CN105714023B - Low-silicon aluminum killed steel refining device and method - Google Patents

Abstract

A refining device and method for low-silicon-aluminum killed steel. The refining device is composed of a lifting hydraulic cylinder, clamps, dipping pipes and bolts. Converter smelting controls the binary basicity of the final slag, the [Si] content of molten steel _at the end of blowing, and the tapping temperature. Aluminum ^deoxidation is added during the tapping process. 50~100mm. After blowing Ar at the bottom of the argon station, use the lifting hydraulic cylinder to lower the preheated immersion tube to 50-150 mm below the molten steel surface, add pre-melted slag to the inside of the immersion tube, add lime to the outside of the immersion tube, and then add Al particles to the immersion tube. And blow Ar at the bottom, after the liquid slag is fully reduced, keep blowing Ar at the bottom, and then perform soft blowing to make the slag surface move slightly without exposing the molten steel. . The invention can achieve the goal of [Si]≤0.03% in the steel, reduce the temperature drop of molten steel in the processing process, effectively remove inclusions in molten steel, improve the cleanliness of molten steel, and reduce costs.

Description

Refining device and method for low-silicon aluminum-killed steel

technical field

The invention belongs to the field of steelmaking technology, and in particular relates to a low-silicon aluminum killed steel refining device and a refining method thereof.

Background technique

In the production process of iron and steel enterprises, some steel types with low silicon content, such as 08Al, SPHC, etc., usually adopt the production process of desulfurization outside the molten iron furnace-converter smelting-LF refining-continuous casting. The biggest problem of this production process is the [ Si] is difficult to control, because the molten steel is reduced by a strong deoxidizer—aluminum, and the phenomenon of silicon reversion occurs, often causing the finished product [Si] to exceed the standard. The [Si] requirement of some low-silicon steel grades is not greater than 0.03%, and even the target is 0.01%. When [Si] in SPHC steel is greater than 0.03%, the yield strength and tensile strength of the steel will increase, and it will seriously affect the stamping formability of cold rolling and the adhesion of zinc during galvanizing. Silicon is an element that is easily removed during BOF smelting, and molten steel [Si] is only a trace amount when the BOF taps, so controlling the increase of [Si] is mainly after the BOF taps, and there are two main aspects to controlling the silicon increase: 1. Control Raw materials brought in. In terms of raw materials, low-silicon or even silicon-free ferroalloys should be used. Silicon-free deoxidizers should be used for deoxidation of molten steel. Silicon-free materials should be used for intermediate covering agents and mold powders to minimize silicon increase in raw materials. 2. Control back to silicon. Strict requirements are put forward for the slag blocking of converter tapping, and the amount of slag under ladle is controlled. In order to ensure that there is no steel left when converter is amount of silicon. At the same time, the slagging process uses a large amount of slag to dilute FeO, MnO and SiO ₂ in the slag to inhibit the reduction of silicon; usually LF is used to quickly deoxidize the white slag for desulfurization. On the premise of ensuring the metallurgical target, the refining time should be shortened as much as possible, and long-term refining is strictly prohibited. Repeated heating of molten steel, try to reduce FeO, MnO and SiO ₂ in the slag, control the stirring intensity of the bottom blowing Ar and the maximum Ar stirring time during the refining process, and violent blowing is strictly prohibited. [Al]+3(SiO ₂ )=2(Al ₂ O ₃ )+3[Si] reaction makes the reaction more likely to proceed in the direction of increasing silicon.

Chinese Patent Application No. 201110051874.6 discloses "a low-silicon-content low-carbon aluminum-killed steel smelting method". Before the blast furnace vanadium-containing molten iron enters the steelmaking process, it first undergoes vanadium extraction and desiliconization processes. The steelmaking process uses semi-steel In steelmaking, the molten steel is pre-deoxidized by adding low-silicon pre-melted composite refining slag during the process of slag blocking, tapping, deoxidation and alloying. Using buckle cover for heat preservation, using aluminum powder as a deoxidizer to quickly produce white slag under the reducing atmosphere of argon blowing and stirring, and then switching to calcium treatment and soft argon blowing, under the premise of ensuring the quality of refining, the thermodynamics and silicon return of molten steel are suppressed. Kinetic conditions, molten steel enters the continuous casting process after the soft argon blowing is completed; the semi-steel [Si] obtained during the process of vanadium extraction and desiliconization treatment of the vanadium-containing molten iron is ≤0.02%; slag blocking measures are adopted during the tapping process , the thickness of the slag layer is less than 50mm, to prevent the refining silicon return caused by a large amount of slag during tapping; the tapping time is required to be more than 5 minutes, and 3-6kg/ts of low-silicon pre-melted composite refining slag is evenly added with the steel flow at the same time as tapping, and the use of Good dynamic conditions during the tapping process, the molten steel is pre-refined in advance, the low-silicon pre-melted composite refining slag is added at 1/4 of the tapping, and the addition is completed at 3/4 of the tapping, after the tapping is completed Then add top slag 1kg/ts into the ladle; molten steel a _O ≤ 10ppm is required after tapping; Use medium-intensity Ar to stir for 3 minutes. The medium-intensity refers to: the intensity of blowing Ar is controlled to produce strong peristalsis on the liquid surface but does not expose the steel surface; at the same time, add Al powder 1kg/ts to the ladle to quickly create white slag; after the white slag is formed , reduce the intensity of Ar blowing to keep the slag liquid level wriggling, continue to add Al powder to maintain the state of white slag, keep the white slag for 8-12 minutes, and then carry out calcium treatment on molten steel, requiring [Ca]/[Al]≥0.1%, continue after calcium treatment Close the cover to perform soft blowing Ar operation, keep the liquid level slightly peristaltic, and keep the soft blowing Ar time at more than 12 minutes. However, this process makes low-silicon and low-carbon aluminum-killed steel have a qualified rate of silicon element of only 98%, and some heats [Si] still exceed the standard and must be reformed, resulting in losses and increasing production costs; this process requires a slag layer If the thickness is less than 50mm, it will inevitably lead to the phenomenon that the molten steel is not completely discharged in order to reduce the slag during the tapping of the converter, which reduces the steelmaking production efficiency; in addition, in order to reduce the temperature drop of the molten steel, it is necessary to adopt the method of buckle cover insulation at the LF furnace station , which in turn occupies the refining station and reduces the productivity of the LF station.

Chinese Patent Application No. 200610166553.X) discloses "a low-silicon-content low-carbon aluminum-killed steel smelting method", which uses molten iron as raw material for converter blowing, converter tapping, argon blowing station refining, and finally molten steel into Low-carbon, low-silicon, aluminum-killed steel can be obtained through full protection casting of the billet continuous casting machine. In the tapping process of the converter, composite slagging containing pre-melted refining slag is added to the molten steel after deoxidation and alloying treatment. The material is prefabricated to slag, and the basicity of the slag is controlled to reach 6.0 to 8.0; the refinement of the argon blowing station includes the following steps in the argon blowing station: (1) Deep deoxidation: the molten steel after the converter is tapped is fed to the Al line Carry out deoxidation, and at the end of the deoxidation period, control the free oxygen content in molten steel between 2 and 5ppm, and [Al]s between 400 and 600ppm; (2) Slagging and refining: add fluorite, aluminum particles and calcium carbide for slag adjustment At the same time, carry out strong bottom argon blowing and stirring, and control the (FeO+MnO) in the slag to not exceed 2% and the (Al ₂ O ₃ ) content to be between 20% and 30% at the end of slagging; (3) Soft blowing refining (4) Calcium treatment: Add silicon-calcium cored wire through the wire feeder, and control the residual [Ca] _t in molten steel to 30-40ppm after calcium treatment. However, the above process method does not mention the control level of [Si] in steel, and during calcium treatment, silicon-calcium cored wire is added through the wire feeder, so it can be seen that the requirements for [Si] in steel are not very strict ;In the above process, slagging, soft blowing refining and calcium treatment need to be carried out in the argon blowing station, which will cause a very large temperature drop of molten steel, requiring the converter to have a high temperature when tapping, which is very harmful to the converter lining big.

Contents of the invention

The present invention aims at the deficiencies of the prior art, and provides a method capable of quickly reducing and alloying molten steel after tapping out of the converter, suppressing the return of molten steel to silicon, removing inclusions in the steel, and reducing the temperature drop of molten steel. A silicon-aluminum killed steel refining device and method.

For this reason, the solution that the present invention takes is:

A low-silicon-aluminum killed steel refining device is characterized in that it consists of a lifting hydraulic cylinder, clamps, immersion pipes and bolts; a clamp is fixed at the front end of the cylinder rod of the lifting hydraulic cylinder, and the front parts of the two clamp arms of the clamp are equipped The arc is provided with a connecting plate at the front end of the arc, and the immersion tube with a turning edge at the upper end is fixed in the arc of the clamp by bolts.

A method for refining low-silicon aluminum-killed steel, characterized in that the specific method and steps are:

(1) Converter is used to smelt molten steel, the binary basicity of the final slag of the converter is controlled at 3-4, the molten steel [Si] at the end of blowing is ≤0.01%, the tapping temperature of the converter is 1660-1680°C, and the temperature is 0.5-1.5kg during tapping Al is added per ton of steel for deoxidation and alloying. The target requirement is that the molten steel a _O ≤ 20×10 ^-6 . The slag blocking operation is adopted during the tapping process, and the thickness of the slag layer is controlled at 50-100mm.

(2) After the converter is tapped, enter the argon blowing station, blow Ar from the bottom of the ladle breathable brick, blow off the slag on the molten steel, and place the immersion tube of the refining device directly above the place where the ladle slag is blown out through the lifting hydraulic cylinder .

(3) Use the lifting hydraulic cylinder to lower the immersion tube that has been preheated to 950-1050 ℃ before use to a depth of 50-150mm below the liquid steel surface, and add pre-melted slag inside the immersion tube to form liquid slag with good fluidity. The amount of addition is 0.4-0.8kg/ton of steel; and lime is added to the steel slag outside the immersion tube to make the alkalinity of the outer steel slag reach 7.3-8.0. This kind of high-alkalinity steel slag has a high melting point and poor fluidity. 4[Al]+3(Si0 ₂ )=3[Si]+2(A1 ₂ O ₃ ), so as to achieve the purpose of reducing silicon back from refining and improve the [Si] qualified rate of low-silicon aluminum-killed steel. Then, 0.2-0.45kg/ton of Al grains are added into the immersion tube to carry out steel slag reduction and molten steel alloying, while maintaining bottom-blowing Ar with a flow rate of 20-40Nm ³ /h.

(4) After the liquid slag is fully reduced, keep the bottom blowing Ar for 5-8 minutes, then reduce the argon flow rate to 4-8Nm ³ /h for soft blowing, so that the slag surface can move slightly without exposing the molten steel, and keep it for 3-7 minutes. From the immersion tube, it goes directly to the continuous casting process for casting. The intermediate covering agent and mold powder are made of silicon-free materials to reduce the silicon increase of molten steel caused by raw materials.

The main components of the pre-melted slag are: CaO: 40-45%, Al ₂ O ₃ : 38-42%, SiO ₂ : 5-9%, MgO: 4-7%, and others are unavoidable impurities.

The CaO content in the lime is more than or equal to 90%.

Compared with prior art, advantage of the present invention is as follows:

1. The present invention can fully achieve the target of [Si]≤0.03% in steel.

2. The present invention can effectively reduce the temperature drop of molten steel during the treatment process, and compared with conventional argon blowing and stirring, the temperature loss can be reduced by 50%.

3. The present invention can effectively remove inclusions in molten steel, make inclusions fully float and be absorbed by steel slag, improve the cleanliness of molten steel, and the amount of pre-melted slag added is only 25% of conventional operation, thereby reducing costs.

4. The refining device of the present invention is simple in structure, easy to operate, low in investment, and does not affect the normal operation of other equipment.

Description of drawings

Fig. 1 is a schematic diagram of the working state of a low-silicon aluminum-killed steel refining device;

Fig. 2 is a top view of a low silicon aluminum killed steel refining device.

In the figure: lifting hydraulic cylinder 1, clamp 2, immersion pipe 3, pre-slag 4, bolt 5, lime 6, molten steel 7, ladle 8, ventilation brick 9.

detailed description

As can be seen from the accompanying drawings, the low-silicon-aluminum killed steel refining device of the present invention is composed of a lifting hydraulic cylinder 1, clamps 2, dipping tube 3, pre-melted slag 4 and bolts 5. The front end of the cylinder rod of the lifting hydraulic cylinder 1 is fixed with a clamp 2. The front parts of the two clamp arms of the clamp 2 have an arc at one end, and a connecting plate protrudes from the front end of the arc. There are bolt holes on the connecting plate. The upper end of shaped immersion tube 3 has a turning edge, and immersion tube 3 is fixed in the circular arc of clamp 2 front parts by bolt 5 .

The concrete steps of the low-silicon aluminum killed steel refining method of the present invention are:

1. The molten steel is smelted in a converter, the binary basicity of the final slag of the converter is controlled at 3-4, the molten steel [Si] at the end of blowing is ≤0.01%, the tapping temperature of the converter is 1660-1680°C, and the temperature is 0.5-1.5kg/ Al is added per ton of steel for deoxidation and alloying. The target requirement is that the molten steel a _O ≤ 20×10 ^-6 . The slag blocking operation is adopted during the tapping process, and the thickness of the slag layer is controlled at 50-100mm.

2. Enter the argon blowing station after the converter is tapped, blow Ar from the bottom of the ladle 8 breathable brick 9, blow off the slag on the molten steel 7, and place the immersion tube 3 of the refining device on the ladle 8 through the lifting hydraulic cylinder 1 to blow the slag. directly above the opening.

3. Use the lifting hydraulic cylinder 1 to lower the immersion tube 3 that has been preheated to 950-1050°C before use to a depth of 50-150 mm below the liquid steel surface, and add pre-melted slag 4 to the inside of the immersion tube 3 to form a liquid with good fluidity. The amount of liquid slag added is 0.4-0.8kg/ton of steel; and lime 5 is added to the steel slag outside the immersion tube 3 to make the alkalinity of the outer steel slag reach 7.3-8.0. This kind of high-alkalinity steel slag has a high melting point and poor fluidity. 4[Al]+3(Si0 ₂ )=3[Si]+2(A1 ₂ O ₃ ) will not occur in this area, so as to achieve the purpose of reducing silicon back from refining and improve the [Si] pass rate of low-silicon aluminum killed steel . Then, 0.2-0.45kg/ton of Al particles are added into the immersion tube 3 to carry out steel slag reduction and alloying of molten steel 7, while maintaining bottom blowing Ar with a flow rate of 20-40Nm ³ /h.

4. After the liquid slag is fully reduced, keep the bottom blowing Ar for 5-8 minutes, then reduce the argon flow rate to 4-8Nm ³ /h for soft blowing, so that the slag surface can move slightly without exposing the molten steel 7, and keep it for 3-7 minutes. From the immersion pipe 3, directly to the continuous casting process for casting, the intermediate covering agent and the mold powder are made of silicon-free materials, so as to reduce the increase of silicon in molten steel caused by raw materials.

Wherein, the main components of the pre-slag 4 are: CaO: 40-45%, Al ₂ O ₃ : 38-42%, SiO ₂ : 5-9%, MgO: 4-7%, others are unavoidable of impurities. The CaO content in the lime 6 is more than or equal to 90%.

The present invention will be further described below in conjunction with embodiment.

The embodiment uses a 100-ton converter, the preheating temperature of the immersion tube 3 before use is 1000°C, and the smelted steel is low-silicon aluminum-killed steel. A total of 4 groups were carried out, of which 1 group was a comparative example, which was carried out at the argon blowing station Instead of using this refining device, perform Ar blowing operation, add pre-melted slag 4 and metal aluminum to reduce the slag, the slag composition on the entire molten steel surface is uniform, and then cast on the machine.

The process parameters, control results and the composition of the pre-melted slag are shown in Table 1 and Table 2, respectively.

Table 1: embodiment and comparative example process parameter and control result

Table 2: Composition of pre-melted slag

It can be seen from Table 1 that using the refining device in the argon blowing station for gas blowing and refining significantly reduces the [Si] content of the finished product to ≤0.02%, and at the same time the oxygen content of the finished product is also greatly reduced, all less than 0.0020%. Improved steel quality. The temperature drop of molten steel is about 40% of the original process, which provides more space for the operation rhythm of molten steel smelting, reduces the temperature loss of molten steel, and is conducive to reducing production costs. It can be seen from Table 2 that the amount of pre-melted slag added is significantly reduced compared with the comparative example, which further reduces the production cost.

Claims (3)

1. a kind of low silicon aluminium killed steel method of refining, the device that the method for refining is used by lifting hydraulic cylinder, clamp, dipping tube and Bolt is constituted；Lifting hydraulic cylinder cylinder rod is fixedly arranged at the front end with a clamp, and two tong arms front portion of clamp carries circular arc, and circular arc front end is set There is connecting plate, upper end carries the dipping tube turned edge and is bolted in clamp circular arc, it is characterised in that specific method and step Suddenly it is：

(1) converter smelting molten steel is used, the control of converter finishing slag dual alkalinity is 3~4, blowing end point molten steel [Si]≤0.01%, 1660~1680 DEG C of Tapping Temperature of Bof, adds aluminium by 0.5~1.5kg/ tons of steel in tapping process and carries out deoxidation, alloying, mesh Mark requires molten steel a_O≤20×10^-6, take pushing off the slag to operate in tapping process, thickness of slag layer is controlled in 50~100mm；

(2) Argon station is entered after converter tapping terminates,, will after the slag above molten steel is blown open from air brick of steel ladle bottom blowing Ar The dipping tube of purifier is placed on the surface that ladle slag blows place open by lifting hydraulic cylinder；

(3) will be dropped to using the dipping tube for being preceding preheated to 950~1050 DEG C 50 under molten steel face using lifting hydraulic cylinder~ 150mm depth, adds pre-melted slag inside dipping tube, and addition is 0.4~0.8kg/ tons of steel；And to steel outside dipping tube Lime is added in slag, outside slag basicity is reached 7.3~8.0；Then 0.20~0.45kg/ of Al grains is added inside dipping tube Ton steel, carries out slag reduction and molten steel alloying, while keeping bottom blowing Ar, bottom blowing Ar flows are 20~40Nm³/h；

(4) after melt cinder is fully reduced, bottom blowing Ar5~8min is kept, argon flow amount is reduced thereafter to 4~8Nm³/ h carries out soft blow, makes Top of the slag fine motion keeps 3~7min without making molten steel exposed, rises dipping tube, is directly cast to continuous casting working procedure.

2. low silicon aluminium killed steel method of refining according to claim 1, it is characterised in that the key component of the pre-melted slag For：CaO:40~45%, Al₂O₃:38~42%, SiO₂:5~9%, MgO:4~7%, other is inevitable impurity.

3. low silicon aluminium killed steel method of refining according to claim 1, it is characterised in that CaO content in the lime >= 90%.