JP2004058090A - Steel strip for granular tin plating and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel strip for granular tin plating which gives an excellent adhesion between the steel strip and the granular tin, and its manufacturing method. <P>SOLUTION: The steel strip for granular tin plating is given an average steel surface roughness Ra<SB>C</SB>0.13 to 0.55μm in the right-angle direction (C direction) with the rolling direction and an average surface roughness Ra<SB>L</SB>0.18 to 0.55μm in the rolling direction (L direction). In a temper rolling process after cold rolling and annealing, dull rolls are used at a first stand of the temper rolling mill and smooth rolls with scratch texture in their circumferential direction are used at a second stand of the mill. The temper rolling mill applies 500kg/mm to 900kg/mm of linear load at the first stand and 300kg/mm to 500kg/mm at the second stand. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an original sheet used for a granular tin-plated steel sheet used for various foods, beverages, and other welding cans suitable for filling and storage, and a method for producing the same.
[0002]
[Prior art]
As a material for containers used for various foods, beverages, and the like, tin-free tin-plated tin-plated steel plates and tin-free steel plated with chrome are generally used.
In particular, tin-free steel is very high in demand and widely used because of its excellent properties such as cost and paint adhesion.
[0003]
This tin-free steel sheet has the disadvantage of poor weldability, and in order to solve this problem, the production of tin-free steel sheet is significantly improved by precipitating granular tin under the chromium plating layer. A method has been established. For example, Japanese Patent Application Laid-Open No. 2-282498 discloses plating conditions for a granular tin-plated steel sheet having excellent weldability and paint adhesion.
However, there is a problem that it is difficult to secure the adhesion between the steel sheet and the granular tin.
As a method for improving the adhesion in the granular tin plating treatment, for example, Japanese Patent Application Laid-Open No. Hei 4-247897 discloses a method in which a very small amount of a brightener is added to a plating bath to obtain flat granular tin, thereby obtaining a contact area with a steel sheet. However, there has been proposed a method of increasing the adhesion by increasing the adhesion, but it has not been possible to eliminate poor adhesion.
[0004]
[Problems to be solved by the invention]
The present invention solves the problems of the prior art as described above, and by setting the surface roughness of a granular plating steel sheet within a specific range, a granular tin plating steel sheet having excellent adhesion between a steel sheet and granular tin. And a method for manufacturing the same.
[0005]
[Means for Solving the Problems]
The present invention has been made as a result of intensive studies to solve the above-mentioned problems, and has an average roughness Ra _C , Ra _{L in a} direction perpendicular to the rolling direction (C direction) and a rolling direction (L direction) of the surface of the steel sheet. Is a specific range, to provide a granular tin-plated steel sheet having excellent adhesion between the steel sheet and the granular tin and a method for producing the same, and the gist thereof is as described in the claims. It is the following contents.
[0006]
(1) The average roughness Ra _C in the direction (C direction) perpendicular to the rolling direction of the steel sheet surface is 0.13 to 0.55 μm, and the average roughness Ra _L in the rolling direction (L direction) of the steel sheet surface. Is 0.18 to 0.55 μm.
(2) In the temper rolling step after cold rolling and annealing, a dull roll is used for the # 1 STD of the temper rolling mill, and a roll provided with a scratch in the circumferential direction of the smooth roll is used for the # 2 STD of the temper rolling mill. Used, and the line load of the # 1 STD of the temper rolling mill is 500 kg / mm to 900 kg / mm, and the line load of the # 2 STD of the temper rolling mill is 300 kg / mm to 500 kg / mm. The method for producing a granular tin-plated steel sheet according to (1).
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing the relationship between the surface roughness of the original plate before granular tin plating and the adhesion in the present invention.
In FIG. 1, the abscissa indicates the average roughness Ra _L in the rolling direction (L direction), and the ordinate indicates the number of coils in which poor adhesion of granular tin occurs.
As can be seen from FIG. 1, when the average roughness Ra _L in the L direction is less than 0.18 μm, a coil having poor adhesion was generated. However, when the average roughness Ra _{L in the} L direction was 0.18 μm or more, all the coils were granular. Tin adhesion was good.
Although the reason for this is not clear, if the average roughness Ra _{L in} the L direction is large, fine irregularities are formed in the L direction of the steel sheet, and granular tin enters the irregularities and is caught and becomes difficult to peel off. It is considered.
FIG. 2 is a schematic view of the surface of the steel sheet for granular tin plating in the present invention.
In FIG. 2, if there is unevenness in the rolling direction (L direction) of the steel sheet, it is considered that granular tin enters the recesses and becomes difficult to peel off, so that the adhesion in the L direction is improved.
[0008]
If the average roughness Ra _{L in the} L direction exceeds 0.55 μm, poor appearance of the plating surface occurs, so it is preferably 0.55 μm or less.
Here, the evaluation of the adhesion of the granular tin was evaluated by the amount of tin powder adhering to the sheet after pressing a sheet of paper against the surface of the tin-plated steel sheet, rubbing the sheet with a jig a certain number of times, and visually inspecting the sheet of paper. Adhesion was poor (x) when metallic luster was observed, and adhesion was good (O) when metallic luster was not observed.
On the other hand, if the surface roughness Ra _C in the direction perpendicular to the rolling direction (C direction) is less than 0.13 μm, the adhesion of granular tin decreases, and if it exceeds 0.55 μm, poor appearance of the plating surface occurs. , 0.13 to 0.55 μm.
[0009]
FIG. 3 is a diagram showing the relationship between the temper rolling conditions of the original sheet before the granular tin plating and the adhesion in the present invention.
In FIG. 3, the horizontal axis shows the linear load (kg / mm) at # 1 STD during temper rolling, and the vertical axis shows the linear load (kg / mm) at # 2 STD.
3 is a range surrounded by a frame in FIG. 3, a line load of 500 to 900 (kg / mm) in the # 1 STD during temper rolling and a range of 300 to 500 (kg / mm) in the # 2 STD. By adjusting the force balance, the roughness value in the rolling direction was adjusted, and the unevenness in the rolling direction was formed, whereby the adhesion of granular tin during plating was improved.
Increasing the line load during temper rolling increases the roughness of the steel sheet surface, but changes the surface appearance.
Further, if the line load during the temper rolling is reduced, the roughness of the steel sheet surface is reduced and the adhesion is reduced, so the above range was selected as the optimum range.
That is, the above-mentioned temper rolling conditions are in a range which does not deviate from the prevention of the stretcher strain and the securing of the glossy appearance which are the original purposes of the temper rolling.
[0010]
FIG. 4 is a diagram showing a configuration of a temper rolling mill used in the present invention.
In FIG. 4, the temper rolling mill includes two stands # 1STD and # 2STD.
The roll of # 1STD is a dull roll having a relatively large roughness, and has random irregularities in both the L and C directions. The roll roughness is preferably 0.8 to 2.8 μm.
[0011]
On the other hand, the roll of # 2STD is a roll provided with a scratch in the circumferential direction of a smooth roll having a relatively small roughness, and the roughness is preferably 0.2 to 0.7 μm.
Due to this scratch, the convex portion in the L direction of the steel plate is crushed, and irregularities are provided in the C direction.
[0012]
【Example】
When the cold-rolled and annealed steel sheet was subjected to temper rolling under the above-mentioned conditions and plated under the following plating conditions, the plating peeling rate, which had been about 20% in the past, became almost 0%, and the effect of the present invention was obtained. Was confirmed.
1) Tin plating conditions / basis weight: 250 mg / m2,
-Sn2 +: 2 to 30 g / L,
-Free acid concentration: 10 to 100 g / L,
・ Bath temperature: 45 ° C,
2) Electrolysis conditions and current density: 3 to 20 A / dm2,
3) Chrome plating conditions: CrO3: 100 g / L,
H2SO4: 1.2 g / L,
・ Bath temperature: 50 ° C,
-Current density: 50A / dm2
[0013]
【The invention's effect】
According to the present invention, the average roughness Ra C of the rolling direction and perpendicular direction of the steel sheet surface (C direction) and the rolling direction (L _direction), by a specific range of Ra _L, adhesion between the steel sheet and granular tin It is possible to provide an excellent granular tin-plated steel sheet.
In addition, by selecting a specific range of the temper rolling conditions, it is possible to provide a method for manufacturing a granular tin-plated steel sheet having excellent adhesion between the steel sheet and the granular tin, and thus has a remarkable industrially useful effect.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the surface roughness and the adhesion of an original plate before granular tin plating in the present invention.
FIG. 2 is a schematic view of the surface of a steel sheet for granular tin plating according to the present invention.
FIG. 3 is a diagram showing the relationship between temper rolling conditions and adhesion of an original sheet before granular tin plating in the present invention.
FIG. 4 is a diagram showing a configuration of a temper rolling mill used in the present invention.

Claims (2)

The average roughness Ra _C in the direction perpendicular to the rolling direction (C direction) of the steel sheet surface is 0.13 to 0.55 μm, and the average roughness Ra _L in the rolling direction (L direction) of the steel sheet surface is 0.1 to 0.5 μm. A granular tin-plated steel sheet having a thickness of 18 to 0.55 μm. In the temper rolling step after cold rolling and annealing, a dull roll is used for the # 1 STD of the temper rolling mill, and a roll provided with a scratch in the circumferential direction of the smooth roll is used for the # 2 STD of the temper rolling mill, In addition, the line load of the # 1 STD of the temper rolling mill is 500 kg / mm to 900 kg / mm, and the line load of the # 2 STD of the temper rolling mill is 300 kg / mm to 500 kg / mm. Item 2. The method for producing a granular tin-plated steel sheet according to Item 1.

Images