Low-magnetic steel material 00Cr20Ni15Mn5Mo3N for ships and preparation method thereof

Abstract

The invention relates to a low-magnetic steel material 00Cr20Ni15Mn5Mo3N for ships and a preparation method thereof.The low-magnetic steel material comprises, by mass, 0.01%-0.02% of [C], smaller than or equal to 0.010% of [P], smaller than or equal to 0.002% of [S], 0.45%-0.60% of [Si], 4.80%-5.00% of [Mn], 2.30%-2.50% of [Mo], 19.30%-19.70% of [Cr], 14.00%-15.00% of [Ni], 0.13%-0.15% of [Nb], 0.15%-0.20% of [N] and the balance [Fe] and trace residual elements, and the low-magnetic steel is prepared through the low-cost preparation method of'medium-frequency induction furnace-argon oxygen refining furnace- Finally, the yield strength is larger than or equal to 600 Mpa, the tensile strength is larger than or equal to 800 Mpa, the ductility A is larger than or equal to 50%, the impact energy Akv at the temperature of-40 DEG C is larger than or equal to 90 J, and the relative permeability mu r after solid solution is smaller than or equal to 1.0001. The preparation method has the advantages that high performance is achieved, and meanwhile the low cost and the short production period are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low magnetic steel manufacturing, and particularly relates to a low magnetic steel material 00Cr20Ni15Mn5Mo3N for ships and a preparation method thereof. BACKGROUND

[0002] Corrosion-resistant low magnetic steel has become an indispensable member in the manufacturing of ship materials due to its superior corrosion resistance, low magnetism and other performances. With the progress of current ship manufacturing technology, the ship manufacturing field has high requirements for low magnetic steel materials, such as high performance, intelligentization and low cost.

[0003] The traditional manufacturing method of low magnetic steel for key parts of ships mostly adopts the mode of smelting + casting + electroslag + forging or rolling. This manufacturing method is a typical "long process, high investment and slow output" path. Its dependence on special equipment, high-purity raw materials and huge energy consumption, combined with its inherent multi-process and slow process, jointly cause the problems of high manufacturing cost and long production cycle of the final product. Therefore, in order to meet the increasing demand of the ship manufacturing field for low magnetic steel materials, it is urgent to optimize the chemical composition and manufacturing process of low magnetic steel materials to ensure that they have low cost on the premise of meeting high performance. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a low-cost low magnetic steel material 00Cr20Ni15Mn5Mo3N for ships from smelting to forging and a manufacturing method thereof. The low magnetic steel material for ships manufactured by the method has a yield strength of ≥600Mpa, a tensile strength of ≥800Mpa, an elongation A of ≥50%, and an impact energy Akv of ≥90J at-40℃, and a relative magnetic permeability μr≤1.0001 after solid solution.

[0005] The present application is realized by the following technical solutions: The application discloses a low magnetic steel material 00Cr20Ni15Mn5Mo3N for a ship, and chemical components of the low magnetic steel material 00Cr20Ni15Mn5Mo3N for the ship include the following according to mass percentage: [C]: 0.01-0.02%, [P]: less than or equal to 0.010%, [S]: less than or equal to 0.002%, [Si]: 0.45-0.60%, [Mn]: 4.80-5.00%, [Mo]: 2.30-2.50%, [Cr]: 19.30-19.70%, [Ni]: 14.00-15.00%, [Nb]: 0.13-0.15%, [N]: 0.15-0.20%, and the rest is [Fe] and trace residual elements, raw materials including a head, ferro-niobium, a nickel plate, high-carbon ferro-chromium, metallic manganese, an aluminum block and ferrosilicon are used, the low magnetic steel material 00Cr20Ni15Mn5Mo3N is obtained through a medium-frequency induction furnace, an AOD argon-oxygen refining furnace, an LF refining furnace and die casting, and after the die casting ingot is forged into a shape, solid solution treatment is carried out to obtain a finished product meeting the quality requirements.

[0006] A preparation method of the low magnetic steel 00Cr20Ni15Mn5Mo3N for a ship is realized through a short smelting process, an oil press forging and precision forging, and the specific technical route is as follows: a medium-frequency induction furnace (IF) + an argon-oxygen refining furnace (AOD) + a refining furnace (LF) -> die casting (IC) -> demolding and cleaning and hot delivery -> heating + forging -> solid solution treatment -> inspection, and the steps of the technical route are as follows: Step 1), a medium-frequency induction furnace (IF) smelting process: according to the finished product chemical component requirements of the low magnetic steel 00Cr20Ni15Mn5Mo3N, the raw materials entering the medium-frequency induction furnace are 319kg / t of Ni5 heads, 300kg / t of non-magnetic heads, 38kg / t of molybdenum iron, 120kg / t of high-carbon ferro-chromium with P less than or equal to 0.03% and 130kg / t of Ni plates; after the smelting of the raw materials is completed, P is less than or equal to 0.018% and the temperature is 1600-1620 DEG C, and after the components are checked, the molten steel is discharged and transferred to the AOD refining station; Step 2), an argon-oxygen refining furnace (AOD) refining process: the temperature in the argon-oxygen refining furnace before the molten steel is added should be greater than or equal to 1000 DEG C, and 1000kg of lime is added in advance; after the molten steel is added, nitrogen and oxygen are used to enter the automatic blowing mode; during the blowing process, 40-60kg / t of lime and 60-80kg / t of high-carbon ferro-chromium are added; The reduction period is calculated according to the sampling results and target components to add ferrosilicon, and nitrogen is used for stirring; then 0-50 kg / t of manganese, 0-3 kg / t of ferro-niobium is added according to the sampling results and target components; after slagging, secondary reduction is performed, and 0-150 kg of fluorite, 0-125 kg of aluminum block and 0-150 kg of aluminum powder are added for slag conditioning, and argon is used for stirring and sampling; the chemical components should meet the following mass ratio: [C]≤0.01%, [P]≤0.010%, [S]≤0.002%, [Si]: 0.45-0.60%, [Mn]: 4.80-5.00%, [Mo]: 2.30-2.50%, [Cr]: 19.30-19.70%, [Ni]: 14.00-15.00%, [Nb]: 0.13-0.15%, [N]: 0.15-0.20%, and the rest is [Fe] and trace residual elements, and the molten steel is transferred to the LF refining furnace; Step 3), refining furnace (LF) refining process: after tapping, the molten steel is transferred to the refining position of the refining furnace, and nitrogen is connected after the refining ladle is in place; aluminum powder 1-2 kg / t and silicon calcium powder 1-2 kg / t are added for slagging according to the slag condition, and electric slagging is performed, and silicon calcium powder 0.5 kg / t and aluminum powder 0.5 kg / t are added for deoxidation during refining, and the adding frequency is 10-30 min / time; 1-3 m / t of silicon calcium wire is fed before weak stirring, nitrogen is used for weak stirring, the weak stirring time is ≥12 min, and the molten steel is prohibited from being exposed during the whole refining process; the chemical components should meet the following mass ratio: [C]≤0.01%, [P]≤0.010%, [S]≤0.002%, [Si]: 0.45-0.60%, [Mn]: 4.80-5.00%, [Mo]: 2.30-2.50%, [Cr]: 19.30-19.70%, [Ni]: 14.00-15.00%, [Nb]: 0.13-0.15%, [N]: 0.15-0.20%, and the rest is [Fe] and trace residual elements, and the ladle mold casting temperature of the refining furnace (LF) is 1470-1480℃ after the ladle mold casting temperature of the refining furnace (LF) is 1470-1480℃, and then the mold casting position is transferred; Step 4), mold casting, demolding and cleaning: carefully select the steel ingot mold with good inner wall quality and polish it, and pre-bake the steel ingot mold before mold casting to ensure that the service temperature is 30-150℃; ensure that the pouring system is clean and dry, and use in-mold argon filling and argon protection pouring throughout the process, and the setting time is ≥10 min; the opening pouring flow is ≥300 kg, and the opening pouring temperature is 1460-1470℃; Step 5), steel ingot surface cleaning: after the steel ingot is demolded, the burrs and flash at both ends are cleaned, and then it is hot sent to the forging process, and the doors and windows around must be closed during the demolding and hoisting and loading process; Step 6), pre-forging homogenization heat treatment: the surface quality of the ingot is checked when forging, the ingot is loaded into a heating furnace, and the ingot is heated to 1210±10 DEG C in two stages for 6-8h to ensure uniform heating; the initial forging temperature is 950-1100 DEG C, and the final forging temperature is greater than or equal to 850 DEG C; Step 7), using an oil press to perform blooming: the ingot completed in step 6) is upset on the upper flat lower platform, the upsetting deformation is 65%-75%, and the height-diameter ratio of the ingot after upsetting is 0.95-1.05; then the ingot is elongated using an upper flat lower V anvil, and the deformation of each pass is 20-30%; if the ingot is heated in the middle, the furnace temperature is 1210±10 DEG C, and the holding time is 1-3h; Step 8), heating: the ingot completed in step 7) is loaded into a heating furnace for heating, the furnace temperature is 1160±10 DEG C, and the holding time is 1-2h; Step 9), forging forming: the ingot completed in step 8) is forged on a precision forging machine, the deformation of the first pass is 35%-25%, the drawing speed is greater than or equal to 3m / min, and the forging frequency is 180 times / min; the deformation of the second pass is 15%-25%, the drawing speed is greater than or equal to 6m / min, and the forging frequency is 180 times / min; Step 10), air cooling: the finished product after step 9) is subjected to air cooling treatment; Step 11), solid solution treatment, the finished product completed in step 10) is subjected to solid solution treatment at a temperature of 1070-1080 DEG C.

[0007] The technical scheme of the present application has the following positive effects: The low magnetic steel forging prepared by the present application can achieve the target value of the content of steel grade C, effectively reduce the content of harmful elements such as sulfur, phosphorus, hydrogen and oxygen, and has a yield strength of greater than or equal to 600Mpa, a tensile strength of greater than or equal to 800Mpa, an elongation A of greater than or equal to 50%, an impact energy Akv of greater than or equal to 90J at-40 DEG C, and a relative magnetic permeability μr of less than or equal to 1.0001 after solid solution. The present application breaks through the bottleneck of long production cycle and high cost of low magnetic steel material for key parts of ships, and can realize batch production after multiple trial production verification. Specific implementation method

[0008] Embodiment 1: The application provides a ship low-magnetic steel material 00Cr20Ni15Mn5Mo3N used for key parts of a ship and a manufacturing method thereof. A medium-frequency induction furnace (IF), an argon-oxygen refining furnace (AOD) and a refining furnace (LF) are used to refine the molten steel meeting the quality requirements, the molten steel is hoisted to a pouring trolley by a crown block and is poured; after demolding, the surface of the ingot is cleaned, and the ingot is hot sent to a forging process, a upsetting and elongating method is used to obtain a forging blank meeting the quality and shape requirements, and then a solid solution treatment is performed to obtain a finished product meeting the performance requirements. The application controls the key points such as the steelmaking raw and auxiliary materials, AOD deep desulfurization operation, AOD [C] removal and [Cr] preservation operation, nitrogen gas nitrogen-increasing operation, molten steel temperature and composition, pouring speed, riser feeding, microstructure refinement, secondary forging and solid solution treatment in the production process, and the finished product quality meets the technical requirements. The die casting ingot specification is a Φ400mm round ingot, the ingot weight is 3.3t, the length is 2790mm, and the finished product specification is Φ320mm. The specific technical scheme is as follows: Step 1), medium-frequency induction furnace (IF) steelmaking process: according to the finished product chemical composition requirements of the low-magnetic steel 00Cr20Ni15Mn5Mo3N, the medium-frequency induction furnace charging raw materials are 319kg / t of Ni5 material head, 300kg / t of non-magnetic material head, 38kg / t of molybdenum iron, 120kg / t of high-carbon chromium iron with P≤0.03% and 130kg / t of Ni plate; the raw materials should be clean and dry, and the surface should be clean and free of oil stains during the medium-frequency induction furnace smelting; before the material head and steel scrap are used, the composition is determined by using a portable spectrometer to ensure that the composition and size of the material head and steel scrap meet the charging requirements; after the furnace charge is melted and cleaned, P≤0.018% is controlled to ensure that P and other elements do not exceed the upper limit of the chemical composition requirements after steel mixing; the temperature is 1600-1620℃, and the composition is checked before tapping to the AOD argon-oxygen refining furnace refining station; Step 2), argon-oxygen refining furnace (AOD) refining process: the AOD furnace temperature should be ≥1000℃ before steel mixing, and 1000kg of lime is added in advance; after steel mixing, nitrogen and oxygen are used to enter the automatic blowing mode; 50kg / t of lime and 70kg / t of high-carbon chromium iron are added during the blowing process; Reduction period, according to the sampling results and target components, the amount of ferrosilicon is calculated, and nitrogen is used for stirring; then according to the sampling results and target components, 0~50kg / t of manganese metal, 0~3kg / t of ferro-niobium is added; after slagging, secondary reduction is carried out, and 0~150kg of fluorite, 0~125kg of aluminum block and 0~150kg of aluminum powder are added for slag conditioning, and argon is used for stirring before sampling; the chemical composition should meet the following mass ratio: [C]≤0.01%, [P]≤0.010%, [S]≤0.002%, [Si]: 0.45~0.60%, [Mn]: 4.80~5.00%, [Mo]: 2.30~2.50%, [Cr]: 19.30~19.70%, [Ni]: 14.00~15.00%, [Nb]: 0.13~0.15%, [N]: 0.15~0.20%, and the rest is [Fe] and trace residual elements, and the temperature is suitable for tapping into the LF refining furnace; Step 3), refining furnace (LF) refining process: after tapping, it is transferred to the refining position of the refining furnace, and the nitrogen is connected after the refining ladle is in place; according to the slag condition, 1~2kg / t of aluminum powder and 1~2kg / t of silicon calcium powder are added for slagging, and the electric slagging is sent, 0.5kg / t of silicon calcium powder and 0.5kg / t of aluminum powder are added for deoxidation during refining, and the adding frequency is 20min / time; 1~3m / t of silicon calcium wire is fed before weak stirring, nitrogen is used for weak stirring, the weak stirring time is ≥12min, and the molten steel is prohibited to be exposed during the whole refining process; the mold casting temperature is 1470~1480℃ from the LF furnace ladle; Step 4), mold casting, demolding and cleaning: carefully select the steel ingot mold with good inner wall quality and polish it, preheat the steel ingot mold before mold casting to ensure that the use temperature is 30~150℃; ensure that the pouring system is clean and dry, use argon filling and argon protection pouring in the whole process, and the setting time is ≥10min; the opening flow is ≥300kg, and the opening temperature is 1460~1470℃; Step 5), steel ingot surface cleaning: after the steel ingot is demolded, the burrs and flash at both ends are cleaned, and then it is hot sent to the forging process, and the doors and windows around must be closed during the demolding and hoisting and loading process; Step 6), homogenization heat treatment before forging: check the surface quality of the mold casting ingot when forging, put the mold casting ingot into the heating furnace, heat it to 1210±10℃ in two stages, and keep it for 6~8h to ensure uniform heating; the initial forging temperature is 950~1100℃, and the final forging temperature is ≥850℃; Step 7: adopt an oil press to perform blooming: the mold casting ingot after step 6) is upset on the upper flat plate and the lower platform, and is upset to H=750mm; then it is elongated to Φ420mm by using the upper flat and lower V anvil; Step 8), heating: the mold casting ingot after step 7) is loaded into the heating furnace for heating, the furnace temperature is 1160±10℃, and the temperature is kept for 1-2h; Step 9), forging forming: the ingot of step 8) is forged on a precision forging machine, the first pass is drawn to Φ380mm, the drawing speed is ≥3m / min, and the forging frequency is 180 times / min; the second pass is drawn to Φ325mm, the drawing speed is ≥6m / min, and the forging frequency is 180 times / min; Step 10), the finished product of step 9) is air-cooled and solid-solution treated after forging, the solid-solution temperature is 1070-1080℃.

[0009] The relative magnetic permeability μ r of the 00Cr20Ni15Mn5Mo3N low magnetic steel produced by the application is ≤1.0001, the chemical composition meets the requirements, and the general porosity, center porosity and segregation are not greater than the 1st level of various ratings specified in GB / T1979 standard.

[0010] Appendix: 00Cr20Ni15Mn5Mo3N low magnetic steel chemical composition table 1, measured performance table 2.

[0011] Table 1 Chemical composition (%) Element Target component This embodiment C ≤0.02 0.02 Si 0.55~0.60 0.58 Mn 4.80~5.00 5.00 P ≤0.020 0.020 S ≤0.005 0.002 Cr 19.30~19.70 19.50 Mo 2.30~2.50 2.50 Ni 14.00~15.00 15.00 Nb 0.13~0.15 0.15 N 0.15~0.20 0.20 Table 2 Measured performance Yield strength Rp0.2 ≥ 600 Mpa 615 Tensile strength Rm ≥ 800 Mpa 820 -40℃ impact energy ≥90J 90 .

Claims

1. A low-magnetic steel material for ships, 00Cr20Ni15Mn5Mo3N, characterized in that: The chemical composition of the low-magnetic steel material 00Cr20Ni15Mn5Mo3N for marine applications, by mass percentage, is as follows: [C]: 0.01~0.02%, [P] ≤0.010%, [S] ≤0.002%, [Si]: 0.45~0.60%, [Mn]: 4.80~5.00%, [Mo]: 2.30~2.50%, [Cr]: 19.30~19.70%, [Ni]: 14.00%. ~15.00%, [Nb]: 0.13~0.15%, [N]: 0.15~0.20%, with the remainder being [Fe] and trace residual elements. Using raw materials such as scrap, niobium iron, nickel plate, high-carbon ferrochrome, metallic manganese, aluminum blocks, and ferrosilicon as raw materials, 00Cr20Ni15Mn5Mo3N low magnetic steel ingots are obtained through medium-frequency induction furnace, AOD argon-oxygen refining furnace, LF refining furnace, and die casting. After forging the ingots, solution treatment is performed to obtain finished products that meet the quality requirements.

2. A method for preparing the low-magnetic steel material 00Cr20Ni15Mn5Mo3N for ships as described in claim 1, characterized in that: A low-cost preparation method is adopted, consisting of "medium-frequency induction furnace (IF) + argon-oxygen refining furnace (AOD) + refining furnace (LF) → ingot casting (IC) → demolding and cleaning, hot delivery → heating + forging → solution treatment → inspection". The specific steps are as follows: Step 1) Medium Frequency Induction Furnace (IF) Steelmaking Process: To meet the chemical composition requirements of the finished low-magnetic steel 00Cr20Ni15Mn5Mo3N, the raw materials fed into the IF furnace are 319 kg / t of Ni5 feedstock, 300 kg / t of non-magnetic feedstock, 38 kg / t of ferromolybdenum, 120 kg / t of high-carbon ferrochrome with P ≤ 0.03%, and 130 kg / t of Ni plate. After the furnace charge is melted and cleared, P ≤ 0.018% and the temperature is 1600~1620℃. After verifying the composition, the steel is tapped and transferred to the AOD refining station. Step 2) Argon-Oxygen Refining Furnace (AOD) Refining Process: Before steel addition, the temperature inside the argon-oxygen refining furnace should be ≥1000℃, and 1000kg of lime should be added to the furnace in advance; after steel addition, nitrogen and oxygen are used to enter the automatic blowing mode; during the blowing process, 40~60kg / t of lime and 60~80kg / t of high-carbon ferrochrome are added. During the reduction period, the amount of ferrosilicon added is calculated based on the sampling results and target composition, and nitrogen is used for stirring. Subsequently, 0~50 kg / t of metallic manganese and 0~3 kg / t of ferroniobium are added based on the sampling results and target composition. After slag removal, a secondary reduction is performed, adding 0~150 kg of fluorite, 0~125 kg of aluminum blocks, and 0~150 kg of aluminum powder for slag conditioning, and argon is used for stirring before sampling. The chemical composition, by mass ratio, should meet the following requirements: [C] ≤ 0.01% and [P] ≤ 0.010%. [S] ≤ 0.002%, [Si]: 0.45~0.60%, [Mn]: 4.80~5.00%, [Mo]: 2.30~2.50%, [Cr]: 19.30~19.70%, [Ni]: 14.00~15.00%, [Nb]: 0.13~0.15%, [N]: 0.15~0.20%, with the remainder being [Fe] and trace residual elements. The steel is then transferred to the LF refining furnace. Step 3) Refining process in the refining furnace (LF): After tapping, the steel is transferred to the refining station in the refining furnace. After the refining ladle is in place, nitrogen is turned on. Depending on the slag condition, 1~2 kg / t of aluminum powder and 1~2 kg / t of silicon-calcium powder are added to form slag. Electrolytic slag is then fed. During refining, 0.5 kg / t of silicon-calcium powder and 0.5 kg / t of aluminum powder are added for deoxidation. The addition frequency is 10~30 min / time. Before weak stirring, 1~3 m / t of silicon-calcium wire is fed in and weak stirring is carried out using nitrogen. The weak stirring time is ≥12 min. The molten steel must not be exposed during the entire refining process. The chemical composition, by mass ratio, should meet the following requirements: [C] ≤ 0.01%, [P] ≤ 0.010%, [S] ≤ 0.002%, [Si]: 0.45~0.60%, [Mn]: 4.80~5.00%, [Mo]: 2.30~2.50%, [Cr]: 19.30~19.70%, [Ni]: 14.00~15.00%, [Nb]: 0.13~0.15%, [N]: 0.15~0.20%, with the remainder being [Fe] and trace residual elements. After being transferred from the refining furnace (LF) ladle to the casting station at a temperature of 1470~1480℃, the product is ready for casting. Step 4) Ingot casting, demolding and cleaning: Carefully select steel ingot molds with good inner wall quality and grind and clean them. Before casting, bake the steel ingot molds to ensure the operating temperature is 30~150℃; ensure the gating system is clean and dry, use argon filling and argon protection throughout the casting process, and the calming time is ≥10min; the initial pouring flow is ≥300kg, and the initial pouring temperature is 1460~1470℃; Step 5) Cleaning the surface of the steel ingot: After the steel ingot is demolded, the burrs and flash at both ends are cleaned, and then it is hot-sent to the forging process. During the demolding and hoisting loading process, the surrounding doors and windows must be closed. Step 6) Homogenization heat treatment before forging: During forging, check the surface quality of the die casting ingot, put the die casting ingot into the heating furnace, heat it in two stages to 1210±10℃, hold it for 6~8h, and ensure uniform heating; the initial forging temperature is 950~1100℃, and the final forging temperature is ≥850℃. Step 7) Using a hydraulic press for billet preparation: The ingot from Step 6) is upset on a flat plate and a lower platform, with an upsetting deformation of 65%~75%, and the height-to-diameter ratio of the upset ingot is 0.95~1.05; then it is drawn using a flat plate and a V-shaped anvil, with a deformation of 20~30% per pass. If it is reheated in the furnace in the middle, the furnace temperature is 1210±10℃ and the holding time is 1~3h. Step 8): Heating: Place the ingot from step 7) into a heating furnace and heat it at a furnace temperature of 1160±10℃ for 1-2 hours. Step 9) Forging: The die casting ingot completed in step 8) is forged on a precision forging machine. The deformation amount of the first pass is 35%~25%, the forging speed is ≥3m / min, and the forging frequency is 180 times / minute; the deformation amount of the second pass is 15%~25%, the forging speed is ≥6m / min, and the forging frequency is 180 times / minute. Step 10): Air cooling: After completing step 9), the finished product is air cooled. Step 11) Solution treatment: The finished product from step 10) is subjected to solution treatment at a temperature of 1070~1080℃.