CN111230123B - Supporting method for preventing titanium-aluminum alloy shaped charge liner compact from sintering cracking - Google Patents
Supporting method for preventing titanium-aluminum alloy shaped charge liner compact from sintering cracking Download PDFInfo
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- CN111230123B CN111230123B CN202010127275.7A CN202010127275A CN111230123B CN 111230123 B CN111230123 B CN 111230123B CN 202010127275 A CN202010127275 A CN 202010127275A CN 111230123 B CN111230123 B CN 111230123B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
Abstract
The invention provides a supporting method for preventing titanium-aluminum alloy liner pressed compact from sintering cracking, and belongs to the technical field of sintering control. According to the invention, by calculating the sintering shrinkage rate of the titanium-aluminum alloy material, the structure of the rigid support body can be reasonably designed, the size of the obtained rigid support body is consistent with the theoretical internal size of a sintered blank obtained after sintering the liner pressed blank, the liner pressed blank can be sufficiently supported, cracking caused by excessive deformation of the liner pressed blank due to gravity and sintering cracking caused by softening and collapse of the liner pressed blank in the sintering process are avoided, and the sintering yield of the pressed blank is remarkably improved. According to the invention, the sand burying can apply inward pressure to the liner pressed compact, so that inward shrinkage of the bottom of the pressed compact in the sintering process is promoted, and further cracks generated in the pressed compact due to asynchronous sintering shrinkage are inhibited. The embodiment shows that the method can avoid the sintering cracking of the titanium-aluminum alloy liner pressed compact, and the sintering yield of the pressed compact can reach more than 99%.
Description
Technical Field
The invention relates to the technical field of sintering control, in particular to a supporting method for preventing titanium-aluminum alloy liner pressed compact from cracking during sintering.
Background
The petroleum perforating bullet is a device for perforating the concrete, rock and soil between the casing and the producing layer and providing a flow passage for oil and gas. At present, the petroleum perforating bullet mostly adopts a shaped charge structure, a liner is a key part of the shaped charge structure, and the production quality of the liner directly determines the effect of the perforating bullet. The traditional liner preparation mostly adopts the processes of smelting casting and hot isostatic pressing sintering, the smelting casting and finish machining method has higher production cost and low utilization rate of raw materials; the hot isostatic pressing sintering needs to prepare a corresponding steel sheath, the production efficiency is low, and the production cost is also increased. Therefore, the titanium-aluminum alloy thin-wall hollow conical part is mostly prepared by adopting a powder metallurgy near-net-shape forming method. The method comprises cold isostatic pressing near net shape forming and normal pressure sintering, wherein a compact slightly larger than the thin-wall hollow conical piece is prepared through cold isostatic pressing, then a sintered blank is prepared through normal pressure sintering, and the sintered blank is subjected to finish machining to obtain a final product. The method has the advantages of low production cost, high efficiency and simple process, and can be used for large-scale production of thin-wall hollow conical parts. But the phenomenon that the pressed compact collapses and deforms in the sintering process to finally cause cracking can occur, the processing size of the product is influenced, and the qualification rate of the product is reduced.
The titanium-aluminum alloy is characterized in that the sum of the mass percentages of titanium powder and aluminum powder in the raw materials is more than 70%, the sintering preparation temperature of the alloy is 1300-1600 ℃, and the melting point of aluminum is 660 ℃, so that aluminum can be melted in the sintering process and exists in the whole green body in a liquid state within a period of time, and a green compact is softened; if the adopted support is too large, the sintered blank is suspended on the support body, and the outer surface of the blank is subjected to tensile fracture under the influence of the self gravity.
Disclosure of Invention
In view of the above, the present invention provides a supporting method for preventing sintering cracking of a titanium-aluminum alloy liner compact. The method can avoid the problem of green compact sintering cracking caused by deformation, softening and collapse of the titanium-aluminum alloy liner green compact in the sintering process, and improve the sintering qualification rate of the green compact.
In order to achieve the purpose of the invention, the invention provides the following technical scheme:
the invention provides a supporting method for preventing a titanium-aluminum alloy shaped charge liner pressed compact from sintering and cracking, which comprises the following steps:
(1) measuring the sintering shrinkage sigma of the titanium-aluminum alloy material;
(2) respectively calculating theoretical sizes of the titanium-aluminum alloy sintered blank according to the formula a, the formula b and the formula c, wherein the theoretical sizes comprise a theoretical bottom inner diameter size, a theoretical inner top platform diameter and a theoretical inner height:
Dsintered compact＝DGreen compactX (1- σ) + σ/cos θ formula a;
in the formula a, DSintered compactIs the theoretical bottom inner diameter of the shaped charge liner sintering blank, mm;
Dgreen compactThe bottom inner diameter of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
the thickness of the liner pressed compact is mm;
theta is 1/2 degree of cone angle of the liner pressed compact;
dsintered compact＝dGreen compactX (1- σ) + σ/cos θ formula b;
in the formula b, dSintered compactIs the diameter of a theoretical inner top platform of a shaped charge liner sintering blank, and is mm;
dgreen compactThe diameter of the internal top platform of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
the thickness of the liner pressed compact is mm;
theta is 1/2 degree of cone angle of the liner pressed compact;
Hsintered compact＝HGreen compactX (1- σ) +0.5h σ formula c;
in the formula c, HSintered compactIs the theoretical internal height of the shaped charge liner sintered blank, mm;
Hgreen compactThe internal height of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
h is the height of the inner platform of the liner pressed compact from the top, and is mm;
(3) determining the size of a rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank obtained in the step (2), and preparing the rigid support body according to the determined size of the rigid support body; the rigid support body is of a truncated hollow cone structure, and the cone angle, the bottom outer diameter, the outer top platform diameter and the outer height of the rigid support body are respectively the same as the cone angle, the theoretical bottom inner diameter, the theoretical inner top platform diameter and the theoretical inner height of the titanium-aluminum alloy sintered blank;
(4) and placing the rigid support body at the central position inside the liner pressed blank, and burying sand outside the liner pressed blank.
Preferably, the sum of the mass percent of the titanium element and the mass percent of the aluminum element in the titanium-aluminum alloy is more than or equal to 70 percent.
Preferably, the method for measuring the sintering shrinkage σ of the titanium-aluminum alloy material includes the following steps:
(a) preparing a titanium-aluminum alloy standard pressed compact, and measuring the length of the standard pressed compact before sintering;
(b) sintering the standard pressed compact by using the same sintering scheme as that for sintering the titanium-aluminum alloy liner pressed compact;
(c) measuring the sintered length of the standard pressed compact, and calculating the sintering shrinkage factor sigma of the titanium-aluminum alloy material according to the formula d;
σ＝1-(Lrear end/LFront side) X 100% of formula d;
in the formula d, sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
Lrear endThe length of the sintered standard pressed compact is mm;
Lfront sideLength before sintering of standard compact, mm.
Preferably, the standard titanium-aluminum alloy compact has a cylindrical shape and a size of Φ 10 × 50 mm.
Preferably, the material of the rigid support body has a melting point of more than 2000 ℃ and a thermal expansion coefficient of less than 9 x 10 under the condition of 2000 DEG C-6A metallic material at/° c.
Preferably, the wall thickness of the rigid support body is 0.015-0.035 times of the outer diameter of the bottom of the rigid support body.
Preferably, the sand used for sand burying is zirconia sand, the particle size of the zirconia sand is 1-5 mm, and the thickness of the sand burying is 0.25-0.5 times of the external height of the liner pressed compact.
Preferably, before the rigid support is placed at the central position inside the liner compact, the method further comprises the step of performing pretreatment on the rigid support, wherein the pretreatment comprises the following steps:
brushing a boron nitride alcohol solution on the surface of the rigid support body, brushing the boron nitride alcohol solution on the surface of the rigid support body, and drying the rigid support body; the mass fraction of boron nitride in the boron nitride alcohol solution is 20-50%.
The invention provides a method for preventing sintering cracking of a titanium-aluminum alloy shaped charge liner pressed compact, which can reasonably design a rigid support body structure by calculating the sintering shrinkage rate of a titanium-aluminum alloy material, wherein the size of the obtained rigid support body is consistent with the theoretical internal size of a shaped charge liner sintering blank, so that the rigid support body structure can play a sufficient supporting role on the shaped charge liner pressed compact, and cracking caused by excessive deformation of the shaped charge liner pressed compact due to gravity and junction cracking caused by softening and collapse in the sintering process are avoided, thereby obviously improving the sintering qualification rate of the pressed compact; meanwhile, the rigid support body can be repeatedly used, so that the production cost can be greatly reduced. According to the invention, the inside pressure can be applied to the liner pressed compact by burying sand outside the liner pressed compact, so that the inward shrinkage of the bottom of the pressed compact in the sintering process is promoted, and further, the cracks generated in the pressed compact due to asynchronous sintering shrinkage are inhibited. The embodiment result shows that the method provided by the invention can avoid sintering cracking of the titanium-aluminum alloy liner pressed compact, and the sintering yield of the pressed compact can reach more than 99%.
Drawings
FIG. 1 is a schematic view showing the structure of a liner compact of a titanium-aluminum alloy in example 1;
FIG. 2 is a schematic structural view of a sintered compact of the liner of a titanium-aluminum alloy in example 1;
FIG. 3 is a schematic structural view of the rigid support in example 1;
FIG. 4 is a physical representation of the rigid support of example 1;
FIG. 5 is a schematic illustration of sand burial of a titanium-aluminum-based alloy liner compact, wherein 1-the liner compact, 2-the rigid support, 3-the zirconia sand;
FIG. 6 is a schematic view of a sintered compact of a titanium-aluminum alloy liner in comparative example 1.
Detailed Description
The invention provides a method for preventing a titanium-aluminum alloy liner pressed compact from sintering and cracking, which comprises the following steps:
(1) measuring the sintering shrinkage sigma of the titanium-aluminum alloy material;
(2) respectively calculating theoretical sizes of the titanium-aluminum alloy sintered blank according to the formula a, the formula b and the formula c, wherein the theoretical sizes comprise a theoretical bottom inner diameter size, a theoretical inner top platform diameter and a theoretical inner height:
Dsintered compact＝DGreen compactX (1- σ) + σ/cos θ formula a;
in the formula a, DSintered compactIs the theoretical bottom inner diameter of the shaped charge liner sintering blank, mm;
Dgreen compactThe bottom inner diameter of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
the thickness of the liner pressed compact is mm;
theta is 1/2 degree of cone angle of the liner pressed compact;
dsintered compact＝dGreen compactX (1- σ) + σ/cos θ formula b;
in the formula b, dSintered compactIs the diameter of a theoretical inner top platform of a shaped charge liner sintering blank, and is mm;
dgreen compactThe diameter of the internal top platform of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
the thickness of the liner pressed compact is mm;
theta is 1/2 degree of cone angle of the liner pressed compact;
Hsintered compact＝HGreen compactX (1- σ) +0.5h σ formula c;
in the formula c, HSintered compactIs a sintered blank of the shaped charge linerThe theoretical internal height of (d), mm;
Hgreen compactThe internal height of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
h is the height of the inner platform of the liner pressed compact from the top, and is mm;
(3) determining the size of a rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank obtained in the step (2), and preparing the rigid support body according to the determined size of the rigid support body; the rigid support body is of a truncated hollow cone structure, and the cone angle, the bottom outer diameter, the outer top platform diameter and the outer height of the rigid support body are respectively the same as the cone angle, the theoretical bottom inner diameter, the theoretical inner top platform diameter and the theoretical inner height of the titanium-aluminum alloy sintered blank;
(4) and placing the rigid support body at the central position inside the liner pressed blank, and burying sand outside the liner pressed blank.
The invention firstly determines the sintering shrinkage sigma of the titanium-aluminum alloy material. In the invention, the sum of the mass percentages of the titanium element and the aluminum element in the titanium-aluminum alloy is preferably more than or equal to 70 percent, and more preferably more than or equal to 75 percent; in the invention, the other elements in the titanium-aluminum alloy are preferably one or two of Nb, Zr, Ta, V and Mo, the mass percentage of the other elements in the alloy material is not particularly required, and the sum of the mass percentage of the other elements in the alloy material and the mass percentage of the Ti element and the aluminum element is equal to 100%. In the specific embodiment of the invention, the titanium-aluminum alloy material preferably contains 75% by mass of titanium and aluminum, 15% by mass of niobium, and 10% by mass of tantalum; or the mass percentage of the titanium and the aluminum is 70 percent, the mass percentage of the zirconium is 20 percent, and the mass percentage of the molybdenum is 10 percent; or the mass percent of the titanium and the aluminum is 80 percent, the mass percent of the tantalum is 15 percent, and the mass percent of the molybdenum is 5 percent. In the present invention, the method for measuring the sintering shrinkage σ of the titanium-aluminum alloy material preferably includes the steps of:
(a) preparing a titanium-aluminum alloy standard pressed compact, and measuring the length of the standard pressed compact before sintering;
(b) sintering the standard pressed compact by using the same sintering scheme as that for sintering the titanium-aluminum alloy liner pressed compact;
(c) measuring the sintered length of the standard pressed compact, and calculating the sintering shrinkage factor sigma of the titanium-aluminum alloy material according to the formula d;
σ＝1-(Lrear end/LFront side) X 100% of formula d;
in the formula d, sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
Lrear endThe length of the sintered standard pressed compact is mm;
Lfront sideLength before sintering of standard compact, mm.
In the present invention, the standard titanium-aluminum alloy compact is preferably cylindrical and has a size of preferably Φ 10 × 50 mm. In the present invention, the method for preparing the titanium-aluminum alloy standard compact is the same as the method for preparing the titanium-aluminum alloy liner compact. The invention preferably uses a vernier caliper to measure the length L of the standard pressed compact before sinteringFront side。
In the invention, the sintering method of the standard pressed compact is the same as the scheme of sintering the titanium-aluminum alloy liner pressed compact, in the specific embodiment of the invention, the sintering is preferably normal-pressure sintering, the sintering is preferably carried out in an argon protective atmosphere, and the sintering temperature is preferably 1300-1600 ℃, more preferably 1400-1500 ℃; the time is preferably 1 to 5 hours, and more preferably 2 to 4 hours. The present invention preferably performs the sintering in a sintering furnace. In the present invention, the standard green compact is preferably placed in a lateral manner during sintering.
After the standard pressed compact is sintered, the length L of the sintered standard pressed compact is preferably measured by using a vernier caliperRear endAnd calculating the sintering shrinkage sigma of the titanium-aluminum alloy material according to the formula d.
After the sintering shrinkage sigma of the titanium-aluminum alloy material is obtained, the theoretical size of the titanium-aluminum alloy sintered blank is calculated according to the formula a, the formula b and the formula c. Before calculating the theoretical size of the titanium-aluminum alloy sintered compact, the present invention preferably constructs a titanium-aluminum alloy compact. The invention has no special requirements on the size of the titanium-aluminum alloy liner compact, and the method is applicable to titanium-aluminum alloy liner compacts with any size. The method for producing the titanium-aluminum alloy green compact of the present invention is not particularly limited, and a method for producing a titanium-aluminum alloy green compact known to those skilled in the art may be used.
In the present invention, the theoretical dimensions of the titanium-aluminum alloy sintered compact include a theoretical bottom inner diameter dimension, a theoretical inner top platform diameter, and a theoretical inner height. Because the titanium-aluminum alloy liner compact shrinks in the sintering process, after the sintering shrinkage factor sigma of the titanium-aluminum alloy material is obtained, the theoretical size of the sintered compact obtained after the titanium-aluminum alloy compact is sintered can be calculated.
After the theoretical size of the titanium-aluminum alloy sintered blank is obtained, the invention determines the size of the rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank and prepares the rigid support body. In the invention, the rigid support body is in a truncated hollow cone structure, and the cone angle, the bottom outer diameter, the outer top platform diameter and the outer height of the rigid support body are respectively the same as the cone angle, the theoretical bottom inner diameter, the theoretical inner top platform diameter and the theoretical inner height of the titanium-aluminum alloy sintered blank. In the present invention, the material of the rigid support is preferably selected from the group consisting of a material having a melting point of > 2000 ℃ and a coefficient of thermal expansion of < 9X 10 at 2000 ℃-6A metallic material of/° c, more preferably one of molybdenum, a molybdenum alloy, tantalum, a tantalum alloy, tungsten, or a tungsten alloy; the present invention does not require any particular shaping method for the rigid support, and can be carried out by shaping means known to those skilled in the art, such as spin forming or powder metallurgy. In the invention, the thermal expansion coefficient of the rigid support body material is less than that of the titanium-aluminum alloy material, so that the cracking of the liner blank caused by the thermal expansion of the rigid support body can be avoided to the greatest extent.
In the invention, the size of the rigid support body is consistent with the theoretical internal size of the liner sintering blank, so that the liner sintering blank can be supported sufficiently, cracking caused by excessive deformation of the liner sintering blank due to gravity and sintering cracking caused by softening and collapse in the sintering process are avoided, and the sintering yield of the liner is improved remarkably; meanwhile, the rigid support body can be repeatedly used, so that the production cost can be greatly reduced.
In the present invention, the rigid support is preferably subjected to a pretreatment, and the pretreatment preferably includes the steps of:
and (3) brushing an alcohol solution of boron nitride on the surface of the rigid support body and drying.
The invention has no special requirement on the brushing mode, and the boron nitride alcohol solution can be uniformly brushed on the surface of the rigid support body by using the brushing mode which is well known to the technical personnel in the field. In the invention, the mass fraction of boron nitride in the boron nitride alcohol solution is preferably 20 to 50%, and more preferably 30 to 40%. In the present invention, the drying is preferably performed in the shade. In the invention, the boron nitride can prevent the sintered blank from being adhered to the support, and the mould coated with the boron nitride alcohol solution is easy to take out and can be reused.
After the rigid support body is obtained, the rigid support body is placed in the center of the inside of the liner pressed compact, and sand burying is carried out on the outside of the liner pressed compact. When the rigid support body is placed, the central axis of the rigid support body is superposed with the central axis of the liner pressed compact. In the invention, the sand used for sand burying is preferably zirconia sand, and the particle size of the zirconia sand is preferably 1-5 mm, and more preferably 2-4 mm; the thickness of the embedded sand is preferably 0.25 to 0.5 times, more preferably 0.3 to 0.4 times of the external height of the liner pressed compact.
After the operation is finished, the invention sinters the liner pressed compact embedded with sand and the rigid support body in the liner pressed compact. The sintering mode is not particularly required by the invention, and a liner compact sintering mode well known to those skilled in the art can be used, and in the specific embodiment of the invention, the sintering is preferably normal pressure sintering. According to the invention, the inside pressure can be applied to the liner pressed compact by burying sand outside the liner pressed compact, so that the inward shrinkage of the bottom of the pressed compact in the sintering process is promoted, and further, the cracks generated in the pressed compact due to asynchronous sintering shrinkage are inhibited.
The supporting method for preventing sintering cracking of the titanium-aluminum alloy liner compact according to the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
(1) Measurement of sintering shrinkage σ of titanium-aluminum alloy Material
Selecting a titanium-aluminum alloy material, wherein the mass percentage of titanium powder and aluminum powder is 75%, the mass percentage of niobium powder is 15%, and the mass percentage of tantalum powder is 10%, pressing the mixed powder into a pressed compact by adopting a process of 300MPa and pressure maintaining for 20min, and processing the pressed compact into a pressed compact with the standard size of phi 10 multiplied by 50 mm; placing the pressed compact in an atmosphere sintering furnace, and carrying out normal pressure sintering by adopting a process of preserving heat at 1500 ℃ for 3 hours and protecting atmosphere by argon; the dimension of the sintered blank is measured to be phi 8.9 multiplied by 44.5mm, and the length direction shrinkage rate sigma of the titanium-aluminum alloy material is calculated to be 11 percent under the condition of heat preservation at 1500 ℃ for 3 hours.
(2) Calculating theoretical size of titanium-aluminum alloy sintered blank
A shape liner pressed compact is shown in figure 1, the inner diameter of the pressed compact is 158mm, the diameter of an inner top platform is 10.2mm, the inner height is 105.54mm, the wall thickness is 10.4mm, the height of the inner platform from the top of the pressed compact is 31mm, the taper angle is 70 degrees, the shrinkage rate is measured according to the step (1), the theoretical size of a titanium-aluminum alloy sintered compact is calculated according to the formulas a, b and c, the calculation result is that the theoretical inner diameter size, the theoretical inner top platform diameter and the theoretical inner height of the shape liner sintered compact are 141.56mm, 10.01mm and 93.53mm respectively, and the schematic diagram of the shape liner sintered compact is shown in figure 2;
(3) determining the size of the rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank and preparing the rigid support body
The dimensional schematic of the rigid support is shown in fig. 3, the cone angle is 70 ° as the cone angle of the liner compact; the outer diameter size, outer tip platform diameter and outer height were 141.56mm, 10.01mm and 93.53mm, respectively; the wall thickness of the rigid support body is 3 mm; the support body is made by spinning a molybdenum plate with the thickness of 3.5mm and then performing finish machining, and the actual figure of the obtained rigid support body is shown in figure 4;
(4) coating an alcohol solution of boron nitride with the mass fraction of 20% on the outer surface of the support body, drying in the shade, and placing the support body in the center of the inside of the liner pressed compact to ensure that the distance between the bottom edge of the support body and the inner ring of the pressed compact is consistent;
(5) sand burying of Ti-Al alloy shaped charge
And (3) paving a layer of zirconia sand with the height of 33.5mm outside the pressed blank for placing the support in the step (4), wherein the grain diameter of the zirconia sand is 2mm, the schematic diagram of sand burying is shown in fig. 5, and in the fig. 5, 1 is a liner pressed blank, 2 is a rigid support, and 3 is the zirconia sand.
And (3) sintering the shaped charge liner pressed blank embedded with the sand and the rigid support body in the shaped charge liner pressed blank at the normal pressure, wherein the sintering temperature is 1500 ℃, and the heat preservation time is 3 hours, so as to obtain the titanium-aluminum alloy shaped charge liner sintered blank. The internal diameter size, internal top platform diameter and internal height of the sintered compact were found to be 141.86mm, 9.94mm and 94.82mm, respectively.
The inner and outer walls of the sintered blank of the titanium-aluminum alloy shaped charge liner after sintering have no obvious cracks and have no serious deformation and cracking phenomena. The error range of the actually measured value and the calculated value of the actually measured inner height of the sintering blank is less than 3 percent of the calculated value, the error range of the actually measured value and the calculated value of the inner diameter of the sintering blank is less than 3 percent of the calculated value, and the bottom of the sintering blank is close to a perfect circle and meets the standard of qualified inspection, so the method provided by the invention can process the shaped charge liner product meeting the requirements.
The titanium-aluminum alloy liner green compact is sintered in batches according to the method, and the sintering qualification rate of the obtained titanium-aluminum alloy liner green compact is more than 99 percent through testing.
Example 2
(1) Measurement of sintering shrinkage σ of titanium-aluminum alloy Material
Selecting a titanium-aluminum alloy material, wherein the mass percentage of titanium powder and aluminum powder is 70%, the mass percentage of zirconium powder is 20%, and the mass percentage of molybdenum powder is 10%, pressing the mixed powder into a pressed blank by adopting a 250MPa pressure maintaining process for 30min, and processing the pressed blank into a pressed blank with the standard size of phi 10 multiplied by 50 mm; placing the pressed compact in an atmosphere sintering furnace, and sintering at the normal pressure by adopting a process of preserving heat at 1550 ℃ for 4 hours and protecting the atmosphere by argon; the dimension of the sintered blank is measured to be phi 8.72 multiplied by 43.51mm, and the calculated shrinkage factor sigma of the titanium-aluminum alloy material in the length direction under the condition of temperature preservation at 1550 ℃ for 4h is 13 percent.
(2) Calculating theoretical size of titanium-aluminum alloy sintered blank
A liner pressed compact, its pressed compact internal diameter 158mm, internal top end platform diameter 10.2mm, internal height 105.54mm, wall thickness 9.86mm, internal platform apart from pressed compact top height 30mm, cone angle 70 °, measure the shrinkage factor according to step (1), according to equation a, equation b and equation c calculate the theoretical size of the titanium-aluminium alloy sintered compact separately, the result of calculation is that the theoretical internal diameter size, theoretical internal top end platform diameter and theoretical internal height of the liner sintered compact are 138.51mm, 9.92mm and 93.77mm respectively;
(3) determining the size of the rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank and preparing the rigid support body
The cone angle of the rigid support body is 70 degrees which is the same as the cone angle of the liner pressed compact; the outer diameter dimension, outer tip platform diameter and outer height are 138.51mm, 9.92mm and 93.77mm, respectively; the wall thickness of the rigid support is 3.5 mm; the support body is prepared by a method of preparing a sintering blank slightly larger than the size of the support body by tungsten powder through a powder metallurgy process and then finely processing the sintering blank;
(4) coating an alcohol solution of boron nitride with the mass fraction of 20% on the outer surface of the support body, drying in the shade, and placing the support body in the center of the inside of the liner pressed compact to ensure that the distance between the bottom edge of the support body and the inner ring of the pressed compact is consistent;
(5) sand burying of Ti-Al alloy shaped charge
And (4) paving a layer of zirconia sand with the height of 40mm outside the pressed blank for placing the support in the step (4), wherein the grain diameter of the zirconia sand is 3 mm.
And (3) sintering the shaped charge liner pressed blank embedded with the sand and the rigid support body in the shaped charge liner pressed blank at the normal pressure, wherein the sintering temperature is 1550 ℃, and the heat preservation time is 4 hours, so as to obtain the titanium-aluminum alloy shaped charge liner sintered blank. The internal diameter size, internal top platform diameter and internal height of the sintered compact were found to be 140.02mm, 9.96mm and 94.53mm, respectively.
The inner and outer walls of the sintered blank of the titanium-aluminum alloy shaped charge liner after sintering have no obvious cracks and have no serious deformation and cracking phenomena. The error range of the actually measured value and the calculated value of the actually measured inner height of the sintering blank is less than 3 percent of the calculated value, the error range of the actually measured value and the calculated value of the inner diameter of the sintering blank is less than 3 percent of the calculated value, and the bottom of the sintering blank is close to a perfect circle and meets the standard of qualified inspection, so the method provided by the invention can process the shaped charge liner product meeting the requirements.
Example 3
(1) Measurement of sintering shrinkage σ of titanium-aluminum alloy Material
Selecting a titanium-aluminum alloy material, wherein the mass percentage of titanium powder and aluminum powder is 80%, the mass percentage of tantalum powder is 15%, and the mass percentage of molybdenum powder is 5%, pressing the mixed powder into a pressed compact by adopting a 280MPa pressure maintaining process for 30min, and processing the pressed compact into a standard size pressed compact with the diameter of phi 10 multiplied by 50 mm; placing the pressed compact in an atmosphere sintering furnace, and carrying out normal pressure sintering by adopting a process of preserving heat at 1600 ℃ for 4 hours and protecting the atmosphere by argon; the dimension of the sintered blank is measured to be phi 8.86 multiplied by 44.27mm, and the calculated shrinkage factor sigma of the titanium-aluminum alloy material in the length direction is 11.5 percent under the condition of heat preservation at 1600 ℃ for 4 hours.
(2) Calculating theoretical size of titanium-aluminum alloy sintered blank
A liner pressed compact, its pressed compact internal diameter 158mm, internal top end platform diameter 10.2mm, internal height 105.54mm, wall thickness 10mm, internal platform distance pressed compact top height 30.4mm, cone angle 70 degrees, according to step (1) measure the shrinkage factor, according to formula a, formula b and formula c calculate the theoretical size of the titanium-aluminium alloy sintered compact separately, the result of calculation is that the theoretical internal diameter size, theoretical internal top end platform diameter and theoretical internal height of the liner sintered compact are 140.77mm, 9.94mm and 95.15mm respectively;
(3) determining the size of the rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank and preparing the rigid support body
The cone angle of the rigid support body is 70 degrees which is the same as the cone angle of the liner pressed compact; the outer diameter size, outer tip platform diameter and outer height were 140.77mm, 9.94mm and 95.15mm, respectively; the wall thickness of the rigid support is 3.5 mm; the support body is prepared by a method of preparing a sintering blank slightly larger than the size of the support body by molybdenum powder through a powder metallurgy process and then finely processing the sintering blank;
(4) coating an alcohol solution of boron nitride with the mass fraction of 40% on the outer surface of the support body, drying in the shade, and placing the support body in the center of the inside of the liner pressed compact to ensure that the distance between the bottom edge of the support body and the inner ring of the pressed compact is consistent;
(5) sand burying of Ti-Al alloy shaped charge
And (4) paving a layer of zirconia sand with the height of 35mm outside the pressed blank for placing the support body in the step (4), wherein the grain diameter of the zirconia sand is 3 mm.
And (3) sintering the shaped charge liner pressed blank embedded with the sand and the rigid support body in the shaped charge liner pressed blank at normal pressure, wherein the sintering temperature is 1600 ℃, and the heat preservation time is 4 hours, so as to obtain the titanium-aluminum alloy shaped charge liner sintered blank. The internal diameter size, internal top platform diameter and internal height of the sintered compact were found to be 142.6mm, 9.93mm and 96.84mm, respectively.
The inner and outer walls of the sintered blank of the titanium-aluminum alloy shaped charge liner after sintering have no obvious cracks and have no serious deformation and cracking phenomena. The error range of the actually measured value and the calculated value of the actually measured inner height of the sintering blank is less than 3 percent of the calculated value, the error range of the actually measured value and the calculated value of the inner diameter of the sintering blank is less than 3 percent of the calculated value, and the bottom of the sintering blank is close to a perfect circle and meets the standard of qualified inspection, so the method provided by the invention can process the shaped charge liner product meeting the requirements.
Comparative example 1
The same composition and size compacts and the same sintering process as in example 3 were used, except that no rigid support was added and no sand burying was performed in this comparative example.
FIG. 6 shows a schematic diagram of a sintered compact of the liner made of a titanium-aluminum alloy obtained after sintering. The bottom of the sintering blank is cracked, the inner diameter size, the diameter of the internal top platform and the internal height of the sintering blank are measured to be 155.21mm, 9.96mm and 88.35mm respectively, and the obtained sintering blank does not meet the qualified standard of inspection due to deformation and bottom cracking.
As can be seen from the above examples and comparative examples, the method of the present invention can avoid the problem of sintering cracking of the titanium-aluminum alloy liner compact due to softening and collapse during sintering, and the sintering yield of the obtained compact is high.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A supporting method for preventing sintering cracking of a titanium-aluminum alloy liner compact comprises the following steps:
(1) measuring the sintering shrinkage sigma of the titanium-aluminum alloy material;
(2) respectively calculating theoretical sizes of the titanium-aluminum alloy sintered blank according to the formula a, the formula b and the formula c, wherein the theoretical sizes comprise a theoretical bottom inner diameter size, a theoretical inner top platform diameter and a theoretical inner height:
Dsintered compact＝DGreen compactX (1- σ) + σ/cos θ formula a;
in the formula a, DSintered compactIs the theoretical bottom inner diameter of the shaped charge liner sintering blank, mm;
Dgreen compactThe bottom inner diameter of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
the thickness of the liner pressed compact is mm;
theta is 1/2 degree of cone angle of the liner pressed compact;
dsintered compact＝dGreen compactX (1- σ) + σ/cos θ formula b;
in the formula b, dSintered compactIs the diameter of a theoretical inner top platform of a shaped charge liner sintering blank, and is mm;
dgreen compactThe diameter of the internal top platform of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
the thickness of the liner pressed compact is mm;
theta is 1/2 degree of cone angle of the liner pressed compact;
Hsintered compact＝HGreen compactX (1- σ) +0.5h σ formula c;
in the formula c, HSintered compactIs the theoretical internal height of the shaped charge liner sintered blank, mm;
Hgreen compactThe internal height of the liner pressed compact is mm;
sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
h is the height of the inner platform of the liner pressed compact from the top, and is mm;
(3) determining the size of a rigid support body according to the theoretical size of the titanium-aluminum alloy sintered blank obtained in the step (2), and preparing the rigid support body according to the determined size of the rigid support body; the rigid support body is of a truncated hollow cone structure, and the cone angle, the bottom outer diameter, the outer top platform diameter and the outer height of the rigid support body are respectively the same as the cone angle, the theoretical bottom inner diameter, the theoretical inner top platform diameter and the theoretical inner height of the titanium-aluminum alloy sintered blank;
(4) and placing the rigid support body at the central position inside the liner pressed blank, and burying sand outside the liner pressed blank.
2. The method according to claim 1, wherein the sum of the mass percentages of the titanium element and the aluminum element in the titanium-aluminum alloy is not less than 70%.
3. The method according to claim 1, wherein the step of determining the sintering shrinkage σ of the titanium-aluminum alloy material comprises the steps of:
(a) preparing a titanium-aluminum alloy standard pressed compact, and measuring the length of the standard pressed compact before sintering;
(b) sintering the standard pressed compact by using the same sintering scheme as that for sintering the titanium-aluminum alloy liner pressed compact;
(c) measuring the sintered length of the standard pressed compact, and calculating the sintering shrinkage factor sigma of the titanium-aluminum alloy material according to the formula d;
σ＝1-(Lrear end/LFront side) X 100% of formula d;
in the formula d, sigma is the sintering shrinkage of the titanium-aluminum alloy material,%;
Lrear endThe length of the sintered standard pressed compact is mm;
Lfront sideLength before sintering of standard compact, mm.
4. A method according to claim 3, characterized in that the standard titanium aluminium alloy compact is cylindrical in shape and has dimensions Φ 10 x 50 mm.
5. The method according to claim 1, wherein the rigid support is made of a material having a melting point > 2000 ℃ and a coefficient of thermal expansion < 9 x 10 at 2000 ℃-6A metallic material at/° c.
6. The method of claim 1 or 5, wherein the wall thickness of the rigid support is 0.015 to 0.035 times the outer diameter of the bottom of the rigid support.
7. The method according to claim 1, wherein the sand used for burying the sand is zirconia sand having a particle size of 1 to 5mm and a height of 0.25 to 0.5 times an outer height of the liner compact.
8. The method of claim 1, further comprising pre-processing the rigid support prior to placing the rigid support in a central position within the liner compact, the pre-processing comprising:
coating an alcohol dispersion liquid of boron nitride on the surface of the rigid support body and drying; the mass fraction of boron nitride in the boron nitride alcohol dispersion liquid is 20-50%.
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