JPH0390528A - Aluminum alloy excellent in mirror finishing characteristic - Google Patents

Abstract

PURPOSE:To produce an Al alloy excellent in mirror-finish characteristics by specifying the major axis and the state of distribution of intermetallic compounds containing Mg and Si and free from Fe, respectively, in an Al alloy containing specific percentages of Mg, Fe, and Si. CONSTITUTION:An aluminum alloy which has a composition containing, as an essential element, 2.5-6.5wt.% Mg, also containing, as impurity elements, <=0.20wt.% Fe and <=0.2wt.% Si, and having the balance essentially Al is prepared so that intermetallic compounds containing Mg or/and Si and free from Fe are distributed in the structure and also the intermetallic compounds of >=1.0mm major axis exist 100-5000 pieces per square millimeter. By this method, the aluminum alloy minimal in the occurrence of defects at the time of mirror finishing can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an aluminum alloy that is subjected to mirror cutting for magnetic disks, copy drums, polygon mirrors, VTR drums, etc. It is difficult.

[Prior Art] Aluminum alloys are usually used for magnetic disks in computers, drums in copying machines, reflectors such as polygon mirrors that reflect light from lasers, and magnetic tape contact members such as drums in VTRs, DATs, etc. There is. These members are used after processing an aluminum alloy material into a predetermined shape, cutting the surface to a mirror finish, and then subjecting it to surface treatment, etc., or without subjecting it to such treatment.

This mirror cutting is usually carried out in several steps such as rough cutting and finishing cutting, and in the finishing cutting, a diamond cutting tool is generally used to perform ultra-precision finishing.

Materials with such ultra-precision machined surfaces are required to have the following properties.

(1) It must have sufficient strength to withstand various movements during various processing and use.

(2) Defects such as scratches and pits do not occur during mirror cutting.

(3) If surface treatments are performed after mirror cutting, defects such as pits should not occur due to those treatments.

AA5 is an aluminum alloy that satisfies these characteristics.
Various alloys are used, such as Al-Mg alloys such as 086 and Al-Mn alloys such as AA3003.

[Problem to be solved by the invention] All of these alloys contain impurities such as Fe and Si, and intermetallic compounds such as Al-Fe based due to these impurities exist in the matrix of the material. . When mirror-cutting these materials, there is a risk that surface defects such as pits or scratches may occur due to the shedding of these intermetallic compounds, and measures such as lowering the cutting speed are taken to prevent these processing defects. This was necessary and therefore caused a loss of productivity.

Various studies have been conducted on materials that are less susceptible to these processing defects, and the following countermeasures are often taken as a practical method.

(These intermetallic compounds are reduced by highly purifying the 11 alloy ingot and reducing impurities such as Fe and Si.

(2) These intermetallic compounds are reduced by increasing the cooling rate during casting using the thin plate casting method.

However, these measures have resulted in higher material prices due to higher raw metal prices, increased equipment costs, etc. Further, various alloy materials using these measures have not always been able to eliminate surface defects and have not been sufficiently effective.

[Means for Solving the Problems] In view of this, the present invention has obtained the following knowledge as a result of detailed study on the structure of the material and the defect generation mechanism during cutting.

Although materials with reduced intermetallic compounds as mentioned above tend to have fewer surface defects,
They do not necessarily disappear, and even within the range of variation, there are cases where defects are equivalent to those without measures or even have more defects than those without measures. On the other hand, even among materials for which no countermeasures are taken, there are materials with very few surface defects.

As a result of a detailed study of the material structure based on these facts,
■The intermetallic compounds that form pits and scratches due to falling off are hard and brittle Al2-Fe-X compounds containing Fe (X
is the third element). ■But Aj! -Not all of the -Fe-X compounds fall off, nor is the largest compound falling off. ■As an intermetallic compound in the structure, AI! In addition to -Fe-X systems, those containing Mg or/and Si, such as Mg Si, A1. zMgt
When other elements such as Mg and/or Mn are added, there are compounds such as A and eMns+ that contain these elements, but for materials in which compounds containing Mg and/or Si are present in a somewhat coarse manner, Although the Al-Fe-X compound falls off, the resulting bits are relatively small and scratches are less likely to occur.

Further analysis of these facts revealed that when the amount of compounds containing Mg and/or Si is small, Aj! -Fe-
X-based compounds tend to fall out in the form of being dug out of the material without being cut by the cutting tool, and at that time, they plastically deform the nearby matrix, forming relatively coarse pits, and in severe cases, they move with the tool. It turned out that it would become a scratch because it would fall off while doing so. However, Mg or/and S
When relatively coarse compounds containing i are uniformly dispersed in the material, these compounds are relatively soft and are easily cut by a tool, and at that time, some of them appear on the tool surface in the shape of a built-up cutting edge. It has the effect of making it difficult for Al2-Fe-X compounds to fall off, and also has the effect of making it difficult for Al2-Fe-X compounds to fall off.
If a compound containing Si is present around an Al-Fe-X compound, on the contrary, the AI-Fe-X compound will easily fall off, and the surrounding area will hardly be deformed when it falls off. It was found that no minute bits were generated and almost no scratches were generated.

The magnitude of these effects varies somewhat depending on the type of compound, with MgzSi having the greatest effect, and AI! 3
M g z has a similarly large effect, but other M
The effects of compounds containing g and/or Si are slightly smaller than those of these compounds.

The present invention has been made based on such knowledge, and claim 1 of the present invention provides that M g 2.5 to 6.5 as an essential element.
wt%, and as an impurity element, Fe≦0.20w
t%, Si20.20wt%, and the remainder is substantially Al, and an intermetallic compound containing Mg or/and Si and no Fe in its structure. In the distribution, the compound with a long axis of 1.01M or more is 10% per 1.0mm2.
It is an aluminum alloy with excellent mirror machinability characterized by the presence of 0 to 5000 pieces, and claim 2 contains 2.5 to 6.5 wt% of Mg as an essential element, and Mn0 as a selectively added element. .01-1.0wt%, Cr 0
．． 01-0.3wt%, Z r 0.005-0.3w
t%, Ti 0.001-0.05 t%, Ni
0.005-0.5wt%, 80.0001-0.01
Fe≦0.20wt%, Si20.20wt% as impurity elements.
, and the remainder is substantially Al, in which an intermetallic compound containing Mg or/and Si and not Fe in the Mi fibers is distributed in the structure of the compound. An aluminum alloy with excellent mirror machinability characterized by having 100 to 5,000 pieces having a long diameter of 1.0 μ or more per 1.0 mm2, and claim 3, as an essential element,
Contains 2.5 to 6.5 wt% of Mg, and as selectively added elements, Cu0.001=2.0 wt%, Zn0. OO1
Contains one or more of ~2°0wt%, and as impurity elements, Fe≦0.20wt%, Si20.2
An aluminum alloy containing 0 wt% and the remainder substantially consisting of ll, which contains Mg or/and Si in its structure and an intermetallic compound that does not contain Fe, has a distribution in its structure. Claim 4 is an aluminum alloy having excellent mirror machinability, characterized in that 100 to 5000 compounds having a long axis of 1.0 μ or more are present per 1.0 mm2, and claim 4 is an aluminum alloy having excellent mirror machinability as an essential element.
2.5 to 6.5 wt%, and as the first selective addition element, Mn0.01 to 1, Qwt%, Cr 0.01
~0.3wt%, Zr 0.005~0.3wt%,
T i 0.001-0.05 wt%, N i O.

005~Q, 5wt%, Bo, 0001~0.01wt
%, and further contains Cu0. % as a second selective element. OO1~2.0wt%, Zn0
．． Fe≦0.20wt%, Si
An aluminum alloy containing 0.20 wt% and the remainder substantially consisting of Al, and has Mg or/and Mg in its structure.
And an intermetallic compound containing Si but not Fe has a long axis of 1.
Otna or more is 100 to 5 per 1.0 mm2
It is an aluminum alloy with excellent mirror machinability and is characterized by the presence of 000 pieces.

[Effect]

The reason for the alloy composition and structure limitation in the present invention will be explained (hereinafter, wt% is simply abbreviated as %).

First, the reason for limiting the composition of the alloy material of the present invention will be explained below.

Mg mainly provides strength and contains Mg, and Fe
It has the effect of improving machinability by creating an intermetallic compound that does not contain in the structure. If it is less than 2.5%, these effects will not be sufficient, and if it exceeds 6.5wt%, the intermetallic compounds containing Mg will increase and become coarse, leading to the risk of deteriorating the corrosion resistance of the material and causing coarse pinto. Sexuality increases.

Mn, CrZr, Ti, Ni, and B each have the effect of refining the crystal grains in the material, contributing to the strength of the material and improving the smoothness of the cut surface. Below the respective lower limits, these effects are not sufficient, and above the upper limits, coarse compounds are produced during casting, increasing the possibility of defects occurring.

Cu and Zn have the effect of making the reactivity of the surface uniform and improving the smoothness of the surface after the treatment when the alloy material of the present invention is subjected to surface treatment with acid or alkali after mirror cutting. In addition, when plating the surface, such as when used for magnetic disks, the zincate particles are made uniform and fine during zincate treatment, which is the base treatment for plating, and this improves the adhesion of the plating and the smoothness of the plating surface. Improve your sexuality.

The impurities contained in the alloy of the present invention are mainly Fe and Si, but if these elements alone exceed 0.20 wt%, the intermetallic compounds in the material will become coarse and there is a risk that defects will occur during mirror cutting. It gets expensive.

Impurities other than the above-mentioned elements do not affect the properties of the alloy material of the present invention even if they are contained as long as they are each 0.05 wt% or less.

It is also possible to add Be to the alloy material of the present invention in an amount of about 0.5 to 200 ppm for the purpose of preventing oxidation of the molten metal.

Next, the reason for limiting the structure of the alloy material of the present invention will be explained.

As mentioned above, an intermetallic compound containing Mg or/and Si and not containing Fe has the effect of suppressing the formation of defects during cutting of the intermetallic compound containing Fe, and this effect is due to the fact that the major axis of the intermetallic compound is 1 It is noticeable in those with a diameter of .0 mm2 or more. In the distribution in the tissue, the compound with a long axis of 1.0 mm2 or more has a concentration of 100 to 100 per 1°011.
The reason why the number is limited to 5,000 is that below the lower limit, this effect is not sufficient, and when it exceeds 5,000, the smoothness of the cut surface is adversely affected.

When determining the distribution of intermetallic compounds in a structure, it is impossible to accurately measure the distribution unless a sufficiently large area is measured. Therefore, when measuring the product of the present invention, it is preferable to measure an area of 1.0 mm 2 or more. In addition, for measurements, a scanning electron microscope (SEM) was used.
Or optical w4? It is common to measure tissue observed with a II mirror, etc. using an image processing device, etc., but if the observation magnification during measurement is small, measurement errors will become large and accurate measurement will not be possible. . Therefore, when measuring the product of the present invention, it is desirable to observe the structure at a magnification of 1000 times or more.

These structural conditions are influenced by the combination of casting conditions and homogenization treatment conditions, and the present invention does not specify these conditions individually. Mg or/
The intermetallic compound containing Si and not Fe crystallizes just before the end of solidification, that is, near the in-phase temperature, and further precipitates during cooling. Therefore, first, the distribution of compounds in the ingot or cast plate is determined by the magnitude of the cooling rate during casting. The cooling rate that becomes an issue at this time is the cooling rate in the temperature range of around 700-580"C when the molten metal solidifies, and the cooling rate in the temperature range of 580-200"C where precipitation occurs after solidification.
This includes any cooling rate in the temperature range of C.

The larger the cooling rate at this time, the finer the size of the compound. Next, the ordinary ingot or cast plate is subjected to heat treatment such as homogenization treatment and annealing. The compound becomes finer. Therefore, these heat treatment temperatures and times should be determined depending on the compound distribution during casting. Usually, the heat treatment temperature for such an alloy is about 450 to 540''C for homogenization treatment, and about 200 to 400''C for annealing treatment. The recommended heat treatment temperature to obtain the target structure of the present invention is 520"C or less. The reason for this is that the diffusion rate of atoms in the material increases exponentially with temperature, so the heat treatment temperature is This is because the higher the temperature, the more fine the compound progresses in a shorter time, making control more difficult and making it difficult to obtain the desired amount of compound.The heat treatment time should be determined by the compound distribution before heat treatment and the heat treatment temperature. be.

In addition, when cooling after heat treatment, coarsening may occur due to redecipitation of the compound, so if the cooling rate is low, it is desirable to make the distribution smaller by heat treatment and achieve the desired distribution by reprecipitation. If it is large, it is desirable to achieve the desired distribution by heat treatment. Note that the adjustment of the compound distribution by these heat treatments does not need to be determined by a single heat treatment, and can be carried out in several parts, such as before processing, during processing, and after processing. In addition, when processing and heat treatment are combined, the strain introduced by processing has the effect of accelerating the diffusion of atoms in the material, and therefore it is possible to refine the compound at relatively low temperatures and in a short time. It is. It is also possible to control the desired compound size and amount by controlling the cooling rate during casting. In this case, the heat treatment after casting is performed using a metal containing Mg or/and Si but not containing Fe. Conditions should be selected that do not significantly affect the size and amount of intercalary compounds, and in this case it is recommended that the heat treatment temperature be 380°C or less.

〔Example] An embodiment of the present invention will be described below.

Example 1 Alloys having the compositions shown in Table 1 were cast to a thickness of 300 mm by DC casting.
It was made into an ingot with a diameter of 600 seconds. The intermetallic compounds in this ingot were observed using an SEM at a magnification of 2000 times, and the ED
While checking the elements contained in the compound using X as needed, identify intermetallic compounds containing Mg and/or Si but not Fe from the tissue, and input the SEM image to the image analysis device. and major axis 1. The size and amount of the compound were measured for 0-groups and above. The measurement area is 1.0mm2
The measurement results are shown in Table 2.

Each side of these ingots costs 10r! After supplementing the ingot by m, it was heat-treated under the homogenization treatment conditions shown in Table 1, paying attention to the distribution of the compound in the ingot, and quickly hot-rolled at the same temperature to a thickness of 4 loaves. It was made into a plate material.

After hot rolling, it was rapidly cooled from that temperature (470 to 380"C) by forced air cooling and cooled to 80°C or less at a cooling rate of 150°C/h or more. Thereafter, cold rolling was performed to 1.6 A test plate with a thickness of m was used.

A circular plate with an outer diameter of 280 m5+ was punched out from this plate material, and 36
After annealing at 0°C for 2 hours, the intermetallic compounds containing Mg and/or Si but not Fc in this plate were measured using the same method as the measurement for the ingot described above, and the results were used in the second test. Shown in the table.

At the same time, this disk was roughly cut into a donut-shaped disk with an outer diameter of 275 mm and an inner diameter of 100 mm, which was then subjected to a machinability test. A natural single-crystal diamond tool is used for cutting.
Rotation speed 2000 rpm, feed speed 0, 05 m/r
Cutting was performed under the conditions of ev and cutting depth of 10 mm2, and the presence or absence of defects such as scratches and bits on the cut surface was visually observed. Machinability test is 1 for one composition.
After cutting 0 sheets on both sides and observing a total of 20 sides, those with defects on 10 or more sides are marked as ×, and those with defects on 2 to 9 sides are marked as △, indicating that no defects have occurred. Those with 2 or fewer sides were rated O. The results are also listed in Table 2. As is clear from this, all the products of the present invention have excellent machinability. However, in a comparative example that deviates from the composition of the present invention, Mg
It is clear that even if the number of intermetallic compounds containing or/and Si and not containing Fe is large or within an appropriate amount, there are many defects due to cutting and the properties are inferior.

Example 2 The ingot of alloy Nα4 of Example 1 was treated under the homogenization treatment conditions shown in Table 3, and then the same steps as in Example 1 were performed to obtain test materials having various compound distributions. The measurement of intermetallic compounds and the machinability test were also conducted in the same manner as in Example 1. 3rd result
Shown in the table. As is clear from these results, the product of the present invention has good machinability. It is clear that comparative examples with distributions outside the scope of the present invention have inferior characteristics.

Example 3 An alloy having the composition shown in Table 4 was cast into a sheet with a thickness of 6 mm using a twin roll casting machine.
．． It was a cast plate with a width of 8 vn and a width of 900 m. This cast plate was heat treated as shown in Table 5, and then cold rolled to a thickness of 1
．． A test plate of 6 rm was used, and the subsequent steps were as in Example 1.
Processing, heat treatment, and evaluation were performed in the same manner as above. The results are shown in Table 5. As is clear from these results, the product of the present invention has good machinability. On the other hand, it is clear that comparative examples having distributions outside the scope of the present invention have inferior characteristics.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain an alloy in which fewer defects occur during mirror cutting, which has a significant industrial effect.

Claims (4)

[Claims] (1) Contains Mg2.5-6.5wt% as an essential element, Fe≦0.20wt%, Si as an impurity element.
≦0.20wt%, the balance being substantially Al, the intermetallic compound containing Mg or/and Si in its structure and not containing Fe in the distribution in its structure. , the major axis of the compound is 1.0
100 to 50 per 1.0 mm^2 of μm or more
An aluminum alloy with excellent mirror machinability characterized by the presence of 00 pieces. (2) Contains 2.5 to 6.5 wt% of Mg as an essential element, and 0.01 to 1.0 w of Mn as an optional additional element.
t%, Cr0.01~0.3wt%, Zr0.005~
0.3wt%, Ti0.001-0.05wt%, Ni
0.005-0.5wt%, B0.0001-0.01
Fe≦0.20wt%, Si≦0.20wt% as impurity elements.
An aluminum alloy containing Mg and/or Si with the remainder substantially consisting of Al, in which an intermetallic compound that contains Mg or/and Si and does not contain Fe has a distribution in the structure of the compound. An aluminum alloy with excellent mirror machinability, characterized by the presence of 100 to 5000 pieces per 1.0 mm^2 with a major axis of 1.0 μm or more. (3) Contains 2.5 to 6.5 wt% of Mg as an essential element, and 0.001 to 2.0 of Cu as an optional addition element.
wt%, Zn0.001 to 2.0wt%, and contains one or more of Zn0.001 to 2.0wt%, and as an impurity element, Fe≦0.2
0wt%, Si≦0.20wt%, and the balance is substantially Al, and the intermetallic compound contains Mg and/or Si and does not contain Fe in its structure. An aluminum alloy with excellent mirror machinability, characterized in that, in the distribution in the structure, there are 100 to 5000 compounds having a major axis of 1.0 μm or more per 1.0 mm^2. (4) Contains 2.5 to 6.5 wt% of Mg as an essential element, and 0.01 to 1 Mn as a first selective addition element.
．． 0wt%, Cr0.01-0.3wt%, Zr0.0
05-0.3wt%, Ti0.001-0.05wt%
, Ni0.005~0.5wt%, B0.0001~0
．． 0.01 wt%, and further contains Cu0.001 to 2.0 wt% as a second selective element.
%, one or two of Zn0.001-2.0wt%
Fe≦0.20w as an impurity element
t%, Si0.20wt%, and the remainder is substantially A.
An aluminum alloy consisting of M in its structure.
In the distribution in the structure of an intermetallic compound containing g or/and Si and not containing Fe, the compound having a long axis of 1.0 μm or more has a concentration of 1 per 1.0 mm^2.
An aluminum alloy with excellent mirror machinability characterized by the presence of 00 to 5000 pieces.