JP2007204788A - Method for manufacturing steel sheet for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a steel sheet for battery which is excellent in workability possible of DI (drawing and ironing) work. <P>SOLUTION: In order to obtaining the steel sheet for battery having the workability sufficiently resist to the DI work, the combination of a component composition and a producing condition is optimized so that the steel sheet is sufficiently softened. Concretely, a slab contains, by mass%, 0.01-0.1% C, ≤0.1% Si, 0.1-1.0% Mn, ≤0.03% P, ≤0.2% S, 0.01-0.08% sol.Al, ≤0.0050% N and the balance Fe with inevitable impurities, is hot-rolled and cold-rolled at 80-90% rolling-reduction ratio and successively, annealed at 600-700°C for 30 sec-5 min, and successively, a skin-pass rolling is performed at 0.5-2.0% expanding ratio, and a plating-treatment is performed and successively, after diffusion-annealing at 650-800°C for 5 min or more, the skin pass-rolling is performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a battery can material formed by DI processing.

  In manufacturing a dry cell can using a steel plate, the dry cell body portion is formed by drawing (Drawing and Ironing) drawing. The DI drawing method is to punch a base material from a sheet-like plated steel plate while drawing it as a shallow cylindrical cup with a bottom wall and a peripheral wall, and this cup is required in the next deep drawing process. It is processed into a cylindrical shape having a depth and a diameter. Thus, in the DI drawing process, only the peripheral wall is stretched in the deep drawing process of the cup. For example, the thickness of the peripheral wall can be reduced to 0.15 mm with respect to the thickness of the bottom wall of 0.4 mm. The ironing rate (decrease rate) with respect to the plate thickness can be made slightly more than twice that of the prior art. And if a surrounding wall is made thin, the volume of a hollow part will become large, a filler will increase (electrolyte capacity increase), and a battery characteristic can be improved. In addition, the machining process requires only a total of two processes, one cupping process for punching a cup from a sheet steel sheet, which is a can-forming material, and one process for the DI process for drawing. Manufacturing costs can be reduced.

  On the other hand, since the DI drawing process uses the above-described processing method, the steel sheet to be used is required to have excellent workability that can withstand DI processing.

    On the other hand, steel plates for dry batteries are usually subjected to hot rolling and cold rolling of slabs, and sometimes annealing (both in case of box annealing and continuous annealing) and temper rolling, followed by a plating process. Manufactured by annealing, temper rolling. However, the annealing conditions are not particularly limited, and depending on the conditions of the first continuous annealing, solid solution elements may remain, so that the material does not soften and may not be a material that can withstand DI processing.

For example, Patent Document 1 discloses a steel plate that suppresses the occurrence of earrings by making the in-plane deviation Δr close to 0 and making the plate thickness uniform in the width direction as a material for a battery can for performing DI processing. .
JP-A-6-344003

  However, when the steel sheet described in Patent Document 1 is used as a material for battery cans that perform DI processing, since solute elements remain, age hardening cannot be avoided, and cracking occurs during DI processing. is there.

  In view of such circumstances, the present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a battery steel sheet that can be processed by DI and has excellent workability.

  The present inventors have intensively studied to solve the above problems. And in order to obtain a battery steel sheet having sufficient workability that can withstand DI processing, it is important to soften the steel sheet, and from the point of softening of the steel sheet, the combination of the composition and production conditions was examined. . As a result, it has been found that it is most effective to control the diffusion annealing condition within an appropriate range for age hardening, and the amount of C is specified as a component composition, and then the second annealing (diffusion annealing). It has also been found that a steel sheet excellent in workability capable of DI processing can be obtained by defining a combination of manufacturing conditions centering on.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] When manufacturing a battery steel sheet for a dry battery body by DI drawing, in mass%, C: 0.01 to 0.1%, Si ≤ 0.1%, Mn: 0.1 to 1.0%, P ≤ 0.03%, S ≤ 0.2%, sol.Al:0.01-0.08%, N ≦ 0.0050%, the slab composed of the balance Fe and inevitable impurities is hot-rolled, cold-rolled at a rolling rate of 80-90%, and then Annealing at a temperature of 600 to 700 ° C for 30 seconds to 5 minutes, then temper-rolling at an elongation of 0.5 to 2.0%, plating, and then diffusion annealing at a temperature of 650 to 800 ° C for 5 minutes or more Then, temper rolling is performed, The manufacturing method of the steel plate for batteries characterized by the above-mentioned.
In addition, in this specification,% which shows the component of steel is mass% altogether.

  According to the present invention, optimization of a series of manufacturing processes (especially the second annealing condition) of steel type selection, slab to hot rolling, cold rolling, annealing, temper rolling, plating, annealing, temper rolling. Thus, the steel plate is sufficiently softened, and a battery steel plate capable of DI processing can be obtained.

  Hereinafter, the present invention will be described in detail.

  First, the reasons for limiting the components of the present invention will be described.

Chemical composition range
C: 0.01-0.1%
C is one of the most important requirements in the present invention. In order to soften the steel sheet, an appropriate combination of C content and manufacturing conditions is essential. When the addition amount of C exceeds 0.1%, workability is inferior and solid solution C remains, age hardening occurs, which is disadvantageous from the viewpoint of softening. Therefore, the C content is 0.1% or less. If the amount is too small, the strength of the can wall will be insufficient, so 0.01% or more from the viewpoint of securing the strength.

Si ≦ 0.1%
Si is an element effective for strengthening steel sheets and can be added as appropriate. However, if the added amount of Si exceeds 0.1%, the surface properties of the steel sheet deteriorate due to the occurrence of red scale, so the Si amount is made 0.1% or less.

Mn: 0.1-1.0%
Mn is an element effective for strengthening steel sheets, but if it is less than 0.1%, it is insufficient as a strengthening element. On the other hand, when the amount of Mn exceeds 1.0%, the surface properties deteriorate. Therefore, the Mn content is 0.1% or more and 1.0% or less.

P ≦ 0.03%
P is an element effective for strengthening steel sheets. However, when the addition amount exceeds 0.03%, the elongation decreases remarkably. Based on the above, the P content is 0.03% or less.

S ≦ 0.2%
If S exceeds 0.2%, Mn / S decreases and defects tend to occur. Therefore, the S content is 0.2% or less.

sol.Al: 0.01-0.08%
sol.Al is an element that fixes solid solution N as AlN and improves aging properties. However, if it is less than 0.01%, it is insufficient to fix N, and if it exceeds 0.08%, the surface properties deteriorate. For this reason, sol.Al is made 0.01% to 0.08%.

N ≦ 0.0050%
If N exceeds 0.0050%, it cannot be fixed as AlN, and the aging property deteriorates. For this reason, N amount shall be 0.0050% or less.

  The remainder other than the above is Fe and inevitable impurities. Moreover, in this invention, as a trace element which does not impair the effect of this invention, Cr and Mo may contain 0.05% or less, for example.

  Next, the manufacturing method of the battery steel plate of this invention is demonstrated.

  The steel plate of the present invention first melts and casts steel having the above component composition. In consideration of productivity and cost, the casting method is a continuous casting method. Next, the cast slab is hot-rolled.

  In hot rolling, a high-temperature cast slab may be rolled as it is, or a slab cooled to room temperature may be reheated and then rolled. In the case of slab heating, if the rolling heating temperature is less than 1100 ° C., the rolling load becomes high, so that rolling becomes difficult. Further, when the slab heating temperature exceeds 1300 ° C., scale defects are easily generated during hot rolling due to excessive generation of primary scale. For this reason, the heating temperature of the slab is preferably 1100 ° C. or higher and 1300 ° C. or lower. After rough rolling, it is finish-rolled and wound on a coil. When finishing rolling at a temperature lower than 850 ° C. during finish rolling, coarse grains are formed. Therefore, the finishing temperature is preferably 850 ° C. or higher.

Winding temperature
There is an effect of coarsening of Fe ₃ C and acceleration of AlN precipitation, and age hardening is reduced. If the coiling temperature is less than 600 ° C., the above effect is not sufficient. On the other hand, when it exceeds 700 ° C., the variation becomes large. Therefore, the coiling temperature is set to 600 ° C or higher and 700 ° C or lower. A preferable winding temperature is 620 to 680 ° C.

By optimizing the cold rolling ratio, can height variation (Δr) during can forming can be reduced. In order to sufficiently obtain this effect, the rolling rate is 80% or more. On the other hand, if the rolling rate exceeds 90%, rolling becomes difficult due to an increase in rolling load. Therefore, the rolling rate is 80% or more and 90% or less.

Continuous annealing is performed for 30 seconds to 5 minutes immediately above the recrystallization temperature of 600 ° C to 700 ° C in an annealing atmosphere. Although it can be performed by box annealing, continuous annealing is preferable in consideration of productivity, cost and the like.

Temper rolling
Temper rolling is performed at an elongation rate of 0.5 to 2.0%.

Ni plating treatment is performed on the steel sheet centering on the inner surface side that contacts the plating electrolyte. The treatment method is not particularly limited, but electroplating is preferable for the reason of the uniformity of the plating thickness. The thickness of the plating layer is preferably 1 μm to 5 μm. It does not matter whether the plating is soft or hard.

Diffusion annealing is one of the important requirements in the present invention. It works effectively against age hardening after overaging treatment, and by optimizing the annealing conditions, it is possible to lower YP and soften the steel sheet. Further, an Fe—Ni diffusion layer is formed between the Ni plating layer and the steel plate. In particular, in the present invention, age hardening due to residual solid solution elements is unavoidable, so the material does not become soft unless the conditions for diffusion annealing after plating are optimized, and DI molding becomes impossible. That is, it is possible to obtain a steel plate and a manufacturing method capable of DI processing only by optimizing a series of manufacturing conditions centering on diffusion annealing.

  In order to investigate the optimum conditions for diffusion annealing, battery steel sheets with varying diffusion annealing temperature (maximum temperature reached) were prepared and the hardness (HV) and tensile properties were investigated. The battery steel plate used at this time was prepared as follows. Steel consisting of C: 0.03%, Si: 0.01%, Mn: 0.2%, P: 0.01%, S: 0.01%, Sol.Al: 0.05%, N: 0.03%, balance Fe and inevitable impurities Was melted and continuously cast into a slab, and then cooled to room temperature. Next, the cast slab was hot-rolled at a heating temperature of 1250 ° C and a finishing temperature of 870 ° C, and wound at 620 ° C. Next, pickling and cold rolling at a rolling rate of 86%, followed by continuous annealing at a soaking temperature of 650 ° C. and an annealing time of 1 minute. Next, temper rolling was performed at an elongation rate of 1.0%, and Ni plating was performed. The Ni plating was applied to both the front and back surfaces by electroplating so that the thickness was 2 μm. Furthermore, with respect to the plated steel sheet obtained as described above, the annealing temperature was changed, diffusion annealing was performed for 10 minutes, and temper rolling was performed again with an elongation rate of 1.0% to obtain a battery steel sheet. The obtained results are shown in FIGS.

From FIG. 1 and FIG. 2, it can be seen that the characteristics change greatly when the diffusion annealing temperature is changed. In particular, when the maximum temperature is around 650 ° C., as YP and YPEL decrease, the hardness (HV) also greatly decreases and the steel sheet becomes soft. This softening of the steel sheet seems to be due to the fact that the annealing temperature becomes higher than the recrystallization temperature, grain growth occurs, and YP decreases.
From the above, the annealing temperature is set to 650 ° C. or more from the viewpoint of softening the steel sheet due to the YP reduction effect. On the other hand, if it exceeds 800 ° C, TS decreases and the strength becomes insufficient. Further, if the annealing time is less than 5 minutes, the diffusion is insufficient. Therefore, the temperature in diffusion annealing is set to 650 ° C. to 800 ° C., and the time is set to 5 minutes or more.

Temper rolling Furthermore, in order to prepare the structure of the plated steel sheet obtained as described above, temper rolling is performed at an elongation of 0.5% to 2.0%.

(Example of the present invention)
Steels having the components shown in Table 1 were melted and continuously cast into slabs, and then cooled to room temperature. Next, the cast slab was hot-rolled at a heating temperature of 1250 ° C. and a finishing temperature of 870 ° C., and wound at 620 ° C. Next, pickling and cold rolling were performed at a rolling rate of 86%, followed by continuous annealing at a soaking temperature of 650 ° C. and an annealing time of 1 minute. Next, temper rolling was performed at an elongation rate of 1.0%, and Ni plating was performed. The Ni plating was applied to both the front and back surfaces by electroplating so that the thickness was 2 μm. Further, the plated steel sheet obtained as described above was subjected to diffusion annealing at an annealing temperature of 650 ° C. and a diffusion time of 10 minutes, and temper rolling was performed again with an elongation rate of 1.0% to obtain a battery steel sheet.
The steel sheet obtained as described above was examined for tensile properties. The tensile properties were determined using JIS No. 5 tensile specimens taken from the rolling direction.
(Comparative example)
A steel plate for a battery was obtained using the same components as those of the above-described example of the present invention, except that the diffusion annealing temperature was set to 450 ° C. and the diffusion time was set to 10 minutes. The tensile properties of the obtained steel plate were investigated. In addition, the measuring method of a tensile characteristic is the same as that of the example of this invention.

  Table 2 shows the results of the characteristics of the steel sheet obtained as described above.

From Table 2, it can be seen that in the present invention example, the YP decreased and the YPEL disappeared before diffusion, and the steel sheet was softened.
On the other hand, in the comparative example, the tensile properties are almost the same as before diffusion, and no decrease in YP is obtained.

Next, DI drawing was performed on the steel sheets of the present invention and the comparative example obtained as described above, and a dry cell body was prepared. The obtained dry cell body was visually inspected for cracks. As a result, the crack occurrence rate was 1 to 5% in the inventive example, and 10 to 30% in the comparative example.
From the above results, it can be seen that in the example of the present invention, the steel sheet was sufficiently softened, so that DI drawing can be performed without generating cracks.

  Since it is suitable for the field of manufacturing a battery outer can, and can be applied to a non-aging steel plate, it can also be applied to applications where box annealing is considered indispensable.

It is a figure which shows the relationship between the highest ultimate temperature in the case of annealing, and YP and YPEL. It is a figure which shows the relationship between the highest ultimate temperature in the case of annealing, and HV.

Claims (1)

In manufacturing a battery steel plate for a dry battery body part by DI drawing, in mass%, C: 0.01 to 0.1%, Si ≤ 0.1%, Mn: 0.1 to 1.0%, P ≤ 0.03%, S ≤ 0.2%, sol.Al: 0.01 to 0.08%, N ≦ 0.0050%, the slab composed of the remaining Fe and inevitable impurities is hot-rolled, cold-rolled at a rolling rate of 80 to 90%, and then 600 to 700 Annealed at a temperature of 30 ° C. for 30 seconds to 5 minutes, then temper-rolled at an elongation of 0.5 to 2.0%, plated, and then subjected to diffusion annealing at a temperature of 650 to 800 ° C. for 5 minutes or more. A method of manufacturing a steel sheet for a battery, comprising performing quality rolling.

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