A method for improving the strength of steel bars

Abstract

A method for improving the strength of steel bars belongs to the technical field of electric furnace steelmaking. The steel bar reinforcer of the present invention includes the following components by weight percentage: active lime: 5%-10%, bauxite: 15%-20%, boron ore: 20%-40%, phosphorus: 20%-30%, and the rest is Fe. Its adding method includes the following steps: steel is tapped after the electric furnace smelting is completed, and the first batch of steel bar reinforcers are added during the steel tapping process; slag is adjusted during the LF smelting process, and the second batch of steel bar reinforcers are added; and casting is performed after the LF smelting is completed. Adding the steel bar reinforcer of the present invention to steel bars can effectively improve the strength of the steel bars and improve the heating efficiency of the LF furnace; at the same time, the amount of alloy added is reduced, thereby reducing production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of electric furnace steelmaking, and more specifically, relates to a steel reinforcing agent and a method for adding the same. Background Art

[0002] Hot-rolled ribbed steel bars are mainly used in concrete building structures, mainly as the skeleton of reinforced concrete building components, and play an important role in enhancing the strength and stability of building structures. With the rapid development of my country's economic construction, the performance requirements of steel bars in industries such as construction and transportation have become increasingly stringent. In 2018, the country formulated a new version of the GB-T 1499.2-2018 standard. The new standard canceled 335MPa grade steel bars and added 600MPa grade steel bars. At the same time, it also put forward higher requirements for the production process, chemical composition, metallographic structure and mechanical properties of hot-rolled ribbed steel bars.

[0003] At present, the strength of hot-rolled ribbed steel bars is mainly improved by adding microalloying elements Nb, V or Ti and phase transformation strengthening (forced cooling through water). With the implementation of the new standard, the method of increasing the strength of steel bars by forced cooling through water has been banned; and when using microalloying elements Nb, V or Ti to improve the strength of steel bars, on the one hand, the high price of alloys such as microalloying elements Nb, V or Ti will increase the production cost, and on the other hand, microalloying elements Nb, V or Ti are easy to cause cracks in the casting, which also limits the further increase of their use. In order to reduce the addition of microalloying elements, lime, bauxite, etc. are often used in the prior art to temper the molten iron.

[0004] For example, patent CN107746907A discloses a method for producing clean steel. The invention provides a method for producing clean steel, comprising the following steps: dephosphorization and desulfurization in a vanadium-extracting converter, dephosphorization and decarbonization in a steelmaking converter, deep dephosphorization in an LF refining furnace, dephosphorization and slagging in a desulfurization station, LF furnace refining, and RH furnace refining. The dephosphorization effect and desulfurization rate are improved by dephosphorization in steps, wherein, in the dephosphorization and decarbonization process of the steelmaking converter, active lime, high-magnesium lime, and slag-making agent are added to the molten iron obtained in step b for dephosphorization; in the deep dephosphorization process of the LF refining furnace, the molten steel after steelmaking in step c is transferred to the LF furnace, active lime and bauxite are added, and after heating for 5 to 15 minutes, active lime and bauxite are added again, and heated to the target temperature of each steel grade, and steel is tapped; in the LF furnace refining process, deoxidizing materials are added to deoxidize the molten steel, desulfurizing agents are added to desulfurize the molten steel, and then 2 to 5 kg / t of active lime and 0.1 to 2 kg / t of slag-adjusting agent are added to alloy the molten steel.

[0005] Patent CN111996327A discloses a dephosphorizing agent for hot metal pretreatment using industrial waste as raw materials, which belongs to the technical field of hot metal pretreatment. The dephosphorizing agent of the present invention is composed of 15%-30% ladle refining slag, 10%-25% lime, 10%-20% red mud, 25%-54% iron oxide, and 2%-5% borax by weight. 2 O 3 It can effectively control the liquid phase ratio in the slag to avoid the liquid phase ratio in the slag being too low to affect the dephosphorization capacity. 2 O and B 2 O 3 The ratio of 2CaO·SiO to 2CaO·SiO can effectively reduce the melting point of the dephosphorizing agent, making the slag formation speed of the dephosphorization process faster and improving the dephosphorization efficiency. 2 ·3CaO·P 2 O 5 The above patents use lime, bauxite and borax to temper molten iron, but they do not significantly improve the strength of steel bars. Summary of the invention

[0006] 1. Problem to be solved

[0007] In view of the problem of low strength of steel bars with low content of microalloy elements in the prior art, the present invention provides a steel bar reinforcing agent and a method for adding the same. The steel bar reinforcing agent of the present invention is added to steel bars to effectively improve the strength of the steel bars.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] The invention discloses a reinforcing steel reinforcing agent and a method for adding the reinforcing steel reinforcing agent. The reinforcing steel reinforcing agent comprises the following components in weight percentage: active lime: 5%-10%, bauxite: 15%-20%, boron ore: 20%-40%, phosphorus: 20%-30%, and the rest is Fe. The weight percentage content of CaO in the active lime is ≥85%, SiO 2 The weight percentage content is ≤3%. Bauxite and boron ore are used to adjust the melting point and viscosity of the slag. In addition, by controlling the addition of bauxite, B 2 O 3 After reduction, the physical properties of the slag undergo significant changes.

[0011] The present invention uses active lime as the main component of the reinforcing agent, and bauxite and boron ore are used to adjust the melting point and viscosity of the slag. In addition, by controlling the addition of bauxite, B 2 O 3After reduction, the physical properties of the slag change greatly. The advantages of active lime are: first, compared with ordinary lime, the reaction efficiency of active lime is higher and the slag forming speed is faster; second, it can adjust the melting point and strength of the reinforcing agent. 2 O 3 The weight percentage content is ≥80%, which is mainly used to adjust the viscosity of slag and promote slag formation. 2 O 3 The weight percentage of boron is ≥35%, and the weight percentage of MgO is ≥5%. 2 O 3 It can not only promote the dissolution of lime and accelerate slag formation, but also some B will enter the molten steel to increase the strength of the steel bar. 2 O 3 The content cannot be too high, which may easily lead to too thin slag and affect the submerged arc effect of LF furnace; the phosphorus content is 20%-30%, phosphorus mainly enters molten steel and is dissolved in steel to play a strengthening role, but the phosphorus content is not easy to be too high. The reason is that P is an element that is easy to segregate and is easy to segregate along the dendrites during the solidification process, reducing the grain boundary bonding strength. Therefore, the present invention further uses boron to reduce the negative effects of phosphorus. The radius of B atoms is small and the diffusion speed is fast. They can occupy the grain boundaries first, reducing the segregation amount of P and easily causing grain boundary embrittlement, thereby further improving the strengthening of steel bars.

[0012] The particle size of the steel reinforcement agent is 5cm-40cm. If the size is too small, it will be easily sucked away under negative pressure. If the size is too large, it will be difficult to melt, affecting the reinforcement effect.

[0013] A method for adding a steel reinforcement agent comprises the following desulfurization steps:

[0014] Step S1, steel tapping: After the electric furnace smelting is completed, the steel is tapped. During the steel tapping process, the first batch of steel reinforcement agent is added so that P in the reinforcement agent enters the molten steel to play a role of solid solution strengthening.

[0015] Step S2, LF smelting: During the LF smelting process, slag is adjusted and a second batch of steel reinforcement agent is added; during the LF smelting process, B 2 O 3 It is reduced to elemental B, which enters the molten steel. On the one hand, it combines with N to improve the strength during the solidification process, and on the other hand, it can be dissolved in the steel to improve the strength of the steel. Slag adjustment can be carried out using lime and pre-melted refined slag. The components of the pre-melted slag include: CaO: 15%-20%, Al 2 O 3 :50%-65%;SiO 2 : 5%-10%, and the rest is Fe.

[0016] Step S3, casting: casting is performed after LF smelting is completed.

[0017] Furthermore, the slag basicity (CaO / SiO 2 ) is 1.5-3.0, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is controlled to 1.4-2.6, and the FeO content in the slag is ≤3%. The present invention adds boron ore and controls the basicity (CaO / SiO 2 ) is 1.5-3.0, the calcium-aluminum ratio is 1.4-2.6, ensuring B 2 O 3 The reduction of P and B makes it enter the molten steel in the form of elemental B to achieve the strengthening effect. Excessive basicity and calcium-aluminum ratio will cause the slag viscosity to be too high and the liquid phase ratio to be too low, which limits the 2 O 3 If the value is too small, the slag will be too thin, which will increase the erosion of the ladle, be unfavorable for the foaming of the slag, and increase the power consumption.

[0018] Furthermore, the amount of the steel reinforcement agent added during the smelting process is controlled to be 1-2kg / t, the amount added during the steel tapping process is controlled to be 80%-90% of the total amount, and the amount added during the LF smelting process is controlled to be 10%-20% of the total amount, wherein a larger amount of the steel reinforcement agent is added during the steel tapping process for coarse adjustment, and a smaller amount of the steel reinforcement agent is added during the LF smelting process for fine adjustment.

[0019] Furthermore, during the LF furnace smelting process, the total amount of slag is controlled to be 1%-3% of the amount of molten steel.

[0020] The steel reinforcement agent of the invention is used in steel bars, the components of which include, by mass fraction, C: 0.23%-0.24%, Si: 0.35%-0.38%, Mn: 1.12%-1.41%, and Nb: 0.26%-0.27%. The steel reinforcement agent can be added to increase the yield strength of the steel bars by 15-30 MPa.

[0021] 3. Beneficial effects

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) A reinforcing steel bar reinforcing agent of the present invention is added to the steel bar to reduce B by controlling the basicity and calcium-aluminum ratio of the slag during the LF furnace smelting process. 2 O 3 , so that it enters the molten steel in the form of single substance B and works together with P to improve the strength of the steel bar;

[0024] (2) A steel reinforcement agent of the present invention can promote lime dissolution by adding bauxite and boron ore, reduce the use of pre-melted refined slag or replace the melted refined slag, and improve the heating efficiency of the LF furnace;

[0025] (3) The present invention can reduce the amount of alloys such as silicon and manganese added to the steel bars by adding a steel reinforcing agent, thereby reducing production costs. DETAILED DESCRIPTION

[0026] The following is an example of an exemplary embodiment of the present invention. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The more detailed description of the embodiments of the present invention below is not intended to limit the scope of the present invention as required, but is merely for illustration and does not limit the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention, and is sufficient to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0027] The present invention is further described below in conjunction with an embodiment, which is carried out on a 150t electric furnace → LF → continuous casting process.

[0028] Table 1 shows the steel reinforcement component parameters, Table 2 shows the slag adjustment process parameters during LF smelting, and Table 3 shows the LF power consumption and steel performance parameters.

[0029] Table 1 is the parameters of the steel reinforcement component

[0030]

[0031] Table 2 Slag adjustment process parameters during LF smelting

[0032]

[0033] Table 3 LF power consumption and steel bar performance parameters

[0034]

[0035] Comparative Example 1

[0036] In Comparative Example 1, no steel reinforcement agent is added, and the method mainly comprises the following steps:

[0037] Step S1, LF smelting: During the LF smelting process, lime and pre-melted refined slag are added to adjust the slag to control the slag basicity (CaO / SiO 2 ) is 4.3, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is 1.5, and the FeO content in the slag is 3.2%;

[0038] Step S2, casting: casting is performed after LF smelting is completed.

[0039] Comparative Example 2

[0040] In Comparative Example 2, no steel reinforcement agent is added, and the method mainly comprises the following steps:

[0041] Step S1, LF smelting: During the LF smelting process, lime and pre-melted refined slag are added to adjust the slag to control the slag basicity (CaO / SiO 2 ) is 2.2, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is 1.7, and the FeO content in the slag is 2.0%;

[0042] Step S2, casting: casting is performed after LF smelting is completed.

[0043] Example 1

[0044] In this embodiment, the steel reinforcement agent includes the following components by weight percentage: active lime: 8%, bauxite: 15%, boron ore: 35%, phosphorus: 23%, and the rest is Fe. 2 O 3 The content of CaO in active lime is ≥85%, and the content of SiO is 8%. 2 The content of SiO is ≤3%. 2 The content should be controlled within a low range, otherwise dicalcium silicate will be produced, and dicalcium silicate will wrap up the lime and hinder the dissolution of lime. 2 O 3 The content of is 83%. In this embodiment, the size of the steel reinforcement agent is 28 cm.

[0045] A method for adding a steel reinforcement agent comprises the following steps:

[0046] Step S1, steel tapping: After the electric furnace smelting is completed, the steel is tapped. During the steel tapping process, the first batch of steel reinforcement agent is added, and the added amount is controlled to be 1.2 kg / t, and is added together with lime when the steel is 1 / 2 tapped;

[0047] Step S2, LF smelting: During the LF smelting process, pre-melted refined slag is added to adjust the slag to control the slag basicity (CaO / SiO 2 ) is 2.3, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is 1.8, the FeO content in the slag is 2.1%, and the second batch of steel reinforcement is added, and the addition amount is controlled to be 0.2kg / t;

[0048] Step S3, casting: casting is performed after LF smelting is completed.

[0049] Example 2

[0050] In this embodiment, the steel reinforcement agent includes the following components by weight percentage: active lime: 10%, bauxite: 17%, boron ore: 40%, phosphorus: 20%, and the rest is Fe. 2 O 3 The content of CaO in active lime is ≥87%, and the content of SiO is 6%. 2 The content of Al in bauxite is ≤3%. 2 O 3 The content of is 86%. In this embodiment, the size of the steel reinforcement agent is 8 cm.

[0051] A method for adding a steel reinforcement agent comprises the following steps:

[0052] Step S1, steel tapping: After the electric furnace smelting is completed, the steel is tapped. During the steel tapping process, the first batch of steel reinforcement agent is added, and the added amount is controlled to be 1.7 kg / t, and is added together with lime when the steel is 1 / 2 tapped;

[0053] Step S2, LF smelting: During the LF smelting process, lime is added to adjust the slag to control the slag basicity (CaO / SiO 2 ) is 1.5-3.0, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is controlled to be 1.4-2.6, and the FeO content in the slag is ≤3%. Specifically, in this embodiment, the slag basicity (CaO / SiO 2 ) is 2.0, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is 1.9, the FeO content in the slag is 1.5%, and the second batch of steel reinforcement is added, and the addition amount is controlled to be 0.2kg / t;

[0054] Step S3, casting: casting is performed after LF smelting is completed.

[0055] Examples 1 and 2 are reinforcement without changing the steel bar composition. Compared with the comparative example, the main advantage of the examples is that the yield strength of the steel bar can be increased by an average of 21 MPa, while the power consumption of LF is significantly reduced. The power consumption of LF furnace is reduced by an average of 5.05 kwh / t, and the average power consumption reduction rate is 13.6%.

[0056] Example 3

[0057] In this embodiment, the steel reinforcement agent includes the following components by weight percentage: active lime: 7%, bauxite: 20%, boron ore: 23%, phosphorus: 28%, and the rest is Fe. 2 O 3 The content of CaO in active lime is ≥85%, and the content of SiO is 7%. 2 The content of Al in bauxite is ≤3%.2 O 3 The content of is 85%. In this embodiment, the size of the steel reinforcement agent is 40 cm.

[0058] A method for adding a steel reinforcement agent comprises the following steps:

[0059] Step S1, steel tapping: After the electric furnace smelting is completed, the steel is tapped. During the steel tapping process, the first batch of steel reinforcement agent is added, and the added amount is controlled to be 0.9 kg / t, and is added together with lime when 1 / 2 of the steel is tapped;

[0060] Step S2, LF smelting: During the LF smelting process, lime or pre-melted refined slag is added to adjust the slag to control the slag basicity (CaO / SiO 2 ) is 1.5-3.0, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is controlled to be 1.4-2.6, and the FeO content in the slag is ≤3%. Specifically, in this embodiment, the slag basicity (CaO / SiO 2 ) is 1.8, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is 2.3, the FeO content in the slag is 1.6%, and the second batch of steel reinforcement is added, and the addition amount is controlled to be 0.1kg / t;

[0061] Step S3, casting: casting is performed after LF smelting is completed.

[0062] Example 4

[0063] In this embodiment, the steel reinforcement agent includes the following components by weight percentage: active lime: 5%, bauxite: 18%, boron ore: 28%, phosphorus: 25%, and the rest is Fe. 2 O 3 The content of CaO in active lime is ≥85%, and the content of SiO is 5%. 2 The content of Al in bauxite is ≤3%. 2 O 3 The content of is 85%. In this embodiment, the size of the steel reinforcement agent is 17 cm.

[0064] A method for adding a steel reinforcement agent comprises the following steps:

[0065] Step S1, steel tapping: After the electric furnace smelting is completed, the steel is tapped. During the steel tapping process, the first batch of steel reinforcement agent is added, and the added amount is controlled to be 1.1 kg / t, and is added together with lime when the steel is 1 / 2 tapped;

[0066] Step S2, LF smelting: During the LF smelting process, lime is added to adjust the slag to control the slag basicity (CaO / SiO 2) is 1.5-3.0, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is controlled to be 1.4-2.6, and the FeO content in the slag is ≤3%. Specifically, in this embodiment, the slag basicity (CaO / SiO 2 ) is 2.8, the calcium-aluminum ratio (CaO / Al 2 O 3 ) is 1.5, the FeO content in the slag is 1.1%, and the second batch of steel reinforcement is added, and the addition amount is controlled to be 0.2kg / t;

[0067] Step S3, casting: casting is performed after LF smelting is completed.

[0068] Embodiments 3 and 4 are for reducing the Mn content in the steel bars for reinforcement. Compared with the comparative example, the main advantage of the embodiments is that the Mn content in the steel bars can be reduced by an average of 0.245% while ensuring that the yield strength of the steel bars is basically the same, which significantly reduces the amount of manganese alloy added and significantly reduces the power consumption of LF. The power consumption of the LF furnace is reduced by an average of 4.75 kwh / t, and the average power consumption reduction rate is 12.8%, which reduces the cost by more than 20 yuan / t of steel in total.

[0069] More specifically, although exemplary embodiments of the present invention have been described herein, the present invention is not limited to these embodiments, but includes any and all embodiments that are modified, omitted, combined (e.g., between the various embodiments), adapted and / or replaced as may be recognized by those skilled in the art based on the foregoing detailed description. The limitations in the claims may be interpreted broadly based on the language used in the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of the application, which examples should be considered non-exclusive. For example, in the present invention, the term "preferably" is not exclusive, where it means "preferably, but not limited to". Any steps listed in any method or process claim may be performed in any order and are not limited to the order presented in the claim. Therefore, the scope of the present invention should be determined solely by the appended claims and their legal equivalents, rather than by the description and examples given above.

Claims

1. A method for improving the strength of steel bars, characterized in that: The following steps are involved: Step S1, steel tapping: steel tapping after electric furnace smelting is completed, and the first batch of steel reinforcement agent is added during the steel tapping process; Step S2, LF smelting: slag adjustment during LF smelting, and adding a second batch of steel reinforcement agent; Step S3, casting: casting is performed after LF smelting is completed; The steel reinforcement agent is composed of active lime: 5%-10%, bauxite: 15%-20%, boron ore: 20%-40%, phosphorus: 20%-30%, and the rest is Fe; The weight percentage of B2O3 in the boron ore is ≥35%, and the weight percentage of MgO is ≥5%; During the LF furnace smelting process, the slag basicity CaO / SiO2 is controlled to be 1.5-3.0, the calcium-aluminum ratio CaO / Al2O3 is controlled to be 1.4-2.6, and the FeO content in the slag is ≤3%.

2. The method according to claim 1, characterized in that: The weight percentage of CaO in the active lime is ≥85%, and the weight percentage of SiO2 is ≤3%.

3. The method according to claim 2, characterized in that The weight percentage of Al2O3 in the bauxite is ≥80%.

4. The method according to claim 3, characterized in that: The particle size of the steel reinforcement agent is 5cm-40cm.

5. The method according to claim 4, characterized in that The total amount of steel reinforcement agent added is controlled to be 1-2kg / t steel.

6. The method according to claim 5, characterized in that In step S1, the amount of the steel reinforcing agent added during the steel tapping process is 80%-90% of the total amount, and in step S2, the amount of the steel reinforcing agent added during the LF smelting process is 10%-20% of the total amount.

7. The method according to claim 6, characterized in that During the LF furnace smelting process, the total amount of slag is controlled to be 1%-3% of the molten steel.

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