DE102015104702A1 - Method for producing a sawing tool - Google Patents

Abstract

The invention relates to a method for producing a sawing tool (10a), having a fastening region 12 for attachment to a drive spindle, and having a working region (14) on which at least one cutting edge (16) is provided, comprising the following steps: (a) Providing a martensitic hardenable steel sheet; (b) removing a blank from the steel sheet; (c) providing a press with a press tool for press hardening the blank; (d) heating the blank to a temperature above the austenitizing temperature and (e) feeding the blank into the die and press-hardening, wherein the blank is hardened at least in the area of its cutting edge (s) (16).

Description

The invention relates to a method for producing a sawing tool with a mounting area for attachment to a drive device and with a work area on which at least one cutting edge is provided.

Sawing tools intended for use with a rotary oscillating drive, whose drive shaft oscillates at high frequency about its longitudinal axis, have been known for years to handle special cutting tasks.

With such sawing tools, in particular, body panels and other types of sheet metal can be easily cut, whereby the risk of injury is minimized by the oscillating drive. Furthermore, such sawing tools for cutting wood, glass fiber reinforced plastic and similar materials are particularly suitable.

The known sawing tools can in one embodiment consist of a flat, circular cutting blade, which has in the middle a central attachment opening for the positive connection with the drive spindle of an oscillating hand tool.

In order to enable a good cutting performance and on the other hand not to overload the drive the sawing tools should have the lowest possible strength,

According to the DE 296 05 728 U1 It is known to produce a circular sawing tool with a bend in the attachment region of two parts by a flat work area, on the outer circumference of a toothing is provided by means of a laser weld or by means of a brazed joint is connected to a bent receiving part.

In this way, a sawing tool with a small thickness of 1 millimeter or less can be produced.

However, such a production is very complicated and expensive.

From the DE 132 297 A1 Another method for producing such a saw blade is known. Here, the saw blade is made in one piece from a hardenable steel sheet with a flat cutting blade and a bent, with respect to the cutting blade plastically protruding fastening part with a central mounting hole. For this purpose, first blanks are separated from a hardenable steel sheet, then then deep-drawn to form the bent attachment part. The mounting holes are preferably made by punching. Subsequently, a plurality of such blanks stacked and clamped together in a device, then recrystallized and austenitized, then quenched and tempered for tempering. Finally, a toothing on the outer edges of the saw blades is generated by grinding.

In this way, one-piece saw blades can be produced in a cranked design.

As before, the production is very complex. In addition, during the hardening process a delay may occur, which leads to the production of rejects, because the saw blades can not be used in the desired manner.

The invention is therefore based on the object to provide an improved method for the production of sawing tools, can be made with the sawing tools of high quality in the simplest and most cost-effective manner.

Furthermore, an improved sawing tool should be specified.

• (a) Bereitstellen eines martensitisch härtbaren Stahlblechs;
• (b) Austrennen eines Rohlings aus dem Stahlblech;
• (c) Bereitstellen einer Presse mit einem Presswerkzeug zum Presshärten des Rohlings;
• (d) Erhitzen des Rohlings auf eine Temperatur oberhalb der Austenitisierungstemperatur; und
• (e) Zuführen des Rohlings in das Presswerkzeug und Presshärten, wobei der Rohling zumindest im Bereich seiner Schneide(n) gehärtet wird.

This object is achieved according to the invention by a method for producing a sawing tool having a fastening region for fastening to a drive device and having a working region on which at least one cutting edge is provided, with the following steps:

• (a) providing a martensitic hardenable steel sheet;
• (b) removing a blank from the steel sheet;
• (c) providing a press with a press tool for press hardening the blank;
• (d) heating the blank to a temperature above the austenitizing temperature; and
• (E) feeding the blank into the pressing tool and press hardening, wherein the blank is hardened at least in the region of its cutting edge (s).

The object of the invention is achieved in this way.

Surprisingly, it has been found that the method of press-hardening, which is generally known in the automotive industry, is also suitable for the production of sawing tools for the production of high-strength structural components. This was not to be expected without further ado, since the strength of structural components in the automotive sector does not correlate with the stability of sawing tools.

It is essential that the area of the cutting edge (s) is hardened martensitic during press hardening. Only in this way can the at least one cutting edge be made sufficiently sharp or provided with sharp and stable sawteeth.

In principle, any shapes of sawing tools can be produced by the method according to the invention. These may be planar sawing tools, cranked or otherwise three-dimensionally shaped sawing tools formed in a circular, part-circular, circular-section, oblong or other shapes. The sawing tools may preferably be designed for use with rotary oscillating drives. In principle, however, other sawing tools, such as circular saw blades, cutting blades (serrated), jigsaw blades and saber saw blades can advantageously be produced in the manner according to the invention.

Preferably, a steel sheet having a thickness of at most 1.0 mm, preferably at most 0.9 mm, more preferably at most 0.8 mm is used.

The use of such thin steel sheets makes it possible to produce sawing tools which are particularly suitable for use with rotary oscillating drivable hand-held power tools.

Surprisingly, it has been shown that even with such thin sheet thicknesses a safe process management can be ensured without the risk of cracking or pinholing. When known in the automotive press hardening sheets are generally used with a thickness of 1.5 to 2.0 mm.

In contrast, there is always the risk of cracking or hole formation when using thinner sheets.

However, it has been shown that with only small degrees of deformation, as they occur in the range of offsets, a safe process management is possible even with thin sheets.

According to a preferred embodiment of the invention, a steel sheet of a steel is used, which contains about 0.22 to 0.25 wt .-% C, 0.25 to 0.35 wt .-% Si, 1.2 to 1.4 wt .-% Mn and 0.005 wt .-% B contains.

This may be a 22MnB5 steel sheet. Also steels of similar composition are suitable, which are marketed by the company ArcelorMittal, Benteler, Thyssen-Krupp Steel and Voestalpine under the brands USIBOR ^®, BTR165 ^®, MBW ^® or PHS Ultraform ^®.

Such steels can be used to produce high strength saw tools with tensile strengths greater than 1200 N / mm ² and up to 1500 N / mm ² or more.

For press hardening, the blank is preferably first heated to a temperature of about 880 ° C to 950 ° C and austenitized.

During the subsequent press-hardening in the pressing tool, the blank is cooled to a temperature of about 150 ° C. to 250 ° C. within about 15 to 60 seconds.

For this purpose, a cooled pressing tool is used, with which the necessary cooling speed is ensured in order to ensure the martensitic hardening, especially in the cutting area. Suitable cooling rates can be deduced from the specific ZTU diagrams for the steel grade used.

The toothing on the at least one cutting edge can be produced according to a first embodiment of the invention after the press hardening, preferably by grinding or by laser cutting.

According to an alternative embodiment of the invention, the toothing on the at least one cutting edge is already produced on the blank and only post-processed after press hardening. Again, this can be done for example by grinding or by means of a laser treatment.

As a result, the production is further simplified or designed more cost-effective.

According to a further embodiment of the invention, a mounting opening is cut off at the attachment area, which is designed for attachment to a drive device.

Preferably, the attachment opening for attachment to an oscillating drivable drive device, preferably on a rotationally oscillating drivable drive spindle, is formed.

The cutting of the blank and the removal of the attachment opening can be carried out for example by means of punching, milling, erosion and / or by means of laser radiation.

If necessary, further cutouts / openings in the sawing tool can be produced as far as necessary.

As already mentioned above, an offset can also be generated during press hardening, which is preferably at the transition between the attachment area and the work area.

Furthermore, areas with different material thicknesses, in particular at the attachment area and / or at the work area, can be produced during press hardening.

It is particularly preferred in this case if the material thickness in the work area is less than the material thickness in the attachment area. While the material thickness should be as low as possible in the work area to allow a good cutting behavior, it may be useful to provide greater material thickness in the attachment area.

Further preferably, during the press-hardening, in addition to the cutting edge, a region enclosing the fastening opening is also hardened.

By these measures, the risk of a rash of the mounting hole is counteracted, which is potentially in the case of using a mounting hole for positive connection with a tool spindle. Also results in a greater stability of the sawing tool.

The invention further provides a sawing tool having a fastening region for attachment to a drive device, and having a working region on which at least one cutting edge is provided, wherein the sawing tool consists of a steel sheet hardened by martensitic hardening at least in the region of the cutting edge.

In this case, a fastening opening is preferably provided on the attachment region, which is designed for connection to a rotationally oscillating drivable drive spindle of a hand tool machine.

According to a further embodiment of the invention, at least one embossment, an undercut and / or a depression, in particular in the form of a groove for chip removal, is introduced into the steel sheet during the press-hardening process.

By embossing results in a stiffening of the tool. As a result, resonances during operation of the tool with high frequency can be suppressed. An undercut increases the cutting performance of the tool. A recess, in particular in the form of a groove, can for improved chip removal this.

By press hardening, embossments, undercuts and / or depressions, in particular grooves for chip removal, can be produced without additional effort. In conventional manufacturing processes, this is either not possible or associated with high head.

Method according to one of the preceding claims, wherein during the press hardening at least one undercut ( 82 ) in the steel sheet ( 50 ) is introduced.

Method according to one of the preceding claims, in which at least one depression ( 84 ), in particular in the form of a groove, in the steel sheet ( 50 ) is introduced.

It is understood that the features of the invention mentioned above and those yet to be explained below can be used not only in the particular combination indicated but also in other combinations or in isolation, without departing from the scope of the invention.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings. Show it:

1 a rotary oscillating drivable hand tool in a perspective view, on which a sawing tool according to the invention is received;

2 a top view of a sawing tool according to the invention;

3 a cross section through the sawing tool according to 2 in an enlarged view;

4 the various steps in the manufacture of a sawing tool according to the invention in a schematic representation;

5 the post-processing of a sawing tool according to the invention after press hardening in a schematic representation to sharpen the toothing by grinding or by means of a laser treatment;

6 a view of another embodiment of a sawing tool according to the invention;

7 a section through the sawing tool according to 6 along the line VII-VII;

8th a view of another embodiment of a sawing tool according to the invention;

9 a section through the sawing tool according to 8th along the line IX-IX;

10 a view of another embodiment of a sawing tool according to the invention and

11 a section through the sawing tool according to 10 along the line XI-XI.

1 shows a rotary oscillating drivable hand tool 30 known type, to which a sawing tool according to the invention is added, the total with the numeral 10 is designated.

The rotary oscillating drivable hand tool 30 has a drive spindle 32 on, around their longitudinal axis 34 With a high frequency of about 15,000 to 30,000 oscillations per minute and a small pivot angle of about 0.5 to 7 ° rotationally driven drivable. On the drive spindle 32 is a sawing tool according to the invention 10 fastened in a manner not shown and secured with a securing element (not shown).

In the case shown is the sawing tool 10 elongated and has a mounting area 12 with a fastening opening (see reference numeral 40 according to 2 ), which results in a positive connection with a corresponding raised protruding part on the drive spindle 32 is trained. A workspace 14 , at the outer end of a cutting edge 16 with a toothing 18 is provided, is about a bend 20 with the attachment area 12 connected.

By a dashed line is in 1 indicated that instead of elongated sawing tools 10 preferably also circular sawing tools 10 can be used.

Such a circular sawing tool is in 2 represented and in total with 10a designated. It has a central attachment area 12 with a mounting hole 40 on that over a bend 20 in a flat circular workspace 14 goes over, on the outer edge of a cutting edge 16 with a toothing 18 is provided.

3 shows the sawing tool 10a in cross section in an enlarged, but not necessarily to scale representation.

Out 3 It can be seen that the strength of the sawing tool d ₁ in the work area 14 of the thickness d _{2 of} the sawing tool 10a in the attachment area 12 may differ.

Preferably, the strength of the sawing tool 10a at the work area 14 in the area of the cutting edge d ₁ slightly less than the thickness d ₂ in the mounting area 12 ,

In this way, the strength of the sawing tool 10a in the area of the cutting edge very thin and can be for example about 0.8 mm. In contrast, the thickness d ₂ in the attachment area 12 be slightly larger to here with a greater strength knocking out the mounting hole 40 counteract.

The production of sawing tools according to the invention 10 respectively. 10a is described below by means of 4 and 5 described in more detail.

The sawing tool 10 respectively. 10a is made by press hardening from a martensitic hardenable steel sheet, which may be, for example, a 22MnB5 steel sheet.

In press hardening, the sawing tool becomes 10 respectively. 10a at least in the area of the cutting edge 16 and optionally additionally in the attachment opening 40 enclosing area hardened martensitic.

The procedure is in 4 shown schematically.

First, steel sheet 50 provided in the form of roll material from which at a cutting station 52 for example by means of a punching tool 54 blanks 58 be cut out. Here, the provided later on the outer circumference toothing 18 already be pre-punched. In addition, the mounting hole 40 punched out.

Subsequently, the blanks 58 in an austenitizing oven 56 heated to a temperature of about 900 ° C and austenitized, which usually only a few minutes (about 4 to 7 minutes) are sufficient.

Austenitizing is followed by actual press hardening in a press 60 at. A blank 58 gets into a pressing tool 62 inserted, which consists of a lower mold half 64 and an upper mold half 66 consists. The pressing tool 62 is suitably cooled to meet the requirements for optimal martensite formation, in particular the A _c3 temperature and the MS temperature and the critical cooling rate vok, which can be deduced from the respective specific ZTU diagram for the steel used.

For the 22MnB5 steel, for example, the ZTU diagram provides a critical cooling rate vok of over 27 K / s, a martensite start temperature MS of about 390 ° C, a martensite finish temperature Mf of about 190 ° C and an A _c3 temperature (above A _c3) excluding austenite) of about 800 ° C.

In the case of using 22MnB5 cooling takes place in the pressing tool to about 190 ° C approximately within 20 to 40 seconds.

After press hardening, only after-treatment of the previously punched-out saw teeth is necessary. This can be done according to 5 for example by means of a grinding tool 70 or alternatively by means of a laser 72 by laser radiation 74 respectively. For simple sawtooth geometries, it may even be possible to do without aftertreatment.

Alternatively, it is also possible to dispense with prior punching and the toothing exclusively in the after-treatment according to 5 be generated.

It is understood that the shape of the sawing tools can be adapted within wide limits to the needs.

Furthermore, the cutting of the blanks and the removal of the mounting holes can also be performed by other methods, such as by laser, eroding or milling.

As a result of the press-hardening process, embossments, undercuts and / or depressions, in particular in the form of grooves for chip evacuation, can also be introduced into the tool without additional effort. These advantageous additional features of sawing tools in conjunction with oscillating drives can be in conventional manufacturing processes either not at all, or only with great effort, for. B. by grinding.

In 6 and 7 is a sawing tool with two embossments 80 represented and in total with 10b designated. Corresponding reference numbers are used for corresponding parts.

For a coinage 80 it is a three-dimensional deformation of the steel sheet, as seen from 7 can be seen. This results in a higher rigidity. At the same time, resonances can be minimized, resulting in better sawing results and reduced sawing noise.

In 6 and 7 is a sawing tool with two embossments 80 represented and in total with 10b designated. Corresponding reference numbers are used for corresponding parts.

In 8th and 9 is a sawing tool with an undercut 82 represented and in total with 10c designated. Corresponding reference numbers are used for corresponding parts.

Through an undercut 82 who exemplifies in 9 is shown, can reduce the friction when sawing, thus improving the cutting performance.

In 8th and 9 is a sawing tool with three recesses 84 represented in the form of grooves for chip removal and total with 10d designated. Corresponding reference numbers are used for corresponding parts.

The sawing tools according to the invention are characterized by a particularly high strength and service life.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 29605728 U1 [0006]
• DE 132297 A1 [0009]

Claims (20)

Method for producing a sawing tool ( 10 . 10a . 10b . 10c . 10d ) with a fastening area ( 12 ) for attachment to a drive spindle ( 32 ) and with a workspace ( 14 ), on which at least one cutting edge ( 16 ), comprising the following steps: (a) providing a martensitic hardenable steel sheet ( 50 ); (b) cutting a blank ( 58 ) from the steel sheet ( 50 ); (c) providing a press with a pressing tool ( 62 ) for press-hardening the blank ( 58 ); (d) heating the blank ( 58 ) to a temperature above the austenitizing temperature; and (e) feeding the blank ( 58 ) in the pressing tool ( 62 ) and press hardening, wherein the blank ( 58 ) at least in the region of its cutting edge (s) ( 16 ) is hardened. Method according to Claim 1, in which a steel sheet ( 50 ) having a thickness of at most 1.0 millimeter, preferably at most 0.9 millimeters, more preferably at most 0.8 millimeters is used. Method according to Claim 1 or 2, in which a steel sheet ( 50 from a steel containing about 0.22 to 0.25 wt.% C, 0.25 to 0.35 wt.% Si, 1.2 to 1.4 wt.% Mn, and 0.005 wt .-% B contains. Method according to one of the preceding claims, in which a steel sheet ( 50 ) From 22MnB5, USIBOR ^{®, ®} BTR165, MBW ^®, or PHS Ultraform ^® is used. Method according to one of the preceding claims, in which the blank ( 58 ) is heated in step (d) to a temperature of about 880 ° C to 950 ° C. Method according to one of the preceding claims, in which the blank ( 58 ) is cooled to a temperature of about 150 ° C to 250 ° C within about 15 to 60 seconds during the press cure in step (e). Method according to one of the preceding claims, in which on the at least one cutting edge ( 16 ) after the press hardening a toothing ( 18 ), preferably by grinding or laser irradiation. Method according to one of claims 1 to 6, wherein the toothing ( 18 ) on the at least one cutting edge ( 16 ) on the blank ( 58 ) and the toothing ( 18 ) is post-processed after press hardening, preferably by means of grinding or laser treatment. Method according to one of the preceding claims, in which at the attachment area ( 12 ) an attachment opening ( 40 ) which is adapted for attachment to a drive device ( 30 ) is trained. Method according to claim 9, wherein at the attachment area ( 12 ) an attachment opening ( 40 ) is separated, which for attachment to an oscillating drivable drive device ( 30 ), preferably on a rotationally oscillating drivable drive spindle ( 32 ), is trained. Method according to one of the preceding claims, in which the blank ( 58 ) is cut by punching, milling, eroding and / or laser cutting. Method according to one of the preceding claims, wherein during the press hardening a bend ( 20 ) preferably at the transition between the attachment area ( 12 ) and workspace ( 14 ) is produced. Method according to one of the preceding claims, wherein areas of different material thicknesses (d ₁ , d ₂ ) at the attachment area (D ₁ , d ₂ ) during the press hardening ( 12 ) and / or at the work area ( 14 ) be generated. Method according to one of the preceding claims, wherein in addition to the at least one cutting edge during the press hardening ( 16 ) also the attachment opening ( 40 ) enclosing area ( 12 ) is hardened. Method according to one of the preceding claims, in which at least one embossing ( 80 ) in the steel sheet ( 50 ) is introduced. Method according to one of the preceding claims, wherein during the press hardening at least one undercut ( 82 ) in the steel sheet ( 50 ) is introduced. Method according to one of the preceding claims, in which at least one depression ( 84 ), in particular in the form of a groove for chip removal, in the steel sheet ( 50 ) is introduced. Sawing tool with a mounting area for attachment to a drive device ( 30 ), and with a workspace ( 14 ), on which at least one cutting edge ( 16 ) is provided, consisting of one at least in the region of the cutting edge Press-hardened martensitic hardened steel sheet, in particular produced by a method according to one of the preceding claims. Sawing tool according to claim 18, wherein at the attachment area ( 12 ) an attachment opening ( 40 ) is provided, which for connection to a rotationally oscillating drivable drive spindle ( 32 ) a hand tool ( 30 ) is trained. Sawing tool according to claim 18 or 19, comprising at least one impression (37) produced by press-hardening ( 80 ), Undercut ( 82 ) and / or depression ( 84 ) having.

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