JPS6354797B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing tinplate for welded cans, which has excellent adhesion of the secondary plating layer to the alloy layer, and is suitable for welding tinplates with a small amount of tin and suitable welding current for tinplates for welded cans such as canned goods. The object of the present invention is to provide a method for producing tin plate for welded coated cans, which can sufficiently expand the range of welding, and therefore has good industrial welding workability and a low defect rate. It has long been widely practiced to produce welded cans for canned food using tin-plated steel sheets (tinplate), but recently, thinned steel sheets with a reduced amount of tin plating (Lightly Tinplate) have been widely used.
The use of coated steel sheets (hereinafter referred to as LTS) for such purposes is becoming practical.
In other words, conventional tinplate (tinning amount is approximately 2.8g/
It uses tin plated wood with a reduced amount of tin plating of 1 g/m ² or less compared to 1 g/m 2 or less, and the cost is low because the amount of ^expensive tin consumed is significantly reduced. The desired welded can for painting can be obtained. However, when manufacturing welded painted cans using such LTS materials, it is clear that the appropriate welding current range must be extremely narrow or non-existent. There is a critical current value (hereinafter referred to as IB) that does not cause peeling (hereinafter referred to as IB), and on the other hand, there is a critical current value that does not cause flaking (hereinafter referred to as IB). Limiting current value (hereinafter referred to as IA)
is also important, and preferably greater than IB and less than IA. In other words, the difference between the expulsion generation limit current value (IA) and the peeling limit current value (IB) (IA - IB ampere)
is the appropriate welding current range, and the larger the value of IA-IB, the more stable and high-quality welding can be performed.However, with LTS materials such as those mentioned above, residual paint after baking in the can manufacturing process Because the amount of unalloyed tin remaining in the alloy is extremely small or completely absent, the value of IA-IB must be extremely small, and in some cases it often becomes a negative value. However, in reality, welding is often performed at the expense of one of the above relationships. In other words, the appropriate welding current range (IA-IB) is industrially preferred to be 100 amperes or more under the conditions of the copper wire seam welding method at a frequency of 400 Hz.
In the case of LTS materials, it is extremely common for the temperature to drop below this level after baking the paint, and of course strict control of welding conditions is required.Moreover, current conditions etc. fluctuate greatly in actual factories, especially when the IA
- If IB is negative, welding must be performed at the expense of either peelability or splintering. The present invention was devised after repeated studies in view of the above-mentioned circumstances. (1) The surface of a steel plate is subjected to primary tin plating and alloyed to form crystals called FexSny (xy). Alternatively, an alloy layer with a tin content of 0.05 to 0.9 g/m ² including crystals is formed by adding elements in the steel other than Fe, and then a light reduction treatment is performed, and the final pass is performed with the steel plate side as the cathode. After electrolytic cleaning, electrolytic pickling, and secondary tin plating, a tin layer of 0.1 to 0.9 g/m ² is formed, and even if reflow treatment, paint baking, or both treatments are performed, alloying will not occur. 0.08g/ ^m2 of unused tin
A method for producing tinplate for welded cans, characterized in that the tinplate for welded cans is made to remain as described above. (2) Primary tin plating is applied to the surface of the steel sheet, alloying treatment is performed, and the tin content is 0.05 to 0.9, including crystals called FexSny (xy) or crystals obtained by adding elements in the steel other than Fe. An alloy layer of g/m ² is formed, then light reduction treatment is performed, the final pass is electrolytic cleaning with the steel plate side as the cathode, electrolytic pickling, and then secondary tin plating with 0.1 to 0.9 Form a tin layer of 170 g/m ²
Copper wire seam welding method at a frequency of 400 Hz, with paint baking at ~230°C for 10 minutes or more, in the presence of at least 0.08 g/ ^m2 of unalloyed tin, and with a suitable welding current range of 100 amperes or more. A method for producing tinplate for welded cans, characterized by adopting the following. It is related to. The manufacturing method for obtaining the above-mentioned welded tin plate for cans is a two-stage plating method, that is, the first tin plating is alloyed, followed by light pressure treatment, and then electrolytic pickling. which can be suitably obtained by secondary tinning, the first
In the next plating, the amount of tin plating necessary to generate the alloy layer as described above is performed, and then this is alloyed, and then a light reduction treatment such as a skin pass is performed, and the final pass is performed with the steel plate side as the cathode. Electrolytic cleaning is carried out, followed by electrolytic pickling, followed by secondary tin plating in an amount corresponding to the above-mentioned tin layer by electroplating. The above-mentioned alloying treatment after the primary tin plating can be appropriately carried out using a continuous annealing line, that is, chemical plating, vapor phase plating,
Crystalline alloying can also be appropriately obtained by applying a predetermined amount of primary tin plating by electroplating or the like and then performing continuous annealing, but of course, such continuous annealing is It goes without saying that alloying treatment may be performed separately. In addition, by adopting a temperature of 496℃ or higher for this alloying treatment, FeSn or
It has been confirmed that alloys such as FeSn + Fe ₃ SnC, which have crystals in which Fe has an atomic ratio of at least the same as or higher than Sn, can be obtained, and such alloy layers are extremely dense and flat in general. You can get the surface. The alloyed product as described above is then subjected to a light reduction such as a skin pass, and then a second tin plating is applied in an amount commensurate with the tin layer described above, resulting in excellent formability as a can body. Although obtained as a product, electrolytic cleaning and electrolytic pickling between the alloying treatment and the secondary tinning are essential for forming a stable tin layer. That is, when electrolytic pickling is also used, a cleaning solution containing an alkali such as sodium hydroxide is used for electrolytic cleaning, and it is carried out under appropriately heated conditions, thereby removing impurities on the surface of the alloy layer formed. . The electrolytic pickling performed after this electrolytic cleaning uses a sulfuric acid solution of an appropriate concentration, but when used together in this way, it is necessary to perform electrolytic cleaning immediately before electrolytic pickling, and the final electrolytic cleaning is It is necessary to set the electrolytic conditions such that the path is the cathode on the steel plate side, and the tinned layer formed by secondary tinning after these treatments is strong and stable, and the alloyed layer It has been confirmed that this is formed on the surface, and a preferable tin plate for welded cans can be obtained. Although no clear conclusion has been reached as to why defects occur in the adhesion of secondary tin plating when the final pass is electrolytic cleaning with the steel plate side as the anode, the findings obtained through experiments are as follows: It has been confirmed that one of the reasons is that a fine oxide layer, hydroxide layer, etc. formed on the surface of the alloy layer hinders the adhesion of the plating layer afterwards. The above-mentioned secondary tin plating is preferably formed by electroplating, and in any case, the secondary tin plating as described above can be used as is (no reflow). ), but it may also be manufactured by reflow processing within ETL. As mentioned above, the alloying treatment after the first plating alloys the entire amount of plated tin, and it is possible to easily form an alloy layer with a precisely specified amount and a flat surface. Therefore, the interface with the tin layer in the subsequent secondary plating is also substantially flat, and in this way, the desired corrosion resistance and weldability can be achieved with a relatively small amount of alloy layer and tin layer. We can be satisfied together.
When the alloyed material undergoes skin pass or other treatment after the first plating, some cracks occur in the crystal alloyed layer, and the second plating tin layer enters into these cracks. However, by undergoing the above-mentioned reflow treatment after such secondary plating, the tin mainly penetrates into the alloy layer and is alloyed in the portion of the tin layer close to the iron base, resulting in a barrier effect. Forms an excellent alloy layer. However, this kind of tin plate for cans is generally subjected to a paint baking process when producing a concrete product (can manufacturing), and even with such baking, the above-mentioned reflow process is not necessary. A similar situation is formed. In any case, the amount of tin alloyed by reflow treatment or baking is small compared to conventional LTS, and the boundary between the alloy layer and the tin layer is ensured to be substantially flat. The amount of alloy layer should be 0.05g/in order to effectively obtain a barrier effect that prevents the bare iron from being exposed.
m ² is the minimum, and the method according to the present invention has an appropriate barrier effect if it is 0.05 g/m ² or more by forming an alloyed layer on the iron base surface in a dense and uniform coating state as described above. can be obtained. The upper limit of this alloy layer is 0.9 g/ ^m2 , and forming an alloy layer in excess of this limit not only increases the consumption of expensive tin but also causes cracks during various processing. Become. Furthermore, regarding the pure tin layer formed on such an alloy layer, the lower limit is 0.1 g/m ² in order to maintain unalloyed tin of 0.08 g/m ² or more after baking the paint.
If the amount of unalloyed tin after painting baking (170 to 230°C, 10 minutes or more) is less than 0.08 g/m ² , effective welding properties cannot be ensured. The upper limit of the tin layer is
0.9 g/m ² , and even if a pure tin layer exceeding this limit is formed, it is formed with a substantially flat boundary surface as described above.Among the products of the present invention, which particularly improves weldability, etc. This goes against the essence of the present invention, which aims to reduce the amount of tin consumed. Specific examples according to the present invention will be described below along with comparative examples. A low carbon steel sheet that was hot rolled, pickled, and then cold rolled to a thickness of 0.22 mm was washed with alkali and then 0.28 g/m ² ,
Electro-tinning of 0.22g/m ² and 0.09g/m ² was performed, and these were continuously annealed at 650℃ for 20 seconds for soaking, which also served as alloying, and then the elongation rate was determined.
1.0% skin pass containing 60% sodium hydroxide (NaOH) at a concentration of 30g/80
Electrolytic cleaning treatment was carried out under the conditions of repeated energization for 0.6 seconds at a current density of 10 A/dm ² in an alkaline cleaning solution at ℃, and after this electrolytic cleaning treatment was performed in a sulfuric acid solution with a concentration of 30 g/dm 2 at a current density of 10 A/dm ² at a current density of 0.6 s. A second cathodic pickling treatment was performed. Note that the electrolytic cleaning was performed under conditions in which the final pass was on the steel plate side as a cathode. It was also manufactured for comparison under conditions where the final pass was the anode. For those that have been subjected to alloying treatment after primary tin plating as described above, and then electrolytically cleaned and electrolytically pickled.
The second of 0.49g/m ² , 0.35g/m ² and 0.38g/m ²
The thus obtained products were subjected to reflow treatment at 250°C and those not treated, respectively, and then chemical treatment,
It was made into a product by electrostatic oil application. That is, the material of the present invention (hereinafter referred to as the product obtained by the method of the present invention) is a material that has been subjected to reflow treatment with a primary tin plating amount of 0.28 g/m ² and a secondary tin plating amount of 0.49 g/m ² . Same) I, and the material that does not reflow is the material of the present invention, and the amount of primary tin plating is
The material of the present invention has a secondary tin plating amount of 0.22 g/m ² and a secondary tin plating amount of 0.35 g/m ² and has been subjected to reflow treatment, and the material that has not been reflowed is the present invention material. The amount of secondary tin plating is 0.09g/ ^m2 .
The material subjected to reflow treatment at 0.38 g/m ² was designated as the material of the present invention, and the material that was not reflowed was designated as the material of the present invention. In addition, the amount of primary tin plating is 0.35 g/m ² and the amount of secondary tin plating is 0.16 g/m ² , and the material subjected to reflow treatment is referred to as the material of the present invention, and the material without reflow treatment is referred to as the material of the present invention. did. In addition, these inventive materials were plated with tin of about 0.8 g/m ² and 0.5 g/m ² as conventional LTS materials, and the LTS materials with and without reflow treatment were plated in the same manner as above. - #25 tin wood was also prepared as a comparative example. The materials of the present invention and the comparative materials were then subjected to dry firing for 40 minutes at a furnace temperature of 200°C. In other words, this dry baking is equivalent to baking after painting, and when baking paint on this type of can stock, the paint on the inner and outer surfaces of the can body is different, and the specific type of paint chosen also varies. Although it is natural that the baking temperature or time employed will differ, in the present invention, the determination is typically made using the heat treatment conditions described above at 200°C for 40 minutes, and such determination It goes without saying that the results can be determined by converting the results appropriately depending on the conditions where the baking temperature or time varies as described above. However, the material of the present invention obtained as described above
Using LTS and #25 tin as materials, 100 welded cans each were manufactured using a copper wire seam welding machine with a frequency of 400 Hz and an overlap width of 0.4 mm. In other words, the appropriate welding current range for the material obtained as described above, the iron elution amount for evaluating the barrier properties of the alloy layer, and the ATC (Alloy-Tin-
The test values (both before dry firing) are summarized in Table 1 below.

【table】

[Table] In other words, even though the amount of tin plated on the materials of the present invention is extremely small at 0.5 to 0.8 g/m ² per side, the appropriate welding current range for all of them is 100 A or more, and welding is successful. As mentioned above, even if it is narrower than 825A of #25 tin, if it is 100A or more, it can be welded with industrially good workability. It is clear that this material has excellent weldability, considering the amount of tin used, compared to the comparative LTS material which has a weldability of around 20A or a negative value.
In addition, the iron elution amount under conditions where the alloy layer is exposed is about 1 mg/cm ² ·20 hr or less, which is 1 mg/cm ² · for all comparative materials including #25 tin wood.
All have excellent barrier properties over 20 hours,
It was confirmed that the ATC value was also good. Table 2 shows the materials of the present invention in Table 1,
, and a comparison material in which electrolytic cleaning was performed with the steel plate side as the "anode" in the final pass prior to secondary tinning (other conditions were the invention material,
, , ) are compared with respect to the adhesion of the tinned layer. In order to investigate whether the second tinned layer was firmly attached to the alloy layer, a bending test (0T bending) was performed on the test material in an unpainted state after manufacture. The outer part of the bent part was peeled off using cellophane tape, and the exposed state of the alloy layer was then observed using a scanning electron microscope to determine the adhesion of the tinned layer on the alloy layer. were evaluated for the present invention material and the comparative material. Evaluation was performed on a five-point scale.

【table】

[Table] Regarding the adhesion state of the tin plating layer of the above-mentioned example, cuts were made in a checkerboard pattern at 1 mm intervals, and after Erikuren processing was applied to this, a peel test was performed using Nichiban cello tape.The results are as follows. All products manufactured by carrying out both electrolytic cleaning and electrolytic pickling before secondary tin plating have extremely stable and strong tin plating adhesion with an average peeling rate of less than 1% over 20 samples. This was confirmed. On the other hand, those that underwent only electrolytic pickling are the same.
The peeling rate was less than 2% on average for 20 samples, and the adhesion was still sufficient. Furthermore, even if electrolytic cleaning is performed, if the final pass is on the steel plate side as the anode, the peeling rate may be around 50%, resulting in a tin-plated adhesion state that is higher than when both electrolytic cleaning and electrolytic pickling are not performed. has a tendency to deteriorate. When the method of the present invention as explained above is used, it is possible to secure a sufficiently expanded appropriate welding current range for tin plate with a significantly small amount of tin, to obtain a desirable welded can with excellent industrial workability, and to prevent defects. This invention aims to manufacture welded coated cans with a low rate of production, and has good iron elution resistance and other properties, and is industrially highly effective.

Claims (1)

[Scope of Claims] 1 The steel plate surface is subjected to primary tin plating and alloyed, and the tin content includes crystals called FexSny (xy) or crystals obtained by adding elements in steel other than Fe to this crystal. An alloy layer of 0.05 to 0.9 g/m ² is formed as an alloy layer, followed by light reduction treatment, a final pass of electrolytic cleaning with the steel plate side as the cathode, electrolytic pickling, and then secondary tin plating. as 0.1~0.9
A welding coating characterized by forming a tin layer of 0.08 g/m ² or ^more unalloyed even after reflow treatment, paint baking, or both. Manufacturing method for tinplate for cans. 2. Primary tin plating is applied to the surface of the steel sheet, alloying treatment is performed, and the tin content is 0.05 to 0.9 g / An alloy layer of m ² is formed, then a light reduction treatment is performed, and the final pass is electrolytic cleaning with the steel plate side as the cathode, electrolytic pickling, and then secondary tin plating with a thickness of 0.1 to 0.9
Form a tin layer of 1.5 g/m ² and bake the paint at 170-230°C for 10 minutes or more, and in the presence of at least 0.08 g/m ² of unalloyed tin, the appropriate welding current range is 100 amperes. A method for manufacturing tinplate for welded painted cans, characterized by adopting a copper wire seam welding method with a frequency of 400Hz as described above.