Corrosion-resistant steel bar and production method thereof

Abstract

The invention provides a corrosion-resistant steel bar and a production method thereof. The corrosion-resistant steel bar comprises the following components in percentage by weight: 0.03-0.09% of C, 0.85-1.25% of Si, 1.51-1.69% of Mn, 0.51-1.90% of Cr, less than or equal to 0.01% of P, less than or equal to 0.01% of S, less than or equal to 0.015% of N, 0.21-0.49% of Al, 0.01-0.05% of La, at least one of Nb, V and Ti, less than or equal to 0.05% of Nb, less than or equal to 0.05% of V, less than or equal to 0.05% of Ti and the balance of Fe and inevitable impurities. Wherein 0.02% < = ([Nb] + [V] + [Ti]) < = 0.05%, 0.3 < = ([Nb] + [V] + [Ti]) / ([C] + [N]) < = 0.8, and 1.8% < = [Cr] + [Si] + [La] + [Al] < = 3.0% are satisfied.

Description

Technical Field

[0001] This application relates to the technical field of steel smelting, and particularly relates to a corrosion-resistant steel bar and a production method thereof. Background Art

[0002] There are numerous cases in actual projects where reinforced concrete structures fail prematurely due to corrosion, which not only increases maintenance costs but also causes a great waste of energy and resources. Currently, by adding a small amount of rare earth elements to steel, the corrosion resistance can be significantly improved.

[0003] However, since carbon has an adverse effect on the corrosion resistance of steel bars, in order to reduce the adverse effect of carbon on corrosion resistance, it is achieved by reducing the carbon content in the corrosion-resistant steel bars. However, it is difficult to ensure the mechanical properties of steel bars with low carbon content. Therefore, in some steel bars, a large amount of precious metal elements such as Cr, Mo, and Ni are added to improve the strength of the steel bars, resulting in a significant increase in cost.

[0004] Currently, there is a problem that the mechanical properties, corrosion resistance, and economy of corrosion-resistant steel bars are difficult to coordinate and match. Summary of the Invention

[0005] The purpose of this application is to provide a corrosion-resistant steel bar, which solves the problem that it is difficult to coordinate and match the mechanical properties, corrosion resistance, and economy in the prior art.

[0006] In order to achieve one of the above-mentioned invention purposes, an embodiment of this application provides a corrosion-resistant steel bar, which contains the following components by weight percentage: C: 0.03 - 0.09%, Si: 0.85 - 1.25%, Mn: 1.51 - 1.69%, Cr: 0.51 - 1.90%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.015%, Al: 0.21 - 0.49%, La: 0.01 - 0.05%, at least one of Nb, V, Ti, and Nb ≤ 0.05%, V ≤ 0.05%, Ti ≤ 0.05%, and the balance is Fe and unavoidable impurities; wherein the following relationships are also satisfied: 0.02% ≤ ([Nb] + [V] + [Ti]) ≤ 0.05%, 0.3 ≤ ([Nb] + [V] + [Ti]) / ([C] + [N]) ≤ 0.8, 1.8% ≤ [Cr] + [Si] + [La] + [Al] ≤ 3.0%.

[0007] As a further improvement of an embodiment of this application, the microstructure of the steel bar includes pearlite, ferrite, and bainite, the volume fraction of ferrite is 40 - 55%, and the volume fraction of bainite ≤ 10%.

[0008] As a further improvement of an embodiment of this application, the yield strength of the steel bar ≥ 435 MPa, the elongation after fracture ≥ 30%, the total elongation at maximum force ≥ 20%, and the ratio of yield strength to tensile strength ≥ 1.35.

[0009] As a further improvement of an embodiment of the present application, in a solution of 5 wt% NaCl, at a temperature of 35 °C and a humidity of 70%, the corrosion rate measured by the weight loss method for 30 days is ≤ 2.0 g·(m 2 ·h) -1 .

[0010] An embodiment of the present application also provides a production method of the corrosion-resistant steel bar described above, including the smelting, LF refining, continuous casting, billet heating, rolling, and cooling processes carried out in sequence. Among them, In the smelting process, when tapping, alloy and slag materials are first added in the order of ferrosilicon manganese alloy, ferrosilicon alloy, and lime, and then ferrochromium alloy, ferroniobium alloy, and vanadium nitride alloy are selectively added according to the target components; In the LF refining process, ferrochromium alloy and ferrosilicon alloy are added when arriving at the station, and then ferro titanium alloy, aluminum pellets, and aluminum lanthanum alloy are selectively and sequentially added according to the target components; In the rolling process, the final rolling temperature is controlled at 900 - 950 °C to obtain the steel bar; In the cooling process, after rolling, it is cooled to 750 - 850 °C at a cooling rate of 10 - 20 °C / s, and then cooled naturally on the cooling bed to room temperature, and the cooling rate of the steel bar on the cooling bed is ≤ 2 °C / s.

[0011] As a further improvement of an embodiment of the present application, the ferrosilicon alloy added in the smelting process is twice that added in the LF refining process, and the ferrochromium alloy added in the smelting process is half of that added in the LF refining process; The addition amount of ferrosilicon manganese alloy is 20 - 30 kg / t, the total addition amount of ferrosilicon alloy in the smelting process and the LF refining process is 15 - 20 kg / t, the total addition amount of ferrochromium alloy in the smelting process and the LF refining process is 10 - 40 kg / t, the addition amount of ferroniobium alloy is 0 - 2 kg / t, and the addition amount of vanadium nitride alloy is 0 - 1.5 kg / t; The addition amount of ferro titanium alloy is 0 - 4 kg / t, the addition amount of aluminum pellets is 1 - 3 kg / t, and the addition amount of aluminum lanthanum alloy is 0.8 - 4 kg / t.

[0012] As a further improvement of an embodiment of the present application, the silicon content in the ferrosilicon manganese alloy is 17 - 20%, the manganese content is 65 - 70%, and the balance is iron and unavoidable impurities; the silicon content in the ferrosilicon alloy is 70 - 75%, and the balance is iron and unavoidable impurities; the ferrochromium alloy uses low-carbon ferrochromium alloy, and the chromium content in the low-carbon ferrochromium alloy is 50 - 60%, the carbon content ≤ 0.1%, and the balance is iron and unavoidable impurities; the niobium content in the ferroniobium alloy is 60 - 70%, and the balance is iron and unavoidable impurities; the vanadium content in the vanadium nitride alloy is 75 - 80%, the nitrogen content is 5 - 10%, and the balance is iron and unavoidable impurities; The titanium content in the ferro-titanium alloy is 35-45%, and the balance is iron and inevitable impurities; the aluminum content in the aluminum granules is ≥95%, and the balance is iron and inevitable impurities; the aluminum content in the aluminum-lanthanum alloy is 65-70%, the lanthanum content is 20-25%, and the balance is iron and inevitable impurities.

[0013] As a further improvement of an embodiment of the present application, in the steelmaking process, the tapping temperature is 1600-1640°C, and in the LF refining process, the tapping temperature is 1540-1560°C.

[0014] As a further improvement of an embodiment of the present application, in the steelmaking process, argon is blown at the bottom throughout the tapping process, the argon pressure in the early stage is 0.4-0.5 MPa, and the argon pressure in the later stage is 0.3-0.4 MPa; in the LF refining process, the soft stirring time is ≥10 min.

[0015] As a further improvement of an embodiment of the present application, in the continuous casting process, the thickness of the mold powder is 8-10 mm; the casting speed is controlled at 2.5-3.5 m / min; after continuous casting is completed, the heating process heats the billet in a staged continuous heating manner, and the total time in the furnace is 60-100 min, where the soaking section temperature is 1100-1200°C, and the soaking section time is not less than 1 / 3 of the total time in the furnace.

[0016] One or more technical solutions provided by the present application have at least the following technical effects or advantages: The corrosion-resistant steel bars provided by the present application, through the associated design of niobium, vanadium, titanium, carbon, and nitrogen, give full play to the coupling strengthening effect of multiple elements, solve the problem of insufficient strength caused by low carbon content, and the problem of performance fluctuations caused by nitrogen content fluctuations, and achieve the coordinated matching of the strength and plasticity of the steel bars; through the associated design of elements such as chromium, silicon, rare earth lanthanum, and aluminum, the corrosion resistance and low cost of the steel bars are ensured, and the coordinated matching of the strength, plasticity, corrosion resistance, and economy of the steel bars is achieved. Specific Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] An embodiment of the present application provides a corrosion-resistant steel bar, which contains the following components by weight percentage: C: 0.03 - 0.09%, Si: 0.85 - 1.25%, Mn: 1.51 - 1.69%, Cr: 0.51 - 1.90%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.015%, Al: 0.21 - 0.49%, La: 0.01 - 0.05%, at least one of Nb, V, Ti, and Nb ≤ 0.05%, V ≤ 0.05%, Ti ≤ 0.05%, and the balance is Fe and inevitable impurities; and the following relationships are also satisfied: 0.02% ≤ ([Nb] + [V] + [Ti]) ≤ 0.05%, 0.3 ≤ ([Nb] + [V] + [Ti]) / ([C] + [N]) ≤ 0.8, 1.8% ≤ [Cr] + [Si] + [La] + [Al] ≤ 3.0%.

[0019] The corrosion-resistant steel bar provided by the present application realizes the coordinated matching of the strength and plasticity of the steel bar through the associated design of niobium, vanadium, titanium, carbon, and nitrogen, giving full play to the coupling strengthening effect of multiple elements, solving the problem of insufficient strength caused by low carbon content and the problem of performance fluctuations caused by nitrogen content fluctuations; through the associated design of elements such as chromium, silicon, rare earth lanthanum, and aluminum, the corrosion resistance and low cost of the steel bar are ensured, and the coordinated matching of the strength, plasticity, corrosion resistance, and economy of the steel bar is realized.

[0020] The functions and mechanisms of each element are specifically described as follows: Carbon (C): It is a strengthening element. However, if the C content is too high, it is easy to form carbides, reducing the corrosion resistance of the steel, and it is also unfavorable for the plasticity, toughness, and welding performance of the steel. Considering comprehensively, when the C content is 0.03 - 0.09%, the effect is the best.

[0021] Silicon (Si): It is a deoxidizer, which can significantly reduce the oxygen content in the steel, reduce the formation of oxide inclusions, and is beneficial to the subsequent addition of rare earth elements. A high Si content is beneficial to the formation of silicate phases on the surface of the steel, blocking the transmission and aggregation of erosion media and improving the corrosion resistance. Si is also a strengthening element and a ferrite-forming element. A high content is beneficial to the regulation of the microstructure. By solid solution strengthening and phase transformation microstructure regulation, the problem of coordinated matching of the strength - plasticity of the steel is solved. However, if the Si content is too high, it is not conducive to welding. Considering comprehensively, when the Si content is 0.85 - 1.25%, the effect is the best.

[0022] Manganese (Mn): It is a solid solution strengthening element. However, if the Mn content is too high, it is easy to form MnS inclusions, reducing the plasticity and corrosion resistance of the steel. Considering comprehensively, when the Mn content is 1.51 - 1.69%, the effect is the best.

[0023] Chromium (Cr): Corrosion-resistant element. Adding a certain amount of Cr can improve the corrosion resistance of steel. Cr is also a solid solution strengthening element. Cr atoms dissolve in ferrite or austenite, causing lattice distortion and improving the strength and hardness of steel. Cr can also delay the decomposition of austenite, improve hardenability, and enable steel to obtain hard phase structures such as bainite and martensite at a lower cooling rate. However, Cr carbonitride is not good for corrosion resistance. Excessive chromium content increases the difficulty of smelting, prolongs the smelting time, increases the cost, and affects the plasticity of steel. Taking all factors into consideration, the best effect is achieved when the chromium content is 0.51~1.90%.

[0024] Phosphorus (P): An impurity element. A high content of P will increase the cold brittleness of steel. A low content will increase the difficulty of smelting. Taking all factors into consideration, the best effect is achieved when the P content is ≤0.01%.

[0025] Sulfur (S): An impurity element that forms MnS inclusions with Mn, affecting corrosion resistance. Low S content will significantly increase smelting difficulty and cost. Taking all factors into consideration, the best effect is achieved when the S content is ≤0.01%.

[0026] Titanium (Ti): Corrosion-resistant and strengthening element; can increase the corrosion potential of steel and improve corrosion resistance; at the same time, it can improve the mechanical properties of steel through fine grain strengthening; however, Ti easily generates oxides, and too high a content can easily block the water outlet during continuous casting; taking all factors into consideration, the best effect is achieved when the Ti content is ≤0.05%.

[0027] Niobium and vanadium (V, Nb): strengthening elements that form carbonitrides in steel and improve the mechanical properties of steel through grain refinement and precipitation strengthening. The strengthening effect is related to the C and N contents. Taking all factors into consideration, V≤0.05%, Nb≤0.05%.

[0028] Aluminum (Al): Deoxidizer. It deoxidizes during the smelting process and reduces the oxygen content in the molten steel, which is beneficial to the addition of rare earth elements and ensures the recovery rate of rare earth elements. Al can also form oxides in steel and accumulate in the rust layer to improve corrosion resistance. However, if the Al content is too high, it is easy to block the water outlet during continuous casting. Taking all factors into consideration, the best effect is achieved when the Al content is 0.21~0.49%.

[0029] Nitrogen (N): It forms carbonitrides with niobium and vanadium, which plays a role in grain refinement and precipitation strengthening. Nitrogen is beneficial to the improvement of strength and pitting corrosion resistance, but is not good for plasticity, and the nitrogen content is not easy to control accurately. Taking all factors into consideration, the best effect is achieved when the N content is ≤0.015%.

[0030] Rare earth lanthanum (La): A rare earth element that mainly modifies inclusions, purifies molten steel, and improves corrosion resistance. At the same time, through rare earth microalloying, the grain size can be refined, and the strength and plasticity can be improved. However, rare earth elements are prone to oxidation, forming large-sized inclusions, which are likely to block the nozzle during continuous casting and increase the smelting difficulty. Considering comprehensively, when the content of rare earth lanthanum is 0.01 - 0.05%, the effect is the best.

[0031] Adding a sufficient amount of carbon is the most effective method to improve the strength of steel. However, with the increase of carbon content, it is not beneficial to plasticity and corrosion resistance. To ensure corrosion resistance, this application adopts a low-carbon content design. At the same time, niobium, vanadium, and titanium strengthening elements are introduced. Through strengthening effects such as grain refinement and precipitation, the problem of strength reduction caused by the decrease of carbon content is compensated. Considering the low carbon content, large fluctuations in nitrogen content, and the differences in the binding abilities of niobium, vanadium, and titanium with carbon and nitrogen, as well as smelting difficulty and smelting cost, when 0.02% ≤ ([Nb] + [V] + [Ti]) ≤ 0.05% and 0.3 ≤ ([Nb] + [V] + [Ti]) / ([C] + [N]) ≤ 0.8, the strengthening effect is the best. In addition, chromium and niobium elements can also adjust the phase transformation products by influencing the phase transformation behavior, and adjust the strength and plasticity of the steel bars through phase transformation strengthening.

[0032] Elements such as chromium, silicon, and aluminum form an oxide film on the surface of the steel, preventing corrosive media from contacting the steel and improving the corrosion resistance of the steel. However, the formation of the surface oxide film has requirements for the addition amount of elements. For example, for chromium element, when the content is greater than 5%, a stable oxide film can be formed on the surface of low-carbon steel. The large addition of alloying elements increases the alloy cost and smelting difficulty. In response to this, the present invention proposes a design idea of composite addition of alloying elements. Through the coupling effect of chromium, silicon, and aluminum elements during the formation of the oxide film on the steel surface, the energy required for the formation of the oxide film is reduced, the density and stability of the oxide film are improved, and while reducing the addition amount of alloying elements, the corrosion resistance of the steel is ensured.

[0033] Adding rare earth elements to steel can reduce the sulfur content in the steel and the number of inclusions. At the same time, manganese sulfide inclusions can be transformed into rare earth sulfur oxides, purifying the molten steel and reducing the corrosion origin points. Rare earth elements can also be enriched inside the rust layer, improving the density of the rust layer. However, the recovery rate of rare earth elements is affected by factors such as the addition method of rare earth alloys and the types of rare earth alloys. When there are strong oxidizing elements such as silicon and aluminum in the steel, it is beneficial to the recovery of rare earth elements. Considering comprehensively, when 1.8% ≤ [Cr] + [Si] + [La] + [Al] ≤ 3.0%, the effect is the best.

[0034] In an embodiment of the present application, the microstructure of the steel bar includes pearlite, ferrite and bainite. The volume fraction of ferrite is 40-55%, and the volume fraction of bainite is ≤10%. The volume fraction of pearlite is 40-55%, the lamellar spacing is 150-200 nm, and the pearlite colony size is 8-11 μm. The duplex microstructure of ferrite, pearlite and bainite enables the significant improvement of the corrosion resistance and mechanical properties of the steel bar without adding Ni and Mo corrosion-resistant alloying elements.

[0035] In an embodiment of the present application, the yield strength of the steel bar is ≥435 MPa, the elongation after fracture is ≥30%, the total elongation at maximum force is ≥20%, and the strength ratio is ≥1.35.

[0036] In an embodiment of the present application, in a 5 wt% NaCl solution, at a temperature of 35 °C and a humidity of 70%, the corrosion rate measured by the weight loss method for 30 days is ≤2.0 g·(m 2 ·h) -1 。

[0037] The embodiment of the present application also provides a production method of the aforementioned corrosion-resistant steel bar, including the smelting, LF refining, continuous casting, slab heating, rolling and cooling processes carried out in sequence. Among them, In the smelting process, when tapping, alloying materials and slag materials are first added in the order of ferrosilicon manganese alloy, ferrosilicon alloy and lime, and then ferrochrome alloy, ferroniobium alloy and vanadium nitride alloy are selectively added according to the target components; In the LF refining process, ferrosilicon alloy and ferrochrome alloy are added when arriving at the station, and then ferro titanium alloy, aluminum pellets and aluminum lanthanum alloy are selectively and sequentially added according to the target components; In the rolling process, the final rolling temperature is controlled at 900-950 °C to obtain the steel bar; In the cooling process, after rolling, it is cooled to 750-850 °C at a cooling rate of 10-20 °C / s, and then cooled naturally on the cooling bed to room temperature, and the cooling rate of the steel bar on the cooling bed is ≤2 °C / s.

[0038] In the smelting process, ferrosilicon manganese alloy and ferrosilicon alloy are first added for deoxidation, and then chromium, niobium, vanadium and nitrogen are added to the molten steel for alloying according to the target components of the steel bar. In the LF refining process, ferrosilicon alloy and ferrochrome alloy are first added, and ferrosilicon alloy is used for deoxidation again to reduce the oxygen content in the molten steel. Then, aluminum lanthanum alloy containing rare earth elements is added, and ferro titanium alloy and aluminum pellets are also added before adding aluminum lanthanum alloy, which can also carry out a certain degree of deoxidation to ensure that rare earth lanthanum is not oxidized, thereby ensuring the recovery rate of rare earth lanthanum.

[0039] The production method of this application undergoes multiple deoxidations during the steelmaking stage (smelting process and LF refining process), ensuring a low oxygen content in the molten steel, enabling a high recovery rate of rare earth lanthanum, reducing the input amount of aluminum lanthanum alloy during steelmaking, and ensuring the stable acquisition of lanthanum element at low cost.

[0040] The rolling process controls a relatively high final rolling temperature, and the cooling process cools at a relatively fast cooling rate and then goes onto the cooling bed. On the premise of meeting the phase transformation thermodynamics, on the one hand, the residence time of the undercooled austenite during continuous cooling in the ferrite phase transformation region is adjusted, thereby adjusting the grain size and volume ratio of ferrite; on the other hand, the energy accumulated during the rapid cooling stage will become the driving force for phase transformation during the subsequent continuous cooling of the undercooled austenite.

[0041] The control of the final rolling temperature, the cooling rate in the cooling process, and the temperature of going onto the cooling bed proposed by the present invention can achieve a large degree of supercooling in the rapid cooling stage, accumulate a large amount of energy, so that the undercooled austenite has a strong phase transformation driving force during the slow cooling stage after going onto the cooling bed, promoting pearlite phase transformation, adjusting the volume ratio, lamellar spacing, and pearlite colony size of pearlite, and at the same time adjusting the pearlite phase transformation behavior, shortening the pearlite phase transformation interval and time, prompting the steel bar to obtain a small amount of bainite, making the final structure of the steel bar a duplex structure of ferrite, pearlite, and bainite, and realizing the coordinated matching of the strength and plasticity of the steel bar.

[0042] In an embodiment of this application, the ferrosilicon alloy added in the smelting process is twice that added in the LF refining process, and the ferrochromium alloy added in the smelting process is half of that added in the LF refining process.

[0043] The addition amount of silicomanganese alloy is 20 - 30 kg / t, the total addition amount of ferrosilicon alloy in the smelting process and LF refining process is 15 - 20 kg / t, the total addition amount of ferrochromium alloy in the smelting process and LF refining process is 10 - 40 kg / t, the addition amount of ferroniobium alloy is 0 - 2 kg / t, and the addition amount of vanadium nitride alloy is 0 - 1.5 kg / t.

[0044] The addition amount of ferrotitanium alloy is 0 - 4 kg / t, the addition amount of aluminum pellets is 1 - 3 kg / t, and the addition amount of aluminum lanthanum alloy is 0.8 - 4 kg / t.

[0045] Add 2 / 3 of the total amount of ferrosilicon alloy in the smelting process to remove a large amount of oxygen in the molten steel in advance, and then add the remaining 1 / 3 for re-deoxidation at the initial stage of the LF refining process. Add 1 / 3 of the total amount of ferrochromium alloy after deoxidation in the smelting process to reduce the amount of alloy added in the LF refining process and avoid the reduction of the molten steel temperature caused by adding too much alloy.

[0046] Among them, in the smelting process, adding ferrosilicon manganese alloy, ferrosilicon alloy, lime, ferrochrome alloy, ferroniobium alloy, and vanadium nitride alloy is bounded by half of the tapping volume. That is, before the tapping volume reaches 1 / 2, ferrosilicon manganese alloy, ferrosilicon alloy, and lime are added. After the tapping volume reaches 1 / 2, ferrochrome alloy, ferroniobium alloy, and vanadium nitride alloy are added.

[0047] In the LF refining process, adding ferrotitanium alloy, aluminum pellets, and aluminum lanthanum alloy is after half of the LF refining process, that is, taking time as the dividing point.

[0048] In an embodiment of the present application, the silicon content in the ferrosilicon manganese alloy is 17 - 20%, the manganese content is 65 - 70%, and the balance is iron and inevitable impurities.

[0049] The silicon content in the ferrosilicon alloy is 70 - 75%, and the balance is iron and inevitable impurities.

[0050] The ferrochrome alloy uses low - carbon ferrochrome alloy. The chromium content in the low - carbon ferrochrome alloy is 50 - 60%, the carbon content ≤ 0.1%, and the balance is iron and inevitable impurities.

[0051] The niobium content in the ferroniobium alloy is 60 - 70%, and the balance is iron and inevitable impurities.

[0052] The vanadium content in the vanadium nitride alloy is 75 - 80%, the nitrogen content is 5 - 10%, and the balance is iron and inevitable impurities.

[0053] The titanium content in the ferrotitanium alloy is 35 - 45%, and the balance is iron and inevitable impurities.

[0054] The aluminum content in the aluminum pellets ≥ 95%, and the balance is iron and inevitable impurities.

[0055] The aluminum content in the aluminum lanthanum alloy is 65 - 70%, the lanthanum content is 20 - 25%, and the balance is iron and inevitable impurities.

[0056] In an embodiment of the present application, in the smelting process, the tapping temperature is 1600 - 1640 °C, and in the LF refining process, the tapping temperature is 1540 - 1560 °C.

[0057] In an embodiment of the present application, in the smelting process, argon is blown from the bottom throughout the tapping process. The argon pressure in the early stage is 0.4 - 0.5 MPa, and the argon pressure in the later stage is 0.3 - 0.4 MPa; in the LF refining process, the soft stirring time ≥ 10 min.

[0058] In the smelting process, the total amount of ferrosilicon manganese alloy and ferrosilicon alloy added in the early stage is relatively large, and a greater air pressure is required for soft stirring. The other alloys added in the later stage are relatively less, and the air pressure is correspondingly reduced to avoid gas waste.

[0059] In an embodiment of the present application, in the continuous casting process, the thickness of the mold powder is 8 - 10 mm; the casting speed is controlled at 2.5 - 3.5 m / min. After continuous casting is completed, in the heating process, the billet is heated in a manner of continuous stepwise temperature increase, and the total time in the furnace is 60 - 100 min, where the soaking temperature is 1100 - 1200 °C, and the soaking time is not less than 1 / 3 of the total time in the furnace.

[0060] In the continuous casting process, a low-carbon steel mold powder is used to prevent the oxidation of active metals in the molten steel. In the heating process, a continuous stepwise temperature increase method is adopted, that is, the temperature is gradually increased to 1100 - 1200 °C in the preheating section, heating section, and soaking section, and the soaking time of the billet in the soaking section is not less than 1 / 3 of the total time in the furnace to ensure uniform temperature on the surface and in the core and avoid temperature difference.

[0061] The technical solution of the present application will be further described below in conjunction with some specific embodiments.

[0062] In the following table, Table 1 shows the chemical compositions and the relationship values of various elements for the examples and comparative examples. It should be particularly noted that in Table 1, the column of Nb + V + Ti represents the sum of the weight percentages of Nb, V, and Ti, and the column of Cr + Si + La + Al represents the sum of the weight percentages of Cr, Si, La, and Al; the column of (Nb + V + Ti) / (C + N) represents the ratio of the sum of the weight percentages of Nb, V, and Ti to the sum of the weight percentages of C and N, so this value does not carry %.

[0063] The steel bars with the chemical compositions shown in Table 1 are obtained through the smelting process, LF refining process, continuous casting process, heating process, rolling process, and cooling process shown in Tables 2 - 5, and the microstructure and properties of the steel bars are shown in Tables 6 and 7.

[0064] Table 1 Chemical Compositions of Examples and Comparative Examples (%)

[0065] Table 2 Production Process Parameters of Examples and Comparative Examples (Smelting Process)

[0066] Table 3 Production Process Parameters of Examples and Comparative Examples (LF Refining)

[0067] Table 4 Production Process Parameters of Examples and Comparative Examples (Continuous Casting Process)

[0068] Table 5 Production Process Parameters of Examples and Comparative Examples (Rolling Process and Cooling Process)

[0069] Table 6 Tissues of Examples and Comparative Examples

[0070] Table 7 Performances of Examples and Comparative Examples

[0071] For the corrosion-resistant steel bars based on the embodiments of the present invention, the yield strength of the steel bars corresponding to Examples 1 to 3 is ≥435 MPa, the tensile strength is ≥598 MPa, the elongation after fracture is ≥30%, the total elongation at maximum force is ≥20%, and the strength ratio is ≥1.35; evaluated by the weight loss method, in a harsh service environment, the corrosion rate in 30 days is ≤2.0 g·(m 2 ·h) -1 ; the comprehensive performance is significantly better than that of Comparative Examples 1 to 3.

[0072] It should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0073] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of this application, and they are not used to limit the protection scope of this application. Any equivalent embodiments or modifications made without departing from the technical spirit of this application should be included in the protection scope of this application.

Claims

1. A corrosion-resistant steel bar, characterized in that, Comprising the following components by weight percentage: C: 0.03 - 0.09%, Si: 0.85 - 1.25%, Mn: 1.51 - 1.69%, Cr: 0.51 - 1.90%, P ≤ 0.01%, S ≤ 0.01%, N ≤ 0.015%, Al: 0.21 - 0.49%, La: 0.01 - 0.05%, at least one of Nb, V, Ti, and Nb ≤ 0.05%, V ≤ 0.05%, Ti ≤ 0.05%, with the balance being Fe and unavoidable impurities; and further satisfying the relationships: 0.02% ≤ ([Nb] + [V] + [Ti]) ≤ 0.05%, 0.3 ≤ ([Nb] + [V] + [Ti]) / ([C] + [N]) ≤ 0.8, 1.8% ≤ [Cr] + [Si] + [La] + [Al] ≤ 3.0%.

2. The corrosion-resistant steel bar according to claim 1, wherein The microstructure of the steel bar includes pearlite, ferrite, and bainite, with the volume fraction of ferrite being 40 - 55% and the volume fraction of bainite ≤ 10%.

3. The corrosion-resistant steel bar according to claim 2, wherein The yield strength of the steel bar ≥ 435 MPa, the elongation after fracture ≥ 30%, the total elongation at maximum force ≥ 20%, and the strength ratio ≥ 1.

35.

4. The corrosion-resistant steel bar according to claim 2, characterized in that, In a solution of 5 wt% NaCl, at a temperature of 35 °C and a humidity of 70%, the corrosion rate measured by the weight loss method for 30 days is ≤ 2.0 g·(m 2 ·h) -1 .

5. The production method of the corrosion-resistant steel bar according to claim 1, characterized in that, Including the following processes carried out in sequence: smelting, LF refining, continuous casting, heating of the casting blank, rolling, and cooling processes, where In the smelting process, when tapping, alloying materials and slag materials are added in the order of ferrosilicon manganese alloy, ferrosilicon alloy, and lime first, and then ferrochrome alloy, ferroniobium alloy, and vanadium nitride alloy are selectively added according to the target components; In the LF refining process, ferrochrome alloy and ferrosilicon alloy are added upon arrival at the station, and then ferrotitanium alloy, aluminum pellets, and aluminum lanthanum alloy are selectively and sequentially added according to the target components; In the rolling process, the final rolling temperature is controlled at 900 - 950 °C to obtain the steel bar; In the cooling process, after rolling, it is cooled to 750 - 850 °C at a cooling rate of 10 - 20 °C / s, and then cooled naturally on the cooling bed to room temperature, with the cooling rate of the steel bar on the cooling bed ≤ 2 °C / s.

6. The production method of the corrosion-resistant steel bars according to claim 5, characterized in that, The ferrosilicon alloy added in the smelting process is twice that added in the LF refining process, and the ferrochrome alloy added in the smelting process is half of that added in the LF refining process; The addition amount of ferrosilicon manganese alloy is 20 - 30 kg / t, the total addition amount of ferrosilicon alloy in the smelting process and the LF refining process is 15 - 20 kg / t, the total addition amount of ferrochrome alloy in the smelting process and the LF refining process is 10 - 40 kg / t, the addition amount of ferroniobium alloy is 0 - 2 kg / t, and the addition amount of vanadium nitride alloy is 0 - 1.5 kg / t; The addition amount of ferrotitanium alloy is 0 - 4 kg / t, the addition amount of aluminum pellets is 1 - 3 kg / t, and the addition amount of aluminum lanthanum alloy is 0.8 - 4 kg / t.

7. The production method of the corrosion-resistant steel bar according to claim 6, characterized in that, The silicon content in ferrosilicon manganese alloy is 17 - 20%, the manganese content is 65 - 70%, and the balance is iron and inevitable impurities; the silicon content in ferrosilicon alloy is 70 - 75%, and the balance is iron and inevitable impurities; ferrochrome alloy adopts low-carbon ferrochrome alloy, in which the chromium content is 50 - 60% and the carbon content ≤ 0.1%, and the balance is iron and inevitable impurities; the niobium content in ferroniobium alloy is 60 - 70%, and the balance is iron and inevitable impurities; the vanadium content in vanadium nitride alloy is 75 - 80% and the nitrogen content is 5 - 10%, and the balance is iron and inevitable impurities; The titanium content in ferrotitanium alloy is 35 - 45%, and the balance is iron and inevitable impurities; the aluminum content in aluminum pellets is ≥ 95%, and the balance is iron and inevitable impurities; the aluminum content in aluminum lanthanum alloy is 65 - 70%, the lanthanum content is 20 - 25%, and the balance is iron and inevitable impurities.

8. The production method of the corrosion-resistant steel bar according to claim 5, characterized in that, In the smelting process, the tapping temperature is 1600 - 1640 °C, and in the LF refining process, the tapping temperature is 1540 - 1560 °C.

9. The production method of the corrosion-resistant steel bar according to claim 5, characterized in that, In the smelting process, argon is blown from the bottom throughout the tapping process, the argon pressure in the early stage is 0.4 - 0.5 MPa, and the argon pressure in the later stage is 0.3 - 0.4 MPa; in the LF refining process, the soft stirring time ≥ 10 min.

10. The production method of the corrosion-resistant steel bar according to claim 5, characterized in that, In the continuous casting process, the thickness of the mold powder is 8 - 10 mm; the casting speed is controlled at 2.5 - 3.5 m / min; after continuous casting, the heating process of the cast billet is heated in a staged continuous heating manner, and the total time in the furnace is 60 - 100 min, among which the soaking section temperature is 1100 - 1200 °C, and the soaking section time is not less than 1 / 3 of the total time in the furnace.

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