JP2001279373A - Cold rolled steel sheet for can reduced in defect caused by inclusion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold rolled steel sheet for a beverage can in which the size and amount of nonmetallic inclusions are prescribed for reducing defects caused by inclusions at the time of working. SOLUTION: This cold rolled steel sheet for a can reduced in defects caused by inclusions is obtained by subjecting a slab having a composition containing, by mass, 0.01 to 0.1% C, 0.001 to 0.1% Si, 0.1% to 1.0% Mn, 0.01 to 0.03% P, 0.001 to 0.03% S and 0.01 to 0.1% Al, and the balance Fe with inevitable impurities to hot rolling and thereafter performing cold rolling. Among inclusions in the cold rolled steel sheet, the oxide nonmetallic inclusions containing Al2O3 and CaO whose total mass (Al2O3+CaO) is >30 mass % and having a grain size of 105 to 200 μm are <=3 pieces per 1 kg of the cold rolled steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-rolled steel sheet for cans having few inclusion defect during processing.

[0002]

2. Description of the Related Art In order to improve the cleanliness of steel materials, various methods have been proposed and implemented in a steelmaking stage (such as a refining method and a continuous casting method). In fact, in recent years, defects in inclusions in cast slabs manufactured by the continuous casting method have been extremely reduced. This is the result of the technical improvement of the deoxidation method at the molten steel stage and the measures taken against various inclusions in continuous casting. (The 126th and 127th Nishiyama Memorial Technical Lecture “High Clean Steel” Nippon Steel Corp. Association, 1988). Here, the inclusions include oxides, sulfides, carbonitrides, and the like. Hereinafter, oxide-based nonmetallic inclusions (including those mainly containing oxides and containing sulfides and the like) will be described. Call.

[0003] In a beverage can, the plate thickness at the time of can production varies depending on the use (for example, carbonated beverage, tea), and the required quality level also varies. Normally, cold-rolled steel sheets for beverage cans are subjected to flaw detection using leakage magnetic flux at the stage of cold-rolled steel sheets,
Only materials that pass the quality standards according to the application are used as materials. If the thickness of the can side wall is large, there is no problem if it passes this inspection, but in severe processing (when the can side wall thickness is thin), the Cracks (hereinafter, referred to as broken bodies) and pinhole-shaped defects (hereinafter, referred to as PH) are regarded as problems. As a countermeasure against these defects, a method for defining the cleanness of a slab (Japanese Patent Laid-Open No. 6-172925, Japanese Patent Laid-Open No.
No.) and those defining the cleanliness of cold-rolled steel sheets (Japanese Unexamined Patent Publication No.
No. 36045, JP-A-11-36048).

Japanese Patent Application Laid-Open No. 6-172925 discloses that inclusions having a thickness of 5 μm or less but having a shape elongated by rolling exist in a row at a defective portion. The inclusions existing in a row after the cold rolling as described above are determined by the melting point of the inclusions, and define the melting point, the inclusion size, and the number density of the inclusions present in the slab. JP-A-7-207403 also discloses JP-A-6-207403.
Based on a concept similar to that of JP-A-172925, the composition relating to the melting point of inclusions, the inclusion size, and the number density are specified. JP-A-7-207403 and JP-A-6-207403
In US Pat. No. 72925, the upper limit of the size of the inclusion is specified, but the lower limit is not specified.

[0005] On the other hand, in Japanese Patent Application Laid-Open No. 11-36048, inclusions broken by rolling exist in rows or layers at defective portions, and the size of the inclusions is 2 to 20 μm.
m. For this reason, Japanese Patent Application Laid-Open No. 11-36048 discloses that all the sizes of the cold-rolled steel sheets have an inclusion number density of 5 μm or more and 10 μm or more. Also, Japanese Unexamined Patent Application Publication No.
JP-A-36045 also discloses Japanese Patent Application Laid-Open No.
The number density of inclusions and the like are defined based on the same concept as that of the publication.

However, in recent years, the need for further weight reduction and cost reduction of beverage cans and the like has led to a reduction in the thickness of cans during manufacture and a reduction in the incidence of required defects. I have. In particular, for thinning,
Defects, which have rarely been a problem, are beginning to be viewed as problems. As a typical defect, there is a minute defect in which a resin film is peeled or broken and a steel part inside is exposed in a beverage can which is formed by applying a resin film after cold rolling and canning. This defect has a significantly higher defect occurrence rate as compared with the conventional broken body and PH, and the yield is deteriorated. As described above, measures for improving the required level by reducing the thickness are not sufficient. In addition, they cannot be made properly according to the required level for each application (including the strictness of processing), which is one of the causes of deterioration in yield.

[0007]

The inclusion composition, size and number density of the cold-rolled steel sheet for preventing the above-mentioned micro defects and also for preventing the previous fracture and PH are defined, and the grade is further defined. The inclusion composition, size and number density of the cold rolled steel sheet according to the requirements.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist thereof is as follows. (1) As mass%, C: 0.01 to 0.1%, Si:
0.001-0.1%, Mn: 0.1-1.0%, P:
0.01-0.03%, S: 0.001-0.03%,
Al: a cold-rolled steel sheet obtained by subjecting a slab comprising 0.01 to 0.1%, the balance of Fe and unavoidable impurities to hot rolling and then cold rolling, and among the inclusions in the cold-rolled steel sheet, Al ₂ O ₃ and CaO, and the total ratio is Al ₂ O ₃ + CaO>
30% by mass of oxide-based nonmetallic inclusions having a particle size of 105 μm or more and 210 μm or less, wherein the number of the oxide-based nonmetallic inclusions is 3 or less per 1 kg of a cold-rolled steel sheet. Less cold-rolled steel sheet for cans. (2) Among the inclusions in the cold-rolled steel sheet, Al ₂ O ₃ and CaO
And oxide-based nonmetallic inclusions having a total proportion of Al ₂ O ₃ + CaO> 30% by mass,
The cold-rolled steel sheet for cans according to the above (1), wherein the number of the oxide-based nonmetallic inclusions having a particle size of μm or less is 10 or less per kg of the cold-rolled steel sheet. (3) Among the inclusions in the cold-rolled steel sheet, Al ₂ O ₃ and CaO
And oxide-based nonmetallic inclusions having a total proportion of Al ₂ O ₃ + CaO> 30% by mass,
(2) The cold-rolled steel sheet for cans according to the above (2), wherein the number of the oxide-based nonmetallic inclusions having a particle size of not more than m is 100 or less per kg of the cold-rolled steel sheet. (4) As mass%, C: 0.01 to 0.1%, Si:
0.001-0.1%, Mn: 0.1-1.0%, P:
0.01-0.03%, S: 0.001-0.03%,
Al: a cold-rolled steel sheet obtained by subjecting a slab comprising 0.01 to 0.1%, the balance of Fe and unavoidable impurities to hot rolling and then cold rolling, and among the inclusions in the cold-rolled steel sheet, Al ₂ O ₃ and CaO, and the total ratio is Al ₂ O ₃ + CaO>
30% by mass of oxide-based nonmetallic inclusions having a particle size of 53 μm or more and 210 μm or less, and 20 μm or more and 210 μm of the oxide-based nonmetallic inclusions
A cold-rolled steel sheet for cans having a small number of inclusion defects, wherein the number of inclusions having the following particle size is 100 or less. (5) Among the inclusions in the cold-rolled steel sheet, Al ₂ O ₃ and CaO
And oxide-based nonmetallic inclusions having a total proportion of Al ₂ O ₃ + CaO> 30% by mass,
(4) wherein the number of inclusions having a particle size of not more than 1 μm is less than 1 and the number of inclusions having a particle size of not less than 20 μm and not more than 210 μm is 50 or less. A cold-rolled steel sheet for cans having few described inclusion defects. (6) As mass%, C: 0.01 to 0.1%, Si:
0.001-0.1%, Mn: 0.1-1.0%, P:
0.01-0.03%, S: 0.001-0.03%,
Al: a cold-rolled steel sheet obtained by subjecting a slab comprising 0.01 to 0.1%, the balance of Fe and unavoidable impurities to hot rolling and then cold rolling, and among the inclusions in the cold-rolled steel sheet, Al ₂ O ₃ and CaO, and the total ratio is Al ₂ O ₃ + CaO>
30% by mass of oxide-based nonmetallic inclusions having a particle size of 53 μm or more and 210 μm or less, and 20 μm or more and 210 μm of the oxide-based nonmetallic inclusions
50 or less inclusions having the following particle size, and 20 for all oxidizable nonmetallic inclusions including the oxide-based inclusions.
A cold-rolled steel sheet for cans with few inclusion defects, wherein the number of inclusions having a particle size of not less than μm and not more than 210 μm is 500 or less. (7) Among inclusions in the cold rolled steel sheet, 50 μm or more and 210 μm
m non-metallic inclusions having a grain size of less than 1 m
The cold-rolled steel sheet for cans according to the above item (6), wherein the number is 50 or less per kg. (8) Of inclusions in the cold-rolled steel sheet, 105 μm or more and 200
The cold-rolled steel sheet for cans according to the above (7), wherein the number of oxide-based nonmetallic inclusions having a particle size of not more than 5 μm is 5 or less per kg of the cold-rolled steel sheet. (9) One or more of Cr, Ti, Nb, Ca, Mg and Zr are contained, and in mass%, 0.01% to 0.1% for Cr and 0.01% for Ti. % ~
0.1%, 0.01% to 0.1% for Nb, Ca
(1), wherein the content is 0.0001% to 0.005%, the content of Mg is 0.0001% to 0.005%, and the content of Zr is 0.01 to 0.1%.
It is a cold-rolled steel sheet for cans with few inclusion defect as described in any one of (8) to (8).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, defects detected as defects in a flaw detection conducted at the stage of a cold-rolled steel sheet were investigated. In such a defective portion, an inclusion (A) containing Al and Ca as main components is used.
l ₂ O ₃ + CaO> 30% by mass), and it was found that the morphology was massive and crushed by rolling. Inclusions having such a composition are inclusions caused by slag and powder, and are spherical inclusions at the slab stage. Further, from the viewpoint of the length of the inclusion, 100 μm
It turned out that the above things were detected.

[0010] Next, a defect of a fractured body generated from a material having a relatively high required level was investigated. The defect part of the cylinder is
It has a two-plate shape, and the length of the two-plate portion is about several hundreds μm to several mm, and inclusions of about 2 to 20 μm are scattered in such a two-plate shape. are doing. This is considered that the inclusions were extended and destroyed by rolling. FIG. 1 shows the inclusion composition detected at the defective portion on the ternary phase diagram. As shown in FIG.
It was found that most of the inclusions containing a and satisfying Al ₂ O ₃ + CaO> 30% by mass. FIG. 2 shows the proportion of inclusions detected at the defective portion. As shown in FIG. 2, 70 to 80% of the inclusions containing Al and Ca and satisfying Al ₂ O ₃ + CaO> 30% by mass are found. From these forms and compositions, it was found that inclusions caused by slag and powder were the major causes of defects.

[0011] Further, in the defect portion of PH, two defect portions are formed in a plate-like manner as in the case of a ruptured body, and the shape and size of the inclusions present in the defect portion are the same, and an inclusion of about 2 μm to 20 μm is spotted. Are there. However, its composition tends to have a high Al content. The width and length of the two plates are small,
It is about several hundred μm.

Further, the minute defect portion which is regarded as a problem in the material having the highest required level contains only an inclusion of 20 μm or more, and other than the above-mentioned inclusion of Al ₂ O ₃ + CaO> 30% by mass. In addition, SiO ₂ and Al ₂ O ₃ alone exist, and all the inclusions cause defects. Those more in composition of inclusions, it is intended Al ₂ O ₃ alone, when the rate of occurrence of minute defects is remarkably deteriorated, inclusions composed mainly of Al and _{Ca (Al 2 O 3 + CaO} > 30% by mass)
It turned out that there are many. In addition, the presence form of the inclusions is often a lump-like form, and is hardly deformed by rolling.

Next, when the inclusions in the case of low-carbon Al-killed steel used for the material for cans are investigated, most of the inclusions are alumina generated by the deoxidation step, and the size is almost 10 μm or less in most cases. is there. Most of alumina having a size of 10 μm or less is a single particle and is dispersed in a steel material, and does not cause a defect in question. Also, alumina clusters in which alumina particles of 10 μm or less are clustered are broken at the time of hot rolling and become individual single particles. It does not cause a sheet. (Inclusions of several tens μm or more are mainly deformed by cold rolling,
Destroyed and scattered.
A sheet-like material causes PH and a broken body. ) 10μ
m or more, only a few particles of alumina are present, but those of 10 to 20 μm do not cause defects.
A single particle having a size of 0 μm or more causes micro defects. In micro defects, inclusions are exposed on the surface of the steel material during can making, which breaks the resin film adhered to the steel material.Because of the strength and elongation characteristics of the resin film itself, inclusions of 20 μm or more It is considered that when exposed, it becomes a defect.

[0014] As inclusions other than alumina, there are extrinsic inclusions caused by slag, powder, refractories, stuffing, tundish heat insulating material, and the like.
The proportion of the total inclusions is very small as compared with alumina. In most cases, these inclusions are physically involved in molten steel, and the minimum size is 20 μm.
It is estimated to be about. Among such inclusions,
Defects at the time of can-making include many inclusions (main components of CaO and Al ₂ O ₃ ) due to slag and powder. Such inclusions are spherical and tightly packed inclusions in molten steel and have a melting point of about 1300 ° C. to 1600 ° C. Such inclusions are completely solid at the hot rolling temperature and are hardly deformed by hot rolling because they are stronger than the strength of the steel sheet. In the subsequent stage of cold rolling, it is destroyed to be crushed,
Forming two sheets, flaw detection of cold rolled steel sheet,
It is presumed to be a PH defect.

Extrinsic inclusions (eg, SiO ₂ and MgO.Al ₂ O ₃ ) other than those caused by slag and powder have a higher melting point than inclusions caused by slag and powder.
C. or higher, and has a very distorted shape, so that even if broken during rolling, broken particles are present alone, and it is considered that this does not lead to the above-mentioned defects.

Further, among the inclusions, Al ₂ O ₃ + CaO <
The inclusions of 30% by mass are presumed to be aggregates of slag or powder-based inclusions and other extrinsic inclusions. In this case as well, exogenous inclusions other than slag or powder-based inclusions are assumed. Similarly to the above, the melting point is high and the shape is also distorted.

In the cold-rolled steel sheet, inclusions of 20 μm or less, such as those found in a defect such as a fractured body or PH, can be ignored compared to inclusions not involved in the defect (alumina which does not cause the above-mentioned defect). Less.

Therefore, 20 μm
Considering that the inclusion number density is important, the inclusions of the cold rolled steel sheet were investigated, and the correspondence with the defect occurrence rate during can making was investigated again. The sample was a 100 × 50 mm plate from the front or tail of the cold-rolled steel plate so that the total weight was 2 kg from the entire width of the steel plate. Inclusion investigation method uses a slime method, uses a resin diaphragm having a 20 μm lattice sieve at the time of electrolysis, and extracts inclusions from the extracted residue using a mesh sieve specified by JIS standards for each size. The number was counted. First, 210μ
Although extraction was performed using a sieve having a size of m, no inclusions remained in the sieve of this size, and the upper limit of the particle size of the inclusions was set to 210 μm. Next, the inclusions extracted with a 105 μm
Inclusions of 5 μm to 200 μm were included, inclusions extracted through a 53 μm sieve were defined as inclusions of 53 μm to 105 μm, and remaining inclusions were defined as inclusions of 20 μm to 53 μm. The obtained number of inclusions was converted to the number per 1 kg of the cold-rolled steel sheet. The extracted inclusions of 20 μm or more are EP
Quantitative analysis was performed using MA. Table 1 shows the inclusion extraction method. Hereinafter, in this specification, 20 μm or more, 53
μm or more and 105 μm or more,
0 μm or more and 210 μm or less, 53 μm or more and 210 μm or less, and 105 μm or more and 210 μm or less. Table 2 shows the types of defects in question for each type of beverage can. In Table 2, A is the lowest grade (low quality requirement level) and D is the highest grade (high quality requirement level). In addition, the pass / fail of the defect occurrence rate during can making was judged as follows.
As the defect index, the pass level of the defect occurrence rate was set to 1 for PH, fractured body, and minute defect (1 or less passed). However, regarding the flaw detection results of the cold-rolled steel sheet, when the acceptance criteria of the low-grade materials (A and B in Table 2) are set to 1, the acceptance criteria of the high-grade materials (C and D in Table 2) are as follows:
0.5. Table 3 shows the acceptance criteria for each defect.
Table 4 shows the components of the beverage can material.

First, the relationship between flaw detection of cold-rolled steel sheets and inclusions was investigated. The material to be surveyed was B in Table 2 and a relatively low grade material was used. The flaw detection portion of the cold-rolled steel sheet contains Al and Ca and contains Al ₂ O ₃ + CaO> 30% by mass.
Therefore, the number of inclusions having the same composition was compared with the number of inclusions having different compositions. The result is shown in FIG. As shown in FIG. 3, if the number of inclusions of 105 μm or more remaining in the cold-rolled steel sheet is 3 / kg or less, the number of inclusions becomes lower than the acceptable level of flaw detection. Preferably, the number of inclusions having a size of 105 μm or more is 3 / kg or less, and the number of inclusions having a size of 53 μm or more is 10 / kg or less. Furthermore, in order to clear the acceptance criterion of high grade materials of 0.5, the number of inclusions of 105 μm or more is 3 / kg or less, and the number of inclusions of 53 μm or more is 10 / kg or less, and It has been found that the number of inclusions of 20 μm or more needs to satisfy 105 or less. In A and B in Table 2, it is sufficient that the above acceptable level 1 or less is satisfied, and in C and D, it must be 0.5 or less.

Next, the same investigation was conducted on the fractured body and PH, which are problems with high-grade materials. The materials to be investigated are C and D in Table 2, and those which passed the flaw detection with the cold rolled steel sheet, that is, the above-mentioned acceptance criteria (Al ₂ O ₃ +
105 μm for inclusions with CaO> 30% by mass
The number of the above inclusions is 3 / kg or less and 53 μm
The number of inclusions of m or more is 10 / kg or less and 20 μm
(The number of inclusions is 100 / kg or less). The inclusions of these cold-rolled steel sheets were compared with the defect occurrence rates. The composition of the inclusions includes Al and Ca
Inclusions satisfying ₂ O ₃ + CaO> 30% by mass were examined. The results are shown in FIG. 4 for PH and in FIG. 5 for the broken body. It was found that when the number of inclusions of 20 μm or more was 100 or less and the number of inclusions of 53 μm or less was less than 1 for can type C, both the PH and the broken body satisfied the acceptable level. For B in Table 2, good results are obtained under these conditions. In addition, for can type D, which is the most high-grade material, when the number of inclusions of 20 μm or more was 50 or less and the number of inclusions of 53 μm or more was less than 1, it was found that both the PH and the broken body satisfied the acceptable level. .

Here, in the above paragraphs [0010] and [0011], 2 to 20 μm is applied to the defective portion of PH or a broken body.
Al ₂ O ₃ + CaO> 30% by mass
It has been described that there is an inclusion that becomes the above, but the reason why the PH and the fractured body can be determined based on the number of the inclusions where Al ₂ O ₃ + CaO> 30 mass% of 20 μm or more is satisfied. Al ₂ O ₃
FIG. 6 schematically shows the deformation behavior of inclusions satisfying + CaO> 30 mass% by rolling. As shown in FIG. 6, there are ones that are not deformed at all by rolling, ones that are deformed to the extent that they are crushed, and ones that become two plates as seen in a broken body or a PH defect. It was found that the number ratio of these inclusions was almost constant. In other words, from the number of inclusions where Al ₂ O ₃ + CaO> 30% by mass is not deformed or the degree of deformation is small and is 20 μm or more, the number of two plate-like shapes as seen in a defective portion is estimated. it can. Therefore, Al ₂ O _{3 of} 20 μm or more
Sufficient evaluation is possible even if the number of inclusions satisfying + CaO> 30% by mass is used.

Lastly, a similar investigation was conducted on micro defects which are most problematic in high grade materials. The material to be investigated is D in Table 2 and has passed the flaw detection with a cold-rolled steel plate, that is, the above-mentioned acceptance criteria (Al ₂ O ₃ + CaO> 30).
In the inclusions of mass%, the number of inclusions of 105 μm or more is 3 / kg or less, the number of inclusions of 53 μm or more is 10 / kg or less, and the number of inclusions of 20 μm or more is 100 / kg or less. ). Regarding minute defects, all inclusions were targeted regardless of the composition of the inclusions. FIG. 7 shows the result. As shown in FIG. 7, it has been found that the microdefect passes when there are 500 or less inclusions having a size of 20 μm or more. Preferably, the number of inclusions of 20 μm or more is 500 or less and 5
When the number of inclusions having a size of 0 μm or more is 50 or less, the low level is stabilized. In addition, the number of inclusions of 20 μm or more is 500 or less, and the number of inclusions of 53 μm or more is 50 or less and 105 μm
If the number of the above inclusions is less than 5, it is expected in the future,
It is thought that it is possible to cope with further reduction in can thickness. Table 2
In the case of medium D, satisfactory results can be obtained by satisfying these conditions in addition to the conditions for the above-mentioned fractured body and PH.

The target components will be described. Since C is an element indispensable for imparting the strength of steel, the lower limit is set to 0.01% by mass, and the upper limit is set to the upper limit of 0.1% by mass obtained from the material (strength and elongation, etc.) as a material for cans. did. In addition, the lower limits of Mn, Si, P, and S are set to values that can be reduced without a significant increase in cost within the range of normal blowing, and the upper limits are adversely affected by the material as a material for cans and continuous casting. The value is such that no defect occurs as a piece. Al is generally used as a deoxidizing element, but Ti, Zr, C
Other deoxidizing elements such as a and Mg may be used. Further, in a material for a can (TFS: tin-free steel) to which a resin film is to be attached, other components may be added depending on the type of can, such as Cr. Further, Nb may be added to secure the strength.

[0024]

Examples are shown below. As test steels, all of A to D in Table 2, which are the highest grade materials among the materials for beverage cans, were used. Table 5 shows the steelmaking conditions and Table 6 shows the rolling conditions.
Shown in In the example of the present invention, CaO and Al are added in order to reform the slag flowing out together with the molten steel after the molten steel is transferred to the molten steel pot after blowing in the converter. The secondary refining uses RH. In the comparative example, the slag reforming was not performed, and the secondary refining also used CAS. The rolling conditions are the same as those of the present invention and the comparative example. The inclusions of the cold-rolled steel sheet were extracted by a slime method, and the number of inclusions having a size of 20 μm or more was measured for each size. Table 7 shows the results.
In the comprehensive evaluation in Table 7, when all the defects have a defect index of 0.5 or less and are very good, ◎ indicates that any one of the defects has a defect index of 0.5 or more and 1 or less. In some cases, 、, when all the defect indices were 1 or less (pass level), Δ, and when there was rejection, ×.

The invention example 1 of the can type A satisfies the condition of claim 3 (also satisfies claims 1 and 2), and has passed the flaw detection of the cold-rolled steel sheet. On the other hand, Comparative Example 1 of the can type A did not satisfy the condition of claim 1, and failed the flaw detection of the cold-rolled steel sheet.

Both the invention examples 1 and 2 of the can type B satisfy the condition of claim 3, pass the flaw detection of the cold rolled steel sheet, and also satisfy the condition of claim 4, so that the PH defect is satisfied. The indicators are also good. The comparative example 1 of the can type B did not satisfy the condition of claim 1, and thus failed the flaw detection of the cold-rolled steel sheet.

Inventive Examples 1 to 3 and Comparative Example 1 of can type C
The condition of claim 3 was satisfied, and the flaw detection of the cold-rolled steel sheet passed. In Comparative Example 2, since the condition of Claim 3 was not satisfied, the test of the cold rolled steel sheet was rejected (cannot be performed).
It has become. Since Examples 1 to 3 of the present invention satisfy the conditions of Claim 4, both the PH and the defect index of the broken body are good. In Comparative Example 1, since the condition of Claim 4 was not satisfied, the PH and the broken body were rejected.

Examples 1 to 4 of the present invention of can type D and Comparative Examples 1 and 2
Has passed the flaw detection of the cold-rolled steel sheet because it satisfies the condition of Claim 3, but Comparative Example 3 failed the flaw detection of the cold-rolled steel sheet because it did not satisfy the condition of Claim 2. Can not be). Inventive Examples 1 and 2 further satisfy Claim 8, and have favorable results. In Example 3 of the present invention,
Since the conditions of claims 7 and 8 are not satisfied, the defect index of the small defect is slightly higher, but the overall evaluation is good. In the present invention example 4, claim 8 is satisfied. However, since the number of inclusions of 20 μm or more that satisfy Al ₂ O ₃ + CaO> 30% by mass is slightly higher at 43 pieces / kg (corresponding to claim 5), PH, Although the defect index of the cylinder was higher, the overall evaluation passed without any problem. Comparative Example 1
In this case, the condition of claim 5 is not satisfied, so that the PH and the broken body are rejected. In Comparative Example 2, since the claim 6 was not satisfied, the minute defect was rejected.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[0029]

From the above results, by using a cold-rolled steel sheet satisfying the conditions of the size and amount of inclusions specified by the method of the present invention as a material for beverage cans, inclusion defect during processing can be significantly reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a view showing the composition of inclusions detected at a crush defect portion.

FIG. 2 is a view showing the ratio of inclusions detected at a broken defect portion.

FIG. 3 is a diagram showing a relationship between the number of inclusions and a flaw detection defect index.

FIG. 4 is a diagram showing a relationship between the number of inclusions and a PH defect index.

FIG. 5 is a diagram showing a relationship between the number of inclusions and a fracture defect index.

FIG. 6 is a view showing a deformation behavior by rolling of an inclusion having Al ₂ O ₃ + CaO> 30% by mass.

FIG. 7 is a diagram showing a relationship between the number of inclusions and a micro defect index.

Claims (9)

[Claims] C: 0.01 to 0.1 as mass%
%, Si: 0.001-0.1%, Mn: 0.1-1.
0%, P: 0.01 to 0.03%, S: 0.001 to
A cold-rolled steel sheet obtained by subjecting a slab comprising 0.03%, Al: 0.01 to 0.1%, the balance Fe and inevitable impurities to hot rolling and then cold rolling, wherein Of the inclusions,
Al ₂ O ₃ and CaO, the total proportion of which is Al ₂ O 3
₃ + CaO> 30% by mass of oxide-based nonmetallic inclusions having a particle size of 105 μm or more and 210 μm or less, wherein the number of the oxide-based nonmetallic inclusions is 3 or less per kg of cold-rolled steel sheet. Cold rolled steel sheet for cans with few inclusion defects. 2. Among the inclusions in the cold-rolled steel sheet, Al ₂ O
₃ and CaO, the total proportion of which is Al ₂ O ₃ + Ca
O> 30% by mass of oxide-based nonmetallic inclusions,
2. The cold-rolled steel sheet for cans according to claim 1, wherein the number of the oxide-based nonmetallic inclusions having a particle size of not less than m and not more than 210 [mu] m is 10 or less per kg of the cold-rolled steel sheet. 3. Among the inclusions in the cold-rolled steel sheet, Al ₂ O
₃ and CaO, the total proportion of which is Al ₂ O ₃ + Ca
O-type nonmetallic inclusions with O> 30% by mass, 20 μm
3. The cold-rolled steel sheet for cans according to claim 2, wherein the number of the oxide-based nonmetallic inclusions having a particle size of not less than m and not more than 210 [mu] m is 100 or less per kg of the cold-rolled steel sheet. 4. As mass%, C: 0.01 to 0.1.
%, Si: 0.001-0.1%, Mn: 0.1-1.
0%, P: 0.01 to 0.03%, S: 0.001 to
A cold-rolled steel sheet obtained by subjecting a slab comprising 0.03%, Al: 0.01 to 0.1%, the balance Fe and inevitable impurities to hot rolling and then cold rolling, wherein Of the inclusions,
Al ₂ O ₃ and CaO, the total proportion of which is Al ₂ O 3
₃ + CaO> 30% by mass, non-metallic oxide-based inclusions having a particle size of not less than 53 μm and not more than 210 μm, and particle diameters of not less than 20 μm and not more than 210 μm The cold-rolled steel sheet for cans with few inclusion defect is characterized in that the number of inclusions is 100 or less. 5. Among the inclusions in the cold-rolled steel sheet, Al ₂ O
₃ and CaO, the total proportion of which is Al ₂ O ₃ + Ca
O> 30% by mass of oxide-based nonmetallic inclusions,
less than one inclusion having a particle size of not less than m and not more than 210 μm;
The cold-rolled steel sheet for cans according to claim 4, wherein the number of inclusions having a particle size of not more than 50 µm is 50 or less. 6. C: 0.01 to 0.1 as mass%
%, Si: 0.001-0.1%, Mn: 0.1-1.
0%, P: 0.01 to 0.03%, S: 0.001 to
A cold-rolled steel sheet obtained by subjecting a slab comprising 0.03%, Al: 0.01 to 0.1%, the balance Fe and inevitable impurities to hot rolling and then cold rolling, wherein Of the inclusions,
Al ₂ O ₃ and CaO, the total proportion of which is Al ₂ O 3
₃ + CaO> 30% by mass, oxide-based nonmetallic inclusions having a particle size of 53 μm or more and 210 μm or less and one or more oxide-based nonmetallic inclusions having a particle size of 20 μm or more and 210 μm or less Of 50 or less inclusions and 5 inclusions having a particle size of 20 μm or more and 210 μm or less in all oxidizing nonmetallic inclusions including the oxide-based inclusions.
A cold-rolled steel sheet for cans having few inclusion defects, wherein the number is not more than 00 pieces. 7. Among the inclusions in the cold-rolled steel sheet, 53 μm
7. The cold-rolled steel sheet for cans according to claim 6, wherein the number of oxide-based nonmetallic inclusions having a particle size of not less than 210 [mu] m is 50 or less per kg of the cold-rolled steel sheet. 8. Among the inclusions in the cold-rolled steel sheet, 105 μm
8. The cold-rolled steel sheet for cans according to claim 7, wherein the number of oxide-based nonmetallic inclusions having a particle size of m to 210 [mu] m is 5 or less per kg of the cold-rolled steel sheet. 9. It contains one or more of Cr, Ti, Nb, Ca, Mg, and Zr, in mass%, of which 0.01% to 0.1% for Cr and 0% for Ti. .01
% To 0.1%, 0.01% to 0.1% for Nb,
2. The composition according to claim 1, wherein the content is 0.0001% to 0.005% for Ca, 0.0001% to 0.005% for Mg, and 0.01 to 0.1% for Zr.
Item 8. The cold-rolled steel sheet for cans with less inclusion defect according to any one of Items 8 to 8.