CN113684339B - Process for smelting stainless steel by LD and GOR duplex method - Google Patents
Process for smelting stainless steel by LD and GOR duplex method Download PDFInfo
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Abstract
The invention aims to provide a process for smelting stainless steel by an LD and GOR duplex method, which reasonably designs the matching relation between the [ Cr ] content and the [ C ] content in molten iron obtained by an LD primary smelting furnace, wherein the [ Cr ] content and the [ C ] content in the molten iron obtained by LD tapping need to meet the following requirements: when the [ Cr ] is less than 5 percent, the [ C ] is more than or equal to 1.5 percent and less than or equal to 3 percent; when Cr is more than or equal to 5 and less than or equal to 13 percent, C is more than or equal to 3 percent and less than or equal to 3.5 percent, the optimal combination mode of LD and GOR is realized, the decarburization capability of LD and GOR is more reasonably utilized, meanwhile, the integral smelting time of LD and GOR is shortened, the integral decarburization efficiency of LD and GOR is improved, and thus, the comprehensive cost of stainless steel smelting is reduced.
Description
Technical Field
The invention belongs to the field of stainless steel smelting, and particularly relates to a process for smelting stainless steel by an LD and GOR duplex method.
Background
GOR smelt stainless steel by bottom blowing mixed gas and top blowing oxygen. In the initial stage of decarburization, efficient decarburization is carried out by top-bottom combined blowing; in the middle and later periods of decarburization, decarburization and chromium retention are realized by bottom blowing of mixed gas (oxygen and inert gas). Due to the characteristics of the GOR furnace body, slag balls can be used for separating slag steel, the problems of resulfurization in subsequent refining and the like are avoided, slag inclusion inclusions in molten steel are reduced, and the cleanliness of the molten steel is improved. In the smelting process, the GOR top-bottom combined blowing has less washing to the furnace lining; meanwhile, the GOR can conveniently replace the furnace bottom. Therefore, the overall campaign of the GOR is mainly affected by the degree of erosion of the slag line of the furnace shell. When the silicon content in the molten steel entering the furnace is higher (the silicon content is higher than 1%), the slag amount in the smelting process is larger, so that the corrosion of a slag line of a furnace body is serious, and the GOR furnace life is reduced. In addition, because GOR top and bottom combined blowing, when the slag quantity is great in the early stage of decarburization, splashing easily occurs, potential safety hazards are brought to a smelting site, and meanwhile, the molten steel loss caused by splashing is reduced to a certain extent.
The LD is decarbonized by blowing inert gas from the bottom and oxygen from the top. Oxygen is blown in at a large flow rate through the top lance, and inert gas is blown in through the bottom lance to stir, so that the rapid desiliconization and decarburization can be realized. However, since the LD furnace cannot blow a mixed gas of oxygen and inert gas at the bottom, the decarburization efficiency is low at a medium-low carbon content (the carbon content is less than 0.5%), and low-carbon stainless steel cannot be efficiently smelted.
At present, chinese patent CN110923389A discloses a method for smelting low-carbon stainless steel by a GOR converter, and provides the distribution characteristics of a GOR top lance and a GOR bottom lance and the control requirements of oxygen and nitrogen flow at each stage of a decarburization process; however, the patent does not consider the adverse effect of high silicon steel liquid as the initial molten steel on GOR smelting.
Chinese patent CN110819880A, "pretreatment process and application of chromium-containing low-nickel molten iron for 200 series stainless steel production", discloses a duplex stainless steel smelting process of a primary smelting furnace and a refining furnace, and adopts the primary smelting furnace to reduce the silicon content and the carbon content of GOR initial molten steel and avoid the adverse effect of high silicon and high carbon on GOR smelting. However, the content of Cr in the crude iron making water obtained from the primary smelting furnace in the patent is above 13.5%, the content of carbon is 1.8% -3.5%, the range of the content of carbon is limited on the basis of reducing the smelting load of the refining furnace as far as possible on the premise of avoiding Cr oxidation, and the influence on the refining furnace and the overall smelting efficiency of the primary smelting furnace and the refining furnace is not considered due to the matching relationship between the content of chromium in the crude iron making water obtained from the primary smelting furnace and the end point carbon content. Therefore, by adopting the duplex stainless steel smelting process of the primary smelting furnace and the refining furnace of the Chinese patent CN110819880A, the overall smelting time of the primary smelting and the refining is often longer (more than 110 min), the smelting efficiency is low, and the metal yield is also low.
Disclosure of Invention
The invention aims to provide a process for smelting stainless steel by an LD and GOR duplex method, which realizes the optimal combination mode of LD and GOR by reasonably designing the matching relation between the [ Cr ] content and the [ C ] content in the molten iron obtained by an LD primary smelting furnace, more reasonably utilizes the decarburization capability of LD and GOR, shortens the integral smelting time of LD and GOR, improves the integral decarburization efficiency of LD and GOR and further reduces the comprehensive cost for smelting stainless steel.
A process for smelting stainless steel by an LD and GOR duplex method comprises the following specific steps:
(1) Adding molten iron into LD, blowing oxygen to carry out desiliconization and primary decarburization, and after the desilting and the tapping are finished, slag stopping and tapping are carried out, wherein the mass fractions of the elements in the LD tapped molten steel are as follows:
[C] the method comprises the following steps 1 to 4%, [ Si ]:0.05 to 0.3% and [ Mn ]: 0.1-1.5%, P is less than or equal to 0.1%, S is less than or equal to 0.1%, and Cr: 5 to 13%, [ Ni ]:0.5 to 5%, [ N ]:0.01 to 0.1 percent, and the balance of Fe and other elements;
meanwhile, the [ Cr ] content and the [ C ] content in the LD tapped molten steel also need to meet the following requirements: when the [ Cr ] is less than 5 percent, the [ C ] is more than or equal to 1.5 percent and less than or equal to 3 percent; when the content of Cr is more than or equal to 5 and less than or equal to 13 percent, the content of C is more than or equal to 3 percent and less than or equal to 3.5 percent;
(2) Adding the LD tapped molten steel in the step (1) into GOR, carrying out top-bottom combined blowing for deep decarburization, and stopping blowing after the content of [ C ] in the molten steel in the GOR furnace is qualified (determined according to the requirements of different steel types on the content of [ C ], usually 0.03-0.3%);
(3) And GOR tapping.
For the step (1), the content of [ Cr ] and the content of [ C ] of molten steel from LD tapping (namely the content of the terminal [ C ] of LD blowing) need to be reasonably designed so as to fully utilize LD to carry out primary decarburization, reduce the oxidation of [ Cr ] and the content of chromium oxide in LD slag and improve the metal yield; meanwhile, when the [ Cr ] is less than 5%, the end point of [ C ] is controlled to be more than or equal to 1.6% and less than or equal to 3%; when the content of Cr is more than or equal to 5 and less than or equal to 13 percent, the end point of C is more than or equal to 3 percent and less than or equal to 3.5 percent, and the content of C and Cr at the end point are not properly controlled, the smelting efficiency of LD and GOR is reduced, and the production cost is increased. When the content of [ C ] and the content of [ Cr ] in LD tapping are higher, a large amount of chromium alloy needs to be supplemented for subsequent GOR smelting, and the chromium alloy mainly comprises two types in the current smelting process: high-carbon ferrochrome and micro-carbon ferrochrome; in order to produce stainless steel at low cost, when the chromium content is insufficient, a large amount of high-carbon ferrochrome is required to be added in the GOR smelting process, and the addition of the large amount of high-carbon ferrochrome inevitably causes the carbon content of GOR entering a furnace to be higher, the GOR smelting burden is further increased, and the GOR smelting period is greatly prolonged; in addition, high-carbon ferrochrome usually contains 3-4% of silicon, and the increase of the content of GOR-in-furnace silicon also increases the GOR smelting slag amount, which easily causes splashing. When the content of Cr in LD tapping is higher and the content of C at the end point is too low, the LD smelting time and the content of chromium oxide in slag are greatly increased, the metal yield is reduced, and the decarburization chromium-keeping capability of the LD and GOR duplex method is not favorably exerted. In general, the decarburization amount and the chromium alloying amount in the LD and GOR smelting are reasonably distributed, so that the effective smelting time of the LD and GOR is effectively shortened, and the overall smelting efficiency is improved; meanwhile, the yield of the [ Cr ] metal can be controlled to be more than 94%, the GOR furnace does not splash, and the average furnace life of the GOR furnace can reach more than 190 furnaces. In addition, in the step (1), LD slag-stopping tapping is carried out, the amount of GOR entering slag is reduced, and the ratio of [ Si ] in the LD tapping molten steel is as follows: 0.05-0.3 percent, and also avoids the generation of excessive smelting slag during GOR smelting, so that the splashing problem can not occur in the GOR smelting process.
The GOR furnace adopts an oxygen blowing mode of top and bottom simultaneous oxygen blowing to carry out deep decarburization. Preferably, the GOR top lance in the step (2) blows oxygen, the bottom lance blows a mixed gas of oxygen and inert gas, and the deep decarburization process of the GOR furnace is divided into the following five stages:
dynamic 1 stage: the oxygen flow of the top lance is 1.2-1.4 Nm 3 /(min. T), the total flow rate of the bottom gun is 1.1-1.2 Nm 3 /(min. T), the volume ratio of bottom gun oxygen to inert gas is 7-10, and the end point of dynamic 1 stage [ C]The content is 0.5 to 0.55 percent;
dynamic 2 stage: the total flow of the top blowing gun and the bottom blowing gun is 1.1 to 1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.8-1, and the end point of the dynamic 2 stage [ C]The content is 0.3-0.35%;
dynamic 3 stage: the flow rate of the bottom lance is 1.1-1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.54-0.6, and the end point of the dynamic 3 stage [ C]The content is 0.19 to 0.21 percent;
dynamic 4 stage: the flow rate of the bottom gun is 1.1-1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.43-0.45, and the end point of the dynamic 4 stage [ C]The content is 0.1-0.15%;
dynamic 5 stage: the flow rate of the bottom gun is 1.1-1.2 Nm 3 And/(min. T), the volume ratio of the oxygen of the bottom gun to the inert gas is 0.25-0.32, end of dynamic 5-stage [ C ]]The content is 0.07-0.12%. Dividing into five dynamic decarburization periods according to the carbon content in the molten steel; and according to the actual smelting condition, the oxygen blowing time of each stage is comprehensively designed, so that the high-efficiency decarburization is realized, the formation of chromium oxide is reduced, and the metal yield of chromium is improved.
Preferably, in the step (3), a reducing agent is first put into the GOR furnace, and the GOR furnace is reduced to form slag with 1.5 to 2.5 alkalinity, and then tapping is performed. After the dynamic decarburization period is finished, a reducing agent is added to reduce metal oxides in the slag, so that the metal yield is improved; meanwhile, the oxygen level of the molten steel is reduced, the desulfurization reaction is promoted, the [ S ] content in the molten steel is reduced to be less than or equal to 0.003 percent, and finally 1.5 to 2.5 alkalinity furnace slag is formed. In the specific implementation process, the reducing agent is silicon-manganese alloy.
Preferably, the GOR slag-retaining tapping is carried out in the step (3). GOR slag stopping and tapping can effectively avoid resulfurization in subsequent refining, reduce slag inclusion in molten steel and ensure molten steel cleanliness.
Preferably, after the LD rotten slag is tapped in the step (1), slag splashing is carried out for furnace protection, and then the slag is poured out. After tapping, the slag splashing furnace protecting process can be adopted to improve the service life of the LD furnace and increase the effective smelting period of the LD.
Detailed Description
The present invention is described in further detail below with reference to examples, and it should be understood that the examples described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.
Example 1
In the embodiment, the LD and GOR duplex method is adopted to smelt stainless steel, the produced steel grade is 09Cr14Mn10Ni2CuN, and the smelting steps are as follows:
(1) Adding molten iron (namely blast furnace molten iron) into LD, blowing oxygen to carry out desiliconization and primary decarburization, adding 7.4t of high-carbon ferrochrome at the final stage of desiliconization and primary decarburization, and stopping slag and tapping after LD blowing is finished; wherein the mass fraction of each element in the blast furnace molten iron is as follows:
[C] the method comprises the following steps 4.35%, [ Si ]:0.85%, [ Mn ]:0.97%, [ P ]:0.024%, [ S ]:0.025%, [ Cr ]:4.92%, [ Ni ]:1.46%, [ Cu ]:0.05%, [ N ]:0.02% and the balance of Fe and other elements; the mass fractions of the elements in the tapped molten steel are as follows: [C] the method comprises the following steps 3.365%, [ Si ]:0.21%, [ Mn ]:0.48%, [ P ]:0.049%, [ S ]:0.071%, [ Cr ]:10.01%, [ Ni ]:1.46%, [ Cu ]:0.02%, [ N ]:0.01 percent, and the balance of Fe and other elements; the contents of the [ Cr ] element and the [ C ] element in the LD tapped molten steel meet the following requirements: when the [ Cr ] is less than 5 percent, the [ C ] is more than or equal to 1.5 percent and less than or equal to 3 percent; when the content of Cr is more than or equal to 5 and less than or equal to 13 percent, the content of C is more than or equal to 3 percent and less than or equal to 3.5 percent;
after LD tapping, adopting a slag splashing furnace protection process, and then pouring out slag;
(2) Adding the LD tapping molten steel in the step (1) into GOR, wherein the weight of the GOR charging molten steel is 85.7t, the charging temperature is 1395 ℃, oxygen is blown again at the top and the bottom for deep decarburization, and blowing is stopped when the content of the molten steel [ C ] in the GOR furnace is 0.07%; the GOR furnace comprises a GOR furnace top gun, a GOR bottom gun and an inert gas, wherein the GOR furnace top gun blows oxygen, the GOR bottom gun blows oxygen and the inert gas, and the deep decarburization process of the GOR furnace comprises the following five stages:
dynamic 1 stage: the oxygen flow of the top lance is 1.2 Nm 3 /(min. T), total bottom gun flow 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 9, end of dynamic 1 stage [ C]The content is 0.5%;
dynamic 2 stage: the top blowing gun is stopped, and the total flow rate of the bottom gun is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 1, end of dynamic 2 stage [ C]The content is 0.3%;
dynamic 3 stage: the total flow rate of the primer is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.6, end of dynamic 3 stage [ C]The content is 0.2%;
dynamic 4 stages: the total flow rate of the primer is 1.2 Nm 3 /(min. T), bottom gun oxygen to inert gas volume ratio of 0.43, end of dynamic 4 stage [ C]The content is 0.1%;
dynamic 5 stage: the total flow rate of the primer is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.25, end of dynamic 5 stage [ C]The content is 0.07%;
(3) And 3.95t of reducing agent silicon-manganese alloy is put into the GOR furnace, reduced to form slag with the alkalinity of 1.8, and then steel tapping is carried out. The GOR tapping molten steel comprises the following components in percentage by mass:
[C] the method comprises the following steps 0.079%, [ Si ]:0.37%, [ Mn ]:10.53%, [ P ]:0.032%, [ S ]:0.002%, [ Cr ]:13.73%, [ Ni ]:1.41%, [ Cu ]:0.85, [ N ]:0.145%, and the balance of Fe and other elements.
The LD furnace in example 1 was desiliconized and preliminarily decarburized by the conventional LD furnace oxygen blowing method (bottom inert gas blowing, top oxygen blowing).
In the embodiment 1, as the content of [ Si ] in molten steel fed with GOR is 0.21 percent, the content is lower, the amount of slag in the smelting process is less, and the GOR does not have splashing phenomenon in the decarburization period; in addition, the LD furnace melting time of example 1 was 29min, the GOR furnace melting time was 55min, the total LD and GOR melting time was 84min, and the [ Cr ] metal yield of example 1 was 95.3%.
Example 2
In this example, the process of smelting stainless steel by LD and GOR duplex method is adopted to produce steel grade 12Cr14Mn10NiN, and the smelting steps are different from those in example 1 in that:
the blast furnace molten iron comprises the following elements in percentage by mass: [C] the method comprises the following steps 4.53%, [ Si ]:0.77%, [ Mn ]:0.96%, [ P ]:0.026%, [ S ]:0.046%, [ Cr ]:5.05%, [ Ni ]:1.45%, [ Cu ]:0.05%, [ N ]:0.018%, the balance being Fe and other elements;
the mass fractions of the elements in the LD tapped molten steel are as follows:
[C] the method comprises the following steps 3.479%, [ Si ]:0.19%, [ Mn ]:0.68%, [ P ]:0.049%, [ S ]:0.033%, [ Cr ]:10.26%, [ Ni ]:1.43%, [ Cu ]:0.02%, [ N ]:0.026%, and the balance of Fe and other elements;
the weight of molten steel entering the GOR furnace is 83t, the temperature of entering the GOR furnace is 1440 ℃, and blowing is stopped when the content of the molten steel [ C ] in the GOR furnace is 0.09%;
the deep decarburization process of the GOR furnace is divided into the following five stages:
dynamic 1 stage: the oxygen flow of the top lance is 1.3 Nm 3 /(min. T), total sole gun flow 1.1 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 7, end of dynamic 1 stage [ C]The content is 0.55 percent;
dynamic 2 phase: the total flow rate of the top blowing gun and the bottom blowing gun is 1.1 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.8, end of dynamic 2 stage [ C]The content is 0.32%;
dynamic 3 stage: the total flow rate of the primer is 1.1 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.54, end of dynamic 3 stage [ C]The content is 0.21%;
dynamic 4 stage: the total flow rate of the primer is 1.1 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.45, end of dynamic 4 stage [ C]The content is 0.15%;
dynamic 5 stage: the total flow rate of the primer is 1.1 Nm 3 /(min. T), bottom gun oxygen to inert gas volume ratio of 0.3, end of dynamic 5 stage [ C]The content is 0.09%;
the addition amount of the reducing agent silicon-manganese alloy is 4.54t.
The GOR tapping molten steel comprises the following components in percentage by mass:
[C] the method comprises the following steps 0.117%, [ Si ]:0.42%, [ Mn ]:9.68%, [ P ]:0.035%, [ S ]:0.002%, [ Cr ]:13.46%, [ Ni ]:1.24%, [ Cu ]:0.32%, [ N ]:0.151%, and the balance of Fe and other elements.
In the embodiment 2, as the content of [ Si ] in GOR molten steel fed into a furnace is 0.19 percent, the content is lower, the slag amount in the smelting process is less, and the phenomenon of splashing does not occur in the GOR decarburization period; in addition, the LD furnace of example 2 had a smelting time of 27min, the GOR furnace had a smelting time of 53min, the total smelting time of LD and GOR was 80min, and the [ Cr ] metal yield of example 2 was 94%.
Example 3
In this example, the LD and GOR duplex process is used to produce 13Cr14Mn10NiN steel, and the difference between the smelting steps and example 1 is that:
the blast furnace molten iron comprises the following elements in percentage by mass: [C] the method comprises the following steps 4.21%, [ Si ]:0.86%, [ Mn ]:0.96%, [ P ]:0.029%, [ S ]:0.043%, [ Cr ]:4.56%, [ Ni ]:1.41%, [ Cu ]:0.03%, [ N ]:0.015 percent, and the balance of Fe and other elements;
the mass fractions of the elements in the LD tapped molten steel are as follows:
[C] the method comprises the following steps 2.1%, [ Si ]:0.17%, [ Mn ]:0.86%, [ P ]:0.046%, [ S ]:0.036%, [ Cr ]:4.93%, [ Ni ]:1.43%, [ Cu ]:0.02%, [ N ]:0.021%, and the balance of Fe and other elements;
the GOR furnace entering molten steel weight is 79t, the furnace entering temperature is 1520 ℃, and blowing is stopped when the content of the molten steel [ C ] in the GOR furnace is 0.116%;
the deep decarburization process of the GOR furnace is divided into the following five stages:
dynamic 1 stage: the oxygen flow of the top lance is 1.4 Nm 3 /(min. T), total bottom gun flow 1.2 Nm 3 /(min. T), the volume ratio of oxygen to inert gas in the bottom lance is 10, and 14t of high carbon ferrochrome is added during the dynamic 1 stage, the end of the dynamic 1 stage [ C]The content is 0.51%;
dynamic 2 stage: the top blowing gun is stopped, the bottom gun flow is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.8, end of dynamic 2 stage [ C]The content is 0.34%;
dynamic 3 stage: the bottom gun flow is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.56, end of dynamic 3 stage [ C]The content is 0.19%;
dynamic 4 stage: the bottom gun flow is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.43, end of dynamic 4 stage [ C]The content is 0.15%;
dynamic 5 stage: the bottom gun flow rate is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.32, end of dynamic 5 stage [ C]The content is 0.116%;
the addition amount of the reducing agent silicon-manganese alloy is 4.73t.
The GOR tapping molten steel comprises the following components in percentage by mass:
[C] the method comprises the following steps 0.123%, [ Si ]:0.45%, [ Mn ]:9.76%, [ P ]:0.033%, [ S ]:0.003%, [ Cr ]:13.41%, [ Ni ]:1.23%, [ Cu ]:0.29%, [ N ]:0.153%, and the balance of Fe and other elements.
In the embodiment 3, as the content of [ Si ] in molten steel fed with GOR is 0.17 percent, the content is lower, the amount of slag in the smelting process is less, and the phenomenon of splashing does not occur in the decarburization period of GOR; the LD furnace smelting time in example 3 was 23min, the GOR furnace smelting time was 64min, the total LD and GOR smelting time was 87min, and the [ Cr ] metal yield in example 3 was 94.6%.
In addition, according to the process for smelting stainless steel by the LD and GOR duplex method of the embodiment 1, 2 or 3, the average GOR furnace life reaches more than 190 furnaces.
Comparative example 1
In the embodiment, the process for smelting stainless steel by GOR is adopted, and the produced steel grade is 09Cr14Mn10Ni2CuN, and the method comprises the following steps:
(1) Directly adding blast furnace molten iron into GOR (good object ratio), wherein the weight of the GOR charged molten iron is 76.1t, the charging temperature is 1300 ℃, and the blast furnace molten iron comprises the following components in percentage by mass: [C] the method comprises the following steps 4.43%, [ Si ]:1.2%, [ Mn ]:1.07%, [ P ]:0.055%, [ S ]:0.044%, [ Cr ]:4.41%, [ Ni ]:1.65%, [ Cu ]:0.04%, [ N ]:0.019%, and the balance of Fe and other elements;
blowing oxygen again at the top and bottom of the GOR furnace for deep decarburization, and stopping blowing when the content of the molten steel [ C ] in the GOR furnace is 0.066%; the GOR furnace is characterized in that oxygen is blown from the top of the GOR furnace, mixed gas of oxygen and inert gas is blown from the bottom of the GOR furnace, and the deep decarburization process of the GOR furnace comprises the following five stages:
dynamic 1 stage: the oxygen flow of the top lance is 1.3 Nm 3 /(min. T), bottom gun flow 1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 9, 18t of high-carbon ferrochrome is added in the process of the dynamic 1 stage, and the end point carbon content of the dynamic 1 is 0.6 percent;
dynamic 2 stage: the flow rate of the bottom lance is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 1, end of dynamic 2 stage [ C]The content is 0.4%;
dynamic 3 stage: the bottom gun flow is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.66, end of dynamic 3 stage [ C]The content is 0.25%;
dynamic 4 stage: the bottom gun flow is 1.2 Nm 3 V (min. T), bottom gun oxygen to inert gas volume ratio of 0.42, end of dynamic 4 stage [ C]The content is 0.15%;
dynamic 5 stage: the bottom gun flow is 1.2 Nm 3 /(min·t)，The volume ratio of oxygen to inert gas of the primer gun is 0.25, and the end point of 5 dynamic stages [ C ]]The content is 0.07%;
(2) After the carbon content of GOR molten steel is qualified, adding a reducing agent silicon-manganese alloy for 5.35t, reducing to form slag with the alkalinity of 1.78, and then tapping; the GOR tapping molten steel comprises the following components in percentage by mass:
[C] the method comprises the following steps 0.074%, [ Si ]:0.37%, [ Mn ]:10.57%, [ P ]:0.036%, [ S ]:0.003%, [ Cr ]:13.67%, [ Ni ]:1.33%, [ Cu ]:0.89%, [ N ]:0.21%, and the balance of Fe and other elements.
In the comparative example 1, the content of silicon fed into the furnace is high, the amount of slag in the smelting process is large, and obvious splashing occurs in the dynamic stage 1, so that the metal yield is only 89%; meanwhile, the GOR furnace life is lower due to large amount of slag, and the average GOR furnace life is 140 furnaces; the decarburization efficiency of the GOR furnace is low, so that a higher top lance oxygen flow is adopted in the dynamic 1 stage of GOR, the smelting time of the GOR furnace is still longer due to the longer oxidation period, 87min is reached, and the GOR smelting efficiency is low.
Comparative example 2
In this embodiment, the LD + GOR process for smelting stainless steel is adopted to produce the steel grade 09Cr14Mn10Ni2CuN, and the smelting steps are different from those of embodiment 1 in that:
the blast furnace molten iron comprises the following elements in percentage by mass: [C] the method comprises the following steps 4.35%, [ Si ]:0.93%, [ Mn ]:0.95%, [ P ]:0.022%, [ S ]:0.046%, [ Cr ]:4.43%, [ Ni ]:1.39%, [ Cu ]:0.04%, [ N ]:0.016% and the balance of Fe and other elements;
adding 17t of high-carbon ferrochrome in the LD smelting process;
the mass fractions of the elements in the LD tapped molten steel are as follows:
[C] the method comprises the following steps 3.2%, [ Si ]:0.4%, [ Mn ]:0.86%, [ P ]:0.046%, [ S ]:0.036%, [ Cr ]:14.6%, [ Ni ]:1.46%, [ Cu ]:0.06%, [ N ]:0.025%, and the balance of Fe and other elements;
the GOR furnace entering molten steel weight is 86t, the furnace entering temperature is 1420 ℃, and blowing is stopped when the content of the molten steel [ C ] in the GOR furnace is 0.076%;
the top and the bottom of the GOR furnace are simultaneously blown with oxygen again for deep decarburization, and blowing is stopped when the content of the molten steel [ C ] in the GOR furnace is 0.066 percent; the GOR furnace comprises a GOR furnace top gun, a GOR bottom gun and an inert gas, wherein the GOR furnace top gun blows oxygen, the GOR bottom gun blows oxygen and the inert gas, and the deep decarburization process of the GOR furnace comprises the following five stages:
dynamic 1 stage: the top gun oxygen flow is 1.3 Nm < 3 >/(min.t), the bottom gun flow is 1.2 Nm < 3 >/(min.t), the volume ratio of the bottom gun oxygen to the inert gas is 9, and the dynamic 1 end point carbon content is 0.63 percent;
dynamic 2 stage: stopping blowing the top gun, wherein the flow rate of the bottom gun is 1.2 Nm < 3 >/(min.t), the volume ratio of oxygen to inert gas of the bottom gun is 1, and the content of the end point [ C ] of the dynamic 2 stage is 0.35 percent;
dynamic 3 stage: the flow rate of the bottom gun is 1.2 Nm3/(min.t), the volume ratio of oxygen to inert gas of the bottom gun is 0.66, and the content of the end point [ C ] of the dynamic 3 stage is 0.25%;
dynamic 4 stage: the bottom gun flow is 1.2 Nm3/(min.t), the volume ratio of oxygen to inert gas of the bottom gun is 0.42, and the content of the end point [ C ] of the dynamic 4 stage is 0.15%;
dynamic 5 stages: the bottom gun flow is 1.2 Nm3/(min.t), the volume ratio of oxygen to inert gas of the bottom gun is 0.25, and the content of the end point [ C ] of the dynamic 5 stage is 0.076%;
(2) After the carbon content of the GOR molten steel is qualified, adding 5.63t of reducing agent silicon-manganese alloy, reducing to form slag with the alkalinity of 1.81, and then tapping; the GOR tapping molten steel comprises the following components in percentage by mass:
[C] the method comprises the following steps 0.081%, [ Si ]:0.41%, [ Mn ]:10.62%, [ P ]:0.031%, [ S ]:0.004%, [ Cr ]:13.73%, [ Ni ]:1.37%, [ Cu ]:0.85%, [ N ]:0.2 percent, and the balance of Fe and other elements.
In comparative example 2, the GOR has higher chromium content in the furnace and lower temperature in the furnace, so that more chromium is oxidized in the molten steel in the earlier stage of smelting, the decarburization efficiency is reduced, the slag amount in the smelting process is obviously increased, the GOR smelting time reaches 77min, the LD smelting time also reaches 35min, and the total LD + GOR smelting time reaches 112min.
The LD furnace in examples 2 and 3 and comparative example 2 was also desiliconized and decarburized by the conventional oxygen blowing method (bottom inert gas blowing, top oxygen blowing) of the LD furnace in example 1.
The contents of [ C ] and [ Cr ] in LD tapping molten steel and the corresponding total smelting time (min), [ Cr ] metal yield (%), and average GOR campaign in the LD tapping molten steel of each of the above examples and comparative examples are listed in the following Table 1:
TABLE 1
In conclusion, the smelting process method can realize efficient smelting of LD and GOR, effectively inhibit splashing in the decarbonization period of GOR and improve the metal yield; by reasonably designing the LD and GOR duplex smelting process, the decarburization efficiency of LD and GOR can be improved, the GOR smelting period is shortened, the furnace life of GOR is prolonged, and the comprehensive cost for smelting stainless steel is reduced.
Claims (7)
1. A process for smelting stainless steel by an LD and GOR duplex method comprises the following specific steps:
(1) Adding molten iron into LD, blowing oxygen to carry out desiliconization and primary decarburization, and after the desilting and the tapping are finished, slag stopping and tapping are carried out, wherein the mass fractions of the elements in the LD tapped molten steel are as follows:
[C] the method comprises the following steps 1 to 4%, [ Si ]:0.05 to 0.3% and [ Mn ]: 0.1-1.5%, P is less than or equal to 0.1%, S is less than or equal to 0.1%, and Cr: 5 to 13%, [ Ni ]:0.5 to 5%, [ N ]:0.01 to 0.1 percent, and the balance of Fe and other elements;
meanwhile, the [ Cr ] content and the [ C ] content in the LD tapped molten steel also need to meet the following requirements: when the [ Cr ] is less than 5 percent, the [ C ] is more than or equal to 1.5 percent and less than or equal to 3 percent; when the content of Cr is more than or equal to 5 and less than or equal to 13 percent, the content of C is more than or equal to 3 percent and less than or equal to 3.5 percent;
(2) Adding the LD tapping molten steel in the step (1) into GOR, carrying out top-bottom combined blowing for deep decarburization, and stopping blowing after the content of the molten steel [ C ] in the GOR furnace is qualified; the content of the molten steel [ C ] in the GOR furnace is qualified according to the requirements of different steel types on the content of the molten steel [ C ], and the content of the molten steel [ C ] in the GOR furnace is 0.03-0.3%;
(3) And GOR tapping.
2. The process for smelting stainless steel by using LD and GOR duplex method according to claim 1, wherein: and (3) carrying out deep decarburization on the GOR furnace in the step (2) by adopting an oxygen blowing mode of simultaneously blowing oxygen from the top and the bottom.
3. The LD and GOR duplex process for smelting stainless steel according to claim 2, wherein: the GOR furnace top gun in the step (2) blows oxygen, the bottom gun blows mixed gas of the oxygen and inert gas, and the deep decarburization process of the GOR furnace is divided into the following five stages:
dynamic 1 stage: the oxygen flow of the top lance is 1.2-1.4 Nm 3 /(min. T), the total flow rate of the bottom gun is 1.1-1.2 Nm 3 V (min. T), the volume ratio of the oxygen of the bottom gun to the inert gas is 7-10, and the end point of the dynamic 1 stage [ C]The content is 0.5-0.55%;
dynamic 2 stage: the total flow of the top blowing gun and the bottom blowing gun is 1.1 to 1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.8-1, and the end point of the dynamic 2 stage [ C]The content is 0.3-0.35%;
dynamic 3 stage: the flow rate of the bottom gun is 1.1-1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.54-0.6, and the end point of the dynamic 3 stage [ C]The content is 0.19 to 0.21 percent;
dynamic 4 stage: the flow rate of the bottom gun is 1.1-1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.43-0.45, and the end point of the dynamic 4 stage [ C]The content is 0.1-0.15%;
dynamic 5 stage: the flow rate of the bottom gun is 1.1-1.2 Nm 3 V (min. T), the volume ratio of oxygen and inert gas of the bottom gun is 0.25-0.32, and the end point of the dynamic 5 stage [ C]The content is 0.07-0.12%.
4. The LD and GOR duplex process for smelting stainless steel according to claim 1, wherein: in the step (3), reducing agent is firstly put into the GOR furnace, and is reduced to form slag with 1.5-2.5 alkalinity, and then tapping is carried out.
5. The LD and GOR duplex process for smelting stainless steel according to claim 4, wherein the process comprises the following steps: the reducing agent is silicon-manganese alloy.
6. The LD and GOR duplex process for smelting stainless steel according to claim 1, wherein: and (4) carrying out GOR slag-stopping and tapping in the step (3).
7. The LD and GOR duplex process for smelting stainless steel according to claim 1, wherein: and (2) after LD rotten slag tapping in the step (1), slag splashing and furnace protection, and then pouring out slag.
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