JP2000119775A - Lead-free free cutting copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the machinability of a copper alloy without the incorporation of Pb by allowing it to have a specified compsn. contg. Cu, Si, and the balance Zn. SOLUTION: This alloy contains, by weight, 69 to 79% Cu, 2.0 to 4.0% Si and the balance Zn. In the case the quantity of Si to be added is <2.0%, the formation of γ phases sufficient for securing industrially satisfiable machinability can not be executed. On the other hand, in the case the quantity of Si to be added exceeds 4.0%, further machinability improving effect is not shown. By the addition of Si, fluidity at the time of casting, strength, wear resistance, stress corrosion cracking resistance and high temp. oxidation resistance are improved as well as machinability. The alloy is preferably incorporated with at least one among 0.02 to 0.4% Bi 0.02 to 0.4% Te and 0.02 to 0.4% Se as well. In this way, even in the case a complicated shape is subjected to machining at a high speed, machinability of a high degree can be exhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free-cutting copper alloy containing no lead component.

[0002]

2. Description of the Related Art As a copper alloy having excellent machinability, generally,
Bronze alloys such as JIS H5111 BC6 and JIS
Brass alloys such as H3250-C3604 and C3771 are known. These have improved machinability by containing about 1.0 to 6.0% by weight of lead, and have ensured industrially satisfactory machinability.

Since lead-containing copper alloys are excellent in machinability as described above, they have been used in various products (for example, faucets for water supply pipes, plumbing fittings, plumbing fittings, valves, etc.). It is useful as a material. However, because lead is a harmful substance that has a negative effect on human health and the environment,
In recent years, their applications tend to be severely limited. For example, metal vapor generated during high-temperature work such as melting and casting of alloys may contain lead components, or lead components may be eluted from faucet fittings or valves due to contact with drinking water or the like. Yes, there are problems with human health and environmental health.

[0004]

Therefore, in recent years, developed countries such as the United States have tended to greatly limit the lead content in copper alloys, and even in Japan, the lead content has been reduced as much as possible. There is a strong demand for the development of machinable copper alloys.

The present invention has been made in response to such global trends and demands, and provides a lead-free free-cutting copper alloy containing no lead and having industrially satisfactory machinability. It is intended for.

[0006]

The present invention proposes the following lead-free free-cutting copper alloy to achieve the above object.

That is, in the first invention, the lead-free free-cutting copper alloy having excellent machinability contains 69 to 79% by weight of copper and 2.0 to 4.0% by weight of silicon, and the balance is as follows. Copper alloy having an alloy composition of zinc (hereinafter referred to as “first invention alloy”
).

[0008] Lead does not form a solid solution in the matrix, but is dispersed in a granular form to improve machinability. On the other hand, silicon contains a γ phase (or κ
By improving the phase, the machinability is improved. As described above, the two have completely different functions in alloy characteristics, but they are common in improving machinability. Focusing on this point, in the first invention alloy,
By adding silicon instead of lead, it is intended to ensure industrially satisfactory machinability. That is, the first invention alloy has improved machinability by forming a γ phase by adding silicon.

[0009] When the amount of silicon is less than 2.0% by weight, γ sufficient to ensure industrially satisfactory machinability is required.
No phase formation takes place. Further, the machinability is improved as the amount of silicon added increases, but even if added over 4.0% by weight, there is no machinability improvement effect commensurate with the added amount. By the way, since silicon has a high melting point and a low specific gravity and is easily oxidized, when silicon alone is charged into a furnace during melting of the alloy, the silicon floats on the molten metal surface and is oxidized at the time of melting to form silicon oxide or silicon oxide. And it becomes difficult to produce a silicon-containing copper alloy. Therefore, in the production of an ingot of a silicon-containing copper alloy, the addition of silicon is usually performed after a Cu-Si alloy is added, which increases the production cost. Even in consideration of such alloy production costs, it is not preferable to add silicon in an amount exceeding the amount (4.0% by weight) at which the machinability improving effect is saturated. Further, according to the experiment, the silicon content was 2.0 to
When 4.0 wt% is added, in order to maintain the original characteristics of the Cu—Zn alloy, the copper content is set in a range of 69 to 79 wt% in consideration of the relationship with the zinc content. Has been found to be preferable. For these reasons, in the first invention alloy, the contents of copper and silicon are set to 69 to 79% by weight and 2.0 to 4.0% by weight, respectively. The addition of silicon improves machinability,
The flowability, strength, wear resistance, stress corrosion cracking resistance and high temperature oxidation resistance during casting are also improved. Also, ductility and dezincification corrosion resistance are improved to some extent.

In the second invention, the lead-free free-cutting copper alloy also having excellent machinability includes 69-79% by weight of copper.
2.0-4.0% by weight of silicon and 0.02-bismuth
An alloy composition containing at least one element selected from the group consisting of 0.4% by weight, 0.02 to 0.4% by weight of tellurium, and 0.02 to 0.4% by weight of selenium, and the balance being zinc. The proposed copper alloy (hereinafter referred to as “second invention alloy”) is proposed.

That is, the second invention alloy is composed of the first invention alloy containing 0.02 to 0.4% by weight of bismuth and 0.02 to 2.0% of tellurium.
The alloy composition further contains at least one of 0.4% by weight and 0.02 to 0.4% by weight of selenium.

Bismuth, tellurium, or selenium, like lead, does not form a solid solution in the matrix but exhibits a function of improving machinability by being dispersed in a granular form, and has a different function from silicon. To improve machinability. Therefore, when these are co-added with silicon,
The machinability can be further improved beyond the limit of machinability improvement by addition of silicon. In the second invention alloy, paying attention to this point, at least one of bismuth, tellurium, and selenium is added to further improve the machinability of the first invention alloy. In particular, by adding bismuth, tellurium, or selenium in addition to silicon, a high degree of machinability is exhibited even when a complicated shape is cut at a high speed. However, the effect of improving the machinability due to the addition of bismuth, tellurium or selenium is not exhibited when the amount of each addition is less than 0.02% by weight. On the other hand, since these are more expensive than copper, even if they are added in excess of 0.4% by weight, the machinability is improved with a slight increase in the added amount, but economically. No effect commensurate with the amount added was observed. If the amount exceeds 0.4% by weight, hot workability (for example, forgeability) deteriorates, and cold workability (ductility) also decreases. Even if heavy metals such as bismuth may have the same problem as lead, it is considered that there is no possibility that a special problem will occur if a trace amount of 0.4 wt% or less is added. From these points, in the second invention alloy, the addition amount of bismuth, tellurium, or selenium is set to 0.02 to 0.4% by weight. Since bismuth, tellurium, or selenium improves machinability by a function different from that of silicon as described above, the proper content of copper and silicon is not affected by their addition. Therefore, the contents of copper and silicon were set to be the same as those of the first invention alloy.

In the third invention, the lead-free free-cutting copper alloy also having excellent machinability includes 70-80% by weight of copper.
1.8 to 3.5% by weight of silicon, 0.3 to 3.5% by weight of tin, 1.0 to 3.5% by weight of aluminum and 0.0% of phosphorus
The present invention proposes a copper alloy containing one or more elements selected from 2 to 0.25% by weight and having an alloy composition consisting of zinc in the remainder (hereinafter, referred to as "third invention alloy").

When tin is added to a Cu—Zn-based alloy,
Like silicon, it forms a γ phase to improve machinability. For example, by adding 1.8 to 4.0% by weight of tin to a Cu-Zn-based alloy containing 58 to 70% by weight of Cu, even if silicon is not added, good machinability is obtained. Show. Therefore, by adding tin to the Cu—Si—Zn-based alloy, the formation of the γ phase can be promoted, and the machinability of the Cu—Si—Zn-based alloy can be further improved. The formation of the gamma phase by tin is 1.0
When the amount reaches 3.5% by weight, a saturated state is reached. If the amount of tin exceeds 3.5% by weight, not only the effect of forming the γ phase becomes saturated, but also the ductility decreases. Also, the amount of tin added was 1.0% by weight.
When the amount is less than 0.5, the effect of forming the γ phase is small, but the amount of addition is 0.1.
When the content is 3% by weight or more, there is an effect of dispersing and homogenizing the γ phase formed by silicon, and the machinability is also improved by the dispersion effect of the γ phase. That is, if the amount of tin added is 0.3% by weight or more, the machinability is improved by the addition.

Aluminum also has a function of accelerating the formation of the γ phase, similar to tin. When added together with or in place of tin, aluminum is added to Cu-Si-Z.
The machinability of the n-based alloy can be further improved. Aluminum has a function to improve the strength, abrasion resistance, resistance to high-temperature oxidation, and a function to lower the alloy specific gravity, in addition to the machinability. It is necessary to add 1.0% by weight. However, 3.
Even if it is added in excess of 5% by weight, the machinability improving effect commensurate with the added amount is not observed, and the ductility is reduced as in the case of tin.

Phosphorus does not have the function of forming a γ phase unlike tin and aluminum, but the γ phase formed by adding silicon or by co-adding one or both of tin and aluminum with phosphorus is uniform. And the function of improving the γ-phase distribution is provided. With such a function, the machinability by the γ-phase formation can be further improved. Also,
By the addition of phosphorus, the crystal grains of the α phase in the matrix are refined at the same time as the dispersion of the γ phase, thereby improving the hot workability and improving the strength and the stress corrosion cracking resistance. Further, there is also an effect of remarkably improving the flowability of the molten metal during casting. Such an effect by the addition of phosphorus is not exhibited when the addition is less than 0.02% by weight. On the other hand, if the added amount of phosphorus exceeds 0.25% by weight, the effect of improving machinability or the like corresponding to the added amount cannot be obtained, and excessive addition leads to deterioration of hot forgeability and extrudability.

In the third invention alloy, focusing on this point,
0.3-3.5% by weight of tin in a Cu-Si-Zn-based alloy,
1.0 to 3.5% by weight of aluminum and 0.02 to phosphorus
By adding at least one of 0.25% by weight, the machinability is further improved.

By the way, tin, aluminum or phosphorus improves the machinability by the function of forming the γ phase or the function of dispersing the γ phase as described above. Has a close relationship with Therefore, in the third invention alloy in which tin, aluminum or phosphorus is added to silicon, the function of improving the machinability by replacing the first invention alloy with silicon is exhibited, and the machinability is improved irrespective of the γ phase. The required addition amount of silicon is smaller than that of the second invention alloy to which bismuth, tellurium, or selenium is added, which exhibits a function of improving (a function of improving machinability by dispersing in a matrix form in a granular form). . That is, even if the silicon addition amount is less than 2.0% by weight, and if it is 1.8% by weight or more, it is possible to obtain industrially satisfactory machinability by co-adding tin, aluminum or phosphorus. it can. But,
Even if the amount of silicon is 4.0% by weight or less, if it exceeds 3.5% by weight, the effect of improving machinability by adding silicon becomes saturated by co-adding tin, aluminum or phosphorus. . From this point, in the third invention alloy, the addition amount of silicon is set to 1.8 to 3.5% by weight. Further, from the relation with the addition amount of silicon and the relation with addition of tin, aluminum or phosphorus, the upper and lower limits of the copper content are slightly larger than those of the second invention alloy, and the preferable content is 70 to 70%. 80
% By weight.

Further, in the fourth invention, the lead-free free-cutting copper alloy also having excellent machinability includes 70-80% by weight of copper.
1.8 to 3.5% by weight of silicon, 0.3 to 3.5% by weight of tin, 1.0 to 3.5% by weight of aluminum and 0.0% of phosphorus
One or more elements selected from 2 to 0.25% by weight;
Bismuth 0.02-0.4% by weight, tellurium 0.02-
A copper alloy containing 0.4% by weight and one or more elements selected from 0.02 to 0.4% by weight of selenium, and a balance of zinc (hereinafter referred to as "the fourth invention alloy") ).

That is, in the fourth invention alloy, bismuth 0.02 to 0.4% by weight and tellurium 0.02 to
The alloy composition further contains at least one of 0.4% by weight and 0.02 to 0.4% by weight of selenium. The reason for adding these elements and the reason for determining the amount of addition are as follows. Same as described.

Further, in the fifth invention, a lead-free free-cutting copper alloy which is excellent in corrosion resistance in addition to machinability is made of copper 69-
79% by weight, silicon 2.0 to 4.0% by weight, tin 0.3%
To 3.5% by weight, phosphorus 0.02 to 0.25% by weight, antimony 0.02 to 0.15% by weight and arsenic 0.02 to 0.
Containing at least one element selected from 15% by weight,
Further, a copper alloy (hereinafter, referred to as a "fifth invention alloy") having an alloy composition of zinc is proposed.

That is, the fifth invention alloy is the same as the first invention alloy except that tin is contained in an amount of 0.3 to 3.5% by weight, phosphorus is used in an amount of 0.02 to 0.25% by weight, antimony is used in an amount of 0.02 to 0.15% by weight, and arsenic is used. 0.
The alloy composition further contains at least one of 02 to 0.15% by weight.

In addition to the function of improving machinability, tin has a function of improving corrosion resistance (anti-zinc corrosion resistance, corrosion resistance) and forgeability. That is, the corrosion resistance of the α-phase matrix can be improved, and the corrosion resistance, forgeability, and stress corrosion cracking resistance can be improved by dispersing the γ phase. In the fifth invention alloy,
Corrosion resistance is improved by such a function of tin, and machinability is improved mainly by the effect of silicon addition. Therefore, the contents of silicon and copper are the same as those of the first invention alloy. On the other hand, in order to exhibit the function of improving corrosion resistance and forgeability, it is necessary that the amount of tin added be at least 0.3% by weight. However, the effect of improving the corrosion resistance and forgeability by adding tin exceeds 3.5% by weight, the effect corresponding to the added amount cannot be obtained, and it is economically useless.

As described above, phosphorus not only has a function of improving machinability but also has a corrosion resistance (dezincification corrosion resistance, It has the function of improving pickling resistance, forgeability, stress corrosion cracking resistance and mechanical strength. In the fifth invention alloy, the function of phosphorus improves corrosion resistance and the like, and the machinability is improved mainly by the effect of silicon addition. The effect of improving the corrosion resistance etc. by adding phosphorus is
This is exhibited by adding a small amount of phosphorus, and is exhibited by adding 0.02% by weight or more. However, 0.25% by weight
If the amount exceeds the above range, not only the effect corresponding to the added amount is not obtained, but also the hot forgeability and the extrudability are rather lowered.

Antimony and arsenic also improve anti-zinc-corrosion resistance and the like in a very small amount (0.02% by weight or more), like phosphorus. However, even if it is added in excess of 0.15% by weight, not only the effect commensurate with the amount added is not obtained, but also the hot forgeability and extrudability are rather reduced, as in the case of excessive addition of phosphorus.

From these facts, in the fifth invention alloy, in addition to the same amount of copper and silicon as in the first invention alloy, at least one of tin, phosphorus, antimony and arsenic as an element for improving corrosion resistance is in the above range. By adding it within, not only the machinability but also the corrosion resistance and the like can be improved. Note that, in the fifth invention alloy, tin and phosphorus mainly function as corrosion resistance improving elements similar to antimony and arsenic, and thus are similar to the first invention alloy in which no machinability improving element is added other than silicon. The amounts of copper and silicon are 69-79% by weight and 2.0-4.0% by weight, respectively.
There is.

In the sixth invention, the lead-free free-cutting copper alloy which is also excellent in machinability and corrosion resistance is copper 69-
79% by weight, silicon 2.0 to 4.0% by weight, tin 0.3%
To 3.5% by weight, phosphorus 0.02 to 0.25% by weight, antimony 0.02 to 0.15% by weight and arsenic 0.02 to 0.
One or more elements selected from 15% by weight and selected from 0.02 to 0.4% by weight of bismuth, 0.02 to 0.4% by weight of tellurium and 0.02 to 0.4% by weight of selenium 1
The present invention proposes a copper alloy (hereinafter, referred to as "sixth invention alloy") containing at least one kind of element and having an alloy composition composed of zinc with the balance being zinc.

That is, in the sixth invention alloy, bismuth 0.02 to 0.4% by weight and tellurium 0.02 to
The alloy composition further comprises at least one of 0.4% by weight and 0.02 to 0.4% by weight of selenium. Similar to the second invention alloy, silicon and bismuth, tellurium and selenium are included. And at least one selected from the group consisting of tin, phosphorus, antimony and arsenic is added to improve the corrosion resistance and the like. Is an improvement. Therefore, copper, silicon, bismuth,
The contents of tellurium and selenium were the same as those of the second invention alloy, and the contents of tin, phosphorus, antimony and arsenic were the same as those of the fifth invention alloy.

Further, in the seventh invention, a lead-free free-cutting copper alloy excellent in machinability, high strength and wear resistance is provided.
62-78% by weight of copper, 2.5-4.5% by weight of silicon,
0.3-3.0% by weight of tin, 0.2-2.5% of aluminum
% Or one or more elements selected from 0.02 to 0.25% by weight of phosphorus and one or more elements selected from 0.7 to 3.5% by weight of manganese and 0.7 to 3.5% by weight of nickel. The present invention proposes a copper alloy (hereinafter, referred to as a "seventh invention alloy") containing at least one kind of element and having an alloy composition composed of zinc with the balance being zinc.

Manganese or nickel combines with silicon to form a fine intermetallic compound of Mn _X Si _Y or Ni _X Si _Y and precipitates uniformly on the matrix, thereby improving wear resistance and strength. Therefore, by adding one or both of manganese and nickel, high strength,
The wear resistance is improved. Such effects are exhibited when manganese and nickel are each added in an amount of 0.7% by weight or more. However, even if it is added in excess of 3.5% by weight, the effect becomes saturated, and an effect commensurate with the added amount cannot be obtained. Silicon is added with manganese or nickel, taking into account the amount of consumption required for the formation of an intermetallic compound with manganese or nickel.
It was decided to add 4.5% by weight.

The addition of tin, aluminum and phosphorus strengthens the α phase of the matrix and improves machinability. Tin and phosphorus improve the strength and wear resistance by dispersing the α phase and the γ phase, and also improve the machinability. Tin improves the strength and machinability by adding 0.3% by weight or more,
When added in excess of 3.0% by weight, ductility decreases. Therefore, in the seventh invention alloy in which high strength and wear resistance are improved, the addition amount of tin is set to 0.3 to 3.0% by weight in consideration of the effect of improving machinability. Aluminum is
It contributes to the improvement of abrasion resistance and the matrix strengthening function is 0.1%.
It is exhibited by addition of 2% by weight or more. However, 2.5
If added in excess of weight percent, the ductility decreases. Therefore, considering the machinability improvement effect, the addition amount of aluminum is set to 0.2 to 2.5% by weight. Further, by adding phosphorus, the crystal grains of the α-phase in the matrix are refined at the same time as the dispersion of the γ-phase, thereby improving the hot workability and improving the strength and wear resistance. In addition, there is also an effect of significantly improving the flowability of the molten metal during casting. Such an effect can be achieved by adding phosphorus to 0.1.
This can be achieved by adding in the range of 02 to 0.25% by weight. The amount of copper was set to 62 to 78% by weight based on the relationship with the amount of silicon added and the relationship between manganese and nickel combined with silicon.

In the eighth aspect of the present invention, the lead-free free-cutting copper alloy also having excellent machinability, high strength and abrasion resistance contains 62 to 78% by weight of copper and 2.5 to 4.5% of silicon. weight%
0.3 to 3.0% by weight of tin and 1.0 to 1.0% of aluminum
At least one element selected from 2.5% by weight and 0.02 to 0.25% by weight of phosphorus, and selected from 0.7 to 3.5% by weight of manganese and 0.7 to 3.5% by weight of nickel; Done 1
More than one element, bismuth 0.02-0.4 wt%, tellurium 0.02-0.4 wt% and selenium 0.02-0.4 wt%.
The present invention proposes a copper alloy (hereinafter, referred to as an "eighth invention alloy") containing at least one element selected from 4% by weight and having an alloy composition of zinc.

That is, in the eighth invention alloy, bismuth 0.02 to 0.4% by weight and tellurium 0.02 to
It is an alloy composition further containing at least one of 0.4% by weight and 0.02 to 0.4% by weight of selenium, and is an element which improves machinability by a function different from silicon as described above. By adding bismuth, etc., the seventh
It is intended to further improve the machinability while ensuring the same high strength and wear resistance as the inventive alloy. Reasons for adding machinability improving elements such as bismuth and reasons for determining the amount
This is the same as the second invention alloy, the fourth invention alloy or the sixth invention alloy. The reasons for adding other elements (copper, zinc, tin, manganese, nickel) and the reasons for determining the amount of addition are the same as in the seventh invention alloy.

Furthermore, in the ninth invention, 69-79% by weight of copper, 2.0-4.0% by weight of silicon, and 0.1-1.5% by weight of aluminum and 0.02-0.25 of phosphorus
The present invention proposes a copper alloy (hereinafter, referred to as a "ninth invention alloy") containing an alloy composition containing 0.1% by weight and the balance being zinc.

Aluminum is an element that improves the strength, machinability and wear resistance, and also improves the high-temperature oxidation resistance. As described above, silicon also has functions of improving machinability, strength, abrasion resistance, stress corrosion cracking resistance, and high temperature oxidation resistance. Improvement of high-temperature oxidation resistance by aluminum is 0.1% by weight by co-addition with silicon.
The above addition is performed. However, aluminum was added to 1.
Even if it is added in excess of 5% by weight, the effect of improving high-temperature oxidation resistance corresponding to the amount added is not observed. From this point, the addition amount of aluminum is set to 0.1 to 1.5% by weight.

[0036] Phosphorus is added to improve the flowability of the molten metal during casting of the alloy. Phosphorus improves not only the flowability of the molten metal but also the high-temperature oxidation resistance in addition to the above-mentioned machinability and dezincification corrosion resistance. The effect of such phosphorus addition is 0.1.
Exhibited at 02% by weight or more. However, 0.25% by weight
Even if added beyond the above, the effect corresponding to the added amount is not seen,
On the contrary, the alloy becomes brittle. From this point,
The addition amount of phosphorus was 0.02 to 0.25% by weight.

Although silicon is added to improve machinability as described above, silicon also has a function of improving the flowability of molten metal like phosphorus. The improvement of the melt flowability by silicon is exhibited by the addition of 2.0% by weight or more, and overlaps the addition range necessary for improving the machinability.
Therefore, the addition amount of silicon is set to 2.0 to 4.0% by weight in consideration of improvement in machinability.

Further, in the tenth invention, a lead-free free-cutting copper alloy also having excellent machinability and high-temperature oxidation resistance,
69-79% by weight of copper, 2.0-4.0% by weight of silicon,
0.1 to 1.5% by weight of aluminum and 0.02 to phosphorus
Alloy composition containing 0.25% by weight and one or more elements selected from 0.02 to 0.4% by weight of chromium and 0.02 to 0.4% by weight of titanium, with the balance being zinc (Hereinafter, referred to as a “tenth invention alloy”).

Chromium and titanium have a function of improving high-temperature oxidation resistance, and the function is particularly remarkably exhibited by the synergistic effect of co-addition with aluminum. Such functions are exhibited at 0.02% by weight or more, regardless of whether they are added alone or co-added,
It is saturated at 0.4% by weight. From such a point, in the tenth invention alloy, chromium 0.0
In order to further improve the high-temperature oxidation resistance of the ninth invention alloy, the alloy composition further contains at least one of 2 to 0.4% by weight and 0.02 to 0.4% by weight of titanium. I have.

Further, in the eleventh invention, a lead-free free-cutting copper alloy also having excellent machinability and high-temperature oxidation resistance,
69-79% by weight of copper, 2.0-4.0% by weight of silicon,
0.1 to 1.5% by weight of aluminum and 0.02 to phosphorus
0.25% by weight, bismuth 0.02 to 0.4% by weight,
Tellurium 0.02-0.4 wt% and selenium 0.02-
A copper alloy containing one or more elements selected from 0.4% by weight and having an alloy composition with the balance being zinc is proposed (hereinafter, referred to as an "eleventh invention alloy").

That is, the eleventh invention alloy is composed of the ninth invention alloy containing 0.02 to 0.4% by weight of bismuth and 0.02% of tellurium.
~ 0.4% by weight and at least one of 0.02 ~ 0.4% by weight of selenium. The alloy composition further improves machinability by a function different from that of silicon as described above. By adding certain bismuth, etc., the ninth
It is intended to further improve the machinability while ensuring the same high-temperature oxidation resistance as the inventive alloy.

Also, in the twelfth invention, a lead-free free-cutting copper alloy, which is also excellent in machinability and high-temperature oxidation resistance,
69-79% by weight of copper, 2.0-4.0% by weight of silicon,
0.1 to 1.5% by weight of aluminum and 0.02 to phosphorus
0.25% by weight, one or more elements selected from 0.02 to 0.4% by weight of chromium and 0.02 to 0.4% by weight of titanium, and 0.02 to 0.4% by weight of bismuth; Copper alloys containing at least one element selected from the group consisting of 0.02 to 0.4% by weight of tellurium and 0.02 to 0.4% by weight of selenium, and a balance of zinc (hereinafter referred to as " Twelfth
Inventive alloy ").

That is, the twelfth invention alloy is the same as the tenth invention alloy, except that 0.02 to 0.4% by weight of bismuth and
An alloy composition further containing at least one of 2 to 0.4% by weight and 0.02 to 0.4% by weight of selenium, and as described above, an element which improves machinability by a function different from silicon. By adding bismuth or the like, the machinability is further improved while maintaining the same high-temperature oxidation resistance as the tenth invention alloy.

Further, in the thirteenth invention, a lead-free free-cutting copper alloy whose machinability is further improved by subjecting each of the above-mentioned alloys to a heat treatment at 400 to 600 ° C. for 30 minutes to 5 hours. (Hereinafter, referred to as a “thirteenth invention alloy”).

The first to twelfth invention alloys are those to which a machinability improving element such as silicon is added, and which have excellent machinability due to the addition of such elements. When there are many phases other than the α, β, γ, and δ phases (mainly the κ phase), the heat treatment changes the κ phase to the γ phase,
When the phase is finely dispersed and precipitated, machinability may be further improved. For example, those having a high copper concentration are excellent in cold workability because the ductility of the matrix is high and the absolute amount of the γ phase is small, but when the cold working and cutting such as caulking are required, the heat treatment described above is performed. It is extremely effective. That is, in the alloys having a high copper concentration and a small γ phase and a large κ phase (hereinafter referred to as “high copper concentration alloy”), the κ phase becomes the γ phase by heat treatment. The machinability is further improved by changing and finely dispersing and precipitating the γ phase. In addition, when assuming the production of actual castings, wrought materials, and hot forged products, depending on the conditions of the casting conditions, productivity after hot working (hot extrusion, hot forging, etc.), work environment, etc. May be forcibly air-cooled or water-cooled. In such a case, in the first to twelfth inventions, those having a low copper concentration (hereinafter, referred to as “low copper concentration alloy”) have a slightly smaller γ phase and include a β phase,
When heat treatment is performed, the β phase changes to the γ phase and the γ phase is finely dispersed and precipitated, thereby improving machinability. According to experiments, it was confirmed that the compounding ratio of copper and silicon to another additive element A (excluding zinc) was 67 ≦ Cu
-3Si + aA high copper concentration alloy or 6
The effect of the heat treatment is particularly remarkable in a low copper concentration alloy having a composition satisfying 4 ≧ Cu-3Si + aA. Note that a
Is a coefficient that varies depending on the additive element A. For example, tin:
a = -0.5, aluminum: a = -2, phosphorus: a =-
3, antimony: a = 0, arsenic: a = 0, manganese: a
= + 2.5, nickel: a = + 2.5.

However, in any case, if the heat treatment temperature is lower than 400 ° C., the above-mentioned phase change rate becomes slow, and the heat treatment takes an extremely long time, so that it is not economically practical. Conversely, when the temperature exceeds 600 ° C., the κ phase increases or the β phase appears, so that the effect of improving machinability cannot be obtained. Therefore, considering practicality,
In order to improve machinability, 30 to 400 ° C to 600 ° C
It is preferable to perform the heat treatment for a period of minutes to 5 hours.

[0047]

EXAMPLE As an example, an ingot (having a cylindrical shape having an outer diameter of 100 mm and a length of 150 mm) having a composition shown in Tables 1 to 35 was extruded into a round bar having an outer diameter of 15 mm while hot (750 ° C.). Then, the first invention alloy No. 1001-No. 100
8, the second invention alloy No. 2001-No. 2011, the third invention alloy No. 3001-No. 3012, 4th invention alloy No. 4001-No. 4049, Fifth invention alloy N
o. 5001-No. 5020, the sixth invention alloy No. 6
001-No. 6105, 7th invention alloy No. 7001
-No. 7030, Eighth Invention Alloy No. 8001-N
o. 8147, ninth invention alloy No. 9001-No. 9
005, 10th invention alloy No. 10001-No. 10
008, Eleventh Invention Alloy No. 11001-No. 11
007 and the twelfth invention alloy no. 12001-No. 1
2021 was obtained. Further, an ingot (having a cylindrical shape having an outer diameter of 100 mm and a length of 150 mm) having the composition shown in Table 36 was extruded into a round bar having an outer diameter of 15 mm by hot (750 ° C.). Heat treatment under the conditions shown in
Inventive alloy No. 3 No. 13001-No. 130006 was obtained. That is, No. 13001 is the first invention alloy No.
An extruded material having the same composition as No. 1005 was heat-treated at 580 ° C. for 30 minutes. 13002 is N
o. Extruded material having the same composition as 13001
No. 10 was heat-treated under the condition of time. 13003
Is the first invention alloy No. The extruded material having the same composition as No. 1007 was No. 1007. No. 13001 was heat-treated under the same conditions (580 ° C., 30 minutes). No. 13004 is No. 10
No. 07 extruded material having the same composition as No. 07 Heat-treated under the same conditions as 13002 (450 ° C., 2 hours)
o. 13005 is the first invention alloy No. The extruded material having the same composition as No. 1008 was No. 1008. Same conditions as 13001 (580
C. for 30 minutes). 1300
No. 6 is No. The extruded material having the same composition as No. 1008 was No. 1008. 1
Heat treatment was performed under the same conditions (450 ° C., 2 hours) as 3002.

As a comparative example, an ingot (having a cylindrical shape having an outer diameter of 100 mm and a length of 150 mm) having the composition shown in Table 37 was extruded hot (750 ° C.) to obtain an outer diameter of 15 mm.
No. extruded material (hereinafter referred to as “conventional alloy”) No. 14
001-No. 140006 was obtained. In addition, No. 140
01 is equivalent to “JIS C3604”,
No. No. 14002 corresponds to “CDA C36000”. 14003 is "JIS C377
No. 1 ". 14004 is "CD
AC69800 ". Also, N
o. 14005 is equivalent to "JIS C 6191" and is an aluminum bronze having the best strength and abrasion resistance among the copper brass products specified in JIS. Also, N
o. 14006 is equivalent to "JIS C4622", and is a naval brass having the best corrosion resistance among the brass products specified in JIS.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

[Table 5]

[0054]

[Table 6]

[0055]

[Table 7]

[0056]

[Table 8]

[0057]

[Table 9]

[0058]

[Table 10]

[0059]

[Table 11]

[0060]

[Table 12]

[0061]

[Table 13]

[0062]

[Table 14]

[0063]

[Table 15]

[0064]

[Table 16]

[0065]

[Table 17]

[0066]

[Table 18]

[0067]

[Table 19]

[0068]

[Table 20]

[0069]

[Table 21]

[0070]

[Table 22]

[0071]

[Table 23]

[0072]

[Table 24]

[0073]

[Table 25]

[0074]

[Table 26]

[0075]

[Table 27]

[0076]

[Table 28]

[0077]

[Table 29]

[0078]

[Table 30]

[0079]

[Table 31]

[0080]

[Table 32]

[0081]

[Table 33]

[0082]

[Table 34]

[0083]

[Table 35]

[0084]

[Table 36]

[0085]

[Table 37]

Then, in order to confirm the machinability of the first to thirteenth invention alloys in comparison with the conventional alloys, the following cutting test was performed, and the main component force of the cutting, the chip state and the cutting surface morphology were determined. .

That is, the outer peripheral surface of each extruded material obtained as described above was cut by a lathe equipped with a serious cutting tool (rake angle: -8 °) at a cutting speed of 50 m / min and a cutting depth (cutting allowance). ): 1.5 mm, feed amount: 0.11 mm / re
v. The signal from the three-component dynamometer attached to the cutting tool was converted into a voltage signal by a heavy strain measuring instrument, recorded by a recorder, and converted into a cutting resistance. by the way,
The magnitude of the cutting force is determined by the three-component force, namely, the main component, the feed component and the back component. In this case, the magnitude of the cutting force is determined by the main component (N) showing the largest value among the three components. It was decided to judge. The results were as shown in Tables 38 to 66.

Further, the state of the chips generated by the cutting was observed and classified into four types as shown in FIGS. 1 (A) to 1 (D) according to their shapes, and the results are shown in Tables 1 to 37. By the way, as shown in Fig. (D), when the chip has a spiral shape of three or more turns, processing of the chip (collection and reuse of the chip, etc.)
In addition, it becomes difficult to perform cutting, and troubles such as chip entanglement with the cutting tool and damage to the cutting surface occur, so that good cutting cannot be performed. Further, as shown in Fig. (C), when the chip has a spiral shape of about two turns from an arc shape of about half a roll, a big trouble such as a spiral shape of three or more turns occurs. However, it is still not easy to treat chips, and in the case of performing continuous cutting, there is a possibility that the cutting tool may be entangled or the cutting surface may be damaged. However, when the chip is sheared into a fine needle-shaped piece as shown in (A) or a fan-shaped piece or an arc-shaped piece as shown in (B), the above trouble does not occur, and (C) Since it is not bulky as shown in the figures and (D), the processing of chips is easy. However, if the chips are sheared into a fine shape as shown in FIG. 3A, the chips may sneak into the sliding surface of a machine tool such as a lathe to cause a mechanical obstacle, or to be stuck by fingers or eyes of an operator. May be dangerous. Therefore, in judging the machinability, the one shown in FIG. (B) is the best, the one shown in (A) follows, and the one shown in (C) or (D) is inappropriate. It is appropriate to do. In Tables 38 to 66, those in which the best chip state shown in FIG.
In the figure, a somewhat good chip condition was observed, and "○"
In the graph, (も の) indicates the case where the bad chip state shown in FIG. 7 (C) was observed, and “×” indicates the case where the worst chip state shown in (D) was observed.

After cutting, the quality of the cut surface was judged by the surface roughness. The results are shown in Tables 38 to 66.
As shown in FIG. By the way, the maximum height (Rmax) is often used as a standard of the surface roughness, and although it depends on the use of the brass product, it is generally judged that if Rmax <10 μm, the machinability is extremely excellent. 10μ
If m ≦ Rmax <15 μm, it can be determined that industrially satisfactory machinability has been obtained, and Rmax ≧ 15 μm
In the case of m, it can be determined that the machinability is poor. Table 38-
In Table 65, the case where Rmax <10 μm is indicated by “○”.
In the case of 10 μm ≦ Rmax <15 μm, “△” indicates that R
The case where max ≧ 15 μm is indicated by “x”.

As is clear from the results of the cutting tests shown in Tables 38 to 66, the first invention alloy No. 1001-No.
1008, the second invention alloy No. 2001-No. 201
1, the third invention alloy No. 3001-No. 3012, 4th invention alloy No. 4001-No. 4049, Fifth Invention Alloy No. 5001-No. 5020, sixth invention alloy N
o. 6001-No. 6105, 7th invention alloy No. 7
001-No. 7030, Eighth Invention Alloy No. 8001
-No. 8147, ninth invention alloy no. 9001-N
o. 9005, 10th invention alloy No. 10001-N
o. 10008, Eleventh Invention Alloy No. 11001-N
o. No. 11007 and the twelfth invention alloy no. 12001-
No. No. 12021 is a conventional alloy no. No. 14001-No. 14003
It has the same machinability as. In particular, as far as the state of chip formation is concerned, the conventional alloy No. having a lead content of 0.1% by weight or less is used. 14004-No. Compared with the conventional alloy No. 14006 containing a large amount of lead, 14001-
No. It has good machinability as compared to 14003.

As is clear from Tables 38 and 65, the thirteenth invention alloy no. No. 13001-No. 1300
No. 6 is a first invention alloy No. 6 having the same composition as these. 10
05, no. 1007 and no. The machinability was improved as compared with 1008, and it was confirmed that the machinability could be further improved by performing an appropriate heat treatment.

Next, in order to confirm the hot workability and mechanical properties of the first to thirteenth invention alloys in comparison with the conventional alloys, the following hot compression test and tensile test were performed.

That is, from each extruded material obtained as described above, the first material having the same shape (outer diameter 15 mm, length 25 mm) was obtained.
And the 2nd test piece was cut out. Then, in the hot compression test, each first test piece was heated to 700 ° C. and held for 30 minutes, and then compressed at a compression rate of 70% in the axial direction (the height (length) of the first test piece was reduced). It was compressed from 25 mm to 7.5 mm), and the surface morphology (deformability at 700 ° C.) after compression was visually determined. The results were as shown in Tables 38 to 66. Judgment of the deformability was visually performed from the state of cracks on the side surface of the test piece, and in Tables 38 to 66, those in which no cracks occurred were indicated by “○”, and those in which small cracks occurred were indicated by “△”, Those having large cracks are indicated by "x". Further, a tensile test was carried out using each of the second test pieces by a conventional method, and the tensile strength (N /
mm ² ) and elongation (%) were measured.

From the results of the hot compression test and the tensile test shown in Tables 38 to 66, the first to thirteenth invention alloys are the same as those of the conventional alloy No. No. 14001-No. 14004 and no. 140
It has a hot workability and a mechanical property equal to or higher than that of 06, and it has been confirmed that it can be industrially suitably used. In particular, regarding the seventh and eighth invention alloys, the conventional alloy No. which is aluminum bronze which is the most excellent in the strength among the copper products according to JIS. 140
It has mechanical properties equivalent to that of No. 05, and is understood to be excellent in high strength.

The first to sixth invention alloys and the ninth to first alloys
In order to confirm the corrosion resistance and stress corrosion cracking resistance of the No. 3 invention alloy in comparison with the conventional alloy, a dezincification corrosion test according to the method specified in "ISO 6509" and "JIS H32"
A stress corrosion cracking test specified in “50” was conducted.

That is, in the dezincification corrosion test of “ISO 6509”, a sample collected from each extruded material was embedded in a phenol resin material such that the surface of the exposed sample was perpendicular to the extrusion direction of the extruded material. The surface of the sample was polished with emery paper to # 1200, and the surface was ultrasonically washed in pure water and dried. The corrosion test sample thus obtained was treated with 1.0% cupric chloride dihydrate (CuCl 2).
Immersed in ₂ · 2H ₂ O) aqueous solution (12.7 g / l), was held for 24 hours at a temperature of 75 ° C., and taken out from the aqueous solution, the maximum value of the dezincification corrosion depth (maximum Dezincification corrosion depth) was measured. The results are shown in Tables 38 to 5
0 and Tables 61 to 66.

As understood from the results of the dezincification corrosion tests shown in Tables 38 to 50 and Tables 61 to 66, the first to fourth invention alloys and the ninth to thirteenth invention alloys produced a large amount of lead. Conventional alloy No. No. 14001-No. 5th and 6th invention alloys which have excellent corrosion resistance compared to 14003, and which improve corrosion resistance as well as machinability,
Conventional alloy No., which is a Naval brass with the highest corrosion resistance among the brass products specified in S. It was confirmed that the material had extremely excellent corrosion resistance as compared with 140006.

In the stress corrosion cracking test of “JIS H3250”, a sample having a length of 150 mm was cut out from each extruded material, and each sample was placed on an arc-shaped jig having a radius of 40 mm. The test piece was bent so that one end thereof was at 45 ° to the other end. Each specimen to which the residual tensile stress was applied in this way was degreased,
After being dried, it was kept in an ammonia atmosphere (25 ° C.) in a desiccator containing 12.5% ammonia water (ammonia diluted with an equal amount of pure water). That is, each test piece is held at a position about 80 mm above the ammonia water level in the desiccator. When the holding time of the test piece in the ammonia atmosphere has passed for 2 hours, 8 hours, and 24 hours, the test piece was taken out of the desiccator, washed with 10% sulfuric acid, and the test piece was cracked. The presence or absence was visually recognized with a magnifying glass (magnification: 10 times). The results were as shown in Tables 38 to 50 and 61 to 66. In these tables, those in which a clear crack was observed when the holding time in the ammonia atmosphere was 2 hours were "XX", and no crack was observed after 2 hours. When a clear crack was observed after 8 hours, it was marked with "X".
No crack was observed after the elapse of time.
A sample in which a clear crack was observed over time was indicated by "△", and a sample in which no crack was observed even after 24 hours was indicated by "○".

As understood from the results of the stress corrosion cracking tests shown in Tables 38 to 50 and Tables 61 to 66, the fifth and sixth invention alloys of which not only the machinability but also the corrosion resistance were improved were used. Also, the first to fourth invention alloys and the ninth to thirteenth invention alloys, for which corrosion resistance is not particularly taken into consideration, also include the conventional alloy 1 which is aluminum bronze containing no zinc.
Conventional alloy No. which is Naval brass, which has the same stress corrosion cracking resistance as 4005 and is the most excellent in corrosion resistance among the brass products specified in JIS. It was confirmed to have stress corrosion cracking resistance superior to 140006.

Further, in order to confirm the high-temperature oxidation resistance of the ninth to twelfth invention alloys in comparison with the conventional alloys, the following oxidation tests were performed.

That is, each extruded material No. 9001-N
o. 9005, no. 10001-No. 10008,
No. 11001-No. No. 11007, no. 1200
1 to No. 12021 and no. 14001 to 1400
From 6, a round bar-shaped test piece whose surface was ground to an outer diameter of 14 mm and cut to a length of 30 mm was obtained, and the weight of each test piece (hereinafter referred to as “weight before oxidation”) was measured.
Thereafter, each test piece was stored in a magnetic crucible,
It was left in an electric furnace maintained at 00 ° C. Then, when the standing time has passed 100 hours, the test piece is taken out of the electric furnace, the weight of each test piece (hereinafter referred to as “post-oxidation weight”) is measured, and the oxidation increase is calculated from the pre-oxidation weight and the post-oxidation weight. did. Here, the oxidation increase refers to the surface area 10c of the test piece.
It indicates the degree of weight increase (mg) due to oxidation per m ² , and “weight increase by oxidation (mg / 10 cm ² ) = (weight after oxidation (mg) −weight before oxidation (mg)) × (10 cm ² )
/ Surface area of test piece (cm ² ) ”. That is, the weight after oxidation of each test piece is greater than the weight before oxidation, which is due to high-temperature oxidation. That is, when exposed to a high temperature, oxygen and copper, zinc, and silicon combine to form Cu ₂ O, ZnO, and SiO ₂ , and the weight increases due to the oxygen increment. Therefore,
It can be said that the smaller the degree of the increase in weight (increase in oxidation), the more excellent the high-temperature oxidation resistance was, and the results shown in Tables 61 to 64 and 66 were obtained.

As is clear from the results of the oxidation tests shown in Tables 61 to 64 and Table 66, the oxidized weight gains of the ninth to twelfth invention alloys are the highest in high temperature oxidation resistance among the copper products specified in JIS. Conventional alloy N which is aluminum bronze
o. 14005, which is much smaller than other conventional alloys. Therefore, it was confirmed that the ninth to twelfth invention alloys were extremely excellent in high-temperature oxidation resistance in addition to machinability.

[0103]

[Table 38]

[0104]

[Table 39]

[0105]

[Table 40]

[0106]

[Table 41]

[0107]

[Table 42]

[0108]

[Table 43]

[0109]

[Table 44]

[0110]

[Table 45]

[0111]

[Table 46]

[0112]

[Table 47]

[0113]

[Table 48]

[0114]

[Table 49]

[0115]

[Table 50]

[0116]

[Table 51]

[0117]

[Table 52]

[0118]

[Table 53]

[0119]

[Table 54]

[0120]

[Table 55]

[0121]

[Table 56]

[0122]

[Table 57]

[0123]

[Table 58]

[0124]

[Table 59]

[0125]

[Table 60]

[0126]

[Table 61]

[0127]

[Table 62]

[0128]

[Table 63]

[0129]

[Table 64]

[0130]

[Table 65]

[0131]

[Table 66]

As a second embodiment, Tables 14 to 3
Ingot of composition shown in 1 (outer diameter 100 mm, length 200 mm
Cylindrical shape) is hot (700 ° C) with an outer diameter of 35 mm
Of the seventh invention alloy No. 7001
a-No. 7030a and the eighth invention alloy no. 8001
a-No. 8147a was obtained. In addition, as a second comparative example, an ingot (outer diameter 100 mm, length 2
Extruded into a round bar-shaped extruded material (hereinafter referred to as “conventional alloy”) having an outer diameter of 35 mm. 14001a-No. 14006a
I got In addition, No. 7001a-No. 7030a,
No. 8001a-No. 8147a and no. 140
01a-No. No. 14006a is the copper alloy No. described above. 7001-No. 7030, no. 8001-N
o. 8147 and no. No. 14001-No. 14006
Have the same alloy composition as

The seventh invention alloy No. 7001a-
No. 7030a and the eighth invention alloy no. 8001a-
No. The wear resistance of conventional alloy No. 8147a was 140
01a-No. The following abrasion test was performed in order to confirm in comparison with 140006a.

That is, each extruded material obtained as described above was cut on its outer peripheral surface, and then punched and cut to obtain an outer diameter of 32 mm and a thickness (length in the axial direction) of 10 mm. After obtaining a ring-shaped test piece, each test piece was fitted and fixed to a rotatable shaft, and a 50 kg load was applied to a SUS304 roll having an outer diameter of 48 mm, whose axis was parallel to the test piece, to make pressure contact. Keep in state. After a while
The SUS304 roll and the test piece rolling thereon are driven to rotate at the same rotation speed (209 rpm) while multi-oil is dropped on the outer peripheral surface of the test piece. When the number of rotations of the test piece reaches 100,000 times, S
The rotation of the US304 roll and the test piece was stopped, and the weight difference before and after the rotation of each test piece, that is, the wear loss (mg)
Was measured. As the wear loss is smaller, it can be said that the copper alloy is more excellent in wear resistance.
~ As shown in Table 77.

As is evident from the results of the wear tests shown in Tables 67 to 77, the seventh invention alloy No. 7 has the following characteristics. 7001a-N
o. 7030a and the eighth invention alloy no. 8001a-N
o. 8147a is a conventional alloy No. No. 14001-No.
14004 and no. JI compared to 14005
Conventional bronze alloy No. S, which is an aluminum bronze having the highest wear resistance among the copper products specified in S.S. It was confirmed that the abrasion resistance was superior to that of 14005. Therefore,
When comprehensively judged also in consideration of the results of the above-described tensile tests, the seventh and eighth invention alloys have JI in addition to machinability.
It can be said that it has the same high strength and wear resistance as aluminum bronze which is the most excellent in wear resistance among the copper products specified in S.

[0136]

[Table 67]

[0137]

[Table 68]

[0138]

[Table 69]

[0139]

[Table 70]

[0140]

[Table 71]

[0141]

[Table 72]

[0142]

[Table 73]

[0143]

[Table 74]

[0144]

[Table 75]

[0145]

[Table 76]

[0146]

[Table 77]

[0147]

As will be easily understood from the above description, the first to thirteenth invention alloys are extremely rich in machinability although they do not contain any lead component which is a machinability improving element. It can safely be used as a substitute for conventional free-cutting copper alloys containing a large amount of lead, and has no environmental health problems including the reuse of chips. Responding to recent trends that are being regulated.

Further, the fifth and sixth invention alloys are excellent in corrosion resistance in addition to machinability, and are used for cutting products, forgings, castings, etc. requiring corrosion resistance (for example, water taps). , Water supply and drain fittings, valves, stems, hot water supply piping parts, shafts, heat exchanger parts, etc.), and their practical value is extremely large.

Further, the seventh and eighth invention alloys are excellent not only in machinability but also in high strength and abrasion resistance, and are required to have high strength and abrasion resistance. Products such as bearings, bolts, nuts, bushings, gears, sewing machine parts, hydraulic parts, etc., and have extremely large practical value. .

Further, the ninth to twelfth invention alloys are excellent in high-temperature oxidation resistance in addition to machinability. For example, it can be suitably used as a constituent material of a nozzle for an oil / gas hot air heater, a burner head, a gas nozzle for a water heater, etc., and its practical value is extremely large.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a form of a chip.

Claims (9)

[Claims] 1. 69 to 79% by weight of copper and 2.0 to 2.0% of silicon
A lead-free free-cutting copper alloy containing 4.0% by weight and the balance being zinc. 2. Tin 0.3 to 3.5% by weight, phosphorus 0.02 to
0.25% by weight, 0.02-0.15% by weight of antimony
2. The composition according to claim 1, further comprising at least one element selected from the group consisting of arsenic and 0.02 to 0.15% by weight.
Lead-free free-cutting copper alloys described in 1. 3. The method according to claim 1, wherein 70 to 80% by weight of copper and 1.8% to silicon
3.5% by weight, and one or more elements selected from 0.3 to 3.5% by weight of tin, 1.0 to 3.5% by weight of aluminum and 0.02 to 0.25% by weight of phosphorus. A lead-free free-cutting copper alloy comprising an alloy composition containing zinc and the balance being zinc. 4. 62 to 78% by weight of copper and 2.5 to 2.5% of silicon
4.5% by weight and one or more elements selected from 0.3 to 3.0% by weight of tin, 0.2 to 2.5% by weight of aluminum and 0.02 to 0.25% by weight of phosphorus; Manganese 0.7-
A lead-free free-cutting copper containing 3.5% by weight and one or more elements selected from 0.7 to 3.5% by weight of nickel, and the balance being an alloy composition consisting of zinc. alloy. 5. Bismuth 0.02 to 0.4% by weight, tellurium 0.02 to 0.4% by weight and selenium 0.02 to 0.4%
The lead-free free-cutting copper alloy according to claim 1, wherein the alloy further contains at least one element selected from the weight percent. 6. Copper 69-79% by weight, silicon 2.0-4.
A lead-free free-cutting copper alloy containing 0% by weight, 0.1-1.5% by weight of aluminum and 0.02-0.25% by weight of phosphorus, and the balance being zinc. . 7. The method according to claim 6, further comprising at least one element selected from 0.02 to 0.4% by weight of chromium and 0.02 to 0.4% by weight of titanium. Lead-free free-cutting copper alloy. 8. Bismuth 0.02 to 0.4% by weight, tellurium 0.02 to 0.4% by weight and selenium 0.02 to 0.4%
The lead-free free-cutting copper alloy according to claim 6 or 7, further comprising one or more elements selected from weight%. 9. A heat treatment at a temperature of 400 to 600 ° C. for 30 minutes to 5 hours. Or the lead-free free-cutting copper alloy according to claim 8.