Invar alloy and rheoforming method thereof

Abstract

The invention provides an invar alloy and a rheoforming method thereof, and relates to the technical field of invar alloy production processes. The rheoforming method of the invar alloy comprises the following steps that alloy raw materials are sequentially subjected to smelting and tundish treatment, and alloy melt is obtained; the superheat degree of the melt is controlled, the alloy melt is subjected to thin-strip continuous casting, and a thin strip is obtained; and the thin strip is sequentially subjected to soaking treatment and rolling deformation, and an invar alloy product is obtained. The rheoforming technology is adopted, the invar alloy can be rapidly solidified, the surface of a casting strip is smooth and free of vibration marks, slag inclusion, flash and the like, segregation of inclusion elements to the grain boundary can be effectively restrained, and oxidation of the casting strip is reduced, so that the hot rolling procedure is shortened or even omitted, the problem of cracking in hot working is fundamentally avoided, the production efficiency and the yield are effectively improved, and the production cost is reduced. Therefore, energy consumption is reduced, production cycle is shortened, and production cost is reduced.

Description

Technical Field

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

[0002] Invar alloy was discovered by French metallurgist Guilaume in 1896. Among Fe-Ni alloys, when the Ni content is 36%, the room temperature expansion coefficient of the alloy is the lowest, the length hardly changes with temperature, and the average linear thermal expansion coefficient from room temperature to Curie temperature is almost close to zero. As a result, a new generation of low expansion materials represented by the classic Invar alloy Fe-36Ni was born, and its abnormal expansion phenomenon is called the Invar effect.

[0003] At present, the production process of Invar alloy generally includes: vacuum induction melting → ingot casting → peeling → heating → forging → grinding → heating → hot rolling → solution treatment → pickling → grinding → coiling → cold rolling → continuous bright heat treatment → cold rolling → continuous bright heat treatment → cold finishing rolling. This production process is very lengthy, and the Invar alloy is always in the austenite single phase region after solidification. During the slow solidification, cooling of the ingot and the reheating of forging / hot rolling, the inclusion elements are easily segregated to the grain boundary and combined with the oxygen diffused from the outer surface, causing severe grain boundary oxidation and intragranular oxidation, greatly deteriorating the hot workability of the Invar alloy, resulting in severe surface cracking 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 Invar 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.

[0004] During the solidification process of the metal, it is disturbed or violently stirred, or the temperature range in which the solid and liquid coexist is controlled, that is, the nucleation and growth process of the primary solid phase is changed, and a solid-liquid mixed slurry in which a certain amount of spherical primary solid phase is uniformly suspended in the liquid metal is obtained. The forming process is carried out using this solid-liquid mixed slurry. The method of forming a metal slurry that is neither completely liquid nor completely solid is called metal semi-solid forming technology (FLEMINGS MC. Behavior of Metal Alloys in the Semisolid State [J]. Met Trans, 1991, 22A: 957-981; Kirkwood DH, Kapranos P. Semisolid Processing of metallic alloys [J]. Metals and materials, 1989, 5 (1): 16-19; 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.).

[0005] 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 1As shown. Among them, mud forming is to obtain a metal billet with spherical grains by electromagnetically stirring the liquid alloy and cooling it to room temperature, and then heating the billet to the semi-solid temperature range to complete the final forming; rheoforming omits the cooling to room temperature process, and directly forms the metal slurry that has been cooled to the semi-solid temperature range and completed the spheroidization treatment; thixoforming is a process in which the semi-solid billet is heated to a semi-solid state with a volume of about 50% liquid phase, 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, КΟPP 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 object of the present invention is to provide an Invar alloy and a rheological forming method thereof. The rheological forming method provided by the present invention has a simplified preparation process, a controllable production process, a short production cycle, stable product quality, and an improved yield rate.

[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 method for preparing an Invar alloy by rheological forming, comprising the following steps:

[0009] (1) melting the alloy raw materials and performing tundish treatment in sequence to obtain an alloy melt;

[0010] (2) performing strip continuous casting on the alloy melt obtained in step (1) to obtain a thin strip;

[0011] (3) The thin strip obtained in step (2) is subjected to heat treatment and rolling in sequence to obtain an Invar alloy product.

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

[0013] Preferably, during the tundish treatment in step (1), the melt temperature is 25 to 70° C. higher than the melting point.

[0014] Preferably, the tundish treatment in step (1) is carried out under argon soft blowing and refining slag protection.

[0015] Preferably, the flow rate of the argon soft blowing is 0.1-0.5 Nm 3 / t, the argon soft blowing time is 3 to 5 minutes.

[0016] Preferably, when the thickness of the thin strip in step (2) is less than 20 mm, the casting speed of the thin strip continuous casting is 4.5 to 7.0 m / min, and the flow rate of the cooling water during the thin strip continuous casting is 5 to 10 m / min. 3 / min, the superheat of the alloy melt is 20~40℃.

[0017] Preferably, when the thickness of the thin strip in step (2) is 20 to 50 mm, the casting speed of the thin strip continuous casting is 4.0 to 6.0 m / min, and the flow rate of the cooling water during the thin strip continuous casting is 8 to 15 m / min. 3 / min, the superheat of the alloy melt is 30-50℃.

[0018] Preferably, when the thickness of the thin strip in step (2) is greater than 50 mm, the casting speed of the thin strip continuous casting is 2.5 to 4.5 m / min, and the flow rate of the cooling water during the thin strip continuous casting is 10 to 25 m / min. 3 / min, the superheat of the alloy melt is 40-60℃.

[0019] Preferably, the soaking treatment in step (3) is carried out in a roller-bottom tunnel heating furnace; the temperature of the thin strip entering the roller-bottom tunnel heating furnace is greater than 850°C, and the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is 980-1150°C; the time of the soaking treatment is 20-40 minutes.

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

[0021] The present invention provides a method for preparing an Invar alloy, comprising the following steps: sequentially smelting and tundish treating the alloy raw materials to obtain an alloy melt; by controlling the superheat of the melt, continuously casting the alloy melt into a thin strip to obtain a thin strip; sequentially performing a heat treatment and rolling on the thin strip to obtain an Invar alloy product. The present invention adopts rheological forming technology, has a controllable production process, low energy consumption, can rapidly solidify the Invar alloy, and the surface of the cast strip is smooth without vibration marks, slag inclusions, flash, etc. It can effectively inhibit the segregation of the inclusion elements to the grain boundary, reduce the oxidation of the cast strip, thereby shortening or even canceling the hot rolling process, fundamentally avoiding the problem of hot working cracking, and having stable product quality, high production efficiency and yield rate, controllable production cycle and production cost, and can realize rapid conversion of different products. The experimental results show that the Invar alloy prepared by the present invention has no defects in appearance, a tensile strength of 479-516 MPa, a yield strength of 313-385 MPa, an elongation after fracture of 25.7-29.8%, and an expansion coefficient of 0.83-1.13×10 -6 / ℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A classification of semi-solid metal forming. DETAILED DESCRIPTION

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

[0024] (1) melting the alloy raw materials and performing tundish treatment in sequence to obtain an alloy melt;

[0025] (2) performing strip continuous casting on the alloy melt obtained in step (1) to obtain a thin strip;

[0026] (3) The thin strip obtained in step (2) is subjected to heat treatment and rolling in sequence to obtain an Invar alloy product.

[0027] The present invention optimizes and regulates the composition of alloy raw materials, controls the content of impurity elements in the alloy from the source, achieves precise control of the alloy composition, and further improves the purity of the melt.

[0028] In the present invention, the alloy raw material is preferably a pure metal block; the pure metal block is preferably a pure nickel block and a pure iron block. The present invention has no special limitation on the specific selection of the pure metal block, and it can be adjusted according to actual needs.

[0029] In the present invention, the pure nickel block preferably includes a pure nickel block 1 and a pure nickel block 2 .

[0030] In terms of mass percentage, the chemical composition of the pure nickel block 1 preferably includes C≤0.005%, Si≤0.001%, P≤0.001%, S≤0.001%, Cu≤0.008%, Fe≤0.005%, Zn≤0.001%, As≤0.0005%, Cd≤0.0002%, Sn≤0.0002%, Sb≤0.0002%, Pb≤0.001%, Bi≤0.0002%, Mg≤0.0005%, Co≤0.01% and the balance Ni; the total mass content of Ni and Co in the pure nickel block 1 is preferably ≥99.95%.

[0031] In terms of mass percentage, the chemical composition of the pure nickel block 2 preferably includes C≤0.01%, P≤0.001%, S≤0.001%, Cu≤0.003%, Fe≤0.1%, Cu≤0.003%, Zn≤0.002%, As≤0.001%, Cd≤0.001%, Sn≤0.0015%, Sb≤0.0015%, Pb≤0.001%, Bi≤0.0015%, Co≤0.1% and the balance Ni; the total mass content of Ni and Co in the pure nickel block 2 is preferably ≥99.6%.

[0032] In the present invention, the pure iron block preferably includes a pure iron block 1 and a pure iron block 2 .

[0033] In terms of mass percentage, the chemical composition of the pure iron block 1 preferably includes C≤0.03%, Si≤0.005%, Mn≤0.01%, P≤0.002%, S≤0.001%, Cu≤0.01%, Ni≤0.05%, Al≤0.01%, Cu≤0.01%, Ti≤0.005% and the balance Fe.

[0034] In terms of mass percentage, the chemical composition of the pure iron block 2 preferably includes C≤0.02%, Si≤0.05%, Mn≤0.08%, P≤0.007%, S≤0.005%, Cu≤0.01%, Ni≤0.08%, Al≤0.05%, Cu≤0.02%, Ti≤0.03% and the balance Fe.

[0035] The present invention has no special limitation on the composition of the alloy raw material, and pure metal or intermediate alloy can be selected and adjusted according to actual needs.

[0036] The present invention has no particular limitation on the size of the alloy raw material, and any size familiar to those skilled in the art may be used.

[0037] In the present invention, the smelting is preferably carried out in a protective atmosphere; the protective atmosphere is preferably argon; the smelting is preferably carried out in an electric furnace or a medium frequency induction furnace. The present invention has no special limitation on the model of the electric furnace or the medium frequency induction furnace, and the furnace capacity is matched accordingly according to the production capacity or production scheduling needs, and instruments and equipment familiar to those skilled in the art can be used.

[0038] The present invention has no special limitation on the smelting temperature and time, which can be conventionally selected according to the actual required Invar alloy.

[0039] In the present invention, the melt temperature during the tundish treatment is preferably 25 to 70°C higher than the melting point; the tundish treatment is preferably carried out under argon soft blowing and refining slag protection; the flow rate of the argon soft blowing is preferably 0.1 to 0.5 Nm 3 / t, more preferably 0.25 to 0.43 Nm 3 / t; the argon soft blowing time is preferably 3 to 5 minutes, more preferably 4 minutes. The present invention adopts argon soft blowing and refined slag protection for tundish treatment to ensure the purity and composition uniformity of the melt.

[0040] In the present invention, the average temperature drop of the melt during the argon soft blowing is preferably 8-10° C. / min.

[0041] The present invention has no particular limitation on the operation of making refined slag, and operations well known to those skilled in the art may be adopted.

[0042] After obtaining the alloy melt, the present invention performs thin strip continuous casting on the alloy melt to obtain a thin strip. The present invention adopts the thin strip continuous casting technology, which can make the Invar alloy solidify quickly, and the surface of the cast strip is smooth and clean without vibration marks, slag inclusions, flash, etc., which can effectively inhibit the segregation of the included elements to the grain boundary and reduce the oxidation of the cast strip, thereby shortening or even eliminating the hot rolling process, fundamentally avoiding the problem of hot working cracking, and stabilizing the product quality, and effectively improving the production efficiency and yield rate.

[0043] In the present invention, the thin strip continuous casting preferably adopts a funnel-shaped crystallizer and a thin strip continuous casting machine. The present invention has no special limitation on the models of the funnel-shaped crystallizer and the thin strip continuous casting machine, and the instruments and equipments well known to those skilled in the art can be adopted.

[0044] In the present invention, the thin strip continuous casting is preferably carried out in a protective slag; the binary basicity of the protective slag is preferably 0.85-1.2, more preferably 0.95-0.985; the melting temperature of the protective slag is preferably 1035-1280°C, more preferably 1085-1150°C; the viscosity of the protective slag at 1300°C is preferably 0.012-0.020 Pa·S, more preferably 0.013-0.015 Pa·S. The present invention uses a protective slag with a low melting point, low viscosity and high fluidity to isolate the contact between air and the melt, and protect the melt from secondary oxidation by air.

[0045] In the present invention, the components of the protective slag are preferably, by mass percentage, CaO 30.98-39.47%, SiO 2 26.33-39.92%, MgO 1.46-7.25%, Al 2 O 3 3.8-5.7%, Na 2 O 0-8.4%, Li 2 O 0-7.1%, C 0-5.88% and ZrO 2 0-3.1%.

[0046] In the present invention, when the thickness of the thin strip is 10 mm ≤ thin strip < 20 mm, the casting speed of the thin strip continuous casting is preferably 4.5 to 7.0 m / min, more preferably 4.5 to 5.0 m / min; the flow rate of cooling water during the thin strip continuous casting is preferably 5 to 10 m / min. 3 / min, more preferably 8 to 10m 3 / min; the superheat of the alloy melt is preferably 20 to 40°C, more preferably 30 to 40°C.

[0047] In the present invention, when the thickness of the thin strip is 20 to 50 mm, the casting speed of the thin strip continuous casting is preferably 4.0 to 6.0 m / min, more preferably 4.5 to 5.0 m / min; the flow rate of cooling water during the thin strip continuous casting is preferably 8 to 15 m / min. 3 / min, more preferably 10 to 13 m 3 / min; the superheat of the alloy melt is preferably 30-50°C, more preferably 38-40°C.

[0048] In the present invention, when the thickness of the thin strip is 50 mm < thin strip ≤ 60 mm, the casting speed of the thin strip continuous casting is preferably 2.5 to 4.5 m / min, more preferably 3.0 to 4.0 m / min; the flow rate of cooling water during the thin strip continuous casting is preferably 10 to 25 m / min. 3 / min, more preferably 15 to 20m 3 / min; the superheat of the alloy melt is preferably 40-60°C, more preferably 45-50°C.

[0049] The invention can realize the rapid solidification of Invar alloy by adjusting the cooling mode of the cooling twin rollers and adopting a smaller casting strip thickness, and the casting strip surface is smooth without vibration marks, slag inclusions, flash, etc., and can effectively inhibit the segregation of inclusion elements to the grain boundary and reduce the oxidation of the casting strip.

[0050] After obtaining the thin strip, the present invention sequentially performs heat treatment and rolling on the thin strip to obtain an Invar alloy product.

[0051] In the present invention, the soaking treatment is preferably carried out in a roller-bottom tunnel heating furnace; the temperature of the thin strip entering the roller-bottom tunnel heating furnace is preferably >850°C, more preferably 860-900°C; the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is preferably 980-1150°C, more preferably 1060-1120°C; the soaking treatment time is preferably 20-40 minutes, more preferably 25-35 minutes. The present invention adopts soaking treatment to achieve effective and stable connection between the thin strip continuous casting machine and the hot rolling mill.

[0052] In the present invention, the roller-hearth tunnel heating furnace is preferably thermally controlled and tracked by PLC. The present invention adopts PLC for thermal control and tracking of billets, with a high degree of automation. Its operation can be fully automatically controlled, or it can be selected between automatic and manual. The mathematical model of the secondary machine optimizes the heating furnace online to achieve optimal operation.

[0053] In the present invention, during single billet rolling, the difference between the temperature of the thin strip entering the roller bottom tunnel heating furnace and the temperature exiting the roller bottom tunnel heating furnace is preferably ±8°C; during semi-headless rolling, the difference between the temperature of the thin strip entering the roller bottom tunnel heating furnace and the temperature exiting the roller bottom tunnel heating furnace is preferably ±12°C.

[0054] After the soaking treatment is completed, the present invention preferably removes the iron oxide scale from the product obtained by the soaking treatment.

[0055] The present invention has no particular limitation on the operation of removing the iron oxide scale, and the operation well known to those skilled in the art may be adopted.

[0056] In the present invention, the rolling is preferably finish rolling.

[0057] In the present invention, the rough rolling and secondary descaling are preferably performed in sequence before the finish rolling; the rough rolling is preferably performed in a four-roller reversible rough rolling mill; the total reduction of the rough rolling is preferably 5 to 16%. The present invention has no special limitation on the model of the four-roller reversible rough rolling mill, and the equipment well known to those skilled in the art can be used.

[0058] The present invention has no particular limitation on the secondary descaling operation, and operations well known to those skilled in the art may be used.

[0059] In the present invention, the finishing rolling is preferably carried out in a 6-stand continuous four-roller rolling mill. The present invention has no particular limitation on the model of the 6-stand continuous four-roller rolling mill, and any equipment well known to those skilled in the art can be used.

[0060] In the present invention, during the finish rolling, the reduction rate of the first rolling mill is preferably <40%, more preferably 26-35%, and more preferably 28-32%; the reduction rate of the second rolling mill is preferably ≤60%, more preferably 40-58.9%, and more preferably 40.5-52.2%; the reduction rate of the third rolling mill is preferably ≤60%, more preferably 40-58.9%, and more preferably 42.3-55.3%; the reduction rate of the fourth rolling mill is preferably ≤60%, more preferably 40-56.6%, and more preferably 42.7-50.8%; the reduction rate of the fifth rolling mill is preferably 29-40%, more preferably 33.71-35.3%, and more preferably 34.8-35%; the reduction rate of the sixth rolling mill is preferably ≤30%, more preferably 14.86-28.9%, and more preferably 15-17.7%.

[0061] After the continuous rolling is completed, the present invention preferably cools and coils the product strip obtained by the continuous rolling in sequence to obtain an Invar alloy product.

[0062] 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.

[0063] In the present invention, the Invar alloy product is preferably an Invar alloy strip.

[0064] The present invention starts with pure metal concentrate, optimizes and improves the production process, simplifies the alloy smelting process, and greatly improves the purity of the melt; the thin strip continuous casting technology is adopted, and by adjusting the cooling double-roller cooling method and the smaller casting strip thickness, the rapid solidification of the Invar alloy can be achieved, and the casting strip surface is smooth, without vibration marks, slag inclusions, flash, etc., which can effectively inhibit the inclusion elements from segregating to the grain boundary and reduce the oxidation of the casting strip. The thin strip continuous casting process can shorten or even eliminate the hot rolling process, and fundamentally avoid the problem of hot working cracking; the present invention can greatly reduce the Invar alloy smelting production process, improve production efficiency and yield rate, the yield rate is more than 80%, shorten the production cycle, reduce production costs, and realize the rapid conversion of different products, and the product has a wide range of applications.

[0065] The present invention also provides an Invar alloy product prepared by the rheological forming method described in the above technical solution.

[0066] 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.

[0067] Example 1

[0068] A rheoforming method for an Invar 4J36 strip comprises the following steps:

[0069] (1) Adding pure nickel block 1, pure nickel block 2, pure iron block 1 and pure iron block 2 into an electric furnace, and melting them under argon protection, pouring the melt into a tundish, performing argon soft blowing and refining slag protection, and obtaining an alloy melt; wherein the mass ratio of pure nickel block 1:pure nickel block 2 is 4:6, and the mass ratio of pure iron block 1:pure iron block 2 is 3:7; the melt temperature is 1515°C, and the flow rate of argon is 0.16Nm 3 / t, argon blowing time 4min, average temperature drop 8℃ / min;

[0070] (2) The alloy melt obtained in the step (1) is subjected to thin strip continuous casting using a funnel-shaped crystallizer and protective slag to obtain a thin strip with a thickness of 52 mm; wherein the protective slag has a binary basicity of 0.95, a melting temperature of 1085° C., a viscosity of 0.015 Pa·S at 1300° C., and a composition by mass percentage of: CaO 36.05%, SiO2 34.25%, MgO 5.73%, Al2O3 5.56%, Na2O 4.55%, Li2O 6.67%, C 5.32% and ZrO2 1.87%; the funnel-shaped crystallizer has a maximum upper opening width of 170 mm and a lower opening width of 52 mm; the casting speed is 3.0 m / min, the superheat is 45° C., and the cooling water flow rate is 15 m 3 / min;

[0071] (3) The thin strip obtained in step (2) is subjected to a soaking treatment in a roller-bottom tunnel heating furnace for 23 minutes, and then the scale remover is used to remove the iron oxide scale to obtain a soaking treated thin strip; wherein the temperature of the thin strip entering the roller-bottom tunnel heating furnace is 860° C., and the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is 1095° C., and the temperature difference control range is ±8° C. for single billet rolling;

[0072] (4) The heat-treated thin strip obtained in step (3) is put into a four-roll reversible rough rolling mill for primary rolling to ensure that the thickness of the thin strip is 46 mm, and then it is descaled for a secondary time, and then it is sent to a 6-stand continuous four-roll rolling mill via a conveyor roller for finish rolling, and then it enters a cooling section via a roller for controlled cooling, and then it is rolled into a strip coil by a coiler to obtain an Invar alloy strip.

[0073] Example 2

[0074] A rheoforming method for an Invar 4J36 strip comprises the following steps:

[0075] (1) Adding pure nickel block 1, pure nickel block 2, pure iron block 1 and pure iron block 2 into an electric furnace, and melting them under argon protection, pouring the melt into a tundish, performing argon soft blowing and refining slag protection, and obtaining an alloy melt; wherein the mass ratio of pure nickel block 1:pure nickel block 2 is 7:3, and the mass ratio of pure iron block 1:pure iron block 2 is 8:2; the melt temperature is 1508°C, and the flow rate of argon is 0.31Nm 3 / t, argon blowing time 3min, average temperature drop 10℃ / min;

[0076] (2) The alloy melt obtained in step (1) is subjected to thin strip continuous casting using a funnel-shaped crystallizer and protective slag to obtain a thin strip with a thickness of 32 mm; wherein the protective slag has a binary basicity of 0.985, a melting temperature of 1055° C., a viscosity of 0.013 Pa·S at 1300° C., and a composition by mass percentage of: CaO 35.81%, SiO2 32.55%, MgO 6.75%, Al2O3 5.49%, Na2O 7.95%, Li2O 6.5% and C 4.95%; the funnel-shaped crystallizer has a maximum upper opening width of 170 mm and a lower opening width of 32 mm; the casting speed is 5.0 m / min, the superheat is 38° C., and the cooling water flow rate is 13 m 3 / min;

[0077] (3) The thin strip obtained in step (2) is subjected to a soaking treatment in a roller-bottom tunnel heating furnace for 21 minutes, and then the scale remover is used to remove the iron oxide scale to obtain a soaking treated thin strip; wherein the temperature of the thin strip entering the roller-bottom tunnel heating furnace is 870° C., and the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is 1085° C., and semi-endless rolling is performed, and the temperature difference control range is ±12° C.;

[0078] (4) The heat-treated thin strip obtained in step (3) is sent to a 6-stand continuous four-roller rolling mill via a conveyor roller for finish rolling, and then enters a cooling section via a roller for controlled cooling, and then is rolled into a strip coil by a coiler to obtain an Invar alloy strip.

[0079] Example 3

[0080] A rheoforming method for an Invar 4J32 strip comprises the following steps:

[0081] (1) adding a pure nickel block 1, a pure nickel block 2, a pure iron block 1, a pure iron block 2 and pure cobalt into an electric furnace, and performing electric melting under argon protection; pouring the melt into a tundish, performing argon soft blowing and refining slag protection, and obtaining an alloy melt; wherein the mass ratio of the pure nickel block 1: the pure nickel block 2 is 5:5, and the mass ratio of the pure iron block 1: the pure iron block 2 is 4:6; the pure cobalt is high-purity cobalt with a cobalt content of not less than 99.999%; the melt temperature is 1521°C, and the flow rate of the argon gas is 0.36Nm 3 / t, argon blowing time 2.6min, average temperature drop 10℃ / min;

[0082] (2) The alloy melt obtained in step (1) is subjected to thin strip continuous casting using a funnel-shaped crystallizer and protective slag to obtain a thin strip with a thickness of 60 mm; wherein the protective slag has a binary basicity of 0.97, a melting temperature of 1065° C., a viscosity of 0.014 Pa·S at 1300° C., and a composition by mass percentage of: CaO 38.41%, SiO2 37.29%, MgO 4.36%, Al2O3 4.23%, Na2O 4.93%, Li2O 5.33%, C 4.53% and ZrO2 0.92%; the funnel-shaped crystallizer has a maximum upper opening width of 170 mm and a lower opening width of 60 mm; the casting speed is 2.5 m / min, the superheat is 60° C., and the cooling water flow rate is 25 m 3 / min;

[0083] (3) The thin strip obtained in step (2) is subjected to a soaking treatment in a roller-bottom tunnel heating furnace for 25 minutes, and then the scale remover is used to remove the iron oxide scale to obtain a soaking treated thin strip; wherein the temperature of the thin strip entering the roller-bottom tunnel heating furnace is 853° C., and the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is 1080-1160° C., and the temperature difference control range is ±8° C. for single billet rolling;

[0084] (4) The heat-treated thin strip obtained in step (3) is sent to a four-roll reversible rough rolling mill for primary rolling, and then descaled for a secondary rolling. Then, it is sent to a 6-stand continuous four-roll rolling mill via a conveyor roller for finish rolling, and then sent to a cooling section via a roller for controlled cooling, and then rolled into a strip coil by a coiler to obtain an Invar alloy strip.

[0085] Example 4

[0086] A rheoforming method for an Invar 4J32 strip comprises the following steps:

[0087] (1) adding a pure nickel block 1, a pure nickel block 2, a pure iron block 1, a pure iron block 2 and pure cobalt into an electric furnace, and performing electric melting under argon protection; pouring the melt into a tundish, performing argon soft blowing and refining slag protection, and obtaining an alloy melt; wherein the mass ratio of the pure nickel block 1: the pure nickel block 2 is 6:4, and the mass ratio of the pure iron block 1: the pure iron block 2 is 5:5; the pure cobalt is high-purity cobalt with a cobalt content of not less than 99.999%; the melt temperature is 1500°C, and the flow rate of the argon gas is 0.355 Nm 3 / t, argon blowing time 2.8min, average temperature drop 10℃ / min;

[0088] (2) The alloy melt obtained in the step (1) is subjected to thin strip continuous casting using a funnel-shaped crystallizer and protective slag to obtain a thin strip with a thickness of 20 mm; wherein the protective slag has a binary basicity of 1.01, a melting temperature of 1045° C., a viscosity of 0.012 Pa·S at 1300° C., and a composition by mass percentage of: CaO 37.28%, SiO2 38.04%, MgO 7.03%, Al2O3 5.83%, Na2O 2.99%, Li2O 3.59%, C 4.96% and ZrO2 0.28%; the funnel-shaped crystallizer has a maximum upper opening width of 170 mm and a lower opening width of 20 mm; the casting speed is 4.5 m / min, the superheat is 40° C., and the cooling water flow rate is 10 m 3 / min;

[0089] (3) The thin strip obtained in step (2) is subjected to a soaking treatment in a roller-bottom tunnel heating furnace for 23 minutes, and then the scale remover is used to remove the iron oxide scale to obtain a soaking treated thin strip; wherein the temperature of the thin strip entering the roller-bottom tunnel heating furnace is 862° C., and the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is 1075° C., and semi-endless rolling is performed, and the temperature difference control range is ±12° C.;

[0090] (4) The heat-treated thin strip obtained in step (3) is sent to a 6-stand continuous four-roller rolling mill via a conveyor roller for finish rolling, and then enters a cooling section via a roller for controlled cooling, and then is rolled into a strip coil by a coiler to obtain an Invar alloy strip.

[0091] The chemical composition of the pure nickel block used in Examples 1 to 4 is shown in Table 1, and the chemical composition of the pure iron block is shown in Table 2.

[0092] Table 1 Chemical composition of pure nickel block (mass fraction) / %

[0093]

[0094] Table 2 Chemical composition of pure iron block (mass fraction) / %

[0095]

[0096]

[0097] The reduction ratios of the first rolling and finish rolling of the thin strip in Examples 1 to 4 are shown in Table 3.

[0098] Table 3 Rolling reduction ratio of thin strips prepared in Examples 1 to 4

[0099]

[0100] The chemical compositions of the Invar alloys prepared in Examples 1 to 4 are shown in Table 4.

[0101] Table 4 Chemical composition of Invar alloys prepared in Examples 1 to 4 (mass fraction) / %

[0102]

[0103] The appearance inspection of the Invar alloys prepared in Examples 1 to 4 is shown in Table 5. The relevant inspection standards refer to the general provisions of GB / T14985-2007 expansion alloy size, shape, surface quality, test methods and inspection rules.

[0104] Table 5 Appearance inspection and yield rate of Invar alloys prepared in Examples 1 to 4

[0105] Serial number Pulling and breaking belt Plate shape problem Roughness Thickness deviation Yield rate (%) Example 1 none none Ra≤1.5μm ±10μm 80 Example 2 none none Ra≤1.6μm ±11μm 82 Example 3 none none Ra≤1.5μm ±10μm 81 Example 4 none none Ra≤1.7μm ±12μm 83

[0106] It can be seen from Table 5 that the Invar alloy prepared in the embodiment has no obvious surface defects and has a high yield rate.

[0107] The mechanical properties of the Invar alloys prepared in Examples 1 to 4 are shown in Table 6. The relevant testing standards refer to the general provisions of GB / T14985-2007 expansion alloy size, shape, surface quality, test methods and inspection rules.

[0108] Table 6 Mechanical properties of Invar alloys prepared in Examples 1 to 4

[0109]

[0110]

[0111] It can be seen from Table 6 that the Invar alloy prepared in the embodiment has excellent mechanical properties.

[0112] It can be seen from the above embodiments that the rheological forming method provided by the present invention simplifies the preparation process and improves the yield rate.

[0113] 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 rheological forming method of Invar alloy, comprising the following steps: (1) melting the alloy raw materials and performing tundish treatment in sequence to obtain an alloy melt; (2) performing strip continuous casting on the alloy melt obtained in step (1) to obtain a thin strip; (3) The thin strip obtained in step (2) is subjected to heat treatment and rolling in sequence to obtain an Invar alloy product.

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

3. The rheological forming method according to claim 1, characterized in that: During the tundish treatment in step (1), the melt temperature is 25 to 70° C. higher than the melting point.

4. The rheological forming method according to claim 1, characterized in that: The tundish treatment in step (1) is carried out under argon soft blowing and refined slag protection.

5. The rheological forming method according to claim 4, characterized in that: The flow rate of the argon soft blowing is 0.1-0.5 Nm 3 / t, the argon soft blowing time is 3 to 5 minutes.

6. The rheological forming method according to claim 1, characterized in that: When the thickness of the thin strip in step (2) is less than 20 mm, the casting speed of the thin strip continuous casting is 4.5 to 7.0 m / min, and the flow rate of the cooling water during the thin strip continuous casting is 5 to 10 m / min. 3 / min, the superheat of the alloy melt is 20~40℃.

7. The rheological forming method according to claim 1, characterized in that: When the thickness of the thin strip in step (2) is 20 to 50 mm, the casting speed of the thin strip continuous casting is 4.0 to 6.0 m / min, and the flow rate of the cooling water during the thin strip continuous casting is 8 to 15 m / min. 3 / min, the superheat of the alloy melt is 30-50℃.

8. The rheological forming method according to claim 1, characterized in that: When the thickness of the thin strip in step (2) is greater than 50 mm, the casting speed of the thin strip continuous casting is 2.5 to 4.5 m / min, and the flow rate of the cooling water during the thin strip continuous casting is 10 to 25 m / min. 3 / min, the superheat of the alloy melt is 40-60℃.

9. The rheological forming method according to claim 1, characterized in that: The soaking treatment in step (3) is carried out in a roller-bottom tunnel heating furnace; the temperature of the thin strip entering the roller-bottom tunnel heating furnace is greater than 850°C, and the temperature of the thin strip exiting the roller-bottom tunnel heating furnace is 980-1150°C; the soaking treatment time is 20-40 minutes.

10. An Invar alloy product prepared by the rheological forming method according to any one of claims 1 to 9.

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