Production process of steel for petroleum and natural gas pipe blank

Abstract

The invention relates to the technical field of production processes of steel for pipe blanks, and discloses a production process of steel for petroleum and natural gas pipe blanks, which comprises the steps of casting blank inspection, heating and rolling, pipe blank head and tail sawing, cold bed slow cooling and finished product detection. Wherein the casting blank inspection comprises the size, the weight, the appearance and the surface quality of a square billet, and during inspection and selection of the square billet, firstly, the square billet can be selected according to the mode; during heating and rolling, firstly, the surface of the pipe blank needs to be cleaned, oil stains, rust and other impurities need to be removed, so that uniform heating is ensured, according to the production process of the steel for the petroleum and natural gas pipe blank, the steel turnover frequency needs to be increased or scale breaking rolling needs to be adopted for the discharged steel blank at a 800 rolling mill by accurately controlling the temperature and carrying out dephosphorization treatment during the period, and the production efficiency is greatly improved. The surface oxide scale is removed thoroughly, the surface pitted surface defect caused by rolling and pressing-in of the oxide scale is avoided, and the situation that surface cracks are generated after the casting blank is rolled can be reduced in cooperation with subsequent slow cooling.

Description

Technical Field

[0001] The invention relates to the technical field of production technology of steel for tube billets, in particular to a production technology of steel for oil and gas tube billets. Background Art

[0002] Oil and gas pipelines are mainly used to manufacture pipelines for transporting oil, natural gas and other media. Pipeline transportation has become an effective tool for long-distance transportation of these media due to its high efficiency, economy, safety and pollution-free characteristics. The production of steel for oil and gas pipe billets is a complex and delicate process involving multiple links and strict quality control. Through scientific production processes and advanced technical means, we can ensure the production of high-quality and high-performance oil and gas pipelines to meet the requirements of safe oil and gas transportation.

[0003] When producing oil and gas pipes, it is necessary to first process the steel into pipe billets. At the same time, during the initial production of the steel, if there are cracks inside or impurities attached to its surface, and if it is not treated during the rolling process, it is easy to cause cracks and scars on the surface of the ingot. Moreover, when the ingot is rolled, due to the high temperature state of the ingot, it is easy for some small cracks on its surface to be difficult to be found, which may cause unqualified products to be ignored in the subsequent processing flow, resulting in a waste of resources. Summary of the invention

[0004] The object of the present invention is to provide a process for producing steel for petroleum and natural gas pipe billets to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: a production process of steel for petroleum and natural gas tube billets, including ingot inspection, hot rolling, tube billet head and tail sawing, cooling bed slow cooling and finished product inspection;

[0006] S1. The inspection of the billet includes the size, weight, shape and surface quality of the billet, and the billet can be selected according to the above method when inspecting and selecting;

[0007] S2. During heating and rolling, first, the surface of the tube billet needs to be cleaned to remove oil, rust and other impurities to ensure uniform heating, and the size, shape and quality of the tube billet need to be checked to ensure that there are no cracks or folding defects; before heating, push the heating equipment and gradually increase the furnace temperature. The heating speed should be adjusted according to the material and specifications of the tube billet. During the heating process, the temperature of the tube billet is monitored in real time by temperature monitoring equipment such as thermocouples to ensure that it reaches the temperature required for rolling. Usually, the temperature of the preheating section does not exceed 800°C, and the heating section is between 1000-1250°C; in the billet rolling stage, the continuous rolling start temperature does not exceed 950°C, and the final rolling temperature does not exceed 850°C. The heating furnace is strictly controlled in accordance with the heating temperature and furnace time in the corresponding steel production process control regulations;

[0008] S3. The tube billet is sawn at the head and tail, and the billet is sawn during rolling.

[0009] S4. After the steel billet is formed, the round steel is transported to the cooling bed and slowly cooled using a heat preservation cover. By slow cooling, the cooling rate of the steel can be controlled to avoid increased internal stress and surface cracks caused by rapid cooling.

[0010] S5. Finally, the finished product of steel should be inspected and accepted. There should be no cracks, scars, folds or inclusions on the surface of steel. Small cracks not exceeding 0.2mm from the actual size are allowed. Surface defects of steel can be removed. The removal depth should not exceed 5% of the nominal diameter from the actual size. The cleaned area should be smooth without edges and corners. The removal width should not be less than 6 times the depth. The maximum removal depth should not exceed 1 in the same section. The surface of steel should not be cleaned with flame.

[0011] Preferably, the casting inspection comprises the following specific steps:

[0012] S1.1. First check the quality certificate of the steel, including information such as steel type, chemical composition, mechanical properties, production date, production batch number, etc. Check whether there are cracks, bubbles, inclusions, and rust defects on the surface of the steel. Use measuring tools to check whether the size of the steel meets the requirements, including whether the length, width, thickness, diameter, etc. meet the requirements. After the steel is tested and found to be correct, it can be put into storage;

[0013] S1.2. Conduct chemical composition analysis. Take samples from each batch of steel for chemical composition analysis to ensure that the carbon, manganese, sulfur, phosphorus and other element contents of the steel meet the standards. Use equipment such as spectrometers to conduct rapid and accurate chemical composition analysis;

[0014] S1.3 Mechanical property test: the yield strength, tensile strength, elongation, impact toughness and other mechanical properties of steel are tested through tensile test and impact test, and the microstructure of steel is observed through metallographic microscope to check the uniformity of organization and the distribution of inclusions.

[0015] Preferably, the equipment heating in the heating rolling comprises the following steps:

[0016] S2.1. First, the rolling grooves, baffles, guides, rollers with sharp corners and burrs must be polished clean. Those that cannot be polished clean must be replaced in time;

[0017] S2.2, then check the firmware of the casting machine. When changing rolls and taking over, check the roll groove of the 800 rolling mill to see if there is severe wear and tear, meat loss, etc. Pay special attention to checking the surface of the push bed and the "vertical roll" to avoid scratches and abrasions on the surface of the red steel by the push bed, which may cause intermittent and superficial folding defects on the surface of the finished product;

[0018] S2.3. During the shift inspection and midway shutdown, check the wear of the rolling groove to see if there are any serious cracks or meat loss; check whether the cooling water pipe nozzle is aligned with the rolling groove, whether the connecting hose is leaking, etc. Check whether the guide is aligned, whether there is iron clamping, wire drawing, guide roller jamming, etc. If any abnormality is found, stop the machine in time for processing or replacement.

[0019] Preferably, the hot rolling comprises the following steps when rolling the cast slab:

[0020] S2.4. Before the ingot is transported out of the foundry, it needs to be preheated to reduce the risk of deformation and cracking during the rolling process. After preheating, the surface of the ingot needs to be cleaned to remove oxide scale and other impurities;

[0021] S2.5. The ingot enters the heating furnace and is heated to the temperature required for rolling. When rolling ingots of different sizes, the temperature is also different. The heating temperature of the ingot with a size of 350mm×450mm does not exceed 860℃, and the temperature of the heating section is 1140-1220℃, and the total heating time is not less than 280 minutes. The heating temperature of the ingot with a size of 280mm×280mm does not exceed 800℃, and the temperature of the heating section is 1150-1220℃, and the total heating time is not less than 180 minutes.

[0022] Preferably, attention should be paid to heating the ingot in S2.5 to ensure uniform temperature of the entire ingot to prevent visible positive and negative surfaces, and the temperature difference between the positive and negative surfaces should not exceed 30°C. If the positive and negative surfaces are obvious, rolling should be stopped immediately and the gas volume of the burner should be increased. Steel can be tapped only after the temperature returns to normal.

[0023] Preferably, when the ingot is pressed in S2.5, the overall temperature of the ingot is ensured to be uniform, and high-pressure water descaling is turned on during rolling. The descaling working pressure is not less than 14Mpa. To ensure the dephosphorization effect of high-pressure water descaling, the descaling pressure needs to be confirmed during rolling. If the iron oxide scale is not removed cleanly, the steel production should be stopped immediately, and a fitter should be arranged to check the water nozzle and pressure. Steel can only be produced after the treatment is completed. For the steel billets that have been discharged from the furnace, the number of steel turning times should be increased at the 800 rolling mill or scale breaking rolling should be adopted to remove the surface iron oxide scale cleanly to avoid surface pitting defects caused by the rolling and pressing of the iron oxide scale.

[0024] Preferably, when rolling the ingot in S2.5, it is also necessary to pay attention to the dephosphorization. If the descaling is not clean, the descaling process should be used for rolling. The 280 square billet must be turned over before rolling at 800 to remove the iron oxide scale that has not been removed from the upper surface. Chemical dephosphorization is to separate the phosphorus element on the surface of the casting from other elements by chemical reaction. Commonly used chemical dephosphorization methods include acid washing, alkali washing, etc. Acid washing usually uses strong acid (such as sulfuric acid, hydrochloric acid, etc.) to dissolve the phosphorus element on the surface of the ingot, while alkali washing uses strong alkali (such as sodium hydroxide, etc.) to react chemically with the phosphorus element to generate soluble phosphates, thereby achieving The purpose of phosphorus removal is that chemical phosphorus removal has a low cost and can reduce the damage of castings, but the concentration and time of chemical agents need to be strictly controlled, otherwise it will cause harm to the environment. At the same time, each batch of online pickling samples are taken during the rolling process. If surface defects such as folds, scratches, ears, scars, cracks, etc. are found on the online pickling surface, the continuous rolling inspection and confirmation should be notified, and the surface quality of each batch of online pickling should be recorded. The sampling personnel should record the surface conditions of each batch of online pickling defects in the MES system. If cracks or folds are found on the online pickling surface, the staff will block the quality.

[0025] Preferably, when sawing the head and tail of the tube billet after the heating and pressing of the ingot is completed, the length of the head and tail of the hot saw should be strictly carried out in accordance with the requirements of the operating procedures. The length can be increased but must not be shorter than the required length. The staff needs to check the sawing of the tail on the cooling bed every hour. If it is not sawed cleanly, the sawing length of the corresponding batch should be increased by about 40 to 220 mm.

[0026] Preferably, when slow cooling is carried out on the cooling bed after the sawing is completed, a heat preservation cover is used for slow cooling after the round steel is placed on the cooling bed, and a blower shall not be used for air cooling on the cooling bed. In order to ensure the temperature of the pit when the round steel goes offline, bundling shall not be stopped manually when collecting and bundling. The round steel shall be put into the pit for slow cooling in time after bundling. Slow cooling refers to the process of transporting the high-temperature ingot, generally above 500°C, into a slow cooling container, and slowly cooling it to below 200°C under an insulating state. This process helps to reduce the generation of micro cracks on the surface of the ingot and improve the quality of the ingot. The cooling rate should be controlled within a certain range to avoid cracks in the ingot due to too fast cooling. The specific cooling rate needs to be determined according to the material and size of the ingot. During the slow cooling process, the temperature of the ingot needs to be monitored regularly. This can be achieved by setting temperature measuring points in the slow cooling pit. The number and position of the temperature measuring points need to be determined according to the size and shape of the ingot to ensure the accuracy of the temperature measurement results. In order to ensure that the ingot can maintain a certain temperature during the slow cooling process, insulation measures need to be taken. This can be achieved by setting an insulation layer in the slow cooling pit and using insulation materials. At the same time, attention should also be paid to the sealing of the slow cooling pit to prevent the entry of cold air from the outside and affect the slow cooling effect.

[0027] Preferably, after the round steel has been cooled, the surface quality of each round steel is first checked during grinding. The folds, scratches, ears, scars, cracks and flash defects on the surface of the finished product should be ground clean. Defects that cannot be ground clean should be repaired. Steel billets that cannot be ground clean after re-repair are treated as unqualified products.

[0028] Compared with the prior art, the present invention provides a production process for steel for petroleum and natural gas pipe billets, which has the following beneficial effects:

[0029] 1. The production process of steel for oil and gas pipe billets can increase the number of steel turning times or adopt scale breaking rolling for the steel billets that have been out of the furnace at the 800 rolling mill to remove the surface oxide scale and avoid the surface pitting defects caused by the rolling and pressing of the oxide scale. In addition, the subsequent slow cooling can reduce the occurrence of surface cracks on the billet after rolling.

[0030] 2. In the production process of steel for petroleum and natural gas pipe billets, online pickling sampling is performed for each batch during the rolling process. When surface defects such as folds, scratches, ears, scars, and cracks are found on the online pickling surface, the continuous rolling mill should be notified for inspection and confirmation, and the surface quality of each batch of online pickling should be recorded. The sampling personnel should record the surface conditions of each batch of online pickling defects in the MES system. If cracks or folds are found on the online pickling surface, the staff will block the quality. Pickling sampling effectively avoids the situation where defective steel is not discovered.

[0031] 3. The production process of steel for oil and gas pipe billets helps to reduce the generation of micro cracks on the surface of the billet and improve the quality of the billet by slowly cooling the billet. The cooling rate should be controlled within a certain range to avoid cracks in the billet due to excessive cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0033] like Figure 1 As shown, the present invention provides a technical solution: a production process for steel for petroleum and natural gas pipe billets.

[0034] Including ingot inspection, hot rolling, tube head and tail sawing, cooling bed slow cooling and finished product inspection;

[0035] S1. The inspection of the billet includes the size, weight, shape and surface quality of the billet, and the billet can be selected according to the above method when inspecting and selecting;

[0036] S2. During heating and rolling, first, the surface of the tube billet needs to be cleaned to remove oil, rust and other impurities to ensure uniform heating, and the size, shape and quality of the tube billet need to be checked to ensure that there are no cracks or folding defects; before heating, push the heating equipment and gradually increase the furnace temperature. The heating speed should be adjusted according to the material and specifications of the tube billet. During the heating process, the temperature of the tube billet is monitored in real time by temperature monitoring equipment such as thermocouples to ensure that it reaches the temperature required for rolling. Usually, the temperature of the preheating section does not exceed 800°C, and the heating section is between 1000-1250°C; in the billet rolling stage, the continuous rolling start temperature does not exceed 950°C, and the final rolling temperature does not exceed 850°C. The heating furnace is strictly controlled in accordance with the heating temperature and furnace time in the corresponding steel production process control regulations;

[0037] S3. The billet is sawn at the head and tail. The billet is sawn during rolling. Sawing is an important part of steel production. It is used to cut the rolled steel into products of required length and shape.

[0038] S4. After the steel billet is formed, the round steel is transported to the cooling bed and slowly cooled using a heat preservation cover. By slow cooling, the cooling rate of the steel can be controlled to avoid increased internal stress and surface cracks caused by rapid cooling.

[0039] S5. Finally, the finished product of steel should be inspected and accepted. There should be no cracks, scars, folds or inclusions on the surface of steel. Small cracks not exceeding 0.2mm from the actual size are allowed. Surface defects of steel can be removed. The removal depth should not exceed 5% of the nominal diameter from the actual size. The cleaned area should be smooth without edges and corners. The removal width should not be less than 6 times the depth. The maximum removal depth should not exceed 1 in the same section. The surface of steel should not be cleaned with flame.

[0040] The ingot inspection includes the following specific steps:

[0041] S1.1. First check the quality certificate of the steel, including information such as steel type, chemical composition, mechanical properties, production date, production batch number, etc. Check whether there are cracks, bubbles, inclusions, and rust defects on the surface of the steel. Use measuring tools to check whether the size of the steel meets the requirements, including whether the length, width, thickness, diameter, etc. meet the requirements. After the steel is tested and found to be correct, it can be put into storage;

[0042] S1.2. Conduct chemical composition analysis. Take samples from each batch of steel for chemical composition analysis to ensure that the carbon, manganese, sulfur, phosphorus and other element contents of the steel meet the standards. Use equipment such as spectrometers to conduct rapid and accurate chemical composition analysis;

[0043] S1.3 Mechanical property test: the yield strength, tensile strength, elongation, impact toughness and other mechanical properties of steel are tested through tensile test and impact test, and the microstructure of steel is observed through metallographic microscope to check the uniformity of organization and the distribution of inclusions.

[0044] Heating equipment during hot rolling includes the following steps:

[0045] S2.1. First, the rolling grooves, baffles, guides, rollers with sharp corners and burrs must be polished clean. Those that cannot be polished clean must be replaced in time;

[0046] S2.2, then check the firmware of the casting machine. When changing rolls and taking over, check the roll groove of the 800 rolling mill to see if there is severe wear and tear, meat loss, etc. Pay special attention to checking the surface of the push bed and the "vertical roll" to avoid scratches and abrasions on the surface of the red steel by the push bed, which may cause intermittent and superficial folding defects on the surface of the finished product;

[0047] S2.3. During the shift inspection and midway shutdown, check the wear of the rolling groove to see if there are any serious cracks or meat loss; check whether the cooling water pipe nozzle is aligned with the rolling groove, whether the connecting hose is leaking, etc. Check whether the guide is aligned, whether there is iron clamping, wire drawing, guide roller jamming, etc. If any abnormality is found, stop the machine in time for processing or replacement.

[0048] The hot rolling process includes the following steps when rolling the cast slab:

[0049] S2.4. Before the ingot is transported out of the foundry, it needs to be preheated to reduce the risk of deformation and cracking during the rolling process. After preheating, the surface of the ingot needs to be cleaned to remove oxide scale and other impurities;

[0050] S2.5. The ingot enters the heating furnace and is heated to the temperature required for rolling. When rolling ingots of different sizes, the temperature is also different. The heating temperature of the ingot with a size of 350mm×450mm does not exceed 860℃, and the temperature of the heating section is 1140-1220℃, and the total heating time is not less than 280 minutes. The heating temperature of the ingot with a size of 280mm×280mm does not exceed 800℃, and the temperature of the heating section is 1150-1220℃, and the total heating time is not less than 180 minutes.

[0051] When heating the ingot in S2.5, attention should be paid to ensure that the overall temperature of the ingot is uniform to prevent the visible positive and negative surfaces. The temperature difference between the positive and negative surfaces should not exceed 30°C. If the positive and negative surfaces are obvious, rolling should be stopped immediately and the gas volume of the burner should be increased. Steel can be tapped only after the temperature returns to normal.

[0052] When pressing the ingot in S2.5, ensure that the overall temperature of the ingot is uniform. Start high-pressure water descaling during rolling. The descaling working pressure is not less than 14Mpa. To ensure the dephosphorization effect of high-pressure water descaling, the descaling pressure needs to be confirmed during rolling. If the iron oxide scale is not removed cleanly, the steel production should be stopped immediately, and the fitter should be arranged to check the water nozzle and pressure. Steel can only be produced after the treatment. For the steel billets that have been discharged from the furnace, the number of steel turning times should be increased at the 800 rolling mill or scale breaking rolling should be adopted to remove the surface iron oxide scale cleanly to avoid surface pitting defects caused by the rolling and pressing of the iron oxide scale.

[0053] When rolling the ingot in S2.5, it is also necessary to pay attention to the dephosphorization. If the descaling is not clean, the descaling process should be used for rolling. The 280 square billet must be turned over before rolling at 800 to remove the unremoved iron oxide scale on the upper surface. Chemical dephosphorization is to separate the phosphorus element on the surface of the casting from other elements by chemical reaction. Commonly used chemical dephosphorization methods include pickling and alkali washing. Pickling usually uses strong acid (such as sulfuric acid, hydrochloric acid, etc.) to dissolve the phosphorus element on the surface of the ingot, while alkali washing uses strong alkali (such as sodium hydroxide, etc.) to react chemically with the phosphorus element to generate soluble phosphates, thereby achieving the purpose of dephosphorization. Purpose: Chemical phosphorus removal has a low cost and can reduce the damage of castings, but the concentration and time of chemical agents need to be strictly controlled, otherwise it will cause harm to the environment. At the same time, each batch of online pickling samples are taken during the rolling process. If surface defects such as folds, scratches, ears, scars, cracks, etc. are found on the online pickling surface, the continuous rolling inspection and confirmation should be notified, and the surface quality of each batch of online pickling should be recorded. The sampling personnel should record the surface conditions of each batch of online pickling defects in the MES system. If cracks or folds are found on the online pickling surface, the staff will block the quality.

[0054] When sawing the head and tail of the tube billet after the heating and pressing of the ingot is completed, the length of the head and tail of the hot saw should be strictly carried out in accordance with the operating procedures. The length can be increased but must not be shorter than the required length. The staff needs to check the sawing condition of the tail on the cooling bed every hour. If it is not sawed cleanly, the sawing length of the corresponding batch should be increased by about 40 to 220 mm.

[0055] After sawing, the round steel is put on the cooling bed and then slowly cooled. A heat preservation cover is used for slow cooling. Blowers shall not be used for air cooling on the cooling bed. To ensure the temperature of the pit when it goes offline, bundling shall not be stopped manually during collection and bundling. The round steel shall be put into the pit for slow cooling in time after bundling. Slow cooling refers to the process of transporting high-temperature ingots, generally above 500°C, into slow cooling containers and slowly cooling them to below 200°C under heat preservation conditions. This process helps to reduce the generation of micro cracks on the surface of the ingot and improve the quality of the ingot. The cooling rate should be controlled within a certain range to avoid cracks in the ingot due to too fast cooling. The specific cooling rate needs to be determined according to the material and size of the ingot. During the slow cooling process, the temperature of the ingot needs to be monitored regularly. This can be achieved by setting temperature measuring points in the slow cooling pit. The number and position of the temperature measuring points need to be determined according to the size and shape of the ingot to ensure the accuracy of the temperature measurement results. In order to ensure that the ingot can maintain a certain temperature during the slow cooling process, insulation measures need to be taken. This can be achieved by setting an insulation layer in the slow cooling pit and using insulation materials. At the same time, attention should also be paid to the sealing of the slow cooling pit to prevent the entry of cold air from the outside and affect the slow cooling effect.

[0056] After the round steel has cooled, the surface quality of each steel bar shall be checked during grinding. The folds, scratches, ears, scars, cracks and flash defects on the surface of the finished product shall be ground clean. If the defects cannot be ground clean, they shall be repaired. If the steel billet cannot be ground clean after repair, it shall be treated as a defective product.

[0057] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A process for producing steel for petroleum and natural gas tube blanks, characterized in that: Including ingot inspection, hot rolling, tube head and tail sawing, cooling bed slow cooling and finished product inspection; S1. The inspection of the billet includes the size, weight, shape and surface quality of the billet. When inspecting and selecting the billet, the billet can first be selected according to the above method; S2. During heating and rolling, first, the surface of the tube billet needs to be cleaned to remove oil, rust and other impurities to ensure uniform heating, and the size, shape and quality of the tube billet need to be checked to ensure that there are no cracks or folding defects; Before heating, push the heating equipment and gradually increase the furnace temperature. The heating speed should be adjusted according to the material and specifications of the tube billet. During the billet rolling stage, the continuous rolling start temperature shall not exceed 950°C, and the final rolling temperature shall not exceed 850°C. The heating furnace shall be strictly controlled according to the heating temperature and furnace time in the production process control regulations of the corresponding steel grade. S3, sawing the head and tail of the tube billet, and sawing the billet after rolling; S4. After the steel billet is formed, the round steel is transported to the cooling bed and then slowly cooled using a heat preservation cover; S5. The last step is the finished steel product acceptance. There shall be no cracks, scars, folds or inclusions on the surface of the steel. Small cracks not exceeding 0.2mm from the actual size are allowed.

2. A process for producing steel for petroleum and natural gas tube blanks according to claim 1, characterized in that: The casting inspection comprises the following specific steps: S1.

1. First check the quality certificate of the steel, including the steel type, chemical composition, mechanical properties, production date, production batch number information, check whether there are cracks, bubbles, inclusions, rust defects on the surface of the steel, use measuring tools to check whether the size of the steel meets the requirements, including whether the length, width, thickness, and diameter meet the requirements. After the steel is tested and found to be correct, it can be put into storage; S1.

2. Conduct chemical composition analysis. Take samples from each batch of steel for chemical composition analysis to ensure that the carbon, manganese, sulfur and phosphorus content of the steel meets the standards. Use spectrometer equipment to conduct rapid and accurate chemical composition analysis; S1.3 Mechanical property test: the yield strength, tensile strength, elongation and impact toughness of steel are tested through tensile test and impact test. The microstructure of steel is observed through metallographic microscope to check the uniformity of organization and the distribution of inclusions.

3. The process for producing steel for petroleum and natural gas tube blanks according to claim 1, characterized in that: The equipment heating in the heating rolling process comprises the following steps: S2.

1. First, the rolling grooves, baffles, guides, rollers with sharp corners and burrs must be polished clean. Those that cannot be polished clean must be replaced in time; S2.2, then check the firmware of the casting machine. When changing rolls and taking over, check the roll grooves of the 800 rolling mill to see if there is severe wear and tear, and pay special attention to checking the surface of the push bed and the "vertical roll"; S2.

3. During the shift inspection and mid-term shutdown, check the wear of the rolling groove to see if there are any serious cracks or loss of meat; check whether the nozzle of the cooling water pipe is aligned with the rolling groove, and whether the connecting hose is leaking.

4. The process for producing steel for petroleum and natural gas tube blanks according to claim 1, characterized in that: The hot rolling includes the following steps when rolling the cast slab: S2.

4. Before the ingot is transported out of the foundry, it needs to be preheated to reduce the risk of deformation and cracking during the rolling process. After preheating, the surface of the ingot needs to be cleaned to remove oxide scale and other impurities; S2.

5. The ingot enters the heating furnace and is heated to the temperature required for rolling. When rolling ingots of different sizes, the temperature is also different.

5. A process for producing steel for petroleum and natural gas tube blanks according to claim 4, characterized in that: When heating the ingot in S2.5, attention should be paid to ensure that the overall temperature of the ingot is uniform, to prevent the visible positive and negative sides, and the temperature difference between the positive and negative sides should not exceed 30°C.

6. A process for producing steel for petroleum and natural gas tube blanks according to claim 5, characterized in that: When the ingot is pressed in S2.5, the overall temperature of the ingot is ensured to be uniform. During the rolling process, high-pressure water descaling is turned on, and the descaling working pressure is not less than 14Mpa. To ensure the dephosphorization effect of high-pressure water descaling, the descaling pressure needs to be confirmed during rolling. If the iron oxide scale is not removed cleanly, the steel production should be stopped immediately, and the fitter should be arranged to check the water nozzle and pressure. Steel can be produced only after the processing is completed.

7. The process for producing steel for petroleum and natural gas tube blanks according to claim 5, characterized in that: When rolling the ingot in S2.5, it is also necessary to pay attention to the dephosphorization and the use of the descaling process when the descaling is not clean. The 280 square billet must be turned over before rolling at 800 to remove the iron oxide scale that has not been removed from the upper surface. At the same time, each batch of online pickling samples are taken during the rolling process. When folds, scratches, ears, scars, and cracks are found on the online pickling surface, the continuous rolling inspection and confirmation should be notified, and the quality of the online pickling surface of each batch should be recorded. The sampling personnel should record the online pickling surface conditions of each batch with defects in the MES system. If cracks and folds are found on the online pickling surface, the staff will block the quality.

8. The process for producing steel for petroleum and natural gas tube blanks according to claim 1, characterized in that: When the billet is cut from head to tail after the billet is heated and pressed, the length of the hot saw cutting from head to tail should be strictly carried out in accordance with the operating procedures. The length can be increased but must not be shorter than the required length.

9. A process for producing steel for petroleum and natural gas tube blanks according to claim 8, characterized in that: When the round steel is placed on the cooling bed for slow cooling after the sawing is completed, a heat preservation cover is used for slow cooling. A blower shall not be used for air cooling on the cooling bed. To ensure the temperature of the steel entering the pit, baling shall not be stopped manually during collection and baling. The steel shall be put into the pit for slow cooling in time after baling.

10. The process for producing steel for petroleum and natural gas tube blanks according to claim 1, characterized in that: After the round steel has been cooled, the surface quality of each round steel is checked during grinding. The folds, scratches, ears, scars, cracks and flash defects on the surface of the finished product must be ground clean. If the defects cannot be ground clean, they should be repaired. If the steel billet cannot be ground clean after repair, it will be treated as a defective product.

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