JP3103268B2 - Method for producing steel sheet for containers with excellent fluting resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a steel sheet for containers having excellent fluting resistance.

[0002]

2. Description of the Related Art As a method for producing a container steel sheet excellent in so-called fluting resistance, it is difficult to form a partial depression when a steel sheet for a container is formed into a can body (circular shape). It is known that a steel sheet for a container having a composition is softened by batch-type annealing. or,
Japanese Patent Application Laid-Open No. 63-33522 discloses a method of producing a surface treatment sheet having a size of T-3 or less by performing continuous annealing in a heat cycle of an overaging pattern.

[0003]

However, according to the former manufacturing method as described above, the softening treatment is performed by batch-type annealing, and the annealing process from the start to the end of the annealing requires a long time of about 70 hours, and the production is difficult. There is a problem that the property is extremely low.
Further, according to the latter manufacturing method, there is a problem that the amount of solid solution C in the steel sheet cannot be sufficiently reduced, and a steel sheet for containers excellent in fluting resistance cannot be manufactured. The present invention has been made to advantageously solve such problems, and a steel sheet for a container having a generally used metal composition is softened and solid-dissolved by a short-time heat treatment by continuous annealing without using batch annealing. It is an object of the present invention to reduce the carbon content and to improve the fluting resistance by high-pressure temper rolling at a total reduction ratio.

[0004]

The features of the present invention are as follows: C: 0.01 to 0.05%, Si: 0.034% or less, Mn: 0.15%
~ 0.35%, P: 0.015% or less, S: 0.023% or less, Al:
A steel slab consisting of 0.055 to 0.085%, N: 0.004% or less, the remaining Fe and impurities is heated to 950 to 1250 ° C, subjected to hot rolling, wound up at a winding temperature of 650 to 700 ° C, and then cold rolled. After annealing at a soaking temperature of 660 to 720 ° C. in the subsequent continuous annealing, it is cooled to 650 to 690 ° C. at a slow cooling rate of 3 to 20 ° C./sec, and then rapidly cooled at a rate of 60 to 200 ° C./sec. 200 ~
After cooling to 300 ° C, it is subjected to an overage treatment at 320 to 450 ° C for 30 to 100 seconds to generate a large amount of carbide in the crystal grains, and then a refining with a total reduction of 1.8 to 5.0%. The present invention relates to a method for producing a steel sheet for containers excellent in fluting resistance by short-time heat treatment, which is characterized by rolling.

[0005]

The above steel composition is characterized by a high Al content of 0.055 to 0.085% and a high N content.
Low content of 0.004% or less, promotes precipitation of AlN during heating of steel slab, provides sufficient AlN precipitation by hot rolling afterwards, reduces solid solution N, grows crystal grains and softens steel sheet In addition, the fluting resistance is improved. The lower limit of the Al content is preferably 0.055%, and the lower the N content, the more preferable. Also, C, Mn
The amount is sufficient in the above range to ensure the strength, hardness, and the like of the steel sheet for a container.

The heating temperature of the steel slab having such a composition is such that the precipitation of AlN is promoted by heating at a low temperature and the precipitation of AlN can be sufficiently promoted at 950 to 1250 ° C., but especially 950 to 1100 ° C. And a low temperature range is preferred. The steel slab heated in this manner is hot-rolled to a winding temperature of 650 to 700.
The formation of giant cementite is prevented by winding at a temperature as low as ℃, and the slab is heated at a low temperature.
The necessary and sufficient AlN precipitation is achieved by the AlN precipitation promoting action.

Next, the hot-rolled steel sheet (band) rolled as described above is formed into a cold-rolled steel sheet (band) by cold rolling, and this steel sheet is subjected to heat treatment by continuous annealing. First, heat to 660 to 720 ° C, soak at this temperature for several tens of seconds to recrystallize,
Cooling at 650-690 ° C at a slow cooling rate of 20 ° C facilitates the formation of cementite nuclei in steel. The steel sheet is further cooled from this temperature at a rapid cooling rate of 60 to 200 ° C to reduce the steel sheet temperature.
Cooling to 200-300 ° C produces cementite nuclei. This heat treatment has a great effect on the fluting resistance. That is, 20
The steel sheet is cooled to 0 to 300 ° C, but the fluting resistance is improved by lowering the temperature to less than 300 ° C, especially less than 250 ° C. However, it is preferable to set the lower limit to 200 ° C. because the temperature variation in the steel strip coil after cooling may increase and the in-furnace passability may deteriorate. The cooling rate is 60 to 200 ° C./sec as described above,
At a rate of less than 60 ° C./sec, nucleation of cementite is insufficient, and it is difficult to maintain fluting resistance. If cooled more rapidly, nucleation of cementite increases and fluting resistance improves. The upper limit is preferably 200 ° C./sec in consideration of the variation in the coil temperature.

[0008] Next, the steel sheet thus quenched is cooled to 320-45.
The temperature is raised to 0 ° C and overaged for 30 to 100 seconds.
The purpose is to reduce the amount of solid solution C in steel, increase the carbide density, increase the amount of carbide in the crystal grains, and introduce a lot of mobile dislocations in the subsequent temper rolling. This heat treatment also has a significant effect on the fluting resistance. That is, as described above, when the heating temperature of the steel sheet exceeds 450 ° C., the precipitated cementite nucleus re-dissolves and disappears. Is not preferred. On the other hand, if the temperature is lower than 320 ° C., little effect such as reduction of the amount of solid solution C can be expected.
Further, the longer the holding time, the better the fluting resistance. However, it is preferably 100 seconds because of productivity and equipment limitations.
If the time is less than seconds, the overaging effect is undesirably reduced.

In this way, the cold-rolled steel sheet (band) heat-treated by continuous annealing is subjected to temper rolling, and the temper rolling is performed with a total reduction of 1.8 to 5.0% in terms of a reduction ratio. That is, the steel sheet for containers has a small thickness and the temper rolling stands are continuously rolled by a plurality of stands (generally two stands), and the rolling reduction of all stands, that is, 1.8 to 5.0% in total rolling reduction. Temper rolling. Since the carbide density in the steel is increased by the heat treatment by the continuous annealing, a large number of mobile dislocations can be introduced by temper rolling, the yield point elongation after aging is reduced, and the fluting resistance is significantly improved, Total rolling reduction
If it is less than 1.8%, a large amount of mobile dislocations cannot be introduced, and the fluting resistance cannot be improved so much. If the total draft is more than 5.0%, the work hardens due to work hardening, making it difficult to work. Therefore, the upper limit is made 5.0% or less. Is preferred. As described above, in the present invention, by generating a large amount of carbides in the crystal grains, a large number of mobile dislocations are introduced by the temper rolling, and the excellent fluting resistance in a short time which cannot be achieved by the conventional overaging treatment. Can be produced.

[0010] Such a steel sheet for a container having excellent fluting resistance can be effectively used, for example, for a battery outer cylinder.

[0011]

Next, examples of the present invention will be described together with comparative examples.

[Table 1] As described above, a steel sheet (belt) having undergone the hot rolling step was subjected to a cold rolling step as described below to produce a steel sheet for a container.

[Table 2]

[Table 3] * 1 After temper rolling, a 0.25 mm thick container steel plate was manufactured. Note 2 The presence or absence of fluting is indicated by the number of cylinders with dents formed by forming 50 cylinders (can bodies) with a diameter of 35 mm and a length of 100 mm from the steel plate for containers manufactured as described above in the normal molding process. .

[0012]

As described above, according to the present invention, a steel sheet for containers having excellent fluting resistance can be manufactured in a short time, and productivity can be remarkably improved. Further, the fluting resistance can be improved more reliably than conventional manufacturing methods, and excellent effects such as great industrial effects can be obtained.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshikazu Nomura 5-3 Tokai-cho, Tokai-shi, Aichi Prefecture Nippon Steel Corporation Nagoya Works (56) References JP-A-61-26725 (JP, A) JP-A-4-327 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D 9/46, 8/02 C22C 38/00-38/60

Claims (1)

(57) [Claims] 1. C: 0.01-0.05%, Si: 0.034% or less, M
n: 0.15 to 0.35%, P: 0.015% or less, S: 0.023% or less, Al: 0.055 to 0.085%, N: 0.004% or less, steel slab consisting of remaining Fe and impurities is heated to 950 to 1250 ° C. Cold rolling, winding at a winding temperature of 650-700 ° C., and continuous annealing after cold rolling, annealing at a soaking temperature of 660-720 ° C., and then gradually cooling at 3-20 ° C./sec. 650-69 at speed
Cool to 0 ° C, then cool to 200-300 ° C at a rapid cooling rate of 60-200 ° C / s, then at 320-450 ° C.
An overage treatment of 30 to 100 seconds is performed to increase the amount of carbide in the crystal grains.
A method for producing a steel sheet for a container having excellent fluting resistance by short-time heat treatment, wherein the steel sheet is subjected to temper rolling at a total draft of 1.8 to 5.0% after being formed .