EP2732056A1

EP2732056A1 - Knife and method for the production thereof

Info

Publication number: EP2732056A1
Application number: EP13700864.5A
Authority: EP
Inventors: Christoph Wolff
Original assignee: Heusch GmbH and Co KG
Current assignee: Heusch GmbH and Co KG
Priority date: 2012-01-12
Filing date: 2013-01-14
Publication date: 2014-05-21
Anticipated expiration: 2033-01-14
Also published as: CN104145031A; EP2732056B9; CN104145031B; EP2732056B1; DE102012200425A1; WO2013104789A1

Abstract

The present invention relates firstly to a method for producing a helical knife (1), wherein the knife (1) is produced from hardenable steel and has a cutting leg (10) which has both a base surface (11) at a lower end and a cutting surface (12) at an upper end, wherein the cutting surface (12) has a cutting edge (9) along a front periphery (13), and secondly to a helical knife (1), wherein the knife (1) is produced from hardenable steel and has a cutting leg (10) which has both a base surface (11) at a lower end and a cutting surface (12) at an upper end, wherein the cutting surface (12) has a cutting edge (9) along a front periphery (13). In order to create a knife and a method for the production thereof, said knife having both stainless properties and sufficient hardness such that it is suitable in particular for use in leather processing, it is proposed according to the invention that a stainless steel be selected as the hardenable steel of the knife (1) and that a surface layer (2) of the knife (1) be enriched with carbon and subsequently hardened, such that the knife (1) has a surface layer (2) that is enriched with carbon and hardened.

Description

Knife and method for its production

description

introduction

The invention relates to a helical knife, wherein the blade is made of hardenable steel and has a cutting leg having both at a lower end a foot surface and at an upper end a cutting surface, wherein the cutting surface along a front edge having a cutting edge.

Moreover, the present invention relates to a method for producing such a helical knife. As "hardenable steels" in the context of the present application ferritic

or martensitic steels, the latter resulting from hardening of a ferritic steel. For hardenability, it is necessary that the steel has a minimum content of alloying elements, for example, at least 0.8% of carbon in the case of unalloyed steel. In the context of the present application, hardening is an increase in the hardness of a steel by means of a heat treatment (heating with subsequent hardening)

Quenching and optionally subsequent tempering) understood, the hardness of a steel, for example in the units HRC (Rockwell) or HV (Vickers) can be specified. Hardening therefore includes both the classic "hardening" (producing a hardness of 50 HRC or> 510 HV) and the classical "tempering" (hardness is increased but 50 HRC or 510 HV are not achieved), since in both processes the hardness of the respective treated steel is increased by means of a heat treatment. Thus, if the present application designates a knife or a certain portion of it as "hardened", it merely means that the hardness of the knife has been increased According to the aforementioned classical definition, which is based on the hardness attained, it may be that a "hardened Knife "in the context of the present application would only be referred to as remunerated. Austenitic steels whose lattice structure undergoes no change in the course of a heat treatment (heating with subsequent quenching) and consequently does not experience an increase in hardness are not specifically designated by the term "hardenable steel." An increase in hardness, if necessary by means of cold forming, is the same as defined above not included, since this is not brought about by means of a heat treatment.

State of the art

Knives of the type described above are particularly in the leather and the

Textile processing known for some time, where they are used in the field of leather processing for so-called "defoliation" and / or "folding" and in textile processing for shearing the textile fibers. As a generic term for a machine that is used for processing either animal skins - especially leather - or fibrous materials - especially textile fibers - is used, the term below

If, on the other hand, reference is made exclusively to leather processing, the terms "debossing aggregate" or "folding aggregate" are used, depending on the application in the context of leatherworking.Measure knives of the type described in the introduction are used, for example, in the cutting unit according to utility model DE 74 03 463 U, where the cutting unit disclosed there is a shearing device for processing textiles., In view of the economic efficiency of the cutting units, on which the blades are mounted, especially long life of the knife are decisive Steels or hardened knives are therefore of central importance in order to minimize abrasion in the area of the cutting edge of the knives and to delay the change of the knives as long as possible f the cutting edge with the zu

However, cutting material inevitably leads to blunting of the cutting edge. This applies in particular to the folding and fleshing out, ie processes in the course of cutting animal skins, since these typically require a relatively high cutting force and the blades are subjected to correspondingly high levels of stress. Another wear the knife or the cutting edge results from a permanent

Re-sharpening the knife by means of a grindstone, which runs automatically.

The problem of the durability of a sharp cutting edge of the knife is also determined or reduced by an oxidation of the blade steel apart from a purely mechanical abrasion. This is particularly problematic in the field of leather processing, since aggressive chemicals are used here in advance of the use of a Entfleischaggregats to rid the dermis of the so-called epidermis. On the other hand, the removal of the subcutaneous skin, which is also connected to the dermis, must be mechanical, which is typically achieved through the use of dehiscing knives. This is known as "devouring." The knives of the trimming unit come into particular contact with the previously used chemicals during this debarking process.The aggressiveness of the chemicals corrodes the steel of the knives particularly quickly, especially when the trimming unit is not permanently in use During operation of the pulping unit, the knives are subject to constant abrasion, so that forming rust, which is very soft, is abraded directly.The amounts of oxidized material (rust) that reach the dermis are so low that However, once the Entfleischaggregat stands still longer time (weekend, holidays,

Non-use, etc.) it comes to the formation of a pronounced rust layer on the knives, since the steel is not able to withstand the aggressive environment of the chemicals used. Once the Entfleischaggregat is put back into operation after the service life, it can be particularly easy to a process-related removal of the resulting rust, which leads to a color impairment of the dermis. Such discolorations can usually not be eliminated, so that the discolored material must be cut out, can not be recycled and thus an economic damage.

To solve the problem, the use of stainless steels for the knives has been considered. However, these have a relatively low hardness of less than 600 HV due to the type and are due to the high mechanical

Stress on the cutting edge of the knife consequently not for the folding or the

Suitable for the meat maker. Especially when folding, that is the processing of the thickness of the

Sclera (ie the cutting of tanned leather), the cutting edges are special strongly abrasive stressed and require for a high durability of the cutting edge sharpness necessarily a high hardness. For these reasons, stainless steels have not yet been realized for making knives for use in the leather sector. DE 695 10 719 12 describes a stainless steel with a particularly hard surface layer which has a hardness in the range of 700 HV to 1050 HV. The steel described is an austenitic steel which, as such, is not curable, as explained above. This is disadvantageous in particular with regard to a core region of the respective component made from this steel, since it can not be tempered and is therefore comparatively soft. The low rigidity of such austenitic steel makes it the base material for a knife

Use in the field of textile or leather processing in such cases only limited use, in which the knife is exposed to greatly increased cutting forces. This is due to the fact that deformations of a knife with comparatively low rigidity under the influence of greatly increased cutting forces would be too high to be a good one

To obtain a cutting result. Furthermore, the steel according to DE 695 10 719 T1 is disadvantageous insofar as it typically contains high amounts of nickel, which in principle has health-damaging potential. Since in the textile and / or leather processing the knives used there must be reground relatively frequently, a steel with a high nickel content is undesirable for reasons of occupational safety alone.

task

The object of the present invention is based on the above

The prior art described therein, a knife and a method for its

Producing produce, which has both corrosion-resistant properties and sufficient hardness and rigidity, so that it is particularly suitable for use in leather processing, even with high demands on the quality of cut. solution

The underlying object is achieved from a process engineering point of view, starting from a method of the type described above according to the invention that the hardenable steel of the knife is also a stainless steel and an edge layer of the knife is enriched with carbon and then cured. Advantageously, the remainder of the blade is hardened simultaneously with the hardening of the edge layer of the blade, that is to say its core region. Depending on the respectively achieved hardness in the different areas of the knife (edge layer, core area) of the

Core area after curing also be referred to as "tempered" (hardness of <50 HRC.) Basically, the "hardening" according to claim 1, an increase in the hardness of at least the edge layer instead (see also introductory definition of "hardenable steel").

As a starting material for carbon enrichment and subsequent hardening, the group of ferritic high-alloyed stainless (chromium) steels is particularly relevant, although the present application is not limited to such steels, provided that said properties "hardenable" and "stainless" are met. After hardening, these steels are referred to as martensitic high-alloyed stainless (chromium) steels, with the martensite of the hardened steel forming during the hardening process from the ferrite of the base steel. Since the freedom from rust is typically generated by the alloying element chromium, the end product can also be appropriately called stainless martensitic chromium steel, which is curable as such in the context of this application, that is curable and / or heat-treatable.

The carbon enrichment step significantly increases the carbon content of the edge layer of the blade relative to its core region. This process of "carburizing" an already hardenable steel, ie a ferritic steel, which already has a minimum content of alloying elements necessary for the hardening is atypical.The enrichment of a carbon steel is usually only carried out if the respective steel is curable at all In contrast to the procedure proposed here, carburizing is normally applied to non-hardenable (ferritic) steels, so-called case hardened steels, which are therefore considered to be non-ferrous Separate enrichment with carbon as non-curable in the context of this application, this is not justified by the fact that it is an austenitic steel in a case-hardening steel - case-hardened steels are basically ferritic -, but the lack of

Hardenability alone due to their low carbon content is present. The further enrichment of the steel with carbon, the so-called "carburizing", which is carried out according to the invention, although the steel is already curable, leads to a significantly improved hardenability of the knife with respect to said surface layer, than the achievable hardness values in the course of a subsequent In this way, hardness values of more than 700 HV can be achieved, although the stainless properties of the steel used in the carburized edge layer of the knife are adversely affected by carbon enrichment, however, the corrosion resistance of the knife is increased In this way, the steel can be further provided with good remaining corrosion resistance with a high hardness, so that the finished knife excellent for the processing of leather, in particular for deferring and folding.

The inventive method includes the step of curing at least the edge layer of the knife, but advantageously the entire knife. Due to the changing carbon content of the knife after its carburisation (only the

Edge layer is carburized), the hardness of the steel varies over the cross section of the knife, which is increased in the boundary layer opposite a core region. By means of a hardening of the knife produced in this way, the hardness of the surface layer can be increased considerably and particularly easily exceed the extent of at least 630 HV. Advantageously, a hardness of at least 670 HV, more preferably at least 720 HV should be exceeded. In the core area of the knife is

advantageously reaches a hardness of more than 300 HV, preferably of more than 350 HV, more preferably of more than 400 HV. Consequently, the hardened core area of the knife is classified as (highly) tempered according to the classical definition (see introductory definition). In the course of a hardness measurement, it should be noted that a known manner in the course of carburizing outer edge oxidation, which typically has a thickness of about 20 μιτι ± 10 μιτι not for the assessment of the hardness of the invention Boundary layer is taken into account. A correct hardness determination is particularly easy by removing the edge oxidation layer on the hardened blade by means of grinding-polishing processes and then with a minimum test load, the metallic bare surface of the knife is checked. The method described above is particularly advantageous when the

Edge layer circumferentially on the knife enriched with carbon and then hardened. In this case, a "peripheral edge layer" is understood as meaning that the edge layer completely encompasses the respectively treated knife, ie, is not merely produced on a specific side or flank of the knife The advantage of a peripherally hard edge layer lies in the stabilization effect of that edge layer Although this side itself does not interfere with the material to be processed and therefore does not in principle make any greater demands on its hardness, it is particularly advantageous due to the positive stabilizing effect of a hard layer that stiffens the entire knife Advantage.

The method can be carried out in a particularly advantageous manner if the base material is a steel having the properties of a martensitic stainless steel of type X20Cr13. Steels of this type are curable and stainless and are particularly well available as standardized steel. As base material, such a steel is not yet available as martensitic but as ferritic steel. The formation of the martensite occurs only in the course of hardening of the steel. If a steel of the aforementioned type X20CM 3 is used as the basis for the method according to the invention, the surface layer of the blade is changed in its structure due to the carburizing process step, since carbon is incorporated. Accordingly, the term X20CM 3 no longer applies after carburizing at least to the surface layer. The underlying object is device-based starting from a knife of the type described above according to the invention solved in that the curable steel of the knife is a stainless steel and the knife has a carbon enriched and hardened surface layer. Advantageously, in addition to the edge layer and the rest of the knife, that is, the core portion thereof, hardened, wherein the hardness of the The core range is typically not raised above 510 HV and is therefore considered to be remunerated according to the classical definition (see introductory definition).

As described above, such a knife can be hardened particularly well, that is to a particularly high degree, and thus both achieve a high hardness in the region of the edge layer (typically of at least 630 HV) and essentially retain its stainless properties and therefore only corrode to a relatively small extent. Experiments have shown that even after considerable residence times of such a knife according to the invention in a corrosive environment only very slight signs of corrosion occur ("rust rust"), while the corrosion is already far advanced in conventional, non-corrosion-resistant knives and the shape of real "rust craters "has assumed great depth.

As already described above, such a knife is particularly advantageous in which a hardness of the surface layer is at least 630 HV, preferably at least 670 HV, more preferably at least 720 HV. Knives that have hardnesses in this area are particularly suitable for textile and leather processing in terms of their susceptibility to abrasive wear, since they are able to withstand the respective textile or leather well.

The knife according to the invention should also be designed so that the carburized edge layer has a thickness between 0.001 mm and 0.30 mm, preferably between 0.05 mm and 0.20 mm. Such a layer thickness is sufficient to guarantee a long service life of the knife, since a removal of this layer thickness in the course of the operation of the associated cutting unit takes some time. Furthermore, the small layer thickness offers the advantage that an even greater part of the knife remains in the core with a low carbon content in relation to the edge layer and the entire knife retains a high degree of toughness despite the particularly hard edge layer, which reduces the risk of breakage. In addition, the carburizing time, that is, the time that the knife steel has to be carburized, can be kept short, resulting in a larger one

Economic efficiency in the production leads. When indicating the thickness of the carburized surface layer, it should be noted that the above-mentioned edge oxidation layer, which is formed in the course of the carburizing process, is not included. In the surface layer, the knife should preferably have a carbon content of more than 0.25%, preferably more than 0.4%, more preferably at least 0.6%. In this way, the edge layer is particularly good curable, so that they can withstand the abrasive stress of the cutting operation by means of curing for a particularly long time.

The curable steel used for the knife should be before carburizing the

Randschicht have a carbon content between 0, 10% and 0.60%, preferably between 0, 15% and 0.50%. Such steels are characterized by a particularly high toughness with good hardenability, with the latter being highly dependent on the proportions of the other alloying elements. By way of example, the type X20Cr 13 from the group of stainless martensitic chromium steels, which by definition has about 0.2% + 0.05% carbon and about 13% ± 1.0% chromium and is curable, may also be mentioned here as a knife steel , The high chromium content gives this steel its corrosion resistance. At the same time it serves as a strong carbide former, which makes the steel, despite the relatively small

Carbon content of 0.2% is curable.

Depending on the composition of the respective steel, a higher carbon content of 0.4% may be expedient, whereby advantageously the steel from which the knife is made should have a chromium content of at least 12.5. By observing this minimum in terms of chromium content, the stainless or corrosion-resistant property of the respective steel is favored or ensured. This applies in particular to the carburized edge layer of the knife, which still retains a high corrosion resistance despite such carburizing despite being carburized to, for example, 1.0% carbon.

Particularly advantageous is a knife whose steel is not alloyed with nickel, in particular a nickel content of at most 1, 0%, preferably at most 0.5%, more preferably at most 0.25%. The low nickel content is particularly advantageous from the point of view of industrial safety, since no harmful nickel is released during grinding operations which have to take place at regular intervals for the purpose of sharpening the knives. Particularly advantageous is such a knife whose inner core region is hardened. Such a hardened core region is particularly advantageous for the applicability of the knife, since the knife thereby obtains a particularly high rigidity. The hardness of the knife in the core region is then advantageously in a range of at least 300 HV, preferably at least 350 HV, more preferably at least 400 HV. Increased stiffness of the knife is particularly advantageous in terms of higher resistance under the action of shear forces, since the deformations of the knife for a

high-quality processing of textiles and / or leather should be kept low.

Further, such a knife is particularly preferable in which the carbon-enriched and hardened surface layer circulates around the blade. The advantages of a circumferentially hardened surface layer are already explained above.

embodiments

The knife according to the invention and the method according to the invention are explained in more detail below with reference to an exemplary embodiment which is illustrated in the figures. It shows:

Fig. 1: A micrograph of a knife according to the invention and

Fig. 2: A Entfleischzylinder with a plurality of the knife according to the invention.

A knife 1 according to the invention, which is shown in FIG. 1, has an edge layer 2 and an edge oxidation layer 3. The boundary layer 2 and the edge oxidation layer 3 merge into one another along a transition region 4. In this case, the edge layer 2 is particularly clearly visible in FIG. 1 by a light representation and the edge oxidation layer 3 by a dark representation. The edge oxidation layer 3 is a product of carburizing the blade 1. It typically has only a very low hardness. The knife 1 is made of a martensitic chromium steel of the type X20CM 3 and accordingly has a carbon content of about 0.2% ± 0.05% and a chromium content of about 13% ± 1, 0%. This steel is hardenable and at the same time corrosion resistant. At the Example of knife 1 meet the specified values on a not shown

Core area, while the edge layer 2 of the blade 1, however, is enriched with carbon and therefore has a carbon content of about 1, 0%. A thickness of the edge layer 2 of the knife 1 is approximately 0.15 mm. The enrichment of the boundary layer 2 with carbon takes place in the course of a so-called "carburizing".

The high carbon content of the edge layer 2 of the blade 1 causes the same in this area as a result of quenching a particularly high hardness developed (the in oxidation become inactive edge oxidation layer 3 remains unconsidered), the steel inherent corrosion resistance, although reduced, but in an extensive Dimensions are retained. By this combination of high hardness with good

Corrosion resistance, the knife 1 is particularly good for use in the

Leather processing can be used.

By way of example, in FIG. 2 a defrosting cylinder 5, which is used in the course of leather processing, is shown. This has a plurality of knives 1 according to the invention, which are arranged on a circumferential surface 6 of a cylinder body 7 of the Entfleischzylinders 5. The Entfleischzylinder 5 rotates in operation about a longitudinal axis 8, wherein a cutting edge 9 of the knife 1 is brought into engagement with a material to be machined and this cuts as a result. The knives 1 each have one

Cutting blade 10, which has at a lower end a foot surface 1 1, with which the blades 1 are each arranged on the lateral surface 6 of the cylinder body 7. Furthermore, the knives 1 at an upper end of the cutting edge 10 a

Cutting surface 12 on. This comprises at a front edge 13, the cutting edge 9 of the knife 1. The blades 1 are fixed by means of caulking with copper 14 in grooves of the cylinder body 7. LIST OF REFERENCE NUMBERS

1 knife

2 edge layer

3 edge oxidation layer 4 transition region

5 demijohns

6 lateral surface

7 cylinder body

8 longitudinal axis

9 cutting edge

10 cutting edges

1 1 foot area

12 cutting surface

13 edge

14 copper

Claims

claims

A method of manufacturing a helical knife (1), wherein the knife (1) is made of hardenable steel and has a cutting leg (10) having a bottom surface (11) at both a lower end and an upper end at a lower end Cutting surface (12), wherein the cutting surface (12) along a front edge (13) has a cutting edge (9), characterized in that the hardenable steel of the knife (1) is a stainless steel and an edge layer (2) of the knife (1) enriched with carbon and then cured.

2. The method according to claim 1, characterized in that the edge layer (2) circumferentially on the blade (1) enriched with carbon and then cured.

3. The method according to claim 1 or 2, characterized in that the knife (1) after the step in which the knife (1) is cured, as a stainless martensitic chrome steel type X20Cr 13 with the carburized edge layer (2).

4. helical knife (1), wherein the knife (1) is made of hardenable steel and having a cutting edge (10), both at a lower end of a foot surface (1 1) and at an upper end of a

Cutting surface (12), wherein the cutting surface (12) along a front edge (13) has a cutting edge (9), characterized in that the hardenable steel of the blade (1) is a stainless steel and the knife (1) with a Having carbon enriched and cured edge layer (2).

5. knife (1) according to claim 4, characterized in that a hardness of

Peripheral layer (2) at least 630 HV, preferably at least 670 HV, more preferably at least 720 HV.

6. knife (1) according to claim 4 or 5, characterized in that the

Edge layer (2) has a thickness between 0.001 mm and 0.30 mm, preferably between 0.05 mm and 0.20 mm.

7. knife (1) according to one of claims 4 to 6, characterized in that the hardenable steel from which the knife (1) is made, in the boundary layer (2) has a carbon content of at least 0.25%, preferably of at least 0.4%, more preferably at least 0.6%.

8. knife (1) according to one of claims 4 to 7, characterized in that the hardenable steel from which the knife (1) is made, in a core region has a carbon content between 0.05% and 0.60%, preferably between 0, 15% and 0.50%.

9. knife (1) according to one of claims 4 to 8, characterized in that the hardenable steel from which the knife (1) is made, has a chromium content of at least 12.5%.

10. Knife (1) according to any one of claims 4 to 9, characterized in that the hardenable steel has a nickel content of at most 1, 0%, preferably at most 0.5%, more preferably at most 0.25.

1 1. Knife (1) according to one of claims 4 to 10, characterized in that the carbon-enriched and hardened edge layer (2) revolves around the knife (1).

12. Knife (1) according to any one of claims 4 to 1 1, characterized in that the hardenable steel is a stainless, martensitic steel of the type X20CM 3.

13. Knife (1) according to one of claims 4 to 12, characterized in that a core region of the blade (1) is hardened and has a hardness of at least 300 HV, preferably of at least 350 HV, more preferably of at least 400 HV.