Method for producing titanium-containing steel in a single lf furnace

Abstract

The application discloses a method for producing titanium-containing steel by a single LF furnace, and comprises the following steps: adjusting the temperature of molten steel after desulfurization to be 1566-1570 DEG C, adjusting argon to a weak blowing state, stopping power supply, adding ferrotitanium to the argon inlet, so that the ferrotitanium directly enters the molten steel without contacting a slag layer, then closing to soft blowing of argon at 5-15 cubic meters per hour, feeding a calcium wire and soft blowing out of the station. By the method, the titanium increase and titanium yield of the LF furnace are both relatively stable, the loss from the addition of ferrotitanium to the finished product is also relatively stable, and the addition amount of titanium can be significantly reduced, so that the cost is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, in particular to a method for producing titanium-containing steel using a single LF furnace. Background Art

[0002] Q345C, Q345T, and Q345GJC are titanium-containing steels. When using the LF→RH process to produce titanium-containing steels, employing both LF and RH titanium alloying processes, with Chongqing Steel primarily using LF and supplemented by RH, the overall yield of 70 ferrotitanium is only around 70%. Analysis revealed that the main reason for this low overall titanium yield is that the addition of 70 ferrotitanium to the LF ladle slag, argon agitation, RH vacuum circulation, and calcium treatment, causes oxidation of the titanium component. A literature review revealed that Rizhao Steel, using the LF→RH process to produce titanium-containing steels, achieved a titanium yield of 96%, using the RH process for full ferrotitanium addition. Given the price of 70 ferrotitanium at 28,241 yuan per ton, this significant difference in yield significantly impacts costs.

[0003] The yield of ferrotitanium added to LF furnaces is far lower than that of RH furnaces in other units. This same issue also occurs in the production of titanium-containing steel in the first steelmaking process at Shaoguan Iron and Steel. Statistics show that, for a 120-ton molten steel using 70% ferrotitanium, the LF furnace typically requires 10 kg more than the RH furnace. For the same increase from 0.002% to 0.028%, the RH furnace requires 50 kg, while the LF furnace requires 60 kg or more. When all ferrotitanium is added in the RH furnace, the average yield is 89.14%, while when all ferrotitanium is added in the LF furnace, the average yield is 74.28%.

[0004] If it is LF+RH process, all ferrotitanium can be added in RH. However, for Q345C steel or some products that only use LF furnace process, the yield of ferrotitanium cannot be as high as that of RH. If RH is removed simply to improve the yield of titanium alloy, the cost of RH will increase.

[0005] In order to solve the problem of low yield of LF plus ferrotitanium, the present invention is proposed. Summary of the Invention

[0006] The object of the present invention is to provide a method for producing titanium-containing steel using a single LF furnace.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a method for producing titanium-containing steel using a single LF furnace, comprising:

[0009] Adjust the temperature of the molten steel after desulfurization to 1566℃-1570℃, adjust the argon to a weak blowing state of 15-25 cubic meters / hour, stop supplying power, the diameter of the bright circle of the argon port is about 25-35 cm, the molten steel penetrates the slag layer and is exposed, and then add ferrotitanium alloy to the center of the argon port so that the ferrotitanium alloy enters the molten steel directly without contacting the slag, and then adjust the argon to a soft blowing state with an argon flow rate of 5-15 cubic meters / hour, feed the calcium line, and soft blow out the station.

[0010] In an optional embodiment, the titanium content in the molten steel is 0.016wt%-0.028wt%;

[0011] Preferably, the titanium-iron alloy is manually cast into the argon port;

[0012] Preferably, after adding the titanium-iron alloy, the calcium wire is fed for 50-100 meters at a wire speed of 150-200 meters per minute.

[0013] In an optional embodiment, before adding the titanium-ferroalloy, deoxidation and desulfurization steps are also included.

[0014] In an optional embodiment, when the converter is tapping, the argon gas at the bottom of the ladle is adjusted to 40-60 cubic meters per hour. When the tapping is to 1 / 5, an aluminum-iron alloy is added to the molten steel for deoxidation. When the tapping is to 1 / 2, slag is added. After the slag is added, the argon gas is reduced to 20-30 cubic meters per hour. After the tapping is completed, sampling is taken, the argon gas is turned off, and the molten steel is transferred to the LF furnace.

[0015] Preferably, the amount of aluminum-iron alloy added = oxygen content at the converter endpoint before tapping / 2.592;

[0016] Preferably, the oxygen content at the converter endpoint before tapping is 200-435 ppm;

[0017] Preferably, the slag material comprises lime, bauxite and silicomanganese alloy, and the mass ratio of the lime, bauxite and silicomanganese alloy to molten steel is 490-510:290-310:2200-2400:110×10 3 -125×10 3 .

[0018] In an optional embodiment, the desulfurization step includes: the temperature of the molten steel to the LF furnace is 1500-1545°C. When the temperature is above 1530°C, the argon flow rate is adjusted to 90-110 cubic meters / hour, and slag is added first and then power is supplied; when the temperature is below 1530°C, slag is added while power is supplied, and the argon flow rate is 40-50 cubic meters / hour; desulfurization material is added to the LF furnace, and the desulfurization material includes lime, high-aluminum slag and fluorite, and the mass ratio of lime, high-aluminum slag and fluorite in the desulfurization material to the molten steel is 300-600:60-80:80-135:110×103 -125×10 3 .

[0019] In an optional embodiment, the content of acid-soluble aluminum in the deoxidized molten steel is greater than 0.004%.

[0020] In an optional embodiment, after adding the desulfurization material to the LF furnace, the slag is moistened by the tumbling molten steel and heated to a molten steel temperature of 1550-1570°C, and desulfurization is carried out by stirring for 2-3 minutes at an argon flow rate of 90-110 cubic meters / hour. After desulfurization is completed, the argon flow rate is adjusted to 15-25 cubic meters / hour.

[0021] In an optional embodiment, a sample is taken after desulfurization is completed. If the sample is white slag or yellow-white slag, the temperature and argon flow rate are adjusted to add titanium-iron alloy; if the sample is neither white slag nor yellow-white slag, ferrosilicon powder or ferrosilicon powder and aluminum particles are added to deoxidize until the sample is white slag or yellow-white slag.

[0022] In an optional embodiment, the titanium-containing steel is at least one of Q345C, Q345T and Q345GJC.

[0023] The present invention has the following beneficial effects:

[0024] Through the above measures and practices of this application, the LF titanium addition and titanium yield are relatively stable, and the loss from adding titanium iron to the finished product is also relatively stable, and the amount of titanium added can be significantly reduced, thereby effectively reducing costs. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0026] The present application provides a method for producing titanium-containing steel in a single LF furnace, comprising:

[0027] Adjust the temperature of the molten steel after desulfurization to 1566℃-1570℃, adjust the argon to a weak blowing state of 15-25 cubic meters / hour, stop supplying power, the diameter of the bright circle of the argon port is about 25-35 cm, the molten steel penetrates the slag layer and is exposed, and then add ferrotitanium alloy to the center of the argon port so that the ferrotitanium alloy enters the molten steel directly without contacting the slag, and then adjust the argon to a soft blowing state with an argon flow rate of 5-15 cubic meters / hour, feed the calcium line, and soft blow out the station.

[0028] Precisely control the temperature. After manually adding the ferro-titanium alloy, do not supply power to prevent it from being burned during the heating process. For example, for Q345C, control the temperature at 1566-1570°C before adding the ferro-titanium. If the temperature is not high enough after manually adding the ferro-titanium, for example, only 1560°C, and then apply power for 60-80 seconds, the ferro-titanium will be burned by about 0.001%, affecting the yield.

[0029] Control the timing of adding ferrotitanium: add ferrotitanium immediately after power is supplied, and adjust the argon flow rate at the same time so that ferrotitanium can be directly added to the molten steel. If you wait too long before adding ferrotitanium, the slag surface temperature will drop and it will gradually become sticky and hard. Part of the ferrotitanium will remain in the slag or stay in the slag for a long time, and will be oxidized by 0.001%-0.002%, affecting the yield.

[0030] Control the adding position of ferrotitanium alloy: Each time adding, adjust the argon to the weak blowing state to expose the molten steel, and add it to the argon port to allow the ferrotitanium to enter the molten steel directly and avoid it from entering the slag.

[0031] In an optional embodiment, the titanium content in the molten steel is 0.016wt%-0.028wt%, and a titanium-iron alloy with a titanium mass fraction of 70% is usually added.

[0032] Ferro-titanium was added manually from the LF alloy silo, allowing 70 titanium to be loaded in 10-kg packages. The reason why 9 kg, 11 kg, or other larger or smaller values ​​were not used here is mainly due to the calculation based on the unit's molten steel volume and composition range. When Shaogang's No. 1 Steelmaking Plant produces Q345C steel, the average molten steel volume is 122.3 tons, with residual titanium content of 0.001%-0.003%, while the required titanium content range is 0.016%-0.028%. To reduce costs, the composition is generally adjusted towards the lower limit. Ideally, the titanium content out of the LF furnace should be controlled within the range of 0.018%-0.021%. Burn-out during continuous casting ranges from 5.5% to 13.8%. Therefore, after deducting the burn-out during continuous casting, the finished product can still guarantee a content of at least 0.016%. In the past, under normal circumstances, the titanium content would be controlled to the upper limit. 70 titanium ferro contained 70% titanium, with a yield of 89.14% and residual titanium of 0.001%. The amount of alloy added = (0.028% - 0.001%) × 122.3 × 1000 / 70% / 89.14% = 52.91 kg, that is, an increase of 0.026% requires 50.95 kg of 70 titanium ferro, which is just enough for 5 hand-cast bags. Now, in order to save alloy costs, the amount is increased to 0.021%, so the amount of alloy added = (0.021% - 0.001%) × 122.3 × 1000 / 70% / 89.14% = 39.19 kg, which is just enough for 4 hand-cast bags of titanium ferro. Based on the above calculations, we plan to set the package weight by increasing the yield of ferrotitanium added to the LF furnace. We plan to hand-feed four packages of ferrotitanium, expecting to achieve a yield of over 84%, and to keep the titanium content out of the LF furnace at 0.019%-0.020%. Therefore, each package will be 10 kg. Under other production conditions, the capacity of each ferrotitanium package can be larger or smaller.

[0033] In an optional embodiment, the titanium-iron alloy is manually injected into an argon port.

[0034] In an optional embodiment, after adding the titanium-iron alloy, the calcium wire is fed for 50-100 meters at a wire speed of 150-200 meters per minute.

[0035] Compared to adding ferrotitanium from a silo, hand-throwing offers the advantage of more precise delivery to the argon inlet. When added from a silo, the alloy collides with the chute, causing it to constantly change its direction of descent. By the time it reaches the chute outlet, it's not a completely straight line, but rather disperses in other directions. This prevents concentrated delivery to the argon inlet, resulting in a 0.0015%-0.0025% reduction in titanium. However, hand-throwing allows for 100% delivery to the argon inlet, allowing it to enter the molten steel directly without contact with the slag layer. Furthermore, ferrotitanium can be added directly to the molten steel, similar to RH furnaces, resulting in a more stable yield. During LF refining, the yield of ferrotitanium addition is affected by the degree of deoxidation, slag volume, and slag fluidity, so hand-throwing effectively mitigates these factors.

[0036] In an optional embodiment, before adding the ferrotitanium alloy, a deoxidation and desulfurization step is further included to meet the production requirement of a converter end-point molten steel with sulfur less than 0.040% or below.

[0037] In an optional embodiment, when the converter is tapped, the argon gas is adjusted to 40-60 cubic meters / hour, at 1 / 5 of the tapping, ferroaluminum alloy is added to the molten steel for deoxidation, at 1 / 2 of the tapping, slag is added, until the slag is completely added, the argon gas is adjusted to 20-30 cubic meters / hour, after the tapping is completed, sampling is performed, the argon gas is turned off, and then the molten steel is transferred to the LF furnace;

[0038] Preferably, the amount of the ferroaluminum alloy added = the oxygen content of the converter end-point before tapping / 2.592;

[0039] Preferably, the oxygen content of the converter end-point before tapping is 200-435 ppm;

[0040] Preferably, the slag includes lime, bauxite and silicon-manganese alloy, and the mass ratio of the lime, bauxite and silicon-manganese alloy to the molten steel is 490-510:290-310:2200-2400:110x10 3 -125x10 3 .

[0041] Generally, the lower the converter end-point oxygen is, the better. In the prior art, the converter end-point oxygen is usually 200-300 ppm. After the scheme is adjusted, the scheme can be applied to the case of high oxygen content of the molten steel. The scheme can still be applied to the case of the converter end-point oxygen content of 430 ppm or above.

[0042] In an optional embodiment, the desulfurization step includes: when the temperature of the molten steel in the LF furnace is 1500-1545℃, the argon gas flow is adjusted to 90-110 cubic meters / hour, and the slag is added first and then power is supplied; when the temperature is below 1530℃, the slag is added while power is supplied, and the argon gas flow is 40-50 cubic meters / hour; desulfurization material is added to the LF furnace, the desulfurization material includes lime, high-aluminum slag and fluorite, and the mass ratio of the lime, high-aluminum slag and fluorite in the desulfurization material to the molten steel is 300-600:60-80:80-135:110x10 3 -125x10 3 .

[0043] The role of lime is desulfurization, and the amount of desulfurization must be controlled. On the one hand, it is to reduce the thickness of the slag layer so that titanium iron can directly enter the molten steel at the argon port, and on the other hand, it is to reduce the nitrogen absorption of the molten steel. The role of high-aluminum slag is to make the slag white (the yield of titanium is directly related to the color of the slag, white: 85%-90%, light yellow or light green: 78%-84%, dark yellow or dark green: 70%-77%, dark gray or black: 60-69%. Although aluminum slag or aluminum can enhance the deoxidation effect and make the slag white, it is not suitable to add too much, because the amount of aluminum slag added is also related to the quality of the molten steel. The higher the aluminum in the molten steel, the more it combines with nitrogen to form aluminum nitride during the refining and heating process. In the process of molten steel forming into billets in the continuous casting crystallizer, the precipitation capacity of aluminum nitride is higher. It is easy to form cracks in the shell, so the deoxidation intensity should be controlled. On the one hand, the slag can be made into white slag or yellow-white slag. Even if the recovery rate of titanium-iron alloy cannot reach 85%, there is still 80% recovery rate; on the other hand, the desulfurization should be controlled, because the greater the amount of aluminum slag or aluminum added, the better the desulfurization effect, and the sulfur in the molten steel has a certain hindering effect on reducing the nitrogen absorption of the molten steel during the refining process. If the desulfurization is too much, the effect of hindering the nitrogen absorption of the molten steel will be smaller, and the molten steel will absorb more nitrogen. The free nitrogen and aluminum nitride formed will naturally be high, and the casting will be prone to cracks). Since each batch of lime has some that are raw, some that are overburned, and some that meet the standards (just like burning charcoal, when a batch of wood is put into the kiln, there will definitely be some that are just burned into charcoal, but there will also be some that are overburned and turn into ash, or some that are not burned through and remain wood), fluorite is needed to adjust the fluidity. More should be added for raw burning and less for overburning. The amount of fluorite added should be adjusted according to the slag on site, and it should also be combined with the temperature of the molten steel arriving at the station. The lower the temperature, the more fluorite should be added (the fluidity is related to the ferrotitanium yield. The better the fluidity, the higher the titanium alloy yield).

[0044] In an optional embodiment, the content of acid-soluble aluminum in the deoxidized molten steel is greater than 0.004%.

[0045] In an optional embodiment, after adding the desulfurization material to the LF furnace, the slag is moistened by the tumbling molten steel and heated to a molten steel temperature of 1550-1570°C, and desulfurization is carried out by stirring for 2-3 minutes at an argon flow rate of 90-110 cubic meters / hour. After desulfurization is completed, the argon flow rate is adjusted to 15-25 cubic meters / hour.

[0046] In an optional embodiment, a sample is taken after desulfurization is completed. If the sample is white slag or yellow-white slag, the temperature and argon flow rate are adjusted to add titanium-iron alloy; if the sample is neither white slag nor yellow-white slag, ferrosilicon powder or ferrosilicon powder and aluminum particles are added to deoxidize until the sample is white slag or yellow-white slag.

[0047] In an optional embodiment, the titanium-containing steel is at least one of Q345C, Q345T and Q345GJC.

[0048] Through the above measures and practices, taking Q345C as an example, 40 kg of 70 titanium ferroalloy is enough for each 122.3 tons of molten steel, the titanium content in the LF is stabilized at 0.0186%-0.0198%, the yield is 80%-85%, and the loss from the addition of titanium ferroalloy to the finished product is also relatively stable, generally at 5%-7%, the titanium content in the finished product is 0.018%-0.019%, which is also at the lower limit of the titanium range 0.016%-0.028%. The use of 70 titanium ferroalloy in each furnace reduces at least one package (10 kg) of 70 titanium ferroalloy, and the price of 70 titanium ferroalloy is 28241 yuan / ton, so the cost reduction per furnace is 282.41 yuan.

[0049] The features and performances of the present application are further described in detail in connection with the following examples. It should be noted that if not specifically stated, the content of components in the following examples is mass fraction.

[0050] Example One

[0051] The present example provides a method for producing Q345C steel in a single LF furnace. The composition range of the Q345C steel finished product is: carbon 0.14%-0.18%, silicon 0.15-0.25%, manganese 1.35%-1.45%, phosphorus less than 0.028%, sulfur less than 0.010%, and titanium 0.016%-0.028%. In the present example, the composition of the molten steel at the end of the converter is as follows: carbon 0.088%, manganese 0.1115%, phosphorus 0.022%, and sulfur 0.027%. The composition is appropriate (as long as the carbon is not greater than 0.014% and the phosphorus is not greater than 0.025%, both of which are less than the appropriate composition), the temperature at the end is 1633℃, the molten steel can be tapped, and the molten steel quantity is 120 tons.

[0052] The electronic scale of the ladle car is reset to zero before tapping (so that the instrument can show how much molten steel is tapped), the bottom argon blowing is turned on at 40 cubic meters / hour, and the tapping starts. When the electronic scale shows that the tapping quantity is 20 tons, the aluminum ferroalloy is added, and when the tapping quantity is 60 tons, the lime, bauxite, and silicon-manganese alloy are added, and then the argon blowing is reduced to 25 cubic meters / hour.

[0053] The addition of aluminum-iron alloy here is calculated based on the carbon content at the converter end point or the oxygen content determined at the end point. In this embodiment, the carbon content is calculated, and the carbon-oxygen product (constant) = 0.000028%. The oxygen content of the molten steel = 0.000028% / 0.088% = 0.0318% (318ppm). Based on the deoxidation of 2.592ppm of aluminum-iron with 50% aluminum content and a yield of 70% per kilogram, (1×0.5×0.7×1000000 / 120000=2.916ppm, it can be obtained from the molecular formula of aluminum oxide that aluminum: oxygen = 2×27 / 3×16=54:48=1 .125, that is, 1.125ppm aluminum can remove 1ppm of oxygen from 120 tons of molten steel, and 2.916ppm aluminum can remove 2.592ppm of oxygen). After all the oxygen is removed, that is, the oxygen content of the molten steel is 318ppm, then the added aluminum and iron = 318 / 2.916 = 109.05 kg. In fact, considering that a little terminal slag or deviation of instrument analysis composition will be brought in in the later stage of steelmaking, the actual oxygen content of the molten steel will be higher than the theoretical value, so 10-20 kg of aluminum and iron will be added. After adding aluminum and iron, 500 kg of lime, 300 kg of bauxite, and 2300 kg of silicomanganese (manganese content 68%, silicon content 18%) will be added.

[0054] After tapping, the molten steel was sampled at 1535°C. The composition was as follows: phosphorus 0.024%, sulfur 0.022%, carbon 0.0911%, silicon 2300 × 0.18 × 0.70 / 120,000 = 0.2415%, manganese 2300 × 0.68 × 0.8 / 120,000 + 0.1115% = 1.107% + 0.1115% = 1.219%, and acid-soluble aluminum 0.004%. After sampling, the argon gas was turned off and the molten steel was transferred to the LF furnace.

[0055] After the molten steel arrives at the LF furnace, the production plan shows that the steel processing time of the furnace is 37 minutes (that is, the total time from entering the station to leaving the station). Turn on the bottom blowing argon gas at 100 cubic meters per hour, measure the temperature at 1532°C, and add lime, fluorite and aluminum slag. The amount of lime added is (0.022%-0.010%) / 0.0033%×100=363.6 kg, lime: fluorite=100:26-29, then 363.6 kg is matched with 94.5-105.4 kg of fluorite. The amount of fluorite added must also be added with the parameters of the temperature measurement at the station. When it is greater than 1530°C, add it according to this ratio. When it is less than 1525°C, add 10 kg more, when it is less than 1515°C, add 20 kg more, when it is less than 1505°C, add 30 kg more... The reason is that the lower the temperature at the station, the harder it is to melt the lime, and the more fluorite is needed. The station temperature is greater than 1530℃, so the amount of fluorite added is 94.5-105.4 kg, the actual amount added is 100 kg, and the aluminum slag is 70 kg (the design principle is to add acid-soluble aluminum in the argon station sample, and adjust the acid-soluble aluminum in the molten steel to 0.010%-0.020%, which is used to deoxidize the slag and make white slag. After deoxidation, the acid-soluble aluminum remaining in the molten steel is generally 0.003-0.006%. The aluminum slag contains 35%-40% aluminum, calculated at 37%, and the yield is 50%, 70×0.37×0.50 / 120000=0.0107%), and is added last. Finally, the total amount of slag added to the LF furnace is 363.6+110+70=543.6 kg. The temperature of every 100 kg of slag drops by 2.2°C, so the temperature drops by 543.6 / 100×2.2=11.9°C. After adding the slag, continue stirring for 2 minutes, stirring and cooling by 2.5°C per minute. It takes a total of 3 minutes from adding to stirring, and the temperature drops by 7.5°C, allowing the rolling molten steel to wet the slag.

[0056] After stirring, adjust the argon gas to 30-40 cubic meters per hour, use 9 gears to send electricity (temperature rise 3 degrees per minute), active power 7500KW, send electricity for 780 seconds and then cut off the power, stir 100 cubic meters per hour of argon for 2 minutes, turn down to 15 cubic meters per hour, take samples, stick slag, measure the temperature (1522-11.9-7.5) + 780 / 60×3-2.5×2=1536.6°C, the color of the slag is light green glass slag, indicating that deoxidation is not enough, throw 20 kg of ferrosilicon powder for deoxidation, continue to send electricity, 40 cubic meters of argon per hour, take samples for 4 minutes, and the remaining processing time is calculated as 37-3-13-4=17 minutes. Select 4 gears to send electricity (temperature rise 6 degrees per minute), send electricity for 6 minutes, and the sample composition is also out at this time, carbon 0.0966%, silicon 0.221%, manganese 0. 1.222%, phosphorus 0.024%, sulfur 0.010%, titanium 0.001%. At this time, the temperature is 1536.6+6×6=1572.6℃. Add 350 kg of high manganese and 50 kg of carbon powder. Stir for 1.5-3 minutes until the actual carbon powder is rolled up by the molten steel. Stir the furnace for 2.5 minutes. Turn the argon gas down to 18 cubic meters / hour. The sticky slag is white slag. At this time, the temperature is 1572.6 -2.5 × 2.5 - (350 + 50) / 100 × 0.5 = 1564°C, leaving 17 - 6 - 2 = 9 minutes. Power is applied at level 4 for 30 seconds, then the power is turned off. 40 kg of ferrotitanium is manually added to the argon inlet. After addition, the gas flow rate is reduced to 10 cubic meters per hour. 60 meters of calcium wire is fed at a line speed of 180 m / min. Six minutes after feeding, the temperature is measured at 1561°C. Sample 2 is taken and discharged, and the refining time is just completed. The mass fractions of the elements in the molten steel are now: carbon 0.143%, silicon 0.222%, manganese 1.401%, phosphorus 0.025%, sulfur 0.008%, and titanium 0.0198%.

[0057] Example 2:

[0058] This embodiment provides a method for producing Q345C steel in a single LF furnace. In this embodiment, the composition of the molten steel at the converter end point is as follows: carbon 0.062%, manganese 0.098%, phosphorus 0.017%, sulfur 0.035%, temperature 1553° C., molten steel is oxygenated, oxygen content is 451 ppm, aluminum iron added to steel tapping = 451 / 2.592 = 173.9 kg, 500 kg of lime, 300 kg of bauxite, and 2300 silicon manganese.

[0059] After the steel was produced, samples were taken, showing carbon 0.066%, silicon 0.0209%, manganese 1.18%, phosphorus 0.18%, sulfur 0.0309%, and temperature 1556°C.

[0060] After the molten steel arrives at the LF furnace, it is found that the processing time is 37 minutes and the arrival temperature is 1545°C. 100 cubic meters / hour of argon is used, and lime (0.0309%-0.010%) / 0.0033%×100=633.3 kg, fluorite=633.3×26 / 100=164.6 kg, and aluminum slag 70 kg, totaling 633.3+164.6+70=867.9 kg, is added. Temperature 867.9 / 100×2.2=21.2℃, continue stirring for 2 minutes after adding, cool down 5℃, turn down the argon flow to 35 cubic meters / hour, use 9th gear power for 180 seconds and then 4th gear power for 480 seconds, heat up 180 / 60×3+480 / 60×6=57℃, stir with 100 cubic meters / hour argon for 2 minutes, cool down 5℃, turn down the argon flow to 20 cubic meters / hour, and measure the temperature 1545-21. 2-5+57-5=1570.8℃, the sticky slag is gray, indicating poor deoxidation. 10 kg aluminum particles and 30 kg ferrosilicon powder are thrown in by hand. It takes 4 minutes to take samples and measure the temperature. Continue to supply power at level 4 for 3 minutes. After the sample comes out, mix it with the alloy. Stir with 100 cubic meters / hour of argon for 3 minutes. Reduce the argon to 30 cubic meters / hour. The sticky slag is white. The temperature is 1570℃. The remaining time is 37-3-3-8-4-3-3=13 The temperature was measured at 1562°C with 9 minutes remaining, at 1570°C - (13-9) × 2 = 1562°C. After one minute of power supply at level 4, the argon flow was reduced to 20 cubic meters per hour. The power was turned off, and 40 kg of ferrotitanium was manually added to the argon inlet. The argon flow was then reduced to 12 cubic meters per hour. A 60-meter calcium wire was fed at a line speed of 200 m / min. Argon was then blown for another 6 minutes, and the temperature was measured at 1562°C. Sample 2 was then taken out of the station. The mass fractions of the elements in the molten steel at this point were: carbon 0.152%, silicon 0.213%, manganese 1.394%, phosphorus 0.018%, sulfur 0.007%, and titanium 0.0187%.

[0061] When the slag is sticky in sample 1 of the above embodiment, the relationship between the slag color and the deoxidation dosage is as follows:

[0062]

[0063] After use, it can basically ensure that the slag will turn white before adding titanium iron. Since 2200-2400 kg of silicon manganese is added during the tapping process, the alloy contains 18% silicon. Under normal circumstances, the addition of aluminum and iron during tapping can completely remove oxygen. Moreover, the alloy is melted and the molten steel contains 0.20%-0.24% silicon, which is sufficient for deoxidizing the molten steel and slag. Unless there is serious slagging or molten steel overoxidation (the end point carbon content is less than 0.08% is considered molten steel overoxidation), the slag can be guaranteed to be yellow-white or light green slag at this time.

[0064] Comparative Example 1:

[0065] The method is basically the same as the first embodiment, except that the amount of aluminum-iron alloy added during the converter tapping process is different, and a fixed amount of 120 kg / furnace is used for addition.

[0066] If the final carbon content is high, the oxygen content of the molten steel is low. If 120 kg of aluminum iron is added, the molten steel will have excess acid-soluble aluminum, which will have no effect on subsequent refining operations, but will affect the quality of the ingot. This is because the molten steel is well deoxidized, the acid-soluble aluminum in the molten steel is high, and it is easier to absorb nitrogen.

[0067] If the final carbon is low, the oxygen content of the molten steel is high, and adding 120 kg of aluminum iron cannot completely deoxidize the molten steel, which will cause the slag to be black when refining sampling 1, affecting the deoxidation and desulfurization of the molten steel and increasing the difficulty of refining treatment. If the slag can be made white before hand-throwing titanium iron, it is normal. If it is not white and the color is green, 50 kg of titanium iron alloy should be added. If the slag is black, 60 kg of titanium iron alloy should be added.

[0068] Comparative Example 2:

[0069] The process is basically the same as that of Example 1, except that during refining sampling 1, no slag was sticky and the slag was not adjusted to white.

[0070] If it is white slag, it will not affect subsequent operations and the ferrotitanium yield, which is generally 84%-89%.

[0071] If it is light yellow or light green, the ferrotitanium yield is 75%-80%, and adding 40 kg will be on the low side, close to the lower limit of the composition range.

[0072] If it is dark yellow or dark green, the titanium iron yield is 68%-73%. Adding 40 kg is not enough, and 50 kg is needed.

[0073] If it is gray or black, the ferrotitanium yield is 60%-65%, and 60 kilograms will be needed.

[0074] Comparative Example 3:

[0075] Basically the same as Example 1, to ensure that the desulfurization reaches the qualified range, 800 kg of refined slagging lime is directly added.

[0076] The advantage is that it can ensure that the sulfur can be removed to within 0.01%.

[0077] The disadvantage is that the larger the slag volume and the thicker the slag layer, the higher the argon flow rate must be to push the slag away. The actual diameter of the bright circle at the argon outlet is 30 cm. Compared to the 20 cubic meters / hour of argon in Example 1, the flow rate should be increased to 35 cubic meters / hour. Furthermore, the higher the argon flow rate, the greater the burnout of ferrotitanium after the addition of argon, resulting in a slightly lower titanium content at the outlet, at 0.018%.

[0078] If the argon gas is not opened, the argon gas inlet will be relatively small, and part of the hand-thrown titanium iron will be burned in the slag, and the titanium content at the outlet will be lower, at 0.017%.

[0079] Comparative Example 4:

[0080] Basically the same as Example 2, after the ingredients are prepared and the temperature is controlled in advance, ferrotitanium is added.

[0081] The advantage is that it can keep titanium iron melting and the composition is accurate; the disadvantage is that titanium is also an easily oxidized element. The earlier it is added, the more it will be oxidized. The titanium out of the station is 0.018%, so the later it is added, the better. However, it is necessary to ensure that after adding, the calcium wire is fed and soft-blown for another 6 minutes before it can be discharged. This kind of steel still needs to rely on argon blowing to remove inclusions to ensure the purity of the molten steel.

[0082] Comparative Example 5:

[0083] Basically the same as Example 2, except for the amount or speed of feeding the calcium line.

[0084] The slower the calcium wire feeding speed, the longer the wire feeding time, the longer the molten steel tumbling time during wire feeding, and the more titanium burnout; but if the calcium wire speed is faster, the calcium recovery rate will be lower.

[0085] The line speed is 180 m / min, and 1 ppm of calcium is added for every 10 m of calcium wire. It takes 20 seconds to print 60 m of wire, and the calcium is 6 ppm. The titanium burn-off is about 0.001% when feeding the wire. If the line speed is reduced to 80 m / min, or 150 m of calcium wire is fed, it takes 45 seconds, then the titanium burn-off is 0.003%, and adding 40 kg of titanium iron will not be enough; but if the line speed is 300 m / min, then after printing 60 m of wire, the calcium is 3 ppm, which shows the impact of low calcium on the fluidity of molten steel.

[0086] Comparative Example 6:

[0087] Basically the same as Example 2, the temperature control is unreasonable.

[0088] If the temperature is too high before adding titanium iron, for example 1580℃, then a larger amount of argon gas will need to be opened later to lower the temperature. The titanium content is 0.017%.

[0089] If the temperature is too low, 1550℃, then after the casting is completed, power must be supplied to raise the temperature to 1565℃ before the temperature is high enough for calcium wire and soft blowing. The power supply process will also burn the casting, and the titanium is 0.018%.

[0090] Therefore, before manually throwing ferrotitanium, try to control the temperature at 1565-1570℃. In this way, even if the temperature is too low, you can supply power for 1 minute before manually throwing ferrotitanium. Or if the temperature is too high, increase the argon gas to lower the temperature to the appropriate range before manually throwing ferrotitanium.

[0091] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for producing titanium-containing steel using a single LF furnace, characterized in that: Including deoxidation and desulfurization steps: When the converter is tapping, the ladle bottom blowing argon flow rate is adjusted to 40-60 cubic meters per hour. When the tapping is completed, aluminum-iron alloy is added to the molten steel for deoxidation. When the tapping is completed, slag is added. After the slag is added, the argon flow rate is reduced to 20-30 cubic meters per hour. After the tapping is completed, sampling is taken, the argon is turned off, and the molten steel is transferred to the LF furnace. The slag includes lime, bauxite and silicon-manganese alloy, and the mass ratio of the lime, bauxite and silicon-manganese alloy to the molten steel is 490-510:290-310:2200-2400:110×10 3 -125×10 3 ; The acid-soluble aluminum content in the molten steel after deoxidation is greater than 0.004%; The desulfurization step includes: when the temperature of the molten steel reaches 1500-1545°C in the LF furnace, when it is above 1530°C, adjusting the argon flow rate to 90-110 cubic meters per hour, adding slag first and then supplying power; when the temperature is below 1530°C, adding slag while supplying power, and the argon flow rate is 40-50 cubic meters per hour; the slag includes lime, high-aluminum slag and fluorite, and the mass ratio of lime, high-aluminum slag and fluorite in the slag to the molten steel is 300-600:60-80:80-135:110×10 3 -125×10 3 After adding the slag to the LF furnace, stir the tumbling molten steel to wet the slag and heat it to a molten steel temperature of 1550-1570 ° C, stir with 90-110 cubic meters / hour of argon flow for 2-3 minutes to desulfurize, and after desulfurization, the argon flow rate is adjusted to 15-25 cubic meters / hour; Adjust the temperature of the molten steel after desulfurization to 1566℃-1570℃, adjust the argon to a weak blowing state, the argon flow rate is 15-25 cubic meters / hour, stop supplying power, the diameter of the bright circle of the argon port is 25-35 cm, the molten steel penetrates the slag layer and is exposed, and then add ferrotitanium alloy to the center of the argon port so that the ferrotitanium alloy enters the molten steel directly without contacting the slag, and then adjust the argon to a soft blowing state, the argon flow rate is 5-15 cubic meters / hour, feed the calcium line, and soft blow out the station.

2. The method for producing titanium-containing steel using a single LF furnace according to claim 1, characterized in that: The titanium content in the molten steel is 0.016wt%-0.028wt%.

3. The method for producing titanium-containing steel using a single LF furnace according to claim 2, characterized in that: The titanium-iron alloy is manually cast into the argon port.

4. The method for producing titanium-containing steel using a single LF furnace according to claim 2, characterized in that: After adding titanium-iron alloy, feed the calcium wire for 50-100 meters at a line speed of 150-200 meters / minute.

5. The method for producing titanium-containing steel using a single LF furnace according to claim 1, characterized in that: The amount of aluminum-iron alloy added is equal to the oxygen content at the converter end point before steel tapping / 2.592, wherein the unit of oxygen content is ppm and the unit of the amount of aluminum-iron alloy added is kilogram.

6. The method for producing titanium-containing steel using a single LF furnace according to claim 1, characterized in that: The oxygen content at the converter end point before tapping is 200-435ppm.

7. The method for producing titanium-containing steel using a single LF furnace according to claim 1, characterized in that: After desulfurization, take samples. If the sample is white slag or yellow-white slag, adjust the temperature and argon flow rate to add titanium-iron alloy; if the sample is neither white slag nor yellow-white slag, add ferrosilicon powder or ferrosilicon powder and aluminum particles to deoxidize until the sample is white slag or yellow-white slag.

8. The method for producing titanium-containing steel using a single LF furnace according to claim 1, characterized in that: The titanium-containing steel is at least one of Q345C, Q345T and Q345GJC.

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