Steelmaking method of low-carbon cold forging steel

Abstract

The invention relates to the technical field of steelmaking, and discloses a steelmaking method of low-carbon cold forging steel, which comprises the following steps: mixing molten iron with scrap steel in a converter; oxygen is continuously blown into the converter, so that the carbon content is lower than 0.04% during tapping; adding slag for the first time in the oxygen blowing process; after silicon in the slag is completely oxidized, iron ore is added, and lime is supplemented for dephosphorization; after dephosphorization is completed, oxygen blowing continues to be conducted for 8-12 min, and tapping is conducted; in the tapping process, carbon powder is added into a steel ladle to reduce the oxygen content, lime is supplemented, and when a small amount of molten steel is left in the converter, an aluminum material is added into the steel ladle for deoxidation; then transferring the steel ladle to an argon station, and supplementing aluminum to the molten steel until the aluminum content is 0.03-0.04%; deoxidation and purification treatment are carried out after aluminum supplementation is finished; adding slag for the second time after the molten steel reaches the LF furnace; and after the second time of slag adding is completed, power transmission-first power-off sampling-matched gold-matched aluminum stirring-power transmission-calcium line beating are carried out. The method saves time and cost.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, in particular to a steelmaking method for low-carbon cold heading steel. Background Art

[0002] The composition of SWRCH6A-D is as follows: carbon 0.04%-0.06%, silicon less than 0.05%, manganese 0.16%-0.19%, phosphorus less than 0.020%, sulfur less than 0.008%, acid-soluble aluminum 0.025%-0.035%. In the prior art, the refining treatment time of the LF furnace is 35 minutes. The general process is to add slag and send electrochemical slag for 10-12 minutes, then take samples and measure the temperature for 2 minutes, continue to send electricity and heat for 7-10 minutes, wait for the sample to come out, mix with gold and large argon gas for 3 minutes, take samples and measure the temperature for 2 minutes, wait for the sample to come out, and see if you need to add alloy. If you need to, wait for 5 minutes after the addition before the large calcium wire soft blowing. If not, you can directly use the large calcium wire soft blowing. By comparison, if the alloy is added in one step after the sample comes out, 5 minutes can be saved. In terms of total refining time control, if the alloy is added in one step after the sample comes out, the total time is 24-29 minutes. If the alloy needs to be added, the total time is 29-34 minutes. Time-based control can reduce the power consumption of LF refining, which is something everyone can think of, but it is difficult to do. The key factor is the precise control of acid-soluble aluminum, because the aluminum loss of acid-soluble aluminum is related to many factors such as temperature, oxygen, slag amount, argon size, slag fluidity, etc., and there is no obvious rule.

[0003] Generally speaking, the higher the final carbon content of the converter, the lower the oxygen content of the molten steel. However, since this type of steel is low carbon steel (0.04%-0.06%), the molten steel will be carbonized in the LF furnace and continuous casting, so the converter must be post-blown to reduce the carbon content to less than 0.04% through peroxidation of the molten steel. In this way, the oxygen content of the molten steel will be very high and unstable. Figure 1 It is the influence of the carbon content at the converter end on the aluminum loss. From the aluminum loss of the acid-soluble aluminum sampled after the converter is finished to the refining sample 1, it can be seen that the higher the carbon content at the converter end, the less the aluminum loss of the acid-soluble aluminum from the sampling after the converter is finished to the refining sample 1.

[0004] In order to further remove oxygen from the molten steel, after the steel is discharged from the converter, the molten steel is sampled at the argon station, and then the aluminum line is deoxidized according to the acid-soluble aluminum content of the molten steel, and the acid-soluble aluminum is controlled at 0.03% to 0.06%. Figure 2 It is the aluminum loss of acid-soluble aluminum from the time when the aluminum wire sampling is completed to the time of refining sampling 1. It can be seen that the better the aluminum deoxidation is in the argon station sampling, the less the aluminum loss will be.

[0005] In the normal process, the slag washing material and alloy added to the converter are fixed. Only after sampling at the argon station, the different amounts of aluminum added will affect the alumina in the slag. That is, the more aluminum added, the better the fluidity of the slag or the thinner the slag. After refining, employees will choose to add lime by observing the fluidity of the slag until the fluidity of the slag is controlled within a range. Figure 3 It is the effect of the amount of lime added in LF refining on the aluminum loss. It can be seen that the better the slag fluidity is, the more lime is added in refining, and the more aluminum loss is from sampling at the argon station to sampling 1 at LF refining.

[0006] On the other hand, slag is sometimes added during the steelmaking process of the converter, which increases the oxygen content of the molten steel and thus increases the aluminum loss of the acid-soluble aluminum. However, in the actual process, Figure 4 As shown, the aluminum loss is not as large as more slag is added and more molten steel is phosphorus recovered, from sampling at the argon station to LF refining sampling 1.

[0007] Since the aluminum wire has been deoxidized in the argon station, the acid-soluble aluminum in the molten steel will be burned during the refining process depending on the length of power supply time. However, in practice, Figure 5 As shown, the longer the power supply time before sampling, the greater the aluminum loss from sampling at the argon station to LF refining sampling 1.

[0008] In theory, the higher the temperature of the molten steel, the more gas is dissolved in the molten steel, and the more the acid-soluble aluminum is burned. However, in the actual process, Figure 6 As shown, the higher the molten steel temperature is when taking refining sample 1, the greater the aluminum loss is from sampling at the argon station to LF refining sample 1.

[0009] Through the above analysis, it can be concluded that there are many factors affecting the burning loss of acid-soluble aluminum in molten steel and there is no regular pattern to follow. In other words, the final carbon of the converter is very low, and the oxygen content of the molten steel is very high. After the aluminum is added and deoxidized at the argon station, when refining sampling 1 is taken, the aluminum loss is sometimes large and sometimes small. Therefore, after refining sampling 1, it is very difficult to adjust the acid-soluble aluminum in the molten steel to a target at one time, so that the acid-soluble aluminum of sample 2 is 0.035%±0.005%. Even if the argon station deoxidizes the molten steel, there is still an unpredictable amount of acid-soluble aluminum in the molten steel during the power supply time and stirring time. Therefore, generally after refining and taking sample 1, some aluminum wire is added to adjust the acid-soluble aluminum to the upper limit +0.010%, that is, 0.045%, and after sample 2 comes out, some aluminum wire is added to adjust the acid-soluble aluminum to the target range, that is, 0.035%±0.005%, preferably 0.030%-0.038%. However, in this way, the refining time will be increased by 5 minutes.

[0010] In view of this, in order to reduce the refining time and improve the accuracy of replenishing aluminum to the target range when refining sample 1, a new method is proposed. Summary of the invention

[0011] The object of the present invention is to provide a steelmaking method for low-carbon cold heading steel.

[0012] The present invention is achieved in that:

[0013] In a first aspect, the present invention provides a steelmaking method for low-carbon cold heading steel, comprising:

[0014] Mixing hot metal with scrap steel in a converter;

[0015] Continuously blow oxygen into the converter to keep the carbon content of the steel below 0.04% when it is tapped;

[0016] During the oxygen blowing process, the first slag addition is carried out, and the added slag materials include lime, light-burned dolomite and magnesium balls;

[0017] After the silicon in the slag added in the first slag addition is completely oxidized, iron ore is added and lime is added for dephosphorization. The dephosphorization time is 35 to 50 seconds.

[0018] After dephosphorization is completed, continue to blow oxygen for 8 to 12 minutes, and control the temperature to 1590 to 1610℃ for steel production;

[0019] During the steel tapping process, carbon powder is added into the ladle to reduce the oxygen content;

[0020] During the steel tapping process, lime is added to the ladle. When there are 10 to 20 tons of molten steel left in the converter, aluminum is added to the ladle for deoxidation.

[0021] After the aluminum material is added, the ladle is transferred to the argon station. After arriving at the argon station, the acid-soluble aluminum content is measured. According to the test results, the molten steel is supplemented with aluminum to 0.03-0.04%;

[0022] After aluminum filling, deoxidation and purification treatment are carried out;

[0023] After the molten steel reaches the LF furnace, the second slag is added, and the added slag includes lime, synthetic slag, aluminum slag and fluorite;

[0024] After the second slag addition is completed, power is supplied until the molten steel temperature reaches 1590-1610℃, then the power is cut off, samples are taken and the results are waited for. After the power is cut off, the temperature is kept at 60-80m 3 / h of large stirring for 2 to 4 minutes. During the stirring process, the alloy is matched and the acid-soluble aluminum is adjusted to 0.055% to 0.060%. Then continue to supply power until the molten steel temperature reaches 1590 to 1610℃ and finally use calcium wire soft blowing;

[0025] In the steelmaking process, the amount of each material used is calculated by weight:

[0026] 110,000 parts of molten iron, 24,660 to 27,120 parts of scrap steel, 2,400 to 2,600 parts of lime added for the first slag addition, 600 to 700 parts of light-burned dolomite, 300 to 400 parts of magnesium balls, 1,500 to 2,000 parts of iron ore, 1,000 to 1,500 parts of lime for dephosphorization, 400 to 600 parts of lime added during steelmaking, 450 to 550 parts of lime added for the second slag addition, 280 to 330 parts of synthetic slag, 180 to 220 parts of aluminum slag, and 60 to 100 parts of fluorite.

[0027] In an optional embodiment, the method of blowing oxygen into the converter includes:

[0028] Monitor the carbon content in the molten steel at all times. When the carbon content is greater than 0.1%, use an oxygen gun to blow oxygen from top to bottom into the molten steel. The oxygen pressure is 0.85-0.88MPa and the oxygen flow rate is 27000-28000m 3 / h, the total bottom blowing argon flow rate is 220~260m 3 / h; when the carbon content is lower than 0.1%, oxygen is blown from top to bottom into the molten steel using an oxygen lance, with an oxygen pressure of 0.88-0.9MPa and an oxygen flow rate of 28000-28600m 3 / h, total bottom blowing argon flow rate 320~400m 3 / h.

[0029] In an optional embodiment, initially, the oxygen lance is 2.4 m above the material level in the converter, and during the oxygen blowing process, the oxygen lance moves at a speed of descending 5 to 10 cm every 20 seconds.

[0030] In an optional embodiment, when the sampling test results show that the acid-soluble aluminum is less than 0.035%, the aluminum wire is supplemented. If it is higher than 0.038%, the aluminum wire is supplemented at 60 to 80 m 3 / h of argon stirring, the acid-soluble aluminum is controlled to decrease to 0.00295-0.038% by burning 0.001% every 10s.

[0031] In an optional embodiment, the deoxidation and purification treatment is as follows: wait for 20 to 25 minutes after the aluminum supplementation is completed;

[0032] Or pass argon gas at a flow rate of 5 to 10 m 3 / h soft blowing 10~20min;

[0033] Or pass argon gas at a flow rate of 10-20m 3 / h weak blowing for 5 to 10 minutes;

[0034] Or pass argon gas at a flow rate of 55-65m 3 / h blowing for 1 to 5 minutes;

[0035] When the deoxidation and purification treatment method is to wait for 20 to 25 minutes after the aluminum supplement is completed, it is before the molten steel reaches the LF furnace, or after the molten steel reaches the LF furnace.

[0036] In an optional embodiment, the carbon powder is added in a manner of first adding a unit amount of carbon powder into an empty ladle, and then adding a unit amount of carbon powder every time 10t of molten steel is poured in, until all the carbon powder is added;

[0037] Optionally, one unit portion is 1 kg.

[0038] In an optional embodiment, the amount of carbon powder added is determined according to formula A, which is: M1=(x / 110)(y-400) / 9, wherein M1 is the amount of carbon powder added, d is in kg; x is the amount of molten iron, in t; y is the oxygen content at the end of the converter, in ppm.

[0039] In an optional embodiment, during the addition of carbon powder, the bottom blowing argon of the ladle is opened to 60-80m 3 / h, after adding, turn down to 10~20m 3 / h.

[0040] In an optional embodiment, the aluminum material is determined according to the aluminum content therein according to formula B, where formula B is: M2=0.5(y-400)*(0.9~0.95), wherein M2 is the amount of aluminum material added, in kg; y is the oxygen content at the end of the converter, in ppm.

[0041] In an optional embodiment, the aluminum material is aluminum iron or aluminum particles.

[0042] The present invention has the following beneficial effects:

[0043] The steelmaking method provided by the present invention reduces the converter temperature by adding excessive scrap steel to the molten iron, and then raises the temperature by blowing over-oxidation, and reduces the carbon content to the required range, and then the molten steel is transferred to the ladle for carbon and aluminum deoxidation, and ensures that there is an appropriate content of acid-soluble aluminum in the molten steel; after the aluminum is supplemented, complete deoxidation is achieved by waiting or blowing argon; due to a series of operations in the converter and in the ladle before reaching the LF furnace to add slag, the operation mode after adding slag to the LF furnace can be changed to power supply-aluminum mixing-sampling-power supply and other samples-aluminum matching to the target range according to the sample. The method is equivalent to optimizing the original sample 2 aluminum matching to the target to the sample 1 aluminum matching to the target through the change of the above operation method, which reduces the time of waiting for one sample. Therefore, the steelmaking method provided by the present invention can save production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 This is a statistical diagram of the relationship between the end point carbon and aluminum loss;

[0046] Figure 2 This is a statistical diagram of the relationship between aluminum and aluminum loss at the argon station;

[0047] Figure 3 This is a statistical chart showing the relationship between the amount of lime added and aluminum loss;

[0048] Figure 4 This is a statistical diagram of the relationship between phosphorus regeneration and aluminum loss;

[0049] Figure 5 This is a statistical diagram of the relationship between power transmission time and aluminum loss of sample 1;

[0050] Figure 6 This is a statistical diagram of the relationship between sample 1 temperature and aluminum loss;

[0051] Figure 7 Aluminum loss from the time it takes from aluminum wire insertion at the argon station to refining sampling. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0053] The percentages mentioned in this application all refer to mass percentages.

[0054] The present invention provides a method for making low-carbon cold heading steel, comprising:

[0055] Mixing hot metal with scrap steel in a converter;

[0056] Continuously blow oxygen into the converter to keep the carbon content of the steel below 0.04% when it is tapped;

[0057] During the oxygen blowing process, the first slag addition is carried out, and the added slag materials include lime, light-burned dolomite and magnesium balls;

[0058] After the silicon in the slag added in the first slag addition is completely oxidized, iron ore is added and lime is added for dephosphorization. The dephosphorization time is 35 to 50 seconds.

[0059] After dephosphorization is completed, continue to blow oxygen for 8 to 12 minutes, and control the temperature to 1590 to 1610℃ for steel production;

[0060] During the steel tapping process, carbon powder is added into the ladle to reduce the oxygen content;

[0061] During the steel tapping process, lime is added to the ladle. When there are 10 to 20 tons of molten steel left in the converter, aluminum is added to the ladle for deoxidation.

[0062] After the aluminum material is added, the ladle is transferred to the argon station. After arriving at the argon station, the acid-soluble aluminum content is measured. According to the test results, the molten steel is supplemented with aluminum to 0.03-0.04%;

[0063] After aluminum filling, deoxidation and purification treatment are carried out;

[0064] After the molten steel reaches the LF furnace, the second slag is added, and the added slag includes lime, synthetic slag, aluminum slag and fluorite;

[0065] After the second slag addition is completed, power is supplied until the temperature of the molten steel is 1590-1610℃, then the power is turned off, samples are taken and the results are waited for, and the power is turned off and stirred at a high speed of 60-80m3 / h for 2-4min. During the stirring process, the alloy is added and the acid-soluble aluminum is added to 0.055%-0.060%, and then the power is continued to be supplied until the temperature of the molten steel is 1590-1610℃, and finally the calcium wire is soft-blown;

[0066] In the steelmaking process, the amount of each material used is calculated by weight:

[0067] 110,000 parts of molten iron, 24,660 to 27,120 parts of scrap steel, 2,400 to 2,600 parts of lime added for the first slag addition, 600 to 700 parts of light-burned dolomite, 300 to 400 parts of magnesium balls, 1,500 to 2,000 parts of iron ore, 1,000 to 1,500 parts of lime for dephosphorization, 400 to 600 parts of lime added during steelmaking, 450 to 550 parts of lime added for the second slag addition, 280 to 330 parts of synthetic slag, 180 to 220 parts of aluminum slag, and 60 to 100 parts of fluorite.

[0068] The steelmaking method provided by the present invention reduces the converter temperature by adding excessive scrap steel to the molten iron, and then raises the temperature by blowing over-oxidation, and lowers the carbon content to the required range, and then the molten steel is transferred to the ladle for carbon and aluminum deoxidation, and ensures that there is an appropriate amount of acid-soluble aluminum in the molten steel; after the aluminum is supplemented, complete deoxidation is achieved by waiting or blowing argon; due to a series of operations in the converter and in the ladle before reaching the LF furnace to add slag, the operation mode after adding slag to the LF furnace can be changed to power supply-power off sampling-alloy aluminum stirring-power supply-calcium line. The method is equivalent to optimizing from the original sample 2 to the target to the sample 1 to the target through the above operation method, reducing the waiting time for one sample and saving about 5 minutes. The molten steel is reduced by 1.5°C per minute during the treatment, and the electricity fee is calculated at 25 yuan per temperature increase of 1°C, and the cost of each furnace of steel is reduced by 5*1.5*25=187.5 yuan. Therefore, the steelmaking method provided by the present invention can save production costs.

[0069] Specifically, the preparation method is:

[0070] S1. Treatment in converter

[0071] (1) Mixing molten iron and scrap steel in a converter.

[0072] Scrap steel is ordinary scrap steel with carbon, silicon and manganese less than 0.90% and trace elements such as phosphorus, sulfur and copper less than 0.050%.

[0073] The ratio of molten iron to scrap steel is: 110,000 parts of molten iron, 24,660 to 27,120 parts of scrap steel. For example, if the molten iron is 110 tons, the molten iron temperature is 1350°C, and the silicon content of the molten iron is 0.30%, the scrap steel is 24.66 to 27.12 tons. The calculation method for the amount of scrap steel added is:

[0074] The amount of scrap steel added = (molten iron temperature * molten iron weight - scrap steel weight * scrap steel temperature drop) / (molten iron weight + scrap steel weight) + molten iron silicon heat = 1380℃-1400℃, where silicon heat = silicon content * 10000, and the temperature of every 1t of scrap steel is reduced by 15℃. For example, the molten iron temperature is 1350℃ and the molten iron silicon is 0.30%. The minimum amount of scrap steel added = (110*1350-x*15) / (110+x) + 0.30% * 100000 = 1400, and x is calculated to be 24.66; the maximum amount added = (110*1350-y*15) / (110+y) + 0.30% * 100000 = 1380, and y is calculated to be 27.12, that is, 110t of molten iron plus 24.66 to 27.12t of scrap steel.

[0075] (2) Continuously blow oxygen into the converter.

[0076] The carbon content of molten iron is generally 3.8% to 4.5%. As oxygen is blown, the carbon is oxidized. The carbon content should be less than 0.04% at the end of converter smelting.

[0077] Specifically, the oxygen blowing method is:

[0078] When the carbon content of molten iron is high, the flame is large during oxygen blowing. When the carbon content of molten iron is getting lower and lower, the flame is getting smaller and smaller, just like burning wood. At the beginning, before it turns into carbon, the flame is large, and after it turns into carbon, the flame is small. When you see a large flame, you know that the carbon content is still high. When the carbon content is greater than 0.1%, use an oxygen gun to blow oxygen from top to bottom to the molten steel. The oxygen pressure is 0.85-0.88MPa and the oxygen flow rate is 27000-28000m 3 / h, the total bottom blowing argon flow rate is 220~260m 3 / h;

[0079] When the converter operator sees the flame shrink, he knows that there is not much carbon in the molten steel. At this time, the carbon content is determined by the instrument and the carbon blowing time is calculated according to the carbon content. When the carbon content is calculated to be less than 0.1%, the oxygen pressure is increased from 0.85-0.88MPa to 0.88-0.9MPa, and the oxygen flow rate is increased from 27000-28000m 3 / h increased to 28000~28600m 3 / h, total bottom blowing argon flow rate 320~400m 3 / h.

[0080] As the carbon content of molten steel decreases, it is necessary to increase the oxygen blowing intensity and the molten steel stirring intensity to reduce the carbon. Therefore, the operation mode is that when the carbon content is greater than 0.1%, the oxygen blowing intensity is small, and when it is less than 0.1%, the oxygen blowing intensity is large.

[0081] Specifically, the converter is a 6-hole bottom blowing converter. When the carbon content is greater than 0.1%, the argon gas flow rate of each hole at the bottom of the converter is 37-43m 3 / h, preferably 40m 3 / h; when the carbon content is less than 0.1%, the argon gas flow rate per hole at the bottom of the converter is 53-67m 3 / h, preferably 60m 3 / h.

[0082] Preferably, after adding scrap steel, part of the scrap steel will float on the surface of the molten iron. To prevent the oxygen lance from hitting the scrap steel, the oxygen lance is initially ignited and blown at a height of 2.4m from the material level in the converter. During the converter smelting process, as the scrap steel melts, the material level continues to drop. Therefore, during the oxygen blowing process, the oxygen lance moves at a speed of 5 to 10cm per 20 seconds, keeping close to the surface of the molten iron without hitting the scrap steel, thereby increasing the oxygen recovery rate. If the lance position is too high, part of the oxygen blown out will not enter the molten iron and will disperse upwards; but if the lance position is too low, it will easily damage the lance head if it hits the scrap steel.

[0083] (3) During the continuous oxygen blowing process, the first slag addition is carried out, and the added slag includes lime, light-burned dolomite and magnesium balls.

[0084] In terms of weight, for every 110,000 parts of molten iron, add 2,400 to 2,600 parts of lime, 600 to 700 parts of light-burned dolomite, and 300 to 400 parts of magnesium balls. For example, taking 110 tons of molten iron as an example, add 2.4 to 2.6 tons of lime, 0.6 to 0.7 tons of light-burned dolomite, and 0.3 to 0.4 tons of magnesium balls.

[0085] The technical parameters of light-burned dolomite are CaO: 35-52%, MgO: 26-34%, and it also contains a small amount of silicon dioxide (SiO), iron (Fe), sulfur dioxide (SO) and carbon (C). The technical parameters of magnesium balls are 80% magnesium oxide, and it also contains a certain amount of impurities such as silicon dioxide, iron oxide, aluminum oxide, etc.

[0086] (4) After silicon is completely oxidized, iron ore is added and then lime is added for dephosphorization.

[0087] Within 3 minutes after the slag is added, oxygen will completely oxidize silicon. The carbon monoxide curve can be used to determine whether silicon is completely oxidized. When there is silicon in the molten iron, oxygen reacts with silicon first. When silicon is basically oxidized, oxygen will react with carbon in the molten iron to generate carbon monoxide. When the carbon monoxide content is greater than 5%, it can be considered that silicon is completely oxidized.

[0088] Preferably, by weight, 1500-2000 parts of iron ore and 1000-1500 parts of lime are added to every 110000 parts of molten iron. For example, for 110 tons of molten iron, the iron ore is 1.5-2 tons and the lime is 1-1.5 tons.

[0089] In order to achieve slag removal and temperature reduction, the low-temperature dephosphorization time is controlled to be about 35 to 50 seconds.

[0090] The dephosphorization time is calculated as follows: 0.30% silicon in molten iron is expected to raise the temperature by 300℃, adding 25t scrap steel will lower the temperature by 375℃, and adding about 4t slag will lower the temperature by 80℃. When the molten iron is completely oxidized, the molten iron temperature is expected to be 1350+300-375-80=1195℃. The additional addition of ore and lime is expected to lower the temperature by 60-70℃. The initial oxygen blowing will raise the temperature by about 1.5-2℃ per second, and the temperature of about 1200℃ can be maintained for about 35-50s.

[0091] (5) After dephosphorization is completed, continue to blow oxygen for 8 to 12 minutes to basically oxidize the carbon, and control the molten steel temperature at 1590 to 1610°C for steel production.

[0092] The treatment in the converter is mainly to add excessive scrap steel to cool down, which makes the final temperature of the converter low, and the method of blowing over oxidation is used to heat it up. Under normal circumstances, 110 tons of molten iron, with a temperature of 1350℃ and a silicon content of 0.3%, is more suitable for 20-22 tons of scrap steel. We increase the amount of scrap steel. When the carbon content is pulled below 0.08% in the later stage of oxygen blowing, the temperature is only 1520-1550℃, which does not meet the conditions for tapping. The temperature can only be raised to 1590-1610℃ to tap steel. Therefore, during this period, the molten steel will be overoxidized due to the blowing of excessive oxygen. The purpose of doing this is, firstly, to ensure that there is sufficient oxygen to bring the carbon into the qualified range (below 0.04% to be qualified), and secondly, to reduce slag consumption. Because adding less scrap steel will make the converter final temperature higher, no post-blowing is required, and the higher the converter final temperature, the more slag is needed to retain phosphorus. According to calculations, for every increase of 1°C, the cost of steel increases by 0.4 yuan. Therefore, the lower the final temperature, the lower the cost. By increasing the amount of scrap steel, it is possible to bring the carbon into the qualified range without high temperature.

[0093] S2. Ladle treatment

[0094] (1) During the steel-making process, carbon powder is added into the ladle to reduce the oxygen content.

[0095] Since this steel is decarburized by post-blowing, the average carbon-oxygen product of this steel is 0.0032%, that is, when the carbon content is 0.04% (400ppm), the oxygen content of the molten steel is 0.08% (800ppm), so the oxygen content can be calculated by detecting the carbon content. When tapping the steel, carbon powder is manually thrown into the ladle according to the oxygen content to deoxidize through carbon-oxygen reaction.

[0096] Specifically, the amount of carbon powder added is determined according to the empirical formula A, which is: M1=(x / 110)(y-400) / 9, where M1 is the amount of carbon powder added, d is in kg; x is the amount of molten iron, in t; y is the oxygen content at the end of the converter, in ppm.

[0097] When the final oxygen is 1000ppm, M1 = (1000-400) / 9 = 66.6kg. Theoretically, 66.6kg of carbon powder is completely melted in about 120t (110t of molten iron + 26t of scrap steel = 136t, converter loss is about 10%, molten steel volume = 136*(1-10%) = 122.4t) of molten steel, with 555ppm of carbon, carbon: oxygen = 12:16, which can react with 740ppm of oxygen. The adding method is to add 10kg to the empty ladle when 0t of steel is tapped, and add 10kg for every 10t of steel tapped, until all the carbon powder is added. During the addition of carbon powder, the bottom blowing argon of the ladle is opened to 60-80m 3 / h, after adding, turn down to 10~20m 3 / h.

[0098] (2) When there are 10 to 20 tons of molten steel left in the converter, add aluminum material into the ladle for deoxidation.

[0099] Preferably, the aluminum material is determined according to the aluminum content thereof according to the empirical formula B, where the formula B is: M2=0.5(y-400)*(0.9-0.95), wherein M2 is the amount of aluminum material added, in kg; y is the oxygen content at the end of the converter, in ppm. According to this formula, adding aluminum can basically remove oxygen completely and allow some acid-soluble aluminum to be added to the molten steel.

[0100] Optionally, the aluminum material is aluminum iron or aluminum particles. Based on 50% aluminum iron by mass, M2 = (1000-400) * (0.9-0.95), which is 540-570 kg.

[0101] (3) After the aluminum material is added, the ladle is transferred to the argon station. After arriving at the argon station, the acid-soluble aluminum content is measured. According to the test results, the aluminum wire is fed into the molten steel with a wire feeder to replenish the aluminum content of the molten steel to 0.03-0.04%.

[0102] (4) After aluminum supplementation, deoxidation and purification treatment are carried out.

[0103] Specifically, the deoxidation and purification treatment is as follows: wait 20 to 25 minutes after the aluminum supplement is completed;

[0104] Or pass argon gas at a flow rate of 5 to 10 m 3 / h soft blowing 10~20min;

[0105] Or pass argon gas at a flow rate of 10-20m 3 / h weak blowing for 5 to 10 minutes;

[0106] Or pass argon gas at a flow rate of 55-65m 3 / h and blow for 1 to 5 minutes.

[0107] When the acid-soluble aluminum in molten steel is greater than 0.025%, the molten steel can be completely deoxidized. If the argon station adds more aluminum, on the one hand, it will cause more waste due to burning, and on the other hand, it will cause the aluminum slag to be diluted and easy to burn in the early stage of LF refining. Compared with the original step, the control range of acid-soluble aluminum in this step becomes smaller and is controlled to the lower limit, which has the disadvantage that the deoxidation strength is not as strong as before.

[0108] In the present application, compensation can be made by increasing the waiting time, that is, after the argon station is replenished with aluminum, the argon gas is usually turned off and the station is directly exited to wait for the crane to lift the molten steel to the LF furnace. After the molten steel arrives at the LF furnace, the molten steel is immediately processed. Now, after the argon station is replenished with aluminum and the gas is turned off and the station is exited, even if the molten steel is lifted to the LF furnace, it is not rushed to process it. Wait for 20 minutes after replenishing the aluminum before processing it. Because during this period of time, although the bottom argon gas is not opened for blowing, there is acid-soluble aluminum in the molten steel, which will continue to react with the sample in the slag or the molten steel, which is equivalent to increasing the static treatment time to improve the effect of deoxidation and purification of the molten steel. By collecting samples at the waiting time points from aluminum striking to the start of refining at multiple different aluminum stations and measuring the aluminum loss therein, the following data can be obtained: Figure 7 The curve shown, from Figure 7 It can be seen that when there is aluminum in the molten steel, it can be deoxidized by waiting quietly, and the deoxidation curve is y = 0.0619e-0.102x. The principle is: when waiting quietly, the aluminum in the molten steel is partially deoxygenated, so when the molten steel is refined in the LF furnace, the oxygen content is not that high. The longer the molten steel waits, the lower the oxygen content is. Therefore, when argon stirring and power supply are turned on during the refining process, the aluminum loss is relatively small.

[0109] If time is tight and there is no long waiting time to deoxidize aluminum, the following method can be used to completely deoxidize aluminum:

[0110] Argon gas is passed at a flow rate of 5 to 10 m 3 / h soft blowing for 10 to 20 minutes; or pass argon gas at a flow rate of 10 to 20m 3 / h weak blowing for 5 to 10 minutes; or pass argon gas at a flow rate of 55 to 65m 3 / h and blow for 1 to 5 minutes.

[0111] S3, LF furnace treatment

[0112] (1) After the molten steel reaches the LF furnace and waits for deoxidation to be completed, the second slag addition is carried out. The added slag includes lime, synthetic slag, aluminum slag and fluorite.

[0113] According to the second addition of slag, there are 450-550 parts of lime, 280-330 parts of synthetic slag, 180-220 parts of aluminum slag, and 60-100 parts of fluorite.

[0114] In terms of weight, for every 110,000 parts of molten iron, add 450-550 parts of lime, 280-330 parts of synthetic slag, 180-220 parts of aluminum slag, and 60-100 parts of fluorite.

[0115] Specifically, the synthetic slag is a mixture of lime and bauxite, each accounting for 50%. The lime component is mainly calcium oxide, accounting for 93%, as well as other oxides such as silicon oxide; the main component of bauxite is aluminum oxide, accounting for 70%, as well as other oxides; the aluminum slag contains 40% aluminum particles, as well as other mixtures, and the aluminum particles are 99% metallic aluminum.

[0116] After the second slag addition is completed, power is supplied until the molten steel temperature reaches 1590-1610℃, then the power is cut off, samples are taken and the results are waited for. After the power is cut off, the temperature is kept at 60-80m 3 / h of large stirring for 2 to 4 minutes. During the stirring process, the alloy is added and the acid-soluble aluminum is adjusted to 0.055% to 0.060%. Then, power is continued to be supplied until the molten steel temperature is 1590 to 1610°C, and finally calcium wire soft blowing is performed.

[0117] The acid-soluble aluminum is adjusted to 0.055% to 0.060%, which is the control range obtained by reverse calculation of aluminum loss. The principle is as follows: According to the conventional process, from sample 2 to the continuous casting product, the acid-soluble aluminum will be 10-15% less according to experience, so we have to make up this aluminum loss value after sample 2 comes out, that is, after sample 2 comes out, the acid-soluble aluminum is adjusted to 0.0295%-0.038%, which can ensure that the finished acid-soluble aluminum is qualified at 0.025%-0.035%. However, before sampling 2, it needs to be stirred with 70m3 / h of argon gas to remove inclusions. There will also be aluminum loss in this process. According to experience, the aluminum loss is 0.020%-0.028%. Therefore, this aluminum is added after sampling 1, and the acid-soluble aluminum is adjusted to 0.056%-0.060% according to the results of sample 1, among which 0.058% of acid-soluble aluminum is the optimal target value. According to this target control, after stirring to remove large particles, the acid-molten aluminum at the original sampling node (temperature of 1590-1610℃) will be 0.030%-0.038%. The operator can directly use the calcium wire for soft blowing, eliminating the aluminum preparation and waiting time after sampling two.

[0118] The best value is to add 0.058% of acid-soluble aluminum to the first sample. After the inclusions can be removed as much as possible by stirring with large argon gas, there is no need to take the second sample, and there is no need to add aluminum wire after the second sample comes out, and the composition of the molten steel product can be within the qualified range. From the perspective of quality, it is better to add less or no acid-soluble aluminum in the later stage, but if too much aluminum is added to the first sample, the finished acid-soluble aluminum will be scrapped. If too little aluminum is added to the first sample, more aluminum will be added after the second sample comes out. Naturally, there will be more inclusions in the molten steel, and it will take time to make another sample.

[0119] Optionally, when the sampling test results show that the acid-soluble aluminum is less than 0.0295%, the aluminum wire is supplemented. If it is higher than 0.038%, the aluminum wire is supplemented at 60-80m 3 / h of argon stirring, the acid-soluble aluminum is controlled to decrease to 0.00295-0.038% by burning 0.001% every 10s.

[0120] By changing the above operation method, it is equivalent to optimizing from the original sample 2 to the target to the sample 1 to the target, reducing the waiting time for one sample, saving about 5 minutes. The molten steel drops 1.5℃ per minute during the treatment, and the electricity cost is 25 yuan per 1℃ increase in temperature. The cost reduction per furnace of steel is 5*1.5*25=187.5 yuan.

[0121] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0122] Example

[0123] In the converter, 26 tons of scrap steel are added to 110 tons of molten iron with a temperature of 1350°C and a silicon content of 0.30%.

[0124] Blow oxygen continuously into the converter. During the oxygen blowing process, the carbon content in the molten steel is constantly monitored. When the carbon content is greater than 0.1%, an oxygen lance is used to blow oxygen from top to bottom into the molten steel. The oxygen pressure is 0.86MPa and the oxygen flow rate is 27500m 3 / h, 6-hole bottom blowing converter, argon flow rate of each hole 40m 3 / h;

[0125] When the carbon content is lower than 0.1%, oxygen is blown from top to bottom into the molten steel using an oxygen lance, with an oxygen pressure of 0.88-0.9 MPa and an oxygen flow rate of 28,000 to 28,600 m3 / h. For a 6-hole bottom-blowing converter, the argon flow rate per hole is 60 m3 / h. 3 / h;

[0126] When oxygen is just blown, the oxygen lance is 2.4m above the material level in the converter. During the oxygen blowing process, the oxygen lance moves at a speed of 8cm every 20s.

[0127] After oxygen blowing is started, slag, 2.5t lime, 0.65t light-burned dolomite and 0.35t magnesium balls are added into the converter;

[0128] 3 minutes after the slag was added, the silicon was completely oxidized, and the temperature was about 1041°C. 1.8 tons of iron ore was added, and 1.3 tons of lime was added for dephosphorization, and the low-temperature dephosphorization time was maintained for 40 seconds.

[0129] After dephosphorization, oxygen blowing is continued for 10 minutes, and the temperature of molten steel is raised to 1600℃ for tapping. At this time, the final oxygen value is 1000ppm.

[0130] According to the endpoint oxygen, the amount of carbon powder added is calculated as (1000-400) / 9=66.6kg. During the steel tapping process, 66.6kg of carbon powder is added to the ladle. The specific method is: when 0t of steel is tapped, 10kg is added to the empty ladle. Every 10t of steel tapped, 10kg is added until all the carbon powder is added. During the addition of carbon powder, the bottom blowing argon gas of the ladle is opened to 70m3 / h. After the addition is completed, it is reduced to 15m 3 / h;

[0131] According to the end point oxygen, the amount of aluminum and iron added is calculated as (1000-400)*0.9-0.95=540kg-570kg. According to the loading amount of 110t+26t and the blowing loss of 10%, the steel output is about (110+26)*90%=122.4t. During the converter steel output process, when there are 10-20t of molten steel left in the converter, that is, when the steel output reaches 102.4t-112.4t, aluminum and iron are added to the ladle for deoxidation, and the addition amount is 550kg.

[0132] After the addition of aluminum and iron is completed, the ladle is transferred to the argon station. After arriving at the argon station, the acid-soluble aluminum content is measured. According to the test results, the aluminum wire is fed into the molten steel by a wire feeder to add aluminum to 0.035%. After adding aluminum, wait for 20 minutes to achieve the deoxidation and purification effect, so as to reduce the loss of acid-soluble aluminum in the LF furnace process;

[0133] After the waiting time is over, the crane will lift the molten steel to the LF furnace, or continue to wait after lifting it to the LF furnace. The total waiting time after the aluminum filling is completed is 20 minutes or more. The LF furnace starts to process the molten steel and add slag for the second time, adding 500kg of lime, 300kg of synthetic slag, 200kg of aluminum slag, and 80kg of fluorite;

[0134] After the second slag addition is completed, power is supplied to the molten steel temperature at 1600℃, then the power is turned off, sample one is taken, and after the components of sample one come out, stirring is carried out at a high speed of 70m3 / h for 3min. During the stirring process, the alloy is added and the acid-soluble aluminum is adjusted to 0.058%, and then power is continued to be supplied to the molten steel temperature at 1600℃, and finally the calcium wire is soft-blown.

[0135] Comparative Example 1

[0136] On the basis of keeping other unchanged in the embodiment, only the loading amount is changed, and the result is as follows: the amount of molten iron is reduced from 110t to 105t, the amount of scrap steel is increased from 26t to 31t, and the total amount is still 136t, then the temperature will be insufficient. The advantage is that there is no need to add cooling materials such as iron ore to maintain the low-temperature dephosphorization time, 1.8t of iron ore is reduced, 1t costs 800t, and 1460 yuan is saved. The disadvantage is insufficient heat. Compared with the embodiment, the heat of 5t molten iron is reduced by 1350℃, and the temperature drop of 5t scrap steel is increased by about 75℃, that is, the terminal temperature will be reduced by 80℃. The cost of steel increases by 0.4 yuan per 1℃ / t of temperature increase, and 121.5*80*0.4=3888 yuan needs to be increased. After comparison, the disadvantages are greater than the advantages, so according to the conditions of molten iron, controlling the loading amount to a certain range is a choice for low-cost smelting.

[0137] Comparative Example 2

[0138] In the embodiment, only the loading amount is changed while keeping other factors unchanged. The result is as follows: if the molten iron is increased from 110t to 115t, the scrap steel is reduced from 26t to 21t, and the total amount is kept at 136t, then there will be a temperature surplus. The heat of molten iron is increased by 5t, the temperature of scrap steel is reduced by 5t, and the temperature is increased by 80℃, which means the terminal temperature is 80℃ higher. The advantage is that the oxygen required for temperature increase is reduced. If the temperature increases by 1℃ every 2s, 40s of oxygen blowing time is saved, and the oxygen consumption per hour is 27000m 3 , oxygen per m 3 / 0.6 yuan, reducing oxygen cost = 27000 / 3600*40*0.6 = 180 yuan, but the disadvantage is that it increases the consumption of cooling materials such as iron ore, because low temperature is conducive to dephosphorization. If the initial temperature is high, the phosphorus cannot be removed, resulting in unqualified phosphorus content, so the excess temperature still needs to be cooled by ore, increasing the ore by 5t, and the cost increases by 5*800=4000 yuan. After comparison, the disadvantages outweigh the advantages, so according to the conditions of the molten iron, controlling the loading amount to a certain range is a low-cost smelting option.

[0139] Comparative Example 3

[0140] On the basis of keeping other aspects unchanged in the embodiment, only the timing of adding iron ore to the converter smelting is changed. The iron ore is added after a long time after the slag is added, when the temperature rises to the temperature in the table below. The results are as follows:

[0141]

[0142] The later the iron ore is added, the lower the dephosphorization rate. If the dephosphorization effect is to be maintained, the later it is added, the more iron ore needs to be added, and the higher the cost. According to 1600℃ versus 1200℃, the iron ore needs to be added 2.3 times, that is, 1.8*2.3=4.14t, 4.14-1.8=2.34t more, and the cost increases by 2.34*800=1872 yuan.

[0143] Comparative Example 4

[0144] On the basis of keeping other unchanged in the embodiment, only the amount of carbon powder added in the steel-making process is changed. In the embodiment, the amount of carbon powder added for deoxidation is calculated to be 66.6 kg according to the end point oxygen. If only 30 kg is added, it is obvious that insufficient deoxidation will occur. The amount of aluminum wire deoxidation is increased. According to carbon: oxygen = 12: 16 aluminum: oxygen = 54: 48, 66.6-30 = 36.6 kg of carbon powder is used less, which will reduce deoxidation = 36.6*16 / 12 = 48.8 kg, increase aluminum = 48.8*54 / 48 = 54.9 kg, aluminum iron 18 yuan / kg, and increase cost = 54.9*18 = 988.2 yuan.

[0145] Comparative Example 5

[0146] On the basis of keeping other things unchanged in the embodiment, only the amount of carbon powder added in the steel-making process is changed. In the embodiment, the amount of carbon powder added for deoxidation is calculated to be 66.6 kg according to the end point oxygen. If 90 kg of carbon powder is added, the advantage is that the amount of aluminum wire deoxidation is saved, but it will cause the carbon to exceed the upper limit, and a furnace of carbon exceeding the standard will be scrapped, and the processing cost of t steel will be 450 yuan, and the cost loss of the furnace is 121.5*450=54675 yuan.

[0147] In addition, carbon powder is not suitable for all-in-one addition and needs to be added separately. The main reason is to reduce the carbon addition to the molten steel and use it more for deoxidation. If it is added all at once, the oxygen in the molten steel per unit time will drop to a very low level instantly, and some excess carbon powder will add carbon to the molten steel, causing the carbon to easily exceed the upper limit and be scrapped.

[0148] Comparative Example 6

[0149] On the basis of keeping other unchanged in the embodiment, only the control range of aluminum supplementation with aluminum wire in the argon station is changed. It is increased from 0.035% to 0.065%. Theoretically, the advantage is to reduce the aluminum loss in the LF furnace process, but in fact, the aluminum loss varies greatly and has no rules. The main reason is that when the carbon is pulled to 0.04% or below, the oxygen in the converter molten steel can be 900-1300ppm. We just count the average value of carbon oxygen product and calculate the oxygen content according to the average value. However, especially when the molten steel is well deoxidized, or the bottom blowing effect of the molten steel is poor, or when the rhythm is tight and the LF furnace has no time to wait, it is very easy to cause the finished acid-soluble aluminum to exceed the upper limit, and the cost loss of one furnace is 54,675 yuan.

[0150] Comparative Example 7

[0151] On the basis of keeping other aspects unchanged in the embodiment, only the control range of aluminum supplementation with aluminum wire in the argon station is changed. It is reduced from 0.035% to 0.015%. The advantage is that it is based on good deoxidation and can save some aluminum wire. However, in practice, most of the deoxidation will be poor. After the molten steel reaches the LF furnace, so much aluminum wire still needs to be supplemented. Therefore, the cost cannot be reduced. Instead, the aluminum oxide generated by the later aluminum supplementation increases, the inclusions in the molten steel increase, the consumption of slag such as lime and the amount of calcium wire increase. Adding 100kg of lime and 30m of calcium wire costs about 120 yuan.

[0152] Theoretically, if the acid-soluble aluminum in the molten steel is greater than 0.030%, the molten steel can be completely deoxidized. Therefore, through practice, we set the target at 0.035%, which ensures that the molten steel is completely deoxidized without wasting too much aluminum wire.

[0153] Comparative Example 8

[0154] On the basis of keeping other unchanged in the embodiment, only the waiting time after the argon station is fed with aluminum wire is changed. The shorter the waiting time, the greater the range of acid-soluble aluminum loss of molten steel when it is treated in the LF furnace, and the longer the waiting time, the smaller the range of acid-soluble aluminum loss of molten steel when it is treated in the LF furnace. The total time from the exit of the argon station to the start of continuous casting is generally 75-85 minutes, the LF furnace treatment cycle is 50 minutes, the molten steel is hoisted for 10 minutes, and there is 15-25 minutes surplus. Therefore, on the basis of keeping the LF furnace treatment time sufficient, the treatment as late as possible is the maximum value to reduce the range of acid-soluble loss in the process. However, if the treatment is too late, the process is afraid of encountering equipment or other abnormalities. Therefore, the control of waiting for 20 minutes is more in line with the actual production situation. Compared with the original direct treatment of molten steel without waiting, the acid-soluble aluminum often fluctuates greatly. The operator does not match the target range at one time, and has to match it again, wasting 5 minutes, and the compensation electricity fee of 130 yuan for the temperature drop during this period. If other steel mills have sufficient time, then the waiting time after the argon station is fed with aluminum wire can be increased.

[0155] Comparative Example 9

[0156] This comparative example is basically the same as the embodiment, except that:

[0157] After the second slag addition is completed, power is supplied to the molten steel temperature at 1600℃, then the power is turned off, sample one is taken, and after the components of sample one are obtained, the temperature is 70m 3 / h of high stirring for 3min. During the stirring process, the alloy was added and the acid-soluble aluminum was adjusted to 0.068%. Then power was continued to be supplied until the molten steel temperature reached 1600℃. Sample 2 was taken. The results of sample 2 showed that the acid-soluble aluminum content was 0.036%-0.048%.

[0158] According to experience, the loss of acid-soluble aluminum from sample 2 to finished product is 10-15%, so the acid-soluble aluminum of the finished product is about 0.0306%-0.0408%. The acid-soluble aluminum of some furnaces will exceed the upper limit of the range of 0.035%, and the cost loss of one furnace will be 54,675 yuan. Or if it is found that the acid-soluble aluminum is too high, the acid-soluble aluminum will be burned by opening a large argon gas explosion, which will also increase the processing time and temperature loss, and increase the power consumption of molten steel heating. It is expected to increase 1-2 minutes of time and 100 yuan of electricity.

[0159] Comparative Example 10

[0160] This comparative example is basically the same as the embodiment, except that:

[0161] Compared with the example, after sampling one, the acid-soluble aluminum content was reduced from 0.058% to 0.048%, and then the power was continued to be supplied until the molten steel temperature was 1600°C. Sample two was taken, and the results of sample two showed that the acid-soluble aluminum content was 0.016%-0.028%. This requires aluminum supplementation, and the more aluminum supplementation, the more inclusions in the molten steel. Compared with the example, the quality of the molten steel is not so good, and the LF furnace processing time and the compensation power consumption of the temperature drop during this period need to be increased. It is expected to increase the time by 1-2 minutes and the electricity fee by 100 yuan.

[0162] In general, according to the minimum aluminum loss calculation, the acid-soluble aluminum of the control sample is less than 0.038%. As long as it is not less than 0.0295%, there is no need to supplement aluminum wire.

[0163] Experimental example

[0164] The various properties or parameters of the low-carbon cold heading steel produced in the embodiments and comparative examples were tested, and the steelmaking time and cost of the embodiments and comparative examples were statistically recorded and recorded in Table 1.

[0165] Table 1 shows the parameters of low carbon cold heading steel in various embodiments and comparative examples as well as the time and cost of the preparation process. “+” in the table means increase.

[0166]

[0167]

[0168] In summary, the steelmaking method provided by the present invention reduces the converter temperature by adding excessive scrap steel to the molten iron, and then raises the temperature by blowing over-oxidation, and lowers the carbon content to the required range, and then the molten steel is transferred to the ladle for carbon and aluminum deoxidation, and ensures that there is an appropriate content of acid-soluble aluminum in the molten steel; after aluminum supplementation, complete deoxidation is achieved by waiting or blowing argon; due to a series of operations in the converter and in the ladle before reaching the LF furnace to add slag, the operation mode after adding slag to the LF furnace can be changed to power supply-aluminum mixing-sampling-power supply and other samples-aluminum matching to the target range according to the sample. The method is equivalent to optimizing the original sample 2 aluminum matching to the target to the sample 1 aluminum matching to the target through the change of the above operation method, which reduces the time of waiting for one sample. Therefore, the steelmaking method provided by the present invention can save production costs.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for making low carbon cold heading steel, characterized in that: include: Mixing hot metal with scrap steel in a converter; Continuously blowing oxygen into the converter so that the carbon content of the steel is less than 0.04% when it is tapped; During the oxygen blowing process, the first slag addition is carried out, and the added slag materials include lime, light-burned dolomite and magnesium balls; After the silicon in the slag added in the first slag addition is completely oxidized, iron ore is added and lime is added for dephosphorization. The dephosphorization time is 35 to 50 seconds. After dephosphorization is completed, continue to blow oxygen for 8 to 12 minutes, and control the temperature to 1590 to 1610℃ for steel production; During the steel tapping process, carbon powder is added into the ladle to reduce the oxygen content; During the steel tapping process, lime is added to the ladle. When there are 10 to 20 tons of molten steel left in the converter, aluminum is added to the ladle for deoxidation. After the aluminum material is added, the ladle is transferred to the argon station. After arriving at the argon station, the acid-soluble aluminum content is measured. According to the test results, the aluminum content of the molten steel is supplemented to 0.03-0.04%; After aluminum filling, deoxidation and purification treatment are carried out; After the molten steel reaches the LF furnace, the second slag is added, and the added slag includes lime, synthetic slag, aluminum slag and fluorite; After the second slag addition is completed, power on until the molten steel temperature reaches 1590-1610℃, take samples and wait for the results to come out, then cut off the power and heat at 60-80m 3 / h of large stirring for 2 to 4 minutes. During the stirring process, the alloy is matched and the acid-soluble aluminum is adjusted to 0.055% to 0.060%. Then continue to supply power until the molten steel temperature reaches 1590 to 1610℃ and finally use calcium wire soft blowing; In the steelmaking process, the amount of each material used is calculated by weight: 110,000 parts of molten iron, 24,660 to 27,120 parts of scrap steel, 2,400 to 2,600 parts of lime added for the first time, 600 to 700 parts of light-burned dolomite, 300 to 400 parts of magnesium balls, 1,500 to 2,000 parts of iron ore, 1,000 to 1,500 parts of lime for dephosphorization, 400 to 600 parts of lime added during steel tapping, 450 to 550 parts of lime added for the second time, 280 to 330 parts of synthetic slag, 180 to 220 parts of aluminum slag, and 60 to 100 parts of fluorite.

2. The steelmaking method according to claim 1, characterized in that The methods of blowing oxygen into the converter include: Monitor the carbon content in the molten steel at all times. When the carbon content is greater than 0.1%, use an oxygen gun to blow oxygen from top to bottom into the molten steel. The oxygen pressure is 0.85-0.88MPa and the oxygen flow rate is 27000-28000m 3 / h, the total bottom blowing argon flow rate is 220~260m 3 / h; when the carbon content is lower than 0.1%, oxygen is blown from top to bottom into the molten steel using an oxygen lance, with an oxygen pressure of 0.88-0.9MPa and an oxygen flow rate of 28000-28600m 3 / h, total bottom blowing argon flow rate 320~400m 3 / h.

3. The steelmaking method according to claim 2, characterized in that Initially, the oxygen lance is 2.4m above the material level in the converter. During the oxygen blowing process, the oxygen lance moves at a speed of 5 to 10cm every 20s.

4. The steelmaking method according to claim 1, characterized in that When the results of the second sampling test show that the acid-soluble aluminum is less than 0.0295%, the aluminum wire is supplemented. If it is higher than 0.038%, the aluminum wire is added at 60-80m 3 / h of argon stirring, the acid-soluble aluminum is controlled to decrease to 0.00295-0.038% by burning 0.001% every 10s.

5. The steelmaking method according to claim 1, characterized in that The method of deoxidation and purification is: wait 20 to 25 minutes after aluminum filling is completed; Or pass argon gas at a flow rate of 5 to 10 m 3 / h soft blowing 10~20min; Or pass argon gas at a flow rate of 10-20m 3 / h weak blowing for 5 to 10 minutes; Or pass argon gas at a flow rate of 55-65m 3 / h blowing for 1 to 5 minutes; When the deoxidation and purification treatment method is to wait for 20 to 25 minutes after the aluminum supplement is completed, it is before the molten steel reaches the LF furnace, or after the molten steel reaches the LF furnace.

6. The steelmaking method according to claim 1, characterized in that: The method of adding the carbon powder is to first add a unit of carbon powder into the empty ladle, and then add a unit of carbon powder every time 10t of molten steel is poured in, until the carbon powder is added completely; Optionally, the one unit portion is 1 kg.

7. The steelmaking method according to claim 1, characterized in that The amount of carbon powder added is determined according to formula A, which is: M1=(x / 110)(y-400) / 9, where M1 is the amount of carbon powder added, d is in kg; x is the amount of molten iron, in t; y is the oxygen content at the end of the converter, in ppm.

8. The steelmaking method according to claim 7, characterized in that During the addition of carbon powder, the bottom blowing argon of the ladle is opened to 60-80m 3 / h, after adding, turn down to 10~20m 3 / h.

9. The steelmaking method according to claim 1, characterized in that: The aluminum material is determined according to the aluminum content thereof according to formula B, where: M2=0.5(y-400)*(0.9-0.95), wherein M2 is the amount of aluminum material added, in kg; and y is the oxygen content at the converter end point, in ppm.

10. The steelmaking method according to claim 1, characterized in that The aluminum material is aluminum iron or aluminum particles.

Images