CN115321494B - Cubic boron nitride alkali treatment and purification process - Google Patents
Cubic boron nitride alkali treatment and purification process Download PDFInfo
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- 239000003513 alkali Substances 0.000 title claims abstract description 191
- 229910052582 BN Inorganic materials 0.000 title claims abstract description 142
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 title claims abstract description 142
- 238000000746 purification Methods 0.000 title claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 100
- 238000009835 boiling Methods 0.000 claims abstract description 76
- 238000000034 method Methods 0.000 claims abstract description 63
- 239000012535 impurity Substances 0.000 claims abstract description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 69
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 24
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 23
- 239000000203 mixture Substances 0.000 claims description 19
- 238000004140 cleaning Methods 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 15
- 238000002791 soaking Methods 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 13
- 238000000926 separation method Methods 0.000 claims description 13
- 239000002253 acid Substances 0.000 claims description 12
- 239000003054 catalyst Substances 0.000 claims description 11
- 238000000498 ball milling Methods 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- 238000007873 sieving Methods 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 6
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 238000004506 ultrasonic cleaning Methods 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 4
- 238000001704 evaporation Methods 0.000 claims description 4
- 230000008020 evaporation Effects 0.000 claims description 4
- 239000012467 final product Substances 0.000 claims description 4
- PXXKQOPKNFECSZ-UHFFFAOYSA-N platinum rhodium Chemical compound [Rh].[Pt] PXXKQOPKNFECSZ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052903 pyrophyllite Inorganic materials 0.000 claims description 4
- 239000011265 semifinished product Substances 0.000 claims description 4
- 238000009210 therapy by ultrasound Methods 0.000 claims description 4
- 238000005259 measurement Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims 1
- 239000000047 product Substances 0.000 abstract description 69
- 238000006243 chemical reaction Methods 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 239000012264 purified product Substances 0.000 abstract description 4
- 238000009776 industrial production Methods 0.000 abstract description 3
- 238000012544 monitoring process Methods 0.000 abstract description 3
- 239000000126 substance Substances 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 15
- 238000002844 melting Methods 0.000 description 9
- 230000008018 melting Effects 0.000 description 9
- 238000003756 stirring Methods 0.000 description 6
- 239000002699 waste material Substances 0.000 description 5
- 238000011010 flushing procedure Methods 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 229910000746 Structural steel Inorganic materials 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- -1 bright surface Substances 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000011538 cleaning material Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004836 empirical method Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
- C01B21/0648—After-treatment, e.g. grinding, purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention belongs to the technical field of superhard material purification, and particularly relates to a cubic boron nitride alkali treatment and purification process. The process can realize the purification of the cubic boron nitride product through the working procedures of pretreatment, alkali dissolving treatment, post treatment and the like, and the impurity content in the purified product is not more than 0.4 weight percent, so that the product meets the acceptance criterion. The process can control key temperature control points in the alkali boiling process, reduce the reverse conversion probability of products and reduce loss, thereby improving the labor efficiency and the product quality and being beneficial to industrial production. The process method ensures the full reaction of the hexagonal boron nitride and the alkali substances by determining the proper alkali dosage and monitoring the slope of the temperature curve, avoids the occurrence of hexagonal boron nitride impurities in the product, lays a foundation for the quality of the product, and greatly reduces the reworking probability.
Description
Technical Field
The invention belongs to the technical field of superhard material purification, and particularly relates to a cubic boron nitride alkali treatment and purification process.
Background
Cubic Boron Nitride (CBN) is an artificially synthesized superhard material, has high hardness and good wear resistance, and has wide application in the machining industry. Cubic boron nitride is synthesized from hexagonal boron nitride and a catalyst at high temperature and high pressure, and can replace artificial diamond in certain fields. The most important characteristic of cubic boron nitride is that after mixing with alkali, when a certain temperature is reached, the cubic boron nitride is reversely converted, namely, part of the cubic boron nitride is converted into hexagonal boron nitride, so that the prepared cubic boron nitride product needs to be purified.
The alkali treatment is a core step in the purification process of the cubic boron nitride product, and mainly comprises the steps of uniformly stirring the cubic boron nitride material (product containing hexagonal boron nitride impurities), industrial alkali (NaOH and the like) and water according to a certain proportion to form a mixture, putting the mixture into an alkali pot (each alkali pot has the capacity of about 24kg and the size of phi 300 x 300), heating the mixture on an electric furnace, reacting the heated alkali liquor with hexagonal boron nitride by utilizing high-temperature alkali liquor to remove the hexagonal boron nitride impurities, and thus realizing the purification of the opposite cubic boron nitride product.
The alkali treatment process of the cubic boron nitride product has 7 key points, specifically: 1. the proportion of alkali to materials; 2. how to lower the melting point; 3. the amount of water used; 4. after the hexagonal boron nitride and the alkali are completely reacted, the temperature point at which the cubic boron nitride starts to reversely transform; 5. the state of the alkali mixture at the beginning of the alkali formation after cooling; 6. alkali dissolving process; 7. and (5) cleaning materials. These key points are all the process steps which can influence the purification effect of the cubic boron nitride product, so accurate regulation and control are required.
However, the existing alkali treatment process of the cubic boron nitride product is basically manually operated, and key control points are all empirically and lack reliability. In order to reduce the risk of the alkali treatment process, improve the efficiency and realize the operation automation, it is necessary to provide a new process for treating and purifying the cubic boron nitride alkali so as to overcome the defects in the prior operation.
Disclosure of Invention
Aiming at the technical problems, the invention aims to provide a process for treating and purifying cubic boron nitride alkali, which can realize the purification of the cubic boron nitride product through the working procedures of pretreatment, alkali dissolving treatment, post-treatment and the like and meets the acceptance standard of national standard (GB/T6408-2018 superhard abrasive cubic boron nitride).
The process can control key temperature control points in the alkali boiling process, reduce the reverse conversion probability of products and reduce loss, thereby improving the labor efficiency and the product quality and being beneficial to industrial production.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a process for treating and purifying cubic boron nitride alkali comprises the following steps:
first pretreatment
(1) Primary separation: adding water into a cubic boron nitride synthetic rod block (the synthetic rod block is a cubic boron nitride semi-finished product synthesized by using hexagonal boron nitride and catalyst raw materials, and contains incompletely converted hexagonal boron nitride, and impurities such as auxiliary carbon paper, metal catalyst, pyrophyllite and the like), stirring and mixing uniformly to obtain a mixture, and vibrating on a shaking table; after separation by a shaking table, ball milling is carried out for 0.5 to 1.5 hours by using a ball mill to remove hexagonal boron nitride stuck on the cubic boron nitride, and the leftover materials formed by the cubic boron nitride crystal are removed, and meanwhile, free hexagonal boron nitride is broken to obtain a mixed material containing the cubic boron nitride, the hexagonal boron nitride and impurities;
(2) Acid soaking: adding industrial hydrochloric acid into the mixture after primary separation for soaking for 20-30 min;
(3) Ultrasonic impurity removal: adding water into the mixed material after acid soaking, and performing ultrasonic treatment for 2-5 min to separate cubic boron nitride from impurities to obtain a cubic boron nitride material;
(II) alkali boiling treatment
(4) Mixing the pretreated cubic boron nitride material with mixed alkali and water to obtain mixed liquid, and heating and boiling alkali by using a thermocouple; when the alkali is boiled, water is evaporated continuously along with the continuous increase of the temperature, when the temperature is increased to the state that the alkali is in a molten state, hexagonal boron nitride starts to react with the alkali, and when the hexagonal boron nitride finishes reacting, cubic boron nitride starts to reversely convert, and heating is stopped at the moment, so that the alkali boiling is completed;
(III) cooling and alkali treatment
(5) Cooling the mixture after alkali boiling treatment, separating alkali from the material and in a semi-solidification state when the temperature is reduced to 140-180 ℃, adding water to dissolve the alkali, adding the water to form semi-solid paste, pouring the alkali out, and finally obtaining the material after alkali boiling and purification;
(IV) post-treatment
(6) Primary cleaning: cleaning the material subjected to alkali boiling and purification by using clear water;
(7) Ultrasonic cleaning: adding deionized water into the cleaned material, and ultrasonically cleaning for 2-5 min;
(8) Sieving: and drying and sieving the cleaned material to obtain a final product.
Preferably, in the step (1), the type of the ball mill used for ball milling is QHQM-100, and the ball milling rotating speed is 40-60 r/min.
Preferably, in the step (2), the addition amount of the industrial hydrochloric acid is as follows: 1800-2000 ml of hydrochloric acid with mass fraction of 37% is added into every 5 ten thousand ct mixed material.
Preferably, in the step (3), the model of an ultrasonic instrument used in ultrasonic treatment is JRC-2500, the ultrasonic power is 2-3 kw, and the ultrasonic impurity removal treatment is carried out for 2-3 times.
Preferably, in the step (4), the ratio (mass ratio) of the obtained cubic boron nitride material to the mixed alkali is 1 (0.2-0.6).
Preferably, in the step (4), the water is used in an amount of: every 3 ten thousand ct (6 kg), the water consumption is 1000 ml-1200 ml water, namely the solid-liquid ratio of the materials and the water is 6g: (1-1.2) mL; in the process of boiling alkali, proper amount of water is added to accelerate the melting speed of alkali liquor, so that the materials and the alkali are fully mixed.
Preferably, in the step (4), the thermocouple is a WRP-130 type platinum-rhodium thermocouple, the working temperature range is 0-1600 ℃, and a stainless steel sleeve is arranged outside the thermocouple.
Preferably, in the step (4), the model of the temperature recorder is FX1004, the specification is-4-3-L, an alarm is arranged on the temperature recorder, and the trend of a temperature curve is monitored through the temperature recorder; the early stage of alkali boiling is water boiling, the temperature slowly rises in the water evaporation process, and the slope of a curve of the temperature changing along with time is relatively stable; when the moisture is completely evaporated, the temperature continues to rise, the alkali is in a molten state, the hexagonal boron nitride reacts with the alkali, and the slope of a curve of the temperature change along with time is slowly increased; when the hexagonal boron nitride is reacted, the cubic boron nitride starts to reversely convert, the temperature is suddenly accelerated to rise, the slope of a curve of the temperature changing along with time is multiplied, the temperature is set to be the alarm temperature of the alarm, and the cubic boron nitride starts to react with alkali at the temperature, and the heating should be stopped immediately to finish the alkali boiling process;
through the test, the following results were obtained:
if the slope of the curve of the temperature change along with time is stable (the alarm temperature is not reached at the moment), stopping heating, and obtaining a product with obvious hexagonal boron nitride impurities when the product is subjected to microscopic examination, wherein the product needs to be reworked, and the material loss is about 2% compared with the weight of the product after alkali boiling;
when the slope of the curve of the temperature change along with time is multiplied greatly (namely, the slope of the temperature change curve suddenly rises and reaches the alarm temperature at the moment), heating is stopped immediately at the moment, the impurity content of the obtained product is not more than 0.4wt% (the quality inspection standard of national standard (GB/T6408-2018 ultra-hard abrasive cubic boron nitride: impurities are not easy to find) after microscopic inspection, at the moment, the material loss is about 3% compared with the weight after alkali boiling, the shape and the angle of the material are clear, and the surface of a few crystal forms has corrosion phenomenon;
when the slope of the curve of the temperature change along with time is multiplied, continuously boiling alkali for a plurality of minutes (when the temperature exceeds the alarm temperature), stopping heating (taking continuous alkali boiling for 10 minutes as an example), and comparing the weight of the material before alkali boiling with that of the material after alkali boiling, wherein the material loses about 10 percent (the material is subjected to inverse conversion and cubic boron nitride participates in reaction), and although impurities are not visible, the surface of the material is completely corroded, and the crystal form is round; although the alkali boiling time can be properly prolonged to obtain materials with different crystal forms after the alarm occurs, the morphology, physical and chemical properties, bulk density and the like of the materials are changed, and the materials cannot be used as raw materials of cutting tools.
Preferably, in the step (4), the proportion of the mixed alkali is as follows: naOH: koh=3 (2 to 2.5) (mass ratio); the melting point of NaOH or KOH is above 318 ℃, and the melting point is not easy to reach by using single alkali, and the energy consumption is increased, so that when NaOH and KOH are mixed in proportion, the melting point is reduced to about 300 ℃, and the melting point in melting is reduced, thereby saving energy.
Preferably, in the step (5), the alkali liquor is prevented from splashing by adding water for a plurality of times, the water is added for 3-5 times, the water adding interval is 2-3 min, and the total water adding amount is 1200-1600 ml.
Preferably, in the step (6), the clean water is washed for 2 to 3 times.
Preferably, in the step (7), the ultrasonic cleaning is carried out for 2 to 3 times.
Preferably, in the step (7), the ultrasonic power is 2-3 kw.
The process can realize the purification of the cubic boron nitride product through the working procedures of pretreatment, alkali treatment, post treatment and the like, and the impurity content in the purified product is not more than 0.4wt% and meets the acceptance standard of national standard (GB/T6408-2018 superhard abrasive cubic boron nitride).
Compared with the prior art, the invention has the beneficial effects that:
1. the alkali treatment method of the invention obviously improves the efficiency and reduces the labor intensity; the process method avoids waste caused by excessive alkali amount and environmental pollution by determining the dosage ratio of the materials and the alkali.
2. The alkali treatment purification process disclosed by the invention can accurately control key points of the inverse transformation of the cubic boron nitride, provides accurate information for operators, and avoids misuse of an empirical method by people.
3. The process method ensures the full reaction of the hexagonal boron nitride and the alkali substances by determining the proper alkali dosage and monitoring the slope of the temperature curve, avoids the occurrence of hexagonal boron nitride impurities in the product, lays a foundation for the quality of the product, and greatly reduces the reworking probability.
4. The process method reduces splashing of alkali liquor, obviously improves the safety coefficient and reduces the potential safety hazard by monitoring the temperature during alkali dissolution.
Drawings
FIG. 1 is a microscopic view of the product of comparative example 1;
FIG. 2 is a microscopic view of the product of example 1;
FIG. 3 is a microscopic view of the product of comparative example 2;
FIG. 4 is a microscopic image of the product of comparative example 3;
FIG. 5 is a microscopic view of the product of example 2;
FIG. 6 is a microscopic image of the product of comparative example 4.
Detailed Description
The following description will clearly and fully describe the technical solutions of the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The cubic boron nitride alkali treatment and purification process comprises the following steps of pretreatment, alkali treatment, post-treatment and the like, and the concrete steps are as follows:
first pretreatment
(1) Separating by a shaking table: placing a synthetic rod block (the synthetic rod block is a semi-finished product of cubic boron nitride synthesized by using hexagonal boron nitride and catalyst raw materials, and contains incompletely converted hexagonal boron nitride, and impurities such as auxiliary carbon paper, metal catalyst, pyrophyllite and the like) in a stirring tank, adding water, fully stirring to obtain a mixture, and vibrating the mixture on a shaking table to perform primary separation of the hexagonal boron nitride and the cubic boron nitride;
(2) Ball milling and separation: after separation by the shaking table, the free hexagonal boron nitride still adheres to the cubic boron nitride, and meanwhile, some cubic boron nitride adheres to each other to form a crystal, so that each single crystal needs to be separated;
the method comprises the following specific steps: ball milling is carried out for 30min (ball milling rotating speed is 45 r/min) by using a ball mill (model: QHQM-100), hexagonal boron nitride stuck on the cubic boron nitride is knocked off, scraps formed by some cubic boron nitride crystal are removed, and meanwhile, free hexagonal boron nitride is smashed, so that a mixed material containing the cubic boron nitride, the hexagonal boron nitride and impurities is obtained;
(3) Acid soaking
Adding industrial hydrochloric acid (the addition amount of the hydrochloric acid is that 2000ml of hydrochloric acid with the mass fraction of 37% is added to every 5 ten thousand ct of mixed materials) into the ball-milled mixed materials for soaking for half an hour, and rubbing for one time; as the hexagonal boron nitride is alkaline, the acid soaking plays a role in neutralization, the hexagonal boron nitride can become loose, the weight of the hexagonal boron nitride becomes light, carbon paper in impurities can become loose after the acid soaking, and the acid can also react with unreacted catalyst (metal) in the mixed material, so that partial impurities in the mixed material are removed, and the separation of a shaking table is facilitated;
(4) Ultrasonic wave edulcoration
Adding water (about 3500 ml) into the kneaded mixture, treating for 3min by using ultrasonic waves (model of ultrasonic instrument: JRC-2500), wherein the ultrasonic power is 2.5kw, part of lighter hexagonal boron nitride and carbon paper impurities can float on the surface, the cubic boron nitride is heavier and can sink, then pouring water and shaking to separate the cubic boron nitride from the impurities, and obtaining the cubic boron nitride material, and the step is operated for 2-3 times;
(II) alkali boiling treatment
(5) Mixing the pretreated cubic boron nitride material with mixed alkali and water, placing the mixture in an alkali pot to obtain mixed liquid, then inserting a temperature guide head of a thermocouple into the mixed liquid for heating, and boiling the alkali, wherein in the embodiment, a WRP-130 type platinum-rhodium thermocouple is adopted, the working temperature range is 0-1600 ℃, and a stainless steel sleeve is arranged outside the thermocouple;
the alkali dosage and the water dosage in the alkali boiling process are specifically as follows:
in the embodiment, the pretreated cubic boron nitride material is a product with the grade of CBN220 (the product with the grade is amber monocrystal, regular crystal form, high crystal transparency, high strength, strong wear resistance, wide application range and stronger service life, and belongs to the class of CBN 200), and after pretreatment, the material with the weight of 3 ten thousand ct (the impurity content is more than 3 wt%) is taken for alkali boiling treatment; in the embodiment, the adding amount of the alkali-boiling mixed alkali is 1.8kg (wherein, the alkali-boiling mixed alkali comprises 1.08kg of NaOH and 0.72kg of KOH, and the ratio of the NaOH to the KOH is 3:2), namely, the mass ratio of the materials to the mixed alkali is=1:0.3, and 1200ml of water is added in the alkali-boiling process; when boiling alkali, the temperature guide head of the thermocouple is inserted into the mixed solution for heating;
according to different product strengths (low-strength, medium-strength and high-strength products according to the strength), the proportion of materials to alkali can be finely adjusted, so that waste caused by excessive alkali consumption is avoided, and the environment is polluted; the waste such as reworking caused by insufficient alkali amount and unclean treatment is avoided;
in the process of boiling alkali, a proper amount of water is added to accelerate the melting speed of alkali liquor, so that the materials and the alkali are fully mixed;
the method for judging the time for completing the alkali boiling comprises the following steps:
the thermocouple is connected with a temperature recorder (model: FX1004 specification: 4-3-L) through an electric signal, the temperature recorder can receive a temperature signal of the thermocouple and record a change curve of temperature along with time, and an alarm is arranged on the temperature recorder; in the measurement process, a curve of temperature change along with time is obtained through a temperature recorder, the slope of the temperature change curve is calculated, and whether to terminate alkali boiling is judged through the change of the slope;
the connection mode of the thermocouple and the temperature recorder in the invention is a common mode in the prior art and is not an invention point of the invention, so that the connection mode is not repeated;
in the process, the trend of a temperature curve needs to be monitored; the early stage of alkali boiling is water boiling, the temperature slowly rises in the water evaporation process, and the slope of a curve of the temperature changing along with time is relatively stable; when the moisture is completely evaporated, the temperature continues to rise, the alkali is in a molten state, the hexagonal boron nitride reacts with the alkali, and the slope of a curve of the temperature change along with time is slowly increased; when the hexagonal boron nitride is reacted, the cubic boron nitride starts to reversely convert, the temperature is suddenly accelerated to rise, the slope of a curve of the temperature changing along with time is multiplied, the temperature is set to be the alarm temperature of the alarm, and the cubic boron nitride starts to react with alkali at the temperature, and the heating should be stopped immediately to finish the alkali boiling process;
finally determining the decision criteria of boiling alkali as follows: taking the abrupt rise of the slope of the temperature change curve as a standard for judging completion of alkali boiling, and setting the temperature at the moment as the alarm temperature of an alarm;
specifically, in this embodiment, the slope of the temperature change curve is recorded, when the alkali is boiled for 90min, the slope of the temperature change curve suddenly rises, it is determined that the alkali is boiled at this time, and the thermocouple is closed;
(III) cooling and alkali treatment
(6) Placing the alkali pot subjected to alkali boiling treatment on an angle iron frame of 30 degrees, cooling for 30 minutes, measuring the temperature of a mixture in the alkali pot subjected to alkali boiling, measuring and displaying the temperature to be 160 ℃, separating alkali from materials and in a semi-solidification state, adding water for alkali dissolving at intervals of 2 minutes, adding water for 3 times, adding water for 1500ml, adding water for alkali to become paste, pouring out the alkali, and finally obtaining the material subjected to alkali boiling and purification;
(IV) post-treatment
(7) Primary cleaning: cleaning the material subjected to alkali boiling and purification by using clear water, flushing the material upwards from the bottom of the material during cleaning to enable the material to roll completely, and then pouring out the water, wherein the operation is repeated for three times;
(8) Ultrasonic cleaning
Adding deionized water into the cleaned material, ultrasonically cleaning for 3min, wherein the ultrasonic power is 2.5kw, slightly rotating the container, pouring out trace impurities, ultrasonically cleaning for two times, and then flushing with warm water for one time;
(9) Sieving
Drying the cleaned material, and then passing through a 40# screen mesh to obtain a final product; the purpose of sieving is that on one hand, the agglomerated materials are passed out (the materials are prevented from being connected with crystals); on the other hand, the hexagonal boron nitride is prevented from being stuck on the material wall during the alkali boiling.
Each index of the purified CBN220 product is tested, the material loss is 3.2 percent, the impurity content is not more than 0.4 weight percent compared with the weight of the product before and after alkali boiling, the standard meets the acceptance standard (impurities are not easy to find) of national standard (GB/T6408-2018 ultra-hard abrasive cubic boron nitride), the surface of the very individual material is slightly corroded, the whole edge angle is clear, the product is sharp when in use (the product granularity is 80/100, and the bulk density is 1.810), and the obtained product result is shown in figure 2.
Comparative example 1
Comparative example 1 differs from example 1 in that the thermocouple was turned off when the alkali was boiled for 80 min; then the treatment is carried out according to the same method as the cooling, alkali treatment and post treatment in the step (III) in the embodiment 1;
each index of the purified CBN220 product is tested, the material loss is 1.7% compared with the weight of the product before and after alkali boiling, the visible impurity accounts for more than 1wt%, the standard of acceptance of the impurity content of less than 0.4wt% in national standard (GB/T6408-2018 ultra-hard abrasive cubic boron nitride) is not met, reworking is required, and the obtained product result is shown in figure 1.
Comparative example 2
Comparative example 2 is different from example 1 in that when the alkali is boiled for 90min, the slope of the temperature change curve suddenly rises, and then the alkali is boiled for 10min continuously, and the thermocouple is turned off; then the treatment is carried out according to the same method as the cooling, alkali treatment and post treatment in the step (III) in the embodiment 1;
each index of the purified CBN220 product is tested, the material loss is 11.6 percent, the material surface is totally corroded, crystal grains are round and smooth, no impurities are found, the impurity content reaches the standard, but the purified product is not sharp and cannot be used as a raw material of a cutting tool, but the product is more wear-resistant (the granularity of the product is 80/100, the stacking density is 1.869, and the obtained product has the result shown in figure 3) and can only be used as a wear-resistant material.
Note that: in example 1, comparative example 2, the packing criteria for the CBN220 product with a particle size of 80/100 are:
in national standard (GB/T6408-2018 superhard abrasive cubic boron nitride), the accumulation is not lower than 1.79;
in the enterprise standard (Q/ZNJT 01-2018 cubic boron nitride technical condition), the stacking is 1.810-1.870.
Example 2
The cubic boron nitride alkali treatment and purification process comprises the following steps of pretreatment, alkali treatment, post-treatment and the like, and the concrete steps are as follows:
first pretreatment
(1) Separating by a shaking table: placing a synthetic rod block (the synthetic rod block is a semi-finished product of cubic boron nitride synthesized by using hexagonal boron nitride and catalyst raw materials, and contains incompletely converted hexagonal boron nitride, and impurities such as auxiliary carbon paper, metal catalyst, pyrophyllite and the like) in a stirring tank, adding water, fully stirring to obtain a mixture, and vibrating the mixture on a shaking table to perform primary separation of the hexagonal boron nitride and the cubic boron nitride;
(2) Ball milling and separation: after separation by the shaking table, the free hexagonal boron nitride still adheres to the cubic boron nitride, and meanwhile, some cubic boron nitride adheres to each other to form a crystal, so that each single crystal needs to be separated;
the method comprises the following specific steps: ball milling is carried out for 1.2h (ball milling rotating speed is 45 r/min) by using a ball mill (model: QHQM-100), hexagonal boron nitride stuck on the cubic boron nitride is removed, scraps formed by continuous crystals of the cubic boron nitride are removed, and meanwhile, free hexagonal boron nitride is broken up, so that a mixed material containing the cubic boron nitride, the hexagonal boron nitride and impurities is obtained;
(3) Acid soaking
Adding industrial hydrochloric acid (the addition amount of the hydrochloric acid is that 2000ml of hydrochloric acid with the mass fraction of 37% is added to every 5 ten thousand ct of mixed materials) into the ball-milled mixed materials for soaking for half an hour, and rubbing for one time; as the hexagonal boron nitride is alkaline, the acid soaking plays a role in neutralization, the hexagonal boron nitride can become loose, the weight of the hexagonal boron nitride becomes light, carbon paper in impurities can become loose after the acid soaking, and the acid can also react with unreacted catalyst (metal) in the mixed material, so that partial impurities in the mixed material are removed, and the separation of a shaking table is facilitated;
(4) Ultrasonic wave edulcoration
Adding water (about 3500 ml) into the kneaded mixture, treating for 3min by using ultrasonic waves (model of ultrasonic instrument: JRC-2500), wherein the ultrasonic power is 2.5kw, part of lighter hexagonal boron nitride and carbon paper impurities can float on the surface, the cubic boron nitride is heavier and can sink, then pouring water and shaking to separate the cubic boron nitride from the impurities, and obtaining the cubic boron nitride material, and the step is operated for 2-3 times;
(II) alkali boiling treatment
(5) Mixing the pretreated cubic boron nitride material with mixed alkali and water, placing the mixture in an alkali pot to obtain mixed liquid, then inserting a temperature guide head of a thermocouple into the mixed liquid for heating, and boiling the alkali, wherein in the embodiment, a WRP-130 type platinum-rhodium thermocouple is adopted, the working temperature range is 0-1600 ℃, and a stainless steel sleeve is arranged outside the thermocouple;
the alkali dosage and the water dosage in the alkali boiling process are specifically as follows:
in the embodiment, the pretreated cubic boron nitride material is a product with the grade of CBN121 (black single crystal, bright surface, medium strength, higher thermal stability and good sharpness and grindability) (the product with the grade of black single crystal, bright surface, medium strength, higher thermal stability and good sharpness and grindability belongs to the grade of CBN 100), and after pretreatment, the material with the weight of 3 ten thousand ct (the impurity content is more than 3 wt%) is taken for alkali boiling treatment; in the embodiment, the adding amount of the alkali boiling mixed alkali is 3kg (wherein, the alkali boiling mixed alkali comprises 1.8kg of NaOH and 1.2kg of KOH, and the ratio of the NaOH to the KOH is 3:2), namely, the mass ratio of the materials to the mixed alkali is=1:0.5, and 1400ml of water is added in the alkali boiling process; when boiling alkali, the temperature guide head of the thermocouple is inserted into the mixed solution for heating;
according to different product strengths (low-strength, medium-strength and high-strength products according to the strength), the proportion of materials to alkali can be finely adjusted, so that waste caused by excessive alkali consumption is avoided, and the environment is polluted; the waste such as reworking caused by insufficient alkali amount and unclean treatment is avoided;
in the process of boiling alkali, a proper amount of water is added to accelerate the melting speed of alkali liquor, so that the materials and the alkali are fully mixed;
the method for judging the time for completing the alkali boiling comprises the following steps:
the thermocouple is connected with a temperature recorder (model: FX1004 specification: 4-3-L) through an electric signal, the temperature recorder can receive a temperature signal of the thermocouple and record a change curve of temperature along with time, and an alarm is arranged on the temperature recorder; in the measurement process, a curve of temperature change along with time is obtained through a temperature recorder, the slope of the temperature change curve is calculated, and whether to terminate alkali boiling is judged through the change of the slope;
the connection mode of the thermocouple and the temperature recorder in the invention is a common mode in the prior art and is not an invention point of the invention, so that the connection mode is not repeated;
in the process, the trend of a temperature curve needs to be monitored; the early stage of alkali boiling is water boiling, the temperature slowly rises in the water evaporation process, and the slope of a curve of the temperature changing along with time is relatively stable; when the moisture is completely evaporated, the temperature continues to rise, the alkali is in a molten state, the hexagonal boron nitride reacts with the alkali, and the slope of a curve of the temperature change along with time is slowly increased; when the hexagonal boron nitride is reacted, the cubic boron nitride starts to reversely convert, the temperature is suddenly accelerated to rise, the slope of a curve of the temperature changing along with time is multiplied, the temperature is set to be the alarm temperature of the alarm, and the cubic boron nitride starts to react with alkali at the temperature, and the heating should be stopped immediately to finish the alkali boiling process;
finally determining the decision criteria of boiling alkali as follows: taking the abrupt rise of the slope of the temperature change curve as a standard for judging completion of alkali boiling, and setting the temperature at the moment as the alarm temperature of an alarm;
specifically, in this embodiment, the slope of the temperature change curve is recorded, when the alkali is boiled for 1.1h, the slope of the temperature change curve suddenly rises, it is determined that the alkali is boiled at this time, and the thermocouple is closed;
(III) cooling and alkali treatment
(6) Placing the alkali pot subjected to alkali boiling treatment on an angle iron frame of 30 degrees, cooling for 40min, measuring the temperature of a mixture in the alkali pot subjected to alkali boiling, measuring and displaying the temperature to be 155 ℃, separating alkali from materials and in a semi-solidification state, adding water for alkali dissolving at intervals of 3min, adding water for 5 times, adding water for 1500ml, adding water for alkali to become paste, pouring out the alkali, and finally obtaining the material subjected to alkali boiling and purification;
(IV) post-treatment
(7) Primary cleaning: cleaning the material subjected to alkali boiling and purification by using clear water, flushing the material upwards from the bottom of the material during cleaning to enable the material to roll completely, and then pouring out the water, wherein the operation is repeated for three times;
(8) Ultrasonic cleaning
Adding deionized water into the cleaned material, ultrasonically cleaning for 3min, wherein the ultrasonic power is 2.5kw, slightly rotating the container, pouring out trace impurities, ultrasonically cleaning for two times, and then flushing with warm water for one time;
(9) Sieving
Drying the cleaned material, and then passing through a 40# screen mesh to obtain a final product; the purpose of sieving is that on one hand, the agglomerated materials are passed out (the materials are prevented from being connected with crystals); on the other hand, the hexagonal boron nitride is prevented from being stuck on the material wall during the alkali boiling.
Each index of the purified CBN121 product is tested, the material loss is 3.6 percent, the impurity content is not more than 0.4 weight percent compared with the weight of the product before and after alkali boiling, the standard meets the acceptance standard (impurities are not easy to find) of national standard (GB/T6408-2018 ultra-hard abrasive cubic boron nitride), the surface of the very individual material is slightly corroded, the whole edge angle is clear, the product is sharp when in use (the product granularity is 80/100, the bulk density is 1.742), and the obtained product result is shown in figure 5.
Comparative example 3
Comparative example 3 differs from example 2 in that the thermocouple was turned off when the alkali was boiled for 90 min; then the treatment is carried out according to the same method as the cooling, alkali treatment and post treatment in the step (III) in the embodiment 2;
each index of the purified CBN121 product is tested, the material loss is 1.2% compared with the weight of the product before and after alkali boiling, the visible impurity content is more than 1wt%, the standard of acceptance of the impurity content of less than 0.4% in national standard (GB/T6408-2018 ultra-hard abrasive cubic boron nitride) is not met, reworking is required, and the obtained product result is shown in figure 4.
Comparative example 4
Comparative example 4 is different from example 2 in that when alkali is boiled for 1.1h, the slope of the temperature change curve suddenly rises, then alkali is boiled for 15min, and the thermocouple is closed; then the treatment is carried out according to the same method as the cooling, alkali treatment and post treatment in the step (III) in the embodiment 2;
each index of the purified CBN121 product is tested, the material loss is 13% compared with the weight of the product before and after alkali boiling, the material surface is completely corroded, crystal grains are round, no impurities are found, the impurity content reaches the standard, but the purified product is not sharp and cannot be used as a raw material of a cutting tool, but the product is more wear-resistant (the granularity of the product is 80/100, the stacking density is 1.798, the obtained product result is shown in fig. 6), and the product can only be used as a wear-resistant material.
Note that: in example 2, comparative example 3, comparative example 4, the packing criteria for CBN121 products with particle size 80/100 were:
in national standard (GB/T6408-2018 superhard abrasive cubic boron nitride), the accumulation is not lower than 1.71;
in the enterprise standard (Q/ZNJT 01-2018 cubic boron nitride technical condition), the stacking is 1.740-1.80.
The process method can be used for purifying the cubic boron nitride products with different brands and meets the acceptance standard of national standards (GB/T6408-2018 superhard abrasive cubic boron nitride), and simultaneously can control key temperature control points in the alkali-boiling process, reduce the product reverse conversion probability and the loss, thereby improving the labor efficiency and the product quality and being beneficial to industrial production.
While specific embodiments of the invention have been described above, it should be understood that the invention is not limited to the particular embodiments described above. Various changes or modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.
Claims (6)
1. The cubic boron nitride alkali treatment and purification process is characterized by comprising the following steps of:
first pretreatment
(1) Primary separation: adding water into the cubic boron nitride synthetic rod block, uniformly mixing, vibrating, and ball-milling for 0.5-1.5 h to obtain a mixed material containing cubic boron nitride, hexagonal boron nitride and impurities; the synthetic rod block is a cubic boron nitride semi-finished product synthesized by using hexagonal boron nitride and catalyst raw materials, and contains incompletely converted hexagonal boron nitride, auxiliary carbon paper, metal catalyst and pyrophyllite impurities;
(2) Acid soaking: adding hydrochloric acid into the mixture after primary separation for soaking for 20-30 min;
(3) Ultrasonic impurity removal: adding water into the mixed material after acid soaking, and performing ultrasonic treatment for 2-5 min to obtain a cubic boron nitride material;
(II) alkali boiling treatment
(4) Mixing the pretreated cubic boron nitride material with mixed alkali and water to obtain mixed liquid, and heating and boiling alkali by using a thermocouple; when the alkali is boiled, the thermocouple is connected with the temperature recorder through an electric signal, the temperature recorder can receive the temperature signal of the thermocouple and record the change curve of the temperature along with time, and an alarm is arranged on the temperature recorder; in the measurement process, a curve of temperature change along with time is obtained through a temperature recorder, the slope of the temperature change curve is calculated, and whether to terminate alkali boiling is judged through the change of the slope;
in the process, the trend of a temperature curve needs to be monitored; the early stage of alkali boiling is water boiling, the temperature slowly rises in the water evaporation process, and the slope of a curve of the temperature changing along with time is relatively stable; when the moisture is completely evaporated, the temperature continues to rise, the alkali is in a molten state, the hexagonal boron nitride reacts with the alkali, and the slope of a curve of the temperature change along with time is slowly increased; when the hexagonal boron nitride is reacted, the cubic boron nitride starts to reversely convert, the temperature is suddenly accelerated to rise, the slope of a curve of the temperature changing along with time is multiplied, the temperature is set to be the alarm temperature of the alarm, and the cubic boron nitride starts to react with alkali at the temperature, and the heating should be stopped immediately to finish the alkali boiling process;
(III) cooling and alkali treatment
(5) Cooling the mixture after alkali boiling treatment, adding water to dissolve alkali when the temperature is reduced to 140-180 ℃, pouring out the alkali, and finally obtaining a material after alkali boiling and purification;
(IV) post-treatment
(6) Primary cleaning: washing the material after alkali boiling and purification by water;
(7) Ultrasonic cleaning: adding water into the cleaned material, and ultrasonically cleaning for 2-5 min;
(8) Sieving: drying and sieving the cleaned material to obtain a final product;
in the step (2), the addition amount of hydrochloric acid is as follows: 1800-2000 ml of hydrochloric acid with mass fraction of 37% is added into every 5 ten thousand ct mixed materials;
in the step (4), the mass ratio of the obtained cubic boron nitride material to the mixed alkali is 1 (0.2-0.6);
in the step (4), the water is used in the following amount: the solid-to-liquid ratio of the materials to water is 6g: (1-1.2) mL;
in the step (4), the mass ratio of the mixed alkali is as follows: naOH: koh=3, (2-2.5).
2. The process of claim 1, wherein in step (1), the ball mill is a QHQM-100 type ball mill.
3. The process of claim 1, wherein in step (3), the ultrasonic treatment is performed using an ultrasonic apparatus of the type JRC-2500, and the ultrasonic power is 2-3 kw.
4. The process of claim 1, wherein in step (4), the thermocouple is a WRP-130 type platinum-rhodium thermocouple; the model of the temperature recorder is FX1004, and the specification is-4-3-L.
5. The process according to claim 1, wherein in the step (5), water is added 3 to 5 times by adding water for 2 to 3 minutes, and the total water amount is 1200 to 1600ml.
6. The process of claim 1, wherein in step (7), the ultrasonic power is 2 to 3kw.
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