Smelting method of ultra-low carbon steel

Abstract

The invention relates to the technical field of steel and iron smelting, in particular to a smelting method of ultra-low carbon steel, which overcomes the defects that secondary oxidation of blown molten steel after strong drawing of a converter easily causes deterioration of steel cleanliness, causes blockage of a water gap and further causes pouring interruption. According to the smelting method, the carbon element content and the oxygen element content in molten steel components are accurately controlled, the cleanliness of the molten steel is improved, ultra-low carbon steel production is achieved under the condition that a converter lining is not damaged, and the castability of the molten steel is ensured through continuous casting protection casting. Meanwhile, the smelting method is safe, reliable, convenient to operate and suitable for mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and in particular to a method for smelting ultra-low carbon steel. Background Art

[0002] The RH method is carried out in a vacuum chamber lined with refractory materials. Vacuum decarburization is completed under the action of generated carbon monoxide. Vacuum decarburization is one of the important functions of RH. Compared with other refining equipment, RH has a high vacuum degree and a high refining intensity by adopting a large amount of argon gas circulation. It is an essential process for smelting ultra-low carbon steel.

[0003] When producing low carbon steel such as HG6B by the BOF basic oxygen converter-LF refining-RH cycle degassing process, the converter needs strong pulling and then blowing for decarburization, which seriously affects the life of the furnace lining and the quality of the molten steel. In addition, the molten steel leaving the low carbon steel converter has strong oxygen content, which requires the consumption of a large amount of deoxidation materials such as aluminum blocks and aluminum wires, increasing costs.

[0004] Based on this, how to stably control the content of each element in molten steel and efficiently smelt and obtain high-quality ultra-low carbon steel is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a smelting method of ultra-low carbon steel, which can stably and efficiently smelt and obtain high-quality ultra-low carbon steel.

[0006] In order to achieve the above object, the present invention provides a smelting method of ultra-low carbon steel, the smelting method comprising:

[0007] 1) The molten iron is blown through a top and bottom double-blown converter to control the quality parameters of the molten steel produced and to produce steel;

[0008] 2) the molten steel produced in step 1) is hoisted to the RH refining process for RH light treatment;

[0009] 3) the molten steel after the RH light treatment in step 2) is hoisted to the LF process for heating, deoxidation and alloying;

[0010] 4) The molten steel after alloying in step 3) is hoisted to the continuous casting process for protective casting; wherein,

[0011] In step 1), no deoxidizing material is added during the steel tapping process.

[0012] Preferably, in step 1), controlling the quality parameters of the produced molten steel includes: controlling the carbon content in the produced molten steel to be 0.06-0.10wt%, the oxygen content to be >0.06wt%, and the tapping temperature to be 1620-1660°C.

[0013] Preferably, in step 1), the blowing is performed by high-draw supplementary blowing.

[0014] Preferably, in step 1), slag is strictly prohibited during the steel tapping process, and steel should be retained if necessary.

[0015] Preferably, the smelting method further comprises: in step 1), argon is blown from the bottom of the ladle throughout the entire process, and after the steel is tapped, the flow rate of the bottom-blown argon is adjusted to a bright surface of 300 to 500 mm.

[0016] Preferably, in step 2), the carbon content in the molten steel after RH refining is controlled at 0.002-0.006wt%.

[0017] Preferably, in step 2), the RH light treatment comprises: maintaining the pressure after reaching the ultimate vacuum, and determining the oxygen after breaking the vacuum.

[0018] Preferably, the ultimate vacuum is 30Pa.

[0019] More preferably, the holding time is >6 min.

[0020] Preferably, the oxygen determination comprises: controlling the content of oxygen in the molten steel to be ≤0.01wt% by adding aluminum wire.

[0021] Preferably, in step 3), a reducing agent may be added to the molten steel during the heating process to perform diffusion deoxidation.

[0022] Preferably, the reducing agent is aluminum particles and / or carbon powder.

[0023] Preferably, in step 4), the protective casting adopts a large-package casing argon blowing protection and integral nozzle casting method.

[0024] Preferably, the protective casting conditions also include: the superheat of the tundish of the first casting furnace is 35-45°C, the superheat of the tundish of the continuous casting furnace is 20-30°C, and the stirring method of crystallizer electromagnetic stirring plus end electromagnetic stirring is adopted during the casting process.

[0025] Through the above technical scheme, the smelting method of ultra-low carbon steel of the present invention adopts LD converter, RH vacuum decarburization, LF refining, and continuous casting process flow, by controlling the content of carbon and oxygen in the molten steel produced by the LD converter, and removing the carbon element in the molten steel by RH off-furnace refining light treatment using carbon-oxygen reaction, and then the molten steel after RH oxygen determination is heated to LF, deoxidized, and alloyed, and finally in the continuous casting process, a large ladle casing is used for argon blowing protection and integral water nozzle casting to perform protective casting and optimize the converter and refining operation processes, white slag operation is performed during the smelting process, and carbon elements in the molten steel are removed by carbon-oxygen reaction, so that the carbon content in the final molten steel is <0.006wt%, and ultra-low carbon steel is successfully developed.

[0026] The ultra-low carbon steel smelting method of the present invention overcomes the defects that secondary oxidation of molten steel after strong pulling in a converter easily leads to deterioration of steel cleanliness, causing nozzle blockage and thus interruption of pouring. In addition, the smelting method of the present invention accurately controls the carbon and oxygen content in the molten steel composition, improves the cleanliness of the molten steel, realizes the production of ultra-low carbon steel without losing the converter lining, and adopts continuous casting protection casting to ensure the castability of the molten steel. At the same time, the smelting method of the present invention is safe and reliable, easy to operate, and suitable for mass production.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0029] The present invention provides a smelting method for ultra-low carbon steel, the smelting method comprising:

[0030] 1) The molten iron is blown through a top and bottom double-blown converter to control the quality parameters of the molten steel produced and to produce steel;

[0031] 2) the molten steel produced in step 1) is hoisted to the RH refining process for RH light treatment;

[0032] 3) the molten steel after the RH light treatment in step 2) is hoisted to the LF process for heating, deoxidation and alloying;

[0033] 4) The molten steel after alloying in step 3) is hoisted to the continuous casting process for protective casting; wherein,

[0034] In step 1), no deoxidizing material is added during the steel tapping process.

[0035] The ultra-low carbon steel smelting method of the present invention adopts the process flow of LD converter, RH vacuum decarburization, LF refining and continuous casting, controls the contents of carbon and oxygen in molten steel produced by the LD converter, removes carbon in the molten steel by RH off-furnace refining and light treatment by carbon-oxygen reaction, then heats the molten steel after RH oxygenation to LF, deoxidizes and alloys it, finally adopts argon blowing protection of large ladle casing and integral water nozzle casting in the continuous casting process to optimize the converter and refining operation process, performs white slag operation in the smelting process, removes carbon in the molten steel by carbon-oxygen reaction, realizes the carbon content in the final molten steel is less than 0.006wt%, and successfully develops ultra-low carbon steel.

[0036] In a preferred embodiment of the present invention, in order to accurately control the carbon content in the molten steel, in step 1), the quality parameters of the output molten steel are controlled, including: controlling the carbon content in the output molten steel to 0.06-0.10wt%, controlling the oxygen content to >0.06wt%, and controlling the tapping temperature to 1620-1660°C.

[0037] In a preferred embodiment of the present invention, in step 1), the blowing is performed by high-draw supplementary blowing.

[0038] In a preferred embodiment of the present invention, in step 1), slag is strictly prohibited during the steel tapping process, and steel should be retained if necessary.

[0039] In a preferred embodiment of the present invention, the smelting method further comprises: in step 1), argon is blown from the bottom of the ladle throughout the whole process, and after the steel is tapped, the bottom blowing argon flow rate is adjusted to 300 to 500 mm above the bright surface; wherein, the bottom blowing argon is based on the condition that the molten steel does not splash out of the ladle.

[0040] In a preferred embodiment of the present invention, in order to accurately control the carbon content in the molten steel, in step 2), the carbon content in the molten steel after RH refining is controlled to be 0.002-0.006 wt%.

[0041] In a preferred embodiment of the present invention, in order to accurately control the oxygen content in the molten steel, in step 2), the RH light treatment includes: maintaining the pressure after reaching the ultimate vacuum, and determining the oxygen after breaking the vacuum.

[0042] In a preferred embodiment of the present invention, the ultimate vacuum is 30Pa.

[0043] In a preferred embodiment of the present invention, the holding time is >6 min.

[0044] In a preferred embodiment of the present invention, in order to accurately control the oxygen content in the molten steel, the oxygen determination includes: controlling the oxygen content in the molten steel to ≤ 0.01 wt % by adding aluminum wire.

[0045] In a preferred embodiment of the present invention, in order to accurately control the oxygen content in the molten steel, in step 3), a reducing agent may be added to the molten steel during the heating process to perform diffusion deoxidation.

[0046] In a preferred embodiment of the present invention, in order to accurately control the oxygen content in the molten steel, the reducing agent is aluminum particles and / or carbon powder.

[0047] In a preferred embodiment of the present invention, in order to accurately control the carbon and oxygen content in the molten steel, a composition adjustment operation is performed after the molten steel is refined and slag is formed, so as to improve the hit rate of the composition adjustment and reduce the number of composition adjustments. After the white slag is formed, the aluminum wire feed amount is adjusted according to the required target value.

[0048] In a preferred embodiment of the present invention, in step 4), the protective casting adopts a large-package casing argon blowing protection and an integral nozzle casting method.

[0049] In a preferred embodiment of the present invention, the protective casting conditions also include: the superheat of the tundish in the first casting furnace is 35-45°C, the superheat of the tundish in the continuous casting furnace is 20-30°C, and the stirring method of crystallizer electromagnetic stirring plus end electromagnetic stirring is adopted during the casting process.

[0050] In summary, the smelting method of ultra-low carbon steel of the present invention overcomes the defects that the secondary oxidation of molten steel after strong pulling in the converter easily leads to the deterioration of steel cleanliness, causing the nozzle to be blocked and then the pouring to be interrupted. In addition, the smelting method of the present invention accurately controls the carbon content and oxygen content in the molten steel composition, improves the cleanliness of the molten steel, realizes the production of ultra-low carbon steel without losing the converter lining, and adopts continuous casting protection casting to ensure the castability of the molten steel. At the same time, the smelting method of the present invention is safe and reliable, easy to operate, and suitable for mass production.

[0051] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0052] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0053] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for smelting ultra-low carbon steel, characterized in that: The smelting method comprises: 1) The molten iron is blown through a top and bottom double-blown converter to control the quality parameters of the molten steel produced and to produce steel; 2) the molten steel produced in step 1) is hoisted to the RH refining process for RH light treatment; 3) the molten steel after the RH light treatment in step 2) is hoisted to the LF process for heating, deoxidation and alloying; 4) The molten steel after alloying in step 3) is hoisted to the continuous casting process for protective casting; wherein, In step 1), no deoxidizing material is added during the steel tapping process.

2. The smelting method according to claim 1, characterized in that: In step 1), the quality parameters of the produced molten steel are controlled, including: controlling the carbon content in the produced molten steel to 0.06-0.10wt%, the oxygen content to >0.06wt%, and the tapping temperature to 1620-1660°C.

3. The smelting method according to claim 1 or 2, characterized in that: In step 1), the blowing is performed by high-draw supplementary blowing.

4. The smelting method according to any one of claims 1 to 3, characterized in that: In step 1), slag is strictly prohibited during the steel tapping process, and steel should be retained if necessary.

5. The smelting method according to any one of claims 1 to 4, characterized in that: The smelting method further comprises: in step 1), argon is blown from the bottom of the ladle throughout the whole process, and after the steel is tapped, the flow rate of the bottom-blown argon is adjusted to a bright surface of 300 to 500 mm.

6. The smelting method according to any one of claims 1 to 5, characterized in that: In step 2), the carbon content in the molten steel after RH refining is controlled at 0.002-0.006 wt%.

7. The smelting method according to any one of claims 1 to 6, characterized in that: In step 2), the RH light treatment includes: maintaining the pressure after reaching the ultimate vacuum, and determining the oxygen after breaking the vacuum; Preferably, the ultimate vacuum is 30Pa; More preferably, the holding time is >6 min.

8. The smelting method according to claim 7, characterized in that: The oxygen determination comprises: controlling the content of oxygen in the molten steel to be ≤0.01wt% by adding aluminum wire.

9. The smelting method according to any one of claims 1 to 8, characterized in that: In step 3), a reducing agent may be added to the molten steel during the heating process to perform diffusion deoxidation; Preferably, the reducing agent is aluminum particles and / or carbon powder.

10. The smelting method according to any one of claims 1 to 9, characterized in that: In step 4), the protective casting adopts a large-package casing argon blowing protection and an integral nozzle casting method; Preferably, the protective casting conditions also include: the superheat of the tundish of the first casting furnace is 35-45°C, the superheat of the tundish of the continuous casting furnace is 20-30°C, and the stirring method of crystallizer electromagnetic stirring plus end electromagnetic stirring is adopted during the casting process.