Austenitic stainless steel with low magnetic conductivity and high corrosion resistance as well as manufacturing method and application thereof

Abstract

The invention belongs to the technical field of stainless steel new materials in the ferrous metallurgy industry, and relates to austenitic stainless steel with low magnetic conductivity and high corrosion resistance as well as a manufacturing method and application of the austenitic stainless steel. The austenitic stainless steel with low magnetic conductivity and high corrosion resistance comprises the following components in percentage by weight: 0.030-0.100% of C; 0.30% to 1.00% of Si; mn: 1.50 to 2.00%; p is less than or equal to 0.035%; s: < = 0.005%; 18.50% to 24.00% of Cr; ni: 10.50% to 12.00%; v: 0.05% to 0.30%; 0.050% to 0.120% of N; 0.30% of Cu, 0.30% or less of Mo, 0.0050% or less of Pb, Sn and As, and the balance Fe and inevitable impurities. By optimizing alloy components, the corrosion resistance of the material is remarkably improved, and the long-term stable use requirement of nuclear magnetic medical equipment in a complex environment is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of new stainless steel materials in the steel and metallurgical industry, and relates to a low magnetic permeability and high corrosion resistance austenitic stainless steel and its manufacturing method and application, and in particular to a low magnetic permeability and high corrosion resistance austenitic stainless steel coil for nuclear magnetic resonance medical equipment and its manufacturing method. Background Art

[0002] MRI medical equipment requires specialized components with exceptional properties. Firstly, the materials must possess excellent corrosion resistance to ensure long-term, stable operation in complex medical environments, preventing corrosion-induced equipment failures or the degradation of test results. Secondly, because MRI equipment operates on strong magnetic fields, the materials must possess extremely low magnetic permeability to prevent interference with the field, thereby ensuring accurate and clear imaging.

[0003] While traditional austenitic stainless steels (such as SUS316L stainless steel) are widely used in general industrial applications, their combined corrosion resistance and low magnetic permeability make them difficult to fully meet the stringent requirements of MRI medical equipment. For example, SUS316L stainless steel may interfere with the magnetic field in MRI environments due to its high magnetic permeability, while its corrosion resistance is still insufficient in certain specific medical environments.

[0004] Some existing research has improved the corrosion resistance of stainless steel by adjusting alloy composition, such as adding molybdenum (Mo) to enhance corrosion resistance. However, these improvements fail to fully consider the low magnetic permeability requirements of MRI equipment, resulting in material performance that cannot fully meet the needs of MRI medical equipment.

[0005] With the rapid development of nuclear magnetic resonance medical technology, the requirements for the material performance of internal components of the equipment are becoming increasingly stringent. Developing an austenitic stainless steel coil and its manufacturing method that can simultaneously meet the requirements of high corrosion resistance and extremely low magnetic permeability while being economical is urgent. Summary of the Invention

[0006] In view of the defects of the prior art, the present invention provides a low magnetic permeability and high corrosion resistance austenitic stainless steel and its manufacturing method and application.

[0007] Specifically, the present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a low magnetic permeability and high corrosion resistance austenitic stainless steel, which comprises, by weight percentage: C: 0.030-0.100%; Si: 0.30-1.00%; Mn: 1.50-2.00%; P≤0.035%; S: ≤0.005%; Cr: 18.50-24.00%; Ni: 10.50-12.00%; V: 0.05-0.30%; N: 0.050-0.120%; Cu≤0.30%, Mo≤0.30%, Pb+Sn+As≤0.0050%, and the balance being Fe and unavoidable impurities.

[0009] The above-mentioned low magnetic permeability and high corrosion-resistant austenitic stainless steel includes, by weight percentage: C: 0.04-0.06%; Si: 0.30-0.50%; Mn: 1.55-1.80%; P: ≤0.035%; S: ≤0.005%; Cr: 18.50-20.00%; Ni: 10.50-11.50%; V: 0.05-0.15%; N: 0.060-0.120%; Cu: ≤0.10%, Mo: ≤0.30%, Pb+Sn+As: ≤0.0050%, and the balance is Fe and unavoidable impurities.

[0010] The above-mentioned low magnetic permeability and high corrosion resistance austenitic stainless steel has an austenite stability coefficient △≥0 and a low temperature martensite transformation temperature M S ≤-269℃, ferrite content ≤3%, magnetic permeability μr ≤1.02, corrosion rate ≤0.005mm / a.

[0011] In a second aspect, the present invention provides a method for preparing low magnetic permeability and high corrosion resistance austenitic stainless steel, comprising:

[0012] (1) A method of medium frequency furnace + converter dephosphorized hot metal - AOD - LTS - continuous casting is used to obtain continuous casting billets;

[0013] (2) soaking, rough rolling, finish rolling, and coiling the continuously cast slab to obtain a hot-rolled coil;

[0014] (3) The hot-rolled coil is subjected to continuous annealing and pickling to obtain a hot-rolled steel strip.

[0015] In the above-mentioned method for preparing low magnetic permeability and high corrosion-resistant austenitic stainless steel, the basicity of the AOD steelmaking slag is controlled between 1.8 and 2.2; the LTS deep desulfurization adopts a slag-forming agent of lime:fluorite = 1.0-1.5, and the target sulfur content S≤0.005%; the continuous casting temperature is 1480-1500°C, and the pulling speed is 0.8-1.4m / min.

[0016] In the above-mentioned method for preparing low magnetic permeability and high corrosion resistance austenitic stainless steel, the target temperature of the soaking is 1250-1300° C., and the holding time is 3-5 min / 10 mm thickness.

[0017] In the above-mentioned method for preparing low magnetic permeability and high corrosion-resistant austenitic stainless steel, the final temperature of the rough rolling is 1080-1150°C, the final temperature of the finishing rolling is 950-1000°C, the intermediate billet thickness is ≤40mm; and the coiling temperature is controlled at 750-800°C.

[0018] In the above-mentioned method for preparing low magnetic permeability and high corrosion-resistant austenitic stainless steel, the target annealing temperature of the annealing is controlled at 1100-1150°C, and the TV value is controlled within 200; the pickling adopts a hydrochloric acid + mixed acid process, wherein the hydrochloric acid concentration is ≥150g / l, the nitric acid concentration is ≥150g / l, the hydrofluoric acid concentration is ≤40g / l, and the acid temperature is controlled at 30-80°C.

[0019] In a third aspect, the present invention provides a low magnetic permeability and high corrosion resistance austenitic stainless steel coil, which is obtained by the above-mentioned method for preparing low magnetic permeability and high corrosion resistance austenitic stainless steel.

[0020] In a fourth aspect, the present invention provides the use of the above-mentioned low magnetic permeability and high corrosion resistance austenitic stainless steel or the above-mentioned low magnetic permeability and high corrosion resistance austenitic stainless steel coil in nuclear magnetic medical equipment.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] (1) High corrosion resistance: By optimizing the alloy composition, the corrosion resistance of the material is significantly improved, meeting the long-term stable use requirements of nuclear magnetic resonance medical equipment in complex environments;

[0023] (2) Extremely low magnetic permeability: By controlling the residual element content and microstructure, the magnetic permeability of the material is significantly reduced, avoiding interference with the magnetic field of the nuclear magnetic resonance equipment and ensuring the accuracy and clarity of imaging;

[0024] (3) Excellent mechanical properties: Through composition design and process optimization, the ferrite content (F) is ≤3%, the room temperature yield strength (Rp0.2) is ≥220MPa, and the tensile strength (Rm) is ≥520MPa, which meets the material strength and toughness requirements of nuclear magnetic resonance medical equipment;

[0025] (4) Economical and environmentally friendly: The hydrochloric acid + mixed acid pickling process reduces the treatment cost of waste sulfuric acid, reduces environmental pollution, and improves production efficiency and material utilization. DETAILED DESCRIPTION

[0026] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process method of the present invention adopts conventional methods or devices in the field. Unless otherwise specified, the following terms used in the present invention are consistent with the common meanings of various scientific and technological terms in the field and the meanings of professional terms defined in various technical dictionaries, textbooks, etc.

[0027] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0028] The idea of the present invention is to achieve the comprehensive performance of μr≤1.02, corrosion rate≤0.005mm / a, and Rp0.2≥220MPa by optimizing the C-Ni-Cr-VN composition system (Δ≥0, Ms≤-269℃), combining AOD-LTS refining, hot rolling temperature control, and hydrochloric acid + mixed acid pickling process. Specifically, the martensitic phase transformation is suppressed by adding austenite stabilizing elements such as Ni and C, while balancing cost and performance; corrosion resistance is enhanced by increasing the Cr content and optimizing the purity, but ferrite formation needs to be avoided; corrosion resistance is increased by adding the stabilizing element V, reducing the material grain size and fixing the C and N elements; and environmental load is reduced by developing a green pickling process, in line with the development needs of green and low-carbon development.

[0029] Specifically, the low magnetic permeability and high corrosion-resistant austenitic stainless steel provided by the present invention includes, by weight percentage: C: 0.030-0.100%; Si: 0.30-1.00%; Mn: 1.50-2.00%; P≤0.035%; S: ≤0.005%; Cr: 18.50-24.00%; Ni: 10.50-12.00%; V: 0.05-0.30%; N: 0.050-0.120%; Cu≤0.30%, Mo≤0.30%, Pb+Sn+As≤0.0050%, and the balance is Fe and unavoidable impurities.

[0030] In the composition design of the present invention:

[0031] C: By increasing the C content, austenite stability is improved and Mo demand is reduced (reducing costs), but the risk of intergranular corrosion must be controlled. Therefore, the present invention limits its content to 0.030-0.100%, preferably 0.040-0.060%.

[0032] Mn, Si: Manganese and silicon are added as deoxidizing elements. If the content is too low, it will be detrimental to the purity of the steel, while if it is too high, it will be detrimental to improving the impact toughness. At the same time, they assist in austenitization and optimize the Δ coefficient (Δ≥0). Therefore, the composition is set to meet Δ≥0 and M S The present invention limits the Mn content to 1.50-2.00%, preferably 1.55-1.80%; and limits the Si content to 0.30-1.00%, preferably 0.30-0.50%.

[0033] Cr: Chromium is an alloying element that gives stainless steel its ferrite structure and excellent corrosion resistance. Cr's greatest impact on stainless steel is its corrosion resistance, primarily improving its resistance to oxidizing and acidic chloride media. In oxidizing media, chromium rapidly forms a chromium oxide (Cr2O3) passivation film on the surface of stainless steel. Therefore, the present invention limits the Cr content to 18.50-24.00%, preferably 18.50-20.00%.

[0034] Nickel: Nickel is a highly effective solid solution strengthening element. Nickel is a large atomic solute. When dissolved in the base metal, it causes lattice distortion, hindering dislocation movement and thereby increasing yield strength. It can significantly improve the strength of stainless steel, significantly enhance low-temperature toughness, lower the Ms temperature (<-269°C), and inhibit martensitic transformation. However, too low a nickel content cannot guarantee Δ ≥ 0, while too high a nickel content increases costs. Therefore, the present invention limits the nickel content to 10.50-12.00%, preferably 10.50-11.50%.

[0035] V: By adding V, the austenitic stainless steel grains are refined while fixing C and N elements to increase corrosion resistance, but the cost cannot be increased too much. Therefore, the present invention limits the V content to 0.05-0.30%, preferably 0.05-0.15%.

[0036] In austenitic stainless steel: Excessive amounts of Cu and Mo promote the precipitation of σ phase, which forms Cu2S with S, exacerbating hot brittleness. Mo and N synergistically improve corrosion resistance, but excessive amounts lead to embrittlement of Cr2N. Pb / Sn / As form a low-melting-point eutectic and synergistically deteriorate high-temperature plasticity with S. P segregates at grain boundaries and forms a brittle phase with Cr / Mo. S destroys the matrix through MnS and forms a eutectic with Cu / Pb. N combines with Ti / Nb to form a stable nitride. This requires coordinated control through composition optimization (e.g., limiting P to ≤ 0.03% and S to ≤ 0.005%) and smelting processes (AOD / LTS). Residual elements such as Cu, Mo, Pb+Sn+As, P, S, and N should be controlled to minimize processing degradation and the risk of hot cracking, achieving a higher purity.

[0037] In some preferred embodiments, in the low magnetic permeability and high corrosion resistance austenitic stainless steel of the present invention, the austenite stability coefficient Δ≥0, the low temperature martensite transformation temperature M S ≤-269℃.

[0038] The austenite stability coefficient Δ is achieved by controlling the content of Ni, Mn, C, Cr, and Mo elements, and the low-temperature martensite transformation temperature Ms is achieved by controlling the content of Cr, Ni, Mn, Si, C, and N elements. S The calculation formula is as follows:

[0039] △=Ni+0.5Mn+35×C-0.0833(Cr+1.5Mo-20) 2 -12;

[0040] M S (℃)={7×(14.6-Cr)+110×(8.9-Ni)+60×(1.33-Mn)+50×(0.47-Si)+3000

[0041] ×[0.068-(C+N)]-32} / 1.84;

[0042] Wherein, chemical elements represent the weight percentage of their corresponding elements.

[0043] On the other hand, the present invention also provides a method for preparing low magnetic permeability and high corrosion resistance austenitic stainless steel, comprising:

[0044] Steelmaking process

[0045] The continuous casting billet is obtained by adopting the method of medium frequency furnace + converter dephosphorized molten iron - AOD - LTS - continuous casting.

[0046] In order to ensure the quality of steel and refining efficiency, the present invention controls the basicity of the AOD steelmaking slag between 1.8 and 2.2. The appropriate basicity helps to form an ideal inclusion morphology, improve the cleanliness and mechanical properties of the steel, and also helps to improve the desulfurization efficiency, thereby reducing the sulfur content in the steel and improving the hot working performance and corrosion resistance of the steel.

[0047] Optionally, the basicity of the AOD tapping slag is controlled at 1.8, 1.9, 2.0, 2.1 or 2.2.

[0048] Among them, slag basicity refers to the ratio of alkaline substances (mainly calcium oxide) to acidic substances (mainly silicon dioxide).

[0049] The present invention removes the slag after AOD tapping and re-slags the steel using the LTS. The LTS uses a lime:fluorite ratio of 1.0-1.5 to create new slag, with a target sulfur content of S≤0.005%. This controls the reduction effect and reduces the number and type of inclusions.

[0050] In order to obtain a good as-cast structure and thus produce a billet with excellent mechanical properties and high surface quality, the present invention controls the casting temperature to 1480-1500° C. and the casting speed to 0.8-1.4 m / min.

[0051] Optionally, the casting temperature is controlled to 1480° C., 1485° C., 1490° C., 1495° C. or 1500° C.; and the pulling speed is controlled to 0.8 m / min, 1.0 m / min, 1.2 m / min, 1.25 m / min or 1.4 m / min.

[0052] Hot rolling process

[0053] The continuous casting slab is subjected to soaking, rough rolling, finish rolling and coiling to obtain a hot rolled coil.

[0054] In some preferred embodiments, the soaking temperature target is 1250-1300° C., and the soaking time is 3-5 min / 10 mm thickness, thereby controlling the uniformity of heating and avoiding excessive generation of ferrite phase.

[0055] Optionally, the uniform heating temperature target is 1250°C, 1260°C, 1270°C, 1280°C, 1290°C or 1300°C; the holding time is 3 min / 10 mm thickness, 3.5 min / 10 mm thickness, 4 min / 10 mm thickness, 4.5 min / 10 mm thickness or 5 min / 10 mm thickness.

[0056] In some preferred embodiments, the final temperature of the rough rolling is 1080-1150° C., the final temperature of the finish rolling is 950-1000° C., and the coiling temperature is controlled at 750-800° C. In order to control the temperature of the steel coil, the present invention adopts a hot coil box process to ensure that the steel coil obtains a good hot-rolled microstructure.

[0057] Optionally, the final temperature of the rough rolling is 1080°C, 1090°C, 1100°C, 1110°C, 1120°C, 1130°C, 1140°C or 1150°C; the final temperature of the finishing rolling is 950°C, 960°C, 970°C, 980°C, 990°C or 1000°C; and the coiling temperature is controlled to be 750°C, 760°C, 770°C, 780°C, 790°C or 800°C.

[0058] In some preferred embodiments, the intermediate billet thickness is ≤40 mm.

[0059] Annealing and pickling process

[0060] The hot-rolled coil is subjected to continuous annealing and pickling to obtain a hot-rolled steel strip.

[0061] In some preferred embodiments, the target annealing temperature of the annealing is controlled at 1100-1150° C., and the TV value is controlled within 200, so that the harmful precipitated phase is fully dissolved and a good grain size is obtained.

[0062] The TV value is the product of thickness (mm) × speed (m / min).

[0063] Optionally, the target annealing temperature is controlled at 1100°C, 1110°C, 1120°C, 1130°C, 1140°C or 1150°C.

[0064] In some preferred embodiments, the pickling adopts a hydrochloric acid + mixed acid process, wherein the hydrochloric acid concentration is ≥150 g / l, the nitric acid concentration is ≥150 g / l, the hydrofluoric acid concentration is ≤40 g / l, and the acid temperature is controlled at 30-80°C. In this way, the iron oxide scale is efficiently removed, the CrO layer is selectively dissolved, the Cr loss is reduced, and the corrosion resistance is improved.

[0065] After testing, the austenitic stainless steel coil obtained according to the method of the present invention has a ferrite content of ≤3%, a magnetic permeability μr ≤1.02, a corrosion rate ≤0.005mm / a, a room temperature yield strength Rp0.2 ≥220MPa, a tensile strength Rm ≥520MPa, and an elongation A ≥40%.

[0066] The austenitic stainless steel coil prepared according to the method of the present invention has excellent corrosion resistance while ensuring extremely low magnetic permeability. By optimizing the manufacturing method, the production cost is reduced and the production efficiency is improved to meet the large-scale production and high performance requirements of nuclear magnetic medical equipment.

[0067] Example

[0068] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. In the following examples, the experimental methods without specific conditions are based on conventional methods and conditions.

[0069] Example 1

[0070] According to the process of the present invention, the steps of producing a low magnetic permeability, high corrosion-resistant austenitic stainless steel coil for nuclear magnetic resonance medical equipment with a target specification of 8.0 mm × 1219 mm × L mm are as follows:

[0071] (1) The desired continuous casting billet was obtained by the method of medium frequency furnace + converter dephosphorized hot metal-AOD-LTS-continuous casting. The nominal thickness was 200 mm. The mass percentage of its chemical composition is shown in Table 1.

[0072] (2) The desired continuous casting billet is obtained by a method of medium frequency furnace + converter dephosphorized hot metal - AOD - LTS - continuous casting, wherein the AOD tapping basicity is controlled at 1.92, the slag is removed after AOD tapping, and LTS is re-slaged, the lime:fluorite = 1.2, the casting temperature is controlled between 1480-1500 °C, and the casting speed is 1.4 m / min;

[0073] (3) The desired hot rolled coil is obtained by soaking-rough rolling-hot coil box-finishing rolling-coiling, wherein: the heating temperature target is 1280°C, the holding time is 80 min; the rough rolling temperature is 1112°C, the finishing temperature of the finishing rolling is 980°C, the coiling temperature is 781°C, the intermediate billet target thickness is 28 mm, and the hot coil target thickness is 8.0 mm;

[0074] (4) The target annealing temperature of the hot coil is 1100-1150℃, the TV value is controlled within 200, and the hot coil pickling adopts hydrochloric acid + mixed acid (nitric acid + hydrofluoric acid) process, with the target concentration of hydrochloric acid: 180g / l; the target concentration of nitric acid: 150g / l; the target concentration of hydrofluoric acid: 30g / l; the acid temperature: ~50℃.

[0075] After the steps are implemented, the performance parameters of the low magnetic permeability and high corrosion resistance austenitic stainless steel coil used for nuclear magnetic resonance medical equipment are shown in Table 2.

[0076] Example 2

[0077] According to the process of the present invention, the steps of producing a low magnetic permeability, high corrosion-resistant austenitic stainless steel coil for nuclear magnetic resonance medical equipment with a target specification of 6.0 mm × 1219 mm × L mm are as follows:

[0078] (1) The desired continuous casting billet was obtained by the method of medium frequency furnace + converter dephosphorized hot metal-AOD-LTS-continuous casting. The nominal thickness was 200 mm. The mass percentage of its chemical composition is shown in Table 1.

[0079] (2) The desired continuous casting billet is obtained by a method of medium frequency furnace + converter dephosphorized hot metal - AOD - LTS - continuous casting, wherein the AOD tapping basicity is controlled at 2.0, the slag is removed after AOD tapping, and LTS is re-slaged, the lime:fluorite ratio is 1.5, the casting temperature is controlled between 1480-1500°C, and the casting speed is 1.4 m / min;

[0080] (3) The desired hot rolled coil is obtained by soaking-rough rolling-hot coil box-finishing rolling-coiling, wherein: the heating temperature target is 1280°C, the holding time is 80 min; the rough rolling end temperature is 1100°C, the finishing rolling end temperature is 988°C, the coiling temperature is 775°C, the intermediate billet target thickness is 28 mm, and the hot coil target thickness is 6.0 mm;

[0081] (4) The target annealing temperature of the hot coil is 1100-1150℃, the TV value is controlled within 200, and the hot coil pickling adopts hydrochloric acid + mixed acid (nitric acid + hydrofluoric acid) process, with the target concentration of hydrochloric acid: 180g / l; the target concentration of nitric acid: 150g / l; the target concentration of hydrofluoric acid: 30g / l; the acid temperature: ~50℃.

[0082] After the steps are implemented, the performance parameters of the low magnetic permeability and high corrosion resistance austenitic stainless steel coil used for nuclear magnetic resonance medical equipment are shown in Table 2.

[0083] Example 3

[0084] According to the process of the present invention, the steps of producing a low magnetic permeability, high corrosion-resistant austenitic stainless steel coil for nuclear magnetic resonance medical equipment with a target specification of 12.0 mm × 1500 mm × L mm are as follows:

[0085] (1) The desired continuous casting billet was obtained by the method of medium frequency furnace + converter dephosphorized hot metal-AOD-LTS-continuous casting. The nominal thickness was 250 mm, and the mass percentage of its chemical composition is shown in Table 1.

[0086] (2) The desired continuous casting billet is obtained by a method of medium frequency furnace + converter dephosphorized hot metal - AOD - LTS - continuous casting, wherein the AOD tapping basicity is controlled at 1.92, the slag is removed after AOD tapping, and LTS is re-slaged, the lime:fluorite = 1.3, the casting temperature is controlled between 1480-1500 °C, and the casting speed is 1.0 m / min;

[0087] (3) The desired hot rolled coil is obtained by soaking-rough rolling-hot coil box-finishing rolling-coiling, wherein: the heating temperature target is 1280°C, the holding time is 100 min; the rough rolling end temperature is 1080°C, the finishing rolling end temperature is 982°C, the coiling temperature is 791°C, the intermediate billet target thickness is 28 mm, and the hot coil target thickness is 12.0 mm;

[0088] (4) The target annealing temperature of the hot coil is 1100-1150℃, the TV value is controlled within 200, and the hot coil pickling adopts hydrochloric acid + mixed acid (nitric acid + hydrofluoric acid) process, with the target concentration of hydrochloric acid: 180g / l; the target concentration of nitric acid: 150g / l; the target concentration of hydrofluoric acid: 30g / l; the acid temperature: ~50℃.

[0089] After the steps are implemented, the performance parameters of the low magnetic permeability and high corrosion resistance austenitic stainless steel coil used for nuclear magnetic resonance medical equipment are shown in Table 2.

[0090] Comparative Example

[0091] According to the SUS316L process, the production target specification is 6.0mm×1500mm×Lmm. The implementation steps are as follows:

[0092] (1) The desired continuous casting billet was obtained by the method of medium frequency furnace + electric furnace-AOD-LF-continuous casting. The nominal thickness was 200 mm. The mass percentage of its chemical composition is shown in Table 1.

[0093] (2) The desired continuous casting billet is obtained by a method of medium frequency furnace + electric furnace - AOD - LF - continuous casting, wherein: the basicity of AOD steel tapping is controlled to be greater than 1.6, the slag thickness after AOD steel tapping is not greater than 200 mm, the amount of lime and fluorite is adjusted according to the slag condition in LF, desulfurization is carried out using a silicon calcium wire, the casting temperature is controlled between 1470-1500 °C, and the casting speed is 0.8 m / min;

[0094] (2) The desired hot rolled coil is obtained by soaking-rough rolling-hot coil box-finishing rolling-coiling, wherein: the heating temperature target is 1280°C, the holding time is greater than 100 min; the rough rolling temperature is greater than 1100°C, the finishing temperature is not greater than 1000°C, the coiling temperature is not controlled, the intermediate billet target thickness is 30 mm, and the hot coil target thickness is 6.0 mm;

[0095] (3) The hot coil is subjected to continuous casting, annealing, and pickling to obtain hot-rolled No. 1 coil, wherein: the target annealing temperature of the hot coil is 1100-1150°C, the TV value is controlled within 200, and the hot coil pickling adopts a sulfuric acid + mixed acid (nitric acid + hydrofluoric acid) process, with a sulfuric acid target concentration of >200 g / l; a nitric acid target concentration of >150 g / l; a hydrofluoric acid target concentration of <30 g / l; and an acid temperature of ~50°C.

[0096] After the above steps are implemented, the performance parameters of the austenitic stainless steel coil are shown in Table 2.

[0097] Table 1 Comparison of chemical compositions of Examples and Comparative Examples, wt%

[0098]

[0099] Table 2 Comparison of performance parameters between the embodiment and the comparative example

[0100] Material No. Austenite stabilization Low temperature martensite Ferrite Yield strength tensile strength Elongation Magnetic permeability Corrosion rate Example 1 1.53 -385 2.1 245 550 45 1.01 0.004 Example 2 1.28 -362 2.3 238 540 43 1.01 0.0045 Example 3 1.85 -410 1.9 250 560 47 1.00 0.0038 Comparative Example -0.16 -186 4.5 210 532 40 1.08 0.012

[0101] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art will appreciate that these embodiments are intended only to illustrate the present invention and are not to be construed as limiting the scope of the present invention. It should be noted that any equivalent variations and substitutions to these embodiments are intended to fall within the scope of the claims. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A low magnetic permeability and high corrosion resistance austenitic stainless steel, characterized in that: Calculated by weight percentage, it includes: C: 0.030-0.100%; Si: 0.30-1.00%; Mn: 1.50-2.00%; P≤0.035%; S: ≤0.005%; Cr: 18.50-24.00%; Ni: 10.50-12.00%; V: 0.05-0.30%; N: 0.050-0.120%; Cu≤0.30%, Mo≤0.30%, Pb+Sn+As≤0.0050%, and the balance is Fe and unavoidable impurities.

2. The low magnetic permeability and high corrosion resistance austenitic stainless steel according to claim 1, characterized in that: Calculated by weight percentage, it includes: C: 0.04-0.06%; Si: 0.30-0.50%; Mn: 1.55-1.80%; P: ≤0.035%; S: ≤0.005%; Cr: 18.50-20.00%; Ni: 10.50-11.50%; V: 0.05-0.15%; N: 0.060-0.120%; Cu: ≤0.10%, Mo: ≤0.30%, Pb+Sn+As: ≤0.0050%, and the balance is Fe and unavoidable impurities.

3. The low magnetic permeability and high corrosion resistance austenitic stainless steel according to claim 1, characterized in that: Austenite stability coefficient △≥0, low temperature martensite transformation temperature M S ≤-269℃, ferrite content ≤3%, magnetic permeability μr ≤1.02, corrosion rate ≤0.005mm / a.

4. The method for preparing the low magnetic permeability and high corrosion resistance austenitic stainless steel according to any one of claims 1 to 3, characterized in that: include: (1) A method of medium frequency furnace + converter dephosphorized hot metal - AOD - LTS - continuous casting is used to obtain continuous casting billets; (2) soaking, rough rolling, finish rolling, and coiling the continuously cast slab to obtain a hot-rolled coil; (3) The hot-rolled coil is subjected to continuous annealing and pickling to obtain a hot-rolled steel strip.

5. The preparation method according to claim 4, characterized in that The basicity of the AOD tapping slag is controlled between 1.8 and 2.2; the LTS deep desulfurization adopts a slag-making agent of lime:fluorite = 1.0-1.5, and the target sulfur content S≤0.005%; the casting temperature of the continuous casting is 1480-1500°C, and the pulling speed is 0.8-1.4m / min.

6. The preparation method according to claim 4, characterized in that The target temperature of the soaking is 1250-1300°C, and the holding time is 3-5 minutes per 10 mm thickness.

7. The preparation method according to claim 4, characterized in that The final temperature of the rough rolling is 1080-1150°C, the final temperature of the finish rolling is 950-1000°C, the thickness of the intermediate billet is ≤40mm; the temperature of the coiling is controlled at 750-800°C.

8. The preparation method according to claim 4, characterized in that The target annealing temperature of the annealing is controlled at 1100-1150°C, and the TV value is controlled within 200; the pickling adopts a hydrochloric acid + mixed acid process, wherein the hydrochloric acid concentration is ≥150g / l, the nitric acid concentration is ≥150g / l, the hydrofluoric acid concentration is ≤40g / l, and the acid temperature is controlled at 30-80°C.

9. A low magnetic permeability and high corrosion resistance austenitic stainless steel coil, characterized in that: The method is obtained by the preparation method according to any one of claims 4 to 8.

10. Use of the low magnetic permeability and high corrosion resistance austenitic stainless steel according to any one of claims 1 to 3 or the low magnetic permeability and high corrosion resistance austenitic stainless steel coil according to claim 9 in nuclear magnetic resonance medical equipment.

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