Smelting method of grinding ball steel 2CR

Abstract

The invention belongs to the technical field of steelmaking, and discloses a smelting method of grinding ball steel 2CR. The method provided by the invention is reliable and stable, can ensure that high-quality grinding ball steel 2CR is produced, and lays a solid foundation for adapting to market development. The method comprises the working procedures of converter smelting, LF refining, VD vacuum treatment and continuous casting. During refining, slagging, deoxidation and calcium treatment are carried out; after vacuum treatment, a manganese iron nitride wire needs to be fed for increasing nitrogen, and then a titanium iron wire is fed for increasing titanium; finally, an aluminum wire is fed for final deoxidation, and the oxygen content in the steel is further reduced; the method provided by the invention is reliable and stable, can ensure that high-quality grinding ball steel 2CR is produced, and lays a solid foundation for adapting to market development.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, in particular to a smelting method of grinding ball steel 2CR. Background Art

[0002] The production technology background of grinding ball steel is closely related to the progress of industrial development and materials science. With the rapid development of industrial technology, the performance and quality requirements of grinding ball steel are getting higher and higher. The traditional grinding ball steel production process has gradually failed to meet the needs of modern industry, so the grinding ball steel production technology is also constantly innovating and improving.

[0003] In terms of materials science, with the development and application of new wear-resistant and corrosion-resistant alloy materials, the performance of grinding ball steel has been significantly improved. These new materials have higher hardness, better wear resistance and corrosion resistance, which enable grinding ball steel to maintain a longer service life even in harsh working environments. At the same time, the progress of steelmaking technology has also provided better conditions for the production of grinding ball steel. Modern steelmaking technology can produce grinding ball steel with more stable performance and more reliable quality by precisely controlling chemical composition and optimizing smelting processes. In the production process of grinding ball steel, advanced processing and heat treatment technologies are also required to ensure the accuracy of its shape, size and performance. These technologies include precision casting, forging, heat treatment, etc., which can achieve precise control and optimization of grinding ball steel, so as to meet the use requirements under various complex working conditions. Magic ball steel has been widely used in the production of many industries such as metallurgy, mining, building materials, chemical industry, electric power and pharmaceuticals due to its high hardness, good toughness, excellent hardenability, good corrosion resistance and reasonable microstructure.

[0004] The growing demand for high-quality grinding ball steel will drive the development of related industrial chains, such as equipment manufacturing, raw material supply, testing services and other industries will benefit. With the continuous expansion of the application field of grinding ball steel, it will also give rise to new industries and market demands, injecting new impetus into economic development. Compared with ordinary steel, grinding ball steel 2CR has higher hardness, better wear resistance and impact resistance, can significantly extend the service life and reduce production costs. In order to meet market demand and promote the development of high-quality grinding ball steel, our factory invented the production process of 2CR grinding ball steel. Summary of the invention

[0005] In response to current market demand, the present invention provides a smelting method for grinding ball steel 2CR.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A grinding ball steel, wherein the components are measured by mass percentage: C: 1.02-1.06%, Si: 0.11-0.17%, Mn: 0.21-0.27%, P: ≤0.020%, S: ≤0.010%, Cr: 1.96-2.02%, Mo: ≤0.080%, Al: 0.016-0.025%, Ti: 0.010-0.022%, Ni: ≤0.100%, Cu: ≤0.100%, V: ≤0.015%, N: 0.006-0.009%, H: ≤0.00015%, Sn: ≤0.015%, Di: 3.10-6.00.

[0008] Furthermore, a grinding ball steel is provided, wherein the components, measured in mass percentage, include: C: 1.04%, Si: 0.14%, Mn: 0.24%, P: ≤0.018%, S: ≤0.010%, Cr: 1.99%, Mo: ≤0.060%, Al: 0.020%, Ti: 0.016%, Ni: ≤0.100%, Cu: ≤0.100%, V: ≤0.010%, N: 0.0075%, H: ≤0.00015%, Sn: ≤0.010%, and Di: 3.10-6.00.

[0009] Note: Di=[0.062+0.409(C%)-0.135(C%)*(C%)]*[1+3.333(Mn%)]*[1+0.7(Si%)]*[1+2.16(Cr%)]*[1+3(Mo%)]*[1+0.363(Ni%)]*[1+0.365(Cu%)]

[0010] A smelting method for grinding ball steel 2CR mainly includes four processes: converter → refining → VD vacuum treatment → continuous casting. The following are the main control points of the four processes.

[0011] (1) Converter:

[0012] The raw and auxiliary materials include molten iron, scrap steel and ladle; the total input of the converter is 53-59 tons, the output is controlled at 50-54 tons, argon is blown at the bottom throughout the process, and the three bottom blowing flows are all controlled at 45.8m 3 / h, the final carbon content of the converter blowing is controlled between 0.08% and 0.30%, and the final temperature is greater than 1600°C; the slag blocking method of the slag blocking cone and the slide plate is used in the steel tapping process, and the deoxidizer, the carburizer, the alloy and the top slag are added in sequence during the steel tapping process, and the composition of the obtained molten steel is controlled to be C: 0.94%-1.00%, Si: 0.07%-0.12%, Mn: 0.10%-0.16%, Cr: 1.82%-1.92%;

[0013] The deoxidizer is an aluminum block.

[0014] When the end point C content is ≤0.05%, the amount of aluminum block added is 50kg / furnace of steel;

[0015] When the end point C content is 0.06-0.12%, the amount of aluminum block added is 40kg / furnace of steel;

[0016] When the final C content is ≥0.13%, the amount of aluminum block added is 30kg / furnace of steel;

[0017] The top slag material is lime and calcium aluminate cleaner, the amount of lime added is 260-300kg / furnace steel, and the amount of calcium aluminate cleaner added is 400-440kg / furnace steel.

[0018] The alloy is selected from high carbon ferromanganese and high carbon ferrochromium.

[0019] (2) Refining:

[0020] The raw and auxiliary materials of the refining furnace include alloys, carburizers, lime, fluorite, silicon carbide, calcium carbide, aluminum wire, and calcium wire; the alloys include silicon manganese alloy, ferrosilicon alloy, medium carbon ferromanganese alloy, high carbon ferromanganese alloy, medium carbon ferrochrome alloy, or high carbon ferrochrome alloy;

[0021] When making slag, lime and a small amount of fluorite are used as slag materials for the refining furnace. The specific amount added is determined by the final carbon content of the converter: when the final carbon content is ≤0.05%, 50-100kg lime / furnace is added; when the final carbon content is between 0.06% and 0.12%, 30-50kg lime / furnace is added; when the final carbon content is ≥0.13%, no lime is added;

[0022] During deoxidation, calcium carbide and silicon carbide are added to the molten steel of the refining furnace for rapid deoxidation, and small amounts are added multiple times; the total deoxidizer usage is ≥80kg / furnace; after slag making and deoxidation, alloy is added according to the composition of the first molten steel sample, and aluminum wire is fed at [Alt] = 0.030%, ensuring that [Alt] of the refining furnace out of the station is between 0.019% and 0.025%;

[0023] After slag making and deoxidation, calcium treatment is carried out when the composition is qualified. The total deoxidation and slag making time before calcium treatment must be greater than 20 minutes; the number of meters of wire feeding is determined according to the slag state, and the number of meters is controlled between 30 and 50 meters;

[0024] The temperature of the first refining furnace to be started up must be between 1600 and 1615°C, and the temperature of the second refining furnace and continuous casting furnace to be started up must be between 1560 and 1570°C.

[0025] (3) VD vacuum treatment:

[0026] The vacuum degree requirement is ≤67Pa, and the high vacuum holding time requirement is ≥15min; after vacuum treatment, nitrided manganese iron wire needs to be fed for nitrogen addition (reference value 15-25 meters), and then titanium iron wire is fed for titanium addition (reference value 25 meters); finally, aluminum wire is fed for "final deoxidation" to further reduce the oxygen content in the steel, and aluminum is directly reacted with residual oxygen in the molten steel to form alumina; 20 meters of calcium wire needs to be fed into the first furnace when the machine is started, and 0-20 meters of calcium wire needs to be fed into the second furnace and the continuous casting furnace according to the slag state; the soft blowing time requirement is ≥20min; the VD leaving station temperature of the first furnace when the machine is started is required to be between 1522 and 1532℃, and the VD leaving station temperature of the second furnace and the continuous casting furnace is required to be between 1490 and 1500℃.

[0027] (4) Continuous casting

[0028] The working layer of the tundish is made of magnesium. The stopper rod for tundish flow control is made of aluminum carbon body + magnesium rod head. The material of the submerged nozzle is aluminum carbon body + zirconium slag line. The material of the long nozzle is aluminum carbon. The type of tundish covering agent is tundish carbon-free covering agent 03. The type of crystallizer protection slag can be SPH-C189 / VV1 or XBF-G1.

[0029] The tundish temperature of the first furnace is controlled between 1477-1492℃, and the superheat is 30-45℃; the tundish temperature of the second furnace is controlled between 1467-1477℃, and the superheat is 20-30℃; the tundish temperature of the continuous casting furnace is the same as the second furnace, and the tundish temperature is controlled between 1467-1477℃, and the superheat is 20-30℃;

[0030] When the steel grade superheat is ≥46℃, the continuous casting speed is 0.85m / min; when the steel grade superheat is 36-45℃, the continuous casting speed is 0.90m / min; when the steel grade superheat is 20-35℃, the continuous casting speed is 0.95m / min; when the steel grade superheat is ≤19℃, the continuous casting speed is 1.00m / min; the adjustment range of the casting speed per minute does not exceed 0.05m / min;

[0031] The crystallizer water flow rate is controlled at above 1900L / min;

[0032] The insertion depth of the submerged nozzle is between 80mm-140mm

[0033] The electromagnetic stirring current of the billet continuous casting machine is 400A, the terminal electric stirring (F-MES) current is 500A, and the frequency is between 1Hz-10Hz;

[0034] The length of the steel head and tail cutting is between 2.5 meters and 4.0 meters.

[0035] The beneficial effects of the present invention are:

[0036] The method provided by the invention is reliable and stable, and can ensure the production of high-quality grinding ball steel 2CR, thus laying a solid foundation for adapting to market development. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The plugging rod curve of the present invention is shown in the following figure. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] There are four main processes in the production of this type of steel in a steel mill: converter → refining → VD vacuum treatment → continuous casting. The following are the main control points of the four processes.

[0040] (I) Key points of converter control

[0041] The converter process mainly involves adding molten iron into the converter and then using an oxygen lance to supply oxygen into the furnace. The molten iron in the furnace begins to undergo an oxidation reaction to consume silicon, manganese, and carbon in the molten iron, and remove harmful elements such as phosphorus and sulfur. Various raw and auxiliary materials need to be added during the blowing process to ensure that the reaction in the furnace proceeds stably and to avoid splashing. When the composition and temperature in the furnace meet the requirements of the steel grade, the steel is tapped, the smelted molten steel is poured into the ladle, and the alloy is deoxidized. After tapping, the molten steel is hoisted to the refining furnace for the next step.

[0042] The specific control points of the converter are as follows:

[0043] 1. Raw and auxiliary materials

[0044] The raw and auxiliary materials used in the converter include molten iron, scrap steel and ladle. Use C, D, E, B (when the Sn element meets the standard requirements, B-type molten iron can be used) molten iron; avoid C-type self-produced scrap steel, D-type self-produced scrap steel, E-type self-produced scrap steel, and F-type self-produced scrap steel to avoid excessive trace elements in alloys. Avoid large and small repair ladles, the first time, and unrefined construction steel ladles; Zirconium (YL-4) drainage sand is used for ladle drainage.

[0045] 2. Loading system

[0046] The total amount of molten steel transferred into the converter is between 53 tons and 59 tons, and it is prohibited to add less or more steel which will affect the blowing; the output of steel is controlled between 50 tons and 54 tons, and the amount of molten steel in the ladle is stabilized to create good conditions for subsequent refining and VD smelting.

[0047] 3. Bottom blowing requirements

[0048] The converter bottom blowing adopts the full argon blowing mode, and the three bottom blowing flows are all controlled at 45.8m 3 / h, allowing uniform reaction in the furnace to increase the dephosphorization rate. Argon is blown from the bottom of the ladle during the entire steel-making process to fully deslagging and avoid alloy agglomeration.

[0049] 4. Converter endpoint control

[0050] The final carbon content of converter blowing is controlled between 0.08% and 0.30%. If the final carbon content is too low, it will easily lead to overoxidation of molten steel and increase the risk of continuous casting floccules. If the final carbon content is too high, the amount of carbon powder added to the steel will be unstable. In addition, the deoxidation and carbon increase in the refining furnace will easily lead to the carbon content of molten steel exceeding the standard. The final temperature must be greater than 1600℃. If it is lower than this temperature, the refining furnace will consume more electrodes for heating, resulting in cost waste.

[0051] 5. Steel tapping control

[0052] The tapping process uses a slag cone and a slide plate to block the slag, which can minimize the rephosphorization. The tapping material is strictly in the order of deoxidizer → carburizer → alloy → top slag; the deoxidizer is aluminum block, and the top slag material is lime and calcium aluminate cleaner, and the specific amount is determined by the end carbon content. The alloy is high carbon ferromanganese and high carbon ferrochrome.

[0053] Deoxidizer dosage:

[0054] name End point C content (%) Addition amount (kg) Aluminum Block ≤0.05 50 Aluminum Block 0.06-0.12 40 Aluminum Block ≥0.13 30

[0055] Top slag material dosage:

[0056] Product Name Range(kg) Target addition amount (kg) lime 260-300 280 Calcium Aluminate Cleaner 400-440 420

[0057] 6. LF entry component target

[0058] In order to stabilize the refining cycle, the composition of the refining furnace entering the station is controlled as follows: C: 0.94%-1.00%, Si: 0.07%-0.12%, Mn: 0.10%-0.16%, Cr: 1.82%-1.92%. The argon blowing station can add an appropriate amount of manganese alloy, but it is forbidden to feed aluminum wire to the argon blowing station.

[0059] (II) Key points of LF refining control

[0060] The steelmaking and refining process is the next process after the converter taps steel. Its main functions are:

[0061] 1) Removal of impurities and oxides in molten steel: Through physical and chemical reactions under high temperature and high pressure, impurities, oxides and other harmful components in molten steel can be effectively removed, making the composition of molten steel purer and more uniform, thereby ensuring the quality and performance of steel.

[0062] 2) Improve the quality and performance of molten steel: Through a sophisticated processing process, the smelting composition of molten steel can be accurately controlled, and the quality, chemical properties, physical properties and process performance of steel can be improved, thereby enhancing the market competitiveness of the product.

[0063] 3) Improve the utilization value of steel: The treatment in the refining furnace helps to homogenize the steel structure, reduce the heterogeneity in the structure, and reduce the impurity content, which is crucial to improving the utilization value of steel.

[0064] The specific control points of the refining furnace are as follows:

[0065] 1. Raw and auxiliary materials

[0066] The raw and auxiliary materials of the refining furnace include alloy, carburizer, lime, fluorite, silicon carbide, calcium carbide, aluminum wire, and calcium wire. When the alloy composition of molten steel is insufficient, silicon manganese alloy, silicon iron alloy, medium carbon manganese iron alloy, high carbon manganese iron alloy, medium carbon ferrochrome alloy, and high carbon ferrochrome alloy can be used.

[0067] 2. Slag making and deoxidation

[0068] After the refining furnace enters the station, slag making and deoxidation are carried out to remove inclusions in the molten steel.

[0069] 2.1 Slag making

[0070] Lime and a small amount of fluorite are used as slag materials for the refining furnace. The specific amount added is determined by the final carbon content of the converter: 50-100kg of lime is added when the final C content is ≤0.05%; 30-50kg of lime is added when the final C content is between 0.06% and 0.12%; no lime is added when the final C content is ≥0.13%.

[0071] Special remarks: 1) When starting the furnace or the converter slag, 0-50kg of lime can be added. 2) After the first sample is taken from the refining furnace, if the slag is foamy, 0-50kg of lime / fluorite can be added.

[0072] 2.2 Deoxygenation

[0073] After the molten steel in the refining furnace enters the station, 20kg of calcium carbide and 40kg of silicon carbide are added for rapid deoxidation. The addition is divided into two times, and 10kg of calcium carbide and 20kg of silicon carbide are added each time. After deoxidation, the first molten steel sample is sent to the laboratory for component detection, and then diffusion deoxidation is carried out, and 10-50kg of calcium carbide is added respectively, and the rest is mainly silicon carbide and calcium carbide is supplemented. Diffusion deoxidation requires "small amounts and multiple times" to add deoxidizers, and the total amount of deoxidizers used is ≥80kg. After slag making and deoxidation, alloys are added according to the composition of the first molten steel sample, and aluminum wire is fed at [Alt] = 0.030% to ensure that the [Alt] of the refining furnace out of the station is between 0.019% and 0.025%.

[0074] 3. Calcium treatment

[0075] After slag making and deoxidation, calcium treatment is carried out when the composition is qualified. The total deoxidation and slag making time before calcium treatment must be greater than 20 minutes. Calcium treatment is beneficial to improve the morphology of inclusions and improve the cleanliness of molten steel. After the morphology of inclusions changes, some inclusions become easier to float to the surface of molten steel and be removed, thereby further purifying the molten steel. The number of meters of wire feeding is determined according to the state of slag, and the number of meters is controlled between 30 meters and 50 meters.

[0076] 4. Temperature control

[0077] Since the wall temperature of the continuous casting ladle in the startup furnace is relatively low, the molten steel temperature and superheat are required to be relatively high to meet the casting speed requirements. The leaving station temperature of the first refining furnace is required to be between 1600℃ and 1615℃, and the leaving station temperature of the second furnace and the continuous casting furnace is required to be between 1560℃ and 1570℃.

[0078] (III) Key points of VD vacuum treatment control

[0079] The VD furnace can effectively reduce the hydrogen and nitrogen content in steel through vacuum refining technology; it can also remove oxygen in steel through carbon-oxygen reaction, and remove sulfur in steel through the reaction of alkaline slag and molten steel components, thereby improving the quality of steel. By removing harmful elements and impurities in steel, the steel refined by the VD furnace has better mechanical properties and meets the needs of various industrial applications.

[0080] The specific control points of VD furnace are as follows:

[0081] 1. Vacuum requirements

[0082] The vacuum degree requirement is ≤67Pa. Data show that when the vacuum degree is ≤66.7Pa, most steel grades can meet the requirement that the hydrogen content in the steel is less than 1E-06.

[0083] The high vacuum holding time requirement is ≥15min. By maintaining the vacuum for a long time, harmful gases such as hydrogen and nitrogen as well as inclusions in the molten steel can be removed more effectively, thereby improving the toughness and fatigue resistance of the steel.

[0084] 2. Alloying

[0085] The nitrogen content of this steel is required to be between 0.006% and 0.009%. After vacuum treatment, it is necessary to feed nitrided manganese iron wire for nitrogen addition (reference value 15-25 meters), and then feed titanium iron wire for titanium addition (reference value 25 meters). Finally, feed aluminum wire for "final deoxidation" to further reduce the oxygen content in the steel. Aluminum directly reacts with residual oxygen in molten steel to form aluminum oxide, which helps to improve the internal and surface quality of the steel.

[0086] 3. Calcium treatment

[0087] VD furnaces and refining furnaces also need to be treated with calcium. Calcium treatment of VD furnaces can effectively remove residual oxygen and metal oxides in molten steel, such as FeO, Cr2O3, MnO, NiO, etc., reduce the oxide content in steel, and improve the purity of molten steel. In addition, calcium treatment can also improve the casting performance of molten steel, reduce the problem of clogging of the water inlet of the tundish, ensure smooth continuous casting, and thus improve production efficiency. The first furnace needs to be fed with 20 meters of calcium wire, and the second furnace and continuous casting furnace need to be fed with 0-20 meters according to the slag state.

[0088] 4. Soft blowing control

[0089] The VD furnace needs to be soft-blown before leaving the station. During the soft-blowing process, it helps to remove inclusions in the molten steel, especially small particles, thereby improving the cleanliness of the steel. Soft-blowing is also conducive to a more uniform distribution of composition and temperature in the molten steel, reducing component segregation and temperature gradient. The soft-blowing time requirement is ≥20min. If the soft-blowing is too short, it is easy to cause insufficient removal of inclusions. If the soft-blowing is too long, more heat will be lost, resulting in unstable temperature control. Before leaving the station, 2-4 bags of carbonized rice husk insulation need to be added for insulation.

[0090] 5. Temperature control

[0091] Since the wall temperature of the continuous casting ladle in the startup furnace is relatively low, the molten steel temperature and superheat are required to be relatively high to meet the casting speed requirements. The VD temperature of the first furnace at startup is required to be between 1522℃ and 1532℃, and the VD temperature of the second furnace and the continuous casting furnace is required to be between 1490℃ and 1500℃.

[0092] (IV) Key points of continuous casting control

[0093] 1. Raw and auxiliary materials

[0094] The working layer of the tundish is made of magnesium, the stopper rod for tundish flow control is made of aluminum carbon body + magnesium rod head, the material of the submerged nozzle is aluminum carbon body + zirconium slag line, the material of the long nozzle is aluminum carbon, the type of tundish covering agent is tundish carbon-free covering agent 03, and the type of crystallizer protective slag can be selected from SPH-C189 / VV1 and XBF-G1.

[0095] 2. Temperature control

[0096] The superheat of molten steel is a key parameter indicator for continuous casting production control. If the superheat is too small, inclusions and nozzle blockage are likely to occur; if the superheat is too large, segregation and cracks are likely to occur, which directly affects the quality of the ingot. The temperature of the tundish determines the superheat. The temperature of the tundish of the first furnace is controlled between 1477-1492℃, and the superheat is 30-45℃; the temperature of the tundish of the second furnace is controlled between 1467-1477℃, and the superheat is 20-30℃; the continuous casting furnace is the same as the second furnace, and the temperature of the tundish is controlled between 1467-1477℃, and the superheat is 20-30℃.

[0097] 3. Pulling speed control

[0098] The higher the superheat of the molten steel, the lower the pulling speed needs to be. This is because the increase in superheat will lead to faster solidification of the ingot and thinner shell thickness, which will increase the risk of leakage. In actual production, the optimal pulling speed control corresponding to the superheat should be determined based on factors such as steel type, ingot cross-sectional dimensions, and cooling conditions. Studies have shown that there is an optimal relationship between pulling speed and superheat, such as V opt =0.0003ΔT 2 -0.0331ΔT+2.942, where V opt is the optimal casting speed, and ΔT is the superheat. The casting speed adjustment range does not exceed 0.05m / min per minute. Except for special circumstances, the continuous casting furnace maintains a constant casting speed. The casting speed corresponding to the superheat of this steel grade is shown in the following table:

[0099]

[0100] 4. Crystallizer

[0101] The crystallizer is called the "heart" of the continuous casting equipment. It has a cooling system inside. Through the cooling water, the liquid metal is gradually solidified into a billet shell of the required specifications and shape. In order to meet the needs of rapid cooling of the billet, the water flow rate of the crystallizer is controlled at more than 1900L / min.

[0102] The insertion depth of the submerged nozzle is an important parameter in the continuous casting process, which directly affects the flow state of molten steel, the temperature field distribution in the crystallizer and the quality of the ingot. Reasonable insertion depth helps the smooth flow and uniform cooling of molten steel, reduces the slag rolling phenomenon of molten steel and improves the quality of ingot. The specific insertion value depends on factors such as the crystallizer size, molten steel superheat, casting speed and cooling conditions. According to production experience, the insertion depth of the submerged nozzle for this steel grade is between 80mm and 140mm.

[0103] 5. Electromagnetic stirring

[0104] Continuous casting electromagnetic stirring uses the principle of electromagnetic induction to generate induced current in molten steel through an alternating magnetic field, which in turn generates electromagnetic force to drive the molten steel to flow and enhance convection, heat transfer and mass transfer processes. The current and frequency of electromagnetic stirring are important factors affecting the stirring effect, and the specific settings are determined according to the type of continuous casting machine, steel grade and process parameters.

[0105] The crystallizer electromagnetic stirring is installed under the crystallizer, mainly to improve the surface quality of the ingot and refine the grains. The current of the crystallizer electromagnetic stirring of the billet continuous casting machine is generally 400A, and the frequency selection is generally in the low frequency range, usually between 1Hz-10Hz. The end electromagnetic stirring is installed at the end of solidification to further refine the equiaxed grains and improve the center segregation and looseness. The current and frequency are slightly larger. The parameters of current and frequency are set as follows:

[0106] Location Current, A Frequency, Hz Mold Electric Stirring (M-MES) 400 2 Terminal Electrospinning (F-MES) 500 10

[0107] 6. Head and tail blanks

[0108] For newly cast continuous casting billets, the joint part should be cut off for no less than a certain length to ensure that defects and impurities generated during the startup process are removed. The tail billet of the last furnace of continuous casting should also be cut off to a certain length to ensure that there are no shrinkage holes and other harmful defects. The specific cutting length is affected by factors such as billet size, steel type and continuous casting machine performance. The length of the head and tail of this steel type is between 2.5 meters and 4.0 meters. The head and tail need to be recycled and reused, and the returned scrap steel type is Class B self-produced scrap steel.

[0109] 7. Sampling requirements

[0110] Long-handle samples should be taken from the continuous casting tundish for subsequent composition analysis, inclusion detection and other tests. The sampling location should be selected in the area where the molten steel fluidity is relatively stable in the tundish, and avoid sampling in the molten steel impact area or dead area. One long-handle sample is taken from each furnace, and the sample is cooled, cleaned and labeled after being taken out, including information such as the furnace number and sample number.

[0111] Take a billet pickling sample from each stream to detect the internal structure and defects of the billet. Cut a representative cross section of the continuous casting billet as a sample, remove the surface oxide layer, and ensure that the sample surface is smooth without obvious scratches. Heat the pickling solution to a certain temperature (70-80℃), then immerse the sample completely in the acid solution and corrode for a certain time (15-20 minutes). After the pickling is completed, take out the sample, rinse off the corrosion products with hot water and blow dry for subsequent observation and testing.

[0112] Take a low-magnification sample of each square billet to check whether the defects in the cross section of the billet are within the allowable range, such as cracks, segregation, slag inclusions and shrinkage holes, and evaluate the internal quality of the billet. Through low-magnification sample testing, we can understand whether the current continuous casting machine is in a controllable state, and find out the factors that affect the smelting, refining and continuous casting operation process and equipment status in time, so as to optimize the process parameters and improve the billet quality.

[0113] After the four processes of our factory are produced according to the above process, the converter-refining-VD component control all meet the requirements, as shown in the following table:

[0114]

[0115]

[0116] The plugging rod curve is as follows Figure 1 As shown in the curve, the casting process is smooth and no abnormalities occur during the casting process.

[0117] The surface inspection of the first batch of steel billets includes the cross-sectional parameters of the billets, the length of the billets, the surface quality of the billets and the cutting quality of the billets. The specific data are as follows:

[0118]

[0119]

[0120] Performance Testing

[0121] The grinding ball steel needs to have high hardness, wear resistance, toughness and tensile strength to ensure long-term stable operation in harsh working environments, reduce replacement frequency and reduce costs. The performance tests of the rolled round steel are as follows:

[0122] 1. Hardness

[0123] The hardness of the steel was tested using a TIME-5300 Leeb hardness tester. The hardness value of the steel was 58HRC. The hardness value of general grinding ball steel is 45HRC. The hardness of the steel meets the use requirements.

[0124] 2. Wear resistance

[0125] The ring-block wear test method is used for detection. This method makes the test wheel and the test block rub against each other on a ring-block wear tester, measures the weight loss, and compares the difference in wear resistance.

[0126] Select 2CR material as the test block, 6542 high-speed tool steel as the test wheel, increase the load to 192N, the rotation speed to 200 rpm, converted to a relative speed of 0.42 m / s, and conduct a dry friction test for 2 hours. After the test, the wear weight loss of the 2CR test block was 0.0065 g, and the wear weight loss of the 6542 test wheel was 0.414 g. Therefore, the wear resistance of 2CR steel is 6.36 times that of 6542 high-speed tool steel, and the steel has good wear resistance.

[0127] 3. Resilience

[0128] The 2CR steel was subjected to a Charpy pendulum impact test to determine the toughness of the metal material. The test notch was placed under the pendulum impact tester with its back facing the pendulum blade, and the pendulum was released to make it fall and break the sample, and the impact absorption energy was measured. The impact test results showed that the steel had an impact absorption energy of 55J at room temperature, showing good toughness.

[0129] 4. Tensile properties

[0130] The tensile strength of 2CR steel samples is calculated by applying gradually increasing tensile force to the samples through a tensile testing machine until the samples break. The calculation formula is as follows:

[0131] σ=Fb / So

[0132] σ represents the tensile strength, the unit is MPa.

[0133] Fb is the maximum force that the specimen is subjected to when it breaks during the tensile process, in Newton (N).

[0134] So is the original cross-sectional area of ​​the specimen, in square millimeters (mm 2 ).

[0135] Calculated through experimental data, the tensile strength of this steel is 868MPa, which has good tensile strength and can meet the use requirements in various complex and harsh working environments.

[0136] In summary, the grinding ball steel 2CR we invented based on the actual situation of the steel plant has good performance. This method is reliable and stable, which can ensure the production of high-quality grinding ball steel 2CR and lay a solid foundation for adapting to market development.

[0137] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A grinding ball steel, characterized in that: The components, measured in mass percentage, include: C: 1.02-1.06%, Si: 0.11-0.17%, Mn: 0.21-0.27%, P: ≤0.020%, S: ≤0.010%, Cr: 1.96-2.02%, Mo: ≤0.080%, Al: 0.016-0.025%, Ti: 0.010-0.022%, Ni: ≤0.100%, Cu: ≤0.100%, V: ≤0.015%, N: 0.006-0.009%, H: ≤0.00015%, Sn: ≤0.015%, Di: 3.10-6.

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2. A grinding ball steel as claimed in claim 1, characterized in that: The components, in percentage by mass, include: C: 1.04%, Si: 0.14%, Mn: 0.24%, P: ≤0.018%, S: ≤0.010%, Cr: 1.99%, Mo: ≤0.060%, Al: 0.020%, Ti: 0.016%, Ni: ≤0.100%, Cu: ≤0.100%, V: ≤0.010%, N: 0.0075%, H: ≤0.00015%, Sn: ≤0.010%, Di: 3.10-6.

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3. The smelting method of grinding ball steel 2CR according to claim 1, characterized in that: The method includes converter smelting, refining, VD vacuum treatment, and continuous casting processes, and the specific process steps are as follows: (1) Converter: The raw and auxiliary materials include molten iron, scrap steel and ladle; the total input of the converter is 53-59 tons, the output is controlled at 50-54 tons, argon is blown at the bottom throughout the process, and the three bottom blowing flows are all controlled at 45.8m 3 / h, the final carbon content of the converter blowing is controlled between 0.08% and 0.30%, and the final temperature is greater than 1600°C; the slag blocking method of the slag blocking cone and the slide plate is used in the steel tapping process, and the deoxidizer, the carburizer, the alloy and the top slag are added in sequence during the steel tapping process, and the composition of the obtained molten steel is controlled to be C: 0.94%-1.00%, Si: 0.07%-0.12%, Mn: 0.10%-0.16%, Cr: 1.82%-1.92%; (2) Refining: The raw and auxiliary materials of the refining furnace include alloys, carburizers, lime, fluorite, silicon carbide, calcium carbide, aluminum wire, and calcium wire; the alloys include silicon manganese alloy, ferrosilicon alloy, medium carbon ferromanganese alloy, high carbon ferromanganese alloy, medium carbon ferrochrome alloy, or high carbon ferrochrome alloy; When making slag, lime and a small amount of fluorite are used as slag materials for the refining furnace; During deoxidation, calcium carbide and silicon carbide are added to the molten steel of the refining furnace for rapid deoxidation, and small amounts are added multiple times; the total deoxidizer usage is ≥80kg / furnace; after slag making and deoxidation, alloy is added according to the composition of the first molten steel sample, and aluminum wire is fed at [Alt] = 0.030%, ensuring that [Alt] of the refining furnace out of the station is between 0.019% and 0.025%; After slag making and deoxidation, calcium treatment is carried out when the composition is qualified. The total deoxidation and slag making time before calcium treatment must be greater than 20 minutes; the number of meters of wire feeding is determined according to the slag state, and the number of meters is controlled between 30 and 50 meters; The temperature of the first refining furnace to be started up must be between 1600 and 1615°C, and the temperature of the second refining furnace and continuous casting furnace to be started up must be between 1560 and 1570°C. (3) VD vacuum treatment: The vacuum degree requirement is ≤67Pa, and the high vacuum holding time requirement is ≥15min; after vacuum treatment, nitrided manganese iron wire needs to be fed for nitrogen addition, and then titanium iron wire needs to be fed for titanium addition; finally, aluminum wire needs to be fed for "final deoxidation" to further reduce the oxygen content in the steel, and aluminum oxide is generated by direct reaction between aluminum and residual oxygen in molten steel; 20 meters of calcium wire needs to be fed into the first furnace when the machine is started, and 0-20 meters of calcium wire needs to be fed into the second furnace and continuous casting furnace according to the slag state; the soft blowing time requirement is ≥20min; the VD leaving station temperature of the first furnace when the machine is started is required to be between 1522 and 1532℃, and the VD leaving station temperature of the second furnace and continuous casting furnace needs to be between 1490 and 1500℃; (4) Continuous casting The working layer of the tundish is made of magnesium. The material of the stopper rod for tundish flow control is aluminum carbon body + magnesium rod head. The material of the submerged nozzle is aluminum carbon body + zirconium slag line. The material of the long nozzle is aluminum carbon. The type of tundish covering agent is tundish carbon-free covering agent 03. The tundish temperature of the first furnace is controlled between 1477-1492℃, and the superheat is 30-45℃; the tundish temperature of the second furnace is controlled between 1467-1477℃, and the superheat is 20-30℃; the tundish temperature of the continuous casting furnace is the same as the second furnace, and the tundish temperature is controlled between 1467-1477℃, and the superheat is 20-30℃; When the steel grade superheat is ≥46℃, the continuous casting speed is 0.85m / min; when the steel grade superheat is 36-45℃, the continuous casting speed is 0.90m / min; when the steel grade superheat is 20-35℃, the continuous casting speed is 0.95m / min; when the steel grade superheat is ≤19℃, the continuous casting speed is 1.00m / min; the adjustment range of the casting speed per minute does not exceed 0.05m / min; The crystallizer water flow rate is controlled at above 1900L / min; The insertion depth of the submerged nozzle is between 80mm-140mm The length of the steel head and tail cutting is between 2.5 meters and 4.0 meters.

4. A method for smelting grinding ball steel 2CR as claimed in claim 3, characterized in that: In step (1), the deoxidizer is an aluminum block. When the endpoint C content is ≤0.05%, the amount of aluminum block added is 50kg / furnace of steel; when the endpoint C content is 0.06-0.12%, the amount of aluminum block added is 40kg / furnace of steel; when the endpoint C content is ≥0.13%, the amount of aluminum block added is 30kg / furnace of steel.

5. The smelting method of grinding ball steel 2CR according to claim 3, characterized in that: In step (1), the top slag material is lime and calcium aluminate cleaner, the amount of lime added is 260-300 kg / furnace steel, and the amount of calcium aluminate cleaner added is 400-440 kg / furnace steel.

6. The smelting method of grinding ball steel 2CR according to claim 3, characterized in that: In step (1), the alloy is selected from high carbon ferromanganese and high carbon ferrochromium.

7. The smelting method of grinding ball steel 2CR according to claim 3, characterized in that: In step (2), the specific amount of lime added is determined according to the final carbon content of the converter: when the final carbon content is ≤0.05%, 50-100 kg of lime / furnace is added; when the final carbon content is between 0.06% and 0.12%, 30-50 kg of lime / furnace is added; when the final carbon content is ≥0.13%, no lime is added.

8. The method for smelting grinding ball steel 2CR according to claim 3, characterized in that: In step (3), after vacuum treatment, nitrided manganese iron wire is fed to increase nitrogen, with a reference value of 15-25 meters; then titanium iron wire is fed to increase titanium, with a reference value of 25 meters.

9. The method for smelting grinding ball steel 2CR according to claim 3, characterized in that: In step (4), the type of mold protection slag is SPH-C189 / VV1 or XBF-G1.

10. The method for smelting grinding ball steel 2CR according to claim 3, characterized in that: In step (4), the electromagnetic stirring current of the crystallizer of the square billet continuous casting machine is 400A, the end electric stirring (F-MES) current is 500A, and the frequency is between 1Hz-10Hz.

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