Method for smelting medium alloy steel in short process

Abstract

The invention relates to the technical field of alloy steel smelting, and particularly discloses a method for smelting medium alloy steel in a short process. Smelting raw materials are added into an electric furnace to be smelted, after the content of C and the content of P meet the matching requirement, carbon powder is injected, and then a first part of alloy raw materials are added for primary alloying; when the obtained primarily alloyed molten steel is tapped to 20%-30%, a second part of alloy raw materials are added for secondary alloying; the obtained secondary alloyed molten steel is subjected to LF refining, and the remaining alloy raw materials are added for microalloying; and casting the obtained third-time alloyed molten steel to obtain the medium alloy steel. According to the method, initial alloying is performed through carbon powder injection and the like in the later stage of electric furnace smelting, equipment investment is not increased, and the production cost is reduced; the three-step alloying method is adopted, efficient and low-consumption production of the medium alloy steel is achieved, the alloy yield is larger than or equal to 95%, molten steel components are more uniform, the cleanliness is high, and a guarantee is provided for production of high-quality medium alloy steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the alloy steel smelting technical field, especially to a short process smelting method of alloy steel. BACKGROUND

[0002] The alloy content of medium alloy steel is 5%~10%, generally alloy preheating or alloy induction furnace heating is adopted, after the end of the electric furnace smelting, primary alloying is carried out in the ladle during the tapping process, and secondary alloying is carried out again when the ladle refining reaches the next process, and finally continuous casting is carried out after vacuum degassing treatment. The existing alloying technology has the following problems: (1) poor alloy component uniformity: due to the high alloy content of medium alloy steel, a large amount of alloy needs to be added at one time during the alloying process of the electric furnace tapping process, resulting in uneven distribution of alloy components in the molten steel, and the molten steel in the ladle is also prone to form a temperature gradient, and even the molten steel at the bottom of the ladle is prone to form cold steel, making smelting difficult and prolonging the refining time. (2) heavy burden on the refining process: two-step alloying is adopted in the post-furnace and refining process, and due to the large amount of alloying, the burden on the refining process is also increased, causing difficulties in refining production, mainly reflected in long heating time, large power consumption, and serious impact on the metallurgical function of refining (i.e. deoxidation, desulfurization and removal of inclusions). (3) serious inclusion problem: two-step alloying makes it difficult to effectively remove the oxygen brought in by the alloy in the molten steel, and the inclusions produced are dispersedly distributed in the molten steel, reducing the quality and performance of the steel. In addition, in order to improve the alloy uniformity, large amount of argon stirring is required during smelting, which is prone to cause slag rolling phenomenon, seriously affecting the cleanliness of the molten steel. (4) heavy reliance on equipment: at present, medium alloy steel cannot be produced by short process, and external alloy baking, preheating, induction furnace and other equipment must be used, increasing the equipment investment cost.

[0003] Therefore, it is urgent to develop a short process smelting method for medium alloy steel, which realizes efficient and low-consumption smelting of medium alloy steel without increasing equipment investment, improves the alloy recovery rate, and improves the quality of molten steel. SUMMARY

[0004] In order to solve the above problems, the present application provides a short process smelting method of medium alloy steel, which realizes efficient production of medium alloy steel by primary alloying through carbon powder injection and other methods in the later stage of electric furnace smelting without increasing equipment investment, adopts three-step alloying method, and the alloy recovery rate is more than 95%.

[0005] To solve the above technical problems, the technical scheme provided by the present application is: A short process smelting method of medium alloy steel, comprising the following steps: S1, electric furnace smelting: smelting raw materials are added to the electric furnace for smelting, after the content of C and P meets the proportioning requirements, carbon powder is injected, and the first part of the alloy raw material is added for primary alloying, and the primary alloyed molten steel is obtained; S2, tapping: when the primary alloyed molten steel is tapped to 20%-30%, the second part of the alloy raw material is added for secondary alloying, and the secondary alloyed molten steel is obtained; S3, LF refining: the secondary alloyed molten steel is subjected to LF refining, the remaining alloy raw material is added for micro-alloying, and the third alloyed molten steel is obtained; S4, the third alloyed molten steel is subjected to casting, and the medium alloy steel is obtained.

[0006] Compared with the prior art, the short process smelting medium alloy steel method provided by the application adopts a new three-step alloying method, primary alloying is performed in the later stage of electric furnace smelting, at this time, the temperature and reducing atmosphere in the electric furnace are conducive to the rapid dissolution and preliminary homogenization of the alloy raw material; secondary alloying is performed during the tapping process, further adjusting the alloy composition of the molten steel; micro-alloying is performed during the LF refining process, accurately controlling the final alloy composition of the molten steel, realizing high-quality production of the medium alloy steel, and making the alloy yield ≥95%.

[0007] By injecting carbon powder, the oxidation of the slag is reduced by the reaction of carbon and oxygen in the slag, and the foamed slag generated by the carbon-oxygen reaction is used to realize a large amount of slag flow, which carries away part of the harmful impurities, is conducive to alloying, improves the alloy yield, and thus reduces the thickness of the slag layer.

[0008] In S1, the smelting raw materials include scrap steel.

[0009] In S1, when the smelting temperature reaches 1580°C or above, sampling is performed to ensure that the content of carbon (C) and phosphorus (P) in the molten steel meets the proportioning requirements. If not, continue smelting until the proportioning requirement range is reached.

[0010] Preferably, in S1, the injection rate of the carbon powder is 0.3 kg / t·min -1 ~0.5 kg / t·min -1 .

[0011] Preferably, in S1, at the end of the injection of the carbon powder, the content of FeO in the slag is ≤15%, and the amount of the flowing slag accounts for 40%-60% of the total amount of the slag.

[0012] By limiting the injection rate of the carbon powder, the content of FeO in the slag can be guaranteed to be ≤15%, the oxidation of the slag is reduced and the slag flow is promoted, the thickness of the slag layer is reduced, the amount of the flowing slag is controlled to account for 40%-60% of the total amount of the slag, and part of the harmful impurities can be carried away by the flowing slag to improve the furnace environment. It should be noted that the end time of the injection of the carbon powder is based on the content of FeO in the slag and the proportion of the flowing slag in the above range.

[0013] Preferably, in S1, the first part of alloy raw materials is added by using a high-position stock bin.

[0014] In the application, the alloy is added into the electric furnace accurately by using a high-position stock bin and a downspout, which can ensure that the alloy raw materials are added into the electric furnace uniformly and stably, avoid local concentration or uneven distribution of the alloy raw materials during the adding process, and be beneficial to the rapid dissolution and uniform distribution of the alloy raw materials in the molten steel.

[0015] Preferably, in S1, the adding amount of the first part of alloy raw materials is 90 kg / t~160 kg / t.

[0016] Preferably, in S1, the oxygen supply amount for smelting is 1.2 Nm 3 / t·min -1 ~1.4 Nm 3 / t·min -1 , the oxygen supply amount for initial alloying is 0.2 Nm 3 / t·min -1 ~0.5 Nm 3 / t·min -1 .

[0017] In the application, the oxygen supply amount is controlled to ensure that the initial alloying process is in a relatively low oxidizing environment, reduce the oxidation reaction in the furnace, and at the same time ensure that the stirring effect generated by the carbon-oxygen reaction is fully utilized, so that the molten steel and the alloy in the molten pool are fully mixed, and the uniform distribution of alloy components is promoted.

[0018] Preferably, in S1, the power supply power for initial alloying is 65%~75% of the power supply power for smelting, and is further preferably 68%~72%.

[0019] In the application, the power supply power of the electric furnace is controlled to maintain the temperature in the electric furnace in a state of slow heating (8 ℃ / min~10 ℃ / min) basically, so as to avoid excessive oxidation of the alloy caused by too high temperature or the influence of the alloy dissolution and reaction speed caused by too low temperature, and ensure the quality of alloying.

[0020] Preferably, in S1, the smelting time for initial alloying is 4.5 min~5.5 min.

[0021] Preferably, in S2, the temperature for tapping is 1610 ℃~1630 ℃.

[0022] Preferably, in S2, the adding amount of the second part of alloy raw materials is 15 kg / t~34 kg / t, and is further preferably 16.8 kg / t~31.3 kg / t.

[0023] Preferably, the mass ratio of the first part of alloy raw material, the second part of alloy raw material and the remaining part of alloy raw material is (78-85):(12.5-18):(1-7), and more preferably (80-82):(15-16):(2-5).

[0024] The present application can further improve the alloying effect of the three-step alloying method by limiting the addition amount and addition ratio of each part of alloy raw material.

[0025] Preferably, in S2, the specific steps of tapping include: When tapping to 9%-11%, a pre-deoxidizer is added for pre-deoxidation; When tapping to 14%-16%, an aluminum ingot is added for deep deoxidation; When tapping to 23%-27%, the second part of alloy raw material is added for the second alloying; When tapping to 33%-37%, lime, synthetic slag, fluorite and aluminum sheet are added for desulfurization and impurity removal; When tapping to 100%, the secondary alloyed molten steel is obtained.

[0026] Further preferably, in S2, the pre-deoxidizer includes the following percentage of chemical components: Al 22%-25%, Al2O3 20%-22%, CaO 25%-27% and Si 8%-9%.

[0027] Further preferably, in S2, the addition amount of the pre-deoxidizer is 0.4 kg / t-0.6 kg / t.

[0028] Further preferably, in S2, the addition amount of the aluminum ingot is 1.8 kg / t-2.2 kg / t.

[0029] Further preferably, in S2, the addition amount of the lime is 5.5 kg / t-6.5 kg / t.

[0030] Further preferably, in S2, the synthetic slag includes the following percentage of chemical components: Al2O3 45%-50%, CaO 32%-40%, SiO2 4%-10% and MgO <3%.

[0031] Further preferably, in S2, the addition amount of the synthetic slag is 3.2 kg / t-3.8 kg / t.

[0032] Further preferably, in S2, the addition amount of the fluorite is 3.0 kg / t-3.5 kg / t.

[0033] Further preferably, in S2, the addition amount of the aluminum sheet is 0.4 kg / t-0.6 kg / t.

[0034] For example, in S2, the content of Al in the aluminum ingot is greater than or equal to 97%, and the content of Al in the aluminum sheet is greater than or equal to 98%.

[0035] Preferably, in S3, the specific steps of the LF refining include: The secondary alloyed molten steel is put into the LF refining furnace, and after power supply for 50s-70s, calcium carbide and aluminum particles are added for deoxidation, and the remaining alloy raw materials are added at 1580-1600 DEG C for micro-alloying, so as to obtain the tertiary alloyed molten steel.

[0036] Further preferably, in S3, the addition amount of the calcium carbide is 0.6-0.8 kg / t.

[0037] Further preferably, in S3, the addition amount of the aluminum particles is 0.4-0.6 kg / t.

[0038] The present application has the following beneficial effects: (1) Reducing equipment investment: through the three-step alloying method, most of the alloying process is completed in the electric furnace, without the aid of external alloy baking, preheating, induction furnace and other equipment, which significantly reduces the equipment investment and floor area, and reduces the production cost.

[0039] (2) Reducing the pressure of the refining process: most of the alloying is completed in the electric furnace, which reduces the burden of the refining process. The refining process can be more focused on key metallurgical tasks such as desulfurization and inclusion removal, fully exerting the metallurgical effect of refining, making the molten steel composition more uniform, and improving the quality stability of the steel.

[0040] (3) Improving the alloy yield: the short process smelting method for alloy steel provided by the present application is suitable for all medium alloy steels with an alloy content of 5%-10%, and the alloy yield can reach more than 95%, effectively improving the utilization rate of alloy, reducing alloy consumption, and further reducing production cost.

[0041] (4) Improving the quality of molten steel: through the precise three-step alloying method and reasonable process operation, the inclusion rating of the molten steel is below 1.0, which significantly reduces the content of inclusions in the molten steel and improves the cleanliness of the molten steel, providing a guarantee for the production of high-quality medium alloy steel. BRIEF DESCRIPTION OF DRAWINGS

[0042] Fig. 1 The metallographic structure diagram of the medium alloy steel 5Cr of Example 1 of the present application.

[0043] Fig. 2 The metallographic structure diagram of the medium alloy steel 7Cr of Example 2 of the present application.

[0044] Fig. 3 The metallographic structure diagram of the medium alloy steel 5Cr of Example 5 of the present application.

[0045] Fig. 4 Microstructure chart of middle alloy steel 3Cr of the present application comparative example 1. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0047] In the present application embodiments and comparative examples, the alloy yield is calculated as follows: alloy yield = (steel product element content - steel residual element content) x steel quantity ÷ alloy element grade.

[0048] In the present application embodiments, the products not specially described can be obtained through market channels.

[0049] In order to better illustrate the present application, further example will be made below through embodiments.

[0050] Embodiment 1 The present embodiment provides a method for short-process smelting of middle alloy steel 5Cr, comprising the following steps: S1, electric furnace smelting: smelting raw materials are added into an electric furnace for smelting, the oxygen supply amount is 1.3 Nm 3 / t·min -1 When the smelting temperature reaches 1585℃, take a spectrum sample, the C content is 0.07%, the P content is 0.007%, which meets the matching requirements; then continuously spray carbon powder at a rate of 0.35 kg / t·min -1 , the FeO content in the slag is 12.2%, the slag amount accounts for 50% of the total slag amount; 105.0 kg / t of the first part of alloy raw materials is added by using a high-position stock bin, the oxygen supply amount is adjusted to 0.35 Nm 3 / t·min -1 , the power supply power is reduced to 70% of that at smelting, primary alloying is carried out, and a spectrum sample is taken for analysis after 5 min, the chemical element content is qualified, and the primary alloyed molten steel is obtained.

[0051] S2, the temperature of the primary alloyed molten steel is 1613℃ when tapping: When tapping to 10%, 0.5 kg / t of pre-deoxidizer is added for pre-deoxidization, the pre-deoxidizer comprises the following percentage chemical components: Al 22.3%, Al2O3 21.1%, CaO 26.7% and Si 8.5%.

[0052] When tapping to 15%, 2.0 kg / t of aluminum ingot is added for deep deoxidization.

[0053] When tapping to 25%, 23.0 kg / t of the second part of the alloying raw material (silicon-manganese alloy and high-carbon chromium-iron alloy) is added for the second alloying.

[0054] When tapping to 35%, 6.0 kg / t of lime, 3.5 kg / t of synthetic slag, 3.2 kg / t of fluorite and 0.5 kg / t of aluminum sheet are added for desulfurization and impurity removal, and the synthetic slag comprises the following percentage of chemical components: Al2O3 47.2%, CaO 35.8%, SiO2 7.2% and MgO 2.3%.

[0055] When tapping to 100% (85 t / heat), the secondary alloying molten steel is obtained.

[0056] S3, LF refining: the secondary alloying molten steel is put into the LF refining furnace, 0.7 kg / t of calcium carbide and 0.5 kg / t of aluminum particles are added for deoxidation after power supply for 60 s, the spectral sample and the refining slag sample are taken for analysis after 11 min, and the remaining alloying raw material is added at 1590℃ for micro-alloying according to the spectral sample analysis result, the mass ratio of the first part of the alloying raw material, the second part of the alloying raw material and the remaining part of the alloying raw material is 80:17.5:2.5, and the tertiary alloying molten steel is obtained.

[0057] S4, the tertiary alloying molten steel is cast to obtain the medium-alloy steel 5Cr.

[0058] After testing, the medium-alloy steel 5Cr comprises the following percentage of chemical components: C 0.13%, Si 0.28%, Mn 0.75%, Cr 5.1%, P≤0.015%, S≤0.005%, and the balance is Fe and inevitable impurity elements. It is calculated that the yield of chromium-iron alloy is 95.5%.

[0059] Example 2 The example provides a method for smelting medium-alloy steel 7Cr in a short process, comprising the following steps: S1, electric furnace smelting: smelting raw materials are added to the electric furnace for smelting, and the oxygen supply amount is 1.4 Nm 3 / t·min -1 When the smelting temperature reaches 1590℃, a spectral sample is taken, the C content is 0.06%, and the P content is 0.007%, which meets the matching requirements; then carbon powder is continuously injected at a rate of 0.45 kg / t·min -1 , the FeO content in the slag is 10.5%, and the amount of slag flow accounts for 55% of the total amount of slag; 140.0 kg / t of the first part of the alloying raw material is added by using the high-position stock bin, the oxygen supply amount is adjusted to 0.38 Nm 3 / t·min -1 , the power supply power is reduced to 68% of that during smelting, the initial alloying is performed, a spectral sample is taken for analysis after 5 min, the chemical element content is qualified, and the initial alloying molten steel is obtained.

[0060] S2, the temperature of the primary alloyed molten steel is 1618℃ when tapping: When tapping to 10%, 0.45kg / t of pre-deoxidizer is added for pre-deoxidation, and the chemical composition of the pre-deoxidizer is the same as that of Example 1.

[0061] When tapping to 15%, 2.1kg / t of aluminum ingot is added for deep deoxidation.

[0062] When tapping to 24%, 21.0kg / t of the second part of the alloying raw material (silicon-manganese alloy and high-carbon ferrochrome) is added for the second alloying.

[0063] When tapping to 33%, 5.8kg / t of lime, 3.6kg / t of synthetic slag, 3.3kg / t of fluorite and 0.5kg / t of aluminum sheet are added for desulfurization and impurity removal, and the chemical composition of the synthetic slag is the same as that of Example 1.

[0064] When tapping to 100%, the secondary alloyed molten steel is obtained.

[0065] S3, LF refining: the secondary alloyed molten steel is put into the LF refining furnace, 0.7kg / t of calcium carbide and 0.5kg / t of aluminum particles are added for deoxidation after 55s of power supply, the spectral sample and the refining slag sample are taken for analysis after 12min, and the remaining alloying raw material is added at 1595℃ according to the analysis result of the spectral sample for micro-alloying, the mass ratio of the first part of the alloying raw material, the second part of the alloying raw material and the remaining part of the alloying raw material is 85:12.75:2.25, and the tertiary alloyed molten steel is obtained.

[0066] S4, the tertiary alloyed molten steel is cast to obtain the medium alloy steel 7Cr.

[0067] After testing, the medium alloy steel 7Cr includes the following percentage chemical composition: C 0.14%, Si 0.30%, Mn 0.70%, Cr 7.0%, P≤0.015%, S≤0.005%, and the balance is Fe and unavoidable impurity elements. After calculation, the yield of ferrochrome is 95.8%.

[0068] Example 3 The present embodiment provides a method for smelting medium alloy steel 5Cr in a short process, comprising the following steps: S1, electric furnace smelting: smelting raw materials are added to the electric furnace for smelting, and the oxygen supply amount is 1.2Nm 3 / t·min -1 When the smelting temperature reaches 1588℃, a spectral sample is taken, the C content is 0.07%, and the P content is 0.006%, which meets the proportioning requirements; then 0.32kg / t·min -1carbon powder at a rate of 0.5 kg / t·min, the FeO content in the slag is 12.8%, and the amount of the slag flow is 45% of the total amount of the slag; 95.0 kg / t of the first part of the alloying raw material is added through the high-position stock bin, and the oxygen supply amount is adjusted to 0.23 Nm 3 / t·min -1 , the power supply power is reduced to 73% of the smelting power, the primary alloying is performed, and the chemical element content is analyzed by taking a spectrum sample after 5 min, and the chemical element content is qualified, thereby obtaining the primary alloyed molten steel.

[0069] S2, the molten steel is tapped when the temperature of the primary alloyed molten steel is 1628℃: When the tapping is to 11%, 0.55 kg / t of the pre-deoxidizer is added for pre-deoxidation, and the chemical composition of the pre-deoxidizer is the same as that in Example 1.

[0070] When the tapping is to 16%, 1.8 kg / t of the aluminum ingot is added for deep deoxidation.

[0071] When the tapping is to 27%, 21.9 kg / t of the second part of the alloying raw material (silicon-manganese alloy and high-carbon chromium-iron alloy) is added for the second alloying.

[0072] When the tapping is to 37%, 6.4 kg / t of lime, 3.3 kg / t of synthetic slag, 3.1 kg / t of fluorite, and 0.44 kg / t of aluminum sheet are added for desulfurization and impurity removal, and the chemical composition of the synthetic slag is the same as that in Example 1.

[0073] When the tapping is to 100%, the secondary alloyed molten steel is obtained.

[0074] S3, LF refining: the secondary alloyed molten steel is put into the LF refining furnace, 0.78 kg / t of calcium carbide and 0.55 kg / t of aluminum particles are added for deoxidation after 65 s of power supply, a spectrum sample and a refining slag sample are taken for analysis after 10 min, the remaining alloying raw material is added at 1600℃ according to the analysis result of the spectrum sample for micro-alloying, the mass ratio of the first part of the alloying raw material, the second part of the alloying raw material, and the remaining part of the alloying raw material is 78:18:4, thereby obtaining the third alloyed molten steel.

[0075] S4, the third alloyed molten steel is cast to obtain the medium-alloyed steel 5Cr.

[0076] After testing, the medium-alloyed steel 5Cr includes the following percentage chemical compositions: C 0.14%, Si 0.29%, Mn 0.73%, Cr 5.2%, P≤0.015%, S≤0.005%, and the balance is Fe and unavoidable impurity elements. After calculation, the yield of the chromium-iron alloy is 95.2%.

[0077] Example 4 The present embodiment provides a method for short-process smelting of medium-alloyed steel 7Cr, including the following steps: S1, Electric furnace smelting: smelting raw materials are added to the electric furnace for smelting, the oxygen supply is 1.3 Nm 3 / t·min -1 When the smelting temperature reaches 1583℃, take the spectrum sample, the C content is 0.07%, the P content is 0.007%, which meets the matching requirements; then continuously spray carbon powder at a rate of 0.4 kg / t·min -1 , the FeO content in the slag is 13.1%, and the slag flow accounts for 50% of the total slag amount; 120 kg / t of the first part of alloy raw materials is added by using the high-position bin, and the oxygen supply is adjusted to 0.43 Nm 3 / t·min -1 , the power is reduced to 70% of the smelting time, and the primary alloying is carried out, and the chemical element content is qualified after 5 min of spectrum sample analysis, and the primary alloyed molten steel is obtained.

[0078] S2, the temperature of the primary alloyed molten steel is 1620℃, and the tapping is carried out: When the tapping is 9%, 0.5 kg / t of pre-deoxidizer is added for pre-deoxidation, and the chemical composition of the pre-deoxidizer is the same as that of example 1.

[0079] When the tapping is 14%, 2.2 kg / t of aluminum ingot is added for deep deoxidation.

[0080] When the tapping is 25%, 22.0 kg / t of the second part of alloy raw materials (silicon-manganese alloy and high-carbon chromium iron alloy) is added for the second alloying.

[0081] When the tapping is 35%, 6.0 kg / t of lime, 3.7 kg / t of synthetic slag, 3.5 kg / t of fluorite and 0.56 kg / t of aluminum sheet are added for desulfurization and impurity removal, and the chemical composition of the synthetic slag is the same as that of example 1.

[0082] When the tapping is 100%, the secondary alloyed molten steel is obtained.

[0083] S3, LF refining: the secondary alloyed molten steel is put into the LF refining furnace, 0.63 kg / t of calcium carbide and 0.44 kg / t of aluminum particles are added for deoxidation after 60 s of power supply, and the spectrum sample and refining slag sample are analyzed after 11 min, according to the spectrum sample analysis result, the remaining alloy raw materials are added at 1585℃ for micro-alloying, the mass ratio of the first part of alloy raw materials, the second part of alloy raw materials and the remaining part of alloy raw materials is 81.8:15:3.2, and the third alloyed molten steel is obtained.

[0084] S4, the third alloyed molten steel is cast to obtain medium-alloy steel 7Cr.

[0085] The medium alloy steel 7Cr includes the following percentage of chemical components: C 0.14%, Si 0.32%, Mn 0.71%, Cr 7.0%, P≤0.015%, S≤0.005%, and the balance of Fe and inevitable impurity elements. The calculated yield of ferrochrome alloy is 95.3%.

[0086] Example 5 The present example provides a method for smelting medium alloy steel 5Cr in a short process, which is similar to Example 1, except that the first part of the alloy raw material is 85.0 kg / t, and the second part of the alloy raw material is 43.0 kg / t, i.e. the mass ratio of the first part of the alloy raw material, the second part of the alloy raw material and the remaining part of the alloy raw material is 64.8:32.7:2.5. The remaining conditions and parameter design are basically similar to Example 1, and are not described herein.

[0087] The medium alloy steel 5Cr includes the following percentage of chemical components: C 0.13%, Si 0.27%, Mn 0.76%, Cr 5.1%, P≤0.015%, S≤0.005%, and the balance of Fe and inevitable impurity elements. The calculated yield of ferrochrome alloy is 92.4%.

[0088] Comparative Example 1 The present example provides a method for smelting low alloy steel 3Cr, which includes the following steps: S1, electric furnace smelting: smelting raw materials are added to the electric furnace for smelting, the oxygen supply amount is 1.3 Nm 3 / t·min -1 , normal power supply, and the electric furnace molten steel is obtained.

[0089] The target chemical composition of the low alloy steel 3Cr includes the following percentage: C 0.13%, Si 0.24%, Mn 0.80%, Cr 3.0%, P≤0.015%, S≤0.005%, and the balance of Fe and inevitable impurity elements.

[0090] S2, tapping when the temperature of the electric furnace molten steel is 1620℃: When tapping to 10%, 0.5 kg / t of pre-deoxidizer is added for pre-deoxidation, and the chemical composition of the pre-deoxidizer is the same as that of Example 1.

[0091] When tapping to 15%, 2.2 kg / t of aluminum ingot is added for deep deoxidation.

[0092] When tapping to 25%, 60.0 kg / t of alloy raw material (silicon-manganese alloy and high-carbon ferrochrome alloy) is added for alloying.

[0093] When tapping to 35%, 6.0 kg / t lime, 3.7 kg / t synthetic slag, 3.5 kg / t fluorite and 0.56 kg / t aluminum sheet are added for desulfurization and impurity removal, and the chemical composition of the synthetic slag is the same as that of Example 1.

[0094] When tapping to 100%, the alloyed molten steel is obtained.

[0095] Due to the large amount of alloying at one time and alloying in the ladle, the uniformity of the alloying composition is poor.

[0096] S3, LF refining: the alloyed molten steel is put into the LF refining furnace, 0.63 kg / t calcium carbide and 0.44 kg / t aluminum particles are added for deoxidation after power supply for 60 s, and the spectral sample and refining slag sample are taken for analysis after 11 min, and the remaining alloying raw materials are added at 1590 ℃ according to the spectral sample analysis result for micro-alloying, and the refined molten steel is obtained.

[0097] Large argon stirring is required during refining, and the stirring time is long, which causes slag entrapment. At the same time, the heating time of the refining process is long, and the power consumption is about 20% higher than that of the implementation.

[0098] S4, the refined molten steel is cast to obtain low alloy steel 3Cr.

[0099] It is found that there are many inclusions in the molten steel, which seriously affects the quality of the steel, and the product that meets the standard requirements of medium alloy steel cannot be smelted (such as the alloy yield cannot be calculated due to the phenomenon of slag entrapment).

[0100] Verification test The inclusions of the refined molten steel / three times alloyed molten steel prepared in Examples 1-5 and Comparative Example 1 are tested according to the standard GB / T 13298-2015, and the results are shown in Table 1. The metallographic structure of the medium alloy steel prepared in Examples 1-2, 5 and Comparative Example 1 is analyzed, and the results are shown in Table 2. Figs. 1-4

[0101] Table 1 Inclusion rating results of refined molten steel / three times alloyed molten steel

[0102] As can be seen from the table and the figure, compared with the prior art which can only smelt low alloy steel (such as 3Cr) and has poor smelting effect, the medium alloy steel prepared by the short process smelting medium alloy steel method provided by the present application has excellent product performance, is suitable for smelting medium alloy steel, the alloy yield can reach 94.8%, the inclusions A / B / C / D of the molten steel are all below 2.0 level, the purity of the alloy steel is high, and the demand of high-end users is met.

[0103] ​The above merely provides the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement or improvement made in the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method of short process smelting of alloy steel, characterized in that, The method comprises the following steps: S1, electric furnace smelting: smelting raw materials are added into an electric furnace for smelting, after the contents of C and P meet the matching requirements, carbon powder is sprayed, the first part of alloy raw materials is added for primary alloying, and primary alloyed molten steel is obtained; S2, tapping: when the primary alloyed molten steel is tapped to 20%-30%, the second part of alloy raw materials is added for secondary alloying, and secondary alloyed molten steel is obtained; S3, LF refining: the secondary alloyed molten steel is subjected to LF refining, the remaining alloy raw materials are added for micro-alloying, and tertiary alloyed molten steel is obtained; S4, the tertiary alloyed molten steel is subjected to casting, and medium-alloyed steel is obtained.

2. The method of short campaign melting of alloy steels of claim 1 wherein, In S1, the injection rate of the carbon powder is 0.3 kg / t·min -1 0.5 kg / t·min -1 When the injection of the carbon powder is completed, the content of FeO in the slag is ≤15%, and the amount of the flow slag accounts for 40%-60% of the total amount of the slag.

3. The method of short campaign melting of alloy steels of claim 1 wherein, In S1, the adding amount of the first part of alloy raw materials is 90 kg / t-160 kg / t; In S2, the adding amount of the second part of alloy raw materials is 15 kg / t-34 kg / t.

4. The method of short campaign melting of alloy steels as claimed in claim 1 or 3, characterized in that, The mass ratio of the first part of alloy raw materials, the second part of alloy raw materials and the remaining part of alloy raw materials is (78-85):(12.5-18):(1-7).

5. The method of short campaign melting of alloy steels of claim 1 wherein, S1, the oxygen supply amount of the smelting is 1.2 Nm 3 / t·min -1 ~1.4 Nm 3 / t·min -1 , the oxygen supply amount of the preliminary alloying is 0.2 Nm 3 / t·min -1 ~0.5 Nm 3 / t·min -1 ; the power supply power of the preliminary alloying is 65%~75% of the power supply power of the smelting; the smelting time of the preliminary alloying is 4.5 min~5.5 min.

6. The method of short campaign melting of alloy steels as claimed in claim 1 or 5, characterized in that, In S1, the first part of alloy raw materials is added by using a high-position stock bin; In S2, the temperature of the tapping is 1610°C-1630°C.

7. The method of short campaign melting of alloy steels of claim 1 wherein, In S2, the specific steps of the tapping include: when the tapping is to 9%-11%, a pre-deoxidizer is added for pre-deoxidation; when the tapping is to 14%-16%, aluminum ingot is added for deep deoxidation; when the tapping is to 23%-27%, the second part of alloy raw materials is added for secondary alloying; when the tapping is to 33%-37%, lime, synthetic slag, fluorite and aluminum sheet are added for desulfurization and impurity removal; when the tapping is to 100%, the secondary alloyed molten steel is obtained; In S3, the specific steps of the LF refining include: the secondary alloyed molten steel is put into an LF refining furnace, after power is supplied for 50 s-70 s, calcium carbide and aluminum particles are added for deoxidation, the remaining alloy raw materials are added at 1580°C-1600°C for micro-alloying, and the tertiary alloyed molten steel is obtained.

8. The method of short campaign melting of alloy steels as claimed in claim 7, wherein, In S2, the pre-deoxidizer comprises the following chemical components in percentage: Al 22%-25%, Al2O3 20%-22%, CaO 25%-27% and Si 8%-9%; In S2, the synthetic slag comprises the following chemical components in percentage: Al2O3 45%-50%, CaO 32%-40%, SiO2 4%-10% and MgO <3%.

9. The method of short campaign melting of alloy steels as claimed in claim 7 wherein, In S2, the adding amount of the pre-deoxidizer is 0.4 kg / t-0.6 kg / t, the adding amount of the aluminum ingot is 1.8 kg / t-2.2 kg / t, the adding amount of the lime is 5.5 kg / t-6.5 kg / t, the adding amount of the synthetic slag is 3.2 kg / t-3.8 kg / t, the adding amount of the fluorite is 3.0 kg / t-3.5 kg / t, and the adding amount of the aluminum sheet is 0.4 kg / t-0.6 kg / t.

10. The method of short campaign melting of alloy steels as claimed in claim 7 wherein, In S3, the adding amount of the calcium carbide is 0.6 kg / t-0.8 kg / t, and the adding amount of the aluminum particles is 0.4 kg / t-0.6 kg / t.

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