CN113481378A

CN113481378A - Solid slag start remelting method for reducing porosity and hydrogen content of bottom of electroslag ingot

Info

Publication number: CN113481378A
Application number: CN202110768293.8A
Authority: CN
Inventors: 常立忠; 张龙飞; 苏云龙
Original assignee: Anhui University of Technology AHUT
Current assignee: Anhui University of Technology AHUT
Priority date: 2021-07-06
Filing date: 2021-07-06
Publication date: 2021-10-08

Abstract

The invention discloses a solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot, and belongs to the technical field of special metallurgy. Preheating a consumable electrode and a crystallizer, and carrying out electroslag remelting on solid slag by using the preheated consumable electrode and the crystallizer; the preheating is to arrange the consumable electrode in a crystallization chamber of the crystallizer, arrange a second heater between the consumable electrode and the inner wall of the crystallizer, introduce flowing preheating gas into the second heater to heat the consumable electrode and the crystallizer, and make the preheating gas continuously sprayed from the second heater to the inner wall of the crystallizer; the flow velocity sprayed by the preheating gas is 3-10 m/s; the temperature T1 of the preheating gas in the second heater is 60 ℃ to 100 ℃, and the preheating gas comprises nitrogen and/or inert gas. The method can effectively reduce the water content of the solid slag starting electroslag system, thereby effectively reducing the porosity and the hydrogen content of the electroslag ingot and stably controlling the hydrogen content to be less than or equal to 2 ppm.

Description

Solid slag start remelting method for reducing porosity and hydrogen content of bottom of electroslag ingot

Technical Field

The invention belongs to the technical field of special metallurgy, and particularly relates to a solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot.

Background

Electroslag remelting is widely applied by the advantages of superior solidification structure control, inclusion removal and the like, and particularly plays an important role in the fields of special stainless steel, tool and die steel and the like. However, the disadvantages of electroslag remelting cannot be ignored, and the most important point is that the hydrogen content at the bottom of an electroslag ingot exceeds the standard and even pores appear, which is more obvious when solid slag is adopted for starting. Once the bottom of the electroslag ingot has pores or the hydrogen content exceeds the standard, the bottom of the electroslag ingot has to be cut off, so that the metal yield is reduced, and the cost is increased. The solid slag starting not only saves the step of melting the solid slag in advance, so that the electroslag remelting operation is simpler and more convenient, but also saves the energy required by melting in advance, and simultaneously avoids the danger caused by adding high-temperature molten metal. Therefore, how to prevent the formation of pores at the bottom of the electroslag ingot and the excessive hydrogen content during the start of solid slag is important.

When solid slag is started, the basic reasons of the generation of gas holes at the bottom of an electroslag ingot and the exceeding of hydrogen content are as follows: 1) the remelting slag system has higher water content; 2) the air humidity is relatively high; therefore, the start-up stage of the solid slag remelting must be started from both aspects. It is worth noting that most enterprises bake the slag at high temperature for a long time before production, and the moisture content in the slag is low and is not enough to cause air holes. However, the influence of the humidity of the air is great, and although many enterprises introduce dry air into the crystallizer before remelting, the problem cannot be solved, and particularly, under the condition of high air humidity, a layer of condensed water exists in the crystallizer and on the surface of a metal electrode, and in the condition, even if slag is roasted, the dry air is introduced, the increase of bottom air holes and hydrogen content cannot be avoided.

Through retrieval, related technical schemes for avoiding the exceeding of the hydrogen content by baking the slag and introducing dry air exist in the prior art. For example, chinese patent 92108419.6 discloses an electroslag technique for preventing hydrogen increase, which mentions that the hydrogen control can be achieved by controlling the hydrogen content in the slag and the humidity of the air. However, it should be noted that the method is started by using liquid slag, that is, the baked slag is subjected to slag forming in a furnace, and then the metal electrode is placed in a crystallizer for remelting, so that a large amount of water on the slag and the surface of the crystallizer is removed due to high-temperature slag forming. Similarly, chinese patent 201210252486.9 discloses a low hydrogen control method for electroslag remelting and a control method for hydrogen content in nuclear power forging material disclosed in chinese patent 201610745746.4, which still adopt the idea of controlling air humidity (or introducing argon) and drying slag, and also start liquid slag, that is, slag is pre-melted and then metal electrode remelting is performed. However, these technologies do not have a good solution for solid slag start, and the current domestic atmosphere protection electroslag furnaces are mainly started from solid slag.

In addition, there are also some electroslag remelting techniques for baking or pre-melting the slag system in advance. For example, an electroslag remelting slag system and a low hydrogen control method for electroslag remelting 40CrNiMoA disclosed in chinese invention patent 201811161191.4, and a low hydrogen permeability slag system for electroslag remelting disclosed in chinese invention patent 200810041982.3, and a preparation method and a use method thereof, the slag system is baked at high temperature before electroslag remelting to remove moisture, and simultaneously premelting slag and argon gas protection measures are adopted to reduce the hydrogen content in the remelted steel, but the above patents do not consider the influence of the electrode surface at the remelting start stage and the condensed water inside the crystallizer.

For solid slag starting, few technical schemes capable of reducing moisture content are adopted in the prior art to effectively reduce the hydrogen content and porosity of the bottom of an electroslag ingot. For example, chinese patent 201210191017.0 discloses a method for controlling hydrogen content in an electroslag remelting smelting steel liquid, which employs blowing dry hot air into the remelting process to remove the condensate water on the surface of the crystallizer. However, it is worth noting that the specific gravity of the hot air is small, so that it is difficult to completely remove the moist air from the crystallizer, especially, the hot air is difficult to drop to the lowest part of the crystallizer, and the remelting starts from the lowest part of the crystallizer, so that the blowholes are more easily generated and the hydrogen content is more excessive. Therefore, when dry hot air is introduced into the crystallizer, the air rotates in the crystallizer due to the difference of the density of the cold air and the density of the hot air, the hot air cannot be completely introduced, and the damp air cannot be completely discharged. Besides, after the crystallizer, under the condition of air humidity, a layer of condensed water is also precipitated on the surface of the electrode, and even if the condensed water in the crystallizer can be removed, the condensed water brought in by the electrode still causes the generation of bottom pores of the electroslag ingot and the increase of hydrogen content.

In conclusion, for the electroslag remelting technology started by utilizing solid slag, how to effectively reduce the gas holes at the bottom of an electroslag ingot and the hydrogen content is not a reasonable scheme provided in the prior art; therefore, there is a need to design a solid slag start electroslag remelting device or method capable of effectively reducing the content of gas holes and hydrogen at the bottom of an electroslag ingot.

Disclosure of Invention

1. Problems to be solved

Aiming at the problem that the influence of water on a slag system cannot be effectively reduced by a solid slag starting technology in the prior art, so that the bottom porosity and the hydrogen content of an electroslag ingot are high, the invention provides a solid slag starting remelting method for reducing the bottom porosity and the hydrogen content of the electroslag ingot; the problem that the porosity and hydrogen content at the bottom of an electroslag ingot are high due to the fact that the influence of moisture on a slag system cannot be effectively reduced by a solid slag starting technology is effectively solved by controlling the flow mode of the preheated gas and utilizing the preheated gas to heat the electrode and the crystallizer.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the invention also provides a solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of the electroslag ingot, which preheats the consumable electrode and the crystallizer, and carries out electroslag remelting on solid slag by utilizing the preheated consumable electrode and the crystallizer; the preheating is to arrange the consumable electrode in a crystallization chamber of the crystallizer, arrange a second heater between the consumable electrode and the inner wall of the crystallizer, introduce flowing preheating gas into the second heater to heat the consumable electrode and the crystallizer, and make the preheating gas continuously sprayed from the second heater to the inner wall of the crystallizer; the flow velocity sprayed by the preheating gas is 3-10 m/s; the temperature T1 of the preheating gas in the second heater is 60 ℃ to 100 ℃, and the preheating gas comprises nitrogen and/or inert gas.

Preferably, the preheating gas is an inert gas with a relative molecular weight not less than 29, and the temperature T1 is 85-95 ℃.

Preferably, the second heater comprises a preheater shell which is annularly arranged, one surface of the preheater shell, which is close to the inner wall of the crystallizer, is an outer wall of the preheater, and a plurality of air outlet holes are formed in the outer wall of the preheater; the diameter L1 of the air outlet holes is 2 mm-6 mm, the distance L2 between the air outlet holes is 10 mm-20 mm, and the preheated gas in the second heater is sprayed to the inner wall of the crystallizer through the air outlet holes.

Preferably, the preheater shell comprises a preheater inner wall and a preheater outer wall, the preheater inner wall is arranged corresponding to the consumable electrode, and the preheater outer wall is arranged corresponding to the crystallizer inner wall; the inner wall of the preheater forms a cylindrical through hole of the preheater, the diameter of the through hole of the preheater is R1, the diameter of the consumable electrode is R4-400 mm-700 mm, and R1 > R4; the diameter of a cylinder formed by the outer wall of the preheater is R2, the diameter of the cylinder formed by the inner wall of the crystallizer, namely the inner diameter of the crystallizer, is R3-600-1000 mm, and R2 is less than R3.

Preferably, the consumable electrode is heated using the first heater while being preheated using the second heater; the preheating gas is argon gas at the temperature of 0-20 ℃, and the argon gas exchanges heat with the first heater to be heated before entering the second heater.

Preferably, the second heater is arranged at the bottom of the crystallizer, the width of the second heater, namely (R2-R1)/2 is 100 mm-300 mm, and the height of the second heater is 20 mm-40 mm; the preheater housing is preferably a dense stainless steel plate.

Preferably, the heating time of the first heater and the second heater is 4-5 h.

Preferably, the first heater is an induction coil formed by winding a metal wire, and a hollow pipeline is arranged in the metal wire to serve as a preheating gas pipeline; and introducing argon into a preheating gas pipeline to exchange heat with the heated metal wire, and then introducing the argon subjected to heat exchange into a second heater to preheat. According to the method, the hollow pipeline formed inside the hollow metal wire is used as the preheating gas pipeline, so that the heating rate of the metal wire can be improved, meanwhile, the heat exchange area between the metal wire and the preheating gas is increased, the heat exchange efficiency is improved, the consumable electrode is uniformly heated at the parts of the first heater and the second heater, and the phenomenon that condensed water is formed on the surface of the consumable electrode due to local supercooling is avoided. The height of the induction coil is 400 mm-600 mm, and the distance from the surface of the consumable electrode is 5 mm-20 mm.

Preferably, the electroslag remelting specifically comprises the following steps:

(1) placing the preheated consumable electrode on a remelting cross arm of an electroslag furnace;

(2) placing the preheated crystallizer on a bottom water tank, fixing the crystallizer and the bottom water tank with each other, then placing the crystallizer and the bottom water tank together below a consumable electrode, covering a protective cover on the top of the crystallizer, and finally placing the consumable electrode into the crystallizer from a protective gas outlet of the protective cover;

(3) introducing protective gas from a protective gas inlet of the protective cover to discharge air;

(4) and (4) arcing, namely adding the baked solid slag into a crystallizer to start remelting.

Preferably, the protective gas in the step (3) includes an inert gas having a relative molecular weight of not less than 29.

Preferably, the flow speed of the protective gas in the step (3) is 10-20 m/s; when the oxygen concentration sensor detects that the oxygen concentration in the crystallizer is less than or equal to 0.02 percent, the flow speed of the protective gas is readjusted to be 5-15 m/s, and the state that the oxygen concentration is less than or equal to 0.02 percent is maintained for 20-30 min.

Preferably, the baking temperature of the solid slag in the step (4) is 400-600 ℃; when remelting is started, cooling water is introduced into a cooling chamber and a bottom water tank of the crystallizer, wherein the introduction mode of the cooling water is as follows: introducing cooling water of 40-45 ℃ for 5min, reducing the temperature of the cooling water to 10-30 ℃, and controlling the flow of the cooling water to be 30-45 cubic meters per ton. After the preheating of the crystallizer is finished, if cooling water is introduced at the moment, the surface of the crystallizer can be rapidly cooled, and condensed water can be formed; therefore, after the crystallizer and the consumable electrode are preheated, the protective cover is installed, and then the protective gas with the relative molecular mass larger than that of air is introduced to sink into the bottom of the crystallizer and discharge the air in the crystallizer. When the air in the crystallizer is discharged to a certain degree, the cooling water is opened again, so that the formation of condensed water on the surfaces of the crystallizer and the consumable electrode can be avoided, and the formation of gas holes at the bottom of the electroslag ingot and the increase of hydrogen content are avoided.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention also provides a solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of the electroslag ingot, which preheats the consumable electrode and the crystallizer, and carries out electroslag remelting on solid slag by utilizing the preheated consumable electrode and the crystallizer; the preheating is to arrange the consumable electrode in a crystallization chamber of the crystallizer, arrange a second heater between the consumable electrode and the inner wall of the crystallizer, introduce flowing preheating gas into the second heater to heat the consumable electrode and the crystallizer, and make the preheating gas continuously sprayed from the second heater to the inner wall of the crystallizer; the flow velocity sprayed by the preheating gas is 3-10 m/s; the temperature T1 of the preheating gas in the second heater is 60-100 ℃, and the preheating gas comprises nitrogen and/or inert gas; by the method, the preheating gas can preheat the consumable electrode and the crystallizer simultaneously in the second heater, the flowing preheating gas can be sprayed to the inner wall of the crystallizer from the gas outlet hole so as to take away condensed water on the inner wall of the crystallizer, and the sprayed preheating gas can flow to the consumable electrode arranged in the middle of the second heater after passing through the inner wall of the crystallizer so as to further take away the condensed water on the surface of the consumable electrode, and because the condensed water on the surfaces of the consumable electrode and the crystallizer are effectively removed after being preheated, the water content of the whole electroslag system can be effectively reduced by carrying out electroslag remelting started by slag solidification, so that the porosity and the hydrogen content of an electroslag ingot are effectively reduced, and the hydrogen content is stably controlled to be less than or equal to 2 ppm.

Drawings

FIG. 1 is a schematic view of the heating apparatus of the present invention heating a consumable electrode and a crystallizer;

FIG. 2 is a schematic diagram of a preheater according to the present invention;

FIG. 3 is a schematic view of a heating apparatus and a crystallizer of the present invention;

FIG. 4 is a schematic view of a heating apparatus of the present invention;

FIG. 5 is a schematic view of a first heater of the present invention;

FIG. 6 is a cross-sectional view of a first heater of the present invention;

FIG. 7 is a schematic view of an electroslag remelting process of the present invention;

FIG. 8 is a schematic flow chart of the solid slag start remelting method of the invention.

In the figure:

100. a heating device;

110. heating the stent; 111. a shaft hole; 112. a thermocouple; 113. universal wheels with brakes;

120. a second heater; 121. a preheater housing; 1211. the inner wall of the preheater; 1212. the outer wall of the preheater; 122. a preheater through hole; 123. a preheating chamber; 124. a detection hole; 125. an air inlet; 126. an air outlet;

130. a first heater; 131. an electrode I end; 132. a preheated gas inlet; 133. an electrode II end; 134. a preheated gas outlet; 135. a coil heating chamber; 136. a pre-hot gas line; 137. a metal wire;

200. a crystallizer; 210. a cooling chamber; 211. a media outlet; 212. a media inlet; 220. a crystallization chamber; 221. the inner wall of the crystallizer;

300. an inductive power supply;

400. a consumable electrode;

500. a protective cover; 510. an oxygen concentration sensor; 520. a shielding gas inlet; 530. a shielding gas outlet;

600. a bottom water tank; 610. a water inlet; 620. and (7) a water outlet.

Detailed Description

The following detailed description of exemplary embodiments of the invention refers to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration exemplary embodiments in which the invention may be practiced, and in which features of the invention are identified by reference numerals. The following more detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the invention, to set forth the best mode of carrying out the invention, and to sufficiently enable one skilled in the art to practice the invention. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention; as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that the method has an excellent technical effect on solid slag initiated electroslag remelting, but does not mean that the solid slag initiated remelting method of the invention is not suitable for liquid slag initiation or premelted slag systems. On the contrary, for a liquid slag starting system and a pre-melting slag system with lower moisture content, better action effect can be obtained after the technical scheme of the invention is used, only the moisture of the two systems is largely removed under the action of high temperature, and unless the gas porosity and the hydrogen content in the electroslag ingot have higher precision requirements, the technical scheme of the invention is used again, so that the two systems are large and small in size. In addition, the invention is particularly suitable for electroslag remelting in a humid environment, and even if the humidity of air is more than or equal to 90 percent, the gas hole formation at the bottom of the electroslag ingot and the increase of hydrogen content can be avoided by the preheater, the heating device thereof, the electroslag remelting system or the solid slag start remelting method.

The invention is further described with reference to specific examples.

Example 1

In the embodiment, a solid slag start remelting method for reducing the porosity and hydrogen content at the bottom of an electroslag ingot is provided, as shown in fig. 8, a consumable electrode 400 and a crystallizer 200 are preheated, and solid slag is electroslag remelted by using the preheated consumable electrode 400 and the crystallizer 200; to implement the solid slag start remelting method, the present embodiment is operated by using the following electroslag remelting system.

An electroslag remelting system according to this embodiment, as shown in fig. 7, includes a consumable electrode 400, a heating device 100, a mold 200, a protective cover 500, and a bottom water tank 600. When the consumable electrode 400 and the crystallizer 200 are preheated before electroslag remelting, the crystallizer 200 is arranged on the heating device 100, the second heater 120 is positioned at the bottom in the inner wall 221 of the crystallizer, and the consumable electrode 400 is arranged in the heating device 100 and the crystallizer 200 in a penetrating manner for heating. During electroslag remelting, the preheated consumable electrode 400, the crystallizer 200, the protective cover 500 and the bottom water tank 600 are used for slag solidification starting.

In the electroslag remelting system, the diameter R4 of the consumable electrode 400 in this embodiment is 500 mm; as shown in fig. 1, the crystallizer 200 includes a crystallization chamber 220 and a cooling chamber 210, and the inner diameter R3 is 800 mm; the crystallization chamber 220 is coaxially arranged and communicated with the preheater through hole 122 and the shaft hole 111, the cooling chamber 210 is annularly arranged along the outer part of the crystallization chamber 220, and the cooling chamber 210 can exchange heat with the crystallization chamber 220; the cooling chamber 210 is provided with a medium inlet 212 and a medium outlet 211. The protective cover 500 includes a protective gas inlet 520, a protective gas outlet 530 and an oxygen concentration sensor 510, and the protective cover 500 may cover the top of the mold 200; the bottom water tank 600 comprises a water inlet 610 and a water outlet 620, and the bottom water tank 600 can be arranged at the bottom of the crystallizer 200 and exchanges heat with the crystallizer 200.

In addition, as shown in fig. 1 to 4, the heating apparatus 100 includes a preheating gas line 136, a first heater 130, a second heater 120, an induction power source 300, and a heating supporter 110.

As shown in fig. 2, in the heating apparatus 100, the width of the second heater 120, i.e., (R2-R1)/2, is 100mm, the height is 40mm, and the second heater includes a preheating chamber 123 arranged along the outer circumference of the consumable electrode 400, and the preheating chamber 123 may be sleeved outside the consumable electrode 400, which is embodied as: the inner wall 1211 of the preheater forms a cylindrical preheater through hole 122, the diameter of the preheater through hole 122 is R1, the diameter of the consumable electrode 400 is R4, and R1 > R4; the size of the preheating cavity 123 is smaller than that of the mold 200, and the preheating cavity 123 may be sleeved inside the mold 200, which is embodied as follows in this embodiment: the cylinder diameter that preheater outer wall 1212 formed is R2, the cylinder diameter that crystallizer inner wall 221 formed is R3, R2 < R3. The preheating cavity 123 is externally provided with a preheater housing 121, the preheater housing 121 is made of a dense stainless steel plate in this embodiment, the preheater housing 121 is provided with an air inlet 125 and an air outlet 126, and the air outlet 126 is arranged corresponding to the inner wall 221 of the crystallizer 200 and is used for blowing the preheating gas in the preheating cavity 123 to the inner wall 221 of the crystallizer. The preheater is annular in this embodiment; the preheater housing 121 includes a preheater inner wall 1211 and a preheater outer wall 1212, the preheater inner wall 1211 is disposed corresponding to the consumable electrode 400, and the preheater outer wall 1212 is disposed corresponding to the crystallizer inner wall 221. The air outlet holes 126 are arranged on the outer wall 1212 of the preheater and are provided in plurality; the diameter L1 of the air outlet holes 126 is 5mm, and the distance L2 between the air outlet holes 126 is 10 mm.

In addition, as shown in fig. 5 and 6, the first heater 130 in the heating apparatus 100 is an induction coil having a height of 400mm and a distance of 5mm from the surface of the consumable electrode, that is, an inner diameter of the induction coil is 510 mm; the induction coil is formed with a coil heating cavity 135 therein, and the consumable electrode 400 can be placed in the coil heating cavity 135 for heating, so that the first heater 130 is used for heating the consumable electrode 400. The first heater 130 is arranged outside the preheating gas pipeline 136, the first heater 130 can exchange heat with the preheating gas in the preheating gas pipeline 136, the induction coil in the embodiment is formed by winding a hollow metal wire 137, in the embodiment, a hollow copper wire is selected as the metal wire 137, the metal wire 137 comprises an electrode I end 131 and an electrode II end 133, the electrode I end 131 and the electrode II end 133 are electrically connected with an induction power supply 300, and the preheating gas pipeline 136 is a hollow pipeline inside the metal wire 137; the preheated gas line 136 includes a preheated gas inlet 132 and a preheated gas outlet 134, and the preheated gas outlet 134 is connected to the gas inlet 125.

The heating support 110 in this embodiment is a heating trolley, as shown in fig. 1, the heating trolley is provided with a shaft hole 111 inside, and a universal wheel 113 with a brake is arranged at the bottom; the first heater 130 is arranged in the shaft hole 111; the second heater 120 is arranged on the heating bracket 110, and a preheater through hole 122 of the second heater 120 is coaxially arranged and communicated with the shaft hole 111; the heating support 110 is further provided with a thermocouple 112, the preheater housing 121 of the second heater 120 is further provided with a detection hole 124, and a temperature measuring end of the thermocouple 112 penetrates through the detection hole 124 and is arranged in the preheating cavity 123.

Therefore, based on the electroslag remelting system, the solid slag start electroslag remelting method of the embodiment specifically comprises the following operation steps:

(1) closing cooling water in the cooling chamber 210 of the crystallizer 200, placing the cooling water on a heating trolley, and then penetrating the consumable electrode 400 into the crystallization chamber 220, the preheater through hole 122 and the shaft hole 111;

(2) argon gas with the temperature of 10 ℃ is introduced from a preheating gas inlet 132, then an induction power supply 300 is turned on to enable an induction coil to start heating, the argon gas enters a preheating cavity 123 of a second heater 120 after heat exchange with a hollow copper wire, and is sprayed out to the inner wall 221 of the crystallizer through a gas outlet 126, and the flow rate of the argon gas is 5 m/s; meanwhile, the thermocouple 112 is started to measure the temperature, and when the temperature of the thermocouple 112 reaches the range of 85-95 ℃, the flow of the preheating gas inlet 132 is adjusted to keep the temperature in the range all the time;

(3) after heating for 4 hours, closing the induction power supply 300, stopping introducing argon gas into the preheating gas inlet 132, lifting the consumable electrode 400 away, and placing the consumable electrode on a remelting cross arm of an electroslag furnace; the mold 200 is lifted up and placed on the bottom water tank 600 and fixed, and at this time, the cooling water in the bottom water tank 600 and the cooling water in the cooling chamber 210 are closed.

(4) The crystallizer 200 and the bottom water tank 600 are lifted together and placed below the consumable electrode 400, then the protective cover 500 covers the top of the crystallizer 200, and finally the consumable electrode 400 is placed into the crystallizer 200 from a protective gas outlet 530 of the protective cover 500;

(5) introducing argon gas from a shielding gas inlet 520 of the protective cover 500 to discharge air at a flow rate of 10 m/s; meanwhile, the oxygen concentration in the crystallizer 200 is detected by an oxygen concentration sensor 510, and when the oxygen concentration in the protective cover 500 is less than or equal to 0.02%, the flow rate of argon at a protective gas inlet 520 is readjusted to be 5m/s, so that the state that the oxygen concentration is less than or equal to 0.02% is maintained for 20 min;

(6) introducing cooling water into the cooling chamber 210 and the bottom water tank 600 of the crystallizer 200, introducing the cooling water with the temperature of 40 ℃ for 5min, and then reducing the temperature of the cooling water to 30 ℃ with the flow of the cooling water being 30 cubic meters per ton; simultaneously, arcing is carried out, solid slag baked at 450 ℃ is directly added into the crystallizer 200 to start remelting, in the embodiment, 410 martensitic stainless steel is used as a consumable electrode, and 70 percent of CaF and 2.30 percent of Al are adopted₂O₃Remelting as solid slag.

And (3) remelting and crystallizing the 410 martensitic stainless steel by the solid slag start remelting method in the steps (1) to (6), sampling at a position 5mm away from the bottom of the electroslag ingot, observing by using a 100-time magnifier, wherein no gas hole is seen at the bottom of the electroslag ingot, and stably controlling the hydrogen content to be 1.5ppm +/-0.5 ppm.

More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, combined, e.g., between various embodiments, adapted and/or substituted, as would be recognized by those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly based the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. The scope of the invention should, therefore, be determined only by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. When a "size, concentration, temperature, time, or other value or parameter is expressed as a range, preferred range, or as a range of values bounded by upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, a range of 1 to 50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, and all fractional values between the above integers, e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, specifically consider "nested sub-ranges" that extend from any endpoint within the range. For example, nested sub-ranges of exemplary ranges 1-50 may include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in another direction. "

Claims

1. A solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot is characterized in that a consumable electrode (400) and a crystallizer (200) are preheated, and the preheated consumable electrode (400) and the preheated crystallizer (200) are used for carrying out electroslag remelting on solid slag;

the preheating is that a consumable electrode (400) is arranged in a crystallization chamber (220) of a crystallizer (200), a second heater (120) is arranged between the consumable electrode (400) and the inner wall (221) of the crystallizer (200), flowing preheating gas is introduced into the second heater (120) to heat the consumable electrode (400) and the crystallizer (200), and the preheating gas is continuously sprayed to the inner wall (221) of the crystallizer by the second heater (120); the flow velocity sprayed by the preheating gas is 3-10 m/s; the temperature T1 of the preheating gas in the second heater (120) is 60 ℃ to 100 ℃, and the preheating gas comprises nitrogen and/or inert gas.

2. The solid slag start remelting method for reducing bottom porosity and hydrogen content of an electroslag ingot according to claim 1, wherein the preheating gas is an inert gas with a relative molecular weight not less than 29, and the temperature T1 is 85-95 ℃.

3. The solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot according to claim 1, wherein the second heater (120) comprises an annularly arranged preheater housing (121), one surface of the preheater housing (121) close to the inner wall (221) of the crystallizer is a preheater outer wall (1212), an air outlet (126) is arranged on the preheater outer wall (1212), and the preheated gas in the second heater (120) is sprayed out to the inner wall (221) of the crystallizer through the air outlet (126); the flow velocity of the preheated gas sprayed from the gas outlet (126) is 3 m/s-10 m/s.

4. The solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot according to claim 1, wherein the consumable electrode (400) is heated by the first heater (130) while being preheated by the second heater (120); the preheating gas is argon gas at the temperature of 0-20 ℃, and the argon gas exchanges heat with the first heater (130) and is heated before entering the second heater (120).

5. The solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot according to claim 4, wherein the heating time of the first heater (130) and the second heater (120) is 4-5 h.

6. The solid slag start remelting method for reducing the porosity and hydrogen content of the bottom of an electroslag ingot according to claim 4, wherein the first heater (130) is an induction coil formed by winding a metal wire (137), and a hollow pipeline is arranged inside the metal wire (137) to serve as a preheating gas pipeline (136); argon is introduced into a preheating gas pipeline (136) to exchange heat with the heated metal wire (137), and then the argon subjected to heat exchange is introduced into the second heater (120) to be preheated.

7. The solid slag start remelting method for reducing the bottom porosity and hydrogen content of an electroslag ingot according to any one of claims 1 to 6, wherein the electroslag remelting specifically comprises the following steps:

(1) placing the preheated consumable electrode (400) on a remelting cross arm of an electroslag furnace;

(2) placing the preheated crystallizer (200) on a bottom water tank (600), fixing the preheated crystallizer and the bottom water tank with each other, then placing the preheated crystallizer and the bottom water tank together below a consumable electrode (400), covering a protective cover (500) on the top of the crystallizer (200), and finally placing the consumable electrode (400) into the crystallizer (200) from a protective gas outlet (530) of the protective cover (500);

(3) introducing protective gas from a protective gas inlet (520) of the protective cover (500) to discharge air;

(4) and (4) arcing, namely adding the baked solid slag into a crystallizer (200) to start remelting.

8. The solid slag initiated remelting method for reducing porosity and hydrogen content of a bottom of an electroslag ingot according to any one of claims 7, wherein the protective gas in the step (3) comprises an inert gas having a relative molecular weight of not less than 29.

9. The solid slag start remelting method for reducing bottom porosity and hydrogen content of an electroslag ingot according to any one of claims 7, wherein the flow rate of the shielding gas in the step (3) is 10-20 m/s; when the oxygen concentration sensor (510) detects that the oxygen concentration in the crystallizer (200) is less than or equal to 0.02 percent, the flow rate of the protective gas is readjusted to be 5m/s to 15m/s, and the state that the oxygen concentration is less than or equal to 0.02 percent is maintained for 20min to 30 min.

10. The solid slag start remelting method for reducing bottom porosity and hydrogen content of an electroslag ingot according to any one of claims 9, wherein the baking temperature of the solid slag in the step (4) is 400-600 ℃; when remelting is started, cooling water is introduced into a cooling chamber (210) and a bottom water tank (600) of the crystallizer (200) in the following modes: introducing cooling water of 40-45 ℃ for 5min, reducing the temperature of the cooling water to 10-30 ℃, and controlling the flow of the cooling water to be 30-45 cubic meters per ton.