Method for producing a tyre moulded part, and tyre moulded part

Abstract

The invention relates to a method for producing a tyre moulded part (1) for producing a tyre, comprising at least the following steps: - providing a main body (2) that is made of a metal material and has a surface (5), wherein the surface (5) forms a negative mould for at least one region of a tyre blank to be vulcanised; - introducing the provided main body (2) into a treatment chamber and treating the main body (2) at a defined temperature with a defined nitrogen concentration for a defined treatment time such that nitrogen diffuses into the metal main body (2) from the surface (5) of the main body (2) to a penetration depth (NT) and forms a nitriding layer (4) in an edge region (3) of the main body (2); - applying a coating (6) to the surface (5) of the main body (2); and - providing the finished tyre moulded part (1).

Description

[0001] 202404118

[0002] Description

[0003] Method for manufacturing a tire molded part and tire molded part

[0004] The invention relates to a method for manufacturing a tire molded part and to a tire molded part manufactured therein.

[0005] To protect tire components used in tire manufacturing, especially sidewall and tread components, from contamination and wear of all kinds, various surface coating processes are employed, generally based on chemical or physical vapor deposition (CVD or PVD processes). Common coating systems used in tire manufacturing are created, for example, by depositing chromium nitride onto the surface of the respective metallic components. These coating systems produce particularly hard wear-resistant layers that often exceed the hardness of the substrate or the component itself many times over.

[0006] Such coating systems are also used in a wide variety of applications as wear protection measures (e.g., for milling or forming tools), as these coatings effectively reduce a broad spectrum of wear mechanisms, such as abrasive, adhesive, or thermal wear. However, as numerous studies in other applications have shown, the abrupt hardness gradient between the coating and the substrate on which the coating is applied plays a crucial role in the coating's durability.

[0007] The high hardness of a surface coating, even one only a few millimeters thick, results in a so-called "eggshell effect" (hardness jump), which is also the primary cause of premature coating failure and thus the loss of wear protection. Since the coating lacks the necessary support from the substrate, various wear mechanisms can lead to premature destruction or unwanted changes in the surface layer's properties. Consequently, the layer can flake off, crack, or become damaged in places, leading to a subsequent increase in abrasion and adhesion, etc.

[0008] The following invention is therefore based on the objective of providing a method for producing tire moldings with high resistance and durability. A further objective of the invention is to provide a durable and long-lasting tire molding.

[0009] These tasks are solved by a method and a tire mold according to the independent claims. The dependent claims specify preferred embodiments.

[0010] According to the invention, a method for producing a tire mold for tire manufacturing is provided, comprising at least the following steps:

[0011] - Providing a base body made of a metallic material with a surface, wherein the surface forms a negative mold for at least one area of ​​a tire blank to be vulcanized;

[0012] - Placing the provided base body in a treatment chamber and treating the base body at a defined temperature with a defined nitrogen concentration for a defined treatment time, so that nitrogen diffuses from the surface of the base body to a penetration depth into the metallic base body and a nitrided layer forms in an edge region of the base body, preferably with a specific nitrogen concentration or density decreasing towards the surface, so that a specific nitriding hardness profile is formed, preferably such that the hardness of the base body in the edge region gradually decreases with increasing distance from the surface of the base body; 202404118

[0013] - Applying a coating to the surface of the base body to complete the tire mold, wherein several such tire molds are then subsequently joined together segmentally for a corresponding system in order to provide a preferably completely rotating negative mold for the tire to be vulcanized.

[0014] The fundamental idea of ​​the invention lies in a gradual adjustment of the hardness gradient of the edge region of the metallic tire molding to ensure increased edge support through the application of a combined surface and edge layer modification based on CVD or PVD processes in combination with a prior nitriding treatment. By adjusting such a hardness gradient, which gradually decreases from the surface of the tire molding, the "eggshell effect" is compensated for, thus achieving a longer service life of the coated tire moldings.

[0015] This is particularly useful in the area of ​​sidewalls and bead rings in tire molds for passenger cars, especially winter tires. Sidewalls and bead rings of winter tires typically exhibit a strong tendency towards adhesive wear and additional surface abrasion, where material components of the sidewall or rim strip compound are deposited on the sidewalls or bead rings due to friction. With increasing heating cycles of the segmented tire mold, these material deposits develop a glossy surface (glossy sidewall or glossy bead), which is transferred to the heated tires. The visual appearance of such tires is impaired and can lead to a heated tire being considered reject and destroyed. However, the present invention can prevent or delay this, thus increasing the service life of the coated tire mold components. 202404118

[0016] Preferably, the penetration depth of the nitrogen into the base body is between 50pm and 500pm, so that the thickness of the nitriding layer can be specifically adjusted according to the application and thus a correspondingly sufficient support effect can be achieved.

[0017] For this purpose, the base body can preferably be treated in the treatment chamber by a gas nitriding process, a plasma nitriding process, or a bath nitriding process to diffuse the nitrogen from the surface of the base body to the required penetration depth into the metallic base body, preferably resulting in compound-layer-free nitriding without a pore border. This leads to increased flexibility and adaptability to the respective tire compound or manufacturing process in which the respective tire molded part is used.

[0018] Those skilled in the art are familiar with the temperatures, nitrogen concentrations, and treatment times within the respective nitriding process which, with a suitable material selection for the substrate, lead to nitrogen diffusion to the specified penetration depth. The precise profile of the nitriding process can also be specifically adjusted by selecting the respective parameters in order to achieve an additional support effect according to the principles of the invention, depending on the application.

[0019] Preferably, a coating with a thickness of between 1 pm and 10 pm is applied to the surface of the base body, preferably a chromium nitride coating to obtain a highly durable and hard wear-resistant layer. It is preferably possible to apply the coating using a CVD or PVD process, thereby ensuring a uniform and durable coating. 202404118

[0020] According to the invention, a tire molding part for tire production is further provided, which is produced in particular by the inventive method and has at least the following features:

[0021] - a base body with a surface made of a metallic material, wherein the surface forms a negative mold for at least one area of ​​a tire blank to be vulcanized, and

[0022] - a coating applied above the surface of the base body, wherein a nitriding layer extends from the surface into the base body in an edge region up to a penetration depth.

[0023] Preferably, the tire molded part can be part of a bead ring, a side shell, or a tread ring, which come into contact with the tire compounds during manufacturing and are therefore subject to increased wear.

[0024] The drawings show:

[0025] Fig. 1 shows a schematic view of a tire mold part;

[0026] Fig. 2 shows a hardness distribution; and

[0027] Fig. 3 shows an exemplary process flow for the production of a tire mold part.

[0028] Figure 1 schematically shows a section of a tire mold 1, which has a metallic base body 2. In an edge region 3 of the metallic base body 2, a nitrided layer 4 is formed by the method according to the invention as described below. A coating 6, for example chromium nitride, is also applied to a surface 5 of the edge region 3 to create a hard wear-resistant layer. The surface 5 of the edge region 3, and thus also an outer surface 7 of the uniformly 202404118

[0029] The thickness D of the coating 6 applied to it has the shape of the respective tire component to be formed (e.g. sidewall, tread, etc.), thus forming the negative shape of a tire blank to be vulcanized.

[0030] Figure 2 shows the hardness H of the individual layers of the tire mold 1 as a function of the distance A to the outer surface 7 of the coated tire mold 1. It can be seen that the hardness H decreases continuously or gradually, i.e., non-abruptly, with increasing distance A to the outer surface 7. Depending on the setting of the process parameters for forming the nitrided layer 4, the gradual decrease in hardness can be adjusted. Additionally, Figure 2 shows, in dashed lines, the hardness H profile according to the prior art, in which the tire mold 1 has a coating 6 but no nitrided layer 4 in the edge region 3 of the base body 2. Accordingly, a jump in hardness H is to be expected at the transition between the base body 2 and the coating 6, leading to a so-called "eggshell effect." Since this has negative effects on the durability of the wear-resistant layer, the tire mold 1 is treated according to the following diagram in Figure 2.3 methods shown:

[0031] In an initial step ST0, the base body 2 of the tire component 1 is first provided. This base body is manufactured in a previous step from a metallic material with a surface 5 corresponding to the shape of the respective tire component. In a first step ST1, the provided base body 2 is then subjected to a diffusion treatment, the so-called "nitriding." In such a diffusion treatment, nitrogen N is diffused into the surface region 3 of the metallic base body 2 within a controlled gas or plasma atmosphere in a treatment chamber. Alternatively, a bath nitriding process is also possible. The nitrogen N reacts with the alloying elements of the metallic base body 2 in its surface region 3 to form nitrogen compounds (nitrides), which exhibit high hardness, thus forming the N nitride layer 4. 202404118

[0032] Since the diffusion rate, and thus the nitride formation, is time-dependent, a broad, application-specific, gradual nitriding profile or nitriding hardness profile for the nitrided layer 4 can be achieved by adjusting the treatment time t in the treatment chamber, the temperature T in the treatment chamber, and the nitrogen content nN in the gas, plasma, or bath within the treatment chamber, as illustrated by example in Fig. 2. The resulting nitrided layer 4 can be fundamentally characterized by the achieved nitrogen penetration depth NT, the so-called nitriding case depth, and the surface layer hardness. Penetration depths NT of a few micrometers to several millimeters are possible. Preferably, the respective nitriding process is carried out in such a way that nitriding is performed without compound layers or pore rims.

[0033] Subsequently, in a second step, the coating 6 is applied to ST2 using a CVD or PVD process, i.e., chemical or physical vapor deposition. For this purpose, gaseous layer components, for example chromium (Cr) and nitrogen (N), flow around the surface 5 of the edge region 3 of the base body 2, i.e., above the nitrided layer 4, at temperatures of approximately 1,000 °C. These gaseous layer components then react with elements from the edge region 3 of the base body 2, resulting in the formation of a coating 6 with very high hardness that superficially covers the edge region 3 above the nitrided layer 4.

[0034] In this way, a tire mold 1 with a combined surface and edge layer modification can be provided in a final step ST3. This mold 1 was produced using a CVD or PVD process in combination with a preceding diffusion treatment. The corresponding system can then be assembled segmentally from several of these tire mold 1s. Figure 2 shows the hardness distribution for such a tire mold 1. With an edge layer 3 produced in this way, including a nitrided layer 4, a so-called "eggshell effect" can no longer occur, as the very hard coating 6 is ideally supported by the gradual decrease in hardness in the nitrided layer 4. The wear-reducing properties of the surface coating 6 are thus made available for a larger number of cycles before the tire mold 1 needs to be recoated.

[0035] This saves not only setup time but also resources for the costly (re-)coating of the tire mold 1. The number of defect-free tires that can be produced with a tire mold 1 treated in this way increases.

[0036] Such a combined surface and edge layer treatment for tire components 1 is applicable to all tire components 1 made of a steel material that come into contact with tire compounds. For passenger car tires, these are the bead rings and sidewalls as tire components 1. For truck tires and specialty tires, the so-called tread rings, which are made of steel alloys, are also included as tire components 1.

[0037] 202404118

[0038] Reference symbol list

[0039] 1 tire mold

[0040] 2 basic shapes

[0041] 3 Edge area

[0042] 4 Nitriding layer

[0043] 5 Surface

[0044] 6 coating

[0045] 7 Outdoor area

[0046] A distance

[0047] Chromium

[0048] D Coating thickness 6

[0049] H hardness

[0050] N nitrogen nN nitrogen content

[0051] NT penetration depth

[0052] Treatment time

[0053] Temperature

[0054] STO, ST1, ST2, ST3 Steps of the procedure

Claims

202404118 Patent claims 1. Method for producing a tire molded part (1 ) for tire manufacturing, comprising at least the following steps: - Providing a base body (2) made of a metallic material with a surface (5) wherein the surface (5) forms a negative shape for at least one area of ​​a tire blank to be vulcanized (ST0); - Place the provided base body (2) into a treatment room and treat the base body (2) at a specified temperature (T) with a specified nitrogen concentration (nN) for a specified treatment time (t), so that nitrogen (N) diffuses from the surface (5) of the base body (2) to a penetration depth (NT) into the metallic base body (2) and a nitriding layer (4) forms in an edge region (3) of the base body (2) (ST1 ); - Applying a coating (6) to the surface (5) of the base body (2) (ST2); and - Providing the finished tire mold part (1 ) (ST3).

2. Method according to claim 1, characterized in that the nitriding layer (4) is formed in such a way that the hardness (H) of the base body (2) in the edge region (3) gradually decreases with increasing distance (A) to the surface (5) of the base body (2).

3. Method according to claim 1 or 2, characterized in that the penetration depth (NT) of the nitrogen (N) into the base body (2) is between 50pm and 500pm.

4. Method according to one of the preceding claims, characterized in that 202404118 the base body (2) in the treatment chamber is treated by a gas nitriding process or a plasma nitriding process or a bath nitriding process in order to diffuse the nitrogen (N) from the surface (5) of the base body (2) to the penetration depth (NT) into the metallic base body (2).

5. Method according to one of the preceding claims, characterized in that nitriding is carried out without a compound layer and without a pore border.

6. Method according to one of the preceding claims, characterized in that a coating (6) with a thickness (D) of between 1 pm and 10 pm is applied to the surface (5) of the base body (2), preferably a coating (6) of chromium nitride.

7. Method according to one of the preceding claims, characterized in that the coating (6) is applied by a CVD process or a PVD process.

8. Tire molded part (1) for tire production, in particular produced by a method according to one of the preceding claims, comprising at least: - a base body (2) with a surface (5) made of a metallic material, wherein the surface (5) forms a negative shape for at least one area of ​​a tire blank to be vulcanized, and - a coating (6) applied above the surface (5) of the base body (2), characterized in that, starting from the surface (5) in an edge region (3) of the base body (2) up to a penetration depth (NT), a nitriding layer (4) is applied into the base body (2). 202404118 is running.

9. Tire molded part (1 ) according to claim 8, the nitriding layer (4) is designed such that the hardness (H) of the base body (2) in the edge region (3) gradually decreases with increasing distance (A) to the surface (5) of the base body (2).

10. Tire molded part (1 ) according to claim 8 or 9, characterized in that the tire molded part (1 ) is a component of a bead ring or a side shell or a tread ring.

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