JPS6289852A - Manufacture of aluminum alloy plate having superior burning hardenability - Google Patents

Abstract

PURPOSE:To obtain an Al alloy plate having superior formability and burning hardenability by rolling and heat treating an Al alloy contg. Mg, Si, Cu and Ti, B or Mn under prescribed conditions. CONSTITUTION:An Al alloy contg. by weight, 0.4-1.5% Mg, 0.3-1.5% Si, 0.2-0.8% Cu and one or more among 0.005-0.1% Ti, 0.0005-0.03% B and <=0.8% Mn is manufactured by melting. An ingot of the alloy is homogenized at a temp. below the burning temp., hot rolled and cold rolled to obtain a plate of a desired thickness. This plate is refined by rapid heating to 430-580 deg.C at >=100 deg.C/min heating rate. It is then held at the temp. for >=3sec and rapidly cooled to 100 deg.C at >300 deg.C/min cooling rate. After the heat treatment is finished, the plate is finally heat treated at 40-120 deg.C for 8-36hr within 72hr.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an aluminum alloy plate having excellent bake hardenability, and more specifically, to an aluminum alloy plate having excellent formability and
Paint baking after forming process relates to a method for manufacturing aluminum alloy plates that have excellent baking hardenability due to heating over time.

[Prior Art] Conventionally, in order to maintain the strength of coatings applied to aluminum alloy materials used for automobile parts and ponds, heating (baking) is performed after coating.
At the same time, this heating is used to improve the strength of aluminum alloy materials.

As this aluminum alloy material, 6009.601
6009.6010 had the effect of improving strength because the coating film was baked at a high temperature of 200° C. and held for 60 to 90 minutes for a long time.

However, recently, in order to save energy and reduce costs during baking, baking temperatures have been lowered.
Moreover, there is a tendency to shorten the heating time.

For example, in Japanese Patent Publication No. 59-039499 and Japanese Patent Publication No. 50-001910, Al-Mg-9i-C
In U-based alloys, after being left at room temperature after heat treatment, 20
The strength is improved by baking at a high temperature for 60 minutes at a temperature of 0℃, but the strength is increased by baking at a temperature of 175℃.
By baking at a low temperature for 0 minutes for a short time, we can hardly expect any improvement in strength, and even if there is, it will only increase by 2 kg/et.
There is no effect with an increase of about a2.

In addition, in the "Aluminum Alloy Plate with Excellent Formability and Bake Hardenability and Method for Producing the Same", which the present inventor has previously completed, it is possible to lower the temperature to 200°C for 30 minutes, which is a short period of time. was completed, but after tempering treatment 3
After being left at room temperature for more than a day, baking at a low temperature for 30 minutes at a temperature of 175° C. improves the strength only slightly and has little effect.

In order to reduce the thickness of the plate, reduce the weight of the product, and reduce the cost of painting and baking, there is a strong demand for aluminum alloy plates that can be baked at low temperatures for a short time to improve strength and have excellent formability.

1 Problems to be Solved by the Invention 1 As explained above, the present invention has been made in view of various problems in conventional bake hardening of aluminum alloy plates, and is the result of intensive research by the inventor. , has the effect of improving strength by holding high temperature for 60 to 90 minutes at a high temperature of 200 ° C, which has been done until now, by heating for a long time,
In addition, we developed a method for producing aluminum alloy sheets that have excellent formability and bake hardenability, resulting in improved strength by short-time baking at a low temperature of 175°C for 30 minutes. .

[Means for Solving the Problems] The method for producing an aluminum alloy plate with excellent bake hardenability according to the present invention is characterized in that Mg 0.4 to 1.5 w.
t%, Si 0.3-1.5wt%, Cu 0.2-0
．． 8 wt%, furthermore, T i 0.005 to 0.1 wt%, B 0.0005
~0.03wt%, Mn 0.8wt% or less, Cr 0
．． 4wt% or less, Fe 0.5wt%, Zr 0.2w
Al-Mg-8, which contains one or more selected from t% or less and V001wt% or less, and contains 0.2wt% or less of unavoidable impurities, with the remainder substantially consisting of Al.
The i-Cu base alloy ingot was subjected to normal homogenization treatment at a temperature below the burning temperature, hot rolled and cold rolled to a desired thickness, and heated at a heating rate of 100 as tempering treatment.
After rapidly heating to 480 to 580°C at a rate of 480 to 580°C at a rate of 100°C/min or more, and maintaining the temperature in this temperature range for 3 seconds or more, heat treatment is performed to rapidly cool the temperature to 100°C at a rate of 300°C/min or more. 8~ at a temperature of 40~120℃ within hours
A final heat treatment is performed for 36 hours.

The method for manufacturing an aluminum alloy plate with excellent bake hardenability according to the present invention will be described in detail below.

First, the components and component ratios of the aluminum alloy used in the method of manufacturing an aluminum alloy plate with excellent bake hardenability according to the present invention will be explained.

Mg1. It is an element that imparts reinforcement in cooperation with tSi,
If the content is less than 0.4 wt%, the strength will be low, and 1.
If the content exceeds 5wL%, moldability will deteriorate.

Therefore, in order to achieve a balance between formability, strength, and strength improvement by baking, the Mg content should be 0.4 to 1.5.
Let it be wt%.

Si is an element that imparts reinforcement in cooperation with Mg, and if the content is less than 34%, the strength is low;
If the content exceeds wt%, moldability will deteriorate.

Therefore, in order to achieve a balance between formability, strength, and improvement in hard deterioration due to baking, the Si content should be set at 0.3 to 1.5.
Let it be u+t%.

Cu is an element that increases strength and strength improvement by baking in proportion to its content, but it is also an element that reduces corrosion resistance, and when the content is 0.
If it is less than 2u+t%, the corrosion resistance is good, but the strength and strength improvement effect by baking are small, and the
If the content exceeds Illt%, the effect of improving the strength and the strength by baking is large, but the corrosion resistance and moldability are reduced. Therefore, the Cu content is 0.2-0.8u+
It is assumed to be t%.

TI is an element that makes the crystal grains of the ingot fine and improves formability.If the content is less than 0.005 wt%, this effect will be small, and if the content exceeds 0.1111 t%. This forms coarse crystallized substances and reduces moldability. Therefore, the Ti content is 0.005 to 0.1ust
%.

Like T1, B is an element that refines the crystal grains of the ingot and improves its formability, and if the content is less than 0.0005%, this effect will be small, and if the content exceeds 0.03wt%. If it is contained, coarse crystallized substances will be formed and the moldability will be deteriorated. Therefore, the B content is 0.0005-0.03
Let it be iuL%.

Note that Ti and rjB are desirably contained in an Al Ti-B intermediate alloy or an Al-Ti intermediate alloy and an Al-B intermediate alloy.

Mn, Cr, Zr, and V have the effect of improving strength, but when their content increases, they produce coarse crystallized products and reduce formability, while Fe has a small strength-improving effect and produces coarse crystallized products. This reduces moldability. Therefore, from a balance between strength improvement and formability, the Mn content should be 0.8Illt% or less, and the Cr content should be 0.8Illt% or less.
Content is 0.4u+t% or less, Fe content is 0.5d%
Below, the Zr content is 0.2 wt% or less, and the ■ content is 0.
ht% or less, and one or more selected from these are preferably included.

In particular, in order to maintain formability and bake hardenability, Mn
, Cr, Zr, V, Fe alone have a content of 0, 1u+t
% or less, or the total amount of Mn+Cr+Zr+V is preferably controlled to be 0.2% or less.

The unavoidable impurities may be contained alone in an amount of 0.2 wt % to the extent that they do not impair bake hardenability and formability.

In addition, in the method of manufacturing an aluminum alloy plate with excellent bake hardenability according to the present invention, the size of the crystallized material affects the formability, and if the long side length of the crystallized material exceeds 1311 m, the formability will deteriorate. Therefore, if both bake hardenability and formability are desired, the longest side length of the crystallized product after final heat treatment is]
, 3+++m or less.

Next, heat treatment in the method for producing an aluminum alloy plate with excellent bake hardenability according to the present invention will be explained.

The homogenization treatment of aluminum alloy ingots with the above-mentioned components and component ratios has a small effect on improving strength during baking at low temperatures and short periods of time, so it is best to perform it at a temperature below the burning temperature. sex,
Composition with bake hardenability (Mn, Cr, Zr, V and Fe alone are 0.11% or less, IIL% or Mn+Cr
The total amount of +Zr+V is controlled to 0.2 wt% or less. )
In the homogenization process, the heating rate to the target temperature is 200℃
/hour or less, or a multi-stage homogenization process of two or more stages may be performed.

Next, hot rolling and cold rolling are performed.
These conditions do not need to be particularly limited because the effect on bake hardenability is small, as in the case of homogenization. Further, rough annealing and intermediate annealing may be performed after hot rolling.

Thermal treatment is a treatment that improves material strength, high formability, and strength after baking by performing rapid heating at high temperature for a short time, followed by rapid cooling.
It is rapidly heated to a high temperature of 480 to 580°C at a heating rate of 100°C/min or more and held at this temperature for 3 seconds or more,
If the heating temperature is less than 4180°C, the strength of the material and the strength after baking will be low, and if the heating temperature exceeds 590°C, burning will occur and the moldability will deteriorate. In addition, 4
At a heating temperature of less than 80° C., if the heating time is held for 3 seconds or less, the strength after baking will not improve much, but if the heating time is held for 30 minutes, the strength after baking will improve. Therefore, in order to improve the strength after baking, it is better to hold it for a long time, and in order to have both moldability and baking properties, it is recommended to hold it for a long time.
It is preferable to set it to about 0 seconds.

Next, the cooling rate up to 150°C is rapidly cooled at a rate of 300°C/min or more;
If the cooling rate is less than 300°C/min, the moldability will decrease and the strength after baking will not improve much, and if the cooling rate to 100°C is 300°C/min or more, the moldability and strength after baking will improve significantly. Become.

Therefore, the tempering treatment is performed at a heating rate of 100°C/min or higher at 48°C.
It is rapidly heated to a temperature of 0 to 580°C, held for 3 seconds or more, and cooled to 100°C at a rate of 300°C/min or more.

By performing a final heat treatment following this tempering treatment, it is possible to improve the strength by holding the temperature at 200°C for 60 minutes, which is different from the conventional high-temperature and long-time baking conditions. , 175°C for 30 minutes) can also have the effect of improving strength.

That is, after tempering treatment, it is heated to a temperature of 40 to 120 degrees Celsius and held at this temperature for 8 to 36 hours, regardless of the heating rate and cooling rate, within 72 hours, but if the temperature is less than 40 degrees Celsius, molding Although baking at a high temperature of 200°C for 60 minutes has the effect of improving strength, the effect of baking at a low temperature and short time, which is traditionally low, has a small strength improvement effect. If it exceeds this, although it has the effect of improving the strength at a conventional high temperature for a long time and at a lower temperature for a short time than a conventional one, it deteriorates formability.

Regarding this holding time, if the holding time is less than 4 hours, there is an effect of improving the strength by baking at high temperature for a long time, but the effect of improving the strength by baking at low temperature for a short time is small, and if it exceeds 48 hours, the moldability decreases and the short time at low temperature is The strength improvement effect of baking is small.

Therefore, the final heat treatment after the tempering treatment is carried out at a temperature of 40 to 120° C. for 8 to 36 hours within 72 hours after the tempering treatment.

Note that when strain correction is performed using a leveler, skin pass, etc. after the final heat treatment, it is desirable that the processing rate be 1.5% or less in order to prevent deterioration in formability.

[Example 1] An example of the method for manufacturing an aluminum alloy plate with excellent bake hardenability according to the present invention will be described.

Example 1 An aluminum alloy having the ingredients and proportions shown in Table 1 was melted and cast in a conventional manner, and the ingot was then placed face to face.
After homogenization treatment, which was maintained at a heating temperature of 530°C for 4 hours at a heating rate of 40°C/hour, hot rolling and cold rolling were performed to obtain a 1.0+am thick plate, which was then heated at a heating rate of 200°C/hour.
The final step is to hold at a temperature of 550°C for 10 seconds, cool down to 150°C at a cooling rate of 800°C/min, then leave at room temperature for 1 day, and hold at a temperature of 70°C for 24 hours. Characteristics of the alloy produced by the method for producing an aluminum alloy plate with excellent bake hardenability according to the present invention after heat treatment and standing at room temperature for 30 days, and comparative alloys, and temperature at 200°C under conventional baking conditions Table 2 shows the yield strength after holding for 60 minutes at a temperature of 175° C. and for 30 minutes at a temperature of 175° C. under conventional low temperature short-time baking conditions.

As is clear from Table 2, the alloys Nos. 1 to 12 manufactured by the method of manufacturing an aluminum alloy plate with excellent bake hardenability according to the present invention are the comparative alloys Nos. 1 to 12.
- Excellent strength and formability compared to No. 8, and in addition to the conventional bake hardenability at high temperature for a long time (held at a temperature of 200"C for 60 minutes), it has a low temperature that is held at a temperature of 175 degrees Celsius for 30 minutes. It can be seen that this is a well-balanced material that has short-term bake hardenability.

Comparative alloy No. 1, which has a low content of Mg, Si, and Cu, shows little improvement in strength and strength due to baking, and comparative alloy No. 1, which has a high content of Mg, Si%Cu,
2 has elongation, low Erichsen value, and too much deterioration in moldability.

In addition, Mn content is 0.8111t%, Cr content ffi
O0? ! +llL%, Zr content 0.2wt%, ■Content 0. lada t%, Fe content 0.5wt%
%, there is an effect of improving strength, but the elongation increases and the Erichsen value decreases significantly, and it can be seen that the deterioration of moldability increases.

Furthermore, the Ti content is 0.14 t% and the B content is 0.14 t%. OS
At 5%, crystallized substances with a large tU are generated, the elongation and Erichsen value are decreased, and the moldability is greatly deteriorated.

No. 2.3.4.10 manufactured by the method of manufacturing an aluminum alloy plate with excellent bake hardenability according to the present invention has a crystallized material with a longest side length of 3 mm or less, and has high formability. 1
It also improves strength by baking at a temperature of 75'C for 30 minutes.

Example 2 The N014 alloy shown in Table 1 of Example 1 was melted and cast using a conventional method, and the ingot was prepared at a heating rate of 4.
The heating temperature was set to 500°C at a rate of 0°C/hour, and after homogenization treatment by holding at this temperature for 6 hours, hot rolling and cold rolling were performed to form a plate with a thickness of 1.0 mm. After heating at a heating rate of 300°C/min to a temperature of 450°C to 590°C and holding at this temperature for 5 to 90 seconds, the temperature is rapidly cooled (quenched in water) at a cooling rate of 200°C/min.
After cooling to 0℃ (to water temperature in the case of rapid cooling), leaving at room temperature for 1 day, final heat treatment at 100℃ for 8 hours, and leaving at room temperature for 30 days, the characteristics are compared with conventional final heat treatment. Table 3 shows a comparison with the characteristics when the test is not carried out.

As is clear from this Table 3, the tempering treatment temperature is 450
℃, there is an improvement in yield strength by conventional baking at 200℃ for 60 minutes, but 1? The effect is small with S'CX for 30 minutes. In addition, at 590°C, the moldability (elongation, Erichsen value) is low due to burning, and the strength improvement effect due to baking is small when the holding time is 0 seconds, but the effect is observed when the holding time is 5 seconds, and furthermore, the cooling rate is 200°C/min. Then 200℃
It can be seen that the yield strength is improved by long-time baking at a high temperature of 175° C. for 30 minutes, but the yield strength is only improved by baking at a low temperature of 175° C. for 30 minutes.

Therefore, in the thermal refining treatment, the heating temperature should be 480 to 590°C, the holding time should be 3 seconds or more, and the cooling rate should be 300°C/min or more.

In addition, if moldability is important, the holding time is 3 to 12
It is preferable to heat for 0 seconds, or for a long time of 30 minutes if strength is important.

Example 3 Alloy N015 shown in Table 1 of Example 1 was melted and cast using a conventional method, and the ingot was then brought to the surface and homogenized at a heating rate of 530° C./hour and maintained at this temperature for 4 hours. The plate thickness is 1.5mm by hot rolling and cold rolling.
On++o, and the plate was heated at a heating rate of 300'C/min.
The temperature is set to 50℃ to 590℃, and after a high-temperature and short-time tempering treatment at this temperature of 90 seconds or less, rapid cooling (quenching in water) is performed at a cooling rate of 200℃/min to a temperature of 100℃ (in the case of rapid cooling) Cool to water temperature) and leave at room temperature for 1 day, then
Table 4 shows the characteristics after a final heat treatment for 24 hours at a temperature of 0''C and after being left at room temperature for 20 days, and for comparison, the characteristics of a conventional heat treatment without low-temperature heating.

As is clear from this Table 4, the tempering treatment temperature is 450
℃, the conventional baking at 200℃ for 60 minutes improves yield strength, but the effect is small at 175℃ for 30 minutes, and at a temperature of 590℃, moldability (elongation, Erichsen value) is low due to burning, and retention is poor. If the time is 0 seconds, the effect due to baking is small, if it is 5 seconds, the baking effect is recognized, and if the cooling rate is 20 U'C/min, it is 200
There is an improvement in yield strength by long-term baking at a high temperature for 6 () minutes at 175"C, but the improvement in yield strength is small when baking at a low temperature for 30 minutes at 175"C/min. It can be seen that there is a sufficient improvement in yield strength even with baking, and the improvement rate is quite large.

Therefore, the heating temperature of the refining treatment is 480 to 590'C,
Holding time is 3 seconds or more, cold mouth speed is 300'C/
It must be at least 1 minute.

In addition, if moldability is important, the holding time is 3 to 120
If strength is important, it is best to hold for a long time, such as 30 minutes.

Example 4 An ingot prepared by melting and casting alloys No. 4 and N005 in Table 1 of Example 1 by a normal method was placed in front of the ingot, and the heating rate was 40.
After homogenization treatment by heating to 530°C at a rate of 530°C/hour and holding at this temperature for 6 hours, hot rolling and cold rolling are performed to reduce the plate thickness to 1.5°C.
8 mm, this plate was intermediately annealed at a temperature of 350°C for 3 hours, cold rolled to a thickness of 1-0, then heated to a temperature of 520°C at a heating rate of 200°C/min, and then heated to this temperature. A high-temperature, short-time tempering treatment is performed for 15 seconds.
Cool to room temperature with continuous cooling at 600℃/min, and then
After being left for 96 hours, a final heat treatment was performed at a temperature of 30 to 150°C for 4 to 48 hours, and the properties and baking properties after being left at room temperature for 30 days are shown in Table S.

As is clear from Table 5, the shorter the time left at room temperature after the tempering treatment until the final heat treatment, the better the baking properties.
For 96 hours, high-temperature and long-term baking at 200℃ for 60 minutes improves yield strength, but low-temperature and short-time baking at 175℃ for 30 minutes does not improve yield strength. There is an improvement in yield strength when baking at a low temperature for a short time, but the improvement in yield strength is small when baking at a low temperature for a short time, and elongation decreases at 150℃, but an improvement is observed when baking at a high temperature for a long time and at a low temperature for a short time. Although baking at high temperature for a long time improves the yield strength, baking at low temperature for a short time does not improve yield strength.
After 48 hours, the elongation is low, and there is no improvement in yield strength with low-temperature, short-time baking. Furthermore, if the final heat treatment is not performed, the yield strength will be improved by baking at high temperature for a long time, but the yield strength will not be improved by baking at low temperature for a short time.

Therefore, the final heat treatment after the tempering treatment is performed at a temperature of 40 to 120° C. for 8 to 36 hours within 72 hours after the tempering treatment.

[Effects of the Invention 1] As explained in 2 below, since the method for producing the aluminum alloy plate with excellent bake hardenability according to the present invention is the method described above, the assembled aluminum alloy plate has good formability. It has an excellent bake hardenability that improves strength in both high-temperature, long-time baking (200' (: 60 minutes) and low-temperature, short-time baking (1 - 5' C x 30 minutes)). .

Patent Applicant Kobe Steel Co., Ltd. I: J'l/, 541 O Self-Procedure Amendment (Voluntary) November 19, 1985 Patent Application No. 210768 2, Name of Invention Manufacturing method of aluminum alloy plate 3, which is steeped in sex, and its relationship with the amended case Patent applicant address 1-3-18 Wakihama-cho, Chuo-ku, Kobe Name (+
19) Kobe Steel Co., Ltd. Representative Fuyuhiko Shinmaki °゛' 4. Agent address: 901 Fujiwa Toyocho Co-op, 2-2-15 Minamisuna, Koto-ku, Tokyo 5. Date of amendment order (voluntary) 6. Subject of amendment ( 1) Column 7 for detailed explanation of the invention in the specification Contents of the amendment As per the attached sheet (+) [and 2] on page 5, lines 17-18 of the specification were carried out, and rough annealing and intermediate annealing were carried out as necessary. ,” is corrected.

(2) Correct r13mmj on page 9, lines 8-9 and 11 of the specification to "r13μm".

(3) "150℃ Hakama rto" on page 11, line 8 of the specification.

'Cl and correct.

(4) Change “150℃” to “100℃” on page 13, line 20 of the specification.
℃”.

(5) r13mm on page 15, line 14 of the specification, 'r13
Correct to μml.

(6) In Table 2, page 17 of the specification, [length of the longest side of the crystallized product, mm] J is corrected to [length of the longest side of the crystallized product, μm] J.

(7) Change “200℃/min” on page 11, line 8 of the specification to “
200°C/min~”.

(8) Change “150℃” to “100℃” on page 11, line 8 of the specification.
℃”.

(9) Change “200℃/min” to “200℃/min” on page 21, line 9 of the specification.
00°C/min~”.

(10) “~590°C” on page 22, line 10 of the specification
580℃”.

Claims (1)

[Claims] Mg0.4-1.5wt%, Si0.3-1.5wt%
, Cu0.2-0.8wt%, and Ti0.005-0.1wt%, B0.0005-0.
03wt%, Mn0.8wt% or less, Cr0.4wt%
Below, Fe0.5wt%, Zr0.2wt% or less, V0
．． Al-Mg-S containing one or more selected from 1 wt% or less, and containing 0.2 wt% or less of unavoidable impurities, with the remainder substantially consisting of Al.
The i-Cu base alloy ingot was subjected to normal homogenization treatment at a temperature below the burning temperature, hot rolled and cold rolled to a desired thickness, and heated at a heating rate of 100 as tempering treatment.
After rapidly heating to 480-580℃ at a rate of ℃/min or more, holding this temperature for 3 seconds or more, heat treatment is performed by rapidly cooling to 100℃ at a rate of 300℃/min or more, and then within 72 hours. A method for producing an aluminum alloy plate with excellent bake hardenability, which comprises performing a final heat treatment at a temperature of 40 to 120°C for 8 to 36 hours.