A medium-oxygen weathering steel and a method for manufacturing the same

Abstract

This invention provides a medium-oxygen weathering steel and its preparation method, belonging to the field of weathering steel production technology. The chemical composition of the medium-oxygen weathering steel includes: C, Si, Mn, P, S, Cr, Cu, Ni, O, and Fe; by mass fraction, the content of C is 0.08%–0.10%, the content of Si is 0.30%–0.50%, the content of Mn is 0.50%–0.65%, the content of P is 0.08%–0.10%, the content of S is ≤0.005%, the content of Cr is 0.40%–0.55%, the content of Cu is 0.30%–0.45%, the content of Ni is 0.10%–0.40%, and the content of O is 0.005%–0.012%. The oxygen content is increased from below 0.003% in ordinary weathering steel to the range of 0.005-0.012%, resulting in silicate inclusions that are more stable and less prone to corrosion. Furthermore, some silicon-manganese-aluminum oxides form composite inclusions with MnS, causing the MnS inclusions to change from long strips to short strips, thus inhibiting corrosion propagation. As a result, the corrosion rate of medium-oxygen weathering steel is reduced by more than 18%, making it suitable for more severe corrosive environments and solving the problem of poor corrosion resistance of ordinary weathering steel in current technologies.

Description

Technical Field

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

[0002] Weathering steel (atmospheric corrosion resistant steel) is made by adding alloying elements such as Cu, Cr, and Ni to ordinary steel. The addition of alloying elements to steel can increase the resistance of the protective rust layer, allow for deposition and overlap on the steel surface, prevent the crystallization of the rust layer, promote the formation of a dense rust layer, hinder the penetration of corrosive substances, and prevent further corrosion of the base material, thereby obtaining excellent corrosion resistance.

[0003] With the successive construction of projects such as the "West-to-East Power Transmission Project", my country's original ordinary weathering steel can no longer meet the requirements of high corrosion resistance and long service life for tower and mast steel. Moreover, the alloying elements used in ordinary weathering steel are expensive, which to some extent limits its promotion and application. Therefore, there is an urgent need to develop weathering steel with stronger corrosion resistance and lower economic cost. Summary of the Invention

[0004] This application provides a medium-oxygen weathering steel and its preparation method. While meeting the mechanical performance requirements of structural steel, it solves the technical problem of poor corrosion resistance of existing weathering steel by controlling the oxygen content in the weathering steel.

[0005] In a first aspect, this application provides a medium-oxygen weathering steel, the chemical composition of which includes: C, Si, Mn, P, S, Cr, Cu, Ni, O, and Fe; by mass fraction,

[0006] The content of C is 0.08%–0.10%, the content of Si is 0.30%–0.50%, the content of Mn is 0.50%–0.65%, the content of P is 0.08%–0.10%, the content of S is ≤0.005%, the content of Cr is 0.40%–0.55%, the content of Cu is 0.30%–0.45%, the content of Ni is 0.10%–0.40%, and the content of O is 0.005%–0.012%.

[0007] Optionally, the oxygen content in the medium-oxygen weathering steel is 0.006% to 0.012%.

[0008] Optionally, the total area content of inclusions in the medium-oxygen weathering steel is 0.02% to 0.10%, and the inclusions in the medium-oxygen weathering steel include silicates, sulfides, and oxygen-sulfur complexes. The content of silicate inclusions is not less than 45%, and the silicate inclusions include complexes of SiO2, Al2O3, and MnO. The sulfides are short strips, and the size of the sulfides is ≤10μm.

[0009] Optionally, the microstructure of the medium-oxygen weathering steel includes ferrite and pearlite.

[0010] Optionally, the medium-oxygen weathering steel meets at least one of the following properties: yield strength ≥350MPa, tensile strength ≥430MPa, elongation after fracture ≥30%, and impact performance reaching the level of Grade D steel.

[0011] Secondly, this application provides a method for preparing medium-oxygen weathering steel, used to prepare the medium-oxygen weathering steel described in any embodiment of the first aspect, the method comprising:

[0012] The smelting process yields a billet with the aforementioned chemical composition, wherein the smelting process employs a silicon-manganese deoxidation process.

[0013] The billet is heated, rolled, cooled, and coiled to obtain medium-oxygen weathering steel.

[0014] Optionally, the heating temperature is 1180℃~1220℃, and the heating holding time is 1h~2h.

[0015] Optionally, the initial rolling temperature is 1130℃~1170℃, the final rolling temperature is 840℃~880℃, and the thickness of the steel plate after rolling in 8-9 passes is 6.5mm~7.5mm.

[0016] Optionally, the cooling is performed using a manifold laminar flow method, with a cooling rate of 15℃ / s to 25℃ / s and a final cooling temperature of 580℃ to 620℃.

[0017] Optionally, the thickness of the cast billet is 120mm to 130mm.

[0018] The technical solutions provided in this application have the following advantages compared with the prior art:

[0019] This application increases the oxygen content from below 0.003% in ordinary weathering steel to the range of 0.005% to 0.012%, obtaining silicate inclusions with more stable properties that are less prone to corrosion. These silicate inclusions replace the large number of easily corroded long strip-shaped sulfide inclusions in ordinary weathering steel. Furthermore, some silicon-manganese-aluminum oxides form composite inclusions with MnS, causing the MnS inclusions to change from long strips to short strips, thus inhibiting corrosion propagation. As a result, the corrosion rate of medium-oxygen weathering steel is reduced by more than 18%, and the corrosion resistance of the steel is enhanced, making it suitable for more severe corrosive environments.

[0020] In particular, while increasing the oxygen content, the amount of expensive alloying elements such as Cr and Ni can be reduced without weakening the corrosion resistance of the steel, thereby significantly reducing production costs and improving economic efficiency.

[0021] In particular, the medium-oxygen weathering steel prepared by this application still has a yield strength of over 350 MPa, a tensile strength of over 430 MPa, an elongation after fracture of over 30%, and impact performance reaching the level of Grade D steel, meeting the mechanical performance requirements of structural steel and facilitating its application in actual industrial production. Attached Figure Description

[0022] 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.

[0023] 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.

[0024] Figure 1 A schematic flowchart illustrating a method for preparing medium-oxygen weathering steel provided in this application embodiment;

[0025] Figure 2 The morphology of typical inclusions in medium-oxygen weathering steel provided in Example 1 of this application;

[0026] Figure 3 The morphology of typical inclusions in the smelted steel provided for Comparative Example 1 of this application;

[0027] Figure 4 The morphology of typical inclusions in the smelted steel provided in Comparative Example 1 of this application. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] Furthermore, in the description of this application, the terms "comprising," "including," etc., 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" 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.

[0031] 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.

[0032] In a first aspect, this application provides a medium-oxygen weathering steel, the chemical composition of which may include: C, Si, Mn, P, S, Cr, Cu, Ni, O, and Fe; by mass fraction,

[0033] The content of C can be 0.08%–0.10%, the content of Si can be 0.30%–0.50%, the content of Mn can be 0.50%–0.65%, the content of P can be 0.08%–0.10%, the content of S can be ≤0.005%, the content of Cr can be 0.40%–0.55%, the content of Cu can be 0.30%–0.45%, the content of Ni can be 0.10%–0.40%, and the content of O can be 0.005%–0.012%.

[0034] The positive effects of controlling the carbon content to 0.08%–0.10% include: carbon can form a solid solution structure, which increases the strength of the steel. The carbon content can be 0.08%, 0.09%, 0.10%, etc.

[0035] The positive effects of controlling the Si content to 0.30%-0.50% and the Mn content to 0.50%-0.65% are as follows: Si and Mn act as deoxidizers to remove oxygen from the molten steel. Simultaneously, Mn reacts with S to form MnS, eliminating the brittleness of S, and Mn also improves the strength of the steel. The Si content can be 0.03%, 0.04%, 0.05%, etc., and the Mn content can be 0.50%, 0.52%, 0.54%, 0.56%, 0.58%, 0.60%, 0.62%, 0.65%, etc.

[0036] The positive effects of controlling the sulfur (S) content to ≤0.005% are as follows: Generally, sulfur is an impurity element in steel and easily forms brittle substances. Excessive sulfur content can lead to the formation of sulfide inclusions, which is detrimental to improving the corrosion resistance of weathering steel. The sulfur content can be 0.002%, 0.003%, 0.004%, 0.005%, etc.

[0037] The positive effects of controlling the phosphorus (P) content to 0.08%–0.10% and the copper (Cu) content to 0.30%–0.45% are as follows: P accelerates the formation of a uniform protective rust layer on the surface of weathering steel, thereby promoting the formation of a dense protective film on the substrate surface and improving the corrosion resistance of the weathering steel. When P and Cu are added to weathering steel simultaneously, these two elements mutually promote each other, resulting in increased Fe... 2+ The formation of a protective rust layer is faster, accelerating the formation of a dense protective film and enhancing the corrosion resistance of weathering steel. Furthermore, Cu dissolves in the inner rust layer of the steel, exhibiting localized segregation within this layer, primarily at cracks and pores. This segregation helps improve the density of the rust layer to some extent, enhancing the corrosion resistance of the alloy steel. The P content can be 0.08%, 0.09%, 0.10%, etc., and the Cu content can be 0.30%, 0.33%, 0.36%, 0.39%, 0.42%, 0.45%, etc.

[0038] The positive effects of controlling the Cr content to 0.40%–0.55% include: Cr can replace iron atoms in ferric hydroxide to form amorphous α-(Fe) oxide. 1-x Cr x )OOH adheres very densely to the matrix, and α-(Fe 1-x Cr x OOH exhibits cation selectivity, effectively preventing the entry of Cl- and increasing the corrosion resistance of steel. The Cr content can be 0.40%, 0.43%, 0.46%, 0.49%, 0.52%, 0.55%, etc.

[0039] The positive effects of controlling the Ni content to 0.10%–0.40% include: Ni increases the density of the rust layer, enhances the self-corrosion potential, increases the number of stable phases in the rust layer, and improves corrosion resistance. The Ni content can be 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, etc.

[0040] The positive effects of controlling the oxygen (O) content to 0.005%–0.012% are as follows: Increasing the O content from below 0.003% in ordinary weathering steel to the range of 0.005–0.012% results in the acquisition of more stable and less corrosion-inducing silicate inclusions, replacing the large number of easily corrosion-inducing elongated sulfide inclusions in ordinary weathering steel. Furthermore, some silicon-manganese-aluminum oxides form composite inclusions with MnS, causing the MnS inclusions to change from elongated to shorter strips, thus inhibiting corrosion propagation. This reduces the corrosion rate of medium-oxygen weathering steel by more than 18%, enhancing the steel's corrosion resistance and making it suitable for more severe corrosive environments. The O content can be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.010%, 0.011%, 0.012%, etc.

[0041] In some embodiments, the oxygen content in the medium-oxygen weathering steel can be 0.006% to 0.012%.

[0042] The content of O can be 0.006%, 0.007%, 0.008%, 0.009%, 0.010%, 0.011%, 0.012%, etc.

[0043] In some embodiments, the total area content of inclusions in the medium-oxygen weathering steel is 0.02% to 0.10%, and the inclusions in the medium-oxygen weathering steel include silicates, sulfides, and oxygen-sulfur complexes. The content of silicate inclusions is not less than 45%, and the silicate inclusions include complexes of SiO2, Al2O3, and MnO. The sulfides are short strips, and the size of the sulfides is ≤10μm.

[0044] The medium-oxygen weathering steel mainly consists of silicate inclusions that are less prone to corrosion, replacing the large number of easily corroded elongated sulfide inclusions found in ordinary weathering steel. Furthermore, some silicon-manganese-aluminum oxides form composite inclusions with MnS, causing the MnS inclusions to change from elongated to shorter, inhibiting corrosion propagation and thus improving corrosion resistance. The total area content of inclusions in this medium-oxygen weathering steel can be 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, etc., the content of silicate inclusions can be 45%, 50%, 55%, 60%, 65%, etc., and the size of the sulfides can be 6μm, 7μm, 8μm, 9μm, 10μm, etc.

[0045] In some embodiments, the microstructure of the medium-oxygen weathering steel includes ferrite and pearlite.

[0046] In some embodiments, the medium-oxygen weathering steel meets at least one of the following properties: yield strength ≥350MPa, tensile strength ≥430MPa, elongation after fracture ≥30%, and impact performance reaching the level of Grade D steel.

[0047] Medium-oxygen weathering steel meets the mechanical property requirements of structural steel, facilitating its application in actual industrial production. Its yield strength can be 350MPa, 360MPa, 370MPa, 380MPa, 390MPa, 400MPa, etc., its tensile strength can be 430MPa, 440MPa, 450MPa, 460MPa, 470MPa, etc., and its elongation after fracture can be 30%, 31%, 32%, 33%, 34%, 35%, etc.

[0048] Secondly, this application provides a method for preparing medium-oxygen weathering steel; please refer to [link to relevant documentation]. Figure 1 The method for preparing the medium-oxygen weathering steel according to any embodiment of the first aspect comprises:

[0049] S1. Smelting to obtain a cast billet with the aforementioned chemical composition, wherein the smelting adopts a silicon-manganese deoxidation process;

[0050] The positive effects of using silicomanganese deoxidation technology in controlled smelting: Compared with aluminum deoxidation technology, silicomanganese deoxidation is gentler and can control the oxygen content to 0.005%–0.012%. With silicomanganese deoxidation, the degree of deoxidation is small, the steel matrix has strong thermodynamic stability, the steel is less susceptible to pitting corrosion, and MnS inclusions change from long strips to short strips, inhibiting corrosion propagation and resulting in strong corrosion resistance of the steel.

[0051] In some embodiments, the thickness of the cast billet can be 120mm to 130mm.

[0052] The thickness of the cast billet can be 120mm, 122mm, 124mm, 126mm, 128mm, 130mm, etc.

[0053] S2. The billet is heated, rolled, cooled and coiled to obtain medium-oxygen weathering steel.

[0054] In some embodiments, the heating temperature is 1180℃~1220℃, and the heating holding time is 1h~2h.

[0055] The heating temperature can be 1180℃, 1185℃, 1190℃, 1190℃, 1200℃, 1205℃, 1210℃, 1215℃, 1220℃, etc., and the heating holding time can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, etc.

[0056] In some embodiments, the initial rolling temperature is 1130℃~1170℃, the final rolling temperature is 840℃~880℃, and the thickness of the steel plate after rolling in 8-9 passes is 6.5mm~7.5mm.

[0057] The initial rolling temperature can be 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, etc., and the final rolling temperature can be 840℃, 850℃, 860℃, 870℃, 880℃, etc. The thickness of the rolled steel plate can be 6.5mm, 6.7mm, 6.9mm, 7.1mm, 7.3mm, 7.5mm, etc.

[0058] In some embodiments, the cooling is performed using a manifold laminar flow method, with a cooling rate of 15°C / s to 25°C / s and a final cooling temperature of 580°C to 620°C.

[0059] The cooling rate can be 15℃ / s, 20℃ / s, 22℃ / s, 25℃ / s, etc., and the final cooling temperature can be 580℃, 590℃, 600℃, 610℃, 620℃, etc.

[0060] The medium-oxygen weathering steel is realized based on the above-mentioned preparation method of medium-oxygen weathering steel. The specific steps of the preparation method of medium-oxygen weathering steel can be referred to the above embodiments. Since the medium-oxygen weathering steel 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.

[0061] 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.

[0062] Example 1: A medium-oxygen weathering steel, the specific steps and parameters are as follows:

[0063] Smelting; hot rolling; cooling and coiling

[0064] The chemical composition of the smelted billet is as follows: C: 0.09wt%, Si: 0.40wt%, Mn: 0.55wt%, P: 0.09wt%, S: ≤0.005wt%, Cr: 0.50wt%, Cu: 0.30wt%, Ni: 0.30wt%, O: 0.005%, with the remainder being Fe and unavoidable impurities. The smelting process uses ferrosilicon and ferromanganese for deoxidation. The inclusions in the smelted steel are mainly granular or strip-shaped silicates (49.4% by quantity, 50.3% by area), with a small amount of short strip-shaped sulfides (27.4% by quantity, 6.7% by area) and oxygen-sulfur composite inclusions. The silicate inclusions mainly exist in the form of SiO2, Al2O3, and MnO composites. The sulfide inclusion length is less than 10μm. Figure 2 As shown in Table 1, the composition of typical inclusions is as follows. The billet thickness is 125 mm. The total area content of inclusions, i.e., the percentage of all inclusions in the analyzed area, is 0.027%.

[0065] In the hot rolling stage, the billet is heated to 1200℃, held for 1.5 hours, and then rolled. The initial rolling temperature is 1150℃, the final rolling temperature is 860℃, and it is rolled into a steel plate with a thickness of 7mm after 9 passes.

[0066] The cooling stage adopts a manifold laminar flow method with a cooling rate of 20℃ / s and a final cooling temperature of 600℃.

[0067] Example 2: A medium-oxygen weathering steel with an oxygen content of 0.0066% and other chemical compositions, processes, and inclusion types identical to those in Example 1. Of all inclusions, silicates accounted for 58.3% and sulfides accounted for 20.4%. The total area content of inclusions was 0.038%.

[0068] Example 3: A medium-oxygen weathering steel with an oxygen content of 0.010% and other chemical compositions, processes, and inclusion types identical to those in Example 1. Of all inclusions, silicates accounted for 76.6% and sulfides for 7.4%. The total area content of inclusions was 0.068%.

[0069] Example 4: A medium-oxygen weathering steel, with an oxygen content of 0.012% and other chemical compositions, processes, and inclusion types identical to those in Example 1. Of all inclusions, silicates accounted for 83.5% and sulfides for 4.2%. The total area content of inclusions was 0.10%.

[0070] Example 5: A medium-oxygen weathering steel, with a chemical composition of Ni: 0.12%, O: 0.006%, and other chemical compositions, processes, and inclusion types as in Example 1. Of all inclusions, silicates accounted for 53.0% and sulfides accounted for 18.4%. The total area content of inclusions was 0.033%.

[0071] Comparative Example 1: A weathering steel with an O content of 0.003% and other chemical components the same as in Example 1. The steel was smelted using an aluminum particle deoxidation process. The inclusions in the smelted steel were mainly elongated sulfides (60.4% of the total), with a small amount of dotted chain-like alumina and oxygen-sulfur composite inclusions. The sulfide inclusions were approximately 20 μm in length. Figure 3 , Figure 4 As shown in Table 1, the composition of typical inclusions is as follows. The total area content of inclusions is 0.01%.

[0072] Table 1. Composition of typical inclusions in Example 1 and Comparative Example 1, mass %

[0073] Location O Al Si S Ti Mn Fe Total Figure 1 P1 53.77 0.54 31.04 - 5.29 1.12 8.25 100 Figure 1 P2 - - - 17.62 - 35.02 47.36 100 Figure 2 P3 - - - 32.75 1.79 55.60 9.85 100 Figure 3 P4 51.08 42.49 - - - - 6.43 100

[0074] The properties of the steel plates obtained using Examples 1 to 5 and Comparative Example 1 are shown in Table 2.

[0075] Table 2 Properties of Steel Plates

[0076]

[0077]

[0078] Compared to the ordinary weathering steel (oxygen content 0.003%) in Comparative Example 1, the oxygen content in Examples 1 to 4 was increased to 0.005%, 0.0066%, 0.010%, and 0.012%, respectively. The main type of inclusions in the steel changed from the elongated sulfides in ordinary weathering steel to the silicate composite inclusions in the oxygen-resistant weathering steel of this invention. The silicate inclusion content was above 45%, and the sulfide size was shortened to below 10 μm. The changes in the main type of inclusions and the size of the sulfides have a significant impact on the corrosion resistance of the steel. That is, the silicate inclusions that are not prone to corrosion in the oxygen-resistant weathering steel of this invention replace the large number of easily corroded elongated sulfide inclusions in ordinary weathering steel. In addition, some silicon-manganese-aluminum oxides form composite inclusions with MnS, which changes the MnS inclusions from elongated to short, inhibiting corrosion propagation and thus helping to improve corrosion resistance.

[0079] In Examples 1 to 5, the total area content of inclusions was controlled within the range of 0.02 to 0.10%, which could prevent the number of inclusions from increasing rapidly and causing a large number of inclusion particles to play a dominant role as pitting corrosion sources, thereby reducing the corrosion resistance of the matrix.

[0080] Compared with the ordinary weathering steel (oxygen content 0.003%) in Comparative Example 1, the oxygen content in Examples 1 to 4 was increased to 0.005%, 0.0066%, 0.010%, and 0.012%, respectively. After 24 hours of full immersion corrosion in 10% H2SO4 + 3.5% NaCl solution, the corrosion rate decreased from 2.42 mm / a to 1.98 mm / a, 1.83 mm / a, 1.70 mm / a, and 1.82 mm / a, respectively, showing a trend of first decreasing and then increasing. The overall corrosion rate was reduced by 18% to 30%, and the corrosion resistance was significantly improved.

[0081] Compared with the ordinary weathering steel (oxygen content 0.003%) in Comparative Example 1, the oxygen content in Example 5 was increased to 0.006%, the Ni content was reduced from 0.30% to 0.12%, and the corrosion rate was reduced from 2.42 mm / a to 2.15 mm / a, which is still a reduction of 11%. This shows that increasing the oxygen content while reducing the amount of the expensive alloying element Ni in the steel does not affect the corrosion resistance.

[0082] Compared with the standard grade of high weathering steel Q295GNH, the yield strength, tensile strength and elongation after fracture of the steels in Examples 1 to 5 can all meet the standard usage requirements, and the impact performance reaches the level of Grade D steel.

[0083] 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 medium-oxygen weathering steel, characterized in that, The chemical composition of the medium-oxygen weathering steel is: C, Si, Mn, P, S, Cr, Cu, Ni, O, and Fe, as well as unavoidable impurities; by mass fraction, The content of C is 0.08%~0.10%, the content of Si is 0.30%-0.50%, the content of Mn is 0.50%~0.65%, the content of P is 0.08%~0.10%, the content of S is ≤0.005%, the content of Cr is 0.40%~0.55%, the content of Cu is 0.30%~0.45%, the content of Ni is 0.10%~0.40%, and the content of O is 0.005%~0.012%. The total area content of inclusions in the medium-oxygen weathering steel is 0.02%~0.10%. The inclusions in the medium-oxygen weathering steel include silicates, sulfides, and oxygen-sulfur complexes. The content of silicate inclusions is not less than 45%. The silicate inclusions include complexes of SiO2, Al2O3, and MnO. The sulfides are short strips with a size ≤10μm. The microstructure of the medium-oxygen weathering steel includes ferrite and pearlite; The medium-oxygen weathering steel meets the following properties: yield strength ≥350MPa, tensile strength ≥430MPa, elongation after fracture ≥30%, and impact performance reaches the level of Grade D steel.

2. The medium-oxygen weathering steel according to claim 1, characterized in that, The oxygen content in the medium-oxygen weathering steel is 0.006%~0.012%.

3. A method for preparing medium-oxygen weathering steel, characterized in that, The method for preparing the medium-oxygen weathering steel according to any one of claims 1-2 comprises: The smelting process yields a billet with the aforementioned chemical composition, wherein the smelting process employs a silicon-manganese deoxidation process. The billet is heated, rolled, cooled, and coiled to obtain medium-oxygen weathering steel.

4. The preparation method according to claim 3, characterized in that, The heating temperature is 1180℃~1220℃, and the heating holding time is 1h~2h.

5. The preparation method according to claim 3, characterized in that, The initial rolling temperature is 1130℃~1170℃, the final rolling temperature is 840℃~880℃, and the thickness of the steel plate after rolling in 8-9 passes is 6.5mm~7.5mm.

6. The preparation method according to claim 3, characterized in that, The cooling is performed using a manifold laminar flow method, with a cooling rate of 15℃ / s to 25℃ / s and a final cooling temperature of 580℃ to 620℃.

7. The preparation method according to claim 3, characterized in that, The thickness of the cast billet is 120mm~130mm.

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