KR100931200B1 - Method and apparatus for manufacturing high strength bolt using extrusion process - Google Patents

Abstract

The present invention relates to a die device for bolt manufacturing, comprising: a die member including a cylindrical machining portion having a two-stage diameter having a relatively large first diameter and a relatively small second diameter, a reinforcing ring surrounding and receiving the die member; It provides a dice device comprising a pressing member for pressing the bolt preform injected into the processing portion. Furthermore, the present invention is a method of forming a bolt using a die apparatus of the cold press type, pressurizing the bolt preform with a raw material input step and a pressing member for inserting the bolt preform into the processing unit bolt head and body It provides a high-strength bolt manufacturing method comprising an extrusion step of manufacturing a part.

In the case of manufacturing the bolt according to the present invention, the die and the pressing member does not take a large load does not significantly reduce the die life, after the cold pressing can be produced a high-strength bolt having a higher tensile strength than the tensile strength of the initial raw material Therefore, it is possible to manufacture a bolt product having a very high tensile strength without performing heat treatment on the material.

Description

Manufacturing Method and Apparatus of High Strength Bolt using Extrusion Process {Manufacturing Method and Apparatus of High Strength Bolt using Extrusion Process}

The present invention relates to a die apparatus used to manufacture bolts by cold working and a method of manufacturing bolts using the same, and more particularly, to manufacturing bolts by using a die apparatus having a processing part having a different diameter. The present invention relates to a die device capable of improving the life of a die device and further obtaining a high strength bolt at low energy and low cost, and a method of manufacturing the bolt using the same.

In recent years, in order to save time and money in bolt manufacturing, research on a technique for manufacturing bolts and steel materials for bolts has been continued. This bolt manufacturing technology is excellent in economy and productivity because the heat treatment can be omitted, but since the strength before processing is directly related to the strength of the finished product, it brings a heavy load on the bolt forming device and die life during cold rolling process, resulting in the life of the die. Eventually, productivity may also be lowered, and thus, the overall benefits of the improvement in productivity are often lost. In particular, this problem is more prominent in the production of high strength bolts with high bolt strength.

Conventionally, when manufacturing a high-strength bolt, a method of lowering the strength of a raw material through a spheroidization heat treatment before cold rolling to enable cold rolling, and then heat-treating again to satisfy the strength required for the product. Specifically, after the wire for sizing purpose is carried out through a wire heat treatment in a wire state, a bolt having a microstructure of the final tempered martensite is subjected to a process of nodular heat treatment, bolt forming, hardening, and soaking. In many cases, the method was produced. Therefore, the strength of the bolt was determined by the composition, quenching, and heat treatment process. In order to secure sufficient strength, about two heat treatments were generally performed to the final product in the bolt manufacturing step.

However, the bolt manufacturing process that has to go through this heat treatment step does not meet the trend aimed at cost reduction through the omission of the process, and the wire rods thus manufactured are also rapidly made of high strength, so that high-strength bolt products can be stably cold pressed. There is an urgent need for technology.

As a technology related to the cold forging die which allows the air discharge to be smoothly related to the above-described prior art, which eliminates the damage of the mold and at the same time eliminates the molding instability of the product (bolt), and enables partial replacement when the mold is broken. In addition, the technology has been shown to simplify the structure of the mold, to partially replace and use the mold, and to smoothly discharge the air. However, such a technique is merely a method and an apparatus for easily using a cold forging die, and thus, there is no indication on how to easily form a high strength material.

In addition, process techniques for reducing the production process, increasing hardness and strength, and obtaining high quality bolts have been shown in the related art, but these techniques are also related to the manufacture of bolt heads, Since the related art is not shown, it is very difficult to easily manufacture bolts having high strength characteristics as a whole.

The present invention is to solve the above problems and at the same time to manufacture a bolt using a high-strength wire that does not require heat treatment, to provide a die having a low life degradation and a method for manufacturing the bolt using such a die. In particular, the present invention provides a method of manufacturing a high strength bolt having a higher initial strength after cold working using a wire rod having a low initial strength and a work hardening phenomenon, and a die apparatus used therein.

The present invention relates to a die device for bolt manufacturing, comprising: a die member including a cylindrical machining portion having a two-stage diameter having a relatively large first diameter and a relatively small second diameter, a reinforcing ring surrounding and receiving the die member; It provides a dice device comprising a pressing member for pressing the bolt preform injected into the processing portion. At this time, the processing unit may be an open type processing unit open in the longitudinal direction, the diameter of the bolt preform may be smaller than the first diameter and larger than the second diameter.

Furthermore, the present invention is a method of forming a bolt using a die apparatus of the cold press type, pressurizing the bolt preform with a raw material input step and a pressing member for inserting the bolt preform into the processing unit bolt head and body It provides a high-strength bolt manufacturing method comprising an extrusion step of manufacturing a part.

In the case of manufacturing the bolt according to the present invention, the die and the pressing member is not subjected to a large load, the die life is increased, and a high strength bolt having a higher tensile strength than the tensile strength of the initial raw material after the cold press can be produced, It is possible to provide a final bolt product having a very high tensile strength without performing any heat treatment on the material at the time of bolt manufacturing.

The wire rod to which the present invention is applied is a wire rod in which heat treatment is completely omitted after manufacture, and this type of wire rod is often referred to as an unstructured wire rod. Products having these characteristics can be manufactured directly by sizing purposes after wire fabrication, and only through bolt forming and final processing.

The biggest feature of this heat treatment omitted wire is that it can reduce the product cost by reducing energy consumed in the heat treatment process, and because heat treatment is not performed, quench crack, bending and other defects due to heat treatment occur. There is an advantage that does not. However, the strength is not secured by heat treatment, but the strength is obtained through cold processing such as drawing, so that ductility reduction and toughness reduction may be a problem.

In order to apply such a heat treatment omitted wire to the present invention, the present invention proposes an apparatus having a form of a die in which cold extrusion and a pressure vessel are simultaneously performed (FIG. 3). The die of the device is generally used in a form enclosed in a reinforcing ring 301, as shown in FIG. 3, and the present invention will be described in detail with reference to the die, the pressing member and the ejector pin in particular. .

Hereinafter, the apparatus of the present invention will be described in detail.

In the present invention, when forming the bolt preform, as shown in Figure 5, using a material having a larger diameter than the preform devised an apparatus and method for producing a high-strength bolt using only the extrusion method in the first step. That is, the conventional method was a method of manufacturing the preform as shown in Figure 5 (a-2) by processing only the head portion using a material of a diameter almost similar to the preform, in the present invention, the body portion and the head using only extrusion Work hardening occurs in all parts, the body part is formed while the diameter of the material is reduced, the head is to have a shape as shown in Figure 5 (b-1) by the pressing member coming down. The right side of FIG. 5 shows the result of numerical calculation of the deformation amount provided through each step.

A die member 302 having a processing unit 304 on which a raw material is processed, a reinforcing ring 301 for accommodating and enclosing the die member, and a pressing member serving to pressurize the raw material fed into the processing unit. 303).

In this case, the processing unit 304 may have a cylindrical shape suitable for bolt molding. In addition, the diameter of the processing unit 304 may exist while having two different diameters (hereinafter, among the two diameters, a relatively large diameter is referred to as a first diameter and a relatively small diameter as a second diameter). In this case, the diameter of the raw material input side, that is, the punch member side should be larger. This is because the raw material input side having a large diameter should be processed to the head of the bolt when forming the bolt.

In addition, the processing unit 304 may be an open processing unit having an open end, which is for the die apparatus of the present invention using only extrusion, unlike the closed processing unit for a conventional pressure-type method, such an open processing unit This eliminates the significant limitations on bolt lengths, allowing the manufacture of bolts of various lengths.

Hereinafter, the method of manufacturing a bolt using the dice apparatus of this invention is demonstrated.

In order to manufacture a bolt with the die apparatus of this invention, a bolt preform is put into the raw material input part of the said process part 304. In this case, the bolt preform uses a diameter larger than the second diameter and smaller than the first diameter, unlike a conventional bolt manufacturing method.

The injected bolt preform is pressed by the pressing member 303 and extruded from the machining portion having the first diameter to the machining portion having the second diameter. Unlike the punch member 403 used in the conventional pressing method, the pressing member 303 is characterized by having a pressing protrusion capable of pressing the preform into the processing unit 304 without the bolt head forming groove. . By this process, the bolt shape is formed by extrusion. Since the conventional pressing method is not used, the pressing member 303 needs to apply an impact like the punch member 403 of the apparatus, which was conventionally forming the bolt in the pressing method. As a result, the life of the pressing member 303 is longer than that of the conventional punch member, and the life of the die apparatus as a whole also increases.

In the case of forming the bolt by extrusion only as in the present invention, the work hardening effect obtained by the extrusion can be used, even if the bolt is formed using a material having a low basic strength, The strength also has the advantage of being able to easily manufacture elevated bolts. Furthermore, since the strength of the initial material is low and the pressure system is not used, the load (load) applied to the die can be reduced, and there is no fear of breakage of the pressurizing member.

The present invention will be described in more detail with reference to the following Examples. However, the following examples are merely examples of the present invention, and the scope of the present invention is not limited or limited by the following examples.

In Table 1 below, bolts were fabricated using a bolt manufacturing die apparatus and a method of the present invention, in which a high-strength wire having a tensile strength of 1350 MPa was manufactured from bolts, and a wire rod having a tensile strength of 1600 MPa by a conventional method was bolted. The examples (comparative examples) which were manufactured by each are shown.

Inventive Example Comparative example Initial material size (mm) 9.4 7.25 Tensile Strength of Initial Material (MPa) 1350 1600 1 ^st step maximum load (kN) 142 131 2 ^st step maximum load (kN) 150 259 3 ^rd step load (kN) 153 252 4 ^th step maximum load (kN) 161 269 End Product Tensile Strength (MPa) 1650 1620 Life in case of die break (product count) 1,031,350 times 2,647 times

The material used in this example was a JIS-SWRS82BC piano wire, and in order to measure the various characteristics and die life of each step, the actual bolt was manufactured until the die was broken and worn to measure the life. The die life was measured by the number of times the die was recessed through a continuous product processing method.

As a result of the experiment, the bolts of the comparative example using the existing method were died at about 2,000 times when continuous product processing was carried out and could no longer be used. On the other hand, the present invention has been found that can be used up to about one million times.

In addition, as a result of measuring the maximum load applied to the comparative example and the invention example, the load change was not large at the maximum load applied to the first and second stages, but the load applied to the second stage tended to decrease rather than the case of the invention example. Was found (see Figure 6).

1 is a schematic diagram showing a step of manufacturing the bolt by using the die apparatus and method of the present invention.

Figure 2 is a schematic diagram showing the step of manufacturing the bolt in a conventional pressure-tack method

3 is a schematic diagram showing the structure of the die apparatus of the present invention;

Figure 4 is a schematic diagram showing the structure of the die apparatus for manufacturing bolts in the conventional pressure vessel method

Figure 5 is a schematic diagram showing the deformation amount for each part, when manufacturing the bolt in the conventional method and the present invention

Figure 6 is a graph showing the amount of load on the die device of the present invention and the conventional method in the manufacture of bolts

Claims (4)

In the bolt-forming die apparatus of the cold pressing system, the die apparatus, A die member comprising a cylindrical machining portion having a first diameter and a two-stage diameter of a second diameter smaller than the first diameter; A reinforcing ring surrounding and receiving the die member; And A pressing member for pressing the bolt preform inserted into the processing portion; And a die processing device including an open processing part which is open in a longitudinal direction. delete The die apparatus according to claim 1, wherein a diameter of the bolt preform is smaller than the first diameter and larger than the second diameter. In the method of shaping a bolt using the die apparatus of a cold press type system, A raw material input step of inserting the bolt preform into the processing portion; And Pressing the bolt preform with a pressing member to produce a bolt head and a body; Method for producing a high strength bolt comprising a.

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