JP2013147744A - Steel sheet for aerosol can bottom and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a steel sheet for an aerosol can bottom having high pressure capacity and excellent workability.SOLUTION: The steel sheet for an aerosol can bottom has component composition containing, in mass%, 0.020-0.090% of C, 0.01-0.05% of Si, 0.05-0.60% of Mn, 0.001-0.100% of P, 0.001-0.025% of S, not less than 0.0010% and less than 0.0070% of N, and 0.0010% to {-4.2×N content(%)+0.11}% of Al, with the balance comprising Fe and unavoidable impurities, wherein sheet thickness is 0.350 mm or less, product of lower yield strength (N/mm) and the sheet thickness (mm) is 195 (N/mm) or less, and product of upper yield strength (N/mm) when performing room temperature aging at 25°C for 10 days after performing rolling strain with a rolling ratio of 10% and square of the sheet thickness (mm) is 52.0 N or more.

Description

  The present invention relates to a steel plate for an aerosol can bottom and a method for producing the same, and particularly to a steel plate for an aerosol can bottom having a high pressure strength and excellent workability and a method for producing the same.

  There are various structures of aerosol cans, and examples include aerosol cans obtained by using a bottom steel plate as a steel plate and winding a bottom steel plate around a can body. The structure of an aerosol can equipped with a bottom is shown in FIG. The bottom 1 of the aerosol can shown in FIG. 1 is obtained by punching a raw material into a circular blank, processing it into a predetermined shape by pressing, and winding it around the can body 2 via a flange portion provided at the edge. . A mounting cap 3 having a function of injecting contents and a spray nozzle 4 are attached to the can body 2 together.

  The aerosol can is filled with a propellant for injecting the contents. For this reason, the inside of the aerosol can is in a high pressure state. Therefore, the bottom of the aerosol can needs to have a sufficiently high pressure strength to withstand the internal pressure.

  As with aerosol cans, for example, the following is disclosed as a technique related to a steel plate used in a container that requires pressure resistance.

  Patent Document 1 discloses a surface treatment original plate for a DI can excellent in pressure strength and necked-in properties and a manufacturing method. % By weight, C: 0.0100-0.0900%, Si: ≦ 0.30%, Mn: 0.05-1.00%, P: ≦ 0.030%, S: ≦ 0.025%, SOl. Al: 0.010-0.100%, N: 0.0005-0.0120%, the balance of steel consisting of iron and inevitable impurities, CT: 660-750 ° C., cold rolling ratio: 84- 91%, annealing temperature: box annealing at a recrystallization temperature of 700 ° C. An annealed sheet with Sno of 9.5 or more and an axial ratio of 1.4 or less is tempered and rolled with an elongation of 2% or more and 30% or less. Hv (10% BH) is 145 or more, Hv (70% BH) ) Is adjusted to 195 or less.

Patent Document 2 discloses a steel plate for DI can excellent in pressure strength and neck workability, and a manufacturing method thereof. % By weight, C: 0.01 to 0.08%, Mn: 0.5% or less, SolAl: 0.20% or less, N: 0.01% or less, and if necessary, 0.1% or less It contains at least one of S, Cr, Cu, Ni and / or at least one of Ti and Nb of 0.1% or less, the amount of solid solution C is 5-25 ppm, and the YP in the L direction is 30-44 kgf. / mm ^2, the difference in YP of L direction and C direction are steel sheet for 2 kgf / mm ² or less of DI can, a hot-rolled sheet of the above ingredients was cooled with cold rolled after recrystallization 60 ° C. / sec The manufacturing method which hold | maintains for 30 to 180 second at 300-450 degreeC, and carries out temper rolling of the rolling rate: 3-12% by wet after that is disclosed.

  Patent Document 3 discloses a steel plate for DI can excellent in deep drawing workability, ironing workability, neck workability and pressure strength. By weight, C: 0.01% or less, Si: 0.05% or less, Mn: 0.5% or less, P: 0.03% or less, S: 0.015% or less, Al: 0.001% After continuously rolling and pickling a continuous cast slab containing 0.1% or less and N: 0.01% or less and comprising the remaining Fe and inevitable impurities, the first is performed in the range of a rolling rate of 50 to 85%. After performing the cold rolling for the first time, and then performing the first recrystallization annealing, the second cold rolling is performed at a rolling rate of 70 to 95%, and then the second recrystallization annealing is performed. Furthermore, a manufacturing method for performing temper rolling of 5 to 35% is disclosed.

  Patent Document 4 discloses a steel plate for cans that has high bake hardenability and does not cause aging deterioration at high temperatures. C: 0.08 wt% or less, Si: 0.10 wt% or less, Mn: 1.5 wt% or less, P: 0.20 wt% or less, S: 0.020 wt% or less, Al: 0.030 to 0.150 wt% , N: A steel slab containing 0.0030 wt% or less is hot-rolled at a finish rolling temperature of 800 to 950 ° C, wound up at 600 ° C or higher, cold-rolled at a reduction rate of 80% or higher, and then 3% hydrogen The above and the balance are substantially composed of nitrogen, and are continuously annealed in an atmosphere having a dew point of −20 ° C. or higher and maintained at a soaking temperature not lower than the recrystallization temperature for 10 seconds to less than 40 seconds. The yield elongation when aging treatment is performed at 250 ° C. for 60 seconds is 3.0 by performing decarburization treatment with a decarburization amount of 5 ppm or more and then performing secondary cold rolling at a reduction rate of 1 to 15%. % After aging resistance and 2% pre-strain, Steel sheet for cans which curing amount is granted bake hardenability is not less than 40MPa when heated for 20 minutes at ℃ is disclosed.

Japanese Patent Laid-Open No. 7-278744 JP-A-8-311609 JP-A-8-60242 Japanese Patent Laid-Open No. 11-199991

  Patent Document 1 discloses a technique for ensuring a compressive strength by defining Hv (10% BH) which is an Hv value after performing BH heat treatment by additional rolling pre-strain with an elongation of 10% and heat treatment at 210 ° C. × 5 min. It is. Certainly, in the case of DI cans, after bottom processing corresponding to 10% additional rolling, heating is performed at 210 ° C. for about 5 min after baking, which is appropriate for evaluating the characteristics by the above method. There is sex. However, since the bottom of the aerosol can shown in FIG. 1 is processed after painting and baking, the above evaluation method cannot evaluate the characteristics. Moreover, although the technique of patent document 1 manufactures by box annealing, this annealing method has a subject in the homogeneity of material and productivity.

  Patent Document 2 is a technique for obtaining predetermined mechanical characteristics by regulating the bake hardenability by defining the amount of solute C and by performing temper rolling at 3 to 12% in a wet manner. Certainly, in the case of DI cans, heating is performed at 210 ° C for about 5 minutes for baking after bottom processing, so it is an effective means to control the amount of solute C that contributes to age hardening at this temperature. It is believed that there is. However, since the bottom of the aerosol can shown in FIG. 1 is not heated at a temperature of about 200 ° C. after the bottom processing, it cannot be expected to be cured by solid solution C, which is not an effective means.

  Patent Document 3 has a drawback in that the manufacturing process and cost increase because the manufacturing process is multi-step.

  Patent Document 4 describes that the bake hardening amount after heat treatment at 210 ° C. for 20 minutes is excellent, but the bottom of the aerosol can shown in FIG. 1 is heat-treated at a temperature of about 200 ° C. after bottom processing. Since it is not performed, there is a problem that curing cannot be expected.

  As described above, technologies that mainly focus on the bottom of DI cans have been proposed for improving pressure resistance, but with regard to aerosol can bottom materials that have different processing and heat treatment conditions from DI cans, improvement of pressure strength is possible. There is no technology for the purpose.

  This invention is made | formed in view of this situation, and it aims at providing the steel plate for aerosol can bottoms which has high pressure strength and favorable workability, and its manufacturing method.

  In order to increase the pressure strength, it is effective to increase the strength of the steel sheet. In addition, since the pressure strength is affected by the shape of the bottom, the bottom of the aerosol can needs to have a structure protruding to the inside of the can. Therefore, the steel plate needs to have workability for processing into such a shape.

The present inventors examined the influence of the mechanical properties and thickness of the steel sheet on the pressure resistance and workability of the aerosol can bottom. As a result, it has been found that the required pressure strength and workability can be achieved by controlling the mechanical properties and the plate thickness to specific conditions. That is, it has been found that a steel plate having both high pressure strength and good workability can be obtained by appropriately controlling the plate thickness and mechanical properties, particularly the yield strength and room temperature age hardening behavior.
In addition, in order to obtain mechanical properties that meet the above specific conditions, Al and N are in a specific content relationship, and by specifying slab heating temperature, winding temperature, etc. as manufacturing conditions, pressure strength and processing It has been found that a steel sheet having excellent properties can be obtained.

The present invention is based on such knowledge, and the gist thereof is as follows.
[1] By mass%, C: 0.020% to 0.090%, Si: 0.01% to 0.05%, Mn: 0.05% to 0.60%, P: 0.00. 001% or more and 0.100% or less, S: 0.001% or more and 0.025% or less, N: 0.0010% or more and less than 0.0070%, Al: 0.010% or more {−4.2 × N Content (%) + 0.11}% or less, the remainder has a component composition consisting of Fe and inevitable impurities, the plate thickness is 0.350 mm or less, the falling yield strength (N / mm ² ) and the above Upper yield strength (N / mm) when the product with the plate thickness (mm) is 195 (N / mm) or less and rolling pre-strain is performed at a rolling rate of 10% and then room temperature aging is performed at 25 ° C. for 10 days. and ^2), aerosol can the product of the square of the plate thickness (mm) is equal to or not less than 52.0N Tom for steel plate.
[2] By mass%, C: 0.020% to 0.090%, Si: 0.01% to 0.05%, Mn: 0.05% to 0.60%, P: 0.0. 001% or more and 0.100% or less, S: 0.001% or more and 0.025% or less, N: 0.0010% or more and less than 0.0070%, Al: 0.010% or more {−4.2 × N Containing a content (%) +0.11}% or less, and melting a steel having a component composition with the balance consisting of Fe and inevitable impurities,
After making a slab by continuous casting and reheating the slab to a temperature of 1150 ° C or higher,
Hot rolling at a coiling temperature of less than 620 ° C., pickling, primary cold rolling, recrystallization annealing,
Secondary cold rolling is performed at a rolling rate of more than 3% and less than 18%, and the sheet thickness is set to 0.350 mm or less,
The product of the yield strength (N / mm ² ) and the plate thickness (mm) of the obtained steel sheet is 195 (N / mm) or less and a rolling pre-strain at a rolling rate of 10% is applied, and then at 25 ° C. for 10 days. The product of the upper yield strength (N / mm ² ) and the square of the plate thickness (mm) when subjected to room temperature aging is 52.0 N or more. .
[3] The method for producing a steel plate for an aerosol can bottom according to [2], wherein 75% or more of the amount of N is left as solid solution N.
[4] The method for producing a steel plate for an aerosol can bottom according to [2] or [3], wherein the difference between the slab surface temperature and the slab center temperature is within 20 ° C. in the reheating of the slab.
In the present invention, “%” indicating the ratio of the component composition is all by mass.

  ADVANTAGE OF THE INVENTION According to this invention, the steel plate for aerosol can bottoms which has high pressure strength and favorable workability can be obtained.

It is a figure which shows the structure of the aerosol can obtained by winding the steel plate for aerosol can bottoms to a can body.

  The present invention is described in detail below.

  First, the component composition will be described. All components are in weight percent.

C: 0.020% or more and 0.090% or less The steel sheet of the present invention is manufactured through each process of continuous casting, hot rolling, pickling, primary cold rolling, recrystallization annealing, and secondary cold rolling. It is a steel plate and needs to have the mechanical characteristics described later. In a steel sheet satisfying such characteristics, the amount of C added as a solid solution strengthening element is important, and the lower limit of the C content is 0.020%. If it is less than 0.020%, the mechanical properties specified in the present invention cannot be obtained. On the other hand, if the amount of addition of C exceeds 0.090%, not only becomes excessively hard, but also a pearlite structure described later tends to be formed. In addition, cracks are likely to occur during the solidification process of the continuously cast slab. Therefore, the upper limit is 0.090%. Preferably they are 0.030% or more and 0.070% or less.

Si: 0.01% or more and 0.05% or less Si is an element that increases the strength of steel by solid solution strengthening. In order to exhibit this effect, the lower limit is made 0.01%. On the other hand, if it is added in a large amount, the corrosion resistance is remarkably impaired. Therefore, the upper limit is made 0.05%.

Mn: 0.05% or more and 0.60% or less Mn is an element effective in preventing hot cracking due to S, and should be added according to the amount of S contained. Further, Mn is an element effective for making the crystal grains fine and improving the strength. In order to exert these effects, the lower limit is made 0.05%. On the other hand, when Mn is added in a large amount, the strength of the steel sheet can be increased, but the corrosion resistance is lowered, so the upper limit is made 0.60%.

P: 0.001% or more and 0.100% or less P is an element having a large solid solution strengthening ability, but if added in a large amount, corrosion resistance is remarkably impaired. Therefore, the upper limit is 0.100%. On the other hand, in order to make P less than 0.001%, the dephosphorization cost becomes excessive. Therefore, the lower limit is made 0.001%.

S: 0.001% or more and 0.025% or less S is an impurity derived from a blast furnace raw material, and combines with Mn in steel to generate MnS. Since MnS precipitates at grain boundaries at high temperatures and causes embrittlement, the upper limit is made 0.025%. On the other hand, desulfurization cost becomes excessive to make S less than 0.001%. Therefore, the lower limit is made 0.001%.

N: 0.0010% or more and less than 0.0070% N is an element contributing to solid solution strengthening and strain age hardening described later. In order to express these effects, the lower limit is made 0.0010%. On the other hand, when added excessively, hot ductility is deteriorated, and workability deteriorates due to excessive hardening of the steel sheet. This is particularly noticeable in steel sheets that are subjected to secondary cold rolling as in the present invention. Therefore, the upper limit is made 0.0070%.

Al: 0.010% or more {-4.2 × N content (%) + 0.11}% or less Al acts as a deoxidizer and is an element necessary for increasing the cleanliness of steel. Al combines with N in the steel to form AlN. In the present invention, since strain age hardening by the action of solute N is used, it is necessary to suppress excessive precipitation of AlN. For this reason, it is necessary to prescribe | regulate the upper limit of Al amount. The amount of precipitation of AlN is determined by the amount of Al, the amount of N, the thermal history in the process of slab solidification to slab reheating, and the thermal history in the winding process of hot rolling. As a result of examining the conditions for suppressing the precipitation of AlN by combination with the manufacturing conditions described later, the upper limit of the Al amount is {−4.2 × N (%) + 0.11}% or less in relation to the N amount. There is a need to. On the other hand, in steels with an Al content of less than 0.010%, deoxidation is insufficient and the cleanliness of the steel deteriorates, so the lower limit is made 0.010%. In the present invention, Al is acid-soluble Al.

  In the present invention, it is preferable that 75% or more of the N amount remains as solid solution N by adjusting the relationship between Al and N described above, and the slab heating temperature described later and the coiling temperature in hot rolling. Due to the remaining solid solution N, strain age hardening at room temperature is effectively exhibited.

  The balance is Fe and inevitable impurities.

  The steel sheet of the present invention preferably has a structure that does not contain a pearlite structure. The pearlite structure is a structure in which a ferrite phase and a cementite phase are precipitated in a layered form. When a coarse pearlite structure is present, there is a risk that it may become a starting point of cracks due to stress concentration during deformation. When the steel plate for an aerosol can bottom is attached to the can body by winding, there is a possibility that cracking of the tightening portion may occur if such a crack starting point exists.

  Next, the relationship between the plate thickness of the steel sheet of the present invention and the mechanical properties will be described.

  The thicker the steel plate used for the aerosol can bottom and the higher the strength, the better. However, excessive plate thickness and strength cause the bottom workability to deteriorate. Specifically, the bottom is not processed into a regular shape, and in the bottom processing step, the processing tool is worn out or frequently damaged. These are caused by an increase in the deformation resistance of the steel sheet due to an excessive thickness and strength, and a high load is applied to the processing tool. Therefore, in order to avoid this, it is necessary to appropriately limit the plate thickness and strength from the viewpoint of workability.

  Aerosol can bottoms need to be designed with economic strength in addition to pressure strength and workability. That is, an excessive plate thickness increases the cost of the steel plate that is the bottom material. From these viewpoints, in the present invention, the thickness of the steel plate is limited to 0.350 mm or less.

  The deformation resistance in the bottom processing depends on the plate thickness, strength, and bottom size of the steel plate. The strength of the steel sheet is affected by the yield strength of the steel sheet before bottom processing. This is thought to be because the bottom is machined at a high degree of work beyond the strain at which the upper yield point appears. The present inventors have found that the product of the yield strength, the plate thickness, and the bottom diameter is an index related to the deformation resistance. In the present invention, the diameter of the bottom is considered in advance as a condition for suppressing the above-described inconvenience even in actual processing at the nominal diameter 211 diameter, which is the largest diameter in practical use in the aerosol can bottom. As an index, the product of the plate thickness and the yield strength of the steel sheet before bottom processing is limited to 195 N / mm or less.

  Even when the same material is used, the smaller the bottom diameter, the lower the deformation resistance. Therefore, when the above evaluation index is applied to the steel plate used for the bottom having a diameter smaller than 211, the deformation resistance is excessive. Never become.

  The bottom of the aerosol can is processed into a shape protruding inside the can in order to withstand the pressure inside the can. This processing introduces strain into the steel sheet. Since the introduction of strain improves the strength of the steel sheet, it contributes to the improvement of the pressure resistance of the bottom of the aerosol can. However, it is not practical to improve the compressive strength to a necessary level only by strain because the degree of processing needs to be very high. Therefore, it is effective to use a high strength steel plate in advance.

  On the other hand, if the strength of the steel plate is too high, bottom processing cannot be performed. In order to overcome such a contradiction, the inventors focused on strain age hardening. That is, attention was paid to hardening the steel sheet by aging after the introduction of strain due to processing.

  The strain age hardening of a steel sheet is generally expressed by intentional heat treatment. For example, paint baking is performed after processing. Therefore, in order to evaluate the strain age hardening behavior of a steel sheet, after performing a predetermined process, an intentional heat treatment of several minutes to several tens of minutes is performed at a temperature of about 170 to 220 ° C. assuming coating baking. Means were taken.

  On the other hand, the heat treatment performed after processing in the manufacture of the aerosol can bottom is a very slight process of several tens of degrees and several minutes in order to dry the sealing compound. And the aerosol can bottom is put into actual use after being stored at room temperature, not immediately after processing. In other words, room temperature aging is the main aging process for aerosol can bottoms.

  Therefore, in order to evaluate the strain age hardening behavior of the steel sheet used for the aerosol can bottom, the conventional means for performing heat treatment at a relatively high temperature for a long time is not appropriate because it gives an excessive heat history. Therefore, in the present invention, with reference to the actual processing of the aerosol can bottom, the aging process until actual use, and the results of the pressure strength at that time, the strain age aging is used as an index of strain aging hardening behavior. Pay attention. Specifically, the yield strength after 10% rolling pre-straining of the steel sheet and then room temperature aging at 25 ° C. for 10 days is used as an index of strain aging hardening behavior.

  Here, the 10% rolling pre-strain is applied to the steel plate in order to reproduce the bottom processing strain. In determining this condition, the present inventors actually processed various aerosol can bottoms and investigated the processing degree. First, a plurality of lines passing through the center of the bottom circular plate are marked at a pitch of 15 ° in the circumferential direction, and a plurality of concentric circles are marked at a pitch of 5 mm in the radial direction. Processed into a bottom. After processing, the distortion in the bottom radial direction and the distortion in the circumferential direction due to the processing were calculated at each position of the bottom based on the marks. Also, the strain in the thickness direction was calculated from the strain of both under the condition of a constant volume. As a result, it was found that the highest degree of processing at various bottoms was about 0.1 in terms of equivalent strain. An equivalent strain of 0.1 corresponds to a rolling reduction of 10% in processing by rolling. From this result, a rolling pre-strain of 10% was adopted as a process for reproducing the distortion of the bottom process.

  In the present invention, room temperature aging conditions are an aging temperature of 25 ° C. and an aging time of 10 days. This is based on the actual use situation of aerosol cans. That is, the aerosol can is stored for a certain period of time after the bottom processing, and thereafter used. As a result of investigating the storage condition and the condition for use, it was found that the temperature was an average of 25 ° C. and the period was an average of 10 days. Therefore, the above conditions were determined as an aging temperature and an aging time.

  The upper yield strength was used for the evaluation of room temperature strain age hardening behavior. This is based on the inventor's experimental results that the bottom pressure strength is reproduced with a higher correlation coefficient at the upper yield point than at the lower yield point.

  The higher the yield strength after aging at room temperature, the higher the compressive strength, but the compressive strength is influenced by the plate thickness in addition to the upper yield strength. As a result of experiments by the present inventors, it has been found that the plate thickness affects the pressure resistance strength by its square. Specifically, as a condition that the pressure resistance at the nominal diameter 211 diameter, which is the largest diameter in practical use in an aerosol can, is 1.65 MPa or more, the product of the upper yield strength after room temperature strain aging and the square of the plate thickness is 52.0 N By limiting to the above, it was found that a steel plate for an aerosol can bottom having excellent pressure strength and workability can be obtained. In the case where the same material is used, the pressure resistance increases as the bottom diameter decreases. Therefore, the above evaluation index can be applied to the steel plate used for the bottom having a diameter smaller than 211 diameters. There is no shortage.

  The yield strength (upper yield strength, lower yield strength) of the present invention was measured in accordance with JISZ2241 “Metal material tensile test method” using a No. 5 test piece defined in JISZ2201 “Metal material tensile test piece”. . For the elongation of 10%, the elongation based on the gauge length of 50 mm was adopted. The tensile direction of the tensile test is the rolling direction of the steel sheet. In general, since the yield strength of a steel sheet is the lowest in the rolling direction, it is a reference for the lower limit value of the bottom pressure strength.

  Next, the manufacturing method of the steel plate for aerosol can bottoms with the high pressure strength of this invention and excellent workability is demonstrated.

  The steel sheet of the present invention is produced through each step of continuous casting, hot rolling, pickling, primary cold rolling, recrystallization annealing, secondary cold rolling, and surface treatment as necessary. Details will be described below.

  A steel having the above-described composition is melted and made into a slab by continuous casting.

  In continuous casting, when a slab is produced by a vertical bending type or curved type continuous casting machine, the surface temperature of the slab corner portion in a region where bending or bending back deformation is applied to the slab shall be 800 ° C. or lower or 900 ° C. or higher. Is preferred. Thereby, the crack in the corner | angular part of the long side and short side in a slab cross section can be avoided.

  The slab after continuous casting is reheated to a slab heating temperature of 1150 ° C. or higher. By reheating the slab at a temperature of 1150 ° C. or higher, the AlN deposited during the slab cooling process can be dissolved.

  In the reheating of the slab, by making the difference between the slab surface temperature and the slab center temperature within 20 ° C., the dissolution of AlN becomes uniform in the slab and the material uniformity is improved. In particular, the crystal structure after the subsequent hot rolling, primary cold rolling, annealing, and secondary cold rolling becomes uniform in the thickness direction of the steel sheet, thereby improving the material uniformity.

Next, the slab is hot-rolled by a conventional method. At this time, the finishing temperature in the hot rolling is preferably set to a temperature equal to or higher than the Ar ₃ transformation point.

  The coiling temperature is less than 620 ° C. When the coiling temperature after finish rolling is 620 ° C. or higher, AlN precipitates and the effect of N in the present invention cannot be obtained. In order to avoid excessive hardening, the winding temperature is preferably 540 ° C. or higher.

  After hot rolling, the cooled hot-rolled steel strip is pickled to remove scale. Pickling can be performed according to a conventional method such as a sulfuric acid method or a hydrochloric acid method.

  Next, primary cold rolling is performed. The primary cold rolling is preferably performed at a rolling rate of 80% or more. This is for crushing the pearlite structure produced after hot rolling. If the primary cold rolling rate is less than 80%, the pearlite structure may remain. The upper limit of the primary cold rolling rate is preferably 95% or less in order to avoid an increase in the load on the rolling mill due to an excessive rolling rate and the accompanying occurrence of rolling defects.

Recrystallization annealing is performed after primary cold rolling. As the recrystallization annealing, continuous annealing is preferable. This is because, in the case of box annealing, solid solution N precipitates as AlN, and room temperature strain age hardening necessary in the present invention may not be obtained. Further, the annealing temperature is preferably less than the A ₁ transformation point. When the annealing temperature and A ₁ transformation point or higher, austenite phase formed during annealing, there are cases where pearlite structure that could be a starting point of cracking when the bottom of the processing are formed.

  After annealing, secondary cold rolling is performed at a rolling rate of more than 3% and less than 18%. By performing secondary cold rolling, predetermined mechanical properties and surface roughness can be imparted to the steel sheet. In the present invention, if the secondary cold rolling rate is 3% or less, the strength of the steel sheet necessary for securing the pressure strength cannot be obtained. On the other hand, when it becomes 18% or more, the steel sheet becomes excessively hard due to work hardening, and workability is impaired. Accordingly, the secondary cold rolling rate is more than 3% and less than 18%.

  The steel sheet of the present invention is preferably subjected to a surface treatment with a plating layer and a surface treatment for applying an organic resin coating on both sides or one side of the steel plate. Thereby, the workability of bottom processing is further improved. This is presumably because the friction coefficient on the steel sheet surface is lowered due to the presence of the organic resin coating, and the workability of the bottom is improved accordingly. The function of the plating layer is to ensure adhesion between the organic resin coating and the steel sheet and to ensure corrosion resistance. Typical examples of surface treatment include the treatment of metals, metal oxides, metal hydroxides, inorganic salts, such as tin plating (tinplate) and chrome plating (tin-free steel) that exhibit the above functions. is there. The organic resin film coating on the upper layer includes an organic resin film laminating process and a coating process.

  In these surface treatments, the steel sheet may be subjected to heat treatment. The steel sheet is subjected to aging by this heat treatment. Also, when the steel sheet is stored in the period before being processed into the bottom, it is subjected to aging according to the storage temperature and period. Furthermore, it is also subjected to aging when painting on steel sheets. However, aging in these original plate states does not affect the effect of the present invention.

  As described above, a steel plate for an aerosol can bottom having high pressure strength and excellent workability is produced.

  Examples will be described below.

  Steel having the composition shown in Table 1 was melted, and hot rolling, primary cold rolling, recrystallization annealing, and secondary cold rolling were performed under the conditions shown in Table 2. Thereafter, for symbols C1, E1, and H1 in Table 2, tin-free steel subjected to chrome plating was used as a surface treatment, and a PET film was laminated to obtain a laminated steel plate. Other than the above in Table 2, tin plating was applied as a surface treatment, and further, coating and baking treatment were performed.

With respect to the steel sheet obtained as described above, the No. 5 test piece defined in JISZ2201 “Metal material tensile test piece” was used, and the yield strength (YP) was determined by a tensile test according to JISZ2241 “Metal material tensile test method”. It was measured. Further, after the steel sheet was subjected to 10% rolling pre-strain, the upper yield strength (YP ^* ) after room temperature aging at 25 ° C. for 10 days was measured. Based on the measurement results of the lower yield strength and the upper yield strength, the product (t · YP) of the lower yield strength (N / mm ² ) and the sheet thickness t (mm), and 25 ° C. after 10% rolling pre-strain. The product (t ² · YP ^* ) of the upper yield strength (N / mm ² ) and the square of the sheet thickness t (mm) when subjected to room temperature aging for 10 days was determined. In addition, as evaluation of workability, when t · YP was 195 N / mm or less, “good”, and when t · YP exceeded 195 N / mm, “x” was given. In addition, as evaluation of the pressure resistance, it was evaluated as “good” when t ² · YP ^* was 52.0 or more, and “x” when t ² · YP ^* was less than 52.0N.

  The obtained results are shown in Table 3.

  From the results of Table 3, it can be seen that when the components and production conditions are within the scope of the claims of the present application, excellent performance is exhibited.

1 Bottom 2 Can body 3 Mounting cap 4 Spray nozzle

Claims (4)

In mass%, C: 0.020% to 0.090%, Si: 0.01% to 0.05%, Mn: 0.05% to 0.60%, P: 0.001% or more 0.100% or less, S: 0.001% or more and 0.025% or less, N: 0.0010% or more and less than 0.0070%, Al: 0.010% or more {-4.2 × N content ( %) + 0.11}% or less, with the balance being composed of Fe and unavoidable impurities, with a plate thickness of 0.350 mm or less, falling yield strength (N / mm ² ) and the plate thickness ( mm) and the yield strength (N / mm ² ) when performing room temperature aging at 25 ° C. for 10 days after rolling pre-strain at a rolling rate of 10%. An aerosol can bottom characterized in that a product of the square of the plate thickness (mm) is 52.0 N or more Steel plate. In mass%, C: 0.020% to 0.090%, Si: 0.01% to 0.05%, Mn: 0.05% to 0.60%, P: 0.001% or more 0.100% or less, S: 0.001% or more and 0.025% or less, N: 0.0010% or more and less than 0.0070%, Al: 0.010% or more {-4.2 × N content ( %) + 0.11}% or less, and the remainder has a component composition composed of Fe and inevitable impurities,
After making a slab by continuous casting and reheating the slab to a temperature of 1150 ° C or higher,
Hot rolling at a coiling temperature of less than 620 ° C., pickling, primary cold rolling, recrystallization annealing,
Secondary cold rolling is performed at a rolling rate of more than 3% and less than 18%, and the sheet thickness is set to 0.350 mm or less,
The product of the yield strength (N / mm ² ) and the plate thickness (mm) of the obtained steel sheet is 195 (N / mm) or less and a rolling pre-strain at a rolling rate of 10% is applied, and then at 25 ° C. for 10 days. The product of the upper yield strength (N / mm ² ) and the square of the plate thickness (mm) when subjected to room temperature aging is 52.0 N or more. .   The method for producing a steel plate for an aerosol can bottom according to claim 2, wherein 75% or more of the N amount is left as solid solution N.   The method for producing a steel plate for an aerosol can bottom according to claim 2 or 3, wherein, in the reheating of the slab, the difference between the slab surface temperature and the slab center temperature is within 20 ° C.

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