JPH049440A - Copper alloy for machining - Google Patents

Abstract

PURPOSE:To provide a copper alloy with excellent hot workability while its machinability is maintained by specifying the content of Pb in a Cu-Zn alloy and adding small amounts of Mn, Zr, Nb, V or the like thereto. CONSTITUTION:The compsn. of a copper alloy for machining is formed of, by weight, 57 to 62% Cu, 0.5 to 3.0% Pb, 0.1 to 1.0% of one or more kinds among Mn, Zr, Nb and V and the balance Zn with inevitable impurities. In the case the content of Pb is regulated to <0.5%, the machinability characteristic of free cutting brass is made insufficient, and in the case of >3%, Pb flocculates, so that defects such as cracking are made easy to form and its hot workability deteriorates. Mn, Zr, Nb and V suppress the growth of crystalline grains in the stage of preheating before hot working as well as suppress the grain boundary precipitation of impurities and have an effect of reducing the sensitivity of brittle fracture in the stage of hot working. In this way, the copper alloy for machining having the machinability equal to that of the conventional Pb-contg. free cutting brass can be obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a copper alloy for cutting.

[Prior art] Copper alloys for cutting can be cut into containers and have a smooth and clean finished surface, and have many advantages such as good corrosion resistance and ease of surface treatment. However, it is inexpensive and its mechanical strength is comparable to that of general brass. For this reason, it is widely used in fields such as parts that require precision processing, screw materials such as bolts and nuts, and membrane accessories.

Examples of the copper alloy for cutting include free-cutting brass, forging brass, naval brass, tellurium copper, and free-cutting nickel silver. Free-cutting brass made of alloy has a free-cutting index of 100, which can be used as a standard for the machinability of other free-cutting brasses.
It is the most typical cutting copper alloy with excellent machinability. The Pb-containing free-cutting brass has Pb dispersed in granular form, and the Pb particularly exhibits the effect of improving free-cutting properties. Such free-cutting brass is melted and forged, then hot worked, and then cold worked and annealed repeatedly.

[Problems to be Solved by the Invention] However, the above-mentioned PB-containing free-cutting brass is more difficult to process than ordinary brass for the following reasons. That is, the free-cutting brass has a crystalline structure (
It has a two-phase structure of α + β) phase, which has contradictory properties: the α phase has excellent cold workability but poor hot workability, and the β phase has excellent hot workability but poor cold workability. has. As a result, hot working and cold working become difficult due to the difference in properties. Particularly in hot working, the presence of Pb also makes processing difficult, resulting in problems such as defects such as cracks and surface peeling during processing. Further, even if defects due to hot working do not occur on the surface, they occur inside, so there is a problem that defects may appear on the surface during subsequent cold working and heat treatment.

The present invention was made to solve the conventional problems, and is a copper alloy for cutting that has excellent hot workability while maintaining the advantages such as free machinability of conventional Pb-containing free-cutting brass. This is what we are trying to provide.

[Means and effects for solving the problem] The present invention provides Cu
57-62% by weight, 0.5-3.0% by weight of pb, M
One or more of n, Zr, Nb, and (2) is added to 0.
This is a copper alloy for cutting, characterized in that it contains Zn in an amount of 1 to 1.0% by weight, with the remainder consisting of Zn and unavoidable impurities.

The reason for limiting the content of Cu is that the content is 57
If the weight is less than 90, the volume fraction of the β phase increases and subsequent cold working becomes difficult, while if the content exceeds 62 balls, the volume fraction of the α phase increases and hot workability becomes difficult. inhibit. In addition, from the viewpoint of cost, the upper limit of the Cu content is set to 62
It is suitable to express it in weight %.

The reason for limiting the content of Pb is that the content is 0.
If the content is less than 5% by weight, the machinability as a free-cutting brass will be insufficient, while if the content exceeds 3.0% by weight, PB will aggregate during hot working and defects such as cracks will easily occur. Hot workability decreases.

The Mn, Zr, Nb, and V each have the effect of suppressing the growth of crystal grains during preheating before hot working, as well as suppressing the grain boundary precipitation of impurities, and reducing the susceptibility to brittle cracking during hot working. . This effect is the same even when two or more of the above metals are contained. The reason for limiting the content of such metals is that the content1ii1 (in the case of two or more types, the total amount)
If it is less than 0.1% by weight, the above effect will not be fully exhibited, and on the other hand, if the content (total amount in case of two or more types) is 1.
If it exceeds 0% by weight, the mechanical strength becomes extremely high, making subsequent cold working difficult.

As mentioned above, Cu; Pb; Mn, Zr, Nb
.

By containing a specific amount of one or more of V and V, with the remainder being Zn, hot workability is improved, and it has free-cutting properties equivalent to conventional Pb-containing free-cutting brass. A copper alloy for cutting can be obtained.

[Example] Examples of the present invention will be described in detail below.

Examples 1 to 4 and Comparative Examples 1 to 3 First, an alloy (free-cutting brass) having the composition shown in Table 1 below was melted and forged in a high-frequency melting furnace to a length of 20 ha and a width of 150 mm.
, an ingot with a thickness of 25 mg+ was obtained. After subjecting this ingot to face side processing, it was heated to 850° C. and hot rolled to a thickness of 8 cm to produce seven types of rolled materials. Next, each rolled material is subjected to external grinding to remove defects such as cracks and surface peeling, and cold rolling and annealing are repeated to obtain a final plate thickness of 0.5mm.
The board was manufactured.

Table 1 In order to examine the hot workability in the manufacturing process described above, the state of defects was visually confirmed for each of the rolled materials, and the amount of defects and the maximum length of defects were measured.

The results are shown in Table 2 below. In addition, in order to investigate the machinability of each plate material obtained, a cutting tool (SKH) was used for each plate material.
) was used for lathe cutting, and the principal component force value and feed component force value were measured.

The results are also listed in Table 2. The cutting conditions are: cutting speed 100+a/min, depth of cut I ram s
The feed rate was 0.01 m1/rev.

can be provided.

Claims (1)

[Claims] 57-62% by weight of Cu, 0.5-3.0% by weight of Pb
, Mn, Zr, Nb) and V in an amount of 0.1 to 1.0% by weight, with the balance being Zn and inevitable impurities.