JP2015206093A - Scale remover of stainless steel weld zone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scale remover preventing use of a compound such as nitric acid and hydrofluoric acid as much as possible, safe in workability and handling and capable of easily and cleanly removing oxidation coating, catching rust, dirty or the like of black color or brown color of a stainless steel weld zone and a heat-affected zone.SOLUTION: A scale remover of a stainless steel weld zone is manufactured by adding at least one kind of organic acid of succinic acid, oxalic acid, acetic acid, acetyl acetone, sulfuric acid, a surfactant of a predetermined amount and an organic thickener of 1 wt.% or less to a reaction product between a solution of magnesium nitrate hexahydrate and a solution of at least one kind of compound of acidic ammonium fluoride, acidic sodium fluoride and acidic potassium fluoride and mixing them.

Description

  The present invention relates to a scale remover used for removing welding burns generated by welding of a chromium-containing alloy steel represented by stainless steel, for example, a scale remover suitable for brush coating.

  When stainless steel is welded, welding burn (oxidation scale) is generated around the welded portion (bead portion), so that welding scoring is conventionally performed. Although the remover used for descaling is commercially available, it has been difficult to completely remove the burn with the conventional remover. If the welding burn remains, the mark of the welded portion remains, so that the appearance is bad and the commercial value is lowered.

  In addition, since the conventional remover contains a strong acid in a high concentration, when immersed or applied in an acid cleaning solution, the stainless steel in that portion is easily whitened and discolored. For this reason, there is a problem that a difference in hue between a portion where the remover is immersed or applied and a portion where the remover is not applied and a portion where the remover is not applied are increased, the gloss is changed, the appearance of the product is deteriorated, and the commercial value is lowered.

  For this reason, as a method of removing the black or brown oxide film and the rust, dirt, etc. of the welded part and the heat affected part of stainless steel, there is a method of brushing a remover mainly composed of nitric acid and hydrofluoric acid. (For example, Patent Document 1 and Patent Document 2).

  However, hydrofluoric acid is a toxic substance and nitric acid is a deleterious substance. Both compounds have a strong irritating odor, and are severely regulated in terms of health, work environment and handling of workers. Further, in the wastewater treatment after use, it was necessary to take measures against poisonous regulations for hydrofluoric acid and total nitrogen regulations for nitric acid.

  In order to solve these problems, Patent Document 3 discloses an acid cleaning liquid containing ferric chloride at a high concentration, Patent Document 4 includes an acid cleaning liquid containing chlorine ions as an essential component, and Patent Document 5 includes An acid cleaning solution containing ammonium chloride as an essential component, Patent Document 6, discloses an acid cleaning solution using a high-concentration hydrochloric acid solution.

  Patent Documents 7, 6, and 8 disclose that an acid cleaning solution containing an inorganic acid is mixed with an aqueous solution of sulfuric acid at 40 to 80 ° C., 50 to 110 ° C. or 80 ° C. or nitric acid at 60 ° C. Has been.

  In Patent Document 9, detergency and safety obtained by reacting nitric acid with nitric acid or a fluorine compound soluble in water and various alkaline earth metal compounds to form a transparent colloidal material as a homogeneous metal double salt. A remover with improved handling and workability is disclosed.

  In Patent Document 9, a magnesium compound and a fluorine compound are reacted to produce colloidal magnesium fluoride, but it is known that the magnesium fluoride thus produced becomes a colloidal material ( For example, refer nonpatent literature 1).

  Patent Document 4 discloses a remover for brush coating in which a thickener made of xanthan gum or diatomaceous earth is added to a mixed aqueous solution of nitrate and hydrochloride by 1 wt% or more. When such an organic thickener is added in an amount of 1% by weight or more, the scale removal effect may be reduced.

JP 2007-297697 A JP 2012-46817 A Japanese Patent Publication No.43-1136 JP-A-2005-232585 Japanese Patent Laid-Open No. 4-120286 Japanese Patent No. 2588646 JP 2012-117116 A JP 59-83783 A JP 2000-297391 A

“Inorganic Compound and Complex Dictionary”, Kodansha 1997, p818

  However, in the methods of Patent Documents 3 to 6, when an aqueous solution containing a high concentration of chlorine ions is applied to welded stainless steel, innumerable pores are formed in the vicinity of the oxide scale, and the appearance after removal of the oxide scale is deteriorated. There's a problem.

  Further, in the methods of Patent Documents 7, 6, and 8, there is a problem that when the inorganic acid solution is heated to a high temperature, the vapor of the inorganic acid is generated, the odor becomes severe, and the working environment is deteriorated.

  In addition, the above technique has a problem that the descaling effect is not sufficient, and since a high concentration of strong acid is used, when the brush is applied near the welded portion, the gloss of the brushed portion disappears and becomes white. There was a problem that the surface gloss and color of the product changed completely and the product value of the product was greatly reduced. There is also a problem that the so-called second burn removal of welding is insufficient. As shown in the schematic plan view of FIG. 11, the second burn is a burn that occurs at a position slightly apart on both sides of the welded portion 10 of the stainless steel SS, and the metal component of the stainless steel moves due to heat during welding. In particular, the components colored in black or brown gather and the second burn 20 occurs. Since such second burning is also conspicuous, it is important to remove both the welding burn (bead part) and the second burning in removing the scale.

  The present invention has been made in view of such problems, and its main purpose is to suppress the use of compounds such as nitric acid and hydrofluoric acid as much as possible, to ensure safe workability and handling, and to weld stainless steel. Another object is to provide a scale remover that can easily and cleanly remove black or brown oxide film, rust rust, dirt, and the like in the heat-affected zone and the heat-affected zone.

  In order to solve the above-mentioned problem, a scale remover according to the present invention is a scale remover for a welded portion of a chromium-containing alloy steel, wherein an aqueous solution of magnesium nitrate hexahydrate, acidic ammonium fluoride, acidic sodium fluoride, and At least one organic acid of succinic acid, oxalic acid, and acetic acid, acetylacetone, sulfuric acid, phosphoric acid, and surface activity are reacted with an aqueous solution of at least one compound of acidic potassium fluoride. A predetermined amount of the agent and an organic thickener of 1% by weight or less can be added and mixed.

  According to the scale remover according to the present invention, the use of a compound such as nitric acid or hydrofluoric acid is suppressed as much as possible, and the workability and handling are safely performed. Easily and cleanly removes coatings, rust, dirt, etc.

It is the photograph which apply | coated the scale remover which concerns on Example 1 on stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on Example 2 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on Example 3 to stainless steel, and image | photographed the mode after progress for 20 minutes, 40 minutes, and 60 minutes. It is the photograph which apply | coated the scale remover which concerns on Example 4 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on Example 5 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on the comparative example 3 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on the comparative example 4 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on the reference example 1 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on the reference example 2 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is the photograph which apply | coated the scale remover which concerns on the reference example 3 to stainless steel, and image | photographed the mode after 20 minutes, 40 minutes, and 60 minutes progress. It is a schematic top view which shows a mode that 2nd burning generate | occur | produces.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a scale remover for embodying the technical idea of the present invention, and the present invention does not specify the scale remover as follows. Moreover, the member shown by the claim is not what specifies the member of embodiment. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the constituent members described in the embodiments are not intended to limit the scope of the present invention only to the description unless otherwise specified. It is just an example. Furthermore, in the following description, the same name and symbol indicate the same or the same members, and detailed description thereof will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing. In addition, the contents described in some examples and embodiments may be used in other examples and embodiments.

  Stainless steel is NO. 1 and NO. Represented by 2B. NO. 1 Stainless steel is surface-treated with acid after the hot rolling step, and has a matte whitish and rough surface. NO. 2B is NO. Since 1 is cold-rolled and the surface is finished roll processed, it has a glossy and smooth surface.

  The scale remover according to this embodiment is a reaction product of an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of at least one compound selected from acidic ammonium fluoride, acidic sodium fluoride, and acidic potassium fluoride. Add and mix at least one organic acid of succinic acid, oxalic acid, acetic acid, acetylacetone, sulfuric acid, phosphoric acid, a predetermined amount of surfactant and 1% by weight or less of organic thickener. Is generated. Here, in order to show the usefulness of the present invention, the scale remover according to Examples 1 to 5 and the scale remover according to Comparative Examples 1 to 5 in which the component ratios were changed were actually used to remove the scale of stainless steel. Went. Note that Lapisol A-80 (manufactured by NOF Corporation) was used as a surfactant, and Kelzan ASXT (manufactured by Miki Co., Ltd.) was used as an organic thickener. The results are shown in Table 1.

  In each of the examples and comparative examples, three test pieces that were electrically welded under the same conditions were prepared on 20 cm × 20 cm stainless steel, and a scale remover was applied to each of them by brush coating. In this state, a photograph after 10 minutes is taken, and after 20 minutes, 40 minutes, and 60 minutes, the scale remover is washed and removed, and a photograph is taken. Whether or not was removed was visually confirmed. The scale remover which concerns on Examples 1-5 was apply | coated to stainless steel, and the photograph which image | photographed in the state wash | cleaned after progress for 20 minutes, 40 minutes, and 60 minutes is shown in FIGS. Photographs of the results of using the remover in the same manner are shown in FIGS. 6 to 7, and further, as Reference Examples 1 to 3, photographs of the results of using commercially available scale remover in the same manner are shown in FIGS. .

  In each photograph, A is a photograph of stainless steel 10 minutes after application of the descaling agent, B is a photograph of the state washed 20 minutes later, C is an enlarged photograph of B, D is a photograph of the state washed 40 minutes later, E is a photograph An enlarged photograph of D, F is a photograph taken after 60 minutes, and G is an enlarged photograph of F. However, only FIG. 9A shows a photograph 13 minutes after application. In Table 1, double circles indicate that the bead portion and second burnt portion have been removed, and x indicates that burn has not been removed. Further, it was visually confirmed whether or not the gloss of the coated part was lowered, and whether or not the dripping occurred when the scale remover was applied with a brush.

  According to the scale removal using the scale remover according to Examples 1 to 5, the weld burn could be removed cleanly in a short time. In particular, as is apparent from the photographs of FIGS. 1 to 5, when the scale remover according to Examples 1 to 5 was used, the scale could be removed cleanly. Moreover, even when 20 minutes had passed, an almost beautiful scale removal result was obtained. In addition, no decrease in gloss was observed.

  On the other hand, in Comparative Examples 1 and 3 (FIG. 6) in which the component ratio was changed, a sufficient scale removal effect was not obtained. In Comparative Example 2, the test was stopped because a strong irritating odor was generated. In Comparative Example 4, although the scale could be removed, a decrease in gloss was observed (FIG. 7). Furthermore, in Comparative Example 5, since the viscosity was too high to be applied, the test was stopped.

  Further, as Reference Examples 1 to 3, a commercially available scale remover was also tested. First, as Reference Example 1, when using SUS Clean # 300 manufactured by Kosatsu Kasei Co., Ltd. (Fig. D), when using Taseto New Bright # 300E as Reference Example 2 (Fig. E), and Daiwatech stainless steel as Reference Example 3. When clean S was used (FIG. F), it was confirmed that whitening was observed on the surface of the stainless steel coated with the scale remover and the appearance of the product was impaired.

  Hereinafter, each example will be described in detail. First, in Example 1, 73 g (28 wt%) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.4 g (6.3 wt%) of acidic ammonium fluoride was dissolved in 43 g of water. Next, the two solutions were slowly mixed using a stirrer and then stirred for about 40 minutes to obtain a viscous colloidal solution. Succinic acid 12 g (4.6 wt%), acetic acid 0.72 g (0.27 wt%), 70% sulfuric acid 17.1 g (4.6 wt%), 75% phosphoric acid 64 g (18.4 wt%) ), 0.72 g (0.27 wt%) of acetylacetone and 1.2 g (0.46 wt%) of Lapisol A-80 (surfactant) were added and stirred for about 1 hour to prepare a scale remover. A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. No dripping occurred during application. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. All the test pieces were welded and burned second, and both were cleanly removed, so that the boundary between the cleaning part and the non-cleaning part could not be distinguished.

  Next, Example 2 will be described. First, 73 g (33 wt%) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.4 g (7.4 wt%) of acidic ammonium fluoride was dissolved in 43 g of water. Next, the two solutions were slowly mixed using a stirrer and then stirred for about 40 minutes to obtain a viscous colloidal solution. To this, 10.5 g (4.6% by weight) of succinic acid, 0.63 g (0.27% by weight) of acetic acid, 15 g (4.6% by weight) of 70% sulfuric acid, 27.9 g (9.5% of 75% phosphoric acid) Weight percent), 0.63 g (0.27 weight percent) of acetylacetone and 1 g (0.47 weight percent) of Lapisol A-80 (surfactant) were added and stirred for about 1 hour to prepare a scale remover. A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. No dripping occurred during application. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. All of the test pieces were welded and burned second, and both were cleanly removed, and the boundary between the cleaning part and the non-cleaning part was so clean that the boundary was not understood. It was found that even if the amount of phosphoric acid used was reduced to ½, brush coating did not occur and there was no problem.

  Furthermore, Example 3 will be described. First, 73 g (30.3% by weight) of magnesium nitrate hexahydrate was dissolved in 39 g of water, and 16.4 g (6.8% by weight) of ammonium ammonium fluoride was dissolved in 52 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. To this, 11.4 g (4.6 wt%) succinic acid, 0.68 g (0.27 wt%) acetic acid, 16.3 g (4.6 wt%) 70% sulfuric acid, 30.5 g 75% phosphoric acid (9 wt%) 0.5 wt%), 0.68 g (0.27 wt%) of acetylacetone, 1.1 g (0.47 wt%) of Lapisol A-80 (surfactant) and stirred for about 1 hour to prepare a scale remover did. A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. No dripping occurred during application. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. All of the test pieces were welded and burned second, and both were cleanly removed, and the boundary between the cleaning part and the non-cleaning part was so clean that the boundary was not understood. Even if the concentration of magnesium nitrate and acidic ammonium fluoride is increased and the concentration of magnesium fluoride produced is reduced to 7.3% by weight, dripping does not occur at the time of brush coating, and the brush coating is uneven. Welding burn was successfully removed.

  Furthermore, Example 4 will be described. First, 58.4 g (24.6% by weight) of magnesium nitrate hexahydrate was dissolved in 25.6 g of water, and 13 g (5.5% by weight) of ammonium ammonium fluoride was dissolved in 35.2 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. To this, 4.7 g (2.0 wt%) of succinic acid, 7.1 g (3.0 wt%) of oxalic acid, 0.24 g (0.1 wt%) of acetic acid, 17 g (5 wt%) of 70% sulfuric acid, 75 % Phosphoric acid 63.4 g (20 wt%), 67.5% nitric acid 10.5 g (3 wt%), acetylacetone 0.71 g (0.3 wt%), lapizole A-80 (surfactant) 1.2 g (0.5 wt%) and 0.59 g (0.25 wt%) of Kelzan ASXT were added and stirred for about 1 hour to prepare a scale remover. A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. No dripping occurred during application. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. All of the test pieces were welded and burned second, and both were cleanly removed, and the boundary between the cleaning part and the non-cleaning part was so clean that the boundary was not understood. Welding burn could be removed without any problem with brush coating unevenness. The passive potential was good at 0.65V.

  Further, a fifth embodiment will be described. First, 73 g (28 wt%) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.4 g (6.2 wt%) of acidic ammonium fluoride was dissolved in 44 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. Succinic acid 5.2g (2.0% by weight) oxalic acid 7.8g (3.0% by weight), acetic acid 0.26g (0.1% by weight), 70% sulfuric acid 18.6g (5% by weight) , 75% phosphoric acid 52.1 g (15 wt%), 67.5% nitric acid 8.6 g (2.2 wt%), acetylacetone 0.77 g (0.3 wt%), Lapisol A-80 (surfactant) ) 0.65 g (0.5 wt%) and 0.65 g (0.25 wt%) Kelzan ASXT were added and stirred for about 1 hour to prepare a scale remover. A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. No dripping occurred during application. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. All of the test pieces were welded and burned second, and both were cleanly removed, and the boundary between the cleaning part and the non-cleaning part was so clean that the boundary was not understood.

  In the above embodiment, acidic ammonium fluoride was used, but instead, acidic sodium fluoride or acidic potassium fluoride may be used. In doing so, care must be taken that their molecular weights are the same.

  As mentioned above, although each Example of the scale remover which was able to perform scoring appropriately was described, the compounding quantity of succinic acid, acetic acid, phosphoric acid, and magnesium nitrate hexahydrate will be described.

  On the other hand, Comparative Example 1 is a comparative example in which succinic acid and acetic acid important for scale removal are not used. 73 g (30% by weight) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.4 g (6.7% by weight) of acidic ammonium fluoride was dissolved in 43 g of water. The two solutions were slowly mixed using a stirrer and then stirred for about 40 minutes. It became a viscous colloidal solution. Succinic acid and acetic acid are not used, 70% sulfuric acid 16 g (4.6 wt%), 75% phosphoric acid 59.7 g (18.4 wt%), acetylacetone 0.66 g (0.27 wt%), lapizole A A scale remover was prepared by adding 1.1 g (0.46 wt%) of -80 (surfactant) and 0.61 g (0.25 wt%) of Kelzan ASXT and stirring for about 1 hour.

  A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. No dripping occurred during application. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. There was no problem with the dripping or unevenness of the brush when the scale remover was applied, but it was not possible to remove the important burns and burns. From the above, it has been found that when succinic acid and acetic acid are not used, the effect of removing welding burns and second burns is less than when not using them.

  Next, Comparative Example 2 is a comparative example in which acetic acid was increased to 3% by weight. First, 73 g (26.6 wt%) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.4 g (6 wt%) of acidic ammonium fluoride was dissolved in 43 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. To this, 12.6 g (4.6% by weight) of succinic acid, 8.2 g (3% by weight) of acetic acid, 18 g (4.6% by weight) of 70% sulfuric acid, 67.2 g (18.4% by weight) of 75% phosphoric acid ), 0.74 g (0.27 wt%) of acetylacetone, 1.26 g (0.46 wt%) of Lapisol A-80 (surfactant) and 0.68 g (0.25 wt%) of Kelzan ASXT (about 1 wt%). The scale remover was formulated by stirring for a period of time. However, the test was discontinued because the odor of acetic acid was strong and could not withstand brushing. From the above, it was found that when acetic acid is 3% by weight or more, handling becomes difficult, so that about 1% by weight or less is desirable.

  Comparative Example 3 is a comparative example in which the concentration of phosphoric acid is increased. First, 51.1 g (21.0 wt%) of magnesium nitrate hexahydrate was dissolved in 22.6 g of water, and 11.3 g (4.6 wt%) of acidic ammonium fluoride was dissolved in 30.6 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. To this, 4.9 g (2 wt%) succinic acid, 7.3 g (3 wt%) oxalic acid, 0.24 g (0.1 wt%) acetic acid, 17.4 g (5 wt%) 70% sulfuric acid, 75% 81.2 g (25% by weight) phosphoric acid, 0.73 g (0.3% by weight) acetylacetone, 1.2 g (0.5% by weight) Lapisol A-80 (surfactant), and 0.61 g (0) Kelzan ASXT .25% by weight) was added and stirred for about 1 hour to prepare the scale remover.

  A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. As shown in FIG. 6, none of the test pieces were completely brushed, but the effect of removing the weld burn was insufficient and the second burn was not removed well. From the above, it was found that the concentration of phosphoric acid is desirably about 22% by weight or less.

  Further, Comparative Example 4 is a comparative example in which the concentration of phosphoric acid is lowered. First, 73 g (33 wt%) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.2 g (7.3 wt%) of acidic ammonium fluoride was dissolved in 43 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. To this, 4.3 g (2% by weight) of succinic acid, 6.5 g of oxalic acid, 0.22 g (0.3% by weight) of acetic acid, 15.5 g (5% by weight) of 70% sulfuric acid, 23.1 g of 75% phosphoric acid (8 wt%), 0.65 g (0.3 wt%) of acetylacetone and 1.1 g (0.5 wt%) of Lapisol A-80 (surfactant) were added and stirred for about 1 hour to prepare a scale remover. did.

  A scale remover was brushed on the welded part and the second burnt part of three stainless steels 20 cm × 20 cm electrically welded at room temperature. Three stainless steels were washed with water after 20 minutes, 40 minutes, and 60 minutes, and the state was observed. As shown in FIG. 7, there was no problem with the effect of removing the welding burn, but the brushing unevenness was severely observed in all the test pieces. In particular, the portions other than the bead portion and the second burnt portion were also white, and the gloss reduction (unevenness) of the coated portion was remarkable. From the above, it was found that the concentration of phosphoric acid is preferably about 9% by weight or more.

  Furthermore, Comparative Example 5 is a comparative example in which the colloid concentration of magnesium fluoride is increased. First, 73 g (38.2 wt%) of magnesium nitrate hexahydrate was dissolved in 32 g of water, and 16.2 g (8.5 wt%) of acidic ammonium fluoride was dissolved in 44 g of water. After slowly mixing both solutions using a stirrer and stirring for about 40 minutes, a viscous colloidal solution was obtained. To this, 1.9 g (1 wt%) of succinic acid, 0.2 g (0.1 wt%) of acetic acid, 5.5 g (2 wt%) of 70% sulfuric acid, 17.8 g (7 wt%) of 75% phosphoric acid, 0.2 g (0.1% by weight) of acetylacetone and 0.2 g (0.1% by weight) of Lapisol A-80 (surfactant) were added and stirred for about 1 hour to prepare a scale remover. As a result, the solution viscosity was too high to be successfully applied, and the following experiment was canceled.

  From the above Comparative Examples 1-5, the colloidal concentration of magnesium fluoride formed from an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of acidic ammonium fluoride is 7 to 10% by weight, succinic acid is 1 to 7% by weight, 1-7 wt% acid, 0.1-1 wt% acetic acid, 0.1-1 wt% acetylacetone, 1-10 wt% sulfuric acid, 9-22 wt% phosphoric acid, 0 surfactant It is desirable that the organic thickener is 0.1 to 1% by weight.

  Here, the concentration of each component will be examined. By applying the scale remover to the weld burned portion of the weld steel by brushing, the necessary amount can be easily and easily supplied to the necessary part. Moreover, the work of impregnating the removing agent into the negative electrode and rubbing with a hand for a certain period of time as in the electropolishing method is unnecessary. Considering the ease of handling during brush application, it is preferable to adjust the viscosity so that it does not drip. Here, the colloidal concentration of magnesium fluoride produced from an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of acidic ammonium fluoride will be examined. Magnesium fluoride colloid is generated by the reaction of magnesium nitrate hexahydrate and acidic ammonium fluoride in a 1: 1 aqueous solution. By changing the amount of the aqueous solution at the time of carrying out this reaction, the concentration of the produced magnesium fluoride changes. Also, the viscosity changes due to the change in concentration. In the test conducted by the present inventor, the viscosity of the scale remover could be adjusted so as not to drip by adjusting the colloidal concentration of magnesium fluoride to 7 to 10% by weight.

  Next, when the concentration of succinic acid and oxalic acid is examined, if it is 1% or less, the effect of removing the scale is small, and it is difficult to achieve the desired clean removal. Further, since the solubility of succinic acid is 7.7 g / 100 ml, succinic acid that does not dissolve is generated at a concentration of 7% by weight or more, and particles are generated in the liquid, which is not preferable. Therefore, the concentration range of succinic acid is preferably 1 to 7% by weight.

  On the other hand, oxalic acid has a solubility of 14 g / 100 ml and can be dissolved more than succinic acid.

  Further, when the concentration of acetic acid is 0.1% by weight or less, the effect of removing scale is reduced, which is not preferable. On the other hand, when the concentration is high, the acetic acid odor becomes large, which may hinder the work. If it is 1% or less, it is a level at which work can be performed with almost no problems. By setting the concentration of acetic acid to 0.1 to 1% by weight, it is possible to realize a scale removing agent that does not deteriorate the working environment and maintains the scale removing effect.

  Further, by adding acetylacetone, the effect of removing the second burn can be increased. However, if it is 0.1% by weight or less, the effect of removing the second burn is reduced. On the other hand, if it is 1% by weight or more, brush marks of brush coating become conspicuous, which is not preferable. Therefore, it can be said that the addition amount of acetylacetone is preferably 0.1 to 1% by weight.

  Furthermore, the concentration of phosphoric acid greatly affects the difference in gloss between the coated part where the scale remover is applied and the non-coated part. That is, when the phosphoric acid concentration is 9% by weight or less, the coated part is whitened, the gloss is greatly lowered, and the surface gloss of the stainless steel in the non-coated part is greatly reduced, which is not preferable. On the other hand, if it exceeds 22% by weight, the burn removal effect of the welded part and the second burnt part becomes small. Therefore, the concentration of phosphoric acid is preferably 9 to 22% by weight.

  Furthermore, the acidity of the scale remover can be maintained by adding sulfuric acid. However, since it corresponds to a deleterious substance when the concentration of sulfuric acid exceeds 10%, sulfuric acid is preferably 1 to 10% by weight. Furthermore, the workability | operativity at the time of application | coating can be improved by adding surfactant and an organic thickener.

  More preferably, the colloidal concentration of the produced magnesium fluoride is 8 to 9% by weight, acetic acid is 0.1 to 0.5% by weight, acetylacetone is 0.1 to 0.5% by weight, and sulfuric acid is 2 to 7% by weight. The phosphoric acid is 10 to 20% by weight.

  As described above, according to the scale remover according to this embodiment described in detail, the use of a compound such as nitric acid or hydrofluoric acid is suppressed as much as possible, and while improving workability and safety, the stainless steel welded portion and the heat The black or brown oxide film on the affected area, rust, dirt, etc. can be removed easily and cleanly. Moreover, this scale remover has almost no irritating odor at the time of use, and the wash water after completion | finish of work can be drained only by adjusting pH. Moreover, the surface gloss after scale removal does not decrease.

  Although the present embodiment has been described above, the embodiment of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the case where it is used for welding burn-off of stainless steel has been described as an example. However, the scale remover according to the above-described embodiment is not limited to stainless steel, and widely removes scale of chromium-containing alloy steel. Can be used for

  In addition, as a scale remover according to the above embodiment, a reaction product of an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of at least one compound selected from acidic ammonium fluoride, acidic sodium fluoride, and acidic potassium fluoride. In addition, at least one organic acid selected from succinic acid, oxalic acid, and acetic acid, acetylacetone, sulfuric acid, phosphoric acid, a predetermined amount of surfactant, and an organic thickener of 1% by weight or less of the predetermined amount However, an aqueous solution to which other additives are added may be used without departing from the gist of the present invention.

  The scale remover of the present invention can be suitably used as a stainless steel brushing detergent.

10 ... weld 20 ... second burnt SS ... stainless steel

In order to solve the above-mentioned problems, a scale remover according to the present invention is a scale remover for a stainless steel welded portion, an aqueous solution of magnesium nitrate hexahydrate, acidic ammonium fluoride, acidic sodium fluoride and acidic fluoride. A reaction product of an aqueous solution of at least one compound selected from the group consisting of potassium with succinic acid and 0.1 to 1% by weight of acetic acid, and an organic acid optionally containing oxalic acid; ~ 1 wt% acetylacetone, 1-10 wt% sulfuric acid, 9-22 wt% phosphoric acid, 0.1-1 wt% surfactant, magnesium nitrate hexahydrate in aqueous solution and acidic in the case of colloid concentration of magnesium fluoride produced from an aqueous solution of ammonium fluoride is 7.2 wt% or less, it is produced by further adding and mixing 1% by weight or less of an organic thickener And features.

Claims (3)

In the scale remover for stainless steel welds,
A reaction product of an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of at least one compound of acidic ammonium fluoride, acidic acidic sodium fluoride, and acidic acidic potassium fluoride,
At least one organic acid selected from succinic acid, oxalic acid, and acetic acid;
A scale remover produced by adding and mixing acetylacetone, sulfuric acid, phosphoric acid, a predetermined amount of a surfactant and 1% by weight or less of an organic thickener.   The colloidal concentration of magnesium fluoride produced from an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of acidic ammonium fluoride is 7 to 10% by weight, succinic acid is 1 to 7% by weight, oxalic acid is 1 to 7% by weight, acetic acid 0.1 to 1% by weight, 0.1 to 1% by weight of acetylacetone, 1 to 10% by weight of sulfuric acid, 9 to 22% by weight of phosphoric acid, 0.1 to 1% by weight of surfactant, The scale remover according to claim 1, wherein the viscosity is 0.1 to 1% by weight.   The colloidal concentration of magnesium fluoride produced from an aqueous solution of magnesium nitrate hexahydrate and an aqueous solution of acidic ammonium fluoride is 8-9% by weight, succinic acid is 1-7% by weight, oxalic acid is 1-7% by weight, acetic acid Is 0.1 to 0.5 wt%, acetylacetone is 0.1 to 0.5 wt%, sulfuric acid is 2 to 7 wt%, phosphoric acid is 10 to 20 wt%, and the surfactant is 0.1 to 0.3 wt%. The scale remover according to claim 1, wherein 5% by weight and the organic thickener is 0.1 to 1% by weight.