JP3826442B2 - Manufacturing method of steel plate for can making with good workability and no rough skin - Google Patents

Description

かくして得た熱延板を酸洗し、圧下率８３％の冷間圧延、７５０℃の再結晶焼鈍後、２％の調質圧延を行い、得られた製品の特性を調査した。その結果は以下のとおりである。
結晶粒度：１０．８
組織の均一性：良好
硬さ：５８（ロックウエル硬さ、ＨＲ３０Ｔ）
ｒ値：塑性ひずみ１５％の測定値
平均ｒ値：１．８（平均ｒ値＝（ｒ_L＋ｒ_C＋２ｒ_D）／４）
Δｒ値：０．１（Δｒ＝（ｒ_L＋ｒ_C−２ｒ_D）／２）
肌あれ：なし
フランジ成形性：フランジ割れなし
（肌あれ及びフランジ成形性は、通常の条件で＃２５相当のすずめっきを行い、これをロールフォーミング、拘束シーム溶接で３ピース缶胴部相当に成形し、これにネッキング成形を施し、肌荒れの有無の判定を行った。）
【００３１】
【実施例２】
また、前記例と同一の成分組成のスラブを、前記例と同一の条件にて粗圧延を終了し、仕上圧延を

巻取温度：６００℃の条件で行い、得られた熱延板を前記例と同様に冷間圧延、再結晶焼鈍、調質圧延を行ったところ、その材質特性は以下のとおりであった。
結晶粒度：１０．９
組織の均一性：良好
硬さ：５９（ロックウエル硬さ、ＨＲ３０Ｔ）
ｒ値：
平均ｒ値：１．９（平均ｒ値＝（ｒ_L＋ｒ_C＋２ｒ_D）／４）
Δｒ値：＋０．０５（Δｒ＝（ｒ_L＋ｒ_C−２ｒ_D）／２）
肌あれ：なし
フランジ割れ：なし
（製品特性値の測定条件は、前記例と同様である）
【００３２】
【比較例】
さらに、前記例と同一の成分組成のスラブを、前記例と同一の条件にて粗圧延を終了し、仕上圧延を

巻取温度：６００℃の条件で行い、得られた熱延板を前記例と同様に冷間圧延、再結晶焼鈍、調質圧延を行ったところ、その材質特性は以下のとおりであった。
結晶粒度：８
組織の均一性：混粒組織
硬さ：５５（ロックウエル硬さ、ＨＲ３０Ｔ）
ｒ値：
平均ｒ値：１．４（平均ｒ値＝（ｒ_L＋ｒ_C＋２ｒ_D）／４）
Δｒ値：−０．３（Δｒ＝（ｒ_L＋ｒ_C−２ｒ_D）／２）
肌あれ：あり
フランジ割れ：一部発生
また、引張試験した際、リジングと思われる模様が発生した。
（製品特性値の測定条件は、前記例と同様である）
【００３３】
上記実施例１および２さらに比較例に示すように、本発明にしたがい仕上圧延過程において加工発熱による逆変態を行わせたものは、熱延板の組織、ひいては最終製品である製缶用鋼板の組織が微細・均一であり、厳しい加工を行っても肌あれなどの欠陥を生ずることがなかった。
これに対し、比較例に示すように本発明を適用しない場合、すなわち、復熱を活用しない場合は、最終製品の特性値が缶用鋼板として望ましくないものになる。
【００３４】
【発明の効果】
以上のように、本発明により極低炭素鋼板の結晶組織を効率的かつ経済的に均一微細化することができ、加工性のよい製缶用鋼板の提供が可能になる。
【図面の簡単な説明】
【図１】本発明による仕上圧延機における圧延スタンドと圧延材の温度の関係図である。
【図２】本発明による仕上圧延機における圧延スタンドと圧延材の温度の他の関係図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a steel plate for can making having good workability and no rough skin, and particularly relates to a method for producing a steel plate for can making such as an ultrathin tin plate or tin-free steel.
[0002]
[Prior art]
Container cans such as beverage cans, 18 liter cans, and pail cans can be roughly classified into two-piece cans and three-piece cans from the production method. A two-piece can is a can consisting of two articles with a tin bottom and a can body formed integrally by applying DWI processing, DRD processing, etc. to a surface-treated steel plate subjected to tin plating, chrome plating, etc. . On the other hand, a three-piece can is a can made of three articles in which a surface-treated steel plate is bent into a cylindrical shape or a rectangular tube shape and ends are joined to each other, and then a canopy and a bottom lid are attached thereto.
[0003]
First of all, the steel sheet for making cans used to manufacture these cans needs to be inexpensive, so that the production is generally high in production efficiency, and the continuous annealing method with excellent yield and surface quality is used. Is done using.
For this purpose, for example, a technique described in Japanese Patent Publication No. 63-10213 is proposed, and as a method for producing a soft steel plate by continuous annealing, for example, Japanese Patent Publication No. 61-207520, Japanese Patent Publication No. 1-52452 is disclosed. Proposals described in this publication have also been made. In these technologies, a low carbon steel plate is used as a raw material, and steel plates for can making having various hardnesses are made by a combination of work hardening after annealing.
[0004]
In recent years, the diameter of the upper lid of the can has been strengthened by reducing the diameter (neck-in), and very low carbon steel plates have come to be frequently used as steel plates for cans having good workability that can withstand them. However, compared with a normal low carbon steel plate (C content of 0.02% by weight or more), the crystal grain size tends to be large, which causes problems such as rough skin after can molding. In order to solve this problem, the structure of the ultra-low carbon steel sheet may be made uniform and fine. As a method for that purpose, a method of making the structure of the hot-rolled steel sheet, which is the material, uniform and fine is generally known.
By the way, the homogenization of the hot-rolled structure of the ultra-low carbon steel can be achieved by rolling at a temperature equal to or higher than the transformation point, but the rolling temperature becomes very high, resulting in an increase in wear of the roll, which is not economical. In addition, the crystal grains are not refined.
On the other hand, as shown in Japanese Patent Publication No. 3-260016 and Japanese Patent Publication No. 5-117759, there is also a means of increasing the temperature by α-γ after rolling and miniaturizing by utilizing recrystallization due to transformation. And the driving force for precipitation of precipitates due to processing strain cannot be used, and the effect on uniform refinement of the structure after cold rolling annealing is particularly small.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to produce a steel sheet that has good workability even when processing under severe conditions such as neck-in processing and has sufficient use characteristics as a steel sheet for can manufacturing at low cost. Proposed method. The present invention also proposes an effective method for efficiently and uniformly making the structure of a hot rolled steel sheet of extremely low carbon steel. And it is in the place which proposes the method of making the structure | tissue of the steel plate for can manufacturing which is a final product uniform fine.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have studied the steel composition and production conditions, and completed the present invention as follows.
That is, the present invention
C: 0.0005 to 0.0150% by weight ratio
Si: 0.2% or less Mn: 0.05 to 0.6%
P: 0.02% or less S: 0.02% or less Al: 0.15% or less N: 0.02% or less, and Nb: 0.003-0.020% as necessary
Ti: 0.003-0.020%
B: 0.0002 to 0.0020%
Cu: 0.5% or less, Ni: 0.5% or less, Cr: 0.5% or less, Mo: 0.2 %% or less To steel slab,
Hot rough rolling is performed under the condition that the total reduction amount is 80% or more, of which the final pass is 20% or more,
Finish hot rolling is reverse transformed by the heat generated by the rolling process when the temperature of the material to be rolled passes through one of the rolling stands of the finish rolling mill so that the finish rolling temperature becomes Ar ₃ -50 ° C or higher. Exit
Winding at a temperature of 550 to 750 ° C. to obtain a hot rolled steel strip,
A method for producing a steel plate for can making having good workability and no roughening, characterized by performing scale removal, cold rolling, recrystallization annealing and temper rolling of 30% or less on the hot-rolled steel strip It is in.
Other solutions and specific embodiments of the problems of the present invention will be described in detail in claims 2 and below and in the examples.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
(1) Composition First, the reasons for limiting the composition will be described.
C: 0.0005 to 0.0150%
In the present invention, ultra-low carbon steel is an object. This is because normal low-carbon steel cannot meet the strict requirements for workability required for steel sheets for cans in recent years, and the structure can be homogenized and refined by the normal hot rolling process. This is because it is not necessary to apply the present invention. Here, the ultra-low carbon steel refers to a steel having C of 0.0150% by weight or less, and preferably 0.005% or less from the viewpoint of workability. In order to obtain a steel sheet with excellent formability, it is desirable that the C content be lower. However, even when the rolling conditions of the present invention are applied, the crystal grain size is still coarse, and decarburization in the steelmaking process Considering the cost, the lower limit is made 0.0005%.
[0008]
For other compositions, the range of alloying elements is determined so as to satisfy the properties required for ordinary steel plates for canning.
Si: 0.2% or less Si deteriorates the surface properties of the steel sheet, hardens the steel, makes the hot rolling process difficult, and hardens the steel as the final product. Therefore, it is 0.2% or less. Particularly in applications where the demand for surface properties is strict, it is preferably 0.050% or less.
[0009]
Mn: 0.6% or less Mn is added in order to avoid hot brittleness, but if it exceeds 0.60%, the transformation point is too low and it is difficult to obtain a preferable hot rolled sheet. Become. Therefore, the Mn content is set to 0.05 to 0.6%.
[0010]
P: 0.02% or less P content is preferably as low as possible in view of the effect of improving corrosion resistance, but excessive reduction leads to an increase in production cost. Therefore, the P content is set to 0.02% or less because of these factors. In order to significantly improve the workability, 0.010% or less is preferable.
[0011]
S: 0.02% or less S is a cause of lowering the local ductility represented by stretch flangeability, so is limited to 0.02% or less. In order to remarkably improve the workability, it is preferably 0.010% or less.
[0012]
sol. Al: 0.15% or less sol. Al is an element necessary for deoxidation, but if it exceeds 0.15%, not only the deoxidation effect is saturated but also inclusions are generated, which adversely affects the formability. For this reason, sol. The Al content is less than 0.15%. In addition, in order to ensure the stable manufacturing conditions, it is preferable to set it as 0.030 to 0.10% of range.
[0013]
N: 0.010% or less When N is left in a solid solution state, the steel is appropriately hardened to improve the balance between strength and workability. Therefore, it is added as appropriate within a range that does not decrease elongation and does not cause slab cracking, that is, within a range of 0.02% or less. In addition, when workability is particularly taken into consideration, it is preferably 0.010% or less.
[0014]
In addition to the above basic composition, in the present invention, the following elements are appropriately added according to the use and performance of the steel sheet.
Nb: 0.003 to 0.020% or less Nb adheres C in the steel sheet, reduces aging, is a useful element for softening the steel, and re-appears in the hot rolling γ region. Crystals are moderately suppressed and a fine structure can be obtained. Therefore, it is appropriately added within a range where the effect is effectively exhibited, that is, within a range of 0.003 to 0.015%.
[0015]
Ti: 0.003-0.020%
Ti brings about the same effect as Nb, and improves the formability by the combined addition with Nb. However, when 0.020% or more is added, the effect is saturated and only the cost is increased. For this reason, content of Ti shall be 0.003-0.020%.
[0016]
B: 0.0002 to 0.0020%
B is an element useful for refining the structure of a hot-rolled sheet in combination with hot-rolling conditions. Furthermore, it plays the role of preventing secondary processing brittleness. However, if added excessively, the fine crystals of austenite are delayed during hot rolling, the load during rolling is increased, and the material of the annealed material, particularly the elongation, is deteriorated, so the content is 0.0002 to 0.0020%. And
[0017]
Cu, Ni, Cr, Mo
These elements, like Mn, are solid solution strengthening elements, and are elements useful for reducing the transformation point and making the structure finer. However, excessive addition is accompanied by an increase in the cost of steel and an increase in cold rolling load due to the hardened hot-rolled sheet, so the upper limit is made 0.5% or less. Note that Mo is made 0.2% or less in consideration of cost.
[0018]
(2) Rough rolling conditions According to normal conditions, slab heating is performed and rough rolling is performed. The rolling reduction of rough rolling is 80% or more in total. This is because the structure on the finishing rolling mill entrance side is made uniform and fine to some extent. In particular, the amount of reduction in the final pass affects the homogenization of the tissue, so it is 20% or more.
If the slab heating temperature is too high, it is not preferable because the grain size of the hot-rolled sheet is reduced, the final product is hardened, and the local deformability is lowered. Therefore, the temperature is set to 1250 ° C. or lower so as to achieve both formability and softening.
[0019]
(3) The finish rolling is performed following the finish rolling rough rolling. In finish hot rolling, after the temperature of the material to be rolled once becomes a temperature of Ar ₃ point or less, when it passes through one of the rolling stands in the finish rolling mill row, heat generation due to the rolling process causes transformation from α phase to γ phase. Performed so that the reverse transformation of the point occurs, finishes so that the finish rolling temperature becomes Ar ₃ −50 ° C. or higher, and winds at a temperature of 550 to 750 ° C. to obtain a hot rolled steel strip. Is called.
In the present invention, in the finish rolling step, the greatest feature is that α-γ reverse transformation is performed to make the structure of the hot-rolled steel sheet uniform and fine.
The finish rolling process accompanied by reverse transformation by recuperation according to the present invention is specifically performed as follows.
[0020]
1 and 2 schematically show changes in the steel sheet surface temperature when the material to be rolled passes through the rolling mills F1 to F7 of the finish rolling mill row.
In FIG. 1, the material to be rolled out from the roughing mill is once cooled to Ar ₃ or less and then guided to the finishing mill. That is, the finishing mill entry side temperature (FET) is Ar ₃ or less.
When rolled by a finish rolling mill, the temperature of the material to be rolled rises due to energy and the like due to rolling. The degree varies depending on the reduction amount and reduction rate, but is about 30 ° C. at a rolling speed of 1200 mpm and a reduction amount of 50% (original plate thickness 30 mm). In the case shown in FIG. 1, the material to be rolled at 860 ° C. (Ar ₃ or less 40 ° C.) is 880 ° C. when passing through F1 and further 900 ° C. when passing through F2 on the entrance side of the finishing mill. Reverse transformation takes place. Further, by repeating the same process, reverse transformation by recuperation is repeated also in the F4 stand.
[0021]
By repeating this reverse transformation and the subsequent introduction of strain due to hot rolling, the structure of the hot-rolled steel sheet is made uniform and refined, and the result is brought after the subsequent cold rolling, and the structure of the steel sheet for can making is changed. Contributes to uniform and fine.
Specifically, when the process according to the present invention is employed, the average grain size of the hot-rolled sheet is about 10.5 to 11, whereas the conventional method (when there is no recuperation) is It was about 8.5 to 9.5.
[0022]
In the case shown in FIG. 2, the material to be rolled enters the finish rolling mill at a temperature of Ar ₃ or higher. Then, it is cooled by the cooling water between the f1 to f2, once reduced to Ar ₃ below. After that, strong pressure reduction is performed at the F2 to F3 stands, and recuperation and reverse transformation are performed.
Also in this case, similarly to the case shown in FIG. 1, a hot rolled steel sheet having a uniform and fine structure can be obtained.
[0023]
In the case of the present invention, temperature control and rolling condition setting of the material to be rolled are particularly important. For example, in the case shown in FIG. 1, the temperature of the material to be rolled before entering the finishing rolling mill row must be set in a range in which reverse transformation is caused by recuperation due to subsequent hot rolling. In general when performing atmospheric pressure (rolling reduction 60%), 30 temperature rise due to rolling, since it is about 30 ° C. in anticipation of transformation heat, the use of the rolling heat generation in the F1 and F2 stand, Ar ₃ or less The finishing mill entry side temperature must be adjusted to about 40 ° C.
[0024]
The heat generated by rolling can be generated not only by reduction energy but also by friction energy during rolling. The calorific value and temperature rise due to these are obtained by empirical accumulation.
In the present invention, in order to repeat the transformation, it is important to appropriately cool or keep warm between the stands. That is, in the case shown in FIG. 1, it is necessary to stop the cooling water between F1 and F2 and to keep the heat, whereas in the example shown in FIG. It must be cooled to below Ar ₃ .
The temperature between the stands is preferably measured by installing a radiation thermometer between the stands. At that time, if the cooling water is stopped, the measurement accuracy can be ensured.
[0025]
It is necessary to finish the hot rolling finishing temperature to be Ar ₃ -50 ° C or higher. This is to make the structure and particle size of the hot rolled sheet uniform and fine. Below that temperature, depending on the coiling temperature, the processed structure remains, which deteriorates the cold rolling property, and further becomes a recrystallized structure that adversely affects the workability. Further, even if there is no processing strain, the structure becomes coarse and the strength-workability balance is deteriorated.
[0026]
In addition, as for rolling, it is desirable to perform rough rolling and finish rolling continuously by performing sheet bar joining. In particular, in the present invention, since double heat in the rolling process is used, it is preferable to perform continuous rolling in which sheet bar bonding is performed so that the effect appears uniformly over the entire steel strip.
[0027]
When the coiling temperature is 720 ° C. or higher, the scale thickness increases remarkably, and the descaling property during pickling deteriorates. Moreover, when it winds up at 550 degrees C or less, a precipitate will not fully precipitate and it will have a bad influence on a recrystallized structure. For this reason, winding temperature shall be 550-750 degreeC.
[0028]
(4) Hot rolled steel sheets such as cold rolled are subjected to cold rolling after pickling. The cold rolling rate is performed at a reduction rate of 70 to 95%. In the steel according to the present invention, the crystal grain size of the hot-rolled sheet is considerably large even when the transformation due to the heat generated by the processing is repeated as described above. It is easy to become. The upper limit of the cold rolling rate is set to 95% so as not to deteriorate the anisotropy of the final product.
[0029]
After cold rolling, annealing is performed according to a conventional method. Annealing is performed above the recrystallization temperature by continuous annealing in terms of productivity.
Thereafter, temper rolling is performed for the purpose of adjusting to the desired tempering degree and for the purpose of anti-stretcher strain. Although temper rolling includes skin pass or secondary rolling, it may be used depending on the desired characteristics of the steel plate for canning. In general, the rolling reduction is 30% or less to maintain a balance between workability and strength, and prevent deterioration of in-plane anisotropy.
[0030]
【Example】
Hereinafter, the present invention will be described with reference to examples.
[Example 1]
By weight ratio: C: 0.004%, Si: 0.04%, Mn: 0.25%, P: 0.007%, Al: 0.05%, S: 0.006%, N: 0.008 %, And other steels made of Fe and inevitable impurities were melted and made into slabs by a continuous casting method.
After heating this slab to 1200 ° C., rough rolling was performed under the conditions of a total rolling reduction rate of 90% and a final pass rolling reduction rate of 25% to obtain a sheet bar having a thickness of 40 mm.
After the roughly rolled sheet bars were joined, finish rolling was performed by complete continuous rolling. The rolling conditions are as follows. In this case, the Ar ₃ transformation point was 880 ° C., and the α-γ reverse transformation temperature was 890 ° C.

The hot-rolled sheet thus obtained was pickled, cold-rolled at a reduction rate of 83%, recrystallized and annealed at 750 ° C., subjected to temper rolling at 2%, and the properties of the obtained product were investigated. The results are as follows.
Crystal grain size: 10.8
Uniformity of tissue: Good hardness: 58 (Rockwell hardness, HR30T)
r value: measured value of plastic strain 15% average r value: 1.8 (average r value = (r _L + r _C + 2r _D ) / 4)
Δr value: 0.1 (Δr = (r _L + r _C −2r _D ) / 2)
Skin roughness: None Flange formability: No flange cracking (Skin roughness and flange formability are tin plating equivalent to # 25 under normal conditions, and this is formed into the equivalent of a 3-piece can body by roll forming and constraining seam welding. This was then subjected to necking molding to determine the presence or absence of rough skin.)
[0031]
[Example 2]
In addition, the slab having the same composition as in the above example is subjected to rough rolling under the same conditions as in the above example, and finish rolling is performed.

When the coiling temperature was 600 ° C. and the obtained hot-rolled sheet was subjected to cold rolling, recrystallization annealing, and temper rolling in the same manner as in the above example, the material properties were as follows.
Crystal grain size: 10.9
Uniformity of tissue: Good hardness: 59 (Rockwell hardness, HR30T)
r value:
Average r value: 1.9 (average r value = (r _L + r _C + 2r _D ) / 4)
Δr value: +0.05 (Δr = (r _L + r _C −2r _D ) / 2)
Skin roughness: None Flange cracking: None (Product characteristic value measurement conditions are the same as in the above example)
[0032]
[Comparative example]
Further, the slab having the same component composition as in the above example is subjected to rough rolling under the same conditions as in the above example, and finish rolling is performed.

When the coiling temperature was 600 ° C. and the obtained hot-rolled sheet was subjected to cold rolling, recrystallization annealing, and temper rolling in the same manner as in the above example, the material properties were as follows.
Crystal grain size: 8
Uniformity of tissue: Mixed grain hardness: 55 (Rockwell hardness, HR30T)
r value:
Average r value: 1.4 (average r value = (r _L + r _C + 2r _D ) / 4)
Δr value: −0.3 (Δr = (r _L + r _C −2r _D ) / 2)
Skin roughness: Yes Flange cracking: Partial occurrence In addition, a pattern that appeared to be ridging occurred during a tensile test.
(Measurement conditions for product characteristic values are the same as in the above example)
[0033]
As shown in Examples 1 and 2 and Comparative Example above, in accordance with the present invention, the material subjected to reverse transformation by processing heat generation in the finish rolling process is the structure of the hot-rolled sheet, and consequently the steel plate for can manufacturing that is the final product. The structure was fine and uniform, and no severe defects such as rough skin were produced even after severe processing.
On the other hand, as shown in the comparative example, when the present invention is not applied, that is, when recuperation is not used, the characteristic value of the final product becomes undesirable as a steel plate for cans.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to efficiently and economically refine the crystal structure of an ultra-low carbon steel plate, and to provide a steel plate for can manufacturing with good workability.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the temperature of a rolling stand and rolled material in a finishing mill according to the present invention.
FIG. 2 is another relationship diagram of the temperature of the rolling stand and the rolled material in the finishing mill according to the present invention.

Claims (3)

By weight ratio C: 0.0005 to 0.0150%
Si: 0.2% or less Mn: 0.05 to 0.6%
P: 0.02% or less S: 0.02% or less Al: 0.15% or less N: 0.02% or less Nb: 0.003 to 0.020% as necessary
Ti: 0.003-0.020%
B: 0.0002 to 0.0020%
Cu: 0.5% or less Ni: 0.5% or less Cr: 0.5% or less Mo: 0.2% or less One or two or more of steels, with the balance being composed of Fe and inevitable impurities To the slab,
Hot rough rolling is performed under the condition that the total reduction amount is 80% or more, of which the final pass is 20% or more,
Finish hot rolling is reverse transformed by the heat generated by the rolling process when the temperature of the material to be rolled passes through one of the rolling stands of the finish rolling mill so that the finish rolling temperature becomes Ar ₃ -50 ° C or higher. Exit
Winding at a temperature of 550 to 750 ° C. to obtain a hot rolled steel strip,
A method for producing a steel plate for can making having good workability and no roughening, characterized by performing scale removal, cold rolling, recrystallization annealing and temper rolling of 30% or less on the hot rolled steel strip In claim 1, on the entry side of the finish hot rolling mill train, the temperature of the material to be rolled is cooled to Ar ₃ point or less, and when passing through any finishing mill, reverse transformation is caused by heat generated by the rolling process. Method for producing steel plate for can making having good workability and no rough skin, characterized in that In Claim 1, the temperature of the material to be rolled on the entry side of the finish hot rolling mill row is set to Ar ₃ point or higher, and after passing through any finish rolling mill, is once cooled to Ar ₃ or lower and then rolled. A method for producing a steel plate for can making having good workability and no rough skin, characterized in that reverse transformation is caused by heat generated during rolling when passing through the machine.

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