Starting method for producing SPHC continuous casting sheet billet

Abstract

The embodiment of the invention provides a starting method for producing an SPHC continuous casting sheet billet. The starting method comprises the steps that argon is poured into a tundish; after the tundish is filled with argon, large ladle casting operation is executed, and molten steel flows into the tundish from the large ladle; and after preset delay time, argon filling is stopped. After the technical scheme is adopted, in the initial stage of large ladle casting, exposed molten steel cannot be in direct contact with air, so that molten steel adhesion caused by oxidation of aluminum in the molten steel is avoided, and successful starting is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of steel manufacturing, and in particular to a starting method for producing SPHC continuous casting slabs. Background Art

[0002] SPHC is a low-carbon and low-silicon aluminum-killed steel, which has good plasticity and weldability. Its composition is C: 0.04 - 0.07, Si ≤ 0.06, Mn: 0.1 - 0.25, P ≤ 0.025, S ≤ 0.03, Cu ≤ 0.1, Cr ≤ 0.1, Ni ≤ 0.1, Ti ≤ 0.01, Alt: 0.02 - 0.05. This steel grade has a low carbon content. In the smelting process, in order to control C in the composition, the oxygen in the molten steel is relatively high when tapping from the converter. During the refining process, aluminum is added to the molten steel to remove the oxygen in the molten steel, and then argon gas is blown into the ladle to promote the floating of the deoxidation products in the molten steel, so as to achieve the purpose of purifying the molten steel. When starting the continuous casting slab, during the period from the start of pouring from the tundish to the molten steel in the tundish covering the tundish nozzle, since the molten steel is exposed and directly contacts the air, the aluminum in the molten steel will be oxidized, which easily causes the molten steel to stick, resulting in the failure of starting. Therefore, how to avoid the failure of starting caused by the sticking of molten steel during the start of pouring from the tundish is a problem to be solved. Summary of the Invention

[0003] An embodiment of the present invention provides a starting method for producing SPHC continuous casting slabs, so that the molten steel does not directly contact the air at the initial stage of starting pouring from the tundish, thereby avoiding the failure of starting caused by the sticking of molten steel.

[0004] To achieve the above object, an embodiment of the present invention provides a starting method for producing SPHC continuous casting slabs, including: injecting argon gas into the tundish; after the tundish is filled with argon gas, performing the starting pouring operation to make the molten steel flow from the ladle into the tundish; after a predetermined delay time, stopping injecting argon gas.

[0005] Further, the delay time ≥ 2 min.

[0006] Further, during the process of injecting argon gas into the tundish, the argon gas flow rate ≥ 500 L / min, and the argon gas pressure is 0.2 MPa.

[0007] Further, the starting method for producing SPHC continuous casting slabs further includes: the time difference between the starting time of injecting argon gas and the starting time of the starting pouring operation is greater than 1.5 min and less than 2 min.

[0008] Further, the starting method for producing SPHC continuous casting slabs further includes: setting the diameter of the upper nozzle of the tundish to 75 mm.

[0009] Further, the method for starting up the machine for producing SPHC continuous casting slabs further includes: setting the diameter of the submerged nozzle of the tundish to 75 mm

[0010] The above technical solution has the following beneficial effects:

[0011] In this technical solution, at the initial stage of the ladle pouring, since the tundish is filled with argon, and the density of argon is greater than that of air, the exposed molten steel will not come into direct contact with air, thus preventing the aluminum in the molten steel from being oxidized and causing the molten steel to stick, and further ensuring the success of starting up the machine.

[0012] In addition, this technical solution also has the following characteristics:

[0013] By configuring the tundish with a tundish nozzle and a submerged nozzle with an increased aperture, the passability of the tundish nozzle and the submerged nozzle is stronger, thereby reducing the blockage caused by the sticking of molten steel and effectively avoiding the failure of starting up the machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0015] Figure 1 is a flowchart of a method for starting up the machine for producing SPHC continuous casting slabs according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0017] As Figure 1 shown, an embodiment of the present invention provides a method for starting up the machine for producing SPHC continuous casting slabs, including:

[0018] S101. Inject argon into the tundish;

[0019] S102. After the tundish is filled with argon, perform the ladle pouring operation to make the molten steel flow from the ladle into the tundish;

[0020] S103. After a predetermined delay time, stop injecting argon.

[0021] To solve the aforementioned problems, in this application, in order to prevent the molten steel exposed in the initial stage of pouring from contacting air and being oxidized, argon is pre-filled in the tundish for protection. Since the density of argon is greater than that of air, after filling, argon will accumulate in the tundish and expel the air. After the tundish is filled (for a conventional 5.75m 3 tundish, through actual measurement, when the argon flow rate is 500L / min and the argon pressure is 0.2MPa, it takes about 1.5 minutes to fill the entire tundish), the ladle pouring operation is carried out. At this time, the exposed molten steel will not contact oxygen, thus avoiding the problem of molten steel sticking caused by the oxidation of molten steel and avoiding the failure of starting the machine.

[0022] After filling with argon, pouring should be carried out as soon as possible. Therefore, under normal circumstances, it is preferably to control the time interval between the start time of argon filling and the start time of the ladle pouring operation within 1.5 minutes to 2 minutes.

[0023] At the same time, after the ladle pouring operation starts, in order to play a good role in isolating oxygen, argon filling should not be stopped immediately, but should be maintained for a period of time. Through actual measurement, at 2 minutes, the liquid level of the molten steel can submerge the ladle nozzle. At this time, even if the argon protection is stopped, the molten steel will not contact oxygen. Therefore, after the ladle pouring operation starts, the argon supply should be delayed for 2 minutes.

[0024] In addition, the inner diameters of the upper nozzle and the lower nozzle of the existing conventional tundish are both 58mm. For SPHC, this smaller aperture is also a factor causing the failure of starting the machine. When the problem of molten steel sticking occurs, the upper nozzle and the lower nozzle with conventional diameters are likely to be blocked. Therefore, in this technical solution, after a large number of tests by the inventor, the tundish is additionally equipped with upper nozzles and lower nozzles with large apertures (inner diameter 75mm). At this time, the passability of the upper nozzle and the lower nozzle is enhanced, which is suitable for solving the blockage problem caused by molten steel sticking, and at the same time will not affect the normal use due to the too large size of the upper nozzle and the lower nozzle. The technical key points and functions of the present invention are shown in Table 1.

[0025] Table 1 Technical key points and functions of the present invention

[0026] Serial number Technical key points Function 1 Argon injection operation in tundish Prevent molten steel from oxidation 2 Use of tundish large-hole upper nozzle Prevent nozzle from being blocked 3 Use of tundish large-hole lower nozzle Prevent nozzle from being blocked

[0027] The following is the implementation process of a specific embodiment:

[0028] 1. Tundish argon filling operation:

[0029] When the tundish baking is completed, argon is filled into the tundish. Since the density of argon is greater than that of air (argon: 1.784kg / m 3 , air: 1.29Kg / m 3), when the tundish is filled with argon, it can prevent the molten steel injected into the tundish during startup from being oxidized by the air in the ladle. In this specific embodiment, the capacity of the tundish is 5.75 m 3 , in order to ensure that the tundish is filled with argon meeting the requirements, the parameters during argon perfusion can be adjusted as follows: argon flow rate 500 L / min, argon pressure 0.2 MPa. At this time, the time required to fill the tundish is 1.5 min.

[0030] 2. Use of the large orifice upper nozzle of the tundish:

[0031] There are two types of upper nozzles for the tundish. One is a conventional medium orifice upper nozzle with an inner diameter of 58 mm, and the other is a large orifice upper nozzle specially set for this application with an inner diameter of 75 mm. When used in the continuous casting slab production of SPHC steel for this application, the 75-mm large orifice upper nozzle can be used for startup. Even in the case of sticky molten steel, the pouring of the molten steel in this furnace can be completed, avoiding startup failure; for the production of other ordinary steels, the 58-mm medium orifice upper nozzle can be switched back.

[0032] 3. Use of the large orifice lower nozzle of the tundish:

[0033] There are two types of lower nozzles for the tundish. One is a medium orifice lower nozzle with an inner diameter of 58 mm, and the other is a large orifice lower nozzle with an inner diameter of 75 mm. This lower nozzle can be used in combination with the aforementioned upper nozzle.

[0034] In the above detailed description, various features are combined in a single embodiment to simplify the present disclosure. This method of disclosure should not be construed as reflecting an intention that the embodiments of the claimed subject matter require more features than those clearly stated in each claim. On the contrary, as reflected in the appended claims, the present invention is in a state with fewer features than all the features of the disclosed single embodiment. Therefore, the appended claims are hereby clearly incorporated into the detailed description, where each claim stands alone as a separate preferred embodiment of the present invention.

[0035] In order to enable any person skilled in the art to implement or use the present invention, the above-described disclosed embodiments are described. For those skilled in the art; various modification methods of these embodiments are obvious, and the general principles defined herein can also be applied to other embodiments without departing from the spirit and protection scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0036] The specific embodiments described above further elaborate on the objective, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for starting a machine for producing SPHC continuous casting slabs, characterized in that: include: Filling argon into the tundish; When the tundish is filled with argon, the ladle pouring operation is carried out to allow the molten steel to flow from the ladle into the tundish; After a preset delay time, stop perfusing argon.

2. The method for starting a machine for producing a SPHC continuous casting slab according to claim 1, characterized in that: The predetermined delay time is ≥ 2 minutes.

3. The method for starting a machine for producing a SPHC continuous casting slab according to claim 2, characterized in that: In the process of injecting argon into the tundish, the argon flow rate is ≥500L / min and the argon pressure is 0.2MPa.

4. The method for starting a machine for producing a SPHC continuous casting slab according to claim 3, characterized in that: Also includes: The time difference between the start time of the argon injection and the start time of the ladle pouring operation is greater than 1.5 minutes and less than 2 minutes.

5. The method for starting a machine for producing a SPHC continuous casting slab according to claim 1, characterized in that: Also includes: Set the diameter of the water inlet of the tundish to 75mm.

6. The method for starting a machine for producing a SPHC continuous casting slab according to claim 1, characterized in that: Also includes: The diameter of the drain port of the tundish is set to 75mm.

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