JP3257342B2 - DTR can-adaptive steel sheet with excellent side wall break resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a DTR (Draw and Thin Red).
raw) The present invention relates to a steel plate for a can which is suitable for use in a can-making process, and provides a steel plate which is unlikely to cause a side wall break phenomenon that becomes apparent during deep drawing of a can body subjected to tension drawing in the can making process.

[0002]

2. Description of the Related Art A shift from a three-piece can to a two-piece can and a reduction in the thickness of a can have been promoted from the viewpoint of weight reduction, omission of processes, and reduction of materials and manufacturing costs, mainly for beverage cans and the like. . Today, the mainstream of two-piece cans for beverage cans is deep drawing (cup) from a circular blank into a cup.
Thereafter, the can body is subjected to ironing two or three times (Ironing) to obtain a thinner side wall portion and a predetermined can height DI (Draw an).
d Ironing) molding method, but is generally limited to positive pressure cans and is not used for negative pressure cans such as retort cans (coffee cans, tea cans) for hot-packing contents.

[0003] Therefore, the DI (Draw and Ironing) molding method for obtaining a thinner side wall and a predetermined can height is generally limited to positive pressure can applications. On the other hand, molding methods that do not involve ironing include: DRD (Draw and ReDraw) molding method, in which the drawing process is performed twice, and a high wrinkle holding force applied to the flange during the second and subsequent drawing processes to suppress the flow from the flange to the side wall, and actively work on the side wall DTR (Draw a)
nd Thin Redraw) molding method has been put to practical use. The biggest feature of these methods is that they do not require ironing, so the use of pre-coated steel sheets or laminated steel sheets not only allows the omission of the process but also enables the production of beverage cans with excellent design and design. It is a point.

[0004] In recent years, a technique for developing the above-mentioned DTR molding for use in beverage cans has been developed and is now in the stage of practical use. Tin free steel (TFS) with a tempering degree generally ranging from T5-CA to DR-9 for this application
After forming a cup using a steel plate laminated with a polyester film (PET) as a raw material, two-step deep drawing with tension is performed. As a result, the thickness of the can side wall can be reduced by more than 20%, and not only can the can be reduced in weight, but also by changing the material thickness and the dome shape of the bottom of the can, it can be used for both positive and negative pressure cans. It is possible to adapt. However, in the molding method, it is necessary to solve the following problems in material design. 1. Peeling of the laminate film due to sliding with the die shoulder during drawing with tension. 2. Since the can wall portion is not restrained between the punch and the die during tensile forming and is subjected to tensile deformation in a free surface state, the rough surface is likely to occur. 3. Since the tension-added drawing is performed at a high speed, the side wall is likely to be broken starting from a portion (shock line) that comes into contact with the punch shoulder at the time of forming each cup.

[0005] Of the above-mentioned technical issues, two and three issues relating to the design of the base steel sheet have been disclosed by several patent techniques. For example, Japanese Patent Application Laid-Open No. 4-314535 discloses a technique in which the crystal grain size of a steel sheet is reduced to a predetermined size or less to suppress skin roughness.

[0006] In particular, regarding the resistance to side wall breakage, refer to Japanese Patent Laid-Open No.
JP-A-34192-34194 discloses a technique for improving workability, roughness, and corrosion resistance by defining the crystal grain size under a certain manufacturing method. These techniques disclose that C and N in solid solution are reduced, the occurrence of constriction and the connection of voids are suppressed, and thereby the resistance to side wall rupture is increased. No portion is mentioned, and it is considered that it is not possible to fundamentally avoid side wall breakage.

[0007] In Japanese Patent Application Laid-Open No. 5-247669, a steel sheet to which B is added for improving hardenability is rapidly cooled from a ferrite-austenite dual phase region during continuous annealing to transform a microstructure into a ferrite phase and a low-temperature transformation. A technique is disclosed in which a two-phase structure is formed to obtain a sufficiently high strength by a single cold pressure. However, in such a two-phase structure, voids are likely to be generated at the interface between the ferrite phase and the hard low-temperature transformation phase due to the DTR processing, so that sufficient sidewall rupture resistance cannot be obtained.

On the other hand, as a disclosure of a technique considered to be involved in a general fracture during drawing, there are disclosed a technique of restricting only steel-making inclusions to reduce machining defects (Japanese Patent Application Laid-Open No. 58-16026). Technology for improving the corrosion resistance and workability by defining the average particle size of cementite (Fe3C) precipitated in steel (JP-A-60-149743, JP-A-60-215739);
Technology for simultaneously defining the size and crystal grain size of non-metallic inclusions such as MnS and AlN generated by solid-phase reaction to improve workability (Japanese Patent Publication Nos. 4-78714 and 6-76618) Is disclosed.

A common feature of these techniques is to reduce the size of the microstructure and the amount of inclusions in the steel, which are the starting points of cracking, based on the principle of metallography.

However, when the individual technologies are examined in detail, it is found that the problem of the can side wall breakage during the DTR molding requires the absolute strength level required for the material, the essential mechanism of the side wall breakage phenomenon, and the optimum How microstructure should be
No optimum technology is disclosed for specific process conditions for obtaining an optimum microstructure. Therefore, 2
It is impossible to stably realize the reduction of the thickness of the side wall portion exceeding 5% within the range of the conventional material design technology, and it is considered that ironing work must be added after all.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to remarkably improve the resistance to side wall breakage among the above-mentioned problems of the prior art for a steel sheet laminated with various resins applied to DTR molding. It is assumed that.

FIG. 9 shows a scanning electron microscope (SEM) of the microstructure of the side wall of a beverage can formed by DTR according to the prior art.
This is the result of observation. The beverage can has the properties required for a beverage can, such as film adhesion, corrosion resistance, surface properties such as rough skin, pressure resistance, side wall paneling strength, and side wall buckling strength.

However, microscopically, many small cracks are observed at the interface between MnS and the matrix or at the interface between cementite and the matrix. Such a material is expected to be broken by a side wall starting from these minute cracks when subjected to more intense tensile deep drawing.

The present invention is to provide a steel sheet which has no side wall breakage when the thickness is reduced to 20% or more and hardly generates such minute cracks even when the thickness is reduced to 30% or more.

[0015]

Means for Solving the Problems The present invention has the following features to achieve the above object.

(1) In mass% (hereinafter the same), 0.03 ≦ C
≦ 0.1%, Si ≦ 0.03%, 0.3 ≦ Mn ≦ 1%, P ≦ 0.03%, S
≦ 0.02%, 0.02 ≦ sol.Al ≦ 0.1%, 0.001 ≦ N ≦ 0.007
%, Total-O ≦ 30ppm, 0.0002 ≦ B ≦ 0.0015% and B
≧ 0.11 S -0.0007 %, with substantial balance
A DTR can-adaptive steel sheet having excellent side wall rupture resistance, characterized by having a component composition of iron and a structure of a ferrite phase and finely dispersed carbide.

Further, in the present invention, in addition to the above basic components, the following components are added for the purpose of further improving the resistance to side wall breakage during DTR molding.

(2) mass%, 0.03 ≦ C ≦ 0.1%, Si ≦
0.03%, 0.3 ≦ Mn ≦ 1%, P ≦ 0.03%, S ≦ 0.02%, 0.02
≦ sol.Al ≦ 0.1%, 0.001 ≦ N ≦ 0.007%, Total-O ≦ 3
0 ppm, 0.0002 ≦ B ≦ 0.0015% and B ≧ 0.11 S-0.
Component composition containing 0007%
Among the fine carbides , the fine carbides defined in FIG. 7 are composed of carbides. Among the fine carbides, the length Lc of the cluster-like cementite extending over the ferrite crystal grains constituting the finely dispersed carbides is 10 μm or less. DTR can-adaptive steel sheet with excellent side wall rupture resistance, characterized in that the average inter-particle distance MFP of fine cementite precipitated in grains is 2 μm or less, and in (3) (1) or (2), 0.002 ≦ Nb
A DTR can-adaptive steel sheet having excellent side wall rupture resistance, characterized by containing Nb in the range of ≦ 0.01%.

[0019]

The basic concept that led to the present invention and the reasons for limiting the present invention constructed based on it will be described below.

First, the present inventors have proposed the present DT shown in FIG.
Focusing on the microstructure of R-formed products, the main causes of sidewall breakage are oxide-based non-metallic inclusions of steelmaking, MnS, AlN, Fe ₃ C and matrix which precipitate by solid-phase reaction in the steel plate manufacturing process. It was clarified that it was easy for small cracks generated at the interface to propagate.

In particular, a slight oxide-based or sulfide-based nonmetallic inclusion present in the steel is likely to coincide with the shock line formed on the shoulder of the punch at the time of DTR forming, causing side wall breakage. The present invention has been made based on the finding that it is extremely important to optimize the microstructure of a steel sheet in order to achieve a higher level of thinning.

As an evaluation method, the present inventors accurately and quantitatively evaluate a significant difference between materials with respect to sidewall rupture resistance, which has been extremely vague and qualitatively evaluated in the prior art. As a possible index, the critical thinning rate (еth) determined by the high-speed draw bead pull-out test method shown in FIG. 8 was used.

According to the DTR simulation, еth is positively correlated with the critical thinning rate of the can body side wall that can be DTR-formed without breaking the lateral wall, and the value of about (еth + 5%) and the critical thinning rate are approximately Confirmed that they match.

Using the high-speed draw bead pull-out test method, specific components and a limited range were determined.

FIG. 5 shows the effect of ferrite crystal grain size and B addition on еth in TFS adjusted to a temper degree equivalent to DR-9. By decreasing the ferrite grain size, еth increases, indicating that grain refinement is effective as a basis for steel sheet design. However, in order to increase the еth to 25% or more by grain refinement alone, it is necessary to refine the grain to d ≦ 2 μm, and it is necessary to perform recrystallization annealing from the full martensite structure, or perform cold rolling and low temperature recrystallization annealing. It is necessary to go through a complicated manufacturing process that repeats.

However, by adding a small amount of B, the criticality d that reaches еth ≧ 25% increases, and production by a normal process becomes possible. This is because B segregated at the ferrite grain boundaries during annealing and soaking, but micro-cracks were generated from the grain boundary cementite during DTR forming to eliminate the precipitation of film-like cementite at the ferrite grain boundaries during cooling. Not only that, but also the propagation of cracks is suppressed by strengthening the ferrite grain boundaries and the interface between cementite and ferrite by B.

Next, FIG. 6 shows the results of evaluating the effect of S and B in steel on еth for a steel sheet in which d was adjusted to 4 to 6 μm. When B is more than 0.0015%, the r-value of the steel sheet is reduced, so that the shrinkage deformation of the flange portion during the DTR forming is hindered, so that еth is reduced. When B is less than 0.0002%, еth is reduced by the above mechanism.

When S exceeds 0.02%, a high eth cannot be obtained regardless of the presence or absence of B addition. In the range where S is 0.02% or less, to obtain еth ≧ 30%, B must be 0.11S-0.0
It must be added in a range that satisfies 007% or more. This is because the propagation of microcracks starting from MnS is prevented by adding B.

From such a viewpoint, B and S are limited as follows. B: Even if B rolls a hot-rolled steel sheet at a relatively low temperature, N
Precipitation and fixation as BN, in addition to reducing the adverse effects on the material due to N, and improving the еth by adding B shown in FIGS. In the region where S is 0.008% or more, the amount of addition is 0.11S
0.0007% or more should be added.

S: S is a very important element in the present invention. In particular, S exists in steel as MnS, and expanded Mn
S tends to be a starting point of cracks that lead to sidewall breakage during DTR molding.
Therefore, it is preferable that S is as small as possible. Conventionally, there is a case where S is added from the viewpoint of corrosion resistance in steel plates for cans.However, in a laminated steel plate applied to DTR, since corrosion resistance is secured by lamination, there is a demand that S should be increased. Disappears.

In particular, in the present invention, by adding a small amount of B, the adverse effect of MnS on the resistance to side wall breakage is reduced. When S is in the range of 0.008% or more, add about 2ppm of B
In order to obtain th ≧ 30%, as shown in FIG.
-It must be added in the range of 0.0007% or more depending on the amount of S.

In the present invention, the upper limit of S at which sufficient side wall rupture resistance cannot be obtained even if such measures are taken is 0.02%.
%.

Next, in addition to the above B and S regulations, the critical significance of the content of each element in the steel sheet will be described.

O: Oxide-based inclusions significantly impair sidewall resistance. The problem with oxide inclusions is Al
_Although it is a ₂ O ₃ system, there are cases where CaO and MnO system inclusions remain. FIG. 1 shows the results obtained by arranging the total oxygen content in the steel sheet and the effect of B on the еth. A good еth can be obtained by setting the total oxygen content to 30 ppm or less (preferably 25 ppm or less). Therefore, in the present invention, the total oxygen content in the steel sheet is reduced to 30
It should be less than ppm.

C: C is a very important element for securing the strength level required for a DTR compatible steel sheet. However, on the other hand, C exceeding 0.02% is perlite.
For C of 0.02% or less, cementite (Fe ₃ C) is present in ferrite crystal grain boundaries or in ferrite crystal grains during annealing.
), The interface between these carbides and the matrix tends to be a starting point of cracking, and as shown in FIG. 9, a large number of minute cracks are generated during DTR molding.

In particular, cementite that precipitates in the form of a film at ferrite crystal grain boundaries easily induces grain boundary peeling. In the second invention and the third invention of the present invention, it is possible to further improve the resistance to side wall breakage by regulating the precipitation form of these carbides.

On the other hand, when C in steel is reduced by oxygen blowing during steel making, if C is less than 0.03%, not only is the steel sheet disadvantageous in terms of steel sheet strength, but also oxygen in molten steel increases and the side wall rupture resistance increases. Deoxidation products deteriorating are increased. On the other hand, when C exceeds 0.1%, immediate wall breakage starting from pearlite becomes apparent. Therefore, the range of C is limited to 0.03 to 0.1%.

Si: Since Si is an element that embrittles steel, a smaller amount is preferable. In addition, it is preferable that the amount of deposition of metal Cr is small in producing TFS. In the present invention, the upper limit that does not cause a practical problem is 0.03%.

Mn: Mn not only prevents the hot cracking of the slab by precipitating S in the steel as MnS,
In the overaging process of continuous annealing, it plays a role in promoting the precipitation of fine cementite in ferrite grains with MnS as a nucleus. In addition, the lower limit is set to 0.3% because it also serves as a solid solution strengthening element to supplement the strengthening by C.

It is effective to add a large amount of Mn to increase the material strength, but on the other hand, the solubility product of MnS increases, so that not only a relatively large MnS is formed in the slab stage, but also the band structure of It promotes the formation and promotes the microscopic non-uniform distribution of C in the steel, and inhibits the fine dispersion of carbides. These are all structures that are disadvantageous to side wall breakage during DTR. Therefore, the upper limit of Mn is set to 1%.

P: Since P is an element which segregates at the ferrite grain boundary and embrittles the grain boundary, it is preferable that P is as small as possible.
In the present invention, the upper limit is 0.02% or less that does not affect practically the side wall rupture resistance.

Sol.Al: sol.Al reduces the adverse effect of solid solution N, which lowers the local ductility of the steel sheet by the dynamic strain aging phenomenon as in the case of solid solution C, by precipitating N in the steel as AlN. . Further, fine AlN is effective not only for refining ferrite grains but also for nuclei of intra-granular precipitation of fine cementite in the overaging process of continuous annealing like MnS. However, when a large amount of Al is added to increase the amount of sol. Al, minute Al ₂ O ₃
Inclusions are more likely to remain, causing the side wall to break. Therefore, the lower limit at which the above-mentioned effect is exerted is set to 0.02%, and the upper limit is set to 0.1% as a limit at which practically any further addition impairs the resistance to side wall breakage.

N: N is finely dispersed as AlN and is used as fine ferrite crystal grains and used as precipitation sites for fine cementite.
m.

In the present invention, the above-mentioned basic component steel is used and its microstructure is made into a substantially ferrite single-phase structure comprising a ferrite phase and finely dispersed carbide. This is because, when a phase (martensite, bainite, etc.) other than the carbide (pearlite or cementite) inevitably present in low carbon steel is intentionally generated, the interface between the hard second phase and the ferrite matrix phase is This is because it becomes a starting point of micro-cracks during DTR molding and further deteriorates the resistance to side wall breakage.

Further, in the present invention, among the finely dispersed carbides described above, a cluster-like cementite caused by pearlite distributed in a hot-rolled sheet and a precipitation state of 0.02% or less of C dissolved and precipitated during annealing are defined. By doing so, stable side wall rupture resistance can be obtained. In other words, the pearlite distributed in the hot-rolled sheet is crushed during cold rolling and spreads in the rolling direction, and presents as a cluster-like cementite in which ferrite grains as shown in FIG. Approximately 0.02% of C, which forms a solid solution in the ferrite phase, precipitates as Fe ₃ C in the ferrite crystal grain boundaries or in the ferrite crystal grains during the cooling process. In particular, when the cooling rate is low, most of C is deposited in the form of a film at ferrite grain boundaries. These carbides
On the other hand, it contributes to the strengthening of the steel sheet, but gives the starting point of micro cracks during DTR forming. Therefore, in the present invention,
By precipitating C finely inside and outside the ferrite grains,
Fine dispersion of cementite below the critical size that induces microcracking.

FIGS. 2 and 3 show the relationship between the length (Lc) of the cluster-like cementite extending over the ferrite grains and the average intergranular distance (MFP) of the fine cementite precipitated in the ferrite grains. This is the result of examining the effect on 0.04-0.09% C steel.

Lc and MFP both affect еth, and Lc is 10 μm
Hereafter, by setting the MFP to 2 μm or less,
Can be obtained. This is because by reducing the size of the cluster-like cementite and by precipitating fine cementite within the ferrite grains, the amount of film-like cementite that precipitates at the ferrite grain boundaries is reduced, thereby reducing This is because the generation of cracks at the interface between the carbide and the ferrite is suppressed. Therefore,
As a microstructure condition for maximizing this effect, a steel sheet in which fine carbides with Lc ≦ 10 μm and MFP ≦ 2 μm are uniformly dispersed inside and outside ferrite crystal grains.

FIG. 5 shows that the present invention improves the eth by reducing the ferrite crystal grain size of the steel sheet. Therefore, in the present invention, a small amount of Nb may be added as a method for refining the ferrite structure.

FIG. 4 is a graph showing the effect of the amount of C in the steel on the ferrite crystal grain size of the steel sheet applied to the DTR can and the effect of the addition of a small amount of Nb. When the amount of C in the steel is reduced, the ferrite grain size tends to increase. This is shown in FIG.
From the results, it is disadvantageous to break the side wall during DTR molding. Therefore, when a small amount of Nb is added, it is possible to achieve a relatively stable refinement up to a low C region. Therefore, the lower limit of the grain size reduction effect in the low C region is defined as 0.002%. The upper limit is set to 0.01% or less as an amount in which necessary and sufficient grain refinement can be expected with respect to the side wall fracture resistance in the steel of the component system.

The steel sheet of the present invention disclosed above has a so-called DTR that performs deep drawing while applying tension regardless of whether the process in can forming is a wet process or a dry process.
This technology can be applied to all steel plates used in the can manufacturing method.

Further, after DTR processing, further ironing (Ir
oning) to reduce the wall thickness.

The properties of tin-plated steel sheets, ultra-thin tin plating, tin-nickel plating, nickel plating, chromium plating, Ni flash-plated steel sheets and the like are not impaired as well as TFS.

These surface-treated steel sheets are applied to DTR cans as they are, or as a film-laminated steel sheet obtained by laminating a resin film such as polyester or a pre-coated steel sheet coated with a paint such as epoxy.

In particular, when these surface-treated steel sheets are used as a base steel sheet of a film-laminated steel sheet or a pre-coated steel sheet, an electrolytic chromic acid-treated steel sheet having a two-layer structure of a lower layer of chromium metal and an upper layer of hydrated chromium oxide, that is, TFS.
Is most desirable from the viewpoint of processing adhesion.

Hereinafter, the effects of the present invention will be described more specifically with reference to examples.

[0056]

【Example】

Example 1 After smelting steel, it was made into a slab by continuous light pressure casting. The slab
After heating to 1200 ℃, finishing temperature: 840 ℃, winding temperature: 600 ℃
A 1.8 mm thick hot rolled sheet was used. In the present invention, P, S
Casting of slabs under light pressure during continuous casting to reduce semi-macro and macro-segregation of slabs, high-temperature heating of slabs (slabs) at 1150 ° C or higher from the viewpoint of uniform refining by re-dissolution of MnS, fine grain of hot-rolled sheet structure A low-temperature finish of 870 ° C. or less is preferred from the viewpoint of crystallization, and a low-temperature winding of 620 ° C. or less is preferred from the viewpoint of fine dispersion of perlite.

The hot-rolled steel sheet was cold-rolled to 0.24 mm after pickling, and subsequently recrystallization-annealed in a continuous annealing furnace (CA) and a box annealing furnace (BA). In continuous annealing, dynamic strain aging reduces the residual solid solution C that degrades the local ductility of the steel, and the precipitation state is controlled so as to be finely dispersed in the ferrite crystal grains. It is effective to perform an overaging treatment in a temperature range of 300 to 400 ° C. and a holding time of 20 seconds or more. In this example, the temperature was set to 350 ° C. and 90 seconds.

Further, in this embodiment, a method (CA + BA) of performing overaging with BA in a temperature range not exceeding 400 ° C. after annealing in a continuous annealing furnace without an overaging treatment zone was also performed.

DR rolling is performed on the annealed steel sheet to reduce the thickness to 0.18.
mm, then metal Cr and Cr on the tin-free plating line
A TFS steel sheet having the chemical composition shown in Table 1 having a multilayer structure of hydrated oxides, the balance being Fe and unavoidable impurities was obtained.

In the laboratory, polyester (PET) was applied to the steel sheet.
The film was heat-sealed and the eth was evaluated by a high speed draw bead pull-out test.

Table 1 shows the obtained results. Although there is a slight difference in the level of еth due to the annealing process, a higher thth can be obtained by using the steel sheet (I) of the present invention than in the comparative steel sheet (C) by any of the annealing methods.
If the value of c is 10 μm or less and the value of MFP is 2 μm or less, or both are satisfied, higher еth is obtained.

[0062]

[Table 1]

Example 2 A slab was produced by smelting steel and then performing continuous light pressure casting. 12
After heating to 00 ℃, finishing temperature: 840 ℃, winding temperature: 620 ℃ 1.
A 6 mm thick hot rolled sheet was used. The hot-rolled steel sheet is cold-rolled to 0.22 mm after pickling, and subsequently heated at 700 ° C and overaged at 3 times.
Continuous annealing was performed at 50 ° C. for 90 seconds. Then, after DR rolling to a thickness of 0.175 mm, tin-free treatment was performed under the same conditions as in Example 1, and the chemical composition shown in Table 2 containing Nb and the balance Fe
And a TFS steel plate composed of unavoidable impurities was obtained.

Thereafter, the polyester (PET) film was subjected to a high-speed draw bead pull-out test after lamination.

Table 2 shows the obtained results. Similarly, the steel sheet of the present invention (I) is higher than the comparative steel sheet (C).
Еth is particularly improved by adding a small amount of Nb, but the effect of reducing the cementite content with the BA material and reducing the ferrite crystal grain size is particularly remarkable.

[0066]

[Table 2]

[0067]

Industrial Applicability The present invention is to prevent the micro cracks at the interface between MnS and the parent phase of the microstructure or at the interface between the carbide and the parent phase, so that the side wall rupture resistance of the steel sheet in the DTR forming subjected to severe tensile deep drawing. Properties have been significantly improved.

For this reason, there is no side wall breakage when the wall thickness is reduced to 20% or more, and even if the wall thickness is reduced to 30% or more, such a DTR can-adaptive steel sheet having excellent side wall breakage resistance that hardly causes such small cracks. Can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing the influence of O and B in a steel sheet on еth.

FIG. 2 is a diagram showing the influence of Lc and B on еth.

FIG. 3 is a diagram showing the influence of MFP and C on еth.

FIG. 4 shows the effect of C and Nb on the average ferrite grain size.
FIG.

FIG. 5 is a graph showing the influence of the average ferrite grain size and B on еth.

FIG. 6 is a diagram showing the influence of S and B on еth.

FIG. 7 is a diagram showing the form of finely dispersed carbides and the definitions of Lc and MFP.

FIG. 8 is a schematic diagram of a high-speed draw bead pull-out test method.

FIG. 9 is a drawing substitute photograph of a cross-sectional microstructure showing a state of a cross-section of a crack in a can side wall portion after DTR molding.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Kawase 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Hideki Nishihara 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (56) References JP-A-5-247669 (JP, A) JP-A-7-3381 (JP, A) JP-A-7-62486 (JP, A) JP-A-4-314535 (JP, A) A) JP-A-3-44423 (JP, A) JP-A-60-149743 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 301 C22C 38/06 C22C 38/12

Claims (3)

(57) [Claims] (1) In mass %, 0.03 ≦ C ≦ 0.1%, Si ≦ 0.03
%, 0.3 ≦ Mn ≦ 1%, P ≦ 0.03%, S ≦ 0.02%, 0.02 ≦ so
l.Al ≦ 0.1%, 0.001 ≦ N ≦ 0.007%, Total-O ≦ 30pp
m, 0.0002 ≦ B ≦ 0.0015% and B ≧ 0.11 S -0.000
DTR with excellent sidewall rupture resistance, characterized in that it contains 7 % and the balance is substantially composed of iron , and is composed of a structure composed of a ferrite phase and finely dispersed carbide.
Steel plate suitable for cans. 2. The mass%, 0.03 ≦ C ≦ 0.1%, Si ≦ 0.03
%, 0.3 ≦ Mn ≦ 1%, P ≦ 0.03%, S ≦ 0.02%, 0.02 ≦ so
l.Al ≦ 0.1%, 0.001 ≦ N ≦ 0.007%, Total-O ≦ 30pp
m, 0.0002 ≦ B ≦ 0.0015% and B ≧ 0.11 S-0.000
Ferrite phase and finely dispersed carbon
Consists of consists of product structure, finely dispersed carbides of fine carbide constituting the length Lc of the community-like cementite across ferrite crystal grains 10μm or less, an average particle fine cementite precipitated in the ferrite grain Distance MFP
A DTR can-adaptive steel sheet having excellent side wall rupture resistance, having a diameter of 2 μm or less. 3. The composition further comprises 0.002 ≦ Nb ≦ 0.0
The composition according to claim 1, further comprising 1% of Nb.
A DTR can-adaptive steel sheet according to claim 2 , which has excellent resistance to side wall breakage.