A preparation method for improving castability of plain carbon steel Q235B

Abstract

This application relates to a method for improving the castability of ordinary carbon steel Q235B, comprising: mixing scrap steel with molten iron and performing oxygen blowing smelting to obtain a first molten steel; performing a first deoxidation on the first molten steel to obtain a first deoxidized molten steel; performing preliminary alloying on the first deoxidized molten steel to obtain a second molten steel; adjusting the temperature of the second molten steel to a set temperature; performing a second deoxidation on the second molten steel at the set temperature to obtain a second deoxidized molten steel; performing final alloying on the second deoxidized molten steel to obtain a third molten steel; and purifying and stirring the third molten steel to obtain pure molten steel. By synergistically controlling the amount of ferrosilicon added during steelmaking and refining, and utilizing the difference in residual calcium absorption rate, calcium enrichment is achieved while precisely controlling silicon content. This method can stabilize the calcium content in molten steel without adding calcium-based alloys, promote the transformation of inclusions into liquid inclusions, thereby improving the purity of molten steel and continuous casting castability, ultimately ensuring long-term stable casting by the casting machine.

Description

Technical Field

[0001] This application relates to the field of metal smelting technology, and in particular to a method for preparing Q235B carbon steel with improved castability. Background Technology

[0002] Q235B carbon steel, used as a basic structural steel, is widely applied in construction, machinery, and other fields. The core smelting process for Q235B carbon steel employs converter-killed tapping. The current mainstream method involves coarsely adjusting the composition and adding most of the ferrosilicon during the converter tapping process, followed by fine-tuning the silicon content in the refining process using a small amount of ferrosilicon to control the steel composition to meet standard requirements.

[0003] However, this process has significant technical bottlenecks: the residual calcium in the ferrosilicon added during converter tapping is severely depleted due to high-temperature oxidation, and the amount of ferrosilicon added during refining is insufficient, resulting in the residual calcium content in the molten steel failing to meet the requirements for inclusion modification. To improve this situation, steel mills generally rely on calcium wire feeding after refining for calcium treatment. However, this method has large fluctuations in calcium absorption rate, long treatment cycles, and significant temperature drops. Furthermore, it generates a large amount of smoke and dust during the wire feeding process, which not only increases production costs but also causes environmental pollution and health hazards to operators. Although some steel mills have attempted to eliminate calcium treatment, they still face problems such as abnormal rise of stopper rods and frequent nozzle blockages during casting, forcing them to repeatedly feed calcium wire during production, making it difficult to achieve continuous and stable casting.

[0004] Currently, the industry still relies on calcium feeding lines at the end of the refining stage as the primary means of controlling the castability of Q235B carbon steel. While this traditional process can barely maintain production, it cannot fundamentally solve the problems of low calcium treatment efficiency, poor environmental performance, and insufficient continuous casting stability, thus hindering the quality improvement and green transformation of carbon steel production. Summary of the Invention

[0005] This application provides a method for improving the castability of plain carbon steel Q235B to solve the following technical problem: how to improve the castability of molten steel without eliminating the calcium feeding wire process.

[0006] This application provides a method for improving the castability of plain carbon steel Q235B, including: Scrap steel is mixed with molten iron and smelted with oxygen to obtain the first molten steel; the temperature of the molten iron is ≥1300℃. The first molten steel is deoxidized once to obtain the first deoxidized molten steel; The first deoxidized molten steel is preliminarily alloyed to obtain the second molten steel; Adjust the temperature of the second molten steel to the set temperature; The second molten steel at the set temperature is subjected to secondary deoxidation to obtain second deoxidized molten steel; The second deoxidized molten steel is then subjected to final alloying to obtain the third molten steel; The third type of molten steel is purified and stirred to obtain pure molten steel.

[0007] Optionally, the final temperature of the oxygen blowing smelting is 1610℃~1655℃.

[0008] Optionally, the oxygen content in the first molten steel is 0.02wt% to 0.08wt%.

[0009] Optionally, during the first deoxidation process, fine-grained quicklime and steel shot aluminum are added sequentially to the first molten steel; The amount of fine-grained quicklime added is 1.5 kg / t molten steel to 3.5 kg / t molten steel, and the amount of steel shot aluminum added is 0.8 kg / t molten steel to 1.5 kg / t molten steel.

[0010] Optionally, during the preliminary alloying process, a first alloy and a carbon raiser are sequentially added to the first deoxidized molten steel; the first alloy includes ferromanganese and ferrosilicon.

[0011] Optionally, the amount of ferrosilicon added, Q = 1000 × (target silicon content - silicon content of the endpoint sample) / (silicon yield × silicon content in ferrosilicon) - 2.0; wherein, the unit of the amount of ferrosilicon added, Q, is kg / t molten steel, the units of the target silicon content, the silicon content of the endpoint sample, and the silicon content in the ferrosilicon are wt%, and the unit of the silicon yield is [missing information].

[0012] Optionally, the set temperature is 1590℃~1610℃.

[0013] Optionally, during the secondary deoxidation process, a deoxidizer is added to the second molten steel to make the oxygen content of the second molten steel ≤0.0005wt%.

[0014] Optionally, during the final alloying process, a second alloy and a carbon raiser are added to the second deoxidized steel, followed by the addition of ferrosilicon to the second deoxidized steel, and the ferrosilicon-containing second deoxidized steel is kept at a constant temperature; the second alloy includes ferromanganese.

[0015] Optionally, the purification stirring is at least one of argon blowing stirring or pure steel circulation treatment.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for improving the castability of ordinary carbon steel Q235B, comprising: mixing scrap steel with molten iron and performing oxygen blowing smelting to obtain a first molten steel; performing a first deoxidation on the first molten steel to obtain a first deoxidized molten steel; performing preliminary alloying on the first deoxidized molten steel to obtain a second molten steel; adjusting the temperature of the second molten steel to a set temperature; performing a second deoxidation on the second molten steel at the set temperature to obtain a second deoxidized molten steel; performing final alloying on the second deoxidized molten steel to obtain a third molten steel; and purifying and stirring the third molten steel to obtain pure molten steel.

[0017] By precisely deconstructing and reconstructing the temperature, oxygen potential, and element addition sequence throughout the entire steelmaking process, a controlled pathway was established for the directional survival and efficient dissolution of endogenous calcium in ferrosilicon. The initial high-temperature molten iron (≥1300℃) provides sufficient physical, thermal, and kinetic conditions for the molten pool, ensuring that subsequent oxygen blowing smelting can efficiently remove impurities and lay the thermodynamic foundation for primary deoxidation. Primary deoxidation and preliminary alloying rapidly establish the basic composition of the molten steel and a low oxygen activity during the converter tapping stage. The key role is to utilize the thermodynamic characteristics of the high-temperature molten steel at this stage, allowing some calcium in ferrosilicon to initially remain in a relatively stable form. Subsequently, the process enters the refining stage centered on calcium activation: firstly, an ideal thermodynamic window is preset for subsequent reactions through temperature regulation, followed by secondary deep deoxidation to reduce the oxygen content of the molten steel below the critical value, fundamentally eliminating the risk of calcium oxidation; the final alloying in this inert environment strictly follows the order of other alloys first, then ferrosilicon, ensuring that ferrosilicon, as the final additive, releases residual calcium when the oxygen potential has dropped to a safe threshold, and heating is strictly prohibited after its addition to prevent calcium from evaporating and escaping due to increased vapor pressure; the final purification stirring promotes the uniform diffusion of dissolved calcium, allowing it to fully interact with the aluminum deoxidation products, transforming them into low-melting-point liquid phase inclusions, thereby achieving deep purification of the molten steel while precisely controlling the composition.

[0018] In summary, by transforming ferrosilicon, a conventional alloy material, into a stable and controllable calcium carrier and release source without relying on external calcium wire, the inherent calcium content in molten steel can be autonomously and precisely controlled. This simultaneously overcomes the inherent problems of traditional calcium wire feeding processes in terms of castability stability, production cost, and environmental pollution. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0021] Figure 1 A flowchart illustrating a method for improving the castability of plain carbon steel Q235B, provided in this application embodiment. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0023] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges between 1 and 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship. "And / or" indicates that multiple situations can exist individually or simultaneously. Expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0024] Figure 1 A flowchart illustrating a method for improving the castability of plain carbon steel Q235B, provided in this application embodiment.

[0025] Please see Figure 1 This application provides a method for improving the castability of plain carbon steel Q235B, comprising: S1. Scrap steel is mixed with molten iron and smelted with oxygen to obtain the first molten steel; the temperature of the molten iron is ≥1300℃. S2. Deoxidize the first molten steel once to obtain the first deoxidized molten steel; S3. The first deoxidized molten steel is preliminarily alloyed to obtain the second molten steel; S4. Adjust the temperature of the second molten steel to the set temperature; S5. The second molten steel at the set temperature is subjected to secondary deoxidation to obtain second deoxidized molten steel; S6. The second deoxidized molten steel is then subjected to final alloying to obtain the third molten steel; S7. The third molten steel is purified and stirred to obtain pure molten steel.

[0026] In the aforementioned technical solution, the initial high-temperature molten iron is mixed with scrap steel and blown, efficiently removing impurities while providing sufficient thermodynamic driving force for subsequent reactions. A subsequent deoxidation and preliminary alloying stage rapidly establishes the basic composition of the molten steel in the converter, and utilizes high-temperature, low-oxygen conditions to initially retain calcium in the ferrosilicon. Upon entering the refining stage, the ideal environment for calcium activation is preset through precise temperature adjustment, followed by a second deep deoxidation to reduce the oxygen potential below the critical value, thus completely eliminating the risk of calcium oxidation. The final alloying operation strictly adheres to the process principle of adding other alloys before ferrosilicon and prohibiting heating after the addition of ferrosilicon, ensuring the stable release of its endogenous calcium in the inert molten pool. Final purification and stirring promote the uniform diffusion of dissolved calcium, achieving effective modification of inclusions. The entire process, through the coordinated control of temperature, oxygen potential, and the timing of element addition, reconstructs ferrosilicon into a self-sufficient calcium source carrier under the condition of eliminating the external calcium addition line, thereby simultaneously solving the core issues of improved castability, reduced production costs, and elimination of environmental pollution.

[0027] In some embodiments, the temperature of the molten iron is ≥1300°C.

[0028] A molten iron temperature of ≥1300℃ creates efficient kinetic conditions for subsequent oxygen blowing smelting, ensuring rapid melting of scrap steel and promoting full oxidation of impurity elements. This avoids incomplete molten pool reaction due to low temperatures, reducing the base for inclusion formation from the source. For example, the molten iron temperature can be 1300℃, 1350℃, 1400℃, 1450℃, etc.

[0029] In some embodiments, the final temperature of the oxygen blowing smelting is 1610°C to 1655°C.

[0030] The final temperature of oxygen blowing smelting is between 1610℃ and 1655℃, precisely balancing metallurgical reaction efficiency and energy consumption. The lower limit of the final temperature ensures the complete completion of the carbon-oxygen reaction, while the upper limit prevents excessive burning of alloying elements caused by high temperatures, thus establishing an ideal thermodynamic starting point for subsequent deoxidation. For example, the final temperature of oxygen blowing smelting can be 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, etc.

[0031] In some embodiments, the oxygen content in the first molten steel is 0.02wt% to 0.08wt%.

[0032] The oxygen content in the first molten steel is between 0.02 wt% and 0.08 wt%, establishing a critical oxygen potential window: the lower limit of oxygen content ensures sufficient slag oxidation capacity in the molten steel, promoting the forward progress of dephosphorization and desulfurization reactions; the upper limit of oxygen content prevents excessive free oxygen from being transferred to the refining process, effectively reducing the secondary deoxidation load. For example, the mass fraction of oxygen in the first molten steel can be 0.02%, 0.04%, 0.06%, 0.08%, etc.

[0033] In some embodiments, during the first deoxidation process, fine-grained quicklime and steel shot aluminum are added sequentially to the first molten steel; The amount of fine-grained quicklime added is 1.5 kg / t molten steel to 3.5 kg / t molten steel, and the amount of steel shot aluminum added is 0.8 kg / t molten steel to 1.5 kg / t molten steel.

[0034] Fine-grained quicklime, when added in a specific amount, rapidly creates a high-alkalinity environment in molten steel, efficiently adsorbing deoxidation products and lowering the melting point of the slag system, thus creating a thermodynamic buffer layer for the subsequent survival of calcium elements. Simultaneously, precisely controlled addition of aluminum in the steel shot avoids excessive aluminum leading to a decrease in calcium solubility while achieving deep deoxidation, thereby precisely maintaining the oxygen activity of the molten steel at the critical threshold. For example, the addition amount of fine-grained quicklime can be 1.5 kg / t of molten steel, 2.5 kg / t of molten steel, 3.5 kg / t of molten steel, etc.; the addition amount of aluminum in the steel shot can be 0.8 kg / t of molten steel, 1.0 kg / t of molten steel, 1.2 kg / t of molten steel, 1.4 kg / t of molten steel, etc.

[0035] In some embodiments, during the preliminary alloying process, a first alloy and a carbon raiser are sequentially added to the first deoxidized molten steel; the first alloy includes ferromanganese and ferrosilicon.

[0036] Ferromanganese is added first, utilizing the high diffusion rate of the high-temperature molten pool to rapidly dissolve manganese, simultaneously consuming residual oxygen atoms in the molten steel and creating a low-oxygen potential buffer environment for the subsequent addition of ferrosilicon. Then, a carburizing agent is precisely added before the addition of ferrosilicon, further reducing the oxygen activity in the molten pool through a carbon-oxygen reaction, forming an instantaneous carbon protective atmosphere; this ensures precise carbon content and provides a retention carrier for calcium in the ferrosilicon. Finally, ferrosilicon is added to the deoxygenated molten pool. The residual calcium in the ferrosilicon remains in an inert form in the molten steel under thermodynamic steady state, thus avoiding early oxidation loss of calcium in traditional processes.

[0037] In some embodiments, the amount of ferrosilicon added, Q = 1000 × (target silicon content - silicon content of the endpoint sample) / (silicon yield × silicon content in ferrosilicon) - 2.0; wherein, the unit of the amount of ferrosilicon added, Q, is kg / t molten steel, the units of the target silicon content, the silicon content of the endpoint sample, and the silicon content in the ferrosilicon are wt%, and the unit of the silicon yield is [missing information].

[0038] In some embodiments, the set temperature is 1590°C to 1610°C.

[0039] To adjust the temperature of the second molten steel, the temperature is first detected. If the detected temperature is lower than the set temperature, the temperature is increased; if the detected temperature is higher than the set temperature, scrap steel is added to cool it down. The set temperature is between 1590℃ and 1610℃ to ensure appropriate superheating during the casting process. For example, the set temperature can be 1590℃, 1600℃, 1610℃, etc.

[0040] In some embodiments, during the secondary deoxidation process, a deoxidizer is added to the second molten steel to make the oxygen content of the second molten steel ≤0.0005wt%.

[0041] Adding a deoxidizer to the second molten steel to achieve an oxygen content ≤0.0005wt% is to create an inert molten pool environment with near-zero oxygen activity, thereby completely eliminating the risk of calcium oxidation. For example, the oxygen content of the second molten steel can be 0.0001wt%, 0.0003wt%, 0.0005wt%, etc.

[0042] In some embodiments, during the final alloying process, a second alloy and a carbon raiser are added to the second deoxidized molten steel, followed by the addition of ferrosilicon to the second deoxidized molten steel, and the ferrosilicon-containing second deoxidized molten steel is kept at a constant temperature; the second alloy includes ferromanganese.

[0043] In the final alloying process, other alloys and carbon raisers, except for ferrosilicon, are first added to the second deoxidized molten steel to achieve precise and zero-loss distribution of the main components, effectively avoiding the competitive oxidation interference between silicon and calcium. Then, ferrosilicon is added to allow the residual calcium elements to be fully released and stably dissolved into the molten steel. During this process, the molten steel is kept at a constant temperature to block the risk of calcium vapor pressure rise and secondary oxidation caused by thermal disturbance, and ultimately ensure that calcium atoms are uniformly integrated into the molten steel in a stable state.

[0044] In some embodiments, the purification stirring is at least one of argon blowing stirring or pure steel circulation treatment.

[0045] Purification stirring involves at least one of argon blowing stirring or pure steel circulation treatment. On one hand, it serves to homogenize the composition of the molten steel and fully utilize the modifying effect of residual calcium in ferrosilicon; on the other hand, it promotes the full flotation of inclusions in the molten steel. Through this treatment, residual calcium can effectively modify inclusions, transforming them into liquid inclusions, thereby significantly reducing the total amount of inclusions in the steel and improving the castability of the molten steel during continuous casting.

[0046] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0047] Example 1 Scrap steel and molten iron are mixed and subjected to oxygen blowing smelting to obtain the first molten steel; wherein, the temperature of the molten iron is 1371℃, the final temperature of oxygen blowing smelting is 1653℃, and the oxygen content of the first molten steel is 0.0516wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.7 kg / t of molten steel, and the amount of steel shot aluminum added is 2.39 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 4.34 kg / t of ferromanganese and 0.65 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1597℃; The second molten steel with a temperature of 1597℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.00028wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed, with a carbon raiser added at a rate of 0.35 kg / t of molten steel. Finally, ferrosilicon is added at a rate of 1.99 kg / t of molten steel, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel is purified and stirred, and then treated with pure argon blowing to obtain pure molten steel.

[0048] Example 2 Scrap steel and molten iron are mixed and subjected to oxygen blowing smelting to obtain the first molten steel; wherein, the temperature of the molten iron is 1351℃, the final temperature of oxygen blowing smelting is 1638℃, and the oxygen content of the first molten steel is 0.048wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.7 kg / t of molten steel, and the amount of steel shot aluminum added is 2.31 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 3.64 kg / t of ferromanganese and 0.76 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1597℃; The second molten steel with a temperature of 1597℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.00025wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed with 0.15 kg / t of ferromanganese and 0.06 kg / t of carburizing agent. Finally, 1.85 kg / t of ferrosilicon is added, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel is purified and stirred, and then treated with pure argon blowing to obtain pure molten steel.

[0049] Example 3 Scrap steel and molten iron are mixed and smelted with oxygen to obtain the first molten steel; the temperature of the molten iron is 1379℃, the final temperature of the oxygen blowing smelting is 1635℃, and the oxygen content of the first molten steel is 0.0435wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.7 kg / t of molten steel, and the amount of steel shot aluminum added is 2.4 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 3.33 kg / t of ferromanganese and 0.9 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1605℃; The second molten steel with a temperature of 1605℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.00029wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed with 0.21 kg / t of ferromanganese and 0.15 kg / t of carburizing agent. Finally, 1.88 kg / t of ferrosilicon is added, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel is purified and stirred, and then treated with pure argon blowing to obtain pure molten steel.

[0050] Example 4 Scrap steel and molten iron are mixed and subjected to oxygen blowing smelting to obtain the first molten steel; wherein, the temperature of the molten iron is 1362℃, the final temperature of oxygen blowing smelting is 1654℃, and the oxygen content of the first molten steel is 0.0488wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.7 kg / t of molten steel, and the amount of steel shot aluminum added is 2.34 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 3.34 kg / t of ferromanganese and 0.74 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1600℃; The second molten steel at 1600℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.00027wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed with 0.16 kg / t of ferromanganese and 0.20 kg / t of carburizing agent. Finally, 1.90 kg / t of ferrosilicon is added, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel is purified and stirred, and then treated with pure argon blowing to obtain pure molten steel.

[0051] Example 5 Scrap steel and molten iron are mixed and smelted with oxygen to obtain the first molten steel; the temperature of the molten iron is 1298℃, the final temperature of the oxygen blowing smelting is 1642℃, and the oxygen content of the first molten steel is 0.0309wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.7 kg / t of molten steel, and the amount of steel shot aluminum added is 1.81 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 3.32 kg / t of ferromanganese and 0.42 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1596℃; The second molten steel with a temperature of 1596℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.00026wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed with 0.61 kg / t of ferromanganese and 0.34 kg / t of carburizing agent. Finally, 1.59 kg / t of ferrosilicon is added, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel is purified and stirred, and then treated with pure argon blowing to obtain pure molten steel.

[0052] Comparative Example 1 Scrap steel and molten iron are mixed and subjected to oxygen blowing smelting to obtain the first molten steel; wherein, the temperature of the molten iron is 1372℃, the final temperature of oxygen blowing smelting is 1658℃, and the oxygen content of the first molten steel is 0.0365wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.67 kg / t of molten steel, and the amount of steel shot aluminum added is 1.59 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 4.34 kg / t of ferromanganese, 1.7 kg / t of ferrosilicon, and 0.62 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1604℃; The second molten steel with a temperature of 1604℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.0003wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed, with a carbon raiser added at a rate of 0.5 kg / t of molten steel. Finally, ferrosilicon is added at a rate of 0.28 kg / t of molten steel, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel was fed into the calcium wire at a rate of 0.29 kg / t and argon gas was weakly blown in for 10 minutes to obtain pure molten steel.

[0053] Comparative Example 2 Scrap steel and molten iron are mixed and subjected to oxygen blowing smelting to obtain the first molten steel; wherein, the temperature of the molten iron is 1324℃, the final temperature of oxygen blowing smelting is 1651℃, and the oxygen content of the first molten steel is 0.0308wt%. The first molten steel is deoxidized once. During the first deoxidation process, the amount of small-particle quicklime added is 2.67 kg / t of molten steel, and the amount of steel shot aluminum added is 1.59 kg / t of molten steel, to obtain the first deoxidized molten steel. The first deoxidized molten steel was initially alloyed. During the initial alloying process, 3.99 kg / t of ferromanganese, 1.44 kg / t of ferrosilicon, and 0.75 kg / t of carburizing agent were added to obtain the second molten steel. Adjust the temperature of the second molten steel to 1599℃; The second molten steel with a temperature of 1599℃ is subjected to secondary deoxidation. During the secondary deoxidation process, a deoxidizing agent is added to the second molten steel to make the oxygen content of the second molten steel 0.0003wt%, thus obtaining the second deoxidized molten steel. The second deoxidized molten steel is then alloyed with 0.33 kg / t of ferromanganese and 0.36 kg / t of carburizing agent. Finally, 0.44 kg / t of ferrosilicon is added, and the second deoxidized molten steel containing ferrosilicon is kept at a constant temperature to obtain the third molten steel. The third type of molten steel was fed into the calcium wire at a rate of 0.31 kg / t and argon gas was weakly blown in for 10 minutes to obtain pure molten steel.

[0054] Effect data: The effect data of Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 1.

[0055] Table 1

[0056] The above effect data table provides a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: As shown in Examples 1-5 and Comparative Examples 1-2, Examples 1-5, relying entirely on optimized ferrosilicon addition strategies to regulate endogenous calcium, consistently achieved a continuous casting capacity of over 10 heats, with the cost per ton of steel controlled at 481 yuan or less. While Comparative Examples 1-2 also achieved continuous casting capacities of 10 or 13 heats using traditional calcium-feeding wire processes, the cost per ton of steel significantly increased to over 486 yuan. This demonstrates that the embodiments of this application, while successfully eliminating the calcium-feeding wire operation and its associated environmental pollution and operational burden, not only maintained the excellent castability of molten steel but also significantly reduced production costs, resulting in outstanding overall technical and economic benefits.

[0057] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: This invention provides a method for improving the castability of Q235B carbon steel. By completely replacing the traditional calcium feeding line operation with a ferrosilicon calcium enrichment process, it significantly shortens the refining cycle and lowers the tapping temperature while eliminating the calcium treatment step. Empirical calculations show that this process can reduce the cost per ton of steel by 10 yuan. Based on a monthly production scale of 40 heats of Q235B carbon steel, the annualized economic benefit reaches 1.44 million yuan. Furthermore, this process fundamentally eliminates the smoke and dust pollution generated by the calcium feeding line, greatly reducing the labor intensity of operators and the pressure on on-site environmental management, achieving a dual improvement in economic benefits and environmental friendliness.

[0058] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for preparing Q235B plain carbon steel with improved castability, characterized in that, The method includes: Scrap steel is mixed with molten iron and smelted with oxygen to obtain the first molten steel; the temperature of the molten iron is ≥1300℃. The first molten steel is deoxidized once to obtain the first deoxidized molten steel; The first deoxidized molten steel is preliminarily alloyed to obtain the second molten steel; Adjust the temperature of the second molten steel to the set temperature; The second molten steel at the set temperature is subjected to secondary deoxidation to obtain second deoxidized molten steel; The second deoxidized molten steel is then subjected to final alloying to obtain the third molten steel; The third type of molten steel is purified and stirred to obtain pure molten steel.

2. The method according to claim 1, characterized in that, The final temperature of the oxygen blowing smelting is 1610℃~1655℃.

3. The method according to claim 1, characterized in that, The oxygen content in the first molten steel is 0.02wt%~0.08wt%.

4. The method according to claim 1, characterized in that, During the first deoxidation process, fine-grained quicklime and steel shot aluminum are added sequentially to the first molten steel; The amount of fine-grained quicklime added is 1.5 kg / t molten steel to 3.5 kg / t molten steel, and the amount of steel shot aluminum added is 0.8 kg / t molten steel to 1.5 kg / t molten steel.

5. The method according to claim 1, characterized in that, In the preliminary alloying process, a first alloy and a carbon raiser are added sequentially to the first deoxidized steel; the first alloy includes ferromanganese and ferrosilicon.

6. The method according to claim 5, characterized in that, The amount of ferrosilicon added, Q, is calculated as follows: Q = 1000 × (target silicon content - silicon content of the endpoint sample) / (silicon yield × silicon content in ferrosilicon) - 2.0; where Q is in kg / t molten steel, the target silicon content, the silicon content of the endpoint sample, and the silicon content in the ferrosilicon are in wt%, and the silicon yield is in [missing information].

7. The method according to claim 1, characterized in that, The set temperature is 1590℃~1610℃.

8. The method according to claim 1, characterized in that, During the secondary deoxidation process, a deoxidizer is added to the second molten steel to make the oxygen content of the second molten steel ≤0.0005wt%.

9. The method according to claim 1, characterized in that, In the final alloying process, a second alloy and a carbon raiser are added to the second deoxidized steel, followed by the addition of ferrosilicon to the second deoxidized steel, and the ferrosilicon-containing second deoxidized steel is kept at a constant temperature; the second alloy includes ferromanganese.

10. The method according to claim 1, characterized in that, The purification stirring is at least one of argon blowing stirring or pure steel circulation treatment.

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