A method for smelting a round billet of a low-carbon large-section hot-rolled seamless line pipe

Abstract

The application discloses a low-carbon large-section hot-rolled seamless pipeline pipe round billet smelting method, and the chemical component mass percentage of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material is as follows: C 0.06-0.12%, Si 0.10-0.40%, Mn 1.35-1.60%, V 0.02-0.05%, Ti 0.005-0.03%, Al 0.005-0.045%, P≤0.015%, S≤0.003%, the rest is Fe and trace impurities, and the total mass percentage is 100%; and the smelting production process comprises the following steps: converter smelting, LF refining, VD vacuum degassing, continuous casting machine continuous casting, fire cutting and warehousing. The application aims to provide a low-carbon large-section hot-rolled seamless pipeline pipe round billet smelting method, which can meet the technical requirements of the large-diameter seamless pipeline pipe for long-distance acid oil and gas transportation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material metallurgy, in particular to a low-carbon large-section hot-rolled seamless pipeline pipe round billet smelting method. BACKGROUND

[0002] The pipeline for oil and gas transportation has the characteristics of economy, safety, high efficiency, uninterruptedness, and no pollution, etc. In addition to being used for long-distance transportation of oil and natural gas, it can also be used as an important means of transportation for coal and other solid materials. The proportion of crude oil transported by pipeline accounts for 85% of the total primary output, the rest is mainly transported by waterway, and the proportion of railway transportation is very small. The proportion of natural gas pipeline transportation is 100%.

[0003] Many oil and natural gas contain corrosive H2S gas, which can cause acid corrosion to the pipeline during transportation, especially low-temperature hydrogen sulfide corrosion, which belongs to local damage and is difficult to prevent. Low-temperature wet hydrogen sulfide corrosion mainly has two damage types of hydrogen-induced cracking (HIC) and stress corrosion (SCC). Therefore, the pipeline pipe for resisting acid corrosion should have low cold crack sensitivity, high strength and toughness performance matching, excellent welding performance and HIC / SSC corrosion resistance. The round billet C content of the present application is controlled below 0.12%, with appropriate Mn element, and micro-alloying elements V and Ti are used for strengthening. The steel has good impact toughness at low temperature and good HIC / SSC corrosion resistance, but the steel belongs to peritectic steel smelting range, which is easy to produce cracks on the outer surface of the round billet. Through the control of the parameters such as secondary cooling water, drawing speed, crystallizer, and straightening temperature during smelting, good round billet quality of peritectic steel smelting is realized, which can meet the technical requirements of low-carbon large-section hot-rolled seamless corrosion-resistant pipeline pipe. SUMMARY

[0004] The purpose of the present application is to provide a low-carbon large-section hot-rolled seamless pipeline pipe round billet smelting method, which can meet the technical requirements of large-diameter acid oil and gas long-distance transportation seamless pipeline pipe.

[0005] To solve the above technical problems, the present application adopts the following technical scheme:

[0006] The application discloses a low-carbon large-section hot-rolled seamless pipeline pipe round billet smelting method, and chemical component mass percentages of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material are as follows: C 0.06-0.12%, Si 0.10-0.40%, Mn 1.35-1.60%, V 0.02-0.05%, Ti 0.005-0.03%, Al 0.005-0.045%, P≤0.015%, S≤0.003%, and the rest is Fe and trace impurities, and the total mass percentage is 100%; and the smelting production process comprises the following steps: converter smelting, LF refining, VD vacuum degassing, continuous casting, fire cutting and warehousing; wherein:

[0007] The converter smelting adopts single slag process smelting, the final slag basicity is controlled to be 3.0, silicon manganese and manganese iron are used for deoxidization and alloying, the final deoxidization adopts aluminum deoxidization process, and the end point control target is P≤0.014%, S≤0.015%; the molten steel must be blocked with slag, and the slag blocking failure must be slagged;

[0008] The LF refining adopts the mode of gradually increasing the heating speed from low levels to high levels, slag making, desulfurization, composition adjustment and heating operation are carried out according to the converter molten steel composition and temperature, white slag is made in the refining, and V iron and Ti iron are added in the middle and late stages of the refining;

[0009] In the VD vacuum degassing production process, the vacuum degree is less than or equal to 0.10 Kpa, the target value is less than or equal to 0.06 Kpa, the deep vacuum time is greater than or equal to 13 minutes, an appropriate amount of calcium wire is fed after the deep vacuum ends, the soft blowing time after the wire feeding is greater than or equal to 13 minutes, the argon flow is controlled in the soft blowing process, and the molten steel cannot be exposed to air;

[0010] In the continuous casting, the crystallizer water quantity parameter is 2500 L / min, the deviation value is less than 50 L / min, the secondary cooling specific water quantity is 0.18 L / kg, the superheat degree is controlled to be 20-30 DEG C, the transverse speed control process is adopted, and the speed control is greater than or equal to 0.55 m / min;

[0011] The round billet after the continuous casting is cut into corresponding billet lengths by fire cutting and then is warehoused.

[0012] Further, the chemical component mass percentages of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material are as follows: C 0.06%, Si 0.10%, Mn 1.35%, V 0.02%, Ti 0.005%, Al 0.005%, P 0.015%, S 0.003%, and the rest is Fe and trace impurities, and the total mass percentage is 100%.

[0013] Further, the chemical composition of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material is as follows: C 0.08%, Si 0.18%, Mn 1.42%, V 0.03%, Ti 0.011%, Al 0.015%, P 0.014%, S 0.002%, the rest being Fe and trace impurities, and the total mass fraction is 100%.

[0014] Further, the chemical composition of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material is as follows: C 0.10%, Si 0.26%, Mn 1.47%, V 0.04%, Ti 0.017%, Al 0.025%, P 0.013%, S 0.002%, the rest being Fe and trace impurities, and the total mass fraction is 100%.

[0015] Further, the chemical composition of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material is as follows: C 0.11%, Si 0.34%, Mn 1.53%, V 0.03%, Ti 0.024%, Al 0.035%, P 0.012%, S 0.002%, the rest being Fe and trace impurities, and the total mass fraction is 100%.

[0016] Further, the chemical composition of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet material is as follows: C 0.12%, Si 0.40%, Mn 1.60%, V 0.05%, Ti 0.030%, Al 0.045%, P 0.010%, S 0.003%, the rest being Fe and trace impurities, and the total mass fraction is 100%.

[0017] Compared with the prior art, the present application has the beneficial technical effects that:

[0018] The low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe round billet of the present application has good surface quality after hot rolling and heat treatment, and the low-carbon anticorrosion pipeline pipe is made of peritectic steel. In the process of peritectic reaction, the peritectic steel is accompanied by large volume shrinkage, which is easy to form depressions on the surface. The cooling and solidification speed of the depression part is slower than that of other parts, the structure is coarsened, and the crack sensitivity is strong. Under the action of thermal stress and static pressure of molten steel, stress concentration is easy to occur at the weak part of the depression, and cracks are easy to occur. Such cracks cannot be rolled in the subsequent pipe rolling process, resulting in many scabs on the finished pipe. By strengthening the converter smelting and LF, VD refining process control, the converter focuses on controlling the end point carbon content, the LF refining strengthens the desulfurization, and the non-metallic inclusions are removed. The purity of the molten steel is improved as much as possible through VD vacuum treatment. Continuous casting is the most important link in peritectic steel smelting. By improving the cooling state of the crystallizer, reducing the cooling intensity of the crystallizer, controlling the superheat degree of the molten steel and increasing the casting speed to control the surface quality of the final round billet, the technical requirements of the low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe can be met. DETAILED DESCRIPTION

[0019] The present application will be described in detail below through specific examples.

[0020] The low-carbon large-section hot-rolled seamless anticorrosion pipeline pipe of the present application is produced by 390 section round billet. The chemical composition of the round billet is as follows: C 0.06-0.12, Si 0.10-0.40, Mn 1.35-1.60, V 0.02-0.05, Ti 0.005-0.03, Al 0.005-0.045, P≤0.015, S≤0.003, and the rest is Fe and trace impurities, and the total mass fraction is 100%.

[0021] C is designed to be 0.06%-0.12%. Low C design is adopted with appropriate amount of Mn to maintain the strength of the steel. Low C design can make the pipeline have better low temperature toughness and weldability. At the same time, more economical alloy elements V and Ti are used. Through subsequent quenching and tempering treatment, the steel pipe has good hydrogen sulfide corrosion resistance.

[0022] The smelting process of the round billet includes: converter smelting→LF refining→VD vacuum degassing→continuous casting machine continuous casting→fire cutting→warehousing.

[0023] The converter smelting and LF refining process control are strengthened. The converter adopts single slag process smelting, the final slag basicity is controlled at 3.0, silicon manganese and manganese iron are used for deoxidation and alloying, the final deoxidization adopts aluminum deoxidization process, the end point C content is controlled, the steel is prevented from over-oxidizing tapping, the tapping must be blocked, the slag must be removed if the blocking fails, and more impurity elements are prevented from flowing into the ladle.

[0024] VD vacuum degassing, vacuum degree ≤0.10 KPa, target value ≤0.06 KPa; deep vacuum time ≥13 minutes; after the deep vacuum ends, feed in appropriate amount of calcium wire, soft blowing time after wire feeding ≥13 minutes, ensuring the deep vacuum and soft blowing time after wire feeding, which can ensure that the inclusions can float up fully, and can reduce the secondary oxidation of molten steel, control the argon flow during the soft blowing process to prevent the molten steel from being exposed to the air, and ensure that the removed inclusions will not flow back to the molten steel.

[0025] The control of the continuous casting process parameters is the most critical process for preventing and improving the surface cracks of the continuous casting round billet. Properly reducing the mold cooling intensity is beneficial to the uniform growth of the billet shell, increasing the inlet water temperature of the mold, controlling the temperature difference between the inlet and outlet water of the mold, the mold water quantity parameter is 2500 L / min, the deviation value is less than 50 L / min, the secondary cooling water quantity is 0.18 L / kg, the weak cooling control mode is adopted, the surface temperature of the billet entering the straightening machine is ≥950℃, the overheating degree of the molten steel is controlled, the drawing speed is appropriately increased, the overheating degree is controlled within 20-30℃, the transverse speed control process is adopted, the drawing speed control is ≥0.55 m / min. The continuous casting of the peritectic steel is prone to transverse cracks, which are invisible to the naked eye and need to be distinguished after hot acid cooking. Therefore, increasing the drawing speed is equivalent to increasing the straightening temperature, so as to avoid the straightening temperature in the brittle temperature range of the billet, 700-900℃, and then cutting into corresponding billet length for storage.

[0026] The chemical composition of the 390mm seamless corrosion-resistant pipe billet obtained in the five examples is shown in Table 1:

[0027] Table 1 Chemical composition test results of round billets of five furnace numbers

[0028]

[0029] The five examples of corrosion-resistant round billets were subjected to hydrogen-induced cracking HIC detection after hot rolling and heat treatment to produce finished pipes, and the results are as follows:

[0030] Table 2 HIC detection results

[0031]

[0032] The round billets produced have no surface cracks. As can be seen from Table 1, the chemical composition of the round billets meets the design requirements. The hydrogen-induced cracking HIC test conducted in the five examples has a crack length rate (CLR), a crack thickness rate (CTR), and a crack sensitivity rate (CSR) of 0, and no hydrogen blistering, indicating that the steel has good corrosion resistance and can meet the technical requirements of large-diameter seamless pipe for long-distance transportation of acidic oil and gas.

[0033] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A method for smelting low-carbon, large-section hot-rolled seamless pipeline round billets, characterized in that, The chemical composition of the low-carbon, large-section hot-rolled seamless pipeline round billet is as follows (mass percentage): C 0.06–0.12%, Si 0.10–0.40%, Mn 1.35–1.60%, V 0.02–0.05%, Ti 0.005–0.03%, Al 0.005–0.045%, P ≤ 0.015%, S ≤ 0.003%, with the remainder being Fe and trace impurities, totaling 100% by mass. Its smelting and production process includes: converter smelting → LF refining → VD vacuum degassing → continuous casting → fire cutting → warehousing; among which: The converter smelting adopts a single-slag process, and the final slag basicity is controlled at 3.

0. Deoxidation and alloying are carried out using ferrosilicon manganese and ferromanganese. The final deoxidation adopts an aluminum-containing deoxidation process, and the endpoint control targets are: P≤0.014% and S≤0.015%. Slag blocking must be carried out when tapping steel. If slag blocking fails, slag must be removed. LF refining adopts a method of gradually increasing the heating rate from low to high levels. Slag formation, desulfurization, composition adjustment and heating operations are carried out according to the composition and temperature of the converter steel. White slag is produced in the refining process, and V iron and Ti iron are added in the middle and late stages of refining. During the VD vacuum degassing process, the vacuum degree is ≤0.10Kpa, and the target value is ≤0.06Kpa; the deep vacuum time is ≥13 minutes; after the deep vacuum is completed, an appropriate amount of calcium wire is fed in, and the soft blowing time after wire feeding is ≥13 minutes. During the soft blowing process, the argon flow rate is controlled, and the molten steel cannot be exposed to the air. In continuous casting, the crystallizer water flow rate is 2500 L / min with a deviation of less than 50 L / min, the secondary cooling water flow rate is 0.18 L / kg, the superheat is controlled between 20℃ and 30℃, and a constant casting speed control process is adopted with a casting speed control ≥0.55 m / min. After continuous casting, the round tube billets are cut into the corresponding billet lengths by fire cutting and then stored in the warehouse.

2. The method for smelting low-carbon, large-section hot-rolled seamless pipeline round billets according to claim 1, characterized in that, The chemical composition of the low-carbon, large-section hot-rolled seamless pipeline round billet is as follows (mass percentage): C 0.06%, Si 0.10%, Mn 1.35%, V 0.02%, Ti 0.005%, Al 0.005%, P 0.015%, S 0.003%, with the remainder being Fe and trace impurities, totaling 100% by mass.

3. The method for smelting low-carbon, large-section hot-rolled seamless pipeline round billets according to claim 1, characterized in that, The chemical composition of the low-carbon, large-section hot-rolled seamless pipeline round billet is as follows (mass percentage): C 0.08%, Si 0.18%, Mn 1.42%, V 0.03%, Ti 0.011%, Al 0.015%, P 0.014%, S 0.002%, with the remainder being Fe and trace impurities, totaling 100% by mass.

4. The method for smelting low-carbon, large-section hot-rolled seamless pipeline round billets according to claim 1, characterized in that, The chemical composition of the low-carbon, large-section hot-rolled seamless pipeline round billet, by mass percentage, is as follows: C 0.10%, Si 0.26%, Mn 1.47%, V 0.04%, Ti 0.017%, Al 0.025%, P 0.013%, S 0.002%, with the remainder being Fe and trace impurities, totaling 100% by mass.

5. The method for smelting low-carbon, large-section hot-rolled seamless pipeline round billets according to claim 1, characterized in that, The chemical composition of the low-carbon, large-section hot-rolled seamless pipeline round billet is as follows (mass percentage): C 0.11%, Si 0.34%, Mn 1.53%, V 0.03%, Ti 0.024%, Al 0.035%, P 0.012%, S 0.002%, with the remainder being Fe and trace impurities, totaling 100% by mass.

6. The method for smelting low-carbon, large-section hot-rolled seamless pipeline round billets according to claim 1, characterized in that, The chemical composition of the low-carbon, large-section hot-rolled seamless pipeline round billet is as follows (mass percentage): C 0.12%, Si 0.40%, Mn 1.60%, V 0.05%, Ti 0.030%, Al 0.045%, P 0.010%, S 0.003%, with the remainder being Fe and trace impurities, totaling 100% by mass.

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