CN107858525B - Electroslag remelting fluorine-free slag process formula and method for electroslag remelting - Google Patents
Electroslag remelting fluorine-free slag process formula and method for electroslag remelting Download PDFInfo
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- CN107858525B CN107858525B CN201710350374.XA CN201710350374A CN107858525B CN 107858525 B CN107858525 B CN 107858525B CN 201710350374 A CN201710350374 A CN 201710350374A CN 107858525 B CN107858525 B CN 107858525B
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
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Abstract
The invention relates to a process formula of electroslag remelting fluorine-free slag and a method for electroslag remelting by using the process formula. The electroslag is heavyThe melting fluorine-free slag comprises the following components in parts by weight: 40-44 parts of CaO and 46-50 parts of Al2O33-5 parts of MgO and 5-10 parts of Li2CO3. The fluorine-free slag and the added Li are adopted according to the proportion2CO3And MgO as a substitute for a part of CaO and Al2O3The slag components and the technological process in the smelting process are more stable; the fluorine-free slag is adopted to carry out electroslag remelting to obtain a steel ingot which has better molding, smooth surface and smaller ingot segregation degree, and is more environment-friendly without sulfide and spherical inclusion.
Description
Technical Field
The invention relates to a process formula of electroslag remelting fluorine-free slag and a method for electroslag remelting by using the process formula.
Background
The electroslag remelting technology is one of effective means for obtaining high-quality steel ingots, in the electroslag remelting process, steel is purified under the condition that liquid slag is fully reflected, the steel is solidified in a water-cooled crystallizer under the protection of high-temperature molten slag, and the surface of the steel ingot is protected by slag crust, so that the steel ingot has a smooth surface, a developed internal axial crystalline structure, and remarkably reduced non-metallic inclusions, and the segregation and loosening defects are greatly improved. The technology is widely applied at home and abroad at present.
Electroslag remelting steelmaking is an important smelting mode for producing high-quality alloy steel and alloy, and remelting slag matched with the electroslag remelting steelmaking is selected in the electroslag remelting process, so that the electroslag remelting steelmaking is an important process technology link, and can be used as a heat source of a consumable electrode, and can also be used for controlling the chemical components of metal, refining molten steel and removing non-metallic inclusions. AH phi-6 slag (CaF) has been widely used for a long time at home and abroad270%+Al2O330%). CaF is commonly used at present2The high-fluorine based remelting slag has high specific conductance, insufficient heat productivity of slag and uncontrollable slag components in the remelting process, thereby influencing the stability of electroslag remelting in the remelting process, and contains a large amount of CaF2In the smelting process, there is SiF4、HF、AlF3And a large amount of volatile fluorine-containing gas escapes, so that the environment is seriously polluted, the human health is harmed, certain hidden dangers exist, the requirements of environmental protection and energy conservation are not met, and related auxiliary environmental protection facilities need to be matched.
The existing fluorine-free heavy slag is mainly developed by CaO-Al2O3And CaO-Al2O3-SiO2The fluorine-free slag can just form stable 12CaO 7Al according to the related data and the introduction of the phase diagram theory2O3And (3) co-crystal. CaO has a melting point of about 2580 ℃ and Al2O3The melting point of the slag is about 2050 ℃, the melting point difference exists between the melting point of the slag and the melting point of the slag, and the electroslag remelting process is carried out under the condition of strong cooling of circulating waterIn this case, CaO having a high melting point is preferred to Al having a low melting point2O3The CaO is reduced along with the smelting process after the solidification on the inner wall of the crystallizer, and the stable 12CaO 7Al is difficult to be formed well2O3. Therefore, the use of CaO: al (Al)2O3The mass ratio of the fluorine-free slag is approximate to 1:1, the thickness of the slag crust is easy to be uneven in the actual production, the surface smoothness of the steel ingot is seriously influenced, and the mixture ratio of the components needs to be properly adjusted according to experience.
Some existing schemes adopt the following technical schemes: an electroslag remelting fluorine-free slag comprises the following components: CaO-Al2O3-MgO-SiO2Although the combination proportion avoids fluorine pollution in the electroslag remelting process, the proportion of alloy elements in the electroslag remelting of materials containing aluminum and titanium elements, such as high-temperature alloy, precision alloy and the like is influenced, so that the requirements of the expected technical standards are not met.
In the electroslag remelting process of high-temperature alloy containing aluminum and titanium, SiO is easy to be replaced and analyzed due to the activity of aluminum and titanium elements2The Si element in the alloy breaks the composition balance. The melting point of the fluorine-free slag is about 100-200 ℃ higher than that of other slag series, and the arc striking is relatively difficult, so that the excellent characteristics of the fluorine-free slag are lost.
In some schemes, the graphite electrode is adopted for arc striking to solve the defect of high melting point, and certain alloy types, particularly the types with the requirement of carbon content less than 0.08 percent, can be influenced.
Disclosure of Invention
Aiming at the defects in the prior art, the technical problems to be solved by the invention are as follows: the method solves and thoroughly replaces the problems of the fluorine-containing slag in the prior art, further provides the electroslag remelting fluorine-free slag which can reduce the pollution to the environment, ensure that the molten steel subjected to electroslag remelting has good fluidity, greatly reduced melting point, good ingot casting forming, smooth surface, small ingot segregation degree, compact and uniform structure and low gas content, and is used for electroslag remelting.
In order to solve the technical problems, the invention adopts the following technical scheme: the electroslag remelting fluorine-free slag comprises the following components in parts by weight: 40-44 parts of CaO and 46-50 parts of Al2O33-5 parts of MgO and 5-10 parts of Li2CO3。
The fluorine-free slag and the added Li are adopted according to the proportion2CO3And MgO as a substitute for a part of CaO and Al2O3The slag components and the technological process in the smelting process are more stable; wherein Li2CO3The melting point of the slag can be reduced: li2CO3Under the condition of heating, the decomposition is into LiO2And CO2，CO2Gas is separated out, and lithium ions are filled among other molecules due to the relatively small volume of the lithium ions, so that the intermolecular acting force is damaged, and the melting point of the lithium ions is reduced by 30-50 ℃; and a small amount of MgO forms a semi-solidified film on the surface of the slag pool, so that the possibility of hydrogen absorption of the slag pool and oxygen transfer of the valence oxides in the slag to a metal molten pool is reduced. In order to compensate the CaO lost by solidification in the smelting process under the strong cold condition. The steel ingot obtained by adopting the fluorine-free slag to carry out electroslag remelting has better molding, smooth surface and smaller ingot segregation degree.
The electroslag remelting fluorine-free slag comprises the following components in parts by weight: 44 parts of CaO and 46 parts of Al2O34 parts of MgO and 6 parts of Li2CO3. By adopting the slag charge with the optimized proportion, the gas content in the ingot can be effectively reduced, and the content of the extension oxides and the sulfide in the steel can be greatly reduced.
The method for carrying out electroslag remelting on the electroslag remelting fluorine-free slag comprises the following steps:
a) baking the fluorine-free slag in a furnace at 800-900 ℃ for 8-10 hours, and taking out for use;
b) welding a consumable electrode on a false electrode, assembling an electroslag remelting furnace, adding a deoxidizer and the fluorine-free slag baked in the step a) into a crystallizer of the electroslag remelting furnace, starting arc by using a metal electrode, observing that the color in the crystallizer becomes bright, then, taking out a graphite electrode after 8-11 minutes; the deoxidizer comprises aluminum powder and calcium particles, and the mass ratio of the aluminum powder to the calcium particles to the fluorine-free slag is 0.3-0.5: 0.3-0.7: 100;
c) after slagging in the step b), replacing a graphite electrode with a consumable electrode for smelting, and setting the voltage to be 62-65V and the current to be 7000-8000A (remark: when selecting the values of voltage and current, setting the values according to different product types and tonnage, not being used as a unique standard value), electrifying and remelting metal, and adding aluminum powder for deoxidation in the remelting process, wherein the addition amount of the aluminum powder is 0.05-0.1% of the weight of the consumable electrode.
Continuing to start the arc by using the metal electrode in the step b), and taking out the metal electrode after the temperature in the crystallizer furnace reaches the expected temperature. Therefore, the fluorine-free slag can be completely melted, the higher temperature of the slag pool is ensured, and the purification efficiency in the consumable electrode smelting process is higher.
The consumable electrode is made of alloy structural steel, alloy tool steel, alloy die steel or austenitic stainless steel, in particular alloy structural steel, alloy tool steel, alloy die steel or austenitic stainless steel containing aluminum or titanium. The method for electroslag remelting the fluorine-free slag has a good quality effect on austenitic steel, so that the two types of steel have good ingot casting forming effect, smooth surface and good desulfurizing effect, and extension sulfides and oxides in the steel are obviously reduced.
Compared with the prior art, the invention has the following advantages:
1. the fluorine-free slag material meets the advantages of the existing fluorine-free slag formula through the synergistic compatibility of the components, such as: the method can ensure that the surface of the steel ingot obtained by remelting is smooth, the segregation degree of the ingot is small, the structure is uniform and compact, the gas content in steel is low, and the problem of uneven thickness and poor finish of the ingot obtained without fluorine slag in the prior art is solved. It is preferable to provide a comparison of the metallographic structure of the steel ingot to show the above advantages, and at the same time, to provide a wider range of steel types, structural alloy steels, tool alloy steels, die alloy steels, austenitic stainless steels, and particularly alloy steels containing aluminum or titanium.
2. Compared with the fluorine-containing slag system in the prior art, the fluorine-free slag of the invention does not volatilize to generate toxic fluoride in the electroslag remelting process, thereby not polluting the environment and harming the human health, and has more environmental protection.
3. The fluorine-free slag is adopted for electroslag remelting, the conventional electroslag remelting equipment can be adopted, the applicability is strong, and the unique preparation advantage is more prominent particularly in vacuum electroslag smelting.
Detailed Description
The present invention will be described in further detail with reference to specific examples. However, the scope of the present invention is not limited to the following examples.
1. Example 1 example of smelting H13 electroslag ingot using the slag system
The electroslag remelting fluorine-free slag comprises the following components in parts by weight: 44 parts of CaO and 46 parts of Al2O34 parts of MgO and 6 parts of Li2CO3The H13 electroslag ingot is produced by adopting the electroslag remelting and fluorine-free slag remelting, and is used for electroslag remelting 3-ton ingot type electroslag ingot. The method is characterized in that the method comprises the following steps:
a) weighing raw materials, baking at 800 deg.C for 7-8 hr, and removing water from slag.
b) Average diameter of crystallizer: phi 580mm
c) Diameter of the consumable electrode: phi 420mm, welding the consumable electrode blank on the false electrode;
d) the amount of slag used: 100Kg
e) Smelting voltage: 72-75V
f) Smelting current: 11000 to 13000A
g) And the smelting result shows that the surface of the electroslag ingot is smooth, and all detection performances of the electroslag ingot after forging meet the technical requirements of GB/T1299 alloy tool steel.
h) Feeding by reducing current step by step. And after feeding and power off, cooling in a crystallizer for 50-60 minutes, demolding, and feeding into a heat-insulating cover to obtain the H13 alloy steel ingot.
i) Comparison of chemical compositions before and after electroslag remelting of H13 steel
2. Example 2 example of GH4169 superalloy electroslag ingot using this slag system (general operation flow example 1, not described again)
a) Used for electroslag remelting 1 ton ingot type electroslag ingot. Three furnaces for total test
b) Crystallizer mean diameter: phi 360mm
c) Consumable electrode diameter: phi 220mm
d) The amount of slag used: 40Kg
e) Smelting voltage: 62-65V
f) Smelting current: 7000 to 8000A
g) And smelting results show that the surface of the electroslag ingot is smooth and clean, and all detection performances after forging meet the technical requirements of customers.
h) Comparison of chemical compositions before and after electroslag remelting of GH4169 is shown in attached tables 2 and 3
The comparison between the items in attached tables 1 and 2 shows that: the contents of nitrogen, hydrogen and oxygen of the steel ingot obtained after remelting are all reduced compared with those of the consumable electrode blank; the content of ductile oxides and sulfides in the steel is also greatly reduced. Further, H13, GH4169 obtained using the fluorine-free slag of the present invention mainly set forth advantages over the reference documents, overcoming those drawbacks in the reference documents.
The slag system is due to the addition of Li2CO3，The melting point of slag is effectively reduced, the fluidity of the slag is good, the slag has obvious advantages for smelting high-temperature alloys such as GH4169 and austenitic stainless steel, and after electroslag remelting, an electroslag ingot has a smooth surface without slag grooves and wrinkles, and can almost adapt to the smelting of all steel types and alloys. Because the slag system has low melting point and good fluidity, the slag crust on the surface of the electroslag ingot is thinner when the slag system is adopted for smelting, the chilling layer of the electroslag ingot is obviously thickened, the internal structure is more compact, and the crystal grains are thinner under the same cooling condition of the crystallizer. The grain size of the forged piece detected after forging can reach more than 8 grades, the carbide particles are distributed fine and uniformly, and the transverse impact energy is obviously increased.
TABLE 1 comparison of chemical compositions before and after electroslag remelting of H13 steel
TABLE 2 comparison of chemical compositions before and after electroslag remelting of GH4169
Attached table 3 detection results of steel ingots before and after electroslag remelting
Description of the drawings: a type: sulfide B type: silicate class C: aluminates D type: non-deforming spherical inclusions
"0" represents a content not currently found; and obtaining data according to GB map contrast by other values.
Claims (8)
1. The electroslag remelting fluorine-free slag is characterized by comprising the following components in parts by weight: 40-44 parts of CaO and 46-50 parts of Al2O33-5 parts of MgO and 5-10 parts of Li2CO3。
2. The electroslag remelting fluorine-free slag according to claim 1, which is characterized by comprising the following components in parts by weight: 44 parts of CaO and 46 parts of Al2O34 parts of MgO and 6 parts of Li2CO3。
3. The method for electroslag remelting fluoride-free slag according to claim 1 or 2, comprising the steps of:
1) baking the electroslag remelting fluorine-free slag in a furnace at 800-900 ℃ for 8-10 hours;
2) welding a consumable electrode on a false electrode, assembling an electroslag remelting furnace, adding a deoxidizer and the fluorine-free slag baked in the step 1) into a crystallizer of the electroslag remelting furnace, starting arc by using a graphite electrode, observing that the color in the crystallizer becomes bright, then, taking out the graphite electrode after 7-12 minutes; the deoxidizer comprises aluminum powder and calcium particles, the mass ratio of the aluminum powder to the calcium particles to the fluorine-free slag is 0.25-0.5: 0.33-0.65: 100, and micro adjustment can be performed according to different steel types so as to adapt to the best quality of the deoxidizer;
3) and 2) after slagging is finished, replacing a graphite electrode with a consumable electrode for smelting, setting the voltage to be 52-54V and the current to be 7500-8100A, electrifying to remelt metal, and adding aluminum powder for deoxidation in the remelting process, wherein the addition amount of the aluminum powder is 0.06-0.10% of the weight of the consumable electrode.
4. The method for electroslag remelting fluorine-free slag according to claim 3, wherein the arc electrode in step 2) is selected from a graphite electrode, a high temperature alloy and a low carbon alloy.
5. The method for electroslag remelting fluorine-free slag according to claim 3, wherein in step 2), the arc is started by a graphite electrode, and the graphite electrode is taken out after 9-12 minutes after the color in the crystallizer furnace becomes bright.
6. The method for electroslag remelting fluorine-free slag according to claim 3, wherein the electroslag remelting metal is electrified by setting a voltage of 52V and a current of 7800A in the step 3).
7. The method for electroslag remelting fluorine-free slag according to claim 3, wherein the consumable electrode is made of austenitic stainless steel, structural alloy steel, tool alloy steel or die alloy steel.
8. The method for electroslag remelting fluoride-free slag according to claim 7, wherein the consumable electrode is made of austenitic stainless steel, structural alloy steel, tool alloy steel, or die alloy steel containing aluminum or titanium.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103667732A (en) * | 2012-09-12 | 2014-03-26 | 上海丰渠特种合金有限公司 | Fluoride-free slag, application thereof, electroslag remelting method and obtained nickel alloy |
| CN104588601A (en) * | 2015-02-14 | 2015-05-06 | 河南通宇冶材集团有限公司 | High-speed wide and thick slab continuous casting mold flux |
| CN105779780A (en) * | 2016-05-30 | 2016-07-20 | 重庆钢铁(集团)有限责任公司 | Electroslag remelting fluoride-free slag and electroslag remelting method thereof |
| CN106270429A (en) * | 2015-06-09 | 2017-01-04 | 宝山钢铁股份有限公司 | Hypoergia covering slag and preparation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60190506A (en) * | 1984-03-09 | 1985-09-28 | Hitachi Ltd | Production of ferrous and non-ferrous super alloy |
| JPS61195934A (en) * | 1985-02-25 | 1986-08-30 | Kobe Steel Ltd | Flux for electro-slag remelting |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103667732A (en) * | 2012-09-12 | 2014-03-26 | 上海丰渠特种合金有限公司 | Fluoride-free slag, application thereof, electroslag remelting method and obtained nickel alloy |
| CN104588601A (en) * | 2015-02-14 | 2015-05-06 | 河南通宇冶材集团有限公司 | High-speed wide and thick slab continuous casting mold flux |
| CN106270429A (en) * | 2015-06-09 | 2017-01-04 | 宝山钢铁股份有限公司 | Hypoergia covering slag and preparation method |
| CN105779780A (en) * | 2016-05-30 | 2016-07-20 | 重庆钢铁(集团)有限责任公司 | Electroslag remelting fluoride-free slag and electroslag remelting method thereof |
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