JPH0348257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a magnetic recording device with excellent corrosion resistance that is suitable for parts of magnetic recording devices that directly contact magnetic tape, such as VTR (video tape recorder) cylinders, fixed or rotating tape guide drums, and head drums. It concerns aluminum alloys. A VTR consists of a metal magnetic head section for magnetically recording and reproducing image signals on a magnetic tape, and a stationary or rotating tape guide drum for stably running the magnetic tape. It is known that parts that come into direct contact with the magnetic tape, such as the rotating magnetic head or the tape guide drum, play an extremely important function in maintaining stable tape running without damaging the tape surface that has magnetic particles attached. Therefore, in order to improve the precision of reproduced images (image clarity, color unevenness, etc.), there is a strong demand for improvements in materials for magnetic tape contact parts. Conventionally, VTR tape contact parts have been made of, for example, a copper alloy with Cr hard plating on the surface, an austenitic SUS material, or the like. However, recently, aluminum alloy castings or ingots have been cut or plastic processed (particularly forged) by taking advantage of the advantages of aluminum alloys, such as their light weight, excellent workability, and non-magnetic properties. ,
Magnetic tape contact parts such as VTR drums began to be manufactured. The properties of the aluminum alloy required for the material for magnetic tape contact parts include the following items. (1) Good abrasion resistance against tape. (2) The coefficient of dynamic friction with the tape is small and the tape runs well. (3) Excellent mechanical strength. (4) Excellent machinability and smooth finished surface. (5) Excellent plastic workability, especially forgeability. (6) Good corrosion resistance in a high temperature and humid atmosphere. For example, the casting alloy JIS class 8 Al-Si-Cu-
Mg-based alloys are excellent in the properties (1) to (5) above, but have the following problem in (6) corrosion resistance in a high temperature and humid atmosphere. If you leave magnetic tape wrapped around a VCR cylinder in a hot and humid atmosphere for a long time,
Moisture condensed between the magnetic tape and the cylinder corrodes the cylinder and causes rust, which not only causes the cylinder surface to lose its smoothness, but also
This rust may become embedded in the magnetic coating of the magnetic tape, causing the magnetic coating to peel off when the tape is peeled off. As a countermeasure to this problem, Japanese Patent Application Laid-Open No. 1984-19472 describes
A technique has been disclosed in which a chemically treated film is applied to the surface of a metal or an alloy, and the film is covered with a sputtered film of chromium or stainless steel. However, this method has the disadvantage that the cost is high because the steps of surface treatment and sputter film coating are added to the normal steps. In view of the current situation, the inventors of the present invention have conducted various researches to develop an aluminum alloy with excellent wear resistance and corrosion resistance in a high temperature and humid atmosphere for use in magnetic tape contact parts. As a result, they discovered that the Mg content has a large effect on corrosion in high-silicon Al-Si-Cu-Mg alloys, and completed the present invention. That is, the object of the present invention is to improve wear resistance, dynamic friction coefficient, and
The object of the present invention is to provide an aluminum alloy for magnetic tape contact parts that has greatly improved machinability (chip disposability) and improved corrosion resistance, and these technical problems are solved by the following configuration. That is, the gist of the first invention of the present application is: In other words, the gist of the first invention of the present application is that Si is 12% by weight.
Cu is over 2% and less than 5%, Cu is over 2% and less than 5%,
Mg0.2~0.8%, Fe0.1% or more, less than 0.5%, Mn0.2
It is an aluminum alloy for magnetic tape contact parts that has excellent corrosion resistance and is made of Al containing ~1.2% and the rest containing ordinary impurities. , Cu exceeds 2%,
5% or less, Ni0.5-2.5%, Mg0.2-0.8%, Fe0.1
% or more and less than 0.5%, and 0.2 to 1.2% Mn, and the remainder is Al containing ordinary impurities.The third and fourth inventions provide an aluminum alloy for magnetic tape contact parts with excellent corrosion resistance. , respectively the first
In addition to the invention, the aluminum alloy of the second invention,
It is an aluminum alloy containing 0.1 to 1.2% Cr. The reason for limiting the composition range of the alloy of the present invention will be explained below. In the description of this specification, the contents of all included elements are expressed in weight %. First, the first invention will be explained. Cu: Cu increases the strength of the alloy base metal and improves machinability. If it is less than 2%, the effect will be insufficient, and if it exceeds 5%, castability, forgeability, and corrosion resistance will deteriorate. Therefore, Cu should be in a range of more than 2% and less than 5%. Si and Mg: Si and Mg form MgSi-based precipitates to increase the strength of the alloy. Mg also improves the mechanical strength of the alloy, especially the yield strength, and Cu
The synergistic effect with this makes machinability even more reliable.
These effects are not sufficient when Mg is 0.2% or less. When Si exceeds 12%, primary silicon crystallizes and wear resistance and cutting processability are significantly improved. Plastic workability becomes difficult when Si is 22% or more.
When Mg is present in the Si region of the present application, it significantly affects corrosion resistance in a high temperature and humid atmosphere. That is, Mg is 0.8
%, corrosion resistance will deteriorate significantly. For this reason, Si is over 12% and less than 22%, and Mg is 0.2%.
The range shall be ~0.8%. Fe: Fe is effective in improving wear resistance and machinability. If it is less than 0.1%, no effect will be observed, and if it is more than 0.5%, forging workability will decrease. Therefore, Fe is in the range of 0.1% or more and less than 0.5%. Mn: Mn improves wear resistance. If it is less than 0.2%, crystallization that contributes to wear resistance will not be sufficient;
If it exceeds this, the crystallized substances will become coarse and machinability will be impaired. Therefore, Mn should be in the range of 0.2 to 1.2%. The second invention of this application is based on the alloy of the first invention,
The wear resistance and machinability are further improved by adding 0.5 to 2.5% Ni. If it is less than 0.5%, no effect will be observed, and if it exceeds 2.5%, coarse intermetallic workpieces will be produced, resulting in decreased forging workability and machinability. Therefore, the range of Ni is 0.5 to 2.5%. The third and fourth inventions of this application are the first and fourth inventions, respectively.
This alloy further improves the wear resistance by adding 0.2 to 1.2% of Cr to the alloy of the second invention. 0.2%
If it is less than that, crystallization that contributes to wear resistance will not be sufficient,
If it exceeds 1.2%, crystallized substances become coarse and machinability is impaired. Therefore, Cr is set in the range of 0.2 to 1.2%. When manufacturing tape contact parts made of the alloy of the present invention, the starting material is not a sand mold or metal mold casting, but rather a long ingot manufactured by a direct cooling continuous casting method with a high cooling rate, and then forged by a long ingot. Most preferably, it is plastically worked and then shaped and finished by mechanical cutting means. In this case, JP-A-56-
Applying the manufacturing method of aluminum alloy for casting described in Publication No. 69348, the cooling rate (cooling rate of the solid-liquid interface during continuous casting) is maintained at 25°C/second or more (especially when the diameter
If a narrow diameter pillar of 100 mm or less is suitable for this condition), castability will be greatly improved, and long ingots can be directly forged without extrusion, improving productivity. The structure has become significantly finer, and the second phase particles made of intermetallic compounds are finely and uniformly dispersed. For this reason, it has high strength and wear resistance, and in addition, it has an extremely excellent surface roughness after being processed to a precise, smooth surface, so-called mirror finishing, which is required for VTR tape contact parts. In general, when a precision finishing surface is required, such as mirror finishing of metal using a cutting tool having a diamond cutting edge, it is known that it is necessary to adjust the structure of the alloy ingot. A long, narrow-diameter ingot of the alloy satisfies these requirements. However, the alloy material of the present invention is not limited to the above-mentioned continuous casting ingots, but also metal molds, sand molds,
Compared to conventional alloy materials, the present invention can be made by molding ingots using a casting method such as die casting, and then manufacturing VTR tape contact parts by cutting or forming the ingots as they are or by applying heat or cold forging. The characteristic effects of are fully exhibited. The present invention will be explained below based on Examples.
Within the scope of the gist, the present invention is not limited to the following examples. Examples and Comparative Examples Table 1 shows Example Alloys No. 1 to 8 and Comparative Example Alloys.
The alloy compositions of Nos. 9 to 11 are shown. In the classification of alloy ingots shown in this table, alloy ingot A is produced by the vertical semi-continuous casting method. The cooling rate was maintained at 28°C/sec, and the ingot was manufactured into a long cylindrical ingot with a diameter of 73 mm. The distance between dendrite arms in the internal structure of the obtained ingot was narrow, and the second phase particles were fine. It was also observed that the particles were uniformly dispersed. Alloy ingot B was obtained by extruding a cylindrical ingot with a diameter of 200 mm obtained by a vertical semi-continuous casting method into a round bar with a diameter of 70 mm. The alloy ingot C was formed into the shape shown in FIG. 1 by die casting. The test pieces for mechanical properties were T6 ingots for alloy materials A and B, and boat bottom mold ingots for alloy C.
Heat treatment (500℃ x 4 hours, water cooling quenching, then
After undergoing artificial aging treatment at 180°C for 8 hours, it was processed into JIS No. 4 test pieces. The test pieces for forgeability evaluation were made by sintering the ingot together with alloy materials A and B (370°C x 4 hours, furnace cooling).
After that, the wedge test piece shown in Figure 2a (L = 150 mm, t ₀ = 3 mm, t ₁ = 15 mm, W = 20 mm)
Processed into. Test pieces for hardness, machinability, surface roughness, and corrosion resistance were formed into the shapes shown in FIG. 1 by forging for alloy materials A and B, and by die casting for alloy material C. After rough cutting these alloy materials, the same conditions as above were applied.
After applying T6 heat treatment, mirror finishing was performed using a cutting tool with a diamond cutting edge, and the dimensions in Fig. 1 were D = 63 mm, d ₁ = 40
mm, d ₂ = 20 mm, H ₁ = 16 mm, H ₂ = 7 mm
It was a VTR rotating drum. The cutting conditions for the outer peripheral surface of the drum on which the tape slides were a cutting speed of 150 m/min, a depth of cut of 0.05 mm, and a cutting tool feed rate of 0.05 mm/rotation. A specific wear amount test piece was cut out from a part of the VTR rotating drum. Table 2 shows the characteristic values of these specimens.

【table】

【table】

[Table] A summary of each test method is as follows. (a) Tensile strength and (b) Elongation A test was conducted using a JIS No. 4 test piece using an Olzen type 50-ton universal testing machine. (c) Forgeability The wedge test piece 1 shown in Fig. 2a is
The specimen was placed on an anvil 2 shown in Figure 1, and forged and stretched using a 1/2 ton hammer 3, and evaluated by comparing the crack occurrence positions in the specimen 4 after forging. The evaluation results are displayed as: ◎: Good, 〇: Fair, △: Slightly poor. (d) Hardness The height directly below the tape sliding surface was measured using a Bitkers hardness tester. (E) Chip disposal property Cutting was performed using an artificial sintered diamond cutting tool at a cutting speed of 150 mm/min and a depth of cut of 0.15 mm, and the shape of the chips was compared and evaluated. The evaluation results are indicated as: ◎: Good, 〇: Fair, △: Slightly poor. (f) Surface roughness The surface roughness of the drum in the axial direction was measured using a stylus roughness tester. (g) Abrasion resistance Using an Okoshi type abrasion tester, the opponent was FC30.
Friction speed 3m/sec, load 2.1Kg, friction distance 600
The test was conducted without lubrication, and the specific wear amount per kg of unit area was measured. (H) Corrosion resistance After wrapping a magnetic tape with a load of 60 gr around a VTR drum and keeping it in an atmosphere with a temperature of 40°C and a humidity of 85% for one week, the state of the parts where the drum and magnetic tape were in contact with each other. observed. The evaluation was in four stages. That is, ◎: No change in drum or magnetic tape. ○: Small corrosion occurred on the drum, no abnormality on the magnetic tape. △: Corrosion occurred on the drum, and magnetic powder was peeled off in some places on the magnetic tape. ×: The drum was severely corroded, and the magnetic powder on the magnetic tape was noticeably peeled off. In the above evaluation, ◎ and ○ indicate that there is no problem in practical use. A sketch of the drum surface obtained from the corrosion resistance test is shown in FIG. 3, and a corresponding sketch of the magnetic tape is shown in FIG. In both Figures 3 and 4, a
corresponds to alloy No. 2, and b corresponds to alloy No. 9. Figure 3b
The black dots on the drum surface are corroded areas, and the black dots on the tape surface in Figure 4b are areas where the magnetic powder has peeled off due to drum corrosion. When the structure of the cross section of the corroded area shown in FIG. 3b was observed, it was revealed that the corrosion was intergranular corrosion that propagated to the grain boundaries. FIG. 6 shows a micrograph of the cross-section of the corroded portion of the drum shown in FIG. 3b. Therefore, corrosion resistance when the VTR drum and magnetic tape are statically left in contact with each other under high temperature and high humidity can be achieved by controlling the Si and Mg contents. As seen in the characteristic values in Table 2, the alloy of the present invention has excellent mechanical properties required for magnetic tape contact parts, and also has excellent corrosion resistance without special treatment such as coating on the part surface. Therefore, it is extremely suitable as a material for magnetic tape contact parts.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a rotating drum-shaped test piece for VTR, Figure 2a is the shape of a wedge test piece for forgeability evaluation, Figure 2b is an explanatory diagram of the forgeability test method, and Figure 3 Figures 4 and 4 show the drum surface (Third
Fig. 4) and the corresponding magnetic tape (Fig. 4), where a is alloy No. 2 and b is alloy No. 2, respectively.
Corresponds to No.9. FIG. 5 is a micrograph of a cross-section of the corroded portion of the drum of FIG. 3b.

Claims (1)

[Claims] 1. Si is more than 12% and less than 22% by weight, and Cu is 2% by weight.
Magnetic tape with excellent corrosion resistance, containing more than 5% but less than 5%, Mg 0.2 to 0.8%, Fe 0.1% or more but less than 0.5%, Mn 0.2 to 1.2%, and the remainder being Al containing normal impurities. Aluminum alloy for contact parts. 2 Si is more than 12% and less than 22% by weight, Cu is 2
Over %, 5% or less, Ni0.5~2.5%, Mg0.2~0.8
%, Fe 0.1% or more, less than 0.5%, Mn 0.2-1.2%, and the remainder is Al containing normal impurities. An aluminum alloy for magnetic tape contact parts with excellent corrosion resistance. 3 Si is more than 12% and less than 22% by weight, Cu is 2
% but not more than 5%, Mg0.2~0.8%, Fe0.1% or more but less than 0.5%, Mn0.2~1.2%, Cr0.2~1.2%, the remainder is Al containing normal impurities. An aluminum alloy for magnetic tape contact parts with excellent corrosion resistance. 4 Si is more than 12% and less than 22% by weight, Cu is 2
Over %, 5% or less, Ni0.5~2.5%, Mg0.2~0.8
%, Fe0.1% or more, less than 0.5%, Mn0.2~1.2%,
An aluminum alloy for magnetic tape contact parts with excellent corrosion resistance, containing 0.2 to 1.2% Cr and the remainder being Al containing ordinary impurities.