High-temperature hot delivery control method for continuous casting square billet

Abstract

The invention discloses a high-temperature hot delivery control method for a continuous casting square billet, relates to a steelmaking continuous casting technology, and provides the scheme aiming at the problem that in the prior art, the hot delivery crack defect of the casting billet is easily generated. Comprising the following steps of increasing the pulling speed, optimizing the secondary cooling strength of a casting blank, improving continuous casting covering slag, improving a blank moving mode and increasing the casting blank charging speed, wherein a blank moving trolley and a hot conveying roller bed motor are accelerated. The method has the advantages that the charging temperature of the continuous casting square billet hot delivery steel billet is increased to be larger than or equal to 850 DEG C through technical measures such as production process adjustment of the continuous casting small square billet, pulling speed increase, secondary cooling strength optimization, heat preservation of the conveying roller way, hot delivery assembly square billet optimization and speed increase matching of the conveying roller way. And the heating temperature of the steel billet in the steel rolling heating furnace is reduced, so that the coal gas consumption is reduced, and the energy is saved. The defect of casting blank red-feeding cracks can be effectively overcome, and gas consumption of a steel rolling heating furnace is reduced.

Description

Technical Field

[0001] The invention relates to steelmaking continuous casting technology, and in particular to a high-temperature heat delivery control method for continuous casting square billets. Background Art

[0002] The hot delivery and hot charging technology of ingots refers to a technology in which ingots produced during steelmaking are directly delivered to the steel rolling heating furnace through hot delivery rollers.

[0003] The existing open patent technology CN110102729A discloses a rapid hot delivery device and hot delivery method for continuous casting high-alloy die steel round billets. In this invention method, the heating furnace temperature requirement reaches ≥550℃. The disadvantage is that the continuous casting billet has not been worked on from the aspects of production process and heat preservation during the conveying process. At the same time, the hot delivery temperature requirements for the production steel type are not high, and the hot delivery temperature is low. It only needs to reach ≥550℃ to meet the production needs. The coal gas consumption of the steel rolling heating furnace is large, and the billet burn loss is large. In the actual production process, the hot delivery and hot charging temperature of the processed material and high-strength rebar is ≥550℃. This temperature is between the phase change temperature A1-A3, which is easy to produce red delivery crack defects of the cast billet, affecting the quality of the rolled material. It belongs to the third category of hot delivery and hot charging technology. This technology has obvious defects in energy consumption control and quality control. Summary of the invention

[0004] The object of the present invention is to provide a high-temperature hot delivery control method for continuous casting billets to solve the problems existing in the above-mentioned prior art.

[0005] The method for controlling high temperature hot delivery of continuous casting billets described in the present invention comprises the following process:

[0006] Increase the casting speed: maintain the continuous casting billet casting superheat within 10-25℃, and set the casting speed ≥4.2m / min;

[0007] Optimize the secondary cooling strength of the ingot: the surface temperature of the ingot at the straightening position is controlled above 980°C, and the cooling strength is 1.76L / kg;

[0008] Improve continuous casting protection slag: select protection slag with physical and chemical indicators: melting point 1035℃, melting speed 34s / 1350℃, viscosity 0.183Pa / s, and basicity 0.93

[0009] Improved billet transfer method: Billet transfer carts are used in groups of 3. After a billet from any flow is in place, it will wait until the billets from the next two flows are in place before it can be transferred.

[0010] Increase the speed of billet entering the furnace: speed up the billet transfer car and hot delivery roller motor.

[0011] The method for controlling high-temperature hot delivery of continuous casting billets described in the present invention has the advantages that, through the production process adjustment of continuous casting billets, the pulling speed is increased, the secondary cooling strength is optimized, the heat preservation of the conveying roller, the optimization of hot delivery of assembled billets, the speed increase and matching of the conveying roller, and other technical measures are implemented to increase the charging temperature of the hot delivery billets of continuous casting billets to ≥850°C. The heating temperature of the billets in the steel rolling heating furnace is reduced, thereby reducing gas consumption and saving energy, which belongs to the second category of hot delivery and hot charging technology. It can effectively solve the crack defects of hot delivery of casting billets and reduce the gas consumption of the steel rolling heating furnace. DETAILED DESCRIPTION

[0012] The high temperature hot delivery control method of continuous casting billet described in the present invention, taking the production of HRB400 (E) coil steel as an example, comprises the following process:

[0013] 1. Increase pulling speed

[0014] Maintain the continuous casting billet casting superheat within 10-25℃, such as 14℃, and stabilize the casting speed at ≥4.2m / min.

[0015] 2. Optimize the secondary cooling strength of the ingot

[0016] The molten steel is cooled through the continuous casting crystallizer to form a cast billet, which is then cooled through the secondary cooling chamber and enters the straightening system. The surface temperature of the cast billet is controlled above 980°C at the straightening position. When the casting speed is stable above 4.2m / min, the cooling intensity is 1.76L / kg. When the five-machine five-stream casting machine is used for production, the temperature change data is shown in Table 1:

[0017] Table 1 Billet surface temperature measurement data before and after improvement

[0018]

[0019] The average surface temperature of the improved ingot is ≥980℃.

[0020] 3. Improve continuous casting slag

[0021] Protective slag plays a key role in continuous casting production. The protective slag is melted by molten steel into liquid slag and flows into the copper tube of the crystallizer and the shell of the ingot to form a slag film, which plays a role in lubrication and heat transfer. However, due to the different raw materials and processes used by each manufacturer, the degree of slag film falling on the surface of the ingot is different, which affects the cooling of the surface of the ingot. By tracking the influence of protective slag on the ingot temperature, the protective slag with physical and chemical indicators of melting point 1035℃, melting speed 34s / 1350℃, viscosity 0.183Pa / s, and basicity 0.93 is selected. When the pulling speed is not less than 4.0m / min, it is more ideal to increase the temperature of the protective slag by 20~32℃ relative to the existing protective slag, as shown in Table 2:

[0022] Table 2 Comparison of casting temperatures of different mold slags

[0023]

[0024]

[0025] 4. Improve the way of transferring the blanks

[0026] The billet transfer car pushes 4 pieces / group in normal operation. After a certain flow of billet is in place, it has to wait for the other three flows of billet to be in place before pushing, which causes a large heat loss in the process. By improving the billet pushing method of the billet transfer car, pushing 4 pieces in a group is changed to pushing 3 pieces in a group, which reduces the waiting time of the continuous casting billet and thus reduces the heat loss. The improved billet temperature is shown in Table 3.

[0027] Table 3 Data comparison of different pushing methods

[0028] Pushing method Average pulling speed / (m / min) Steel turning temperature / ℃ Rolling furnace temperature / ℃ Billet casting running time / min Three per group 4.5 895 845 5.5 Four per group 4.5 895 805 6.51 Difference 0 0 40 -1.01

[0029] From the above data, it can be seen that under the same pulling speed, the time from the steel turning machine to entering the heating furnace for pushing 3 billets is 1.01min shorter than that for pushing 4 billets, and the furnace entry temperature is increased by 40°C, and the billet temperature is significantly improved.

[0030] 5. Increase the speed of billet entering the furnace

[0031] After being flame cut by the flame cutting machine, the billet enters the conveyor roller. The running speed of the billet from the conveyor roller to the rolling mill is mainly controlled by the running speed of the billet transfer car and the hot delivery roller. Therefore, the speed of the billet transfer car and the hot delivery roller motor is increased. The billet transfer car motor frequency is increased from 30Hz to 40Hz, and the running time is shortened from 45s to 37s. The hot delivery roller frequency is increased from 8Hz to 10Hz, and the running time is shortened from 25s to 18s. By adjusting the running parameters of the billet transfer car and the hot delivery roller motor, the running time of the billet is shortened by 15s, and the temperature loss during the billet running process is reduced.

[0032] 6. Reduce the number of waiting times for billets at the rolling mill lifting chain

[0033] By orderly organizing the billet off-line, when the continuous casting speed is greater than the steel rolling speed, the billets are organized onto the cooling bed to reduce the pushing of hot billets to the steel rolling, thereby reducing the waiting time of the billets at the steel rolling lifting chain, and also avoiding the slow speed of steel rolling billets affecting the pulling speed control of the continuous casting billets and the temperature loss of the billets out of the second cooling chamber.

[0034] 7. Install insulation cover on hot rollers from steelmaking to rolling

[0035] The length of the hot delivery roller from steelmaking to steel rolling is 15.23 meters. The ingots need to be transported and wait here, which takes a long time. The ingots lose a lot of heat. By installing a thermal insulation cover on the roller, the heat loss of the ingots is reduced. The temperature drop rate is 4.6℃ / min. Without the thermal insulation cover, the temperature drop rate is 11℃ / min, which reduces the temperature loss of the ingot casting process and increases the furnace entry temperature.

[0036] 8. Collect monthly statistics on the temperature data of the hot ingots entering the furnace and conduct continuous monitoring.

[0037] 9. Comparison of crack defects in hot casting

[0038] Comparison of the advantages and disadvantages of hot delivery methods Hot delivery and hot loading temperature (℃) Monthly scrap volume of red cracks (tons) Original process ≥550 450 High temperature heat transfer method ≥850 none

[0039] This high-temperature hot delivery control method is used to organize hot delivery and hot loading, and the quality of the rolled products is good.

[0040] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for controlling high temperature heat delivery of continuous casting billets, characterized in that: The following processes are included: Increase the casting speed: maintain the continuous casting billet casting superheat within 10-25℃, and set the casting speed ≥4.2m / min; Optimize the secondary cooling strength of the ingot: the surface temperature of the ingot at the straightening position is controlled above 980°C, and the cooling strength is 1.76L / kg; Improve continuous casting protection slag: select protection slag with physical and chemical indicators of melting point 1035℃, melting speed 34s / 1350℃, viscosity 0.183Pa / s, and basicity 0.93 Improved billet transfer method: Billet transfer carts are used in groups of 3. After a billet from any flow is in place, it will wait until the billets from the next two flows are in place before it can be transferred. Increase the speed of billet entering the furnace: speed up the motors of the billet transfer car and hot delivery roller table.

2. A method for controlling high temperature hot delivery of continuous casting billets according to claim 1, characterized in that: Reduce the waiting time of the ingot at the rolling mill lifting chain.

3. A method for controlling high temperature hot delivery of continuous casting billets according to claim 1, characterized in that: Install thermal insulation covers on the hot conveyor rollers from steelmaking to steel rolling.

4. A method for controlling high temperature hot delivery of continuous casting billets according to claim 1, characterized in that: The temperature data of hot ingots fed into the furnace are collected monthly for continuous monitoring.

5. A method for controlling high temperature hot delivery of continuous casting billets according to claim 1, characterized in that: The speed of the motors of the billet transfer car and the hot delivery roller is increased as follows: the motor frequency of the billet transfer car is set to 40Hz, and the running time is 37s; the frequency of the hot delivery roller is set to 10Hz, and the running time is 18s.

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