JPS6032707B2 - Steel plate for easy open lid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel plate for easy-open lids that has excellent can opening properties.

BACKGROUND ART In recent years, easy-open lids, which can be opened without the use of tools such as can openers or bottle openers, have come into widespread use as can lids for beer, carbonated drinks, fruit juice drinks, and the like. As materials for this type of easy-open lid, steel plates are used for the contents, which have problems in terms of corrosion resistance, but aluminum is generally used. Easy-open lids made of aluminum can be opened more easily than easy-open lids made of steel plates, but in terms of cost, they are considerably more expensive than the easy-open lids made of steel plates. Development is strongly desired. It has been empirically known that the ease of opening an easy-open lid, that is, the can opening performance, can be improved by increasing the depth of the score engraved on the lid and reducing the remaining thickness.

However, if this score residual thickness is made too thin,
Cracks occur and penetrate to the surface opposite to the scored surface (hereinafter referred to as the back surface), causing leakage of contents. Therefore, in order to manufacture an easy-open lid with good opening performance, it is necessary to prevent cracks from penetrating all the way to the back, and to prevent transportation and
It is necessary to make the remaining thickness of the score as thin as possible without damaging the diamond during handling such as storage. The present invention is based on the above-mentioned circumstances, and aims to obtain a steel plate with a thin limit score remaining thickness that has excellent score workability and can be opened by punching, cutting, and opening force. As a result of repeated experiments and research, we have provided a steel plate with extremely good score workability, which forms three layers with greatly different grain sizes in the thickness direction, as shown in Figures 1 and 2. It is.

The reason why the steel plate of the present invention allows the critical score residual thickness to be significantly thinner than the conventional steel plate for easy-open lids is presumed as follows.

In other words, the steel sheet of the present invention has three layers with significantly different crystal grain sizes, that is, the center layer is coarse grained and the surface layer is fine grained, or the center layer is pongee grained and the surface layer is coarse grained. There is.

Here, the larger the grain size number (represents the size of crystal grains in the steel structure, according to JIS G 0552), the smaller the average size of the grains. For example, if the grain size number increases by 1, the unit area The number of crystal grains per unit is doubled, that is, the size of the crystal grains becomes smaller. On the other hand, the structure with a smaller grain size number, that is, the structure with larger grains, has a lower deformation resistance to processing. Therefore, when score processing is applied to the steel sheet of the present invention, the layer of the structure with a smaller grain size number, which has a lower deformation resistance, is deformed first. However, after the deformation resistance of this layer becomes equal to the deformation resistance of the layer with a structure with a large grain size number due to work hardening, the layer with a structure with a large grain size number is considered to be deformed by further processing. . Therefore, compared to the case of a single structure, even if the same amount of score processing is applied, the layer of the structure with a large grain size number of the steel sheet of the present invention has a small amount of deformation, and even if the layer of the structure with a small grain size number has a crack. Even if cracks occur, cracks are less likely to occur in layers with a structure with a large grain size number.
Cracks occur in the layer of the structure with a large grain size number,
Cracks penetrate through the plate when a layer with a structure with a large grain size number is processed beyond the limit processing amount. Therefore, it is thought that the critical score residual thickness of a steel plate having two or more layers of structure with greatly different grain sizes is thinner than that of a single coarse crystal structure or a single pongee grain structure. Among the multiple layers of two or more layers, steel plates with four or more layers have a complicated manufacturing process and are not economical, and two-layer steel plates do not have sufficient score workability for reasons that are unclear. , the steel sheet having the three-layer structure of the present invention is the most excellent.

The reasons for limiting the components, crystal grain size, etc. will be explained below. Since C deteriorates corrosion resistance and riveting workability when increased, the upper limit was set at 0.13%. Also, if it is less than 0.02%, the strength as a lid will be insufficient, so the lower limit should be set to 0.
．． 02%. Mn is added to prevent hot embrittlement of the steel plate due to S present in steel as an unavoidable impurity, and a lower limit was set from this point of view. Further, if it exceeds 0.7%, ductility decreases and rivet formability deteriorates, so the upper limit was set at 0.7%. AI is added for the purpose of deoxidizing molten steel, but if it is not added in an amount of 0.01% or more, nonmetallic inclusions will increase the force P and reduce workability, so the lower limit was set at 0.01%. Furthermore, if 0.1% or more is added, the surface quality will deteriorate due to alumina clusters, so the upper limit was set at 0.1%. Next, the crystal structure is distinguished by the grain size number: 8.5 or more is fine grain structure, and less than &5 is coarse grain structure, and the difference between the structure grain size of the pongee grain structure layer and the structure grain size of the coarse grain structure layer. The reason why is set to 2 or more in grain size number will be explained.

Of the three layers composed of the coarse grain structure layer and the coarse grain structure layer,
The coarse grain structure layer is formed by coarsening the fine grain structure. The grain size of the pongee grain structure layer is easy to adjust, but the grain size of the coarse grain structure layer formed by coarsening the pongee grain structure is difficult to control when the grain size number is 8.5 or higher, and due to manufacturing difficulties. The particle size number was set to be less than 8.5. The coarse grain structure layer causes roughness during processing, but in order to suppress the roughness, the grain size number of the fine grain structure layer is set to 8.5 or more.
In addition, the reason why the difference between the grain size number of the phase grain structure layer and the grain size number of the pongee grain structure layer is set to 2 or more is that if it is less than 2, the effect of improving the critical score residual thickness, which is the objective of the present invention, will be 4. . The thickness of each layer is determined by determining the thickness of the center layer, and the thickness of the center layer is limited to 30 to 90% of the board thickness.
If the thickness of the center layer is outside this range, even if there are 3 layers, 1
This is because sufficient improvement has not been made compared to the critical score residual thickness in the case of layers. In addition, as an aspect of the three layers, pongee grain structure layer (surface layer) - coarse grain structure layer (center layer) - pongee grain structure layer (
surface layer), coarse grain structure layer (surface layer) - fine grain structure layer (center layer)
- There is a hammered grain structure layer (surface layer), but the former two layers of pongee grain structure and the latter two parent grain structure layers each have their structure grain size,
The layer thicknesses are substantially equivalent. Here, the photographs shown in FIGS. 1 and 2 will be explained.

Figure 1 is an enlarged cross-sectional photograph of a steel plate that has a three-layer structure with different grain sizes in the plate thickness direction, with the surface layer having a pongee grain structure and the center having a hammered grain structure, where 3 is the structure with a large grain size number. layer of, 4
The grain size number is small and the structure is layered.

Figure 2 is an enlarged cross-sectional photograph of a steel plate that has a three-layer structure with different grain sizes in the plate thickness direction, with the surface layer having a coarse-grain structure and the center having Hosokojuku Toori, where 5 is the grain size number. large tissue layers,
6 is a layer with a structure having a small grain size number.

Now, the steel plate of the present invention as described above can be used as a steel plate or subjected to surface treatments such as tin plating, chrome plating, phosphate treatment, chromic acid treatment, etc., and is coated with paint as necessary to form an easy-open lid. Used as industrial steel plate.

The effects of embodiments of the present invention will be described below.

Among the steel plates shown in Table 1, A to E are steel plates of the present invention,
G and H' are steel plates used as comparison materials.

Component composition: C: 0.05%, Mn: 0.33%, AI:
For low carbon steel with the balance being 0.056% Fe and unavoidable impurities, after cold rolling to a thickness of 0.235 bars for A, B, C, G, and 0.260 bars for D, E, The following treatments were performed. A, B, and C are mackerel hammered continuously between 2 sands with a side 000, D and E are box-type chicks that were trained at 670℃ for 15 hours, and A and C were trained with an elongation rate of 1.5%. B was subjected to rough rolling with an elongation rate of 0.6%, and D and E were subjected to cross-rolling with a 10% elongation. After that, A, B, and D were subjected to rolling at 630°C for 6 hours. Perform box type shozu, C and E are 720
At oo, I performed a series of gun blunts between 6 different styles. G is a steel plate used for ordinary easy-open lids, and is subjected to continuous tempering between two top sands at a total temperature of 0°C. After continuous annealing between two holes at 680°C in H', temper rolling was performed with an elongation rate of 1.5%, and then box-shaped hammering was performed at 690°C for 1 hour. After applying the treatment as described above, A, B, C, and Day are subjected to temper rolling with an elongation rate of 1%, and ○, E, and G are subjected to temper rolling with an elongation rate of 1.5%, and the final thickness is 0.23. It was made into a sail and then tin-plated using Ferrostan grade. Table 1 The steel plates produced in this manner were subjected to score processing at various depths, and the critical score residual thickness was measured.

Using a penetrating deep scratching agent, it was checked whether the cracks penetrated to the back side of the score processing, and the minimum remaining thickness at which the cracks did not penetrate to the back side was defined as the critical score remaining thickness of the steel plate. For evaluation of can openability, the opening force was measured as a score remaining thickness 15 degrees thicker than the critical score remaining thickness, taking into account the variation in the score remaining thickness that must be expected in terms of lid making technology.
As shown in Table 1, the steel plates A to E of the present invention have a thinner critical score residual thickness than the steel plate G, which is normally used for easy-open lids, and the steel plate with coarse grains on the entire surface. As is clear from the measurement results, it is superior to the steel plate normally used for easy-open lids. The fall strength was measured by wrapping an easy-open lid around a can filled with contents, dropping the can with the easy-open lid facing downward, and measuring the maximum height at which the score part would not break.
All of the steel plates had a thickness of 1 m or more. Furthermore, no cracks were observed in the easy-open lid after the drop test. Therefore, it is considered that accidents such as damage to the lid during normal handling such as storage and transportation will not occur.
As shown in the examples above, it can be seen that the steel plate of the present invention has excellent characteristics as a steel plate for easy-open lids.

[Brief explanation of the drawing]

The drawings are enlarged cross-sectional photographs showing embodiments of the present invention.
The figure shows an enlarged cross-sectional photograph of a steel plate that has a three-layer structure with different grain sizes in the thickness direction, with the surface layer having a fine-grain structure and the center having a coarse-grain structure. Figure 2 shows a steel plate with different grain sizes in the thickness direction. This is an enlarged cross-sectional photograph of a steel plate having a three-layer structure, with a coarse grain structure in the surface layer and a pongee grain structure in the center. 3, 5... Fine grain structure, 4, 6... Kasu grain structure. Figure 1 Figure 2

Claims (1)

[Claims] 1 In the steel plate for easy open lids subjected to score processing, its composition is carbon 0.02 to 0.13%, Mn0
．． 1~0.7%, Al0.01~0.12%, balance F
e and unavoidable impurities, grain size number (JIS
According to G0522), the fine grain structure (grain size number 8.5 or more) and coarse grain structure (grain size number less than 8.5) are divided in the plate thickness direction from fine grain structure (surface layer) to coarse grain structure (center layer: thickness of 30 to 90% of the plate thickness) - fine grain structure (surface layer), or coarse grain structure (surface layer) - fine grain structure (center layer: 30 to 90% of the plate thickness)
90% thickness) - A steel plate for an easy-open lid, which forms three layers of a coarse-grained structure (surface layer) and has a difference in grain size number between the fine-grained structure and the coarse-grained structure of 2 or more.