High-strength heat-resistant brass alloy and preparation method thereof

Abstract

The invention relates to a high-strength heat-resistant brass alloy and a preparation method thereof, and belongs to the technical field of copper alloys. The high-strength heat-resistant brass alloy comprises, by mass, 69%-75% of Cu, 0.1%-1% of Sn, 1%-4% of Al, 0.5%-1.5% of Ni, 0.5%-1% of Fe and the balance Zn. The high-strength heat-resistant brass alloy comprises a core-shell structure precipitated phase with Fe wrapped by NiAl. The preparation method comprises the following steps: step 1, preparing materials; step 2, smelting; step 3, casting; fourthly, hot rolling is conducted after high-temperature solid solution; fifthly, a roughly-rolled plate is obtained through cold rolling; step 6, softening and annealing; seventhly, a finish-rolled plate is obtained through cold rolling; and step 8, performing stress relief annealing to obtain the high-strength heat-resistant brass alloy. By reasonably selecting alloy components and further regulating and controlling the heat treatment process, the brass alloy has high strength, high elongation, high hardness, high-temperature stability and excellent electric conductivity.

Description

Technical Field

[0001] This invention relates to high-strength heat-resistant brass alloys and their preparation methods, belonging to the field of copper alloy technology. Background Technology

[0002] High-strength, heat-resistant copper alloys are widely used in aerospace, high-power electronic devices, and advanced nuclear energy due to their excellent mechanical properties, good high-temperature stability, and electrical conductivity. Currently, the most widely used high-strength, heat-resistant copper alloy system is aluminum bronze, with a core chemical composition of Cu-Al (8%~10%)-Ni (4%~5%). The high-temperature resistant second phase, Cu3Al2, is precipitated. Taking QAl17 strip as an example, this alloy has a strength of approximately 585MPa-740MPa, an elongation after fracture of approximately 5%-11.3%, a hard state ≥5%, a semi-hard state ≥10%, and a softening temperature up to 450℃. However, its high Al and high Ni solid solution content results in low plasticity, limiting its application range. For example, low-plasticity copper alloys cannot meet the bending resistance requirements of electronic devices. The development of such copper alloys mainly focuses on adjusting the types and contents of alloying elements and improving heat treatment processes to optimize the alloy's microstructure and properties. However, strength, plasticity, high-temperature stability, and electrical conductivity of copper alloys are usually not simultaneously achieved.

[0003] Furthermore, the high-strength copper alloys currently widely used in the civilian sector are mainly tin bronze, with a main chemical composition of Cu-Sn (2%~10%)-P (0.01%~0.1%). Taking grade C51900 strip as an example, this alloy has a strength of approximately 550MPa-620MPa, an elongation after fracture of approximately 10%-18%, and a softening temperature of approximately 350℃-400℃. However, its high Sn and high Cu composition characteristics result in high costs, limiting its commercialization and large-scale application.

[0004] Common brass based on Cu-Zn has a significant cost advantage and good corrosion resistance and machinability. Zn in brass is inexpensive, non-toxic, and environmentally friendly. However, its relatively low strength (490MPa~530MPa) and softening temperature (240℃) make it unsuitable for applications in extreme environments. Current research on brass focuses primarily on corrosion resistance and wear resistance, with limited research on its plasticity, high-temperature stability, and electrical conductivity. There is a lack of brass grades on the market that offer a balance of strength, high-temperature stability, and electrical conductivity. Summary of the Invention

[0005] To overcome the above-mentioned defects of the prior art, the present invention provides a high-strength heat-resistant brass alloy and its preparation method. By rationally selecting the alloy composition and further controlling the heat treatment process, the brass alloy has high strength, high elongation, high hardness, high temperature stability and excellent conductivity.

[0006] The technical solution adopted in this invention is: a high-strength heat-resistant brass alloy, comprising, by mass percentage, 69%~75% Cu, 0.1%~1% Sn, 1%~4% Al, 0.5%~1.5% Ni, 0.5%~1% Fe, with the balance being Zn; the high-strength heat-resistant brass alloy includes a core-shell structure precipitate phase of Fe encapsulated by NiAl.

[0007] Preferably, the NiAl-encapsulated Fe core-shell precipitate is formed by the segregation of Ni atoms and Al atoms at the Fe phase interface.

[0008] Preferably, the NiAl-encapsulated Fe core-shell precipitate is coherent with the copper matrix.

[0009] Preferably, the size of the NiAl-encapsulated Fe core-shell precipitate is 10 nm to 20 nm.

[0010] Preferably, the NiAl-encapsulated Fe core-shell precipitate is dispersed in the copper matrix.

[0011] Preferably, the NiAl-encapsulated Fe core-shell precipitate is precipitated during the stress-relief annealing process of the high-strength heat-resistant brass alloy.

[0012] Preferably, the stress-relief annealing temperature is 300℃~500℃, and the holding time is 1h~3h.

[0013] Furthermore, the stress-relief annealing temperature is 450℃, and the holding time is 1 hour.

[0014] Preferably, the high-strength heat-resistant brass alloy has a strength of 662MPa~820MPa, an elongation of 3%~23%, a hardness of 213HV~256HV, and a conductivity of 16%IACS~20%IACS.

[0015] The preparation method of any of the high-strength heat-resistant brass alloys disclosed in this invention includes the following steps: Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy; Step 2: Melt the prepared raw materials. After melting pure Cu, first add Fe and Ni, keep it warm for a period of time and stir to melt evenly. Then add low melting point Sn, Al and Zn, stir to melt evenly again, add cryolite, stir to remove slag, keep it warm for a period of time and then remove it from the furnace. Step 3: Pour the molten alloy into a mold and air cool it. After it has completely cooled, you will get the alloy casting. Step 4: The casting is subjected to high-temperature solution treatment, then hot-rolled, and water-quenched to obtain hot-rolled sheet metal; Step 5: Cold roll the hot-rolled sheet to obtain a rough-rolled sheet; Step Six: Soften and anneal the rough-rolled sheet to allow it to fully recrystallize; Step 7: Cold roll the sheet material to obtain a precision-rolled sheet material; Step 8: Perform stress-relief annealing on the precision-rolled plate to precipitate the core-shell structured precipitate phase of NiAl encapsulating Fe, thereby obtaining the high-strength heat-resistant brass alloy (plate).

[0016] Preferably, in step two, a medium-frequency induction melting furnace is used to melt the prepared raw materials.

[0017] Preferably, in step two, the smelting is carried out with charcoal covering, a molybdenum crucible is used, and cryolite is used as a flux.

[0018] Preferably, in step two, the melting temperature is 1100℃~1700℃.

[0019] Preferably, in step three, the mold is a graphite mold, and the mold is dried and dehydrated before casting (this can be done in an electric furnace), and then zinc oxide is coated on the inner wall of the mold.

[0020] Preferably, in step four, the casting is first milled and then subjected to high-temperature solution treatment.

[0021] Furthermore, the high-temperature solution treatment temperature is 750℃~1000℃, and the holding time is 1h~8h.

[0022] Furthermore, the high-temperature solution treatment temperature is 800℃~850℃, and the holding time is 1 hour.

[0023] Preferably, in step four, the hot rolling process employs multi-pass rolling.

[0024] Furthermore, the single-pass processing rate of hot rolling is 15%~20%, and the total deformation is 70%~90%.

[0025] Preferably, in step four, the hot rolling termination temperature is 650°C to 750°C.

[0026] Preferably, in step five, the single deformation amount of cold rolling is 3% to 10%, and the total deformation amount is 70% to 90%.

[0027] Preferably, in step five, the thickness of the rough-rolled plate is 0.6 mm to 3.5 mm.

[0028] Preferably, in step six, the rough-rolled sheet is first milled and then softened and annealed.

[0029] Preferably, in step six, the softening annealing temperature is 300℃~900℃, and the holding time is 2h~8h.

[0030] Furthermore, the softening annealing temperature is 400℃~630℃.

[0031] Furthermore, the softening annealing temperature is 450℃.

[0032] Preferably, in step seven, the sheet material is first milled and then cold-rolled.

[0033] Preferably, in step seven, the cold rolling process employs multi-pass rolling.

[0034] Furthermore, the single deformation amount of cold rolling is 2% to 5%, and the total deformation amount is 60% to 88%.

[0035] Preferably, the thickness of the precision-rolled plate is 0.05mm to 3.0mm.

[0036] Preferably, in step eight, the precision-rolled sheet is first milled and then subjected to stress-relieving annealing.

[0037] Preferably, in step eight, the stress-relief annealing temperature is 300℃~500℃, and the holding time is 1h~3h.

[0038] Furthermore, the stress-relief annealing temperature is 450℃, and the holding time is 1 hour.

[0039] Steps three through five can be replaced by continuous casting and rolling processes.

[0040] The cold rolling (or precision rolling) in step seven can be performed twice. Between the two cold rolling operations, the sheet is subjected to continuous annealing and solution treatment at a temperature of 700℃~900℃.

[0041] The beneficial effects of this invention are as follows: By rationally selecting alloy components and further controlling the heat treatment process, this invention successfully prepares a brass alloy with high strength, high elongation, high hardness, high-temperature stability, low cost, and relatively ideal electrical conductivity. After stress-relief annealing, a core-shell structured NiAl-encapsulated Fe precipitate phase will form in the alloy. This precipitated NiAl-encapsulated Fe core-shell structured second phase is coherent with the copper matrix. The precipitation of this coherent second phase results in a brass alloy with a strength of 662 MPa to 820 MPa, an elongation of 3% to 23%, a hardness of 213 HV to 256 HV, an electrical conductivity of 16% IACS to 20% IACS, and a softening temperature greater than 450℃. In this invention, due to the addition of Fe, Ni and Al can precipitate the NiAl phase (in the form of a NiAl phase with Fe as the core) with relatively small amounts of Fe. The hot rolling, rough rolling, and finish rolling deformation processes used in the material forming are mature and easy to control, and the preparation process has universal applicability. Attached Figure Description

[0042] Figure 1 This is a flowchart of the preparation method of the high-strength heat-resistant brass alloy of the present invention; Figure 2 This is a comparison of the hardness versus temperature curves of the precision rolled plates of Examples 1 (450℃ / 6h) and 2 (500℃ / 2h) of the present invention after holding at different stress-relief annealing temperatures for 1h. Figure 3 This is a comparison of the hardness of the precision-rolled sheet material of Embodiment 1 of the present invention under three different stress-relief annealing temperatures as a function of holding time. Figure 4 This is a comparison chart of the engineering stress-strain tensile curves of the fine-rolled plate of Example 1 without stress-relief annealing, the high-strength heat-resistant brass alloy plate of Example 1, the high-strength heat-resistant brass alloy plate of Example 2, and the high-strength heat-resistant brass alloy plate of Example 3 of the present invention. Figure 5 a) is a transmission image of the high-strength heat-resistant brass alloy of Embodiment 1 of the present invention; Figure 5 b) is the EDS image of Al; Figure 5 c) is an EDS image of Fe; Figure 5 d) is the EDS image of Ni. Detailed Implementation

[0043] This invention discloses a high-strength heat-resistant brass alloy, which, by mass percentage, comprises 69%~75% Cu, 0.1%~1% Sn, 1%~4% Al, 0.5%~1.5% Ni, 0.5%~1% Fe, and the balance being Zn; the high-strength heat-resistant brass alloy includes a core-shell structure precipitate phase of Fe encapsulated by NiAl.

[0044] The core-shell structured precipitate of Fe encapsulated by NiAl is formed by the segregation of Ni atoms and Al atoms at the Fe phase interface. The precipitated NiAl second phase (the core-shell structured precipitate of Fe encapsulated by NiAl) is coherent with the copper matrix, with a size of 10nm~20nm, and is diffusely distributed in the copper matrix.

[0045] The NiAl-encapsulated Fe core-shell precipitate phase precipitates during the stress-relief annealing process of the high-strength heat-resistant brass alloy. The stress-relief annealing temperature is typically 300℃~500℃, preferably 450℃, and the holding time is typically 1h~3h, preferably 1h. The precipitation of the coherent second phase gives the high-strength heat-resistant brass alloy a strength of 662MPa~820MPa, an elongation of 3%~23%, a hardness of 213HV~256HV, and a conductivity of 16%IACS~20%IACS.

[0046] See Figure 1The present invention also discloses a method for preparing any of the high-strength heat-resistant brass alloys described herein, comprising the following steps: Step 1: Ingredients: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy; Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. After pure Cu is melted, Fe and Ni are added first, and the mixture is kept at a certain temperature for a period of time (usually 0.5h~2h) and stirred to make the fusion uniform. Then, low-melting-point Sn, Al and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred and slag is removed, and the mixture is kept at a certain temperature for a period of time (usually 10min~30min) before being taken out of the furnace. Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained. Step 4: Hot rolling: Before hot rolling, the casting is milled, then subjected to high-temperature solution treatment, and then hot rolled. The hot rolling process is multi-pass rolling, and the hot-rolled plate is obtained after water quenching. Step 5: Rough rolling: The hot-rolled sheet is cold-rolled to obtain a rough-rolled sheet; Step 6: Softening Annealing: The rough-rolled sheet is milled and then softened and annealed at 300℃~900℃ for 2h~8h to allow the sheet to recrystallize completely. Step 7: Finish rolling: The sheet metal is cold rolled to obtain a finish rolled sheet metal. Before cold rolling, the sheet metal is milled. In order to prevent cracking during the rolling process, the cold rolling adopts a multi-pass rolling process. Step 8: Stress-relief annealing: The precision-rolled plate is milled and then held at 300℃~500℃ for 1h~3h to relieve stress and precipitate the core-shell structure of NiAl-encapsulated Fe to obtain the high-strength heat-resistant brass alloy (plate).

[0047] In step two, the preferred melting temperature is 1100℃~1700℃.

[0048] In step four, the preferred temperature for high-temperature solid solution is 750℃~1000℃, and the preferred holding time is 1h~8h.

[0049] In step four, the single-pass processing rate of hot rolling is preferably 15% to 20%, and the total deformation is preferably 70% to 90%.

[0050] In step four, the termination temperature of hot rolling is preferably 650°C to 750°C to suppress the precipitation of the β phase.

[0051] In step five, the single deformation amount of cold rolling is preferably 3% to 10%, the total deformation amount is preferably 70% to 90%, and the thickness of the obtained rough-rolled plate is preferably 0.6 mm to 3.5 mm.

[0052] In step six, the softening annealing temperature is preferably 400℃~630℃.

[0053] In step seven, the single deformation amount of cold rolling is preferably 2% to 5%, the total deformation amount is preferably 60% to 88%, and the thickness of the resulting precision rolled plate is preferably 0.05 mm to 3.0 mm.

[0054] In step eight, the preferred temperature for stress-relief annealing is 450°C, and the preferred holding time is 1 hour.

[0055] Steps three through five can be replaced by continuous casting and rolling processes.

[0056] The cold rolling (or precision rolling) in step seven can be performed twice, with continuous annealing and solution treatment of the sheet material between the two cold rolling operations. The annealing temperature is preferably 700℃~900℃.

[0057] The following are examples of methods for preparing high-strength, heat-resistant brass alloys: Example 1: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein Cu is 75% by mass, Sn is 0.5% by mass, Al is 1% by mass, Ni is 1.5% by mass, Fe is 0.8% by mass, and the balance is Zn.

[0058] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1300℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0059] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0060] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 800℃ for 2 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 15%. After multiple rolling passes, the final rolling temperature is 650℃. After water quenching, hot-rolled plate is obtained.

[0061] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 10%. After multiple rolling passes, a rough-rolled plate with a thickness of 2.0 mm is obtained.

[0062] Step 6: Softening Annealing: The rough-rolled plate is milled and then softened and annealed at 450℃ for 6 hours to allow the grains to recrystallize.

[0063] Step 7: Finish rolling: Before finish rolling, the plate is milled to remove the surface oxides. Then, the plate is cold rolled. The deformation amount of a single cold rolling is 3%. After multiple rolling passes, a finish rolled plate with a thickness of 0.5 mm is obtained.

[0064] Step 8: Stress-relief annealing: The precision-rolled plate is milled and then held at 450℃ for 1 hour to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0065] Example 2: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein Cu is 73% by mass, Sn is 0.1% by mass, Al is 4% by mass, Ni is 1% by mass, Fe is 0.5% by mass, and the balance is Zn.

[0066] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1300℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0067] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0068] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 750℃ for 5 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 15%. After multiple rolling passes, the final rolling temperature is 650℃. After water quenching, hot-rolled plate is obtained.

[0069] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 3%, and the total deformation is 80%. After multiple rolling passes, a rough-rolled plate with a thickness of 3mm is obtained.

[0070] Step 6: Softening Annealing: The rough-rolled plate is milled and then held at 500℃ for 2 hours for softening annealing to allow the grains to recrystallize.

[0071] Step 7: Finish rolling: Before finish rolling, the plate is milled to remove the surface oxides. Then, the plate is cold rolled. The deformation amount of a single cold rolling is 2%. After multiple rolling passes, a finish rolled plate with a thickness of 0.5 mm is obtained.

[0072] Step 8: Stress-relief annealing: The precision-rolled plate is milled and then held at 450℃ for 1 hour to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0073] Example 3: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein Cu is 75% by mass, Sn is 0.5% by mass, Al is 1% by mass, Ni is 1.5% by mass, Fe is 0.8% by mass, and the balance is Zn.

[0074] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1300℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0075] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0076] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 800℃ for 2 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 15%. After multiple rolling passes, the final rolling temperature is 650℃. After water quenching, hot-rolled plate is obtained.

[0077] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 10%. After multiple rolling passes, a rough-rolled plate with a thickness of 2.0 mm is obtained.

[0078] Step 6: Softening Annealing: The rough-rolled plate is milled and then softened and annealed at 450℃ for 6 hours to allow the grains to recrystallize.

[0079] Step 7: Finish rolling: Before finish rolling, the plate is milled to remove the surface oxides. Then, the plate is cold rolled. The deformation amount of a single cold rolling is 5%. After multiple rolling passes, a finish rolled plate with a thickness of 0.3 mm is obtained.

[0080] Step 8: Stress-relief annealing: The precision-rolled plate is milled and then held at 450℃ for 1 hour to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0081] Example 4: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein the mass percentage of Cu is 69%, the mass percentage of Sn is 1%, the mass percentage of Al is 2%, the mass percentage of Ni is 0.5%, the mass percentage of Fe is 1%, and the balance is Zn.

[0082] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1700℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0083] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0084] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 900℃ for 6 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 20%. After multiple rolling passes, the final rolling temperature is 680℃. After water quenching, hot-rolled plate is obtained.

[0085] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 3%, and the total deformation is 75%. After multiple rolling passes, a rough-rolled plate with a thickness of 3mm is obtained.

[0086] Step 6: Softening Annealing: The rough-rolled plate is milled and then softened and annealed at 300℃ for 6 hours to allow the grains to recrystallize.

[0087] Step 7: Finish rolling: Before finish rolling, the plate is milled to remove the surface oxides. Then, the plate is cold rolled. The deformation amount of a single cold rolling is 5%. After multiple rolling passes, a finish rolled plate with a thickness of 0.2 mm is obtained.

[0088] Step 8: Stress-relief annealing: The precision-rolled plate is milled and then held at 500℃ for 3 hours to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0089] Example 5: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein the mass percentage of Cu is 74%, the mass percentage of Sn is 0.8%, the mass percentage of Al is 1.5%, the mass percentage of Ni is 1.3%, the mass percentage of Fe is 0.7%, and the balance is Zn.

[0090] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1100℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0091] Step 3: Continuous casting and rolling: The alloy is cast into the tundish, and a covering agent is added to keep it warm and isolate it from the air. The internal temperature is maintained at about 1050℃. Then it is distributed to the crystallizer to cool and obtain the billet. The billet is then sent to the continuous rolling mill for rolling. After the continuous rolling is completed, it is water-cooled to obtain the continuously cast and rolled plate.

[0092] Step 4: Annealing: Anneal the continuously cast and rolled plate by holding it at 450℃ for 6 hours to obtain an alloy plate with matching strength and toughness.

[0093] Step 5: Finish rolling: Before finish rolling, the plate is milled to remove the surface oxides. Then, the plate is cold rolled. The single deformation of cold rolling is 2%, and the total deformation is 88%. After multiple rolling passes, a finish rolled plate with a thickness of 0.3 mm is obtained.

[0094] Step 6: Stress-relief annealing: The precision-rolled plate is milled and then held at 450℃ for 1 hour to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0095] Example 6: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein the mass percentage of Cu is 72%, the mass percentage of Sn is 0.2%, the mass percentage of Al is 3%, the mass percentage of Ni is 0.8%, the mass percentage of Fe is 0.6%, and the balance is Zn.

[0096] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1300℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0097] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0098] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 1000℃ for 6 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 18%. After multiple rolling passes, the final rolling temperature is 750℃. After water quenching, hot-rolled plate is obtained.

[0099] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 5%, and the total deformation is 90%. After multiple rolling passes, a rough-rolled plate with a thickness of 0.8mm is obtained.

[0100] Step 6: Softening Annealing: The rough-rolled plate is milled and then softened and annealed at 630℃ for 8 hours to allow the grains to recrystallize.

[0101] Step 7: First precision rolling: First, the plate is milled to remove the surface oxides, and then the plate is cold rolled in multiple passes to obtain a first precision rolled plate with a suitable pre-finished thickness.

[0102] Step 8: Continuous annealing and solution treatment: The first precision rolled plate is subjected to continuous annealing and solution treatment at an annealing temperature of 700℃~900℃. The precipitated phase is then further dissolved, and the solution treatment result is controlled by grain size.

[0103] Step 9: Second precision rolling: First, the plate is milled to remove the surface oxides, and then the plate is cold rolled. After multiple rolling passes, a second precision rolled plate with a thickness of 0.41mm is obtained.

[0104] Step 10: Stress-relief annealing: The second-rolled plate is milled and then held at 450℃ for 3 hours to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0105] Example 7: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein the mass percentage of Cu is 72%, the mass percentage of Sn is 0.2%, the mass percentage of Al is 3%, the mass percentage of Ni is 0.8%, the mass percentage of Fe is 0.6%, and the balance is Zn.

[0106] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1300℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0107] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0108] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 1000℃ for 6 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 18%. After multiple rolling passes, the final rolling temperature is 750℃. After water quenching, hot-rolled plate is obtained.

[0109] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 5%, and the total deformation is 90%. After multiple rolling passes, a rough-rolled plate with a thickness of 0.8mm is obtained.

[0110] Step 6: Softening Annealing: The rough-rolled plate is milled and then softened and annealed at 630℃ for 8 hours to allow the grains to recrystallize.

[0111] Step 7: First precision rolling: First, the plate is milled to remove the surface oxides, and then the plate is cold rolled in multiple passes to obtain a first precision rolled plate with a suitable pre-finished thickness.

[0112] Step 8: Continuous annealing and solution treatment: The first precision rolled plate is subjected to continuous annealing and solution treatment at an annealing temperature of 700℃~900℃. The precipitated phase is then further dissolved, and the solution treatment result is controlled by grain size.

[0113] Step 9: Second precision rolling: First, the plate is milled to remove the surface oxides, and then the plate is cold rolled. After multiple rolling passes, a second precision rolled plate with a thickness of 0.358mm is obtained.

[0114] Step 10: Stress-relief annealing: The second-rolled plate is milled and then held at 390℃ for 3 hours to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0115] Example 8: Step 1: Batching: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy, wherein the mass percentage of Cu is 72%, the mass percentage of Sn is 0.2%, the mass percentage of Al is 3%, the mass percentage of Ni is 0.8%, the mass percentage of Fe is 0.6%, and the balance is Zn.

[0116] Step 2: Smelting: The prepared raw materials are smelted in a medium-frequency induction furnace. Charcoal is used for covering during smelting, a molybdenum crucible is used, and cryolite is used as a flux. The smelting temperature is 1300℃. First, pure Cu is melted, then Fe and Ni are added. The mixture is kept at this temperature for a period of time and stirred. After Cu, Fe, and Ni are fully and evenly fused together, Sn, Al, and Zn are added and stirred to make the fusion uniform. Cryolite is added, stirred, and slag is removed. The mixture is kept at this temperature for a period of time before being taken out of the furnace (stirring is required during the holding process).

[0117] Step 3: Casting: Using a graphite mold, the mold is dried and dehydrated in an electric furnace before casting. Then, a layer of zinc oxide is coated on the inner wall of the mold. The molten alloy is poured into the mold and air-cooled. After complete cooling, the alloy casting is obtained.

[0118] Step 4: Hot rolling: Before hot rolling, the casting is milled and then heat-treated at 1000℃ for 6 hours for high-temperature solution treatment. Then, it is hot rolled. The single deformation of hot rolling is 18%. After multiple rolling passes, the final rolling temperature is 750℃. After water quenching, hot-rolled plate is obtained.

[0119] Step 5: Rough rolling: Before rough rolling, the plate is milled to remove the surface oxides. Then, the hot-rolled plate is cold-rolled. The single deformation of cold rolling is 5%, and the total deformation is 90%. After multiple rolling passes, a rough-rolled plate with a thickness of 0.8mm is obtained.

[0120] Step 6: Softening Annealing: The rough-rolled plate is milled and then softened and annealed at 630℃ for 8 hours to allow the grains to recrystallize.

[0121] Step 7: First precision rolling: First, the plate is milled to remove the surface oxides, and then the plate is cold rolled in multiple passes to obtain a first precision rolled plate with a suitable pre-finished thickness.

[0122] Step 8: Continuous annealing and solution treatment: The first precision rolled plate is subjected to continuous annealing and solution treatment at an annealing temperature of 700℃~900℃. The precipitated phase is then further dissolved, and the solution treatment result is controlled by grain size.

[0123] Step 9: Second precision rolling: First, the plate is milled to remove the surface oxides, and then the plate is cold rolled. After multiple rolling passes, a second precision rolled plate with a thickness of 0.305mm is obtained.

[0124] Step 10: Stress-relief annealing: The second-rolled plate is milled and then held at 300℃ for 3 hours to relieve stress and precipitate a core-shell structure of NiAl-encapsulated Fe to obtain a high-strength heat-resistant brass alloy plate.

[0125] The performance data for each preparation stage of Examples 1 and 2 are shown in Table 1.

[0126] Table 1. Comparison of performance data at each preparation stage in Examples 1 and 2.

[0127] The hardness of stress-relief annealing performed in Examples 1 and 2 by holding at different temperatures for 1 hour is shown in Table 2.

[0128] Table 2. Hardness comparison of Example 1 and Example 2 after stress-relief annealing at different temperatures for 1 hour.

[0129] The hardness of stress-relief annealing performed in Example 1 at different temperatures and for different times is shown in Table 3.

[0130] Table 3. Hardness comparison of stress-relief annealing in Example 1 at different temperatures and for different durations.

[0131] The physical performance data of each embodiment are shown in Table 4.

[0132] Table 4 Comparison of physical properties of each embodiment

[0133] According to each table and Figure 4 The brass alloy sheet of Example 1 has an engineering stress-strain strength of 775 MPa, an elongation of 23%, and a conductivity of 20% IACS; the brass alloy sheet of Example 2 has an engineering stress-strain strength of 755 MPa, an elongation of 20%, and a conductivity of 18.9% IACS; the brass alloy sheet of Example 3 has an engineering stress-strain strength of 700 MPa, an elongation of 19.2%, and a conductivity of 18% IACS.

[0134] Combination Figure 2 As shown in Table 2, brass alloys exhibit good resistance to high-temperature softening when the softening annealing temperature is 500℃. Combined with... Figure 3 As shown in Table 3, the hardness of brass alloys after stress-relief annealing is 214 HV and 202.5 HV after holding at 400℃ for 1 h and 24 h, respectively; 211 HV and 193.3 HV after holding at 450℃ for 1 h and 24 h, respectively; and 185 HV and 185.4 HV after holding at 500℃ for 1 h and 24 h, respectively. The stress-relief annealing temperature of 500℃ is least affected by the holding time. Combined with... Figure 4As shown in Table 4, the best tensile strength of Example 1 without stress-relief annealing was 926 MPa, but the elongation was low at 3% due to the lack of stress-relief annealing. The brass alloy prepared in Example 1 had the best overall performance, with a tensile strength of 775 MPa and an elongation of 23%. The brass alloy prepared in Example 2 had the second best performance, with a strength of 755 MPa and an elongation of 20%. The brass alloy prepared in Example 3 had a tensile strength of 700 MPa and an elongation of 19.8%. Due to its thickness of only 0.3 mm, the tensile strength and elongation of Example 3 were slightly lower than those of Examples 1 and 2. The conductivity of the alloy did not change significantly after undergoing different processing techniques, remaining between 18% and 20% IACS.

[0135] Figure 5 a) is a transmission image of the brass alloy after stress-relief annealing in Example 1. The bright field image scale bar is 70nm. The arrow indicates the NiAl-encapsulated Fe core-shell precipitate at 10nm~20nm. The high-resolution global Fourier transform confirms that the copper matrix is ​​α-Cu and the NiAl-encapsulated Fe core-shell precipitate is coherent with the α-Cu matrix. Figure 5 b) is an EDS image of Al, showing Al atom segregation in the α-Cu matrix; Figure 5 c) is an EDS image of Fe, showing Fe atom segregation in the α-Cu matrix; Figure 5 d) shows the EDS image of Ni, revealing Ni atom segregation in the α-Cu matrix. The corresponding EDS images of Al, Fe, and Ni elements demonstrate that the NiAl-encapsulated Fe core-shell precipitate is dispersed within the copper matrix. The above phase, composition, morphology, and elemental characterization fully confirm the existence of the NiAl-encapsulated Fe core-shell precipitate in the brass alloy, and explain its morphology, size, and distribution within the matrix.

[0136] The brass alloy of this invention has an ultimate tensile strength of 840MPa-950MPa, an elongation of 2%-3%, a conductivity of 15%-20%IACS, and an initial hardness of 255HV-265HV. After aging at 450℃ for 1 hour (after stress-relief annealing), Ni and Al atoms segregate at the Fe phase interface to form a NiAl-encapsulated Fe core-shell precipitate, maintaining high strength (662MPa-820MPa), high elongation (3%-23%), high hardness (213HV-256HV), and excellent conductivity (16%-20%IACS), with a softening temperature greater than 450℃. In this invention, the NiAl-encapsulated Fe core-shell precipitate is a high-temperature stable phase and is used for the first time in a brass alloy (NiAl is a body-centered cubic ordered phase with a melting point of 1638℃), significantly improving the high-temperature stability of the brass alloy and maintaining high electrical conductivity.

[0137] In summary, the brass alloy of the present invention has high tensile strength, high elongation, high hardness, good electrical conductivity and excellent high-temperature stability.

Claims

1. A high-strength, heat-resistant brass alloy, characterized in that... The alloy comprises, by mass percentage, 69%–75% Cu, 0.1%–1% Sn, 1%–4% Al, 0.5%–1.5% Ni, 0.5%–1% Fe, with the balance being Zn; the high-strength heat-resistant brass alloy comprises a core-shell structure precipitate of Fe encapsulated by NiAl.

2. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... The core-shell structured precipitate of Fe encapsulated by NiAl is formed by the segregation of Ni atoms and Al atoms at the Fe phase interface.

3. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... The core-shell structured precipitate of Fe encapsulated in NiAl is coherent with the copper matrix.

4. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... The size of the NiAl-encapsulated Fe core-shell precipitate is 10 nm to 20 nm.

5. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... The NiAl-encapsulated Fe core-shell precipitate is dispersed in the copper matrix.

6. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... The core-shell structured NiAl-encapsulated Fe precipitate is formed during the stress-relief annealing process of the high-strength heat-resistant brass alloy.

7. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... The stress-relief annealing temperature is 300℃~500℃, and the holding time is 1h~3h.

8. The high-strength heat-resistant brass alloy according to claim 1, characterized in that... Its strength is 662MPa~820MPa, elongation is 3%~23%, hardness is 213HV~256HV, and conductivity is 16%IACS~20%IACS.

9. The method for preparing the high-strength heat-resistant brass alloy according to any one of claims 1-8, characterized in that... Includes the following steps: Step 1: Prepare the raw materials according to the mass percentage of each component of the high-strength heat-resistant brass alloy; Step 2: Melt the prepared raw materials. After melting pure Cu, first add Fe and Ni, stir and melt evenly, then add Sn, Al and Zn, stir and melt evenly again, then add cryolite, stir and remove slag, keep warm for a period of time and then remove from the furnace. Step 3: Pour the molten alloy into a mold and air cool it. After it has completely cooled, you will get the alloy casting. Step 4: The casting is subjected to high-temperature solution treatment, then hot-rolled, and water-quenched to obtain hot-rolled sheet metal; Step 5: Cold roll the hot-rolled sheet to obtain a rough-rolled sheet; Step Six: Soften and anneal the rough-rolled sheet to allow it to fully recrystallize; Step 7: Cold roll the sheet material to obtain a precision-rolled sheet material; Step 8: Perform stress-relief annealing on the precision-rolled plate to precipitate the core-shell structured phase of NiAl encapsulating Fe, thereby obtaining the high-strength heat-resistant brass alloy.

10. The method for preparing the high-strength heat-resistant brass alloy according to claim 9, characterized in that... The stress-relief annealing temperature in step eight is 300℃~500℃, and the holding time is 1h~3h.

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