Brass-aluminum-manganese-iron alloy

Abstract

The brass-aluminum-manganese-iron alloy, with micro-addition of niobium and as a raw melt product, is particularly, but not exclusively, applicable in the production of valve bodies, bearings and bushings and it comprises, by mass: 14.0 to 18.0% zinc (Zn); 5.0 to 7.5% aluminum (Al); 2.5 to 5.0% manganese (Mn); 2.0 to 4.0% iron (Fe); 0.1 to 0.2% niobium (Nb) and the remainder of copper (Cu). The alloy may optionally contain the following impurities, by mass: maximum 0.2% lead (Pb), maximum 0.2% tin (Sn), maximum 1.0% nickel (Ni) and maximum 0.2% silicon (Si).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Brazilian Patent Application BR 10 2025 001349 5, filed Jan. 23, 2025, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to a brass-aluminum-manganese-iron alloy, containing micro-addition of niobium and obtained by casting, allowing the achievement of effective advantages from a technical-metallurgical point of view and presenting differentials in mechanical properties that demonstrate gains in performance and durability.BACKGROUND OF THE INVENTION

[0003] Different brass-aluminum-manganese-iron alloys are obtained from the basic components defined by copper, zinc, aluminum, manganese and iron, which define the phases and intermetallics of brass-aluminum-manganese-iron, and to which different elements, such as nickel and / or silicon, tin and lead, may optionally be added to adjust specific properties for the final products to be obtained by casting the alloy components and which may or may not be subsequently subjected to machining steps, by means of a manufacturing process known as subtractive manufacturing.

[0004] In products defined by solid bodies, such as valve bodies and bushings, it may be desirable that their production be made from a copper alloy with differentiated mechanical properties and that it be obtained from the casting of its constituent elements and any subsequent steps, such as hot extrusion, drawing and heat treatment to relieve residual stresses, according to the specifications and standards to be complied with in relation to the final product to be obtained.

[0005] Although conventional brass-aluminum-manganese-iron alloys are commonly used in the manufacture of different products, they still need tribological improvements required in different applications, mainly when applied in aerospace, maritime (in the naval segment) and agricultural products. The composition of these known alloys also leads to a relatively high cost of preventive maintenance, due to the high mechanical resistance of these alloys, which ends up causing greater wear on the counter parts that are assembled in the products obtained with this material, such as valve bodies, bearings and bushings, causing the replacement of the entire assembly instead of just the replacement of the bushings, for example.

[0006] The conventional brass-aluminum-manganese-iron alloys designed for the manufacture of aerospace, maritime and agricultural products are formed from the addition of zinc (Zn), aluminum (Al), iron (Fe) and manganese (Mn) to copper (Cu). For brass-aluminum-manganese-iron alloys, zinc (Zn) is added to obtain a higher limit of tensile strength and lower ductility with the formation of the beta phase; iron (Fe) performs the role of inoculant in copper alloys, by refining the grain size and, consequently, by improving several properties of the material, including mechanical strength, wear resistance, fatigue and impact, but due to the occurrence of hard spots in brasses, the iron content is usually reduced to values below 0.05%; the addition of aluminum (Al) to brass improves tensile strength, hardness, wear resistance, and corrosion resistance, and this element also contributes to the stabilization of the beta phase in the microstructure; the addition of manganese (Mn) to brass enhances the fluidity of the liquid metal during the casting process, resulting in improved quality of the cast parts. Furthermore, manganese contributes to corrosion resistance in underwater environments, such as seawater, making alloys containing this element widely used in these scenarios.

[0007] Despite their widespread use in aerospace, maritime, and agricultural products, the conventional brass-aluminum-manganese-iron alloys still exhibit mechanical strength characteristics (microstructure) that limit the efficiency of these products, indicating the need to seek brass-aluminum-manganese-iron alloys with improved tribological properties to better meet the requirements of applications in the aerospace, maritime, and agricultural areas.SUMMARY OF THE INVENTION

[0008] Due to the aforementioned limitation related to conventional brass-aluminum-manganese-iron alloys, the present disclosure provides a brass-aluminum-manganese-iron alloy exhibiting differences in mechanical strength, while maintaining the same machinability cost, in relation to those of known brass-aluminum-manganese-iron alloys.

[0009] According to embodiments, the alloy comprises a composition obtained by casting and which, besides comprising the usual elements defined by coper, zinc, aluminum, manganese and iron, it also includes the micro-addition of the niobium element that is responsible for the difference in the mechanical resistance characteristic.DESCRIPTION OF THE INVENTION

[0010] According to embodiments, the brass-aluminum-manganese-iron alloy comprises, in its basic form (in % by mass), 14.0 to 18.0% zinc (Zn); 5.0 to 7.5% aluminum (Al); 2.5 to 5.0% manganese (Mn); 2.0 to 4.0% iron (Fe); 0.1 to 0.2% niobium (Nb) and a remainder of copper (Cu).

[0011] In embodiments, the brass-aluminum-manganese-iron alloy comprises 14.3% zinc (Zn); 6.16% aluminum (Al); 3.5% manganese (Mn); 2.4% iron (Fe); 0.16% niobium (Nb) and the remainder of copper (Cu).

[0012] The addition of aluminum (Al) to copper alloys promotes the formation of a highly protective layer when exposed to corrosive agents such as salt or brackish water. This barrier comprises of a thin film of approximately 25 nm thickness on the metal surface, which exerts a passivating effect. Furthermore, the addition of aluminum to brass improves tensile strength, hardness, wear resistance, and corrosion resistance. This element also contributes to the stabilization of the beta phase in the microstructure. Aluminum contents of up to 2.0% result in an irregular structure composed of alpha+beta (α+β) phases. This is due to the formation of the more stable alpha phase from the metastable beta phase during the homogenization and air cooling process. However, when aluminum contents are increased from 4.0 to 6.0%, it is observed the formation of a single beta phase which is constituted by beta grains having a same axis. When aluminum contents are extrapolated to values above 6.0%, a gamma (γ) solid solution phase is formed, which has a primitive structure with a stoichiometry of Cu5Zn8.

[0013] The addition of iron (Fe) performs the function of an inoculant in copper alloys, by refining the size of the grains and, consequently, by improving several properties of the material, including mechanical strength, wear resistance, fatigue, and impact resistance. Its low solubility in copper and its molten alloys facilitates the refinement of copper grains. For example, the solubility of iron in 60 / 40 brass is of 1.5% at 1020° C. and of 0.04% at 950° C. During the solidification process of the liquid metal in the mold, the reduction in temperature induces the precipitation of small iron particles, which act as cores for the formation of new grains, resulting in a significant refinement. However, due to the occurrence of hard spots in yellow brasses, the iron content is usually reduced to values below 0.05%. This makes iron, by itself, less effective as a grain refining agent, making it desirable to add other elements to enhance its inoculation capacity, such as boron and aluminum.

[0014] The addition of manganese (Mn) to brass enhances the fluidity of the liquid metal during the casting process, resulting in improved quality of the cast parts. Furthermore, manganese contributes to the corrosion resistance in underwater environments, such as seawater, making alloys containing this element widely used in these scenarios. Increasing the manganese content also increases hardness and tensile strength due to solid solution formation and beta phase dispersion.

[0015] The alloy described herein may be obtained by casting at a temperature sufficient to promote the diffusion of all the elements of its constitution, including the element niobium (Nb) which participates in the composition on a micro scale. It has been found that a temperature of 1,500° C. can be used to obtain the casting of all the elements.

[0016] Depending on the application of the product to be obtained from the alloy described herein, the latter may undergo subsequent cold or hot forming, machining or heat treatment processes.

[0017] The material may be subjected to heat treatment to promote the removal of residual stresses resulting from the cooling rates applied in the solidification process.

[0018] The alloy may comprise, in its composition, impurities which, although can be present, do not directly influence in the desired properties of the material, provided that they meet the indicated quantities (in % by mass): maximum 0.2% lead (Pb), maximum 0.2% tin (Sn), maximum 1.0% nickel (Ni) and maximum 0.2% silicon (Si).TABLE 1Properties in the raw melt product of the alloy.SpecificationObtained with the alloyHardness (HB)143.0 + / − 1.3MicrostructureIntermetallic microconstituents

[0019] The alloy described herein comprises a microstructure composed by phases: alpha and beta and intermetallic microconstituents dispersed throughout the microstructure (small and large sizes). The larger precipitates have a needle-like shape with a composition (by mass %) of: 70.45% iron, 8.93% aluminum, 11.46% copper, 5.95% manganese, and 3.21% silicon. The alloy described herein also comprises intermetallic microconstituents with a composition (by mass %) of: 39.43% iron, 48.15% niobium, and 12.42% copper. The intermetallics serve as a promoter of greater hardness of the alloy.

[0020] The alloy described herein comprises hardness values of 143.0+ / −1.3 HB, values that can be compared with commercial alloys from the UNS C86100 to UNS C86800 family, which have hardness values from 80 to 225 HB. The alloy described herein comprises a hardness value compatible with the manganese-brass family.

Claims

1. A brass-aluminum-manganese-iron alloy comprising, as a raw melt product, by mass:14.0 to 18.0% zinc (Zn);5.0 to 7.5% aluminum (Al);2.5 to 5.0% manganese (Mn); 2.0 to 4.0% iron (Fe);0.1 to 0.2% niobium (Nb); anda remainder of copper (Cu).

2. The brass-aluminum-manganese-iron alloy according to claim 1, further comprising the following impurities, by mass:maximum 0.2% lead (Pb);maximum 0.2% tin (Sn);maximum 1.0% nickel (Ni); andmaximum 0.2% silicon (Si).

3. The brass-aluminum-manganese-iron alloy according to claim 1, wherein the brass-aluminum-manganese-iron alloy comprises:14.3% zinc (Zn);6.16% aluminum (Al);3.5% manganese (Mn);2.4% iron (Fe);0.16% niobium (Nb); andthe remainder of copper (Cu).

4. The brass-aluminum-manganese-iron alloy according to claim 2, wherein the brass-aluminum-manganese-iron alloy comprises:14.3% zinc (Zn);6.16% aluminum (Al);3.5% manganese (Mn);2.4% iron (Fe);0.16% niobium (Nb); andthe remainder of copper (Cu).