High-strength and high-conductivity iron bronze alloy and preparation method and application thereof

Abstract

The invention discloses a high-strength and high-conductivity iron bronze alloy as well as a preparation method and application thereof. The iron bronze alloy comprises the following components in percentage by mass: 2.1-2.4 wt% of Fe, 0.015-0.1 wt% of P, 0.05-0.15 wt% of Zn, less than or equal to 0.1 wt% of impurities and the balance of Cu, the structure of the iron bronze alloy comprises a matrix phase and a second phase, the second phase comprises particle-shaped Fe3P phases and fibrous Fe-rich phases, the size of the particle-shaped Fe3P phases is 100-150 nm, the diameter of the fibrous Fe-rich phases is smaller than 2 micrometers, and the distance between the fibrous Fe-rich phases is smaller than 10 micrometers. The tensile strength of the iron bronze alloy is 600 MPa or above, the electric conductivity is 70% IACS or above, and the iron bronze alloy has wide application prospects in preparation of vehicle gauge grade IGBT contact pins.

Description

Technical Field

[0001] The present invention relates to the field of copper alloys, and in particular to a high-strength and high-conductivity iron-bronze alloy and a preparation method and application thereof. Background Art

[0002] As a typical representative of Cu-Fe-P alloys, C19400 alloy exhibits excellent comprehensive performance due to its unique composition design and microstructure. By precisely controlling the ratio of iron and phosphorus elements, it forms a highly dispersed strengthening phase after aging treatment, achieving a perfect balance between high strength and high conductivity. The tensile strength can reach over 550MPa and the conductivity exceeds 70% IACS. As a lead frame material, it not only ensures efficient signal transmission in complex electronic devices, but also has excellent anti-softening and anti-fatigue properties, ensuring the long-term and stable operation of equipment. In mechanical manufacturing, C19400 alloy can be used to manufacture precision parts due to its good formability and wear resistance; in the transportation and shipbuilding fields, its excellent corrosion resistance and strength provide reliable protection for key structural parts, and it occupies an important position in the modern industrial system.

[0003] However, as integrated circuits develop towards miniaturization and high integration, especially in the field of automotive-grade IGBT module pins, C19400 materials are required to maintain high reliability under large currents. This requires the material to have good conductivity to reduce heat generation, and at the same time have high strength and high resistance to high-temperature softening to ensure pin stability. Generally, the tensile strength is required to be greater than 600MPa and the conductivity is required to be greater than 70% IACS.

[0004] Currently, C19400 material is primarily used in lead frame materials. For example, Chinese patent publication CN114990377A discloses a high-strength, high-conductivity iron-bronze alloy for electrical connectors and its preparation method. By combining the proper proportions of trace components such as magnesium, chromium, and rare earth elements, and combining a process involving hot-rolled ingot casting, solution treatment, secondary aging, and tertiary cold rolling, the iron-bronze alloy significantly improves its tensile strength and electrical conductivity. The resulting finished C19400 strip achieves optimal performance of approximately 560 MPa and a conductivity of approximately 74.2% IACS. However, this still falls short of achieving high strengths exceeding 600 MPa. Furthermore, this method is primarily used in strip production. Existing technical literature lacks information on high-strength, high-conductivity wire products for the pin connector market.

[0005] The invention patent application with publication number CN106591623A discloses a high-temperature resistant iron bronze, which comprises the following weight percentages: Fe: 0.05-3.0%, Sn: 0.005-0.25%, P: 0.01-0.30%, and the balance being Cu and unavoidable impurities. This invention patent application achieves an alloy tensile strength of over 450 MPa, a conductivity of over 85% IACS, and a hardness of over 130 HV by strictly controlling the ratio and content of elements such as Fe, Sn, and P, as well as the precipitation of iron-phosphorus intermetallic compounds and tin-phosphorus intermetallic compounds in the alloy microstructure. Furthermore, after being held at 500°C for 5 minutes, the hardness retention rate is ≥80% of the original hardness, demonstrating excellent high-temperature softening resistance and suitability for use as connector and lead frame materials at high temperatures. The preparation method ensures that Fe and P are dissolved in the copper alloy matrix, while excess Fe and P form iron-phosphorus intermetallic compounds and tin-phosphorus intermetallic compounds with Sn, achieving dispersion strengthening and precipitation. This improves the strength and hardness of the alloy without reducing its conductivity. However, the strength of the iron bronze disclosed in this patent application still fails to meet the requirement of over 600 MPa.

[0006] Therefore, in view of the above-mentioned deficiencies in the existing technology, there is an urgent need to find a high-strength and high-conductivity iron-bronze alloy wire material that is suitable for the IGBT pin field. Summary of the Invention

[0007] The invention provides a high-strength and high-conductivity iron-bronze alloy, which has high tensile strength and electrical conductivity.

[0008] The present invention provides a high-strength and high-conductivity iron-bronze alloy, wherein the iron-bronze alloy comprises Fe: 2.1-2.4wt%, P: 0.015-0.1wt%, Zn: 0.05-0.15wt%, impurity content ≤0.1wt%, and the balance is Cu;

[0009] The structure of the iron-bronze alloy includes a matrix phase and a second phase, the second phase includes a granular Fe3P phase and a fibrous Fe-rich phase, the size of the granular Fe3P phase is 100-150nm, the diameter of the fibrous Fe-rich phase is less than 2μm, and the distance between the fibrous Fe-rich phases is less than 10μm.

[0010] The functions of the elements provided by the present invention are:

[0011] As the main strengthening phase of C19400 alloy, Fe element can mainly refine the microstructure grains and react with P element to generate granular Fe3P phase to further strengthen the matrix. At the same time, at high temperature, it prevents the matrix from recrystallizing and improves the resistance to high temperature softening. However, Fe element is prone to segregation, which deteriorates the performance.

[0012] As a deoxidizer, P can remove oxygen from the melt, preventing Fe from combining with oxygen to form Fe oxides, which affects the processing performance. At the same time, P combines with Fe to form a second phase, which has a certain degree of strengthening effect. However, the P element cannot be too much, otherwise the conductivity of the matrix will be seriously reduced, and secondly, the Fe3P phase will grow excessively.

[0013] Zn element can also be used as an oxygen scavenger, while reducing production costs.

[0014] Preferably, the Fe content is controlled at 2.1-2.2%, the P content is controlled at 0.015-0.02%, and the Zn content is controlled between 0.05-0.10%. If the Zn content exceeds 0.10%, it will have a greater impact on the conductivity, thereby affecting the conductivity of the finished product. At the same time, Zn also has certain deoxidation properties, reducing the oxidation of the Fe element and avoiding the formation of Fe oxides, which leads to the formation of hard spots in the finished product and affects the strength of the finished product. Therefore, in order to ensure the deoxidation effect, it is recommended that the Zn element be controlled at more than 0.05%.

[0015] Preferably, the diameter of the fibrous Fe-rich phase is less than 1 μm, and the distance between the fibrous Fe-rich phases is less than 5 μm.

[0016] Preferably, the average grain size of the iron-bronze alloy is 5 to 10 μm. The finer the grains, the more grain boundaries there are, the stronger the barrier to dislocations, the more obvious the effect of grain refinement strengthening, and the greater the contribution to the high strength target. However, more grain boundaries have a greater impact on the electron scattering ability and conductivity.

[0017] On the other hand, the present invention also provides a method for preparing a high-strength and high-conductivity iron-bronze alloy, comprising: batching → semi-continuous casting → hot extrusion → solid solution → first stretching → first annealing → second stretching → second annealing → finished product cold drawing;

[0018] Wherein, the ingredients are prepared according to the mass percentage of the high-strength and high-conductivity iron-bronze alloy;

[0019] During the semi-continuous casting process, the red ingot is kept drawn;

[0020] The annealing temperature of the first annealing is 350-400° C., and the holding time is 8-16 hours.

[0021] The present invention controls the temperature of the first annealing at a relatively low temperature and the holding time for a relatively long time, so that the second phase Fe3P phase and the iron-rich phase can be slowly precipitated, thereby avoiding excessive precipitation of the second phase that is too large, and a large amount of P element can be precipitated. Therefore, after the first annealing process, the size of the granular Fe3P phase in the billet is 80-120nm, the size of the fibrous Fe-rich phase is less than 10μm, and the spacing is less than 30μm, making it possible to subsequently control the size and spacing of the fibrous Fe-rich phase and fully precipitate the P element.

[0022] Preferably, during the semi-continuous casting process, the surface temperature of the ingot is above 600°C to 700°C when it exits the crystallizer to maintain the red ingot casting and ensure that the cooling intensity is not too high. By maintaining the red ingot casting during the casting process, the present invention reduces the cooling intensity of the casting process and prevents excessive growth of Fe phase dendrites during the melting and casting process. The size of the Fe phase and the spacing between Fe-rich phases in the ingot are respectively less than 20μm and 40μm, thereby laying the foundation for ultimately achieving smaller Fe phase size and spacing between Fe-rich phases.

[0023] Preferably, the first annealing atmosphere is a hydrogen-containing protective atmosphere to prevent the generation of copper oxide powder on the surface of the rod blank and increase the contact resistance of the finished pin.

[0024] Preferably, the first annealing temperature is 350-380° C., and the holding time is 12-15 hours.

[0025] Preferably, the processing rate of the second stretching is above 80%. After the first annealing, the second phase is analyzed in the middle of the matrix and acts as a strengthening phase in the matrix to pin dislocations. At this time, at a high processing rate, a large number of dislocations gather around the iron-rich phase and the Fe3P phase, accumulating momentum for the subsequent precipitation of the second phase.

[0026] Preferably, the second annealing temperature is 420-450°C for 18-25 hours. The large amount of deformation energy accumulated in the previous step serves as precipitation motive force. By controlling the annealing temperature and time, the Fe3P phase is fully precipitated, increasing the size of the Fe3P phase to 100-150 nm and improving conductivity. At the same time, recrystallization of dislocations around the fibrous iron-rich phase is ensured, refining the structure. The increase in grain boundaries increases the number of dislocations around the fibrous iron-rich phase. During this process, the billet has a hardness of no less than 110 Hv, a conductivity of no less than 80% IACS, and an iron-rich phase size of less than 6 μm.

[0027] Preferably, the processing rate of the finished cold-drawn product is 85-95%. The present invention controls the processing rate of the finished cold-drawn product, slightly reduces the conductivity, and through the high processing rate, a large number of dislocations around the fibrous iron-rich phase are blocked by the fibrous iron-rich phase, thereby greatly improving the strength.

[0028] Preferably, the melting process of the semi-continuous casting is as follows: first, the electrolytic plate is added to the smelting furnace, the temperature is increased to melt, calcined charcoal is added during the heating process, after the electrolytic plate is melted and the temperature rises to 1200-1256°C, the zinc ingot is added, and after keeping warm for 10-15 minutes, the temperature is increased to 1250-1300°C, half of the phosphorus-copper alloy in the ingredients is added, and the melt is stirred, and then the copper-iron master alloy is added, and after keeping warm for 30-90 minutes, the remaining phosphorus-copper alloy is added and kept warm for 5-10 minutes.

[0029] Preferably, the temperature of the hot extrusion is 900-1000° C., and the heat preservation time is 4-6 hours.

[0030] Preferably, the solutionizing temperature is 850-950° C., the time is 45-90 min, and pickling is performed after the solutionizing to remove oxide scale on the surface.

[0031] Further preferably, the solution temperature is 880-900° C., the time is 50-70 min, and the conductivity of the rod blank after solution is below 25% IACS, ensuring that some elements precipitated during the extrusion process are re-dissolved into the matrix.

[0032] Preferably, the first stretching is performed by cold rolling. Compared with other processes such as cold drawing, cold rolling can ensure that the entire cross section of the bar can be deformed; and the cold working rate is above 60%.

[0033] The present invention also provides the use of the high-strength and high-conductivity iron-bronze alloy in the preparation of IGBT pins.

[0034] The present invention prepares high-strength and high-conductivity C19400 wire through multiple (two or more) low-temperature, long-term annealing + high processing rate control without adding other elements, which is very suitable for automotive-grade IGBT pin products.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention controls the P content and the size of the Fe3P phase to allow the P element to be fully precipitated, and avoids the P element from remaining in the matrix as much as possible to affect the conductivity of the material, thereby ensuring the conductivity of the material.

[0037] The present invention reduces the size of the Fe-rich phase and the spacing between the Fe-rich phases, thereby avoiding the enrichment of the iron phase as much as possible, reducing the crack source generated at the position of the iron-rich phase and affecting the strength of the material, so that the fibrous iron-rich phase provided by the present invention exerts a significant strengthening effect.

[0038] Through the above-mentioned element and microstructure regulation, the iron-bronze alloy provided by the present invention has a tensile strength of more than 600 MPa and a conductivity of 70% IACS and above, and has broad application prospects in the preparation of automotive-grade IGBT pins. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a metallographic diagram of the iron-bronze alloy prepared in Example 1 of the present invention;

[0040] Figure 2 This is a metallographic diagram of the blank after the first annealing provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited to the following examples.

[0042] The raw materials used in the present invention are all commercially available.

[0043] Example 1 Preparation of φ1.2mm C19400 alloy wire:

[0044] 1) In the batching process, raw materials that meet the requirements are prepared according to a proportion, wherein the raw materials include a copper raw material with a purity greater than 99.995%, a zinc ingot with a purity greater than 99.99%, a copper-iron master alloy, and a phosphorus-copper master alloy, wherein the Fe content of the copper-iron master alloy is 50%, and the P content of the phosphorus-copper alloy is 15%.

[0045] 2) Semi-continuous casting: first add the electrolytic plate to the smelting furnace, heat it up and melt it, add calcined charcoal during the heating process, wait for the electrolytic plate to melt and the temperature rises to 1200℃, then add the zinc ingot, keep it warm for 10 minutes, then heat it up to 1300℃, add half of the phosphor-copper alloy in the ingredients, and stir the melt, then add the copper-iron intermediate alloy, keep it warm for 60 minutes, add the remaining phosphor-copper alloy, keep it warm for 5 minutes, and start casting. Keep the red ingot casting during the casting process. The temperature of the ingot is above 650℃ when it comes out of the crystallizer. The casting specification of the alloy melt is φ245mm round ingot.

[0046] 3) Hot extrusion: The semi-continuous casting ingot is heated to 940°C, kept warm for more than 4 hours, and extruded to a specification of φ30mm.

[0047] 4) Solution pickling: solution temperature 900℃, time 45min, pickling after solution, no oxide scale on the surface.

[0048] 5) Extension: The extruded rod is cold rolled to φ18mm.

[0049] 6) First low temperature annealing: The cold rolled bar is subjected to low temperature and long time annealing, the annealing temperature is 350℃, and the holding time is 15h.

[0050] 7) Extension: The annealed rod is cold rolled to φ6mm.

[0051] 8) Second low-temperature annealing: The cold-rolled rod blank is annealed at 420°C for 20 hours.

[0052] 9) Cold drawn to finished product φ1.2mm.

[0053] Example 2 Preparation of φ1.0 mm C19400 alloy wire:

[0054] 1) In the batching process, raw materials that meet the requirements are prepared according to a proportion, wherein the raw materials include a copper raw material with a purity greater than 99.995%, a zinc ingot with a purity greater than 99.99%, a copper-iron master alloy, and a phosphorus-copper master alloy, wherein the Fe content of the copper-iron master alloy is 50%, and the P content of the phosphorus-copper alloy is 15%.

[0055] 2) Semi-continuous casting: first add the electrolytic plate to the smelting furnace, heat it up and melt it, add calcined charcoal during the heating process, wait for the electrolytic plate to melt and the temperature rises to 1230℃, then add the zinc ingot, keep it warm for 10 minutes, then heat it up to 1300℃, add half of the phosphor-copper alloy in the ingredients, and stir the melt, then add the copper-iron intermediate alloy, keep it warm for 60 minutes, add the remaining phosphor-copper alloy, keep it warm for 5-10 minutes, and start casting. Keep the red ingot casting during the casting process. The temperature of the ingot is above 650℃ when it comes out of the crystallizer. The casting specification of the alloy melt is φ255mm round ingot.

[0056] 3) Hot extrusion: The semi-continuous casting ingot is heated to 940°C, kept warm for more than 4 hours, and extruded to a specification of φ25mm.

[0057] 4) Solution pickling: solution temperature 880℃, time 60min, pickling after solution, no oxide scale on the surface.

[0058] 5) Extension: The extruded rod is cold rolled to φ12mm.

[0059] 6) First low-temperature annealing: The cold-rolled bar is subjected to low-temperature, long-term annealing at 350°C for 15 hours.

[0060] 7) Extension: The annealed rod is cold rolled to φ4mm.

[0061] 8) Second low-temperature annealing: The cold-rolled rod blank is annealed at 440°C for 18 hours.

[0062] 9) Cold drawing to finished product φ1.0mm.

[0063] Example 3 Preparation of φ0.8mm C19400 alloy wire

[0064] 1) In the batching process, raw materials that meet the requirements are prepared according to a proportion, wherein the raw materials include a copper raw material with a purity greater than 99.995%, a zinc ingot with a purity greater than 99.99%, a copper-iron master alloy, and a phosphorus-copper master alloy, wherein the Fe content of the copper-iron master alloy is 50%, and the P content of the phosphorus-copper alloy is 15%.

[0065] 2) Semi-continuous casting: first add the electrolytic plate to the smelting furnace, heat it up and melt it, add calcined charcoal during the heating process, wait for the electrolytic plate to melt and the temperature rises to 1250℃, then add the zinc ingot, keep it warm for 15 minutes, then heat it up to 1300℃, add half of the phosphor-copper alloy in the ingredients, and stir the melt, then add the copper-iron intermediate alloy, keep it warm for 90 minutes, add the remaining phosphor-copper alloy, keep it warm for 10 minutes, and start casting. Keep the red ingot casting during the casting process. The temperature of the ingot is above 650℃ when it comes out of the crystallizer. The casting specification of the alloy melt is φ245mm round ingot.

[0066] 3) Hot extrusion: The semi-continuous casting ingot is heated to 960°C, kept warm for more than 4 hours, and extruded to a specification of φ20mm.

[0067] 4) Solution pickling: solution temperature 880℃, time 50min, pickling after solution, no oxide scale on the surface.

[0068] 5) Extension: The extruded rod is cold rolled to φ8mm.

[0069] 6) First low-temperature annealing: The cold-rolled bar is subjected to low-temperature, long-term annealing at 380°C for 15 hours.

[0070] 7) Extension: The annealed rod is cold rolled to φ3mm.

[0071] 8) Second low-temperature annealing: The cold-rolled rod blank is annealed at 420°C for 20 hours.

[0072] 9) Cold drawn to finished product φ0.8mm.

[0073] Comparative Example 1 Preparation of φ1.2mm C19400 alloy wire:

[0074] 1) In the batching process, raw materials that meet the requirements are prepared according to a proportion, wherein the raw materials include a copper raw material with a purity greater than 99.995%, a zinc ingot with a purity greater than 99.99%, a copper-iron master alloy, and a phosphorus-copper master alloy, wherein the Fe content of the copper-iron master alloy is 50%, and the P content of the phosphorus-copper alloy is 15%.

[0075] 2) Semi-continuous casting: first add the electrolytic plate to the smelting furnace, heat it up and melt it, add calcined charcoal during the heating process, wait for the electrolytic plate to melt and the temperature to rise to 1200℃, then add the zinc ingot, keep it warm for 10 minutes, then heat it up to 1300℃, add half of the phosphor-copper alloy in the ingredients, and stir the melt, then add the copper-iron intermediate alloy, keep it warm for 60 minutes, add the remaining phosphor-copper alloy, keep it warm for 5 minutes, and start casting. Keep the red ingot casting during the casting process. The temperature of the ingot is 650℃ when it comes out of the crystallizer. The casting specification of the alloy melt is φ245mm round ingot.

[0076] 3) Hot extrusion: The semi-continuous casting ingot is heated to 940°C, kept warm for more than 4 hours, and extruded to a specification of φ30mm.

[0077] 4) Solution pickling: solution temperature 900℃, time 45min, pickling after solution, no oxide scale on the surface.

[0078] 5) First stretching: The extruded bar is cold rolled to φ18mm.

[0079] 6) First annealing: The cold rolled bar is annealed at 500°C for 5 hours.

[0080] 7) Second stretching: The annealed rod blank is cold rolled to φ6mm.

[0081] 8) Second annealing: anneal the cold-rolled rod blank at 450°C for 5 hours.

[0082] 9) Cold drawn to finished product φ1.2mm.

[0083] Comparative Example 2 Preparation of φ1.2mm C19400 alloy wire

[0084] 1) In the batching process, raw materials that meet the requirements are prepared according to a proportion, wherein the raw materials include a copper raw material with a purity greater than 99.995%, a zinc ingot with a purity greater than 99.99%, a copper-iron master alloy, and a phosphorus-copper master alloy, wherein the Fe content of the copper-iron master alloy is 50%, and the P content of the phosphorus-copper alloy is 15%.

[0085] 2) Semi-continuous casting: first add the electrolytic plate to the smelting furnace, heat it up and melt it, add calcined charcoal during the heating process, wait for the electrolytic plate to melt and the temperature rises to 1200℃, then add the zinc ingot, keep it warm for 10 minutes, then heat it up to 1300℃, add half of the phosphor-copper alloy in the ingredients, and stir the melt, then add the copper-iron intermediate alloy, keep it warm for 60 minutes, add the remaining phosphor-copper alloy, keep it warm for 5 minutes, and start casting. During the casting process, the water ingot is drawn and cast, and the temperature of the ingot is above 200℃ when it comes out of the crystallizer. The casting specification of the alloy melt is φ245mm round ingot.

[0086] 3) Hot extrusion: The semi-continuous casting ingot is heated to 940°C, kept warm for more than 4 hours, and extruded to a specification of φ30mm.

[0087] 4) Solution pickling: solution temperature 900℃, time 45min, pickling after solution, no oxide scale on the surface.

[0088] 5) Extension: The extruded rod is cold rolled to φ18mm.

[0089] 6) First low temperature annealing: The cold rolled bar is subjected to low temperature and long time annealing, the annealing temperature is 350℃, and the holding time is 15h.

[0090] 7) Extension: The annealed rod is cold rolled to φ6mm.

[0091] 8) Second low-temperature annealing: The cold-rolled rod blank is annealed at 420°C for 20 hours.

[0092] 9) Cold drawn to finished product φ1.2mm.

[0093] Comparative Example 3 Preparation of φ1.2mm C19400 alloy wire:

[0094] 1) In the batching process, raw materials that meet the requirements are prepared according to a proportion, wherein the raw materials include a copper raw material with a purity greater than 99.995%, a zinc ingot with a purity greater than 99.99%, a copper-iron master alloy, and a phosphorus-copper master alloy, wherein the Fe content of the copper-iron master alloy is 50%, and the P content of the phosphorus-copper alloy is 15%.

[0095] 2) Semi-continuous casting: first add the electrolytic plate to the smelting furnace, heat it up and melt it, add calcined charcoal during the heating process, wait for the electrolytic plate to melt and the temperature rises to 1200℃, then add the zinc ingot, keep it warm for 10 minutes, then heat it up to 1300℃, add half of the phosphor-copper alloy in the ingredients, and stir the melt, then add the copper-iron intermediate alloy, keep it warm for 60 minutes, add the remaining phosphor-copper alloy, keep it warm for 5 minutes, and start casting. Keep the red ingot casting during the casting process. The temperature of the ingot is above 650℃ when it comes out of the crystallizer. The casting specification of the alloy melt is φ245mm round ingot.

[0096] 3) Hot extrusion: The semi-continuous casting ingot is heated to 940°C, kept warm for more than 4 hours, and extruded to a specification of φ30mm.

[0097] 4) Solution pickling: solution temperature 900℃, time 45min, pickling after solution, no oxide scale on the surface.

[0098] 5) Extension: The extruded rod is cold rolled to φ18mm.

[0099] 6) First low temperature annealing: The cold rolled bar is subjected to low temperature and long time annealing, the annealing temperature is 350℃, and the holding time is 15h.

[0100] 7) Extension: The annealed rod is cold rolled to φ6mm.

[0101] 8) Second low-temperature annealing: The cold-rolled rod blank is annealed at 420°C for 20 hours.

[0102] 9) Cold drawn to finished product φ1.2mm.

[0103] Table 1 shows the alloy element ratios of Examples 1 to 3 and Comparative Examples 1 to 2

[0104]

[0105]

[0106] The performance of the embodiments and comparative examples was tested, and the test data is shown in Table 2. As can be seen from Table 2, the electrical conductivity and tensile strength of Examples 1-3 provided by the present invention are higher than those of Comparative Examples 1-2, and the size of the Fe-rich phase and the spacing between the Fe-rich phases are smaller. As can be seen from Comparative Example 3, when the P content is too high, even through the process control provided by the present invention, there is no way to fully precipitate the P element, resulting in lower conductivity.

[0107] The room temperature tensile test was carried out on an electronic universal mechanical properties testing machine in accordance with GB / T 228.1-2010 Metallic materials tensile tests Part 1: Room temperature test methods.

[0108] Conductivity test: Measure the electrical conductivity of the alloy in accordance with GB / T 351-2019 "Metallic Materials Resistivity Test Method".

[0109] Microstructure grain size test: in accordance with GB / T 16394-2017 "Method for determination of average grain size of metals".

[0110] Table 2 shows the alloy performance test results of Examples 1 to 3 and Comparative Examples 1 to 2

[0111]

[0112]

[0113] like Figure 1 As shown in a and b, Figure 1 Figure a is the metallographic structure diagram of the cross section of the finished wire, in which the black granular substance is the iron-rich phase with an average size of 1.6μm. Figure b is the metallographic structure diagram of the longitudinal section of the finished wire, in which the elongated fibrous structure is the processed iron-rich phase structure with an average spacing of 5.6μm.

[0114] like Figure 2 As shown in a and b in FIG, the metallographic structure after the first annealing in Example 1, Figure 2 Figure a is the metallographic structure diagram of the cross section of the wire after the first annealing, in which the blocky structure material is the iron-rich phase with an average size of 8.9μm. Figure b is the metallographic structure diagram of the longitudinal section of the wire after the first annealing, in which the elongated fibrous structure is the processed iron-rich phase structure with an average spacing of 21μm.

Claims

1. A high-strength and high-conductivity iron-bronze alloy, characterized in that: The iron-bronze alloy comprises by weight 2.1-2.4 wt% of Fe, 0.015-0.1 wt% of P, 0.05-0.15 wt% of Zn, an impurity content of ≤0.1 wt% and the balance being Cu; The structure of the iron-bronze alloy includes a matrix phase and a second phase, the second phase includes a granular Fe3P phase and a fibrous Fe-rich phase, the size of the granular Fe3P phase is 100-150nm, the diameter of the fibrous Fe-rich phase is less than 2μm, and the distance between the fibrous Fe-rich phases is less than 10μm.

2. The high-strength and high-conductivity iron-bronze alloy according to claim 1, characterized in that: The iron-bronze alloy has an average grain size of 10 μm or less.

3. A method for preparing a high-strength and high-conductivity iron-bronze alloy, characterized in that: The process flow of the preparation method includes: batching → semi-continuous casting → hot extrusion → solution treatment → first extension → first annealing → second extension → second annealing → cold drawing of finished product; Wherein, the ingredients are prepared according to the mass percentage of the high-strength and high-conductivity iron-bronze alloy; The annealing temperature of the first annealing is 350-400° C., and the holding time is 8-16 hours.

4. The method for preparing a high-strength and high-conductivity iron-bronze alloy according to claim 3, characterized in that: During the semi-continuous casting process, the surface temperature of the ingot when it leaves the crystallizer is between 600°C and 800°C.

5. The method for preparing a high-strength and high-conductivity iron-bronze alloy according to claim 3, wherein: The processing rate of the second stretching is above 80%.

6. The method for preparing a high-strength and high-conductivity iron-bronze alloy according to claim 3, wherein: The second annealing temperature is 420-450° C. and the time is 18-25 hours.

7. The method for preparing a high-strength and high-conductivity iron-bronze alloy according to claim 3, wherein: The processing rate of the finished cold-drawn product is 85-95%.

8. The method for preparing a high-strength and high-conductivity iron-bronze alloy according to claim 3, wherein: The temperature of the solid solution is 850-950° C., the time is 45-90 min, and pickling is performed after the solid solution.

9. The method for preparing a high-strength and high-conductivity iron-bronze alloy according to claim 3, wherein: The first stretching is cold rolling, and the cold working rate is above 60%.

10. Use of the high-strength and high-conductivity iron-bronze alloy according to any one of claims 1 to 2 in the preparation of IGBT pins.

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