NL2017180B1

NL2017180B1 - Additive manufactured tooth for dredging or mining

Info

Publication number: NL2017180B1
Application number: NL2017180A
Authority: NL
Inventors: Hemmati Ismail
Original assignee: Ihc Holland Ie Bv
Priority date: 2016-07-18
Filing date: 2016-07-18
Publication date: 2018-01-24
Also published as: CN110226011A; EP3485100A1; WO2018016948A1

Abstract

The invention relates to a cutting element for cutting material in underwater 5 operations, the cutting element comprising at least first and second cutting sections wherein the first cutting section comprises a first metal alloy and the second cutting section comprises a second metal alloy different to the first metal alloy, wherein the first and second cutting section are deposited by additive manufacturing and wherein the first and second cutting section are interconnected by meltbond.

Description

Background

The present invention relates to a cutting element for cutting material in underwater operations like for example rock cutting teeth. The invention also relates to the manufacturing or refurbishing a cutting element for cutting material in underwater operations.

The majority of rock cutting teeth for dredging applications are produced by casting/forging and a subsequent heat-treatment. Although cast or forged teeth are cost competitive and could be produced in large numbers, these suffer from several shortcomings. Firstly, the lifetime is limited due to loss of strength and hardness because of the heat generated by friction between the teeth and rock material. Secondly, premature fracture occurs due to limited impact resistance of the teeth material in connection with martensitic structure of the material.

Another type of a rock cutting tooth is a cast steel casing with a tungsten carbide composite insert or aluminium oxide insert fitted into the cast steel casing.

This technique is used to produce what is considered premium rock-cutting teeth.

Problems associated with this insert type of teeth are as follows. Firstly, the inserts fail mainly due to premature fracture. This is because of inherent brittleness of composite material that are used. Secondly, production of these teeth needs multiple steps including compaction and sintering of the insert, production of the casing and the complex fitting of the insert in the core. Lastly, because of its lower hardness, the steel casing usually wears faster. This leaves the insert without support and accelerates the premature failure of the insert.

Another example of a tooth system is found in W02005005737. The tooth has a core. This tooth system has similar problems as the one with the insert.

Summary of the invention

The invention aims to enhance the performance and lifetime of cutting elements like rock cutting teeth.

Another object of the invention is to improve known cutting elements in that a problem associated therewith is at least partly solved.

Yet another object of the invention is to provide an alternative cutting element.

According to a first aspect of the invention this is realized with a cutting element for cutting material in underwater operations, the cutting element comprising at least first and second cutting sections wherein the first cutting section comprises a first metal alloy and the second cutting section comprises a second metal alloy different to the first metal alloy, wherein the first and second cutting section are deposited by additive manufacturing and wherein the first and second cutting section are interconnected by meltbond.

In particular, the first and second cutting section are deposited by high power additive manufacturing. Laser based processes or arc-based processes are known examples of high power additive manufacturing methods. A meltpool is created by the power of the laser or arc and the metal alloy(s) are added in the meltpool.

Having two sections results in the ability to combine different materials. The sections being interconnected by meltbond enables to obtain a cutting element of one piece having improved durability and reliability. Durability relates to wear resistance and reliability to impact resistance. Hence, increasing the durability and reliability means that the cutting element has a higher wear resistance and a larger capacity to absorb the impact loads without fracture of the cutting element.

The above-mentioned additive manufacturing processes at least involve that the first and second metal alloy are being deposited by injecting these in for example powder form, into a meltpool. This results in smooth and gradual transition from the first cutting section to the other one and enables to control this transition. This improves the thermal properties of the cutting element as a whole. This laser based technology includes at least Laser Metal Deposition (LMD), Laser cladding and Directed Energy Deposition (DED). It should be noted that the laser based processes involve a beam (laser or electron), and material addition (powder or wire).

Examples of cutting elements are cutting teeth used on a dredging cutter head, and bits used on a mining cutter head or a trenching cutter head.

In an embodiment, the cutting element comprises a base section configured in order to connect to a cutting head, and wherein the base section supports the first and second cutting section. The base section supports the first and second cutting section such that the cutting element maintains his position while cutting. The first and second cutting sections may be deposited directly on the base section if desired.

In an embodiment, the cutting element has in use a line of attack, wherein an interface between the first and second cutting section extends transverse relative to the line of attack. In this way the combined properties of the first and second metal alloys are best utilized. In particular, the interface between the first and section cutting section extends substantially parallel to a longitudinal axis of the cutting element. This is true for a so called core/shell combination. Other configurations are however conceivable such as alternating layers of the first and second metal alloys.

In an embodiment of the cutting element, the first and second cutting section extend co-axially. This allows to maintain the cutting performance of the cutting element constant over its lifetime.

In an embodiment of the cutting element, the first and second metal alloys differ at least in their elasticity and hardness properties.

In an embodiment of the cutting element, the first cutting section extends at an inner core of the cutting element and the first metal alloy has a Rockwell C (HRc) Hardness between 60 - 80 HRc, more specifically between 65 - 75 HRc.

In an embodiment of the cutting element, the first metal alloy has a wear resistance according to ASTM G65-04 Procedure A resulting in a mass loss of about or less than 0.07 g (+/- 0.01) after about 6,000 test cycles.

In an embodiment of the cutting element, the second cutting section extends at an outer periphery of the cutting element and the second metal alloy hardens upon impact. In particular the second metal alloy comprises an austenitic structure at room temperature that transforms to a martensite structure at temperature. More specifically, the second metal alloy comprises at least Fe, Mn, and C.

In an embodiment of the cutting element, the first and second cutting section in use extend over a cutting surface of the cutting element. This ensures the ability to enjoy the cutting properties of the cutting element. It will be clear that in case of a core shell configuration, initially only the outer one of the first and second cutting section will extend over a cutting surface.

In an embodiment of the cutting element, the first and second cutting section are melt bonded over the whole of their mutual overlap. This ensures a higher integrity of the cutting element in particular during its entire life.

The invention also relates to a tooth system comprising a base structure and a cutting element according to the invention detachably connected to the base structure, wherein the base structure is configured for secure mounting to a cutter head by e.g. means of welding or mechanical fastening means.

The invention further relates to a cutting head comprising a cutting element according to a preceding claim. The cutting head can for example be designed for dredging, mining or trenching.

According to a further aspect of the invention this is realized with a method for manufacturing a cutting element for cutting strata including rock, the cutting element comprising at least first and second cutting sections, wherein the method comprises;

a. depositing a first metal alloy by additive manufacturing for providing the first cutting section,

b. changing over a material supply from the first metal alloy to a second metal alloy in order to stop depositing the first metal alloy and to start depositing the second metal alloy,

c. depositing a second metal alloy by additive manufacturing for providing the second cutting section such that the first and second cutting section interconnect by meltbond.

In an embodiment of the method, step b is without interrupting depositing of the first or second metal alloy or a combination thereof

In an embodiment, the method comprises;

d. manufacturing the cutting element layer by layer, and at least once changing over from the first metal alloy to the second metal alloy per layer for forming the first and second cutting sections.

In an embodiment of the method, step b comprises

e. controlling a ratio between supply of the first metal alloy and the second metal alloy during changing over from the first metal alloy to the second metal alloy in order to configure an interface between the first and second cutting section.

In an embodiment, the method comprises on site performing any of steps a-e. This is done on an intended location such as the project site.

In an embodiment, the method comprises refurbishing a damaged cutting element. In this manner, the top edge of the worn-out element is cut off and afterwards the element is brought back to its original dimensions or a different one, by depositing several layers consisting of the first and second material alloys.

The invention further relates to a device comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The invention further relates to a method comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages.

Description of the drawings

The invention will be further elucidated referring to a preferred embodiment shown in the schematic drawings wherein shown in:

Fig. 1 a perspective cutaway view of a cutting element according to the invention; fig. 2a a cross sectional top view of the cutting element the according to fig. 1; fig. 2b a cross sectional top view of another embodiment of the cutting element; fig 3a a cross section of fig. 2;

fig. 3b a detail of fig. 3a;

fig 4 an apparatus for manufacturing the cutting element according to the invention; and fig. 5 a cutter head provided with cutting elements according to the invention.

Detailed description of embodiments

In figure 1 a cutting element 3 according to the invention is shown. The cutting element 3 is suitable and configured for cutting material in underwater operations. The cutting element 3 comprising at least first 1 and second 2 cutting sections. The first cutting section 1 comprises a first metal alloy and the second cutting section 2 comprises a second metal alloy. The second metal alloy is different compared to the first metal alloy. The first 1 and second 2 cutting sections are both deposited by laser based additive manufacturing processes, for example by DED or laser cladding. The first 1 and second 2 cutting section are interconnected by meltbond. Here, the first 1 and second 2 cutting section are melt bonded over the whole of their mutual overlap. The cutting element 3 comprises a base section 4 that is only schematically depicted. The base section 4 is designed to support the cutting sections 1, 2 during cutting operations. The base section 4 is also configured to detachably connect the cutting element 3 to a cutter head 5 as shown in fig. 5 to be able to change cutting elements 3. During operating, cutting elements 3 may be worn out already after for example half an hour and then need to be replaced.

The skilled person will appreciate that the base section 4 in connection with the cutting sections 1, 2 can be an adaptor from a cutting head (not shown) or any other suitable means.

The cutting element 3 of fig. 1 has a so called core shell configuration. In other words, the first cutting section 1 extends at an inner core while the second cutting section 2 extends at an outer periphery of the cutting element 3. The first 1 and second cutting sections extend along a longitudinal axis 7 of the cutting element 3. Here, the first 1 and second 2 cutting section extend co-axially along the longitudinal axis 7.

Here, an interface 6 between the first 1 and second section 2 extends substantially parallel to a longitudinal axis 7 of the cutting element. In this case, the interface 6 is cone shaped. It should be noted that the interface 6 can be a fading interface comprising at least one of the alloys of the first 1 and second section 2.

The first cutting section 1 and the second cutting section 2 form a cutting element here in the form of a cone shaped cutting tooth. Both the first cutting section 1 and the second cutting section 2 provide strength and integrity to the cutting element in connection with the cutting force Fc. In this case, both the first cutting section 1 and the second cutting section 2 extend over about half of the diamater of the cutting element at the base thereof. The base of the cutting element 3 is the side facing the base section 4.

The cutting element 3 has in use a line of attack 8 that is the line along which a cutting force Fc acts on the cutting element 3. The interface 6 between the first 1 and second 2 cutting section extends transverse relative to the line of attack 8. Here, it is shown in a way that the longitudinal axis 7 of the cutting element 3 extends transverse relative to the line of attack 8. It will be clear the other mutual orientations of the longitudinal axis 7 of the cutting element 3 and the line of attack 8 are possible. The cutting force Fc is applied on the outer surface of the cutting element 3.

Fig. 2a is a cross sectional top view of the cutting element 3 shown in fig. 1.

Here, it can be best seen that the cutting element 3 of fig. 1 has a core shell configuration. The first 1 and second 2 cutting section extend co-axially along and around the longitudinal axis 7. Fig. 2b is a cross sectional top view of the cutting element 3 in an alternative configuration. The difference compared with the view of fig. 2a is that the cutting element 3 has alternating layers of the first and second metal alloys. This even more improves thermal properties and cutting characteristics of the cutting element 3.

The cutting element 3 is manufactured through a laser based additive manufacturing method. This also means that in general the cutting element 3 will be manufactured in a layer wise manner. Fig 3a shows a cross section of such a layer 20.

fig. 2; The layer 20 is grown by laying weld beads that are shown as a semicircular shape that can be best seen in fig. 3B that shows a detail of fig. 3a. The first 1 and second 2 cutting sections are shown as well as an interface 6 between the first 1 and second 2 cutting sections. The first cutting section 1 is made of a first metal alloy. The second cutting 2 is made of a second metal alloy. The second metal alloy is different to the first metal alloy. The first and second metal alloys differ in their elasticity and hardness properties. The first metal alloy has a Rockwell C (HRc) Hardness between 60 - 80 HRc, more specifically between 65 - 75 HRc. In addition, the first metal alloy has a wear resistance according to ASTM G65-04 Procedure A resulting in a mass loss of about or less than 0.07 g (+/- 0.01) after about 6,000 test cycles. The second metal alloy is, at least initially, softer than the first metal alloy. However, the second metal alloy hardens upon impact. Metal alloys that harden upon impact are known per se. The second metal alloy comprises Fe, Mn, and C for determining the hardness properties of the second metal alloy. An example of an alloy that can be chosen as the second metal alloy is Hadfield steel.

Fig. 4 schematically shows an apparatus 9 for manufacturing the cutting element 3 according to the invention. A method for manufacturing the cutting element will now be described referring to the apparatus 9. The method involves depositing a first metal alloy 13 by additive manufacturing for providing the first cutting section 1. The first metal alloy 13 is stored in powder form in a first container 10. The first metal alloy 13 is transported to the melting pool on the substrate through a first supply line 14, a mixing device 17 and finally through an exit nozzle 16. The method involves depositing a second metal alloy 12 by additive manufacturing for providing the second cutting section 2. The second metal alloy 12 is stored in powder form in a second container 11. The second metal alloy 12 is transported to the melting pool on the substrate through a second supply line 15, a mixing device 17 and finally through an exit nozzle 16. Here, the first metal alloy 13 and the second metal alloy 12 exit through a common exit nozzle 16. The method also involves changing over a material supply from the exit nozzle 16 to the melting pool from the first metal alloy 13 to the second metal alloy 12 in order to stop depositing the first metal alloy 13 and to start depositing the second metal alloy 12. The changeover is directed by the mixing device 17 that has the first metal alloy 13 and the second metal alloy 12 as inputs through respective first and second 15 supply lines and has the common exit nozzle 16 as its output. The mixing device 16 can mix the first metal alloy 13 and the second metal alloy 12 as desired between 100% first metal alloy 13 and 100% second metal alloy 12. The changeover can be done gradually. The change over from the first metal alloy 13 to the second metal alloy 12 can be done gradually so that the width of the interface 6 can be a number of weld beads.

As an example, the change over from the first metal alloy 13 to the second metal alloy 12 is done stepwise. At each circumambulation of a weld bead around the longitudinal axis 7 a step is made in the mixing proces to provide a gradual change over from the first metal alloy 13 to the second metal alloy 12.

A gradual change over from the first metal alloy 13 to the second metal alloy 12 improves the thermal properties of the cutting element 3 by preventing a sudden transition from one material to the other one. This will decrease the amount of mismatch, or in other words thermal stress, between the two materials once they are heated by the friction of the operation. This is important in view of the high temperatures and number of temperature cycles during use of the cutting element. In other words, the method involves controlling a ratio between supply of the first metal alloy 13 and the second metal alloy 12 during changing over from the first metal alloy to the second metal alloy in order to configure an interface 6 between the first 1 and second 2 cutting section. The mixing device 17 has a controller 22 to control the mixture of the first metal alloy 13 and the second metal alloy 12. The controller 22 can be internal or external as desired. The changeover is without interrupting depositing of the first 13 or second 12 metal alloy or a combination thereof This promotes the mechanical integrity of the cutting element 3.

For illustration purposes, one manufactured layer 20 of the cutting element is shown on a carrier 21. It will be clear that many more layers will follow to constitute a cutting element 3. At least once a changeover is required for a layer 20. In case of the shell core configuration, two change overs are required per layer from the first metal alloy to the second metal alloy for forming the first and second cutting sections.

An example of a weld bead laying strategy would be to start from the outer side of the layer 20 with Hadfield steel and move towards inside in a spiral pattern and reverse the sequence in the next layer, and so on. In this way, the entire section could be deposited without interruption and with minimum switching, which is changing over, between materials.

An alternative weld bead laying strategy implies the deposit of the layer 20 from outside towards the inside of the cutting element 3 in a spiral pattern and start again either from the outside or the inside to deposit the next layer.

The skilled person will appreciate that the first 13 and second 12 metal alloys can be provided in a different form than powder i.e. wire, wherein two wires are simultaneously fed to produce the interface 6. Instead of controlling the mixture of powder, the feeding speed of the wires is controlled. Nonetheless, there may be areas of the interface 6, wherein only one metal alloy is provided by means of a wire, and other areas of the interface 6 where the metal alloy is provided with one or two wires having similar or different alloys. Also a combination of powder feedstock and wire feedstock is conceivable.

In case of refurbishing a damaged cutting element 3, the method may comprise the scanning of the damaged cutting element to build a 3d data model and then adjust the deposition process to the 3d data model.

Fig. 5 schematically shows a cutter head 5 provided with cutting elements 3 according to the invention. The cutter head 5 has a central axis 23. In use, the cutter head 5 rotates around the central axis 23.

It will also be obvious after the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person which are within the scope of protection and the essence of this invention and which are obvious combinations of prior art techniques and the disclosure of this patent.

Claims

Conclusions

A cutting element for cutting material in underwater operations, the cutting element comprising at least first and second cutting sections, the first cutting section comprising a first metal alloy and the second cutting section comprising a second metal alloy other than the first metal alloy wherein the first and second cutting section are deposited by means of additive manufacturing and wherein the first and second cutting section are interconnected by melt bonding.

A cutting element according to claim 1, comprising a base section configured to connect to a cutter head, and wherein the base section supports the first and second cutting sections.

3. Cutting element as claimed in any of the foregoing claims, with, in use, a working line, wherein an interface between the first and second cutting section extends transversely to the working line.

4. Cutting element according to a preceding claim, wherein the interface between the first and second cutting section extends substantially parallel to a longitudinal axis of the cutting element.

5. Cutting element according to a preceding claim, wherein the first and second cutting section extend coaxially.

Cutting element according to a preceding claim, wherein the first and second metal alloys differ at least in their elasticity and hardness properties.

The cutting element of any preceding claim, wherein the first cutting section extends at an inner core of the cutting element and the first metal alloy has a Rockwell C (HRc) Hardness between 60-80 HRc, more particularly between 6575 HRc.

A cutting element according to any preceding claim, wherein the first metal alloy has a wear resistance according to ASTM G65-04 Procedure A resulting in a mass loss of about or less than 0.07 g (+/- 0.01) after 6,000 test cycles.

9. Cutting element as claimed in any of the foregoing claims, wherein the second cutting section extends at an outer circumference of the cutting element and the second metal alloy hardens upon impact.

The cutting element according to any preceding claim, wherein the second metal alloy comprises at least Fe, Mn and C.

11. Cutting element according to a preceding claim, wherein the first and second cutting section, in use, extends over a cutting surface of the cutting element.

12. Cutting element as claimed in any of the foregoing claims, wherein the first and second cutting section are melt-bonded over their entire mutual overlap.

A tooth system comprising a basic construction and a cutting element according to any one of the preceding claims 1-12 detachably connected to the basic construction, wherein the basic construction is configured for fixed mounting on a cutting head by means of, for example, welding or mechanical fastening means.

14. Cutting head comprising a cutting element according to a preceding claim 1-12.

A method of manufacturing a cutting element for cutting layers including rock, the cutting element comprising at least first and second cutting sections, the method comprising;

a. depositing a first metal alloy by additive manufacturing to provide the first cutting section,

b. switching from a supply of material from the first metal alloy to a second metal alloy in order to stop depositing the first metal alloy and starting depositing the second metal alloy,

c. depositing a second metal alloy by additive manufacturing to provide the second cutting section such that the first and second cutting sections interconnect through melt bonding.

5

The method of claim 15, wherein step b is without interruption of depositing the first or second metal alloy or a combination thereof.

17. Method according to claim 15 or 16, comprising

d. manufacture the cutting element layer by layer, and switch over at least once

10 from the first metal alloy to the second metal alloy per layer to form the first and second cutting sections.

The method of any one of claims 15-17, wherein step b comprises

e. controlling a ratio between the supply of the first metal alloy and the

Second metal alloy during switching from the first metal alloy to the second metal alloy to configure an interface between the first and second cutting section.

The method of any one of claims 15-18, comprising performing on site

20 of one of steps a-e.

A method according to any of claims 15-19, comprising renovating a damaged cutting element.

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