Preparation method of high-quality large-size niobium-tungsten alloy plate

Abstract

The application discloses a preparation method of high-quality large-size niobium-tungsten alloy plate, and belongs to the technical field of the preparation of the niobium-tungsten alloy plate. The method comprises the following steps: firstly, after the ingot is detected and qualified, the ingot is cut; secondly, vacuum annealing is carried out; thirdly, low-temperature forging is carried out to obtain a processed thick slab; fourthly, after machining, vacuum annealing is carried out to obtain an annealed thick slab; fifthly, after detection and qualification, first one-way rolling is carried out to obtain a medium-thickness plate; sixthly, vacuum annealing is carried out to obtain an annealed medium-thickness plate; seventhly, second one-way rolling is carried out to obtain a finished thickness plate; eighthly, vacuum annealing and flattening are carried out to obtain a flattened plate; and ninthly, vacuum annealing and detection are carried out to obtain a finished plate. The method breaks through the limitation of the traditional process, can realize the preparation of the large-size niobium-tungsten alloy plate with a single weight greater than 50 kg, a width greater than 1000 mm, high grain equiaxialization, small mechanical property anisotropy, no hardening on the surface and no damage detection, and meets the urgent demand of the high-temperature propeller of the present stage of spaceflight for the high-quality niobium-tungsten plate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of niobium alloy manufacturing, and particularly relates to a preparation method of high-quality large-size niobium-tungsten alloy plate. BACKGROUND

[0002] Niobium-tungsten alloy (Nb-5W-2Mo-1Zr) is a high-temperature niobium alloy, and can be stably used at a working temperature of 1500 DEG C to 1600 DEG C under the protection of a coating, and is widely used in liquid rocket engine nozzles and their extension sections, attitude and orbit control of strategic weapons, etc., and gradually replaces nickel-based high-temperature alloy to become the first choice of aerospace high-temperature propeller.

[0003] At present, the processing technology of domestic niobium-tungsten alloy plate is similar to that of foreign countries, and the finished product is prepared by taking a smelted ingot as a raw material, and then by hot extrusion round bar breakdown, blanking, hot forging plate blank, intermediate annealing, warm rolling breakdown, intermediate annealing, cold rolling and finished product annealing. However, since the smelting temperature of the niobium-tungsten alloy is higher than 3500 DEG C to ensure the stability of the metal bath, the great overheating degree at this temperature can lead to the development of coarse columnar crystals, and the direct forging of the ingot is extremely easy to cause intergranular cracking or even complete scrap, and the traditional hot extrusion breakdown makes the cross section diameter of the blank to be reduced to about Φ110mm, which limits the subsequent blanking weight, and causes the preparation of the finished product plate with a single weight greater than 50kg and a width greater than 1000mm to be difficult to realize. In addition, the current niobium-tungsten alloy plate has the shortcomings of unidirectional rolling, traditional leveling after the finished product plate annealing, and then poor grain equiaxiality (length-width ratio greater than 3), large strength difference (≥30MPa) in the transverse and longitudinal directions, surface work hardening, etc., which finally causes the micro-crack defects of the flared section horn of the plate spinning nozzle, the deep wrinkle of the inner and outer surfaces, even cracking, and seriously affects the yield, and causes great economic losses. In addition, thanks to the development of ultrasonic C-scan nondestructive testing technology, the user puts forward higher requirements for the internal defects and organization uniformity of the plate, which is also a technical difficulty not concerned in the previous plate processing.

[0004] High-temperature structural parts with few welding points and large size become a trend. In the aspect of the plate, the industry has an increasing demand for high-quality niobium-tungsten alloy plates with a single weight of more than 50kg, a width greater than 1000mm and a flaw detection qualified, and the present application aims to solve the practical problems and also fill the technical gap. SUMMARY

[0005] The technical problem solved by the present application is to provide a preparation method of high-quality large-size niobium-tungsten alloy plate to solve the problems of the prior art.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is a preparation method of high-quality large-size niobium-tungsten alloy plate, characterized by comprising the following steps:

[0007] Step one, using a niobium-tungsten alloy ingot as raw material, after ultrasonic flaw detection, sawing and cutting;

[0008] Step two, the niobium-tungsten alloy ingot sawed in step one is subjected to first vacuum annealing to obtain an annealed ingot;

[0009] Step three, the annealed ingot in step two is subjected to low-temperature forging, the hammer head surface of the forging hammer is installed with a pure niobium pad to completely cover the ingot, and slow hammering is adopted to obtain a processed thick slab;

[0010] Step four, the six surfaces of the processed thick slab in step three are machined, and then subjected to second vacuum annealing to obtain an annealed thick slab;

[0011] Step five, the annealed thick slab in step four is subjected to ultrasonic flaw detection, and after passing the detection, is heated and subjected to first rolling to obtain an intermediate-thickness plate;

[0012] Step six, the intermediate-thickness plate in step five is subjected to surface and edge treatment, and then subjected to third vacuum annealing to obtain an annealed intermediate-thickness plate;

[0013] Step seven, the annealed intermediate-thickness plate in step six is subjected to second rolling to obtain a finished-thickness plate;

[0014] Step eight, the finished-thickness plate in step seven is subjected to fourth vacuum annealing, and then subjected to leveling treatment to obtain a leveled plate;

[0015] Step nine, the leveled plate in step eight is subjected to fixed-length cutting and surface treatment, and then subjected to fifth vacuum annealing, and after passing the ultrasonic flaw detection, a finished niobium-tungsten alloy plate is obtained.

[0016] The preparation method of the high-quality large-size niobium-tungsten alloy plate material has the characteristics that the diameter size of the niobium-tungsten alloy ingot in step one is Φ220mm-Φ300mm, the standard damage of ultrasonic detection is Φ3.2mm, and the ratio of the blanking length to the diameter is (1.5-2.5):1.

[0017] The preparation method of the high-quality large-size niobium-tungsten alloy plate material has the characteristics that the temperature of the first vacuum annealing in step two is 1500-1700℃, the holding time is 240-480min, the vacuum degree is less than 10 - 2 Pa, and furnace cooling is performed after the holding is completed.

[0018] The preparation method of the high-quality large-size niobium-tungsten alloy plate material has the characteristics that the temperature of the low-temperature forging in step three is 800-900℃, the hammer head surface of the forging hammer is installed with a pure niobium plate with a thickness of 50-100mm and a size equal to the area of the hammer head as a pressing pad, wherein the pure niobium plate is a commercially available national standard grade, the forging direction is along the radial direction of the ingot, the forging hammer completely covers the length direction of the ingot at each time, the pass reduction is 5-10mm, the forging hammer is slowly hit at a frequency of 10-20 times / min, and the ingot is shaped when the thickness reaches 100-140mm to obtain a thick slab with a nominal thickness of 100-140mm and a width of 250-600mm.

[0019] The preparation method of the high-quality large-size niobium-tungsten alloy plate material has the characteristics that the thickness of the machining in step four is 90-130mm, the width is 230-580mm, the second vacuum annealing temperature is 1300-1400℃, the holding time is 90-150min, and the vacuum degree is less than 10 -2 Pa.

[0020] The preparation method of the high-quality large-size niobium-tungsten alloy plate material has the characteristics that the standard damage of ultrasonic detection in step five is Φ2.0mm, the heating temperature of the first rolling is 400-500℃, one-way rolling is adopted, the rolling direction is along the short direction of the slab, the single-pass processing rate is 10-20%, the rolling speed is 30-50m / min, and the rolling thickness is Xmm, wherein X=(machining thickness of the forged slab × product thickness) 1 / 2 , and the calculation result is rounded.

[0021] The preparation method of the high-quality large-size niobium-tungsten alloy plate material has the characteristics that the temperature of the third vacuum annealing in step six is 1100-1200℃, the holding time is 60-120min, and the vacuum degree is less than 10 -2 Pa.

[0022] The preparation method of the high-quality large-size niobium-tungsten alloy plate has the characteristics that the second rolling in the seventh step is cold rolling, one-way rolling is adopted, the rolling direction is perpendicular to the rolling direction in the fifth step, the single-pass processing rate is 5% to 15%, and the roller speed is 10 m / min to 20 m / min.

[0023] The preparation method of the high-quality large-size niobium-tungsten alloy plate has the characteristics that the fourth vacuum annealing in the eighth step is performed at a temperature of 1000 DEG C to 1100 DEG C, for a holding time of 60 min to 120 min, and under a vacuum degree of less than 10 -2 Pa, and the unevenness of the plate after leveling is less than 3%.

[0024] The preparation method of the high-quality large-size niobium-tungsten alloy plate has the characteristics that the fifth vacuum annealing in the ninth step is performed at a temperature of 1250 DEG C to 1350 DEG C, for a holding time of 90 min to 150 min, and under a vacuum degree of less than 10 -2 Pa, and the standard damage of ultrasonic flaw detection is Φ0.8 mm.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The present application does not need a hot extrusion process, directly uses an ingot for warm working, effectively improves the utilization rate of the material, significantly increases the weight of the blank, and can produce a high-quality niobium-tungsten alloy plate with a single weight greater than 50 kg, a width greater than 1000 mm, good grain equiaxiality, small mechanical property anisotropy, and a qualified ultrasonic C-scan detection, which fills the technical gap in the industry.

[0027] 2. The melting speed of the niobium-tungsten alloy is fast (more than 80 kg / h), the solidification speed difference of the liquid metal in the radial direction is large, and there is a large macro stress in the ingot, which is the main source of the macro crack origin. The present application applies high-temperature long-time vacuum annealing to the ingot, fully releases the stress in the ingot, reduces the probability of core cracking in subsequent forging, and at the same time, annealing at a temperature of 1500 DEG C or above can not only make the internal dispersion strengthening phase of the alloy change from needle-shaped to spherical to homogenize the performance, but also can make the brittle phase zirconium carbide on the grain boundary re-dissolve in the matrix, soften the grain boundary, and reduce the micro crack source along the grain. After high-temperature long-time vacuum annealing, the hardness of the ingot can be reduced from the original HBW130 to about HBW110, so that low-temperature forging of the ingot is possible, and the processing safety is improved.

[0028] 3、The forging of the present application adopts low-temperature forging, and a pure niobium pad is installed on the hammer head surface of the forging hammer, which completely covers the length direction of the ingot during each strike of the forging hammer, and in combination with slow striking of the forging hammer, the problem of easy cracking of the niobium-tungsten alloy ingot can be solved, and high-quality thick slabs can be obtained. Among them, low-temperature forging can avoid serious oxidation of the alloy and reduce material waste; the pure niobium pad with plasticity higher than that of the niobium-tungsten alloy installed on the hammer head surface can slow down the stress impact, reduce the strain rate, and avoid the occurrence of cracks; the complete coverage type forging makes the whole blank in the pressure processing range, reduces the strain without restraint in the local area (such as both ends) of the blank, and eliminates the risk of internal through cracks; slow forging can reduce the hardening index of niobium-tungsten processing, give the material stress concentration propagation time, and reduce the probability of crack generation.

[0029] 4、The niobium-tungsten alloy has high room temperature strength and poor plasticity, and conventional cross-rolling can cause the grains to fail to twist and coordinate deformation, and can easily cause serious edge cracking or delamination, resulting in scrap. The present application creatively designs an intermediate rolling thickness and increases stress relief annealing between the two one-way rolling, which can avoid edge cracking or delamination caused by frequent reversing rolling, achieves the purpose of cross-rolling, and the stress relief annealing can treat the two rolling as one rolling between the thick slab and the finished product thickness without changing the grain shape and texture characteristics, which is beneficial to the performance control of the plate. In addition, the thickness of the intermediate thickness plate designed in the present application can be ensured within the total rolling processing rate range of the slab, and the rolling transverse and longitudinal processing rate distribution is basically equal, wherein the transverse processing rate = (forging slab machine added thickness-intermediate rolling thickness) / forging slab machine added thickness x 100%, and the longitudinal processing rate = (intermediate rolling thickness-finished product thickness) / intermediate rolling thickness x 100%. This rolling method not only helps to achieve high grain equiaxialization after vacuum annealing, but also can significantly reduce the plate texture strength, weaken the difference in strength between the transverse and longitudinal directions of the plate, and improve the subsequent spinning quality.

[0030] 5、Compared with the traditional flattening process after recrystallization annealing, the present application sequentially performs stress relief annealing, flattening and recrystallization annealing on the finished plate, which solves the problem of plate surface hardening without changing the mechanical properties and flatness of the plate.

[0031] 6、The present application performs ultrasonic flaw detection on the ingot and thick slab, which can detect and locate the internal defects of the plate before rolling, prevent defects from flowing into subsequent processes with the progress of plastic processing, and is crucial for the preparation of high-quality plates, which can increase the plate yield.

[0032] The technical solutions of the present application will be further described in detail below in combination with the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1is a thick slab forging schematic diagram of the high-quality large-size niobium-tungsten alloy plate of the present application.

[0034] Figure 2 is a metallographic picture of the longitudinal section structure of the niobium-tungsten alloy plate with a thickness of 6.0 mm prepared by a traditional process.

[0035] Figure 3 is a metallographic picture of the longitudinal section structure of the finished niobium-tungsten alloy plate with a thickness of 3.0 mm prepared by the embodiment 1 of the present application.

[0036] Figure 4 is a metallographic picture of the longitudinal section structure of the finished niobium-tungsten alloy plate with a thickness of 6.0 mm prepared by the embodiment 2 of the present application.

[0037] Figure 5 is a metallographic picture of the longitudinal section structure of the finished niobium-tungsten alloy plate with a thickness of 9.0 mm prepared by the embodiment 3 of the present application. DETAILED DESCRIPTION

[0038] The preparation method of the high-quality large-size niobium-tungsten alloy plate of the present application comprises the following steps:

[0039] Step one, using niobium-tungsten alloy ingot as raw material, after ultrasonic flaw detection qualified saw cutting blank; the diameter size of the niobium-tungsten alloy ingot is Φ220mm-Φ300mm, the standard damage of ultrasonic flaw detection is Φ3.2mm, the length to diameter ratio of blank is (1.5-2.5):1;

[0040] Step two, the niobium-tungsten alloy ingot sawed in step one is subjected to first vacuum annealing to obtain an annealed ingot; the temperature of the first vacuum annealing is 1500-1700 DEG C, the holding time is 240-480 min, the vacuum degree is less than 10 -2 Pa, furnace cooling after holding;

[0041] Step three, the annealed ingot in step two is subjected to low temperature forging, the hammer head surface of the forging hammer is installed with pure niobium pad, the ingot is completely covered, slow type hammering is adopted to obtain a processed thick slab; the temperature of the low temperature forging is 800-900 DEG C, the hammer head surface of the forging hammer is installed with pure niobium plate with a thickness of 50-100 mm and a size equal to the area of the hammer head as a pressing pad, wherein the pure niobium plate is a commercially available national standard grade; the forging direction is along the radial direction of the ingot, the forging hammer completely covers the length direction of the ingot each time, the pass reduction is 5-10 mm, the forging hammer is slowly hit, the frequency is 10-20 times / min, the ingot is shaped when the thickness reaches 100-140 mm to obtain a thick slab with a nominal thickness of 100-140 mm and a width of 250-600 mm;

[0042] Step four, machine the six surfaces of the processed thick slab in step three, and then perform a second vacuum annealing to obtain an annealed thick slab; the machine thickness is 90mm-130mm, the width is 230mm-580mm, the second vacuum annealing temperature is 1300-1400℃, the holding time is 90-150min, and the vacuum degree is less than 10 -2 Pa;

[0043] Step five, perform ultrasonic flaw detection on the annealed thick slab in step four, and after passing the detection, perform heating and first rolling to obtain an intermediate-thickness plate; the standard flaw of the ultrasonic flaw detection is Φ2.0mm, the heating temperature of the first rolling is 400-500℃, the rolling direction is along the short direction of the slab, the single-pass processing rate is 10-20%, the roller speed is 30-50m / min, and the rolling thickness is Xmm, wherein X=(machine thickness of the thick slab × thickness of the finished product) 1 / 2 , and the calculation result is rounded to an integer;

[0044] Step six, perform surface and edge treatment on the intermediate-thickness plate in step five, and then perform third vacuum annealing to obtain an annealed intermediate-thickness plate; the third vacuum annealing temperature is 1100-1200℃, the holding time is 60-120min, and the vacuum degree is less than 10 -2 Pa;

[0045] Step seven, perform second rolling on the annealed intermediate-thickness plate in step six to obtain a finished-thickness plate; the second rolling is cold rolling, the rolling direction is perpendicular to the rolling direction in step five, the single-pass processing rate is 5-15%, and the roller speed is 10-20m / min;

[0046] Step eight, perform fourth vacuum annealing on the finished-thickness plate in step seven, and then perform leveling treatment to obtain a leveled plate; the fourth vacuum annealing temperature is 1000-1100℃, the holding time is 60-120min, the vacuum degree is less than 10 -2 Pa, and the unevenness of the leveled plate is less than 3%;

[0047] Step nine, perform fixed-length cutting and surface treatment on the leveled plate in step eight, and then perform fifth vacuum annealing to obtain a finished niobium-tungsten alloy plate after passing the ultrasonic flaw detection; the fifth vacuum annealing temperature is 1250-1350℃, the holding time is 90-150min, the vacuum degree is less than 10 -2 Pa, and the standard flaw of the ultrasonic flaw detection is Φ0.8mm.

[0048] The following detailed description, in conjunction with specific embodiments, illustrates the content of this invention. These descriptions are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions.

[0049] Example 1

[0050] This example provides a method for preparing a high-quality, large-size niobium-tungsten alloy plate. The plate has dimensions of 3.0×1000×2000mm and a single weight of 53kg. The method includes the following steps:

[0051] Step 1: Ingot preparation: Use 220mm diameter niobium-tungsten alloy ingots as raw materials. Use a 3.2mm standard flaw control block to perform ultrasonic testing on the ingots. After the flaw test is qualified, cut the ingots into pieces. The cutting length is controlled to be 1.5 times the diameter of the ingot, i.e., 330mm.

[0052] Step 2: Ingot Annealing Treatment: The niobium-tungsten alloy ingots sawn in Step 1 are subjected to a first vacuum annealing in a vacuum annealing furnace to obtain annealed ingots. The temperature of the first vacuum annealing is 1500℃, the holding time is 240 min, and the vacuum degree is less than 10. -2 Pa, furnace cooling after heat preservation;

[0053] Step 3, Ingot Forging: (e.g.) Figure 1 As shown, firstly, a commercially available national standard grade pure niobium plate with a thickness of 50mm and a size equal to the area of ​​the hammer head is installed as a pressure pad on the contact surface of the forging hammer head. Then, the annealed ingot is fully preheated to 800℃ in the heating furnace and then forged. During forging, the ingot is laid down on the anvil of the forging hammer, that is, the forging hammer strikes the radial direction of the ingot. Each strike of the forging hammer must completely cover the length direction of the ingot. The reduction per pass is 10mm. The forging hammer strikes slowly at a frequency of 20 times / min. When the thickness of the ingot reaches 100mm, it is shaped to obtain a processed thick slab blank with nominal dimensions of 100mm×250mm×500mm.

[0054] Step 4: Slab Annealing: The six surfaces of the machined thick slab described in Step 3 are machined to ensure complete removal of surface defects. The thickness is controlled at 90mm, the width at 230mm, and the length at 480mm. Then, a second vacuum annealing is performed to obtain the annealed thick slab. The second vacuum annealing temperature is 1300℃, the holding time is 90 minutes, and the vacuum degree is less than 10. -2 Pa;

[0055] Step five, once rolling: the annealed slab in step four is subjected to ultrasonic flaw detection using a standard flaw of Φ2.0 mm, and after the detection is qualified, the slab is loaded into an electric resistance furnace for preheating, the heating temperature is 400℃, and after the temperature reaches, the slab is subjected to one-way rolling, the rolling direction is along the short direction of the slab, the rolling single pass processing rate is 10%~20%, the rolling speed is 50m / min, the thickness of the rolled slab is (90×3) 1 / 2 , the result is rounded to 16mm, the 230mm is extended to about 1250mm, and the intermediate thickness slab is obtained;

[0056] Step six, stress relief annealing: the intermediate thickness slab in step five is subjected to surface polishing using a grinding wheel, and after the oxidation and other defects are removed, the slab is cut and leveled around using water cutting to ensure no defects, the length is controlled to be 470mm, and the width is controlled to be 1100mm, and then the third vacuum annealing, i.e. stress relief annealing, is performed, and the annealed intermediate thickness slab is obtained; the temperature of the third vacuum annealing is 1100℃, the holding time is 60min, and the vacuum degree is less than 10 -2 Pa;

[0057] Step seven, second rolling: the annealed intermediate thickness slab in step six is subjected to one-way cold rolling, the rolling direction is perpendicular to the rolling direction in step five, the rolling speed is 20m / min, the single pass processing rate is 5%~15%, and the rolling thickness is 3mm, the 470mm is extended to more than 2200mm, and the finished thickness slab is obtained;

[0058] Step eight, stress relief annealing and leveling: the finished thickness slab in step seven is subjected to the fourth vacuum annealing, i.e. stress relief annealing, and then leveling treatment, and the leveled slab is obtained; the temperature of the fourth vacuum annealing is 1000℃, the holding time is 60min, the vacuum degree is less than 10 -2 Pa, and the unevenness of the slab after leveling is less than 3%;

[0059] Step nine, recrystallization annealing and flaw detection: the leveled slab in step eight is subjected to size cutting and surface treatment, and a slab with a size of 3mm×1000mm×2000mm is obtained, and then the fifth vacuum annealing, i.e. recrystallization annealing, is performed, and the finished niobium-tungsten alloy slab is obtained after the ultrasonic flaw detection is qualified; the temperature of the fifth vacuum annealing is 1250℃, the holding time is 90min, the vacuum degree is less than 10 -2 Pa, and the standard flaw of the ultrasonic flaw detection is Φ0.8mm.

[0060] The niobium-tungsten alloy slab prepared in this embodiment is subjected to longitudinal section structure analysis, and room temperature mechanical property test is performed, and the specific results are shown in Figure 3and Table 1. It can be seen from the table that the grains of the niobium-tungsten alloy plate prepared in the embodiment are fully recrystallized, the average grain size is about 26.7 μm, the grains are equiaxed (the length-width ratio is about 1), and the maximum difference in strength in the transverse, longitudinal and 45° directions is only 5 MPa, and the difference in elongation is 2%, which significantly reduces the anisotropy of the plate.

[0061] Table 1. Room temperature mechanical properties of the niobium-tungsten alloy plate prepared in Example 1

[0062] Sample test direction Tensile strength / MPa Yield strength / MPa Elongation / % Transverse direction 511 363 39 45° direction 516 368 38 Machine direction 514 365 40

[0063] Example 2

[0064] The present example provides a preparation method of high-quality large-size niobium-tungsten alloy plate, the plate size is 6.0×1500×2000 mm, and the single weight is 158 kg, and the method specifically comprises the following steps:

[0065] Step one, ingot preparation: a niobium-tungsten alloy ingot with a diameter of Φ260 mm is used as a raw material, a contrast block with a standard damage of Φ3.2 mm is used for ultrasonic flaw detection on the ingot, and after the flaw detection is qualified, the ingot is sawn and cut into a length of 2.0 times the diameter of the ingot, i.e. 520 mm;

[0066] Step two, ingot annealing treatment: a vacuum annealing furnace is used to perform first vacuum annealing on the niobium-tungsten alloy ingot sawn in step one, to obtain an annealed ingot; the first vacuum annealing temperature is 1600℃, the holding time is 360 min, the vacuum degree is less than 10 -2 Pa, and the furnace is cooled after the holding is completed;

[0067] Step three, ingot forging: as shown in Figure 1 , first, a commercially available national standard level pure niobium plate with a thickness of 80 mm and a size equal to the area of the hammer head is installed as a pressing pad on the contact surface of the hammer head of the forging hammer, then the annealed ingot is fully preheated to 850℃ in a heating furnace, and the furnace is taken out for forging; during forging, the ingot is laid down on the anvil surface of the forging hammer, i.e. the ingot is forged in the radial direction by the forging hammer; the hammer surface of the forging hammer needs to completely cover the length direction of the ingot during each strike; the pass reduction is 7 mm; the forging hammer is struck at a slow speed, and the frequency is 15 times / min; after the thickness of the ingot reaches 125 mm, the ingot is shaped, to obtain a processed thick slab with a nominal size of 125 mm×410 mm×540 mm;

[0068] Step four, slab annealing: the six surfaces of the processed thick slab in step three are machined to ensure that the surface defects are completely removed, the thickness is controlled to be 115 mm, the width is 390 mm, and the length is 520 mm, and then second vacuum annealing is performed, to obtain an annealed thick slab; the second vacuum annealing temperature is 1350℃, the holding time is 120 min, and the vacuum degree is less than 10 -2 Pa;

[0069] Step five, once rolling: the annealed slab in step four is subjected to ultrasonic flaw detection using a standard flaw of Φ2.0mm, and after the detection is qualified, the slab is loaded into a resistance furnace for preheating, the heating temperature is 450℃, and after the temperature reaches, one-way rolling is carried out, the rolling direction is along the short direction of the slab, the rolling single pass processing rate is 10%~20%, the rolling speed is 40m / min, the thickness of the rolled plate is (115x6) 1 / 2 , the result is rounded to 26mm, the 390mm is extended to about 1700mm, and the intermediate thickness plate is obtained;

[0070] Step six, stress relief annealing: the intermediate thickness plate in step five is subjected to surface polishing using a grinding wheel, and after the oxidation and other defects are removed, the plate is cut and leveled around using water cutting to ensure no defects, the length is controlled to be 510mm, and the width is controlled to be 1600mm, and then the third vacuum annealing, i.e. stress relief annealing, is carried out, to obtain the annealed intermediate thickness plate; the temperature of the third vacuum annealing is 1150℃, the holding time is 90min, and the vacuum degree is less than 10 -2 Pa;

[0071] Step seven, second rolling: the annealed intermediate thickness plate in step six is subjected to one-way cold rolling, the rolling direction is perpendicular to the rolling direction in step five, the rolling speed is 15m / min, the single pass processing rate is 5%~15%, and the rolling thickness is 6mm, the 510mm is extended to more than 2100mm, and the finished thickness plate is obtained;

[0072] Step eight, stress relief annealing and leveling: the finished thickness plate in step seven is subjected to the fourth vacuum annealing, i.e. stress relief annealing, and then leveling treatment, to obtain the leveled plate; the temperature of the fourth vacuum annealing is 1050℃, the holding time is 90min, and the vacuum degree is less than 10 -2 Pa, and the unevenness of the plate after leveling is less than 3%;

[0073] Step nine, recrystallization annealing and flaw detection: the leveled plate in step eight is subjected to fixed cutting and surface treatment, to obtain a plate with a size of 6mmx1500mmx2000mm, and then the fifth vacuum annealing, i.e. recrystallization annealing, is carried out, and after the ultrasonic flaw detection is qualified, the finished niobium-tungsten alloy plate is obtained; the temperature of the fifth vacuum annealing is 1300℃, the holding time is 120min, and the vacuum degree is less than 10 -2 Pa, and the standard flaw of the ultrasonic flaw detection is Φ0.8mm.

[0074] The niobium-tungsten alloy plate prepared in this embodiment is subjected to longitudinal section structure analysis, and room temperature mechanical property test, and the specific results are shown in Figure 4 and Table 2. Compared with Figure 2In comparison, the Nb-W alloy plate prepared in the embodiment is fully recrystallized, the average grain size is about 31.8 μm, the grains are equiaxed (the length-width ratio is about 1), the maximum difference in strength in the transverse, longitudinal and 45° directions is only 7 MPa, and the difference in elongation is 3%, which significantly reduces the anisotropy of the plate.

[0075] Table 2 Room temperature mechanical properties of the Nb-W alloy plate prepared in Example 2

[0076] Sample test direction Tensile strength / MPa Yield strength / MPa Elongation / % Transverse direction 494 352 37 45° direction 501 356 36 Machine direction 498 357 39

[0077] Example 3

[0078] The present example provides a preparation method of high-quality large-size Nb-W alloy plate, the plate size is 9.0×2000×2000 mm, and the single weight is 317 kg, and the method specifically comprises the following steps:

[0079] Step one, ingot preparation: a Nb-W alloy ingot with a diameter of Φ300 mm is used as a raw material, a contrast block with a standard damage of Φ3.2 mm is used for ultrasonic flaw detection on the ingot, the ingot is cut after the flaw detection is qualified, and the cutting length is controlled to be 2.5 times the diameter of the ingot, that is, 750 mm;

[0080] Step two, ingot annealing treatment: a vacuum annealing furnace is used to perform first vacuum annealing on the Nb-W alloy ingot cut in step one, to obtain an annealed ingot; the temperature of the first vacuum annealing is 1700 ℃, the holding time is 480 min, the vacuum degree is less than 10 -2 Pa, and the furnace is cooled after the holding is completed;

[0081] Step three, ingot forging: as shown in Figure 1 , first, a commercially available national standard level pure niobium plate with a thickness of 100 mm and a size equal to the area of the hammer head is installed as a pressing pad on the contact surface of the hammer head of the forging hammer, then the annealed ingot is fully preheated to 900 ℃ in a heating furnace, and the furnace is taken out for forging; during forging, the ingot is placed on the anvil surface of the forging hammer, that is, the ingot is hit in the radial direction by the forging hammer; the hammer surface of the forging hammer needs to completely cover the length direction of the ingot during each hit; the pass reduction is 5 mm; the forging hammer is hit slowly, and the frequency is 10 times / min; after the thickness of the ingot reaches 140 mm, the ingot is shaped, to obtain a processed thick slab with a nominal size of 140 mm×600 mm×630 mm;

[0082] Step four, slab annealing: the six surfaces of the processed thick slab in step three are machined to ensure that the surface defects are completely removed, the thickness is controlled to be 130 mm, the width is 580 mm, and the length is 610 mm, then second vacuum annealing is performed, to obtain an annealed thick slab; the temperature of the second vacuum annealing is 1400 ℃, the holding time is 150 min, and the vacuum degree is less than 10 -2 Pa;

[0083] Step five, once rolling: the annealed slab in step four is subjected to ultrasonic flaw detection using a standard flaw of Φ2.0 mm, and after the detection is qualified, the slab is loaded into an electric resistance furnace for preheating, the heating temperature is 500℃, and after the temperature reaches, the slab is subjected to one-way rolling, the rolling direction is along the short direction of the slab, the rolling single pass processing rate is 10%~20%, the rolling speed is 30m / min, the thickness of the rolled slab is (130×9) 1 / 2 , the result is rounded to 34mm, the 580mm is extended to about 2200mm, and the intermediate thickness slab is obtained;

[0084] Step six, stress relief annealing: the intermediate thickness slab in step five is subjected to surface polishing using a grinding wheel, and after the oxidation and other defects are removed, the slab is cut and leveled around using water cutting to ensure no defects, the length is controlled to be 600mm, and the width is controlled to be 2100mm, and then the third vacuum annealing, i.e. stress relief annealing, is performed, and the annealed intermediate thickness slab is obtained; the temperature of the third vacuum annealing is 1200℃, the holding time is 120min, and the vacuum degree is less than 10 -2 Pa;

[0085] Step seven, second rolling: the annealed intermediate thickness slab in step six is subjected to one-way cold rolling, the rolling direction is perpendicular to the rolling direction in step five, the rolling speed is 10m / min, the single pass processing rate is 5%~15%, and the rolling thickness is 9mm, the 600mm is extended to more than 2200mm, and the finished thickness slab is obtained;

[0086] Step eight, stress relief annealing and leveling: the finished thickness slab in step seven is subjected to the fourth vacuum annealing, i.e. stress relief annealing, and then leveling treatment, and the leveled slab is obtained; the temperature of the fourth vacuum annealing is 1100℃, the holding time is 120min, the vacuum degree is less than 10 -2 Pa, and the unevenness of the slab after leveling is less than 3%;

[0087] Step nine, recrystallization annealing and flaw detection: the leveled slab in step eight is subjected to size cutting and surface treatment, and a slab with a size of 9mm×2000mm×2000mm is obtained, and then the fifth vacuum annealing, i.e. recrystallization annealing, is performed, and after the ultrasonic flaw detection is qualified, the finished niobium-tungsten alloy slab is obtained; the temperature of the fifth vacuum annealing is 1350℃, the holding time is 150min, the vacuum degree is less than 10 -2 Pa, and the standard flaw of the ultrasonic flaw detection is Φ0.8mm.

[0088] The niobium-tungsten alloy slab prepared in this embodiment is subjected to longitudinal section structure analysis, and room temperature mechanical property test, and the specific results are shown in Figure 5and Table 3. It can be seen that the niobium-tungsten alloy plate prepared in the embodiment is fully recrystallized, the average grain size is about 44.5 μm, the grains are equiaxed (the length-width ratio is about 1), the maximum difference of the strength in the transverse, longitudinal and 45° directions is only 10 MPa, and the difference of the elongation is 4%, which significantly reduces the anisotropy of the plate.

[0089] Table 3 Room temperature mechanical properties of the niobium-tungsten alloy plate prepared in Example 3

[0090] Sample test direction Tensile strength / MPa Yield strength / MPa Elongation / % Transverse direction 487 349 39 45° direction 495 352 35 Machine direction 485 348 38

[0091] The above is only the preferred embodiment of the present application, and does not limit the present application. Any simple modification, change and equivalent structural change made according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical solution of the present application.

Claims

1. A method for preparing high-quality, large-size niobium-tungsten alloy plates, characterized in that, Includes the following steps: Step 1: Using niobium-tungsten alloy ingots as raw materials, the ingots are sawed and cut after passing ultrasonic flaw detection. Step 2: Perform a first vacuum annealing on the niobium-tungsten alloy ingot after sawing in Step 1 to obtain an annealed ingot; the temperature of the first vacuum annealing is 1500℃~1700℃, the holding time is 240min~480min, and the vacuum degree is less than 10. - 2 Pa, furnace cooling after heat preservation; Step 3: Perform low-temperature forging on the annealed ingot described in Step 2. A pure niobium pad is installed on the hammerhead of the forging hammer to completely cover the ingot. Slow-speed hammering is used to obtain a machined thick slab. The low-temperature forging temperature is 800℃~900℃. A pure niobium plate with a thickness of 50mm~100mm and dimensions equal to the hammerhead area is installed on the hammerhead as a pressure pad. The pure niobium plate is commercially available and meets national standards. The forging direction is along the radial direction of the ingot. Each strike of the forging hammer completely covers the length of the ingot, with a reduction of 5mm~10mm per pass. The forging hammer strikes slowly at a frequency of 10 to 20 times per minute. When the ingot thickness reaches 100mm~140mm, it is shaped to obtain a thick slab with a nominal thickness of 100mm~140mm and a width of 250mm~600mm. Step 4: Machining the six surfaces of the processed thick slab described in Step 3, followed by a second vacuum annealing, to obtain the annealed thick slab. Step 5: Perform ultrasonic testing on the annealed thick slab described in Step 4. After passing the test, heat it and then perform the first rolling to obtain a plate of intermediate thickness. Step 6: Perform surface and edge treatment on the intermediate thickness plate described in Step 5, and then perform a third vacuum annealing to obtain an annealed intermediate thickness plate. Step 7: Perform a second rolling on the annealed intermediate thickness plate described in Step 6, with the rolling thickness being the finished product thickness, to obtain the finished thickness plate; Step 8: Perform a fourth vacuum annealing on the finished thickness plate described in Step 7, and then perform leveling treatment to obtain a flat plate. Step 9: Cut the flat plate described in Step 8 to length and perform surface treatment, then perform a fifth vacuum annealing, and after passing ultrasonic flaw detection, obtain the finished niobium-tungsten alloy plate.

2. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The diameter of the niobium-tungsten alloy ingot mentioned in step one is Φ220mm~Φ300mm, the standard flaw for ultrasonic testing is Φ3.2mm, and the ratio of the blank length to the diameter is (1.5~2.5):

1.

3. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The machining thickness in step four is 90mm–130mm, the width is 230mm–580mm, the second vacuum annealing temperature is 1300℃–1400℃, the holding time is 90min–150min, and the vacuum degree is less than 10. -2 Pa.

4. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The standard flaw for ultrasonic testing in step five is Φ2.0mm. The heating temperature for the first rolling is 400℃~500℃, unidirectional rolling is used, the rolling direction is along the shorter direction of the slab, the single-pass processing rate is 10%~20%, the roll speed is 30m / min~50m / min, and the rolling thickness is Xmm, where X = (machined thickness of forged slab × finished product thickness). 1 / 2 The calculation result is rounded to the nearest integer.

5. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The third vacuum annealing in step six is ​​performed at a temperature of 1100℃~1200℃, with a holding time of 60min~120min and a vacuum degree of less than 10. -2 Pa.

6. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The second rolling process described in step seven is cold rolling, which is unidirectional rolling. The rolling direction is perpendicular to the rolling direction in step five. The single-pass processing rate is 5% to 15%, and the roll speed is 10m / min to 20m / min.

7. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The fourth vacuum annealing in step eight is performed at a temperature of 1000℃~1100℃, with a holding time of 60min~120min, and a vacuum degree of less than 10. -2 Pa, the flatness of the board after leveling is less than 3%.

8. The method for preparing a high-quality, large-size niobium-tungsten alloy plate according to claim 1, characterized in that, The fifth vacuum annealing in step nine is performed at a temperature of 1250℃~1350℃, with a holding time of 90min~150min and a vacuum degree of less than 10. -2 Pa, the standard flaw for ultrasonic testing is Φ0.8mm.

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