A method for low-cost and efficient production of ultra-low phosphorus steel

Abstract

The present application belongs to the technical field of steel metallurgy, and particularly relates to a method for producing ultra-low phosphorus steel at low cost and high efficiency, which is produced by adopting a brand-new process of 'converter + post-furnace stirring dephosphorization + post-furnace ladle replacement'. The smelting of ultra-low phosphorus steel no longer needs 'three dephosphorizations', and there is no special requirement for the temperature and composition of the molten iron. The physical heat loss of the molten iron is small, the temperature of the molten iron entering the furnace is high, the loss of steel and alloy in the converter blowing process is small, the removal time of the post-furnace oxidizing top slag is shorter than the smelting cycle of the converter, which is beneficial to continuous and stable production, and the hit rate of the phosphorus content is high, so that the continuous, low-cost and high-efficiency and stable production of ultra-low phosphorus steel can be realized, and a strong technical guarantee is provided for improving the smelting quality.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a low-cost and high-efficiency method for producing ultra-low phosphorus steel. Background Technology

[0002] Currently, the international and domestic steelmaking industries commonly use triple desilication (desiliconization, dephosphorization, and desulfurization) of molten iron, dual-converter processes (one converter for dephosphorization and another for decarburization), or converter "double slag" or even "triple slag" methods to produce ultra-low phosphorus steel. When using these processes to produce ultra-low phosphorus steel, not only are the requirements for molten iron temperature and composition strict, but the phosphorus hit rate at the blowing endpoint is also low, making it difficult to achieve continuous and stable production of ultra-low phosphorus steel. Furthermore, these processes result in high converter blowing losses, high steel feed consumption, low alloy element recovery rates, significant energy waste, and low output, leading to high production costs for ultra-low phosphorus steel. Summary of the Invention

[0003] To address the problems existing in the prior art, the main objective of this invention is to propose a low-cost and high-efficiency method for producing ultra-low phosphorus steel. This method has no special requirements for the temperature and composition of molten iron, does not require three-stage hot metal removal, can be produced using a single converter, has little impact on the smelting cycle and tapping temperature of the converter, and can achieve continuous and stable production of ultra-low phosphorus steel.

[0004] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0005] A low-cost, high-efficiency method for producing ultra-low phosphorus steel includes the following steps:

[0006] S1, Converter blowing

[0007] The final phosphorus content of the molten steel produced by converter smelting is ≤0.015wt%, and the oxygen content is 400~700ppm;

[0008] S2, Converter tapping

[0009] Dephosphorizing lime is added to the ladle during steel tapping from the converter, at a rate of 3–6 kg / t. 钢 ;

[0010] S3, Argon blowing and stirring after furnace

[0011] The argon flow rate for bottom blowing agitation in the ladle is 400–800 NL / min, and the argon stirring time is ≥5 min;

[0012] S4, Replace the bag and remove slag

[0013] The molten steel is changed into a ladle to ensure that all oxidizing top slag remains in the original ladle;

[0014] S5, Refined

[0015] Molten steel is hoisted to the refining LF furnace for refining to obtain ultra-low phosphorus molten steel with a phosphorus content of ≤0.006wt%.

[0016] As a preferred embodiment of the method for producing ultra-low phosphorus steel at low cost and high efficiency according to the present invention, in step S1, the final temperature of the converter smelting is 1580-1620℃.

[0017] As a preferred embodiment of the method for producing ultra-low phosphorus steel at low cost and high efficiency according to the present invention, in step S2, after the converter tapping amount is 1 / 4, dephosphorizing lime is added to the ladle.

[0018] As a preferred embodiment of the method for producing ultra-low phosphorus steel at low cost and high efficiency according to the present invention, in step S3, the bottom blowing of the ladle is carried out by stirring with double permeable bricks.

[0019] As a preferred embodiment of the method for producing ultra-low phosphorus steel at low cost and high efficiency according to the present invention, in step S4, the ladle is hoisted to the casting platform, the ladle sliding mechanism is connected, the slide plate is opened, and the molten steel is changed into a ladle. When slag is seen, the slide plate is closed to ensure that all the oxidizing top slag remains in the original ladle.

[0020] As a preferred embodiment of the method for producing ultra-low phosphorus steel at low cost and high efficiency according to the present invention, in step S4, the ladle changing time is less than 30 minutes.

[0021] As a preferred embodiment of the method for producing ultra-low phosphorus steel at low cost and high efficiency according to the present invention, in step S5, molten steel is hoisted to the refining LF furnace, and after heating, slag, alloy and deoxidizer are added for conventional process operation.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention proposes a low-cost and high-efficiency method for producing ultra-low phosphorus steel. It adopts a novel "converter + post-furnace stirring dephosphorization + post-furnace ladle change" process. The smelting of ultra-low phosphorus steel no longer requires "three dephosphorizations" and has no special requirements for the temperature and composition of the molten iron. The physical heat loss of the molten iron is small, the temperature of the molten iron entering the furnace is high, the loss of steel materials and alloys during the converter blowing process is small, and the removal time of the oxidizing top slag after the furnace is shorter than the converter smelting cycle, which is conducive to continuous and stable production. Moreover, the phosphorus content hit rate is high, which can realize the continuous, low-cost, high-efficiency and stable production of ultra-low phosphorus steel, and provide strong technical support for improving the smelting quality. Detailed Implementation

[0024] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention proposes a low-cost and high-efficiency method for producing ultra-low phosphorus steel. This method has no special requirements for the temperature and composition of molten iron, does not require three-stage hot metal removal, can be produced using a single converter, has little impact on the smelting cycle and tapping temperature of the converter, and can achieve continuous and stable production of ultra-low phosphorus steel.

[0026] According to one aspect of the present invention, the present invention provides the following technical solution:

[0027] A low-cost, high-efficiency method for producing ultra-low phosphorus steel includes the following steps:

[0028] S1, Converter blowing

[0029] The molten iron added to the converter is molten iron that has not undergone three removal processes. The final phosphorus content of the molten steel at the converter smelting endpoint is ≤0.015wt%, and the oxygen content is 400~700ppm.

[0030] S2, Converter tapping

[0031] Dephosphorizing lime is added to the ladle during steel tapping from the converter, at a rate of 3–6 kg / t. 钢 ;

[0032] S3, Argon blowing and stirring after furnace

[0033] Bottom blowing and stirring of the ladle creates kinetic conditions for dephosphorization, with an argon flow rate of 400-800 NL / min and an argon stirring time of ≥5 min.

[0034] S4, Replace the bag and remove slag

[0035] The ladle-changing operation is performed on the molten steel to ensure that all the oxidizing top slag remains in the original ladle, preventing the molten steel from reverting to phosphorus after refining and deoxidation;

[0036] S5, Refined

[0037] Molten steel is hoisted to the refining LF furnace for refining to obtain ultra-low phosphorus molten steel with a phosphorus content of ≤0.006wt%.

[0038] This invention utilizes the oxygen content of molten steel after tapping from the converter, adds lime for further dephosphorization, creates kinetic conditions for dephosphorization through bottom blowing and stirring in the ladle, and then separates the dephosphorized molten steel from the high-phosphorus oxidizing top slag to prevent phosphorus reversion in the molten steel after refining and deoxidation, thus enabling the stable production of ultra-low phosphorus steel.

[0039] Preferably, in step S1, the final temperature of the converter smelting is 1580–1620°C. Specifically, the final temperature of the converter smelting can be, for example, any one or a range between any two of 1580°C, 1590°C, 1600°C, 1610°C, and 1620°C; the final oxygen content of the converter smelting can be, for example, any one or a range between any two of 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, 650 ppm, and 700 ppm.

[0040] Preferably, in step S2, after the converter has tapped 1 / 4 of its steel, dephosphorizing lime is added to the ladle. The amount of dephosphorizing lime added can be 3 kg / t. 钢 3.5kg / t 钢 4kg / t 钢 4.5kg / t 钢 5kg / t 钢 5.5kg / t 钢 6kg / t 钢 The range between any one or any two of these; the higher the phosphorus content of the molten steel at the end of converter smelting, the more dephosphorizing lime should be added.

[0041] Preferably, in step S3, the bottom blowing of the ladle employs a double-permeable brick agitation. Specifically, the argon flow rate for bottom blowing agitation in the ladle can be, for example, any one or a range between any two of 400NL / min, 450NL / min, 500NL / min, 550NL / min, 600NL / min, 650NL / min, 700NL / min, 750NL / min, and 800NL / min, and the argon agitation time can be, for example, any one or a range between any two of 5min, 6min, 7min, 8min, 9min, and 10min.

[0042] Preferably, in step S4, the ladle is hoisted to the casting platform, the ladle sliding mechanism is connected, the slide plate is opened, and the molten steel is changed into a ladle. When slag is seen, the slide plate is closed to ensure that all oxidizing top slag remains in the original ladle.

[0043] Preferably, in step S4, the package changing time is less than 30 minutes.

[0044] Preferably, in step S5, during the LF furnace refining process, conventional operation can be used, that is, the molten steel is hoisted to the refining LF furnace, and after heating, slag, alloy and deoxidizer are added, and conventional process operation is carried out.

[0045] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0046] Example 1

[0047] A low-cost, high-efficiency method for producing ultra-low phosphorus steel, using hydrogen-resistant 12Cr2Mo1R steel with a phosphorus content ≤0.008wt%, includes the following steps:

[0048] S1, Converter blowing

[0049] The final temperature of the molten steel after converter smelting was 1593℃, the phosphorus content was 0.011wt%, and the oxygen content was 660ppm.

[0050] S2, Converter tapping

[0051] After the converter tapped 1 / 4 of its steel, dephosphorizing lime was added to the ladle; the tapping volume of the converter in this heat was 143t, and the amount of dephosphorizing lime added was 550kg.

[0052] S3, Argon blowing and stirring after furnace

[0053] The argon flow rate for bottom blowing stirring in the ladle is 500 NL / min, and the argon stirring time is 6 min;

[0054] S4, Replace the bag and remove slag

[0055] The ladle is hoisted to the casting platform. After the ladle sliding mechanism is connected, the slide plate is opened to perform the ladle replacement operation. When slag is seen, the slide plate is closed to ensure that all the oxidizing top slag remains in the original ladle. The ladle replacement time is 27 minutes.

[0056] S5, Refined

[0057] The molten steel was hoisted to the refining LF furnace, heated, and then slag, alloys, and deoxidizers were added before sampling. The phosphorus content of the molten steel was 0.0046 wt%.

[0058] Example 2

[0059] A low-cost and high-efficiency method for producing ultra-low phosphorus steel, the steel grade being 09MnNiDR, with a phosphorus content requirement of ≤0.006wt%, includes the following steps:

[0060] S1, Converter blowing

[0061] The final temperature of the molten steel after converter smelting was 1585℃, the phosphorus content was 0.009wt%, and the oxygen content was 580ppm.

[0062] S2, Converter tapping

[0063] After the converter has tapped 1 / 4 of its steel, dephosphorizing lime is added to the ladle; the converter tapping volume for this heat is 140t, and the amount of dephosphorizing lime added is 480kg.

[0064] S3, Argon blowing and stirring after furnace

[0065] The argon flow rate for bottom blowing agitation in the ladle is 600 NL / min, and the argon stirring time is 7 min.

[0066] S4, Replace the bag and remove slag

[0067] The ladle is hoisted to the casting platform. After the ladle sliding mechanism is connected, the slide plate is opened to perform the ladle replacement operation. When slag is seen, the slide plate is closed to ensure that all the oxidizing top slag remains in the original ladle. The ladle replacement time is 25 minutes.

[0068] S5, Refined

[0069] The molten steel was hoisted to the refining LF furnace, heated, and then slag, alloys, and deoxidizers were added before sampling. The phosphorus content of the molten steel was 0.0037 wt%.

[0070] Example 3

[0071] A low-cost, high-efficiency method for producing ultra-low phosphorus steel, the steel grade being X65M (HIC), with a phosphorus content requirement of ≤0.006wt%, includes the following steps:

[0072] S1, Converter blowing

[0073] The final temperature of the molten steel after converter smelting was 1608℃, the phosphorus content was 0.013wt%, and the oxygen content was 692ppm.

[0074] S2, Converter tapping

[0075] After the converter tapped 1 / 4 of its steel, dephosphorizing lime was added to the ladle; the tapping volume of the converter in this heat was 137t, and the amount of dephosphorizing lime added was 653kg.

[0076] S3, Argon blowing and stirring after furnace

[0077] The argon flow rate for bottom blowing agitation in the ladle is 700 NL / min, and the argon stirring time is 7 min.

[0078] S4, Replace the bag and remove slag

[0079] The ladle is hoisted to the casting platform. After the ladle sliding mechanism is connected, the slide plate is opened to perform the ladle replacement operation. When slag is seen, the slide plate is closed to ensure that all oxidizing top slag remains in the original ladle. The ladle replacement time is 24 minutes.

[0080] S5, Refined

[0081] The molten steel was hoisted to the refining LF furnace, heated, and then slag, alloys, and deoxidizer were added before sampling. The phosphorus content of the molten steel was 0.0032 wt%.

[0082] Comparative Example 1

[0083] The difference from Example 1 is that steps S2-S4 are not performed, the final temperature of the molten steel at the converter smelting point is 1614℃, the phosphorus content is 0.014wt%, and the oxygen content is 670ppm.

[0084] The phosphorus content of the refined molten steel is 0.015 wt%.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that steps S3-S4 are not performed, the final temperature of the molten steel in the converter smelting is 1606℃, the phosphorus content is 0.012wt%, and the oxygen content is 574ppm; the phosphorus content of the refined molten steel is 0.013wt%.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that step S4 is omitted, the final temperature of the molten steel at the converter smelting point is 1589°C, the phosphorus content is 0.010 wt%, and the oxygen content is 543 ppm; the phosphorus content of the refined molten steel is 0.011 wt%.

[0089] The novel "converter + post-furnace stirring dephosphorization + post-furnace ladle change" process described in this invention eliminates the need for "three dephosphorizations" in the smelting of ultra-low phosphorus steel. It also removes special requirements for molten iron temperature and composition, minimizes physical heat loss, results in higher molten iron temperature at the furnace, reduces steel and alloy losses during converter blowing, and shortens the removal time of oxidizing top slag compared to the converter smelting cycle. This facilitates continuous and stable production, and achieves a high phosphorus content hit rate, enabling continuous, low-cost, high-efficiency, and stable production of ultra-low phosphorus steel. This provides strong technical support for improving smelting quality. In contrast, in Comparative Examples 1-3, which do not use the method described in this invention, the phosphorus content of the steel tapped from the converter remains almost unchanged or slightly increases after refining, making it impossible to achieve low-cost and high-efficiency production of ultra-low phosphorus steel.

[0090] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A low-cost, high-efficiency method for producing ultra-low phosphorus steel, characterized in that, Includes the following steps: S1, Converter blowing The final phosphorus content of the molten steel after converter smelting is ≤0.015wt%, and the oxygen content is 400~700ppm; the final temperature of converter smelting is 1580~1620℃. S2, Converter tapping After the converter has tapped 1 / 4 of its steel, dephosphorizing lime is added to the ladle at a rate of 3-6 kg / t. 钢 ; S3, Argon blowing and stirring after furnace The argon flow rate for bottom blowing agitation in the ladle is 400~800 NL / min, and the argon agitation time is ≥5min; bottom blowing agitation in the ladle uses double permeable bricks. S4, Replace the bag and remove slag The ladle is hoisted to the casting platform, the ladle sliding mechanism is connected, the slide plate is opened, and the molten steel is changed into a new ladle. When slag is seen, the slide plate is closed to ensure that all oxidizing top slag remains in the original ladle. The ladle changing time is less than 30 minutes. S5, Refined Molten steel is hoisted to the refining LF furnace, where it is heated and slag, alloys, and deoxidizers are added. Conventional process operations are then performed to obtain ultra-low phosphorus molten steel with a phosphorus content of ≤0.006wt%.