Rolling temperature control process for improving surface quality of alloy pipe blank T12

Abstract

The invention relates to the technical field of ferrous metallurgy, and discloses a rolling temperature control process for improving the surface quality of an alloy pipe blank T12, which comprises the following steps: S1, preheating pretreatment of a casting blank, S2, segmented heating control of a heating furnace, S3, precise calibration of tapping temperature, S4, dynamic temperature control in a rolling process, S5, slow cooling treatment after rolling, and S6, whole-process temperature monitoring and adjustment. According to the process, the risk of initial thermal stress is reduced, specifically, the preheating temperature is stabilized at 400-600 DEG C through segmented preheating and stepped heating control before the casting blank enters a furnace, the temperature difference between the surface and the core of the casting blank is effectively reduced, initial thermal stress generated due to the too large temperature difference is avoided, generation and expansion of subsurface cracks are prevented from the rolling source, a brittle zone is avoided, and the production efficiency is improved. Material plasticity is improved, specifically, the staying time of the steel billet in a brittleness interval is shortened by rapidly passing through a low-temperature section of a third brittleness temperature zone through a segmented heating process; and the temperature is subsequently increased to 1180-1250 DEG C, heat preservation is conducted for 2.0-4.0 h, it is ensured that the steel billet is completely austenitized, grains are refined, the material brittleness is remarkably reduced, and the crack resistance in the rolling process is enhanced.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a rolling temperature control process for improving the surface quality of alloy tube blank T12. Background Technology

[0002] Low-carbon steel with a carbon content of less than 0.15% is prone to peritectic reaction and is easily placed in the third brittle temperature zone of 700-900℃ during rolling. In this zone, the material has poor plasticity and is extremely sensitive to thermal and mechanical stress. The existing rolling temperature control process has significant defects: The lack of scientific preheating treatment before the billet enters the furnace results in excessive temperature differences between the surface and core, inducing initial thermal stress; the heating process does not employ a segmented heating mode, causing the billet to remain in the third brittle temperature zone for an extended period with insufficient heat homogenization and insulation, leading to uneven internal composition and temperature distribution, and the inability to eliminate subcutaneous microcracks generated during continuous casting; the lack of precise calibration of the exit temperature easily leads to overheating at high temperatures or hard rolling at low temperatures; the absence of temperature monitoring for each pass during rolling results in some passes falling into the brittle zone, causing the billet to undergo rolling deformation in a brittle state, further expanding cracks; the crude post-rolling cooling method, with strong winds causing rapid cooling of the billet surface, generates thermal stress, and closed microcracks are prone to reopening; the incomplete temperature monitoring system throughout the entire process prevents timely adjustments after temperature deviations, resulting in frequent defects such as scrap and cracks, low finished product qualification rates, and a significant increase in production costs due to batch scrap, severely impacting production efficiency and product market competitiveness. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a rolling temperature control process for improving the surface quality of alloy tube billets T12. This process has advantages such as reducing the risk of initial thermal stress and solves the problems of crude post-rolling cooling methods, strong direct wind blowing causing rapid cooling of the billet surface, generating thermal stress, and easily reopening closed microcracks.

[0004] (II) Technical Solution To achieve the above-mentioned goal of reducing the risk of initial thermal stress, the present invention provides the following technical solution: a rolling temperature control process for improving the surface quality of alloy tube billet T12, including S1 billet preheating and pretreatment, S2 segmented heating furnace temperature control, S3 precise calibration of furnace exit temperature, S4 dynamic temperature control during rolling process, S5 slow cooling treatment after rolling, and S6 full-process temperature monitoring and adjustment. The S2 segmented heating furnace temperature control includes S201 first stage heating, S202 second stage heating and S203 heat soaking and heat preservation. The dynamic temperature control of the S4 rolling process includes the S401 initial rolling temperature, the S402 inter-pass temperature maintenance, and the S403 final rolling temperature control.

[0005] Preferably, the S1 billet undergoes preheating and pretreatment: Before the billet is put into the furnace, it is preheated in sections. The preheating temperature is controlled at 400-600℃ and the holding time is 1.5-3.0h. A stepped heating method is adopted, with an initial heating rate of ≤100℃ / h and a later heating rate of ≤150℃ / h, to avoid excessive temperature difference between the surface and core of the billet, thereby preventing thermal stress and the propagation of subcutaneous cracks.

[0006] Preferably, the first stage of heating in S201 involves raising the temperature from the preheating temperature to 850-900℃ at a rate of 120-180℃ / h, avoiding the low-temperature section of the third brittle temperature zone (700-900℃) and reducing the residence time of the billet in the brittle zone.

[0007] Preferably, the second stage of heating in S202 involves raising the temperature from 850-900℃ to 1180-1250℃ at a rate of 100-150℃ / h, ensuring complete austenitization of the steel billet, refining the grains, and reducing material brittleness.

[0008] Preferably, the S203 heat-soaking insulation is performed at a temperature of 1180-1250℃ for 2.0-4.0 hours to ensure the uniformity of the composition and temperature of the billet, eliminate the hidden danger of subcutaneous micro-cracks generated during continuous casting, and ensure that the temperature fluctuation inside the furnace during the insulation stage is ≤±15℃.

[0009] Preferably, the S3 furnace exit temperature is precisely calibrated: Thirty minutes before the billet is tapped out of the furnace, an infrared thermometer is used to measure the temperature at multiple points on each billet (3-5 points per billet) to ensure that the tapping temperature is stable at 1150-1220℃ and the temperature difference between points on a single billet is ≤25℃. If the temperature is below 1150℃, extend the heating time by 30-60 minutes; if the temperature is above 1220℃, reduce the furnace power and wait for the temperature to drop to the set range before removing the product from the furnace to avoid defects caused by overheating or low-temperature rolling.

[0010] Preferably, the initial rolling temperature of S401 is controlled at 1120-1180℃ to ensure good material plasticity in the early stage of rolling and reduce the mechanical stress impact of rolling force on the billet. S402 Interpass Temperature Maintenance: After each rolling pass, the billet temperature is monitored in real time by infrared thermography to ensure that the temperature between each pass is maintained at 950-1100℃, always higher than the upper limit of the third brittle temperature zone, so as to avoid the billet from being subjected to rolling deformation in a brittle state.

[0011] Preferably, the final rolling temperature control of S403 is as follows: the final rolling temperature is strictly controlled at 900-950℃ to ensure that the billet temperature after final rolling is still higher than the upper limit of the brittle zone, and to prevent cracks from being generated due to a sudden drop in temperature during the final rolling process.

[0012] Preferably, the S5 post-rolling slow cooling treatment: After the final rolling is completed, the steel billet enters the slow cooling zone for controlled cooling. The cooling rate is controlled at 5-15℃ / min. After cooling to below 600℃, it is then transferred to natural cooling. During the slow cooling process, avoid strong winds blowing directly on the billet and use a uniform air supply method to prevent the rapid cooling of the billet surface from generating thermal stress and to prevent closed micro-cracks from reopening.

[0013] Preferably, the temperature in step S6 is monitored and adjusted throughout the entire process: An online infrared temperature measurement system is configured, with temperature measurement points set at the outlet of the heating furnace, the inlet of the roughing mill, the inlet and outlet of the finishing mill, and the outlet of the slow cooling zone. Temperature data is recorded every 30 minutes to form a temperature curve for the entire process. If the temperature of any step is found to deviate from the set range (the temperature at the finishing mill exit is below 900℃ or above 950℃), the heating furnace temperature, rolling rhythm or slow cooling air speed should be adjusted immediately to ensure that the process parameters are matched in real time. Three to five billets from each batch are randomly selected for temperature traceability analysis. Combined with the finished product quality inspection results, the temperature control parameter range is dynamically optimized.

[0014] (III) Beneficial Effects Compared with the prior art, the present invention provides a rolling temperature control process for improving the surface quality of alloy tube blank T12, which has the following beneficial effects: 1. The rolling temperature control process for improving the defects of rotten steel in T12 round steel reduces the risk of initial thermal stress: by segmented preheating and step-by-step temperature control before the billet enters the furnace, the preheating temperature is stabilized at 400-600℃, which effectively reduces the temperature difference between the surface and core of the billet and avoids the generation of initial thermal stress due to excessive temperature difference, thus preventing the initiation and propagation of subcutaneous cracks from the rolling source.

[0015] 2. The rolling temperature control process for improving the defects of rotten T12 steel round bars avoids the brittle zone and improves the plasticity of the material: a segmented heating process is adopted to quickly pass through the low-temperature section of the third brittle temperature zone (700-900℃), reducing the residence time of the billet in the brittle zone; the temperature is then raised to 1180-1250℃ and held for 2.0-4.0h to ensure that the billet is fully austenitized and the grains are refined, which significantly reduces the brittleness of the material and enhances the crack resistance during the rolling process.

[0016] 3. The rolling temperature control process for improving the defects of rotten T12 steel round bars eliminates potential crack hazards: precise control of furnace exit temperature (1150-1220℃) and temperature difference at individual billet points avoids high-temperature overheating or low-temperature hard rolling; during the rolling process, the temperature between passes is maintained at 950-1100℃ and the final rolling temperature is maintained at 900-950℃, always above the upper limit of the brittle zone, preventing the billet from being deformed in a brittle state, inhibiting the expansion of the original micro-cracks, and at the same time, the heat soaking and heat preservation process can effectively eliminate the hidden danger of subcutaneous cracks remaining from continuous casting.

[0017] 4. The rolling temperature control process for improving the defects of T12 steel round bars is as follows: This process prevents the reopening of cracks after rolling. After rolling, a controllable slow cooling rate of 5-15℃ / min is adopted to cool to below 600℃ and then switch to natural cooling. This avoids the rapid cooling of the surface caused by strong wind blowing and prevents the reopening of closed micro-cracks due to thermal stress. At the same time, it reduces the generation of high-temperature oxides and improves the surface quality of round bars.

[0018] 5. The rolling temperature control process for improving the defects of rotten steel in T12 round steel enhances production stability and yield: a multi-point temperature monitoring and real-time adjustment mechanism throughout the entire process ensures accurate matching of temperature parameters at each stage, avoiding quality fluctuations caused by temperature deviations; combined with batch traceability and parameter optimization, it continuously improves process adaptability, significantly reduces the incidence of rotten steel and crack defects, increases the yield of finished products, reduces scrap losses, lowers production costs, and enhances production stability and product market competitiveness. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a technical solution, specifically a rolling temperature control process for improving the surface quality of alloy tube billet T12, comprising the following process: S1 billet preheating and pretreatment: Before the billet is put into the furnace, it is preheated in sections. The preheating temperature is controlled at 400-600℃ and the holding time is 1.5-3.0h. A stepped heating method is adopted, with an initial heating rate of ≤100℃ / h and a later heating rate of ≤150℃ / h, to avoid excessive temperature difference between the surface and core of the billet, thereby preventing thermal stress and subcutaneous crack propagation. S2 heating furnace segmented temperature control: S201 First stage of heating: from the preheating temperature to 850-900℃, the heating rate is 120-180℃ / h, avoiding the low temperature section of the third brittle temperature zone (700-900℃), and reducing the residence time of the billet in the brittle zone; S202 second stage heating: from 850-900℃ to 1180-1250℃, heating rate 100-150℃ / h, to ensure complete austenitization inside the billet, refine grains, and reduce material brittleness; S203 heat preservation: heat preservation at 1180-1250℃ for 2.0-4.0h to ensure the uniformity of billet composition and temperature, eliminate the hidden danger of subcutaneous micro-cracks generated during continuous casting, and ensure that the temperature fluctuation inside the furnace during the heat preservation stage is ≤±15℃. S3 furnace exit temperature precise calibration: Thirty minutes before the billet is tapped out of the furnace, an infrared thermometer is used to measure the temperature at multiple points on each billet (3-5 points per billet) to ensure that the tapping temperature is stable at 1150-1220℃ and the temperature difference between points on a single billet is ≤25℃. If the temperature is below 1150℃, extend the heating time by 30-60 minutes; if the temperature is above 1220℃, reduce the furnace power and wait for the temperature to drop to the set range before removing the product from the furnace to avoid defects caused by overheating or low-temperature rolling. Dynamic temperature control during S4 rolling process: S401 initial rolling temperature: The initial rolling temperature of the first pass is controlled at 1120-1180℃ to ensure good material plasticity in the early stage of rolling and reduce the mechanical stress impact of rolling force on the billet. S402 Interpass Temperature Maintenance: After each rolling pass, the billet temperature is monitored in real time by infrared thermography to ensure that the temperature between each pass is maintained at 950-1100℃, always higher than the upper limit of the third brittle temperature zone, so as to avoid the billet from being subjected to rolling deformation in a brittle state. S403 Final Rolling Temperature Control: The final rolling temperature is strictly controlled at 900-950℃ to ensure that the billet temperature after final rolling is still higher than the upper limit of the brittle zone, and to prevent cracks from occurring due to a sudden drop in temperature during the final rolling process. S5 post-rolling slow cooling treatment: After the final rolling is completed, the steel billet enters the slow cooling zone for controlled cooling. The cooling rate is controlled at 5-15℃ / min. After cooling to below 600℃, it is then transferred to natural cooling. During the slow cooling process, avoid strong winds blowing directly on the surface and use a uniform air supply method to prevent the rapid cooling of the steel billet surface from generating thermal stress and to prevent closed microcracks from reopening. S6 Temperature Monitoring and Adjustment Throughout the Flow: An online infrared temperature measurement system is configured, with temperature measurement points set at the outlet of the heating furnace, the inlet of the roughing mill, the inlet and outlet of the finishing mill, and the outlet of the slow cooling zone. Temperature data is recorded every 30 minutes to form a temperature curve for the entire process. If the temperature of any step is found to deviate from the set range (the temperature at the finishing mill exit is below 900℃ or above 950℃), the heating furnace temperature, rolling rhythm or slow cooling air speed should be adjusted immediately to ensure that the process parameters are matched in real time. Three to five billets from each batch are randomly selected for temperature traceability analysis. Combined with the finished product quality inspection results, the temperature control parameter range is dynamically optimized. Furthermore, this process reduces the risk of initial thermal stress: by segmented preheating and step-by-step temperature control before the billet enters the furnace, the preheating temperature is stabilized at 400-600℃, which effectively reduces the temperature difference between the billet surface and the core, avoids the generation of initial thermal stress due to excessive temperature difference, and prevents the initiation and expansion of subcutaneous cracks from the rolling source. Furthermore, this process avoids the brittle zone and improves the material's plasticity: a segmented heating process is adopted to quickly pass through the low-temperature section of the third brittle temperature zone (700-900℃), reducing the time the billet spends in the brittle zone; the subsequent heating to 1180-1250℃ and holding for 2.0-4.0 hours ensures complete austenitization and grain refinement of the billet, significantly reducing material brittleness and enhancing crack resistance during rolling. Furthermore, this process eliminates potential cracking hazards: precisely controlling the furnace exit temperature (1150-1220℃) and the temperature difference at individual billet points avoids high-temperature overheating or low-temperature hard rolling; maintaining the inter-pass temperature at 950-1100℃ and the final rolling temperature at 900-950℃ during rolling, always above the upper limit of the brittle zone, preventing the billet from being deformed in a brittle state, inhibiting the expansion of existing micro-cracks, and at the same time, the heat soaking and heat preservation process can effectively eliminate the hidden danger of subcutaneous cracks remaining from continuous casting; Furthermore, this process prevents the reopening of cracks after rolling: after rolling, a controllable slow cooling rate of 5-15℃ / min is adopted, and the temperature is cooled to below 600℃ before natural cooling is introduced. This avoids the rapid cooling of the surface caused by strong winds, prevents closed microcracks from reopening due to thermal stress, and reduces the generation of high-temperature oxides, thereby improving the surface quality of round steel. Furthermore, this process enhances production stability and yield: a multi-point temperature monitoring and real-time adjustment mechanism throughout the entire process ensures precise matching of temperature parameters at each stage, avoiding quality fluctuations caused by temperature deviations; combined with batch traceability and parameter optimization, it continuously improves process adaptability, significantly reduces the incidence of defects such as rotten steel and cracks, increases the yield of finished products, reduces scrap losses, lowers production costs, and enhances production stability and product market competitiveness.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rolling temperature control process for improving the surface quality of alloy tube billet T12, comprising: S1 billet preheating and pretreatment; S2 segmented heating furnace temperature control; S3 precise furnace exit temperature calibration; S4 dynamic temperature control during rolling; S5 slow cooling treatment after rolling; and S6 full-process temperature monitoring and adjustment, characterized in that: The segmented heating control of the S2 heating furnace includes S201 first stage heating, S202 second stage heating and S203 heat equalization and heat preservation; The dynamic temperature control of the S4 rolling process includes the S401 initial rolling temperature, the S402 inter-pass temperature maintenance, and the S403 final rolling temperature control.

2. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The preheating and pretreatment of the S1 billet: Before the billet is put into the furnace, it is preheated in sections. The preheating temperature is controlled at 400-600℃ and the holding time is 1.5-3.0h. A stepped heating method is adopted, with an initial heating rate of ≤100℃ / h and a later heating rate of ≤150℃ / h, to avoid excessive temperature difference between the surface and core of the billet, thereby preventing thermal stress and the propagation of subcutaneous cracks.

3. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The first stage of heating in S201 involves raising the temperature from the preheating temperature to 850-900℃ at a rate of 120-180℃ / h, avoiding the low-temperature section of the third brittle temperature zone (700-900℃) and reducing the residence time of the billet in the brittle zone.

4. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The second stage of heating in S202 involves raising the temperature from 850-900℃ to 1180-1250℃ at a rate of 100-150℃ / h to ensure complete austenitization of the steel billet, refine the grains, and reduce material brittleness.

5. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The S203 heat-soaking and heat preservation method involves maintaining the temperature at 1180-1250℃ for 2.0-4.0 hours to ensure the uniformity of the billet composition and temperature, eliminate the potential for subcutaneous micro-cracks generated during continuous casting, and ensure that the temperature fluctuation inside the furnace during the heat preservation stage is ≤±15℃.

6. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The S3 furnace exit temperature is precisely calibrated: Thirty minutes before the billet is tapped out of the furnace, an infrared thermometer is used to measure the temperature at multiple points on each billet (3-5 points per billet) to ensure that the tapping temperature is stable at 1150-1220℃ and the temperature difference between points on a single billet is ≤25℃. If the temperature is below 1150℃, extend the heating time by 30-60 minutes; if the temperature is above 1220℃, reduce the furnace power and wait for the temperature to drop to the set range before removing the product from the furnace to avoid defects caused by overheating or low-temperature rolling.

7. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The S401 initial rolling temperature is controlled at 1120-1180℃ to ensure good material plasticity in the early stage of rolling and reduce the mechanical stress impact of rolling force on the billet. S402 Interpass Temperature Maintenance: After each rolling pass, the billet temperature is monitored in real time by infrared thermography to ensure that the temperature between each pass is maintained at 950-1100℃, always higher than the upper limit of the third brittle temperature zone, so as to avoid the billet from being subjected to rolling deformation in a brittle state.

8. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The S403 final rolling temperature control: The final rolling temperature is strictly controlled at 900-950℃ to ensure that the billet temperature after final rolling is still higher than the upper limit of the brittle zone, and to prevent cracks from being generated due to a sudden drop in temperature during the final rolling process.

9. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The S5 post-rolling slow cooling treatment: After the final rolling is completed, the steel billet enters the slow cooling zone for controlled cooling. The cooling rate is controlled at 5-15℃ / min. After cooling to below 600℃, it is then transferred to natural cooling. During the slow cooling process, avoid strong winds blowing directly on the surface and use a uniform air supply method to prevent the rapid cooling of the billet surface from generating thermal stress and to prevent closed micro-cracks from reopening.

10. The rolling temperature control process for improving the surface quality of alloy tube blank T12 according to claim 1, characterized in that: The S6 temperature is monitored and adjusted throughout the entire process: An online infrared temperature measurement system is configured, with temperature measurement points set at the outlet of the heating furnace, the inlet of the roughing mill, the inlet and outlet of the finishing mill, and the outlet of the slow cooling zone. Temperature data is recorded every 30 minutes to form a temperature curve for the entire process. If the temperature of any step is found to deviate from the set range (the temperature at the finishing mill exit is below 900℃ or above 950℃), the heating furnace temperature, rolling rhythm or slow cooling air speed should be adjusted immediately to ensure that the process parameters are matched in real time. Three to five billets from each batch are randomly selected for temperature traceability analysis. Combined with the finished product quality inspection results, the temperature control parameter range is dynamically optimized.