Method for producing thick aluminum sheet material, and thick aluminum sheet material

Abstract

Provided is a method for manufacturing a thick aluminum sheet material, characterized by comprising, when the longitudinal direction of an aluminum ingot or an aluminum alloy ingot is set as Z direction, a first reduction step for reducing the size of the ingot in the Z direction by reducing the ingot in the Z direction by hot-forging the ingot, thereby obtaining a hot-forged product, and a second reduction step for reducing the size of the ingot in the Z direction by hot-forging the ingot in the Z direction. And a second reduction step in which the hot-forged article is reduced in the Z direction by hot rolling the hot-forged article, thereby reducing the size of the hot-forged article in the Z direction, and obtaining a thick aluminum plate. According to the present invention, it is possible to provide a method for producing a thick aluminum sheet material with which it is possible to produce a thick sheet material having few internal pores in the production of a thick aluminum or aluminum alloy sheet material having a relatively thick sheet thickness.

Description

Technical Field

[0001] This invention relates to thick plates of aluminum or aluminum alloys with few internal pores. Background Technology

[0002] Previously, thick aluminum or aluminum alloy plates were widely used as blanks for processing vacuum chambers, semiconductor manufacturing equipment, and the like. With the increasing size of these devices, ultra-thick plates with significant thicknesses are also required. In these thick aluminum alloy plates, reducing internal porosity is necessary to ensure airtightness, reduce venting, and / or improve the uniformity of surface treatment and enhance mechanical strength (especially fatigue strength). Particularly in ultra-thick plates, there is a tendency for internal porosity to increase, making this a significant technical challenge.

[0003] In addition, reducing internal porosity is a common challenge in billets used in other fields requiring high reliability, such as high-speed rail, shipbuilding, and aerospace.

[0004] Thick aluminum alloy plates are typically manufactured by hot rolling from roughly rectangular DC ingots (slabs). These slabs have a certain degree of internal porosity, particularly tending to have large and numerous internal pores near the center of the slab's thickness.

[0005] When a slab with a thickness of about 500mm is hot-rolled to a thickness of less than 100mm using conventional hot rolling with a relatively high reduction rate (above 80%), the porosity caused by material deformation is pressed and eliminated to near the center of the slab thickness, thus achieving a state with fewer internal pores.

[0006] In contrast, during the hot rolling process to produce plates with thicknesses of, for example, 200-400 mm, there is a problem where the size and / or number of internal pores increase compared to the original slab. This is believed to be because light / moderate reduction is insufficient to cause deformation that compresses existing pores; instead, it promotes pore enlargement and / or connection, and also contributes to the formation of new pores at grain boundaries and / or intermetallic compound particle interfaces. In particular, in conjunction with the different deformation state near the center of the plate thickness, pores already present from the slab state are usually not eliminated, and their size and / or number actually increase.

[0007] Thus, it is well known that increasing the hot rolling reduction rate can reduce the internal porosity of hot-rolled plates. However, there are limits to the thickness of DC slabs and / or the maximum material thickness entering the hot rolling mill in industrial applications. Therefore, especially when manufacturing thick plates, there are limits even to increasing the hot rolling reduction rate. Consequently, extremely thick plates are prone to retaining internal porosity.

[0008] Therefore, Patent Document 1 discloses the following technology: suppressing the amount of hydrogen gas by degassing during casting, mainly controlling the reduction rate of one pass in hot rolling, thereby reducing the porosity of the aluminum thick plate.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2009-090372 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] However, the method in Patent Document 1 does not adequately improve the reduction of porosity in extremely thick plates.

[0014] Therefore, the purpose of this invention is to provide a method for manufacturing thick aluminum plates, which can produce thick plates with fewer internal pores in the manufacturing of thick aluminum or aluminum alloy plates with relatively thick plate thickness.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research and discovered that, in the manufacture of thick aluminum or aluminum alloy plates with relatively thick thickness, by combining hot forging and hot rolling of ingots to form thick plates, it is possible to reduce internal porosity in thick plates with relatively thick thickness, thereby completing the present invention.

[0017] That is, the present invention (1) provides a method for manufacturing thick aluminum plates, characterized in that, when the long side direction of the aluminum ingot or aluminum alloy ingot is set as the Z direction, it has the following characteristics:

[0018] The first pressing process involves hot forging the ingot, pressing it down along the Z-direction to reduce its Z-direction dimension, thus obtaining a hot-forged product; and

[0019] The second pressing process involves hot rolling the hot forging to press it down along the Z-direction, reducing the Z-direction dimension of the hot forging to obtain a thick aluminum sheet.

[0020] In addition, the present invention (2) provides a method for manufacturing aluminum thick plates of (1), characterized in that the total reduction rate in the first pressing step and the second pressing step is 75.0% or more.

[0021] In addition, the present invention (3) provides a method for manufacturing aluminum thick plates of (1) or (2), characterized in that the first reduction rate in the first reduction process is 60.0% or more.

[0022] In addition, the present invention (4) provides a method for manufacturing aluminum thick plates of (1) or (2), characterized in that the second reduction rate in the second reduction process is 0.5% or more.

[0023] In addition, the present invention (5) provides a method for manufacturing the aluminum thick plate of (1) or (2), characterized in that the thickness of the aluminum thick plate is 100 mm or more.

[0024] In addition, the present invention (6) provides a method for manufacturing aluminum thick plates of (1) or (2), characterized in that the Z-direction dimension of the above-mentioned ingot is 800 mm or more.

[0025] Furthermore, the present invention (7) provides a method for manufacturing the aluminum thick plate of (1) or (2), characterized in that, when the short side direction of the above-mentioned ingot is set as the X direction,

[0026] The ratio of the Z-direction dimension of the aforementioned ingot to the X-direction dimension of the aforementioned ingot (Z-direction dimension / X-direction dimension) is 2.0 or more.

[0027] In addition, the present invention (8) provides a thick aluminum plate, characterized in that it is obtained by performing the following process when the long side direction of an aluminum ingot or an aluminum alloy ingot is set to the Z direction:

[0028] The first pressing process involves hot forging the ingot, pressing it down along the Z-direction to reduce its Z-direction dimension, thus obtaining a hot-forged product; and

[0029] The second pressing process involves hot rolling the hot forging to press it down along the Z-direction, reducing the Z-direction dimension of the hot forging to obtain a thick aluminum sheet.

[0030] In addition, the present invention (9) provides a thick aluminum plate, characterized in that it is composed of aluminum or an aluminum alloy containing more than 80% by mass of aluminum.

[0031] The plate thickness is 100mm or more.

[0032] Microscopic observation of a cross-section parallel to the plate thickness direction revealed that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of the cross-section, when divided into three parts along the plate thickness direction, was 0.15 pores / mm. 2 the following.

[0033] In addition, the present invention (10) provides a thick aluminum plate, characterized in that it is composed of an Al-Mg alloy containing 1.50% by mass or more of Mg.

[0034] The plate thickness is 100mm or more.

[0035] Microscopic observation of a cross-section parallel to the plate thickness direction revealed that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of the cross-section, when divided into three parts along the plate thickness direction, was 0.15 pores / mm. 2 the following.

[0036] The effects of the invention

[0037] According to the present invention, a method for manufacturing thick aluminum plates can be provided, which can produce thick plates with fewer internal pores in the manufacturing of thick aluminum or aluminum alloy plates with relatively thick plate thickness. Attached Figure Description

[0038] Figure 1 This is a schematic perspective view of an example of the shape of a hot-forged ingot according to the present invention.

[0039] Figure 2 This is a schematic perspective view illustrating the manufacturing process of the aluminum sheet material of the present invention.

[0040] Figure 3 This is a schematic cross-sectional view of the aluminum sheet material of the present invention cut parallel to the thickness direction.

[0041] Figure 4 The results are observations of the cross-section of the thick aluminum plate in Example 1 based on fluorescence penetrant testing.

[0042] Figure 5 The results are based on the observation of the cross-section of the thick aluminum plate of Comparative Example 1 using fluorescence penetrant testing.

[0043] Figure 6 This is a SEM image of the cross-section of the thick aluminum plate from Example 1.

[0044] Figure 7 This is a SEM image of the cross-section of the thick aluminum plate in Comparative Example 1.

[0045] Figure 8 This is an optical microscope image of the cross-section of the thick aluminum plate of Example 1.

[0046] Figure 9 This is an optical microscope image of the cross-section of the thick aluminum plate of Comparative Example 1. Detailed Implementation

[0047] The method for manufacturing aluminum alloy thick plates of the present invention is characterized in that, when the long side direction of the aluminum ingot or aluminum alloy ingot is set as the Z direction, it has the following properties:

[0048] The first pressing process involves hot forging the ingot, pressing it down along the Z-direction to reduce its Z-direction dimension, thus obtaining a hot-forged product; and

[0049] The second pressing process involves hot rolling the hot forging to press it down along the Z-direction, reducing its Z-direction dimension to obtain a thick aluminum plate. It should be noted that in this invention, both thick plates made of pure aluminum and thick plates made of aluminum alloys are collectively referred to as thick aluminum plates.

[0050] The method for manufacturing aluminum thick plates of the present invention comprises a composite hot working process that combines a first pressing step of forging and a second pressing step of hot rolling.

[0051] The first pressing process is a hot forging process that involves pressing down aluminum ingots or aluminum alloy ingots.

[0052] Aluminum ingots are those hot-forged in the first pressing process and are made of pure aluminum from the 1000 series. Aluminum alloy ingots are those hot-forged in the first pressing process and are made of aluminum alloys. There are no particular limitations on the types of aluminum alloys; examples include 2000, 3000, 4000, 5000, 6000, 7000, and 8000 series aluminum alloys. In particular, 5000 and 6000 series aluminum alloys are used in semiconductor manufacturing equipment.

[0053] As an ingot for hot forging (the ingot before hot forging), an example is an ingot produced by the conventional semi-continuous casting (DC casting) method. Semi-continuous casting of aluminum or aluminum alloys typically involves supplying molten aluminum or aluminum alloy from above a horizontally positioned mold with both ends open, pouring cooling water or the like under the mold, thereby cooling and solidifying it within the mold, and then discharging it downwards. In semi-continuous casting, the horizontal direction of the mold corresponds to the X and Y directions of the ingot (described later), and the casting direction corresponds to the Z direction of the ingot (described later).

[0054] In the first pressing process, the ingot undergoing hot forging (the ingot before hot forging) is rectangular in shape. (Refer to...) Figure 1 The dimensions of the ingots to be hot-forged are described. Figure 1 This is a schematic perspective view of an example of the shape of a hot-forged ingot according to the present invention. Figure 1 In this process, the ingot 1 subjected to hot forging is a cuboid. The direction in which the longest of the three sides of ingot 1 extends is designated as the long side direction, which is set as the Z direction. The direction in which the shortest of the three sides of ingot 1 extends is designated as the short side direction, which is set as the X direction. The direction in which the second longest of the three sides of ingot 1 extends is designated as the Y direction. It should be noted that the Z, Y, and X directions are orthogonal.

[0055] In the first pressing process, the Z-direction dimension of the hot-forged ingot is preferably 800 mm or more, more preferably 1000 mm or more, and even more preferably 1500 mm or more. Furthermore, in the first pressing process, the X-direction dimension of the hot-forged ingot is approximately 350 to 700 mm.

[0056] In the first pressing process, the ratio of the Z-direction dimension to the X-direction dimension of the hot-forged ingot (Z-direction dimension / X-direction dimension) is preferably 2.0 or more, more preferably 3.0 or more, and even more preferably 3.5 or more. By ensuring that the ratio of the Z-direction dimension to the X-direction dimension of the hot-forged ingot (Z-direction dimension / X-direction dimension) is within the above range, the effect of reducing internal porosity is enhanced, especially the effect of reducing internal porosity near the center of the plate thickness is enhanced. Furthermore, to ensure safety, the ratio of the Z-direction dimension to the X-direction dimension of the hot-forged ingot (Z-direction dimension / X-direction dimension) is preferably 6.0 or less.

[0057] In the first pressing process, there are no particular restrictions on the manufacturing method of the ingot for hot forging; for example, conventional melt treatment can be performed. Through melt treatment, the hydrogen content of the product becomes approximately 0.2 cc / 100g or less. Furthermore, the obtained ingot can be homogenized and surface-cut using conventional methods. The homogenization temperature can be appropriately set for each alloy.

[0058] In the first pressing process, the ingot to be hot-forged (the ingot before hot forging) is pressed down by hot forging, reducing the ingot's Z-direction dimension. The hot forging performed in the first pressing process is a free forging process where the aluminum or aluminum alloy ingot is compressed along the Z-direction at a temperature above its recrystallization temperature. More specifically, free forging can include upsetting, drawing, and widening. In hot forging (free forging), there is a constraint force generated by friction acting on the surface in contact with the die, resulting in small deformation; therefore, unlike rolling, the strain in the central part is larger.

[0059] The temperature of hot forging in the first pressing process has an optimal value for each pure aluminum or aluminum alloy and is not particularly limited. For example, the preheating temperature is preferably 300~550℃, and the material temperature during hot forging is preferably 300℃~500℃.

[0060] In the first pressing process, the hot-forged object is hot-forged until the thickness in the Z direction of the hot-forged object reaches the desired thickness. The hot forging can be performed once or more. That is, in the first pressing process, the ingot can be compressed to the desired thickness by one hot forging, or it can be compressed to the desired thickness by performing hot forging on the ingot twice or more.

[0061] The first reduction rate in the first pressing step is preferably 60.0% or more, more preferably 70.0% or more, and even more preferably 80.0% or more. Since the upper limit of the first reduction rate is not limited here due to limitations of the apparatus, etc., it is preferably around 95%. By keeping the first reduction rate in the first pressing step within the above range, the effect of reducing internal porosity is enhanced. It should be noted that in this invention, the first reduction rate is a value calculated using the following formula.

[0062] First reduction rate (%) = ((Z-direction dimension of the ingot before initial hot forging - Z-direction dimension of the ingot after final hot forging) / Z-direction dimension of the ingot before initial hot forging) × 100

[0063] Thus, a hot forging is obtained by performing the first pressing process. The hot forging obtained by the first process can be directly used as the object of hot rolling in the second pressing process, or the surface of the hot forging obtained by the first process that contacts the die can be surface-cut before performing the second pressing process, and then the surface-cut hot forging can be used as the object of hot rolling in the second pressing process.

[0064] Furthermore, after the first pressing process and before the second pressing process, the outer diameter shape of the raw material for the second pressing process can be adjusted to a cuboid shape suitable for rolling by machining, cutting, and / or side surface cutting, as needed, thereby adjusting the dimensions. At this time, the radius (R) and / or chamfering of the corners and / or edges can also be performed as needed.

[0065] The second pressing process is a hot rolling process that presses down the hot forging obtained from the first pressing process.

[0066] In the second pressing process, the hot forging obtained in the first pressing process is pressed down by hot rolling, reducing the Z-direction dimension of the hot forging. The hot rolling in the second pressing process is a plastic forming process in which the hot forging is pressed down along the Z-direction of the hot-rolled material between rotating rolls at a temperature above the recrystallization temperature of the hot forging. In the second pressing process, the hot forging obtained in the first pressing process is compressed along the Z-direction of the hot-rolled material to achieve the desired thickness. During hot rolling, shear forces are generated due to friction between the rolls and the material, resulting in a more intense processing of the surface portion of the material compared to the center.

[0067] It should be noted that, in this invention, the Z-direction of the hot-forged material corresponds to the Z-direction of the ingot before hot forging in the first pressing process, and is the direction in which the ingot is compressed in the first pressing process. (Refer to...) Figure 2 The Z-direction of hot forgings is explained. Figure 2 This is a schematic perspective view illustrating the manufacturing process of the aluminum sheet material of the present invention. Figure 2In the process, the hot-forged ingot 1 undergoes a first pressing process 11 to reduce its Z-direction dimension. Next, the hot-forged material 2 obtained from the first pressing process 11 undergoes a second pressing process 12 to reduce its Z-direction dimension, resulting in an aluminum sheet 3. At this point, the Z-direction of the hot-forged material 2 is the same as the Z-direction of the ingot 1 before hot forging, and is the direction in which the ingot is compressed during hot forging. In other words, the Z-direction of the hot-forged material 2 is the thickness direction of the aluminum sheet 3 obtained from the second pressing process 12. That is, from the perspective of the final aluminum sheet 3, the thickness direction of the aluminum sheet 3 is the Z-direction of the aluminum sheet 3, the Z-direction of the hot-forged material 2, and the Z-direction of the ingot 1.

[0068] The hot rolling temperature in the second pressing process has an optimal value for each type of pure aluminum or aluminum alloy and is not particularly limited. For example, the material temperature during hot rolling is preferably 400°C to 500°C. In addition, dimensional accuracy and / or surface smoothness in the hot rolling of the second pressing process can be managed in essentially the same way as in the hot rolling of conventional sheet metal.

[0069] In the second pressing process, the hot-rolled material is hot-rolled until the thickness of the aluminum sheet in the Z direction reaches the desired thickness. The hot rolling can be performed once or more. That is, in the second pressing process, the hot-forged material can be compressed to the desired thickness through one hot rolling operation, or it can be compressed to the desired thickness through two or more hot rolling operations.

[0070] The second reduction rate in the second pressing step is preferably 0.5% or more, more preferably 15.0% or more, and even more preferably 30.0% or more. There is no particular upper limit, but it is preferably around 80%. By keeping the second reduction rate in the second pressing step within the above range, the reduction effect on internal porosity is increased. It should be noted that in this invention, the second reduction rate is a value calculated using the following formula.

[0071] Second reduction rate (%) = ((Z-direction dimension of the hot forging before initial hot rolling - Z-direction dimension of the aluminum sheet after final hot rolling) / Z-direction dimension of the hot forging before initial hot rolling) × 100

[0072] The total reduction rate in the first and second pressing steps is preferably 75.0% or more, more preferably 85% or more, and even more preferably 90% or more. By keeping the total reduction rate in the first and second pressing steps within the above range, the effect of reducing internal porosity is enhanced. It should be noted that, in this invention, the total reduction rate in the first and second pressing steps is a value calculated using the following formula.

[0073] Total reduction rate (%) in the first and second pressing processes = [((Z-direction dimension of the ingot before initial hot forging - Z-direction dimension of the aluminum sheet after final hot rolling) / Z-direction dimension of the ingot before initial hot forging)] × 100

[0074] It should be noted that when surface cutting (intermediate surface cutting) is performed after hot forging, the above total reduction rate is calculated as follows.

[0075] Total reduction rate (%) in the first and second pressing processes = [{Z-direction dimension of the ingot before initial hot forging - (Z-direction dimension of the aluminum sheet after final hot rolling × Z-direction dimension after hot forging / Z-direction dimension at the start of hot rolling)} / Z-direction dimension of the ingot before initial hot forging)] × 100

[0076] That is, it can be expressed by the following formula.

[0077] Total reduction ratio = [{Z0-Z3×(Z1 / Z2)} / Z0]×100, or

[0078] Total reduction rate (%) in the first and second pressing processes = 100 - (100 - RD1) × (100 - RD2) / 100

[0079] Z0: Z-axis dimension of the ingot before initial hot forging.

[0080] Z1: Z-direction dimension after hot forging

[0081] Z2: Z-direction dimension at the start of hot rolling

[0082] Z3: Z-direction dimension after hot rolling

[0083] RD1: Reduction rate of the first pressing process (hot forging)

[0084] RD2: Reduction rate of the second reduction process (hot rolling)

[0085] In the method for manufacturing aluminum thick plates of the present invention, after the first pressing process and the second pressing process, cutting to a specified shape, annealing, heat treatment (solution treatment and quenching, aging treatment), and shape correction (stretching, compression, etc.) can be performed as needed.

[0086] Annealing and heat treatment conditions vary depending on the alloy system. For example, they can be carried out according to the standard conditions described in the "Aluminum Handbook, 6th Edition", pp. 9-11.

[0087] As the final state of thick plates, in non-heat-treated alloys (3000 series, 5000 series and pure aluminum = 1000 series), H112 and O are the main components.

[0088] Regarding heat-treated alloys (2000 series, 6000 series and 7000 series), in addition to H112 and O, T3, T4, T6, T7 and their variations (T651 and / or T7, etc.) after precipitation aging also become the final state of thick plates.

[0089] The condition of each alloy is in accordance with the provisions of JIS H0001 and JIS H4000.

[0090] Thus, in the method for manufacturing aluminum thick plates of the present invention, it is possible to obtain aluminum thick plates with no internal pores or with significantly reduced internal pores.

[0091] In hot forging (free forging), the material near the surface in contact with the die is constrained by friction, and material flow near the center in the compression direction is dominant. Conversely, in hot rolling, shear forces are generated due to friction between the rolls and the material, resulting in more intense processing of the surface portion of the material compared to the center, and material flow near the surface is dominant. Furthermore, in the method for manufacturing thick aluminum sheets of the present invention, by performing hot forging followed by hot rolling, the aforementioned effects of hot forging and hot rolling can be combined, reducing internal porosity.

[0092] The aluminum sheet produced by the method for manufacturing aluminum sheet according to the present invention preferably has a thickness of 100 mm or more, more preferably 150 mm or more. In conventional methods for manufacturing thick plates using only hot rolling, the presence of internal porosity is particularly problematic when the manufactured aluminum sheet has a thickness of 100 mm or more. While the method for manufacturing aluminum sheet according to the present invention can also be used for manufacturing aluminum sheets with a thickness less than 100 mm, the reduction in internal porosity achieved by the method for manufacturing aluminum sheet according to the present invention is most effective in manufacturing aluminum sheets with a thickness of 100 mm or more. It should be noted that the upper limit of the thickness (final sheet thickness) of the aluminum sheet depends on the processing range of the hot rolling mill. For example, if a rolling mill capable of rolling from 600 mm is used, a sheet with a thickness of 570 mm can also be manufactured. Thus, it is possible to manufacture aluminum sheets with a thickness greater than the original ingot's X-direction dimension (slab thickness) and to reduce internal porosity. For example, it is possible to manufacture aluminum sheets with reduced internal porosity with a thickness of 550 mm using an ingot with a dimension of 500 mm in the X direction.

[0093] The aluminum sheet produced by the manufacturing method of the present invention has very few internal pores of 50 μm or more, especially the number density of internal pores of 50 μm or more in the center of the sheet thickness is much lower than the number density in the center of the sheet thickness obtained by conventional manufacturing methods. Furthermore, because the aluminum sheet produced by the manufacturing method of the present invention has very few internal pores of 50 μm or more, its fatigue strength is higher than that of thick sheets obtained by conventional manufacturing methods.

[0094] For example, for an ingot with a dimension of 600 mm in the X direction, without hot forging, simply hot rolling along the X direction to achieve a final plate thickness of approximately 60 mm or less (approximately a reduction rate of 90% or more) yields an aluminum plate with relatively few internal pores. On the other hand, for an ingot with a dimension of 600 mm in the X direction, without hot forging, simply hot rolling to achieve a final plate thickness of approximately 100 mm or more (approximately a reduction rate of 83% or less) does not produce a thick aluminum plate with few internal pores. Therefore, to obtain an extremely thick plate with a thickness of 100 mm or more through hot rolling with the same 90% reduction rate as the aforementioned 60 mm plate, it is necessary to hot roll a slab with a dimension of 1200 mm or more in the X direction. The casting and hot rolling of such slabs are difficult to implement within the specifications and / or conventional conditions of industrial equipment.

[0095] In contrast, in the method for manufacturing thick aluminum sheets of the present invention, the pressing process along the Z-direction is fundamentally different from conventional processes for ingots with a Z-direction dimension preferably of 800 mm or more, more preferably 1000 mm or more, and even more preferably 1500 mm or more. For example, if the blank has a Z-direction dimension of 1200 mm or more, hot forging is performed in the first pressing process, followed by hot rolling in the second pressing process, pressing along the Z-direction with a total reduction rate of 90% or more. Thus, even if the final sheet thickness is 100 mm or more, thick aluminum sheets with fewer internal pores can be obtained.

[0096] The aluminum sheet material of the first aspect of the present invention is characterized in that it is obtained by performing the following steps when the long side direction of an aluminum ingot or an aluminum alloy ingot is set to the Z direction:

[0097] The first pressing process involves hot forging the ingot, pressing it down along the Z-direction to reduce its Z-direction dimension, thus obtaining a hot-forged product; and

[0098] The second pressing process involves hot rolling the hot forging to press it down along the Z-direction, reducing the Z-direction dimension of the hot forging to obtain a thick aluminum sheet.

[0099] The first and second pressing steps of the aluminum sheet in the first embodiment of the present invention are the same as the first and second pressing steps of the aluminum sheet manufacturing method of the present invention. Through a composite hot working process based on hot forging and rolling, the internal pores are effectively compressed and eliminated.

[0100] The second aspect of the aluminum sheet material of the present invention is characterized in that it is composed of aluminum or an aluminum alloy containing more than 80% by mass of aluminum.

[0101] The plate thickness is 100mm or more.

[0102] Microscopic observation of a cross-section parallel to the plate thickness direction revealed that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of the cross-section, when divided into three parts along the plate thickness direction, was 0.15 pores / mm. 2 the following.

[0103] The second aspect of the present invention uses an aluminum sheet containing 80% by mass or more aluminum or an aluminum alloy, thereby ensuring the material's ductility. In a combined hot working process based on hot forging and rolling, internal porosity is effectively compressed and eliminated. The aluminum sheet or aluminum alloy of the second aspect of the present invention further preferably contains 90% by mass or more aluminum.

[0104] The aluminum sheet thickness of the second aspect of the present invention is 100 mm or more, preferably 150 mm or more.

[0105] In the second aspect of the aluminum sheet of the present invention, under a microscope, when the cross-section is divided into three parts in the thickness direction, the number density of internal pores with a Freret diameter of 50 μm or more in the central part is 0.15 pores / mm. 2 The preferred value is 0.10 pieces / mm. 2 The fatigue strength is increased by ensuring that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of a cross-section parallel to the plate thickness direction is within the aforementioned range.

[0106] In this invention, the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of a section divided into three parts along the thickness direction is the analytical value obtained from scanning electron microscopy (SEM) observation of a section parallel to the thickness direction. In SEM observation, firstly, the cross-section of the analytical object is prepared by appropriately smoothing the cross-section parallel to the thickness direction. Then, the cross-section is observed using a scanning electron microscope to obtain an SEM image of the analytical object cross-section. Next, in the obtained SEM image of the cross-section, the central part, when divided into three parts along the thickness direction, is divided, and the number of internal pores with a Ferete diameter of 50 μm or more present in that division and the area (mm²) of that division are determined. 2The number density of internal pores with a Ferrette diameter of 50 μm or more is calculated. Furthermore, in this invention, when analyzing the number density of internal pores with a Ferrette diameter of 50 μm or more in the central portion of a section divided into three parts along the thickness direction, an optical microscope can be used instead of a SEM to obtain an observation image. In the obtained optical microscope image, the number density of internal pores with a Ferrette diameter of 50 μm or more is determined using the same method as in the SEM observation case.

[0107] It should be noted that, referring to Figure 3 The central portion and the entire cross-section are explained when the cross-section is divided into three parts along the thickness direction. Figure 3 This is a schematic cross-sectional view of a thick aluminum plate 20mm thick, cut parallel to the plate thickness direction at 13mm. Figure 3 When the section 11 is divided into three equal parts along the thickness direction 13, the middle part is the central part 14, and the parts on both sides are the outer parts 15a and 15b. In addition, the outer parts 15a, the central part 14, and the outer parts 15b, that is, the entire cross-sectional area 16 from one surface 12a to another surface 12b of the aluminum sheet 20, constitute the entire cross-sectional area 16.

[0108] The second aspect of the present invention uses an aluminum alloy ingot containing 80% by mass or more, preferably 90% by mass or more, of aluminum or an aluminum alloy as an ingot hot-forged in the first pressing process, and performs the above-described method for manufacturing the aluminum thick sheet of the present invention, thereby manufacturing it appropriately.

[0109] The third-party aluminum sheet of the present invention is characterized in that it is composed of an Al-Mg alloy containing 1.50% by mass or more of Mg.

[0110] The plate thickness is 100mm or more.

[0111] Microscopic observation of a cross-section parallel to the plate thickness direction revealed that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of the cross-section, when divided into three parts along the plate thickness direction, was 0.15 pores / mm. 2 the following.

[0112] The third-order aluminum sheet of the present invention is composed of an Al-Mg alloy containing 1.50% by mass or more of Mg. The Mg content of the Al-Mg alloy in the third-order aluminum sheet of the present invention is 1.50% by mass or more, preferably 2.2 to 6.0% by mass, more preferably 3.5 to 6.0% by mass. For example, 5000 series alloys can be cited as Al-Mg alloys in the third-order aluminum sheet of the present invention. By keeping the Mg content of the Al-Mg alloy within the above range, it is suitable for use as a thick plate in stress-bearing parts. On the other hand, even if the Mg content of the Al-Mg alloy is less than the above range, the effect of reducing porosity can be obtained, but it is not suitable for use as a structural component. Examples of Al-Mg alloys in the third-order aluminum sheet of the present invention include Al-Mg alloys containing 1.50% by mass or more, preferably 2.20 to 6.00% by mass, more preferably 3.50 to 6.00% by mass of Mg, with the balance being Al and unavoidable impurities. Furthermore, as a third-party Al-Mg alloy for thick aluminum plates according to the present invention, examples of such Al-Mg alloys include those containing 1.50% by mass or more, preferably 2.20 to 6.00% by mass, and more preferably 3.50 to 6.00% by mass of Mg, and also containing one or more of the following: 0.05 to 0.35% by mass of Cu, 0.05 to 0.35% by mass of Zn, 0.05 to 0.35% by mass of Cr, 0.05 to 1.0% by mass of Mn, 0.05 to 0.35% by mass of Zr, 0.05 to 0.35% by mass of Sc, 0.05 to 0.35% by mass of V, 0.05 to 0.35% by mass of Ni, 0.005 to 0.20% by mass of Ti, 0.001 to 0.04% by mass of Be, and 0.001 to 0.02% by mass of B, with the balance being Al and unavoidable impurities.

[0113] The aluminum sheet material of the third type of this invention has a thickness of 100 mm or more, preferably 150 mm or more. Through a composite hot working process based on hot forging and rolling, the internal pores are effectively compressed and eliminated.

[0114] In the third-party aluminum sheet of the present invention, under microscopic observation of a cross-section parallel to the thickness direction, the number density of internal pores with a Freret diameter of 50 μm or more in the central part of the cross-section when the cross-section is divided into three parts in the thickness direction is 0.15 pores / mm. 2 The preferred value is 0.10 pieces / mm. 2 The fatigue strength is increased by ensuring that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of a cross-section parallel to the plate thickness direction is within the aforementioned range.

[0115] The third-party aluminum thick plate of the present invention uses an aluminum alloy ingot with a Mg content of 1.50% by mass or more as the ingot for hot forging in the first pressing process, and performs the above-described method for manufacturing the aluminum thick plate of the present invention, thereby appropriately manufacturing it.

[0116] The following examples illustrate the present invention in detail, but the present invention is not limited to the examples shown below.

[0117] Example

[0118] (Example 1)

[0119] A DC slab (JIS 5083 alloy, thickness 600 mm (X direction dimension), width 1505 mm (Y direction dimension), length 2090 mm (Z direction dimension)) with the chemical composition shown in Table 1, produced by semi-continuous casting, was heated to a temperature of 360~420°C, above the recrystallization temperature (350°C). It was then pressed down along the Z direction using a 15000tf hot forging press, undergoing multiple compressions until the Z direction dimension reached 350 mm. The initial reduction rate at this point was 83.2%.

[0120] Next, the surface is cut until the Z-axis dimension becomes 334 mm, and then it is reheated to a temperature of 530°C, above the recrystallization temperature (350°C). It is then rolled in multiple passes along the Z-axis using a hot rolling mill until the Z-axis dimension becomes 180 mm, resulting in a thick plate. The second reduction rate at this point is 45.6%. Furthermore, the total reduction rate of the first and second reduction processes is 90.9%. The total reduction rate is calculated as follows.

[0121] Total reduction rate (%) = (Z-direction dimension of DC slab before initial hot forging - Z-direction dimension after hot rolling × Z-direction dimension after hot forging / Z-direction dimension at the start of hot rolling) / Z-direction dimension of DC slab before initial hot forging × 100) = (2090 - 180 × 350 / 334) / 2090 × 100 = 90.9

[0122] (Comparative Example 1)

[0123] A JIS 5083 alloy plate with an X-axis dimension reduced from 600 mm to 180 mm was used as a comparison material by hot rolling of DC slabs with the chemical composition shown in Table 1 using conventional processes. The reduction rate of this hot rolling was approximately 70%.

[0124] Evaluation of internal porosity based on fluorescence penetrant testing

[0125] The cross-section along the thickness direction of a thick plate was observed using fluorescence penetrant testing. The results are shown below. Figure 4 (Example 1) and Figure 5 (Comparative Example 1)

[0126] The operation and conditions of fluorescent penetrant testing are as follows.

[0127] After surface cutting and cleaning of the rolled section of the thick plate, a fluorescent penetrant (Super Glo OD-2800N, manufactured by MARKTEC) is applied to the observation surface. After penetrating the pores, the remaining penetrant is washed away. The plate is then dried and observed under black light, where the areas where the fluorescent penetrant has penetrated are identified by the light spots. These light spots are considered the locations of the pores.

[0128] The observations showed that in the conventionally hot-rolled material of Comparative Example 1, specifically the 180mm thick 5083 alloy sheet, luminescent points indicating internal pores were clustered in a region approximately one-third of the sheet thickness in the central part of the cross-section. In contrast, no significant luminescent points or clusters of luminescent points were found in the cross-section of the thick sheet of Example 1. Therefore, it can be concluded that, according to the manufacturing method of the present invention, the internal pores of the thick sheet are essentially eliminated, and the problem of internal pores is essentially resolved.

[0129] Evaluation of internal pores based on microscopic observation

[0130] A cross-section parallel to the thickness direction of a thick plate was analyzed using a scanning electron microscope (SEM). The results are presented below. Figure 6 (Example 1) and Figure 7 (Comparative Example 1). Furthermore, the cross-section along the thickness direction of the thick plate was analyzed using an optical microscope. The results are shown below. Figure 8 (Example 1) and Figure 9 (Comparative Example 1). It should be noted that, in Figures 6-9 In the study, although small black dots with a maximum Ferete diameter (hereinafter referred to as Ferete diameter) of less than 50 μm and mostly between 5 and 20 μm were observed, the intermetallic compound particles of Mg2Si, composed of elements lighter than Al, also mostly appeared black in SEM. Analysis confirmed that these were not internal pores. However, these black dots included pores created when Mg2Si and / or intermetallic compound particles containing transition elements such as Fe were detached during the grinding process of preparing the observation samples. Of course, in comparative materials where internal porosity could not be reduced, fine internal pores were also observed as black dots, making them difficult to distinguish rigorously. Therefore, in this invention, the number density of pores with a Ferete diameter of 50 μm or more and pores with a Ferete diameter of 100 μm or more is used as an indicator for comparatively evaluating the effect of reducing internal porosity.

[0131] Next, SEM was used to observe the area near the center of the plate thickness. Image analysis of the obtained SEM images was performed to determine the number density per unit area of ​​internal pores with a Ferete diameter of 50 μm or more and internal pores with a Ferete diameter of 100 μm or more in a region centered on the center of the plate thickness in the thickness direction (the central part when the plate thickness is divided into three parts). The results are shown in Table 2.

[0132] [Table 1]

[0133]

[0134] [Table 2]

[0135]

[0136] The analysis showed that in Comparative Example 1, the conventionally hot-rolled material was enclosed within the pores, while in Example 1, the internal pores disappeared. Therefore, according to the manufacturing method of the present invention, the internal pores of thick plates are essentially eliminated, and the problem of internal pores is essentially resolved.

[0137] Evaluation based on rotational bending fatigue strength

[0138] The example of rotational bending fatigue strength illustrates that the elimination of porosity based on the method of the present invention is related to the improvement of mechanical properties.

[0139] Rotational bending fatigue tests were conducted according to JIS Z2278. Test specimens (80 mm in length, 8 mm in parallel section diameter) were collected from a region representing one-third of the thickness of a 180 mm thick hot-rolled plate (5083-H112) centered on the center of the plate thickness in the thickness direction (the central portion when the plate is divided into three parts in the thickness direction). The fatigue strength was evaluated based on 10^7 repeated stresses.

[0140] As a result, the rotational bending fatigue strength was 152 MPa in Example 1 of the present invention and 69 MPa in Comparative Example 1. In the conventional hot-rolled material of the Comparative Example, internal pores present near the center of the plate thickness played the same role as notches, reducing fatigue strength. In the embodiments of the present invention, internal pores were eliminated, resulting in a significantly higher fatigue strength compared to the Comparative Example.

[0141] (Example 2)

[0142] A DC slab (JIS 5083 alloy, 600 mm thickness (X-direction dimension), 1505 mm width (Y-direction dimension), and 2090 mm length (Z-direction dimension)) with the same chemical composition as in Example 1, produced by semi-continuous casting, was heated and pressed down along the Z-direction at a temperature of 360-420°C, above the recrystallization temperature (350°C). Multiple compressions were performed until the Z-direction dimension reached 350 mm. The initial reduction rate was 83.2%.

[0143] Next, the surface is cut until the Z-axis dimension becomes 334 mm, then reheated to a temperature of 530°C, above the recrystallization temperature, and rolled in one pass along the Z-axis using a hot rolling mill until the Z-axis dimension becomes 331 mm, resulting in a thick plate. The second reduction rate at this point is 0.9%. Furthermore, the total reduction rate in the first and second reduction processes is 83.4%.

[0144] Next, scanning electron microscopy (SEM) was used to observe the area near the center of the plate thickness. Image analysis of the obtained SEM images was performed to determine the number density per unit area of ​​internal pores with a Ferete diameter of 50 μm or larger and internal pores with a Ferete diameter of 100 μm or larger in a region of 1 / 3 of the plate thickness centered on the center along the thickness direction. The result showed that the number density of internal pores with a Ferete diameter of 50 μm or larger was 0 pores / mm. 2 The number density of internal pores with a diameter greater than 100 μm in the Ferrette is 0 pores / mm. 2 .

[0145] (Comparative Example 2)

[0146] A JIS 5083 alloy plate with the same chemical composition as Comparative Example 1, which was hot-rolled using conventional processes to reduce the X-axis dimension from 600 mm to 331 mm, was used as the comparative material. The reduction rate during this hot rolling was approximately 45%.

[0147] Next, scanning electron microscopy (SEM) was used to observe the area near the center of the plate thickness. Image analysis of the obtained SEM images was performed to determine the number density per unit area of ​​internal pores with a Ferete diameter of 50 μm or larger and internal pores with a Ferete diameter of 100 μm or larger in a region of 1 / 3 of the plate thickness centered on the center along the thickness direction. The result showed that the number density of internal pores with a Ferete diameter of 50 μm or larger was 0.9 pores / mm. 2 The number density of internal pores with a diameter greater than 100 μm in the Ferrette is 0.4 pores / mm. 2 .

[0148] The rotational bending fatigue strength of the 5083 alloy H112 material in the region of 1 / 3 of the plate thickness centered on the center in the thickness direction is 179 MPa in Example 2 and 76 MPa in Comparative Example 2.

[0149] These results show that, according to the manufacturing method of the present invention, the internal porosity of the thick plate is essentially eliminated, and the problem of internal porosity is essentially resolved. Furthermore, it is also evident that the reduction in internal porosity using the manufacturing method of the present invention leads to a significant improvement in fatigue strength.

[0150] (Example 3)

[0151] A DC slab (JIS 5052 alloy, after cutting / surface machining: thickness 630 mm (X direction dimension), width 1505 mm (Y direction dimension), length 1968 mm (Z direction dimension)) with the chemical composition shown in Table 3, produced by semi-continuous casting, was heated and pressed down along the Z direction at a temperature of 360~420°C, above the recrystallization temperature (350°C). Multiple compressions were performed until the Z direction dimension reached 488 mm. The initial reduction rate at this point was 75.2%.

[0152] Next, the surface is cut to a Z-axis dimension of 457 mm, and then reheated to a temperature of 530°C, above the recrystallization temperature, and hot-rolled in multiple passes using a hot rolling mill to a Z-axis dimension of 297 mm. At this point, the second reduction rate is 35.0%, and the total reduction rate is 83.9%.

[0153] Next, the area near the center of the plate thickness was observed using an optical microscope. The resulting images were analyzed to determine the number density per unit area of ​​internal pores with a Ferete diameter greater than 50 μm and those with a Ferete diameter greater than 100 μm in a region representing one-third of the plate thickness centered on the center along the thickness direction. The result showed that the number density of internal pores with a Ferete diameter greater than 50 μm was 0 pores / mm. 2 The number density of internal pores with a diameter greater than 100 μm in the Ferrette is 0 pores / mm. 2 .

[0154] (Comparative Example 3)

[0155] The DC slabs with the chemical composition shown in Table 3 were hot-rolled using conventional processes, with a JIS 5052 alloy plate having its X-axis dimension reduced from 533 mm to 297 mm used as a comparison material. The reduction rate during this hot rolling was approximately 44%.

[0156] Next, the area near the center of the plate thickness was observed using an optical microscope. The resulting images were analyzed to determine the number density per unit area of ​​internal pores with a Ferete diameter of 50 μm or larger and those with a Ferete diameter of 100 μm or larger in a region representing one-third of the plate thickness centered on the center along the thickness direction. The result showed that the number density of internal pores with a Ferete diameter of 50 μm or larger was 0.23 pores / mm. 2 The number density of internal pores with a diameter greater than 100 μm in the Ferrette is 0.05 pores / mm. 2 .

[0157] [Table 3]

[0158]

[0159] Compared with the conventional hot-rolled material of Comparative Example 3, the internal porosity of the 5052 alloy H112 material of Example 3 was significantly reduced.

[0160] The rotational bending fatigue strength of the material in the region of 1 / 3 thickness centered on the center of the plate thickness direction was 115 MPa in Example 3 and 95 MPa in Comparative Example 3, with Example 3 showing a higher value than Comparative Example 3.

[0161] (Example 4)

[0162] Under the same conditions as in Example 3, a DC slab (JIS6061 alloy) with the chemical composition in Table 4 was pressed to obtain a material with a Z-direction dimension of 297 mm. The material was then subjected to a solution treatment of holding at 525°C for 1 h and water quenching, followed by an artificial aging treatment of holding at 170°C for 8 h to produce T6 material.

[0163] Image analysis of the 6061 alloy T6 material using an optical microscope was performed to determine the number density of internal pores with a Ferrette diameter greater than 50 μm and those with a Ferrette diameter greater than 100 μm in a region centered on the center of the plate thickness along the thickness direction, representing one-third of the plate thickness. The result showed that the number density of internal pores with a Ferrette diameter greater than 50 μm was 0 pores / mm. 2 The number density of internal pores with a diameter greater than 100 μm in the Ferrette is 0 pores / mm. 2 .

[0164] (Comparative Example 4)

[0165] The DC slab with the chemical composition in Table 4 was hot rolled using conventional processes, reducing the X-direction dimension from 533 mm to 297 mm. The 6061 alloy T6 material, which underwent the same heat treatment as in Example 4, was used as a comparative material.

[0166] In the central region of the thickness of the comparative material, the number density of internal pores with a diameter of 50 μm or more is 0.17 pores / mm. 2 The number density of internal pores with a diameter greater than 100 μm in the Ferrette is 0.04 pores / mm. 2 .

[0167] [Table 4]

[0168]

[0169] Compared with Comparative Example 4 based on conventional hot rolling, the internal porosity of Example 4 of 6061 alloy T6 material is significantly reduced.

[0170] The rotational bending fatigue strength of the material in the region of 1 / 3 thickness centered on the center of the plate thickness direction was 135 MPa in Example 4 and 95 MPa in Comparative Example 4, with Example 4 showing a higher value than Comparative Example 4.

Claims

1. A method for manufacturing a thick aluminum plate, characterized in that, When the long side direction of an aluminum ingot or an aluminum alloy ingot is set as the Z direction, it has the following characteristics: The first pressing process involves hot forging the ingot, pressing it down along the Z-direction to reduce its Z-direction dimension, thus obtaining a hot-forged product; and The second pressing process involves hot rolling the hot forging to press it down along the Z-direction, reducing the Z-direction dimension of the hot forging to obtain a thick aluminum sheet.

2. The method for manufacturing thick aluminum plates according to claim 1, characterized in that, The total reduction rate in the first and second pressing processes is 75.0% or higher.

3. The method for manufacturing thick aluminum plates according to claim 1 or 2, characterized in that, The first reduction rate in the first pressing process is 60.0% or higher.

4. The method for manufacturing thick aluminum plates according to claim 1 or 2, characterized in that, The second reduction rate in the second pressing process is 0.5% or more.

5. The method for manufacturing thick aluminum plates according to claim 1 or 2, characterized in that, The thickness of the aluminum sheet is 100mm or more.

6. The method for manufacturing thick aluminum plates according to claim 1 or 2, characterized in that, The Z-axis dimension of the ingot is 800 mm or more.

7. The method for manufacturing thick aluminum plates according to claim 1 or 2, characterized in that, When the short side direction of the ingot is defined as the X direction, The ratio of the Z-direction dimension of the ingot to the X-direction dimension of the ingot, i.e., the Z-direction dimension / X-direction dimension, is 2.0 or greater.

8. A thick aluminum plate, characterized in that, It is obtained by performing the following process when the long side direction of an aluminum ingot or aluminum alloy ingot is set to the Z direction: The first pressing process involves hot forging the ingot, pressing it down along the Z-direction to reduce its Z-direction dimension, thus obtaining a hot-forged product; and The second pressing process involves hot rolling the hot forging to press it down along the Z-direction, reducing the Z-direction dimension of the hot forging to obtain a thick aluminum sheet.

9. A thick aluminum plate, characterized in that, It is composed of aluminum or aluminum alloys containing more than 80% aluminum by mass. The plate thickness is 100mm or more. Microscopic observation of a cross-section parallel to the plate thickness direction revealed that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of the cross-section, when divided into three parts along the plate thickness direction, was 0.15 pores / mm. 2 the following.

10. A thick aluminum plate, characterized in that, It is composed of an Al-Mg alloy containing more than 1.50% by mass of Mg. The plate thickness is 100mm or more. Microscopic observation of a cross-section parallel to the plate thickness direction revealed that the number density of internal pores with a Ferete diameter of 50 μm or more in the central part of the cross-section, when divided into three parts along the plate thickness direction, was 0.15 pores / mm. 2 the following.

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