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CN-121975999-A - Smelting method for reducing calcium-containing large-size inclusion in cord steel

CN121975999ACN 121975999 ACN121975999 ACN 121975999ACN-121975999-A

Abstract

The invention relates to a smelting method for reducing calcium-containing large-size inclusion in cord steel, which comprises the following steps of KR desulfurization, primary smelting, LF refining and continuous casting, wherein calcium-silicon premelting slag, lime and light burned dolomite are added in the later stage of tapping in the primary smelting step to carry out slag formation, the LF refining step controls the slag alkalinity, calcium carbide deoxidization is forbidden to be adopted to control slag components at the end of the LF refining step, a ladle and a continuous casting tundish are both made of low-calcium refractory materials, the size and the quantity of the calcium-containing inclusion of a continuous casting blank can be synergistically and effectively reduced through the whole flow control of slag formation timing, refining regulation and control and refractory material selection, the large-size calcium-containing inclusion can be reduced to less than or equal to 0.04 pieces/mm 2 , the broken wire rate of the cord steel is facilitated to be obviously reduced, and the smelting method is particularly suitable for the cord steel with different carbon contents of 70 level, 80 level, 90 level and the like.

Inventors

  • LI SHIJIAN
  • LI GANG
  • HAN DEFEI
  • ZHANG HUA

Assignees

  • 江苏永钢集团有限公司
  • 联峰钢铁（张家港）有限公司

Dates

Publication Date
20260505
Application Date
20260401

Claims (10)

  1. 1. A smelting method for reducing calcium-containing large-size inclusions in cord steel is characterized by comprising the following working procedures of KR desulfurization, primary smelting, LF refining and continuous casting in sequence; when the tapping amount in the primary smelting process reaches 3/4~4/5, adding calcium-silicon premelting slag, lime and light burned dolomite to perform slag formation; The LF refining process controls the alkalinity of slag to be 0.9-1.2, calcium carbide deoxidization is forbidden, and the slag components at the end of the LF refining process are required to meet ：ω(CaO)：37%~48%、ω(SiO 2 )：39%~44%、ω(Al 2 O 3 )<0.7%、ω(MgO)：10%~15%、ω(FeO+MnO)<4.0%, according to mass fraction, and the rest are unavoidable impurities; The ladle used in the LF refining and the continuous casting tundish used in the continuous casting process are low-calcium refractory materials with the weight percentage of omega (CaO) less than or equal to 3 percent.
  2. 2. The method for reducing calcium-containing large-size inclusions in a cord steel according to claim 1, wherein the primary smelting furnace in the primary smelting step is a converter or an electric furnace, and the tapping condition is that the carbon content is controlled to be 0.08-0.20% and the molten steel temperature is 1600-1650 ℃.
  3. 3. The method for reducing calcium-containing large-size inclusions in a steel cord according to claim 1, wherein the tapping operation in the primary refining step is performed in stages, and ferrosilicon and ferromanganese are added to alloy the steel cord when the tapping amount reaches 1/4.
  4. 4. The smelting method for reducing calcium-containing large-size inclusions in cord steel according to claim 1, wherein the calcium-silicon premelting slag, lime and light burned dolomite are added sequentially, the calcium-silicon premelting slag is added in an amount of 7.5-9.0 kg/t molten steel, the lime is added in an amount of 0.5-1.7 kg/t molten steel, and the light burned dolomite is added in an amount of 1.5-3.6 kg/t molten steel.
  5. 5. The method for smelting calcium-containing large-size inclusions in a cord steel according to claim 4, wherein the components of the calcium-silicon premelted slag are, by mass, 42% -45% of omega (CaO), 50% -53% of omega (SiO 2 ) and the balance of unavoidable impurities, and the components of the light burned dolomite are, by mass, 52% -54% of omega (CaO), 30% -35% of omega (MgO) and the balance of unavoidable impurities.
  6. 6. The method for smelting calcium-containing large-size inclusions in a cord steel according to claim 1, wherein the LF refining process uses silicon carbide for slag surface diffusion deoxidation, the addition amount of the silicon carbide is 0.5-0.8 kg/t molten steel, and the slag amount is 10-13 kg/t molten steel.
  7. 7. The method for smelting calcium-containing large-size inclusions in a cord steel according to claim 1, wherein the total refining time of the LF refining process is 65 to 95min, the soft blowing time is 15 to 30min, and the flow rate is 20 to 50nl/min.
  8. 8. The smelting method for reducing calcium-containing large-size inclusions in a cord steel according to claim 1, wherein the molten pool bricks and slag line bricks of the ladle are magnesium-carbon refractory materials, and the composition of the magnesium-carbon refractory materials is equal to or more than 75% of ω (MgO), equal to or more than 10% of ω (C), and equal to or less than 3% of ω (CaO) in mass fraction.
  9. 9. The smelting method for reducing calcium-containing large-size inclusions in a cord steel according to claim 1, wherein the slag line refractory and the molten pool refractory of the continuous casting tundish are magnesium dry materials, and the composition of the magnesium dry materials is equal to or more than 80% of ω (MgO), equal to or less than 5% of ω (C), and equal to or less than 3% of ω (CaO) in mass fraction.
  10. 10. The method for smelting calcium-containing large-size inclusions in a cord steel according to any one of claims 1 to 9, wherein the cord steel includes LX70A, LX80A, LX82A, LX a steel grade.

Description

Smelting method for reducing calcium-containing large-size inclusion in cord steel Technical Field The invention belongs to the technical field of ferrous metallurgy production, and particularly relates to a smelting method for reducing calcium-containing large-size inclusions in cord steel. Background The cord steel is a framework material used in rubber products, and particularly has wide application in tire manufacturing, and wire rods are required to be drawn into filaments by taking wire rods as parent materials when the cord steel is produced, so that the wire breakage rate of the cord steel is an important standard for measuring the quality of the wire rods. In the smelting process of 70-90 grade cord steel such as LX70A, LX80A, LX82A, LX A, a calcium-containing slag former is generally added in the tapping stage of a primary smelting furnace, in order to realize strong deoxidization and reducing slag production, slag formation such as calcium carbide, lime and the like is also added in LF refining, and a certain content of residual aluminum is inevitably present in alloy and refractory materials, so that calcium-containing inclusions of a CaO-SiO 2-MgO-Al2O3 system are easy to form in the steel, are in a liquid state at the steelmaking temperature, have generally larger size and high floating removal difficulty, and even if optimized operations such as slag blocking, ladle bottom blowing argon and the like are implemented in the primary steel-making process, the inclusion rating exceeds the standard and the broken wire rate of the cord steel is easily increased. In addition, in the subsequent steel rolling heating process, the calcium-containing large-size inclusion can be recrystallized to separate out high-melting-point non-deforming magnesia-alumina spinel or alumina inclusions, the inclusions cannot be broken in the drawing process, the large-size or non-ideal deformation inclusions in the steel can damage the continuity of a matrix, and stress concentration is caused in the drawing or stranding process, so that the wire breakage abnormality is further aggravated. Therefore, the control of large-size calcium-containing inclusions in continuous cord steel billets is an important direction of attack in the field of cord steel metallurgy, and it is highly desirable to construct a fine control system to suppress the generation of calcium-containing inclusions. Disclosure of Invention The invention aims to solve at least one of the technical problems to a certain extent, and provides a smelting method for reducing calcium-containing large-size inclusions in cord steel, which is particularly suitable for steel types such as LX70A, LX80A, LX82A, LX A and the like by starting from the source of inhibiting the generation of the calcium-containing inclusions, effectively avoiding the large-size CaO-SiO 2-MgO-Al2O3 inclusions through a full-flow fine control strategy, and being beneficial to obviously reducing the breakage rate of the cord steel. The inventor finds that the generation of large-size CaO-SiO 2-MgO-Al2O3 inclusion is not only related to a tapping slagging system, but also closely related to a plurality of links such as slag alkalinity regulation, refractory selection and the like in the LF refining process, and the single operation optimization is difficult to realize high-efficiency control, and based on the high-efficiency control, a full-flow refined control strategy is constructed from the source of inhibiting the generation of calcium-containing inclusion, and the technical scheme adopted for solving the technical problems is as follows: A smelting method for reducing calcium-containing large-size inclusions in cord steel comprises the following steps of KR desulfurization, primary smelting, LF refining and continuous casting: When the tapping amount of the primary smelting process reaches 3/4~4/5, adding calcium-silicon premelting slag, lime and light burned dolomite for slagging, and performing slagging operation in the later stage of tapping can obviously weaken the slag steel mixing degree, reduce the risk of difficult floating after the low-alkalinity slag is involved in molten steel, and reduce the initial sources of inclusions. The LF refining process controls the alkalinity of slag to be 0.9-1.2, belongs to a low alkalinity range, can inhibit the reaction intensity of slag steel, weakens the calcium transfer capability of slag to molten steel, inhibits the use of calcium carbide deoxidation, avoids calcium carbide decomposition under high-temperature electric arcs, generates simple substance calcium due to CaC 2 - & gt Ca+2C, further prevents simple substance calcium from reacting with deoxidized products in molten steel to generate calcium-containing inclusions, satisfies ：ω(CaO)：37%~48%、ω(SiO2)：39%~44%、ω(Al2O3)<0.7%、ω(MgO)：10%~15%、ω(FeO+MnO)<4.0%, and other unavoidable impurities according to mass fraction at the end of the LF refining process, can keep the slag low alkalinity