Method and device for repairing cutting edge of steel saw blade

Abstract

The invention relates to a method and a device (10) for repairing a cutting edge (2) of a hacksaw blade (1), in particular a circular hacksaw blade, a strip hacksaw blade or a wire saw blade. According to the invention, the method comprises the following steps: S1) selecting a metal filiform filler material (3) for repairing at least one cutting edge (2) of the hacksaw blade (1) to be repaired; s2) placing the female die (4) of the at least one cutting edge (2) of the hacksaw blade (1) on the at least one cutting edge (2) of the hacksaw blade (1) to be repaired; s3) performing a welding process for melting the selected metal filiform filler material (3) to form a cutting edge (2) of the hacksaw blade (1) to be repaired; and S4) reprocessing all the repaired cutting edges (2) of the hacksaw blade (1).

Description

Field of the Invention

[0001] The present invention relates to a method and apparatus for repairing the cutting edge of a hacksaw blade, in particular a circular hacksaw blade, a band saw blade or a wire saw blade. Background Art

[0002] Hacksaw blades are generally used for cutting or severing various workpieces made of different materials. For this purpose, circular hacksaw blades with circular saw blades are used, on the circumference of which cutting edges are arranged and can be provided. Band saw blades, in which the cutting edges are arranged on one side of a rotating hacksaw blade, or wire saw blades, in which the cutting edges are arranged along a short, slender saw blade, are also possible. The saw blade and the cutting edges are made of particularly hard and wear-resistant materials, usually metals and metal alloys. The cutting edges are usually specially hardened and sometimes also coated with hard materials such as ceramics or mineral particles. So-called high-speed steel, a high-alloy tool steel, is used as the material for cutting tools and hacksaw blades. Ordinary tool steel loses its hardness from around 200 °C, while high-speed steel (HSS) retains its hardness up to around 600 °C. The most important alloying elements of high-speed steel are carbon, tungsten, molybdenum, vanadium, chromium and cobalt.

[0003] Despite the use of particularly hard materials for hacksaw blades, wear of the cutting edges of the hacksaw blades or breakage of individual cutting edges can still occur, especially with hard workpieces made of metal or metal alloys and after long-term use. Used hacksaw blades are often discarded in a wasteful manner because expensive repairs are usually not worthwhile. As an alternative, used hacksaw blades with worn and damaged cutting edges can also be processed by forming new cutting edges using material removal methods (such as milling or grinding). This results in the circumference or width of the hacksaw blade being smaller than that of the original hacksaw blade. This makes processing more difficult because processing machines are usually designed for certain saw blade sizes, which makes it more difficult to process with other smaller hacksaw blades.

[0004] Another option is a material application repair method, whereby material is applied to the damaged area of the cutting edge of a worn hacksaw blade or a prefabricated new cutting edge is used instead. This can be done using a welding process (so-called repair welding), whereby a metal material is melted and bonded to the used hacksaw blade. After the surfacing process, the newly applied area or the cutting edge of the hacksaw blade is restored to the size of the original saw by a material removal process (such as grinding or polishing).

[0005] For example, CA253844A and CA306886A describe a repair welding process for circular hacksaw blades for replacing broken teeth, repairing cracks or other defects. After the repair welding process, the repair area is ground and polished. Finally, the welded area is tempered to increase density.

[0006] Similar welding repair methods are described in CN 112676678 A and CN 112676680 A. Before the welding process, rust and oil are removed from the worn hacksaw blade. Preheating of the hacksaw blade before the welding process is also mentioned.

[0007] In summary, the traditional methods of repairing hacksaw blades using welding methods to apply metal materials are usually very time-consuming and expensive, which is why these methods are rarely used for economic reasons. Instead, used hacksaw blades are usually discarded, and at most the materials can be recycled. Summary of the Invention

[0008] The object of the present invention is to create a method for repairing hacksaw blades that can be implemented simply, quickly and inexpensively, and shows very good results. For economic and environmentally friendly reasons, it should be possible to repair hacksaw blades instead of discarding them. The disadvantages of the known methods of repairing hacksaw blades should be avoided or at least reduced.

[0009] The object of the present invention is solved by the above method comprising the following method steps:

[0010] S1) Select a metal wire-like filler material for repairing at least one cutting edge of the hacksaw blade to be repaired;

[0011] S2) Place the female mold of at least one cutting edge of the hacksaw blade on at least one cutting edge of the hacksaw blade to be repaired;

[0012] S3) Perform a welding process for melting the selected metal wire-like filler material to form the cutting edge of the hacksaw blade to be repaired;

[0013] S4) Reprocess all the repaired cutting edges of the hacksaw blade.

[0014] According to the present invention, the hacksaw blade is repaired using a welding process and a suitable metal wire-shaped filler material. By using a female mold of at least one cutting edge of the hacksaw blade to be replaced or repaired, only as much material as is truly necessary needs to be added by surfacing. In the absence of such a female mold, the material is typically applied in an uncontrolled manner, and in subsequent reworking steps, the material has to be removed again in a time-consuming and expensive manner to obtain the desired shape of the cutting edge of the hacksaw blade. In this regard, the method according to the present invention saves both material, since only as much metal wire-shaped filler material as is truly necessary is used, and time, since reworking the hacksaw blade is simpler and faster. The cutout of the female mold corresponds to the shape of one or more cutting edges or teeth of the hacksaw blade. With the help of the female mold, the three sides of the cutting edge to be repaired are optimally restricted, which is why only minimal reworking of these three sides is required. During the reworking step, only the open side of the female mold may require more material to be removed (e.g., ground off). This repair method can repair a hacksaw blade to have the same dimensions as a new hacksaw blade. The repaired circular hacksaw blade has the same outer diameter as a new circular hacksaw blade after repair, and the repaired band-shaped hacksaw blade has the same width as a new band-shaped hacksaw blade after repair. This simplifies the machining of workpieces using the repaired hacksaw blade, as no machine conversion is required. Using the repair method of the present invention, the hacksaw blade can be repaired more easily, quickly, and economically, and thus can be used for a longer time. Therefore, the method according to the present invention helps to conserve resources in a sustainable manner, and the method avoids wasteful discarding of the hacksaw blade and instead uses a welding device to perform a cost-saving repair of the damaged hacksaw blade.

[0015] Preferably, the metal wire-shaped filler material for forming the cutting edge of the hacksaw blade to be repaired is selected from a material substantially the same as the cutting edge of the hacksaw blade. A filler wire of the same / similar material as the saw blade is selected and a mold is used to keep the molten pool in "shape" and no more filler material than necessary is applied.

[0016] If the metal wire-shaped filler material is formed of steel or a steel alloy, very good results and high strength values for the repaired hacksaw blade can be obtained. A metal wire-shaped filler material made of SKH-9 (high-speed steel, a tungsten-molybdenum series ordinary melting high-speed tool steel with good toughness and high performance) is particularly suitable for repairing a hacksaw blade that is typically also made of SKH-9.

[0017] Preferably, the wire-shaped filler material is formed with a wire diameter of 1 to 1.6 mm. This diameter range represents a suitable size for the wire-shaped filler material to form the teeth or cutting edges of the hacksaw blade by manually actuating the welding torch and manually feeding the wire-shaped filler material. The suitable thickness of the wire-shaped filler material depends on the size and thickness of the hacksaw blade to be repaired and the size of the area to be repaired on the hacksaw blade.

[0018] If the hacksaw blade is preheated before the welding process, the heat input into the hacksaw blade during the welding process can be reduced, and the stress in the formed hacksaw blade can be avoided.

[0019] Preheating to a temperature of 200 °C to 300 °C has proven to be particularly suitable.

[0020] Another feature of the method according to the invention is that the hacksaw blade is electrically preheated. Of course, other types of preheating of the hacksaw blade can also be envisaged.

[0021] Preferably, in step S2) of the method, a female mold made of a ceramic material, in particular alumina (Al2O3), is used. Ceramics are particularly suitable for use in molds due to their high heat resistance. The mold can be made entirely of ceramic material or made of a metallic material with a coating made of ceramic material.

[0022] If a female mold of at least one cutting edge of the hacksaw blade is used in step S2), and the female mold is larger than the cutting edge of the hacksaw blade to be repaired, the shrinkage (referred to as sintering shrinkage) that occurs when the metal hardens can be taken into account. The female mold can be, for example, 8% to 12% larger than the size of the cutting edge of the saw blade to be repaired.

[0023] Step S3) is preferably carried out by a welding process using a non-consumable electrode, in particular a TIG welding process, and particularly preferably a cyclic TIG welding process. The cyclic welding process using a non-consumable electrode is an intermittent welding process, in which a certain number of cycles are used, and in each welding cycle, a higher main welding current alternates with a lower base current during the intermittent time period. This type of welding process makes it easier to control the molten pool while ensuring the target heat input.

[0024] Normally, a manual welding process is carried out, and the selected wire-shaped filler material is manually fed. Nevertheless, an automatic welding process can also be envisaged.

[0025] Particularly advantageous results have been obtained by using a welding process with the following welding parameters:

[0026] Number of cycles n: 3 - 5

[0027] Main current I M : 200 - 240 A

[0028] Base current I B : 0 A

[0029] Interval time t I : 0.02 s – 0.08 s

[0030] Interval interruption time t B : 0.02 s – 0.05 s.

[0031] Due to the precisely controlled heat input, these welding parameters are ideal for repair welding.

[0032] A shielding gas, such as acetylene gas, is preferably used in the welding process.

[0033] If the hacksaw blade is pretreated before being inserted into the female mold according to step S2), and the welding process is started according to step S3), improved results can be obtained.

[0034] For example, the hacksaw blade is derusted and degreased to remove the corresponding impurities on the used hacksaw blade. In addition, the hacksaw blade can be ground.

[0035] Optionally, after step S3 of the welding process, the hacksaw blade can be cooled according to a predetermined temperature curve over time. By this stress relief heat treatment, welding residual stresses can be reduced.

[0036] In order to make the hacksaw blade precisely reach the dimensions of a brand-new hacksaw blade after the repair process, each repaired cutting edge of the hacksaw blade is reprocessed by grinding and / or polishing according to step S4). Preferably, the grinding and / or polishing is carried out after the hacksaw blade has cooled, for example, at a maximum temperature of 150 °C. The temperature of the hacksaw blade also affects the dimensions of the blade.

[0037] In addition, each repaired cutting edge of the hacksaw blade can be reprocessed by a slag removal process according to step S4). For example, the slag can be removed by mechanically affecting the welding surface.

[0038] Optionally, each repaired cutting edge of the hacksaw blade can be reprocessed by hammering and / or rolling according to step S4) to eliminate the stress in the welding area.

[0039] Furthermore, the hacksaw blade can be heat-treated / hardened after step S3) or after step S4). The heat treatment can be carried out, for example, by selectively heating and cooling the hacksaw blade in accordance with a predetermined temperature / time curve. For example, the heat treatment can be carried out in a suitable heating chamber.

[0040] Preferably, quality control is carried out after step S4) of the repair method in order to determine the quality of the repaired hacksaw blade. In addition to visual quality control methods, automatic quality control methods using ultrasonic waves or an image processing system can preferably be carried out.

[0041] The problem of the present invention is also solved by a device for implementing the above method. Such a device includes a welding device, in particular a welding device that welds with a non-consumable electrode, such as a TIG welding device, a metal wire filler material, and a female mold into which the hacksaw blade to be repaired is inserted. Other devices for pre-treatment and post-treatment of the hacksaw blade, such as a grinding device, a polishing device, a heating chamber, etc. are also possible. For the advantages that can be achieved, reference is made to the description of the method for repairing the cutting edge of a hacksaw blade above. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be explained in more detail with reference to the accompanying drawings. They show:

[0043] Figure 1A show a damaged hacksaw blade;

[0044] Figure 1B show a female mold;

[0045] Figure 1C show a device for implementing the method according to the present invention;

[0046] Figure 1D show a hacksaw blade inserted between female molds;

[0047] Figure 2 show a flow chart of a method for repairing the cutting edge of a hacksaw blade according to the present invention; and

[0048] Figure 3 show the current of a preferred welding process for repairing the cutting edge of a hacksaw blade. DETAILED DESCRIPTION

[0049] Figure 1A show a damaged hacksaw blade, Figure 1B show a female mold, Figure 1C show a device for implementing the method according to the present invention, Figure 1DShows a hacksaw blade inserted between the female dies. The hacksaw blade 1 to be repaired is shown here as a circular hacksaw blade. Other types of hacksaw blades 1, such as band hacksaw blades, can of course be repaired in the same way. The hacksaw blade 1 is inserted into the female die 4 of at least one cutting edge 2 of the hacksaw blade 1 to be repaired. The female die 4 defines the cutting edge 2 to be repaired on three sides and is preferably made of ceramic material. The device 10 for implementing this method also includes a welding device 11, in particular a TIG welding device, which is used to implement the welding process with a non-consumable welding electrode 5, in particular a tungsten electrode, arranged on the welding torch 13. The metal wire filling material 3 is wound onto a wire reel 12 and is manually (or automatically) fed to the welding point during the welding process. The gas cylinder 14 can contain a shielding gas G, which can be supplied to the welding torch 13. Other devices for pre-treating or post-treating the saw blade 1, such as grinders, polishers or heating boxes, etc., are not shown. The device 10 is realized relatively simply and inexpensively and is capable of environmentally friendly repair of the hacksaw blade 1 having the same dimensions as a new saw blade.

[0050] Figure 2 Shows a flow chart illustrating a method for repairing the cutting edge 2 of a hacksaw blade 1 according to the present invention. According to the present invention, the method for repairing the cutting edge 2 of a hacksaw blade 1 includes the following steps:

[0051] S1) Select a metal wire filling material 3 for repairing at least one cutting edge 2 of the hacksaw blade 1 to be repaired;

[0052] S2) Place the female die 4 of at least one cutting edge 2 of the hacksaw blade 1 on at least one cutting edge 2 of the hacksaw blade 1 to be repaired;

[0053] S3) Perform a welding process for melting the selected metal wire filling material 3 to form the cutting edge 2 of the hacksaw blade 1 to be repaired;

[0054] S4) Reprocess all the repaired cutting edges 2 of the hacksaw blade 1.

[0055] In addition to the four method steps shown, further pre-treatment or post-treatment can also be carried out as described above.

[0056] Finally, Figure 3 Shows the current of the preferred welding process for repairing the cutting edge 2 of the hacksaw blade 1 according to the process of the present invention. The cyclic welding process using a non-consumable electrode is an intermittent welding process, where a certain number of cycles n are used, and in each welding cycle, during the interval time t I a higher main welding current I M during the interval interruption time t BLower base current I during B Alternates. This type of welding process makes it easier to control the molten pool while ensuring the target heat input. Usually, a manual welding process is carried out, and the selected metal wire-shaped filler material is fed manually. Nevertheless, an automatic welding process can also be envisaged.

[0057] Particular advantages have been obtained with a welding process having the following welding parameters:

[0058] Number of cycles n: 3 - 5

[0059] Main current I M : 200 - 240 A

[0060] Base current I B : 0 A

[0061] Interval time t I : 0.02 s – 0.08 s

[0062] Interval interruption time t B : 0.02 s – 0.05 s.

[0063] Due to the precisely controlled heat input, these welding parameters are ideal for repair welding.

[0064] List of reference signs

[0065] 1 Hacksaw blade

[0066] 2 Cutting edge of hacksaw blade 1

[0067] 3 Metal wire-shaped filler material

[0068] 4 Female mold for the cutting edge 2 of the hacksaw blade 1 to be repaired

[0069] 5 Non-fusible electrode

[0070] 10 Device for repairing the cutting edge 2 of the hacksaw blade 1

[0071] 11 Welding device

[0072] 12 Wire reel

[0073] 13 Torch

[0074] 14 Gas cylinder for shielding gas G

[0075] D Z Diameter of the metal wire-shaped filler material 3

[0076] G Shielding gas

[0077] I B Base current

[0078] I M Main current

[0079] n Cycle number

[0080] t B Interval interruption time

[0081] t I Interval time

[0082] T Temperature

Claims

1. A method for repairing a cutting edge (2) of a hacksaw blade (1), in particular a circular hacksaw blade, a band saw blade or a wire saw blade, the method comprising the following steps: S1) Select a metallic filamentous filler material (3) for repairing at least one cutting edge (2) of the hacksaw blade (1) to be repaired; S2) Place a female mold (4) of at least one cutting edge (2) of the hacksaw blade (1) on at least one cutting edge (2) of the hacksaw blade (1) to be repaired; S3) Perform a welding process for melting the selected metallic filamentous filler material (3) to form the cutting edge (2) of the hacksaw blade (1) to be repaired; S4) Reprocess all the repaired cutting edges (2) of the hacksaw blade (1).

2. The method according to claim 1, characterized in that The metallic filamentous filler material (3) for forming the cutting edge (2) of the hacksaw blade (1) to be repaired is selected from a material substantially the same as the cutting edge (2) of the hacksaw blade (1).

3. The method according to claim 1 or 2, characterized in that The metallic filamentous filler material (3) is formed of steel or a steel alloy.

4. The method according to claim 1 or 2, characterized in that The metallic filamentous filler material (3) is formed with a wire diameter (Dz) of 1 to 1.6 mm.

5. The method according to claim 1 or 2, characterized in that Preheat the hacksaw blade (1) before the welding process.

6. The method according to claim 5, characterized in that Preheat the hacksaw blade (1) to a temperature (T) of 200 °C to 300 °C.

7. The method according to claim 5, characterized in that Electrically preheat the hacksaw blade (1).

8. The method according to claim 1 or 2, characterized in that Use a female mold (4) made of a ceramic material, in particular alumina (Al2O3), in step S2).

9. The method according to claim 1 or 2, characterized in that Use a female mold (4) of at least one cutting edge (2) of the hacksaw blade (1) in step S2), the female mold (4) being 8% to 12% larger in size than at least one cutting edge (2) of the hacksaw blade (1).

10. The method according to claim 1 or 2, characterized in that Step S3) is performed by a welding process using a non-consumable electrode (5), in particular a TIG welding process, and particularly preferably a cyclic TIG welding process.

11. The method according to claim 10, characterized in that Perform a manual welding process and manually feed the selected metallic filamentous filler material (3).

12. The method according to claim 10, characterized in that Use the following welding parameters in the welding process: Number of cycles (n): 3 - 5 Main current (I M ): 200 - 240 A Base current (I B ): 0 A Interval time (t I ): 0.02 s - 0.08 s Interval interruption time (t B ): 0.02 s - 0.05 s.

13. The method according to claim 1 or 2, characterized in that Use a shielding gas (G), in particular acetylene gas, in the welding process.

14. The method according to claim 1 or 2, characterized in that Pretreat the hacksaw blade (1) before performing step S2).

15. The method according to claim 14, characterized in that Remove rust and degrease the hacksaw blade (1).

16. The method according to claim 14, characterized in thatGrind the hacksaw blade (1).

17. The method according to claim 1 or 2, characterized in that After the welding step S3), cool the hacksaw blade (1) according to a predetermined temperature curve over time.

18. The method according to claim 1 or 2, characterized in that Reprocess each repaired cutting edge (2) of the hacksaw blade (1) by grinding according to step S4).

19. The method according to claim 1 or 2, characterized in that Reprocess each repaired cutting edge (2) of the hacksaw blade (1) by polishing according to step S4).

20. The method according to claim 1 or 2, characterized in that Reprocess each repaired cutting edge (2) of the hacksaw blade (1) by a slag removal process according to step S4).

21. The method according to claim 1 or 2, characterized in that Reprocess each repaired cutting edge (2) of the hacksaw blade (1) by hammering and / or rolling according to step S4).

22. The method according to claim 1 or 2, characterized in that Perform heat treatment / hardening on the hacksaw blade (1) after step S3) or after step S4).

23. The method according to claim 1 or 2, characterized in that Perform quality control after step S4).

24. A device (10) for repairing the cutting edge (2) of a repair hacksaw blade (1) for implementing the method according to any one of claims 1 to 23.

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