JPH0414169B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a steel plate for easy-open can lids with excellent can opening properties. (Prior Art) Easy-open cans allow cans to be opened without any tools such as a can opener, and are used for beer cans, carbonated beverage cans, food cans, fruit juice cans, and the like. Easy-open cans are manufactured using sheet steel in addition to aluminum. It is said that easy-open cans made of steel sheets are inferior to those made of aluminum, but studies are being conducted to improve the opening performance of easy-open cans made of steel sheets. For example, in Special Publication No. 58-30923, C is defined as a low carbon of less than 0.02%.
Cold-rolled steel plate with Si: 0.1% or less, Mn: 0.1-0.5%, oxygen 0.01% or less, and the sum of 1/2 carbon content and oxygen content is 0.020% or less, and the balance is iron and unavoidable impurities. A method of manufacturing a steel plate for easy-open can lids has been proposed in which the steel sheet is continuously annealed and then subjected to skin pass rolling at a reduction rate of 6 to 20% to improve can openability and score workability. Also, in JP-A No. 60-56052, C
0.0035% or less, Al is added to reduce solid solution N to reduce strain age hardening and prevent an increase in the strength of the score processed part, and further skin pass rolling at a reduction rate of 5% or more to increase the hardness to H _R 30T. A method for manufacturing a steel plate for easy-open can lids has been proposed, which has a hardness of 58 or higher and improves can opening performance. (Problems to be Solved by the Invention) Although the ease of opening steel plate cans has been improved by these methods, it is still not fully satisfactory and further study is required. That is the reality. The object of the present invention is to provide a steel plate for easy-open can lids that further improves can opening performance. (Means for Solving the Problems) The present inventors conducted studies to obtain a steel plate for easy-open can lids with excellent can opening properties. Up until now, efforts have been made to improve can openability by increasing the thickness of the remaining score, preventing an increase in the strength of the score processed part, and increasing the hardness, but experiments and research from a different perspective revealed that the thickness of the steel plate It has been found that this has a large effect on can opening performance, and when the plate thickness is made thinner (0.15 mm or more and less than 0.23 mm) compared to the conventional 0.23 mm or more, the pop value tear when opening an easy-open can is improved. It was found that as both values decreased, the bending resistance of the easy-open opening piece decreased, and the can opening performance was further improved. Furthermore, conventionally discussions have been based only on hardness, but if the yield point is 30Kg/mm ² or less and the tensile strength is 39Kg/mm ² or less, it is soft (equivalent to T-3 or less in terms of hardness). ,
It was found that the pop value further decreased. Furthermore, as a result of comparing the box annealing method and the continuous annealing method in the annealing process, it was found that the tear value when opening the can decreases even if the plate thickness and strength are the same when using the continuous annealing method. (Function) The present invention was made based on this knowledge, and will be explained in detail below. Low carbon steel slabs with various C contents are hot rolled and descaled, then cold rolled to reduce the plate thickness.
Cold-rolled sheets with various thicknesses between 0.12 mm and 0.26 mm were obtained, and then continuously annealed at 680°C for 1 minute or at 600°C.
The steel plate was box annealed for 2 hours, temper-rolled, and then tin-plated to produce a steel plate for easy-open can lids. Easy-open can lids were manufactured from these steel plates. Note that the score was carved with a residual thickness (score residual thickness) of 60 μm. These easy-open can lids were subjected to an opening test, and the results are shown in FIGS. 1 and 2. Figure 1 shows the results of an investigation into the effects of plate thickness and tensile strength on the pop value (maximum load at the start of opening). As recognized by this,
It can be seen that the influence of the plate thickness on the pop value is large; the thinner the plate, the lower the drop, and the lower the tensile strength, the greater the drop. In terms of plate thickness, the tensile strength is 39Kg/mm ² or less when the thickness is less than 0.23mm to 0.15mm or more, and the pop value is 1.5Kg.
This makes it very easy to open the can. Figure 2 shows the results of investigating the influence of plate thickness and tensile strength on the tear value (maximum load when tearing an open piece). Thin materials with a thickness of less than 0.15 mm to 0.15 mm or more and low tensile strength are smaller. For this reason, in the present invention, the thickness of the steel plate is set to 0.15 mm or more and less than 0.23 mm. If the plate thickness becomes too thin, the stress will be dispersed when the can is opened, and the stress concentration on the score-processed area will decrease, resulting in a sharp increase in the pop value. Also, since the Bekotsuki phenomenon occurs, the lower limit is
It is set to 0.15mm. On the other hand, if the plate thickness is too high, the rigidity will increase and the opening performance will deteriorate, so the thickness should be less than 0.22 mm. The preferred plate thickness range is 0.15 to 0.22 mm. In conventional steel plates for easy-open can lids, the remaining thickness of the score has to be made as thin as possible, or the steel plate can withstand processing to reduce the remaining thickness, or the strength of the part where the score has been processed can be increased. Research has been carried out to reduce the number of steel plates used, but the thickness of the steel plate has hardly been studied, and the thickness and openability of the steel plate itself were not known. As for the tensile strength, as mentioned above, a low tensile strength will lower the pop value and tear value, so it is 29Kg/mm ²
The following shall apply. By the way, even if the tensile strength is 39 Kg/mm ² or less, the yield point is higher than 30 Kg/mm ² because the pop value is large.
It must be less than Kg/mm ² . Preferred strength ranges are a tensile strength of 37 Kg/mm ² or less and a yield point of 30 Kg/mm ² or less. Here, the yield point of the present invention refers to the lower yield point. Note that the above tensile property values are managed for a soft material with a hardness of T-3 or less. Next, the manufacturing method of the present invention will be described. First, regarding the steel composition, C=0.0010 to 0.08%. The upper limit was determined from the viewpoint of stably manufacturing the soft material. Also, if it is less than 0.0010%, steel manufacturing costs will increase significantly. The preferred range is 0.0045 to 0.0045 in terms of production cost, production of clean steel, and stable softness.
It is 0.060%. Mn is at least 0.05% to prevent hot brittleness
is necessary, but if it exceeds 0.40% it will become hard.
Set at 0.05-0.40%. The preferred range is 0.35% or less. Both P and S have an impurity range of 0.030.
% is allowed. If this value is exceeded, riveting performance deteriorates. The preferred range of P is 0.015% or less. S is preferably 0.015% or less. Al is required in an amount of at least 0.005% for deoxidation and to reduce the amount of 0 in the steel to 0.0045% or less. Also
If it exceeds 0.100%, the surface properties of the steel plate will deteriorate and it will also have an adverse effect on corrosion resistance, so it should be set at 0.005 to 0.100%. 0 is from the point of view of riveting workability and corrosion resistance.
0.0045% or less. If N is included in large amounts, it will harden the steel.
Must be 0.0080% or less. The preferred range is 0.0035% or less. A slab made of the above components is hot rolled in a conventional manner, descaled and then cold rolled. At this time, if the hot rolling finishing temperature is less than 800°C, riveting workability deteriorates, so it is necessary to set it to 800°C or higher, but from the viewpoint of softening the steel sheet, it is preferably 870°C or higher. Also, the winding temperature is 500 for box annealing.
~750℃. Below 500℃, steel becomes hard;
When the temperature exceeds 750°C, carbides aggregate and become coarse, deteriorating riveting workability and corrosion resistance. In the case of continuous annealing, the winding temperature is 670 to 750°C. The reason for setting the upper and lower limits in this case is the same as in the case of box annealing. In cold rolling, the final product is rolled so that the plate thickness is 0.15 mm or more and less than 0.23 mm, but the cold rolling reduction rate does not need to be specified. Thereafter, recrystallization annealing at a temperature higher than the recrystallization temperature and lower than 800° C. is performed by box annealing or continuous annealing, and the effects of the present invention are further improved by using the continuous annealing method for the reasons described later. Then, it is subjected to temper rolling. In pressure adjustment, the tempering reduction rate is set so that the yield point of the steel plate is 30 Kg/mm ² or less and the tensile strength is 39 Kg/mm ² or less, but in order to soften the steel plate in the present invention, it should be 3.5% or less. is preferred.
A more preferable range is 3.0% or less. The product is then subjected to surface treatment using conventional methods. The present invention has been described above, but in the present invention, can closure performance is further improved by performing recrystallization annealing as continuous annealing, so continuous annealing is specified in the second invention. In other words, steel plates for easy-open can lids that are within the range specified by the present invention, have the same thickness, and have approximately the same strength are manufactured by box annealing and continuous annealing, and their openability is compared. found that the Theia value was reduced by about 5 to 10%. When manufacturing by continuous annealing, the component is C in order to stably maintain the strength below the upper limit specified in the present invention.
=0.0045-0.060%, P≦0.015%, N≦0.0035%
It is preferable that Further, in continuous annealing, after recrystallization treatment for 3 minutes or less in a temperature range above the recrystallization temperature and below 800°C, overaging treatment is performed at a temperature range of 300 to 450°C for 5 minutes or less. If continuous annealing is performed at over 800℃,
Furthermore, if the soaking time exceeds 3 minutes, the crystal grains become too coarse and the riveting processability is reduced. Further, the overaging treatment needs to be carried out at a temperature of 300° C. or more and 450° C. or less in order to soften the material and reduce the pop value. If the processing time becomes longer, the pop value reduction effect will be weakened, so the processing time is set to 5 minutes or less. Note that the cooling rate after recrystallization is preferably 10° C./sec or more.
In addition, in order to stably secure the yield point of 30 Kg/mm ² or less, the thermal reduction reduction ratio is preferably 2.0% or less than 3.0%. (Example) A slab having the components shown in Table 1 is manufactured by continuous casting, hot rolled to a thickness of 2.0 to 3.0 mm under the conditions shown in Table 1, descaled, cold rolled, annealed, and pressure controlled to form a steel plate. did. Next, tin plating was applied using a regular electric plating line. After painting the obtained steel plate, the score remaining thickness is 65μ
We manufactured a partially open type easy-open can lid for M. In the case of continuous annealing, the annealing rate is 10°C/sec after heating to (670°C to 710°C) x (40 to 50) seconds.
After cooling at the above cooling speed (350-400℃) x (1-2 minutes)
The aging process was carried out. In the case of box annealing, it was performed for (630 to 660°C) x (2 to 4) hours. Table 1 also shows the relationship between product board thickness, strength, and can opening force. Steel plate 1 has a thick plate thickness, and steel plate 5 has a high pressure regulation rate, so it has a high yield point, and steel plate 7 has high C, Mn, and pressure regulation ratio, so it has a high yield point and tensile strength. All of these steel plates have higher can-opening force than Invention Steels 2, 3, 4, and 6. On the other hand, the steel of the present invention shows good values in both pop and tear values, without any difference compared to aluminum easy-open can lid (EOE) (pop = 1.41 kgf, tear = 2.72 kgf). In addition, the steel plates 2, 4, and 6 of the present invention have almost the same thickness and strength, but the steel plates 2 and 6 produced by continuous annealing have a tear value compared to steel plate 4 produced by box annealing. is good as it decreases.

【table】

[Table] ○ indicates the present invention (effects of the invention) As described above, the present invention is a steel plate for easy-open cans that has excellent can-opening properties and is easy to open with low force, especially for non-internal pressure cans. Suitable for easy-open can lids.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the results of an investigation into the influence of plate thickness and tensile strength on pop value. FIG. 2 is a diagram showing the results of an investigation into the influence of plate thickness and tensile strength on theia value.

Claims (1)

[Claims] 1% by weight, C=0.0010~0.08%, Mn=0.05~
0.40%, P≦0.015%, S≦0.015%, Al=0.005~
0.100%, O≦0.0045%, N≦0.0080%, with the balance consisting of iron and unavoidable impurities.
Hot-rolled at a temperature of 870℃ or higher, then rolled at a temperature of 500 to 750℃, descaled, and then cold-rolled to a temperature higher than the recrystallization temperature.
Box annealing and temper rolling are performed at 800℃ or less, and the resulting steel plate is thin with a thickness of 0.15 mm or more and less than 0.23 mm, has a yield point of 30 Kgf/mm ² or less, and has a tensile strength of 39 Kg.
A method for producing a steel plate for easy-open can lids, characterized by being soft with f/mm ² or less. 2 Weight%, C=0.0010~0.06%, Mn=0.05~
0.40%, P≦0.015%, S≦0.015%, Al=0.005~
A slab consisting of 0.100%, O≦0.0045%, N≦0.0035%, the balance being iron and unavoidable impurities, is hot rolled at a temperature of 870℃ or higher, then rolled up in the range of 670 to 750℃, descaled, and then cold rolled. , recrystallization temperature over 800℃
A steel plate obtained by continuous annealing consisting of heating for 3 minutes or less in the following temperature range and overaging treatment for 5 minutes or less in the temperature range of 300 to 450℃, and temper rolling with a rolling reduction of 3% or less. It is thin with a thickness of 0.15 mm or more and less than 0.23 mm, a yield point of 30 Kgf/mm ² or less, and a tensile strength of 39 Kg.
A method for producing a steel plate for easy-open can lids, characterized by being soft with f/mm ² or less.