Hard metal tool and method for fixing a hard tip

Abstract

A cemented carbide tool, wherein a hard tip (3) is fitted into an internally threaded tip hole (2) formed on a steel base metal (1), and from there, an externally threaded sleeve (5) is screwed into the internal thread of the tip hole (2) to press and fix the hard tip (3), wherein a flange (31) is integrally formed on a base part of the hard tip (3), the flange (31) having an outer diameter equal to an inner diameter of the tip hole (2), and a lower surface of the sleeve (5) is in close contact with an upper surface of the flange (31), the internal thread being provided in the steel base metal (1).

Description

Technical area

[0001] The present invention relates to a method for fixing a hard tip to a tool such as a drill or a striking tool (hereinafter referred to as "carbide tool") provided with a cemented carbide tip or a ceramic tip (hereinafter referred to as "hard tip"). State of the art

[0002] Drills, finishing tools for masonry, and other work typically include a hard point (generally a cemented carbide point) set into a steel base metal. One method for attaching the hard point is a brazing process, in which a point hole is drilled, a hard point is fitted into a base metal, and then the hard point is fitted into the point hole, although a shrink-fit process may also be used.

[0003] However, this poses the problem that, in a tool to which the hard tip is fixed using the aforementioned brazing or shrink-fitting process, the hard tip may be damaged or loosened due to thermal stress because the tool is heated to a high temperature when the workpiece is at a high temperature. For example, a taphole in a blast furnace is closed again after tapping molten pig iron to proceed to the subsequent melting step.When a tool bit is used for opening the taphole or for flattening an opening part during the taphole closing (a front end of a taphole plugging machine used for closing needs to be flattened to make close contact with an opening periphery of the taphole), there arises a problem that a cemented carbide tip is quickly loosened by the high temperature of the furnace wall when a tool bit prepared by brazing a hard tip or a shrink-fit tool bit is used.

[0004] Patent Document 1 discloses a known method for fixing a tool bit to a drilling machine, which reduces the likelihood of tip loosening. According to this method, irregularities are formed on a side surface of a base end of the tip, and welding is performed to cover the side surface.

[0005] Further relevant status is mentioned in US 4 199 035 A. Prior art documentPatent document

[0006] Patent Document 1: Published Unexamined Japanese Patent Application No. 2003-214080 Summary of the inventionProblem of the invention

[0007] Since the method of Patent Document 1 performs direct welding to cover an outer peripheral surface of the tip, the tip is at least firmly fixed. However, when a cemented carbide tip made of a fragile material is used, a crack may be generated due to thermal or other impact. This poses a practical problem. Various methods have been proposed in addition to the above-mentioned method, but no practical method for fixing a cemented carbide tip or the like for use at a high temperature has been provided. Therefore, an object of the present invention is to provide a fixing method capable of firmly holding a hard tip such as a cemented carbide tip so that the tip does not come off when used at a high temperature. Problem solving

[0008] According to the present invention, a hard metal tool having the features of claim 1 is provided.

[0009] In addition, a method for fixing a hard tip with the features of claim 2 is specified.

[0010] Because the cemented carbide tool according to the present invention mechanically pushes and fixes a hard tip into a tip hole using a threaded sleeve, it can be used at high temperatures such as for opening a tap hole of a blast furnace. Furthermore, according to the hard tip fixing method of the present invention, the hard tip is held in a fitted manner in the tip hole formed on a base metal and is pushed therefrom by a sleeve, the sleeve is screwed into an internal thread on an inner periphery of the tip hole and firmly fixed, so that the hard tip is solidly held. With this fixing method, the hard tip is not heated to a high temperature during fixing, so that cracks do not occur in the hard tip.Furthermore, this process does not use brazing materials and, unlike a shrink-fit process, does not involve thermal expansion. Therefore, there is no risk of the tip becoming loose when exposed to high temperatures during use. Brief description of the drawings Fig. 1 is a sectional view showing a fixation method. Fig. 2 is a sectional view showing corresponding procedures. Fig. 3 includes a top view (a) and a side view (b) of a base metal. Fig. 4 is a sectional view showing two tip holes on the base metal on the right and left sides, respectively. Fig. Figure 5 is a cross-sectional view of the base metal. Fig. 6 includes a plan view (a) and a side view (b) showing a tool insert for opening a tap hole. Fig. Fig. 7 is a sectional view showing an embodiment different from the above-described embodiment. The embodiment in Fig. 7 falls under the wording of claims 1 and 2. The further embodiments which are related to Fig. 1 to 6 and 9 and 10 are helpful for understanding the present invention. Fig. Fig. 8 is a sectional view showing that the embodiment provides a fixed connection. Fig. 9 is a view showing a reference example different from the embodiment. Fig. 10 is a sectional view showing that the reference example provides a fixed connection. Preferred embodiments of the invention

[0011] In the following, various embodiments are explained in detail. In the following embodiments, the embodiments are those relating to Fig. 1 to 6 and on Fig. 9 and Fig. 10 are helpful for understanding the present invention. The embodiment in Fig. 7 and Fig. 8 is an embodiment according to the present invention. Example 1 (unclaimed example)

[0012] Fig. 1 shows a cemented carbide tool according to the present invention, in which a base portion of a hard tip 3 (in this case, a cemented carbide tip) is fitted into a tip hole 2 formed on a head portion of a steel base metal 1. A bottom surface of the tip 3 makes close contact with a bottom surface 7 of the tip hole 2.

[0013] As in Fig. As shown in Figure 2, the hard tip 3 includes a head portion 3a, a body portion 3b, and a base portion 3c. The head portion 3a is substantially conical, with a small diameter at its front end and a large diameter at the body portion. The body portion 3b is a circular cylinder with a constant diameter, while the base portion 3c is formed as an inclined surface having a conical cross-section with a small diameter at the body portion and a gradually increasing diameter at the base portion.

[0014] An inner diameter of the tip hole 2 on the base metal 1 is larger than an outer diameter of the major part of the base portion of the hard tip 3, maintaining a gap 4 between an inner wall surface of the tip hole and an outer peripheral surface of the tip. An internal thread 2a is provided on an inner periphery of the tip hole 2.

[0015] A sleeve 5 is provided at a central portion with a fitting hole 6 into which upper and lower central portions of the hard tip 3 are fitted. An inner peripheral surface of the fitting hole 6 is formed as a trumpet-like inclined surface that is narrower at the upper side and wider at the lower side to make close contact with the inclined outer peripheral surface of the base portion 3c of the tip 3. Furthermore, an external thread 5a to be screwed into the internal thread 2a of the tip hole 2 is formed on an outer periphery of the sleeve 5. The sleeve 5 is screwed into the internal thread of the tip hole 2 of the base metal. Therefore, the sleeve 5 is preferably provided with engagement means such as a screw boss surface or an engagement pin hole for engagement with a tool such as a wrench.

[0016] To fix the hard tip 3 to the base metal 1, first, the hard tip 3 is fitted into a central part of the tip hole 2 and from there covered with the sleeve 5, thereby fitting the hard tip 3 into the fitting hole 6. In this state, the sleeve 5 is screwed into the internal thread of the tip hole 2 until the sleeve 5 makes close contact with the hard tip 3. In the shown example, the inner peripheral surface of the fitting hole 6 of the sleeve 5 is formed as an inclined surface that makes close contact with an inclined surface of the base part of the hard tip 3. Therefore, the sleeve 5, whose inner peripheral surface makes close contact with an outer peripheral surface of the hard tip, does not reach the bottom surface 7 of the tip hole 2, so that a gap is formed between the bottom surface and a lower surface of the sleeve 5. Therefore, the tip 3 is pressed and fixed by the sleeve 5.In particular, in the examples shown by . Fig. 6 and Fig. 7, the outer peripheral surface of the tip 3 is formed as a conical inclined surface, and the inner peripheral surface of the sleeve 5 is formed as a trumpet-shaped inclined surface that fits onto the outer peripheral surface of the tip. Thus, the inner peripheral surface of the fitting hole on the sleeve 5 makes close contact with the outer peripheral surface of the tip, allowing the tip to be firmly fixed.

[0017] Fig. 3 to Fig. 5 show the base metal 1. The base metal 1 is formed of steel and is provided with a plurality of tip holes 2 and a flashing hole 8 on an upper surface (front end surface) including four cutting wings 13, and further with a flashing hole 9 on a side surface. The reference numeral 20 in Fig. 5 indicates a threaded hole for attaching a drill rod. Fig. 6 shows the appearance of a tool insert in a completed state in which the hard tip 3 is firmly fixed to the base metal 1.

[0018] In the example shown, an upper surface of the sleeve 5 to which the hard tip 3 is fixed slightly protrudes from the surface of the base metal 1. However, the sleeve 5 may be designed to be substantially flush with the surface of the base metal 1. When a tool bit is used for opening a tap hole, the hard tip is damaged even during the first use due to the high temperature applied during opening. Therefore, the tool bit is usually discarded after use. Therefore, for the process of fixing the hard tip, the appearance, etc., of the hard tip is not a problem as long as the hard tip can be solidly fixed, thus ensuring practical use. Example 2 (embodiment according to the invention)

[0019] Fig. 7 and Fig. 8 shows an embodiment slightly different from the above-described embodiment. In this example, a flange 31 is integrally formed on a base part of a hard tip 3. The outer diameter of the flange 31 is substantially equal to the inner diameter of a tip hole 2, the height of which is several millimeters. A sleeve 5 is screwed onto the flange. The lower surface of the sleeve 5 comes into close contact with the upper surface of the flange 31. The flange 31, integrally formed with the hard tip 3, is pressed as described above, so that the hard tip 3 can be fixed more reliably. Example 3 (unclaimed example)

[0020] Fig. 9 and Fig.10 shows a reference example different from the above-described example. In this example, an external thread 14 is directly provided on an outer periphery of a base part of a hard tip 13. The hard tip 13 is directly screwed into an internally threaded tip hole 2. Thus, the hard tip 13 is directly screwed into a base metal 1. Components are usually screwed into a base material. Generally, a hard tip is fragile, so it is not fixed using a screw. However, because most tools for opening a tap hole are generally discarded after a single use, the above-described fixing method using a screw can be applied. As described above, an external thread can be formed on a hard tip. However, it is generally difficult to thread a hard tip.Therefore, the hard tip is preferably pressed as described above for the example using the sleeve 5.

[0021] As explained above, the hard tip fixing method according to the present invention can mechanically and firmly fix a hard tip such as a cemented carbide tip to a steel base material. The hard tip is less prone to loosening when used on a high-temperature workpiece. Furthermore, the hard tip is not subject to thermal stress during the fixing process. Therefore, the cemented carbide tip made of a fragile material can be reliably fixed. Industrial applicability

[0022] With the method for fixing a hard seat to a cemented carbide tool according to the present invention, the hard seat can be firmly and easily fixed to a steel base metal, and the method can also be used for fixing a seat to a cemented carbide tool that is exposed to a high temperature. List of reference symbols 1 base metal 2 tip holes 3 hard tip 5 sleeve 13 hard tip 31 flange

Claims

[1] A cemented carbide tool, wherein a hard tip (3) is fitted into an internally threaded tip hole (2) formed on a steel base metal (1), and from there, an externally threaded sleeve (5) is screwed into the internal thread of the tip hole (2) to press and fix the hard tip (3), a flange (31) is integrally formed on a base part of the hard tip (3), the flange (31) having an outer diameter equal to an inner diameter of the tip hole (2), and a lower surface of the sleeve (5) is in close contact with an upper surface of the flange (31), the internal thread being provided in the steel base metal (1). [2] A method for fixing a hard tip (3), wherein a tip hole (2) larger than an outer diameter of the hard tip (3) is formed at a corresponding position on a steel base metal (1) and an internal thread (2a) is formed on an inner circumference of the tip hole (2), the hard tip (3) having an integrally formed flange (31) projecting in an outer circumferential direction at a bottom is fitted into the tip hole (2), and a sleeve (5) having an external thread (5a) on an outer circumference to be screwed into the internal thread (2a) of the tip hole (2), is screwed into the internal thread (2a) of the tip hole (2) while the hard tip (3) is inserted in the through hole (6) to press the flange (31) of the hard tip (3), thereby fixing the hard tip (3) in the threaded hole of the base metal (1), wherein the flange (31) has an outer diameter equal to an inner diameter of the tip hole (2), and a lower surface of the sleeve (5) is in close contact with an upper surface of the flange (31), wherein the internal thread is provided in the steel base metal (1).

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