KR910006021B1 - Al alloy for head drum of audio tape recorder and the method - Google Patents

Abstract

An Al alloy for head drum is characterized by the composition of 5-10 wt.% Si, 2-3.5 wt.% Cu, 0.2-1.2 wt.% Mg, 0.15-0.2 wt.% Ti, 0.015-0.03 wt.% Sr, 0.01-0.02 wt.% Na, and balance Al. In methods for the fabrication of Al alloy for head drum of DAT, a method is characterized by (1) melting mother alloy with some alloying elements at 700-800 deg.C; (2) before solidification, casting it at a pressure of a 1 ton/cm2; (3) homonizing it at 400-450 deg.C for 4-10 hrs; (4) extruding it with a speed of 3 m/min at 320-400 deg.C; (5) annealing it at 300- 400 deg.C; (6) after solid solution treatment at 500-520 deg.C for 1-4 hrs, aging it 170-190 deg.C for 7-10 hrs. It has advantages of grain refinging of Si and enhancing wear resistance property and glassy machinability. It is applied for head drum of DAT recorder operated under severe conditions.

Description

Aluminum alloy for head drum of digital audio tape recorder (DAT) and manufacturing method

1 is a state diagram of the ingot structure by the general casting method observed with an optical microscope.

2 is a state diagram of the ingot structure by the high-pressure casting method observed with an optical microscope.

3a is a graph of hardness values after solution treatment and ageing heat treatment.

3b is a graph of hardness values after solution treatment.

4 is a cross-sectional view of the high pressure casting apparatus.

* Explanation of symbols for main parts of the drawings

1: process Si 2: process Al

a: Graph of hardness value after solution treatment and ageing heat treatment of ingot by high pressure casting method

b: Graph of hardness value after solution treatment and ageing heat treatment of ingot by general casting method

a ': Graph of hardness value after solution treatment of ingot by high pressure casting method

b ': Graph of hardness value after solution treatment of ingot by general casting method

31: mold 32: base plate

33: Punch 34: Melt

The present invention relates to an Al-Si-Cu-Mg-based alloy in which the aluminum alloy for head drum, which is a magnetic recording and reproducing apparatus of a digital audio tape recorder (DAT), is improved in wear resistance and machinability by adding Ti, Sr and Na. will be.

Conventionally, Al-Cu-based alloys and Al-Cu-Si-based alloys have been used for video tape recorder (VTR) head drums, but they are more abrasion resistant for use in DAT head drums, which have a higher level of functionality than conventional VTR head drums. Insufficiency in the machinability and improvement of the machinability, the content of Si is made into the Al-Si overprocessing zone, the primary Si is dispersed in the Al base to increase wear resistance and mechanical strength, and the machinability is increased by adding Mg. An improved Al-Si-Cu-Mg-based alloy was used, but the problem of unstable abrasion resistance was exposed due to the phenomenon that primary Si peeled from the Al base. In addition, the problem of shortening the life of the tool during the cutting process, no matter how poor the machining precision and the alloy having an over-process Si content, it is difficult to expect the improvement of properties or reduction of bonding by a predetermined processing. In addition, in the casting method of the alloy, in the conventional case, casting defects in which a large amount of pores are formed in the ingot by casting the Al alloy for the VTR head drum by the general casting method occurs, and it is difficult to obtain a dense process structure of Al. It became.

The present invention is to solve the above problems in the existing Al-Si-Cu-Mg-based alloy to configure the adjustment range of each component differently and to add a new component, that is, Sr, Na and Ti while the alloy consisting of the components By casting by high pressure casting method instead of conventional casting method, it is possible to minimize the formation of pores formed in the ingot by using the high pressure casting method and to minimize casting defects and to make the aluminum process structure in the alloy more dense. The ingot made by the method was melted for 1-4 hours in the temperature range of 500-520 ° C, and then subjected to T ₆ heat treatment for aging for 7-10 hours in the temperature range of 170-190 ° C. An object of the present invention is to produce an alloy having excellent machinability and good surface roughness and cold forging.

The present invention having such an object will be described in detail with reference to the embodiments and the accompanying drawings. Since the DAT head drum has a higher function than the conventional VTR head drum, an alloy having better characteristics is required. The DAT head drum has to be excellent in wear resistance, machinability, surface roughness and cold forging. In order to satisfy the above conditions, in the present invention, the composition range of the alloy component is shown in Table 1 as follows.

Si 5-10.5 wt% Cu 2-3.5 wt%

Mg 0.2-1.2 wt% Ti 0.15-0.2 wt%

Sr 0.015-0.03 wt% Na 0.01-0.02 wt%

The remainder is composed of Al and trace impurities.

Table 1 shows the composition of the alloy components according to the present invention in comparison with various comparative agents which are existing alloys.

TABLE 1

If you describe the characteristics of each component constituting the above alloy

A. Si

Si forms a process structure and has excellent abrasion resistance and combines with other alloying elements to form intermetallic compounds. This mainly serves to improve the wear resistance and mechanical strength of the alloy. The reason for limiting the composition range of Si to 5-10.5% by weight in the alloy of the present invention is that if the Si is less than 3% by weight in the alloy, the functional effect is insufficient, and if it is 11% or more, cold forging is lowered.

N. Cu

Cu imparts heat treatment to the alloy and improves strength and machinability. The reason for limiting the composition range of Cu in the alloy of the present invention to 2-3.5% by weight is that when Cu is less than 1% by weight in the alloy, the strength and machinability are insufficient, and when it exceeds 3.5%, the plastic machinability and castability of the alloy are deteriorated. to be.

C. Mg

Mg increases and accelerates the precipitation strengthening of the alloy and further improves the machinability of the alloy. The reason for limiting the composition range of Mg to 0.2-1.2% by weight in the alloy of the present invention is that when Mg is 0.3% by weight in the alloy, the cutting resistance is minimized, and when it exceeds 1.5%, the oxidation of the alloy capacity is promoted, so that the plastic workability is increased. Because it hurts.

D. Sr

Sr is a component added to the weighing effect of the alloy of the present invention, the composition range of the range of 0.015-0.03% by weight is due to the improvement treatment effect of Sr 0.01% by weight or more in the alloy, 0.03% or more This is because the tool wear becomes severe when added.

M. Na

Na is a component that participated as an improvement treatment agent along with Sr of the alloy of the present invention, and its composition range was limited to 0.01-0.02% by weight, because Na reduced the cutting resistance and reduced the amount of tool wear around 0.015% by weight. This is because improved treatment effects such as surface roughness improvement and cutting property improvement are exhibited.

Iii. Ti

Ti serves to further refine the grains of primary aluminum in the alloy of the present invention, and exhibits the best effect when it is 0.15-0.2% by weight in the alloy. At this time, the Ti composition does not exhibit a micronization effect at 0.15% or less on the basis of the weight, and at 0.3% or more, the micronization effect is similar to the above composition range, but when a large amount of Ti is added, segregation is generated, which is undesirable. As described above, when the alloy of the present invention is dissolved and cast, Sr and Na are improved and Ti is added to further refine the grain structure of primary aluminum. Referring to the process for producing an alloy of the present invention as described above as follows.

[Preparation process]

As a master alloy manufacturing and preparatory step, dissolve and cast a master alloy such as Al-Si, Al-Cu, Al-Ni, Al-Ti, Al-Sr, and wash and dry now to dissolve the weight. do.

[Step 1]

As the dissolution step, Al now and the master alloy are added and dissolved at 700-800 ° C. higher than the melting temperature of 650 ° C. to prepare a molten metal.

[Step 2]

As a high pressure casting step, as shown in FIG. 4, the molten metal is injected into a metal mold and then cast by pressing at a pressure of 1ton / Cm ² before solidifying. In other words, the molten metal 34 is poured into the mold 31 and subjected to considerable mechanical pressure (1 ton / cm ² ) from the outside using the punch 33 before solidification. At this time, the molten metal in the mold is partially compressed by hydrostatic pressure until the end of solidification without any movement. Therefore, due to the pressure of the punch 33 applied to the molten metal 34, the process structure becomes fine and a casting ingot, i.e., a complete ingot having almost no pores is obtained. Here, reference numeral 32 is a base plate.

[Step 3]

As the homogenizing step, Al alloy is dissolved at a temperature of 650 ° C. or higher to remove stress of the kitchen tissue at 400-450 ° C. for 4-10 hours.

[Step 4]

As an extrusion step, the Al alloy is extruded at a speed of 3 m / min after heat treatment at 320-400 ° C. to prevent cracking of the Al alloy during the processing.

[Step 5]

In the forging step, the annealing treatment is performed at 300-400 ° C. to prevent cracking of the Al alloy during the processing.

[Step 6]

As the heat treatment step, the ingot subjected to the above step is subjected to solution treatment at 500-520 ° C. for 1-4 hours. At this time, if the temperature is higher than 520 ℃ or longer time, the grain size of primary Al is grown, so it is carried out under the above conditions. It is also aged for 7-10 hours at a temperature and time of 170-190 [deg.] C., which is generally used to obtain an age hardening effect in Al alloys.

[Finishing process]

As a precision machining step, an alloy manufactured by the high pressure casting method is precisely processed. The structure of the alloy ingot of the present invention obtained by the above method and the ingot manufactured by the general casting method is observed in an optical microscope as shown in FIG. 1 and FIG. 2. FIG. 1 is a state diagram of the structure of the ingot by the general casting method. The particle size of the molten Al (2) and the size of the process Si (1) particles formed at the grain boundary are large and the shape is long along the grain boundary rather than isotropic. It shows the state that it is. Therefore, it does not show much effect even after solution treatment and aging treatment and causes problems in mirror processing. FIG. 2 shows the texture state of the ingot cast by the high pressure casting method, which is much smaller than the process Al (2) particle size of FIG. 1 and shows that the structure is relatively dense and the process Si (1) particles are relatively isotropic. . On the other hand, FIG. 3 shows the hardness values obtained after the solution cast by the general casting method and the high pressure casting method at 460 ° C. to 520 ° C. at 20 ° C. for 1 hour and the hardness value after the aging treatment. Data.

As a result of analyzing the data, the graph (a) of FIG. 3 (a) shows that the hardness value after T ₆ treatment (solution treatment + aging treatment) of the tissue cast by the high pressure casting method is changed according to the change of solution treatment temperature. The graph (b) shows the change in hardness value after T ₆ treatment of the structure cast by the general casting method. The graph (a ') of FIG. 3 (b) shows a state in which the hardness value in the case of solution treatment of the cast tissue by the high pressure casting method changes with the change in solution treatment temperature. It shows the change of hardness value when only the solution cast by the general casting method is dissolved.

Analysis of the data showed that the hardness value of T ₆ (Solution + Aging) at 520 ° C was the highest, and the structure of the alloy cast using the high pressure casting method was higher than that cast using the general casting method. It suggests high hardness. Effects of the present invention according to the above principle are as follows.

In the Al-Si alloy, the alloy according to the present invention can obtain a dense process structure, which is impossible by the general casting method, and can obtain a good ingot having a small particle size of primary Al and no pores. In addition, by improving the addition of Sr and Na, the size of Si particles scattered in the Al base is minutely distributed, and the shape of Si in the grain boundary isotropically formed under appropriate heat treatment conditions, thereby obtaining an alloy having excellent wear resistance and cutting property. Lose.

General characteristics of the alloy according to the present invention are shown in Table 2 in comparison with those of the comparative agent.

TABLE 2

Claims (2)

In the alloy for DAT head drum, Al is mainly composed of Si 5-10.5%, Cu 2-3.5%, Mg 0.2-1.2%, Ti 0.15-0.2%, Sr 0.015-0.03%, Na 0.01-0.02% Aluminum alloy comprising a. A method for producing an aluminum alloy for a DAT head drum, comprising: i) a first step of dissolving a master alloy at 700-800 ° C; ii) a second step of high-pressure casting at a pressure of 1 ton / cm ² before solidifying the molten metal obtained in the first step; iii) a third step of homogenizing by removing stress for 4-10 hours at 400-450 ° C .; iv) a fourth step of extruding at 3 m / min at 320-400 ° C .; v) a fifth step of annealing at 300-400 ° C .; vi) A method for producing an aluminum alloy for a head drum of a digital audio tape recorder, comprising a sixth step of solution treatment at 500-520 ° C. for 1-4 hours and aging at 170-190 ° C. for 7-10 hours. .

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