Steel-making method of deformed steel bar without passing through LF furnace

Abstract

The invention relates to the technical field of steelmaking, and discloses a deformed steel bar steelmaking method without passing through an LF furnace. Comprising the steps that before converter tapping, the carbon content in molten steel is adjusted to be not smaller than 0.12%, and manganese oxide and manganese silicate can be prevented from being generated in the tapping process to a certain extent; and in order to further prevent the generation of manganese oxide and manganese silicate, lime is added to increase the alkalinity of the molten steel when the molten steel reaches the argon station, so that manganese in the molten steel is reduced. Through the operation, manganese in the molten steel can be effectively reduced, so that the molten steel can be used for refining deformed steel bars without being subjected to LF treatment, and the production cost can be effectively reduced. By means of the method, manganese in the molten steel can be effectively reduced, the molten steel can be refined without being subjected to LF treatment, and the production cost can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking, and in particular to a method for making threaded steel without using an LF furnace. Background Art

[0002] Rebar generally follows the process path of converter-argon station-continuous casting. However, if it is processed in LF furnace, the refining cost can be reduced, and the cost of one furnace of steel can be reduced by 4,500 yuan. However, because it does not pass the LF furnace, the tapping temperature of the converter needs to be increased when tapping steel. Compared with the average tapping temperature of LF furnace of 1610℃, it needs to be increased to 1635℃. For every 1℃ increase, the cost of 130 tons of molten steel will increase by 520 yuan. At the same time, because it does not pass the LF, the yield of the alloy will be lower. The main reason is that during the tapping process, the free oxygen in the molten steel will react with silicon, manganese and iron, and it cannot be reduced during the argon station treatment. According to statistics, 0.02-0.08% of manganese will be oxidized in each furnace of steel, depending on the oxygen content and slag amount at the end of the converter. Therefore, a method of reducing manganese is needed on site.

[0003] Prior art 201510296049.0 "A method for improving the manganese recovery rate of molten steel from direct alloying of manganese ore" discloses a method of reducing manganese in the molten steel fed into the molten steel in the refining process of steelmaking by making a mixed powder of manganese ore, lime or light-burned dolomite, anthracite or coke in a certain proportion, preparing aluminum powder and / or silicon powder as spare materials, using the two materials to make cored wire. Mn2O3, MnO2, and MnCO3 are easily decomposed and reduced to manganese by carbon in the charge within 1200°C, while MnSiO3 in manganese ore needs to be reduced at a higher temperature and a reducing atmosphere. When the silicon dioxide content in the converter steelmaking slag is high, it is easy to combine with manganese oxide, and the manganese silicate produced is difficult to reduce. At the same time, some slag will be discharged in the later stage of the converter steelmaking, and the slag also contains manganese oxide, so each furnace of steel will have some manganese silicate and manganese oxide wasted in the slag.

[0004] In view of this, the present invention is proposed to reduce the manganese wasted in the slag and reduce the alloy cost. Summary of the invention

[0005] The object of the present invention is to provide a method for making rebar without using an LF furnace.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a method for making threaded steel without using an LF furnace, comprising:

[0008] After mixing the molten iron and scrap steel, oxygen is blown into the converter, and the carbon content in the molten steel is measured when the temperature of the molten steel rises to 1630-1650°C; if the carbon content in the molten steel is less than 0.12%, carbon powder is added to the empty ladle to adjust the carbon content in the molten steel to 0.12%-0.13%, and then the converter is tapped;

[0009] During the steel tapping process, alloy and carbon powder are added to the ladle. The amount of carbon powder added is based on adjusting the carbon content in the molten steel to 0.2-0.22%;

[0010] After the steel is tapped, the ladle is transferred to the argon station, where lime and ferrosilicon powder are added to the ladle, followed by sampling, alloying, and husk delivery.

[0011] By weight, the amount of molten steel is 126,000 parts, lime is 100-150 parts, ferrosilicon powder is 18-22 parts, and rice husk is 18-22 parts.

[0012] In an optional embodiment, when tapping steel, the converter argon flow rate is 20-30m 3 / h.

[0013] In an optional embodiment, the argon flow rate of the ladle bottom blowing at the argon station is set to 5-10m 3 / h, then add lime and ferrosilicon powder, and adjust the bottom blowing argon gas to 60-70m 3 / h, stirring for 30-60s;

[0014] After stirring, adjust the argon gas to 5-10m 3 / h sampling.

[0015] In an optional embodiment, after the sampling results come out, the alloy is matched and the argon gas is adjusted to 5-10m 3 / h, blow for 3-5 minutes, and then throw the husks out of the station.

[0016] In an optional embodiment, during the steel tapping process, alloy and carbon powder are added when 1 / 4 to 1 / 3 of the molten steel remains in the converter.

[0017] In an optional embodiment, the mass ratio of molten iron to scrap steel is 100-110:30-40.

[0018] In an optional embodiment, when the temperature of the molten steel is 1560-1570°C when it arrives at the argon station, the amount of lime added is 100-125 parts; when the temperature of the molten steel is 1570-1580°C when it arrives at the argon station, the amount of lime added is 125-150 parts.

[0019] In an optional embodiment, the lime is lime that is scattered and collected again in the converter secondary raw material feeding belt system.

[0020] In an alternative embodiment, the silicon content of the ferrosilicon is 85% and the iron content is 14%.

[0021] The present invention has the following beneficial effects:

[0022] Adjusting the carbon content in the molten steel to not less than 0.12% before tapping the converter can prevent the generation of manganese oxide and manganese silicate during the tapping process to a certain extent; and in order to further prevent the generation of manganese oxide and manganese silicate, lime is added to increase the alkalinity of the molten steel when the molten steel reaches the argon station to reduce the manganese in the molten steel. Through the above operation, the manganese in the molten steel can be effectively reduced, so that the molten steel does not need to be treated with LF to produce rebar, which can effectively reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure 1 This is a statistical chart of the relationship between carbon powder and deoxidation before steelmaking. DETAILED DESCRIPTION

[0025] 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.

[0026] In view of existing problems and existing technologies, the researchers have conducted the following considerations:

[0027] The steel-tapping temperature of the converter is greater than 1630℃, which belongs to the high temperature area. Silicon manganese, ferrosilicon, high manganese and other alloys will be added in the steel-tapping process, which will definitely produce manganese silicate that is difficult to reduce. The weight produced is related to the amount of molten steel, the oxygen content of the molten steel, the amount of slag, etc. Therefore, according to different situations, manganese is reduced and new methods are proposed to reduce alloy consumption.

[0028] Originally, when spiral mosquito steel was processed by the argon station and discharged from the converter, no slag was added, only alloy was added. After the steel was discharged, it was sent to the argon station to blow argon to even out the composition, take samples, and adjust the composition to the target range after the samples came out. After the composition was qualified, 80 kg of rice husks were thrown in by hand to keep it warm before it was discharged. Since manganese oxide and manganese silicate will be produced during the steel discharge process, and these manganese cannot be reduced during the argon blowing process at the argon station, it is necessary to add reducing agents, such as calcium oxide and magnesium oxide. On the other hand, we have proved through experiments that it is not the case that manganese oxide and manganese silicate can be reduced to manganese as long as reducing agents are added. This is directly related to the amount of molten steel and the oxygen content of molten steel. Among them, the more molten steel, the more reducing agents need to be added. This is a physical phenomenon that is easy to be understood by everyone, but the oxygen content of molten steel is an unknown number, so how much reducing agent is needed to reduce manganese oxide is also a problem to be solved by this technology.

[0029] The percentages involved in this application all refer to mass percentages.

[0030] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0031] The present invention provides a method for making threaded steel without using an LF furnace, comprising:

[0032] After mixing the molten iron and scrap steel, oxygen is blown into the converter, and the carbon content in the molten steel is measured when the temperature of the molten steel rises to 1630-1650°C; if the carbon content in the molten steel is less than 0.12%, carbon powder is added to the molten steel to adjust the carbon content in the molten steel to 0.12%-0.13% before tapping the converter;

[0033] During the steel tapping process, alloy and carbon powder are added to the ladle. The amount of carbon powder added is based on adjusting the carbon content in the molten steel to 0.2-0.22%;

[0034] After the steel is tapped, the ladle is transferred to the argon station, where lime and ferrosilicon powder are added to the ladle, followed by sampling, alloying, and husk delivery.

[0035] By weight, the amount of molten steel is 126,000 parts, lime is 100-150 parts, ferrosilicon powder is 18-22 parts, and rice husk is 18-22 parts.

[0036] The steelmaking method provided by the present invention adjusts the carbon content in the molten steel to not less than 0.12% before the converter tapping, which can prevent the generation of manganese oxide and manganese silicate during the tapping process to a certain extent; and in order to further prevent the generation of manganese oxide and manganese silicate, lime is added to increase the alkalinity of the molten steel when the molten steel reaches the argon station to reduce the manganese in the molten steel. Through the above operation, the manganese in the molten steel can be effectively reduced, so that the molten steel does not need to be further treated with LF to produce rebar, which can effectively reduce the production cost.

[0037] Specifically, the steelmaking method is:

[0038] S1. Processing in converter and steel tapping

[0039] The molten iron and scrap steel are mixed in a converter, and then oxygen is blown to raise the temperature. When the temperature of the molten steel rises to 1630-1650℃, the carbon content in the molten steel is measured.

[0040] Specifically, the scrap steel is ordinary scrap steel, and the requirements for trace elements are: chromium less than 0.2%, molybdenum less than 0.025%, copper less than 0.35%, and arsenic less than 0.2%.

[0041] Regarding the control of oxygen content in molten steel, for the steel grades with carbon content requirements in the range of 0.21% to 0.25% for screw steel, of course, the higher the carbon content in the converter, the better. The principle is that the carbon-oxygen product is a constant. The higher the carbon content, the lower the oxygen content. After adding silicon-containing alloys during the converter steelmaking process, the less manganese silicate is produced. Naturally, the less reducing agents such as lime need to be added. However, in the actual process, the control of the final carbon content in the converter is constrained by the comprehensive prices of scrap steel, molten iron, etc., that is, when scrap steel is cheap, each factory will add more scrap steel and use less molten iron. When iron ore is cheap and the cost of molten iron is low, each factory will add more molten iron and less scrap steel. According to experience, 1 ton of scrap steel affects the converter end temperature by about 12°C, and 1 ton of hot metal affects the converter end temperature by about 4°C. With the same loading of 140 tons, scrap steel + hot metal can be 40+100 or 30+110, and the difference in the converter end temperature is (40*12+100*4)-(30*12+110*4)=80°C. Calculated by removing 0.01% of carbon every two seconds, the end carbon of two different loading ratios will differ by 80 / 2*0.01%=0.40%. In addition, the price of raw materials changes every day, and the blast furnaces of various steel plants are not necessarily the same. Therefore, it is difficult to formulate a parameter to control the converter end carbon within the ideal range by relying solely on technical personnel to do experiments.

[0042] According to the above analysis, the method provided by the present invention is more suitable for use on steels with high carbon content such as screw steel, because only steels with high carbon content and low phosphorus requirements can have the opportunity to reduce the final oxygen content. After all, the product of carbon and oxygen is a constant, and the oxygen content of steel with low carbon must be higher. In order to reduce the production of manganese oxide and manganese silicate during steel tapping, the carbon content at the converter end must be controlled. The ideal range is greater than 0.12%. When the average carbon-oxygen product of the plant is 0.0031%, when the carbon is 0.12%, the oxygen content of the molten steel is 0.000031% / 0.12%=0.0258%, that is, the oxygen content of the molten steel is 258ppm. In order to control within this range, when the converter oxygen blowing reaches 600-620s, an automatic temperature measurement sampling gun is used to measure the temperature and carbon of the molten steel. Then, according to the carbon content of the molten steel, 0.01% of carbon is removed every 2 seconds, and the temperature rises by 1°C for every 1 second of oxygen blowing. The oxygen blowing time is calculated to remove carbon to 0.12%, and the molten steel temperature is greater than 1630°C. However, in the actual process, due to the influence of multiple factors such as molten iron temperature and charging amount, when the converter oxygen blowing reaches 600-620s, the carbon of the molten steel is generally 0.40%-0.70%, and the molten steel temperature ranges from 1560-1590°C. Operators generally choose to raise the temperature to 1630°C for steelmaking. For the carbon content at the end of the converter, it depends on how much carbon is left when the temperature reaches this high. Here, it is easier to control the carbon to the ideal range under high temperature conditions, but for low temperatures, as the oxygen blowing time increases, the carbon will definitely be very low, resulting in a high oxygen content in the molten steel.

[0043] In view of the low tapping temperature and carbon content below 0.12%, in order to reduce the production of manganese oxide and manganese silicate during tapping, carbon powder pre-deoxidation operation is adopted before tapping. Figure 1 It is experimental data. From the comparison of the two curves, we can see that even if the molten steel is under the same oxygen content condition, the deoxidation amount of the molten steel will increase with the increase of the amount of carbon powder added, but not all the added carbon powder can be used for deoxidation, and part of it will increase the carbon content of the molten steel. Moreover, as the oxygen content of the molten steel is lower, more carbon powder will be allocated to increase the carbon content, and less will be allocated to deoxidation of the molten steel.

[0044] Therefore, we use a certain ratio of carbon powder for deoxidation according to the final carbon content of the converter. That is, according to the final carbon content of the converter, the carbon powder that is expected to adjust the carbon content in the molten steel to 0.12%~0.13% is first added into the ladle, and then the steel is tapped. Through this operation, the oxygen content of the molten steel can be reduced to 110~130ppm.

[0045] It should be noted that the higher the carbon content, the more beneficial it is to reduce the oxygen content of molten steel. The reason why more carbon powder is not added here to increase the carbon content is that if too much carbon powder is added, it may cause the molten steel to roll due to the generation of CO explosion, thereby causing a safety accident. Especially when the final carbon content of the converter is lower than 0.06%, adding carbon powder will instantly cause the molten steel to roll over.

[0046] In order to reduce the production of manganese oxide, 2400kg of silicon manganese (18% silicon, 68% manganese) and carbon powder are added when 1 / 4 to 1 / 3 of the molten steel in the converter is left. The purpose of adding alloy here is to adjust the element content in the molten steel to meet the requirements of rebar. When adding alloy, the bottom blowing argon flow rate of the ladle is increased from 10m 3 / h increased to 40m 3 / h, to promote rapid melting of the alloy. After adding, when the alloy and carbon powder are melted, turn down the argon gas until the steel is tapped.

[0047] The amount of carbon powder added here is based on adjusting the carbon content in the molten steel to 0.2-0.22%.

[0048] S2. Argon station processing

[0049] Specifically, after the operation of step S1, the generation of manganese oxide and manganese silicate during the steel tapping process can be reduced, but it cannot be completely reduced. They will always be generated, especially during slagging in the later stage of steel tapping, so it is necessary to reduce this part of manganese oxide.

[0050] We collect lime powder in advance. In the belt system for feeding the auxiliary raw materials of the converter, a lot of lime powder is scattered every day. Generally, people are asked to clean it regularly and pack it in bags, and then transport it out for disposal as garbage. Now, these lime powders are collected and packed in two layers of bags, with the inner layer being a nylon bag and the outer layer being a snakeskin bag. This can reduce the infiltration of lime powder and prevent the bags from being broken during transportation. Each bag contains 5 to 10 kg for easy hand throwing. After loading, it is transported to the argon station operating platform for standby.

[0051] After the molten steel arrives at the argon station, the bottom blowing argon is opened to 5-10m 3 / h, then hand throw bagged lime powder to cover the surface of molten steel. The amount of lime used for every 126 tons of molten steel is 100-150kg. Then hand throw 18-22kg ferrosilicon powder on it. After throwing it all, adjust the bottom blowing argon gas to 60-70m 3 / h, stir for 30-60s to homogenize the composition and promote the reduction of manganese in the slag, then turn down the argon gas to 5-10m 3 / h sampling, and after the sample comes out, mix it with gold, and then 3 / h argon is blown for 3 to 5 minutes to make the composition and temperature uniform, and then 18 to 22 kg of rice husks are thrown out by hand.

[0052] Specifically, the ferrosilicon used in the embodiment of the present invention has a silicon content of 85% and an iron content of 14%.

[0053] The principle of adding lime to reduce manganese in slag is as follows: when the converter oxygen blowing reaches the end, the oxygen in the molten steel is relatively high, generally greater than 260ppm, so during the steel tapping process, the oxygen in the molten steel will still react with the carbon and manganese in the steel. Even if it is pre-deoxidized by carbon powder, it is still inevitable that the manganese in the molten steel will be oxidized; on the other hand, in the later stage of steel tapping, in order to finish the molten steel and reduce waste, some slag is generally mixed into the molten steel, even if the slide is closed the second the slag is seen, and only a small amount of tens of kilograms of slag is mixed in, which is also inevitable. These manganese oxides and slag are on the surface of the molten steel, and it is difficult to reduce them only by blowing argon, so a certain alkalinity reduction slag is required to reduce these manganese oxides, or to reduce part of them. According to our experiments, after adding lime powder, when the basicity of the slag can reach 1.2 or above, manganese oxide can be reduced in the original slag. To achieve this basicity, at least 90kg of lime powder must be added to 126 tons of molten steel. Therefore, we stipulate that the lower limit of hand-thrown lime powder is 100kg. Why do we stipulate the range of 100-150kg? This is based on the arrival temperature of the molten steel at the argon station. If the temperature of the molten steel at the arrival station is relatively high, more lime powder should be thrown in by hand to try to reduce more manganese oxide. If the temperature is low, add less. This can be controlled by the experience of the on-site employees, because the temperature drop of each ladle is different, and the processing time plus the waiting time are different. Generally speaking, if the temperature of this furnace of steel arrives at 1575℃, and the on-site workers add 100kg of lime powder, the temperature is still a little surplus, then the next furnace steel can be added to 120kg or more. Generally, for example, when the temperature of molten steel reaches the argon station at 1560-1570℃, the amount of lime added is 100-125kg; when the temperature of molten steel reaches the argon station at 1570-1580℃, the amount of lime added is 125-150kg. The general principle is to add as much as possible. The more you add, the more manganese is reduced, and the lower the cost. However, if we only increase the steel-out temperature of the converter and the arrival temperature of the molten steel at the argon station, it is not cost-effective. For every 1℃ increase, the cost of 130 tons of molten steel will increase by 520 yuan. Therefore, here, we convert the weight of added husks into the amount of lime added for the lowest slag basicity, and reduce the manganese oxide in the slag on the existing basis to achieve the effect of reducing the alloy cost.

[0054] Adding lime will reduce manganese oxide, so why not just add more lime here? The reason is that in addition to the temperature cost, the total amount of reduction is limited. We found in experiments that after carbon powder pre-deoxidation, not much manganese oxide and manganese silicate are produced during the steelmaking process. We also tried to add 20, 30, 50, 80, 100, 200, 300, 400, 500, 600, 700 kg of lime, with alkalinity ranging from 0.9 to 2.3. For the furnace without slag, about 0.03% of manganese can be reduced, and for the furnace with slag, at most 0.06% of manganese can be reduced. Therefore, the conclusion is that adding more is useless. As long as the alkalinity is added to 1.2, the manganese oxide in the slag can be basically reduced. But it should be noted that if the alkalinity is not enough, it is likely that it will not be reduced at all. As for how to judge whether the alkalinity is sufficient, you only need to add lime powder and stir it, then use a steel pipe to stick some slag to see if it is transparent glass slag. If it is transparent glass slag, it means that the silica content in the slag is too high and the alkalinity is not enough. If it is opaque slag, it means that there is enough calcium oxide and the alkalinity is enough.

[0055] Through the above operation, not only can the lime powder be turned into treasure, but also at least 0.04% of manganese can be effectively reduced, reducing the consumption of ferromanganese. Based on the high manganese price of 5356 yuan / ton steel, 18 kg of high manganese is required for each 0.01% increase, and the cost reduction per furnace = 5.356*18*4 = 385.63 yuan. In addition, since the hand-ash lime powder makes a layer of slag on the surface of the molten steel, it reduces the subsequent temperature drop of the molten steel, so 18-22 kg of rice husk can play a role in heat preservation.

[0056] Example 1

[0057] Taking HRB400E-01 as an example, the screw steel has carbon 0.21-0.25%, silicon 0.25-0.35%, manganese 1.35-1.45%, phosphorus less than 0.040%, and sulfur less than 0.040%. The molten steel components are added according to the target, carbon 0.23%, silicon 0.30%, and manganese 1.40%.

[0058] Add 30 tons of scrap steel to 110 tons of molten iron in the converter, blow oxygen to increase the temperature, and measure the carbon content in the molten steel when the temperature rises to 1630°C. The measured carbon content is 0.09% and the manganese content is 0.11%. The tapping temperature and carbon content meet the requirements, and tapping begins;

[0059] Before tapping, add 45kg of carbon powder into the empty ladle, which is expected to increase the carbon content in the molten steel to 0.12%. Then tap the steel. When there is 1 / 3 of molten steel left in the converter, add 2400kg of alloy silicon manganese and 130kg of carbon powder. When adding alloy and carbon powder, the argon flow rate is increased from 10m 3 / h increased to 40m 3 / h, after the alloy and carbon powder are melted, close the bottom of the ladle and blow argon to 10m 3 / h.

[0060] After the steel is tapped, the ladle is transferred to the argon station and argon is blown from the bottom of the ladle for 10m. 3 / h, after the molten steel arrives at the argon station, the temperature of the molten steel is manually measured to be 1570℃, then 120kg of lime powder is thrown into the bag and spread on the surface of the molten steel, and then 20kg of ferrosilicon powder is thrown on it. After throwing, the bottom blowing argon is adjusted to 60m 3 / h, stir for 60s, then turn down the argon gas to 10m 3 / h sampling, the test results are: carbon 0.21%, silicon 0.24%, manganese 1.27%, etc. After the sample comes out, add 260kg silicon manganese, 30kg carbon powder, and then add 6m 3 / h argon blowing for 5 minutes, and then 20kg of rice husks are thrown out of the station by hand.

[0061] lime Husk Toner Silicon Manganese Ferrosilicon Total cost (yuan) Addition amount (kg) 120 20 205 2660 0 / Unit price (yuan / kg) 0.6 0.3 0.2 5.8 6.3 / Cost (Yuan) 72 6 41 15428 0 15547

[0062] Example 2

[0063] Add 40 tons of scrap steel to 100 tons of molten iron in the converter, blow oxygen to raise the temperature, and measure the carbon content in the molten steel when the temperature rises to 1630°C. The measured carbon content is 0.15%, and the manganese content is 0.13%. The tapping temperature and carbon content meet the requirements, and tapping begins;

[0064] When there is 1 / 3 of molten steel left in the converter, add 2400kg of alloy silicon manganese and 100kg of carbon powder. When adding alloy and carbon powder, the argon flow rate is increased from 10m 3 / h increased to 40m 3 / h, after the alloy and carbon powder are melted, close the bottom of the ladle and blow argon to 10m 3 / h.

[0065] After the steel is tapped, the ladle is transferred to the argon station and argon is blown from the bottom of the ladle for 10m. 3 / h. After the molten steel arrives at the argon station, the temperature of the molten steel is manually measured to be 1575℃. Then 150kg of lime powder is thrown into the bag and spread on the surface of the molten steel. Then 20kg of ferrosilicon powder is thrown on it. After throwing, the bottom blowing argon is adjusted to 70m 3 / h, stir for 30s, then turn down the argon gas to 5m 3 / h sampling, the test results are: carbon 0.22%, silicon 0.26%, manganese 1.28%, etc. After the sample comes out, add 240kg silicon manganese, 15kg carbon powder, and then 7m 3 / h argon blowing for 5 minutes, and then 20kg of rice husks are thrown out of the station by hand.

[0066] lime Husk Toner Silicon Manganese Ferrosilicon Total cost (yuan) Addition amount (kg) 150 20 115 2640 0 / Unit price (yuan / kg) 0.6 0.3 0.2 5.8 6.3 / Cost (Yuan) 90 6 23 15312 0 15431

[0067] Comparative Example 1

[0068] This comparative example is basically the same as Example 1, except that no carbon powder is added to the empty ladle. 2400kg silicon manganese and 210kg carbon powder are directly added, and the test results of the samples taken at the argon station are: carbon 0.22%, silicon 0.20%, manganese 1.24%, etc. After the samples are taken, the alloy is supplemented with 300kg silicon manganese, 90kg ferrosilicon, and 15kg carbon powder.

[0069] For decarburization of molten steel, the effects of adding carbon powder first in the early stage and adding carbon powder and alloy together in the middle stage are different. If carbon powder is added first, oxygen in molten steel will mainly react with carbon powder; if carbon powder is added together with alloy, oxygen in molten steel will react with alloy first, so the silicon and manganese contents of comparative example 1 will be relatively low. Although adding lime powder at the argon station can reduce part of the carbon, the original amount is not as high as that of the embodiment, so the amount of ferrosilicon and ferromanganese alloy added will still be a little more.

[0070] lime Husk Toner Silicon Manganese Ferrosilicon Total cost (yuan) Addition amount (kg) 150 20 225 2700 90 / Unit price (yuan / kg) 0.6 0.3 0.2 5.8 6.3 / Cost (Yuan) 90 6 45 15660 567 16368

[0071] Comparative Example 2

[0072] This comparative example is basically the same as Example 1, except that no carbon powder was added when adding alloy during the steel tapping process. The test results of the samples taken at the argon station were: 0.08% carbon, 0.15% silicon, and 1.21% manganese. After the samples were taken out, 380kg of silicon and manganese, 150kg of ferrosilicon, and 230kg of carbon powder were added to the alloy. Since no carbon powder was added during the steel tapping process, the high oxygen content in the molten steel will oxidize more silicon and manganese. At the same time, the high oxygen content in the molten steel will not play a reducing role due to the low alkalinity of the lime added at the argon station. In addition, adding a large amount of carbon powder after argon sampling will increase the heat absorption of the molten steel, resulting in low temperature, and increase the risk of the molten steel not being fully pulled out.

[0073] lime Husk Toner Silicon Manganese Ferrosilicon Total cost (yuan) Addition amount (kg) 150 20 230 2780 150 / Unit price (yuan / kg) 0.6 0.3 0.2 5.8 6.3 / Cost (Yuan) 90 6 46 16124 945 17211

[0074] Comparative Example 3

[0075] This comparative example is basically the same as Example 1, except that no lime was added during the argon blowing process, and the amount of rice husk added was changed to 80 kg. After adding lime, a slag layer will be formed on the surface of the molten steel, which can replace part of the amount of rice husk added to achieve the same insulation effect. However, the manganese oxide and manganese silicate in the slag cannot be reduced, which increases the alloy cost, which is the same as Comparative Example 2.

[0076] lime Husk Toner Silicon Manganese Ferrosilicon Total cost (yuan) Addition amount (kg) 0 80 230 2780 150 / Unit price (yuan / kg) 0.6 0.3 0.2 5.8 6.3 / Cost (Yuan) 0 24 46 16124 945 17139

[0077] Comparative Example 4

[0078] This comparative example is basically the same as Example 1, except that lime powder is not collected and lime pellets are added directly. The advantage is that it saves manpower and can be added directly from the silo. The disadvantage is that it melts slowly and absorbs a lot of heat. It is necessary to wait until the lime is completely melted before replacing the manganese oxide and manganese silicate in the slag. In comparison, the tapping temperature has to be increased by 3°C, and the cost of a single furnace increases by 3*520=1560 yuan. The total cost is equal to 15547+1560=17107 yuan.

[0079] lime Husk Toner Silicon Manganese Ferrosilicon Total cost (yuan) Addition amount (kg) 120 20 205 2660 0 / Unit price (yuan / kg) 0.6 0.3 0.2 5.8 6.3 / Cost (Yuan) 72 6 41 15428 0 15547

[0080] Comparative Example 5

[0081] This comparative example is basically the same as Example 1, except that lime powder is added during the steel tapping process, not at the argon station. Since lime powder is very light, the bag is burned when it is added to the ladle, and the steel tapping process is dust-removing. After the bag of added lime powder is burned, the floating lime powder will be completely sucked out. The addition effect is poor, resulting in insufficient lime on the surface of the molten steel, which cannot play the role of reducing manganese oxide and manganese silicate. When the molten steel is processed at the argon station, it still has to add as much alloy as in Comparative Example 2, and 80 kg of husks have to be added.

[0082]

[0083]

[0084] Experimental example

[0085] The cost of each embodiment and comparative example was calculated and the statistical results were recorded in Table 1.

[0086] Table 1 Test results of various embodiments and comparative examples

[0087]

[0088] In summary, from a cost perspective, the main difference is between silicon manganese and ferrosilicon alloys. Adding carbon powder for deoxidation and lime for reduction can effectively reduce alloy consumption.

[0089] In summary, the rebar steelmaking method without LF furnace provided by the present invention adjusts the carbon content in the molten steel to not less than 0.12% before the converter tapping, which can prevent the generation of manganese oxide and manganese silicate during the tapping process to a certain extent; and in order to further prevent the generation of manganese oxide and manganese silicate, lime is added to increase the alkalinity of the molten steel when the molten steel reaches the argon station to reduce the manganese in the molten steel. Through the above operation, the manganese in the molten steel can be effectively reduced, so that the molten steel does not need to be further treated with LF to produce rebar, which can effectively reduce the production cost.

[0090] 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 threaded steel without using an LF furnace, characterized in that: include: After mixing the molten iron and scrap steel, oxygen is blown into the converter, and the carbon content in the molten steel is measured when the temperature of the molten steel rises to 1630-1650°C; If the carbon content in the molten steel is less than 0.12%, carbon powder is added to the empty ladle to adjust the carbon content in the molten steel to 0.12% to 0.13%, and then the converter is used to tap the steel; During the steel tapping process, alloy and carbon powder are added to the ladle. The amount of carbon powder added is based on adjusting the carbon content in the molten steel to 0.2-0.22%; After the steel is tapped, the ladle is transferred to the argon station, where lime and ferrosilicon powder are added to the ladle, followed by sampling, alloying, and husk delivery. In terms of weight, the amount of molten steel is 126,000 parts, lime is 100-150 parts, ferrosilicon powder is 18-22 parts, and rice husk is 18-22 parts.

2. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: When tapping steel, the converter argon gas flow rate is 20-30m 3 / h.

3. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: The argon flow rate of the ladle bottom blowing at the argon station is set to 5-10m 3 / h, then add lime and ferrosilicon powder, and adjust the bottom blowing argon gas to 60-70m 3 / h, stirring for 30-60s; After stirring, adjust the argon gas to 5-10m 3 / h sampling.

4. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: After the sampling results come out, adjust the argon gas to 5-10m 3 / h, blow for 3-5min, and then throw the husk out of the station.

5. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: During the steel tapping process, alloy and carbon powder are added when there is 1 / 4 to 1 / 3 of molten steel left in the converter.

6. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: The mass ratio of molten iron to scrap steel is 100-110:30-40.

7. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: When the temperature of the molten steel reaches the argon station is 1560-1570℃, the amount of lime added is 100-125 parts; when the temperature of the molten steel reaches the argon station is 1570-1580℃, the amount of lime added is 125-150 parts.

8. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: The lime is lime that is scattered in the converter auxiliary raw material feeding belt system and then collected again.

9. The method for making threaded steel without using an LF furnace according to claim 1, characterized in that: The silicon content of the ferrosilicon is 85% and the iron content is 14%.

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