Control method for stabilizing carbon content of medium-carbon series steel finished product

Abstract

The invention discloses a control method for stabilizing the carbon content of a medium-carbon series steel finished product. The method comprises the following steps: smelting medium-carbon steel in a converter; before converter tapping, a first carburant is added into a steel ladle through a refining blanking system; a second carburant is added into the steel flow in the tapping process, and deoxidation alloying operation is synchronously carried out; in the tapping process, the flow of argon blown from the bottom of the steel ladle is controlled by stages: strong stirring is carried out by adopting a first flow range in the initial tapping stage, and weak stirring is carried out by adopting a second flow range in the later tapping stage; after steel tapping is completed, argon bottom blowing of the steel ladle is adjusted to a third flow range, and first soft blowing treatment is carried out; component fine adjustment is conducted on the molten steel at the refining station, and the components of the molten steel are adjusted to the target range before refining is finished; and before the molten steel leaves the station, argon bottom blowing of the steel ladle is controlled to be in a fourth flow range, second soft blowing treatment is carried out, the duration time of the second soft blowing treatment is longer than that of the first soft blowing treatment, and then the molten steel is hoisted to the continuous casting procedure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgy, and particularly relates to a method for controlling carbon content of finished product of medium-carbon series steel. BACKGROUND

[0002] Medium-carbon steel (such as 45# steel) is widely used in manufacturing important structural parts such as mechanical parts, shafts and gears due to its good comprehensive mechanical properties. The stability and uniformity of carbon content of finished product are key indicators determining the final performance. Fluctuation of carbon content and serious center segregation can lead to uneven hardness of product, decline of mechanical properties, and even early failure, so the control of carbon content in the steelmaking process has very high requirements.

[0003] Firstly, in the process of adding carbon additive, the current common method is to manually add all the carbon additive at once during the tapping process of the converter. The carbon additive used is usually packaged in small bags of 20 kg, and the operator needs to manually put all the carbon additive into the steel stream at the time of tapping. This operation method not only has high labor intensity, but also the accuracy and timeliness of manual addition are difficult to guarantee in the fast-paced tapping process, which increases the instability and safety risk of production.

[0004] Secondly, since the specific gravity of the carbon additive is much smaller than that of the molten steel, there is a significant hysteresis effect in melting and dissolving. The addition of all the carbon additive at the end of tapping results in insufficient melting and diffusion time of the carbon additive in the molten steel. In addition, the yield of the carbon additive fluctuates greatly under different process conditions (such as tapping temperature and steel flow impact) of different heats, which directly causes the instability of the carbon content control of the molten steel from the end of the converter to the beginning of the refining, low hit rate of the carbon content of the finished product, and difficulty in achieving precise control.

[0005] The existing process often fails to provide sufficient and effective stirring to promote the uniform distribution of carbon elements. After the one-time addition of the carbon additive, the soft blowing stirring time of the refining process is often compressed to ensure the production rhythm. Insufficient stirring leads to uneven distribution of carbon elements in the molten steel, and this unevenness is further amplified during the solidification process of the molten steel, ultimately causing serious carbon segregation in the billet and subsequent rolled material, which seriously affects the uniformity of the structure and the consistency of the performance of the product. SUMMARY

[0006] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a method for controlling carbon content of finished product of medium-carbon series steel to solve the problems raised in the background art.

[0007] The technical scheme adopted by the present application to solve its technical problems is as follows: a method for controlling carbon content of finished product of medium-carbon series steel, comprising the following steps:

[0008] S1, smelting medium carbon steel in a converter, controlling the carbon content of the molten steel at the end point not higher than 0.15wt%, and the tapping temperature not lower than 1570℃;

[0009] S2, before tapping in the converter, adding a first carbon additive into the ladle through a refining downfeed system; performing tapping operation in the converter, adding a second carbon additive into the steel stream during the tapping process, and simultaneously performing deoxidization and alloying operation;

[0010] S3, during the tapping process, controlling the argon flow rate of the ladle bottom blowing in stages: using a first flow rate range for strong stirring in the early stage of tapping, and using a second flow rate range for weak stirring in the later stage of tapping, wherein the first flow rate range is greater than the second flow rate range;

[0011] S4, after the tapping is completed, adjusting the argon flow rate of the ladle bottom blowing to a third flow rate range and performing first soft blowing treatment, and then hoisting the molten steel to a refining station;

[0012] S5, performing composition fine adjustment on the molten steel at the refining station, and adjusting the composition of the molten steel to the target range before the end of refining;

[0013] S6, before the molten steel leaves the station, controlling the argon flow rate of the ladle bottom blowing to a fourth flow rate range and performing second soft blowing treatment, the duration of the second soft blowing treatment is longer than that of the first soft blowing treatment, and then hoisting the molten steel to a continuous casting process.

[0014] As a further improvement of the present application: in the step S1, comprising:

[0015] Smelting medium carbon series steel in a converter, controlling the carbon content of the molten steel at the end point ≤0.15wt%, the phosphorus content ≤0.03wt%, the sulfur content ≤0.03wt%, and the tapping temperature ≥1570℃;

[0016] The medium carbon series steel includes 45# steel, and the target finished product chemical composition of the 45# steel is: carbon: 0.42-0.46%, silicon: ≤0.37%, manganese: ≤0.65%, phosphorus: ≤0.03%, sulfur: ≤0.03%, and the rest is Fe and impurities.

[0017] As a further improvement of the present application: in the step S2, comprising: before tapping in the converter, transporting the ladle to a refining station, and adding a first predetermined amount of bulk carbon additive to the bottom of the ladle through a refining downfeed system;

[0018] Performing tapping operation in the converter, manually adding a second predetermined amount of bagged carbon additive into the steel stream during the tapping process, and simultaneously performing deoxidization and alloying operation;

[0019] The chemical composition of the carbon additive used needs to meet: carbon content ≥94%, phosphorus content ≤0.05%, and sulfur content ≤0.45% by weight percentage.

[0020] As a further improvement of the present application: in the step S3, it comprises: during the tapping process, the argon flow rate of the ladle bottom is controlled in stages: within the first 2 minutes from the beginning of the steel flow impacting the ladle, a first high flow rate is used for strong stirring, the first high flow rate is 240-260 m3 / h; after 2 minutes until the end of tapping, a first low flow rate is used for weak stirring, the first low flow rate is 80-100 m 3 / h.

[0021] As a further improvement of the present application: in the step S4, it comprises: after the completion of tapping, the argon flow rate of the ladle bottom is adjusted to a second low flow rate and a first soft blowing operation is performed, the second low flow rate is 45-55 m3 / h, the duration of the first soft blowing operation is 1.5-2.5 minutes, and then the molten steel is lifted to the LF refining station.

[0022] As a further improvement of the present application: in the step S6, it comprises: before the molten steel leaves the station, the argon flow rate of the ladle bottom is controlled to the second low flow rate and a second soft blowing operation is performed, the duration of the second soft blowing operation is not less than 10 minutes.

[0023] As a further improvement of the present application: in the step S2, it further comprises:

[0024] The first predetermined amount is 280-320 kg of bulk carbon additive, and the first predetermined amount of bulk carbon additive is pre-added to the bottom of the ladle before tapping and is primarily melted and dispersed by the steel flow during tapping;

[0025] The second predetermined amount is 50-150 kg of bagged carbon additive, and the second predetermined amount of bagged carbon additive is adjusted and added during the tapping process according to the final carbon content of the converter and the target finished product carbon content to control the carbon content of the molten steel entering the refining process.

[0026] As a further improvement of the present application: in the step of controlling the argon flow rate in stages, the first high flow rate used in the strong stirring stage is 250 m3 / h, and the first low flow rate used in the weak stirring stage is 90 m 3 / h.

[0027] As a further improvement of the present application: in the step S4, it further comprises: in the first soft blowing operation after the completion of tapping, the argon flow rate of the ladle bottom is 50 m3 / h, and the soft blowing duration is 2 minutes, so that the molten steel is primarily uniform before entering the LF refining station.

[0028] As a further improvement of the present application: in the step S6, it further comprises: in the second soft blowing operation after the end of the LF refining, the argon flow rate of the ladle bottom is 50 m3 / h, and the soft blowing duration is at least 10 minutes.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] The method for controlling the carbon content of the finished product of the stable medium-carbon series steel according to the present application is beneficial to eliminating the carbon segregation of the finished product, promoting the performance stability of the billet and the rolled product, reducing the amount of the carbon additive added during the tapping process of the converter on the one hand, and reducing the labor intensity of the post operation, and on the other hand, by adding the carbon additive in advance of the ladle operation, fully utilizing the molten steel stirring during the tapping of the converter, promoting the rapid melting of the carbon additive into the molten steel, and by increasing the soft blowing time, realizing the accurate control of the carbon content of the process and the end point, and reducing the carbon element distribution segregation. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a schematic diagram of the method according to the present application. DETAILED DESCRIPTION

[0032] In order to clearly and completely understand the technical solutions, the present application will be further described in combination with the embodiments and the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, and all other embodiments obtained by a person skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or collections thereof.

[0034] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clearly indicated by the context, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0035] It should be further understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0036] The embodiments of the present application provide a method for controlling the carbon content of a finished product of a stable medium-carbon series steel, comprising the following steps:

[0037] S1, smelting the medium-carbon steel in a converter, controlling the carbon content of the molten steel at the end point to be not higher than 0.15wt%, and the tapping temperature to be not lower than 1570℃;

[0038] S2, before the converter tapping, a first carbon additive is added into the ladle through a refining down system; a converter tapping operation is performed, a second carbon additive is added into the steel stream during the tapping process, and a deoxidation and alloying operation is simultaneously performed;

[0039] S3, during the tapping process, the argon flow rate of the ladle bottom blowing is controlled in stages: a first flow rate range is used for strong stirring in the early stage of tapping, and a second flow rate range is used for weak stirring in the late stage of tapping, wherein the first flow rate range is greater than the second flow rate range;

[0040] S4, after the tapping is completed, the argon flow rate of the ladle bottom blowing is adjusted to a third flow rate range and a first soft blowing treatment is performed, and then the molten steel is lifted to a refining station;

[0041] S5, the composition of the molten steel is finely adjusted at the refining station, and the composition of the molten steel is adjusted to the target range before the refining is completed;

[0042] S6, before the molten steel leaves the station, the argon flow rate of the ladle bottom blowing is controlled to a fourth flow rate range and a second soft blowing treatment is performed, the duration of the second soft blowing treatment is longer than that of the first soft blowing treatment, and then the molten steel is lifted to a continuous casting process.

[0043] According to the stable medium carbon series steel product carbon content control method, the carbon content of the end-point molten steel in the converter smelting stage is controlled to be ≤0.15wt%, a reasonable adjustment space is reserved for carbon addition, and the problem that the carbon additive cannot be accurately supplemented due to too high end-point carbon is avoided. The first carbon additive is added into the ladle before tapping to realize coarse adjustment of the carbon content, the second carbon additive is added during the tapping process to realize secondary fine adjustment, and the composition is finally corrected at the refining station to ensure that the carbon content of the molten steel gradually approaches the target range. The first carbon additive is added into the ladle before tapping, and the impact stirring of the steel stream during the converter tapping can be used to melt into the molten steel in advance, thereby avoiding the problem of melting lag caused by the concentrated addition of the carbon additive. In addition, the argon gas is blown in stages, and strong stirring can promote the rapid dispersion of the carbon additive. The first soft blowing treatment can further ensure that the carbon additive is completely melted, reduce the yield fluctuation caused by the unmelted carbon additive, and finally greatly reduce the fluctuation range of the product carbon content. The first flow rate is used for strong stirring in the early stage of tapping, which can quickly disperse the first carbon additive and the second carbon additive in the steel stream, thereby avoiding local carbon enrichment. The second flow rate is used for weak stirring in the late stage of tapping, which can not only maintain the stirring effect to ensure the uniformity of the carbon element, but also avoid the splashing of the molten steel and the local composition unevenness caused by high flow rate. The first soft blowing treatment can eliminate the carbon element distribution difference caused by the impact of the steel stream during the tapping process, and ensure that the carbon distribution of the molten steel entering the refining station is preliminarily uniform. The second soft blowing treatment has a longer duration than the first soft blowing, and the micro composition gradient of the molten steel after refining is further eliminated through gentle stirring, thereby avoiding the segregation caused by uneven diffusion of the carbon element during the continuous casting solidification process of the molten steel.

[0044] In an embodiment of the present application, the step S1 comprises:

[0045] The converter smelts the medium carbon series steel, controls the carbon content of the terminal molten steel to be ≤0.15wt%, the phosphorus content to be ≤0.03wt%, the sulfur content to be ≤0.03wt%, and the tapping temperature to be ≥1570℃;

[0046] The medium carbon series steel includes 45# steel, and the target finished product chemical composition of the 45# steel is as follows in terms of percentage by weight: carbon: 0.42-0.46%, silicon: ≤0.37%, manganese: ≤0.65%, phosphorus: ≤0.03%, sulfur: ≤0.03%, and the rest is Fe and impurities.

[0047] In one embodiment of the present application, the step S2 comprises: before the converter tapping, transporting the ladle to a refining station, and adding a first predetermined amount of bulk carbon additive to the bottom of the ladle through a refining downcomer system;

[0048] The converter tapping operation is performed, and in the tapping process, a second predetermined amount of bagged carbon additive is manually added to the steel stream, and a deoxidation alloying operation is simultaneously performed;

[0049] The chemical composition of the carbon additive used needs to meet the following requirements in terms of percentage by weight: carbon content ≥94%, phosphorus content ≤0.05%, and sulfur content ≤0.45%.

[0050] Further, the step S2 further comprises: the first predetermined amount is 280-320kg of bulk carbon additive, the first predetermined amount of bulk carbon additive is pre-added to the bottom of the ladle before tapping, and is preliminarily melted and dispersed by the steel stream during tapping; and the second predetermined amount is 50-150kg of bagged carbon additive, the second predetermined amount of bagged carbon additive is adjusted and added during the tapping process according to the carbon content of the converter terminal and the target finished product carbon content to control the carbon content of the molten steel entering the refining process.

[0051] In the prior art, the production of medium carbon series steel needs to manually add all the carbon additive during the tapping process, and the single furnace usage is 350-450kg, which not only consumes a lot of physical strength, but also needs to be continuously operated beside the high-temperature steel stream, and there is a risk of scalding. In the present embodiment, the carbon additive is divided into bulk addition before tapping and bagged addition during tapping: the first predetermined amount of 280-320kg of bulk carbon additive is automatically added to the bottom of the ladle through the refining downcomer system, without manual intervention; only the second predetermined amount of 50-150kg of bagged carbon additive needs to be manually added, which greatly reduces the labor intensity of the post, shortens the operation time of the operator in the high-temperature area, and improves the operation safety. On the other hand, the bulk carbon additive is added to the bottom of the ladle before tapping, and the high-temperature steel stream impacts the bottom of the ladle when the converter is tapped, which can quickly melt and preliminarily disperse the bulk carbon additive, reducing the fluctuation of the carbon content of the molten steel after tapping.

[0052] In one embodiment of the present application, the step S3 comprises: controlling the argon flow rate in the ladle bottom blowing in stages during the tapping process: within the first 2 minutes from the start of the steel flow impacting the ladle, a first high flow rate is used for strong stirring, the first high flow rate being 240-260 m3 / h; after 2 minutes until the end of the tapping, a first low flow rate is used for weak stirring, the first low flow rate being 80-100 m 3 / h.

[0053] Further, in the step of controlling the argon flow rate in the ladle bottom blowing in stages, the first high flow rate used in the strong stirring stage is 250 m3 / h, and the first low flow rate used in the weak stirring stage is 90 m 3 / h.

[0054] Before tapping, 280-320 kg of bulk carbon additive has been added to the bottom of the ladle, and at the initial stage of tapping, the bulk carbon additive is prone to form local accumulation when the high-temperature steel flow impacts the bottom of the ladle; the high flow rate of 240-260 m3 / h of argon can generate a strong stirring flow field, rapidly break the accumulated carbon additive particles, increase the contact area between the carbon additive and the molten steel, and combine the kinetic energy and thermal energy of the steel flow impact to increase the melting speed of the carbon additive; the 50-150 kg of bagged carbon additive manually added during the tapping process will enter the ladle with the steel flow, and the high flow rate of the strong stirring can simultaneously disperse the bagged carbon additive into the molten steel, avoiding the formation of a local high-carbon area at the impact point of the steel flow.

[0055] In one embodiment of the present application, the step S4 comprises: after the completion of the tapping, adjusting the argon flow rate in the ladle bottom blowing to a second low flow rate and performing a first soft blowing operation, the second low flow rate being 45-55 m3 / h, and the duration of the first soft blowing operation being 1.5-2.5 minutes, and then hoisting the molten steel to the LF refining station.

[0056] Further, in the step S4, the argon flow rate in the first soft blowing operation after the completion of the tapping is 50 m3 / h, and the soft blowing duration is 2 minutes, so as to preliminarily homogenize the molten steel before entering the LF refining station.

[0057] During the tapping process, although the step S3 is used for the stirring in the ladle bottom blowing in stages, the steel flow impact and the batched addition of the carbon additive can still cause local composition gradients in the molten steel, and the low flow rate of 45-55 m3 / h of argon can form a mild convection of the molten steel, which can drive the slow circulation of the molten steel, diffuse the locally enriched carbon elements and alloy elements to the whole molten steel, and will not cause the molten steel to roll and suck in air due to the over-strong stirring; the high flow rate of the stirring can accelerate the heat exchange between the molten steel and the air, causing the temperature to rapidly decrease, and the low flow rate can greatly reduce the heat loss rate, so as to ensure that the temperature of the molten steel still meets the refining requirements when hoisted to the LF refining station.

[0058] In one embodiment of the present application, the step S6 comprises: before the molten steel leaves the ladle, the argon flow rate of the bottom blowing is controlled to the second low flow rate and a second soft blowing operation is performed, and the duration of the second soft blowing operation is not less than 10 minutes.

[0059] Further, the step S6 further comprises: in the second soft blowing operation after the LF refining is completed, the argon flow rate of the bottom blowing is 50 m3 / h, and the soft blowing duration is at least 10 minutes.

[0060] Although the LF refining stage completes the fine adjustment of the composition of the molten steel, there may still be microscopic composition differences in the process of alloy addition and temperature adjustment. The low flow rate of 50 m3 / h of argon can drive the slow circulation of the molten steel, which can diffuse the micro-enriched carbon elements and alloy elements to the whole molten steel, and also will not cause the molten steel to roll and suck in air due to excessive stirring, thereby ensuring the purity of the molten steel. The long-time soft blowing of 10 minutes can make the carbon content of the molten steel uniform through sustained and gentle stirring.

[0061] Case 1:

[0062] In this embodiment, the medium-carbon series steel produced is mainly 45# steel, which has the following chemical composition by weight percentage: C: 0.42-0.46wt%; Si: ≤0.37wt%; Mn: ≤0.65wt%; P ≤0.03wt%; S ≤0.03wt%, and the rest is Fe and unavoidable impurities.

[0063] The steelmaking process thereof is: converter smelting → deoxidation and alloying → LF refining → continuous casting.

[0064] The carbon additive used has the following chemical composition requirements by weight percentage: C: ≥94wt%; P ≤0.05wt%; S ≤0.45wt%, and there are two packaging methods, one is bulk ton bag packaging, and the other is 20kg / bag ton bag packaging. The bulk carbon additive is added to the ladle by the refining downflow system before tapping, and the 20kg / bag carbon additive is manually added to the molten steel during the tapping process.

[0065] The chemical composition of the molten steel at the end of the converter smelting has the following chemical composition by weight percentage: C: ≤0.15wt%; P ≤0.03wt%; S ≤0.03wt%, and the molten steel at the end of smelting is ≥1570℃.

[0066] The addition of the carbon additive mainly includes two parts: before tapping, 300kg of bulk carbon powder is first added to the ladle by the refining downflow system, and 50-150kg of bagged carbon powder is manually added to the molten steel during the tapping process.

[0067] The carbon increaser is added into the ladle in two steps, i.e. 300 kg is added into the ladle through the refining discharging system before the converter tapping, and 50-150 kg is added into the ladle manually during the tapping process, so as to reduce the labor intensity of the converter tapping operation and facilitate the full melting of the carbon increaser in the molten steel.

[0068] The argon flow rate of the ladle bottom blowing is controlled in stages during the tapping process, i.e. the argon flow rate is 250 m3 / h in the first 2 minutes, and the argon flow rate is 90 m3 / h after the tapping for 2 minutes.

[0069] The stirring intensity of the ladle bottom blowing is controlled in stages during the tapping process, i.e. the argon flow rate of the ladle bottom blowing is 250 m3 / h in the first 2 minutes, and the argon flow rate of the ladle bottom blowing is 90 m3 / h after the tapping for 2 minutes, so as to facilitate the full melting and uniform distribution of the carbon increaser.

[0070] After the tapping is completed, the molten steel is softly blown for 2 minutes under the condition of the argon flow rate of 50 m3 / h, and then the LF refining operation is performed. After the tapping is completed, the molten steel is softly blown for 2 minutes under the condition of the argon flow rate of 50 m3 / h, and then the LF refining operation is performed, so as to ensure that the sampling result of the molten steel entering the LF refining is more representative.

[0071] Before the LF refining is completed, the composition and temperature of the molten steel are adjusted, and before the molten steel leaves the station, the molten steel is softly blown for not less than 10 minutes under the condition of the argon flow rate of 50 m3 / h, and then the molten steel is lifted to the continuous casting process. Before the LF refining is completed, the composition and temperature of the molten steel are adjusted, and before the molten steel leaves the station, the molten steel is softly blown for not less than 10 minutes under the condition of the argon flow rate of 50 m3 / h, and then the molten steel is lifted to the continuous casting process, so as to fully and uniformly adjust the composition and temperature of the molten steel through the soft blowing and reduce the composition segregation.

[0072] Example Two:

[0073] Control of the production of medium carbon steel 45#:

[0074] The chemical composition standard of the medium carbon steel 45# in terms of weight percentage is as follows: C: 0.42-0.46 wt%; Si: ≤0.37 wt%; Mn: ≤0.65 wt%; P ≤0.03 wt%; S ≤0.03 wt%, and the rest is Fe and unavoidable impurities.

[0075] The nominal capacity of the converter is 120 tons, and the expected yield of the molten steel per furnace is 120 tons. During the smelting of the molten steel, 105 tons of hot metal is added, and the composition of the hot metal is as follows: C: 4.28%; Si: 0.32%; Mn: 0.28%; P: 0.148%; S: 0.023%, and the temperature of the hot metal is 1299℃. 24 tons of scrap steel is added.

[0076] The high-ladle-blowing-reducing-blowing process is adopted for the converter smelting, and the composition of the molten steel at the end of the smelting is as follows: C: 0.10%; Mn: 0.15%; P: 0.021%; S: 0.018%, and the temperature of the molten steel at the end of the smelting is 1575℃.

[0077] Converter tapping, the steel ladle tank truck into the refining station, by refining down the system to the ladle to add bulk carbon 300 kg, then the steel ladle tank truck to the tapping position.

[0078] Converter tapping, shaking furnace to 70 ° ladle began to bottom blowing, the first 2 minutes flow 250 m3 / h, tapping 2 minutes to complete, the flow 90 m3 / h.25108736

[0079] Tapping 1 / 4 start deoxidation alloying operation, adding deoxidizer and prepared in advance of ferrosilicon and silicon manganese alloy, tapping process adding carbon 120 kg, tapping complete adjustment ladle bottom blowing flow to 50 m3 / h soft blowing 2 minutes before lifting to the refining process.

[0080] The molten steel into the LF refining sampling composition: C: 0.382%; Si: 0.25wt%; Mn: 0.57wt%; P: 0.018wt%; S: 0.017wt%, the rest is Fe and inevitable impurities.

[0081] LF refining by electrode power to the molten steel to the appropriate temperature to meet the continuous casting, by adding 80 kg of carbon steel composition of the fine-tuning, LF refining sampling composition: C: 0.445%; Si: 0.25wt%; Mn: 0.58wt%; P: 0.018wt%; S: 0.005wt%, the rest is Fe and inevitable impurities, after refining sampling molten steel in the 50 m3 / h bottom blowing argon flow conditions soft blowing 10 minutes after lifting to continuous casting.

[0082] Continuous casting for 5 machine 5 flow R9m arc 155 mm x 155 mm small billet caster, continuous casting sampling composition: C: 0.448%; Si: 0.24wt%; Mn: 0.57wt%; P: 0.019wt%; S: 0.005wt%. 1-5 flow billet composition segregation sample, 1 / 4 billet and core billet sampling, composition segregation is within 3%, segregation data as follows:

[0083] Table 1 carbon steel 45# steel segregation data

[0084] Furnace number Side 1 Side 2 Center Side 3 Side 4 Average Segregation ratio 25207841-1 0.44 0.45 0.45 0.45 0.46 0.45 100.00％ 25207841-2 0.45 0.45 0.45 0.45 0.45 0.45 100.00％ 25207841-3 0.46 0.46 0.45 0.45 0.46 0.46 101.33％ 25207841-4 0.45 0.45 0.44 0.45 0.45 0.45 101.82％ 25207841-5 0.45 0.46 0.44 0.45 0.45 0.45 102.27％

[0085] In summary, the ordinary skill in the art after reading the present invention document, according to the technical scheme and technical concept of the present invention without creative mental effort to make other various corresponding transformation scheme, all belong to the scope of the present invention.

Claims

1. A method of controlling the carbon content of a finished product of a medium carbon series steel, characterized by, The method comprises the following steps: S1, smelting medium carbon steel in a converter, controlling the carbon content of the molten steel at the end point to be not higher than 0.15wt%, and the tapping temperature to be not lower than 1570℃; S2, before tapping in the converter, adding a first carbon additive into the ladle through a refining downfeed system; performing tapping operation in the converter, adding a second carbon additive into the steel stream during the tapping process, and simultaneously performing deoxidization and alloying operation; S3, during the tapping process, controlling the argon flow rate of the bottom blowing of the ladle in stages: using a first flow rate range for strong stirring in the early stage of tapping, and using a second flow rate range for weak stirring in the later stage of tapping, wherein the first flow rate range is greater than the second flow rate range; S4, after the tapping is completed, adjusting the argon flow rate of the bottom blowing of the ladle to a third flow rate range and performing first soft blowing treatment, and then hoisting the molten steel to a refining station; S5, adjusting the composition of the molten steel in the refining station, and adjusting the composition of the molten steel to the target range before the refining is completed; S6, before the molten steel leaves the station, controlling the argon flow rate of the bottom blowing of the ladle to a fourth flow rate range and performing second soft blowing treatment, the duration of the second soft blowing treatment is longer than that of the first soft blowing treatment, and then hoisting the molten steel to a continuous casting process.

2. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 1, characterized in that, In the step S1, the following are included: Smelting medium carbon series steel in a converter, controlling the carbon content of the molten steel at the end point to be ≤0.15wt%, the phosphorus content to be ≤0.03wt%, the sulfur content to be ≤0.03wt%, and the tapping temperature to be ≥1570℃; The medium carbon series steel includes 45# steel, and the target finished product chemical composition of the 45# steel is, by weight percentage: carbon: 0.42-0.46%, silicon: ≤0.37%, manganese: ≤0.65%, phosphorus: ≤0.03%, sulfur: ≤0.03%, and the rest is Fe and impurities.

3. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 1, characterized in that, In the step S2, the following are included: before tapping in the converter, transporting the ladle to a refining station, and adding a first predetermined amount of bulk carbon additive to the bottom of the ladle through a refining downfeed system; Performing tapping operation in the converter, manually adding a second predetermined amount of bagged carbon additive into the steel stream during the tapping process, and simultaneously performing deoxidization and alloying operation; The chemical composition of the carbon additive used needs to meet the following requirements by weight percentage: carbon content ≥94%, phosphorus content ≤0.05%, and sulfur content ≤0.45%.

4. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 1, characterized in that, The step S3 comprises: in the tapping process, the argon flow rate of the ladle bottom blowing is controlled in stages: within the first 2 minutes from the beginning of the steel flow impacting the ladle, a first high flow rate is adopted for strong stirring, the first high flow rate being 240-260 m3 / h; after 2 minutes until the end of the tapping, a first low flow rate is adopted for weak stirring, the first low flow rate being 80-100 m3 / h. 3 / h.

5. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 1, characterized in that, In the step S4, the following are included: after the tapping is completed, adjusting the argon flow rate of the bottom blowing of the ladle to a second low flow rate and performing first soft blowing operation, the second low flow rate is 45-55m3 / h, the duration of the first soft blowing operation is 1.5-2.5 minutes, and then hoisting the molten steel to an LF refining station.

6. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 1, characterized in that, In the step S6, the following are included: before the molten steel leaves the station, controlling the argon flow rate of the bottom blowing of the ladle to the second low flow rate and performing second soft blowing operation, and the duration of the second soft blowing operation is not less than 10 minutes.

7. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 3, characterized in that, In the step S2, the following are also included: The first predetermined amount is 280-320kg of bulk carbon additive, and the first predetermined amount of bulk carbon additive is pre-added to the bottom of the ladle before tapping, and is preliminarily melted and dispersed by the steel stream during tapping; The second predetermined amount is 50-150 kg of bagged carburant, and the second predetermined amount of bagged carburant is added according to the end-point carbon content of the converter and the target finished product carbon content during the tapping process, so as to control the carbon content of the molten steel entering the refining process.

8. A method of controlling the carbon content of a finished product of a medium carbon series steel as defined in claim 4, characterized in that, In the step of controlling the flow of the bottom argon blowing in stages, the first high flow of 250 m3 / h is used in the strong stirring stage, and the first low flow of 90 m3 / h is used in the weak stirring stage. 3 / h.

9. A method of controlling the carbon content of a finished product of a medium carbon series steel as defined in claim 5, characterized in that, In the first soft blowing operation after the tapping is completed, the bottom blowing argon flow is 50 m3 / h, and the soft blowing duration is 2 minutes, so that the molten steel is preliminarily and uniformly distributed before entering the LF refining station.

10. A method of controlling the carbon content of a finished product of a stable medium carbon series steel according to claim 6, characterized in that, In the second soft blowing operation after the LF refining is completed, the bottom blowing argon flow is 50 m3 / h, and the soft blowing duration is at least 10 minutes.

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