CN-117265210-B - Preparation method of industrial pure iron

CN117265210BCN 117265210 BCN117265210 BCN 117265210BCN-117265210-B

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method of industrial pure iron, which comprises the following components of [ C ] less than or equal to 0.01%, [ Si ] less than or equal to 0.01%, [ Mn ] less than or equal to 0.05%, [ P ] less than or equal to 0.01%, [ S ] less than or equal to 0.010%, [ Al ] 0.03-0.05%, total oxygen less than or equal to 0.005% and the balance of Fe in percentage by weight. The oxygen isolating agent, the calcium carbide and the aluminum particles are added into the LF refining furnace to make white slag, so that the oxygen content of molten steel can be controlled to be 0.05-0.09% while the FeO content of slag is less than or equal to 1%, the decarburization requirement of the RH furnace under the condition of no oxygen blowing is ensured, aluminum is added to remove oxygen in the molten steel after the decarburization of the RH furnace is finished, the FeO content of slag can be finally controlled to be less than 2%, and smooth casting of aluminum-containing steel in the billets is realized.

Inventors

GUAN TING
LIN JUN
WANG CHENG
ZHOU MIAO
YANG CHENGWEI
MENG XIAOLING
QU ZHIDONG
GUO DONGDONG

Assignees

中天钢铁集团有限公司
常州中天特钢有限公司

Dates

Publication Date: 20260505
Application Date: 20230907

Claims (6)

1. A preparation method of industrial pure iron is characterized in that the industrial pure iron comprises the following components in percentage by weight of [ C ] < 0.01%, [ Si ] < 0.01%, [ Mn ] < 0.05%, [ P ] < 0.01%, [ S ] < 0.010%, [ Al ] 0.03-0.05%, total oxygen < 0.005% and the balance Fe, wherein the preparation method of the industrial pure iron adopts a 120t converter for smelting, and the smelting process comprises KR molten iron desulfurization, BOF smelting, LF refining slag modification, RH decarburization deoxidation and continuous casting, and specifically comprises the following steps: step one, KR molten iron desulfurization, wherein the sulfur content of the molten iron after desulfurization is controlled below 0.001%; The BOF smelting is carried out, wherein a smelting mode of desulphurized molten iron and clean scrap steel is adopted in converter smelting, the molten iron ratio is controlled to be 75% -90%, the scrap steel ratio is controlled to be 10% -25%, the molten iron manganese content requirement is less than or equal to 0.35%, the scrap steel manganese content requirement is less than or equal to 0.35%, the double slag method smelting is adopted, the primary deslagging molten pool temperature is controlled to 1300% -1400 ℃ while the slag alkalinity is controlled to be 1.0% -1.5, the slag MgO is controlled to be 10% -15%, the blowing end temperature is controlled to be 1620% -1650 ℃, the end component is controlled to be [ C ] less than or equal to 0.05%, the [ Mn ] is less than or equal to 0.05%, the [ P ] is less than or equal to 0.015%, the [ S ] is less than or equal to 0.01%, the [ O ] is 0.06% -0.1%, the blowing end slag component is CaO 30% -45%, mgO is 10% -20%, siO 2 % -20%, feO is 12% -25%, mnO is 5% -10%, and some unavoidable impurities are not added, a deoxidizing agent and alloy is not added in the process, and a sliding plate is used for carrying out a double-stop operation; LF refining, wherein the LF to-station slag composition is controlled to be 40% -50% of CaO, 3% -5% of CaF 2 ：10~20%,MgO：3%~10%,SiO 2 , 10% -20% of FeO, 1% -3% of MnO and some unavoidable impurities, the molten steel is electrified and heated after reaching refining, the temperature of the molten steel is controlled to be 1640-1680 ℃, then an oxygen barrier, calcium carbide and aluminum particles are added to carry out modification treatment on slag, the modified slag composition is ：CaO：55%~65%,CaF 2 ：8~15%,MgO：3%~5%,SiO 2 ：3%~5%,FeO≤1%,MnO：1%~3%,Al 2 O 3 ：5~10%, and some unavoidable impurities, the molten steel composition is [ C ] < 0.05% >, [ Mn ] < 0.05% >, [ P ] < 0.015% >, [ S ] < 0.01% >, and [ O ] 0.05% -0.09%, the oxygen barrier is prepared by uniformly mixing aluminum powder and lime powder, then a layer of molten steel is wrapped outside, the oxygen barrier composition is 20% -40% of CaO, the Al is 10% -20%, the Fe is 40% -60% and some unavoidable impurities, and the granularity of the oxygen barrier is controlled to be 20% -40.40 mm, and the density of the oxygen barrier is controlled to be 20% -40.5.5 cm/5; Step four, RH decarburization and deoxidation, wherein the RH arrival temperature is controlled to 1630-1660 ℃, the molten steel is subjected to cyclic decarburization treatment after reaching RH, argon is adopted as lifting gas, the vacuum degree is controlled to be within 133Pa, oxygen is fixed after decarburization is finished, the carbon content of the molten steel is required to be less than or equal to 0.002%, aluminum particles are added according to the oxygen fixing result to carry out deoxidation treatment, the aluminum content of the molten steel is controlled to be 0.03-0.05% after deoxidation is finished, the oxygen content of the molten steel is less than or equal to 0.0015%, and a low-carbon ladle covering agent with the carbon content of less than or equal to 2% is added after emptying; Step five, continuous casting, namely producing a section of 160mm multiplied by 160mm, adopting protection casting, adopting an integral coating material stopper rod for the continuous casting tundish, baking the tundish to 1050-1150 ℃, controlling the pulling speed to 2.0-2.5 m/min, adopting electromagnetic stirring and non-sinusoidal vibration modes for a crystallizer, adopting aerosol cooling and weak cooling water distribution for secondary cooling, and adopting a low-carbon tundish covering agent with carbon content less than or equal to 2% and ultra-low carbon covering slag with carbon content less than or equal to 8% in the continuous casting process.
2. The method for preparing industrial pure iron according to claim 1, wherein the modification treatment comprises the steps of firstly opening ladle bottom blowing flow to an anti-blocking mode, controlling the bottom blowing flow to be 50-100L/min, reducing slag-metal reaction, then uniformly adding an oxygen-separating agent into the ladle, wherein the adding amount of the oxygen-separating agent is 200-500 kg, the oxygen-separating agent can prevent molten steel from transferring oxygen to slag, and finally adding 50-100 kg of calcium carbide and 30-60 kg of aluminum particles to make white slag, and removing oxygen in the slag.
3. The method for preparing industrial pure iron according to claim 1, wherein the argon flow of the cyclic decarbonization in the fourth step is 100-150 Nm 3 /h, and the cycle time is controlled to be 3-8 min.
4. The method for producing industrial pure iron according to claim 1, wherein aluminum particles are added according to the oxygen content of molten steel after the decarburization in the fourth step, 65-75 kg of aluminum particles are added when the oxygen content of molten steel is less than or equal to 0.01%, 80-90 kg of aluminum particles are added when the oxygen content of molten steel is less than or equal to 0.02% and 95-105 kg of aluminum particles are added when the oxygen content of molten steel is less than or equal to 0.02% and the oxygen content of molten steel is less than or equal to 0.03%.
5. The method for producing industrially pure iron according to claim 1, wherein, after the RH treatment in the fourth step is completed, the slag contains 45 to 60% CaO, 25 to 40% CaF 2 ：5~10%,MgO：3%~8%,SiO 2 ：2%~5%,FeO：≤2%,Al 2 O 3 , and some unavoidable impurities.
6. The method for preparing industrial pure iron according to claim 1, wherein the electromagnetic stirring current of the crystallizer in the fifth step is 120-180A, the frequency is 2.2-2.8 Hz, the amplitude of the crystallizer is controlled to be-2.5 mm, and the frequency is controlled to be 130+40V opm.

Description

Preparation method of industrial pure iron Technical Field The invention belongs to the technical field of metallurgy, and particularly relates to a preparation method of industrial pure iron. Background The industrial pure iron is a metal material with very low carbon content, the chemical components of the industrial pure iron are mainly iron, and the lower the other alloy elements are, the better. The room temperature structure of the industrial pure iron mainly comprises ferrite, has the characteristics of soft texture, large toughness, good ductility, excellent electromagnetic performance and the like, and occupies an increasingly wide market position. The smelting process flow of the industrial pure iron comprises the steps of molten iron pre-desulfurization, converter, LF refining furnace, RH vacuum treatment and continuous casting. Oxygen blowing decarburization and aluminum deoxidation are usually carried out under RH vacuum conditions, soft blowing is carried out after air breaking, and standing is carried out for more than 12min (patent CN 113512619A), or oxygen blowing decarburization and aluminum deoxidation are carried out under RH vacuum conditions, and 40Al modifier (patent CN 113774277A) is added, so that the RH working procedure period is longer. The method comprises the steps of carrying out molten steel oxygen content at the end point of a converter at 0.05-0.1%, carrying out electric heating on an LF furnace, carrying out no deoxidization and no white slag generation, carrying out oxygen blowing treatment on an RH furnace, carrying out decarburization by using the oxygen content of the molten steel, removing residual oxygen of the molten steel by using aluminum after decarburization, and adding a slag modifier to the slag surface. In the continuous casting process, ferric oxide in slag reacts with Al in molten steel to generate a large amount of Al 2O3, so that a water gap of a crystallizer and a water gap of a ladle are blocked and dead, the inclusion content of a cast blank is high, the total oxygen content of the cast blank is high, and the component requirements cannot be met. Patent CN102978505A discloses a smelting method of high-strength IF steel, after converter tapping, adding medium-carbon ferromanganese alloy, simultaneously adding small-grain lime and a slow-release deoxidizer containing 40% -50% of metallic aluminum to modify slag, carrying out decarburization deep treatment by adopting molten steel free oxygen and carbon reaction in RH treatment, further modifying slag by adding the slow-release deoxidizer after decarburization and air breaking, and finally controlling the FeO content of RH outbound slag to be within 10%, thereby meeting the casting requirement of a slab automobile plate. However, the billet caster requires a lower FeO content of the furnace, and the patented method is not applicable. The patent CN111518988A discloses a method for modifying ultra-low carbon steel refining slag, which comprises the steps of tapping after converter smelting is finished, adding small-grain lime and a first slow-release deoxidizer containing 55-65% of metal aluminum in the tapping process to obtain molten steel of first modified slag, decarburizing the molten steel of the first modified slag in an RH furnace, adding a second slow-release deoxidizer containing 40-50% of metal aluminum in the slag surface, covering a ladle cover, spraying fuel gas and oxygen in the ladle cover to burn the slag surface to promote slag melting, and finally controlling the FeO content in the refining slag to be within 3% after the RH treatment is finished. The technology of the patent needs to additionally reform the ladle cover so as to enable the ladle cover to have a heating function, and the technological process is complex. Patent CN111893245A discloses an ultra-low carbon steel refining slag modifier and a modification method thereof, aiming at ultra-low carbon steel smelting, the tapping temperature is controlled to 1680-1700 ℃, the carbon content is controlled to 0.03-0.05%, the oxygen content is controlled to 0.05-0.075%, a sliding plate is adopted for slag blocking in the tapping process, and molten steel is transferred to an RH station after tapping is finished without adding any slag forming material. In the RH treatment process, molten steel is subjected to oxygen decarburization, aluminum pellets are added for deoxidization, a modifier is added after the deoxidization is finished to prevent oxygen in slag from being transferred to the molten steel, other alloys are added for alloying the molten steel, the molten steel is broken for 6-10min in a pure cycle, the molten steel is sedated for 25-40 min after vacuum breaking, and finally the molten steel is cast on a continuous casting platform. The modifier is spherical, the inner core is aluminum-iron alloy, the periphery is mixed slag, the aluminum content in the aluminum-iron alloy is 38-42%, the aluminum-iron alloy accounts for 20-30