JPH07113136B2 - Free-Cutting Aluminum Alloy Cast Material and Manufacturing Method Thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improved free-cutting aluminum alloy cast material capable of coping with ultra-high speed cutting and heavy cutting, and an improvement in its manufacturing method.

(Prior art and its problems) Free-cutting aluminum alloys include Al-Cu, Si, Fe, Zn, Mn,
It is an alloy containing elements such as Mg, and further containing low melting point metals such as Pb and Bi.

The conventional method for producing free-cutting aluminum alloy is to produce a billet for extrusion having an outer diameter of 8 ″ or more by vertical semi-continuous casting of a molten metal in which a low melting point metal is uniformly dispersed, and then hot extruding it In general, a process of obtaining a desired size and shape by processing is performed, and in some cases, such free-cutting aluminum alloy material is further subjected to casting and final cutting.

In such free-cutting aluminum alloys containing low melting point metals, good machinability and fine cutting chips can be obtained mainly due to the added low melting point metal and the second phase such as intermetallic compounds. This is because the particles are dispersed in the matrix. However, in the conventional process "process of plastically deforming an extrusion billet manufactured by vertical semi-continuous casting hot and cold", there is a limit to the fine dispersion of low melting point metals and intermetallic compounds that contribute to free-cutting properties. was there.

With the recent automatic cutting machine, the cutting speed of about 200 to 500 m / min was used for ultra high-speed cutting of about 1000 m / min. There are now some cases where the chips are continuous and the chip disposability does not meet the specifications of the cutting machine.

(Problems to be Solved by the Invention) In a free-cutting aluminum alloy containing a low melting point metal, good machinability and fine cutting chips are obtained because of the added low melting point metal or intermetallic compound. This is because the second phase particles such as are dispersed in the matrix on the microstructure. Depending on the particle size and degree of dispersion of the low melting point metal and intermetallic compound in such a matrix, the shape of the cutting chips during cutting,
The machinability of the material such as size is governed. The added low melting point metal itself does not form a solid solution in the aluminum melt and is present in the final solidification portion between the dendrite secondary arms in the solidification process. Further, the alloy composition to which the second phase particles such as intermetallic compounds are added is crystallized by being concentrated between the secondary arms of the dendrite in the solidification process. All are unevenly distributed between the secondary arms of the dendrite, which is the final solidification part.

The present invention has been made based on the above findings, by appropriately adjusting the particle size of the low melting point metal or intermetallic compound, the degree of dispersion and the dendrite secondary arm spacing, aluminum alloy casting excellent in free-cutting property The present invention has led to the finding that a material can be obtained.

(Means and Actions for Solving Problems) The present invention has been made in view of the above problems, and the first invention thereof contains Cu3 to 6%, Si0.1 to 1.5%, Fe0.1 to 2.0%, and P
0.5 to 2% in total of two or more elements selected from b, Bi and Sn
The balance including Au and Cu is aluminum and its impurities.
The average particle size of the second phase of the intermetallic compound is 15μm or less, maximum
25 μm or less, and the secondary dendrite arm spacing is
A free-cutting aluminum alloy casting material having a fine structure of 25 μm or less, and having a low melting point metal particle size of 15 μm or less on average and 25 μm or less at the maximum evenly and finely dispersed.

The second invention is based on the alloy composition of the first invention with Mg 0.3 to 1.8%,
And a free-cutting aluminum alloy casting material containing 0.05 to 1.2% of Mn. Further, the third invention is Zn0.05 to 0.3%, Cr0.05 to 0.2%, Ti0. 001 to 0.1
% Is a free-cutting aluminum alloy casting material containing at least one element.

Therefore, the fourth to sixth inventions are directed to a mold in which the aluminum alloys having the compositions of the above first to third inventions are horizontally arranged.
It is characterized by supplying high temperature molten metal of 710 ° C or higher, quenching and solidifying the molten metal in the mold at a cooling rate of 35 ° C / sec or more, and drawing the ingot horizontally while stirring the molten metal immediately before the mold. It is a method of manufacturing a free-cutting aluminum alloy cast material.

The content of each additive element is limited as described above in the alloy composition range of the present invention for the following reason. That is, Cu is an element for forming an intermetallic compound of Al-Cu and strengthening the heat-treatability and matrix structure of the material, but if it is less than 3%, it is insufficient to improve the strength. Deteriorate quality. Si, like Cu, contributes to strengthening the matrix structure, but if Si is less than 0.1%, its effect is small.
If it exceeds 1.5%, the castability is deteriorated as in the case of Cu. Fe contributes to the improvement of machinability, but if it is less than 0.1%, its effect is small, and if it exceeds 2.0%, it deteriorates the cutting tool.

Also, Pb, Bi and Sn improve the machinability and the chip disposability by adding two or more kinds, but if the total amount is less than 0.5%, it is not very effective, and if it exceeds 2%, the strength and cutting surface are Deteriorate. Next, Mg contributes to the strengthening of the matrix structure like Cu, and also improves the machinability by forming an intermetallic compound of Al-Cu-Mg and Al-Mg-Si.
If it is less than 3%, it is not so effective, and if it exceeds 1.8%, the castability is deteriorated. Mn contributes to the improvement of machinability by forming an Al-Mn-Fe intermetallic compound.
If it is less than 1.2%, the effect is small and if it exceeds 1.2%, the cutting tool is deteriorated. Further, addition of a small amount of Zn, Cr, and Ti all work to improve corrosion resistance and pitting corrosion resistance, but below the lower limit, there is no effect, and above the upper limit, machinability deteriorates.

The present invention is Al-Cu, Al-Cu-M of the above aluminum alloy.
g, Al-Mg-Si, Al-Mn-Fe, and other intermetallic compounds have a second-phase particle diameter of 15 μm or less on average, 25 μm or less at the maximum, and a dendrite secondary arm interval of 25 μm or less. And low melting point particle diameter is 15μm or less on average, 25μ at maximum
The particles are uniformly and finely dispersed in a size of m or less.

The second particle size of the above intermetallic compound exceeds 15 μm on average,
Also, for coarse particles with a maximum of more than 25 μm, even if they are finely dispersed, they do not contribute to the improvement of machinability. Also, the dendrite secondary arm interval exceeds 25 μm, and the low melting point particle diameter is 15 μm on average, and maximum 25 μm Even if it exceeds, the effect of improving the machinability becomes small.

However, in order to refine the second-phase particle size, secondary dendrite arm spacing, and low-melting metal particle size of these intermetallic compounds, the high-temperature molten metal is agitated by the horizontal continuous casting method in which the cooling rate is relatively high. Although this is achieved by rapidly solidifying the ingot, the temperature of the molten metal is supplied to the mold at a high temperature of 710 ° C or higher, and the molten metal cooling rate in the mold is rapidly solidified at 35 ° C / sec or higher. It is what
This causes coarsening of the overall microstructure even if the temperature of the melt is less than 710 ° C and the cooling rate is less than 35 ° C / sec, and if the melt is not agitated, it will be localized in the ingot cross section. This is because it is impossible to prevent large variations in the microstructure.

Next, the manufacturing method of the present invention will be described.

There are various horizontal continuous casting methods, but the one shown in FIG. 1 is used in the present invention. That is, the molten aluminum alloy (2) in the tundish (1) is 71
It is kept at 0 ° C. or higher and agitated by an impeller (4) attached to the tip of the agitating carbon shaft (3).
The molten aluminum alloy that has reached a predetermined temperature is discharged from a molten metal inlet (6) provided in the lower part of the header plate (5) and rapidly cooled and solidified by cooling water (8) introduced into a water mold (7), The ingot (9) is produced and horizontally drawn by a take-up machine (not shown). In addition, (10) is a cooling water inlet / outlet.

By such a horizontal contact casting method, the molten metal temperature is supplied to the mold at a high temperature of 710 ° C or higher, and the molten metal cooling rate in the mold is 35
By rapidly solidifying at ℃ / sec or more, and casting the molten metal while stirring, the second phase particle size of intermetallic compound, dendrite secondary arm interval, low melting point particle size, etc. can be adjusted to a predetermined value. Is.

(Example) An example of the present invention will be described below.

Example 1. Molten metal temperature 715-720 by the horizontal continuous casting method shown in FIG.
C., the cooling rate was changed to 40 to 45.degree. C./sec, and an ingot of 65 mm.phi. Was produced with the alloy composition of the present invention. For comparison, the composition of the present invention having no molten metal stirring and the one having a slow cooling rate were manufactured, and as a conventional example, a billet having an outer die of 9 inches φ was produced by a vertical semi-continuous casting method. After homogenizing these,
Plasticity processing by cold drawing was added, and T6 heat treatment was performed to evaluate the machinability. The machinability was evaluated by setting the cutting conditions to two levels, the normal cutting speed of 300 m / min and the ultra-high cutting speed of 1000 m / min, and the cutting depth of 0.2 mm and the feed rate of 0.025-
100 chips when cut at 0.1 mm / rev without using lubricant
The weight per piece was evaluated. Table 1 shows the alloy composition, casting conditions, ingot microstructure, machinability and the like.

As is clear from Table 1, the microstructure is refined under the manufacturing conditions of the present invention. By casting the molten metal while stirring, the dispersion of the second phase particles and the low melting point metal particles is reduced, and the DAS is also small. In the present invention having such a miniaturized microstructure, the chips are finely divided even in the ultra-high speed cutting degree region, and it is recognized that the cutting workability is superior to that of the conventional process.

Example 2. The alloy composition of the present invention by the same horizontal continuous casting method as in Example 1, while performing molten metal stirring at a molten metal temperature of 715 to 725 ° C and a cooling rate of 40 to 50 ° C / sec, an outer diameter 65φ ingot was formed. Manufactured. The microstructure of this ingot had a second phase grain size of Max. 6 to 13 μm, a dendrite secondary arm spacing (DAS) of 8 to 15 μm, and a low melting point metal grain size of Max. 12 to 18 μm. JIS alloy as a comparison material, 2
011, 2014, 2017, 2218 was manufactured by a conventional process, that is, a vertical semi-continuous casting method to produce a billet having an outer diameter of 9 ″ φ, and a T6 round bar extruded after homogenization treatment was used as a raw material. As in 1., the degree of fineness of the cutting chips depends on the cutting speed.
It was evaluated by the weight per 100 pieces.

Table 2 shows the alloy composition of the test materials and the machinability evaluation results.

As is clear from Table 2, it is clear that the conventional alloy produced by extrusion has a difficulty in cutting with an automatic processing machine because the chips are continuous in the ultra-high cutting speed range. On the other hand, it is recognized that the alloy of the present invention is clearly excellent in machinability due to cutting of chips.

(Effect) According to the present invention, it is possible to obtain a free-cutting aluminum alloy cast material having a fine microstructure by defining the aluminum alloy composition as in the present invention and performing the continuous casting conditions as in the present invention. It has been made possible and can be widely used as an optical component for automatic cutting under severe conditions and an automobile component, and has an extremely high industrial value.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a horizontal continuous casting method used in the present invention. 1 ... Tundish, 2 ... Melt, 3 ... Stirring carbon shaft, 4 ... Impeller, 5 ... Header plate, 6 ... Molten inlet, 7 ... Water cooling mold, 8 ... Cooling water, 9 ... … Ingot, 10 …… Cooling water inlet / outlet

Claims (6)

[Claims] 1. Cu3-6%, Si0.1-1.5%, Fe0.1-2.0%
Containing at least two elements of Pb, Bi, and Sn in a total amount of 0.5 to 2% and the balance consisting of aluminum and its impurities, and the second-phase particle diameter of the intermetallic compound of Al-Cu is 15 μm on average.
m or less, maximum 25 μm or less, and dendrite secondary arm interval has a fine structure of 25 μm or less, and low melting point metal particles have an average diameter of 15 μm or less and a maximum fineness of 25 μm or less. Free-cutting aluminum alloy cast material. 2. Cu3-6%, Si0.1-1.5%, Fe0.1-2.0
%, Mg 0.3-1.8%, Mn 0.05-1.2%, and Pb, B
The total amount of two or more elements selected from i and Sn is 0.5 to 2%, and the balance is aluminum and its impurities.
The average particle size of the second phase of intermetallic compounds such as Al-Cu-Mg, Al-Mg-Si, and Al-Mn-Fe is 15 μm or less, the maximum is 25 μm or less, and the dendrite secondary arm interval is 25 μm or less. A free-cutting aluminum alloy casting material having a structure, and having a low melting point metal particle diameter of 15 μm or less on average and 25 μm or less at maximum, dispersed uniformly and finely. 3. Cu3-6%, Si0.1-1.5%, Fe0.1-2.0
%, Mg 0.3 to 1.8%, Mn 0.05 to 1.2%, and a total amount of 0.5 to 2% of any two or more elements of Pb, Bi and Sn, and Z
n0.05-0.2%, Cr0.05-2%, Ti0.001-0.1% and at least one element, and the balance consisting of aluminum and its impurities, Al-Cu, Al-Cu-Mg, Al-Mg-Si, Al-
The average particle size of the second phase of intermetallic compounds such as Mn-Fe is 15 μm
It is characterized by having a fine structure with a maximum of 25 μm or less and a secondary dendrite arm spacing of 25 μm or less, and low-melting-point metal particles uniformly dispersed in an average of 15 μm or less and a maximum of 25 μm or less. Free-cutting aluminum alloy casting material. 4. Cu3-6%, Si0.1-1.5%, Fe0.1-2.0%
In a casting in which an aluminum alloy containing 0.5 to 2% of Pb, Bi, or Sn in a total amount of 0.5 to 2% and the balance of aluminum and its impurities is horizontally arranged.
By supplying high temperature molten metal of 0 ℃ or more, cooling rate of molten metal in the mold is 3
A method for producing a free-cutting aluminum alloy cast material, which comprises quenching and solidifying at 5 ° C / sec or more and drawing the ingot horizontally while stirring the molten metal immediately before the mold. 5. Cu3-6%, Si0.1-1.5%, Fe0.1-2.0
%, Mg 0.3-1.8%, Mn 0.05-1.2% and Pb, Bi, S
A high temperature molten metal of 710 ° C. or higher is supplied to a mold in which an aluminum alloy composed of 0.5 to 2% of any of n elements in a total amount of 0.5 to 2% and the balance being aluminum and its impurities is horizontally arranged, A method for producing a free-cutting aluminum alloy cast material, which comprises quenching and solidifying the melt at a cooling rate of 35 ° C./sec or more and drawing the ingot horizontally while stirring the melt immediately before the mold. 6. Cu3-6, Si0.1-1.5%, Fe0.1-2.0%, M
g 0.3-1.8%, Mn 0.05-1.2%, Pb, Bi, Sn, 2 or more elements in total 0.5-2%, and Zn0.0
Aluminum alloy containing 5 to 0.2%, Cr 0.05 to 2%, and Ti 0.001 to 0.1% at least one element, and the balance aluminum and its impurities in a horizontal mold.
It is characterized by supplying high temperature molten metal of 710 ° C or higher, quenching and solidifying the molten metal in the mold at a cooling rate of 35 ° C / sec or more, and drawing the ingot horizontally while stirring the molten metal immediately before the mold. Manufacturing method of free-cutting aluminum alloy cast material.