BRPI0516067B1 - COPPER / ZINC / SILICY ALLOY, AND ITS PRODUCTION PROCESS - Google Patents

Abstract

A Cu-Zn-Si alloy includes, in % by weight, 70 to 80% of copper, 1 to 5% of silicon, to 0.5% of boron, up to 0.2% of phosphorus and/or up to 0.2% of arsenic, a remainder of zinc, plus inevitable impurities. Products using the alloy and processes for producing the alloy are also provided. The alloy is distinguished by an improved resistance to oxidation and by uniform mechanical properties.

Description

Report of the Invention Patent for "COPPER / ZINC / SILICY ALLOY, AND THEIR PRODUCTION PROCESS". The present invention relates to a copper-zinc silicon alloy and to the use and production of such a copper-zinc silicon alloy.

A priority need for copper-zinc silicon alloys is for them to be tenure resistant and machinable. Hitherto, good machinability properties of such brass alloys have been achieved with the addition of lead, as described, for example, in EP 1 045 041 A1. Recently, however, lead-free brass alloys with good machinability properties have been developed, as described, for example, in EP 1 038 981 A1 and DE 103 08 778 B3. Both lead-free Cu-Zn-Si and lead-containing alloys have a tendency to oxidize and form a scale of scale at temperatures between 300Ό and 800Ό. This layer of scale is only slightly bonded to the metal and can easily be removed from the metal so that it is then dispersed through the production equipment, with the result that this layer has a destructive contaminating effect. Cleaning production equipment is costly, making production costs high. Another disadvantage of known Cu-Zn-Si alloys is that the mechanical properties of the material change to long workpieces as the material lacks homogeneity.

In view of these facts, the present invention is therefore based on the problem of providing a copper-zinc silicon alloy that is improved in terms of its homogeneity and, moreover, less prone to scale formation, and provide the use and production of such a brass alloy. The first objective in relation to the alloy is achieved according to the invention by a copper-zinc silicon alloy comprising, by weight, 70 to 80% copper, 1 to 5% silicon, 0.0001 to 0.5% boron, 0 to 0.2% phosphorus and / or arsenic, the remaining zinc plus the inevitable impurities. The copper content is between 70 and 80%, since a copper content of less than 70% or above 80% would have an adverse effect on alloy machining properties. The same applies if the silicon concentration is outside the indicated range of 1% to 5%. The boron concentration in the alloy is between 0.0001 and 0.5%. Surprisingly, it has now been found that the addition of boron within the claimed concentration range on the one hand reduces scale formation and on the other hand significantly improves the agglutination of the remaining scale on the material. In addition, it is also surprising that the addition of boron improves the microstructure homogeneity and thus prevents fluctuations in mechanical properties. Phosphorus and arsenic may each be present in the alloy at a concentration of up to 0.2%, and may be substituted for each other. Phosphorus and arsenic have a beneficial effect on the initial ingot casting microstructure and corrosion properties, and further improve melt flow properties and reduce the susceptibility to stress corrosion fracture. The major remaining component of the alloy is zinc.

In addition to the advantages listed above in avoiding the easily detachable scale layers that increase production costs and improve mechanical properties, good machining properties and forming properties are provided in combination with a High corrosion resistance, tensile strength and stress corrosion fracture resistance are also particularly pronounced in the invention. Tenification tests performed in accordance with ISO 6509 give tenification depths of only up to 26 pm. The second objective, in relation to the use of such a copper-zinc silicon alloy, is achieved by its use for electrical engineering components, for sanitary ware components, for containers for transporting or storing liquids or gases, for twisted loading components, for recyclable components, for mechanical hammer forged components, for semi-finished products, for strips, for sheets, for profiled sections, for sheets or as a cast, rolled or ingot alloy. Cu-Zn-Si alloy is used for contacts, pins or safety elements in electrical engineering, for example as stationary contacts or fixed contacts, including fixing and bonding connections or bonding contacts. The alloy has a high corrosion resistance to liquid and gaseous media. In addition, it is extremely resistant to decincification and stress corrosion fracture. Accordingly, the alloy is particularly suitable for use for containers for transporting or storing liquids or gases, in particular for containers used for refrigeration or for pipes, water fittings, valve extensions, pipe fittings and valves in sanitary ware.

Low corrosion rates also ensure that metal leaching, that is, the property of loss of the binding constituents through the action of liquid or gaseous media, is inherently low. In this respect, the material is suitable for application areas requiring low pollutant emissions to protect the environment. Therefore, alloy according to invention can be used in the field of recyclable components. The lack of susceptibility to stress corrosion fracture means that the alloy is recommended for use in bolted or stapled connections in which high elastic energies are stored for technical reasons. Therefore, the alloy is particularly suitable for all components that are subjected to tension and / or torsion loads, in particular for nuts and bolts. After cold forming, the material achieves high stress proof values. Consequently, higher tightening torques can be realized on bolted connections that should not be deformed plastic. The ratio of the yield strength of Cu-Zn-Si alloy is lower than in the case of machining free brass. Bolted connections that are tightened only once and in the process are deliberately extended thus achieve particularly high maintenance forces.

Possible uses of Cu-Zn-Si alloy result in starting materials in both tube and strip form. The alloy is also eminently suitable for strips, sheets and plates that can be milled or punched, in particular for keys, cut out, for decorative purposes or for leadframe applications. The third objective concerning the production of such a copper-zinc silicon alloy is achieved by conventional continuous casting and hot rolling at a temperature between 600 and 760 ° C with subsequent deformation, in particular cold rolling, preferably with the addition of annealing and deformation steps. The objective concerning the production of such a copper-zinc silicon alloy is also achieved by conventional continuous casting and extrusion to 760 ° C, preferably between 650 and 680 ° C, followed by air cooling.

In an advantageous Cu-Zn-Si alloy refining, the alloy comprises 75 to 77% copper, 2.8 to 4% silicon and 0.001 to 0.1% boron as well as 0.03 to 0.1%. phosphorus and / or arsenic, as well as zinc as the remaining element plus the inevitable impurities.

In a preferred alternative, the copper-zinc silicon alloy comprises at least one element by weight% selected from the group consisting of 0.01 to 2.5% lead, 0.01 to 2% by weight. tin, 0.01 to 0.3% iron, 0.01 to 0.3% cobalt, 0.01 to 0.3% nickel and 0.01 to 0.3% manganese. The addition of lead has a positive influence on machining properties. The alloy in this case advantageously comprises at least one element by weight% selected from the group consisting 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.

In a preferred refining, Cu-Zn-Si alloy in addition comprises at least one element by weight, from up to 0.5% silver, to 0.5% aluminum, to 0.5% magnesium, up to 0.5% antimony, up to 0.5% titanium and up to 0.5% zirconium, and preferably selected from the group consisting 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.

In an advantageous alternative, the Cu-Zn-Si alloy in addition comprises at least one element by weight% selected from the group consisting of up to 0.3% cadmium, up to 0.3% chrome, up to 0%. Selenium, up to 0.3% tellurium and up to 0.3% bismuth, preferably selected 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 is explained in more detail with reference to the drawing and with reference to the following description.

In the drawings: Figure 1 - shows the formation of a scale of scale after annealing for 2 h at 600 ° C in a CuZn21Si3P alloy without addition of boron (a), a CuZn21Si3P alloy containing 0.0004% boron (b ), and a CuZn21Si3P alloy containing 0.009% boron (c), and Figure 2 - shows the formation of the ingot microstructure of a CuZn21Si3P alloy without the addition of boron (a), a 0.0004% boron CuZn21Si3P alloy ( b), and a CuZn21Si3P alloy containing 0.009% boron (c).

CuZn21Si3P alloys, on which the exemplary modality is based, have variations in component concentrations, with copper totaling between 75.8 and 76.1%, silicon totaling between 3.2 and 3.4% and phosphorus totaling between 0.07 and 0.1%, together with zinc as the remaining element plus the inevitable impurities. Alloy examples have different boron contents of 0%, 0.004% and 0.009%. The alloys are produced by continuous casting followed by extrusion at temperatures below 760 ° C, preferably between 650 and 680 ° C, followed by rapid cooling.

All alloys have excellent tensile strength. A decoding test performed in accordance with ISO 6509 reveals decoding depths of just under 26 pm.

If CuZn21Si3P alloys are exposed to temperatures of 300-800 ° C, for example during hot work, the scale is formed, and this scale can easily become detached and contaminates production equipment. An extensively scaled surface of a boron-free CuZn21Si3P alloy is illustrated in Figure 1a. The surface of the specimen appears predominantly grayish in Figure 1a. This gray color reveals the CuZn21Si3P alloy scale surface. Only a few points of individual brightness without any regular distribution are visible on the alloy surface. In contrast, CuZn21Si3P alloy with a 0.0004% boron content in Figure 1b has a much larger number of white dots on the alloy surface than boron-free alloy. These white dots represent regions of metallic alloy shine. These regions of metallic luster, that is, regions without any scale, are evenly distributed over the alloy surface. The proportion of the surface on which the scale has been formed is considerably reduced and the remaining scale is more firmly adhered to the metal than in the case of the boron-free alloy. Figure 1c illustrates a CuZn21Si3P alloy containing 0.009% boron. This figure clearly shows that the number of shiny metallic surfaces, ie white dots, has also increased. In some areas there are relatively large continuous regions of shiny metallic material, and the figure also reveals a very even distribution on the alloy surface. The proportion of the surface on which the scale was formed has also decreased, and the remaining scale is safely attached to the metal. Therefore it was surprisingly found that low boron concentrations of 0.0001 - 0.5% restrict the scale formation in Cu-Zn-Si alloys and at the same time considerably increase the agglutination of the scale to the metal, with the result that a Unwanted contamination of production equipment is avoided.

A similar result was also found for Cu-Zn-SiP alloys with different lead contents, such as, for example, 0.01%, 0.05%, 0.1% or 2.5%.

In addition to the reduced susceptibility to scale formation of Cu-Zn-Si alloys, boron also has a positive effect on mechanical properties as boron makes the alloy microstructure more homogeneous. This change in the alloy microstructure is illustrated in Figure 2 as a function of boron concentrations. While a non-boron CuZn21Si3P alloy has a crude, non-homogeneous microstructure (Figure 2a), a 0.0004% boron CuZn21Si3P alloy has a significantly more homogeneous microstructure that already has very uniform grain sizes (Figure 2a). 2b). Another increase in the boron content to 0.009% results in an even more uniform CuZn21Si3P alloy of even greater homogeneity in which the microstructure grains can no longer be seen with the naked eye (Figure 2c).

In addition to optical changes to the microstructure, the addition of boron also has beneficial effects on mechanical properties. This is particularly apparent on rods that have been extruded from Cu-Zn-Si alloys. To determine mechanical properties, samples were taken at the beginning and end of such rods. The tensile strength limit of a rod made of CuZn21Si3P alloy without the addition of boron differs by more than 60 N / mm2 at the beginning of the rod compared to the end of the rod. A corresponding alloy with a 0.0004% boron content, in contrast, has a tensile strength limit difference of only less than 40 N / mm2 between the start and end of the rod. If 0.009% boron is added to a CuZn21Si3P alloy, the difference in tensile strength between the start and the end of the rod is less than 5 N / mm2.

Therefore, the material has identical mechanical properties throughout its length. Consequently, a uniform strength is achieved over the entire extruded length. The reason for this is the action of boron grain refinement. The table shows the relationship between the boron content of a Cu-Zn-Si alloy and the increasing homogeneity of the alloy microstructure or decreasing strength differences within the extruded workpieces.

Claims (7)

1. Cu-Zn-Si alloy, characterized in that it comprises by weight%: 70 to 80% copper, 1 to 5% silicon, 0,0001 to 0,5% boron, and 0 to 0 , 2% phosphorus and / or arsenic, the remainder being zinc plus the inevitable impurities. Cu-Zn-Si alloy according to claim 1, characterized in that it comprises by weight%: 75 to 77% copper, 2.8 to 4% silicon, 0.0001 to 0, 01% boron, and 0.03 to 0.1% phosphorus and / or arsenic. Cu-Zn-Si alloy according to Claim 1 or 2, characterized in that it comprises, in addition, at least one element by weight% selected from the group consisting of: 0,01 to 2.5% lead, 0.01 to 2% tin, 0.01 to 0.3% iron, 0.01 to 0.3% cobalt, and 0.01 to 0.3% manganese. Cu-Zn-Si alloy according to claim 3, characterized in that it comprises, in addition, at least one element, by weight%, selected from the group consisting 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, and 0.01 to 0.1% manganese. Cu-Zn-Si alloy according to any one of Claims 1 to 4, characterized in that it comprises, in addition, at least one element by weight% selected from the group consisting 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 consisting 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 0.1% titanium, and 0.01 to 0.1% zirconium. Cu-Zn-Si alloy according to any one of Claims 1 to 5, characterized in that it comprises, in addition, at least one element by weight% selected from the group consisting of: up to 0 Cadmium, up 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 to 0 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 . Process for producing a Cu-Zn-Si alloy as defined in any one of claims 1 to 6, characterized in that it is by conventional continuous casting and extrusion at a temperature of up to 76013, preferably between 65013 and 68013. followed by air cooling.