Corrosion-resistant steel bars and production methods thereof

Abstract

The present application provides a corrosion-resistant steel bar and a production method thereof. The corrosion-resistant steel bar comprises the following components, calculated 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, and Ti, with Nb≤0.05%, V≤0.05%, and Ti≤0.05%, with the balance being Fe and unavoidable impurities; wherein the following relationship is also satisfied: 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%.

Description

Technical Field

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

[0002] In actual construction, there are numerous cases of premature failure of reinforced concrete structures due to corrosion, which not only increases maintenance costs but also results in a significant waste of energy and resources. Currently, by adding small amounts of rare earth elements to steel, significant corrosion resistance can be achieved.

[0003] However, since carbon has an adverse effect on the corrosion resistance of steel bars, the carbon content in corrosion-resistant steel bars is often reduced to mitigate this. However, the mechanical properties of steel bars with low carbon content are difficult to guarantee. Therefore, some steel bars are added with large amounts of precious metals such as Cr, Mo, and Ni to increase their strength, significantly increasing their costs.

[0004] Currently, corrosion-resistant steel bars have problems in coordinating and matching mechanical properties, corrosion resistance and economy. Summary of the Invention

[0005] The purpose of this application is to provide a corrosion-resistant steel bar that solves the problem in the prior art of difficulty in coordinating and matching mechanical properties, corrosion resistance and economy.

[0006] In order to achieve one of the above-mentioned objects of the invention, an embodiment of the present application provides a corrosion-resistant steel bar, 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, and Ti, with Nb ≤ 0.05%, V ≤ 0.05%, Ti ≤ 0.05%, and the balance being Fe and unavoidable impurities; wherein the following relations are also satisfied: 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%.

[0007] As a further improvement of one embodiment of the present application, the structure of the steel bar includes pearlite, ferrite and bainite, the volume proportion of ferrite is 40-55%, and the volume proportion of bainite is ≤10%.

[0008] As a further improvement of 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-to-yield ratio is ≥1.35.

[0009] As a further improvement of one 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 over 30 days was measured by weight loss method and was ≤2.0 g·(m 2 h) -1 .

[0010] One embodiment of the present application further provides a method for producing the aforementioned corrosion-resistant steel bar, comprising the steps of smelting, LF refining, continuous casting, heating the ingot, rolling, and cooling in sequence, wherein:

[0011] During the smelting process, when tapping steel, alloys and slag are first added in the order of silicon-manganese alloy, ferrosilicon alloy, and lime, and then ferrochromium alloy, ferroniobium alloy, and vanadium-nitrogen alloy are selectively added according to the target composition;

[0012] In the LF refining process, ferrochrome and ferrosilicon are added to the station, and then ferrotitanium, aluminum particles and aluminum-lanthanum alloy are added selectively and sequentially according to the target composition;

[0013] During the rolling process, the final rolling temperature is controlled at 900-950°C to obtain steel bars;

[0014] During the cooling process, after rolling is completed, the steel bar is cooled to 750~850℃ at a cooling rate of 10~20℃ / s, and then naturally cooled to room temperature on a cooling bed. The cooling rate of the steel bar on the cooling bed is ≤2℃ / s.

[0015] As a further improvement of one embodiment of the present application, the amount of ferrosilicon alloy added in the smelting process is twice that of the ferrosilicon alloy added in the LF refining process, and the amount of ferrochrome alloy added in the smelting process is half that of the ferrochrome alloy added in the LF refining process;

[0016] The addition amount of silicon manganese alloy is 20~30kg / t, the total addition amount of ferrosilicon alloy in the smelting process and LF refining process is 15~20kg / t, the total addition amount of ferrochromium alloy in the smelting process and LF refining process is 10~40kg / t, the addition amount of ferroniobium alloy is 0~2kg / t, and the addition amount of vanadium nitrogen alloy is 0~1.5kg / t;

[0017] The addition amount of titanium-iron alloy is 0~4kg / t, the addition amount of aluminum particles is 1~3kg / t, and the addition amount of aluminum-lanthanum alloy is 0.8~4kg / t.

[0018] As a further improvement to one embodiment of the present application, the silicon-manganese alloy has a silicon content of 17-20%, a manganese content of 65-70%, and the balance is iron and inevitable impurities; the silicon-ferrosilicon alloy has a silicon content of 70-75%, and the balance is iron and inevitable impurities; the ferrochrome alloy uses a low-carbon ferrochrome alloy, wherein the chromium content is 50-60%, the carbon content is ≤0.1%, and the balance is iron and inevitable impurities; the niobium content of the ferroniobium alloy is 60-70%, and the balance is iron and inevitable impurities; the vanadium-nitrogen alloy has a vanadium content of 75-80%, a nitrogen content of 5-10%, and the balance is iron and inevitable impurities;

[0019] The titanium content in titanium-ferroalloy is 35~45%, and the balance is iron and inevitable impurities; the aluminum content in aluminum particles 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.

[0020] As a further improvement of one embodiment of the present application, in the smelting process, the tapping temperature is 1600~1640℃, and in the LF refining process, the tapping temperature is 1540~1560℃.

[0021] As a further improvement of one embodiment of the present application, in the smelting process, argon is blown from the bottom throughout the steel tapping process, with the argon pressure in the early stage being 0.4~0.5MPa and the argon pressure in the later stage being 0.3~0.4MPa; in the LF refining process, the soft stirring time is ≥10min.

[0022] As a further improvement of an embodiment of the present application, in the continuous casting process, the thickness of the protective slag is 8~10mm; the pulling speed is controlled to be 2.5~3.5m / min; after the continuous casting is completed, the heating process adopts a staged continuous temperature increase method to heat the ingot, and the total time in the furnace is 60~100min, of which the soaking section temperature is 1100~1200℃, and the soaking section time is not less than 1 / 3 of the total time in the furnace.

[0023] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0024] The corrosion-resistant steel bars provided in this application fully utilize the multi-element coupling strengthening effect through the associated design of niobium, vanadium, titanium, carbon, and nitrogen, thereby solving the problem of insufficient strength caused by low carbon content and the problem of performance fluctuation caused by fluctuations in nitrogen content, and achieving a coordinated match between 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 guaranteed, and a coordinated match between the strength, plasticity, corrosion resistance, and economy of the steel bars is achieved. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] An embodiment of the present application provides a corrosion-resistant steel bar, 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, and Ti, with Nb≤0.05%, V≤0.05%, and Ti≤0.05%, with the balance being Fe and unavoidable impurities; wherein the following relationship is also satisfied: 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%.

[0027] The corrosion-resistant steel bars provided in this application fully utilize the multi-element coupling strengthening effect through the associated design of niobium, vanadium, titanium, carbon, and nitrogen, thereby solving the problem of insufficient strength caused by low carbon content and the problem of performance fluctuation caused by fluctuations in nitrogen content, and achieving a coordinated match between 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 guaranteed, and a coordinated match between the strength, plasticity, corrosion resistance, and economy of the steel bars is achieved.

[0028] The following is a detailed description of the role and mechanism of each element:

[0029] Carbon (C): A strengthening element. However, if the C content is too high, carbides will easily form, reducing the corrosion resistance of the steel. It is also detrimental to the plasticity, toughness and welding performance of the steel. Taking all factors into consideration, the best effect is achieved when the C content is 0.03~0.09%.

[0030] Silicon (Si): A deoxidizer that can significantly reduce the oxygen content in steel, reduce the formation of oxide inclusions, and facilitate the subsequent addition of rare earth elements. A high Si content is beneficial for the formation of silicate phases on the steel surface, blocking the transmission and aggregation of corrosive media and improving corrosion resistance. Si is also a strengthening element and a ferrite-forming element. A high Si content is beneficial for regulating the structure, solving the problem of steel strength-plasticity coordination through solid solution strengthening and phase transformation structure regulation. However, too high a Si content is not conducive to welding. Taking all factors into consideration, the best effect is achieved when the Si content is 0.85~1.25%.

[0031] Manganese (Mn): A solid solution strengthening element. However, if the Mn content is too high, MnS inclusions will easily form, reducing the plasticity and corrosion resistance of the steel. Taking all factors into consideration, the best effect is achieved when the Mn content is 1.51~1.69%.

[0032] Chromium (Cr): A 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 increasing the strength and hardness of the steel. Cr also retards the decomposition of austenite, improving hardenability and enabling the formation of hard phases such as bainite and martensite at lower cooling rates. However, Cr carbonitrides are detrimental to corrosion resistance. Excessive Cr content increases smelting difficulty, time, and cost, and also affects the steel's plasticity. Taking all factors into consideration, a chromium content of 0.51% to 1.90% achieves optimal results.

[0033] 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%.

[0034] 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%.

[0035] Titanium (Ti): a corrosion-resistant and strengthening element; it can increase the corrosion potential of steel and improve its corrosion resistance; at the same time, it can improve the mechanical properties of steel through grain refinement; however, Ti easily generates oxides, and if its 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 Ti content is ≤0.05%.

[0036] Niobium and vanadium (V, Nb): Strengthening elements that form carbonitrides in steel, improving the mechanical properties of steel through grain refinement and precipitation strengthening. The strengthening effect is related to the C and N content. Taking all factors into consideration, V ≤ 0.05%, Nb ≤ 0.05%.

[0037] Aluminum (Al): Deoxidizer, deoxidizes during the smelting process, reduces the oxygen content in the molten steel, facilitates the addition of rare earth elements, and ensures the recovery rate of rare earth elements; Al can also form oxides in steel, enriched in the rust layer, and 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%.

[0038] Nitrogen (N): forms carbonitrides with niobium and vanadium, which play a role in grain refinement and precipitation strengthening. Nitrogen is beneficial to improving strength and pitting corrosion resistance, but is not conducive to plasticity, and the nitrogen content is not easy to accurately control. Taking all factors into consideration, the best effect is achieved when the N content is ≤0.015%.

[0039] Rare earth lanthanum (La): A rare earth element that mainly plays the role of modifying inclusions, purifying molten steel, and improving corrosion resistance; at the same time, through rare earth microalloying, it can refine grains and improve strength and plasticity; but rare earth elements are easily oxidized, forming large-sized inclusions, which can easily block the water outlet during continuous casting and increase the difficulty of smelting; taking all factors into consideration, the best effect is achieved when the rare earth lanthanum content is 0.01~0.05%.

[0040] Adding sufficient carbon is the most effective way to increase steel strength, but increased carbon content is detrimental to both plasticity and corrosion resistance. To ensure corrosion resistance, this application adopts a low-carbon design and simultaneously introduces strengthening elements such as niobium, vanadium, and titanium. These elements, through strengthening effects such as grain refinement and precipitation, compensate for the reduced strength caused by the decrease in carbon content. Considering the low carbon content, large fluctuations in nitrogen content, differences in the binding abilities of niobium, vanadium, and titanium with carbon and nitrogen, as well as the difficulty and cost of smelting, the optimal strengthening effect is achieved when 0.02% ≤ ([Nb] + [V] + [Ti]) ≤ 0.05% and 0.3 ≤ ([Nb] + [V] + [Ti]) / ([C] + [N]) ≤ 0.8. Furthermore, chromium and niobium can adjust the phase transformation products by influencing phase transformation behavior, thereby adjusting the strength and plasticity of the steel bar through phase transformation strengthening.

[0041] Elements such as chromium, silicon, and aluminum form an oxide film on the surface of steel, which prevents corrosive media from contacting the steel and improves the corrosion resistance of the steel. However, the formation of the surface oxide film has requirements on the amount of elements added. For example, chromium can only form a stable oxide film on the surface of low-carbon steel when its content is greater than 5%. The large-scale addition of alloying elements increases the cost of the alloy and the difficulty of smelting. In this regard, the present invention proposes a design concept of composite addition of alloying elements. Through the coupling effect of chromium, silicon, and aluminum elements in the process of oxide film formation on the surface of steel, the energy required for the formation of the oxide film is reduced, the density and stability of the oxide film are improved, and the corrosion resistance of the steel is guaranteed while reducing the amount of alloying elements added.

[0042] Adding rare earth elements to steel can reduce the sulfur content and the number of inclusions. It can also convert manganese sulfide inclusions into rare earth sulfur oxides, purifying the molten steel and reducing corrosion sources. Rare earth elements can also accumulate within the rust layer, improving its density. However, the recovery rate of rare earth elements is affected by factors such as the method and type of rare earth alloy added. The presence of highly oxidizing elements such as silicon and aluminum in the steel facilitates their recovery. Taking all factors into consideration, the optimal effect is achieved when the [Cr]+[Si]+[La]+[Al] ratio is 1.8% ≤ ≤ 3.0%.

[0043] In one embodiment of the present application, the steel bar structure includes pearlite, ferrite, and bainite, with ferrite accounting for 40-55% by volume and bainite accounting for ≤10% by volume. Pearlite accounts for 40-55% by volume, with interlamellar spacing of 150-200 nm and pearlite cluster size of 8-11 μm. This composite structure of ferrite, pearlite, and bainite significantly improves the corrosion resistance and mechanical properties of the steel bar without the addition of corrosion-resistant alloying elements such as Ni and Mo.

[0044] In one 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-yield ratio is ≥1.35.

[0045] In one 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 over 30 days was measured by weight loss method and was ≤2.0 g·(m 2 h) -1 .

[0046] The present application also provides a method for producing the aforementioned corrosion-resistant steel bar, comprising the following steps: smelting, LF refining, continuous casting, heating the ingot, rolling, and cooling, wherein:

[0047] During the smelting process, when tapping steel, alloys and slag are first added in the order of silicon-manganese alloy, ferrosilicon alloy, and lime, and then ferrochromium alloy, ferroniobium alloy, and vanadium-nitrogen alloy are selectively added according to the target composition;

[0048] In the LF refining process, ferrosilicon and ferrochrome are added to the station, and then ferrotitanium, aluminum particles and aluminum-lanthanum alloy are added selectively and sequentially according to the target composition;

[0049] During the rolling process, the final rolling temperature is controlled at 900-950°C to obtain steel bars;

[0050] During the cooling process, after rolling is completed, the steel bar is cooled to 750~850℃ at a cooling rate of 10~20℃ / s, and then naturally cooled to room temperature on a cooling bed. The cooling rate of the steel bar on the cooling bed is ≤2℃ / s.

[0051] During the smelting process, silicon-manganese alloy and ferrosilicon alloy are first added for deoxidation. Chromium, niobium, vanadium, and nitrogen are then added to the molten steel for alloying according to the target rebar composition. During the LF refining process, ferrosilicon and ferrochromium are first added. The ferrosilicon alloy is then used for further deoxidation to reduce the oxygen content in the molten steel. Finally, an aluminum-lanthanum alloy containing rare earth elements is added. Prior to the addition of the aluminum-lanthanum alloy, titanium-ferroalloy and aluminum particles are also added to achieve a certain degree of deoxidation, preventing oxidation of the rare earth lanthanum and thus ensuring the yield of the rare earth lanthanum.

[0052] The production method of the present application undergoes multiple deoxidation steps during the steelmaking stage (smelting process and LF refining process) to ensure that the oxygen content of the molten steel is low, thereby achieving a higher yield of rare earth lanthanum, reducing the input of aluminum-lanthanum alloy during the steelmaking process, and ensuring low-cost and stable acquisition of lanthanum elements.

[0053] The rolling process controls a relatively high final rolling temperature, and the cooling process cools at a relatively fast cooling rate before being placed on the cooling bed. Under the premise of satisfying the phase transformation thermodynamics, on the one hand, the residence time of the supercooled austenite in the ferrite phase transformation zone during continuous cooling is adjusted, thereby adjusting the grain size and volume proportion of the ferrite; on the other hand, the energy accumulated in the rapid cooling stage will become the driving force for the phase transformation during the subsequent continuous cooling of the supercooled austenite.

[0054] The control of the final rolling temperature, the cooling rate in the cooling process and the upper cooling bed temperature proposed in the present invention can achieve a large degree of supercooling in the rapid cooling stage and accumulate a large amount of energy, so that the supercooled austenite has a strong phase transformation dynamics in the slow cooling stage after the upper cooling bed, promotes the pearlite phase transformation, adjusts the volume proportion of pearlite, the interlamellar spacing and the size of pearlite clusters, and at the same time adjusts the pearlite phase transformation behavior, shortens the pearlite phase transformation range and time, and promotes the steel bar to obtain a small amount of bainite, so that the final structure of the steel bar is a complex phase structure of ferrite, pearlite and bainite, thereby achieving a coordinated match between the strength and plasticity of the steel bar.

[0055] In one embodiment of the present application, the amount of ferrosilicon alloy added in the smelting process is twice that of the ferrosilicon alloy added in the LF refining process, and the amount of ferrochrome alloy added in the smelting process is half that of the ferrochrome alloy added in the LF refining process.

[0056] The addition amount of silicon manganese alloy is 20~30kg / t, the total addition amount of ferrosilicon alloy in the smelting process and LF refining process is 15~20kg / t, the total addition amount of ferrochromium alloy in the smelting process and LF refining process is 10~40kg / t, the addition amount of ferroniobium alloy is 0~2kg / t, and the addition amount of vanadium nitrogen alloy is 0~1.5kg / t.

[0057] The addition amount of titanium-iron alloy is 0~4kg / t, the addition amount of aluminum particles is 1~3kg / t, and the addition amount of aluminum-lanthanum alloy is 0.8~4kg / t.

[0058] Two-thirds of the total amount of ferrosilicon is added during the smelting process to pre-deoxidize the molten steel. The remaining one-third is added at the beginning of the LF refining process for further deoxidation. One-third of the total amount of ferrochrome is added after deoxidation in the smelting process to reduce the amount of alloy added during the LF refining process and avoid excessive addition of alloy, which may cause the molten steel temperature to drop.

[0059] Among them, the addition of silicon-manganese alloy, ferrosilicon alloy, lime and the addition of ferrochromium alloy, ferroniobium alloy and vanadium-nitrogen alloy in the smelting process is limited to 1 / 2 of the steel tapping, that is, silicon-manganese alloy, ferrosilicon alloy and lime are added before the steel tapping reaches 1 / 2, and ferrochromium alloy, ferroniobium alloy and vanadium-nitrogen alloy are added after the steel tapping reaches 1 / 2.

[0060] In the LF refining process, the titanium-iron alloy, aluminum particles and aluminum-lanthanum alloy are added after the LF refining process is halfway through, that is, at a dividing point in time.

[0061] In one embodiment of the present application, the silicon-manganese alloy contains 17-20% silicon, 65-70% manganese, and the remainder is iron and unavoidable impurities.

[0062] The silicon content in ferrosilicon alloy is 70~75%, and the balance is iron and inevitable impurities.

[0063] The ferrochrome alloy adopts a low-carbon ferrochrome alloy, in which the chromium content is 50-60%, the carbon content is ≤0.1%, and the balance is iron and inevitable impurities.

[0064] The niobium content in ferroniobium alloy is 60~70%, and the balance is iron and inevitable impurities.

[0065] The vanadium content in vanadium-nitrogen alloy is 75-80%, the nitrogen content is 5-10%, and the balance is iron and inevitable impurities.

[0066] The titanium content in ferrotitanium alloy is 35~45%, and the balance is iron and inevitable impurities.

[0067] The aluminum content in aluminum particles is ≥95%, and the remainder is iron and inevitable impurities.

[0068] The aluminum content in aluminum-lanthanum alloy is 65~70%, the lanthanum content is 20~25%, and the balance is iron and inevitable impurities.

[0069] In one 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.

[0070] In one embodiment of the present application, in the smelting process, argon is blown from the bottom throughout the steel tapping process, with an argon pressure of 0.4-0.5 MPa in the early stage and 0.3-0.4 MPa in the later stage; in the LF refining process, the soft stirring time is ≥10 min.

[0071] In the smelting process, the total amount of silicon-manganese alloy and ferrosilicon alloy added in the early stage is relatively large, and a higher atmospheric pressure is required for soft stirring. The other alloys added in the later stage are relatively small, and the air pressure is correspondingly reduced to avoid gas waste.

[0072] In one embodiment of the present application, during the continuous casting process, the mold slag thickness is 8-10 mm, and the casting speed is controlled at 2.5-3.5 m / min. After continuous casting, the heating process uses a staged continuous temperature increase method to heat the cast slab. The total furnace time is 60-100 minutes, with the soaking period temperature at 1100-1200°C, and the soaking period lasts for at least one-third of the total furnace time.

[0073] The continuous casting process uses low-carbon steel mold slag to prevent oxidation of active metals in the molten steel. During the heating process, the temperature is gradually raised to 1100-1200°C in the preheating, heating, and soaking stages. The duration of the cast in the soaking stage is maintained at least one-third of the total time in the furnace, ensuring uniform temperature between the surface and the core to avoid temperature differences.

[0074] The technical solution of the present application is further described below with reference to some specific embodiments.

[0075] In the following table, Table 1 shows the chemical compositions and the relationship values of each element of the Examples and Comparative Examples. It should be noted that in Table 1, the column Nb+V+Ti is the sum of the weight percentages of Nb, V, and Ti; the column Cr+Si+La+Al is the sum of the weight percentages of Cr, Si, La, and Al; and the column (Nb+V+Ti) / (C+N) is 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 include %.

[0076] After the smelting process, LF refining process, continuous casting process, heating process, rolling process and cooling process shown in Tables 2 to 5, steel bars with the chemical composition shown in Table 1 were obtained. The structure and properties of the steel bars are shown in Tables 6 and 7.

[0077] Table 1 Chemical composition of examples and comparative examples (%)

[0078]

[0079] Table 2 Production process parameters (smelting process) of the examples and comparative examples

[0080]

[0081] Table 3 Production process parameters of Examples and Comparative Examples (LF refining)

[0082]

[0083] Table 4 Production process parameters of the embodiment and comparative example (continuous casting process)

[0084]

[0085] Table 5 Production process parameters (rolling process and cooling process) of the embodiment and comparative example

[0086]

[0087] Table 6 Organization of Examples and Comparative Examples

[0088]

[0089] Table 7 Performance of Examples and Comparative Examples

[0090]

[0091] The corrosion-resistant steel bars according to the embodiments of the present invention have yield strengths of ≥435 MPa, tensile strengths of ≥598 MPa, elongation after fracture of ≥30%, total elongation at maximum force of ≥20%, and strength-to-yield ratio of ≥1.35. The corrosion rate under harsh service environment after 30 days is ≤2.0 g·(m 2 h) -1 ; The comprehensive performance is significantly better than that of Comparative Examples 1 to 3.

[0092] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0093] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of this application. They are not intended to limit the scope of protection of this application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of this application should be included in the scope of protection of this application.

Claims

1. A corrosion-resistant steel bar, characterized in that: The invention comprises the following components in 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, and Ti, with Nb≤0.05%, V≤0.05%, and Ti≤0.05%, and the balance is Fe and unavoidable impurities; wherein the following relations are satisfied: 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%; The corrosion-resistant steel bar is prepared by the following method: The method comprises the steps of smelting, LF refining, continuous casting, heating of the cast billet, rolling and cooling in sequence, wherein: During the smelting process, when tapping steel, alloys and slag are first added in the order of silicon-manganese alloy, ferrosilicon alloy, and lime, and then ferrochromium alloy, ferroniobium alloy, and vanadium-nitrogen alloy are selectively added according to the target composition; In the LF refining process, ferrochrome and ferrosilicon are added to the station, and then ferrotitanium, aluminum particles and aluminum-lanthanum alloy are added selectively and sequentially according to the target composition; During the rolling process, the final rolling temperature is controlled at 900-950°C to obtain steel bars; During the cooling process, after rolling is completed, the steel bar is cooled to 750~850℃ at a cooling rate of 10~20℃ / s, and then naturally cooled to room temperature on a cooling bed. The cooling rate of the steel bar on the cooling bed is ≤2℃ / s.

2. The corrosion-resistant steel bar according to claim 1, characterized in that: The structure of the steel bar includes pearlite, ferrite and bainite, the volume proportion of ferrite is 40-55%, and the volume proportion of bainite is ≤10%.

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

35.

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

5. A method for producing corrosion-resistant steel bars according to claim 1, characterized in that: It includes the following steps: smelting, LF refining, continuous casting, heating of ingots, rolling and cooling, among which: During the smelting process, when tapping steel, alloys and slag are first added in the order of silicon-manganese alloy, ferrosilicon alloy, and lime, and then ferrochromium alloy, ferroniobium alloy, and vanadium-nitrogen alloy are selectively added according to the target composition; In the LF refining process, ferrochrome and ferrosilicon are added to the station, and then ferrotitanium, aluminum particles and aluminum-lanthanum alloy are added selectively and sequentially according to the target composition; During the rolling process, the final rolling temperature is controlled at 900-950°C to obtain steel bars; During the cooling process, after rolling is completed, the steel bar is cooled to 750~850℃ at a cooling rate of 10~20℃ / s, and then naturally cooled to room temperature on a cooling bed. The cooling rate of the steel bar on the cooling bed is ≤2℃ / s.

6. The method for producing corrosion-resistant steel bars according to claim 5, characterized in that: The amount of ferrosilicon added in the smelting process is twice that of the ferrosilicon added in the LF refining process, and the amount of ferrochrome added in the smelting process is half that of the ferrochrome added in the LF refining process; The addition amount of silicon manganese alloy is 20~30kg / t, the total addition amount of ferrosilicon alloy in the smelting process and LF refining process is 15~20kg / t, the total addition amount of ferrochromium alloy in the smelting process and LF refining process is 10~40kg / t, the addition amount of ferroniobium alloy is 0~2kg / t, and the addition amount of vanadium nitrogen alloy is 0~1.5kg / t; The addition amount of titanium-iron alloy is 0~4kg / t, the addition amount of aluminum particles is 1~3kg / t, and the addition amount of aluminum-lanthanum alloy is 0.8~4kg / t.

7. The method for producing corrosion-resistant steel bars according to claim 6, wherein: The silicon content of silicon-manganese alloy is 17-20%, the manganese content is 65-70%, and the balance is iron and inevitable impurities; the silicon content of ferrosilicon alloy is 70-75%, and the balance is iron and inevitable impurities; the ferrochrome alloy adopts low-carbon ferrochrome alloy, in which the chromium content is 50-60%, the carbon content is ≤0.1%, and the balance is iron and inevitable impurities; the niobium content of ferroniobium alloy is 60-70%, and the balance is iron and inevitable impurities; the vanadium content of vanadium-nitrogen alloy is 75-80%, the nitrogen content is 5-10%, and the balance is iron and inevitable impurities; The titanium content in titanium-ferroalloy is 35~45%, and the balance is iron and inevitable impurities; the aluminum content in aluminum particles 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 method for producing corrosion-resistant steel bars according to claim 5, characterized in that: In the smelting process, the tapping temperature is 1600~1640℃, and in the LF refining process, the tapping temperature is 1540~1560℃.

9. The method for producing corrosion-resistant steel bars according to claim 5, characterized in that: During the smelting process, argon is blown from the bottom throughout the steelmaking process. The argon pressure is 0.4~0.5MPa in the early stage and 0.3~0.4MPa in the later stage. During the LF refining process, the soft stirring time is ≥10min.

10. The method for producing corrosion-resistant steel bars according to claim 5, characterized in that: During the continuous casting process, the thickness of the protective slag is 8~10mm; the pulling speed is controlled at 2.5~3.5m / min; after the continuous casting is completed, the heating process adopts a staged continuous temperature increase method to heat the ingot, and the total time in the furnace is 60~100min, of which the soaking section temperature is 1100~1200℃, and the soaking section time is not less than 1 / 3 of the total time in the furnace.

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