KR100627430B1 - Steel sheet for container and method of producing the same - Google Patents

Abstract

An object of the present invention is to provide a steel sheet for a container having a welded portion, which can prevent a decrease in productivity due to buckling in a steel sheet annealing step, cracking in a welded portion at the time of steelmaking, and cracking in a welded portion at the time of use of the can. Invention.

1st invention of this invention contains C: 0.0050% or less and N: 0.0060% or less by mass%; The ratio of B / N is controlled within the range of 0.40 to 2.0; Satisfies the formula (N present in AlN) / (N present in BN) ≦ 0.40;

If necessary, Al / B is controlled to 30 or less; It is characterized by controlling the slab reheating temperature in hot rolling to 1100 ° C or more.

2nd invention of this invention is mass%, C: 0.0005%-0.040%, Si: 0.002%-0.50%, Mn: 0.03%-2.00%, P: 0.002%-0.080%, S: 0.0100%-0.0600 It relates to a steel sheet for a container having excellent moldability and fatigue characteristics in a welded part, which contains%, Al: 0.0010% to 0.0700% and N: 0.0020% to 0.0300%, and the content of solid solution N is 20ppm to 300ppm.

Description

Steel plate for containers and method for manufacturing same {STEEL SHEET FOR CONTAINER AND METHOD OF PRODUCING THE SAME}

The present invention relates to a steel sheet used as a material for cans produced by welding and to a method for producing the same, as represented by the production of a three-piece can. That is, this invention provides the ultra-thin material for containers which can be manufactured with high productivity and is excellent in the moldability of a weld part in the manufacturing field of a steel plate, and a steel manufacturing field.

In the manufacturing field of beverage cans, food cans, and the like, containers called three-piece cans and whose can bodies are formed by welding are used. In order to attach a can bottom and a can lid to this can body, a flange process which expands a can body opening part is performed, In this case, a weld part requires good flange formability. In large containers and the like, welding is often used to attach a metal handle to the container, and the strength, in particular, the fatigue strength at the welded part may be a problem.

On the other hand, the steel sheet for containers has been thinned from the viewpoint of cost reduction, thereby deteriorating the ductility and fatigue properties of the steel sheet. Accordingly, good formability and high strength of welded parts are also required in ultrathin steel sheets. In addition, the ultra-thin steel sheet cold rolled to the product thickness tends to generate a buckling called heat-buckle during continuous annealing, which significantly lowers the flowability and significantly lowers the productivity.

In order to solve this problem, the DR material by the so-called DR method (twice cold rolling method) which processes the steel plate thicker than the final product at the time of annealing and obtains the thickness of the final product by the second cold rolling after the annealing is disclosed in Japanese Patent Laid-Open No. 3- 257123, Japanese Patent Laid-Open No. 2-118026, and the like. However, in the steel sheet hardened by secondary cold rolling, the softening of the material due to the recovery of the material and the recrystallization occurs in the welded portion due to the heat generation during welding, so that the stress concentration increases in the vicinity of the welded portion and the moldability and fatigue characteristics are reduced.

In addition, Japanese Laid-Open Patent Publication No. 10-72640 discloses a method of securing the strength of a steel sheet by increasing the solid solution N. However, this method causes excessive stress concentration in the welded portion, and thus formability and fatigue strength of the welded portion. Is not sufficiently improved.

Further, Japanese Patent Laid-Open No. 2-118028 discloses a method of improving flange formability by lowering the solid solution C and N or improving the Rankford value. In addition, Japanese Patent Laid-Open No. 63-89625 discloses a technique for minimizing grain size by adding Nb and B to improve flange formability. In addition, Japanese Unexamined Patent Publication No. 61-34159 discloses a technique for minimizing cementite and improving flange formability. Japanese Unexamined Patent Publication No. 63-310922 discloses an overaging heat treatment condition to improve flange workability. The technique to make is disclosed.

On the other hand, Japanese Unexamined Patent Publication No. 63-317625 discloses that when welding a steel sheet for automobiles, Ti, Nb and B are added to increase the strength of the welded portion in connection with softening of the heat affected zone by welding as a cause of cracking. A technique for preventing cracks in welds is disclosed. However, in the case of ultrathin material, if the weld strength is too high, the crack in the raw material portion becomes remarkable, and the flange formability deteriorates rather.

As described above, the mechanism of improving flange formability has not yet been identified, and therefore, various measures for improving flange formability have been taken. However, these countermeasures do not take into account the thinness of the ultrathin material in the annealing furnace, and by simply adding Ti, Nb and B, the recrystallization temperature of the steel sheet must be increased to increase the annealing temperature. The mail order in is markedly lowered.

This invention is made | formed in view of the above-mentioned situation, and provides the steel plate for containers. ADVANTAGE OF THE INVENTION According to this invention, the ultra-thin material used for the container which has a welded part can be manufactured with high productivity, without impairing the board | substrate at the time of annealing, and the moldability of the welded part at the time of piping can be improved, and it is a problem at the time of use. The crack at the welded portion can be reduced.

The present invention provides a method of improving the flange formability of the welded portion at the time of can forming and the fatigue strength of the welded portion at the time of use by appropriately setting the material so that the material of the welded portion which is likely to cause stress concentration at the time of forming or use is suitable for the purpose. That is, this invention relates to the method of further improving a characteristic in B-added ultra low carbon steel by adjusting the form of nitride to an appropriate range, and adding a trace amount element.

More specifically, this invention relates to the steel plate for containers excellent in the moldability and fatigue characteristic of a welded part, and its manufacturing method. The present invention consists of the following terms.

(1) at mass%,

C: 0.0050% or less,

N: 0.0060% or less, and

B is contained so as to be B / N: 0.40 to 2.00,

A steel sheet for a container having excellent moldability and fatigue characteristics, characterized in that AlN and BN in steel satisfy (N in AlN / N in BN) ≦ 0.40.

(2) The method according to (1),

In mass%, Al: 0.040% or less is further contained,

A container steel sheet excellent in formability and fatigue properties of a welded portion, characterized by an Al / B ratio of 30 or less.

(3) The method according to (1) or (2),

A steel sheet for containers excellent in moldability and fatigue properties of a welded portion, characterized by further containing, in mass%, O: 0.0010% to 0.0070%.

(4) The method according to any one of (1) to (3),

Si: 0.015%-2.00%,

Mn: 0.05% to 2.00%, and

P: 0.005%-0.080% of steel containers for containers excellent in moldability and fatigue characteristics, characterized in that it further contains.

(5) The method according to any one of (1) to (4),

Ti: 0.010% or less and

Nb: 0.010% or less of steel plate for containers excellent in the moldability and fatigue characteristics of a welded part characterized by the above-mentioned.

(6) The method according to any one of (1) to (5),

A container steel sheet having excellent formability and fatigue properties of a welded part, wherein a sulfide contained in the steel satisfies the formula (S present as Cu sulfide) / (S present as Mn sulfide) ≦ 0.10.

(7) When the steel sheet for a container is manufactured by the usual manufacturing process using the steel containing the component of any one of (1)-(6), slab reheating temperature is 1100 degreeC or more in hot rolling. The manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of a welded part characterized by controlling by.

(8) When manufacturing the steel plate for a container by a normal manufacturing process using the steel containing the component as described in any one of (1)-(6), the winding temperature is 730 degrees C or less in hot rolling. The manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part characterized by controlling.

(9) When the steel sheet for a container is manufactured by the normal manufacturing process using the steel containing the component of any one of (1)-(6), the annealing temperature after cold rolling is made into 700 degrees C or less. The manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part characterized by controlling.

(10) at mass%,

C: 0.0005%-0.040%,

Si: 0.002%-0.50%,

Mn: 0.03%-2.00%,

P: 0.002% to 0.080%,

S: 0.0100%-0.0600%,

Al: 0.0010% to 0.0700% and

N: 0.0020% to 0.0300%,

The content of N dissolved in the steel is 20ppm to 300ppm,

A steel sheet for a container having excellent moldability and fatigue characteristics, wherein the remainder is made of Fe and unavoidable impurities.

(11) The method according to (10),

In mass%,

Nb: 0.0005% to 0.0050%,

Ti: 0.0005% to 0.0050% and

B: The steel plate for containers excellent in the moldability and fatigue characteristics of a welded part which further contains 1 or more types of 0.0010% or less.

(12) The method according to (10) or (11),

In mass%,

O: 0.0015% to 0.0090% of the steel sheet for containers excellent in the moldability and fatigue properties of the weld zone, characterized by further containing.

(13) The method according to any one of (10) to (12),

In mass%,

Cu: 0.0005% to 0.050%,

Ni: 0.0005% to 0.100% and

Cr: 0.005% to 0.100% of the container steel sheet excellent in formability and fatigue properties of the weld zone, characterized in that it further contains at least one.

(14) The method according to any one of (10) to (13),

In mass%,

Sn: 0.0002% to 0.0050% of the container steel sheet excellent in the moldability and fatigue properties of the weld portion, characterized in that it further contains.

(15) The method according to any one of (10) to (14),

A container steel sheet having excellent formability and fatigue properties of a welded part, wherein a sulfide contained in the steel satisfies the formula (S present as Cu sulfide) / (S present as Mn sulfide) <0.30.

(16) A method for producing a steel sheet for a container having excellent moldability and fatigue characteristics of a welded portion according to any one of (10) to (15).

A method for producing a steel sheet for a container having excellent moldability and fatigue characteristics, characterized in that secondary cold rolling is performed at a rolling reduction of 20% or less after continuous casting, hot rolling, pickling, cold rolling, and annealing of molten steel.

(17) In the manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part in any one of (1)-(16),

Initiating hot rolling under the condition that the heat history in the temperature range of 1000 ° C. to 1300 ° C. after the continuous casting of molten steel before the start of hot rolling starts satisfies the temperature (° C. × time (minutes) ≦ 200000). The manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part characterized by the above-mentioned.

(18) A method for producing a steel sheet for a container having excellent moldability and fatigue characteristics of a welded portion according to any one of (1) to (17).

A method of manufacturing a steel sheet for a container having excellent formability and fatigue characteristics of a welded part, wherein the steel sheet is hot rolled by controlling the average cooling rate to 30 ° C / sec or less during the time from the start of finish hot rolling to the winding after completion of the finish hot roll. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the method of evaluating the workability of a weld part.

It is a figure which shows the method of evaluating the workability of a weld part by a tension test.

3 is a view showing a method for evaluating the fatigue strength of the welded portion.

4 is a graph showing the relationship between (N present in AlN) / (N present in BN) and workability.

5 is a graph showing the relationship between (N present in AlN) / (N present in BN) and fatigue strength.

 <Embodiment 1>

The invention according to claims 1 to 9 is described in detail below.

First, a chemical component is demonstrated below. In the description, the content of each chemical component is expressed in mass%.

It is preferable that C is generally as low as possible from the viewpoint of workability, and therefore sets an upper limit to 0.0050%. In particular, when the ductility is excellent and the aging needs to be small, the C can be reduced to 0.0015% or less to significantly improve the characteristics. However, too decreasing the C content not only leads to an increase in cost but also softens the steel sheet to lower the can strength, so the lower limit is preferably 0.0030%.

N is an important element controlling nitride formation, which is an important requirement of the present invention. An excessive amount of N results in the formation of a large amount of nitride, and the object of the present invention cannot be achieved, so the upper limit is set to 0.0060%. In the case where the amount of B added is relatively small, as described below, problems related to aging due to the remaining of solid solution N may occur, so that the N content is preferably controlled to 0.0030% or less in order to reduce the aging effect. In addition, when the vacuum degassing treatment is sufficiently performed to control the N content to 0.0020% or less, formation of nitride is suppressed and moldability is particularly improved.

B influences the form of the nitride, changes the material of the weld heat affected zone, and lowers the recrystallization temperature of the steel sheet by appropriate addition, thereby enabling annealing at a lower temperature, and consequently, the flowability at the time of annealing. Since it improves, it adds as an essential element in this invention. However, excessive addition of B causes the weld to be excessively hardened, degrading the workability, raising the recrystallization temperature, and increasing the annealing temperature. As a result, thermal buckling easily occurs. The important point is the ratio of B to N, and the ratio of B / N is set to 0.40 to 2.00, preferably 0.60 to 1.40.

An important condition in the present invention is the control of the type and amount of nitride, and the ratio of N present as AlN and N present as BN in the B-added ultra low carbon steel should be 0.40 or less, preferably 0.20 or less.

Here, N present as AlN is a value obtained by analyzing the amount of Al in the residue when the steel sheet is dissolved in an iodine alcohol solution, and then calculating all the amounts of Al as constituents of AlN and calculating the amount of N. . In addition, N which exists as BN is a value obtained by analyzing the amount of B in the residue at the time of melt | dissolving a steel plate in iodine alcohol solution, and considering all this B amount as a component of BN, and calculating N amount.

As described above, in order to control the nitride, the amount of addition of Al and B and the ratio of Al / B, the oxide acting as the nuclei of the nitride, that is, the O content in the steel, and the thermal history throughout the manufacturing process are important factors. do. By controlling Al / B to 30 or less, preferably 20 or less, and Al to 0.04% or less, preferably 0.020% or less, when solid solution N present in excess in the steel precipitates nitride, And, accordingly, the type and amount of the nitride can be preferably controlled.

O is effective for nitride control in the range of 0.0010% to 0.0070%. The reason is that O in steel exists as an oxide containing trace elements such as Si, Al, Mn and Fe, and also Ca, Mg, and when the O content present is appropriate, O acts effectively as a precipitation nucleus of nitride. Therefore, it is thought that preferable nitride control becomes possible. However, an excessive amount of O in the steel coarsens the oxide and acts as a starting point for cracking during processing, thereby significantly reducing product quality. Therefore, the upper limit of O content is set to 0.0070%.

As described above, in order to control the preferred form of the oxide, or to improve the workability and fatigue strength by adjusting the strength of the base steel sheet to relieve stress concentration in the vicinity of the weld, adding Si, Mn, P, etc. It is possible. The addition amount is set to Si: 0.015%-2.00%, Mn: 0.05%-2.00%, P: 0.005%-0.080%, respectively. If the added amount is out of this range, the oxide form changes or the weld is abnormally softened or hardened, so that the desired properties are not obtained.

In the case of drawing forming or the like, the provision of an upper limit of the inevitably contained Ti and Nb content from scrap or the like added or incorporated in the steelmaking step to improve drawing formability is also an important requirement of the present invention. Therefore, the content of each element is set to 0.010% or less, respectively. When the content exceeds the upper limit, the recrystallization temperature of the steel sheet rises and the plateability of the annealing process is significantly decreased, and the crystal structure becomes abnormally coarsened and softened by the heat effect near the welded portion. Stress concentration is promoted, and thus moldability and fatigue strength may decrease.

It is also important to suppress the formation of Cu sulfides for sulfides in steel. In general, S in steel must be fixed as a sulfide with respect to hot rolling properties, so in the present invention, it is preferable to fix S as MnS.                 

In the present invention, the ratio of (S present as Cu sulfide) and (S present as MnS) is set to 0.10 or less. The reason for this is that fine precipitation of Cu sulfide not only increases the recrystallization temperature of the steel sheet but also forms a complex precipitate of B and Al nitride, and thus nitride becomes an undesirable form.

Here, (S present as Cu sulfide) is a value obtained by quantitatively measuring the amount of Cu in the residue obtained by electrolytic extraction of the steel sheet, and converting the amount of Cu into the amount of S using Cu / S = 2/1, ( S) present as Mn sulfide is a value obtained by quantitatively measuring the amount of Mn in the residue obtained by electrolytic extraction of the steel sheet, and converting the amount of Mn into the amount of S using Mn / S = 1/1.

The manufacturing process of this invention includes processes, such as hot rolling, winding, pickling, cold rolling, annealing, a skin path | pass, which are normally performed.

Regarding the heat history in the manufacturing process, the influence of the slab reheating temperature at the time of hot rolling, the coiling temperature, and the annealing temperature after cold rolling are large, and the slab heating temperature at the time of hot rolling is 1100 ° C or more, and the winding temperature at the time of hot rolling is 730 ° C or less, By limiting the annealing temperature after cold rolling to 700 degrees C or less, the workability and fatigue strength of a weld part can be improved further. The cause is not clear, but it is considered that the influence of the form of the nitride or the form of precipitates other than the nitride.

By limiting the annealing temperature after cold rolling to 700 ° C. or less, the occurrence of thermal buckling is suppressed to improve the mail flow of the annealing process, and therefore it has industrially significant importance.

As mentioned above, the mechanism of improving the workability and fatigue strength of the welded portion, in particular by controlling the form of the nitride, is not clear, but in terms of development, the hardness of the material at the welded portion and the heat affected zone near it is appropriately controlled, and Due to this the stress concentration at that site can be alleviated and the desired hardness can be obtained. In the welded part and its vicinity, nitride melt | dissolves by the temperature rise at the time of welding, hardness is determined by the fine nitride which resolves in the cooling process and the remaining fine nitride which both solid solution N and solid solution B do not fully melt | dissolve. Therefore, in order to obtain the desired forms of solid solution N, solid solution B and nitride, it is necessary to control the form of nitride in steel before welding, as specified in the present invention.

In manufacture of ultra-thin steel plate for containers, in order to ensure the strength of a container, the steel plate hardened by work hardening by 2CR rolling after annealing may be used. Also in such a steel plate, this invention can obtain the effect of improving the workability and fatigue strength of a welded part. In addition, even when an element for improving corrosion resistance and other properties is added, the effect of the present invention is not lost.

Sn, W, Mo, Ca, Cr, Ni in order to improve the properties not described in the specification of the present invention, such as workability including the drawability and secondary workability of the steel sheet, corrosion resistance of the steel sheet, sheet-flow properties in various processes, etc. Even if it contains V, Sb, etc., the effect of this invention will never be lost. However, excessive inclusion of these elements lowers the annealing flowability due to an increase in recrystallization temperature, and therefore it is preferable to control each element to 0.10% or less, in total, 0.50% or less.

The steel sheet according to the present invention is generally used as a disc of a surface-treated steel sheet, and even in this case, the effect of the present invention is never impaired by the surface treatment. As the surface treatment for cans, a treatment method using tin, chromium (non-tin), nickel, zinc, aluminum, or the like is adopted. Moreover, the steel plate concerning this invention can be used as a disc of the laminated steel plate with an organic film currently used, without impairing the effect of this invention.

<Embodiment 2>

The invention according to claims 10 to 16 is described in detail below.

First, a chemical component is demonstrated below. In the description, the content of each chemical component is expressed in mass%.

When C exceeds 0.040%, the carbide coarsens and acts as a breakdown point in the vicinity of the weld where stress is concentrated. On the other hand, too decreasing the C content leads to an increase in cost, and therefore sets the lower limit to 0.0005%.

In general, Si is preferably as low as possible in view of corrosion resistance. However, when it is applied to the so-called laminated steel sheet which has a resin film adhered to the surface and demand is increasing in recent years, it is preferable that Si content is high from a viewpoint of suppressing the fall of corrosion resistance and suppressing stress concentration in a weld part. On the other hand, excessively reducing the Si content makes it difficult to control the oxide form as described later, thus setting the Si content to 0.002% to 0.5%.

Mn has the same effect as Si, and the optimum range is 0.03% to 2.00%, more preferably 0.05% to 1.00%.

It is preferable that P is as low as possible from a viewpoint of corrosion resistance and stress concentration in a weld part. However, it is a useful element for controlling the strength of the steel sheet at low cost. The limiting range of P is 0.002% to 0.080%, preferably 0.002% to 0.030%.

S combines with Mn, Cu, Ti and the like in the steel to form sulfides. In the present invention, S is an essential and important element for relieving stress concentration in the welded portion by remaining an appropriate amount of sulfide in the steel. In order to obtain the effect of the present invention, an S content of at least 0.0100% is required. However, when the S content is excessive, the oxide may coarsen and act as a starting point of destruction, and therefore the upper limit is set to 0.0600%.

If the content of Al is too low in relation to the amount of oxygen described later, deoxidation in the steelmaking process will be insufficient. On the other hand, if the Al content is too high, not only solid solution N is secured, but fine AlN is formed in a large amount, and the recrystallization temperature of the steel sheet rises, which causes a significant decrease in the flow through in the annealing process. Therefore, the Al content is determined in the range of 0.0010% to 0.0700%.

N is an important element controlling nitride formation, which is one of the important requirements of the present invention. If the addition amount is small, the effect of the present invention is insufficient. Therefore, N is added at least 0.0020%. On the other hand, when N is contained in a large amount, Fe nitride is produced in a large amount even when there is little Al, and thus serves as a starting point for breakdown in the welded portion. Therefore, the upper limit of N is made 0.0300%. Here, with regard to the method of adding N, N may be added in the molten steel stage as in the case of a normal steel sheet, or N may be added by heat-treating the steel sheet in an ammonia-containing atmosphere, that is, by nitriding. .                 

In order to calculate the amount of solid solution N, the amount of precipitation N which can be measured by the method of dissolving steel in a bromine ester solution is subtracted from the total amount of N in steel. When the amount of solid solution N is small, softening in the vicinity of the weld cannot be suppressed. When the amount of solid solution N is excessive, the aging property increases and the ductility decreases. Therefore, the solid solution N is limited to the range of 20ppm to 300ppm.

Since Nb, Ti and B combine with N to form precipitates, and Ti forms S and precipitates, the addition of trace amounts of these elements effectively acts to control the solid solution N and sulfide forms as described above. The effect of becomes more remarkable. On the other hand, if the addition amount is excessive, the form of solid solution N and sulfide becomes undesirable, and therefore, the effect of the present invention is not only impaired, but also the recrystallization temperature of the steel sheet tends to rise, and the flowability during annealing tends to decrease. Not. The preferred range of these elements is Nb: 0.0005% to 0.0050%, Ti: 0.0005% to 0.0050%, and B: 0.0010% or less.

O is an important element for properly controlling the oxide form, which is an important factor in the present invention. If the O content is too small, the amount of oxides for suppressing material softening due to heat generation during welding is insufficient, and therefore, a sufficient effect cannot be obtained. On the other hand, when the O content is excessive, the oxide is a starting point of destruction during molding. Therefore, in the case of adding O, the content range is determined to be 0.0015% to 0.0090%, preferably 0.0030% to 0.0090%.

In the present invention, it is not clear why the oxygen amount has a remarkable effect, but the fine oxide suppresses grain growth in the high temperature region at the time of welding, and the shape of the fine oxide itself does not change due to the temperature rise such as near the weld. Therefore, it is considered that this is because the softening inhibitory effect is maintained. In practice, it is important to define the size, number and density of the oxides of Fe, Al, Si and Mn in the steel, and as long as the content of Al, Si, Mn and O is controlled within the scope of the present invention, The oxide form can be controlled preferably, and a preferable effect can be obtained.

Cu, Ni, and Cr serve to improve the corrosion resistance of the steel sheet and to suppress material softening during welding, so that these elements are contained as necessary. Too high content of these elements may cause ductility deterioration of the material, and when these elements are added, Cu: 0.0005% to 0.050%, Ni: 0.0005% to 0.100%, Cr: 0.0005% to 0.100% It is desirable to.

Sn is generally an element segregated at the grain boundaries of the steel sheet. Sn can be contained in steel since it has the effect of suppressing abnormal grain growth due to heat generation during welding and thus suppressing softening of the material. Since addition of excess Sn reduces ductility, when adding Sn, it is preferable to control in 0.0002%-0.0050% of range.

In the steel sheet according to the present invention, by appropriately controlling the form of the sulfide, softening of the weld portion can be suppressed and desirable characteristics can be obtained. The size, number, density, and the like of the sulfides can be specified, but in the present invention, sulfides in the steel are defined as (S present as Cu sulfide) / (S present as Mn sulfide) <0.30. Although the cause of the above-mentioned effect is not clear, since CuS has lower stability at high temperature than MnS, it is thought to be because it melt | dissolves or coarsens by the temperature rise at the time of welding, and the softening suppression effect of a material lose | disappears easily.                 

Here, (S present as Cu sulfide) is a value obtained by quantitatively measuring the amount of Cu in the residue obtained by electrolytic extraction of the steel sheet, and converting the amount of Cu into the amount of S using an atomic ratio of Cu / S = 2/1. (S present as Mn sulfide) is a value obtained by quantitatively measuring the amount of Mn in the residue obtained by electrolytic extraction of a steel sheet, and converting the amount of Mn into an amount of S using an atomic ratio of Mn / S = 1/1. to be.

The method of satisfying (S) present as Cu sulfide / (S present as Mn sulfide) < 0.30 is not particularly limited, and can be achieved, for example, by specifying the ratio of components, in particular, Mn and Cu. It is also possible to control the hot rolling conditions, in particular by controlling the average cooling rate between the hot rolling inlet and the start of winding (for example, controlling the cooling rate from 10 ° C./sec to 50 ° C./sec, etc.) or combining them.

The steel according to the present invention is produced through continuous casting, hot rolling, pickling, cold rolling, annealing and re-rolling for subsequent steel sheet shape control or material property control. At this time, in the case of the steel sheet re-rolled at a high reduction ratio, that is, the steel sheet hardened by the processing effect, the recovery of the material tends to be easy in the vicinity of the welded portion due to the temperature rise during welding, and the steel sheet tends to soften. Therefore, it is preferable to make a reduction rate into 20% or less.

In addition, W, Mo, Ca, V, Sb, etc. may be used in order to improve characteristics not described in the specification of the present invention, such as workability, corrosion resistance, plateletability in various processes, and the like, including drawing property and secondary workability of the steel sheet. Even if it contains, the effect of this invention will never be lost.

The steel sheet according to the present invention is generally used as an original plate of a surface-treated steel sheet, and even in this case, the effect of the present invention is never impaired by the surface treatment. As the surface treatment for cans, a treatment method usually using tin, chromium (non-tin), nickel, zinc, aluminum, or the like is adopted. Moreover, the steel plate concerning this invention can be used as a disc of the laminated steel plate with an organic film currently used, without impairing the effect of this invention.

The present invention according to claims 17 and 18 will be described in detail below.

The steel according to the present invention is characterized by dispersing a second phase consisting of oxides, nitrides, sulfides, etc. on a base material consisting of Fe, and in order to obtain the effects of the present invention, the shape of the second phase must be properly controlled. do. For this purpose, it is particularly effective to control the thermal history before the hot rolling process. For example, hot rolling is performed under the condition that the thermal history in the temperature range of 1000 ° C to 1300 ° C from the time of producing slab by continuously casting molten steel to the start of hot rolling satisfies the formula of temperature (° C) x time (minutes) ≤ 200000. It is preferable to start and to perform hot rolling by controlling the average cooling rate for the time from the start of finish hot rolling to the winding after completion of finish hot roll to 30 degrees C / sec or less. The reason is not clear, but if steel is kept for a long time at high temperature, sulfides and nitrides coarse and disperse into the second phase of a fairly large size, in particular oxides act as precipitation sites for sulfides and nitrides, thus welding It is thought that the effect of suppressing the softening of the steel sheet due to the thermal effect of is reduced. In general, it is not desirable that the cooling rate be too fast in the temperature range of about 1000 ° C. or less after finishing hot rolling. The reason is that when the cooling rate is high in the above temperature range, when N and S which have already been dissolved precipitate into nitrides and sulfides, the sizes of nitrides and sulfides become very fine, and nitrides and sulfides are also caused by heat during welding of the product steel plate. It is thought that this is because the effect of dissolving melts and the softening of the material is easily lost. In particular, in the case where the cooling rate is fast at this stage, S tends to form Cu sulfides, and thus the stability to heat during welding is further lowered. In view of the above situation, as a method of controlling sulfide and nitride in an appropriate form, the thermal history in the temperature range of 1000 ° C to 1300 ° C from the molten steel continuous casting to the start of hot rolling is measured as the temperature (° C). Method of performing hot rolling by starting hot rolling under the condition of satisfying the formula of x time (minutes) ≤ 200000, controlling the average cooling rate from the start of finish hot rolling to the winding after completion of finish hot rolling at 30 ° C / sec or less. This is recommended. Here, as a method of controlling so that the thermal history in the temperature range of 1000 ° C to 1300 ° C from the time of producing slab by continuously casting molten steel to the start of hot rolling satisfies the formula of temperature (° C) x time (minutes) ≤ 200000 , So-called direct rolling (CC-DR) which starts hot rolling without soaking the slab in a reheating furnace after casting and so-called thin slab continuous casting which thins the thickness of the casting slab to simplify or omit the hot rolling.

<Example 1>

In order to evaluate the workability of the welded portion, as shown in FIG. 1, the rectangular steel sheet is welded by seam welding, as in the case of canning of the can body of a conventional three-piece beverage can, and the cylindrical portion joined along the weld line. The opening was expanded by pressing a conical die into the opening, and the deformation amount until cracking occurred at the end of the opening was calculated by the following equation (1).

{(Diameter at crack occurrence)-(initial diameter)} / (initial diameter) (1)

In order to evaluate the strength of a welded part, as shown in FIG. 2, two rectangular steel sheets were spot-welded by the welding current just before scattering generation, and the maximum load evaluation in the tension test was performed.

In order to evaluate the fatigue strength, a test piece having a width of 20 mm having a welded portion in the center was cut from a cylindrical welding can body molded as shown in FIG. 1, and a tensile fatigue test was performed by one side vibration to obtain a 1000 The maximum load that can withstand 10,000 cycles was measured.

Thermal buckling was determined by the presence or absence of thermal buckling generated when a cold rolled coil having the same thickness and width was passed through the same annealing line at a recrystallization temperature of + 40 ° C. , ×: often indicated by symbols of occurrence.

The effects of the present invention are determined by comprehensively determining the four items described above, and include: ◎: fairly good (inventive steel), ○: good (inventive steel), Δ: good for some evaluation items (inventive steel), ×: conventional The symbol of level (comparative steel) is shown.

<Example 1-1>

After casting the steel of the chemical composition shown in Table 1 into a slab having a thickness of 250 mm, a hot rolled sheet having a thickness of 2.0 mm was prepared under conditions of a slab reheating temperature of 1150 ° C. and a coiling temperature of 650 ° C., pickling, and a reduction ratio of 92%. After cold annealing at 680 ° C. for 1 minute, a steel sheet having a thickness of 0.16 mm was manufactured through a skin pass rolling process of 3%, and the prepared steel sheet was evaluated.

As can be clearly seen from Table 2, the steel produced within the range defined in the present invention exhibits excellent properties in all evaluation items such as workability, strength and fatigue strength, and heat buckling resistance of welded portions.

<Example 1-2>

As shown in Table 3, the steels with different contents of Ti and Nb were evaluated. Manufacturing conditions were the same as those of Example 1.

As can be clearly seen from Table 4, the steel produced within the preferred range shows excellent properties in all evaluation items such as workability, strength and fatigue strength, and heat buckling resistance of the welded portion.

<Example 1-3>

As shown in Table 5, steels with different ratios of CuS to MnS were evaluated. Manufacturing conditions are the same as those of Example 1.

As can be clearly seen from Table 6, the steel produced within the preferred range shows excellent properties in all evaluation items such as workability, strength and fatigue strength, and heat buckling resistance of the welded portion.

<Example 1-4>

The steel produced by different manufacturing conditions after hot rolling was evaluated. The conditions other than the slab reheating temperature at the time of hot rolling, the coiling temperature, and the annealing temperature after cold rolling were the same as in Example 1. The results are shown in FIGS. 4 and 5.

Fig. 4 shows the relationship between (N present in AlN) / (N present in BN) and workability, and Fig. 5 shows the relationship between (N present in AlN) / (N present in BN) and the fatigue strength. .

In FIG.4 and FIG.5, manufacture condition 1 and manufacture condition 2 are as follows.

Manufacturing condition 1: slab reheating temperature> 1100 ℃,

Or winding temperature <730 ° C,

Or annealing temperature <700 ° C

Manufacturing conditions 2: slab reheating temperature <1100 ° C.,

Also the coiling temperature> 730 ℃,

Also annealing temperature> 700 ℃

As can be clearly seen from FIGS. 4 and 5, the steel produced within the preferred range exhibits excellent properties in weldability and fatigue strength.

As mentioned above, according to this invention, the moldability defect by welding and the crack generation during use of the can which has a weld part can be reduced. In addition, the steel according to the present invention exhibits excellent characteristics even at annealing temperatures lower than the normal annealing temperature, and therefore can prevent the occurrence of thermal buckling, and can produce ultra-thin materials for containers with high efficiency.                 

<Example 2>

In order to evaluate the workability of the welded portion, as shown in FIG. 1, a rectangular steel sheet is formed into a cylindrical shape by seam welding in the same manner as in the case of canning of a can body of a conventional three-piece beverage can, and conical in the opening portion. The opening was expanded by press-fitting the die, and the deformation amount until cracking occurred at the end of the opening was calculated by the following equation (1).

{(Diameter at crack occurrence)-(initial diameter)} / (initial diameter) (1)

In order to evaluate the strength of a welded part, as shown in FIG. 2, two rectangular steel sheets were spot-welded by the welding current just before scattering generation, and the maximum load in a tension test was evaluated.

In order to evaluate the fatigue strength, a test piece having a width of 20 mm having a welded portion in the center was cut from a cylindrical welding can body molded as shown in FIG. 1 and subjected to a tensile fatigue test of one side vibration as shown in FIG. The maximum load that can withstand the cycle was measured.

Thermal buckling was determined by the presence or absence of thermal buckling generated when a cold rolled coil having the same thickness and width was passed through the same annealing line at a recrystallization temperature of + 40 ° C. , ×: often indicated by symbols of occurrence.

The effects of the present invention are determined by comprehensively determining the four items described above, and include: ◎: fairly good (inventive steel), ○: good (inventive steel), Δ: good for some evaluation items (inventive steel), ×: conventional The symbol of level (comparative steel) is shown.
Specific Example 5
After casting the steel of the chemical composition shown in Table 7 to a slab having a thickness of 250 mm, a hot rolled sheet having a thickness of 2.2 mm was prepared under conditions of slab reheating temperature of 1150 ° C and winding temperature of 520 ° C to 730 ° C. Pickling, 92% Cold rolling was carried out at a rolling reduction rate of 660 ° C. to 720 ° C. for 1 minute, and a cold rolling process was performed at a rolling reduction of 10% to prepare a 0.16 mm thick steel sheet. The results are shown in Table 8.
As can be clearly seen from Table 8, the steel produced within the range defined in the present invention exhibits excellent characteristics in all evaluation items such as workability, strength and fatigue strength, and heat buckling resistance of welded portions.

<Specific Example 6>

As shown in Table 9, steels with different O contents were evaluated. Manufacturing conditions were the same as those of Example 1. The results are shown in Table 10.

As can be clearly seen from Table 10, the steel produced within the preferred range shows excellent properties in all evaluation items such as workability, strength and fatigue strength, and heat buckling resistance of the welded portion.                 

<Specific Example 7>

As shown in Table 11, steels having different Cu contents were evaluated. Manufacturing conditions were the same as those of Example 1. The results are shown in Table 12.

As can be clearly seen from Table 12, the steel produced within the preferred range shows excellent characteristics in all evaluation items such as workability, strength and fatigue strength, and heat buckling resistance of the welded portion.                 

As mentioned above, according to this invention, the moldability defect by welding and the crack generation during use of the can which has a weld part can be reduced. In addition, the steel according to the present invention exhibits excellent characteristics even at annealing temperatures lower than the normal annealing temperature, and therefore can prevent the occurrence of thermal buckling, and can produce ultra-thin materials for containers with high efficiency.

Claims (18)

In mass%, C: 0.0050% or less, Si: 0.015%-2.00%, Mn: 0.05%-2.00%, N: 0.0060% or less, Al: 0.040% or less, P: 0.005% to 0.080%, 0: 0.0010% to 0.0070%, and B is contained so as to be B / N: 0.40 to 2.00, AlN and BN in the steel are (N present in AlN) / (N present in BN) ≦ 0.40 and Al / B: 30 or less, A steel sheet for a container having excellent moldability and fatigue characteristics, wherein the remainder is made of Fe and unavoidable impurities. delete delete delete The method of claim 1, Ti: 0.010% or less and Nb: 0.010% or less of steel plate for containers excellent in the moldability and fatigue characteristics of a welded part characterized by the above-mentioned. The method according to claim 1 or 5, A container steel sheet having excellent formability and fatigue properties of a welded part, wherein a sulfide contained in the steel satisfies the formula (S present as Cu sulfide) / (S present as Mn sulfide) ≦ 0.10. A slab reheating temperature is controlled to be 1100 ° C or higher in hot rolling when the steel sheet for a container is manufactured by a conventional manufacturing process using the steel containing the component according to claim 1 or 5. A method for producing a steel sheet for a container having excellent moldability and fatigue characteristics. When the steel sheet for a container is manufactured by the normal manufacturing process using the steel containing the component of Claim 1 or 5, the winding temperature is controlled to 730 degrees C or less by hot rolling, The shaping | molding of a weld part characterized by the above-mentioned. Method for producing steel sheet for containers with excellent properties of fatigue and fatigue. When the steel sheet for a container is manufactured by the normal manufacturing process using the steel containing the component of Claim 1 or 5, the annealing temperature after cold rolling is controlled to 700 degrees C or less, The shaping | molding of a weld part characterized by the above-mentioned. Method for producing steel sheet for containers with excellent properties of fatigue and fatigue. In mass%, C: 0.0005%-0.040%, Si: 0.002%-0.50%, Mn: 0.03%-2.00%, P: 0.002% to 0.080%, S: 0.0100%-0.0600%, Al: 0.0010% to 0.0700% and N: 0.0053% to 0.0300%, The content of N dissolved in the steel is 20ppm to 300ppm, For sulfides in steel, (S present as Cu sulfide) / (S present as Mn sulfide) <0.30, A steel sheet for a container having excellent moldability and fatigue characteristics, wherein the remainder is made of Fe and unavoidable impurities. The method of claim 10, In mass%, Nb: 0.0005% to 0.0050%, Ti: 0.0005% to 0.0050% and B: 0.0010% or less, O: 0.0015% to 0.0090%, Cu: 0.0005% to 0.050%, Ni: 0.0005%-0.100%, Cr: 0.0005%-0.100%, Sn: The container steel plate excellent in the moldability and fatigue characteristic of the weld part further containing 1 type (s) or 2 or more types of 0.0002%-0.0050%. delete delete delete delete In the manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part of Claim 10 or 11, A method for producing a steel sheet for a container having excellent moldability and fatigue characteristics, characterized in that secondary cold rolling is performed at a rolling reduction of 20% or less after continuous casting, hot rolling, pickling, cold rolling, and annealing of molten steel. In the manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part in any one of Claims 1, 5, 10, or 11, Initiating hot rolling under the condition that the heat history in the temperature range of 1000 ° C. to 1300 ° C. after the continuous casting of molten steel before the start of hot rolling starts satisfies the temperature (° C. × time (minutes) ≦ 200000). The manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part characterized by the above-mentioned. In the manufacturing method of the steel plate for containers excellent in the moldability and fatigue characteristic of the weld part in any one of Claims 1, 5, 10, or 11, A method of manufacturing a steel sheet for a container having excellent formability and fatigue characteristics of a welded part, wherein the steel sheet is hot rolled by controlling the average cooling rate to 30 ° C / sec or less during the time from the start of finish hot rolling to the winding after completion of the finish hot roll. .

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