JPH10102191A - Stock for steel sheet for can, excellent in ridging resistance and deep drawability after cold rolling-annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the production of a cold rolled steel sheet for can, having ridging resistance and deep drawability, by specifying the average crystalline grain size of a steel sheet containing specific essential components and also specifying the colony size and the degree of orientational concentration in the colony, respectively. SOLUTION: A steel, which has a composition containing, as essential components, 0.0005-0.0150%, by weight, C, <=0.10% Si, 0.1-0.6% Mn, <=0.02% each of P and S, 0.015-0.15% Al, and <=0.02% N and having the balance Fe with inevitable impurities, is used. Moreover, the average crystalline grain size (d) and the average colony size are regulated to <=35/μm and <=80μm, respectively, and the degree S of orientational concentration in the colony, represented by S=X20 deg./X30 deg., is regulated to <=0.8, where X30 deg. means the area of colonies where the orientation difference between adjacent crystalline grains is <=30 deg. and X20 deg. means the area of colonies where the orientation difference between adjacent crystalline grains is <=20 deg., among X30 deg.. By this method, a wide range of application ranging from a dry cell inner package can, etc., to various household electrical and potential parts, automobile parts, etc., can be expected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a two-piece or three-piece hot rolling method for low-temperature finishing (ferrite finishing rolling) in order to save energy, extend the life of rolling rolls, and reduce pickling costs. The present invention relates to a material for a steel sheet for cans, which can provide a steel sheet having excellent deep drawability useful for uses such as a steel sheet for cans and does not generate ridging when processed as a can body.

[0002]

2. Description of the Related Art Among various types of cans, a cold-rolled steel sheet used for two-piece cans is required to have an excellent deep drawability as a characteristic. In order to improve the deep drawability, a high r value (Rankford value) is required as a mechanical property of the steel sheet. Such deep-drawn cold-rolled steel sheets are subjected to hot rolling at the Ar ₃ transformation point or higher, then cold-rolled to a thin sheet of final thickness, and then subjected to recrystallization annealing to produce cold-rolled steel sheets Was commonly used.

In recent years, in such cold-rolled steel sheets, attempts have been made to terminate finish rolling at a temperature not higher than the Ar ₃ transformation point for the purpose of energy saving in the hot rolling process and cost reduction by improving yield. However, there is a problem in that when the finish rolling is actually finished below the Ar ₃ transformation point, a peculiar phenomenon called “ridging” tends to occur.

[0004] This ridging is a phenomenon in which fine streak-like wrinkles are formed along the rolling direction when a thin plate is subjected to deformation such as tension or deep drawing. Generally, ferritic stainless steel such as 17% Cr stainless steel is used. For steel, see the Journal of the Japan Institute of Metals, Vol. 31, No. 4 (1967), p.
Vol. 31, No. 6 (1967), p. 717 ”.

Conventionally, the occurrence of the ridging had been believed stainless steel unique, Ar ₃ in the general cold-rolled steel sheet
It has become known that this is likely to occur when finish rolling is completed at or below the transformation point. These steel plates for cans, stainless steel plates, and steel plates for automobiles are not only mechanical properties but also surface smoothness and beauty are also important properties, and when such ridging occurs, it is a fatal product. It can be a defect.

From this point of view, research into the causes and mechanisms of ridging from various viewpoints, such as steel composition and manufacturing methods, has been made, but no unified opinion has yet been issued. In addition, as means for suppressing ridging,
`` Iron and Steel Vol. 77, No. 8 (1991) p. 84 '' and `` Iron and Steel Vol. 78, N
o.4 (1992) p.124 ''.
Means such as increasing the time between coarse rolling passes or performing hot-rolled sheet annealing or inter-pass annealing have been proposed.However, these methods are used for deep drawing, which is based on the premise of producing thin steel sheets at low cost. In the case where it is applied to the production of a cold-rolled steel sheet, it does not provide a proper and efficient means.

Further, Japanese Patent Application Laid-Open No. 63-121623 relates to a method for producing a cold-rolled steel sheet having excellent ridging resistance and chemical conversion treatment properties, and relates to a steel having a specific relationship between the amounts of C, N, S and Ti. Discloses a method in which a hot rolling is performed at a finishing temperature of 600 to 800 ° C. and at least one pass is finished with a lubricating oil, then cold rolled at a reduction of 50 to 95%, and then recrystallized and annealed. Have been. However, in this method, at least one pass needs to be rolled while using a lubricating oil, so that a problem such as slip occurs at the time of rolling, and there is a possibility that productivity may be significantly reduced.

[0008]

The present invention advantageously solves the above-mentioned problems, and focuses on a colony of a hot-rolled steel sheet as a material of a cold-rolled steel sheet for deep drawing, and regulates the state of the colony. Accordingly, an object of the present invention is to propose a material for a steel plate for cans having excellent ridging resistance and deep drawability, which can be manufactured without reducing the productivity of the hot rolling step.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to improve the ridging resistance and deep drawability of a cold-rolled steel sheet, and as a result, have limited the hot-rolled steel sheet as follows. By doing so, it has been found that a cold-rolled steel sheet for deep drawing excellent in ridging resistance can be manufactured. The gist configuration of the present invention based on the above findings is as follows. C: 0.0005 to 0.0150 wt%, Si: 0.10 wt% or less, Mn:
0.1 to 0.6 wt%, P: 0.02 wt% or less, S: 0.02 wt% or less, Al: 0.015 to 0.15 wt% and N: 0.02 wt% or less as a basic component, and the balance is based on the composition of Fe and inevitable impurities. And the average crystal grain size d is 35 μm or less, the average colony size is 80 μm or less, and the orientation concentration S in the colony shown below is 0.8 or less. Cold rolling-ridging resistance and depth after annealing Material for steel plate for cans with excellent drawability. Here serial S = X ₂₀ ° / X ₃₀ °, X ₃₀ °: adjacent colony area X ₂₀ ° misorientation is within 30 ° between the crystal grains: among X ₃₀ °, the orientation difference between adjacent grains Is 20
° In addition to the colony area and basic components, Ti: 0.001 to 0.020 wt% and N
b: A material for a steel sheet for cans having excellent ridging resistance and deep drawability after cold rolling and annealing, characterized by containing at least one of 0.001 to 0.020 wt%, and B: A material for steel sheets for cans having excellent ridging resistance and deep drawability after cold rolling and annealing, characterized by containing 0.0001 to 0.0030 wt%.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The results of research on which the present invention is based will be described below. C: 0.002 wt%, Si: 0.01 wt%, Mn:
0.2 wt%, P: 0.01 wt%, S: 0.005 wt%, Al: 0.04 wt
%, N: 0.002 wt% and Nb: 0.005 wt%, the balance being 12% of a sheet bar composed of Fe and unavoidable impurities.
After heating to 00 ° C-soaking, 1 pass rolling at 1050 ° C, 700 ~ Ar
After two-pass rolling in a temperature range of _three transformation points at a rolling reduction of 50 to 90%, a coil winding treatment was performed at 700 ° C. for one hour. Subsequently, after cold rolling of 90%, recrystallization annealing at 750 ° C. for 20 seconds was performed.

FIG. 1 shows the influence of the orientation concentration and the colony size in the colony of the hot-rolled steel sheet on the ridging resistance of the cold-rolled steel sheet. In addition, the ridging evaluation index was obtained by visually evaluating a cold-rolled steel sheet processed into a JIS No. 5 tensile test piece and having a 15% tensile strain. Those having a ridging evaluation index of 2 or less are ridging levels having no practical problem. Also, the degree of azimuth concentration in the colony is Electron Back Scatte
The crystal orientation of a steel sheet with a thick cross section is measured for each crystal using the ring Diffraction Patern, and the orientation difference between adjacent crystal grains is determined.
The crystal grain groups within 20 ° and within 30 ° were regarded as colonies, respectively, and were determined by their area ratio. That is, the azimuth concentration S in the colony is S = X ₂₀ ° / X ₃₀ °, where X
₃₀ °: a colony area where the difference in orientation between adjacent crystal grains is within 30 °, and X ₂₀ °: a colony area where the difference in orientation between adjacent crystal grains is within ₂₀ ° among X ₃₀ °. As can be seen from FIG. 1, the ridging resistance of the cold-rolled steel sheet strongly depends on the degree of orientation concentration in the colony of the hot-rolled steel sheet in the ferrite region. When it is 80 μm or less, a cold rolled steel sheet for cans having excellent ridging resistance can be manufactured.

As a result of various studies based on the above experimental results, the inventors have determined the present invention as follows. (1) Steel component (a) C: 0.0005 to 0.0150 wt% It is preferable that C is as small as possible, because the deep drawability is improved. However, if the content is 0.015 wt% or less, it does not exert much adverse effect, so 0.015 wt% or less. And limited. On the other hand, C
If the amount is less than 0.0005 wt%, the crystal grains become coarse, a hot-rolled steel sheet having a desired grain size cannot be obtained, and the crystal grains after cold rolling and annealing also become coarse, which may cause a rough surface of the steel sheet surface during drawing. The lower limit was set to 0.0005 wt% because of the nature of the material. (b) Si: 0.10 wt% or less Si has the effect of strengthening steel, and the necessary amount is added depending on the desired strength. However, if the added amount exceeds 0.10 wt%, the steel sheet becomes excessively hard, 0.10wt due to poor deep drawability
% Or less. (c) Mn: 0.1 to 0.6 wt% Mn is a component necessary for preventing red hot embrittlement during hot rolling due to S as an impurity. Therefore, 0.1 wt% or more is required. If the content exceeds wt%, cracks may occur during slab rolling, or the steel sheet may become excessively hard.
Limited to the range of ~ 0.6 wt%.

(D) P: not more than 0.02 wt% P has the effect of strengthening the steel, and the necessary amount is added according to the desired strength. If the added amount exceeds 0.02 wt%, the deep drawability becomes poor. Since it is inferior, it was limited to 0.02 wt% or less. (e) S: 0.02 wt% or less S is an impurity component that causes red hot embrittlement during hot rolling, and is desirably as small as possible. However, since it is an unavoidable component, the upper limit is 0.02 wt%. And

(F) Al: 0.015 to 0.15 wt% Al is deoxidized and added as needed to improve the yield of carbonitride forming components, but the content of Al is 0.015 wt%.
If it is less than 0.15% by weight, no additional effect will be obtained.
Limited to 0.15 wt%. (g) N: 0.02 wt% or less N is preferably as small as possible because the deep drawability is improved. However, if the content of N is 0.02 wt% or less, there is no significant adverse effect, so N was limited to 0.02 wt% or less.

In addition to the above basic components, the present invention provides
One or more of Ti and Nb and / or B can be contained. (h) Ti: 0.001 to 0.02 wt% Ti is reduced by precipitating and fixing solid solution C in steel as a carbide, and has an effect of preventing deep drawability deterioration due to solid solution C. When the amount is 0.001 wt% or less, there is no effect of addition, while
Even if added in excess of 0.02 wt%, no further effect can be obtained, and conversely, deep drawability is deteriorated.
%. (i) Nb: 0.001 to 0.02 wt% Nb has an effect of reducing solid solution C in steel by precipitation and fixing it as carbide, thereby preventing deep drawability deterioration due to solid solution C.
If the addition amount is less than 0.001 wt%, there is no addition effect, while
Even if added in excess of 0.02 wt%, no further effect is obtained, and conversely, deep drawability is deteriorated, so 0.001 to 0.02 wt%
%. (j) B: 0.0001 to 0.0030 wt% B is added for improving the resistance to secondary working brittleness of steel. However, if the addition amount is less than 0.0001 wt%, there is no addition effect.
On the other hand, if added in excess of 0.0030 wt%, on the contrary, deep drawability will deteriorate, so the content was limited to 0.0001 to 0.0030 wt%.

(2) The degree of orientation concentration in the colony of the hot-rolled steel sheet The degree of orientation concentration in the colony of the hot-rolled steel sheet is most important in the present invention. In order to improve the ridging resistance after cold rolling and annealing, 0.8 degree of orientation concentration in the colony of hot rolled steel
It must be: That is, when the degree of orientation concentration in the colony of the hot-rolled sheet is higher than 0.8, excellent ridging resistance cannot be obtained even if the steel composition and the cold-rolling-annealing conditions are changed.

The effect of improving ridging resistance by regulating the degree of azimuth concentration in a colony is considered as follows. The present inventors have conducted various studies on the ridging resistance of the hot-rolled material in the ferrite region. As a result, the most influential factor of the ridging resistance was the colony formed on the hot-rolled sheet (between adjacent crystal grains). (Electron Back Scattering D)
A study using iffraction patern revealed this.
And it has been found that randomizing the crystal grains in the colonies is most effective for improving the ridging resistance. Orientation degree of concentration in the colonies of the degree of randomization of the crystal grains in that colony: Heading by various experiments that expressed by S, here S = X ₂₀ ° / X ₃₀ °, X ₃₀ °: adjacent crystal grains colonies area X ₂₀ ° misorientation is within 30 ° between: among X ₃₀ °, the orientation difference between adjacent grains is 20
The colony area was within °.

Incidentally, in order to randomize the colonies formed on the hot-rolled sheet in the ferrite region, it is necessary to randomize the crystal grains in the colonies. The inventors have found from various experiments that crystal grains in a colony are randomized by repeating processing-recrystallization twice or more during finish rolling. In order to repeat the processing and recrystallization twice or more during such finish rolling, it is necessary to cause recrystallization between passes of the finish rolling mill. Since the time between passes is short in a normal hot rolling process, it is difficult to cause recrystallization between passes. However, for example, by performing one-pass idle rolling during finish rolling, a time period during which recrystallization occurs between passes is ensured, and processing-recrystallization can be repeated twice or more during finish rolling.

(3) Average Colony Size of Hot-Rolled Steel Sheet The average colony size of a hot-rolled steel sheet is also important in the present invention. In order to improve ridging resistance after cold rolling and annealing, the average The colony size must be less than 80μm. That is, although the detailed mechanism is unknown, when the average colony size of the hot-rolled sheet is larger than 80 μm, excellent ridging resistance cannot be obtained even if the steel composition and the conditions of cold rolling and annealing are changed. In order to reduce the size of the colonies formed on the hot-rolled sheet in the ferrite region to 80 μm or less, it is effective to perform the rough rolling at a reduced temperature and at a high pressure.
The temperature is not higher than 00 ° C, preferably not higher than 1000 ° C. The rolling reduction during rough rolling is also important, and it is preferable to perform the rough final pass at a rolling reduction of 25% or more.

(4) Average Crystal Grain Size of Hot-Rolled Steel Sheet In a two-piece can subjected to deep drawing, it is important that earring properties are small, that is, ears after deep drawing are small. Since the part where this earring has occurred must be cut off after deep drawing of the can, if this earring is large, not only the material yield will deteriorate, but also in some cases, the required molding height will not be obtained, and the molded product will not be obtained. You have to destroy everything. Therefore,
It is desirable that earrings generated during deep drawing are as small as possible. By the way, the height of the earring is r
Value in-plane anisotropy: Δr (= (r ₀ + r ₉₀ −r ₄₅ ) / 2)
(R ₀ , r ₉₀ , r ₄₅ are 0 °, 90 °,
(R value in the 45 ° direction), and it is known that if Δr = 0, the earring height becomes zero. Here, in order to make Δr close to 0, 0.5 g after finish rolling is completed.
Start water cooling of the hot-rolled steel strip within seconds, quench at a cooling rate of 70 ° C / s or more, cool to at least 750 ° C or less, and refine the crystal grain size of the hot-rolled sheet to 35 μm or less. It was also found that the Δr value of the product sheet after cold rolling, annealing and further temper rolling was reduced. Therefore, in the present invention, the average crystal grain size of the hot-rolled sheet is set to 35 μm or less, and during hot rolling, water-cooling of the hot-rolled steel strip is started within 0.5 seconds after finishing rolling as described later, and the temperature is reduced to 70 ° C. It is preferable to rapidly cool at a cooling rate of at least 750 ° C./s to at least 750 ° C. or less.

(5) Hot Rolling Step The slab heating temperature is 1200 ° C. for energy saving.
Or less, more preferably 1100 ° C. or less. Further, the rough rolling (Ar ₃ transformation point +150 ℃) ~ (Ar ₃ transformation point + 5
(0 ° C.). this is,
When the rough rolling is performed at a temperature lower than this temperature range, the hot rolled sheet becomes coarse crystal grains even if a suitable cooling method described later is employed, and the desired ridging resistance is not obtained since the miniaturization of colonies is not achieved. The property cannot be obtained. On the other hand, when rough rolling is performed at a high temperature exceeding this range, the life of the rolling rolls is shortened. Therefore, the rolling end temperature range (Ar
It is preferred _{that 3} transformation point +150 ° C.) ~ and (Ar ₃ transformation point + 50 ° C.) to. Further, in order to randomize the crystal grains in the colony, it is important to repeat the processing and recrystallization during the finish rolling. Therefore, it is preferable to perform the high-pressure reduction in a high temperature region during the finish rolling. In addition, in order to reduce the Δr of the product sheet, water cooling of the hot-rolled steel strip is started within 0.5 seconds after the finish rolling, quenched at a cooling rate of 70 ° C / s or more, and cooled to at least 750 ° C or less. There is a need to. If the air cooling time from the end of finish rolling to the start of water cooling exceeds 0.5 seconds, or if the cooling rate is less than 70 ° C./s, the crystal grain growth proceeds, and the crystal grains cannot be refined. The winding temperature is preferably set to 650 ° C or higher and 800 ° C or lower. To randomize the grains in a colony,
It is necessary to raise the winding temperature and hold the film in a high temperature region for a certain period of time or more, whereby the crystal structure in the colony is randomized by recrystallization of the rolled structure. If the winding temperature is lower than 650 ° C., recrystallization does not proceed, and randomization of crystal grains cannot be achieved. On the other hand, the winding temperature is 80
If the temperature exceeds 0 ° C., the scale growth after winding will be remarkable, and the pickling property will be reduced. In addition, the crystal grains will become coarser and the material will be deteriorated, and the rough surface resistance will be deteriorated. Was set to 800 ° C. It is to be noted that strong rolling after finish rolling which promotes recrystallization of a hot-rolled sheet is an effective means for improving ridging resistance. In addition, performing lubrication rolling during finish rolling is effective in uniformizing the rolling structure and reducing the rolling load,
It does not hinder the invention.

(6) Cold Rolling Step This step is essential for obtaining a high r-value, and the cold rolling reduction is preferably set to 80 to 95%. (7) Continuous annealing step Continuous annealing requires an annealing temperature equal to or higher than the recrystallization end temperature, but if the annealing temperature is too high, the crystal grains abnormally coarsen,
The upper limit of the temperature is desirably 750 ° C., because the surface roughness after processing becomes large, and thin materials such as steel plates for cans have a high risk of breakage in the furnace and occurrence of buckling.

(8) Temper Rolling The reduction ratio of the temper rolling is determined at any time according to the degree of tempering of the steel sheet. In order to prevent the occurrence of stretcher strain, rolling is performed at an abnormal reduction ratio of 0.5%. There is a need. On the other hand, if the rolling is performed at a rolling reduction exceeding 40%, the steel sheet becomes excessively hard and the workability is reduced, and the r-value is reduced (depth drawability is deteriorated). Is preferred.

[0024]

EXAMPLE A slab was heated to 1200 ° C. and heated to 1200 ° C. to obtain the composition shown in Table 1, and then a hot-rolled steel strip having a thickness of 2.5 mm was formed under the hot rolling conditions shown in Table 2. Table 2 also shows the degree of orientation concentration in the colony of the hot-rolled steel sheet obtained at this time. Subsequently, a cold-rolled steel strip having a thickness of 0.25 mm was formed by cold rolling and subjected to recrystallization annealing at 750 ° C. for 20 seconds. The material properties of the obtained cold rolled steel sheet were investigated.
Tensile properties were measured using JIS No. 5 tensile test pieces. The r value is measured by the three-point method after 15% tensile prestrain is applied, and the L direction (rolling direction), D (45 degree direction in rolling direction) and C direction (90 degree direction in rolling direction) Were determined as the average r value and Δr by the following formulas, respectively. Average r value = (r ₀ + 2r ₄₅ + r ₉₀ ) / 4 In-plane anisotropy of r value = (r ₀ + r ₉₀ -r ₄₅ ) / 2) (r ₀ , r ₉₀ , and r ₄₅ are each 0 ° in the rolling direction. , 90 °,
(R value in the 45 ° direction) The ridging resistance was determined using a ridging evaluation index, and a steel sheet processed into a JIS No. 5 tensile test piece, which was given a 15% tensile strain, was visually evaluated. . Those having a ridging evaluation index of 2 or less are ridging levels having no practical problem. Table 2 shows the material properties of the final product. It can be seen that the material for a cold-rolled steel sheet manufactured according to the present invention, when processed into a cold-rolled steel sheet, has superior ridging resistance and deep drawability as compared with Comparative Examples.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

According to the present invention, a colony of a hot-rolled steel sheet is miniaturized and the degree of azimuth concentration in the colony is limited, so that the ridging resistance and the deep drawability are far superior to those of the prior art. Production of cold-rolled steel sheets for cans becomes possible. The steel sheet of the present invention can be used not only as a tin-plated steel sheet and tin-free tetyl, but also as a zinc-plated, Ni-plated and oil-coated steel sheet. In addition to various metal cans such as food cans and beverage cans, which can be used for a variety of applications, it can be expected to be used in a wide range of applications, from interior cans for dry batteries to various home appliances, potential parts, and automobile parts.

[Brief description of the drawings]

FIG. 1 is a diagram showing the influence of the orientation concentration and colony size in a colony of a hot-rolled steel sheet on ridging resistance.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Takashi Sakata 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Inventor Takashi Ohara 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki (72) Inventor Hideo Kuguminato 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Chiba Works

Claims (3)

[Claims] 1. C: 0.0005 to 0.0150 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 0.6 wt%, P: 0.02 wt% or less, S: 0.02 wt% or less, Al: 0.015 to 0.15 wt% and N: 0.02 wt% or less as a basic component, the balance being composed of Fe and unavoidable impurities, and having an average crystal grain size d of 35 μm or less, an average colony size of 80 μm or less, and a degree of orientation concentration in the colony shown below. A material for a steel sheet for cans having excellent ridging resistance and deep drawability after cold rolling and annealing, wherein S is 0.8 or less. Here serial S = X ₂₀ ° / X ₃₀ °, X ₃₀ °: adjacent colony area X ₂₀ ° misorientation is within 30 ° between the crystal grains: among X ₃₀ °, the orientation difference between adjacent grains Is 20
° Colony area within ° 2. The composition according to claim 1, further comprising at least one of 0.001 to 0.02% by weight of Ti and 0.001 to 0.02% by weight of Nb in addition to the basic components.
A steel sheet material for cans having excellent ridging resistance and deep drawability after cold rolling and annealing as described. 3. The can according to claim 1, which further comprises B: 0.0001 to 0.0030% by weight in addition to the basic component, which is excellent in ridging resistance and deep drawability after cold rolling and annealing. Material for steel plate.