KR20150044069A - Leadless free cutting brass alloy - Google Patents

Abstract

The present invention provides a leadless free cutting brass alloy that provides an enhanced machinability by using Bismuth (Bi) and avoiding the addition of lead (Pb), an enhanced corrosion resistance with the addition of nickel (Ni) or iron (Fe), and an enhanced machinability and intensity with the addition of one of 1-2.5% of Sn, 8-12% of Zn, 1-2.5% of Si, 0.5-1.0% of Bi, equal to or less than 0.02% of P, 0.5-10% of Ni, 0.05-0.3% of Fe (by weight), of Cu, and unavoidable impurities.

Description

[0001] LEAD FREE FREE CUTTING BRASS ALLOY [0002]

The present invention relates to a lead-free bronze alloy, and more particularly, to a lead-free bronze alloy which comprises silicon (Si) and zinc (Zn), which are easy to obtain by replacing the content of tin (Ni) or iron (Fe) together with an alloy (Bi) as an alloying element to eliminate the content of lead (Pb) and improve cutting performance.

Bronze is the oldest copper alloy among copper alloys and is mainly copper (Cu) and tin (Sn) alloys. Bronze is basically an alloy of copper (Cu) and tin (Sn), although aluminum (Al) or manganese is contained as a substitute for tin (Sn) This bronze is called tin (Sn) bronze.

There are various types of tin (Sn) bronze, such as money, bronze for plaque, bronze for Jingcheng, craft bronze, mirror bronze, mechanical bronze, special bronze, etc. Because of their high mechanical properties, excellent corrosion resistance, It is widely used as various industrial materials.

In the case of gunmetal for machinery, 90% copper and 10% tin alloy are used for gun cannons, valves, gears, flanges, pistons, and spindles.

Phosphor bronze is excellent in corrosion resistance and abrasion resistance, and has high strength and bending property. Also, since the electric conductivity is high, it is easy to be bonded even with lead (Pb) solder, and it has a strong resistance to chemical corrosion as well as good plating. Examples used are bushings, gears, bolts, nuts, automotive parts and so on.

Leaded Tin Bronze is suitable for high pressure bearing, high bearing, good intimacy and good scoring ability.

Special bronzes include aluminum (Al) bronze, manganese bronze, silicon bronze, and nickel (Ni) bronze.

These bronze are mainly composed of tin (Sn), copper (Cu), zinc (Zn), etc., and other small amounts of lead (Pb) and residual components. Tin (Sn) Bronze is added as a main component of copper (Cu) and tin (Sn) added is added to suppress elution of lead (Pb) by improving main constitution and corrosion resistance. The lead (Pb) used here is mainly used for improving the machinability of bronze. However, the lead (Pb) added for machinability is already well known as an environmental problem or a health problem, and the use of lead (Pb) is strictly restricted. For example, when a product such as a water pipe is produced by using bronze containing lead (Pb), lead (Pb) may be eluted in the water, and the damage of the body may be considered .

Therefore, development of bronze which does not use lead (Pb) is demanded. However, when the lead (Pb) is not used in forming the bronze, the machinability is deteriorated because the cutting ability is lowered. Research is underway to increase the cutting workability.

According to Korean Patent Registration No. 10-0864909, a free-cutting copper alloy containing calcium (Ca) is provided. In constituting the bronze alloy, copper (Cu), zinc (Zn) and calcium (Ca) , But the copper is 59-79 wt%, the calcium (Ca) is 0.1-1.5 wt%, and the balance is zinc (Zn).

On the other hand, Korean Patent Registration No. 10-0864909 is characterized in that cutting workability is improved by adding 0.7 to 2.50% by weight of bismuth (Bi) and 0.30 to 1.0% by weight of selenium (Se) together.

Korean Patent No. 10-0864909 Korean Patent No. 10-0864909

An object of the present invention is to dramatically reduce manufacturing costs by using silicon (Si) and zinc (Zn) which are readily available by replacing expensive tin (Sn), which is a main alloy element, in a conventional lead-free bronze alloy.

In addition, by adding bismuth (Bi) while excluding the addition of lead (Pb), it is possible to improve cutting resistance and strength by adding nickel (Ni) or iron (Fe) In order to simplify and improve convenience.

The present invention relates to a nickel-based alloy comprising 1 to 2.5% of Sn, 8 to 12% of Zn, 1 to 2.5% of Si, 0.5 to 1.0% of Bi, 0.02 to less of P, 0.5 to 1.0% of Ni, 0.05 to 0.3% of Fe, and the remainder of Cu and inevitable impurities.

Here, when Fe is included, it is preferable to further include Zr of 0.05% or less for the refinement treatment.

In addition, when Fe is included, it is preferable to further contain 1 to 1.5% of Si and 1.0% or less of Mn to improve toughness.

The use of lead (Pb) in the present invention is excluded. As described above, the cutting workability of the bronze alloy can be remarkably improved by adding lead (Pb), but the use of lead (Pb) is limited due to toxicity, and in particular, Is limited. Lead (Pb) is the most heavy and flexible metal among industrial metals. It is rich in electric current and easy to roll, so it can be made into a plate or pipe shape, but it is not flexible enough to be drawn. Due to such flexibility, when the lead (Pb) is mixed, the cutting workability is excellent. On the other hand, when the lead (Pb) is not used, the cutting workability is bad. In the present invention, bismuth (Bi) is added instead of lead (Pb) in order to improve cutting workability without adding lead (Pb) as an alloying element because of the harmfulness of lead (Pb). In addition, iron (Fe) is used for the purpose of adding Ni (Ni) to improve the corrosion resistance or improving the machinability and improving the strength.

In the present invention, bismuth (Bi) is added in an amount of 0.5 to 1.0% by weight. Addition of bismuth (Bi) exceeding the above range may cause problems in durability when used for a long time. Do.

The present invention has the effect of drastically reducing the manufacturing cost by using zinc (Zn) which is readily available by replacing expensive tin (Sn) which is a main alloy element in the conventional lead-free bronze alloy according to the present invention.

In addition, despite the fact that the addition of lead (Pb) is eliminated, it is possible to improve the production process of the bronze casting easily and conveniently because of excellent cutting workability, and there is an advantage that the generation of industrial waste is reduced.

Accordingly, there is an advantage that a good product such as various water valves, water meters, faucets, and various fittings using the lead-free bronze alloy according to the present invention can be supplied to the domestic and overseas markets at a lower price.

Figs. 1a to 1c are graphs showing the results of a comparison between the bronze alloy (specimen 1 - 0 wt.% Ni), the bronze alloy (specimen 2 - 1.0 wt.% Ni) This graph shows the change of cutting force.
Figs. 2A to 2C are graphs showing the results of measurement of surface roughness of a machined surface of a bronze alloy (specimen 1 - 0 wt.% Ni), a bronze alloy (specimen 2 - 1.0 wt.% Ni) Graph.
3A to 3C are graphs showing the shape of a cutting chip of a bronze alloy (specimen 1 - 0 wt.% Ni), a bronze alloy according to the present invention (specimen 2 - 1.0 wt.% Ni) It is a photograph.
4 is a graph comparing the tensile properties of a bronze alloy (specimen 1 - 0 wt.% Ni) according to a comparative example, bronze alloys (specimen 2 - 1.0 wt.% Ni) and commercial CAC 902 according to the present invention.
5 is a graph comparing the hardness characteristics of the bronze alloy (specimen 1 - 0 wt.% Ni) according to the comparative example, bronze alloys (specimen 2 - 1.0 wt.% Ni) and commercial grade CAC 902 according to the present invention.
6A to 6D are graphs showing changes in rotational force during drilling of a specimen 3 (0.1 wt.% Fe) and a specimen 4 (0.2 wt.% Fe) which are bronze alloys according to the present invention and a commercial material CAC902 , 1000 rpm (Fig. 6A), 3000 rpm (Fig. 6B), 5000 rpm (Fig. 6C), and 7000 rpm (Fig.
7A and 7B are graphs showing changes in the cutting force of the specimen 3 (0.1 wt.% Fe) and the specimen 4 (0.2 wt.% Fe), which are the bronze alloys according to the present invention, when measuring the cutting resistance.
8A to 8C are graphs of the surface roughness of a machined surface of a specimen 3 (0.1 wt.% Fe), a specimen 4 (0.2 wt.% Fe) and a commercial material CAC902, which are bronze alloys according to the present invention.
9 is a graph comparing the hardness characteristics of the test piece 3 (0.1 wt.% Fe) and the test piece 4 (0.2 wt.% Fe), which are bronze alloys according to the present invention, and the comparative hardness CAC902.
10 is a graph comparing the tensile properties of the test piece 3 (0.1 wt.% Fe) and the test piece 4 (0.2 wt.% Fe), which are the bronze alloys according to the present invention, and the commercial CAC902.
Figs. 11A and 11B are graphs showing changes in the cutting force of the specimen 5 (1 wt.% Mn) and the conventional material CAC902 alloy, which are bronze alloys according to the present invention, when measuring the cutting resistance.
12A and 12B are graphs of surface roughness measurement of a machined surface of a specimen 5 (1 wt.% Mn) and a commercially available CAC902 alloy, which are bronze alloys according to the present invention, respectively.
13 is a graph showing the tensile properties of a specimen 5 (1 wt.% Mn) and a commercially available CAC 902 alloy, which are bronze alloys according to the present invention, in comparison.
14 is a graph comparing hardness characteristics of a specimen 5 (1 wt.% Mn) and a comparative CAC 902 alloy, which are bronze alloys according to the present invention.

Hereinafter, the present invention will be described on the basis of examples. The following examples illustrate preferred embodiments of the present invention, which should not be construed as limiting the scope of the present invention, and the scope of the present invention will be defined by the following claims.

Pure Copper, Pure Zinc, Pure Tin and parent alloys for alloying element addition were dissolved in a high frequency melting furnace. Basically, experiments were carried out to confirm improvement of machinability with addition of bismuth (Bi) The results of the analysis of the components of the specimen provided in the experiment are shown.

Psalter Cu Sn Zn Si Ni Fe Bi Zr Mn P Pb One Rem 2.08 10.85 1.85 - - 0.98 - - 0.0129 <0.01 2 Rem 2.1 10.75 1.99 0.97 - 1.05 - - 0.0128 <0.01 3 Rem 2.01 10.61 1.38 - 0.14 1.03 0.0252 - 0.0104 <0.01 4 Rem 1.96 10.70 1.42 - 0.25 1.1 0.0270 - 0.0116 <0.01 5 Rem 1.89 10.3 0.92 - 0.24 1.04 - 0.946 0.0106 <0.01

% Ni) and specimen 2 (1 wt.% Ni) were compared with those of the conventional alloy (Bi-Ni) to confirm the addition of Ni to improve the corrosion resistance of the Sn- Ni-based bronze alloy).

In order to improve the machinability of specimen 3 (0.1 wt.% Fe) and specimen 4 (0.2 wt.% Fe), the hardness of the workpiece was reduced to CAC 902 level. (Bi-Fe-based bronze alloy) for confirming the presence of Zr.

In order to confirm that the test for imparting toughness to the material was carried out by adding Mn of about 1.0% while reducing the addition amount of Si somewhat, the test piece 5 (1.0 wt.% Mn) Mn-based bronze alloy), and the fineness treatment by Zr does not proceed.

The mechanical properties of all of the examples were as follows: CAC 902 alloy (4-6 wt.% Sn, 1-2 wt.% Bi, 0.05-0.5 wt.% Sb, 5-8 wt.% Zn, Cu) was used as a comparative material.

The cutting resistance according to Ni addition is shown in Table 2 above. Experiments were conducted using a tool dynamometer. Cutting resistance was compared with the cutting force of the cutting tool in the transport direction and the cutting force in the rotating direction.

It was confirmed that the addition of 1 wt.% Of Ni increased the cutting force in both the transport direction and the radial direction, and the cutting force increased by more than 10 N before the addition of Ni. It is believed that the formation of Ni rich phase, which is observed in the microstructure, rather adversely affects the cutting characteristics. However, in the cutting and milling of specimens using the band saw and the general machining on the lathe, the difference in the machinability of the three workpieces measured by the tool dynamometer was insignificant so that the operator could not feel the difference in cutting performance.

FIGS. 1A to 1C are graphs showing a cutting force acting on a workpiece in measuring a cutting resistance using a tool dynamometer. As shown in the graph of FIG. 1C, it can be seen that the height of the waveform of the radial cutting force is large and the irregularity is large. It is expected to also affect the surface roughness measurement results of Table 3 (obtained from the cutting surface roughness measurement graph shown in Figs. 2A to 2C). The surface roughness of 1.0 wt% Ni added specimen (specimen 2) was the best, and the surface roughness of CAC902, which had the lowest cutting resistance, was not as good as that of other workpieces because both Ra (arithmetic average roughness) and Rz Characteristics.

FIGS. 3A to 3C are photographs of cutting chips that occurred during the measurement of the cutting resistance. The cutting depths of the cutting chips were 2 mm and the ribbons were dried. In each of the three kinds of workpieces, It is impossible to evaluate the cutting force.

 Therefore, it is considered that CAC902, which is an important evaluation item of cutting characteristics, which is poor in surface roughness, has a better cutting characteristic than other workpieces even though it shows low cutting resistance.

4 and 5 are graphs showing the tensile and hardness characteristics, respectively. However, a decrease in elongation of more than 50% was observed with an increase in strength of 29 N / mm ^{2 with} addition of 1.0 wt% of Ni, and an elongation of 14% There was no problem. In the hardness characteristics, hardness increase of about 25% was observed with the addition of Ni. The addition of Ni increased the cutting resistance of the workpiece, but the mechanical properties were improved except for the elongation, and it was considered that it could be more useful than the CAC902 in the parts requiring mechanical strength.

In addition, the Bi-Ni based bronze alloy showed no corrosion of dezinc, regardless of whether or not 1.0 wt% of Ni was added, thus confirming excellent corrosion resistance.

The cutting resistance of the Ø3.5 carbide drill was measured under the condition of measuring the cutting resistance according to the number of revolutions of the carbide drill and the cutting resistance measurement condition using the tool dynamometer. The results were compared with each other.

Table 4 is a table showing the average value of the torque acting on the workpiece according to the number of revolutions of the drill and the maximum value of the rotational force generated during drilling, and FIGS. 6A to 6D are graphs showing changes in the rotational force during drilling .

In Table 4, the average and maximum values of the rotational force applied to the workpieces showed similar values for all three workpieces under the entire rotation range from 1000 rpm to 7000 rpm. By adding 0.1 wt.% Fe and 0.2 wt.% Fe, And it was observed that they showed similar values of cutting resistance. 6A to 6D, the rotational force acting on the drill was lowered as the number of revolutions of the drill was increased for all the three workpieces, and it was observed that stable drilling was performed with almost constant rotational force under all drill rotation conditions.

Table 5 shows the measurement results of the cutting force measured by the tool dynamometer. All of the three workpieces exhibited similar cutting force measurements as those of drilling. The difference was small, but the addition of 0.1 wt.% Fe showed less cutting force measurements than CAC902. 7A and 7B showing the cutting force acting on the workpiece in measuring the cutting resistance using the tool dynamometer, it was observed that the forces acting in the transport direction and the rotation direction were stably loaded.

It was also observed that the surface roughness of the machined surface is superior to that of CAC902 in the surface roughness measurement results shown in Table 6 and Figs. 8A to 8C.

9 and 10 are graphs showing hardness and tensile properties according to the amount of Fe added. As the Si content decreased from 2.0 wt.% To 1.5 wt.%, The hardness decreased and the Fe content increased from 0.1 wt.% To 0.2 wt.%. As the content of Si decreased, tensile strength was not decreased. As Fe was added, the strength increased and the elongation decreased. As Fe was added, the elongation was lower than CAC 902, but hardness and tensile strength were better.

The corrosion characteristics of 0.1 wt.% Fe or 0.2 wt.% Fe are considered to have no influence on the corrosion resistance due to the small addition amount of Fe, No dezinc corrosion occurred and excellent corrosion resistance was confirmed.

Table 7 and Figs. 11A and 11B show the measurement results of the cutting force of the workpiece to which Mn is added by using a tool dynamometer. In the previous Cu-2Sn-10Zn-1.5Si-1Bi-0.2Fe bronze alloy (specimen 4), the Si content was reduced to 1.0 wt.% And Mn was added in 1.0 wt.%, But the cutting force was about 65 N I could confirm that there was no. In the graph of the cutting force change, the cutting characteristics were more stable than that of CAC902, and it was confirmed that surface roughness values of the cutting surfaces of Table 8 and FIGS. 12A and 12B were better than those of CAC902.

13 and 14 are graphs showing tensile and hardness characteristics. The addition of 1.0wt.% Mn showed 74HB hardness, which was not much different from CAC902, which was about 72HB. However, it was observed that the elongation at around 20% was greatly increased to more than 60%. Therefore, it is considered that the present invention can be suitably applied to a portion requiring cutting force and high toughness.

Claims (3)

By weight,
1 - 2.5% Sn,
8 - 12% Zn,
1 - 2.5% of Si,
0.5 - 1.0% Bi,
0.02% or less of P,
0.5 to 1.0% of Ni, and 0.05 to 0.3% of Fe,
Cu and a balance consisting of an inevitable impurity.
The method according to claim 1,
And further contains Zr of not more than 0.05% when Fe is included.
The method according to claim 1,
And further contains 1 to 1.5% of Si and 1.0% or less of Mn when Fe is included.

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