A design method for continuous drawing of metal round rod wire

Abstract

The present invention belongs to the technical field of metal round bar drawing, and specifically discloses a design method for continuous drawing of metal round bar wire. In the design method of the present invention, when calculating the deformation amount distribution of a single pass, the outer diameter of the incoming metal round bar, the theoretically optimized drawing hole taper angle, the maximum tension degree, and the outer diameter of the finished rod are all combined for calculation. While obtaining a maximized deformation amount, the process safety can also be ensured; the calculation is carried out step by step from the finished pass to the first pass direction, and finally the total drawing deformation amount is maximized. The design method of the present invention can greatly exert the drawing production potential, reduce the wear and tear of working dies, and reduce the production cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal round rod drawing, and particularly relates to a design method for continuous drawing of metal round rod wire. Background Art

[0002] Continuous conical die drawing is an important method for metal plastic processing and forming. It can quickly and effectively achieve material strength strengthening and size reduction and sizing, and is widely used in the production of metal round rod wire. In the existing production technology, the deformation amount distribution of continuous conical die drawing is mainly determined by the empirical trial-and-error method. When the total reduction rate of the round rod wire is very large, multiple-pass drawing processes are required to organize production. In this continuous drawing production, on the one hand, when the designed drawing passes are too few and the deformation amount per pass is too large, it is easy to cause drawing wire breakage, resulting in the failure of the process design in production organization; on the other hand, when the designed drawing passes are too many, it will increase time and die wear, making the design cost of the drawing equipment higher and the die consumable cost higher during production organization, and ultimately the total production cost is too high. Therefore, the industrial drawing test carried out by the empirical trial-and-error method also brings a significant cost increase. Therefore, a process design method that can maximize the deformation amount during the continuous drawing of metal round rod wire is needed, that is, for the process equipment with a determined number of drawing passes, the total metal deformation amount can be maximized. Correspondingly, for a determined total metal drawing deformation amount, the number of drawing passes can be minimized, ultimately achieving the purpose of reducing costs and improving efficiency during the organization of continuous conical die drawing process production. Summary of the Invention

[0003] Aiming at the problems of high cost and low efficiency in the above-mentioned prior art of distributing the deformation amount in the continuous drawing process by the empirical trial-and-error method, the present invention will provide a design method for continuous drawing of metal round rod wire.

[0004] To achieve the above object, the specific technical solutions include the following:

[0005] A design method for continuous drawing of metal round rod wire includes the following steps:

[0006] (1) Conduct a tensile test on the metal round rod to obtain the yield strength of the metal round rod ;

[0007] (2) Obtain multiple groups of stress-strain curves of the metal round rod through Gleeble tests, and obtain the flow stress model of the metal round rod through the multiple groups of stress-strain curves of the metal round rod;

[0008] (3) Preset a conical die, and perform the nth pass drawing on the inlet metal round rod to obtain a finished rod. Among them, for the nth pass drawing, it is set that n>2, and the outer diameter of the inlet metal round rod wire is and the outer diameter of the finished rod is , the linear velocity of the exit rod is , the processing deformation temperature is T, and the real-time drawing stress is , the drawing hole cone angle is , the friction coefficient between the metal round rod and the die is ; Determine the specific values of n, , and T according to the actual process, and test to obtain ;

[0009] Based on the plastic mechanics formula and the rheological stress model of the metal round rod, with as the variable, perform iterative calculations to obtain the corresponding . During the iterative calculation process, make approach 0.75 times of . The termination condition of the iterative calculation is shown in Equation 10 below; after terminating the calculation, obtain the corresponding , of the nth pass. The plastic mechanics formula includes the following Equations 4 - 9;

[0010] The calculation formula for the optimal drawing hole cone angle is:

[0011]

[0012] In the formula,

[0013] is the optimal drawing hole cone angle;

[0014] is the friction coefficient between the metal round rod and the die;

[0015] is the equivalent deformation degree of the metal in the deformation zone, and its calculation formula is:

[0016]

[0017] In the formula,

[0018] is the outer diameter of the finished rod at the exit of the nth drawing pass;

[0019] is the outer diameter of the metal round rod at the entrance of the nth drawing pass;

[0020] The real-time drawing stress The calculation formula is:

[0021]

[0022] In the formula,

[0023] is the real-time drawing stress;

[0024] is the average flow stress in the drawing deformation zone, which can be calculated based on the pass structure parameters and the flow stress model of the metal round rod. During the calculation process, the approximate value calculation formula of the equivalent strain degree is:

[0025]

[0026] The equivalent strain rate calculation formula is:

[0027]

[0028] In the formula, t is the deformation time of the metal passing through the deformation zone, and its calculation formula is:

[0029]

[0030] In the formula,

[0031] is the drawing rate of the metal round rod in the nth pass of drawing;

[0032] The condition for terminating the iterative calculation is:

[0033]

[0034] In the formula, is the allowable deviation value in engineering design, and its value is close to 0;

[0035] (4) Take as the diameter of the metal round rod at the exit of the (n - 1)th pass, and refer to the process of steps (1) - (3) to calculate the diameter of the metal round rod at the entrance of the (n - 1)th pass of drawing and the drawing hole cone angle;

[0036] (5) Calculate the diameter of the metal round rod at the entrance and the drawing hole cone angle of the (n - 2)th... 3rd, 2nd, and 1st passes respectively in the manner of step (4), and determine the outer diameter, drawing rate, and drawing temperature of the finished rod corresponding to each pass respectively.

[0037] Through the design method of the present invention, while realizing the maximization of the continuous drawing deformation amount, the drawing stress on the metal round rod outside the drawing tool during the process is calculated and controlled from the perspective of engineering science, avoiding the breakage of the metal drawing due to excessive metal deformation amount at any pass during the drawing process, and realizing the improvement of efficiency and production stability.

[0038] Specifically, in the design method of the present invention, the deformation amount distribution of the final single pass is first calculated through computer programming iteration. During the calculation process, the outer diameter of the incoming metal round rod, the theoretically optimized drawing die cone angle, the maximum tension degree, and the outer diameter of the finished rod are all combined for calculation, so that the drawing stress on the rod at the exit of the drawing die is in the mechanical state of the maximum tension degree, that is, 0.75 times the yield strength value of the metal round rod. Thus, while obtaining a maximized deformation amount, the process safety can be ensured, that is: the drawn workpiece neither breaks nor enters the plastic state outside the drawing die. Then, based on the same calculation method for the final finished pass, the design calculation is carried out pass by pass from the final finished pass towards the first pass direction. For each pass, the maximum feasible outer diameter of the metal round rod at the entrance of this pass is deduced from the outer diameter of the finished rod at the exit. After calculating one pass, continue to deduce the maximum rod diameter of the incoming material corresponding to the maximized deformation amount of the previous pass until the first pass is calculated. Finally, the total deformation amount of the continuous drawing process is maximized.

[0039] Preferably, in step (1), during the tensile test process, the yield strength of the metal considering work hardening is determined through multiple groups of tests.

[0040] Preferably, in step (2), the flow stress model of the metal round rod is the Johnson-Cook flow stress model.

[0041] Preferably, in step (3), the is 3 - 5 mm.

[0042] Preferably, in step (3), the is 200 - 1100 mm / s.

[0043] Preferably, in step (3), the is 15 - 50 °C.

[0044] Preferably, in step (3), the is 8 - 20 °.

[0045] Preferably, in step (3), the n is 3 - 5, and n is a positive integer.

[0046] Preferably, in step (5), the outer diameter of the incoming metal round rod for the first pass drawing is 8 - 20 mm.

[0047] In the method of the present invention, starting from the last pass (n), the parameters of the previous pass are calculated successively.

[0048] Preferably, in step (5), the < 1%, and more preferably < 0.1%.

[0049] Compared with the prior art, the present invention has the following beneficial effects: In the design method of the present invention, on the one hand, the process design is carried out based on the method of scientific engineering calculation. While obtaining the maximum deformation amount of continuous drawing, it is possible to avoid wire breakage and drawing instability caused by large deformation in a single pass, improve the yield rate of production, and improve efficiency. On the other hand, when the incoming material specifications and finished product specifications are determined, the method of engineering science calculation can be used to design the minimum number of drawing passes, which can greatly exert the drawing production potential. In this way, both the tooling loss cost is reduced, and the on-site operation implementation difficulty of the production process is also reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a calculation flow chart of a single pass in an embodiment of the present invention.

[0051] Figure 2 It is a geometric parameter of the deformation zone and a simplified force diagram of the rod at the nth pass in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below through specific embodiments. The test methods used in the embodiments and / or comparative examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0053] The units of the parameters involved in this article are as follows: and both have the unit of mm; has the unit of mm / s; T has the unit of °C, has the unit of °, and the radian unit rad is used in the formula calculation; and and both have the unit of MPa.

[0054] Embodiment 1

[0055] A design method for continuous drawing of a metal round rod wire. The calculation process of a single pass is as Figure 1 shown, and the overall process includes the following steps:

[0056] (1) Obtain the yield strength of the metal round rod: Obtain the yield strength value of the metal through a tensile test. Considering that metals with different work-hardening degrees have different yield strength values, multiple sets of tensile tests are set here so that the metal round rod obtains the same specification of the finished product after different work-hardening degrees. After obtaining the grouped yield strength values in this way, the yield strength corresponding to the metal in this processing process can be estimated by the interpolation method .

[0057] For example, the as-cast drawn specimen is used as the tensile sample without work hardening, the tensile specimen obtained after the equivalent strain degree has accumulated to 0.4 through cold drawing of the as-cast specimen is regarded as the sample after medium work hardening, and the tensile specimen obtained after the equivalent strain degree has accumulated to 0.85 through cold drawing of the as-cast specimen is regarded as the sample after high work hardening. The corresponding metal yield strength values are obtained by testing the drawn samples respectively, and thus the actual metal yield strength in the drawing deformation can be estimated by the interpolation method. 。

[0058] (2) Obtain the JC model: Apply the Gleeble testing machine to conduct tensile tests under different temperatures and strain rates, and use the flow stress model to fit the stress-strain curve obtained from the tensile test to obtain the material constants in the flow stress model of the metal for subsequent calculations. Taking the Johnson-Cook model as an example of the flow stress model, the following formula is used:

[0059]

[0060] In the formula,

[0061] is the average flow stress in the drawing deformation zone;

[0062] A, B, C, n, m are all material constants;

[0063] is the equivalent strain degree;

[0064] is the dimensionless equivalent strain rate, and its calculation formula is:

[0065]

[0066] In the formula, is the equivalent strain rate, is the reference value of the equivalent strain rate, is the dimensionless temperature coefficient, and its calculation formula is:

[0067]

[0068] In the formula, , , are the average deformation temperature, the reference room temperature, and the melting point temperature of the metal material undergoing the current processing deformation, respectively.

[0069] (3) For the nth pass of drawing, set the outer diameter of the inlet metal round rod wire to be , the outer diameter of the finished rod to be , the outlet rod wire speed to be , the processing deformation temperature to be T, and the drawing stress to be , the drawing hole cone angle is , and the friction coefficient between the metal round rod and the die is ; Determine the specific values of n, , and T according to the actual process.

[0070] (3-1) Select a given pass, and the specific values of n, , and T can be determined. Determine the actual feasible specific drawing passes of the continuous drawing equipment, the finished rod specifications of the round rod wire, the drawing speed at the outlet of the final pass, and the range of the metal processing deformation temperature during the drawing process;

[0071] (3-2) The determination of the drawing deformation amount for each pass is achieved by determining the maximum outer diameter value of the feed metal round rod at the inlet of the pass and the maximum outer diameter value of the finished rod at the outlet. Since in step (3-1), the maximum outer diameter value of the finished rod has been preset , that is known, only the of the feed metal for this pass needs to be determined. The calculation formulas used in the calculation process are briefly described as follows.

[0072] First, calculate the theoretical optimal drawing hole cone angle , and its calculation formula is:

[0073]

[0074] In the formula,

[0075] is the optimal drawing hole cone angle;

[0076] is the friction coefficient between the metal round rod and the die;

[0077] is the equivalent deformation degree of the metal in the deformation zone, and its calculation formula is:

[0078]

[0079] In the formula,

[0080] is the diameter of the metal round rod at the outlet of the nth drawing pass;

[0081] is the diameter of the metal round rod at the inlet of the nth drawing pass;

[0082] The calculation formula for the real-time drawing stress is:

[0083]

[0084] In the formula,

[0085] is the real-time drawing stress;

[0086] is the average flow stress value in the drawing deformation zone, which can be calculated by the above Johnson-Cook deformation resistance model. In the calculation, the equivalent strain degree The approximate calculation formula is:

[0087]

[0088] The equivalent strain rate The calculation formula is:

[0089]

[0090] In the formula, t is the deformation time of the metal passing through the deformation zone, and its calculation formula is:

[0091]

[0092] In the formula, is the drawing rate of the metal round rod in the nth pass;

[0093] (3-3) Based on the above formula, with as the variable, iterative calculation is performed to obtain the corresponding . During the iterative calculation process, make close to 0.75 times of . The termination condition of the iterative calculation is:

[0094] In the formula,

[0095] is the allowable deviation value in engineering design, and its value is close to 0;

[0096] After terminating the calculation, the , in the nth pass can be obtained;

[0097] The iterative calculation process specifically includes the following process:

[0098] S1: First, preset as a specific value;

[0099] S2: Then, through the known , , calculate and obtain the inlet rod linear velocity , and thus the drawing rate of the metal round rod in the nth pass can be determined.;in, , , , , The calculation methods between are all general conventional calculation methods;

[0100] S3: Calculate the strain degree by the above formula and strain rate , average flow stress , Optimal drawing taper angle And real-time tensile stress ;

[0101] S4: Reset (i.e. is a variable) and iteratively calculates Close to 0.75 times , the condition for termination of iterative calculation is:

[0102]

[0103] In the formula, is the deviation value allowed by engineering design. Close to 0;

[0104] After the calculation is terminated, the corresponding nth pass is obtained , ;

[0105] (4) Referring to the process of steps (1-3), calculate the outer diameter and the taper angle of the drawing hole of the feed metal round rod for the n-1, n-2, ..., 2 and 1 passes respectively, and determine the outer diameter, drawing rate and drawing temperature of the corresponding finished rod.

[0106] For the convenience of comparison, the same product as that in Comparative Example 1 is produced in this embodiment. Therefore, taking the final pass n=4 as an example, the design and calculation are started from the drawing process of the 4th pass according to the method of the present invention. =3.918mm, the line drawing speed of the finished rod at the final outlet of the conical die is 10000mm / s, the friction coefficient The values ​​are the same as those in Table 2, and the values ​​of the drawing deformation temperature are also the same as those in Table 2. By constantly assuming that the rod diameter of the drawing feed Value, so that the drawing stress on the rod diameter at the exit of the drawing die In the state of maximum tension to ensure process safety, that is The value is equal to 0.75 times the metal yield strength For the value states, calculate or determine the outer diameter of the feed metal round rod and the drawing die cone angle for the 4th, 3rd, 2nd, and 1st passes respectively, and determine the outer diameter, drawing rate, and drawing temperature of the corresponding finished rod. The results are shown in Table 1. Through production verification, according to the design in Process Table 1, continuously drawing oxygen-free copper rod with a continuous conical die (the material constants A, B, C, n, and m corresponding to its Johnson-Cook deformation resistance model are 70, 310, 0.37, 0.018, and 0.96 respectively) can organize production normally.

[0107] Table 1

[0108]

[0109] Comparative Example 1

[0110] The process table for continuously drawing a certain metal round rod line (the same as in Example 1) with a four-pass continuous conical die designed by the traditional empirical method is as shown in Table 2 below.

[0111] Table 2

[0112]

[0113] By comparing the maximum feed rod diameter in the 1st pass in Table 1 and Table 2, it can be found that when still using a metal round rod with a rod diameter of about 7.5 mm to produce a finished round rod of 3.918 mm, according to the process design of the present invention, the number of drawing dies required can be reduced by one, which reduces the tooling loss and production organization cost; when using four-pass drawing in the same way, the maximum initial feed rod diameter can reach 9.35 mm, which significantly increases the total deformation amount of the metal in the continuous drawing process, and the total reduction rate of the cross-sectional area increases by 9.73% (total reduction rate increment ), indicating that the method of the present invention expands the applicable range of the feed of the drawing equipment and promotes the exertion of the equipment production capacity.

[0114] The present invention ensures the simultaneous use of an optimized cone angle and the maximum deformation amount during the drawing process through a process design optimization strategy, and guarantees the safety and stability of the process, so that the production potential of the continuous drawing equipment can be maximally exerted, reducing tooling loss and production cost. This can improve the process technology level and create economic benefits in actual production.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A design method for continuous drawing of metal round rod wire, characterized in that: The steps include: (1) Perform a tensile test on the metal round bar to obtain the yield strength of the metal round bar ; (2) Obtaining stress-strain curves of multiple groups of metal round rods through Gleeble test, and obtaining the rheological stress model of the metal round rods through the stress-strain curves of multiple groups of metal round rods; (3) Based on the conical die, the inlet metal round rod is drawn for the nth time to obtain the finished rod, where n>2 is set for the nth drawing, and the outer diameter of the inlet metal round rod wire is The outer diameter of the finished rod is , the outlet rod linear speed is , the processing deformation temperature is T, and the real-time drawing stress is , the taper angle of the drawing hole is , the friction coefficient between the metal round rod and the mold is ; Determine n according to the actual process, , and specific values ​​of T, and test to obtain ; Based on the plastic mechanics formula and the rheological stress model of the metal round rod, As variables, iterative calculations are performed to obtain the corresponding , in the iterative calculation process, Close to 0.75 times The condition for the termination of the iterative calculation is shown in the following formula 10; after the calculation is terminated, the corresponding n-th pass is obtained. , , the plastic mechanics formula includes the following formulas 4 to 9; Optimal taper angle of drawing hole The calculation formula is: In the formula, is the optimal taper angle of the drawing hole; is the friction coefficient between the metal round rod and the die; is the equivalent deformation degree of the metal in the deformation zone, and its calculation formula is: In the formula, is the outer diameter of the finished rod at the exit of the nth drawing pass; is the outer diameter of the metal round rod at the entrance of the nth drawing pass; Real-time tensile stress The calculation formula is: In the formula, is the real-time tensile stress; is the average flow stress in the drawing deformation zone, which can be calculated based on the hole structure parameters and the flow stress model of the metal round rod. During the calculation process, the equivalent strain degree The approximate value calculation formula is: Equivalent strain rate The calculation formula is: Where t is the deformation time of the metal passing through the deformation zone, and its calculation formula is: In the formula, is the drawing rate of the metal round rod drawing in the nth pass; The conditions for terminating the iterative calculation are: In the formula, It is the deviation value allowed in engineering design, and its value is close to 0; (4) As the metal round rod diameter at the exit of the n-1th pass, and referring to the process of steps (1) to (3), calculate the metal round rod diameter at the entrance of the n-1th drawing pass and the taper angle of the drawing hole; (5) According to step (4), the diameter of the metal round rod at the entrance and the taper angle of the drawing hole of the n-2th, 3rd, 2nd and 1st passes are calculated respectively, and the outer diameter, drawing rate and drawing temperature of the finished rod corresponding to each pass are determined respectively.

2. The design method for continuous drawing of metal round rod wire according to claim 1, characterized in that: In step (1), during the tensile test, the yield strength of the metal pipe taking into account work hardening is measured through multiple groups of tests.

3. The design method for continuous drawing of metal round rod wire according to claim 1, characterized in that: In step (2), the rheological stress model of the metal round rod is the Johnson-Cook rheological stress model.

4. The design method for continuous drawing of metal round rod wire according to claim 1, characterized in that: In step (3), the 3-5mm.

5. The design method for continuous drawing of metal round rod wire according to claim 1, characterized in that: In step (3), the 200-1100mm / s.

6. The design method for continuous drawing of metal round rod wire according to claim 1, characterized in that: In step (3), the 15-50℃.

7. The design method for continuous drawing of metal round rod wire according to claim 1, characterized in that: In step (3), the 8-20°.

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