JPH0247244A - Production of rolled sheet of aluminum-base alloy - Google Patents

Abstract

PURPOSE:To prevent the occurrence of fluctuations in sheet thickness at the time of cold rolling by subjecting an ingot of Al-Mn-Mg alloy to soaking treatment and to hot rolling into a coiled state and then applying annealing to the above coil under specific conditions determined according to treatment temp. and coil temp. CONSTITUTION:An ingot of Al alloy containing Mn and Mg by >=0.3wt.%, respectively, is subjected to soaking treatment and then hot-rolled into a coiled state. The coil is annealed at a temp. in the range represented by -0.4TH +530<=Tmin<=400 and Tmax-Tmin<=200-0.5Tmin, where TH means soaking treatment temp. and Tmax and Tmin mean the values of the maximum temp. and the minimum temp. in the coil at the point of time when the maximum temp. of the coil is reached at the time ot annealing, respectively. After the above annealing, cold rolling is applied to the above coil to form the final product. By this method, the rolled sheet ot Al-base alloy can be produced without causing deterioration in quality, such as fluctuations in sheet thickness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is aimed at reducing the periodicity that occurs during cold rolling due to hot-rolled coil annealing when manufacturing cambodies and closures by rolling A1-based alloys. The present invention relates to a method of manufacturing an A1-based alloy rolled plate that prevents plate thickness fluctuations.

[Problems to be solved by conventional technology and invention] Normally A
1-Mn-Mg alloy contains Mn-based fine precipitates and solid solution Mg.
It is generally difficult to recrystallize because of its large recrystallization inhibiting effect. In addition, plates made of these alloys that have been hot rolled have reduced strain accumulation due to dynamic recovery during hot rolling.

Therefore, A, e-Mn-Mg alloys that are hot-rolled and wound into a coil shape (hereinafter referred to as hot-rolled coils) are difficult to recrystallize during the next annealing process, so they are usually heated at a relatively high temperature ( It was often annealed at a temperature of 350 to 400°C. Even when annealing under these conditions, if the hot-rolled coil is of the size commonly used in the past, the temperature distribution within the coil is small, so there will be no problem of plate thickness variation during the next cold rolling process. There wasn't.

However, as ingots have become larger in order to improve yield and productivity, the diameter of hot-rolled coils has recently become larger. For such a large-sized coil, the temperature difference within the coil becomes large under conventional annealing conditions, resulting in the above-mentioned plate thickness variation. For example JI330
04 alloy (1,0~1.5 wt%M n -0,8~
1.3 wt%MCJ-A1) and JI33105 alloy (
0,30~0.8 wt%Mn-0,20~0.8 Growth t%Mg-/Mri etc. A, g-M After hot rolling the n-Mg alloy into a hot-rolled coil If annealing is performed in a batch-type atmosphere-controlled furnace (CA furnace) without cold rolling, and cold rolling is performed in the next process, periodic sheet thickness fluctuations will occur during the cold rolling. There are things to do. This problem is more likely to occur as the size of the ingot is increased and the diameter of the coil becomes larger, leading to a decline in product quality such as plate thickness accuracy, and hindering the increase in size of the ingot.

[Means to solve the problem]

Therefore, the present inventor investigated and researched the cause of the above-mentioned plate thickness variation, and found that the mechanism is as shown below.

(1) Moisture in the coolant remains on the surface of the hot rolled coil during hot rolling.

(2) During annealing of the hot-rolled coil, the surface of the material reacts with residual moisture to form an oxide film.

(3) The thickness of the facial film changes due to the temperature difference within the coil during annealing.

(4) Due to the difference in M film thickness, the coefficient of friction during cold rolling changes, resulting in fluctuations in plate thickness.

In the case of ZARANI/1-Mn-Mg alloy, hot-rolled sheets have a small working degree and the recrystallization retardation force due to Mn-based fine precipitates and solid solution Mg is large, so in order to stably complete recrystallization, The annealing temperature is often set high, and therefore the Mg in the composition is easily oxidized, so AJ7
-Mn-Mg hot-rolled sheets tend to undergo surface oxidation during annealing.

As the coil becomes larger, the flow of furnace air changes in a typical flow air furnace, and the temperature difference within the coil tends to increase. For example, when annealing is performed at 380℃ for 2 hours, under conventional conditions, a coil weighing 5 tons will have a maximum temperature difference of 5 to 10℃, whereas a coil weighing 110 tons will have a difference of 5 to 10℃. It reaches 10-30℃.

As a result, variations in plate thickness due to variations in temperature distribution during annealing, which were not a problem with conventionally sized coils, occur extremely frequently with large coils, reducing productivity and yield. It was revealed.

As a result of a rough study, the present invention has developed an A1-based alloy rolled plate that prevents the occurrence of periodic sheet thickness fluctuations caused by hot-rolled coil annealing during cold rolling in an A1-based alloy even when a large ingot is used. This is the result of the decision on how to make it.

That is, the present invention relates to a manufacturing method in which an aluminum alloy ingot containing 0.3 wt% or more of Mn and Mg each is soaked and then hot rolled to form a coil, annealed, and then cold rolled as shown by the following formula. It is characterized by being annealed in a temperature range.

-0,4Tl-1+530≦Tnun≦400 ・(
1) Tmax Tnun≦200-0.57rmn
...(2) However, TH: Soaking temperature ("C) T7: Value of the maximum temperature inside the coil when the maximum temperature of the coil is reached during annealing (℃) Tnun: The value of the maximum temperature inside the coil when the maximum temperature of the coil is reached during annealing The value of the lowest temperature ("C) [Function] Among the A1-Mn-Mg alloys mentioned above, for alloys containing less than 0.3 wt% of Mn or Mg, plate thickness fluctuations due to surface oxidation are unlikely to occur, and For products that are cold rolled before annealing during the process, the moisture on the surface of the material is replaced with cold rolling oil, the degree of work increases, and the recrystallization temperature decreases, so thickness fluctuations are less likely to occur. In this case, deterioration in quality due to plate thickness accuracy is not a problem.

Next, the reason why the temperature range of the annealing performed before cold rolling is limited as shown in the above equations (1) and (2) is as follows.

That is, first, in equation (1), Thmn is -0,4Th+
This is because if it is less than 530, recrystallization may not be completed and the purpose of annealing cannot be achieved. King □ again. is 40
If the temperature exceeds 0° C., the oxide film becomes extremely thick, causing problems such as discoloration.

The soaking treatment applied to the ingot is important for controlling the morphology and distribution density of Mn-based precipitates; the higher the temperature TH, the coarser the precipitates will be and the more likely they will be recrystallized during annealing. Temperature drops. Equation (1) shows that when TH is increased, recrystallization occurs even if T□In is low, and conversely, when T)I is low, it becomes necessary to increase T□1o. .

Next, Trmx Tm1n expressed by equation (2) is the temperature distribution within the coil, and if this is large, a difference in oxide film thickness will occur, which will cause plate thickness variation during cold rolling.

However, if the temperature of the entire coil is low, the oxide film will grow less, and plate thickness variations will be less likely to occur even with a relatively large temperature difference. Therefore, the condition of equation (2) is required.

The following can be seen from these conditions. That is, during annealing, if the difference between the ambient temperature and the coil temperature is reduced, Tmax T
Although nnn can be made smaller, in this case, the annealing time becomes extremely long. Therefore, in the case of a large coil where TIT, -T□1o tends to be large, it is operationally advantageous to perform a high temperature soaking treatment commensurate with the size of the coil to lower Tm1n. On the other hand, in a small coil with a small Trmx Tm+n, it is not necessary to strictly control the soaking temperature and the atmosphere during annealing. As described above, based on the conditions of the present invention, the conditions that are most convenient for operation can be selected for any size coil, and variations in plate thickness can be suppressed while reducing costs and improving productivity.

〔Example〕

An A1-based alloy ingot having the composition shown in Table 1 was produced by a conventional method, and subjected to soaking treatment and hot rolling at the temperature shown in Table 2,
Plate thickness 2.4M and coil weight 6tOn or 10ton
After that, each hot rolled coil was annealed under the conditions shown in Table 2, and then cold rolled to obtain a thin plate with a final thickness of 0.35 m.

For these hot-rolled coils after annealing, the plate thickness variation range after one pass of cold rolling was investigated, and the values were classified as follows, and each was evaluated using the following symbols and listed in Table 2.

O・・・・・・Para±10μm Δ・・・・・・
・・・Things between ±10 and ±15μm×・・・・・・・・・
The performance of these thin plates as products was investigated, and the results are also listed in Table 2.

Of the manufacturing methods in Table 2, TH-600°C
The range of annealing conditions for the method of the present invention expressed by equations (1) and (2) is indicated by diagonal lines in FIG. According to FIG. 1, it can be seen that the methods A and B of the present invention are within the condition range of the method of the present invention, and the comparative methods F and G are outside the range.

Similarly, when T = 550°C, the range of annealing conditions of the present invention method expressed by equations (1) and (2) is
It is indicated by diagonal lines in the figure. According to FIG. 2, it can be seen that methods C, D, and E of the present invention are within the range of the method of the present invention, and comparative method H is outside the range.

The following describes each manufacturing method shown in Tables 1 and 2, and the results of plate thickness variation and product performance.

First, method A of the present invention is a method in which a large coil is soaked at 600°C, and the temperature difference between the atmosphere during annealing and the coil is reduced to suppress plate thickness variation.Although the annealing time is slightly longer, the plate thickness variation width is reduced. It can be seen that the final product has good strength and selvage.

Next, in method B of the present invention, a large coil is soaked at 600°C, and by utilizing this high temperature soaking (TH-600°C), the TmI during annealing is
o is set low and the annealing time is shortened.
Although the temperature difference inside the coil is large, the plate thickness variation and product performance are good.

In addition, in method C of the present invention, a large coil is soaked at 550°C, and the T
Although the m and o@ stage settings and the annealing time are slightly longer, both plate thickness variation and product performance are excellent.

In addition, in the method of the present invention, a relatively small coil is soaked at 550℃, and because the coil is relatively small, the temperature difference inside the coil during annealing is small, so plate thickness variation and product performance are excellent. .

Roughly speaking, method E of the present invention also involves soaking a relatively small coil at 550°C and raising the ambient temperature during annealing by taking advantage of the characteristics of the relatively small size. Thickness variation is maintained well and product performance is also excellent.

On the other hand, in Comparative Method F, a large coil was soaked at 600°C, but since the large coil was used, the temperature difference within the coil during annealing became large, resulting in plate thickness variation.

In Comparative Method G, a large coil was soaked at 600° C. to reduce the temperature difference between the annealing atmosphere and the coil, but the annealing temperature itself was set high, resulting in large variations in plate thickness.

Roughly Comparative Method H is a method in which a large coil is soaked at 550℃, but Tm+n is the soaking temperature (TH=550
℃), the recrystallization was not completed and the strength became excessive, resulting in a large selvage rate and poor performance.

〔Effect of the invention〕

As described above, according to the present invention, rolled sheets of A1-based alloy can be manufactured under manufacturing conditions according to the coil size without causing quality defects such as sheet thickness variations, and excellent productivity and cost reduction can be achieved. This has a remarkable industrial effect.

[Brief explanation of the drawing]

Figure 1 is a hatched line diagram showing the range of annealing conditions according to the present invention when TH = 800°C, and Figure 2 is a diagram showing the range of annealing conditions according to the present invention when TH = 800°C.
FIG. 2 is a diagram in which the range of annealing conditions according to the present invention method at 0° C. is indicated by diagonal lines. Tmax - Tmin (0C) Tmax - Tmin (0C)

Claims (1)

[Claims] (1) In a manufacturing method in which an aluminum alloy ingot containing 0.3 wt% or more of Mn and Mg each is soaked, hot rolled to form a coil, annealed, and then cold rolled at a temperature expressed by the following formula: A method for manufacturing an aluminum-based alloy rolled plate, characterized by annealing in a range. −0.4T_H+530≦T_m_i_n≦400 T_m_a_x−T_m_i_n≦200−0.5T_
m_i_n However, T_H: Soaking temperature (℃) T_m_a_x: Value of the maximum temperature inside the coil when the maximum temperature of the coil is reached during annealing (℃) T_m_i_n: Value of the minimum temperature inside the coil when the maximum temperature of the coil is reached during annealing ( ℃)