JPH0460727B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for drawing metal tubes or wires. More specifically, we will discuss a method for drawing metal tubes that can prevent vibrations generated in the plug installed through the core metal inside the die hole during the drawing process of metal tubes, and the above-mentioned plug via the core metal. This invention relates to a method for drawing metal tubes or wires without using. (Prior art) The drawing method for metal materials is a processing method in which a metal tube or wire is pulled from the front through a hole (die) of a tool to reduce its cross-sectional area or change its shape. , by adding strength etc.
It is used to process products such as boiler tubes and steel pipes for machine structures. FIG. 5 shows an example of a pipe manufacturing apparatus using a cold drawing method. A cylindrical plug 2 attached to the other end of the core metal 1 with one end fixed is installed inside the hole of the die 3, and the die is pulled while pulling the metal tube 4 having an outer diameter larger than the hole diameter of the die 3. Product 5 that passes through the hole and has the desired cross-sectional shape
I am getting . At this time, lubricating oil is dripped onto the outer and inner surfaces of the metal tube to reduce the frictional force generated between the plug 2 and the metal tube 4, thereby improving workability. By the way, in such a method of drawing a metal tube, vibrations occur in the plug 2 because the rate of change of the frictional force with respect to the relative speed between the plug 2 and the metal tube 4 is a negative value. That is, the frictional force between the plug 2 and the metal tube 4 is a value determined by the relative speed of these two.
When the relative speed with respect to the plug is 0 (adhered/stuck state), the plug is pulled in due to the large frictional force, and when it is pulled in to a certain extent, it enters a sliding state (slip state), the relative speed increases and the frictional force decreases, so this vibration Gradually grows and becomes larger. Generally, such vibration is called a stick slip phenomenon. In order to express analytically the staple slip phenomenon, the pipe manufacturing apparatus shown in FIG. 5a is schematically shown using a vibration model in FIG. 5b. Figure 5b
The equation of motion for plug 2 is: mx¨+(c+c')x〓+kx=f...(1) Also, if we ignore the dynamic characteristics of the frictional force, f=F(V-x〓)... (2), and considering the dynamic characteristics of frictional force, K・df/dt+f=F(V−x〓)……(3). However, m: equivalent mass of the plug core k: equivalent spring rigidity of the core c: equivalent viscous damping coefficient of the core c': equivalent damping coefficient acting on the plug V: withdrawal speed f: friction force F: steady friction force (Function) K: Time constant x: Plug displacement, and when the rate of change of steady frictional force with respect to relative velocity F'(V-x〓)<0, self-excited vibration called the stick-slip phenomenon is thought to occur. When such vibration occurs, it not only deteriorates the surface quality of the drawn material, but also accelerates tool wear and tear, ultimately leading to equipment damage. Therefore, if this vibration occurs during machining,
``Method of weakening vibration by reducing the pulling speed and adjusting it to a machining speed that does not generate vibration''
128665) was widely used in the past. In addition, if the vibrations do not subside even after reducing the machining speed, measures may be taken to reduce the machining rate and change the schedule to one that does not generate vibrations, or to change the lubricant used during machining to one with higher quality properties. was being carried out. Another proposal to reduce plug vibration is to use ultrasonic waves to vibrate the plug and improve its frictional characteristics.
``Method of Preventing Plug Vibration''
No. 116157, No. 51-126368, etc.) are publicly known. (Problems to be Solved by the Invention) However, these methods cannot prevent vibrations generated in the plug during drawing without reducing productivity. In other words, JP-A-1973-
All of the methods disclosed in No. 128665 reduce the processing efficiency of drawing processing. In other words, if the machining speed is reduced, the machining efficiency will naturally decrease.
Furthermore, if the degree of machining is lowered, the number of steps required to finish the product to the final dimensions increases, so the machining efficiency decreases no matter which method is used. Furthermore, changing the lubricant is not only an auxiliary measure, but also requires additional man-hours and costs. In other words, if such measures were used, the productivity of the drawing process would be significantly reduced, and the vibrations generated in the plug 2 could not be prevented. Furthermore, the methods disclosed in JP-A-51-116157 and JP-A-51-126368 require expensive and large-scale equipment to generate ultrasonic waves and apply them to the plug, making it difficult to use in practice. I can't. Also magazines (TUBE INTERNATIONAL,
(March 1986 issue, p. 39 - p. 43) describes a method of fixing the core metal via a hydrostatic thrust bearing and using the damping effect of this hydrostatic thrust bearing to reduce plug vibration. Disclosed. However, with this method, it is difficult to adjust the spring constant and damping coefficient of the thrust bearing, and it is not possible to eliminate vibrations generated in the plug 2 during the drawing process. An object of the present invention is to provide a metal tube or wire that can prevent vibrations generated in a plug installed through a core metal inside a die hole during drawing of metal tubes or wires without reducing productivity. The object of the present invention is to provide a method for drawing a tube or wire. (Means for Solving the Problems) As a result of various studies to solve the above problems, the inventor of the present invention found that, instead of directly fixing the core metal, by installing the core metal through a fluid pressure cylinder, The present invention was completed based on the knowledge that it is possible to completely prevent vibrations occurring in the plug. The gist of the present invention is that a metal tube having one end fixed and a plug attached to the other end of a metal tube is installed inside a hole of a die, and has an outer diameter larger than the hole diameter of the die. In this method of drawing metal tubes, a product with a cross section corresponding to the hole diameter is obtained by passing through a hole in a die while pulling the metal tube.In this method, the core metal is installed so that it can move in the drawing direction via a hydraulic cylinder. Additionally, this is a method for drawing metal tubes, which is characterized in that during processing, the piston is maintained in a state where it is supported via a fluid layer within the cylinder. (Function) Next, the method for drawing a metal tube according to the present invention will be explained using examples. Figures 1a and 1b are schematic views showing the drawing method according to the present invention, with Figure 1a showing the state before drawing and Figure 1c showing the state during drawing. There is. A core metal 1 supporting a plug 2 installed inside a hole of a die 3 is installed via a fluid pressure cylinder 6. Further, the fluid pressure cylinder 6 is connected to a compression system circuit consisting of a flow rate regulating valve 7, an accumulator 8, and a fluid pressure pump 9 as shown in FIG. This makes it possible to move the cylinder 6 to the piston return limit position. First, before the drawing process, the fluid pressure pump 9 is operated. Then, the pumped fluid is temporarily held by the accumulator 8 and sent into the fluid pressure cylinder 6. Piston 1 in hydraulic cylinder 6
0 is pressed by a preset pressure P, that is, a compressive force slightly smaller than the tension generated in the core metal during processing, and is therefore fixed at the piston return limit position within the fluid pressure cylinder 6. This state is shown in FIG. 1a. The magnitude of the value of P can be determined by measuring the magnitude of the tension generated in the core metal 1 during processing using a strain gauge, etc., and setting it to a value that is slightly smaller than the steady value of this measured value. good. That is, the value of the output of the piston due to the pressure P may be a value slightly smaller than the steady value of the tension actually generated in the core metal 1 during processing. It goes without saying that the pressure in the compression system circuit after the flow rate regulating valve may be determined by dividing the determined P value by the effective area of the piston. The flow rate regulating valve has the function of increasing fluid pressure in proportion to the flow rate of fluid per unit time, and corresponds to the damping effect of a piston. In addition, in this embodiment, the accumulator 8 is used as a device that increases the fluid pressure in proportion to the displacement of the fluid pressure cylinder 6 in the drawing direction, and the accumulator 8 is used as a device that increases the fluid pressure in proportion to the flow rate of fluid per unit time. Although the regulating valve 7 was used and the fluid pressure pump 9 was used as the pressurizing device, the present invention is not limited to these means. In other words, any hydraulic circuit that connects a device that increases fluid pressure in the fluid pressure cylinder 6 in proportion to the displacement in the drawing direction, a device that increases the fluid pressure in the cylinder in proportion to the flow rate of fluid, and a pressurizing device can be used. Similarly, the effects of the present invention are achieved. Further, the flow rate regulating valve 7 must be such that the pressure difference increases in proportion to the unit time flow rate. However, it goes without saying that there are no particular restrictions on the types of the accumulator 8 and the fluid pressure pump 9. After this state, the metal tube is drawn. When the metal tube 4 is pulled by the gripper 11 and moved in the direction of the arrow from the state shown in FIG. Therefore, the piston 10 in the fluid pressure cylinder 6 via the core metal 1 is pulled to the right, that is, in the direction of the piston's extension, by a tensile force P', and thus moves. However, before pressurization, the fluid pressure pump 9 enters the inside of the fluid pressure cylinder 6.
When a pressure P slightly smaller than P' is applied and the piston moves further in the withdrawal direction, the gas in the accumulator is compressed and the fluid pressure increases, reaching a position where it is balanced with P' (the extension limit and return limit of the piston 10). It stops approximately halfway between the two. This state is shown in FIG. 1b. As is clear from FIG. 1b, during the drawing process, the core metal 1 is supported via the fluid in the hydraulic cylinder 6. Therefore, when further drawing is performed after this, the vibrations that were previously generated in the plug 2 are immediately absorbed by the flow resistance of the fluid in the fluid pressure cylinder 6.
This makes it possible to prevent vibrations in the plug 2. The present invention thus absorbs the vibrations generated in the plug 2 due to the fluid flow resistance of the hydraulic cylinder 6. The vibration model for the plug 2 shown in FIG. 1b explained above is as shown in FIG. _At this time, the equation of motion regarding the plug 2 is mx¨+c′x〓+c(x〓−x〓 _p )+k(x−x _p )=f m _{p x¨ p} +c _p ) + k (x _p - x) = f _p If we ignore the dynamic characteristics of the frictional force, f = F (V - x 〓), and if we consider the dynamic characteristics of the frictional force, then K・df/dt+f=F(V-x〓) where: m _p : Equivalent mass of the piston c _p : Equivalent damping coefficient of the piston k _p : Equivalent spring stiffness of the piston x _p : Displacement of the piston f _p : Force acting on the piston It is. At this time, by appropriately selecting c _p and k _p ,
A stable solution satisfying the above equation is obtained. Here, the spring stiffness k _p of the piston is determined by the gas pressure in the accumulator, and the damping coefficient c _p of the piston is
is determined by the opening degree of the flow rate regulating valve. Therefore c _p ,
By selecting k _p in the range where a stable solution can be obtained in the above equation, it is possible to suppress vibrations occurring in the plug 2. By the way, in the embodiments of the present invention that have been described so far, as shown in FIGS. 1a and 1b, a liquid volume adjustment valve 7, an accumulator 8 and Although a compression system circuit consisting of a fluid pressure pump 9 was installed, as an alternative method, as shown in FIG.
A compression system circuit consisting of a flow rate adjustment valve 7, an accumulator 8, and a fluid pressure pump 9 is added to the liquid inlet on the fixed end side of the cylinder 6, and by applying prepressure to the piston 10 from both sides of the cylinder 6, the drawing process can be performed. Another possible method is to maintain the state shown in FIG. 1b from the beginning. Furthermore, even in processing methods that do not use the plug 2 and the core metal 4, vibrations may occur because the material tube side acts as a spring. As shown in Figures a and 4b, an apparatus embodying the method of the present invention is shown in (a), which comprises a compression system circuit consisting of a flow rate regulating valve 7, an accumulator 8, and a fluid pressure pump 9, and a cylinder 6. Method of installing between the die and the die fixing part (b) A method of installing between the gripper 11 that holds the material and the carriage 12 that pulls the gripper is effective. In the method shown in FIG. 4a or FIG. 4b,
It can be applied when the plug 2 and the core metal 4 are not used, but it can also be applied in exactly the same way to the processing method that uses the plug 2 and the core metal 4, and in either case, the problem occurs in the metal pipe or wire. Vibration can be prevented. That is, in either method, the fluid pressure cylinder absorbs and removes vibrations generated in the plug or metal pipe, making it possible to completely prevent vibrations from occurring. Further, examples of the present invention will be described in detail to further clarify the effects of the present invention. (Example) A metal tube 4 was drawn by the drawing method according to the present invention as shown in FIGS. 1a and 1b, and vibrations generated in the plug 2 during processing were examined using a strain gauge. . As a comparative example, a metal tube of the same size was subjected to a drawing process with the same working degree using the apparatus shown in FIG. 5a. The experimental conditions and results are shown in Table 1.

[Table] As is clear from Table 1, it can be seen that the vibration of the plug 2 can be completely suppressed by the method according to the present invention. (Effects of the Invention) According to the present invention, it is possible to completely prevent vibrations generated in a plug installed inside a die hole via a core metal during drawing of a metal tube using a simple and inexpensive device. It became possible. For this reason, () it is possible to perform drawing processing with a high degree of processing.
The process can be shortened. () Can be processed at high drawing speed, improving productivity. () Can be processed using low-grade lubricants or lubrication methods, reducing costs. () Because it can absorb the load that was occurring on the tool,
Tool damage can be prevented, reducing costs and
Productivity can be improved. () It is possible to prevent the occurrence of surface patterns on the material tube due to vibrations and improve dimensional accuracy, improving product quality.
Yield is improved. This effect was obtained. The practical significance of the present invention having such effects is extremely significant.

[Brief explanation of the drawing]

1a and 1b are schematic diagrams showing the drawing method according to the present invention; FIG. 2 is a model diagram of the drawing method according to the present invention; FIG.
A schematic diagram showing another embodiment of the drawing method according to the present invention; FIG. 4 is a schematic diagram showing still another embodiment of the drawing method according to the present invention; and FIGS. b is a schematic diagram and a model diagram of a conventional drawing method. 1: Core metal, 2: Plug, 3: Die, 4: Metal pipe, 5: Product, 6: Fluid pressure cylinder, 7: Flow rate adjustment valve, 8: Accumulator, 9: Fluid pressure pump, 10: Piston, 11: Grizpur, 12:
Carriage.

Claims (1)

[Claims] 1. A plug with one end fixed to the other end of the metal core is installed inside the hole of the die, and while pulling a metal tube having an outer diameter larger than the hole diameter of the die. In the drawing process of metal tubes, which obtains a product with a cross section according to the hole diameter by passing through a hole in a die, the core bar is installed so that it can move in the drawing direction via a hydraulic cylinder, and during processing, the cylinder is A method for drawing a metal tube, characterized in that the process is carried out while a piston is supported through a fluid layer inside the tube. 2 A metal tube or wire having an outer diameter larger than the hole diameter of the die is held by a gripper, and the gripper is pulled by a carriage while passing through the hole of the die to obtain a product having a cross section corresponding to the hole diameter. In this method of drawing pipes or wires, the die is installed so that it can move in the drawing direction via a fluid pressure cylinder, and during processing, the piston is supported within the cylinder via a fluid layer while processing is performed. A method of drawing metal tubes or wires. 3 A metal tube or wire having an outer diameter larger than the hole diameter of the die is held by a gripper, and the gripper is pulled by a carriage while passing through the hole of the die to obtain a product having a cross section corresponding to the hole diameter. In the drawing process for pipes or wires, the gripper is movable in the drawing direction via a fluid pressure cylinder and installed in a carriage, and the piston is maintained in a supported state via a fluid layer within the cylinder during processing. A drawing process for metal tubes or wires, which is characterized by the process of drawing metal tubes or wires. 4. Claim 1, wherein the fluid pressure cylinder is connected to a device that increases the fluid pressure according to a position in the cylinder in the drawing direction and a device that increases the fluid pressure according to the flow rate of the fluid. A method for drawing a metal tube or wire according to any one of claims 1 to 3.