JPS6056037A - Copper-base alloy having excellent corrosion resistance and machineability - Google Patents

Abstract

PURPOSE:To provide a copper-base alloy which has excellent corrosion resistance and machineability and good workability and hot forgeability by incorporating Cu, Pb, Sn and Sb respectively at prescribed ratios into said alloy and consisting of the balance Zn and unavoidable impurities. CONSTITUTION:A copper-base alloy consists, by weight, of 58-63% Cu, 1.0- 2.0% Pb, 0.4-1.5% Sn, 0.01-0.05% Sb and the balance Zn and unavoidable impurities. This copper-base alloy has the characteristic in that the resistance to dezincification corrosion indicated by the dezincification ratio (gamma value) of the equation I and the total corrosion weight loss (DELTAT) of the equation II is remarkably improved as a corrosion resistance characteristic. Such improvement is attained mainly by adding Sb to the alloy in the prescribed range. The alloy exhibits also the excellent machineability by a machining test or punching test, good elongation and high workability. The copper-base alloy is therefore extremely suitable as a material for valve parts and in resembling fields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copper-based alloy with excellent corrosion resistance and machinability.

Conventionally, when copper-based alloys are used as materials for main components of valves, such as valve seats and stems, free-cutting brass rods and forged brass rods with good machinability have often been used. However, these have problems in corrosion resistance and are particularly susceptible to dezincification corrosion in the presence of chloride ions. As a copper-based alloy with good corrosion resistance.

There are naval brass rods, high-strength brass rods, and special aluminum bronze rods, but on the other hand, these have poor machinability. For this reason, copper-based alloys with excellent corrosion resistance and machinability have long been desired as materials of this type.

An object of the present invention is to provide a copper-based alloy that meets this requirement. For this purpose, the present inventors conducted various test studies and found that Cu: 58 to 63% by weight.

Pb i 1.0-2.0% by weight + Sn: 0.4
~1.5% by weight.

It has been found that a copper-based alloy consisting of 0.05% by weight of sb, o, oi, the balance being Zn and unavoidable impurities exhibits excellent properties in both corrosion resistance and machinability.

The copper-based alloy of the present invention is as shown in the examples below.

One of the characteristics of corrosion resistance is that the resistance to dezincification corrosion, as shown by the dezincification ratio (r value) and total corrosion amount (ΔT), has been significantly improved, and this is mainly due to the addition of sb within a specified range. This is due to In addition, the machinability in turning tests and drilling tests is very good, and the elongation is high and the workability is also good. The properties that combine such excellent corrosion resistance, machinability, and processability are due to Cu, Pb, Sn,
It can be obtained by appropriately balancing the amount of Zn and adding an appropriate amount of Sb. The reason why the chemical composition values of each of these alloy components are determined as in the claims is as follows.

Cu: 58% by weight or more of C, u is required to maintain appropriate tensile strength, elongation, and hardness. but.

If it exceeds 63% by weight, the α phase will increase and hot workability will drop sharply, and from an economic standpoint, it is desirable to reduce the amount of Cu used as much as possible.

The Cu content is 58 to 63% by weight.

pb and pb are elements that provide an effect of improving machinability. If it is less than 1.0% by weight, the improvement in machinability is not sufficient, while if it is added in excess of 2.0% by weight, as seen in samples No. 3 and N15 in Table 2 below,
Since hardness increases, elongation decreases, and workability deteriorates, the content is set in the range of 1.0 to 2.0% by weight.

Sn; Sn is an element that improves corrosion resistance and increases tensile strength and hardness. However, if it is less than 0.4% by weight, 1lh3 in Table 3 below. m4 and N115
As seen in the sample, the effect of improving corrosion resistance was not sufficient. On the other hand, if it is added in excess of 1.5% by weight.

It becomes hard and brittle and has poor hot workability. Furthermore, from an economic point of view, it is advantageous to reduce the amount of Sn used as much as possible. For these reasons, the Sn content is set in the range of 0.4 to 1.5% by weight.

sb; As shown in Table 3 below, sb can be added in an appropriate amount without impairing machinability and workability.

It is an element that has a great effect on the corrosion resistance of the alloy of the present invention, particularly on suppressing dezincification corrosion. However, if the amount is less than 0.01% by weight, the effect will not be sufficiently exhibited.

On the other hand, if it is added in an amount exceeding 0.05% by weight, processability will decrease. Therefore, the Sb content is 0.01~
It is important for the purposes of the present invention that it be added in a range of 0.05% by weight.

The characteristics of the alloy of the present invention will be specifically explained below with reference to typical examples.

Alloy No. 1-11kL5 whose chemical composition is shown in Table 1
was prepared, and its mechanical properties, machinability, corrosion resistance, and hot forgeability were investigated. The results are shown in Tables 2 and 3.

Alloy number 1 and N [12 are copper-based alloys of the present invention, 11k
No. 13 is a commercially available copper base metal for cutting to which 3% by weight or more of PB is added, No. 4 is a commercially available copper base metal for forging, and 11kL5 is a commercially available copper base alloy that has both machinability and forgeability.

The machinability of the machinability tests in Table 2 is as follows.

When cutting each sample with a lathe using a cutting tool (SKH) (cutting conditions: 1 rotation speed i 1000 r, p, m, depth of cut: 1 mm + feed: 0.1 mm /rev), calculate the principal component force and the feeding force. It was measured and evaluated using a cutting tool dynamometer. In addition, the perforability was measured when each sample was perforated with an automatic drilling machine using a drill with a diameter of 6 mm (drilling conditions: 1 rotation speed: 14
The thrust and rotational torque of BOr, p, m, drilling depth i 20+++n+, feed; 0.116 mm/rev) were measured and evaluated using a rotary tool dynamometer.

The corrosion resistance test shown in Table 3 followed the dezincification corrosion test method described below, since selective dezincification corrosion is more important than overall corrosion loss when it comes to corrosion of brass. The outline of the method is to immerse a specimen in a 5% hydrochloric acid aqueous solution at 60℃ with the dissolved oxygen level constant through air saturation for 72 hours, and measure the change in weight of the specimen as well as the concentration of copper ions and zinc ions in the solution. Figure 1 shows an outline of the equipment used in the test. Specifically, as shown in Figure 9, 250 ml of 5% hydrochloric acid aqueous solution 3 was placed in a three-necked flask 2 (500 ml capacity) equipped with a reflux device 1, and a specimen 4 was inserted into it.
・Hang this flask by a plastic thread 5 and place it in a constant temperature bath 6 kept at 60℃.
Leave it for 2 hours. 7 is water, 8 is a heater, 9 is a temperature regulator, 10 is a temperature needle, and 11 is a heat insulating material. After this test, the specimen 4 is taken out and the change in weight before and after immersion is measured, and the concentration of Cu2+ ions and Zn2+ ions eluted into the aqueous hydrochloric acid solution are quantified. Then, find the weight ratio of zinc and copper contained in this aqueous hydrochloric acid solution.

Calculate the r value expressed by . When the r value is 1, it means that there was no dezincification corrosion, and as the r value becomes larger than 1, it means that the dezincification corrosion is significant. The dezincing ratio (r) in Table 3 indicates this r value.

In addition, the amount of copper corresponding to the amount of Zn2+ ions eluted into the liquid is the sum of the amount of Cu2+ ions eluted into the liquid and the amount of Cu present in the dezincing layer on the brass surface, so it will vary depending on the leaching test described above. What is the amount of brass per unit surface area of light?

+ (Zn”))X (V/S) It is expressed as

However, the symbols in formula 2 are as follows.

ΔT: Total corrosion amount (mg/cd) (Zn”); Zn2+ ion concentration in the liquid (II1g/
j! ) ■: Test liquid volume (J) S: Specimen surface area (cd) Total corrosion 48T in Table 3 is a value calculated using this formula, and the larger this ΔT value, the more severe the dezincification corrosion. It is shown that.

Further, the depth of the dezincing layer in Table 3 is determined by observing the cross section of the specimen after the test with an optical microscope and determining the distance of the dezincing corrosion layer from the surface.

In addition to the above corrosion resistance test, hot forgeability was also examined, which was determined by the constant load upsetting rate at 700°C. This constant load upsetting rate is the maximum upsetting rate obtained by free forging using a 150) press, and its magnitude indicates the hot deformation resistance. The results are shown in Table 3.

(Margins below this page) From the results in Table 2, 9 invention alloy floors 1 and 2 are Pb
A commercially available copper-based alloy for cutting 11h with improved machinability and forgeability.
It can be seen that compared to No. 5, the feeding force on the lathe is low and the turning performance is good. Regarding the perforation properties, Na3 and! It has properties equivalent to or better than the copper base metal of lh5.

Furthermore, the alloy of N11 and N112 of the present invention is N11
3~! The hardness is lower than that of No. 5 alloy.

On the other hand, from the results in Table 3, it is clear that copper-based alloy Na without sb addition
Compared to No. 3 to No. 5, the copper-based alloys Nal and No. 2 of the present invention have lower dezincification ratio (r) and total corrosion amount (ΔT), and the dezincification layer depth is also lower, and the dezincification corrosion resistance is lower. It can be seen that this has been significantly improved.

The copper base metal of the present invention with sb added has forgeability equal to or better than commercially available copper base metal for forging 11h3.

As described above, the copper-based alloy of the present invention has both good machinability and corrosion resistance, and also has good workability and hot forgeability, so it is suitable for use in valve parts and similar fields. It is a very suitable material.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing test equipment for a dezincification corrosion test. 3...5% hydrochloric acid aqueous solution, 4...test piece, 6... constant temperature bath. Applicant Dowa Mining Co., Ltd. Nihon Plus Kogyo Co., Ltd.

Claims (1)

[Claims] Cu: 5B to 63% by weight, Pb: 1.0 to 2
．． 0% by weight, Sn; 0.4-1.5% by weight, Sb
A copper-based alloy with excellent corrosion resistance and machinability, consisting of 0.01 to 0.05% by weight, the balance being Zn and unavoidable impurities.