JPH0372693B2 - - Google Patents

Description

[Detailed description of the invention]

"Purpose of the invention" (Industrial application field) An aluminum free-cutting alloy that has high strength and good hot workability. (Prior Art) In the past, zinc alloys, cast iron, steel, etc. have been used as mold materials for molding soft materials such as plastics and rubber. However, recently, JIS 7000, an Al-Zn-Cu-Mg based material with excellent properties such as light weight and machinability, has been introduced.
Extruded materials made from high-strength aluminum alloys, such as those made from high-strength aluminum alloys, are being used to take advantage of their characteristics. (Problems to be Solved by the Invention) Although the above Al-Zn-Cu-Mg alloy can be made to have extremely high strength by heat treatment, tool wear occurs during cutting for the machining process. It has disadvantages in terms of hardness, chip disposal, etc., resulting in poor machining efficiency, and is also poor in hot workability, resulting in problems in its use, such as extremely slow extrusion speeds. "Structure of the Invention" (Means for Solving the Problems) The inventors of the present invention have repeatedly conducted various studies and ideas in order to improve the above-mentioned problems, and as a result, the above-mentioned Al-Zn-
By containing two or more types of Mn, Zr, and Cr and two or more types of Pb, Sn, and Bi within a specific amount range in a specific Cu-Mg alloy, the above-mentioned tool wear resistance and chip disposal properties can be improved. The present invention was completed by confirming that not only machinability but also hot workability can be appropriately improved. That is, the present invention includes (a) Zn: 5.0 to 8.0 wt%, Mg: 1.5 to 3.0 wt%,
Contains Cu: 1.4-3.0wt%, (b) Cr: 0.05-0.3wt%, Mn: 0.05-0.5wt%,
Contains two or more of Zr: 0.03 to 0.3 wt%, and (c) Pb: 0.2 to 1.0 wt%, Sn: 0.2 to 1.0 wt%, Bi:
It is a high-strength aluminum free-cutting alloy characterized by containing two or more of any one of 0.2 to 1.0 wt%, with the remainder consisting of Al and impurities. (Function) Each element of group (a) of Zn, Mg, and Cu functions as a precipitation hardening element, and by adding two or more of each element belonging to group (b) and group (c) in combination, This improves machinability and hot workability such as extrusion and hot rolling. (a) Group elements include wt% (hereinafter simply referred to as %)
So, Zn: 5.0~8.0%, Mg: 1.5~3.0%, Cu: 1.4~
3.0%, and if each element is less than the lower limit, sufficient strength cannot be obtained, while if it exceeds the upper limit, hot workability is also deteriorated. Group (b), Cr, Mn, and Zr, when two or more of them are added, can strongly develop a fiber structure during hot working and improve the strength and toughness of the alloy. is combined with Al to form fine crystallized substances, improving hot formability. Zr not only improves strength and toughness but also refines recrystallized grains during hot working process.
Further improves hot workability. Such action is caused by Cr: 0.05-0.3%, Mn: 0.05-0.5%, Zr: 0.03
It is necessary to add two or more of ~0.3%, and even if one type is added in an increased amount, the crystallized material will become large, and if two or more types are added, the fibers will be The structure does not develop, resulting in poor strength, toughness and hot workability. Even if two or more types are contained, the addition effect is insufficient below the lower limit,
Moreover, if the addition exceeds the upper limit, giant compounds will crystallize, deteriorating machinability, strength, and toughness, and further reducing hot workability. By adding two or more of group (c) Pb, Sn, and Bi, chip separation during cutting is improved, and
Reduces cutting tool wear and improves tool life. Such an effect is caused by Pb: 0.2~1.0%, Sn: 0.2~1.0%, Bi: 0.2~
This can be ensured by adding two or more types of 1.0%, and it is insufficient if only one type is added even if the amount added is increased. Also, each
If it is less than 0.2%, it will not be possible to obtain a suitable result even if the three types are contained, while if each exceeds 1.0%, the castability will deteriorate and cracks will occur during industrial high-speed casting. (Example) Regarding Zn, Cu, and Mg, the above Al-Zn-Cu-
The standard contents for Mg-based aluminum alloys are Zn: 6.0%, Cu: 2.0%, Mg: 2.0%, and alloys with various compositions as shown in Table 1 below are:
Molten by conventional method and then semi-continuous casting method
A billet with a diameter of 200 mm was manufactured.

【table】

[Table] Each billet obtained was homogenized at 480°C for 6 hours, and then extruded at 400°C into a round bar with a diameter of 35 mm to measure extrudability, and the round bar was used as a test material. The results of measurements of tensile strength, machinability, and tool life after T6 treatment are shown in Table 2 below.

[Table] The test method and evaluation method in this case are as follows. (1) Test method (a) Tensile strength The tensile strength of T6 material was measured by subjecting the test material to solution treatment at 480℃ for 1 hour, water quenching, and artificial aging treatment at 120℃ for 24 hours. did. (b) Extrusion processability When the sample billet was heated to 400°C and extruded, the limit extrusion speed at which hot cracking would not occur was investigated. (c) Cutting method Using a high speed steel bit (SKH4 equivalent),
Dry cutting was performed under the conditions of a cutting speed of 250 m/min, a depth of cut of 1.0 mm, and a feed rate of 0.05 mm/rev, and the breakup of chips was investigated. (d) Tool life The wear width of the flank surface of the cutting tool was measured after approximately 30 minutes of cutting under the above cutting conditions. (2) Evaluation criteria Table 3 shows the evaluation criteria for the above test.

[Table] That is, according to the results in Table 2 above, the alloy of the present invention has strength comparable to that of JIS7075 alloy and JIS7075 alloy, and has a lower tool life in terms of hot workability, cutting workability, and tool wear. It is clear that the alloys are sufficiently superior to the JIS7050 and 7075 alloys and the comparative alloys in all properties. "Effects of the Invention" The product according to the present invention as explained above has sufficient characteristics as an aluminum alloy such as light weight, and has good strength and other mechanical properties.
It is suitably excellent in hot workability such as extrusion, chip disposal, and tool life, and is excellent when applied to various rubber or plastic molds and other machine parts. This invention is industrially highly effective because it can exhibit such advantages.

Claims (1)

[Claims] 1 (a) Zn: 5.0 to 8.0 wt%, Mg: 1.5 to 3.0 wt%,
Contains Cu: 1.4-3.0wt%, (b) Cr: 0.05-0.3wt%, Mn: 0.05-0.5wt%,
Contains two or more of Zr: 0.03 to 0.3 wt%, and (c) Pb: 0.2 to 1.0 wt%, Sn: 0.2 to 1.0 wt%, Bi:
A high-strength aluminum free-cutting alloy characterized by containing any two or more of 0.2 to 1.0 wt%, with the remainder consisting of Al and impurities.