Axle steel Ds type inclusion smelting control method, axle steel

Abstract

The present invention provides a method for controlling the smelting of Ds-type inclusions in an axle steel and the axle steel. The present invention adopts a "silicon deoxidation + aluminum deoxidation" composite deoxidation rapid slag formation and slag preservation process method to achieve rapid slag formation in the smelting of the axle steel, and the LF refining cycle is controlled within 80 minutes or less, thereby shortening the refining cycle. The present invention also achieves rapid smelting of the axle steel with a low soft blowing time, which is beneficial for controlling the refining slag system of Ds-type inclusions, achieves stable control of Ds-type inclusions in the axle steel, meets the control requirements of the steel grade for Ds-type inclusions, and the first-time qualified rate of inclusion inspection of the rolled axle steel billet reaches 100%, wherein the Ds-type inclusion ratings are all below level 1.0.

Description

Technical Field

[0001] The present invention relates to the field of iron and steel metallurgy, and in particular to a method for controlling smelting of Ds-type inclusions in an axle steel and an axle steel. Background Art

[0002] Axles have high fatigue performance requirements, requiring strict control of the type and level of inclusions in axle steel. This is particularly true for brittle inclusions and point-like, non-deformable inclusions that can easily lead to axle fatigue failure. Axle steel generally requires a Ds inclusion rating of ≤2.0. For high-speed axles (above 200 km / h), the Ds inclusion rating must be ≤1.5.

[0003] Axle steel smelting production mainly adopts high alkalinity + calcium treatment continuous casting process. High alkalinity can effectively promote the degeneration of type B inclusions in steel, and calcium treatment can effectively improve the castability of molten steel. However, if the timing and amount of calcium treatment are not stably controlled, it will often lead to excessive control of type Ds inclusions in steel.

[0004] A domestic steel plant uses a high-alkalinity + calcium treatment continuous casting process for axle steel smelting and production. However, due to unstable control of the calcium treatment effect, although the castability of the molten steel is good, the proportion of Ds-type inclusions that fail the inspection is high, and the proportion of initial inspection of the axle billet that fails even exceeds 33%.

[0005] The patent "A method and application for controlling Ds inclusions in steelmaking continuous casting process" with publication number CN 113621758 A, published on November 9, 2021, discloses a method for controlling Ds-type inclusions under vacuum post-calcium line treatment process conditions. By controlling the Ca content in molten steel at 2-5ppm and performing temperature compensation through long-term molten steel static treatment + induction heating of the tundish, stable and effective control of Ds-type inclusions is achieved. However, this method has problems such as long processing cycle, large process temperature drop, and high production cost.

[0006] The patent with publication number CN 109055664 A published on December 21, 2018, "A method for controlling the deoxidation of molten bearing steel without Ds-type inclusions", discloses a method for controlling the deoxidation of molten bearing steel without Ds-type inclusions. By silicon deoxidation during steel tapping, low-basicity refined slag (CaO / SiO2 final slag basicity 1.1-1.6) is produced. The RH vacuum treatment time is controlled at 15-20 minutes and the soft blowing time is ≥35 minutes, which can ensure that the Ds-type inclusions are level 0. This method is suitable for silicon-manganese deoxidized steel. For aluminum-killed steel, low-basicity refined slag will cause continuous reaction between steel slags, which is not conducive to the control of oxygen content in steel and will reduce the purity of steel.

[0007] Publication No. CN 108456762 A "A Method for Controlling Ds-Type Inclusions in Alloy Tool Steel" published on August 28, 2018 discloses a method for controlling Ds-type inclusions under high-basicity slag conditions. By controlling the CaO / SiO2 basicity of the refined slag to 6-8 and the Al2O3 content to 30-40%, performing slag deoxidation in small batches and multiple batches during the LF refining process, and controlling the RH vacuum treatment time to ≥20 minutes and the soft blowing time to ≥20 minutes, the level of Ds-type inclusions in the steel can be controlled to ≤1.0. However, performing slag deoxidation in batches and small batches during the LF refining process will cause the post-deoxidation products to be fine and difficult to float up and remove, which is not conducive to the control of total oxygen in the steel.

[0008] Publication No. CN 114086062 A "A steel for high-speed rail axles and its production method" published on February 25, 2022 provides a slag pouring operation before VD vacuum treatment (30-40% of the refined slag is poured out), and after vacuum treatment, 30-80m of silicon calcium wire is fed for calcium treatment, the inclusions are denatured, and soft blowing is strengthened (soft blowing time is 30-40 minutes), so that the axle Ds inclusions are stably controlled below level 0.5. This method requires slag pouring. On the one hand, the smelting cycle is long, and on the other hand, the process temperature drop is large. In addition, the soft blowing time after wire feeding is long, which is not conducive to efficient and economical production. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for controlling the smelting of Ds-type inclusions in axle steel, which adopts a "silicon deoxidation + aluminum deoxidation" composite deoxidation rapid slag formation and slag preservation process method to achieve rapid slag formation in axle steel smelting, and the LF refining cycle is controlled to ≤80min; and rapid smelting of axle steel with a low soft blowing time is achieved, which is conducive to controlling the refined slag system of Ds-type inclusions and realizing stable control of Ds-type inclusions in axle steel.

[0010] The present invention also provides axle steel produced by adopting the above smelting control method.

[0011] The specific technical solutions of the present invention are as follows:

[0012] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0013] 1) The molten iron entering the furnace must have a P content of ≤0.014% and a S content of ≤0.040%;

[0014] 2) The smelting endpoint control requirements are C content 0.10%-0.25%, P content ≤0.012%, [O] content ≤250ppm, and the endpoint temperature is 1630-1680℃;

[0015] 3) Deoxidation and alloying during the steel tapping process;

[0016] 4)LF refining;

[0017] 5) Vacuum refining;

[0018] 6) Protect casting.

[0019] In step 1), electric furnace smelting is adopted, the iron-steel ratio is controlled at 30-70%, the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0020] In the present invention, step 1) sets requirements for the content of molten iron entering the furnace, reduces the burden on the primary smelting furnace, and facilitates the control of the smelting endpoint of the primary smelting furnace;

[0021] In step 2), the steel is tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention amount of 5-10t and a slag amount controlled to ≤3kg / ton of steel;

[0022] Step 2) is the endpoint control of the primary furnace, which is particularly critical for inclusion control. The main idea is to retain carbon and reduce the endpoint oxygen content, thereby reducing the use of subsequent deoxidizers and the formation of inclusions. The control of P content is mainly based on meeting product requirements. The control of the endpoint temperature is mainly to reduce the burden of subsequent refining while meeting the control of C and P contents.

[0023] Step 3) specifically comprises: deoxidizing the molten steel and slag using a silicon deoxidizer and aluminum iron;

[0024] In step 3), when 1 / 4-1 / 3 of the steel is tapped, silicon deoxidizer, aluminum iron, slag material and alloy are added in sequence;

[0025] The amount of silicon deoxidizer added is 0.5-1.0 kg / ton of steel, the amount of aluminum iron added is 2.5-3.0 kg / ton of steel, and the amount of slag material added is 5.5-8.0 kg / ton of steel; the target amount of alloy addition is controlled according to the internal control lower limit of the steel grade;

[0026] Preferably, the siliceous deoxidizer comprises the following components by mass percentage: Si content 40-60%, S≤0.20%, P≤0.10%; the particle size of the siliceous deoxidizer is 10-40 mm;

[0027] The slag-making material includes lime and pre-melted refined slag;

[0028] Preferably, the pre-melted refined slag mainly comprises the following components in mass percentage: CaO content 40-60%, Al2O3 content 30-50%, and the particle size of the pre-melted refined slag is 5-40 mm;

[0029] The amount of lime added is 3.0-4.5 kg / ton of steel, and the amount of pre-melted refined slag added is 2.5-3.5 kg / ton of steel;

[0030] Step 3) During the tapping process, the ladle is strongly stirred and the bottom blowing argon flow rate is controlled at 400-600 NL / min;

[0031] Step 3) Deoxidation and alloying are performed during the tapping process, mainly utilizing the mixed impact of molten steel during the tapping process to perform pre-slag making and pre-alloying treatments using a double deoxidizer, thereby reducing the refining burden and improving refining efficiency.

[0032] In step 4), the LF refining cycle is controlled to be ≤80 min;

[0033] In step 4), the aluminum content alloying in the LF refining process is controlled in the early stage of refining, and aluminum particles are added to perform aluminum alloying; because the early stage of refining is conducive to the effective removal of inclusions generated after the addition of aluminum particles during the refining process;

[0034] In step 4), after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the top slag condition to make slag, and the refining process makes slag quickly; specifically, after the molten steel enters the LF, the top slag condition is checked. If the top slag is thin, lime needs to be added. If the top slag is clumped and not melted, pre-melted refined slag needs to be added. If the slag amount is small, both lime and pre-melted refined slag need to be added. The slag making process is judged by sampling the color and thickness of the refined slag, and subsequent slag making is carried out by component analysis to meet the refined slag composition control requirements.

[0035] In step 4), the composition of the refined slag after slag formation is required to meet the following conditions: CaO content 40-55%, SiO2 content 10-18%, Al2O3 content 20-35%, (FeO+MnO)≤1.0%, binary basicity (CaO / SiO2) is controlled at 2.8-5.0, CaO / Al2O3 ratio is controlled at 1.0-2.0, and the amount of refined slag is controlled at 12-15 kg / ton of steel;

[0036] In step 4), aluminum particles or silicon deoxidizer are added to maintain slag after rapid slag formation and subsequent refining process is completed to ensure that the LF final slag can also meet the requirements of the above-mentioned refined slag composition; the silicon deoxidizer is selected from silicon ball deoxidizer or silicon carbide;

[0037] In step 4), after the rapid slag formation is completed, the slag preservation is specifically as follows:

[0038] The amount of aluminum particles added during the heating process is controlled according to (1.5-2.5×T1) kg, where T1 is the heating time (in minutes); or the amount of silicon deoxidizer added is controlled according to (2.5-3.5×T1) kg;

[0039] The amount of aluminum particles added during the alloying process is controlled according to (1.0-2.0×T2)kg, T2 is the strong stirring time of the time, in min, or the amount of silicon deoxidizer added is controlled according to (2.0-3.0×T2)kg; when calculating above, just substitute the value before the unit into the calculation.

[0040] In step 4), when the binary basicity (CaO / SiO2) of the refined slag after rapid slag formation is 4.5-5.0, only silicon deoxidizer can be added during the heating and alloying processes, and aluminum particles cannot be added; when the CaO / Al2O3 ratio of the refined slag is 1.8-2.0, only aluminum particles can be added during the heating and alloying processes, and silicon deoxidizer cannot be added; when the binary basicity and CaO / Al2O3 ratio of the refined slag are under other conditions, aluminum particles or silicon deoxidizer can be added.

[0041] Step 4) mainly performs slag making and alloying operations to achieve stable control of the refining top slag composition and stable control of the molten steel composition and temperature; the aluminum particles or silicon deoxidizer added during the heating and alloying process are used to perform slag maintenance operations, that is, to control the LF final slag to ensure that the LF final slag can also meet the above-mentioned refining slag composition requirements.

[0042] In step 5), the vacuum refining controls the vacuum degree to ≤100Pa, the vacuum treatment cycle is 15min or more, the hydrogen content before breaking the air is ≤1.0ppm, and 180-220kg of insulation agent is evenly added to the slag surface after breaking the air to keep it warm and inhibit secondary oxidation. After the insulation agent is added, the molten steel is soft-blown, and the bottom blowing flow rate is controlled to 10-20NL / min. The top slag is kept without a bright surface and slightly floating, and the soft blowing time is 5-10min; a covering agent commonly used in this field can be added, which can play a role in insulation on the one hand and inhibit the secondary oxidation of the molten steel by air on the other hand.

[0043] Step 5) vacuum degassing operation is performed. Under the above vacuum conditions, the gas in the steel can be effectively removed, especially the H content. On the other hand, the vacuum cycle process can effectively promote the aggregation, growth and removal of inclusions;

[0044] Step 6) specifically includes: after the molten steel is put on the platform, it is left to stand for 20-30 minutes before pouring to promote the floating removal of inclusions;

[0045] In step 6), the casting process needs to be well protected by "long nozzle for large ladle + medium ladle + immersed nozzle" and the Als loss should be controlled to ≤40ppm when the RH is sampled from the exit of the ladle to the medium ladle, that is, when the large ladle is cast for 1 / 2.

[0046] Step 6) Protective casting during the continuous casting process can greatly reduce the degree of secondary oxidation of the molten steel and reduce the formation of inclusions.

[0047] The axle steel provided by the present invention is produced by adopting the above-mentioned axle steel Ds type inclusion smelting control method, and the Ds type inclusion rating of the produced axle steel is all below level 1.0;

[0048] For the axle steel produced, the stability of Class A inclusions is controlled below Level 1.0, the stability of Class B inclusions is controlled below Level 0.5, there are no Class C inclusions, and the stability of Class D inclusions is controlled below Level 1.0.

[0049] The inventors conducted a scanning-energy spectrum quantitative analysis of excessive Ds-type inclusions, revealing that they were primarily composite inclusions composed primarily of calcium aluminates, endogenous inclusions in the molten steel. The present invention optimizes and improves the process to increase the qualified rate of Ds-type inclusion control. By effectively controlling the carbon content at the smelting endpoint, the present invention reduces the oxygen content in the tapping, minimizing the use of deoxidizers and the formation of deoxidized inclusions. The use of a dideoxidizer for slagging during tapping facilitates control of top slag composition, reduces refining pressure, enables rapid slagging, shortens refining time, and improves smelting efficiency. The present invention can control the LF refining cycle to 80 minutes or less, thereby improving refining efficiency and reducing refining costs. The present invention eliminates calcium treatment, which can shorten the refining time and reduce production costs. The present invention also reduces the RH soft blowing time (the soft blowing time is controlled to be 5-10 minutes), thereby better achieving furnace-machine matching. After production, the Ds-type inclusion rating is all below level 1.0, and the control of other types of inclusions can meet requirements. Class A inclusions are all stably controlled below level 1.0, Class B inclusions are all stably controlled below level 0.5, there are no Class C inclusions, and Class D inclusions are all stably controlled below level 1.0. The produced axle steel has a first-time pass rate of 100%.

[0050] Compared with the existing technology, the present invention adopts a "silicon deoxidation + aluminum deoxidation" composite deoxidation rapid slag formation and slag preservation process method to achieve rapid slag formation in axle steel smelting, and the LF refining cycle is controlled at ≤80min, shortening the refining cycle; and realizes rapid smelting of axle steel with low soft blowing time, which is conducive to controlling the refining slag system of Ds-type inclusions, and realizes stable control of Ds-type inclusions in axle steel, meeting the control requirements of steel grades for Ds-type inclusions, and the one-time pass rate of inclusion inspection of rolled axle steel billets reaches 100%, among which the Ds-type inclusion ratings are all below level 1.0. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a rating chart of Ds-type inclusions in axles or axle blanks of some embodiments of the present invention, with ratings of 0.5 (upper left), 1.0 (upper right), 1.0 (lower left), and 0 (lower right).

[0052] Figure 2 These are the Ds inclusion rating diagrams for some comparative example axles or axle blanks of the present invention, with ratings of 2.0 (upper left), 2.0 (upper right), 2.0 (lower left), and 2.0 (lower right). DETAILED DESCRIPTION

[0053] The siliceous deoxidizer used in the present invention has a Si content of 40-60%, S ≤ 0.20%, and P ≤ 0.10% by weight. The siliceous deoxidizer has a particle size of 10-40 mm. The pre-melted refined slag has a CaO content of 40-60%, an Al2O3 content of 30-50%, and a particle size of 5-40 mm. Other raw materials not specifically specified can be commercially available.

[0054] Example 1

[0055] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0056] 1) The steel produced in this embodiment is axle steel LZ50, the molten iron has a P content of 0.014%, an S content of 0.038%, an iron-steel ratio of 30%, and the scrap steel is low-sulfur scrap steel (the S content in the scrap steel is ≤0.010%);

[0057] 2) The final C content of electric furnace smelting was 0.18%, the P content was 0.012%, the final [O] content was 147ppm, the final temperature was 1657°C, and the steel was tapped using the "eccentric furnace bottom + steel retention" method. The steel retention was 8t, and the slag amount was about 3kg / ton of steel.

[0058] 3) When 1 / 3 of the steel is tapped, add 0.5kg / ton of silicon deoxidizer, 2.5kg / ton of aluminum iron, 4.0kg / ton of lime, and 3.0kg / ton of pre-melted refined slag. The target amount of alloy addition is controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate is 500NL / min, and strong stirring is performed for 5 minutes.

[0059] 4) The aluminum content alloying control in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 20 minutes to form white slag, of which the composition and mass percentage of the refined slag are: CaO content 48%, SiO2 content 17%, Al2O3 content 25%, binary basicity (CaO / SiO2) = 2.8, CaO / Al2O3 = 1.9, (FeO+MnO ) content is 1.0%, the refined slag amount is 15kg / ton steel, the subsequent heating time after slag formation is T1=12min, the alloying strong stirring time is T2=5min, a total of 31.5kg of slag-preserving aluminum particles are added, the LF final slag has a CaO content of 46%, a SiO2 content of 16%, an Al2O3 content of 27%, a (FeO+MnO) content of 0.8%, a binary basicity (CaO / SiO2)=2.9, CaO / Al2O3=1.7; the LF refining cycle is 80min;

[0060] 5) Vacuum refining: vacuum degree 67Pa, vacuum treatment cycle 15min, hydrogen [H] content 1.0ppm before breaking, adding 205kg of heat preservation agent, soft blowing argon flow rate 15NL / min, soft blowing time 10min;

[0061] 6) The molten steel is put on the platform and left to stand for 30 minutes. During the casting process, the "long nozzle of the large ladle + the medium ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 28ppm when sampling from the RH station to the medium ladle (when the large ladle is cast 1 / 2).

[0062] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 1.0 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 0.5 level. Class A inclusions are stably controlled below level 1.0, Class B inclusions are stably controlled below level 0.5, there are no Class C inclusions, and Class D inclusions are stably controlled below level 1.0.

[0063] Example 2:

[0064] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0065] 1) The steel produced in this embodiment is axle steel LZ50, the molten iron has a P content of 0.012%, an S content of 0.030%, an iron-steel ratio of 50%, and the scrap steel is low-sulfur scrap steel (the S content in the scrap steel is ≤0.010%);

[0066] 2) The end-point C content of electric furnace smelting is 0.25%, the P content is 0.011%, the end-point [O] content is 120ppm, the end-point temperature is 1630℃, and the steel is tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention of 10t and a slag discharge of approximately 2kg / ton of steel;

[0067] 3) When 1 / 3 of the steel is tapped, add 0.8kg / ton of silicon deoxidizer, 3.0kg / ton of aluminum iron, 4.5kg / ton of lime, and 2.5kg / ton of pre-melted refined slag. The target amount of alloy addition is controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate is 500NL / min, and strong stirring is performed for 6 minutes.

[0068] 4) The alloying control of aluminum content in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 18 minutes to form white slag, wherein the refined slag after slag making is controlled to have the following composition and content: CaO content 55%, SiO2 content 13%, Al2O3 content 28%, (FeO+MnO) content 0.9%, binary basicity (CaO / SiO2) = 4.2, CaO / Al2O3=2.0; refined slag amount 14kg / ton steel, subsequent heating time after slag formation T1=10min, alloying strong stirring time T2=6min, a total of 29kg slag-preserving aluminum particles were added, LF final slag CaO content 51%, SiO2 content 12%, Al2O3 content 30%, (FeO+MnO) content 0.6%, binary basicity (CaO / SiO2)=4.3, CaO / Al2O3=1.7; LF refining cycle 60min;

[0069] 5) Vacuum refining: vacuum degree 99Pa, vacuum treatment cycle 18min, hydrogen [H] content 0.8ppm before breaking, adding 203kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 10min;

[0070] 6) The molten steel is put on the platform and left to stand for 20 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 40ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0071] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 1.0 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 1.0 level. The control of other types of inclusions can meet the requirements.

[0072] Example 3:

[0073] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0074] 1) The steel produced in this embodiment is axle steel LZ50, the molten iron has a P content of 0.010%, an S content of 0.032%, and an iron-steel ratio of 60%; the scrap steel is low-sulfur scrap steel (the S content in the scrap steel is ≤0.010%);

[0075] 2) The final C content of the electric furnace is 0.12%, the P content is 0.008%, the final [O] content is 199ppm, the final temperature is 1680℃, and the steel is tapped using the "eccentric furnace bottom + steel retention" method. The steel retention amount is 8t, and the slag amount is about 1.5kg / ton of steel.

[0076] 3) When 1 / 4 of the steel is tapped, add 1.0 kg / ton of silicon deoxidizer, 3.0 kg / ton of aluminum iron, 3.0 kg / ton of lime, and 2.5 kg / ton of pre-melted refined slag. The target amount of alloy addition is controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate is 500 NL / min, and strong stirring is performed for 6 minutes;

[0077] 4) The alloying control of aluminum content in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the top slag condition to make slag. The LF is refined for 19 minutes to form white slag, and the refined slag is controlled to have the following composition and content: CaO content 43%, SiO2 content 15%, Al2O3 content 32%, (FeO+MnO) content 0.6%, binary basicity 2.9, CaO / Al2O3=1.3, and the refined slag amount is 12kg / ton of steel. After the slag is formed, the subsequent heating time T1=13min, the alloying strong stirring time T2=5min, and a total of 34kg of slag-keeping aluminum particles are added. The CaO content of the LF final slag is 40%, the SiO2 content is 14%, the Al2O3 content is 35%, the (FeO+MnO) content is 0.6%, the binary basicity is 2.9, and CaO / Al2O3=1.1; the LF refining cycle is 68min;

[0078] 5) Vacuum refining: vacuum degree 54Pa, vacuum treatment cycle 16min, hydrogen [H] content 0.6ppm before breaking, adding 202kg of heat preservation agent, soft blowing argon flow rate 10NL / min, soft blowing time 7min;

[0079] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 19ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0080] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 0.5 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 0 level. The control of other types of inclusions can meet the requirements.

[0081] Example 4:

[0082] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0083] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron has a P content of 0.014%, an S content of 0.026%, and an iron-steel ratio of 30%; the scrap steel is low-sulfur scrap steel (the S content in the scrap steel is ≤0.010%);

[0084] 2) The EAF endpoint carbon content is 0.10%, phosphorus content is 0.006%, and [O] content is 250ppm. The endpoint temperature is 1680°C, and the slag quantity is approximately 3kg / ton of steel. The steel is tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention quantity of 6t.

[0085] 3) When 1 / 3 of the steel is tapped, add 0.5kg / ton of silicon deoxidizer, 3.0kg / ton of aluminum iron, 4.5kg / ton of lime, and 3.5kg / ton of pre-melted refined slag. The target amount of alloy addition is controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate is 500NL / min, and strong stirring is performed for 6 minutes.

[0086] 4) LF refining process aluminum content alloying control is carried out in the early stage of refining; after LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the top slag condition to make slag, and LF is refined for 20min to form white slag, wherein the refined slag has a CaO content of 48%, a SiO2 content of 12%, an Al2O3 content of 25%, a (FeO+MnO) content of 0.6%, a binary basicity (CaO / SiO2)=4.0, CaO / Al2O3=1.9, and a refined slag amount of 15kg / ton of steel. After the slag is formed, the subsequent heating time T1=10min, the alloying strong stirring time T2=5min, and a total of 30kg of slag-keeping aluminum particles are added. The LF final slag has a CaO content of 45%, a SiO2 content of 11%, an Al2O3 content of 29%, a (FeO+MnO) content of 0.7%, a binary basicity (CaO / SiO2)=4.1, and CaO / Al2O3=1.6; the LF refining cycle is 75min;

[0087] 5) Vacuum refining: vacuum degree 89Pa, vacuum treatment cycle 17min, hydrogen [H] content 0.5ppm before breaking, adding 201kg of heat preservation agent, soft blowing argon flow rate 15NL / min, soft blowing time 8min;

[0088] 6) The molten steel is put on the platform and left to stand for 20 minutes. During the casting process, the "long nozzle of the large ladle + the medium ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 35ppm when sampling from the RH station to the medium ladle (when the large ladle is cast 1 / 2).

[0089] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 1.0 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 1.0 level. The control of other types of inclusions can meet the requirements.

[0090] Example 5:

[0091] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0092] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron has a P content of 0.013%, an S content of 0.031%, and an iron-steel ratio of 40%; the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0093] 2) The EAF end-point carbon content was 0.15%, phosphorus content was 0.008%, [O] content was 176ppm, the end-point temperature was 1661°C, and the slag quantity was approximately 1.9kg / ton of steel. The steel was tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention quantity of 8t.

[0094] 3) When 1 / 3 of the steel is tapped, add 0.7kg / ton of silicon deoxidizer, 2.7kg / ton of aluminum iron, 4.0kg / ton of lime, and 3.0kg / ton of pre-melted refined slag. The target amount of alloy addition is controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate is 500NL / min, and strong stirring is performed for 5 minutes.

[0095] 4) During the LF refining process, the alloying of aluminum content is controlled in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 18 minutes to form white slag, wherein the refined slag has a CaO content of 45%, a SiO2 content of 10%, an Al2O3 content of 35%, a (FeO+MnO) content of 0.6%, a binary basicity of 4.5, a calcium-aluminum ratio of 1.3, and a refined slag amount of 13kg / ton of steel. After the slag is formed, the subsequent heating time is T1=11min, the alloying strong stirring time is T2=6min, and a total of 48kg of slag-preserving silicon ball deoxidizer is added. The CaO content of the LF final slag is 44%, the SiO2 content is 14%, the Al2O3 content is 32%, the (FeO+MnO) content is 0.5%, the binary basicity is 3.1, and the CaO / Al2O3 is 1.4. The LF refining cycle is 71min.

[0096] 5) Vacuum refining: vacuum degree 69Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.7ppm before breaking, adding 200kg of heat preservation agent, soft blowing argon flow rate 10NL / min, soft blowing time 10min;

[0097] 6) The molten steel is put on the platform and left to stand for 30 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 30ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0098] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 1.0 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 0.5 level. The control of other types of inclusions can meet the requirements.

[0099] Example 6:

[0100] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0101] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron has a P content of 0.011%, an S content of 0.037%, and an iron-steel ratio of 50%; the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0102] 2) The EAF end-point carbon content was 0.18%, phosphorus content was 0.010%, and [O] content was 135 ppm. The end-point temperature was 1659°C, and the slag amount was approximately 1.4 kg / ton of steel. The steel was tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention of 6 tons.

[0103] 3) When 1 / 3 of the steel is tapped, add 1.0kg / ton of silicon deoxidizer, 2.5kg / ton of aluminum iron, 3.5kg / ton of lime, and 3.5kg / ton of pre-melted refined slag. The target amount of alloy addition is controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate is 500NL / min, and strong stirring is performed for 5 minutes.

[0104] 4) During the LF refining process, the alloying of aluminum content is controlled in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process depending on the condition of the top slag to make slag. The LF is refined for 19 minutes to form white slag, wherein the refined slag has a CaO content of 50%, a SiO2 content of 16%, an Al2O3 content of 25%, a (FeO+MnO) content of 1.0%, a binary basicity of 3.1, a CaO / Al2O3 ratio of 2.0, and a refined slag amount of 12 kg / ton of steel. After the slag is formed, the subsequent heating time is T1=13 min, the alloying strong stirring time is T2=5 min, and a total of 33.5 kg of slag-preserving aluminum particles are added. The final LF slag has a CaO content of 49%, a SiO2 content of 15%, an Al2O3 content of 28%, a (FeO+MnO) content of 0.5%, a binary basicity of 3.3, and a CaO / Al2O3 ratio of 1.8. The LF refining cycle is 74 minutes.

[0105] 5) Vacuum refining: vacuum degree 66Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 198kg of heat preservation agent, soft blowing argon flow rate 15NL / min, soft blowing time 6min;

[0106] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 19ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0107] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion rating is 0.5 level. The axle Ds inclusion inspection is qualified once, among which the Ds type inclusion rating is 0.5 level. The control of other types of inclusions can meet the requirements.

[0108] Example 7:

[0109] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0110] 1) The steel produced in this embodiment is axle steel EA4T, the molten iron has a P content of 0.010%, an S content of 0.026%, and an iron-steel ratio of 60%; the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0111] 2) The EAF end-point C content was 0.11%, P content was 0.007%, [O] content was 225ppm, the end-point temperature was 1674°C, and the slag quantity was approximately 2.7kg / ton of steel. The steel was tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention quantity of 10t.

[0112] 3) During the tapping process, 0.6 kg of silicon deoxidizer per ton of steel, 2.9 kg of aluminum iron per ton of steel, 4.1 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0113] 4) During the LF refining process, the alloying of aluminum content is controlled in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process depending on the condition of the top slag to make slag. The LF is refined for 17 minutes to form white slag, wherein the refined slag has a CaO content of 50%, a SiO2 content of 14%, an Al2O3 content of 25%, a (FeO+MnO) content of 0.7%, a binary basicity of 3.6, a calcium-aluminum ratio of 2.0, and a refined slag amount of 13kg / ton of steel. After the slag is formed, the subsequent heating time is T1=12min, the alloying strong stirring time is T2=6min, and a total of 33kg of slag-preserving aluminum particles are added. The final LF slag has a CaO content of 47%, a SiO2 content of 13%, an Al2O3 content of 30%, a (FeO+MnO) content of 0.5%, a binary basicity of 3.6, and a calcium-aluminum ratio of 1.6; the LF refining cycle is 64min.

[0114] 5) Vacuum refining: vacuum degree 64Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.6ppm before breaking, adding 203kg of heat preservation agent, soft blowing argon flow rate 10NL / min, soft blowing time 7min;

[0115] 6) The molten steel is put on the platform and left to stand for 20 minutes. During the casting process, the "long nozzle of the large ladle + the medium ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 35ppm when sampling from the RH station to the medium ladle (when the large ladle is cast 1 / 2).

[0116] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 1.0 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 0.5 level. The control of other types of inclusions can meet the requirements.

[0117] Example 8:

[0118] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0119] 1) The steel produced in this embodiment is axle steel EA4T, the P content of the molten iron entering the furnace is 0.012%, the S content is 0.031%, and the iron-steel ratio is 40%; the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0120] 2) The EAF end-point carbon content was 0.13%, phosphorus content was 0.009%, and [O] content was 192 ppm. The end-point temperature was 1671°C, and the slag quantity was approximately 1.8 kg / ton of steel. The steel was tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention quantity of 6 t.

[0121] 3) During the tapping process, 0.7 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.0 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 6 minutes.

[0122] 4) During the LF refining process, the alloying of aluminum content is controlled in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process depending on the condition of the top slag to make slag. The LF is refined for 21 minutes to form white slag, wherein the refined slag has a CaO content of 50%, a SiO2 content of 10%, an Al2O3 content of 29%, a (FeO+MnO) content of 0.7%, a binary basicity of 5, a CaO / Al2O3 ratio of 1.7, and a refined slag amount of 12 kg / ton of steel. After the slag is formed, the subsequent heating time T1=15 min, the alloying strong stirring time T2=5 min, and a total of 57.5 kg of slag-preserving silicon ball deoxidizer are added. The LF final slag has a CaO content of 48%, a SiO2 content of 13%, an Al2O3 content of 30%, a (FeO+MnO) content of 0.5%, a binary basicity of 3.7, and a CaO / Al2O3 ratio of 1.6. The LF refining cycle is 76 minutes.

[0123] 5) Vacuum refining: vacuum degree 75Pa, vacuum treatment cycle 16min, hydrogen [H] content 0.5ppm before breaking, adding 201kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 8min;

[0124] 6) The molten steel is put on the platform and left to stand for 20 minutes. During the casting process, the "long nozzle of the large ladle + the medium ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 25ppm when sampling from the RH station to the medium ladle (when the large ladle is cast 1 / 2).

[0125] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion is rated as 1.0 level. The axle Ds inclusion inspection is qualified once, and the Ds type inclusion is rated as 0.5 level. The control of other types of inclusions can meet the requirements.

[0126] Example 9:

[0127] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0128] 1) The steel produced in this embodiment is axle steel EA4T, the molten iron has a P content of 0.009%, an S content of 0.024%, and an iron-steel ratio of 70%; the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0129] 2) The EAF end-point C content is 0.15%, P content is 0.006%, end-point [O] content is 183ppm, end-point temperature is 1661°C, and the slag amount is approximately 1.5kg / ton of steel. The steel is tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention amount of 5-10t.

[0130] 3) During the tapping process, 0.9 kg of silicon deoxidizer per ton of steel, 2.5 kg of aluminum iron per ton of steel, 4.5 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0131] 4) During the LF refining process, the alloying of aluminum content is controlled in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 20 minutes to form white slag, wherein the refined slag contains 55% CaO, 12% SiO2, 32% Al2O3, 0.6% (FeO+MnO), 4.6 binary basicity, 1.7 calcium-aluminum ratio, and 13kg / ton steel of refined slag. After the slag is formed, the subsequent heating time is T1=12min, the alloying strong stirring time is T2=5min, and a total of 48.5kg of slag-preserving silicon ball deoxidizer is added. The final LF slag contains 51% CaO, 13% SiO2, 31% Al2O3, 0.5% (FeO+MnO), 3.9 binary basicity, and 1.6 calcium-aluminum ratio. The LF refining cycle is 69min.

[0132] 5) Vacuum refining: vacuum degree 63Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.6ppm before breaking, adding 201kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 10min;

[0133] 6) The molten steel is put on the platform and left to stand for 23 minutes. During the casting process, the "long nozzle of the large ladle + the medium ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 27ppm when sampling from the RH station to the medium ladle (when the large ladle is cast 1 / 2).

[0134] 7) After the ingot is rolled, the shaft billet inclusion inspection is qualified once, among which the Ds type inclusion rating is 0.5 level. The axle Ds inclusion inspection is qualified once, among which the Ds type inclusion rating is 0.5 level. The control of other types of inclusions can meet the requirements.

[0135] Comparative Example 1:

[0136] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0137] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron has a P content of 0.011%, an S content of 0.033%, and an iron-steel ratio of 50%; the scrap steel is low-sulfur scrap steel, and the S content in the scrap steel is ≤0.010%;

[0138] 2) C content at the end of the electric furnace is 0.09% , P content 0.006%, End point [O] content 261ppm The final temperature is 1657℃, the slag amount is about 2.3kg / ton of steel; the steel is tapped using the "eccentric furnace bottom + steel retention" method, with a steel retention amount of 8t;

[0139] 3) During the tapping process, 0.8 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.3 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0140] 4) During the LF refining process, the aluminum content alloying control is carried out in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process depending on the condition of the top slag to make slag. The LF is refined for 20 minutes to form white slag, of which the CaO content is 51%, the SiO2 content is 13%, the Al2O3 content is 32%, the (FeO+MnO) content is 0.6%, the binary basicity (CaO / SiO2) is controlled at 3.9, and the CaO / Al2O3 ratio is controlled at 1.6. The amount of refined slag is 15 kg / ton of steel. The subsequent heating time after slag formation is T1 = 12 min, the alloying strong stirring time is T2 = 5 min, and a total of 49 kg of slag-preserving silicon ball deoxidizer is added. The CaO content of the LF final slag is 48%, the SiO2 content is 15%, the Al2O3 content is 30%, the (FeO+MnO) content is 0.5%, the binary basicity (CaO / SiO2) is controlled at 3.2, and the CaO / Al2O3 ratio is controlled at 1.6; the LF refining cycle is 72 min;

[0141] 5) Vacuum refining: vacuum degree 63Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 202kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 10min;

[0142] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 31ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0143] 7) After the billet is rolled, the initial inspection of the shaft billet inclusion test fails. Among them, the Ds inclusions are rated 2.0, and the re-inspection After the test, the axle failed the Ds inclusion test and the Ds inclusion rating was 2.0. This is mainly because the oxygen content at the end of smelting is high, the amount of deoxidizer added is large (including molten steel deoxidation and top slag deoxidation), the number of inclusions generated is large, and it is difficult to remove them.

[0144] Comparative Example 2:

[0145] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0146] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.012%, an S content of 0.031%, and an iron-steel ratio of 50%;

[0147] 2) The C content at the end of the electric furnace is 0.12%, the P content is 0.008%, the [O] content at the end is 213ppm, and the end temperature is 1646°C. The slag amount is about 3.1kg / ton of steel;

[0148] 3) During the tapping process, 0.5 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.0 kg of lime per ton of steel, and 3.5 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 6 minutes.

[0149] 4) LF refining process aluminum content alloying control is carried out in the early stage of refining; after LF enters the station, lime, pre-melted refined slag and other slag materials are added in the first heating process according to the top slag condition for slagging. LF is refined for 22 minutes to form white slag, wherein the CaO content is 52%, the SiO2 content is 12%, the Al2O3 content is 26%, the (FeO+MnO) content is 0.9%, the binary basicity (CaO / SiO2) is controlled at 4.3, and the CaO / Al2O3 ratio is 2; the refined slag amount is 14kg / ton steel, the subsequent heating time after slag formation is T1=13min, the alloying strong stirring time T2=5min, and a total of 34kg of slag-keeping aluminum particles are added. The CaO content of the LF final slag is 49%, the SiO2 content is 11%, the Al2O3 content is 29%, the (FeO+MnO) content is 0.5%, the binary basicity (CaO / SiO2) is controlled at 4.5, and the CaO / Al2O3 ratio is controlled at 1.7; the LF refining cycle is 71min;

[0150] 5) Vacuum refining: vacuum degree 74Pa, vacuum treatment cycle 16min, hydrogen [H] content 0.5ppm before breaking, adding 202kg of heat preservation agent, soft blowing argon flow rate 15NL / min, soft blowing time 10min;

[0151] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 31ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0152] 7) After the billet is rolled, the initial inspection of the shaft billet inclusion test fails. Among them, the Ds inclusion rating is 2.0, and the axle Ds The inclusion inspection passed, and the Ds type inclusion rating was 1.5. This is mainly because the large amount of slag will increase the amount of deoxidizer added and the amount of deoxidized inclusions generated, making it difficult to remove.

[0153] Comparative Example 3:

[0154] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0155] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.012%, an S content of 0.031%, and an iron-steel ratio of 50%;

[0156] 2) The electric furnace end point carbon content is 0.13%, phosphorus content is 0.009%, end point [O] content is 201ppm, end point temperature is 1658°C, and the slag amount is about 2.6kg / ton steel;

[0157] 3) Add during steel tapping Aluminum iron 3.5kg / ton steel , lime 4.5kg / ton steel, pre-melted refined slag 3.0kg / ton steel, ladle bottom blowing argon flow rate 500NL / min during tapping, strong stirring 5min;

[0158] (4) The aluminum content alloying control in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the top slag condition to make slag. The LF is refined for 20 minutes to form white slag, in which the CaO content is 55%. SiO2 content 7% , Al2O3 content 31%, (FeO+MnO) content 0.6%, binary basicity (CaO / SiO2) ＝7.9 , CaO / Al2O3 ratio is controlled at 1.8, refined slag amount is 13kg / ton steel, subsequent heating time after slag formation is T1=12min, alloying strong stirring time is T2=5min, a total of 49kg of slag-preserving silicon ball deoxidizer is added, LF final slag Ca content is 53%, SiO2 content is 10%, Al2O3 content is 29%, (FeO+MnO) content is 0.5%, binary basicity (CaO / SiO2) ＝5.3 , CaO / Al2O3 ratio is controlled at 1.8; LF refining cycle is 71min;

[0159] 5) Vacuum refining: vacuum degree 66Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 201kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 5min;

[0160] 6) The molten steel is put on the platform and left to stand for 23 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 24ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0161] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds inclusion rating is 2.5, and the axle Ds inclusion rating is 2.5. The debris inspection failed, and the Ds inclusion rating was 2.0. Comparative Example 3 uses aluminum deoxidation, and the basicity of the refined top slag is high, which increases the activity of calcium ions and denatures the inclusions to form Ds-type inclusions, which are difficult to remove.

[0162] Comparative Example 4:

[0163] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0164] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.012%, an S content of 0.028%, and an iron-steel ratio of 40%;

[0165] 2) The electric furnace end point carbon content is 0.13%, phosphorus content is 0.006%, end point [O] content is 213ppm, end point temperature is 1630°C, and the slag amount is about 3.0kg / ton steel;

[0166] 3) During the tapping process, 0.5 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.0 kg of lime per ton of steel, and 3.5 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0167] 4) The alloying control of aluminum content in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process depending on the top slag condition to make slag. The LF is refined for 24 minutes to form white slag, wherein the CaO content is 51%, the SiO2 content is 13%, the Al2O3 content is 25%, the (FeO+MnO) content is 0.8%, the binary basicity (CaO / SiO2) is controlled at 3.9, the CaO / Al2O3 ratio is controlled at 2.0, the refined slag amount is 15kg / ton of steel, the subsequent heating time after the slag is formed is T1=16min, the alloying strong stirring time T2=5min, and a total of 40kg of slag-keeping aluminum particles are added. The CaO content of the LF final slag is 48%, the SiO2 content is 11%, the Al2O3 content is 30%, the (FeO+MnO) content is 0.5%, the binary basicity (CaO / SiO2) is controlled at 4.4, and the CaO / Al2O3 ratio is controlled at 1.6; LF Essence Training cycle 81 minutes ;

[0168] 5) Vacuum refining: vacuum degree 64Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 201kg of heat preservation agent, soft blowing argon flow rate 15NL / min, soft blowing time 10min;

[0169] 6) The molten steel is put on the platform and left to stand for 26 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 35ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0170] 7) After the billet is rolled, the initial inspection of the shaft billet inclusion test fails. Among them, the Ds inclusion rating is 2.0, and the axle Ds The inclusion inspection passed, and the Ds type inclusion rating was 1.5. The LF refining cycle of Comparative Example 4 exceeds 80 minutes. The long LF refining time not only affects the molten steel in the secondary oxidation and generates a large amount of inclusions, but also increases the corrosion of the ladle refractory by the molten steel and the top slag, which easily leads to the formation of Ds-type inclusions.

[0171] Comparative Example 5:

[0172] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0173] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.011%, an S content of 0.026%, and an iron-steel ratio of 50%;

[0174] 2) The electric furnace end point carbon content is 0.15%, phosphorus content is 0.007%, end point [O] content is 184ppm, end point temperature is 1657°C, and the slag amount is about 2.5kg / ton steel;

[0175] 3) Add during steel tapping Silica deoxidizer 1.8kg / ton steel, aluminum iron 1.4kg / ton steel , lime 4.5kg / ton steel, pre-melted refined slag 3.0kg / ton steel, alloy addition target is controlled according to the lower limit of steel grade internal control; during the steel tapping process, the ladle bottom blowing argon flow rate is 500NL / min, and strong stirring is 5min;

[0176] 4) During the LF refining process, the aluminum content alloying control is carried out in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 22 minutes to form white slag, of which the CaO content is 52%, the SiO2 content is 18%, the Al2O3 content is 22%, the (FeO+MnO) content is 0.8%, and the binary basicity (CaO / SiO2) is controlled at 2.9. The CaO / Al2O3 ratio is controlled at 2.4, The amount of refined slag is 14kg / ton of steel. The subsequent heating time after slag formation is T1=12min, and the alloying strong stirring time is T2=5min. A total of 29kg of slag-preserving aluminum particles are added. The Ca0 content of the LF final slag is 51%, the SiO2 content is 17%, the Al2O3 content is 24%, and the (FeO+MnO) content is 0.8%. The binary basicity (CaO / SiO2) is controlled at 3.0. The CaO / Al2O3 ratio is controlled at 2.1 ;LF refining cycle 76min;

[0177] 5) Vacuum refining: vacuum degree 63Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 199kg of insulation agent, soft blowing argon flow rate 20NL / min, soft blowing time 7min;

[0178] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 25ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0179] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds type inclusions were rated 2.0, and the shaft blank was re-classified.The refined slag (CaO / Al2O3) of Comparative Example 5 is greater than 2.0, the top slag has poor fluidity, poor adsorption capacity for inclusions, and great difficulty in removing inclusions.

[0180] Comparative Example 6:

[0181] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0182] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.012%, an S content of 0.032%, and an iron-steel ratio of 40%;

[0183] 2) The electric furnace end point carbon content is 0.12%, phosphorus content is 0.009%, end point [O] content is 232ppm, end point temperature is 1662°C, and the slag amount is about 2.5kg / ton steel;

[0184] 3) During the tapping process, 0.6 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 3.0 kg of lime per ton of steel, and 2.5 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0185] 4) The aluminum content alloying control in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the top slag condition to make slag. The LF is refined for 20 minutes to form white slag. CaO content 39％ , SiO2 content is 14%, Al2O3 content is 33%, (FeO+MnO) content is 0.8%, binary basicity (CaO / SiO2) is controlled at 2.8, CaO / Al2O3 ratio is controlled at 1.2, refined slag amount is 12kg / ton steel, subsequent heating time after slag formation is T1=12min, alloying strong stirring time is T2=5min, a total of 32kg of slag-preserving aluminum particles are added, LF final slag Ca0 content is 35%, SiO2 content is 11%, Al2O3 content is 36%, (FeO+MnO) content is 0.6%, binary basicity (CaO / SiO2) is controlled at 3.2, CaO / Al2O3 ratio is 0.97; LF refining cycle 72min;

[0186] 5) Vacuum refining: vacuum degree 69Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.7ppm before breaking, adding 201kg of heat preservation agent, soft blowing argon flow rate 15NL / min, soft blowing time 10min;

[0187] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the medium ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 33ppm when sampling from the RH station to the medium ladle (when the large ladle is cast 1 / 2).

[0188] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds inclusion rating is 2.0, and the axle Ds inclusion The material inspection failed, and the Ds inclusion rating was 2.0. This is mainly because the LF final slag (CaO / Al2O3) is less than 1.0, the top slag is too thin, and the adsorption capacity for inclusions is poor.

[0189] Comparative Example 7:

[0190] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0191] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.013%, an S content of 0.028%, and an iron-steel ratio of 30%;

[0192] 2) The electric furnace end point carbon content is 0.11%, phosphorus content is 0.008%, end point [O] content is 214ppm, end point temperature is 1656°C, and the slag amount is about 2.1kg / ton steel;

[0193] 3) During the tapping process, 0.8 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.5 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0194] 4) During the LF refining process, the aluminum content alloying control is carried out in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 21 minutes to form white slag, of which the CaO content is 55%, the SiO2 content is 16%, the Al2O3 content is 23%, the (FeO+MnO) content is 0.6%, and the binary basicity (CaO / SiO2) is 3.4. CaO / Al2O3 ratio = 2.4, The amount of refined slag is 14kg / ton steel. The subsequent heating time after slag formation is T1=12min, the alloying strong stirring time is T2=5min, and a total of 32kg of slag-preserving aluminum particles are added. The Ca0 content of the LF final slag is 53%, the SiO2 content is 15%, the Al2O3 content is 25%, and the (FeO+MnO) content is 0.5%. The binary basicity (CaO / SiO2) is controlled at 3.5. CaO / Al2O3 ratio = 2.1, (CaO / Al2O3) is greater than 2.0, and the LF refining cycle is 73min;

[0195] 5) Vacuum refining: vacuum degree 68Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 198kg of insulation agent, soft blowing argon flow rate 15NL / min, soft blowing time 8min;

[0196] 6) The molten steel is placed on the platform and allowed to stand for 25 minutes. When the RH is discharged from the station and the tundish is sampled (when the ladle is 1 / 2 cast), the Als loss is controlled at 27ppm.

[0197] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds inclusion rating is 2.5, and the axle Ds inclusion The material inspection failed, and the Ds inclusion rating was 2.0. This is mainly because (CaO / Al2O3) is greater than 2.0, the top slag has poor fluidity, poor adsorption capacity for inclusions, and great difficulty in removing inclusions.

[0198] Comparative Example 8:

[0199] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0200] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.011%, an S content of 0.034%, and an iron-steel ratio of 50%;

[0201] 2) The electric furnace has an endpoint carbon content of 0.15%, a phosphorus content of 0.007%, an [O] content of 185 ppm, an endpoint temperature of 1662°C, and a slag quantity of approximately 2.5 kg / ton of steel;

[0202] 3) During the tapping process, 0.8 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.0 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0203] (4) The alloying control of aluminum content in the LF refining process is carried out in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 20 minutes to form white slag, of which the CaO content is 50%, the SiO2 content is 12%, the Al2O3 content is 30%, the (FeO+MnO) content is 0.6%, the binary basicity (CaO / SiO2) is controlled at 4.2, and the CaO / Al2O3 ratio is controlled at 1.7. The amount of refined slag is 13kg / ton steel. The subsequent heating time after slag formation is T1=12min, the alloying strong stirring time is T2=5min, and a total of 49kg of slag-preserving silicon ball deoxidizer is added. The CaO content of the LF final slag is 49%, the SiO2 content is 14%, the Al2O3 content is 30%, and the (FeO+MnO) content is 0.5%. The binary basicity (CaO / SiO2) is controlled at 3.5, and the CaO / Al2O3 ratio is controlled at 1.6. The LF refining cycle is 73min.

[0204] 5) Vacuum refining: vacuum degree 66Pa, vacuum treatment cycle 15min, hydrogen [H] content before breaking the air is 0.6ppm, Breaking the Sky Add insulation, soft blowing argon flow rate 15NL / min, soft blowing time 10min;

[0205] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 37ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0206] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds inclusions were rated as 2.0, and the shaft blank was rated as II Class Axle, Axle Ds Class Inclusion Rating 2.0. This is mainly because no insulation agent is added. On the one hand, it is greatly affected by secondary oxidation, and on the other hand, the top slag is prone to crusting, and the ability to adsorb and remove inclusions is poor.

[0207] Comparative Example 9:

[0208] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0209] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.010%, an S content of 0.028%, and an iron-steel ratio of 60%;

[0210] 2) The electric furnace end point carbon content is 0.15%, phosphorus content is 0.006%, end point [O] content is 184ppm, end point temperature is 1661°C, and the slag amount is about 1.8kg / ton steel;

[0211] 3) During the tapping process, 0.9 kg of silicon deoxidizer per ton of steel, 2.6 kg of aluminum iron per ton of steel, 4.3 kg of lime per ton of steel, and 3.0 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0212] 4) During the LF refining process, the aluminum content alloying control is carried out in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 20 minutes to form white slag, of which the CaO content is 54%, the SiO2 content is 13%, the Al2O3 content is 31%, the (FeO+MnO) content is 0.6%, the binary basicity (CaO / SiO2) is controlled at 4.2, and the CaO / Al2O3 ratio is controlled at 1.7. The amount of refined slag was 14 kg / ton of steel. The subsequent heating time after slag formation was T1 = 12 min, the alloying strong stirring time was T2 = 5 min, and a total of 49 kg of slag-preserving silicon ball deoxidizer was added. The CaO content of the LF final slag was 51%, the SiO2 content was 15%, the Al2O3 content was 30%, and the (FeO+MnO) content was 0.5%. The binary basicity (CaO / SiO2) was controlled at 3.4, and the CaO / Al2O3 ratio was controlled at 1.7. The LF refining cycle was 71 min.

[0213] 5) Vacuum refining: vacuum degree 66Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 204kg of heat preservation agent, soft blowing argon flow rate 20NL / min, Soft blowing time 4min;

[0214] 6) The molten steel is put on the platform and left to stand for 26 minutes. During the casting process, the "long nozzle of the large ladle + the middle ladle + the immersed nozzle" should be used to protect the casting. The Als loss is controlled at 33ppm when sampling from the RH station to the middle ladle (when the large ladle is cast 1 / 2).

[0215] 7) After the billet is rolled, the shaft billet inclusion inspection fails. Among them, the Ds inclusion rating is 2.0, and the axle Ds inclusion The material inspection failed, and the Ds inclusion rating was 2.0. This is mainly because the soft blowing time after RH breaks the air is less than 5 minutes, and the power for inclusions to accumulate, float up and be removed is weak.

[0216] Comparative Example 10:

[0217] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0218] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.011%, an S content of 0.025%, and an iron-steel ratio of 60%;

[0219] 2) The electric furnace end point carbon content is 0.14%, phosphorus content is 0.009%, end point [O] content is 192ppm, end point temperature is 1664°C, and the slag amount is about 2.4kg / ton steel;

[0220] 3) During the tapping process, 0.7 kg of silicon deoxidizer per ton of steel, 3.0 kg of aluminum iron per ton of steel, 4.0 kg of lime per ton of steel, and 3.2 kg of pre-melted refined slag per ton of steel were added. During the tapping process, the ladle bottom was blown with an argon flow rate of 500 NL / min and strong stirring was performed for 5 minutes.

[0221] 4) During the LF refining process, the aluminum content alloying control is carried out in the early stage of refining. After the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 22 minutes to form white slag, of which the CaO content is 54%, the SiO2 content is 11%, the Al2O3 content is 31%, the (FeO+MnO) content is 0.6%, the binary basicity (CaO / SiO2) is controlled at 4.9, and the CaO / Al2O3 ratio is controlled at 1.7. The amount of refined slag was 14 kg / ton of steel. The subsequent heating time after slag formation was T1 = 13 min, the alloying strong stirring time was T2 = 5 min, and a total of 52 kg of slag-preserving silicon ball deoxidizer was added. The CaO content of the LF final slag was 52%, the SiO2 content was 14%, the Al2O3 content was 29%, and the (FeO+MnO) content was 0.5%. The binary basicity (CaO / SiO2) was controlled at 3.7, and the CaO / Al2O3 ratio was controlled at 1.8. The LF refining cycle was 67 min.

[0222] 5) Vacuum refining: vacuum degree 59Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.5ppm before breaking, adding 203kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 10min;

[0223] 6) The molten steel was placed on the platform and allowed to stand for 19 minutes During the casting process, the "long nozzle for large ladle + medium ladle + immersed nozzle" protection casting should be done well, and the Als loss is controlled at 26ppm when sampling from RH out of the station to the medium ladle (when the large ladle is cast 1 / 2).

[0224] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds inclusion rating is 2.0, and the axle Ds inclusion The material inspection passed once, and the Ds inclusion rating was 1.5. This is mainly because the molten steel stays on the platform for less than 20 minutes, which is not conducive to the aggregation, floating and removal of inclusions.

[0225] Comparative Example 11:

[0226] A method for controlling DS-type inclusions in axle steel during smelting, comprising the following steps:

[0227] 1) The steel produced in this embodiment is axle steel EA1N, the molten iron entering the furnace has a P content of 0.012%, an S content of 0.032%, and an iron-steel ratio of 60%;

[0228] 2) The electric furnace end point carbon content is 0.10%, phosphorus content is 0.008%, end point [O] content is 243ppm, end point temperature is 1671°C, and the slag amount is about 2.9kg / ton steel;

[0229] 3) During the tapping process, 0.6 kg of silicon deoxidizer per ton of steel, 2.9 kg of aluminum iron per ton of steel, 4.1 kg of lime per ton of steel, and 2.7 kg of pre-melted refined slag per ton of steel were added. The target amount of alloy addition was controlled according to the lower limit of the internal control of the steel grade. During the tapping process, the ladle bottom blowing argon flow rate was 500 NL / min, and strong stirring was performed for 5 minutes.

[0230] 4) The aluminum content alloying control in the LF refining process is carried out in the early stage of refining; after the LF enters the station, lime, pre-melted refined slag and other slag materials are added during the first heating process according to the condition of the top slag to make slag. The LF is refined for 21 minutes to form white slag, of which the CaO content is 53%, the SiO2 content is 11%, the Al2O3 content is 33%, the (FeO+MnO) content is 0.6%, the binary basicity (CaO / SiO2) is controlled at 4.8, and the CaO / Al2O3 ratio is controlled at 1.6. The amount of refined slag is 15kg / ton steel. The subsequent heating time after slag formation is T1=12min, the alloying strong stirring time is T2=5min, and a total of 49kg of slag-preserving silicon ball deoxidizer is added. The Ca content of the LF final slag is 51%, the SiO2 content is 14%, the Al2O3 content is 32%, and the (FeO+MnO) content is 0.5%. The binary basicity (CaO / SiO2) is controlled at 3.6, and the CaO / Al2O3 ratio is controlled at 1.6. The LF refining cycle is 72min.

[0231] 5) Vacuum refining: vacuum degree 73Pa, vacuum treatment cycle 15min, hydrogen [H] content 0.6ppm before breaking, adding 204kg of heat preservation agent, soft blowing argon flow rate 20NL / min, soft blowing time 8min;

[0232] 6) The molten steel is put on the platform and left to stand for 25 minutes. During the casting process, the “large ladle long nozzle + middle ladle + immersed nozzle” protection casting should be done well. When sampling from the RH station to the tundish (when the ladle was halfway through pouring), the Als loss was 41ppm, which may be caused by improper protection pouring operation;

[0233] 7) After the billet is rolled, the shaft billet inclusions are unqualified in the initial inspection. Among them, the Ds inclusion rating is 2.0, and the axle Ds inclusion The material inspection failed, and the Ds inclusion rating was 2.0. This is mainly because the aluminum loss in the tundish exceeds 40ppm, the molten steel is severely subjected to secondary oxidation during the casting process, and the resulting inclusions are difficult to remove.

[0234] The underlined data above are data that do not meet the requirements of the present invention.

Claims

1. A method for controlling smelting of Ds-type inclusions in axle steel, characterized in that: The axle steel Ds-type inclusion smelting control method comprises the following steps: 1) The molten iron entering the furnace must have a P content of ≤0.014% and a S content of ≤0.040%; 2) Smelting endpoint control requirements include C content of 0.10%-0.25%, P content ≤0.012%, [O] content ≤250ppm, and endpoint temperature of 1630-1680℃; 3) Deoxidation and alloying during the steel tapping process; 4) LF refining; 5) Vacuum refining; 6) Protect casting; In step 3), when 1 / 4-1 / 3 of the steel is tapped, silicon deoxidizer, aluminum iron, slag material and alloy are added in sequence; The amount of the silicon deoxidizer added is 0.5-1.0 kg / ton of steel, the amount of aluminum and iron added is 2.5-3.0 kg / ton of steel, and the amount of slag material added is 5.5-8.0 kg / ton of steel; In step 4), the aluminum content alloying in the LF refining process is controlled in the early stage of refining. After the LF enters the station, lime and pre-melted refined slag are added to make slag. After slagging, the refined slag composition meets the following conditions: CaO content 40-55%, SiO2 content 10-18%, Al2O3 content 20-35%, (FeO+MnO) ≤ 1.0%, binary basicity (CaO / SiO2) controlled at 2.8-5.0, CaO / Al2O3 ratio controlled at 1.0-2.0, and the refined slag amount controlled at 12-15 kg / ton of steel; In step 4), the slag is quickly formed and the subsequent refining process is completed by adding aluminum particles or silicon deoxidizer to maintain the slag; The specific slag protection is as follows: the amount of aluminum particles added during the heating process is controlled according to (1.5-2.5×T1) kg, where T1 is the heating time at that time, in minutes; or the amount of silicon deoxidizer added is controlled according to (2.5-3.5×T1) kg; The amount of aluminum particles added during the alloying process is controlled according to (1.0-2.0×T2) kg, where T2 is the strong stirring time (in minutes), or the amount of silicon deoxidizer added is controlled according to (2.0-3.0×T2) kg; The axle steel produced has Ds inclusion ratings below level 1.0, A inclusions are stably controlled below level 1.0, B inclusions are stably controlled below level 0.5, there are no C inclusions, and D inclusions are stably controlled below level 1.

0.

2. The method for controlling Ds-type inclusions in axle steel according to claim 1, characterized in that: The slag-making material includes lime and pre-melted refined slag; the amount of lime added is 3.0-4.5 kg / ton of steel, and the amount of pre-melted refined slag added is 2.5-3.5 kg / ton of steel.

3. The method for controlling Ds-type inclusions in axle steel according to claim 1, characterized in that: In step 5), the vacuum degree of vacuum refining is controlled to be ≤100Pa, the vacuum treatment cycle is more than 15min, the hydrogen content before breaking the air is ≤1.0ppm, and the insulation agent is evenly added to the slag surface after breaking the air. After the insulation agent is added, the molten steel is soft-blown, and the bottom blowing flow rate is controlled to be 10~20NL / min, and the soft blowing time is 5~10min.

4. The method for controlling Ds-type inclusions in axle steel according to claim 1, characterized in that: Step 6) is as follows: after the molten steel is put on the platform, it is allowed to stand for 20-30 minutes before pouring, and protective casting is adopted. The Als loss is controlled to be ≤40ppm from the time of leaving the station to sampling in the tundish.

Images