CN112725631A - Medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B and use method - Google Patents
Medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B and use method Download PDFInfo
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The invention relates to a medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B and a use method thereof, belongs to the technical field of electroslag special metallurgy, and is used for solving the problems of high energy consumption and high fluorine slag volatilization pollution of the conventional electroslag smelting slag system containing B. The medium-high fluorine slag system comprises the following components in percentage by mass: CaF2：40.26％～46.79％，Al2O3：23.07％～33.99％，CaO：22.25％～24.83％，MgO：3％～5％，B2O3: 0.5 to 1.5 percent, and the balance of impurities; SiO in impurities2Is less than 0.5 percent. The medium-high fluorine slag system of the invention reduces the volatilization pollution of the high-fluorine slag, and has low power consumption and good comprehensive metallurgical performance when in use.
Description
Technical Field
The invention relates to the technical field of electroslag special metallurgy, in particular to a medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B and a use method thereof.
Background
China is the first world-wide country of large electric power production and consumption, and the proportion of thermal power generation in China is 70-80%. However, most thermal power generating units are generally low in efficiency, which not only causes energy waste, but also brings serious environmental pollution. Therefore, China is urgently required to develop a high-efficiency power generation technology from both an economic perspective and an environmental protection perspective. The method for improving the generating efficiency of the power station comprises a reasonable management technology and a method for improving the unit efficiency, wherein the effective method for improving the unit efficiency is to improve the steam parameter level and develop the (supercritical) thermal power unit. At present, the heat-resistant steel rotor with 9-12% of Cr has good application performance, wherein European COST-FB2 is a typical leading edge steel type of 9Cr heat-resistant steel, contains about 0.01% of B, and has a melting temperature range of about 1330-1500 ℃.
The development of the supercritical rotor material and the key manufacturing technology thereof in China still needs to start from the aspects of smelting, heat treatment and the like. The smelting process is mainly used for improving the uniformity and purity of components and structures of cast ingots, and electroslag remelting is an important special smelting means. For example, FB2 steel of a generator set in China basically depends on import, and the important point is that some difficulties exist in electroslag smelting, such as control of narrow element components of a special slag system for FB2 steel and large-diameter electroslag ingots.
For a slag system for B-containing steel electroslag smelting, taking FB2 steel as an example, the conventional smelting slag system includes: (1) ternary slag system CaF2，Al2O3CaO and the balance of impurities, and is used for smelting COST-FB2 steel or CB2 steel and the like; (2) slag system CaF of five elements2，CaO，Al2O3，MgO，B2O3The slag system of (2).
But country of ChinaThe two slag systems are designed and selected from CaF2-Al2O3Determining the main component of the-CaO ternary slag, and adding a certain amount of MgO and B2O3The slag system design is completed by methods of equal components, the slag system selection is carried out by the experimental thought of a tentative slag system adding member, and the slag system design is usually not considered in place in theory. The two existing slag systems have high fluorine content and great pollution; and high energy consumption. For the heat-resistant steel containing B for the high-pressure rotor and the special slag system for electroslag smelting of other stainless steel containing B which is less than or equal to 0.015 percent, the system optimization still needs to be further developed based on theoretical calculation from the aspects of energy conservation, consumption reduction, smelting stability and environmental protection.
Disclosure of Invention
In view of the above analysis, the embodiments of the present invention are directed to provide a medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B and a use method thereof, so as to solve the problems of high energy consumption and high fluorine slag volatilization pollution of the existing electroslag smelting slag system containing B.
On one hand, the invention provides a medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B, wherein the medium-high fluorine slag system comprises the following components in percentage by mass: CaF2：40.26％～46.79％，Al2O3：23.07％～33.99％，CaO：22.25％～24.83％，MgO：3％～5％，B2O3: 0.5 to 1.5 percent, and the balance of impurities; SiO in impurities2＜0.5％。
Furthermore, in the medium-high fluorine slag system, CaO/(SiO)2+0.5*Al2O3) The range of (1) to (2.2).
Furthermore, in the medium-high fluorine slag system, (CaO + MgO)/(SiO)2+Al2O3) The range of (A) is 0.74 to 1.29.
Further, the basic physical properties of the medium-high fluorine slag system are as follows: the melting point is 1320-1350 ℃, the density is 2.60-2.68 g/cm at 1600-1800 DEG C3The viscosity is less than or equal to 0.015Pa · S, and the conductivity range is 1.97-3.03S/cm.
On the other hand, the invention also provides a preparation method of the medium-high fluorine slag system, which comprises the following steps:
step 1: for industrial pure CaF2Baking at high temperature for later use;
step 2: using industrial pure CaF2、CaO、Al2O3、MgO、B2O3Preparing a slag system according to the mass percentage of the target slag system components, and drying for later use;
and step 3: heating and melting the prepared slag system melting point to obtain a molten slag product;
and 4, step 4: and (3) carrying out water spraying treatment on the produced molten slag product, cooling to obtain a medium-high fluorine slag system, and crushing for later use.
Further, in the step 1, the high-temperature baking temperature is 801-850 ℃, and the baking time is 2-3 hours.
Further, in the step 3, the roasted CaF prepared in the step 1 is added after melting2The components are finely adjusted to obtain a finally produced molten slag product which meets the target slag system.
Further, in the step 2, the prepared components are dried for 2-3 hours at 501-550 ℃.
Further, in the step 3, the temperature for heating and melting is higher than the melting point temperature of the slag system, and the difference between the temperature for heating and melting and the melting point temperature of the slag system is more than 50 ℃.
On the other hand, the invention also provides a use method of the medium-high fluorine slag system, which comprises the following steps:
step 1: baking the blocky premelting slag for 2-4 hours at the temperature of 401-450 ℃ for later use;
step 2: and (3) charging the slag into an electroslag furnace, lowering the metal electrode bar in the electroslag furnace, and electrifying for smelting until the electrode bar is completely molten.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
1. compared with high-fluorine slag system, the invention properly reduces CaF2The addition amount of the fluorine-containing volatile matter is reduced by 3-5%, and the volatilization pollution of the high-fluorine slag is reduced. The invention is realized by adding B2O3，B2O3The steel slag melting furnace has the advantages that B elements which are easy to burn and lose among steel slag can be balanced, the burning loss of B is reduced, the content of the B elements in the steel slag is ensured, the energy-saving effect is achieved, and the technical requirements of difficult electroslag melting of 9Cr rotor steel are met.
2. When the slag system electroslag of the invention is smelted in a steady state, 50 to 65 percent of CaF is mixed with2Compared with the high-fluorine slag system, the power consumption can be reduced by 5-10%, the thickness of the slag crust is below 1.6mm when the steady-state smelting energy is reasonably input, and the comprehensive metallurgical performance is good.
3. And 5% -30% of CaF2Compared with the low-fluorine slag, the slag system of the invention has the advantages of easy arc striking, thinner slag crust and better steel ingot surface quality, can optimize and improve the steel ingot solidification condition, and is easy to realize shallow molten pool control.
4. The slag system has low fluorine content, small environmental pollution, good fluidity, low viscosity, small surface tension, good refining effect and good surface quality of the electroslag ingot obtained by refining.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description.
Detailed Description
The following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying examples, which form a part of this application, illustrate the principles of the invention and, together with the embodiments of the invention, serve to explain the principles of the invention and not to limit the scope of the invention.
The invention provides a medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B, which comprises the following components in percentage by mass: CaF2：40.26％～46.79％，Al2O3：23.07％～33.99％，CaO：22.25％～24.83％，MgO：3％～5％，B2O3: 0.5 to 1.5 percent, and the balance of impurities; SiO in impurities2＜0.5％。
Specifically, the rotor steel ingot is a 9Cr rotor steel ingot containing less than or equal to 0.015% of B.
In particular, the crown of the inventionThe basic physical properties of the fluorine slag system are as follows: the melting point is 1320-1350 ℃, the density is 2.60-2.68 g/cm at 1600-1800 DEG C3Viscosity is less than or equal to 0.015Pa · S (for example, 0.007 to 0.015Pa · S), and conductivity is in a range of 1.97 to 3.03S/cm (for example, 2.36 to 3.03S/cm).
It should be noted that in the production of a 9Cr rotor steel ingot containing B by electroslag remelting, the physicochemical properties of the slag system affect the production quality of the steel ingot. The method comprises the following specific steps:
(1) melting point: the melting point affects the conductivity, viscosity and heat generation of the slag system. The over-high or over-low melting point is not beneficial to the physicochemical reactions of dephosphorization and desulfurization and the like, and is easy to cause the problems of internal and surface quality of steel ingot products and metallurgical defects of cavities, air holes, inclusions and the like. Therefore, the melting point range of the slag system is designed to be 1320-1350 ℃, so that the uniform surface quality of the steel ingot is ensured, and no air holes are generated on the surface.
(2) Viscosity: the viscosity of the slag influences the circulating flow speed of the slag, and the low-viscosity slag has a strong stirring effect due to the action of electromagnetic stirring force, so that the fluidity of the slag can be enhanced, heat transfer is facilitated, and meanwhile, the diffusion of a reaction interface can be enhanced. The viscosity of the slag system is less than or equal to 0.015 Pa.s at 1600-1800 ℃, so that the good fluidity of the steel slag in smelting is ensured, the heat and mass transfer efficiency in the smelting furnace is improved, and the energy loss is reduced.
(3) Density: the density of the slag system mainly determines the slag consumption in the electroslag remelting process, the rate of a melting point penetrating through a slag layer in the electroslag remelting process, the residence time and the like, so that the purification and purification effects in the electroslag remelting process are determined, the difficulty degree of slag-metal separation in the electroslag remelting process is determined, and the like, so that the selection of the proper density of the slag system has certain influence on the metallurgical quality in the electroslag remelting process. The slag system of the present invention has a density of 2.60 to 2.67g/cm at 1600 to 1800 DEG C3The method ensures the uniform quality of the steel ingot and less impurity content, and simultaneously ensures the better separation of the steel ingot and the electroslag surface.
(4) Conductivity: the slag bath can be regarded as a resistor in the loop of the whole electroslag remelting process, and provides required resistance heat for remelting. When the current and the voltage passing through the slag bath and the effective area of the slag bath are fixed, the distance between the consumable electrode and the metal molten bath is in direct proportion to the conductivity of the slag. The too small conductivity can cause the reduction of the inter-polar distance (the distance between the consumable electrode and the metal molten pool), the too short inter-polar distance can easily cause the instability of the electroslag remelting process, and simultaneously, the reaction time of the steel slag in the falling process of the small metal molten drops is also influenced, and the removal of impurities is not facilitated. The electric conductivity of the slag system is 2.36-3.03S/cm at 1600-1800 ℃, so that sufficient heat transmission is provided for the electroslag smelting process, and the smooth operation of the electroslag smelting process is ensured.
Specifically, the component design of the medium-high fluorine slag system is based on the following principle:
CaF2can reduce the melting point, viscosity and surface tension of the slag in a slag system, but compared with other components, CaF2The conductivity of (2) is higher; the CaO in the slag system has the functions of increasing the alkalinity of the slag, improving the desulfurization efficiency and reducing the conductivity of the slag; al (Al)2O3The conductivity of the slag can be obviously reduced in a slag system, the power consumption is reduced, and the productivity is improved.
The MgO has two functions in a slag system, firstly, because the rotor steel has strict requirements on the mass fraction of H in a steel ingot, a certain amount of MgO needs to be added into the slag system in the design of the slag system to reduce the permeability of H and also has the function of reducing oxygen and nitrogen in a molten pool; and MgO can form a layer of semi-solidified film on the surface of the slag pool, so that the radiation heat loss of the slag surface to the atmosphere is reduced.
B2O3The function in the slag system is to balance the B element which is easy to burn and lose in the slag system.
Therefore, in order to ensure proper melting point, viscosity, density and conductivity of the slag system, the invention further optimizes the slag system components, particularly, the characteristic alkalinity (CaO/(SiO) of the slag system is defined in the slag system components2+0.5*Al2O3) The range of 1.3 to 2.2), the characteristic alkalinity of the slag system is controlled in the range, the desulfurization rate is good, and the method is suitable for smelting electrode rods with the S less than or equal to 0.020.
Among the above slag components, the general basicity ((CaO + MgO)/(SiO)) of the slag is defined2+Al2O3) Am of (a)The range of 0.74 to 1.29 is enclosed, the generalized alkalinity of the slag system is controlled in the range, and the slag system has better capability of adsorbing impurities.
Among the above slag system components, MgO/Al is controlled2O3The range of the oxygen content in the slag bath is 0.08-0.22, so that a good slag crust solidified film is obtained, oxygen absorption in the slag bath is effectively reduced, and oxygen increment of the metal melting bath is reduced.
The medium-high fluorine slag system of the invention contains 3-5% of MgO and 0.5-1.5% of B2O3CaF of2-Al2O3And (3) calculating the specific content of each component in the slag system according to the physical property of the rotor steel containing B and the temperature range of the required slag system by using a thermodynamic phase diagram of CaO, wherein the obtained slag system has stable component structure, can balance B elements which are easy to burn and lose among steel slag, has the advantage of energy-saving effect and the like, meets the technical requirements of the electroslag smelting difficulty of the 9Cr high-pressure rotor steel containing B and the like, and provides technical support for the electroslag smelting of new materials.
Different from the existing high-fluorine slag system, the application adopts the high-fluorine slag system, and CaF in the slag system2Reduced content of CaO and Al2O3The content is increased. CaF2MgO is related to the viscosity of the slag system. CaF2The addition amount of (A) is in negative correlation with the viscosity of the slag system, and CaF2The addition amount of (b) increases, and the viscosity of the slag system decreases. The slag system has low melting point and viscosity and good fluidity, and is beneficial to the smooth operation of the electroslag remelting process. Thus, the CaF of the present application2The addition amounts of MgO and MgO are respectively 40.26-46.79% and 3-5%, the viscosity of the slag system at 1600-1800 ℃ is less than or equal to 0.015 Pa.s, and the surface of the slag crust is uniform at the viscosity.
At high temperatures, both the density and surface tension of the slag system decrease with increasing temperature, and with CaF2The content and MgO content increase and decrease gradually. The slag system has low fluorine content, small environmental pollution, good fluidity, low viscosity, small surface tension, good refining effect and good surface quality of the electroslag ingot obtained by refining.
In particular, the inventor of the invention finds that through deep thermal state experiments and production researches, the electroslag is ensured to be in a long-time smelting processStable composition, uniform slag crust surface, B2O3The content of the elements is controlled between 0.5 percent and 1.5 percent.
The element B can react in the smelting process as follows:
3[Si]+2(Al2O3)＝3(SiO2)+4[Al](formula 1)
4[Nb]+5(SiO2)＝2(Nb2O5)+5[Si](formula 2)
2[Mn]+(SiO2)＝2(MnO)+[Si](formula 3)
4[B]+3(SiO2)＝2(B2O3)+3[Si](formula 4)
In order to accurately control the mass fraction of main alloy elements in steel and prevent easy-to-oxidize elements in molten steel from being burnt, SiO in a slag system2The mass fraction must be small. And SiO is used for controlling the mass fraction of the main strengthening element B in the steel to be stable2The content of (A) should be controlled below 0.5%.
On the other hand, the invention provides a preparation method of a medium-high fluorine slag system, which comprises the following steps:
step 1: for industrial pure CaF2Baking at high temperature for later use;
step 2: using industrial pure CaF2、CaO、Al2O3、MgO、B2O3Preparing a slag system according to the mass percentage of the target slag system components, and drying for later use;
and step 3: heating and melting the prepared slag system melting point to obtain a molten slag product;
and 4, step 4: and (3) spraying water on the produced molten slag product, cooling, and crushing into 8-15 mm block-shaped premelting slag for later use.
In the step 1, considering that there may be environmental moisture in the processing, production and transportation of industrial raw materials, it is necessary to use industrial pure CaF2Baking at 801-850 deg.C for 2-3 hr for removing water and impurities.
Specifically, in the step 2, the CaF content in the slag system is reduced2And (3) volatilizing, namely drying the prepared components in the step (2) at 501-550 ℃ for 2-3 hours for later use, and removing moisture and impurities.
Specifically, in step 3, in order to ensure sufficient melting, the temperature for heating and melting is higher than the melting point temperature of the slag system, and the difference between the temperature for heating and melting and the melting point temperature of the slag system is 50 ℃ or higher.
In particular, consider CaF2Has the characteristic of easy consumption, in the step 3, the roasted CaF prepared in the step 1 is added after being melted2The components are finely adjusted to obtain a finally produced molten slag product which meets the target slag system.
On the other hand, the invention provides a use method of a medium-high fluorine slag system, which comprises the following steps:
step 1: baking the blocky premelting slag for 2-4 hours at the temperature of 401-450 ℃ for removing water for later use;
step 2: and (3) charging the slag into an electroslag furnace, lowering the metal electrode bar in the electroslag furnace, and electrifying for smelting until the electrode bar is completely molten.
In step 2, for the cold start electroslag furnace, after the slag baked in step 1 is added into a crystallizer of the electroslag furnace, the electroslag furnace lowers a metal electrode rod, and the metal electrode rod is electrified and smelted until the electrode rod is melted. Wherein, the addition of the slag adopts the following method: firstly, adding slag before an electrode is arranged in a crystallizer of an electroslag furnace, and uniformly spreading part of the slag to the bottom of the crystallizer; uniformly adding the residual slag into the crystallizer by using a feeder, and finishing the addition within 1-4 h; the method aims to slowly add slag after a metal molten pool and a slag pool are formed in an electroslag crystallizer, so that the phenomenon of difficult slag melting caused by excessive slag inclusion in a short time is avoided. Meanwhile, low-speed slag charging is selected, the slag charging time is properly prolonged, and B after the slag charging can be delayed to a certain extent2O3Decomposition of (3). It is noted that the amount of the slag charge added first accounts for 5 to 20 percent of the total mass of the added slag charge.
In the step 2, for the hot start electroslag furnace, the baked slag is melted into a liquid state at a temperature of "melting point +50 ℃ or higher" by using a heating furnace, and then the liquid state is added into a crystallizer to perform electric smelting, or the baked slag in the step 1 is added into the crystallizer of the electroslag furnace, and then a graphite electrode is used for supplying electricity to heat the slag at a temperature higher than the melting point until molten slag liquid is formed, and then the electric smelting is performed.
For example, when pilot-scale production is carried out in a 5t electroslag furnace, about 100-120 kg of slag is taken before, and the slag is baked for 3 hours at the temperature of 430 ℃ for removing water. Adding 5-20 kg of slag to the bottom of the crystallizer before the electroslag crystallizer is filled with the electrode, wherein the slag is uniformly spread and is not accumulated. And uniformly adding the residual slag into the crystallizer by using a feeder, wherein the addition is preferably finished within 1-4 hours. And then, 1.8-2.2 t of smelting electrode rods are filled into the crystallizer of the electroslag furnace. The electrode components meet the component requirements of FB2 steel, and the surface is polished and peeled, and the surface is glossy and has no oxide layer for standby. And (5) detecting and testing systems such as water, electricity and gas of the atmosphere protection electroslag furnace equipment at 5t, and preparing for standby.
For example, pilot production is performed in a 5t electroslag furnace, and the key process conditions are as follows: the electrode diameter is 375mm, the crystallizer diameter is 435mm, the slag layer is designed to be about 160mm, the power input in an arc starting stage is about 450-550 kW, the power input in a steady state stage is 690-720 kW, and the average melting speed is about 4.7 kg/min. The smelting effect is as follows: the height of the ingot after smelting is 1.73m, and the actual ingot weighs about 2 tons. The elements in the length direction of the ingot are uniformly distributed and reach the control standard, the surface quality is good, the thickness distribution of the slag crust is uniform, and the average slag crust thickness of the middle section of the steel ingot is less than or equal to 1.4 mm.
The high fluorine slag used in the following comparative examples 1-3 was the existing 50% -65% CaF2The high fluorine slag system. The low-fluorine slag system for comparison is the existing 5-30 percent CaF2The low-fluorine slag system.
Example 1
The embodiment provides a medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B, wherein the slag system comprises the following components in percentage by mass: CaF2；40.26％，Al2O3：33.99％，CaO；22.25％，MgO：3％，B2O3: 0.5 percent, and the balance of impurities; SiO in impurities2Quality of (1)The content percentage is less than 0.5 percent.
The basic physical properties of the slag of the present example are: the melting point is 1331 ℃, the density ranges from 2.67 to 2.70g/cm at 1600 to 1800 DEG C3The viscosity is 0.011 to 0.021 Pa.s, and the conductivity is 1.58 to 2.36S/cm.
The preparation method of the slag system comprises the following steps:
step 1: considering the factors of processing, production and transportation of industrial raw materials, such as possible environmental humidity, and the like, the industrial pure CaF is treated2Baking at 820 deg.C for 3 hr for use to remove water and impurities;
step 2: using industrial pure CaF2、CaO、Al2O3、MgO、B2O3Preparing a slag system according to the mass percentage of the designed target slag system components, and baking the slag system for 3 hours at 520 ℃ for later use to remove water and impurities;
and step 3: melting the prepared slag system at 1390 ℃ according to the characteristic of self melting point, because CaF2Has the characteristic of easy damage and consumption, and is mixed with roasted CaF after being melted2Fine adjusting the components to obtain a finally produced molten slag product which meets the target slag system;
and 4, step 4: and (3) spraying water on the produced molten slag product, cooling, and crushing into 8-10 mm block-shaped premelting slag for later use.
The use method of the slag system comprises the following steps:
step 1: baking the blocky premelting slag for 4 hours at the temperature of 420 ℃ so as to remove water for later use;
step 2: and (3) for the cold start electroslag furnace, after the slag baked in the step (1) is added into a crystallizer of the electroslag furnace, lowering the metal electrode bar of the electroslag furnace, and electrifying for smelting until the electrode bar is melted.
The application and implementation effects of the slag system of this example are compared as shown in table 1 below:
TABLE 1 Effect of the embodiment
Example 2
The embodiment provides a medium-high fluorine slag system for electroslag remelting of a B-containing 9Cr rotor steel ingot, which comprises the following components in percentage by mass: CaF2；46.79％，Al2O3：23.56％，CaO；24.15％，MgO：5％，B2O3: 0.5 percent, and the balance of impurities; SiO in impurities2The mass percentage content of the components is less than 0.5 percent.
The basic physical properties of the slag of the present example are: the melting point is 1327 ℃, 1600 ℃ to 1800 ℃, and the density ranges from about 2.60 g/cm to 2.64g/cm3The viscosity is about 0.007 to 0.014Pa · S, and the conductivity is 2.25 to 3.03S/cm.
The preparation method of the slag system comprises the following steps:
step 1: considering the factors of processing, production and transportation of industrial raw materials, such as possible environmental humidity, and the like, the industrial pure CaF is treated2Baking at 820 deg.C for 3 hr for use to remove water and impurities;
step 2: using industrial pure CaF2、CaO、Al2O3、MgO、B2O3Preparing a slag system according to the mass percentage of the designed target slag system components, and baking the slag system for 3 hours at 520 ℃ for later use to remove water and impurities;
and step 3: the prepared slag system is melted at 1380 ℃ according to the characteristic of self melting point, because CaF2Has the characteristic of easy damage and consumption, and is mixed with roasted CaF after being melted2The components are finely adjusted to obtain a finally produced molten slag product which meets the target slag system.
And 4, step 4: and (3) spraying water on the produced molten slag product, cooling, and crushing into 9-15 mm block-shaped premelting slag for later use.
The use method of the slag system comprises the following steps:
step 1: baking the massive pre-melted slag for 3 hours at the temperature of 440 ℃ for removing water for later use;
step 2: the method comprises the steps of adopting a hot start electroslag furnace, melting baked slag into liquid at 1380 ℃ by using a heating furnace, adding the liquid slag into a crystallizer, descending a metal electrode bar by using the electroslag furnace, and electrifying for smelting until the electrode bar is melted.
The application and implementation effects of the slag system of this example are compared as shown in table 2 below:
TABLE 2 Effect of implementation
Example 3
The embodiment provides a medium-high fluorine slag system for electroslag remelting of a B-containing 9Cr rotor steel ingot, which comprises the following components in percentage by mass: CaF2；46.10％，Al2O3：23.07％，CaO；24.83％，MgO：5％，B2O3: 1% and the balance of impurities; SiO in impurities2The mass percentage content of the components is less than 0.5 percent.
The basic physical properties of the slag of the present example are: the melting point is 1324 ℃, 1600 ℃ to 1800 ℃, and the density ranges from about 2.60 g/cm to 2.64g/cm3The viscosity is about 0.007 to 0.014Pa · S, and the conductivity is 2.24 to 3.02S/cm.
The preparation method of the slag system comprises the following steps:
step 1: considering the factors of processing, production and transportation of industrial raw materials, such as possible environmental humidity, and the like, the industrial pure CaF is treated2Baking at 820 deg.C for 3 hr for use to remove water and impurities;
step 2: using industrial pure CaF2、CaO、Al2O3、MgO、B2O3Preparing a slag system according to the mass percentage of the designed target slag system components, and baking the slag system for 3 hours at 520 ℃ for later use to remove water and impurities;
and step 3: the prepared slag system is melted at 1380 ℃ according to the characteristic of self melting point, because CaF2Has the characteristic of easy damage and consumption, and is mixed with roasted CaF after being melted2Fine-tuning the composition to obtain the final produced molten slag productAccording with the target slag system;
and 4, step 4: and (3) spraying water on the produced molten slag product, cooling, and crushing into 8-12 mm block-shaped premelting slag for later use.
The use method of the slag system comprises the following steps:
step 1: baking the massive pre-melted slag for 3 hours at the temperature of 440 ℃ for removing water for later use;
step 2: and (2) adopting a hot start electroslag furnace, adding the slag baked in the step (1) into a crystallizer of the electroslag furnace, electrifying by using a graphite electrode, heating the slag at a temperature higher than a melting point until molten slag liquid is formed, lowering a metal electrode rod of the electroslag furnace, and electrifying and smelting until the electrode rod is melted.
The application and implementation effects of the slag system of this example are compared as shown in table 3 below:
TABLE 3 Effect of implementation
The implementation effect of the embodiment 1-3 of the invention can show that the slag system electroslag of the invention is mixed with 50% -65% CaF in steady state smelting2Compared with the high-fluorine slag system, the power consumption can be reduced by 5-10%, and the thickness of the slag crust is below 1.6mm when the steady-state smelting energy is reasonably input; and 5% -30% of CaF2Compared with the low-fluorine slag system, the slag system of the invention has the advantages of easy arc striking, thinner slag crust, better steel ingot surface quality and good comprehensive metallurgical performance.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. A medium-high fluorine slag system for electroslag remelting rotor steel ingot containing B is characterized in that the medium-high fluorine slag system comprises the following components in percentage by mass: CaF2：40.26％～46.79％，Al2O3：23.07％～33.99％，CaO：22.25％～24.83％，MgO：3％～5％，B2O3: 0.5 to 1.5 percent, and the balance of impurities; SiO in impurities2＜0.5％。
2. The medium and high fluorine slag system according to claim 1, wherein in the medium and high fluorine slag system, CaO/(SiO)2+0.5*Al2O3) The range of (1) to (2.2).
3. The medium-high fluorine slag system according to claim 1, wherein in the medium-high fluorine slag system, (CaO + MgO)/(SiO)2+Al2O3) The range of (A) is 0.74 to 1.29.
4. The medium-high fluorine slag system according to claim 1, characterized in that the basic physical properties of the medium-high fluorine slag system are as follows: the melting point is 1320-1350 ℃, the density is 2.60-2.68 g/cm at 1600-1800 DEG C3The viscosity is less than or equal to 0.015Pa · S, and the conductivity range is 1.97-3.03S/cm.
5. The preparation method of the medium-high fluorine slag system is characterized by comprising the following steps of:
step 1: for industrial pure CaF2Baking at high temperature for later use;
step 2: using industrial pure CaF2、CaO、Al2O3、MgO、B2O3Preparing a slag system according to the mass percentage of the target slag system components, and drying for later use;
and step 3: heating and melting the prepared slag system melting point to obtain a molten slag product;
and 4, step 4: and (3) carrying out water spraying treatment on the produced molten slag product, cooling to obtain a medium-high fluorine slag system, and crushing for later use.
6. The method for preparing the medium and high fluorine slag system according to claim 5, wherein in the step 1, the high temperature baking temperature is 801-850 ℃, and the baking time is 2-3 hours.
7. The method for preparing middle and high fluorine slag system according to claim 5, wherein the roasted CaF prepared in step 1 is added after melting in step 32The components are finely adjusted to obtain a finally produced molten slag product which meets the target slag system.
8. The method for preparing the medium and high fluorine slag system according to claim 5, wherein in the step 2, the prepared components are dried at 501-550 ℃ for 2-3 hours.
9. The method for preparing a medium-high fluorine slag system according to claim 5, wherein in the step 3, the temperature for heating and melting is higher than the melting point temperature of the slag system, and the difference between the temperature for heating and melting and the melting point temperature of the slag system is more than 50 ℃.
10. The use method of the medium-high fluorine slag system is characterized in that the medium-high fluorine slag system is the medium-high fluorine slag system in the claims 1 to 4 or the medium-high fluorine slag system prepared in the claims 5 to 9, and comprises the following steps:
step 1: baking the blocky premelting slag for 2-4 hours at the temperature of 401-450 ℃ for later use;
step 2: and (3) charging the slag into an electroslag furnace, lowering the metal electrode bar in the electroslag furnace, and electrifying for smelting until the electrode bar is completely molten.
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