HK1031132B - Nickel-free white copper alloy material - Google Patents

Description

White copper alloy material without nickel

The present invention relates to a nickel-free (nickel-free) white copper alloy material having excellent strength, hardness, ductility, workability, and corrosion resistance. The copper alloy is suitable for use, for example, as a member on a slide fastener, a slider, a plug, etc.; or as an accessory for clothing such as a metal button, a clothing binding, or as a trim suitable for a hanging ornament or a breast ornament; or as spectacle frames, which do not cause allergy (skin allergy) problems and have a high-grade white tone.

Conventional copper alloys used for the above-mentioned fasteners include copper-nickel-zinc alloys, such as nickel-silver alloys having a white alloy color, copper-zinc alloys represented by red brass and brass, and the like. The nickel silver alloy has excellent corrosion resistance because it contains nickel as an alloy component. However, when it is used as a slide fastener, since the slider of the slide fastener is frequently in contact with the skin of a human body, an allergic problem due to nickel is generated. On the other hand, copper-zinc alloys typified by red brass or brass do not contain nickel, and therefore do not cause the problem of the allergy of nickel. However, the copper-zinc alloy containing no nickel tends to be yellowish in color tone, and a white alloy cannot be obtained.

On the other hand, various alloys having a white color tone have been proposed. Although these alloys are whitened by slight modification of the alloy composition, it is a yellowish or reddish white tone, and the tone of the alloy is thus altered. In addition, consumer needs are also different. In some cases, a slightly yellowish or reddish white hue is desired, and manufacturers respond to such a need. The problem is that it is desirable to provide a white material free of nickel, which meets the requirements for mechanical properties for use in various applications, regardless of whether the hue varies slightly. However, in the past, problems have been presented when such materials are provided in the form of alloys: it is difficult to provide an alloy that can satisfy both the color tone and the mechanical properties.

Therefore, one object of the present invention is: to provide a white copper alloy material which is excellent in strength and hardness comparable to those of nickel silver and which is excellent in workability, corrosion resistance and white tone in addition to excellent ductility; in addition, the copper alloy of the present invention does not have an allergic problem because it does not contain nickel. The present invention also provides a white copper alloy material that can be finely adjusted in color tone according to the needs of consumers while obtaining satisfactory color tone and mechanical properties.

The invention includes several aspects as follows:

(1) a white copper alloy material containing no nickel, characterized in that a white coating layer containing no Ni nickel is formed on a base material composed of an alloy represented by the following general formula:

Cu_aZn_bMn_cM_dX_e

wherein M is at least one element selected from Al and Sn; x is at least one element selected from the group consisting of Si, Ti and Cr; b. c and d respectively represent the following weight percentages: 0. ltoreq. b < 22, 7. ltoreq. c.ltoreq.20, 0. ltoreq. d.ltoreq.5, and 0. ltoreq. e.ltoreq.0.3, a representing the balance, the alloy occasionally containing some unavoidable elements.

(2) A nickel-free white copper alloy material according to (1), wherein M is Al, and b, c and d respectively represent the following weight percentages: b is more than or equal to 0.5 and less than 5, c is more than or equal to 7 and less than or equal to 17, and d is more than or equal to 0.5 and less than or equal to 4.

(3) A nickel-free white copper alloy material as defined in (1) or (2), wherein the coating layer of the base material has a defined a of JIS Z8729 representing a color tone^*、b^*A value in the range of-2 < a^*＜5，-3＜b^*＜16。

(4) A nickel-free white copper alloy material as defined in (1) or (2), wherein the coating layer has a defined a of JIS Z8729 representing a color tone^*、b^*A value in the range of-2 < a^*＜3，-3＜b^*＜15。

In the composition of the alloy matrix material of the invention, Zn plays a role in improving the mechanical properties of the alloy through the solid solution strengthening effect (solid solution strengthening effect) of Zn, and simultaneously, the manufacturing cost of the alloy is reduced. If the Zn content is more than 22%, the season cracking resistance of the alloy is lowered and the crystal structure starts to become alpha + beta phase, whereby it is difficult to obtain satisfactory cold workability. If the Zn content is 5% or more, the solid solution coexistence temperature range of the alloy becomes wide, the macrosegregation phenomenon is easily accelerated, the heat conduction property is deteriorated, and the productivity is deteriorated. Further, by limiting the Zn content to less than 5%, the above-mentioned problem of the deterioration of the season cracking resistance of the alloy is not at all caused even if the element X mentioned below is added, and the alloy can be maintained in a more stable state. By setting the Zn content to 0.5% or more, the effects of reducing the cost and increasing the strength can be expected. For these reasons, it is preferable that the Zn content is set in the range of more than 0.5% or more to less than 5%. In order to obtain the above-mentioned effect more remarkably, it is more preferable that the upper limit of the Zn content is set to 4%.

Mn functions to improve mechanical characteristics of the alloy by a solid solution strengthening effect, and at the same time, to reduce the manufacturing cost of the alloy. Further, the addition of Mn alloy in the above-mentioned specific amount as a substitute for Zn in whole or in part can improve the season cracking resistance and prevent the color tone of the alloy from becoming excessively yellowish. The addition of Mn also has the effect of lowering the melting point of the alloy. Thereby improving the castability of the alloy and inhibiting evaporation of Zn from the metal melt.

If Mn is added in an amount less than 7%, this will result in yellowing of the alloy tone. On the contrary, if the Mn content is more than 23%, the crystal structure develops into α + β phase, which makes it impossible to obtain satisfactory cold workability. The upper limit of the Mn content is preferably 15%.

Al and/or Sn have the following functions: the season cracking resistance of the alloy is improved by forming a stable oxide film on the surface of the alloy. Al and/or Sn also have the effect of improving the mechanical properties of the alloy by a solid solution strengthening effect, and also have the effect of reducing the cost. The lower limit of the amount of Al and/or Sn added is 0.5%. However, if the amount of Al and/or Sn added is too low, the season cracking resistance and strengthening effect of the alloy will be insufficient. On the other hand, if the amount of Al and/or Sn added is more than 5%, cold workability becomes unsuitable as the crystal structure progresses to the α + β phase. Preferably, the amount of Al added is 2% or less.

General formula Cu_aZn_bMn_cAl_dX_eThe element X (at least one element selected from the group consisting of Si, Ti and Cr) in (A) has the following effects: when the alloy is smelted, a coating layer is formed on the surface of the metal melt, and the X element also hasPreventing Mn from oxidizing and Zn from evaporating. Further, by forming a stable oxide coating layer on the surface of the alloy, it is possible to prevent Mn from being removed during annealing and to improve the season cracking resistance of the alloy, and at the same time, it is possible to prevent the color tone from changing with time during the oxidation of Mn.

The amount of the element X added may be any value less than 0.3%. However, if the addition amount of X is too small, sufficient effects as described above cannot be obtained. Therefore, the amount of the X element added is preferably 0.02% or more. If the amount of the X element added is more than 0.3%, the X element and other elements in the alloy form intermetallic compounds, so that the cold workability is lowered.

The base material alloy of the present invention is composed of a single alpha phase, so that sufficient cold workability can be ensured. If the composition of the alloy material components exceeds the above-mentioned composition range in the present invention, the crystal structure of the alloy is easily transformed into the α + β phase, which deteriorates the formability thereof.

As an alloy system of the base material usable in the present invention, an alloy having a general formula as described below can be applied:

general formula I: cu_balMn_7-20

General formula II: cu_balMn_7-20Al_0.5-5

General formula III: cu_balMn_7-20Zn_0-22(wherein the Zn content does not include 0)

General formula IV: cu_balMn_7-20Zn_0-22Al_0.5-5(wherein the Zn content does not include 0)

General formula V: cu_balMn_7-20Zn_0-22Al_0.5-5X_0-0.3(wherein X is at least one element selected from the group consisting of Si, Ti and Cr, and the contents of Zn and X do not include 0.)

Among the above formulas I-V, a particularly useful series of alloys are those of the following formulas VI and VII:

general formula VI: cu_balZn_0.5-5Mn_7-17Al_0-4X_0-0.3(wherein X is at least one element selected from the group consisting of Si, Ti and Cr, the content of Zn does not include 5, and the contents of Al and X do not include 0)

General formula VII: cu_balZn_5-22Mn_7-17Al_0-4X_0-0.3(wherein X is at least one element selected from the group consisting of Si, Ti and Cr, the content of Zn does not include 5, and the contents of Al and X do not include 0)

The alloy material of formula VI is most effective in view of the mechanical properties of the alloy, while it is more preferable for the alloys of formula VI and formula VII that the alloy material contains 0.5% or more of Al.

The color tone range of the alloy material of the invention is-2 < a^*＜5，-3＜b^*< 16. They are color charts based on the L a b color series defined in JIS Z8729.

Note that the alloy chromaticities described in the present specification are expressed as a psychological lightness index L (lightness; L-star) and two psychological chromaticity indices, i.e., a (greenish-reddish; a-asterisk) and b (bluish-yellowish; b-asterisk). The psychological brightness index and the psychological chromaticity index are expressed by a method for expressing the color of an object defined in JIS Z8729. In particular, in an alloy, in order to exhibit a white color which is a feature of the present invention, it is preferable that the color is close to achromatic (colorless), in which case the psychological color index a is as described above^*And b^*The value of (b) is the above range.

In the present invention, a color close to achromatic color is particularly preferable. In this case, it is particularly effective that the color tone of the coating layer has a color index a defined in JIS Z8729^*And b^*When the value is expressed, it is-2 < a^*＜3，-3＜b^*A range of < 15.

The coating layer having the color tone is an Sn plating layer, a Cr plating layer, an Ag plating layer or a Cu-Sn plating layer. Any plating layer other than the above-mentioned plating layers may be applied as long as the above-mentioned plating layer can take the form of the above-mentioned color tone.

In the present invention, a color close to achromatic color is particularly preferable. In this case, it is particularly effective that the color tone of the coating layer has a color index a defined in JIS Z8729^*And b^*When the value is expressed, it is-2 < a^*＜3，-3＜b^*A range of < 15.

In the case of forming the coating layer by an electroplating method, the above method may be wet plating. Dry plating is also possible. For example, as the wet plating method, electrolytic plating, electroless plating, melt plating, or the like may be used, and as the dry plating method, Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), or the like may be used.

The effective range of the thickness of the coating layer is 0.001 to 10 μm. If the coating layer is less than 0.001 μm in thickness, the effect of coating the base material cannot be expected, and also, for example, in the case of use as a slide fastener, abrasion at the time of sliding of the slider is considered to be caused. The thickness of the coating layer is not limited. However, in view of production cost, the thickness of the coating layer exceeding 10 μm will be too large and not effective.

When the coating layer is applied to a post-processing such as cutting or bending, the thickness of the coating layer is preferably in the range of 0.005 to 5 μm in consideration of the possibility of abrasion, cracking, or the like due to the post-processing. If the thickness of the coating layer is less than 0.005 μm, the coating layer is liable to be mechanically peeled off or abraded after post-processing such as cutting or bending. On the other hand, if the coating thickness is more than 5 μm, cracking or the like is likely to occur in the post-processing. In the coating layer not subjected to the post-processing, the thickness of the coating layer is preferably in the range of 0.001 to 10 μm from the economical point of view. For example, in a manufacturing process of a fastener element, a metal wire whose section is Y-shaped is manufactured, and then, the wire is cut into a predetermined size. The cut wire material is caulked and fixed to one side edge of a fastener chain tape to obtain a fastener chain. After the coating layer is formed on the wire rod having the Y-shaped cross section, the wire rod is cut or bent as described above, and then the coating layer is formed to have a thickness of preferably 0.005 to 5 μm in consideration of the post-processing. However, when the coating layer is formed on the member portion of the fastener chain, the thickness of the coating layer may be in the range of 0.001 to 10 μm since post-processing is not necessary to be considered.

The present invention will be described in more detail below with reference to examples.

(base Material of the invention)

The test materials of the base materials 1 to 14 of the present invention shown in Table 1 and the base materials 1 to 9 of the present invention shown in Table 2 were prepared and evaluated in the following manner.

Weighing pure Cu (99.9%), pure Zn (99.9-99.99%), pure Mn (99.9%), pure Al (99.9%), pure Ti, pure Si and pure Cr for preparing a predetermined composition of 200cm³Batches of ingot components. Each batch was melted in a high-frequency induction furnace under argon (100mmHg) and, after holding for 4 minutes, poured into a copper casting mold (. phi.40 mm. times.28 mm in length). Casting the obtained ingot (200 cm)³) Cutting into alloy blank with length of about 70mm, and extruding. And extruding and molding the alloy blank under the conditions that the temperature of the alloy blank is 800 ℃ and the temperature of a container is 600 ℃. Next, the resulting extruded material (8 mm. times.1300 mm) was heat-treated at 800 ℃ for 1 hour, and then cooled in an oven (the above-mentioned treatment process is hereinafter referred to as "heat treatment"). The extruded material (metal wire rod) subjected to the above heat treatment was used as a base material for the test.

TABLE 1

		The weight of the alloy composition								Color tone			Structure of the product	Hardness (Hv)	Cracking after 80% deformation	Degree of color change	Resistance to season cracking
																		Examples		Cu	Zn	Mn	Al	Ti	Si	Cr	Ni	Color tone	a*	b*
1	Balance of	2.5	14	1	-	-	-	-	White colour (Bai)	3.09	9.66	α	110	○	6.09	○
																	2		Balance of	3	15	2	-	-	-	-	White colour (Bai)	3.12	9.78	α	113	○	6.48	○
3	Balance of	2	10	1	-	-	-	-	White colour (Bai)	4.52	10.27	α	105	○	6.15	○
																	4		Balance of	4	15	1	-	-	-	-	White colour (Bai)	3.01	7.75	α	114	○	6.24	○
5	Balance of	4	7	1	-	-	-	-	White colour (Bai)	3.08	9.63	α	113	○	6.12	○
																	6		Balance of	4	15	0.5	-	-	-	-	White colour (Bai)	2.86	9.41	α	113	○	6.23	○
7	Balance of	1	14	1.5	-	-	-	-	White colour (Bai)	3.03	9.73	α	111	○	6.93	○
																	8		Balance of	2.5	14	1	0.05	-	-	-	White colour (Bai)	2.89	9.09	α	101	○	6.73	○
9	Balance of	2.5	14	1	-	0.05	-	-	White colour (Bai)	3.00	9.87	α	102	○	5.17	○
																	10		Balance of	3	14	1	-	-	0.02	-	White colour (Bai)	3.03	9.66	α	101	○	5.49	○
11	Balance of	2.5	13	1	-	0.1	-	-	White colour (Bai)	3.62	7.07	α	131	○	7.15	○
																	12		Balance of	2	14	1	-	0.3	-	-	White colour (Bai)	3.29	9.40	α	154	○	7.52	○
13	Balance of	2.5	12	1	-	0.05	0.02	-	White colour (Bai)	3.53	8.18	α	130	○	8.53	○
																	14		Balance of	2.5	14	1	0.05	0.05	-	-	White colour (Bai)	3.30	8.33	α	172	○	5.86	○

TABLE 2

		The weight of the alloy composition								Color tone			Structure of the product	Hardness (Hv)	Cracking after 80% deformation	Degree of color change	Resistance to season cracking
																				Cu	Zn	Mn	Al	Ti	Si	Cr	Ni	Color tone	a*	b*
Base material	1	Balance of	9	14	1	0.3	-	-	-	White colour (Bai)	2.38	7.54	α	136	○	5.67	○
																		2	Balance of	9	14	1	-	0.3	-	-	Yellow colour	2.44	8.19	α	129	○	6.43	○
	3	Balance of	10	15	1	-	-	0.02	-	White colour (Bai)	2.40	7.68	α	123	○	5.94	○
																		4	Balance of	17	13	0.5	0.1	-	-	-	White colour (Bai)	1.65	7.51	α	115	○	6.23	○
	5	Balance of	14	10	1	-	0.1	0.02	-	White colour (Bai)	0.46	14.23	α	142	○	5.34	○
																		6	Balance of	17	8	1	0.3	-	-	-	Yellow colour	0.25	12.98	α	129	○	5.67	○
	7	Balance of	18	10	2	-	0.2	-	-	White colour (Bai)	0.32	10.41	α	126	○	6.65	○
																		8	Balance of	20	8	1	-	0.05	0.02	-	White colour (Bai)	0.04	12.68	α	143	○	5.23	○
	9	Balance of	18	10	2	005	0.05	-	-	White colour (Bai)	0.38	10.35	α	138	○	5.72	○

The test base material obtained above was mirror-polished with SiC polishing paper and a diamond paste, and tested using a color difference meter (CR-300, manufactured by Minolta corporation). The test results are represented by L, a, and b as defined in JIS Z8729.

All of the test materials (base materials) of the present invention have a white color tone and can be used for the fastener element portion, thereby obtaining a fastener element having a high-grade feeling.

Furthermore, in each of the alloys of the present invention produced by the above-described method, it can be seen that the test materials shown in Table 2 have a value of a of 3 or less than 3, and thus show a nearly and achromatic white hue.

The microstructure of each of the test materials (base materials) obtained as above was observed. The test materials of the present invention are all single alpha phase alloy compositions and provide good cold workability. If a second phase is present in the alloy, cracking or the like occurs during cold working. However, in the matrix material of the present invention, the above-described phenomenon such as cracking is not observed. In particular, when the fastener element is applied to a fastener member, the Y-shaped attachment is caulked and fixed to clothes. The zipper accessory made of the material can be firmly attached to clothes without cracking and the like.

Hardness (Hv) represents the value of DPN measured with a Vickers microhardness tester under a load of 25 g. It can be seen that the material of the embodiment of the present invention has hardness equal to or greater than that of nickel silver alloy currently used as a fastener fitting, and has excellent mechanical properties such as high strength, high hardness, etc., suitable for use as a fastener fitting.

Further, by a cold compression test, the above test material (base material) was subjected to a strain of 80%, and the presence or absence of cracking of the surface was observed.

In tables 1 and 2, the "∘" mark means that there was no cracking on the surface of the base material, and it is clear that there was no cracking at all in the example materials of the present invention. Thus, when used in a fastener fitting such as a slide fastener, as described above, the cold working method generates a strain of at most 80% when the fastener fitting is attached to clothing. It is clear, however, that although cold working produces a strain of up to 80%, the base material of the present example does not suffer any cracking problems.

The color change resistance was measured by subjecting the test material (base material) obtained above to mirror polishing with-SiC polishing paper and a diamond paste, and then subjecting the resulting material to a constant temperature and humidity test in an atmosphere of 80 ℃ and 90% RH. Then, the resistance to discoloration of the surface of the sample material was measured by a color difference meter. The discoloration resistance was evaluated by substituting the values before and after the constant temperature and humidity test into the following formula and calculating the values.

(wherein a, b and L are indices before constant temperature and humidity test, and a ', b ' and L ' are indices after constant temperature and humidity test.)

As is apparent from the test results shown in tables 1 and 2 above: the materials of the embodiments of the present invention give smaller values in the above equations and therefore have excellent anti-discoloration properties. From this fact can be understood: when the material of the present invention is used as a fastener component such as a fastener component, it shows high resistance to discoloration when washed with hot water. In this test, the hot water washing was carried out under the standard washing conditions of warm water washing in europe.

The season cracking resistance was evaluated as follows. In the cold press test, the test material was strained 80% and exposed to ammonia from a 12.5% ammonia solution. The material was observed for surface cracking after exposure to ammonia. In tables 1 and 2, the "∘" mark means that there was no cracking on the surface of the material, and it can be understood that there was no cracking at all in the materials of the examples of the present invention. It can thus be understood that: the present invention can provide a material that: the material is free from cracking due to strain even when used as a fastener fitting such as a fastener element to be inserted into and fixed to clothing. Among these tables, although tables 1 and 2 show excellent season cracking resistance, the materials shown in table 1 show particularly excellent results than those shown in table 2.

As the extruded material (metal wire) of the test material obtained as described above, there are, for example, a round metal wire whose sectional shape is a circle, a straight-angled metal wire whose sectional shape is a rectangle, and a deformed metal wire whose sectional shape is an irregular shape. In addition, the metal wire rod having a circular or rectangular shape is rolled in multiple stages to obtain a deformed metal wire rod having a gradually changing cross-sectional shape. Such metal wire materials can be used directly (without forming a coating layer) for a slide fastener member, slider, and plug; and buttons and fastening buttons used on the clothes; accessories for spectacle frames, accessories for rings or earrings; or materials which may come into contact with a human body such as a pen tip for a ballpoint pen. In the present invention, the coating layer is formed on the base material as described below, also in consideration of the design and mechanical properties.

Example 1

A Cu-based alloy is prepared by the same method as the above-mentioned method for preparing a base material_balZn₃Mn₁₃Al₁Si_0.05(wt.%) of a metal wire rod having a Y-shaped cross-section. And performing Sn electroplating on the metal wire rod by an electroless plating method in an acid bath with Sn concentration of 14-24g/l at the temperature of 48-52 ℃ to form the coating layer.

Example 2

In acid bath with Sn concentration of 30-80g/l at 15-50 deg.C and 2-100A/dm²The metal wire material formed in example 1 was subjected to Sn plating by an electroless plating method to form a coating layer.

Example 3

A Cu alloy was prepared in the same manner as in example 1_balZn₁₆Mn₁₃Al₁Gold having a Y-shaped cross-sectionBelongs to a wire. In an acid bath with Ag concentration of 0.8-40g/l, at 20-30 deg.C and 0.5-4A/dm²The current density of (2) is obtained by applying Ag plating to the metal wire by electroless plating to form a coating layer.

Example 4

A Cu alloy was prepared in the same manner as in example 1_balZn₁Mn₁₀Al₁Si_0.03(wt.%) of a metal wire rod having a Y-shaped cross-section. At a Cu concentration of 10.5g/l, a Sn concentration of 35.0g/l, a temperature of 60 ℃ and a temperature of 0.5A/dm²The metal wire is subjected to Cu-Sn plating by an electroless plating method under the condition of the current density of (1) to form a coating layer.

Each of the metal wires of examples 1 to 4 on which the coating layer was formed was cut into a set size. The cut wire was caulked and fixed to the side edge portion of the tape for a fastener chain to obtain a fastener chain. Evaluation was performed as follows.

Example 5

A Cu alloy was prepared in the same manner as in example 1_balZn₁₇Mn₁₄Al₁(wt.%) of a metal wire rod having a Y-shaped cross-section. Each wire rod is cut into a set size. The cut wire was caulked and fixed to the side edge portion of the tape for a fastener chain to obtain a fastener chain. Then, a Sn plating coating layer was formed under the same conditions as in example 1.

Example 6

An Sn plated coating layer was formed on the fastener chain of example 5 under the same conditions as in example 2.

Example 7

A Cu alloy was prepared in the same manner as in example 1_balZn₂Mn₁₂Al₁Si_0.05(wt.%) of a metal wire rod having a Y-shaped cross-section. This was used to form a fastener chain in the same manner as in example 5. Then, in the same way asAn Ag plated coating layer was formed under the conditions of example 3.

Example 8

A Cu alloy was prepared in the same manner as in example 1_balZn₃Mn₁₃Al₁Si_0.05(wt.%) of a metal wire rod having a Y-shaped cross-section. The wire was used to form a fastener chain in the same manner as in example 5. Then, a Cu — Sn plating coating layer was formed under the same conditions as in example 4.

Comparative example 1

A Cu alloy was prepared in the same manner as in example 1_balZn₁₅(wt.%) of a metal wire rod having a Y-shaped cross-section. The wire was used to form a fastener chain in the same manner as in example 5. Then, a Sn plating coating layer was formed under the same conditions as in example 1.

Comparative example 2

The coating layer was plated with Sn under the same conditions as in example 2 for the slide fastener chain of comparative example 2.

Comparative example 3

A Cu alloy was prepared in the same manner as in example 1_balZn₃₀(wt.%) of a metal wire rod having a Y-shaped cross-section. The wire was used to form a fastener chain in the same manner as in example 5. Then, an Ag plating coating layer was formed under the same conditions as in example 3.

Comparative example 4

A Cu alloy was prepared in the same manner as in example 1_balZn₂₄Ni₁₃(wt.%) of a metal wire rod having a Y-shaped cross-section. This was used to form a fastener chain in the same manner as in example 5. Then, a Cu — Sn plating coating layer was formed under the same conditions as in example 4.

The fastener chains for slide fasteners obtained in example-8 and comparative examples 1-4 were subjected to corrosion resistance, decorative property and Ni allergy tests.

The corrosion resistance test was performed in such a manner that: the metal wire was exposed to an atmosphere of 80 ℃ at one atmosphere and 90% RH for 2 hours. The constant temperature and humidity test was performed, and after the test, the change in chromaticity (discoloration) of the surface of the part was visible to the naked eye. In the evaluation, a part which was visually recognized and had a change in chromaticity due to the test was marked as "x", and a part on which a change in chromaticity was not visually recognized was marked as "o". The decorative test was carried out as follows: the slider of the slide fastener was attached to the pair of fastener chains obtained as described above, and the fastener chain was subjected to a durability test of 3000 times of reciprocal opening and closing, and it was visually observed whether or not the base material was exposed from the coating layer. The evaluation was that the fastener chain with the exposed surface of the base material was visually observed after the test and marked as "x", and the fastener chain with the unexposed surface of the base material was visually observed after the test and marked as "o".

The nickel allergy test was carried out by attaching a slider for a slide fastener to a pair of fastener chains obtained as described above, performing a reciprocating opening and closing durability test 3000 times, and performing the test and evaluation according to european standard EN 1811. It is evaluated as "x" when it does not satisfy european standard EN1811 and "o" when it satisfies european standard EN 1811.

The evaluation results are shown in Table 3. As can be seen from table 3, the alloy material (chain member for slide fastener) of the present invention has excellent corrosion resistance, decorativeness, and Ni allergy. In addition, the above-mentioned slide fastener chain was sewed to clothes and subjected to various wash tests, and as a result, the slide fastener chain using the alloy material of the present invention showed excellent corrosion resistance and decorative effects.

TABLE 3

	Corrosion resistance	Decorative effect	Allergic property
				Example 1 example 2 example 3 example 4 example 5 example 6 example 7 example 8	○○○○○○○○	○○○○○○○○	○○○○○○○○
Comparative example 1 comparative example 2 comparative example 3 comparative example 4	○○○○	×××○	○○○×

Further, the above-mentioned slide fastener chain is evaluated for the transverse chain tensile strength, bending property and extrusion strength, member smoothness and tensile property, sliding resistance, slider braking property, repeated opening/closing durability (M-class), etc. prescribed in JIS S3015 standard, and excellent properties similar to those of the nickel-silver alloy materials used heretofore can be obtained.

The present invention provides a nickel-free white copper alloy material, which is a white copper alloy material having excellent strength and hardness comparable to those of nickel-silver alloys, and having ductility, excellent workability, and corrosion resistance. Since the coating layer having a white color tone is formed on the base material, a copper alloy material having a color tone satisfying various needs of customers can be provided by the coating layer. Meanwhile, since the base material is white, the appearance properties of the alloy material of the present invention are not greatly impaired even if the coating layer is not formed on the base material or even if the coating layer is exposed to the base material by being subjected to peeling, cracking, or the like. Moreover, since the alloy base material and the coating layer thereof of the present invention do not contain nickel, there is no fear that the alloy material product will cause an allergic reaction when the copper alloy material of the present invention is used as, for example, a member, slider, plug, etc. on a slide fastener, or as an accessory such as a metal button, clothing fastener, etc., as an ornament such as a spectacle frame, ring, necklace, earring, etc., and a product in contact with the skin of a human body.

Claims (3)

1. A white copper alloy material containing no nickel, characterized in that a white coating layer containing no Ni and nickel is formed on a base material composed of an alloy represented by the following general formula:

Cu_aZn_bMn_cM_dX_e

wherein M is at least one element selected from Al and Sn; x is at least one element selected from the group consisting of Si, Ti and Cr; b. c, d and e respectively represent the following weight percentages: 0. ltoreq. b < 22, 7. ltoreq. c.ltoreq.20, 0. ltoreq. d.ltoreq.5, and 0. ltoreq. e.ltoreq.0.3, a representing the balance, said alloy occasionally containing oneSome inevitable elements, the base material and the coating layer having a defined a of JIS Z8729 for characterizing color tone^*、b^*A value in the range of-2 < a^*＜5，-3＜b^*＜16。

2. The nickel-free white copper alloy material according to claim 1, wherein M is Al, and b, c and d respectively represent the following weight percentages: b is more than or equal to 0.5 and less than 5, c is more than or equal to 7 and less than or equal to 17, and d is more than or equal to 0.5 and less than or equal to 4.

3. The nickel-free white copper alloy material according to claim 1 or 2, wherein the base material and the coating layer have a defined a of JIS Z8729 that characterizes color tone^*、b^*A value in the range of-2 < a^*＜3，-3＜b^*＜15。