CN113667882A - Cold heading steel and production method thereof - Google Patents

Cold heading steel and production method thereof Download PDF

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Publication number
CN113667882A
CN113667882A CN202110988766.5A CN202110988766A CN113667882A CN 113667882 A CN113667882 A CN 113667882A CN 202110988766 A CN202110988766 A CN 202110988766A CN 113667882 A CN113667882 A CN 113667882A
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slag
steel
argon blowing
argon
aluminum
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Inventor
刘志龙
黄利
王冠
寻忠忠
曾令宇
余大华
黄含哲
邓长付
佟迎
郭峻宇
胡现锋
任世岗
刘志明
张志明
刘金源
黄德智
周楠
雷中钰
农之江
黄回亮
谭奇峰
叶德兴
黎莉
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SGIS Songshan Co Ltd
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SGIS Songshan Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

The application relates to cold heading steel and a production method thereof, belonging to the field of steel smelting. According to the method, the argon blowing process of the cold forging steel in the LF refining process is strictly controlled, the argon blowing process is subdivided into 5 stages, and the argon blowing flow and the argon blowing time of each stage are controlled, so that large particles, small particles and other impurities in the steel can be effectively floated, and the adsorption effect of liquid level steel slag on the impurities is improved; and further eliminating inclusions in the cold forging steel by finely controlling a plurality of process nodes in other smelting steps, including slag washing of aluminum slag balls in converter smelting, quantitative addition of aluminum wires, deoxidation of the aluminum slag balls in LF refining, aluminum supplement and calcium supplement treatment.

Description

Cold heading steel and production method thereof
Technical Field
The application relates to the field of steel smelting, in particular to cold forging steel and a production method thereof.
Background
The cold heading steel is mainly used for producing parts such as bolts, screws, nuts, sleeves and the like, and is mainly applied to industries such as automobiles, engineering buildings, machinery, electronics, light steel structures, buildings and the like. The cold heading steel must have good cold heading performance, and in order to ensure that the cold heading steel does not crack and lose efficacy in the subsequent cold heading processing process, the purity of molten steel needs to be improved as much as possible, inclusions in the steel are reduced, and the plasticity of the cold heading steel is improved. The improvement of the purity of the molten steel requires strict control of specific processes in each link of cold forging steel smelting to enable alloy components of the cold forging steel to reach a required range, and particularly, the content of elements such as silicon, oxygen, aluminum and the like in the steel needs to be strictly controlled. The prior art is not deep enough in control research on inclusions in cold forging steel, particularly low-silicon high-aluminum cold forging steel, and is systematic. The on-site production cannot be accurately guided, and the finished cold heading steel still has a high failure rate in the downstream use feedback.
Therefore, how to provide the cold forging steel with low inclusion content and high use reliability and the production process thereof is a technical problem which needs to be solved urgently in the field.
Disclosure of Invention
The application aims to provide the cold heading steel and the production method thereof, and the production process system can be accurately guided by the method, so that the purity of molten steel in the smelting process is improved, inclusions in the cold heading steel are reduced, and the reliability of the cold heading steel in the subsequent processing and using processes is greatly improved.
The first aspect of the application provides a production method of cold forging steel, which comprises the working procedures of molten iron pretreatment, converter smelting, LF refining, continuous casting and rolling;
the LF refining procedure comprises an argon blowing process, and the argon blowing process comprises the following stages:
in the stage of slag melting, the argon blowing flow is controlled to be 30-50NM3H, argon blowing time is 5-10 min;
in the power transmission stage, the argon blowing flow is controlled to be 20-40NM3H, argon blowing time is 15-25 min;
in the strong stirring stage, the argon blowing flow is controlled to be 60-80NM3H, argon blowing time is 3-6 min;
in the weak stirring stage, the argon blowing flow is controlled to be 10-20NM3H, the argon blowing time is 5-10min
And (3) soft blowing stage: controlling the argon blowing flow to be 5-10NM3And h, the argon blowing time is 15-25 min.
In an optional scheme, the converter smelting process comprises a slag washing step in the converter tapping process, and the materials used in the slag washing step are aluminum slag balls.
In an alternative scheme, the converter smelting process comprises a deoxidation alloying treatment of the tapped molten steel in an argon station, and the addition amount of the aluminum wire is determined according to the oxygen content of the molten steel in the deoxidation alloying treatment.
In an alternative scheme, the deoxidation alloying treatment specifically comprises: the oxygen content of the argon station is less than or equal to 3ppm, no aluminum wire is fed, the oxygen content of the argon station is 3ppm to 5ppm, the aluminum wire is fed by 50 to 100 meters, the oxygen content of the argon station is 5ppm to 10ppm, the aluminum wire is fed by 100 plus materials 150 meters, the oxygen content of the argon station is 10ppm to 20ppm, the aluminum wire is fed by 150 plus materials 200 meters, the oxygen content of the argon station is more than 20ppm, the aluminum wire is fed ((200 plus materials 250) + (oxygen content value-20)) meters, and the Als of the argon station is controlled to be between 0.030 percent and 0.060 percent.
In an optional scheme, the slag in LF refining is high-alkalinity and high-Al2O3And low SiO2Slag system, wherein, Al2O3The content is controlled between 27-33%.
In an optional scheme, the LF refining process further comprises a slag surface deoxidation process, wherein aluminum slag balls are adopted to deoxidize refining top slag, and the adding amount of the aluminum slag balls is 150-200 kg/furnace.
In an alternative arrangement, the late stage of LF refining includes an aluminium supplement and calcium treatment, wherein the last aluminium supplement is carried out at the latest 10 minutes before the calcium treatment.
In an alternative scheme, molten steel calcium treatment is carried out at the end of LF refining, and the calcium content in the molten steel is controlled to be between 15 and 25 ppm.
In an optional scheme, the cold forging steel is low-silicon high-aluminum steel, and the chemical components of the cold forging steel in percentage by mass are as follows: 0.18-0.23% of C, less than or equal to 0.1% of Si, 0.7-1.0% of Mn, Als: 0.020-0.060%, P is less than or equal to 0.025%, S is less than or equal to 0.015%, and the balance of Fe and inevitable impurities.
The second aspect of the application is to provide cold forging steel which is prepared by the production method in the technical scheme.
The beneficial effect of this application includes: the argon blowing process of the cold forging steel in the LF refining process is strictly controlled, the argon blowing process is subdivided into 5 stages, and the argon blowing flow and the argon blowing time of each stage are controlled, so that large particles, small particles and other impurities in the steel can be effectively promoted to float, and the adsorption effect of the liquid level steel slag on the impurities is improved; and further eliminating inclusions in the cold forging steel by finely controlling a plurality of process nodes in other smelting steps, including slag washing of aluminum slag balls in converter smelting, quantitative addition of aluminum wires, deoxidation of the aluminum slag balls in LF refining, aluminum supplement and calcium supplement treatment.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1(a), (b): schematic representation of group B coarse inclusions of the cold heading steel in example 1;
fig. 2(a), (b): schematic representation of B-type fine inclusions of the cold heading steel in example 1;
FIG. 3: a schematic diagram of Ds type inclusions of the cold heading steel in example 1;
FIG. 4: schematic diagram of B-type fine inclusions of the cold heading steel in comparative example 1;
FIG. 5: comparative example 2 schematic view of Ds-type inclusions of cold heading steel;
FIG. 6: schematic diagram of B-type fine inclusions of the cold heading steel in comparative example 3;
FIG. 7: a schematic diagram of Ds type inclusions of the cold heading steel in comparative example 4;
FIG. 8: a schematic diagram of Ds type inclusions of the cold heading steel in comparative example 5.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments.
Thus, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Hereinafter, "%" means mass percent.
The cold forging steel needs to be deformed at room temperature, so that the requirement on the purity of the steel is high, and the key point for controlling the purity of the steel is the reasonable selection and accurate control of each process parameter in the smelting process.
One of the purposes of the application is to provide a production method of cold forging steel, which comprises the working procedures of molten iron pretreatment, converter smelting, LF refining, continuous casting and rolling;
the LF refining procedure comprises an argon blowing process, and the argon blowing process comprises the following stages:
in the stage of slag melting, the argon blowing flow is controlled to be 30-50NM3H, argon blowing time is 5-10 min;
power transmission stageStage, controlling argon blowing flow rate to be 20-40NM3H, argon blowing time is 15-25 min;
in the strong stirring stage, the argon blowing flow is controlled to be 60-80NM3H, argon blowing time is 3-6 min;
in the weak stirring stage, the argon blowing flow is controlled to be 10-20NM3H, the argon blowing time is 5-10min
And (3) soft blowing stage: controlling the argon blowing flow to be 5-10NM3And h, the argon blowing time is 15-25 min.
In the technical scheme, the argon blowing process is divided into 5 stages, the first stage is a slag melting stage, and slag can be fully melted and prevented from agglomerating by argon blowing in the stage; the second stage is a power transmission stage, and the temperature and components of the molten steel can be homogenized by argon blowing in the second stage, so that impurities are promoted to float; the third stage is a strong stirring stage, and most of deoxidation products can be promoted to quickly float upwards by argon blowing in the third stage; the fourth stage is a weak stirring stage, and fine inclusions in the steel can be promoted to float upwards through argon blowing in the fourth stage; the fifth stage is a soft blowing stage, and fine inclusions in the steel can be further promoted to float by argon blowing in the stage.
The stages are divided according to the function of argon blowing, and the change rule of the argon blowing intensity (flow) is as follows: strong-medium-strong-weak. The argon blowing processes in each stage are mutually influenced, and fine inclusions can be better removed only according to the argon blowing processes and the operation sequence of each stage. In addition, calcium treatment is generally needed before molten steel is soft blown, impurities in steel are denatured after calcium treatment, the impurities are increased in the calcium treatment process, and soft blowing is needed to further promote the floating of fine impurities in the steel.
The steel grade inclusions can be obviously reduced by prolonging the refining soft blowing time, the soft blowing time is increased from 12 minutes to 20 minutes by improving the SWRCH22A soft blowing time, and compared with the large-size inclusions in the core part, the drawing and wire breaking times caused by the inclusions are obviously reduced. Therefore, under the condition that production conditions allow (according to actual conditions), the soft blowing time is properly prolonged, and floating removal of large-particle inclusions is facilitated.
Through more careful and accurate control of the argon blowing process in the LF refining process, the recovery rate of inclusions in molten steel can be improved, and the purity of the molten steel is improved.
Further, the converter smelting process comprises a slag washing step in the converter tapping process, and the materials used in the slag washing step are aluminum slag balls.
Adding ferro-aluminium to deoxidize in the tapping process to produce a large amount of Al2O3Inclusion, a large amount of impurities float into slag in the tapping slag washing process, the floating effect of the impurities in the tapping process is determined according to the quality of the tapping slag washing effect, lime is added into a converter in the original slag washing process of cold forging steel, but when only lime is added, the content of CaO in the slag is high after tapping is finished, so that the melting point of the slag is high, and the slag is difficult to melt; adding aluminum slag balls (the main components are Al and Al)2O3) Can increase Al in slag2O3The content of the (B) is reduced, the melting point of the slag is reduced, so that the slag washing effect is improved, and simultaneously, the slag can be deoxidized, the adding amount is controlled according to 80-150 kg/furnace, the adding amount is too small, the deoxidizing and slag washing improving effects are not good, and the cost is increased due to too much adding amount.
Further, the converter smelting process comprises a deoxidation alloying treatment of the tapped molten steel in an argon station, wherein the addition amount of the aluminum wire is determined according to the oxygen content of the molten steel in the deoxidation alloying treatment.
The control of the Als in the argon station is also one of key links for smelting cold forging steel, and the phenomenon that the Als in the refining process is too high and cannot be reduced due to the fact that the Als in the argon station is controlled too high can cause large loss of the Als in the subsequent refining process and increase of generated inclusion. When the content of Als in the argon station is too low and less than or equal to 0.020%, the deoxidation of molten steel in the argon station is poor, so that the deoxidation of a refining process is difficult, the time delay of white slag affects the removal of refining inclusions, and the actual content of Als in the argon station is preferably controlled to be 0.030-0.060%.
Further, the deoxidation alloying treatment specifically comprises: the oxygen content of the argon station is less than or equal to 3ppm, no aluminum wire is fed, the oxygen content of the argon station is 3ppm to 5ppm, 100 meters of aluminum wire is fed, the oxygen content of the argon station is 5ppm to 10ppm, 150 meters of aluminum wire is fed, the oxygen content of the argon station is 10ppm to 20ppm, 200 meters of aluminum wire is fed, the oxygen content of the argon station is more than 20ppm, the aluminum wire (200+ oxygen content value-20) meters are fed, and the Als content of the argon station is controlled between 0.030 percent and 0.060 percent.
Further, the slag in LF refining is high in alkalinity and Al2O3And low SiO2Slag system, wherein, Al2O3The content is controlled between 27-33%.
The cold forging steel is low-silicon high-aluminum steel, and is refined into high-alkalinity and high-Al steel2O3And low SiO2Slag system, Al in refining slag2O3Content of (A) is based on the fluidity of slag and Al adsorbed by slag2O3The capability of inclusions is of vital importance, Al in the slag2O3Low time, the slag adsorbs Al2O3High capacity of inclusion and Al in slag2O3When the content is too high, it is preferable to use Al2O3The adsorption capacity of the inclusions is reduced, and Al in the slag is analyzed according to actual production data2O3When the content is controlled to be between 27 and 33 percent, the slag has good fluidity, the slag has strong adsorption capacity to the impurities, and the number of the excessive impurities is reduced.
Further, the LF refining process also comprises a slag surface deoxidation process, wherein aluminum slag balls are adopted to deoxidize the refining top slag, and the adding amount of the aluminum slag balls is 80-150 kg/furnace.
The slag surface deoxidation can effectively reduce the oxidability in slag and improve the adsorption capacity of slag on impurities in steel, the original process adopts hand-thrown aluminum particles to carry out slag surface deoxidation, when the aluminum particles are used for carrying out slag surface deoxidation, most of the aluminum particles can enter molten steel, only a small part of the aluminum particles are on the slag surface to carry out deoxidation on the slag, and the deoxidation effect is poor. The subsequent improvement is that the refining top slag is deoxidized by using aluminum slag balls (the addition amount is 80-150 kg/furnace), the deoxidizing speed is high, the white slag can be generally reached within 10 minutes, and meanwhile, the white slag is added by using a storage bin, so that the stability of the white slag process is ensured, and the labor intensity of field workers is reduced.
Further, the later stage of LF refining comprises aluminum supplement and calcium treatment, wherein the last aluminum supplement is carried out at the latest 10 minutes before the calcium treatment.
The refining time of the cold forging steel is generally controlled between 40 and 45 minutes, aluminum supplement is required to be carried out as early as possible in the refining process, and the aluminum supplement in the later period of refining can cause newly added aluminum to continuously react with oxygen in the steel to generateTo Al2O3The aluminum-like impurities are mixed, and the last aluminum supplementing time of refining is changed from 5 minutes before calcium treatment to 10 minutes before calcium treatment by optimizing the process, so that Al in the later stage of refining is reduced2O3The generation of inclusion-like substances.
Further, molten steel calcium treatment is carried out at the end of LF refining, and the calcium content in the molten steel is controlled to be 15-25 ppm.
The calcium treatment process mainly controls the calcium content in the steel after calcium treatment, generally when the calcium content is between 15ppm and 25ppm, the castability of molten steel can be ensured, the erosion to a continuous casting stopper rod water gap can be reduced, the calcium yield is stabilized by improving the purity of the molten steel and the equipment state of a wire feeding machine, the calcium treatment amount is continuously reduced after the calcium yield is stabilized, wherein in the case of SWRCH22A, the actual calcium treatment amount is reduced from 250 meters per furnace to 180 meters per furnace (the weight of a calcium core is 65 g/m), the calcium treatment amounts of other steel types are also reduced by 20-80 meters, the purity of the molten steel is improved, the erosion to a stopper rod water gap refractory material is reduced, and the generation of large-size inclusions is reduced.
Further, the cold forging steel is low-silicon high-aluminum steel, and the chemical components of the cold forging steel in percentage by mass are as follows: 0.18-0.23% of C, less than or equal to 0.1% of Si, 0.7-1.0% of Mn, Als: 0.020-0.060%, P is less than or equal to 0.025%, S is less than or equal to 0.015%, and the balance of Fe and inevitable impurities.
The second aspect of the application is to provide cold heading steel which is prepared by the production method in the technical scheme.
The cold forging steel prepared by the method is graded according to GB/T10561 national standard, A-type and C-type inclusions are not found, and the sizes of B-type and Ds-type inclusions are smaller, wherein B-type coarse inclusions are below 1.5, some B-type coarse inclusions can reach 0.5, B-type fine inclusions are below 2.0, some B-type fine inclusions can reach 0.5, and Ds-type inclusions are below 1.5, so that the requirements of the cold forging steel on inclusions are completely met.
Specific examples of the technical solutions of the present application are provided below:
example 1
The SWRCH22A cold forging steel was used as a sample, and its composition was C0.23%, Si 0.05%, Mn 0.82%, Alt 0.034%, P0.009%, S0.001%, and the balance Fe and inevitable impurities.
Preparing molten iron by using the components of the cold forging steel, and pretreating the molten iron; then, converter smelting is carried out, the molten steel amount is 125 tons, 100kg of aluminum slag balls are added in the tapping process for slag washing treatment, then argon blowing is carried out at an argon station, oxygen is determined to be 1.2ppm at the argon station, an aluminum wire is not fed, and the content of Als in the argon station is controlled to be 0.058%.
Then LF refining is carried out, and the refining slag system is high alkalinity and high Al2O3And low SiO2Slag system, Al in slag2O3The content of the aluminum slag is 29.47 percent, and then 100kg of aluminum slag balls are added to deoxidize the slag surface.
Argon is blown in the whole refining process, and the argon blowing flow is controlled to be 45NM in the slag melting stage3H, argon blowing time is 8 min; controlling the argon blowing flow to be 30NM in the power transmission stage3H, argon blowing time is 15 min; the strong stirring stage controls the argon blowing flow to be 70NM3H, argon blowing time is 5 min; the weak stirring stage controls the argon blowing flow to be 15NM3H, argon blowing time is 8 min; the soft blowing stage controls the argon blowing flow to be 6NM3And h, the argon blowing time is 20 min.
And after refining for 26min, supplementing aluminum, wherein the aluminum supplementing time is 10min before calcium treatment, refining is continued after the aluminum supplementing is finished, and finally calcium treatment is carried out, wherein the adding amount of the calcium core is 240 m, and the weight of the calcium core per meter is 65 g.
Comparative example 1
The SWRCH22A cold forging steel as a sample comprises C0.23%, Si 0.05%, Mn 0.81%, Alt 0.04%, P0.011%, S0.002%, and the balance Fe and inevitable impurities.
Preparing molten iron by using the components of the cold forging steel, and pretreating the molten iron; then, converter smelting is carried out, the amount of molten steel is 126 tons, and 100kg of aluminum slag balls are added for slag washing treatment in the tapping process; then argon blowing is carried out in an argon station, oxygen is set at 5.2ppm in the argon station, the length of an aluminum wire is fed to be 150m, and the content of Als in the argon station is controlled to be 0.053%.
Then LF refining is carried out, and the refining slag system is high alkalinity and high Al2O3And low SiO2Slag system, Al in slag2O3The content is 29.61%, and then 100kg of aluminum slag balls are added to deoxidize the slag surface.
Argon blowing is carried out in the whole refining process, and the argon blowing flow is controlled to be 53NM in the slag melting stage3H, argon blowing time is 9 min; controlling the argon blowing flow to be 33NM in the power transmission stage3H, the argon blowing time is 17 min; the strong stirring stage controls the argon blowing flow to be 75NM3H, argon blowing time is 5 min; the weak stirring stage controls the argon blowing flow to be 25NM3H, argon blowing time is 2 min; the soft blowing stage controls the argon blowing flow to be 7NM3And h, the argon blowing time is 16 min.
And (3) after refining for 23 minutes, supplementing aluminum, wherein the aluminum supplementing time is 10 minutes before calcium treatment, refining is continued after the aluminum supplementing is finished, and finally calcium treatment is carried out, wherein the adding amount of the calcium core is 240 meters, and the weight of the calcium core per meter is 65 g.
Comparative example 2
The SWRCH22A cold-heading steel was used as a sample, and its composition was C0.2%, Si 0.05%, Mn 0.81%, Alt 0.04%, P0.014%, S0.001%, and the balance Fe and unavoidable impurities.
Preparing molten iron by using the components of the cold forging steel, and pretreating the molten iron; then, converter smelting is carried out, the amount of molten steel is 124 tons, and 100kg of aluminum slag balls are added for slag washing treatment in the tapping process; and then argon blowing is carried out in an argon station, oxygen is determined to be 1.2ppm in the argon station, no aluminum wire is fed, and the content of Als in the argon station is controlled to be 0.057%.
Then LF refining is carried out, and the refining slag system is high alkalinity and high Al2O3And low SiO2Slag system, Al in slag2O3The content is 29.43 percent, and then 100kg of aluminum slag balls are added to deoxidize the slag surface.
Argon is blown in the whole refining process, and the argon blowing flow is controlled to be 48NM in the slag melting stage3H, argon blowing time is 8 min; controlling the argon blowing flow to be 38NM in the power transmission stage3H, argon blowing time is 18 min; the strong stirring stage controls the argon blowing flow to be 77NM3H, argon blowing time is 5 min; the weak stirring stage controls the argon blowing flow to be 17NM3H, argon blowing time is 8 min; the soft blowing stage controls the argon blowing flow to be 18NM3And h, the argon blowing time is 8 min.
And (3) after refining for 29 minutes, supplementing aluminum, wherein the aluminum supplementing time is 10 minutes before calcium treatment, refining is continued after the aluminum supplementing is finished, and finally calcium treatment is carried out, wherein the adding amount of the calcium core is 240 meters, and the weight of the calcium core per meter is 65 g.
Comparative example 3
The SWRCH22A cold-heading steel was used as a sample, and the components thereof were C0.22%, Si 0.06%, Mn 0.84%, Alt 0.032%, P0.012%, S0.001%, and the balance Fe and unavoidable impurities.
Preparing molten iron by using the components of the cold forging steel, and pretreating the molten iron; then, converter smelting is carried out, the molten steel amount is 127 tons, and 100kg of aluminum slag balls are added for slag washing treatment in the tapping process; then argon blowing is carried out in an argon station, oxygen is set at 25ppm in the argon station, the length of an aluminum wire is fed to be 80m, and the content of Als in the argon station is controlled to be 0.01%.
Then LF refining is carried out, and the refining slag system is high alkalinity and high Al2O3And low SiO2Slag system, Al in slag2O3The content is 31.69%, and then 100kg of aluminum slag balls are added to deoxidize the slag surface.
Argon blowing is carried out in the whole refining process, and the argon blowing flow is controlled to be 38NM in the slag melting stage3H, argon blowing time is 8 min; the argon blowing flow is controlled to be 34NM in the power transmission stage3H, argon blowing time is 20 min; the strong stirring stage controls the argon blowing flow to be 78NM3H, argon blowing time is 4 min; the weak stirring stage controls the argon blowing flow to be 14NM3H, argon blowing time is 5 min; the soft blowing stage controls the argon blowing flow to be 9NM3And h, the argon blowing time is 18 min.
And after the refining is carried out for 27 minutes, aluminum supplement is carried out, the aluminum supplement time is 10 minutes before the calcium treatment, the refining is continued after the aluminum supplement is finished, and finally the calcium treatment is carried out, wherein the adding amount of the calcium core is 240 meters, and the weight of the calcium core per meter is 65 g.
Comparative example 4
The SWRCH22A cold forging steel is used as a sample, and comprises the components of C0.2%, Si 0.08%, Mn 0.82%, Alt 0.039%, P0.012%, S0.002%, and the balance of Fe and inevitable impurities.
Preparing molten iron by using the components of the cold forging steel, and pretreating the molten iron; then, converter smelting is carried out, the molten steel amount is 128 tons, and 100kg of aluminum slag balls are added for slag washing treatment in the tapping process; then argon station argon blowing is carried out, oxygen is set for 3.7ppm in the argon station, the length of an aluminum wire is fed to be 100m, and the content of Als in the argon station is controlled to be 0.051%.
Then LF refining is carried out, and the refining slag system is high alkalinity and high Al2O3And low SiO2Slag system, Al in slag2O3The content is 23.36 percent, and then 20kg of aluminum slag balls are added to deoxidize the slag surface.
Argon blowing is carried out in the whole refining process, and the argon blowing flow is controlled to be 47NM in the slag melting stage3H, argon blowing time is 9 min; controlling the argon blowing flow to be 30NM in the power transmission stage3H, argon blowing time is 18 min; the strong stirring stage controls the argon blowing flow to be 68NM3H, argon blowing time is 6 min; the weak stirring stage controls the argon blowing flow to be 15NM3H, argon blowing time is 8 min; the soft blowing stage controls the argon blowing flow to be 6NM3And h, the argon blowing time is 22 min.
And after refining for 25 minutes, supplementing aluminum, wherein the aluminum supplementing time is 10 minutes before calcium treatment, refining is continued after the aluminum supplementing is finished, and finally calcium treatment is carried out, wherein the adding amount of the calcium core is 240 meters, and the weight of the calcium core per meter is 65 g.
Comparative example 5
The SWRCH22A cold forging steel as a sample comprises C0.2%, Si 0.08%, Mn 0.8%, Alt 0.042%, P0.018%, S0.001%, and the balance of Fe and inevitable impurities.
Preparing molten iron by using the components of the cold forging steel, and pretreating the molten iron; then, converter smelting is carried out, the molten steel amount is 124 tons, and during tapping, 500kg of lime is added for slag washing treatment; then argon blowing is carried out in an argon station, oxygen is determined for 15ppm in the argon station, the length of an aluminum wire is fed for 180m, and the content of Als in the argon station is controlled to be 0.036%.
Then LF refining is carried out, and the refining slag system is high alkalinity and high Al2O3And low SiO2Slag system, Al in slag2O3The content was 32.18%, and 70kg of aluminum pellets were then charged to deoxidize the slag surface.
Argon blowing is carried out in the whole refining process, and the argon blowing flow is controlled to be 37NM in the slag melting stage3H, blowing argonThe time is 7 min; controlling the argon blowing flow to be 25NM in the power transmission stage3H, argon blowing time is 20 min; the strong stirring stage controls the argon blowing flow to be 67NM3H, argon blowing time is 5 min; the weak stirring stage controls the argon blowing flow to be 16NM3H, argon blowing time is 7 min; the soft blowing stage controls the argon blowing flow to be 5NM3And h, the argon blowing time is 23 min.
And after refining for 24 minutes, supplementing aluminum, wherein the aluminum supplementing time is 10 minutes before calcium treatment, refining is continued after the aluminum supplementing is finished, and finally calcium treatment is carried out, wherein the adding amount of the calcium core is 240 meters, and the weight of the calcium core per meter is 65 g.
The steels obtained in the above examples and comparative examples were examined. As shown in FIGS. 1 to 3, it was found that the steel material of example 1 had no inclusions of the type A and the type C, and had smaller sizes of the type B and the type Ds, wherein the coarse inclusions of the type B were of the order of 1.5 or less, some were of the order of 0.5, the fine inclusions of the type B were of the order of 2.0 or less, some were of the order of 0.5, and the Ds were of the order of 1.5 or less, and thus completely satisfied the inclusion requirements of the cold heading steel.
As shown in fig. 4, the flow rate of argon in the weak stirring stage of the argon blowing process in comparative example 1 is out of the appropriate range, and the argon blowing time is less than the appropriate length of time, resulting in the size of B-type fine inclusions thereof reaching 2.5 grade; as shown in fig. 5, in the soft-blowing stirring stage of the argon blowing process in comparative example 2, the argon flow exceeds a suitable range, and the argon blowing time is less than a suitable length of time, resulting in that the size of Ds-type inclusions reaches 2.5 grade; as shown in fig. 6, the argon station in comparative example 3 has a higher oxygen content, but the length of the fed aluminum wire is less than required, resulting in a class B fine inclusion size of 2.5; as shown in FIG. 7, LF refined mold flux Al used in comparative example 42O3A content of 23.36%, which is below the appropriate range, resulting in a Ds inclusion level of 2.5; as shown in FIG. 8, comparative example 5, in which lime was added for slag washing during tapping, and aluminum shot was not added, resulted in a Ds-type inclusion size of 2.5. As can be seen, in the comparative example, the production process does not meet the requirements, so that the size of the inclusions in the cold forging steel is overlarge, and the product quality standard is not met.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. The production method of the cold heading steel comprises the working procedures of molten iron pretreatment, converter smelting, LF refining, continuous casting and rolling;
the method is characterized in that the LF refining process comprises an argon blowing process, and the argon blowing process comprises the following stages:
in the stage of slag melting, the argon blowing flow is controlled to be 30-50NM3H, argon blowing time is 5-10 min;
in the power transmission stage, the argon blowing flow is controlled to be 20-40NM3H, argon blowing time is 15-25 min;
in the strong stirring stage, the argon blowing flow is controlled to be 60-80NM3H, argon blowing time is 3-6 min;
in the weak stirring stage, the argon blowing flow is controlled to be 10-20NM3H, the argon blowing time is 5-10min
And (3) soft blowing stage: controlling the argon blowing flow to be 5-10NM3And h, the argon blowing time is 15-25 min.
2. The method for producing cold heading steel according to claim 1, wherein the converter smelting process comprises a slag washing step in a converter tapping process, and materials used in the slag washing step are aluminum slag balls.
3. The method for producing cold heading steel according to claim 1, wherein the converter smelting step includes deoxidation alloying of the tapped molten steel in an argon station, and the deoxidation alloying determines the amount of aluminum wire added according to the oxygen content of the molten steel.
4. A method for producing cold heading steel according to claim 3, wherein the deoxidation alloying is specifically: the oxygen content of the argon station is less than or equal to 3ppm, no aluminum wire is fed, the oxygen content of the argon station is 3ppm to 5ppm, the aluminum wire is fed by 50 to 100 meters, the oxygen content of the argon station is 5ppm to 10ppm, the aluminum wire is fed by 100 plus materials 150 meters, the oxygen content of the argon station is 10ppm to 20ppm, the aluminum wire is fed by 150 plus materials 200 meters, the oxygen content of the argon station is more than 20ppm, the aluminum wire is fed ((200 plus materials 250) + (oxygen content value-20)) meters, and the Als of the argon station is controlled to be between 0.030 percent and 0.060 percent.
5. The method for producing cold forging steel as claimed in claim 1, wherein slag in LF refining is high alkalinity and high Al2O3And low SiO2Slag system, wherein, Al2O3The content is controlled between 27-33%.
6. The method for producing cold forging steel as claimed in claim 5, wherein the LF refining process further comprises a slag surface deoxidation process, wherein the refined top slag is deoxidized by using aluminum slag balls, and the adding amount of the aluminum slag balls is 80-150 kg/furnace.
7. The method for producing cold heading steel according to claim 1, wherein the LF refining late stage comprises aluminum supplement and calcium treatment, wherein the last aluminum supplement is performed at the latest 10 minutes before the calcium treatment.
8. A method for producing cold heading steel as claimed in claim 7, wherein the molten steel is subjected to calcium treatment at the end of LF refining to control the calcium content in the molten steel to 15-25 ppm.
9. The production method of cold heading steel according to claim 1, wherein the cold heading steel is low-silicon high-aluminum steel and comprises the following chemical components in percentage by mass: 0.18-0.23% of C, less than or equal to 0.1% of Si, 0.7-1.0% of Mn, Als: 0.020-0.060%, P is less than or equal to 0.025%, S is less than or equal to 0.015%, and the balance of Fe and inevitable impurities.
10. Cold heading steel, characterized in that it is produced by the production method according to any one of claims 1 to 9.
CN202110988766.5A 2021-08-26 2021-08-26 Cold heading steel and production method thereof Pending CN113667882A (en)

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Application publication date: 20211119