A method for preparing amorphous strip cooling roller

Abstract

The present invention relates to a method for preparing an amorphous strip cooling roller, firstly, the molybdenum powder is graded, then the graded molybdenum powders of different grades with normal distribution are selected for mixing, the mixed powder is pressed into a blank and sintered, and then the sintered blank is machined into a molybdenum flywheel according to the designed shape; then the tantalum strip is rolled and pressed, and then it is tightly connected to the outer cylindrical surface of the molybdenum flywheel through high-frequency heating and pressure, and the connection between the tantalum strip and the molybdenum flywheel is metallurgically bonded to obtain a finished cooling roller. The method can reduce the porosity of the sintered blank, and improve the corrosion resistance of the contact part between the molybdenum flywheel and the amorphous strip without changing the thermal conductivity of the molybdenum flywheel.

Description

Technical Field

[0001] The invention belongs to the technical field of amorphous strips, and in particular relates to a method for preparing an amorphous strip cooling roller. Background Art

[0002] Amorphous metals are completely different from crystalline metals in terms of atomic arrangement. Their special microstructure also gives them good strength, toughness, wear resistance, magnetism, electrical and chemical properties. When preparing amorphous strips, the molten alloy is mainly poured onto a rotating cooling roller to quickly solidify the alloy to form an amorphous strip. Molybdenum, as a high-temperature metal commonly used in industry, is used on cooling rollers in the amorphous strip industry because of its excellent strength, melting point and excellent thermal conductivity.

[0003] However, the molybdenum flywheel used for cooling rollers in the amorphous strip industry prepared by traditional processes is prone to poor cooling effect and corrosion due to the large porosity and low density of the sintered blanks, which has a great impact on the production and preparation of amorphous strip products. The use of refractory metals such as tantalum and niobium prepared by vacuum melting as cooling rollers can reduce porosity and increase thermal conductivity. However, the substantial increase in cost has also become a major factor restricting its application in amorphous strips. Therefore, how to reduce the porosity of the molybdenum flywheel sintered blank, increase the density of the sintered blank, and increase the corrosion resistance of the product has become the main means to improve the thermal conductivity of molybdenum flywheel products for cooling and even increase their service life. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing an amorphous strip cooling roller, which can reduce the porosity of the sintered blank and improve the corrosion resistance of the contact part between the molybdenum flywheel and the amorphous strip without changing the thermal conductivity of the molybdenum flywheel, thereby laying a theoretical and practical foundation for improving the performance of the amorphous strip cooling roller.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for preparing an amorphous strip cooling roller, firstly, the molybdenum powder is graded, and then the molybdenum powders of each grade whose particle sizes conform to the normal distribution after classification are selected and mixed, the mixed powder is pressed into a blank and sintered, and then the sintered blank is machined into a molybdenum flywheel according to the designed shape; then the tantalum strip is rolled and pressed, and is tightly connected to the outer cylindrical surface of the molybdenum flywheel through processes such as high-frequency heating and pressure, and the connection between the tantalum strip and the molybdenum flywheel is metallurgically bonded to obtain a finished cooling roller.

[0006] The average particle size of the molybdenum powder after classification is 3.0-4.5um, and the purity of the molybdenum powder is 99.95%.

[0007] The classified molybdenum powders are mixed under an argon protective atmosphere for 12-24 hours.

[0008] The mixed powder is placed in a flexible mold and pressed into a powdery blank using cold isostatic pressing.

[0009] The pressing pressure of the cold isostatic pressing method is 160~280Mpa, and the holding time is: 10~30min.

[0010] After the mixed powder is pressed into a blank, the sintering atmosphere during the sintering process is hydrogen, the sintering temperature is 1850°C-1950°C, and then the blank is cooled to room temperature with the furnace to obtain a sintered blank.

[0011] The density of the sintered blank obtained by sintering is ρ2≥96%ρ1, where ρ1 is the theoretical density of the finished molybdenum flywheel.

[0012] When the tantalum belt is connected to the molybdenum flywheel, a high-frequency heating device is used to heat the tantalum belt and the molybdenum flywheel simultaneously. The high-frequency heating power is 30KW-50KW, and the heating time is 6-10h; the pressing pressure is 20Mpa-50Mpa, and the pressing time is 30min-120min.

[0013] The beneficial effects of the present invention are as follows: 1. The present invention adopts powder metallurgy, and the airflow classifier classifies the molybdenum powder into particle sizes, takes the appropriate particle size for powder mixing, and then obtains the molybdenum flywheel cooling surface composed of tantalum strips by high-frequency heating. It not only improves the density of the molybdenum product itself, reduces the porosity, and effectively improves the thermal conductivity of the molybdenum flywheel; at the same time, the working surface of the cooling roller composed of tantalum strips also greatly improves the corrosion resistance of the molybdenum product surface. The product is superior to molybdenum flywheel products of the same specifications, in order to lay a theoretical and practical foundation for the preparation of amorphous strip cooling rollers with high thermal conductivity and high corrosion resistance.

[0014] 2. The preparation method of the amorphous strip cooling roller disclosed in the present invention, wherein: a) in the present invention, an air flow classifier is used to classify the molybdenum powder into particle sizes, and then the powder is mixed. The distribution of each particle size powder in the mixed powder must conform to the normal distribution to avoid excessive porosity in the sintered blank and too low density of the sintered blank due to the mismatch of the particle size of the molybdenum powder, thereby affecting the thermal conductivity of the molybdenum flywheel product; b) high-frequency heating equipment and pressurizing equipment are used to heat and pressurize the molybdenum flywheel after fine turning and the tantalum thin ring formed by rolling tantalum strips of corresponding specifications at the same time, so that the two are tightly connected, and the connection method is metallurgical bonding. After the treatment, the working surface composed of tantalum strips showed no corrosion pits after 2000 hours of use (ordinary molybdenum flywheels will have corrosion pits after 1000 hours of use), indicating that after the working surface is covered with tantalum strips, the high-temperature corrosion resistance of the molybdenum flywheel cooling roller can be greatly improved, and the performance and durability of the amorphous strip cooling roller can be significantly improved. Then, in coordination with the particle size classification and sintering process, a cooling roller for amorphous strips with excellent thermal conductivity and corrosion resistance can be prepared. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below, but it is not intended to limit the invention in any way.

[0016] A method for preparing an amorphous strip cooling roller, wherein the cooling roller is used in the preparation process of the amorphous strip, and the method comprises the following preparation steps:

[0017] Step 1: powder selection. Use an airflow classifier to classify the molybdenum powder into particle sizes. After classification, the distribution of each particle size powder must conform to the normal distribution. The average particle size of the molybdenum powder after classification is: 3.0-4.5um, and the purity of the molybdenum powder used for classification is: 99.95%;

[0018] Step 2: Mixing powders: Use a V-type mixer under an argon protective atmosphere to mix the graded powders of different particle sizes evenly. The mixing time is 12h-24h to obtain mixed powders.

[0019] Step 3: Pressing and molding: placing the mixed powder in a flexible mold, using cold isostatic pressing, the pressing pressure is 160-280 MPa, the holding time is 10-30 min, and a powder blank is obtained for standby use. The size after pressing is (Φ500-Φ850) × L mm, where L is the length of the powder blank;

[0020] Step 4: sintering: placing the prepared powder blank in a medium frequency sintering furnace for sintering, the sintering atmosphere is hydrogen, the sintering temperature is 1850°C-1950°C, and then cooling to room temperature with the furnace to obtain a sintered blank; the theoretical density of the molybdenum flywheel product is ρ1, and the density of the sintered blank obtained by sintering is ρ2≥96%ρ1;

[0021] Step 5: Machining: Place the sintered blank on a lathe and finish-process it to the size and shape of the drawing for later use;

[0022] Step 6: Use a rolling press to roll the tantalum strip to form a tantalum ring with a size that is substantially consistent with the outer diameter of the molybdenum flywheel, and the inner diameter of the rolled tantalum ring can closely match the outer diameter of the molybdenum flywheel;

[0023] Step 7, using high-frequency heating equipment and pressure equipment, heat and pressurize the tightly matched molybdenum flywheel and tantalum ring at the same time, so that they are tightly connected, and the connection is metallurgical bonding; the high-frequency heating equipment is a high-frequency heating machine, the high-frequency heating power is: 30KW-50KW, the heating time is: 6-10h; the pressure equipment is an oil press, the pressure is: 20Mpa-50Mpa, the pressurization time is: 30min-120min;

[0024] Step eight, post-processing, cleaning, inspecting and packaging the product after the previous step of machining to obtain an amorphous strip cooling roller.

[0025] The following is a combination of specific embodiments and comparative examples to illustrate that the amorphous strip cooling roller prepared by the technical solution of the present invention has excellent performance.

[0026] Embodiment 1: A method for preparing an amorphous strip cooling roller, comprising the following preparation steps:

[0027] Step 1: Powder selection: Use an airflow classifier to classify the molybdenum powder into particle sizes. After classification, the distribution of each particle size powder must conform to the normal distribution. The average particle size of the molybdenum powder after classification is: 3.0um, and the purity of the molybdenum powder is: 99.95%;

[0028] Step 2: Powder mixing: Use a V-type mixer under an argon protective atmosphere to mix the powders evenly for 12 hours to obtain molybdenum powder with a suitable particle size and evenly mixed.

[0029] Step 3, pressing and molding: placing the mixed powder in a flexible mold, using cold isostatic pressing method, the pressing pressure is 160Mpa, the holding time is: 30min, and a powder blank is obtained for standby use. The size of the powder blank after pressing is Φ500×80 mm;

[0030] Step 4: Sintering: Place the powdery blank in a medium frequency sintering furnace for sintering. The sintering atmosphere is hydrogen. The sintering temperature is 1850°C. Then cool it to room temperature with the furnace to obtain a sintered blank. The density of the sintered blank is 9.82 g / cm 3 (The theoretical density of the finished product, i.e. the density of molybdenum, is ρ1=10.2 g / cm 3 , 96%ρ1=9.72 g / cm 3 );

[0031] Step 5: Machining: Place the sintered blank on a lathe and finish-machine it to the drawing size of Φ420×60 mm to obtain a molybdenum flywheel for standby use;

[0032] Step 6: Use a rolling press to roll the tantalum strip of 1320×3mm to make it basically consistent with the outer diameter of the molybdenum flywheel, and the inner diameter of the rolled tantalum ring is Φ420mm, which can fit closely with the outer diameter of the molybdenum flywheel;

[0033] Step 7: Use high-frequency heating equipment and pressure equipment to heat and pressurize the tightly matched molybdenum flywheel and tantalum ring at the same time, so that they are tightly connected and the connection is metallurgical bonding; high-frequency heating power: 30KW, heating time: 6h; pressure: 20Mpa, pressurization time: 30min;

[0034] Step 8, post-processing: cleaning, inspecting and packaging the product after the previous step of machining to obtain an amorphous strip cooling roller.

[0035] After inspection and testing, the tantalum ring and the molybdenum flywheel are tightly connected, and the bonding method is metallurgical bonding. The tensile strength of the connection surface is 194Mpa, and the elongation is 12.6%. The density of the sintered blank is 9.82 g / cm 3 (Under the same specifications, pure molybdenum, ordinary powder, sintered compact density is: 9.5 g / cm 3 ). It shows that the method of the present invention can be used to prepare molybdenum flywheels, which can effectively improve the density of molybdenum flywheels and the thermal conductivity of materials; and the working surface formed by the connection of tantalum strips has a relatively high strength at the connection interface, and the connection method is metallurgical bonding. After 2000 hours of use, no pits appear on the surface (ordinary molybdenum flywheels will have pits after 1000 hours of use), indicating that after the working surface is covered with tantalum strips, the high-temperature corrosion resistance of the molybdenum flywheel cooling roller can be greatly improved, and the performance and durability of the amorphous strip cooling roller can be significantly improved.

[0036] Embodiment 2: A method for preparing an amorphous strip cooling roller, comprising the following preparation steps:

[0037] Step 1: Powder selection: Use an airflow classifier to classify the molybdenum powder into particle sizes. After classification, the distribution of each particle size powder must conform to the normal distribution. The average particle size of the molybdenum powder after classification is: 4.2um, and the purity of the molybdenum powder is: 99.95%;

[0038] Step 2: Powder mixing: Use a V-type mixer under an argon protective atmosphere to mix the powders evenly for 24 hours to obtain molybdenum powder with a suitable particle size and evenly mixed.

[0039] Step 3, pressing and molding: placing the mixed powder in a flexible mold, using cold isostatic pressing method, the pressing pressure is 260Mpa, the holding time is: 10min, and a powder blank is obtained for standby use. The size of the powder blank after pressing is Φ850×110 mm;

[0040] Step 4: Sintering: Place the powdery blank in a medium frequency sintering furnace for sintering. The sintering atmosphere is hydrogen and the sintering temperature is 1950°C. Then cool it to room temperature with the furnace to obtain a sintered blank. The density of the sintered blank is 9.96 g / cm 3 (Theoretical density of finished product ρ1=10.2 g / cm 3 , 96%ρ1=9.72 g / cm 3 );

[0041] Step 5: Machining: Place the sintered blank on a lathe and finish-machine it to the drawing size of Φ780×80 mm to obtain a molybdenum flywheel for use;

[0042] Step 6: Use a rolling machine to roll the tantalum strip 2550×3mm to make it basically consistent with the outer diameter of the molybdenum flywheel, and the inner diameter of the rolled tantalum ring is Φ780mm, which can fit closely with the outer diameter of the molybdenum flywheel;

[0043] Step 7: Use high-frequency heating equipment to heat the tightly matched molybdenum flywheel and tantalum ring to make them tightly connected and the connection is metallurgical bonding; high-frequency heating power: 50KW, heating time: 10h; pressure: 50Mpa, pressurization time: 120min;

[0044] Step 8, post-processing: cleaning, inspecting and packaging the product after the previous step of machining to obtain an amorphous strip cooling roller.

[0045] After inspection and testing, the tantalum ring and the molybdenum flywheel are tightly connected, and the bonding method is metallurgical bonding. The tensile strength of the connection surface is 218Mpa, and the elongation is 14.1%. The density of the sintered blank is 9.82 g / cm 3 (Under the same specifications, pure molybdenum, ordinary powder, sintered compact density is: 9.5 g / cm 3 ). It shows that the method of the present invention can be used to prepare molybdenum flywheels, which can effectively improve the density of molybdenum flywheels and the thermal conductivity of materials; and the working surface formed by the connection of tantalum strips has a relatively high strength at the connection interface, and the connection method is metallurgical bonding. After 2000 hours of use, no pits appear on the surface (ordinary molybdenum flywheels will have pits after 1000 hours of use), indicating that after the working surface is covered with tantalum strips, the high-temperature corrosion resistance of the molybdenum flywheel cooling roller can be greatly improved, and the performance and durability of the amorphous strip cooling roller can be significantly improved.

[0046] Comparative Example 1: The only difference between Comparative Example 1 and Example 1 is that the molybdenum powder is not graded, screened and mixed, and pure molybdenum powder is directly used for subsequent preparation.

[0047] After inspection and testing, the density of the sintered blank is 9.56 g / cm 3 , the sintered density is significantly lower than that of Example 1. This shows that the pores of ordinary molybdenum powder particles are not easily filled during sintering due to the uneven composition of coarse molybdenum powder and fine molybdenum powder, resulting in high porosity and poor density. However, this process uses an air flow classifier to grade the molybdenum powder, and then selects powders with particle size distributions that conform to normal distribution for mixing, pressing and sintering, which can effectively improve the density and thermal conductivity of molybdenum flywheel products.

[0048] The difference between Comparative Example 2 and Example 1 is that step 6 and step 7 are deleted.

[0049] After inspection and testing, pits appeared on the surface of the molybdenum flywheel after 1041 hours of use (after this process, no pits appeared on the surface after 2000 hours of use), indicating that due to the limitations of the powder metallurgy process of molybdenum products, there is a certain porosity on the working surface of the molybdenum flywheel, which makes it inevitable to cause certain pits when the molybdenum flywheel is subjected to high-temperature rapid cooling of amorphous strip products. After this process, the corrosion resistance of the working surface is significantly better than that of ordinary molybdenum flywheels.

[0050] In the above examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be purchased commercially.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation modes of the present invention may be modified or replaced by equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A method for preparing an amorphous strip cooling roller, characterized in that: First, the molybdenum powder is graded, and then the graded molybdenum powders with normal distribution are mixed, the mixed powder is pressed into a blank and sintered, and then the sintered blank is machined into a molybdenum flywheel according to the designed shape; then the tantalum strip is rolled and pressed, and is tightly connected to the outer cylindrical surface of the molybdenum flywheel through a high-frequency heating and pressure process, and the connection between the tantalum strip and the molybdenum flywheel is metallurgically bonded, so as to obtain a finished cooling roller; The average particle size of the molybdenum powder after classification is 3.0-4.5um, and the purity of the molybdenum powder is: 99.95%; The classified molybdenum powders are mixed under an argon protective atmosphere for 12-24 hours; When the tantalum belt is placed on the molybdenum flywheel, a high-frequency heating device is used to heat the tantalum belt and the molybdenum flywheel simultaneously. The high-frequency heating power is 30KW-50KW, and the heating time is 6-10h; the pressing pressure is 20Mpa-50Mpa, and the pressing time is 30min-120min.

2. The method for preparing an amorphous strip cooling roller according to claim 1, characterized in that: The mixed powder is placed in a flexible mold and pressed into a powdery blank using cold isostatic pressing.

3. The method for preparing an amorphous strip cooling roller according to claim 2, characterized in that: The pressing pressure of the cold isostatic pressing method is 160~280Mpa, and the holding time is: 10~30min.

4. The method for preparing an amorphous strip cooling roller according to claim 1, characterized in that: After the mixed powder is pressed into a blank, the sintering atmosphere during the sintering process is hydrogen, the sintering temperature is 1850°C-1950°C, and then the blank is cooled to room temperature with the furnace to obtain a sintered blank.

5. The method for preparing an amorphous strip cooling roller according to claim 3, characterized in that: The density of the sintered blank obtained by sintering is ρ2≥96%ρ1, where ρ1 is the theoretical density of the finished molybdenum flywheel.