Brass-Aluminum-Manganese-Iron Alloy

Description

1 / 7 Brass-Aluminum-Manganese-Iron Alloy Technical field

[001] The present invention 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

[002] Different brass-aluminum-manganese-iron alloys are known in the art, 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.

[003] In products defined by solid bodies, such as valve bodies and bushings, it is 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, depending on the specifications and standards to be met in relation to the final product to be obtained. Petition 870250059098, dated 11 / 07 / 2025, page 5 / 12 2 / 7

[004] Although well-known brass-aluminum-manganese-iron alloys are commonly used in the manufacture of different products, they still require tribological improvements demanded in different applications, especially when applied in aerospace, marine (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 products obtained with this material, such as valve bodies, bearings and bushings, resulting in the replacement of the entire assembly instead of just the replacement of the bushings, for example.

[005] The well-known brass-aluminum-manganese-iron alloys designed for the manufacture of aerospace, marine, 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 tensile strength and lower ductility with the formation of the beta phase; iron (Fe) acts as an inoculant in copper alloys, refining the grain size and consequently improving various material properties, including mechanical strength, wear resistance, fatigue, and impact resistance; however, due to the occurrence of hard spots in brasses, the iron content is generally 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 Petition 870250059098, dated 11 / 07 / 2025, page 6 / 12 3 / 7 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.

[006] Despite their widespread use in aerospace, marine and agricultural products, the well-known 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 demands of applications in the aerospace, marine and agricultural sectors. Summary of the invention

[007] Due to the aforementioned limitation related to known brass-aluminum-manganese-iron alloys, the present invention aims to provide a new 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.

[008] According to the invention, the new alloy has a composition obtained by casting and which, in addition to comprising the usual elements defined by copper, zinc, aluminum, manganese and iron, also includes the micro-addition of the element niobium, responsible for the difference in the characteristic. Petition 870250059098, dated 11 / 07 / 2025, page 7 / 12 4 / Ί of mechanical resistance. Description of the invention

[009] According to the invention, 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 the remainder copper (Cu).

[0010] In a preferred form, the brass-aluminum-manganese-iron alloy in question comprises 14.3% zinc (Zn); 6.16% aluminum (Al); 3.5% manganese (Mn); 2.4% iron (Fe); 0.16% niobium (Nb) and the remainder copper (Cu).

[0011] 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 consists of a thin film approximately 25 nm thick 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 to 4.0 to 6.0%, the formation of a single beta phase, consisting of equiaxed beta grains, is observed.When aluminum levels are extrapolated to values ​​above 6.0%, a solid solution phase forms. Petition 870250059098, dated 11 / 07 / 2025, page 8 / 12 5 / 7 gamma (γ), which has a primitive structure with a stoichiometry of Cu5Zn8.

[0012] The addition of iron (Fe) acts as an inoculant in copper alloys, refining grain size and consequently improving various material properties, 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 1.5% at 1020°C and 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 nuclei for the formation of new grains, resulting in 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 necessary to add other elements to enhance its inoculation capacity, such as boron and aluminum.

[0013] The addition of manganese (Mn) to brass enhances the fluidity of the molten metal during the casting process, resulting in improved casting quality. Furthermore, manganese contributes to 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.

[0014] The alloy, the subject of the present invention, must be ob Petition 870250059098, dated 11 / 07 / 2025, page 9 / 12 6 / Ί obtained by means of 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 was found that a temperature of 1,500°C can be used to obtain the casting of all the elements.

[0015] Depending on the application of the product to be obtained from the alloy of the invention, the latter may undergo subsequent cold or hot forming, machining or heat treatment processes.

[0016] It is recommended that the material be subjected to heat treatment to promote the removal of residual stresses resulting from the cooling rates applied in the solidification process.

[0017] The alloy of the invention may contain impurities in its composition which, although present, do not directly influence 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).

[0018] Table 1: Properties in the as-melt product of the alloy of the invention. Specification Obtained in the alloy of the invention Hardness (HB) 143.0 + / - 1.3 Microstructure Intermetallic microconstituents

[0019] The new alloy has a microstructure composed of alpha and beta phases and intermetallic microconstituents dispersed throughout the microstructure (small and large sizes). The larger precipitates have a needle-like shape with Petition 870250059098, dated 11 / 07 / 2025, p. 10 / 12 7 / 7 composition (by mass %) of: 70.45% iron, 8.93% aluminum, 11.46% copper, 5.95% manganese, and 3.21% silicon. The new alloy also features 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 alloy hardness.

[0020] The new alloy exhibits 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 exhibit hardness values ​​from 80 to 225 HB. The new alloy exhibits a hardness value compatible with the manganese brass family. Petition 870250059098, dated 11 / 07 / 2025, p. 11 / 12

Claims

1 / 1 CLAIMS 1. Brass-aluminum-manganese-iron alloy characterized by comprising, as a crude 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) and the remainder copper (Cu).

2. Brass-aluminum-manganese-iron alloy, according to claim 1, characterized in that it further comprises 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).

3. Brass-aluminum-manganese-iron alloy, according to either claim 1 or 2, characterized in that it comprises 14.3% zinc (Zn); 6.16% aluminum (Al); 3.5% manganese (Mn); 2.4% iron (Fe); 0.16% niobium (Nb) and the remainder copper (Cu). Petition 870250005509, dated 23 / 01 / 2025, p. 20 / 23