Vacuum consumable smelting Mn yield estimation method and steel ingot smelting method

Abstract

The invention relates to the technical field of metal smelting, and provides a vacuum consumable smelting Mn yield estimation method and a steel ingot smelting method. The method for estimating the yield of the Mn in the vacuum consumable smelting comprises the steps that the size of a vacuum consumable ingot type of the vacuum consumable smelting and a vacuum indoor pressure value and a smelting speed parameter corresponding to a target smelting stage are obtained, an estimation formula C = 0.4 + 0.012 * V / A + 0.3 * P is established on the basis of the size, the vacuum indoor pressure value and the smelting speed parameter, C is the Mn yield of the target smelting stage, V is the smelting speed of the target smelting stage, A is the size of the vacuum consumable ingot type, and P is the Mn yield of the target smelting stage; p is the pressure value in the vacuum chamber of the target smelting stage, and the Mn yield corresponding to the target smelting stage is estimated through an estimation formula. According to the scheme, the disadvantage of estimation depending on experience or similar components is avoided, the accuracy of Mn yield estimation is improved, complex technological processes are not needed, the complexity of Mn yield estimation and the production cost are reduced, and the method is suitable for large-scale smelting in factories.

Description

Technical Field

[0001] The present invention relates to the technical field of metal smelting, and in particular to a method for predicting the Mn recovery rate in vacuum consumable melting and a method for melting ingots. Background Art

[0002] Vacuum Arc Remelting (VAR) is a smelting technology carried out in a vacuum environment for producing high-quality metal materials. The preliminarily smelted metal is made into a consumable electrode, which is installed as an anode in a vacuum consumable furnace. After the furnace is evacuated to a high vacuum, an arc is generated between the electrode and the cathode at the bottom of the water-cooled copper mold. The arc releases a large amount of heat, causing the end of the electrode to gradually melt. The melted metal falls into the molten pool in the water-cooled copper mold below in the form of droplets through the high-temperature arc zone. Under the forced cooling of the water-cooled copper mold, the molten metal in the molten pool gradually solidifies from bottom to top, and finally an ingot is formed.

[0003] During the vacuum consumable melting process, it is generally necessary to evaluate in advance the recovery rate of Mn content during the vacuum consumable melting process and leave a surplus for Mn volatilization in a vacuum consumable remelting process, especially for medium and low alloy ultra-high strength steels. However, the existing methods for predicting the Mn recovery rate are generally based on past production experience, borrowing similar compositions and using similar vacuum consumable processes to predict the Mn recovery rate during vacuum consumable melting. On the one hand, this leads to low accuracy in predicting the Mn recovery rate, and on the other hand, the process flow is complex and not suitable for the large-scale melting process in factories.

[0004] In summary, there is an urgent need for a method for predicting the Mn recovery rate in vacuum consumable melting that can improve the accuracy of predicting the Mn recovery rate in vacuum consumable melting while not requiring a complex process flow. Summary of the Invention

[0005] Aiming at the problems in the prior art that, based on past production experience, borrowing similar compositions and using similar vacuum consumable processes to predict the Mn recovery rate during vacuum consumable melting, on the one hand, this leads to low accuracy in predicting the Mn recovery rate, and on the other hand, the process flow is complex and not suitable for the large-scale melting in factories, the present disclosure provides a method for predicting the Mn recovery rate in vacuum consumable melting and a method for melting ingots.

[0006] According to a first aspect of the present invention, there is provided a method for predicting the Mn recovery rate in vacuum consumable melting, including: Obtain the size of the consumable electrode ingot type for vacuum consumable melting, the pressure value in the vacuum chamber and the melting rate parameter corresponding to the target melting stage, and construct an estimation formula C = 0.4 + 0.012 * V / A + 0.3 * P based on these three. Here, C is the Mn recovery rate of the target melting stage, V is the melting rate of the target melting stage, A is the size of the consumable electrode ingot type, and P is the pressure value in the vacuum chamber of the target melting stage. Estimate the Mn recovery rate corresponding to the target melting stage through the estimation formula.

[0007] In some embodiments, the size of the consumable electrode ingot type matches the size of the consumable electrode. The consumable electrode is prepared from alloy elements and Mn element raw materials, and the Mn element content in the consumable electrode is 1.20 - 1.45%.

[0008] In some embodiments, the vacuum consumable melting process includes: controlling each melting stage of the vacuum consumable melting to be in an ultimate vacuum environment, with the hot vacuum degree in the vacuum chamber ≤ 1.0 Pa, the air leakage rate ≤ 0.2 Pa / min, and the actual vacuum degree value in the vacuum chamber ≤ 0.5 Pa.

[0009] In some embodiments, the consumable electrode is prepared through the process flow of eccentric bottom tapping - ladle refining furnace - vacuum degassing device - continuous caster from alloy elements and Mn element raw materials, and the Mn element content in the consumable electrode is 1.2 - 1.4%.

[0010] In some embodiments, the vacuum consumable melting process further includes: Controlling the actual vacuum degree value in the vacuum chamber of each melting stage in the vacuum consumable melting process to be 0.08 - 0.12 Pa, the arcing time of the arcing melting stage to be 110 min, the current rising from 2 KA to 18 KA and then dropping to 15 KA, the voltage to be 22 - 24 V, the melting rate of the normal melting stage dropping from 7.3 kg / min to 6.7 kg / min, and the droplet rate to be 2.0 - 6.0 s -1 , in the feeding stage, the current drops from 11 KA to 6.5 KA, the voltage is 22 - 24 V, and the melting rate ≥ 2 kg / min.

[0011] In some embodiments, the consumable electrode is prepared from alloy elements and Mn element raw materials through a vacuum induction furnace, and the Mn element content in the consumable electrode is 1.3 - 1.45%.

[0012] In some embodiments, the vacuum consumable melting process further includes: Control the actual vacuum degree in the vacuum chamber during each melting stage of the vacuum consumable melting process to be 0.05 - 0.07 Pa, the arcing time in the arcing melting stage is 130 min, the current rises from 3 KA to 10 KA and then drops to 9 KA, the voltage is 23 - 25 V, the melting rate in the normal melting stage drops from 5.5 kg / min to 5.0 kg / min, and the droplet rate is 2.0 - 6.0 s -1 , in the feeding stage, the current drops from 8 KA to 4 KA, the voltage is 23 - 25 V, and the melting rate ≥ 1.5 kg / min.

[0013] In some embodiments, the vacuum consumable electrode is prepared by using alloy element and Mn element raw materials via a vacuum induction furnace, and the Mn element content in the vacuum consumable electrode is 1.20 - 1.35%.

[0014] In some embodiments, the vacuum consumable melting process further includes: Control the actual vacuum degree in the vacuum chamber during each melting stage of the vacuum consumable melting process to be 0.08 - 0.12 Pa, the arcing time in the arcing melting stage is 135 min, the current rises from 3 KA to 11 KA and then drops to 10 KA, the voltage is 23 - 25 V, the melting rate in the normal melting stage drops from 5.8 kg / min to 5.4 kg / min, and the droplet rate is 2.0 - 6.0 s -1 , in the feeding stage, the current drops from 10 KA to 4 KA, the voltage is 23 - 25 V, and the melting rate ≥ 2 kg / min.

[0015] According to the second aspect of the present invention, there is also provided a steel ingot melting method, including: predicting the Mn recovery rate corresponding to different melting stages by using the Mn recovery rate prediction method of the vacuum consumable melting as described in any one of the above; adjusting the pressure value in the vacuum chamber and the melting rate parameters of the corresponding melting stage of the vacuum consumable melting process and the size of the corresponding vacuum consumable ingot type according to the Mn recovery rate target value and the predicted Mn recovery rate to obtain a target steel ingot.

[0016] The above method for predicting the Mn recovery rate in vacuum consumable melting obtains the size of the vacuum consumable ingot type in vacuum consumable melting, the pressure value in the vacuum chamber corresponding to the target melting stage, and the melting rate parameter. Based on these three factors, a prediction formula C = 0.4 + 0.012 * V / A + 0.3 * P is constructed. Here, C is the Mn recovery rate in the target melting stage, V is the melting rate in the target melting stage, A is the size of the vacuum consumable ingot type, and P is the pressure value in the vacuum chamber in the target melting stage. Through this prediction formula, the Mn recovery rate corresponding to the target melting stage can be predicted. This method for predicting the Mn recovery rate only needs to obtain three parameters: the size of the vacuum consumable ingot type, the pressure value in the vacuum chamber corresponding to the target melting stage, and the melting rate parameter, to predict the Mn recovery rate in the target melting stage, avoiding relying on experience or similar compositions for prediction, which is beneficial to improving the accuracy of Mn recovery rate prediction. At the same time, the prediction process does not require complex technological processes and is calculated through this simple prediction formula, greatly reducing the complexity of Mn recovery rate prediction, reducing production costs, and being suitable for large-scale melting in factories. At the same time, it can be clearly seen from this prediction formula that the Mn recovery rate can be increased by increasing the melting rate V, reducing the cross-sectional area size A of the consumable ingot, and increasing the pressure value P in the vacuum chamber.

[0017] Meanwhile, the steel ingot melting method of the present application can also achieve the above technical effects and will not be elaborated here. Detailed implementation manners

[0018] The following further describes in detail the implementation manners of the present disclosure in combination with embodiments. The detailed descriptions of the following embodiments are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms, not limited to the specific embodiments disclosed herein, but including all technical solutions falling within the scope of the claims.

[0019] These embodiments are provided by the present disclosure to make the present disclosure thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, the components of materials, numerical expressions, and numerical values described in these embodiments should be interpreted as merely exemplary, rather than as limitations.

[0020] In addition, words such as "including" or "comprising" used in the present disclosure mean that the elements before this word are covered by the elements listed after this word, and do not exclude the possibility of also covering other elements.

[0021] All terms used in this disclosure have the same meanings as those understood by those of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in common dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense, unless specifically defined as such herein.

[0022] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the specification.

[0023] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments of the present invention are described in detail, those skilled in the art can easily appreciate that various modifications are feasible without substantially departing from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, parameters, etc. of the following exemplary embodiments without departing from the gist of the present invention.

[0024] A method for predicting the Mn recovery rate in vacuum consumable melting provided by an embodiment of the present invention includes: obtaining the size of the vacuum consumable ingot type in vacuum consumable melting, the pressure value in the vacuum chamber corresponding to the target melting stage, and the melting rate parameter, and constructing a prediction formula C = 0.4 + 0.012 * V / A + 0.3 * P based on the three, where C is the Mn recovery rate in the target melting stage, V is the melting rate in the target melting stage, A is the size of the vacuum consumable ingot type, and P is the pressure value in the vacuum chamber in the target melting stage, and predicting the Mn recovery rate corresponding to the target melting stage through the prediction formula.

[0025] Specifically, the vacuum consumable melting process includes an arc starting melting stage, a normal melting stage, and a feeding stage, and the target melting stage is one of the above three melting stages. The unit of the size of the vacuum consumable ingot type is m 2, the unit of the pressure value in the vacuum chamber corresponding to the target melting stage is Pa, the unit of the melting rate parameter corresponding to the target melting stage is kg / min, and the Mn recovery rate C has no dimension. Among them, V is the average melting rate within the target melting stage interval, A is the size of the vacuum consumable ingot type, referring to the cross-sectional area of the vacuum consumable ingot type, and P is the average pressure value in the vacuum chamber within the target melting stage interval. The sizes of the vacuum consumable ingot types include Φ406mm, Φ508mm, Φ660mm, Φ810mm, Φ920mm, Φ1050mm. The size of the vacuum consumable ingot type matches the size of the vacuum consumable electrode. For example, the diameter of the vacuum consumable electrode + 60mm = the diameter of the vacuum consumable ingot type. If the size of the vacuum consumable electrode is Φ606mm, the size of the vacuum consumable ingot for melting is Φ660mm. At the same time, it can be clearly seen from this estimation formula that the Mn recovery rate can be increased by increasing the melting rate V, reducing the cross-sectional area size A of the consumable ingot type, and increasing the pressure value P in the vacuum chamber.

[0026] For the above method for estimating the Mn recovery rate in vacuum consumable melting, only three parameters, namely the size of the vacuum consumable ingot type, the pressure value in the vacuum chamber corresponding to the target melting stage, and the melting rate parameter, need to be obtained to estimate the Mn recovery rate in the target melting stage, avoiding the disadvantages of relying on experience or similar compositions for estimation, which is beneficial to improving the accuracy of Mn recovery rate estimation. At the same time, the estimation process does not require complex technological processes and is calculated through this simple estimation formula, greatly reducing the complexity of Mn recovery rate estimation, reducing production costs, and being suitable for large-scale melting in factories.

[0027] According to several embodiments of the present invention, the size of the vacuum consumable ingot type matches the size of the vacuum consumable electrode. The vacuum consumable electrode is prepared from alloy elements and Mn element raw materials, and the content of Mn element in the vacuum consumable electrode is 1.20 - 1.45%.

[0028] Specifically, the vacuum consumable electrode will self-melt and then solidify to form a vacuum consumable ingot in a vacuum arc consumable furnace. The size of the vacuum consumable ingot matches the size of the vacuum consumable electrode. For example, the diameter of the vacuum consumable electrode + 60mm = the diameter of the vacuum consumable ingot type. If the size of the vacuum consumable electrode is Φ606mm, the size of the vacuum consumable ingot for melting is Φ660mm. Depending on the type of steel ingot finally melted, the contents of alloy elements and Mn elements will vary. For medium and low alloy ultra-high strength steel ingots, the vacuum consumable electrode is prepared from alloy elements, Mn element raw materials, and other remaining elements. The alloy elements include Cr, Mn, Si, Ni, Mo, W, etc. Controlling the content of Mn element in the prepared vacuum consumable electrode to be within 1.20 - 1.45% can reasonably control the content of Mn element in the vacuum consumable electrode, which can improve the strength and hardness properties of the steel ingot while ensuring the uniformity of the steel ingot composition.

[0029] According to several embodiments of the present invention, the vacuum consumable melting process includes: controlling each melting stage of the vacuum consumable melting to be in an ultimate vacuum environment, with the hot vacuum degree in the vacuum chamber ≤ 1.0 Pa, the air leakage rate ≤ 0.2 Pa / min, and the actual value of the vacuum degree in the vacuum chamber ≤ 0.5 Pa. By reasonably controlling the three parameters of the hot vacuum degree in the vacuum chamber, the air leakage rate, and the actual value of the vacuum degree in the vacuum chamber, it can be ensured to the greatest extent that each melting stage of the vacuum consumable melting is in an ultimate vacuum environment, so that the vacuum consumable melting process is fully melted.

[0030] According to several embodiments of the present invention, the vacuum consumable electrode is prepared by passing alloy element and Mn element raw materials through the process flow of eccentric bottom tapping - ladle refining furnace - vacuum degassing device - continuous caster. The content of Mn element in the vacuum consumable electrode is 1.2 - 1.4%. The process flow of eccentric bottom tapping - ladle refining furnace - vacuum degassing device - continuous caster is also the process flow of an electric furnace (EBT + LF + VD + MC). When preparing the vacuum consumable electrode through the electric furnace preparation process, the gas content in the electrode is relatively large and not very stable. When preparing the vacuum consumable electrode through the electric furnace process flow, the vacuum degree in the vacuum chamber during vacuum consumable smelting can be estimated to be about 0.05 - 0.30 Pa to improve the stability of the preparation process.

[0031] According to several embodiments of the present invention, the vacuum consumable melting process further includes: controlling the actual value of the vacuum degree in the vacuum chamber during each melting stage of the vacuum consumable melting process to be 0.08 - 0.12 Pa, the arcing time in the arcing melting stage to be 110 min, the current to rise from 2 KA to 18 KA and then drop to 15 KA, the voltage to be 22 - 24 V, the melting rate in the normal melting stage to drop from 7.3 kg / min to 6.7 kg / min, and the droplet rate to be 2.0 - 6.0 s -1 , in the feeding stage, the current drops from 11 KA to 6.5 KA, the voltage is 22 - 24 V, and the melting rate ≥ 2 kg / min.

[0032] According to several embodiments of the present invention, the vacuum consumable electrode is prepared by passing alloy element and Mn element raw materials through a vacuum induction furnace. The content of Mn element in the vacuum consumable electrode is 1.3 - 1.45%. The vacuum induction furnace process flow is also the VIM process flow. When preparing the vacuum consumable electrode through the VIM process flow, the gas content in the electrode is extremely small, and the vacuum degree in the vacuum chamber during vacuum consumable smelting can be estimated to be about 0.05 - 0.15 Pa.

[0033] The gas contents in the vacuum consumable electrodes prepared by the VIM process and those prepared by the electric furnace process are different, and the abilities of different vacuum consumable furnace seats to control the ultimate vacuum are different, resulting in large fluctuations in the recovery rate of Mn during the vacuum consumable melting process. During the vacuum consumable melting process, due to the relatively high vapor pressure of manganese element, the whole process of consumable electrode melting - droplet - molten pool - solidification is prone to volatilization in the vacuum high-temperature environment, resulting in large fluctuations in its content. Based on the metallurgical kinetics of manganese element volatilization under vacuum high-temperature conditions, the higher the vacuum degree, the greater the volatilization amount of Mn, and the longer the whole process of consumable electrode melting - droplet - dripping - molten pool - solidification persists in the vacuum chamber, the greater the volatilization amount of Mn element.

[0034] According to several embodiments of the present invention, the vacuum consumable melting process further includes: controlling the actual vacuum degree in the vacuum chamber during each melting stage of the vacuum consumable melting process to be 0.05 - 0.07 Pa, the arc starting time in the arc starting melting stage to be 130 min, the current rising from 3 KA to 10 KA and then dropping to 9 KA, the voltage to be 23 - 25 V, the melting rate in the normal melting stage dropping from 5.5 kg / min to 5.0 kg / min, and the droplet rate to be 2.0 - 6.0 s -1 , the current in the feeding stage dropping from 8 KA to 4 KA, the voltage to be 23 - 25 V, and the melting rate ≥ 1.5 kg / min.

[0035] According to several embodiments of the present invention, the vacuum consumable electrode is prepared by using alloy elements and Mn element raw materials through a vacuum induction furnace, and the Mn element content in the vacuum consumable electrode is 1.20 - 1.35%.

[0036] According to several embodiments of the present invention, the vacuum consumable melting process further includes: controlling the actual vacuum degree in the vacuum chamber during each melting stage of the vacuum consumable melting process to be 0.08 - 0.12 Pa, the arc starting time in the arc starting melting stage to be 135 min, the current rising from 3 KA to 11 KA and then dropping to 10 KA, the voltage to be 23 - 25 V, the melting rate in the normal melting stage dropping from 5.8 kg / min to 5.4 kg / min, and the droplet rate to be 2.0 - 6.0 s -1 , the current in the feeding stage dropping from 10 KA to 4 KA, the voltage to be 23 - 25 V, and the melting rate ≥ 2 kg / min.

[0037] For a further understanding of a method for predicting the Mn recovery rate in vacuum consumable melting of the present invention, the following will be further elaborated in detail in specific embodiments.

[0038] Example 1 Taking the preparation of vacuum consumable electrodes by the vacuum induction furnace (VIM) process and the vacuum consumable remelting to prepare medium - low alloy ultra - high strength steel 300M (40Si2Ni2CrMoVA) as an example.

[0039] The medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is smelted in a vacuum induction furnace (VIM) process to obtain a vacuum consumable electrode (or vacuum arc consumable electrode), and the Mn content in the vacuum consumable electrode is controlled to be 1.3~1.45%.

[0040] Casting Φ606mm vacuum consumable electrode, vacuum arc consumable remelting (VAR) melting low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) ingot Φ660mm, the size of the vacuum consumable ingot is Φ660mm, and its corresponding cross-sectional area is 0.342m 2 The extreme vacuum setting is adopted in the arc starting-normal smelting-shrinkage feeding stages, and the actual pressure range in the smelting vacuum chamber is 0.05~0.07Pa.

[0041] In the arc starting stage, the current combined with voltage control mode is adopted, the arc starting time is 130min, the current increases from 3KA to 10KA, and then decreases to 9KA, and the voltage is 23~25V; in the normal melting stage, the melting speed combined with the droplet control mode is adopted, the melting speed is 5.5kg / min and slowly decreases to 5.0kg / min, and the droplet speed is 2.0~6.0 s -1 ; During the feeding stage, the current combined with voltage control mode is adopted, the current is slowly reduced from 8KA to 4KA, the voltage is controlled at 23~25V, the weight of the vacuum consumable electrode is 900kg at the beginning of the feeding stage, the feeding melting rate is ≥1.5kg / min, and the weight is 100kg at the end.

[0042] According to the actual vacuum consumable smelting process of low-alloy ultra-high strength steel in the above-mentioned embodiment 1, the Mn recovery rate was estimated by using the estimation formula using the pressure value in the vacuum chamber, the consumable ingot size, and the melting rate parameters in the vacuum consumable smelting process. The Mn recovery rate was compared with the actual Mn recovery rate. The results are shown in Table 1.

[0043] Table 1 Estimated and actual Mn yield of vacuum consumable ingot Φ660mm medium-low alloy ultra-high strength 300M steel

[0044] It can be seen from Table 1 that the deviation between the Mn yield estimated by the aforementioned estimation formula and the actual Mn yield is in the range of 1.50% to 2.88%, which is extremely small. The Mn yield estimated by the vacuum consumable smelting Mn yield estimation method of the present application is highly accurate.

[0045] Example 2 Taking the preparation of medium-low alloy ultra-high strength steel D406A (30Si2MnCrMoVE) by vacuum induction furnace (VIM) process combined with vacuum consumable remelting as an example.

[0046] The vacuum consumable electrode of medium-low alloy ultra-high strength steel D406A (30Si2MnCrMoVE) is melted by vacuum induction furnace (VIM) process, and the Mn content in the vacuum consumable electrode is controlled to be 1.20 - 1.35%.

[0047] When casting a Φ606mm vacuum consumable electrode and remelting the ingot of medium-low alloy ultra-high strength steel D406A (30Si2MnCrMoVE) with a Φ660mm vacuum arc consumable remelting (VAR), when the size of the vacuum consumable ingot is Φ660mm, its corresponding cross-sectional area is 0.342m 2 , and the ultimate vacuum setting is adopted in the arc starting - normal smelting - feeding stage, and the actual pressure range in the smelting vacuum chamber is 0.08 - 0.12 Pa.

[0048] In the arc starting stage, the current combined with voltage control mode is adopted. The arc starting time is 135 min, the current rises from 3 KA to 11 KA and then drops to 10 KA, and the voltage is 23 - 25 V; in the normal smelting stage, the melting rate combined with droplet control mode is adopted. The melting rate slowly decreases from 5.8 kg / min to 5.4 kg / min, and the droplet rate is 2.0 - 6.0 s -1 ; in the feeding stage, the current combined with voltage control mode is adopted. The current slowly drops from 10 KA to 4 KA, and the voltage is controlled at 23 - 25 V. The weight of the vacuum consumable electrode at the beginning of the feeding stage is 900 kg, the feeding melting rate ≥ 2 kg / min, and the weight at the end is 100 kg.

[0049] According to the actual vacuum consumable smelting process of medium-low alloy ultra-high strength steel in Example 2 above, the Mn recovery rate is estimated by the estimation formula using the pressure value in the vacuum chamber, the size of the consumable ingot, and the melting rate parameters during the vacuum consumable melting process, and it is compared with the actual Mn recovery rate. The results are shown in Table 2.

[0050] Table 2 Estimated and actual Mn recovery rates of medium-low alloy ultra-high strength D406A steel with a vacuum consumable ingot of Φ660mm

[0051] It can be seen from Table 2 that the deviation range between the Mn recovery rate estimated by the foregoing estimation formula and the actual Mn recovery rate is 2.80% - -0.71%, and this deviation is extremely small. The accuracy of the Mn recovery rate estimated by the vacuum consumable melting Mn recovery rate estimation method of this application is relatively high.

[0052] Example 3 Taking the preparation of vacuum consumable electrodes by the electric furnace (EBT+LF+VD+MC) process and the vacuum consumable remelting to prepare medium and low alloy ultra-high strength steel 300M (40Si 2 Ni2CrMoVA) as an example.

[0053] The medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) is melted into a vacuum consumable electrode through the electric furnace (EBT+LF+VD+MC) process, and the Mn content in the vacuum consumable electrode is controlled to be 1.2~1.4%.

[0054] When casting a Φ810mm vacuum consumable electrode and remelting the medium and low alloy ultra-high strength steel 300M (40Si2Ni2CrMoVA) ingot of Φ920mm by vacuum arc consumable remelting (VAR), the size of the vacuum consumable ingot is Φ920mm, and its corresponding cross-sectional area is 0.664m 2 , and the ultimate vacuum setting is adopted in the arc starting-normal smelting-feeding stage, and the actual pressure range in the smelting vacuum chamber is 0.30~0.40Pa.

[0055] In the arc starting stage, the current combined with voltage control mode is adopted. The arc starting time is 110min, the current rises from 2KA to 18KA and then drops to 15KA, and the voltage is 22~24V; in the normal smelting stage, the melting rate combined with droplet control mode is adopted. The melting rate slowly decreases from 7.3kg / min to 6.7kg / min, and the droplet rate is 2.0~6.0 s-1; in the feeding stage, the current combined with voltage control mode is adopted. The current slowly drops from 11KA to 6.5KA, and the voltage is controlled at 22~24V. The weight of the vacuum consumable electrode at the beginning of the feeding stage is 1100kg, the feeding melting rate ≥2kg / min, and the weight at the end is 100kg.

[0056] According to the actual vacuum consumable smelting process of medium and low alloy ultra-high strength steel in Example 3 above, the Mn recovery rate is estimated through the estimated formula by using the pressure value in the vacuum chamber, the size of the consumable ingot, and the melting rate parameters during the vacuum consumable melting process, and it is compared with the actual Mn recovery rate. The results are shown in Table 3.

[0057] Table 3 Estimated and actual Mn recovery rates of medium and low alloy ultra-high strength 300M steel with a vacuum consumable ingot of Φ920mm

[0058] As can be seen from Table 3, the deviation range between the Mn recovery rate estimated by the aforementioned estimation formula and the actual Mn recovery rate is 1.08% - 3.39%. This deviation is extremely small, indicating that the accuracy of the Mn recovery rate estimated by the vacuum consumable melting Mn recovery rate estimation method of the present application is relatively high. At the same time, by further comparing the corresponding result tables 1 - 3 obtained in Examples 1 - 3, it can be seen that the greater the melting speed V, the smaller the cross-sectional area size A of the consumable ingot type, and the greater the pressure value in the vacuum chamber, the greater the corresponding Mn recovery rate. The vacuum consumable melting Mn recovery rate estimation method of the present application, while ensuring the accuracy of the Mn recovery rate estimation, does not require complex technological processes, is simple and easy to operate, and improves efficiency.

[0059] According to the second aspect of the present invention, there is also provided a steel ingot melting method, including: estimating the Mn recovery rate corresponding to different melting stages by using the vacuum consumable melting Mn recovery rate estimation method described in any one of the above; adjusting the pressure value in the vacuum chamber and the melting speed parameters of the corresponding melting stage in the vacuum consumable melting process and the size of the vacuum consumable ingot type according to the Mn recovery rate target value and the predicted Mn recovery rate to obtain a target steel ingot.

[0060] In a specific embodiment, the target steel ingot includes medium - low alloy ultra - high strength steel ingots, and the medium - low alloy ultra - high strength steel ingots include alloy elements and other remaining elements. For example, the medium - low alloy ultra - high strength steel ingots include C, Cr, Mn, Si, Ni, Mo, W, etc. Among them, the content of alloy elements is less than or equal to 10%, the C content is 0.16 - 0.45%, the Cr content is 0.5 - 4.0%, the Mn content is 0.2 - 1.5%, the Si content ≤ 2.5%, the Ni content ≤ 5%, the Mo content is 0.2 - 1.5%, the W content ≤ 3.5%. The medium - low alloy ultra - high strength steel ingots also include trace - added elements, such as V and Nb. The content of V is 0.01 - 0.40%, and the content of Nb is 0.01 - 0.05%. The steel grades of the medium - low alloy ultra - high strength steel ingots include 340 (40CrNi2MoA), D6AC (45CrNiMo1VA), N31 (30CrMnSiNi2A), D406A (30Si2MnCrMoVE), 300M (40Si2Ni2CrMoVA), etc.

[0061] So far, the embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details well - known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0062] Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration purposes and not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or equivalent substitutions can be made for some technical features without departing from the scope and spirit of the present disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way.

Claims

1. A method for estimating the Mn yield of vacuum consumable smelting, characterized in that: include: The size of the vacuum consumable ingot for vacuum consumable smelting and the pressure value in the vacuum chamber and the melting rate parameters corresponding to the target melting stage are obtained, and an estimation formula C=0.4+0.012*V / A+0.3*P is constructed based on the three, wherein C is the Mn yield in the target melting stage, V is the melting rate in the target melting stage, A is the size of the vacuum consumable ingot, and P is the pressure value in the vacuum chamber in the target melting stage. The Mn yield corresponding to the target melting stage is estimated by the estimation formula.

2. The method for estimating Mn yield by vacuum consumable smelting according to claim 1, characterized in that: The size of the vacuum consumable ingot matches the size of the vacuum consumable electrode. The vacuum consumable electrode is prepared from alloy elements and Mn element raw materials. The Mn element content in the vacuum consumable electrode is 1.20-1.45%.

3. The method for estimating Mn yield by vacuum consumable smelting according to claim 2, characterized in that: The vacuum consumable melting process includes: controlling each melting stage of the vacuum consumable melting to be in an extreme vacuum environment, with the hot vacuum degree in the vacuum chamber being ≤1.0Pa, the air leakage rate being ≤0.2Pa / min, and the actual value of the vacuum degree in the vacuum chamber being ≤0.5Pa.

4. The method for estimating Mn yield by vacuum consumable smelting according to claim 3, characterized in that: The vacuum consumable electrode is prepared by using alloy element and Mn element raw materials through a process of eccentric furnace bottom steel tapping - ladle refining furnace - vacuum degassing device - continuous casting machine, and the Mn element content in the vacuum consumable electrode is 1.2-1.4%.

5. The method for estimating Mn yield by vacuum consumable smelting according to claim 4, characterized in that: The vacuum consumable melting process also includes: The actual value of the vacuum degree in the vacuum chamber at each melting stage during the vacuum consumable melting process is controlled to be 0.08-0.12 Pa, the arc starting time in the arc starting melting stage is 110 min, the current increases from 2KA to 18KA and then decreases to 15KA, the voltage is 22-24 V, the melting rate in the normal melting stage decreases from 7.3 kg / min to 6.7 kg / min, and the droplet rate is 2.0-6.0 s -1 , the current in the shrinkage stage is reduced from 11KA to 6.5KA, the voltage is 22~24V, and the melting rate is ≥2kg / min.

6. The method for estimating Mn yield by vacuum consumable smelting according to claim 3, characterized in that: The vacuum consumable electrode is prepared by using alloy elements and Mn element raw materials through a vacuum induction furnace, and the Mn element content in the vacuum consumable electrode is 1.3-1.45%.

7. The method for estimating Mn yield by vacuum consumable smelting according to claim 6, characterized in that: The vacuum consumable melting process also includes: The actual value of the vacuum degree in the vacuum chamber at each melting stage during the vacuum consumable melting process is controlled to be 0.05-0.07 Pa, the arc starting time in the arc starting melting stage is 130 min, the current increases from 3KA to 10KA and then decreases to 9KA, the voltage is 23-25 ​​V, the melting rate in the normal melting stage decreases from 5.5 kg / min to 5.0 kg / min, and the droplet rate is 2.0-6.0 s -1 , the current in the shrinkage stage is reduced from 8KA to 4KA, the voltage is 23~25V, and the melting rate is ≥1.5kg / min.

8. The method for estimating Mn yield by vacuum consumable smelting according to claim 3, characterized in that: The vacuum consumable electrode is prepared by using alloy elements and Mn element raw materials through a vacuum induction furnace, and the Mn element content in the vacuum consumable electrode is 1.20-1.35%.

9. The method for estimating Mn yield by vacuum consumable smelting according to claim 8, characterized in that: The vacuum consumable melting process also includes: The actual value of the vacuum degree in the vacuum chamber at each melting stage during the vacuum consumable melting process is controlled to be 0.08-0.12 Pa, the arc starting time in the arc starting melting stage is 135 min, the current increases from 3KA to 11KA and then decreases to 10KA, the voltage is 23-25 ​​V, the melting rate in the normal melting stage decreases from 5.8 kg / min to 5.4 kg / min, and the droplet rate is 2.0-6.0 s -1 , the current in the shrinkage stage is reduced from 10KA to 4KA, the voltage is 23~25V, and the melting rate is ≥2kg / min.

10. A method for smelting steel ingots, characterized in that: include: The Mn yield corresponding to different smelting stages is estimated by the vacuum consumable smelting Mn yield estimation method according to any one of claims 1 to 9; According to the Mn recovery target value and the predicted Mn recovery rate, the vacuum chamber pressure value and melting rate parameters of the corresponding smelting stage of the vacuum consumable smelting process and the size of the vacuum consumable ingot are adjusted to obtain the target steel ingot.

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