Preparation method of iron-based superconducting wire strip

Abstract

The invention belongs to the technical field of superconducting wire strip preparation, and particularly relates to a preparation method of an iron-based superconducting wire strip. According to the method, the large-area reduction forming advantage of extrusion forming is utilized, the high-strength densification process is activated in the iron-based superconducting wire strip preparation process, the density of the superconducting core in the iron-based superconducting wire strip is greatly improved, the thin-wall stainless steel outer wrapping sleeve with the initial wall thickness smaller than 0.3 mm is adopted, the silver material serves as the inner wrapping sleeve, and the thickness of the inner wrapping sleeve is larger than that of the thin-wall stainless steel outer wrapping sleeve. The iron-based superconducting wire strip is ensured to have good mechanical properties, mechanical strength and flexibility are considered, and the iron-based superconducting wire strip has flexible bending capacity, is low in cost, can be prepared on a large scale and is high in applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting wire strip preparation, and in particular relates to a method for preparing an iron-based superconducting wire strip. Background Art

[0002] Iron-based superconductors have the advantages of high critical transition temperature, low anisotropy and high upper critical field. They are widely used in energy, medical and large scientific engineering fields. They are the most promising new high-temperature superconductors. High-performance superconducting wires and strips are the basis for the practical application of superconductors. c In the 4.2K, 0~10T condition, it has exceeded 10 5 A / cm 2 , providing a basis for large-scale production and application.

[0003] Although the transmission performance of iron-based superconducting wire strips is relatively high, since they are silver-coated strips with low mechanical strength, the transmission performance is attenuated by nearly 20% in a bending experiment with a bending radius of 1 cm (winding before sintering, 4.2K, 10T). It does not support direct winding of sintered strips, which greatly affects the application of iron-based superconducting wire strips.

[0004] In order to make up for the above shortcomings, researchers have developed iron-based superconducting wire strips with stainless steel outer sheaths with good mechanical strength. However, the thickness of the stainless steel outer sheath is too large (~0.5mm), resulting in poor bending flexibility. The minimum bending radius is generally above 3cm, and it is impossible to wind small-sized coils with a radius of less than 3cm. This also limits the further research and development of iron-based superconducting devices and equipment. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing an iron-based superconducting wire strip. The iron-based superconducting wire strip obtained by the preparation method provided by the present invention has both mechanical strength and flexibility.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing an iron-based superconducting wire strip, comprising the following steps:

[0008] The iron-based superconducting precursor powder is loaded into a silver material tube and then degassed, sealed, extruded and drawn in sequence to obtain an iron-based superconducting wire;

[0009] The iron-based superconducting wire is coated with a stainless steel outer sheath, and then rolled and sintered in sequence to obtain the iron-based superconducting wire strip; the initial wall thickness of the stainless steel outer sheath is less than 0.3 mm.

[0010] Preferably, the material of the silver material tube includes silver or silver alloy; the silver alloy includes one or more of silver-tin alloy, silver-copper alloy and silver-manganese alloy.

[0011] Preferably, the diameter of the silver material tube is 2 to 60 mm.

[0012] Preferably, the filling rate of the iron-based superconducting precursor powder in the silver material tube is 20-40%.

[0013] Preferably, the degassing is vacuum degassing; the vacuum degree of the degassing is 10 -4 ~10 -5 Pa.

[0014] Preferably, the extrusion ratio of the extrusion is 8 to 20, the extrusion temperature is 200 to 500° C., and the extrusion speed is 1 to 10 mm / min.

[0015] Preferably, the target diameter of the drawing is 0.5 to 4 mm.

[0016] Preferably, the material of the stainless steel outer sheath includes 304 stainless steel or 306 stainless steel.

[0017] Preferably, the rolling is stopped when the thickness of the stainless steel outer sheath is 0.26-0.6 mm and the thickness of the inner sheath is 0.1-0.3 mm.

[0018] Preferably, the sintering is carried out in a vacuum or protective atmosphere; the peak temperature of the sintering is 550-900° C., and the peak temperature insulation sintering time is 0.1-10 h.

[0019] The present invention provides a method for preparing an iron-based superconducting wire strip. The present invention utilizes the large-surface reduction forming advantage of extrusion forming, activates a high-strength densification process during the preparation of the iron-based superconducting wire strip, greatly improves the density of the superconducting core in the iron-based superconducting wire strip, and uses a thin-walled stainless steel outer sheath with an initial wall thickness of less than 0.3 mm and a silver material as an inner sheath, thereby ensuring that the iron-based superconducting wire strip has good mechanical properties, takes into account both mechanical strength and flexibility, has flexible bending ability, is low in cost, can be prepared on a large scale, and has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1The actual picture of the iron-based superconducting wire strip of Example 1 (left) and the actual picture of the coil with a radius of 1 cm (right);

[0022] Figure 2 This is a transmission performance diagram of the iron-based superconducting wire strip of Example 1 before winding and after winding into a coil with a radius of 1 cm;

[0023] Figure 3 : is the strength curve of a 7 cm sample prepared using the iron-based superconducting wire tape of Example 2. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing an iron-based superconducting wire strip, comprising the following steps:

[0025] The iron-based superconducting precursor powder is loaded into a silver material tube and then degassed, sealed, extruded and drawn in sequence to obtain an iron-based superconducting wire;

[0026] The iron-based superconducting wire is coated with a stainless steel outer sheath, and then rolled and sintered in sequence to obtain the iron-based superconducting wire strip; the initial wall thickness of the stainless steel outer sheath is less than 0.3 mm.

[0027] The present invention loads the iron-based superconducting precursor powder into a silver material tube and then sequentially degasses, seals, extrude and draw to obtain an iron-based superconducting wire. In the present invention, the material of the silver material tube preferably includes silver or a silver alloy; the silver alloy preferably includes one or more of a silver-tin alloy, a silver-copper alloy and a silver-manganese alloy. The outer sheath of the present invention adopts high-strength, thin-walled stainless steel, and the inner sheath adopts a silver material. The mechanical properties of the inner and outer sheaths complement each other, so that the iron-based superconducting wire strip has good mechanical strength and flexibility, and the room temperature tensile strength is 1.2GPa.

[0028] In the present invention, the diameter of the silver material tube is preferably 2 to 60 mm, specifically 2 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm or 60 mm. In the present invention, the iron-based superconducting precursor powder is loaded into a metal tube to form an inner sheath. In the present invention, the inner sheath acts as a deformation buffer layer, and the superconducting core can still ensure that the critical current does not decay even when the iron-based superconducting wire strip is subjected to a large bending deformation. According to tests, the iron-based superconducting wire strip of the present invention can be used to prepare a coil with a bending radius of 1 cm, and the coil does not experience performance decay compared to the current of an unbent conductor.

[0029] In the present invention, the filling rate (volume percentage) of the iron-based superconducting precursor powder in the silver material tube is preferably 20-40%, specifically 25%, 30% or 35%.

[0030] In the present invention, the degassing is preferably vacuum degassing; the vacuum degree of the degassing is preferably 10 -4 ~10 -5Pa, specifically 1×10 -5 , 2×10 -5 , 3×10 -5 , 5×10 -5 ,7×10 -5 ,9×10 -5 , 1×10 -4 The present invention removes gas and impurities between powder particles by degassing.

[0031] In the present invention, the seal is preferably a welding seal. The present invention obtains a vacuum initial tube blank through sealing, which is used as a raw material for subsequent extrusion.

[0032] In the present invention, the extrusion equipment is preferably an extruder; the extrusion ratio of the extrusion is preferably 8 to 20, specifically 10, 14 or 18, the extrusion temperature is preferably 200 to 500°C, specifically 300°C, 350°C, 400°C or 450°C, and the extrusion speed is preferably 1 to 10 mm / min, specifically 3 mm / min, 5 mm / min, 7 mm / min or 9 mm / min. The present invention prepares iron-based superconducting wires by extruding a large deformation amount, and the single-pass strain reaches up to 0.75, which is far higher than the single-pass strain in the traditional method (less than 0.01), and the superconducting core obtains a density of more than 90% under large strain.

[0033] In the present invention, the target diameter of the drawing is preferably 0.5-4 mm, specifically 1 mm, 2 mm or 3 mm.

[0034] After obtaining the iron-based superconducting wire, the present invention coats the iron-based superconducting wire with a stainless steel outer sheath and then sequentially rolls and sinters to obtain the iron-based superconducting wire strip. In the present invention, the initial wall thickness of the stainless steel outer sheath is less than 0.3 mm, and specifically can be 0.25 mm, 0.2 mm, 0.15 mm, 0.1 mm or 0.05 mm. The present invention uses a thin-walled outer sheath for compounding to obtain an iron-based superconducting wire with a stainless steel outer sheath.

[0035] In the present invention, the material of the stainless steel outer sheath preferably includes 304 stainless steel or 306 stainless steel.

[0036] In the present invention, the rolling is preferably stopped when the thickness of the stainless steel outer sheath is 0.26-0.6 mm and the thickness of the inner sheath is 0.1-0.3 mm.

[0037] In the present invention, the sintering is preferably carried out in a vacuum or protective atmosphere; the protective atmosphere is preferably argon; the peak temperature of the sintering is preferably 550-900°C, specifically 600°C, 700°C or 800°C, and the peak temperature insulation sintering time is preferably 0.1-10h, specifically 1h, 3h, 5h, 7h or 9h.

[0038] The preparation method provided by the present invention has strong applicability and is applicable to all types of existing iron-based superconducting wires and strips, such as iron-based superconducting material 122, iron-based superconducting material 11, iron-based superconducting material 1111 and iron-based superconducting material 1144, and can prepare single-core or multi-core wires.

[0039] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0040] Example 1

[0041] The iron-based superconducting precursor powder was placed in a silver tube with a diameter of 8.0 mm and vacuum degassed to 10 -5 Pa vacuum degree and then welded to obtain the initial tube blank. The initial tube blank was extruded by an extruder with an extrusion ratio of 10, an extrusion temperature of 300°C, and an extrusion speed of 2mm / min to obtain a single core wire with a diameter of 2.6mm. The single core wire was drawn to a diameter of 1.01mm to obtain an iron-based superconducting wire; the iron-based superconducting wire was compounded with a thin-walled 0.3mm 304 stainless steel outer sheath, rolled to an outer sheath thickness of 0.30mm, an inner sheath thickness of 0.2mm, sintered in vacuum conditions for 2h, with a peak temperature of 900°C, to obtain an iron-based superconducting wire strip.

[0042] Example 2

[0043] The iron-based superconducting precursor powder was placed in a silver tube with a diameter of 16.0 mm and vacuum degassed to 10 -5 Pa vacuum degree and then welded to obtain the initial tube blank. The initial tube blank is extruded by an extruder with an extrusion ratio of 20, an extrusion temperature of 360°C, and an extrusion speed of 10mm / min to obtain a single core wire with a diameter of 6.6mm. The single core wire is drawn to a diameter of 1.03mm to obtain an iron-based superconducting wire; the iron-based superconducting wire is compounded with a thin-walled 0.3mm 304 stainless steel outer sheath, rolled to an outer sheath thickness of 0.30mm, an inner sheath thickness of 0.2mm, sintered for 3h in vacuum conditions, with a peak temperature of 880°C to obtain an iron-based superconducting wire strip.

[0044] Test Example 1

[0045] The iron-based superconducting wire strip of Example 1 and the coil wound with a radius of 1 cm were measured and observed. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that the iron-based superconducting wire strip provided by the present invention has extremely strong bending flexibility.

[0046] Test Example 2

[0047] The transmission performance of the iron-based superconducting wire strip of Example 1 was tested before winding and after winding into a 1 cm radius coil. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the superconducting performance of the iron-based superconducting wire strip does not decay after winding. c Over 155A.

[0048] Test Example 3

[0049] The strength of three 7 cm samples prepared by the iron-based superconducting wire strip of Example 2 was tested by static tensile method according to the international standard IEC 61788-25:2018. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the room temperature tensile strength of the iron-based superconducting wire strip (3 samples) provided by the present invention exceeds 1.0 GPa.

[0050] It can be seen from the above embodiments that the preparation method provided by the present invention ensures that the iron-based superconducting wire strip has good mechanical properties, takes into account both mechanical strength and flexibility, has flexible bending ability, is low in cost, can be prepared on a large scale, and has strong applicability.

[0051] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an iron-based superconducting wire strip, characterized in that: The following steps are involved: The iron-based superconducting precursor powder is loaded into a silver material tube and then degassed, sealed, extruded and drawn in sequence to obtain an iron-based superconducting wire; The iron-based superconducting wire is coated with a stainless steel outer sheath, and then rolled and sintered in sequence to obtain the iron-based superconducting wire strip; the initial wall thickness of the stainless steel outer sheath is less than 0.3 mm.

2. The preparation method according to claim 1, characterized in that: The material of the silver material tube includes silver or silver alloy; the silver alloy includes one or more of silver-tin alloy, silver-copper alloy and silver-manganese alloy.

3. The preparation method according to claim 1 or 2, characterized in that: The diameter of the silver material tube is 2 to 60 mm.

4. The preparation method according to claim 1, characterized in that: The filling rate of the iron-based superconducting precursor powder in the silver material tube is 20-40%.

5. The preparation method according to claim 1, characterized in that: The degassing is vacuum degassing; the vacuum degree of the degassing is 10 -4 ~10 -5 Pa.

6. The preparation method according to claim 1 or 5, characterized in that: The extrusion ratio of the extrusion is 8-20, the extrusion temperature is 200-500° C., and the extrusion speed is 1-10 mm / min.

7. The preparation method according to claim 1, characterized in that: The target diameter of the drawing is 0.5 to 4 mm.

8. The preparation method according to claim 1 or 2, characterized in that: The material of the stainless steel outer sheath includes 304 stainless steel or 306 stainless steel.

9. The preparation method according to claim 1, characterized in that: The rolling is stopped when the thickness of the stainless steel outer sheath is 0.26-0.6 mm and the thickness of the inner sheath is 0.1-0.3 mm.

10. The preparation method according to claim 1, characterized in that: The sintering is carried out in a vacuum or protective atmosphere; the peak temperature of the sintering is 550-900° C., and the peak temperature insulation sintering time is 0.1-10 hours.

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