JPS6138254B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to aluminum alloys, and more specifically, contact parts for magnetic recording and reproducing devices (hereinafter referred to as VTR) such as guide drums, and sliding and rotating parts of optical equipment and other precision equipment (hereinafter referred to as these). The present invention relates to an aluminum alloy suitable for use as contact parts (generally referred to as contact parts). The properties required of aluminum alloys will be explained below, mainly using magnetic tape contact parts for VTRs as an example. In a VTR, video and audio signals are recorded and played back by running magnetic tape on a drum, and this drum is generally made of aluminum alloy. The reason is that non-magnetism and light weight are the basic properties of metallic aluminum, and wear resistance etc. are improved by adding various alloying elements. Here, the drum includes a rotating magnetic head section that is attached with a magnetic head and rotates in contact with the magnetic tape, and a fixed or rotating tape guide that is in contact with the magnetic tape to keep the magnetic tape running stably. It consists of a drum. The magnetic tape surface with which these rotating magnetic heads and tape guide drums are in direct contact must not be damaged during running, and the properties of the aluminum alloy are extremely important to meet this requirement. This is well recognized, and its properties are understood through the concept of magnetic tape running properties. In particular, in order to improve the clarity, color unevenness, etc. of reproduced images, it is strongly desired to improve the running properties of the magnetic tape from both the viewpoint of the material of the aluminum alloy and the workability of the running surface of the magnetic tape. The required properties of the aluminum alloy for magnetic tape contact parts that affect the running properties of the magnetic tape are as follows. (a) Less wear due to magnetic tape. In other words, it should have good wear resistance. It goes without saying that abrasion resistance is necessary because when the drum or the like is worn out, the magnetic tape sticks to the magnetic tape guide surface of the drum, making the feeding of the magnetic tape less smooth. (b) The coefficient of friction with the magnetic tape is small. This is a property required to run the magnetic tape smoothly and stably. (c) Good mechanical properties, especially strength. This is because the VTR drum is a lightweight, small component that requires excellent mechanical properties. (d) Good machinability. VTR drums are finally finished by cutting, and the smoothness of the finished surface is extremely important, so it goes without saying that this is a required property. Note that the dimensional accuracy of aluminum alloys, such as cylindricity and roundness, is usually affected by residual stress during heat treatment.
Since the smoothness of the finished surface is also affected, it is also important to reduce the generation of residual stress due to heat treatment. (e) Excellent plastic workability, especially cold forgeability. This is a property required to improve the productivity of products with the required performance. (f) The coefficient of thermal expansion is small compared to other aluminum alloys. Conventionally, castings of Al-Cu alloys such as AC8B and AC8C, and extruded materials of Al-Cu-Si alloys such as 6000 series have been widely used as drums for VTRs. However, these materials have come to be unsatisfactory for VTR applications, which are becoming increasingly demanding, and patents have been issued to improve the composition of aluminum alloys with the aim of improving some of the above properties. An application has been filed. For example, JP-A-53-93807, JP-A-54-
According to JP-A No. 164110 and JP-A-52-89512, wear resistance and mechanical strength are improved by setting the silicon content to the Al-Si hypereutectic region and dispersing primary Si into the aluminum matrix. It was a step beyond the conventional technology in that it was made with magnesium to provide free machinability without impairing these properties, but the hard primary crystal silicon had a tendency to peel off from the aluminum matrix. One drawback of these aluminum alloys is that their wear resistance is unstable. In addition, when cutting the Al-Si-Cu-Mg alloy, the tool life is short, the machined surface roughness is not sufficient, and the finished dimensional accuracy is not good. Furthermore, this alloy is a cast alloy due to its hypereutectic silicon content, and it is difficult to expect properties to be improved or defects to be reduced by plastic working. In addition, the above-mentioned Japanese Patent Application Publication No. 52
No. 89512 describes that VTR drums are cast using a mold, etc., but the composition and mold casting do not increase the grain size of the Si crystals in the eutectic structure. Unavoidably, the free machinability due to the addition of magnesium will be impaired by the coarse Si crystals. Next, JP-A-54-153715 and JP-A-55-
Publication No. 11118 does not improve wear resistance by generating a large amount of hard crystals (Si crystals) in the aluminum base as in the above-mentioned publication, but instead focuses on machinability and adds copper. I am proposing that. This alloy is formed into a VTR drum through plastic working such as forging and extrusion.
However, while this material has good machinability,
Although the lower wear resistance compared to silicon-containing alloys can be tolerated, the disadvantage is that the finished surface precision and water repellency are inferior. In view of the above-mentioned current situation, the present inventors have conducted various researches with the technical objective of developing a highly practical aluminum alloy that has the multifaceted properties required for drums that come into contact with magnetic tapes such as VTRs. As a result, we have arrived at the present invention. The technical issues that the inventor has specifically focused on are:
The first point is that it has high and stable wear resistance as a VTR drum, and also has machinability, which is generally considered to be contradictory to metal materials. The second point is that the running of the magnetic tape is stable, the third point is that it has good water repellency even without a high silicon content, and the second point is that the magnetic tape has the property of being stable in running.
-The fourth point is that the machined surface roughness (accuracy) is better than either the Si-Cu-Mg system or the Al-Cu-Mg system, and the silicon content is kept low enough to be suitable for plastic working, and it is generally It is an object of the present invention to provide an aluminum alloy for contact parts that simultaneously satisfies the fifth point of maintaining better wear resistance, which is considered to be proportional to silicon content in the field of aluminum alloy materials. These technical problems can be solved by the composition and structure of the alloy as shown below. In other words, the compositional requirements for the alloy are the first in this application.
The invention and the second invention contain 2.0 to 6.0 silicon by weight.
%, copper 0.5-4.0%, magnesium 0.1-1.2%,
At least one element selected from the group of lead, bismuth, tin, and antimony in a total amount of 0.5 to 2.0%
It is an alloy containing , and the remainder consisting of unavoidable impurities and aluminum. And the third invention and the fourth invention of the present application contain 2.0 to 6.0% silicon, 0.5 to 4.0% copper, 0.1 to 1.2% magnesium, and at least one member selected from the group of lead, bismuth, tin, and antimony. Contains 0.5 to 2.0% of the elements in total, and 0.1 to 2.0% of manganese.
1.0%, nickel 0.2-2.0%, zinc 0.1-1.0%, chromium 0.1-1.0%, molybdenum 0.05-1.0% and niobium 0.05-1.0%.
It is an alloy that further contains certain elements, with the remainder consisting of unavoidable impurities and aluminum. Furthermore, as for the structural requirements of the alloy, the first and third inventions of the present application are characterized by a specific cast structure, and include Si in the Al-Si eutectic structure and crystallized substances consisting of intermetallic compounds. Precipitate particle size is 15
The alloy is characterized by having a microstructure in which the dendrite secondary arm spacing (hereinafter abbreviated as DAS) does not exceed 20 microns. The second invention and the fourth invention of the present application are characterized by a specific plastic working structure, and the particle size of crystallized substances and precipitates made of Si and intermetallic compounds in the Al-Si eutectic structure is This alloy is characterized by having a uniformly dispersed microstructure with a grain size of 10 microns or less and an average particle spacing of 10 microns or less. Below, the composition, structure, and manufacturing method of the aluminum alloy of the present invention (hereinafter abbreviated as alloy) will be explained in relation to the properties required when it is used, for example, as a drum for a VTR. First, the reason for limiting the composition of the alloy of the present invention will be explained. (1) Silicon In addition to exhibiting excellent properties as a constituent phase of the eutectic structure, silicon acts synergistically as an intermetallic compound combined with other alloy components, primarily imparting wear resistance to the alloy. . In addition, in the present invention, the silicon content is determined so as not to be on the hypereutectic side, so that the plastic workability of the alloy
In particular, cold workability is extremely good. Although conventional high-concentration silicon-containing aluminum alloys can be cold-forged, there are restrictions on the shape of the product and/or the material, and complex processing is not possible.
It is now possible to manufacture contact parts such as drums for VTRs, and exhibits ideal cold forging properties. Further, silicon is an element that lowers the thermal expansion coefficient of metal aluminum and improves water repellency. If the silicon content is less than 2.0%, the wear resistance will be unsatisfactory, and if it exceeds 6.0%, the plastic workability will be poor.
In particular, cold forgeability is extremely reduced. The preferred silicon content is 4.0-5.5%. (2) Copper Copper is an element that is dissolved in the aluminum alloy matrix to increase the strength of the alloy and improve machinability, and also improves these properties by imparting heat treatability to the alloy. Its content is
If it is less than 0.5%, strength and machinability are insufficient, and heat treatability is also not remarkable. On the other hand, if the copper content exceeds 40%, the castability of the alloy ingot deteriorates, and there is a problem in that it is particularly susceptible to hot cracking. Furthermore, if the copper content exceeds 4.0%, the plastic workability during forming of the alloy will also deteriorate. The preferred copper content is 1.0-2.5%. (3) Magnesium Magnesium forms a solid solution in the alloy base, and also exists in the alloy as precipitates such as Mg ₂ Si by combining with excess silicon and the like. Magnesium contributes to improving the mechanical strength of the alloy, particularly its yield strength, and imparts heat treatability to the alloy. Magnesium further improves the machinability of the alloy due to the synergistic effect of solid solution with copper in the matrix. In addition, by producing Mg ₂ Si, a synergistic effect between magnesium and silicon appears, further reducing the coefficient of dynamic friction of the alloy, and thereby improving compatibility with the magnetic tape. Magnesium content
Below 0.1%, this effect is small, and 1.2%
Exceeding this is not preferable because the oxidation of the molten alloy will be accelerated by the magnesium and the plastic workability will also deteriorate. The preferred magnesium content is
It is 0.4-1.0%. (4) Lead, bismuth, tin, and antimony These elements are soft metals with a low melting point, and exist alone or as a compound with a small amount of solid solution in aluminum, thereby significantly improving the machinability of the alloy. . Improving machinability means reducing cutting resistance, fragmenting chips into fine particles, and improving the accuracy of the cut surface, and two or more types are more effective than using them alone. If the total amount of at least one of these elements is less than 0.5%, there will be no effect on the above properties, and if it is more than 2.0%, the plastic workability and toughness will be extremely reduced, which is not a good idea. The preferred content is 0.8-1.4%. Next, the additive elements of the third and fourth inventions of the present application will be explained. (5) Manganese, nickel, zinc, chromium, molybdenum, and niobium All of these elements, in the following content ranges, further refine the structure of the alloy, especially Al
-It has the effect of actively forming Si eutectic, which results in an even denser and smoother tape contact surface after cutting, which increases the coefficient of kinetic friction with the tape.
Contributes to improved familiarity. Its content is manganese 0.1-1.0%, preferably 0.3-0.8%, nickel 0.2-2.0%, preferably 0.5-1.5%, zinc 0.1-1.0%, preferably 0.3-0.7%, chromium
0.1-1.0%, preferably 0.4-0.8%, molybdenum 0.05-1.0%, preferably 0.1-0.7%, niobium
0.05-1.0%, preferably 0.1-0.7%. Below the lower limit of these elements, there is no effect of microstructural refinement, and when the upper limit is exceeded, workability (cutting and plastic workability) is adversely affected. Note that it is also effective to add Ti-B in a total amount of 0.01 to 0.1% by weight to the alloy of the present application to further refine the structure. The total content of impurities is usually preferably 2.0% or less. Next, the reasons for limiting the structural requirements of the alloy of the present invention will be explained. The first form of use of the alloy of the present invention is as a cast material, which is subjected to cutting to be finished formed into a contact part. In that case, the machinability of the alloy material (cutting processability, surface roughness of the cut surface, drilling performance)
It was also found that the dynamic friction coefficient and wear resistance of magnetic tapes are closely related to the particle sizes of DAS, crystallized substances, and precipitates in the cast structure. In other words, cast materials with improved properties listed above include:
DAS in tissue does not exceed 20 microns and Al
−Cu, Mg−Si, Al−Mn−Fe, Al−Fe−Si, Al
- It is necessary that the particle size of intermetallic compounds such as Cu-Mg and crystallized substances and precipitates such as Si in the Al-Si eutectic structure does not exceed 15 microns. As a method for manufacturing a cast material having such a structure,
This can be achieved by rapid cooling casting at a solidification rate of 15°C/sec or higher at any location within the ingot. Such a solidification rate cannot be obtained by simple mold casting or die casting, and a continuous casting method with a high cooling rate is suitable. In particular, the gas pressurized hot-top continuous casting method disclosed in Japanese Patent Publication No. 54-42847 is suitable, as it not only satisfies the above-mentioned microstructural requirements but also provides a homogeneous ingot with a smooth cast surface. The second form of use of the alloy of the present invention is as a plastically worked material, which is subjected to a cutting process and then finished formed into a contact part. Here, plastic working includes stretching processing of a cast material, such as hot/cold forging, rolling, drawing, swaging, wire drawing, and extrusion. Such a plastically worked material has the contradictory properties of machinability and wear resistance, and its various properties are further improved compared to the above-mentioned cast material. However, it goes without saying that this improvement in properties is due to the plastic working structure and DAS has virtually disappeared, but it is due to the intermetallic compounds mentioned above and crystallized substances such as Si in the Al-Si eutectic structure. It was also observed that the precipitates were only manifested when the particle size was 10 microns or less, the average particle spacing was 10 microns or less, and the microstructure was uniformly dispersed. Such a plastically worked material can be obtained by subjecting a forged material that satisfies the above-mentioned structural requirements to plastic working at a processing rate of 30% or more. The total volume percentage of the crystallized and precipitated particles is mainly determined by the alloy composition and is constant, but by plastic working, these particles are divided into fine particles, and the number of particles is increased, that is, the particle spacing is reduced. , the microstructure is controlled by uniform dispersion of fine particles through plastic flow. As a result, the workability of the alloy material and its properties as a contact part are further improved. Among the forged materials mentioned above, the cast materials manufactured by the gas pressurized hot-top continuous forging method disclosed in Japanese Patent Publication No. 54-42847 have good plastic workability, especially cold forgeability, and are suitable for complex processing. Even when added at a high forging ratio, not only is cracking less likely to occur, but the mechanical properties are also improved. The alloy of the present invention is used as a cast material or a plastically worked material without being heat treated, or after being subjected to heat treatment such as homogenization treatment or _T6 treatment. Hereinafter, the present invention will be explained based on examples. However, the present invention is not limited to the examples. Examples Alloys whose compositions are shown in Table 1 were prepared by casting. Alloy materials No.1 to No.14 and No.17 to 19 in Table 1
was manufactured into a vertically continuously cast bar with a diameter of 68 mm by the above-mentioned gas-pressure hot-top continuous casting while maintaining the solidification rate at 23°C/sec. When the internal structure of the obtained ingot cross section was observed, precipitates and It was observed that the crystallized substances were finely and uniformly dispersed. As a representative example, a 100x microscopic micrograph of alloy material No. 4 is shown in Figure 1. In this composition photograph, the maximum size of DAS was 16 microns, and the maximum particle size of precipitates and crystallized substances was 7 microns. Next, alloy materials No. 15 and No. 16 in Table 1 are alloy materials of comparative examples obtained by molding alloys with the same composition as the present invention into a cylindrical shape with the same diameter as above by die casting. The structure was coarser than that of the alloy material of the present invention described above. Figure 2 shows the microscopic structure of alloy material No. 15. The maximum size of this DAS was 36 microns, the maximum particle size of precipitates and crystallized substances was 15 microns, and the particle spacing was 13 microns or less. All of the above ingots were subjected to homogenization heat treatment at 480° C. for 1 hour after having their surface cast surfaces scraped using a peeling machine. The analytical values in Table 1 show the analytical values of the alloy material after this treatment. In addition, we directly cut out the cast material treated in this way and conducted strength property tests (tensile strength, elongation) and machinability tests (chip handling properties,
Test piece a for the drilling property test and cold forgeability test was cut and formed. On the other hand, test piece b for surface roughness, specific wear amount, tape runnability, coefficient of dynamic friction, and roundness was
With the exception of alloy materials No. 13 and No. 14, the cast materials after the above homogenization treatment were subjected to cold forging at a processing rate of 60% into the VTR drum shape shown in FIG. 3, and were further cut and formed. The above test pieces a and b were both T6 heat treated (heated at 500°C for 4 hours, then quenched in hot water, then quenched at 170°C for 9 hours.
It was tested after undergoing artificial aging treatment. Test piece b
The specifications before T6 heat treatment are D=63mm, d=40.5mm,
H ₁ =16 mm, H ₂ =8 mm, and after the T6 heat treatment, finishing cutting was performed using a cutting tool having a diamond cutting blade to make the entire surface mirror-finished. This specimen b
DAS cannot be observed in any of the structures, and Al−Si
The particles of Si in the eutectic structure and crystallized substances and precipitates made of intermetallic compounds have a maximum particle size of 5 microns, and the average particle spacing is 7.5 microns or less, presenting a uniformly dispersed microstructure. Ta. Test pieces b of alloy materials No. 13 and No. 14 were formed into the shape shown in FIG. 3 by cutting the cast material after the above-mentioned homogenization treatment without plastic working. The microstructures had a maximum DAS size of 15 microns and a maximum particle size of crystallized matter and precipitates of 8 microns. The outline of each test method is as follows. (a) Surface roughness The roughness of the diamond cutting tool machined surface was measured using a surface roughness meter. (b) Wear resistance Using an Okoshi type abrasion tester, the mating material was FC30, the friction speed was 3 m/sec, the load was 18.2 kg, and the friction distance was measured.
Tested at 600m without lubrication, kg per unit area
The specific wear amount per contact was measured. (c) Tape running properties After running the VTR magnetic tape for 1500 hours, the stability of the reproduced image was tested using a VTR. (d) Coefficient of dynamic friction When running in the same way as VTR, one side of the specimen was
Load a reverse tension (W _p ) of 50 gr, run the magnetic tape over the specimen at a speed of 18.0 cm/sec, measure the acting load (W _r ) on one side facing the load, and measure the coefficient of dynamic friction. did. (E) Roundness After cold forging, T6 heat treatment, and finishing cutting, the roundness of the finished surface was measured using a coordinate measuring machine. (f) Cold forgeability Wedge test piece 1 shown in Figure 4 (L=150
mm, t ₀ = 15 mm, t ₁ = 3 mm, W = 20 mm) was placed on the anvil 2 as shown in Fig. 5, and forged with a 1/2 ton hammer 3, reaching the limit due to cracks in the specimen 4 after forging. The processing rate was measured by (ta-ta'/ta). A limit machining rate of 60% or more is considered "good", a limit of less than 45% is "poor",
A score in the middle was rated as "somewhat good." (G) Machinability Cutting was performed using a Compax Diamond cutting tool at a cutting speed of 200 m/min and a depth of cut of 0.15 mm, and the processability was evaluated based on the shape of chips. That is, if the shape of the chips (chip) was granular or finely arcuate, it was evaluated as "good", if it was in the shape of a fine ring, it was evaluated as "slightly good", and if it was continuous in a spiral shape, it was evaluated as "poor". Also, using a 1.5mm carbide drill,
Drillability was evaluated based on the amount of wear on the drill when drilling holes in a test piece with a thickness of 8 mm 100 times in a row at 450 rpm. These results are shown in Table 2.

【table】

[Table] From the above explanation, it is clear that the alloy of the present invention has comprehensive performance suitable for contact parts, and its good properties are used in magnetic recording and reproducing devices, various optical machines, and other applications. It will also be understood that it is extremely suitable for sliding and rotating parts of precision equipment.

[Brief explanation of the drawing]

Figure 1 shows a microscopic structure photograph (100x) of a continuously cast material of the invention alloy, Fig. 2 shows a microscopic structure photograph (100x) of a mold cast material of a comparative example alloy, and Fig. 3 shows a VTR. Drawing of rotating drum shape test piece for
FIG. 4 and FIG. 5 are explanations of the cold forging test piece and the test method, respectively. 1...Test piece, 2...Anvil, 3...1/2 ton hammer, 4...Test piece.

Claims (1)

[Claims] 1. Silicon 2.0 to 6.0%, copper 0.5 to 4.0% by weight,
0.1-1.2% magnesium and at least one selected from the group of lead, bismuth, tin and antimony
Crystallized substances and precipitates containing 0.5 to 2.0% of seed elements in total, with the remainder consisting of inevitable impurities and aluminum, and consisting of Si in an Al-Si eutectic structure and intermetallic compounds. The particle size does not exceed 15 microns and the dendrite secondary arm spacing is
An aluminum alloy for contact parts, characterized by having a microstructure not exceeding 20 microns. 2 By weight, silicon 2.0-6.0%, copper 0.5-4.0%,
0.1-1.2% magnesium and at least one selected from the group of lead, bismuth, tin and antimony
Crystallized substances and precipitates containing 0.5 to 2.0% of seed elements in total, with the remainder consisting of inevitable impurities and aluminum, and consisting of Si in an Al-Si eutectic structure and intermetallic compounds. An aluminum alloy for contact parts, characterized by having a uniformly dispersed microstructure with a particle size of 10 microns or less and an average particle spacing of 10 microns or less. 3 By weight, silicon 2.0-6.0%, copper 0.5-4.0%,
0.1-1.2% magnesium and at least one selected from the group of lead, bismuth, tin and antimony
Contains 0.5~2.0% of total amount of seed elements, manganese 0.1~1.0%, nickel 0.2~2.0%, zinc 0.1~
1.0%, chromium 0.1~1.0%, molybdenum 0.05~1.0
% and at least one element selected from the group of 0.05 to 1.0% niobium, the balance consisting of inevitable impurities and aluminum, and Al
- It has a microstructure in which the particle size of crystallized substances and precipitates made of Si and intermetallic compounds in the Si eutectic structure does not exceed 15 microns, and the distance between secondary dendrite arms does not exceed 20 microns. Aluminum alloy for contact parts featuring: 4 By weight, silicon 2.0-6.0%, copper 0.5-4.0%,
0.1-1.2% magnesium and at least one selected from the group of lead, bismuth, tin and antimony
Contains 0.5~2.0% of total amount of seed elements, manganese 0.1~1.0%, nickel 0.2~2.0%, zinc 0.1~
1.0%, chromium 0.1~1.0%, molybdenum 0.05~1.0
% and 0.05 to 1.0% of niobium, and the remainder consists of unavoidable non-trees and aluminum, and Al
-Characterized by having a uniformly dispersed microstructure in which the particle size of crystallized substances and precipitates made of Si and intermetallic compounds in the Si eutectic structure is 10 microns or less, and the average particle spacing is 10 microns or less. Aluminum alloy for contact parts.