JPH03281749A - Free cutting copper alloy - Google Patents

Abstract

PURPOSE:To improve the workability, particularly piercing properties of a free cutting copper alloy and to improve its working accuracy, particularly in the prolongation of the service life of a tool by specifying the compsn. of a Cu-Zn-Pb series alloy and the amt. of a beta phase in the alloy. CONSTITUTION:This free cutting copper alloy contains, by weight, 59 to 64% Cu, 0.5 to 4% Pb and the balance Zn, and the amt. of a beta phase in the alloy is regulated to 1 to 20vol.%. In this alloy, Pb is present in alpha brass as a dispersed phase, has a lubricating effect and reduces its cutting force; in the case of <0.5%, the sufficient lubricating effect can not be obtd., and in the case of >4%, its hot working is made hard. As for Cu, in the case of >64f%, the betaphase does not appear, and in the case of <59%, the amt. of the beta phase exceeds 20% and its cold workability is reduced. As for the beta phase, in the case of <1%, the increase of its cutting force particularly at the time of deep hole drilling is remarkable, which becomes the cause of the reduction of the service life of a tool; and its dimensional accuracy, and in the case of >20%, its cutting force increases and the face to be cut is roughened to reduce the working accuracy.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a free-cutting copper alloy used as a material for machined parts such as machine parts and valves.

[Conventional technology]

Cu-Z rr containing 0.6-3.7wt 1% Pb
Gold alloy (free-cutting brass) is a copper alloy whose cutting resistance has been lowered by the addition of Pb, and has been widely used as a cutting material for machine parts because of its excellent rigidity. However, in recent years, demands on machining technology have become stricter, such as miniaturization of machine parts and improvement of machining accuracy, and due to the trade-offs of automatic machine tools, extending the life of tools has become a particularly important issue. Cutting methods include planing, milling,
There are things like drilling, but drilling with a drill causes more wear and tear on the tool than other processing methods. In recent years, drilling conditions have become more severe, such as small hole drilling and deep hole drilling, and when conventional free-cutting brass is used, the drill is prone to wear and tear, and sufficient processing precision is not enough. There were some problems, such as not being able to obtain the desired results. Therefore, we not only improve the tools, but also the rigid materials.
Even higher rigidity than before is now required.

[Problem to be solved by the invention]

The present invention solves the drawbacks of such conventional materials and makes Cu-Z
The objective is to improve the rigidity of n-Pb alloys to extend the life of machining tools such as drills and improve machining accuracy.

[Means to solve the problem]

The present inventors have developed CuZn-Pb to solve the above problems.
As a result of various studies on the system alloy, the amount of β phase in the alloy was reduced to 1.
It has been found that by setting the amount to ~20% by volume, the rigidity during machining, especially the perforation performance, is significantly improved, and the machining accuracy is improved, as well as the tool life is greatly improved. We have reached the first point. That is, the first aspect of the present invention contains 59 to 64% by weight of Cu, 0.5 to 4% by weight of Pb, etc., and the remainder consists essentially of Zn, and the β phase in the alloy is 1% by volume. It is a free-cutting copper alloy characterized in that the content of impurities SL and P in the copper alloy is o and oo, respectively.
'IIJI by setting it to less than i% by weight. It was discovered that the life span could be further improved, leading to the second invention. That is, the second aspect of the present invention contains 59 to 64% by weight of Cu and 0.5 to 4% by weight of Pb, and
and a free-cutting copper alloy having a Si content of 0001% by weight or less, the remainder substantially consisting of Zn, and the amount of β phase in the alloy being 1 to 20% by volume. be.

[Effect]

Pb does not form a solid solution in α-brass, but exists as a dispersed phase. This Pb phase has a lubricating effect and reduces cutting resistance, so it is contained in an amount of 0.15 to 4% by weight. Here, if the Pb-containing lid is less than 0.5% by weight, a sufficient lubricating effect cannot be obtained, while if it is contained in more than 4% by weight, hot working becomes difficult, so the Pb content is 0.5-4%. Weight%. Regarding Cu, if it exceeds 641Ji%, the β phase will not appear regardless of the process, so 64111
Does it need to be less than %? Furthermore, if CIJ is less than 59% by weight, the amount of β phase exceeds 20% by volume, which increases cutting resistance and reduces cold workability.
Is it necessary to make it 9% or more? In the above C1 component range, depending on the annealing conditions, β
The amount and distribution of phases changes. The reason why the β phase content is set to 1 to 20 volume % is that a β phase content of less than 1 volume % will significantly increase the cutting force, especially in deep hole machining, and cause a reduction in tool life and dimensional accuracy. This is to become. On the other hand, if the amount of β phase exceeds 20% by volume, the cutting resistance increases and the cut surface becomes rough, resulting in a decrease in machining accuracy. Therefore, the amount of β phase needs to be 1 to 20% by volume. Furthermore, the reason why the content of Si and P is set at 0.00101% by weight is that when these elements are contained at 0.001% by weight, they combine with impurities such as Fe that are normally contained in copper alloys. This is because a hard dispersed phase is formed7, which causes abrasion and wear of the tool and significantly shortens the tool life. Ii of the alloy of the present invention! During construction, normal atmospheric dissolution,
The ingot obtained by processing by atmospheric melting or the like is hot rolled or hot extruded and then pressed into a desired shape by repeating cold sweat rolling, cold wire drawing, and annealing. Note that the lid and distribution of the β phase in the alloy of the present invention can be changed during the process depending on the annealing conditions of the material, and the optimum conditions are determined by the cutting conditions applied to the material.

【Example】

Copper scrap (1st IFI) and free-cutting brass scrap were mixed to have a predetermined composition, and five types of alloys were melted and cast in the atmosphere using a high-frequency melting furnace. Four types of alloys were also produced using commercially available electrolytic copper, electrolytic zinc, and granular lead as raw materials. Table 1 shows the chemical analysis values for each alloy. Each ingot was hot extruded at 750°C to form a bar with a diameter of 5.0rnrn. At that time, ingot No. 9 containing Pb in an amount higher than the component range of the present invention developed hot cracking and could not be further processed. N that was within the composition range of the present invention and did not cause hot cracking
011~8 was made into a diameter of 2.5 mm by repeating cold wire drawing and annealing at 450°C for 1 hour.
Annealing was performed for 1 hour at each temperature of 50 to 700°C to vary the amount of β phase. Thereafter, cold wire drawing was performed again to obtain a wire rod with a diameter of 2.0 mm. These wire rods were classified according to the β dosage range of the present invention, and 61 alloys of the present invention and 7 comparative alloys were subjected to a stiffness test.The amount of β phase in each alloy was determined by X-ray diffraction method. β
It was determined from the ratio of the diffraction peak intensities of each phase. In addition, Xls! In order to support the identification of the amount of β phase using the measured value by diffraction method, for some samples with a coarse β phase structure, the amount of β phase was also determined from the area ratio of each phase in optical microscope FI observation. However, the values for both people were almost the same. Table 2 shows the annealing conditions and β phase content measurement results for the alloys of the present invention and comparative alloys. (Margins below this page) The rigidity of each alloy was evaluated by conducting the following tests. First, use a high-speed steel twist drill with a diameter of 1 mm to a depth of 7 mm.
The hole diameter of mm was drilled 1000 times, the hole diameter was measured, and those within 1 mm ± 10 μm were considered good, and the others were judged defective. The failure rate for each alloy is shown in Table 2, and as a result of continuous hole-cutting CT processing 1000 times,
Table 2 also shows the tool life expressed in terms of the number of holes drilled until the tool breaks or the defect rate decreases to 1%. The alloy of the present invention does not produce any defects even after being processed up to 1,000 times, and the tool life has exceeded 10,000 times in all cases. On the other hand, the comparative alloys had many defects, the tool life was less than ioooo times, and it was found that the rigidity was poor.

【Effect of the invention】

As mentioned above, the alloy of the present invention is a copper alloy with excellent rigidity, and by using it as a material for cutting, it is possible to improve the machining accuracy of machine parts and the like, as well as the tool life.

Claims (2)

[Claims] (1) Contains 59 to 64% by weight of Cu and 0.5 to 4% by weight of Pb, with the remainder essentially consisting of Zn, and the amount of β phase in the alloy is 1 to 20% by volume. A free-cutting copper alloy characterized by: (2) Contains 59 to 64% by weight of Cu and 0.5 to 4% by weight of Pb, and has a P and Si content of 0.5% to 0.5% by weight, respectively.
A free-cutting copper alloy characterized in that the amount of β phase in the alloy is 1 to 20% by volume, with the balance being substantially Zn.