CUTTING ELEMENT FOR A SAW CHAIN AND METHOD FOR THE PRODUCTION THEREOF

Abstract

A cutting member for a saw chain and a method for the production thereof, the cutting member comprising a support part made of a steel alloy and a cutting part welded to the support part along a welding connection made of a high speed steel. The steel alloy of the support part is a tool steel that has the following composition (specifications in % by weight):

TABLE-US-00001 Carbon (C) 0.4 to 1.0 Silicon (Si) up to 1.8 Manganese (Mn) up to 0.6 Chromium (Cr) 4.5 to 12 Molybdenum (Mo) up to 3 Vanadium (V) up to 2
Iron (Fe) and accompany elements caused by melting and impurities as the remainder. The steel alloy of the support part in a quenched and tempered state has a hardness of more than 600 HV and a tensile strength of more than 2000 MPa as a result of curing at a suitable temperature above the austenitizing temperature of the high speed steel.

Claims

1. A cutting member for a saw chain comprising a support part made of a steel alloy and a cutting part welded to the support part along a welding connection made of a high speed steel, wherein the steel alloy of the support part is a tool steel that has the following composition (specifications in % by weight): TABLE-US-00007 Carbon (C) 0.4 to 1.0 Silicon (Si) up to 1.8 Manganese (Mn) up to 0.6 Chromium (Cr) 4.5 to 12 Molybdenum (Mo) up to 3 Vanadium (V) up to 2 Iron (Fe) and accompanying elements caused by melting and impurities as the remainder, wherein the steel alloy of the support part in a quenched and tempered state has a hardness of more than 600 HV and a tensile strength of more than 2000 MPa as a result of curing at a temperature above the austenitizing temperature of the high speed steel.

2. The cutting member according to claim 1, wherein the steel alloy of the support part in the quenched and tempered state has a hardness between 630 and 750 HV and a tensile strength between 2100 and 2500 MPa.

3. The cutting member according to claim 1, wherein the steel alloy of the support part has the following composition (specification in % by weight): TABLE-US-00008 Carbon (C) 0.45 to 0.8 Silicon (Si)] up to 1.3 Manganese (Mn) up to 0.6 Chromium (Cr) 6 to 10 Molybdenum (Mo) up to 1.6 Vanadium (V) up to 1 Iron (Fe) and accompanying elements caused by melting and impurities as the remainder.

4. The cutting member according to claim 1, wherein the high speed steel of the cutting part has the following composition (specifications in % by weight): TABLE-US-00009 Carbon (C) 0.5 to 1.1 Silicon (Si) up to 0.5 Manganese (Mn) up to 0.5 Chromium (Cr) 3.5 to 4.5 Molybdenum (Mo) 2 to 6 Vanadium (V) 0.5 to 3.0 Tungsten (W) up to 3 Cobalt (Co) up to 10 Iron (Fe) and accompanying elements caused by melting and impurities as the remainder.

5. The cutting member according to claim 1, wherein the steel alloy of the support part and the high speed steel of the cutting part form a material compound, which are welded with laser or electron radiation via a welded seam, wherein the welded seam is in a less loaded region of the cutting member.

6. The cutting member according to claim 5, wherein a geometrically narrower lower track of the welded seam is arranged on the outside of the cutting member and an upper track of the welded seam is arranged on the inside of the cutting member.

7. The cutting member according to claim 1, wherein the cutting member has a depth limiter that at least partially consists of high speed steel.

8. The cutting member according to claim 1, wherein the cutting part has a smaller thickness than the support part.

9. A saw chain for motorised chainsaws, comprising: drive links and a cutting member according to claim 1.

10. A method for producing the cutting member of claim 1, the method comprising: arranging at least one first flat strip material made of high speed steel along a second and third flat strip material made of steel alloy that can be quenched and tempered; welding a first, second and third flat strip material together along strip edges thereof by means of welded seams to form a material compound strip; removing the cutting member from the material compound strip in such a way that the support part of the cutting member consists of the second and third flat strip material and the cutting part of the cutting member consists of the first flat strip material; and heating the cutting member to a temperature above the austenitizing temperature of the high speed steel.

11. The method according to claim 10, wherein the temperature is more than 1000° C. above the austenitizing temperature of the high speed steel.

12. The method according to claim 11, wherein the temperature ranges from 1050 to 1200° C. above the austenitizing temperature of the high speed steel.

13. The method according to claim 12, wherein the temperature ranges from 1100 to 1160° C. above the austenitizing temperature of the high speed steel.

14. The method according to claim 10, further comprising tempering the cutting member at a temperature ranging from 500 to 600° C.

15. The method according to claim 14, wherein the cutting member is tempered at a temperature ranging from 520 to 560° C.

16. The method according to claim 10, wherein the thickness of the first flat strip material is less than the thickness of the second and third flat strip materials.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Various aspects of the present disclosure are discussed herein with reference to the accompanying Figures. It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements can be exaggerated relative to other elements for clarity or several physical components can be included in one functional block or element. Further, where considered appropriate, reference numerals can be repeated among the drawings to indicate corresponding or analogous elements. For purposes of clarity, however, not every component can be labelled in every drawing. The Figures are provided for the purposes of illustration and explanation and are not intended as a definition of the limits of the disclosure.

[0038] FIG. 1 is a side view of a cut-out of a saw chain.

[0039] FIG. 2 is a three-dimensional view of an implementation of a cutting member of the saw chain of FIG. 1, consisting of a material compound and a welded seam.

[0040] FIG. 3 is a cross-section of the cutting tooth of a cutting member according to the present disclosure.

[0041] FIG. 4 is a material compound with schematically depicted punching blanks.

[0042] FIG. 5 is a cross-section of the material compound of FIG. 4 along the line V-V.

[0043] FIG. 6 is a cross-section corresponding to FIG. 5 of a variant of a compound material, in which the high speed steel has a smaller thickness d.sub.2.

[0044] FIG. 7 is a diagram that reproduces the influence of curing temperature and tempering temperature on the hardness of the cutting material.

[0045] FIG. 8 shows comparable recordings of progressive attrition on cutting edges according to the present disclosure and cutting edges of the prior art.

[0046] FIG. 9 a diagram of the quantitatively measured attrition as a function of the machining value.

DETAILED DESCRIPTION

[0047] FIG. 1 shows a side view of a saw chain, as is explained in more detail by way of example in the European patent application EP 0 592 389 B1. The saw chain labelled throughout with the reference numeral 10 has a series of cutting members 11 and driving members 12. The cutting members 11 are connected to the drive links together with counter links 13 via rivets 14. Moreover, in the depicted example, drive links are also connected to one another by rivets 14 via interlinks 15. Each cutting member 11 has a support part 16 made of constructive steel and a cutting part 17 made of high speed steel. The support part 16 and the cutting part 17 are connected to each other along a welded seam 18. The cutting members 11 have depth limiters 20 which, in the implementation of FIG. 1, consist completely of the unbreakable steel alloy of the support part 16.

[0048] FIG. 2 shows a three-dimensional view of an implementation of a cutting member 11. The cutting member 11 of the implementation of FIG. 2 substantially corresponds to the cutting member 11 of the saw chain of FIG. 1. The support part 16 is made of tool steel and is connected to the cutting part 17 made of high speed steel by means of welded seams 18. The cutting teeth 19 and, in contrast to the variant of FIG. 1, at least one partial region of a depth limiter 20 is formed from the cutting part 17. As a result of the clearly improved service life of the cutting teeth, the depth limiter in particular is also subjected to increased abrasion attrition. Since the depth limiter is also designed from high speed steel, this can withstand the increased abrasion attrition well. The thickness of the cutting part and support part are labelled in FIG. 2 with d.sub.1 and d.sub.2.

[0049] FIG. 3 shows a cross-section of a cutting member in the region of the cutting tooth 19. The cross-sectional depiction shows, in particular, the position and the shape of the welded seam 18 when transitioning from the support part 16 to the cutting part 17 particularly clearly. The smaller welded seam width of the root seam on the cutting tooth outside 22 and the larger welded seam width or the upper track on the tension-reduced cutting tooth inside 21 the cutting tooth 19 are also depicted.

[0050] FIG. 4 shows a material compound strip 30 for producing cutting members for the saw chain according to the present disclosure. The material compound strip is produced by means of laser or electron beam welding devices and the welded seam course is arranged by targeted positioning of the compound strip when removing the cutting member blanks and subsequent reshaping in such a way that the smaller welded seam width of the root seam is on the outside 22 of the later cutting tooth 19, and the larger welded seam width or the upper track with possible undercuts or with possible welded seam grooves is on the inside 21 of tension-reduced cutting tooth that arises during reshaping of the cutting tooth. This can be easily seen, in particular, in the cross-sectional depiction of FIG. 3.

[0051] As can be seen in FIG. 4, the material compound strip 30 made of a first central flat strip material 31 made of high speed steel is welded on its two strip edges along a second or third flat strip material 32, 33 along welding lines 18. The schematically indicated punching contours 34, 35 are arranged in such a way that the support part 16 of the later cutting members 11 is in the second and third flat strip material 32, 33 made of tool steel, while the cutting part 17 is arranged in the region of the first central flat strip material 31 made of high speed steel. It can be seen that cutting members 11 with particularly low material loss or right/left cutting members made of the material compound strip can be separated by targeted arrangement of the punch contours on both sides of the flat high speed steel strip 31. In this implementation, the punching contours 34, 35 are arranged in such a way that the depth limiter 20 is completely in the region of the second and third strip material 32, 33, i.e. as is implemented in FIG. 1 without high speed steel. Yet, it can also be seen that the implementation of FIG. 2 would be able to be produced by targeted choice of the geometry of the punching contours 34, 35, in which the tip of the depth limiter 20 would then reach into the first strip material made of high speed steel.

[0052] The flat strip materials can have the same or different thicknesses. In the present context, “thickness” means the dimension of the strip materials perpendicular to their planar extension. In FIG. 5, a cross-section along the line V-V from FIG. 4 is depicted. In this variant, the strip materials 31, 32, 33 have the same thickness d. In this variant, there is no step on the welded seams 18.

[0053] In the alternative implementation depicted in FIG. 6, the first flat strip material 31′, made of high speed steel, has a smaller thickness d.sub.2 than the thickness d.sub.1 of the flat strip materials 32′, 33′. In this variant, steps emerge on the welded seams 18′ which can be flattened by post-processing steps. In order to lessen the difference in thickness at the outset, as depicted in FIG. 6, the hems 36′, 37′ of the flat strip materials 32, 33, said hems being adjacent to the welded seams 18′, can be chamfered.

[0054] Comparative Trials

[0055] The advantageous use of saw chains in which the cutting members consist of the material compound is depicted the following comparative trials.

[0056] 1. Heat Treatment [0057] Better attrition behaviour than a conventional carbon steel is achieved by the use of a high speed steel in the material compound (see also the attrition tests presented under 2.). However, the use of this high speed steel in turn requires an increased austenitizing temperature. Accordingly, the development in terms of material of a suitable support strip for the material compound is of great significance. Thus, heat treatment trials have been carried out, wherein samples have been cured in a salt bath and then tempered twice. The hardness and the tensile strength have then been determined. [0058] The influence of curing or tempering temperature on said properties is summarized in Table 1 below. It can be seen that the strength values of the support material according to the disclosure are, regardless of the heat treatment, higher than the strength values of the conventional carbon steel.

TABLE-US-00005 TABLE 1 Influence of curing temperature and tempering temperature on the tensile strength and hardness of different support strip materials after a short-term heat treatment in a salt bath (salt bath curing of up to 10 min). Curing Tempering Tensile Support strip temperature temperature strength Hardness material [° C.] [° C.] [MPa] [HV] 63NiNb4 810 250 2205 649 270 2090 630 830 250 2205 625 270 2035 601 Present 1140 520 2330 658 Disclosure 540 2430 660 560 2264 652 1160 520 2140 674 540 2380 703 560 2460 712 [0059] Furthermore, heat treatment trials have been carried out, wherein samples were cured in a vacuum oven at different temperatures and then tempered twice at 550° C. The hardness and the tensile strength were then also determined. The influence of curing or tempering temperature on tensile strength and hardness are summarised in Table 2 below.

TABLE-US-00006 TABLE 2 Influence of curing temperature and tempering temperature on the tensile strength and hardness on the support strip according to the disclosure after a long-term heat treatment in a vacuum (vacuum curing over more than 60 min). Curing Tempering Tensile Support strip temperature temperature strength Hardness material [° C.] [° C.] [MPa] [HV] Present 1030 550 2370 700 Disclosure 1050 2505 742 1070 2435 735

[0060] 2. Attrition Resistance [0061] In order to assess the attrition resistance of the material compound, machining attempts have been carried out on so-called wood shaving lightweight boards. Such boards are produced from long-stranded planed spruce or pine wood, wherein these fibres are bound by cement. Such attrition trials simulate extremely practical cases, which are particularly relevant with regard to frequently occurring abrasive contamination in wood, such as sand, for example, or typically in the felling region as a result of soil. [0062] In general, the attrition behaviour of a high speed steel correlates to its hardness and toughness. An optimum combination of these two properties is obtained by the curing and tempering of the high speed steel at slightly higher temperatures of the secondary curing maximum. The secondary curing potential is determined by the curing temperature and the holding period. Thus, with suitable choice of these parameters with different hardness technologies (salt bath curing or vacuum curing), the same hardness can be set. By way of example, FIG. 5 shows the curing-tempering curve of the cutting material, of the material compound according to the disclosure which, on the one hand, has been cured in the vacuum and, on the other hand, in the salt bath. It turns out that, regardless of the curing technology, equivalent hardness can be achieved in the cutting material and thus an equivalent attrition resistance is to be expected. [0063] For such trials, wood plane knives made of the cutting materials of the material compound according to the disclosure have been concretely produced from a high speed steel cutting part (composition (in % by weight): 0.75% C, 0.3% Si, 0.25% Mn, 4% Cr, 5% Mo, 1% V, 1% W, 8% Co) and a tool steel support (composition (in % by weight): 0.55% C, 1% Si, 0.4% Mn, 8% Cr, 0.5% Mo, 0.5% V) with a cutting angle of 47 degrees. These wood plane knives have been compared to geometrically corresponding wood plane knives made of a conventional carbon steel of the class 63NiNb4, as is conventionally used in the sawing industry. The assessment of the attrition progress has been carried out by measuring the cutting geometry after defined machining paths (L.sub.W). [0064] FIG. 8 representatively shows the continuous attrition of the cutting edges. The partial depictions a), b) and c) in FIG. 8 show the attrition of the conventional wood plane knives made of carbon steel before the start of the attrition trial (L.sub.W=0 mm or with machining paths of 6,000 mm and 24,000 mm. The partial depictions d), e) and f) in FIG. 8 show corresponding results with wood plane knives, the cutting edge of which consists of high speed steel. It can clearly be seen that the attrition on the cutting edge of the convention carbon steel is significantly higher than with high speed steel of the material compound. [0065] In order to quantify the attrition progress, the geometric surface loss has been measured and applied across the machining path. The corresponding results (quantitatively measured attrition as a function of the machining path) are depicted in the diagram of FIG. 9 for cutting edges made of carbon steel 63NiNb4 or a cutting material of the material compound according to the disclosure. The data can be reproduced easily by regression straight lines, attrition rates being able to be ascertained from the inclination thereof. Thus, for the carbon steel 63NiNb4, an attrition rate of 2.8304 μm.sup.2/mm, and for the high speed steel of the material compound according to the disclosure, an attrition rate of 0.481 μm.sup.2/mm emerge. This evaluation makes clear the particularly advantageous use of cutting members, which are produced from the material compound according to the disclosure.