JPH0629465B2 - Method for producing steel plate for DI can having good bakeability and bake hardenability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICABILITY The present invention relates to DI as a two-piece can used for various cans.
The present invention relates to a method for producing a tin-plated steel sheet (tin plate) used for cans, and more particularly to a method for producing a steel sheet for DI cans having bake hardenability and excellent flange formability by applying a continuous annealing method.

2. Description of the Related Art Conventionally, DI cans have been used for food cans such as beam cans and soft drink cans. This DI can is formed into a cup shape by drawing a circularly drawn metal base plate into a cup shape, and then passes through several dies having an inner diameter smaller than the outer diameter of the cup-shaped molded product to reduce the thickness of the can body wall. The can is made by performing an ionicing process (ironing process) that reduces and increases the can height, and is used as a two-piece can because the seamless body wall and bottom are integrally manufactured. .

Aluminum and Sn-plated steel plate, that is, tin plate are generally used as materials for such DI cans.
Conventionally, aluminum, which has good wrought workability, has often been used as the main material, but in recent years, the use of steel has progressed along with the improvement in the quality of tinplate. However, when steel is used again, there has been a problem in terms of material that the rate of flange cracking during can body flange processing in the process of attaching a can lid is higher than that of aluminum. Therefore, when steel-making a DI can using a tin plate, development of the Sn plating steel plate excellent in flange workability is strongly desired.

By the way, as steel sheets having good flange formability for DI cans, there are those disclosed in JP-B-55-2461 and those disclosed in JP-A-58-141364. That is, in the former publication, it is explained that the one in which the crystal grain axial ratio is reduced to 1.8 or less can significantly reduce the ironing molding defective rate and the flange molding defective rate. The grain size is G. S.
No. Is 9.2 or more and the center line roughness of the plate surface Ra (μ
It is described that an ultrathin cold-rolled steel sheet having excellent can-forming properties can be produced by setting the difference from m) to 9.0 or less and setting the hardness H _R 30T to be in the range of 46 to 60. And with these methods,
In each case, as described in the examples, a foil annealing method with an annealing temperature of 580 to 765 ° C. and a temperature rising rate of 20 to 2000 ° C./hr is applied.

However, since the foil annealing method requires a long processing time, not only the work efficiency is low, but also the heat treatment in the coil state causes a difference in heating and cooling speeds in the coil radial direction.
As a result, it is not possible to obtain a uniform material over the entire coil and there are drawbacks such as a decrease in yield. Therefore, there is established a method of applying the continuous annealing method and producing a steel plate for DI can with excellent flange formability. Is desired.

Attempts have been made to apply the continuous annealing material to DI cans, but the conventional ordinary continuous annealing method and the ordinary Sn method have been used.
In combination with the plating method, since the cooling after soaking in continuous annealing is rapid cooling, the solid solution C in the steel hardly remains as a carbide and remains in the solid solution state, and at the time of reflow treatment after Sn plating. There is a problem that hardening occurs due to solid solution C, and as a result, there is a high risk of breaking the can body wall during DI can manufacturing, and there is a large problem of earrings during drawing prior to DI processing, that is, ears are large. There is a problem.

When the ears are large like this, there is a risk that the ears are stretched at the time of making the DI can and the thickness of the ears is greatly changed in the circumferential direction, so that the thin parts may be cracked during the flange processing after trimming. There is.

Therefore, in JP-A-58-151426, the hot rolling finishing temperature is set to A
It discloses a method of producing an ultra-thin steel sheet having a small in-plane anisotropy by a combination of r ₃ points or more and a winding temperature of 580 to 740 ° C. However, in this proposed method, the winding temperature is
Since the medium temperature to high temperature of 580 ° C. or higher is inevitably large, the crystal grain size is inevitably large, and the flange formability tends to be deteriorated as described in, for example, JP-A-58-141364. Further, when the coiling temperature is increased as in the above proposal, coarse agglomerated cementite precipitates in the steel sheet to deteriorate the corrosion resistance and may cause a flange crack. Further, if the winding temperature is set high, there is a problem that the oxide layer on the surface of the steel sheet becomes thick during winding and the line speed is lowered in the pickling step, resulting in poor productivity.

Problems to be Solved by the Invention When the box annealing method is applied as described above, there are problems of work efficiency, material uniformity, and yield. Therefore, the continuous annealing method is applied to the Sn-plated steel sheet for DI cans. Although it is desired to manufacture it, the conventional continuous annealing method and the conventional S
In combination with the n-plating method, there was a problem that the wall of the barrel can was broken at the time of DI can making, and the ears became large at the time of drawing before DI processing. The above-mentioned Japanese Patent Laid-Open No. 58-1 is intended to reduce the occurrence of ears.
In the method of Japanese Patent No. 51426, since the coiling temperature after hot rolling is high, the crystal grain size becomes large, the flange formability deteriorates, the corrosion resistance decreases, and the line speed in the pickling process decreases. Is also occurring.

Therefore, in the present invention, the continuous annealing method is applied, the coiling temperature after hot rolling is set lower than in the conventional case, and a tin-plated steel sheet for a DI can that has little flange cracking and edge generation and is bake hardenable is manufactured. It is intended to provide a method.

It should be noted that JP-A-59-38336 and JP-A-59-38338 have already disclosed a method for producing a surface-treating original sheet with a small ear occurrence by applying a continuous annealing method. The method is so-called overaging treatment in the continuous annealing step to sufficiently precipitate the solid solution C in the steel, thereby softening with extremely little age hardening (that is, T1 to T3 grade with a tempering degree specified by JIS G 3303). In contrast to this, in the present invention, by allowing the solid solution C to remain in the amount of light, it is possible to age-harden during the coating after the production of DI can and the drying / baking after printing. Such Sn-plated steel sheet, that is, Sn of T4 grade or higher having bake hardenability
It is intended to obtain a make-up steel plate, and in that sense, it is basically different from the purpose of the above proposal.

Means for Solving the Problems As a result of the inventors' earnest experiments and examinations in order to achieve the above-mentioned object, as a result of using a steel material of a specific component, the heating temperature before hot rolling is 1200 ° C. or more. By setting the coil temperature to a high temperature, the coiling temperature after hot rolling to a low temperature of less than 580 ° C, and controlling the cooling rate after continuous annealing appropriately and further controlling other conditions, it is possible to obtain fine crystal grains. The inventors have found that an Sn-plated steel sheet having excellent bakeability, a small earring rate, and a bake hardenability can be obtained, and the present invention has been accomplished.

Specifically, the method for producing a steel sheet for a DI can of the present invention uses C0.01 to 0.10% by weight, Mn 0.50% or less, sol.Al.
Contains 0.003 to 0.050%, N 0.0040% or less, the balance is F
Steel made of e and inevitable impurities is used as a material, the steel material is heated to a temperature of 1200 ° C or higher and hot-rolled, and the hot-rolled sheet after the hot-rolling is wound in a temperature range of 580 ° C or less. When performing continuous annealing after further cold rolling, the temperature is soaked to a recrystallization temperature Ac of ₁ point or less, and in the subsequent cooling process, the temperature range of 500 to 400 ° C. is cooled for 10 seconds or more and continuously. After the annealing is finished, temper rolling is performed, and subsequently, electrotin plating is performed.

Operation First, the experiments that became the basis for making this invention will be explained.

C0.05%, Mn0.21%, Si0.009%, P0.012%, S
i 0.007%, sol.Al 0.035%, N 0.0020%,
A steel slab whose balance consists of Fe and unavoidable impurities
After heating to 1270 ° C. or 1100 ° C., hot rolling was completed at a finishing temperature of 850 ° C., and wound at various temperatures of 500 to 650 ° C. After that, heating rate of temperature rise 20 ℃ / sec, soaking temperature 670
℃, soaking time 20sec, cooling rate 8 ℃ / sec or 15 ℃
/ Sec for continuous annealing, and a rolling reduction of 1.5%
After the temper rolling was performed, the # 20 electric Sn plating was performed and then the DI processing was performed to examine the occurrence of ears. The results are shown in FIG. 1 corresponding to the winding temperature. Here, the ear height ΔH is evaluated by ΔH = [height of peak] − [height of valley], and at the same time, the grain size is also checked, and the value is the first value.
It is also shown in the figure.

As is clear from Fig. 1, the slab heating temperature is low (11
In the case of (00 ℃), if the coiling temperature is low, the ear height is △
On the other hand, when the slab heating temperature is high (1270 ° C), the ear height ΔH does not increase so much even if the slab heating temperature is high (1270 ° C), and steel plates with a small ΔH are manufactured. It turned out to be possible. It was also found that the crystal grain size was small under the conditions of high slab heating temperature and low coiling temperature.

Next, C0.041%, Si0.011%, Mn0.22%, Si0.00
A steel slab containing 8%, sol.Al0.025%, N0.0025%, the balance Fe and unavoidable impurities
℃ or 1250 ℃ for 30 minutes and hot rolling, 86
After the hot rolling was completed at 0 ° C and the plate thickness was 2.5 mm,
Winding was carried out at various temperatures from 0 to 700 ° C. After pickling, plate thickness 0.30
After cold rolling to mm, heating rate 20 ° C / sec, soaking temperature 660-720 ° C, soaking time 20sec, cooling rate 10 ° C / se
Continuous annealing under conditions of c or 25 ° C / sec, or box annealing under conditions of heating rate 30 ° C / hr, soaking temperature 630 ° C, soaking time 3hr, cooling rate 30 ° C / hr, Further reduction rate
After 1.5% temper rolling, # 15 electric Sn plating was applied and DI processing was performed. After that, flange processing was performed, and the can expanding ratio up to the occurrence of flange cracking was investigated, and the relationship between the crystal grain size and the can expanding ratio is shown in FIG. Here, the can expansion ratio in flange processing is the initial can outer diameter before processing d
_o , the outer diameter of the can at the time of flange cracking was d, and the can expansion ratio = {(d-d _o ) / d _o } × 100.

From FIG. 2, it can be seen that the smaller the grain size, the higher the can expanding rate and the better the flange workability, and that the high temperature slab heating-low temperature winding-continuous annealing low-speed cooling material (steel of the present invention) is a box annealing material. And low temperature slab heating-high temperature coiling-continuous annealing High can expanding ratio compared to high speed cooling material (comparative steel), especially even if comparing with the same grain size, can expanding ratio is higher than comparative steel, and flange formability. Is clearly superior.

As is clear from the above-mentioned experiments, the steel sheet obtained by the method of the present invention has small ears and has a good can expanding ratio during flanging (that is, good flanging property).
The reason for this is not clear yet, but it can be considered as follows.

In other words, the reason why almost no ears are generated is that the amount of N contained in the steel is regulated to 0.004% or less and the coiling temperature is set to a low temperature of less than 580 ° C. Is suppressed and consequently after cold rolling (111)
It is considered that the texture did not develop much and other orientations developed and the inner surface anisotropy became smaller.

Further, the reason why the can expansion ratio during flanging is high and the flanging property is good is that the crystal grains of the hot rolled mother plate become fine due to high temperature slab heating-low temperature winding.
It is caused by the fact that the amount of solid solution C and N is relatively small and the degree of freedom of dislocation during flange processing is increased by decreasing the amount and setting the cooling rate of continuous annealing to 10 ° C / sec or less. it is conceivable that.

Next, the reasons for limiting the components of the steel material in the method of the present invention will be described.

C 0.01 to 0.10%: The higher the content of C, the finer the crystal grains of the material, and the better the can expanding property in flange processing. 0.01%
If it is less than 100%, the crystal grains are large and the can-spreading property deteriorates, so the lower limit was made 0.01%. On the other hand, if C exceeds 0.10%, coarse cementite precipitates and the can-spreading property deteriorates, so the upper limit was made 0.10%.

Mn 0.50% or less: Mn is an element effective in fixing S that causes hot cracking, but if it exceeds 0.5%, it hardens the material and makes DI processing difficult. The upper limit of is 0.50
%.

sol.Al 0.003 to 0.050%: Al is an element effective as a deoxidizer in the ordinary steelmaking process, and for that purpose, at least 0.003 as sol.Al.
% Content is required. However, sol.Al is 0.05%
If a large amount of Al is added so as to exceed the range, the cost will increase, so the upper limit was made 0.05%.

N 0.0040% or less: N is effective for increasing the can expanding rate during flange processing because it refines the crystal grains similarly to C, but in the case of the method of the present invention, the winding temperature is low. Since there is little precipitation as AlN in the hot rolled coil state, it is important to reduce the amount of N as much as possible in order to improve workability. In order to obtain sufficient workability, it is necessary to regulate N to 0.0040% or less, and more preferably 0.0030% or less.

Other steel contains Si, S, P, etc. as unavoidable impurities, and it is desirable to reduce these as much as possible, but this is not particularly specified in the present invention.

Next, manufacturing conditions in the method of the present invention will be described.

First, the steel slab having the above-mentioned composition is heated and hot-rolled. The slab heating temperature before this hot-rolling is 1200 ° C.
It is necessary to raise the temperature above. The reason for this is that, as is clear from the above experimental results, it is advantageous to heat the slab at a high temperature together with the low-temperature winding in order to reduce the crystal grains and improve the can expanding property during flange processing. This is because a slab heating temperature of 1200 ° C. or higher is effective for grain refinement.

Hot rolling after heating the slab may be performed according to a conventional method, but winding after hot rolling needs to be performed at a low temperature of less than 580. The reason for setting the coiling temperature below 580 ° C is
As is clear from the above experimental results, in combination with high temperature slab heating, it is effective in refining the crystal grains and is effective in preventing the precipitation of coarse cementite, thus improving the flange formability. It is effective for.

After winding, it is usually pickled and then cold-rolled, but these may be carried out by a conventional method. Continuous annealing is performed after cold rolling. In the continuous annealing, the soaking temperature is set to the recrystallization temperature or higher and the Ac ₁ point or lower. When annealed at a temperature lower than the recrystallization temperature, the work structure remains and ductility and drawability are inferior, and therefore the steel sheet may be broken during the drawing process in the DI can, so the lower limit of the annealing soaking temperature is set to the lower limit. Temperature. Further, since heating at a temperature exceeding the Ac ₁ point causes an increase in the amount of solid solution C and an increase in the crystal grain size, the upper limit of the annealing soaking temperature is set to the Ac ₁ point. Furthermore, when cooling in continuous annealing, it is necessary to cool between 500 ° C and 400 ° C over 10 seconds. The reason is that the temperature range of 500 to 400 ° C is the temperature range in which carbides easily precipitate, and the temperature range is 10
This is because slow cooling at a temperature of not less than ° C / sec is effective in reducing the amount of dissolved C.

After continuous annealing, temper rolling is performed to improve plating properties and adjust hardness. Although the rolling reduction of the temper rolling is not particularly limited, it is usually 0.5 to 3.0%.

After temper rolling, electric Sn plating is applied. Conventional electric S
In the n-plating step, reflow treatment is often performed after Sn plating to obtain surface gloss, but in the case of the method of the present invention, it is desirable not to perform reflow treatment. That is, when the reflow process is performed, a hard Sn-F
An e-alloy layer is generated, ironing workability deteriorates, and the unevenness of the steel plate surface decreases, which increases friction between the inner and outer surfaces of the can, which is one of the factors that make ironing difficult, resulting in ironing. Sometimes there is a risk of the steel plate breaking. Further, when the reflow treatment is performed, age hardening of the base steel sheet occurs at that time, the workability deteriorates, and the hardening ability during baking decreases. From these viewpoints, it is desirable that the steel sheet for a DI can having the bake hardenability, which is the object of the present invention, is not subjected to reflow treatment. Not performing the reflow treatment is also effective in increasing the can expansion rate during flange processing.

As described above, the Sn-plated steel sheet for DI cans obtained as described above has less ears during DI can manufacturing and spreads until flange cracking during flanging. Since the can rate is large, the risk of flange cracking is low.

After the DI can is manufactured, it is usually baked and dried after painting and printing, but the steel sheet of the present invention has bake hardenability. That is, since the steel sheet of the present invention is manufactured by the continuous annealing method, it is gradually cooled in the temperature range of 500 to 400 ° C. after continuous annealing, but the amount of C and N remaining in the steel in a solid solution state. Is much larger than the case of box annealing,
Therefore, during baking and drying, C and N precipitate and age-harden,
The pressure resistance of the can increases.

Example For steels A, B, and C having the composition shown in Table 1, the molten steel was made into a slab having a thickness of 200 mm by continuous casting, and then the second
As shown in the table, after heating the slab for 30 minutes at various temperatures of 1100 to 1280 ℃, hot rolling was performed, and hot rolling was completed in the temperature range of 780 to 850 ℃ to obtain a plate thickness of 2.5 mm. And then 500
Winding was done at various temperatures of ~ 660 ° C. After pickling, cold rolling was performed to obtain a cold rolled sheet having a sheet thickness of 0.32 mm. After that, continuous annealing method (soaking: 650-740 ° C x 20-30sec, cooling: 5-22 ° C / sec)
Or box annealing (soaking: 630 ℃ × 3hr, cooling: 30 ℃ / h
Recrystallization annealing was performed by r) and temper rolling with a rolling reduction of 1.5% was performed. Then, # 20 electric Sn plating was also performed. No reflow treatment was applied to the electric Sn plating.

Subjected to DI processing to each steel sheet after Sn plating ear occurrence (△ H), it was examined the hardness (H _R 30T) and拡缶rate during flanging. The results are shown in Table 2. Here, the definition of the ΔH value of the ear occurrence state and the can expansion rate during flange processing is as described above.

As is clear from Table 2, when steels A and B within the composition range of the present invention were treated according to the manufacturing conditions of the present invention (Nos. 1, 2, and 5), there was little earing and the flange It was found that the can expansion rate during processing was high.
On the other hand, even with steels A and B within the composition range of the present invention, when the hot-rolled sheet winding temperature is high (No. 3), the selvages are large, and when the slab heating temperature is low or continuous annealing is performed. When the cooling rate was high (No.4, No.6, No.7), the can expanding ratio during flange processing was small in all cases. Further, even if the manufacturing conditions were within the range of the present invention, in the case of steel C having a high N content (No. 8), the ear occurrence was small but the can expanding rate was low.

EFFECTS OF THE INVENTION As is clear from the above description, according to the method of the present invention, it is possible to obtain a steel sheet for DI can which has little seizure due to continuous annealing, is excellent in flange formability, and has bake hardenability. Further, since the continuous annealing method is applied in the method of the present invention, it is possible to obtain a steel sheet having a high productivity and a homogeneous material. Further, in the present invention, since the hot-rolled sheet winding temperature is low, not only is it excellent in flange formability as described above, but also because there is no agglomeration of coarse cementite, corrosion resistance is excellent and the formation of an oxide layer during winding is reduced. The effect of improving pickling efficiency is also obtained. Further, since the steel sheet obtained by the method of the present invention has the bake hardenability, it can be age hardened in the drying / baking of the coating / printing after the production of the DI can to increase the pressure resistance.

[Brief description of drawings]

Fig. 1 shows the winding temperature of hot-rolled sheet and the ear height during DI can making (△
H), a graph showing the relationship between the crystal grain size of the steel sheet, and FIG. 2 is a graph showing the relationship between the crystal grain size of the steel sheet and the can expansion ratio during flanging.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Sekita 1 Kawasaki-cho, Chiba City, Chiba Prefecture Chiba Works, Kawasaki Steel Co., Ltd. (56) Reference JP 58-27930 (JP, A) Toyo Steel sheet "Kito and Tin Free Steel" (published by Agnes, September 30, 1970), pages 25 and 63

Claims (1)

[Claims] 1. C0.01-0.10% and Mn0.50% in weight%
Below, sol.Al 0.003-0.050%, N 0.0040% or less is contained, and the balance is made of steel consisting of Fe and unavoidable impurities. The steel material is heated to a temperature of 1200 ° C or higher and hot rolled. In addition, when the hot-rolled sheet that has undergone the hot rolling is wound in a temperature range of less than 580 ° C. and further cold-rolled and then subjected to continuous annealing, the temperature is recrystallized to a temperature of Ac ₁ point or less. Heated to 500-400 ° C in the subsequent cooling process
DI having good bake hardenability with good flange formability, characterized by cooling in the temperature range of 10 seconds or more, performing temper rolling after completion of continuous annealing, and subsequently performing electrotin plating.
Manufacturing method of steel plate for can.