JPS6299527A - Wear-resistance cutting blade for construction machine and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the breakage of a cutting blade, enhance the penetrating force of the blade, land lengthen the wear-resistant life of the blade by fitting a superhard alloy into grooves formed in the longitudinal direction of the front face to be worn out of a steel cutting blade and then fixed by brazing. CONSTITUTION:Rectangular or square grooves 3 of a width of 10mm or less are formed in the front face to be worn out 2 of a lipper point 1. A superhard alloy piece 4 formed by sintering tungsten carbode fine particles with 3-30wt% Co, Ni, etc., in an amount of 0.5-100g with 3-50vol% are buried through a heat-resistant thin solder plate 5 having specific hardness and composition in the grooves 3. They are then heated to temperature higher than the melting point of the solder 5 under vacuum or in an inert atmosphere to form the melt of the solder 5 and then slowly cooled to just below the solidifying point of the solder 5 into solid form. Furthermore, cold inert gas is blown onto them to quickly cool to fix the superhard alloy pieces 4 by soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a steel cutting blade made of cemented carbide with high wear resistance for use in construction machinery, and a method for manufacturing the same.

Conventional technology Construction machines such as bulldozers and power shovels have steel cutting blades called lymph points and bucket teeth attached to the tip of the earthmoving equipment, and are used to excavate rock. For example, the shape of a conventionally used brim point 1 is as shown in FIG. 3, and a wear allowance portion 2 is provided in advance at its tip. FIG. 3 shows the initial shape, but after wear it wears down to the position indicated by the broken line 6, and the tip becomes blunt. In other words, the life span is reached when the cutting edge has become worn down to a predetermined level and the tip of the cutting edge has become dull.

Problems that the invention aims to solve In recent years, as machines have become larger, the load applied to these cutting blades has increased significantly, and as they are used under harsh working conditions, their lack of wear resistance has become a problem. However, there is a problem in that the tip of the cutting edge becomes dull in a short period of time, reducing the penetration force.

In particular, bulldozer lymph points are subject to significant wear as they excavate through hard rock, and in extreme cases can reach the end of their lifespan after less than an hour of work.

In such harsh work, the temperature at the tip of the cutting edge is 6.
The temperature rises to 00-700°C. Therefore, even if alloy steel with high resistance to temper softening is used, there is a problem that the alloy steel constituting the cutting edge undergoes deterioration and softening, accelerating wear and shortening the wear life.

Conventionally, in order to prevent this softening, steels with high resistance to tempering and softening have been developed by adding large amounts of silicon and elements that tend to form strong carbides. However, the effect of such measures is limited to approximately 550°C. On the other hand, as a material that maintains high hardness at higher temperatures, cemented carbide, which is made by bonding fine particles of tungsten carbide with cobalt, nickel, and iron, is known. However, cemented carbide has poor toughness, and when used as a cutting blade for construction machinery, there is a problem in that the cutting blade breaks, so it has not been put to practical use at present.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems and provide a cutting blade for construction machinery that is difficult to break and has excellent wear resistance.

Another object of the present invention is to provide a helical cutting blade that is excellent in wear resistance, has a self-blurring effect, and has increased penetration force, and a method for manufacturing the same.

Another object of the present invention, in conjunction with the above object, is to provide a steel cutting blade for construction machinery that is optimally designed to provide a long wear life, and a method for manufacturing the same.

Still other objects of the present invention are a cemented carbide base metal suitable for cutting blades for construction machinery having excellent performance as described above, a composite method of simply attaching F111 to a steel cutting blade of cemented carbide, and Our goal is to provide brazing filler metals that are suitable for this purpose.

Means for Solving the Problems In order to solve the problems mentioned above, we installed a cemented carbide stopper, which has significantly greater wear resistance than steel, on the front surface of the wear area of the cutting edge. It has been found that combining them is effective.

That is, in the present invention, an abnormal sound is formed in the longitudinal direction on the front surface of the wear portion of the steel cutting blade, and a carbide alloy is embedded in the hole and brazed to the 7' (long) wear housing. For controllable construction machinery! It provides an M surface cutting edge.

The cemented carbide base metal used here includes 3 to 30 carbide particles.
It is preferable to use a metal bonding phase sintered with a metal bonding phase of 3 to 50 mm.
A range of % body weight is preferred.

Further, the cross-sectional shape of the groove is preferably rectangular or square with a width tOW or less from the viewpoint of groove machinability, prevention of macro-fracture of the cemented carbide, and prevention of destruction of the brazing material joint.

In this way, brazing is done using carbide composite cutting blades! 18
In accordance with the present invention, the i-manufacturing method involves forming a groove in the elongated direction on the front surface of the wear portion of the steel cutting blade, and attaching a cemented carbide alloy piece to the groove with a thin brazing filler metal interposed therebetween. The attachment is heated in a vacuum or in an inert atmosphere above the melting point of the filler metal to form a melt of the filler metal between the cemented carbide and the steel, and then gradually cooled to just below the solidification temperature of the filler metal. The best method is to solidify the brazing filler metal and then rapidly cool it by blowing cold inert gas onto it.

Effects and aspects of the invention As explained above, a wear allowance is provided in advance at the tip of the flange point as shown in Fig. The replacement portion is made of cemented carbide, which provides outstanding wear resistance.

The easiest way to integrate cemented carbide into a steel cutting blade is to braze the cemented carbide and steel. in this case,
Cemented carbide is brazed with a thin plate of filler metal interposed, but in order to improve positioning accuracy, reduce exposure, and increase joint strength, a steel cutting blade, such as the lymph point shown in Figure 1, is used. A groove 3 is formed in the longitudinal direction on the front face of the wear allowance portion 2 of 1, a piece of cemented carbide 4 is inserted into this groove 3, and a brazing filler metal 5 is formed.
Braze by. By brazing the front part, which is subjected to a large load, the volume fraction of cemented carbide can be reduced, and the wear resistance is improved, and the wear resistance is different from that of the rear part. By this,
In other words, since the rear surface deteriorates quickly, a self-sharpening effect occurs in which the wear margin becomes sharper as it is used, and the penetration force can be maintained. In addition, since cemented carbide base metal has an elastic modulus approximately 25 to 3 times that of steel, greater stress is generated during excavation work than that of the 51fI4 base metal, which may cause fractures in the cemented carbide, which has a strong tendency to be brittle. . In order to prevent this, it is effective to braze a plurality of pieces of cemented carbide into the groove in the form of small pieces of 0.5 to 100 y. By doing this, stress relaxation is realized by the soft brazing material layer, and even if a crack occurs in one piece of cemented carbide, it is possible to prevent the crack from propagating to other pieces.

The cross-sectional shape of the groove provided in the steel cutting blade is preferably square or rectangular from the viewpoint of ease of groove machining and ease of forming the cemented carbide ingot. A number of cemented carbide nodules, which are divided into several lengthwise sections, or, if appropriate, one mass over the entire length of the groove, are embedded and soldered. A cutting blade made of cemented carbide in this way has approximately twice the wear resistance as compared to a conventional steel cutting blade. However, if the size and shape of the groove to which the cemented carbide is brazed is not appropriate, for example when hard rock is excavated, macro-fracture of the cemented carbide or brazing may cause the cemented carbide to be cut due to fracture of the part. It fell off the blade.

In fact, it has been found that the wear resistance is lower than that of a single steel cutting edge, and this problem becomes more pronounced as the width of the groove into which the cemented carbide is brazed becomes wider. Such macro-fractures of the cemented carbide and destruction of the brazing material joints can be almost prevented by making the @ of the grooves 1° or less, and excellent wear resistance can be obtained.

FIG. 4 is a model showing the state in which rock is excavated using the groove 3 in which the cemented carbide 4 is brazed. The largest force acting on the cemented carbide lump is the force l·゛ applied to the corner of the tip, which is expressed as F-W. Here, f is the force applied per unit height of the tip corner, and tV is the width of the groove 3.

Therefore, if the angle between F and the longitudinal direction of the groove is θ, the force that tends to shear the cemented carbide 4 at the brazed portion is Fcosθ=f−Wcosθ.

On the other hand, the surface BS of the part where the cemented carbide is brazed to the cutting edge
is the length of the cemented carbide and the height is H, then 5=tI/·L+211L.

Therefore, the shear stress τ of the brazed portion becomes τ.

As is clear from equation 4e(1) above, the shear stress τ
becomes smaller as H becomes larger and as W becomes smaller.

Brazing makes parts less likely to break. However, from a practical point of view, in order to ensure breakage resistance of the cutting edge, H cannot be increased arbitrarily. Therefore, brazing is #! in order to prevent parts from breaking. p width I
It is effective to secure the volume fraction of the cemented carbide in the wear area of the cutting edge by decreasing P' and increasing the number of grooves. This means that, as will be explained later, the shear strength of the brazing filler metal is approximately 30 k at maximum. / myti, which is significantly lower than the respective shear strengths of the cutting blade base material and cemented carbide.

#The disadvantage of having a large width W is that it promotes macrofracture of the cemented carbide. Cemented carbide, which is a brittle material, is prone to crack propagation, so if IV is large, cracks will cross n@, and large chunks will likely fall off.

However, the above analysis is qualitative and does not determine the limit value of the groove width W. Actual rock excavation work is complicated, and parameters f and θ are difficult to measure in practice. Further, the length L of the cemented carbide also changes with wear. Therefore,
The optimum value of the groove width W must be determined by hard rock excavation tests for large construction machines that require these bank wear-resistant cutting edges. Therefore, as shown in Example 2 described later,
As a result of an excavation test using Komatsu's D455 bulldozer, one of the largest bulldozers in the world, the trench width W was I
It has become clear that O+a+ or lower is effective.

As for the brazing method, as mentioned above, a groove 3 formed in the longitudinal direction on the front surface of the wear allowance part 2 of the steel section is used.
Preferably, a cemented carbide piece 4 is mounted with a thin plate-shaped brazing filler metal 5 having a composition and hardness as described later interposed therebetween, and the cemented carbide piece 4 is heated to a temperature higher than the melting point of the brazing filler metal in a vacuum or an inert atmosphere. Normal brazing is performed by forming a melt of the filler metal between the cemented carbide and the steel, and then cooling to solidify the filler metal. As a result, a brazed joint with heat resistance and strength can be obtained. In this case, the brazing temperature is approximately 1000℃
1 In the normal brazing method, the hardness of the steel base material is /
/RC25 or less, and the cutting edge may become deformed during excavation work. To prevent this problem, it is necessary to use steel such as S
In addition to selecting a material with high hardenability such as KD 6J, the cooling rate is increased by gradually cooling the filler metal to a temperature just below the solidification temperature and then blowing cold inert gas from the temperature just below the solidification temperature of the filler metal. This is effective, and by doing this, the base material will be quenched,
It becomes possible to increase the hardness of steel to Hac30 or higher.

The amount of cemented carbide added to the wear portion of the steel cutting edge is 3 to 50.
Volume 1 is preferred. If the content of cemented carbide is less than 3 volumes, the wear resistance effect will be small, and if it is more than 50 volumes, the resistance to breakage will be low, which is not preferable.

In addition, as a cemented carbide, tungsten carbide fine particles't
A cemented carbide sintered with -3 to 30% by weight of cobalt, nickel, iron, or an alloy thereof is optimal. The fewer the number of bonded metal-layer fibers in the cemented carbide, the greater the wear resistance, but if it is less than 3 layers, it becomes brittle and easily breaks. On the other hand, 30
If it exceeds #f by weight, the effect of improving the abrasion properties will be small, which is not preferable.

The effects of the volume fraction of the cemented carbide in the steel and the amount of the cemented carbide interlayer on the wear resistance will be explained using test examples.

Test example Accurate measurement of the wear resistance of cutting blades at work sites is
This is difficult because the properties of the bedrock are not constant. Therefore,
A wear resistance test was conducted using a gouging wear test that modeled cutting edge wear.

5 i￥I indicates a test piece containing cemented carbide corresponding to the wear allowance of the cutting edge, and 5KD6J steel bar 7 with a diameter of 10 mm was heat treated to hardness Noah RC50, and 3% and 10% were added. A rod g made of cemented carbide made of tungsten carbide fine particles sintered with 30% cobalt was penetrated at various volume percentages. The volume fraction of the cemented carbide was varied depending on its diameter and the number of penetrations. For example, if two cemented carbide rods with a diameter of 4 mm are penetrated, this corresponds to 32 volume squares. Also, Huc
50's 5KD61 steel has about the same wear resistance as conventional cutting edges.

Figure 6 shows an outline of the gouging wear test device. Circumferential speed +
35m Rotates in 1 minute Particle size 24, Cohesion degree l? SiCI of
The test piece 10 is pressed against the J vitrified grindstone 9 under a surface pressure of 52 k, and the wear resistance is evaluated from the wear volume.

This method has been confirmed to reproduce the wear condition of the cutting edge well, and under the above conditions, it has been confirmed that this method can reproduce the wear condition of the cutting edge well. It has been previously measured that the wear surface temperature is approximately 700°C.

The results of the J-ring test (above) are shown in FIGS. 7 and 8. 7th
As shown in the figure, the wear ratio (5KI) of An
It has become clear that there is no simple linear relationship between the amount of wear (when the amount of wear is taken as 1) and the content of cemented carbide. That is, a clear effect of reducing the amount of wear is seen when the three cemented carbide alloys exceed tA%, and the amount of wear rapidly decreases up to 20 to 30 volume. However, at 50 volume squares or more, the tendency for the amount of wear to decrease decreases. Furthermore, the effect of improving wear resistance is greatly affected by the amount of the binder metal phase in the cemented carbide, and those with a cobalt content of 22 layers are significantly less effective than those with a 6 to 1 Si layer. (See Figure 8)
.

EXAMPLES Hereinafter, the present invention will be specifically explained by explaining examples shown in the accompanying drawings.

Example 1 As shown in Fig. 1, the front part of the wear allowance part 2 of the lymph point 1 made of 5KI) 61 steel has a width of 5 strips, a depth of 9 m+,
Form 7 #3 grooves with a length of 102 cm, and in this groove 3, as shown in Figure 2, have a thickness of 4.7 mm, a width of &6 mm,
28 cemented carbide pieces 4 with a length of 255 m+ are embedded and vacuum brazed with a brazing filler metal 5, and then the end portions are hardened by blowing nitrogen gas made from vaporized liquefied nitrogen during the brazing process. Hardened.

When brazing cemented carbide to a steel cutting blade, it is desirable to use a brazing material with high heat resistance.

When brazing cemented carbide and steel, silver solder or brass solder is generally used for cutting tools and the like. However, as mentioned above, when cutting blades for construction machinery are used, the temperature at the tip of the cutting blade rises to 600 to 700 degrees Celsius during work, and large stresses are generated, so these general brazing materials have poor heat resistance. and is insufficient in terms of strength. In addition, pure copper solder and Ni-Mn eutectic solder are also known as high-temperature brazing fillers, but it has been revealed that the former has low strength and corrodes the grain boundaries of steel, and the latter is used for cemented carbide. It has become clear that it is eroding.

The present inventors conducted research to solve such problems and found that the following brazing filler metal is optimal for brazing cemented carbide to cutting blades for construction machinery.

Figure 9 shows the microstructure of the cross section of the joint where cemented carbide and steel are brazed with pure copper, and Figure 10 shows the microstructure of the joint where cemented carbide and steel are brazed with Cu-2.
The microstructure of a cross section of a joint brazed with 2Mn-I0co-9Ni brazing material is shown. In addition, Fig. 11 shows the effect of Si addition amount on the hardness of copper alloy brazing filler metal.
Further, FIG. 12 shows the relationship between the brazing strength of cemented carbide and steel and the hardness of the brazing metal, measured according to the shear strength measurement method shown in FIG. 13. In addition, in FIG. 13 schematically showing the above shear strength measurement method, P is load, 11 is cemented carbide, 1 is
Reference numeral 2 indicates steel brazed to both sides of the cemented carbide, and reference numeral 13 indicates a stand.

The brazing material according to the present invention is also a brazing material based on Cu, but pure CTL has the above-mentioned problem that it erodes the grain boundaries of steel and has low shear strength (see FIG. 9). Ni and L have the effect of preventing such grain boundary erosion of steel, and furthermore, Mn forms a solid solution phase at the interface between the brazing metal and steel and improving the "wettability" of the brazing metal and steel. was found (see Figure 10).

In addition, Co has the function of increasing the hardness of the brazing filler metal and forming a solid solution phase at the interface between the cemented carbide and the brazing filler metal.
It was found that the "wettability" with cemented carbide was improved.

In addition, Si has a large effect of increasing the hardness of the brazing filler metal,
As shown in FIG. 11, it can be seen that the hardness increases from HV 25 to 35 by adding % Silil.

On the other hand, as a brazing filler metal for cutting blades of construction machinery, it is desirable that the liquid phase formation temperature of the filler metal is 950°C or higher from the viewpoint of heat resistance.If the temperature exceeds 1150°C, the crystal grains of the steel will become coarse. The temperature is preferably 1150°C or lower since it lowers the strength of the base material.

AIn, St lowers the liquid phase formation temperature, and Ni, Co
increases, so the liquid phase formation temperature of the brazing filler metal i 950
In order to achieve a temperature in the range of ~1150°C, there are limits to the combinations of these alloying elements and their composition ranges.

It was also found that although the hardness of the brazing filler metal strongly depends on the Co content and the St content, especially the St content, there is no linear relationship between the shear strength and hardness of the joint.

That is, as shown in FIG. 12, the shear strength of the joint increases with hardness up to a hardness of BV150, but decreases above this, and in particular, when the hardness is #V2O0 or higher, it becomes a brittle fracture state. Therefore, there is an upper limit to the amount of Co, especially the amount of St, in terms of shear strength.

The optimum composition range of the brazing filler metal for the present invention is determined comprehensively based on the characteristics of such alloying elements.
-Ni-Si system: 2-10% Ni, preferably 5-1
0% Ni, 1~8%Si; Cu-Mn-Ni-Si system: lO~25%Mn, 5~IO%Ni11~
3%SL; or Cu-un-Ni-Co-Si
In the system, I 5-30%Mn, 5-I 0%Ni,
5 to IO% Co and 0.5 to 1.5% Si are suitable.

Also, the hardness of the brazing filler metal is approximately 7 Vickers hardness from Figure 12.
The range of 100 to 200 psi is more preferable than 5 to 200 ψ.

Example 2 037%C, 0.68%SL, 1.09%Mn,
0.93 Cr, 1.03% JIio, 0.51
A ripper point was manufactured by hot forging steel consisting of %V1 balance Ft.

Next, after annealing, cores with various cross-sectional dimensions were formed in the longitudinal direction on the front surface of the wear portion of each ripper point, as shown in FIG. 1, by machining.

The cross-sectional shape of the grooves was cut using a long knife, and the number of grooves was increased to the maximum so that the volume of the groove portion was 15 to 20% of the volume of the worn portion of the original lymph point. W C-14 in this groove part
Cemented carbide with a composition of %Co is embedded, CL-N
Vacuum brazing is performed using an i-Si brazing machine, and then during the brazing process, the mesh part is quenched and hardened by blowing nitrogen gas made by vaporizing liquefied nitrogen, and the hardness is reduced to 1 iac.
Adjusted to 5 Q.

The Soba Point manufactured in this way was installed on a large bulldozer I)z55 made by Komatsu Ltd., and a rock excavation test was conducted to evaluate the wear resistance, the extent to which the cemented carbide fell off, and the depth of penetration of the ripper point into the rock. was evaluated. The rock mass tested was chert with an elastic wave propagation velocity of 2200 m, Aec, and rock density, which is among the hardest rock mass.

The performance evaluation was performed by changing the cross-sectional shape of the groove, but for comparison, we also tested a plain steel laminated point without any cemented carbide composite. The results are shown in Table 1 below.

As is clear from Margin Table 1 below, when the groove width W is 101, some of the cemented carbide falls off due to macro-fracture and brazing of the cemented carbide, but the wear resistance is , the improvement effect on penetration depth is also maintained. However, when the groove width W is set to 20 m, the brazing part breaks, the cemented carbide falls off, and no improvement effect is seen. When the groove width W is 6mm and By, the brazing causes only a few parts to break and the cemented carbide to fall off is very rare.
Excellent improvement effects were obtained.

Effects of the Invention As described above, the wear-resistant cutting blade for construction machinery according to the present invention has the following advantages:
A groove is formed in the longitudinal direction on the front surface of the wear area of the steel cutting blade, and cemented carbide is embedded in this groove and brazed to it, so it has excellent wear resistance and is difficult to break. This has the advantage that it has a different wear resistance from the rear part, and as it is used, a self-sharpening effect develops and the wear margin becomes sharper, making it possible to sustain one penetration force. By brazing multiple pieces of cemented carbide into this groove, even if greater stress is generated in the cemented carbide than in the steel base material during excavation work, the soft brazing material layer can relieve the stress. This prevents chipping of the cemented carbide, and even if a crack occurs in one of the cemented carbide pieces, it prevents the crack from propagating to other pieces, and furthermore, the brazing into the groove prevents the cemented carbide from being positioned. The accuracy of
The advantage is that the amount of exposure can be reduced and the bonding strength can also be increased.

Further, by setting the width of the groove to 10 mm or less, it is possible to compensate for the drawback of cemented carbide which is prone to brittle fracture, and to reduce shear fracture in the brazing material portion having low shear strength. As a result, the wear life is more than 1.5 times longer than that of conventional steel cutting blades, and even in the advanced stage of wear, excellent purchasing power against hard rock can be obtained.

With these characteristics and the hardness of the steel parts, Jlnc
A cemented carbide composite cutting edge of 3 Q or more can be easily obtained by the method of the present invention. In addition, by using the optimal brazing filler metal as described above, the joint part has both heat resistance and strength when brazing the steel part and the cemented carbide. It has the advantage of fully exhibiting all of the above characteristics.

In recent years, with the progress of civil engineering development, the need to destroy hard rock has increased. Many of these work sites are located close to residential areas, so blasting cannot be used and it is necessary to excavate the rock using construction machinery. The present invention greatly improves the life span and workability of cutting edges, which have been major problems in such working machines, and is extremely effective in industry.

Although the above-mentioned embodiments have shown the effectiveness with respect to ripper points for bulldozers, the present invention can be similarly applied to cutting edges of bulldozers and motor graders, power shovels, bulldozers, packet teeth of wheel loaders, etc. Not even.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment in which the present invention is applied to a lymph point, FIG. 2 is a cross-sectional view taken along the line n-II in FIG. 1, and FIG.
The figure is a perspective view of a conventional ripper point. Figure 6 is a schematic diagram showing the concept of the gouging wear test, Figure 7 is a graph showing the relationship between the wear amount ratio and the cemented carbide volume fraction, and Figure 8 is the relationship between the wear amount ratio and the amount of OCO in the cemented carbide. Figure 9 is a micrograph X (magnification X 40 (J), 10th
The figure shows cemented carbide and steel Cu-22WyL-IQCo-q
A micrograph (magnification x 400) of a cross-section of a joint brazed with Ni brazing filler metal, Figure 11 is a graph showing the relationship between the hardness of copper alloy brazing filler metal and Si addition, and Figure 12 is a graph showing the relationship between cemented carbide and steel. FIG. 13 is a graph showing the relationship between the brazing joint strength (shear fracture strength) and the hardness of the brazing material, and is a schematic diagram of the shear strength measuring method. 1... Lymph point, 2... Wear area, 3...
- Groove, 4... Cemented carbide piece, 5... Brazing metal. Fig. 2 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Figure Si addition t <wz)

Claims (1)

[Claims] 1. A steel cutting blade for construction machinery, in which a groove is formed in the longitudinal direction on the front surface of the cutting blade's buffing area, and a cemented carbide is embedded and brazed in the groove. 2. The cross-sectional shape of the groove is rectangular or square, and the width is 10 mm.
A cutting blade according to claim 1 as follows: 3. The cutting blade according to claim 1 or 2, which contains 3 to 50% by volume of cemented carbide in the wear portion. 4. The cutting blade according to claim 1 or 3, wherein the cemented carbide contains 3 to 30% by weight of a metal binder phase. 5. The brazing filler metal is Cu-Ni-Si type, Cu-M
n-Ni-Si system or Cu-Mn-Ni-Co-Si
The cutting blade according to any one of claims 1 to 4, which is brazed. 6. The cutting blade according to page 5 of the claims, wherein the brazing filler metal is a Cu-Ni-Si brazing filler metal having a composition of 2 to 10% by weight Ni, 1 to 8% by weight Si, and the balance Cu. . 7. The brazing filler metal contains 10 to 25% by weight Mn, 5 to 1
The cutting blade according to claim 5, which is a Cu-Mn-Ni-Si brazing filler metal having a composition of 0% by weight Ni, 1 to 3% by weight Si, and the balance Cu. 8. The brazing filler metal contains 15 to 30% by weight Mn, 5 to 1
Cu-Mn-Ni- having a composition of 0 wt% Ni, 5 to 10 wt% Co, 0.5 to 1.5 wt% Si, and the balance Cu.
The cutting blade according to claim 5, which is a Co-Si brazing filler metal. 9. The cutting blade according to any one of claims 1 to 8, wherein the steel part has a hardness of H_R_C30 or more. 10. The cutting blade according to any one of claims 1 to 9, wherein the cemented carbide is made of small pieces having a weight in the range of 0.5 to 100 g, and a plurality of the small pieces are brazed together. . 11. A groove is formed in the longitudinal direction on the front surface of the wear area of the steel cutting blade, a piece of cemented carbide is installed in the groove with a thin plate brazing material interposed, and the installed object is placed in a vacuum or an inert atmosphere. A melt of the filler metal is formed between the cemented carbide and the steel by heating it above the melting point of the filler metal, and then slowly cooling it to just below the solidification temperature of the filler metal. A method for manufacturing steel cutting blades for construction machinery, which is characterized by rapid cooling by spraying with inert gas.