EP3649267A1 - Zinc wrought alloy with improved coatability - Google Patents
Zinc wrought alloy with improved coatabilityInfo
- Publication number
- EP3649267A1 EP3649267A1 EP18743410.5A EP18743410A EP3649267A1 EP 3649267 A1 EP3649267 A1 EP 3649267A1 EP 18743410 A EP18743410 A EP 18743410A EP 3649267 A1 EP3649267 A1 EP 3649267A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- weight
- content
- alloy
- zinc
- wrought alloy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C18/00—Alloys based on zinc
- C22C18/04—Alloys based on zinc with aluminium as the next major constituent
Definitions
- the present invention relates to a zinc wrought alloy with improved coating properties as compared to known wrought alloys, and to the use thereof for preparing semifinished products, forgings, turned parts, locks, screw connections, locking cylinders, sleeves, fittings, pressed parts, pneumatic parts, hydraulic parts, mountings, valves and ball valves.
- EP 2675971 A “Accessory consisting of a lock accessory” may be mentioned. It discloses a zinc alloy with an Al content of from 13 to 25%, a Cu content of from 0.2 to 3.5%, and an Mg content of less than 0.1%, which is employed for lock accessories.
- EP 2 385 148 A - "Zinc alloy with high creep resistance” relates to a zinc-aluminum alloy with an Al content of 10 to ⁇ 25%, a Cu content of 0.05 to 3%, an Mg content of from 0.001 to 0.1%, an Mn content of 0.05% to 1.0% and an Si content of from 0.05 to 1%.
- the disclosed alloy has a high creeping resistance and is suitable for the furnace brazing and normal brazing of heat exchangers.
- US 3,734,785 - "Zinc forging alloy” claims a zinc-based alloy with an Al content of 9 to 22%, a Cu content of 0.5 to 1.5%, and an Mg content of 0.01 to 0.03%, which is particularly suitable for hot formability.
- EP 0 679 198 A "Method for producing Zn-AI-Cu alloy articles by centrifugal or die casting" describes a zinc alloy with an Al content of 6.0 to 8.0%, a Cu content of 3.2 to 4.3%, for preparing articles by centrifugal casting in a rubber mold, or pressure die-casting in a metal mold.
- ZAMAK ® zinc pressure die-casting alloys
- the coatability of zinc alloys is also relevant.
- Semifinished products, forgings, turned parts, locks, screw connections, locking cylinders, sleeves, fittings, pressed parts, pneumatic parts, hydraulic parts, mountings, valves and ball valves consisting of corresponding alloys are often provided with different coatings for improving the appearance and/or for improving the corrosion resistance.
- a copper- copper-nickel coating serves for both corrosion resistance and appearance.
- the coating with zinc and passivation mainly serves for a very high corrosion resistance, being an inexpensive alternative for a copper-copper-nickel coating .
- the prior art with previous zinc wrought alloys is problematic, especially in view of surface coating. It has been the object of the present invention to provide a zinc- based wrought alloy having improved coating properties as compared to the prior art. This is to be achieved without including lead in the alloy. In addition, the coating should have good corrosion properties, i.e., have as little tendency to corrosion as possible. Surprisingly, it has been found that this is enabled by a low aluminum content of at most 12% by weight in zinc wrought alloys.
- Alloying basically means the preparation of an alloy by melting a metal together with at least one other metal or non-metal . If in the present application it is referred to the fact that a metal or non-metal is not alloyed to an alloy, this means that the metal or non-metal in question is not actively added.
- the object of the present invention is achieved by the use of a zinc wrought alloy having an Al content of from 5% by weight to 12% by weight, a Cu content of from 0.1% by weight to 4% by weight, an Mg content of from 0.001% by weight to 0.05% by weight, wherein Zn is the balance to 100%, for preparing forgings, turned parts, locks, screw connections, locking cylinders, sleeves, fittings, pressed parts, pneumatic parts, hydraulic parts, mountings, valves and/or ball valves.
- the alloy according to the invention is free of zirconium.
- the surface coating of the parts prepared can be improved by limiting the aluminum content to a maximum of 12% by weight.
- Other zinc wrought alloys (as disclosed, for example, in EP 2675971 - "Accessory consisting of a lock accessory") have poorer coating properties.
- an improved adhesion strength and density of the coating could be achieved by limiting the aluminum content in zinc-aluminum-copper-magnesium alloys. This results in an improved corrosion protection. All methods of surface treatment (such as electroplating, PVD, CVD, passivation, coating, cathodic dip painting, powder coating) are suitable for the present invention without limitation.
- Alloying with lead is not necessary.
- lead is not alloyed.
- Preferred is a Pb content in the alloy according to the invention of ⁇ 0.003% by weight, which is present in the alloy as an impurity of zinc, in particular, but not as an additional alloy component.
- a zinc wrought alloy with a content of Al of from 5% to 12% by weight, preferably from 5% to 8% by weight, or from 9% to 12% by weight. These ranges are preferred because all alloys are supereutectic therein, and there is a first beta phase in the crystal structure. This beta phase is preferred because it recrystallizes at room temperature very slowly (> 10 years).
- a zinc wrought alloy with a content of Cu of from 0.1% by weight to 2.5% by weight, especially from 0.5% by weight to 1.5% by weight. This range is preferred to achieve the maximum mechanical strength, and to avoid the risk of forming of a brittle epsilon phase in the crystal structure.
- a zinc wrought alloy with a content of Mg from 0.003% to 0.05% by weight, especially from 0.003% by weight to 0.03% by weight. This range serves as a precaution to prevent intercrystalline corrosion by the residual traces of impurities.
- the zinc wrought alloy used according to the invention may further contain silicon. If it contains silicon, the content of silicon in the alloy is in particular within a range of from 0.005% by weight to 0.02% by weight. The silicon content is determined by the selection of Al content, because it is an impurity in aluminum.
- an alloy having an Al content of from 5% to 8% by weight, a Cu content of from 0.5% by weight to 1.5% by weight, an Mg content of from 0.003% by weight to 0.05% by weight, with zinc as the balance to reach 100% by weight has particularly good coating properties.
- Particularly preferred according to the invention is a zinc wrought alloy with an Al content of from 9% by weight to 12% by weight, a Cu content of from 0.5% by weight to 1.5% by weight, an Mg content of from 0.003% by weight to 0.05% by weight, with zinc as the balance to reach 100% by weight.
- Corresponding alloys have good coating properties. Therefore, such an alloy, or the use thereof, is preferred.
- an alloy according to the invention may further comprise up to 1% by weight titanium (Ti).
- Ti titanium
- the titanium content of at most 1% in the zinc alloy is limited by the solubility of titanium. Titanium is an extremely effective alloy element, strongly affecting the microstructure and the mechanical properties of the alloy already in the ppm range because of its lattice structure. Corresponding alloys have an improved machinability.
- the alloy used according to the invention may also comprise impurities resulting from the fact that these components are derived from recycling .
- impurities are not critical. Common impurities are the presence of Cd, Pb, Sn and/or Fe. Preferably, these impurities are contained only in very small amounts, so that they do not adversely affect the properties of the alloy according to the invention. Therefore, preferred is a Pb content of ⁇ 0.003% by weight, and/or a Cd content of ⁇ 0.003% by weight, especially ⁇ 0.0005% by weight, and/or an Sn content of
- the content of all stated impurities is below the mentioned upper limits.
- the content of all impurities is 0.07% by weight or less.
- the present invention relates to the use of the zinc wrought alloy according to the invention for preparing semifinished products and articles with improved coating properties.
- the alloy according to the invention in the present application, this is supposed to mean the alloy used according to the invention.
- This semifinished product may be, in particular, a billet, an extruded section, a drawn section, a wire, a strip, a powder, or a pressure die-cast alloy.
- the article may be a forging, turned part, lock, screw connection, locking cylinder, sleeve, fitting, pressed part, pneumatic part, hydraulic part, mounting, valve or ball valve.
- the semifinished product according to the invention can be prepared, for example, by casting the zinc wrought alloy according to the invention into a mold .
- a section can be prepared therefrom by reshaping by means of extrusion.
- the zinc wrought alloy according to the invention can be processed by different reshaping methods. Such reshaping methods include, in particular, rolling, forging and drawing. Further, the semifinished products prepared from the zinc wrought alloy according to the invention are processed further, for example, into forgings, turned parts, locks, screw connections, locking cylinders, sleeves, fittings, pressed parts, pneumatic parts, hydraulic parts, mountings, valves and ball valves using different processing methods. These articles according to the invention are excellently suitable for being subjected to coating methods.
- the zinc wrought alloy according to the invention and the articles prepared therefrom exhibit improved coating properties as compared to conventional ZnAI/ZnAICu/ZnAICuMg alloys. These include an improved adhesion and density of the coating on the substrate material, and an improved corrosion resistance resulting therefrom, which shows in the results in a salt spray mist test, condensation water test, or thermal shock test.
- the requirement for the invention is to enhance the coatability and corrosion resistance. This object was achieved by limiting the aluminum content in the alloy according to the invention to a maximum of 12% by weight. There may be mentioned, in particular, the coating properties that were significantly improved thereby, so that an improved corrosion resistance can be achieved. In the experiments, it is found that this can be achieved by reducing the aluminum content.
- the prepared products comprising and, in particular, made of the zinc alloy according to the invention have an excellent processability, especially coatability, caused by the optimum composition of zinc, aluminum, copper and magnesium.
- a qualification of zinc wrought alloys is usually affected by means of the following five methods delimited from one another:
- a microscopic examination of the coating by analogy with DIN EN ISO 1463 : 2004-08 is performed .
- This serves for testing the layer thickness and the bonding of the coating to the substrate material.
- polished transverse sections of the coated specimens are prepared . Thereupon, the sections are embedded, ground and polished.
- the surface of the specimen is etched with aqueous sodium hydroxide (NaOH) solution. The testing requirements are considered to be met if the coating has a good bonding to the substrate material and reaches the desired layer thickness.
- NaOH sodium hydroxide
- a salt spray test with a sodium chloride solution having a neutral pH is performed .
- the testing requirements are considered to be met if no corrosion in the form of white rust occurs on the surface after 96 hours in the salt spray test.
- a test with a condensation water constant climate is performed .
- distilled water is filled into the base tray of a suitable sealed chamber.
- the chamber is heated at (40 ⁇ 3) °C, reaching a relative humidity of about 100%.
- the test requirements are considered to be met if no blistering or corrosion (in the form of white rust) occurs on the surface of the specimen after 96 hours in a condensation water chamber.
- a zinc wrought alloy as described in EP 2 675 971 was used as a comparative material (information in column “zinc alloy” in Table 1).
- billets having a diameter of 135 mm were prepared, which served as a starting point for the qualification :
- the specimens were pretreated in accordance with their alloy composition. Thereafter, the specimens were coated with different systems and tested according to the above-mentioned testing requirements. In the coating process, the same process times were used for all specimens for direct comparability.
- the coating with a cyanidic Cu-Cu-Ni system is shown in some detail.
- the salt spray test showed that no corrosion (in the form of white rust) has occurred on the surface of the specimens for specimen 1 and specimen 2. Thus, the substrate material under the coating was not attacked despite a highly stressing environment.
- the present invention had improved coating properties as compared to the prior art. This was shown in the different testing methods. The testing requirements were met in all methods. The bonding of the coating to the substrate material was good according to the requirements, and neither corrosion (in the form of white rust) nor chipping nor blistering occurred on the surface of the specimens. Further, the present invention surprisingly showed an enhanced deposition rate and thus achieved shorter process times. The particularly good test results of specimen 2 are to be mentioned . In addition, a more environment-friendly kind of coating is surprisingly enabled by the present invention by means of cyanide-free copper plating.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP17179645 | 2017-07-04 | ||
PCT/EP2018/067824 WO2019007909A1 (en) | 2017-07-04 | 2018-07-02 | Zinc wrought alloy with improved coatability |
Publications (1)
Publication Number | Publication Date |
---|---|
EP3649267A1 true EP3649267A1 (en) | 2020-05-13 |
Family
ID=59325135
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP18743410.5A Pending EP3649267A1 (en) | 2017-07-04 | 2018-07-02 | Zinc wrought alloy with improved coatability |
Country Status (3)
Country | Link |
---|---|
US (1) | US20210147962A1 (en) |
EP (1) | EP3649267A1 (en) |
WO (1) | WO2019007909A1 (en) |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA919458A (en) | 1969-12-31 | 1973-01-23 | Cominco Ltd. | Zinc forging alloy |
US3880679A (en) | 1971-07-21 | 1975-04-29 | Noranda Mines Ltd | Method of forming zinc-aluminum alloys with good machinability |
US4126450A (en) * | 1977-03-29 | 1978-11-21 | Ball Corporation | Continuously castable zinc base alloy |
CA1230993A (en) * | 1984-11-02 | 1988-01-05 | Maheswar Sahoo | Zinc-aluminum alloy sand casting |
US4882126A (en) * | 1987-07-01 | 1989-11-21 | Mitsui Mining & Smelting Co., Ltd. | High-strength zinc base alloy |
FR2700343B1 (en) | 1993-01-14 | 1995-03-17 | France Sa Union Miniere | Process for manufacturing articles of Zn-Al-Cu alloy by centrifugal casting or pressure casting. |
EP2385148B1 (en) | 2010-05-03 | 2016-10-19 | Grillo-Werke AG | Zinc alloy with high creep resistance |
ITMI20110218A1 (en) | 2011-02-15 | 2012-08-16 | Almar S P A | ACCESSORY MADE OF LOCK OR SIMILAR |
-
2018
- 2018-07-02 US US16/623,019 patent/US20210147962A1/en not_active Abandoned
- 2018-07-02 WO PCT/EP2018/067824 patent/WO2019007909A1/en unknown
- 2018-07-02 EP EP18743410.5A patent/EP3649267A1/en active Pending
Also Published As
Publication number | Publication date |
---|---|
US20210147962A1 (en) | 2021-05-20 |
WO2019007909A1 (en) | 2019-01-10 |
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