KR100892159B1 - Shank for core drill manufactured by cold forging process and Method thereof - Google Patents

Abstract

The present invention uses a cold forging method to reduce the processing time by a simple process, increase the hardness and strength, and by forming the coupling portion 20 and the shank 30 integrally to increase the resistance to torsion stress to minimize the failure rate A core drill shank 10 and a method of manufacturing the same, which can be mass-produced at a low cost with high durability, the core drill shank 10 includes: a material cutting step of cutting a prepared material of a predetermined shape into a predetermined size; Annealing heat treatment step of annealing the cut material at room temperature of 830 to 850 ° C. in an annealing furnace for 3 to 5 hours, and then furnace-cooling at 500 ° C .; A short treatment step of shorting the annealing heat treated material; Lubricating the surface of the shorted material and forming a film; Pressing the coated material into a mold installed in a forging machine of a predetermined pressure to form a basic shape of the core drill shank 10 in which the coupling part 20 and the shank 30 are integrated; And a core drill shank composed of a step of finishing the inner and outer diameters of the shank 30 formed by the molding step, a screw processing step of the coupling part 20, and a groove processing and an angle processing step of the shank 30 side ( It is produced through the finishing processing step of 10).

Cold Forging Method, Shank, Joint, Material, Lubrication, Film, Annealing Heat Treatment

Description

Shank for core drill manufactured by cold forging process and Method et al.

1 is a manufacturing process diagram of a conventional core drill shank for processing raw materials such as round bar directly;

Figure 2 is a manufacturing process of the conventional core drill shank welded using a pipe,

3 is a manufacturing process diagram of the shank for core drill using the cold forging method according to the present invention,

Figure 4 is a partial cutaway view of the (a) material of the shank for core drill produced by the cold forging method according to the present invention, (b) the basic shape formed and (c) the finished shank.

The present invention relates to a shank for a core drill and a method for manufacturing the same, and more particularly, by using a cold forging method, to reduce machining time by a simple process, increase hardness and strength, and torsional stress by integrally forming the coupling part and the shank. The present invention relates to a core drill shank manufactured by a cold forging method which can be mass-produced at a low cost with high durability and to minimize the defective rate by increasing resistance to the same.

In general, a core drill is used in a drilling operation, and is composed of a coupling portion coupled to the core drill body, a shank having a discharge groove formed on an outer circumferential surface thereof, and a plurality of diamond tips formed by a rim or segment on a lower circumferential surface of the shank.

Couplings are known that are threaded or hollow cylindrical, protruding from the shank. The female threaded joint is manufactured by direct processing of a raw material such as a round bar, and the shank fixedly attached to the hollow cylindrical joint has a hollow cylindrical shape having the same diameter so as to be attached by welding.

Such a conventional method of manufacturing a core drill shank is illustrated in FIGS. 1 and 2.

Shank manufactured by the method of directly processing the raw material shown in Fig. 1, the inner diameter roughing operation of the first round through the CNC (Computerized Numerical Control) after the round bar cut to a predetermined length is subjected to the outer diameter processing in the secondary processing . Afterwards, the inner diameter finishing process, which is the third process, the outer diameter finishing process, which is the fourth process, and the inner thread processing, which is the fifth process, are carried out. Manufacture shank.

As such, the direct processing method of raw materials in Korea depends on imports of iron ore, which leads to lower production costs due to raw material loss during raw material purchase and cutting, as well as excessive internal machining time, resulting in low productivity. As it is not possible to supply high-quality products, in particular, the strength is not high, there is a problem that the crack and breakage of the shank occurs because the durability against torsional stress due to high speed rotation is reduced.

In addition, the shank for core drill manufactured by the method of welding using the pipe shown in FIG. 2 cuts the hollow cylindrical pipe which both sides penetrated to predetermined length, and after performing inner diameter finishing and outer diameter finishing, The core drill shank is manufactured by a process of performing an inner and outer diameter finishing process, a grooving process, and an anodizing process after performing machining and anodizing, and then welding the joint or a workpiece having a predetermined width to one side of the cut pipe.

In the manufacturing method using such a pipe, there is a problem in that the weldability decreases due to the material difference between the pipe and the joining part (or the processed product), thereby increasing the defective rate such as cracking of the weld part. There is a problem that the durability against the torsional stress due to rotation is significantly reduced in the weld.

In addition, the conventional shank for core drill has a problem that the strength of the shank itself is weak and the durability of abrasion due to contact with the workpiece during the drilling operation is remarkably low and often needs to be replaced after use.

The present invention has been made to solve the above problems, an object of the present invention by using a cold forging method to reduce the processing time by a simple process, increase the hardness and strength, and torsional stress by forming the coupling portion and the shank integrally The present invention provides a core drill shank manufactured by a cold forging method which can be mass-produced at a low cost with high durability while minimizing a defect rate by increasing resistance to the same, and a method of manufacturing the same.

In order to achieve the object of the present invention as described above, the present invention,

In the method of manufacturing a core drill consisting of a coupling part, shank, and tip,

Cutting the prepared material into a predetermined size in a predetermined shape;

Annealing heat treatment step of annealing the cut material in an annealing furnace at a room temperature of 830 to 850 ° C. for 3 to 5 hours and then furnace-cooling at 500 ° C .;

A short treatment step of shorting the annealing heat treated material;

Lubricating and forming a coating on the surface of the shorted material;

Pressing the coated material into a mold installed in a forging machine of a predetermined pressure to form a basic shape of the shank for core drill in which the coupling part and the shank are integrated; And

And finishing the inner and outer diameters of the shank formed by the forming step, and finishing the step of finishing the core drill shank consisting of a screwing step of the coupling part and a groove processing and an angle processing step of the shank side. It features.

In addition, the lubrication and film forming step of the material surface,

Alkaline degreasing with alkaline degreasing agent of 30 ± 5p for 5-10 minutes, degreasing with water for 10-30 seconds in water of pH 8-10, pickling for 3-5 minutes with hydrochloric acid with 15-20% concentration, pH 4 Rinsing for 10-30 seconds in water of ~ 7, coating the water-soluble film for 5-10 minutes with a complex compound having an acidity of 10-20p, and then washing 1, 2 times for 10-30 seconds in water of pH 5-7, And neutralizing in water of pH 8-9 and then drying to form MoS ₂ with a lubricant having a concentration of 30-40%.

In the present invention, the core drill shank is manufactured by using the cold forging method.

In general, forging refers to an operation of making a solid metal material into a uniform shape by hammering or pressing a metal material with a hammer, and forging at a temperature higher than the temperature at which recrystallization of the solid material proceeds. This is called hot forging, and forging at lower temperature or room temperature is called cold forging.

Cold forging has more uniform structure, higher hardness and higher precision than hot forging, but requires surface lubrication.

Surface lubrication in cold forging is to improve the lubricity of the product during processing and to prevent sticking with the mold. Conventional surface lubrication is degreasing-> washing-> washing sulfuric acid-> washing-> Hwaseong (zinc phosphate coating) )-> Washing-> Neutralization-> Lubrication-> Drying etc. It is performed sequentially by about 9 processes.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

Figure 3 shows the manufacturing process of the core drill shank using the cold forging method according to the invention, Figure 4 (a) ~ (c) is the material of the core drill shank produced by the cold forging method according to the invention, Some cutaway views of the molded basic shape and some forward cross-sectional views of the finished shank.

As shown in Figure 3 and 4, the shank for core drill 10 using the cold forging method according to the present invention, the coupling portion 20 and the shank 30 is configured integrally, cutting material (S10) , Through annealing heat treatment step (S20), short treatment step (S30), lubrication and film forming step (S40), basic shape forming step (S50), and finishing processing step (S60).

In the material cutting step (S10),

According to the desired product, a rod-shaped material of predetermined dimensions is selected, and then cut to the desired weight and size. In this case, the material used is SM20C, which has excellent corrosion resistance, cold workability, drillability, and cold forging.The weight of the cut material is preferably about 1,030g ± 10g, and the outer diameter of the round bar is about Ø65 ± 0.3. Do.

In the annealing heat treatment step (S20),

After the cut material is annealed for 3 to 5 hours in an annealing furnace at room temperature of 830 ~ 850 ℃, it is preferable to be cooled at 500 ℃ to a hardness value of HRB60 or less. This annealing heat treatment is to soften the material and to remove the internal stress to improve the cold workability.

The annealing conditions and cooling conditions described above are preferable numerical ranges in the manufacture of the shank for core drill according to the present invention. Depending on the numerical range, the plastic flow characteristics of the metal and the mechanical properties such as the size, hardness and strength of the crystal grains vary. If the annealing heat treatment is carried out outside the numerical range, as a result, problems such as microcracks due to shear cracking occur during extreme deformation of the material by cold forging.

In the short processing step S30,

The annealing heat-treated material is put into a shot machine and shot processed for 30 minutes or more using a shot ball having a diameter of 0.8.

This short treatment is to remove the strong foreign matter and scale attached to the surface of the material so that the appropriate roughness acts on the surface, thereby making the subsequent lubrication and film formation efficient and smooth.

Lubricating and film forming step (S40),

In order to increase the lubricity of the product during processing and to prevent the adhesion with the mold to form a film, which is described in sequence as follows.

(1) The surface of the shortened material is degreased with an alkali degreaser having an alkalinity of 30 ± 5p in a coating line for 5 to 10 minutes. Degreasing by alkaline degreasing agents is an efficient process that not only removes all contaminants in a single operation but is also easy to control.

Next, (2) degreasing washed in water of pH 8-10 for 10-30 seconds. This is to clean all the alkaline agent remaining on the surface of the material.

Next, (3) Pickling with hydrochloric acid having a concentration of 15 to 20% for 3 to 5 minutes. This is to increase the surface area of the material and to remove the remaining foreign matter and scale (scale) to increase the weight of the film after the film formation and the film efficiently to increase the formability of cold forging.

Next, (4) washed with water at pH 4-7 for 10-30 seconds. This is to clean all hydrochloric acid remaining on the surface of the material.

Next, (5) A water-soluble film is formed for 5 to 10 minutes with a composite compound having an acidity of 10 to 20 p. This is different from the usual zinc phosphate coating process, which prevents the occurrence of sintering with the mold in the basic shape forming step of the shank for core drill, as well as excellent surface treatment of the material surface in the plastic deformation step. To prevent cracks and smooth lubrication process.

In the case where the zinc phosphate coating is formed on the surface of the material, problems such as poor rear surface treatment of the material surface occur.

Next, (6) 1st and 2nd washings for 10-30 seconds in water of pH 5-7. This is to clean all hydrochloric acid remaining on the surface of the material.

Next, (7) neutralized water in water of pH 8-9, and after drying, MoS _{2 with a} lubricant (high purity molybdenum disulfide system) having a concentration of 30-40%. A lubrication layer is formed.

Through this coating step, the film thickness of 5 ~ 8㎛ is maintained and the appearance inspection of the material is completed. The coated material M is shown in Fig. 4A.

In the basic shape molding step (S50),

When the coated material is placed on a die of a press mold installed in a cold forging machine at a constant pressure, and the upper punch of a predetermined diameter is lowered, the material is pressurized, causing plastic deformation to flow along the upper punch, and at the same time, in the recess formed in the die. The basic shape of the core drill shank 10 in which the coupling portion 20 and the shank 30 of the core drill are integrated is formed (see FIG. 4B).

The pressure of the cold forging machine can be selected in a variety of 20 ~ 1150 tons in accordance with the desired product, of course, it is also not limited to the above pressure range is possible to work at a pressure of less or more.

In addition, the length of the shank 30 is kept constant by the upper punch, the diameter and length of the shank 30 is variable by the shape of the press mold and the pressure used.

In this way, by integrally forming the coupling portion 20 and the shank 30 by cold forging, the number of processing steps are reduced, the machining time is reduced, the hardness and strength is increased, and the coupling portion 20 and the shank 30 Since integrally formed, the resistance to torsional stress during drilling is increased and the durability is high.

In the finishing processing step (S60),

Finishing the inner and outer diameter of the molded shank 30 by a known finishing method, and also screwed into the coupling portion 20, the side of the shank 30, the workpiece generated during the drilling operation, In order to facilitate the discharge of dust, frictional heat, air, etc., grooves (H) of various shapes such as spirals are subjected to a bilateral processing (see FIG. 4C).

A diamond tip of rim type or segment type is attached to the lower circumferential surface of the core drill shank 10 manufactured according to the above method, and then connected to the core drill body to perform a drilling operation.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, other various modifications and variations may be made without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to cover such modifications and variations as fall within the true scope of the invention.

The shank for core drill according to the present invention has an effect of reducing the processing time by a simple process, because the coupling portion and the shank connected to the core drill body is integrally formed using a cold forging method.

In addition, the microstructure of the material is changed by the cold forging method to increase the hardness and strength of the shank for core drill, as well as to increase the resistance to torsion stress by the integrally formed coupling portion and the shank.

In addition, the shank for core drill produced according to the present invention has the effect that the defect rate is minimized and the durability is high and the mass production is possible at low cost.

Claims (3)

In the method of manufacturing a core drill consisting of a coupling part, shank, and tip, Cutting the prepared material into a predetermined size in a predetermined shape; Annealing heat treatment step of annealing the cut material in an annealing furnace at a room temperature of 830 to 850 ° C. for 3 to 5 hours and then furnace-cooling at 500 ° C .; A short treatment step of shorting the annealing heat treated material; Lubricating and forming a coating on the surface of the shorted material; Pressing the coated material (M) with a mold installed in a forging machine of a predetermined pressure to form a basic shape of the core drill shank 10 in which the coupling part 20 and the shank 30 are integrated; And For core drill consisting of finishing the inner and outer diameters of the shank 30 formed by the forming step, the screw processing step of the coupling portion 20 and the groove processing and the angle processing step of the shank 30 side Includes; finishing processing step of the shank 10, The lubricating and film forming step of the material surface, Alkaline degreasing with alkaline degreasing agent of 30 ± 5p for 5-10 minutes, degreasing with water for 10-30 seconds in water of pH 8-10, pickling for 3-5 minutes with hydrochloric acid with 15-20% concentration, pH 4 Rinsing for 10-30 seconds in water of ~ 7, coating the water-soluble film for 5-10 minutes with a complex compound having an acidity of 10-20p, and then washing 1, 2 times for 10-30 seconds in water of pH 5-7, And neutralizing in water of pH 8-9, and then drying to form MoS ₂ with a lubricant having a concentration of 30-40% by using a cold forging method. delete delete

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