Cr-Ni high-grade corrosion-resistant steel bar for ocean engineering and production method and application thereof

Abstract

The application discloses a Cr-Ni high-grade corrosion-resistant steel bar for ocean engineering and a production method and application thereof, and belongs to the technical field of steel bars for ocean engineering. The technical method and route are as follows: converter, LF refining furnace, continuous casting machine, billet inspection, heating of bar No. 3 and bar No. 5 heating furnace, rolling, inspection, cold bed cooling, fixed-length shearing, fixed-branch packaging, weighing, hanging up, and warehousing. The alloy component of the HRB400Y corrosion-resistant steel bar for ocean engineering is optimized and designed, so that a high-strength long-service-life corrosion-resistant steel bar component system meeting the corrosion resistance requirement in a coastal erosion environment is obtained. Through the research on the steelmaking and rolling process of the HRB400Y corrosion-resistant steel bar for ocean engineering, an efficient low-cost industrialized production smelting and rolling process of the corrosion-resistant steel bar is formulated.

Description

TECHNICAL FIELD

[0001] The application relates to a Cr-Ni high-grade corrosion-resistant steel bar for marine engineering and a production method and application thereof, and belongs to the technical field of steel bars for marine engineering. BACKGROUND

[0002] With the development of infrastructure construction such as large-scale bridges across rivers and seas and seaport terminals, more stringent requirements are put forward for materials for marine engineering, and more and more building groups are facing the severe challenge of chlorine salt corrosion. The development of large-scale national coastal engineering will certainly drive the development and application of corrosion-resistant steel bars and promote the use of steel bars for marine engineering.

[0003] With the development of marine engineering as a new growth point and important driving force for China's economic development, more and more infrastructure will be built in the sea and on the coast, and steel bars and concrete are very important raw materials for these infrastructures. The ordinary carbon steel bars existing in the market at the present stage cannot meet the demand in terms of corrosion performance, and the use range of steel bars is expanding day by day, so the development of various corrosion-resistant steel bars and weather-resistant steel bars for marine engineering is imminent. Therefore, the HRB400Y corrosion-resistant steel bar for marine engineering has a wide demand in coastal areas.

[0004] Current research shows that as a corrosion-resistant steel bar for marine engineering, it has the characteristics of poor thermal plasticity, strong crack sensitivity, etc., and is prone to uneven initial blank shell thickness, fracture along the dendrite or austenite grain boundary, continuous expansion in the secondary cooling process, and finally crack. In this regard, steelmaking plants need to do a lot of detailed research and analysis work. SUMMARY

[0005] The application aims to provide a production method of a Cr-Ni high-grade corrosion-resistant steel bar for marine engineering, which obtains a high-efficiency and low-cost corrosion-resistant steel bar.

[0006] Meanwhile, the application provides a Cr-Ni high-grade corrosion-resistant steel bar for marine engineering.

[0007] Meanwhile, the application provides an application of the Cr-Ni high-grade corrosion-resistant steel bar for marine engineering in marine engineering.

[0008] To solve the above technical problems, the technical scheme adopted by the application is as follows:

[0009] A production method of a Cr-Ni high-grade corrosion-resistant steel bar for marine engineering, comprising the following steps:

[0010] Technical method and route: converter -> LF refining furnace -> continuous casting machine -> billet inspection -> bar three and bar five heating furnace heating -> rolling -> inspection -> cold bed cooling -> fixed-length shearing -> fixed-branch packaging -> weighing -> hanging plate -> warehousing.

[0011] 1. Composition system: including the following components by mass percentage: C≤0.12%, Si: 0.4-0.6%, Mn: 1.4-1.6%, P≤0.01%, S≤0.01%, Ni≤0.50%, Cr: 2.35-3.46%, V: 0.03-0.04%, and the balance of Fe; the total amount of C, Cr, Ni and V is 3.0-4.0%.

[0012] Working principle: a micro-alloying route is adopted. In addition to the need for micro-alloying, the corrosion-resistant steel bar for ocean engineering also needs to increase a certain amount of Cr and Ni. A low-C+Cr+Ni+V alloy system is adopted, on the basis of comprehensive investigation and technical research, the C content is further reduced, and the role of Ni in the corrosion-resistant steel bar for ocean engineering is increased, the total amount of C+Cr+Ni+V alloy is controlled to be 3.0-4.0%, and it is determined to be composed of bainite and martensite composite phase structure. Compared with HRB400 in GB / T 1499.2, the relative corrosion rate of the HRB400Y obtained by the application is lower than 20%, which can replace the use of stainless steel bar in ocean engineering.

[0013] 2. Converter smelting

[0014] The converter smelting is carried out by adding 50t of molten iron and 5-10t of clean scrap steel, and the tapping temperature is ≥1620℃. After tapping, the raw materials are added in the argon blowing station. In the converter smelting process, a double-slag method is adopted for dephosphorization, which can control the P in the steel to be below 0.010%, and a high carbon tapping is adopted, the carbon content at the end of the converter is controlled to be 0.05-0.07%, which effectively reduces the oxygen content of the molten steel, and the converter tapping adopts a slide plate slag stopping, which can avoid the tapping slag, reduces the oxidizability of the molten steel from the source, reduces the total amount of inclusions in the steel, and improves the cleanliness of the steel. The raw materials must be high-temperature roasted. The residual element Cu of each furnace is ≤0.08%.

[0015] The molten iron requires C≥3.5%, Si: 0.8-1.25%, S: 0.0050-0.070%, P: 0.170-0.200%, and Mn>1.00%.

[0016] The clean scrap steel requires Cr≤0.05%, Ni≤0.05%, Cu≤0.05%, and Mo≤0.02%.

[0017] The double-slag method is prior art.

[0018] Specific process of converter smelting:

[0019] (1) According to the tapping temperature ≥1620℃ requirement, 50 tons of molten iron and 5-10 tons of clean scrap steel are charged into the converter according to 85%-90% of the total charge of the converter, the molten iron requirement is phosphorus: 0.170-0.200%, silicon: 0.8-1.25%, and the temperature of the molten iron is ≥1360℃;

[0020] (2) The first stage of converter smelting is 0-6 minutes, 100-120 kg of active lime is added into the converter, the bottom blowing gas is nitrogen, and the flow is 300 L / min;

[0021] (3) The oxygen lance of the converter adopts constant flow 650 NM 3 / h variable gun position operation, the standard gun position of the converter is opened at 0 min, and the gun position is increased by 5 mm after 2 min;

[0022] (4) After the completion of the first stage of converter smelting, the furnace is shaken to pour part of the slag, and the amount of slag pouring is 30-50% of the total weight of the slag;

[0023] (5) The second stage of converter smelting (from 10 min to 15 min) continues to use the oxygen lance (standard gun position, constant flow 650 NM 3 / h) to supply oxygen for blowing, active lime is added into the converter, and the active lime addition amount is 20-25 kg / t of steel, the bottom blowing gas is argon, and the flow is 300 L / min;

[0024] (6) The late stage of converter smelting (15-30 min) adopts higher gun position (0.5 m higher than the standard gun position, constant flow 650 NM 3 / h) to open blowing;

[0025] (7) Within 70-75% of the total blowing oxygen consumption, fluorite is added in multiple small batches (3-5 batches) within 25-30 min, and the total amount of fluorite is 2-3.5 kg / t of steel;

[0026] (8) The converter smelting is completed, the converter is shaken to pour slag, temperature is measured, and sample is taken; At this time, the basicity R of the slag is 2.2-2.4;

[0027] (9) The converter is tapped, and the carbon content at the end of the converter is controlled to be 0.05-0.07%, and the phosphorus content is ≤0.010%.

[0028] Alloy furnace charge (i.e. raw material) baking: The alloy baking furnace is a special equipment for baking ferroalloy. Through dehydration baking of alloy furnace charge: silicon manganese alloy, high carbon chromium iron and vanadium nitrogen alloy, first dehydration baking of free water at 200℃, and then dehydration baking of crystallization water at 400-600℃. Make the alloy furnace charge reach the required temperature, meet the requirements of steelmaking process, shorten the smelting time, and improve the steel quality.

[0029] 3. Argon blowing station:

[0030] After converter smelting, the molten steel directly enters the argon blowing station, and first adds 60-80 kg of aluminum cake, then adds 100 kg of silicon-manganese alloy, then adds 15-18 kg of high-carbon chromium iron, then adds 1.5-1.8 kg of vanadium-nitrogen alloy, then adds 60 kg of calcium carbide, 80 kg of calcium aluminate and 250 kg of lime, and uses multiple argon blowing. After the first argon blowing for 10 min, the temperature of the molten steel is 1550℃, the argon flow rate of the first argon blowing is 1.05 Nm 3 / min / t; then the second argon blowing is carried out, after the second argon blowing for 3 min, the temperature of the molten steel is 1580℃, the argon flow rate of the second argon blowing is 1.05 Nm 3 / min / t; then the third argon blowing is carried out, first feeding 40 kg / t of high-carbon chromium iron to make the Cr content in the range of 2.35-3.46%, then adding 100 kg of carbonized rice husk, after the third argon blowing for 5 min, the temperature of the molten steel is 1590℃, the argon flow rate of the third argon blowing is 0.05 Nm 3 / min / t, so that the composition is guaranteed to be C≤0.12%, Si: 0.4-0.6%, Mn: 1.4-1.6%, P≤0.01%, S≤0.01%, Ni≤0.50%, Cr: 2.35-3.46%, V: 0.03-0.04% and the balance of Fe; the total amount of C, Cr, Ni and V is in the range of 3.0-4.0%.

[0031] 4. LF refining:

[0032] LF fine-tunes according to the composition of the argon blowing station, and LF does not need to be specially added after the argon blowing station meets the standard. If a certain element does not meet the standard, it can be appropriately supplemented. When supplementing, all added alloys are low-nickel alloys, the Ni content of the low-nickel alloy is within 10%, the addition amount is 5-40 kg, and the number of non-deformable inclusions in the steel is reduced.

[0033] Deoxidation control is carried out throughout the refining process, which can stably control the oxygen in the steel to be within 15 ppm. At 1650-1680℃, first feed aluminum blocks 15-20 kg in the refining furnace, pre-deoxidize for at least 8 min, make the slag gradually white, and use CaO-Al2O3-SiO2-MgO slag system, which includes CaO: 30-35 wt%, Al2O3: 23-33 wt%, SiO2: 13-18 wt% and the balance of MgO.

[0034] After refining for 13-15 minutes, the temperature is 1660-1690°C, and limestone 200-300 kg and fluorite 80-150 kg are added to the slag to reduce the slag basicity R to 1.5-1.8, and the refining white slag is finished, and after the composition is adjusted (adjusted to C≤0.12%, Si: 0.4-0.6%, Mn: 1.4-1.6%, P≤0.01%, S≤0.01%, Ni≤0.50%, Cr: 2.35-3.46%, V: 0.03-0.04%, and the balance of Fe; the total amount of C, Cr, Ni, and V is 3.0-4.0%), the slag is changed, the slag basicity R is reduced to 1.7 or less, the inclusions in the steel are subjected to sufficient plasticization treatment, low-melting deformable inclusions are obtained, and sufficient refining soft blowing is ensured, the time is≥15 min, the refining soft blowing gas is argon, the flow is 0.05 Nm 3 / min / t, the inclusions in the steel are sufficiently floated, and the top slag is adsorbed and denatured (the top slag is the floated inclusions, the amount and size of the inclusions in the steel decrease with the increase of the basicity of the top slag, the mass ratio of CaO to Al2O3 in the slag represents the adsorption capacity of the slag to the inclusions, and the denaturation is the change of the basicity, the basicity is reduced from 2.2-2.4 to 1.5-1.8), which not only effectively reduces the total amount of inclusions in the steel, but also obtains relatively small inclusions (about 15 μm), and the inclusion size of the finished steel bar is generally less than 25 μm. The outlet temperature is≤1620°C.

[0035] 5. Continuous casting

[0036] The whole continuous casting process adopts protective casting, and the long nozzle (800 mm) and submerged nozzle argon sealing are opened to avoid the pollution of molten steel to the whole continuous casting process. A production process with low superheat, weak flow secondary cooling water, and low drawing speed is adopted, the superheat of continuous casting is 25-28°C in total, the specific water amount is controlled to be 0.20-0.26 L / Kg, and the average drawing speed is 2.4 m / min, which fully guarantees the surface quality of the continuous casting billet. At the same time, the mold electromagnetic stirring M-EMS and the solidification end electromagnetic stirring F-EMS are adopted, the current is 225 A, and the frequency is 3 Hz, to guarantee the macrostructure quality of the continuous casting billet, the M-EMS and F-EMS electromagnetic stirring are combined to control segregation, the secondary cooling of the continuous casting adopts strong cooling 0.20-0.26 L / kg, the dendritic structure of the billet is refined and controlled, to improve the macrostructure such as center segregation and center porosity of the billet, and the center C segregation is controlled to be≤1.05%. The actual measured straightening temperature is 980-1010°C, which meets the requirement of good plastic zone, and can reduce the crack generation in the straightening stage. It is verified by production that the continuous casting billet has no squareness and diamond variation, the pickling surface has no crack, and the macrostructure test piece has no various crack defects.

[0037] The meaning of weak flow secondary cooling in weak flow secondary cooling water quantity is: a small water flow uniformly cools the billet in the length interval from the crystallizer outlet to the length interval of the straightening machine. This length interval from the crystallizer outlet to the length interval of the straightening machine is called the secondary cooling zone.

[0038] 6. Shot blasting and flaw detection inspection

[0039] The flaw detection inspection result of the billet shows that the original continuous casting billet surface quality of the steel grade is good, and there is no crack, slag groove, scab and other defects on the surface and under the vibration mark. The billet sampling detection result shows that the continuous casting billet only has local, less than 0.4 mm, intergranular slight decarburization. In order to ensure that the billet surface is free of cracks and other defects, the billet shot blasting and flaw detection inspection is required. The shot blasting process further removes the surface grinding burrs and flash of the billet, avoiding more micro defects in rolling; the artificial magnetic powder flaw detection of the four sides of the billet ensures that the billet surface is free of defects.

[0040] 7. Steel rolling:

[0041] The controlled rolling and controlled cooling scheme adopts long-time high-temperature heating-high-temperature rolling-weak water penetration process, and the specific steps are as follows: the billet is cooled to normal temperature 15-35℃, and then heated in the heating furnace, 4-stage temperature control step beam heating is adopted to ensure that the rolling temperature is above 1170℃, and red billet is obtained.

[0042] Step 1, the red billet enters the first stage cooling water tank after large reduction of the intermediate rolling mill group in the form of 41-42*41-42cm ellipse billet at a speed of 7-8m / s, to prevent the continuous growth of austenite grain size, suppress the core temperature of the billet, and cool the red billet at 1100-1170℃ to 1030-1050℃, and the water pressure is 1.7-2.0MPa.

[0043] Step 2, the red billet enters the finishing rolling mill group after the tail residual billet is cut off by the 2# flying shear.

[0044] Step 3, the red billet enters the second stage long-time water cooling section at a speed of 6-7m / s by the transmission roller after passing through the finishing rolling mill group. The water cooling section adopts 50-52cm diameter, 1-stage water penetration pipe.

[0045] Step 4, the finished steel bar is cut by the 3# flying shear to remove the unqualified residual billet at the head and tail to ensure the outer shape size.

[0046] Step 5, the finished steel bar is put into the tail speed reduction device (reduced from 10.5m / s to 7.5m / s) by the transmission roller, and finally enters the cooling bed at a speed of 7.5m / s, the cooling bed temperature is 1000-1050℃, and then the billet is turned and translated at a speed of 3.5m / s to ensure that the microstructure transformation is continuous and uniform in the air cooling state.

[0047] The steel rolling process of the application, the billet temperature is cooled to normal temperature 15-35℃, the cold material is charged into the furnace, the casting billet is charged into the furnace below Ar1 temperature, the coarse grain structure of the casting billet before rolling is prevented, the combination of the micro-alloy elements and C, N is ensured to be sufficient, and the low mechanical property is avoided.

[0048] The steel rolling process of the application uses the advanced 4-stage temperature control walking beam type heating furnace, the preheating stage is fast improved, from 20℃ to 850℃, the time is 30min; the first heating stage is slowly heated, from 850℃ to 1150℃, the time is 30min; the second heating stage is slowly heated again, from 1150℃ to 1220℃, the time is 30min, the precise temperature adjusting means of the holding stage is used, the temperature is controlled in 1220-1250℃, the time is 30min. Under the premise of improving the temperature of the heating stage, the micro-cracks of the billet are prevented, the stable heating atmosphere of the holding stage is used, the micro-alloy in the billet is fully dissolved again, the holding stage is required to be less than 30min, the decarburization layer thickness is ensured to be less than 0.02mm, and the sufficient mechanical property is ensured.

[0049] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering obtained by the application has the relative corrosion rate lower than 20% compared with HRB400.

[0050] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering obtained by the application is applied in marine engineering, and the marine engineering includes large-scale bridges and / or marine ports.

[0051] The application has the following beneficial effects:

[0052] 1. The alloy component of the HRB400Y corrosion-resistant steel bar for marine engineering is optimized and designed, and the corrosion-resistant steel bar component system for marine engineering with high strength and long service life meeting the corrosion resistance requirements in coastal erosion environment is obtained.

[0053] 2. The steel rolling process of the HRB400Y corrosion-resistant steel bar for marine engineering is researched, and the efficient and low-cost industrialized production rolling process of the corrosion-resistant steel bar is formulated.

[0054] According to the component design and rolling process prediction, the cost of the HRB400Y is increased by 1500-2000 yuan / ton compared with the ordinary HRB400 steel bar, but the relative corrosion rate is lower than 20%, and the use in the related engineering in the marine splash area can be met. After the project is successfully completed, the market competitiveness of the enterprise is improved, and the solid foundation for increasing more benefits is laid. DETAILED DESCRIPTION

[0055] Figure 1 is the macrostructure diagram of the application;

[0056] Figure 2 is the microstructure diagram of the finished steel bar 20mm (core part) of the application;

[0057] Figure 3 is Figure 2 a close-up view of DETAILED DESCRIPTION

[0058] The application will be further described below in conjunction with the accompanying drawings and specific examples. The following examples are only used to illustrate the application and not intended to limit the scope of the application.

[0059] Example 1

[0060] A production method of a Cr-Ni high-grade corrosion-resistant steel bar for ocean engineering comprises the following steps:

[0061] S01, converter smelting: according to the requirement of tapping temperature 1620℃, 50t of molten iron and 5t of clean scrap steel are charged into the converter according to that the weight of molten iron and clean scrap steel accounts for 85% of the total charge of the converter, the P content of the molten iron is 0.170%, the Si content is 0.8%, and the temperature of the molten iron is 1360℃; after three stages of converter smelting, the converter smelting is completed, the converter is shaken and the slag is discharged, the temperature is measured, and the sample is taken; at this time, the basicity R of the slag is 2.2; then the converter is tapped, and the C content is controlled to be 0.05% and the P content is 0.010% at the end of the converter;

[0062] The process of three stages of converter smelting is as follows:

[0063] (1) In the first stage of converter smelting, 100kg of active lime is added into the converter, the bottom blowing gas is nitrogen, and the flow rate is 300L / min;

[0064] (2) The oxygen lance of the converter adopts constant flow 650NM 3 / h variable gun position operation, the converter is blown at the standard gun position at 0min, and the gun position is increased by 5mm after 2min;

[0065] (3) After the completion of the first stage of converter smelting, the furnace is shaken and part of the slag is discharged, and the amount of discharged slag is 30% of the total weight of the slag;

[0066] (4) In the second stage of converter smelting, 10-15min, continue to use the oxygen lance to supply oxygen for blowing, the standard gun position, constant flow 650NM 3 / h, active lime is added into the converter, the active lime addition amount is 20kg / t of steel, the bottom blowing gas is argon, and the flow rate is 300L / min;

[0067] (5) In the later stage of converter smelting, 15-30min, blow with high gun position, which is 0.5m higher than the standard gun position, and the constant flow is 650NM 3 / h;

[0068] (6) Within 70% of the total blowing oxygen consumption, fluorite is added in three batches within 25-30min, and the total amount of fluorite is 2kg / t of steel.

[0069] S02, argon blowing station:

[0070] After the converter smelting, the molten steel directly enters the argon blowing station, 60 kg of aluminum cake is first added to the molten steel, then 100 kg of silicon manganese alloy, 15 kg of high-carbon chromium iron, 1.5 kg of vanadium-nitrogen alloy, 60 kg of calcium carbide, 80 kg of calcium aluminate and 250 kg of lime are added, and multiple argon blowing is used, with a total argon blowing time of 18 min, so that the composition is guaranteed to be C: 0.12%, Si: 0.4%, Mn: 1.4%, P: 0.01%, S: 0.01%, Ni: 0.50%, Cr: 2.35%, V: 0.03% and the balance of Fe; the total amount of C, Cr, Ni and V is 3.0%;

[0071] The process of multiple argon blowing is as follows:

[0072] After the first argon blowing for 10 min, the temperature of the molten steel is 1550℃, and the argon flow rate of the first argon blowing is 1.05 Nm 3 / min / t;

[0073] Then the second argon blowing is carried out, after the second argon blowing for 3 min, the temperature of the molten steel is 1580℃, and the argon flow rate of the second argon blowing is 1.05 Nm 3 / min / t;

[0074] Then the third argon blowing is carried out, 40 kg / t of high-carbon chromium iron is first fed to make the Cr content 2.35%, and then 100 kg of carbonized rice husk is added, after the third argon blowing for 5 min, the temperature of the molten steel is 1590℃, and the argon flow rate of the third argon blowing is 0.05 Nm 3 / min / t;

[0075] In S02, the silicon manganese alloy, high-carbon chromium iron and vanadium-nitrogen alloy are dehydrated and roasted, first dehydrated and roasted at 200℃ to remove free water, and then dehydrated and roasted at 400℃ to remove crystallization water.

[0076] S03, LF refining:

[0077] The whole refining process is controlled by deoxidation, and the oxygen in the steel is controlled within 15 ppm, 15 kg of aluminum block is first fed into the refining furnace at 1650℃, and pre-deoxidation is carried out for 8 min to make the slag gradually white, and the CaO-Al2O3-SiO2-MgO slag system is used; the CaO-Al2O3-SiO2-MgO slag system includes CaO: 30wt%, Al2O3: 23wt%, SiO2: 13wt% and the balance of MgO;

[0078] After refining for 13 minutes, the temperature is 1660°C, and 200 kg of limestone and 80 kg of fluorite are added until the slag basicity R reaches 1.5, and the refining of the white slag is completed. After the composition is adjusted in place (when the composition is adjusted in place: C: 0.12%, Si: 0.4%, Mn: 1.4%, P: 0.01%, S: 0.01%, Ni: 0.50%, Cr: 2.35%, V: 0.03% and the balance Fe; the total amount of C, Cr, Ni and V is 3.0%), the slag changing operation is performed to reduce the slag basicity R to below 1.7. At the same time, the refining soft blowing time is 15 minutes, the refining soft blowing gas is argon, and the refining soft blowing gas argon flow rate is 0.05 Nm 3 / min / t; outlet temperature 1620℃;

[0079] S04, continuous casting:

[0080] The entire continuous casting process uses protected casting, with a long 800mm shroud and submerged argon sealing. A production process with low superheat, weak secondary cooling water flow, and low casting speed is adopted. The overall superheat of continuous casting is 25°C, the specific water content is controlled at 0.20L / Kg, and the average casting speed is 2.4m / min. M-EMS electromagnetic stirring at the mold and F-EMS electromagnetic stirring at the end of solidification are also used, with a current of 225A and a frequency of 3Hz.

[0081] In this embodiment, continuous casting ensures the low-magnification quality of the continuous casting billet. The results of the low-magnification test are shown in Figure 1 , Figure 1 The low-magnification data of the left and right images are shown in Table 1 below.

[0082] Table 1 Macroscopic test data

[0083]

[0084] From Table 1 and Figure 1 It can be seen from the figure that the quality of the ingot in this embodiment is good, the dendritic structure of the steel ingot is refined and controlled, and the low-magnification structures such as central segregation and central porosity of the ingot are improved.

[0085] S05, shot blasting inspection;

[0086] S06, Steel Rolling:

[0087] The controlled rolling and controlled cooling scheme uses a long-term high-temperature heating-high-temperature rolling-weak water penetration process. The specific steps are as follows: the billet temperature is cooled to room temperature (15°C), and then heated in a heating furnace using a four-stage temperature-controlled walking beam heating method to ensure the starting rolling temperature is 1170°C to obtain a red billet;

[0088] Step 1, the red billet is cooled to 1030℃ from 1170℃ by the first water cooling tank after the large reduction of the intermediate rolling mill group, the water pressure is 1.7 MPa, and the speed is 7 m / s;

[0089] Step 2, the red billet is cut by the 2# flying shear after the tail billet is cut, and then is rolled by the finishing rolling mill group;

[0090] Step 3, the red billet is cooled by the second long-time water cooling section after the finishing rolling mill group, the speed is 6 m / s, the diameter of the water pipe is 50 cm, and the water pipe is one section;

[0091] Step 4, the finished steel bar is cut by the 3# flying shear, and the tail billet is cut to ensure the size;

[0092] Step 5, the finished steel bar is put into the tail speed reduction device through the transmission roller way, the speed is reduced from 10.5 m / s to 7.5 m / s, and finally the finished steel bar is quickly put into the cooling bed at the speed of 7.5 m / s, the temperature of the cooling bed is 1000℃, then the finished steel bar is turned and translated at the speed of 3.5 m / s to ensure the uniform organization transformation in the air cooling state;

[0093] In S06, the process of the 4-section temperature control step beam heating is as follows: the preheating section is quickly raised from 20℃ to 850℃, and the time is 30 min;

[0094] The first heating section is slowly heated from 850℃ to 1150℃, and the time is 30 min;

[0095] The second heating section is slowly heated again from 1150℃ to 1220℃, and the time is 30 min;

[0096] The temperature of the holding section is accurately controlled to be 1220℃, and the time is 30 min.

[0097] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering obtained by the production method of the embodiment has a relative corrosion rate of less than 20% compared with HRB400.

[0098] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering of the embodiment is applied to marine engineering, including large bridges and / or marine ports.

[0099] Embodiment 2

[0100] A production method of a Cr-Ni high-grade corrosion-resistant steel bar for marine engineering, comprising the following steps:

[0101] S01, converter smelting: according to the tapping temperature 1650℃ requirement, according to the weight of molten iron and clean scrap steel is 90% of the total charge of the converter into the converter 50t molten iron and clean scrap steel 10t, into the converter molten iron requirement P: 0.200%, Si: 1.25%, molten iron temperature 1400℃; after three stages of converter smelting, the converter smelting is finished, the converter is shaken and the slag is poured, the temperature is measured, and the sample is taken; at this time, the slag basicity R is 2.4; then the converter is tapped, and the C content is controlled to be 0.07% at the end of the converter, and the P content is 0.005%;

[0102] The process of three stages of converter smelting is:

[0103] (1) the first stage of converter smelting 0-6min, 120kg of active lime is added into the converter, the bottom blowing gas is nitrogen, and the flow is 300L / min;

[0104] (2) the oxygen lance of the converter uses constant flow 650NM 3 / h variable gun position operation, the standard gun position of the converter is blown at 0min, and the gun position is increased by 5mm after 2min;

[0105] (3) after the first stage of converter smelting is completed, the furnace is shaken and part of the slag is poured, and the amount of slag poured is 50% of the total weight of the slag;

[0106] (4) the second stage of converter smelting 10-15min, continue to use the oxygen lance to supply oxygen blowing, the standard gun position, constant flow 650NM 3 / h, active lime is added into the converter, the active lime addition amount is 25kg / t steel, the bottom blowing gas is argon, and the flow is 300L / min;

[0107] (5) in the later stage of converter smelting 15-30min, blow with high gun position, which is 0.5m higher than the standard gun position, constant flow 650NM 3 / h;

[0108] (6) within 75% of the total blowing oxygen consumption, fluorite is added in 5 batches within 25-30min, and the total fluorite consumption is 3.5kg / t steel.

[0109] S02, argon blowing station:

[0110] After converter smelting, the molten steel directly enters the argon blowing station, 80 kg of aluminum cake is first added into the molten steel, then 100 kg of silicon-manganese alloy, 18 kg of high-carbon chromium iron, 1.8 kg of vanadium-nitrogen alloy, 60 kg of calcium carbide, 80 kg of calcium aluminate and 250 kg of lime are added, multi-argon blowing is used, the total argon blowing time is 18 min, so that the composition is guaranteed to be C: 0.10%, Si: 0.6%, Mn: 1.6%, P: 0.005%, S: 0.001%, Ni: 0.40%, Cr: 3.46%, V: 0.04% and the balance of Fe; the total amount of C, Cr, Ni and V is 4.0%;

[0111] The process of multi-argon blowing is as follows:

[0112] After the first argon blowing for 10 min, the temperature of the molten steel is 1550°C, the argon flow rate of the first argon blowing is 1.05 Nm 3 / min / t;

[0113] Then the second argon blowing is carried out, after the second argon blowing for 3 min, the temperature of the molten steel is 1580°C, the argon flow rate of the second argon blowing is 1.05 Nm 3 / min / t;

[0114] Then the third argon blowing is carried out, 40 kg / t of high-carbon chromium iron is first fed to make the Cr content 3.46%, then 100 kg of carbonized rice husk is added, after the third argon blowing for 5 min, the temperature of the molten steel is 1590°C, the argon flow rate of the third argon blowing is 0.05 Nm 3 / min / t;

[0115] In S02, the silicon-manganese alloy, high-carbon chromium iron and vanadium-nitrogen alloy are dehydrated and roasted, first deionized water is roasted at 200°C, then crystallization water is roasted at 600°C.

[0116] S03, LF refining:

[0117] The whole refining process is deoxidized control, the oxygen in the steel is controlled within 10 ppm, 20 kg of aluminum block is first fed in the refining furnace at 1680°C, pre-deoxidation is carried out for 10 min, so that the slag gradually becomes white, CaO-Al2O3-SiO2-MgO slag system is used;

[0118] The CaO-Al2O3-SiO2-MgO slag system includes CaO: 35 wt%, Al2O3: 33 wt%, SiO2: 18 wt% and the balance of MgO;

[0119] After refining for 15 min at a temperature of 1690°C, limestone 300 kg and fluorite 150 kg are added to the slag to reduce the slag basicity R to 1.8, and after the composition is adjusted (when the composition is adjusted: C: 0.10%, Si: 0.6%, Mn: 1.6%, P: 0.005%, S: 0.001%, Ni: 0.40%, Cr: 3.46%, V: 0.04%, and the balance of Fe; the total amount of C, Cr, Ni, and V is 4.0%), a slag changing operation is performed to reduce the slag basicity R to 1.7 or less, and at the same time, the soft-blowing time during refining is 18 min, the soft-blowing gas during refining is argon, the flow rate of the soft-blowing gas argon during refining is 0.05 Nm 3 / min / t; the outgoing temperature is 1600°C;

[0120] S04, continuous casting:

[0121] The entire continuous casting process adopts protective casting, and the long nozzle (800 mm) and submerged nozzle argon seal are opened; a production process with lower superheat, weak flow secondary cooling water, and low casting speed is adopted, the overall superheat during continuous casting is 28°C, the specific water amount is controlled to be 0.26 L / Kg, and the average casting speed is 2.4 m / min; at the same time, the mold electromagnetic stirring M-EMS and the solidification end electromagnetic stirring F-EMS are adopted, the current is 225 A, and the frequency is 3 Hz;

[0122] S05, shot blasting and flaw detection inspection;

[0123] S06, rolling:

[0124] The controlled rolling and controlled cooling scheme adopts long-time high-temperature heating-high-temperature rolling-weak water passing process, and the specific steps are as follows: the billet is cooled to room temperature 35°C, and then reheated in the heating furnace, 4-stage temperature control step beam heating is adopted to ensure the opening rolling temperature to be 1190°C, and red billet is obtained;

[0125] Step 1: After the red billet passes through the large reduction of the intermediate rolling mill group, it enters the first-stage cooling water tank at an elliptical billet of 42*42 cm and a speed of 8 m / s, and the 1100°C red billet is cooled to 1050°C, and the water pressure is 2.0 MPa;

[0126] Step 2: After the red billet passes through the 2# flying shear to cut off the tail residual billet, it enters the finishing rolling mill group for rolling;

[0127] Step 3: After the red billet passes through the finishing rolling mill group, it enters the second-stage long-time water cooling section at a speed of 7 m / s by the transmission roller way, and the water cooling section adopts a 52 cm diameter and 1-stage water passing pipe;

[0128] Step 4: The finished steel bar passes through the 3# flying shear to cut off the unqualified residual billet at the head and tail which is removed to ensure the external size;

[0129] Step 5, the finished steel bar passes through the conveying roller, is put into the tail speed reduction device, is reduced from 10.5 m / s to 7.5 m / s, and finally is quickly put into the cooling bed at a speed of 7.5 m / s, the temperature of the cooling bed is 1050℃, and then is turned and translated at a speed of 3.5 m / s to ensure that the organization transformation is continuous and uniform in the air cooling state;

[0130] In S06, the process of the four-stage temperature control step-by-step beam heating is: the preheating stage is quickly raised from 20℃ to 850℃ in 30 minutes;

[0131] The first heating stage is slowly heated from 850℃ to 1150℃ in 30 minutes;

[0132] The second heating stage is again slowly heated from 1150℃ to 1220℃ in 30 minutes;

[0133] The temperature control in the holding stage is accurate to ensure that the temperature is controlled at 1250℃ in 30 minutes.

[0134] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering obtained by the production method of the embodiment has a relative corrosion rate of less than 20% compared with HRB400.

[0135] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering of the embodiment is applied in marine engineering, which includes large-scale bridges and / or harbor wharfs across rivers and seas.

[0136] Embodiment 3

[0137] A production method of a Cr-Ni high-grade corrosion-resistant steel bar for marine engineering, comprising the following steps:

[0138] S01, converter smelting: according to the requirement of tapping temperature 1700℃, 50t of molten iron and 10t of clean scrap steel are loaded into the converter according to that the weight of the molten iron and the clean scrap steel accounts for 90% of the total loading amount of the converter, the molten iron entering the converter requires P: 0.18%, Si: 1.00%, and the temperature of the molten iron is 1390℃; after three stages of converter smelting, the converter smelting is completed, the converter is shaken and the slag is discharged, the temperature is measured, and the sample is taken; at this time, the basicity R of the slag is 2.3; then the converter is tapped, and the C content at the end of the converter is controlled to be 0.06%, and the P content is 0.001%;

[0139] The process of the three stages of converter smelting is:

[0140] (1) the first stage of converter smelting 0-6min, 110kg of active lime is added into the converter, the bottom blowing gas is nitrogen, and the flow rate is 300L / min;

[0141] (2) the oxygen lance of the converter adopts constant flow 650NM 3 / h variable gun position operation, the converter standard gun position open blowing at 0 min, 5 mm gun position is improved after 2 min;

[0142] (3) After the first stage of converter smelting is completed, the furnace is shaken to pour off part of the slag, and the amount of slag pouring is 40% of the total weight of the slag;

[0143] (4) In the second stage of converter smelting for 10-15 min, continue to use oxygen lance to supply oxygen blowing, standard gun position, constant flow 650 NM 3 / h, active lime is added to the converter, the active lime addition amount is 22 kg / t steel, the bottom blowing gas uses argon, the flow is 300 L / min;

[0144] (5) In the later stage of converter smelting for 15-30 min, use high gun position to open blowing, which is 0.5 m higher than the standard gun position, constant flow 650 NM 3 / h;

[0145] (6) Within 72% of the total blowing oxygen consumption, fluorite is added in 4 batches within 25-30 min, the total fluorite consumption is 3 kg / t steel.

[0146] SO2, argon blowing station:

[0147] After the converter smelting is finished, the molten steel directly enters the argon blowing station, 70 kg of aluminum cake is first added to the molten steel, then 100 kg of silicon-manganese alloy, 16 kg of high-carbon chromium iron, 1.7 kg of vanadium-nitrogen alloy, 60 kg of calcium carbide, 80 kg of calcium aluminate and 250 kg of lime are added, multiple argon blowing is used, the total argon blowing time is 18 min, so that the composition is guaranteed to be C: 0.11%, Si: 0.5%, Mn: 1.5%, P: 0.001%, S: 0.001%, Ni: 0.45%, Cr: 2.9%, V: 0.04% and the balance of Fe; The total amount of C, Cr, Ni and V is 3.5%;

[0148] The process of multiple argon blowing is:

[0149] After the first argon blowing for 10 min, the molten steel temperature is 1550℃, the argon flow rate of the first argon blowing is 1.05 Nm 3 / min / t;

[0150] Then the second argon blowing is carried out, after the second argon blowing for 3 min, the molten steel temperature is 1580℃, the argon flow rate of the second argon blowing is 1.05 Nm 3 / min / t;

[0151] The third argon blowing is carried out, 40 kg / t of high-carbon ferrochrome is fed first to make the content of Cr 2.9%, and then 100 kg of carbonized rice husk is added, after the third argon blowing for 5 min, the temperature of the molten steel is 1590℃, and the argon flow rate of the third argon blowing is 0.05 Nm 3 / min / t;

[0152] In S02, the silicon-manganese alloy, high-carbon ferrochrome and vanadium-nitrogen alloy are dehydrated and baked, first dehydrated and baked at 200℃ to remove free water, and then dehydrated and baked at 500℃ to remove crystallization water.

[0153] S03, LF refining:

[0154] The whole refining process is controlled to remove oxygen, and the oxygen in the steel is controlled to be less than 10 ppm, 18 kg of aluminum block is fed in the refining furnace at 1660℃ first, and pre-deoxidation is carried out for 15 min, so that the slag becomes white piece by piece, and the slag system of

[0155] CaO-Al2O3-SiO2-MgO slag system; the CaO-Al2O3-SiO2-MgO slag system includes CaO: 32wt%, Al2O3: 30wt%, SiO2: 15wt% and the balance of MgO;

[0156] After refining for 14 min, the temperature is 1675℃, 250 kg of limestone and 100 kg of fluorite are added to the slag to reduce the slag basicity R to 1.7, and after the composition is adjusted (when the composition is adjusted: C: 0.11%, Si: 0.5%, Mn: 1.5%, P: 0.001%, S: 0.001%, Ni: 0.45%, Cr: 2.9%, V: 0.04% and the balance of Fe; the total amount of C, Cr, Ni and V is 3.5%), the slag is changed, the slag basicity R is reduced to below 1.7, and at the same time, the soft blowing time of the refining is 16 min, the soft blowing gas of the refining is argon, and the flow rate of the argon gas of the soft blowing gas of the refining is 0.05 Nm 3 / min / t; the outlet temperature is 1610℃;

[0157] S04, continuous casting:

[0158] The whole continuous casting process adopts protective casting, and the long nozzle (800 mm) and submerged entry nozzle argon sealing protection are opened; a lower superheat, weak flow secondary cooling water quantity and low casting speed production process is adopted, the overall superheat of the continuous casting is 26℃, the specific water quantity is controlled to be 0.23 L / Kg, and the average casting speed is 2.4 m / min; at the same time, the mold electromagnetic stirring M-EMS and the solidification end electromagnetic stirring F-EMS are adopted, the current is 225 A, and the frequency is 3 Hz;

[0159] S05, shot blasting flaw detection;

[0160] S06, rolling:

[0161] The controlled rolling and controlled cooling scheme adopts long-time high-temperature heating-high-temperature rolling-weak water cooling process, and the specific steps are as follows: the billet is cooled to room temperature 25℃, and then heated in a heating furnace, 4-stage temperature control step beam heating is adopted to ensure the opening rolling temperature of 1200℃, and red billet is obtained;

[0162] Step 1: After the red billet passes through the large reduction of the intermediate rolling mill group, it enters the first stage cooling water tank at a speed of 7.5m / s in the form of an elliptical billet with a size of 42*42cm, and the red billet at 1150℃ is cooled to 1040℃, and the water pressure is 1.8MPa;

[0163] Step 2: After the red billet passes through the 2# flying shear to cut off the tail residual billet, it enters the finishing rolling mill group for rolling;

[0164] Step 3: After the red billet passes through the finishing rolling mill group, it enters the second stage long-time water cooling section at a speed of 6.5m / s by the transmission roller way, and the water cooling section adopts a 51cm diameter water cooling pipe with 1 stage;

[0165] Step 4: The finished steel bar passes through the 3# flying shear to cut off the unqualified residual billet at the head and tail which is removed to ensure the outer size;

[0166] Step 5: The finished steel bar passes through the transmission roller way and is put into the tail speed reduction device, which reduces the speed from 10.5m / s to 7.5m / s, and finally enters the cooling bed at a speed of 7.5m / s, and the temperature on the cooling bed is 1025℃, then it is turned and translated at a speed of 3.5m / s to ensure that the organization transformation is continuous and uniform in the air cooling state;

[0167] In S06, the process of 4-stage temperature control step beam heating is: the preheating stage is quickly raised from 20℃ to 850℃, which takes 30min;

[0168] The first heating stage is slowly heated from 850℃ to 1150℃, which takes 30min;

[0169] The second heating stage is slowly heated again from 1150℃ to 1220℃, which takes 30min;

[0170] The temperature control in the holding stage is accurate to ensure that the temperature is controlled at 1230℃, which takes 30min.

[0171] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering obtained by the production method of the embodiment has a relative corrosion rate of less than 20% compared with HRB400.

[0172] The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering of the embodiment is applied in marine engineering, which includes large-scale bridges and / or harbor wharfs across rivers and seas.

[0173] Example 4

[0174] The difference between this embodiment and embodiment 1 is only that:

[0175] When the ingredients are adjusted in place: C: 0.09%, Si: 0.55%, Mn: 1.55%, P: 0.001%, S: 0.003%, Ni: 0.35%, Cr: 2.73%, V: 0.03% and the balance of Fe; the total amount of C, Cr, Ni and V is 3.2%.

[0176] The CaO-Al2O3-SiO2-MgO slag system includes CaO: 30wt%, Al2O3: 30wt%, SiO2: 15wt% and the balance of MgO.

[0177] Figure 2 And Figure 3 is a microstructure diagram of the finished steel bar 20mm (core) of embodiment 1, from which it can be seen that the microstructure of the finished steel bar is F+P+B+ a small amount of M.

[0178] The mechanical properties of the finished steel bar obtained by the application are shown in Table 2 below, and the corrosion resistance is that HRB400Y is compared with HRB400 in GB / T1499.2, and the relative corrosion rate is less than 20% (the meaning of the relative corrosion rate is that the corrosion rate of HRB400 steel bar is 100%, and the corrosion rate of HRB400Y is 20% lower than that of HRB400 steel bar).

[0179] Relative corrosion rate: average corrosion rate of corrosion-resistant steel bar / average corrosion rate of comparison steel bar x 100%

[0180] The test method and process are performed according to YB / T 4367.

[0181] The test methods of tensile strength, yield strength, A, Agt, strength yield ratio and yield strength index ratio are all common test methods in the industry, and all meet the requirements of the national standard.

[0182] A: elongation after fracture; Agt: total elongation at maximum force.

[0183] Table 2 Mechanical properties of finished steel bars

[0184]

[0185] It should be understood that, for brevity and clarity sake, in the foregoing description of the exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description of related features. However, this method of disclosure should not be interpreted as reflecting an intention that the application requires more features than are explicitly recited in each claim. Rather, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby expressly incorporated into this detailed description, with each claim acting as a separate embodiment of the application. In closing, the claims are what define the scope of the application. Therefore, the specific embodiments described in the specification are not to be construed as limiting the scope of the application. The scope of the application is to be determined by the claims.

[0186] While the application has been described in terms of several embodiments, those skilled in the art will recognize that the application can be practiced with modifications and alterations within the spirit and scope of the application. Accordingly, the application is not intended to be limited to the described embodiments, but intended to encompass a wider array of equivalents. Furthermore, it is to be understood that the use of certain terms to describe the application is neither meant to limit the scope of the application nor to imply that the terms are meant to be synonymous.

[0187] The above description is only preferred embodiments of the application. It should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the application, and these improvements and refinements should also be considered as falling within the scope of the application.

Claims

1. A method for producing high-grade Cr-Ni corrosion-resistant steel bars for marine engineering, characterized in that: The following steps are involved: S01, converter smelting: Based on the requirement of a tapping temperature ≥ 1620°C, 50 tons of molten iron and 5-10 tons of clean scrap are charged into the converter, with the weight of the molten iron and clean scrap accounting for 85%-90% of the total converter charge. The molten iron requirements for the converter are P: 0.170-0.200%, Si: 0.8-1.25%, and the molten iron temperature ≥ 1360°C. After three stages of converter smelting, the converter smelting is completed, the converter is shaken, the slag is drained, the temperature is measured, and sampling is performed. At this time, the slag basicity R is between 2.2 and 2.

4. The converter is then tapped, and the converter endpoint is controlled to have a C content of 0.05-0.07% and a P content of ≤ 0.010%. S02, argon blowing station: After tapping the converter, the molten steel directly enters the argon blowing station. First, 60-80 kg of aluminum cake is added to the molten steel, followed by 100 kg of silicon-manganese alloy, 15-18 kg of high-carbon ferrochrome, 1.5-1.8 kg of vanadium-nitrogen alloy, 60 kg of calcium carbide, 80 kg of calcium aluminate, and 250 kg of lime. Argon blowing is then used multiple times to ensure that the composition is within the range of C ≤ 0.12%, Si: 0.4-0.6%, Mn: 1.4-1.6%, P ≤ 0.01%, S ≤ 0.01%, Ni ≤ 0.50%, Cr: 2.35-3.46%, V: 0.03-0.04%, and the balance Fe; the total amount of C, Cr, Ni, and V is within the range of 3.0-4.0%. S03, LF refining: Deoxidation is controlled throughout the refining process to keep oxygen in the steel within 15ppm. 15-20kg of aluminum blocks are first fed into the refining furnace at 1650-1680℃ for at least 8 minutes of pre-deoxidation to gradually whiten the slag. The CaO-Al2O3-SiO2-MgO slag system is used. After refining for 13-15 minutes, the temperature is 1660-1690℃. 200-300kg of limestone and 80-150kg of fluorite are added until the slag basicity R reaches 1.5-1.

8. The refining of white slag is completed. After the composition is adjusted, the slag changing operation is carried out to reduce the slag basicity R to below 1.

7. At the same time, the refining soft blowing time is ≥15min, the refining soft blowing gas is argon, and the outlet temperature is ≤1620℃. S04, continuous casting: The entire continuous casting process uses protected casting, with a long shroud and submerged argon sealing. A production process with low superheat, weak secondary cooling water flow, and low casting speed is employed. The overall superheat for continuous casting is between 25 and 28°C, the specific water content is controlled between 0.20 and 0.26 L / Kg, and the average casting speed is 2.4 m / min. M-EMS (Mold Electromagnetic Stirrer) and F-EMS (End-of-Solidification Electromagnetic Stirrer) are also used, with a current of 225 A and a frequency of 3 Hz. S05, shot blasting inspection; S06, Steel Rolling: The controlled rolling and controlled cooling scheme uses a long-term high-temperature heating-high-temperature rolling-weak water penetration process. The specific steps are as follows: the billet temperature is cooled to room temperature (15-35°C), and then heated in a heating furnace using a four-stage temperature-controlled walking beam heating method to ensure that the starting rolling temperature is above 1170°C to obtain a red billet; Step 1: After the red billet passes through the intermediate rolling mill with a large reduction, it enters the first cooling water tank at a speed of 7-8 m / s as an oval billet of 41-42 × 41-42 cm, and is cooled from 1100-1170°C to 1030-1050°C at a water pressure of 1.7-2.0 MPa. Step 2: The red billet is sheared off by the 2# flying shear to remove the tail billet and then enters the finishing mill for rolling; Step 3: After the red slab passes through the finishing mill, it enters the second long water cooling section at a speed of 6-7 m / s via a transfer roller. This water cooling section uses a 50-52 cm diameter, one section of water pipe; Step 4: The finished steel bar is sheared by 3# flying shear to remove the unqualified remaining blanks at the head and tail to ensure the outer dimensions; In step 5, the finished steel bars pass through the conveyor roller and are put into the tail speed reduction device, reducing the speed from 10.5m / s to 7.5m / s, and finally enter the cooling bed at a speed of 7.5m / s. The upper cooling bed temperature is between 1000 and 1050℃, and then it is flipped and translated at a speed of 3.5m / s to ensure continuous and uniform structural transformation under air cooling.

2. The production method according to claim 1, characterized in that In S01, the three-stage converter smelting process is: (1) In the first stage of converter smelting, 100-120 kg of active lime is added to the converter for 0-6 minutes, and nitrogen is used as the bottom blowing gas at a flow rate of 300 L / min; (2) The converter oxygen lance adopts a constant flow rate of 650Nm 3 / h gun position change operation, at 0min, the converter standard gun position starts blowing, and after 2min, the gun position is raised by 5mm; (3) After the first stage of converter smelting is completed, shake the furnace to pour out part of the slag, and the amount of slag poured out is 30-50% of the total weight of the slag; (4) The second stage of converter smelting is 10~15min, and oxygen blowing is continued using oxygen lance, standard lance position, constant flow rate 650Nm 3 / h, add active lime into the converter, the amount of active lime added is 20-25kg / t steel, and the bottom blowing gas is argon with a flow rate of 300L / min; (5) During the last 15-30 minutes of converter smelting, the high lance position is used for blowing, which is 0.5m higher than the standard lance position, with a constant flow rate of 650Nm 3 / h; (6) Fluorite is added in 3 to 5 batches within 25 to 30 minutes within 70 to 75% of the total blowing oxygen consumption. The total amount of fluorite is 2 to 3.5 kg / t steel.

3. The production method according to claim 1, characterized in that In S02, the process of multiple argon blowing is: After the first argon blowing for 10 minutes, the temperature of the molten steel is 1550℃, and the argon flow rate of the first argon blowing is 1.05Nm 3 / min / t; Then the second argon blowing was carried out. After 3 minutes of the second argon blowing, the molten steel temperature was 1580℃ and the argon flow rate of the second argon blowing was 1.05Nm 3 / min / t; Next, the third argon blowing was carried out. First, 40kg / t of high carbon ferrochrome was fed to make the Cr content between 2.35% and 3.46%, and then 100kg of carbonized rice husk was added. After the third argon blowing for 5 minutes, the molten steel temperature was 1590℃. The argon flow rate of the third argon blowing was 0.05Nm 3 / min / t.

4. The production method according to claim 3, characterized in that In S02, the silicon-manganese alloy, high carbon ferrochrome and vanadium-nitrogen alloy are dehydrated and baked, first at 200°C to remove free moisture, and then at 400-600°C to remove crystallized moisture.

5. The production method according to claim 1, characterized in that In S03, the CaO-Al2O3-SiO2-MgO slag system includes CaO: 30~35wt%, Al2O3: 23~33wt%, SiO2: 13~18wt% and the balance MgO.

6. The production method according to claim 1, characterized in that In S03, when the composition is adjusted to the following: C≤0.12%, Si: 0.4~0.6%, Mn: 1.4~1.6%, P≤0.01%, S≤0.01%, Ni≤0.50%, Cr: 2.35~3.46%, V: 0.03~0.04% and the balance Fe; the total amount of C, Cr, Ni and V is 3.0~4.0%; the flow rate of refining soft blowing gas argon is 0.05Nm 3 / min / t.

7. The production method according to claim 1, characterized in that In S04, the shroud length is 800mm.

8. The production method according to claim 1, characterized in that In S06, the process of 4-stage temperature-controlled walking beam heating is as follows: the preheating stage is rapidly increased from 20°C to 850°C in 30 min; Heating: Slow heating from 850°C to 1150°C in 30 minutes; The second heating stage is to slowly heat again from 1150°C to 1220°C in 30 minutes; The temperature in the insulation section is precisely adjusted to ensure that the temperature is controlled at 1220~1250℃, which takes 30 minutes.

9. The Cr-Ni high-grade corrosion-resistant steel bar for marine engineering obtained by the production method according to any one of claims 1 to 8, characterized in that: Compared with HRB400, the relative corrosion rate of Cr-Ni high-grade corrosion-resistant steel bars used in marine engineering is less than 20%.

10. The use of the Cr-Ni high-grade corrosion-resistant steel bar for marine engineering according to claim 9 in marine engineering, characterized in that: Marine engineering projects include large bridges across rivers and seas or harbor terminals.

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