steel, which does not leave hexavalent chromium after electrolytic descaling treatment.
Another object of the present invention is to provide a descaling method for stainless steel using the descaling liquid.
Means for solving the problems
The present inventors have conducted extensive studies to achieve the above object, and as a result, have found that hexavalent chromium is not left after electrolytic deoxidation treatment by adding ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), or the like to the deoxidized skin solution, thereby completing the present invention.
Namely, the present invention provides the following [1] to [6 ].
[1] A descaling liquid for stainless steel, which is an aqueous solution for electrolytic descaling treatment of stainless steel,
the scale removing liquid contains an electrolyte and a chelating agent, wherein the electrolyte is at least 1 selected from neutral salt solution, dilute sulfuric acid and nitric acid, the chelating agent is at least 1 selected from ethylene diamine tetraacetic acid and nitrilotriacetic acid, the ethylene diamine tetraacetic acid is at least 1 selected from ethylene diamine tetraacetic acid, ethylene diamine tetraacetic acid salt and hydrates thereof, and the nitrilotriacetic acid is at least 1 selected from nitrilotriacetic acid, nitrilotriacetic acid salt and hydrates thereof.
[2] The descaling liquid for stainless steel according to [1], wherein the content of the chelating agent is 0.01 to 20 mass%. Wherein the content of the ethylenediaminetetraacetic acid compound is a content converted to ethylenediaminetetraacetic acid, and the content of the nitrilotriacetic acid compound is a content converted to nitrilotriacetic acid.
[3] The descaling liquid for stainless steel according to [1] or [2], which has a pH of 2 to 5.
[4] A method of deoxidizing skins of stainless steel, the method comprising:
an electrolytic descaling process for stainless steel using the descaling solution for stainless steel according to any one of the above [1] to [3 ].
[5]According to the above [4]]The method for deoxidizing skin of stainless steel according to (1), wherein the electrical density of the anodic electrolysis in the electrolytic deoxidation treatment is 5.0C/dm 2 Above and 300.0C/dm 2 The following.
[6] The method for deoxidizing skin of stainless steel according to the above [4] or [5], wherein the stainless steel after being subjected to the electrolytic descaling treatment is further subjected to a dipping treatment using an acid aqueous solution.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a descaling solution can be provided in which hexavalent chromium does not remain after electrolytic descaling.
Detailed Description
[ De-oxidized scale solution ]
The scale removing solution for stainless steel of the present invention (hereinafter also referred to simply as "scale removing solution of the present invention") is an aqueous solution used for electrolytic scale removing treatment of stainless steel, and contains an electrolytic solution of at least 1 kind selected from a neutral salt solution, dilute sulfuric acid and nitric acid, and a chelating agent of at least 1 kind selected from ethylenediaminetetraacetic acids and nitrilotriacetic acids.
The ethylenediaminetetraacetic acid is at least 1 selected from the group consisting of ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid salts, and hydrates thereof, and the nitrilotriacetic acid is at least 1 selected from the group consisting of nitrilotriacetic acid, nitrilotriacetic acid salts, and hydrates thereof.
When electrolytic descaling treatment is applied to stainless steel using the descaling solution of the present invention, hexavalent chromium (Cr) can be suppressed 6+ ) The residue of (1). The reason (mechanism) is presumed as follows.
First, Cr contained in the scale of stainless steel is deoxidized by electrolysis 2 O 3 Becomes stable and water-soluble Cr 6+ And ions dissolved in the de-skinning solution.
However, Cr dissolved in the scale removing solution 6+ The ions are immediately reduced by ethylenediaminetetraacetic acid (EDTA) and/or nitrilotriacetic acid (NTA) to form Cr 3+ Ions. Produced Cr 3+ The ions react with EDTA and/or NTA to form chelate compounds (Cr) 3+ ion-EDTA chelate and/or Cr 3+ ion-NTA chelate). Thus, hexavalent chromium (Cr) can be prevented from being generated 6+ ) And the residual in the de-oxidized leather liquid after the electrolytic de-oxidized leather treatment.
In general, Cr is 3+ The chelate-forming reaction of ionic hydrates with EDTA and/or NTA is very slow. However, with respect to Cr newly generated by reduction 3+ Ions react very easily with EDTA and/or NTA in a short time before the water molecules coordinate. I.e. Cr 3+ The ions are immediately subjected to a precipitation reaction and are discharged outside the system.
Electrolyte solution
The electrolyte (electrolyte solution) is at least 1 selected from a neutral salt solution, dilute sulfuric acid, and nitric acid. That is, the electrolyte may be a mixed solution of 2 or more selected from a neutral salt solution, dilute sulfuric acid, and nitric acid. The dilute sulfuric acid is an aqueous sulfuric acid solution having a concentration of less than 90 mass%.
The solvent of the electrolyte is preferably water.
The electrolyte is preferably a neutral salt solution. Examples of the neutral salt (electrolyte) in the neutral salt solution include sodium sulfate (Na) 2 SO 4 ) Sodium carbonate (Na) 2 CO 3 ) Etc., preferably sodium sulfate.
In the scale removing solution of the present invention, the content of a neutral salt (electrolyte) such as sodium sulfate is preferably 3.0 mass% or more, more preferably 10 mass% or more, and further preferably 15 mass% or more. On the other hand, the upper limit is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less.
Chelating agent
The chelating agent is at least 1 selected from ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA).
EDTA derivatives
The ethylenediaminetetraacetic acid (EDTA) is at least 1 selected from ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetate (EDTA salt), and hydrates thereof.
Examples of the EDTA salt include disodium ethylenediaminetetraacetate (EDTA.2Na), trisodium ethylenediaminetetraacetate (EDTA.3Na), tetrasodium ethylenediaminetetraacetate (EDTA.4 Na), etc., and EDTA.2Na is preferable.
The hydrate of EDTA and/or EDTA salt may be dihydrate or octahydrate.
NTA classes
The nitrilotriacetic acid (NTA) is at least 1 selected from nitrilotriacetic acid (NTA), nitrilotriacetic acid salt (NTA salt), and hydrates thereof.
Examples of the NTA salt include monosodium nitrilotriacetate (NTA · Na), disodium nitrilotriacetate (NTA · 2Na), trisodium nitrilotriacetate (NTA · 3Na), and the like.
Examples of the hydrate of NTA and/or NTA salt include dihydrate and octahydrate.
Content (content)
From the viewpoint of further suppressing the residual of hexavalent chromium, the total content of the chelating agents (EDTA and/or NTA) in the descaling solution of the present invention is preferably 0.01 mass% or more, more preferably more than 1 mass%, even more preferably 3 mass% or more, and particularly preferably 5 mass% or more.
On the other hand, if the content of the chelating agent is too large, the effect of suppressing the residual hexavalent chromium may be saturated, or insoluble components of EDTA and/or NTA may clog the pipes of the pickling equipment.
Therefore, the content of the chelating agent (EDTA and/or NTA) in the scale removing solution of the present invention is preferably 20 mass% or less in total, and more preferably 15 mass% or less. From the viewpoint of cost, it is more preferably 10% by mass or less.
The content of EDTA compounds is converted to the content of EDTA.
The NTA content is converted to NTA content.
Reducing agent
The deoxidized skin liquor of the invention can also contain hexavalent chromium (Cr) with oxidation-reduction potential ratio 6+ ) A high reducing agent. This promotes the conversion from Cr 6+ Ion orientation Cr 3+ The reduction of the ions makes the chelation reaction with EDTA and/or NTA more rapid.
Examples of such a reducing agent include hydrates of iron (II) sulfate, phosphorous acid, iron (II) phosphate, hydrogen peroxide, and peroxodisulfuric acid.
The content of the reducing agent in the scale removing solution of the present invention is preferably 0.01 mass% or more, and preferably 50 mass% or less.
〈pH〉
The pH of the descaling solution of the invention is preferably 2 to 5 for reasons described later.
For example, when a neutral salt solution containing a neutral salt such as sodium sulfate is used as the electrolyte, an acid such as sulfuric acid is added to the neutral salt solution. Thus, even when the neutral salt solution is used as the electrolyte, the pH of the scale removing solution can be adjusted to a range of 2 to 5.
Examples of the sulfuric acid include concentrated sulfuric acid (an aqueous sulfuric acid solution having a concentration of 90% by mass or more) and dilute sulfuric acid (an aqueous sulfuric acid solution having a concentration of less than 90% by mass) (the same applies hereinafter).
[ stainless steel ]
The type of steel of stainless steel subjected to electrolytic descaling treatment using the descaling solution of the present invention is not particularly limited, and examples thereof include: SUS430(16 mass% Cr), SUS304(18 mass% Cr-8 mass% Ni), SUS430J1L (19 mass% Cr-0.5 mass% Cu-0.4 mass% Nb), SUS443J1(21 mass% Cr-0.4 mass% Cu-0.3 mass% Ti), and the like.
Such stainless steel is used in which oxide scale is formed by annealing the stainless steel in a combustible gas atmosphere containing oxygen at a percentage of about several percent (for example, a gas atmosphere in which coke oven gas is combusted). The annealing conditions such as annealing temperature and annealing time are not particularly limited, and conventionally known conditions may be appropriately selected according to the type of stainless steel and the like.
[ Deoxidizing method of skins ]
The descaling method for stainless steel according to the present invention (hereinafter also referred to simply as "descaling method according to the present invention") is a method for descaling stainless steel according to the present invention in which electrolytic descaling treatment is performed on stainless steel using the descaling liquid according to the present invention.
The electrolytic deoxidation of the skins is not particularly limited, and conventionally known electrolytic treatments such as indirect electrolytic treatment, direct electrolytic treatment, through electrolytic treatment, and alternate plate electrolytic treatment can be suitably used.
The electric density of the anodic electrolytic treatment in the electrolytic descaling treatment is preferably 5.0C/dm from the viewpoint of rapidly conducting the descaling 2 From the viewpoint of satisfactory deoxidizing property, the above content is more preferably 10.0C/dm 2 The above.
On the other hand, from the viewpoint of improving the surface properties of stainless steel, the electric energy density of the anodic electrolysis treatment in the electrolytic descaling treatment is preferably set to be high300.0C/dm 2 Hereinafter, more preferably 100.0C/dm 2 Hereinafter, more preferably 70.0C/dm 2 The following.
Here, the cell density of the anodic electrolytic treatment (electrolytic treatment using stainless steel as an anode) is particularly limited.
This is because Cr in the oxide scale is contained only in the case of electrolytic treatment using stainless steel as an anode 2 O 3 Dissolution occurs. In the electrolytic treatment using stainless steel as a cathode, oxide scale is not dissolved, electrochemical decomposition reaction of water occurs, and only O is generated 2 。
However, when conventional electrolytic treatment such as indirect electrolytic treatment, direct electrolytic treatment, through electrolytic treatment, and cross plate electrolytic treatment is performed, it is generally necessary to perform cathodic electrolytic treatment (electrolytic treatment using stainless steel as a cathode) as well as anodic electrolytic treatment.
That is, even in the case of performing the anodic electrolytic treatment, it is necessary to perform the cathodic electrolytic treatment in which the same quantity of electricity density as that of the anodic electrolytic treatment is applied.
In the case of performing the anodic electrolytic treatment in advance, Cr may be formed 3+ Since the ions are inversely attached to the stainless steel, it is preferable to perform the cathodic electrolysis treatment first.
When the scale is thin (for example, scale of stainless steel SUS430), the scale can be sufficiently removed from the surface of the stainless steel only by the electrolytic descaling treatment using the descaling solution of the present invention. Therefore, it is not necessary to immerse the substrate in an acid aqueous solution.
On the other hand, in the case where the scale is thick (for example, scale of stainless steel SUS304, SUS430J1L, SUS443J1), the scale may be insufficiently deoxidized only by the electrolytic descaling treatment using the descaling liquid of the present invention.
In this case, it is useful to further perform a treatment (immersion treatment) of immersing the stainless steel subjected to the electrolytic descaling treatment in an aqueous acid solution. As a result, the acid aqueous solution enters minute defects formed in the scale by the electrolytic descaling treatment, and reaches the interface between the scale and the stainless steel (base steel sheet), thereby dissolving the base steel sheet.
In this case, it is preferable to lower the pH of the scale removing solution used for electrolytic scale removing treatment to the acidic side (specifically, the pH is set to 2 or more and 5 or less). Thus, the base steel sheet is dissolved even in the previous electrolytic descaling process, and the contact of the acid with the base steel sheet in the subsequent dipping process can be facilitated, whereby the descaling time can be shortened. Thus, the de-oxidized skin is finished.
Examples of the acid contained in the aqueous acid solution used in the immersion treatment after the electrolytic descaling include nitric hydrofluoric acid, sulfuric acid, nitric acid, sulfuric hydrofluoric acid, and salts thereof.
The content of acid in the aqueous acid solution is preferably 10g/L or more, more preferably 30g/L or more, in total.
On the other hand, the content of acid in the aqueous acid solution is preferably 200g/L or less, more preferably 150g/L or less, in total.
Examples
The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples.
[ preparation of feed Material ]
A cold-rolled sheet (cold-rolled material) of stainless SUS430 having a sheet thickness of 1.5mm was prepared.
In addition, cold-rolled sheets (cold-rolled materials) of stainless steels SUS304, SUS430J1L, and SUS443J1 having a sheet thickness of 1.2mm were prepared.
The composition of each stainless steel is shown in table 1 below (the balance being Fe and unavoidable impurities).
TABLE 1
The prepared cold-rolled sheet was annealed in a laboratory to obtain a cold-rolled annealed sheet.
More specifically, coke oven gas and air are mixedGas (containing CH) mixed at an air ratio of 1.2 and combusted by direct firing of a burner 4 : 0 vol.% CO 2 : 7.0 vol%, CO: 0% by volume H 2 : 0% by volume H 2 O: 21.0 vol%, O 2 : 3.2 vol%, and N 2 : 68.8% by volume gas) atmosphere. The composition of the gas was quantitatively analyzed using ion chromatography.
The annealing temperature was 860 ℃ for SUS430, 1100 ℃ for SUS304, 1050 ℃ for SUS430J1L, and 950 ℃ for SUS443J 1.
The annealing time was set to 60 seconds.
The cold-rolled annealed sheet obtained by annealing was cut into a size of 40mm × 70mm to prepare a test material. The front and back surfaces of the test piece were sealed with adhesive tapes, and the range of 40mm × 50mm was set as the target of electrolytic descaling treatment described later.
[ preparation of scale removing solution ]
By adding sodium sulfate (Na) as a neutral salt 2 SO 4 ) EDTA-2 Na dihydrate and/or NTA-Na dihydrate as a chelating agent were added to the aqueous solution of (1) to (8) to prepare scale removing solutions shown in Table 2 below.
Removing Na in each scale removing liquid 2 SO 4 The contents of (A) are shown in Table 2 below.
In addition, the content of EDTA · 2Na · dihydrate in terms of EDTA and the content of NTA · Na · dihydrate in terms of NTA are shown in table 2 below for each of the desquamation solutions. In the case where these chelating agents were not added, they are shown as "-" in table 2 below.
The pH of each scale removal solution is also shown in table 2 below.
The pH (for example, pH of 5 or less) of each scale removing solution is adjusted by adding sulfuric acid (concentrated sulfuric acid or dilute sulfuric acid).
TABLE 2
[ test example 1]
Electrolytic descaling treatment was performed on the test material (SUS430) using the descaling solutions 1 to 3.
The electrolytic descaling treatment was performed by a method of directly connecting the electrolytic jig to the test material (direct energization method). More specifically, first, a sample was immersed in a scale removing solution (400mL) set to 80 ℃ in a thermostatic bath. Then, the charge density was repeated 3 times using an external rectifier: -30C/dm 2 →+30C/dm 2 Is energized.
That is, the sample material was used as a cathode at 30C/dm 2 The electrolytic treatment (cathodic electrolytic treatment) was carried out at a cell density of 30C/dm with the test material as the anode 2 The electric charge density of (b) was subjected to electrolytic treatment (anodic electrolytic treatment). This operation was repeated 3 times.
Such electrolytic treatment is performed because when a large charge density is applied at a time, damage is likely to occur on the surface of stainless steel, and damage to the electrode may be accelerated.
Immediately after electrolytic descaling, the sample was taken out of the deoxidized skin solution, washed with ion-exchanged water, wiped on the surface with a nonwoven fabric, and dried with hot air.
In each of the scale removing solutions, 4 pieces of the test materials were subjected to electrolytic scale removing treatment.
The surface properties of the sample after the electrolytic descaling treatment were confirmed by visual observation and SEM observation, and the area ratio (unit:%) of the residual scale was measured. The scale removal ratio (100-area ratio of residual scale) was determined from the measured area ratio of residual scale.
In addition, the reduction (scale removal amount) of the test piece by the electrolytic descaling treatment was measured.
The results are shown in table 3 below.
The appearance of the scale-removing solution was also observed.
The scale-removing liquid 2 after electrolytic scale-removing treatment is reddish brown, which indicates the existence of Cr 6+ Ions. In contrast, the descaling solutions 1 and 3 appeared pale green immediately after the start of the electrolytic descaling treatment, indicating the presence of Cr 3+ Ions.
Therefore, the deoxidized skin liquid after electrolytic deoxidation treatment was quantitatively analyzed, and Cr was measured 6+ And (4) concentration. The results are shown in table 3 below.
For Cr 6+ The concentrations of the respective deoxidized skin liquids after the electrolytic deoxidation treatment were each diluted and measured by an absorptiometry using diphenylcarbazide as a color developer. The same applies to test example 2 described later.
TABLE 3
Summary of results of test example 1
As shown in table 3, in any case, complete removal of the scale and good surface properties were confirmed after the electrolytic descaling treatment. The weight loss caused by the electrolytic descaling treatment was almost equal in all cases.
However, after the electrolytic descaling treatment, Cr in the scale removing solution 2 containing no chelating agent (EDTA-based and/or NTA-based) 6+ The concentration was 6 mg/L. In contrast, Cr of the scale-removing solutions 1 and 3 containing chelating agent (EDTA-based and/or NTA-based) 6+ The concentration was 0mg/L, and Cr was not detected 6+ Ions.
From the above results, it is understood that in test example 1, in comparison with the case of using the scale removing liquid 2 (comparative example), in the case of using the scale removing liquid 1 or 3 (inventive example), Cr was suppressed after the electrolytic descaling treatment 6+ And (4) residual of ions.
[ test example 2]
The sample materials (SUS304, SUS430J1L, or SUS443J1) were subjected to electrolytic descaling treatment using the descaling solutions 1 and 4 to 8 under the same conditions as in test example 1. In each of the scale removing solutions, 3 pieces of the test materials were subjected to electrolytic scale removing treatment.
The reduction in the amount of the test material (the amount of scale removed) by the electrolytic descaling treatment was measured.
In addition, Cr in the scale-removed solution after electrolytic descaling treatment was measured in the same manner as in test example 1 6 + concentration.
The results are shown in table 4 below.
The stainless steel used in test example 2 had a thick scale due to a high annealing temperature, and the electrolytic descaling treatment alone could not sufficiently deoxidize the scale.
Therefore, the sample after the electrolytic descaling treatment was subjected to an immersion treatment in an acid aqueous solution at 60 ℃. As the acid aqueous solution, an aqueous solution of nitric acid and hydrofluoric acid containing 50g/L of nitric acid and 30g/L of hydrofluoric acid was used. At this time, the dipping time was changed to evaluate the descaling property.
The immersion time and the reduction (scale removal) of the test piece after the immersion treatment are shown in table 4 below.
The surface properties of the test materials after the dipping treatment were confirmed by visual observation and SEM observation, and the scale removal ratio was determined. The results are shown in table 4 below.
TABLE 4
Summary of results of test example 2
As shown in Table 4, Cr in the descaling solution 7 containing no chelating agent (EDTA and/or NTA) was removed after the electrolytic descaling 6+ The concentration is 2, 4 or 7 mg/L. In contrast, the descaling solutions 1, 4, 5, 6 and 8 containing chelating agents (EDTA and/or NTA) contained Cr 6+ The concentration was 0mg/L, and Cr was not detected 6+ Ions.
From the above results, it is understood that in test example 2, the scale removing liquid 7 (comparative example) was used in comparison with the case of using the scale removing liquid 7In the case of the scale removing solution 1, 4, 5, 6 or 8 (inventive example), Cr is suppressed after electrolytic descaling treatment 6+ And (4) residual of ions.
Comparison was made between the cases of using the desquamation solutions 1, 4, 5, 6, and 8 containing the chelating agent (EDTA and/or NTA).
When the scale removing solution 1 having a pH of 6 was used and the immersion time in the immersion treatment was as short as 10 seconds (Nos. 4-1 and 12-1), scale residue occurred.
When the scale removing solution 6 having a pH of 1 was used and the immersion time in the immersion treatment was as long as 60 seconds (No.7-3), surface roughening occurred.
On the other hand, in the case of using the scale removing solution 4, 5 or 8 having a pH in the range of 2 or more and 5 or less, complete removal of scale and good surface properties were confirmed after the immersion treatment regardless of the immersion time.
Claims (6)
1. A descaling solution for stainless steel, which is an aqueous solution for electrolytic descaling treatment of stainless steel,
the de-oxidized skin liquid contains electrolyte and chelating agent, the electrolyte is at least 1 selected from neutral salt solution, dilute sulphuric acid and nitric acid, the chelating agent is at least 1 selected from ethylene diamine tetraacetic acid and nitrilotriacetic acid,
the ethylene diamine tetraacetic acid is at least 1 selected from ethylene diamine tetraacetic acid, ethylene diamine tetraacetic acid salt and hydrates thereof,
the nitrilotriacetic acid is at least 1 selected from the group consisting of nitrilotriacetic acid, nitrilotriacetic acid salts, and hydrates thereof.
2. The descaling fluid for stainless steel according to claim 1,
the content of the chelating agent is 0.01-20% by mass,
wherein the content of the ethylene diamine tetraacetic acid is the content converted into ethylene diamine tetraacetic acid, and the content of the nitrilotriacetic acid is the content converted into nitrilotriacetic acid.
3. The descaling liquid according to claim 1 or 2, wherein the pH is 2 or more and 5 or less.
4. A method of deoxidizing skins of stainless steel, the method comprising:
an electrolytic descaling process for stainless steel using the descaling solution for stainless steel according to any one of claims 1 to 3.
5. The descaling method for stainless steel according to claim 4,
the electric quantity density of the anode electrolysis treatment in the electrolytic deoxidation skin treatment is 5.0C/dm 2 300.0C/dm above 2 The following.
6. The descaling method according to claim 4 or 5, wherein,
the stainless steel after the electrolytic descaling treatment is further subjected to an immersion treatment using an aqueous acid solution.
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| PCT/JP2021/005076 WO2021166775A1 (en) | 2020-02-19 | 2021-02-10 | Descaling liquid for stainless steel and descaling method for stainless steel |
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| JP2006002209A (en) * | 2004-06-17 | 2006-01-05 | Taiho Ind Co Ltd | Neutral electropolishing liquid composition for descaling stainless steel surface, and treatment method for stainless steel surface |
| JP2012117116A (en) * | 2010-12-01 | 2012-06-21 | Institute Of National Colleges Of Technology Japan | Agent for removing scale from welded portion of stainless steel and method for removing scale |
| JP2013093299A (en) * | 2011-01-17 | 2013-05-16 | Jfe Steel Corp | Method for manufacturing stainless steel for fuel battery separators, stainless steel for fuel battery separators, fuel battery separator, and fuel battery |
| JP2017031267A (en) * | 2015-07-30 | 2017-02-09 | 独立行政法人国立高等専門学校機構 | Scale remover for stainless steel |
| JP2019119909A (en) * | 2017-12-28 | 2019-07-22 | 株式会社日本科学エンジニアリング | Electrolytic polishing liquid for stainless steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101289147B1 (en) | 2010-12-28 | 2013-07-23 | 주식회사 포스코 | Environmental-Friendly and High Speed Pickling Process for Ferritic Stainless Cold Strip with Good Surface Quality |
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2021
- 2021-02-10 CN CN202180014868.5A patent/CN115103933A/en active Pending
- 2021-02-10 WO PCT/JP2021/005076 patent/WO2021166775A1/en active Application Filing
- 2021-02-10 KR KR1020227026026A patent/KR20220119722A/en unknown
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| JPS61207600A (en) * | 1985-03-11 | 1986-09-13 | Kurinatsupu Kk | Electrolytic descaling agent and descaling method for stainless steel |
| JPH0827600A (en) * | 1994-07-14 | 1996-01-30 | Nisshin Steel Co Ltd | Descaling method and device for stainless steel strip |
| CN1123345A (en) * | 1994-07-28 | 1996-05-29 | 株式会社日立制作所 | Method and apparatus for processing neutral salt electolysing liquid |
| JP2001234372A (en) * | 2000-02-25 | 2001-08-31 | Shinko Tokushu Kokan Kk | Scale removing method for stainless steel surface |
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| JP2012117116A (en) * | 2010-12-01 | 2012-06-21 | Institute Of National Colleges Of Technology Japan | Agent for removing scale from welded portion of stainless steel and method for removing scale |
| JP2013093299A (en) * | 2011-01-17 | 2013-05-16 | Jfe Steel Corp | Method for manufacturing stainless steel for fuel battery separators, stainless steel for fuel battery separators, fuel battery separator, and fuel battery |
| JP2017031267A (en) * | 2015-07-30 | 2017-02-09 | 独立行政法人国立高等専門学校機構 | Scale remover for stainless steel |
| JP2019119909A (en) * | 2017-12-28 | 2019-07-22 | 株式会社日本科学エンジニアリング | Electrolytic polishing liquid for stainless steel |
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| JPWO2021166775A1 (en) | 2021-08-26 |
| KR20220119722A (en) | 2022-08-30 |
| JP7217901B2 (en) | 2023-02-06 |
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