Method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and P at low cost

Abstract

The invention discloses a method for smelting heat-resistant steel 0Cr25Ni20 through low-cost iron and P removal, and the method comprises the steps of material preparation, P and Fe removal treatment, material distribution, AOD (argon oxygen decarburization) refining, LF (ladle furnace) refining and continuous casting, and the chemical components of the heat-resistant steel 0Cr25Ni20 are controlled in percentage by mass: less than or equal to 0.080% of C; si < = 1.00%; mn < = 2.00%; p is less than or equal to 0.04%; s is less than or equal to 0.02%; ni: 19%-22%; according to the invention, a material separation form is adopted, heat-resistant steel for continuous casting of two furnaces can be produced at the same time, the process flow is convenient, the AOD smelting time is shorter, and the quantity production is guaranteed. The low control of p is realized, high manganese is used for replacing a manganese-iron alloy material, the production cost is reduced, the low-p molten nickel iron is smelted by removing iron and p from high-p pig iron, and the use of pure nickel is reduced. And common high-carbon ferrochrome is adopted, so that the use of imported ferrochrome is reduced. Meanwhile, the chromium melting water in the intermediate frequency furnace reduces oxidation of chromium and improves the recovery rate of chromium. Iron and p are removed at low cost, and iron-removed slag is recycled, so that the production cost is reduced while the production efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost. Background Art

[0002] 0Cr25Ni20 is a high-chromium-nickel austenitic stainless steel. Due to its excellent corrosion resistance in oxidizing media and good high-temperature mechanical properties, its oxidation resistance, pitting corrosion resistance, and stress corrosion resistance are superior to those of ordinary stainless steels. Therefore, it can be used for both corrosion-resistant accessories and heat-resistant steel, and is widely used in industries such as metallurgy, petroleum, chemical engineering, and energy and power. During the smelting process, low p control requirements and a high degree of alloying are required. The high nickel content also requires the addition of nickel plates or sintered nickel to increase nickel content. When the p-to-steel ratio is too high, gold and manganese must be added, which is very costly. Furthermore, the relatively high amount of feed required in high-chromium, high-nickel AOD leads to prolonged smelting times.

[0003] Therefore, in view of the above-mentioned characteristics of low production efficiency and high production cost, it is necessary to provide a low-cost method for removing iron and phosphorus from smelting heat-resistant steel 0Cr25Ni20 to solve the above-mentioned technical problems. Summary of the Invention

[0004] In order to solve some or all of the technical problems existing in the above-mentioned prior art, the present invention provides a method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at a low cost.

[0005] The low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 comprises the following steps: material preparation - dephosphorization and deFe treatment - material separation - AOD refining - LF refining - continuous casting. The chemical composition of the heat-resistant steel 0Cr25Ni20 is controlled by mass percentage to be: C≤0.080%; Si≤1.00%; Mn≤2.00%; P≤0.04%; S≤0.02%; Ni: 19%-22%; Cr: 24.00%-26.00%, with the remainder being iron and unavoidable impurities.

[0006] Material preparation: The heat-resistant steel is smelted in a medium frequency furnace to form the first bag of molten steel. After the first bag of molten steel is tapped, high carbon ferrochrome and nickel are smelted in a medium frequency furnace to form the second bag of molten steel.

[0007] P and Fe removal treatment: After the first batch of molten steel is tapped, it is transferred to the AOD furnace for P and Fe removal treatment, and slag removal is carried out after P removal is completed to ensure that it is completely removed;

[0008] Material division: the molten steel after AOD removal of P and Fe is divided into two parts and loaded into the second furnace shell and the third furnace shell respectively. After the second bag of molten steel is tapped, it is evenly added into the second furnace shell and the third furnace shell according to the amount of molten steel;

[0009] AOD refining: The molten steel in the second and third furnace shells is smelted simultaneously through the AOD furnace, and samples are taken for analysis. Based on the sampling results, decarburization smelting is carried out in the AOD furnace respectively to make the molten steel composition meet the target requirements;

[0010] LF refining: The molten steel after decarburization in the AOD furnace is transferred to the LF furnace, lime and fluorite are added in batches to form slag, and argon blowing and stirring are performed after slag formation;

[0011] Continuous casting: Casting the molten steel after LF refining.

[0012] Furthermore, in the above-mentioned low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20, during the material preparation process, the tapping time of the second ladle of molten steel must be consistent with the tapping time of the first ladle of molten steel after dephosphorization and deFe treatment.

[0013] Furthermore, in the above-mentioned low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20, during the dephosphorization and deFe treatment process, the AOD gas flow ratio is O2:Ar=7.5:1, pig iron is added in batches during the AOD oxygen blowing process, and the process temperature is controlled at 1580℃~1620℃.

[0014] Furthermore, in the above-mentioned low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20, during the AOD refining process, target weights of lime, high chromium, magnesium balls, fluorite, ferrosilicon and high carbon ferromanganese are added to the second furnace shell and the third furnace shell respectively according to the weight of the molten steel in the second furnace shell and the third furnace shell and the sampling analysis results.

[0015] Furthermore, in the above-mentioned low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20, the inlet temperature is controlled at 1575°C during the LF refining process, and the temperature is raised to 1627°C after 20 minutes, and the outlet temperature is controlled at 1542°C.

[0016] The low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 of the present invention has the following advantages and beneficial effects:

[0017] The present invention removes iron and phosphorus at low cost, recycles the iron removal slag, and uses high manganese for manganese regulation. At the same time, continuous casting can replace the previous mold casting method, effectively reducing production costs.

[0018] The coordination between material preparation, dephosphorization and de-Fe treatment, and material separation effectively shortens the smelting time and improves production efficiency.

[0019] By using a medium frequency furnace to make chromium water, the oxidation of chromium is effectively reduced and the yield of ferrochrome is increased. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] The low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 comprises the following steps: material preparation - dephosphorization and deFe treatment - material separation - AOD refining - LF refining - continuous casting. The chemical composition of the heat-resistant steel 0Cr25Ni20 is controlled by mass percentage to be: C≤0.080%; Si≤1.00%; Mn≤2.00%; P≤0.04%; S≤0.02%; Ni: 19%-22%; Cr: 24.00%-26.00%, with the remainder being iron and unavoidable impurities.

[0022] Material preparation: The heat-resistant steel is smelted in a medium frequency furnace to form the first bag of molten steel. After the first bag of molten steel is tapped, high carbon ferrochrome and nickel are smelted in a medium frequency furnace to form the second bag of molten steel.

[0023] P and Fe removal treatment: After the first batch of molten steel is tapped, it is transferred to the AOD furnace for P and Fe removal treatment, and slag removal is carried out after P removal is completed to ensure that it is completely removed;

[0024] Material division: the molten steel after AOD removal of P and Fe is divided into two parts and loaded into the second furnace shell and the third furnace shell respectively. After the second bag of molten steel is tapped, it is evenly added into the second furnace shell and the third furnace shell according to the amount of molten steel;

[0025] AOD refining: The molten steel in the second and third furnace shells is smelted simultaneously through the AOD furnace, and samples are taken for analysis. Based on the sampling results, decarburization smelting is carried out in the AOD furnace respectively to make the molten steel composition meet the target requirements;

[0026] LF refining: The molten steel after decarburization in the AOD furnace is transferred to the LF furnace, lime and fluorite are added in batches to form slag, and argon blowing and stirring are performed after slag formation;

[0027] Continuous casting: Casting the molten steel after LF refining.

[0028] The reasons for adopting the process of material preparation - P and Fe removal - material separation - AOD refining - LF refining - continuous casting in the present invention are as follows:

[0029] Since AOD has no P removal function for chromium steel, it is difficult to adjust the smelting of low-P steel grades under high steel mixing conditions. Therefore, the AOD is used to remove Fe and P, and the medium-frequency furnace is used to smelt chromium water. The de-ironized molten steel and chromium iron water are then divided into two parts and added to two other furnace shells for smelting. The rhythm control arrangement is as follows: the first batch of molten steel in the medium-frequency furnace is added to the AOD for Fe and P removal smelting, and chromium water is started after the medium-frequency furnace is tapped. The tapping of the chromium iron water in the medium-frequency furnace is controlled according to the AOD Fe and P removal conditions, ensuring that the AOD nickel iron water and the medium-frequency furnace chromium iron water are tapped simultaneously. The two furnace shells smelt 0Cr25Ni20 steel according to the established temperature and gas control regulations.

[0030] Furthermore, in the low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 of the present invention, during the material preparation process, the tapping time of the second ladle of molten steel must be consistent with the tapping time of the first ladle of molten steel after dephosphorization and deFe treatment.

[0031] Furthermore, in the low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 of the present invention, during the dephosphorization and deFe treatment process, the AOD gas flow ratio is O2:Ar=7.5:1, pig iron is added in batches during the AOD oxygen blowing process, and the process temperature is controlled at 1580℃~1620℃.

[0032] Furthermore, in the low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 of the present invention, during the AOD refining process, target weights of lime, high chromium, magnesium balls, fluorite, ferrosilicon and high carbon ferromanganese are added to the second furnace shell and the third furnace shell respectively according to the weight of the molten steel in the second furnace shell and the third furnace shell and the sampling analysis results.

[0033] Furthermore, in the low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 of the present invention, the inlet temperature is controlled at 1575°C during the LF refining process, the temperature is raised to 1627°C after 20 minutes, and the outlet temperature is controlled at 1542°C.

[0034] The following describes in detail the method for smelting heat-resistant steel 0Cr25Ni20 with low cost by removing iron and phosphorus from the present invention in conjunction with specific embodiments.

[0035] Example 1

[0036] Example 1 of the present invention This example is implemented on a 30t medium frequency furnace + 45t AOD + 45t LF furnace, and the specific implementation is as follows:

[0037] Preparation:

[0038] The raw material composition is: C: 1.41%; Si: 1.02%; Mn: 0.35%; P: 0.018%; S: 0.050%; Cr: 1.20%; Ni: 20.24%, and the rest is iron and inevitable impurities; the loading weight is 34t, and it is loaded into the medium frequency furnace for smelting to form the first bag of molten steel. The tapping temperature of the medium frequency furnace is: 1633℃;

[0039] After the first ladle of molten steel is tapped from the intermediate frequency furnace, the second ladle is immediately loaded and smelted. The raw materials used are 25 tons of high-carbon ferrochrome and 5 tons of nickel. The raw material composition is: C: 1.95%; Si: 0.95%; P: 0.025%; Mn: 0.25%; S: 0.055%; Cr: 45.2%; Ni: 5.2%, with the remainder being iron and unavoidable impurities. The tapping temperature of the intermediate frequency furnace is 1633°C. During the material preparation process, the tapping time of the second ladle of molten steel must coincide with the tapping time of the first ladle of molten steel after dephosphorization and de-Fe treatment.

[0040] P and Fe removal treatment:

[0041] The first package of molten steel has the following composition: C: 1.45%; Si: 1.10%; Mn: 0.33%; P: 0.19%; S: 0.061%; Cr: 1.20%; Ni: 20.19%, and the rest is iron and unavoidable impurities. It is transferred to AOD smelting for P removal, with an addition amount of 35t and an AOD gas flow ratio of O2:Ar=7.5:1. During the AOD oxygen blowing process, 20t of pig iron (composition: C: 0.05%; Si: 0.061%; Cr: 1.20%; Ni: 20.19%) is added in batches. :0.11%; P: 0.016%; S: 0.068%; Cr: 0.02%; Ni: 19.07%, the rest is iron and unavoidable impurities), the AOD oxygen consumption in the P and Fe removal process is: 4500Nm3, lime consumption is 6t, and fluorite consumption is 0.5t. The process temperature is controlled at 1580℃~1620℃, and the tapping capacity is 42t of molten steel. After the P removal is completed, the slag is discharged. The slag must be discharged cleanly, and the composition is analyzed after the slag is discharged.

[0042] The results of sampling and analysis of components are:

[0043] C: 0.0071%; Si: 0.004%; Mn: 0.011%; P: 0.001%; S: 0.047%; Cr: 0.033%; Ni: 41.086%, the rest is iron and unavoidable impurities;

[0044] Dividing materials:

[0045] First, the molten steel, after being dephosphorized and de-Fe treated, was evenly divided into two 20-ton packages, each charged to the second and third furnace shells. Simultaneously, the tapped steel from the second package was evenly charged to the AOD furnace, 15 tons per furnace, charged to the second and third furnace shells. Both AOD shells were smelted simultaneously. After the additions, a resample was taken, revealing the following composition: (C: 1.87%; Si: 0.55%; P: 0.015%; S: 0.075%; Cr: 24.23%; Ni: 19.17%, with the remainder being iron and unavoidable impurities).

[0046] AOD Refining:

[0047] The second and third AOD shells begin decarburization smelting based on the sampled components;

[0048] In the second shell process, 5t of lime, 3t of high chromium, 0.6t of magnesium balls, 0.5t of fluorite, 0.6t of ferrosilicon, and 1t of high carbon ferromanganese were added;

[0049] In the third shell process, 5.5t of lime, 2.5t of high chromium, 0.6t of magnesium balls, 0.5t of fluorite, 0.7t of ferrosilicon, and 1.2t of high carbon ferromanganese were added;

[0050] The final sample composition analysis results after AOD refining are:

[0051] Second furnace shell: C: 0.04%; Si: 0.45%; Mn: 1.2%; P: 0.010%; S: 0.001%; Cr: 24.3%; Ni: 19.7%; N: 0.04%, the rest is iron and unavoidable impurities;

[0052] Third furnace shell: C: 0.045%; Si: 0.55%; Mn: 1.3%; P: 0.008%; S: 0.001%; Cr: 24.5%; Ni: 19.5%; N: 0.035%, the rest is iron and unavoidable impurities;

[0053] LF Refining:

[0054] After AOD tapping, the molten steel enters the LF station for treatment. The temperature at the station is 1575℃. After 20 minutes of power supply, the temperature is measured at 1627℃. 1.5t of lime and 0.6t of fluorite are added in batches for slagging. After slagging, argon blowing and stirring are carried out. The temperature at the LF station is 1542℃.

[0055] Continuous Casting:

[0056] The molten steel after LF refinement is cast.

[0057] In summary, compared with the prior art, the low-cost deironing and dephosphorization method for smelting heat-resistant steel 0Cr25Ni20 of the present invention has the following advantages and beneficial effects:

[0058] The present invention adopts a split material form, which can simultaneously produce heat-resistant steel cast in two furnaces, has a convenient process flow, a shorter AOD smelting time, and guaranteed production. Low-p control is achieved, and low-p high-grade heat-resistant stainless steel can be produced. Manganese-iron alloy materials can be smelted entirely with high manganese, which reduces production costs. The raw materials are deironized and de-phosphorized by high-p pig iron to smelt low-p nickel iron water, which reduces the cost of pure nickel. Ordinary high-carbon ferrochrome is used to reduce the use of imported ferrochrome. At the same time, the medium-frequency furnace chromium water reduces chromium oxidation and improves the chromium recovery rate. Low-cost deironization and de-phosphorization, the deironization slag is recycled, and the subsequent deironization slag is used in the electric furnace, which improves production efficiency while reducing production costs.

[0059] It should be noted that, in this document, unless otherwise expressly specified or limited, the term "connect" or its synonyms should be understood in a broad sense. For example, "connection" can mean a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication between two elements or the interaction between two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. Moreover, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. At the same time, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost, characterized in that: The method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost comprises: material preparation - removal of phosphorus and iron - material separation - AOD refining - LF refining - continuous casting, wherein the chemical composition of the heat-resistant steel 0Cr25Ni20 is controlled by mass percentage to be: C≤0.080%; Si≤1.00%; Mn≤2.00%; P≤0.04%; S≤0.02%; Ni: 19%-22%; Cr: 24.00%-26.00%, and the remainder is iron and unavoidable impurities; Material preparation: The heat-resistant steel is smelted in a medium frequency furnace to form the first bag of molten steel. After the first bag of molten steel is tapped, high carbon ferrochrome and nickel are smelted in a medium frequency furnace to form the second bag of molten steel. P and Fe removal treatment: After the first batch of molten steel is tapped, it is transferred to the AOD furnace for P and Fe removal treatment, and slag removal is carried out after P removal is completed to ensure that it is completely removed; Material division: the molten steel after AOD removal of P and Fe is divided into two parts and loaded into the second furnace shell and the third furnace shell respectively. After the second bag of molten steel is tapped, it is evenly added into the second furnace shell and the third furnace shell according to the amount of molten steel; AOD refining: The molten steel in the second and third furnace shells is smelted simultaneously through the AOD furnace, and samples are taken for analysis. Based on the sampling results, decarburization smelting is carried out in the AOD furnace respectively to make the molten steel composition meet the target requirements; LF refining: The molten steel after decarburization in the AOD furnace is transferred to the LF furnace, lime and fluorite are added in batches to form slag, and argon blowing and stirring are performed after slag formation; Continuous casting: Casting the molten steel after LF refining.

2. The method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost according to claim 1, characterized in that: During the material preparation process, the tapping time of the second ladle of molten steel must be consistent with the tapping time of the first ladle of molten steel after de-P and de-Fe treatment.

3. The method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost according to claim 1, characterized in that: During the P and Fe removal treatment process, the AOD gas flow ratio is O2:Ar=7.5:1, pig iron is added in batches during the AOD oxygen blowing process, and the process temperature is controlled at 1580℃~1620℃.

4. The method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost according to claim 1, characterized in that: During the AOD refining process, target weights of lime, high chromium, magnesium balls, fluorite, ferrosilicon and high carbon ferromanganese are added to the second and third furnace shells respectively according to the weight of the molten steel in the second and third furnace shells and the sampling analysis results.

5. The method for smelting heat-resistant steel 0Cr25Ni20 by removing iron and phosphorus at low cost according to claim 1, characterized in that: During the LF refining process, the inlet temperature is controlled at 1575℃, the temperature is raised to 1627℃ after 20 minutes, and the outlet temperature is controlled at 1542℃.