JPS5811289A - Cutter bit for drilling machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cutter bit for an excavator, and more particularly, to a cutter bit for an excavator, the cutter bit is connected to each of a plurality of bearing shafts provided at equally divided positions in the circumferential direction of the lower part of a body that is driven in revolution. To provide a cutter bit for an excavator having excellent durability by improving the wear resistance and fatigue resistance of the bearing surface of the cutter, in a cutter bit having a cutter rotatably mounted on the cutter. It is something.

This type of cutter bit is used to form drilling holes in the ground or rock.It is attached to the digging tip of a polling machine (excavation machine) to control its rotational drive from the ground. It has become.

FIGS. 1 and 2- are diagrams showing an example of the overall structure of a cutter bit for an excavator of this type to which the present invention is applied.

In FIGS. 1 and 2, a body 1 attached to the lower end of a vertical drive shaft of an excavator (poling machine) and driven in revolution has a plurality of legs (
Legs) 2 are fixed by bolts 3 and welds 4. These legs 2 are provided to protrude downward from the body 1, and in the example shown, three legs are fixed at equal intervals on the circumference.

A bearing shaft 5 is fixed to the lower part of each astragalus 2, and a cutter 7 is automatically attached to each bearing shaft 5 via a roller 6 which is a rolling element. The rolling element 6 is constituted by a plurality of rollers arranged on the circumference of the bearing shaft 50.

In this way, while the cutter bit enters into the ground or rock, the entire cutter bit is made to revolve through the body 1 and each cutter 7 is rotated on its own axis on the bearing shaft 5, thereby achieving the second point in the middle. chain line 8
An excavation hole like the one shown can be formed in the bedrock.

As shown in 1E, each cutter 7 is prevented from being removed by a plurality of balls 11 housed along the bearing shaft 5 and ball seats 9 and 10 formed at the fitting portion of the cutter. has been done. In addition, the nose pin 12 for good center positioning, which is formed at the bottom of the fitting hole of each cutter and is fitted into a nine-centered recessed hole, is fitted into the recessed hole 13 formed at the tip surface of the bearing shaft 5. , the bearing shaft 5 and the cutter 7 are aligned. The thrust load of the nose pin 12 is supported by a thrust metal 14 inserted into the center concave portion of the cutter 7.

On the surface of each cutter 70, several stages of cutting blades 15 are formed which are arranged in the shape of teeth in the circumferential direction around the axis of rotation. The entire cutter 7 including these digging blades 15 is J
Using structural case hardening steel such as IS standard 8NCM815,
Its surface is hardened by carburizing and quenching. That is,
The entire outer surface including the excavating blade 15 and the completely destroyed inner surface of the recessed hole including the bearing surface 16 were carburized and quenched to form a carburized hardened layer. On the other hand, the surface of the bearing shaft 5 was also carburized and hardened to form a carburized layer.

In conventional cutter bits for excavators,
The bearing surface L6-ffi of the cutter 7, that is, the outer race surface of the rolling element (low?-) 6, is formed of a carburized hardened layer. 16, the bearing surface 16 is worn out by the hard particles, resulting in a problem that the life of the cutter 7 is shortened.

In this type of cutter bit for excavators, a large impact load is applied to the bearing part between the cutter 7 and the bearing shaft 5 during excavation, and at the same time, dirt particles easily enter the bearing part, so the life of the cutter bit is shortened. It is limited by the wear and fatigue resistance of this bearing part. However, in the prior art, the bearing surface 16 of the cutter 7 and the bearing surface 17 of the bearing shaft 5
However, the overall life of the cutter bit was limited to the life of the bearing part, especially the wear resistance of the bearing surface 16 of the cutter 7 and the wear resistance of the bearing surface 16 of the cutter. There was a problem in that the cutter 7 had to be replaced frequently due to limitations in fatigue resistance. Ninthly, the improvement in efficiency of mMIJ work was also hindered.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
The object of the present invention is to improve the wear resistance and fatigue resistance of the hardened portion by forming a hardened layer on the bearing surface of the cutter using metal cementation and carburizing in combination.

4iVvI1 of the present invention. The method is to form a metal diffusion layer of Sifrom carbide by subjecting the bearing surface of the cutter to chromizing treatment and carburizing and quenching.

That is, according to the present invention, a body driven to revolve;
A plurality of legs fixed around the body and protruding downward, a bearing shaft provided at the bottom of each leg, and a plurality of cutters rotatably attached to each bearing shaft via rolling elements. There is provided a cutter bit for an excavator, characterized in that a metal diffusion layer of PM chloride is formed on the bearing surface of the cutter.

In this case, if a metal diffusion layer of chromium carbide is also formed on the bearing surface of the bearing shaft, the wear resistance and fatigue resistance of the bearing shaft can be further improved.

According to the second embodiment of the present invention, Cr (chromium) and mulv
A mixture of 1:1 powder with Om (alumina) was added to the bearing surface 16 of the cutter 7 of structural case hardening steel SNCM815, and heated to 100OC in an NH4Ct (ammonium chloride) atmosphere to form a chroma. An Ising treatment was performed to form a chromium diffusion layer, ie, a layer of cementation (alloy) substituted for metal, approximately 0.25 W+ thick. Next, carburizing and quenching was performed for hours to form a hardened layer with a thickness of about 1 to 1.51 mm.

The ht, o, and powders are removed after chromizing treatment to prevent agglomeration and assimilation of Cr powder and to uniformly disperse metallic chromium. In addition, the NH, Ct
The gas atmosphere is a reducing atmosphere and is intended to prevent oxidation of the Cr powder.

Through the above treatment, a metal diffusion layer (precipitation layer) of chromium carbide (CrllCR) is formed on the cutter bearing rkJ16.
A cutter bit for an excavator is manufactured using the
We conducted a trial excavation with this product and compared it with a product made using the conventional SN0M815 carburizing method, and the results were as follows.

The test conditions were: the bit was an 8-inch steel tooth type for medium hard rock, the bit rotation speed was 125 R, P, M, and the water flow was 3501.
The drilling was carried out using bentonite mud water for 1 minute, bit supply pressure of 2 to 7 tons, and the rock to be drilled was square tuff.

As a result, the bearing life of conventional cutter bits has increased by 3
In contrast, the bearing life of the above embodiment of the present invention was 45 to 55 hours.

That is, according to the above embodiment, the bearing life could be improved by about 1.4 times on average compared to the conventional technology.

According to the second embodiment of the present invention, Cr powder: At.

The ratio of Os powder was set to 1:3, and a metal diffusion layer of Cr was formed in a reducing atmosphere of NH, C23N, and a hydrogen flow rate of 1017 hours. All other conditions were the same as in the first example described above.

As a result, the bearing life could be improved to I[, which is the same as in the first embodiment described above, compared to the conventional product.

In the third embodiment of the present invention, the ratio of Cr powder:Mut*OS powder is 1:3, NH4Ct is 2X, and 8NCM81
A cutter of No. 5 was heated with granular graphite and activated carbon at 3% and in barium carbonate (BcLCOm) IX to remove Cr and C.
A diffusion layer of chromium carbide with a depth of 1.2 mm was obtained by simultaneous diffusion of the following, and then quenching and tempering was performed.

As a result of carrying out a bearing durability test on the cutter bit obtained in this way, the average cutter bit life was improved to 6071 in terms of digging distance, and the average bearing life was about 1.7 times longer than that of the conventional product (carburized and quenched product of 8NCM815). is obtained.

The third graph is a graph illustrating a comparison between a chromium carbide diffusion layer according to the present invention and a conventional single carburized and quenched layer from the viewpoint of hardness distribution characteristics with respect to depth from the surface. In FIG. 3, curve A illustrates a case where conventional case hardening steel is carburized and quenched, and curve B illustrates a case where a chromium carbide diffusion layer is formed on case hardened steel according to the present invention. In addition, the curve X in Figure 3
exemplifies the case where a chromium diffusion layer is formed on case hardened steel.

As is clear from this glass, according to the present invention, compared to the conventional carburizing method, the hardness of the hardened layer can be significantly improved by the amount shown by the shaded area without reducing the depth of the hardened layer. By increasing the hardness of such a hardened layer, the wear resistance and fatigue resistance of the cutter bearing surface and the bearing shaft bearing surface can be improved, and the bearing life can be increased by approximately 1.5 to 1.7 times. .

The bearing life of a cutter bit for an excavator can be increased as described above simply by forming the aforementioned chromium carbide diffusion layer on the bearing surface 16 of the cutter 7; It is also possible to form a similar diffusion layer of chromium carbide to further extend the bearing life. This is because the bearing life of an excavator cutter bit of the type shown in FIGS. 1 and m2- generally depends on the life of the bearing surface 16 of the cutter 7.

As is clear from the above description, according to the present invention, a cutter bit for an excavator with excellent bearing life and excellent durability can be obtained.

[Brief explanation of the drawing]

The first figure is a partially omitted vertical sectional view illustrating the main parts of a cutter bit for an excavator suitable for applying the present invention, and the second figure is a first figure.
#If of the borehole formed by the cutter bit in the figure
The third explanatory diagram showing the entire T-plane locus is a graph illustrating a comparative example of the conventional technology and the present invention using examples of hardness distribution characteristics with respect to depth within the hardened layer of the bearing surface. DESCRIPTION OF SYMBOLS 1...Body, 2...Leg, 5...Bearing shaft, 6...Rolling element (roller), 7...Cutter, 8...Drilling hole, 15...Drilling blade, 16 ...
Bearing surface (cutter), 17...Bearing surface (
bearing shaft). Agent Tatsuyuki Unuma (2 people) Figure 2 8 Figure 3 Surface force depth (mm) 443-

Claims (1)

[Claims] +IJ A body that is driven to revolve, a plurality of legs that are fixed to the axis of the body and protrude downward, a bearing shaft provided at the bottom of each leg, and a bearing shaft provided at the bottom of each leg. A cutter bit for an excavator comprising a plurality of cutters rotatably mounted via rolling elements, characterized in that a metal diffusion layer of chromium carbide is formed on the bearing surface of the cutter. bit. (2) The cutter bit for an excavator according to claim (1), characterized in that an entire island diffusion layer of vertical chromium is formed also on the bearing surface of the bear link shaft.