JP2000239763A - Copper-base alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper-base alloy excellent in heat-resisting properties, such as high temperature oxidation resistance and high temperature deformation resisting strength, as well as in hot forgeability and machinability and extremely suitable for component material for various parts and products used under high temperature conditions, e.g. a petroleum carburetor nozzle of an oil/gas hot-air heater, a gas heater, a burner head or the like. SOLUTION: The copper-base alloy has an alloy composition consisting of, by weight, 61.0-67.0% copper, 0.3-2.0% aluminum, 0.5-2.5% lead and the balance zinc. In order to improve the denseness of an extremely thin aluminum oxide film resultant from initial high temperature oxidation to a greater extent, one or more elements selected from 0.02-0.5 wt.% chromium, 0.02-0.5 wt.% titanium and 0.01-0.2 wt.% phosphorus are further added to the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to brass suitable as a constituent material of various parts and products used under high-temperature conditions (for example, a petroleum vaporizer nozzle of a hot gas / gas hot air heater, a gas stove, and a burner head). It relates to a copper-based alloy.

[0002]

2. Description of the Related Art For example, at the start of use, a vaporizer of an oil heater is heated by a sheathed heater (electric type) to evaporate kerosene, and then the heat of the burner is absorbed by a heat receiving portion of the vaporizer.
This heat is used to vaporize kerosene. recent years,
The demand for rapid heating from the user side is high, and low-quality kerosene is circulating due to the liberalization of petroleum-related products. As a result, a situation has arisen in which the kerosene boiling point in an oil heater rises. The demand for improving the performance of the oil heater and the deterioration in the quality of the kerosene used have made it necessary to increase the heating temperature of the vaporizer. As described above, in the case of the oil vaporizer of the oil heater and the like, the use temperature tends to be higher in recent years due to a demand for performance improvement.

[0003] On the other hand, as a constituent material of a nozzle or the like used in an oil vaporizer of an oil heater, in general, an inexpensive aluminum die cast, which can be easily processed into a complicated shape, is used. Forging brass bars (JIS C3771) and free-cutting brass bars (JIS C36)
04) is used, but such aluminum or brass is not suitable as a constituent material of parts and products in which the use temperature tends to be high, and various problems occur when used as a constituent material. Occurs.

That is, since aluminum has a melting point of 250 ° C. lower than that of brass, it cannot meet the above-mentioned demand for high-temperature use.
In known brass such as 1 ", high-temperature oxidation becomes remarkable as the temperature rises, and the efficiency of heat absorption deteriorates. In addition, there arises a problem that the nozzle is clogged by the generated oxide, and the function as a vaporizer cannot be performed due to peeling of the oxide film. Further, in parts and products using brass as a constituent material, as the operating temperature increases, the strength of the material decreases, causing local deformation, causing a problem that the function of the vaporizer greatly decreases.

[0005]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention has excellent hot workability and cutting workability,
An object of the present invention is to provide a copper-based alloy capable of avoiding oxidation and thermal deformation as much as possible even under high temperature conditions.

[0006]

According to the present invention, in order to achieve the above object, 61.0-67.0% by weight of copper, 0.3-2.0% by weight of aluminum and 0.5-2. A copper-based alloy containing 5% by weight and having the balance of zinc is proposed.

In such a copper-based alloy, copper, aluminum
The ratio of lead and copper is copper content: W ₁Wt%, aluminum
Um content: W_TwoWt%, lead content: W_Three% By weight
In the case, 60.0 ≦ W₁-3 · W_Two+ 0.6W_Three≦ 6
It is preferable to decide so that the relationship is 2.0
No.

In the above copper-based alloy, in order to further improve high-temperature oxidation resistance, 0.02-0.5% by weight of chromium, 0.02-0.5% by weight of titanium, and 0.01-0.5% by weight of phosphorus.
It is preferable to further contain one or more elements selected from 0.2% by weight.

Aluminum dissolves in brass, but when heated in air, aluminum atoms near the surface diffuse and move to the surface and combine with oxygen in the air to form an aluminum-rich oxide film. This aluminum-rich oxide film is very thin (0.1 μm or less) and cannot be seen with the naked eye or a microscope, but it is strong and hard to peel off, is extremely dense, and is stable in a high-temperature atmosphere. is there. Therefore, once an aluminum-rich oxide film is formed, oxygen in the atmosphere is prevented from entering the oxide film, and does not reach the inside of the material. Become.
That is, the high-temperature oxidation resistance can be significantly improved by adding aluminum. Of course, since the oxide film is extremely thin, there is no fear that the thermal efficiency of the copper-based alloy product is greatly reduced by the film formation. Aluminum also has a function of improving resistance to deformation at high temperatures. Such an effect by adding aluminum is exhibited by adding aluminum to 0.3% by weight or more, and is not sufficiently exhibited by adding less than 0.3% by weight. However, even if added in excess of 2.0% by weight, there is no effect according to the added amount, and rather, hot forgeability and machinability are reduced. For these reasons, the addition amount of aluminum is set to 0.3 to 2.0% by weight.

In the case of known brass such as "JIS C3771", when exposed to high temperatures, the zinc component in brass and oxygen in the atmosphere combine to form zinc oxide (ZnO). Unlike the above-mentioned aluminum-rich oxide film, it has no denseness and has a porous form. Oxidation (especially, oxidation of zinc) proceeds at a high speed in combination with the fact that oxygen in the atmosphere easily enters the inside of the material from the oxide film and the oxide film easily peels off. Will be. That is, by exposure to a high-temperature atmosphere, an element having a strong affinity for oxygen is selectively oxidized.When the element is aluminum, the oxide film becomes dense and strong as described above. Although the progress of oxidation can be suppressed, when the element is zinc, the progress of oxidation cannot be suppressed because the oxide film is porous and easily peeled off.

[0011] Lead does not form a solid solution in the matrix but is dispersed in the form of particles to improve machinability. Such a function of improving the machinability of lead is exhibited by adding 0.5% by weight or more. However, even if added in an amount exceeding 2.5% by weight, the effect of improving machinability saturates, and a remarkable effect corresponding to the added amount does not appear, but rather the hot forgeability is reduced. For this reason, the amount of lead added is 0.5 to
2.5% by weight.

[0012] Copper is a main element in the copper-based alloy of the present invention and forms the basis of all properties such as mechanical strength, elongation, machinability, and forgeability. It has a significant effect on hot workability (hot forgeability) and deformation strength at high temperatures. However, the hot workability and the deformation strength at high temperature are contradictory phenomena. That is, the lower the copper content, the higher the hot workability, but the lower the high-temperature deformation strength. In terms of metallographic structure, brass is an alloy composed of two phases, an α phase and a β phase, and the hot workability (hot forgeability) improves as the β phase increases. The higher the α phase, the higher the high temperature deformation strength. The ratio of the β phase satisfying both characteristics is 5% ≦ β phase ≦ 30% in the state of a forged product or a bar. This corresponds to a copper content of 61.0% by weight or more and 67.0% by weight or less. That is, when the content of copper is less than 61.0% by weight, the high-temperature deformation strength decreases, and the ductility at room temperature decreases. On the other hand, when the content of copper exceeds 67.0% by weight, hot forgeability is significantly reduced, and mechanical properties are also reduced. For this reason, the content of copper is set to 61.0% by weight to 67.0% by weight.

Incidentally, such properties of copper are greatly affected by the addition amount of other elements. For example, even when a small amount of aluminum is added, a remarkable increase in the β phase is recognized. Thus, the properties of copper are greatly influenced by the correlation between the copper content (W ₁ % by weight), the aluminum content (W ₂ % by weight) and the lead content (W ₃ % by weight). As a result of many experiments and researches by the inventor, the above relationship was considered to be 6 in order to maximize the characteristics.
It has been found that it is extremely effective that 0.0 ≦ W ₁ −3 · W ₂ + 0.6 · W ₃ ≦ 62.0. That is,
The contents of copper, aluminum, and lead are in the above-described range (copper: 61.0%) on the assumption that such a relationship is satisfied.
To 67.0% by weight, aluminum: 0.3 to 2.0% by weight, lead: 0.5 to 2.5% by weight) is extremely effective in improving high-temperature characteristics. Become.

By adding (co-adding) chromium, titanium, and phosphorus together with aluminum, there is a function of further improving the denseness of the very thin aluminum oxide film generated by the initial high-temperature oxidation. In addition, chromium, titanium, and phosphorus improve the heat resistance or the strength under high-temperature conditions by increasing the solid solution in the matrix, thereby increasing the high-temperature deformation strength, and increase the mechanical strength at room temperature. There is also. Such a function can be achieved by adding 0.02 to chromium and titanium regardless of whether they are added alone or co-added.
% Or more, and about 0.01% by weight or more for phosphorus. However, such a function is saturated at 0.5% by weight for chromium and titanium and at 0.2% by weight for phosphorus, and an effect corresponding to the added amount cannot be expected even if it is added excessively. Excessive addition beyond such a saturated state of the function will rather decrease hot forgeability and machinability. From such a point, irrespective of whether it is added alone or co-added, 0.02-0.5% by weight of chromium, 0.02-0.5% by weight of titanium, and 0.01-0.5% by weight of phosphorus.
0.2% by weight was regarded as an appropriate addition amount.

[0015]

EXAMPLE As an example, an ingot (having a cylindrical shape with an outer diameter of 100 mm and a length of 150 mm) having the composition shown in Tables 1 and 2 was extruded into a round bar having an outer diameter of 20 mm while hot (750 ° C.). The copper-based alloy of the present invention (hereinafter referred to as “inventive alloy”) No. 1 to
No. 21 was obtained.

As a comparative example, an ingot having the composition shown in Table 3 was hot-extruded under the same conditions (ingot shape and extrusion conditions) as in the above example, and the extruded material (a round bar having an outer diameter of 20 mm) was obtained. ) Is cooled to room temperature to obtain a copper-based alloy (hereinafter referred to as “comparison alloy”) having a composition outside the scope of the present invention.
o. 31-No. 37 was obtained. In addition, due to the alloy composition, the comparative alloy No. No. 31 is “JIS C3771”. No. 32 corresponds to “JIS C3604” and Comparative Alloy No. Reference numerals 33 correspond to “JIS C3712”, respectively. In addition, the comparative alloy No. 34-No. 37 is
The composition of "JIS C3711" is aluminum,
This corresponds to the addition of titanium, chromium, and phosphorus. In addition,
Invention Alloy No. 1 to No. 21 and Comparative Alloy No. 3
2, No. In the case of _No. 33, between the copper content (W ₁ % by weight), the aluminum content (W ₂ % by weight) and the lead content (W ₃ % by weight), 60.0 ≦ W ₁ -3 · W ₂ + 0.6W
There is a relationship of ₃ ≦ 62.0.

[0017] Inventive alloy No. 1 to No. No. 21 was compared with the alloy No. 21 for comparison. 31-No. In order to confirm in comparison with 37, a cutting test using the following drill was performed, and the cutting force (torque and thrust) acting on the workpiece
The machinability was determined according to.

That is, each alloy No. 1 to No. 21 and No. 21. 31-No. A first test piece (length: 30 mm) cut and sampled from 37 was set on a commercially available AST type rotary tool dynamometer (AST-BM type, manufactured by Miho Electric Co., Ltd.), and a drill was formed on the first test piece. Diameter: 3.5 mm, drill rotation speed: 1250 rpm. , Drill feed (axial feed): 0.17 mm / rev. Drilling is performed under the conditions described above, and the torque (kg
f · cm) and thrust (kgf). In addition,
The AST type rotary tool dynamometer has a thrust transducer for detecting elastic strain caused by thrust from a drill with a resistance strain gauge and a torque transducer for detecting elastic strain caused by torque from a drill with a strain gauge. In this method, the cutting force acting on the first test piece at the time of drilling with a drill can be simultaneously measured separately for rotational force (torque) and thrust (thrust).

The torque and thrust measured by the AST type rotary tool dynamometer were as shown in Table 4. As is clear from the results of the cutting test shown in Table 4, the alloy No. 1 of the present invention. 1 to No. Comparative alloy No. 21 is the most excellent in machinability. Compared to 32, the cutting force (torque and thrust) is less than twice, and good cutting can be performed. From this, it is understood that the copper-based alloy of the present invention has machinability that is sufficiently satisfactory industrially.

Next, the invention alloy No. 1 to No. The hot workability and mechanical properties of Comparative Alloy No. 21 31-N
o. The following hot compression test and tensile test were carried out to confirm by comparison with 37.

That is, each alloy No. which is a round bar extruded material (outer diameter 20 mm). 1 to No. 21 and No. 21. 31-N
o. From No. 37, round bar-shaped second to fourth test pieces which were ground to an outer diameter of 15 mm and cut to a length of 24 mm were obtained. And in the hot compression test, each second
The test piece was heated to 725 ° C., held for 30 minutes, and then compressed in the axial direction at a compression ratio of 75% (compressed until the height (length) of the second test piece was reduced from 24 mm to 6.0 mm). ,
The surface morphology (deformability at 725 ° C.) after compression was visually determined.
The results were as shown in Table 4. 725 ° C
Judgment of the deformability was performed based on whether or not a visible crack was generated on the side surface of the second test piece. In Table 4, the case where no crack was generated is indicated by "O",
Those having cracks are indicated by "x". In addition, each third
A normal tensile test was performed on the test piece, and its tensile strength (N / mm ² ) and elongation (%) were measured. The results were as shown in Table 4.

From the results of the hot compression test and the tensile test shown in Table 4, the alloy No. 1 of the invention was obtained. 1 to No. No. 21 did not cause any cracks and was confirmed to have excellent hot workability. For tensile strength and elongation,
Comparative alloy No. 31-No. It was confirmed that it was equal to or more than 37 and excellent in mechanical properties.
Therefore, it is understood that the copper-based alloy of the present invention can be hot-worked (hot-forged) into a complicated shape in practical use.

Each of the fourth test pieces (outer diameter 15 mm, length 24 mm) obtained as described above was heated and held at 500 ° C. and 550 ° C. for 2 hours, and then subjected to a compression test to determine the deformation strength ( N / mm ² ), that is, the high-temperature deformation strength was determined. The results are as shown in Table 5, and the results of Invention Alloy No. 1 to
No. The hot deformation strength of No. 21 was about 1.5 times that of the comparative alloy at the same temperature. In addition, the invention alloy No. 1 to N
o. In all cases, the deformation strength at 550 ° C. of Comparative Alloy No. 21 was 550 ° C. 31-No. 37 exceeds the deformation strength at 500 ° C. From these points, it is understood that the copper-based alloy of the present invention does not thermally deform even under a high temperature condition of 500 ° C. or more and has a sufficient heat resistance.

In addition, the invention alloy No. 1 to No. The high-temperature oxidation resistance of Comparative Alloy No. 21 31-No. The following oxidation test was carried out to confirm by comparison with 37.

That is, with a round bar extruded material (outer diameter 20 mm)
Certain alloy Nos. 1 to No. 21 and No. 21. 31-N
o. From 37, the surface is ground so that the outer diameter becomes 14 mm.
And a round bar-shaped fifth test piece cut to a length of 30 mm
And the weight of each fifth test piece (hereinafter referred to as “weight before oxidation”).
Was measured. Thereafter, each of the fifth test pieces is placed in a magnetic crucible.
And kept at 500 ° C and 550 ° C
It was left in the electric furnace. Then, when left for 7 days,
Removed from the furnace, and weighed each fifth test piece (hereinafter referred to as “oxidized
Weight), and the weight before oxidation and the weight after oxidation.
From the amount, the oxidation increase was calculated. Here, the oxidation increase is
Surface area of the fifth test piece 10 cm^TwoIncrease due to peroxidation
It indicates the degree of weight (mg) and is expressed as "oxidized weight increase (m
g / 10cm ^Two) = (Weight after oxidation (mg) −weight before oxidation)
(Mg)) x (10 cm^Two/ Surface area of test piece (c
m^Two)). That is, each
The weight after oxidation of the fifth test piece is greater than the weight before oxidation
However, this is due to high temperature oxidation. In other words, high temperatures
When exposed, oxygen combines with copper, zinc, and aluminum.
Cu _TwoO, ZnO, Al_TwoO_ThreeAnd the oxygen increment
The weight increases. So this increase
The lower the weight (increase in oxidation), the better the high-temperature oxidation resistance
And the results shown in Table 5 were obtained.

As is clear from the results of the oxidation test shown in Table 5, the alloy No. 1 of the present invention was obtained. 1 to No. The oxidation increase of 21 is 5
At both the 00 ° C and the 550 ° C, the comparative alloy No. 31-No. It is significantly less than 37. In addition, invention alloy No. 1 to No. 21 at 550 ° C
The oxidation increase in Comparative Alloy No. 31-No. 37
Is equivalent to the increase in oxidation at 500 ° C.

When a Cu—Zn alloy is oxidized at a high temperature, the zinc component in the alloy is selectively oxidized to form an oxide layer on the surface of the alloy. Since this layer is extremely thin, it is difficult to measure the layer thickness even with a microscope. However, the zinc in the oxide layer is obtained by diffusing zinc existing in the matrix near the surface of the alloy by oxidation, and the oxidation reduces the zinc near the surface of the alloy. That is, when the zinc component decreases, the zinc-rich β phase disappears and changes to a single α phase. Therefore, the degree of high-temperature oxidation can be determined based on the thickness of the α single phase region, that is, the thickness of the α single phase layer.
Therefore, in order to more accurately confirm the high-temperature oxidation property, the oxidation increase of each fifth test piece heated in an electric furnace was measured as described above, and the thickness of the α single phase layer was further measured.

That is, each of the fifth test pieces whose weights were measured after oxidation (the test pieces heated to 500 ° C. and the
) Was cut at an appropriate position, and the thickness (μm) of the α single-phase layer was measured at the cut surface. The results were as shown in Table 5.

As apparent from the measurement results of the thickness of the α single phase layer shown in Table 5, the comparative alloy No. 31-No.
With regard to the alloy No. 37, although the α single-phase layer was extremely thick even when heated at 500 ° C., 1 to N
o. The thickness of the α-single-phase layer of No. 21 was less than 5 μm for those heated and held at 500 ° C., and most of those also kept at 550 ° C. were 5 μm or less,
The largest one is only 20 μm. In particular, the invention alloy No. to which chromium, titanium, and phosphorus were added was used. 9-No. In the case of No. 21, both the increase in oxidation and the thickness of the α single phase layer are extremely small.

From the measurement results of the increase in oxidation and the thickness of the α-single-phase layer, the copper-based alloy of the present invention is extremely excellent in high-temperature oxidation resistance, and the vaporizer which tends to be used at a high temperature as described at the beginning. It is understood that it can be used very suitably as a constituent material of various parts such as nozzles and products.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

As can be easily understood from the above description, the copper-based alloy of the present invention has not only hot forgeability and machinability but also heat resistance such as high temperature oxidation resistance and high temperature deformation strength. It is extremely suitable as a constituent material for various parts and products used under high-temperature conditions (for example, oil vaporizer nozzles for gas / gas hot air heaters, gas stoves, burner heads, etc.). The practical value is extremely large.

Claims (3)

[Claims] 1. Copper 61.0 to 67.0% by weight, aluminum 0.3 to 2.0% by weight and lead 0.5 to 2.5% by weight.
A copper-based alloy having an alloy composition consisting of zinc and the balance being zinc. 2. 0.02 to 0.5% by weight of chromium, 0.02 to 0.5% by weight of titanium and 0.01 to 0.2% by weight of phosphorus.
The copper-based alloy according to claim 1, further comprising at least one element selected from the group consisting of: 3. The value of 60.0 ≦ W ₁ -3 · W ₂ between the copper content (W ₁ % by weight) and the aluminum content (W ₂ % by weight) and the lead content (W ₃ % by weight). + 0.6 · W ₃ ≦ 6
The copper-based alloy according to claim 1, wherein the copper-based alloy has a relationship of 2.0.