A method for calibrating a roll gap of a billet continuous casting soft reduction and straightening machine

Abstract

The application discloses a billet continuous casting light press-down straightening machine roll gap calibration method, and belongs to the technical field of continuous casting, and comprises the following steps: placing a calibration rod on a casting flow billet roller bed, and sequentially dividing a straightening machine set into a first part, a second part and a third part; sending the calibration rod to the first part through a jog mode; pressing down a first straightening machine to a calibration pressure, obtaining a roll gap value to be calibrated, and correcting the roll gap value according to an actual thickness of the calibration rod; sending the calibration rod into a second straightening machine position; comparing the roll gap value with upper and lower limit reference values at a limit position of the first straightening machine respectively, completing calibration after an error meets a requirement, and sequentially completing calibration of all straightening machines. The method improves calibration efficiency and precision, and can guarantee accuracy of light press-down press-down amount control.

Description

Technical Field

[0001] This application belongs to the field of continuous casting technology, specifically relating to a roll gap calibration method for a light-pressure pull-down straightening machine for billet continuous casting. Background Technology

[0002] In the steel production industry, billet continuous casting machines are mainly used to produce high-quality, high-grade, high-value-added wire rods, high-alloy steel pipes, as well as bearing steel, bars, and other raw material billets. To control internal quality defects in billets that are prone to occur during billet continuous casting, such as center segregation and center porosity, the light reduction technique is the most effective process control method. Light reduction refers to applying a uniform external force to the end region of the liquid core of the continuously cast billet, creating a certain amount of compression to compensate for the solidification shrinkage of the billet. This eliminates or reduces internal voids formed by billet shrinkage, preventing the molten steel enriched with solute in the intergranular spaces from flowing laterally towards the center of the billet. Furthermore, the squeezing effect generated by light reduction can also promote the reverse flow of molten steel enriched with solute in the liquid core along the casting direction, causing a redistribution of solute elements in the molten steel. This results in a more uniform and dense solidification structure in the billet, achieving the goal of improving center segregation and reducing center porosity.

[0003] In the implementation of light reduction technology, the precise control of the reduction amount directly determines the quality of the cast billet, and the roll gap accuracy of the straightener is the core factor affecting the reduction amount. In actual production, the roll gap of the straightener may shift due to mechanical wear, sensor errors, equipment maintenance, and process adjustments. Therefore, it is necessary to calibrate the roll gap of the straightener regularly and irregularly to ensure the accuracy of the reduction amount control under light reduction. Summary of the Invention

[0004] In view of this, this application provides a roll gap calibration method for a light-pressure straightening machine for continuous casting of billets. The main purpose is to accurately calibrate the roll gap of the straightening machine to ensure the accuracy of the light-pressure reduction control, thereby improving the internal quality of the billet and reducing defects such as center segregation and center porosity.

[0005] To achieve the above objectives, this application mainly provides the following technical solutions:

[0006] This application provides a method for calibrating the roll gap of a light-pressure pull-down straightening machine for continuous casting of billets, including:

[0007] The calibration rod is placed on the billet exit roller table. A straightening unit is provided on the upstream side of the billet exit roller table. The straightening unit is divided into a first part, a second part and a third part in sequence along the head to tail direction of the billet exit roller table.

[0008] Start the billet exit roller conveyor and push the head of the calibration rod to the second part of the straightening unit along the running direction of the billet exit roller conveyor from the tail to the head.

[0009] Start multiple tension levelers in the third part of the tension leveling unit, and use the inching mode to clamp and feed the calibration rod, so that the head of the calibration rod is transferred to the first part of the tension leveling unit;

[0010] Press down the first tension leveler in the first part of the tension leveler unit to make the pressure applied by the first tension leveler reach the calibrated pressure value, and obtain the roll gap value to be calibrated of the first tension leveler at this time.

[0011] Based on the actual thickness of the calibration rod, the displacement sensor of the first tension leveler is calibrated, and the roll gap value to be calibrated is revised to the actual thickness of the calibration rod;

[0012] Start the straightening unit and, along the running direction from the head to the tail of the billet exit roller table, remove the head of the calibration rod from the first straightening machine and move it to the position of the second straightening machine.

[0013] The first tension leveler is raised and lowered to the first and second limit positions, respectively. The roll gap value corresponding to the first tension leveler at the first limit position is compared with the upper limit reference value of the roll gap, and the roll gap value corresponding to the first tension leveler at the second limit position is compared with the lower limit reference value of the roll gap. When the difference between the roll gap value corresponding to the first tension leveler at the first limit position and the upper limit reference value of the roll gap, and the difference between the roll gap value corresponding to the first tension leveler at the second limit position and the lower limit reference value of the roll gap are both less than or equal to the first preset error threshold, the calibration of the first tension leveler is completed.

[0014] According to the arrangement order of the tension levelers in the tension leveling unit, the head of the calibration rod is moved sequentially to the position of each uncalibrated tension leveler, and the calibration steps of the first tension leveler are repeated until the calibration of all tension levelers in the tension leveling unit is completed.

[0015] Optionally, the straightening path of the straightening unit is an arc-shaped structure, and the upward direction of the arc-shaped structure extends toward the continuous casting machine.

[0016] Optionally, the calibration rod includes multiple calibration chain sections, which are hinged end-to-end.

[0017] Optionally, the pitch between two adjacent sections of the calibration chain is equal to the center distance between two adjacent straighteners; the number of sections of the calibration chain is greater than or equal to the number of straighteners; during the calibration process, the roller axis of each straightener coincides with the center line of the corresponding calibration chain, so that the roller of the straightener acts at the center of the corresponding calibration chain.

[0018] Optionally, the calibrated pressure value is 14t to 16t.

[0019] Optionally, the first preset error threshold is 1 mm.

[0020] Optionally, after calibrating the displacement sensor of the first tension leveler based on the actual thickness of the calibration rod and revising the roll gap value to be calibrated to the actual thickness of the calibration rod, the method further includes:

[0021] Raise the first tension leveler to the first limit position and press it down again so that the pressure applied by the first tension leveler reaches the calibrated pressure value again, and obtain the calibrated roll gap value of the first tension leveler at this time.

[0022] The calibration results of the first tension leveling machine are analyzed based on the comparison results by comparing the calibrated roll gap value with the actual thickness of the calibration rod.

[0023] Optionally, when the difference between the calibrated roll gap value and the actual thickness of the calibration rod is less than or equal to a second preset error threshold, the calibration result of the first tension leveling machine is determined to be valid.

[0024] Optionally, the second preset error threshold is 0.4 mm.

[0025] Optionally, before placing the calibration rod on the billet exit roller conveyor, the method further includes:

[0026] The calibration rod is preprocessed.

[0027] By employing the above technical solution, this application has at least the following beneficial effects:

[0028] The roll gap calibration method for a light-pressure straightening machine in billet continuous casting provided in the embodiments of this application can accurately calibrate the displacement sensor of the straightening machine and revise the roll gap value to be calibrated to the actual thickness of the calibration rod, ensuring that the roll gap set value is consistent with the actual value. This allows the compression applied during the light-pressure process to accurately compensate for the solidification shrinkage of the billet, effectively controlling quality defects such as center segregation and center porosity. Specifically, the straightening machine is divided into three parts, executed in the following order: pushing the calibration rod from the tail to the head, transferring the third part to the first part, calibrating the first straightening machine, and calibrating the remaining straightening machines one by one. The process is clear and logical, avoiding confusion in the calibration process and improving operational efficiency. Furthermore, in addition to calibrating the displacement sensor based on the actual thickness of the calibration rod, the accuracy of the roll gap calibration results is verified by moving the straightening machine to the first and second limit positions and comparing them with the upper and lower limit reference values ​​of the roll gap, respectively. This ensures the reliability of the calibration results and reduces roll gap offset. In addition, according to the arrangement of the straightening machines, the head of the calibration rod is moved to the position of each uncalibrated equipment in turn, and the calibration steps are repeated to ensure that the roll gap accuracy of all straightening machines in the straightening unit is consistent. This avoids the impact of the error of a single equipment on the overall reduction control, ensures that the continuous casting billet is subjected to uniform force during the straightening process, and improves the continuity of production and the stability of product quality. Attached Figure Description

[0029] Figure 1 A flowchart illustrating a roll gap calibration method for a light-pressure pull-down straightening machine for billet continuous casting, as an optional embodiment of this application;

[0030] Figure 2 This is a schematic diagram of the structure of a tension straightening unit according to an optional embodiment of this application. Detailed Implementation

[0031] The present application will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present application can be combined with each other.

[0032] This embodiment provides a roll gap calibration method for a light-pressure pull-down straightening machine for billet continuous casting, see [link to relevant documentation]. Figure 1 As shown, the method includes:

[0033] Step S101: Place the calibration rod on the billet exit roller table. A straightening unit is provided on the upstream side of the billet exit roller table. The straightening unit is divided into a first part, a second part and a third part in sequence along the head to tail direction of the billet exit roller table.

[0034] The roll gap calibration method for a light-pressure straightening machine in billet continuous casting provided in this application can be applied to continuous casting control and detection in steel production, specifically to the periodic and irregular roll gap calibration scenarios of straightening machines. When calibrating the roll gap of the straightening machine, firstly, the calibration rod can be placed on the billet exit roller table. Here, the billet exit roller table refers to the roller table at the billet exit end of the continuous casting machine, and a straightening unit is located upstream of the billet exit roller table. The straightening unit consists of multiple straightening machines, and its straightening path has an arc-shaped structure. The upward direction of this arc-shaped structure extends towards the continuous casting machine, meaning the opening of the arc-shaped structure faces away from the billet exit direction. Therefore, the billet exit roller table can only move the calibration rod to the near-straight section of the arc-shaped structure, that is, the area where the bottom of the arc-shaped structure is nearly horizontal. Then, through the clamping and driving of multiple straightening machines, the calibration rod is further moved from the near-straight section into the entire arc-shaped structure, completing the calibration rod transfer. It is understandable that when calibrating the roll gap of the tension leveler, the tension path of the arc-shaped structure is the transfer path of the calibration rod.

[0035] To achieve precise control of the calibration rod along the conveying path of the arc-shaped structure, the straightening unit is divided into three parts along the head to tail direction of the billet exit roller conveyor. Here, the third part refers to the multiple straightening machines corresponding to the near-straight section of the arc-shaped structure; the first part refers to the multiple straightening machines corresponding to the near-vertical section of the arc-shaped structure; and the second part refers to the multiple straightening machines corresponding to the transitional curved section between the near-straight and near-vertical sections of the arc-shaped structure.

[0036] The calibration rod comprises multiple calibration chain sections, which are hinged end-to-end, giving the calibration rod flexible bending capabilities to adapt to the arc-shaped conveying path of the tension leveling unit. Each calibration chain section is a rigid metal component; each section has the same thickness; the pitch between adjacent sections is equal to the center distance between adjacent tension leveling machines; the number of calibration chain sections is greater than or equal to the number of tension leveling machines; during calibration, the roller axis of each tension leveling machine coincides with the center line of the corresponding calibration chain, so that the rollers of the tension leveling machine act on the center of the corresponding calibration chain.

[0037] In some specific examples, after the calibration rod completes the full path transfer of the arc structure, all tension levelers are simultaneously pressed down, and the roll gap calibration operation of all tension levelers is carried out synchronously. In other specific examples, after the calibration rod completes the full path transfer of the arc structure, the first tension leveler closest to the continuous casting machine is pressed down first for roll gap calibration. After the first tension leveler is calibrated, the calibration rod is withdrawn from the first tension leveler in the opposite direction of the transfer and moved to the position of the next tension leveler. The process of pressing down the tension leveler, calibrating the roll gap, and withdrawing and moving is repeated to complete the calibration of all tension levelers one by one. Here, the roll gap calibration of all tension levelers is carried out by operating one by one. By operating one by one, it can be ensured that each tension leveler acts on the same calibration chain of the calibration rod during roll gap calibration, avoiding the accumulation of errors caused by differences in calibration position and improving calibration accuracy.

[0038] Step S102: Start the billet exit roller conveyor and push the head of the calibration rod to the second part of the straightening unit along the running direction of the billet exit roller conveyor from the tail to the head.

[0039] In this embodiment, activating the cast billet exit roller conveyor drives the calibration rod to move towards the straightening unit, pushing the head of the calibration rod to the second part of the straightening unit, namely the transition bending section, so that it can be subsequently clamped and transferred by the straightening machine. Here, the driving of the cast billet exit roller conveyor ensures that the calibration rod can stably and accurately enter the arc-shaped path of the straightening unit. This arc-shaped path is the transfer path of the arc-shaped structure used for the calibration rod in the initial stage of the calibration process, and this transfer path is the straightening path of the upper arc-shaped structure.

[0040] Step S103: Start multiple tension levelers in the third part of the tension leveling unit, and use the inching mode to clamp and feed the calibration rod, so that the head of the calibration rod is transferred to the first part of the tension leveling unit.

[0041] In this embodiment, multiple straighteners in the third section of the straightening unit are activated, clamping the calibration rod in a jogging mode. The clamping force of these multiple straighteners in the third section gradually pushes the head of the calibration rod to the first section, causing the calibration rod to transition from a near-straight section to a near-vertical section along an arc-shaped path, covering the entire straightening path. Here, the jogging mode avoids the calibration rod shifting due to inertia, ensuring that each section of the calibration chain accurately corresponds to the roll gap of the straightener.

[0042] Among them, see Figure 2As shown, taking a straightening unit consisting of nine straightening machines as an example, the nine straightening machines are named sequentially along the billet discharge direction as the first straightening machine, the second straightening machine, the third straightening machine, the fourth straightening machine, the fifth straightening machine, the sixth straightening machine, the seventh straightening machine, the eighth straightening machine, and the ninth straightening machine. In step S102, the head of the calibration rod is pushed to the fifth straightening machine located in the middle of the straightening unit via the billet discharge roller conveyor. In step S103, the sixth, seventh, eighth, and ninth straightening machines work together in a jogging clamping mode, gradually moving the head of the calibration rod along an arc-shaped path to the end of the straightening unit near the continuous casting machine, ultimately accurately positioning it at the position of the first straightening machine, completing the full path positioning of the calibration rod within the straightening unit.

[0043] Step S104: Press down the first tension leveler in the first part of the tension leveler unit to make the pressure applied by the first tension leveler reach the calibrated pressure value, and obtain the roll gap value to be calibrated of the first tension leveler at this time.

[0044] In this embodiment, the first straightening machine is the one closest to the continuous casting machine in the straightening unit. The roll gap to be calibrated is the reading of the displacement sensor on the first straightening machine when the pressure applied by the first straightening machine reaches the calibration pressure value. Here, by obtaining the roll gap to be calibrated value of the first straightening machine, the raw data of the first straightening machine can be obtained, providing a benchmark for subsequent calibration.

[0045] The calibration pressure value is between 14t and 16t. It is understood that if the calibration pressure value is below 14t, the mechanical gap between the roller surface of the leveling machine and the calibration rod cannot be effectively eliminated, affecting the calibration accuracy; while if the calibration pressure value exceeds 16t, it may cause deformation of the calibration rod, thus affecting the accuracy of the calibration results. In this embodiment, the preferred calibration pressure value is 15t.

[0046] Step S105: Based on the actual thickness of the calibration rod, calibrate the displacement sensor of the first tension leveler and revise the roll gap value to be calibrated to the actual thickness of the calibration rod.

[0047] In this embodiment, the actual thickness of the calibration rod is a known standard value, which can be used as an absolute reference for calibration. Here, calibrating the displacement sensor using the actual thickness of the calibration rod can eliminate displacement sensor errors, thereby achieving the purpose of calibrating the roll gap of the first tension leveler.

[0048] Taking the actual thickness of the calibration rod as 316.0 mm as an example. If the displacement sensor reading of the first tension leveling machine is 314.0 mm in step S104, then in step S105, the displacement sensor of the first tension leveling machine is calibrated based on an error of 2.0 mm so that the displacement sensor reading of the first tension leveling machine is displayed as 316.0 mm.

[0049] Step S106: Start the straightening unit and move the head of the calibration rod from the first straightening machine to the second straightening machine along the running direction from the head to the tail of the billet exit roller table.

[0050] In this embodiment, the calibration rod of the starting tension leveling unit is moved from the first tension leveling machine to the position of the second tension leveling machine. This operation serves a dual purpose: firstly, by moving sequentially, each tension leveling machine is calibrated independently, ensuring that each machine receives accurate calibration; secondly, the roll gap accuracy of the first tension leveling machine, which has already been calibrated, can be verified simultaneously during the movement. Here, this step-by-step calibration method ensures both the independence of individual machine calibration and establishes a continuous quality verification mechanism.

[0051] Step S107: Raise and lower the first straightening machine to the first limit position and the second limit position respectively. Compare the roll gap value corresponding to the first straightening machine at the first limit position with the upper limit reference value of the roll gap, and compare the roll gap value corresponding to the first straightening machine at the second limit position with the lower limit reference value of the roll gap. When the difference between the roll gap value corresponding to the first straightening machine at the first limit position and the upper limit reference value of the roll gap, and the difference between the roll gap value corresponding to the first straightening machine at the second limit position and the lower limit reference value of the roll gap, are both less than or equal to the first preset error threshold, the calibration of the first straightening machine is completed.

[0052] In this embodiment, the first tension leveler is raised to the first limit position, i.e., the maximum opening, and the roll gap value is recorded and compared with the upper limit reference value of the roll gap; the first tension leveler is pressed down to the second limit position, i.e. the minimum opening, and the roll gap value is recorded and compared with the lower limit reference value of the roll gap. This can verify the measurement accuracy of the first tension leveler throughout the entire stroke range and ensure that the mechanical limits match the displacement sensor readings.

[0053] The first preset error threshold is preferably 1mm, which can ensure that the first tension leveler after calibration has a good light pressing effect. Here, if the difference between the roll gap value corresponding to the first limit position and the upper limit reference value of the roll gap, and the difference between the roll gap value corresponding to the second limit position and the lower limit reference value of the roll gap, of the first tension leveler are both less than or equal to 1mm, then the first calibration is deemed qualified; otherwise, recalibrate and repeat steps S104 to S107.

[0054] Step S108: According to the arrangement order of the tension levelers in the tension leveling unit, move the head of the calibration rod to the position of each uncalibrated tension leveler in turn, and repeat the calibration steps of the first tension leveler until the calibration of all tension levelers in the tension leveling unit is completed.

[0055] In this embodiment, the calibration rod is moved sequentially to the position of each uncalibrated straightening machine according to the arrangement of the straightening machines, and steps S104 to S107 are repeated until all straightening machines are calibrated. This ensures that the roll gap calibration of each straightening machine is independent and accurate, avoiding error accumulation; it also ensures that each straightening machine operates on the same calibration chain, avoiding the influence of thickness differences between different calibration chains; furthermore, the sequential calibration along the arc-shaped path from the near-vertical section to the near-horizontal section conforms to the actual billet movement direction.

[0056] By applying the technical solution of this embodiment, the displacement sensor of the tension leveler can be accurately calibrated, and the roll gap value to be calibrated can be revised to the actual thickness of the calibration rod, ensuring that the roll gap set value is consistent with the actual value. This allows the compression applied during the light pressing process to accurately compensate for the solidification shrinkage of the cast billet, effectively controlling quality defects such as center segregation and center porosity. Specifically, the tension leveler unit is divided into three parts, executed in the following order: pushing the calibration rod from the tail to the head, transferring it from the third part to the first part, calibrating the first tension leveler, and calibrating the remaining tension levelers one by one. The process is clear and logical, avoiding confusion in the calibration process and improving operational efficiency. Furthermore, in addition to calibrating the displacement sensor based on the actual thickness of the calibration rod, the accuracy of the roll gap calibration results is verified by moving the tension leveler to the first and second limit positions and comparing them with the upper and lower limit reference values ​​of the roll gap, respectively. This ensures the reliability of the calibration results and reduces roll gap offset. In addition, according to the arrangement of the straightening machines, the head of the calibration rod is moved to the position of each uncalibrated equipment in turn, and the calibration steps are repeated to ensure that the roll gap accuracy of all straightening machines in the straightening unit is consistent. This avoids the impact of the error of a single equipment on the overall reduction control, ensures that the continuous casting billet is subjected to uniform force during the straightening process, and improves the continuity of production and the stability of product quality.

[0057] Furthermore, as a refinement and extension of the specific implementation of the above embodiments, in order to fully illustrate the specific implementation process of this embodiment, another roll gap calibration method for a light-pressure pull-down straightening machine for billet continuous casting is provided, the method comprising:

[0058] Step S201: Pre-process the calibration rod;

[0059] Step S202: Place the calibration rod on the billet exit roller table. A straightening unit is provided on the upstream side of the billet exit roller table. The straightening unit is divided into a first part, a second part and a third part in sequence along the head to tail direction of the billet exit roller table.

[0060] Step S203: Start the billet exit roller conveyor and push the head of the calibration rod to the second part of the straightening unit along the running direction of the billet exit roller conveyor from the tail to the head.

[0061] Step S204: Start multiple tension levelers in the third part of the tension leveling unit, and use the jog mode to clamp and feed the calibration rod, so that the head of the calibration rod is transferred to the first part of the tension leveling unit;

[0062] Step S205: Press down the first tension leveler in the first part of the tension leveler unit to make the pressure applied by the first tension leveler reach the calibrated pressure value, and obtain the roll gap value to be calibrated of the first tension leveler at this time.

[0063] Step S206: Based on the actual thickness of the calibration rod, calibrate the displacement sensor of the first tension leveler and revise the roll gap value to be calibrated to the actual thickness of the calibration rod;

[0064] Step S207: Raise the first tension leveler to the first limit position and press it down again so that the pressure applied by the first tension leveler reaches the calibrated pressure value again, and obtain the calibrated roll gap value of the first tension leveler at this time.

[0065] Step S208: Compare the calibrated roll gap value with the actual thickness of the calibration rod, analyze the calibration result of the first tension leveler based on the comparison result, and determine that the calibration result of the first tension leveler is valid when the difference between the calibrated roll gap value and the actual thickness of the calibration rod is less than or equal to the second preset error threshold.

[0066] Step S209: Start the straightening unit and move the head of the calibration rod from the first straightening machine to the second straightening machine along the running direction from the head to the tail of the billet exit roller table.

[0067] Step S210: Raise and lower the first tension leveler to the first limit position and the second limit position respectively. Compare the roll gap value corresponding to the first tension leveler at the first limit position with the upper limit reference value of the roll gap, and compare the roll gap value corresponding to the first tension leveler at the second limit position with the lower limit reference value of the roll gap. When the difference between the roll gap value corresponding to the first limit position and the upper limit reference value of the roll gap, and the difference between the roll gap value corresponding to the second limit position and the lower limit reference value of the roll gap, are both less than or equal to the first preset error threshold, the calibration of the first tension leveler is completed.

[0068] Step S211: According to the arrangement order of the tension levelers in the tension leveling unit, move the head of the calibration rod to the position of each uncalibrated tension leveler in turn, and repeat the calibration steps of the first tension leveler until the calibration of all tension levelers in the tension leveling unit is completed.

[0069] In step S201, compressed air can be used to purge and clean the calibration rod before calibration to ensure that the surface of the calibration rod is clean and free of foreign matter. It is understandable that, in order to improve the roll gap calibration accuracy, after purging and cleaning the calibration rod, compressed air can also be used to purge and clean the rollers of the tension leveler to ensure that the roller surface is clean and free of foreign matter.

[0070] In step S207, after the initial calibration is completed, the tension leveler is pressed down again from its maximum opening, i.e., the first limit position, to the specified calibration pressure value, and the roll gap value at this time is recorded. This process aims to verify whether the tension leveler response is consistent and stable after the initial calibration, ensuring that high accuracy is maintained even during movement.

[0071] In step S208, the validity of the calibration is evaluated by comparing the obtained roll gap value after calibration with the actual thickness of the calibration rod. If the difference between the two does not exceed a predetermined error range, i.e., a second preset error threshold, the calibration is considered successful and accurate. This step helps to confirm the calibration effect of the displacement sensor and the reliability of the entire calibration process. Here, the second preset error threshold is preferably 0.4 mm, which is beneficial to improving the accuracy of the roll gap calibration.

[0072] By applying another technical solution in this embodiment, and by repeatedly measuring and comparing the results under different conditions, it is ensured that the calibration process is not just a one-time adjustment, but a verified and reliable calibration process, which can effectively reduce measurement errors and ensure the accuracy of calibration data.

[0073] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the apparatus or process shown in the drawings is not necessarily necessary for implementing this application. Any variations that can be conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A method for calibrating the roll gap in a light-pressure pull-down straightening machine for continuous casting of billets, characterized in that, include: The calibration rod is placed on the billet exit roller table. A straightening unit is provided on the upstream side of the billet exit roller table. The straightening unit is divided into a first part, a second part and a third part in sequence along the head to tail direction of the billet exit roller table. Start the billet exit roller conveyor and push the head of the calibration rod to the second part of the straightening unit along the running direction of the billet exit roller conveyor from the tail to the head. Start multiple tension levelers in the third part of the tension leveling unit, and use the inching mode to clamp and feed the calibration rod, so that the head of the calibration rod is transferred to the first part of the tension leveling unit; Press down the first tension leveler in the first part of the tension leveler unit to make the pressure applied by the first tension leveler reach the calibrated pressure value, and obtain the roll gap value to be calibrated of the first tension leveler at this time. Based on the actual thickness of the calibration rod, the displacement sensor of the first tension leveler is calibrated, and the roll gap value to be calibrated is revised to the actual thickness of the calibration rod; Raise the first tension leveler to the first limit position and press it down again so that the pressure applied by the first tension leveler reaches the calibrated pressure value again, and obtain the calibrated roll gap value of the first tension leveler at this time. The calibration results of the first tension leveling machine are analyzed by comparing the calibrated roll gap value with the actual thickness of the calibration rod. When the difference between the calibrated roll gap value and the actual thickness of the calibration rod is less than or equal to the second preset error threshold, the calibration results of the first tension leveling machine are determined to be valid. Start the straightening unit and, along the running direction from the head to the tail of the billet exit roller table, remove the head of the calibration rod from the first straightening machine and move it to the position of the second straightening machine. The first tension leveler is raised and lowered to the first and second limit positions, respectively. The roll gap value corresponding to the first tension leveler at the first limit position is compared with the upper limit reference value of the roll gap, and the roll gap value corresponding to the first tension leveler at the second limit position is compared with the lower limit reference value of the roll gap. When the difference between the roll gap value corresponding to the first tension leveler at the first limit position and the upper limit reference value of the roll gap, and the difference between the roll gap value corresponding to the first tension leveler at the second limit position and the lower limit reference value of the roll gap are both less than or equal to the first preset error threshold, the calibration of the first tension leveler is completed. According to the arrangement order of the tension levelers in the tension leveling unit, the head of the calibration rod is moved sequentially to the position of each uncalibrated tension leveler, and the calibration steps of the first tension leveler are repeated until the calibration of all tension levelers in the tension leveling unit is completed.

2. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 1, characterized in that, The straightening path of the straightening unit is an arc-shaped structure, and the upward direction of the arc-shaped structure extends towards the continuous casting machine.

3. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 1, characterized in that, The calibration rod comprises multiple calibration chain sections, which are hinged end to end.

4. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 3, characterized in that, The pitch between two adjacent sections of the calibration chain is equal to the center distance between two adjacent straighteners; the number of sections of the calibration chain is greater than or equal to the number of straighteners; during the calibration process, the roller axis of each straightener coincides with the center line of the corresponding calibration chain, so that the roller of the straightener acts at the center of the corresponding calibration chain.

5. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 1, characterized in that, The calibrated pressure value is 14t to 16t.

6. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 1, characterized in that, The first preset error threshold is 1 mm.

7. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 1, characterized in that, The second preset error threshold is 0.4 mm.

8. The roll gap calibration method for a light-pressure pull-down straightening machine for continuous casting of billets according to claim 1, characterized in that, Before placing the calibration rod on the billet exit roller conveyor, the method further includes: Preprocess the calibration rod.

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