Defect length design method of electron beam pre-control shell

Abstract

According to the defect length design method of the electron beam pre-control shell, the defect length l is controlled by four parameters including the target design tensile strength sigma 1 of the electron beam pre-control shell, the tensile strength sigma 0 of a shell base material, the shell thickness L and the included angle theta between the incident direction of an electron beam and the normal direction of the surface of the shell. According to the method, the defect length of the electron beam pre-control shell can be quantitatively controlled, the accuracy is high, the method is simple and practical, and the method has important theoretical and economic values and is worthy of large-scale popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of material microstructure design, and relates to a method for designing the defect length of an electron beam pre-controlled shell. Background Art

[0002] The electron beam projectile pre-control technology is a new type of pre-control fragment forming technology that does not require cutting the projectile like mechanical grooving. It has the advantages of improving the fragment killing power of the projectile and ensuring the structural strength, and has a very wide application prospect in the warhead of high chamber pressure guided projectiles.

[0003] After electron beam pre-control, a modified area grid will be formed on the projectile body, and holes will be reserved at the bottom of the modified area, resulting in a decrease in the overall strength, which poses a certain potential safety hazard in the launch safety of high chamber pressure guided projectiles. To eliminate the hidden danger and ensure launch safety, it is necessary to ensure that the designed strength of the pre-controlled projectile body is higher than the service strength.

[0004] However, at present, complex microstructure transformations occur in the projectile body after electron beam pre-control, the microstructure distribution is non-linear and non-uniform, the law of mechanical property transformation is not clear, and there is a lack of a mature theoretical method to guide the design of hole defects after electron beam pre-control. There is an urgent need for a method for designing the defect length of an electron beam pre-controlled shell to ensure that the designed strength of the pre-controlled projectile body is higher than the service strength. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for designing the defect length of an electron beam pre-controlled shell, which can quantitatively control the defect length of the electron beam pre-controlled shell, and has the characteristics of being simple, practical, highly accurate and low cost.

[0006] The technical solution adopted by the present invention to solve the above technical problem is: a method for designing the defect length of an electron beam pre-controlled shell, characterized in that: the defect length l is controlled by four parameters: the target design tensile strength σ1 of the electron beam pre-controlled shell, the tensile strength σ0 of the shell matrix material, the shell thickness L, and the angle θ between the electron beam incident direction and the shell surface normal direction. The defect length l is:

[0007]

[0008] Further, the shell matrix material is 40CrMnSiB material, and a grid-shaped modified area is formed on the surface of the electron beam pre-controlled shell after electron beam pre-control.

[0009] Preferably, the angle θ between the electron beam incident direction and the shell surface normal direction is 30° ± 1°, and most preferably 30°.

[0010] Further, the tensile strength σ0 of the shell matrix material is the self-strength of the shell before electron beam pre-control, which is generally used as the technical input document for the electron beam pre-control process and has been obtained through previous tensile experiments.

[0011] Finally, the defect is a hole defect formed due to the failure to timely backfill the shell material during electron beam modification. The hole defect shows an irregular strip shape with an aspect ratio greater than 1 in the radial cross-section of the shell. The hole defect is located inside the shell, surrounded by a martensite modified zone structure, and the martensite modified zone structure is surrounded by a tempered troostite structure of the steel matrix.

[0012] Compared with the prior art, the advantages of the present invention are as follows:

[0013] By quantitatively controlling the defect length l of the electron beam pre-controlled shell through four parameters: the target design tensile strength σ1 of the electron beam pre-controlled shell, the tensile strength σ0 of the shell matrix material, the shell thickness L, and the angle θ between the electron beam incident direction and the normal direction of the shell surface, the average value of the strength experiment of the electron beam pre-controlled shell after defect processing with a length of l can have an error within 5% of the target design strength. The present invention can quantitatively control the defect length of the electron beam pre-controlled shell, with high accuracy, simplicity and practicality, and has important theoretical and economic value, worthy of large-scale popularization and use. Description of the Drawings

[0014] Figure 1 is the electron microscope image of the material structure after electron beam pre-control provided by the present invention;

[0015] Figure 2 are the CT images of the electron beam pre-controlled metal shells 1#, 2#, and 3#;

[0016] Figure 3 is the schematic diagram of the electron beam pre-controlled metal shell. Detailed Embodiments

[0017] The present invention will be further described in detail below in conjunction with the embodiments of the drawings.

[0018] As Figures 1-3 shown, a method for designing the defect length of an electron beam pre-controlled shell, the defect length l is controlled by four parameters: the target design tensile strength σ1 of the electron beam pre-controlled shell, the tensile strength σ0 of the shell matrix material, the shell thickness L, and the angle θ between the electron beam incident direction and the normal direction of the shell surface. The defect length l is:

[0019]

[0020] The shell matrix material is 40CrMnSiB material, and the surface of the electron beam pre-controlled shell forms a grid-like modified zone after electron beam pre-control.

[0021] The angle θ between the electron beam incident direction and the normal direction of the shell surface is 30°.

[0022] The tensile strength σ0 of the housing base material is the strength of the housing itself before electron beam pre-control. Generally, it is used as the technical input document for the electron beam pre-control process and has been obtained through previous tensile experiments.

[0023] The length l of the defect refers to the average value of the defect lengths after actual electron beam processing, which can be obtained from the CT image of the metal housing cross-section. In actual operation, the average value of the lengths of the top ten longest defects in a certain CT cross-section can be selected. The defect is a hole defect formed due to the failure of the housing material to be backfilled in time during electron beam modification. The hole defect shows an irregular long strip shape with an aspect ratio greater than 1 in the radial cross-section of the housing. The hole defect is located inside the housing, and the martensite modification zone tissue surrounds the hole defect, and the tempered troostite tissue of the steel matrix surrounds the martensite modification zone tissue. It should be noted that by adjusting and optimizing the process parameters of electron beam modification, a process for forming defects with a specific length can be obtained, that is, according to the use strength, the defect length meeting the emission safety requirements can be designed according to the present invention, and then a housing with a corresponding defect length can be produced through a specific process, ultimately realizing the safe and efficient production of the housing.

[0024] The present invention will be further specifically described below through three housing experiments:

[0025] As shown in Table 1, the target design strengths of housings 1 - 3# are 1347 MPa, 1310 MPa, and 1240 MPa respectively. Through the four parameters of the target design tensile strength σ1, the tensile strength σ0 (1423 MPa) of the housing base material, the housing thickness L (7 mm), and the angle θ (30°) between the electron beam incident direction and the housing surface normal, according to defect holes with average lengths of 0.64 mm, 1.05 mm, and 1.77 mm are quantitatively designed. Tensile specimens are cut from housings 1 - 3# by wire cutting for tensile strength experiments, and the results are shown in Table 1 below.

[0026] Table 1 Comparison table of experimental values and theoretical values of tensile strength under different defect design lengths

[0027]

[0028]

[0029] It can be seen from the data in Table 1 that the error between the average value of the tensile strength of the electron beam pre-controlled housing and the target design value is within 5%, and the accuracy is relatively high.

[0030] The above is only the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for designing defect length of an electron beam pre-controlled housing, characterized in that: The defect length l is controlled by four parameters: the target tensile strength σ1 of the electron beam pre-controlled shell, the tensile strength σ0 of the shell matrix material, the shell thickness L, and the angle θ between the electron beam incident direction and the shell surface normal. The defect length l is:

2. The defect length design method according to claim 1, characterized in that: The shell substrate material is 40CrMnSiB material, and the surface of the electron beam pre-controlled shell forms a grid-shaped modified area after electron beam pre-control.

3. The defect length design method according to claim 1, characterized in that: The angle θ between the incident direction of the electron beam and the normal direction of the shell surface is 30°±1°.

4. The defect length design method according to claim 1, characterized in that: The tensile strength σ0 of the shell matrix material is the strength of the shell itself before electron beam pre-control, which is generally used as a technical input file for the electron beam pre-control process and has been known through preliminary tensile tests.

5. The defect length design method according to claim 1, characterized in that: The defect is a hole defect formed when the shell material is not backfilled in time during electron beam modification. The hole defect appears as an irregular long strip with an aspect ratio greater than 1 in the radial cross-section of the shell. The hole defect is located inside the shell. The hole defect is surrounded by a martensite modified zone structure, and the martensite modified zone structure is surrounded by a tempered troostite structure of the steel matrix.

Images