JPS61119643A - Free-cutting aluminum alloy and its production - Google Patents

Abstract

PURPOSE:To obtain the free-cutting aluminum alloy causing little strain after cutting as well as having superior machinability, by providing an aluminum alloy containing specific amounts of Mn, Mg, Cu, Fe, Si, Pb, and Sn. CONSTITUTION:The aluminum alloy ingot consisting of, by weight, 0.5-1.5% Mn, 0.2-0.9% Mg, 0.15-0.9% Cu, 0.1-0.5% Fe, 0.05-0.2% Si, 0.15-1% Pb, 0.6-1.5% Sn, and the balance Al with inevitable impurities. This alloy ingot is homogenized at 520-600 deg.C and hot-worked, which is subjected to cold working at 15-70% draft and to annealing at 200-300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a free-cutting aluminum alloy that has excellent machinability, generates little distortion after cutting, and is low-cost, and a method for producing the same.

Conventional technology Conventionally, aluminum alloys for cutting used in optical instruments, precision instruments, etc. include Al-Cu-based 2011 alloy, AI-M (I-based 5056 alloy, AI-M!J-8).
I-based 6262 alloy is known as a typical alloy.

These alloys are widely used in various fields including optical equipment, but they have the following characteristics and problems.

Although the 2011 alloy has extremely excellent chip disposal properties as a high-strength free-cutting alloy, its disadvantage is that it has many cuts and poor corrosion resistance.

On the other hand, since the 6262 alloy is based on the AI-Ma-3i system, it is a free-cutting aluminum alloy that has better corrosion resistance than the 2011 alloy.

However, since 2011 alloy and 6262 alloy are heat-treatable alloys, pretreatment I is required to obtain excellent chip control properties and a specified strength. ! (quenching, tempering) is required. During quenching, the material is rapidly cooled from a high temperature, resulting in large quenching residual stress and quenching distortion, and it is extremely difficult to completely remove stress and distortion once generated.

Therefore, heat treatable alloys such as 2011 alloy and 6262 alloy inevitably result in significantly higher stresses remaining in the final product.

For this reason, there is a problem in that highly accurate dimensional tolerances cannot be achieved due to residual stress when precision machining optical equipment parts and the like.

Generally speaking, these alloys require heat treatment, so 50
There is a problem in that the cost is higher than that of non-heat treated alloys such as 56 alloy.

On the other hand, since the 5056 alloy is a non-heat treatable alloy that is used in a soft or semi-hard state, there is no problem with the amount of cutting due to residual stress that occurs with heat treatable alloys. However, although this alloy has good corrosion resistance and good finish on the cut surface, it has extremely poor chip disposal properties, which poses a problem when cutting with an automatic turning machine.

The problem that should be solved.

This invention has excellent chip disposal properties and dimensional accuracy after cutting,
Furthermore, the present invention aims to provide a low-cost free-cutting aluminum alloy and a method for producing the same.

The structure of the present invention to provide the above-mentioned free-cutting aluminum alloy and its manufacturing method to solve the problem is as follows.

(1) MnO05-1.5%, Ma 0.
2-0.9%, Cu 0.15-0.9%, Fe 0.
10-0.5%, 3i0.05-0.2%, pb 0.
A free-cutting aluminum alloy containing 15% to 1.0% Sn, 0.6% to 1.5% Sn, and the remainder consisting of aluminum and impurities, and has excellent machinability and less distortion after cutting.

■ The alloy with the above composition was homogenized at 520-600°C and then hot worked, and after 15-10% cold working, it was heated to 200-300°C.
A method for producing a free-cutting aluminum alloy that has excellent machinability and generates little distortion after cutting by annealing at 00°C.

The reason why the composition of the aluminum alloy is limited is explained based on the effect of each component: Pb, Sn: Pb and Sn
Coexistence in aluminum has the effect of significantly improving machinability. This is because the Pb-8n-based low melting point compound melts due to processing heat during cutting, resulting in fine fractures of chips. If the amount added is less than the lower limit, machinability will not be sufficient, and if it exceeds the upper limit, there will be a problem of embrittlement during hot working.

Mn: Mn improves the strength of the alloy, as well as pb,
Although the effect is smaller than that of Sn, it has an effect that contributes to improving machinability.

This is because Mn crystallizes as an Al-Mn-based or Al-Mn-1"e-based intermetallic compound, and when a large amount of the compound is present in the matrix, it facilitates the breakage of chips.Additional amount If it is less than the lower limit, the effect of improving strength and machinability will be small, and if it exceeds the upper limit, there will be a problem that large intermetallic compounds will crystallize.

Mill: Ml) has the effect of improving the strength of the alloy, and is an essential additive element in order to obtain a predetermined strength required for optical devices and the like.

If the amount added is less than the lower limit, the effect of improving strength will be small, and if it exceeds the upper limit, machinability will decrease. This is because M(J and 5n form a M(] z Sn metal compound, and 5nftt, which is effective for improving machinability, decreases).

Cu: Cu has the effect of improving strength and machinability, and below the lower limit this effect is small, and beyond the upper limit the effect does not improve and corrosion resistance decreases.

Fe: Fe has the effect of making crystal grains finer and improving the strength of the alloy.

This effect occurs when the amount added is below the lower limit. is not sufficient and exceeds the upper limit, crystal grains Not only does the miniaturization effect become saturated, Corrosion resistance, cut surface finish, surface treatment Sexuality, etc. decreases.

3i: 3i has the effect of improving the strength of the alloy and improving the machinability. If it is less than the lower limit, this effect will not be sufficient, and if it exceeds the upper limit, a MO2Si-based coarse compound will be formed, which will reduce the strength-improving effect of M9 addition, resulting in a decrease in strength and machinability.

To explain each step in the manufacturing method, in order to obtain good performance, it is necessary to process the invention alloy under the following manufacturing conditions.

Homogenization treatment: The ingot of the invention alloy is homogenized at 520 to 600°C to precipitate Mll dissolved in solid solution during casting and to refine the crystal grains of hot-worked materials and final products. If the homogenization temperature is below the lower limit, crystal grains will become coarse, and if it exceeds the upper limit, eutectic melting will occur.

In addition, the homogenization treatment time is 2 hours. The above is desirable.

Hot processing: Normal hot extrusion processing is sufficient.

Cold working: The ingot after homogenization treatment is hot worked and then cold worked, and the degree of working is preferably 15% or more. If it is less than the lower limit, there is a problem that the machining strain is not sufficiently recovered even by subsequent annealing and residual stress becomes high. Even if the processing exceeds the upper limit, the degree of reduction in residual stress does not change.

Annealing: Cold-worked materials are annealed, but if the annealing temperature is below the lower limit, the strength is high and the machinability is good, but the removal of residual stress is insufficient, resulting in distortion during precision cutting. occurs.

Residual stress occurs when the annealing temperature exceeds the upper limit. is significantly reduced, even after precision cutting. No amount of cutting occurs, but strength and machinability decreases significantly.

! 1U1 The present invention will be specifically explained below with reference to Examples.

As samples, aluminum alloys having the compositions shown in Table 1 below were used.

However, No. 1 to 9 are alloys of this invention, and No. 10 to 9 are alloys of this invention.
21 is a comparative example, of which No. 20 is a 5056 alloy.
〇 material, N 0.21 is 2011 alloy-C8 material.

Table 1 Chemical composition of alloy (%) The alloy with the above composition was made into an ingot for extrusion with a diameter of 250 au+,
It was processed and treated under the conditions described in the Examples described below, and its properties were tested.

Example 1 After homogenizing the above ingot at 580°C for 10 hours,
Heat to 0℃ and extrude into 55φx65φx
5. I made it into an Ot tube. This tube was cold drawn by 41% to 50%
φ×56φx 3. After the temperature was set to Ot, it was annealed at 250°C for 1 hour.

The properties of these materials were as shown in Table 2 below.

Rotation speed 2000 rpm Rake angle 5° Feed 0.1
am/rev Incision 1 cm 12 Average residual stress measured by incision method (kQ/mm2) 1 base pipe 5
1.5φx54.5φx 1. Amount of change in roundness measured after cutting into the shape of St (Kaku) From the above results, the following characteristics or problems are recognized for each alloy.

The invention alloys Nos. 011 to 9 have fine crystal grains, excellent strength and machinability, and also have good dimensional accuracy after cutting, and have excellent properties.

No. 10-11 alloys have poor machinability.

The N0,12 alloy and the N0.13 alloy have low strength.

Alloy No. 14 had coarse grains and had a poor finish on the cut surface.

N0.15 alloy has low strength.

N0.16 alloy has poor machinability.

N0.17 alloy has low strength.

N0.18 alloy has poor machinability and low strength.

No. 19 alloy has poor machinability.

The 5056 alloy with p4 o, 20 has poor machinability.

The 2011 alloy with 1'J of 0.21 has poor dimensional accuracy after cutting.

Example 2 Some of the alloys (250 mm diameter ingots) having the compositions shown in Table 1 above were processed into pipes under the manufacturing conditions shown in Table 3 below.

Table 3 Pipe manufacturing conditions Nos. 11 to 9 are examples, Nos. 10 onwards are comparative examples. The properties of the pipes manufactured under the conditions shown in Table 3 above are as follows
Shown in the table.

Table 4 Characteristics of manufactured tubes The evaluation methods for 1 to 3 are the same as in Example 1. From the results in Table 4 above, the following characteristics are recognized for 8 tubes.

According to the manufacturing conditions of Nos. 1 to 9 of the present invention, the crystal grains are fine, the strength, machinability, finish of the cut surface, etc. are excellent, and the residual stress is low, resulting in free machining with good dimensional accuracy after cutting. It becomes possible to obtain an aluminum alloy.

No. 10 had coarse crystal grains and poor surface finish.

N 0.12 and N 0.13 have large residual stress and poor dimensional accuracy after cutting.

No. 14 and No. 15 have poor machinability.

N0916 has coarse grains, poor surface finish, and high residual stress, resulting in poor dimensional accuracy after cutting.

1 shellfish! 81 [As is clear from the above description, according to the present invention, a free-cutting aluminum alloy with excellent machinability, a small amount of cutting, and a low cost can be obtained.

Claims (2)

[Claims] (1) Mn0.5-1.5%, Mg0.2-0.9%,
Cu0.15-0.9%, Fe0.10-0.5%, S
i0.05-0.2%, Pb0.15-1.0%, Sn
A free-cutting aluminum alloy containing 0.6 to 1.5% and the remainder consisting of aluminum and impurities, which is characterized by excellent machinability and low distortion after cutting. (2) Mn0.5-1.5%, Mg0.2-0.9%,
Cu0.15-0.9%, Fe0.10-0.5%, S
i0.05-0.2%, Pb0.15-1.0%, Sn
An alloy ingot containing 0.6 to 1.5% and the remainder consisting of aluminum and impurities is hot worked at 520 to 600°C after homogenization, and after cold working to 15 to 70%, the alloy ingot is made of aluminum and impurities.
A method for producing a free-cutting aluminum alloy which has excellent machinability and generates little distortion after cutting, characterized by annealing at 00°C.