CN108411161B - Negative electrode alloy wire of K-type thermocouple and preparation process thereof - Google Patents
Negative electrode alloy wire of K-type thermocouple and preparation process thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C22C19/007—Alloys based on nickel or cobalt with a light metal (alkali metal Li, Na, K, Rb, Cs; earth alkali metal Be, Mg, Ca, Sr, Ba, Al Ga, Ge, Ti) or B, Si, Zr, Hf, Sc, Y, lanthanides, actinides, as the next major constituent
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- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
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Abstract
The invention relates to the technical field of thermocouples, in particular to a negative alloy wire of a K-type thermocouple and a preparation process thereof, which solve the problem of poor temperature measurement accuracy of the K-type thermocouple in the prior art at a high temperature higher than 1000 ℃, and the technical scheme is characterized in that the negative alloy wire of the K-type thermocouple is made of nickel-aluminum alloy, and comprises 0.4-1.2% of cobalt, 0.8-1.7% of manganese, 1.2-2.5% of aluminum, 0.05-0.2% of iron, 0.05-0.2% of yttrium, 0.1-0.5% of niobium, 0.1-0.5% of vanadium, 0.05-0.1% of carbon and the balance of nickel by mass, the negative alloy wire is prepared by adopting the preparation ratio and the preparation process in the patent, and the positive alloy wire is prepared by adopting a standard nickel-chromium alloy wire to carry out temperature accuracy detection display, all meet the industrial grade I standard at the temperature of 0-1000 ℃, and all meet the industrial grade II standard at the high temperature of 0-1200 ℃. Compared with a K-type thermocouple in the prior art, the precision is obviously improved under the high-temperature condition.
Description
Technical Field
The invention relates to the technical field of thermocouples, in particular to a negative electrode alloy wire of a K-type thermocouple and a preparation process thereof.
Background
The thermocouple is a long-used temperature measuring element in a temperature measuring instrument, directly measures temperature, converts a temperature signal into a thermal electromotive force signal, and converts the thermal electromotive force signal into the temperature of a measured medium through an electric instrument.
The K-type thermocouple is a cheap gold thermocouple with the largest use amount at present, the use amount of the K-type thermocouple is the sum of other thermocouples, the use temperature range of the K-type thermocouple is about 0 ℃ to 1300 ℃, the performance of an alloy wire of the K-type thermocouple influencing the temperature measuring performance of the K-type thermocouple is mainly the performance of the alloy wire, the national standard GB/T2614-2010 specifies that the alloy wire requires the use temperature to be 800 ℃ for a long time and 900 ℃ for a short time, and is limited by the performance of the K-type thermocouple alloy wire in the prior art, the positive pole of the K-type thermocouple in the prior art is mostly made of nickel-silicon alloy, the negative pole is mostly made of nickel-silicon alloy (containing 97 mass percent of nickel and 3 mass percent of silicon), and the nickel is easily further oxidized at the high temperature of about 1000 ℃ and above due to the unstable high-temperature thermoelectric performance of the. The deviation between the measured temperature value and the actual value of the K-type thermocouple made of the nickel-silicon alloy is usually larger and reaches +/-6 ℃, and the precision is poorer.
Disclosure of Invention
The invention aims to provide a negative electrode alloy wire of a K-type thermocouple and a preparation process thereof, which have the advantage that the high measurement precision can be still kept under the high-temperature condition that the temperature exceeds 1000 ℃.
The technical purpose of the invention is realized by the following technical scheme:
the negative electrode alloy wire of the K-type thermocouple is made of nickel-aluminum alloy and comprises, by mass, 0.4% -1.2% of cobalt, 0.8% -1.7% of manganese, 1.2% -2.5% of aluminum, 0.05% -0.2% of iron, 0.05% -0.2% of yttrium, 0.1% -0.5% of niobium, 0.1% -0.5% of vanadium, 0.05% -0.1% of carbon and the balance of nickel.
By adopting the technical scheme, the toughness of the alloy wire is improved, the strength and the hardness of the alloy wire are improved, and the hot-working performance of the alloy wire is improved by adding manganese.
By adding iron, the toughness of the alloy wire is improved.
After the aluminum is added, the oxidation resistance of the negative electrode alloy wire is greatly improved, a compact aluminum oxide film is formed on the surface, and particularly, the stability of the aluminum oxide film can be kept at a high temperature when the temperature is lower than 1300 ℃, so that the continuous oxidation can be prevented; meanwhile, the aluminum has the effect of refining grains, and the high-temperature corrosion resistance of the alloy wire is improved.
By adding yttrium, the diffusion of aluminum in the alloy is accelerated, and the forming speed of the aluminum oxide film is improved; meanwhile, at the junction of the aluminum yttrium oxide film and the alloy matrix, yttrium oxide is distributed to the matrix in a dendritic form to play a role of pinning, and the scattered yttrium oxide causes a vacancy trap effect, so that the bonding strength of the oxide film and the matrix is improved, and the oxidation resistance of the alloy is improved; meanwhile, compared with the common aluminum oxide film, the yttrium aluminum composite oxide film has the advantages that the oxidation resistance is improved, the stability is high, and the stability of the alloy wire at high temperature is improved.
By adding vanadium and carbon, vanadium can play a role in refining grains, so that the strength and the toughness are improved, and simultaneously, vanadium and carbon form carbides in the alloy, so that the hydrogen corrosion resistance is improved.
Preferably, the negative electrode alloy wire also comprises lanthanum-rich rare earth with the mass fraction of 0.05-0.2%.
By adopting the technical scheme, the lanthanum-rich rare earth is added to play a role in refining crystal grains in the alloy, and meanwhile, the lanthanum-rich rare earth plays a role in a long-acting weaving agent in the alloy, so that the remelting and recession resistance of the alloy is improved. Therefore, the alloy wire can still keep a stable state in the process of using at high temperature, and the thermal stability of the negative electrode alloy wire is improved.
Preferably, the negative electrode alloy wire further comprises silicon with the mass fraction of 0.3% -0.7%.
By adopting the technical scheme, the silicon-aluminum composite oxide film is easily formed on the surface of the alloy by adding the silicon, and has higher compactness compared with a common aluminum oxide film, so that the silicon-aluminum composite oxide film has stronger oxidation resistance in a high-temperature environment, meanwhile, the aluminum and the silicon form an aluminum-silicon binary alloy, the silicon-aluminum binary alloy has soft α -aluminum and hard phase silicon, has good wear resistance, does not generate the phenomenon of enhanced dissolution or aggregation after the temperature is raised, and has good heat resistance.
Meanwhile, the lanthanum-rich misch metal has a modification effect on the eutectic silicon, so that the eutectic silicon is changed into a fibrous shape, and the integral strength and plasticity of the alloy are improved.
Preferably, the negative electrode alloy wire further comprises 0.4-0.8 mass percent of copper.
By adopting the technical scheme, the nickel and the copper form high-strength single-phase austenite, and the single-phase austenite is more corrosion-resistant than other nickel-based alloys in a reducing medium and more corrosion-resistant than nickel and copper in an oxidizing medium facing phosphoric acid, sulfuric acid, hydrochloric acid and organic acid.
A preparation process of a negative electrode alloy wire of a K-type thermocouple is characterized by comprising the following steps:
s1, shearing: shearing the raw materials into strip blocks or balls;
s2, batching: proportioning the raw materials after shearing according to a proportion;
s3, smelting: putting the raw materials after the burdening into a vacuum smelting furnace for vacuum smelting and cooling and forming;
s4, forging: forging and correcting the smelted wire;
s5, processing: drawing the forged wire to form a finished product;
s6, checking and warehousing: and (5) inspecting the processed finished product, and storing the qualified product in a warehouse.
By adopting the technical scheme, the raw materials are cut into small pieces by shearing, so that the raw materials are convenient to mix and smelt; and the cooled and formed wire is forged through forging, so that the defects of air holes and shrinkage cavities on the wire are reduced, and the microtube structure of the wire is optimized.
Preferably, S5 specifically includes:
a1, first annealing treatment: performing primary annealing treatment on the forged wire rod, wherein the primary annealing treatment is cover annealing;
a2, first drawing treatment: drawing for multiple times, and gradually drawing from 8.5mm to 2.6mm in diameter;
a3, first acid washing: pickling the wire subjected to the first round of drawing treatment to remove surface oxide skin and rusty materials;
a4, second annealing treatment: carrying out secondary annealing treatment on the forged wire rod, wherein the secondary annealing treatment is continuous annealing;
a5, second round drawing treatment: drawing for multiple times, and gradually drawing from the diameter of 2.6mm to 1.37mm to prepare a semi-finished product;
a6, screening: screening finished products after the second round of drawing treatment, manufacturing unqualified products into other products according to conditions, and continuously performing A7 on qualified semi-finished products;
a7, third drawing treatment: drawing for multiple times, and gradually drawing to 0.53mm from 1.37mm in diameter to obtain a finished product;
a8, secondary acid washing: pickling the screened qualified semi-finished product, and removing oxide skin and rusty materials on the surface of the qualified semi-finished product;
a9, third annealing treatment: and carrying out third annealing treatment on the semi-finished product subjected to the second pickling, wherein the third annealing treatment is continuous annealing.
By adopting the technical scheme, the coiled wire is subjected to heat treatment by first annealing treatment and cover annealing, and the single heat treatment amount is large and the use is convenient; through the second annealing treatment and continuous annealing, the wire rod passes through the heat treatment furnace at a high speed, so that deformed crystal grains in the wire rod are converted into uniform equiaxial crystal grains again, and simultaneously, the work hardening and residual internal stress are eliminated.
The defects of inconsistent size or deformation and the like can occur in the drawing process of part of the wire rods, so that the defects can be found in time after screening after the first round of drawing, the semi-finished products which do not meet the requirements can be screened out in advance, and the unqualified products can be made into other products with lower requirements according to the actual conditions; and the qualified product is continuously drawn by the second round to be made into a finished product, so that the yield is greatly improved, and the waste of materials is reduced.
After the wire is drawn, oxide scale and rusty materials remain on the surface of the wire, and the oxide scale and the rusty materials are removed by reacting with acid after twice pickling.
Preferably, the S3 specifically includes the following steps:
b1, firstly, smelting aluminum and nickel into an intermediate alloy, wherein the intermediate alloy comprises 60 mass percent of nickel and 40 mass percent of aluminum, and adding the proportioned aluminum and nickel into a vacuum smelting furnace for smelting;
b2, after the aluminum and the nickel are fully melted, adding lanthanum-rich rare earth, continuously melting, and pouring into a steel mould for cooling after melting for 1 minute at 1500 ℃;
b3, sampling and detecting the nickel-aluminum alloy, calculating the amount of the added intermediate alloy according to the requirement of the aluminum content in the formula, and adding the rest nickel;
and B4, putting the proportioned intermediate alloy and nickel into a vacuum smelting furnace, heating and smelting, and adding other small materials into the vacuum smelting furnace after the intermediate alloy and the nickel are fully molten.
By adopting the technical scheme, the melting point of the aluminum is 660 ℃, the melting point of the nickel is 1453 ℃, and the density of the aluminum is 2.7g/cm3And the density of nickel is 8.9g/cm3In the conventional smelting mode, because the melting points and the densities of aluminum and nickel are greatly different, the heating temperature needs to be increased and the smelting time needs to be prolonged in the direct smelting process, and meanwhile, burning loss and segregation phenomena are easy to generate, and the actual yield is low, so that the phase smelting of aluminum and nickel is difficult to realize. Particularly, in the alloy wire used as the thermocouple, because the proportion of nickel in the alloy is far greater than that of aluminum, and aluminum is added into nickel, the difference of melting points is large, and aluminum and nickel are difficult to form uniform crystal grains, the produced alloy wire has uneven texture and uneven properties, and the accuracy of thermocouple temperature measurement is influenced.
The intermediate alloy of aluminum and nickel is firstly prepared, the content of nickel is more than that of aluminum, and the burning loss rate is lower after vacuum melting; after the lanthanum-rich rare earth is added, the wetting visual angle between the nickel solution and the aluminum is increased, the uniform degree of aluminum distribution in the nickel is improved, and the segregation of the aluminum is prevented. The produced aluminum-nickel intermediate alloy is uniformly and dispersedly distributed, and the crystal grains are fine, so that when the intermediate alloy is added into other raw materials to be mixed, the phase melting speed is accelerated, and the burning loss and the uneven distribution of aluminum are reduced.
Preferably, after A8 is finished, the method continues
A10, dehydrogenation treatment: and blowing the surface of the smelted finished product by using a high-pressure spray gun.
By adopting the technical scheme, the high-pressure spray gun is used for blowing the surface of the finished product, so that on one hand, the possibly residual oxide skin or rust on the surface of the wire rod is blown off, and the influence of the oxide skin and the rust on the performance of the wire rod is reduced.
On the other hand, after the acid pickling, the scale or rust reacts with the acid to generate hydrogen, and part of the hydrogen adheres to the surface of the wire rod. Although the wire has good hydrogen corrosion resistance, the wire has extremely strict dimensional requirements due to the special use of the thermocouple, and therefore, small amount of hydrogen corrosion on the surface of the wire still causes small change on the dimension of the wire, thereby causing reduction of the temperature measurement precision of the thermocouple. The high-pressure spray gun blows the surface of the wire to blow out hydrogen molecules attached to the surface of the wire, so that the source of diffused hydrogen is cut off, hydrogen corrosion is further reduced, and the temperature measurement precision of a thermocouple made of the alloy wire is improved.
Preferably, during dehydrogenation treatment, the finished product is placed in a high-temperature reaction kettle, and the gas used by the high-pressure spray gun is carbon dioxide.
By adopting the technical scheme, carbon dioxide reacts with hydrogen at high temperature, and CO2+H2→CO+H2O, thereby facilitating the removal of hydrogen from the high pressure lance.
Preferably, an alkaline drying agent is placed in the high-temperature reaction kettle.
By adopting the technical scheme, on one hand, the alkaline drying agent in the high-temperature reaction kettle can absorb water generated by the reaction of carbon dioxide and hydrogen in time, so that the forward proceeding of the reaction of carbon dioxide and hydrogen is facilitated, and simultaneously, the reaction of carbonic acid molecules generated by mixing carbon dioxide and water and the alkaline drying agent is reduced, so that the waste of carbon dioxide is reduced;
on the other hand, because the alloy has good acid corrosion resistance, part of acid can be attached to the surface of the wire after acid washing, volatilization can be generated under a high-temperature environment, and more acid can be absorbed through the alkaline drying agent, so that the corrosion of the more acid to the high-temperature reaction kettle is reduced.
In conclusion, the invention has the following beneficial effects:
1. through multi-wheel drawing and screening, the yield is improved, and the waste of materials is reduced;
2. by adding the intermediate alloy, the problem that nickel and aluminum are difficult to melt is solved, and the reliability of the alloy wire is improved;
3. the wire rod after acid cleaning is blown with carbon dioxide by a high-pressure spray gun, so that the surface hydrogen corrosion of the wire rod is reduced;
4. the negative electrode alloy wire is prepared by adopting the component proportion and the preparation process in the patent, and a thermocouple made of a standard positive electrode nickel-chromium alloy wire is adopted for temperature precision detection, so that the standard I-grade standard of the industry is met at the temperature of 0-1000 ℃, and the standard II-grade standard of the industry is met at the high temperature of 0-1200 ℃. Compared with a K-type thermocouple in the prior art, the precision is obviously improved under the high-temperature condition.
Drawings
FIG. 1 is a schematic structural view of a high-temperature reaction kettle;
FIG. 2 is a schematic view of the internal structure of a high-temperature reaction vessel;
FIG. 3 is a schematic view of the blowing apparatus and mounting assembly;
fig. 4 is an enlarged view of a portion a in fig. 3.
In the figure: 1. a base; 11. a control panel; 2. a kettle body; 21. a snap ring; 3. a blowing device; 31. blowing a pipe; 311. a blowing unit; 312. a breather pipe; 313. blowing holes; 32. a gas cylinder; 33. an air pump; 4. a heating assembly; 5. mounting the component; 51. mounting a bracket; 511. a support shaft; 512. a support disc; 52. a drive motor; 53. a mounting head; 531. mounting holes; 532. a deformation groove; 533. a deformable sheet; 534. anti-skid lines; 54. and (4) clamping the nut.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The various raw materials and sources used in this patent are as follows:
the lanthanum-rich rare earth (the mass fractions of the components are 45% of lanthanum, 15% of cerium, 18% of praseodymium, 16% of neodymium and 6% of other rare earth elements) is tin-free.
A negative electrode alloy wire of a K-type thermocouple is made of nickel-aluminum alloy and comprises, by mass, 0.4% -1.2% of cobalt, 0.8% -1.7% of manganese, 1.2% -2.5% of aluminum, 0.05% -0.2% of iron, 0.05% -0.2% of yttrium, 0.1% -0.5% of niobium, 0.1% -0.5% of vanadium, 0.05% -0.1% of carbon, 0.3% -0.7% of silicon, 0.4% -0.8% of copper, 0.05% -0.2% of lanthanum-rich rare earth and the balance of nickel.
A preparation process of a negative electrode alloy wire of a K-type thermocouple comprises the following steps:
s1, shearing: shearing the raw materials into strip blocks or balls;
cutting nickel into strips with the length of 5-8cm, the width of 5-8cm and the height of 20-30 cm; beating the silicon into a spherical shape with the diameter of about 2 cm; cutting the cobalt, yttrium and lanthanum-rich rare earth into 1 × 3cm strips.
S2, batching: proportioning the raw materials after shearing according to a proportion;
s3, smelting: putting the raw materials after the burdening into a vacuum smelting furnace for vacuum smelting;
wherein S3 specifically includes:
b1, firstly, smelting aluminum and nickel into an intermediate alloy, wherein the intermediate alloy comprises 60 mass percent of nickel and 40 mass percent of aluminum, and adding the proportioned aluminum and nickel into a vacuum smelting furnace for smelting;
b2, after the aluminum and the nickel are fully melted, adding lanthanum-rich rare earth, continuously melting, and pouring into a steel mould for cooling after melting for 1 minute at 1500 ℃;
b3, sampling and detecting the nickel-aluminum alloy, calculating the amount of the added intermediate alloy according to the requirement of the aluminum content in the formula, and adding the rest nickel;
and B4, putting the proportioned intermediate alloy and nickel into a vacuum smelting furnace, heating and smelting, and adding other small materials into the vacuum smelting furnace after the intermediate alloy and the nickel are fully molten.
S4, forging: forging and correcting the smelted wire, wherein the surface is required to be smooth, burr-free and pit-free;
s5, processing: processing the forged wire rod into a finished product;
wherein, S5 specifically includes:
a1, first annealing treatment: performing primary annealing treatment on the forged wire rod, wherein the primary annealing treatment is cover annealing;
after the wire rod is charged into a furnace, vacuumizing is firstly carried out, argon is charged until the pressure is-0.4 MPa, the temperature is kept for 0.5h at 400 ℃, then the temperature is raised to 900 ℃, the temperature is kept for 2.5h, then the temperature is lowered to 400 ℃, the temperature is kept for 0.5h, and then the first annealing treatment is completed;
a2, first drawing treatment: drawing for many times, wherein the diameter is 8.5mm to 8mm, then drawing to 7.5mm, 7mm, 6.5mm, 6mm, 5.5mm, 5mm, 4.5mm, 4mm, 3.5mm and 3mm in sequence, and finally drawing to 2.6 mm;
a3, first acid washing: pickling the wire subjected to the first round of drawing treatment to remove surface oxide skin and rusty materials;
a4, second annealing treatment: carrying out secondary annealing treatment on the forged wire rod, wherein the secondary annealing treatment is continuous annealing;
after the wire rod is charged into a furnace, vacuumizing is firstly carried out, argon is charged until the pressure is minus 0.1MPa, the temperature is kept at 850 ℃ for 0.5h, then the temperature is reduced to 800 ℃, the temperature is kept for 2.5h, finally the temperature is reduced to 600 ℃, the temperature is kept for 0.5h, and then secondary annealing is completed;
a5, second round drawing treatment: drawing for multiple times, namely drawing from 2.6mm to 2.3mm in diameter, then drawing to 2mm, 1.8mm, 1.58mm and 1.48mm in sequence, and finally drawing to 1.37mm to prepare a semi-finished product;
a6, screening: screening finished products after the second round of drawing treatment, continuing unqualified products, and continuing A7 on qualified semi-finished products;
a7, third drawing treatment: drawing for multiple times, namely drawing to 1.18mm from the diameter of 1.37mm, then drawing to 1mm, 0.82mm and 0.65mm in sequence, and finally drawing to 0.53mm to obtain a finished product;
a8, secondary acid washing: pickling the screened qualified semi-finished product, and removing oxide skin and rusty materials on the surface of the qualified semi-finished product;
a9, third annealing treatment: and carrying out third annealing treatment on the semi-finished product subjected to the second pickling, wherein the specific steps of the third annealing treatment are consistent with those of the second annealing treatment.
A10, dehydrogenation treatment: and placing the smelted finished product in a high-temperature reaction kettle, and blowing carbon dioxide on the surface of the finished product by using a high-pressure spray gun. And an alkaline drying agent is placed in the high-temperature reaction kettle.
Referring to fig. 1 and 2, the high-temperature reaction kettle used in the preparation process comprises a base 1, a kettle body 2, a blowing device 3, a heating assembly 4 and a mounting assembly 5 for mounting wires. The cauldron body 2 is installed on base 1, and installation component 5 installs in the cauldron body 2, and heating element 4 installs on the inner peripheral surface of the cauldron body 2. One side of the base 1 is provided with a control panel 11.
The blowing device 3 comprises a blowing pipe 31 arranged in the kettle body 2, an air bottle 32 communicated with the blowing pipe 31 and an air pump 33 arranged between the air bottle 32 and the blowing pipe 31. Carbon dioxide in the gas cylinder 32 is sent into the kettle body 2 through the blowing pipe 31 by the air pump 33.
Referring to fig. 3, the blowing pipe 31 is configured in a tower shape with multiple layers, and includes multiple annular blowing units 311, adjacent blowing units 311 are connected by multiple air pipes 312, and the air pipes 312 are uniformly distributed along the blowing units 311. The blowing unit 311 has a plurality of blowing holes 313 opened toward the mounting block 5.
A plurality of clamping rings 21 are arranged on the inner wall of the kettle body 2, and the blowing pipe 31 is clamped in the clamping rings 21, so that the blowing pipe 31 is fixedly installed.
The mounting assembly 5 comprises a mounting bracket 51 mounted in the middle of the kettle body 2, a driving motor 52 mounted on the top of the kettle body 2, and a plurality of mounting heads 53 mounted on the mounting bracket 51. The mounting bracket 51 comprises a supporting shaft 511 which rotates synchronously with the rotating shaft of the driving motor 52 and a supporting plate 512 mounted on the upper part of the supporting shaft 511, and the mounting heads 53 are uniformly distributed on the lower surface of the supporting plate 512.
Referring to fig. 3 and 4, the mounting head 53 is provided at a middle portion thereof with a mounting hole 531 for inserting a wire, the mounting head 53 is provided at a lower end of a sidewall thereof with a plurality of deformation grooves 532, the deformation grooves 532 divide the sidewall of the mounting head 53 into a plurality of deformation pieces 533, and the mounting head 53 is provided at an upper portion thereof with a clamping nut 54 for pressing the deformation pieces 533. The mounting head 53 gradually increases in diameter from an end distant from the mouth of the mounting hole 531 to an end close to the mouth of the mounting hole 531.
When the wire is installed, the wire is installed in the installation hole 531, the deformation piece 533 is pressed by rotating the clamping nut 54, and the deformation piece 533 clamps the wire, thereby realizing the installation and fixation of the wire.
The inner side of the deformation sheet 533 is provided with the anti-slip texture 534, so that the friction force between the deformation sheet and the wire rod is increased, and the stability of the wire rod installation is improved.
During operation, carbon dioxide is blown to the mounting bracket 51 through the blowing pipe 31 by the air pump 33, the driving motor 52 drives the mounting assembly 5 to rotate, and further drives the wires mounted on the mounting assembly 5 to rotate, so that the blowing of the carbon dioxide to the wires is more uniform. On one hand, the high-temperature airflow blows out the hydrogen on the surface of the wire rod, so that the amount of the hydrogen attached to the surface of the wire rod is quickly reduced; on the other hand, in a high-temperature environment, carbon dioxide reacts with hydrogen, thereby removing hydrogen.
S6, checking and warehousing: and (4) inspecting the processed finished product by using a thermocouple verification furnace, storing the qualified product in a storehouse, and returning the unqualified product to the furnace for smelting again.
Thermocouples made of negative electrode alloy wires with different raw material ratios were tested according to the relevant regulations of the JJG351-1996 working base metal thermocouple calibration protocol.
Negative electrode alloy wire of thermocouple in comparative example 1: replacing the aluminum in the patent with the increased silicon content in the alloy to prepare a negative alloy wire;
negative electrode alloy wire of thermocouple in comparative example 2: removing yttrium in the alloy to prepare a negative alloy wire;
negative electrode alloy wire of thermocouple in comparative example 3: removing yttrium in the alloy and adding silicon to replace aluminum in the alloy to prepare a negative alloy wire;
negative electrode alloy wire of thermocouple in comparative example 4: a common negative electrode nickel-silicon alloy wire is sold in the market.
The positive electrode alloy wires are standard nickel-chromium alloy wires (containing 10 mass percent of chromium and 90 mass percent of nickel) with uniform specification, thermocouples are prepared, and the standard nickel-chromium alloy wires are obtained by measuring for 200 hours at the conditions of 0 ℃, 100 ℃, 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ and 1200 ℃ respectively.
Table 1 table for measuring the accuracy of alloy wires with different contents of components under high temperature condition
According to the regulation of the K-type thermocouple tolerance in GB/T16839.2, the alloy wires are prepared according to the component proportion and the preparation process in the patent, and the thermocouples made of the standard positive electrode nichrome wires meet the industrial grade I standard at the temperature of 0-1000 ℃ and meet the industrial grade II standard at the high temperature of 0-1200 ℃. Compared with a K-type thermocouple in the prior art, the precision is obviously improved under the working environment of 0-1200 ℃.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (9)
1. The negative electrode alloy wire of the K-type thermocouple is characterized by being made of nickel-aluminum alloy and comprising, by mass, 0.4% -1.2% of cobalt, 0.8% -1.7% of manganese, 1.2% -2.5% of aluminum, 0.05% -0.2% of iron, 0.05% -0.2% of yttrium, 0.1% -0.5% of niobium, 0.1% -0.5% of vanadium, 0.05% -0.1% of carbon and the balance of nickel;
the negative electrode alloy wire also comprises lanthanum-rich rare earth with the mass fraction of 0.05-0.2%;
a preparation process of a negative electrode alloy wire of a K-type thermocouple comprises the following steps:
s1, shearing: shearing the raw materials into strip blocks or balls;
s2, batching: proportioning the raw materials after shearing according to a proportion;
s3, smelting: putting the raw materials after the burdening into a vacuum smelting furnace for vacuum smelting and cooling and forming;
s4, forging: forging and correcting the smelted wire;
s5, processing: drawing the forged wire to form a finished product;
a1, first annealing treatment: performing primary annealing treatment on the forged wire rod, wherein the primary annealing treatment is cover annealing;
a2, first drawing treatment: drawing for multiple times, and gradually drawing from 8.5mm to 2.6mm in diameter;
a3, first acid washing: pickling the wire subjected to the first round of drawing treatment to remove surface oxide skin and rusty materials;
a4, second annealing treatment: carrying out secondary annealing treatment on the forged wire rod, wherein the secondary annealing treatment is continuous annealing;
a5, second round drawing treatment: drawing for multiple times, and gradually drawing from the diameter of 2.6mm to 1.37mm to prepare a semi-finished product;
a6, screening: screening the semi-finished products after the second round of drawing treatment, manufacturing unqualified products into other products according to conditions, and continuously performing A7 on qualified semi-finished products;
a7, third drawing treatment: drawing for multiple times, and gradually drawing to 0.53mm from 1.37mm in diameter to obtain a finished product;
a8, secondary acid washing: pickling the screened qualified semi-finished product, and removing oxide skin and rusty materials on the surface of the qualified semi-finished product;
a9, third annealing treatment: carrying out third annealing treatment on the semi-finished product subjected to the second pickling, wherein the third annealing treatment is continuous annealing;
s6, checking and warehousing: and (5) inspecting the processed finished product, and storing the qualified product in a warehouse.
2. The negative electrode alloy wire of a K-type thermocouple according to claim 1, wherein the negative electrode alloy wire further comprises silicon in an amount of 0.3 to 0.7 mass%.
3. The negative electrode alloy wire of a K-type thermocouple according to claim 1, further comprising copper in an amount of 0.4% to 0.8% by mass.
4. A process for preparing a negative electrode alloy wire of a K-type thermocouple according to any one of claims 1 to 3, comprising the steps of:
s1, shearing: shearing the raw materials into strip blocks or balls;
s2, batching: proportioning the raw materials after shearing according to a proportion;
s3, smelting: putting the raw materials after the burdening into a vacuum smelting furnace for vacuum smelting and cooling and forming;
s4, forging: forging and correcting the smelted wire;
s5, processing: drawing the forged wire to form a finished product;
s6, checking and warehousing: and (5) inspecting the processed finished product, and storing the qualified product in a warehouse.
5. The preparation process of the negative electrode alloy wire of the K-type thermocouple according to claim 4, wherein the S5 specifically comprises the following steps:
a1, first annealing treatment: performing primary annealing treatment on the forged wire rod, wherein the primary annealing treatment is cover annealing;
a2, first drawing treatment: drawing for multiple times, and gradually drawing from 8.5mm to 2.6mm in diameter;
a3, first acid washing: pickling the wire subjected to the first round of drawing treatment to remove surface oxide skin and rusty materials;
a4, second annealing treatment: carrying out secondary annealing treatment on the forged wire rod, wherein the secondary annealing treatment is continuous annealing;
a5, second round drawing treatment: drawing for multiple times, and gradually drawing from the diameter of 2.6mm to 1.37mm to prepare a semi-finished product;
a6, screening: screening the semi-finished products after the second round of drawing treatment, manufacturing unqualified products into other products according to conditions, and continuously performing A7 on qualified semi-finished products;
a7, third drawing treatment: drawing for multiple times, and gradually drawing to 0.53mm from 1.37mm in diameter to obtain a finished product;
a8, secondary acid washing: pickling the screened qualified semi-finished product, and removing oxide skin and rusty materials on the surface of the qualified semi-finished product;
a9, third annealing treatment: and carrying out third annealing treatment on the semi-finished product subjected to the second pickling, wherein the third annealing treatment is continuous annealing.
6. The preparation process of the negative electrode alloy wire of the K-type thermocouple according to claim 4, wherein the step S3 specifically comprises the following steps:
b1, firstly, smelting aluminum and nickel into an intermediate alloy, wherein the intermediate alloy comprises 60 mass percent of nickel and 40 mass percent of aluminum, and adding the proportioned aluminum and nickel into a vacuum smelting furnace for smelting;
b2, after the aluminum and the nickel are fully melted, adding lanthanum-rich rare earth, continuously melting, and pouring into a steel mould for cooling after melting for 1 minute at 1500 ℃;
b3, sampling and detecting the nickel-aluminum alloy, calculating the amount of the added intermediate alloy according to the requirement of the aluminum content in the formula, and adding the rest nickel;
and B4, putting the proportioned intermediate alloy and nickel into a vacuum smelting furnace, heating and smelting, and adding other small materials into the vacuum smelting furnace after the intermediate alloy and the nickel are fully molten.
7. The process for preparing the negative electrode alloy wire of the K-type thermocouple according to claim 5, wherein the process is continued after A9 is finished
A10, dehydrogenation treatment: and blowing the surface of the smelted finished product by using a high-pressure spray gun.
8. The process for preparing the negative electrode alloy wire of the K-type thermocouple according to claim 7, wherein during dehydrogenation, a finished product is placed in a high-temperature reaction kettle, and carbon dioxide is used as a gas for a high-pressure spray gun.
9. The process for preparing the negative electrode alloy wire of the K-shaped thermocouple according to claim 8, wherein an alkaline drying agent is placed in the high-temperature reaction kettle.
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| CN111057908A (en) * | 2019-12-26 | 2020-04-24 | 江阴市诚信合金材料有限公司 | High-adaptability low-cost nickel-chromium-nickel-silicon thermocouple wire and production process thereof |
| CN112760501B (en) * | 2020-12-22 | 2022-02-01 | 江苏威拉里新材料科技有限公司 | High-temperature-resistant nickel-based alloy integrated equipment and processing technology |
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