NL2032597A

NL2032597A - Base steel with sanded surface, preparation method and tinplate/tin free steel plate thereof

Info

Publication number: NL2032597A
Application number: NL2032597A
Authority: NL
Inventors: Yu Wei; Huang Jiugui; Guo Hong
Original assignee: Jiangsu Shagang Group Co Ltd; Zhangjiagang Yangzi River Cold Rolled Sheet Co Ltd; Institute Of Res Of Iron & Steel Shagang Jiangsu Province/Sha Steel Co Ltd
Priority date: 2021-07-28
Filing date: 2022-07-25
Publication date: 2023-02-01
Also published as: WO2023004907A1; NL2032597B1; MX2024001158A; CN113578965B; KR20230170643A; CN113578965A

Abstract

The present application provides a method for preparing a base steel with a sanded surface, comprising providing a temper mill. The temper mill comprises a first stand and a second stand. The first stand comprises a first work roll and a third work roll arranged oppositely, and the second stand comprises a second work roll and a fourth work roll arranged oppositely. The first work roll and the second work roll are located on the same side. The first work roll is an electrical discharge texturing roll, and the second work roll is a polished smooth roll. The surface roughness of the first work roll is 1.6-2.2 um, and the surface roughness of the second work roll is 0.35-0.75 pm. The base steel is passed between the first work roll and the third work roll, and between the second work roll and the fourth work roll in sequence, so that the sanded surface is formed on a first surface of the base steel. When the base steel with the sanded surface is processed into a necked-in can or an easy-open end after tin plating or chrome plating, the coating at the necked-in and pre-scoring positions is not easily damaged, and has good corrosion resistance.

Description

BASE STEEL WITH SANDED SURFACE, PREPARATION METHOD AND

TINPLATE/TIN FREE STEEL PLATE THEREOF

FIELD OF THE INVENTION

The present application relates to the technical field of metal material processing, and more particularly to a base steel with a sanded surface, a preparation method and a tinplate/tin free steel (TFS) plate thereof.

DESCRIPTION OF THE RELATED ART

The tinplate/tin free steel (TFS) plate is widely used in beverage packaging, and usually made of the steel strip with the thickness about 2.0 mm which is obtained by hot-rolling steel billets in steel plants, and then performed with pickling, annealing, leveling, tin/chrome plating, passivation and other processes. The tinplate/TFS plate is made into can body through iron printing and can-making processes to contain various beverages. Since the contents contained are acidic and high-protein substances, the product made of the tinplate/TFS plate is required to have high corrosion resistance.

Currently, the tinplate/TFS plate selected to make into the necked-in can (FIG. 1) or the easy-open end (FIG. 2) has the R1 (fine stone-textured surface) surface, and the roughness Ra of 0.29-0.55 um. The tinplate/TFS plate is stone-textured, and has average scratching texture (visually similar to small, shallow and short scratches) and lighter graininess under strong light. However, the necked-in can or easy-open end made of the tinplate/TFS plate is easily corroded by the contents at the necked- in or pre-scoring positions (the formed easy-open end is required to pre-score at the opening portion to guide the opening direction) in the use, which cannot meet the requirements of corrosion resistance.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present application is to provide a tinplate/tin free steel (TFS) plate. A necked-in can or an easy-open end made of the tinplate/TFS plate has good corrosion resistance, which is not corroded by the contents.

To solve the above-mentioned technical problem, the technical solutions employed by the present application are as follows: Afirst aspect of the present application provides a method for preparing a base steel with a sanded surface, comprising the following steps: providing a temper mill comprising a first stand and a second stand, wherein the first stand comprises a first work roll and a third work roll arranged oppositely, and the second stand comprises a second work roll and a fourth work rol! arranged oppositely, the first work roll and the second work roll are located on the same side, and the first work roll and the second work roll are used to contact a first surface of the base steel and form the sanded surface, the first work roll is an electrical discharge texturing roll, and the second work roll is io a polished smooth roll; a surface roughness of the first work roll is 1.6-2.2 um, and a surface roughness of the second work roll is 0.35-0.75 pm; and sending the base steel to be cold-rolled into the temper mill to pass between the first work roll and the third work rolt, and between the second work roll and the fourth work roll in sequence, so that the sanded surface is formed on the first surface of the base steel.

Further, a rolling force of the first stand is 3500-4500 kN, and a rolling force of the second stand is 3500-4000 kN.

Preferably, a roll changing cycle and a rolling tonnage of the first work roll and the second work roll are 120 + 20 km and 150 + 30 t, respectively.

Preferably, when a second surface of the base steel is a bright surface, the third work roll and the fourth work roll are both polished smooth rolls; the surface roughness of the first work roll is 1.8 + 0.2 um, the surface roughness of the second work roll is 0.70 + 0.05 um, a surface roughness of the third work roll is 0.70 £ 0.05 um, and a surface roughness of the fourth work roll is 0.40 + 0.05 um; the rolling force of the first stand is 3500 + 100 kN, and the rolling force of the second stand is 3500 + 100 kN; the bright surface is formed on the second surface of the base steel after being cold-rolled by the temper mill.

Preferably, when the second surface of the base steel is a fine stone-textured surface, the third work roll is the electrical discharge texturing roll, and the fourth work roll is the polished smooth roll; the surface roughness of the first work roll is 2.0 £ 0.2

Um, the surface roughness of the second work roll is 0.40 + 0.05 um, the surface roughness of the third work roll is 1.2 + 0.2 um, and the surface roughness of the fourth work roll is 0.40 + 0.05 pm; the rolling force of the first stand is 4000 + 100 kN, and the rolling force of the second stand is 3500 + 100 kN; the fine stone-textured surface is formed on the second surface of the base steel after being cold-rolled by the temper mill.

Preferably, when the second surface of the base steel is a rough stone-textured surface, the third work roll is the electrical discharge texturing roll, and the fourth work roll is the polished smooth roll; the surface roughness of the first work roll is 2.0 £ 0.2

Mm, the surface roughness of the second work roll is 0.40 + 0.05 um, the surface roughness of the third work roll is 1.5 £ 0.2 um, and the surface roughness of the fourth work roll is 0.70 = 0.05 um; the rolling force of the first stand is 4500 + 100 kN, and the rolling force of the second stand is 4000 + 100 kN; the rough stone-textured surface is formed on the second surface of the base steel after being cold-rolled by the temper mill.

A second aspect of the present application provides a base steel with a sanded surface made by the method of the first aspect. A first side of the base steel is the sanded surface, and a second side of the base steel is a non-sanded surface. The sanded surface comprises a bottoming texture in a dot concave-convex shape and a filiform line located on a part of the bottom grain. The distribution of the bottoming texture and the filiform line makes a roughness of the sanded surface to be 0.50- 0.80 um.

Preferably, the base steel is an MR-type base steel, an L-type base steel or a D-type base steel.

Preferably, the non-sanded surface is a bright surface, the fine stone-textured surface, the rough stone-textured surface, a silver surface, a silver rough surface and a matte surface.

A third aspect of the present application provides the tinplate. The tinplate is prepared after electroplating metallic tin and performing reflow on the surface of the base steel of the second aspect.

Preferably, when electroplating the metallic tin, a concentration of divalent tin in an electroplating bath is 20-25 g/L, a concentration of methanesulfonic acid is 30-50 mb/L, a concentration of an antioxidant is 35-60 mL/L, and a concentration of an additive is 20-30 mbL/L. In the electroplating process, a temperature of the electroplating bath is controlled to be 38-45 °C, and a current density is controlled to be 22-28 A/mm?.

Preferably, when the reflow is performed, a reflow setting temperature is 260-290 °C, a reflow feedback temperature is 255-295 °C, and a reflow power ratio is 30%-50%.

Preferably, the first side of the base steel is the sanded surface, and the second side of the base steel is the fine stone-textured surface.

A fourth aspect of the present application provides the TFS plate. The TFS plate is prepared by electroplating the metallic chromium and chromium oxide on the surface of the base steel of the second aspect.

Preferably, when the metallic chromium is electroplated, a concentration of chromic anhydride in the electroplating bath is 140-160 g/L, and a concentration of ammonium fluoride is 3-4 g/L. In the electroplating process, the temperature of the electroplating bath is controlled to be 36-40 °C, and the current density is controlled to be 50-80 A/mm2. The concentration of chromic anhydride in a first recovery tank is controlled to be < 50 g/L, and the concentration of chromic anhydride in a second recovery tank is controlled to be <40 g/L.

Preferably, when chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating bath is 60-70 g/L, the concentration of ammonium fluoride is 1-2 g/L, and a concentration of sodium hydroxide is 8-10 g/L. In the electroplating process, the temperature of the electroplating bath is controlled to be 31-35 °C, and the current density is controlled to be 9-22 A/mm2. A weight of a chromium oxide layer obtained is 8-15 g/m2.

A fifth aspect of the present application provides a necked-in can. The necked-in can is made of the tinplate or the TFS plate.

A sixth aspect of the present application provides an easy-open end. The easy-open end is made of the tinplate.

Compared with the prior art, the beneficial effects of the present application are as follows: 1. The present application creatively proposes a new treatment process of the tinplate/TFS plate, so that the base steel has two different inner and outer surfaces.

The sanded surface with the roughness of 0.50-0.80 pm made on the inner surface used to form the inner wall of the can body, including the bottoming texture in the dot-like concave-convex shape and the filiform line located on the part of the bottoming texture in the microscopic morphology. The coating is capable of being more evenly distributed on the surface of the base steel in the tin plating or chrome plating process of the base steel with the sanded surface. Therefore, when the obtained tinplate/TFS plate is processed into the necked-in can or the easy-open end, the coating with good corrosion resistance is not easily damaged at the necked- in and pre-scoring positions, and not corroded by the contents. The outer surface used to form the outer wall of the can body is capable of retaining the original surface morphology, so that the tinplate/TFS plate of the present application made into the can-packaging products is capable of retaining the visual characteristics of the existing can-packaging products. Therefore, the marketing cost caused by switching 5 the new can-packaging products is avoided. The base steel of the present application has better universality. 2. The present application improves the existing tin plating and chrome plating processes. The new electroplating process of the present application improves the compactness of the tin-plating layer and the chrome-plating layer and the coverage uniformity of the alloy layer, and reduces the pore depth, so that the coating is capable of protecting the base steel better. Thus, the corrosion resistance of the base steel is further improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of a necked-in can;

FIG. 2 is a structural diagram of an easy-open end;

FIG. 3 is a texture of a R1 surface under a microscope;

FIG. 4 is a texture of a Rs surface under the microscope;

FIG. 5 is a scratching texture diagram of the R1 surface (a) and the Rs surface (b) ;

FIG. 6 is a surface morphology diagram of a tin layer on a base steel when adopting the existing tin plating process (a) and a tin plating process of the present application (b);

FIG. 7 is a surface morphology diagram of an alloy layer on the base steel when adopting the existing reflow process (a, b, and c) and the tin plating process of the present application (d, e, and f);

FIG. 8 is a surface morphology diagram of a metallic chromium layer obtained by a process for electroplating metallic chromium of the present application; and

FIG. 9 is an integrated surface morphology diagram of the metallic chromium layer and a chromium oxide layer obtained by a process for electroplating chromium oxide of the present application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present disclosure will be further described below in conjunction with the accompanying drawings and specific examples, so that those skilled in the art can understand and implement the present application better. However, the examples are not intended to limit the present application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by these ordinarily skilled in the art. The terms used in the description of the present application are intended to describe specific examples, not to limit the present application. The term "and/or" used herein includes any and all combinations of one or more of the related items listed.

As described in the background art, the existing tinplate/TFS plate selected to make into the necked-in can (FIG. 1) or the easy-open end (FIG. 2) has the R1 (fine stone- textured surface) surface, and the roughness Ra of 0.29-0.55 um. The tinplate/TFS plate is stone-textured, and has average scratching texture (similar to small, shallow and short scratches visually) and lighter graininess under strong light. However, the necked-in can or easy-open end made of the tinplate/TFS plate is easily corroded by the contents at the necked-in or pre-scoring positions in the use, which cannot meet the requirements of corrosion resistance.

After long-term research, the inventors have found that the main reason to cause the easy corrosion of the necked-in or pre-scoring positions by the contents is the surface morphology of the tinplate/TFS plate. Since the content surface of the base steel in the prior art is the fine stone-textured surface R1 with scratching morphology which causes the obviously rough and uneven surface of the base steel. As shown in FIG. 3, the scratching portion shows serious unevenness observed under the microscope, which is groove-like distributed on the surface of the base steel.

Taking the tinplate as an example, when tin is electroplated on the base steel, under the condition of a certain amount of tin deposition, the amount of tin plated on the protruding portions of the base steel is greater than that on the recessed portions due to scratching, resulting in that the uniform deposition of tin is blocked. In the reflow process, tin deposited on the base steel melts and flows. When tin flows to the recessed portions, the recessed portions block the melted tin to further flow, so that the leveling of the melted tin is blocked. Ultimately, the formation of the alloy layer is affected. Therefore, when tin is electroplated on the fine stone-textured surface, the distribution of the tin layer is not uniform, and the tin content in the scratching portion is obviously less, resulting in that the tin layer at the scratching portion is further damaged in the can-making or end-making process due to the necked-in deformation or the end pre-scoring, so that the base steel at the scratching portion is directly externally exposed due to no protection of the tin layer, and the corrosion resistance of the scratching portion is decreased sharply.

The TFS plate has the same issue. When the metallic chromium is electroplated on the surface of the base steel, there are few pores in the deep-pit shape on the surface of the coating, which are mainly caused by the body-centered cubic structure of the electroplated metallic chromium layer formed by the preferential orientation growth of the lattice with the change of current density. What’s more, the current efficiency for chrome plating is generally 20%-25%, and the side reaction is hydrogen evolution reaction, which increases the generation of pores in the longitudinal direction of the metallic chromium layer. In addition, due to the filiform scratches in the longitudinal direction on the fine stone-textured surface of the base steel, the pores in the longitudinal direction are further deepened, and the deposition of the metallic chromium at the bottom of the scratching grooves in the chrome plating process is further reduced. The chromium oxide layer has the net-like or layer-like structure.

The protection of the metallic chromium layer is further reduced as the grooves are deepened, resulting in that the corrosion resistance of the TFS plate is decreased.

Inthe existing can-making industry, the surface morphology of the base steel made into the tinplate/TFS plate is B (bright surface), R1 (fine stone-textured surface), R2 {rough stone-textured surface), S1 (silver surface), S2 (silver rough surface) and M (matte surface), the specifications and standards for the morphology of the products are shown in Table 1.

Table 1 Specifications and standards for the morphology of the existing tinplate/TFS plate

Surface Target value of

Surface _

Code [roughness range surface Characteristics finishes

Ra (um) roughness (um)

Bright Bright glazed surface, strong scratching texture, "9 B 0.30-0.45 0.35 and better reflective performance after tin surface (chrome) plating.

Fine stone- .

Stone-texiured, average scratching texture, and textured R1 0.29-0.55 0.42 / == Î lighter graininess under strong light. surface

Rough . one: Stone-textured, strong scratching texture, and ° R2 0.42-0.72 0.55 graininess and deep and uniform scratching textured texture under strong light. surface si Having graininess under normal light and strong ner S1 0.77-1.27 1.02 light, silver-white glazed surface with fine and surface / / uniform grains, and poor reflectivity.

Silver Having graininess under normal light and strong rough S2 1.19-1.99 1.50 light, silver-white glazed surface with rough and surface large grains, and poor reflectivity.

Matte

M 0.77-1.27 1.02 Whitish surface without reflectivity surface

The inventors have found that the above-mentioned surface morphology is not suitable for the inner surface of the can and end. To overcome the problem that the tinplate/TFS plate in the prior art is easily corroded, the inventors have researched and designed a new surface morphology of the tinplate/TFS plate, which is defined as a sanded surface and expressed in Rs. As shown in FIG. 4, the Rs surface has the bottoming texture in the dot-like concave-convex shape and the filiform line located on the part of the bottoming texture under the microscope, and the roughness of the sanded surface is 0.50-0.80 um due to the distribution of the bottoming texture and the filiform line. When observed under normal light, the Rs surface has fine graininess, slight scratching texture under strong light, light-silver glazed surface, and poor reflectivity. As shown in FIG. 5, the Rs surface of the present application has short and shallow scratching texture over the R1 surface.

Thus, the degree of scratching is reduced, and the impact of grooves of the base steel caused by scratching on the leveling of tin in the deposition and reflow process of the electroplated tin is eliminated, so that the surface of the base steel is evenly covered with the tin layer and the alloy layer. Due to the good ductility of tin, the corrosion resistance of the deformation zone in the can-making and end-making process is finally increased.

The present application provides a method for preparing the base steel with the sanded surface, comprising the following steps: (i) A temper mill is provided. The temper mill comprises a first stand and a second stand. The first stand comprises a first work roll and a third work roll arranged oppositely, and the second stand comprises a second work roll and a fourth work roll arranged oppositely. The first work roll and the second work roll are located on the same side of the first stand, and the first work roll and the second work roll are used to contact a first surface of the base steel to form the sanded surface.

The first work roll is the electrical discharge texturing roll, and the second work roll is the polished smooth roll. The surface roughness of the first work roll is 1.6-2.2 um, and the surface roughness of the second work roll is 0.35-0.75 um. (if) The base steel to be cold-rolled is sent into the temper mil! to pass between the first work roll and the third work roll, and between the second work roll and the fourth work roll in sequence, so that the sanded surface is formed on the first surface of the base steel.

The electrical discharge texturing roll is prepared by the electrical discharge texturing technique, which produces pit-like burrs on the surface of the roll based on the principle of electric spark discharge. The base steel has a grainy surface rolled by the electrical discharge texturing roll. The polished smooth roll is formed on the surface of the roll based on the polishing process. The base steel has a filiform surface rolled by the polished smooth roll. In the present application, the morphology and roughness of the roll surface are printed on the surface of the base steel under the action of the external rolling force by controlling the morphology and roughness of the surfaces of the first work roll and the second work roll, so that the sanded surface is formed on the surface of the base steel. Preferably, the rolling force applied by the first stand to the first work roll is 3500-4500 kN, and the rolling force applied by the second stand to the second work roll is 3500-4000 kN.

The first work roll and the second work roll are required to be replaced after being used for a certain period of time. The replacement of the first work roll and the second work roll is determined by the roll changing cycle or the rolling tonnage. The rol! changing cycle refers to the total length of the base steel rolled by the work rolls, and the rolling tonnage refers to the total weight of the base steel rolled by the work rolls.

For example, if the roll changing cycle is 120 km, it means that the work rolls stop to be changed after rolling 120 km of the base steel. Similarly, if the rolling tonnage is 150 tons, it means that the work rolls stop to be changed after rolling 150 tons of the base steel. In the present application, the rol! changing cycle and the rolling tonnage of the first work roll and the second work roll are preferably 120 + 20 km and 150 t 30t, respectively.

In addition, the inventors have abandoned the traditional double-sided R1 surface production process, and adopted a new differential surface morphology control. The outer surface of the can body still adopts the original R1 surface, and the inner surface of the can body adopts the Rs surface of the present application, to obtain the base steel with the Rs/R1 differential surface morphology. Through the differential surface morphology control (Rs content surface/R1 outer surface), the compactness and uniformity of the coating of the base steel during the electroplating process are improved, so that the base steel is not easily deformed and damaged during the expansion and contraction. Thus, the internal corrosion resistance of the can body is improved, while maintaining the visibility of the outside of the can body.

The base steel with the Rs/R1 differential surface morphology can be made into the necked-in can or easy-open end after tin plating, and made into the necked-in can after chrome plating.

The invention can utilize the base steels commonly used in the can-making industry, and preferably MR-type base steel, L-type base steel or D-type base steel.

The base steel with the Rs/R1 differential surface morphology can be made by controlling the types, surface roughness and rolling force of the third work roll and the fourth work roll. Specifically, the third work roll is the electrical discharge texturing roll, and the fourth work roll is the polished smooth roll. The surface roughness of the first work roll is 2.0 £ 0.2 pm, the surface roughness of the second work roll is 0.40 t 0.05 um, the surface roughness of the third work roll is 1.2 £ 0.2 um, and the surface roughness of the fourth work roll is 0.40 + 0.05 pm. The rolling force of the first stand is 4000 + 100 kN, and the rolling force of the second stand is 3500 + 100 kN. the fine stone-textured surface (R1) is formed on the second surface of the base steel after being cold-rolled by the temper mill.

The base steel with other surface morphologies formed on the second surface can be obtained by the same method, such as the Rs/B base steel, the Rs/R2 base steel and the like.

The method for preparing the Rs/B base steel is as follows: The third work roll and the fourth work roll are the polished smooth rolls. The surface roughness of the first work roll is 1.8 + 0.2 um, the surface roughness of the second work roll is 0.70 £ 0.05 um, the surface roughness of the third work roll is 0.70 + 0.05 um, and the surface roughness of the fourth work roll is 0.40 £ 0.05 um. The rolling force of the first stand is 3500 + 100 kN, and the rolling force of the second stand is 3500 + 100 kN. The bright surface (B) is formed on the second surface of the base steel after being cold-

rolled by the temper mill.

The method for preparing the Rs/R2 base steel is as follows: The third work roll is the electrical discharge texturing roll, and the fourth work roll is the polished smooth roll. The surface roughness of the first work roll is 2.0 + 0.2 um, the surface roughness of the second work roll is 0.40 + 0.05 um, the surface roughness of the third work roll is 1.5 + 0.2 um, and the surface roughness of the fourth work roll is 0.70 + 0.05 um. The rolling force of the first stand is 4500 + 100 kN, and the rolling force of the second stand is 4000 + 100 kN. The rough stone-textured surface (R2) is formed on the second surface of the base steel after being cold-rolled by the temper mill.

The roll matching solution for preparing the above-mentioned base steel with differential surface morphologies is shown in detail in Table 2.

Table 2 The roll matching solution of the temper mill for preparing the base steel with differential surface morphologies

B/Rs 35004100 35004100 /1.820.2 (EDT) /0.70+0.05 (B)

Rs/B 35002100 3500100 10.70+0.05 (B) /0.40+0.05 (B)

Ps | Gemzen | onse | Wow | en

R1/Rs 4000+100 3500+100 12.0+0.2 (EDT) 10.40+0.05 (B)

Rs/R1 40002100 3500100 /1.230.2 (EDT) /0.40+0.05 (B)

Em | oreon | onse | Wow | sew

R2/Rs 45001100 4000+100 /2.040.2 (EDT) 10.40+0.05 (B)

Rs/R2 45002100 4000100 /1.520.2 (EDT) 10.70+0.05 (B)

According to the different needs of downstream users, the base steel with other differential surface morphologies, such as the Rs/S1 base steel, the Rs/S2s base steel, and the Rs/M base steel can also be prepared by the same method, and the specific methods will not be repeated here.

In addition to the surface morphology of the base steel, the impact of the electroplating process on the corrosion resistance of the tinplate/TFS plate can also not be ignored. Therefore, the present application further studies the tin electroplating and reflow process of the base steel.

Table 3 Parameters of the existing tin electroplating process

Current . | Methanesulf- oo u Electroplating

Items density Bivalent tin onic acid Antioxidant Additive bath

Lm | ELL range

Observing the surface of the tinplate through the microscope, it has found that the tin layer and the alloy layer are not completely and densely covered on the surface of the base steel by adopting the existing tin electroplating process. As shown in FIG. 6 (a), the grains of the tin layer are rough and loose, and the gap between grains is large, which would lead to poor corrosion resistance of the tinplate. Therefore, it is primary to improve the compactness of the tin layer and the coverage of the alloy layer to improve the corrosion resistance of the tinplate.

The inventors have improved the existing tin electroplating process and provided a new tin electroplating process, as shown in Table 4. When the metallic tin is electroplated, the concentration of divalent tin in the electroplating bath is 15-25 g/L, the concentration of methanesulfonic acid is 30-50 mL/L, the concentration of the antioxidant is 35-60 mL/L, and the concentration of the additives is 25-30 mL/L.

During the electroplating process, the temperature of the electroplating bath is controlled to be 38-45 °C, and the current density is controlled to be 22-28 A/mm2.

Preferably, the concentration of divalent tin in the electroplating bath is controlled to be 20 g/L, the concentration of methanesulfonic acid is controlled to be 40 mL/L, the concentration of antioxidant is controlled to be 45 mU/L, and the concentration of additive is controlled to be 25 mbL/L, the temperature of the electroplating bath is controlled to be 42 °C, and the current density is controlled to be 25 A/mm2.

It shall be pointed out that the above-mentioned antioxidant can be selected from those commonly used in the art, including but not limited to one or more of phenol, hydroquinone, resorcinol, and catechol. In the present application, the antioxidant used is QUAKERTIN™ TPMW AOX Antioxidant from Quaker Chemical Corporation.

The additive can be selected from those commonly used in the art, including but not limited to one or more of surfactants and grain refiners. In the present application, the additive used is QUAKERTIN™ Additive from Quaker Chemical Corporation.

Table 4 Parameters of the tin electroplating process of the present application density g/L) {mi/L) oxidant {mi/L) bath rm 30-50 35-60 20-30 38-45 range 25 40 45 25 42 target

Using the improved tin electroplating process of the present application, the surface morphology of the tin layer on the base steel is shown in FIG. 6 (b). It can be seen that the grains of the tin layer are fine and compact, and the gap between grains is small, which can protect the base steel better and improve the corrosion resistance of the base steel.

After tin electroplating, the tin layer melts and flows through the reflow process to obtain the alloy layer, so that the uniformity of the tin plating layer is improved. The parameters of the existing reflow process after tin electroplating are shown in Table 5.

Table 5 Parameters of the existing reflow process after tin electroplating

Item Height of reflow box | Reflow setting Reflow feedback Reflow power (m) temperature (°C) temperature (°C) ratio (%)

Te | 68 mew | meee | wm

Control 6.5 290 295 50 target

As shown in FIG. 7 (a)-(c), the grains formed on the alloy layer are relatively fine by adopting the existing reflow process. Thus, the corrosion resistance is also poor.

The reflow process improved by the present application is shown in Table 6. During the reflow process, the height of the reflow box used is 3.5-5.5 m, the reflow setting temperature is 260-290 °C, the reflow feedback temperature is 255-295 °C, and the reflow power ratio is 30%-50%. Preferably, the height of the reflow box used is 4.5 m, the reflow setting temperature is 270 °C, the reflow feedback temperature is 275 °C, and the reflow power ratio is 40%.

Table 6 Parameters of the reflow process of the present application

Item Height of reflow box | Reflow setting Reflow feedback Reflow power (m) temperature (°C) temperature (°C) ratio (%) 45 270 275 40 target

The surface morphology of the alloy layer is shown in FIG. 7(d)-(f) by adopting the reflow process of the present application. It can be seen that the grains of the alloy layer are rough, large and columnar, and have good continuity. Thus, the corrosion resistance is also better.

Further, the present application also studies the chrome plating process of the base steel.

As mentioned above, when adopting the existing tin electroplating process (as shown in Table 7), the pores in the deep-pit shape are generated in the longitudinal direction on the metallic chromium layer due to the preferential orientation growth of the lattice and the characteristics of the chrome plating process (the current efficiency of 20%-25%, and the hydrogen evolution reaction as the side reaction).

Therefore, to improve the corrosion resistance of the TFS plate, it is important to improve the compactness of grains and reduce the depth of pores during the deposition of the metallic chromium.

Table 7 Parameters of the existing process for electroplating the metallic chromium

Chromic Ammonium Temperature of Concentration | Concentration anhydride | fluoride (g/L) | electroplating of chromic of chromic urren } (g/L) bath (°C) anhydride in anhydride in

Items density / the first the second (A/mm?) recovery tank | recovery tank (g/L) (g/L) 25-50 100-120 | 3-4 32-36 < 80 < 60 range 35 110 35 34 40 30 target

The process for electroplating the metallic chromium improved by the present application is shown in Table 8. When the metallic chromium is electroplated, the concentration of chromic anhydride in the electroplating bath is 140-160 g/L, the concentration of ammonium fluoride is 3-4 g/L, the concentration of chromic anhydride in the first recovery tank is < 50 g/L, and the concentration of chromic anhydride in the second recovery tank is < 40 g/L. In the electroplating process, the temperature of the electroplating bath is controlled to be 33-43 °C, and the current density is controlled to be 25-100 A/mm2. Preferably, when the metallic chromium is electroplated, the concentration of chromic anhydride in the electroplating bath is controlled to be 150 g/L, the concentration of ammonium fluoride is controlled to be 3.5 g/L, the concentration of chromic anhydride in the first recovery tank is 30 g/L, and the concentration of chromic anhydride in the second recovery tank is controlled to be 10 g/L. In the electroplating process, the temperature of the electroplating bath is controlled to be 38 °C, and the current density is controlled to be 65 A/mm?2.

Table 8 Parameters of the process for electroplating the metallic chromium of the present application

Chromic Ammonium Temperature of | Concentration | Concentration 6 t anhydride | fluoride (g/L) | electroplating of chromic of chromic urren / {g/L) bath (°C) anhydride in anhydride in

Items density , the first the second (A/mm?) recovery tank | recovery tank (lL) (g/L)

Target 50-80 140-160 | 3-4 36-40 < 50 <40 range oon sw js Je Je Jo 65 150 3.5 38 30 10 target

The surface morphology of the metallic chromium layer obtained by adopting the process for electroplating the metallic chromium of the present application is shown in FIG. 8 . It can be seen that the metallic chromium layer with shallow and dense pits is obtained by the above-mentioned electroplating process. The metallic chromium layer can protect the base steel better and improve its corrosion resistance.

In the chrome electroplating process, the interaction between the metallic chromium and chromium oxide is mutual. When the metallic chromium is deposited, chromium oxide is produced; and when chromium oxide is deposited, the metallic chromium is produced. As shown in Table 9, the main components of the chromium oxide layer generated are Cr2O3, CrOOH, Cr(OH)3 when chromium oxide is electroplated by the existing process, and the pores on the surface are flat and small. The chromium oxide layer is in the net-like and layer-like structure, mainly blocking the tiny pores of the metallic chromium layer. Therefore, the improved compactness of the net-like structure of the chromium oxide layer can improve the corrosion resistance of the

TFS plate.

Table 9 Parameters of the existing process for electroplating chromium oxide 6 t Chromic Ammonium Temperature of | Concentration Weight of urren . anhydride fluoride (g/L} | electroplating of sodium chromium

Items density , . (g/L) bath (°C) hydroxide (g/L) | oxide layer (A/mm?) (g/m?)

Target 1-10 60-80 1-2 25-40 6-14 5-15 range aoe se Ee 5 70 1.5 35 10 25 target

To improve the compactness of the net-like structure of the chromium oxide layer, the present application improves the process for electroplating chromium oxide, as shown in Table 10. When chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating bath 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 bath is controlled to be 27-37 °C, the current density is controlled to be 9-22 A/mm?, and the weight of the chromium oxide layer obtained is controlled to be 8-15 g/m2. Preferably, when chromium oxide is electroplated, the concentration of chromic anhydride in the electroplating bath is controlled to be 65 g/L, the concentration of ammonium fluoride is controlled to be 1.5 g/L, and the concentration of sodium hydroxide is controlled to be 9 g/L, the temperature of the electroplating bath is controlled to be 32 °C, the current density is controlled to be 19 A/mm?, and the weight of the chromium oxide layer obtained is controlled to be = 10 g/m.

Table 10 Parameters of the process for electroplating chromium oxide of the present application

Current Chromic Ammonium | Temperature Concentration of | Weight of oo (A/mm3) (g/L) electroplating | hydroxide (g/L) oxide layer bath (°C) (g/m?) range

Sh [= Jw

The integrated surface morphology of the metallic chromium layer and the chromium oxide layer obtained by adopting the above-mentioned process for electroplating chromium oxide is shown in FIG. 9. It can be seen that the dense net-like chromium oxide layer is obtained according to the process for electroplating chromium oxide of the present application, which is beneficial to improve the corrosion resistance of the

TFS plate.

To sum up, the present application provides the new surface morphology Rs for the tinplate/TFS plate. For the base steel with such a surface morphology, the coating is distributed more uniformly in the electroplating process. Thus, the coating at necked- in and pre-scoring positions is not easily deformed and damaged when making the base steel into the necked-in can/easy-open end, thereby improving the corrosion resistance of the necked-in can/easy-open end. In addition, the present application also improves the tin plating and chrome plating processes to improve the compactness of the coating, so that the corrosion resistance of the necked-in can/easy-open end is also improved.

The above-mentioned examples are only preferred examples for illustrating the present application better, and the protection scope of the present application is not limited thereto. Equivalent replacements or modifications made by those skilled in the art based on the present application shall fall within the protection scope of the present application. The protection scope of the present application is defined by the claims.

Claims

Conclusions

A method of preparing a base steel having a ground surface, comprising the steps of: providing a tempering mill comprising a first stand and a second stand, the first stand comprising a first work roll and a third work roll arranged oppositely, and the second stand includes a second work roll and a fourth work roll arranged oppositely, the first work roll and the second work roll are located on the same side as the first stand, and the first work roll and the second work roll are used to form a first surface of the contacting base steel to form the abraded surface, the first work roll is an electric discharge texture roll, and the second work roll is a polished smooth roll, a surface roughness of the first work roll is 1.6-2.2 um, and a surface roughness of the second work roll is 0.35-0.75 µm; and sending the base steel to be cold rolled to the tempering mill to pass between the first work roll and the third work roll, and sequentially between the second work roll and the fourth work roll such that the abraded surface is formed on the first surface of the base steel.

The method for preparing the base steel with the abraded surface according to claim 1, wherein, a rolling force of the first position is 3500-4500 KN, and a rolling force of the second position is 3500-4000 kN.

The method for preparing the base steel with the abraded surface according to claim 1, wherein, a roll changing cycle and a roll tonnage of the first work roll and the second work roll are 120 + 20 km and 150 + 30 t, respectively.

The method for preparing the base steel with the abraded surface according to claim 1, wherein when a second surface of the base steel is a bright surface, the third work roll and the fourth work roll are both polished smooth rolls; the surface roughness of the first work roll is 1.8 + 0.2 um, the surface roughness of the second work roll is 0.70 + 0.05 um, a surface roughness of the third work roll is 0.70 + 0.05 um, and a surface roughness of the fourth working roll is 0.40 + 0.05 µm; the rolling force of the first stand is 3500 + 100 kN, and the rolling force of the second stand is 3500 * 100 kN; the shiny surface is formed on the second surface of the base steel after being cold rolled by the tempering mill.

The method for preparing the base steel with the abraded surface according to claim 1, wherein when the second surface of the base steel is a fine stone texture surface, the third work roll is an electric discharge texture roll, and the fourth work roll is a polished smooth roll ; the surface roughness of the first work roll is 2.0 + 0.2 um, the surface roughness of the second work roll is 0.40 + 0.05 um, the surface roughness of the third work roll is 1.2 + 0.2 um, and the surface roughness of the fourth working roll is 0.40 + 0.05 µm; the rolling force of the first stage is 4000 + 100 kN, and the rolling force of the second stage is 3500 + 100 kN; the fine stone structure surface is formed on the second surface of the base steel after being cold rolled by the tempering mill.

6. The method for preparing the base steel with the abraded surface according to claim 1, wherein when the second surface of the base steel is a rough stone texture surface, the third work roll is an electric discharge texture roll, and the fourth work roll is a polished giad roll. is; the surface roughness of the first work roll is 2.0 + 0.2 um, the surface roughness of the second work roll is 0.40 + 0.05 um, the surface roughness of the third work roll is 1.5 + 0.2 um, and the surface roughness of the fourth working roll is 0.70 + 0.05 µm; the rolling force of the first stage is 4500 + 100 kN, and the rolling force of the second stage is 4000 + 100 kN; the rough stone structure surface is formed on the second surface of the base steel after being cold rolled by the tempering mill.

A base steel with an abraded surface obtained by the method described in any one of claims 1 to 6, wherein, a first side of the base steel is an abraded surface, and a second side of the base steel is a non-abrasive surface; the abraded surface includes a soil texture in a dot-like concave-convex shape and a filiform line located on part of the soil texture; the distribution of the soil texture and the filiform line makes a roughness of the abraded surface of 0.50-0.80 um.

The abraded surface base steel according to claim 7, wherein, the base steel is an MR type base steel, an L type base steel or a D type base steel.

The base steel with the abraded surface according to claim 7, wherein, the non-abrasive surface is a bright surface, a fine stone texture surface, a rough stone texture surface, a silver surface, a silver rough surface or a matt surface.

A tin plate, wherein the tin plate is prepared by electroplating metal tin and then performing reflow on the surface of the base steel according to claim 7.

The tin plate according to claim 10, wherein when metal tin is electroplated, a concentration of divalent tin in a plating bath is 20-g/L, a concentration of methanesulfonic acid is 30-50 mL/L, a concentration of an antioxidant is 35-60 mL/L, and a concentration of an additive is 20-30 mL/L; in the plating process, a temperature of the plating bath is controlled to be 38-45°C, and a current density is controlled to be 22-28 A/mm? to be. 25

The tin plate according to claim 10, wherein when reflux is performed, a reflux set temperature is 260-290°C, a reflux feedback temperature is 255-295°C, and a reflux power ratio is 30%-50%.

The tin plate according to any one of claims 10 to 12, wherein, a first side of the base steel is a sanded surface, and a second side of the base steel is a fine stone structure surface.

A tin free steel (TFS) plate, wherein, the TFS plate is prepared by electroplating chromium metal and chromium oxide on the surface of the base steel according to claim 7.

The TFS plate according to claim 14, wherein when metal chromium is electroplated, a concentration of chromium anhydride in the plating bath is 140-160 g/L, and a concentration of ammonium philuoride is 3-4 g/L; in the plating process, the temperature of the plating bath is controlled to be between 36-40 °C, and the current density is controlled to be between 50-80 A/mm? to be; the concentration of chromium anhydride in a first receiver is controlled to be < 50 g/L, and the concentration of chromium anhydride in a second receiver is controlled to be < 40 g/L.

The TFS plate according to claim 14, wherein when chromium oxide is electroplated, the concentration of chromium anhydride in the plating bath is 60-70 g/L, the concentration of ammonium fluoride is 1-2 g/L, and a concentration of sodium hydroxide is between 8-10g/L; in the plating process, the temperature of the plating bath is controlled to be between 31-35 °C, the current density is controlled to be between 9-22 A/mm? to be, and a mass of an obtained chromium oxide layer is controlled to be between 8-15 g/m? to be.

The TFS plate according to any one of claims 14 to 16, wherein, a first side of the base steel is a sanded surface, and a second side of the base steel is a fine stone textured surface.

A constricted can, wherein, the constricted can is made from the tin plate of claim 13.

A constricted can, wherein, the constricted can is made from the TFS sheet of claim 17.

An easy open end, wherein, the easy open end is made from the tin plate of claim 13.