JP6523698B2 - Chip bonding method - Google Patents

Description

The present invention, the band saw blade, the saw tooth tip of the saw blade base metal in the saw blade, such as a circular saw blade, about the chip bonding method for bonding a rigid tip made of a hard material by electrical resistance welding.

  In recent years, each saw blade of a saw blade base metal, which is a saw blade main body of a saw blade such as a band saw blade, is provided with a hard tip made of hard material such as cemented carbide or cermet at the tip portion (tip portion of each saw blade). It has increased. Also, when joining a hard tip to the tip of the saw tooth of the saw blade base metal, electrical resistance welding is used in addition to brazing. Then, with reference to FIGS. 8 (a) and 8 (b), a conventional method for joining the hard tip 14 to the tip of the sawtooth 12 of the saw blade base metal 10 by electric resistance welding will be briefly described. In FIG. 8, “L” indicates the left direction, “R” indicates the right direction, “U” indicates the upward direction, and “D” indicates the downward direction.

  The saw blade base metal 10 is gripped from the horizontal direction (left and right direction) by the first electrode (vis electrode) 16 with the sawtooth recess 12a formed at the tip of the saw tooth 12 of the saw blade base metal 10 facing upward. An example of retention). Subsequently, the cylindrical hard tip 14 is vertically oriented (vertically) by the electrode recess 18a formed at the tip of the second electrode (tip electrode) 18 and the sawtooth recess 12a formed in the sawtooth 12 of the saw blade base metal 10. Hold from. In other words, the hard tip 14 is held by the electrode recess 18 a of the second electrode 18 in a state where the outer peripheral surface of the hard tip 14 is in surface contact with the sawtooth recess 12 a of the sawtooth 12 of the saw blade base metal 10. Thus, preparation for joining the hard tip 14 to the tip of the sawtooth 12 of the saw blade base metal 10 (preparation for joining the hard tip 14) can be performed.

  After preparing the bonding of the hard tip 14, the second electrode 18 is pressed to the first electrode 16 side, in other words, the hard tip 14 is pressed against the tip of the saw tooth 12 of the saw blade base metal 10. . The welding current (direct current or alternating current) is applied between the first electrode 16 and the second electrode 18 in a state where the hard tip 14 is pressurized with a predetermined pressure against the tip of the sawtooth 12 of the saw blade base metal 10 The welding current is applied to supply electric energy. Thus, the tip of the sawtooth 12 of the saw blade base metal 10 and the hard tip 14 are melted by Joule heat (resistance heat), and the hard tip 14 is relatively pushed into the saw tooth 12 side of the saw base metal 10. , Can be joined to the tip of the saw teeth 12 of the saw blade base metal 10. After the relative pressing amount of the hard tip 14 reaches a predetermined pressing amount, or after the current application time of the welding current has passed a predetermined current application time, the distance between the first electrode 16 and the second electrode 18 is increased. Stop the welding current.

  Subsequently, in a state where the hard tip 14 is pressed against the tip end of the saw tooth 12 of the saw blade base metal 10, the joint portion between the saw blade base metal 10 and the tip end of the saw tooth 12 and the hard tip 14 Leave until the temperature of the Then, the pressing of the hard tip 14 against the tip of the saw tooth 12 of the saw blade base metal 10 is released, and the gripping state by the first electrode 16 is released. Thereby, the saw blade base metal 10 provided with the hard tip 14 at the tip of the saw blade 12 can be removed from the first electrode 16.

  As prior art related to the present invention, there are those shown in Patent Document 1 to Patent Document 3.

JP, 2011-167807, A JP 2011-255444 A JP 2001-277043 A

  By the way, the material of the hard tip (hard tip 14) is very expensive and the material cost is high. In addition, the polishing time (polishing time) for forming the hard tip into a cutting edge shape (final shape) is long, and the polishing cost is high. Therefore, conventionally, the volume of the hard tip (for example, the outer diameter of the hard tip) is reduced to reduce the material cost of the hard tip, and the polishing cost of the hard tip for forming the hard tip into a cutting edge shape. In other words, there is a demand to reduce the manufacturing cost of the saw blade.

  On the other hand, as a result of conducting the bonding strength test of the hard tip, when the volume of the hard tip is reduced, the average value of the bonding strength of the hard tip is reduced, and the incidence of defects due to insufficient bonding strength of the hard tip is increased. confirmed. That is, the hard tip (the outer diameter size is 2.5 times the thickness dimension of the saw blade base metal) which is the present implementation product, and the hard tip which is the comparison product (the outer diameter size is 1 the thickness dimension of the saw blade base metal) Bond strength test was performed for the cases where the actual product was joined to the tip of the saw tooth of the saw blade base metal (in the case of the conventional example) and the comparative product (in the case of the comparative example). . Summarizing the results, as shown in FIG. 9, it was confirmed that in the case of the comparative example, the average value of the bonding strength of the hard tip is lower than in the case of the conventional example. In the case of the conventional example, the incidence rate of defects due to insufficient bonding strength of hard chips is 1%, whereas in the case of the comparative example, the incidence rate of defects due to insufficient bonding strength of hard chips is 10%. It was confirmed that there is. In addition to the decrease in the contact area (bonding area) of the tip of the saw tooth of the saw blade base metal and the hard tip due to the reduction in the volume of the hard tip (or the outer diameter of the hard tip), This is considered to be due to the fact that the hard chip tends to overheat and the range of conditions for appropriate bonding is narrowed. In addition, as an example, the incidence rate of defects due to insufficient bonding strength of hard chips refers to the generation rate where the bonding strength of hard chips is less than 50 kgf, and 50 kgf is a standard for stabilizing the bonding state of hard chips. Bond strength. FIG. 9 shows the incidence of hard chips less than 50 kgf, the incidence of 50 to 100 kgf, the incidence of 100 to 150 kgf, the incidence of 150 to 200 kgf, and the incidence of 200 to 250 kgf. ing.

  Further, in the case of the conventional example, no crack occurs in the hard tip, but as shown in FIGS. 10 (a), (b) and (c), in the case of the comparative example, the hard tip is a saw blade base It was confirmed that there was a case where the chip was joined in a state of being inclined with respect to the thickness direction of the gold and a crack was generated in the hard tip. This is because the hard tip is relative to the saw tooth side of the saw blade base metal in a state where the temperature distribution (heat balance) of the hard tip is generated (heat balance) during welding current application. It is thought that it is because it was pushed down.

  In other words, it is difficult to reduce the incidence rate of defects due to insufficient bonding strength of the hard tips and to prevent the occurrence of cracks in the hard tips while reducing the volume of the hard tips to reduce the manufacturing cost of the saw blade There is a problem of being

Therefore, the present invention aims to provide a novel chip bonding method that can solve the above-mentioned problems.

A feature of the present invention is the saw blade held by the first electrode in a tip bonding method for bonding a hard tip made of a hard material by electric resistance welding to a tip end of a saw blade of a saw blade base metal in a saw blade. In a state where the hard tip held by the second electrode is relatively pressed against the tip of the saw tooth of the base metal, in other words, between the first electrode and the second electrode, in other words, A welding current is supplied between the tip of the saw tooth of the saw blade base metal and the hard tip to supply electrical energy, whereby the contact point of the tip of the saw tooth of the saw blade base metal and the hard tip Primary electric conduction step (temporary jointing step) of temporarily joining (welding) only the periphery (including the contact portion) by Joule heat (resistance heat), and after completion of the primary electric conduction step, the saw teeth of the saw blade base metal Phase the hard tip against the tip of the The saw blade is energized by supplying a welding current between the first electrode and the second electrode in a state of being pressurized and supplying electrical energy higher than the electrical energy in the primary energization process. The tips of the saw teeth of the base metal and the hard tips are melted by Joule heat, and the hard tips are relatively pushed toward the saw teeth side of the saw blade base metal, so that the saw teeth of the saw blade base metal are made The present invention is characterized in that a secondary energization process (main bonding step) of bonding (main bonding) to the tip end portion is included.

  In the description of the specification and the claims of the present application, "holding" is not only the meaning of holding in a narrow sense but also the meaning of holding in a broad sense including support and gripping.

According to the feature of the present invention, in the primary energization step, a temporary joint (welded portion) as a current passage is formed between the tip of the saw and the hard tip of the saw blade base metal. In the secondary electrification step, the initial electric resistance between the tip of the saw tooth of the saw blade base metal and the hard tip can be stabilized low. As a result, the temperature distribution (heat balance) of the hard tip in the secondary energization step is brought close to a uniform state along the thickness direction of the saw blade base metal (the axial direction of the hard tip), It is possible to stabilize the bonding of

  According to the present invention, since the temperature distribution of the hard tip in the secondary energization step can be brought close to a uniform state along the thickness direction of the saw blade base metal, the bonding of the hard tip can be stabilized. Even if the volume of the hard tip is reduced, the inclination of the hard tip with respect to the thickness direction of the saw blade base metal can be reduced while sufficiently securing the bonding strength of the hard tip. Therefore, according to the present invention, it is possible to reduce the material cost of the hard tip and the polishing cost of the hard tip for forming the cutting edge shape, in other words, reduce the manufacturing cost of the saw blade. It is possible to reduce the incidence of defects due to insufficient bonding strength of the hard tip and to prevent the occurrence of cracks in the hard tip.

FIG. 1 is a schematic view for explaining a chip bonding method according to an embodiment of the present invention, as viewed from the left surface side (one side in the thickness direction) of a saw blade base metal. FIG. 2 is a schematic view for explaining the chip bonding method according to the embodiment of the present invention, as viewed from the side of the scooping surface of the saw tooth of the saw blade base metal. FIG. 3 (a) is a schematic view explaining a first modification of the embodiment of the present invention, and FIG. 3 (b) is a schematic view explaining a second modification of the embodiment of the present invention. a) (b) is the figure seen from the left surface side of saw blade base metal. FIG. 4 (a) is a schematic view for explaining a third modification of the embodiment of the present invention, and FIG. 4 (b) is a schematic view for explaining a fourth modification of the embodiment of the present invention. a) (b) is the figure seen from the left surface side of saw blade base metal. FIG. 5 is a photographic view showing a state after completion of the primary energization process in the chip bonding method according to the embodiment of the present invention, viewed from the right surface side (the other side in the thickness direction) of the saw blade base metal. It is a photograph figure. FIG. 6 is a graph showing the relationship between the bonding strength and the incidence of the hard tip in the case of the invention example. 7 (a), (b) and (c) are photographs showing the bonding state of the hard tips in the case of the invention example, and FIG. 7 (a) is a photograph seen from the side of the cutting face of the saw teeth of the saw blade base metal. 7 (b) is a photograph seen from the left surface side of the saw blade base metal, and FIG. 7 (c) is a photograph seen from the right surface side of the saw blade base metal. FIGS. 8 (a) and 8 (b) are schematic diagrams for explaining a conventional method for joining a hard tip to an end of a saw tooth of a saw blade base metal by electric resistance welding, and FIG. 8 (a) is Fig. 8 (b) is a view seen from the left side of the saw blade base metal. FIG. 9 is a graph showing the relationship between the bonding strength and the incidence of hard chips in the case of the conventional example and in the case of the comparative example. 10 (a) (b) (c) are photographs showing the bonding state of the hard tips in the case of the comparative example, and FIG. 10 (a) is a photograph seen from the side of the cutting face of the saw tooth of the saw blade base metal 10 (b) is a photograph seen from the left surface side of the saw blade base metal, and FIG. 10 (c) is a photograph seen from the right surface side of the saw blade base metal.

  Embodiments of the present invention, modifications of the embodiments, and examples will be described with reference to the drawings. In the drawings, “L” indicates the left direction, “R” indicates the right direction, “U” indicates the upward direction, and “D” indicates the downward direction.

  As shown in FIG. 1 and FIG. 2, the tip joining method according to the embodiment of the present invention has a cylindrical shape at the tip of the saw teeth 22 of the saw blade base metal 20 in a saw blade (not shown) such as a band saw blade or a circular saw blade. A method for joining hard tips 24 of a shape by electrical resistance welding, which comprises (i) joining preparation step, (ii) primary energization step (temporary joining step), (iii) leaving step (heat radiation step), (iv 2.) A secondary energization process (main bonding process), (v) a tertiary energization process (annealing process), and (vi) a base metal removing process. Moreover, the electrical resistance welding apparatus 26 is used for implementation of the chip | tip joining method which concerns on embodiment of this invention.

  Before describing the specific content of each step in the chip bonding method according to the embodiment of the present invention, the configuration of the electrical resistance welding device 26 will be briefly described.

  The electric resistance welding apparatus 26 includes an apparatus main body (not shown), and the apparatus main body is provided with a first electrode (a vise to hold) the saw blade base metal 20 from the horizontal direction (left and right direction). An electrode 28 is provided, and the first electrode 28 is made of a copper alloy in order to lower the electrical resistance (contact resistance) with the saw blade base metal 20. Further, the welding head 30 is provided above the first electrode 28 in the apparatus body so as to be movable in the vertical direction, and the welding head 30 is vertically (vertically) driven by an actuator 32 such as a cylinder. It is what moves. Furthermore, the welding head 30 is provided with a second electrode (tip electrode) 34 for holding the hard tip 24. The second electrode 34 is made of copper in order to lower the electrical resistance to the hard tip 24. It is made of an alloy. An electrode recess 34 a having a shape corresponding to the outer peripheral surface of the hard tip 24 is formed at the tip (lower end) of the second electrode 34. And the welding power supply 36 which supplies a welding current (direct current or a welding current of a direct current) between the 1st electrode and the 2nd electrode, and supplies an electrical energy is provided in the suitable position of an apparatus main body. The electrode terminal 36 a of the welding power source 36 is connected to the first electrode 28 via the conductive cable 38, and the electrode terminal 36 b of the welding power source 36 is connected to the second electrode 34 via the conductive cable 40. The moving direction of the welding head 30 is vertical (vertical direction), but if it is a direction substantially perpendicular to the flat surface 22 a formed at the tip of the saw teeth 22 of the saw blade base metal 20, the vertical direction It does not have to be.

  Subsequently, specific contents of each step in the chip bonding method according to the embodiment of the present invention will be described.

(i) Bonding preparation step With the flat surface 22a of the saw teeth 22 of the saw blade base metal 20 facing upward, the saw blade base metal 20 is gripped from the horizontal direction by the first electrode 28. Subsequently, by moving the welding head 30 downward by driving the actuator 32, the cylindrical hard tip 24 is made vertical by the electrode recess 34a of the second electrode 34 and the flat surface 22a of the sawtooth 22 of the saw blade base metal 20. Hold from the direction (vertical direction). In other words, while the outer peripheral surface of the hard tip 24 is in line contact with the flat surface 22 a of the saw teeth 22 of the saw blade base metal 20 along the left-right direction (thickness direction of the saw blade base metal 20), the second electrode The hard tip 24 is held by the electrode recess 34 a of 34. In this way, preparation for joining the hard tip 24 to the tip of the saw tooth 22 of the saw blade base metal 20 can be performed (joining preparation).

  Here, the saw blade base metal 20 is made of, for example, an alloy steel such as spring steel, and the hard tip 24 is made of, for example, a hard material such as cemented carbide or a cermet. Further, the outer diameter dimension S of the hard tip 24 is 0.5 to 2.0 times the thickness dimension T of the saw blade base metal 20. If it is less than 0.5 times that the thickness dimension T of the saw blade base metal 20 is 0.5 times or more, the volume of the hard tip 24 becomes smaller, and the junction temperature in the secondary energization process becomes stable In addition, the contact area (bonding area) of the tip of the saw tooth 22 of the saw blade base metal 20 and the hard tip 24 becomes small, and it becomes difficult to sufficiently secure the bonding strength of the hard tip 24. . The reason why the thickness dimension T of the saw blade base metal 20 is 2.0 times or less is because the material cost and the polishing cost of the hard tip 24 increase when it exceeds 2.0 times.

(ii) Primary bonding process (temporary bonding process)
After the completion of the welding preparation process, the welding head 30 and the second electrode 34 are pressed downward (the first electrode 16 side) by driving the actuator 32, in other words, the tip of the saw tooth 22 of the saw blade base metal 20 And press the hard tip 24 downward. Then, in a state where the hard tip 24 is pressed downward with a predetermined pressure against the saw blade base metal 20 by the drive of the actuator 32, the welding power source 36 separates the first electrode 28 and the second electrode 34, in other words If so, welding current is supplied between the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24 to supply electrical energy. As a result, the tip of the saw tooth 22 of the saw blade base metal 20 and the hard tip 24 are melted by Joule heat, and the hard tip 24 is relatively pushed into the saw tooth 22 side of the saw base metal 20 Temporary bonding (welding) is made to the tip of the saw tooth 22 of the gold 20. In other words, only the tip portion of the sawtooth 22 of the saw blade base metal 20 and the periphery of the contact portion (including the contact portion) of the hard tip 24 are temporarily joined by Joule heat. After temporarily joining only the tip of the saw teeth 22 of the saw blade base metal 20 and the periphery of the contact portion between the hard tip 24, the application of welding current between the first electrode 28 and the second electrode 34 is stopped.

  Here, in the primary energization step, energization of the welding current between the first electrode 28 and the second electrode 34 is performed in a state where the tip of the saw tooth 22 of the saw blade base metal 20 and the hard tip 24 are in line contact. It has started. Also, as an example, the welding current in the primary energization step is 600 to 800 A (amperes), and the energization time between the first electrode 28 and the second electrode 34 in the primary energization step is 20 to 50 mm. It is a second, and the pressing amount of the hard tip 24 to the saw blade base metal 20 is 0.1 mm or less.

(iii) Leaving process (heat release process)
After completion of the primary bonding step, the actuator 32 is driven to press the hard tip 24 downward with a predetermined pressure against the tip of the saw teeth 22 of the saw blade base metal 20, and the first electrode 28 and the second electrode 34 With the welding current stopped between the above, and left for a predetermined time (for example, 1 second). Thus, it is possible to dissipate the heat generated around the temporary joint (including the temporary joint) between the tip end of the saw tooth 22 of the saw blade base metal 20 and the hard tip 24.

(iv) Secondary energization process (main joining process)
After completion of the standing step, the welding power source 36 sets the first electrode 28 and the second electrode 34 in a state where the hard tip 24 is pressed downward against the saw blade base metal 20 by a predetermined pressure by driving the actuator 32. The welding current is supplied during the period of time to supply electric energy higher than the electric energy in the primary energization process. As a result, the tip of the saw tooth 22 of the saw blade base metal 20 and the hard tip 24 are melted by Joule heat, and the hard tip 24 is relatively pushed into the saw tooth 22 side of the saw base metal 20 It can be joined (mainly joined) to the tip of the saw tooth 22 of the gold 20. After the relative pressing amount of the hard tip 24 reaches the predetermined pressing amount, or after the current application time of the welding current has passed the predetermined current application time, the distance between the first electrode 28 and the second electrode 34 is Stop the welding current.

  Here, as an example, the welding current in the secondary conduction step is 800 to 1200 A (amperes), and the conduction time between the first electrode 28 and the second electrode 34 in the secondary conduction step is 0.1 The pressing amount of the hard tip 24 with respect to the saw blade base metal 20 is 0.1 to 0.3 mm for .about.0.3 seconds.

(v) Third Energization Step After completion of the second energization step, the welding power supply 36 is used to press the hard tip 24 downward with a predetermined pressure against the saw blade base metal 20 by driving the actuator 32. A welding current is applied between the first electrode 28 and the second electrode 34. In this way, it is possible to heat and anneal around the junction (including the junction) of the tip of the saw tooth 22 of the saw blade base metal 20 and the hard tip (including the junction). After heating the periphery of the joint between the tip end of the saw tooth 22 of the saw blade base metal 20 and the hard tip, the application of welding current between the first electrode 28 and the second electrode 34 is stopped.

  Here, as an example, the welding current in the third conduction step is 500 to 700 A (amperes), and the conduction time between the first electrode 28 and the second electrode 34 in the second conduction step is 0.7. ~ 1.0 second cycle.

(vi) Base metal removing step In the state where the hard tip 24 is pressed downward at a predetermined pressure to the tip of the saw teeth 22 of the saw blade base metal 20 by driving of the actuator 32 after completion of the third electrification step. The temperature is maintained until the temperature around the joint between the saw blade base metal 20 and the tip of the saw tooth 22 and the hard tip 24 is lowered. Then, the welding head 30 is moved upward by the drive of the actuator 32, and the pressing of the hard tip 24 against the tip of the saw tooth 22 of the saw blade base metal 20 is released, and the gripping state by the first electrode 28 is released. . Thereby, the saw blade base metal 20 provided with the hard tip 24 at the tip of the saw tooth 22 can be removed from the first electrode 28.

  Note that, after the hard tip 24 is joined to the tip end of the saw tooth 22 of the saw blade base metal 20, the tip joining method according to the embodiment of the present invention is also applied to the tip end of the remaining saw tooth 22 of the saw tooth base metal 20. The hard tip 24 is joined by In addition, after the hard tip 24 is joined to the tip of each saw tooth 22 of the saw blade base metal 20, polishing is performed on the rake face side, flank face side, left face side and right face side of each hard tip 24. Thus, each hard tip 24 is formed (finished) into a cutting edge shape (final shape).

  Subsequently, the operation and effects of the embodiment of the present invention will be described.

  In the primary energization process, a temporary joint (welded portion) as a current passage is formed between the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24. The tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24 reduce the influence of external factors such as oxide film formed on the surface of the tip portions of the saw teeth 22 of the blade base metal 20 and inclusion of foreign matter. The initial electrical resistance during this period can be low and stable. In particular, since the heat generated around the temporary joining portion between the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24 is dissipated before starting the secondary energization process, in the secondary energization process, The initial electrical resistance between the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24 can be made more stable. As a result, the temperature distribution (heat balance) of the hard tip 24 in the secondary energization step is brought close to a uniform state along the left-right direction (thickness direction of the saw blade base metal 20), and bonding of the hard tip 24 (joined state ) Can be stabilized.

  In the primary energization step, energization of the welding current between the first electrode 28 and the second electrode 34 is started in a state where the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24 are in line contact. Therefore, in the primary energization process, the initial electric resistance between the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24 can be stabilized. As a result, it is possible to form a temporary joint that is continuous along the left-right direction between the tip of the saw teeth 22 of the saw blade base metal 20 and the hard tip 24, thereby further stabilizing the bonding of the hard tip 24. it can.

  When the saw blade base metal 20 contains carbon of 0.7% by weight or more, the saw blade base metal 20 is locally quenched in the secondary current application process, but in the third current application process, the saw blade base metal is Since the area around the joint between the tip of the 20 saw teeth 22 and the hard tip is heated by Joule heat for annealing, the metal structure of the saw blade base metal 20 is stabilized and the hardness of the saw blade base metal 20 is It can be lowered.

  Therefore, according to the embodiment of the present invention, the temperature distribution of the hard tip 24 in the secondary electrification step is brought close to a uniform state along the left-right direction (the thickness direction of the saw blade base metal 20). Since the bonding can be made more stable, the bonding strength of the hard tip 24 can be sufficiently secured even if the volume of the hard tip 24 (or the outer diameter of the hard tip 24) is reduced. The inclination of the hard tip 24 in the thickness direction can be reduced. Therefore, according to the embodiment of the present invention, the material cost of the hard tip 24 is reduced, and the cost of polishing the hard tip 22 for forming the cutting edge is reduced, in other words, the cost of manufacturing the saw blade is reduced. It is possible to reduce the occurrence rate of defects due to insufficient bonding strength of the hard tip 24 and to prevent the occurrence of cracks in the hard tip 24 while achieving.

  Even when the saw blade base metal 20 contains carbon of 0.7% by weight or more, the metal structure of the saw blade base metal 20 can be stabilized and the hardness of the saw blade base metal 20 can be lowered. The breakage of the saw blade can be prevented to improve the life of the saw blade.

(Modification of the embodiment of the present invention)
As shown in FIG. 3A, in the first modification of the embodiment of the present invention, a triangular prism-shaped hard tip 42 is used in place of the cylindrical hard tip 24 (see FIG. 2). In this case, the shape of the electrode recess 34 a of the second electrode 34 has a shape corresponding to the outer surface (peripheral surface) of the hard tip 42, and the outer surface of the hard tip 42 is a sawtooth of the saw blade base metal 20. A convex curved surface 22 b is formed at the tip of the saw tooth 22 of the saw blade base metal 20 so as to be in line contact with the tip of the tooth 22.

  As shown in FIG. 3B, in the first modification of the embodiment of the present invention, a hard tip 44 having a substantially triangular prism shape (a shape approximate to a triangular prism shape) is used in place of the cylindrical hard tip 24. There is. In this case, the shape of the electrode recess 34 a of the second electrode 34 has a shape corresponding to the outer surface of the hard tip 44, and the outer surface of the hard tip 44 is a flat surface of the saw teeth 22 of the saw blade base metal 20. A row of protrusions (protrusions) 44a extending in the left-right direction is formed on at least one of the outer side surfaces (in the first modification, each outer side surface) of the hard tip 44 so as to be in line contact with 22a. The tip angle θ of the projection row 44 a of the hard tip 44 is preferably 160 to 176 degrees. If the tip angle θ of the projection row 44a of the hard tip 44 is set to 176 degrees or less, the outer surface of the hard tip 44 is flat surface 22a of the saw teeth 22 of the saw blade base metal 20 in the primary energization process Because there is a risk of surface contact. If the tip angle θ of the projection row 44a of the hard tip 44 is set to 160 ° or more, if it is less than 160 °, it becomes difficult to sufficiently reduce the polishing amount of the hard tip 44 after bonding the hard tip 44 It is from.

  As shown in FIG. 4A, in the third modification of the embodiment of the present invention, a hard tip 46 having a fan-like shape (cross-sectional fan shape) is used in place of the cylindrical hard tip 24. In this case, the shape of the electrode recess 34 a of the second electrode 34 has a shape corresponding to the outer surface (outer peripheral surface) of the hard tip 46.

  As shown in FIG. 4B, in the fourth modification of the embodiment of the present invention, a semi-cylindrical hard tip 48 is used in place of the cylindrical hard tip 24. In this case, the shape of the electrode recess 34 a of the second electrode 34 has a shape corresponding to the outer surface (peripheral surface) of the hard tip 48. Further, in the fourth modification of the embodiment of the present invention, the flat surface 22a of the sawtooth 22 is inclined relative to the horizontal direction in order to avoid the interference between the leading sawtooth 22 (not shown) and the second electrode 34. In this state, the saw blade base metal 20 is gripped by the first electrode 28 (see FIGS. 1 and 2).

  The cross-sectional area of the hard tip 42 (44, 46, 48) is within the range of the cross-sectional area of a virtual circle whose diameter is 0.5 to 2.0 times the thickness dimension of the saw blade base metal 20 There is. This is for the same reason as that for defining the outer diameter dimension S (see FIG. 2) of the hard tip 24.

  And in the modification 1 to the modification 4 of the embodiment of the present invention, since the shape of the hard tip 42 (44, 46, 48) is closer to the cutting edge shape (final shape) compared to the hard tip 24, the hard tip The polishing amount of the hard tip 42 (44, 46, 48) after the bonding of 42 (44, 46, 48) can be sufficiently reduced. Therefore, in the modification 1 to the modification 4 of the embodiment of the present invention, in addition to the material cost of the hard tip 42 (44, 46, 48), the polishing cost of the hard tip 42 (44, 46, 48) is reduced This can further reduce the manufacturing cost of the saw blade.

  The present invention is not limited to the description of the above-described embodiment, and can be implemented in various aspects as follows. For example, when the saw blade base metal 20 contains carbon of 0.5% by weight or less, the tertiary current application process may be omitted. In addition, after removing the saw blade base metal 20 provided with the hard tip 24 at the tip end of the saw tooth 22 from the first electrode 28, in the vicinity of the joint between the tip end of the saw blade 22 of the saw blade base metal 20 and the hard tip 24 Alternatively, annealing may be performed again.

  And the scope of the right to be included in the present invention is not limited to the above-described embodiment and the modification of the embodiment, and the tip portion of the sawtooth 22 (each sawtooth 22) of the saw blade base metal 20 is made of hard material. The hard tip 24 (42, 44, 46, 48) extends to a saw blade such as a band saw blade or a circular saw blade joined by the tip bonding method according to the embodiment of the present invention.

(Example of the present invention)
Hard tip of which diameter is smaller than that of the hard tip (the outer diameter is 2.5 times the thickness of the saw blade base) which is the current implementation product (the outer diameter is 1.5 times the thickness of the saw base) A hard tip which is the same as a comparative product is prepared, and small diameter hard tips are joined by the tip joining method according to the embodiment of the present invention. In addition, after completion of the primary energization step in the chip bonding method according to the embodiment of the present invention, as shown in FIG. 5, temporary bonding is performed between the tip of the saw tooth of the saw blade base metal and the small diameter hard tip. It was confirmed that a part (welded part) was formed.

  And the joining strength test was done about the case (in the case of an invention example) of a small diameter hard tip joined by the tip joining method concerning an embodiment of an invention. The results are summarized in FIG. In the case of the invention example, it was confirmed that the incidence rate of defects due to insufficient bonding strength of the hard tip is 0%. Moreover, although illustration is abbreviate | omitted, when the outer diameter of a hard tip is 0.5 to 2.0 times the thickness dimension of the saw blade base metal 20, it was confirmed that the same result is obtained. In addition, as an example, the incidence rate of defects due to insufficient bonding strength of hard chips refers to the generation rate where the bonding strength of hard chips is less than 50 kgf, and 50 kgf is a standard for stabilizing the bonding state of hard chips. Bond strength. FIG. 6 shows that the bonding strength of hard chips is less than 50 kgf, less than 50 and less than 100 kgf, less than 100 and less than 150 kgf, less than 150 and less than 200 kgf, and less than 200 and less than 250 kgf. ing.

  Moreover, as shown to FIG. 7 (a) (b) (c), in the case of an invention example, it was confirmed that a crack does not generate | occur | produce in a hard tip. Although not shown, when the outer diameter of the hard tip is 0.5 to 2.0 times the thickness dimension of the saw blade base metal 20, no crack is generated in the hard tip. Was confirmed.

Reference Signs List 20 saw blade base metal 22 sawtooth 22a flat surface 24 hard tip 26 electric resistance welding device 28 first electrode 30 welding head 32 actuator 34 second electrode 34a electrode recess 36 welding power source 38 conductive cable 40 conductive cable 42 hard tip 44 hard tip 44a Projection row 46 Hard tip 48 Hard tip

Claims (6)

In a tip joining method for joining a hard tip made of a hard material by electric resistance welding to a tip end of a saw blade of a saw blade base metal in a saw blade,
The first electrode and the second electrode in a state in which the hard tip held by the second electrode is relatively pressed against the tip of the saw tooth of the saw blade base metal held by the first electrode; A primary electrification step of temporarily joining only the tip of the saw tooth of the saw blade base metal and the periphery of the contact portion of the hard tip by Joule heat by supplying a welding current between the electrode and supplying electric energy. When,
After completion of the primary energization process, welding is performed between the first electrode and the second electrode in a state in which the hard tip is relatively pressed against the tip end of the saw tooth of the saw blade base metal By supplying an electric current and supplying electric energy higher than the electric energy in the primary energization step, the tips of the serrations of the saw blade base metal and the hard tip are melted by Joule heat to make the hard And a secondary energizing step of joining the tip of the saw blade base metal with the tip of the saw blade base metal by relatively pushing the tip toward the saw tooth side of the saw blade base metal. .   After the completion of the primary energization process and before the start of the secondary energization process, relative pressure is applied to the hard tip against the saw blade base metal, and between the first electrode and the second electrode And holding the welding current for a predetermined time in a state in which the application of the welding current is stopped, the heat generation step for dissipating the heat generated around the temporary bonding portion between the tip of the saw tooth of the saw blade base metal and the hard tip The chip bonding method according to claim 1, characterized in that:   Welding is performed between the first electrode and the second electrode in a state in which the hard tip is relatively pressed against the tip end of the saw tooth of the saw blade base metal after completion of the secondary energization process. A third electrification step is provided, which heats and anneals the periphery of the joint between the tip end of the saw tooth of the saw blade base metal and the hard tip by applying an electric current. The chip bonding method according to claim 1 or 2.   In the primary energization step, energization of a welding current between the first electrode and the second electrode is started in a state in which the tip of the saw tooth of the saw blade base metal and the hard tip are in line contact. The chip bonding method according to any one of claims 1 to 3, characterized in that:   The shape of the hard tip is a cylindrical shape, and the outer diameter size of the hard tip is 0.5 to 2.0 times the thickness size of the saw blade base metal. The chip bonding method according to any one of claims 1 to 4.   The shape of the hard tip is a shape other than a cylindrical shape, and the cross-sectional area of the hard tip is a virtual circle whose diameter is 0.5 to 2.0 times the thickness dimension of the saw blade base metal. The chip bonding method according to any one of claims 1 to 4, wherein the chip bonding method is in the range of the area.