Preparation method of uniform low stress cone shaped charge liner

Abstract

A preparation method of a uniform low stress cone shaped charge liner includes the steps of multi-pass extrusion forming, vibration aging treatment, and cryogenic treatment. The step of multi-pass extrusion forming refers to 4 to 8 passes of extrusion deformation under the actions of a three-dimensional compressive stress and a deformation rate of 5 to 10 mm/s, having a deformation amount of 5 to 50% for each pass. The shaped charge liner prepared by the present invention has high dimensional accuracy, good geometric symmetry, low stress value, and excellent stability in the precise machining process and in use, which may significantly improve the penetration capability and stability of the shaped charge liner of high-explosive anti-tank warheads.

Claims

1. A method of preparing a cone-shaped charge liner having a uniform distribution of stress, the method comprising: a first step of preparing a copper rod to obtain a billet; a second step of annealing the billet in a vacuum heat treatment furnace at a temperature of 380° C. to 550° C. for 1 hour to 3 hours, and then the billet being cooled to below 100° C. with the vacuum heat treatment furnace to obtain a heat-treated billet, a vacuum degree of the vacuum heat treatment furnace is less than or equal to 3×10.sup.−3 Pa; a third step of performing a multi-pass extrusion on the heat-treated billet, the multi-pass extrusion comprising 4 to 8 passes of an extrusion deformation under a three-dimensional compressive stress and a deformation rate of 5 mm/s to 10 mm/s for each extrusion deformation, wherein a deformation amount of the heat-treated billet for each pass of the extrusion deformation is 5% to 50%, wherein the heat-treated billet is placed in a mold cavity of an extrusion die during the multi-passes extrusion to obtain an extruded cone-shaped charge liner, wherein a difference of a circumferential wall thickness of the extruded cone-shaped charge liner is less than or equal to 0.1 mm, and wherein during the multi-pass extrusion a surface of the heat-treated billet and an inner surface of the mold cavity are respectively coated with a lubricant; a fourth step of subjecting the extruded cone-shaped charge liner to a vibration aging treatment for 1 to 3 times to obtain an aged cone-shaped charge liner, wherein each vibration aging treatment occurs between the 4 to 8 passes of the extrusion deformation or after the third step is completed, and wherein a processing time of each of the vibration aging treatments is 20 min to 60 min; a fifth step of performing a heat treatment on the aged cone-shaped charge liner by placing the aged cone-shaped charge liner in the vacuum heat treatment furnace, and keeping the aged cone-shaped charge liner at 150° C. to 350° C. for 45 min to 75 min to obtain a heat-treated cone-shaped charge liner; a sixth step of placing the heat-treated cone-shaped charge liner in the mold cavity of the extrusion die and performing a fine shaping to obtain a fine-shaped cone-shaped charge liner, the fine shaping comprising 1 to 4 passes of fine-shaped extrusion deformation under the three-dimensional compressive stress and the deformation rate of 5 mm/s to 10 mm/s for each fine-shaped extrusion deformation, wherein a deformation amount of the fine-shaped cone-shaped charge liner for each pass of the fine-shaped extrusion deformation is less than or equal to 2%, wherein a difference of a circumferential wall thickness of the fine-shaped cone-shaped charge liner is less than or equal to 0.1 mm, and wherein a surface roughness of the fine-shaped cone-shaped charge liner is Ra 0.2 μm; and a seventh step of performing a cryogenic treatment to the fine-shaped cone-shaped charge liner by placing the fine-shaped cone-shaped charge liner in a cryogenic treatment device to obtain the cone-shaped charge liner having the uniform distribution of stress, wherein the cryogenic treatment uses a cryogenic medium comprising liquid nitrogen, is performed at a cooling temperature of −135° C. to −145° C., and comprises a cooling time of 15 min to 45 min, and wherein the cryogenic treatment is performed 2 to 4 times.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

(2) FIG. 1 is a diagram showing a grain structure of a red copper billet (metallographic microscope is magnified 100 times, and average grain size is about 130 μm);

(3) FIG. 2 is a diagram showing a multi-pass extrusion forming process of a double cone-shaped charge liner;

(4) FIG. 3 is a diagram showing a vibration aging treatment;

(5) FIG. 4 is a diagram showing a microstructure of a cone-shaped charge liner after a fine shaping (metallographic microscope is magnified 500 times, and average grain size is about 10 μm);

(6) FIG. 5 is a diagram of a stress test of different parts of a shaped charge liner.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) The present invention is further described below with reference to the specific embodiments.

Embodiment 1

(8) (1) Preparation of billet: taking a shaped charge liner having a shape of a double cone structure and a tapered wall thickness as an example, the shaped charge liner has an aperture of ϕ185 mm, a height of 170 mm, an inner cone depth of 162 mm, a wall thickness of 4.0 mm to 5.5 mm, a small cone angle of 30°, a large cone angle of 60°, and a transition arc R between the large and small cone angle of 152 mm; according to plastic forming theory and near-uniform plastic deformation principle, a machining allowance of 1 mm is left on the outer surface of the shaped charge liner, and a forming process boss of ϕ20 mm is designed on the top of the cone-shaped charge liner; the forming process is simulated and optimized by UG and DEFORM software, and the volume of the billet is calculated. The extruded T2 copper rod of ϕ90 mm is selected as the raw material, and the outer surface of the rod was cut to make a billet having a diameter of 88 mm and a height of 55 mm; the content of the impurity element of the T2 red copper rod is as shown in Table 1:

(9) TABLE-US-00001 TABLE 1 Content of impurity element of T2 copper rod Brand Bi Sb As Fe Ni Sn S O Zn Total T2 0.001 0.002 0.002 0.005 0.002 0.002 0.004 0.005 0.004 0.1

(10) (2) Homogenizing heat treatment: the billet obtained in step (1) is kept in a VQG-2500 intelligent temperature-controlled vacuum heat treatment furnace at 480±1° C. for 1 h, and the degree of vacuum is 1.5×10.sup.−3 Pa. After the heat treatment, the billet experiences furnace cooling until 80° C. to obtain a billet with uniform composition and structure. The hardness is from HB35 to HB38, and the grain size of copper is about 130 μm, as shown in FIG. 1.

(11) (3) Multi-pass extrusion forming: the billet obtained in step (2) is placed in the mold cavity of the extrusion die, under the actions of the three-dimensional compressive stress and a certain deformation rate, 7 passes of the extrusion deformation are performed to obtain the cone-shaped charge liner, and its forming process is shown in FIG. 2, the deformation amount arrangement for each pass is shown in Table 2. The multi-pass extrusion die includes die system, punch system, and ejection system, the multi-pass extrusion forming equipment is 1600 t hydraulic press, and deformation rate of the hydraulic machine is 5 mm/s to 10 mm/s, the die system of the extrusion die is installed on the work surface of the hydraulic press, the ejection system is connected with the ejector mechanism of the hydraulic press, the punch system is connected with the working slider of the hydraulic press, and the extrusion punch is driven by the working slider of the hydraulic press to perform extrusion. The extrusion punch cooperates with the extrusion concave die to make the billet in a three-dimensional stress state. The first pass is a large deformation cogging process to obtain a cone billet; the subsequent 2 to 6 passes are reaming extrusion (the deformation amount is less than 40%), so that the wall thickness of the shaped charge liner is gradually thinned. As the extrusion pass increases, the work hardening effect is enhanced, and the deformation amount gradually decreases; the last pass is the final shaping, which improves the dimensional accuracy and dimensional stability of the formed component, and the deformation amount is generally less than 10%. After the multi-pass extrusion forming, a shaped charge liner having the required shape, size, surface quality, and a certain mechanical property is obtained.

(12) TABLE-US-00002 TABLE 2 Process parameters of the extrusion deformation Deformation Deformation Amount Deformation Deformation Pass Arrangement Rate Temperature Lubricant 1 48% 8 mm/s 25-30° C. Tea oil 2 38% 3 31% 4 25% 5 20% 6 16% 7  6%

(13) (4) Vibration aging treatment: the IFVSR-2000 type device is used, and the formant is automatically selected by the device through sweeping frequency, which can be controlled by the acceleration amplitude during the treatment, 3 times of vibration aging treatment are set in step (3), as shown in FIG. 3. The first vibration aging treatment is performed after the second deformation pass, and the vibration time is 25 min; the second vibration aging treatment is performed after the fifth deformation pass, and the vibration time is 35 min; and the third vibration aging treatment is performed after the seventh deformation pass, and the vibration time is 45 min.

(14) (5) Recrystallization heat treatment: the cone-shaped charge liner obtained in step (4) is placed in a vacuum heat treatment furnace, and is kept at 320° C. for 60 min, then the grain boundary optimization, and the dislocation slip and dislocation climbing are performed by recrystallization annealing treatment, causing the change of the local lattice and the interface orientation of grain boundary, promoting the formation of dynamic recrystallization and twinning during annealing, and reducing the work hardening effect. The average grain size of the cone-shaped charge liner is 10 μm, as shown in FIG. 4.

(15) (6) Fine shaping: the component obtained in step (5) is placed in the mold cavity of the extrusion die, under the actions of three-dimensional compressive stress and deformation rate of 5 mm/s, 2 passes of fine shaping are performed, and the deformation amount for each pass is about 1%, the difference of circumferential wall thickness of the cone-shaped charge liner is 0.04 mm to 0.07 mm, and the surface roughness is Ra 0.12 μm to Ra 0.2 μm, and the deviation value of the taper angle is less than or equal to 2′.

(16) (7) Cryogenic treatment: the component obtained in step (6) is placed in a cryogenic treatment device, the cryogenic medium is liquid nitrogen (−196° C.), the cooling temperature is −135° C. to −145° C., and the number of the cooling times is 2, with 30 min for each time, and the time interval between the two times of cryogenic treatment is 1 h.

(17) The stress value of the above-mentioned shaped charge liner is tested by using the X-ray stress test method, the obtained stress values are shown in Table 3. The average stress value along the circumferential direction, and the direction of generatrix is from 19 MPa to 22 MPa.

(18) TABLE-US-00003 TABLE 3 Stress values of different parts of shaped charge liner Average Test part 1 2 3 4 5 value 1-small cone 23.9 20.1 21.5 22.8 24.3 22.52 2-circular arc 22.3 19.4 20.4 17.3 19.4 19.76 3-big cone 16.5 18.3 20.7 19.6 20.1 19.04 4-opening 23.2 19.7 18.3 20.2 18.6 20.00 Average value 21.475 19.375 20.225 19.975 20.6

Embodiment 2

(19) (1) Preparation of billet: taking a shaped charge liner having an inner shape of single cone structure and an equal wall thickness as an example, the shaped charge liner has an aperture of ϕ160 mm, a height of 152 mm, an inner cone depth of 138 mm, a wall thickness of 4.2 mm, and an inner taper angle of 60°; according to plastic forming theory and near-uniform plastic deformation principle, a machining allowance of 0.8 mm is left on the outer surface of the shaped charge liner formed by multi-pass extrusion forming, and a forming process boss of ϕ15 mm is designed on the top of the shaped charge liner; the forming process is simulated and optimized by UG and DEFORM software, and the volume of the billet is calculated. The stretched T2 copper rod of ϕ50 mm is selected as the raw material, and the outer surface of the rod was cut to make a billet having a diameter of 49 mm and a height of 80 mm.

(20) (2) Homogenizing heat treatment: the billet obtained in step (1) is kept in a VQG-2500 intelligent temperature-controlled vacuum heat treatment furnace at 420±1° C. for 1 h, and the degree of vacuum is 1.5×10.sup.−3 Pa. After the heat treatment, the billet experiences furnace cooling until 80° C. to obtain a billet having uniform composition and structure. The hardness is from HB32 to HB35, and the grain size of the copper is about 70 μm.

(21) (3) Multi-pass extrusion forming: the billet obtained in step (2) is placed in the mold cavity of the extrusion die, under the actions of the three-dimensional compressive stress and a certain deformation rate, 6 passes of the extrusion deformation are performed, and the deformation amount arrangement for each pass is shown in Table 4. The multi-pass extrusion die includes die system, punch system, and ejection system, the multi-pass extrusion equipment is 1600 t hydraulic press, and deformation rate of the hydraulic machine is 5 mm/s to 10 mm/s, the die system of the extrusion die is installed on the work surface of the hydraulic press, the ejection system is connected with the ejector mechanism of the hydraulic press, the punch system is connected with the working slider of the hydraulic press, and the extrusion punch is driven by the working slider of the hydraulic press to perform extrusion. The extrusion punch cooperates with the extrusion concave die to make the billet in a three-dimensional stress state. The first pass is a large deformation cogging to obtain a cone billet; the subsequent 2 to 5 passes are reaming extrusion (the deformation amount is less than 40%), so that the wall thickness of the shaped charge liner is gradually thinned. As the extrusion pass increases, the work hardening effect is enhanced, and the deformation amount gradually decreases; the last pass is the final shaping, which improves the dimensional accuracy and dimensional stability of the formed component, and the deformation amount is generally less than 10%. After the multi-pass extrusion forming, a shaped charge liner having the required shape, size, surface quality, and a certain mechanical property is obtained.

(22) TABLE-US-00004 TABLE 4 Parameters of deformation pass Deformation Deformation Amount Deformation Deformation Pass Arrangement Rate Temperature Lubricant 1 42% 6 mm/s 25-30° C. Rapeseed oil 2 30% 3 25% 4 22% 5 15% 6  8%

(23) (4) Vibration aging treatment: the IFVSR-2000 type device is used, and the formant is automatically selected by the device through sweeping frequency, which can be controlled by the acceleration amplitude during the treatment, 2 times of vibration aging treatment are set in step (3). The first vibration aging treatment is performed after the third deformation pass with the vibration time of 30 min; and the second vibration aging treatment is performed after the sixth deformation pass with the vibration time of 45 min.

(24) (5) Recrystallization heat treatment: the cone-shaped charge liner obtained in step (4) is placed in a vacuum heat treatment furnace, and kept at 250° C. for 60 min, then the grain boundary optimization, the dislocation slip and dislocation climbing are performed by recrystallization annealing treatment, causing the change of local lattice and the interface orientation of grain boundary, promoting the formation of dynamic recrystallization and twinning during annealing, and reducing the work hardening effect. The average grain size of the cone-shaped charge liner is 5 μm.

(25) (6) Fine shaping: the component obtained in step (5) is placed in the mold cavity of the extrusion die, under the actions of three-dimensional compressive stress and deformation rate of 5 mm/s, 1 pass of fine shaping are performed, and the deformation amount is about 1.5%, the difference of circumferential wall thickness of the cone-shaped charge liner is 0.03 mm to 0.05 mm, and the surface roughness is Ra 0.08 μm to Ra 0.16 μm, and the deviation value of the taper angle is less than or equal to 2′.

(26) (7) Cryogenic treatment: the component obtained in step (6) is placed in a cryogenic treatment device, the cryogenic medium is liquid nitrogen (−196° C.), the cooling temperature is −135° C. to −145° C., and the number of the cooling times is 5 with 1 h for each time, and the time interval between each two times of cryogenic treatment is 1 h.

(27) The stress value of the above-mentioned shaped charge liner is tested by using the X-ray stress test method, the obtained stress values are shown in Table 5. The average stress value along the circumferential direction and the direction of generatrix is between 18 MPa to 22 MPa.

(28) TABLE-US-00005 TABLE 5 Stress values of different parts of shaped charge liner Average Test part 1 2 3 4 5 value 1-small cone 20.6 21.3 20.9 22.8 22.7 21.66 2-circular arc 19.5 19.6 18.8 18.9 17.2 18.80 3-big cone 18.3 18.9 17.4 19.7 18.1 18.48 4-opening 21.1 20.4 19.3 18.3 16.5 19.12 Average value 19.875 20.05 19.10 19.925 18.625

(29) The results show that the low stress, uniform and fine equiaxed crystal structure shaped charge liner obtained by this method has an average grain size of less than or equal to 10 μm, the average stress value in the circumferential direction and the direction of generatrix thereof is about 22 MPa, the difference of circumferential wall thickness of the shaped charge liner is less than or equal to 0.07 mm, the surface roughness reaches Ra 0.2 μm, and the deviation value of the taper angle is less than or equal to 2′.