KR20050046248A - A dice for thermal induced exhaustion - Google Patents

Abstract

The present invention relates to a hot extrusion die, more specifically, when shrinking the die tip in the die case, internal stress caused by the difference in heat deformation between the die case of heat-treated steel and the die tip of cemented carbide or industrial diamond Since no damage due to such stress does not occur, there is an advantage that can significantly improve the life and reliability of the product.

Description

 Hot Extrusion Dies {a dice for thermal induced exhaustion}

 The present invention relates to a hot extrusion die, and more particularly to a hot extrusion die to prevent the generation of stress due to heat deformation between different materials.

 The die used for hot extrusion is an important factor in determining the size and surface quality of the product as well as forming the product.

 The main part of a general extrusion die consists of the introduction part 2, the bearing part 4, and the exit part 6, as shown in FIG.

Such extrusion dies require properties that must be easily processed into a desired shape, strength and hardness properties that must be supported so that shapes can be made properly when extruded, and wear resistance properties that can be used continuously or for long term.

In order to satisfy these characteristics, carbide materials having excellent wear resistance and hardness have been used in recent years, and industrial diamond having the best wear resistance among existing materials is used as a main material as a tip of a cutting tool.

In this case, when the die is used as a whole material of cemented carbide or diamond material having excellent wear resistance, etc., the die is expensive and difficult to process, and general lathes, milling or drilling, etc. are not smooth, and mainly electric discharge machining. In order to require time and costly processing steps such as wire cutting and the like, the entire die is hardly produced from cemented carbide or industrial diamond.

Therefore, most extrusion dies consist of heat treated steel except for the most important bearing part.

Figure 2 is a cross-sectional perspective view showing a schematic structure of an extrusion die divided into several parts.

Referring to FIG. 2, the hot extrusion die is usually embedded in a die case 15 through which a coupling hole 18 penetrates at a central portion thereof, and is inserted into a coupling hole 18 of the die case 15. Extrusion hole 19 through which the object to be extruded is composed of a die tip 25 is formed through.

In addition, a fixing ring 30 is provided at one side of the die tip 25.

The extrusion die of FIG. 2 is mainly assembled by shrink fit, as shown in FIG. 3, in order to prevent the die tip 25 and the die case 15 made of cemented carbide or industrial diamond from movement during assembly tolerance and use.

That is, the die case 15 and the die tip 25 are manufactured with appropriate tolerances.

At this time, the coupling hole 18 of the die case 15 generally applies a negative tolerance (-) which is slightly smaller in diameter than the die tip 25 so that the die tip 25 is fitted.

When the die case 15 manufactured by applying the negative tolerance is put into the chamber at a predetermined temperature and sufficient time has elapsed, the coupling hole 18 expands while the die case 15 whose temperature rises expands. The tip 25 may be fitted into the coupling hole 18 of the die case 15.

Next, when the temperature is gradually lowered to the room temperature by re-injecting the same into the same chamber, the die case 15 contracts and the inner wall surface of the coupling hole 18 presses the circumferential wall of the die tip 25. Can be assembled.

However, when the die tip 25 is shrinked in the die case 15 as described above, the internal stress is increased due to the heat deformation difference between the die case 15, which is a heat-treated steel, and the die tip 25, which is a cemented carbide material or industrial diamond. Inevitably occurs.

The die case 15, which is a heat-treated steel surrounding the die tip 25, has a coefficient of thermal expansion of about 12-14 μ / 占 폚, and the die tip 25 has a coefficient of thermal expansion of 5-7 μ / 占 폚 when it is a cemented carbide material. In the case of industrial diamond, the coefficient of thermal expansion is about 2-4 μ / ° C., because the coefficient of thermal expansion of the die case 15 is larger than that of the die tip 25, so that the die tip 25 compresses, in particular, the stress concentration coefficient. Large stresses occur at both ends of the large die tip 25.

Therefore, due to such a stress, as shown in FIG. 4, since the cracks such as cracks 1 occur around the extrusion hole 19 of the die tip 25, the die tip 25 is cemented. Alternatively, since the die case 15 is made of industrial diamond and is made of a different material of heat-treated steel, there is a problem that the original intention to increase the life of the die is not satisfied.

The present invention is to solve the problems described above, an object of the present invention is to prevent the occurrence of stress caused by the difference in thermal deformation in the die for hot extrusion, the main part of the die and two stages of cemented carbide and heat treatment steel or industrial diamond and heat treatment steel It is intended to provide a hot extrusion die that is constructed in a structure so that the life and reliability of the product can be significantly improved.

In order to solve the above problems, the present invention has a die case formed with a coupling hole penetrated in the center, and a die tip formed in the coupling hole of the die case with an extrusion hole through which an extruded object passes. In the hot extrusion die comprising, the coupling hole of the die case is composed of the first coupling hole and the second coupling hole having a larger diameter than the first coupling hole, the die tip is a first die tip embedded in the first coupling hole and The coefficient of thermal expansion is smaller than that of the die case, and is made of a second die tip embedded in the second coupling hole, and the diameter of the second coupling hole is relatively larger than the diameter of the second die tip. It is an object of the present invention to provide a hot extrusion die in which a tolerance is formed between the inner wall surfaces of the second joining holes, which are spaced apart by a predetermined interval.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

In addition, this embodiment does not limit the scope of the present invention, but is presented by way of example only and the same parts as in the conventional configuration using the same reference numerals and names.

5 is a sectional view showing a schematic configuration of a die according to the present invention.

As shown in FIG. 5, the hot extrusion die according to the present invention includes a die case 15 having a coupling hole 18 and 22 penetrated therein, and a coupling hole 18 and 22 of the die case 15. In the hot extrusion die which is embedded in the shrink fit and the die tip (25, 35) formed through the extrusion hole 19 through which the extrudate passes through, the coupling hole (18, 22) of the die case (15) ) Is composed of a first coupling hole 18 and a second coupling hole 22 having a larger diameter than the first coupling hole 18, and the die tip 25 is formed in the first coupling hole 18. The first die tip 25 and the die case 15 is made of a material having a smaller coefficient of thermal expansion is made of a second die tip 35 embedded in the second coupling hole 22, the diameter of the second coupling hole 22 Tolerance 45, which is a space portion spaced apart from the outer circumferential surface of the second die tip 35 and the inner wall surface of the second coupling hole 22, is made larger than the diameter of the second die tip 35. It is characterized.

As shown, the hot extrusion die is embedded in the die case 15, the coupling holes (18, 22) formed in the center, the coupling holes (18, 22) of the die case 15 in a shrink fit and the central portion thereof The die tip 25, 35 through which the extrusion hole 19 through which the extrudate passes is formed is the same as in the prior art.

In this case, the die case 15 has coupling holes 18 and 22 formed at the center thereof with first and second coupling holes 18 and 22, and the die tips 25 respectively include first and second dies. It consists of tips 25 and 35.

As shown in Fig. 5, the second die tip 35, which is a bearing portion that actually affects the dimensions and surface quality of the product by making the die tips 25 and 35 constituting the main portion of the die, is made of cemented carbide or industrial diamond. In addition, the lower first die tip portion 25 of the second die tip portion 35 uses general heat-treated steel made of the same material as the die case 15.

In addition, the die tips 25 and 35 are shrinked and fixed to the coupling holes 18 and 22 of the die case 15, but the die tips 25 and 35 may be processed in two stages by the die holes 15 and 22. The second engagement hole 22, which is a portion in contact with the second die tip 35 (the bearing portion, which is the main part of the die) of the tip 25, has a negative diameter relatively smaller than that of the second die tip 35. It does not have a tolerance, but rather it is processed to a positive tolerance formed relatively larger than the diameter of the second die tip 35 in consideration of the difference in thermal deformation.

Accordingly, a positive tolerance 45 is formed between the outer circumferential surface of the second die tip 35 and the inner wall surface of the second coupling hole 22 at a predetermined interval.

At this time, the tolerance 45 is determined by the difference between the heat deformation of the two materials, the size of the die case 15, the size of the die tip 25 and the use temperature.

And the determination of the tolerance 45 is determined by the following [Equation 1].

[Equation 1]

Die case tolerance = D × (A-B) × (T-T _r )

Where D is the die tip representation (the hydraulic diameter of the die tip).

         A: Larger coefficient of thermal expansion among coefficients of thermal expansion of the first and second die tips

         B: small coefficient of thermal expansion among the coefficients of thermal expansion of the first and second die tips

         T: Temperature for Extrusion

T _r: Room temperature.)

Using the above equation, the first coupling hole 18 of the die case 15, that is, the first coupling hole 18 in which the first die tips 25 of the die tips 25 and 35 are embedded is negative. A negative tolerance is set, and the second die tip 35 on the upper side of the first die tip 25 sets a positive tolerance 45.

At this time, the tolerance 45 is preferably formed in the range of 70 to 130% of the reference value calculated in Equation 1 above.

In fact, when the first die tip 25 is circular, the representative length of the first die tip 25 is its diameter, otherwise the concept of hydraulic diameter is used.

In fact, the allowable tolerance of the die case 15 is calculated as follows.

1) when the diameter of the first and second die tips 25 and 35 made of cemented carbide is 30 mm and the use temperature is 500 ° C.,

Tolerance of die case = 30 × (14-7) × 10e-6 × (500-30) ≒ 0.1 mm

(Coefficient of thermal expansion of steel: 12-14 μ / ° C., cemented carbide thermal expansion coefficient: 5-7 μ / ° C.)

Of course, the coefficient of thermal expansion of the material is slightly different depending on the measurement, so it is preferable to apply the above value with a slight margin.

2) When the diameters of the first and second die tips 25 and 35 made of industrial diamond are 30 mm and the use temperature is 500 ° C.,

Tolerance of die case = 30 × (14-4) × 10e-6 × (500-30) ≒ 0.15 mm (Diameter's coefficient of thermal expansion: 2-4μ / ℃)

Of course, in the above two cases, the first coupling hole 18 of the die case 15 has a negative tolerance (0.07 mm) and applies shrink fit.

According to the hot extrusion die configured as described above, the die case 15 is inserted into a chamber at a predetermined temperature and thermally expanded, and then the first and second die tips 25 and 35 are respectively made of the thermally expanded die case 15. The first and second die tips 25 and 35 are inserted into the first and second coupling holes 18 and 22 of the die case 15 so as to be inserted into the first and second coupling holes 18 and 22, respectively. When the temperature is gradually lowered to the same temperature in the same chamber, the die cases 15 are contracted again so that the first and second die tips 25 and 35 are first and second coupling holes 18 and 22 of the die case 15. ) Is shrinked in each.

At this time, the first die tip 25 is made of heat-treated steel of the same material as the die case 15, so the coefficient of thermal expansion is the same, so that the first die tip 25 is formed by the inner wall surface of the first coupling hole 18. While no stress is applied, a positive tolerance is formed between the outer circumferential surface of the second die tip 35 and the inner wall surface of the second coupling hole 22, so that the die case 15 shrinks again. Since an excessive force is not applied to the second die tip 35 by the inner wall surface of the second coupling hole 22 due to the contracting force, the first and second dies 15, which are heat-treated steel, and cemented carbide or industrial diamond. The internal stress is not generated by the difference in heat deformation of the die tips 25 and 35.

Therefore, since such damage does not occur due to such a stress, there is an advantage that can significantly improve the life and reliability of the product.

As described above, according to the present invention, when shrinking the die tip in the die case, the internal stress does not occur due to the difference in heat deformation between the die case, which is a heat-treated steel, and the die tip, which is a cemented carbide or an industrial diamond. Since no damage or the like is caused, a new configuration of hot extrusion die can be provided, which can significantly improve the life and reliability of the product.

1 is a structural diagram of a main part of a conventional die;

2 is a cross-sectional perspective view of a conventional dice.

3 is a plan view showing a shrink fit state of a conventional dice.

Figure 4 is a damage form of a conventional dice.

5 is a cross-sectional view showing a schematic configuration of a die according to the present invention.

<Explanation of symbols for main parts of the drawings>

10. Die Case 18. First Joining Hole

22. 2nd engagement hole 25. 1st die tip

35. Second die tip

Claims (3)

 In the hot extrusion die comprising a die case formed through the coupling hole in the center, and a die tip embedded in the coupling hole of the die case, the die tip formed through the extrusion hole through which the extrudate passes.  The coupling hole of the die case comprises a first coupling hole and a second coupling hole having a larger diameter than the first coupling hole;  The die tip is made of a first die tip embedded in the first coupling hole and a second die tip embedded in the second coupling hole of a material having a coefficient of thermal expansion smaller than that of the die case; The diameter of the second coupling hole is made larger than the diameter of the second die tip, characterized in that the clearance is formed between the outer peripheral surface of the second die tip and the inner wall surface of the second coupling hole a predetermined interval spaced Hot extrusion dies.  The method of claim 1,  The first die tip and the second die tip of the die tip is made of heat-treated steel and cemented carbide material, or hot extrusion die, characterized in that made of heat-treated steel and industrial diamond.  The method of claim 1,  The tolerance formed between the outer circumferential surface of the second die tip and the inner wall surface of the second coupling hole is formed by 70 to 130% of the reference value calculated by Equation 1 below. [Equation 1] Die case tolerance = D × (A-B) × (T-T _r ) Where D is the die tip representation (the hydraulic diameter of the die tip).          A: Larger coefficient of thermal expansion among coefficients of thermal expansion of the first and second die tips          B: small coefficient of thermal expansion among the coefficients of thermal expansion of the first and second die tips          T: Temperature for Extrusion T _r: Room temperature.)