CN117840391A - Method for effectively adding transition elements of large-size ingot casting - Google Patents
Method for effectively adding transition elements of large-size ingot casting Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000005266 casting Methods 0.000 title claims abstract description 21
- 238000001816 cooling Methods 0.000 claims abstract description 139
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 27
- 239000000956 alloy Substances 0.000 claims abstract description 27
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 230000007246 mechanism Effects 0.000 claims description 48
- 239000002826 coolant Substances 0.000 claims description 22
- 239000000155 melt Substances 0.000 claims description 18
- 238000007670 refining Methods 0.000 claims description 16
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- 229910052726 zirconium Inorganic materials 0.000 claims description 16
- 238000007599 discharging Methods 0.000 claims description 13
- 238000005070 sampling Methods 0.000 claims description 10
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- 238000004458 analytical method Methods 0.000 claims description 9
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 8
- 239000002994 raw material Substances 0.000 claims description 8
- 229910052719 titanium Inorganic materials 0.000 claims description 8
- 239000010936 titanium Substances 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 7
- 239000002893 slag Substances 0.000 claims description 7
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 6
- 229910052691 Erbium Inorganic materials 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 239000011651 chromium Substances 0.000 claims description 6
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 6
- 229910052706 scandium Inorganic materials 0.000 claims description 6
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 239000011572 manganese Substances 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 230000007423 decrease Effects 0.000 claims description 4
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 4
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Abstract
The invention relates to a method for effectively adding transition elements of a large-size ingot casting. The method comprises the steps of feeding an alloy melt containing a transition element into a crystallizer for casting, so that the cooling rate of an ingot from the core to the surface of the ingot is not less than 2 ℃ per second, and the maximum difference between the cooling rates from the core to the R/2 position of the ingot is not more than 2 ℃ per second, wherein R is the distance from the center of the radial section of the ingot to the surface of the ingot. According to the invention, the cast ingot has higher cooling rate from the core part to the surface thereof, and the fluctuation range of the cooling rate is smaller, so that the addition amount of transition elements is greatly increased, the obtained cast ingot has better uniformity and better morphology, the size of the solidified crystalline phase of the transition elements is obviously reduced, the distribution density of the dispersive phase is obviously increased after the subsequent heat treatment, and the mechanical property of the large-size cast ingot is effectively improved.
Description
Technical Field
The invention relates to the technical field of aluminum alloy casting, in particular to a method for effectively adding transition elements of large-size ingots.
Background
The addition of transition elements to alloy ingots generally has a significant impact on the structure and properties of the alloy. During homogenizing annealing of the cast ingot, dispersed particles are generated, and the particles block migration of dislocation and grain boundary, so that the recrystallization temperature is increased, and growth of grains is effectively prevented; secondly, the dispersed particles can also have strong pinning effect on dislocation, so that the dislocation movement is hindered, the shear stress required by dislocation slip is increased, the dispersion strengthening effect is achieved, and the transition elements are added to form a fine second phase structure to a certain extent, so that the effect of refining the grain structure is achieved.
For adding transition elements to large-size ingots, due to the fact that the cooling rates of the surfaces of the ingots and the core parts are greatly different, when the cooling rates of the surfaces of the ingots are higher, a proper amount of transition elements are added, coarse second phases containing the transition elements are not easy to appear on the surfaces of the ingots, and the transition elements mainly exist in a solid solution form in an aluminum alloy matrix. At low cooling rates, the ingot core has only a small amount of transition elements present in the aluminum alloy matrix in solid solution and a large amount of transition elements present in the coarse second phase. Even if the addition amount of the transition element is very low, coarse second phases containing the transition element are very easy to appear in the core part of the cast ingot, and the coarse second phases containing the transition element are mostly flaky and needle-shaped tissues, can generate serious splitting action on a matrix, easily generate stress concentration and become crack sources, thereby reducing the mechanical properties of the alloy and particularly improving the strength and plastic performance.
In order to avoid the occurrence of coarse second phase structures containing transition elements in the core of large-size ingots, the current industry takes the core cooling rate (the position of the minimum cooling rate of the whole ingot) as a reference to determine the addition amount of the transition elements, and the addition amount of the transition elements is relatively low, so that the occurrence of coarse second phase structures containing the transition elements can be avoided to a certain extent, but the method is a non-trivial way to trade off the performance of the ingots and subsequent products.
Aiming at the existing problems, enterprises adopt an external physical field (electromagnetic stirring, mechanical stirring, ultrasonic stirring and other modes) to reduce the difference of the cooling rates of the surface and the core of the large-size cast ingot, but the practical improvement is limited. In order to refine the core structure of the ingot, enterprises build-in extrusion ingots in the core of the ingot, the method improves the cooling rate of the core of the ingot to a certain extent, but the cooling rate from the surface of the ingot to the core of the ingot is distributed in a dumbbell shape, the minimum value of the cooling rate is positioned near the R/2 position of the ingot, the position of the ingot structure between the maximum value and the minimum value of the cooling rate shows nonlinear gradient change, and the uneven structure not only affects the overall performance of the ingot, but also directly affects the processing performance and mechanical performance of products. Although the adding mode improves the cooling rate of the core part of the ingot, as the fluctuation range of the cooling rate of the whole ingot is not required, the crystal phase and the dispersed phase of the ingot and the subsequent product are greatly different in size, size and distribution density under different cooling rates, and the microstructure of the difference directly influences the improvement of the whole performance of the ingot and the subsequent product to a certain extent.
In recent years, with further increase of the size of the ingot, the defects or shortages caused by the conventional addition mode are also highlighted, the larger the size of the ingot is, the smaller the addition amount of transition elements is, the more serious the tissue non-uniformity of the whole ingot is, and the development of the ingot preparation technology with larger size is limited to a certain extent. Thus, new technologies are urgently needed to innovate and break this constraint.
Disclosure of Invention
The invention aims to provide a method for effectively adding transition elements in a large-size ingot, which can add more transition elements into the ingot, and the ingot has smaller size of a solidification crystalline phase of the transition elements in the solidification process, and the distribution density of a disperse phase after heat treatment is increased, so that the uniformity is better.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for effectively adding transition elements in large-size cast ingots comprises the steps of feeding an alloy melt containing transition elements into a crystallizer for casting, so that the cooling rate of the cast ingot from the core part to the surface of the cast ingot is not less than 2 ℃/s, and the maximum difference between the cooling rate from the core part to the R/2 part of the cast ingot is not more than 2 ℃/s, wherein R is the distance from the center of the radial section of the cast ingot to the surface of the cast ingot.
Preferably, when only one transition element is added, the addition amount of the transition element is greater than or equal to 0.15%; when two or more transition elements are added, the addition amount of each transition element is 0.1% or more.
Preferably, the average size of the solidified crystal phase of the ingot transition element is not more than 20 mu m, and the average size of the nano-scale dispersed phase of the ingot after heat treatment is not more than 300nm.
Preferably, in aluminum alloys, the transition elements are generally those elements that form a dispersed phase with aluminum.
In some embodiments, the transition element comprises one or more of manganese, vanadium, chromium, titanium, zirconium, erbium, scandium.
Further, when the transition element includes manganese, the manganese accounts for 0.2 to 2% of the total mass of the ingot.
Further, when the transition element includes vanadium, the vanadium accounts for 0.1 to 2% of the total mass of the ingot.
Further, when the transition element includes chromium, the chromium accounts for 0.2 to 2% of the total mass of the ingot.
Further, when the transition element includes titanium, the titanium accounts for 0.1 to 0.15% of the total mass of the ingot.
Further, when the transition element includes zirconium, the zirconium accounts for 0.1 to 0.2% of the total mass of the ingot.
Further, when the transition element includes erbium, the erbium accounts for 0.1 to 0.2% of the total mass of the ingot.
Further, when the transition element includes scandium, the scandium accounts for 0.1-0.2% of the total mass of the ingot.
In some embodiments, the ingot comprises, based on 100% of the total mass of the ingot:
9 to 11 percent of silicon,
0.5 to 1 percent of copper,
0.5 to 1 percent of magnesium,
0.1 to 0.15 percent of iron,
manganese 0.5-0.7%,
0.1 to 0.15 percent of titanium,
zirconium 0.1-0.2%,
0.1 to 2 percent of vanadium,
and the balance of aluminum.
Further, the ingot comprises, based on 100% of the total mass of the ingot:
9.5 to 10.5 percent of silicon,
copper 0.7-0.9%,
0.7 to 0.9 percent of magnesium,
0.1 to 0.12 percent of iron,
manganese 0.55-0.65%,
0.1 to 0.12 percent of titanium,
zirconium 0.13-0.18%,
vanadium 0.13-0.18%,
and the balance of aluminum.
Preferably, the large-size ingot is an ingot with a radial section size of 400mm or more.
Further preferably, the large-size ingot is an ingot having a radial cross-sectional dimension of 600mm or more.
Preferably, n groups of cooling units are arranged in the crystallizer, the first group of cooling units to the n groups of cooling units are sequentially arranged from inside to outside, n is an integer greater than or equal to 2, the first group of cooling units are provided with a cooling mechanism and are coaxial with the crystallizer, the n groups of cooling units are provided with a plurality of cooling mechanisms which are uniformly distributed around the axial lead of the crystallizer, and the distance between the cooling mechanism of the n groups of cooling units and the axial lead is L n ，L n = (50-150 mm) × (n-1), the heat exchange coefficient of the cooling mechanism in the first to n-th sets of cooling units gradually decreases, and the cooling mechanism in the first to n-th sets of cooling units is partially inserted into the alloy melt.
Further preferably, 1/2 R.ltoreq.L n ≤2/3R。
Further preferably L n = (80 to 120 mm) × (n-1), more preferably L n ＝(90～110mm)×(n-1)。
In some embodiments, the cooling mechanism comprises a hollow shell, a feeding pipeline communicated with the shell and used for introducing cooling medium, and a discharging pipeline communicated with the shell and used for discharging the cooling medium, wherein one end of the feeding pipeline is positioned at the bottom of the shell, and the other end of the feeding pipeline extends out of the shell and is communicated with a cooling medium source; one end of the discharging pipeline is positioned at the upper part of the shell, and the other end of the discharging pipeline extends out of the shell and is communicated with a cooling medium source.
Further, the housing is cylindrical, and the housing outer diameters of the cooling mechanisms in the first to nth sets of cooling units gradually decrease.
Further, the outer diameter of the shell is D 1 The outer diameter of the shell of the cooling mechanism in the nth group of cooling units is D n ，D 1 Is 30 to 60mm, D n ＝(D 1 -10×(n-1))mm。
Preferably, the shell is made of graphite. The heat exchange coefficient of the cooling mechanism can be adjusted by the type, temperature, flow rate, pressure and the like of the cooling medium.
Preferably, the cooling medium is cooling water.
Further preferably, the flow rates of the feeding pipeline and the discharging pipeline are the same and are 0.5-1.5 m 3 /h。
Further preferably, the pressure of the cooling medium is 0.01 to 0.15Mpa.
In some embodiments, the cooling mechanism is an extruded bar and/or an ingot, and the structure and the material of the extruded bar and the ingot can refer to the prior art.
Preferably, the cooling mechanism is arranged in the crystallizer in a lifting manner through a bracket.
Preferably, the heat exchange coefficient of the first group of cooling units is 7000-9000W/(m) 2 K) the heat exchange coefficient of the nth group of cooling units is K n ，K n ＝[(7000～8000)-2000×(n-1)]W/(m 2 ·k)。
In some embodiments, 3 groups of cooling units are arranged in the hot top crystallizer, wherein the heat exchange coefficient of the cooling mechanism of the second group of cooling units is 5000-5500W/(m) 2 K), the heat exchange coefficient of the cooling mechanism of the third group of cooling units is 3000-4000W/(m) 2 ·k)。
Preferably, the nth group of cooling units has m cooling units, m=3× (n-1).
Preferably, the bottom end surfaces of the cooling means in the first to nth sets of cooling units are 80 to 120mm, e.g. 80mm, 90mm, 100mm, 110mm, etc. from the alloy melt level.
Preferably, the preparation method of the alloy melt comprises the following steps:
(1) Batching according to the target components;
(2) Smelting part of raw materials in a melting furnace at 750-770 ℃, taking a furnace front sample after the furnace burden is completely melted and the components are uniform, carrying out primary refining by high-purity argon after the furnace front analysis is qualified at 720-760 ℃, wherein the refining time is 10-20min, and slagging off after refining;
(3) After slag skimming, adding the rest raw materials into a system, adding the raw materials at 730-750 ℃, stirring the melt uniformly after complete melting, refining the melt with high purity argon for a second time when the temperature of the melt is 740-750 ℃, refining for 10-20min, skimming the scum on the surface of the melt, standing after slag skimming, sampling the secondary components, and adjusting the components of the melt according to the analysis result to ensure that the chemical composition of the alloy melt is the same as that of the target components.
Further preferably, the remaining raw material is a transition element that is susceptible to sinking, which is dosed in the form of a master alloy.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
according to the invention, the core part of the ingot has higher cooling rate and the surface of the ingot has smaller fluctuation range of the cooling rate, so that the addition amount of the transition element is greatly increased, the size of the solidification crystalline phase of the transition element in the solidification process of the ingot is reduced, the distribution density of the diffusion phase of the ingot after heat treatment is obviously increased, the obtained ingot has better uniformity and better morphology, and the mechanical property of the large-size ingot is effectively improved.
Drawings
FIG. 1 is a schematic diagram of a mold in example 1 in a simulated manner;
fig. 2 is a sectional view of the cooling mechanism in embodiment 1;
FIG. 3 is a schematic top view of the mold of example 1 when casting ingot;
FIG. 4 is a scanning electron microscope image of the microstructure at the R/2 position of an aluminum alloy ingot of example 1, wherein light gray is eutectic structure and white is dispersed phase;
FIG. 5 is a scanning electron microscope image of the microstructure at the R/2 position of the aluminum alloy ingot of comparative example 1, wherein the color of the image is from deep to light, and the image sequentially comprises a micron-sized solidification crystal phase containing Zr and V, a eutectic phase and primary alpha aluminum;
FIG. 6 is a schematic diagram of a simulation of the casting of the mold of comparative example 2;
FIG. 7 is a scanning electron microscope image of the microstructure at the R/2 position of the aluminum alloy ingot of comparative example 2, which is sequentially from deep to light in color and comprises a micron-sized Zr-containing, V-containing solidified crystalline phase, a eutectic phase and primary alpha aluminum;
FIG. 8 is a drawing showing the aluminum alloy ingot R/2 position after heat treatment (Al, si) of example 1 3 (Zr, V) phase distribution scanning electron microscope pictures, wherein gray is an aluminum matrix, and white is a nano-scale disperse phase;
FIG. 9 is a drawing showing the aluminum alloy ingot of comparative example 1 after heat treatment at the R/2 position (Al, si) 3 (Zr, V) phase distribution scanning electron microscope pictures, wherein gray is an aluminum matrix, and white is a nano-scale disperse phase;
FIG. 10 is a drawing showing the aluminum alloy ingot R/2 position after heat treatment (Al, si) 3 (Zr, V) phase distribution scanning electron microscope pictures, wherein gray is an aluminum matrix, and white is a nano-scale disperse phase;
1, a shell; 2. a feed conduit; 3. a discharge pipe; 4. alloy melt; 5. a crystallizer;
A. a cooling mechanism of a first group of cooling units; B. a cooling mechanism of a second group of cooling units; C. and a cooling mechanism of the third group of cooling units.
Detailed Description
The inventor provides higher and uniformly distributed cooling rate for the whole cast ingot by internally arranging a plurality of groups of cooling units, under the higher and uniformly distributed cooling rate, the addition amount of transition elements of the large-size cast ingot can be greatly increased, the size of a solidified crystalline phase of the transition elements of the cast ingot is obviously reduced in the solidification process, and the distribution density of disperse phases of the cast ingot after subsequent heat treatment is obviously increased, so that the mechanical properties of the large-size cast ingot and subsequent products are effectively improved.
The invention is further described below with reference to examples. The present invention is not limited to the following examples. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions which are not noted are conventional conditions in the industry. The technical features of the various embodiments of the present invention may be combined with each other as long as they do not collide with each other.
Unless otherwise specified, the crystallizer 5 used in the embodiment of the present invention is a common same-level hot top crystallizer, and 3 groups of cooling units are disposed in the crystallizer 5, and referring to fig. 1, the cooling units of the first group, the cooling units of the second group and the cooling units of the third group are sequentially disposed from inside to outside. Referring to fig. 3, the first group of cooling units has one cooling mechanism, the cooling mechanism a of the first group of cooling units being located in the core of the ingot (coaxial with the axis of the crystallizer 5); the second group of cooling units are provided with 3 cooling mechanisms, the 3 cooling mechanisms are uniformly distributed around the axial lead of the crystallizer 5, and the axial center of the cooling mechanism B of the second group of cooling units is 100mm away from the axial lead; the third group of cooling units is provided with 6 cooling mechanisms, the 6 cooling mechanisms are uniformly distributed around the axial lead of the crystallizer 5, and the axial center of the cooling mechanism C of the third group of cooling units is 200mm away from the axial lead. As shown in fig. 2, the cooling mechanism comprises a hollow heat dissipation shell 1 made of graphite, and a feeding pipeline 2 and a discharging pipeline 3 which are respectively communicated with the shell 1, wherein the feeding pipeline 2 is used for feeding cooling medium, one end of the feeding pipeline 2 is positioned at the bottom of the shell 1, and the other end of the feeding pipeline extends out of the shell 1 and is communicated with a cooling medium source; the discharging pipeline 3 is used for discharging cooling medium, one end of the discharging pipeline is positioned at the upper part of the shell 1, the other end of the discharging pipeline extends out of the shell 1 and is communicated with a cooling medium source, and the cooling medium is normal-temperature (25+/-5 ℃) circulating cooling water. Preferably, the shell 1 has a cylindrical structure, and the cooling mechanisms of the first to third groups of cooling units have the same structure, and the difference is that the sizes of the shells 1 are different, the outer diameter of the shell 1 of the cooling mechanism A of the first group of cooling units is 50mm, and the wall thickness is 5mm; the outer diameter of the shell 1 of the cooling mechanism B of the second group of cooling units is 40mm, and the wall thickness is 5mm; the housing 1 of the cooling mechanism C of the third group of cooling units has a diameter of 30mm and a wall thickness of 5mm. According to the present invention, the cooling mechanism is arranged on the crystallizer 5 in a liftable manner by a bracket, and the arrangement method is specifically referred to the prior art (for example, patent CN 115921801B), and the present invention is not particularly limited.
The preparation method of the alloy melt 4 containing the transition element according to the invention is as follows, unless otherwise specified:
(1) Dosing according to Table 1 aluminum alloy standard composition
TABLE 1 main component of test alloy, balance aluminum
(2) Raw materials Al-Si, al-Cu, al-Mg, al-Fe, al-Mn and Al-Ti intermediate alloy are put into a melting furnace for melting, the melting temperature is 750-770 ℃, the furnace charge is completely melted, the furnace charge is sampled after the components are uniform, and the sampling temperature is 720-760 ℃; after the analysis in the furnace is qualified, when the temperature of the melt is 750 ℃, high-purity Ar gas (the purity is more than or equal to 99%) is used for primary refining, the refining time is 10-20min, and slag is removed after refining. After slag skimming, adding Al-Zr and Al-V intermediate alloy (zirconium and vanadium are easy to sink if added at the beginning of smelting) into the system, and stirring the melt uniformly after the addition is completely melted at 730-750 ℃. And (3) refining the melt with high-purity Ar gas for the second time when the temperature of the melt is 740-750 ℃ for 10-20min, removing scum on the surface of the melt after refining, standing after removing slag, preserving heat and standing for about 30min, sampling secondary components, adjusting the components of the melt according to the analysis result, and ensuring that the chemical composition of the alloy melt 4 is the same as that of Table 1.
Unless otherwise specified, the following examples and comparative examples refer to the prior art by measuring the temperature of the melt alloy and ingot by a thermocouple.
Unless otherwise indicated, the term "about" as used herein to modify a numerical value refers to a defined range around that value, and if "X" is a value, "about X" will generally refer to a value of 0.95X to 1.05X.
Example 1
A method for adding transition elements of large-size ingot comprises feeding alloy melt 4 into crystallizer 5 (size of 630 mm), inserting alloy melt 4 into the bottom of each cooling mechanism and keeping distance from the surface of alloy melt 4 by 100mm, continuously feeding cooling medium into feeding pipe 2 of each cooling mechanism, and controlling flow rate, pressure and water temperature of cooling medium to make interface heat exchange coefficient of cooling mechanism of first to third groups of cooling units about 8000 (W/m 2 .k)、5000(W/m 2 K) and 4000 (W/m 2 K) (heat exchange coefficient the heat exchange coefficient of the cooling mechanism can be obtained by measuring the temperature of the melt at a point near the cooling mechanism and inputting the temperature at the point into a numerical simulation model (casting software) for back calculation. The cooling medium of the first to third groups of cooling units is normal temperature water, and the flow rates are respectively 1.2m 3 /h、0.8m 3 /h and 0.5m 3 And/h, the pressure is respectively 0.1MPa, 0.06MPa and 0.03MPa. The casting speed is controlled to be 40mm/min, the casting temperature is 730 ℃ to 740 ℃, and the cooling water quantity of the crystallizer 5 is maintained to be 4m 3 And/h, the water pressure is 0.1MPa, and the cooling water temperature is 25+/-5 ℃.
The cooling rate of the whole cast ingot (namely the cast ingot core to the surface thereof) is more than or equal to 3.5 ℃/s, and the maximum difference between the cooling rate of the cast ingot R/2 and the core cooling rate is 1.2 ℃/s.
After casting, sampling and microstructure performance analysis are carried out on the microstructure of the R/2 position of the cast ingot, wherein the sampling position is 400mm away from the casting ending gate, and the microstructure of the sample is shown in figure 4.
Example 2
Substantially the same as in example 1, the main difference is that:
by controlling the cooling mediumThe flow rate and the pressure of the cooling mechanism of the first to third groups of cooling units are such that the interfacial heat exchange coefficient is about 6000 (W/m 2 .k)、4000(W/m 2 K) and 3000 (W/m 2 K), wherein the unit cooling medium is normal-temperature water, the flow rates are respectively 0.6m3/h, 0.5m3/h and 0.3m3/h, and the pressures are respectively 0.05MPa, 0.03MPa and 0.02MPa.
The cooling rate of the whole cast ingot is more than or equal to 2 ℃/s, and the maximum difference between the R/2 of the cast ingot and the core cooling rate is 1.8 ℃/s.
Comparative example 1
Introducing the alloy melt 4 into a same-level hot top crystallizer 5 (with the size phi 630 mm) for casting, wherein the casting speed is 40mm/min, the casting temperature is 730-740 ℃, and the cooling water quantity is maintained at 4m 3 And/h, the water pressure is 0.1MPa, and the cooling water temperature is 25+/-5 ℃. The same-level hot top crystallizer 5 in this comparative example is a common same-level hot top crystallizer 5, and no cooling unit is provided in the crystallizer 5.
After casting, sampling and microstructure performance analysis are carried out on the microstructure of the R/2 position of the cast ingot, wherein the sampling position is 400mm away from the casting ending gate, and the microstructure of the sample is shown in FIG. 5.
Comparative example 2
Substantially the same as in example 1, the main difference is that: the core of the hot top crystallizer 5 in this comparative example is provided with only one cooling unit (only one cooling mechanism a), as shown in fig. 6.
The cooling unit is substantially identical in construction to the first set of cooling units described above, except that the outer diameter of the housing 1 is 250mm.
The cooling medium was continuously introduced into the feed line 2 of the cooling unit so that the interface heat exchange coefficient of the cooling unit was about 8500 (W/m 2 K) the unit cooling medium is warm water with the flow of 1.2m 3 And/h, wherein the pressure is 0.1MPa, the cooling rate of the whole cast ingot is distributed between 1-10 ℃/s, and the maximum difference between the R/2 of the cast ingot and the core cooling rate is more than 5 ℃/s.
After casting, sampling and microstructure performance analysis are carried out on the microstructure of the R/2 position of the cast ingot, wherein the sampling position is 400mm away from the casting ending gate, and the microstructure of the sample is shown in FIG. 7.
As is found by comparing FIGS. 4, 5 and 7, the R/2 site of the ingot of example 1 did not exhibit a significant Zr and V coarse solidification crystalline phase structure, and the R/2 site of the ingot of comparative example 1 and comparative example 2 exhibited a significant Zr and V coarse second phase structure (i.e., solidification crystalline phase), and the Zr and V coarse second phase structure of comparative example 2 was smaller than that of comparative example 1.
The inventors further increased the outer diameter of the shell 1 on the basis of comparative example 2, found that when the outer diameter of the shell 1 is 400mm or more, the alloy melt 4 is completely solidified with the vicinity of the shell 1, and the cooling shell is locked by the solidified melt and cannot be continuously cast.
After each cast ingot is subjected to T6 heat treatment, the average mechanical properties of the R/2 position samples of the cast ingots of the example 1 (the test method refers to a GB/T228-2002 room temperature tensile test method for metal materials): the yield strength is 280Mpa, the tensile strength is 380Mpa and the elongation is 7%. Example 2 average mechanical properties of ingot R/2 position samples: the yield strength is 265Mpa, the tensile strength is 340Mpa and the elongation is 4.6%. Comparative example 1 average mechanical properties of ingot R/2 position samples: the yield strength was 250MPa, the tensile strength was 300MPa and the elongation was 2.1%. Comparative example 2 average mechanical properties of ingot R/2 position samples: the yield strength is 260Mpa, the tensile strength is 330Mpa and the elongation is 3.3%. Therefore, the mechanical property of the prepared cast ingot is better. .
After each cast ingot is subjected to T6 heat treatment, R/2 position sample disperse phase electron microscopy images of cast ingots of the embodiment 1, the comparative embodiment 1 and the comparative embodiment 2 are respectively shown in fig. 8 to 10, R/2 position disperse phase size (less than 300 nm) of the cast ingots of the embodiment 1 is far smaller than that of the cast ingots of the embodiment 1 and the comparative embodiment 2, and the disperse distribution density is far higher than that of the cast ingots of the embodiment 1 and the comparative embodiment 2, which indicates that the method not only refines Zr-containing and V-containing second phase tissues of large-size cast ingots, but also obtains Zr-containing and V-containing disperse properties with smaller size and higher distribution density after heat treatment, and greatly improves mechanical properties of the cast ingots, in particular to the aspect of elongation improvement.
The present invention has been described in detail with the purpose of enabling those skilled in the art to understand the contents of the present invention and to implement the same, but not to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of the present invention.
Claims (12)
1. A method for effectively adding large-size ingot casting transition elements is characterized by comprising the following steps: and (3) feeding the alloy melt containing the transition element into a crystallizer for casting, so that the cooling rate of the cast ingot from the core part to the surface of the cast ingot is not less than 2 ℃ per second, the maximum difference between the cooling rates from the core part to the R/2 part of the cast ingot is not more than 2 ℃ per second, and R is the distance from the center of the radial section of the cast ingot to the surface of the cast ingot.
2. The method for effectively adding large-size ingot transition elements according to claim 1, wherein: when only one transition element is added, the addition amount of the transition element is greater than or equal to 0.15%; when two or more transition elements are added, the addition amount of each transition element is 0.1% or more.
3. The method for effectively adding large-size ingot transition elements according to claim 1 or 2, characterized in that: the average size of the solidified crystalline phase of the transition element of the cast ingot is not more than 20 mu m, and the average size of the nano-scale dispersed phase of the cast ingot after heat treatment is not more than 300nm.
4. The method for effectively adding large-size ingot transition elements according to claim 1, wherein: the transition elements include one or more of manganese, vanadium, chromium, titanium, zirconium, erbium and scandium.
5. The method for effectively adding large-size ingot transition elements according to claim 1, wherein: when the transition element comprises manganese, the manganese accounts for 0.2-2% of the total mass of the ingot; and/or the number of the groups of groups,
when the transition element comprises vanadium, the vanadium accounts for 0.1-2% of the total mass of the ingot; and/or the number of the groups of groups,
when the transition element comprises chromium, the chromium accounts for 0.2-2% of the total mass of the ingot; and/or the number of the groups of groups,
when the transition element comprises titanium, the titanium accounts for 0.1-0.15% of the total mass of the ingot; and/or the number of the groups of groups,
when the transition element comprises zirconium, the zirconium accounts for 0.1-0.2% of the total mass of the ingot; and/or the number of the groups of groups,
when the transition element comprises erbium, the erbium accounts for 0.1-0.2% of the total mass of the ingot; and/or the number of the groups of groups,
when the transition element comprises scandium, the scandium accounts for 0.1-0.2% of the total mass of the ingot.
6. The method for effectively adding large-size ingot transition elements according to claim 1, wherein: the large-size cast ingot is an cast ingot with the radial section size of more than 400 mm.
7. The method for effectively adding large-size ingot transition elements according to claim 1, wherein: the crystallizer is internally provided with n groups of cooling units, the first to n groups of cooling units are sequentially arranged from inside to outside, n is an integer greater than or equal to 2, the first group of cooling units are provided with a cooling mechanism and coaxial with the crystallizer, the n groups of cooling units are provided with a plurality of cooling mechanisms uniformly distributed around the axial lead of the crystallizer, and the distance between the cooling mechanism of the n groups of cooling units and the axial lead is L n ，L n = (50-150 mm) × (n-1), the heat exchange coefficient of the cooling mechanism in the first to n-th sets of cooling units gradually decreases, and the cooling mechanism in the first to n-th sets of cooling units inserts into the alloy melt.
8. The method for efficient addition of large-size ingot transition elements of claim 7, wherein: the cooling mechanism comprises a hollow shell, a feeding pipeline which is communicated with the shell and is used for introducing cooling medium, and a discharging pipeline which is communicated with the shell and is used for introducing the cooling medium, wherein one end of the feeding pipeline is positioned at the bottom of the shell, and the other end of the feeding pipeline extends out of the shell and is communicated with a cooling medium source; one end of the discharging pipeline is positioned at the upper part of the shell, and the other end of the discharging pipeline extends out of the shell and is communicated with a cooling medium source;
or the cooling mechanism is an extruded bar and/or an ingot.
9. The method for efficient addition of large-size ingot transition elements of claim 8, wherein: the cooling mechanism is arranged in the crystallizer in a lifting manner through a bracket; and/or the number of the groups of groups,
the housing is cylindrical, and the housing outer diameters of the cooling mechanisms in the first to nth sets of cooling units gradually decrease.
10. The method for efficient addition of large-size ingot transition elements of claim 7, wherein: the heat exchange coefficient of the first group of cooling units is 7000-9000W/(m) 2 K) the heat exchange coefficient of the nth group of cooling units is K n ，K n ＝[(7000～8000)-2000×(n-1)]W/(m 2 ·k)。
11. The method for efficient addition of large-size ingot transition elements of claim 7, wherein: the bottom end surfaces of the cooling mechanisms in the first group to the nth group of cooling units are 80-120 mm away from the liquid level of the alloy melt.
12. The method for effectively adding large-size ingot transition elements according to claim 1, wherein: the preparation method of the alloy melt comprises the following steps:
(1) Batching according to the target components;
(2) Smelting part of raw materials in a melting furnace at 750-770 ℃, taking a furnace front sample after the furnace burden is completely melted and the components are uniform, carrying out primary refining by high-purity argon after the furnace front analysis is qualified at 720-760 ℃, wherein the refining time is 10-20min, and slagging off after refining;
(3) After slag skimming, adding the rest raw materials into a system, adding the raw materials at 730-750 ℃, stirring the melt uniformly after complete melting, refining the melt with high purity argon for a second time when the temperature of the melt is 740-750 ℃, refining for 10-20min, skimming the scum on the surface of the melt, standing after slag skimming, sampling the secondary components, and adjusting the components of the melt according to the analysis result to ensure that the chemical composition of the alloy melt is the same as that of the target components.
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