CN117230277A - Deoxidization control method for high alloy steel casting - Google Patents
Deoxidization control method for high alloy steel casting Download PDFInfo
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- 239000010959 steel Substances 0.000 claims abstract description 197
- 238000003723 Smelting Methods 0.000 claims abstract description 51
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- 238000010079 rubber tapping Methods 0.000 claims abstract description 34
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- 238000010438 heat treatment Methods 0.000 description 3
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The application belongs to the technical field of steel casting production, and provides a deoxidization control method for a high alloy steel casting, which comprises the following steps of smelting in an EAF furnace: before tapping, adding a composite deoxidizer into molten steel for the first time, and tapping; adding a composite deoxidizer for the second time in the tapping process, and adding the deoxidizer before tapping until the residual molten steel in the ladle is one third of the total molten steel; after tapping to the rest of the molten steel being two thirds of the total molten steel, adding a synthetic refining agent into the molten steel, and adding the synthetic refining agent before tapping to the rest of the molten steel in the ladle being one third of the total molten steel. Smelting in an LF furnace for the first time: deoxidizing, desulfurizing and alloying smelting the molten steel in the furnace. Smelting in a VOD furnace: and (3) carrying out vacuumizing, oxygen blowing, decarburization and smelting on the molten steel in the furnace. Smelting in an LF furnace for the second time: active lime and fluorite are added into molten steel in a furnace to make slag have strong alkalinity, and then a composite deoxidizer is added. The method improves the purity of the molten steel and meets the technical specification requirements.
Description
Technical Field
The application belongs to the technical field of steel casting production, and provides a deoxidization control method for a high alloy steel casting.
Background
When an arc furnace is adopted in the smelting process of the steel castings, many of the steel castings need to be subjected to an oxidation process, oxygen needs to be blown into molten steel in an oxidation period so as to form a C-O reaction in the molten steel to cause a molten pool boiling phenomenon, thereby achieving the processes of decarburization, dephosphorization, degassing and impurity removal, further leading to the fact that after the oxidation period is finished, the oxygen content in the molten steel far exceeds the technical internal control requirement and reaches more than 1000ppm, therefore, the molten steel needs to be fully deoxidized, and the oxygen content in the steel is reduced to the minimum level.
Since the solubility of oxygen in pure iron bath is 0.23% at 1600 c, the maximum solubility of oxygen is 0.05% at room temperature. Therefore, if the molten steel is poorly deoxidized, the temperature is significantly reduced during solidification, and the precipitated oxygen reacts with carbon in the molten steel to produce CO gas, which causes a casting to produce blowholes, and reacts with elements such as Al, si, mn, cr in the molten steel to produce nonmetallic inclusions, which, if not removed from the molten steel, cause a decrease in the performance of the cast steel. Therefore, how to deoxidize in the smelting process to improve the performance of the steel casting needs to be solved.
Disclosure of Invention
In view of the above-mentioned technical problems, it is necessary to provide a deoxidizing control method for high alloy cast steel.
The deoxidation control method for the high alloy steel casting comprises the following steps of:
smelting in an EAF furnace: before tapping, adding a composite deoxidizer into molten steel for the first time, and tapping; adding a composite deoxidizer for the second time in the tapping process, and adding the deoxidizer before tapping until the residual molten steel in the ladle is one third of the total molten steel; after tapping to the rest molten steel which is two thirds of the total molten steel, adding a synthetic refining agent into the molten steel, and adding the synthetic refining agent before tapping to the rest molten steel in the ladle which is one third of the total molten steel;
smelting in an LF furnace for the first time: deoxidizing, desulfurizing and alloying smelting the molten steel in the furnace;
smelting in a VOD furnace: carrying out vacuumizing, oxygen blowing, decarburization and smelting on molten steel in a furnace;
smelting in an LF furnace for the second time: active lime and fluorite are added into molten steel in a furnace to make slag have strong alkalinity, electrode carburetion is reduced in the heating process by increasing the slag quantity, and then a composite deoxidizer is added to improve the reducibility of the slag.
Further, in the EAF furnace smelting step, the mass of the first addition of the composite deoxidizer is the same as the mass of the second addition of the composite deoxidizer. The composite deoxidizer is added in a batch mode, so that the absorption rate of the composite deoxidizer is improved, and the molten steel is rapidly deoxidized.
Further, in the EAF furnace smelting step, the total mass of the first addition of the composite deoxidizer and the mass of the second addition of the composite deoxidizer is 2 kg/ton of steel to 4 kg/ton of steel. Through repeated experiments, when the addition amount is between 2 kg/ton steel and 4 kg/ton steel, other deoxidized alloy is not needed to be added, and the free oxygen in the molten steel can be quickly and effectively reduced to the minimum level.
Further, in the step of smelting in the EAF furnace, adding the composite deoxidizer into the molten steel for the second time in a batch mode; preferably, the composite deoxidizer is added for 2 to 3 times respectively, the addition amount of each time can be set according to the actual working condition, and the harmful effects of secondary oxidation of molten steel in the tapping process can be partially counteracted by adding the composite deoxidizer in batches. In the comprehensive deoxidization process, ferrosilicon and ferromanganese cannot be added for comprehensive deoxidization, and deoxidization products and MnS inclusions of the ferrosilicon and ferromanganese are difficult to be adsorbed and float in molten steel.
Further, in the melting step of the EAF furnace, adding the synthetic refining agent into the molten steel in a batch mode; preferably, 2 to 3 times of addition are adopted, and each addition amount can be set according to actual working conditions so as to ensure that the synthetic refining agent is melted and reacted in the ladle for a sufficient time; after the synthetic refining agent is completely added, the argon pressure is increased, and the synthetic refining agent is fully contacted and reacted with molten steel through argon stirring, so that the floating of inclusions and the removal of gas are facilitated. By means of the scouring force of molten steel and the strong stirring force formed by blowing argon into the molten steel, the synthetic refining agent fully contacts and reacts with the molten steel, the probability of collision growth of nonmetallic inclusion in the molten steel is increased, the floating of the inclusion is promoted, and the purity of the molten steel is further improved.
Further, in the EAF furnace smelting step, the mass of the synthetic refining agent is 3 kg/ton steel to 4 kg/ton steel, and a slag layer with a certain thickness is formed to cover molten steel so as to prevent the molten steel from being oxidized.
Further, in the second LF smelting step, adding the composite deoxidizer into molten steel in a batch mode; preferably, 3 to 5 times of adding the surface of the molten steel are adopted, and each adding amount can be set according to actual working conditions so as to diffuse through a steel slag interface.
Further, in the second LF furnace smelting step, the mass of the composite deoxidizer is 1 kg/ton steel to 2 kg/ton steel, and the oxygen content in the molten steel is further reduced in a diffusion deoxidizing mode.
Further, in the second LF furnace smelting step, the mass of active lime is 10 kg/ton steel to 20 kg/ton steel, and the mass of fluorite is 1 kg/ton steel to 2 kg/ton steel, so that the temperature drop of molten steel is more due to longer adjustment time of the whole components, continuous power transmission and temperature rise are required, and the carburetion of the molten steel is reduced by increasing the thickness of a slag layer.
Further, in the second LF furnace smelting step, active lime and fluorite are added into molten steel in a furnace to enable the alkalinity R value of steel slag on the surface of the molten steel to be 2.5-4, and then a composite deoxidizer is added in batches to ensure high-alkalinity white slag refining.
Further, in the EAF furnace smelting step, the smelting step further comprises sampling and analyzing the P content after oxygen blowing in the smelting process is finished until the P is less than or equal to 0.005%, then heating to 1600-1650 ℃ for tapping, and avoiding molten steel cooling, blocking and argon blowing ventilation plugs in the tapping process.
Further, in the first LF furnace smelting step, after molten steel is placed in an LF furnace, firstly measuring the oxygen activity of the molten steel by an oxygen meter, adding aluminum of 1 kg/ton steel to 2 kg/ton steel and aluminum-calcium alloy balls of 1 kg/ton steel to 3 kg/ton steel according to the measurement condition for deoxidization, and then adding active lime and fluorite of 10 kg/ton steel to 20 kg/ton steel for high-temperature desulfurization; when the temperature is more than or equal to 1580 ℃ and the oxygen activity is less than or equal to 10ppm, sampling and analyzing chemical components, adjusting and adding Co, mo, cr, ni and other non-oxidizable alloys to the lower limit of the specification according to the spectrum sample result, adjusting C to 0.2-0.4%, then adjusting the temperature of molten steel to about 1620 ℃ and tapping to a VOD furnace, ensuring the starting oxygen blowing temperature to be between 1580 ℃ and 1600 ℃, and improving the recovery rate of chromium by controlling the temperature of the molten steel.
Further, in the VOD furnace smelting step, after vacuumizing 6KPa to 8KPa, oxygen blowing is carried out in a temperature range of 16000 ℃ to 1620 ℃, and meanwhile, the flow of argon is increased to improve the C-O reaction rate; after oxygen blowing is finished, continuously increasing vacuum to below 67Pa, increasing argon flow, keeping for more than 15min, and properly prolonging time under the condition of allowing conditions, so as to further react C and O in molten steel and achieve the effects of reducing carbon, removing gas and removing impurities; after the vacuum is released, adding 10 kg/ton steel to 20 kg/ton steel of CaO, 3 kg/ton steel to 5 kg/ton steel of fluorite, 1 kg/ton steel to 3 kg/ton steel of SiCa, 0.5 kg/ton steel to 1 kg/ton steel of Al particles, 0.8 kg/ton steel to 1.5 kg/ton steel of ferrotitanium and other deoxidizers for pre-reduction operation, keeping the reduction time to be more than or equal to 10min, and then tapping to an LF furnace for adjusting the composition and the temperature.
Further, the chemical components of the mixed flow vane are as follows: 0.11% or less of C or less than 0.14%,0.20% or less of Si or less than 0.30%,0.80% or less of Mn or less than 1.0%, P or less than 0.015%, S or less than 0.010%,9.00% or less of Cr or less than 9.60%,1.40% or less of Mo or less of 1.60%,0.10% or less of Ni or less of 0.20%,0.015% or less of N or less of 0.030%,0.90% or less of Co or less of 1.10%,0.008% or less of B or less of 0.013%, sb or less of 0.001%, al or less of 0.02%, sn or less of 0.015%, cu or less of 0.1%, as or less of 0.025%,0.18% or less of V or less of 0.22%, and 0.05% or less of Nb or less of 0.07%.
The application has the beneficial effects that:
according to the deoxidation control method for the high-alloy steel castings, provided by the application, the composite deoxidizer and the synthetic refining agent are mainly added at different stages of the EAF furnace tapping, so that the oxygen activity in molten steel is reduced, and the smelting efficiency of the refining furnace is improved; meanwhile, deoxidizing agents such as aluminum ingots (grains), silicon calcium, titanium iron, silicon calcium manganese rare earth barium and the like are added in the refining process of the LF furnace and the VOD furnace, the reducibility of slag is improved, and measures such as controlling the flow of argon, prolonging the refining time and the like are taken, so that the total oxygen content in molten steel is finally less than 20ppm, the area content of inclusions is about 0.01%, the purity of the molten steel is improved, the technical specification requirement is met, and meanwhile, the production technical difficulty is also solved.
Detailed Description
In order that the application may be understood more fully, a more particular description of the application will be rendered by reference to the appended claims. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
In the embodiment, the ZG13Cr9Mo2Co1VNbNB material mixed flow type blade steel casting is taken as an example, and the material comprises the following chemical components: 0.11% or less of C or less than 0.14%,0.20% or less of Si or less than 0.30%,0.80% or less of Mn or less than 1.0%, P or less than 0.015%, S or less than 0.010%,9.00% or less of Cr or less than 9.60%,1.40% or less of Mo or less of 1.60%,0.10% or less of Ni or less of 0.20%,0.015% or less of N or less of 0.030%,0.90% or less of Co or less of 1.10%,0.008% or less of B or less of 0.013%, sb or less of 0.001%, al or less of 0.02%, sn or less of 0.015%, cu or less of 0.1%, as or less of 0.025%,0.18% or less of V or less of 0.22%, and 0.05% or less of Nb or less of 0.07%. The deoxidation control method specifically comprises the steps of an EAF furnace, a first LF furnace, a VOD furnace and a second LF furnace, and specifically comprises the following steps:
step one
Smelting in an EAF furnace: an oxidation smelting process is adopted and is mainly used for providing crude molten steel; the furnace burden mainly comprises scrap steel and carbon steel return materials, and the adding ratio is 6:4; lime 30 kg/ton steel to 60 kg/ton steel, carburant 1.0% to 1.5%, and residual element Ni0.1% to 0.2% and P less than or equal to 0.01%.
Sampling and analyzing C, P content after furnace burden is melted (i.e. solid state is changed into liquid state), then carrying out P removal operation, and tilting a furnace door to flow oxidizing slag in the oxygen blowing decarburization process; when the temperature of molten steel is more than or equal to 1620 ℃, oxygen blowing decarburization is started, and the decarburization amount is more than or equal to 0.3%, so that the refining effect of degassing and removing impurities is achieved by utilizing the boiling of molten steel formed by decarburization reaction; and after oxygen blowing is finished, sampling and analyzing the P content, and then heating to 1600-1650 ℃ to prepare steel tapping when the P content is less than or equal to 0.005%.
Before tapping, adding a composite deoxidizer into molten steel for the first time, and tapping; adding a composite deoxidizer for the second time in the tapping process, wherein the composite deoxidizer is added in 2-3 batches, and the addition is completed before tapping until the residual molten steel in the ladle is one third of the total molten steel; after tapping to the rest of the molten steel which is two thirds of the total molten steel, adding a synthetic refining agent into the molten steel for 2-3 times, and adding before tapping to the rest of the molten steel in the ladle which is one third of the total molten steel; to remove most of the free oxygen and other inclusions in the raw molten steel. Slag closing operation is adopted, slag discharging amount is reduced, the tapping speed of a tapping hole is ensured to be more than 7t/min in the tapping process, scattered flow is reduced, and secondary oxidation of molten steel is avoided.
Specifically, the mass of the composite deoxidizer added for the first time is the same as that of the composite deoxidizer added for the second time, and the total mass of the two added amounts is 2 kg/ton steel to 4 kg/ton steel; in the comprehensive deoxidization process, ferrosilicon and ferromanganese cannot be added for comprehensive deoxidization. Preferably, the composite deoxidizer is a Si-Ca-Mn-RE-Ba composite deoxidizer.
Specifically, the mass of the synthetic refining agent is 3 kg/ton steel to 4 kg/ton steel, after all the synthetic refining agent is added, the argon pressure is properly increased, and the synthetic refining agent is fully contacted and reacted with molten steel through argon stirring, so that the floating of inclusions and the removal of gas are facilitated.
After the oxidation period of the general EAF furnace, the oxygen content in the molten steel is up to more than 1000ppm, so that the crude steel-making liquid is required to be pre-deoxidized, most of free oxygen in the molten steel is removed, the oxygen in the molten steel in the earlier stage of refining of the LF furnace can be rapidly reduced, and the smelting efficiency is improved; by adopting the pre-deoxidation mode, namely adding the composite deoxidizer and the synthetic refining agent at different stages of the tapping of the EAF furnace, after the molten steel is deoxidized by the mode, when the molten steel is placed in LF, an oxygen analyzer is used for measuring that the oxygen activity of the molten steel is less than 80ppm, the oxygen activity is reduced from 200ppm to below 80ppm, the purpose of rapid deoxidization of the molten steel is realized, and the deoxidization effect of single Al ingot (grain) added in a ladle is better than that of common technicians.
Step two
Smelting in an LF furnace for the first time: deoxidizing, desulfurizing and alloying smelting the molten steel in the furnace; after molten steel is placed in an LF furnace, firstly measuring the oxygen activity of the molten steel by an oxygen meter, adding aluminum of 1 kg/ton steel to 2 kg/ton steel and aluminum-calcium alloy balls of 1 kg/ton steel to 3 kg/ton steel according to the measurement condition to deoxidize, and simultaneously adjusting the alkalinity R of slag to be within the range of 2.5-4 to ensure that S in the molten steel is less than or equal to 0.008%; then adding 10 kg/ton of steel to 20 kg/ton of active lime and fluorite of the steel to carry out high-temperature desulfurization; when the temperature is more than or equal to 1580 ℃ and the oxygen activity is less than or equal to 10ppm, sampling and analyzing chemical components, adjusting and adding Co, mo, cr, ni and other non-oxidizable alloys to the lower limit of the specification according to the spectrum sample result, adjusting C to 0.2-0.4%, and then adjusting the temperature of molten steel to about 1620 ℃ to discharge steel to a VOD furnace.
Step three
Smelting in a VOD furnace: carrying out vacuumizing, oxygen blowing, decarburization and smelting on molten steel in a furnace; after vacuumizing 6KPa to 8KPa, oxygen blowing is carried out within the temperature range of 16000 ℃ to 1620 ℃, and meanwhile, the flow of argon is increased to improve the C-O reaction rate; after oxygen blowing is finished, continuously increasing vacuum to below 67Pa, increasing argon flow, keeping for more than 15min, and properly prolonging time under the condition of allowing conditions, so as to further react C and O in molten steel and achieve the effects of reducing carbon, removing gas and removing impurities; after the vacuum is released, 10 kg/ton steel to 20 kg/ton steel of CaO, 3 kg/ton steel to 5 kg/ton steel of fluorite, 1 kg/ton steel to 3 kg/ton steel of SiCa, 0.5 kg/ton steel to 1 kg/ton steel of Al particles, 0.8 kg/ton steel to 1.5 kg/ton steel of ferrotitanium and other deoxidizers are added, the reduction time is not less than 10min, and then tapping to an LF furnace for further refining.
Step four
Smelting in an LF furnace for the second time: after molten steel reaches an LF furnace from a VOD furnace, taking a gas sample to analyze the H/N/O content, wherein the oxygen content in the molten steel is generally 80-150 ppm, adding 0.8-1.5 Kg/ton of silicon-calcium alloy of steel for reduction according to the gas analysis result, and controlling the Al content in the molten steel to be 0.01-0.025% during refining.
Adding 10 kg/ton steel to 20 kg/ton steel of active lime and 1 kg/ton steel to 2 kg/ton steel of fluorite into molten steel in a furnace, enabling the alkalinity R value of steel slag on the surface of the molten steel to be 2.5-4, adding a composite deoxidizer in batches, adding 3-5 batches of the composite deoxidizer into the surface of the molten steel, setting each adding amount according to actual working conditions, further reducing the oxygen activity of the molten steel through a steel slag interface diffusion deoxidizing mode, observing the color change condition of the steel slag at the moment during the adding period, stopping adding the composite deoxidizer after the steel slag turns from black to yellow and turns white again and is kept for a certain time, and adding ferroboron and ferroniobium to adjust the Nb and B contents at the moment. Preferably, the composite deoxidizer is a Si-Ca-Mn-RE-Ba composite deoxidizer.
Specifically, in the smelting process of the furnace, the refining time is prolonged by more than 60 minutes under the conditions of low argon supply intensity and low flow. The stirring molten steel increases the probability of collision and growth of nonmetallic inclusions in the molten steel, and the floating argon bubbles are equivalent to a vacuum chamber, so that the gas in the molten steel can be absorbed, the inclusions suspended in the molten steel can be adhered, and the adhered inclusions are brought to a steel slag interface to be absorbed by the steel slag, therefore, the floating of most of the inclusions in the steel is ensured under the condition that the soft blowing of argon is kept for a certain time.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (10)
1. A method for controlling deoxidization of a high alloy cast steel, comprising the steps of:
smelting in an EAF furnace: before tapping, adding a composite deoxidizer into molten steel for the first time, and tapping; adding a composite deoxidizer for the second time in the tapping process; after tapping until the residual molten steel is two thirds of the total molten steel, adding a synthetic refining agent into the molten steel;
smelting in an LF furnace for the first time: deoxidizing, desulfurizing and alloying smelting the molten steel in the furnace;
smelting in a VOD furnace: carrying out vacuumizing, oxygen blowing, decarburization and smelting on molten steel in a furnace;
smelting in an LF furnace for the second time: active lime and fluorite are added into molten steel in a furnace to make slag have strong alkalinity, and then a composite deoxidizer is added.
2. The method of controlling deoxidation of high-alloy cast steel parts according to claim 1, wherein in the EAF furnace smelting step, the mass of the first-added composite deoxidizer is the same as the mass of the second-added composite deoxidizer.
3. The method of controlling deoxidation of high-alloy cast steel according to claim 2, wherein in the EAF furnace smelting step, the total mass of the first-added composite deoxidizer and the mass of the second-added composite deoxidizer is 2 kg/ton of steel to 4 kg/ton of steel.
4. A method of controlling the deoxidation of high alloy cast steel articles according to any one of claims 1 to 3, wherein the addition of the composite deoxidizer to the molten steel in the second step of the EAF furnace smelting is performed in batch mode.
5. The method according to claim 1, wherein the step of melting in the EAF furnace is performed in batch mode when adding the synthetic refining agent to the molten steel.
6. The method according to claim 5, wherein the synthetic refining agent is added in the EAF furnace smelting step in a mass of 3 kg/ton steel to 4 kg/ton steel.
7. The method for controlling the deoxidation of high alloy cast steel according to claim 1, wherein the composite deoxidizer is added to the molten steel in a batch mode in the second LF furnace smelting step.
8. The method of controlling deoxidation of high alloy cast steel according to claim 7, wherein the mass of the composite deoxidizer added in the second LF furnace smelting step is 1 kg/ton steel to 2 kg/ton steel.
9. The method according to claim 1, wherein in the second LF furnace smelting step, active lime is added in a mass of 10 kg/ton steel to 20 kg/ton steel and fluorite is added in a mass of 1 kg/ton steel to 2 kg/ton steel.
10. The method according to claim 7, wherein in the second LF furnace smelting step, active lime and fluorite are added to molten steel in the furnace so that the basicity R value of steel slag on the surface of the molten steel is 2.5 to 4, and then a composite deoxidizer is added in batches.
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