Steel, preparation method thereof and steel product

Abstract

The invention relates to steel, a preparation method thereof and a steel product. The steel is prepared from the following components in percentage by mass: 0.04 percent to 0.08 percent of C, 0.12 percent to 0.27 percent of Si, 0.0005 percent to 0.0015 percent of S, 1.13 percent to 1.55 percent of Mn, 0 to 0.016 percent of Nb, 0 to 0.05 percent of V, 0 to 0.01 percent of Mo, 0.001 percent to 0.012 percent of P, 0.05 percent to 0.23 percent of Cu, 0.25 percent to 0.40 percent of Ni, 0 to 0.20 percent of Cr, 0.0005 percent to 0.0035 percent of Ca, 0.0002 percent to 0.0015 percent of B, 0.003 percent to 0.021 percent of N, 0.001 percent to 0.005 percent of O, 0.001 percent to 0.025 percent of Al, 0.008 percent to 0.045 percent of Mg, 0.015 percent to 0.032 percent of Ti, 0.001 percent to 0.018 percent of Zr and the balance of Fe and inevitable impurities. The mass percent of the components is 0.5 lt; (Mg + Al) / (Ti + Zr) lt; 1.

Description

Technical Field

[0001] The present application relates to the field of alloy technology, and in particular to a steel material and a preparation method thereof, and a steel product. Background Art

[0002] With economic development, structural steel in high-rise buildings, ship transportation, offshore platforms, oil storage and other fields has begun to develop in the direction of large-scale and high-strength, and the steel plates used are generally characterized by large thickness and high strength. At the same time, under the consideration of economy and efficiency, the welding time used in splicing these structural steels should be as short as possible to meet the requirements of rapid manufacturing. Generally speaking, the traditional welding process can account for more than 30% of the manufacturing time, and the use of single-pass high-energy line welding can greatly reduce the time consumed in the welding process. However, traditional high-strength steel (600 MPa grade) will have a significant reduction in yield strength after high-energy line welding.

[0003] Therefore, it is necessary to improve the traditional technology. Summary of the invention

[0004] Based on this, the present application provides a steel material and a preparation method thereof, and a steel product, wherein the steel material still maintains a relatively high yield strength after high-line energy welding.

[0005] The technical solution of this application to solve the above technical problems is as follows.

[0006] On the one hand, the present application provides a steel material, which comprises the following components by mass percentage:

[0007] C 0.04%~0.08%, Si 0.12%~0.27%, S 0.0005%~0.0015%, Mn 1.13%~1.55%, Nb 0~0.016%, V 0~0.05%, Mo 0~0.01%, P 0.001%~0.012%, Cu 0.05%~0.23%, Ni 0.25%~0.40%, Cr0~0.20%, Ca 0.0005%~0.0035%, B 0.0002%~0.0015%, N 0.003%~0.021%, O 0.001%~0.005%, Al 0.001%~0.025%, Mg 0.008%~0.045%, Ti 0.015%~0.032% and Zr 0.001%~0.018%, and the rest are Fe and inevitable impurities; wherein the mass percentages of the components satisfy 0.5<(Mg+Al) / (Ti+Zr)<1.

[0008] In some embodiments, the steel material comprises the following components by mass percentage:

[0009] C 0.04%~0.08%, Si 0.15%~0.22%, S 0.001%~0.0015%, Mn 1.20%~1.50%, Nb0.005%~0.015%, V 0.02%~0.05%, Mo 0.005%~0.01%, P 0.003%~0.010%, Cu 0.10%~0.20%, Ni0.30%~0.40%, Cr 0.10%~0.20%, Ca 0.001%~0.003%, B 0.0005%~0.0013%, N 0.01%~0.02%, O0.002%~0.004%, Al 0.01%~0.025%, Mg 0.008%~0.02%, Ti 0.02%~0.032% and Zr 0.008%~0.015%, and the rest are Fe and inevitable impurities.

[0010] In some embodiments, the steel material comprises the following components by mass percentage:

[0011] C 0.05%~0.07%, Si 0.15%~0.20%, S 0.0012%~0.0015%, Mn 1.20%~1.50%, Nb0.010%~0.015%, V 0.03%~0.045%, Mo 0.007%~0.009%, P 0.005%~0.008%, Cu 0.14%~0.018%, Ni 0.31%~0.38%, Cr 0.12%~0.15%, Ca 0.001%~0.0023%, B 0.0008%~0.0012%, N0.01%~0.015%, O 0.0025%~0.004%, Al 0.01%~0.021%, Mg 0.01%~0.15%, Ti 0.022%~0.031% and Zr 0.008%~0.014%, and the rest are Fe and inevitable impurities.

[0012] In some of the embodiments, in the steel, the mass percentage of the components satisfies 0.55≤(Mg+Al) / (Ti+Zr)≤0.8.

[0013] In some of the embodiments, in the steel material, the inclusions in the steel material are evenly distributed.

[0014] In some embodiments, the steel comprises first inclusions with a size of 0.5 μm to 5 μm; optionally, among the first inclusions, the mass proportion of inclusions with a size of 1 μm to 3 μm is ≥60%; optionally, among the first inclusions, the number of inclusions with a spherical or ellipsoidal morphology is ≥80%; optionally, the surface density of the first inclusions is ≥800 pcs / mm 2 .

[0015] In some embodiments, in the steel, the number of Ti-Mg-Al-Zr-Mn-SON composite inclusions in the first inclusions accounts for ≥60%; optionally, in the Ti-Mg-Al-Zr-Mn-SON composite inclusions, the mass proportion of Ti is 10%~30%, the mass proportion of Mg is 5%~20%, and the mass proportion of Zr is 1%~10%.

[0016] On one hand, the present application provides a method for preparing steel, comprising the following steps:

[0017] Providing raw materials according to the composition of the above steel;

[0018] Mixing and smelting the raw materials to obtain molten steel;

[0019] The molten steel is cast to prepare the steel material.

[0020] In some embodiments, in the method for preparing the steel, the mixed smelting comprises the following steps:

[0021] The molten iron pretreatment, combined blowing converter, LF preheating, RH vacuum refining and LF refining are carried out in sequence to obtain molten steel.

[0022] In some of the embodiments, in the steel preparation method, in the double-blowing converter step, the oxygen content in the molten steel after the converter is 50 ppm to 130 ppm; and / or

[0023] In the LF refining step, the oxygen content in the refined molten steel is 30 ppm to 90 ppm.

[0024] In some of the embodiments, in the method for preparing steel, in the RH vacuum refining step, the inlet temperature of the molten steel is ≥1580°C.

[0025] On one hand, the present application provides a steel product, including the above-mentioned steel or the steel produced by the above-mentioned preparation method.

[0026] Compared with the prior art, the steel material of the present application has the following beneficial effects:

[0027] The steel of the present application reacts C, Si, S, Mn, Nb, V, Mo, P, Cu, Ni, Cr, Ca, B, N, O, Al, Mg, Ti and Zr with Fe in specific proportions, especially controls the content of Mg and the proportions between Mg, Al and Ti, Zr, promotes the heterogeneous shape of acicular ferrite, refines the austenite grain size, and forms high-density Mg-containing composite inclusions; the composite inclusions have a pinning effect and can effectively induce the formation of IAF (intracrystalline acicular ferrite), thereby effectively improving the toughness of the steel and the post-weld performance of the heat-affected zone of the steel, so that the steel still maintains a high yield strength after high-line energy welding, and has good low-temperature impact toughness, effectively solving the problems of low welding efficiency of high-strength steel plates (600 MPa grade) and deterioration of performance after high-line energy welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation or the description of the prior art will be briefly introduced below.

[0029] Figure 1 This is the morphology and composition distribution diagram of Ti-Al-Mg composite inclusions in the steel prepared in Example 1. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in conjunction with the accompanying drawings, implementation modes and examples. It should be understood that these implementation modes and examples are only used to illustrate the present application and are not used to limit the scope of the present application. The purpose of providing these implementation modes and examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0031] It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the present application, and the equivalent forms obtained also fall within the scope of protection of the present application. For example, the features illustrated or described as part of one embodiment can be combined in another embodiment in a suitable manner to produce a new embodiment. In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing implementation modes and embodiments and are not intended to limit this application.

[0033] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0034] In the present application, "plurality", "multiple", "multiple times", etc., unless otherwise specified, refer to a quantity greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0035] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0036] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0037] Herein, "preferred", "better", "more preferred", and "suitable" are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute a limitation on the scope of protection of this application. If multiple "preferred" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "preferred" item is independent.

[0038] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0039] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0040] In the present application, the terms "first", "second", "third", "fourth", etc. in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0041] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0042] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0043] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0044] In this application, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0045] In this application, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0046] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

[0047] The mass or weight of the relevant components mentioned in the specification of the embodiments of the present application may not only refer to the specific content of each component, but also indicate the proportional relationship of the mass or weight between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the embodiments of the present application, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass or weight described in the specification of the embodiments of the present application may be units known in the chemical industry such as μg, mg, g, and kg.

[0048] An embodiment of the present application provides a steel material, which comprises the following components by mass percentage:

[0049] C 0.04%~0.08%, Si 0.12%~0.27%, S 0.0005%~0.0015%, Mn 1.13%~1.55%, Nb 0~0.016%, V 0~0.05%, Mo 0~0.01%, P 0.001%~0.012%, Cu 0.05%~0.23%, Ni 0.25%~0.40%, Cr0~0.20%, Ca 0.0005%~0.0035%, B 0.0002%~0.0015%, N 0.003%~0.021%, O 0.001%~0.005%, Al 0.001%~0.025%, Mg 0.008%~0.045%, Ti 0.015%~0.032% and Zr 0.001%~0.018%, and the rest are Fe and inevitable impurities; wherein the mass percentages of the components satisfy 0.5<(Mg+Al) / (Ti+Zr)<1.

[0050] The steel of the present application reacts C, Si, S, Mn, Nb, V, Mo, P, Cu, Ni, Cr, Ca, B, N, O, Al, Mg, Ti and Zr with Fe in specific proportions, especially controls the content of Mg and the proportions between Mg, Al and Ti, Zr, promotes the heterogeneous shape of acicular ferrite, refines the austenite grain size, and forms high-density Mg-containing composite inclusions; the composite inclusions have a pinning effect and can effectively induce the formation of IAF (intracrystalline acicular ferrite), thereby effectively improving the toughness of the steel and the post-weld performance of the heat-affected zone of the steel, so that the steel still maintains a high yield strength after high-line energy welding, and has good low-temperature impact toughness, effectively solving the problems of low welding efficiency of high-strength steel plates (600 MPa grade) and deterioration of performance after high-line energy welding.

[0051] Among them, carbon (C) is a key element to enhance the strength of steel. In order to ensure a specific strength, the lower limit of C content is 0.04%. At the same time, in order to suppress the content of island martensite structure in the heat-affected zone, the upper limit is set at 0.08%.

[0052] Silicon (Si): As an important pre-deoxidation element, silicon has a strengthening effect on the base material. It is necessary to ensure that the Si content is above 0.12%. When the Si content exceeds 0.27%, too much island martensite will be generated in the heat-affected zone of high heat input welding, which will deteriorate the toughness.

[0053] Manganese (Mn): As a pre-deoxidation and base metal strengthening element, the Mn content needs to be above 1.13% to reduce dependence on other precious metal elements. However, excessive Mn will lead to central segregation of the slab, and at the same time lead to hardening and island martensite formation in the heat-affected zone of high heat input welding, reducing the toughness of the heat-affected zone, so the upper limit of Mn is controlled at 1.55%.

[0054] Phosphorus (P): Phosphorus is a harmful element in steel. By controlling the P content, it can be avoided that it causes central segregation and affects the toughness of the heat affected zone.

[0055] Sulfur (S): Existing as an impurity element, too high S content will not only lead to central segregation of the slab, but also form large-sized sulfide composite inclusions, inhibit the formation of fine dispersed oxide composite inclusions, and is not conducive to improving the toughness of the base material and the welding heat affected zone.

[0056] Nickel (Ni): Ni is an effective element for improving strength and low-temperature toughness, and its lower limit is 0.25%. However, due to its high price, the upper limit is 0.4% for cost considerations.

[0057] Niobium (Nb): Nb is an effective element for ensuring the strength, toughness of the base material and the strength of the joint, but excessive addition of Nb will promote the formation of island martensite in the heat-affected zone and deteriorate toughness.

[0058] Vanadium (V): V can improve the hardenability and resistance to temper softening, and help to improve the strength of the heat-affected zone in high heat input welding, but excessive V will reduce the toughness of the base material and the heat-affected zone.

[0059] Aluminum (Al): Exists as an impurity element. Limiting the acid-soluble Al content to below 0.025% can reduce the number of alumina inclusions in the steel and increase the titanium content of oxide inclusions, which is beneficial to the formation of fine dispersed composite oxide inclusions, thereby improving welding performance; in addition, reducing acid-soluble aluminum also helps to reduce the production of lath ferrite on the grain boundary side and improve low-temperature toughness.

[0060] Titanium (Ti): During solidification, dispersed Ti oxide particles are formed, which serve as the core for the subsequent formation of Mg and Zr composite oxide inclusions, helping to inhibit the coarsening of austenite in the weld heat affected zone or promote the deformation nucleation of intragranular ferrite phase, thereby improving toughness. The smaller the size of the Ti-containing oxide particles, the better the effect of pinning the austenite grain boundaries and promoting the nucleation of fine intragranular ferrite. Ensuring the content of composite oxide inclusions with a size of less than 1.0μm is a key measure to ensure the performance of the heat affected zone of high heat input welding. If the Ti content is less than 0.015%, the amount of Ti-containing inclusions cannot be ensured; too high a Ti content is prone to form coarse titanium oxide inclusions, which is not conducive to the size control of composite oxide inclusions.

[0061] Boron (B): B is an element that improves hardenability, can refine the steel plate structure and increase strength. In the steel of the present application, the addition of trace amounts of B is beneficial to the phase transformation behavior of the steel plate during the welding thermal cycle, inhibits the formation of grain boundary widmanstattenite and side plate strip ferrite, and creates prerequisites for composite inclusions to promote the nucleation of intracrystalline ferrite. Since B easily reacts with free oxygen and nitrogen in steel and loses the above beneficial effects, titanium iron fixed oxygen and residual nitrogen elements must be added first at the RH station, and then an appropriate amount of ferroboron is added.

[0062] Oxygen (O) is a key element in the formation of composite oxide inclusions in the steel of this application. In order to ensure the formation of a large number of fine dispersed composite oxide inclusions to pin the austenite grain boundaries and promote the nucleation of intragranular ferrite, thereby improving the toughness of the heat-affected zone of high heat input welding, the O content is not less than 0.001%. On the other hand, excessive O will form coarse Ti-containing oxide particles during Ti deoxidation, which will have a negative impact on the toughness of the heat-affected zone.

[0063] Magnesium (Mg) and zirconium (Zr) are important elements for forming composite oxide inclusions, which are beneficial to promote the multidimensional nucleation of ferrite. Mg and Zr have stronger high-temperature reducibility than titanium (Ti), and can form Mg-Al-Ti, Zr-Al-Ti or Mg-Al-Zr-Ti composite inclusions when the surface of Ti2O3 inclusion particles is oxidized. When 0.5<(Mg+Al) / (Ti+Zr)<1, the above effect can achieve the best effect, so it needs to be controlled within this range. The precipitation of Mg and Zr on the surface of Ti2O3 inclusions can both disperse the oxide particles and refine their size. These composite inclusions. In the preparation process, they are added through the alloy cored wire after LF refining.

[0064] It can be understood that in the steel, by mass percentage, C includes but is not limited to 0.04%, 0.05%, 0.06%, 0.07%, 0.08%; Si includes but is not limited to 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%; S includes but is not limited to 0.0005%, 0.001%, 0.0011%, 0.0012%, 0.0013%, 0.0014%, 0.0015%; Mn includes but is not limited to 1.13%, 1.14%, 1.15%, 1.16% , 1.17%, 1.18%, 1.19%, 1.2%, 1.21%, 1.22%, 1.23%, 1.24%, 1.25%, 1.26%, 1.27%, 1.28%, 1.29%, 1.3%, 1.31%, 1.32%, 1.33%, 1.34%, 1.35%, 1.36%, 1.37%, 1.38%, 1.39%, 1.4%, 1.41%, 1.42%, 1.43%, 1.44%, 1.45%, 1.46%, 1.47%, 1.48%, 1.49%, 1.5%, 1.51%, 1.52%, 1.55%; Nb includes but is not limited to 0.005%, 0.010%, 0.011%, 0. 0.012%, 0.0013%, 0.014%, 0.015%, 0.016%; V includes but is not limited to 0.02%, 0.03%, 0.04%, 0.05%; Mo includes but is not limited to 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%; P includes but is not limited to 0.001%, 0.003%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.012%; Cu includes but is not limited to 0.05%, 0.06%, 0.07%, 0.08%, 0.1%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.1 7%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%; Ni includes but is not limited to 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.35%, 0.36%, 0.38%, 0.39%, 0.40%; Cr includes but is not limited to 0.1%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%; Ca includes but is not limited to 0.0005%, 0.001%, 0.0015%, 0.002%, 0.0025%, 0.003%, 0.0.035%; B includes but is not limited to 0.0002%, 0.0005%, 0.0008%, 0.001%, 0.0012%, 0.0013%, 0.0015%; N includes but is not limited to 0.003%, 0.01%, 0.012%, 0.015%, 0.018%, 0.02%, 0.021%; O includes but is not limited to 0.001%, 0.002%, 0.003%, 0.004%, 0.005%; Al includes but is not limited to 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.012%, 0.015%, 0.018%, 0.02%, 0.022%, 0.025%; Mg includes but is not limited to 0.008%, 0. 0.01%, 0.012%, 0.015%, 0.018%, 0.02%, 0.022%, 0.025%, 0.028%, 0.03%, 0.032%, 0.035%, 0.038%, 0.04%, 0.042%, 0.045%; Ti includes but is not limited to 0.015%, 0.015%, 0.018%, 0.02%, 0.022%, 0.025%, 0.028%, 0.03%, 0.032%; Zr includes but is not limited to 0.001%, 0.002%, 0.005%, 0.008%, 0.01%, 0.012%, 0.015%, 0.018%; in some examples, any two of these point values ​​can be used as the range of end values, the same below. .

[0065] In some of these examples, the steel includes the following components by mass percentage:

[0066] C 0.04%~0.08%, Si 0.15%~0.22%, S 0.001%~0.0015%, Mn 1.20%~1.50%, Nb0.005%~0.015%, V 0.02%~0.05%, Mo 0.005%~0.01%, P 0.003%~0.010%, Cu 0.10%~0.20%, Ni0.30%~0.40%, Cr 0.10%~0.20%, Ca 0.001%~0.003%, B 0.0005%~0.0013%, N 0.01%~0.02%, O0.002%~0.004%, Al 0.01%~0.025%, Mg 0.008%~0.02%, Ti 0.02%~0.032% and Zr 0.008%~0.015%, and the rest are Fe and inevitable impurities.

[0067] In some of these examples, the steel includes the following components by mass percentage:

[0068] C 0.05%~0.07%, Si 0.15%~0.20%, S 0.0012%~0.0015%, Mn 1.20%~1.50%, Nb0.010%~0.015%, V 0.03%~0.045%, Mo 0.007%~0.009%, P 0.005%~0.008%, Cu 0.14%~0.018%, Ni 0.31%~0.38%, Cr 0.12%~0.15%, Ca 0.001%~0.0023%, B 0.0008%~0.0012%, N0.01%~0.015%, O 0.0025%~0.004%, Al 0.01%~0.021%, Mg 0.01%~0.15%, Ti 0.022%~0.031% and Zr 0.008%~0.014%, and the rest are Fe and inevitable impurities.

[0069] It can be understood that (Mg+Al) / (Ti+Zr) refers to the ratio of "the sum of the mass percentages of Mg and Al" to "the sum of the mass percentages of Ti and Zr"; it can be further understood that (Mg+Al) / (Ti+Zr) includes but is not limited to 0.52, 0.55, 0.56, 0.58, 0.6, 0.62, 0.64, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, and 0.98.

[0070] In some of the examples, in the steel, the mass percentages of the components satisfy 0.55≤(Mg+Al) / (Ti+Zr)≤0.8.

[0071] In some of these examples, the inclusions within the steel are dispersed.

[0072] It can be understood that dispersed distribution means uniform distribution. Dispersed inclusions in steel can not only pin the welding austenite grain boundaries to prevent coarsening during the welding thermal cycle of the heat-affected zone, but also induce the formation of acicular ferrite, thereby refining the grains and significantly improving the steel's resistance to high-wire energy welding.

[0073] In some of the examples, the steel material includes first inclusions having a size of 0.5 μm to 5 μm.

[0074] It is understood that the steel also includes inclusions whose sizes are not within the range of 0.5 μm to 5 μm, such as inclusions whose sizes are greater than 5 μm.

[0075] In some of the examples, in the steel, among the first inclusions, the mass proportion of inclusions with a size of 1 μm~3 μm is ≥60%.

[0076] In some of the examples, in the steel, among the first inclusions, the mass proportion of inclusions with a size of 1 μm~3 μm is ≥70%.

[0077] Furthermore, in some of the examples, in the steel material, among the first inclusions, inclusions with a size of 1 μm to 3 μm account for 75% to 85% by mass.

[0078] The spherical inclusions with a size of 1 μm~3 μm and dispersed distribution are the best grain boundary pinning particles and acicular ferrite nucleation sites, which can effectively improve the steel to maintain a high yield strength and low-temperature impact toughness after high-line energy welding.

[0079] In some examples, the surface density of the first inclusions in the steel is ≥ 800 / mm 2 .

[0080] In some examples, the surface density of the first inclusions in the steel is ≥ 850 / mm 2 .

[0081] Furthermore, the surface density of the first inclusions is 855 / mm 2 ~905 pieces / mm 2 .

[0082] In some of the examples, in the steel, among the first inclusions, the number of inclusions with spherical or ellipsoidal morphology accounts for ≥80%.

[0083] In some of the examples, in the steel, among the first inclusions, the number of inclusions with spherical or ellipsoidal morphology accounts for ≥90%.

[0084] In some of the examples, in the steel, the number of Ti-Mg-Al-Zr-Mn-SON complex inclusions in the first inclusions accounts for ≥60%.

[0085] In some of the examples, in the Ti-Mg-Al-Zr-Mn-SON composite inclusions in steel, the mass proportion of Ti is 10%~30%, the mass proportion of Mg is 5%~20%, and the mass proportion of Zr is 1%~10%.

[0086] In some of these examples, the yield strength of the steel is ≥600 Mpa.

[0087] In some of the examples, for steel, under a welding line energy of 300 kJ / cm~600 kJ / cm, the impact toughness value of the weld at -20℃ is ≥60 J, and the impact toughness value of the base material and the heat-affected zone at -20℃ is ≥200 J.

[0088] An embodiment of the present application provides a method for preparing a steel material, comprising the following steps:

[0089] Providing raw materials according to the composition of the above steel;

[0090] Mixing and smelting the raw materials to obtain molten steel;

[0091] The molten steel is cast to prepare steel products.

[0092] In some of the examples, in the method for preparing the steel, the mixed smelting includes the following steps:

[0093] The molten iron pretreatment, combined blowing converter, LF preheating, RH vacuum refining and LF refining are carried out in sequence to obtain molten steel.

[0094] In some of the examples, in the steel preparation method, in the double-blowing converter step, the oxygen content in the molten steel after the converter is 50 ppm~130 ppm.

[0095] It can be understood that in the double-blowing converter step, the oxygen content in the molten steel after the converter includes but is not limited to 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, and 130 ppm.

[0096] In some of the examples, in the steel production method, in the double-blowing converter step, the oxygen content in the molten steel after the converter is 80 ppm to 120 ppm. Optionally, the oxygen content in the molten steel after the converter is 90 ppm to 110 ppm.

[0097] By controlling the oxygen content in the molten steel after the converter, the austenite grain size can be further refined, thereby further improving the toughness of the steel and the post-weld performance of the heat-affected zone of the steel.

[0098] In some of the examples, in the steel preparation method, in the double-blowing converter step, silicon, manganese and lime are added to the ladle within 1 / 4 of the converter tapping time, and titanium and iron are added within 3 / 4 of the tapping time.

[0099] In some of the examples, in the steel preparation method, after the steel leaves the converter and the deoxidizing elements and necessary alloying elements are added, LF preheating is performed to make the converter outlet temperature ≥1630°C.

[0100] In some of the examples, in the steel preparation method, in the RH vacuum refining step, the station temperature is ≥1580℃.

[0101] Furthermore, in the RH vacuum refining step, the inlet temperature of the molten steel is 1580°C~1600°C.

[0102] It can be understood that in the RH vacuum refining step, the inlet temperature of the molten steel includes but is not limited to 1580°C, 1585°C, 1589°C, 1590°C, 1592°C, 1593°C, 1595°C, 1597°C, and 1600°C.

[0103] Optionally, in the RH vacuum refining step, the inlet temperature of the molten steel is 1589°C~1597°C.

[0104] In some of these examples, the RH vacuum refining time in the steel preparation method is 15 min~20 min.

[0105] In some of these examples, in the steel preparation method, in the LF refining step, the oxygen content in the refined molten steel is 30 ppm~90 ppm.

[0106] It can be understood that in the LF refining step, the oxygen content in the refined molten steel includes but is not limited to 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, and 90 ppm.

[0107] In some of these examples, in the steel preparation method, in the LF refining step, the oxygen content in the refined molten steel is 50 ppm~80 ppm.

[0108] By controlling the oxygen content in the refined molten steel, the austenite grain size can be further refined, thereby further improving the toughness of the steel and the post-weld performance of the heat-affected zone of the steel.

[0109] In some of these examples, in the steel preparation process, magnesium, aluminum, and zirconium cored wires are added during the LF refining step, and oxide metallurgy and desulfurization and denitrification are carried out.

[0110] In some of the examples, in the steel preparation method, in the LF refining step, the argon blowing time of the ladle after wire feeding is ≥ 8 minutes.

[0111] In some of the examples, the method for preparing the steel material further includes a step of feeding an alloy core wire after the LF refining step and before the casting step.

[0112] In some of the examples, the method for preparing the steel material further includes, after the casting step, a step of rolling the cast steel billet.

[0113] That is, in some of the examples, the method for preparing the steel material includes the following steps:

[0114] The raw materials are provided according to the composition of the above steel, and the steel is prepared through the following processes: molten iron pretreatment → double-blowing converter → LF preheating → RH vacuum refining → LF refining → continuous casting → rolling.

[0115] In some of the examples, in the steel preparation method, the rolling step includes rough rolling and finish rolling; optionally, the cumulative reduction rate of rough rolling is 60%~70%, and the cumulative reduction rate of finish rolling is 30%~40%.

[0116] By adopting a two-stage rolling process, the austenite grain size can be further refined, thereby further improving the toughness of the steel and the post-weld properties of the heat-affected zone of the steel.

[0117] In some examples, the method for preparing the steel includes the following steps:

[0118] (1) Converter smelting process: pre-treated molten iron and scrap steel are loaded into the converter, and the molten iron temperature is 1300℃~1320℃; silicon, manganese and lime are added in sequence within 1 / 4 of the steel-making process, and the oxygen content in the molten steel after the converter is controlled to be 50 ppm~130 ppm;

[0119] (2) LF preheating process: slag and remaining alloy materials (nickel, chromium, copper, molybdenum, niobium, vanadium and other alloy materials, except zirconium) are added during the heating process, and the station is exited when the temperature is ≥1630℃;

[0120] (3) RH vacuum refining process: inlet temperature ≥ 1580°C, vacuum treatment time 15 min ~ 20 min;

[0121] (4) LF refining process: the inlet temperature is ≥1550℃, and the oxygen content in the refined molten steel is controlled to be 30 ppm~90ppm; titanium iron is added to the molten steel, and then silicon-zirconium alloy cored wire is fed into the ladle, followed by desulfurization, denitrification and alloy fine-tuning. After the composition and temperature are qualified, soft blowing is carried out for more than 8 minutes, and finally the steel is discharged from the station;

[0122] (5) Continuous casting process: the casting temperature is controlled at 1530℃~1550℃;

[0123] (6) Rolling process: The TMCP rolling process is used to roll the continuous casting billet into steel of the required thickness.

[0124] The preparation method of the steel provided in the present application can significantly increase the number of oxide inclusions in steel for high-heat input welding, so that the surface density of the inclusions is ≥850 / mm², and the composition, size and morphology of the oxide inclusions are controlled to be in an optimal state that can promote the nucleation of acicular ferrite. The first inclusions of 0.5 μm~5 μm in the steel, the proportion of Ti-Mg-Al-Zr-Mn-SON composite inclusions is ≥60%, of which the proportion of inclusions with a size of 1 μm~3 μm is ≥70%, and the proportion of spherical or ellipsoidal morphology is ≥90%.

[0125] An embodiment of the present application provides a steel product, including the above-mentioned steel or the steel produced by the above-mentioned preparation method.

[0126] The steel product provided in the present application includes the above-mentioned steel or the steel produced by the above-mentioned preparation method, and can provide the same advantages as the above-mentioned steel or the steel produced by the above-mentioned preparation method.

[0127] It can be understood that steel products include but are not limited to steel structure buildings, machine tools, construction machinery (excavators, cranes), transportation vehicles (cars, rails), furniture hardware, tools (wrenches, pliers), petrochemical equipment (oil drilling rigs, chemical reactors), power equipment (transmission towers, transformer cores), etc.

[0128] The present application is further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present application are not limited thereto.

[0129] The following examples and comparative examples use the following preparation method to prepare steel plates of different thicknesses:

[0130] The manufacturing process flow is: hot metal pretreatment → 180-ton combined-blowing converter smelting → LF preheating → RH vacuum refining → LF refining → alloy cored wire feeding → continuous casting → rolling; the specific steps are as follows:

[0131] (1) Converter smelting process: pre-treated molten iron and scrap steel are loaded into the converter, and the molten iron temperature is 1300℃~1320℃; silicon, manganese and lime are added in sequence within 1 / 4 of the steel-making process, and the oxygen content in the molten steel after the converter is controlled to be 50 ppm~130 ppm;

[0132] (2) LF preheating process: slag and remaining alloy materials (nickel, chromium, copper, molybdenum, niobium, vanadium and other alloy materials, except zirconium) are added during the heating process, and the station is exited when the temperature is ≥1630℃;

[0133] (3) RH vacuum refining process: inlet temperature ≥ 1580°C, vacuum treatment time 15 min ~ 20 min;

[0134] (4) LF refining process: the inlet temperature is ≥1550℃, and the oxygen content in the refined molten steel is controlled to be 30 ppm~90ppm; titanium iron is added to the molten steel, and then silicon-zirconium alloy cored wire is fed into the ladle, followed by desulfurization, denitrification and alloy fine-tuning. After the composition and temperature are qualified, soft blowing is carried out for more than 8 minutes, and finally the steel is discharged from the station;

[0135] (5) Continuous casting process: the casting temperature is controlled at 1530°C to 1550°C, the casting speed is controlled at 0.9 m / min, and finally a continuous casting billet with a thickness of 330 mm is obtained;

[0136] (6) Rolling process: The TMCP rolling process is used to roll the continuous casting billet into steel plates of the required thickness.

[0137] The components of the steel materials of Examples 1 to 5 are shown in Table 1, with the remainder being Fe.

[0138] Table 1

[0139]

[0140] The specific process parameters of the steel materials of Examples 1 to 5 are shown in Table 2:

[0141] Table 2

[0142]

[0143] Comparative Example 1

[0144] It is basically the same as Example 1, except that: Al 0.022%, Mg 0.001%, Ti 0.028%, Zr 0.008%; (Mg+Al) / (Ti+Zr)= 0.64, and other components and proportions are the same as Example 1.

[0145] Comparative Example 2

[0146] It is basically the same as Example 1, except that: Al 0.001%, Mg 0.009%, Ti 0.032%, Zr 0.018%; (Mg+Al) / (Ti+Zr)=0.20, and other components and proportions are the same as Example 1.

[0147] Comparative Example 3

[0148] It is basically the same as Example 1, except that: Al 0.025%, Mg 0.02%, Ti 0.014%, Zr 0.013%; (Mg+Al) / (Ti+Zr)=1.67, and other components and proportions are the same as Example 1.

[0149] Comparative Example 4

[0150] The invention is basically the same as Example 1, except that Mo is 0.3%, and other components and proportions are the same as Example 1.

[0151] Comparative Example 5

[0152] It is basically the same as Example 1, except that Si is 0.05%, and other components and proportions are the same as Example 1.

[0153] The inclusion characteristics and weld joint performance of each embodiment and comparative example were tested, and the results are shown in Table 3.

[0154] Table 3

[0155]

[0156] As can be seen from Tables 1 to 3, compared with the comparative example, the steel prepared in the embodiment has a higher surface density of inclusions. Among the inclusions of 0.5 μm to 5 μm, the mass of inclusions with a size of 1 μm to 3 μm accounts for a higher proportion, and the proportion of spherical or ellipsoidal morphology is higher. The morphology and composition surface distribution diagram of Ti-Al-Mg composite inclusions in the steel prepared in Example 1 are as follows: Figure 1 shown.

[0157] Mechanical experiments show that there is no significant difference in the strength of the parent materials of the embodiments and the comparative examples. However, after welding with a heat input of 300 kJ / cm~600 kJ / cm, the yield strength of the welded joints of the embodiments remains high, especially embodiments 1~3 can still meet the requirement of ≥600MPa, while the comparative example shows a more serious softening phenomenon. On the other hand, the impact toughness of the heat affected zone of the embodiments at -20°C is high, and the impact toughness of the weld at -20°C is high, the impact toughness of the heat affected zone at -20°C is ≥200J, and the impact toughness of the weld at -20°C is ≥60J.

[0158] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0159] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the contents of the attached claims, and the description and drawings can be used to explain the contents of the claims.

Claims

1. A steel material, characterized in that: Calculated by mass percentage, it includes the following components: C 0.04%~0.08%, Si 0.12%~0.27%, S 0.0005%~0.0015%, Mn 1.13%~1.55%, Nb 0~0.016%, V 0~0.05%, Mo 0~0.01%, P 0.001%~0.012%, Cu 0.05%~0.23%, Ni 0.25%~0.40%, Cr0~0.20%, Ca 0.0005%~0.0035%, B 0.0002%~0.0015%, N 0.003%~0.021%, O 0.001%~0.005%, Al 0.001%~0.025%, Mg 0.008%~0.045%, Ti 0.015%~0.032% and Zr 0.001%~0.018%, and the rest are Fe and inevitable impurities; wherein the mass percentages of the components satisfy 0.5<(Mg+Al) / (Ti+Zr)<1.

2. The steel material according to claim 1, characterized in that: Calculated by mass percentage, it includes the following components: C 0.04%~0.08%, Si 0.15%~0.22%, S 0.001%~0.0015%, Mn 1.20%~1.50%, Nb 0.005%~0.015%, V 0.02%~0.05%, Mo 0.005%~0.01%, P 0.003%~0.010%, Cu 0.10%~0.20%, Ni 0.30%~0.40%, Cr 0.10%~0.20%, Ca 0.001%~0.003%, B 0.0005%~0.0013%, N 0.01%~0.02%, O0.002%~0.004%, Al 0.01%~0.025%, Mg 0.008%~0.02%, Ti 0.02%~0.032% and Zr 0.008%~0.015%, and the rest are Fe and inevitable impurities.

3. The steel material according to claim 1, characterized in that: Calculated by mass percentage, it includes the following components: C 0.05%~0.07%, Si 0.15%~0.20%, S 0.0012%~0.0015%, Mn 1.20%~1.50%, Nb 0.010%~0.015%, V 0.03%~0.045%, Mo 0.007%~0.009%, P 0.005%~0.008%, Cu 0.14%~0.018%, Ni0.31%~0.38%, Cr 0.12%~0.15%, Ca 0.001%~0.0023%, B 0.0008%~0.0012%, N 0.01%~0.015%, O 0.0025%~0.004%, Al 0.01%~0.021%, Mg 0.01%~0.15%, Ti 0.022%~0.031% and Zr0.008%~0.014%, and the rest are Fe and inevitable impurities.

4. The steel material according to claim 1, characterized in that: The mass percentage of the components satisfies 0.55≤(Mg+Al) / (Ti+Zr)≤0.8; and / or The inclusions in the steel are evenly distributed.

5. The steel material according to claim 4, characterized in that: The steel material includes first inclusions with a size of 0.5 μm to 5 μm; optionally, among the first inclusions, the mass proportion of inclusions with a size of 1 μm to 3 μm is ≥60%; optionally, among the first inclusions, the number of inclusions with a spherical or ellipsoidal morphology is ≥80%; optionally, the surface density of the first inclusions is ≥800 pcs / mm 2 .

6. The steel material according to claim 5, characterized in that: The quantity of the Ti-Mg-Al-Zr-Mn-SON composite inclusions in the first inclusions accounts for ≥60%; optionally, in the Ti-Mg-Al-Zr-Mn-SON composite inclusions, the mass proportion of Ti is 10%-30%, the mass proportion of Mg is 5%-20%, and the mass proportion of Zr is 1%-10%.

7. A method for preparing steel, characterized in that: The following steps are involved: Providing raw materials according to the composition of the steel material as claimed in any one of claims 1 to 6; Mixing and smelting the raw materials to obtain molten steel; The molten steel is cast to prepare the steel material.

8. The method for preparing the steel material according to claim 7, characterized in that: The mixed smelting comprises the following steps: The molten iron pretreatment, combined blowing converter, LF preheating, RH vacuum refining and LF refining are carried out in sequence to obtain molten steel.

9. The method for preparing the steel material according to claim 8, characterized in that: In the double-blowing converter step, the oxygen content in the molten steel after the converter is 50 ppm to 130 ppm; and / or In the LF refining step, the oxygen content in the refined molten steel is 30 ppm to 90 ppm; and / or In the RH vacuum refining step, the inlet temperature of the molten steel is ≥1580°C.

10. A steel product, characterized in that: Including the steel material as described in any one of claims 1 to 6 or the steel material prepared by the preparation method as described in any one of claims 7 to 9.

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