A method for treating excessive manganese content in molten rebar.

Abstract

This invention belongs to the field of converter smelting technology and discloses a method for treating excessive manganese content in molten rebar. When the manganese content in molten steel exceeds the standard, the manganese is removed without removing other alloying elements. Specifically, after tapping, if excessive manganese content is found in the molten steel, the ladle is moved to the LF station, a certain amount of manganese-removing agent is added, and bottom blowing is started for stirring. By controlling the composition and dosage of the manganese-removing agent, and setting the flow rate and time of bottom blowing, manganese removal is achieved in the molten steel without removing other alloying elements. This invention avoids the loss caused by remelting due to excessive manganese content in molten steel caused by improper operation during rebar smelting. It is low-cost, highly efficient, and worthy of widespread application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of converter steelmaking, and particularly relates to a processing method for excessive manganese content of screw steel molten steel, and belongs to the technical field of smelting. BACKGROUND

[0002] Screw steel is hot-rolled ribbed steel, and is a kind of steel material that must be used in medium-sized or larger building components, and is widely used in civil engineering construction such as houses, bridges and roads. From large public facilities such as highways, railways, bridges, culverts, tunnels, flood control and dams to small building foundations, beams, columns, walls and boards, screw steel is an indispensable structural material. With the deepening of urbanization in China, the vigorous development of infrastructure construction and real estate has a strong demand for screw steel. Screw steel has relatively strict requirements on its mechanical properties, and in order to ensure the qualified mechanical properties, the manganese content in the steel material usually needs to be controlled. If the manganese content in the steel material is too low, the mechanical properties will be unqualified, and if the manganese content is too high, the plasticity of the steel material will decrease, causing brittle fracture.

[0003] Chinese patent CN110453032A provides a method for smelting ultra-low manganese steel by using high-manganese molten iron, in which a double-slag method is used to remove most of the manganese elements in the molten iron in the converter process, and a converter low-temperature tapping and LF refining deep manganese removal process is used to further remove manganese, so as to stably control the molten steel manganese content below 0.02% under the condition that the molten iron manganese content is higher than 0.40%. In the patent, oxygen is blown in the converter to remove manganese, and in the refining process, the molten steel is further removed by free oxygen and Fe2O3 as the main component of the oxide scale ball. However, for the screw steel after adding alloy, the molten steel has no free oxygen, and the silicon content in the molten steel is high. If Fe2O3 is used as the oxide to remove manganese, the silicon will be preferentially removed due to the lower oxygen potential of silicon, and the manganese can be removed after the silicon is removed. For the alloyed screw steel without free oxygen, how to efficiently and accurately remove manganese is a technical problem to be solved by the present application. SUMMARY

[0004] The composition of screw steel mainly includes C 0.20-0.25%, Si 0.50-0.80%, Mn 1.35-1.45%, P 0-0.045%, S 0-0.045%, V 0.02-0.03%, and N 50-100ppm. In the production of screw steel, a straight-up fast smelting process is generally adopted, and the smelting process route is converter→argon station→continuous casting. In order to reduce the alloying in the argon station, the manganese content of the molten steel is generally adjusted during the tapping process of the converter, and the alloy content can be slightly adjusted during the treatment process in the argon station.

[0005] The inventors find that in actual production process, when encountering large pieces of manganese-containing alloy, the tapping process is not completely melted, the manganese content of the argon station sampling molten steel does not reach the target, and the excessive manganese-containing alloy is added, which will cause the manganese content of the molten steel to exceed the standard. In this case, the molten steel needs to be remelted, which increases the cost of steelmaking.

[0006] In view of the above situation, the purpose of the present application is to provide a treatment method for the case that the manganese content of the deformed steel exceeds the standard, which removes the manganese content of the molten steel without removing other alloying elements when the manganese content of the molten steel exceeds the standard.

[0007] The specific method steps and control method parameters are as follows:

[0008] A treatment method for the case that the manganese content of the deformed steel exceeds the standard, which is a remedial method for the case that the manganese content of the molten steel exceeds the standard during the deformed steel smelting. The method comprises the following steps: after finding that the manganese content of the ladle molten steel exceeds the standard, the ladle is transported to the LF station, a certain amount of manganese removal agent is added, and manganese removal is carried out through high-flow bottom argon blowing.

[0009] As a preferred embodiment, the main components of the manganese removal agent are: MgO 10-20%, CaO 5-10%, SiO2 60-80%, and other impurities.

[0010] As a preferred embodiment, the amount of manganese removal agent added is 2850×([%Mn] 初始 -[%Mn] 目标 ) / ([%SiO2]+1 / 4[%MgO]) kg / t; in the formula, %SiO2 and %MgO are the percentage contents of SiO2 and MgO in the manganese removal agent, [%Mn] 初始 and [%Mn] 目标 are the initial manganese content and the target manganese content of the molten steel, respectively.

[0011] As a preferred embodiment, the argon flow rate of bottom blowing is 10-20 L / min, and the stirring time is 5-10 min.

[0012] The advantages of the present application mainly lie in the following aspects:

[0013] 1. A manganese removal method is provided, which removes the manganese content of the molten steel without removing other alloying elements in the molten steel when the manganese content of the molten steel exceeds the standard. SiO2 is used as the main deoxidizer, which can directly remove manganese without causing desiliconization reaction.

[0014] 2. The application provides a manganese removal agent, which is mainly composed of 10-20% of MgO, 5-10% of CaO and 60-80% of SiO2, wherein the SiO2 serves as an oxidant to oxidize the manganese content in molten steel into MnO; in addition, the MgO in the manganese removal agent can protect the ladle lining and reduce the erosion of the ladle lining by SiO2; meanwhile, the MgO can form a solid solution with the MnO to promote the manganese removal reaction.

[0015] 3. The application provides a manganese removal agent adding method, which can accurately remove the manganese content in molten steel. DETAILED DESCRIPTION

[0016] The application is further described below in combination with examples:

[0017] The components of the screw steel mainly include C 0.20-0.25%, Si 0.50-0.80%, Mn 1.35-1.45%, P 0-0.045%, S 0-0.045%, V 0.02-0.03% and N 50-100ppm.

[0018] The smelting process route is converter→argon station→continuous casting.

[0019] Example 1

[0020] During the argon station treatment process, it is found that the manganese content in molten steel exceeds the standard, and the specific components are C 0.23%, Si 0.56%, Mn 1.52%, P 0.025%, S 0.023%, V 0.025% and N 70ppm; the temperature of the molten steel is 1580℃; and the amount of the molten steel is 128t. The target Mn content is determined to be 1.41%.

[0021] The molten steel is transported to the LF furnace for manganese removal treatment, the temperature of the molten steel arriving at the LF furnace is 1575℃, the manganese removal agent is selected, and the specific components of the manganese removal agent are MgO 18%, CaO 6% and SiO2 75%, and the others are impurities. According to the formula 2850x([%Mn] 初始 -[%Mn] 目标 ) / ([%SiO2]+1 / 4[%MgO])kg / t, the adding amount of the manganese removal agent is calculated to be 3.94kg / t, after the manganese removal agent is added, the temperature of the molten steel is 1568℃; the temperature is increased to 1580℃ by power supply, and the bottom blowing argon stirring is started, the bottom blowing flow is controlled to be 15L / min, and the stirring time is 8min.

[0022] After the stirring is finished, the molten steel sample is taken, and the components of the molten steel are C 0.23%, Si 0.59%, Mn 1.42%, P 0.025%, S 0.023%, V 0.025% and N 70ppm; the requirements of the steel grade are met.

[0023] Example 2

[0024] The argon station treatment process found that the manganese content of the molten steel exceeded the standard, and the specific composition was C 0.22%, Si 0.60%, Mn 1.65%, P 0.022%, S 0.025%, V 0.025%, N 75ppm; the molten steel temperature was 1575℃; and the molten steel amount was 130t. The target Mn content was determined to be 1.44%.

[0025] The molten steel was adjusted and transported to the LF furnace for treatment, the LF furnace to station molten steel temperature was 1569℃, the specific composition of the manganese removal agent was MgO 16%, CaO 5%, SiO2 77%, and the others were impurities; according to the formula 2850x([%Mn] 初始 -[%Mn] 目标 ) / ([%SiO2]+1 / 4[%MgO])kg / t, the amount of manganese removal agent added was calculated to be 7.39kg / t, the molten steel temperature was 1563℃; the power was turned on to raise the temperature to 1580℃ and the bottom blowing argon stirring was started, the bottom blowing flow was controlled at 15L / min, and the stirring time was 8min.

[0026] After the stirring was finished, the molten steel sample was taken, and the composition of the molten steel was C 0.22%, Si 0.66%, Mn 1.43%, P 0.022%, S 0.025%, V 0.025%, N 75ppm; which met the requirements of the steel grade.

[0027] Comparative Example 1

[0028] The steel grade composition requirement was C 0.23%, Si 0.56%, Mn 1.41%, P 0.025%, S 0.023%, V 0.025%, N 70ppm. The smelting process route was converter→argon station→continuous casting.

[0029] The argon station treatment process found that the manganese content of the molten steel exceeded the standard, and the specific composition was C 0.23%, Si 0.56%, Mn 1.52%, P 0.025%, S 0.023%, V 0.025%, N 70ppm; the molten steel temperature was 1580℃; and the molten steel amount was 128t. The target Mn content was determined to be 1.41%.

[0030] The molten steel was adjusted and transported to the LF furnace for treatment, the LF furnace to station molten steel temperature was 1575℃, 4.0kg / t of ore was added, the molten steel temperature was 1559℃, the composition of the ore was Fe2O3 91%, CaO 6%, SiO2 2%, and the others were impurities; the power was turned on to raise the temperature to 1580℃ and the bottom blowing argon stirring was started, the bottom blowing flow was controlled at 15L / min, and the stirring time was 8min.

[0031] After the stirring, the molten steel sample is taken, and the composition of the molten steel is C 0.22%, Si 0.50%, Mn 1.50%, P 0.025%, S 0.023%, V 0.025%, and N 70 ppm; the content of manganese in the molten steel is basically not removed. In the comparative example, the conventional oxidizing agent ore is used for removing manganese, and it is found that the amount of removed manganese is small, the silicon in the molten steel is mainly removed, and the temperature of the molten steel is greatly reduced.

[0032] Comparative example 2

[0033] The argon station treatment process shows that the content of manganese in the molten steel exceeds the standard, and the specific composition is C 0.22%, Si 0.60%, Mn 1.65%, P 0.022%, S 0.025%, V 0.025%, and N 75 ppm; the temperature of the molten steel is 1575℃; and the amount of the molten steel is 130 t. The target content of Mn is determined to be 1.44%.

[0034] The molten steel is transported to the LF furnace for treatment, the temperature of the molten steel arriving at the station is 1569℃, 7.5 kg / t of the manganese removal agent is added, and the temperature of the molten steel is 1563℃; the specific composition of the manganese removal agent is CaO 7.3%, SiO2 91.5%, and the others are impurities; the temperature is raised to 1580℃ by power supply, and the bottom blowing argon stirring is started, the flow rate of the bottom blowing is controlled to be 15 L / min, and the stirring time is 8 min.

[0035] After the stirring, the molten steel sample is taken, and the composition of the molten steel is C 0.22%, Si 0.64%, Mn 1.49%, P 0.022%, S 0.025%, V 0.025%, and N 75 ppm. In the comparative example, the manganese removal agent does not contain MgO, and compared with example 2, the manganese removal effect is poor.

[0036] The above describes only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacement or change according to the technical solution and concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

[0037] The present application is not limited to the following specific embodiments, and those skilled in the art can use other various specific embodiments to implement the present application according to the disclosed content of the present application, or any simple change or modification using the design structure and concept of the present application, which falls within the protection scope of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for treating a threaded steel with an excessive manganese content in the molten steel, characterized in that: After discovering that the ladle molten steel manganese content is overproof, the ladle is transported to the LF station, a manganese removal agent is added, and argon is blown at the bottom to stir and remove manganese; the main components of the manganese removal agent are: MgO 10-20%, CaO 5-10%, SiO2 60-80%, and other impurities.

2. The method according to claim 1, characterized in that: The amount of manganese-removing agent added is 2850 × ([%Mn]). 初始 -[%Mn] 目标 ) / ([%SiO2]+1 / 4[%MgO])kg / t; where %SiO2 and %MgO are the percentage contents of SiO2 and MgO in the manganese removal agent, and [%Mn] is the percentage content of MgO and MgO in the manganese removal agent. 初始 and [%Mn] 目标 These refer to the initial manganese content and the target manganese content in the molten steel, respectively.

3. The method of claim 1, wherein the method further comprises: The argon flow rate is 10-20 L / min, and the stirring time is 5-10 min. ​ 4. The method of claim 1, wherein the method further comprises: The component requirements of the deformed steel bar are: C 0.20-0.25%, Si 0.50-0.80%, Mn 1.35-1.45%, P 0-0.045%, S 0-0.045%, V 0.02-0.03%, and N 50-100 ppm. ​