Steel for a Sawing Device

Abstract

A steel for a sawing device (100) containing in wt. %: C: 0.7-1.2 Mn: 0.3-0.7 Cr: 0-1.05 Ni: 0-1.5 Al: 0-0.5 Si: 0-0.5 wherein the total amount of C, Mn, Cr, Ni, Al, and Si is 1.5-4.5 wt. % and the balance being Fe and incidental elements and wherein the microstructure of the steel alloy is bainitic or a mixture of bainite and martensite with dispersed Fe.sub.3C-particles.

Claims

1. A sawing device comprising steel containing in wt. %: TABLE-US-00004 C: 0.7-1.2 Mn: 0.2-0.8 Cr:   0-1.0 Ni:   0-1.5 Al:   0-0.5 Si:   0-0.5 wherein the total amount of C, Mn, Cr, Ni, Al, and Si is 1.5-4.5 wt. % and the balance being Fe and incidental elements and wherein the microstructure of the steel alloy is bainitic or a mixture of bainite and martensite with dispersed Fe.sub.3C-particles.

2. The sawing device according to claim 1, wherein the amount of C is 0.8-1.1.

3. The sawing device according to claim 1, wherein the amount of Cr is 0.1-1.0.

4. The sawing device according to claim 1, wherein the amount of Ni is 0.5-1.0.

5. The sawing device according to claim 1, wherein the amount of Al is 0-0.3.

6. The sawing device according to claim 1, wherein the amount of Si is 0-0.3.

7. The sawing device according to claim 1, wherein the total amount of Al and Si is ≤0.6 wt. %.

8. The sawing device according to claim 1, wherein the total amount of C, Mn, Cr, Ni, Al, and Si is 1.5-4.0 wt. %

9. (canceled)

10. The sawing device according to claim 1, wherein the steel comprises a wear resistant coating.

11. The sawing device according to claim 10, wherein the sawing device comprises a cutting link for a sawing chain.

12. A method for manufacturing a sawing device comprising the steps: providing a sawing device manufactured from a steel containing in wt. %: TABLE-US-00005 C: 0.7-1.2 Mn: 0.2-0.8 Cr:   0-1.0 Ni:   0-1.5 Al:   0-0.5 Si:   0-0.5 wherein the total amount of C, Mn, Cr, Ni, Al, and Si is 1.5-4.5 wt. % and the balance being Fe and incidental elements; hardening the sawing device by heating to austenitization temperature followed by cooling to an isothermal temperature to obtain a microstructure of bainite or bainite and martensite; applying a wear resistant coating onto at least a portion of the surface of the sawing device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1a, 1b: Diagrams showing hardness of the steel before and after tempering.

[0023] FIG. 2: A photograph in 5000× magnification of a sample of the steel according to the present disclosure.

[0024] FIG. 3: A diagram showing hardness decrease after 1 h tempering of the steel.

[0025] FIG. 4: A diagram showing hardness decrease after high temperature tempering of the steel according to the present disclosure.

[0026] FIG. 5: A diagram showing hardness decrease after tempering the steel of the present disclosure for increasing time periods.

[0027] FIG. 6: A schematic drawing of a sawing device according to the present disclosure.

[0028] FIG. 7: A flowchart showing a method for manufacturing the sawing device according to the present disclosure.

DESCRIPTION OF EXAMPLES

[0029] The steel according to the present disclosure is in the following described with reference to the following non-limiting examples.

[0030] Samples of the steel were prepared by conventional steel making methods. A comparative sample S1* was prepared and then inventive samples S2-S4 were prepared having a varying carbon content within the composition of the comparative sample S1*.

[0031] The samples had the following compositions:

TABLE-US-00002 TABLE 1 Wt. % C Mn Cr Ni Al Si P S Fe S1* 0.62 0.36 0.10 0.9 0.004 0.21 0.009 0.0007 Bal. S2 0.73 0.36 0.10 0.9 0.004 0.21 0.009 0.0007 Bal. S3 0.79 0.36 0.10 0.9 0.004 0.21 0.009 0.0007 Bal. S4 0.89 0.36 0.10 0.9 0.004 0.21 0.009 0.0007 Bal. (S1* is a comparative sample with low carbon content.)

[0032] The samples were hardened by heating the samples above the austenitization temperature followed by cooling to an isothermal temperature to obtain a bainite/martensite matrix with dispersed Fe.sub.3C particles.

[0033] The hardness of the hardened samples was measured in HV1 and are shown in the diagram 1a.

[0034] Next, the hardened samples were tempered at a temperature of 300° C. for 1 hour. The hardness of the samples was measured again. The hardness of the samples is shown in FIG. 1b.

[0035] From the initial hardness measurements shown in FIGS. 1a and 1b it is clear that the hardness increases with increasing carbon content, this is also true from the hardness after tempering for 1 h.

[0036] FIG. 3 shows the decrease in hardness of each hardened sample after tempering. Surprisingly, the decrease in hardness is smaller for the samples 2-4 with higher carbon content than for the low carbon comparative sample 1. Thus, higher carbon content slows the decrease in hardness during tempering.

[0037] A further study was made on samples of the steel according to the present disclosure. A comparative sample S5* was prepared together with inventive samples S6-S8. The compositions of the samples are shown in table 2.

TABLE-US-00003 TABLE 2 Wt. % C Mn Cr Ni Al Si P S Fe S5* 0.61 0.36 0.10 0.9 0.004 0.21 0.009 0.0007 Bal. S6 0.72 0.66 0.23 0.03 0.033 0.24 0.001 0.001 Bal. S7 0.816 0.47 0.095 0.056 0.020 0.164 0.009 0.0006 Bal. S8 0.99 0.43 0.2 0.051 0.005 0.234 0.009 0.0006 Bal. (S5* is a comparative sample with low carbon content.)

[0038] The samples were hardened by heating the samples above the austenitization temperature followed by cooling to an isothermal temperature to obtain a bainite/martensite matrix with dispersed Fe.sub.3C particles.

[0039] Samples having the composition shown in table 2 were thereafter subjected to tempering. The samples were thereby heated in a furnace to various specific temperatures in the range of 275-450° C., held for 1 hour at the specific temperature. Subsequently, the samples were removed from the furnace and allowed to cool to room temperature. Hardness testing at HV1 was subsequently performed at room temperature.

[0040] The result of the high temperature tempering hardness testing is shown in FIG. 4. As can be seen in FIG. 4 the carbon has a large effect on the tempering properties over a large tempering range, further, the influence of higher amount of alloying addition is also shown in by comparing S6 and S7 where S6 have lower carbon while S7 have slightly higher alloying addition highlighting the influence and importance of the combination of both carbon as well as additional alloying elements,

[0041] Samples having the composition shown in table 2 were also subjected to tempering at constant temperature during an increasing period of time. The samples were thereby heated to 300° C. in a furnace and periodically removed from the furnace after a predetermined period of time and allowed to cool to room temperature. Hardness testing of each sample was performed at room temperature at HV1.

[0042] The result of the hardness testing is shown in FIG. 5. As was earlier described for FIG. 4 similar effects are seen during a prolonged isothermal tempering thus highlighting the improvement of desired tempering properties where carbon is a key element.

[0043] The isothermal temperature at sample preparation was in the range at or above the Ms-temperature and the samples were kept at this temperature for about 1 hour after which the samples where quenched in order to obtain a bainite/martensite matrix.

DETAILED DESCRIPTION OF EMBODIMENTS

[0044] FIG. 5 shows schematically a sawing device 1 having at least one cutting tooth 2 according to an aspect of the present disclosure. The sawing device is typically configured for wood sawing and for use in a handheld motor driven sawing apparatus (not shown). In FIG. 5, the sawing device is exemplified as a cutting link for a sawing chain 3 of a chainsaw. However, also other sawing devices are feasible, for example reciprocating sawblades or circular sawblades. Other sawing apparatuses are also feasible, for example clearing saws. The sawing device may comprise a wear resistant coating on at least a portion of its outer surface, for example chromium.

[0045] FIG. 6 shows schematically the steps of a method for manufacturing the sawing device according to the present disclosure.

[0046] In a first step 1000 a sawing device provided. The sawing device is manufactured by conventional metal and machining operations from a steel according to the present disclosure as described above.

[0047] In a second step 2000 the sawing device is hardened by heating the sawing device to the austenitization temperature followed by rapid cooling to an isothermal temperature. The isothermal temperature may be at or above the Ms-temperature for the steel composition of the sawing device. The sawing device is thereby held in the temperature range at or above Ms and kept for a predetermined time, such as about 1 hour, after which it is cooled to room temperature to obtain a microstructure of bainite or bainite/martensite with dispersed Fe.sub.3C-particles. The heat treatment parameters, i.e. austenitization temperature, cooling speed and the isothermal temperature vary in dependency of the composition of the steel of the sawing device and may be determined by the skilled person by look-up tables, practical trials or by commercially available modeling computer programs. Cooling may for example be performed in air, oil, salt or water. The microstructure of the samples may be evaluated by microscopy.

[0048] In a third step 3000 a wear resistant coating is applied onto at least a portion of the surface of the sawing device.