CN109365789B - Nitrogen-containing steel die casting covering slag - Google Patents
Nitrogen-containing steel die casting covering slag Download PDFInfo
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- CN109365789B CN109365789B CN201811270136.9A CN201811270136A CN109365789B CN 109365789 B CN109365789 B CN 109365789B CN 201811270136 A CN201811270136 A CN 201811270136A CN 109365789 B CN109365789 B CN 109365789B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/18—Measures for using chemical processes for influencing the surface composition of castings, e.g. for increasing resistance to acid attack
Abstract
The invention discloses a nitrogen-containing steel die casting protective slag, which comprises the following chemical components in percentage by mass: CaO: 12-27%，NaO2：5‑10%，Li2O：1‑3%，MgO：2‑6%，Al2O3：8‑15%，SiO2：28‑45%，Fe2O3：2‑4%，CaF2: 4-8%, C: 0.6-1.2%, BN: 1 to 4 percent. According to the invention, BN part replaces C to be used as skeleton particles, so that the carbon content in the casting powder is reduced, and the recarburization phenomenon of the finished steel ingot is prevented; the protective slag forms a layer of thin and uniform slag film between the ingot mold and the steel ingot, so that the shrinkage resistance between the steel ingot and the ingot mold is reduced, the secondary oxidation of molten steel is avoided, and the surface quality of the steel ingot is improved; the covering slag forms a uniform and stable three-layer structure, so that the capability of absorbing nonmetallic inclusions is improved, and the generation of defects such as cracks, surface inclusions and the like is prevented.
Description
Technical Field
The invention belongs to the field of auxiliary materials for steelmaking steel ingots, and particularly relates to a nitrogen-containing steel die casting protective slag.
Background
The mold powder should have the following functions: the spreading performance is good, the coating can be uniformly covered on the surface of molten steel to isolate air, and the secondary oxidation of the molten steel is prevented; the good heat insulation and preservation performance can prevent the molten steel from being solidified early to avoid the heavy skin, reduce the heat dissipation of the head and reduce the shrinkage cavity; the protective slag forms a molten layer with a certain thickness as soon as possible, fills the molten layer between the ingot mould and the steel ingot, lubricates the inner wall of the ingot mould, reduces the heat effect when the steel ingot is solidified, and prevents cracks from being generated; the carbon material in the covering slag which plays the role of isolation and skeleton should reduce the recarburization of the molten steel as much as possible.
Carbon materials such as graphite and carbon black used for preparing the die casting covering slag often cause local carburization of steel ingots. The research work of domestic low-carbon and micro-carbon covering slag is improved to a certain extent, the defect of recarburization is improved, and the problems of poor heat insulation performance, mucosa and the like are caused.
Nitrogen-containing steel has strict requirements on corrosion resistance, oxidation resistance, high temperature and heat strength, and has high requirements on the surface and internal quality of steel materials and non-metallic inclusions. The nitrogen content of the nitrogen-containing steel is relatively high, nitrogen bubbles are separated out below the surface of the steel ingot, and the nitrogen dissolved in the molten steel is continuously separated out in the solidification process, so that air holes are easily generated. The air holes can not only reduce the effective sectional area of the steel ingot, but also concentrate local stress and generate cracks.
Therefore, the nitrogen-containing steel die casting protective slag is developed, the defects of local stress concentration, crack sources and the like caused by the separation of nitrogen bubbles on the surface of a steel ingot are overcome, and the nitrogen-containing steel die casting protective slag has better social benefit and economic benefit.
Disclosure of Invention
The invention aims to provide a nitrogen-containing steel die casting protective slag. The invention improves the defects of local stress concentration, crack source and the like of the nitrogen-containing steel caused by the separation of nitrogen bubbles on the surface of the steel ingot due to the increase of the nitrogen content.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 12-27% of NaO2：5-10%，Li2O：1-3%，MgO：2-6%，Al2O3：8-15%，SiO2：28-45%，Fe2O3：2-4%，CaF2：4-8%，C：0.6-1.2%，BN：1-4%。
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 16-25% of NaO2：8-10%，Li2O：1.2-2.7%，MgO：3-5%，Al2O3：10-13%，SiO2：30-40%，Fe2O3：2-3.5%，CaF2：6-8%，C：0.7-1.0%，BN：2-3.5%。
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 25% of NaO2：8%，Li2O：1.7%，MgO：3%，Al2O3：12%，SiO2：35%，Fe2O3：3%，CaF2：8%，C：0.8%，BN：3.5%。
The melting point of the nitrogenous steel die casting protective slag is 1180-1200 ℃, and the viscosity of the nitrogenous steel die casting protective slag is 3.1-3.5 Pa.s at 1350 ℃.
The grain diameter of BN in the components of the nitrogen-containing steel die casting protective slag is 0.5-1.5 mu m, and the specific surface area is 25-40m2·g-1The purity is more than or equal to 99.5 percent.
The incidence rate of air holes and cracks in steel ingots for smelting nitrogen-containing steel by using the nitrogen-containing steel die casting covering slag is less than or equal to 1.5 percent, and the number of inclusions is less than or equal to 105Per ton of steel.
The standard of the detection method of the nitrogenous steel die casting covering slag product refers to YB/T190.13-2014 continuous casting covering slag, silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide and full iron content determination wavelength dispersion X-ray fluorescence spectrometry, YB/T186-2014 continuous casting covering slag melting temperature test method and YB/T185-2014 continuous casting covering slag viscosity test method.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: 1. according to the invention, BN part replaces C to be used as skeleton particles, so that the carbon content in the casting powder is reduced, and the recarburization phenomenon of the finished steel ingot is prevented. 2. The protective slag forms a layer of thin and uniform slag film between the ingot mold and the steel ingot, so that the shrinkage resistance between the steel ingot and the ingot mold is reduced, the secondary oxidation of molten steel is avoided, and the surface quality of the steel ingot is improved. 3. The covering slag of the invention forms a uniform and stable three-layer structure, improves the capability of absorbing nonmetallic inclusions, and prevents the generation of defects such as cracks, surface inclusions and the like. 4. The invention improves the defects of local stress concentration, crack sources and the like of the nitrogen-containing steel caused by the separation of nitrogen bubbles on the surface of the steel ingot due to the increase of the nitrogen content. 5. The incidence rate of gas holes and cracks in steel ingots for smelting nitrogen-containing steel by using the nitrogen-containing steel die casting covering slag is less than or equal to 1.5 percent, and the number of inclusions is less than or equal to 105Per ton of steel.
Detailed Description
Example 1
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 25% of NaO2：8%，Li2O：1.7%，MgO：3%，Al2O3：12%，SiO2：35%，Fe2O3：3%，CaF2: 8%, C: 0.8%, BN: 3.5 percent. The die casting protective slag with the components in the proportion has the most stable performance, the melting point is 1189 ℃, and the viscosity is 3.2 Pa.s at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 1.0. mu.m, and the specific surface area was 32m2·g-1And the purity is 99.8%.
Example 2
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 16% of NaO2：7%，Li2O：2.5%，MgO：6%，Al2O3：8%，SiO2：45%，Fe2O3：3.5%，CaF2: 7%, C: 1.0%, BN: 4 percent. The melting point of the covering slag at the above component ratio is 1195 ℃, and the viscosity is 3.4 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 1.2. mu.m, and the specific surface area was 35m2·g-1And the purity is 99.6%.
Example 3
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 20% of NaO2：10%，Li2O：2%，MgO：5%，Al2O3：10%，SiO2：40%，Fe2O3：2.5%，CaF2: 6%, C: 0.7%, BN: 3.8 percent. The melting point of the covering slag at the above component ratio is 1192 ℃, and the viscosity is 3.3 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 0.7. mu.m, and the specific surface area was 27m2·g-1And the purity is 99.7%.
Example 4
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 27% of NaO2：5%，Li2O：1%，MgO：2%，Al2O3：15%，SiO2：42.4%，Fe2O3：2%，CaF2：4%，C: 0.6%, BN: 1 percent. The melting point of the covering slag at the above component ratio is 1180 ℃, and the viscosity is 3.5 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 0.5. mu.m, and the specific surface area was 40m2·g-1And the purity is 99.65%.
Example 5
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 12% of NaO2：9%，Li2O：3%，MgO：4%，Al2O3：12%，SiO2：43%，Fe2O3：4%，CaF2: 8%, C: 1.2%, BN: 3.8 percent. The melting point of the mold flux at the above composition ratio was 1200 ℃ and the viscosity was 3.1 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 1.5. mu.m, and the specific surface area was 25m2·g-1Purity 99.72%.
Example 6
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 25% of NaO2：9%，Li2O：3%，MgO：5%，Al2O3：14%，SiO2：28%，Fe2O3：4%，CaF2: 7%, C: 1%, BN: 4 percent. The melting point of the covering slag at the above component ratio is 1190 ℃, and the viscosity is 3.4 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 0.8. mu.m, and the specific surface area was 30m2·g-1The purity is 99.5%.
Example 7
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 14% of NaO2：6%，Li2O：2.7%，MgO：5.5%，Al2O3：13%，SiO2：30%，Fe2O3：2.6%，CaF2: 7.5%, C: 0.9%, BN: 2 percent. The melting point of the covering slag at the above component ratio is 1192 ℃, and the viscosity is 3.3 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 0.9. mu.m, and the specific surface area was 28m2·g-1Purity 99.62%.
Example 8
The nitrogen-containing steel die casting protective slag comprises the following chemical components in percentage by mass: CaO: 23% of NaO2：9.5%，Li2O：1.2%，MgO：4.5%，Al2O3：11%，SiO2：38%，Fe2O3：3.3%，CaF2: 6.5%, C: 0.8%, BN: 2.8 percent. The melting point of the covering slag at the above component ratio is 1184 ℃, and the viscosity is 3.4 pas at 1350 ℃.
In the composition of the mold flux for nitrogen-containing steel mold casting of this example, the particle size of BN was 0.7. mu.m, and the specific surface area was 36m2·g-1Purity 99.72%.
Example 9
The embodiment aims to prove that the effect of smelting the nitrogen-containing steel by applying the die casting covering slag for the nitrogen-containing steel is better.
In this example, nitrogen-containing gas valve steel was produced using the above-described mold powder for nitrogen-containing steel in examples 1 to 8 and conventional mold powder MS-1, respectively.
The specific smelting method of the nitrogen-containing gas valve steel comprises the following steps: electric furnace EAF-ladle refining furnace AOD-ladle refining furnace LF-die casting ICM. In the smelting process of an electric furnace EAF, nitrogen is adopted for bottom stirring, the slag-pulling temperature is controlled to be more than or equal to 1650 ℃, and the tapping temperature is controlled to be more than or equal to 1620 ℃; adding alloy material at the temperature of more than or equal to 1670 ℃ in the AOD refining process of the ladle refining furnace, and controlling the contents of Cr and Mn in the molten steel; in the LF process of the ladle refining furnace, the ladle temperature is 1460-1470 ℃, and the upper limit ladle is controlled; during the molding of the ICM, an argon blanket is applied.
TABLE 1 nitrogenous steel mold flux and conventional mold flux MS-1 in examples 1 to 8
Performance comparison of smelting nitrogen-containing gas valve steel
From top to bottomAs can be seen from examples 1 to 9 and Table 1, the steel ingots obtained by using the mold flux for producing nitrogen-containing steels according to this example had a porosity and a crack rate of 1.5% or less and a number of inclusions of 10 or less5Per ton of steel. The gas hole incidence and the crack incidence of the casting powder produced by the conventional die casting are both close to 10 percent, and the quantity of inclusions per ton of steel is increased in a step manner. Therefore, the defects of local stress concentration, crack sources and the like caused by the precipitation of nitrogen bubbles on the surface of the steel ingot of the nitrogen-containing steel smelted by the nitrogen-containing steel die casting covering slag are obviously improved.
The above examples are only used to illustrate the present invention and not to limit the technical solutions described in the present invention. It will be understood by those skilled in the art that the present invention may be modified and equivalents may be substituted. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (2)
1. The nitrogen-containing steel die casting protective slag is characterized by comprising the following chemical components in percentage by mass: CaO: 16-25% of Na2O：8-10%，Li2O：1.2-2.7%，MgO：3-5%，Al2O3：10-13%，SiO2：30-40%，Fe2O3：2-3.5%，CaF2：6-8%，C：0.7-0.9%，BN：2-3.5%；
The grain diameter of BN in the components of the nitrogen-containing steel die casting protective slag is 0.5-1.5 mu m, and the specific surface area is 25-40m2·g-1The purity is more than or equal to 99.5 percent;
the melting point of the nitrogenous steel die casting protective slag is 1180-1200 ℃, and the viscosity of the nitrogenous steel die casting protective slag is 3.1-3.5 Pa.s at 1350 ℃;
the incidence rate of gas holes and cracks in the steel ingot for smelting the nitrogen-containing steel by the nitrogen-containing steel die casting covering slag is less than or equal to 1.5 percent, and the number of inclusions is less than or equal to 105Per ton of steel.
2. The nitrogen-containing steel die casting mold flux as claimed in claim 1, wherein the nitrogen-containing steel die casting mold flux comprises the following chemical components in percentage by mass: CaO: 25% of Na2O：8%，Li2O：1.7%，MgO：3%，Al2O3：12%，SiO2：35%，Fe2O3：3%，CaF2：8%，C：0.8%，BN：3.5%。
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| CN1788880A (en) * | 2004-12-14 | 2006-06-21 | 上海盘龙实业有限公司 | Dual-functional composite solid protective slag for stainless steel die casting |
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| CN87108182A (en) * | 1987-12-23 | 1988-08-10 | 地方国营西峡县石墨矿 | The manufacture method of composite protective dreg for model cast |
| CN101468388B (en) * | 2007-12-27 | 2011-01-26 | 攀钢集团攀枝花钢铁研究院 | Continuous casting mould fluxes and preparation method thereof |
| CN102652989A (en) * | 2012-05-10 | 2012-09-05 | 江苏大学 | Tundish molten steel covering agent for high-cleanness steel pouring and preparation method and application of tundish molten steel covering agent |
| CN104646650A (en) * | 2015-02-03 | 2015-05-27 | 舞阳钢铁有限责任公司 | Ultra-low carbon covering slag used for 50t-level large flat ingot die casting |
| CN108465791B (en) * | 2018-07-09 | 2020-08-18 | 西峡龙成冶金材料有限公司 | Low-nickel high-nitrogen austenitic stainless steel continuous casting crystallizer casting powder |
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| CN1788880A (en) * | 2004-12-14 | 2006-06-21 | 上海盘龙实业有限公司 | Dual-functional composite solid protective slag for stainless steel die casting |
Non-Patent Citations (1)
| Title |
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| BN对超低碳钢连铸保护渣性能的影响;李九霄等;《包头钢铁学院学报》;20050930;第24卷(第3期);第207-209页 * |
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