A method for preparing a MnNiCr alloy narrow thin strip

Abstract

This invention discloses a method for preparing narrow thin strips of MnNiCr alloy, belonging to the field of metal material processing technology. The method includes: vacuum melting and casting MnNiCr alloy into ingots; homogenizing and annealing the ingots followed by multi-directional forging to create a blank; then preparing precision wire using a combination of die rolling and multi-pass drawing; finally, forming the narrow thin strip through precision rolling and online winding. This invention eliminates the need for electromagnetic stirring casting, effectively breaking up segregation and coarse grains in the as-cast microstructure through multi-directional forging. Combined with a continuous forming process of die rolling-drawing-narrow strip rolling, it achieves efficient and stable preparation of narrow thin strips of MnNiCr alloy. The product obtained by this invention has high dimensional accuracy, excellent surface quality, and good consistency in mechanical properties, making it suitable for high-temperature brazing thin strip materials in aerospace, nuclear industry, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, and specifically relates to a method for preparing narrow thin strips of MnNiCr alloy. Background Technology

[0002] MnNiCr alloys are an important class of manganese-based brazing filler metals, possessing excellent high-temperature brazing performance, good wettability, and oxidation resistance. They are widely used in the brazing of high-temperature structural components such as aero-engines and hot-end parts of spacecraft. Among them, BMn... 70 Ni 25 MnNiCr alloys, represented by Cr5, have high manganese content and a wide crystallization temperature range, belonging to an alloy system with a large tendency for solidification segregation.

[0003] Currently, the preparation of narrow MnNiCr strips mostly adopts the "vacuum melting - hot rolling - cold rolling - slitting" process. However, this process has the following problems: First, high-manganese alloys are prone to oxidation and gas absorption during melting and casting. Casting defects such as central shrinkage cavities and porosity are common in ingots, which makes them prone to cracking during subsequent hot forging and resulting in a yield of less than 50%. Second, the central area of ​​the ingot solidifies last, making it difficult to obtain effective feeding. Even after hot rolling and forging, large concentrated shrinkage cavities are difficult to completely weld together, making it difficult to form fine wires and resulting in a low yield. Third, the slitting process is costly in preparing ultra-narrow strips and is prone to defects such as sickle bends, burrs, and twists, which seriously affect the dimensional accuracy and surface quality of the product. At the same time, the material loss is large, further reducing the yield.

[0004] Therefore, in view of the shortcomings of the existing technology, there is an urgent need to develop a method for preparing narrow strips of MnNiCr alloy that can eliminate ingot defects, improve yield, and at the same time ensure the dimensional accuracy and surface quality of the narrow strips. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing narrow and thin strips of MnNiCr alloy, which can eliminate ingot defects, improve yield, and ensure the dimensional accuracy and surface quality of the narrow and thin strips.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing narrow thin strips of MnNiCr alloy includes the following steps: (1) Vacuum melting: MnNiCr alloy is melted in a vacuum induction melting furnace and cast into ingots with round or square cross sections. Then, homogenization annealing is carried out to eliminate element segregation.

[0007] (2) Multi-directional forging: The ingot after annealing in step (1) is forged in three orthogonal directions to obtain a round bar forging billet, and then annealed to break the as-cast structure, improve the uniformity of the structure, and eliminate or reduce as-cast defects.

[0008] (3) Rolling through a die: The round bar forging billet after annealing in step (2) is rolled through a die to obtain wire, and then annealed to further refine the microstructure.

[0009] (4) Drawing: The wire after annealing in step (3) is drawn in multiple passes, with the diameter reduced step by step. After each pass, vacuum annealing is performed to finally obtain fine wire.

[0010] (5) Precision rolling: Calculate the diameter of the fine wire corresponding to the target narrow strip size according to the empirical formula for rolling width in one pass, and directly roll the fine wire from step (4) into the target narrow strip.

[0011] (6) Annealing and winding: The narrow strip from step (5) is subjected to vacuum annealing and wound up under tension control to obtain a narrow strip of MnNiCr alloy.

[0012] Preferably, in step (1) of this invention, the MnNiCr alloy is a MnNiCr brazing alloy with a Mn content ≥ 60wt%, such as BMn 70 Ni 25 Cr5.

[0013] Preferably, in step (1) of the present invention, the melting temperature of vacuum melting is 1300~1400 ℃, the casting temperature is 1250~1350 ℃, and the conditions for homogenization annealing are: annealing temperature is 850~950 ℃, holding time is 2~4 h, and air cooling is performed after furnace cooling.

[0014] Preferably, in step (2) of the present invention, the initial forging temperature of multi-directional forging is 700~900 ℃, and the final forging temperature is not lower than 700 ℃; the multi-directional forging method is: 3~6 passes of multi-directional forging are performed in the order of three orthogonal directions of Z-axis-Y-axis-X-axis, the deformation amount of each pass is ≥30%, and the last forging is a round bar forging blank of Ø20~Ø25 mm.

[0015] Preferably, in step (2) of the present invention, the annealing conditions are: annealing temperature of 700~900 ℃ and holding time of 30~60 min.

[0016] Preferably, in step (3) of the present invention, the rolling method of the die is: using a round-elliptical-round die system, and finally rolling to a bar with a diameter of Ø7-Ø10 mm; the annealing conditions are: annealing temperature of 700~900 ℃ and holding time of 20~40 min.

[0017] Preferably, in step (4) of the present invention, the drawing conditions are as follows: using tungsten carbide or natural diamond wire drawing dies, the drawing speed is 10~100 m / min, and the reduction rate of the drawing pass is 10%~20%; the vacuum annealing conditions are as follows: the annealing atmosphere is an inert gas, the annealing temperature is 700~900 ℃, and the holding time is 20~40 min.

[0018] Preferably, in step (5) of this invention, the empirical formula for the width expansion of a single rolling pass is: Where, a is the required width of the narrow and thin strip, and b is the required thickness of the narrow and thin strip. The diameter of the filament used to roll the narrow, thin strip required for this objective.

[0019] Preferably, in step (5) of the present invention, the conditions for precision rolling are as follows: a four-roll or twelve-roll precision calender is used, the rolling speed is 20~80 m / min, the width of the narrow strip is 0.5~5 mm, the thickness is 0.02~0.5 mm, and the width-to-thickness ratio is ≥10.

[0020] Preferably, in step (6) of the present invention, the conditions for vacuum annealing are: the annealing atmosphere is an inert gas, the annealing temperature is 500~600℃, and the annealing speed is 5~15 m / min; the conditions for winding are: the winding tension is controlled at 5~20 N, and the winding is flat and without twisting.

[0021] Another object of the present invention is to provide a narrow thin strip of MnNiCr alloy prepared by the above method.

[0022] The MnNiCr alloy narrow strips prepared by the method of this invention have a smooth surface, are free from oxidation, cracks, and burrs, with a width tolerance of ≤ ±0.01 mm and a thickness tolerance of ≤ ±0.002 mm.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a multi-directional forging process to significantly improve the as-cast structure of MnNiCr alloy and effectively improve the plastic processing performance of MnNiCr alloy; high-precision wire is obtained by using a die rolling and drawing process, which provides an ideal billet for narrow strip rolling; the billet can be directly rolled into shape without slitting, avoiding edge defects; and MnNiCr alloy narrow strips with a thickness of 0.02~0.5mm and a width of 0.5~5mm can be stably produced.

[0024] (2) The MnNiCr alloy narrow strip prepared by the present invention has the characteristics of high dimensional accuracy and good surface quality. How the high dimensional accuracy is manifested and how the good surface quality is manifested need to be explained in detail. It is suitable for high temperature brazing strips in aviation, aerospace, nuclear energy and other fields, and has a clear industrial application prospect. Attached Figure Description

[0025] Figure 1 This is the preparation of BMn in Example 1 of the present invention. 70 Ni 25 Flowchart of the preparation process for Cr5 alloy narrow thin strips; Figure 2 BMn prepared in Example 1 of this invention 70 Ni 25 Diagram of surface porosity and central shrinkage cavity defects in Cr5 alloy ingot; Figure 3 BMn prepared in Example 1 of this invention 70 Ni 25 Cross-sectional view of Cr5 alloy ingot after hot multi-directional forging. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 This embodiment provides a BMn with a width of 1.4 mm and a thickness of 0.1 mm. 70 Ni 25 The preparation method of Cr5 alloy narrow thin strips is as follows: (1) Vacuum melting: BMn 70 Ni 25 The Cr5 alloy was melted in a vacuum induction furnace at a temperature of 1350℃. After melting, it was cast into a cylindrical ingot with a diameter of 80 mm and a length of 200 mm at 1250℃. Then, it was homogenized and annealed at 850℃ for 2 h, followed by furnace cooling and air cooling.

[0028] (2) Multi-directional forging: Set the initial forging temperature to 870 ℃ and the final forging temperature to ≥700 ℃. Perform 4 passes of multi-directional forging on the cylindrical ingot after annealing in step (1) in the order of Z-axis-Y-axis-X-axis (one pass in each direction of Z-axis-Y-axis-X-axis is one cycle, and the cycle is 4 times). The deformation amount of each pass is 40%. The last forging is to form a round bar billet of Ø20 mm. After air cooling, it is annealed at 750 ℃ ​​for 60 min.

[0029] (3) Rolling through a die: The round bar forging billet after annealing in step (2) is rolled through a die in 12 passes using a round-elliptical-round die system, and finally rolled to Ø8 mm wire. After each 4 passes of rolling, it is annealed at 750 ℃ ​​for 40 min.

[0030] (4) Drawing: Using a tungsten carbide drawing die, the wire after annealing in step (3) is drawn to form a fine wire of Ø0.75 mm at a speed of 30 m / min and a reduction rate of 15%. During the drawing process, after each reduction of 2 mm in diameter, the wire is vacuum annealed at 750℃ for 20 min under argon protection.

[0031] (5) Precision rolling: Calculate the diameter of the fine wire corresponding to the target narrow strip size according to the empirical formula for rolling width in one pass. In this embodiment, the target narrow strip width is 1.4 mm and the thickness is 0.1 mm. Therefore, the diameter of the fine wire for rolling the target narrow strip is Ø = 0.75 mm (actually Ø = 0.75 mm). Then, a four-roll precision calender is used with a rolling speed of 40 m / min to directly roll the fine wire into a narrow strip of 1.4 mm × 0.10 mm.

[0032] (6) Annealing and winding: The narrow and thin strip is vacuum annealed in a vacuum continuous annealing furnace at 600 °C and 10 m / min under argon protection. The winding tension is controlled at 10 N. When the wire is neat and without twist, it is wound to obtain BMn. 70 Ni 25 Narrow strip of Cr5 alloy.

[0033] In this embodiment, BMn with a width of 1.4 mm and a thickness of 0.1 mm was prepared. 70 Ni 25 The Cr5 alloy narrow strip has a bright, scratch-free, and oxidation-free surface, with a width tolerance ≤ ±0.01 mm and a thickness tolerance ≤ ±0.002 mm. This BMn 70 Ni 25 The performance of the finished Cr5 alloy narrow strip meets the requirements for brazing.

[0034] Example 2 This embodiment provides a BMn with a width of 3 mm and a thickness of 0.15 mm. 70 Ni 25 The preparation method of Cr5 alloy narrow thin strips is as follows: (1) Vacuum melting: BMn 70 Ni 25The Cr5 alloy was melted in a vacuum induction furnace at a temperature of 1350℃. After melting, it was cast into a cylindrical ingot with a diameter of 80 mm and a length of 200 mm at 1250℃. Then, it was homogenized and annealed at 850℃ for 2 h, followed by furnace cooling and air cooling.

[0035] (2) Multi-directional forging: Set the initial forging temperature to 870 ℃ and the final forging temperature to ≥700 ℃. Perform 4 passes of multi-directional forging on the cylindrical ingot after annealing in step (1) in the order of Z-axis-Y-axis-X-axis (one pass in each direction of Z-axis-Y-axis-X-axis is one cycle, and the cycle is 4 times). The deformation amount of each pass is 40%. The last forging is to form a round bar billet of Ø20 mm. After air cooling, it is annealed at 750 ℃ ​​for 30 min.

[0036] (3) Rolling through a die: The round bar forging billet after annealing in step (2) is rolled through a die in 12 passes using a round-elliptical-round die system, and finally rolled to Ø8 mm wire. After each 4 passes of rolling, it is annealed at 750 ℃ ​​for 20 min.

[0037] (4) Drawing: Using a tungsten carbide drawing die, the wire after annealing in step (3) is drawn to form a fine wire of Ø1.5 mm at a speed of 30 m / min and a reduction rate of 15%. During the drawing process, after each reduction of 2 mm in diameter, the wire is vacuum annealed at 750℃ for 40 min under argon protection.

[0038] (5) Precision rolling: Calculate the diameter of the fine wire corresponding to the target narrow strip size according to the empirical formula for the width of the strip in one pass. In this embodiment, the target narrow strip width is 3 mm and the thickness is 0.15 mm. Therefore, the diameter of the fine wire for rolling the target narrow strip is Ø = 1.575 mm (actually Ø = 1.5 mm). Then, a four-roll precision calender is used, and the rolling speed is set to 10 m / min to directly roll the fine wire into a narrow strip of 3 mm × 0.15 mm.

[0039] (6) Annealing and winding: The narrow and thin strip is vacuum annealed in a vacuum continuous annealing furnace at 600 °C and 10 m / min under argon protection. The winding tension is controlled at 10 N. When the wire is neat and without twist, it is wound to obtain BMn. 70 Ni 25 Narrow strip of Cr5 alloy.

[0040] In this embodiment, BMn with a width of 3 mm and a thickness of 0.15 mm was prepared. 70 Ni 25 The Cr5 alloy narrow strip has a bright, scratch-free, and oxidation-free surface, with a width tolerance ≤ ±0.01 mm and a thickness tolerance ≤ ±0.002 mm. This BMn 70 Ni25 The performance of the finished Cr5 alloy narrow strip meets the requirements for brazing.

[0041] Example 3 This embodiment provides a BMn with a width of 1.4 mm and a thickness of 0.1 mm. 70 Ni 25 The preparation method of Cr5 alloy narrow thin strips is as follows: (1) Vacuum melting: BMn 70 Ni 25 The Cr5 alloy was melted in a vacuum induction furnace at a temperature of 1400℃. After melting, it was cast into a cylindrical ingot with a diameter of 80 mm and a length of 200 mm at 1350℃. Then, it was homogenized and annealed at 950℃ for 2 h, followed by furnace cooling and air cooling.

[0042] (2) Multi-directional forging: Set the initial forging temperature to 800 ℃ and the final forging temperature to ≥700 ℃. Perform 4 passes of multi-directional forging on the cylindrical ingot after annealing in step (1) in the order of Z-axis-Y-axis-X-axis (one pass in each direction of Z-axis-Y-axis-X-axis is one cycle, and the cycle is 4 times). The deformation amount of each pass is 40%. The last forging is to form a round bar billet of Ø20 mm. After air cooling, it is annealed at 900 ℃ for 60 min.

[0043] (3) Rolling through a die: The round bar forging billet after annealing in step (2) is rolled through a die in 12 passes using a round-elliptical-round die system, and finally rolled to Ø8 mm wire. After each 4 passes of rolling, it is annealed at 900 ℃ for 40 min.

[0044] (4) Drawing: Using a tungsten carbide drawing die, the wire after annealing in step (3) is drawn to form a fine wire of Ø0.75 mm at a speed of 30 m / min and a reduction rate of 20%. During the drawing process, after each reduction of 2 mm in diameter, the wire is vacuum annealed at 900℃ for 20 min under argon protection.

[0045] (5) Precision rolling: Calculate the diameter of the fine wire corresponding to the target narrow strip size according to the empirical formula for the width of the strip in one pass. In this embodiment, the target narrow strip width is 1.4 mm and the thickness is 0.1 mm. Therefore, the diameter of the fine wire for rolling the target narrow strip is Ø = 0.75 mm (actually Ø = 0.75 mm). Then, a four-roll precision calender is used with a rolling speed of 20 m / min to directly roll the fine wire into a narrow strip of 1.4 mm × 0.10 mm.

[0046] (6) Annealing and winding: The narrow and thin strip was vacuum annealed in a vacuum continuous annealing furnace at 600 °C and 5 m / min under argon protection. The winding tension was controlled at 10 N. When the wire was neat and without twist, it was wound up to obtain BMn. 70 Ni 25 Narrow strip of Cr5 alloy.

[0047] In this embodiment, BMn with a width of 1.4 mm and a thickness of 0.1 mm was prepared. 70 Ni 25 The Cr5 alloy narrow strip has a bright, scratch-free, and oxidation-free surface, with a width tolerance ≤ ±0.01 mm and a thickness tolerance ≤ ±0.002 mm. This BMn 70 Ni 25 The performance of the finished Cr5 alloy narrow strip meets the requirements for brazing.

[0048] Example 4 This embodiment provides a BMn with a width of 1.4 mm and a thickness of 0.1 mm. 70 Ni 25 The preparation method of Cr5 alloy narrow thin strips is as follows: (1) Vacuum melting: BMn 70 Ni 25 The Cr5 alloy was melted in a vacuum induction furnace at a temperature of 1300℃. After melting, it was cast into a cylindrical ingot with a diameter of 80 mm and a length of 200 mm at 1250℃. Then, it was homogenized and annealed at 950℃ for 2 h, followed by furnace cooling and air cooling.

[0049] (2) Multi-directional forging: Set the initial forging temperature to 700 ℃ and the final forging temperature to ≥700 ℃. Perform 4 passes of multi-directional forging on the cylindrical ingot after annealing in step (1) in the order of Z-axis-Y-axis-X-axis (one pass in each direction of Z-axis-Y-axis-X-axis is one cycle, and the cycle is 4 times). The deformation amount of each pass is 40%. The last forging is to form a round bar billet of Ø20 mm. After air cooling, it is annealed at 700 ℃ for 60 min.

[0050] (3) Rolling through a die: The round bar forging billet after annealing in step (2) is rolled through a die in 12 passes using a round-elliptical-round die system, and finally rolled to Ø8 mm wire. After each 4 passes of rolling, it is annealed at 700 ℃ for 40 min.

[0051] (4) Drawing: Using a tungsten carbide drawing die, the wire after annealing in step (3) is drawn to form a fine wire of Ø0.75 mm at a speed of 30 m / min and a reduction rate of 10%. During the drawing process, after each reduction of 2 mm in diameter, the wire is vacuum annealed at 700℃ for 20 min under argon protection.

[0052] (5) Precision rolling: Calculate the diameter of the fine wire corresponding to the target narrow strip size according to the empirical formula for the width of the strip in one pass. In this embodiment, the target narrow strip width is 1.4 mm and the thickness is 0.1 mm. Therefore, the diameter of the fine wire for rolling the target narrow strip is Ø = 0.75 mm (actually Ø = 0.75 mm). Then, a four-roll precision calender is used, and the rolling speed is set to 80 m / min to directly roll the fine wire into a narrow strip of 1.4 mm × 0.10 mm.

[0053] (6) Annealing and winding: The narrow and thin strip was vacuum annealed in a vacuum continuous annealing furnace at 500 °C and 15 m / min under argon protection. The winding tension was controlled at 10 N. When the wire was neat and without twist, it was wound up to obtain BMn. 70 Ni 25 Narrow strip of Cr5 alloy.

[0054] In this embodiment, BMn with a width of 1.4 mm and a thickness of 0.1 mm was prepared. 70 Ni 25 The Cr5 alloy narrow strip has a bright, scratch-free, and oxidation-free surface, with a width tolerance ≤ ±0.01 mm and a thickness tolerance ≤ ±0.002 mm. This BMn 70 Ni 25 The performance of the finished Cr5 alloy narrow strip meets the requirements for brazing.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing narrow thin strips of MnNiCr alloy, characterized in that, Includes the following steps: (1) Vacuum melting of MnNiCr alloy, casting into ingots, and homogenization annealing treatment; (2) The ingot after annealing in step (1) is forged in multiple directions to obtain a round bar forging billet, and then annealed. (3) The round bar forging billet after annealing in step (2) is rolled in a die to obtain wire, and then annealed. (4) The wire after annealing in step (3) is drawn in multiple passes, and vacuum annealing is performed after each pass to finally obtain fine filaments. (5) Precision roll the fine filaments from step (4) into narrow and thin strips; (6) Vacuum annealing is performed on the narrow strip material obtained in step (5), and the strip material is wound up to obtain a narrow strip material of MnNiCr alloy.

2. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (1), the MnNiCr alloy is a MnNiCr brazing alloy with a Mn content ≥ 60wt%.

3. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (1), the melting temperature of vacuum melting is 1300~1400℃, the casting temperature is 1250~1350℃, and the conditions for homogenization annealing are: annealing temperature is 850~950℃, holding time is 2~4 h, and air cooling is performed after furnace cooling.

4. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (2), the multi-directional forging method is as follows: the initial forging temperature is 700~900 ℃, the final forging temperature is not lower than 700 ℃, and 3~6 passes of multi-directional forging are carried out in the order of Z-axis-Y-axis-X-axis, with a deformation amount of ≥30% in each pass, and finally forging into a round bar billet of Ø20~Ø25 mm.

5. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (2), the annealing conditions are: annealing temperature of 700~900 ℃ and holding time of 30~60 min.

6. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (3), the rolling method is as follows: a round-elliptical-round die system is adopted, and the final rolling is to a bar with a diameter of Ø7-Ø10 mm; the annealing conditions are as follows: annealing temperature is 700~900 ℃, and holding time is 20~40 min.

7. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (4), the drawing conditions are: the drawing speed is 10~100 m / min, and the reduction rate of the drawing pass is 10%~20%; the vacuum annealing conditions are: the annealing atmosphere is an inert gas, the annealing temperature is 700~900 ℃, and the holding time is 20~40 min.

8. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (5), the conditions for precision rolling are: rolling speed of 20~80 m / min, width of narrow strip of 0.5~5 mm, thickness of 0.02~0.5 mm, and width-to-thickness ratio ≥10.

9. The method for preparing narrow thin strips of MnNiCr alloy according to claim 1, characterized in that, In step (6), the conditions for vacuum annealing are: the annealing atmosphere is an inert gas, the annealing temperature is 500~600 ℃, and the annealing speed is 5~15m / min; the conditions for winding are: the winding tension is controlled at 5~20 N, and the winding is flat and without twisting.

10. A narrow strip of MnNiCr alloy prepared by the method according to any one of claims 1 to 9.

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