Pipe product and method for producing same

Abstract

The present invention relates to a tube product (1) with a base tube (10) made of a steel alloy with an inner circumference surface and an outer circumference surface, wherein the base tube (10) has a coating system (100) on at least part of the circumference surfaces, which has the following layer structure: zinc layer (11) with a predominant zinc portion; passivation layer (12), which is Cr-VI-free; sealing layer (13)
characterized in that the zinc layer (11) comprises at least three tiers (110), the sealing layer (13) has organic compounds which are based on plastics and the sealing layer (13) on the passivation layer (12) has a layer thickness between 0.5 and 15 m. Furthermore the invention relates to a method for manufacturing such tube product (1).

Claims

1. Tube product (1) with a base tube (10) made of a steel alloy with an inner circumference surface and an outer circumference surface, wherein the base tube (10) has a coating system (100) on at least part of the circumference surfaces, which has the following layer structure: zinc layer (11), wherein the majority of the zinc layer (11) comprises zinc; passivation layer (12), which is Cr-VI-free; sealing layer (13) characterized in that the zinc layer (11) comprises at least three tiers (110), the sealing layer (13) has at least one from the group consisting of acrylate, polyester, polyacrylate, and nanoscale silicon oxide particles or silicates, and the sealing layer (13) on the passivation layer (12) has a layer thickness between 0.5 and 15 m.

2. Tube product according to claim 1, characterized in that the sealing layer (13) has acrylate, polyester and/or polyacrylate at a portion of at least 70%.

3. Tube product according to claim 1, characterized in that the tiers (110) in the zinc layer (11) each have a layer thickness from 1 m to 10 m.

4. Tube product according to claim 1, characterized in that the zinc layer (11) has an overall layer thickness in the range from 3 to 40 m.

5. Tube product according to claim 1, characterized in that the sealing layer (13) on the passivation layer (12) has a layer thickness between 0.9 m and 10 m.

6. Tube product according to claim 1, characterized in that a formed tube bend sample of the tube product (1) with a bending angle of 180 and a bending radius of at least 1.5outer tube diameter has a white rust resistance of at least 24 hours in the neutral salt spray test according to DIN EN ISO 9227.

7. Tube product according to claim 6, characterized in that the tube bend sample of the tube product (1) has a length section, which is arch shaped in the axial direction, wherein the bending radius at the outer circumference surface is 2.5outer tube diameter.

8. Tube product according to claim 1, characterized in that the zinc layer (11) has an overall layer thickness in the range from 4 to 25 m.

9. Tube product according to claim 1, characterized in that the sealing layer (13) on the passivation layer (12) has a layer thickness in the range from 0.5 m to 5 m.

10. Tube product according to claim 1, characterized in that the sealing layer (13) on the passivation layer (12) has a layer thickness in the range from 0.5 to 3 m.

11. Tube product according to claim 1, characterized in that a formed tube bend sample of the tube product (1) with a bending angle of 180 and a bending radius of at least 1.5outer tube diameter has a white rust resistance of at least 96 hours in the neutral salt spray test according to DIN EN ISO 9227.

12. Tube product according to claim 1, characterized in that a formed tube bend sample of the tube product (1) with a bending angle of 180 and a bending radius of at least 1.5outer tube diameter has a white rust resistance of at least 168 hours in the neutral salt spray test according to DIN EN ISO 9227.

13. Method for manufacturing a tube product, characterized in that the method at least comprises the following steps for applying a coating system (100) onto a base tube (10): applying at least three tiers (110) of a zinc layer (11) onto the base tube (10) made of a steel alloy, wherein the majority of the zinc layer (11) comprises zinc; applying a Cr-VI-free passivation agent for creating a passivation layer (12) on the zinc layer (11); applying a sealing agent, wherein the sealing agent has at least one from the group consisting of acrylate, polyester, polyacrylate, and nanoscale silicon oxide particles or silicates, onto the passivation layer (12) for creating a sealing layer (13) with a layer thickness between 1 and 15 m.

14. Method according to claim 13, characterized in that the method steps for applying the coating system (100) are carried out as a continuous method.

15. Method according to claim 13, characterized in that the throughput rate is at least 5 m/min.

16. Method according to claim 13, characterized in that the tube product is formed after the application of the coating system (100).

17. Method according to claim 13, characterized in that the tube is heated before and/or after the application of the sealing layer (13).

18. Method according to claim 13, characterized in that the throughput rate is at least 10 m/min.

19. Method according to claim 13, characterized in that the tube product is bent after the application of the coating system (100).

20. Method according to claim 17, characterized in that the tube is inductively heated before and/or after the application of the sealing layer (13).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described again with reference to the enclosed drawings, wherein:

(2) FIG. 1 shows a schematic block diagram of a line for carrying out one embodiment of the method according to the invention;

(3) FIG. 2 shows a schematic depiction of an embodiment of the tube product according to the invention;

(4) FIG. 3 shows a schematic sectional view of the layer structure of the coating system on a tube;

(5) FIG. 4 shows a tube sample of a tube product according to the invention in comparison to two tube samples of conventionally galvanized and passivated tubes at neutral salt spray test (NSS Test) according to DIN EN ISO 9227 after 96 hours; and

(6) FIG. 5 shows a tube sample of a tube product according to the invention in comparison to two tube samples of conventionally galvanized and passivated tubes at neutral salt spray test (NSS Test) according to DIN EN ISO 9227 after 168 hours.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) In FIG. 1 a schematic block diagram a line for carrying out an embodiment of the method according to the invention is shown. The line is shown in FIG. 1 as a four strand line, wherein four base tubes may be treated simultaneously.

(8) In a pretreatment device 20 the base tube 10 is pretreated and in particular cleaned. In a galvanizing device 21, the zinc layer or zinc coating 11 is applied onto the base tube 10. In a passivation device 22 a passivation layer 12 is created on the zinc layer 11. In the embodiment, which is shown in FIG. 1, the thus coated tube is subsequently fed to an induction device 23, wherein the passivation agent of the passivation layer 12 is dried. Finally, the tube is fed to a sealing device 24, in which the sealing layer 13 is applied onto the passivation layer 12. A further heating device, for example hot air device (not shown), in which the sealing layer 13 is cured in particular by crosslinking of plastics of the sealing agent, may be arranged after the sealing device 24.

(9) The galvanizing device 21 in the depicted embodiment is designed as a four stage type. For example, four galvanic zinc coating baths may be connected in series. Between the individual stages of the galvanizing device 21, in particular between the baths, drying devices (not shown) may be provided, which respectively dry the zinc tier 110 which has been created in the previous stage. With the line shown in FIG. 1, a zinc layer 11 is generated, which has four tiers 110. Due to the length of the individual stages of the galvanizing device and/or the applied current of the galvanic baths in combination with the throughput rate a desired layer thickness of the individual zinc tiers 110 can be adjusted. The throughput rate in the method according to the invention may for example be at least 5 m/min and preferably at least 10 m/min. The further parameters such as for example the bath length and current are preferably chosen such that the layer thickness of the individual zinc tiers 110 is in the range of 1 m to 10 m and preferably in the range of 0.5 to 3 m. Thereby a zinc layer 11 with an overall layer thickness from 4 m to 40 m can be applied onto the base tube 10.

(10) The structure of the coating system 100 is schematically shown again in FIG. 3. In this embodiment four zinc tiers 110, which create the zinc layer 11, are applied onto the base tube 10. On the zinc layer 11 a passivation layer 12 is applied, onto which a sealing layer 13 is applied. As can be derived from this schematic depiction, the individual layers of the coating system 100 are relatively thin, whereby the coating system 100 is not damaged even during a forming of the tube product 1.

(11) With the line shown in FIG. 1 a continuous process can be carried out. In particular, the application of the coating system 100, which consists of the zinc layer 11, of the passivation layer 12 and of the sealing layer 13, can be performed in a continuous process. The throughput rate in the method according to the invention may for example be at least 5 m/min and preferably at least 10 m/min, that means the base tube is forwarded through the devices 20 to 24 at that speed, until the tube product 1 according to the invention is obtained.

(12) A schematic depiction of a tube product 1 is schematically shown in FIG. 2, wherein for better visibility the individual layers of the coating system 1 are partially not shown.

(13) In FIG. 4 a tube sample of a tube product according to the invention is shown in comparison to two tube samples of conventionally galvanized and passivated tubes at neutral salt spray test (NSS Test) according to DIN EN ISO 9227 after 96 hours. The tube samples have a diameter of 15 mm and a wall thickness of 1.2 mm. The tube samples have been bent with a bending radius of 2.5 outer tube diameter. The samples, which are also referred to as tube bends, herein have been bent after the application of the coating system. As can be derived from FIG. 4, the conventionally coated tube bends show strong white rust already after 96 hours. The tube bends from the tube product according to the invention in contrast essentially show no white rust.

(14) In FIG. 5 a tube sample of a tube product according to the invention is shown in comparison to two tube samples of conventionally galvanized and passivated tubes at neutral salt spray test (NSS Test) according to DIN EN ISO 9227 after 168 hours. The tube samples have a diameter of 15 mm and a wall thickness of 1.2 mm. The tube samples have been bent at 180 with a bending radius of 2.5 outer tube diameter. Also from FIG. 5 it can be derived, that even after 168 hours, the tube bends from the tube product according to the invention essentially show no white rust, while the white rust occurrence at the comparative samples has further increased.

(15) The invention is not limited to the depicted embodiments. For example the tube product may have an additional lacquer layer on the sealing layer, which may be applied on the sealing layer for example by powder lacquering or wet varnishing. The lacquer layer essentially serves for decorative purposes and is not mandatory according to the invention, since the corrosion resistance by the coating system according to the invention is sufficient.

REFERENCE NUMBERS

(16) 1 tube product 10 base tube 100 coating system 11 zinc layer 110 tier 12 passivation layer 13 sealing layer 20 Pretreatment device 21 Galvanizing device 22 Passivation device 23 Induction device 24 Sealing device