Large-size fine-grain yttrium target material and preparation method thereof

Abstract

The invention discloses a preparation method of a large-size fine-grain yttrium target material, which comprises the following steps: carrying out vacuum melting to obtain a metal yttrium cast ingot, and carrying out surface machining to obtain a metal yttrium blank; the metal yttrium blank is subjected to vacuum heat treatment and vacuum forging, and then a metal yttrium forge piece is obtained; carrying out isothermal rolling on the metal yttrium forge piece in a protective atmosphere, and carrying out heat treatment in the protective atmosphere to obtain a metal yttrium rolled piece; and carrying out dry cutting on the metal yttrium rolled piece to obtain the yttrium target material. The metal yttrium target obtained through the preparation method is large in finished product size range and good in flatness, toughness is improved while strength is improved, crystal grains are small, the crystal grain size is uniform, compactness is good, the surface is smooth and free of defects, the purity and components of raw materials cannot be changed, the sputtering face is compact, and sputtering performance is good.

Description

Technical Field

[0001] The present invention belongs to the field of thermal processing of ultra-high purity refractory rare earth metal materials, and in particular relates to a large-size fine-grained yttrium target material and a preparation method thereof. Background Art

[0002] Target manufacturing first requires a unique process design based on the performance and needs of downstream application fields, and then repeated plastic deformation, heat treatment, etc., during which key indicators such as grain size and crystal orientation need to be precisely controlled, and then welding, machining, cleaning and drying, vacuum packaging, etc. are required. Currently, the main methods for preparing target materials are casting and powder metallurgy.

[0003] Rare earth metals usually have the characteristics of high hardness and poor plasticity. At present, vacuum melting is generally used for rare earth metal casting, and the rare earth metal ingots obtained usually have metallurgical defects such as shrinkage cavities, pores, inclusions, and cracks. After mechanical processing, defects such as black spots and cracks may appear on the surface of the target material, with a low yield rate, which also has a great impact on the sputtering effect of the target material. In addition, the rare earth metal ingots obtained by vacuum melting are almost entirely composed of columnar crystal regions, with coarse overall grains and extremely uneven grain sizes. Limited by the capacity of smelting equipment, the geometric dimensions of the ingots are usually small.

[0004] In addition, the metal yttrium target produced by conventional hot rolling is severely oxidized during the rolling process, the finished product cracks severely, and the yield rate is very low; the surface of the machined product still has defects such as pores and pinholes, which appear as black spots after oxidation, and the qualified rate is low.

[0005] Rare earth elements have strong chemical activity and strong affinity for oxygen atoms (easy to oxidize). In addition, the cooling after full melting of casting is uneven (insufficient shrinkage compensation), which easily forms defects such as internal holes and interlayers, resulting in black spots and cracks on the surface of the product. If the grain structure is to be significantly refined, it can only be improved through plastic deformation; the high temperature environment causes serious oxidation and loosening of the material surface, and the pressure deformation during the hot rolling process is prone to cracking. In addition, the metal needs to keep the cutting fluid to cool the material during the grinding process, but the anti-oxidation effect is poor, and the surface oiling protection effect is not good during the process. Oxidation and black spots appear on the surface of the product after grinding, and the qualified rate is low.

[0006] On the other hand, the cooling process after the ingot is smelted is from the outside to the inside, resulting in smaller grains on the surface of the ingot and coarser grains inside, with uneven grain size. At the same time, the casting process is limited by the crucible capacity of the equipment and the size of the mold, resulting in a smaller ingot size.

[0007] In view of the technical problems existing in the prior art, the present invention improves the manufacturing process and forms a key technology for preparing high-purity rare earth metal dense target materials and large-size target materials. Summary of the invention

[0008] Based on this, the purpose of the present invention is to prepare a large-size fine-grained yttrium target material, and provide a method for preparing a large-size fine-grained yttrium target material, comprising the following steps: vacuum melting to obtain a metal yttrium ingot, and surface machining to obtain a metal yttrium blank; vacuum heat treatment and vacuum forging of the metal yttrium blank to obtain a metal yttrium forging; isothermal rolling of the metal yttrium forging under a protective atmosphere to obtain a metal yttrium rolled piece, and the isothermal rolling includes heating and heat treatment stages; dry cutting of the metal yttrium rolled piece to obtain a yttrium target material.

[0009] Furthermore, before isothermal rolling, the metal yttrium forging is subjected to non-destructive testing and surface defects are removed.

[0010] Furthermore, the heating temperature of the vacuum heat treatment is 500°C-1000°C, and the holding time is 1-4h.

[0011] Furthermore, the vacuum degree of the vacuum forging is 10 -3 Pa-10 -1 Pa, forging ratio 1.05-1.4, and heat treatment for 10-40 minutes per pass.

[0012] Furthermore, the protective atmosphere used in the isothermal rolling is argon, the heating temperature is 550-1100° C., the holding time is 0.5-3.5 h, the number of passes is 5-20, and the pass processing rate is 2%-20%.

[0013] Furthermore, the heat treatment temperature of the isothermal rolling is 350-700° C., and the holding time is 0.5-2.5 h.

[0014] Furthermore, the dry cutting process is a fully enclosed process, and argon gas is used for air cooling during the process.

[0015] The process of the present invention can also prepare refractory heavy rare earth pure metals such as Lu, Sc, Tm, Er, Ho, etc.

[0016] Beneficial effects:

[0017] 1. The entire forging process is in a vacuum environment, the material does not oxidize, and there is less cracking after forging.

[0018] 2. The entire heating and heat treatment process of isothermal rolling is in an argon environment. The temperature of the rolling process is stable, the material is basically not oxidized, the finished product has high dimensional accuracy, and the incoming material for rolling is a forging with good density and processing performance, and there is no crack on the surface after rolling.

[0019] 3. The process of vacuum forging + argon heating + isothermal rolling + composite vacuum / argon heat treatment is adopted to obtain target products with a large size range, high strength and good toughness, fine and uniform grain size, good density, smooth and defect-free surface, and high yield rate.

[0020] The metal yttrium target obtained by the preparation method of the present invention has a large size range of finished products, good flatness, improved toughness while improving strength, fine grains, uniform grain size, good density, smooth surface without defects, and will not change the purity and composition of the raw materials. The sputtering surface is dense and has good sputtering performance. The process has a high degree of automation, is suitable for mass production by enterprises, and is widely used in flat panel displays, semiconductors and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flowchart of a manufacturing method according to an embodiment of the present invention.

[0022] Figure 2 This is a metallographic diagram of the product of the present invention, with fine grains and uniform grain size.

[0023] Figure 3 Product photo of large-size yttrium target manufactured by the process of the present invention. DETAILED DESCRIPTION

[0024] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0025] Unless otherwise specified, the test materials and equipment used in the examples are common commercial products and can be purchased in the market.

[0026] In order to better understand and implement the present invention, the following is a detailed description of the present invention in conjunction with specific embodiments. Figure 1 As shown, the specific steps include:

[0027] 1. Ultra-high purity yttrium metal with a relative purity of Y / TREM ≥ 99.99% is used to obtain a metal yttrium ingot by vacuum smelting, and the metal yttrium ingot is subjected to surface machining to obtain a metal yttrium blank.

[0028] 2. Perform vacuum heat treatment on the metal yttrium blank obtained in step 1. This process reduces the hardness of the material and improves the plasticity to reduce the tendency of subsequent pressure processing cracking; the vacuum heat treatment temperature is 500°C-1000°C, and the heat preservation time is 1h-4h.

[0029] 3. The yttrium metal heat-treated parts obtained in step 2 are subjected to vacuum forging, wherein the heating, forging, supplementary heat, leveling and cooling stages are all carried out in a vacuum environment. This process is to open the blank, break the grains of the organization, and the finished product has fine grains and the grain size tends to be uniform, while improving the internal defects of the material. The vacuum degree is 10 -3 Pa-10-1 Pa, forging ratio 1.05-1.4, and hot-drying for 10min-40min per pass.

[0030] 4. The metal yttrium forging obtained in step 3 is machined, then subjected to nondestructive testing, and the surface of the forging is further precision machined according to the testing results. This process removes surface defects of the forging.

[0031] 5. The metal yttrium forging obtained in step 4 isothermally rolled, and the heating and heat treatment stages of this process are carried out in an argon atmosphere. After heating in an argon environment, the front and rear rollers of the rollers are heated and temperature controlled by electromagnetic induction, and reciprocating rolling is performed to the finished product. The process does not require reheating, and the extreme difference in rolling temperature is controlled within 50°C. After rolling, it is leveled, and then heat treated in an argon environment. The heat treatment temperature is 350°C-700°C, and the holding time is 0.5h-2.5h. This process further welds the internal defects of the target material, extends the length of the target material, and obtains a large-sized target material with fine equiaxed grains. The heating temperature of isothermal rolling is 550°C-1100°C, the holding time is 0.5h-3.5h, the number of passes is 5-20, and the pass processing rate is 2%-20%.

[0032] 6. The metal yttrium rolled piece obtained in step 5 is subjected to dry cutting to obtain an ultra-high purity large-size fine-grained yttrium target product with a smooth surface, high smoothness, metallic color, and no surface defects.

[0033] Example 1

[0034] 1. Use ultra-high purity yttrium metal with a relative purity of Y / TREM ≥ 99.99%, obtain a metal yttrium ingot by vacuum smelting, and perform surface machining on it to obtain a metal yttrium blank (the finished product is required to have a smooth metallic color, uniform thickness, and no visual defects).

[0035] 2. Perform vacuum heat treatment on the metal yttrium blank obtained in step 1. This process reduces the hardness of the material and improves the plasticity to reduce the tendency of subsequent pressure processing cracking; the vacuum heat treatment temperature is 1000°C and the temperature is kept for 1 hour.

[0036] 3. The yttrium metal heat-treated parts obtained in step 2 are subjected to vacuum forging, wherein the heating, forging, supplementary heat, leveling and cooling stages are all carried out in a vacuum environment. This process is to open the blank, break the grains of the organization, and the finished product has fine grains and the grain size tends to be uniform, while improving the internal defects of the material. The vacuum degree is 10 -1 Pa, forging ratio 1.07, and hot-dip 12min per pass.

[0037] 4. The metal yttrium forging obtained in step 3 is machined (the finished product is required to have a smooth metallic surface, uniform thickness, and no visual defects), and then non-destructive testing is performed, and the surface of the forging is further precision machined according to the testing results. This process removes surface defects of the forging.

[0038] 5. The metal yttrium forging obtained in step 4 is isothermally rolled, and the heating and heat treatment stages of this process are carried out in an argon atmosphere. After heating in an argon environment, the front and rear rollers of the rollers are heated and temperature controlled by electromagnetic induction, and reciprocating rolling is performed to the finished product. The process does not require reheating, and the extreme difference in rolling temperature is controlled within 50°C. After rolling, it is leveled, and then heat treated in an argon environment at a heat treatment temperature of 700°C and a holding time of 0.5h. This process further welds the internal defects of the target material, extends the length of the target material, and obtains a large-sized target material with fine equiaxed grains. The heating temperature of isothermal rolling is 950°C, the holding time is 1h, the processing rate of the first 5 passes is 3%, the processing rate of the middle 10 passes is 8%, and the processing rate of the last 4 passes is 5%.

[0039] 6. The metal yttrium rolled piece obtained in step 5 is cut to obtain an ultra-high purity large-size fine-grained yttrium target product with a smooth surface, high smoothness, metallic color, and no surface defects.

[0040] The average grain size of the target material obtained in Example 1 is less than 80 μm.

[0041] Example 2

[0042] 1. Use ultra-high purity yttrium metal with a relative purity of Y / TREM ≥ 99.99%, obtain a metal yttrium ingot by vacuum smelting, and perform surface machining on it to obtain a metal yttrium blank (the finished product is required to have a smooth metallic color, uniform thickness, and no visual defects).

[0043] 2. Perform vacuum heat treatment on the metal yttrium blank obtained in step 1. This process reduces the hardness of the material and improves the plasticity to reduce the tendency of subsequent pressure processing cracking; the vacuum heat treatment temperature is 800°C and the temperature is kept for 2 hours.

[0044] 3. The yttrium metal heat-treated parts obtained in step 2 are subjected to vacuum forging, wherein the heating, forging, supplementary heat, leveling and cooling stages are all carried out in a vacuum environment. This process is to open the blank, break the grains of the organization, and the finished product has fine grains and the grain size tends to be uniform, while improving the internal defects of the material. The vacuum degree is 10 -1 Pa, forging ratio 1.15, and hot-dip 20min per pass.

[0045] 4. The metal yttrium forging obtained in step 3 is machined (the finished product is required to have a smooth metallic surface, uniform thickness, and no visual defects), and then non-destructive testing is performed, and the surface of the forging is further precision machined according to the testing results. This process removes surface defects of the forging.

[0046] 5. The metal yttrium forging obtained in step 4 is isothermally rolled, and the heating and heat treatment stages of this process are carried out in an argon atmosphere. After heating in an argon environment, the front and rear rollers of the rollers are heated and temperature controlled by electromagnetic induction, and reciprocating rolling is performed to the finished product. The process does not require reheating, and the extreme difference in rolling temperature is controlled within 50°C. After rolling, it is leveled, and then heat treated in an argon environment at a heat treatment temperature of 550°C and a holding time of 1h. This process further welds the internal defects of the target material, extends the length of the target material, and obtains a large-sized target material with fine equiaxed grains. The heating temperature of isothermal rolling is 800°C, the holding time is 1.5h, the processing rate of the first 3 passes is 5%, the processing rate of the middle 6 passes is 10%, and the processing rate of the last 3 passes is 6%.

[0047] 6. The metal yttrium rolled piece obtained in step 5 is cut to obtain an ultra-high purity large-size fine-grained yttrium target product with a smooth surface, high smoothness, metallic color, and no surface defects.

[0048] The average grain size of the target material obtained in Example 2 is less than 50 μm.

[0049] Example 3

[0050] 1. Use ultra-high purity yttrium metal with absolute purity Y / TREM ≥ 99.99%, obtain metal yttrium ingot by vacuum smelting, perform surface machining on it, and obtain metal yttrium blank (the finished product is required to have a smooth metallic color, uniform thickness, and no visual defects).

[0051] 2. Perform vacuum heat treatment on the metal yttrium blank obtained in step 1. This process reduces the hardness of the material and improves the plasticity to reduce the tendency of subsequent pressure processing cracking; the vacuum heat treatment temperature is 650°C and the temperature is kept for 3.5 hours.

[0052] 3. The yttrium metal heat-treated parts obtained in step 2 are subjected to vacuum forging, wherein the heating, forging, supplementary heat, leveling and cooling stages are all carried out in a vacuum environment. This process is to open the blank, break the grains of the organization, and the finished product has fine grains and the grain size tends to be uniform, while improving the internal defects of the material. The vacuum degree is 10 -1 Pa, forging ratio 1.36, and hot-dip 30min per pass.

[0053] 4. The metal yttrium forging obtained in step 3 is machined (the finished product is required to have a smooth metallic surface, uniform thickness, and no visual defects), and then non-destructive testing is performed, and the surface of the forging is further precision machined according to the testing results. This process removes surface defects of the forging.

[0054] 5. The metal yttrium forging obtained in step 4 is isothermally rolled, and the heating and heat treatment stages of this process are carried out in an argon atmosphere. After heating in an argon environment, the front and rear rollers of the rollers are heated and temperature controlled by electromagnetic induction, and reciprocating rolling is performed to the finished product. The process does not require reheating, and the extreme difference in rolling temperature is controlled within 50°C. After rolling, it is leveled, and then heat treated in an argon environment at a heat treatment temperature of 400°C and a holding time of 2h. This process further welds the internal defects of the target material, extends the length of the target material, and obtains a large-sized target material with fine equiaxed grains. The heating temperature of isothermal rolling is 650°C, the holding time is 3h, the processing rate of the first 2 passes is 8%, the processing rate of the middle 2 passes is 13%, and the processing rate of the last 2 passes is 6%.

[0055] 6. The metal yttrium rolled piece obtained in step 5 is cut to obtain an ultra-high purity large-size fine-grained yttrium target product with a smooth surface, high smoothness, metallic color, and no surface defects.

[0056] The average grain size of the target material obtained in Example 3 is less than 20 μm.

[0057] Furthermore, in some specific embodiments, the cutting process is performed by a fully enclosed grinding machine. More specifically, after the rolled plate is sawed and milled, the surface of the product is dry ground by using an atmosphere-protected cooling grinding technology. The entire grinding process is in an argon environment, isolating the outside air, and there is no oxidation during the process. The product has a metallic luster after processing. In addition, argon is used for air cooling during the processing, and large-sized plates are not deformed during processing. This avoids the existing grinding machine equipment from grinding in the atmosphere, using cutting fluid for cooling, and oxidation cannot be avoided during the processing process, and the surface of the product becomes dark and black after processing. Effect: The surface of the product after processing is smooth and free of oxidation, with good flatness and no surface defects.

[0058] The process of the present invention is applicable to refractory heavy rare earth pure metals, such as Y, Lu, Sc, Tm, Er, Ho, etc. The present invention adopts vacuum forging of rare earth metals, and performs heating → forging (reheating during the process) → leveling → cooling in a vacuum environment, and adopts a robot to operate the whole process. During the forging process, the material surface does not oxidize, the forgings have less cracking, the grains are completely broken, the grains are small after forging, the grain size is uniform, and the material is densified, which is conducive to subsequent pressure processing. At the same time, isothermal rolling is adopted, heating and post-rolling heat treatment are carried out in an argon environment, and the temperature difference is controlled during the rolling process to ensure that the temperature of the billet is uniform and stable. No heat supplementation is required during the process, and continuous rolling is achieved. In this way, the production efficiency can be improved, the surface of the rolled plate is less oxidized and crack-free, the dimensional accuracy is high, and the finished product is evenly distributed fine equiaxed crystals; internal defects are further welded, and the qualified rate of machined products is high. Figure 2 and Figure 3 As shown, Figure 2 This is a metallographic diagram of the cross section of the product of the present invention, showing that the surface and internal grain sizes are uniform and the density is good. Figure 3This is a product photo of a large-size yttrium target produced by the process of the present invention.

[0059] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing a large-size fine-grained yttrium target, characterized in that: The method comprises the following steps: vacuum melting to obtain a metal yttrium ingot, and surface machining to obtain a metal yttrium blank; The metal yttrium blank is subjected to vacuum heat treatment and vacuum forging to obtain a metal yttrium forging; The metal yttrium forging is isothermally rolled under a protective atmosphere to obtain a metal yttrium rolled piece; the isothermal rolling includes a heating and heat treatment stage; The yttrium target material is obtained by dry cutting the metal yttrium rolled piece.

2. The method for preparing a yttrium target according to claim 1, characterized in that: The heating temperature of the vacuum heat treatment is 500° C.-1000° C., and the insulation time is 1-4 hours.

3. The method for preparing a yttrium target according to claim 1, characterized in that: The vacuum degree of the vacuum forging is 10 - 3 Pa-10 -1 Pa, forging ratio 1.05-1.4, and heat treatment for 10-40 minutes per pass.

4. The method for preparing a yttrium target according to claim 1, characterized in that: The protective atmosphere used in the isothermal rolling is argon, the heating temperature is 550° C.-1100° C., and the insulation time is 0.5-3.5 h.

5. The method for preparing a yttrium target according to claim 1, characterized in that: The number of isothermal rolling passes is 5-20, and the pass processing rate is 2%-20%.

6. The method for preparing a yttrium target according to claim 1, characterized in that: The heat treatment temperature of the isothermal rolling is 350° C.-700° C., and the holding time is 0.5-2.5 h.

7. The method for preparing a yttrium target according to claim 1, characterized in that: Before the isothermal rolling, the metal yttrium forging is subjected to nondestructive testing and surface defects are removed.

8. The method for preparing a yttrium target according to claim 1, characterized in that: The dry cutting process is a fully enclosed process, and argon gas is used for air cooling during the process.

9. The method for preparing a yttrium target according to any one of claims 1 to 8, characterized in that: Used to prepare rare earth pure metals Lu, Sc, Tm, Er, and Ho.

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