A method for determining the temperature of an annular furnace for a seamless steel tube low temperature rolling process

Abstract

The application discloses a method for determining the temperature of a ring furnace for a low-temperature rolling process of seamless steel pipes, and comprises the following steps: determining the deformation resistance and the area reduction; determining the material and the specification of the low-temperature rolling process; comparing the continuous rolling load, and if the load is too high, the temperature is increased and the comparison is continued; determining whether the area reduction at the temperature is greater than a set value, and if the area reduction is too small, the temperature is increased and the comparison is continued; determining the piercing temperature according to the temperature drop from the piercing to the continuous rolling; comparing the piercing load, and if the load is too high, the temperature is increased and the comparison is continued; determining whether the area reduction at the temperature is greater than a set value, and if the area reduction is too small, the temperature is increased and the comparison is continued; determining the pipe blank temperature of the ring furnace according to the temperature drop from the ring furnace to the piercing; determining the quality risk, and determining the delivery temperature of the ring furnace; and determining the delivery temperature of the ring furnace according to the difference between the flue gas temperature and the pipe blank temperature. According to the deformation resistance and the area reduction of the material, the delivery temperature of the ring furnace is determined in combination with the rolling mill load, the temperature drop and the quality.

Description

Technical Field

[0001] This invention relates to seamless steel pipe rolling technology, and more specifically, to a method for determining the temperature of an annular furnace in a low-temperature rolling process for seamless steel pipes. Background Technology

[0002] Low-temperature rolling technology has wide applications in the hot-rolled production of medium and heavy plates, strips, and bars. This technology plays a significant role in refining the microstructure of steel materials, improving the strength and low-temperature toughness of steel products, and fully tapping the performance potential of steel materials. However, in the field of seamless steel pipes, due to the constraints of product shape and production process, the billet heating temperature is significantly higher than that of other hot-rolled products, resulting in significantly higher energy consumption per ton of steel, severe oxidation loss, and coarse microstructure. In the production of some thick-walled carbon steel and low-alloy steel, the high-temperature plasticity and low deformation resistance are observed during production, resulting in lower actual mill loads and a capacity margin, allowing for a reduction in furnace exit temperature. Furthermore, this also limits the development of hot-rolled seamless steel pipes towards high performance and low cost. Currently, there is no method to determine the ring furnace exit temperature based on the material's deformation resistance and reduction of area, combined with mill load, temperature drop, and quality conditions.

[0003] Existing patent applications, such as Chinese patent CN 105921524A, disclose a controlled rolling method for the hot rolling process of seamless tubes. This method uses the lower limit of the complete recrystallization temperature and the upper limit of the non-recrystallization temperature of the experimental steel grade as design premises. It sets the temperatures of the piercing mill inlet and outlet, the tube rolling mill inlet and outlet, and the tension reduction / sizing mill inlet and outlet for the target specification seamless tube rolling process using conventional methods, as well as the rolling pass patterns for the piercing, tube rolling, and tension reduction / sizing steps. It adjusts the rolling deformation and designs the rolling temperature by treating the piercing and tube rolling steps as roughing and the tension reduction / sizing step as finishing. Finally, it controls the finishing rolling temperature by employing a certain method to achieve controlled rolling process. However, this method does not propose a method for determining the ring furnace temperature under low-temperature rolling conditions. Therefore, it is not applicable to determining the ring furnace temperature under low-temperature rolling conditions.

[0004] For example, Chinese patent CN103649344A discloses a controlled rolling method for seamless steel pipes with excellent strength and low-temperature toughness applied to the manufacturing process of seamless steel pipes. This controlled rolling method includes piercing rolling in the recrystallization region of the γ phase (above approximately 950°C); extension rolling and reduction rolling in the non-recrystallization region of the γ phase (950°C to the Ar3 transformation point) during the extension rolling and reduction rolling steps; and controlled cooling or quenching immediately after reduction rolling. If a sizing mill is used for the reduction rolling step, rolling is performed in the (α+γ) two-phase temperature region (from the Ar3 transformation point to the Ar1 transformation point) during the reduction rolling step. This controlled rolling method can solve the problems of a significant increase in thermal deformation resistance and a significant deterioration in thermal deformation capacity (hot working performance) caused by low-temperature rolling. However, it does not propose a method for determining the ring furnace temperature under low-temperature rolling conditions. Therefore, it is not applicable to determining the ring furnace temperature under low-temperature rolling conditions. Summary of the Invention

[0005] In view of the deficiencies in the existing technology, the purpose of this invention is to provide a method for determining the temperature of an annular furnace in the low-temperature rolling process of seamless steel pipes. The calculation of the annular furnace exit temperature fully considers the high-temperature performance of the material during the hot rolling process of seamless steel pipes for the first time, and combines the load and quality conditions of the piercing and continuous rolling mills, thus providing an important and reliable basis for the low-temperature rolling process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for determining the temperature of an annular furnace in a low-temperature rolling process for seamless steel pipes includes the following steps:

[0008] S1. Determine the deformation resistance and reduction of area at different temperatures;

[0009] S2. Determine the material and specifications for the low-temperature rolling process;

[0010] S3. Set the continuous rolling start temperature, extract the loads of different materials of the same specification from the load database, compare the continuous rolling loads, and if the continuous rolling load exceeds the set value, increase the temperature and continue the comparison until the continuous rolling load meets the set value.

[0011] S4. Determine whether the section reduction rate at this temperature is greater than the set value. If it is less than the set value, increase the temperature and continue to compare until the section reduction rate meets the set value.

[0012] S5. Determine the temperature of the piercing roll based on the temperature drop from piercing to continuous rolling.

[0013] S6. Extract the loads of different materials of the same specification from the load database, compare them with the perforation load. If the perforation load exceeds the set value, increase the temperature and continue the comparison until the perforation load meets the set value.

[0014] S7. Determine whether the cross-sectional reduction rate at the temperature is greater than the set value. If it is less than the set value, increase the temperature and continue to compare until the cross-sectional reduction rate meets the set value.

[0015] S8. Determine the billet temperature of the annular furnace based on the temperature drop from the annular furnace to the piercing.

[0016] S9. Determine the flue gas heating temperature of the annular furnace based on the difference between the flue gas temperature and the billet temperature.

[0017] Preferably, in step S1, the deformation resistance and the reduction of area are determined by using a Gleeble thermal simulator with deformation resistance test and thermoplasticity test.

[0018] Preferably, the deformation rate in the deformation resistance test is 10~50s. -1 The degree of deformation is 40-60%;

[0019] The deformation rate of the thermoplasticity test is 10~50s. -1 .

[0020] Preferably, the deformation resistance and the reduction of area are measured at 50°C intervals from 850 to 1250°C.

[0021] Preferably, in step S3, the load values ​​of different materials of the same specification in the load database include historical data on material, pass type series, continuous rolling wall thickness, continuous rolling temperature, continuous rolling load, temperature drop from piercing to continuous rolling, piercing temperature, piercing load, deformation resistance value, section shrinkage rate value, temperature drop from annular furnace to piercing, and the difference between annular furnace flue gas temperature and billet temperature.

[0022] Ideally, when encountering a non-existent temperature value during calculation, the deformation resistance and reduction of area should be calculated using the difference.

[0023] Preferably, when comparing the load in steps S3 to S7, the deformation resistance is taken as the maximum value of the current temperature.

[0024] Preferably, the temperature increase in steps S3 and S6 is 5°C.

[0025] The method for determining the temperature of an annular furnace in the low-temperature rolling process of seamless steel pipes provided by this invention has the following beneficial effects:

[0026] 1) The method for determining the temperature of the annular furnace in this invention is based on the deformation resistance of the material measured by the Gleeble thermal simulator, combined with the hole size and specifications, and compared with the deformation resistance and load values ​​of existing materials. It is feasible and accurate for mature and fixed production processes.

[0027] 2) The method for determining the temperature of the annular furnace in this invention uses the cross-sectional shrinkage rate measured by the Gleeble thermal simulator, combined with the actual temperature, to judge the quality problems caused by the plasticity of the tube blank during the production process, which has strong intuitiveness. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the method for determining the temperature of a ring furnace according to the present invention. Detailed Implementation

[0029] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] Combination Figure 1 As shown, the present invention provides a method for determining the temperature of an annular furnace in a low-temperature rolling process for seamless steel pipes, comprising the following steps:

[0031] S1. Deformation resistance and reduction of area were determined using a Gleeble thermal simulator through deformation resistance testing and thermoplasticity testing. Deformation resistance and reduction of area were measured at 50°C intervals from 850°C to 1250°C, i.e., at nine temperatures: 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, and 1250°C. The deformation resistance and reduction of area between each temperature were obtained using a difference method.

[0032] S2. Determine the material and specifications for the low-temperature rolling process.

[0033] S3. Set the continuous rolling start temperature. For example, if it is set to 1000℃, extract the loads of different materials of the same specification from the load database and compare them with the continuous rolling load. If the continuous rolling load exceeds the set value, the temperature is increased by 5℃ and the comparison continues until the continuous rolling load meets the set value.

[0034] S4. Then determine whether the section reduction rate at this temperature is greater than the set value. If it is less than the set value, increase the temperature by 5°C and continue to compare until the section reduction rate meets the set value.

[0035] S5. Determine the piercing roll temperature based on the temperature drop from piercing to continuous rolling, and so on.

[0036] S6. Extract the load values ​​of different materials of the same specification from the load database, compare them with the perforation load. If the perforation load exceeds the set value, increase the temperature by 5°C and continue the comparison until the perforation load meets the set value.

[0037] S7. Then determine whether the cross-sectional reduction rate at the temperature is greater than the set value. If it is less than the set value, increase the temperature and continue to compare until the cross-sectional reduction rate meets the set value.

[0038] S8. Determine the billet temperature of the annular furnace based on the temperature drop from the annular furnace to the piercing.

[0039] S9. Determine the flue gas heating temperature of the annular furnace based on the difference between the flue gas temperature and the billet temperature.

[0040] In step S1 above, deformation resistance and reduction of area are determined by using a Gleeble thermal simulator with deformation resistance test and thermoplasticity test.

[0041] The deformation rate for the deformation resistance test was 10~50 l / s, and the deformation degree was 40~60%.

[0042] The deformation rate for thermoplasticity testing is 10~50 l / s.

[0043] The load database contains historical data on material, pass type series, continuous rolling wall thickness, continuous rolling temperature, continuous rolling load, temperature drop from piercing to continuous rolling, piercing temperature, piercing load, deformation resistance, reduction of area, temperature drop from the annular furnace to piercing, and the temperature difference between the annular furnace flue gas temperature and the billet temperature.

[0044] When comparing the load in steps S3 to S7 above, the deformation resistance is taken as the maximum value of the current temperature.

[0045] Example

[0046] This embodiment uses 20 steel and 20G steel. The method for determining the ring furnace temperature of the two steel materials according to the present invention is shown in Table 1 below:

[0047] Table 1

[0048] Material Hole type series Continuous rolling wall thickness Continuous rolling temperature Continuous rolling load (1#) Temperature drop from piercing to continuous rolling Perforation temperature Perforation load Temperature drop from ring furnace to perforation Flue gas and billet temperature difference 20 152.5 5 1050 142 130 1200 663 50 30 20G 152.5 5 1050 142 130 1200 730 50 30

[0049] The deformation resistance and reduction of area of ​​the material are shown in Table 2 below:

[0050] Table 2

[0051] Material Deformation resistance values ​​(850~1250℃) Reduction of area numerical value 20 223.12，132.34，116.36，109.41，76.61，58.35，54.64，45.60，37.52 39.2，46.8，48.6，50.5，62.1，73.5，82.3，96.9，92.5，94.4 20G 245.63，146.25，128.52，133.23，85.24，65.12，60.53，50.25，41.28 39.6，46.7，48.9，50.8，62.5，73.9，82.6，97.2，92.9，94.8

[0052] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the essential spirit of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method for determining the temperature of an annular furnace in a low-temperature rolling process for seamless steel pipes, characterized in that, Includes the following steps: S1. Determine the deformation resistance and reduction of area at different temperatures; S2. Determine the material and specifications for the low-temperature rolling process; S3. Set the continuous rolling start temperature, extract the loads of different materials of the same specification from the load database, compare the continuous rolling loads, and if the continuous rolling load exceeds the set value, increase the temperature and continue the comparison until the continuous rolling load meets the set value. S4. Determine whether the section reduction rate at this temperature is greater than the set value. If it is less than the set value, increase the temperature and continue to compare until the section reduction rate meets the set value. S5. Determine the temperature of the piercing roll based on the temperature drop from piercing to continuous rolling. S6. Extract the loads of different materials of the same specification from the load database, compare them with the perforation load. If the perforation load exceeds the set value, increase the temperature and continue the comparison until the perforation load meets the set value. S7. Determine whether the cross-sectional reduction rate at the temperature is greater than the set value. If it is less than the set value, increase the temperature and continue to compare until the cross-sectional reduction rate meets the set value. S8. Determine the billet temperature of the annular furnace based on the temperature drop from the annular furnace to the piercing. S9. Determine the furnace outlet temperature of the annular furnace based on the difference between the flue gas temperature and the billet temperature.

2. The method for determining the temperature of an annular furnace for low-temperature rolling of seamless steel pipes according to claim 1, characterized in that: In step S1, the deformation resistance and the reduction of area are determined by using a Gleeble thermal simulator with deformation resistance test and thermoplasticity test.

3. The method for determining the temperature of an annular furnace for low-temperature rolling of seamless steel pipes according to claim 2, characterized in that: The deformation rate of the deformation resistance test is 10~50s. -1 The degree of deformation is 40-60%; The deformation rate of the thermoplasticity test is 10~50s. -1 .

4. The method for determining the temperature of an annular furnace for low-temperature rolling of seamless steel pipes according to claim 2, characterized in that: The deformation resistance and the reduction of area were measured at 50°C intervals from 850 to 1250°C.

5. The method for determining the temperature of an annular furnace for low-temperature rolling of seamless steel pipes according to claim 1, characterized in that: In step S3, the load values ​​of different materials of the same specification in the load database include historical data of material, pass type series, continuous rolling wall thickness, continuous rolling temperature, continuous rolling load, temperature drop from piercing to continuous rolling, piercing temperature, piercing load, deformation resistance value, section shrinkage rate value, temperature drop from annular furnace to piercing, and the difference between annular furnace flue gas temperature and billet temperature.

6. The method for determining the temperature of an annular furnace for low-temperature rolling of seamless steel pipes according to claim 1, characterized in that: When a non-existent temperature value is encountered during the calculation, the deformation resistance and reduction of area are calculated using the difference.

7. The method for determining the temperature of an annular furnace for low-temperature rolling of seamless steel pipes according to claim 1, characterized in that: The temperature is increased by 5°C in steps S3 and S6.

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