Cutting tools

Abstract

The present invention relates to a cutting tool comprising a cemented carbide substrate with an Fe-based binder, wherein the cemented carbide further contains Ni, Cr, and Al such that the weight fraction of Ni / (Fe+Ni) is 0.10 to 0.25, the weight fraction of Cr / (Fe+Ni+Cr+Al) is 0.005 to 0.05, and the weight fraction of Al / (Fe+Ni+Cr+Al) is 0.01 to 0.05, and the amount of Fe in the metal binder is at least 70% by weight. The present invention also relates to a method for manufacturing such a cutting tool.

Description

[Technical Field]

[0001] The present invention relates to a cutting tool comprising a cemented carbide substrate with an Fe-based binder, wherein the cemented carbide further comprises Ni, Cr, and Al. The present invention also relates to a method for manufacturing such a cutting tool. [Background technology]

[0002] Cemented carbides based on WC with cobalt binders have been known in the art for nearly 100 years. Other metals known as binders in cemented carbides are iron and nickel, but cobalt is by far the most commonly used in cutting tool applications.

[0003] Due to its environmental and health impacts, efforts are ongoing to find alternative binders to cobalt. However, substituting or limiting the amount of cobalt without adversely affecting the properties of the material is difficult. In the case of cutting tools, the properties of the base material are crucial to the overall performance of the tool, and even slight changes in composition can have detrimental effects on performance.

[0004] In cemented carbides containing Co-bonding agents, there is a stable relationship between toughness and hardness. For example, it is difficult to increase toughness without decreasing hardness, or vice versa.

[0005] Iron is a known binder element, but it is generally undesirable because it is thought to adversely affect the toughness of cemented carbides. Pure iron binders tend to form brittle phases (i.e., martensite, Fe carbides, etc.). In addition, controlling the carbon balance is difficult to produce a defect-free microstructure such as (W,Me)C subcarbide or graphite precipitates.

[0006] The object of the present invention is to provide cemented carbide alloys with an alternative binder phase that have equivalent or improved properties compared to cemented carbide alloys with a Co binder. [Brief explanation of the drawing]

[0007] [Figure 1] The HV-K1c values ​​are shown in comparison with cemented carbide alloys containing Co as a binder (solid line). Sample numbers 1 to 5 are samples according to the present invention from Example 1, and sample numbers 1c to 4c are comparative samples from Example 1. [Figure 2] This shows the effect of different Al additions; positive "delta" values ​​indicate improved properties compared to WC-Co cemented carbide, while negative "delta" values ​​indicate deteriorated properties compared to WC-Co cemented carbide. [Figure 3] This shows the effects of different Ni / Ni+Fe ratios on HV30 and K1C (calculated as delta). [Figure 4a] The diffraction pattern of the cemented carbide according to the present invention is shown. [Figure 4b] The diffraction pattern of the cemented carbide according to the present invention is shown. [Modes for carrying out the invention]

[0008] The present invention relates to a cutting tool comprising a cemented carbide base material, wherein the cemented carbide comprises a hard phase comprising WC and 3 to 20% by weight of an Fe-based metal binder containing Fe, Ni, Cr, and Al, and the amounts of the elements Fe, Ni, Cr, and Al in the cemented carbide are The weight fraction of -Ni / (Fe+Ni) is 0.10 to 0.25. The weight fraction of -Cr / (Fe+Ni+Cr+Al) is 0.005 to 0.05. -Al / (Fe+Ni+Cr+Al) is such that the weight fraction is between 0.01 and 0.05. The present invention relates to a cutting tool in which the amount of Fe in the metal binder is at least 65% by weight.

[0009] The amount of metallic binder in the cemented carbide is preferably 3 to 20% by weight, more preferably 5 to 15% by weight. The amount of metallic binder can be determined by image analysis of the cemented carbide composition or by chemical analysis. The metallic binder is Fe-based, and in this specification, the metallic binder means containing more than 65% by weight of Fe.

[0010] The cemented carbide contains Ni in such an amount that the weight fraction of Ni / (Fe+Ni) is 0.10 to 0.25, preferably 0.13 to 0.20, and more preferably 0.14 to 0.18. If the Ni content is too low, the binder has a ferrite (bcc) structure with little or no retained austenite, and if the Ni content is too high, the cemented carbide has a binder with stable austenite (fcc) that cannot undergo stress-induced transformation.

[0011] The cemented carbide contains an amount of Cr such that the weight fraction of Cr / (Fe+Ni+Cr+Al) is 0.005 to 0.05, preferably 0.015 to 0.035. If the Cr content is too low, retained austenite may decompose excessively quickly, and if the Cr content is too high, the cemented carbide will have a reduced K1c-HV combination due to the formation of Cr carbides.

[0012] The cemented carbide contains an amount of Al such that the weight fraction of Al / (Fe+Ni+Cr+Al) is 0.01 to 0.05, preferably 0.015 to 0.04, and more preferably 0.02 to 0.035. If the Al content is too low, the austenite stabilization effect is not observed, and the material properties (K1c-HV) are insufficient. If the Al content is too high, the stability and amount of austenite (fcc) increase, and the cemented carbide loses some of its K1c-HV properties, as is the case when the Ni content is too high.

[0013] In one embodiment of the present invention, some of the Al exists as Al2O3 particles embedded in the microstructure of the cemented carbide. Because Al is highly reactive, it can react with any trace amounts of oxygen that may be present during sintering. Oxygen can be present, for example, as an impurity in the raw material, and even small amounts of oxygen can be present in the sintering furnace.

[0014] The main elements in the metal binder are Fe, Cr, Ni, and Al. The binder may also contain other elements present in the cemented carbide, such as W or C, which inevitably dissolve into the binder during sintering.

[0015] In one embodiment of the present invention, the total amount of elements Fe, Cr, Ni, and Al in the metal binder is at least 90% by weight of the binder, preferably at least 95% by weight of the binder.

[0016] The carbon content in the sintered cemented carbide should be selected so that neither eta phase nor free graphite exists in the microstructure of the sintered cemented carbide. If the carbon content is too low, an eta phase can be formed. Also, retained austenite transforms rapidly to martensite during cooling, and the resulting properties (combination of HV - K1c) are low. If the carbon content is too high, graphite may be formed in the material, and the resulting properties (K1c - HV) may also decrease.

[0017] Methods for adjusting the carbon content in cemented carbide during production by simply adding W or W2C to reduce the overall carbon balance or adding carbon black to increase the overall carbon balance are well known to those skilled in the art. How much of such additives need to be added depends on the type of sintering furnace, the amount of oxygen in the raw materials, etc.

[0018] The cemented carbide preferably does not essentially contain Co, whereby in this specification, Co is not added as a raw material and Co is present in the cemented carbide at an impurity level, preferably less than 1% by weight, more preferably less than 0.5% by weight. For example, some manufacturing equipment such as crushers contains cemented carbide containing Co, and a small amount of Co is usually detected because its contribution to the overall composition may be small.

[0019] As used herein, cemented carbide means that at least 50% by weight of the hard phase is WC.

[0020] The average particle size of WC is preferably 0.2 - 10 μm, preferably 0.2 - 5 μm. The average particle size of WC can be measured, for example, using the average linear section method of SEM / LOM images.

[0021] In one embodiment of the present invention, WC is the only hard phase.

[0022] In one embodiment of the present invention, the cemented carbide consists of WC, Fe, Ni, Cr, Al, W, and C, as well as unavoidable impurities.

[0023] In one embodiment of the present invention, the metal binder contains a certain amount of austenite. The remaining phase(s) in the binder are mostly martensite (bct) and / or ferrite (bcc).

[0024] Fraction I of fcc (austenite) in the metal binder fr_fcc In this specification, the fcc peak, I(111) fcc , and the bct / bcc peak, I(110) bct / bcc The fcc peak in the XRD diffraction pattern, I(111), is part of the total intensity. fcc The fraction of intensity achieved from, i.e., I fr_fcc =I(111) fcc / (I(111) fcc +I(110) bct / bcc ) is shown as such.

[0025] The fraction of fcc (austenite) as shown herein is preferably greater than 25%, preferably 25-95%, and more preferably 45-75%. The fraction of austenite (fcc) can be determined by XRD, as will be described in more detail in Example 1.

[0026] In this specification, "cutting tool" means a cutting tool insert, end mill, or drill.

[0027] In one embodiment of the present invention, the cemented carbide substrate contains WC and 3 to 20% by weight of an Fe-based metal binder containing Fe, Ni, Cr, and Al, such that the weight fraction of Ni / (Fe+Ni) is 0.13 to 0.2, the weight fraction of Cr / (Fe+Ni+Cr+Al) is 0.015 to 0.035, and the weight fraction of Al / (Fe+Ni+Cr+Al) is 0.015 to 0.04, with the amount of Fe in the metal binder being at least 72.5% by weight.

[0028] In one embodiment of the present invention, the cemented carbide substrate contains WC and 3 to 20% by weight of an Fe-based metal binder containing Fe, Ni, Cr, and Al, such that the weight fraction of Ni / (Fe+Ni) is 0.13 to 0.2, the weight fraction of Cr / (Fe+Ni+Cr+Al) is 0.015 to 0.035, and the weight fraction of Al / (Fe+Ni+Cr+Al) is 0.02 to 0.035, with the amount of Fe in the metal binder being at least 73% by weight.

[0029] The present invention also relates to a method for manufacturing the above-mentioned cutting tool, which includes the above-mentioned cemented carbide base material. - The process of providing WC powder, - A step of providing a powder (or more) containing the elements Al, Fe, Ni, and Cr, - A step of providing a pulverizing liquid, -The process of making cemented carbide involves crushing the powder, drying it, press molding it, and sintering it. Includes.

[0030] Raw materials containing the elements Al, Fe, Ni, and Cr may be added as pure metals, one or more alloys of two or more metals, or as carbides, nitrides, or carbonitrides thereof. The raw materials should be added in such quantities that the bonded phase after sintering has the above-described composition.

[0031] In one embodiment of the present invention, the powder is selected from NiAl, Cr3C2, Fe, and Ni.

[0032] The WC powder is preferably used with an average particle size of 0.2 to 10 μm, more preferably 0.2 to 5 μm (FSSS).

[0033] Any liquid commonly used as a grinding liquid in conventional cemented carbide manufacturing can be used. The grinding liquid is preferably water, alcohol, or an organic solvent, more preferably water or a mixture of water and alcohol, and most preferably a mixture of water and ethanol. The properties of the slurry depend on the amount of grinding liquid added. Since energy is required to dry the slurry, the amount of liquid should be kept to a minimum to reduce costs. However, sufficient liquid must be added to achieve a pumpable slurry and avoid system clogging. Other compounds commonly known in the art, such as dispersants and pH adjusters, can also be added to the slurry.

[0034] An organic binder is also added to the slurry, if desired, to facilitate granulation during the subsequent spray-drying operation, but it also functions as a press-forming agent for any subsequent press-forming and sintering operations. The organic binder can be any binder commonly used in the art. Examples of organic binders include paraffin, polyethylene glycol (PEG), and long-chain fatty acids. The amount of organic binder is preferably 15 to 25% by volume based on the total dry powder volume, and the amount of organic binder is not included in the total dry powder volume.

[0035] A slurry containing powders forming hard components, powders forming a binder phase, and optionally an organic binder is suitably mixed by grinding in either a ball mill or an attritor mill. Grinding is suitably carried out by first forming a slurry containing the metal binder powder, the first and second powder fractions, and optionally the organic binder. The slurry is then suitably ground in a ball mill or attritor mill to obtain a homogeneous slurry blend. For small-scale experiments, the powder mixture can be homogenized using an agate mortar and then press-molded into a green body to be sintered.

[0036] A slurry containing an organic liquid and, optionally, a powder material mixed with an organic binder, is sprayed through a suitable nozzle in a drying tower. The droplets are then instantaneously dried by a high-temperature gas stream, such as a nitrogen stream, to form aggregated granules. For small-scale experiments, other drying methods, such as pan drying, can also be used.

[0037] Subsequently, green bodies are formed from the dried powder / granules through press molding operations such as uniaxial press molding and multiaxial press molding.

[0038] The green body formed from the powder / granules produced according to the present invention is then sintered according to any conventional sintering method, such as vacuum sintering, sintering HIP, discharge plasma sintering, gas pressure sintering (GPS), etc.

[0039] In one embodiment of the present invention, the sintering temperature is 1350 to 1550°C.

[0040] In one embodiment of the present invention, the sintering method includes a sintering HIP step carried out at a temperature of 1350 to 1550°C and a pressure of at least 40 Bar, preferably 40 to 80 Bar. Typically, an inert argon atmosphere is used during the high-pressure (HIP) step without the intentional addition of CO or H2. However, residual gases (H2O, CO, CO2) may be generated in situ during the sintering method.

[0041] The present invention also discloses cutting tools made of cemented carbide according to the method described above. [Examples]

[0042] Example 1 According to Table 1, cemented carbide samples were prepared from raw material powders WC, Cr3C2, NiAl (50 / 50 wt), Ni, Fe, and carbon black. Here, the amounts of different raw materials are shown as weight % of the total powder weight. The average particle size of the WC powder was 1.2–1.4 μm (FSSS).

[0043] The raw material powder was ground in a ball mill for 8 hours with an organic binder (2% by weight of PEG based on the total powder weight) and a grinding solution (water / ethanol) to form a slurry. This slurry was dried and then ground in an agate mortar to obtain a powder blend. The powder was then press-molded into green bodies.

[0044] To reduce the porosity of the sample, the green body was sintered in a HIP (Hot Isostatic Pressurization) furnace with a maximum sintering temperature of 1410°C and a sintering time of 1 hour at 40 mbar vacuum sintering, followed by a 15-minute high-pressure sintering process under 50 bar of Ar. The average cooling rate was 1.6°C / min between 1410°C and 1100°C, and 6.6°C / min between 1100°C and 100°C. TIFF2026511733000002.tif100170

[0045] Chemical analysis was performed on the sintered samples. The results can be seen in Table 2. The elements Al, Co, Cr, Fe, and Ni were analyzed using wavelength-dispersive X-ray fluorescence (WD-XRF). The instrument used was an Axios max-Advanced. Prior to analysis, the samples were prepared by crushing the cemented carbide into powder, and then the powder was oxidized at 800°C for 2 hours. Using lithium tetraborate as a flux, homogeneous and uniform pellets were prepared from the oxidized powder by fusion.

[0046] Oxygen and carbon were analyzed using LECO. The carbon content was measured using LECO CS-844. Approximately 0.2 grams of a pre-weighed sample was combusted in a stream of oxygen purified using RF induction to heat the sample. The carbon present in the sample was oxidized to carbon dioxide (CO2) and swept by an oxygen carrier through a heated dust filter, a drying reagent, and then a non-dispersive infrared (NDIR) cell.

[0047] Oxygen was measured using LECO ON-836. A pre-weighed sample was placed in a graphite crucible, which was heated in an impulse furnace to release the analyte gas. The oxygen present in the sample reacted with the graphite crucible to produce CO and CO2. An inert gas carrier, typically helium, swept the released analyte gas out of the furnace through a mass flow controller and a series of detectors. CO and CO2 were detected using a non-dispersive infrared (NDIR) cell. TIFF2026511733000003.tif64170

[0048] For the sintered body after grinding and polishing, toughness (K1C) and hardness (HV30) were measured. HV30 was measured according to ASTM B294. The fracture toughness K1C was measured according to Shetty. The results can be seen in Table 3 together with the fraction of the fcc phase (austenite) in the binder determined according to the method described below. The weight fractions of the elements shown in Table 3 were calculated from the powder composition shown in Table 1, and the weight fractions from chemical analysis are shown in parentheses.

[0049] XRD IμS Microfocus Source(CuK αXRD measurements were performed using a Davinci-designed Bruker Discover D8 diffractometer equipped with a line (λ=1.5418Å), Vantec-500 area detector, and a 1 / 4 Eulerian cradle. The X-ray source was operated at 50kV and 1mA. The sample was attached to the sample holder with adhesive tape. A collimator size of 1.0mm in diameter was used in all experiments. Measurements were performed on the polished surface of the sample being investigated. Measurements were performed on the polished surface away from edges and other areas that could be strongly affected during sample machining.

[0050] Data was collected in the 2θ range of 34° to 54°. 1D data was extracted from the 2D detector (Vantec-500) using the software DIFFRAC.EVA.

[0051] To obtain the fraction of the austenite phase in the binder, two peaks were used from the diffraction pattern. The (111) peak near 43.5° was used to quantify the fraction of the austenite phase (fcc), and the (110) peak near 44.5° was used to quantify the martensite / ferrite phase (bct / bcc).

[0052] Fraction I of fcc (austenite) in the metal binder fr_fcc In this specification, the fcc peak, I(111) fcc , and the bct / bcc peak, I(110) bct / bcc The fcc peak in the XRD diffraction pattern, I(111), is part of the total intensity. fcc The fraction of intensity achieved from, i.e., I fr_fcc =I(111) fcc / (I(111) fcc +I(110) bct / bcc It is shown as follows. The intensity was determined as the peak height minus the background. Subtraction of other overlapping peaks should also be performed as needed.

[0053] Figures 4a and 4b show diffraction patterns from one of the samples according to the present invention. TIFF2026511733000004.tif120170

[0054] The results are plotted in Figures 1 and 2. Figure 1 shows the HV-K1c values ​​compared to cemented carbide with Co as a binder (solid line). The solid line is a curve based on numerous HV-K1c measurements for cemented carbide with Co as a binder. Sample numbers 1 to 5 are samples according to the present invention, and sample numbers 1c to 4c are comparative samples.

[0055] As can be seen from the figure, all samples according to the present invention are above the curve.

[0056] Figure 2 shows the effect of different Al (x-axis) additions, where the value delta on the y-axis is the distance from the WC-Co baseline to the experimentally measured values ​​of HV and KIC. Delta is expressed by the following equation. TIFF2026511733000005.tif10170

[0057] In the formula, ΔHV and ΔKIC are the difference between the measured (HV, KIC) value and the calculated (HVcalc, KICcalc) value, and the coefficient I obtains a value of -1 when ΔHV and ΔKIC are negative numbers, and a value of +1 when ΔHV and ΔKIC are positive numbers. ΔHV = HV - HVcalc, (2) ΔKIC = KIC - KICcalc, (3) TIFF2026511733000006.tif20170

[0058] In the formula, a, b, and c are constants determined by substituting experimentally measured HV and KIC values ​​into Equation 4, where a = 2,670,000, b = 4,590, and c = 1,240.

[0059] Example 2 A cemented carbide sample was prepared from the same raw materials as described in Example 1, but the average particle size (FSSS) of the WC raw materials was 4.8 μm.

[0060] Different powder compositions are shown in Table 4. No chromium (Cr) was added to these samples.

[0061] A sintered sample is prepared from the powder blend using the same method as in Example 1. TIFF2026511733000007.tif81170

[0062] The toughness (K1C) and hardness (HV30) of the sintered body after grinding and polishing were measured using the same method as in Example 1. The results can be seen in Table 5. The weight fractions shown in Table 5 are calculated from the powder composition shown in Table 4. TIFF2026511733000008.tif77170

[0063] Figure 3 shows the effect of different Ni / (Ni+Fe) ratios (x-axis), and the value delta on the y-axis is determined as described above.

Claims

1. A cutting tool comprising a cemented carbide base material, wherein the cemented carbide comprises a hard phase comprising WC and 3 to 20% by weight of an Fe-based metal binder containing Fe, Ni, Cr, and Al, and the amounts of the elements Fe, Ni, Cr, and Al in the cemented carbide are The weight fraction of Ni / (Fe+Ni) is 0.10 to 0.

25. The weight fraction of Cr / (Fe+Ni+Cr+Al) is 0.005 to 0.

05. A cutting tool having a weight fraction of Al / (Fe+Ni+Cr+Al) of 0.01 to 0.05, and the amount of Fe in the metal binder being at least 65% by weight.

2. The weight fraction of Ni / (Fe+Ni) is 0.13 to 0.

20. The weight fraction of Cr / (Fe+Ni+Cr+Al) is 0.015 to 0.

035. The weight fraction of Al / (Fe+Ni+Cr+Al) is between 0.015 and 0.

04. The cutting tool according to claim 1.

3. The cutting tool according to claim 1 or 2, wherein the total amount of the elements Fe, Ni, Cr, and Al is at least 90% by weight of the metal binder.

4. A cutting tool according to any one of claims 1 to 3, wherein the cemented carbide is essentially cobalt-free.

5. Fraction I of austenite (fcc) in metal binder ｆｒ＿ｆｃｃ The percentage is over 25%, ｆｒ＿ｆｃｃ is, I ｆｒ＿ｆｃｃ = I(111) ｆｃｃ / (I(111) ｆｃｃ +I(110) ｂｃｔ／ｂｃｃ The fcc peak I(111) in the XRD diffraction pattern obtained by ) ｆｃｃ , and the I(110) peak which is the bct / bcc peak. ｂｃｔ／ｂｃｃ A cutting tool according to any one of claims 1 to 4, wherein the cutting tool is a fraction of the intensity achieved from the fcc peak I(111)fcc of the total intensity.

6. A cutting tool according to any one of claims 1 to 5, wherein the cemented carbide consists of WC, Fe, Ni, Cr, Al, W, C and unavoidable impurities.

7. A method for manufacturing a cutting tool according to claims 1 to 6, which includes a cemented carbide substrate, The process of providing WC powder, A step of providing a powder (or more) containing the elements Al, Fe, Ni, and Cr, The process of providing the pulverizing liquid, To create a cemented carbide base material, the process involves crushing the powder, drying it, press molding it, and sintering it. Methods that include...

8. The method according to claim 7, wherein a raw material containing the elements Al, Fe, Ni, and Cr is added as one or more of a pure metal, an alloy of two or more metals, or as a carbide, nitride, or carbonitride thereof.

9. The method according to claims 7 to 8, wherein the sintering step includes a sintering HIP step carried out at a temperature of 1350 to 1550°C and a pressure of at least 40 Bar, preferably 40 to 80 Bar.

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