WO2006039951A1

WO2006039951A1 - Copper/zinc/silicon alloy, use and production thereof

Info

Publication number: WO2006039951A1
Application number: PCT/EP2005/005238
Authority: WO
Inventors: Heinz Strobl; Klaus Schwarm; Hermann Mayer; Norbert Gaag; Ulrich Rexer; Klaus Marstaller
Original assignee: Diehl Metall Stiftung & Co. Kg
Priority date: 2004-10-11
Filing date: 2005-05-13
Publication date: 2006-04-20
Also published as: JP5148279B2; EP1812612A1; BRPI0516067A; JP2008516081A; ATE466965T1; PL1812612T3; ES2343532T3; BRPI0516067B1; CN101023191A; CN100510132C; MY145376A; US20090280026A1; TW200611985A; CA2582972A1; CA2582972C; EP1812612B1; DE502005009545D1; PT1812612E; US20060078458A1; TWI369405B

Abstract

The invention relates to a Cu-Zn-Si alloy comprising 70-80 wt. % copper, 1 -5 wt. % silicon, 0.0001 0.5 % boron, up to 0.2 % phosphorus and/or up to 0.2 % arsenic, the rest being zinc in addition to unavoidable impurities. The information further relates to the use and production of said alloy. The alloy is characterized by improved resistance to oxidation and by uniform mechanical properties.

Description

Dien! Metal Foundation & Co. KG, Heinrϊch-Diehl-Str. 9, 90552 Röthenbach

Copper-zinc-silicon alloy, its use and its manufacture

The invention relates to a copper-zinc-silicon alloy and a use and production of such a copper-zinc-silicon alloy.

The overriding requirement for copper-zinc-silicon alloys is that they be dezincification-resistant and machinable. A good machinability of such

Brass alloys have hitherto been realized by the addition of lead, as described for example in EP 1 045 041 A1. Recently, however, lead-free brass alloys have been developed with good machining properties, as described for example in EP 1 038 981 A1 and DE 103 08 778 B3. Both the lead-free and lead-containing Cu-Zn-Si alloys tend to oxidize at temperatures between 300 ⁰ C and 800 ⁰ C and form a scale layer. This scale layer adheres only loosely to the metal, dissolves easily and spreads over the production facilities, with the result that they are contaminated disturbing. The cleaning of the production equipment is complex, whereby the production costs are high. A disadvantage of the previously known Cu-Zn-Si alloys is that the mechanical properties of the material change over long workpieces, since the material is not homogeneous.

In recognition of these circumstances, the present invention is therefore the

Problem to provide a copper-zinc-silicon alloy, which is improved in terms of their homogeneity and also has a lower tendency to form scale, and to indicate a use and manufacture of such brass alloy. The first object with respect to an alloy is achieved according to the invention by a copper-zinc-silicon alloy comprising in weight percent 70 to 80% copper, 1 to 5% silicon, 0.0001 to 0.5% boron, 0 to 0.2% Phosphorus and / or arsenic as well as the remainder of zinc and unavoidable impurities.

The copper content is between 70 and 80%, because copper contents below 70% or above 80% would adversely affect the machinability of the alloy. The same applies when leaving the specified silicon concentration range of 1% to 5%. The boron concentration in the alloy is between 0.0001 to 0.5%. Surprisingly, it has now been found that, on the one hand, by adding boron corresponding to the claimed concentration range, it is achieved that the scale formation is lower and at the same time the adhesion of the remaining scale to the material is markedly increased. On the other hand, it is also surprising that the addition of boron improves the homogeneity of the microstructure and thus avoids fluctuations in the mechanical properties. Phosphorus and arsenic can each be contained in the alloy with a concentration content of up to 0.2% and can be substituted with one another. By phosphorus and arsenic, the formation of the initial cast structure and the

In addition, the flow properties of the melt is increased and the susceptibility to stress corrosion cracking is reduced. The remaining essential alloying content is zinc.

In addition to the above-mentioned advantages that easily solubilized, the production cost increasing scale layers are avoided and the mechanical properties are improved and beyond good machinability and good formability is given in conjunction with high corrosion resistance, in the invention just the

Resistance to dezincification and stress corrosion cracking particularly pronounced. Dezincification tests according to ISO 6509 result in dezincification depths of only up to 26 μm.

The second object with regard to the use of such a copper

Zinc-silicon alloy is solved by a use for electrotechnical Components for sanitary engineering components, for containers for the transport or storage of liquids or gases, for components subject to torsion, for recyclable components, for drop forgings, for semi-finished products, for strips, for sheets, for profiles, for sheets or as kneading or rolling cast alloys.

The Cu-Zn-Si alloy is used for contacts, pins or fasteners in electrical engineering, for example, as a stationary contacts or fixed contacts to which also clamps and connectors or plug contacts belong.

The alloy has a high corrosion resistance to liquid and gaseous media. In addition, it is extremely resistant to dezincification and stress corrosion cracking. As a result, the alloy is particularly suitable for use in containers for the transport or storage of liquids or gases, in particular for containers in the

Refrigeration technology or for pipes, water fittings, tap extensions, pipe connectors and valves in sanitary engineering.

The low corrosion rates also ensure that the metal permeability, that is the property by the action of liquid or gaseous media

Alloy shares carry, in itself is low. In this respect, the material is suitable for applications requiring low pollutant emissions to protect the environment. Thus, the use of the alloy according to the invention is in the field of recyclable components.

The insensitivity to stress corrosion cracking recommends the alloy for use in screwed or clamped connections in which large elastic energy sources are stored for technical reasons. Thus, the use of the alloy is particularly suitable for all tensile and / or torsional stressed components, in particular for screws and nuts. After cold forming, the material reaches high values for the yield strength. Thus, in screw, which must not deform plastically, larger tightening torques can be realized. The yield ratio of the Cu-Zn-Si alloy is smaller than that of automatic brass. Screw connections that are tightened only once and deliberately overstretched, thus achieve particularly high holding forces. Uses of Cu-Zn-Si alloy arise for both tubular and band-shaped starting materials. It is also well suited for milling or punching tapes, sheets and plates, especially for keys, engraving, for decorative purposes or for punched grid applications.

The third object with regard to a production of such a copper-zinc-silicon alloy is achieved by conventional continuous casting and hot rolling between 600 to 760 ⁰ C with subsequent forming, in particular cold rolling, preferably supplemented by further annealing and

Forming steps.

The object with regard to a production of such a copper-zinc-silicon alloy is also achieved by conventional continuous casting and extrusion at up to 76O ⁰ C, preferably between 650 and 680 ⁰ C and cooling in air.

In an advantageous development of the Cu-Zn-Si alloy, this comprises 75 to 77% copper, 2.8 to 4% silicon and 0.001 to 0.1% boron and 0.03 to 0.1% phosphorus and / or arsenic, in addition to zinc as a residual element and unavoidable impurities.

In a preferred alternative, the copper-zinc-silicon alloy comprises at least one element in wt .-% from the group lead with 0.01 to 2.5%, tin with 0.01 to 2%, iron with 0.01 to 0.3%, cobalt at 0.01 to 0.3%, nickel at 0.01 to 0.3% and manganese at 0.01 to 0.3%. By adding lead, the machinability can be positively influenced.

The alloy advantageously comprises at least one element in wt .-% from the group 0.01 to 0.1% lead, 0.01 to 0.2% tin, 0.01 to 0.1% iron, 0, 01 to 0.1% cobalt, 0.01 to 0.1% nickel and 0.01 to 0.1% manganese.

In a preferred development, the Cu-Zn-Si alloy additionally comprises at least one element in% by weight with up to 0.5% silver, up to 0.5%

Aluminum, up to 0.5% magnesium, up to 0.5% antimony, up to 0.5% titanium and up to 0.5% zirconium, preferably from the group from 0.01 to 0.1% silver, 0 , 01 to 0.1% aluminum, 0.01 to 0.1% magnesium, 0.01 to 0.1% antimony, 0.01 to 0.1% titanium and 0.01 to 0.1% zirconium.

In an advantageous alternative, the Cu-Zn-Si alloy additionally comprises at least one element in wt .-% from the group of up to 0.3% cadmium, to

0.3% chromium, up to 0.3% selenium, up to 0.3% tellurium and up to 0.3% bismuth, preferably from the group consisting of 0.01-0.3% cadmium, 0.01-0.3% Chromium, 0.01 - 0.3% selenium, 0.01 - 0.3% tellurium and 0.01 - 0.3% bismuth.

An exemplary embodiment will be explained in more detail with reference to the drawing and the description below. Show

1 shows the formation of a scale layer after annealing for ² h at 600 ⁰ C on a CuZn21Si3P alloy without added boron (a), a CuZn21 Si3P alloy with 0.0004% boron (b) and a CuZn21Si3P alloy with

0.009% boron (c) and

Fig. 2 shows the formation of the cast structure of a CuZn21Si3P alloy without added boron (a), a CuZn21Si3P alloy with 0.0004% boron (b) and a CuZn21 Si3P alloy with 0.009% boron (c).

The CuZn21Si3P alloys underlying the exemplary embodiment have concentration variations of the proportions, with copper between 75.8 and 76.1%, silicon between 3.2 and 3.4% and phosphorus between 0.07 and 0.1% together with zinc as remaining portion and inevitable impurities. The

Alloy examples show a different boron content of 0%, 0.004% and 0.009%. The alloys are produced by continuous casting, followed by extrusion at temperatures below 76O ⁰ C, preferably between 650 and 68O ⁰ C, and rapid cooling.

All alloys have excellent dezincification resistance. A dezincification test according to ISO 6509 results in dezincification depths of only less than 26 μm.

Be CuZn21Si3P alloys, for example, in the hot deformation,

Temperatures of 300 - 800 ⁰ C exposed, forming scale, which is easy replaces and pollutes the production facilities. A highly scaled surface of a boron-free CuZn21Si3P alloy is shown in Fig. 1a. The surface of the sample appears in Fig. 1 a for the most part gray. This gray color reflects the scaled surface of the CuZn21Si3P alloy. There are only a few, isolated bright spots on the alloy surface to recognize that are not regularly distributed. In contrast, the CuZn21Si3P alloy with a boron content of 0.0004% in Fig. 1b shows a much larger number of white-appearing spots on the surface of the alloy than the boron-free alloy. These white spots give metallic bright areas of the alloy. These bright metallic areas, ie areas that are not scaled, are evenly distributed over the surface of the alloy. The proportion of the scale surface is significantly reduced, and the remaining scale adheres more firmly to the metal than to the boron-free alloy. A CuZn21Si3P alloy comprising 0.009% boron is shown in Figure 1c. Here it can be clearly seen that the number of bright metallic surfaces, ie the white

Stains, has continued to increase. Partly larger contiguous areas of bare metallic material are present, and a very regular distribution on the surface of the alloy can be seen. The scaled surface portion has continued to decrease and the remaining scale adheres firmly to the metal. It has surprisingly been found that low

Boron concentrations of 0.0001 - 0.5% limit the formation of scale in Cu-Zn-Si alloys while significantly increasing the adhesion of the scale to the metal, thereby avoiding undesirable contamination of the production equipment.

A similar result has also been found for Cu-Zn-Si-P alloys having different levels of lead, such as 0.01%, 0.05%, 0.1% or 2.5%.

In addition to reducing the tendency for scaling of Cu-Zn-Si

Alloys Boron also has a positive effect on the mechanical properties, since boron makes the alloy structure more homogeneous. This change in the alloy structure is shown in FIG. 2 as a function of the boron concentration. While a CuZn21Si3P alloy without the addition of boron shows a coarse, inhomogeneous structure (FIG. 2a), a CuZn21Si3P alloy with 0.0004% boron has a much more homogeneous microstructure, which is already very much shows uniform grain sizes (Fig. 2b). A further increase in the boron content to 0.009% causes a CuZn21Si3P alloy is even more uniform or the homogeneity has become even greater, the grain structure is no longer visible to the naked eye (Fig. 2c).

In addition to optical changes in the structure, the addition of boron also has a positive effect on the mechanical properties. This is particularly noticeable on rods pressed from Cu-Zn-Si alloys. To determine the mechanical properties samples were taken at the beginning and at the end of such rods. The tensile strength of a rod from a

CuZn21 Si3P alloy without addition of boron differs at the beginning compared to the end of the rod by more than 60 N / mm ² . By contrast, a corresponding alloy with a boron content of 0.0004% has only a difference in tensile strength of less than 40 N / mm ² between the beginning and the end of the rod. By adding 0.009% boron to a CuZn21Si3P alloy is the

Deviation in the tensile strength between bar start and end below 5 N / mm ² .

The material thus has consistently identical mechanical properties. It is therefore achieved a uniform strength over the entire press length away. The reason for this is the grain-refining effect of the boron.

The table summarizes the relationship between the boron content of a Cu-Zn-Si alloy and the increasing homogeneity of the alloy structure or the decreasing strength differences within a pressed workpiece.

Claims

claims

1. Cu-Zn-Si alloy comprising in wt .-% 70 to 80% copper, 1 to 5% silicon and 0.0001 to 0.5% boron and 0 to 0.2% phosphorus and / or arsenic and the rest Zinc plus unavoidable impurities.

2. Cu-Zn-Si alloy according to claim 1, characterized by in wt .-% 75 to 77% copper, 2.8 to 4% silicon and 0.0001 to 0.01% boron and 0.03 to 0, 1% phosphorus and / or arsenic.

3. Cu-Zn-Si alloy according to claim 1 or 2, characterized by additionally at least one element in wt .-% from the group of 0.01 to 2.5% lead, 0.01 to 2% tin, 0, 01 to 0.3% iron, 0.01 to 0.3% cobalt, 0.01 to 0.3% nickel, 0.01 to 0.3% manganese.

4. Cu-Zn-Si alloy according to claim 3, characterized by additionally at least one element in wt .-% from the group of 0.01 to 0.1% lead, 0.01 to 0.2% tin, 0, 01 to 0.1% iron, 0.01 to 0.1% cobalt, 0.01 to 0.1% nickel and 0.01 to 0.1% manganese.

5. Cu-Zn-Si alloy according to one of the preceding claims, characterized by additionally at least one element in wt .-% from the group of up to 0.5% silver, up to 0.5% aluminum, up to 0, 5% magnesium, up to 0.5% antimony, up to 0.5% titanium and up to 0.5% zirconium, preferably from the group of 0.01 to 0.1% silver, 0.01 to 0.1 % Aluminum, 0.01 to 0.1% magnesium, 0.01 to 0.1% antimony, 0.01 to 0.1% titanium and 0.01 to 0.1% zirconium.

6. Cu-Zn-Si alloy according to one of the preceding claims, characterized by additionally at least one element in wt .-% from the group of up to 0.3% cadmium, to 0.3% chromium, to 0.3% selenium to 0.3% tellurium and to 0.3% bismuth, preferably from the group of 0.01 to 0.3% cadmium, 0.01 to

0.3% chromium, 0.01 to 0.3% selenium, 0.01 to 0.3% tellurium and 0.01 to 0.3% bismuth.

7. Use of a Cu-Zn-Si alloy according to one of claims 1 to 6 for electrical components, for sanitary components, for containers for

Transport or storage of liquids or gases, for components subject to torsional stress, for recyclable components, for

Drop forgings, for semi-finished products, for strips, for sheets, for profiles, for plates or as a kneading, rolled or cast alloy.

8. A method for producing a Cu-Zn-Si alloy according to any one of claims 1 to 6 by conventional continuous casting and hot rolling between 600 to 760 ⁰ C followed by forming, in particular cold rolling, preferably supplemented by further annealing and forming steps.

9. A process for producing a Cu-Zn-Si alloy according to any one of claims 1 to 6 by conventional continuous casting and extrusion at up to 76O ⁰ C, preferably between 650 and 68O ⁰ C and cooling in air.