CN114875206B - Double dephosphorization and chromium protection process for smelting chromium-containing high-phosphorus metal liquid from laterite-nickel ore - Google Patents
Double dephosphorization and chromium protection process for smelting chromium-containing high-phosphorus metal liquid from laterite-nickel ore Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a double dephosphorization and chromium protection process for smelting chromium-containing high-phosphorus metal liquid from laterite-nickel ore, belonging to the technical field of ferrous metallurgy. The double process method for removing phosphorus and protecting chromium comprises the following steps: the P can be caused by respectively adding the chromium-containing high-phosphorus molten metal into the laterite-nickel ore smelting and the surface at the same time 2 O 5 Is lower than Cr 2 O 3 Generating free energy additives, namely dephosphorization cored wires and top slag, so that chromium and phosphorus in the inside and the surface of the laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid are selectively oxidized; wherein: chromium is reserved in the molten metal, phosphorus oxide generated in the molten metal floats up to the top slag, and phosphorus oxide generated on the surface layer of the molten metal is directly reserved in the top slag. The invention has the advantages of high comprehensive utilization value of laterite nickel ore, high quality of stainless steel and alloy steel, simple and convenient process operation, good rhythm matching performance, multi-ring dephosphorization, abundant and non-toxic slag system resources, and reduced phosphorus content below 0.05 percent and chromium retention rate above 84 percent.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and relates to a double process for dephosphorizing and protecting chromium in laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid.
Background
At present, dephosphorization is carried out in a conventional mode under the condition of molten iron in an oxidizing atmosphere, which inevitably leads to simultaneous removal of chromium in the molten iron and causes waste of chromium element.
This is because phosphorus and chromium have similarity in redox thermodynamic conditions of molten iron, i.e., phosphorus and chromium are similar in redox thermodynamic conditions at 1350-1500 ℃, dephosphorization entails a large loss of chromium, and vice versa; in the reduced state of the molten metal, chromium enters the molten metal and phosphorus also enters the molten metal, which causes serious deterioration of the quality of the molten metal. Especially in smelting chromium-containing high-phosphorus molten iron from laterite nickel ores.
Laterite nickel ore is a very large stock of iron, nickel, chromium and cobalt metal resources, and as the demand for nickel increases, nickel in the laterite nickel ore can be better utilized, but the higher content of chromium and phosphorus contained in the laterite nickel ore cannot be effectively applied.
When nickel is obtained from laterite-nickel ore, chromium and iron in the laterite-nickel ore need to be removed in order to obtain higher nickel purity; since this is done under oxidising conditions, phosphorus will enter the slag phase with the iron and chromium, so the phosphorus in the laterite nickel ore is also removed with the removal of chromium and iron. However, nickel, chromium and iron are the main components of alloy steel and stainless steel in the smelting process for obtaining alloy steel and stainless steel raw materials, and the value of chromium is also great, so that if chromium is removed for dephosphorization and enters a slag phase, the process is very pleasant.
In the existing comprehensive utilization method of laterite-nickel ore, when smelting by adopting an ore smelting furnace, only the yield of iron is reduced and the yield of chromium is not considered in order to remove phosphorus or enrich nickel, so that molten metal (molten iron and molten steel) with low phosphorus content is obtained. In the blast furnace smelting process, iron, chromium and nickel are completely obtained, and meanwhile, harmful element phosphorus is also obtained, so that the difficult problem of the subsequent steelmaking process is caused: and the contradiction between chromium retention and dephosphorization.
Dephosphorization processes have been widely studied since the seventh eighties of the last century. For example, dephosphorization studies under reducing conditions have been conducted in China and Japan. Although the dephosphorization effect by reduction is excellent, the Ca is generated 3 P 2 PH capable of generating extremely toxic by contact with water vapor 3 So the study is ultimately not practical.
Meanwhile, japanese iron and steel enterprises seek to perform slag-making, oxidative dephosphorization with alkali metal oxides. For example, using Li 2 CO 3 10％、CaO 14％、CaF 2 47% FeO 29% slag system, adding dephosphorization slag 70kg per ton molten iron at 1400-1500 ℃ to dephosphorize the stainless steel raw material molten iron containing 2.5% -6.0% carbon, 11-25% chromium and less than 8% nickel, and dephosphorizing the dephosphorization rate can reach 60%.
Decarburization, dephosphorization and chromium retention in CN 112375974A are realized through complex operations such as molten iron smelting, blowing of a top-bottom combined blown converter, gun position changing operation of constant oxygen pressure and the like of high-chromium molten iron, and are not suitable for large-scale industrial production.
In the large steelmaking process, the method cannot be widely used on an industrial scale due to poor matching of rhythms or scarcity and toxicity of slag system resources.
An enterprise adopting laterite nickel ore resources to carry out stainless steel smelting, the current chromium-preserving and phosphorus-reducing method is to add prefabricated iron or steel with very low phosphorus into metal liquid with high phosphorus and chromium content, and the process cost is increased.
Therefore, in view of the technical problems of huge stock of the existing laterite nickel ore resources and chromium and phosphorus protection, a process which can realize the process rhythm of phosphorus and chromium protection in a large steelmaking flow and has the advantages of abundant and non-toxic slag system resources, reduced phosphorus content below 0.05 percent and chromium protection rate above 84 percent is sought, and the process is necessary to ensure the smooth production and reduce the cost.
Disclosure of Invention
The invention solves the technical problem that in the smelting process of laterite-nickel ore resources, in order to remove phosphorus or enrich nickel, phosphorus and chromium are simultaneously removed, so that the waste of chromium resources is caused; in the blast furnace smelting, iron, chromium and nickel are obtained together with harmful element phosphorus, and the waste of chromium resources is avoided, but the defect that the performance of molten metal is deteriorated due to high phosphorus content exists.
In order to solve the technical problems, the invention provides the following technical scheme:
a double dephosphorization and chromium protection process for smelting chromium-containing high-phosphorus metal liquid by laterite-nickel ore comprises the following steps: the P can be caused by respectively adding the chromium-containing high-phosphorus molten metal into the laterite-nickel ore smelting and the surface at the same time 2 O 5 Is lower than Cr 2 O 3 An additive generating free energy, so that chromium and phosphorus in the inside and the surface of the laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid are selectively oxidized; wherein: the chromium is reserved in the metal liquid, and phosphorus oxide generated in the metal liquid is reacted by the additive to release CO 2 And forming bubbles to drag and float to the top slag, and directly leaving phosphorus oxide generated on the surface layer of the molten metal in the top slag.
Preferably, the additives respectively added in the laterite-nickel ore smelting chromium-containing high-phosphorus molten metal and on the surface are dephosphorization cored wires and top slag respectively.
Preferably, the dephosphorization cored wire comprises a wire core and an outsourcing steel belt; the composition of the wire core comprises an alkali metal compound K 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 At least one of CaO and CaF as other functional compounds 2 、FeOx。
Preferably, the composition of the top slag comprises K 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 CaCO, at least one of which is a compound with other functions 3 、CaF 2 、FeOx。
Preferably, in the wire core, the mass of the alkali metal compound accounts for 25-40% of the total mass, and the mass ratio of the compound with other functions is as follows: 10-15% of CaO and CaF 2 20-30%, feOx 30-40%, and the balance of unavoidable impurities; among the impurities, the content of sulfur, phosphorus, lead, tin, arsenic, antimony and bismuth is as low as possible; stringent control of water content<0.5％。
Preferably, the alkali metal compound K 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 The function of (3): dephosphorization strengthening agent, which reduces the free energy of dephosphorization reaction and leads phosphorus to be oxidized in preference to chromium;
the effect of the other functional compounds is as follows:
CaO: dephosphorization regulating agent provided by more than one level of metallurgical lime (CaO >90 percent);
CaF 2 : flux, which reduces the melting temperature of dephosphorization top slag, accelerates the melting of synthetic slag and is provided by fluorite;
FeOx: oxidizing agent of phosphorus to oxidize phosphorus at the interface of molten metal slag into P 2 O 5 Is provided by low-phosphorus iron oxide scale and hematite;
Cr 2 O 3 : can improve slag phase Cr 2 O 3 The action concentration (activity) of the chromium in the molten metal is reduced to generate Cr 2 O 3 Oxidation potential.
Preferably, the mass of the alkali metal compound in the top slag accounts for 10-20% of the total massThe method comprises the steps of carrying out a first treatment on the surface of the The mass ratio of the compounds with other functions is as follows: ca (Ca) 2 CO 3 15-25％、CaF 2 20-30%, feOx 30-40%, and the balance of unavoidable impurities.
Preferably, the double process for removing phosphorus and protecting chromium comprises the following steps: during the initial stage of smelting, the phosphorus content is high, surface slag is scraped off, a layer of top slag with the thickness of 200-300mm is covered on the surface layer of the molten metal, and a wire feeder is used for feeding a cored wire into the molten metal; wherein: the feeding speed of the cored wire is determined by the depth of the molten metal and is 90-120 m.min -1 。
Preferably, the double process for removing phosphorus and protecting chromium comprises the following steps: when the AOD molten steel enters LF refining, phosphorus exceeds standard or does not meet the requirement, covering a layer of top slag with the thickness of 200-300mm on the surface layer of the molten metal, feeding a cored wire into the molten metal by using a wire feeder, and detecting the phosphorus content until the phosphorus content reaches the standard.
Preferably, the double process for removing phosphorus and protecting chromium comprises the following steps: in the smelting process of AOD or other stainless steel, the dephosphorization cored wire with higher alkali metal compound content is fed in the middle dephosphorization converting period or for better dephosphorization, the top slag with high alkali metal compound content is replaced.
Preferably, the wire cores are uniformly mixed in a powder form, the granularity of the powder is 0.9-1.5mm, and the deeper molten metal is selected to have larger granularity according to the depth of the molten metal; the diameter of the dephosphorization cored wire is 14-16mm, and the thickness of the outer wrapping steel belt is 0.2-0.4mm.
Preferably, in the smelting process, the dephosphorization and chromium-protection double process method needs to stir molten metal to promote dephosphorization products to float upwards; the stirring power is 50-150W per ton of molten metal, and the reference is that the surface of the molten metal does not have large fluctuation.
Compared with the problems of chromium and phosphorus retention in the existing laterite-nickel ore smelting, the technical scheme provided by the invention has the beneficial effects of low cost, good efficiency and suitability for large-scale steel smelting:
the double-process for dephosphorizing and protecting chromium of the high-phosphorus chromium-containing metal liquid for smelting laterite-nickel ore overcomes the technical defects of chromium resource waste and performance deterioration of the high-phosphorus-content metal liquid in the smelting process of laterite-nickel ore resources.
The invention utilizes the alkali metal compound to greatly reduce P at 1300-1500 DEG C 2 O 5 Free energy of generation of (c) such that P 2 O 5 Is significantly lower than Cr 2 O 3 Free energy is generated, so that the selective oxidation of chromium and phosphorus is realized, and the thermodynamic condition requirement of chromium retention and dephosphorization is realized.
According to the invention, the dephosphorization cored wire is fed into the molten metal, and the cored wire has the best dephosphorization thermodynamic condition and dynamic condition in the melting and floating process, so that the ideal dephosphorization priority can be realized; alkali metal compound K in wire core 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 For reducing P in molten metal 2 O 5 The free energy of formation of (2) promotes the preferential oxidation of phosphorus over chromium; CO release 2 And (3) forming bubbles, and dragging dephosphorization products to float from the metal liquid phase into top slag to be absorbed by the top slag.
The invention has the effect of covering the top slag on the surface of the molten metal, firstly absorbing dephosphorization products floating up of the molten metal, and secondly generating dephosphorization reaction at the interface of the molten metal and the top slag.
The technical scheme provided by the invention has the beneficial effects of high comprehensive utilization value of laterite nickel ore, high quality of stainless steel and alloy steel, simple and convenient process operation, good rhythm matching performance, multi-ring dephosphorization, abundant and non-toxic slag system resources, reduced phosphorus content below 0.05% and chromium retention rate above 84%.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a double process for dephosphorizing and preserving chromium in the smelting of chromium-containing high-phosphorus molten metal from laterite-nickel ore in example 1 of the invention.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
Example 1:
dephosphorization pretreatment of chromium-containing high-phosphorus molten iron produced by a blast furnace.
The molten iron smelted by the blast furnace is 60 tons, the ingredients during tapping are shown in table 1, the phosphorus content is 0.094%, and the chromium content is 4.32%.
The high silicon content in the molten iron can cause the temperature to rise rapidly during AOD blowing, and even if chromium is lost during blowing, phosphorus is difficult to effectively remove.
The double process method for removing phosphorus and protecting chromium comprises the following steps:
s1, firstly determining the final content of phosphorus after dephosphorization of chromium-containing high-phosphorus molten iron
In order to reduce the loss of chromium in the subsequent AOD converting process, as shown in figure 1, a double pre-dephosphorization treatment process of top slag and dephosphorization cored wire in a ladle during tapping of a blast furnace is adopted, and dephosphorization is carried out until the phosphorus content is lower than 0.05%.
S2, determining component content selection and addition amount of the top slag and the dephosphorized cored wire according to the final content of phosphorus after dephosphorization of the chromium-containing high-phosphorus molten iron
The top slag comprises the following components in percentage by mass: k (K) 2 CO 3 10％、Na 2 CO 3 10％、CaCO 3 20％、CaF 2 20% of FeOx 40%, and the mixture was prepared into powder with a powder particle size of 4mm and packed in bags, and each bag weighed 50kg.
The dephosphorization cored wire comprises the following components in percentage by mass: k (K) 2 CO 3 20％、Na 2 CO 3 20％、CaO 10％、CaF 2 20% of FeOx and 30%, wherein the diameter of the dephosphorization cored wire is 14-16mm, the granularity of powder is 1.5mm, and the thickness of the coated steel belt is 0.2-0.4mm.
S3, adding mode of top slag and dephosphorization cored wire
The total mass of the top slag was 2.4 tons calculated as 4% of the tapping amount. Before tapping, 1.2 tons of top slag are added to the bottom of the ladle, and 1.2 tons of top slag are continuously added into the iron stream during tapping. And (5) after the ladle is moved to a molten iron treatment station, feeding the dephosphorized cored wire.
Stirring the ladle bottom by blowing nitrogen gas to expose the liquid surface of the molten iron to the diameter of 60-100 cm. Feeding dephosphorization cored wire with length of 350m and feeding line speed of 100m min -1 。
S4, dephosphorization and chromium retention properties of chromium-containing high-phosphorus molten iron
After the treatment, the phosphorus content in the molten iron is reduced to 0.045%, the chromium content is reduced to 3.69%, and the chromium retention rate is 85.4%.
Table 1 mass percentages of the components before and after the treatment of the chromium-containing high-phosphorus molten iron in example 1
| Element(s) | C | Mn | Si | S | P | Cr | Ni |
| Pretreatment amount% | 4.05 | 0.71 | 2.48 | 0.058 | 0.094 | 4.32 | 2.33 |
| Post-treatment amount% | 4.00 | 0.65 | 2.35 | 0.045 | 0.045 | 3.69 | 2.33 |
Example 2:
and (5) treating exceeding of molten steel phosphorus in the nickel-containing stainless steel produced by AOD.
The AOD molten steel is 60 tons, and enters LF to find out that the phosphorus exceeds the standard, the composition is shown in Table 2, the phosphorus content is 0.07%, and the chromium content is 16.3%.
The double process method for removing phosphorus and protecting chromium comprises the following steps:
s1, firstly determining the final content of phosphorus after dephosphorization of molten steel in nickel-containing stainless steel
Clearly, the distance standard requires a phosphorus content of 0.05% which does not differ very much, corresponding to the need to strip 0.2kg of phosphorus per ton of steel. Therefore, in LF, a double dephosphorization process of top slag and dephosphorization cored wires is adopted, and the amount of top slag required for top slag dephosphorization is small.
S2, determining component content selection and addition amount of top slag and dephosphorized cored wire according to final content of dephosphorized molten steel in nickel-containing stainless steel
The top slag comprises the following components in percentage by mass: k (K) 2 CO 3 10％、Na 2 CO 3 10％、CaCO 3 20％、CaF 2 20% of FeOx 40%, and the mixture was prepared into powder with a powder particle size of 4mm and packed in bags, and each bag weighed 50kg.
The dephosphorization cored wire comprises the following components in percentage by mass: li (Li) 2 CO 3 10％、K 2 CO 3 10％、Na 2 CO 3 10％、CaO 15％、CaF 2 25 percent of FeOx 30 percent, and the diameter of the dephosphorization cored wire is 14 percent16mm, powder granularity of 0.9mm and thickness of the steel belt for wrapping of 0.2-0.4mm.
S3, adding mode of top slag and dephosphorization cored wire
The surface layer of the molten steel is covered with 200mm thick top slag. Stirring for 5 minutes by blowing argon forcefully, wherein the power of stirring molten iron is 80W per ton.
Feeding 300 m-long dephosphorized cored wire with a feeding speed of 120m min -1 。
S4, dephosphorization and chromium retention properties of molten steel in nickel-containing stainless steel
After the treatment, the phosphorus content in the molten iron is reduced to 0.045%, the chromium content is reduced to 16.0%, and the chromium retention rate is 98.1%. Meets the standard requirements.
Table 2 mass percentages of components before and after treatment of nickel-containing stainless steel in example 2
| Element(s) | C | Mn | Si | S | P | Cr | Ni |
| Standard requirements% | ＜0.06 | ＜1.00 | ＜1.00 | ＜0.015 | ≤0.05 | ＞16.0 | ＞1.0 |
| Pretreatment amount% | 0.05 | 0.89 | 0.56 | 0.008 | 0.07 | 16.3 | 1.33 |
| Post-treatment amount% | 0.05 | 0.65 | 0.55 | 0.005 | 0.045 | 16.0 | 1.33 |
Example 3:
and (5) treating exceeding of molten steel phosphorus in the production of high-end nickel-chromium alloy steel by AOD.
The AOD molten steel is 60 tons, and enters LF to find out that the phosphorus exceeds the standard, the composition is shown in Table 3, the phosphorus content is 0.07%, and the chromium content is 2.10%.
The double process method for removing phosphorus and protecting chromium comprises the following steps:
s1, firstly determining the final content of dephosphorized molten steel in high-end nickel-chromium alloy steel
The high-end nichrome steel requires ultra-low phosphorus sulfur content, wherein the phosphorus content should be below 0.02%. Therefore, a double dephosphorization process of top slag and dephosphorization cored wires is adopted in LF, the thickness of the top slag and the length of the dephosphorization cored wires are higher, and the content of alkali metal compounds is also higher.
S2, determining component content selection and addition amount of top slag and dephosphorization cored wire according to final content of dephosphorization after dephosphorization of molten steel in high-end nickel-chromium alloy steel
The top slag comprises the following components in percentage by mass: k (K) 2 CO 3 10％、Na 2 CO 3 10％、CaCO 3 20％、CaF 2 20% of FeOx 40%, and the mixture was prepared into powder with a powder particle size of 4mm and packed in bags, and each bag weighed 50kg.
The dephosphorization cored wire comprises the following components in percentage by mass: k (K) 2 CO 3 20％、Na 2 CO 3 20％、CaO 10％、CaF 2 20 percent and 30 percent of dephosphorization cored wires with the diameter of 14-16mm, the granularity of powder of 1.2mm and the thickness of the coated steel belt of 0.2-0.4mm.
S3, adding mode of top slag and dephosphorization cored wire
The surface layer of the molten steel is covered with 300mm thick top slag. Stirring for 5 minutes by blowing argon forcefully, wherein the power of stirring molten iron is 150W per ton.
Feeding dephosphorization cored wire with 350m length and feeding line speed of 120m min -1 。
S4, dephosphorization and chromium retention properties of molten steel in high-end nickel-chromium alloy steel
After the treatment, the phosphorus content in the molten iron is reduced to 0.015 percent, the chromium content is reduced to 1.99 percent, and the chromium retention rate is 94.8 percent.
TABLE 3 mass percent of the Components before and after treatment of high-end nichrome steel in example 3
| Element(s) | C | Mn | Si | S | P | Cr | Ni |
| Pretreatment amount% | 0.30 | 0.28 | 0.08 | 0.006 | 0.07 | 2.10 | 3.00 |
| Post-treatment amount% | 0.30 | 0.28 | 0.08 | 0.002 | 0.015 | 1.99 | 3.00 |
Example 4:
AOD refines high phosphorous stainless steel liquid.
The phosphorus content of low-nickel iron blocks smelted by laterite nickel ores purchased in the market is uncertain, and the dephosphorization and chromium-protection effects are required to be adjusted according to the phosphorus content when stainless steel is smelted.
When the phosphorus content in the low nickel iron block is higher than 0.06% and lower than 0.1%, the total mass of the alkali metal compound in the top slag accounts for 10% of the total slag mass, and the total mass of the alkali metal compound in the dephosphorization cored wire accounts for 25% of the total slag mass. The molten steel surface layer is covered with 200mm thick top slag, and 300m long dephosphorized cored wire is fed.
When the phosphorus content in the low nickel iron block is higher than 0.1%, the total mass of the alkali metal compounds in the top slag accounts for 20% of the total slag mass, and the total mass of the alkali metal compounds in the dephosphorization cored wire accounts for 40% of the total slag mass. The molten steel surface layer is covered with top slag with the thickness of 300mm, and dephosphorization cored wires with the length of 350m are fed.
The specific operation of the double process for dephosphorization and chromium protection is described in example 2.
In the scheme, the double dephosphorization and chromium protection process for smelting the chromium-containing high-phosphorus metal liquid by the laterite-nickel ore overcomes the technical defects of chromium resource waste and performance deterioration of the metal liquid due to high phosphorus content in the laterite-nickel ore resource smelting process.
The invention utilizes the alkali metal compound to greatly reduce P at 1300-1500 DEG C 2 O 5 Free energy of generation of (c) such that P 2 O 5 Is significantly lower than Cr 2 O 3 Free energy is generated, so that the selective oxidation of chromium and phosphorus is realized, and the thermodynamic condition requirement of chromium retention and dephosphorization is realized.
According to the invention, the dephosphorization cored wire is fed into the molten metal, and the cored wire has the best dephosphorization thermodynamic condition and dynamic condition in the melting and floating process, so that the ideal dephosphorization priority can be realized; alkali metal compound K in wire core 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 For reducing P in molten metal 2 O 5 The free energy of formation of (2) promotes the preferential oxidation of phosphorus over chromium; CO release 2 And (3) forming bubbles, and dragging dephosphorization products to float from the metal liquid phase into top slag to be absorbed by the top slag.
The invention has the effect of covering the top slag on the surface of the molten metal, firstly absorbing dephosphorization products floating up of the molten metal, and secondly generating dephosphorization reaction at the interface of the molten metal and the top slag.
The technical scheme provided by the invention has the beneficial effects of high comprehensive utilization value of laterite nickel ore, high quality of stainless steel and alloy steel, simple and convenient process operation, good rhythm matching performance, multi-ring dephosphorization, abundant and non-toxic slag system resources, reduced phosphorus content below 0.05% and chromium retention rate above 84%.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.
Claims (5)
1. The double dephosphorization and chromium protection process for smelting the chromium-containing high-phosphorus metal liquid by the laterite-nickel ore is characterized by comprising the following steps of: the P can be caused by respectively adding the chromium-containing high-phosphorus molten metal into the laterite-nickel ore smelting and the surface at the same time 2 O 5 Is lower than Cr 2 O 3 An additive generating free energy, so that chromium and phosphorus in the inside and the surface of the laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid are selectively oxidized; wherein: the chromium is reserved in the metal liquid, and phosphorus oxide generated in the metal liquid is reacted by the additive to release CO 2 Forming bubbles to drag and float to the top slag, and directly leaving phosphorus oxide generated on the surface layer of the molten metal in the top slag;
additives which are respectively added into the inside and the surface of the laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid are dephosphorization cored wires and top slag respectively;
the dephosphorization cored wire comprises a wire core and an outer wrapping steel belt; the composition of the wire core comprises an alkali metal compound K 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 At least one of CaO and CaF as other functional compounds 2 FeOx; in the wire core, the mass of the alkali metal compound accounts for 25-40% of the total mass, and the mass ratio of the compounds with other functions is as follows: 10-15% of CaO and CaF 2 20-30%, feOx 30-40%, and the balance of unavoidable impurities; stringent control of water content<0.5％；
The composition of the top slag comprises K 2 CO 3 、Li 2 CO 3 、Na 2 CO 3 CaCO, at least one of which is a compound with other functions 3 、CaF 2 FeOx; the mass of the alkali metal compound in the top slag accounts for 10-20% of the total mass; the mass ratio of the compounds with other functions is as follows: ca (Ca) 2 CO 3 15-25％、CaF 2 20-30%, feOx 30-40%, and the balance of unavoidable impurities.
2. The dual process for dephosphorization and chromium protection of laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid according to claim 1, which is characterized by comprising the following steps: during the initial stage of smelting, the phosphorus content is high, surface slag is scraped off, a layer of top slag with the thickness of 200-300mm is covered on the surface layer of the molten metal, and a wire feeder is used for feeding a cored wire into the molten metal; wherein: the feeding speed of the cored wire is determined by the depth of the molten metal and is 90-120 m.min -1 。
3. The dual process for dephosphorization and chromium protection of laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid according to claim 1, which is characterized by comprising the following steps: when the AOD molten steel enters LF refining, phosphorus exceeds standard or does not meet the requirement, covering a layer of top slag with the thickness of 200-300mm on the surface layer of the molten metal, feeding a cored wire into the molten metal by using a wire feeder, and detecting the phosphorus content until the phosphorus content reaches the standard.
4. The dual process for dephosphorization and chromium protection of laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid according to claim 1, which is characterized by comprising the following steps: in the smelting process of AOD or other stainless steel, the dephosphorization cored wire with higher alkali metal compound content is fed in the middle dephosphorization converting period or for better dephosphorization, the top slag with high alkali metal compound content is replaced.
5. The dual process for dephosphorizing and protecting chromium of the laterite-nickel ore smelting chromium-containing high-phosphorus metal liquid according to claim 1, wherein the wire cores are uniformly mixed in the form of powder, and the granularity of the powder is 0.9-1.5mm; the diameter of the dephosphorization cored wire is 14-16mm, and the thickness of the outer wrapping steel belt is 0.2-0.4mm.
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