Design method for continuous drawing of metal round rod wire

Abstract

The invention belongs to the technical field of metal round rod drawing, and particularly discloses a design method for continuous drawing of a metal round rod wire. According to the design method, during distribution calculation of the deformation amount of a single pass, the outer diameter of a feeding metal round rod, a theoretically optimized drawing hole taper angle, the maximum tension degree and the outer diameter of a finished rod are combined together for calculation, the maximum deformation amount is obtained, and meanwhile the process safety can be guaranteed; according to the design, calculation is conducted one by one in the direction from the finished product pass to the first pass, and finally the total drawing deformation is maximized. By means of the design method, the drawing production potential can be brought into full play, tool and mold losses are reduced, and the production cost is reduced.

Description

Technical Field

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

[0002] Continuous tapered die drawing is an important method for metal plastic forming. It can quickly and effectively achieve material strength enhancement and sizing in dimensional specifications, and is widely used in the production of metal round rods and wires. In existing production technologies, the deformation distribution of continuous tapered die drawing is mainly determined by empirical trial and error. When the total diameter reduction rate of round rods and wires is large, it is necessary to organize production through multiple drawing processes. In this continuous drawing production, on the one hand, when the number of designed process drawing passes is too small, the deformation of a single pass is too large, which can easily cause wire breakage during drawing, resulting in failure of process design in production organization; on the other hand, when the number of designed process drawing passes is too large, it will increase time and mold loss, making the design cost of drawing equipment higher, the mold consumables cost when organizing production is also higher, and the total production cost is ultimately too high. Therefore, industrial drawing tests conducted by empirical trial and error also bring significant cost increases. Therefore, a process design method is needed to maximize the deformation during the continuous drawing of metal round rods, that is, to maximize the total deformation of the metal for a certain number of drawing passes, and correspondingly, to minimize the number of drawing passes for a certain total amount of metal drawing deformation, thereby ultimately achieving the purpose of reducing costs and improving efficiency when organizing the production of continuous tapered die drawing processes. Summary of the invention

[0003] In view of the problem that the above-mentioned prior art involves high cost and low efficiency in allocating the deformation amount in the continuous drawing process through empirical trial and error, the present invention will provide a design method for continuous drawing of metal round rods.

[0004] To achieve the above purpose, the following technical solutions are specifically included: A design method for continuous drawing of a metal round rod wire comprises the following steps: (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.

[0005] Through the design method of the present invention, while maximizing the continuous drawing deformation, 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 metal drawing wire breakage due to excessive metal deformation at any pass in the drawing process, thereby improving efficiency and production stability.

[0006] Specifically, in the design method of the present invention, the deformation distribution of the final single pass is calculated iteratively by computer programming. In the calculation process, the outer diameter of the feed metal round rod, the theoretically optimized taper angle of the drawing hole, the maximum tension, and the outer diameter of the finished rod are all combined and calculated, so that the drawing stress on the rod at the exit of the drawing die is in the mechanical state of maximum tension, that is, 0.75 times the yield strength of the metal round rod, so that while obtaining the maximum deformation, the process safety can also be guaranteed, that is: the drawing 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 performed one by one from the final finished pass to the first pass. For each pass, the maximum feasible outer diameter of the metal round rod at the entrance of the pass is calculated from the outer diameter of the finished rod at the exit. After calculating one pass, the maximum incoming rod diameter corresponding to the maximum deformation of the previous pass is continued to be calculated until the calculation is completed in the first pass, and finally the total deformation of the continuous drawing process is maximized.

[0007] Preferably, in step (1), during the tensile test, the metal yield strength taking into account work hardening is determined through multiple groups of tests.

[0008] Preferably, in step (2), the rheological stress model of the metal round rod is the Johnson-Cook rheological stress model.

[0009] Preferably, in step (3), the 3-5mm.

[0010] Preferably, in step (3), the 200-1100mm / s.

[0011] Preferably, in step (3), the 15-50℃.

[0012] Preferably, in step (3), the 8-20°.

[0013] Preferably, in step (3), n is 3-5, and n is a positive integer.

[0014] Preferably, in step (5), the outer diameter of the feed metal round rod drawn in the first pass is 8-20mm.

[0015] In the method of the present invention, the calculation starts from the last pass (n), and the parameters of the previous pass are calculated one by one.

[0016] Preferably, in step (5), the <1%, more preferably <0.1%.

[0017] 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 scientific engineering calculations, and while obtaining the maximum deformation of continuous drawing, it is possible to avoid wire breakage and drawing instability caused by large deformation in a single pass, thereby improving the production yield and efficiency; on the other hand, when the specifications of incoming materials and finished products are determined, the minimum number of drawing passes can be designed through engineering scientific calculation methods, which can greatly tap the potential of drawing production, thereby reducing the cost of tool and die loss and reducing the difficulty of on-site operation implementation of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a calculation flow chart of a single pass in an embodiment of the present invention.

[0019] Figure 2 1 is the geometric parameters of the deformation zone at the nth pass and the simplified force diagram of the rod in the embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific examples. The test methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0021] The units of the parameters involved in this article are as follows: , The unit is mm; The unit of is mm / s; the unit of T is ℃, The unit is °, and the radian unit rad is used in the formula calculation; , , The unit is MPa.

[0022] Example 1 A design method for continuous drawing of metal round rod wire, the calculation process of a single pass is as follows Figure 1 As shown, the whole process includes the following steps: (1) Obtaining the yield strength of metal round rods: The yield strength value of the metal is obtained through tensile tests. Considering that metals with different degrees of work hardening have different yield strength values, multiple sets of tensile tests are set here so that the metal round rods can obtain finished products of the same specifications after different degrees of work hardening. After obtaining the yield strength values ​​of the groups, the yield strength of the metal corresponding to this processing process can be estimated by interpolation method. .

[0023] For example, the as-cast drawn specimen is regarded as a tensile specimen without work hardening, the tensile specimen obtained after the as-cast specimen is cold drawn with an equivalent strain degree of 0.4 is regarded as a medium-hardened specimen, and the tensile specimen obtained after the as-cast specimen is cold drawn with an equivalent strain degree of 0.85 is regarded as a highly work-hardened specimen. The corresponding metal yield strength values ​​are obtained by drawing the samples separately. In this way, the actual metal yield strength in the drawing deformation can be estimated by interpolation method. .

[0024] (2) Obtaining the JC model: Use the Gleeble testing machine to perform tensile tests under different temperatures and strain rates, and use the deformation resistance model to fit the stress-strain curve obtained from the tensile test to obtain the material constants in the deformation resistance model of the metal for subsequent calculations. Take the Johnson-Cook model as an example and use the following formula: In the formula, is the average flow stress in the drawing deformation zone; A, B, C, n, and m are all material constants; is the equivalent strain degree; is the dimensionless equivalent strain rate, and the calculation formula is: In the formula, is the equivalent strain rate, is the reference value of equivalent strain rate, is the dimensionless temperature coefficient, and its calculation formula is: In the formula, , , They are respectively the average deformation temperature of the metal material currently being deformed, the reference room temperature, and the melting point temperature of the material.

[0025] (3) For the nth drawing pass, the outer diameter of the inlet metal round rod wire is set to The outer diameter of the finished rod is , the outlet rod linear speed is , processing deformation temperature is T, 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 the specific value of T.

[0026] (3-1) Select a given pass and you can determine n, , and the specific values ​​of T. Determine the specific drawing passes that can be actually implemented for continuous drawing equipment, the specifications of round rod wire finished rods, the final pass exit drawing speed, and the metal processing deformation temperature range controlled during the drawing process; (3-2) The determination of the deformation amount of each drawing pass is achieved by determining the maximum outer diameter of the feed metal round rod at the inlet of the drawing pass and the maximum outer diameter of the finished rod at the outlet. In step (3-1), the maximum outer diameter of the finished rod has been pre-set. ,Right now It is known that we only need to determine the feed metal . For calculation The calculation formula used in the process is briefly described as follows.

[0027] First, calculate the theoretical optimal taper angle of the drawing hole , and its 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 diameter of the metal round rod at the exit of the nth drawing pass; is the diameter of the metal round bar 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 value in the drawing deformation zone, which can be calculated using the above-mentioned Johnson-Cook deformation resistance model. The equivalent strain degree can be taken in the calculation 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; (3-3) Based on the above formula, Iterate the variables to get the corresponding , in the iterative calculation process, Close to 0.75 times , the condition for termination of iterative calculation is: In the formula, It is the deviation value allowed in engineering design, and its value is close to 0; After the calculation is terminated, the nth pass can be obtained , ; The iterative calculation process specifically includes the following steps: S1: Preset is a specific value; S2: Then through the known , , calculate the entrance rod linear velocity , from which the drawing rate of the nth metal round rod drawing can be determined ;in, , , , , The calculation methods between are all general conventional calculation methods; S3: Calculate the strain degree by the above formula and strain rate , average flow stress , Optimal drawing taper angle And real-time tensile stress ; S4: Reset (i.e. is a variable) and iteratively calculates Close to 0.75 times , the condition for termination of iterative calculation is: In the formula, is the deviation value allowed by engineering design. Close to 0; After the calculation is terminated, the corresponding n-th pass is obtained. , ; (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.

[0028] 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 The outer diameter of the feed metal round rod and the taper angle of the drawing hole of the 4th, 3rd, 2nd and 1st passes are calculated or determined respectively, and the outer diameter, drawing rate and drawing temperature of the corresponding finished rod are determined. The results are shown in Table 1. After production verification, according to the design of process table 1, the continuous tapered die drawing oxygen-free copper rod (the material constants A, B, C, n and m of the corresponding Johnson-Cook deformation resistance model are 70, 310, 0.37, 0.018 and 0.96 respectively) can be organized for production normally.

[0029] Table 1 Comparative Example 1 The process table for drawing a metal round rod wire (same as Example 1) using a four-pass continuous tapered die designed by the traditional empirical method is shown in Table 2 below.

[0030] Table 2 By comparing the maximum feed rod diameter in the first pass in Table 1 and Table 2, it can be found that when still using about Production of 7.5mm diameter metal round rods When the finished round rod is 3.918mm, 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 the same four-pass drawing is used, the maximum initial feed rod diameter can reach 9.35mm, which significantly increased the total deformation of the metal in the continuous drawing process, and the total reduction rate increased by 9.73% (the total reduction rate increment ), which shows that the method of the present invention increases the applicable range of feeding of the drawing equipment and promotes the production capacity of the equipment.

[0031] The present invention ensures that the optimized taper angle and the maximum deformation are used simultaneously in the drawing process through a process design optimization strategy, and ensures the safety and stability of the process, so that the production potential of the continuous drawing equipment can be maximized, the tooling loss is reduced, and the production cost is reduced. This can improve the process technology level and create economic benefits in actual production.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution 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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