阅读说明：本技术 带砂光面的基板，其制备方法以及镀锡板/镀铬板 (Substrate with frosted surface, preparation method thereof and tin plate/chromium plate ) 是由 黄久贵 俞炜 郭宏 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种带砂光面的基板的制备方法,包括：提供一平整机,其包括第一机架和第二机架,第一机架包括相对设置的第一工作辊和第三工作辊,第二机架包括相对设置的第二工作辊和第四工作辊,第一工作辊和第二工作辊位于同一侧；第一工作辊为电火花毛化轧辊,第二工作辊为磨削光辊；第一工作辊表面的粗糙度为1.6～2.2μm,第二工作辊表面的粗糙度为0.35～0.75μm；使基板依次于第一工作辊和第三工作辊之间、第二工作辊和第四工作辊之间通过,从而在基板的第一表面上形成砂光面。上述带砂光面的基板经过镀锡或镀铬后,在加工成缩颈罐或易开盖时,缩颈处和预划膜处的镀层不易被破坏,具有良好的耐蚀性。(The invention discloses a preparation method of a substrate with a frosted surface, which comprises the following steps: providing a flat machine, wherein the flat machine comprises a first machine frame and a second machine frame, the first machine frame comprises a first working roll and a third working roll which are arranged oppositely, the second machine frame comprises a second working roll and a fourth working roll which are arranged oppositely, and the first working roll and the second working roll are positioned on the same side; the first working roll is an electric spark texturing roll, and the second working roll is a grinding smooth roll; the roughness of the surface of the first working roll is 1.6-2.2 mu m, and the roughness of the surface of the second working roll is 0.35-0.75 mu m; and enabling the substrate to pass between the first working roll and the third working roll and between the second working roll and the fourth working roll in sequence, thereby forming a frosted surface on the first surface of the substrate. After the substrate with the frosted surface is tinned or chromed, when the substrate is processed into a necking can or an easy-open cover, the plating layers at the necking position and the pre-scribing position are not easy to damage, and the substrate has good corrosion resistance.)

1. A preparation method of a substrate with a frosted surface is characterized by comprising the following steps:

providing a leveler, the leveler comprising a first frame and a second frame,

the first frame comprises a first working roll and a third working roll which are arranged oppositely, the second frame comprises a second working roll and a fourth working roll which are arranged oppositely,

the first working roll and the second working roll are positioned on the same side and are used for contacting with the first surface of the substrate and forming the sanding surface, wherein:

the first working roll is an electric spark texturing roll, and the second working roll is a grinding smooth roll; the roughness of the surface of the first working roll is 1.6-2.2 mu m, and the roughness of the surface of the second working roll is 0.35-0.75 mu m;

and conveying the substrate to be cold-rolled into the temper mill, and enabling the substrate to sequentially pass between the first working roll and the third working roll and between the second working roll and the fourth working roll, so that the frosting surface is formed on the first surface of the substrate.

2. The method for preparing a substrate with a frosted surface according to claim 1, wherein the rolling force of the first frame is 3500-4500 kN, and the rolling force of the second frame is 3500-4000 kN.

3. The method for preparing the substrate with the frosted surface according to claim 1, wherein the roll change period of the first working roll and the second working roll is 120 +/-20 km, and the rolling tonnage is 150 +/-30 t.

4. The method of claim 1, wherein when the second surface of the substrate is shiny, the third and fourth work rolls are grinding and polishing rolls, the roughness of the first work roll surface is 1.8 ± 0.2 μm, the roughness of the second work roll surface is 0.70 ± 0.05 μm, the roughness of the third work roll surface is 0.70 ± 0.05 μm, the roughness of the fourth work roll surface is 0.40 ± 0.05 μm, the rolling force of the first frame is 3500 ± 100kN, and the rolling force of the second frame is 3500 ± 100 kN; and after the substrate is subjected to cold rolling by the temper mill, a bright surface is formed on the second surface of the substrate.

5. The method of claim 1, wherein when the second surface of the substrate is a fine grained surface, the third work roll is an electric spark texturing roll, the fourth work roll is a grinding and polishing roll, the roughness of the first work roll surface is 2.0 ± 0.2 μm, the roughness of the second work roll surface is 0.40 ± 0.05 μm, the roughness of the third work roll surface is 1.2 ± 0.2 μm, the roughness of the fourth work roll surface is 0.40 ± 0.05 μm, the rolling force of the first stand is 4000 ± 100kN, and the rolling force of the second stand is 3500 ± 100 kN; and after the substrate is subjected to cold rolling by a flattening machine, a fine stone grain surface is formed on the second surface of the substrate.

6. The method of claim 1, wherein when the second surface of the substrate is rough stone, the third work roll is an electric spark texturing roll, the fourth work roll is a grinding and burnishing roll, the roughness of the first work roll surface is 2.0 ± 0.2 μm, the roughness of the second work roll surface is 0.40 ± 0.05 μm, the roughness of the third work roll surface is 1.5 ± 0.2 μm, the roughness of the fourth work roll surface is 0.70 ± 0.05 μm, the rolling force of the first stand is 4500 ± 100kN, and the rolling force of the second stand is 4000 ± 100 kN; and after the substrate is subjected to cold rolling by a flattening machine, a rough stone grain surface is formed on the second surface of the substrate.

7. The substrate with the sanding surface prepared by the preparation method of any one of claims 1 to 6, wherein one surface of the substrate is a sanding surface, the other surface of the substrate is a non-sanding surface, the sanding surface comprises dotted concave-convex priming lines and filiform lines positioned on part of the priming lines, and the distribution of the priming lines and the filiform lines ensures that the roughness of the sanding surface is 0.50-0.80 μm.

8. The substrate with the frosted surface according to claim 7, wherein the material of the substrate is MR type, L type or D type original plate steel.

9. The substrate with a frosted surface of claim 7, wherein the non-frosted surface is a smooth surface, a fine stone grain surface, a rough stone grain surface, a silvery surface, a rough silvery surface, or a matte surface.

10. A tin-plated plate obtained by plating metallic tin on the surface of the substrate according to claim 7 and reflowing the tin-plated plate.

11. The tin-plated plate according to claim 10, wherein, when the metallic tin is electroplated, the concentration of the divalent tin in the electroplating solution is 20 to 25g/L, the concentration of the methanesulfonic acid is 30 to 50mL/L, the concentration of the antioxidant is 35 to 60mL/L, and the concentration of the additive is 20 to 30 mL/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 38-45 ℃, and the current density is controlled to be 22-28A/mm²。

12. The tin-plated plate according to claim 10, wherein the reflow setting temperature is 260 to 290 ℃, the reflow feedback temperature is 255 to 295 ℃, and the reflow power is 30 to 50% during reflow.

13. A tin-plated board according to any one of claims 10 to 12, wherein one surface of the substrate is a sanded surface and the other surface is a fine-grained surface.

14. A chromium plated sheet obtained by plating the surface of the substrate according to claim 7 with metallic chromium and chromium oxide.

15. A chromium-plated plate according to claim 14, wherein when chromium metal is plated, the concentration of chromic anhydride in the plating solution is 140 to 160g/L, and the concentration of ammonium fluoride is 3 to 4 g/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 36-40 ℃, and the current density is 50-80A/mm²The concentration of chromic anhydride in the first recovery tank is less than or equal to 50g/L, and the concentration of chromic anhydride in the second recovery tank is less than or equal to 40 g/L.

16. The chromium-plated plate according to claim 14, wherein when chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating solution is 60-70 g/L, the concentration of ammonium fluoride is 1-2 g/L, and the concentration of sodium hydroxide is 8-10 g/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 31-35 ℃, and the current density is controlled to be 9-22A/mm²The weight of the generated chromium oxide layer is 8-15 g/m²。

17. The chrome-plated plate according to any one of claims 14 to 16, wherein one surface of the substrate is a polished surface, and the other surface is a fine-grained surface.

18. A necking can, characterized in that the necking can is prepared from the tin-plated sheet according to claim 13.

19. A necking can, characterized in that the necking can is produced from the chromium plated sheet according to claim 17.

20. An easy open end characterized in that it is prepared from the tin-plated sheet as set forth in claim 13.

Technical Field

The invention relates to the technical field of metal material processing, in particular to a substrate with a frosted surface, a preparation method of the substrate and a tin plate/chromium plate.

Background

The tin plate/chromium plate is widely used for packaging beverages, and is usually rolled from a steel billet into a strip steel with a thickness of about 2.0mm by hot rolling in a steel mill, then the strip steel is subjected to processes such as acid rolling, annealing, leveling, tin plating/chromium plating, passivation and the like to prepare the tin plate/chromium plate, and then the tin plate/chromium plate is subjected to processes such as iron printing and can making to prepare a can body for containing various beverages. Because the contained contents are acidic, high-protein and the like, the tin plate/chromium plate product is required to have high corrosion resistance.

At present, the tin plate/chromium plating plate selected for the necking can (figure 1) or the easy-open lid (figure 2) has the surface appearance of R1 (fine stone surface), the roughness Ra is controlled to be 0.29-0.55 mu m, the surface texture is in a stone shape, the wire drawing feeling is general (similar to thin and shallow short scratch by visual observation), and the wire drawing feeling presents lighter granular feeling under strong light irradiation. However, in the use of the tin-plated sheet/chromium-plated sheet for the necking can or the easy-open lid, the necking or pre-scored portion (which is required to be pre-scored at the target opening portion after the easy-open lid is formed to guide the opening direction of the lid) is easily corroded by the contents, and thus the requirement for corrosion resistance cannot be satisfied.

Disclosure of Invention

The invention aims to provide a tin plate/chromium plate, and a necking can or an easy-open end prepared from the tin plate/chromium plate has good corrosion resistance, so that the tin plate/chromium plate is not corroded by contents.

In order to solve the technical problems, the invention provides the following technical scheme:

the invention provides a preparation method of a substrate with a frosted surface, which comprises the following steps:

providing a leveler, the leveler comprising a first frame and a second frame,

the first frame comprises a first working roll and a third working roll which are arranged oppositely, the second frame comprises a second working roll and a fourth working roll which are arranged oppositely,

the first working roll and the second working roll are positioned on the same side and are used for contacting with the first surface of the substrate and forming the sanding surface, wherein:

the first working roll is an electric spark texturing roll, and the second working roll is a grinding smooth roll; the roughness of the surface of the first working roll is 1.6-2.2 mu m, and the roughness of the surface of the second working roll is 0.35-0.75 mu m;

and conveying the substrate to be cold-rolled into the temper mill, and enabling the substrate to sequentially pass between the first working roll and the third working roll and between the second working roll and the fourth working roll, so that the frosting surface is formed on the first surface of the substrate.

Furthermore, the rolling force of the first rack is 3500-4500 kN, and the rolling force of the second rack is 3500-4000 kN.

Further, the roll changing period of the first working roll and the second working roll is 120 +/-20 km, and the rolling tonnage is 150 +/-30 t.

Further, when the second surface of the substrate is a bright surface, the third working roll and the fourth working roll are both grinding smooth rolls, the roughness of the surface of the first working roll is 1.8 ± 0.2 μm, the roughness of the surface of the second working roll is 0.70 ± 0.05 μm, the roughness of the surface of the third working roll is 0.70 ± 0.05 μm, the roughness of the surface of the fourth working roll is 0.40 ± 0.05 μm, the rolling force of the first frame is 3500 ± 100kN, the rolling force of the second frame is 3500 ± 100kN, and the substrate is cold-rolled by a leveler to form a bright surface on the second surface thereof.

Further, when the second surface of the substrate is a fine stone grain surface, the third working roll is an electric spark texturing roll, the fourth working roll is a grinding smooth roll, the roughness of the surface of the first working roll is 2.0 +/-0.2 microns, the roughness of the surface of the second working roll is 0.40 +/-0.05 microns, the roughness of the surface of the third working roll is 1.2 +/-0.2 microns, the roughness of the surface of the fourth working roll is 0.40 +/-0.05 microns, the rolling force of the first rack is 4000 +/-100 kN, the rolling force of the second rack is 3500 +/-100 kN, and the substrate is subjected to cold rolling by a machine to form the fine stone grain surface on the flat second surface.

Further, when the second surface of the substrate is a rough stone surface, the third working roll is an electric spark texturing roll, the fourth working roll is a grinding smooth roll, the roughness of the surface of the first working roll is 2.0 +/-0.2 μm, the roughness of the surface of the second working roll is 0.40 +/-0.05 μm, the roughness of the surface of the third working roll is 1.5 +/-0.2 μm, the roughness of the surface of the fourth working roll is 0.70 +/-0.05 μm, the rolling force of the first rack is 4500 +/-100 kN, the rolling force of the second rack is 4000 +/-100 kN, and the substrate is subjected to cold rolling by a flattening machine to form the rough stone surface on the second surface of the substrate.

The invention provides a substrate with a frosted surface, which is prepared by the preparation method of the first aspect, wherein one surface of the substrate is a frosted surface, the other surface of the substrate is a non-frosted surface, the frosted surface comprises dotted concave-convex bottoming lines and filiform lines positioned on part of the bottoming lines, and the distribution of the bottoming lines and the filiform lines ensures that the roughness of the frosted surface is 0.50-0.80 mu m.

Furthermore, the base plate is made of MR type, L type or D type original plate steel.

Further, the non-sanding surface is a smooth surface, a fine stone grain surface, a rough stone grain surface, a silvery surface, a rough silvery surface or a dull surface.

The third aspect of the present invention provides a tin-plated sheet obtained by electroplating metallic tin on the surface of the substrate according to the second aspect and reflowing the same.

Further, when the metallic tin is electroplated, the concentration of the divalent tin in the electroplating solution is 20-25 g/L, the concentration of the methanesulfonic acid is 30-50 mL/L, the concentration of the antioxidant is 35-60 mL/L, and the concentration of the additive is 20-30 mL/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 38-45 ℃, and the current density is controlled to be 22-28A/mm²。

Further, during reflow, the reflow setting temperature is 260-290 ℃, the reflow feedback temperature is 255-295 ℃, and the reflow power accounts for 30% -50%.

Furthermore, one side of the substrate is a sanding side, and the other side of the substrate is a fine stone grain side.

The invention provides a chromium-plated plate obtained by electroplating metallic chromium and chromium oxide on the surface of the substrate according to the second aspect.

Further, when the metal chromium is electroplated, the concentration of chromic anhydride in the electroplating solution is 140-160 g/L, and the concentration of ammonium fluoride is 3-4 g/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 36-40 ℃, and the current density is 50-80A/mm²The concentration of chromic anhydride in the first recovery tank is less than or equal to 50g/L, and the concentration of chromic anhydride in the second recovery tank is less than or equal to 40 g/L.

Furthermore, when chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating solution is 60-70 g/L, the concentration of ammonium fluoride is 1-2 g/L, and the concentration of sodium hydroxide is 8-10 g/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 31-35 ℃, and the current density is controlled to be 9-22A/mm²The weight of the generated chromium oxide layer is 8-15 g/m²。

Furthermore, one side of the substrate is a sanding side, and the other side of the substrate is a fine stone grain side.

A fifth aspect of the invention provides a necking can prepared from the tin-plated sheet or the chromium-plated sheet.

The invention provides an easy-open end, which is prepared from the tin-plated plate.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention creatively provides a brand new treatment process of a tinned/chromeplated substrate, so that the substrate has an inner surface and an outer surface, a new surface appearance, namely a frosted surface, is manufactured on the inner surface for forming the inner wall of a tank body, the roughness of the frosted surface is 0.50-0.80 mu m, and the micro appearance comprises dotted concave-convex priming lines and filiform lines positioned on partial priming lines. The substrate with the sanding surface can be more uniformly distributed on the surface of the substrate in the tinning or chromium plating process. Therefore, when the obtained tin-plated sheet/chromium-plated sheet is processed into a necking can or an easy-open lid, the plating layer at the necking and pre-drawn film is not easily damaged, and the tin-plated sheet/chromium-plated sheet has good corrosion resistance and is not corroded by contents. The original surface appearance can be kept when the tin-plated/chromium-plated substrate manufactured by the invention is used for forming the outer surface of the outer wall of the tank body, so that the visual characteristics of the existing tank body packaging products can be kept when various tank body packaging products are manufactured and formed, the marketing cost caused by switching new tank body packaging products is avoided, and the substrate has stronger universality.

2. The invention improves the existing tin plating and chromium plating process, and the new electroplating process improves the compactness of the tin plating layer and the chromium plating layer and the covering uniformity of the alloy layer and reduces the depth of the holes, thereby leading the plating layer to better protect the substrate and further improving the corrosion resistance of the substrate.

Drawings

FIG. 1 is a schematic view of the construction of a necking can;

FIG. 2 is a schematic view of the structure of the easy open end;

FIG. 3 is a microscopic plate texture of the R1 surface;

FIG. 4 is a microscopic plate surface texture of the Rs surface;

fig. 5 is a schematic drawing of striae of surface (a) of R1 and surface (b) of Rs;

FIG. 6 is a surface topography of a tin layer on a substrate using a prior art tin plating process (a) and a tin plating process of the present invention (b);

FIG. 7 is a graph of the surface topography of the alloy layer on the substrate using a prior art reflow process (a, b, c) and a tin plating process of the present invention (d, e, f);

FIG. 8 is a surface topography of a metallic chromium layer obtained using the chromium metal electroplating process of the present invention;

FIG. 9 is a graphical representation of the integrated surface topography of metallic chromium layers and chromium oxide layers resulting from the electroplated chromium oxide process of the present invention.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As described in the background art, at present, the tin plate/chromium plate selected for the necking can (figure 1) or the easy-open lid (figure 2) has the surface appearance of R1 (fine stone surface), the roughness Ra is controlled to be 0.29-0.55 μm, the surface texture is in a stone shape, the wire drawing feeling is general (similar to a fine and shallow short scratch by eyes), and the wire drawing feeling is light granular under the irradiation of strong light. However, in the use of the necking can or the easy-open lid made of such a tin-plated sheet or chromium-plated sheet, the necking or pre-scored portion is easily corroded by the contents, and the requirement for corrosion resistance cannot be satisfied.

The inventor finds that the surface appearance of the tin/chromium plating base plate is the main reason that the necking part or the pre-scratching film part is easily corroded by the content. Because the content object surface of the substrate in the prior art is a fine stone surface R1, the surface of the substrate has a wiredrawing appearance. The presence of the wire-drawing causes the surface of the substrate to have a distinct height difference, as shown in fig. 3, and the wire-drawing portion shows a severe height irregularity as if the grooves were generally distributed on the surface of the substrate when observed under a microscope.

In the case of a tin-plated plate, for example, when tin is electroplated on such a substrate, in the case where the amount of tin deposited is constant, the amount of tin plating at the protruding portion of the substrate is greater than that at the recessed portion due to the presence of the drawn wire, thereby preventing uniform deposition of tin. In the reflow process, tin deposited on the substrate is melted and flows, and after the tin flows to the concave part, the concave part hinders further flow of the tin melt, further hinders leveling of the molten tin, and finally influences formation of the alloy layer. Therefore, when tin is electroplated on the fine stone grain surface, the distribution of the tin layer is not uniform, and the tin content of the wire drawing part is obviously less. This causes a problem that, in the can or cap making process, the base material of the drawn portion is not protected by the tin layer and is directly exposed to the outside, and the corrosion resistance of the drawn portion is drastically reduced, because the drawn portion itself has a small tin layer and is further damaged by necking deformation or the cap pre-coating process.

The same applies to chromium-plated sheets. When the metal chromium is electroplated on the surface of the substrate, the pores on the surface of the plating layer are less but in a deep pit shape, which is mainly formed by the fact that the electroplated metal chromium layer is of a body-centered cubic structure and grows in a preferred orientation along with the change of current density; the current efficiency of chromium plating is generally 20-25%, and the side reaction is hydrogen evolution reaction, so that the longitudinal generation of pores of the metal chromium layer is increased. In addition, the existence of the scratch on the fine stone surface of the base material along the longitudinal wire drawing shape causes the further deepening of the longitudinal pore, so that the deposition of the metal chromium at the bottom of the wire drawing gully in the chromium electroplating process is further reduced. The chromium oxide layer is a net-shaped and layered structure, and the protection of the chromium layer of the chromium plating plate is further reduced along with the increase of the gully degree, so that the corrosion resistance of the chromium plating plate is reduced.

At present, in the can manufacturing industry, the substrate surface appearance of the tin plate/chromium plate has B (smooth surface), R1 (fine grained surface), R2 (coarse grained surface), S1 (silvery surface), S2 (coarse silvery surface), M (dull surface), and the appearance specifications and standards of each product are shown in table 1.

TABLE 1 Specification and Standard of the appearance of existing tin plate/chromium plate products

The inventors have found that none of the above surface topographies are suitable as inner surfaces of can and lid materials. In order to overcome the problem that the tin plate/chromium plate in the prior art is easy to corrode, the inventor researches and designs a novel surface appearance of the tin plate/chromium plate substrate, which is defined as a frosting surface and is expressed by Rs. As shown in fig. 4, when observed under a microscope, the Rs surface has dotted concave-convex priming lines and filiform lines on part of the priming lines, and the distribution of the priming lines and the filiform lines enables the roughness of the sand smooth surface to be 0.50-0.80 μm. When observed under normal light, the Rs surface has granular feel and is fine and smooth, slight silking feel exists under strong light irradiation, the glossiness of the board is slightly light silver, and the light reflection performance is poor. As shown in fig. 5, compared with the R1 surface, the Rs surface of the present invention has short and shallow wire drawing lines, so as to reduce the degree of wire drawing (scratching), and eliminate the influence of substrate gully caused by wire drawing on the deposition of electroplated tin and the leveling of tin during the soft melting process, so as to uniformly cover the tin layer and the alloy layer on the substrate surface; and because tin has good ductility, the corrosion resistance of a deformation zone in the process of manufacturing the can and the cover is finally improved.

The invention provides a preparation method of a substrate with a frosted surface, which comprises the following steps:

(1) providing a leveling machine, the leveling machine includes first frame and second frame, first frame is including relative first work roll and the third work roll that sets up, the second frame is including relative second work roll and the fourth work roll that sets up, first work roll and second work roll are located same one side, this first work roll and second work roll be used for with the first surface contact of base plate forms dull and stereotyped face, wherein:

the first working roll is an electric spark texturing roll, and the second working roll is a grinding smooth roll; the roughness of the surface of the first working roll is 1.6-2.2 mu m, and the roughness of the surface of the second working roll is 0.35-0.75 mu m;

(2) and conveying the substrate to be cold-rolled into the temper mill, and enabling the substrate to sequentially pass between the first working roll and the third working roll and between the second working roll and the fourth working roll, so that the frosting surface is formed on the first surface of the substrate.

The electric spark texturing roller is a roller prepared by adopting an electric spark texturing (EDT) technology, generates pit-shaped burrs on the surface of the roller based on an electric spark discharge principle, and can form granular morphology on the surface of a substrate by rolling of the electric spark texturing roller. The grinding smooth roll is formed on the surface of the roll based on a grinding process, and the surface of the substrate can be formed into a wiredrawing shape by rolling of the grinding smooth roll. According to the invention, by controlling the surface appearance and roughness of the first working roll and the second working roll, the appearance and roughness of the roll surface are printed on the surface of the substrate under the action of the external rolling force, so that the frosted surface appearance is formed on the surface of the substrate. Preferably, the rolling force applied to the first working roll by the first machine frame is 3500-4500 kN, and the rolling force applied to the second working roll by the second machine frame is 3500-4000 kN.

The first working roll and the second working roll need to be replaced after being used for a certain time, and whether the first working roll and the second working roll need to be replaced can be determined according to the roll replacement period or the rolling tonnage. Wherein the roll change cycle refers to the total length of the base material rolled by the working roll, and the rolling tonnage refers to the total weight of the base material rolled by the working roll. For example, the roll changing period is 120km, namely the line is stopped and the roll is changed after the working roll reaches 120km of base material, and similarly, the rolling tonnage is 150 tons, namely the line is stopped and the roll is changed after the working roll reaches 150 tons of base material. In the invention, the roll changing period of the first working roll and the second working roll is preferably 120 +/-20 km, and the rolling tonnage is preferably 150 +/-30 t.

In addition, the inventor abandons the traditional production manufacturing process of double-sided R1 surfaces, adopts novel differential surface topography control, adopts the original R1 surface on the outer surface of the tank body, and adopts the Rs surface on the inner surface of the tank body, thereby obtaining a substrate Rs/R1 with differential topography. Through the control of differentiated shapes (Rs content object surface/R1 outer surface), the compactness and uniformity of the coating of the substrate in the electroplating process are improved, so that the plate is not easy to deform and break when expanding and contracting, the corrosion resistance of the inner part of the tank body is improved, and the visibility of the outer part of the tank body is ensured. The Rs/R1 differential morphology substrate can be used for preparing necking cans or easy-open ends after tin plating, and can be used for preparing necking cans after chromium plating.

The substrate can be made of substrate materials commonly used in the can making industry, and is preferably made of MR type, L type or D type original plate steel.

The Rs/R1 substrate with the differential morphology can be prepared by controlling the types and the surface roughness of the third working roll and the fourth working roll and the rolling force. Specifically, the third working roll is controlled to be an electric spark texturing roll, the fourth working roll is a grinding smooth roll, the roughness of the surface of the first working roll is 2.0 +/-0.2 mu m, the roughness of the surface of the second working roll is 0.40 +/-0.05 mu m, the roughness of the surface of the third working roll is 1.2 +/-0.2 mu m, the roughness of the surface of the fourth working roll is 0.40 +/-0.05 mu m, the rolling force of the first rack is 4000 +/-100 kN, the rolling force of the second rack is 3500 +/-100 kN, and the substrate is subjected to cold rolling by a flattening machine to form a fine grained surface (R1) on the second surface of the substrate.

By the same method, the base plate with the second surface having the different topography with other topography, such as an Rs/B base plate, an Rs/R2 base plate and the like, can be obtained.

The method for preparing the Rs/B substrate comprises the following steps: and controlling the third working roll and the fourth working roll to be grinding smooth rolls, wherein the roughness of the surface of the first working roll is 1.8 +/-0.2 mu m, the roughness of the surface of the second working roll is 0.70 +/-0.05 mu m, the roughness of the surface of the third working roll is 0.70 +/-0.05 mu m, the roughness of the surface of the fourth working roll is 0.40 +/-0.05 mu m, the rolling force of the first rack is 3500 +/-100 kN, the rolling force of the second rack is 3500 +/-100 kN, and the substrate is cold-rolled by a planisher to form a bright surface (B) on the second surface of the substrate.

The method for preparing the Rs/R2 substrate comprises the following steps: controlling the third working roll to be an electric spark texturing roll, controlling the fourth working roll to be a grinding smooth roll, controlling the roughness of the surface of the first working roll to be 2.0 +/-0.2 mu m, the roughness of the surface of the second working roll to be 0.40 +/-0.05 mu m, the roughness of the surface of the third working roll to be 1.5 +/-0.2 mu m, the roughness of the surface of the fourth working roll to be 0.70 +/-0.05 mu m, the rolling force of the first rack to be 4500 +/-100 kN, the rolling force of the second rack to be 4000 +/-100 kN, and forming a rough stone surface (R2) on the second surface of the substrate after cold rolling by a flattening machine.

Table 2 shows in detail the roll-matching scheme for preparing several substrates of different morphologies as described above.

TABLE 2 grading machine roll scheme for metal substrates with different morphologies

Of course, according to different requirements of downstream users, other substrates Rs/S1, Rs/S2S, and Rs/M with different morphologies can be prepared by the same method, and the specific method is not described herein again.

The effect of the electroplating process on the corrosion resistance of tin/chrome plated plates is also not negligible, apart from the surface topography of the substrate. Therefore, the invention further researches the processes of electrotinning and reflow of the substrate.

TABLE 3 Current tin electroplating Process parameters

As shown in fig. 6(a), the tin layer is coarse and loose in crystal grains and the gaps between the crystal grains are large, which leads to poor corrosion resistance of the tin plate. Therefore, in order to improve the corrosion resistance of the tin-plated plate, the density of the tin layer and the coverage of the alloy layer are the primary measures.

The inventor improves the existing tin electroplating process and provides a new tin electroplating process, which is shown in table 4. When the metallic tin is electroplated, the concentration of the divalent tin in the electroplating solution is 15-25 g/L, the concentration of the methanesulfonic acid is 30-50 mL/L, the concentration of the antioxidant is 35-60 mL/L, and the concentration of the additive is 25-30 mL/L. Controlling the temperature of the electroplating solution to be 38-45 ℃ in the electroplating process,the current density is 22-28A/mm². Preferably, the concentration of the divalent tin in the electroplating solution is controlled to be 20g/L, the concentration of the methanesulfonic acid is 40mL/L, the concentration of the antioxidant is 45mL/L, the concentration of the additive is 25mL/L, the temperature of the electroplating solution is controlled to be 42 ℃, and the current density is 25A/mm²。

It should be noted that the antioxidant can be selected from the oxidizing agents commonly used in the art, including but not limited to one or more of phenol, hydroquinone, resorcinol, and catechol. In the present invention, the antioxidant used is Quaktoichchemical Quaktin^TMTPMW AOX antioxidant. The additives can be selected from additives commonly used in the art, including but not limited to one or more of surfactants and grain refiners. In the present invention, the additive used is Quaktoidin^TMAdditive additives.

TABLE 4 Process parameters for electrotinning of the present invention

Tin plating was performed using the improved plating process of the present invention, and the surface topography of the tin layer on the substrate was as shown in fig. 6 (b). As can be seen from the figure, the tin layer has fine and compact crystal grains, and the gaps between the crystal grains are small, so that the substrate can be better protected, and the corrosion resistance of the substrate can be improved.

After the tin plating, the tin layer is melted and flowed through a reflow process to obtain an alloy layer, so that the uniformity of the tin plating layer can be improved. Table 5 shows the current electroplated tin reflow process parameters.

TABLE 5 Current Process parameters for electrolytic tinning reflow

Item	Reflow oven height (m)	Reflow set temperature (. degree. C.)	Reflow feedback temperature (. degree. C.)	Ratio of reflow Power (%)
					Target range	6-8	280-300	280-310	40-70
Control target	6.5	290	295	50

As shown in fig. 7(a) to (c), the alloy layer formed by the conventional reflow process has relatively fine crystal grains, and thus has poor corrosion resistance.

The invention also improves the reflow process, as shown in table 6. When in reflow, the height of a used reflow oven is 3.5-5.5 m, the set temperature of the reflow is 260-290 ℃, the feedback temperature of the reflow is 255-295 ℃, and the ratio of the reflow power is 30-50%. Preferably, the height of the used reflow oven is 4.5m, the set reflow temperature is 270 ℃, the feedback reflow temperature is 275 ℃, and the ratio of the reflow power is 40%.

TABLE 6 reflow Process parameters of the invention

Item	Reflow oven height (m)	Reflow set temperature (. degree. C.)	Reflow feedback temperature (. degree. C.)	Ratio of reflow Power (%)
					Target range	3.5-5.5	260-290	255-295	30-50
Control target	4.5	270	275	40

The surface morphology of the alloy layer obtained by the reflow process of the present invention is shown in fig. 7(d) - (f). As can be seen from the figure, the alloy layer has coarse and columnar crystal grains and is better in continuity, and therefore, the corrosion resistance is also better.

Further, the present invention also provides a research on a chrome plating process of the substrate.

As described above, when the conventional process (as shown in table 7) is used for electroplating chromium metal, the chromium metal layer generates deep-pit-shaped pores in the longitudinal direction due to the preferred orientation growth of crystal lattices and the characteristics of the chromium plating process (the current efficiency is low, generally 20% to 25%, and the side reaction is a hydrogen evolution reaction). Therefore, the method improves the compactness of crystal grains in the deposition process of the metal chromium and reduces the depth of pores, and is an important measure for improving the corrosion resistance of the chromium-plated plate.

TABLE 7 Current Process parameters for electroplating chromium Metal

The present invention improves the process of electroplating chromium metal as shown in table 8. When metal chromium is electroplated, the concentration of chromic anhydride in the electroplating solution is controlled to be 140-160 g/L, the concentration of ammonium fluoride is controlled to be 3-4 g/L, the concentration of chromic anhydride in the first recovery tank is not more than 50g/L, and the concentration of chromic anhydride in the second recovery tank is not more than 40 g/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 33-43 ℃, and the current density is controlled to be 25-100A/mm². Preferably, when the metal chromium is electroplated, the concentration of chromic anhydride in the electroplating solution is controlled to be 150g/L, the concentration of ammonium fluoride is controlled to be 3.5g/L, the concentration of chromic anhydride in the first recovery tank is controlled to be 30g/L, and the concentration of chromic anhydride in the second recovery tank is controlled to be 10 g/L; during the electroplating process, the temperature of the electroplating solution is controlled to be 38 ℃, and the current density is 65A/mm²。

TABLE 8 Process parameters for chromium metal electroplating of the present invention

The surface topography of the resulting metallic chromium layer is shown in FIG. 8. As can be seen from the figure, the compact metal chromium layer with shallow depth of the deep pit can be obtained by the electroplating process, and the metal chromium layer with the shape can better protect the substrate and improve the corrosion resistance of the substrate.

In the chromium electroplating process, the metal chromium and the chromium oxide are mutually acted, namely, the metal chromium is deposited and the chromium oxide is generated at the same time, and the metal chromium is deposited and the chromium oxide is generated at the same time and is interwoven with each other. As shown in Table 9, when chromium oxide was electroplated by the conventional process, the chromium oxide layer formed was composed mainly of Cr₂O₃、CrOOH、Cr(OH)₃The surface pores are flat and fine. It is a net-shaped and layered structure, mainly plays a role in sealing the micro-structure of the metal chromium layerThe function of small pores. Therefore, the compactness of the reticular structure of the chromium oxide layer is improved, and the corrosion resistance of the chromium-plated plate can also be improved.

TABLE 9 Current Process parameters for electroplating chromium oxide

In order to improve the compactness of the chromium oxide layer network structure, the invention improves the chromium oxide electroplating process, as shown in table 10. When chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating solution is 60-70 g/L, the concentration of ammonium fluoride is 1-2 g/L, and the concentration of sodium hydroxide is 6-12 g/L; in the electroplating process, the temperature of the electroplating solution is controlled to be 27-37 ℃, and the current density is controlled to be 9-22A/mm²The weight of the generated chromium oxide layer is 8-15 g/m². Preferably, when the chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating solution is 65g/L, the concentration of ammonium fluoride is 1.5g/L, and the concentration of sodium hydroxide is 9 g/L; during the electroplating process, the temperature of the electroplating solution is controlled at 32 ℃, and the current density is controlled at 19A/mm²The weight of the generated chromium oxide layer is more than or equal to 10g/m²。

TABLE 10 Process parameters for electroplating chromium oxide according to the invention

The integrated surface morphology of the metallic chromium layer and the chromium oxide layer obtained by adopting the electroplating chromium oxide process is shown in FIG. 9. As can be seen from the figure, according to the chromium oxide electroplating process, a compact reticular chromium oxide layer can be obtained, thereby being beneficial to improving the corrosion resistance of the chromium-plated plate.

In summary, the present invention provides a new surface morphology Rs of tin/chrome plated substrate, and the distribution of the plating layer is more uniform during the electroplating process of the substrate with the surface morphology Rs, so that the plating layer at the necking part and the pre-scribing part is not easy to deform and break during the process of preparing the necking can/easy-open lid, thereby improving the corrosion resistance of the necking can/easy-open lid. In addition, the invention also improves the tin plating and chromium plating process, improves the compactness of the plating layer, and can improve the corrosion resistance of the necking can/easy-open end.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.