WO2015016538A1 - 고크롬 페라이트계 스테인리스강의 산세 방법 - Google Patents

고크롬 페라이트계 스테인리스강의 산세 방법 Download PDF

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WO2015016538A1
WO2015016538A1 PCT/KR2014/006812 KR2014006812W WO2015016538A1 WO 2015016538 A1 WO2015016538 A1 WO 2015016538A1 KR 2014006812 W KR2014006812 W KR 2014006812W WO 2015016538 A1 WO2015016538 A1 WO 2015016538A1
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pickling
steel sheet
electrolytic
cold rolled
sulfuric acid
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PCT/KR2014/006812
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English (en)
French (fr)
Korean (ko)
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김진석
이용헌
김지훈
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주식회사 포스코
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Priority to CN201480043240.8A priority Critical patent/CN105431574B/zh
Priority to JP2016531518A priority patent/JP6105167B2/ja
Publication of WO2015016538A1 publication Critical patent/WO2015016538A1/ko

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    • 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
    • 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
    • C23G1/081—Iron or steel solutions containing H2SO4
    • 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
    • C23G1/086—Iron or steel solutions containing HF

Definitions

  • the present invention relates to a method for pickling high chromium ferritic stainless steel cold rolled steel sheets requiring high surface quality at high speed, and more specifically, to adjust the amount of applied current during electrolytic pickling according to the annealing temperature and the steel grade component system,
  • the present invention relates to a method for effectively removing annealing scale present in the cold rolled steel sheet by pickling by adjusting the free hydrofluoric acid content and redox potential in the solution.
  • ferritic stainless steels are classified into low chromium ferritic stainless steels and high chromium ferritic stainless steels depending on the chromium content.
  • a chromium content of 11 to 14% by weight is called low chromium ferritic stainless steel, and a chromium content of 17 to 26% by weight is called high chromium ferritic stainless steel.
  • the pickling method according to the chromium content should be performed differently. In general, in the case of low chromium ferrite steel, the scale is thickly formed during the annealing heat treatment, and in the case of the high chromium ferrite steel, the scale is thinner than the low chromium ferrite steel.
  • such a scale may not only reduce the appearance quality of the product, but also may cause corrosion from the oxidized scale to reduce the corrosion resistance, it is necessary to remove the scale formed on the surface through the pickling process.
  • one-step electrolytic pickling such as electrolytic descaling
  • two-step mixed acid immersion such as chemical descaling
  • the process of pickling stainless steel cold rolled steel sheet has conventionally been performed using a mixed acid solution containing 80 to 180 g / L nitric acid and 2 to 40 g / L hydrofluoric acid.
  • the nitric acid contained in the mixed acid solution lowers the pH in the pickling bath to increase the activity of hydrofluoric acid, and serves to maintain a redox potential appropriate for pickling by oxidizing divalent iron ions dissolved in the surface of the steel sheet to trivalent. It generates NOx, an air emission control substance, and contains a large amount of nitrate nitrogen (NO 3 -N) in waste acid and washing water.
  • US Patent Publication No. 5908511 contains sulfuric acid, hydrofluoric acid, iron salts and hydrogen peroxide is regularly added, and the pickling is adjusted by adjusting the composition of the wetting agent, the brightening agent, the corrosion inhibitor, etc., the pickling solution is Fe (III) and redox accordingly
  • ORP oxidation-reduction potential
  • the production cost of the product is more than 20% higher than the conventional, and adopts a complex solution composition and management method, which is a problem, and most crucially, the pickling rate is 1.5 to It has a relatively slow speed of about 3 g / m 2 ⁇ min and poses a problem that it is not suitable for high speed pickling lines in which mixed acid pickling should be completed within 10 to 100 seconds.
  • European Patent Publication No. 1040211 and US Patent Publication No. 2000-560982 have proposed a method of increasing the pickling rate by adding copper and chlorine ions to the pickling composition, but the method
  • OCP open circuit potential
  • the pickling solution contains more than a certain concentration of chlorine ions, pitting corrosion may occur.
  • the present invention makes it possible to provide a stainless steel sheet having no residual oxidation scale and excellent surface glossiness.
  • the present invention when immersing the steel sheet in the mixed acid solution, it is possible to determine the appropriate amount of hydrogen peroxide to be added to the mixed acid solution according to the redox potential, so that the surface of the steel sheet is not pickled or over-acidified, or black phenomena occur To prevent it.
  • the present invention does not use nitric acid as a mixed acid solution used in the pickling process of the steel sheet, it is possible to reduce the burden of treatment for waste water and exhaust gas.
  • It comprises a mixed acid immersion step of immersing the cold rolled steel sheet subjected to the electrolytic pickling in a mixed acid solution containing sulfuric acid and hydrofluoric acid,
  • the sum of the application of the electrolytic neutral salt during the pickling step pickling current and applied to the electrolytic pickling sulfate, the amount of current provides a pickling method of the high-chromium ferritic stainless cold-rolled steel sheet, which is adjusted to not more than 12A / dm 2 or more 20A / dm 2.
  • It comprises a mixed acid immersion step of immersing the cold rolled steel sheet subjected to the electrolytic pickling in a mixed acid solution containing sulfuric acid and hydrofluoric acid,
  • the sum of the applied current amount of neutral salt electrolytic pickling and the applied current amount of sulfuric acid electrolytic pickling is adjusted to 30 A / dm 2 or more and 50 A / dm 2 or less, to provide a method for pickling a high chromium ferritic stainless steel cold rolled steel sheet.
  • the amount of applied current of the neutral salt electrolytic pickling may be 8 A / dm 2 or more, and the amount of applied current of sulfuric acid electrolytic pickling may be 0 or 8 A / dm 2 or more.
  • the silicon (Si) content is 0.3% by weight or less or the molybdenum (Mo) content is 0.5% by weight or less with respect to the total weight of the cold rolled steel sheet,
  • the mixed acid solution used in the mixed acid immersion step includes 80 to 150 g / L sulfuric acid and 5 to 12 g / L free hydrofluoric acid, and an redox potential (ORP) may be 550 mV or more.
  • Hydrogen peroxide may be added to the mixed acid solution such that the redox potential of the mixed acid solution is maintained at 550 mV or more.
  • the silicon (Si) content is more than 0.3% by weight or the molybdenum (Mo) content is more than 0.5% by weight relative to the total weight of the cold rolled steel sheet,
  • the mixed acid solution used in the mixed acid immersion step includes 80 to 150 g / L sulfuric acid and 20 to 30 g / L free hydrofluoric acid, and an redox potential (ORP) may be 320 mV or more.
  • Hydrogen peroxide may be added to maintain the redox potential of the mixed acid solution at 320 mV or more.
  • the neutral salt electrolytic pickling may be performed using an electrolyte solution containing sodium sulfate at a concentration of 100 to 250 g / L.
  • the temperature of the electrolyte used during the neutral salt electrolytic pickling may be 50 ⁇ 90 °C.
  • the neutral salt electrolytic pickling may be performed for 24 to 100 seconds.
  • the sulfuric acid electrolytic pickling is an electrolyte solution comprising a metal sulfate formed by dissolving at least one metal selected from the group consisting of iron, chromium, nickel, copper, manganese and titanium in 50 to 150 g / l sulfuric acid or 50 to 150 g / l sulfuric acid.
  • a metal sulfate formed by dissolving at least one metal selected from the group consisting of iron, chromium, nickel, copper, manganese and titanium in 50 to 150 g / l sulfuric acid or 50 to 150 g / l sulfuric acid.
  • the temperature of the electrolyte solution used in the sulfuric acid electrolytic pickling may be 30 ⁇ 60 °C.
  • the sulfuric acid electrolytic pickling may be performed for 10 to 50 seconds.
  • the mixed acid immersion step may be performed for 25 to 90 seconds.
  • the surface potential of the cold rolled steel sheet during the mixed acid immersion step may be maintained in the range of -0.2 to 0V.
  • the present invention provides a high chromium ferritic stainless steel cold rolled steel sheet having no residual oxidation scale and excellent surface glossiness.
  • the present invention when immersing the steel plate in the mixed acid solution, it is possible to determine the appropriate amount of hydrogen peroxide that is added to the mixed acid solution according to the redox potential, so that the surface of the steel sheet is not pickled or over-acidified, or black phenomena occur To prevent it.
  • the present invention does not use nitric acid as a mixed acid solution used in the pickling process of the steel sheet, it is possible to reduce the burden of treatment for waste water and exhaust gas.
  • 1 is a graph showing the Cr / Fe content ratio according to the depth of the annealing scale of the 439 steel and 441 steel.
  • Figure 2 shows the applied current region of the electrolytic pickling neutral salt electrolytic cell and sulfuric acid electrolytic cell according to the annealing temperature.
  • Figure 3 shows the concentration of free hydrofluoric acid contained in the mixed acid solution used in the mixed acid immersion step and the redox potential region of the mixed acid solution according to the content of silicon and molybdenum contained in the cold rolled steel sheet.
  • Figure 4 (a) to (d) shows a photograph of the surface of the stainless steel after pickling in Comparative Example 1, Example 1, Comparative Example 8 and Comparative Example 9.
  • FIG. 5A to 5C show photographs of the surface of stainless steel after pickling in Comparative Examples 16, 6, and 28.
  • FIG. 6 (a) and 6 (b) show photographs of the surface of stainless steel after pickling in Comparative Examples 29 and 31.
  • Figure 7 (a) and (b) is a photograph showing the surface of the stainless steel after pickling in Comparative Example 32 and Example 16.
  • FIG. 8 are photographs of the surface of stainless steel after pickling in Comparative Examples 33 and 19.
  • the present invention relates to a method for pickling to remove an oxidation scale present on the surface of a high chromium ferritic stainless steel cold rolled steel sheet containing 17 to 26% by weight chromium based on the total weight of the cold rolled steel sheet.
  • the method for pickling a high chromium ferritic stainless steel cold rolled steel sheet includes an electrolytic pickling step of neutral salt electrolytic pickling and sulfuric acid electrolytic pickling of the high chromium ferritic stainless steel cold rolled steel sheet and a cold rolled steel sheet subjected to the electrolytic pickling.
  • an electrolytic pickling step of neutral salt electrolytic pickling and sulfuric acid electrolytic pickling of the high chromium ferritic stainless steel cold rolled steel sheet and a cold rolled steel sheet subjected to the electrolytic pickling To include a mixed acid immersion step immersed in a mixed acid solution containing sulfuric acid and hydrofluoric acid, the amount of applied current is adjusted according to the annealing temperature during the electrolytic pickling step, free hydrofluoric acid contained in the mixed acid solution according to the steel species component during the mixed acid immersion step It is characterized by adjusting the content of (Free HF) and the redox potential (ORP).
  • the high chromium ferritic stainless steel cold rolled steel sheet may be subjected to a neutral salt electrolytic pickling and sulfuric acid electrolytic pickling in an electrolytic pickling process.
  • the neutral salt electrolytic pickling may be performed using an electrolyte solution containing sodium sulfate of 100 ⁇ 250g / L concentration as an electrolyte, specifically after immersing the cold rolled steel sheet in the electrolyte solution having a temperature of 50 ⁇ 90 °C
  • a current of 8 to 30 A / dm 2 may be applied for 24 to 100 seconds.
  • the sulfuric acid electrolytic pickling is a sulfuric acid of 50 ⁇ 150g / l or a metal sulfate formed by the electrochemical dissolution of at least one metal selected from the group consisting of iron, chromium, nickel, copper, manganese and titanium in the sulfuric acid of the concentration. It can be carried out using an electrolyte containing an electrolyte, specifically, after immersing the cold rolled steel sheet in the electrolyte having a temperature of 30 ⁇ 60 °C, the potential of the steel plate surface at least once in the order of +,-, + It can be carried out by applying a current of 0 ⁇ 30A / dm 2 density for 10 to 50 seconds to be charged over.
  • the content of chromium is high in the scale generated during annealing, in particular, the higher the annealing temperature, the higher the chromium content.
  • the higher the chromium content contained in the annealing scale the easier the dissolution of the oxide during neutral salt electrolytic pickling.
  • the annealing temperature is 1030 ° C. or higher
  • the concentration of the chromium is severely concentrated, and the neutral salt and sulfuric acid electrolytic pickling is performed. Under high application current conditions, there is a risk of overacid washing due to surface melting.
  • the sum of the applied current amount of neutral salt electrolytic pickling and the applied current amount of sulfuric acid electrolytic pickling If less than 12A / dm 2 , fine pickling may occur, and if it exceeds 20A / dm 2 , surface erosion may occur due to over pickling. Therefore, for effective pickling, the amount of applied current of neutral salt electrolytic pickling and sulfuric acid electrolytic pickling the sum is preferably adjusted to 20A / dm 2 or less than 12A / dm 2.
  • 930 °C When electrolytic pickling of the cold rolled steel sheet annealed at a relatively low temperature of less than 1030 °C, if the sum of the applied current amount of neutral salt electrolytic pickling and the applied current amount of sulfuric acid electrolytic pickling is less than 30A / dm 2 , fine pickling may occur, If it exceeds 50A / dm 2 , surface erosion may occur due to over pickling. Therefore, for effective electrolytic pickling, the sum of the applied current of neutral salt electrolytic pickling and the applied current of sulfuric acid electrolytic pickling is 30 A / dm 2 or more and 50 A / dm 2 or less It is preferable to adjust so that.
  • the amount of applied current of neutral salt electrolytic pickling is 8 A / dm 2 or more, and the amount of applied current of sulfuric acid electrolytic pickling is 0 or 8 A / dm 2 or more regardless of the annealing temperature during electrolytic pickling.
  • the amount of applied current during neutral salt electrolytic pickling is less than 8 A / dm 2 , the surface potential for dissolving the annealing scale is not formed, and the effect of the neutral salt electrolytic pickling may be insignificant. It is preferable that the amount of applied current is 8 A / dm 2 or more.
  • the value is determined by the sum of the applied current amounts of the two electrolytic pickling, but is not particularly limited, but it is economical such as operating cost
  • the upper limit of the amount of applied current is preferably 30 A / dm 2 or less.
  • FIG. 2 is a diagram illustrating an applied current region of a neutral salt electrolytic cell and a sulfuric acid electrolytic cell that are electrolytic pickled according to an annealing temperature in the present invention.
  • an annealing temperature of a ferritic stainless steel containing 17 to 26% by weight of chromium is 1030.
  • the applied current range of the neutral salt electrolytic cell and sulfuric acid electrolytic cell which can be pickled in the region of -1050 ° C is shown, and the area II shows the applied current range of the neutral salt electrolytic cell and sulfuric acid electrolytic cell which can be pickled at annealing temperature of 930 ° C or more and less than 1030 ° C.
  • the silicon oxide layer may remain. Therefore, in the pickling method of the present invention, the silicon oxide remaining on the steel sheet by performing the mixed acid immersion step of immersing the cold rolled steel sheet subjected to the electrolytic pickling in the electrolytic pickling step in a mixed acid solution containing sulfuric acid and hydrofluoric acid. The layer of can be removed.
  • Hydrofluoric acid (HF) contained in the mixed acid solution used in the mixed acid immersion step is dissociated in the solution as shown in the following formula (1), and hydrogen ions (H +) provided by dissociating sulfuric acid as shown in the following formula (2)
  • the equilibrium state is changed by the concentration of c, i.e. acidity.
  • hydrofluoric acid in the case of hydrofluoric acid, it has a pickling force in a free hydrofluoric acid (Free HF) state, and the free hydrofluoric acid penetrates the interface between the silicon oxide and the base material to dissolve silicon oxide and iron (Fe), and then dissolves silicon. Ions and iron ions are combined in the form of FeF x (3-x) , H 2 SiF 6 and the like to remove them from the steel sheet surface.
  • the mixed acid immersion step it is preferable to use a mixed acid solution having a concentration of 5 to 30 g / L of free hydrofluoric acid.
  • concentration of free hydrofluoric acid is less than 5 g / L, the concentration of free hydrofluoric acid is small, so that there is a lack of solubility in the silicon oxide layer may cause the problem of fine pickling on the surface of the steel sheet, when the concentration exceeds 30 g / L, The rate of erosion of the base material may increase, resulting in a rough surface of the steel sheet after pickling.
  • the hydrofluoric acid contained in the mixed acid solution provides pickling force capable of removing the silicon oxide layer on the surface of the steel sheet, but it is necessary to maintain the effective free hydrofluoric acid concentration in the mixed acid solution above a certain acidity. Therefore, in the present invention, in order not to dissociate the hydrofluoric acid contained in the mixed acid solution, it is preferable that the mixed acid solution contains sulfuric acid at a predetermined concentration or more together with the hydrofluoric acid.
  • a suitable sulfuric acid concentration is preferably 80 to 150 g / l, and when the concentration of sulfuric acid is less than 80 g / l, the effective free hydrofluoric acid concentration is not maintained, so that dissociation of hydrofluoric acid occurs and the pickling force is weakened. If the concentration is more than 150g / L may cause problems such as heat generation during the sulfuric acid dilution operation is difficult to operate.
  • Fe 2+ is eluted from the base material, and the eluted Fe 2+ is oxidized to Fe 3+ when reacted with an oxidizing agent such as hydrogen peroxide, and then combined with free hydrofluoric acid to form a FeF x (3-x) complex.
  • an oxidizing agent such as hydrogen peroxide
  • free hydrofluoric acid to form a FeF x (3-x) complex.
  • the reaction may be expressed as in the following formulas (3) to (6), it is possible to increase the pickling rate only when such a process proceeds smoothly.
  • the content and redox of the free hydrofluoric acid (Free HF) contained in the mixed acid solution according to the content of silicon (Si) and molybdenum (Mo) contained in the cold rolled steel sheet Pickling can be effectively performed by adjusting the potential ORP.
  • the mixed acid solution when the silicon content is 0.3% by weight or less or the molybdenum content is 0.5% by weight or less, the mixed acid solution preferably includes 80-150 g / L sulfuric acid and 5-12 g / L free hydrofluoric acid. In order to prevent blackening, it is preferable to add hydrogen peroxide such that the redox potential (ORP) of the mixed acid solution is maintained at 550 mV or more.
  • ORP redox potential
  • the silicon (Si) content in the high chromium ferritic stainless steel exceeds 0.3% by weight, a large amount of silicon oxide may be present on the surface of the steel sheet before the immersion step in the mixed acid solution after electrolytic pickling, in order to effectively remove Preference is given to using high concentrations of free hydrofluoric acid.
  • the mixed acid solution when the silicon content is more than 0.3% by weight or the molybdenum content is more than 0.5% by weight, the mixed acid solution includes sulfuric acid at a concentration of 80 to 150 g / L and free hydrofluoric acid at a concentration of 20 to 30 g / L.
  • the redox potential range of the mixed acid solution does not have to be particularly limited in its upper limit regardless of the silicon and molybdenum content contained in the stainless steel,
  • the metal content is very high, and in such a situation, if the redox potential is kept high, the excessive amount of fruit may be excessive, which may be an economical problem.
  • the upper limit is preferably maintained at 600 mV or less.
  • Figure 3 shows the concentration of free hydrofluoric acid contained in the mixed acid solution used in the mixed acid immersion step and the redox potential region of the mixed acid solution according to the content of silicon and molybdenum contained in the cold rolled steel sheet in the present invention.
  • region III of FIG. 3 shows free hydrofluoric acid concentration which can be pickled when immersed in a mixed acid solution after electrolytic pickling in a stainless steel component having a Si content of 0.3 wt% or less or a Mo content of 0.5 wt% or less in a high chromium ferritic stainless steel. Is 5-12 g / L, and the redox potential range of the solution is 550 mV or more.
  • the region IV of FIG. 3 is capable of pickling when immersed in a mixed acid solution after electrolytic pickling with a stainless steel component system having a Si content of more than 0.3 wt% or a Mo content of more than 0.5 wt% in a high chromium ferritic stainless steel.
  • Free hydrofluoric acid concentration is 20 ⁇ 30g / L
  • the redox potential range of the solution is more than 320mV.
  • the surface potential of the cold rolled steel sheet during the mixed acid immersion step is preferably maintained in the range of -0.2 to 0V.
  • the dissolution rate and pattern are determined according to the surface potential.
  • the base metal is mainly dissolved as Fe 2+ and reacts with SO 4 2- to form FeSO 4 compound on the surface. Black phenomena may form on the surface, in which case the specific orientation of the grains dissolves severely when the base material is dissolved on the surface, and the surface becomes very rough, and Fe 3+ , which can be removed only at a high surface potential, is not removed.
  • the tax and tax may be mixed.
  • the execution time of the mixed acid immersion step is not particularly limited and may vary depending on operating conditions. However, according to the pickling method of the present invention, it may be performed within a short time of 25 to 90 seconds.
  • 441 steel and 439 steel were used in the following examples, and the expression of the 441 steel and 439 steel indicates the content ratio of Cr / Fe component in the annealing scale, and the 441 steel was 1050 ° C. and the 439 steel was 970 ° C. heat-treated.
  • the composition ratio of Cr / Fe content in the annealing scale is 8.5 in 441 steel and 4.3 in 439 steel.
  • the chromium content is about 17 wt% based on the total weight, but the Cr / Fe ratio in the annealing scale is different due to the difference in annealing temperature due to the characteristics of the steel grade.
  • both the 439 and 441 steels have high chromium content in the annealing scale, which is advantageous for neutral salt electrolytic pickling, but the 441 steel having a high Cr / Fe ratio may be more advantageous.
  • FIG. 1 is a graph showing the Cr / Fe ratios of the annealing scales of the 439 steel and the 441 steel, and the 439 steel and the 441 steel have a tendency to increase Cr / Fe due to the increase in the chromium content from the outer layer to the inner layer. Once fully entered into the base material, it can be seen that it converges to the Cr / Fe content ratio of the base material.
  • Electrolytic pickling was carried out by adding a current density as shown in Table 1 below to a salt acid electrolyzer containing sodium sulfate as an electrolyte for 441 steel having an annealing temperature of 1050 ° C, and adding a current density as shown in Table 1 below to a sulfuric acid bath containing sulfuric acid as an electrolyte.
  • a sulfuric acid bath containing sulfuric acid as an electrolyte.
  • the residual hydrogen peroxide concentration was added to 3g / L to maintain the redox potential of the solution above 550mV.
  • the neutral salt electrolytic cell current is 8A / dm 2 or more
  • sulfuric acid electrolytic cell current is 0 or 8A / dm 2 or more
  • the sum of the two electrolytic cell applied current amount is 12 A / dm 2. If more than 20 a / dm 2 or less can be seen a normal acid washing.
  • Figure 4 (a) to (d) is a photograph showing the surface of the stainless steel after pickling in Comparative Example 1, Example 1, Comparative Example 8 and Comparative Example 9, (a) is not pickled because the amount of applied current is insufficient It can be seen that there is a residual scale, and (b) can see the normal pickling surface according to Example 1. In addition, (c) it can be seen that the surface is not good due to the surface erosion occurs due to the pickling, (d) can also be seen that the surface is not good due to uneven pickling.
  • the embodiment of the scale components in the chromium component ratio is high through the electrolytic pickling during pickling it is possible in a relatively low electrolytic current of 12A / dm 2 or more 20A / dm 2 or less the sum of the applied two electrolytic cell of the neutral salt electrolytic bath and the sulfuric acid electrolytic cell amperage It can be seen that.
  • Electrolytic pickling was carried out by adding a current density as shown in Table 2 to the acidic salt bath containing sodium sulfate as an electrolyte in 439 steel having an annealing temperature of 970 ° C, and adding a current density as shown in Table 1 below to a sulfuric acid bath containing sulfuric acid as an electrolyte.
  • a sulfuric acid bath containing sulfuric acid as an electrolyte was then immersed in a mixed acid solution at 40 ° C. containing 80 g / L sulfuric acid and 8 g / L free hydrofluoric acid for 30 seconds.
  • the residual hydrogen peroxide concentration was added to 3g / L to maintain the redox potential of the solution above 550mV.
  • the neutral salt electrolyzer current is 8 A / dm 2 or more, and the sum of the two electrolytic cell applied currents of the neutral salt electrolyzer and the sulfuric acid electrolyzer is 30 A / dm 2 or more and 50 A / dm 2 or less The case can be seen from the normal pickling surface.
  • the case where the applied current of the sulfuric acid electrolyzer is less than 8 A / dm 2 is a nonuniform pickling surface as shown in FIG. It is not preferable to represent.
  • the electrolytic pickling hour neutral salt electrolytic bath is the electrolytic pickling hour neutral salt electrolytic bath, and two electrolytic cell applied current sum is 30A / dm 2 or more very high applied current of 50 A / dm 2 or less for the sulfuric acid electrolytic bath It can be seen that it is necessary.
  • FIGS. 6A and 6B the surface pictures of the stainless steel after pickling in Comparative Examples 29 and 31 are shown in FIGS. 6A and 6B, and the surface pictures of the stainless steel after pickling in Comparative Examples 32 and 16 are shown in FIG. A) and (b) are shown, and the surface photographs of the stainless steel after pickling in Comparative Examples 33 and 19 are shown in FIGS. 8A and 8B.
  • the 439 steel grade does not include molybdenum (Mo), and a silicon (Si) content of 0.3 wt% or less was used.
  • the redox potential can be pickled if it is 320 mV or more, and even if there is no residual hydrogen peroxide, it is possible if the ratio of Fe 3+ ions and Fe 2+ ions (Fe 3+ / Fe 2+ ) in the metal ions in the solution is 1 or more. In general, a constant amount of hydrogen peroxide must be injected to maintain the redox potential above 320 mV.
  • Figure 6 (a) and (b) is a photograph showing the surface of the stainless steel after pickling in Comparative Examples 29 and 31, (a) is the free hydrofluoric acid concentration and redox potential of the mixed acid solution in Comparative Example 29 It can be seen that the pickling occurs on the surface according to the low all, (b) can be seen that in the case of applying the concentration of free hydrofluoric acid in Comparative Example 31 exceeds the range of the present invention, the super-acid is generated, the surface erosion occurred .

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PCT/KR2014/006812 2013-07-31 2014-07-25 고크롬 페라이트계 스테인리스강의 산세 방법 WO2015016538A1 (ko)

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CN201480043240.8A CN105431574B (zh) 2013-07-31 2014-07-25 酸洗高铬铁素体不锈钢的方法
JP2016531518A JP6105167B2 (ja) 2013-07-31 2014-07-25 高クロムフェライト系ステンレス冷延鋼板の酸洗方法

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CN114150124A (zh) * 2021-12-09 2022-03-08 山西太钢不锈钢股份有限公司 一种高铬镍不锈钢冷轧钢带退火酸洗工艺方法

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CN114150124A (zh) * 2021-12-09 2022-03-08 山西太钢不锈钢股份有限公司 一种高铬镍不锈钢冷轧钢带退火酸洗工艺方法

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