JPH03107439A - Aluminum alloy for warm forming - Google Patents

Abstract

PURPOSE:To manufacture the Al alloy having good warm formability by preparing an Al alloy contg. a specified amt. of Mg, in which the total content of Fe, Si, Mn, Cr and Zn as impurities and other impurity elements is regulated and having specified grain size of intermetallic compounds. CONSTITUTION:An Al alloy contg., by weight, 2.0 to 6.0% Mg, in which the content of Fe, Si, Mn, Cr and Zr as impurities is respectively regulated so that <=0.2% Fe, <=0.2% Si, <=0.05% Mn, <=0.05% Cr and <=0.05% Zr are satisfied and the total content of other impurity elements is regulated to <=0.1% and having <=10mu grain size in the grains of intermetallic compounds is prepd. In this way, the Al alloy having remarkably high warm formability in the temp. range of 150 to 350 deg.C can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aluminum alloy rolled plate for warm forming, that is, an aluminum alloy used after being formed at a temperature within the range of 150 to 350°C. be.

Conventional technology In recent years, various superplastic materials have been developed that exhibit large elongation of approximately 300% or more without causing local deformation (neck) when tension is applied at an appropriate strain rate at high temperatures of 400°C or higher. Superplastic materials have also been developed for aluminum alloys. Conventionally, such aluminum-based superplastic materials include AA'
-78% Zn alloy, Al-33% Cu alloy, AI-6%
Cu-0,4% Zr alloy (“5UPR^pi”), Al-
Zn-MgCu alloy (A standard 7475 alloy, 70
75 alloy, etc.), A I-2,, 5-6.0% Mg-0.
05 to 0.6% Zr alloys are known. All of these materials can undergo large deformations at high temperatures of 400° C. or higher, so they have the advantage of being easily molded into complex shapes.

Problems to be Solved by the Invention In order for the above-mentioned aluminum-based superplastic materials to elongate as much as 300% or more, it is necessary to give an appropriate strain rate at a high temperature of 400°C or more, and generally the most The strain rate showing elongation (optimum strain rate) is said to be on the order of 10-3/sec to 10-'/sec. However, such a strain rate is much slower than in the case of molding by boat, and when such a strain rate is applied, one molding process takes several minutes to several tens of minutes, making it difficult to perform on a factory scale. In the case of mass production, there is a problem that significantly impedes productivity. Furthermore, it is generally considered difficult to control the plate thickness distribution when deforming due to superplasticity. Therefore, the reality is that the practical application of superplastic working on a mass production scale using aluminum-based superplastic materials as described above has been discouraged.

By the way, although it is lower than the superplastic processing temperature range,
In the case of so-called hot-open forming in the temperature range of 150 to 350°C, Al-Mg alloys can obtain a relatively large elongation at normal forming speeds compared to forming at room temperature, and the plate after deformation in that case It is known that the thickness distribution is uniform, so if hot-open forming is performed using Al-Mg alloy, it will be relatively easy to form complex shapes on a mass production scale without hindering productivity. Conceivable.

However, in conventional hot-open forming of general Al-Mg alloys, the formability is significantly inferior to that in the case of superplastic working. Therefore, there has been a strong desire to develop a material that has even better warm formability than conventional general Al-Mg alloys as a material for warm forming suitable for practical use on a mass production scale.

This invention was made against the background of the above circumstances, and AI! -Mg alloy.

Means for Solving the Problems The inventors of the present invention have conducted extensive experiments and studies to solve the above-mentioned problems, and have found that the content of various elements contained as impurities in Al-Mg alloys has been reduced to below specific trace amounts. The inventors have discovered that by regulating the diameter of the intermetallic compound based on impurity elements to a certain size or less, warm formability can be significantly improved compared to the conventional method, and this invention has been completed.

Specifically, the aluminum alloy for warm forming of the invention according to claim 1 contains 2.0 to 6.0% Mg, and contains Fe, Si, Mn, and Cr as impurities.

Zr is 0.2% or less for Fe, 0.2% or less for Si, 0.05% or less for Mn, 0.05% or less for Cr, and Zr.
r is regulated to 0.05% or less, the total amount of other impurity elements is regulated to 0.01% or less, the remainder is substantially composed of AA', and the particle size of the intermetallic compound particles is 10.0% or less. m or less.

Further, the aluminum alloy for warm forming of the invention according to claim 2 contains 2.0 to 6.0% of Mg, and also contains C.
Contains one or two of u 0.05 to 2.0% and Zn 0.5 to 2.5%, and Fe as an impurity,
Si, Mn, Cr, and Zr each have Fe of 0.2% or less, Si of 0.02% or less, Mn of 0.059fi or less, and Cr
is regulated to 0.05% or less, Zr is regulated to 0.05% or less,
Moreover, the total amount of other impurity elements is regulated to 0.1% or less, the balance is substantially composed of AA', and the particle size of the intermetallic compound particles is 10 degrees or less.

Function First, the reason for limiting the ingredients of the aluminum alloy for warm forming of the present invention will be explained.

Mg: Mg is an element that improves warm formability by promoting process softening or dynamic recrystallization during warm forming. If the Mg content is less than 2.0%, warm formability will be insufficient and the strength of various molded parts will also be insufficient. On the other hand, if Mg exceeds 6.0%, hot rolling properties and cold rolling properties deteriorate, making it difficult to manufacture a rolled plate. Therefore M
The content of g needs to be within the range of 2.0 to 6.0%.

Mn, Cr, Zr, Fe, Si, and other impurities: Mn, Cr, Zr, Fe, and Si all tend to form coarse intermetallic compounds during casting, and these intermetallic compounds once formed, It cannot be removed by subsequent processing or heat treatment. If the particle size of these intermetallic compounds exceeds 10 degrees, it becomes a starting point for breakage during warm forming and significantly deteriorates warm formability. In order to prevent the formation of intermetallic compounds whose particle size exceeds IO, M as an impurity must be
n 0.05% or less, Cr 0.05% or less, Zr o
, o5og5, Fe and Si must be regulated to 0.2% or less and Si to 0.2% or less, and the total amount of other impurities must be regulated to 0.1% or less.

Both of Cu and Zn have the effect of increasing the strength and increasing the stacking fault energy to strengthen the dislocation cell structure during processing and improve formability. Any one or two of the following for alloy rolled plates
Contains seeds. Cu less than 0.005%, Zn 0.05%
If Cu is less than 2.0%, the above effects cannot be sufficiently obtained; on the other hand, if Cu is less than 2.
If the Zn content exceeds 0% or 2.5%, the corrosion resistance will decrease.

Therefore, Cu is 0.05-2.0% and Zn is 0.05-2.0%.
It was set within the range of 5%.

The remainder of each of the above components may be substantially An. However, in ordinary aluminum alloys, a small amount of Ti1 or Ti and B is sometimes added to refine the ingot crystal grains, and in the case of this invention, a small amount of Ti1 or Ti is also added.
and B may be contained. Here, if the Ti content exceeds 0.15%, primary TiAl3 particles will crystallize and impair the formability, and if the B content exceeds 0.05%, the T
i B Since coarse particles of 2 are formed and impair moldability, T
It is preferable that i be 0.15% or less and B be 0.05% or less.

Furthermore, when a large amount of Mg is contained, the molten metal is likely to oxidize, and Be is generally added to prevent oxidation of the molten metal. Be may be added for prevention 11-. However, if the amount of I'3e added is less than IIlpm, the effect cannot be obtained, and on the other hand, if it exceeds 1100 pp, the effect is saturated, so when adding Be, the amount of addition is
It is preferably within the range of 1 to 1100 pp.

The aluminum alloy of the present invention having the above-mentioned composition has a formability (warm formability) in warm forming at a temperature within the range of 150 to 350°C that is higher than that of conventional A.
It is much better than A-Mg alloy.

Next, a method for manufacturing an aluminum alloy for warm forming according to the present invention will be explained.

First, a molten aluminum alloy having the above-mentioned composition is melted in accordance with a conventional method, and is made into an ingot by a DC casting method (semi-continuous casting method) or directly into a thin plate by a continuous sheet casting method (continuous casting and rolling method). shall be.

When an ingot is produced by the DC casting method, the ingot is heated before being hot rolled, then hot rolled, and then cold rolled if necessary. Product board thickness. Moreover, intermediate annealing may be performed between hot rolling and cold rolling, or in the middle of cold rolling, if necessary.

It is desirable that each of these steps be carried out under the following conditions.

That is, it is desirable to heat the ingot before hot rolling at a temperature within the range of 450 to 580°C for 05 to 48 hours. If the ingot heating temperature is less than 450°C, hot rolling properties will deteriorate, while if it exceeds 580°C, there is a risk that intermetallic compounds will become coarse and eutectic melting will occur. Furthermore, if the ingot heating time is less than 0.5 hours, there is a risk that the ingot will not be heated uniformly, while if it exceeds 48 hours, there is a risk that the intermetallic compounds will become coarse. Hot rolling may be carried out according to a conventional method, and intermediate annealing may also be carried out under conventional conditions. When intermediate annealing is performed, the rolling reduction ratio of cold rolling is preferably 1596 or more as the rolling ratio of cold rolling after intermediate annealing. If the cold rolling ratio is less than 15%, there is a risk that the recrystallized grains of the recrystallized structure obtained in the subsequent final annealing or the recrystallized structure obtained during preheating for hot open forming may become coarse.

After the product board is thickened as described above, it is generally subjected to final annealing to generate a recrystallized structure.

This final annealing may be either batch annealing or continuous annealing, and the final annealing conditions may be as long as the temperature and time are such that a recrystallized structure is obtained, but in the case of batch annealing,
It is common to hold the temperature within the range of 5G to 400℃ for 0.5 hours or more, while in the case of continuous annealing, the temperature is 350 to 550℃.
No hold or hold for less than 180 seconds at a temperature in the range of °C is common. Note that hot-open forming of the rolled plate of the product is carried out at 150 to 350°C; in this case, the rolled plate is set in a heated mold and held until the material temperature reaches a predetermined temperature, and then the forming is carried out. It is then heated in a separate preheating furnace and then placed in a mold for shaping. In this case, if the temperature and time of holding or preheating are such that recrystallization occurs, it is not necessary to obtain a recrystallized structure by final annealing, and therefore, in that case, final annealing can be omitted.

Moreover, when applying a thin plate continuous casting method instead of DC casting, it is possible to omit the steps up to hot rolling among the above-mentioned steps. However, in this case, in order to improve rolling properties, it is preferable to perform a homogenization treatment on the cast coil before cold rolling.

The homogenization treatment conditions in this case may be the same as the ingot heating conditions before hot rolling when the above-mentioned DC casting is applied.

Example Aluminum alloys having the compositions shown in alloy numbers 1 to 7 in Table 1, that is, alloys 1 to 4 within the composition range of the present invention and alloys 5 to 7 of comparative examples outside the composition range of the present invention, were subjected to conventional methods. DC casting was performed according to the method, and the obtained ingot was heated at 530°C x 10
After homogenizing for a long time, the plate thickness is 4mm according to the usual method.
The plate was hot-rolled to a thickness of 1 mm, and then cold-rolled to a thickness of 1 mm. Thereafter, final annealing was performed at 320°C for 2 hours.

After final annealing as described above, each rolled plate was polished in parallel to the rolled surface, and the maximum diameter of the intermetallic compound particles in the plane parallel to the rolled surface was measured using an image analysis device. The results are shown in Table 2.1.

As is clear from Table 2, within the composition range of this invention -
All of the rolled sheets of alloys with alloy numbers 1 to 4 have intermetallic compound particles having a diameter of 10 degrees or less.

In addition, each rolled plate after final annealing was warm tensile processed at 300°C to give 50% elongation, and then J
Table 3 shows the results of cutting IS No. 5 tensile test pieces and examining their room temperature strength (tensile strength and yield strength) after warm tensile processing.

From Table 3, the aluminum alloys of the examples of this invention are:
It can be seen that even after warm forming, the material has a strength sufficient to be used in practical applications such as automobile parts and various casings.

Furthermore, tensile test pieces were cut out from each rolled plate after the final annealing, and a warm tensile test was performed on each test piece at 250°C to examine the elongation. Table 4 shows the results. In addition, in the warm tensile test at this time, tension was started after holding the temperature at 250°C for 30 minutes, and the tensile strain rate was 2.22X 1
The speed was set at 0-2/sec, and the gauge distance was 10 mm2.

From Table 4, it can be seen that the rolled aluminum alloy sheets of the examples of the present invention exhibited a large elongation of 160% or more by hot-opening forming, and had extremely good warm formability.

Furthermore, in order to investigate the deformability during actual hot-opening molding,
Five sheets of each rolled plate were successively subjected to hot-open forming using a die punch, and the average formed height at breakage was examined. The conditions for hot-opening molding are a molding temperature of 250°C and a blank diameter of 250+a.
+a, the punch diameter was 50 mm, the die diameter was 53 M, the L pressure was 1000 kg, and molydeben disulfide was used as the lubricant. The results are shown in Table 5.

From Table 5, the aluminum alloys of the examples of this invention are:
It can be seen that the formability during warm forming is actually extremely excellent.

Table 1 - Component composition of the sample material (unit w196) Maximum compound size 5 Table 3: Room temperature strength after warm tension Table 4: Elongation in warm tension test at 250°C 1.6 Table 5: Effect of the Invention on Forming Height by Warm Opening As is clear from the above examples, the aluminum alloy of the present invention has extremely good warm formability. Hot-open molding in the temperature range of ~350°C can be put to practical use with high productivity. Therefore, the aluminum alloy of the present invention can be used for objects with complex shapes, as well as electrical controller housings, measuring instrument housings, chassis of VTRs and other light electrical equipment, etc.
Furthermore, it is suitable for use in small parts such as automobile bodies, gasoline tanks, and oil pans.

Claims (2)

[Claims] (1) Contains 2.0 to 6.0% Mg (wt%, same hereinafter) and contains Fe, Si, Mn, Cr, and Z as impurities
r is respectively Fe 0.2% or less, Si 0.2% or less, Mn 0.05% or less, Cr 0.05% or less, Zr
is regulated to 0.05% or less, and the total amount of other impurity elements is regulated to 0.1% or less, with the remainder consisting essentially of Al, and the particle size of the intermetallic compound particles is 10 μm or less. A warm-forming aluminum alloy for forming at temperatures in the range of 150 to 350°C, characterized in that: (2) Contains Mg2.0 to 6.0% and Cu
0.05-2.0%, 1 of Zn0.5-2.5%
Fe, Si containing one or two species and as impurities
, Mn, Cr, Zr, Fe is 0.2% or less, S
i is 0.2% or less, Mn is 0.05% or less, and Cr is 0.
Zr is regulated to 0.05% or less, Zr is regulated to 0.05% or less, the total amount of other impurity elements is regulated to 0.1% or less, the balance is substantially made of Al, and the particle size of the intermetallic compound particles is 150-3, characterized in that it is 10 μm or less
Warm forming aluminum alloy for forming at temperatures in the range of 50°C.