CN115612786B - SPHC steel CaO/Al 2 O 3 Accurate control method for value - Google Patents
SPHC steel CaO/Al 2 O 3 Accurate control method for value Download PDFInfo
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- CN115612786B CN115612786B CN202211211522.7A CN202211211522A CN115612786B CN 115612786 B CN115612786 B CN 115612786B CN 202211211522 A CN202211211522 A CN 202211211522A CN 115612786 B CN115612786 B CN 115612786B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/076—Use of slags or fluxes as treating agents
Abstract
The invention discloses an SPHC steel CaO/Al 2 O 3 An accurate control method of values belongs to the technical field of external refining. The invention relates to SPHC steel CaO/Al 2 O 3 According to the method for precisely controlling the value, LF refining is carried out after converter tapping, lime and composite refining slag are added in batches in the LF refining heating process, the total lime addition amount is controlled to be 8-12kg/t, and when the ladle erosion rate is less than or equal to 1.2mm/min, the total lime addition amount is controlled to be 5-6kg/t; when 1.2mm/min<The steel ladle erosion rate is less than or equal to 2.0mm/min, and the total lime addition amount is controlled to be 6-8kg/t; at ladle erosion rate>And when the lime is 2.0mm/min, the total addition amount of lime is controlled to be 8-12kg/t. The invention dynamically controls the smelting process of SPHC steel, in particular the slag forming process of LF furnace and the argon blowing flow, thereby effectively realizing the CaO/Al of the SPHC steel 2 O 3 Accurate control of the values.
Description
Technical Field
The invention belongs to the technical field of external refining, and in particular relates to an SPHC steel CaO/Al 2 O 3 A method for precisely controlling the value.
Background
SPHC steel is low-carbon low-silicon aluminum killed steel, is widely applied to manufacturing of household electrical parts, automobile structural parts, hardware machinery and the like, and is required to have good extensibility and cold workability, and in order to ensure the workability, the sulfur content and nonmetallic inclusion level in the SPHC steel are required to be strictly controlled.
LF has good functions of heating, alloy fine adjustment, deoxidization, desulfurization and nonmetallic inclusion control, is an important process link between steelmaking and continuous casting, and is widely used for carrying out external refining treatment on primary steelmaking water. Order of (A)SPHC steel produced by most of domestic iron and steel enterprises before the past needs to realize desulfurization and control of nonmetallic inclusion in the steel through an LF process. Desulfurization and control of nonmetallic inclusions in steel during LF refining are mainly achieved by controlling CaO/Al of refining slag 2 O 3 The value is realized, however, the CaO/Al of the refining slag in the current SPHC steel refining process 2 O 3 The control of the value is not accurate enough, so that unstable control of desulfurization and nonmetallic inclusion is caused, the LF smelting period is influenced, and the stability of the quality of the SPHC steel product is also influenced.
Disclosure of Invention
1. Problems to be solved
The invention aims at the existing SPHC steel CaO/Al 2 O 3 The problem of inaccurate value control is solved, and the SPHC steel CaO/Al is provided 2 O 3 A method for precisely controlling the value. The invention dynamically controls the smelting process of SPHC steel, in particular the slag forming process of LF furnace and the argon blowing flow, thereby effectively realizing the CaO/Al of the SPHC steel 2 O 3 Accurate control of the values.
2. Technical proposal
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the invention relates to SPHC steel CaO/Al 2 O 3 According to the method for precisely controlling the value, LF refining is carried out after converter tapping, lime and composite refining slag are added in batches in the LF refining heating process, the total lime addition amount is controlled to be 8-12kg/t, and when the ladle erosion rate is less than or equal to 1.2mm/min, the total lime addition amount is controlled to be 5-6kg/t; when 1.2mm/min<The steel ladle erosion rate is less than or equal to 2.0mm/min, and the total lime addition amount is controlled to be 6-8kg/t; at ladle erosion rate>And when the lime is 2.0mm/min, the total addition amount of lime is controlled to be 8-12kg/t.
According to the invention, the lime addition amount in the refining heating process is strictly controlled by matching the lime addition amount and the ladle erosion amount, so that the accurate control of the calcium-aluminum ratio of slag is facilitated, the viscosity of slag is proper, and the phenomenon that the viscosity is too high or too low in the slag forming process is avoided, and the yield of aluminum particles is influenced.
Further, 1-3kg/t lime, 5-12kg/t aluminum particles and 0.3-0.8kg/t low-carbon ferromanganese are added in the LF refining and slagging process, and argon blowing and stirring are carried out to produce white slag.
Furthermore, the LF refining slagging time (the time before white slag) is controlled to be 8-15min, aluminum particles are added in 2-4 batches in the slagging process, the total slag amount is controlled to be 18-30kg/t, and the white slag time (the holding time after white slag) is controlled to be 5-20min.
Furthermore, the argon flow Q is related to the total slag quantity Z in the LF refining slag-making process, and the two conditions are as follows: q= 1211.7-69.1×z+2.04×z 2 (L/min). By correlating the argon blowing flow with the total slag quantity, the argon blowing quantity in the refining and slagging process is controlled according to the total slag quantity, so that the problems of serious naked molten steel leakage, serious aluminum burning loss, and difficult control of the calcium-aluminum ratio caused by small slag quantity and large argon blowing quantity can be avoided, and the problems of difficult slag dissolution and full deoxidization of aluminum particles caused by large slag quantity and small argon blowing quantity can be avoided, and the control of the calcium-aluminum ratio is also avoided.
Furthermore, the temperature in the LF heating process is controlled to 1580-1610 ℃, the pressure in the LF furnace is controlled to be micro-positive pressure, and the micro-positive pressure control range is 5-230Pa, so that negative pressure in the LF furnace can be prevented, a large amount of air is sucked in, oxidation of slag and molten steel is caused, burning loss of aluminum is increased, and accurate control of the calcium-aluminum ratio is further guaranteed.
Further, the content of metal Al in the composite refining slag is 15-25%, and Al 2 O 3 15-40%, 12-30% CaO, and SiO 2 Less than or equal to 5 percent of CaCO 3 The content is 3-8%.
Furthermore, oxygen is fixed before tapping of the converter, and the slag quantity of the converter is controlled to be 2-6kg/t of steel.
Further, the converter slag-down amount was determined based on the amount of rephosphorization, and the slag-down amount= (amount of rephosphorization-phosphorus carried by alloy)/phosphorus content in slag, which was obtained by XRF fluorescence analysis.
Further, 3-6kg/t of aluminum iron is added when 1/3 of the converter is tapped, and 3-6kg/t of lime and 1-3kg/t of composite refining slag are added when 1/2 of the converter is tapped; the adding amount of the composite refining slag in the LF refining heating process is 2-4kg/t, and the argon flow is controlled to be 100-200L/min; after LF refining white slag is finished, soft argon blowing is carried out, the argon flow is controlled to be 50-100L/min, and the soft argon blowing time is 8-10 minutes. According to the invention, through the cooperation of the adding technology of each material in the converter tapping, LF refining furnace heating and refining slagging processes, the accurate control of the calcium-aluminum ratio is further ensured.
Further, the erosion rate V (mm/min) =0.04×t (min) +0.000005×t (inbound temperature in ℃), the erosion rate V (mm/min) =0.083×t (min) +0.000011×t of the new ladle, where T is inbound temperature in ℃.
In summary, compared with the prior art, the invention can obtain the following beneficial effects:
(1) The invention relates to SPHC steel CaO/Al 2 O 3 The accurate control method of the value is beneficial to realizing CaO/Al by optimally designing the LF refining process of the SPHC steel, particularly controlling the lime addition amount in the LF refining heating process according to the ladle erosion rate 2 O 3 Accurate control of the values; simultaneously, the control of the slag discharging amount of converter tapping, slag adjusting control in the tapping process, refining heating and refining slagging process and argon flow control in the refining slagging process are also assisted, thereby being beneficial to further ensuring CaO/Al 2 O 3 Accurate control of the values.
(2) The invention relates to SPHC steel CaO/Al 2 O 3 Accurate control method of value by CaO/Al 2 O 3 The precise control of the value can improve the desulfurization efficiency, shorten the LF smelting period by 10-20%, and effectively improve the control level of inclusions in steel, so that the level of B-type inclusions is reduced from 1.0-1.5 to 0.5, thereby improving the stability of the product quality.
Drawings
FIG. 1 shows the argon flow rate change during the slag formation of example 1.
Detailed Description
The invention relates to SPHC steel CaO/Al 2 O 3 A method for accurate control of values, comprising the steps of:
a. controlling the steel type of the smelting steel of the previous furnace of the ladle to be SPHC steel, controlling the slag quantity of the ladle to be 0-4kg/t steel, and controlling the slag quantity of the ladle to be 0-4kg/t steelThe lining material is high alumina brick, al 2 O 3 The content is more than or equal to 90 percent.
b. Oxygen is fixed before tapping of the converter, and the slag quantity of the converter is controlled to be 2-6kg/t of steel; specifically, the slag quantity under the converter is determined according to the rephosphorization quantity, the slag quantity= (rephosphorization quantity-phosphorus carried by alloy)/the phosphorus content in the slag, and the phosphorus content in the slag is obtained through XRF fluorescence analysis.
c. According to the difference of oxygen content of molten steel at the end point of the converter, 3-6kg/t of aluminum iron is added when tapping is performed about 1/3, and 3-6kg/t of lime and 1-3kg/t of composite refining slag are added when tapping is performed 1/2.
d. 5-12kg/t lime and 2-4kg/t composite refining slag are added in the LF refining heating process, the argon flow is controlled to be 100-200L/min, the temperature in the LF heating process is controlled to be 1580-1610 ℃, and the lime and the composite refining slag are added for 4-5 times. Specifically, when the ladle erosion rate is less than or equal to 1.2mm/min, the lime addition is controlled to be 5-6kg/t; when the steel ladle erosion rate is less than or equal to 2.0mm/min and is less than or equal to 1.2mm/min, the lime addition amount is controlled to be 6-8kg/t; when the ladle erosion rate is more than 2.0mm/min, the lime addition amount is controlled to be 8-12kg/t.
The erosion amount of the ladle lining is calculated as follows: the erosion rate V (mm/min) =0.04×t (min) +0.000005×t (inbound temperature ℃), the erosion rate V (mm/min) =0.083×t (min) +0.000011×t (inbound temperature ℃) for the new ladle.
e. Adding 1-3kg/t lime, 5-12kg/t aluminum particles and 0.3-0.8kg/t low-carbon ferromanganese in the LF refining slagging process, blowing argon and stirring to produce white slag, controlling the total slag amount to 18-30kg/t, controlling the white slag time to 5-20min, and associating the argon flow (Q) with the slag amount (Z) in the slagging process, wherein the two conditions are as follows: q= 1211.7-69.1×z+2.04×z 2 The aluminum particles are added in batches of 2-4 in the slag forming process, and the invention can control the naked leakage of molten steel and stabilize the burning loss of aluminum in the molten steel by controlling the flow rate of argon and the slag quantity.
In the invention, the pressure in the LF furnace is controlled to be micro-positive pressure, and the micro-positive pressure is controlled to be 5-230Pa, so that secondary oxidization of molten steel and maintenance of white slag in the LF refining process can be avoided, the CaO content in lime for refining is more than or equal to 85%, the Al content in aluminum iron is more than or equal to 40%, the Al content in aluminum particles is more than or equal to 98%, and the granularity is less than or equal to 5mm; the content of metal Al in the composite refining slag is 15-25%, al 2 O 3 15-40%, 12-30% CaO, and SiO 2 Less than or equal to 5 percent of CaCO 3 The content is 3-8%.
f. And (3) carrying out soft argon blowing after the white slag is finished, controlling the argon flow to be 50-100L/min, and taking a slag sample after the soft blowing is finished, wherein the soft blowing time is 8-10 minutes.
The invention is further described below in connection with specific embodiments.
Examples 1 to 7
Examples 1-7 were all carried out on a 120tLF furnace, the steel grade was SPHC steel, specifically, the steel grade was SPHC in the smelting process of the previous furnace of the ladle was controlled, 3-6kg/t aluminum iron was added when tapping about 1/3 according to the difference of the oxygen content of the molten steel at the end point of the converter, 3-6kg/t lime and 1-3kg/t composite refining slag were added when tapping 1/2, then the slag discharge amount of the converter was determined according to the molten steel back phosphorus, the addition amounts of lime, aluminum particles and composite refining slag in the heating process, the slagging process and the addition amounts of argon in the slagging process were determined according to the slag discharge amount and the ladle erosion rate, and the argon flow rate in the slagging process was controlled in batches, the technological parameters in the implementation process were controlled according to the concrete table 1, the refining slag control conditions were shown in the table 2, and the comparison of the implementation effects were shown in the table 3, wherein fig. 1 shows the argon flow rate change in the slagging process of example 1.
Comparative examples 1 to 7
The process flow of SPHC steel smelting in comparative examples 1-7 is basically the same as examples 1-7, and the difference is mainly that the process parameters and additive addition amounts of each process are different, the process parameters are specifically shown in Table 1, the control conditions of refining slag are shown in Table 2, and the implementation effect comparison is shown in Table 3.
Table 1 implementation of process control parameters
TABLE 2 refining slag control
TABLE 3 effect comparison
| Heat of furnace | Endpoint S/% | Desulfurization rate/% | Refining time/min | Class A class | Class B class |
| Example 1 | 0.002 | 93.2 | 32 | 0 | 0.5 |
| Example 2 | 0.003 | 90.5 | 28 | 0 | 0.5 |
| Example 3 | 0.002 | 94.6 | 31 | 0.5 | 0.5 |
| Example 4 | 0.003 | 91.4 | 35 | 0 | 0.5 |
| Example 5 | 0.002 | 92.5 | 34 | 0.5 | 0.5 |
| Example 6 | 0.002 | 93.1 | 36 | 0.5 | 0.5 |
| Example 7 | 0.004 | 90.7 | 31 | 0 | 0.5 |
| Comparative example 1 | 0.003 | 85.6 | 38 | 1 | 1.5 |
| Comparative example 2 | 0.004 | 83.6 | 35 | 0.5 | 1 |
| Comparative example 3 | 0.003 | 90.1 | 39 | 1 | 1.5 |
| Comparative example 4 | 0.005 | 87.5 | 41 | 1 | 1 |
| Comparative example 5 | 0.004 | 84.6 | 40 | 0.5 | 1 |
| Comparative example 6 | 0.004 | 86.2 | 37 | 0.5 | 1.5 |
| Comparative example 7 | 0.005 | 81.2 | 39 | 0.5 | 1 |
The invention obviously improves the CaO/Al content of the SPHC steel by controlling the slag discharging amount, the ladle erosion amount of the converter and lime, composite refining slag, aluminum iron and aluminum particles in the tapping, heating and slag forming processes and accurately adjusting the dynamic argon blowing flow and the pressure in the converter 2 O 3 Control accuracy of the values. With reference to tables 2 and 3, the refining slag CaO/Al of examples 1 to 7 is compared with comparative examples 1 to 7 2 O 3 The value is more accurate, and the refining slag CaO/Al 2 O 3 The fluctuation range of the value is reduced to +/-0.1 from +/-0.3, the average desulfurization rate is improved to 92.3 percent from 85.5 percent, the average refining time is shortened to about 20 percent, the class A inclusion grade is reduced to 0-0.5 grade from 0.5-1 grade, the class B inclusion grade is reduced to 0.5 grade from 1-1.5 grade, and the yield and quality are improved.
Claims (5)
1. SPHC steel CaO/Al 2 O 3 The accurate control method of the value is characterized in that: carrying out LF refining after tapping of the converter, and adding lime and composite refining slag in batches in the LF refining heating process, wherein when the steel ladle erosion rate is less than or equal to 1.2mm/min, the total addition amount of lime is controlled to be 5-6kg/t; when 1.2mm/min<The steel ladle erosion rate is less than or equal to 2.0mm/min, and the total lime addition amount is controlled to be 6-8kg/t; at ladle erosion rate>When the lime is 2.0mm/min, the total addition amount of lime is controlled to be 8-12kg/t; adding 1-3kg/t lime, 5-12kg/t aluminum particles and 0.3-0.8kg/t low-carbon ferromanganese in the LF refining slagging process, and blowing argon to stir to produce white slag;
in the LF refining slagging process, the argon flow Q is related to the total slag quantity Z, and the two conditions are satisfied: q= 1211.7-69.1×z+2.04×z 2 Q is L/min, and the total slag amount Z is kg/t; the content of metal Al in the composite refining slag is 15-25%, al 2 O 3 The content is 15-40%,CaO content is 12-30%, siO 2 Less than or equal to 5 percent of CaCO 3 The content is 3-8%; oxygen is fixed before tapping of the converter, and the slag quantity of the converter is controlled to be 2-6kg/t of steel; 3-6kg/t of aluminum iron is added when 1/3 of converter tapping is performed, and 3-6kg/t of lime and 1-3kg/t of composite refining slag are added when 1/2 of converter tapping is performed; the adding amount of the composite refining slag in the LF refining heating process is 2-4kg/t, and the argon flow is controlled to be 100-200L/min; after LF refining white slag is finished, soft argon blowing is carried out, the argon flow is controlled to be 50-100L/min, and the soft argon blowing time is 8-10 minutes.
2. The SPHC steel CaO/Al according to claim 1 2 O 3 The accurate control method of the value is characterized in that: the LF refining slagging time is controlled to be 8-15min, aluminum particles are added in 2-4 batches in the slagging process, the total slag amount is controlled to be 18-30kg/t, and the white slag time is controlled to be 5-20min.
3. An SPHC steel CaO/Al according to claim 1 or 2 2 O 3 The accurate control method of the value is characterized in that: the temperature in the LF heating process is controlled to 1580-1610 ℃, the pressure in the LF furnace is controlled to be micro-positive pressure, and the micro-positive pressure control range is 5-230Pa.
4. An SPHC steel CaO/Al according to claim 1 or 2 2 O 3 The accurate control method of the value is characterized in that: the slag quantity of the converter is determined according to the rephosphorization quantity, the slag quantity= (rephosphorization quantity-phosphorus carried by alloy)/the phosphorus content in slag, and the phosphorus content in slag is obtained through XRF fluorescence analysis.
5. An SPHC steel CaO/Al according to claim 1 or 2 2 O 3 The accurate control method of the value is characterized in that: the erosion rate v=0.04×t+0.000005×t of the continuous ladle, the erosion rate v=0.083×t+0.000011×t of the new ladle, wherein T is the entering temperature, c; t is refining time, min; v is in mm/min.
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