Steel and preparation method and application thereof

Abstract

The invention relates to steel and a preparation method and application thereof. The steel comprises the following chemical components in percentage by mass: 0.045% to 0.065% of C, 0.28% to 0.40% of Si, 0.60% to 0.80% of Mn, 0.072% to 0.090% of P, 0.001% to 0.010% of S, 0.25% to 0.28% of Cu, 0.32% to 0.42% of Cr, 0.015% to 0.030% of Ti, less than or equal to 0.007% of N, 0.015% to 0.050% of Als and the balance of Fe and inevitable impurities. The steel is nickel-free, low in production cost, low in yield ratio, excellent in mechanical property, good in stamping performance, good in weather resistance and high in yield, and is suitable for the weather-resistant steel for the low-yield-ratio container for stamping.

Description

Technical Field

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

[0002] The container body is mainly divided into the top plate, bottom plate and side plate. The top plate is processed by one-time stamping, the floor is a hot-rolled steel strip flat plate, and the side plate is processed by roller forming. Furthermore, the top plate stamping depth is about 15.5mm to 17.5mm, and the elongation and yield strength ratio of the material are higher than those of roller pressing or bending processing. The top plate often cracks during the stamping process. Therefore, it is necessary to develop a low yield strength ratio weathering steel for stamping containers to improve the yield rate of the top plate.

[0003] Traditional methods generally achieve this goal by changing the alloy composition. For example, a method for producing container plates by continuous casting and rolling of thin slabs has been reported. The yield strength ratio of its example products is greater than 0.75 and most of them are greater than 0.80, but 0.03% to 0.10% of precious metal nickel (Ni) is added to its composition, resulting in high cost, and the yield strength ratio of its products cannot be stably lower than 0.8. Or, a rolling method for weathering steel used for stamping thin-gauge container top plates, the yield strength ratio of its example products is greater than 0.80, and 0.08% to 0.12% of precious metal Ni is also added to its composition, resulting in high alloy cost. Summary of the invention

[0004] Based on this, the present invention provides a nickel-free steel with low production cost, low yield ratio, good stamping performance, good weather resistance and high yield rate, and also provides a preparation method and application of the steel.

[0005] The technical solution is as follows:

[0006] A steel material, whose chemical composition, measured by mass percentage, includes: C: 0.045%-0.065%, Si: 0.28%-0.40%, Mn: 0.60%-0.80%, P: 0.072%-0.090%, S: 0.001%-0.010%, Cu: 0.25%-0.28%, Cr: 0.32%-0.42%, Ti: 0.015%-0.030%, N: ≤0.007%, Als: 0.015%-0.050%, and the balance is Fe and unavoidable impurities.

[0007] In one of the embodiments, the Si content of the steel is 0.29% to 0.38% by mass.

[0008] In one of the embodiments, the Mn content of the steel is 0.62% to 0.78% by mass.

[0009] In one of the embodiments, the P content of the steel is 0.072% to 0.088% by mass.

[0010] In one of the embodiments, the S content of the steel is 0.003% to 0.008% by mass.

[0011] In one of the embodiments, the Cr content of the steel is 0.35% to 0.42% by mass.

[0012] In one embodiment, the steel has a Ti content of 0.016% to 0.028% by mass.

[0013] In one of the embodiments, the Als content of the steel is 0.020% to 0.045% by mass.

[0014] In one embodiment, the yield strength of the steel is 360MPa to 500MPa.

[0015] In one embodiment, the tensile strength of the steel is 500MPa to 600MPa.

[0016] In one embodiment, the elongation of the steel is greater than 30%.

[0017] In one embodiment, the steel has a yield strength ratio of less than 0.8.

[0018] The present invention also provides a method for preparing the steel material as described above, and the technical solution is as follows:

[0019] A method for preparing the steel material as described above comprises the steps of converter smelting, LF refining, thin slab continuous casting, heating in a heating furnace and hot continuous rolling.

[0020] In one of the embodiments, in the converter smelting step, the controlled composition percentages of the converter final molten steel are C: 0.020%~0.050%, Si: 0.20%~0.30%, Mn: 0.30%~0.40%, P: 0.020%~0.050%, S: 0.001%~0.010%, Cu: 0.20%~0.25%, Cr: 0.20%~0.30%.

[0021] In one of the embodiments, in the converter smelting step, the final temperature is 1590°C to 1660°C.

[0022] In one embodiment, in the LF refining step, the controlled composition percentages of the molten steel at the end point of LF refining are C: 0.045% to 0.065%, Si: 0.28% to 0.40%, Mn: 0.60% to 0.80%, P:

[0023] 0.072%~0.090%, S: 0.001%~0.010%, Cu: 0.25%~0.28%, Cr: 0.32%~0.42%, Ti: 0.015%~0.030%, N: ≤0.007%, Als: 0.015%~0.050%, the balance is Fe and unavoidable impurities.

[0024] In one embodiment, in the LF refining step, the inlet temperature is 1550°C to 1600°C.

[0025] In one embodiment, in the LF refining step, the refining time is 40 min to 100 min.

[0026] In one embodiment, in the LF refining step, the soft blowing time is 6 min to 20 min.

[0027] In one of the embodiments, in the LF refining step, the molten steel calming time is 10 min to 30 min.

[0028] In one of the embodiments, in the LF refining step, the outlet temperature is 1580°C to 1620°C.

[0029] In one of the embodiments, in the thin slab continuous casting step, the temperature of the molten steel in the tundish is 1540°C to 1555°C.

[0030] In one of the embodiments, in the step of continuous casting of the thin slab, the continuous casting machine pulling speed is 4.0 m / min to 4.2 m / min.

[0031] In one of the embodiments, in the step of heating in the heating furnace, the continuous casting slab entering the furnace has a temperature ≥ 950°C.

[0032] In one of the embodiments, in the step of heating in the heating furnace, the temperature of the heating section is 1230°C to 1270°C.

[0033] In one of the embodiments, in the step of heating in the heating furnace, the time in the furnace is 15 minutes to 35 minutes.

[0034] In one of the embodiments, in the step of heating in the heating furnace, the furnace outlet temperature is 1140°C to 1180°C.

[0035] In one embodiment, during the hot rolling step, the dephosphorization pressure is 21 MPa to 24 MPa.

[0036] In one embodiment, in the hot rolling step, the final rolling temperature is 890°C to 910°C.

[0037] In one embodiment, in the hot rolling step, the layer cooling mode is front-stage concentrated cooling.

[0038] In one embodiment, in the hot rolling step, the coiling temperature is 610°C to 630°C.

[0039] The present invention also provides the application of the steel material as described above, and the technical solution is as follows:

[0040] (1) A plate comprising the steel material as described above, or a steel material produced according to the method for producing the steel material as described above.

[0041] (2) A container roof comprising the plate material as described above.

[0042] The present invention has at least the following beneficial effects:

[0043] The present invention provides a steel with a low yield ratio by regulating the chemical composition of the steel, especially regulating the element types and content percentages. At the same time, since the chemical composition of the steel of the present invention does not contain precious metals such as Ni, the production cost of the steel is significantly reduced. In addition, the steel also has excellent weather resistance and mechanical properties, good stamping performance, high yield rate, and has broad application prospects.

[0044] The steel preparation method of the present invention has the advantages of simple operation, high efficiency, good repeatability, green environmental protection, low energy consumption, low production cost, etc., and is suitable for industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a 200X metallographic structure diagram of a steel material prepared according to one embodiment of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below in conjunction with specific embodiments and accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0048] Where “including,” “having,” and “comprising” are used herein, it is intended to cover a non-exclusive inclusion, and another component may also be added unless explicit limiting terms such as “only,” “consisting of,” etc. are used.

[0049] The words "preferably", "more preferably", "preferably", "better", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the statement of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention. That is, in the present invention, "preferably", "more preferably", "preferably", "better", etc. are only used to describe implementation methods or examples with better effects, but do not constitute a limitation on the scope of protection of the present invention.

[0050] In the present invention, “further”, “furthermore”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0051] In the present invention, "at least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multilayer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of the present invention, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0052] When a numerical range is disclosed in the present invention, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when the range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the range can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. And only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can also be combined with any other upper limit to form an unambiguous range. In addition, each individually disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0053] If not otherwise specified, all steps of the present invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0054] Unless mentioned to the contrary, terms in the singular may include plural forms and should not be construed as being one in number.

[0055] The temperature parameters in the present invention, if not specifically limited, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument.

[0056] The weights of the relevant components mentioned in the embodiments of the present invention description may not only refer to the specific content of each component, but also indicate the weight ratio between the components. Therefore, as long as the content of the relevant components in the embodiments of the present invention description is proportionally enlarged or reduced, it is within the scope disclosed in the embodiments of the present invention description. Specifically, the weights described in the embodiments of the present invention description may be mass units known in the chemical industry such as μg, mg, g, and kg.

[0057] In the present invention, when referring to the unit of the data range, if there is a unit only after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 800-850nm means that the units of the left endpoint "800" and the right endpoint "850" are both nm (nanometers).

[0058] In the present invention, "above" or "below" both include the number itself, for example, below 1 means less than or equal to 1 (≤1), and above 1 means greater than or equal to 1 (≥1).

[0059] In the present invention, "A and B are independently selected from x, y or z" means that A and B are independent events, and event A does not affect the occurrence of event B. Therefore, when A is selected from x, B can be selected from any one of x, y or z; when A is selected from y, B can be selected from any one of x, y or z; when A is selected from z, B can be selected from any one of x, y or z.

[0060] Unless mentioned to the contrary, terms in the singular may include plural forms and should not be construed as being one in number.

[0061] The technical solution of the present invention is as follows:

[0062] A steel material, whose chemical composition, measured by mass percentage, includes: C: 0.045%-0.065%, Si: 0.28%-0.40%, Mn: 0.60%-0.80%, P: 0.072%-0.090%, S: 0.001%-0.010%, Cu: 0.25%-0.28%, Cr: 0.32%-0.42%, Ti: 0.015%-0.030%, N: ≤0.007%, Als: 0.015%-0.050%, and the balance is Fe and unavoidable impurities.

[0063] Carbon (C) is an effective strengthening element in steel. It exists in the form of carbides in steel and combines with alloy elements to exert precipitation strengthening and grain refinement, but excessive C can reduce the corrosion resistance of steel. Taking all factors into consideration, the present invention controls the C content in the steel to be 0.045% to 0.065%, which can be understood to include but not limited to 0.045%, 0.046%, 0.047%, 0.048%, 0.049%, 0.050%, 0.051%, 0.052%, 0.053%, 0.054%, 0.055%, 0.056%, 0.057%, 0.058%, 0.059%, 0.060%, 0.061%, 0.062%, 0.063%, 0.064% or 0.065%.

[0064] Silicon (Si) has the functions of deoxidation, corrosion resistance and solid solution strengthening, but excessive Si will lead to poor weldability of steel and deteriorate the toughness of steel. Taking all factors into consideration, the present invention controls the Si content in the steel to be 0.28% to 0.40%, which can be understood to include but not limited to 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39% or 0.40%. Preferably, the Si content of the steel is 0.29% to 0.38% by mass percentage.

[0065] Manganese (Mn) can toughen, solid solution strengthen, improve the strength and toughness of steel, and has low cost, but excessive amount will lead to poor weldability of steel. Taking all factors into consideration, the present invention controls the Mn content in the steel to be 0.60% to 0.80%, which can be understood to include but not limited to 0.60%, 0.62%, 0.65%, 0.68%, 0.70%, 0.72%, 0.75%, 0.78% or 0.80%. Preferably, the Mn content of the steel is 0.62% to 0.78% by mass.

[0066] Phosphorus (P) can increase the corrosion resistance of steel, but will deteriorate the toughness of steel. Taking all factors into consideration, the P content in the steel is controlled to be 0.072% to 0.090% in the present invention, which may include but is not limited to 0.072%, 0.075%, 0.078%, 0.080%, 0.082%, 0.085%, 0.088% or 0.090%. Preferably, the P content of the steel is 0.072% to 0.088% by mass.

[0067] Sulfur (S) can deteriorate the corrosion, ductility and toughness of steel, which is mainly due to the poor plasticity of iron sulfide formed by sulfur and iron, but manganese sulfide formed by sulfur and manganese can improve the machinability of steel. Taking all factors into consideration, the present invention controls the S content in the steel to be 0.001% to 0.010%, which can be understood to include but not limited to 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009% or 0.010%. Preferably, the S content of the steel is 0.003% to 0.008% by mass.

[0068] Copper (Cu) is beneficial to improving the mechanical properties (such as strength and hardness) and corrosion resistance of steel, and is beneficial to extending the working performance and service life of steel, but excessive Cu will deteriorate the weldability of steel. Taking all factors into consideration, in the present invention, the Cu content in the steel is controlled to be 0.25% to 0.28%, which can be understood to include but not limited to 0.25%, 0.26%, 0.27% or 0.28%.

[0069] Chromium (Cr) can improve the anti-oxidation and anti-corrosion ability of steel, and chromium can significantly increase the strength and hardness of steel, as well as hardenability, but it can also increase the temper brittleness tendency of steel. An appropriate amount of chromium can improve mechanical properties, but excessive chromium will lead to poor toughness of steel. Taking all factors into consideration, in the present invention, the Cr content in the steel is controlled to be 0.32% to 0.42%, which can be understood to include but not limited to 0.32%, 0.35%, 0.38%, 0.40% or 0.42%. Preferably, the Cr content of the steel is 0.35% to 0.42% by mass.

[0070] Titanium (Ti) can refine the grain structure of steel, thereby improving the strength and toughness of steel. In stainless steel, titanium can eliminate or reduce the intergranular corrosion phenomenon of steel, and titanium is a strong deoxidizer in steel, which can make the internal structure of steel dense, refine the grains, reduce aging sensitivity and cold brittleness, and improve welding performance. In addition, titanium has a strong solid solution strengthening effect, but reduces the toughness of the solid solution, solid solution in austenite improves the hardenability of steel, but chemical titanium reduces the hardenability of steel. Comprehensively considered, the present invention controls the Ti content in the steel to be 0.015% to 0.030%, which can be understood to include but not limited to 0.015%, 0.016%, 0.018%, 0.020%, 0.022%, 0.025%, 0.028% or 0.030%. Preferably, the Ti content of the steel is 0.016% to 0.028% by mass percentage.

[0071] The role of nitrogen (N) in steel is similar to that of carbon. N mainly has fine grain strengthening, precipitation strengthening, improved wear resistance, corrosion resistance, and prevention of intergranular corrosion or pitting corrosion, but excessive N will increase intergranular corrosion, or form pores in the steel or embrittle the steel. Taking all factors into consideration, the present invention controls the N content of the steel to be ≤0.007%, including but not limited to 0, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006% or 0.007%.

[0072] Aluminum (Al) can be used as a deoxidizer to remove oxygen and nitrogen, and can reduce the austenite phase region in the steel, including acid-soluble aluminum (Als) and acid-insoluble aluminum. In order to improve the performance of the steel, the present invention controls the Als content of the steel to be 0.015% to 0.050%, including but not limited to 0.015%, 0.020%, 0.025%, 0.030%, 0.035%, 0.040%, 0.045%, or 0.050%. Preferably, the Als content of the steel is 0.020% to 0.045% by mass.

[0073] The present invention regulates the chemical composition of the steel, especially regulates the element types and content percentages, and the steel does not contain expensive Ni, thereby providing a nickel-free steel with low production cost, low yield ratio, good stamping performance, good weather resistance and high yield rate, so as to solve the cracking phenomenon in the stamping process of the container top plate and improve the yield rate.

[0074] Figure 1 200X metallographic structure diagram of the steel prepared in one embodiment of the present invention, Figure 1 It can be seen that the structure is F+P and the grain size is level 10.

[0075] In one embodiment, the yield strength of the steel is 360MPa to 500MPa.

[0076] In one embodiment, the tensile strength of the steel is 500MPa to 600MPa.

[0077] In one embodiment, the elongation of the steel is greater than 30%.

[0078] In one embodiment, the yield strength ratio of the steel is less than 0.8. Furthermore, the yield strength ratio of the steel is less than 0.75.

[0079] The present invention also provides a method for preparing the steel material as described above, and the technical solution is as follows:

[0080] A method for preparing the steel material as described above comprises the steps of converter smelting, LF refining, thin slab continuous casting, heating in a heating furnace and hot continuous rolling.

[0081] In one of the embodiments, in the converter smelting step, the controlled composition percentages of the converter final molten steel are C: 0.020%~0.050%, Si: 0.20%~0.30%, Mn: 0.30%~0.40%, P: 0.020%~0.050%, S: 0.001%~0.010%, Cu: 0.20%~0.25%, Cr: 0.20%~0.30%.

[0082] In one of the embodiments, in the converter smelting step, the final temperature is 1590°C to 1660°C.

[0083] In one of the embodiments, in the LF refining step, the controlled composition percentages of the molten steel at the LF refining endpoint are C: 0.045% ~ 0.065%, Si: 0.28% ~ 0.40%, Mn: 0.60% ~ 0.80%, P: 0.072% ~ 0.090%, S: 0.001% ~ 0.010%, Cu: 0.25% ~ 0.28%, Cr: 0.32% ~ 0.42%, Ti: 0.015% ~ 0.030%, N: ≤ 0.007%, Als: 0.015% ~ 0.050%, and the balance is Fe and unavoidable impurities.

[0084] In one embodiment, in the LF refining step, the inlet temperature is 1550°C to 1600°C.

[0085] In one embodiment, in the LF refining step, the refining time is 40 min to 100 min.

[0086] In one of the embodiments, in the LF refining step, the soft blowing time is 6 min to 20 min.

[0087] In one of the embodiments, in the LF refining step, the molten steel calming time is 10 min to 30 min.

[0088] In one of the embodiments, in the LF refining step, the outlet temperature is 1580°C to 1620°C.

[0089] In one of the embodiments, in the step of continuous casting of thin slabs, the temperature of molten steel in the tundish is 1540°C to 1555°C.

[0090] In one of the embodiments, in the step of continuous casting of the thin slab, the continuous casting machine pulling speed is 4.0 m / min to 4.2 m / min.

[0091] Furthermore, in the step of continuous casting of the thin slab, the temperature of the molten steel in the tundish is 1540°C ~ 1555°C, the pulling speed of the continuous casting machine is controlled at 4.0m / min ~ 4.2m / min, and constant pulling speed casting is required after reaching the target pulling speed. The protective slag used is low-carbon protective slag, and weak cooling is used for the first and second cooling. Dynamic light pressure is used for continuous casting to press the continuous casting billet to a thickness of 70mm.

[0092] In one of the embodiments, in the step of heating in the heating furnace, the continuous casting slab entering the furnace has a temperature ≥ 950°C.

[0093] In one of the embodiments, in the step of heating in the heating furnace, the temperature of the heating section is 1230°C to 1270°C.

[0094] In one of the embodiments, in the step of heating in the heating furnace, the time in the furnace is 15 minutes to 35 minutes.

[0095] In one of the embodiments, in the step of heating in the heating furnace, the furnace outlet temperature is 1140°C to 1180°C.

[0096] In one embodiment, during the hot rolling step, the dephosphorization pressure is 21 MPa to 24 MPa.

[0097] In one embodiment, in the hot rolling step, the final rolling temperature is 890°C to 910°C.

[0098] In one embodiment, in the hot rolling step, the layer cooling mode is front-stage concentrated cooling.

[0099] In one embodiment, in the hot rolling step, the coiling temperature is 610°C to 630°C.

[0100] The present invention ensures strength through solid solution strengthening of elements such as C, Si, Mn, P, Cr, and a cooling mode of concentrated cooling in the front section, reduces the yield ratio through higher final rolling temperature and coiling temperature, and avoids cracks caused by copper embrittlement due to the lack of Ni addition through higher slab furnace entry temperature and high-temperature rapid firing in the heating furnace.

[0101] The present invention also provides the application of the steel material as described above, and the technical solution is as follows:

[0102] (1) A plate comprising the steel material as described above, or a steel material produced according to the method for producing the steel material as described above.

[0103] (2) A container roof, comprising the plate material as described above. Further, the container roof is a one-time stamping formed roof.

[0104] The present invention will be further described below with reference to examples.

[0105] In the following examples, the mechanical properties of the steel coils were tested as follows:

[0106] The tensile test was carried out in accordance with standard GB / T228.1-2010.

[0107] Embodiment 1 to Embodiment 5

[0108] The process flow is as follows: converter smelting, LF refining, thin slab continuous casting and hot rolling.

[0109] The following equipment is used: 100t converter, 100t LF refining, thin slab continuous casting: continuous casting slab width 900-1600mm, thickness 70mm, roller bottom soaking furnace, 1780 rolling mill.

[0110] The specific operation steps and process parameter control of each process are as follows:

[0111] (1) Converter smelting process:

[0112] ① Bottom blowing adopts full argon blowing mode.

[0113] ② The furnace mouth pressure must ensure positive pressure to prevent air inhalation, especially in the later stage of refining.

[0114] ③ Slag washing requirements: add 350±60kg of lime.

[0115] ④ Use low-carbon ferromanganese (or silicon manganese), ferrophosphorus, aluminum blocks (or aluminum iron) and other deoxidation alloys.

[0116] ⑤ During the steel-making process, argon should be blown from the bottom of the ladle throughout the entire process. It is strictly prohibited to blow steel with violent blowing or without argon blowing.

[0117] ⑥ After the ladle reaches the argon station, immediately stop bottom blowing of argon and take temperature measurements and samples.

[0118] ⑦ Main ingredients and temperature control are shown in Table 1.

[0119] Table 1: End point composition and temperature of converter step

[0120]

[0121] (2) LF refining process:

[0122] ① The ladle enters the station for temperature measurement and sample analysis;

[0123] ② The molten steel is subjected to conventional methods such as heating with electricity, adding alloy to fine-tune the composition, and calcium treatment; the process parameters of each embodiment are shown in Table 3, and the end point composition is shown in Table 4.

[0124] ③ Slag making system: yellow slag or yellow-white slag. The amount of refined lime added is ≥500Kg (the amount of lime added in the refined slag circulation furnace is ≥300kg), which can be appropriately increased or decreased according to the actual slag conditions.

[0125] ④Maintain a slight positive pressure on the flue gas during the entire treatment process to prevent the inhalation of air during the treatment process from causing nitrogen absorption by the molten steel.

[0126] ⑤ It is forbidden to add aluminum blocks within 5 minutes before calcium treatment, and it is forbidden to feed aluminum wire within 3 minutes before calcium treatment.

[0127] ⑥ After the other components and temperature of the molten steel are qualified, calcium treatment shall be carried out. After calcium treatment, it is strictly forbidden to supply power, stir strongly and add materials.

[0128] ⑦Soft blowing time ≥ 6min, molten steel calming time ≥ 10min.

[0129] Table 2: LF refining process

[0130]

[0131] Table 3: LF refining step end point composition

[0132]

[0133] (3) Thin slab continuous casting process:

[0134] The temperature of the molten steel in the tundish is 1540℃~1555℃, and the casting speed of the continuous casting machine is controlled at 4.0m / min~4.2m / min. After reaching the target casting speed, constant casting speed casting is required. The protective slag used is low-carbon protective slag. The primary and secondary cooling methods use weak cooling. Dynamic light pressure is used for continuous casting to press the continuous casting billet to a thickness of 70mm. The specific process conditions of the thin slab continuous casting process are shown in Table 5.

[0135] Table 5: Process conditions for thin slab continuous casting process

[0136] Group Tundish molten steel temperature / ℃ Continuous casting machine speed / m / min Example 1 1551 4 Example 2 1549 4.1 Example 3 1552 4.2 Example 4 1545 4.1 Example 5 1551 4.2

[0137] (4) Heating process of heating furnace:

[0138] The continuous casting slab entering the furnace temperature is ≥950℃, the heating section temperature is 1230℃~1270℃, the furnace time is 15min~35min, and the furnace exit temperature is 1140℃~1180℃. The specific process conditions are shown in Table 6.

[0139] Table 6: Process conditions of heating furnace heating process

[0140]

[0141] (5) Hot rolling process: dephosphorization pressure 21MPa~24MPa, final rolling temperature 890℃~910℃, layer cooling mode is front-end concentrated cooling, coiling temperature 610℃~630℃. Specific process conditions are shown in Table 7, and mechanical properties of steel coils are shown in Table 8.

[0142] Table 7: Process conditions of hot rolling process

[0143]

[0144]

[0145] Table 8: Mechanical properties of steel coils

[0146]

[0147] In summary, the present invention adopts a short production process of continuous casting and rolling, does not contain precious metals such as Ni, and has low cost. Through component design and controlled rolling and controlled cooling process technology, the yield ratio can be ensured to be less than 0.8, good stamping performance can be obtained, and low-cost, low-yield ratio container plate production can be achieved.

[0148] 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.

[0149] The above-described embodiments only express several implementation methods of the present invention, which are convenient for understanding the technical solutions of the present invention in detail, but they 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, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. 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 by the present invention are all within the protection scope of the claims attached to the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the contents of the attached claims, and the description and drawings can be used to interpret the contents of the claims.

Claims

1. A steel material, characterized in that: The chemical composition includes, by mass percentage, C: 0.045% to 0.065%, Si: 0.28% to 0.40%, Mn: 0.60% to 0.80%, P: 0.072% to 0.090%, S: 0.001% to 0.010%, Cu: 0.25% to 0.28%, Cr: 0.32% to 0.42%, Ti: 0.015% to 0.030%, N: ≤0.007%, Als: 0.015% to 0.050%, and the balance is Fe and unavoidable impurities.

2. The steel material according to claim 1, characterized in that: Calculated by mass percentage, the Ti content of the steel is 0.016% to 0.028%.

3. The steel material according to claim 1, characterized in that: Calculated by mass percentage, one or more of the following (1) to (6) are met: (1) The Si content of the steel is 0.29% to 0.38%; (2) The Mn content of the steel is 0.62% to 0.78%; (3) The P content of the steel is 0.072% to 0.088%; (4) The S content of the steel is 0.003% to 0.008%; (5) The Cr content of the steel is 0.35% to 0.42%; (6) The Als content of the steel is 0.020% to 0.045%.

4. The steel material according to any one of claims 1 to 3, characterized in that: Satisfy one or more of the following (1) to (4): (1) The yield strength of the steel is 360 MPa to 500 MPa; (2) The tensile strength of the steel is 500 MPa to 600 MPa; (3) The elongation of the steel is 30% or more; (4) The yield strength ratio of the steel is less than 0.

8.

5. A method for preparing the steel material according to any one of claims 1 to 4, characterized in that: include: Converter smelting, LF refining, thin slab continuous casting, heating furnace heating and hot rolling steps.

6. The method for preparing the steel material according to claim 5, characterized in that: In the converter smelting step, one or more of the following (1) to (2) are met: (1) The controlled composition percentage of the molten steel at the end of the converter is C: 0.020% ~ 0.050%, Si: 0.20% ~ 0.30%, Mn: 0.30% ~ 0.40%, P: 0.020% ~ 0.050%, S: 0.001% ~ 0.010%, Cu: 0.20% ~ 0.25%, Cr: 0.20% ~ 0.30%; (2) Final temperature 1590℃~1660℃.

7. The method for preparing the steel material according to claim 5, characterized in that: In the LF refining step, one or more of the following (1) to (6) are satisfied: (1) The controlled composition percentage of molten steel at the end point of LF refining is C: 0.045% ~ 0.065%, Si: 0.28% ~ 0.40%, Mn: 0.60% ~ 0.80%, P: 0.072% ~ 0.090%, S: 0.001% ~ 0.010%, Cu: 0.25% ~ 0.28%, Cr: 0.32% ~ 0.42%, Ti: 0.015% ~ 0.030%, N: ≤ 0.007%, Als: 0.015% ~ 0.050%, and the balance is Fe and unavoidable impurities; (2) The inlet temperature is 1550℃~1600℃; (3) The refining time is 40 min to 100 min; (4) Soft blowing time is 6min to 20min; (5) The cooling time of molten steel is 10 to 30 minutes; (6) The outlet temperature is 1580℃~1620℃.

8. The method for preparing the steel material according to claim 5, characterized in that: In the step of continuous casting of thin slabs, one or more of the following (1) to (2) are satisfied: (1) The temperature of molten steel in the tundish is 1540℃~1555℃; (2) The continuous casting machine pulling speed is 4.0m / min~4.2m / min.

9. The method for preparing a steel material according to any one of claims 5 to 8, characterized in that: In the step of heating in the heating furnace, one or more of the following (1) to (4) are satisfied: (1) The continuous casting slab furnace temperature is ≥950℃; (2) The temperature of the heating section is 1230°C to 1270°C; (3) The time in the furnace is 15min to 35min; (4) The furnace temperature is 1140℃~1180℃.

10. The method for preparing a steel material according to any one of claims 5 to 8, characterized in that: In the hot rolling step, one or more of the following (1) to (4) are satisfied: (1) The phosphorus removal pressure is 21MPa~24MPa; (2) The final rolling temperature is 890℃~910℃; (3) The layer cooling mode is front-stage centralized cooling; (4) The coiling temperature is 610℃~630℃.

11. A plate, characterized in that: The invention comprises the steel material according to any one of claims 1 to 4, or the steel material produced by the method for producing the steel material according to any one of claims 5 to 10.

12. A container roof, characterized in that: The invention comprises the plate material as claimed in claim 11.

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