JPH0116901B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention applies to magnetic tape contact parts such as VTR (video tape recorder) cylinders, fixed or rotating drums for guiding the tape, etc.
The present invention relates to an aluminum alloy with excellent corrosion resistance suitable for parts of magnetic recording devices that come into direct contact with magnetic tape. A VTR consists of a rotating magnetic head for magnetically recording and reproducing video 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 cold forgeability. (6) Good corrosion resistance of magnetic tape contact parts in a high temperature and humid atmosphere. Conventionally, JIS2000 series alloys were used as alloys for plastic working.
Al--Cu alloys are well known and widely used as aluminum alloys for magnetic tape contact parts.Although this alloy is excellent in properties 1) to 5) above, There are the following problems with corrosion resistance in a high temperature and humid atmosphere. If magnetic tape is left wrapped around parts that come into contact with the magnetic tape, such as a VTR cylinder, and left in a hot and humid atmosphere for a long time, the parts that come in contact with the magnetic tape, such as the cylinder, will be corroded by moisture that has condensed between the magnetic tape and the cylinder. Not only does this rust occur and the necessary surface smoothness of cylinders etc. is lost, but this rust also embeds the magnetic coating on the magnetic tape, causing the magnetic coating to peel off when the tape is removed. I have come to understand this. 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 alloy, and the film is covered with a sputtered film of chromium or stainless steel. However, this method has the disadvantage of being expensive because the steps of surface treatment and sputter film coating are added to the normal steps. In view of the current situation, the present inventors have developed an aluminum alloy for magnetic tape contact parts that has excellent mechanical properties and excellent corrosion resistance at the magnetic tape contact area in a high temperature and humid atmosphere. As a result of various studies, we found that the content of Si and Mg in particular has a large effect on corrosion in JIS 2000 series Al-Cu alloys for wrought materials, which have been widely used until now. , completed the invention. That is, an object of the present invention is to provide a magnetic tape contacting part that has improved corrosion resistance without impairing properties such as wear resistance, coefficient of dynamic friction, mechanical strength, machinability, plastic workability, and forgeability. The purpose of the present invention is to provide an aluminum alloy, and this technical problem is solved by the following configuration. That is, the gist of the first invention of the present application is as follows: Cu 1 to 6% by weight, Si and Mg, point A (0.15% Si, 0.2% Mg), point B (less than 0.5% Si,
Mg0.2%), point C (Si less than 0.5%, Mg0.8%), point D
(Si0.4%, Mg0.8%), point E (Si0.4%, Mg1.8%),
Corrosion resistance consisting of the amount in the range surrounded by point F (0.15% Si, 1.8% Mg), 0.1 to 1.0% Fe, 0.005 to 0.2% Ti, and the remainder is Al containing normal impurities. The gist of the second invention is to provide an aluminum alloy for magnetic tape contact parts that is excellent in terms of weight. .2%), point B (Si less than 0.5%,
Mg0.2%), point C (Si less than 0.5%, Mg0.8%), point D
(Si0.4%, Mg0.8%), point E (Si0.4%, Mg1.8%),
The amount in the range surrounded by point F (Si0.15%, Mg1.8%), Fe0.1~1.0%, Ti0.005~0.2%, and further includes Mn0.2~1.2%, Cr0.2 The purpose of the third invention is to provide an aluminum alloy for magnetic tape contact parts with excellent corrosion resistance, which contains at least one element among ~1.2%, and the remainder is Al containing ordinary impurities. In Fig. 1, Cu1~6%, Si and Mg were added to point A (Si0.15%, Mg0.2%) and point B (Si less than 0.5%,
Mg0.2%), point C (Si less than 0.5%, Mg0.8%), point D
(Si0.4%, Mg0.8%), point E (Si0.4%, Mg1.8%),
It contains the amount in the range surrounded by point F (0.15% Si, 1.8% Mg), 0.1 to 1.0% Fe, 0.005 to 0.2% Ti, and one of Pb, Bi, Sn, and Sb. The present invention provides an aluminum alloy for magnetic tape contact parts having excellent corrosion resistance, which contains 0.5 to 2% of the total amount of elements of 0.5 to 2%, and the remainder is Al containing ordinary impurities. Cu 1 to 6% by weight, Si and Mg, point A (Si 0.15%, Mg 0.2%), point B (Si less than 0.5%,
Mg0.2%), point C (Si less than 0.5%, Mg0.8%), point D
(Si0.4%, Mg0.8%), point E (Si0.4%, Mg1.8%),
The amount in the range surrounded by point F (Si0.15%, Mg1.8%), Fe0.1~1.0%, Ti0.005~0.2%, and further includes Mn0.2~1.2%, Cu0.2 Contains a total of 0.5 to 2% of one or more elements among ~1.2% and one or more elements of Pb, Bi, Sn, and Sb, and the remainder is Al containing normal impurities. Excellent corrosion resistance. The present invention provides an aluminum alloy for magnetic tape contact parts. 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 and improves machinability. If it is less than 1%, the effect will be insufficient, and if it exceeds 6%, castability, forgeability, and corrosion resistance will deteriorate. Therefore, Cu is in the range of 1 to 6%. Si and Mg: Si and Mg form Mg ₂ Si-based precipitates to increase the strength of the alloy. In addition, Mg improves the mechanical strength of the alloy, especially its yield strength, and its synergistic effect with Cu further ensures machinability.
These effects are not sufficient if Si is less than 0.15% and Mg is less than 0.2%. Furthermore, if Si exceeds 0.5% and Mg exceeds 1.8%, a satisfactory finished surface roughness cannot be obtained when cutting magnetic tape contact parts. The content of Si and Mg significantly affects corrosion resistance in a high temperature and humid atmosphere. Corrosion resistance deteriorates significantly in the region where the Si content exceeds 0.4% and the Mg content exceeds 0.8%. Therefore, the amounts of Si and Mg are set within the range surrounded by points A, B, C, D, E, and F in FIG. 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 exceeds 1.0%, forging workability will decrease. Therefore, Fe is in the range of 0.1 to 1.0%. Ti: Ti is an important element because it is effective in making the structure finer and thereby allows achieving finished dimensional accuracy (on the order of μm) of magnetic tape contact parts. If Ti is less than 0.005%, this effect is not recognized, and if it exceeds 0.2%, not only the effect is saturated, but also the forging workability decreases. Therefore, Ti is
It should be in the range of 0.005-0.2%. In carrying out the present invention, 0.0004 to 0.002% of B may be added in addition to the above-mentioned additional elements. In this way, the coexistence of Ti and B further enhances the crystal refinement effect and improves the finished dimensional accuracy of parts. The second invention of this application is based on the alloy of the first invention,
The wear resistance is further improved by adding one or more elements among 0.2 to 1.2% of Mn and 0.2 to 1.2% of Cr. If both Mn and Cr are less than 0.2%, there will be insufficient crystallized substances contributing to wear resistance, and if they exceed 1.2%, the crystallized substances will become coarse and impair machinability. Therefore,
Mn and Cr are in the range of 0.2 to 1.2%. The third invention of this application is based on the alloy of the first invention,
Total amount of one or more elements among Pb, Bi, Sn, and Sb
By adding 0.5 to 2%, the machinability of the alloy is further improved. 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 it is less than 0.5%, it has no effect on the above properties, and if it exceeds 2.0%, it is not a good idea because the plastic workability and toughness will be extremely reduced. If the content of these elements (total amount if two or more types) is less than 0.5%, there will be little effect on the above properties, and if it exceeds 2.0%, plastic workability and mechanical strength, especially toughness, will be extremely reduced. . The preferred content is 0.8-1.4%. The fourth invention of this application further improves the machinability of the alloy by adding a total amount of 0.5 to 2% of one or more elements among Pb, Bi, Sn, and Sb to the alloy of the second invention. This is what I did. When manufacturing a tape contact part 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 produced 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 forging 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 pillaret of 100 mm or less is suitable for this condition), castability will be greatly improved, and long ingots can be forged in diameter without extrusion, which will improve 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. It is truly an ideal alloy material. 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 the alloy compositions of Example Alloys No. 1 to 10 and Comparative Example Alloys No. 11 to 15. 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. 2 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. For the test pieces for cold forgeability evaluation, the ingots of both alloy materials A and B were subjected to annealing heat treatment (370°C x 4 hours, furnace cooling).
After that, the wedge test piece shown in Figure 3a (L=
150 mm, t ₀ = 3 mm, t ₁ = 15 mm, W = 20 mm). Test pieces for hardness, machinability, surface roughness, coefficient of dynamic friction, and corrosion resistance were formed into the shapes shown in FIG. 2 by cold forging for alloy materials A and B, and by die casting for alloy C. After rough-machining these alloy materials, they were subjected to T6 heat treatment under the same conditions as above, and then mirror-finished using a cutting tool with a diamond cutting blade, so that the dimensions in Fig. 2 were D.
= 63mm, d ₁ = 40mm, d ₂ = 20mm, H ₁ = 16mm, H ₂ =
The VTR rotating drum is made of 7mm. The cutting conditions for the outer peripheral surface of the drum where the tape slides is a cutting speed of 150.
m/min, depth of cut 0.05mm, cutting tool feed rate 0.05
mm/rotation. The specific wear test piece is the VRT above.
It was cut out from a part of the rotating drum and examined. 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 Tests were conducted using JIS No. 4 test pieces using an Olsen 50-ton universal testing machine. c) Cold forgeability The wedge test piece 1 shown in Fig. 3a is shown in Fig. 3b.
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 ◎:
Good, ○fair, △: Displayed as slightly poor. d) Hardness The hardness directly below the tape sliding surface was measured using a Bitkers hardness meter. e) Chip disposal property Cutting was performed using an artificial sintered diamond cutting tool at a cutting speed of 150 m/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, ○: Fair, and △: 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 test material was FC30.
Friction speed 3m/sec, load 2.1Kg, friction distance 600
The test was conducted without lubrication, and the amount of specific friction per kg of unit area was measured. H) Coefficient of Dynamic Friction A reverse tension (Wp) of 50gr was applied to one side of the magnetic tape using the same running method as a VTR.
The coefficient of dynamic friction was calculated by rotating the test material at a relative speed of seconds and measuring the acting load (WT) on one side facing the magnetic tape load. li) Corrosion resistance of magnetic tape contact parts After wrapping magnetic tape with a load of 60 gr around a VTR drum and keeping it in an atmosphere of 40°C and 85% humidity for one week, the drum and magnetic tape were in contact with each other. I observed the condition of the parts that were in use. 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 above corrosion resistance test is shown in FIG. 4, and a corresponding sketch of the magnetic tape is shown in FIG. In both FIGS. 4 and 5, a corresponds to alloy No. 2 and b corresponds to alloy No. 12. The black dots on the drum surface in FIG. 4b are corroded areas, and the black dots on the tape surface in FIG. 5b are areas where magnetic powder has peeled off due to drum corrosion. When the structure of the cross section of the corroded area shown in FIG. 4b was observed, it became clear 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. 4b. 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 diagram showing the component range of Si and Mg;
Figure 2 is a cross-sectional view of a rotating drum-shaped specimen for VTR.
Figure 3a shows the shape of a wedge test piece for forgeability evaluation, Figure 3b is an explanatory diagram of the forgeability test method, and Figures 4 and 5 show the shape of a wedge test piece for forgeability testing. These are sketches of the thus obtained drum surface (FIG. 4) and the corresponding magnetic tape (FIG. 5), in which a corresponds to alloy No. 2 and b corresponds to alloy No. 12, respectively. FIG. 6 is a micrograph of a cross-section of the corroded portion of the drum of FIG. 4b.

Claims (1)

[Claims] 1. 1 to 6% Cu by weight, Si and Mg,
Point A (Si0.15%, Mg0.2%), point B (less than Si0.5%, Mg0.2%), point C (less than Si0.5%, Mg0.8%),
Point D (Si0.4%, Mg0.8%), Point E (Si0.4%, Mg1.8
%), the amount in the range surrounded by point F (Si0.15%, Mg1.8%), Fe0.1~1.0%, Ti0.005~0.2%,
An aluminum alloy for magnetic tape contact parts with excellent corrosion resistance, the remainder of which is Al containing normal impurities. 2 Cu 1 to 6% by weight, Si and Mg in the first
Point A (Si0.15%, Mg0.2%), point B (less than Si0.5%, Mg0.2%), point C (less than Si0.5%, Mg0.8%),
Point D (Si0.4%, Mg0.8%), Point E (Si0.4%, Mg1.8
%), the amount in the range surrounded by point F (Si0.15%, Mg1.8%), Fe0.1~1.0%, Ti0.005~0.2%,
An aluminum alloy for magnetic tape contact parts that further contains 0.2 to 1.2% Mn and 0.2 to 1.2% Cr, and the remainder is Al containing ordinary impurities, and has excellent corrosion resistance. 3 Cu 1-6% by weight, Si and Mg in the first
Point A (Si0.15%, Mg0.2%), point B (less than Si0.5%, Mg0.2%), point C (less than Si0.5%, Mg0.8%),
Point D (Si0.4%, Mg0.8%), Point E (Si0.4%, Mg1.8
%), the amount in the range surrounded by point F (Si0.15%, Mg1.8%), Fe0.1~1.0%, Ti0.005~0.2%,
Furthermore, this aluminum alloy for magnetic tape contact parts has excellent corrosion resistance and contains a total of 0.5 to 2% of one or more elements among Pb, Bi, Sn, and Sb, with the remainder being Al containing ordinary impurities. 4 Cu 1-6% by weight, Si and Mg in the first
Point A (Si0.15%, Mg0.2%), point B (less than Si0.5%, Mg0.2%), point C (less than Si0.5%, Mg0.8%),
Point D (Si0.4%, Mg0.8%), Point E (Si0.4%, Mg1.8
%), the amount in the range surrounded by point F (Si0.15%, Mg1.8%), Fe0.1~1.0%, Ti0.005~0.2%,
Furthermore, it contains one or more elements among 0.2 to 1.2% Mn, 0.2 to 1.2% Cr, and 0.5 to 2% in total of one or more elements among Pb, Bi, Sn, and Sb, with the balance being normal. An aluminum alloy for magnetic tape contact parts that has excellent corrosion resistance and is made of Al containing impurities.