Method for protecting a mechanical element of a welding assembly from welding resistance and spatter and coated mechanical element of a

Abstract

A method (1) for protecting a mechanical element (A) of a welding assembly from welding residues and spatters for a mechanical element (A) designed to hold together metal parts to be welded; the method comprises the following steps: applying an aluminum powder coating (1) on the surface of a mechanical element (A) to be protected of the welding assembly; and holding the at least two metal parts together with such a mechanical element (A) provided with such a coating (1) so that they are welded to one another.

Description

Technical Field

[0001] The invention relates to a method for protecting mechanical elements of a welded assembly from welding residues and spatters by means of a coating, and the associated coated mechanical elements of a welded assembly (ie also a protective coating for mechanical elements of a welded assembly is defined). Background Art

[0002] Weld spatter is an extremely negative phenomenon that accompanies all welding processes: Weld spatter is formed by droplets of molten metal (the case of molten copper is of particular interest) or, in some cases, also of non-metallic materials, which can be generated during the welding process.

[0003] Small droplets of hot material may be ejected as spatter from welding and impact an area adjacent to the weld of the material to be welded, a mechanical element holding the parts to be welded, or another surrounding area. As the droplets cool, they form small, generally round balls of material where they land.

[0004] The life of the mechanical elements of a laser welding machine is often limited by the adhesion of spatter and particles of molten metal (the case of molten copper is of particular interest) which become attached to the surface and are difficult to remove.

[0005] These deposits are problematic for two reasons: they render the machine element unusable for a short time, especially if the parts to be welded are not perfectly clean or if the welding parameters are particularly critical, thus increasing the generation of spatter; these deposits can change the geometry and color of the machine element to the extent that they constitute a problem for any vision component fitted to the welding machine (the function of which is to control and check the quality of the weld performed, using the contrast of the weld point relative to the machine elements arranged in close proximity).

[0006] As mentioned above, the accumulation of weld spatter on machine elements, such as clamps, fixtures and support elements, in addition to negatively changing the appearance of the machine elements, may also lead to functional degradation over time to the extent that the machine elements cannot perform their function.

[0007] It is known to use protective screens that can be replaced periodically, but this technical solution is not the most suitable for automatic machines since it means introducing periodic maintenance operations that require shutting down the device and incur costs that may be considerable.

[0008] In some cases, machine elements made of materials having poor compatibility with the molten metal generating the spatter (the case of molten copper is of particular interest) may be used so that the spatter does not adhere to the surface of the machine element.

[0009] Unfortunately, however, this strategy is not always feasible, since it is essential that, in many cases, the mechanical elements (in particular, grippers, clamps and similar components designed to hold the parts to be welded) should not experience degradation and / or changes in shape and size and / or softening even at high temperatures (in particular, reaching temperatures close to the melting temperature of the metals to be welded). Summary of the invention

[0010] The object of the present invention is to solve the above-mentioned drawbacks by providing a method for protecting mechanical elements of a welded assembly from welding residues and spatters, which method makes it possible to avoid frequent maintenance operations requiring machine shutdowns.

[0011] Within this aim, an object of the invention is to provide a method for protecting mechanical elements of a welded assembly from welding residues and spatters, which method makes it possible to use mechanical elements consisting of materials with high mechanical strength and high melting and softening temperatures (higher than or equal to the melting and softening temperatures of the parts to be welded).

[0012] Another object of the present invention is to provide a method for protecting mechanical elements of a welded assembly from welding residues and spatter, which method is suitable for providing a coating that ensures that the mechanical elements comprising the coating retain dimensions substantially similar to the initial dimensions even after deposition of such coating.

[0013] Another object of the invention is to provide a method for protecting mechanical components of a welded assembly from welding residues and spatters which increases the service life of the mechanical components subjected to the method.

[0014] Another object of the present invention is to provide a coating for protecting a mechanical element of a welded assembly from welding residues and spatters which minimizes maintenance interventions on the mechanical element comprising the coating.

[0015] Another object of the invention is to provide a coating for protecting mechanical elements of a welded assembly from welding residues and spatters, which coating ensures excellent quality of the welds performed.

[0016] Another object of the present invention is to provide a coating for protecting mechanical elements from welding residues and spatter, and an associated coating for protecting mechanical elements of a welded assembly, which is low-cost, easy and practical to implement, and safe to use.

[0017] This object and these and other purposes, which will become more apparent hereinafter, are achieved by a method for protecting a mechanical element of a welded assembly from welding residues and spatters, the method being intended for a mechanical element designed to hold together metal parts to be welded, wherein the method comprises the following steps:

[0018] - depositing aluminum powder on the surface of the mechanical element to be protected of the welded assembly in order to obtain a coating on the mechanical element;

[0019] - In a welding operation, use is made of a machine element provided with a coating, wherein the coated machine element holds the metal parts together so that they can be welded to each other.

[0020] Such purpose and such aims are also achieved by a coated machine element for holding metal parts to be welded, the element comprising an at least partially coated surface, wherein the coating consists of aluminum powder deposited on the surface in order to protect the machine element from welding residues and spatter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other characteristics and advantages of the invention will become more apparent from the following detailed description of a preferred but non-exclusive embodiment of a coating for protecting mechanical elements of a welded assembly from welding residues and spatters, which embodiment is illustrated by way of non-limiting example in the accompanying drawings, in which:

[0022] Figure 1 is a schematic front elevational view of a first embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0023] Figure 2 is a schematic bottom perspective view of a second embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0024] Figure 3 yes Figure 2 A schematic top perspective view of a mechanical element;

[0025] Figure 4 is a schematic bottom perspective view of a third embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0026] Figure 5 yes Figure 4 A schematic top view of a mechanical element of;

[0027] Figure 6is a schematic front elevational view of a fourth embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0028] Figure 7 is a schematic bottom perspective view of a fifth embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0029] Figure 8 yes Figure 7 A schematic top view of a mechanical element of;

[0030] Fig. 9 is a schematic bottom perspective view of a sixth embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0031] Fig.10 is a schematic bottom perspective view of a seventh embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0032] Fig.11 is a schematic front elevational view of an eighth embodiment of a mechanical element of a welding assembly, in particular a clamping tool, which is provided with a protective coating according to the invention;

[0033] Fig.12 yes Fig.11 A magnified view of the details. DETAILED DESCRIPTION

[0034] With particular reference to the drawings, reference numeral 1 generally designates a coating for protecting a mechanical element A of a welded assembly from welding residues and spatter.

[0035] In particular, the invention is intended for forming a protective coating for a mechanical element A having high mechanical strength: such a mechanical element may therefore be made of a metal or a metal alloy including, for non-limiting example purposes, iron alloys, alloys including titanium, nickel alloys, etc.

[0036] It should be noted that preferably the mechanical element A of the welding assembly is made of steel.

[0037] In order to overcome the aforementioned drawbacks, the possibility of using different technologies to produce a mechanical element A that is located closer to the welding point during its use has been evaluated (the attached figure shows a specific mechanical element A of a welding assembly, which is designed to hold together the parts to be welded, this mechanical element is of a known type and can be subjected to protection measures against material splashes and residues that may be deposited during the welding operation). Three possible alternatives have been identified: using a mechanical element made of steel, the surface of which is laser microstructured; using a mechanical element made of steel with various types of surface deposits; using materials other than steel without additional treatment or deposition.

[0038] Based on preventive checks carried out during research and development activities, it has been found that the option of using laser microstructuring of the surfaces of mechanical components and of using materials other than steel does not give completely satisfactory results (e.g. with regard to the occurrence of oxidation phenomena, excessive increase in costs and complexity of production).

[0039] Specifically, these preventive inspections have indirectly shown that, for the prevention of spatter adhesion on the surface of mechanical elements, the embodiment of the present invention that requires depositing a protective coating on the surface of such mechanical elements of the welding assembly close to the parts to be welded appears to be the most effective solution and the easiest to implement.

[0040] With regard to the deposition of coatings on some of the surfaces of such mechanical elements, it has been demonstrated that, so far, such methods have only been employed for modifying the coefficient of friction of this surface (with reference to the relative movement with respect to another surface), increasing the surface hardness or protecting the surface from oxidation phenomena.

[0041] In the main known applications, no dedicated coatings are envisaged and / or employed for counteracting the adhesion phenomenon of spatters of molten material that may occur during the welding process. In this technical solution, many options have been analyzed, including coatings with low-roughness ceramic materials, coatings with aluminum oxide (Al2O3, also known as aluminum oxide), coatings with titanium nitride (optionally also alloyed with other materials such as aluminum and / or carbon), coatings with aluminum nitride (optionally also alloyed with other materials such as chromium and / or titanium), chromium nitride, coatings with niobium nitride.

[0042] All tests carried out on these types of coatings have shown that they are not suitable for reducing the amount of spatter of molten metal (according to the preferred solution, molten copper) solidifying on and adhering to the surface.

[0043] This preventive experimental phase then enables the identification of a specific type of coating 1 according to the invention and a method of providing this coating.

[0044] The method for protecting a mechanical element A of a welded assembly from welding residues and spatter is applicable to a mechanical element A made of a material capable of withstanding the stresses generated during welding (the material includes a metal, such as some metal alloys having high mechanical strength) and designed to hold metal parts to be welded to each other. The method according to the invention is particularly applicable to protecting a mechanical element A of a welded assembly made of steel.

[0045] In particular, it should be noted that the method according to the invention can be advantageously applied to mechanical elements designed to hold together metal parts to be welded to each other, in particular copper terminals: conveniently, these copper terminals can be parts of windings (for example of electronic machines such as motors, generators, transformers), in which circuit continuity is precisely ensured by welding these ends together.

[0046] The method according to the invention comprises a first step of depositing a powder on the surface of the mechanical element A to be protected of the welding assembly, such powder comprising aluminum (generally a powder of aluminum). The possibility of utilizing aluminum in forms other than powder is not excluded (depending on the specific plasma deposition device used), such as granules, rods, ingots, etc.

[0047] The coating with aluminum powder can be performed using different powder deposition techniques available in the prior art. According to an embodiment, the coating with aluminum powder can be performed using a thermal deposition technique, preferably using plasma, i.e. by plasma plating and / or using a plasma arc as a heat source (using a technique called "plasma transferred arc"). By applying the high temperature generated by the plasma arc, the aluminum powder and the surface of the mechanical element A to be coated are rapidly heated, melted, mixed, spread and solidified.

[0048] After the plasma arc is extinguished, the molten metal cools, solidifies and forms a coating 1 that is perfectly bonded to the surface. By utilizing the plasma arc, the deposition of the aluminum coating 1 occurs quickly while still ensuring excellent stability of the layer on the surface and optimal controllability of the fusion depth.

[0049] The coating 1 consisting of deposited aluminum powder is produced by initially forming a fused joint between the surface of the mechanical element A and the molten aluminum powder, thereby combining them exactly at this joint, which ensures a perfect connection. The mutual dilution of the material constituting the surface (usually steel) and the aluminum coating is minimal, and each material therefore retains its chemical / physical properties.

[0050] After the deposition of coating 1 (as shown in the previous step) is complete, a mechanical element A provided with such layer 1 consisting of a deposit of a powder comprising aluminum, typically aluminum powder, can be utilized to hold specific metal parts together during their welding.

[0051] Thanks to the presence of the coating 1, there will be no accumulation of welding spatter (splashes are splashes, droplets, residues and fragments of molten material which solidify and are welded to the surface of the mechanical element A). In fact, the coating 1 according to the invention, due to the fact that it is at least partially composed of aluminum, ensures that the coating 1 exhibits properties similar to those of aluminum.

[0052] In fact, when subjected to adhesion tests against molten copper splashes, aluminum exhibits ideal properties, since the surface of the machine element that is affected by the molten copper splashes remains completely clean without any molten material splashes adhering to the surface.

[0053] It should be noted that the method according to the invention may also advantageously comprise, after the step of applying the aluminum powder coating, an additional subsequent step of sulfuric acid anodizing carried out on the surface of the coating 1 , which additional subsequent step may affect, by way of non-limiting example, a portion of the total thickness of the coating 1 , of the order of 8 to 10 μm.

[0054] Specifically, such sulfuric acid anodizing will be configured to impart a matte black color to the surface to which it is applied. Such coloring and such matte finishes are particularly useful because they allow a vision system installed at a welded assembly to acquire images of the component (before and after welding) with high accuracy without the treated surface creating noise or deteriorating the quality of the acquired image.

[0055] It should be noted that the method according to the invention can also advantageously include a preliminary preparation step of preparing the surface of the mechanical element A to be protected of the welded assembly, which needs to be performed before applying the aluminum powder coating 1. This preliminary preparation step can in turn consist of at least one operation selected from cleaning, machining, laser machining, plasma machining, photoengraving, laser cleaning, plasma cleaning, etc.

[0056] The term "cleaning" means all industrial cleaning operations that may require the use of water, solvents, detergents and other chemical agents to eliminate any residues of previous processing and any accumulation of material (even of infinitesimal thickness) from the treated surface.

[0057] On the other hand, all the other forms of preliminary processes mentioned (including laser cleaning and plasma cleaning) serve to modify the properties of the surface to be treated (perhaps even just by eliminating the surface oxide film present on the surface) (even just at the microscopic level) in order to make the surface better suited to receive the coating comprising aluminum applied using the plasma coating technique1.

[0058] The possibility cannot be excluded that such operations may even be redundant in some cases.

[0059] It should also be noted that the step of applying a powder deposit on the surface of the mechanical element A to be protected of the welded assembly, wherein such powder comprises aluminum (typically aluminum powder), can advantageously be configured to impart to this surface a surface roughness not greater than 0.6 μm, preferably close to 0.4 μm or in any case below this value.

[0060] The low surface roughness of the coating 1 according to the invention makes it possible to minimize the extent of the surface that will come into contact with molten metal (splatters or fragments or splashes), thereby reducing the risk that these molten metals can adhere to the surface.

[0061] This roughness value can be ensured directly via the deposition of the aluminium powder coating 1 , but does not exclude the possibility of performing (conventional) surface machining to apply the desired surface roughness value.

[0062] It should be noted that the surface of the mechanical element A on which the aluminum powder deposition is performed is preferably composed of an iron alloy, in particular, steel.

[0063] The coating 1 obtained by the method described and consisting at least partially of aluminum ensures high resistance and tolerance to high temperatures: preferably, the coating 1 should be able to withstand temperatures of about 1,800° C. for at least 0.4 seconds without experiencing any kind of damage (in particular, these values ​​relate to the method of welding copper parts and the phenomenon of spatter typical of this material).

[0064] The coating 1 produced with the method according to the invention may also be of the passivating type, or alternatively it may have been passivated by means of a specific method.

[0065] Passivation is a chemical process that enables metals to better withstand the effects of corrosive agents. The result of metal passivation is the formation of a thin, dense and uniform film that protects the metal from oxidants. The passivation film can completely protect the metal by blocking or extremely delaying the chemical process of corrosion. This process will be unpredictable and slow in nature, and can be controlled and accelerated using specific chemical treatments to meet industrial schedules. Taking into account the effects of corrosive agents, ambient temperature and humidity, the most appropriate treatment can be selected based on the environment in which the metal is arranged, taking into account the effects of corrosive agents, ambient temperature and humidity. Specifically, sulfuric acid anodizing is an excellent electrolytic passivation process, preferably used for aluminum coatings. Alternatively, other chemical processes can be used.

[0066] The invention extends its protection to a coated mechanical element A designed to hold metal parts to be welded. This element A comprises a surface at least partially covered with a coating 1; the coating 1 consists of aluminum powder deposited on the surface of the element A to protect the mechanical element A from welding residues and spatters.

[0067] The coating 1 can advantageously be obtained by a deposition method available in the prior art. According to some embodiments, the deposition method is of thermal type, preferably of a type chosen from plasma deposition methods (also known as plasma plating), plasma transferred arc techniques and the like.

[0068] Furthermore, the coating 1 may conveniently have a thickness between 0.1 μm and 1000 μm.

[0069] In more detail, a portion of the coating 1 may advantageously be further subjected to an anodizing process applied on the outer surface of the coating 1. In such a case, the depth of the anodized portion of the coating 1 is distributed over an anodizing thickness that is less than the thickness of the entire coating 1. It is useful to note that there is no exact ratio between the thickness of the coating and the thickness of the anodized layer, but it has been shown that in order to successfully achieve an anodized thickness of 20 μm, the underlying aluminum powder coating must be the maximum achievable so that a sufficient amount of material is actually left for oxidation.

[0070] It is further emphasized that the anodizing process can advantageously be of the sulfuric acid anodizing type; in such a case, the color of the surface of the anodized coating 1 will be matte black.

[0071] The deposition of the coating on element A may advantageously be carried out so as to leave a surface roughness of no greater than 0.6 μm, preferably close to 0.4 μm.

[0072] Finally, it should be noted that the surface of the mechanical element A on which the aluminium powder coating 1 is applied may conveniently be made of an iron alloy, in particular steel.

[0073] The invention can therefore also relate to a coating 1 for protecting a machine element A from welding residues and spatter.

[0074] In particular, the coating 1 according to the invention will be of a type suitable for application on a mechanical element A made of hard material and designed to hold together metal parts to be welded (by way of example: clamping a copper wire terminal that needs to be welded, in order to close an electrical circuit and / or complete an electrical winding).

[0075] It should be noted that the mechanical elements will preferably be made of steel. In particular, high-strength steel (such as, for example, the material sold by the company Bohler under the designation W360) may be used, which may, for example, include about 0.5% carbon, about 0.2% silicon, about 0.25% manganese, about 4.5% chromium, about 3% molybdenum and about 0.6% vanadium. However, the possibility of using different types of steel or other metal alloys or other materials is not excluded, and in particular, stainless steel may be used.

[0076] Such a coating 1 according to the invention comprises at least one layer consisting at least partly of aluminium, which is deposited on at least one of the surfaces of the mechanical element A of the welded assembly to be protected.

[0077] It should be noted that the mechanical element A can be completely coated with the coating 1, or only some surfaces (those facing the parts that will be subjected to being welded together) that are more susceptible to being hit by welding spatter can be selected to be coated with this coating. The accompanying drawings show an embodiment in which the coating 1 is present only on some surfaces to make this convenience clear: however, the possibility of covering the mechanical element A as a whole is not excluded.

[0078] As has been explained in detail previously, the at least one layer that will constitute the coating 1 according to the invention may conveniently be deposited on at least one surface of the mechanical element A and will have a thickness comprised between 0.1 μm and 1000 μm.

[0079] It should also be noted that at least one layer at least partially consisting of aluminium may advantageously be of anodised type, with the anodisation thickness being between 5 μm and 20 μm, preferably between 8 μm and 10 μm.

[0080] It should also be noted that such anodized layer can be of the sulphuric acid type and have a matte black appearance: this appearance has a positive effect since it renders the coating 1 free of optical noise (such as reflections) and it increases the contrast for any vision system whose task is to monitor the parts to be welded in a welded assembly.

[0081] Finally, it should be noted that, as previously explained above, at least one layer may advantageously have a surface roughness of not more than 0.6 μm, preferably close to 0.4 μm or below this value. As previously explained, a low surface roughness reduces the area of ​​the surface on which any weld spatter impinges, thus minimizing the risk of weld spatter adhering to the coating 1.

[0082] The coating 1 according to the invention is particularly advantageous since it can be carried out on steel, the material constituting substantially all the mechanical elements of the welding assembly, including the mechanical equipment, in particular the grippers and fixtures designed to hold the parts to be welded, and since, at least partially consisting of aluminium, it makes it possible to minimise the risk of adhesion of splashes or fragments or spatters of molten material, with particular reference to molten copper.

[0083] Furthermore, the coating 1 according to the invention may be reprocessed after deposition and may therefore be subjected to any kind of treatment, for example a treatment aimed at modifying the surface roughness so that it is as low as possible, for example having values ​​of about 0.4 μm or lower.

[0084] The coating 1 according to the invention will be particularly suitable for withstanding very high temperatures (such as for example the temperature of molten copper) for a time sufficient to ensure that the heat is dissipated without experiencing any kind of damage (for example, the coating 1 according to the invention will be able to beneficially withstand approximately 1800° C. for approximately 0.4 seconds without experiencing any damage or any degradation).

[0085] The surface of the coating 1 according to the invention will be passivated to provide stable properties and to be as similar as possible chemically and physically to the surface of an anodized aluminum sheet (this ensures that the adhesion of splashes and spatters of molten material (particularly molten copper) is significantly reduced to the point of elimination).

[0086] Thus, the application of the method according to the invention, the coated machine element A and the use of the coating 1 according to the invention ensure that the following items are achieved:

[0087] - Extended service life of mechanical element A;

[0088] - prolongation of the time intervals that elapse between successive ordinary maintenance operations (cleaning is usually required more frequently due to splashes of molten material (in particular copper) adhering to the unprotected surfaces of the mechanical element A);

[0089] - Improved stability of the process of welding components (specifically, copper terminals for electrical conductors constituting electrical windings) because the equipment remains cleaner;

[0090] - The quality of the images acquired by an artificial vision system associated with a welding assembly is improved, thereby making it possible to better and more quickly recognize the shapes of the parts to be welded and of the parts already welded.

[0091] Advantageously, the present invention solves the above mentioned problems by providing a method for protecting a mechanical element A of a welding assembly from welding residues and spatters, which method makes it possible to avoid frequent non-routine maintenance operations requiring machine shutdowns.

[0092] Conveniently, the method 1 according to the invention makes it possible to use a mechanical element A consisting of a material having high mechanical strength and high melting and softening temperatures (higher than or equal to the melting and softening temperatures of the parts to be welded).

[0093] Advantageously, the method according to the invention is suitable for providing a coating 1 which ensures that the mechanical element A comprising it retains dimensions substantially similar to the initial dimensions even after deposition of such coating 1. In fact, protection against adhesion of splashes of molten material, in particular molten copper, is ensured even if the thickness of the coating 1 is very thin (close to the lower limit previously mentioned above).

[0094] Advantageously, the method 1 according to the invention increases the useful life of a mechanical element A comprising a coating 1 deposited using this method.

[0095] Conveniently, the coating 1 according to the invention for protecting a mechanical element A of a welded assembly from welding residues and spatters minimizes periodic maintenance interventions on the mechanical element comprising the coating.

[0096] Usefully, the coating 1 according to the invention ensures that the excellent quality of the welds performed is maintained even over extremely long operating times.

[0097] Advantageously, the method and coating 1 according to the invention are relatively easy and practical to implement and are low-cost: these characteristics make the method and coating 1 according to the invention innovative and safe to use.

[0098] The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the appended claims. Furthermore, all the details may be replaced by other technically equivalent elements.

[0099] In the embodiments shown, individual characteristics shown with respect to specific examples may in fact be interchanged with other different characteristics existing in other embodiments.

[0100] In practice, the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.

[0101] The disclosures in Italian Patent Application No. 102022000014680 from which this application claims priority are incorporated herein by reference.

[0102] In case technical features mentioned in any claim are followed by reference signs, the sole purpose of including those reference signs is to increase the intelligibility of the claims and therefore, such reference signs do not have any limiting effect on the interpretation of each element identified by such reference signs by way of example.

Claims

1. A method for protecting a mechanical element (A) of a welded assembly from welding residues and spatter, the method being applied to a mechanical element (A) designed to hold together metal parts to be welded, characterized in that The method comprises the following steps: - depositing aluminum powder on the surface of the mechanical element (A) to be protected of the welded assembly, so as to obtain a coating (1) on the mechanical element (A); - using the machine element (A) provided with the coating (1) in a welding operation, wherein the coated machine element (A) holds metal parts together so that the metal parts are welded to each other.

2. The method according to claim 1, characterized in that The step of aluminum powder deposition is performed by a method selected from the following types: plasma transferred arc technology and plasma deposition, also known as plasma plating, among others.

3. The method according to claim 1, characterized in that After the aluminum powder deposition step, the method comprises a further step of performing sulfuric acid anodization on the surface of the coating (1).

4. The method according to claim 3, characterized in that The sulfuric acid anodizing is performed so that the surface to which the sulfuric acid anodizing is applied has a matte black color.

5. Method according to one or more of the preceding claims, characterized in that Prior to the step of depositing the aluminum powder, the method includes a preparation step of preparing the surface of the mechanical element (A) to be protected of the welding assembly, the preparation step consisting of at least one operation selected from the following items: cleaning, machining, laser machining, plasma machining, photoengraving, laser cleaning, plasma cleaning, etc.

6. Method according to one or more of the preceding claims, characterized in that The step of depositing aluminum powder on the surface of the mechanical element (A) to be protected of the welded assembly is performed so that the surface roughness of said surface is not greater than 0.6 μm, preferably not greater than 0.4 μm.

7. Method according to one or more of the preceding claims, characterized in that The surface of the mechanical element (A) on which the aluminum powder deposition is performed is made of an iron alloy, in particular of steel.

8. A coated mechanical element (A) for holding metal parts to be welded, said element (A) comprising a surface which is at least partially coated with a coating (1), characterised in that The coating (1) consists of aluminum powder deposited on the surface to protect the machine element (A) from welding residues and spatter.

9. The coated mechanical element (A) according to claim 8, characterized in that The coating (1) is obtained by means of a method selected from the following types: plasma transferred arc technology, plasma deposition methods also known as plasma coating, etc.

10. The coated mechanical element (A) according to claim 8 or 9, characterized in that The coating (1) has a thickness between 0.1 μm and 1000 μm.

11. Coated machine element (A) according to one or more of claims 8 to 10, characterised in that A portion of the coating (1) is further subjected to a process of applying anodizing on the outer surface of the coating (1), and wherein the depth of the anodized portion of the coating (1) is distributed over an anodizing thickness that is less than the thickness of the entire coating (1).

12. The coated mechanical element (A) according to claim 11, characterized in that The anodizing process is of sulfuric acid anodizing type, and wherein the surface of the coating (1) after anodizing is matte black.

13. Coated machine element (A) according to one or more of claims 8 to 12, characterised in that The deposited coating (1) formed by performing the deposition has a surface roughness of not more than 0.6 μm, preferably close to 0.4 μm.

14. Coated machine element (A) according to one or more of claims 8 to 13, characterised in that The surface of the mechanical element (A) to which the aluminum powder coating (1) is applied is made of an iron alloy, in particular steel.

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