JPH08206706A - Hot rolling method of al-li alloy - Google Patents

Abstract

PURPOSE: To provide a hot rolling method of an Al-Li alloy by which the generation of edge crack and surface defects is prevented. CONSTITUTION: In the method for hot-rolling the Al-Li alloy, a cast billet of the Al-Li alloy contg. 0.5-3.0% Li, further, one or >=2 kinds of 1.0-3.0% Cu, 0.5-2.0% Mg, 0.06-0.3% Zr, 0.06-0.3% V, 0.06-0.3% Mn, 0.06-0.3% Cr, 0.02-0.3% Ti as a selective component, the balance Al and inevitable impurities is homogenized in the temp. range of 520±50 deg.C for 1-24hours. After that, hot rolling is started in the temp. range of 520±30 deg.C and completed at >=250 deg.C, preferably, >=300 deg.C. As rolling reduction per pass, 3-30mm is preferable and it is preferable to execute rolling of 5-50mm in the width direction on one side by the number of >=20% of the total number of rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can prevent the occurrence of cracks such as edge cracks and the occurrence of surface defects such as striped patterns in the hot rolling method for Al-Li alloys, especially in the hot rolling process. The present invention relates to a hot rolling method for an Al-Li alloy.

[0002]

2. Description of the Related Art Al-Li alloys, which have high strength and rigidity and low density, are excellent in specific strength and specific rigidity and are expected as materials for aerospace, but their manufacturing technology is not yet fully established. It has not been. For example, even in hot rolling, edge cracks and surface defects are more likely to occur than in conventional aluminum alloys, and establishment of rolling technology is desired.

In order to prevent cracks and surface results that occur during hot rolling of Al-Li alloys, the inventors have studied alloy components, ingot surface chamfering method, ingot homogenization treatment, rolling conditions and the like. We conducted basic experimental studies on the relevance of
We obtained various findings.

[0004]

The present invention has been made on the basis of the knowledge obtained from the above-mentioned basic experimental examinations, and its purpose is to provide cracks and patterns such as ear cracks in the hot rolling process. A that prevents surface defects such as generation
An object of the present invention is to provide a hot rolling method for 1-Li alloy.

[0005]

A method of hot rolling an Al--Li alloy according to the present invention for achieving the above-mentioned object is L
i0.5-3.0%, further Cu1.0-3.0% (however, if Mg is not contained 1.5-5.5%), Mg0.5
.About.2.0%, Zr0.06 to 0.3%, V0.06 to 0.3%, Mn0.
An ingot of an Al-Li alloy containing one or more of 06 to 0.3%, Cr 0.06 to 0.3%, and Ti 0.02 to 0.3%, and the balance being Al and unavoidable impurities, ℃
The first feature is that after heating to a temperature range of ± 50 ° C and holding for 1 to 24 hours, hot rolling is started in the temperature range and hot rolling is finished at a temperature of 250 ° C or higher. .

Further, it contains Li 0.5 to 3.0%, Zr 0.06 to 0.3%, V 0.06 to 0.3%, Mn 0.06 to 0.3%.
%, Cr 0.06 to 0.3%, and one or more of them, the balance being Al and unavoidable impurities.
The ingot of Li alloy is heated to a temperature range of 450 ° C ± 30 ° C for 1 to 30 hours, and then heated to a temperature range of 520 ° C ± 50 ° C for 1 hour.
The second feature of the present invention is to hold for up to 24 hours, then start hot rolling within the temperature range, and finish hot rolling at a temperature of 250 ° C. or higher.

Further, if the amount of reduction per hot rolling is 3 to 30 mm excluding the final rolling, the side surface of the rolled plate is rolled at 20% or more of the total rolling times. Performing widthwise rolling of 5 to 50 mm on one side, and A
The rolled surface and the side surface of the ingot of the l-Li alloy are chamfered by 5 mm or more, and the surface roughness Ra is 2 μm or less and the waviness is 200 μm or less. Characterize.

In order to achieve the object of the present invention, the composition of the Al--Li alloy of the present invention must first be limited to a specific range. Explaining the meaning and limitation reason of the alloying element in the Al-Li alloy used in the present invention, Li is an element that reduces the weight of the alloy material and improves the strength, and the preferable content range is 0.5 to 3.0%, and 1.
If it is less than 0%, the effects of weight reduction and improvement of specific strength and specific rigidity cannot be obtained, and if it exceeds 3.0%, the susceptibility to casting cracking is increased, and at the same time, a coarse δ'phase is formed and the ductility and toughness of the alloy are increased. Lower.

Cu is a plate-like precipitate θ'of Al-Cu system.
(Al ₂ Cu) or Al-Cu-Li-based plate-like precipitate T ₁
It forms a phase (Al ₂ CuLi) and contributes to the improvement of strength and toughness. The preferred content range is 1.0 to 3.0%,
If it is less than 1.0%, the effect becomes insufficient, and if it exceeds 3.0%, the effect of improving the strength and toughness is saturated and the weight reduction is impaired. When Mg is not contained in the alloy, Cu is preferably contained in the range of 1.5 to 5.5%. In addition, when Mg is contained in the alloy, the strength improving effect of Mg can be expected, so the content of Cu is set to 1.
It can also be reduced to the range of 0-2.5%.

[0010] Mg solid-solves in the alloy matrix to strengthen the alloy without lowering the ductility and toughness of the alloy, and at the same time, the plate-like precipitate of the Al-Cu-Mg metastable phase, S '(Al. ₂ CuMg) to further improve the strength. The preferred content range is 0.5 to 2.0
%, The effect is small if less than 0.5%, and if it exceeds 2.0%, the strength is improved but the ductility and toughness of the alloy are deteriorated.

Zr, V, Mn, Cr and Ti have the effects of refining the alloy structure and suppressing recrystallization, and are included to form a fine and unrecrystallized crystal structure. , A preferable content range is Zr,
V, Mn and Cr are 0.1 to 0.3%, Ti is 0.02 to 0.3
%. If the amount is less than the lower limit, a sufficient effect cannot be obtained. If the amount exceeds the upper limit, a coarse intermetallic compound is formed to reduce strength and toughness, and the effect is saturated.

In the Al--Li alloy of the present invention, 0.30%
Fe below, 0.20% or below Si, 0.25% or below Zn, 0.
10% or less Cr, 0.10% or less Mn, 0.15% or less Ti
Is acceptable as impurities without impairing the effect of the present invention, but since these impurities may reduce the toughness due to the formation of compounds, segregation to subgrain boundaries, etc., Fe0.10% Below, Si0.10% or less, Zn0.10
% Or less, Cr 0.05% or less, Mn 0.05% or less, Ti 0.05%
It is more preferable to limit to the following.

The Al-Li alloy of the present invention is melted and continuously cast to produce an ingot for rolling. Li, which is an alloy component, and other contained components are easily segregated on the surface of the ingot, and if it is rolled as it is. Since the starting point of cracking may occur during rolling, the rolling surface and side surface of the ingot should be 5 m before hot rolling.
After chamfering more than m, the surface has a roughness Ra of 2 μm or less and waviness
It is preferable to finish so that the thickness is 200 μm or less.

The ingot is made of AlLi, CuA during casting.
Coarse intermetallic compounds such as l ₂ , Mg ₂ Si, and FeAl ₃ are generated, and these intermetallic compounds cause cracks during rolling and inhibit the alloy strengthening effect, so that the coarse intermetallic compounds are decomposed, In order to homogenize, the chamfered ingot is heated and held at a high temperature for homogenization. The preferred homogenization temperature is in the range of 520 ° C ± 50 ° C, and the holding time is preferably 1 to 24 hours. The higher the homogenization temperature is, the more efficient it is, but if it is too high, the compound or matrix may be partially dissolved. If it is too low, the temperature needs to be maintained for a long time, which lowers the production efficiency. It is also not preferable because it reacts with the water content of the product and oxidizes to deteriorate the properties of the product.

Zr, V, Mn as alloy components in the alloy,
When Cr is contained, a compound of these elements and aluminum is finely dispersed and precipitated in a matrix, and the ingot is first heated at 450 ° C in order to improve the quality and properties of the product plate.
Hold in the temperature range of ± 30 ° C for 1 to 30 hours, then 520 ° C ±
It is preferred to heat to a homogenization treatment temperature of 50 ° C.

The inventors of the present invention investigated Cu, Z and Z in order to investigate the relationship between the processing temperature and the limit processing rate in Al-Li alloys.
For Al-Li alloys containing r and Mg, samples with a diameter of 20 mm and a height of 20 mm were prepared, and the limit processing rate at each processing temperature was determined from the cracking that occurred when the samples were indented and forged at each temperature. . An example of the result is shown in FIG. As can be seen from FIG. 1, in the Al—Li alloy, it is necessary to perform hot working in a specific temperature range in order to prevent cracking during working.

Based on the above experiment, the Al-L of the present invention is used.
As a result of studying the hot rolling temperature of the i alloy, when the ingot is hot rolled after the homogenization treatment, side cracks (ear cracks) during rolling, cracks such as rolling surface cracks, striped patterns, etc. 520 ℃ ± to prevent the occurrence of surface defects
It has been found to be preferable to start hot rolling in the temperature range of 50 ° C and finish hot rolling at a temperature of 250 ° C or higher. The end temperature is more preferably 300 ° C or higher.

In the hot rolling of Al-Li alloy, it was found that the amount of reduction per rolling has a great influence on the occurrence of cracks. From the viewpoint of cracking, it is preferable that the amount of reduction per operation is as small as possible.
If it is too small, the number of times of rolling until rolling to a plate of a predetermined thickness increases and the rolling time becomes long, so the temperature of the rolled plate tends to be lower than the above end temperature, and the production efficiency becomes poor. On the other hand, if the amount of reduction per one time is too large, cracks in the edges or the like occur during rolling. The optimum amount of reduction per rolling, which was found as a result of experiments and studies, is 3 to 30 mm, except for the final rolling for adjusting the strip thickness, and hot rolling is performed using a reversible rolling mill. It is preferably carried out.

Furthermore, in order to prevent the occurrence of defects, especially edge cracks, which occur during the hot rolling of the Al--Li alloy, it is effective to use the width rolling roll installed in the rolling mill. The width rolling roll is for rolling the side surface portion of the ingot for rolling or the rolled plate, and it is more preferable to perform the width rolling after each rolling, but it lowers the productivity and lowers the temperature of the side surface portion. Since there is a problem such as causing the ear cracks to occur, in the present invention, in the number of times of rolling at least 20% of the total number of hot rolling,
Roll widthwise from 5 to 50 mm on one side.

[0020]

In the present invention, Li: 0.5 to 3.0% is contained,
Further, as a selective component, a specific amount of Cu, Mg, Zr, V,
Using an Al-Li alloy containing Mn, Cr and Ti,
Ingot ingot surface cutting conditions, ingot homogenization treatment conditions, and hot rolling conditions are specified, and by combining these, generation of cracks and surface defects during hot rolling of Al-Li alloy is prevented, quality and properties To obtain an excellent Al-Li alloy plate material.

[0021]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 An ingot of an Al-Li alloy having the composition shown in Table 1 was produced by continuous casting, and the rolled surface of the ingot was chamfered by 10 mm to obtain a test ingot. First, the test ingot No. A to D 450 ℃
After heating at 24 ° C for 24 hours, the temperature was raised to 520 ° C and held for 6 hours. Then, hot rolling was started at 500 ° C. The thickness of the test ingot is 260 mm, 20 mm per time
It was rolled a total of 14 times with a rolling amount of 10 to obtain a 20 mm thick Al-Li alloy plate. The hot rolling was completed at a temperature of 400 ° C. Although width-direction rolling was not performed, the edge crack that occurred was about 10 mm and
It was a material that could be sufficiently used as a Li alloy plate material.

[0022]

[Table 1]

Example 2 In Example 1, each time an odd number of rollings were completed, rolling was performed 7 times (the number of times corresponding to 50% of the total number of rollings) in the width direction of 10 mm on one side. As a result, the occurrence of ear cracks was completely prevented.

Comparative Example 1 Test ingot No. E (260 mm thick) was heated to a temperature of 450 ° C. for 10 hours, then heated to a temperature of 540 ° C. and held for 6 hours, and then hot rolling was started at a temperature of 420 ° C.
Rolling is performed with a rolling reduction of 15 mm each time, and one side is used for each rolling.
When 15 mm width direction rolling is performed, the plate thickness is 16 times.
Although it was rolled to 20 mm, the temperature of the rolled plate reached 230 ° C and large edge cracks occurred.

Example 3 In Comparative Example 1, when the hot rolling start temperature was 500 ° C. and rolling was completed at 380 ° C., edge cracking was completely prevented.

Example 4 Test ingot No. 3 in Table 3 F (260 mm thick) was heated at a temperature of 450 ° C. for 24 hours, then heated to a temperature of 550 ° C. and held for 10 hours, and then hot rolling was started at a temperature of 550 ° C.
A rolling amount of 25 mm was set for each rolling, widthwise rolling was performed on one side for 15 mm in the first rolling, and by 10 rolling and final rolling with a rolling reduction of 12 mm, the rolling end temperature was 450 ° C and a plate material with a thickness of 8 mm was obtained. . The plate material was not at a level that could not be used as a plate at all, but considerable ear cracking occurred, resulting in poor yield.

Example 5 In Example 4, when widthwise rolling of 15 mm on one side was carried out after completion of the first, third and fifth rolling, the edge crack was completely prevented.

Comparative Example 2 In Example 4, when the hot rolling start temperature was 420 ° C., the rolling finish temperature was 210 ° C., and striped patterns were formed on the entire surface of the plate, which was unacceptable as a plate product. .

Example 6 Test ingot No. 1 in Table 1 When the ingot having the same composition as F was ground by 10 mm on each of the rolled surface and the side surface and treated in the same process as in Example 4, only about 10 mm of ear cracks occurred on the rolled plate.

[0030]

As described above, according to the present invention, Al-
When hot-rolling a Li alloy, a hot-rolling method for an Al-Li alloy is provided, which can prevent the occurrence of cracks such as edge cracks and rolling surface cracks and the occurrence of surface defects such as striped patterns. It is useful for practical use of alloys.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the processing temperature of an Al—Li alloy and the limit processing rate.

Claims (5)

[Claims] 1. A method of hot rolling an Al--Li alloy, which contains Li 0.5 to 3.0% (wt%, hereinafter the same),
Further, Cu1.0 to 3.0% (however, Cu1.5 to 5.5% when Mg is not contained), Mg0.5 to 2.0%, Zr0.06
~ 0.3%, V0.06-0.3%, Mn0.06-0.3%, Cr0.
An ingot of Al-Li alloy containing one or two or more of 06 to 0.3% and Ti 0.02 to 0.3%, and the balance of Al and unavoidable impurities in a temperature range of 520 ° C ± 50 ° C. After heating for 1 to 24 hours, hot rolling is started in the temperature range, and hot rolling is finished at a temperature of 250 ° C. or higher. . 2. A method of hot rolling an Al--Li alloy, which contains Li 0.5 to 3.0% and further Zr 0.06 to 0.
3%, V0.06-0.3%, Mn0.06-0.3%, Cr0.06-
It contains one or more of 0.3% and the balance is A
The ingot of Al-Li alloy consisting of 1 and unavoidable impurities is heated to a temperature range of 450 ° C ± 30 ° C for 1 to 30 hours and then to a temperature range of 520 ° C ± 50 ° C for 1 to 24 hours. Al-characterized in that it is held, and then hot rolling is started in the temperature range, and hot rolling is finished at a temperature of 250 ° C or lower.
Method for hot rolling Li alloy. 3. The method of hot rolling an Al--Li alloy according to claim 1, wherein the reduction amount per hot rolling is 3 to 30 mm except for the final rolling. Hot rolling method of Al-Li alloy. 4. A method for hot rolling an Al-Li alloy, wherein widthwise rolling of 5 to 50 mm on each side is performed on each side surface of a rolled plate at a rolling stage of 20% or more of the total rolling times. The Al-Li according to claim 1, wherein
Hot rolling method for alloys. 5. A method of hot rolling an Al—Li alloy, wherein the rolling surface and the side surface of the ingot of the Al—Li alloy are 5 mm.
After cutting, roughness Ra is less than 2 μm and waviness is 200 μ
It is finished to m or less.
4. The hot rolling method of the Al-Li alloy according to 4.