Clean and rapid smelting method in an electric arc furnace with full scrap steel

Patent metadata

Field	Value
Publication number	US-2019048430-A1
Application number	US-201816052629-A
Country	US
Kind code	A1
Filing date	Aug 2, 2018
Priority date	Aug 10, 2017
Publication date	Feb 14, 2019
Grant date	—

Abstract

A clean and rapid smelting method in an electric arc furnace with full scrap steel, is suitable for smelting process of 30˜300 t electric arc furnace with full scrap steel. In the smelting process of the electric arc furnace with full scrap steel, different kinds of medium is injected by an injection lance which is installed inside refractory material of sidewall at the bottom of the electric arc furnace in different stages of smelting; carburization is utilized in molten pool to accelerate melting down and improve carbon content of the molten pool at the stage of recarburizing and fluxing; reaction in the molten pool is intensified at the stage of high efficiency dephosphorization and deep denitrogenation, to enhance efficient dephosphorization and deep denitrification of the reaction in the molten pool, thereby accelerating the smelting speed of the electric arc furnace with full scrap steel, improving effect of dephosphorization and denitrification.

First claim

We claim:

1 . A clean and rapid smelting method in an electric arc furnace with full scrap steel, wherein, an online dynamic switching for different kinds of medium of pure gas, carrier gas A-recarburization powder and carrier gas B-dephosphorization powder in injection mode is utilized, to finish the process of blowing in turn below molten steel level of molten pool in different stages of smelting for the different kinds of media: in a stage of recarburizing and fluxing, the carrier gas A-recarburization powder is injected into the molten pool to improve the carbon content of the molten pool, and to improve flow velocity of the molten steel that has formed the molten pool; carburization is utilized to accelerate the melting of scrap steel, such that the carbon content of the molten steel in the molten pool reaches to 0.40%˜2.0% after completing melting process of scrap steel; in a stage of high efficiency dephosphorization, the carrier gas B-dephosphorization powder is injected into the molten pool to improve kinetic conditions for dephosphorization, and high efficiency dephosphorization in the furnace is achieved by systematic dephosphorization of slag particle in molten state, to make the content of phosphorus in molten steel equal to or less than 0.010%; in a stage of deep denitrogenation, O 2 or gas mixture of O 2 —CO 2 is injected into the molten pool to intensify decarburization in the molten pool, meanwhile a large number of CO bubbles produced by the metallurgical reaction in molten pool effectively removes [N] in the molten steel; in a stage of smelting endpoint, the carrier gas B-dephosphorization powder is injected to prevent the molten steel from “rephosphorization”, then Ar is injected into the molten pool largely, to homogenize the composition and temperature of the molten pool, to finally achieve that the carbon content of the molten steel is equal to or more than 0.10%, the phosphorus content of the molten steel is equal to or less than 40*10 −6 , and the nitrogen content of the molten steel is, equal to or less than 50*10 −6 .

2 . The clean and fast smelting method in the electric arc furnace with full scrap steel according to claim 1 , comprising the following steps:
step 1: in a time period after outputting steel from the electric arc furnace but prior to adding furnace material, a recarburization path automatic shut-off valve is closed by a control system, a dephosphorization path automatic shut-off valve is opened by the control system, and injection is performed through a transmission pipeline for dephosphorization; N 2 is injected through a central tube and a circular seam tube of an injection lance, and a flow rate of the central tube is 50˜500 Nm 3 /h, a flow rate of the circular seam tube is 50˜200 Nm 3 /h, so as to prevent the injection lance from blocking and burning; step 2: a feeding stage of the electric arc furnace: injection is performed continuously through the transmission pipeline for dephosphorization; O 2 is injected by the central tube of the injection lance, and the flow rate is 50˜300 Nm 3 /h; propane or natural gas is injected by the circular seam tube; and the flow rate is 50˜200 Nm 3 /h, which ensures a normal operation of the injection lance in the feeding process; step 3: a stage of recarburizing and fluxing: carbon powder is injected into the molten pool formed by melting of the scrap steel, to improve the carbon content of the molten pool, and carburization is utilized to accelerate the melting of scrap steel; following steps are performed: 1) an early stage of melting: the recarburization path automatic shut-off valve is opened by the control system, and the dephosphorization path automatic shut-off valve is closed by the control system; injection is performed through the transmission pipeline for recarburization; the mode of the carrier gas A-recarburization powder is performed in the central tube of the injection lance, to accelerate the carburizing and melting of the scrap steel; a shallow molten pool is formed in this stage, so the velocity of powder injection must be controlled to improve the carburizing efficiency, wherein the velocity of powder injection is 1˜5 kg/min, the flow rate of the carrier gas A is 100˜300 Nm 3 /h; propane or natural gas is injected by the circular seam tube of the injection lance, and the flow rate is 50˜200 Nm 3 /h; 2) a middle stage of melting: injection is performed continuously through the transmission pipeline for recarburization; the mode of A-recarburization powder is performed by the central tube of the injection lance; the molten pool has a certain depth in this stage, and the velocity of powder injection is controlled to improve carburizing efficiency, wherein the velocity of powder injection is 5˜10 kg/min, the flow rate of the carrier gas A is 200˜500 Nm 3 /h; propane or natural gas is injected by the circular seam tube of the injection lance, and the flow rate is 50˜200 Nm 3 /h; 3) a later stage of melting: injection is performed continuously through the transmission pipeline for recarburization; the mode of A-recarburization powder is performed in the central tube of the injection lance; the molten pool is deep in this stage, and carburizing and stirring are intensified in the molten pool, wherein the velocity of powder injection is 10˜20 kg/min, and the flow rate of the carrier gas A is 200˜600 Nm 3 /h; propane or natural gas is injected by the circular seam tube of the injection lance, and the flow rate is 50˜200 Nm 3 /h; step 4: a stage of pipeline cleaning: pipeline is cleaned by using large flow N 2 or CO 2 ; the following steps are performed: the recarburization path automatic shut-off valve is opened by the control system, and the dephosphorization path automatic shut-off valve is closed by the control system; injection is performed through the transmission pipeline for dephosphorization; injection of N 2 or CO 2 by the central tube of the injection lance is controlled to clean the pipeline, wherein the flow rate is 400˜600 Nm 3 /h, the time is 20˜30 s; step 5: a stage of high efficiency dephosphorization: high speed dephosphorized particle-gas flow is injected directly to the molten pool below the molten steel level, to effectively remove phosphorus in the molten steel; following steps are performed: injection is performed continuously through the transmission pipeline for dephosphorization; the mode of the carrier gas B-dephosphorization is performed in the central tube of the injection lance, and the carrier gas B and dephosphorization powder are directly input into the molten steel and the stirring ability of the molten pool is intensified, to dephosphorize efficiently, wherein the velocity of powder injection is 10˜50 kg/min, and the flow rate of the carrier gas is 100˜1000 Nm 3 /h; propane or natural gas is injected in the circular seam tube of the injection lance, and the flow rate is 50˜200 Nm 3 /h; step 6: a stage of deep denitrogenation: denitrogenation is performed by intense carbon oxygen reaction inside the molten pool; following steps are performed: injection is performed continuously through the transmission pipeline for dephosphorization; gas mixture of O 2 —CO 2 is injected to intensify decarburization in the molten pool, and a large number of CO bubbles produced by the reaction is utilized to effectively removes [N] in the molten steel, wherein the flow rate of the central tube is 100˜1000 Nm 3 /h, the volume flow rate of CO 2 in mixture gas can be adjusted in a range of 0˜100%; propane or natural gas is injected by the circular seam tube of the injection lance, and the flow rate is 50˜200 Nm 3 /h; step 7: a stage of smelting endpoint: the molten steel is prevented from “rephosphorization”, and denitrogenation is further performed to purify the molten steel; following steps are performed: 1) injection is performed continuously through the transmission pipeline for deph

Assignees

• Univ Beijing Science & Technology

Inventors

• Zhu Rong
• Wei Guangsheng
• Dong Kai
• Zhao Jingxin
• Wu Xuetao
• Tang Tianping
• Wang Xueliang
• Wu Wenhe
• Hu Shaoyan
• Wang Yun

Classifications

• C21C7/0645 Primary

  Agents used for dephosphorising or desulfurising · CPC title

• C21C7/072

  Treatment with gases (C21C7/06, C21C7/064, C21C7/068 take precedence) · CPC title

• C21C7/0025

  Adding carbon material · CPC title

• C21C2005/5258

  with crater formed by down-melting of scrap or charge through electrode or lance · CPC title

• C21C5/5264 Primary

  Manufacture of alloyed steels including ferro-alloys · CPC title