JP4818755B2 - Steel plate for welding can - 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.

  Welding cans are made by a wire seam welding method and have been put to practical use mainly for retort beverages such as coffee in Japan. The wire seam welding method has been developed by Sudronic (Switzerland) and has rapidly progressed as a welding can body joining technique. Cans manufactured by this welding method have been widely put into practical use in the beverage can field. The wire seam resistance welding method means that the welded part is overlapped by 0.3 to 0.5 mm, sandwiched between two circular electrodes wound with copper wire at a constant pressure, and an alternating current is passed between the plates. This is a welding method in which a steel plate-steel plate interface in contact with heat generated by electrical resistance is brought into a molten or semi-molten state and the can body is joined.

  One of the features of this welding method is that high-speed welding at 600 to 800 cans / minute can be stably performed by adjusting the waveform and frequency of the alternating current to be applied and the pressure between the electrodes. Also, in this welding method, the lower the electrical contact resistance value on the surface of the steel plate to be welded, the more uniform current distribution occurs between the electrodes, and uniform welding can be performed. It is said to be excellent in nature. Therefore, in many cases, this type of welding has been invented a steel plate plated with Sn that has excellent corrosion resistance and has the effect of greatly reducing contact resistance. For example, Japanese Patent Laid-Open No. 60-208494 (Patent Document) 1) and Japanese Patent Laid-Open No. 60-13098 (Patent Document 2) have been put to practical use.

  On the other hand, as disclosed in, for example, Japanese Patent Laid-Open No. 56-169788 (Patent Document 3) and Japanese Patent Laid-Open No. 59-197597 (Patent Document 4), Sn is not plated. A steel plate plated with is also invented. Although Ni is excellent in corrosion resistance, it does not have the effect of reducing the contact resistance as much as Sn, but it is practically used because it has excellent forgeability (characteristic for bonding at a temperature below the melting point). .

JP 60-208494 A JP-A-60-13098 JP 56-169788 A JP 59-197597 A

  After coating or film is laminated on the side corresponding to the inside of these plated steel sheets, and the coated, printed or printed film is laminated on the side corresponding to the outer surface of the can, it is cut into a size corresponding to one can. Then, a welding can is manufactured through processes such as a welding process and a neck-flanging process. Recently, laminated cans, which are advantageous in terms of clean appearance and cost reduction in the can manufacturing process, have become mainstream.

  Welding cans are competing with materials such as aluminum cans, PET bottles, and paper containers in the container market, and there is a tendency to reduce the plate thickness of steel sheets due to the need for cost reductions and light weight market needs. . In the past, the plate thickness was 0.2 mm or more, but in recent years, weld cans having a plate thickness of less than 0.2 mm and 0.19, 0.18, and 0.17 mm have been put to practical use. In the wire seam welding method, it is known that welding becomes difficult when the plate thickness is reduced. In particular, when the thickness is 0.19 mm or less, welding becomes extremely difficult. This is because when the plate thickness is reduced, the current-carrying region of the current flowing between the upper and lower electrodes becomes narrower. In order to ensure stable weldability in a narrow current-carrying region, an Sn-based steel plate having a low contact resistance is used. Since it is advantageous, the use of Ni-plated steel sheets has been reduced.

  However, recently, in order to improve the product strength of welded cans, embossed cans that have been embossed on a portion of the can body, barrel cans that have been expanded into a barrel shape, and a reseal function have been added. In order to do so, overhanging cans such as resealed cans that have undergone screw processing have appeared. When Sn-plated steel plate is applied to such processing, soft Sn is greatly plastically deformed or partially damaged, and adhesion with the outermost layer coating or film becomes insufficient, and there is a wrinkle in severely processed areas. And the problem that peeling easily occurs has been recognized.

  Since the Ni-plated steel sheet is not as soft as Sn, even with processing, adhesion to the coating and film is maintained, and problems such as wrinkling and peeling do not occur. Therefore, Ni-plated steel sheets are suitable for the above-mentioned embossed cans, barrel cans, reseal cans, etc., and Ni-plated steel sheets that ensure good weldability even when the plate thickness is thin and 0.19 mm or less are strongly sought. It was.

  The inventors first examined the cause of significant deterioration of the weldability of the Ni-plated steel sheet when the plate thickness was 0.19 mm or less in order to improve the weldability of the Ni-plated steel sheet. The weldability in the wire seam welding method is evaluated based on the appropriate welding current range. The appropriate welding current range is determined by gradually increasing the welding current, the current at which sufficient joining strength has been secured as the lower limit current, and further increasing the welding current, and the current at which the scattering starts to occur as the upper limit current. Yes.

  It is said that the wider the appropriate welding current range is, the better the material is. In the case of a Ni-plated steel sheet, the appropriate welding current range is suddenly narrowed when the thickness is 0.19 mm or less, and the proper welding current range is almost lost when the thickness is 0.18 or 0.17 mm. As a result of observing the welding nugget at this time, the welding nugget at the lower limit current changes greatly when the plate thickness is reduced, and it becomes difficult to join, and the nugget at the upper limit current also changes greatly, and the welding current slightly increases. However, it was found that the heat generated greatly, and scattering is easy to occur.

  In addition, as a result of investigating the relationship between the appropriate welding current range and the surface roughness, it was found that even if the roughness was changed when the plate thickness was 0.2 mm or more, there was no significant effect on the appropriate welding current range. It was found that when the thickness is 0.19 mm or less, the appropriate welding current range greatly changes as the roughness changes. That is, when the plate thickness is 0.19 mm or less, the appropriate welding current range is narrowed when the roughness is large, but when the roughness is small and appropriate, the proper welding current range is not narrowed.

The details of this mechanism have not been clarified, but if there are excessive irregularities in the roughness of the surface, current concentration occurs in the high protrusions, scattering tends to occur, and the deep depressions do not join and become defects, It is estimated that the cause is that the bonding strength is not ensured.
Based on the phenomenon found this time, the inventors of the present invention have made extensive investigations on scratch rolling that enables temper rolling under high pressure that is advantageous for industrial production. As a result, productivity, weldability, adhesion, and corrosion resistance are improved. As a steel plate for welding cans by Ni plating, which has also been used, the following invention has been achieved.

That is, the present invention
(1) the following be plated thickness 0.19 mm, has a Ni plated layer of 200~1200mg / m ^2, further a metal Cr equivalent amount in the outermost layer has a chromate film of 2 to 20 mg / m ² The weldability is characterized in that the roughness in the direction perpendicular to the rolling direction is 0.1 to 0.3 μm in centerline average roughness and 20 to 200 peaks / cm in height of 0.25 μm or more. Steel plate for welding cans with excellent paint adhesion, film adhesion, and corrosion resistance.

(2) The steel pit for welding cans having excellent weldability, paint adhesion, film adhesion, and corrosion resistance according to claim 1, wherein the area ratio of the oil pit is 10% or less.
( 3 ) Refining rolling is performed using a scratch roll having an axial center line average roughness of 0.1 to 0.35 μm and a peak number of 50 to 400 / cm in height of 0.25 μm or more. The plating original plate having a thickness of 0.19 mm or less is subjected to 200 to 1200 mg / m ² of Ni plating, and further, the outermost layer is provided with a chromate film of ^{2 to} 20 mg / m ^{2 in} terms of metal Cr. The manufacturing method of the steel plate for welding cans which was excellent in weldability, paint adhesion, film adhesion, and corrosion resistance.

( 4 ) The area ratio of the oil pits of the plating original plate is 10% or less, the center line average roughness in the axial direction of the body portion is 0.1 to 0.35 μm, and the number of peaks having a height of 0.25 μm or more is 50 to 400. 200 to 1200 mg / m ² of Ni plating is applied to a plating base plate having a thickness of 0.19 mm or less that has been subjected to temper rolling using a piece / cm scratch roll, and the outermost layer is 2 to 2 in terms of metallic Cr. It is a method for producing a steel sheet for a welding can excellent in weldability, paint adhesion, film adhesion, and corrosion resistance, characterized by providing a chromate film of 20 mg / m ² .

  As described above, the steel sheet for welding cans produced according to the present invention has excellent weldability, paint adhesion, film adhesion, and corrosion resistance.

Hereinafter, the present invention will be described in detail.
An original sheet having a thickness of 0.19 mm or less used in the present invention is temper rolled using a scratch roll in which grooves are processed in the circumferential direction on an annealed steel sheet after hot rolling, pickling and cold rolling. Manufactured by. An original sheet with a thickness of 0.19 mm or less is said to be an ultra-thin material, and since the production (weight) per unit time is low and the production cost is high, temper rolling under high pressure that can produce a steel sheet with high productivity is possible. It is economically advantageous. However, when a high pressure is applied with a scratch roll, the roughness is transferred deeply, and there are a large number of high convex portions and deep concave portions, so that weldability is not ensured.

  Therefore, the scratch rolling is performed twice, and the second rolling is performed so that the convex portion of the steel plate and the peak portion of the rolling roll overlap each other in order to cancel the unevenness generated by the first rolling. Roughness is achieved. Similarly, when the temper rolling is performed three or more times, the roll position may be finely adjusted and rolled so as to cancel the unevenness imparted immediately before. Furthermore, although the roll used for scratch rolling is scratched, uniform roughness can be formed in the width direction by using a roll having the same scratch interval. Moreover, although it is disadvantageous for productivity, if it is lightly reduced even in one temper rolling, temper rolling is performed by using a scratch roll with granular chrome plating, which is expensive or expensive. There is also a method.

  By performing temper rolling with a scratch roll using the above method, the roughness in the direction perpendicular to the rolling direction is 0.1 to 0.3 μm in centerline average roughness and the height is 0.25 μm or more. Linear irregularities are provided parallel to the rolling direction so that the number of peaks is 200 / cm or less. If the roughness in the direction perpendicular to the rolling direction exceeds 0.3 μm in centerline average roughness, or if the number of peaks with a height of 0.25 μm or more exceeds 200 pieces / cm, scattering tends to occur during welding. The appropriate welding current range is narrow and industrially stable welding cannot be performed.

  However, the weldability is gradually improved by lowering the roughness, and the mean center line roughness is 0.3 μm or less and the peak of 0.25 μm or more is reduced to 200 pieces / cm or less, thereby suppressing welding scattering. As a result, the production of welding can be carried out industrially stably. Furthermore, if the roughness is reduced, welding scattering is suppressed even at high welding currents, the appropriate welding current range is widened, and the weldability is improved, but if the center line average roughness is less than 0.1 μm, welding Since the effect of suppressing the scattering is saturated and the rolling cost is also increased, it is disadvantageous economically. Therefore, lines parallel to the rolling direction are arranged so that the roughness in the direction perpendicular to the rolling direction is 0.1 to 0.3 μm in centerline average roughness and 200 or less peaks at a height of 0.25 μm or more. It is necessary to give the shape unevenness.

  Many oil pits have a depth of 10 μm or more, and if the area ratio of the oil pits increases, defects in the joints occur during welding, a welding current higher than usual is required, and the lower limit current tends to increase. is there. Accordingly, it is better to reduce the number of oil pits. When the area ratio is 10% or less, the lower limit current value does not increase and a wide appropriate welding current range can be obtained. In order to reduce the oil pits, it is effective to set the viscosity of the rolling oil used for cold rolling to 0.70 to 1.20 cP, or to reduce the cold rolling rate. Oil pits can also be reduced by temper rolling. It is effective to control the rolling reduction to 4 to 14% by temper rolling twice or more, and to control the rolling speed from 500 mpm to 600 mpm.

The plating original plate produced as described above is subjected to Ni plating following degreasing and pickling. The purpose of Ni plating is to ensure weldability and corrosion resistance. In practice, in order to ensure excellent weldability and corrosion resistance, the Ni plating amount on the steel sheet surface needs to be 200 mg / m ² or more. As the amount of Ni plating increases, the effect of improving weldability and corrosion resistance gradually increases. However, when the amount of Ni plating exceeds 1200 mg / m ² , the improvement effect is saturated, which is economically disadvantageous. Therefore, the Ni plating amount is restricted to ²⁰⁰ to 1200 mg / m ² .

  There is no particular restriction on the method of Ni plating. An electroplating method, a vapor phase plating method, or the like may be used. However, the electroplating method is economically advantageous because of its high productivity. A chromate treatment is performed on the upper layer of the Ni plating in order to provide a chromate film composed of hydrated Cr oxide or metal Cr and hydrated Cr oxide in order to ensure excellent corrosion resistance and paint adhesion. Corrosion resistance is improved in proportion to the amount of chromate film, because the metal Cr or hydrated chromium oxide composing the chromate film has excellent chemical stability. Since excellent adhesiveness is exhibited by performing chemical bonding, the adhesiveness increases as the amount of adhesion increases.

In order to exhibit practically sufficient corrosion resistance and adhesion, a chromate film of ² mg / m ² or more in terms of metal Cr is required. Increasing the amount of chromate film also increases the effect of improving corrosion resistance and adhesion, but the hydrated Cr oxide in the chromate film is an electrical insulator and has a very high electrical resistance, which causes deterioration of weldability. When the amount of chromate film exceeds 20 mg / m ^{2 in} terms of metal Cr, the weldability is extremely deteriorated, so the amount of chromate film must be 20 mg / m ² or less in terms of metal Cr.

  The chromate treatment method may be any method such as immersion treatment with various sodium salts, potassium salts, and ammonium salts of Cr acid, spray treatment, electrolytic treatment, etc., but cathode electrolytic treatment is particularly excellent. In particular, it is considered industrially best to perform cathodic electrolysis in an aqueous solution in which sulfate ions, fluoride ions (including complex ions) or a mixture thereof is added to Cr acid as a plating aid.

Examples of the present invention and comparative examples are described below, and the results are shown in Table 1.
After cold rolling, an annealed steel sheet having a thickness of 0.2 to 0.3 mm was prepared as a plating base plate having a thickness of 0.19 mm or less by the method described below, and then Ni plating and chromate treatment were performed to prepare a sample. .

(1) Temper rolling Rolling at 550 mpm using a scratch roll having a center line average roughness of 0.35 μm and a height of 0.25 μm or more with a peak number of 250 pieces / cm, gives the steel sheet a linear roughness. After that, the position is adjusted so that the convex portion of the roughness and the convex portion of the scratch of the rolling roll almost overlap, and the second rolling is performed at 550 mpm, and the final reduction ratio is 5 to 40%. The reduction rate was adjusted so that a plating original plate of 0.19 mm or less was produced. In order to obtain a predetermined surface roughness and plate thickness, the rolling reduction was appropriately set. Moreover, in order to perform rolling stably, rolling oil was used suitably.

(2) Ni plating: Immersion in a Ni plating bath at 40 ° C. consisting of Ni ions: 5 to 45 g / l, sulfate ions: 15 g / l, chlorine ions: 10 g / l, boric acid: 20 g / l, 15 A / dm Ni was plated by electrolysis at ² . The amount of Ni plating was controlled by adjusting the electrolysis time.
(3) Chromate treatment A chromate treatment was performed by dipping in a chromate treatment at 40 ° C. consisting of Cr oxide: 40 g / l, sulfate ion: 0.8 g / l, and electrolysis at 3-15 A / dm ² . The amount of chromate film deposited was controlled by adjusting the electrolysis time.

About the said processing material, performance evaluation was performed about each item of (A)-(D) shown below. (A) Seam weldability Seam weldability was evaluated under the following welding conditions for test pieces that had been baked at 200 ° C. for 30 minutes. Welding is performed by changing the current under the conditions of a lapping margin of 0.5 mm, a pressing force of 45 daN, and a welding wire speed of 60 m / min, and the maximum current at which sufficient welding strength can be obtained and welding defects such as scattering start to become noticeable Judging comprehensively from the width of the appropriate current range consisting of current values, the evaluation was made in four stages (◎: very wide, ○: wide enough to cause no practical problem, Δ: slightly narrow, ×: narrow).

(B) Corrosion resistance Corrosion resistance was implemented by the UCC (under cutting corrosion) evaluation test performed on condition of the following. Apply a 20μm thick epoxyphenolic resin to the test piece, bake at 200 ° C for 30 min, and then make a crosscut until it reaches the ground iron, then mix 1.5% citric acid-1.5% salt The sample was immersed in a test liquid consisting of a liquid at 55 ° C. for 4 days under atmospheric release. After the test is completed, the scratch part and the flat part are immediately peeled off with tape, and the corrosion situation near the scratch part, the pitting situation of the scratch part, and the paint peel condition of the flat part are classified into four levels (◎: no peeling and corrosion) Not recognized, ◯: There is a slight exfoliation to the extent that there is no problem in practical use, but no corrosion is observed, △: Slight exfoliation is present and minute corrosion is observed, ×: Mostly exfoliated and severe corrosion is observed Evaluated).

(C) Film adhesion A 15 μm PET film was laminated on the test piece, the laminate surface was used as the inner surface, the bottom cover was subjected to END processing, and a retort treatment at 125 ° C. for 30 minutes was performed. Thereafter, the peeling state of the film is classified into four stages (◎: no peeling, ○: slight peeling is observed in the processed part, Δ: peeling is recognized in more than half of the processed part, x: processed part and flat part Evaluation was made on the basis of peeling.

(D) Paint adhesion A 20μm thick epoxy phenolic resin is applied to the test piece, baked at 200 ° C for 30 minutes, and then a crosscut is made on the grid at 1 mm intervals until reaching the ground iron. The tape is peeled off and the resin is peeled in four stages (◎: no peeling is observed, ○: slight peeling is observed, Δ: peeling is observed in about half the area, x: most Evaluation was made on the basis of peeling.


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

Claims (4)

The following be plated thickness 0.19 mm, has a Ni plated layer of 200~1200mg / m ^2, further a metal Cr equivalent amount in the outermost layer has a chromate film of 2 to 20 mg / m ^2, the rolling direction 0.1~0.3μm center line average roughness perpendicular roughness relative weldability was characterized by height 0.25μm or more peaks is 20 to 200 pieces / cm, paint adhesion Steel plate for welding cans with excellent properties, film adhesion, and corrosion resistance. The steel plate for a welding can excellent in weldability, paint adhesion, film adhesion, and corrosion resistance according to claim 1, wherein the area ratio of the oil pit is 10% or less. Thickness subjected to temper rolling using a scratch roll having an axial centerline average roughness of 0.1 to 0.35 μm and a height of 0.25 μm or more of peaks of 50 to 400 pieces / cm. Weldability characterized by applying 200 to 1200 mg / m ² of Ni plating to a plating original plate of 0.19 mm or less, and further providing a ² to 20 mg / m ² chromate film in terms of metallic Cr on the outermost layer. The manufacturing method of the steel plate for welding cans which was excellent in paint adhesiveness, film adhesiveness, and corrosion resistance. The area ratio of the oil pit of the plating original plate is 10% or less, the center line average roughness in the axial direction of the trunk is 0.1 to 0.35 μm, and the number of peaks having a height of 0.25 μm or more is 50 to 400 / cm. 200 mm to 1200 mg / m ² of Ni plating is applied to a plating base plate having a thickness of 0.19 mm or less subjected to temper rolling using a scratch roll of ² to 20 mg / m 2 in terms of metal Cr in the outermost layer. ^A method for producing a steel sheet for a welding can excellent in weldability, paint adhesion, film adhesion, and corrosion resistance, characterized by providing a chromate film of ² .