Method for manufacturing a component, component and gas hob

The present invention relates to a method for manufacturing a component for a gas hob, a component for a gas hob, and a gas hob.

Usually, gas hobs comprise a top sheet and a gas burner arranged at a through-hole of the top sheet. The gas hob may comprise a pan support. Such a pan support may be provided as a removable part, e.g. for facilitating cleaning the top sheet and/or the pan support itself. Pan supports are configured to hold the pan above the flames of the gas burner in operation. The gas hob may have further parts, in particular profiles, which are visible for a user of the gas hob and which, thus, may provide an aesthetic value as gas burners and pan supports. The gas burner, the pan support and the further parts of the gas hob may be made of aluminum. Such parts may be subjected to wear during cleaning and, thus, should have an increased abrasion resistance and chemical resistance.

It is one object of the present invention to provide an improved method for manufacturing a component for a gas hob.

Accordingly, a method for manufacturing a component for a gas hob is provided. The method comprises treating a surface by plasma electrolytic oxidation (PEO).

This has the advantage that a component for a gas hob can be provided which has a high degree of hardness. The Vickers hardness (HV) may be greater than 1000 HV, in particular 1000 HV 10 or in particular 1000 HV 30 (according to ISO 6507-1 to ISO 6507- 4). Thus, the cleanability, abrasion and wear resistance of the component can be improved. Therefore, the component can withstand aggressive cleaning agents or materials using for example hard metallic pads to remove burnt food and the like. Further, a PEO coating has a high elastic module such that the elastic recovery rate of the PEO coating provides sufficient deformation ability under shear stress preventing cracking. Furthermore, when using PEO, a costly preparation of the surface before the treatment is not absolutely necessary. Additionally, it is possible to get new aesthetics, in particular colors or matt/glossy finishes. The gas hob may be provided as part of a gas stove. Plasma electrolytic oxidation, also known as electrolytic plasma oxidation (EPO) or microarc oxidation (MAO), is an electrochemical surface treatment process for generating oxide coatings on metals. It is similar to anodizing, but it employs higher potentials, so that discharges occur and the resulting plasma modifies the structure of the oxide coating. This process can be used to grow thick (tens or hundreds of micrometers), largely crystalline, oxide coatings on metals, e.g. such as aluminum, magnesium and titanium. Because they exhibit high hardness and a continuous barrier, these coatings can offer protection against wear, corrosion or heat as well as electrical insulation.

PEO comprises the steps of:

a) providing a substrate, in particular a semi-finished product, having the surface, b) bringing the substrate into contact with an electrolyte, in particular at least partially or completely immersing the substrate in the electrolyte,

c) connecting the substrate as an anode to a voltage source, and

d) applying a voltage between 200 - 900 V, in particular 300 - 900 V, 400 - 900 V or 500 - 900 V, by means of the voltage source.

Preferably, treating the surface is done with a current density of less than 0.3 A/cm ² . In particular, the component is an outer or exterior part of the gas hob, e.g. which is visible for a user of the gas hob when standing in front of the gas hob. Preferably, the component is a part of the gas hob which is configured to be removably coupled to the gas hob, in particular to a top sheet of the gas hob. Preferably, the substrate is made of a metal. In particular, the substrate is manufactured by means of die-casting or stamping.

According to an embodiment, the component is a gas burner, a pan support or a profile part, in particular a rear, front or side profile.

Thus, a gas burner, a pan support or a profile part can be provided having a hard and durable coating.

According to a further embodiment, the method comprises a step of providing a semi finished product having the surface, wherein the semi-finished product is made of an aluminum alloy. This has the advantage that a hard coating can be provided on the aluminum alloy by means of PEO. Aluminum components can be produced as cost-efficient light weight parts. Preferably, the semi-finished product has a gas burner shape (e.g. disk shape), a pan support shape (e.g. grid shape) or a, in particular elongated, profile shape (e.g. bar shape).

According to a further embodiment, the aluminum alloy comprises copper and/or magnesium and/or silicon.

Preferably, the aluminum alloy comprises a silicon content between 0,4 - 12%. This has the advantage that a casting process of the alloy is facilitated.

According to a further embodiment, the aluminum alloy is AISi9Cu3(Fe), AISi11Cu2(Fe) or AIMgSil

AISi9Cu3(Fe) preferably comprises a silicon content between 0,8 - 12%, in particular 8 - 11% and can e.g. be referred as EN AC 46000. AISi11Cu2(Fe) preferably comprises a silicon content between 10 - 11% and can e.g. be referred as EN AC 46100. AIMgSil preferably comprises a silicon content between 0,4 - 0,8% and can e.g. be referred as EN AW 6081.

According to a further embodiment, the treating of the surface comprises manufacturing a coating on the surface.

Such a PEO coating may comprise oxidized elements of the substrate metal and components of the electrolyte. For example, the coating comprises predominantly aluminum alloy and other components derived from the electrolyte or from the aluminum alloy. Preferably, the coating covers a complete surface of the substrate.

According to a further embodiment, the surface treated until a thickness of the coating between 40 and 50 pm is obtained.

This has the advantage that the hardness of the component can significantly be increased. The thickness of the coating can be adjusted by means of the time applying PEO and the coating rate. Preferably, treating of the surface is conducted until the thickness of the coating between 43 and 48 pm is achieved.

According to a further embodiment, AI ₂ O ₃ and/or CUAI ₂ O ₄ and/or MgCu ₂ C> ₄ and/or AISiOOH and/or AI ₂ Si ₂ 0 ₅ (0H) ₂ is formed in the coating.

In particular, the coating comprises a-AI ₂ C> ₃ (e.g. up to 70%) and/or CuAI ₂ C> ₄ and/or MgCu ₂ C> ₄ , in particular when the substrate is an Al-Cu-Mg alloy. Preferably, the coating may comprise a and/or Y-AI2O3, in particular 10-20%, in particular mainly mullite

(AleOi ₃ Si ₂ ), in particular when the substrate is an Al-Si alloy having more than (i.e. ³) 0,5% silicon (high Si alloys). In particular, the coating comprises a-A^Ch (e.g. up to 60%) and/or g- AI2O3 and/or AISiOOH and/or AL ₂ Si ₂ 0s(0H) ₂ , in particular when the substrate is an Al- Si alloy having less than (i.e. £) 0,5% silicon (low Si alloys).

According to a further embodiment, the method comprises the step of pretreating the surface with abrasive particles.

It has been observed that the pretreatment of the surface with abrasive particles result in a more homogenous coating growth with a higher coating rate resulting in a greater thickness of the coating. Preferably, the surface is pretreated by polishing, in particular with greenstone. In particular, the surface is polished between 20 and 30 min, in particular 25 min. This has the advantage that a bonding between the coating and the substrate is facilitated. Additionally or alternatively, the pretreatment comprises, e.g. only, a light degrease.

According to a further embodiment, the treating comprises immersing the surface in an electrolyte, wherein the electrolyte comprises an alkaline solution, free chrome and/or free vanadium and/or free nickel.

Preferably, the electrolyte has a pH value between 10 - 12. In particular, the total salt content is less than 4%.

According to a further embodiment, the plasma electrolytic oxidation treating is conducted 5 to 50 min. This means that the substrate is immersed in the electrolyte, connected to the voltage source and that the voltage source is activated.

According to a further embodiment, a process temperature is between 10 - 30°C when treating the surface.

This may mean that the temperature of the electrolyte and/or the substrate is between 10 - 30°C.

According to a further embodiment, a coating rate is between 1 and 5 pm/min.

Preferably, the coating rate is between 3 and 5 pm/min. Thus, a treating time can be reduced.

Further, a component for a gas hob is provided. The component is obtained by the method as described herein.

According to a further embodiment, the component is a gas burner, a pan support or a profile part, in particular a rear, front or side profile.

The gas burner may be disk shaped and/or may have channels for channelizing a gas air mixture. The gas burner may comprise an opening (or openings) on a bottom face for receiving the gas air mixture and upper gas burner openings for releasing the gas air mixture. The pan support may comprise a frame and a plurality of fingers and/or a grid structure.

Furthermore, a gas hob comprising such a component is provided.

The gas hob comprises the top sheet, at least one gas burner and/or the pan support. The gas burner and the pan support may be removably coupled to the top sheet. Further, the gas hob may comprise the profile part, in particular the rear and/or front and/or side profile, which may be an outer part of the gas hob. The embodiments and features described with reference to the method of the present invention apply mutatis mutandis to the component and the gas hob of the present invention and vice versa.

Further possible implementations or alternative solutions of the invention also encompass combinations - that are not explicitly mentioned herein - of features described above or below with regard to the embodiments. The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention.

Further embodiments, features and advantages of the present invention will become apparent from the subsequent description and dependent claims, taken in conjunction with the accompanying drawings, in which:

Fig. 1 shows a schematic view of a gas hob;

Fig. 2 shows schematically a PEO process;

Fig. 3 shows a schematic cross-section of a component; and

Fig. 4 shows a block diagram of a method for manufacturing the component.

In the Figures, like reference numerals designate like or functionally equivalent elements, unless otherwise indicated.

Fig. 1 shows a gas hob 1. The gas hob 1 comprises a top sheet 2 at which a gas burner 3 and a pan support 4 are arranged. The pan support 4 is configured to hold a pan or pot above the gas burner 3. Preferably, a further gas burner 5 or gas burners and a further pan support 6 or pan supports are provided. One pan support 6 may, for example, be provided for one gas burner 3. Alternatively, the pan support 4 may be provided for two, three, four or five gas burners surrounding the same. In particular, the gas hob 1 comprises a profile part 7, 8, 9, in particular a rear profile 7 and/or a side profile 8, 9. The profile part may e.g. be provided as front profile. Fig. 2 shows a PEO process 10. A receptacle 11 is provided which contains an electrolyte 12. A substrate 17 is immersed into the electrolyte 12. The substrate 17 is for example a semi-finished gas burner 3, 5, pan support 4, 5 or the profile part 7, 8, 9, in particular a rear 7 or side profile 8, 9, from Fig. 1. Further, the substrate 17 is connected to a voltage source 14 as an anode. Furthermore, a cathode 15 is connected to the voltage source 14. The cathode 15 may be a separate body immersed in the electrolyte 12. Alternatively, the receptacle 11 may be used as cathode. The substrate 17 is provided as semi-finished product having a surface 16 which is in contact with the electrolyte 12 during the PEO process.

PEO is a high voltage electrochemical process which generates a plasma-discharge in the metal-electrolyte interface so that the surface 16 may be transformed into a hard and dense ceramic oxide coating 18 (see Fig. 3). The composition of such a ceramic coating involves oxides and components of the electrolyte 12. Plasma discharges occur when the voltage applied exceeds a "breakdown value" (usually several hundred volts). PEO process involves creation of a plasma discharge around the substrate 17 immersed in a bath of electrolyte 12. The electrolyte 12 may comprise silicate, phosphates, fluorides, free of chrome and/or vanadium and/or nickel, in particular having a total salt content less than 4%. The pH of the electrolyte 12 varies between 10-12. Therefore, the electrolyte 12 and the PEO process are environmentally acceptable. The mechanism of oxide layer formation during the PEO process may involve oxide growth with subsequent fusing, re crystallization of the oxide film and also partial substrate metal dissolution at microscopic levels.

During the PEO process 10 the voltage source 14 preferably produces a voltage between 200-900V. As the PEO process 10 uses controlled high voltage power, the productivity of this process is high. A density of current is preferably less than 0.3A/cm ² . A process temperature is e.g. between 10 - 30°C when treating the surface 16.

Further advantages of PEO are that e.g. it is not necessary to pretreat the surface 16. Alternatively, the surface 16 can be polished or grinded for increasing a bonding effect to the hard ceramic coating 18 (see Fig. 3). Components 3, 4, 5, 6, 7, 8, 9 treated with PEO show a high corrosion resistance. For example, when using aluminum as substrate being treated with PEO, the component 3, 4, 5, 6, 7, 8, 9 can stay more than 2000 hours inside the salt spray chamber until corrosion appears, according to ISO 9227. Compared to that, a substrate treated with hard anodizing achieves 1000 hours, a substrate treated with electroless nickel plating achieves 500 hours, and hard chrome achieves less than 100 hours. The external porosity of the PEO coating is appropriate for the application of paint or lacquer. Further, it is possible manufacture a colored surface by adding suitable reagents to the electrolyte 12.

Fig. 3 shows a cross-section of the component 3, 4, 5, 6, 7, 8, 9. The component 3, 4, 5,

6, 7, 8, 9 comprises the substrate 17 and a coating 18 on the substrate 17, wherein the coating 18 is manufactured by PEO. Preferably, the substrate 17 is made of an aluminum alloy which comprises copper and/or magnesium and/or silicon. The aluminum alloy is e.g. AISi9Cu3(Fe), AISi11 Cu2(Fe) or AIMgSil The coating 18 is manufactured on the former surface 16 which is now covered by the coating 18. A thickness 19 of the coating 18 may be between 20 and 50 pm, in particular 40 and 50 pm. The coating 18 comprises a, Y -AI2O3 and/or CUAI2O4 and/or MgCu204 and/or AISiOOH and/or AfeS^OsiOH^

In particular, the coating 18 comprises a and or Y-AI2O3 (e.g. up to 70%) and/or CUAI2O4 and/or MgCu2C>4, in particular when the substrate 17 is an Al-Cu-Mg alloy. Preferably, the coating 18 may comprise a and/or Y-AI2O3, preferably 10-20%, in particular mainly mullite (AleOi ₃ Si ₂ ), in particular when the substrate 17 is an Al-Si alloy having more than 0,5% silicon (high Si alloys). In particular, the coating comprises a-A^Ch (e.g. up to 60%) and/or Y-AI2O3 and/or AISiOOH and/or AbShOsiOH^, in particular when the substrate 17 is an Al- Si alloy having less than 0,5% silicon (lower Si alloys).

It is advantageous to provide a thickness 19 of the coating 18 which is less than 50 microns in order to achieve the minimum possible porosity that is important to facilitate the cleaning of these parts in use.

Aluminum treated with PEO may achieve a Vickers hardness around 2000 HV, in particular 2000 HV 10 or 2000 HV 30 (according to ISO 6507-1 to ISO 6507-4). and is, thus, harder than hard chrome, hardened tool steel, hard anodized aluminum, stainless steel, mild steel and aluminum. For example, a Vickers hardness of 1 150 ± 83 HV, in particular 1150 ± 83 HV 10 or in particular 1 150 ± 83 HV 30 (according to ISO 6507-1 to ISO 6507-4). of the component 3, 4, 5, 6, 7, 8, 9 has been tested when using AIMgSh for the substrate 17 and a thickness 19 of the coating 19 between 44 and 50 pm. In this example, the surface 16 has been polished with greenstone (e.g. 25 min) before applying PEO. Further, a current density of 220 mA/cm ² , a voltage between 300 - 600 V, a process temperature between 10 - 30 °C and a coating rate between 1 - 5 pm/min has been provided as process parameters of the PEO process 10 (see Fig. 2). As electrolyte 12 an aqueous alkaline solution having free Cr and V has been used. It has been observed that the pretreatment of the surface 16 with abrasive particles result in a more homogenous coating growth with a higher coating rate resulting in a greater thickness 19 of the coating 18.

Fig. 4 shows a block diagram of the method for manufacturing the component 3, 4, 5, 6, 7, 8, 9 for the gas hob 1. In a step S1 the substrate 17, in particular a semi-finished product, having the surface 16 is provided. In an optional step S2 the surface 16 is pretreated by means of degreasing and/or polishing the same. In a step S3 the substrate 16 is immersed into the electrolyte 12. In a step S4 the substrate 16 is connected as the anode to the voltage source 14. In a step S5 a voltage between 200 - 900 V, in particular 300 - 900 V, 400 - 900 V or 500 - 900 V, is applied by means of the voltage source 14. After forming the coating 18 on the substrate 17 a step S6 of painting the component 3, 4, 5, 6, 7, 8, 9 or an additional coating can be provided.

Although the present invention has been described in accordance with preferred embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments.

Reference Numerals:

1 gas hob

2 top sheet

3 burner

4 pan support

5 burner

6 pan support

7 profile

8 profile

9 profile

10 PEO process set up

11 receptacle

12 electrolyte

14 voltage source

15 cathode

16 surface

17 substrate

18 coating

19 thickness

51 step

52 step

53 step

54 step

55 step

56 step