An on-line adjustment method for the execution error of the continuous casting soft reduction process

Abstract

The present invention relates to the technical field of continuous casting straightening rolls, and particularly to an on-line adjustment method for the execution error of the continuous casting soft reduction process, including: collecting the pressure values of the reduction rolls, and calculating the average straightening roll pressure at the same position for the total number of stream passes of a certain roll in a certain casting; calculating the average pressure of the reduction rolls at the same position of a certain roll for several castings; judging whether the pressure values of two consecutive rolls are within the confidence interval to determine the abnormal roll, and calculating the reduction compensation amount of the abnormal roll, so as to compensate the reduction amount of the abnormal roll. The problem solved by the present invention is that it is difficult to stop the machine for a moment to correct the accuracy during the normal production process of a certain casting in continuous casting, resulting in the inability to obtain relatively stable low magnification quality of the cast slab.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting straightening rolls, and particularly to an on-line adjustment method for the execution error of the continuous casting soft reduction process. Background Art

[0002] Because the continuous casting straightening rolls work in harsh environments such as high temperature and high pressure, and to improve efficiency and reduce refractory costs, the maximum number of heats produced in one casting campaign can reach more than 30 heats of steel, and the continuous casting equipment can continuously work for more than 20 hours. In this case, when implementing the soft reduction process at the end of solidification, there may be a large error in the reduction accuracy. Facts have proved that such a situation will significantly affect the center quality of the continuous casting billet. At this time, if the pouring is stopped, the production efficiency will inevitably be affected. If production continues, the evaluation indexes of the center quality of the billet, such as reduction cracks, shrinkage cavities, segregation, and porosity, will be significantly affected.

[0003] CN113084111A "A Method for Calibrating the Reduction Accuracy of a Continuous Casting Straightening Machine" provides a method for effectively calibrating the displacement accuracy of the straightening rolls. However, this method requires the equipment to be stopped for debugging and does not explain how to take measures when such problems occur during the production process. Because even if the roll gap of the straightening rolls is accurately calibrated, the reduction accuracy sometimes still has a large error, which is caused by the long-term operation of the continuous casting machine. Summary of the Invention

[0004] Aiming at the deficiencies of the existing algorithms, the problem solved by the present invention is that it is difficult to stop the machine for a moment to correct the accuracy during the normal production process of a certain heat in continuous casting, resulting in an inability to obtain relatively stable low magnification quality of the casting billet.

[0005] The technical solution adopted by the present invention is: an on-line adjustment method for the execution error of the continuous casting soft reduction process includes the following steps:

[0006] Step 1: Collect the pressure values of the reduction rolls and calculate the average straightening roll pressure at the same position for the total number of heats of a certain roll in a certain casting campaign.

[0007] Further, the calculation formula for the average straightening roll pressure at the same position for the total number of heats of a certain roll in a certain casting campaign is:

[0008]

[0009] Wherein, X mi is the straightening roll pressure value at the same position for the i-th heat of the m-th roll; N is the total number of heats.

[0010] Further, Step 1 further includes: calculating the pressure deviation index between the straightening roll pressure value at the same position for the i-th heat of the m-th roll and the average straightening roll pressure at the same position for the total number of heats of the m-th roll, and the formula is:

[0011]

[0012] Among them, X mi is the straightening roll pressure value at the same position in the i-th pass of the m-th roll, and X m is the average value of the straightening roll pressure at the same position for the total number of passes of a certain roll in a certain casting sequence.

[0013] Furthermore, when the pressure deviation index exceeds the threshold, the straightening roll pressure value at the same position in the i-th pass of the m-th roll is excluded.

[0014] Step 2: Calculate the average value of the reduction roll pressure at the same position of a certain roll for several casting sequences;

[0015] Furthermore, the calculation formula for the average value of the reduction roll pressure at the same position of a certain roll for several casting sequences is:

[0016]

[0017] Among them, M is the total number of casting sequences; N is the total number of passes, and X mij is the straightening roll pressure value at the same position in the i-th pass of the j-th casting sequence of the m-th roll.

[0018] Step 3: Determine whether the pressure values of two consecutive rolls are within the confidence interval, identify the abnormal roll, calculate the reduction compensation amount of the abnormal roll, and thus compensate the reduction amount of the abnormal roll.

[0019] Furthermore, the confidence interval is

[0020] Furthermore, the formula for calculating the reduction compensation amount of the abnormal roll is:

[0021]

[0022] Among them, h is the set reduction amount of the soft reduction process for this roll.

[0023] Advantages of the present invention:

[0024] 1. Determine the abnormal roll based on whether the average value of the reduction pressure of two consecutive rolls is within the confidence interval, and adjust the roll pressure through the compensation amount, thereby improving the central quality of the slab. Description of the Drawings

[0025] Figure 1 is the flowchart of the online adjustment method for the execution error of the continuous casting soft reduction process of the present invention;

[0026] Figure 2 is the low-magnification slab drawing before compensation of the present invention;

[0027] Figure 3 is the low-magnification slab drawing after compensation of the present invention. Detailed Embodiments

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner, and therefore it only shows the components related to the present invention.

[0029] like Figure 1 As shown, an online adjustment method for execution error of a continuous casting soft reduction process comprises the following steps:

[0030] 1) Use a 160x160 section 10 machine 10 strand small square billet continuous casting machine, require the use of static light pressure reduction process, constant pulling speed operation, single roll pressure reduction should be between 3mm and 5mm, and the number of straightening rolls performing the pressure reduction process is usually 3 to 6;

[0031] 2) During the normal casting process of continuous casting and stable billet drawing, record the pressure value of each pressing roller. Considering that the pressure of the pressing roller in the continuous casting process presents a steady-state fluctuation, the recorded pressure value usually only needs to retain two significant digits;

[0032] Calculate the average pressure of the straightening roller at the same position of the total flow of the mth roller in a certain casting, the formula is:

[0033]

[0034] Among them, X mi is the tension roller pressure value of the same position of the mth roller in the i-th flow; N is the total number of flows, and in this embodiment, N=10;

[0035] 3) Calculate the pressure deviation index between the straightening roller pressure value at the same position of the mth roller in the i-th flow and the average straightening roller pressure value at the same position of the mth roller in the total flow. The formula is:

[0036]

[0037] If σ m If the pressure is greater than the threshold value, in this embodiment, the threshold value = 0.2, the pressure value of the corresponding flow of the roller is removed from the pressure value record table of the pressing roller;

[0038] 4) Repeat several times and calculate the average pressure of the mth roller at the same position. The formula is

[0039]

[0040] Where M is the total number of pouring times; N is the total number of flows; X mij The tension and straightening roller pressure value at the same position of the mth roller, the jth pouring, and the ith flow;

[0041] And set the confidence interval to

[0042] 5) During the continuous casting process with stable billet drawing, record the pressure values of each reduction roll. If the pressures of two consecutive rolls are not within the confidence interval range, it is considered that the reduction amount of the previous roll is abnormal. Calculate the reduction compensation amount of the abnormal roll. The formula is:

[0043]

[0044] where h is the set reduction amount of the light reduction process of this roll.

[0045] Note: The present invention corrects the reduction accuracy online according to the straightening roll pressure. The abnormal change of the pressure is usually caused by the reduction displacement error. Therefore, if the pressure of a certain roll is abnormal and not within the confidence interval range, it usually indicates that the reduction amount deviation of this roll is too large.

[0046] If only the pressure of one roll is not within the confidence interval range, and the pressures of the two rolls before and after it are within the confidence interval range, it is considered that there is a problem with the pressure sensor of this roll, the reduction amount is normal, and the reduction amount of this roll is not adjusted. The current casting heat can be produced normally;

[0047] If the pressures of three consecutive rolls are not within the confidence interval range, it is considered that it is not suitable to take temporary compensation measures at this time, and this strand should be immediately stopped.

[0048] Note: Because the reduction error of the previous roll causes a large size deviation of the billet after passing through this roll, and the set roll gap of the next roll remains unchanged, its reduction amount will inevitably be affected. Therefore, if there is an error in the reduction accuracy of a certain roll, usually two straightening rolls with abnormal pressure changes occur, that is, the first situation is common, and the second and third situations are occasional. For example, if the previous roll should have reduced by 4 mm but actually only reduced by 1 mm, the pressure of this roll will be significantly smaller, and the 3 mm less reduced will be compensated by the next roll, and the pressure of the next roll will increase significantly.

[0049] 6) After calculating △h according to step (5), if the pressure of the abnormal reduction roll is small, its reduction amount should be increased by △h, otherwise its reduction amount should be decreased by △h, and the reduction amounts of other reduction rolls remain unchanged. Preferably, when △h≥0.5 mm, it should be adjusted step by step at a step size of 0.5 mm, and the time interval between each adjustment should be ≥5 min.

[0050] 7) After adjusting the reduction amount of the abnormal reduction roll, the pressure change of the next roll should be tracked. The pressure of the next roll usually automatically changes to within the confidence interval range.

[0051] Example 1

[0052] The continuous caster was tested with 10B21 at a drawing speed of 2.3 m / min. The average values of the pressures of rolls 1-4 accumulated through steps (1)-(4) of the invention content They are 200 kN, 280 kN, 300 kN, and 320 kN respectively, and the confidence intervals are 160 kN - 240 kN, 230 kN - 330 kN, 240 kN - 360 kN, and 260 kN - 380 kN respectively (retaining two significant figures).

[0053] According to step (5), the pressures of the 1st - 4th rolls of the 1st - 10th strands of a certain heat of steel are counted as shown in Table 1. It can be clearly seen that the outliers are the first and second rolls of the 10th strand. It is judged that the first roll is the abnormally pressed roll. Substituting it into formula (4) for calculation, the compensation amount can be obtained as |(120 / 200)^2 - 1| * 4 = 2.56 mm.

[0054] Table 1 Pressures of the 1st - 4th rolls of the 1st - 10th strands of a certain heat of steel

[0055]

[0056]

[0057] The reduction amount of the first roll of the 10th strand is increased by 2.56 mm, and the reduction amount is changed in steps of 0.5 mm / min; longitudinal section macro photographs of the continuous casting billets are taken before and after the change. Figure 2 , 3 are the continuous casting billet diagrams before and after compensation. Obviously Figure 2 There are serious shrinkage cavities and pressing cracks in the continuous casting billet, which are caused by the too small reduction amount of the 1st roll and the too large reduction amount of the 2nd roll. Figure 3 The central quality of the continuous casting billet is significantly improved after compensation.

[0058] Taking the ideal embodiments of the present invention described above as inspiration, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An online adjustment method for the execution error of the continuous casting soft reduction process, characterized in that It includes the following steps: Step 1: Collect the pressure values of the straightening rolls and calculate the average pressure of the straightening rolls at the same position for the total number of passes of a certain casting and a certain roll; The calculation formula for the average pressure of the straightening rolls at the same position for the total number of passes of a certain casting and a certain roll is: Among them, X mi is the straightening roll pressure value at the same position in the i-th pass of the m-th roll; N is the total number of passes; Calculate the pressure deviation index between the pressure value of the straightening roll at the same position for the i-th pass of the m-th roll and the average pressure of the straightening roll at the same position for the total number of passes of the m-th roll. The formula is: Among them, X mi is the straightening roll pressure value at the same position in the i-th pass of the m-th roll, and is the average straightening roll pressure at the same position for the total number of passes of a certain roll in a certain casting When the pressure deviation index exceeds the threshold, eliminate the pressure value of the straightening roll at the same position for the i-th pass of the m-th roll; Step 2: Calculate the average pressure of the straightening rolls at the same position for a certain roll in several castings; The formula is: Among them, M is the total number of casting heats; N is the total number of strands, and X mij is the straightening roll pressure value at the same position for the i-th strand of the j-th casting heat of the m-th roll. Step 3. Determine whether the pressure values of two consecutive rolls are within the confidence interval to identify the abnormal roll. The confidence interval is Calculate the roll gap compensation amount of the abnormal roll where h is the set roll gap of the abnormal roll in the light reduction process; Thus, compensate the roll gap reduction for the abnormal roll.

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