JPH0947845A - Method for producing continuously cast and rolled aluminum alloy sheet with excellent ironing workability - Google Patents

Abstract

(57) [Summary] [Structure] A solid lubricant having an average particle diameter of 0.1 to 50 µm is applied to a casting roll used for continuous casting and rolling, and the solid lubricant is continuously cast and rolled using this roll. By transferring, press-fitting and embedding on the surface of the continuous casting and rolling plate, an initial solid lubricant layer is formed, followed by rolling,
The area ratio of the solid lubricant having an average particle size of 0.1 to 50 μm on the surface of the final rolled plate is 20% or more. [Effect] To provide an aluminum alloy continuous casting and rolling plate for forming, which has excellent ironing workability not only in the 3000 series aluminum alloys that have been conventionally used but also in the 5000 series alloy composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy sheet which is resistant to galling during ironing by a continuous casting and rolling method, and more particularly to a method for producing an aluminum alloy sheet suitable as a can body. In the present invention, the aluminum alloy plate means an industrial pure aluminum plate and various aluminum alloy plates.

[0002]

2. Description of the Related Art Generally, drawing processing (Dra
Wing) and ironing (Ironing) are added (DI
(Processing and generic name), during the ironing process, scratches and discoloration, so-called galling, may occur on the surface of the material plate almost parallel to the ironing direction. This goring significantly deteriorates the quality of the surface of the material plate, and especially in the case where the aluminum base is exposed instead of coating the entire can body like an aluminum can, the occurrence of this goring does not occur. It is a fatal surface defect that significantly impairs the appearance of the product.

Further, the occurrence of goring causes damage to tools such as dies and shortens tool life.

Further, when the galling is severe, troubles such as material breakage may occur during the ironing process, interrupting the work and lowering the work rate, and the debris sometimes damages the ironing work tool and the processing equipment. is there.

Due to these problems, it is strongly desired to suppress the occurrence of galling during ironing.

The mechanism of galling in an aluminum plate is that the ironing die is brought into direct contact with the surface of the aluminum alloy plate due to poor lubrication during ironing, and the aluminum alloy pieces and hard particles such as Al ₂ O _{3 form the} alloy plate. It is considered that it is caused by peeling from the surface and adhering to the ironing die, and the agglomerated mass rubbing the surface of the aluminum alloy plate. Therefore, various methods have been devised to suppress the occurrence of galling by improving lubrication as compared with the related art.

As to the lubricating oil to be applied, 1) as a pre-treatment for ironing, a lubricating oil stock solution is applied to an aluminum alloy plate to perform re-oiling treatment for improving lubricity. 2) Use various combinations of the composition ratio of the lubricating oil during ironing, and use a lubricating oil with an appropriate composition ratio that will not run out easily. 3) Adjust the roughness of the surface of the material plate to improve the oil retaining property by the unevenness of the surface of the plate. There is a method such as.

Further, it is also practiced to suppress the occurrence of galling by controlling the material characteristics such as the structure of the aluminum alloy plate. For example, AA3004 alloy is currently widely used for can body materials. One of the reasons is that it has relatively high strength, excellent formability, and relatively low work hardening during ironing. Although it can be said that it is excellent, a large amount of Al—Mn—Fe-based coarse crystallization compounds also exist, and this coarse crystallization compound exhibits solid lubricity, and due to the voids formed in the vicinity of the crystallization compound, the oil retaining property is improved. It is also one of the reasons why this alloy is adopted as a practical alloy because it is less likely to cause galling due to the effects such as improvement of the heat treatment and the effect of self-cleaning of the ironing die.

[0009]

As described above, various methods have been devised as a countermeasure against the galling, but the present situation is that they are not yet sufficient.

In the method using the lubricating oil, in the case of multi-stage processing in which ironing with a large degree of processing such as can forming is performed several times in succession, although the lubricating property is shown in the first processing, the lubricating oil is used as the processing progresses. Is peeled off and oil runs out.

A method of applying a solid lubricant to the surface of the plate instead of the lubricating oil has also been devised. However, although it is effective to process only once, in multi-step processing such as can forming, the lubricant applied in the first to second processing is stripped off, and the lubricant is applied in subsequent processing. There is a problem that shortage occurs and goring occurs.

Also, in the method of improving the material properties by devising the manufacturing conditions of the plate so as to have the characteristics such as the structure in which the galling is unlikely to occur, the manufacturing conditions for forming the specific structure become complicated and the cost becomes high. There are problems that the condition range is narrow and advanced technology is required for manufacturing. Further, when the degree of processing is large, sufficient galling resistance cannot be obtained only by improving the characteristics of the material.

[0013] Further, a uni-alloying method in which a can lid material and a can body material are made of the same alloy, which has been conventionally made of different alloy materials, has been studied from the viewpoint of productivity and recyclability. The limited methods of improving ironing workability prevent this uni-alloying. Therefore, there has been a demand for a method for improving ironing workability other than improving the alloy components and properties of the material itself.

Further, the conventional 3004 is used.
Even in the case of alloys, in the production method in which the cooling rate during casting is faster than in the commonly used DC casting method such as continuous casting and rolling, the crystallized compound diameter is small and the amount of solid solution of alloy components such as Mn is large. Therefore, although the strength is improved, work hardening is large and it becomes difficult to perform ironing as in the case of the 5000 series alloy, and galling is likely to occur.

In view of the above problems, the present invention improves the ironing workability by suppressing the occurrence of galling in the current aluminum alloy plate for a can body and the aluminum alloy plate such as a high-strength material which is currently poor in the ironing workability. The purpose is to supply a material suitable for a DI processed can body material suitable for high strength thinning.

[0016]

According to the present invention, a means for solving the problem is to embed a solid lubricant on the surface of a plate to improve the lubricity of the surface of the plate, thereby improving the workability of the plate, especially ironing. It is intended to improve workability and suppress the occurrence of goring.

According to the present invention, a solid lubricant having an average particle size of 0.1 to 50 μm is applied to a casting roll used for continuous casting and rolling, and the solid lubricant is continuously cast by using this roll for continuous casting and rolling. An area occupied by a solid lubricant having an average particle size of 0.1 to 50 μm on the surface of the final rolled plate by forming an initial solid lubricant layer by transferring, press-fitting and embedding it on the surface of the rolled plate, and then performing rolling. 20% rate
The method for producing an aluminum alloy continuous casting and rolling plate for forming, which is excellent in ironing workability, is characterized by the above.

[0018]

The function of the present invention will be described below.

As the solid lubricant to be used, those generally used may be used, but typical ones are molybdenum disulfide, tungsten disulfide, graphite (graphite),
Boron nitride, graphite fluoride (CF) _n , metal oxides (lead oxide, molybdenum oxide, zinc oxide, etc.), fluorides (calcium fluoride, barium fluoride, sodium fluoride, etc.),
Silicon nitride or a mixture of two or more kinds of these solid lubricants can be used.

The average particle size of the solid lubricant used is 0.1
It is 50 μm. If it is less than 0.1 μm, the coefficient of friction becomes large, and if it exceeds 50 μm, the load bearing performance deteriorates.

In order to obtain a good surface lubricating layer, it is necessary to transfer a sufficient amount of solid lubricant during continuous casting and rolling. For that purpose, for example, 20 to 4 having a higher concentration than usual is used.
A 0% colloidal solid lubricant aqueous solution may be applied to the casting roll by spraying, brushing, or using a coater roll. If the concentration is lower than this, a sufficient amount of the solid lubricant does not adhere, and if it is too high, there is a problem that the cooling effect of the molten metal by the casting rolls is obstructed and the casting and rolling conditions become unstable.

Conventionally, solid lubricants have been used as release agents for continuous casting and rolling, but they prevent adhesion of aluminum alloys to be cast and rolled to rolls, and the cast plate is easily peeled off from the casting rolls. It is for doing. Therefore, it is common to spray-coat a casting roll with an aqueous solution of a colloidal solid lubricant having a concentration of 10% or less. However, in the case of the present invention, since it is necessary to transfer and embed the solid lubricant on the plate surface, not just for the releasing action, it is appropriate to use an aqueous solution having a concentration of about 20 to 40%.

It is possible to directly supply the solid lubricant to the surface of the molten metal instead of applying it to the casting roll, but in the normally used continuous casting machine, the place where the lubricant supplying machine can be installed becomes extremely local because of the design. Technically difficult.

The area ratio of the plate surface of the solid lubricant at the end of continuous casting and rolling needs to be 20% or more, preferably 30% or more. If it is less than the above range, the area ratio of the solid lubricant on the final plate surface may not be 20% or more when the surface area of the plate is increased by the subsequent cold rolling. If it is 30% or more, even if the plate surface area is increased by cold rolling, the solid lubricant is simultaneously destroyed by cold rolling, and the number and area of the solid lubricant are increased by cleavage and peeling. The area ratio on the final plate can be 20% or more.

Further, during continuous casting and rolling, 5% or more, especially 10%
A casting method in which rolling is performed at a reduction rate of -20% is desirable. As a result, the solid lubricant is firmly embedded in the surface layer, and the amount of solid lubricant that falls off during cold rolling can be reduced.

By hot-rolling and cold-rolling the plate thus formed with the initial solid surface lubricating layer, a continuous cast rolled plate having an area ratio of solid lubricant of 20% or more in the final plate is obtained. Obtainable. Hot rolling may be performed as necessary, and heat treatment such as annealing may be performed before and after cold rolling as usual, and cold rolling may be performed twice or more. In the cold rolling, the surface of the plate may be supplemented with a solid lubricant for rolling.

The depth of the plate surface layer in which the solid lubricant is embedded may be determined according to the workability such as the plate thickness and ironing rate of the aluminum alloy plate, but is 0.1 to 1 from the plate surface.
A depth of 50 μm is suitable. If the solid lubricant is present only in the range of less than 0.1 μm, the amount is too small to produce the solid lubricating effect, and when it is embedded, it tends to be buried or peeled off conversely. In some cases, a sufficient lubrication effect cannot be obtained for the newly formed surface. That is, it is important that the solid lubricant is distributed to a depth of about one layer, and it is effective if it is embedded in the plate. Further, even if it is embedded to a depth of more than 150 μm, further improvement in performance cannot be expected, but especially when heavy working or a large number of workings are performed, even if the solid lubricant near the surface is taken away by the heavy working, the deep part will be replaced instead. Since the solid lubricant of (3) is exposed on the surface, it is preferable that the solid lubricant is deeply distributed.

In the present invention, it is important that a part of the solid lubricant is exposed on the surface of the plate. If the solid lubricant is completely buried inside the aluminum alloy plate, galling prevention and ironing are not performed. The effect of improving the sex is lost.

The mechanism of the occurrence of galling in the aluminum plate is (1) direct contact between the surface of the aluminum alloy plate and the ironing die due to poor lubrication such as oil film breakage during ironing, and aluminum alloy pieces sticking to the die.
(2) The hard particles of oxides such as Al ₂ O ₃ and MgO and the fine intermetallic compounds such as Al (Mn, Fe) Si formed on the surface of the aluminum alloy plate are peeled from the surface where they are adhered to the ironing die. It is believed that the coagulated lumps formed by doing so rub against the surface of the aluminum alloy plate.

On the other hand, in the aluminum alloy plate according to the present invention, the solid lubricant is embedded in the surface layer of the plate and a part of the solid lubricant is exposed on the plate surface. Reduces the frequency of direct contact with the aluminum alloy, reduces friction, and prevents the oxides, etc., formed on the surface of the aluminum alloy plate from being peeled off by the die.As a result, the aluminum alloy flakes, oxides, and intermetallic compounds coagulate in the die. It is possible to prevent wearing and prevent occurrence of goring.

In addition, in the multi-stage ironing, which involves a significant reduction in plate thickness and the formation of a new surface, the conventional simple coating of the solid lubricant reduces the lubrication ability during the machining, resulting in a sufficient effect. Although not obtained, according to the aluminum alloy plate of the present invention, since the solid lubricant is embedded in the plate surface, even if the plate thickness is remarkably reduced or a new surface is formed, the lubricant is not removed from the plate surface. Since it is not peeled off, a sufficient lubrication effect is obtained even in multi-step ironing, and no galling occurs.

The above-mentioned action of the present invention can be further improved by using it together with a mineral lubricating oil, a vegetable lubricating oil, a synthetic lubricating oil or a mixed lubricating oil thereof.

[0033]

EXAMPLES Examples of the present invention will be described. The aluminum alloy used as the test material is JISA3004, J
ISA5052 and JISA5182 were used. The alloy composition is shown in Table 1.

[0034]

[Table 1]

Aluminum alloy plates were prepared using the alloys having the components shown in Table 1. In the manufacturing process, a continuously cast plate having a plate thickness of 7 mm was obtained by continuous casting and rolling, and this was cold-rolled to 0.
A plate having a thickness of 75 mm, and then subjected to an intermediate annealing in which a heating rate of 20 ° C./sec, an reached temperature of 520 ° C., and a cooling rate of 20 ° C./sec without holding after reaching the annealing were performed in a continuous annealing furnace
Further, final cold rolling was performed to obtain a plate thickness of 0.30 mm.
The solid lubricant was applied as follows. (I) In continuous casting and rolling, a solid lubricant (shown in each table) in a colloidal state was applied to a casting roll and embedded in the plate surface layer. (II) A solid lubricant was applied to the surface of a plate prepared by the conventional continuous casting method immediately before the pulling test. (Use of a solid lubricant during continuous casting is applied only in an amount that acts as a release agent.) (III) Manufacturing by conventional continuous casting method. (When using solid lubricant during continuous casting, apply only an amount that acts as a release agent.)

A conventional example by the DC casting method was also prepared. The process was to obtain an ingot with a plate thickness of 500 mm by DC casting, hot rolling to a plate thickness of 3.5 mm, and then cold rolling to 0.75 mm, then intermediate annealing and final cold rolling under the same conditions as above. Then, a plate having a plate thickness of 0.30 mm was obtained.

Using this test material, the galling resistance was evaluated by a pull-out test. The shape of the test piece was 10 mm in width and 150 mm in length. Pulling speed is 500m
In / mm, 20% reduction in plate thickness, 2 times in succession, 1
A mineral oil-based lubricating oil was applied only for the first time. By visually observing the occurrence of goring, ○ = no occurrence of goring,
Evaluation was made in three grades: Δ = weak galling occurred, × = strong galling occurred.

[Example 1] Table 2 shows an example evaluated using conventional materials and molybdenum disulfide (MoS ₂ ) as a solid lubricant.

[0039]

[Table 2]

No. 1 in Table 2 is a 3004DC cast material that has been conventionally used as a can body material, and no galling occurred because the alloy characteristics were suitable for ironing.
No. 2 is a comparative example by the conventional continuous casting and rolling method. Since the solid lubricant is applied only as a mold release material, the area ratio is remarkably small at 2%, and sufficient lubricity cannot be obtained and galling occurs. Nos. 3, 4 and 5 are MoS ₂ as a solid lubricant in the example of the present invention made of a continuously cast rolled material of 3004 alloy.
Is used. In both cases, the first pull-out test was 2
At both times, no galling occurred and good ironing property was exhibited. No. 6 is the same as No. 2 solid lubricant MoS immediately before drawing into a continuously cast material sample without embedding solid lubricant.
_The test was carried out by applying No. 2, and the effect of the applied solid lubricant was obtained without the occurrence of galling in the first drawing, but the applied solid lubricant was stripped off by this drawing. Goring has occurred in the second time. [Example 2] Molybdenum disulfide (Mo) as a solid lubricant
Examples using a mixture of S ₂ ) and graphite are shown in Table 3.

[0041]

[Table 3]

Nos. 7 to 10 are 3004 as in the first embodiment.
A continuous cast rolled plate of an alloy was used, and a solid lubricant in which MoS ₂ having an average particle diameter of 5 μm and graphite were mixed in equal amounts was used. Nos. 7 and 8 are examples of the present invention, and showed good ironing property. On the other hand, in No. 9, the area ratio of the solid lubricant was less than 20%, and a slight effect was recognized in the first ironing, but strong galling occurred in the second ironing. Similarly, in No. 10 as well, since the area ratio is small, goring has occurred.

[Example 3] Table 4 shows the results of an example in which the solid lubricant was changed to boron nitride (BN) using a 5052 alloy which was not suitable for drawing and ironing conventionally.

[0044]

[Table 4]

Nos. 11, 12, and 13 are examples of the present invention,
It showed a good ironing property. On the other hand, in No. 14, since the average particle size of the solid lubricant was smaller than 0.1 μm, a sufficient lubricating effect was not obtained and galling occurred. No15
The area ratio of the solid lubricant is too small, and the galling is strongly generated. Further, No. 16 was obtained by applying the solid lubricant BN to the surface of the plate manufactured by the conventional method immediately before the drawing test, and the drawing was effective in the first drawing, but galling occurred in the second drawing. No17
Indicates the result of the plate manufactured by the conventional method, and the occurrence of galling was recognized from the first pull-out test.

[Example 4] 5182 aluminum alloy
Table 5 shows examples in which the solid lubricant is changed to graphite.

[0047]

[Table 5]

Nos. 18 and 19 are examples of the present invention, which showed good ironing property. On the other hand, in No. 20, the area ratio of the solid lubricant is too small to cause galling, and in No. 21, the average particle diameter of the solid lubricant is too small to cause galling. Nos. 22 and 23 are continuous casting and rolling plates manufactured by the conventional method, and all have galling. Even when graphite was applied immediately before the pull-out test as in No. 22, galling occurred in the second time.

[0049]

As described above in detail, according to the present invention, 3
Not limited to aluminum plates produced by the 004 series aluminum alloy DC casting method, even aluminum alloys having different metal structures such as rapidly solidified materials such as 3004 series continuously cast rolled materials,
Alternatively, even with an alloy system having poor ironing property such as 5000 series, the ironing property can be improved and the occurrence of galling can be eliminated. Further, since the adhesion of aluminum powder or the like to a tool such as a die is also reduced, it is possible to reduce the number of man-hours required for exchanging the die, screening the die, etc., and thus improving the workability. Further, it also has the effect of reducing the tool wear due to the deposits and extending the tool life.

Claims (1)

[Claims] 1. A continuous casting and rolling plate obtained by applying a solid lubricant having an average particle size of 0.1 to 50 μm to a casting roll used for continuous casting and rolling, and continuously casting and rolling using this roll. An initial solid lubricant layer is formed by transferring, press-fitting and embedding it on the surface of the steel sheet, followed by rolling, and an average particle size of 0.1 to 50 μm on the surface of the final rolled plate.
An area ratio of the solid lubricant of m is 20% or more, and a method for producing a continuously cast rolled aluminum alloy plate for forming, which is excellent in ironing workability.