CN113564376B - Method for preparing H13 steel through electroslag remelting - Google Patents
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Abstract
The invention provides a method for preparing H13 steel through electroslag remelting, and belongs to the technical field of metallurgy. According to the method for preparing H13 steel through electroslag remelting, the pre-melted slag containing rare earth is added, the silicon-calcium-iron reducing agent is added at the same time, and the addition amount of the pre-melted slag and the silicon-calcium-iron reducing agent is controlled, so that the prepared H13 steel is fine in crystal grains and uniform in structure, and the rare earth content in the steel is stable and controllable; meanwhile, the method has no special requirements on electroslag remelting equipment and environment, can realize preparation of high-quality H13 steel by using limited conditions, has simple and easy process, is safe and controllable, is more beneficial to large-scale production of H13 steel, and can meet the requirements of China on high-quality H13 steel.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a method for preparing H13 steel through electroslag remelting.
Background
The die steel is mainly classified into plastic die steel, cold work die steel and hot work die steel according to the use and service conditions, wherein the hot work die steel is mainly used for manufacturing dies for carrying out hot forming treatment on metals in a high temperature state, such as hot forging dies, hot extrusion dies, die casting dies and the like. The H13 steel is a hot-work die steel with wider application, the high-quality H13 steel can be produced by adopting an electroslag remelting process, the electroslag remelting technology is adopted when H13 steel is produced by some domestic manufacturers, a steel piece to be processed can be used as a consumable electrode to be smelted and poured when the electroslag remelting technology is utilized, and rare earth is added in the process to improve the cleanliness, the uniformity and the isotropy of the structure of the steel and refine grains. However, due to the limitations of equipment and smelting technology, secondary oxidation of molten steel is easily caused in the electroslag remelting process, and the loss of rare earth in the electroslag remelting process can reduce the yield of rare earth in steel, so that the yield of rare earth in steel is unstable and uncontrollable, the steel has more problems in structure, and the use requirements of high-quality die steel are difficult to meet.
Therefore, a method for preparing H13 steel by electroslag remelting is urgently needed to ensure that the rare earth content in the prepared steel is stable and controllable so as to meet the requirement of China on high-quality H13 steel.
Disclosure of Invention
The invention aims to provide a method for preparing H13 steel through electroslag remelting, and the H13 steel prepared by the method is fine in crystal grain, uniform in structure and stable and controllable in rare earth content.
In order to achieve the above object, the present invention provides the following technical solutions:
the technical scheme of the invention provides a method for preparing H13 steel by electroslag remelting, which comprises the steps of taking H13 steel to be treated as a consumable electrode, and carrying out electroslag remelting on the consumable electrode by using pre-melted slag and a reducing agent to obtain H13 steel;
the pre-melted slag comprises the following components in percentage by mass: CaF 2 40-50%, CaO 15-30%, rare earth oxide 20-30%, and Al 2 O 3 5-15%, 1-3% of MgO and 3-5% of NaF;
the reducing agent comprises the following components in percentage by mass: 55-65% of Si, 24-31% of Ca and the balance of Fe;
the reducing agent and the pre-melted slag have a relation shown in formula I;
m and also ＝(0.1～15)×10 -3 m Slag Formula I;
wherein m is And also Kg, mass of reducing agent; m is Slag Kg is the mass of the pre-melted slag.
Preferably, the consumable electrode comprises the following components in percentage by mass: 0.35-0.41% of C, 1.00-1.20% of Si, 0.20-0.50% of Mn, 5.00-5.50% of Cr, 1.3-1.75% of Mo, 0.80-1.00% of V, less than or equal to 0.002% of O, less than or equal to 0.002% of S, less than or equal to 0.02% of P and the balance of Fe.
Preferably, the rare earth oxide in the pre-melted slag is CeO 2 And La 2 O 3 One or two of them.
Preferably, the electroslag remelting comprises slag melting, consumable electrode remelting and ingot stripping which are sequentially carried out;
when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 400-700 mm, the remelting current is 6 multiplied by 10 3 ～1×10 4 A, remelting voltage is 55-73V; when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 700-1000 mm, the remelting current is 1 multiplied by 10 4 ～1.5×10 4 A, remelting voltage is 73-91V.
Preferably, the pre-melted slag is pretreated before slagging, and the pretreatment comprises pre-melting, cooling, crushing and drying which are sequentially carried out.
Preferably, the atmosphere of the pretreatment is an inert gas.
Preferably, the temperature of the pre-melting is 1500-1600 ℃, and the heat preservation time at the temperature of the pre-melting is 8-12 min.
Preferably, the particle size of the crushed pre-melted slag is 0.01-10 mm.
Preferably, the mass percentage of the crystal water in the dried premelting slag is lower than 0.01%.
Preferably, when the diameter of a crystallizer of a smelting furnace used for remelting the consumable electrode is 400-700 mm, the usage amount of the pre-melted slag is calculated according to a formula II; when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 700-1000 mm, the usage amount of the pre-smelting slag is calculated according to a formula III;
wherein m in formula II and formula III Slag Kg is the mass of the pre-melted slag; d in formula II and formula III Knot Is the inner diameter of the crystallizer, mm.
The invention provides a method for preparing H13 steel by electroslag remelting, which comprises the steps of taking H13 steel to be treated as a consumable electrode, and carrying out electroslag remelting on the consumable electrode by using pre-melted slag and a reducing agent to obtain H13 steel; the pre-melted slag comprises the following components in percentage by mass: CaF 2 40-50%, CaO 15-30%, rare earth oxide 20-30%, and Al 2 O 3 5-15%, 1-3% of MgO and 3-5% of NaF; the reducing agent comprises the following components in percentage by mass: 55-65% of Si, 24-31% of Ca and the balance of Fe; the reductant has a relationship with the pre-melted slag as shown in formula I. According to the invention, in the electroslag remelting process, the consumable electrode of H13 steel to be treated is treated by using the pre-melted slag containing rare earth and the silicon-calcium-iron reducing agent, so that a part of rare earth elements can enter the molten steel due to the interaction effect of the steel slag at high temperature, meanwhile, the silicon-calcium-iron reducing agent can reduce rare earth oxides in the slag to enable the rare earth elements to enter the molten steel, and the content of the rare earth in the steel can be effectively regulated and controlled by regulating the addition amount of the silicon-calcium-iron reducing agent, so that the H13 steel can obtain stable and controllable content of the rare earth; the rare earth elements obtained by the interaction of the steel slag and the addition of the reducing agent can form rare earth oxides and rare earth oxysulfides with impurities in the molten steel, such as O, S and the like, can promote heterogeneous nucleation of the molten steel, and are uniformly distributed in a dispersed manner, so that the effects of refining a solidification structure and inhibiting segregation are achieved; meanwhile, by controlling the dosage relation of the reducing agent and the pre-melted slag, namely adopting the relation shown in the formula I, the invention can lead the reducing agent and the pre-melted slag to have synergistic action, namely, utilize the reduction action of a slag pool formed by the pre-melted slag and the reducing agent to jointly inhibit the burning loss of the rare earth, thereby further ensuring that the content of the rare earth in the H13 steel is more stable and controllable.
The results of the examples show that the difference between the rare earth content of the H13 steel prepared by the process and the target rare earth content is not more than 0.001%, which shows that the rare earth content of the finished H13 steel is stable and controllable, and the H13 steel has fine grains and uniform structure.
Drawings
FIG. 1 is a metallographic structure diagram of an H13 steel S1 sample prepared in example 1 of the present invention;
FIG. 2 is a metallographic structure of a sample of annealed H13 steel obtained by conventional forging and annealing according to example 1 of the present invention;
FIG. 3 is a metallographic structure diagram of H13 steel in a post-forging annealed condition obtained by carrying out the same conventional forging and annealing as in example 1 in comparative example 1 of the present invention;
FIG. 4 is a metallographic structure diagram of a sample T1 of annealed H13 steel prepared in example 7 of the present invention.
Detailed Description
The technical scheme of the invention provides a method for preparing H13 steel by electroslag remelting, which comprises the steps of taking H13 steel to be treated as a consumable electrode, and carrying out electroslag remelting on the consumable electrode by using pre-melted slag and a reducing agent to obtain H13 steel;
the pre-melted slag comprises the following components in percentage by mass: CaF 2 40-50%, CaO 15-30%, rare earth oxide 20-30%, and Al 2 O 3 5-15%, 1-3% of MgO and 3-5% of NaF;
the reducing agent comprises the following components in percentage by mass: 55-65% of Si, 24-31% of Ca and the balance of Fe;
the reducing agent and the pre-melted slag have a relation shown in formula I;
m and also ＝(0.1～15)×10 -3 m Slag Formula I;
wherein m is And also Kg, mass of reducing agent; m is Slag Kg is the mass of the pre-melted slag.
The method takes H13 steel to be treated as a consumable electrode, and pre-melted slag and a reducing agent are used for carrying out electroslag remelting on the consumable electrode to obtain H13 steel.
In the present invention, the consumable electrode preferably comprises the following components by mass percent: 0.35-0.41% of C, 1.00-1.20% of Si, 0.20-0.50% of Mn, 5.00-5.50% of Cr, 1.3-1.75% of Mo, 0.80-1.00% of V, less than or equal to 0.002% of O, less than or equal to 0.002% of S, less than or equal to 0.02% of P and the balance of Fe. According to the invention, the H13 steel to be treated is used as a consumable electrode, and the content of each component is controlled within the range, so that the burning loss of components such as Si and the like caused by violent steel slag reaction in the remelting process can be reduced, and large-size inclusions formed under the condition that the O and S contents are too high and the O and S contents have strong affinity with rare earth elements are avoided, thereby being more beneficial to obtaining the H13 steel with uniform structure and fine grains.
The preparation method of the consumable electrode is not particularly limited, and the method for preparing the H13 steel consumable electrode well known in the field can be adopted.
In the invention, the pre-melted slag comprises the following components in percentage by mass: CaF 2 40-50 parts of CaO, 15-30 parts of rare earth oxide, 20-30 parts of Al 2 O 3 5-15 parts of MgO, 1-3 parts of MgO and 3-5 parts of NaF, preferably CaF 2 43-48 parts of CaO, 18-25 parts of CaO, 23-28 parts of rare earth oxide and Al 2 O 3 8-12 parts of MgO, 1.5-2.5 parts of NaF and 3.5-4.5 parts of NaF. The invention finally makes the rare earth simple substance enter the molten steel in the form of rare earth simple substance by adjusting the components of the pre-melted slag, namely taking a calcium-aluminum compound as a main body, adding rare earth oxide and controlling the content of the rare earth oxide in the above range, and making the calcium-aluminum compound and the reducing agent react with each other at the high temperature of electroslag remelting to reduce the rare earth oxide, and forming rare earth oxide and rare earth oxysulfide with impurities in the molten steel, such as O, S and the like, thereby promoting heterogeneous nucleation of the molten steel and realizing dispersion and uniform distribution, and achieving the effects of refining solidification structure and inhibiting segregation; meanwhile, the melting temperature of the pre-melted slag can be reduced by adding NaF and controlling the content of NaF within the range, and the pre-melted slag is pre-melted before the consumable electrode is melted, so that the consumable electrode is protected from being oxidized by contacting with air after being melted; the MgO is added and the content of the MgO is controlled within the range, so that a layer of protective film is formed on the surface of the slag pool after the pre-melted slag is melted, and the burning loss of the rare earth elements is effectively reduced.
In the present invention, the rare earth oxide in the pre-melted slag is preferably CeO 2 And La 2 O 3 One or two of them, more preferably CeO 2 . The invention is realized by selectingCeO 2 And La 2 O 3 One or two of the two kinds of the rare earth elements are used as a rare earth source in the pre-melted slag, so that the grains of the H13 steel can be refined, and the segregation of the H13 steel can be greatly reduced, thereby being more beneficial to obtaining the H13 steel with fine grains and uniform structure.
In the invention, the reducing agent comprises the following components in percentage by mass: 55-65% of Si, 24-31% of Ca and the balance of Fe; preferably 58-62% of Si, 28-30% of Ca and the balance of Fe. According to the invention, the silicon-calcium-iron is selected as the reducing agent of the electroslag remelting H13 steel, and the content of each component is controlled within the range, so that the rare earth oxide in the slag can be effectively reduced, and the H13 steel can obtain stable and controllable rare earth content.
In the invention, the reducing agent and the premelting slag have a relation shown in a formula I;
m and also ＝(0.1～15)×10 -3 m Slag Formula I;
wherein m is And also Kg is the mass of the reducing agent; m is Slag Kg is the mass of the pre-melted slag.
According to the invention, by controlling the dosage relation of the reducing agent and the premelting slag, namely adopting the relation shown in the formula I, the reduction reaction between the slag pool formed by the premelting slag and the reducing agent can be controlled to control the rare earth content in the steel, so that the rare earth content in the H13 steel is stable and controllable.
In the invention, the target rare earth content of the H13 steel is preferably 0.003-0.04% by mass percent, and more preferably 0.01-0.03% by mass percent. According to the invention, the target content of the H13 steel is set within the range, and the reducing agent can be better utilized to effectively reduce the rare earth oxide in the pre-melted slag into the rare earth simple substance, so that the H13 steel closer to the target rare earth content is obtained.
In the invention, the electroslag remelting preferably comprises slagging, remelting of a consumable electrode and stripping of an ingot which are sequentially carried out.
In the invention, the pre-melted slag is preferably pretreated before slagging, and the pretreatment preferably comprises pre-melting, cooling, crushing and drying which are sequentially carried out.
In the present invention, the atmosphere of the pretreatment is preferably an inert gas. The kind of the inert gas is not particularly limited in the present invention, and inert gases known to those skilled in the art may be used. In the present invention, the inert gas is preferably argon gas.
In the invention, the pre-melting temperature is preferably 1500-1600 ℃, and more preferably 1550 ℃; and after the slag is completely melted, preferably, the heat preservation time at the pre-melting temperature is 8-12 min, and more preferably 10 min. In the present invention, the holding time at the premelting temperature is preferably a holding time after the premelting slag is completely melted. The method can ensure that the pre-melted slag is fully melted and all components of the pre-melted slag are uniformly fused by controlling the pre-melting temperature and time of the pre-melted slag, thereby obtaining the pre-melted slag with all components uniformly distributed.
The cooling method and crushing operation of the pre-melted slag are not particularly limited in the invention, and the pre-melted slag is cooled to room temperature and crushed to the required particle size by adopting the cooling method and crushing operation which are well known to those skilled in the art.
In the invention, the grain size of the crushed pre-melted slag is preferably 0.01-10 mm, and more preferably 0.1-5 mm. The pre-melted slag is crushed into fine particles, and the particle size of the fine particles is controlled to be within the range, so that the pre-melted slag is more favorably and uniformly melted during slag melting, a stable slag pool is formed, and the consumable electrode is more favorably protected from being oxidized and burnt during melting.
In the present invention, the mass percentage of the crystal water in the dried premelting slag is preferably less than 0.01%, and more preferably less than 0.008%. According to the invention, by controlling the moisture content of the pre-melted slag to be as low as possible, the moisture content introduced through the slag pool can be effectively avoided and decomposed into oxygen and hydrogen at high temperature, so that the formation of molten steel inclusion and oxidation can be effectively avoided.
The drying operation is not particularly limited in the present invention, and the premelting slag can be brought into the range of crystal water control by a drying method well known to those skilled in the art. In the invention, the drying temperature is preferably 600-900 ℃, and the drying time is preferably 6-10 h. By controlling the drying temperature and time, the invention can ensure that the pre-melted slag is prevented from burning loss at higher temperature during drying and ensure that the crystal water content of the pre-melted slag meets the lower requirement.
In the present invention, the electroslag remelting is preferably performed under an inert atmosphere; the inert gas atmosphere is not particularly limited in the present invention, and inert gases known to those skilled in the art may be used. In the present invention, the inert gas is preferably nitrogen or argon, more preferably argon.
In the invention, when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 400-700 mm, the usage amount of the pre-smelting slag is preferably calculated according to a formula II; when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 700-1000 mm, the usage amount of the pre-smelting slag is preferably calculated according to a formula III;
wherein m in formula II and formula III Slag Kg is the mass of premelting slag; d in formula II and formula III Knot Is the inner diameter of the crystallizer, mm.
According to the invention, different pre-melted slag adding qualities are selected according to the sizes of the crystallizers of the smelting furnaces used in the remelting of different consumable electrodes, so that the slag pool after the pre-melted slag is melted can be effectively ensured to be fully covered on the surface of the molten steel, the molten steel is effectively prevented from being oxidized and burned out by contacting air, and the H13 steel with stable rare earth content is further ensured to be obtained.
The slagging operation is not particularly limited in the invention, and the premelted slag can be uniformly melted by adopting the slagging operation known by the technicians in the field.
In the invention, when remelting the consumable electrode, the reducing agent is preferably added into the slag pool according to the formula IV when the consumable electrode is melted by 10 mm;
m throw-in ＝(10/H Self-consuming )×m And also Formula IV;
wherein m is Throw-in The mass of reducing agent, kg, put into the consumable electrode every 10mm of melting; h Self-consuming The total length of the consumable electrode is mm; m is a unit of And also Is the mass of the reducing agent, i.e. the total preset input amount of the reducing agent.
According to the formula IV, when the consumable electrode is remelted, reducing agents are added into the consumable electrode every 10mm, namely, the reducing agents are added in batches, so that the uniformity of rare earth elements in an electroslag ingot can be ensured, the effect of reducing the oxidation burning loss of rare earth in a metal molten pool can be achieved, and the stability and controllability of the rare earth content in the finally prepared H13 steel can be further ensured.
In the present invention, when the diameter of the crystallizer of the melting furnace used for remelting the consumable electrode is 400 to 700mm, the remelting current is preferably 6 × 10 3 ～1×10 4 A, more preferably 7X 10 3 ～9×10 3 A; the remelting voltage is preferably 55-73V, and more preferably 60-70V; when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 700-1000 mm, the remelting current is preferably 1 x 10 4 ～1.5×10 4 A, more preferably 1.2X 10 4 ～1.4×10 4 A; the remelting voltage is preferably 73-91V, and more preferably 80-90V. The invention can melt the consumable electrode evenly and stably and effectively reduce the element burning loss caused by melting the consumable electrode by selecting different remelting currents and voltages according to the sizes of the smelter crystallizers used for remelting different consumable electrodes.
The present invention is not particularly limited to the operation of the stripping, and a stripping method known to those skilled in the art may be used.
According to the method for preparing the H13 steel through electroslag remelting, the prepared H13 steel is fine in crystal grain and uniform in structure, and the rare earth content in the steel is stable and controllable and is uniformly distributed; meanwhile, the method has no special requirements on electroslag remelting equipment and environment, can realize preparation of high-quality H13 steel by using limited conditions, has simple and easy process, is safe and controllable, and is more favorable for large-scale production of H13 steel so as to meet the requirements of China on high-quality H13 steel.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Taking H13 steel to be processed as a consumable electrode, and carrying out electroslag remelting on the consumable electrode by using pre-melted slag and a reducing agent to obtain H13 steel;
the consumable electrode comprises the following components in percentage by mass: 0.40% of C, 1.10% of Si, 0.40% of Mn, 5.25% of Cr, 1.35% of Mo, 0.9% of V, 0.002% of O, 0.0019% of S, 0.02% of P and the balance of Fe; the target rare earth content of the H13 steel is 0.022%;
the pre-melted slag comprises the following components in percentage by mass: CaF 2 40 percent of rare earth oxide (the rare earth oxide is 20 percent of CeO by mass percent) 2 And 80% of La 2 O 3 Composition) CaO 19%, Al 2 O 3 10%, MgO 3% and NaF 3%;
the reducing agent comprises the following components in percentage by mass: 62.0% of Si, 27.2% of Ca and the balance of Fe.
The reducing agent and the dosage of the pre-melted slag have the relationship shown in formula I; the usage amount of the pre-melted slag is calculated according to a formula II, the usage amount of the pre-melted slag obtained through calculation is 51.2kg, and the usage amount of the reducing agent obtained through calculation is 0.5 kg;
m and also ＝9.766×10 -3 m Slag Formula I;
wherein m is And also Kg is the mass of the reducing agent; m is a unit of Slag Kg is the mass of the pre-melted slag.
The electroslag remelting process of the embodiment specifically comprises slagging, remelting of a consumable electrode and stripping of ingots which are sequentially carried out; electroslag remelting is carried out under the protective atmosphere of argon;
the method comprises the following steps of (1) preprocessing pre-melted slag before slagging, wherein the preprocessing comprises pre-melting, cooling, crushing and drying in sequence; the pretreatment is carried out in the protective atmosphere of argon; the premelting temperature of the premelting slag is 1550 ℃, and the heat preservation time at the premelting temperature is 10 min; cooling to room temperature after the premelting is finished, and then crushing, wherein the grain size of the crushed premelting slag is 5 mm; and finally, drying the pre-melted slag at 800 ℃ for 10 hours, wherein the mass percent of crystal water in the dried pre-melted slag is less than 0.01 percent.
Melting the pretreated pre-melted slag, remelting a consumable electrode after the melting is finished, wherein the diameter of a crystallizer of a smelting furnace used for remelting the consumable electrode is 400mm, the remelting voltage is 55V, and the current is 6000A; when remelting the consumable electrode, adding 0.005kg of reducing agent into the slag pool according to a formula IV every time the consumable electrode melts 10mm (the total length of the consumable electrode is 1000 mm); and remelting the consumable electrode and removing the ingot to obtain an H13 steel S1 sample.
Example 2
This example requires a target rare earth La content of 0.018% for H13 steel; the pre-melted slag components in example 1 were replaced with the following components in mass percent: CaF 2 40％，La 2 O 3 20％，CaO 20％，Al 2 O 3 15%, MgO 1% and NaF 4%; the rest of the technical characteristics are the same as those of the embodiment 1, and a H13 steel S2 sample is obtained.
Example 3
The present example requires a target rare earth Ce content of 0.015% for H13 steel; the pre-melted slag component in the example 1 is replaced by the following components in percentage by mass: CaF 2 40％，CeO 2 20％，CaO 20％，Al 2 O 3 15%, MgO 1% and NaF 4%; the other technical characteristics are the same as those of the example 1, and a H13 steel S3 sample is obtained.
Example 4
This example requires a target rare earth content of 0.018% for H13 steel; the pre-melted slag component in the example 1 is replaced by the following components in percentage by mass: CaF 2 40% of rare earth oxide (20% of rare earth oxide of CeO) 2 And 80% La 2 O 3 )，CaO 20％，Al 2 O 3 15%, MgO 1% and NaF 4%; the other technical characteristics are the same as those of the example 1, and a H13 steel S4 sample is obtained.
Example 5
This example requires a target rare earth Ce content of 0.024% for H13 steel; the pre-melted slag component in the example 1 is replaced by the following components in percentage by mass: CaF 2 45％，CeO 2 25％，CaO 15％，Al 2 O 3 10%, MgO 2% and NaF 3%; the rest of the technical characteristics are the same as those of the embodiment 1, and a H13 steel S5 sample is obtained.
Example 6
This example requires a target rare earth Ce content of 0.024% for H13 steel; the pre-melted slag component in the example 1 is replaced by the following components in percentage by mass: CaF 2 50％，CeO 2 25％，CaO 15％，Al 2 O 3 5%, MgO 2% and NaF 3%; the other technical characteristics are the same as those of the example 1, and a H13 steel S6 sample is obtained.
Comparative example 1
The premelting slag in the embodiment 1 is replaced by the traditional pseudo-ginseng slag, namely, the pseudo-ginseng slag with CaF in percentage by mass 2 70% and Al 2 O 3 30% pre-melted slag and no reducing agent were added, the remaining technical characteristics were the same as in example 1, and a comparative H13 steel S7 sample was finally prepared.
Samples of H13 steel, namely S1-S7, obtained in examples 1-6 and comparative example 1 are sampled according to the same position, then the contents of rare earth, O, S and P are detected, the metallographic structure of the sample S1 in example 1 is observed, the component detection results are shown in the following table 1, and the metallographic structure of the sample S1 in example 1 is shown in fig. 1.
Table 1 test results (mass%,%) of rare earth, O, S and P contents of H13 steel obtained in example 1 and comparative H13 steel samples
As can be seen from table 1 comparing the detection results of the samples in examples 1 to 7 and comparative example 1, the H13 steel prepared by the method in examples 1 to 7 by using the pre-melted slag containing the rare earth oxide can not only obtain higher rare earth content, but also the content of the rare earth in the finally prepared H13 steel is close to the target content of the rare earth, and the difference between the content of the rare earth and the target content of the rare earth is not more than 0.001%; meanwhile, the O, S, P content of the finally prepared H13 steel is also reduced, which shows that the cleanliness of the prepared H13 steel can be obviously improved by adopting the method of adding pre-melted slag containing rare earth oxides for electroslag remelting; meanwhile, the addition amount of the pre-melted slag designed according to the electroslag remelting method provided by the invention can effectively add rare earth elements into H13 steel, and the effects of desulfurization, deoxidation and dephosphorization are well achieved.
As can be seen from fig. 1, H13 steel prepared by the electroslag remelting process of example 1 has a fine dendritic structure and dendrite segregation is well controlled.
TABLE 2 dendrite segregation and liquated carbide levels of as-cast H13 steel in examples 1 and 2
The secondary dendrite arm spacing in table 2 can be used to characterize the degree of segregation in the as-cast steel, and liquated carbides are carbides present in the as-cast steel. As can be seen from Table 2, the process for preparing the H13 steel containing the rare earth by electroslag remelting of the slag containing the rare earth oxide can effectively dissolve the rare earth elements into the H13 steel, thereby improving the solidification structure of the steel and refining the liquated carbide.
The H13 steel and the comparative H13 steel samples obtained in example 1 and comparative example 1 were subjected to conventional forging and annealing treatment (forging parameters: the initial forging temperature is 1150 ℃, the final forging temperature is 900 ℃, the forging ratio is 6; the annealing temperature is 860 ℃, and the holding time at the annealing temperature is 600min) to obtain annealed H13 steel and comparative annealed H13 steel samples, respectively, and metallographic observation was performed, wherein metallographic structures are shown in FIGS. 2 and 3, respectively.
FIG. 2 is a metallographic structure of a steel in a post-forging annealed condition H13 obtained by subjecting example 1 to conventional forging and annealing, FIG. 3 is a metallographic structure of a steel in a post-forging annealed condition H13 obtained by subjecting comparative example 1 to the same conventional forging and annealing as in example 1, and it can be seen from FIGS. 2 and 3 that the carbide distribution of the steel in the post-forging annealed condition H13 in example 1 is significantly more uniform than that in comparative example 1.
Example 7
Taking H13 steel to be processed as a consumable electrode, and carrying out electroslag remelting on the consumable electrode by using pre-melted slag and a reducing agent to obtain H13 steel;
the consumable electrode comprises the following components in percentage by mass: 0.40% of C, 1.10% of Si, 0.40% of Mn, 5.30% of Cr, 1.30% of Mo, 0.9% of V, 0.002% of O, 0.0020% of S, 0.02% of P and the balance of Fe; the target rare earth Ce content of the H13 steel is 0.012%;
the pre-melted slag comprises the following components in percentage by mass: CaF 2 40％，CeO 2 25％，CaO 15％，Al 2 O 3 15%, MgO 1% and NaF 4%;
the reducing agent consists of the following components in percentage by mass: 62.0% of Si, 27.2% of Ca and the balance of Fe.
The reducing agent and the dosage of the pre-melted slag have the relationship shown in formula I; the usage amount of the pre-melted slag is calculated according to a formula II, the usage amount of the pre-melted slag is 140kg, and the usage amount of the reducing agent is 0.7 kg;
m and also ＝5×10 -3 m Slag Formula I;
wherein m is And also Kg is the mass of the reducing agent; m is a unit of Slag Kg is the mass of the pre-melted slag.
The electroslag remelting process of the embodiment specifically comprises slagging, remelting of a consumable electrode and stripping of ingots which are sequentially carried out; electroslag remelting is carried out under the protective atmosphere of argon;
wherein, the pre-melted slag is firstly pretreated before slagging, and the pretreatment comprises pre-melting, cooling, crushing and drying which are sequentially carried out; the pretreatment is carried out in the protective atmosphere of argon; the premelting temperature of the premelting slag is 1550 ℃, and the heat preservation time at the premelting temperature is 10 min; cooling to room temperature after the pre-melting is finished, and crushing, wherein the particle size of the crushed pre-melted slag is 5 mm; and finally, drying the pre-melted slag at 800 ℃ for 10 hours, wherein the mass percent of crystal water in the dried pre-melted slag is less than 0.01 percent.
Melting the pretreated pre-melted slag, remelting a consumable electrode after the melting is finished, wherein the diameter of a crystallizer of a smelting furnace used for remelting the consumable electrode is 600mm, the remelting voltage is 67V, and the current is 9000A; when remelting the consumable electrode, 0.0058kg of reducing agent is added into the slag pool according to a formula IV every time the consumable electrode is melted by 10mm (the total length of the consumable electrode is 1200 mm); and remelting the consumable electrode and removing the ingot to obtain the H13 steel sample T1.
Example 8
In the embodiment, the target rare earth Ce content of the H13 steel is 0.020%, the dosage of the reducing agent and the premelting slag in the embodiment 7 is replaced by the following relation according to the formula I, and the dosage of the reducing agent obtained by calculation is 1 kg; when remelting the consumable electrode, feeding 0.0083kg of reducing agent into the slag pool according to a formula IV every time the consumable electrode is melted by 10mm (the total length of the consumable electrode is 1200 mm); the other technical characteristics were the same as in example 7, and thus H13 steel sample No. T2 was obtained.
m And also ＝7.143×10 -3 m Slag Formula I;
wherein m is And also Kg is the mass of the reducing agent; m is a unit of Slag Kg is the mass of the pre-melted slag.
Example 9
In the embodiment, the target rare earth Ce content of the H13 steel is 0.040%, the dosage of the reducing agent and the pre-melted slag in the embodiment 7 is replaced by the following relation according to the formula I, and the dosage of the reducing agent obtained by calculation is 2 kg; when remelting the consumable electrode, when the consumable electrode is melted by 10mm (the total length of the consumable electrode is 1200mm), 0.0164kg of reducing agent is added into the slag pool according to a formula IV each time; the other technical characteristics are the same as those of example 7, and H13 steel sample No. T3 is obtained.
m And also ＝14.286×10 -3 m Slag Formula I;
wherein m is And also Kg is the mass of the reducing agent; m is Slag Kg is the mass of the pre-melted slag.
Comparative example 2
Without using any reducing agent and the remaining technical characteristics being the same as those of example 7, a H13 steel sample No. T4 was obtained.
Rare earth element Ce content detection is carried out on H13 steel obtained in examples 7-9 and comparative example 2, namely samples T1-T4, and metallographic structure observation is carried out on the samples T1 of example 7. The results are shown in Table 3, and the metallographic structure is shown in FIG. 4.
Table 3 results of rare earth contents detected by H13 steels (T1-T4) samples obtained in examples 7-9 and comparative example 2
| T1 | T2 | T3 | T4 | |
| Addition amount of reducing agent (kg) | 0.7 | 1 | 2 | 0 |
| Rare earth Ce content (%) | 0.011 | 0.0190 | 0.0410 | 0.0027 |
As can be seen from Table 3, the rare earth content of the H13 steel finally prepared in the embodiments 7-9 of the invention is close to the target rare earth content, and the difference is only 0.001% compared with the target rare earth content; meanwhile, the rare earth content of the H13 steel prepared in the condition of comparative example 2 without adding a reducing agent is significantly lower than that of the T1 sample of example 1. Therefore, the method for preparing H13 steel through electroslag remelting provided by the invention can effectively regulate the rare earth content in H13 steel by regulating the dosage of the added reducing agent, so that the rare earth content of H13 steel is stable and controllable.
As can be seen from fig. 4, the annealing structure is still uniform and the grains are fine by using the electroslag remelting technique of the present invention.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A method for preparing H13 steel by electroslag remelting is characterized in that H13 steel to be treated is used as a consumable electrode, pre-melted slag and a reducing agent are used for carrying out electroslag remelting on the consumable electrode, and H13 steel is obtained;
the pre-melted slag comprises the following components in percentage by mass: CaF 2 40-50%, CaO 15-30%, rare earth oxide 20-30%, Al 2 O 3 5-15%, 1-3% of MgO and 78-5% of NaF 3;
the reducing agent comprises the following components in percentage by mass: 55-65% of Si, 24-31% of Ca and the balance of Fe;
the reducing agent and the pre-melted slag have a relation shown in formula I;
m and also ＝(0.1～15)×10 -3 m Slag Formula I;
wherein m is And also Kg, mass of reducing agent; m is Slag Kg is the mass of premelting slag;
the consumable electrode comprises the following components in percentage by mass: 0.35-0.41% of C, 1.00-1.20% of Si, 0.20-0.50% of Mn, 5.00-5.50% of Cr, 1.3-1.75% of Mo1, 0.80-1.00% of V, less than or equal to 0.002% of O, less than or equal to 0.002% of S, less than or equal to 0.02% of P and the balance of Fe.
2. The method of claim 1, wherein the rare earth oxide in the pre-melted slag is CeO 2 And La 2 O 3 One or two of them.
3. The method of claim 1, wherein the electroslag remelting comprises slagging, remelting of a consumable electrode, and stripping in sequence;
when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 400-700 mm, the remelting current is 6 multiplied by 10 3 ～1×10 4 A, remelting at a voltage of 55-73V; when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 700-1000 mm, the remelting current is 1 multiplied by 10 4 ～1.5×10 4 A, remelting voltage is 73-91V.
4. The method of claim 3, wherein the pre-melted slag is pre-treated prior to slagging, and the pre-treatment comprises pre-melting, cooling, crushing and drying in sequence.
5. The method of claim 4, wherein the pre-treatment atmosphere is an inert gas.
6. The method of claim 4, wherein the temperature of the pre-melting is 1500-1600 ℃ and the holding time at the temperature of the pre-melting is 8-12 min.
7. The method according to claim 4, wherein the size of the crushed pre-melted slag is 0.01-10 mm.
8. The method of claim 4, wherein the mass percentage of crystal water in the dried premelted slag is less than 0.01%.
9. The method according to claim 3, wherein when the diameter of a smelter crystallizer used for remelting the consumable electrode is 400-700 mm, the usage amount of the pre-melted slag is calculated according to formula II; when the diameter of a smelting furnace crystallizer used for remelting the consumable electrode is 700-1000 mm, the usage amount of the pre-smelting slag is calculated according to a formula III;
wherein m in formula II and formula III Slag Kg is the mass of premelting slag; d in formula II and formula III Knot Is the inner diameter of the crystallizer, mm.
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