Steel for 400MPa-grade high-manganese non-magnetic reinforcing steel bar and production method

Abstract

The invention provides steel for a 400MPa-grade high-manganese non-magnetic reinforcing steel bar and a production method. The steel comprises the following components: 0.15-0.35% of C, 0.20-0.40% of Si, 18-28% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, 0.05-0.10% of V, 2.0-4.0% of Al, 0.01-0.02% of N and the balance of Fe and inevitable impurity elements, and 4.2 < = L = 1.5 * [C] + 0.20 * [Mn] + 10.0 * [N] < = 5.8. Compared with the prior art, the components are adopted, steel making and steel rolling processes are combined, an austenite structure is formed at the room temperature, the magnetic conductivity is smaller than or equal to 1.05, ReL is larger than or equal to 400 MPa, Rm is larger than or equal to 600 MPa, A is larger than or equal to 30%, and the technical requirements of key projects for the mechanical property of the non-magnetic steel bar can be met. The coating does not contain Cr element and is low in cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot-rolled steel bars for reinforced concrete and their production processes, and particularly relates to a steel for 400MPa grade high manganese non-magnetic steel bars and a production method thereof. Background Art

[0002] In the steel industry, electric furnaces, extra-high voltage electrical rooms in the power industry, and large nuclear fusion devices, etc., are related to buildings in strong magnetic environments. If ordinary hot-rolled ribbed steel bars are used, they will be continuously stressed under the action of the magnetic field, and ultimately may cause the concrete protective layer to crack or even the component to be damaged. Therefore, non-magnetic steel bars must be used to replace ordinary hot-rolled ribbed steel bars to ensure the safe use of relevant buildings.

[0003] The invention patent with the publication number CN 115449598A, which was published on December 9, 2022, discloses a method for preparing non-magnetic steel bars. The disclosed preparation method includes: KR pretreatment for desulfurization of hot metal, converter smelting, nitrogen blowing, LF refining, VD vacuum refining, continuous casting, shot peening inspection, and rolling; among which, low-S hot metal is obtained by using KR pretreatment before smelting; in addition, in the nitrogen blowing step, calcium carbide, calcium aluminate, lime, and iron oxide scale are added to the molten steel, and with this unique top slag process, under sufficient refining nitrogen blowing time, the inclusions in the molten steel are effectively deformed and floated up and absorbed into the top slag, and the size of the inclusions in the final finished steel bars is generally less than 20μm.

[0004] However, in the above-mentioned prior art, there is no clear means for performance strengthening, and it is very likely that the mechanical properties cannot stably reach the 400MPa grade, and it does not meet the engineering application conditions. Therefore, it is very necessary to provide a steel for 400MPa grade high manganese non-magnetic steel bars. Summary of the Invention

[0005] The purpose of the present invention is to provide a steel for 400MPa grade high manganese non-magnetic steel bars and a production method thereof. By adding Mn and Al, and combining with the steelmaking and rolling processes, an austenite structure is formed at room temperature to meet the requirement of magnetic permeability ≤ 1.05. By adding V and utilizing its precipitation strengthening effect, the mechanical properties of the steel bars are improved to reach R eL ≥400MPa, R m ≥600MPa, A≥30%, which can meet the technical requirements of the mechanical properties of non-magnetic steel bars for key projects. The present invention does not contain Cr element, has low cost, and the production process is not complicated, which is suitable for large-scale industrial production and popularization and application.

[0006] The specific technical solution of the present invention is as follows:

[0007] A steel for 400MPa grade high manganese non-magnetic steel bars, including the following components by mass percentage:

[0008] C 0.15 - 0.35%, Si 0.20 - 0.40%, Mn 18 - 28%, P ≤ 0.025%, S ≤ 0.025%, V 0.05 - 0.10%, Al 2.0 - 4.0%, N 0.01 - 0.02%, and the balance is Fe and inevitable impurity elements.

[0009] The chemical composition of the steel for 400 MPa grade high manganese non - magnetic steel bars satisfies: 4.2 ≤ L = 1.5×[C] + 0.20×[Mn] + 10.0×[N] ≤ 5.8. In the formula, C, Mn, and N affect the strength performance and non - magnetic performance. Calculated according to this formula, the strength and non - magnetic performance of the product are ensured.

[0010] In the formula, each symbol represents the corresponding chemical composition content × 100%.

[0011] The microstructure of the steel for 400 MPa grade high manganese non - magnetic steel bars is austenite.

[0012] The R of the steel for 400 MPa grade high manganese non - magnetic steel bars eL ≥400 MPa, R m ≥600 MPa, A ≥ 30%, and the relative magnetic permeability ≤ 1.05.

[0013] Preferably, the R of the steel for 400 MPa grade high manganese non - magnetic steel bars eL ≥450 MPa, R m ≥650 MPa, A ≥ 47%, and the relative magnetic permeability ≤ 1.05.

[0014] A kind of steel for 400 MPa grade high manganese non - magnetic steel bars provided by the present invention includes the following technological processes:

[0015] Electric furnace smelting → LF furnace refining → RH vacuum treatment → continuous casting → rolling.

[0016] The specific production key points are as follows:

[0017] For the electric furnace smelting: First, add scrap steel + ferromanganese alloy, and then pour in hot metal, where the proportion of hot metal is 30 - 50%, and the proportion of scrap steel + ferromanganese alloy is 70 - 50%. Turn on the electrodes and start the oxygen lance to heat up. The end - point requirements are: P ≤ 0.010%, S ≤ 0.010%, and the temperature is 1575 - 1625 °C; slag - stopping tapping, add ferrotitanium and slag materials when 1 / 4 of the molten steel is tapped, add aluminum cakes when 3 / 4 of the molten steel is tapped, and after tapping is completed, sprinkle an appropriate amount of aluminum particles evenly on the steel slag surface according to the amount of slag flowing down.

[0018] The LF furnace refining: argon is blown from the bottom of the ladle throughout the whole process, and the argon flow rate is based on the molten steel not splashing out of the ladle; 0.83-1.65kg / t of pre-melted refining slag and 6.67-8.33kg / t of lime are added, TFe+MnO in the slag is ≤1.0%, and alloys are added before, during and after LF furnace refining to adjust the content of Si, Mn, V and Al elements according to the component analysis results before entering the LF furnace, wherein Al is added by feeding aluminum wire, and other alloys are added in blocks through the feeding system. The temperature out of the LF furnace is 1580-1620℃.

[0019] The RH vacuum degassing: the temperature of the molten steel entering the RH vacuum furnace is 1540-1560°C; in the early stage of vacuum, the vacuum holding time is ≥12 minutes, and the composition is adjusted in the middle stage of vacuum according to the composition analysis results in the early stage of vacuum, and the vacuum holding time is guaranteed to be ≥8 minutes after adjustment. The temperature out of the RH vacuum furnace is 1500-1520°C.

[0020] Continuous casting: small billet continuous casting adopts full-process protection casting, the pouring temperature is 1465-1485℃, the crystallizer cooling water flow rate is 3000 liters / minute, and the secondary cooling water volume is 0.8-1.2 liters / kg to ensure the surface quality of the billet.

[0021] The rolling is carried out by a continuous bar mill: the heating temperature is controlled at 1150-1250°C, the steel tapping temperature is controlled at 980-1080°C, three-stage water cooling is adopted after finish rolling, the temperature drops by 150-250°C, and the upper cooling bed temperature is controlled at 800-900°C.

[0022] The design ideas of the present invention are as follows: (1) According to the actual national conditions of my country, which lacks Ni and Cr but is rich in Mn, a high Mn composition design is adopted, and a certain amount of C, N, and Al are added at the same time to cooperate with Mn to expand and stabilize the austenite phase region, and form a single austenite structure at room temperature, thereby ensuring the low magnetic permeability of the steel bar. Mn is a strong austenite-forming element, which can enable steel to obtain a single-phase austenite structure at room temperature and greatly reduce the magnetic permeability of the steel. The key point of the present invention is to organically combine the composition optimization adjustment with metallurgical quality control, so that the steel bar obtains high strength and toughness while obtaining excellent non-magnetic properties. (2) A certain amount of V is added to utilize its precipitation strengthening effect to improve the mechanical properties of the steel bar. (3) The steel billet is heated at a higher temperature to promote the solid solution of the above elements. (4) After rolling, three-stage water cooling is adopted to reduce the temperature by 150 to 250°C to avoid the formation of martensite and other structures, thereby ensuring the magnetic permeability of the steel bar at room temperature.

[0023] In the present invention, C: an element conducive to the formation of a single-phase austenite structure, which also has a good solid solution strengthening effect and is effective in improving the strength of steel. However, with the increase of the C content, although a single austenite structure can be obtained under water quenching or air cooling conditions, too high a C content will reduce the plasticity of the steel and increase the tendency of austenite grain growth, thus leading to an increase in magnetic permeability. The C content in the present invention is controlled at 0.15 - 0.35%.

[0024] Si: Its main role in steel is deoxidation. Since the atomic radius of Si is much smaller than that of the austenite phase, its solid solution strengthening effect is obvious. However, Si is a non-carbide forming element, which can reduce the solubility of C in austenite, thus causing the precipitation of carbides in the steel and being unfavorable to the stability of the austenite structure. The Si content in the present invention is controlled at 0.20 - 0.40%.

[0025] Mn: A very strong austenite forming element, which can expand the austenite region and make the austenite structure stable. Most of the Mn in the steel can be dissolved in austenite to form a substitutional solid solution, and with the increase of the Mn content, the transformation temperature from austenite to martensite further decreases, increasing the stability of austenite. The Mn content in the present invention is controlled at 18 - 28%.

[0026] V: An element that strongly forms carbonitrides. The fine and dispersed precipitates of VC, VN, and V(CN) formed inhibit the growth of austenite grains. At the same time, the fine and dispersed precipitates of VC, VN, and V(CN) are conducive to the nucleation of austenite and improve the strength of the steel through the co-lattice distortion and dispersion strengthening effects. The V content in the present invention is controlled at 0.05 - 0.10%.

[0027] Al: It can increase the stacking fault energy of austenite, strongly inhibit the martensite transformation, and stabilize the austenite structure. It is one of the key elements of austenitic steel. However, the upper limit of the Al content depends on whether high-temperature δ-ferrite appears, and the lower limit depends on whether the transformation from low-temperature austenite to martensite can be avoided. The Al content in the present invention is controlled at 2.0 - 4.0%.

[0028] N: A strong austenite forming element and an interstitial solid solution element. It forms VN and V(CN) compounds with V, greatly improving the strength of the steel. The N content in the present invention is controlled at 0.01 - 0.02%.

[0029] P, S: Belong to harmful impurity elements, which are not conducive to ensuring the strength, plasticity, and low magnetic properties of the steel. The P and S contents in the present invention are controlled at ≤0.025%.

[0030] The non-magnetic properties and mechanical properties of the steel bars in the present invention are achieved by the combined action of the above elements, rather than the individual action of each element.

[0031] With the rapid development of many fields in China such as electric power, rail transit, construction, and national defense industry, there is a demand for non-magnetic steel and non-magnetic steel bars. Compared with the existing technology, the present invention adopts the above components and production methods to obtain a yield strength R eL ≥400 MPa, a tensile strength R m ≥600 MPa, and an elongation after fracture A≥30%; it is evaluated by the measurement method of the magnetic permeability of weak magnetic materials in GJB 937-90, and its relative magnetic permeability ≤1.05. Its mechanical properties meet the requirements of HRB400E steel bars in GB 1499.2 and can meet the needs of construction in non-magnetic fields such as China's national defense industry. In addition, the steel bars of the present invention do not need to use scarce Cr elements, have low production costs, and feasible production processes, and have good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the room temperature structure (magnification 100) of the typical 400 MPa high manganese non-magnetic steel bar of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] The present invention provides a steel for 400 MPa grade high manganese non-magnetic steel bars, including the following components by mass percentage:

[0035] C 0.15 - 0.35%, Si 0.20 - 0.40%, Mn 18 - 28%, P≤0.025%, S≤0.025%, V 0.05 - 0.10%, Al 2.0 - 4.0%, N 0.01 - 0.02%, and the rest are Fe and inevitable impurity elements.

[0036] The chemical composition of the steel for 400 MPa grade high manganese non-magnetic steel bars satisfies: 4.2 ≤ L = 1.5×[C] + 0.20×[Mn] + 10.0×[N] ≤ 5.8.

[0037] In the formula, each symbol represents the corresponding chemical composition content × 100%.

[0038] The above-mentioned steel for 400 MPa grade high manganese non-magnetic steel bars includes the following technological processes:

[0039] Electric furnace smelting → LF furnace refining → RH vacuum treatment → continuous casting → rolling.

[0040] The specific production key points are as follows:

[0041] For the electric furnace smelting: First, add scrap steel + ferromanganese alloy, and then tap the hot metal. The proportion of hot metal is 30 - 50%, and the proportion of scrap steel + ferromanganese alloy is 70 - 50%. Turn on the electrodes and start the oxygen lance to heat up. The end-point requirements are: P ≤ 0.010%, S ≤ 0.010%, and the temperature is 1575 - 1625°C; slag blocking for tapping. When 1 / 4 of the molten steel is tapped, add ferrotitanium and slag materials. When 3 / 4 of the molten steel is tapped, add aluminum cakes. After tapping is completed, according to the amount of slag flowing down, evenly sprinkle an appropriate amount of aluminum particles on the steel slag surface.

[0042] For the LF furnace refining: Bottom blowing argon gas throughout the ladle. The argon gas flow rate is based on the molten steel not splashing out of the ladle; add 0.83 - 1.65 kg / t of pre-melted refining slag and 6.67 - 8.33 kg / t of lime. TFe + MnO in the slag ≤ 1.0%. According to the component analysis results before entering the LF furnace, add alloys to adjust the contents of Si, Mn, V, and Al elements during the early, middle, and late stages of LF furnace refining. Among them, Al is added in the form of feeding aluminum wire, and other alloys are added in block form through the feeding system. The temperature when leaving the LF furnace is 1580 - 1620°C.

[0043] For the RH vacuum degassing: The temperature of the molten steel entering the RH vacuum furnace is 1540 - 1560°C; in the early stage of vacuum, the vacuum holding time ≥ 12 minutes. According to the component analysis results in the early stage of vacuum, component adjustment is carried out in the middle stage of vacuum, and the vacuum holding time after adjustment is guaranteed to be ≥ 8 minutes. The temperature when leaving the RH vacuum furnace is 1500 - 1520°C.

[0044] Continuous casting: Small billet continuous casting, using full-process protected casting. The tapping temperature is 1465 - 1485°C, the cooling water flow rate of the mold is 3000 liters per minute, and the specific secondary cooling water volume is 0.8 - 1.2 liters per kilogram to ensure the surface quality of the billet.

[0045] For the rolling, continuous bar mill is used for rolling: The heating temperature is controlled at 1150 - 1250°C, the tapping temperature is controlled at 980 - 1080°C. After finish rolling, three-stage water cooling is adopted, and the temperature drops by 150 - 250°C. The temperature for entering the cooling bed is controlled at 800 - 900°C.

[0046] The microstructure of the steel for 400 MPa grade high manganese non-magnetic steel bars produced by the above components through the above method is austenite. Its properties are: R eL ≥ 400 MPa, R m ≥ 600 MPa, A ≥ 30%, and the relative magnetic permeability ≤ 1.05.

[0047] The following are several specific implementation cases of the present invention:

[0048] Examples 1 - 2

[0049] A steel for 400MPa grade high manganese non-magnetic steel bars, comprising the following components by mass percentage: As shown in Table 1, the balance not shown in Table 1 is Fe and inevitable impurity elements.

[0050] Comparative example

[0051] A steel for high manganese non-magnetic steel bars, comprising the following components by mass percentage: As shown in Table 1, the balance not shown in Table 1 is Fe and inevitable impurity elements.

[0052] Table 1 Melting chemical compositions of examples and comparative examples (%)

[0053] Case C Si Mn P S V Al N L value Example 1 0.31 0.35 18.5 0.011 0.010 0.09 2.4 0.012 4.29 Example 2 0.28 0.33 20.6 0.008 0.008 0.07 2.2 0.018 4.72 Comparative example 0.16 0.35 19.0 0.015 0.007 0.08 2.3 0.010 4.14

[0054] The production method of the steel for 400MPa grade high manganese non-magnetic steel bars described in Example 1, comprising the following steps:

[0055] (1) Electric furnace smelting (producing 120 tons per furnace): First add scrap steel + ferromanganese alloy, then pour in hot metal, with the hot metal accounting for 40% and the scrap steel + ferromanganese alloy accounting for 60%. Turn on the electrodes and start the oxygen lance to heat up. End point: 0.010% P, 0.010% S, temperature 1595°C. Skim the slag and tap the steel. When about 1 / 4 of the molten steel is tapped, add ferrotitanium and slag materials. When about 3 / 4 of the molten steel is tapped, add aluminum cakes. After tapping is completed, according to the amount of slag falling, evenly sprinkle an appropriate amount of aluminum particles on the steel slag surface.

[0056] (2) LF furnace refining: Bottom blow argon gas throughout the ladle, with the argon gas flow rate based on the molten steel not splashing out of the ladle; Add 150 kg of pre-melted refining slag and 900 kg of lime, with 1.0% TFe + MnO in the slag. According to the component analysis results before entering the LF furnace, add alloys during the pre-stage, middle-stage, and post-stage of LF furnace refining to adjust the contents of Si, Mn, V, and Al elements. Among them, Al is added by feeding aluminum wire, and other alloys are added in block form through the feeding system. The temperature out of the LF furnace is 1600°C.

[0057] (3) RH vacuum degassing: The temperature of the molten steel entering the RH vacuum furnace is 1550°C. The vacuum holding time in the early stage of vacuum is 12 minutes, and the vacuum holding time after component adjustment in the middle stage of vacuum is 8 minutes. The temperature out of the RH vacuum furnace is 1510°C.

[0058] (4) Bloom continuous casting: Adopt full protection casting. The tapping temperature is 1475°C, the cooling water flow rate in the mold is 3000 liters per minute, and the specific secondary cooling water volume is 1.0 liter per kilogram.

[0059] (5) Rolling on the bar mill: The heating temperature, tapping temperature control, and temperature on the cooling bed are shown in Table 2.

[0060] The production method of the steel for 400MPa grade high manganese non-magnetic steel bars described in Example 2, comprising the following steps:

[0061] (1) Electric furnace smelting: First, add scrap steel + ferromanganese alloy, then pour in hot metal, with the proportion of hot metal being 30% and that of scrap steel + ferromanganese alloy being 70%. Start the electrodes and oxygen lance to heat up. Endpoint: 0.007% P, 0.008% S, temperature 1575°C. Skim the slag when tapping the steel. When about 1 / 4 of the molten steel is tapped, add ferrotitanium and slag materials. When about 3 / 4 of the molten steel is tapped, add aluminum cakes. After tapping is completed, sprinkle an appropriate amount of aluminum particles evenly on the steel slag surface according to the amount of slag falling through.

[0062] (2) LF furnace refining: The ladle is bottom-blown with argon throughout the process, and the argon flow rate is based on the condition that the molten steel does not splash out of the ladle. Add 100 kg of pre-melted refining slag and 800 kg of lime. The content of 0.8% TFe + MnO in the slag. Adjust the contents of Si, Mn, V, and Al elements by adding alloys before, during, and after the LF furnace refining according to the component analysis results before entering the LF furnace. Among them, Al is added in the form of feeding aluminum wire, and other alloys are added in bulk through the feeding system. The temperature when leaving the LF furnace is 1580°C.

[0063] (3) RH vacuum degassing: The temperature of the molten steel in the ladle entering the RH vacuum furnace is 1540°C; the vacuum holding time in the early stage of vacuum is 14 minutes. According to the component analysis results in the early stage of vacuum, the vacuum holding time is 10 minutes after the component adjustment in the middle stage of vacuum. The temperature when leaving the RH vacuum furnace is 1500°C.

[0064] (4) Continuous casting of small billets: Adopt full-process protected casting. The pouring temperature is 1465°C, the cooling water flow rate in the mold is 3000 liters per minute, and the specific water consumption for secondary cooling is 0.8 liters per kilogram.

[0065] (5) Rolling on the bar mill: The heating temperature, tapping temperature control, and temperature on the cooling bed are shown in Table 2.

[0066] The high manganese non-magnetic steel described in the comparative example includes the following steps:

[0067] (1) Electric furnace smelting: First, add scrap steel + ferromanganese alloy, then pour in hot metal, with the proportion of hot metal being 40% and that of scrap steel + ferromanganese alloy being 60%. Start the electrodes and oxygen lance to heat up. Endpoint: 0.014％P 0.007% S, temperature 1623°C. Skim the slag when tapping the steel. When about 1 / 4 of the molten steel is tapped, add ferrotitanium and slag materials. When about 3 / 4 of the molten steel is tapped, add aluminum cakes. After tapping is completed, sprinkle an appropriate amount of aluminum particles evenly on the steel slag surface according to the amount of slag falling through.

[0068] (2)LF furnace refining: Argon is blown from the bottom throughout the ladle, and the argon flow rate is based on preventing the molten steel from splashing out of the ladle; 180 kg of pre-melted refining slag and 950 kg of lime are added. The content of 0.7% TFe+MnO in the slag. According to the component analysis results before entering the LF furnace, alloys are added during the pre-stage, middle-stage, and post-stage of LF furnace refining to adjust the contents of Si, Mn, V, and Al elements. Among them, Al is added by feeding aluminum wire, and other alloys are added in block form through the feeding system. The temperature when tapping from the LF furnace is 1615 °C.

[0069] (3)RH vacuum degassing: The temperature of the molten steel in the ladle entering the RH vacuum furnace is 1555 °C; the vacuum holding time in the early stage of vacuum is 15 minutes. According to the component analysis results in the early stage of vacuum, after the component adjustment in the middle stage of vacuum, the vacuum holding time is ensured to be 12 minutes. The temperature when tapping from the RH vacuum furnace is 1513 °C.

[0070] (4)Continuous casting of billets: Full protection casting is adopted. The pouring temperature is 1478 °C, the cooling water flow rate in the mold is 3000 liters per minute, and the specific water consumption for secondary cooling is 1.2 liters per kilogram to ensure the surface quality of the billets.

[0071] (5)Rolling on bar mill: The heating temperature, tapping temperature control, and temperature on the cooling bed are shown in Table 2.

[0072] Table 2 Rolling parameters of each example and comparative example

[0073] Case Heating temperature (°C) Tapping temperature (°C) Temperature on cooling bed (°C) Example 1 1200 1040 850 Example 2 1180 1020 845 Comparative example 1160 990 900

[0074] The mechanical properties, metallographic structures, and magnetic permeabilities of the examples and comparative examples of the present invention are shown in Table 3. Among them: R eL is the yield strength; R m is the tensile strength; A is the elongation after fracture at a gauge length of 5d (d is the nominal diameter of the steel bar).

[0075] Table 3 Properties of examples and comparative examples

[0076] Case <![CDATA[R eL (MPa)]]> <![CDATA[R m (MPa)]]> A(％) Metallographic structure Relative permeability Example 1 415 630 47 Austenite 1.002 Example 2 450 645 47 Austenite 1.001 Comparative example 385 630 46 Austenite 1.003

[0077] The underlined data above do not meet the requirements of the present invention.

[0078] The above description of the examples is for the convenience of those of ordinary skill in the art to understand and use the invention. Those familiar with the technology in the field can obviously make various modifications to these examples easily and apply the general principles described herein to other examples without creative labor. Therefore, the present invention is not limited to the above examples, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A steel for 400MPa grade high manganese non-magnetic steel bars, characterized in that, The steel for 400MPa grade high manganese non-magnetic steel bars comprises the following chemical components by mass percentage: C 0.15 - 0.35%, Si 0.20 - 0.40%, Mn 18 - 28%, P ≤ 0.025%, S ≤ 0.025%, V 0.05 - 0.10%, Al 2.0 - 4.0%, N 0.01 - 0.02%, and the balance is Fe and inevitable impurity elements.

2. The steel for 400MPa grade high manganese non-magnetic steel bars according to claim 1, characterized in that, The chemical composition of the steel for 400MPa grade high manganese non-magnetic steel bars satisfies: 4.2 ≤ L = 1.5×[C] + 0.20× [Mn] + 10.0×[N] ≤ 5.

8.

3. The steel for 400MPa grade high manganese non-magnetic steel bars according to claim 1 or 2, characterized in that, The structure of the steel for 400MPa grade high manganese non-magnetic steel bars is austenite.

4. The steel for 400MPa grade high manganese non-magnetic steel bars according to claim 1 or 2, characterized in that The R of the steel for 400MPa grade high manganese non-magnetic steel bars eL ≥ 400MPa, R m ≥ 600MPa, A ≥ 30%, relative magnetic permeability ≤ 1.

05.

5. A production method of the steel for 400MPa grade high manganese non-magnetic steel bars according to any one of claims 1 - 4, comprising the following technological processes: Electric furnace smelting → LF furnace refining → RH vacuum treatment → continuous casting → rolling.

6. The production method according to claim 5, characterized in that, The electric furnace smelting: First add scrap steel, and then pour in hot metal, where the proportion of hot metal is 30 - 50% and the proportion of scrap steel is 70 - 50%; End point requirements: P ≤ 0.010%, S ≤ 0.010%, temperature 1575 - 1625°C.

7. The production method according to claim 5, characterized in that, The LF furnace refining: The ladle is bottom-blown with argon throughout the process, and the argon flow rate is based on ensuring that the molten steel does not splash out of the ladle; Add 0.83 - 1.65 kg / t of pre-melted refining slag and 6.67 - 8.33 kg / t of lime, with TFe + MnO in the slag ≤ 1.0%, and the temperature out of the LF furnace is 1580 - 1620°C.

8. The production method according to claim 5, characterized in that, The RH vacuum degassing: The temperature of the molten steel entering the RH vacuum furnace is 1540 - 1560°C; In the early stage of vacuum, the vacuum holding time ≥ 12 minutes, and composition adjustment is carried out in the middle stage of vacuum. After adjustment, ensure a vacuum holding time of ≥ 8 minutes, and the temperature out of the RH vacuum furnace is 1500 - 1520°C.

9. The production method according to claim 5, characterized in that, The continuous casting: Small billet continuous casting, with full protection casting, the starting casting temperature is 1465 - 1485°C, the cooling water flow rate of the mold is 3000 liters / minute, and the specific secondary cooling water volume is 0.8 - 1.2 liters / kg.

10. The production method according to claim 5, characterized in that, The rolling: The heating temperature is controlled at 1150 - 1250°C, the tapping temperature is controlled at 980 - 1080°C, three-stage water cooling is adopted after finish rolling, the temperature drops by 150 - 250°C, and the temperature on the cooling bed is controlled at 800 - 900°C.

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