CN111957913A - MST coating crystallizer for improving slag line cracks and manufacturing method and application thereof - Google Patents

MST coating crystallizer for improving slag line cracks and manufacturing method and application thereof Download PDF

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CN111957913A
CN111957913A CN202010836810.6A CN202010836810A CN111957913A CN 111957913 A CN111957913 A CN 111957913A CN 202010836810 A CN202010836810 A CN 202010836810A CN 111957913 A CN111957913 A CN 111957913A
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crystallizer
mst
coating
slag line
improving
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刚占库
李宝雄
庄绪成
夏广林
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Dongchuang Boshi Shenyang Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/059—Mould materials or platings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/057—Manufacturing or calibrating the moulds
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • C23C4/129—Flame spraying

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  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Coating By Spraying Or Casting (AREA)

Abstract

An MST coating crystallizer for improving slag line cracks and a manufacturing method and application thereof belong to the field of continuous casting steel. The MST coating crystallizer for improving the slag line cracks comprises a wide plate and a narrow plate, wherein an MST coating is arranged in the wide plate of the crystallizer between 0mm and 200mm away from a casting gate of the crystallizer, and the thickness of the MST coating is plus (1-3) mm based on the thickness of the slag line cracks. The MST coating comprises the following chemical elements in percentage by mass: al (Al)2O3<1.0%, and the balance of Cu and inevitable impurities. The MST coating and the crystallizer base material are well combined by adopting HVAF, and the original physical property of the original aluminum oxide dispersion strengthened copper is not changed by the MST through the improvement of the processThe MST coating crystallizer for improving the slag line cracks can improve the slag line cracks, reduce the defects of the crystallizer and prolong the service life of the crystallizer under the condition of improving high heat flux in the continuous steel casting process.

Description

MST coating crystallizer for improving slag line cracks and manufacturing method and application thereof
Technical Field
The invention relates to the technical field of continuous casting, in particular to an MST coating crystallizer for improving slag line cracks and a manufacturing method and application thereof.
Background
The crystallizer is a key component on a continuous casting machine, and the quality of the crystallizer directly influences the surface quality of a continuous casting billet, the operation rate of the continuous casting machine and the cost of the continuous casting billet. The development of efficient continuous casting technology puts higher demands on the quality of the crystallizer: high strength, high wear resistance, corrosion resistance and good thermal conductivity are important indicators for the quality of the crystallizer. The copper crystallizer base material with good heat conductivity used at home and abroad can not meet the use requirement. In addition, copper is a harmful element for most steel grades, and the copper flushed into the steel slab by molten steel causes star-shaped cracks on the surface of the cast slab, thereby causing surface defects. Suitable substrates for crystallizers and the necessary surface treatment of the substrates are the conditions necessary for continuous casting production. At present, one or more materials are plated on the surface of the crystallizer by adopting surface treatment methods such as electroplating, thermal spraying and the like widely in China to obtain a special functional surface, and various coatings with good bonding performance with a base material, good wear resistance and good corrosion resistance are obtained under the condition of ensuring that the thermal conductivity of the coating is not influenced a little.
Most of the existing materials for plating the surface of the crystallizer are ceramic coatings, such as cobalt-coated tungsten carbide WC-12Co powder, WC-17Co powder, WC-10Co-4Cr powder and the like, the ceramic coatings have stable and good application effect on the basic required process of the narrow-edge copper plate, but in the production process, for the production conditions with high heat flux, such as the increase of the pulling speed, the heat flow temperature conduction at the copper plate slag line is not in time, so that the copper plate base metal is softened to generate cracks, thereby causing the ceramic coating to crack and go off line, so that the surface of the forged steel has slag line cracks (see figure 1), moreover, the slag line cracks are mostly vertical cracks, and the problem is not solved in time after a plurality of process improvements (such as material improvement of a submerged nozzle and crystallizer covering slag), and the reason of the problem is not determined.
The aluminum oxide dispersion strengthened copper (MST) has the excellent characteristics of high strength, good electric conduction and thermal conductivity and the like, simultaneously has the capabilities of high-temperature softening resistance, arc erosion resistance and abrasion resistance, and is widely applied to electrodes, electric contacts and lead frame materials. And the aluminum oxide dispersion strengthened copper is easy to recrystallize in the reprocessing process, so that the dispersibility of the aluminum oxide dispersion strengthened copper is lost, and the excellent characteristics of the original aluminum oxide dispersion strengthened copper are changed.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an MST coating crystallizer for improving slag line cracks and a manufacturing method and application thereof. The MST coating is adopted to carry out surface treatment on the existing crystallizer, so that the crystallizer has wear resistance and high softening temperature, the provided manufacturing method can ensure that the bonding property of the MST coating and a base material is good, the MST does not change the original physical property of the original aluminum oxide dispersion strengthened copper through the improvement of the process, and the MST coating crystallizer for improving the slag line cracks can improve the slag line cracks, reduce the defects of the crystallizer and prolong the service life of the crystallizer under the condition of high heat flux (such as large steel passing amount or high pulling speed) in the continuous steel casting process.
The MST coating crystallizer for improving the slag line cracks comprises a crystallizer wide plate and a crystallizer narrow plate, wherein an MST coating is arranged between the crystallizer wide plate and a casting opening of the crystallizer by 0-200mm, and the thickness of the MST coating is plus (1-3) mm, preferably 1-10mm, based on the thickness of the slag line cracks.
The narrow plate of the crystallizer can also be selected to be provided with an MST coating between 0mm and 200mm away from a casting opening of the crystallizer according to the actual use condition of the crystallizer, and the thickness of the MST coating is plus (1-3) mm, preferably 1-10mm, based on the thickness of the slag line crack.
The thickness of the slag line crack is determined by the influence of the process conditions of the type, the drawing speed and the excessive steel quantity of the continuous casting steel.
The wide crystallizer plate and the narrow crystallizer plate have the same height and thickness and different widths, the relatively wide crystallizer plate is the wide crystallizer plate, and the relatively narrow crystallizer plate is the narrow crystallizer plate.
The MST coating comprises the following chemical elements in percentage by mass: al (Al)2O3<1.0%, and the balance of Cu and inevitable impurities.
Further, it is more preferable that the MST coating is provided between 80mm and 200mm of the wide plate of the crystallizer from the casting opening of the crystallizer.
The MST coating crystallizer for improving the slag line cracks, which is prepared by the invention, has the softening temperature of over 930 ℃ at the position of 80-200mm, the electric conductivity of 85% IACS, and the Vickers hardness of 136-160 at the temperature of normal temperature-800 ℃, particularly the Vickers hardness of 136-160 at the temperature of 600-800 ℃.
Further, a ceramic coating is arranged on the inner wall of the MST coating crystallizer for improving slag line cracks, and the ceramic coating is preferably a WC coating; it is more preferred that the lower part of the MST coated crystallizer, which improves slag line cracking, is provided with a ceramic coating.
The invention relates to a preparation method of an MST coating crystallizer for improving slag line cracks, which comprises the following steps:
step 1:
machining the crystallizer base material to remove the corresponding position according to the setting position of the MST coating in the MST coating crystallizer for improving the slag line cracks, so as to obtain the treated crystallizer base material;
step 2:
carrying out sand blasting cleaning and roughening on the position where the MST coating is arranged in the treated crystallizer base material to obtain the sand blasted crystallizer base material; in the sand blasting process, the temperature of the crystallizer base material is controlled to be less than or equal to 50 ℃;
and step 3:
spraying the position of the MST coating on the crystallizer base material subjected to sand blasting by using the MST as a spraying material by using an HVAF method to obtain the MST coated crystallizer; wherein the particle size of MST is 100-300 meshes;
the spraying process of the HVAF method comprises the following steps: the combustion improver is air, the air pressure is 95-100psi, the fuel is propane or propylene, the air pressure of the fuel is 70-90psi, the flow rate of nitrogen is 12-16L/min, the flow rate of hydrogen is 10-15L/min, the spraying distance is 150-180mm, and the powder conveying amount is 130-170 g/min;
and 4, step 4:
and (3) flattening the MST coating crystallizer, and then assembling to obtain the MST coating crystallizer for improving slag line cracks.
In the step 2, the sand blasting is preferably cold sand blasting.
The MST coating crystallizer for improving the slag line cracks has the advantages that the bonding force of the MST coating at the joint and the crystallizer is 40-70 MPa.
An application of MST coating crystallizer for improving slag line crack is used for continuous casting of plate blank, large-section square blank and special-shaped blank.
The manufacturing method of the MST coating crystallizer for improving the slag line cracks can also be used for repairing the existing crystallizer and prolonging the service life.
The MST coating crystallizer for improving the slag line cracks and the manufacturing method and the application thereof have the beneficial effects that:
1. according to the invention, the MST coating is coated on the specific position of the existing crystallizer copper plate, so that the high wear resistance and high softening temperature can be achieved, and the slag line cracks can be improved in the process of high-heat-flux continuous casting of steel billets.
2. In addition, by combining the HVAF spraying process, the aluminum oxide dispersion strengthened copper and the crystallizer base material have good binding property, the coating is prevented from falling off, and the original physical property of the original aluminum oxide dispersion strengthened copper is not changed by the MST through the improvement of the process; the preparation method can also be used for repairing the crystallizer; meanwhile, the HVAF of the invention does not need heat treatment after MST spraying.
3. The MST coating crystallizer for improving the slag line cracks is used for casting steel, and the obtained steel plate has a smooth surface and has no cracks.
Drawings
FIG. 1 is a diagram of slag line cracking after casting in a conventional crystallizer;
FIG. 2 is a schematic structural diagram of an MST coating crystallizer wide plate for improving slag line cracks in example 1 of the invention;
FIG. 3 is a schematic structural diagram of an MST coating crystallizer for improving slag line cracks in the embodiment 1 of the invention;
FIG. 4 is a comparison graph of Vickers hardness at different temperatures for a CuCrZr coated crystallizer and a MST coated crystallizer;
FIG. 5 is a metallographic structure of the MST coating in the MST coated crystallizer improving slag line cracking;
FIG. 6 is a schematic structural diagram of an MST coating crystallizer wide plate for improving slag line cracks in embodiment 2 of the invention;
FIG. 7 is a schematic structural diagram of an MST coating crystallizer for improving slag line cracks in example 2 of the invention;
in the above figures, 1 is a wide plate of the crystallizer, 2 is an MST coating, 3 is a narrow plate of the crystallizer, and 4 is an MST coating crystallizer for improving slag line cracks.
Detailed Description
The present invention will be described in further detail with reference to examples.
In order to clarify the cause of slag line crack generation and an improvement method, the invention detects the hardness of a narrow-side crystallizer copper plate (with the specification of 92.5mm multiplied by 1200mm) after being off-line, a TH110 Richter hardness tester is used for detecting the Brinell hardness HB of the narrow-side crystallizer copper plate, and the adopted detection method is that 10 indication values are transversely measured from left to right from the upper end to the lower end of the copper plate at each position, and the details are shown in the table I:
table-Brinell hardness test result of narrow-side crystallizer copper plate after use
Position of HB1 HB2 HB3 HB4 HB5 HB6 HB7 HB8 HB9 HB10 Average hardness
10 99 101 102 95 99 97 94 97 97 94 97.5
60 102 97 99 101 98 101 97 98 99 96 98.8
80 101 96 91 87 84 80 77 85 88 91 88
100 52 52 49 51 51 47 52 50 51 50 50.5
120 52 51 53 49 50 51 51 51 51 52 51.1
140 53 51 52 52 51 50 51 52 52 58 52.2
160 86 83 61 53 54 53 55 70 78 81 67.4
180 88 82 85 71 68 71 79 82 85 86 79.7
200 92 89 83 80 76 80 83 80 85 89 83.7
300 96 94 87 86 87 86 86 89 91 90 89.2
400 94 90 87 87 86 90 87 90 89 93 89.3
500 95 89 85 90 91 94 89 93 95 94 91.5
600 96 96 94 95 96 95 97 89 99 95 95.2
700 90 91 91 92 93 93 93 89 91 90 91.3
800 100 97 99 94 92 91 90 89 94 89 93.5
900 100 92 93 95 97 96 97 94 98 98 96
1000 101 95 99 96 94 96 98 96 100 99 97.4
1100 100 104 104 106 104 100 104 105 105 106 103.8
1200 101 101 103 103 102 105 101 102 96 100 101.4
89.37 86.89 85.11 83.32 82.79 82.95 83.21 84.26 86.53 86.89
Through the analysis of the data in the table, molten steel enters a crystallizer, a meniscus is formed at a position of 80mm, and the molten steel is condensed into a blank shell; the solidified shell is closely contacted with the hot surface of the copper plate at the position of 80-200mm, and the steel shell transfers heat to the copper plate in a conduction mode; at 200-. Therefore, the copper plate is most easily softened and thermally fatigued in the direct heat conduction area of 80-200mm, and the measured data reflects the hardness value of the area at the lower most end of the hardness value of 50%. Therefore, the area of the narrow-side mold copper plate of more than 200mm is the key point of needing the performance improvement.
By measuring that the crack depth at the slag line is not more than 0.5mm, and after the removal amount of the machined copper plate exceeds 0.5mm, the minimum value of the hardness at the position of 80-200mm of the narrow-side crystallizer copper plate exceeds HB 80.
Therefore, the improvement of the crystallizer copper plate with the thickness of 0.5mm and the narrow edge of 80-200mm is determined.
Example 1
An MST coating crystallizer for improving slag line cracks is characterized in that an MST coating is arranged between a position 80mm away from a crystallizer casting gate and a position 200mm away from the crystallizer casting gate, the thickness of the MST coating is 0.7mm, a structural schematic diagram of a copper plate adopted by the MST coating crystallizer for improving the slag line cracks is shown in figure 2, a MST coating crystallizer 4 for improving the slag line cracks is shown in figure 3, wherein MST coatings 2 are arranged on a wide plate 1 of the crystallizer and a narrow plate 3 of the crystallizer, and the arrangement positions are consistent.
The MST coating comprises the following chemical elements in percentage by mass: 0.6% of Al2O3And the balance being Cu.
A preparation method of an MST coating crystallizer for improving slag line cracks comprises the following steps:
step 1: copper plate pretreatment
(1) Straightening the surface of the copper plate: straightening the copper plate to obtain a straightened copper plate;
(2) machining and milling a to-be-sprayed area with the depth of 0.7mm at a position of 80-200mm of the copper plate;
(3) degreasing the surface of the copper plate: deoiling and purifying the machined copper plate to obtain a deoiled and purified copper plate;
step 2: sand blasting of copper plate surface
Starting an HVAF spraying system, delivering sand blasting powder, and performing cold sand blasting coarsening on an MST coating area to be sprayed of the deoiled and purified copper plate to obtain a purified copper plate; in the sand blasting process, the temperature of the copper plate is controlled to be less than or equal to 50 ℃;
and step 3: MST coating area surface spraying of copper plate
Starting an HVAF spraying system, setting a spraying process program, sending a spraying material, and spraying an MST coating on the area to be sprayed with the MST coating on the purified copper plate; wherein the spraying material adopts MST powder, and the granularity of the MST powder is 300 meshes; in the spraying process, the temperature of the copper plate is controlled to be less than or equal to 50 ℃; the spraying thickness is 0.8 mm;
the MST spraying process parameters of the HVAF method are as follows: the combustion improver is air, the air pressure is 100psi, the fuel is propane or propylene, the air pressure of the fuel is 80psi, the flow of nitrogen is 15L/min, the flow of hydrogen is 12L/min, the spraying distance is 180mm, and the powder feeding amount is 150 g/min.
The prepared MST coating crystallizer for improving the slag line cracks has the softening temperature of over 900 ℃ within 80-200mm of a casting opening of the crystallizer, the electric conductivity of more than or equal to 80 percent IACS, the heat conductivity of 350--6K, Brinell hardness HB is more than or equal to 80.
In the MST coating crystallizer for improving slag line crack, the metallographic structure diagram of the MST coating is shown in figure 5, and as can be seen from figure 5, in the MST coating, Al2O3The MST coating is still dispersed and distributed in the copper base material, and aggregation and crystallization do not occur, which shows that the method of the invention can well combine the MST coating and the crystallizer base material copper plate, and keeps the good physical and mechanical properties of the MST.
Comparative example
The preparation method of the MST coating crystallizer for improving the slag line cracks is the same as the preparation method of the MST coating crystallizer in the example 1, and is characterized in that:
in step 3, the HVAF process parameters are: the combustion improver is air, the air pressure is 100psi, the fuel is propane or propylene, the air pressure of the fuel is 98psi, the flow of nitrogen is 18L/min, the flow of hydrogen is 25L/min, the spraying distance is 110mm, and the powder feeding amount is 120 g/min;
detecting the prepared MST coating crystallizer for improving the slag line cracks, and finding that Al appears in MST in the MST coating prepared by the parameters2O3Crystal nuclei formed by crystallization, Al2O3And is not uniformly dispersed in the copper substrate, the dispersion strengthening effect disappears.
Example 2
An MST coating crystallizer for improving slag line cracks is characterized in that an MST coating is arranged in a position, 200mm away from a casting opening of the crystallizer, of a wide plate of the crystallizer, the thickness of the MST coating is 0.7mm, a structural schematic diagram of a copper plate adopted by the MST coating crystallizer for improving the slag line cracks is shown in figure 6, a structural schematic diagram of the MST coating crystallizer for improving the slag line cracks is shown in figure 7, and an MST coating is not arranged on a narrow plate of the crystallizer.
The MST coating comprises the following chemical elements in percentage by mass: 0.6% of Al2O3And the balance being Cu.
A preparation method of an MST coating crystallizer for improving slag line cracks comprises the following steps:
step 1: copper plate pretreatment
(1) Straightening the surface of the copper plate: straightening the copper plate to obtain a straightened copper plate;
(2) machining and milling a 0.7mm deep area to be sprayed at a position of 0-200mm of the copper plate;
(3) degreasing the surface of the copper plate: deoiling and purifying the machined copper plate to obtain a deoiled and purified copper plate;
step 2: sand blasting of copper plate surface
Starting an HVAF spraying system, delivering sand blasting powder, and performing cold sand blasting coarsening on an MST coating area to be sprayed of the deoiled and purified copper plate to obtain a purified copper plate; in the sand blasting process, the temperature of the copper plate is controlled to be less than or equal to 50 ℃;
and step 3: MST coating area surface spraying of copper plate
Starting an HVAF spraying system, setting a spraying process program, sending a spraying material, and spraying an MST coating on the area to be sprayed with the MST coating on the purified copper plate; wherein the spraying material adopts MST powder, and the granularity of the MST powder is 100 meshes; in the spraying process, the temperature of the copper plate is controlled to be less than or equal to 50 ℃; the spraying thickness is 0.8 mm;
the MST spraying process parameters of the HVAF method are as follows: the combustion improver is air, the air pressure is 95psi, the fuel is propane or propylene, the air pressure of the fuel is 90psi, the flow of nitrogen is 12L/min, the flow of hydrogen is 15L/min, the spraying distance is 150mm, and the powder feeding amount is 120 g/min.
Example 3
An MST coating crystallizer for improving slag line cracks is characterized in that an MST coating is arranged between a crystallizer casting opening and a position 200mm away from the crystallizer casting opening, a ceramic coating is arranged between the position 200mm away from the crystallizer casting opening and a crystallizer casting outlet, the thickness of the MST coating is 0.7mm, and the thickness of the ceramic coating is 0.7 mm.
The MST coating comprises the following chemical elements in percentage by mass: 0.6% of Al2O3And the balance being Cu. The ceramic coating is a WC coating.
A preparation method of an MST coating crystallizer for improving slag line cracks comprises the following steps:
step 1: copper plate pretreatment
(1) Straightening the surface of the copper plate: straightening the copper plate to obtain a straightened copper plate;
(2) machining and milling a 0.7mm deep area to be sprayed at a position of 0-200mm of the copper plate;
(3) degreasing the surface of the copper plate: deoiling and purifying the machined copper plate to obtain a deoiled and purified copper plate;
step 2: sand blasting of copper plate surface
Starting an HVAF spraying system, delivering sand blasting powder, and performing cold sand blasting coarsening on an MST coating area to be sprayed of the deoiled and purified copper plate to obtain a purified copper plate; in the sand blasting process, the temperature of the copper plate is controlled to be less than or equal to 50 ℃;
meanwhile, carrying out sand blasting coarsening on the ceramic coating area to be sprayed of the copper plate after oil removal and purification;
and step 3: MST coating area surface spraying of copper plate
Starting an HVAF spraying system, setting a spraying process program, sending a spraying material, and spraying an MST coating on the area to be sprayed with the MST coating on the purified copper plate; wherein the spraying material adopts MST powder, and the granularity of the MST powder is 200 meshes; in the spraying process, the temperature of the copper plate is controlled to be less than or equal to 50 ℃; the spraying thickness is 0.8 mm;
the ceramic coating part at the lower part of the crystallizer adopts WC powder with the granularity of 200 meshes as a spraying material;
the MST spraying process parameters of the HVAF method are as follows: the combustion improver is air, the air pressure is 95psi, the fuel is propane or propylene, the air pressure of the fuel is 70psi, the flow of nitrogen is 16L/min, the flow of hydrogen is 10L/min, the spraying distance is 170mm, and the powder feeding amount is 170 g/min;
the WC spraying technological parameters of the HVAF method are as follows: the combustion improver is air, the air pressure is 95psi, the fuel is propane or propylene, the air pressure of the fuel is 102psi, the flow of nitrogen is 25L/min, the flow of hydrogen is 15L/min, the spraying distance is 50mm, and the powder feeding amount is 80 g/min;
and sealing holes and curing the sprayed WC.
Application example 1
Vickers hardness comparison
The crystallizers of different coatings were made and their softening temperature (. degree. C.) was determined by measuring the Vickers hardness comparison at different temperatures, see Table below, and the Vickers hardness comparison curves of the CuCrZr coated crystallizer and the MST coated crystallizer at different temperatures are shown in FIG. 4.
Vickers hardness At normal temperature 400℃ 500℃ 600℃ 700℃ 800℃
Example 1 MST coating 176 174 136 160 136 139
Comparative example 1 CuCrZr 148 149 122 107 86 83
Comparative example 2 WC coating 1400 1386 1427 1528 1518 1532
Although chromium zirconium copper (CuCrZr) is a better raw material for manufacturing the crystallizer copper plate as the third generation copper alloy in terms of thermal conductivity, strength and the like, the above table shows that the softening hardness of the MST coating of the invention is slower than that of chromium zirconium copper in the temperature raising process, and the brinell hardness of the MST coating is about 20% higher than that of chromium zirconium copper in each same temperature stage, which indicates that the softening temperature of the crystallizer is obviously raised by the improvement of the MST coating of the invention.
Application example 2
Thermal shock test of coating
Red copper was used as a base material, and a ceramic coating WC of a mold copper plate was sprayed on the surface thereof by an HVAF process, as a comparative example 2. In the other method, red copper is used as a base material, and after 0.5mm MST coating is sprayed on the surface of the base material, the ceramic coating WC of the crystallizer copper plate is sprayed on the surface of the base material.
Cutting the two into 40mm × 40mm squares, respectively preserving heat at 500 deg.C, 600 deg.C, 700 deg.C for 10 min, and quenching in normal temperature water. And observing the peeling condition of the coating.
The thermal shock test data of the top three coatings are as follows:
Figure BDA0002640007360000081
Figure BDA0002640007360000091
according to the table, the MST coating is well combined with the base material copper base material and does not fall off after the MST coating is added. The WC coating of the surface has almost no difference in the failure times whether the coating is carried out on the basis of red copper or MST.
The results of multiple experiments and related data search are summarized as follows
Figure BDA0002640007360000092
Through the data analysis, the heat-conducting performance index of MST is close to oxygen-free copper and is better than that of copper alloy, and the softening temperature can reach near 900 ℃ and is higher than that of copper and copper alloy by more than 300 ℃, so that the MST can be completely applied to a crystallizer copper plate. The MST coating is applied to the local part of the crystallizer copper plate, so that the MST coating is the best scheme for solving the problems of cost and slag line cracks.

Claims (10)

1. The MST coating crystallizer for improving the slag line cracks is characterized by comprising a crystallizer wide plate and a crystallizer narrow plate, wherein an MST coating is arranged between the crystallizer wide plate and a casting opening of the crystallizer by 0-200mm, and the thickness of the MST coating is plus (1-3) mm based on the thickness of the slag line cracks.
2. The MST coating crystallizer for improving the slag line crack of claim 1, wherein the narrow plate of the crystallizer is provided with an MST coating between 0mm and 200mm away from a casting opening of the crystallizer according to the actual use condition of the crystallizer, and the thickness of the MST coating is plus (1-3) mm based on the thickness of the slag line crack.
3. The MST coating crystallizer for improving slag line cracks of claim 1, wherein the MST coating comprises the following chemical elements in percentage by mass: al (Al)2O3<1.0%, and the balance of Cu and inevitable impurities.
4. The MST coated crystallizer for improving slag line cracking of claim 1, wherein the MST coating is disposed between 80mm and 200mm from the crystallizer casting gate.
5. The MST coating crystallizer for improving the slag line crack as set forth in the claims 1-4, characterized in that the MST coating crystallizer for improving the slag line crack is prepared with a softening temperature of 930 ℃ or more, an electrical conductivity of 85% IACS at 80-200mm, and a Vickers hardness of 136-176 at the normal temperature-800 ℃.
6. The MST-coated crystallizer for improving the slag line crack of the claims 1-4 is characterized in that a ceramic coating is also arranged on the inner wall of the MST-coated crystallizer for improving the slag line crack.
7. The slag line crack improving MST coated crystallizer of claim 6, wherein a ceramic coating is provided on a lower portion of the slag line crack improving MST coated crystallizer.
8. The method for preparing a MST coated crystallizer with improved slag line cracking as claimed in any one of claims 1 to 4, comprising the steps of:
step 1:
machining the crystallizer base material to remove the corresponding position according to the setting position of the MST coating in the MST coating crystallizer for improving the slag line cracks, so as to obtain the treated crystallizer base material;
step 2:
carrying out sand blasting cleaning and roughening on the position where the MST coating is arranged in the treated crystallizer base material to obtain the sand blasted crystallizer base material; in the sand blasting process, the temperature of the crystallizer base material is controlled to be less than or equal to 50 ℃;
and step 3:
spraying the position of the MST coating on the crystallizer base material subjected to sand blasting by using the MST as a spraying material by using an HVAF method to obtain the MST coated crystallizer; wherein the particle size of MST is 100-300 meshes;
the spraying process of the HVAF method comprises the following steps: the combustion improver is air, the air pressure is 95-100psi, the fuel is propane or propylene, the air pressure of the fuel is 70-90psi, the flow rate of nitrogen is 12-16L/min, the flow rate of hydrogen is 10-15L/min, the spraying distance is 150-180mm, and the powder conveying amount is 130-170 g/min;
and 4, step 4:
and (4) carrying out flattening treatment on the MST coating crystallizer to obtain the MST coating crystallizer for improving slag line cracks.
9. The method for preparing the MST coating crystallizer for improving the slag line crack according to claim 8, wherein the bonding force between the MST coating and the crystallizer at the joint is 40-70 MPa.
10. Use of a slag line crack mitigating MST coated crystallizer as claimed in any one of claims 1 to 4, wherein the slag line crack mitigating MST coated crystallizer is used in slab continuous casting, large cross-section billet continuous casting and beam blank continuous casting.
CN202010836810.6A 2020-08-19 2020-08-19 MST coating crystallizer for improving slag line cracks and manufacturing method and application thereof Pending CN111957913A (en)

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