CN114438338B - Arc remelting method for preventing stress cracking of cast ingot and improving internal quality of cast ingot - Google Patents
Arc remelting method for preventing stress cracking of cast ingot and improving internal quality of cast ingot Download PDFInfo
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Abstract
The invention discloses a method for preventing stress cracking of an ingot and improving the internal quality of the ingot by adopting a multi-inlet multi-outlet water-cooled crystallizer, wherein at the initial stage of arc remelting, a water inlet at the bottom and a water outlet at the top of the crystallizer are in an open mode, and the rest water inlets are in a closed mode; the rest water inlets are opened and closed along with the liquid level of the metal molten pool along with the arc remelting, so that the lower cooling rate and the upper cooling rate of the cast ingot are low, the martensitic transformation stress of the cast ingot is reduced, and the cast ingot is prevented from cracking; the metal molten pool is shallow and flat, solidification segregation is reduced, and meanwhile, the side wall of the metal molten pool has reasonable cooling rate, and meanwhile, the surface and internal quality of the cast ingot are improved. In the prior art, a single-inlet single-outlet water-cooled crystallizer is adopted, and the problems of deep metal molten pool, serious solidification segregation, martensitic transformation stress cracking of cast ingots, poor surface quality and the like exist in any way of adjustment. The invention not only prevents the martensitic transformation stress cracking of the cast ingot, but also improves the surface and internal quality of the cast ingot.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a process method and a device for preventing stress cracking of an ingot and improving the internal quality of the ingot.
Background
The inert atmosphere arc remelting is used as an equipment process for producing high alloy steel and large-size cast ingots thereof, and is often encountered in the production of martensitic steel, and coarse carbide is caused by solidification segregation, so that the mechanical property of cast ingot rolled products is reduced, and the problem of coarse carbide in the large-size rolled products is particularly outstanding. In order to improve the solidification segregation, the solidification rate of the metal molten pool is improved by a method of increasing the water flow rate in the water-cooling crystallizer; but simultaneously brings about the phenomena of too fast cooling speed of the lower cast ingot, low-temperature martensitic transformation and cast ingot cracking of structural stress, thereby leading to cast ingot scrapping. Therefore, the prevention of martensitic transformation stress cracking, the improvement of the internal quality of cast ingot and the surface quality are key for producing martensitic steel.
The prior production process of the inert atmosphere arc remelting comprises the steps of melting a metal electrode under the arc heat of the metal electrode and a bottom plate in the early stage of arc remelting, continuously melting the metal electrode into liquid drops under the action of the arc heat and a water-cooling crystallizer, and solidifying into an ingot under the action of the water-cooling crystallizer, thereby completing the preparation of the whole ingot along with the continuous melting of the metal electrode and the continuous rising of the ingot.
When the existing arc remelting technology is used for producing large-size martensitic steel, the surface quality of an ingot is poor and center segregation is serious. Although the center segregation phenomenon of the cast ingot can be improved by improving the cooling water flow of the crystallizer, the phenomenon of structural stress cracking caused by overlarge cooling speed at the lower part of the cast ingot and martensitic transformation occurs, so that the cast ingot is scrapped, and the development of arc remelting martensitic steel is restrained.
In conclusion, on the premise of preventing the martensitic transformation stress cracking of the cast ingot in arc remelting, improving the internal quality and the surface quality of the cast ingot is of great significance for producing high-quality martensitic steel.
Disclosure of Invention
The technical problem to be solved by the invention is to prevent the martensitic transformation stress cracking of the cast ingot, improve the internal quality and the surface quality of the cast ingot and provide high-quality cast ingot for high-performance martensitic steel products.
In order to solve the technical problems, the invention provides an arc remelting device and an arc remelting process based on a multi-inlet multi-outlet water-cooling crystallizer, and particularly adopts the following technical scheme:
a method for preventing stress cracking of an ingot and improving the internal quality of the ingot by arc remelting, wherein a bottom water tank is combined with a multi-inlet multi-outlet cooling mode, comprises the following steps: when arc remelting, the bottom water tank is always opened for water cooling, and the bottommost water inlet and the uppermost water outlet are always opened; in the arc remelting process, when the liquid level of the metal molten pool reaches 25-30 cm above the water inlet, the water inlet is in an open mode, and other water inlets except the bottommost water inlet are in a closed mode; when the liquid level of the metal molten pool in the crystallizer reaches 3-5 cm above the water outlet, the water outlet is in an open mode, and other water outlets except the uppermost water outlet are in a closed mode. Preferably, the water flow rates of all the water inlets are the same, and the water flow rates of all the water outlets are the same.
The invention discloses an arc remelting device for the method for preventing stress cracking of an ingot and improving the internal quality of the ingot, which comprises a water-cooling crystallizer, wherein the water-cooling crystallizer comprises a plurality of water inlets and a plurality of water outlets; the water inlets are arranged up and down along the height of the crystallizer, and the water outlets are arranged up and down along the height of the crystallizer. The invention provides a novel water-cooling crystallizer, which is characterized in that a multi-inlet multi-outlet cooling is adopted by the water-cooling crystallizer and comprises a plurality of water inlets and a plurality of water outlets; the water inlets and the water outlets are arranged up and down along the height of the crystallizer.
As a general knowledge, the arc remelting device of the multi-inlet multi-outlet type water-cooled crystallizer of the invention has basic components of a conventional arc remelting device, such as a power supply, a water-cooled cable, a metal electrode, a bottom water tank, an electric arc, the water-cooled crystallizer and a molten metal pool. The water-cooling crystallizer is provided with a water inlet and a water outlet, and is communicated with the interlayer of the water-cooling crystallizer, and the cooling of the crystallizer is realized by circulating flow. In the invention, a plurality of water inlets and a plurality of water outlets are arranged up and down along the height direction of the water-cooled crystallizer, and as a common knowledge, one water inlet is positioned at the bottom of the crystallizer, and one water outlet is positioned at the top of the crystallizer, which is the existing water-cooled crystallizer. Preferably, the plurality of water inlets and the plurality of water outlets are vertically arranged up and down along the height direction of the water-cooled crystallizer. Further preferably, each water inlet and each water outlet are provided with a flow regulating valve, the water outlet at the top of the crystallizer is provided with a liquid flowmeter, all water inlets are all connected into a water supply total loop, all water outlets are finally all connected into a water return total loop, and the water return total loop is provided with the liquid flowmeter. The cooling water flow of each water outlet of the crystallizer is respectively regulated, so that the metal molten pool is shallow and flat, the solidification rate of the metal molten pool is increased, the crystal grains of the ingot tissue are refined, and the surface quality of the ingot is improved; the cooling water flow of each water inlet of the crystallizer is respectively regulated, so that the cooling speed of the lower cast ingot is slowed down on the premise of ensuring the cooling speed of the upper cast ingot, and the cracking of the martensitic transformation stress of the lower cast ingot is prevented.
In the invention, the number of the water inlets is 2-4, and the water inlets are vertically arranged at different heights of the crystallizer; the number of the water outlets is 2-10, and the water outlets are vertically arranged at different heights of the crystallizer; at least one water inlet is positioned below all water outlets, and as common knowledge, the water inlet and the water outlet are not positioned on the same side of the crystallizer, and the lower part refers to the upper and lower relation not to the right lower part. Among the water outlets, the distance between the lowest water outlet and the bottom surface of the crystallizer is more than 20cm, and the water outlets between the lowest water outlet and the uppermost water outlet are uniformly distributed; among the water inlets, the distance between the uppermost water inlet and the top of the crystallizer is more than 70 cm, and the water inlets between the lowermost water inlet and the uppermost water inlet are uniformly distributed. . Specifically, among the plurality of water inlets, the lowest water inlet is positioned at the bottom of the crystallizer, and the distance between the uppermost water inlet and the top of the crystallizer is more than 70 cm, preferably more than 70 cm and less than 120 cm; among the water inlets, the water inlets between the lowest water inlet and the uppermost water inlet are uniformly distributed. The distance between the lowest water outlet among the plurality of water outlets and the bottom surface of the crystallizer is more than 20cm, preferably more than 20cm and less than 40 cm; among the water outlets, the water outlet between the lowest water outlet and the uppermost water outlet is uniformly distributed, namely the rest water outlets are uniformly distributed between the lowest water outlet and the topmost water outlet according to the height, and the intervals are kept consistent.
The invention relates to a method for arc remelting by using an arc remelting device of a multi-inlet multi-outlet water-cooling crystallizer, which is a method for arc remelting for preventing stress cracking of an ingot and improving the internal quality of the ingot, and comprises the following steps: the bottom water tank of the arc remelting device is opened for water cooling, the water inlet at the bottommost part of the crystallizer and the water outlet at the uppermost part of the crystallizer are opened, arc remelting is started, and the bottom water tank and the water outlet at the uppermost part of the crystallizer are continuously opened until the arc remelting is finished; when the liquid level of the metal molten pool reaches 25-30 cm above the current water inlet, the current water inlet is in an opening mode; when the liquid level of the metal molten pool in the crystallizer reaches 3-5 cm above the water outlet, the water outlet and the top water outlet are opened, and the rest water outlets are closed until arc remelting is completed; the water flow of all water inlets is the same, the water flow of all water outlets is the same, and the water flow of each water inlet is adjusted according to the opening quantity of the water inlets and the opening quantity of the water outlets.
Specific examples are as follows:
(1) The multi-water-inlet multi-water-outlet water-cooling crystallizer is adopted, wherein the multi-water-inlet multi-water-outlet water-cooling crystallizer consists of a topmost water outlet, a plurality of water outlets vertically arranged along the height direction of the crystallizer, a bottommost water inlet and a plurality of water inlets vertically arranged along the height direction of the crystallizer, and when arc remelting is carried out, the opening and closing of each water inlet and each water outlet are regulated according to the liquid level height of a metal molten pool in the crystallizer, and the bottommost water inlet and the bottommost water outlet are opened directly;
(2) In the arc remelting process, circulating cooling water of a bottom water tank is always in an open mode, a water outlet at the top of a water-cooling crystallizer is always in an open cooling mode, and other water outlets are sequentially opened and closed according to the liquid level height of a metal molten pool;
(3) The arc remelting is started, circulating cooling water of the bottom water tank is in an opening mode, and the water cooling crystallizer adopts a single-inlet single-outlet cooling mode of water inlet of a lower water inlet, water outlet of a water outlet at the top and closing of other water outlets;
(4) Along with the continuous rising of the cast ingot, when the liquid level of the metal molten pool reaches 3-5 cm above the water outlet at the lowest part of the crystallizer, the water outlet (the first water outlet at the lower end of the crystallizer) and the water outlet at the top are in an open mode, and the other water outlets are in a closed mode; when the liquid level of the metal molten pool reaches 3-5 cm above the second water outlet from the lower part of the crystallizer, the second water outlet and the topmost water outlet of the crystallizer are in an open mode, and the other water outlets are in a closed mode; when the liquid level of the metal molten pool reaches 3-5 cm above a third water outlet from below the crystallizer, the third water outlet and the topmost water outlet of the crystallizer are in an open mode, and the other water outlets are in a closed mode; when the liquid level of the metal molten pool reaches 3-5 cm above the fourth water outlet and the fifth water outlet from the lower part of the crystallizer, the fourth water outlet and the fifth water outlet are circularly opened and the rest water outlets are closed in turn by analogy, and the current water outlet and the top water outlet of the crystallizer are kept in an opening mode, and the rest water outlets are in a closing mode;
(5) When the liquid level of the metal molten pool reaches 25-30 cm above a second water inlet from the lower part of the crystallizer, the second water inlet of the crystallizer is in an open mode, the bottommost water inlet (the first water inlet from the lower part of the crystallizer) is in an open mode, and the other water inlets are in a closed mode; when the liquid level of the metal molten pool reaches 25-30 cm above a third water inlet from below the crystallizer, the third water inlet of the crystallizer is in an open mode, the water inlet at the bottommost part is in an open mode, and the other water inlets are in a closed mode; when the liquid level of the metal molten pool reaches 25-30 cm above a fourth water inlet from the lower part of the crystallizer, the fourth water inlet of the crystallizer is in an open mode, the water inlet at the bottommost part is in an open mode, and the other water inlets are in a closed mode;
the above is exemplified by four water inlets and six water outlets, and those skilled in the art will recognize other numbers and refer to this.
In the invention, the side wall of the water-cooling crystallizer is provided with an interlayer for circulating water cooling, and the bottom of the water-cooling crystallizer is provided with a bottom water tank for bottom water cooling. The water-cooling crystallizer consists of a plurality of water inlets and water outlets which are vertically arranged along the height direction of the crystallizer, and the opening and closing of each water inlet and each water outlet can be dynamically adjusted; the water inlet flow rate and the water outlet flow rate are the same.
The water outlet at the top of the crystallizer is always opened, so that the side wall of the metal molten pool is always in a reasonable cooling mode, and the smoothness of the surface of the cast ingot is improved; as a preferred example, when the liquid level of the molten metal pool reaches 4cm above the current water outlet, the current water outlet is opened, so that the water flow in the crystallizer lower than the current water outlet is increased, the cooling strength of the cast ingot lower than the corresponding height is obviously increased, the molten metal pool is shallow and flat, the central segregation of the cast ingot is reduced, the structure grains are thinned, and the aim of improving the surface and internal quality of the cast ingot is fulfilled. When the liquid level of the metal molten pool reaches 27cm above the current water inlet, the current water inlet is opened, the water flow of the water inlet at the bottommost part of the crystallizer is reduced to half, so that the water flow of the crystallizer lower than the current water inlet is reduced, the cooling strength of the cast ingot lower than the corresponding height is obviously reduced, and the cracking phenomenon of the low-temperature martensitic transformation stress of the cast ingot is prevented.
In order to control the opening and closing of each water inlet and each water outlet on different heights of the crystallizer, the invention also discloses a calculation method for judging the melting weight of the metal electrode and the rising height of the liquid level of the metal molten pool, which is used for controlling the opening and closing of each water inlet and each water outlet of the crystallizer according to the melting weight of the metal electrode, wherein the diameter of an upper round opening of the crystallizer is smaller than that of a lower round opening, and the diameter of the upper round opening of the crystallizer has a certain taper, which is common sense. The calculation is as follows:
（1）
wherein the radius of the round opening on the crystallizer isrThe radius of the lower round mouth of the crystallizer isRThe height of the crystallizer isLThe height of the liquid level of the molten metal pool isHThe length units are cm; the total weight of the metal electrode isMThe unit is kg; the density of the metal electrode ispUnit kg/cm 3 。
The invention discloses the height of the liquid level of the metal molten pool for the first time according to the weight of a tested metal electrode, and the multi-inlet multi-outlet water-cooled crystallizer is combined to realize the aims of preventing stress cracking of a martensitic structure of an ingot and improving the internal quality and surface quality of the ingot; the problems that martensitic transformation stress cracking of an ingot cannot be prevented and arc remelting products of the internal quality and the surface quality of the ingot cannot be improved in the prior art are effectively solved.
Compared with the prior art, the invention has the following advantages and technical effects:
firstly, the multi-inlet multi-outlet water-cooled crystallizer and the use method thereof are adopted, the cooling strength of the lower cast ingot is obviously reduced, and the low-temperature martensitic transformation stress cracking of the cast ingot is prevented.
Secondly, a multi-inlet multi-outlet water-cooled crystallizer and a use method thereof are adopted, the cooling intensity of the upper cast ingot is obviously increased, the metal molten pool is shallow and flat, the solidification rate is accelerated, the segregation of the cast ingot is improved, the structure grains are refined, and the like.
Thirdly, the multi-inlet multi-outlet water-cooling crystallizer and the use method thereof are adopted, so that the side wall of the metal molten pool is in reasonable water-cooling strength under the condition that the shallow flatness of the metal molten pool and the cooling strength of the upper cast ingot are obviously increased, and the surface smoothness of the cast ingot is improved.
The invention discloses a calculation method for the molten weight of a metal electrode and the liquid level of a metal molten pool for the first time, and the opening and closing of each water inlet and each water outlet of a crystallizer can be automatically controlled according to the electrode weight indication on an electric arc remelting furnace control console.
Compared with the prior art, the invention has the following creativity: 1) The invention discloses a multi-inlet multi-outlet water-cooled crystallizer and a use method thereof for the first time, wherein the water flow of each water inlet can be dynamically adjusted, so that the water flow in the axial direction of the crystallizer is slow in the water flow of the lower crystallizer of the current opened water inlet, and the low-temperature martensitic transformation stress cracking of an ingot is prevented; the water flow of each water outlet can be dynamically regulated, so that the water flow in the axial direction of the crystallizer is fast in the water flow of the lower crystallizer of the current open water outlet and slow in the water flow of the upper crystallizer of the current open water outlet, and the aim of improving the internal quality and the surface quality of the cast ingot is fulfilled.
Drawings
FIG. 1 is a schematic diagram of a multi-inlet multi-outlet water-cooled crystallizer with an interlayer;
FIG. 2 is a schematic diagram of an arc remelting apparatus of a multi-inlet multi-outlet water-cooled crystallizer;
FIG. 3 is a schematic diagram of an arc remelting apparatus of a conventional single-inlet single-outlet water-cooled crystallizer;
FIG. 4 is a schematic view of an arc remelting apparatus employing a multi-inlet multi-outlet water-cooled crystallizer of an embodiment, with size parameter marks;
wherein: 1-1# water outlet, 2-2# water outlet, 3-3# water outlet, 4-4# water outlet, 5-5# water outlet, electric control valve of 7-1# water outlet, electric control valve of 8-2# water outlet, electric control valve of 9-3# water outlet, electric control valve of 10-4# water outlet, electric control valve of 11-5# water outlet, liquid flowmeter of 13-1# water outlet, 15-1# water inlet, 16-2# water inlet, electric control valve of 17-1# water inlet, electric control valve of 18-2# water inlet, 19-water cooled crystallizer copper inner layer, 20-water cooled crystallizer steel outer layer, 21-metal electrode, 22-cast ingot, 24-molten metal bath, 25-arc, 26-bottom water tank, 27-inert gas protection cover.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it. The specific components and the specific connection method of the components are conventional methods, such as installation and control of a water outlet valve. The specific experiment and the testing method of the invention are the prior art, and the secondary dendrite spacing is the average value.
Example 1
As shown in fig. 1, the inert atmosphere arc remelting device of the multi-inlet multi-outlet water-cooled crystallizer comprises a water-cooled crystallizer and other conventional components, wherein the water-cooled crystallizer is the multi-inlet multi-outlet water-cooled crystallizer according to a circulating water mode, and comprises a 1# water outlet 1, a 2# water outlet 2, a 3# water outlet 3, a 4# water outlet 4, a 5# water outlet 5, an electric regulating valve 7 of the 1# water outlet, an electric regulating valve 8 of the 2# water outlet, an electric regulating valve 9 of the 3# water outlet, an electric regulating valve 10 of the 4# water outlet, an electric regulating valve 11 of the 5# water outlet, a water inlet 15 of the 1# crystallizer and a water inlet 16 of the 2# crystallizer are communicated with a sandwich layer of the crystallizer, and the copper inner layer 19 and the steel outer layer 20 of the water-cooled crystallizer. Cooling water enters the interlayer from the water inlet 15 or the water inlets 15 and 16, two water inlets are vertically arranged up and down, and five water outlets are vertically arranged up and down.
In addition, the inert atmosphere arc remelting device is provided with a conventional arc 25, a metal electrode 21, a bottom water tank 26 and a power supply, wherein a multi-inlet multi-outlet water-cooling crystallizer is arranged on the bottom water tank, and a No. 1 water outlet is externally connected with a liquid flowmeter as shown in fig. 2.
During arc remelting in inert atmosphere, the metal electrode is melted under arc heat and resolidified into an ingot under the cooling of a water-cooled crystallizer, and each water inlet and each water outlet of the water-cooled crystallizer can be dynamically adjusted through an adjusting valve.
During arc remelting, after being electrified under the protection of inert atmosphere, an arc heat is adopted to melt a metal electrode, and the metal electrode is melted into molten drops under the arc heat, passes through an arc and forms an ingot under the cooling of a water-cooling crystallizer. In the arc remelting process, circulating cooling water of the bottom water tank is always in an open mode, a water outlet at the top of the water-cooling crystallizer is always in an open mode, and other water outlets are sequentially opened and closed according to the height of the liquid level of the metal molten pool. In the early stage of arc remelting, circulating cooling water of a bottom water tank is always in an open mode, and a water cooling crystallizer adopts a single-inlet single-outlet cooling mode with a lower water inlet, a top water outlet and other water outlets closed; along with the continuous rising of the cast ingot, when the liquid level of the metal molten pool reaches 27cm above the second water inlet, the second water inlet is in an open mode, and the first water inlet at the bottommost part is in an open mode; along with the continuous rising of the cast ingot, when the liquid level of the metal molten pool reaches 4cm above the first water outlet, the first water outlet and the topmost water outlet are in an open mode, and the other water outlets are in a closed mode; when the liquid level of the metal molten pool reaches 4cm above the second water outlet, the second water outlet and the water outlet at the top are in an open mode, and the other water outlets are in a closed mode; and by analogy, when the liquid level of the metal molten pool reaches 4cm above the third water outlet and the fourth water outlet, sequentially and circularly opening the third water outlet and the fourth water outlet and closing the rest water outlets. In the invention, when the liquid level of the metal molten pool reaches 27cm above the second water inlet, the second water inlet is opened, the water flow of the water inlet at the bottommost part of the crystallizer is reduced to half, the water flow of the crystallizer lower than the height of the second water inlet is reduced besides keeping the water inlet and the water outlet consistent, the cooling strength of the cast ingot lower than the corresponding height is obviously reduced, and thus the cracking phenomenon of low-temperature martensitic transformation stress of the cast ingot at the lower part is prevented; the water flow rate in the crystallizer higher than the second water inlet is increased, so that the cooling strength of the upper cast ingot is obviously increased, and the metal molten pool is in a shallow flat shape. The water outlet at the top of the crystallizer ensures that the side wall of the metal molten pool is always in a reasonable cooling mode, and the surface smoothness of the cast ingot is improved. When the liquid level of the metal molten pool reaches 4cm above the current water outlet, the current water outlet is opened, so that the cooling intensity of the cast ingot lower than the corresponding height is obviously increased, the metal molten pool is shallow and flat, the grains of the internal structure of the cast ingot are thinned, and the aim of improving the surface and internal quality of the cast ingot is fulfilled.
The electric arc remelting furnace adopted by the invention is an existing commercial product, and only the water cooling structure of the existing water cooling crystallizer is replaced by the water cooling structure of the multi-inlet multi-outlet water cooling crystallizer and each electric control valve control system provided with a water inlet and a water outlet is needed; the specific operation method and the test method are all conventional methods in the field, and the water inlet is the warm water. The azimuth relation of the invention is the position relation in actual production.
Example two
On the basis of the first embodiment, two water inlets are adjusted to be three water outlets which are vertically arranged up and down; the five water outlets are adjusted to eight water outlets which are vertically arranged up and down, and the rest is unchanged. After the ingot is obtained, the cracking incidence rate of the low-temperature martensitic transformation stress of the ingot is low; and detecting the cast structure of the cast ingot with the corresponding height between two adjacent water outlets, wherein the structure grains in the cast ingot are fine.
Comparative example one
As shown in fig. 3, on the basis of the first embodiment, two water inlets are adjusted to be one water inlet, which is located at the lowest position; five water outlets are adjusted to be one water outlet, the water outlet is positioned at the uppermost part, the rest of the water outlets are unchanged, the obtained ingot tissue grains are coarse, and the cracking phenomenon of low-temperature martensitic transformation stress occurs.
Application example one
Referring to FIG. 4, a two-inlet five-outlet type water-cooled crystallizer was used, the heights of the water outlets from the bottom of the crystallizer are shown in Table 1, the inner diameter of the lower opening of the crystallizer is 54cm, the inner diameter of the upper opening of the crystallizer is 48cm, and the height of the upper opening of the crystallizer is 185cm. The metal electrode adopts M50 bearing steel cylindrical casting blank with diameter of 38cm and density of 7.9 g/cm 3 。
Remelting metal electrode in a two-inlet and five-outlet water-cooled crystallizer of arc remelting furnace, wherein the current and voltage in the arc remelting process are 9000A and 58V respectively, the electrode melting rate is 350kg/h, the flow of inert argon gas into the furnace is 25 NL/min, and the flow of circulating cooling water of a bottom water tank is 20 m 3 And/h, circulating cooling water flow in the crystallizer is shown in table 1.
In the inert atmosphere arc remelting process, the height of the cast ingot is gradually increased along with the melting of the metal electrode. The correspondence of the electrode melting weight to the metal bath level height was calculated according to the formula (1), as shown in table 1. The distances from the positions of the water outlets of the crystallizer to the bottom of the crystallizer are shown in table 1. When the liquid level of the metal molten pool reaches 4cm above the corresponding water outlet, the corresponding water outlet is in an opening mode; when the liquid level of the metal molten pool reaches 27cm above the corresponding water inlet, the corresponding water inlet is in an open mode; the correspondence between the opening and closing modes of each water inlet and water outlet of a specific crystallizer and the electrode smelting weight (the liquid level of a molten metal pool) is shown in table 1.
Demoulding after the arc remelting in inert atmosphere is finished to obtain 3000kg of M50 aviation bearing steel with smooth surface, and the surface of the cast ingot is smooth, defect-free and good in quality. Sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to be 188 mu m by using a metallographic microscope; sampling the central part of the ingot with the height of 130cm, and observing and measuring the secondary dendrite spacing of 190 mu m by using a metallographic microscope; indicating that the cast ingot has good solidification structure.
TABLE 1 opening and closing operation of the respective water outlets with the melting weight of the metal electrode (the level of the molten metal bath)
Comparative application example 1
Based on the first application example, the two-inlet five-outlet water-cooled crystallizer is replaced by the single-inlet single-outlet water-cooled crystallizer in FIG. 3, and the water flow of the water inlet and the water outlet is 45 m 3 Flow rate of circulating cooling water of bottom water tank is 20 m 3 And/h, the rest is unchanged. And the M50 aviation bearing steel subjected to inert atmosphere arc remelting is subjected to the same, so that the cast ingot is flat in surface and good in quality. Sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to be 250 mu m by using a metallographic microscope; sampling the central part of the ingot with the height of 130cm, and observing and measuring the secondary dendrite spacing of 255 microns by using a metallographic microscope; indicating poor solidification structure of the ingot.
Comparative application example two
Based on the first application example, the two-inlet five-outlet water-cooled crystallizer is replaced by the single-inlet single-outlet water-cooled crystallizer in FIG. 3, and the water flow of the water inlet and the water outlet is 90 m 3 Flow rate of circulating cooling water of bottom water tank is 20 m 3 And/h, the rest is unchanged. And carrying out arc remelting on M50 aviation bearing steel in the same inert atmosphere to obtain the cast ingot with extremely poor surface quality, and the cast ingot surface is subjected to serious cracking phenomenon and cast ingot scrapping. Sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to be 206 mu m by using a metallographic microscope; the 130cm high center of the ingot was sampled and observed with a metallographic microscope to determine that the secondary dendrite spacing was 208. Mu.m.
Comparative application example III
Based on the first application example, the two-inlet five-outlet water-cooled crystallizer is replaced by the single-inlet single-outlet water-cooled crystallizer in FIG. 3, and the water flow of the water inlet and the water outlet is 70 m 3 Flow rate of circulating cooling water of bottom water tank is 20 m 3 And/h, the rest is unchanged. Carrying out arc remelting on M50 aviation bearing steel in the same inert atmosphere to obtain rough surface quality of an ingot; and the surface of the cast ingot is cracked and the cast ingot is scrapped. Sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to be 220 mu m by using a metallographic microscope;sampling the central part of the ingot with the height of 130cm, and observing and measuring the secondary dendrite spacing of 225 mu m by using a metallographic microscope; indicating that the coagulated structure is inferior to that of comparative application example two and inferior to that of application example two.
The comparative examples demonstrate the superiority of the multi-inlet multi-outlet water-cooling crystallization provided by the invention in preventing cracking of low-temperature martensitic transformation stress of cast ingots and refining the grain size of the cast ingot structure.
The invention adopts multi-inlet multi-outlet water-cooling crystallization, and can simultaneously obtain cast ingots with smooth surfaces and excellent internal quality. Furthermore, the invention adopts multi-inlet multi-outlet water-cooling crystallization, and on the premise of preventing cracking of low-temperature martensitic transformation stress of the cast ingot, the side wall of the metal molten pool is in a reasonable cooling mode, the cast ingot is in a strong water-cooling mode, and meanwhile, the structure grains of the cast ingot are thinned and the surface quality is improved. This has important practical production significance for producing large forgings.
When the cooling intensity of the water-cooling crystallizer is too small, the solidification rate of a metal molten pool of the existing inert atmosphere arc remelting device is slowed down, a large number of segregation inclusions and coarse structural grains are generated, and the internal quality of an ingot is seriously influenced; when the cooling strength of the water-cooling crystallizer is too high, the problems of poor surface quality of the cast ingot, cracking of low-temperature martensitic transformation stress of the cast ingot and the like are caused. The dynamic process of arc remelting in inert atmosphere is complex, and relates to dynamic changes of heat transfer, ingot solidification and structural phase change stress, so that the prior art cannot meet the requirements of ingot maximization and product high performance.
Application example II
On the basis of the first application embodiment, when the liquid level of the metal molten pool reaches 2cm above the corresponding water outlet, the corresponding water outlet is in an open mode, and the rest is the same, so that the cast ingot of the M50 aviation bearing steel is obtained. Sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to 187 mu m by using a metallographic microscope; sampling the central part of the ingot with the height of 130cm, and observing and measuring the secondary dendrite spacing of 192 mu m by using a metallographic microscope; the solidification structure is not quite different from that of the application example. However, the surface smoothness of the obtained cast ingot is reduced, and the surface quality of the cast ingot is obviously inferior to that of the application example, but is superior to that of the comparison application.
Application example III
On the basis of the first application embodiment, when the liquid level of the metal molten pool reaches 6cm above the corresponding water outlet, the corresponding water outlet is in an open mode, and the rest water outlets are the same, so that M50 aviation bearing steel with smooth surface is obtained, and the ingot casting has smooth surface, no defect and good quality; sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to be 195 mu m by using a metallographic microscope; sampling the central part of the ingot with the height of 130cm, and observing and measuring the secondary dendrite spacing of 205 mu m by using a metallographic microscope; the coagulated tissue was inferior to the application example but significantly superior to the comparative application.
Application example IV
On the basis of the first application embodiment, when the liquid level of the metal molten pool reaches 20cm above the second water inlet, the corresponding water inlet is in an open mode, and the rest water inlets are the same, so that the M50 aviation bearing steel with a smooth surface is obtained, and the ingot casting has a smooth surface, no defects and good quality; sampling the center part of the top of the ingot, and observing and measuring the secondary dendrite spacing of the ingot to 196 mu m by using a metallographic microscope; sampling the central part of the ingot with the height of 130cm, and observing and measuring the secondary dendrite spacing of 204 mu m by using a metallographic microscope; the solidification structure of an ingot with a height of 130cm is inferior to that of the application example, but is obviously superior to that of the comparison application.
Application example five
On the basis of the first application embodiment, when the liquid level of the metal molten pool reaches 35cm above the corresponding water inlet, the corresponding water inlet is in an open mode, and the rest is the same, the surface of the obtained cast ingot is cracked, and the cast ingot is scrapped.
According to the description, the invention develops a novel inert atmosphere arc remelting technology of the multi-inlet multi-outlet water-cooled crystallizer. In the inert atmosphere arc remelting, as the ingot is continuously raised, when the liquid level of a metal molten pool reaches 3-5 cm above a first water outlet, the first water outlet and the topmost water outlet of the crystallizer are opened, and the rest water outlets are all in a closed mode. This water outlet mode makes the flow rate of cooling water in the upper crystallizer higher than the first water outlet in a reasonable mode, and the flow rate of cooling water in the lower crystallizer lower than the first water outlet is significantly increased: namely, the side wall of the metal molten pool higher than the first water outlet presents a reasonable cooling mode, and the cooling strength of the part lower than the first water outlet is obviously increased, so that the metal molten pool presents a shallow flat shape, thereby refining the ingot tissue grains. The side wall of the metal molten pool is a forming area of the surface of the cast ingot, and a reasonable cooling mode ensures that the surface of the cast ingot obtains good surface quality
In conclusion, on the premise of ensuring the surface quality of the cast ingot, the solidification speed of the metal molten pool is improved, so that the structure grains can be thinned, and the mechanical property of the product is improved. In particular, the invention discloses the change relation of the melting weight of the metal electrode along with the liquid level height of the metal molten pool for the first time, and the actual production verifies that the method has obvious technical progress and provides feasibility guarantee for industrial production.
The invention discloses a process and a method for preventing phase change stress cracking of an ingot and improving the internal quality of the ingot in an inert atmosphere arc remelting furnace. In order to realize the process, the invention also develops a multi-inlet multi-outlet water-cooled crystallizer which consists of a plurality of water inlets and water outlets which are vertically arranged along the height direction of the crystallizer. At the early stage of arc remelting, a water inlet at the bottom of the crystallizer and a water outlet at the top of the crystallizer are in an open mode, and the rest water gaps are in a closed mode; along with the arc remelting, when the liquid level of the metal molten pool reaches 3-5 cm above the current water outlet, the current water outlet and the top water outlet are in an open mode, and the rest water outlets are in a closed mode; when the liquid level of the metal molten pool reaches 25-30 cm above the current water inlet, the current water inlet is in an open mode, the water inlet at the bottommost part of the crystallizer is in a half open mode, and the other water inlets are in a closed mode. The multiple crystallizer water inlets of the process and the device enable the cast ingot to be low in lower cooling rate and high in upper cooling rate, reduce the martensitic transformation stress of the cast ingot, and prevent the cast ingot from cracking; the plurality of crystallizer water outlets enable the metal molten pool to be shallow and flat, lighten solidification segregation, and simultaneously the side wall of the metal molten pool has reasonable cooling rate, and simultaneously improves the surface and internal quality of the cast ingot. In the prior art, a single-inlet single-outlet water-cooled crystallizer is adopted, so that the problems of deep metal molten pool, serious solidification segregation, ingot martensitic transformation stress cracking, poor surface quality and the like are caused when the water flow rate of the crystallizer is reduced, and the water flow rate of the crystallizer is increased. The multi-inlet multi-outlet water-cooling crystallizer developed by the invention not only prevents the martensitic transformation stress cracking of the cast ingot, but also improves the surface and internal quality of the cast ingot.
Claims (10)
1. A method for preventing stress cracking of an ingot and improving the internal quality of the ingot by arc remelting is characterized in that a bottom water tank is combined with a multi-inlet multi-outlet cooling mode for a crystallizer, and the method comprises the following steps: when arc remelting, the bottom water tank is always opened for water cooling, and the bottommost water inlet and the uppermost water outlet are always opened; in the arc remelting process, when the liquid level of the metal molten pool reaches 25-30 cm above the water inlet, the water inlet is in an open mode, and other water inlets except the bottommost water inlet are in a closed mode; when the liquid level of the metal molten pool in the crystallizer reaches 3-5 cm above the water outlet, the water outlet is in an open mode, and other water outlets except the uppermost water outlet are in a closed mode.
2. The method for arc remelting for preventing stress cracking and improving internal quality of ingot according to claim 1, wherein in the cooling mode of multiple-inlet multiple-outlet, the number of water inlets is 2-4, and the number of water outlets is 2-10.
3. The method for arc remelting for preventing stress cracking of an ingot and improving the internal quality of the ingot according to claim 2, wherein the water inlets are arranged up and down; the water outlets are arranged up and down; at least one water inlet is positioned below all water outlets.
4. The method for arc remelting for preventing stress cracking of an ingot and improving internal quality of the ingot according to claim 2, wherein in the water outlets, a distance between a lowest water outlet and a bottom surface of the crystallizer is more than 20cm, and water outlets between the lowest water outlet and the uppermost water outlet are uniformly distributed; among the water inlets, the distance between the uppermost water inlet and the top of the crystallizer is more than 70 cm, and the water inlets between the lowermost water inlet and the uppermost water inlet are uniformly distributed.
5. The method of arc remelting for preventing stress cracking and improving the internal quality of ingots according to claim 1, wherein the water flow of all water inlets is the same and the water flow of all water outlets is the same.
6. The method of arc remelting for preventing stress cracking and improving the internal quality of an ingot according to claim 1, wherein the relation between the melting weight of the metal electrode and the liquid level of the molten metal pool is as follows:
wherein the radius of the round opening on the crystallizer isrThe radius of the lower round mouth of the crystallizer isRThe height of the crystallizer isLThe height of the liquid level of the molten metal pool isHThe length units are cm; the total weight of the metal electrode isMThe unit is kg; the density of the metal electrode ispUnit kg/cm 3 。
7. An arc remelted ingot produced by the arc remelting method for preventing stress cracking of an ingot and improving internal quality of an ingot as set forth in claim 1.
8. The arc remelting apparatus for the arc remelting method for preventing stress cracking of an ingot and improving internal quality of an ingot according to claim 1, comprising a water-cooled crystallizer, wherein the water-cooled crystallizer comprises a plurality of water inlets and a plurality of water outlets; the water inlets are arranged up and down along the height of the crystallizer, and the water outlets are arranged up and down along the height of the crystallizer.
9. A calculation method for judging the melting weight of a metal electrode and the rise height of the liquid level of a metal bath is characterized in that the change relation of the melting weight of the metal electrode along with the liquid level of the metal bath is as follows:
wherein the radius of the round opening on the crystallizer isrThe radius of the lower round mouth of the crystallizer isRThe height of the crystallizer isLThe height of the liquid level of the molten metal pool isHThe length units are cm; the total weight of the metal electrode isMThe unit is kg; the density of the metal electrode ispUnit kg/cm 3 。
10. Use of the arc remelting apparatus of claim 8 in the method of claim 1 for preventing stress cracking of an ingot and improving the internal quality of the ingot.
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| CA2431136A1 (en) * | 2000-12-12 | 2002-06-20 | Netanya Plasmatec Ltd. | Treating molten metals by moving electric arc |
| JP2009039752A (en) * | 2007-08-09 | 2009-02-26 | Nikkei Mc Aluminum Co Ltd | Casting apparatus |
| CN102773424A (en) * | 2012-07-23 | 2012-11-14 | 辽宁科技大学 | Water/air cooled steel ingot die capable of realizing progressive solidification of steel ingots and application method of water/air cooled steel ingot die |
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