METHOD FOR PRODUCING A STRIP STEEL KNIFE, AND STRIP STEEL KNIFE FOR TOOLS

Abstract

Method and strip steel knife from a steel strip having a bainite and decarburized surface. The steel strip has a generally rectangular cross-section, and the method includes machining a plurality of beveled surfaces in a region of a longitudinal edge of the steel strip to create at least a cutting surface defining a longitudinal cutting edge; first hardening at least a part of the cutting surface to form a first cutting edge region of the longitudinal cutting edge; smoothing the cutting surface of at least the first cutting edge region toward the longitudinal cutting edge; and at least one further hardening in the first cutting edge region to form a distal cutting edge region of the longitudinal cutting edge within the first cutting edge region having an increased material hardness with respect to the first cutting edge region located outside the distal cutting edge region.

Claims

1. A method for producing a strip steel knife with a hardened cutting edge from a steel strip comprising bainite and having a decarburized surface, the steel strip having a generally rectangular cross-section the method comprising: machining a plurality of beveled surfaces in a region of a longitudinal edge of the steel strip to create at least a cutting surface defining a longitudinal cutting edge; first hardening at least a part of the cutting surface to form a first cutting edge region of the longitudinal cutting edge; smoothing the cutting surface of at least the first cutting edge region toward the longitudinal cutting edge; and at least one further hardening in the first cutting edge region to form a distal cutting edge region of the longitudinal cutting edge within the first cutting edge region having an increased material hardness with respect to the first cutting edge region located outside the distal cutting edge region.

2. The method according to claim 1, wherein the machining of the plurality of beveled surfaces comprises shaving, and wherein the first hardening comprises inductive hardening, of at least the first cutting edge region to a value of 550 to 700 HV.

3. The method according to claim 1, wherein, after the first hardening, the cutting surfaces layers of at least the first cutting edge region are smoothed with roughness values Ra of 0.005 to 0.12 m and Rz of 0.05 to 1.2 m, and an edge radius of the longitudinal cutting edge is 2.5 m, and wherein Ra and Rz are in accordance with NORM EN ISO 4287 or ASME B46.1.

4. The method according to claim 1, wherein parameters of the at least one further hardening are determined based on a geometric embodiment of the first cutting edge region and a local energy input into the smoothed cutting surface layers.

5. The method according to claim 4, wherein the at least one further hardening produces a material hardness of over 650 HV in the distal cutting edge region proximally from the longitudinal cutting edge to a depth of up to 0.05 to 0.15 mm into the first cutting edge region.

6. The method according to claim 1, wherein the at least one further hardening produces a material hardness of over 650 HV in the distal cutting edge region proximally from the longitudinal cutting edge to a depth of up to 0.05 to 0.15 mm into the first cutting edge region.

7. A strip steel knife comprising: a strip steel body having, in cross section, at least partial bainitic microstructure and at least one cutting edge bevel forming a longitudinal cutting edge having a maximum radius of 2.5 m; a first cutting edge region of the longitudinal cutting edge includes a smoothed surface layer of the at least one longitudinal cutting edge bevel; a distal cutting edge region, which is formed in the first cutting edge region and includes the longitudinal cutting edge, has a material hardness of at least 650 HV up to a depth of 0.05 to 0.15 mm from the longitudinal cutting edge, wherein a material hardness outside of the distal cutting region decreases in a direction away from the longitudinal cutting edge.

8. The strip steel knife according to claim 7, wherein the at least one cutting edge bevel comprises a plurality of cutting edge bevels having smoothed surface layers exhibiting roughness values Ra of 0.005 to 0.12 m and Rz of 0.05 to 1.2 m, wherein Ra and Rz are in accordance with NORM EN ISO 4287 or ASME B46.1.

9. The strip steel knife according to claim 7, wherein a surface layer comprising at least one of an oxide layer, a sliding layer or a hard material layer is formed in the distal cutting edge region.

10. The strip steel knife according to claim 7, wherein the first cutting edge region is hardened from the distal cutting edge region to a depth of 300 m from the longitudinal cutting edge to a hardness greater than a hardness of the strip steel body outside of the first cutting edge region.

11. A tool comprising the strip steel knife according to claim 7, wherein the strip steel knife is configured for processing planar materials.

12. The tool according to claim 11, wherein the planar materials to be processed comprise at least one of cardboard, corrugated cardboard or plastic films.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

[0038] FIG. 1 shows in cross section a theoretical construction and an arrangement of regions of a strip steel knife according to the invention;

[0039] FIG. 2 shows a metallographic structural depiction of a strip steel knife according to the invention; and

[0040] FIG. 3 shows a detailed illustration of FIG. 2 in the bevel region.

DETAILED DESCRIPTION

[0041] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

[0042] FIG. 1 schematically shows a strip steel knife in cross section, formed from a steel strip 1 with a skin decarburization 4; 4 and cutting edge bevels 3; 3 towards the cutting edge 2 that are positioned on the narrow side of the steel strip and each have an additional bevel 5; 5.

[0043] Even though such a cross-section shape of a strip steel knife with a cutting edge 2 and at least one bevel 3; 3 can be produced using various machining processes, a shaping is in many cases carried out by a shaving of a steel strip 1 and a hardening with an induction heating of the region of the cutting edge 2.

[0044] However, a material removal at least involves the creation of process score marks in the workpiece and/or a roughness of a surface layer 8, 8 in the surface of cutting edge bevels 3; 3 on the strip steel knife, which cause consistently unfavorable adhesive tendencies between the tool and workpiece when a planar material is being cut. it has already been attempted to smooth the surface of the cutting edge bevels 3; 3 by polishing or fine-grinding in order to overcome this disadvantage.

[0045] In contrast to expert opinion, however, it was discovered that, for an advantageous release of the planar material from at least the surface layer 8 of cutting edge bevels 3, 3 on the strip steel knife, both a maximum value and a minimum measure of roughness preferably constitute limit values. Accordingly, values for Ra are to be set between 0.005 to 0.12 m and the values for Rz are between 0.05 to 1.2 m via precision processing by smoothing. These roughness values Ra and Rz are in accordance with the standards described in NORM EN ISO 4287 or ASME B46.1.

[0046] However, a targeted high-performance precision processing on the cutting edge bevels 3; 3 in the region towards the cutting edge 2 may be accompanied by a decrease in the material hardness in this region, i.e., in a direction away from the cutting edge 2. According to embodiments, the material hardness in a distal (second) cutting edge region 7 is to be set to over 650 HV proximally on the cutting edge 2 up to a depth of 0.15 mm by a subsequent hardening or by subsequent hardenings, whereby a high edge-holding ability of the strip steel knife is achieved. Further, surface layer 8, 8 in the smoothed first cutting edge region 6 after the first hardening, and/or at least, in the distal cutting edge region 7 after the at least one subsequent hardening, comprise at least an oxide layer and/or a sliding layer and/or a hard material layer.

[0047] FIG. 2 shows in cross section a strip steel knife according to embodiments following an etching treatment for the purpose of illustrating the structure. A steel strip 1 with a bainite and a skin decarburization at the surface (brightly etched) respectively comprises multi-section bevels with a cutting edge. A (first) cutting edge region 6 shows a hardened and tempered structure that extends from the cutting edge 2 through approximately 300 m into the cutting edge bevel 3, 3. From the cutting edge 2 through approximately 145 m into the cutting edge region, the hardened and tempered structure of the distal (second) cutting edge region 7 is formed by a subsequent hardening as a finely structured hardened structure, which is brightly etched.

[0048] FIG. 3 shows the cutting edge bevel 3, 3 from. FIG. 2 in an enlarged view.

[0049] It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

[0050] The following list of reference numerals is intended to provide easier association of the regions of a strip steel knife according to the invention: [0051] 1 Steel strip [0052] 2 Longitudinal cutting edge [0053] 3; 3 Cutting edge bevels [0054] 4; 4 Skin decarburization [0055] 5; 5 Additional bevel section(s) [0056] 6 First cutting edge region, hardened [0057] 7 Distal cutting edge region with subsequent hardening(s) [0058] 8 Surface layer