JPS59100252A - Al alloy having excellent moldability and quench hardenability and its production - Google Patents

Abstract

PURPOSE:To produce an Al alloy having excellent moldability and quench hardenability by subjecting a cast ingot of an Al-Cu-Mg-Si alloy to a heat treatment and rolling treatment under a specific condition. CONSTITUTION:A cast alloy ingot contg., by weight %, 1.5-2.5% Cu, 0.5-1.0% Mg, 0.3-1.0% Si, 0.005-0.05% Ti, 0.0005-0.03% B, contg. <=0.04% Mn, Cr, V, Zr individually and <=0.09% in total and <=0.25% Fe, contg. <=1.1 Si/Mg by weight, and consisting of the balance substantially Al is subjected to the following treatment: Said cast alloy ingot is heated at <=200 deg.C/hour heating rate or is heated and held for >=1hr to and at 300-400 deg.C and is then heated to 450- 530 deg.C, whereby the ingot is homogenized. Such ingot is cold rolled at >=40% draft after hot rolling and is quickly heated to 500-555 deg.C at >=100 deg.C/min heating rate as a final treatment, then it is held for 5-90sec in said temp. region. Thereafter the rolled sheet is quickly cooled to 150 deg.C at >=300 deg.C/min cooling rate whereby the max. long side length of the crystallized matter is made <=13mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an Al alloy with excellent formability and bake hardenability, and a method for producing the same.

Conventionally, aluminum alloy materials used in automobile parts and other applications are sometimes heated (baked) after painting in order to maintain the strength of the painted film. Efforts have been made to improve the strength of Al alloy materials. Therefore, 2002 alloy and 2036 alloy are used as Al alloy materials, but the baking conditions for coating films of these alloys require high temperature and long hours of holding at a temperature of 200° C. for 90 minutes.

However, recently, in order to save energy and reduce baking costs, baking temperatures have been lowered and
There is a growing demand for an Al alloy that tends to shorten heating time, has good formability, and improves strength at a low temperature of 200° C. or less and in a short time of 90 minutes or less. For example, in the case of exposed 2002 alloy or 2036 alloy, no improvement in strength can be expected by baking at a low temperature for a short time such as heating at 75° C. for 30 minutes.

The present invention was developed as a result of research by the inventor in view of the various problems of the prior art as explained above. Al alloy whose strength improves with baking time, i.e.
The present invention provides an Al alloy with excellent formability and bake hardenability, and a method for producing the same.

Al alloy with excellent formability and bake hardenability according to the present invention,
and its manufacturing method, (1) Cu1.5-2.5wt%,
Mg0.5-1.0wt%, Si0.3-1.0wt%
, Ti0.005~0.05wt%, B0.0005~
0.03wt%, Mu, Cr, V, and Zr are regulated to 0.04wt% or less individually and 0.09wt% or less in total, Fe is regulated to 0.25wt% or less, and the Si/Mg weight ratio is is 1.1 or less and the remainder consists essentially of Al
The first invention is an Al alloy which is a Cu-Mg-Si based alloy and has excellent formability and bake hardenability in which the minimum long side length of a crystalline substance is 13 μm or less, (2) Cu1.5~ 2.5
wt%, Mg0.5-1.0wt%, Si0.3-1.
0wt%, Ti0.005-0.5wt%, B0.00
05 to 0.03 wt%, Mu, Cr, V, and Zr are regulated to 0.04 wt% or less individually and 0.09 wt% or less in total, and Fe is regulated to 0.25 wt% or less, and Si/M
An Al-Cu-Mg-Si alloy ingot having a weight ratio of 1.1 or less and the remainder substantially consisting of Al was heated at a heating rate of 20
Homogenize by heating to 450-530°C at a rate of 0°C/hour or less,
After hot rolling, cold rolling is performed at a rolling rate of 40% or more, and as a final heat treatment, the material is heated at a heating rate of 100°C/min or more to a temperature of 500 to 50%.
After rapidly heating to 50°C and holding in this temperature range for 5 to 90 seconds, heat treatment is performed to rapidly cool the crystallized material at a cooling rate of 300°C/min or more to 150°C, and the longest side length of the crystallized material is reduced to 13 μm.
A second invention provides a method for producing an Al alloy plate with excellent formability and bake hardenability, which is characterized by the following: (3) Cu1
．． 5-2.5wt%, Mg0.5-1.0wt%, Si
0.3-1.0wt%, Ti0.005-0.05wt
%, B0.0005-0.03wt%, Mu, C
Each of r, V, and Zr is 0.04 wt% or less, and the total content is 0.04 wt% or less.
An Al-Cu-Mg-Si alloy ingot is regulated to 0.09 wt% or less and Fe0.25 wt% or less, and the Si/Ms weight ratio is 1.1 or less, the remainder substantially consisting of Al.
Heated and held at 300-400℃ for more than 1 hour, then heated to 450℃
Homogenize by heating to ~530°C, and after hot rolling, the rolling rate is 40.
% or more, and as a final heat treatment, the material is rapidly heated to 500 to 555 °C at a heating rate of 100 °C / min or more,
After holding this temperature range for 5 to 90 seconds, heat treatment is performed to rapidly cool the crystallized material at a cooling rate of 300°C/min or more to 150°C, and the length of the longest side of the crystallized material is reduced to 13 μm or less. This invention consists of three inventions, with the third invention being a method for manufacturing an Al alloy plate with excellent properties and bake hardenability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An Al alloy with excellent formability and bake hardenability according to the present invention and a method for producing the same (hereinafter sometimes simply referred to as the alloy of the present invention and the method of the present invention) will be described in detail.

First, the components and component ratios of the alloy of the present invention will be explained.

Cu increases strength in proportion to its content, but is an element that reduces elongation, so if the content is less than 1.5 wt%, the strength will be low, and if the content exceeds 2.5 wt%, the strength will decrease. The moldability deteriorates, and the rate of increase in strength after baking decreases as the Cu content increases. Therefore, in order to increase the strength and formability of the material and the strength after baking, the Cu content is set to 1.5 to 2.5 wt%.

Mg increases the strength of the material and the strength after baking, but on the other hand it reduces the formability of the material, and the content is 0.5w.
If the content is less than t%, the strength of the material and after baking will be low, and if the content exceeds 1.5wt%, the strength after baking will be high, but the moldability of the material will be low. Therefore, in order to increase the strength and formability of the material and the strength after baking,
The Mg content is 0.5 to 1.0 wt%.

Si increases the strength of the material and the strength after baking, but reduces the formability of the material, and if the content is less than 0.3 wt%, the formability of the material increases, but the strength and the strength after baking decrease. Moreover, if the content exceeds 1.0 wt%, the strength and the strength after baking will increase, but the moldability will decrease. Therefore, in order to improve strength, formability, and strength after baking, the Si content should be 0.3 to 1.0.
Let it be wt%.

Ti is an element that improves formability, and the content is 0.0
If the content exceeds 0.05 wt%, the moldability will improve as the content increases, but if the content exceeds 0.05 wt%, coarse crystallized substances will be produced and the moldability will be deteriorated. Therefore, Ti
The content is 0.005 to 0.05 wt%.

Like Ti, B is an element for improving formability, and when the content exceeds 0.0005wt%, the formability is improved, but when the content exceeds 0.03wt%, coarse crystallized substances are formed. , which reduces moldability.

Therefore, the B content is set to 0.0005 to 0.03 wt%.

Note that Ti and B are preferably contained in an Al-Ti-B intermediate alloy.

When Mn, Cr, V, and Zr are contained in an amount exceeding 0.04 wt% individually, and in a total amount exceeding 0.09 wt%, the strength is improved, but the formability is reduced.
Zr content is 0.04 wt% or less individually, 0.0 in total
It must be regulated to 9wt% or less.

If Fe is contained in an amount exceeding 0.25 wt%, formability will be reduced, so the Fe content must be regulated to 0.25 wt% or less.

Note that it is desirable to suppress Zn to 0.5 wt% or less.

The reason why the weight ratio of Si/Mg is 1.1 or less is to improve the strength of the material and after baking and to improve the formability of the material.If the weight ratio of Si/Mg exceeds 1.1, It improves the strength of the material and after baking, but it reduces the formability of the material. Therefore, the weight ratio of Si/Mg is 1.1
The following shall apply.

The components and proportions of the components explained above are also explained in the examples described later.

Next, the method of the present invention will be explained.

For homogenization treatment, if the heating rate to the homogenization treatment temperature is too fast, the moldability of the material will decrease significantly and the strength improvement due to baking will be reduced, so the heating rate should be set to 200℃/200℃.
If the homogenization temperature is less than 450°C, the moldability of the material and the strength after baking will decrease, while if it exceeds 530°C, burning will occur. Therefore, the homogenization treatment temperature is set at 450 to 530°C.

In addition, if heating cannot be carried out at a heating rate of 200°C/hour or less, regardless of the heating rate, after heating and holding at 300-400°C for 1 hour, homogenization treatment at 450-530°C is performed.
The same moldability as when the heating rate is 200° C./hour or less can be obtained. Note that the homogenization treatment time at 450 to 530°C is preferably about 1 to 10 hours.

Cold rolling is performed after hot rolling, and the higher the cold rolling rate, the better the formability of the material after final heat treatment.
If the rolling rate is less than 40%, the formability of the material will decrease, so
The cold rolling rate shall be 40% or more.

Furthermore, the final heat treatment involves rapid heating, high temperature heating for a short time, and then rapid cooling.
The strength and moldability of the material and the strength after baking can be improved. That is, the substance is heated at a rate of 100°C/
Rapidly heat to 500-555℃ for more than 5 minutes to this temperature.
If the heating rate is less than 100°C/min and the heating temperature is less than 500°C, the strength of the material and the strength after baking will be low, and if it exceeds 560°C, burning will occur and the molding will fail. Sexuality decreases, and
For example, if the heating time is 120 seconds at
If the heating time is 60 seconds at 75°C, the strength after baking will be low. Regarding the subsequent cooling rate to 150℃,
When the cooling rate is less than 300°C/min, the moldability of the material decreases and the rate of increase in strength after baking is small; when the cooling rate is 300°C/min or more, the strength and formability of the material and the strength after baking improve. Furthermore, when heating is performed in a conventional batch-type air furnace, the heating rate is slow and the storage time is long, resulting in coarse grains and poor formability of the material. Therefore, the final heat treatment is performed at a heating rate of 100°C on the substance itself, that is, on the material to be treated.
Rapid heating to 500-555℃ at a rate of 500℃/min or more, holding time 5-90 seconds, cooling rate to 150℃ 300℃/min.
It takes more than a minute.

The size of the crystallized material of the material when the above steps are completed is
If the length of the longest side exceeds 13 μm, formability deteriorates, so the final crystallized material of the Al alloy plate needs to be 13 μm or less.

In addition, after the final heat treatment, a leveler or
When performing distortion correction using skin pass etc., the processing rate is 1.5%.
The following is desirable from the viewpoint of preventing deterioration of moldability.

Examples of an Al alloy with excellent formability and bake hardenability and a method for producing the same according to the present invention will be described.

Example 1 Table 1 shows that the heating rate was 40°C/hour and the heating temperature was 520°C.
Homogenization treatment by holding for a period of time: A 1 mm thick plate that has been subjected to 75% cold rolling after hot rolling is held at 530°C for 30 seconds at a heating rate of 200°C/min, and then at a cooling rate of 800°C/min. A final heat treatment is performed to cool down to 150°C and then to room temperature for 30°C.
The various properties of the present invention alloy and comparative alloy after being left in the sun are shown.

As is clear from this Table 1 and the continuation of Table 1, the invention alloy No. Comparative alloy No. 1 and No. 3 are superior in material strength and formability, and strength after baking, compared to comparative alloy No. Compared to No. 14 and No. 15 (2002, 2036), the alloy of the present invention has excellent formability of the material and also has excellent strength improvement by baking.

On the other hand, comparative alloy No. 1 with a Cu content of less than 1.5 wt%.
Comparative alloy No. 1 has low strength, and comparative alloy No. 1 has a Cu content of more than 2.5 wt%. In No. 2, the moldability deteriorates. Similarly, comparative alloy No. 1 with low Mg and Si contents. Comparative alloy No. 3 has low strength, and the Mg and Si contents are too high.
．． 4 alloy deteriorates formability.

Ti content of less than 0.005wt%, also 0.05w
Comparative alloy No. containing more than t%. Comparative alloy No. 6, 7 has low formability of the leaf material, and the B content is less than 0.0005 wt%, and the B content exceeds 0.03 wt%. 7 and 8 have low formability, and comparative alloy No. 7 and 8 have low formability. 9
When Mn, Cr, V, and Zr are contained as in No. 12, the strength is improved, but the formability is low, and No. 1 containing as much as 0.5% Fe. In No. 13, the formability of the material decreases, and Si
/Mg weight ratio is that of comparative alloy No. If it is 1.4, such as 5, the moldability decreases.

Next, looking at the length of the longest side of the crystallized material, the present invention alloy No. Comparative alloy No. 1 to No. 3 had a diameter of 8 to 10 μm, indicating good formability, but when Mn, Cr, V, Zr, and Fe were contained in the specified amounts or more, comparative alloy No. 15-21μ for 9-15
It can be seen that the moldability has deteriorated.

Example 2 Table 2 shows the invention alloy No. 1 shows the homogenization treatment conditions and material properties. That is, the alloy No. of the present invention. 1 ingot 50~40
Homogenization was carried out by holding at 400 to 575°C for 4 hours at a heating rate of 0°C/hour, and homogenization was held at 350°C for 1 hour and then at 520°C for 4 hours regardless of the heating rate. A 1 mm plate that has been subjected to 77% cold rolling after inter-rolling is held at 530°C for 30 seconds at a heating rate of 200°C/min, and then subjected to a final heat treatment in which it is cooled to 150°C at a cooling rate of 700°C/min. These are characteristic values after being left at room temperature for 30 days.

As can be seen from Table 2, as the heating rate increases, the formability decreases, and at 400°C/hour, the decrease in formability is large, so it is best to keep it at 200°C/hour or less, and homogenization treatment Formability improves as the temperature rises, but at 575°C it begins to deteriorate due to burning, so if the heating rate cannot be lowered to 200°C/hour or less, heating to 300-400°C for 1 hour or more is recommended. After, 450
When the temperature is raised to ~530°C, moldability equivalent to that obtained when the heating rate is 200°C/hour or less can be obtained.

Example 3 Table 3 shows the invention alloy No. The relationship between the final cold rolling rate and formability of No. 1 is shown. That is, the alloy No. of the present invention. A 1 mm ingot was homogenized by holding it at 520 °C for 4 hours at a heating rate of 100 °C/hour, hot rolled, and cold rolled by 30 to 75%.
This is the value after the plate was left at room temperature for 30 days after a final heat treatment in which the body was held at 530°C for 15 seconds at a heating rate of 200°C/min, then cooled to 150°C at a cooling rate of 300°C/min.

As is clear from Table 3, formability improves as the cold rolling rate increases from 30%, and formability is low below 30%, so the cold rolling rate needs to be 40% or higher. be.

Example 4 Table 4 shows the invention alloy No. 2 shows the final heat treatment conditions and material properties. That is, the ingot was heated to 520°C at a heating rate of 100°C/hour.
A 1 mm plate that has been homogenized at ℃ for 5 hours, hot rolled, and 70% cold rolled is heated at a heating rate of 200.
After high-temperature short-time heating at 475-560°C for 5-120 seconds at a cooling rate of 200°C/min (quenching in water), it is cooled to 150°C (to water temperature in the case of rapid cooling), and then cooled to room temperature. This is the value after being left for 30 days. For comparison, values obtained using a conventional heat treatment method using an air furnace are also shown.

As is clear from Table 4, when comparing the conventional heat treatment method using an air furnace and the method of the present invention (high temperature short time heating method), the heat treatment method using an air furnace has high strength but low formability. Regarding the final heat treatment in the present invention, at temperatures below 500°C, rhyudus marks occur and there is little improvement in strength after baking, and at temperatures above 560°C, moldability decreases due to burning, and at 530°C, If held for seconds, the recrystallized grains will become coarser and formability will deteriorate. Furthermore, the cooling rate up to 150°C is 200°C.
/min or less, the formability is low and the yield strength after baking is not improved much.

Therefore, the optimal conditions for the final heat treatment in the method of the present invention are a heating rate of 100°C/min or more, and a heating temperature of 500 to 55°C.
The temperature is 5°C, the holding time is 5 to 90 seconds, and the cooling rate to 150°C is 300°C or more.

Claims (3)

[Claims] (1) Cu1.5-2.5wt%, Ms0.5-1.0
wt%, Si0.3-1.0wt%, Ti0.005-
0.5 wt%, B0.0005 to 0.03 wt%, Mu, Cr, V, Zr alone 0.04 wt% or less,
0.09wt% or less in total and 0.25wt Fe
% or less, and the weight ratio of Si/Ms is 1.1 or less, and the remainder is substantially Al, and the longest side length of the product is 13 μm or less. Al alloy with excellent formability and bake hardenability. (2) Cu1.5-2.5wt%, Ms0.5-1.0
wt%, Si0.3-1.0wt%, Ti0.005-
0.5 wt%, B0.0005 to 0.03 wt%, Mu, Cr, V, Zr alone 0.04 wt% or less,
0.09wt% or less in total and 0.25wt Fe
% or less, and the weight ratio of Si/Ms is 1.1 or less, and the remainder is substantially Al. 5
Homogenize by heating to 30°C, then cold rolling at a rolling reduction of 40% or more after hot rolling, and as a final heat treatment, heat the material at a heating rate of 1.
Heat treatment is performed by rapidly heating to 500-555°C at a rate of 00°C/min or more, maintaining this temperature range for 5-90 seconds, and rapidly cooling to 150°C at a cooling rate of 300/min or more. A method for producing an Al alloy with excellent formability and bake hardenability, characterized by having a side length of 13 μm or less. (3) Cu1.5-2.5wt%, Mg0.5-1.0
wt%, Si0.3-1.0wt%, Ti0.005-
0.5 wt%, B0.0005 to 0.03 wt%, Mu, Cr, V, Zr alone 0.04 wt% or less,
0.09wt% or less in total and 0.25wt Fe
% or less, and the weight ratio of Si/Ms is 1.1 or less, and the remainder is substantially Al, an Al-Cu-Mg-Si alloy ingot is heated and held at 300 to 400°C for more than 1 hour. Then, it is cold rolled to 450-530°C, and as a final heat treatment, it is heated to 500-550°C at a heating rate of 100°C/min or more.
After rapidly heating to ℃ and holding in this temperature range for 5 to 90 seconds,
A with excellent formability and bake hardenability, characterized by performing heat treatment at a cooling rate of 300°C/min or more to 150°C, and making the longest side length of the crystallized product 13 μm or less.
l alloy manufacturing method.