JPH08311561A - Production of steel sheet suited to dtr can, excellent in side wall fracture resistance - Google Patents

Abstract

PURPOSE: To provide a steel sheet for cans, suited to DTR (Draw and Thin Redraw) can manufacturing purpose and hardly causing the side wall fracture phenomenon occurring at the time of tension-giving deep drawing (or can body in the can manufacturing process. CONSTITUTION: A steel slab, having a composition containing, by weight, 0.03-0.1% C, <=0.03% Si, 0.3-1% Mn, <=0.03% P, <=0.02% S, 0.02-0.1% sol.Al, 0.001-0.007% N, <=30ppm Total O, and 0.0002-0.0015% B, is hot-rolled under the conditions of >=1150 deg.C heating temp., <=870 deg.C hot rolling finishing temp., and <=620 deg.C coiling temp. The resulting hot rolled steel plate is successively subjected to cold rolling, continuous annealing, temper rolling or DR rolling, surface preparation, and surface treatment for DTR, by which the steel sheet for DTR can is produced. At this time, the cooling rate through the temp. region between 600 and 500 deg.C at the cooling at the time of the continuous annealing is regulated to >=40 deg.C/sec, and further, overaging treatment is done at 400-300 deg.C for >=20sec after cooling down to <=400 deg.C, by which the steel sheet having a structure consisting of ferritic phases and finely dispersed carbides can be produced.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a DTR (Draw and Thin Red)
A steel sheet for cans that is suitable for use in can making, and provides a method for producing a steel sheet that is less likely to cause a side wall fracture phenomenon that becomes apparent during tension-added deep drawing of a can body performed in the can making process. is there.

[0002]

2. Description of the Related Art Focusing on beverage cans and the like, from the viewpoints of weight reduction, process omission, material and manufacturing cost reduction, the shift from 3 piece cans to 2 piece cans and further reduction of the thickness of the can body are being promoted. . The mainstream of two-piece cans for beverages today is the deep drawing of circular blanks into cups (Draw).
After that, the can body is ironed by ironing 2-3 times to obtain a thin wall and obtain a predetermined can height DI (Draw an
d Ironing) molding method, but is generally limited to positive pressure can applications and is not used for negative pressure cans such as retort cans (coffee cans, tea cans) that hot-pack contents.

On the other hand, as a forming method which does not involve ironing, a DRD (Draw and ReDraw) forming method in which drawing is performed twice and a flange with a high wrinkle holding force applied to the flange portion during the second and subsequent drawing DTR (Draw and Draw and thin) to reduce the thickness of the can body by suppressing the flow from the wall to the side wall and applying tension deep drawing to positively apply tension to the side wall.
Thin Redraw) molding method has been put to practical use. The greatest advantage of these methods is that they do not undergo ironing, so the use of pre-coated steel sheets and laminated steel sheets enables the production of beverage cans not only with a simplified process but also with good design and design. That is the point.

In recent years, a technique for developing the above-mentioned DTR molding for use in beverage cans has been developed and is in the stage of practical application. For this application, tin-free steel (TFS), which generally has a temper degree from T5-CA to DR-9, is used.
After forming a cup from a steel sheet laminated with a polyester film (PET) as a raw material, two-stage tensioning deep drawing is performed. As a result, the thickness of the can side wall has been reduced by 20% or more, and the weight of the can has been reduced. It is possible to adapt. However, in the molding method, it is necessary to solve the following problems in designing the material. 1. Peeling of the laminated film by sliding with the shoulder of the die during tension drawing. 2. During tension drawing, the can wall portion is not constrained between the punch and the die and is subjected to tensile deformation in a free surface state, so that rough skin is likely to occur. 3. Since tension drawing is performed at a high speed, side wall rupture is likely to occur at the point of contact with the punch shoulder (shock line) at the time of forming each cup.

Regarding the problems 2 and 3 relating to the design of the base steel sheet in each of the above technical problems, some patented technologies have been disclosed conventionally. For example, Japanese Patent Application Laid-Open No. 4-314535 discloses a technique of reducing the crystal grain size of a steel sheet to a predetermined size or less to suppress rough skin.

Particularly, regarding the side wall rupture resistance, JP-A-7-
Japanese Patent Nos. 34192 to 34194 disclose a technique of improving workability, skin roughness, and corrosion resistance by defining the crystal grain size. These techniques disclose that solid solution C and N are reduced by overaging treatment to suppress the occurrence of necking and void coupling, thereby improving the side wall fracture resistance, but continuous annealing or box annealing is disclosed. The overaging treatment condition at time is 400 ° C as described in the specification.
It is ~ 500 ° C, and it is expected that precipitation of film-like cementite at the ferrite grain boundaries will be unavoidable.

A technique of adding B to a steel sheet applied to DTR forming is disclosed in Japanese Patent Laid-Open No. 5-247669, but B is added for the purpose of improving hardenability, and Since the basic structural requirement is to make the microstructure a two-phase structure consisting of ferrite and low-temperature transformation, voids are likely to occur along with the DTR processing at the interface between the ferrite phase and the hard low-temperature transformation phase. It is expected that the side wall fracture resistance will not be obtained.

[0008] On the other hand, as a disclosure of a technique considered to be involved in breakage during general drawing, a technique of restricting only steel-making inclusions to reduce processing defects (JP-A-58-16026), Technology for improving the corrosion resistance and workability by defining the average grain size of cementite (Fe ₃ C) precipitated in steel (JP-A-60-149743, JP-A-60-215739),
Technology to improve the workability by simultaneously defining the size and crystal grain size of non-metallic inclusions such as MnS and AlN generated in the solid state reaction (Japanese Patent Publication No. 4-78714, Japanese Patent Publication No. 6-76618) Is disclosed.

[0009] Common to these techniques is the starting point of micronization and cracking of the structure on the basis of the metallographic principle principle, against the problems of skin roughness and breakage of the can side wall during DTR molding. It is intended to reduce inclusions in steel.

However, a detailed study of the individual technologies shows that the absolute strength level required for the material, the essential mechanism of the sidewall breakage phenomenon, and the optimum mechanism against the problem of the can sidewall breakage during DTR molding. The ideal microstructure,
The optimum technique has not been disclosed for specific process conditions for obtaining the optimum microstructure. Therefore, 2
It is considered impossible to stably achieve a wall thickness reduction of more than 5% within the range of the conventional material design technology, and it is thought that ironing will have to be added after all.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art with respect to steel sheets laminated with various resins applied to DTR forming, and precoated steel sheets coated with various paints. The purpose is to significantly improve breakability.

FIG. 6 shows a scanning electron microscope (SEM) of the microstructure of the side wall of a beverage can DTR-molded by the conventional technique.
It is the result of observation. The beverage can has film adhesion, corrosion resistance, surface properties such as rough skin, pressure resistance, sidewall paneling strength, sidewall buckling strength, and other properties required for a beverage can.

However, microscopically, many small cracks are observed at the interface between MnS and the matrix or at the interface between the carbide and the matrix. When such a material is subjected to further intense deep drawing, it is expected that these minute cracks will cause the side walls to fracture.

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

[0015]

Means for Solving the Problems The subject matter of the present invention in order to achieve the above object is as follows. (1) 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
% Of the steel slab into a hot rolled steel sheet under the conditions of a slab heating temperature: 1150 ° C or higher, a hot rolling finishing temperature: 870 ° C or lower, and a winding temperature: 620 ° C or lower, followed by cold rolling, continuous annealing, DTR in temper rolling or DR rolling, base surface treatment, DTR surface treatment process
When manufacturing steel sheets for DTR cans in a series of process steps for cans, the cooling rate during the continuous annealing was between 600 and 500 ° C was 40 ° C / sec or more, and was cooled to 400 ° C or less. After that, over-aging treatment is performed at a temperature of 400 to 300 ° C for 20 seconds or more, which is a method for producing a DTR can-compatible steel sheet having a structure composed of a ferrite phase and finely dispersed carbide.

Further, in the present invention, in addition to the above basic constitutional requirements, it is effective to add the following constitutional requirements in order to further enhance the side wall fracture resistance during DTR molding.

(2) In addition to (1), 0.002≤Nb≤0.010
% Of Nb is contained in the DTR can-compatible steel sheet.

[0018]

The basic concept of the present invention and the present invention constructed on the basis of the basic reasons will be described below.

First, the inventors of the present invention have shown the current DT shown in FIG.
Focusing on the microstructure of R-formed products, the main causes of side wall rupture are MnS, AlN, and Fe ₃ C, which are precipitated by the solid-state reaction in the steel sheet manufacturing process, in addition to the steelmaking oxide-based nonmetallic inclusions. It has been clarified that the microcracks generated at the interface with the matrix are easy to propagate.

It is also true that side wall rupture is caused by matching the shock line portion formed on the punch shoulder portion during DTR forming with a certain probability that there is a slight amount of non-metallic inclusions present in the steel. It was found that it is extremely important to optimize the microstructure of the steel sheet itself in order to achieve a higher level of thinning, and for that purpose, hot rolling conditions and continuous annealing conditions are extremely important. .

As an evaluation method, the inventors of the present invention accurately and quantitatively evaluate the significant difference between the materials with respect to the sidewall breakage resistance, which has been extremely vague and qualitatively evaluated by the conventional techniques. As a possible index, the limiting thinning rate (еth) obtained by the high-speed draw bead drawing test method shown in FIG. 5 was used.

According to the DTR simulation, еth has a positive correlation with the limit thinning rate of the side wall of the can body that can be DTR-molded without side wall breakage, and a value of about (еth + 5%) and a limit thinning rate are approximately. I confirmed that they match.

Using this high-speed draw bead pull-out test method, specific constitutional requirements and limiting ranges were defined.

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

Further, in the present invention, among the above-mentioned finely dispersed carbides, the group-like cementite due to pearlite distributed in the hot-rolled sheet and the precipitation state of C of 0.02% or less which is dissolved and precipitated during annealing are described. Stable sidewall rupture resistance is obtained by defining a manufacturing method for maintaining good conditions.

That is, the pearlite distributed in the hot-rolled sheet is crushed during cold rolling and spread in the rolling direction, and at the time of annealing, a group-like cementite (Lc) having ferrite crystal grains as shown in FIG. ), Which forms a solid solution in the ferrite phase during annealing, precipitates as Fe ₃ C in the ferrite grain boundaries or in the ferrite crystal grains during the cooling process.

Especially when the cooling rate is low, most of C is deposited in a film form on the ferrite crystal grain boundaries. On the other hand, these carbides contribute to strengthening the steel sheet, but at the same time, they give the starting points of microcracks during DTR forming. Therefore, in the present invention, a certain amount of C is finely precipitated in the ferrite crystal grains (the average inter-grain distance MFP of the fine cementite) to finely disperse the cementite below the critical size that induces microcracks.

FIG. 3 shows the effects of the ferrite grain size and the overaging temperature during continuous annealing and the effect of B addition on еth in TFS adjusted to a temper degree equivalent to DR-9. By decreasing the ferrite crystal grain size, еth increases, indicating that grain refining is effective as the basis of material design. However, only with the refinement
In order to achieve a grain size of 25% or more, it is necessary to reduce the grain size to d ≤ 2 μm, and perform a recrystallization annealing from the full martensite structure, or a complicated manufacturing process such as cold rolling and low temperature recrystallization annealing. Need to go through.

However, by performing the overaging treatment in the temperature range of 300 to 400 ° C. and simultaneously adding a trace amount of B, not only the critical d reaching еth ≧ 25% is increased, but also еth ≧ 30%. % Can be stably obtained.

This is because B segregated at the ferrite grain boundaries during soaking during annealing eliminates the precipitation of film-like cementite at the ferrite grain boundaries during cooling, and 600 to 5
By quenching between the temperature of 00 ℃ and overaging in the temperature range of 300 to 400 ℃, the precipitation of fine cementite in the crystal grains is promoted, and the fine grain from the grain boundary cementite during DTR forming is promoted. This not only reduces the occurrence of cracks, but also suppresses the propagation of cracks by strengthening the ferrite grain boundaries and the cementite-ferrite interface with B.

In the present invention, in order to achieve a finely dispersed carbide distribution, the steel sheet components and manufacturing conditions are limited to the following ranges.

B: B is 0.0002% as the lower limit at which the precipitation suppressing effect of film-like cementite on the ferrite grain boundaries is recognized, and the effect is saturated. In addition, the structure of the hot-rolled sheet becomes a needle-like ferrite structure, 0.0015% is specified as the upper limit that does not deteriorate the ductility.

S: S is an extremely important element in the present application. In particular, S is present in steel as MnS, and expanded MnS
Tends to be the starting point of cracks that lead to side wall fracture during DTR forming.
Therefore, it is preferable that S is as small as possible. Conventionally, there are cases where S is added to the steel sheet for cans from the viewpoint of corrosion resistance, but in laminated steel sheets applied to DTR, since S is laminated, the effect of S on corrosion resistance is not a problem. Particularly in the present application, the adverse effect of MnS on the side wall fracture resistance is reduced by adding a trace amount of B, but the upper limit is 0.02%.

C: C is an extremely important element for ensuring the strength level required as a DTR compliant steel sheet. However, on the other hand, about 0.02%, as perlite,
About 0.02% or less, cementite (Fe ₃ C) exists in the ferrite grain boundaries or inside the ferrite crystal grains during annealing.
As a result, the interface between these carbides and the mother phase easily becomes the starting point of cracking, and as shown in FIG. 6, a large number of minute cracks occur during DTR molding.

Cementite, which is deposited in the form of a film at the ferrite crystal grain boundaries, easily induces grain boundary separation. On the other hand, when C in steel is reduced by oxygen blowing during steelmaking, not only is it disadvantageous in terms of material strength in the range of less than 0.03%, but also oxygen in molten steel increases, and side wall fracture resistance deteriorates. Deoxidation products increase. 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%.

O: Oxide inclusions remarkably impede side wall fracture resistance. Al is a problem as oxide inclusions
_Although it is a ₂ O ₃ type, there are cases where CaO and MnO type inclusions remain. Fig. 1 shows the results of arranging the еth of various materials by the total oxygen content in the steel. By setting the total oxygen content to 30 ppm or less (preferably 25 ppm or less), good еth can be obtained. Therefore, in the present invention, the total oxygen content in the steel is limited to 30 ppm or less.

Si: Si is an element that causes embrittlement of steel, so it is preferable that the amount of Si is small. In addition, it is preferable that the production of TFS is small with respect to the electrodeposition of metal Cr. The upper limit is set to 0.03%, which is not a practical problem.

Mn: Mn not only prevents hot cracking of the slab by precipitating S in the steel as MnS, but also, in the overaging process of continuous annealing, fine cementite in the ferrite crystal grains centered on MnS. It plays a role of promoting precipitation.
It also serves as a solid solution strengthening element to supplement the strengthening by C. In the present application, as a lower limit sufficient to precipitate and fix S, 0.3
Specify%.

Although adding a large amount of Mn is effective for increasing the strength of the material, on the other hand, the solubility product of MnS increases, and not only a relatively large MnS is formed in the slab stage, but also the band structure of the bunting structure is formed during hot rolling. It promotes the formation and promotes a microscopic non-uniform distribution of C in the steel, which hinders the fine dispersion of carbides. All of these provide a detrimental structure for sidewall fracture during DTR. Therefore, the upper limit of Mn is set to 1%.

P: P is an element that segregates at ferrite crystal grain boundaries and embrittles the grain boundaries, so it is preferably as small as possible. As an upper limit that does not practically affect the sidewall rupture resistance, 0.03
% Or less.

Sol.Al: sol.Al reduces the adverse effect of solute N which reduces local ductility of the steel sheet by dynamic strain aging phenomenon as in the case of solute C by precipitating N in steel as AlN. . In addition, fine AlN is not only effective for refining ferrite crystal grains, but, like MnS, in the overaging process of continuous annealing,
It serves as a nucleus for precipitation of fine cementite in ferrite crystal grains.

However, in order to increase the amount of sol.Al, a large amount of Al
If it is added, minute Al ₂ O ₃ inclusions tend to remain, which causes sidewall breakage. Therefore, 0.02% is set as the lower limit at which the above effects are exhibited, and 0.1% is set as the upper limit as a limit at which addition of more than this practically impairs sidewall rupture resistance.

N: N is finely dispersed as AlN and utilized as a fine grain of ferrite crystal grains and as a precipitation site of fine cementite, and its range is 10 to 70 pp from the economical point of view.
Let m.

As an effective and highly productive method for realizing the above-mentioned carbide distribution, the hot rolling conditions and the continuous annealing conditions are limited as follows.

Hot rolling conditions: Slab heating temperature: 1150 ° C. or higher,
Hot rolling finishing temperature: 870 ° C or lower, winding temperature: 620 ° C or lower.

The hot rolling conditions are important for finely dispersing MnS and pearlite. Especially, MnS has a billet heating temperature of 115
Fine dispersion is achieved by re-solidifying at 0 ° C. or higher and then hot rolling. For pearlite, the austenite grains are refined after the hot rolling finishing temperature is 870 ° C or less and then ferrite transformation is performed. Fine dispersion can be achieved by suppressing the formation.

Steel pieces include slabs and thin cast plates. The continuous annealing condition is that after cooling, the cooling rate between 600 and 500 ° C is 40 ° C / sec or more in the cooling after annealing, and after cooling to 400 ° C or less, it is kept in the temperature range of 400 to 300 ° C for 20 seconds or more. I do.

In the present application, it is further dissolved and precipitated during annealing.
It was found that stable sidewall rupture resistance can be obtained by defining the precipitation state of C of 0.02% or less. That is, pearlite distributed in the hot-rolled sheet is crushed during cold rolling and spread in the rolling direction, and exists as community-like cementite that cleaves ferrite crystal grains during annealing, but is present in the ferrite phase during annealing. Approximately 0.02% of C that forms a solid solution is Fe in the ferrite grain boundaries or inside the ferrite crystal grains during the cooling process.
Precipitates as ₃ C. Especially when the cooling rate is slow or the overaging temperature is high, most of C is deposited in a film form on the ferrite grain boundaries. These ferrite grain boundary carbides provide the starting points for microcracks during DTR forming. Therefore, in the present invention, a certain amount of C is finely precipitated inside and outside the ferrite crystal grains to finely disperse the cementite to a size not larger than the critical size that induces microcracks.

FIG. 2 shows 600 at the time of continuous annealing over еth.
It is a figure showing the influence of the cooling rate and the overaging treatment temperature between ~ 500 ° C. As is clear from the figure, 30% or more of еth is obtained under the conditions of cooling rate between 600 and 500 ℃: 40 ℃ / sec or more and overaging temperature: 400-300 ℃.

This is because when the overaging temperature exceeds 400 ° C., film-like cementite precipitates at the ferrite grain boundaries during overaging and becomes a starting point of cracking, and below 300 ° C., the residual solid solution C increases. This is because the local ductility of the steel sheet deteriorates.

On the other hand, when the cooling rate is less than 40 ° C./sec,
Driving force for precipitation of solid solution C sufficient to precipitate fine cementite in ferrite crystal grains (depending on supersaturation degree of solid solution C)
Is not obtained.

The annealing temperature of the continuous annealing is set to a temperature not lower than the recrystallization temperature and not higher than the Ac ₃ point to prevent the hard second phase from being generated. The annealing temperature and the cooling rate up to 600 ° C may be rapid cooling or slow cooling, and the cooling rate from 500 ° C to the overaging temperature may be rapid cooling or slow cooling.

In the present invention, it is shown in FIG. 3 that еth can be improved by reducing the ferrite crystal grain size of the steel sheet. Therefore, in the present invention, a trace amount of Nb of 0.002 to 0.01% may be added as a method of refining the ferrite structure.

L of the steel sheet obtained by the manufacturing method according to the present invention
The preferred ranges of c and MFP are 10 μm or less,
It is 2 μm or less.

The surface treatment of the base material of the present invention is not limited to TFS, but includes tin-plated steel sheets, ultra-thin tin-plated steel sheets, tin-Ni plating, and Ni.
The characteristics of flash-plated steel sheets and Cr-plated steel sheets are not impaired. In particular, when these surface-treated steel sheets are used as a base treatment for film-laminated steel sheets and pre-coated steel sheets, a tin-free steel sheet is most desirable from the viewpoint of work adhesion.

The surface treatment for DTR of the present invention can be applied to various kinds of laminates, and its performance is essentially unchanged depending on the type of resin and the like. Similarly, it can be applied to various types of precoats and types of paints. The performance is essentially unchanged by.

The manufacturing method of the steel sheet of the present invention disclosed above is
Regardless of whether the can forming process is the Wet process or the Dry process, this is a technology that can be applied to the production of all steel sheets used in the so-called DTR can manufacturing method in which deep drawing is performed while applying tension.

After the DTR processing, further ironing (Ir
It can also be applied when thinning is performed by carrying out oning).

The effects of the present invention will be described more specifically below with reference to examples.

[0060]

【Example】

Example 1 Steel was melted and then cast into a slab by continuous light pressure casting. 11 for the slab
After heating to 20 to 1200 ° C., a finishing temperature: 840 to 890 ° C., a winding temperature: 580 to 680 ° C., and a hot rolled sheet having a thickness of 1.8 mm was obtained. The hot-rolled steel sheet was pickled, cold-rolled to 0.24 mm, and subsequently recrystallized in a continuous annealing furnace. In continuous annealing, the cooling rate between 600 and 500 ° C of the cooling up to the overaging treatment temperature after annealing is changed in the range of 20 to 100 ° C / sec, and the overaging treatment is performed at 250 to 450 ° C. It went for 90 seconds.

The annealed steel plate is DR rolled to a thickness of 0.18.
mm, and then metal Cr and Cr on the tin-free plating line
A TFS steel sheet having a multi-layered structure of hydrated oxide and having the chemical composition shown in Table 1 and the balance Fe and unavoidable impurities was manufactured.

A PET film was heat-sealed to the steel sheet in a laboratory, and еth was evaluated by a high speed draw bead pulling test.

The results obtained are shown in Table 2. By combining the steel sheet components specified in the present invention with the hot rolling and continuous annealing conditions, a high еth is obtained, suggesting that it has excellent DTR formability.

[0064]

[Table 1]

[0065]

[Table 2]

In the continuous annealing, after cooling after annealing, the cooling rate between 600 and 500 ° C. is set to 40 ° C./sec or more,
The box may be annealed at an overaging temperature of 400 to 300 ° C.

[0067]

EFFECT OF THE INVENTION The present invention prevents the minute cracks at the interface between MnS and the matrix phase of the microstructure or at the interface between the carbide and the matrix phase, so that the side wall resistance of the steel sheet in DTR forming undergoing intense tensile deep drawing is prevented. The breakability was remarkably improved.

Therefore, when the wall thickness is reduced to 20% or more, there is no side wall fracture, and even if the wall thickness is reduced to 30% or more, such a small crack hardly occurs. Can be provided.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the influence of a cooling rate of 600 to 500 ° C. and an overaging treatment temperature during continuous annealing on еth.

FIG. 3 is a diagram showing the influence of B and the average crystal grain size on еth.

FIG. 4 is a diagram showing the morphology of finely dispersed carbide and the definitions of Lc and MFP.

FIG. 5 is a schematic view of a high speed draw bead pull-out test method.

FIG. 6 is a drawing-substituting photograph of a cross-sectional microstructure showing a cross-sectional state of cracks in a side wall of a can after DTR molding.

Front Page Continuation (72) Inventor Yukio Kawase 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. In the company

Claims (2)

[Claims] 1. In weight% (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%, Tot
Steel billet containing al-O ≦ 30ppm, 0.0002 ≦ B ≦ 0.0015%, billet heating temperature: 1150 ℃ or more, hot rolling finishing temperature: 870 ℃
Hereafter, after making hot rolled steel sheet under the condition of coiling temperature: 620 ° C or less, steel sheet for DTR can is manufactured by cold rolling, continuous annealing, temper rolling or DR rolling, base surface treatment, and surface treatment process for DTR. In the case of doing, 600 ~ 5 of the cooling during the continuous annealing.
The cooling rate between 00 ℃ is 40 ℃ / sec or more, and after cooling to 400 ℃ or less, overaging treatment is performed at the temperature of 400 to 300 ℃
A method for producing a DTR can-compatible steel sheet having a structure consisting of a ferrite phase and finely divided carbide, characterized by being applied for at least 2 seconds. 2. The method for producing a DTR can-compatible steel sheet according to claim 1, which contains Nb in the range of 0.002 ≦ Nb ≦ 0.01%.