JP3377825B2 - Steel plate for can and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to tempers T1 to T6, D
R8 to 10 steel plates for cans and methods for manufacturing the same, and particularly, a thin plate for 3 piece cans, a high-strength and good weldability plate for cans, and a thin plate for 2 piece cans and deep drawing The present invention relates to a plated original plate for cans having good properties and a method for producing the same.

[0002]

[Prior art]

(1) Types of cans There are two-piece cans and three-piece cans manufactured from steel plates. The former is SDC (SHALLOW-DRAWN CAN), DRDC (DRA
WN & REDRAWN CAN), DTRC (DRAWN & THIN REDRAWN CA
N) and DWIC (DRAWN & WALL IRONINED CAN).

(2) Types of Steel Plates for Cans and Manufacturing Methods Thereof These cans are manufactured by subjecting appropriately plated steel plates to can forming processes such as deep drawing, ionization, bending, stretching and welding. However, the original plate has tempers T1 to T6, DR8 depending on the characteristics of the can to be manufactured and the manufacturing method.
It is divided into ~ 10. T1 to T3 are soft original plates, T4 to T6
Is called a hard original plate, and both are manufactured by subjecting a cold-rolled steel plate to one temper rolling. On the other hand, DR8 ~
DR10, which is called a DR original plate, is manufactured by rolling a cold rolled steel plate with a high reduction ratio.

Conventionally, these steel sheets are basically different in requirements such as strength and workability. Therefore, a base material having different components is prepared from the beginning, and hot rolling, cold rolling, annealing conditions and the like are individually performed. It was manufactured by changing it. Therefore, the manufacturing cost must be relatively high because the process needs to be switched for different production. (3) Three-piece steel plate for cans and its problems Steel plates for cans are required to be thin and have high strength in order to reduce the cost of cans. Three-piece cans are no exception. A three-piece can is required to have better high-speed weldability. In particular, a good seam is required to be obtained by the electric seam welding method with a welding speed of 70 mpm or more.

However, in the conventional technique, when the wall thickness is reduced, the proper welding current range is narrowed, and when the welding current is increased, splash is generated during welding and the hardness of the welded portion is increased. The heat affected zone of the weld, that is, the HAZ zone (HEAT AFFE
Flange cracks tended to occur in CTED ZONE).

However, the joint strength must be high in view of the function of the can, so that the welding current must be set high and HAZ cracks are likely to occur. In addition, in recent years, in the can manufacturing process, in order to improve the efficiency of the coating process, coil coating has been performed in which the coating process is performed at the stage of coiling the steel plate for a can. It is desired to apply this method to the high-speed welding method. To do this, the varnish cutting part (the unpainted welded part) is made parallel to the rolling direction, and the winding direction of the can body is set to the rolling direction. It is necessary to make them parallel to each other.

However, when the can body is wound and welded in this direction and then flange processing is performed, cracks occur at the HAZ portion. Therefore, conventionally, a varnish cutting portion (uncoated portion) is provided at right angles to the rolling direction, and therefore high-speed welding cannot be performed on a coil-coated steel strip. (4) Steel plate for two-piece can and its problems Conventional conventional steel plate for two-piece can used a soft original plate having good press workability. Further, since tin is generally plated, tin does not have to be particularly large because tin serves as a lubricant for press working.

However, when an ultra-thin and high-strength steel sheet is used, the r value of the steel sheet is generally low, so that the deep drawability is poor, and the periphery of the cup bottom sometimes breaks during processing. Further, if the Δr value is large, the earring becomes large during the cup processing, and therefore the blank diameter must be increased, which is uneconomical. Further, since the ultra-thin steel sheet has a low rigidity, wrinkles may occur on the body wall or the shoulder portion of the punch may be broken during press working.

[0009] The same problem occurs in such a hard master plate as in the DR master plate. (5) Problem of plating thickness In general, can steel plates are often tin-plated, but the tin areal weight has been reduced due to cost reduction and resource saving. For example, in recent years, those having a basis weight of 2.8 g / m ^{2 and} a weight of less than 1 g / m ² have been used in recent years.

In that case, it is necessary to improve the corrosion resistance of the steel sheet itself. Many efforts have been made in the past to solve these problems. For example, Japanese Patent Publication 1-5245
Japanese Unexamined Patent Publication No. 0 discloses a method of manufacturing a steel sheet for cans of T1 to T3 by subjecting ultra-low carbon steel to continuous annealing and then temper rolling, but all of the above problems can be solved. is not.

[0011]

The object of the present invention therefore lies in the following points. (1) T1 by changing only the condition of temper rolling from the cold rolled steel sheet manufactured under the same composition and the same rolling condition
Providing technology for manufacturing T6, DR8 to DR10 plating base plates, (2) Providing can steel plates with good high-speed weldability and free from HAZ cracks, (3) Rolling direction of can barrel In parallel, and to provide a plating base plate that enables high-speed welding, and (4) to provide an ultrathin, high-strength can steel plate with good press workability,
(5) It is to provide a steel plate for a can having good corrosion resistance even with a light weight.

[0012]

To achieve the above object, the present invention has the following constitution. That is, the present invention provides C
≤0.004%, Si≤0.03%, Mn: 0.05-0.6%, P≤0.02
%, S ≦ 0.02%, N ≦ 0.01%, Al: 0.005 to 0.1%, N
b: 0.001 to 0.1%, B: 0.0001 to 0.005% (both by weight) , Sn ≧ 0.001%, Sb ≧ 0.001%,
Contains one or more of As ≧ 0.0001% and Te ≧ 0.0001%
However , the others are steel sheets made of Fe excluding unavoidable impurities, the recrystallized grain size of which is 30 μm or less at the maximum, and 5
A steel sheet for cans in which the area ratio occupied by recrystallized grains of .about.25 .mu.m is 50% or more, and the present invention is C.ltoreq.0.004%, Si.ltoreq.0.03.
%, Mn: 0.05 to 0.6%, P ≦ 0.02%, S ≦ 0.02%, N ≦
0.01%, Al: 0.005-0.1%, Nb: 0.001-0.1%,
B: comprises 0.0001 to 0.005% (all% by weight), further
, Sn ≧ 0.001%, Sb ≧ 0.001%, As ≧ 0.0001%, Te ≧
Contains at least one of 0.0001%, and the balance is substantially
Ultra-low carbon steel slab made of Fe is heated to 1000-1200 ℃,
Hot rolling finish temperature 800 ~ 900 ℃, coiling temperature 500 ~ 650 ℃, hot rolling, pickling, cold rolling, continuous annealing 650 ~ 800
This is a method for producing a steel plate for a can at 60 ° C within 60 seconds.

[0013] steel sheet for cans of the present invention, as possible out to contain more than 0.1% of Ti as required. Then, in the above steel sheet, inevitable impurities are limited as follows. Cr ≦ 0.1%, Cu ≦ 0.1%, Ni ≦ 0.1%, Mo ≦ 0.01
%, O ≦ 0.01%, V ≦ 0.01%, Zr ≦ 0.01%, Ca ≦ 0.005
%, REM ≤ 0.005%, Mg ≤ 0.001% and Na ≤ 0.001
%.

The steel sheet is usually tin-plated or chromated before use.

[0015]

[Action]

I. Basic findings As a result of intensive research conducted on the steel sheet for cans by the present inventors,
The following findings were obtained and the present invention was completed. (1) HAZ cracking in the process of manufacturing a three-piece can HAZ cracking is affected by the C content of the steel sheet and the grain size of recrystallized grains.

A) First, regarding the effect of C: It is customary that the hardness of the nugget portion of a steel sheet increases due to rapid heating / cooling to the vicinity of the melting point during high speed welding. However, in the case of ultra low carbon steel, it softens. Therefore, the total thickness of the nugget portion can be reduced, and the amount of deformation during flanging can be reduced. b) Effect of crystal grains: There is an optimum value for the size of crystal grains. If the size is too large, stress concentration causes grain boundary fracture and fracture occurs.

(2) Deep drawability of a two-piece can The r value, Δr value, and the occurrence of orange peel are important factors for the deep drawability of a two-piece can. a) r value and orange peel: The r value is improved by increasing the crystal grains. However, in that case, orange peel is likely to occur. There is a range of crystal grain size that maintains the balance between the two, and the manufacturing conditions described below are important for adjusting to that range.

B) Δr value: This value is poor in the D direction (direction of rolling direction and 45 °) because the cold reduction ratio is high in the steel sheet for cans. However, this can be solved by increasing the crystal grain size and making the distribution appropriate. (3) Adjustment of crystal grains As described above, it is important to adjust the crystal grains of the original plate for both the two-piece can and the three-piece can. As a means for that purpose, it is important to add a trace amount of Nb and B as the chemical composition of the steel sheet. Further, in order to avoid work hardening and strain age hardening, it is important to fix N in steel by adding an appropriate amount of Al.

Further, hot rolling conditions, cold rolling reduction,
The selection of annealing conditions is also important. The present inventors have clarified an appropriate range of these conditions and a combination condition. (4) Corrosion resistance It has been found that the cause of deteriorating the corrosion resistance of the thin tin-plated steel sheet is the precipitation of carbides at the grain boundaries of the steel sheet surface. In order to suppress the precipitation of carbides, it is preferable to use an extremely low carbon Al-killed steel composition, perform hot rolling at a lower temperature than usual, and employ a continuous annealing method.

II. Detailed Description of the Invention (1) The chemical component C affects the hardness, recrystallized grain size and earring of the tin plate. The effect on hardness is shown in FIG. 1 and the effect on earring development is shown in FIG. From these data, it is necessary to keep the tempering degree T1 or less by continuous annealing and to set C to 0.004% or less, preferably 0.003% or less in order to reduce the occurrence of earrings.

The occurrence of earrings was evaluated as shown in FIG. 2, where the maximum height of the can after pressing was Hmax and the minimum height was Hmin, {(Hmax-Hmin) / Hmin} × 100.
Expressed as (%). Since Si is a substitutional solid solution strengthening element that significantly deteriorates the corrosion resistance of tinplate and further hardens the material extremely, it should be avoided that Si is excessively contained. That is, if Si exceeds 0.03%, it hardens to produce a tin plate having a temper T1 to T3. Therefore, Si needs to be 0.03% or less.

Mn must be added to prevent the occurrence of ear cracks in the hot rolled coil. That is, if Mn is less than 0.05%, it is impossible to prevent the occurrence of ear cracking, while Mn is
If it exceeds 0.6%, the crystal grain size becomes finer and hardens, so Mn
Must be within the range of 0.05-0.6%. The amount of Mn added is also regulated as described later depending on the relationship with the S content in steel.

Since P is an element that hardens the material and deteriorates the corrosion resistance of tinplate, its excessive content is not preferable and P must be 0.02% or less. S causes cracks in the edges of the hot-rolled coil and sulfide-based inclusions that cause press defects, so S must be 0.02% or less. If the Mn / S ratio is smaller than 8, the above-mentioned edge cracking press defect is likely to occur, so this value is preferably set to 8 or more.

N is contained as a result of N in the air being mixed in during the steel manufacturing process. N is an interstitial solid solution strengthening element, and when N is dissolved in steel, a soft steel sheet can be obtained. Absent. Therefore, N needs to be 0.01% or less. Al is an element that exerts the function of a deoxidizer in the manufacturing process of steel, and the cleanliness of steel increases as the content in steel increases, so it is necessary to add an appropriate amount, but excessive addition of steel Since it suppresses the growth of recrystallized grains, Al needs to be 0.10% or less. On the other hand, if Al content is less than 0.005%, N in steel
The amount increases. Therefore, Al is made 0.005 to 0.10% in range.

Nb and B are important elements that affect the recrystallized grain size after annealing. That is, in the ultra-low carbon steel such as the steel of the present invention in which the amount of C is extremely reduced, the crystal grain size becomes very coarse, and the orange peel may occur as described below with the grain size exceeding 30 μm. To solve this problem and suppress the crystal grain size, it is necessary to add Nb and B together.

Nb is an element necessary for suppressing the excessive growth of crystal grains, and also has a function of forming carbonitrides to reduce the residual amount of solid solution C and N and improve workability. Have. To obtain these effects, 0.001% or more must be added. On the other hand, when a large amount is added, the recrystallization temperature becomes high due to the pinning effect of the crystal grain boundary due to Nb-based precipitates,
Nb should be 0.1% or less because the workability of the continuous annealing furnace is deteriorated.

When B is present together with Nb, it has an effect of preventing excessive coarsening of crystal grains. It is also useful for preventing secondary processing brittleness. That is, when a carbide forming element is added to the base of ultra-low carbon steel and the solid solution C is extremely reduced, the strength of the recrystallized grain boundary becomes weak, and the cryogenic temperature becomes low depending on the use of the can or the canning method. When it is stored in, there is a concern that embrittlement cracking may occur, but when B is added, embrittlement failure does not occur. B also forms carbides and nitrides and is therefore effective for softening. However, during continuous annealing, B segregates at the recrystallized grain boundaries and delays recrystallization, so it is 0.005% or less, and the lower limit is the above effect. 0.0001 needed to demonstrate
Must be at least%.

In order to adjust the recrystallized grains, which is the most important point of the present invention, Nb: 0.003 to 0.02%, B : 0.0003
It is preferably added in the range of 0.002%. Since Ti is a carbide and nitride forming element, it has a function of reducing the residual amount of solid solution C and solid solution N and improves workability. on the other hand,
When a large amount is added, microscopic observation of the cross section of the thin steel sheet reveals a sharp, extremely hard precipitate. In the steel sheet for cans, it is considered that such inclusions deteriorate the corrosion resistance and cause scratches when press working. Therefore, Ti should be 0.1% or less and added as necessary.

Since Sn, Sb, As and Te are easily enriched and concentrated on the surface of the thin steel sheet during annealing, the surface becomes inactive, so that enrichment and enrichment of C (graphite), which significantly deteriorates the corrosion resistance of tinplate, can be prevented. adhesion of the plating to effective element der Ri添 pressurized to improve the corrosion resistance. Addition of 0.001% or more of Sn and Sb is effective, and addition of 0.0001% or more of As and Te is effective. Further, excessive addition causes a decrease in workability, so the upper limit is made 0.01% for each.

Ca forms CaO in molten steel, on which Al₂O₃
Reacts with, ultra-hard Al with a high melting point ₂O₃The melting point of inclusions
It lowers the hardness and also reduces the hardness.₂O₃Is thin steel
Even if it remains on the plate, it is soft and can be subjected to severe cold rolling.
It is divided and becomes small, and quality deterioration can be prevented. Obey
If necessary, 0.0001% or more may be added. However
If it is present in excess, inclusions increase, which is not preferable.
0.005% or less when added or present as impurities
And

When a large amount of O (oxygen) is contained, A in steel
l, Mn or Si in refractory, Ca, Na in flux,
It forms an oxide with F and the like, which causes cracking during press working and also causes deterioration of the corrosion resistance of the can. Therefore,
It should be 0.01% or less. Mo, V, and Zr are all elements that increase the recrystallization temperature during continuous annealing. Also C
r, Cu , Ni, Na , Mg, and REM are elements that increase recrystallization temperature and at the same time reduce rollability, and it is difficult for continuous annealing or rollability to reduce the thickness of can steel sheet. Will cause. Therefore, when the stripability is a problem, 0.01% or less for Mo, V, and Zr, and 0.1 for Cr, Cu, and Ni.
%, Na and Mg should be 0.001% or less, and REM should be 0.005% or less.

(2) Grain size If the grain size is too large or too small, HAZ cracks will occur frequently. FIG. 6 shows the maximum crystal grain size and HAZ of the steel sheet for cans when the winding direction of the can body is parallel to the rolling direction of the steel sheet, rather than the direction perpendicular to the conventional rolling direction of the steel sheet.
The correlation of cracking is shown.

From FIG. 6, when the winding direction of the can body is taken parallel to the rolling direction of the steel sheet, the recrystallized grains are 30 μm or less at the maximum,
It is understood that HAZ cracks tend to occur frequently unless the thickness is preferably 25 μm or less. On the other hand, FIG. 7 shows the relationship between the degree of thickness reduction of the welded portion and the rate of occurrence of HAZ cracks when the can body of a three-piece can is joined by high-speed welding.

As shown here, when the total thickness after welding is 1.4 times or more the thickness of the original plate, stress concentration that occurs during flanging becomes severe and HAZ cracks frequently occur. The recrystallized grain size of the original plate affects the total plate thickness of the welded portion. According to experiments conducted by the present inventors, when the area ratio occupied by crystal grains of 5 μm or more is 50% or more, the total plate thickness of the welded portion is 1.4 times or less of the original plate thickness during normal high speed welding. I understood.

FIG. 4 is a graph showing the relationship between the area ratio of recrystallized grains of 5 to 25 μm and the degree of earring when deep-drawing was applied to a plated original plate of C: 0.004% or less ultra-low carbon steel.
As shown here, the area ratio of recrystallized grains of 5 to 25 μm is 50
% Or less, earrings tend to occur, which is unsuitable as a material for 2-piece cans. In addition, the limit of the crystal grain size at which orange peel occurs in the manufacturing process of 2-piece cans is 30μ.
It is m, and it has been found that orange peel is likely to occur when the particle size is larger than m.

In summary of the above points, the crystal grain size required for the original plating plate must be within the range of 30 μm or less at the maximum, and the area ratio of 5 to 25 μm must be 50% or more. The crystal grain size can be measured by observing the cross section of the original plate in the rolling direction under a microscope and calculating the average value of the dimensions in the major axis direction and the minor axis direction.

(3) Rolling conditions In order to obtain the crystal grain size after annealing as described above, it is necessary to make the hot rolling finishing temperature appropriate. If the hot rolling finish rolling temperature (FDT) is too high or too low, the recrystallized grain size after annealing becomes coarser than necessary. Moreover, since the product thickness of the steel sheet for cans is particularly thin, the hot rolled finish sheet thickness is as thin as 2 to 3 mm, the rolling time becomes long in relation to the ability of the hot rolling mill, and the temperature drop during rolling is large. Become.

Therefore, if the FDT is to be heated to a high temperature, a very high slab heating temperature (SRT) is required, which causes the problems described below and causes a large temperature drop during rolling, which causes material variations. Therefore, FDT has a grain size and material uniformity of 800 ° C to prevent precipitation of carbides.
900 ℃

On the other hand, if the SRT is too high, the roll surface is apt to be cracked by thermal shock, and the roll life is shortened.
And surface defects, and SRT 1000 ℃
If it is lower, the FDT cannot be secured, so the slab heating temperature is limited to 1000 to 1200 ° C. Coil winding temperature (C
When T) is raised to a high temperature, recrystallization and grain growth are facilitated, and a (111) recrystallized texture preferable for improving press workability can be developed. However, the material becomes non-uniform as the temperature decreases in the rolling direction and the front and rear ends. Further, since the scale growth amount of the hot rolled sheet increases, the pickling property is deteriorated.
Therefore, CT should be 650 ℃ or less. If the temperature of CT is too low, the grain size of the crystal becomes too fine and the rolling property deteriorates.

The hot-rolled steel strip rolled as described above is pickled and cold-rolled by a conventional method, and continuously annealed at 650 to 800 ° C. for 60 seconds or less. Here, the reduction ratio of cold rolling affects the crystal grain size, and if the reduction ratio is too low, the crystal grain size becomes coarse and the uniformity of the grain size tends to decrease. Therefore, the rolling reduction is preferably 80% or more.

If the continuous annealing temperature is too low, it hardens, and if it is too high, the crystal grains become coarse. Therefore, the temperature is 650 ℃ ~
The temperature is set to 800 ° C and the time is set to 60 seconds or less in order to improve productivity in the continuous annealing furnace. The steel sheet obtained as described above is temper-treated by temper rolling with an appropriately selected reduction ratio, and the tempers T1 to T
6. Steel sheets for cans having any temper of DR8 to DR10 can be manufactured.

FIG. 5 shows an example of the relationship between the temper ratio (HR30T) and the temper rolling reduction ratio. As is clear from the example shown in FIG. 5, when it is desired to obtain a steel sheet having a temper T1 (49 ± 3 for HR30T), temper rolling should be performed on a continuous annealed sheet with a reduction ratio of several%. Good. For the temper T2, the rolling reduction may be about 10%, so that the rolling reduction at the time of temper rolling may be selected from FIG. 5 for the desired temper. As described above, in the present invention, can steel sheets of all tempers can be manufactured with one steel type.

The present invention will be specifically described below based on examples.

[0044]

EXAMPLE Steels having the composition shown in Table 1 were smelted in a 270t bottom-blown converter and C0.03% was added to the steel. Then R
After H-vacuum degassing treatment to decarburize to 0.004% or less of C, Al is added, followed by addition of carbide forming elements, nitride forming elements and, if necessary, thickening elements on the surface of the steel sheet. Had made. Each of these was cast by using a continuous casting machine to promote floating separation of inclusions, and cast into a steel piece having excellent cleanliness. Each of these steel pieces was rolled at a hot rolling temperature shown in Table 2 to form a hot rolled coil having a thickness of 2.0 mm, then pickled and descaled. 0.2m with 6 stand tandem cold rolling mill
After rolling to an ultra-thin plate thickness of m (cold rolling rate 90%), HNX
Continuous annealing (CA) in a gas atmosphere (10% H ₂ + 90% N ₂ )
L) was applied. The heat cycle was at the temperature shown in Table 2 and was at the level of 60 seconds. Then, a tempering rolling mill was used to select a rolling ratio as shown in Table 2 and temper rolling was performed to manufacture steel sheets having various tempers.

The temper-rolled steel sheet was continuously subjected to # 25 tin plating and reflow treatment (molten tin treatment) in a halogen type electric tin plating process to finish a tin plate. Further, the temper-rolled steel sheet was subjected to chromate treatment under the following conditions to produce TFS (Tin Free steel). Specimens were sampled from tinplate and TFS, and hardness (HR
30T), and the average r value and Δr were measured according to JIS G 3135. Roughness evaluation of earrings and cans was measured, and bending processing was performed to perform a fluting resistance test. The fluting test was evaluated by bending it so that it would be equivalent to forming a can body, and the folds that occurred on the body were unbearable to see as a product (marked with a cross).
And it was judged to be the other (displayed with a circle).

With respect to the original steel plate, the hardness distributions at the beginning and end of temper rolling were investigated at the strip width edge, the central portion and the strip width edge, and the uniformity of the material of the obtained steel strip was evaluated. . The results are shown in Table 2. Also, 2 piece cans, 3
Table 3 shows the results of evaluation by making cans into piece cans.
From these results, it is clear that the steel sheet of the present invention is superior to the comparative steel sheet in workability and material uniformity.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

[0052]

[Table 6]

[0053]

[Table 7]

[0054]

[Table 8]

[0055]

[Table 9]

The Sn plating bath and reflow conditions used are as follows. Sn plating bath composition: stannous chloride 75 g / l pH 2.7 sodium fluoride 25 g / l potassium hydrogen fluoride 50 g / l sodium chloride 45 g / l Sn ²⁺ 36 g / l Sn ⁴⁺ 1 g / l bath temperature 65 ° C. current density 48 A / dm ² reflow condition Electric heating (280 ° C) Chromate treatment bath and conditions are as follows.

Chromate treatment bath composition: CrO ₃ 180 g / l H ₂ SO ₄ 0.758 g / l Na ₂ SiF ₅ 8 g / l Treatment conditions: Liquid temperature 50 ° C. Current density 80 A / dm ² Cathodic treatment time 1.2 sec

[0058]

According to the present invention, the ultra low carbon steel capable of increasing the grain size is used, so that the T1 material which could not be produced by the conventional continuous annealing method can be produced. Further, if the crystal grain size becomes too large, rough skin (orange peel) will occur when canned by press working, but the grain size was regulated so that it could be prevented. On the other hand, if the particle size becomes too small or the large and small mixed particle sizes become large, the press workability deteriorates. Therefore, the large and small mixed particle sizes were also regulated. It was also regulated to have excellent deep drawability.

Since the T1 material can be made,
T1 to T6, DR8 to DR10 by adding work hardening method
Now, it is possible to manufacture the gold tempering quality original plate with a single steel grade.
As a result, the process and time can be significantly streamlined and shortened. Furthermore, since the hot rolling temperature and the continuous annealing temperature can be finished at a low temperature or a medium temperature, the material of the entire width and the entire length of the coil becomes uniform. Therefore, it has become possible to obtain a product having a quality that can sufficiently cope with the current extremely thin plate thickness.

As a result of the above, in the case of box-type annealing, several 10 to 20 ton coils were piled up and annealed for about a week, but this requires a factory on a large site and it takes too much time. However, it was possible to cope with this problem with a single continuous annealing furnace in a short time. In addition, the quality problem of the box-type annealed material can be solved, and corrosion resistance is strongly required because of the canned food, but it can be provided with confidence and the customer's reputation has improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the influence of the C content in steel on the tin hardness (HR30T).

FIG. 2 is a diagram illustrating earrings that occur during press working.

FIG. 3 is a diagram showing the effect of C content in steel on earrings.

[Fig. 4] 5-25μ in steel with a C content of 0.004% or less
It is a figure which shows the influence which the area ratio of the recrystallized grain of m gives to an earring.

FIG. 5 is a graph showing the relationship between tint hardness (HR30T) and temper rolling reduction.

FIG. 6 is a diagram showing the relationship between the maximum crystal grain size and HAZ cracking.

FIG. 7 is a diagram showing the relationship between the total thickness of welded portions and HAZ cracks.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fuyuhiko Ishikawa 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Works (56) Reference JP 3-285046 (JP, A) JP JP 2-118028 (JP, A) JP 63-109121 (JP, A) JP 61-246344 (JP, A) JP 61-26757 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00-38/60

Claims (5)

(57) [Claims] 1. C ≦ 0.004%, Si ≦ 0.03%, Mn: 0.05-
0.6%, P ≦ 0.02%, S ≦ 0.02%, N ≦ 0.01%, Al: 0.
005 to 0.1%, Nb: 0.001 to 0.1%, B: 0.0001 to 0.0
Including 05% , Sn ≧ 0.001%, Sb ≧ 0.001%, As
Contains one or more of ≧ 0.0001% and Te ≧ 0.0001%
However , the other is an ultra-low carbon steel can steel sheet excluding unavoidable impurities, which has a recrystallized grain size of 30 μm or less and an area ratio of recrystallized grains of 5 to 25 μm is 50% or more. Steel sheet for cans characterized in that 2. The steel plate for a can according to claim 1, which contains 0.1% or less of Ti. 3. A process according to claim 1 or Oite 2, a steel sheet for cans comprising limiting the unavoidable impurities as follows. Cr ≦ 0.1%,
Cu ≦ 0.1%, Ni ≦ 0.1%, Mo ≦ 0.01%, O ≦ 0.01%, V
≤0.01%, Zr≤0.01%, Ca≤0.005%, REM ≤0.005
%, Mg ≤ 0.001% and Na ≤ 0.001%. 4. C ≦ 0.004%, Si ≦ 0.03%, Mn: 0.05-
0.6%, P ≦ 0.02%, S ≦ 0.02%, N ≦ 0.01%, Al: 0.
005 to 0.1%, Nb: 0.001 to 0.1%, B: 0.0001 to 0.0
Including 05% , Sn ≧ 0.001%, Sb ≧ 0.001%, As
Contains one or more of ≧ 0.0001% and Te ≧ 0.0001%
However , the balance is a continuous cast slab consisting of ultra-low carbon steel consisting essentially of Fe, heated at 1000-1200 ℃, and the finishing temperature 8
The hot-rolled steel sheet obtained by hot rolling at 00 to 900 ° C and a winding temperature of 500 to 650 ° C is pickled and cold-rolled by a conventional method to obtain a cold-rolled steel sheet. A method for producing a steel sheet for a can, which comprises continuously annealing at 650 to 800 ° C for 60 seconds or less, and then temper rolling. 5. The refining degree: T according to the method of claim 4.
1-T6 or DR8-10 Method for producing can steel sheet.