JP4280181B2 - Steel plate for welding cans with excellent weldability, adhesion and corrosion resistance - Google Patents

Description

  The present invention relates to a steel sheet for a welding can that is particularly excellent in weldability, paint adhesion, film adhesion, and corrosion resistance as a can-making material.

  In recent years, welding can manufacturing technology using wire seam resistance welding has been rapidly advanced, and practical application in the beverage can field has been rapidly progressing. The steel plate for cans used in this type of welding can is, for example, disclosed in Japanese Patent Application Laid-Open No. 60-208494 (Patent Document 1), after performing Fe—Ni alloy plating by electroplating, Sn. There has been proposed a method for producing a surface-treated steel sheet for can making, which is excellent in seam weldability, in which plating, further tin treatment, and chromate treatment are performed.

  Further, as disclosed in Japanese Patent Laid-Open No. 60-13098 (Patent Document 2), a seam excellent in paint adhesion and weldability is obtained by applying an Fe—Ni alloy, followed by Sn plating and chromate treatment. A method for producing a surface-treated steel sheet for a welding can has been proposed. Certainly, such a manufacturing method provides a surface-treated steel sheet for a welding can having weldability, corrosion resistance, and paint adhesion. Furthermore, using these surface-treated steel sheets for containers, paint baking is performed on the inner surface of the can to ensure corrosion resistance, and multicolor printing is performed on the outer surface of the can. Thereafter, the can is made by a wire seam welding method and put into practical use.

JP 60-208494 A JP-A-60-13098

  In recent years, combined with further advancement in can manufacturing technology and reduction in can manufacturing costs, aiming at significant productivity improvement in the can manufacturing process, instead of painting and printing, organic can inner and / or outer surface Film laminated materials have been used. However, when the above-described surface-treated steel sheet for containers is used as an object for laminating an organic film on the inner surface and / or outer surface of the can, paint and film adhesion defects occur in the vicinity of the weld.

  This is because the above-mentioned surface-treated steel sheet for containers contains metal Sn that is not alloyed in the plating layer, and the plating layer melts in the vicinity of the weld where the temperature rises to the Sn melting point or higher due to the residual heat of welding. At this time, since the paint or film on the plating layer is in a state of floating on the molten liquid metal Sn, the adhesion of the paint or film becomes extremely low, and the paint or film is peeled off by the cooling air or the paint or film. The coating and film shrinkage easily occur due to the internal stress. As a result, the paint or film is peeled off.

  If the coating amount of metal Sn is reduced and the coverage of metal Sn is reduced in order to avoid poor coating and film adhesion, the coating and film adhesion will surely improve. However, if the amount of Sn plating decreases, weldability and corrosion resistance, which are characteristics that should be provided as a steel sheet for welded cans, will deteriorate, so the production of welded can materials that satisfy all of weldability, paint and film adhesion, and corrosion resistance. Was difficult.

  In order to solve these problems, the present inventors have formed a plating structure in which Sn is formed into an island, and a coating layer in which metal Sn is not present and a Fe—Ni or Fe—Ni—Sn alloy plating layer having excellent film adhesion are exposed. It has been found that excellent adhesion can be ensured even at locations where the steel plate having a temperature exceeding the melting point of Sn, such as the weld heat affected zone. However, it became clear that, although the paint and film adhesion is improved by forming Sn into an island shape, the corrosion resistance is weakened at the portion where Sn is not present, and this becomes a starting point of corrosion. In addition, a method for industrially forming islands of Sn stably is also required.

  Therefore, as a result of intensive investigations on the above-mentioned problems that have been clarified by making Sn into islands, the present inventors have found that if there is a nitride layer on the surface of the steel plate (original plate) to be plated, The inventors have come to know that the corrosion resistance can be improved and the island-shaped Sn can be stably manufactured. Although the detailed mechanism of this phenomenon is not clear, the solid solution nitrogen and nitride contained in the nitride layer formed by nitriding treatment improve the corrosion resistance, and the nitrogen of the nitride layer is alloyed by heating during molten molten tin. It is presumed that the corrosion resistance of the alloy layer is improved. In addition, it is estimated that this nitride layer reduces the wettability of Sn melted during the molten tin treatment and makes it easier to play Sn, and as a result, it has become possible to industrially produce island-like Sn.

That is, the gist of the present invention is that
(1) a nitride layer containing nitrogen amounts 100~6000ppm formed in the surface 1/8 thickness region of the steel sheet, in the steel sheet, subjected to Ni plating layer or Fe-Ni alloy plating contains 5 to 150 mg / m ² of Ni Then, an Ni layer is formed by nitriding and 300-3000 mg / m ² of Sn plating is applied, and a part or all of the underlying Ni layer and a part of the Sn plating layer are alloyed by molten tin treatment. An island-like Sn plating layer is formed, and the outermost layer is provided with a chromate film of ^{2 to} 30 mg / m ^{2 in} terms of metallic Cr, weldability, paint adhesion, film adhesion, Steel plate for welding cans with excellent corrosion resistance.

(2) according to the melting溶錫processing performed steel sheet, a metal not alloyed contained in Sn plating layer Sn wherein the (free Sn) is characterized in that it is 100 mg / m ² or more (1) Steel plate for welding cans with excellent weldability, paint adhesion, film adhesion, and corrosion resistance.
( 3 ) The chromate film is composed of hydrated chromium oxide or hydrated chromium oxide and metal chromium. The weldability, paint adhesion, film adhesion, and corrosion resistance described in (1) or 2 above Excellent steel plate for welding cans.

  As described above, a steel plate for a welding can having excellent weldability, corrosion resistance, paint and film adhesion can be produced by the present invention.

The steel sheet for a welding can excellent in weldability, corrosion resistance, paint and film adhesion, which is an action of the present invention, will be described in detail below.
In the present invention, the steel plate before nitriding is a steel plate used as a normal container material. The components are not particularly restricted, and ordinary low carbon steel or extremely low carbon steel may be used. The manufacturing method and material of the steel plate are not particularly restricted, and the steel plate is manufactured through a normal slab manufacturing process through processes such as hot rolling, pickling and cold rolling.

  Nitriding treatment is performed on the steel sheet, but the nitriding treatment is performed for corrosion resistance and generation of island-like Sn, and therefore, only the surface layer may be performed. When the nitriding treatment is performed on the entire thickness of the steel sheet, nitrogen is solid solution strengthened, so that the material becomes harder than necessary and the can manufacturing process is deteriorated. Therefore, it is necessary to nitride the surface layer of the steel sheet. The corrosion resistance improvement and island-like Sn formation effect due to the nitridation of the surface layer starts to be exerted remarkably from 100 ppm or more as the N content of the surface layer 1/8 thickness region, and the effect increases as the nitrogen content increases. However, if the N content in the surface layer 1/8 thickness region exceeds 6000 ppm, the improvement effect is saturated, which is economically disadvantageous. Therefore, the nitridation amount of the surface layer is desirably 100 to 6000 ppm as the N amount in the surface layer 1/8 thickness region.

  Nitriding may be performed only on the surface layer of the steel plate, or may be performed on both the base Ni layer and the steel plate. (In this case, nitriding after forming the underlying Ni layer) In the former case, the surface layer 1/8 region refers to a region from the surface of the steel plate to a depth of 1/8 the thickness of the can steel plate, and in the latter case, the surface of the Ni plating layer To a depth of 1/8 of the total thickness of both the base Ni layer and the steel plate.

  There are no particular restrictions on the nitriding method. For example, a necessary amount of nitrogen gas or ammonia may be introduced into a temperature atmosphere of 600 to 700 ° C. Further, since the amount of nitriding increases with the processing time, the temperature, gas concentration, and processing time may be adjusted according to the apparatus to be used. Moreover, although it does not regulate in particular about a processing apparatus, it is economically advantageous to utilize a continuous annealing furnace or a batch annealing furnace from industrial production.

Ni-based plating of Ni or Fe—Ni alloy plating is performed on the steel plate subjected to nitriding treatment. The purpose of providing the Ni-based plating layer is to ensure corrosion resistance. Since Ni is a highly corrosion-resistant metal, the corrosion resistance of the alloy layer formed during the molten tin treatment can be improved by plating Ni. The effect of improving the corrosion resistance of the alloy layer by Ni starts to appear when the amount of Ni to be plated starts from 5 mg / m ² or more, so the Ni amount needs to be 5 mg / m ² or more. As the amount of Ni increases, the corrosion resistance improvement effect of the alloy layer increases. However, if it exceeds 150 mg / m ² , the improvement effect is saturated, and Ni is an expensive metal, so more Ni is plated. Doing so is also economically disadvantageous. Therefore, the amount of Ni needs to be ⁵ to 150 mg / m2.

  In addition, when Ni diffusion plating is performed, after Ni plating, diffusion treatment is performed in an annealing furnace to form a Ni diffusion layer. However, the present invention can be performed even before or after or simultaneously with the Ni diffusion treatment. The effect of Ni as the Ni-based plating layer and the effect of the nitriding layer can be obtained. About the method of Ni plating and Fe-Ni alloy plating, the well-known method generally performed by the electroplating method should just be used.

Sn plating is performed after the Ni-based plating. Sn plating mentioned here is metal Sn, but inevitable impurities may be mixed, and trace elements may be added. There is no particular restriction on the Sn plating method. A known electroplating method or a method of plating by immersing in molten Sn may be used. The purpose of Sn plating is to ensure corrosion resistance and weldability. Since Sn itself has high corrosion resistance, it exhibits excellent corrosion resistance both as metal Sn and as alloy Sn formed by the reflow treatment described below. The excellent corrosion resistance of Sn is remarkably improved from 300 mg / m ² or more, and the corrosion resistance is improved as the Sn plating amount is increased, but the effect is saturated at 3000 mg / m ² or more. Therefore, the Sn plating amount is desirably 3000 mg / m ² or less from an economical viewpoint.

In addition, Sn having a low electric resistance is soft, and when Sn is pressed between the electrodes during welding, it spreads and a stable energization area can be secured, so that particularly excellent weldability is exhibited. This excellent weldability is exhibited if the amount of metal Sn is 100 mg / m ² or more. Moreover, if it is the range of Sn plating amount of this invention, it is not necessary to prescribe | regulate the upper limit of metal Sn amount.

  After Sn plating, molten tin treatment is performed. The purpose of the molten tin treatment is to melt Sn and alloy it with a nitride layer or a base metal to form a Sn—Fe or Sn—Fe—Ni alloy layer containing nitrogen, thereby improving the corrosion resistance of the alloy layer. The island-shaped Sn is formed industrially stably by the effect of the nitride layer. In the molten tin treatment, it is only necessary to perform a heat treatment exceeding the melting point of Sn. For example, a method such as energization heating, induction heating, or furnace heating may be used.

  Subsequently, after the molten tin treatment, a chromate film is applied for the purpose of coating, film adhesion, and corrosion resistance. The chromate film mentioned here refers to two cases: a hydrated chromium oxide single film, that is, an original chromate film, and a film composed of two layers of a lower layer of metal chromium and an upper layer of hydrated chromium oxide layer. Yes. The hydrated chromium oxide layer may contain sulfate ions or fluorine ions which are plating aids described later. The paint and film adhesion and corrosion resistance are ensured by a strong chemical bond between the functional group of the hydrated chromium oxide and the functional group of the paint or film.

Accordingly, if the chromate film adhesion amount is less than 2 mg / m ^{2 in} terms of metal Cr, the effect of improving the adhesion between the paint and the film cannot be obtained, so it is necessary to adhere ² mg / m ² or more. On the other hand, as the amount of chromate coating increases, the effect of improving paint and film adhesion increases, but the hydrated chromium oxide coating is an electrical insulator and therefore has a very high electrical resistance. Therefore, an excessive amount of chromate film deteriorates weldability. Therefore, the chromate adhesion amount needs to be 30 mg / m ² or less.

  The chromate treatment method may be performed by any method such as immersion treatment with various sodium salts, potassium salts, and ammonium salts of chromic acid, spray treatment, electrolytic treatment, etc., but cathodic electrolytic treatment is particularly excellent. In particular, cathodic electrolysis in an aqueous solution in which sulfate ions, fluoride ions (including soot ions) or a mixture thereof is added to chromic acid as a plating aid is most excellent.

Next, examples and comparative examples of the present invention will be described, and the results are shown in Table 1. Samples were prepared by the methods shown in the following (1) to (3), and performance evaluation was performed for each item (A) to (E). (1) Sample preparation method 1
After cold rolling, continuous annealing was performed in a 5% ammonia atmosphere and the surface layer was nitrided. Thereafter, a 0.20 mm-thick plating original plate in which the surface layer was nitrided was produced by temper rolling at 0.7%. This plating base plate is electrolytically degreased in 5% caustic soda, washed with water, electrolytically pickled in 10% sulfuric acid, surface-treated after surface activation, electrolyzed at a current density of 10 A / dm ² using a sulfuric acid bath, perform Ni content of 20% Fe-Ni alloy plating was carried out Sn plating by electrolyzing at a current density of 20A / dm ² from Ferrostan bath. Thereafter, the molten tin treatment was carried out by induction heating, and subsequently a chromate film was applied by electrolysis at a current density of 40 A / dm ² using a chromic acid-sulfuric acid bath to prepare a sample.

(2) Sample preparation method 2
After cold rolling, Ni plating was performed from a watt bath, and continuous annealing was performed in a 10% ammonia atmosphere to form a Ni diffusion layer and a nitride layer on the surface layer. Thereafter, a 0.19 mm thick plating original plate having a nitrided surface layer was produced by temper rolling at 2%. This plating base plate is electrolytically degreased in 5% caustic soda, washed with water, electrolytically pickled in 10% sulfuric acid, surface-treated after surface activation, electrolyzed at a current density of 20 A / dm ² from a ferrostan bath, and Sn plated. Went. Thereafter, the molten tin treatment was performed by energization heating and induction heating, and subsequently a chromate film was applied by electrolysis at a current density of 40 A / dm ² using a chromic acid-fluorination bath to prepare a sample.

(3) Sample preparation method 3
After cold rolling, continuous annealing was performed in a 2% ammonia atmosphere and the surface layer was nitrided. Thereafter, a 0.20 mm-thick plating original plate in which the surface layer was nitrided was produced by temper rolling at 1.2%. This plating base plate was electrolytically degreased in 5% caustic soda, washed with water, electrolytically pickled in 10% sulfuric acid, surface-treated after surface activation, electrolyzed at a current density of 8 A / dm ² using a Watt bath, Ni plating was performed, and Sn plating was performed by electrolysis from a ferrostan bath at a current density of 20 A / dm ² . Thereafter, molten tin treatment was carried out by energization heating, and subsequently, a chromate film was applied by electrolysis at a current density of 40 A / dm ² using a chromic acid-sulfuric acid bath to prepare a sample.

(A) Welding test The test piece was baked under the condition that the temperature was raised to 320 ° C. in 23 seconds assuming the coating baking condition in a short time at high temperature, and the seam weldability was evaluated under the following welding conditions. Welding is performed by changing the current under the conditions of a lapping margin of 0.5 mm, a pressing force of 45 kgf, and a welding wire speed of 80 m / min, and the maximum current value at which sufficient welding strength can be obtained and welding defects such as scattering start to stand out. Judging comprehensively from the width of the appropriate current range consisting of current values, evaluation was made in four stages (◎: very wide, ○: wide, Δ: no practical problem, ×: narrow).

(B) Paint adhesion test 55 mg / dm ² of epoxy phenolic paint is applied to the surface corresponding to the inner surface of the test piece, and 40 mg / dm ² of clear lacquer is applied to the surface corresponding to the outer surface of the can. It was dried and cured under baking conditions of 15 sec. Subsequently, scratches were placed on each surface at intervals of 1 mm, and approximately 100 grids were prepared. The tape was peeled off quickly, and the peeling situation was observed. Four steps (◎: no peeling, ○: very slight) Paint adhesion was evaluated by peeling, Δ: slight peeling, x: peeling in most cases.

(C) Film adhesion test After laminating a PET (polyethylene terephthalate) film having a thickness of 15 um on the test piece, a crosscut was made until it reached the ground iron, quickly heated to 240 ° C, and 5 kg / The air gas of cm ² was blown vertically, and the film peeling state was evaluated in four stages (◎: no peeling, ○: slight peeling, Δ: slight peeling, x: most peeling) .

(D) Corrosion resistance test 1
In order to evaluate the corrosion resistance of the surface corresponding to the inner surface of the can of the test piece, a PET (polyethylene terephthalate) film having a thickness of 15 μm was laminated on the surface corresponding to the inner surface of the can. Then, the crosscut was put in until it reached the ground iron, and it was immersed in the test liquid which consists of a 1.5% citric acid-1.5% sodium chloride mixed solution at 55 degreeC x 4 days in open air. After the test is completed, the scratch part and the flat part are peeled off with tape immediately, and the corrosion situation near the scratch part, the pitting situation of the scratch part, and the film peeling situation of the flat part are evaluated in four stages (◎: no peeling and corrosion is recognized) No, ○: There is very little peeling but no corrosion is observed, △: There is slight peeling and minute corrosion is observed, ×: Most peeling and severe corrosion are recognized) Evaluated.

(E) Corrosion resistance test 2
In order to evaluate the corrosion resistance of the surface corresponding to the inner surface of the can of the test piece, a PET (polyethylene terephthalate) film having a thickness of 15 μm was laminated on the surface corresponding to the inner surface of the can to prepare a welded can. The can was filled with commercial coffee, left to stand at 40 ° C. for 3 months, then opened, and the inner surface side was corroded in 4 stages (◎: no spot-like corrosion was observed, ○: very few dots) △: Spot-like corrosion is observed, and a slightly deeper object is recognized, ×: Many point-like corrosion is recognized, and pitting corrosion more than half of the plate thickness is recognized). .

特許出願人 新日本製鐡株式会社
代理人 弁理士 椎 名 彊 他１

Patent applicant: Nippon Steel Corporation
Attorney Attorney Shiina and others 1

Claims (3)

Forming a nitride layer containing nitrogen amounts 100~6000ppm the surface 1/8 thickness region of the steel sheet, in the steel sheet subjected to Ni plating layer or Fe-Ni alloy plating contains 5 to 150 mg / m ² of Ni nitrided The base Ni layer was coated with 300 to 3000 mg / m ² of Sn plating, and a part or all of the base Ni layer and part of the Sn plating layer were alloyed by molten tin treatment to form an island. Sn-plated layer is formed, and the outermost layer is provided with a chromate film of ^{2 to} 30 mg / m ^{2 in} terms of metal Cr. Excellent weldability, paint adhesion, film adhesion, and corrosion resistance Steel plate for welding cans. The weldability according to claim 1, wherein the non-alloyed metal Sn (free Sn) contained in the Sn plating layer of the steel sheet subjected to the molten tin treatment is 100 mg / m ² or more. Steel sheet for welding cans with excellent paint adhesion, film adhesion, and corrosion resistance. The welding excellent in weldability, paint adhesion, film adhesion, and corrosion resistance according to claim 1 or 2 , wherein the chromate film is composed of hydrated chromium oxide or hydrated chromium oxide and metal chromium. Steel plate for cans.