A calculation method for the low point of surface carbon concentration in pulse carburizing, a calculation method for pulse time in vacuum carburizing, storage medium

Abstract

The present invention provides a calculation method for the low point of surface carbon concentration in pulse carburizing and a calculation method for the pulse time in vacuum carburizing, belonging to the technical field of vacuum carburizing. The refined control of carbon concentration during the carburizing process is the basis for regulating the structure and properties of carburized parts. The present invention can accurately calculate the time of all strong carburizing processes and diffusion processes in vacuum carburizing under the condition of a fixed number of pulses. The error between the carburized layer depth of the workpiece obtained according to the above-mentioned pulse carburizing time and the target value is less than 0.01%, which is a significant improvement compared with 10% of the traditional algorithm, providing a process calculation method support for the refined control of the carburizing process.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum carburizing, and in particular to a method for calculating the low point of surface carbon concentration in pulse carburizing, a method for calculating the pulse time of vacuum carburizing, and a storage medium. Background Art

[0002] Vacuum low-pressure carburizing usually uses acetylene as the carburizing medium and adopts a vacuum low-pressure carburizing process with a pulse working mode. Along with worldwide problems such as environmental deterioration and energy crisis, vacuum low-pressure carburizing, as a clean, efficient, and green heat treatment technology, has received extensive attention.

[0003] Vacuum low-pressure carburizing adopts a pulse carburizing method, and a pulse is formed by strong carburizing - diffusion. During the strong carburizing process, the surface carbon concentration of the material is increased by supplying the carburizing medium to reach the high point of surface carbon concentration (generally the austenite saturated carbon concentration); during the diffusion process, the surface carbon concentration of the material is decreased by the diffusion of carbon in the material to reach the low point of surface carbon concentration. During the final diffusion process, the surface carbon concentration of the material reaches the target surface carbon concentration through diffusion. In process calculation, the specific times of the strong carburizing process and the diffusion process are usually calculated respectively based on the high point of surface carbon concentration and the low point of surface carbon concentration. Thus, it can be seen that the low point of surface carbon concentration is an important parameter of the vacuum low-pressure carburizing process.

[0004] The traditional calculation method of carburizing pulse parameters takes the target surface carbon content, the target carburized layer depth, the high point of surface carbon concentration, and the low point of surface carbon concentration as input parameters to calculate the carburizing process, and performs iterative calculation by increasing the number of pulses. The algorithm termination condition is that the calculated carburized layer depth is greater than the target carburized layer depth. This method has low calculation accuracy, and the low point of surface carbon concentration is generally roughly set according to experience. The deviation between the calculated carburized layer depth and the target carburized layer depth is about 10%, which cannot meet the requirements of refined control of the carburized layer. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the low point of surface carbon concentration in pulse carburizing, a method for calculating the pulse time of vacuum carburizing, and a storage medium. The error is small when calculating the carburized layer depth based on the low point of surface carbon concentration calculated by the present invention.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a method for calculating the low point of surface carbon concentration in pulse carburizing, including the following steps:

[0008] (1) Provide the target carburized layer depth h d , the carbon concentration C corresponding to the target carburized layer depth c , the target surface carbon concentration C d, material parameters, number of carburizing pulses n, left value C of the low point of the pulsed carburizing surface carbon concentration l,l , right value C of the low point of the pulsed carburizing surface carbon concentration l,r , error E; matrix carbon concentration < the C l,l < the C l,r < austenite saturation carbon concentration;

[0009] (2) According to the C c , C d , material parameters, n and left value C l,l obtain the case depth h when the low point of the surface carbon concentration is C l,l , if h l < h l < h d , reduce C l,l , repeat step (2) until h l ≥ h d ;

[0010] If h l ≥ h d , continue to step (3);

[0011] (3) According to the C c , C d , material parameters, n and right value C l,r obtain the case depth h when the low point of the surface carbon concentration is C l,r , if h r > h r > h d , increase C l,l , repeat step (3) until h r ≤ h d ;

[0012] If h r ≤ h d , continue to step (4);

[0013] (4) Calculate C l,l and C l,r calculate C l,h ;

[0014] The C l,h = xC l,l + (1 - x)C l,r , where 0 < x < 1;

[0015] (5) According to the C c , C d , material parameters, n and C l,h obtain the case depth h when the low point of the surface carbon concentration is C l,h ;

[0016] If |h - h d | ≤ E, C l,h is the low point of the surface carbon concentration;

[0017] If |h - h d | > E and h > h d , then C l,h = C l,l , repeat steps (4) and (5) until |h - h d | ≤ E;

[0018] If |h - h d | > E and h < h d , then C l,h = C l,r , repeat steps (4) and (5) until |h - h d | ≤ E.

[0019] Preferably, the material parameters include a surface transfer coefficient, a diffusion coefficient, and a matrix carbon content.

[0020] Preferably, the difference between the C l,l and the matrix carbon concentration is 0.1 wt%.

[0021] Preferably, the difference between the austenite saturated carbon concentration and the C l,r is 0.1 wt%.

[0022] Preferably, the error E ≤ 0.001 kg / m 2 .

[0023] Preferably, the calculation method of the case depth h in steps (2), (3), and (5) preferably includes solving Fick's law by the finite difference method, solving Fick's law by the finite element method, or an analytical equation.

[0024] Preferably, the x is 1 / 2.

[0025] The present invention also provides a calculation method for the vacuum carburizing pulse time, including the following steps: calculating the strong carburizing time and the diffusion time of the vacuum carburizing pulse according to the low point of the pulse carburizing surface carbon concentration obtained by the calculation method according to the above technical solution.

[0026] The present invention also provides a storage medium, characterized in that it stores a computer program for executing the calculation method according to the above technical solution.

[0027] The present invention provides a calculation method for the low point of the pulse carburizing surface carbon concentration, including the following steps:

[0028] (1) Provide the target case depth h d , the carbon concentration C corresponding to the target case depthc , Target surface carbon concentration C d , material parameters, carburizing pulse number n, left value C of the low carbon concentration point on the pulse carburizing surface l,l , the right value C of the low carbon concentration point on the pulse carburizing surface l,r , Error E; Matrix carbon concentration < said C l,l <C l,r <austenite saturation carbon concentration;

[0029] (2) According to the C c , C d , material parameters, n and left value C l,l The lowest point of surface carbon concentration is C l,l The depth of the penetration layer h l , if h l <h d , reduce C l,l , repeat step (2) until h l ≥h d ;

[0030] If h l ≥h d , proceed to step (3);

[0031] (3) According to the C c , C d , material parameters, n and right value C l,r The lowest point of surface carbon concentration is C l,r The depth of the penetration layer h r , if h r >h d , increase C l,l , repeat step (3) until h r ≤h d ;

[0032] If h r ≤h d , proceed to step (4);

[0033] (4) According to C l,l and C l,r Calculate C l,h ;

[0034] The C l,h =xC l,l +(1-x)C l,r , where 0 <x<1;

[0035] (5) According to the C c , C d , material parameters, n and C l,h The lowest point of surface carbon concentration is C l,hThe case depth h at that time;

[0036] If |h - h d | ≤ E, C l,h is the low point of the surface carbon concentration;

[0037] If |h - h d | > E and h > h d , then C l,h = C l,l , repeat steps (4) and (5) until |h - h d | ≤ E;

[0038] If |h - h d | > E and h < h d , then C l,h = C l,r , repeat steps (4) and (5) until |h - h d | ≤ E.

[0039] (1) The refined control of the carbon concentration during the carburizing process is the basis for the regulation of the structure and properties of carburized parts. The present invention can accurately calculate the time of all the strong carburizing processes and diffusion processes in vacuum carburizing under the condition of a fixed number of pulses. The error between the case depth of the workpiece obtained based on the above pulse carburizing time and the target value is less than 0.01%, which is a significant improvement compared with 10% of the traditional algorithm, providing a process calculation method support for the refined control of the carburizing process.

[0040] (2) Carburizing needs to be carried out at high temperature, which is a process with high energy consumption. The case depth calculated by the traditional method is often higher than the target case depth. The higher the case depth, the greater the deviation value, and the longer the calculated process time. The deviation value of the present invention is low, which can avoid the above problems, not only reduce the process time, improve the carburizing efficiency, but also reduce the holding time of the workpiece at the carburizing temperature and reduce the energy consumption.

[0041] (3) In the traditional calculation method, the number of carburizing pulses is obtained according to the algorithm and cannot be adjusted. The number of pulses of the present invention is preset. By changing the number of pulses, the time of all the strong carburizing processes and diffusion processes in vacuum carburizing can be obtained. Generally speaking, the more the number of pulses, the shorter the strong carburizing time, and the higher the requirements for the equipment. The present invention can, for the vacuum carburizing equipment, by adjusting the number of pulses, obtain the corresponding pulse carburizing process time. Therefore, the present invention has greater adjustability in the actual carburizing equipment and process operation process, and is of great significance in the actual process conditions. Description of the Drawings

[0042] Figure 1 is the flow chart of the calculation method of the present invention;

[0043] Figure 2For the change trend of the carburized layer concentration during the calculation process with the increase in the number of cycles;

[0044] Figure 3 For the change trend of the low point of carbon concentration during the calculation process with the increase in the number of cycles;

[0045] Figure 4 It is the process flow chart for calculating the pulse carburizing time by the traditional algorithm. Specific implementation manner

[0046] The present invention provides a method for calculating the low point of the surface carbon concentration in pulse carburizing, including the following steps:

[0047] (1) Provide the target carburized layer depth h d , the carbon concentration C corresponding to the target carburized layer depth c , the target surface carbon concentration C d , material parameters, the number of carburizing pulses n, the left value C of the low point of the pulse carburizing surface carbon concentration l,l , the right value C of the low point of the pulse carburizing surface carbon concentration l,r , the error E; the matrix carbon concentration < the C l,l < the C l,r < the austenite saturation carbon concentration;

[0048] (2) According to the C c , C d , material parameters, n and the left value C l,l obtain the carburized layer depth h l,l when the low point of the surface carbon concentration is C l , if h l < h d , reduce C l,l , repeat step (2) until h l ≥ h d ;

[0049] If h l ≥ h d , continue with step (3);

[0050] (3) According to the C c , C d , material parameters, n and the right value C l,r obtain the carburized layer depth h l,r when the low point of the surface carbon concentration is C r , if h r > h d , increase C l,l , repeat step (3) until h r ≤ h d ;

[0051] If h r ≤ hd , continue with step (4);

[0052] (4) According to C l,l and C l,r calculate C l,h ;

[0053] The described C l,h = xC l,l + (1 - x)C l,r , where 0 < x < 1;

[0054] (5) According to the described C c , C d , material parameters, n, and C l,h obtain the case depth h when the low point of the surface carbon concentration is C l,h ;

[0055] If |h - h d | ≤ E, C l,h is the low point of the surface carbon concentration;

[0056] If |h - h d | > E and h > h d , then C l,h = C l,l , repeat steps (4) and (5) until |h - h d | ≤ E;

[0057] If |h - h d | > E and h < h d , then C l,h = C l,r , repeat steps (4) and (5) until |h - h d | ≤ E.

[0058] (1) Provide the target case depth h d , the carbon concentration C c corresponding to the target case depth, the target surface carbon concentration C d , material parameters, the number of carburizing pulses n, the left value C l,l of the low point of the surface carbon concentration of pulse carburizing, the right value C l,r of the low point of the surface carbon concentration of pulse carburizing, the error E; the matrix carbon concentration < the described C l,l < the described C l,r < the austenite saturation carbon concentration.

[0059] In the present invention, the matrix carbon concentration < the described C l,l < the described C l,r < the austenite saturation carbon concentration. The described C l,l and C l,rIt can be given according to the experience of those skilled in the art. In the present invention, the difference between the C l,l and the matrix carbon concentration is preferably 0.1 wt%; the difference between the austenite saturated carbon concentration and C l,r is preferably 0.1 wt%.

[0060] In the present invention, the material parameters preferably include the surface transfer coefficient, the diffusion coefficient, and the matrix carbon content.

[0061] (2) The present invention obtains the case depth h c C d , material parameters, n, and the left value C l,l when the low point of the surface carbon concentration is C l,l . If h l <h l <h d , reduce C l,l , and repeat step (2) until h l ≥h d ;

[0062] If h l ≥h d , proceed to step (3).

[0063] In the present invention, the reduced C l,l still needs to satisfy the requirement that the matrix carbon concentration < the C l,l < the C l,r < the austenite saturated carbon concentration.

[0064] (3) According to the C c C d , material parameters, n, and the right value C l,r obtain the case depth h l,r when the low point of the surface carbon concentration is C r . If h r >h d , increase C l,l , and repeat step (3) until h r ≤h d ;

[0065] If h r ≤h d , proceed to step (4).

[0066] In the present invention, the increased C l,r still needs to satisfy the requirement that the matrix carbon concentration < the C l,l < the C l,r < the austenite saturated carbon concentration.

[0067] (4) According to C l,l and Cl,r Calculate C l,h ;

[0068] The said C l,h = xC l,l + (1 - x)C l,r , where 0 < x < 1, and the said is preferably 1 / 2;

[0069] (5) According to the said C c , C d , material parameters, n and C l,h obtain the case depth h when the low point of the surface carbon concentration is C l,h ;

[0070] If |h - h d | ≤ E, C l,h is the low point of the surface carbon concentration;

[0071] If |h - h d | > E and h > h d , then C l,h = C l,l , and repeat steps (4) and (5) until |h - h d | ≤ E;

[0072] If |h - h d | > E and h < h d , then C l,h = C l,r , and repeat steps (4) and (5) until |h - h d | ≤ E.

[0073] In the present invention, the calculation method of the case depth h in steps (2), (3) and (5) preferably includes solving Fick's law by the finite difference method, solving Fick's law by the finite element method or an analytical equation, and more preferably the calculation method in Application No. 202310591341.X.

[0074] The present invention also provides a calculation method for the vacuum carburizing pulse time, including the following steps: calculating the strong carburizing time and diffusion time of the vacuum carburizing pulse according to the low point of the surface carbon concentration of the pulse carburizing obtained by the calculation method described in the above solution.

[0075] The flowchart of the calculation method of the present invention is as Figure 1 shown.

[0076] The present invention also provides a storage medium storing a computer program for executing the calculation method described in the above technical solution.

[0077] The following is a detailed description of a calculation method for the low point of the surface carbon concentration in pulse carburizing, a calculation method for the pulse time of vacuum carburizing, and a storage medium provided by the present invention in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0078] Embodiment 1

[0079] In this embodiment, the target surface carbon concentration is 0.7 wt.%, the target case depth is 0.5 mm, and the carbon concentration corresponding to the case depth is 0.35 wt.%. The material parameters are as follows: surface transfer coefficient: 5×10 -8 m / s, diffusion coefficient: 1×10 -11 m 2 / s, austenite saturation carbon concentration: 1.6 wt.%, matrix carbon concentration: 0.2 wt.%, density: 7.8×10 3 kg / m 3 ; the number of pulses is 9, the left value is 0.3 wt.%, the right value is 1.5 wt.%, and the error is 5×10 -6 kg / m 2 . The carburizing gas is acetylene.

[0080] (1) Provide the target case depth h d , the carbon concentration C c corresponding to the target case depth, the target surface carbon concentration C d , material parameters, the number of carburizing pulses n, the left value C l,l of the low point of the pulse carburizing surface carbon concentration, the right value C l,r of the low point of the pulse carburizing surface carbon concentration, and the error E; the matrix carbon concentration < the C l,l < the C l,r < the austenite saturation carbon concentration;

[0081] (2) According to the C c , C d , material parameters, n, and the left value C l,l to obtain the case depth h l,l when the surface carbon concentration low point is C l . If h l < h d , reduce C l,l , and repeat step (2) until h l ≥ h d ;

[0082] If h l ≥ h d , continue to step (3);

[0083] (3) According to the C c , C d , material parameters, n, and the right value Cl,r Obtain the case depth h when the low surface carbon concentration is C l,r ; if h r >h r >, increase C d and repeat step (3) until h l,l ≤h r ; d ;

[0084] If h r ≤h d , proceed to step (4);

[0085] (4) Calculate the average value C l,l according to C l,r and C l,h ;

[0086] The said C l,h =(C l,l +C l,r ) / 2;

[0087] (5) Obtain the case depth h when the low surface carbon concentration is C c according to the said C d , C l,h , material parameters, n and C l,h ;

[0088] If |h - h d |≤E, C l,h is the low surface carbon concentration;

[0089] If |h - h d |>E and h>h d , then C l,h =C l,l , and repeat steps (4) and (5) until |h - h d |≤E;

[0090] If |h - h d |>E and h<h d , then C l,h =C l,r , and repeat steps (4) and (5) until |h - h d |≤E.

[0091] The method of "calculating the strong carburizing time and diffusion time of the vacuum carburizing pulse according to C c , C d , material parameters, n and C l,h (C l,r or C l,l )" is as follows:

[0092] Step 1: For the strong carburizing process, assume a carburizing time t (t > 0), solve Fick's law according to the finite difference method to obtain the surface carbon concentration at the carburizing time t; if the surface carbon concentration is lower than the austenite saturation carbon concentration, increase t; if the surface carbon concentration is higher than the austenite saturation carbon concentration, decrease t; repeat the above process until the time t when the surface carbon concentration of the workpiece in the strong carburizing process reaches the austenite saturation carbon concentration (i.e., the strong carburizing time t 1 ), and obtain the carbon concentration distribution at the carburizing time t by solving Fick's law, which is used as the initial value of the carbon concentration distribution for the next strong carburizing process.

[0093] Step 2: For the diffusion process, assume a carburizing time t, solve Fick's law according to the finite difference method to obtain the surface carbon concentration at the carburizing time t; if the surface carbon concentration is higher than the low point C l,h of the pulse carburizing surface carbon concentration, increase t; if the surface carbon concentration is lower than the low point C l，h of the pulse carburizing surface carbon concentration, decrease t; repeat the above process until the time t when the surface carbon concentration of the workpiece in the diffusion process reaches the low point C l of the pulse carburizing surface carbon concentration (i.e., the diffusion time t 2 ), and obtain the carbon concentration distribution at the carburizing time t by solving Fick's law, which is used as the initial value of the carbon concentration distribution for the next diffusion process.

[0094] Step 3: Cross-cycle Steps 1 and 2 seven times to obtain t 3 ~t 16 , and then execute Step 1 to obtain t 17 .

[0095] Step 4: Assume a carburizing time t, solve Fick's law according to the finite difference method to obtain the surface carbon concentration at the carburizing time t; if the surface carbon concentration is higher than C d , increase t; if the surface carbon concentration is lower than C d , decrease t; repeat the above process until the time t when the surface carbon concentration is C d (i.e., the diffusion time t 18 ), and obtain the carbon concentration distribution at the carburizing time t by solving Fick's law.

[0096] Step 5: Assume a case depth h, calculate the carbon concentration at the h position according to the carbon concentration distribution calculated in Step 4; if the carbon concentration is lower than C c , decrease h; if the carbon concentration is higher than C c , increase h; repeat the above process until the case depth h corresponding to C c .

[0097] Finally, the pulse carburizing time is shown in Table 1:

[0098] Table 1 Pulse carburizing time obtained by the algorithm in the present invention

[0099] Intensive penetration process (s) Diffusion process (s) <![CDATA[t 1 > 216 <![CDATA[t 2 > 152 <![CDATA[t 3 > 78 <![CDATA[t 4 > 231 <![CDATA[t 5 > 71 <![CDATA[t 6 > 309 <![CDATA[t 7 > 68 <![CDATA[t 8 > 386 <![CDATA[t 9 > 66 <![CDATA[t 10 > 464 <![CDATA[t 11 > 65 <![CDATA[t 12 > 542 <![CDATA[t 13 > 65 <![CDATA[t 14 > 620 <![CDATA[t 15 > 64 <![CDATA[t 16 > 700 <![CDATA[t 17 > 64 <![CDATA[t 18 > 2759

[0100] Comparative Example 1

[0101] Using Figure 4 The process flow chart of the traditional algorithm shown to calculate the pulse carburizing time.

[0102] Table 2 Pulse carburizing time obtained by the traditional algorithm

[0103] Intensive penetration process (s) Diffusion process (s) 216 199 86 320 79 440 77 561 75 684 74 808 74 933 74 1060 73 2917

[0104] Figure 1 is the algorithm flow chart according to the calculation method in the present invention.

[0105] Figure 2 、 Figure 3 are respectively the changing trends of the carburized layer depth and the low point of carbon concentration with the increase of the number of cycles during the calculation process. It can be seen from the figure that with the increase of the number of cycles, the carburized layer depth continuously approaches the target carburized layer depth, and finally the error between the two is less than E, meeting the condition for the algorithm to end, and the obtained pulse carburizing time is the final result. It can be seen from Figure 3 that the best low point value of carbon concentration corresponding to 9 pulses is 0.8677 wt.%.

[0106] Table 1 and Table 2 are respectively different carburizing processes obtained by using the calculation method in the present invention and the traditional algorithm. Using the traditional algorithm, when the carburized layer depth is set to 0.5 mm, the carburized layer depth after the actual operation of the calculated process is 0.54760 mm, with an error of 9.52%, and the entire process time is 8751 s. Using the algorithm in the present invention, when the carburized layer depth is set to 0.5 mm and the number of carburizing pulses is 9 (the same as the number of pulses in the traditional algorithm), the carburized layer depth after the actual operation of the calculated process is 0.4998 mm, with an error of only 0.092%. Since the calculated carburized layer depth is more accurate, the entire process time is 6919 s, which is 26.5% shorter than the traditional process.

[0107] Using the algorithm in the present invention, when the number of pulses is 15, the entire process time is 6336 s, which is 8.5% shorter than when the number of carburizing pulses is 9. The algorithm in the present invention takes the number of carburizing pulses as an input variable, and can determine the number of pulses according to the actual situation of the equipment, so as to calculate the process, shorten the process cycle, and improve production efficiency.

[0108] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for calculating the low point of carbon concentration on a pulse carburizing surface, characterized in that: The following steps are involved: (1) Provide target penetration depth h d , Target penetration depth corresponds to carbon concentration C c , Target surface carbon concentration C d , material parameters, carburizing pulse number n, left value C of the low carbon concentration point on the pulse carburizing surface l,l , the right value C of the low carbon concentration point on the pulse carburizing surface l,r , Error E; Matrix carbon concentration < said C l,l <C l,r <austenite saturation carbon concentration; (2) According to the C c , C d , material parameters, n and left value C l,l The lowest point of surface carbon concentration is C l,l The depth of the penetration layer h l , if h l <h d , reduce C l,l , repeat step (2) until h l ≥h d ; If h l ≥h d , proceed to step (3); (3) According to the C c , C d , material parameters, n and right value C l,r The lowest point of surface carbon concentration is C l,r The depth of the penetration layer h r , if h r >h d , increase C l,r , repeat step (3) until h r ≤h d ; If h r ≤h d , proceed to step (4); (4) According to C l,l and C l,r Calculate C l,h ; The C l,h =xC l,l +(1-x)C l,r , where 0 <x<1; (5) According to the C c , C d , material parameters, n and C l,h The lowest point of surface carbon concentration is C l,h The depth of the permeable layer at h; If |h - h d | ≤ E, C l,h is the low point of the surface carbon concentration; If |h - h d | > E and h > h d , then C l,h = C l,l , repeat steps (4) and (5) until |h - h d | ≤ E; If 丨h - h d 丨 > E and h < h d , then C l,h = C l,r , repeat steps (4) and (5) until 丨h - h d 丨 ≤ E.

2. The calculation method according to claim 1, characterized in that: The material parameters include surface transfer coefficient, diffusion coefficient and matrix carbon content.

3. The calculation method according to claim 1, characterized in that: The C l,l The difference with the matrix carbon concentration is 0.1wt% 。 4. The calculation method according to claim 1, characterized in that: The austenite saturated carbon concentration and C l,r The difference is 0.1wt%.

5. The calculation method according to claim 1, characterized in that: The error E≤0.001kg / m 2 .

6. The calculation method according to claim 1, characterized in that: The calculation method of the penetration layer depth in steps (2), (3) and (5) includes solving Fick's law by finite difference method, solving Fick's law by finite element method or analytical equation.

7. The calculation method according to claim 1, characterized in that: The x is 1 / 2.

8. A method for calculating vacuum carburizing pulse time, characterized in that: The following steps are involved: The strong carburizing time and diffusion time of the vacuum carburizing pulse are calculated according to the low point of the pulse carburizing surface carbon concentration obtained by the calculation method according to any one of claims 1 to 7.

9. A storage medium, characterized in that: A computer program is stored for executing the calculation method described in any one of claims 1 to 7.

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