JP4535964B2 - Drilling bit - Google Patents

Description

  The present invention relates to a drill bit used for drilling a tapping hole sleeve of a steelmaking converter.

  The tapping hole of the converter for steel making is provided with a tapping sleeve made of refractory bricks. If repeated tapping, the inner diameter of the sleeve will gradually increase due to wear and melting caused by the tapping steel flow, making it impossible to perform proper tapping. . For this reason, it is necessary to disassemble the tapping sleeve every several hundred charges and replace it with a new one. As shown in FIG. 1, this operation is performed by attaching a drill bit 3 to the tip of the rod 2 of the dismantling machine 1 and drilling the tap hole sleeve 4 while rotating. The temperature of the tapping hole sleeve 4 at the time of drilling is generally a high temperature of 500 to 1000 ° C.

  For this purpose, a drilling bit 3 having a structure in which a number of cemented carbide tips made of cemented carbide are brazed onto the drilled surface of the bit body is used. However, such a drilling bit 3 is a diversion of a technique used in a rock drill for construction or mine excavation, and is not sufficiently considered for use in a high temperature region of 500 to 1000 ° C. Carbide tips sometimes dropped out.

  As shown in Patent Document 1, a hot drilling bit in which a water or air ejection hole is formed in the bit body and the bit body is cooled has also been proposed. Oxidation wear and erosion can not be effectively prevented, and the carbide tip may fall off early, and once the carbide tip is dropped, it will be loosely embedded in the bit body, Since it is easy to drop out again, complete repair is difficult, and the entire bit body must be replaced with a new one.

Thus, conventionally, expensive hot drilling bits have to be frequently replaced, which has been a cost-up factor. Also, if the load is reduced, such as by reducing the number of rotations of the hot drilling bit in order to prevent the carbide tip from falling off, it will take a long time to drill the tap hole sleeve, leading to a reduction in the operating rate of the converter. There was a problem.
Japanese Utility Model Publication No. 6-47348 (Claim 2, FIG. 6)

  Therefore, the object of the present invention is to improve the durability by making it possible to easily repair even when worn by making build-up welding for hardening, and to efficiently perforate the tapping sleeve of the converter. It is to provide a hot drilling bit having excellent properties.

The hot drilling bit of the present invention made to solve the above-mentioned problems is a hard cladding on the tapered front surface and the outer peripheral surface of the bit body used for drilling the tapping sleeve of the converter. A chip made of a welding material is formed. The hard build-up welding material is preferably a metal having a hardness at 800 ° C. of 200 HV or higher, and particularly preferably a stellite or a heat-resistant steel system. Moreover, it is preferable that the area which the chip | tip which consists of hard build-up welding materials occupies 10 to 50% of the drilling surface of a bit main body.

Since the hot drilling bit of the present invention is formed by forming a chip made of hard build-up welding material on the drilling surface of the bit body, the welding force is strong because it is a fusion welding with the bit body made of tool steel. If the tip is worn, it can be easily repaired by overlay welding. For this reason, it is possible to efficiently perforate the tapping hole sleeve. The present invention can also be carried out by a method in which when a conventional cemented carbide chip made of a cemented carbide is dropped, the portion is formed into a chip made of hard overlay welding material, which is also effective as a repair technique. .

Preferred embodiments of the present invention are shown below.
2 and 3 show an embodiment of a hot drilling bit according to the present invention, wherein 10 is a shank attached to the tip of the rod 2 of the dismantling machine 1, and 11 is a bit formed at the tip of the shank 10. This is a main body, and in this embodiment, a large drill bit having an outer diameter of 520 mm. The bit body 11 has an umbrella shape in the cross section of FIG. 2 and a petal shape of eight valves partitioned by the radiation groove 12 in the front view of FIG. The tapered front surface and outer peripheral surface of the bit body 11 are perforated surfaces 13 and 14, and a large number of tips 15 are formed on these perforated surfaces 13 and 14 by overlay welding.

The build-up welding of the tip 15 is performed using a hard build-up welding material. As the hard overlay welding material, a metal having a hardness at 800 ° C. of 200 HV or more is preferable. 800 ° C. is a typical temperature for hot drilling of the tap hole sleeve, and if the hardness at this temperature is lower than this, the wear of the tap hole sleeve 4 made of refractory bricks is fast and sufficient. This is not preferable because a lifetime cannot be obtained. Typical examples of the hard overlay welding material having such hot hardness are stellite and heat-resistant steel. Stellite is a Co—Cr—W alloy and has a hardness of 450 HV or higher at 800 ° C.

  In the present invention, the shape of the chip 15 is not particularly limited, but the head protruding from the bit body 11 has a dome shape like the conventional carbide chip, and the lower half of the columnar shape is formed on the bit body 11. A shape supported by the holes 16 is preferable. Cutting is performed at the protruding head portion, and the cutting powder is discharged from the gap between the chips 15. For this reason, it is preferable that the area which the chip | tip 15 consisting of a hard build-up welding material occupies is 10 to 50% of the drilling surfaces 13 and 14 of the bit main body 11 from a viewpoint of cutting performance and the discharge | emission property of cutting powder. If it is less than 10%, a sufficient drilling speed cannot be obtained, and if it exceeds 50%, clogging with cutting powder occurs and the drilling speed is also lowered.

Hot boring bit of the present invention as described above, the chip 15 made of a hard overlay welding material perforated surface of the bit body 11 is made by forming a build-up welding, all chips 15 rigid cladding initially Even if the structure is made of a welding material, or when the conventional carbide tip is dropped from the bit body 11, the portion is repaired with the tip 15 made of a hard overlay welding material, so that the carbide tip and the tip 15 can be repaired. It may be a mixed structure. In either case, the tip 15 can be easily formed by overlay welding.

  In addition, the tip 15 itself made of hard build-up welding material has the same durability as the case where the conventional carbide tip does not fall off and the tip portion can be easily regenerated, so the bit body 11 should be used semipermanently. It is possible to reduce the cost significantly.

  Drilling bits are made on the drilling surface of the bit body shown in FIG. 2 by fixing the tips made of the four types of materials shown in Table 1 below by welding or overlay welding, and drilling the tapping sleeve sleeve of the converter Evaluation of durability and cost when used in As shown in the table, it can be seen that the drilling bit of the example exhibits excellent characteristics in both durability and cost.

It is explanatory drawing of the drilling operation | work of the tapping hole sleeve. It is sectional drawing of the bit for punching. It is a front view of the bit for punching of this invention. It is an enlarged view of a chip part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dismantling machine 2 Rod 3 Bit for drilling 4 Hot spring hole sleeve 10 Shank 11 Bit body 12 Radiation groove 13 Perforated surface 14 Perforated surface 15 Tip

Claims (4)

A drill bit characterized in that a tip made of a hard welding material is formed on a tapered front surface and an outer peripheral surface of a bit body used for drilling a tapping sleeve of a converter.   The drill bit according to claim 1, wherein the hard build-up welding material is a metal having a hardness at 800 ° C. of 200 HV or more.   3. The drill bit according to claim 2, wherein the hard build-up welding material is stellite or heat-resistant steel.   2. The drilling bit according to claim 1, wherein an area occupied by the chip made of the hard overlay welding material is 10 to 50% of the drilling surface of the bit body.

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