JP5715413B2 - Method for producing plate material for high-strength can body with good surface properties - Google Patents

Description

  The present invention relates to a method for producing a plate material for a high-strength can body having a good surface property applied to a can body of an aluminum can.

For the can body of the aluminum can, an Al—Mn—Mg based alloy hard plate such as JIS3004 (AA3004) or JIS3104 alloy is used. The alloy hard plate is required to have strength and corrosion resistance necessary for use as a container, a beautiful appearance, and excellent formability.
The said alloy hard plate is manufactured through processes, such as melting | dissolving, casting, homogenization, hot rolling, cold rolling, like a general aluminum alloy plate. Usually, the can body is tempered from 3/4 hard (H16 or H36) to special hard (H19 or H39) with an optimal balance of strength and formability. That is, the aluminum alloy plate is recrystallized once in the course of rolling to be in a soft state, and then cold-rolled with a reduction rate of about 50 to 90% to obtain an appropriate strength mainly by work hardening.

When an aluminum alloy sheet is rolled using a recent industrial cold rolling mill, the material temperature becomes high due to heat generated by rolling, so that sufficient ductility can be obtained even with rolling. Therefore, the aluminum alloy sheet is usually used in a tempered condition (H16 to H19) as it is rolled. When sufficient ductility cannot be obtained, for example, when the rolling speed of the aluminum alloy plate is low, it may be possible to perform stabilization annealing and use the aluminum alloy plate with H3X refining.
However, if the mechanical properties of the aluminum alloy rolled plate are anisotropic, the formability when forming the can body is hindered, the symmetry of the can body after forming is reduced, and the material usage yield is reduced. There are problems such as lowering. The anisotropy of the rolled sheet depends on the crystal grain orientation distribution (texture). In view of this, the anisotropy of the aluminum alloy rolled sheet is reduced by taking into account the change in texture due to cold rolling and controlling the texture generated by recrystallization before cold rolling.

From the above viewpoint, in order to control the anisotropy of the aluminum alloy rolled sheet, it is important how to control recrystallization before cold rolling. From this point of view, the manufacturing method of the aluminum can body material can be classified into the following three types.
(1) Hot rolling → Recrystallization → Final cold rolling In the first method, hot rolling is performed to a relatively thin aluminum alloy sheet of, for example, 3 mm or less, and after hot rolling, it is wound on a coil. This is a method in which recrystallization is performed as it is, or after artificial annealing and recrystallization, and then cold rolling. This method usually uses a hot roughing mill and a 3-4 stand tandem finishing hot rolling mill. In this case, it is possible to sufficiently develop the cube texture after recrystallization by controlling the hot finish rolling conditions. Therefore, even if the reduction ratio of the cold rolling is relatively high, for example, about 90%, the anisotropy of the finally obtained aluminum plate can be relatively small.

(2) Hot rolling-> cold rolling under low pressure->recrystallization-> final cold rolling The second method is to hot-roll into a relatively thin aluminum alloy sheet of, for example, 3 mm or less, and then at a relatively low pressure. For example, in the technique described in Patent Document 1 below, a method of performing cold rolling of 6 to 15% on an aluminum alloy sheet, then annealing, and finally performing final cold rolling with a reduction rate of about 90% It is. Compared with the first method described above, a process called cold rolling at a relatively low pressure is added, but this cold rolling process promotes the development of the cube texture during annealing. Therefore, an effect can be expected when sufficient cube orientation cannot be obtained only by controlling the hot finish rolling conditions. In the techniques described in the following Patent Documents 2, 3, 4 and the like, this method is proposed when a reversible rolling mill (reversing mill) is used as a hot finish rolling mill.

(3) Hot rolling → cold rolling → recrystallization using a continuous annealing furnace → final cold rolling at a relatively low pressure The third method is to perform first cold rolling after hot rolling of an aluminum alloy sheet. Thereafter, using a continuous annealing furnace, annealing is performed by rapid heating to a relatively high temperature, followed by rapid cooling, and finally cold rolling at a relatively low pressure reduction rate, for example, about 60%. Unlike the second method described above, this method has no upper limit on the reduction ratio of the first cold rolling. Therefore, a can body material can be manufactured even in a rolling mill that cannot achieve a thin wall finish of about 3 mm by hot rolling. That is, a can body material can be produced even from a hot-rolled sheet hot-rolled to about 6 to 10 mm, for example, using a hot rolling mill for both rough rolling and finishing rolling, which has a winding device only on one side of the rolling mill. Does not require expensive hot finishing mills.

  However, if the cold rolling reduction after hot rolling is high, sufficient cube orientation cannot be developed during the subsequent recrystallization annealing, so if the cold rolling reduction after intermediate annealing is high, the final plate material will be different. The directivity becomes too large. Therefore, in the third method, intermediate annealing is performed at a relatively high temperature, rapid cooling is performed, and an intermetallic compound such as Mg, Si, or Cu is formed into a solution. For this reason, a precipitation hardening effect can be obtained at the time of baking after coating after being formed on the can body, and sufficient strength can be obtained even if the rolling reduction of the final cold rolling is as low as about 60%. (See Patent Document 5)

By the way, the demand for lower prices for aluminum cans is severe, and therefore, attempts to reduce the amount of material used as much as possible continue. However, if the material plate thickness is reduced, it is difficult to ensure the strength of the bottom of the can body, and if the can body wall portion is thinned, pinholes and the like are likely to occur in the distribution process after filling the beverage, and the contents are likely to leak. There was a problem.
In response to such problems, the present inventors have previously proposed an aluminum alloy plate material suitable for manufacturing a can body having excellent pinhole resistance. And as an example of the preferable manufacturing method in that case, using the continuous annealing furnace, it proposes that the manufacturing method which carries out the intermediate annealing which rapidly heats to comparatively high temperature and then rapidly cools is proposed.

The aluminum can body is manufactured by drawing and ironing an aluminum alloy hard plate such as JIS3004. The can body wall becomes a glossy and uniform surface by ironing. Further, the Al—Mn—Mg alloy has excellent corrosion resistance. Therefore, a beautiful appearance and good corrosion resistance can be obtained simply by performing cleaning and chemical conversion treatment after ironing and applying a relatively thin coating. Therefore, when compared with steel cans or the like, a lower coating cost is an advantage of aluminum cans. However, if there is a defect on the surface of the can wall, even a fine defect cannot be concealed by thin coating, so it is important to prevent the defect from occurring.
As a defect that causes the above problems, there is a linear defect along the rolling direction. This type of defect is called a “flow line” because it forms a loop-like shape when molded into a can body. The cause of the flow line is said to be scratches generated on the surface of the plate and uneven transfer of roll coating during hot rolling. (See Non-Patent Document 1)

Japanese Patent No. 3644819 Japanese Patent No. 3644819 Japanese Patent No. 3871462 Japanese Patent No. 3871473 Japanese Patent Publication No. 60-35424

Onishi's commentary: Defect prevention on plate surfaces, aluminum products and manufacturing technology, edited by the 50th Anniversary Business Executive Committee of the Japan Institute of Light Metals, page 76 (4), published on October 31, 2001

Based on the above-mentioned research by the present inventor, it is possible to produce a high-strength aluminum can body material with excellent pinhole resistance by a production method in which intermediate annealing is performed using a continuous annealing furnace, which is effective for reducing the price of the can body. It was found that a thin material can be achieved.
However, even if the previous technique is used, in the mass production line, defects may occur on the surface of the rolled plate, which causes a problem in the appearance of the can body. As a result, it was found that a defect (hereinafter referred to as a “flow line defect”) having a shape similar to that of the flow line considered to be caused by the surface flaw but not caused by the surface flaw was generated.

  Therefore, when the present inventors examined the occurrence rate and cause of flow line defects in detail, the homogenization conditions before hot rolling and the rolling conditions in the final hot rolling influence the defect occurrence rate. It has been clarified that blisters observed on the surface of the plate in the processes after hot rolling are the cause. Furthermore, it became clear that the molten metal treatment conditions of the aluminum alloy also affect the rate of occurrence of flow line defects.

The present invention has been made on the basis of these findings, and by controlling the temperature and time of the homogenization treatment, and further regulating the rolling conditions of the final hot rolling pass, no flow line defects are generated. It is a first object to provide a method for producing a can body plate.
The second object of the present invention is to improve productivity and yield, which are reduced as a result of solving the first object.
That is, in the present invention, the temperature after the final hot rolling pass and the upper limit of the rolling reduction according to the temperature are regulated. For this reason, in order to reduce temperature, the speed at the time of hot rolling is reduced, or the plate | board thickness which can be rolled by hot rolling increases.
Furthermore, in the present invention, since the purpose is to reduce the thickness of the material, the object is to produce a material having a smaller plate thickness than the conventional one, in addition to achieving the above-mentioned object.
Accordingly, the cold rolling reduction required to reach the final thickness after hot rolling increased. For this reason, problems such as an increase in the number of cold rolling passes, an increase in the number of trims at the sheet width end performed between passes, and a decrease in yield are caused. Therefore, a third object of the present invention is to address these problems and provide an industrially optimal manufacturing method.

In order to solve the above problems, the present invention employs the following configuration.
The manufacturing method of the board | plate material for high-strength can bodies with the favorable surface property of this invention is the mass%, Mn: 0.7-1.1%, Mg: 0.9-1.7%, Si: 0.25. ~ 0.45%, Fe: 0.35-0.55%, Cu: 0.25-0.45%, Zn: 0.05-0.30%, Ti: 0.15% or less, The ingot of aluminum alloy having the composition of the remaining inevitable impurities is homogenized and soaked, then hot rolled and cold rolled, continuously annealed, and finally cold rolled to a thickness of 0.23 mm or more. A method for producing a plate material for a high-strength can body having a good surface property of 4 mm or less, wherein the homogenization treatment is performed at a temperature of 555 to 580 ° C. for 1 to 12 hours, and the soaking treatment is performed at a temperature of 535 to 555 ° C. When the temperature is kept for 1 hour or more and the total time of the homogenization treatment time and the soaking time is 40 hours or less Moni, the case where homogenization treatment and the soaking dedicated heat treatment of each furnace, among time lowering the time and the homogenization temperature of heated to the homogenization temperature, 535 ° C. wherein the lower limit of the soaking temperature The above-mentioned time is included as part of the total time of the homogenization treatment time and the soaking time, and when the homogenization treatment and the soaking treatment are performed in a combined furnace, the total of the homogenization treatment time and the soaking time The time is defined as the time from reaching the lower soaking temperature lower limit of 535 ° C. until the ingot is taken out, and the reduction ratio of the final hot rolling pass is not more than (85−0.08T)% (where T is hot After the final pass of rolling, the temperature immediately after winding from the hot rolling mill is indicated), and the coil temperature immediately after winding from the hot rolling mill is 270 ° C. or higher and 460 ° C. or lower until the continuous annealing after hot rolling. First cold rolling reduction rate of 40% or more, continuous annealing The final cold rolling reduction ratio to the final thickness, characterized in that 70% or less than 55%.
The method for producing a plate material for a high-strength can body having a good surface property according to the present invention is such that when the homogenization treatment and the soaking treatment are performed in a dual-purpose furnace, the soaking temperature is 10 ° C. or more lower than the homogenization temperature. And when the temperature of the ingot is raised, the temperature of the ingot is made to reach the homogenization temperature −10 ° C., and then the temperature of the ingot is homogenized through the time set as the homogenization temperature. From the temperature to the soaking temperature, when the temperature is lowered, the homogenization temperature is −10 ° C. or the higher temperature of the soaking temperature + 10 ° C. is defined as the homogenization treatment time. The temperature is defined as the time from when the soaking temperature is reduced to 10 ° C. or less after the temperature is lowered from the homogenization temperature to the soaking temperature until the ingot is taken out from the combined furnace.
The method for producing a plate material for a high-strength can body having a good surface property according to the present invention includes a hot finishing pass of the last 2 passes or more and 4 passes or less in the hot rolling, and a hot having a winding device on both sides of the rolling mill. A method of rolling using a rolling machine while winding a rolled plate material in a coil shape with a winder, wherein a hot finishing pass start plate thickness in the hot rolling is 18 mm or more and 30 mm or less, The first cold rolling reduction in cold rolling is 88% or less.
The present invention is characterized in that Mg: 1.30 to 1.7% and Cu: 0.30% to 0.45% in the above-described manufacturing method.

  In the present invention, an aluminum alloy having a specific composition is homogenized and soaked, the total time thereof is defined, and the rolling reduction of the final hot rolling pass is not more than (85-0.08T)% (T is the final hot Since the coil temperature immediately after winding from the hot rolling mill is within the specified range, and the first cold rolling rate and final cold rolling reduction are within the specified range. As a result of finish rolling at an appropriate reduction rate and an appropriate temperature in the final hot rolling pass, the occurrence of flow line defects can be suppressed. Thereby, even if it is a case where it is processed into a can body, there exists an effect which can provide the board | plate material for can bodies which does not produce the damage | wound resulting from a flow line-like defect on the surface.

FIG. 1 is an explanatory view showing an apparatus and steps used in carrying out the manufacturing method according to the present invention. FIG. 2 is a structural photograph showing a part of a flow line defect formed in a can body of an aluminum can. FIG. 3 is a perspective view showing an example of a flow line-like defect formed in a can body of an aluminum can.

Hereinafter, a method for producing a plate material for a high-strength can body with good surface properties according to the present invention will be described. First, the plate thickness and alloy composition of a plate material for a high-strength can body (aluminum alloy plate for a can body) will be described. To do.
The plate material for the high-strength can body of the aluminum alloy of the present embodiment has a target plate thickness of 0.23 mm or more and 0.4 mm or less, in terms of mass%, Mn: 0.7 to 1.1%, Mg: 0.00. 9 to 1.7%, Si: 0.25 to 0.45%, Fe: 0.35 to 0.55%, Cu: 0.25 to 0.45%, Zn: 0.05 to 0.30% , Ti: 0.15% or less, the balance is made of an aluminum alloy having the composition of inevitable impurities and aluminum.
[Ingredient composition]
Hereinafter, the component composition limited in the board | plate material for high-strength can bodies with the favorable surface property of this invention is demonstrated. In addition, content of each element described in this specification is mass% unless otherwise specified, and includes an upper limit and a lower limit unless otherwise specified. Therefore, for example, the notation of 0.7 to 1.1% means 0.7% or more and 1.1% or less.

"Mn" 0.7-1.1%
Mn forms an Al-Mn-Fe intermetallic compound in the plate material for high strength can body with good surface properties of the present invention, and exhibits a dispersion hardening action as a crystallization phase and a dispersed phase. It has the effect of preventing seizure from occurring on the die during molding.
When the content of Mn is less than 0.7%, the amount of Al—Mn—Fe intermetallic compound becomes too small to obtain sufficient curing characteristics, and seizure to the ironing mold is likely to occur. . When the content of Mn exceeds 1.1%, the amount of Al—Mn—Fe intermetallic compound is excessively increased, workability deteriorates due to a decrease in toughness, and pinholes (PH) are likely to occur. Therefore, the Mn content is preferably in the range of 0.7 to 1.1%.

"Mg" 0.9-1.7%
Mg has a solid solution strengthening action in the plate material for high-strength can body having a good surface property of the present invention, enhances work hardenability at the time of rolling, and disperse hardening and precipitation hardening action by coexisting with Si and Cu. To improve the strength.
If the Mg content is less than 0.9%, sufficient strength cannot be obtained. If the Mg content exceeds 1.7%, side cracks are likely to occur, the rollability is lowered, the strength is too high, the workability is lowered, and the can is cut as a can body. Is likely to occur. Therefore, the Mg content is preferably in the range of 0.9 to 1.7%. Moreover, when the plate | board thickness of the board | plate material for can bodies finally obtained is 0.23 mm or more and 0.30 mm or less, about the content of Mg, the range of 1.30-1.7% is more preferable. If the Mg content is less than 1.30%, the strength tends to be insufficient when the plate thickness is 0.30 mm or less.

"Si" 0.25-0.45%
Si forms a compound together with Mg or the like contained at the same time in the plate material for a high strength can body having a good surface property of the present invention, and improves the strength by precipitation hardening and dispersion hardening action. It is contained in an intermetallic compound and has an effect of preventing seizure against a die during ironing.
If the Si content is less than 0.25%, sufficient strength cannot be obtained, and the intermetallic compound size increases. If the Si content exceeds 0.45%, the strength becomes too high, and when a can body is produced, it becomes easy to be cut out of the cylinder, side cracks are likely to occur, and workability deteriorates. Further, if the Si content exceeds 0.45%, the amount of Al-Mn-Fe intermetallic compound increases, and further, the intermetallic compound with Mg, Cu, Al cannot be solutionized, and the toughness is increased. The pinhole is likely to occur. Therefore, the Si content is preferably in the range of 0.25 to 0.45%.

"Fe" 0.35-0.55%
Fe increases the amount of Al-Mn-Fe intermetallic compound in the plate material for high-strength can bodies with good surface properties according to the present invention, so that the fineness of crystals and seizure to the die during ironing processing. It has the effect of preventing the occurrence.
If the Fe content is less than 0.35%, the amount of the Al—Mn—Fe intermetallic compound becomes too small, and seizure to the ironing die tends to occur. When the content of Fe exceeds 0.55%, the amount of Al—Mn—Fe intermetallic compound becomes too large, workability deteriorates due to a decrease in toughness, and pinholes are likely to occur. Therefore, the Fe content is preferably in the range of 0.35 to 0.55%.

“Cu” 0.25 to 0.45%
Cu forms an intermetallic compound with Mg or the like in the plate material for a high strength can body having a good surface property of the present invention, and has an effect of increasing strength by solid solution hardening, precipitation hardening and dispersion hardening.
If the Cu content is less than 0.25%, a sufficient strength improvement effect cannot be obtained. If the Cu content exceeds 0.45%, side cracks are likely to occur, the rollability is lowered, the strength becomes too high, and the body is easily cut when it is made as a can body. In addition, the intermetallic compound with Mg, Si, and Al cannot be in solution, and the workability deteriorates due to a decrease in toughness, and pinholes are likely to occur. Therefore, the Cu content is preferably in the range of 0.25 to 0.45%. Moreover, when the plate | board thickness of the board | plate material for can bodies finally obtained is 0.23 mm or more and 0.30 mm or less, about 0.30 to 0.45% of range of Cu content is more preferable. If the Cu content is less than 0.30%, the strength tends to be insufficient when the plate thickness is 0.30 mm or less.

“Zn and Ti” Zn: 0.05% or more and 0.30% or less, Ti: 0.15% or less The plate material for a high-strength can body having good surface properties according to the present invention is Zn: 0.05% in mass%. As mentioned above, it can be set as the component composition containing 0.30% or less and Ti: 0.15% or less.
Zn has the effect of refining the precipitated intermetallic compounds of Mg, Si, and Cu, but when it contains Zn, used aluminum cans (UBC) and recycled materials can be effectively used as raw materials. If the Zn content is less than 0.05%, it is difficult to use UBC or recycled material as a raw material. When the Zn content exceeds 0.30%, the corrosion resistance deteriorates. Therefore, the Zn content is preferably 0.05% or more and 0.30% or less.
Ti has the effect of refining crystal grains and improving workability in the plate material for a high-strength can body having good surface properties according to the present invention. When the Ti content exceeds 0.15%, the amount of intermetallic compounds increases so much that the toughness decreases and pinholes are likely to occur. Therefore, the Ti content is preferably 0.15% or less.
Further, the aluminum alloy used in the present invention may contain 0.05% or less of other elements as impurities.

In the method for producing a plate material for a high-strength can body having a good surface property according to the present embodiment, for example, an aluminum alloy slab having the above composition is melted and subjected to homogenization treatment and soaking treatment. By processing according to the order shown in 1, a plate material for a high-strength can body having a good target surface property is obtained.
In the process shown in FIG. 1, hot roughing is performed to a thickness of about 16 mm using the hot roughing mill 1 shown in FIG. 1A, and then hot finishing is shown in FIG. 1B. It hot-rolls to about 2 mm in thickness using the rolling mill 2, and then cold-rolls in the cold rolling apparatus 3 which shows an outline in FIG.1 (C), and shows an outline in FIG.1 (D) next. Annealing is performed in the continuous annealing furnace 4, cold rolling is performed again to a target plate thickness in the cold rolling apparatus 5 as shown in FIG. 1E, and finally a plate material having a target thickness as shown in FIG. Can be obtained.

The hot rough rolling mill 1 shown in FIG. 1 (A) includes, for example, upper and lower work rolls 10 and 11 and backup rolls 12 and 13 and a transport path 14 in which a plurality of transport rollers are arranged, and has been transported aluminum. This is an apparatus for rolling an alloy plate 15 to a desired thickness by passing between work rolls 10 and 11. In FIG. 1 (A), the conveyance path 14 is shown only on the left side, but actually it is also installed on the right side, and it is repeatedly supplied alternately to the work rolls 10 and 11 from the left and right conveyance paths. By sequentially performing rough rolling, the hot rough rolling mill 1 can roll the plate material 15 to a required thickness.
The hot finish rolling mill 2 shown in FIG. 1 (B) includes, for example, upper and lower work rolls 16 and 17 and backup rolls 18 and 19, and a reel-type delivery winding device 20 installed on the entry side of these rolls, And a reel-type delivery take-up device 21 installed on the delivery side. The hot finish rolling mill 2 is configured to wind the sheet material that is hot-rolled from the feed winder 20 and passed between the work rolls 16 and 17 by the feed winder 21, and from the feed winder 21. The operation of winding the sheet material hot-rolled again by passing between the work rolls 16 and 17 with the feed winder 20 is repeated as many times as necessary, and the interval between the work rolls 16 and 17 is gradually adjusted for each rolling operation. By doing so, it is an apparatus for hot rolling an aluminum alloy plate material to a target plate thickness.

  1C includes, for example, upper and lower work rolls 22 and 23 and backup rolls 24 and 25, a reel-type delivery winding device 26 installed on the entry side of these rolls, and an exit side. And a reel-type delivery take-up device 27 installed in the machine. The cold rolling mill 3 performs an operation of winding the sheet material, which is fed from the take-up take-up device 26 and passed between the work rolls 22, 23, by the take-up take-up device 27, and again from the take-up take-up device 27. The operation of winding the sheet material cold-rolled by passing between the work rolls 22 and 23 with the feed winder 26 is repeated as many times as necessary, and the interval between the work rolls 22 and 23 is gradually adjusted for each rolling operation. Thus, the aluminum alloy plate material is sequentially rolled to the target plate thickness.

A continuous annealing furnace 4 shown in FIG. 1D includes an annealing furnace 32 having a heating zone 30 and a cooling zone 31, a feeding device 33 and an accumulator 34 for feeding a plate material to the annealing furnace 32, and an annealing furnace 32. And an accumulator 35 and a winding device 36 for pulling out and winding the plate material. The continuous annealing furnace 4 is an apparatus known as an apparatus capable of rapid heating, rapid cooling, and annealing at a high temperature for a short time.
The cold rolling device 5 shown in FIG. 1 (E) has the same configuration as that of the previous cold rolling device 3, but it is cold rolled into a sheet material thinner than the cold rolling device 3 by adjusting the interval between the work rolls 22 and 23. It is configured to be able to.
By using each device outlined in FIG. 1 as a main body and sequentially carrying out the steps described in detail below, a plate material for a high-strength can body with good target surface properties can be produced.

"Melting / Casting"
After the aluminum alloy having the above-described composition is melted, treatments such as dehumidification, component adjustment, degassing, molten metal filtration, and addition of a fine material are performed by a general method. Degassing is performed in a melting furnace, a holding furnace, or an in-line molten metal processing apparatus, and the final hydrogen concentration is preferably 0.15 cc / 100 g or less, more preferably 0.10 to 0.12 cc / 100 g. preferable. Thereafter, the slab is cast by semi-continuous casting.
Chlorine gas may be used for degassing the in-line molten metal treatment apparatus, but it is more preferable not to use chlorine gas because flow line defects are less likely to occur. Further, for the refinement of the cast structure, a refined material such as Al—Ti—B may be used, but it is more preferable not to use it because a flow line defect is less likely to occur. The slab thickness produced in the casting process can be about 500 to 600 mm.

"Homogenization and soaking process"
The aluminum alloy is cast to obtain a slab of a predetermined size, and then homogenized in the slab state. In the homogenization treatment, the slab is heated to a temperature range not lower than the lower limit temperature and not higher than the upper limit temperature by a general method such as heating in a heating furnace, and within the same temperature range, not lower than the lower limit time and not higher than the upper limit time. Hold on.
When a dedicated furnace is used for the homogenization treatment, it is once cooled to near room temperature after the completion of the above holding. Then, after chamfering, reheat to a temperature range above the lower limit of the soaking temperature and below the upper limit in a soaking furnace, hold it for at least the lower limit time in the same temperature range, then take out hot rolling from the furnace Start.
When a homogenization treatment and soaking furnace are used, the slab after chamfering is heated to the homogenization treatment temperature range, and after holding in the homogenization treatment temperature range, the upper limit of the soaking temperature is below, and Then, after cooling to the lower limit or more and holding the same temperature range for the lower limit time or more, the hot rolling is taken out from the furnace.
Elements such as Si, Mn, Cu, and Mg contained in aluminum greatly change their equilibrium solid solution amount in a temperature range of about 400 to 580 ° C. Therefore, if the holding time in the soaking temperature range is too short, the dispersion of the solid solution amount at the start of hot rolling becomes large, and the dispersion of the mechanical properties of the final product becomes large.
The total of the homogenization treatment time and the soaking time indicates the total time that is maintained above the lower limit temperature of soaking in both treatments. Accordingly, when the homogenization treatment is performed using a dedicated furnace, the time until cooling to below the lower limit of the soaking temperature is included when cooling to near room temperature after homogenization.

Specifically, the homogenization temperature is preferably in the range of 555 to 580 ° C. When the homogenization temperature is less than 555 ° C., the solute component is not sufficiently solutioned, and when the temperature exceeds 580 ° C., the occurrence rate of flow line defects increases.
Specifically, the homogenization treatment time is preferably in the range of 1 hour to 12 hours, more preferably in the range of 4 hours to 8 hours. If the homogenization treatment time is less than 1 hour, the solution of the solute component tends to be insufficient, the crystallization phase is not sufficiently α-ized, and the seizure resistance tends to be insufficient. When the homogenization treatment time exceeds 12 hours, the effect is saturated and time is wasted. Therefore, the homogenization treatment time is preferably within 12 hours.

Specifically, the soaking temperature is preferably in the range of 535 to 555 ° C. When the soaking temperature is less than 535 ° C., the solid solution amount of the component elements is not stable, and the mechanical properties of the final product tend to vary. When the soaking temperature exceeds 555 ° C., the rate of occurrence of flow line defects increases.
Specifically, the soaking time is preferably 1 hour or longer. If the soaking time is less than 1 hour, the solid solution amount of the component elements is not stable, and the mechanical properties and the like of the final product may vary.
Furthermore, in the present embodiment, it is preferable that the total time of the homogenization treatment time and the soaking time (the time in which the temperature is maintained in the temperature range of 535 ° C. to 580 ° C.) be 40 hours or less. If this total time seems to exceed 40 hours, the incidence of flow line defects increases.

"Hot rolling"
After the soaking process, the slab taken out from the furnace usually starts hot rolling immediately, but if the slab temperature does not become less than 500 ° C., the start of hot rolling may be delayed. The number of hot rolling passes depends on the slab thickness, finish thickness, slab width, alloy composition, and the like, but is generally in the range of tens of passes to tens of passes.
In hot rolling, while the rolled material is thick, a one-stand reversible rolling mill (hot rough rolling mill 1 having the configuration shown in FIG. 1A) in which a conveyance table is installed before and after the normal rolling mill is used. And roll. However, when the plate is thinned, the necessary transport table length is increased, the slack due to the weight of the plate is increased, and the plate is likely to be cooled. For this reason, in order to hold | maintain with a conveyance table, plate | board thickness needs to be 10 or more mm. The minimum plate thickness depends on the coil weight and plate width, but is preferably about 16 mm or more in the case of the weight and width used industrially.
When the aluminum alloy sheet becomes thinner than the above thickness, hot rolling is performed by the hot finish rolling mill 2 having the configuration shown in FIG.

The rolling reduction of the final pass of hot finish rolling needs to be (85−0.08 × T)% or less when the coil temperature immediately after winding the plate material after the final pass is T ° C. If this condition is not met, the rate of occurrence of flow line defects increases.
The coil temperature immediately after winding the coil after the final hot rolling pass needs to be 270 ° C. or higher and 460 ° C. or lower. During the cold rolling after hot rolling, it is necessary to trim the end of the plate in order to prevent coil breakage. As will be described later, the higher the cold rolling reduction, the greater the number of necessary trims. However, if the coil temperature immediately after winding the coil after the final hot rolling pass is less than 270 ° C., the further necessary number of trims Will increase. More preferably, 10% or more of the plate thickness is recrystallized after the coil is cooled after winding. On the other hand, when the coil temperature immediately after being wound on the coil after the final pass of hot rolling exceeds 460 ° C., surface oxidation until the coil is cooled after hot rolling becomes remarkable, and the surface appearance deteriorates.

Immediately before winding the coil in the final pass of the hot rolling, the both ends of the plate are cut with a trimmer and the end surfaces are trimmed, thereby preventing the occurrence of cracks from the end surfaces during the subsequent cold rolling.
The plate thickness after hot rolling needs to be 1.3 mm or more and 12 mm or less. If the plate thickness is less than 1.3 mm, the coil temperature after winding becomes too low, and the final plate becomes too thin when cold rolling is performed at the required reduction rate. If the plate thickness exceeds 12 mm, winding becomes difficult.

“When using a hot rolling mill with winding devices on both sides of the rolling mill”
In this embodiment, in order to suppress the occurrence of flow line defects, the upper limit of the rolling reduction must be regulated in the final pass of hot rolling.
For example, when a rough rolling / finish rolling combined hot rolling mill with a winding device installed only on one side is used, there is a minimum value for the plate thickness that can be held on the transfer table, so rolling is performed by hot rolling. The minimum possible plate thickness will increase. For this reason, the cold rolling reduction after hot rolling increases. Furthermore, due to the influence of a reduction in the final product sheet thickness, there arises a problem that the number of passes of cold rolling is increased or the required number of trims to be performed between passes of cold rolling is increased as compared with the conventional case.
The rolling reduction of the final hot rolling pass can be increased by lowering the coiling temperature, but in order to lower the temperature immediately after winding, it is necessary to lower the rolling speed, and the hot rolling productivity is reduced. descend. Furthermore, if the temperature immediately after winding is lowered, the load required for rolling increases, so if the width of the rolled sheet is wide, it may exceed the allowable load of the rolling mill, and is below the above-mentioned allowable reduction ratio. However, there are cases where rolling is not possible.

For these reasons, in order to prevent a decrease in productivity and yield, a hot rolling mill having a winding device on both sides of the rolling mill (hot finishing rolling mill 2 shown in FIG. 1B) is used. Otherwise, it is preferable to use a multi-stand tandem hot rolling mill to reduce the thickness of the hot rolled finish plate. However, in the manufacturing method of the present embodiment, in order to increase the final cold rolling rate, which will be described later, preferably to 60% or higher, for example, about 90%, the hot rolling conditions are controlled to develop a cube texture. That is not the purpose.
Accordingly, even when a tandem hot rolling mill is used, 3 to 4 stands are not always necessary, and two stands can sufficiently achieve the object. Moreover, even when a finishing mill having a winding device on both sides of a hot rolling mill is used, it is not necessary to use a rolling mill dedicated to finishing rolling, and winding is performed on both sides of a rough rolling / finishing combined hot rolling mill. The purpose can also be achieved by installing a device.
Therefore, if the manufacturing method of this embodiment is adopted, the can body material can be manufactured with the minimum equipment according to the required production amount.
Below, conditions suitable when using a hot rolling mill having a winding device on both sides of the rolling mill (corresponding to the hot finishing rolling mill 2 having the configuration shown in FIG. 1B) will be described. In addition, about the case where a rough rolling / finish rolling combined use hot rolling mill is used, the rolling using a winding device is called finish rolling.

Specifically, the hot finish rolling start temperature is preferably in the range of 380 ° C. or higher and 480 ° C. or lower, and more preferably in the range of 420 ° C. or higher and 480 ° C. or lower. If the hot finish rolling start temperature is less than 380 ° C., the final coiling temperature is lowered, and the number of trims required until continuous annealing is increased. When the hot finish rolling start temperature exceeds 480 ° C., surface oxidation until the coil is cooled after hot rolling becomes remarkable, and the surface appearance is deteriorated.
Specifically, the hot finish rolling start plate thickness is preferably in the range of 16 to 30 mm. When the hot finish rolling start plate thickness is less than 16 mm, the slack on the table becomes large, and a material having a large plate width cannot be used. If the hot finish rolling start plate thickness exceeds 30 mm, the plate thickness after the first pass becomes too large, and it is difficult to wind the coil around the coil.
From the above, it is preferable that the rolling reduction per pass of hot finish rolling is in the range of 35% or more and 60% or less.

"First cold rolling"
After cooling after hot pressing, cold rolling is performed at a rolling reduction of 40% or more (more preferably more than 60%). The technique described in Patent Document 1 (Patent No. 364449) is 25% or less, the technique described in Patent Document 2 (Patent No. 3871462) is 60% or less, and the technique described in Patent Document 3 (Patent No. 3871473). Proposes a cold rolling rate of 50% or less.
In the proposals described in these patents, the cold rolling under a relatively low pressure after the hot rolling is intended to promote the development of the cube texture during the subsequent annealing as described above. For such purposes, it is proposed that a partially recrystallized state is preferable after hot rolling.
As a result of the study by the present inventors, when the manufacturing method as described in these patent documents is adopted, the crystal grains become coarse and breakage is likely to occur during ironing when manufacturing the can body. In addition, under such manufacturing conditions, the recrystallization rate varies in the thickness direction of the hot-rolled sheet, so the crystal grain size after intermediate annealing also changes in the sheet thickness direction, and a uniform structure is obtained. Absent. Further, since the hot rolling speed has to be lowered even at the front and rear ends of the coil, the anisotropy differs from the longitudinal central portion where the steady speed is obtained. For this reason, there exists a problem that a yield falls.
In the present embodiment, the rolling reduction of the first cold rolling is 40% or more, preferably over 60%. For this reason, even if there is variation in the recrystallization rate after hot rolling in the plate thickness direction or the coil longitudinal direction, a homogeneous structure can be obtained after intermediate annealing. Moreover, anisotropic longitudinal variation is small, and the yield is improved.

Regarding the reduction ratio of the first cold rolling, in the range of more than 66% to 88%, the intermediate trim is performed after the intermediate trim is performed on the final pass of the hot rolling and before the continuous annealing is performed (for example, immediately before the continuous annealing). Is required.
Regarding the reduction ratio of the first cold rolling, if it is in the range of over 88% to 91%, one intermediate trim is required after performing the second hot rolling to the continuous annealing. It becomes.
When the reduction ratio of the first cold rolling is in the range of more than 91%, there are three or more intermediate trims or additional intermediate annealings after trimming in the final pass of hot rolling until continuous annealing. Necessary.

"Continuous annealing, final cold rolling"
As a condition for performing continuous annealing, heating is performed at an average heating rate of 10 to 50 ° C./s to a predetermined temperature of 400 ° C. or more and 600 ° C. or less, and then at an average cooling rate of 30 to 150 ° C./s from normal temperature to 100 ° C. Cool to a predetermined temperature.
Thereafter, the final cold rolling is performed at a rolling reduction of 55% to 70%. The final cold rolling is preferably performed in one pass, and the winding temperature is preferably in the range of 80 ° C to 140 ° C.

"Thickness of aluminum alloy sheet for can body"
The plate thickness of the plate material for a high-strength can body having a good surface property finally obtained by the present embodiment is in the range of 0.230 mm to 0.4 mm.
When the plate thickness is less than 0.230 mm, it becomes difficult to obtain sufficient pressure resistance when canned and made into a can body. On the other hand, if the plate thickness exceeds 0.4 mm, the weight of the bottom of the can body becomes heavy, and the manufacturing cost increases, which is not economical. The plate thickness of the plate material for a high-strength can body having good surface properties is more preferably in the range of 0.230 mm to 0.3 mm, and still more preferably in the range of 0.230 mm to 0.27 mm.

EXAMPLES Hereinafter, although an Example is shown and the manufacturing method of the board | plate material for high-strength can bodies with the favorable surface property based on this invention is demonstrated in detail, this invention is not limited to a following example.
Al-0.3% Si-0.43% Fe-0.38% Cu-0.99% Mn-1.48% Mg-0.03% Cr-0.18% Zn-0.04% Ti The aluminum alloy having the composition was melted, degassed and filtered with a molten metal, and then cast into a slab having a thickness of 600 mm, a width of 1100 mm, and a length of 4.5 m by semi-continuous casting.
In-line degassing was performed by Ar blowing using an apparatus with a rotating nozzle. Chlorine was not added into Ar. Further, Ti in the alloy was mainly contained in the raw material UBC and scrap, and in some samples, it was added for component adjustment in a holding furnace. However, addition of a refined rod-type Al-Ti-B alloy with a transfer rod was not performed. According to the analysis of samples taken after in-line degassing, the hydrogen content of all samples was in the range of 0.10 to 0.12 cc / 100 g.

Next, after chamfering the slab, homogenization and soaking were performed using a homogenizing and soaking furnace. The homogenization treatment and soaking temperature described in Table 1 showing the test results described later are set temperatures.
After the slab was heated and reached the homogenization temperature set value of −5 ° C., the slab temperature was within ± 5 ° C. of the homogenization set temperature in all cases until the temperature was lowered to the soaking temperature. Further, the temperature reduction started from the homogenization temperature, and after reaching the soaking temperature set value + 5 ° C., the slab temperature was within the soaking temperature set value ± 5 ° C. until the slab was taken out from the furnace.

The homogenization treatment time starts the heating of the slab, and after the slab reaches the homogenization temperature set temperature −10 ° C., the temperature lowering to the soaking temperature starts, and the homogenization temperature set value −10 ° C. or the soaking temperature +10 It was set as time until it became lower than the higher one of ° C. The soaking time was defined as the time from when the soaking temperature was lowered to 10 ° C. or lower after the temperature was lowered from the homogenizing temperature to the soaking temperature until the slab was taken out from the furnace. The total of the homogenization time and the soaking time indicates the total time that is maintained above the lower limit temperature of soaking in both treatments, so the slab heating is started and the lower limit of the soaking temperature reaches 535 ° C. This corresponds to the time until the slab is removed from the furnace.
After soaking, the slab taken out from the furnace was hot-rolled. The time from taking out from the furnace to starting the first hot rolling pass was 4 to 5 minutes. The hot-rolled plate was trimmed with a trimmer at the end just before winding into a coil after rolling. The coil wound up after hot rolling was cooled to room temperature and then cold rolled. When the number of intermediate trims was two, the first intermediate trim was applied with a plate thickness of 2.2 to 2.8 mm. In the case where the number of times of trimming was two or one, the trimming was performed immediately before heating the plate material with the entry side trimmer installed in the continuous annealing furnace.

A continuous annealing furnace was used for the intermediate annealing. The plate material is heated from room temperature to 500 ° C. during about 20 seconds passing through the heating zone of the continuous annealing furnace, and immediately thereafter cooled to 70 ° C. or less in about 10 seconds passing through the cooling zone. After the intermediate annealing, it was cold-rolled to the final thickness in one pass using a 2 stand tandem cold rolling mill.
The flow line defect was determined by observing the surface of the can after DI molding and degreasing.
First, it was visually confirmed whether or not a linear defect along the rolling direction of the base plate had occurred. The flow line defect has a width corresponding to from ten to several hundred μm and a long length corresponding to the end of the blank before forming. In the visual observation, those having a length of about 1 mm or more and distinguishable from linear defects were detected. Flow line defects are similar in appearance to flow lines due to dirt and non-uniform transfer of hot rolled roll coating. Therefore, as a precaution, the linear defect portion was cut out and observed with an optical microscope to confirm that it was a flow line defect.
FIG. 2 shows an enlarged photograph of the flow line defect generated in the sample No. 5, and FIG. 3 shows an example of the flow line defect. A scale-like structure is observed as shown in the photograph in FIG. 2, and a part of the scale is peeled off as shown in the photograph. Even in the case of a flow line defect, there is a portion along which the scaly surface layer is almost peeled off along its entire length. Such a site has a form similar to a flow line caused by surface flaws. However, since the scaly tissue remained at least partially in the flow line defect, it was confirmed with an optical microscope that scaly sites were observed. Moreover, as shown in FIG. 3, the part produced | generated in a U shape on the cup-shaped can side surface is an example of a flow line-like defect.
For each condition, 10,000 cans were observed, and the number of detected flow line defects was shown in Tables 1 to 3 below.
The crystal grain size was determined by buffing the surface of the plate material, electrolytically polishing to give a mirror surface, anodizing with Barker's solution, and observing the polarization with an optical microscope. Then, the case where the average edge length in the plate width direction is 25 μm or less is evaluated as “◯”, the case where it exceeds 25 μm is Δ, and the case where it exceeds 30 μm is ×.

In the results shown in Tables 1 to 3, no. 1-No. Sample 5 has a different homogenization temperature. No. The samples 1 to 3 are all examples of the present invention. Samples 4 and 5 were higher than the range defined in the present invention, and flow line defects were generated.
No. Samples 6 to 9 are cases where the homogenization treatment time or soaking time is long and soaking + homogenization time is long. No. Samples 6-8 are within the scope of the present invention. Sample 9 was longer than the range of the present invention, and flow line defects were generated.
No. Samples 10 and 11 are cases where the soaking temperature is high. No. Ten samples are within the scope of the present invention. Eleven samples were higher than the scope of the present invention, and flow line defects were generated.
No. Samples 12 to 18 are cases where the rolling reduction of the final pass of hot rolling and the coil temperature immediately after the end of hot rolling were changed. No. Samples 12 to 14 are cases where the relationship between the rolling reduction of the final pass and the coil temperature immediately after the end of hot rolling satisfies the relationship of the present invention. No. Samples 15 to 18 are those in which the final pass reduction ratio is higher than the case where the relationship between the final pass reduction ratio of the present invention and the coil temperature immediately after the end of hot rolling is satisfied. did.
The sample No. 19 was a sample in which the coil temperature after hot rolling was 470 ° C., but the surface oxidation became remarkable and the appearance became a color close to white.

No. Sample No. 20 was subjected to intermediate trimming at 2.5 mm when the rolling reduction of the first cold rolling was as high as 91.4%, but breakage occurred in the final pass of the first cold rolling.
No. Sample No. 21 was produced when the rolling reduction of the first cold rolling was as low as 87.4%, and only by performing trimming on the inlet side of the continuous annealing furnace.
The sample No. 22 also has a low rolling reduction of 17.4% in the first cold rolling, but after the hot rolling, the coil temperature is 260 ° C., which is lower than the range of the present invention, and the final pass of the first cold rolling. Ruptured.

No. Samples 23 to 31 are obtained by using a hot finish rolling mill in which winding devices are installed on both sides of the hot rolling mill. No. Samples 23 to 26 are cases where the rolling reduction of the final pass of hot rolling and the coil temperature immediately after the end of hot rolling were changed. When the final pass reduction ratio is higher than the case where the relationship between the final pass reduction ratio of the present invention and the coil temperature immediately after completion of hot rolling is satisfied (samples Nos. 24 and 26), flow line defects are generated. did.
No. Samples 27 and 28 were able to be manufactured without intermediate trim when the reduction ratio of the first cold rolling was lower than 66%. No. Sample No. 29 was intended to be produced without intermediate trim when the rolling reduction of the first cold rolling was higher than 66%, but production was stopped because it broke in the furnace during continuous annealing.
No. Sample No. 30 was a case where the rolling reduction of the first cold rolling was lower than 40%, and the crystal grains became coarse.
The sample of No. 31 is a sample having a rolling rate lower than 60%, which is the preferred cold rolling rate of the first cold rolling. did it.
Samples Nos. 1 to 22 shown in Tables 1 to 3 are examples using a hot rolling mill for both rough rolling / finish rolling in which a winding device is installed only on one side (number of hot finishing mill passes). No. 23 to 31 is an example in which a dedicated hot finish rolling mill equipped with a winding device on both sides of the rolling mill is used (number of hot finishing mill passes 1 to 4 times). It is.

  DESCRIPTION OF SYMBOLS 1 ... Hot rough rolling mill, 2 ... Hot finish rolling mill, 3, 5 ... Cold rolling apparatus, 4 ... Continuous annealing furnace, 6 ... Coil, 30 ... Heating zone, 31 ... Cooling zone, 32 ... Annealing furnace.

Claims (4)

In mass%, Mn: 0.7 to 1.1%, Mg: 0.9 to 1.7%, Si: 0.25 to 0.45%, Fe: 0.35 to 0.55%, Cu: Homogenizing an ingot of aluminum alloy containing 0.25 to 0.45%, Zn: 0.05 to 0.30%, Ti: 0.15% or less, and the balance having the composition of inevitable impurities and aluminum After soaking and heat-treating, hot rolling and cold rolling are performed, and after continuous annealing, a final cold rolling is performed to obtain a plate material for a high-strength can body having a good surface property of 0.23 mm or more and 0.4 mm or less. A method of manufacturing comprising:
The homogenization treatment is performed at a temperature of 555 to 580 ° C. for 1 to 12 hours, the soaking treatment is performed at a temperature of 535 to 555 ° C. for 1 hour or more, and the total time of the homogenization treatment time and the soaking treatment time is 40 hours or less. And
When the homogenization treatment and the soaking treatment are each performed in a dedicated furnace, the temperature is 535 ° C. or more, which is the lower limit of the soaking temperature, among the time to raise the temperature to the homogenization temperature and the time to lower the temperature from the homogenization temperature. A part of the total time of the homogenization treatment time and the soaking time,
When performing the homogenization treatment and the soaking process in a dual-purpose furnace, the total time of the homogenization treatment time and the soaking time is the time from reaching the lower soaking temperature lower limit of 535 ° C. until the ingot is taken out,
The rolling reduction of the final hot rolling pass is set to (85-0.08T)% or less (where T is the temperature ° C immediately after winding from the hot rolling mill after the hot rolling final pass) The coil temperature immediately after winding from the cold rolling mill is 270 ° C. or more and 460 ° C. or less, the first cold rolling reduction ratio after hot rolling to continuous annealing is 40% or more, the final cold to the final sheet thickness after continuous annealing A method for producing a plate material for a high-strength can body having a good surface property, wherein the rolling reduction ratio is 55% or more and 70% or less.   When the homogenization treatment and the soaking treatment are performed in a dual-purpose furnace, the soaking temperature is set to a temperature that is 10 ° C. or more lower than the homogenization temperature, and the temperature of the ingot is increased when the ingot is heated. After reaching the homogenization temperature −10 ° C., the homogenization temperature −10 ° C. or the soaking temperature is lowered when the temperature of the ingot is lowered from the homogenization temperature to the soaking temperature. The homogenization time is defined as the time at which the heat temperature is increased to a higher temperature of 10 ° C., and the soaking time is the soaking temperature after the temperature of the ingot starts to be lowered from the homogenizing temperature to the soaking temperature. The method for producing a plate material for a high-strength can body with good surface properties according to claim 1, characterized in that the time from when the temperature becomes + 10 ° C or lower to when the ingot is taken out from the dual-purpose furnace is used.   In the hot rolling, a hot finishing pass of the last 2 passes or more and 4 passes or less is used, a hot rolling mill having a winding device on both sides of the rolling mill is used, and the rolled plate material is wound into a coil by the winding machine. A hot finishing pass start plate thickness in the hot rolling is 18 mm or more and 30 mm or less, and a first cold rolling reduction in the cold rolling is 88% or less. The manufacturing method of the board | plate material for high-strength can bodies with favorable surface property of Claim 1 or 2.   The surface property according to any one of claims 1 to 3, wherein Mg: 1.30 to 1.7% and Cu: 0.30% to 0.45% are included. A method for manufacturing a plate material for a strong can body.