Annular furnace temperature determination method for seamless steel tube low-temperature rolling process

Abstract

The invention discloses an annular furnace temperature determination method for a seamless steel tube low-temperature rolling process. The method comprises the following steps: measuring deformation resistance and reduction of area; determining the material and specification of a low-temperature rolling process; comparing the continuous rolling load, and if the continuous rolling load exceeds the standard, raising the temperature and continuously comparing; determining whether the reduction of area at the temperature is greater than a set value or not, and if so, raising the temperature to continue comparison; the punching temperature is determined according to the temperature drop from punching to continuous rolling; comparing the perforation load, and if the perforation load is exceeded, raising the temperature and continuing comparison; determining whether the reduction of area at the temperature is greater than a set value or not, and if so, raising the temperature to continue comparison; determining the tube blank temperature of the annular furnace according to the temperature drop from the annular furnace to the perforation; the quality risk is judged, and the tapping temperature of the annular furnace is determined; and the tapping temperature of the annular furnace is determined according to the difference value between the flue gas temperature and the tube blank temperature. The tapping temperature of the annular furnace is determined according to the deformation resistance and the reduction of area of a material in combination with rolling mill load, temperature drop and quality conditions.

Description

Technical Field

[0001] The invention relates to a seamless steel pipe rolling technology, and more specifically to a method for determining the temperature of a ring furnace used in a seamless steel pipe low-temperature rolling process. Background Art

[0002] Low-temperature rolling technology is widely used in the fields of hot-rolled medium and thick plates, strip steel, and bar rolling. This technology has played a huge role in refining the organization of steel materials, improving the strength and low-temperature toughness of steel products, and fully tapping the performance potential of steel materials. In the field of seamless steel pipes, due to the constraints of product form and production process, the heating temperature of the billet is significantly higher than that of other hot-rolled varieties, resulting in significantly higher energy consumption per ton of steel, severe oxidation and burning, and coarse organization. In the production process of some thick-walled plain carbon steel and low-alloy steel, the high-temperature plasticity is high, the deformation resistance is low, the actual load of the rolling mill is low, the capacity is surplus, and there is room to reduce the furnace temperature. In addition, it also limits the development of hot-rolled seamless steel pipes towards high performance and low cost. At present, there is no method to determine the furnace temperature of the ring furnace based on the deformation resistance and cross-sectional shrinkage of the material, combined with the mill load, temperature drop and quality.

[0003] In existing patent applications, such as Chinese patent CN 105921524A, a controlled rolling method in the hot rolling process of seamless pipes is disclosed. The method is based on the lower limit of the complete recrystallization temperature and the upper limit of the non-recrystallization temperature of the experimental steel type as the design premise, and the temperatures of the piercing machine entrance and exit, the tube rolling machine entrance and exit, the stretching / sizing machine entrance and exit of the target specification seamless pipes are rolled by conventional processes, and the rolling pass types of the piercing, tube rolling and stretching / sizing steps. The rolling deformation is adjusted and the rolling temperature is designed with the two steps of piercing and tube rolling as rough rolling and the stretching / sizing step as finishing rolling, and the roughing final rolling temperature and the finishing rolling start rolling temperature are controlled by a certain method to finally realize the controlled rolling process. This method does not propose a method for determining the temperature of the ring furnace under low-temperature rolling process conditions. It is not suitable for determining the temperature of the ring furnace 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 seamless steel pipe manufacturing process, which includes piercing rolling in the recrystallization region of the γ phase (above about 950°C); extending rolling and reducing rolling in the non-recrystallization region of the γ phase (950°C to Ar3 transformation point) in the extending rolling step and the reducing rolling step; and controlled cooling or quenching immediately after the reducing rolling. If the sizing mill is used for the reducing rolling step, rolling is performed in the (α+γ) two-phase temperature region (Ar3 transformation point to Ar1 transformation point) in the reducing rolling step. This controlled rolling method can solve the problem of significant increase in thermal deformation resistance and significant deterioration in thermal deformation capacity (hot working performance) caused by low-temperature rolling, but does not propose a method for determining the temperature of the ring furnace under low-temperature rolling process conditions. It is not suitable for determining the temperature of the ring furnace under low-temperature rolling conditions. Summary of the invention

[0005] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for determining the temperature of a ring furnace for the low-temperature rolling process of seamless steel pipes. The calculation of the outlet temperature of the ring furnace fully considers the high-temperature properties of the material during the hot rolling process of the seamless steel pipe for the first time, and combines the load and quality conditions of the perforation and continuous rolling units, thereby providing an important and reliable basis for the low-temperature rolling process.

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

[0007] A method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process comprises the following steps:

[0008] S1. Determine deformation resistance and section shrinkage;

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

[0010] S3, extracting the loads of different materials with the same specifications from the load database, and comparing them with the continuous rolling loads. If the continuous rolling load exceeds the set value, the temperature is increased and the comparison is continued until the continuous rolling load meets the set value;

[0011] S4, determining whether the cross-sectional shrinkage at the temperature is greater than the set value, if less than the set value, increasing the temperature and continuing the comparison until the cross-sectional shrinkage meets the set value;

[0012] S5. Determine the temperature of the perforating roller according to the temperature drop from perforating to continuous rolling;

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

[0014] S7, determine whether the cross-sectional shrinkage rate at the temperature is greater than the set value, if less than the set value, increase the temperature and continue to compare until the cross-sectional shrinkage rate meets the set value;

[0015] S8, determining the tube temperature of the annular furnace according to the temperature drop from the annular furnace to the perforation;

[0016] S9. Determine the flue gas heating temperature of the annular furnace according to the difference between the flue gas temperature and the tube blank temperature.

[0017] Preferably, in the step S1, the deformation resistance and the cross-sectional shrinkage are measured by a Gleeble thermal simulator using a deformation resistance measurement test and a thermoplasticity measurement test.

[0018] Preferably, the deformation rate of the deformation resistance test is 10 to 50 l / s, and the deformation degree is 40 to 60%;

[0019] The deformation rate of the thermoplasticity test is 10 to 50 l / s.

[0020] Preferably, the deformation resistance and the cross-sectional shrinkage are measured at a value every 50°C from 850°C to 1250°C.

[0021] Preferably, in step S3, the values ​​of the loads of different materials of the same specification in the load database include historical data of material, hole series, continuous rolling wall thickness, continuous rolling temperature, continuous rolling load, temperature drop from perforation to continuous rolling, perforation temperature, perforation load, deformation resistance value, cross-sectional shrinkage value, temperature drop from annular furnace to perforation, and the difference between the flue gas temperature of the annular furnace and the temperature of the billet.

[0022] Preferably, when a non-existent temperature value is encountered during calculation, the deformation resistance and the cross-sectional shrinkage are calculated by difference.

[0023] Preferably, when comparing the loads in steps S3 to S7, the deformation resistance takes the maximum value of the current temperature.

[0024] Preferably, the temperature in step S3 and step S6 is increased to 5°C.

[0025] The method for determining the temperature of a ring furnace for a seamless steel pipe low-temperature rolling process provided by the present invention has the following beneficial effects:

[0026] 1) The method for determining the temperature of the annular furnace of the present 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 the existing material, which is feasible and accurate for mature and fixed production processes;

[0027] 2) The method for determining the temperature of the annular furnace of the present invention uses the cross-sectional shrinkage rate measured by the gleeble thermal simulator and combines the actual temperature to judge the quality problems affected by the plasticity of the tube blank during the production process, which has strong intuitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic flow chart of the method for determining the temperature of an annular furnace of the present invention. DETAILED DESCRIPTION

[0029] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is 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 a ring furnace for a seamless steel pipe low-temperature rolling process, comprising the following steps:

[0031] S1. Deformation resistance and section shrinkage are measured by using Gleeble thermal simulator using deformation resistance test and thermoplasticity test. Deformation resistance and section shrinkage are measured at every 50℃ from 850 to 1250℃, i.e., the deformation resistance and section shrinkage at nine temperatures of 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃ and 1250℃ are measured. The deformation resistance and section shrinkage between each temperature are obtained by the difference method.

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

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

[0034] S4, then determine whether the cross-sectional shrinkage at the temperature is greater than the set value. If it is less than the set value, the temperature is increased by 5°C and the comparison is continued until the cross-sectional shrinkage meets the set value;

[0035] S5, determining the temperature of the perforating roller according to the temperature drop from perforating to continuous rolling, and determining the temperature of the perforating roller by analogy;

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

[0037] S7, then determine whether the cross-sectional shrinkage 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 shrinkage rate meets the set value;

[0038] S8, determining the tube temperature of the annular furnace according to the temperature drop from the annular furnace to the perforation;

[0039] S9. Determine the flue gas heating temperature of the annular furnace according to the difference between the flue gas temperature and the tube blank temperature.

[0040] In the above step S1, the deformation resistance and the cross-sectional shrinkage are measured by using a Gleeble thermal simulator to perform a deformation resistance measurement test and a thermoplasticity measurement test.

[0041] The deformation rate of the deformation resistance test is 10-50 l / s, and the deformation degree is 40-60%;

[0042] The deformation rate of the thermoplasticity test is 10 to 50 l / s.

[0043] The values ​​of the load database include historical data of material, hole 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, cross-sectional shrinkage value, temperature drop from annular furnace to piercing, and difference between annular furnace flue gas temperature and billet temperature.

[0044] When comparing the loads in the above steps S3 to S7, the deformation resistance takes the maximum value of the current temperature.

[0045] Example

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

[0047] Table 1

[0048]

[0049]

[0050] The deformation resistance and section shrinkage rate of the material are shown in Table 2 below:

[0051] Table 2

[0052]

[0053] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process, characterized in that: The following steps are involved: S1. Determine deformation resistance and section shrinkage; S2. Determine the material and specifications of the low temperature rolling process; S3, extracting the loads of different materials with the same specifications from the load database, and comparing them with the continuous rolling loads. If the continuous rolling load exceeds the set value, the temperature is increased and the comparison is continued until the continuous rolling load meets the set value; S4, determining whether the cross-sectional shrinkage at the temperature is greater than the set value, if less than the set value, increasing the temperature and continuing the comparison until the cross-sectional shrinkage meets the set value; S5. Determine the temperature of the perforating roller according to the temperature drop from perforating to continuous rolling; S6. Extract the loads of different materials with the same specifications from the values ​​of the load database and compare them with the perforation load. If the perforation load exceeds the set value, increase the temperature and continue to compare until the perforation load meets the set value. S7, determine whether the cross-sectional shrinkage rate at the temperature is greater than the set value, if less than the set value, increase the temperature and continue to compare until the cross-sectional shrinkage rate meets the set value; S8, determining the tube temperature of the annular furnace according to the temperature drop from the annular furnace to the perforation; S9. Determine the outlet temperature of the annular furnace according to the difference between the flue gas temperature and the tube billet temperature.

2. The method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process according to claim 1, characterized in that: In the step S1, the deformation resistance and the cross-sectional shrinkage are measured by a Gleeble thermal simulator through a deformation resistance measurement test and a thermoplasticity measurement test.

3. The method for determining the temperature of the ring furnace for the low temperature rolling process of seamless steel pipe according to claim 2, characterized in that: The deformation rate of the deformation resistance test is 10 to 50 l / s, and the deformation degree is 40 to 60%; The deformation rate of the thermoplasticity test is 10 to 50 l / s.

4. The method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process according to claim 2, characterized in that: The deformation resistance and the cross-sectional shrinkage are measured at a temperature of 850°C to 1250°C at intervals of 50°C.

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

6. The method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process according to claim 1, characterized in that: When a non-existent temperature value is encountered during calculation, the deformation resistance and cross-sectional shrinkage are calculated by difference.

7. The method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process according to claim 1, characterized in that: When comparing the loads in steps S3 to S7, the deformation resistance takes the maximum value of the current temperature.

8. The method for determining the temperature of a ring furnace for a seamless steel pipe low temperature rolling process according to claim 1, characterized in that: The temperature in step S3 and step S6 is increased to 5°C.

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