Expansion alloy and thixoforming method thereof

Abstract

The invention provides a thixoforming preparation method of an expansion alloy, and belongs to the technical field of expansion alloy production processes. According to the method, the thixoforming technology is adopted, the alloy powder serves as the raw material, then cold pressing forming, microwave heating and dynamic pressing are conducted, the rapid solidification technology, the dynamic recovery recrystallization technology and the powder metallurgy technology are combined, the production process of the expansion alloy is greatly shortened, the product purity and the yield are improved, the production period is shortened, and the production cost is reduced. And the production cost is reduced, different products can be quickly changed, and the product performance is excellent.

Description

Technical Field

[0001] The invention belongs to the technical field of expansion alloy production, and in particular relates to an expansion alloy and a thixoforming method thereof. Background Art

[0002] Expansion alloy is a metal material with special thermal expansion properties. As an important component of precision alloys, it is mainly used to manufacture electric vacuum devices, precision instruments, instrument components, automatic control components and for geodetic measurement, etc.

[0003] At present, the production process of expansion alloys includes smelting, forming, and subsequent hot and cold processing. The final products are forging materials, cold-rolled strips, pipes, wires, cold-drawn rods and polished rods. Among them, the process of forging materials includes raw material preparation → smelting (vacuum or non-vacuum) → ingot casting → steel ingot peeling, steel ingot grinding → forging or hot rolling blanking → strip blank, tube blank, rod and wire blank; the process of cold-rolled strip includes strip blank → alkali immersion loosening → pickling → grinding → hot rolling → softening treatment → pickling → grinding → four-roll cold rolling → intermediate heat treatment → multi-roll cold rolling → finished product inspection → packaging and warehousing; the process of pipes includes tube blank → alkali immersion, pickling → Grinding → hot perforation → alkali immersion, pickling → grinding → drawing or rolling → intermediate heat treatment → finished product inspection → packaging and warehousing; the wire material process includes square billet → pickling → grinding → hot rolling → wire rod → softening heat treatment → alkali immersion, pickling → grinding → cold drawing → intermediate heat treatment → multi-mode cold drawing → continuous furnace annealing → finished product inspection → packaging and warehousing; the cold drawn rod and polished rod process includes rod billet → straightening → polishing → finished product inspection → packaging and warehousing; rod billet → softening heat treatment → alkali immersion, pickling → grinding → cold drawing → finished product inspection → packaging and warehousing.

[0004] It can be seen that no matter whether the final product of expansion alloy is strip, tube or wire, there are some common problems in the production process: the production process is lengthy, and during the slow solidification and cooling of the ingot and the reheating of forging and hot rolling, the inclusion elements tend to be segregated to the grain boundary and combined with the oxygen diffused from the outer surface, causing serious grain boundary oxidation and intragranular oxidation, which greatly deteriorates the hot workability of the expansion alloy, resulting in serious surface cracking, uneven plate shape, easy rust, etc. during forging and hot rolling. The surface oxide layer and cracks must be completely removed by grinding, which greatly reduces the yield rate and production efficiency of the tile alloy. Therefore, how to simplify the preparation process and improve the yield rate has become a technical problem that needs to be solved in this field.

[0005] Semi-solid forming process refers to the forming process of semi-solid metal billets with a temperature between the solidus temperature and the liquidus temperature. The basic concept and process of this process were proposed and created by Professor Flemings and his research team at the Massachusetts Institute of Technology in the 1970s (SPENCER DB, MEHRABIAN R, FLEMINGS MC. Rheological Behavior of Sn-15 Pct Pb in the Crystalliza-tion Range [J]. Metallurgical & Materials Transactions B, 1972, 3 (3): 1925-1932; FLEMINGS MC. Behavior of Metal Alloys in the Semisolid State [J]. Met Trans, 1991, 22A: 957-981.). Semi-solid forming utilizes the characteristics of metal when it transitions from liquid to solid or from solid to liquid (i.e., solid-liquid coexistence), and combines the advantages of solidification processing and plastic processing. Its process characteristics are to strongly stir the solidifying metal or control the solidification conditions to inhibit the formation of dendrites or break the generated dendrites, and prepare a suspended semi-solid slurry with equiaxed, uniform, and fine primary phases uniformly distributed in the liquid phase. Under the action of external force, this slurry still has good thixotropic fluidity even if the solid phase ratio reaches 60%, and can be processed and formed by die casting, extrusion, die forging, casting and rolling (ATKINSON H, RASSILI A, ATKINSON H, Rassili A (Eds.), Thixoforming Steel Shaker Verlag, Aachen, Germany, pp. 13-18). According to the different heating processes of the blank before forming, semi-solid forming can be further divided into mud forming, rheological forming, and thixoforming, such as Figure 1Thixoforming is a process in which a semi-solid blank is heated to a semi-solid state with a liquid phase of about 50% by volume, and then placed in a mold groove with a slightly higher preheating temperature for one-time forming to obtain a product with a size close to the desired finished part (ATKINSON H, RASSILI A, ATKINSON H, Rassili A (Eds.), Thixoforming Steel Shaker Verlag, Aachen, Germany, pp. 13-18; KIUCHI M, KΟPP R. Mushy / semi-solid Metal Forming Technology-Present and Future [J]. CIRP Annals-Manufacturing Technology, 2002, 51 (2): 653-670.). Summary of the invention

[0006] The purpose of the present invention is to provide a method for producing expansion alloy by microwave heating thixoforming. The preparation method provided by the present invention simplifies the preparation process, shortens the production cycle, and improves the yield rate and product performance.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a thixoforming method for an expansion alloy, comprising the following steps:

[0009] (1) mixing and cold pressing high-purity alloy powders in sequence to obtain a green body;

[0010] (2) subjecting the green body obtained in step (1) to microwave heating and forming, wherein the microwave heating and forming system comprises a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section, and performing pressure processing on the green body during the heating process to obtain a high-temperature green body;

[0011] (3) thermally deforming the high-temperature billet obtained in step (2) to obtain an expanded alloy product.

[0012] Preferably, the mixing in step (1) is carried out in a protective atmosphere.

[0013] Preferably, the cold pressing pressure in step (1) is ≥150 MPa, and the cold pressing time is ≥15 min.

[0014] Preferably, in step (2), the constant temperature of the first heating and insulation section is 300-600°C, the insulation time of the first heating and insulation section is 10-45 minutes, and the speed of heating from room temperature to the constant temperature of the first heating and insulation section is 10-15°C / min.

[0015] Preferably, in step (2), the constant temperature of the second heating and insulation section is 700-950°C, the insulation time of the second heating and insulation section is 5-45 minutes, and the speed of heating from the constant temperature of the first heating and insulation section to the constant temperature of the second heating and insulation section is 12-28°C / min.

[0016] Preferably, in step (2), the constant temperature of the third heating and insulation section is 900-1080°C, the insulation time of the third heating and insulation section is 10-50 min, and the speed of heating from the constant temperature of the second heating and insulation section to the constant temperature of the third heating and insulation section is 10-35°C / min.

[0017] Preferably, in step (2), the constant temperature of the fourth heating and insulation section is 1050-1190°C, the insulation time of the fourth heating and insulation section is 10-60 min, and the speed of heating from the constant temperature of the third heating and insulation section to the constant temperature of the fourth heating and insulation section is 12-28°C / min.

[0018] Preferably, the reduction rate of the first pressurization in step (2) is 5 to 12%.

[0019] Preferably, the reduction rate of the second pressurization in step (2) is 8 to 15%.

[0020] The present invention also provides an expansion alloy product prepared by the thixoforming method described in the above technical solution.

[0021] The present invention provides a thixoforming method for an expansion alloy, comprising the following steps: mixing and cold-pressing high-purity alloy powders in sequence to obtain a green billet; subjecting the green billet to microwave heating and forming, wherein the microwave heating and forming system comprises a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section in sequence, and performing pressure processing on the green billet during the heating process to obtain a high-temperature billet; subjecting the high-temperature billet to thermal deformation to obtain an expansion alloy product. The present invention adopts thixoforming technology, uses alloy powder as raw material, and then cold presses, microwave heats and dynamically presses, combines rapid solidification technology, dynamic recovery recrystallization technology with powder metallurgy technology, greatly shortens the production process of the expansion alloy, improves the purity and yield rate of the product, and shortens the production cycle. Experimental results show that the tensile strength of the expansion alloy product prepared by the present invention is 483-549MPa, the yield strength is 302-372MPa, the elongation after fracture is 23.5-29.6%, and the expansion coefficient is (0.82-8.4)×10 -6 / ℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a classification of semi-solid forming. DETAILED DESCRIPTION

[0023] The present invention provides a thixoforming method for an expansion alloy, comprising the following steps:

[0024] (1) mixing and cold pressing high-purity alloy powders in sequence to obtain a green body;

[0025] (2) subjecting the green body obtained in step (1) to microwave heating and forming, wherein the microwave heating and forming system comprises a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section, and performing pressure processing on the green body during the heating process to obtain a high-temperature green body;

[0026] (3) thermally deforming the high-temperature billet obtained in step (2) to obtain an expanded alloy product.

[0027] The present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0028] The invention uniformly mixes alloy powders and cold presses them in sequence to obtain green compacts.

[0029] In the present invention, the alloy powder is preferably metal powder; the metal powder preferably includes at least one of iron powder, nickel powder, cobalt powder and chromium powder.

[0030] In the present invention, the iron powder preferably includes iron powder 1 and iron powder 2 .

[0031] In terms of mass percentage, the chemical composition of the iron powder 1 preferably includes C≤0.005%, Si≤0.02%, Mn≤0.10%, P≤0.005%, S≤0.005%, O≤0.005% and Fe≥99.5%; the hydrogen loss of the iron powder 1 is preferably ≤0.1wt%.

[0032] In the present invention, the physical and technological properties of the iron powder 1 preferably include: bulk density 2.8-3.05 g / cm 3 , fluidity ≤30s / 50g, compressibility (600MPa) ≥7.03g / cm 3 , nearly spherical.

[0033] In the present invention, taking the mass of iron powder 1 as 100%, the mass content of 150μm≤iron powder 1<180μm is preferably ≤1%, the mass content of 80μm≤iron powder 1<150μm is preferably ≤8%, the mass content of <60μm is preferably 20-40% and the mass content of 60μm≤iron powder 1<80μm is preferably the remainder.

[0034] In terms of mass percentage, the chemical composition of the iron powder 2 preferably includes C≤0.01%, Si≤0.05%, Mn≤0.15%, P≤0.008%, S≤0.008%, O≤0.01% and Fe≥99%; the hydrogen loss of the iron powder 2 is preferably ≤0.2wt%.

[0035] In the present invention, the physical and technological properties of the iron powder 2 preferably include: bulk density 2.9-3.15 g / cm 3 , fluidity ≤27s / 50g, compressibility (600MPa) ≥7.10g / cm 3 , dendritic.

[0036] In the present invention, taking the mass of iron powder 2 as 100%, the mass content of 150μm≤iron powder 2<180μm is preferably ≤2%, the mass content of 80μm≤iron powder 2<150μm is preferably ≤10%, the mass content of <60μm is preferably 15-35% and the mass content of 60μm≤iron powder 2<80μm is preferably the remainder.

[0037] In the present invention, the nickel powder preferably includes nickel powder 1 and nickel powder 2.

[0038] In terms of mass percentage, the chemical composition of the nickel powder 1 preferably includes C≤0.01%, Si≤0.01%, Mn≤0.002%, P≤0.005%, S≤0.001%, Cu≤0.015%, Fe≤0.05%, Mg≤0.01%, O≤0.02% and the balance Ni.

[0039] In the present invention, the physical and technological properties of the nickel powder 1 preferably include: bulk density ≥ 4.5 g / cm 3 , tap density ≥5.2g / cm 3 , fluidity ≤21s / 50g, nearly spherical.

[0040] In the present invention, the D of the nickel powder 1 10 Preferably, the D of the nickel powder 1 is 20 to 30 μm and 50 to 70 μm; 50 The preferred range is 35 to 45 μm.

[0041] In the present invention, based on the mass of nickel powder 1 being 100%, the mass content of nickel powder 1>55 μm is preferably ≤3% and the mass content of 20 μm≤nickel powder 1≤55 μm is preferably the balance.

[0042] In terms of mass percentage, the chemical composition of the nickel powder 2 preferably includes C≤0.08%, Si≤0.06%, Mn≤0.05%, P≤0.002%, S≤0.003%, Cu≤0.09%, Fe≤0.08%, Mg≤0.07%, O≤0.05% and the balance Ni.

[0043] In the present invention, the physical and technological properties of the nickel powder 2 preferably include: bulk density ≥ 4.5 g / cm 3 , tap density ≥5.2g / cm 3 , fluidity ≤21s / 50g, dendritic.

[0044] In the present invention, based on the mass of nickel powder 2 being 100%, the mass content of nickel powder 2>150μm is preferably ≤3%, the mass content of nickel powder 2≤50μm is preferably ≤3% and the mass content of nickel powder 50μm<nickel powder 2≤150μm is preferably the remainder.

[0045] In terms of mass percentage, the chemical composition of the chromium powder is preferably C≤0.02%, Si≤0.01%, P≤0.005%, S≤0.005%, Fe≤0.15%, O≤0.04% and the balance Cr.

[0046] In the present invention, the physical and technological properties of the chromium powder preferably include: bulk density ≥ 4.6 g / cm 3 , tap density ≥5.1g / cm 3 , fluidity ≤17s / 50g, nearly spherical.

[0047] In the present invention, based on the mass of chromium powder being 100%, the mass content of chromium powder >75 μm is preferably ≤5% and the mass content of chromium powder 35 μm ≤ chromium powder ≤ 75 μm is preferably the remainder.

[0048] The present invention has no particular limitation on the source of the cobalt powder, and high-purity cobalt powder well known to those skilled in the art can be used.

[0049] The composition and physical process performance requirements of the pure metal iron, nickel and chromium used in the present invention are shown in Tables 1 to 4. Other metals used in small amounts may be prepared in accordance with the technical standards for high-purity metals, such as pure cobalt, which may be prepared in accordance with the technical standards for high-purity cobalt. The ingredients shall be prepared according to the composition control requirements of the final product.

[0050] The present invention uses high-purity metal powder to avoid the introduction of other impurity elements in the conventional smelting process, and through the combination of metal powders with different compositions and physical and chemical performance indicators, accurate control of the alloy composition can be achieved.

[0051] The present invention has no special limitation on the composition of the alloy powder, which can be adjusted according to actual needs.

[0052] The present invention has no special limitation on the mixing operation, as long as the alloy powders are mixed uniformly.

[0053] In the present invention, the mixing is preferably carried out in a protective atmosphere; the protective atmosphere is preferably argon. The mixing in the protective atmosphere of the present invention can prevent the metal powder from being oxidized in the air.

[0054] In the present invention, the cold forming is preferably carried out in a hydraulic cold isostatic press. The present invention has no special limitation on the model of the hydraulic cold isostatic press, as long as the forming size specifications and pressure requirements are met.

[0055] In the present invention, the cold press forming pressure is preferably ≥150 MPa, more preferably 160-250 MPa; the cold press forming time is preferably ≥15 min, more preferably 20-30 min.

[0056] After obtaining the green blank, the present invention subjects the green blank to microwave heating and molding, and performs pressure processing on the blank during the heating process to obtain a high-temperature blank. The present invention performs pressure processing on the blank during the heating process in the first pressurizing section and the second pressurizing section, and each heating and heat preservation section does not perform pressure processing.

[0057] In the present invention, the microwave heating molding is preferably carried out in a protective atmosphere; the protective atmosphere is preferably argon.

[0058] In the present invention, the microwave heating forming includes a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section which are performed in sequence.

[0059] In the present invention, the constant temperature of the first heating and insulation section is preferably 300-600°C, more preferably 480-550°C, and more preferably 500-520°C; the insulation time of the first heating and insulation section is preferably 10-45min, more preferably 18-30min, and more preferably 20-25min; the speed of heating from room temperature to the constant temperature of the first heating and insulation section is preferably 10-15°C / min, and more preferably 12-13°C / min.

[0060] In the present invention, the constant temperature of the second heating and insulation section is preferably 700-950°C, further preferably 750-850°C, and more preferably 800-880°C; the insulation time of the second heating and insulation section is preferably 5-45min, and more preferably 15-35min; the speed of heating from the constant temperature of the first heating and insulation section to the constant temperature of the second heating and insulation section is preferably 12-28°C / min, and more preferably 15-25°C / min.

[0061] In the present invention, the constant temperature of the third heating and insulation section is preferably 900-1080°C, more preferably 980-1020°C; the insulation time of the third heating and insulation section is preferably 10-50min, more preferably 15-25min, more preferably 18min; the speed of heating from the constant temperature of the second heating and insulation section to the constant temperature of the third heating and insulation section is preferably 10-35°C / min, more preferably 18-30°C / min, more preferably 20-25°C / min.

[0062] In the present invention, the constant temperature of the fourth heating and insulation section is preferably 1050-1190°C, more preferably 1080-1130°C; the insulation time of the fourth heating and insulation section is preferably 10-60min, further preferably 20-40min, more preferably 25-30min; the speed of heating from the constant temperature of the third heating and insulation section to the constant temperature of the fourth heating and insulation section is preferably 12-28°C / min, further preferably 15-25°C / min, more preferably 16-20°C / min.

[0063] In the present invention, the constant temperature of the third heating and heat-insulating section is preferably lower than the constant temperature of the fourth heating and heat-insulating section.

[0064] In the present invention, the reduction rate of the first pressurizing stage is preferably 6 to 12%, more preferably 8 to 12%. The present invention has no special limitation on the pressure and time of the first pressurizing stage, as long as the reduction rate meets the above requirements.

[0065] In the present invention, the temperature in the first pressurizing stage is preferably the same as the constant temperature in the second heating and heat preservation stage, which will not be described in detail herein.

[0066] In the present invention, the reduction rate of the second pressurizing stage is preferably 8-15%, more preferably 10-13%. The present invention has no special limitation on the pressure and time of the second pressurizing stage, as long as the reduction rate meets the above requirements.

[0067] In the present invention, the temperature in the second pressurizing stage is preferably the same as the constant temperature in the third heating and heat preservation stage, which will not be described in detail here.

[0068] The present invention can further improve the performance of the expansion alloy by controlling the process parameters of microwave heating forming.

[0069] After obtaining the high-temperature billet, the present invention performs thermal deformation on the high-temperature billet to obtain an expansion alloy product.

[0070] In the present invention, the thermal deformation is preferably hot rolling; the hot rolling preferably includes rough rolling and finish rolling performed sequentially.

[0071] In the present invention, the iron oxide scale of the high-temperature blank is preferably removed before the hot deformation.

[0072] The present invention has no particular limitation on the operation of removing the iron oxide scale of the high-temperature blank, and the operation well known to those skilled in the art may be adopted.

[0073] In the present invention, the rough rolling preferably includes a primary rough rolling and a secondary rough rolling performed sequentially.

[0074] In the present invention, the primary rough rolling is preferably carried out in a two-roll reversible rough rolling mill; the total reduction ratio of the primary rough rolling is preferably 22-35%, more preferably 29-34%. The present invention has no special limitation on the model of the two-roll reversible rough rolling mill, and the equipment well known to those skilled in the art can be used. The present invention has no special limitation on the number of passes of the primary rough rolling, as long as the total reduction ratio meets the above requirements.

[0075] In the present invention, the secondary rough rolling is preferably carried out in a four-roller reversible rough rolling mill; the total reduction rate of the secondary rough rolling is preferably 15-40%, more preferably 20-30%; the temperature of the secondary rough rolling is preferably 1030-1085°C. The present invention has no special restrictions on the model of the four-roller reversible rough rolling mill, and the instruments and equipment familiar to those skilled in the art can be used. The present invention has no special restrictions on the number of passes of the secondary rough rolling, as long as the total reduction rate meets the above requirements.

[0076] After the rough rolling is completed, the product obtained by the rough rolling is preferably subjected to secondary descaling in the present invention. The present invention has no special limitation on the operation of the secondary descaling, and the operation well known to those skilled in the art can be adopted.

[0077] In the present invention, the total reduction ratio of the finishing rolling is preferably 12.2-31.5%, more preferably 19.8-28.6%, and more preferably 20-23.2%. The present invention has no particular limitation on the number of passes of the finishing rolling, as long as the total reduction ratio meets the above requirements.

[0078] After hot rolling is completed, the present invention preferably cools and coils the hot-rolled product in sequence to obtain an expanded alloy product.

[0079] The present invention has no particular limitation on the cooling and winding operations, and operations well known to those skilled in the art may be adopted.

[0080] In the present invention, the expansion alloy product is preferably an expansion alloy strip.

[0081] The present invention optimizes the raw materials and improves the production process. The existing metallurgical process needs to go through the processes of melting and blowing. During this process, the metal melt undergoes various inevitable physical and chemical reactions with the oxygen in the atmosphere and the refractory material in the furnace body, and various impurity elements and non-metallic oxide inclusions are introduced. The design of the pure metal powder in the present invention can effectively avoid the above-mentioned problems. The pure metal powder ingredients are directly pressed and formed, and inert gas protection is adopted without going through the melting and blowing process, which largely avoids the introduction of impurity elements and inclusions, improves the purity and performance of the product, reduces various defects in the product, and can reduce the probability of defective products in the subsequent processing process, thereby improving the yield rate. Through cold pressing, microwave heating and dynamic pressing, the rapid solidification technology, dynamic recovery recrystallization technology and powder metallurgy technology are combined, which greatly shortens the expansion alloy smelting production process, improves the product purity and yield rate, and the yield rate is above 75%, shortens the production cycle, reduces the production cost, and can achieve rapid conversion of different products. The product has excellent performance and a wide range of applications.

[0082] The present invention also provides an expansion alloy product prepared by the thixoforming method described in the above technical solution.

[0083] The present invention provides a method for preparing an expansion alloy with simple production process, short production cycle, high yield rate, excellent performance and wide application, so as to solve the problems existing in the field of expansion alloy materials for precision instruments and meters, such as complex production process flow, large fluctuation in product performance and long product production cycle.

[0084] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0085] Example 1

[0086] A thixoforming method for an expansion alloy 4J36 strip comprises the following steps:

[0087] (1) adding pure nickel powder 1, pure nickel powder 2, pure iron powder 1 and pure iron powder 2 into a mixing bin, passing Ar gas protection, stirring and mixing, and then forming the metal powder on a hydraulic cold isostatic press to obtain a green body after pressure relief; wherein the mass ratio of pure nickel powder 1 to pure nickel powder 2 is 6:4, and the mass ratio of pure iron powder 1 to pure iron powder 2 is 4:6; the size of the mold is 230 mm×558 mm×2500 mm (thickness×width×length); the forming pressure is 151 MPa, and the pressure is maintained for 16 minutes;

[0088] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section in sequence; the constant temperature of the first heating and heat preservation section is 500°C, the heat preservation time of the first heating and heat preservation section is 20min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 12°C / min; the constant temperature of the second heating and heat preservation section is 950°C, the heat preservation time of the second heating and heat preservation section is 30min, and the heating speed from the first heating and heat preservation section ...1 The speed of heating from the constant temperature of the first heating and heat preservation section to the constant temperature of the second heating and heat preservation section is 15℃ / min; the constant temperature of the third heating and heat preservation section is 1000℃, the heat preservation time of the third heating and heat preservation section is 15min, and the speed of heating from the constant temperature of the second heating and heat preservation section to the constant temperature of the third heating and heat preservation section is 25℃ / min; the constant temperature of the fourth heating and heat preservation section is 1100℃, the heat preservation time of the fourth heating and heat preservation section is 20min, and the speed of heating from the constant temperature of the third heating and heat preservation section to the constant temperature of the fourth heating and heat preservation section is 20℃ / min; the pressure roller reduction rate of the first pressurizing section is 10%, and the temperature is 950℃; the pressure roller reduction rate of the second pressurizing section is 12%, and the temperature is 1000℃;

[0089] (3) The billet obtained in step (2) is subjected to a descaling machine to remove iron oxide scale, and then enters a two-roll reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 34%. The billet then enters a heat preservation and heating section, infrared heating to 1080° C., and then enters a four-roll reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 21.7%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roll rolling mill via a conveyor roller for finish rolling with a total reduction rate of 20%, thereby obtaining a finished product with a thickness of 3.25 mm. The billet then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0090] Example 2

[0091] A thixoforming method for an expansion alloy 4J36 strip comprises the following steps:

[0092] (1) adding pure nickel powder 1, pure nickel powder 2, pure iron powder 1 and pure iron powder 2 into a mixing bin, passing Ar gas protection, stirring and mixing, and then forming the metal powder on a hydraulic cold isostatic press to obtain a green body after pressure relief; wherein the mass ratio of pure nickel powder 1 to pure nickel powder 2 is 4:6, and the mass ratio of pure iron powder 1 to pure iron powder 2 is 5:5; the mold specification size is 180 mm×558 mm×3195 mm (thickness×width×length); the forming pressure is 155 MPa, and the pressure is maintained for 19 minutes;

[0093] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section in sequence; the constant temperature of the first heating and heat preservation section is 600° C., the heat preservation time of the first heating and heat preservation section is 18 min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 15° C. / min; the constant temperature of the second heating and heat preservation section is 900° C., the heat preservation time of the second heating and heat preservation section is 25 min, and the heat preservation time from the first heating and heat preservation section to the constant temperature of the first heating and heat preservation section is 15° C. / min. The speed of heating from the constant temperature of the hot insulation section to the constant temperature of the second heating insulation section is 18°C / min; the constant temperature of the third heating insulation section is 1000°C, the insulation time of the third heating insulation section is 10min, and the speed of heating from the constant temperature of the second heating insulation section to the constant temperature of the third heating insulation section is 20°C / min; the constant temperature of the fourth heating insulation section is 1080°C, the insulation time of the fourth heating insulation section is 20min, and the speed of heating from the constant temperature of the third heating insulation section to the constant temperature of the fourth heating insulation section is 15°C / min; the pressure roller reduction rate of the first pressurizing section is 12%, and the temperature is 900°C; the pressure roller reduction rate of the second pressurizing section is 10%, and the temperature is 1000°C;

[0094] (3) The billet obtained in step (2) is subjected to a descaling machine to remove iron oxide scale, and then enters a two-roll reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 22%. The billet then enters a heat preservation and heating section, infrared heating to 1080° C., and then enters a four-roll reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 38.9%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roll rolling mill via a conveyor roller for finish rolling with a total reduction rate of 12.2%, to obtain a finished product with a thickness of 1.85 mm, and then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0095] Example 3

[0096] A thixoforming method for an expansion alloy 4J36 strip comprises the following steps:

[0097] (1) adding pure nickel powder 1, pure nickel powder 2, pure iron powder 1 and pure iron powder 2 into a mixing bin, passing Ar gas protection, stirring and mixing, and then forming the metal powder on a hydraulic cold isostatic press to obtain a green body after pressure relief; wherein the mass ratio of pure nickel powder 1 to pure nickel powder 2 is 5:5, and the mass ratio of pure iron powder 1 to pure iron powder 2 is 3:7; the mold specification size is 230 mm×558 mm×11000 mm (thickness×width×length); the forming pressure is 221 MPa, and the pressure is maintained for 35 minutes;

[0098] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section in sequence; the constant temperature of the first heating and heat preservation section is 300° C., the heat preservation time of the first heating and heat preservation section is 30 min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 10° C. / min; the constant temperature of the second heating and heat preservation section is 700° C., the heat preservation time of the second heating and heat preservation section is 35 min, and the temperature from the first heating and heat preservation section .... The speed of heating from the constant temperature of the hot insulation section to the constant temperature of the second heating insulation section is 12°C / min; the constant temperature of the third heating insulation section is 900°C, the insulation time of the third heating insulation section is 50min, and the speed of heating from the constant temperature of the second heating insulation section to the constant temperature of the third heating insulation section is 10°C / min; the constant temperature of the fourth heating insulation section is 1190°C, the insulation time of the fourth heating insulation section is 30min, and the speed of heating from the constant temperature of the third heating insulation section to the constant temperature of the fourth heating insulation section is 15°C / min; the pressure roller reduction rate of the first pressurizing section is 6%, and the temperature is 700°C; the pressure roller reduction rate of the second pressurizing section is 8%, and the temperature is 900°C;

[0099] (3) The billet obtained in the step (2) is subjected to a descaling machine to remove iron oxide scale, and then enters a two-roller reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 33.8%. The billet then enters a heat preservation and heating section, infrared heating to 1180° C., and then enters a four-roller reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 19.6%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roller rolling mill via a conveyor roller for finish rolling with a total reduction rate of 31.5%, thereby obtaining a finished product with a thickness of 2.45 mm. The billet then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0100] Example 4

[0101] A thixoforming method for an expansion alloy 4J32 strip comprises the following steps:

[0102] (1) adding pure nickel powder 1, pure nickel powder 2, pure iron powder 1, pure iron powder 2 and pure cobalt powder into a mixing bin, passing Ar gas protection, stirring and mixing, and then forming the metal powder on a hydraulic cold isostatic press to obtain a green body after pressure relief; wherein the mass ratio of pure nickel powder 1 to pure nickel powder 2 is 7:3, and the mass ratio of pure iron powder 1 to pure iron powder 2 is 6:4; the cobalt content in the pure cobalt powder is not less than 99.999wt%; the mold specification size is 230mm×558mm×5500mm (thickness×width×length); the molding pressure is 185MPa, and the pressure is maintained for 28min;

[0103] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section in sequence; the constant temperature of the first heating and heat preservation section is 480°C, the heat preservation time of the first heating and heat preservation section is 20min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 10°C / min; the constant temperature of the second heating and heat preservation section is 880°C, the heat preservation time of the second heating and heat preservation section is 35min, and the temperature of the green body from the first heating and heat preservation section ... The speed of heating from the constant temperature of the insulation section to the constant temperature of the second heating insulation section is 15°C / min; the constant temperature of the third heating insulation section is 1020°C, the insulation time of the third heating insulation section is 20min, and the speed of heating from the constant temperature of the second heating insulation section to the constant temperature of the third heating insulation section is 18°C / min; the constant temperature of the fourth heating insulation section is 1130°C, the insulation time of the fourth heating insulation section is 25min, and the speed of heating from the constant temperature of the third heating insulation section to the constant temperature of the fourth heating insulation section is 16°C / min; the pressure roller reduction rate of the first pressurizing section is 8%, and the temperature is 880°C; the pressure roller reduction rate of the second pressurizing section is 10%, and the temperature is 1020°C;

[0104] (3) The billet obtained in step (2) is subjected to a descaling machine to remove iron oxide scale, and then enters a two-roll reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 34.2%. The billet then enters a heat preservation and heating section, infrared heating to 1130° C., and then enters a four-roll reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 18.2%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roll rolling mill via a conveyor roller for finish rolling with a total reduction rate of 28.6%, thereby obtaining a finished product with a thickness of 2.15 mm. The billet then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0105] Example 5

[0106] A thixoforming method for an expansion alloy 4J32 strip comprises the following steps:

[0107] (1) adding pure nickel powder 1, pure nickel powder 2, pure iron powder 1, pure iron powder 2 and pure cobalt powder into a mixing bin, passing Ar gas protection, stirring and mixing, and then forming the metal powder on a hydraulic cold isostatic press to obtain a green body after pressure relief; wherein the mass ratio of pure nickel powder 1 to pure nickel powder 2 is 6:4, and the mass ratio of pure iron powder 1 to pure iron powder 2 is 8:2; the cobalt content in the pure cobalt powder is not less than 99.999wt%; the mold specification size is 130mm×558mm×9730mm (thickness×width×length); the molding pressure is 185MPa, and the pressure is maintained for 28min;

[0108] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section which are performed in sequence; the constant temperature of the first heating and heat preservation section is 460° C., the heat preservation time of the first heating and heat preservation section is 20 min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 10° C. / min; the constant temperature of the second heating and heat preservation section is 870° C., the heat preservation time of the second heating and heat preservation section is 35 min, and the temperature of the green body from the first heating and heat preservation section ... The speed of heating from the constant temperature of the insulation section to the constant temperature of the second heating insulation section is 13°C / min; the constant temperature of the third heating insulation section is 1010°C, the insulation time of the third heating insulation section is 20min, and the speed of heating from the constant temperature of the second heating insulation section to the constant temperature of the third heating insulation section is 17°C / min; the constant temperature of the fourth heating insulation section is 1130°C, the insulation time of the fourth heating insulation section is 25min, and the speed of heating from the constant temperature of the third heating insulation section to the constant temperature of the fourth heating insulation section is 15°C / min; the pressure roller reduction rate of the first pressurizing section is 9%, and the temperature is 870°C; the pressure roller reduction rate of the second pressurizing section is 9%, and the temperature is 1010°C;

[0109] (3) The billet obtained in step (2) is subjected to a descaling machine to remove iron oxide scale, and then enters a two-roll reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 33%. The billet then enters a heat preservation and heating section, infrared heating to 1130° C., and then enters a four-roll reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 25.2%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roll rolling mill via a conveyor roller for finish rolling with a total reduction rate of 23.2%, to obtain a finished product with a thickness of 1.49 mm, and then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0110] Example 6

[0111] A thixoforming method for an expansion alloy 4J29 strip comprises the following steps:

[0112] (1) adding pure nickel powder 1, pure nickel powder 2, pure iron powder 1, pure iron powder 2 and pure cobalt powder into a mixing bin, passing Ar gas protection, stirring and mixing, and then forming the metal powder on a hydraulic cold isostatic press to obtain a green body after pressure relief; wherein the mass ratio of pure nickel powder 1 to pure nickel powder 2 is 5.5:4.5, and the mass ratio of pure iron powder 1 to pure iron powder 2 is 7:3; the cobalt content in the pure cobalt powder is not less than 99.999wt%; the mold specification size is 230mm×558mm×6500mm (thickness×width×length); the molding pressure is 190MPa, and the pressure is maintained for 30min;

[0113] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section, which are performed in sequence; the constant temperature of the first heating and heat preservation section is 470°C, the heat preservation time of the first heating and heat preservation section is 25min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 12°C / min; the constant temperature of the second heating and heat preservation section is 880°C, the heat preservation time of the second heating and heat preservation section is 30min, and the temperature of the green body from the first heating and heat preservation section ... The speed of heating from the constant temperature of the insulation section to the constant temperature of the second heating insulation section is 13°C / min; the constant temperature of the third heating insulation section is 1028°C, the insulation time of the third heating insulation section is 23min, and the speed of heating from the constant temperature of the second heating insulation section to the constant temperature of the third heating insulation section is 16°C / min; the constant temperature of the fourth heating insulation section is 1135°C, the insulation time of the fourth heating insulation section is 30min, and the speed of heating from the constant temperature of the third heating insulation section to the constant temperature of the fourth heating insulation section is 15°C / min; the pressure roller reduction rate of the first pressurizing section is 7%, and the temperature is 880°C; the pressure roller reduction rate of the second pressurizing section is 9%, and the temperature is 1028°C;

[0114] (3) The billet obtained in step (2) is passed through a descaling machine to remove iron oxide scale, and then enters a two-roll reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 35%. The billet then enters a heat preservation and heating section, infrared heating to 1130° C., and then enters a four-roll reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 28.1%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roll rolling mill via a conveyor roller for finish rolling with a total reduction rate of 19.8%, thereby obtaining a finished product with a thickness of 2.38 mm. The billet then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0115] Example 7

[0116] A thixoforming method for an expansion alloy 4J28 strip comprises the following steps:

[0117] (1) pure iron powder 1, pure iron powder 2 and nearly spherical pure chromium powder are added to a mixing bin, and Ar gas is passed through for protection, and the mixture is stirred and mixed, and then the metal powder is molded on a hydraulic cold isostatic press, and a green body is obtained after pressure relief; wherein the mass ratio of pure iron powder 1 to pure iron powder 2 is 5:5; the mold specification size is 230 mm×558 mm×8500 mm (thickness×width×length); the molding pressure is 192 MPa, and the pressure is maintained for 32 minutes;

[0118] (2) feeding the green body obtained in step (1) into a segmented microwave heating and pressurizing system on a roller conveyor belt for microwave heating and forming, and the whole system is protected by argon gas to obtain a green body; wherein the segmented microwave heating and pressurizing system is composed of a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section, which are performed in sequence; the constant temperature of the first heating and heat preservation section is 455°C, the heat preservation time of the first heating and heat preservation section is 25min, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 10°C / min; the constant temperature of the second heating and heat preservation section is 875°C, the heat preservation time of the second heating and heat preservation section is 33min, and the temperature of the green body from the first heating and heat preservation section ... The speed of heating from the constant temperature of the insulation section to the constant temperature of the second heating insulation section is 14°C / min; the constant temperature of the third heating insulation section is 1040°C, the insulation time of the third heating insulation section is 25min, and the speed of heating from the constant temperature of the second heating insulation section to the constant temperature of the third heating insulation section is 18°C / min; the constant temperature of the fourth heating insulation section is 1120°C, the insulation time of the fourth heating insulation section is 30min, and the speed of heating from the constant temperature of the third heating insulation section to the constant temperature of the fourth heating insulation section is 18°C / min; the pressure roller reduction rate of the first pressurizing section is 8%, and the temperature is 875°C; the pressure roller reduction rate of the second pressurizing section is 9%, and the temperature is 1040°C;

[0119] (3) The billet obtained in step (2) is passed through a descaling machine to remove iron oxide scale, and then enters a two-roll reversible roughing mill for multiple passes of reciprocating rolling with a small reduction rate, with a total reduction rate of 29%. The billet then enters a heat preservation and heating section, infrared heating to 1100° C., and then enters a four-roll reversible roughing mill for multiple passes of reciprocating rolling with a total reduction rate of 30.96%. Subsequently, secondary descaling is performed, and then the billet is sent to a 7-stand continuous four-roll rolling mill via a conveyor roller for finish rolling with a total reduction rate of 21.4%, obtaining a finished product with a thickness of 3.82 mm, and then enters a cooling section via a roller for cooling, and then is rolled into a strip coil by a coiler to obtain an expanded alloy.

[0120] The composition and physical process performance requirements of pure metal iron, nickel and chromium in Examples 1 to 7 are shown in Tables 1 to 4.

[0121] Table 1 Chemical composition of pure iron powder (mass fraction) / %

[0122] project C Si Mn P S O Hydrogen loss Fe Iron powder 1 ≤0.005 ≤0.02 ≤0.10 ≤0.005 ≤0.005 ≤0.005 ≤0.1 ≥99.5 Iron Fan 2 ≤0.01 ≤0.05 ≤0.15 ≤0.008 ≤0.008 ≤0.01 ≤0.2 ≥99

[0123] Table 2 Chemical composition of pure nickel powder and pure chromium powder (mass fraction) / %

[0124]

[0125] Table 3 Physical and process properties of pure iron powder

[0126]

[0127] Table 4 Physical and process properties of pure nickel powder, pure cobalt powder and pure chromium powder

[0128]

[0129] The rolling process of the expansion alloys prepared in Examples 1 to 7 is shown in Table 5.

[0130] Table 5 Rolling process of Examples 1 to 7 The chemical composition of the expansion alloys prepared in Examples 1 to 7 is shown in Table 6.

[0131]

[0132] Table 6 Chemical composition (mass fraction) of the expansion alloys prepared in Examples 1 to 7

[0133]

[0134] The mechanical properties of the expansion alloys prepared in Examples 1 to 7 are shown in Table 7. The relevant testing standards refer to the general provisions of GB / T14985-2007 on expansion alloy dimensions, shapes, surface quality, test methods and inspection rules.

[0135] Table 7 Mechanical properties data of expansion alloys prepared in Examples 1 to 7

[0136]

[0137]

[0138] It can be seen from Table 7 that the expansion alloy prepared in the embodiment has excellent mechanical properties and a high yield rate.

[0139] It can be seen from the above embodiments that the thixoforming method provided by the present invention simplifies the preparation process and improves the yield rate.

[0140] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A thixoforming method for an expansion alloy, comprising the following steps: (1) mixing and cold pressing high-purity alloy powders in sequence to obtain a green body; (2) subjecting the green body obtained in step (1) to microwave heating and forming, wherein the microwave heating and forming system comprises a first heating and heat preservation section, a second heating and heat preservation section, a first pressurizing section, a third heating and heat preservation section, a second pressurizing section and a fourth heating and heat preservation section, and performing pressure processing on the green body during the heating process to obtain a high-temperature green body; (3) thermally deforming the high-temperature billet obtained in step (2) to obtain an expanded alloy product.

2. The thixoforming method according to claim 1, characterized in that: The mixing in step (1) is carried out in a protective atmosphere.

3. The thixoforming method according to claim 1, characterized in that: The cold pressing pressure in step (1) is ≥150 MPa, and the cold pressing time is ≥15 min.

4. The thixoforming method according to claim 1, characterized in that: In the step (2), the constant temperature of the first heating and heat preservation section is 300-600°C, the heat preservation time of the first heating and heat preservation section is 10-45 minutes, and the speed of heating from room temperature to the constant temperature of the first heating and heat preservation section is 10-15°C / min.

5. The thixoforming method according to claim 1, characterized in that: In the step (2), the constant temperature of the second heating and insulation section is 700-950°C, the insulation time of the second heating and insulation section is 5-45 minutes, and the speed of heating from the constant temperature of the first heating and insulation section to the constant temperature of the second heating and insulation section is 12-28°C / min.

6. The thixoforming method according to claim 1, characterized in that: In the step (2), the constant temperature of the third heating and insulation section is 900-1080°C, the insulation time of the third heating and insulation section is 10-50 minutes, and the speed of heating from the constant temperature of the second heating and insulation section to the constant temperature of the third heating and insulation section is 10-35°C / min.

7. The thixoforming method according to claim 1, characterized in that: In the step (2), the constant temperature of the fourth heating and insulation section is 1050-1190°C, the insulation time of the fourth heating and insulation section is 10-60 minutes, and the speed of heating from the constant temperature of the third heating and insulation section to the constant temperature of the fourth heating and insulation section is 12-28°C / min.

8. The thixoforming method according to claim 1, characterized in that: The reduction rate of the first pressing in the step (2) is 5 to 12%.

9. The thixoforming method according to claim 1, characterized in that: The reduction rate of the second pressing in the step (2) is 8 to 15%.

10. An expansion alloy product prepared by the thixoforming method according to any one of claims 1 to 9.

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