JPS62103341A - Steel sheet for easily opening end excellent in can-openability and its production - Google Patents

Abstract

PURPOSE:To improve can-openability by incorporating prescribed percentage of B and N to a dead Al killed steel and by dispersing BN precipitates into steel. CONSTITUTION:A steel consisting of, by weight, <=0.005% C, 0.08-0.4% Mn, 0.005-0.08% Al (expressed in terms of acid-soluble Al), <=0.015% N, -0.001-0.0025% (B-0.7N), <0.012% P, and the balance Fe is refined. This steel is hot-rolled, finished at >=840 deg.C, and wound up at >=550 deg.C, followed by cold rolling. Then the cold-rolled steel sheet is subjected to recrystallization annealing and to temper rolling at a draft of <=5%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an easy open-end steel plate with excellent can opening properties and a manufacturing method thereof.

(Prior Art) Recently, easy-open cans that can be easily opened by hand have become increasingly popular for beer, carbonated drinks, juices, etc. in place of glass containers.

Both aluminum and tin are used as materials for easy-open cans, but when the contents of modern sports drinks, which contain all salt, are packed in all-aluminum cans, chlorine ions form an oxide film on the surface. Tinplate is used for these beverage cans because electrochemical reactions cause corrosion and pitting. However, tinplate is generally said to have poorer opening properties than aluminum.

Therefore, several techniques have been proposed for the purpose of producing steel plates for easy open ends with excellent can opening properties. For example, in Japanese Patent Publication No. 58-30932, after fully continuous annealing of low carbon M-killed steel with C: less than 0.02%,
A method for producing a steel sheet for easy-open cans is disclosed, which is characterized by skin and +ss rolling at a rate of 20%.

According to this, due to the synergistic effect of continuous annealing and skin pass rolling, the force required for tearing the scored part is reduced, the can opening property is good, and the scoring processability is also excellent, which is a considerable improvement.

By the way, can openability can be classified in detail as the force required to first destroy a portion of the score by placing your finger on the outside of the ring-shaped tab attached to the lid of an easy-open can. It can be divided into the force that continuously tears apart the remaining part of the score (called the tear value) by inserting your finger into the tab hole and holding it still. The above-cited Japanese Patent Publication No. 58-30932 is particularly effective means for completely reducing the tear value by temper rolling under high pressure.

(Problem that the invention attempts to solve) The present invention has been studied to further improve can opening performance.

As a result, if the composition of ultra-low carbon M-killed steel is completely B-contained, B nitrides are formed, dispersed and precipitated in the steel, and a skin pass is applied after annealing at a low reduction rate of 5 mm or less, hops It is our hope that an easy open-end steel plate with low value and tier value and excellent overall opening performance will be manufactured.

(Means for solving the problem) The present invention was made based on this knowledge, and its gist is: c: o, oos% or less, Mn: 0.08% or more
．． 40% or less, A+! : 0.005% or more and 0.08% or less as acid-soluble AA, N: 0.015% or less, B: 6"
-0,0010% or more 0.0025 as 71N (%)
P: less than 0.012%, the balance being iron and unavoidable impurities, which is a steel plate for easy open ends with excellent can opening properties, and furthermore, the steel is hot rolled to a temperature of 840C or higher, and the steel is finished at a temperature of 550C or higher. A method for manufacturing an easy open-end steel plate with excellent can-openability, characterized by cold rolling after rolling, recrystallization annealing, and skin pass rolling at a rolling reduction of 5% or less.

The present invention will be explained in detail below.

C is the score of easy open end - The residual thickness after processing is limited to 0.005% or less in order to obtain workability that allows it to be made as thin as possible. Preferably 0.003
% or less is better.

Mn is unavoidable in steel (() is necessary to completely prevent hot embrittlement due to the presence of S, but if it is too large, it will become hard and it will be difficult to obtain low hardness (). 08-0.4
Set to 0%.

Together with B, which will be described later, N is an element necessary to ensure good can opening properties (low tear value) in the low-pressure skin pass, which is the object of the present invention. It was discovered that this improvement in can openability was achieved by dispersing BN, which is produced by the reaction between N and B, into the steel. In addition to causing damage, small cracks occur on the surface during the process of manufacturing billets from molten steel, so the N content i is set to 0.015% or less.

B is necessary for fixing Ni and increasing the can opening ability, and for that purpose, B-0,7NN (%) (as a straight line, -0,
It is necessary to set it to 0010% or more. On the other hand, if there is too much B, the solid solution will harden, so the upper limit is 0.0025.
%.

M is acid soluble, 89 and 0.00 to completely prevent oxygen from lowering grain boundary strength and deteriorating score processability.
0.005% or more is required. However, if the amount is too high, AA will fix Ni and completely suppress the production of BH, so 0.08%
is the upper limit.

Since P is harmful to score processability, it is set to less than 0.012 inches. When Pk is defined in this way, can opening performance is also improved. Si that is unavoidably contained in the pond.

For S, etc., the smaller the number, the better the score processability (soft jC
preferred). Among these, it is effective to make S'i 0.008 or less.

The steel having the above components is formed into a steel billet by a normal process and finish rolled at a hot rolling temperature of 8400 or more. The reason why the finishing temperature is regulated is that if the temperature is lower than that, the non-uniformity of the structure within the thickness of the hot-rolled sheet becomes large and the score processability is completely deteriorated (according to /C).

The winding temperature is 550 to soften and increase BN.
C or more, but if it is too high, the pickling property will be completely reduced, so it is preferably 700C or less. After hot rolling, it is pickled, cold rolled, and annealed at a temperature higher than the recrystallization temperature.

The annealed steel plate is temper rolled at a reduction ratio of 5 or less. This temper rolling has the effect of completely eliminating the yield point and elongation of the annealed plate, but if the tempering pressure F rate is increased, the pop value at the time of opening the can increases, so the upper limit of the rolling reduction rate is set at 5%. .

The steel sheet manufactured by the above method is usually then subjected to plating and chemical conversion treatment with tin, chromium, nickel, aluminum, etc., and then used for easy-open cans.

A hardness of IHq of 56 or less is effective for thinning the remaining thickness of the score, that is, lowering the pop value.

(Example) After melting *Th of the ingredients shown in Table 1 and making it into a steel billet,
Similarly, under the hot rolling conditions shown in Table 1, it was hot rolled to a plate thickness of 2.3. After pickling, it was cold rolled to 0.2311111, annealed at 710C for 60 seconds, and temper rolled.

Next, it was tin-plated and processed into an easy-open can lid with a score remaining thickness of 60 μm, and the can opening performance was completely evaluated. The results are shown in Table 1.

As is clear from the table, steel A-1- with the composition range of the present invention
Even though the skin pass rolling rate is low, A-4 can obtain a low tier value similar to the high reduction skin pass rolling of comparative steel B-1, and a lower pop value than comparative steel mB-1. It will be done.

As is clear from the above explanation, according to the present invention, it is possible to produce an easy-open end steel plate with a low thermal reduction rate (even with a low pop value and tear value) and excellent overall can opening performance. .

(Effects of the Invention) The present invention provides a method for adding B and Ni to the soft base of ultra-low carbon M-killed steel.
By containing a large amount of BN and completely dispersing the BN precipitates, it is possible to produce an easy open-end steel plate with completely improved can openability by low reduction skin pass rolling, and its industrial effects are outstanding.

Claims (1)

[Claims] 1. C: 0.005% or less, Mn: 0.0 as weight%
8% or more and 0.40% or less, Al: 0.005% or more and 0.08% or less as acid-soluble Al, N: 0.015% or less, B: -0.0010 as B-0.7xN (%) % or more and 0.0025% or less, P: less than 0.012%, and the balance is iron and unavoidable impurities. 2, C: 0.005% or less, Mn: 0.08% or more 0.
40% or less, Al: 0.005% or more and 0.08% or less as acid-soluble Al, N: 0.015% or less, B: -0.0010% or more and 0.0025 as B-0.7xN (%) % or less, P: less than 0.012%, the balance consisting of iron and unavoidable impurities is finished by hot rolling at 840°C or higher, rolled at 550°C or higher, cold rolled, and recrystallized annealed. A method for producing an easy open-end steel plate with excellent can-opening properties, characterized by subjecting it to temper rolling at a rolling reduction of 5% or less.