JPH06346205A - Production of aluminum alloy sheet for drawing - Google Patents

Abstract

PURPOSE:To provide an Al alloy sheet excellent in deep drawability and earing ratio by subjecting an Al alloy having specified components to continuous casting, thereafter reheating it, subjecting it to hot rolling and subsequently executing rapid cooling, cold rolling and process annealing. CONSTITUTION:The componental compsn. of an aluminum alloy is constituted of a one contg., by weight, 0.1 to 1.5% Mn, <=0.7% Fe, <=0.3% S, <=0.25% Cu and <=0.25% Zn, and the balance Al with inevitable impurities. This alloy is subjected to continuous casting and is thereafter rapidly cooled to a room temp. at a rate at which precipitation does not occur. Then, it is reheated to a prescribed temp., is subjected to hot rolling and is rapidly cooled to a room temp. Next, cold rolling and process annealing are executed by the conventional method. In this way, the Al alloy sheet also good in surface roughening conditions can be produced.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy sheet for draw forming, and more specifically, for draw forming used as a material for aluminum food cans and beverage cans. The present invention relates to a method for manufacturing an aluminum alloy plate. [0002] In general, aluminum alloy sheets have extremely good draw formability. Therefore, as a material for food cans, beverage cans, etc., aluminum alloys have recently been used in place of steel and tin plates. There are many things going on. The use of this aluminum alloy is mainly for weight reduction. As a conventional method for producing an aluminum alloy sheet for forming, an ingot is cast by a DC casting method (semi-continuous casting method), and chamfering, soaking, hot rolling, cold rolling, annealing, etc. It is manufactured through the process of. The thus-produced ameminium alloy plate for draw forming has good draw formability and maintains a certain level of strength. However, recently, there has been a strong demand for improvement in productivity and a strong demand for cost reduction. For that reason, continuous casting and continuous rolling methods are used. A method of casting a cast plate having a plate thickness of about 4 to 25 mm from molten alloy by applying it, then performing continuous hot rolling, and omitting chamfering and homogenizing heat treatment is being studied. However, in this method, since direct rolling is performed at the hot rolling temperature without cooling to room temperature even after casting, it is difficult to generate a driving force for causing sufficient precipitation and the density of the precipitate is lowered. To do. Therefore, when annealing is performed after cold rolling, the pinning effect of the crystal grains due to the precipitates cannot be sufficiently exerted, and the recrystallized grains become abnormally coarse, resulting in rough surface during drawing. There is a problem that it is easy to do. SUMMARY OF THE INVENTION As described above, the present invention solves the problems of the conventional manufacturing method for continuously casting and rolling an aluminum alloy sheet excellent in draw forming. For this reason, the present inventors have conducted diligent research, and as a result of repeated studies, after rapid cooling of the aluminum alloy cast plate obtained by continuous casting, the solid solution amount is reduced by hot rolling, and precipitates are It was found that the density becomes fine and the surface roughness at the time of forming is improved, and by adjusting the manufacturing conditions based on this knowledge, a method for manufacturing an aluminum alloy sheet having excellent draw formability was developed. The features of the method for producing an aluminum alloy sheet for drawing according to the present invention are as follows:
Mn 0.1-1.5 wt%, Mg 0.8-5.0 wt
%, Fe 0.7 wt% or less, S 0.3 wt% or less, C
u After continuously casting an aluminum alloy containing 0.25 wt% or less and Zn 0.25 wt% or less and the balance Al and unavoidable impurities, it is rapidly cooled to room temperature at a rate at which precipitation does not occur, and a predetermined temperature is reached. It is to re-heat up to step 1, perform hot rolling, then rapidly cool to room temperature, and then perform cold rolling and intermediate annealing by a usual method. The method for producing the aluminum alloy sheet for drawing according to the present invention will be described in detail below. First, in the method for producing an aluminum alloy sheet for draw forming according to the present invention, the content components and component ratios of the aluminum alloy used will be described. Mn improves strength by solid solution strengthening,
It is an element that improves the ironing workability due to the l-Fe-Mn-based crystallized substance, and if the content is less than 0.1 wt%, the strength improving effect due to solid solution strengthening cannot be expected, and
If the content exceeds 1.5 wt%, the strength becomes too high and the formability deteriorates. Therefore, the Mn content is 0.1 to 1.
It is set to 5 wt%. Mg is an element for improving the strength, and in particular, exhibits the precipitation effect by the Al-Cu-Mg system precipitates,
It is effective in strengthening hardness, and its effect is small when the content is less than 0.8 wt%, and when it exceeds 5.0 wt%, the strength becomes too high and the moldability is deteriorated. Therefore, the Mg content is 0.8 to 5.0 wt%. Fe, Si, Cu and Zn are elements that improve the strength, and have an Fe content of 0.7 wt% and Si.
Content of 0.3wt%, Cu content of 0.25wt%, Z
If the content of n exceeds 0.25 wt%, a coarse insoluble compound is inevitably generated, resulting in deterioration of moldability. Therefore, the Fe content is 0.7 wt% or less, the Si content is 0.3 wt% or less, and the Cu content is 0.2 wt% or less.
The Zn content is 5 wt% or less, and the Zn content is 0.25 wt% or less. Next, the manufacturing conditions in the manufacturing method of the aluminum alloy sheet for drawing according to the present invention will be described. In the method for producing an aluminum alloy sheet for draw forming according to the present invention, the aluminum alloy is melted and then continuously cast. In this case, the aluminum alloy is made to have a dendrite branch interval of 60 μm or less. . Examples of the continuous casting method include a water-cooled continuous casting method, a twin roll continuous casting method (Hunter Engineering Co., Ltd.), a belt type continuous casting method (Hatherley Co., Ltd.), and a block type continuous casting method (Arswiss Co., Ltd.). By thus setting the dendrite spacing of the aluminum alloy to be 60 μm or less, the contained element is dissolved in supersaturation to form a solid solution, and the crystallized product can be made finer. The size of the precipitate that precipitates during heating becomes fine. If the dendrite branch spacing exceeds 60 μm, the supersaturated solid solution effect and the refinement effect cannot be sufficiently exerted. Therefore, the dendrite branch spacing is 60μ
m or less. The dendrite branch spacing d (μm) is
It is related to the cooling rate T (° C / s) during solidification, and the relational expression in the aluminum alloy used in the method for producing an aluminum alloy sheet for drawing according to the present invention is represented by d = 48.9T ^-0.43. . Therefore, in order to set the dendrite branch spacing to 60 μm or less, from this relational expression, the cooling rate at the time of solidification is set to 0.
It should be 6 ° C / s or more. Further, as a means for setting the cooling rate at the time of solidification to 0.6 ° C./s or more, the ingot size (particularly the thickness) is made small, or the material of the mold is made to have good thermal conductivity. Alternatively, the amount of cooling water may be increased. By rapidly cooling the continuously cast aluminum alloy ingot to room temperature at a rate at which precipitation does not occur, the driving force for precipitation increases. Further, the thermal equilibrium atomic vacancies existing in the high temperature region generate lattice defects such as dislocation loops and vacancies as secondary defects during the rapid cooling, and the nucleation sites of the precipitates increase. From these,
During the subsequent reheating, high-density fine precipitates are deposited. The rapid cooling rate of the aluminum alloy ingot after continuous casting to room temperature is optimally set to 50 ° C./s or more, and the rate at which precipitation occurs in the continuously cast aluminum alloy ingot (50 ° C./s (less than s), when rapidly cooled to room temperature and then reheated, the driving force for precipitation is small and the nucleation sites of the precipitate are small, so the precipitate has low density. Therefore, the continuously cast aluminum alloy ingot is rapidly cooled to room temperature and then reheated at a rate (50 ° C./s or more) at which precipitation does not occur. The temperature increase rate of this reheating depends on the size of the ingot and the rolling temperature, but it is optimal to be 100 to 400 ° C./m. Heating is not possible, and if the temperature exceeds 400 ° C./m, the lattice defect, which becomes the nucleation site of the precipitate, disappears before the precipitation occurs, so the precipitate has a low density. Further, rapid cooling after hot rolling is a step necessary for suppressing coarsening of precipitates and preventing rough skin, and the rapid cooling rate is optimally 10 ° C./s or more. EXAMPLES Examples of the method for producing an aluminum alloy sheet for drawing according to the present invention will be described together with comparative examples. Example 1 A non-metallic inclusion was removed by passing a molten metal obtained by melting an aluminum alloy having the contained elements and component ratios shown in Table 1 through a filter,
Continuous casting is performed to a thickness of 7 mm. At this time,
The dendrite branch spacing was about 40 μm. After casting, after cooling to room temperature at a cooling rate of 60 ° C./s, it was reheated to a temperature of 450 ° C. at a temperature rising rate of 30 ° C./m to a rolling start temperature of 45 mm up to a thickness of 3 mm.
Perform hot rolling at 0 ℃, rolling end temperature 340 ℃, 20 ℃
Cooling was performed at a cooling rate of / s. After that, rough annealing was performed at a temperature of 400 ° C. for 1 hour, cold rolling was performed to a thickness of 1 mm, and rapid heating was performed at a temperature of 530 ° C. for 1 minute, followed by rapid cooling. Cold rolling was performed to manufacture an aluminum alloy plate having a thickness of 0.3 mm. Regarding the manufactured aluminum alloy plate,
The deep drawability, ear ratio, and rough skin conditions were tested, and the results are shown in Table 2. It can be seen from Table 2 that the aluminum alloy sheet produced by the method for producing an aluminum alloy sheet for draw forming according to the present invention is far more excellent in deep drawability, ear ratio, and rough skin than the comparative example. . [Table 1] [Table 2] Example 2 A molten metal obtained by melting an aluminum alloy having the contained elements and component ratios shown in Table 3 was passed through a filter to remove non-metallic inclusions,
Continuous casting is performed to a thickness of 7 mm. At this time,
The dendrite arm spacing is shown in Table 3. After continuous casting, the aluminum alloy ingots are shown in Table 3.
After cooling to room temperature at the cooling rate shown in Table 3, reheating was performed at the temperature rising rate shown in Table 3 to obtain a rolling start temperature of 450 ° C.
The thickness was 3 mm by hot rolling at a rolling finish temperature of 340 ° C., and cooling was performed at the cooling rate shown in Table 3. After that, rough annealing was performed at a temperature of 400 ° C. for 1 hour, cold rolling was performed to a thickness of 1 mm, and the temperature was maintained at 530 ° C. for 1 minute by rapid heating, followed by rapid cooling, and then cold rolling. Rolling was performed to produce an aluminum alloy plate having a thickness of 0.3 mm. The aluminum alloy sheet was tested for deep drawability, ear ratio, and rough skin. The results are shown in Table 4. It can be seen from Table 4 that the aluminum alloy sheet produced by the method for producing an aluminum alloy sheet for drawing according to the present invention is excellent in deep drawability and ear ratio, and is also excellent in rough skin condition. Recognize. [Table 3] [Table 4] As described above, since the method for producing an aluminum alloy sheet for draw forming according to the present invention has the above-mentioned constitution, it is excellent in deep drawability and ear ratio, and the rough skin condition. Also has the effect of being good.

Claims (1)

Claims Mn 0.1-1.5 wt%, Mg 0.8-5.0 wt
%, Fe 0.7 wt% or less, S 0.3 wt% or less, Cu
After continuously casting an aluminum alloy containing 0.25 wt% or less and Zn 0.25 wt% or less and the balance Al and unavoidable impurities, it is rapidly cooled to room temperature at a rate at which precipitation does not occur and reaches a predetermined temperature. The method for producing an aluminum alloy sheet for drawing according to claim 1, wherein the aluminum alloy sheet for draw forming is characterized in that the aluminum alloy sheet is subjected to hot-rolling, hot-rolling, and then rapidly cooling to room temperature, and then cold-rolling and intermediate-annealing by a usual method.