Non-magnetic reinforcing bar and method of manufacturing the same

Abstract

The application relates to the technical field of non-magnetic steel bar production, in particular to a non-magnetic steel bar and a preparation method thereof.The method comprises the following steps: heating a casting blank with a set chemical composition; rolling the heated casting blank, and controlling the process parameters of the rolling to obtain a hot-rolled steel; and cooling the hot-rolled steel, and controlling the end point temperature of the cooling to obtain a non-magnetic steel bar.The absolute magnetic permeability of the non-magnetic steel bar is 1.28*10-6-1.30*10-6 h / m, which can meet the non-magnetic or extremely low magnetic requirement of the steel bar for a magnetic levitation railway track.

Description

Technical Field

[0001] This application relates to the field of non-magnetic steel bar production technology, and in particular to a non-magnetic steel bar and its preparation method. Background Technology

[0002] Maglev railway is a new type of transportation system that uses the repulsive force generated by an electromagnetic system to lift the train, suspending it above the guide rails. Electromagnetic force is used for guidance, and a linear motor directly converts electrical energy into propulsion. It eliminates wheel-rail contact, reduces frictional resistance, minimizes vertical load on the track, allows for high speeds, produces no pollution, and is safe, reliable, and comfortable.

[0003] The steel bars used in maglev railway tracks are required to be non-magnetic or have extremely low magnetic properties. However, conventional steel bars are currently magnetic and do not meet the magnetic requirements of non-magnetic steel. Therefore, it is necessary to develop a non-magnetic or extremely low magnetic steel bar to meet the requirements of steel bars used in maglev train tracks. Summary of the Invention

[0004] This application provides a non-magnetic steel bar and its preparation method to solve the technical problem of high magnetism in existing steel bars used in maglev train tracks.

[0005] In a first aspect, this application provides a method for preparing non-magnetic steel bars, the method comprising:

[0006] Heating a billet with a set chemical composition;

[0007] The heated billet is rolled, and the rolling process parameters are controlled to obtain hot-rolled steel;

[0008] The hot-rolled steel is cooled, and the final temperature of the cooling is controlled to obtain non-magnetic steel bars.

[0009] Optionally, the specified chemical composition includes:

[0010] C, Si, Mn, P, S, Cr, V, O, N, and Fe; where, by mass fraction,

[0011] The C content is 0.55-0.65%, the Si content is 0.45-0.55%, the Mn content is 18.0-18.5%, and the P content is...

[0012] The content of sulfur is ≤0.010%, the content of sulfur is ≤0.010%, the content of chromium is 3.0-3.5%, the content of chromium is 1.70-1.73%, the content of oxygen is 0-0.0010%, and the content of nitrogen is 0.0140-0.0150%.

[0013] Optionally, in the specified chemical composition, by mass fraction, the content of C is 0.60%, the content of Si is 0.50%, the content of Mn is 18.2%, the content of P is ≤0.0006%, the content of S is ≤0.0005%, the content of Cr is 3.3%, the content of V is 1.71%, the content of O is 0.0008%, and the content of N is 0.0146%.

[0014] Optionally, the rolling process parameters include: the initial rolling temperature and the finishing rolling inlet temperature.

[0015] Optionally, the initial rolling temperature is 1080-1130℃.

[0016] Optionally, the finishing mill inlet temperature is 930-960℃.

[0017] Optionally, the final temperature of the cooling is 400-450°C.

[0018] Optionally, the heating process parameters include: heating section temperature, soaking section temperature, and furnace heating time; wherein,

[0019] The temperature of the heating section is 970-1120℃, the temperature of the soaking section is 1100-1200℃, and the heating time in the furnace is 1.8-2.1 hours.

[0020] Secondly, this application provides a non-magnetic steel bar, which is prepared by the method described in any embodiment of the first aspect.

[0021] Optionally, the absolute magnetic permeability of the non-magnetic steel bar is 1.28 × 10⁻⁶. -6 -1.30×10 -6 h / m.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] The method for preparing the non-magnetic steel bar provided in this application has been optimized in terms of chemical composition control, rolling process parameters, and cooling process. The produced non-magnetic steel bar has excellent comprehensive mechanical and magnetic properties, meeting the requirements for steel bars used in maglev railway tracks, and possesses superior mechanical properties. This method is applicable to the production control of non-magnetic steel bars on steel bar production lines. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart illustrating a method for preparing non-magnetic steel bars according to an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0029] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] Firstly, this application provides a method for preparing non-magnetic steel bars; please refer to [link to relevant documentation]. Figure 1 The method includes:

[0032] S1. Heating the billet with the set chemical composition;

[0033] The complete process for preparing the above-mentioned non-magnetic steel bars is as follows: molten iron → converter smelting → alloy addition → LF refining → continuous casting into small square billets → heating in a heating furnace → controlled rolling → controlled cooling; wherein, in the molten steel smelting: alloys are added at the end of the converter process, and continuous casting adopts fully protected pouring, with the superheat controlled not exceeding 35°C.

[0034] In some embodiments, the specified chemical composition includes: C, Si, Mn, P, S, Cr, V, O, N, and Fe; wherein, by mass fraction, the content of C is 0.55-0.65%, the content of Si is 0.45-0.55%, the content of Mn is 18.0-18.5%, the content of P is ≤0.010%, the content of S is ≤0.010%, the content of Cr is 3.0-3.5%, the content of V is 1.70-1.73%, the content of O is 0-0.0010%, and the content of N is 0.0140-0.0150%.

[0035] In some embodiments, the specified chemical composition, by mass fraction, includes: C 0.60%, Si 0.50%, Mn 18.2%, P ≤0.0006%, S ≤0.0005%, Cr 3.3%, V 1.71%, O 0.0008%, and N 0.0146%.

[0036] In the embodiments of this application, the positive effect of controlling the C content to 0.55-0.65% is to obtain suitable strength and ductility. If the C content is too high, it will increase the brittleness of the material to some extent; if the C content is too low, it will reduce the strength of the material to some extent. Specifically, the C content can be 0.55%, 0.60%, 0.65%, etc.

[0037] The positive effects of controlling the Si content to 0.45-0.55% include obtaining a suitable yield point and ensuring weldability. If the Si content is too high, it will reduce weldability to some extent; if the Si content is too low, it will reduce the material's yield point to some extent. Specifically, the Si content can be 0.45%, 0.50%, 0.55%, etc.

[0038] The positive effects of controlling the Mn content to 18.0-18.5% include: expanding the austenite region, forming a single austenite structure, and reducing the material's magnetic properties. If the Mn content is too high, it will reduce plasticity and increase cost to some extent; if the Mn content is too low, it will shrink the austenite region to some extent, making it impossible to achieve a single austenite structure and thus impossible to achieve low magnetic properties. Specifically, the Mn content can be 18.0%, 18.2%, 18.4%, 18.5%, etc.

[0039] The positive effects of controlling the phosphorus (P) content to ≤0.0006% and the sulfur (S) content to ≤0.0005% are as follows: Under normal circumstances, P and S are harmful elements in steel. P increases the cold brittleness of steel, worsens weldability, reduces plasticity, and worsens cold bending performance. S causes hot brittleness in steel, reducing its ductility and toughness. Therefore, the lower the P and S content in steel, the better. However, excessively low requirements will increase equipment and cost investment. Specifically, the P content can be 0.010%, 0.009%, 0.008%, etc.; the S content can be 0.010%, 0.009%, 0.008%, etc.

[0040] The positive effect of controlling the Cr content to 3.0-3.5% is that it enhances the corrosion resistance of the material. If the Cr content is too high, it will increase costs to some extent; if the Cr content is too low, it will reduce corrosion resistance to some extent. Specifically, the Cr content can be 3.0%, 3.2%, 3.4%, 3.5%, etc.

[0041] The positive effects of controlling the V content to 1.70-1.73% include: obtaining suitable grain size and strength, forming vanadium carbonitride precipitation, and reducing the magnetic properties of the material. If the V content is too high, it will result in excessive strength to some extent; if the V content is too low, it will reduce the strength to some extent, failing to achieve low magnetic properties. Specifically, the V content can be 1.70%, 1.71%, 1.72%, 1.73%, etc.

[0042] The positive effect of controlling the O content to 0-0.0010% is to obtain high material purity. If the O content is too high, it will increase the inclusion content to some extent. Specifically, the O content can be 0.0010%, 0.0009%, 0.0008%, etc.

[0043] The positive effects of controlling the nitrogen (N) content to 0.0140-0.0150% include promoting vanadium nitride precipitation, increasing strength, and reducing magnetic properties. If the N content is too high, it will increase the material's brittleness to some extent; if the N content is too low, it will reduce the precipitation strengthening effect to some extent and will not achieve the desired low magnetic properties. Specifically, the N content can be 0.0140%, 0.0143%, 0.0147%, 0.00150%, etc.

[0044] Preferably, the content of C is 0.60%, the content of Si is 0.50%, the content of Mn is 18.2%, the content of P is ≤0.0006%, the content of S is ≤0.0005%, the content of Cr is 3.3%, the content of V is 1.71%, the content of O is 0.0008%, and the content of N is 0.0146%.

[0045] In some embodiments, the heating process parameters include: heating section temperature, soaking section temperature, and furnace heating time; wherein,

[0046] The temperature of the heating section is 970-1120℃, the temperature of the soaking section is 1100-1200℃, and the heating time in the furnace is 1.8-2.1 hours.

[0047] In this embodiment, the heating is carried out in a heating furnace, and controlling the heating section temperature to 970-1120℃ has the positive effect of ensuring uniform heating. If the heating section temperature is too high, it will cause uneven heating of the steel billet to a certain extent; if the heating section temperature is too low, it will cause insufficient heating of the steel billet to a certain extent. Specifically, the heating section temperature can be 970℃, 1000℃, 1030℃, 1060℃, 1100℃, 1120℃, etc.

[0048] Maintaining the soaking zone temperature at 1100-1200℃ has the positive effect of ensuring sufficient alloy solution. If the soaking zone temperature is too high, it can cause overheating of the billet; if it is too low, it can lead to insufficient alloy solution. Specifically, the soaking zone temperature can be 1100℃, 1120℃, 1140℃, 1160℃, 1180℃, 1200℃, etc.

[0049] In some implementations, the heating time in the furnace is 1.8-2.1 hours.

[0050] In the embodiments of this application, the positive effect of controlling the heating time in the furnace to 1.8-2.1 hours is that it ensures the alloy is fully dissolved without overheating. If the time is too long, it will cause the billet to overheat to some extent; if the time is too short, it will cause the alloy to be insufficiently dissolved to some extent. Specifically, the heating time in the furnace can be 1.8 hours, 2.0 hours, 2.1 hours, etc.

[0051] S2. The heated billet is rolled, and the rolling process parameters are controlled to obtain hot-rolled steel;

[0052] In some embodiments, the rolling process parameters include: the initial rolling temperature and the finishing rolling inlet temperature.

[0053] In some embodiments, the initial rolling temperature is 1080-1130°C.

[0054] In some embodiments, the finishing mill inlet temperature is 930-960°C.

[0055] In the embodiments of this application, the positive effects of controlling the initial rolling temperature to 1080-1130℃ include grain refinement and reduced magnetic properties of the reinforcing steel. If the initial rolling temperature is too high, it can lead to coarse austenite, which is detrimental to the control of high strength and low magnetic properties of the reinforcing steel; if the initial rolling temperature is too low, it can increase equipment wear and tear costs. Specifically, the initial rolling temperature can be 1080℃, 1100℃, 1120℃, 1130℃, etc.

[0056] The positive effects of controlling the finishing mill inlet temperature to 930-960℃ include: continuous grain refinement of the steel sheet and reduction of magnetic properties. If the finishing mill inlet temperature is too high, it can lead to coarse austenite formation in the steel sheet, which is detrimental to high strength and low magnetic properties; if the finishing mill inlet temperature is too low, it can increase equipment wear and tear costs. Specifically, the finishing mill inlet temperatures are 930℃, 940℃, 950℃, and 960℃.

[0057] S3. Cool the hot-rolled steel and control the final temperature of the cooling to obtain non-magnetic steel bars.

[0058] In some implementations, the final temperature of the cooling is 400-450°C.

[0059] In this embodiment, the cooling method is water cooling. Controlling the final cooling temperature to 400-450℃ has the positive effect of continuous grain refinement. If the final cooling temperature is too high, it can cause austenite coarsening, which is detrimental to high strength and low magnetic properties; if the final cooling temperature is too low, it can cause material cracking. Specifically, the final cooling temperature can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, etc.

[0060] Secondly, this application provides a non-magnetic steel bar, which is prepared by the method described in any embodiment of the first aspect.

[0061] In some embodiments, the absolute magnetic permeability of the non-magnetic steel bar is 1.28 × 10⁻⁶. -6 -1.30×10 -6 h / m.

[0062] In this embodiment, the microstructure of the non-magnetic steel bar is austenite, and its yield strength Rp 0.2 The range is 550-600 MPa, and the tensile strength R m The range is 950–1060 MPa, elongation after fracture (A) is 39–45%, reduction of area (Z) is 40–50%, elastic modulus (E) is 185–195 GPa, strength factor (K) is 2030–2055 MPa, impact energy (AKv) is 77–85 J, and absolute magnetic permeability is 1.28 × 10⁻⁶. -6 -1.30×10 -6 h / m. This ensures both the strength and elongation plasticity of the material, while also meeting the magnetic permeability requirements of non-magnetic steel.

[0063] The non-magnetic steel bar is realized based on the above-described method for preparing non-magnetic steel bars. The specific steps of the method for preparing non-magnetic steel bars can be referred to the above embodiments. Since the non-magnetic steel bar adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0064] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0065] This application provides a method for preparing non-magnetic steel bars, the method comprising:

[0066] S11. Heating the billet with the set chemical composition;

[0067] S21. The heated billet is rolled, and the rolling process parameters are controlled to obtain hot-rolled steel;

[0068] S31. The hot-rolled steel is cooled, and the final temperature of the cooling is controlled to obtain a non-magnetic steel bar. The chemical composition is specified in Table 1, the preparation process parameters for the non-magnetic steel bar are specified in Table 2, and the properties of the non-magnetic steel bar are specified in Table 3.

[0069] Table 1. Chemical composition (wt%) of non-magnetic steel bars, balance being Fe and unavoidable impurities.

[0070]

[0071]

[0072] Table 2. Manufacturing process parameters for non-magnetic steel bars

[0073]

[0074] Table 3 Performance of Non-Magnetic Steel Bars

[0075]

[0076] As shown in Tables 1-3, the non-magnetic steel bars produced by the preparation method of this application have excellent comprehensive mechanical and magnetic properties, meeting the requirements for non-magnetic or extremely low magnetic properties of steel bars used in maglev railway tracks. In contrast, Comparative Example 1 did not use the method of this application, and the material has a multiphase structure rather than a single austenitic structure. The material has a coarse metallographic structure, severe mixed crystals, and a high absolute magnetic permeability.

[0077] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing non-magnetic steel bars suitable for use in magnetic levitation railway tracks, characterized in that, The method includes: A cast billet with a predetermined chemical composition is heated. This predetermined chemical composition includes: C, Si, Mn, P, S, Cr, V, O, N, and Fe, as well as unavoidable impurities. Specifically, by mass fraction, the content of C is 0.55-0.65%, Si is 0.45-0.55%, Mn is 18.0-18.5%, P is ≤0.010%, S is ≤0.010%, Cr is 3.0-3.5%, V is 1.70-1.73%, O is 0-0.0010%, and N is 0.0140-0.0150%. The heating process parameters include: a heating zone temperature of 970-1120℃, a soaking zone temperature of 1100-1200℃, and a furnace heating time of 1.8-2.1 hours. The heated billet is rolled, and the rolling process parameters are controlled to obtain hot-rolled steel. The initial rolling temperature is 1080-1130℃, and the finishing rolling inlet temperature is 930-960℃. The hot-rolled steel is cooled, and the final temperature of the cooling is controlled at 400-450℃ to obtain non-magnetic steel bars with an absolute magnetic permeability of 1.28 × 10⁻⁶. -6 -1.30×10 -6 h / m.

2. The method according to claim 1, characterized in that, In the specified chemical composition, by mass fraction, the content of C is 0.60%, the content of Si is 0.50%, the content of Mn is 18.2%, the content of P is ≤0.0006%, the content of S is ≤0.0005%, the content of Cr is 3.3%, the content of V is 1.71%, the content of O is 0.0008%, and the content of N is 0.0146%.

3. A non-magnetic steel bar, characterized in that, The non-magnetic steel bar is prepared by the method described in any one of claims 1-2.

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