CN-122012841-A - Nodular cast iron water smelting method based on deep desulfurization phosphorus pretreatment

CN122012841ACN 122012841 ACN122012841 ACN 122012841ACN-122012841-A

Abstract

The invention relates to the technical field of ferrous metallurgy and casting, in particular to a spheroidal graphite cast iron water smelting method based on deep desulfurization phosphorus pretreatment. The method takes common blast furnace molten iron as a raw material, and sequentially carries out initial refining of oxidation slagging and deep purification of a composite solvent in a steelmaking converter. And then adding a specific compound solvent to synchronously realize deep desulfurization and removal of anti-graphitization elements. The carbon content in the molten iron is controlled to be 2.0% -3.8%, the phosphorus is less than or equal to 0.05%, the sulfur is less than or equal to 0.02%, and the total amount of anti-graphitization elements is less than or equal to 0.10%. The obtained molten iron can be directly used for nodular cast iron production or cast into high-quality pig iron blocks after silicon increase. The method finishes the purification of molten iron in the converter at one time, has short flow, high efficiency and low cost, and is particularly suitable for large-scale production of high-quality spheroidal graphite cast iron.

Inventors

SUN WEI
YU HAO
ZHAO ZHIHONG
LI YONGXIN
CHEN XIAONAN

Assignees

沈阳亚特重型设备制造有限公司

Dates

Publication Date: 20260512
Application Date: 20260416

Claims (10)

1. The nodular cast iron water smelting method based on deep desulfurization phosphorus pretreatment is characterized by comprising the following steps of: s1, preparing and charging raw materials, namely providing common blast furnace molten iron as raw materials, and adding the common blast furnace molten iron into a steelmaking converter; S2, oxidizing and slagging and initial refining, namely adding an alkaline slagging agent mainly comprising lime into a converter, blowing oxygen, and decarburizing, heating, deep dephosphorization and preliminary desulfurization under the conditions of high-temperature, high-oxidability and high-alkalinity slag, wherein the slag alkalinity R=CaO/SiO 2 is more than 3.0; S3, deeply purifying the composite solvent, namely, in the later stage of S2, when dephosphorization is basically finished and the temperature of a molten pool is increased to more than 1500 ℃, adding the composite solvent into a converter, wherein the composite solvent comprises at least two functional components, and realizing deep synchronous purification of sulfur and anti-graphitization elements by utilizing the high temperature and strong stirring conditions in the converter; s4, controlling smelting to stop at the end point that the carbon content in the molten iron is 2.0-3.8%, the phosphorus content is less than or equal to 0.05%, the sulfur content is less than or equal to 0.02%, the total amount of anti-graphitization elements is less than or equal to 0.10%, and the temperature is 1480-1550 ℃ so as to obtain the end point molten iron meeting the production requirements of the spheroidal graphite cast iron.
2. The method for smelting spheroidal graphite cast iron water based on deep desulfurization phosphorus pretreatment according to claim 1, wherein in S3, the composite solvent is a composition of sodium carbonate and calcium carbide or a composition of sodium carbonate and rare earth ferrosilicon alloy.
3. The method for smelting spheroidal graphite cast iron water based on deep desulfurization and phosphorus pretreatment according to claim 1, wherein in S3, after the composite solvent is added, the stirring strength of the bottom-blown gas of the converter is enhanced, and the bottom-blown gas is argon.
4. The method for smelting spheroidal graphite cast iron water based on deep desulfurization phosphorous pretreatment according to claim 1, wherein in S4, the anti-graphitizing element comprises one or more of titanium, vanadium, chromium, lead, and antimony.
5. The method for smelting spheroidal graphite cast iron water based on deep desulfurization phosphorus pretreatment according to claim 1, wherein in S4, the endpoint sulfur content is controlled to be less than or equal to 0.015%.
6. The method for smelting spheroidal graphite cast iron water based on deep desulfurization phosphorus pretreatment according to claim 1, wherein in S4, the total amount of control end point anti-graphitization elements is less than or equal to 0.05%.
7. The ductile iron water smelting method based on deep desulfurization phosphorous pretreatment according to any one of claims 1 to 6 wherein after S4 is completed to obtain the terminal molten iron, one of the following subsequent treatments is optionally performed: Silicon is added to the terminal molten iron and then cast into pig iron blocks; or tapping the final molten iron to a holding furnace for component fine adjustment, and then using the final molten iron in spheroidization, inoculation and pouring of spheroidal graphite cast iron.
8. The method for smelting spheroidal graphite cast iron water based on deep desulfurization phosphorus pretreatment according to claim 7, wherein the casting into pig iron block after silicon increase is: Adding ferrosilicon alloy into the terminal molten iron in a converter to increase silicon, adjusting the silicon content to 1.5% -3.5%, and then tapping and casting to obtain ingots.
9. The method for smelting spheroidal graphite cast iron water based on deep desulfurization and phosphorus pretreatment according to claim 7, wherein the component fine adjustment to the holding furnace is as follows: tapping the terminal molten iron to a medium-frequency induction furnace, adjusting the silicon and manganese content in the furnace, and homogenizing the temperature.
10. The method for smelting spheroidal graphite cast iron water based on deep desulfurization phosphorus pretreatment according to claim 7, wherein after finishing the smelting of the first heat of S4, part of the final slag is reserved in the converter for the smelting of the next heat of S2.

Description

Nodular cast iron water smelting method based on deep desulfurization phosphorus pretreatment Technical Field The invention relates to the technical field of ferrous metallurgy and casting, in particular to a spheroidal graphite cast iron water smelting method based on deep desulfurization phosphorus pretreatment. Background The core of the performance of spheroidal graphite cast iron is the sphericization of graphite inside, which requires that the raw material molten iron must have extremely high purity. Specifically, sulfur (S) and phosphorus (P) seriously deteriorate toughness of materials, and anti-graphitizing elements such as titanium (Ti), vanadium (V), chromium (Cr), lead (Pb), antimony (Sb) and the like seriously interfere formation and growth of graphite nodules, resulting in substandard product performance. At present, the industrial production of nodular cast iron raw materials mainly depends on two technical routes, namely, firstly, the selected low-phosphorus low-sulfur high-quality iron ore is directly smelted in a blast furnace, the method is limited by scarce and expensive ore resources, and secondly, pure scrap steel is smelted in an intermediate frequency furnace and carburised, and the method has extremely high requirements on the quality of the scrap steel, large component fluctuation and high carburising cost. Both routes have the fundamental defects of high raw material cost, unstable supply, long process flow and great difficulty in controlling the components of the product. Therefore, developing a method for producing high-purity spheroidal graphite cast iron raw materials by using large-scale and low-cost common raw materials through an efficient and stable short-flow process becomes an urgent need in the industry. Disclosure of Invention The invention aims to provide a nodular cast iron water smelting method based on deep desulfurization phosphorus pretreatment, which solves the contradiction between retaining high carbon content and deeply removing sulfur, phosphorus and anti-graphitization microelements in a single converter process by combining two stages of oxidizing slagging and deep purification of a composite solvent. The invention utilizes widely available common blast furnace molten iron, and finally produces high-purity nodular cast iron raw materials which can be directly used for casting or cast into standard pig iron blocks through modifying and utilizing the existing steelmaking converter technology, so as to solve the problems in the prior art. In order to achieve the above purpose, the invention provides a spheroidal graphite cast iron water smelting method based on deep desulfurization phosphorus pretreatment, which comprises the following steps: S1, raw material preparation and furnace charging: The blast furnace molten iron is prepared from (by mass) C3.8-4.5%, si 0.3-1.5%, P0.08-0.25% and S0.03-0.10%. The molten iron is added into a steelmaking converter, preferably a converter with top-bottom combined blowing function, so as to strengthen the stirring of a molten pool. S2, oxidizing slagging and primary refining (dephosphorization, decarburization and primary desulfurization): Molten iron is added into a steelmaking converter with good stirring capability (preferably top-bottom combined blowing), and an alkaline slag former mainly comprising lime (CaO) is added and oxygen blowing is started. This step, under high temperature, high oxidizing property and high basicity (r=cao/SiO 2 > 3.0) slag conditions, undergoes the following core reactions: Decarburization and heating [. Sup.C ] +1/2{O 2 } = CO ≡.. This reaction is strongly exothermic, is the primary source of heat for the bath to warm (to 1450-1600 ℃) and provides the necessary thermodynamic driving force for all subsequent endothermic reactions. At the same time, the carbon content is accurately adjusted from the pig iron level to the middle range (2.0% -3.8%) required by the spheroidal graphite cast iron by controlling the oxygen blowing amount, rather than the extremely low carbon content of steelmaking. Deep dephosphorization, namely oxidizing phosphorus by 2[P +5 (FeO) = (P 2O5) +5[ Fe ] in a strong oxidizing atmosphere, wherein the product P 2O5 is an acidic oxide, is unstable at high temperature, but can be immediately combined with free CaO with high concentration in slag to generate stable calcium phosphate which is dissolved in the slag, (P 2O5）+4（CaO）=（4CaO·P2O5), and the high-alkalinity slag ensures that the reaction is carried out rightwards, so that the depth of phosphorus is removed to be less than or equal to 0.05%. And (3) primary desulfurization, namely, carrying out gasification desulfurization and slag-Jin Jiemian desulfurization in the presence of high alkalinity and ferric oxide (FeO), wherein [ S ] +O 2-=（S2-) + [ O ] and [ S ] + (CaO) = (CaS) + [ O ], and part of sulfur can be removed initially at the stage. S3, deep purification (extreme desulfurization and anti-graphitization elem