Mining cutter with asymmetric cutting teeth

Abstract

A percussion drilling bit for drilling a borehole, comprising: a bit body having a front end face surrounded by a gauge; and a longitudinal bit center axis; and a plurality of gauge protection teeth, wherein the plurality of gauge protection teeth are embedded in the gauge protection part; wherein the gauge teeth have a longitudinal tooth central axis, a cylindrical shank portion, a working tip portion, a radially inner side, and a radially outer side, the radially inner side being located on the side closest to the drill bit central axis, and the radially outer side being located on the side remote from the drill bit central axis; the gauge protection tooth is characterized in that the operation end part of the gauge protection tooth has an asymmetric geometrical shape, and the volume of the material on the radial outer side is larger than that of the material on the radial inner side.

Description

Technical Field

[0001] This invention relates to a carbide tooth with an asymmetric shape for impact drilling applications. Background Technology

[0002] Carbide teeth are used in impact drill bits. The front teeth are typically arranged in multiple circumferential rows on the front face of the drill bit, with a row of gauge-maintaining teeth extending around the front teeth adjacent to the outer peripheral edge of the drill bit end face. When the gauge-maintaining teeth wear down below a certain level, the steel of the drill bit comes into contact with the rock being drilled; this is called negative taper. The problem with negative taper is that because the carbide teeth have worn down to the same diameter as the steel drill bit body, there is insufficient or no space for the chips to be removed. This leads to a reduced penetration rate or the drill bit getting stuck in the hole because the chips cannot be removed. Therefore, it accelerates wear on the steel drill bit body and reduces the life of the drill bit.

[0003] One possible way to delay the occurrence of negative taper is to increase the tooth protrusion height; however, this would increase the likelihood of tooth breakage.

[0004] Therefore, the problem to be solved is how to avoid or delay the occurrence of negative taper in order to improve the life of the drill bit, while maintaining the drilling rate and not increasing the risk of tooth breakage.

[0005] US5588497 discloses a method for installing teeth. EP2011890 discloses a cemented carbide containing fine-grained chromium. US2020030886 discloses a chromium-containing cemented carbide rock drill tooth. WO2022263477 discloses a method for processing cemented carbide teeth containing an eta phase core. WO2023 / 285316 discloses cemented carbide teeth including a gamma phase. US2013 / 105231 discloses drilling cutting teeth including platinum, palladium, rhenium, rhodium, and / or ruthenium. Summary of the Invention

[0006] According to a first aspect of the invention, one object is to provide a carbide tooth for mining or rock cutting applications, the carbide tooth comprising an impact drill bit for drilling boreholes (also referred to as drill holes), the impact drill bit comprising: a drill body having a front end face surrounded by a gauge protection portion; and a longitudinal drill center axis; and a plurality of gauge protection teeth embedded in the gauge protection portion; wherein the gauge protection teeth have a longitudinal tooth center axis, a cylindrical shank portion; a working end portion; a radially inner side and a radially outer side, the radially inner side being located on the side closest to the drill center axis, and the radially outer side being located on the side furthest from the drill center axis; wherein the working end portion of the gauge protection tooth has an asymmetrical geometry; wherein the volume of material on the radially outer side is greater than the volume of material on the radially inner side.

[0007] Advantageously, the increased volume of material on the radially outer side of the gauge teeth (i.e., the surface of the teeth that contacts the rock in the borehole) means an increased distance between the steel drill bit body and the borehole wall. This increases the drilling distance before steel contact occurs without increasing the bending motion of the teeth, which would otherwise lead to premature tooth breakage and failure. Consequently, this reduces the likelihood of negative taper occurring / delays its occurrence, thus increasing the life of the drill bit. Furthermore, the space between the steel drill bit body and the rock, allowing for chip removal, is maintained longer, thus enabling higher drilling speeds to be maintained over greater drilling distances. Overall, this translates to an increased lifespan for the drill bit.

[0008] In some embodiments, a distance (L) exists between the outermost portion of the drill bit body and the borehole wall, wherein L > 0.6 mm. Advantageously, this provides sufficient space for chip removal and delays the occurrence of negative taper.

[0009] In some embodiments, the working end portion of the gauge-maintaining tooth has a height (H), wherein L / H > 0.15. Advantageously, this range allows for improved wear resistance and increased drilling capability before the steel comes into contact with the rock being drilled, without adversely affecting the torque on the gauge-maintaining tooth, which would otherwise increase the risk of premature tooth breakage.

[0010] In some embodiments, the diameter of the gauge-keeping teeth is between 6 and 24 mm. Advantageously, this geometry range strikes a balance between being small enough to provide sufficient space within the steel drill bit body to accommodate the gauge-keeping teeth, and large enough to be robust enough to prevent premature breakage. Teeth with this diameter range are suitable for down-the-hole (DTH) and top hammer products.

[0011] In some embodiments, a first angle (α) exists between the central axis of the caliper tooth and the central axis of the drill bit; wherein α is between 10 and 50°. Advantageously, this provides a balance between sufficient space between the borehole wall and the steel drill bit body without drastically increasing the angle and thus increasing the risk of tooth failure.

[0012] In some embodiments, the working end portion of the gauge-maintaining tooth comprises a material volume on the radially outer side of the gauge-maintaining tooth that is 5% to 60% higher than the material volume on the radially inner side of the gauge-maintaining tooth. Advantageously, this delays the occurrence of negative taper without reducing the drilling rate.

[0013] In some embodiments, the working end portion of the gauge-maintaining tooth has a ballistic geometry. Advantageously, this geometry provides increased drilling speed.

[0014] In some alternative embodiments, the working end portion of the caliper has a dome geometry. Advantageously, this geometry provides improved wear resistance.

[0015] In some embodiments, a second angle (β) exists on the gauge-maintaining tooth, the second angle (β) being between the tooth's central axis and the tangent at the point on the working end portion of the gauge-maintaining tooth that is axially furthest from the drill bit's central axis; wherein β is between 0 and 35°. Ideally, β should be as low as possible, which provides optimal geometry for delaying / reducing the occurrence of negative taper without being reduced so much that the second angle causes pressing difficulties, which would lead to breakage problems.

[0016] In some embodiments, the cemented carbide used for the teeth comprises a hard component in a metal binder phase, wherein the content of the metal binder phase in the cemented carbide is between 4 and 20% by weight. Advantageously, this provides teeth with sufficiently high hardness and toughness.

[0017] In some embodiments, the metal binder phase of the carbide tooth comprises at least 80% by weight of one or more metallic elements selected from Co, Ni, and Fe.

[0018] In some embodiments, the carbide teeth further include a γ phase at a weight of 0.8-10 wt%. Advantageously, this provides carbide mining teeth with improved wear resistance without increasing brittleness. Therefore, tooth life is increased. Furthermore, this makes it easier to use recycled carbide, which typically has a higher γ phase content, acceptable for carbide grades commonly used in spent mining or cutting applications.

[0019] In some embodiments, the carbide teeth further include Cr in an amount such that the Cr / Co mass ratio in the bulk is between 0.04 and 0.19. Advantageously, the presence of chromium improves the plasticity of the carbide, which allows for the introduction of higher compressive stresses into the carbide when it is treated with surface hardening processes (e.g., tumbling). This increase in compressive stress provides a significant increase in hardness, which improves the wear resistance of the carbide without reducing its toughness.

[0020] In some embodiments, the carbide teeth have a corrected CoM / wt% Co ratio between 0.70 and 0.81 and are substantially free of the η phase, wherein the η phase is M6C or M 12 C, where M = (Co, W, Cr); wherein the corrected CoM / wt% Co ratio is calculated according to the following formula: Corrected CoM / weight% Co = (Magnetic% Co + 1.13) % Cr (by weight) / % Co (by weight) Wherein, % Co (magnetic % Co) is the weight percentage of magnetic Co, while % Co (weight % Co) and % Cr (weight % Cr) are the weight percentages of Co and Cr in the cemented carbide, respectively, measured according to the methods defined in the specification. Advantageously, when teeth with this particular range of corrected CoM / % Co (weight % Co) are subjected to static / low strain rate contact stress (which can be achieved through mechanical sintering post-processing (such as high-energy tumbling) and / or through actual drilling processes), the strain hardening capacity of the material will be enhanced. The material will also exhibit enhanced ultimate compressive strength (UCS), thereby reducing the risk of premature tooth breakage in rock drilling applications. Additionally, it has been found that if the corrected CoM / % Co (weight % Co) is within this range, the wear properties of the tooth are improved, which also contributes to increasing the tooth's lifespan in the field.

[0021] In some embodiments, the binder in the carbide tooth has a concentration gradient from one region of the tooth to another. Advantageously, this provides a tooth with both harder and tougher regions. Attached Figure Description

[0022] Specific embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 A schematic diagram of a drill bit including gauge-maintaining teeth with asymmetrical shapes is shown.

[0023] Figure 2 A side view of an asymmetric caliber-maintaining tooth with ballistic geometry is shown.

[0024] Figure 3aA side view schematic diagram of an asymmetric caliber-maintaining tooth with ballistic geometry is shown.

[0025] Figure 3b The cut along line AA is shown. Figure 3a The cross-section of the asymmetric tooth is shown.

[0026] Figure 4 This is a comparison graph of the penetration rate (ROP) as a function of the number of meters drilled, for drill bits using symmetrical gauge teeth and drill bits using asymmetrical gauge teeth. Detailed Implementation

[0027] Figure 1 A percussion drill bit 2 for drilling borehole 28 is shown. The percussion drill bit 2 includes a drill body 4 having a front face 6 surrounded by a gauge protection portion 8; a longitudinal drill center axis 10; a plurality of front teeth (not shown) embedded in the front face; and a plurality of gauge protection teeth 14 embedded in the gauge protection portion 8. The teeth are also referred to as ball teeth. The gauge protection teeth 14 have a longitudinal tooth center axis 16, a cylindrical shank portion 18 (i.e., without a tapered section on the shank), and a working end portion 20, wherein the cylindrical shank portion 18 is fixed by an interference fit to a socket already drilled into the drill body 4, and the working end portion 20 protrudes from the steel drill body 4. The cylindrical shape of the shank portion 18 facilitates better clamping force between the teeth 14 and the drill body 4. Both the front teeth and the gauge protection teeth are used for impacting and fracturing the drilled rock. The front face teeth are arranged in one or more circumferential rows on the front face 6. The gauge protection tooth 14 extends around or adjacent to the outer peripheral edge of the drill bit 2. The gauge protection tooth 14 contacts the hole wall 26 of the borehole 28.

[0028] The gauge-maintaining tooth 14 has a radially inner side 22 located on the side closest to the drill bit's central axis 10 and a radially outer side 24 located on the side furthest from the drill bit's central axis 10. The working end portion 20 of the gauge-maintaining tooth 14 has an asymmetrical geometry, wherein the volume of material on the radially outer side 24 is greater than the volume of material on the radially inner side 22. In other words, the side of the gauge-maintaining tooth 14 with the larger volume of material is positioned on the side that contacts the borehole wall 26 of the borehole 28.

[0029] The axial highest point 34 of the asymmetric sizing-maintaining tooth 14 is aligned with the tooth's central axis 16. In other words, the maximum height of the tooth (measured from the base of the tooth) is located at the axial center of tooth 14. This contributes to increased tooth life. In other words, the geometry of the sizing-maintaining tooth 14 is based on a hemispherical geometry, where additional material volume is added to the radially outer side 24. Asymmetry is achieved by adding material to the radially outer side 24 without removing any material volume from the radially inner side 22, compared to a standard tooth.

[0030] A tooth with an asymmetrical geometry is defined by dividing the tooth into two non-mirror halves by any plane parallel to and passing through the tooth's central axis 16. This is the opposite of a tooth with a symmetrical geometry that has symmetry in all planes parallel to and passing through the tooth's central axis 16. If viewed from above and cut through by a plane passing through the tooth's central axis 16, the volume of material in the half of the end portion 20 farther from the drill bit's central axis 10 is greater than the volume of material in the half of the end portion 20 closer to the drill bit's central axis 10.

[0031] Figure 1 The enlarged view shown illustrates the distance (L) between the outermost portion 32 of the steel drill bit body 4 and the hole wall 26 of the borehole 2. L is, for example, >0.6 mm or >1.3 mm. The working end portion 20 of the gauge-keeping tooth has a height (H). H is also equal to the height of the gauge-keeping tooth 14 protruding from the gauge-keeping portion 8. L / H is, for example, >0.15 or >0.2. Compared to symmetrical teeth, when the teeth have the same height (H), L increases proportionally more for asymmetrical teeth. For a drill bit 2 with a steel drill bit body 4 having the same diameter at the widest point of the steel drill bit body 4 and with gauge-keeping teeth 14 of the same height H, when the gauge-keeping tooth 14 has an asymmetrical geometry, the diameter from the widest point of the gauge-keeping tooth 14 to its outer peripheral edge is larger than when the gauge-keeping tooth 14 has a symmetrical geometry. Therefore, when using an asymmetrical gauge-keeping tooth 14, internal diameter wear increases. H is measured at the highest point of tooth 14, which will be aligned with the tooth's central axis 16.

[0032] In some embodiments, the diameter of the retaining tooth 14 is between 6 and 24 mm, for example, between 7 and 20 mm.

[0033] like Figure 1 As shown, there is a first angle (α) between the tooth center axis 16 of the gauge-maintaining tooth 14 and the drill bit center axis 10. For example, α is between 10-50°, or for example, α is between 25-45°.

[0034] Figure 2 The working end portion 20 of the caliper 14 is shown to have an asymmetrical ballistic shape. This geometry may also be referred to as a distorted or eccentric or unbalanced or skewed ballistic geometry, or an asymmetrical or distorted or eccentric or unbalanced or skewed apex geometry, or an asymmetrical or distorted or eccentric or unbalanced or skewed peak geometry.

[0035] Figure 3aThe working end portion 20 of the caliper 14 is shown to have an asymmetrical dome shape, also known as a dome shape. This geometry can also be referred to as a distorted or eccentric or unbalanced or skewed dome geometry, or an asymmetrical or distorted or eccentric or unbalanced or skewed spherical geometry.

[0036] Figure 3b The cross-section taken perpendicular to the tooth's central axis 16 in the working end portion 20 of tooth 14 has a substantially elliptical geometry. In other words, when viewed from above, the asymmetric tooth 14 has a substantially elliptical geometry. This is beneficial for reducing wear.

[0037] The caliper 14 can also have any other suitable asymmetric geometry, such as a semi-ballistic geometry.

[0038] In some embodiments, the volume of material included on the radially outer side 24 of the working end portion of the gauge-keeping tooth 14 is 5-60% larger, for example, 10-40% larger, than the volume of material on the radially inner side 22 of the gauge-keeping tooth. The volume of material on the radially outer side 24 is considered to be the material in the half of the working end portion furthest from the drill bit central axis 10, and the volume of material on the radially inner side 22 is considered to be the material in the half of the working end portion closest to the drill bit central axis 10.

[0039] like Figure 2 As shown, the second angle (β) on the gauge-maintaining tooth 14 is located between the tangent of the tooth center axis 16 and the point on the working end portion 20 of the gauge-maintaining tooth 14 that is furthest from the drill bit center axis 10 along the axial direction on the tooth 30; wherein β is between 0 and 35°. β is, for example, between 0 and 35° or between 3 and 25°.

[0040] In some embodiments, the cemented carbide for teeth 12, 14 comprises a hard component in the metal binder phase, and wherein the content of the metal binder phase in the cemented carbide is between 4 and 20% by weight, for example between 5 and 15% by weight.

[0041] Typically, the hard component comprises at least 50% by weight of WC and other possible hard components commonly found in the manufacture of cemented carbide. In one embodiment of the method, the cemented carbide mining tooth comprises a hard phase comprising at least 80% by weight of WC, for example, at least 90% by weight.

[0042] The metal binder phase may be selected from one or more of Fe, Co, and Ni. For example, the metal binder phase of the cemented carbide tooth 14 includes at least 80% by weight of one or more metallic elements selected from Co, Ni, and Fe. The cemented carbide metal binder may include other elements dissolved in the metal binder during sintering, such as W and C derived from WC. Depending on what other types of hard components are present, other elements may also be dissolved in the binder.

[0043] In some embodiments, the average WC grain size in the cemented carbide is between 0.8 and 18 μm, for example between 1.5 and 10 μm, for example between 1 and 5 μm.

[0044] In some embodiments, the proportion of WC added is derived from a zinc recycling process (PRZ) using sintered hard alloy mining waste, resulting in a so-called "PRZ feedstock" that primarily contains WC and Co. In some embodiments, up to 100% of the added Co is derived from the PRZ feedstock.

[0045] In some embodiments, the cemented carbide tooth 14 further includes 0.8-10% by weight, for example 1-8% by weight, of a γ phase. The added γ phase forming a carbide, nitride, or carbonitride can be any of Ta, Nb, Ti, Zr, or Hf.

[0046] In some embodiments, the carbide tooth 14 further includes Cr in such an amount that the Cr / Co mass ratio in the whole is 0.04-0.19, for example, between 0.075-0.17.

[0047] In some embodiments, the carbide tooth 14 has a corrected CoM / wt% Co ratio between 0.70 and 0.81 and is substantially free of the η phase, wherein the η phase is M6C or M 12 C, where M = (Co, W, Cr); wherein the corrected CoM / wt% Co ratio is calculated according to the following formula: Corrected CoM / weight% Co = (Magnetic% Co + 1.13) % Cr (by weight) / % Co (by weight) Wherein, % Co is the weight percentage of magnetic Co, while % Co and % Cr are the weight percentages of Co and Cr in the cemented carbide, respectively.

[0048] The corrected CoM / wt% Co of the sintered sample was measured and calculated using a commercially available Foerster Koerzimat CS 1.096 instrument. The sample was weighed and then placed in a magnetic coil as described in the Koerzimat CS 1.096 V3.09 manual.

[0049] In different embodiments, the adhesive in the carbide tooth 14 has an adhesive concentration gradient from one region of the tooth to another.

[0050] In some embodiments, the carbide tooth 14 undergoes post-processing surface hardening and toughening treatment. For example, the sintered carbide tooth undergoes a tumbling process. Alternatively, the sintered carbide tooth undergoes a high-energy tumbling process (HET). HET is considered a tumbling process in which a deformation-hardened homogeneous carbide mining tooth is post-tumbled such that ΔHV3% ≥ 9.72 – 0.00543. HV3 bulk ΔHV3% is the percentage difference between the HV3 measurement at 0.3 mm from the surface and the HV3 measurement throughout the whole. HET can also be understood as a tumbling process that causes a hardness difference of at least 20 HV3 between 0.3 mm from the surface and the whole. HET can also be understood as causing an increase in both hardness and toughness from the surface to the whole.

[0051] Many different possible process settings exist for introducing HET, including the type of roller, the volume of added media (if any), the processing time, and the process settings, such as the RPM of a centrifugal roller. Therefore, the most appropriate way to define HET is "any process setting that introduces a specific degree of deformation hardening in a homogeneous carbide mining tooth composed of WC-Co with a mass of approximately 20 g." In this disclosure, HET is defined as the following tumbling treatment that, after tumbling, introduces at least the following hardness change (HV3%) as measured using HV3: ΔHV3% = 9.72 – 0.00543 HV3 bulk (Equation 1) in: ΔHV3% = 100 (HV3 0.3mm – HV3 bulk ) / HV3 bulk (Equation 2) HV3 bulk It is the average of at least 10 indentation points measured on the innermost (center) side of the carbide mining tooth, and HV3 0.3mmIt is the average of at least 10 indentation points located 0.3 mm below the tumbled surface of the cemented carbide mining tooth. This is based on measurements taken on a cemented carbide mining tooth with homogeneous properties. "Homogeneous properties" means that, after sintering, the hardness difference from the surface area to the innermost integral area does not exceed 1%. The tumbling parameters used to achieve the strain hardening described in equations (1) and (2) on a homogeneous cemented carbide mining tooth will be applied to a cemented carbide body with gradient properties.

[0052] HET tumbling is typically performed using the following equipment and parameters: Using an ERBA 120 model with a turntable size of approximately 600 mm, the tumbling operation is performed at approximately 180 RPM if there is no medium or if the medium is larger than the teeth being tumbled; or at approximately 240 RPM if the medium is smaller than the teeth being tumbled. Alternatively, using a Rösler roller with a turntable size of approximately 350 mm, the tumbling operation is performed at approximately 280 RPM if there is no medium or if the medium is larger than the teeth being tumbled; or at approximately 320 RPM if the medium is smaller than the teeth being tumbled. Generally, the parts are tumbled for at least 40-80 minutes.

[0053] In some embodiments, HET is performed at a high temperature of 100°C or above, for example, at a temperature of 200°C or above, such as between 200°C and 450°C. In some embodiments, teeth 12 and 14 are preheated prior to HET treatment. In some embodiments, HET is performed under dry conditions. “Dry” conditions mean that no liquid is added during the process.

[0054] In one embodiment, the difference between the average hardness at 0.3 mm below the surface of the rock drill bit and the average hardness of the entire rock drill bit (i.e., the innermost part) is at least 20 HV3, for example at least 30 HV3, for example at least 40 HV3, wherein the hardness is measured according to ISO EN6507.

[0055] Example

[0056] Example 1 - Diameter of the drill bit

[0057] Drill bits were tested in an underground mine in Sweden to compare the performance of gauss-keeping teeth with and without asymmetric trajectories. The tests used identical bit bodies, the same number and distribution of teeth, and the same tooth diameter. All teeth were made of the same cemented carbide material (comprising 6 wt% Co + 0.6 wt% Cr + balance WC and no PRZ), with HV20 of 1440 and Palmqvist K of 11. 1CThe D50 WC grain size was measured using EBSD at 2.1 μm, and both underwent the same HET treatment after sintering. The only difference was the geometry of the gauge teeth. Table 1 shows the diameter of the drill bit and the distance drilled after drilling.

[0058]

[0059] Table 1: Drilling Test Results

[0060] As shown in Table 1, compared to drill bits with symmetrical teeth, drill bits with asymmetrical teeth have a larger diameter after drilling (even after achieving a greater drilling distance). This indicates that wear on the steel body is reduced when using asymmetrical teeth.

[0061] Example 2 - Penetration Rate

[0062] Figure 4 The diagram shows the drilling rate of penetration (ROP) as a function of the number of meters drilled. The solid line represents the result for symmetrical teeth, and the dashed line represents the result for asymmetrical teeth. It can be seen that the drill bit with symmetrical teeth has a higher initial drilling rate. However, after approximately 37 m, the drill bit with symmetrical teeth experiences steel-to-diameter contact, and the penetration rate decreases significantly (i.e., the steel of the drill bit body contacts the borehole wall), meaning less space is left for chip removal, which adversely affects the penetration rate. However, for the drill bit with asymmetrical teeth, steel-to-diameter contact does not occur (i.e., there is still carbide in contact with the borehole wall), and therefore sufficient space is maintained for chip removal, resulting in a longer-lasting high penetration rate.

[0063] Example 3 - Tooth Compression Test

[0064] The tooth compression test method involves compressing a 10 mm diameter drill bit tooth between two parallel, hard, opposing surfaces at a constant displacement rate until tooth failure. A test fixture based on ISO 4506:2017(E) standard "Hard metals – Compression test" is used, with a carbide anvil from Hyperion, grade H6F, having a hardness exceeding 2000 HV. The test method itself is suitable for toughness testing of rock drill bits. The fixture is mounted on an Instron 5989 test fixture.

[0065] The loading axis is the same as the rotational symmetry axis of the tooth. The relative surfaces of the fixture meet the parallelism required in ISO 4506:2017(E) standard, i.e., a maximum deviation of 0.5 μm / mm. The tested tooth is loaded at a constant beam displacement rate of 0.6 mm / min until failure, while recording the load-displacement curve. Before test evaluation, the compliance of the test equipment and test fixture is subtracted from the measured load-displacement curve. Three teeth are tested each time. Damage to the relative surfaces is checked before each test. Tooth failure is defined as a sudden drop in the measured load of at least 1000 N. Subsequent inspection of the tested tooth confirms that this is consistent with the occurrence of macroscopically visible cracks in all cases. Material strength is characterized by the total deformation energy absorbed before fracture. A summary of the tooth breaking strength (kN) and fracture energy in joules (J) required for the sintered tooth is shown in Table 2 below:

[0066] Table 2: Tooth compression test results after sintering.

[0067] Tooth compression tests were also used to analyze teeth from the same batch that underwent high-energy tumbling treatment, and the results are shown in Table 3 below:

[0068] Table 3: Tooth compression test results after high-energy tumbling

[0069] As can be seen from Tables 2 and 3, compared with symmetrical teeth, asymmetrical teeth have higher tooth breaking strength and fracture energy during breaking, which will reduce the possibility of tooth fracture and thus increase tooth life.

[0070] Example 4 - Hardness gradient in a 10mm asymmetric tooth after HET

[0071] Hardness was measured using a Vickers hardness indenter with a 3kg load HV3 on 10mm asymmetric teeth from the same batch as used in Example 3, after HET tumbling.

[0072] HV3 indentations were made on cut and polished samples at distances of 0.3, 0.6, 1.2, and 4.6 mm from the tooth surface. The average HV3 at 4.6 mm was considered the overall hardness value, and the average HV3 at 0.3 mm from the surface was considered the surface hardness value. The difference in HV3 relative to the average overall HV3 was calculated at different profiles, and the percentage increase in HV3 was calculated relative to the average HV3 in the whole. The change of 100.

[0073]

[0074] Table 4: Hardness Measurement Values ​​of 10mm Teeth

[0075] Example 5 - Hardness gradient in a 7mm asymmetric tooth after HET

[0076] Producing the following teeth: HET-treated asymmetric 7mm diameter teeth, consisting of 5% by weight Co, 0.5% by weight Cr and WC, wherein 45% of the total WC-Co content (corresponding to 94% of the total Co content) is added as PRZ prior to grinding (grade A); and HET-tumbled 7mm diameter asymmetric ballistic teeth, consisting of 6% by weight Co and WC, wherein 50% of the total WC-Co content (corresponding to 52% of the total Co content) is added as PRZ (grade B).

[0077] Both grades of teeth were measured using a Vickers hardness indenter with a 3 kg load (HV3). HV3 indentations were made on cut and polished samples at 0.3 mm and 3 mm from the tooth surface, where the average HV3 at 3 mm was considered the overall hardness, and the average HV3 at 0.3 mm from the surface was considered the surface hardness. The difference between HV3 and the average overall HV3 was calculated, and the percentage increase in HV3 was calculated relative to the average HV3 in the whole. The change of 100.

[0078]

[0079] Table 5: Hardness Measurement Values ​​on 7mm Teeth

Claims

1. An impact drill bit (2) for drilling boreholes (28), comprising: The drill bit body (4) has a front end face (6) surrounded by a diameter protection part (8); Longitudinal drill bit center axis (10); and multiple gauge protection teeth (14) embedded in the gauge protection part (8); The gauge-maintaining tooth (8) has a longitudinal tooth center axis (16), a cylindrical shank portion (18), a working end portion (20), a radially inner side (22) located on the side closest to the drill bit center axis (10), and a radially outer side (24) located on the side far from the drill bit center axis (10). Its features are: The working end portion (20) of the caliper (14) has an asymmetrical geometry, wherein the volume of material on the radially outer side (24) is greater than the volume of material on the radially inner side (22).

2. The impact drill bit (2) according to claim 1, wherein, There is a distance (L) between the outermost part (32) of the drill bit body (4) and the hole wall (26) of the borehole (28), and where L>0.6mm.

3. The impact drill bit (2) according to claim 1 or 2, wherein, The working end portion (20) of the caliper (14) has a height (H), wherein L / H > 0.

15.

4. The impact drill bit (2) according to any one of the preceding claims, wherein, The diameter of the diameter-maintaining tooth (14) is between 6 and 24 mm.

5. The impact drill bit (2) according to any one of the preceding claims, wherein, There is a first angle (α) between the tooth center axis (16) of the gauge-maintaining tooth (14) and the drill bit center axis (10); wherein α is between 10° and 50°.

6. The impact drill bit (2) according to any one of the preceding claims, wherein, The volume of material included on the working end portion (20) of the gauge retainer (14) on the radially outer side (24) of the gauge retainer is 5-60% larger than the volume of material on the radially inner side (22) of the gauge retainer.

7. The impact drill bit (2) according to any one of the preceding claims, wherein, The working end portion (20) of the caliper (14) has a ballistic geometry.

8. The impact drill bit (2) according to any one of claims 1-6, wherein, The working end portion (20) of the caliper (14) has a dome geometry.

9. The impact drill bit (2) according to any one of the preceding claims, wherein, A second angle (β) exists on the gauge-maintaining tooth (14), which is located between the tooth center axis (16) and the tangent of the working end portion (20) of the gauge-maintaining tooth (14) at the point on the tooth that is axially furthest from the drill bit center axis (10); wherein β is between 0 and 35°.

10. The impact drill bit (2) according to any one of the preceding claims, wherein, The cemented carbide used for the teeth (12, 14) comprises a hard component in a metal binder phase, and the content of the metal binder phase in the cemented carbide is between 4% and 20% by weight.

11. The impact drill bit (2) according to claim 10, wherein, The metal binder phase of the teeth (12, 14) made of cemented carbide comprises at least 80% by weight of one or more metallic elements selected from Co, Ni and Fe.

12. The impact drill bit (2) according to any one of claim 10 or 11, wherein, The teeth (12, 14) made of cemented carbide also include a γ phase in the range of 0.8-10% by weight.

13. The impact drill bit (2) according to any one of claim 10 or 11, wherein, The teeth (12, 14) made of cemented carbide also include Cr, the amount of which is such that the Cr / Co mass ratio in the whole is 0.04-0.

19.

14. The impact drill bit (2) according to claim 13, wherein, The teeth (12, 14) made of cemented carbide have a corrected CoM / wt% Co ratio between 0.70 and 0.81 and are substantially free of the η phase, wherein the η phase is M6C or M 12 C, where M = (Co, W, Cr); wherein the corrected CoM / wt% Co ratio is calculated according to the following formula: Corrected CoM / weight% Co = (Magnetic% Co + 1.13) % Cr (by weight) / % Co (by weight) Wherein, % Co is the weight percentage of magnetic Co, and % Co and % Cr are the weight percentages of Co and Cr in the cemented carbide, respectively, and they are measured according to the methods defined in this specification.

15. The impact drill bit (2) according to any one of the preceding claims, wherein, The binder in the teeth (12, 14) made of cemented carbide has a concentration gradient from one region of the teeth (12, 14) to another region of the teeth (12, 14).

16. The impact drill bit (2) according to any one of the preceding claims, wherein, The working end portion (20) of the tooth (14) is substantially elliptical in plan view.

17. The impact drill bit (2) according to any one of the preceding claims, wherein, The highest point of the tooth (14) is aligned with the corresponding tooth center axis (16).

Images