阅读说明：本技术 用于电渣重熔含b的转子钢锭的中低氟渣系及使用方法 (Medium-low fluorine slag system for electroslag remelting rotor steel ingot containing B and use method thereof ) 是由 林腾昌 杨勇 李龙飞 姚同路 崔怀周 梁强 赵吉庆 何西扣 刘正东 杨刚 于 2020-12-29 设计创作，主要内容包括：本发明涉及一种用于电渣重熔含B的转子钢锭的中低氟渣系及使用方法,属于电渣特种冶金技术领域,用以解决现有含B的电渣熔炼渣系能耗高及高氟渣挥发污染的问题。所述中低氟渣系中各个组分的质量百分含量为：CaF-2；30.06％～39.30％,Al-2O-3：34.02％～43.79％,CaO；18.31％～22.72％,MgO：3％～5％,B-2O-3：0.10％～3.50％,其余为杂质；杂质中SiO-2＜0.5％。其中,CaO/(SiO-2+0.5*Al-2O-3)的范围为0.7～1.4。本发明的中低氟渣系减少了高氟渣挥发污染,使用时电耗低,综合冶金性能良好。(The invention relates to a medium-low 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-low fluorine slag system comprises the following components in percentage by mass: CaF 2 ；30.06％～39.30％，Al 2 O 3 ：34.02％～43.79％，CaO；18.31％～22.72％，MgO：3％～5％，B 2 O 3 : 0.10-3.50 percent, and the balance of impurities; SiO in impurities 2 Is less than 0.5 percent. Wherein, CaO/(SiO) 2 +0.5*Al 2 O 3 ) The range of (A) is 0.7 to 1.4. The medium-low fluorine slag system of the invention reduces the volatilization pollution of high fluorine slag, has low power consumption in use and good comprehensive metallurgical performance.)

1. A medium and low fluorine slag system for electroslag remelting rotor steel ingot containing B is characterized in that the medium and low fluorine slag system comprises the following components in percentage by mass: CaF₂；30.06％～39.30％，Al₂O₃：34.02％～43.79％，CaO；18.31％～22.72％，MgO：3％～5％，B₂O₃: 0.10-3.50 percent, and the balance of impurities; SiO in impurities₂≤0.5％。

2. The medium and low fluorine slag system according to claim 1, wherein in the medium and low fluorine slag system, CaO/(SiO)₂+0.5*Al₂O₃) The range of (A) is 0.7 to 1.4.

3. The medium and low fluorine slag system according to claim 1, wherein in the medium and low fluorine slag system, (CaO + MgO)/(SiO)₂+Al₂O₃) The range of (A) is 0.5 to 0.75.

4. The medium and low fluorine slag system according to claim 1, wherein MgO/Al is present in the medium and low fluorine slag system₂O₃The range of (A) is 0.05 to 0.15.

5. The method of claim 1The medium-low fluorine slag system is characterized in that the basic physical properties of the medium-low fluorine slag system are as follows: the melting point is 1320-1370 ℃; at 1700-1800 ℃, the density is 2.67-2.78 g/cm³Viscosity of 0.011 to 0.021 Pa.s and conductivity of 1.23 to 2.31S/cm.

6. A preparation method of the medium-low fluorine slag system, which is used for preparing the medium-low fluorine slag system according to any one of claims 1 to 5, and 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-low fluorine slag system, and crushing for later use.

7. The method for preparing a medium-low fluorine slag system according to claim 6, wherein in the step 2, the drying temperature is 551-599 ℃ and the drying time is 2-4 hours.

8. The method for preparing middle and low fluorine slag system according to claim 6, 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.

9. The use method of the medium-low fluorine slag system is characterized in that the medium-low fluorine slag system is the medium-low fluorine slag system in the claims 1 to 5 or the medium-low fluorine slag system prepared in the claims 6 to 8, and comprises the following steps:

step 1: drying the blocky premelting slag 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.

10. The use method of the medium and low fluorine slag system according to claim 9, wherein in the step 1, the drying temperature is 451-499 ℃ and the drying time is 3-4 hours.

Technical Field

The invention relates to the technical field of electroslag special metallurgy, in particular to a medium-low 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. The existing 9-12% Cr heat-resistant steel rotor 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 1329-1504 ℃.

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(high fluorine content), CaO, Al₂O₃，MgO，B₂O₃The slag system of (2).

However, domestic research institutions and slag production enterprisesThe slag service enterprises select CaF as the design choice of the two slag systems₂-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 the problems of high fluorine content, great pollution and insufficient structural stability of slag system components in the long-time electroslag smelting process. 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 embodiment of the present invention aims to provide a medium-low 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-low fluorine slag system for electroslag remelting rotor steel ingot containing B, wherein the medium-low fluorine slag system comprises the following components in percentage by mass: CaF₂；30.06％～39.30％，Al₂O₃：34.02％～43.79％，CaO；18.31％～22.72％，MgO：3％～5％，B₂O₃: 0.10-3.50 percent, and the balance of impurities; SiO in impurities₂≤0.5％。

Furthermore, in the medium-low fluorine slag system, CaO/(SiO)₂+0.5*Al₂O₃) The range of (A) is 0.7 to 1.4.

Furthermore, in the medium-low fluorine slag system, (CaO + MgO)/(SiO)₂+Al₂O₃) The range of (A) is 0.5 to 0.75.

Further, in the medium-low fluorine slag system, MgO/Al₂O₃The range of (A) is 0.05 to 0.15.

Further, the basic physical properties of the medium-low fluorine slag system are as follows: the melting point is 1320-1370 ℃; at 1700-1800 ℃, the density is 2.67-2.78 g/cm³Viscosity of 0.011 to 0.021 Pa.s and conductivity of 1.23 to 2.31S/cm.

On the other hand, the invention provides a preparation method of a medium-low 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-low fluorine slag system, and crushing for later use.

Further, in the step 2, the drying temperature is 551-599 ℃, and the drying time is 2-4 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.

In another aspect, the invention provides a use method of a medium-low fluorine slag system, comprising the following steps:

step 1: drying the blocky premelting slag 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.

Further, in the step 1, the drying temperature is 451-499 ℃, and the drying time is 3-4 hours.

Compared with the prior art, the invention can realize at least one of the following beneficial effects:

1. compared with the high-fluorine slag system, the invention reduces CaF₂The addition amount of the fluorine-containing volatile matter is reduced by more than 6 percent, and the volatile pollution of the high-fluorine slag is reduced.

2. When the slag system of the invention is used for electroslag steady smelting, 50 to 70 percent CaF is mixed with₂Compared with the high-fluorine slag system (such as ANF-6 slag), the power consumption can be reduced by 10 percentAnd in addition, the thickness of the slag crust is below 1.8mm when the steady-state smelting energy is reasonably input.

3. The slag system has low fluorine content, small environmental pollution, good fluidity, low viscosity, small surface tension, good refining effect, good surface quality of the electroslag ingot obtained by refining and good comprehensive metallurgical performance.

4. 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.

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-low fluorine slag system for electroslag remelting rotor steel ingot containing B. The medium-low fluorine slag system comprises the following components in percentage by mass: CaF₂；30.06％～39.30％，Al₂O₃：34.02％～43.79％，CaO：18.31％～22.72％，MgO：3％～5％，B₂O₃: 0.10-3.50 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 0.02% of B.

Specifically, the basic physical properties of the medium-low fluorine slag system are as follows: the melting point is 1320-1370 ℃; at 1700-1800 ℃, the density is 2.67-2.78 g/cm³Viscosity of 0.011 to 0.021 Pa.s and conductivity of 1.23 to 2.31S/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.

(1) Melting point: the melting point of the slag affects the conductivity, viscosity and heat productivity 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. The design melting point range is 1320-1370, the surface quality of the steel ingot is ensured to be uniform, 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 steel slag is 0.011-0.021 Pa.s at 1700-1800 ℃, so that the steel slag in smelting has good fluidity, the heat and mass transfer efficiency in a 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 density of the invention is 2.67-2.78 g/cm at 1700-1800 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 electric slag smelting furnace is 1.23-2.31S/cm at 1700-1800 ℃, 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-low 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 effect of CaO in the slag system increases the alkalinity of the slag, improves the desulfurization efficiency and reduces the slag conductivity; 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) 0.7 to 1.4, and the characteristic alkalinity of the slag system is controlled in the above range, and the desulfurization rate is good.

Specifically, a proper slag system proportion is selected according to the requirement of steel grade on the S content, and when the S content in the electrode bar is less than 0.005%, a slag system with the characteristic alkalinity of 0.7-0.99 is selected for smelting; when S in the electrode bar is more than or equal to 0.005% and less than 0.015%, smelting by using a slag system with characteristic alkalinity of 1-1.4.

Specifically, the generalized basicity ((CaO + MgO)/(SiO)) of the slag system is defined₂+Al₂O₃) In the range of 0.5 to 0.75), and the slag system has good impurity adsorption capability by controlling the generalized alkalinity of the slag system in the range.

In particular, slag-based MgO/Al₂O₃The range of (A) is 0.05-0.15, so that a better slag crust solidified film is obtained, the transfer of oxygen in a slag pool is effectively reduced, and the oxygen increment of a metal molten pool is reduced.

The slag system of the invention is based on the slag system containing 3 to 5 percent of MgO and 0.1 to 3.5 percent 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 invention adopts a medium-low fluorine slag system, and CaF in the slag system₂Reduced content of CaO and Al₂O₃The content is increased. In the research, CaF is found₂CaF, which is associated with the viscosity of the slag system₂The 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.

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 discovers through deep thermal state experiments and production researches that the composition of the electroslag is stable in the long-time smelting process, the surface of the slag crust is uniform, and B₂O₃The content of the elements should be controlled between 0.1% and 3.5%.

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-low 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 3-6 mm block-shaped premelting slag for later use.

In the step 1, considering factors such as the possible environmental humidity in the processing, production and transportation processes of industrial raw materials, the industrial pure CaF2 is baked at a high temperature of 851-900 ℃ for 2-4 hours for standby application, so as to remove moisture and impurities;

specifically, in the step 2, the CaF content in the slag is reduced₂Volatilizing, and baking at 551-599 ℃ for 2-4 hours for later use, so as to remove water 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, melting is carried outBlending into the baked CaF prepared in step 1₂The 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-low fluorine slag system, which comprises the following steps:

step 1: baking the massive pre-melted slag at the temperature of 451-499 ℃ for 3-4 hours, and 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, the slag charge is added at a lower speed (after the slag charge is finished within 1-4 h), the slag charge time is properly prolonged, and the slag charge B 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 4 hours at the temperature of 460 DEG CThe purpose is to remove moisture. Before an electrode is arranged in an electroslag crystallizer, 10-15 kg of slag is added to the bottom of the crystallizer, and the slag is uniformly spread and is not accumulated. The residual thermal state slag is uniformly added into the crystallizer by a feeder, and the addition is preferably finished within 1-4 hours, so that the slag is slowly added after a metal molten pool and a slag pool are formed in the electroslag crystallizer, and 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). And then, 1.9-2.1 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, and the dosage of the added arc striking is increased by 30 percent (compared with 50 to 65 percent of CaF)₂The high fluorine slag system), the power input in the arc starting stage is about 700-1200 kW, the power input in the steady state stage is 450-550 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 1.76m, 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 1.8 mm.

The high fluorine slag systems described below for comparison in examples 1-5 are now 50% to 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-low fluorine slag system for electroslag remelting rotor steel ingot containing B, wherein the slag system comprises the following components in percentage by mass: CaF₂：33.20％，Al₂O₃：43.79％，CaO：19.50％，MgO：3％，B₂O₃: 0.5 percent; the rest is impurities, wherein SiO is contained in the impurities₂The mass percentage content of the component (A) is less than or equal to 0.5 percent.

The basic physical properties of the slag system of the embodiment are as follows: the melting point is 1352 ℃, 1700 to 1800 ℃, and the density ranges from 2.70 to 2.71g/cm³The viscosity is 0.016 to 0.021 Pa.s, and the conductivity is 1.23 to 1.62S/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 860 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 560 ℃ for later use to remove moisture and impurities;

and step 3: melting the prepared slag system at 1410 ℃ 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 3-5 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 4 hours at the temperature of 460 ℃ for removing 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 electric slag furnace, the metal electrode bar is lowered down by the electroslag furnace, and the electric melting is carried out 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-low fluorine slag system for electroslag remelting rotor steel ingot containing B, wherein the slag system comprises the following components in percentage by mass: CaF₂：39.30％，Al₂O₃：34.02％，CaO：22.68％，MgO：3％，B₂O₃: 1 percent; the rest is impurities, wherein SiO is contained in the impurities₂The mass percentage content of the component (A) is less than or equal to 0.5 percent.

The basic physical properties of the slag system of the embodiment are as follows: the melting point is 1333 ℃, the density ranges from 2.67 g/cm to 2.69g/cm at 1700 ℃ to 1800 DEG C³The viscosity is 0.011 to 0.015Pa · S, and the conductivity is 1.92 to 2.31S/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 860 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 560 ℃ for later use to remove moisture 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 3-6 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 4 hours at the temperature of 460 ℃ 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-low fluorine slag system for electroslag remelting of a B-containing 9Cr rotor steel ingot, wherein the slag system comprises the following components in percentage by mass: CaF₂：30.06％，Al₂O₃：41.22％，CaO：22.72％，MgO：3％，B₂O₃: 3 percent; the rest is impurities, wherein SiO is contained in the impurities₂The mass percentage content of the component (A) is less than or equal to 0.5 percent.

The basic physical properties of the slag of the present example are: the density is 2.76-2.78 g/cm at the melting point of 1361 ℃ and the temperature of 1700-1800 DEG C³The viscosity is about 0.015 to 0.021 Pa.s, and the conductivity is 1.23 to 1.62S/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 860 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 560 ℃ for later use to remove moisture and impurities;

and step 3: melting the prepared slag system at 1420 ℃ 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) carrying out water spraying treatment on the produced molten slag product, cooling, and crushing into blocky premelting slag with the size less than 3-5 mm for later use.

The use method of the slag system comprises the following steps:

step 1: baking the massive pre-melted slag for 4 hours at the temperature of 460 ℃ 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 electric slag 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

Example 4

The embodiment provides a medium-low fluorine slag system for electroslag remelting of a B-containing 9Cr rotor steel ingot, wherein the slag system comprises the following components in percentage by mass: CaF₂：36.08％，Al₂O₃：36.84％，CaO：21.58％，MgO：5％，B₂O₃: 0.5 percent; the rest is impurities, wherein SiO is contained in the impurities₂The mass percentage content of the component (A) is less than or equal to 0.5 percent.

The basic physical properties of the slag of the present example are: the melting point is 1339 ℃, the density ranges from 2.70 g/cm to 2.71g/cm at 1700 ℃ to 1800 DEG C³The viscosity is about 0.012 to 0.016 pas, and the conductivity is 1.52 to 1.91S/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 860 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 560 ℃ for later use to remove moisture and impurities;

and step 3: melting the prepared slag system at 1400 ℃ 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 blocky premelted slag with the size less than 5mm for later use.

The use method of the slag system comprises the following steps:

step 1: baking the massive pre-melted slag for 4 hours at the temperature of 460 ℃ 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 in table 4 below:

TABLE 4 Effect of the embodiment

Example 5

The embodiment provides a medium-low fluorine slag system for electroslag remelting of a B-containing 9Cr rotor steel ingot, wherein the slag system comprises the following components in percentage by mass: CaF₂：39.14％，Al₂O₃：34.55％，CaO：18.31％，MgO：5％，B₂O₃: 3 percent; the rest is impurities, wherein SiO is contained in the impurities₂The mass percentage content of the component (A) is less than or equal to 0.5 percent.

The basic physical properties of the slag of the present example are: the melting point is 1341 ℃, the temperature is 1700 to 1800 ℃, and the density ranges from 2.70 to 2.72g/cm³The viscosity is about 0.012 to 0.016 pas, and the conductivity is 1.55 to 1.94S/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 860 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 560 ℃ for later use to remove moisture and impurities;

and step 3: melting the prepared slag system at 1400 ℃ 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 blocky premelted slag with the size less than 5mm for later use.

The use method of the slag system comprises the following steps:

step 1: baking the massive pre-melted slag for 4 hours at the temperature of 460 ℃ 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 electric slag 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 in table 5 below:

TABLE 5 Effect of the embodiment

By the inventionThe implementation effect of the examples 1-5 can be seen 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.