Method for smelting cold-rolled quenched and tempered saw blade steel from high-silicon-titanium vanadium-containing molten iron

Abstract

The invention discloses a method for smelting cold-rolled quenched and tempered saw blade steel from high-silicon-titanium vanadium-containing molten iron. The method comprises the steps of desulfurization, converter smelting, LF refining and continuous casting. In the step of converter smelting, 6.25 to 9.09 kg / t of light-burned dolomite and 18.75 to 21.21 kg / t of machine-burned ore are added from smelting oxygen supply; the operation of small oxygen pressure and low lance position is adopted in the early stage of blowing, the oxygen pressure is controlled to be 0.60-0.75 Mpa, and the oxygen supply amount of a top lance is 30000-32000 Nm < 3 > / h; in the initial stage of C-O reaction, the gun lifting position is 300-400 cm; and when Si + Ti oxidation is finished and slag pieces are splashed outwards from the furnace mouth, the lance is lifted, oxygen supply is stopped, and earlier-stage slag is poured. According to the method, splashing caused by high silicon and high titanium and erosion to the converter lining are effectively controlled, the service life of the converter lining is prolonged, and accidents such as safety, smoking and environmental protection caused by splashing are reduced; and meanwhile, the yield of the casting blank is also ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a method for smelting cold-rolled quenched and tempered saw blade steel with high silicon-titanium and vanadium-containing molten iron. Background Art

[0002] In recent years, with the intensification of competition, resource utilization has become the mainstream trend for reducing costs and improving efficiency, and low-cost, high-quality smelting technology has become one of the main technical research directions.

[0003] Saw blade steel is an ultra-high strength steel with high strength and toughness, good hardenability, and high fatigue limit and multiple impact resistance after quenching and tempering. However, due to the high carbon, manganese and chromium content in the steel, it is sensitive to overheating, difficult to produce, and highly sensitive to surface cracks on the ingot. The formation of surface cracks or even fish-scale cracking during the rolling process, as well as the induction of surface quality problems, will cause a large number of products to be scrapped, increasing smelting costs. Summary of the invention

[0004] The purpose of the present invention is to provide a method for smelting cold-rolled quenched and tempered saw blade steel from high-silicon-titanium-vanadium-containing molten iron, which can not only effectively control the splashing and erosion of the furnace lining caused by high silicon and high titanium, thereby increasing the service life of the converter lining, but also eliminate the sensitivity of surface cracks of overheated ingots, thereby ensuring the yield rate of ingots.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for smelting cold-rolled quenched and tempered saw blade steel from high-silicon-titanium-vanadium-containing molten iron, comprising desulfurization, converter smelting, LF refining and continuous casting.

[0007] Preferably, the converter smelting of the present invention: when the supply of high-quality scrap steel is insufficient, the furnace with Si+Ti>0.4% is used to pour the early slag; 6.25-9.09 kg / t of light-burned dolomite and 18.75-21.21 kg / t of machine-burned ore are added at the beginning of smelting oxygen supply; the purpose is to oxidize silicon and titanium in the molten iron during the iron charging process to avoid early temperature rise too fast and cause early splashing; "low oxygen pressure, low gun position" operation is adopted in the early stage of blowing, the oxygen pressure is controlled at 0.60-0.75 Mpa, and the oxygen supply of the top gun is 30000-32000 Nm 3 / h to control the early reaction speed; in the early stage of CO reaction, lift the gun to 300-400cm to slow down the CO reaction and prevent splashing caused by excessive temperature rise; when Si+Ti oxidation is completed and slag flakes splash out of the furnace mouth, lift the gun, stop oxygen supply and pour out the early slag.

[0008] Preferably, the converter smelting of the present invention: preferentially use Mo-containing scrap steel, ferromolybdenum is added to the converter together with the scrap steel, the amount of ferromolybdenum added is 450±5Kg / furnace, S≤0.025% in the furnace, the terminal temperature of the first converter furnace is 1645-1665°C, and the continuous pulling temperature is 1620-1640°C. According to the flame state and the sound in the furnace, the slag removal situation and the blowing state are determined, the gun position and the addition of cold material are adjusted in time, and the blowing is stably controlled; the converter endpoint control C: 0.06-0.12%, P≤0.012%, S≤0.020%; before tapping and alloying, an appropriate amount of carbon particles are added according to the endpoint oxygen for gasification deoxidation, which can reduce the oxygen content in the steel, thereby reducing the consumption of deoxidizer, improving the alloy yield, and reducing production costs.

[0009] Preferably, in the LF refining of the present invention, the flow rate is set to 800-1500NL / min according to the air permeability of the argon station ladle, lime is added after the deoxidizer and slag material are added, and the material is fully stirred and melted after the addition is completed, and the argon gas is adjusted to 150-300NL / min; according to the molten steel inlet temperature, the process target temperature requirements, the opening time and the ladle condition, a reasonable voltage and a reasonable arc length are selected for heating treatment, and a long arc is used for good slag in the early stage of electrode heating. If the noise is large during heating, 50-100kg of slag-removing agent is added for slag removal; the total time of a single lower electrode is less than 10min, and 500-800NL / min of argon is used to stir for 1-2min to make the temperature uniform after the heating is completed; when the predetermined temperature is met, the temperature is adjusted Desulfurization is carried out at 800-1500NL / min of argon. The color and state of the sticky slag are observed and adjusted, and deoxidizer and lime are added to form white slag for alloying. The argon is adjusted to 150-300NL / min for stirring to make the temperature and the composition of the molten steel uniform. Temperature measurement and sampling are carried out. Water cooling is prohibited for the samples, and air cooling is carried out to avoid cracks in the samples and make them unrepresentative. When the composition of the molten steel meets the requirements, the argon is adjusted to 30-80NL / min, and the calcium wire is fed at 150-300m / furnace without exposing the liquid surface. Argon is blown weakly for ≥12min to denature the inclusions and float them into the slag to purify the molten steel. At the end of refining, [O]≤25ppm, [N]≤40ppm.

[0010] Furthermore, the saw blade steel of the present invention is 42CrMo steel.

[0011] Furthermore, the chemical composition and mass percentage of the saw blade steel described in the present invention are: C: 0.41-0.43%, Si: 0.22-0.28%, Mn: 0.57-0.63%, p≤0.015%, S≤0.008%, Cr: 0.97-1.13, Mo: 0.15-0.20%, Als: 0.020-0.040%, and the remainder is Fe and unavoidable impurities.

[0012] The saw blade steel continuous casting billet obtained by the method of the present invention has specifications of 1.5-14.0 mm after hot rolling, yield strength Rel / Mpa≥350, tensile strength Rm / Mpa≥450, elongation A≥10%, and meets the mechanical property requirements of the steel.

[0013] The inventive principle of the technical solution of the present invention is that the content of Si and Ti in molten iron is relatively high, and the molten iron slag is relatively thin and easy to form foam slag. In addition, the content of Tfe in the slag is relatively high, and its surface tension is reduced; due to the strong affinity of Si and Ti with oxygen in the early stage of smelting, Si and Ti are rapidly oxidized and release heat. When the molten pool is heated, it often causes fierce carbon oxygen anti-oxidation, which hinders the smooth discharge of CO gas, causing the slag layer to expand and thicken, and in severe cases, it can rise to the furnace mouth; at this time, as long as there is a small thrust, the slag will be ejected from the furnace mouth, and the metal liquid entrained by the slag will come out and form splashes. Therefore, the adjustment and control principle in the early stage of smelting is to slag early and well, correctly control the early temperature, determine the slag slag situation and blowing state according to the flame state and the sound in the furnace, adjust the gun position and cold material addition in time, and control the blowing steadily and heat steadily. Before steel tapping and alloying, adding an appropriate amount of carbon particles according to the end oxygen for gasification deoxidation can reduce the oxygen content in the steel, achieve the purpose of reducing the consumption of deoxidizer, improving the alloy yield, shortening the LF refining and smelting cycle, and reducing production costs.

[0014] The beneficial technical effects of the technical solution of the present invention are:

[0015] The present invention optimizes the smelting process of high-silicon and high-titanium hot metal in the converter, which not only effectively controls the splashing and erosion of the furnace lining caused by high silicon and high titanium, and improves the service life of the converter lining, but also reduces the occurrence of safety and smoke accidents caused by splashing; and before steel tapping and alloying, an appropriate amount of carbon particles are added according to the end oxygen for gasification and deoxidation, which can reduce the oxygen content in the steel, thereby reducing the consumption of deoxidizers, improving the alloy yield, and reducing production costs. At the same time, by effectively controlling each process, the sensitivity of cracks on the surface of the overheated ingot is eliminated, the problem of high production difficulty and defects on the surface of the steel plate is solved, the ingot yield rate is guaranteed, and the added value of the product is improved.

[0016] The continuous casting slab obtained by the present invention has the specifications of 1.5-14.0 mm after hot rolling, yield strength Rel / Mpa≥350, tensile strength Rm / Mpa≥450, elongation A≥10%, and meets the mechanical property requirements of the steel. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described in detail below through embodiments.

[0018] Examples 1-6

[0019] A method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron, including desulfurization, converter smelting, LF refining and continuous casting, with specific control parameters as follows:

[0020] (1) Converter steelmaking: At the beginning of smelting, add 6.25-9.09 kg / t of light-burned dolomite and 18.75-21.21 kg / t of machine-burned ore; in the early stage of blowing, adopt "low oxygen pressure, low gun position" operation, the oxygen pressure is controlled at 0.60-0.75 MPa, and the oxygen supply of the top gun is 30000-32000 Nm 3 / h; at the initial stage of CO reaction, lift the gun to 300-400cm; when Si+Ti oxidation is completed and slag flakes splash out of the furnace mouth, lift the gun, stop supplying oxygen and pour out the early slag.

[0021] Mo-containing scrap steel is preferentially used in converter smelting. Molybdenum iron is added to the converter together with the scrap steel. The amount of molybdenum iron added is 450±5Kg / furnace, S is ≤0.025% in the furnace, the terminal temperature of the first converter is 1645-1665℃, and the continuous pulling temperature is 1620-1640℃; the converter terminal control C: 0.06-0.12%, P≤0.012%, S≤0.020%; before tapping and alloying, carbon particles are added according to the terminal oxygen for gasification and deoxidation.

[0022] The control parameters of the converter steelmaking process of Examples 1-6 are shown in Table 1.

[0023] Table 1 Parameters of converter steelmaking process in Example 1-6

[0024]

[0025] (2) LF refining: According to the permeability of the ladle at the argon station, the argon flow rate is set to 800-1500 NL / min. After adding the deoxidizer and slag material, add lime. After adding the materials, stir and melt them thoroughly, and adjust the argon to 150-300 NL / min. In the early stage of electrode heating, long arc is used to slag well. If the noise is loud during heating, 50-100 kg of slag-removing agent is added for slag removal; the total time of a single electrode lowering is less than 10 minutes, and 500-800 NL / min of argon is used for stirring for 1-2 minutes after the heating is completed; when the predetermined temperature is met, the argon is adjusted to 800-1500 NL / min for desulfurization; the color and state of the sticky slag are observed and adjusted to add deoxidizer and lime, and the argon is strongly stirred to form white slag for alloying, and the argon is adjusted to 150-300 NL / min; temperature measurement and sampling, the sample is prohibited from water cooling, and air cooling is performed; when the composition of the molten steel meets the requirements, the argon is adjusted to 30-80 NL / min, and the calcium iron wire is fed 150-300m / furnace without exposing the liquid surface, and the weak argon blowing is ≥12 minutes. After refining, [O]≤25ppm, [N]≤40ppm.

[0026] The control parameters of the LF refining process of Examples 1-6 are shown in Table 2.

[0027] Table 2 Parameters of LF refining process in Example 1-6

[0028]

[0029] (3) Continuous casting process: achieving constant casting speed.

[0030] Table 3: Main chemical components and mass percentages of the molten steel obtained in Examples 1-6.

[0031] Table 3 Chemical composition and mass percentage of molten steel in Examples 1-6 (%)

[0032] Example C Si Mn P S Cr Mo Als N / ppm O / ppm 1 0.41 0.22 0.57 0.011 0.005 0.97 0.15 0.020 20 5 2 0.42 0.23 0.58 0.010 0.004 1.03 0.18 0.28 12 3 3 0.43 0.24 0.60 0.013 0.005 1.06 0.16 0.030 18 6 4 0.42 0.25 0.62 0.012 0.006 1.08 0.19 0.033 19 5 5 0.43 0.26 0.61 0.010 0.004 1.10 0.17 0.038 13 8 6 0.43 0.28 0.63 0.015 0.003 1.13 0.20 0040 40 25

[0033] In Table 3, the remainder is Fe and unavoidable impurities.

[0034] The mechanical properties of the continuous casting slabs obtained in each embodiment after hot rolling are shown in Table 4.

[0035] Table 4 Mechanical properties of continuous casting slabs obtained in various embodiments after hot rolling

[0036] Example Specification / mm Yield strength Rp0.2 / Mpa Tensile strength Rm / Mpa Elongation A / % 1 1.5 350 450 10 2 1.8 680 650 15 3 2.0 600 830 18 4 6.0 625 900 16 5 8.0 630 720 13 6 14 535 960 12

[0037] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron, characterized in that: It includes desulfurization, converter smelting, LF refining and continuous casting; in the converter smelting, 6.25-9.09 kg / t of light-burned dolomite and 18.75-21.21 kg / t of machine-burned ore are added at the beginning of smelting oxygen supply; in the early stage of blowing, "low oxygen pressure and low gun position" operation is adopted, the oxygen pressure is controlled at 0.60-0.75 Mpa, and the oxygen supply of the top gun is 30000-32000 Nm 3 / h; at the initial stage of CO reaction, lift the gun to 300-400cm; when Si+Ti oxidation is completed and slag flakes splash out from the furnace mouth, lift the gun, stop supplying oxygen and pour out the early slag.

2. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: In the converter smelting, Mo-containing scrap steel is preferentially used, and ferromolybdenum is added to the converter together with the scrap steel. The amount of ferromolybdenum added is 450±5Kg / furnace, S is ≤0.025% when entering the furnace, the terminal temperature of the first converter is 1645-1665°C, and the continuous pulling temperature is 1620-1640°C; the converter terminal control C is 0.06-0.12%, P ≤0.012%, and S ≤0.020%; before steel is tapped for alloying, carbon particles are added according to the terminal oxygen for gasification and deoxidation.

3. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: In the LF refining, the argon flow rate is set to 800-1500 NL / min according to the permeability of the ladle in the argon station, lime is added after the deoxidizer and slag material are added, and after the addition is completed, the materials are fully stirred and melted, and the argon flow is adjusted to 150-300 NL / min.

4. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: In the LF refining, long arc is used to slag in the early stage of electrode heating. If the noise is loud during heating, 50-100 kg of slag-removing agent is added to remove the slag; the total time of a single electrode lowering is less than 10 minutes, and 500-800 NL / min argon is used for stirring for 1-2 minutes after the heating is completed; when the predetermined temperature is met, the argon is adjusted to 800-1500 NL / min for desulfurization operation; Observe the color and state of the sticky slag, adjust and add deoxidizer and lime, use argon to stir deeply for deep deoxidation to form white slag for alloying, and adjust the argon to 150-300 NL / min; measure temperature and take samples, water cooling of the samples is prohibited, and air cooling is carried out; when the composition of the molten steel meets the requirements, adjust the argon to 30-80NL / min, feed calcium iron wire at 150-300m / furnace without exposing the liquid surface, and weakly blow argon for ≥12 min.

5. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: In the LF refining, [O]≤25ppm, [N]≤40ppm after refining.

6. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: The Si+Ti content of the high silicon titanium and vanadium-containing molten iron is greater than 0.4%.

7. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: The chemical composition and mass percentage of the saw blade steel are: C: 0.41-0.43%, Si: 0.22-0.28%, Mn: 0.57-0.63%, p≤0.015%, S≤0.008%, Cr: 0.97-1.13, Mo: 0.15-0.20%, Als: 0.020-0.040%, and the remainder is Fe and unavoidable impurities.

8. The method for smelting cold-rolled quenched and tempered saw blade steel from high silicon titanium and vanadium-containing molten iron according to claim 1, characterized in that: The saw blade steel is 42CrMo steel.

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