EP2450118A1 - Method for producing a tube - Google Patents

Abstract

Producing tube, comprises coating a support element (1) using a thermal spraying method, with a coating material comprising a material of subsequently molded tube, and releasing the coating from the support element to form the tube. The spray angle with which the coating material is sprayed on the support element, is selected such that a low adhesion of the coating is obtained on the support element.

Description

The present invention relates to a method for producing a tube, wherein a carrier element is coated by means of a thermal spraying method and the material of the later formed tube is selected as coating material, and wherein subsequently the coating forming the tube is released from the carrier element.

State of the art

Traditionally, to produce seamless tubes, a block or billet of, for example, steel cylinders is first formed into a billet, a short and thick-walled tube. This billet is then further processed in a subsequent process step by, for example, the pilgering process or the cross rolling to a tube of thinner diameter.

More recently, seamless tubes have also been produced by various thermal spraying techniques. In this case, a powder coating material is introduced into a heated process gas jet. The powder particles melt or on. On the basis of a spray nozzle, the process gas is sprayed onto a carrier element, so that a layer is formed on the carrier element. The layer must fulfill two requirements. For one thing, the layer should adhere to the carrier element during the process. Because only in this way can a pipe be made with fixed specifications. On the other hand, it is necessary that the coating material or later the finished tube can be as easily as possible detached from the carrier element in order to avoid subsequent damage to the tube.

An appropriate method is used for example in the WO 2009/109016 A1 described. In this case, seamless tubes are produced by means of a cold spraying process and then the finished tube is released from the carrier element by cooling or heating the tube and / or the carrier element or, alternatively, the carrier element is melted, vaporized or broken.

Depending on the layer thickness, the material of the coating material and the carrier element, there is a high or low adhesion between the coating material and the carrier element. In this case, a high adhesion to the fact that the coating material adheres well to the support member during the injection process, but is difficult to solve after completion of the support element. Which may entail increased time and cost as a result of further process steps. Low adhesion in turn means that the coating material is minimally or not at all adhered to the carrier element during the injection process, but is very easy to detach from the carrier element after completion. This in turn can cause complications during the application of the layer to the support member.

It is therefore desirable to adjust the adhesion between the coating material and the carrier element, that the required adhesion and also layer properties are guaranteed and at the same time manufacturing costs can be minimized.

Disclosure of the invention

According to the invention, a method for producing a pipe with the features of claim 1 is proposed. Advantageous embodiments of the invention are the subject of the dependent claims and the following description.

Advantages of the invention

According to the invention, a thermal spraying process is used for producing a pipe, in particular a seamless pipe, by means of which a high adhesive tensile strength is provided. The adhesive tensile strength results from the relationship between adhesion and layer properties. While the layer properties are largely due to the materials of coating material and carrier element as well as to the gas and the temperature used for this purpose, the adhesion properties are adaptable or adjustable according to the invention via the spray angle. The spray angle is selected in the inventive method so that adhesion is sufficient, so that the coating material adheres to the carrier element, and at the same time is so low that the tube after completion without the use of costly process steps can be easily solved by the support element. At ideal spray angle, there is minimal adhesion of the coating to the substrate at the same time optimum layer properties, which can be recognized by the fact that the coating or the subsequent tube is tight and free from pores. The introduction of a coolant within the carrier element and the associated shrinking process should be sufficient to release the adhesion between the coating material or tube and carrier element.

At a spray angle of 90 °, the process gas is sprayed in the solder onto the carrier element, so that maximum adhesion forms between the coating material and the carrier element. At a spray angle of 0 °, the process gas is sprayed parallel to the carrier element. This creates no contact and thus no adhesion between the coating material and the carrier element. An injection angle, which causes sufficient adhesion between the coating material and the carrier element, is therefore between more than 0 ° and 90 °. The above considerations apply analogously to the angular range of 90 ° to 180 ° (spraying from the "other side"). In the following, for the sake of simplicity, reference will only be made to the acute angle range (0 ° to 90 °).

Advantageously, in a preferred embodiment, at the beginning of the thermal spraying process, a flange-like layer is applied at an angle of 90 ° to the carrier element, so that, due to a specific layer thickness, an edge of the layer directed towards the carrier element is formed. Subsequently, the jet of the process gas is aligned with the spray device so that the angle to the flank of the layer is about 90 °. In this angular position, the sprayer then remains until the completion of the coating, so that a uniform dense and non-porous layer with low adhesion at the same time.

Conveniently, a hollow mandrel is selected as the carrier element, the outer surface of which is coatable with the coating material. As a result, the tube gets its shape. Depending on the size of the mandrel, the corresponding diameter of the pipe can be selected.

After the desired length of the tube has been effected by coating the carrier element, the coating material must be released from the carrier element. This is preferably done by introducing a coolant into the hollow mandrel so that the entire inner surface of the mandrel is cooled. The coolant may be carbon dioxide (CO ₂ ) or nitrogen (N ₂ ), in particular in the liquid state.

The introduction of the coolant leads to a shock-like shrinking process of the mandrel, wherein the mandrel changes in size, so that the coating material dissolves from the mandrel, without this being damaged. After the mandrel returns to ambient temperature, it expands to its initial size and can be used for the next manufacturing process.

In the production of pipes according to the invention as a thermal spraying method, a cold gas spraying process is preferably used. The method is characterized in that the powder particles of the coating material are not heated to the melting temperature, but are sprayed onto the carrier element with high pressure (temperature approx. 600 ° C, particle velocity> 1000m / s). Layers of extreme adhesion strengths can be produced which are extremely dense and nonporous. Due to the relatively low temperature compared to other thermal spray processes, the spray material is thermally influenced little and much less oxidized. Also, the coated substrate shows no material change due to heat. Methods of cold gas spraying are also in the patent WO 2009/109016 described.

Among other things, the cold gas spraying process allows the use of titanium as a coating material. In cold gas spraying, the corrosion- and temperature-resistant titanium is heated only to the extent that it can be applied to the carrier element by means of the cold gas spraying method, without losing its strength properties. At higher temperatures, the titanium would become brittle quickly.

As support element preferably aluminum is used. Aluminum is a highly corrosion-resistant element that is easy to mold at low temperatures. Upon introduction of coolant into the hollow mandrel, which in the preferred embodiment is aluminum, the mandrel shrinks, thereby releasing the coating material from the mandrel.

A preferred embodiment of the spray system is designed so that move during the coating process, the carrier element and the spray device relative to each other, in particular parallel to the surface of the carrier material. There is a movement of Spray device and carrier element with different speeds in the same direction as well conceivable, as an opposite direction of the carrier element and spray device. Likewise, it is provided that either only the carrier element or only the spray device move in one direction.

Further advantages and embodiments of the invention will become apparent from the accompanying drawings and the embodiment illustrated therein.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of embodiments in the drawing and will be described in detail below with reference to the drawings.

Figur 1

zeigt das Einstellen der Spritzvorrichtung zur Wahl eines Spritzwinkels; und

Figur 2

zeigt ein Verfahren zum Herstellen eines Rohres in seinen einzelnen Schritten.

figure description

FIG. 1

shows the setting of the spray device for selecting a spray angle; and

FIG. 2

shows a method of manufacturing a tube in its individual steps.

Embodiments of the invention

FIG. 1 shows the carrier element 1 in the form of a hollow mandrel, the spray device 2, the flange-like layer 3, the process gas jet 4 and the coating 5 consisting of the coating material. The position A of the spray device 2 serves to apply the flange-like layer 3 to the carrier element 1, wherein the process gas jet 4 strikes the carrier element 1 at an angle of 90 ° 6b. Carrier element 1 and spray device 2 do not move in this case in the axial direction of the mandrel to each other. In this position, the process gas jet 4 with the powdery coating material located therein is directed perpendicular to the carrier element 1, so that the flange-like layer 3 with a certain height, preferably 0.5 to 20 mm, is formed. The finished tube is then about as thick as the flange. After the flange-like layer 3 has reached the predetermined layer thickness, the position of the spray device 2 changes. This is illustrated by an intermediate position B. Before starting the actual coating process, the exact position C of the spray device 2 is selected. For this purpose, the process gas jet 4 is aligned by means of the spray device 2 in the solder 6a to the flank 9 of the flange-like layer 3. Thus, the angle 6a between propagation direction of the process gas jet 4 and flank 9 of the flange-like layer 3 is substantially 90 °, wherein a possible deviation from the solder should not be more than +/- 10 °.

$$\mathrm{Spritzwinkel}\left(8\right)=90°-\mathrm{Flankenwinkel}\left(7\right)$$

In addition to the 90 ° angle 6a, there are two more angles that are important. On the one hand, the flank angle 7 and the spray angle 8. In the extension of the process gas jet 4 forms an angle between them Extension and the support element 1. This angle is referred to as the spray angle 8, as it describes the angle at which the coating material impinges on the support element 1. At the same time, a flank angle 7 is formed between the flank 9 and the carrier element 1. This angle describes the angle at which the flank 9 of the flange-like layer 3 faces the carrier element 1. With the help of the flank angle 7 can be measured, the spray angle 8 can be calculated. Due to the fact that in a triangle the three interior angles yield an angle sum of 180 °, can be seen for the triangle, in the separate section of the FIG. 1a set up the following equation: $$90°+\mathrm{<figure-callout\; id="7"\; label="flank\; angle"\; filenames="imgf0002.png"\; state="\{\{state\}\}">flank\; angle</figure-callout>}\left(7\right)+\mathrm{spray\; angle}\left(\mathrm{8th}\right)=180°$$

$$\mathrm{spray\; angle}\left(\mathrm{8th}\right)=90°-\mathrm{<figure-callout\; id="7"\; label="flank\; angle"\; filenames="imgf0002.png"\; state="\{\{state\}\}">flank\; angle</figure-callout>}\left(7\right)$$

After the spray device 2 has been brought into position C, a uniform layer 5 of the coating material is sprayed onto the carrier element 1, the coating 5 having optimum layer properties with low adhesion.

The FIG. 2 shows the sequential process steps of the invention, the image 1 is only an example of a spray angle 8 of 0 ° show and thus is not to be regarded as a process step.

The inventive method begins with Figure 2. In Figure 2, first, the flange-like layer 3 is sprayed onto the carrier element 1, wherein the spray device 2 is aligned at 90 ° angle 6b to the support element 1. In Figure 3, the spray device 2 is changed in its position so that the process gas jet 4 is at 90 ° angle 6a to the flank 9 of the flange layer 3. The spray device 2 moves in image 3, for example, in the axial direction of the mandrel and parallel to the surface of the support member 1, while the mandrel 1 rotates about its longitudinal axis to form the tube circumference. In Figure 4, the approach of a coating 5 of the coating material on the support element 1 can be seen. In Figure 5, the coating 5 of the support member 1 has progressed so far that already the entire portion of the mandrel is covered by the coating material 5. In Figure 6, the coating 5 of the coating material is now to be released from the carrier element 1 by a particular liquid coolant 11 is introduced consisting of CO ₂ or N ₂ in the hollow mandrel. During the cooling process, if it is an endless tube, the spraying process can continue. In Figure 7, both the mandrel and the spray device 2 are at a standstill, so that the tube 10 can be removed from the mandrel 1. At the same time, further coolant 11 is injected into the hollow mandrel to avoid cracks or other side effects when releasing the mandrel. Figure 8 shows the separation process between tube 10 and mandrel at an advanced stage. After the tube 10 has been completely detached from the carrier element 1 or the mandrel, the finished tube 10 with a predetermined diameter of the selected material, in particular titanium, with the desired layer thickness and the corresponding optimum layer properties.

LIST OF REFERENCE NUMBERS

1

support element

2

sprayer

3

flange-like layer

4

Process gas stream

5

coating

6a

Angle based on flange-like layer

6b

Angle based on carrier element

7

flank angle

8th

spray angle

9

flank

10

pipe

11

coolant

Claims (12)

Method for producing a tube (10), wherein a carrier element (1) is coated by means of a thermal spraying method, wherein the material of the subsequently formed tube (10) is selected as the coating material, and wherein the coating (5) forming the tube (10) is selected is released from the carrier element (1),
characterized in that
the spray angle (8) under which the coating material is sprayed onto the carrier element (1) is chosen such that a low adhesion of the coating (5) to the carrier element (1) is achieved. A method according to claim 1 or 2, characterized in that the coating material in a spray angle (8) of more than 0 ° to 90 ° is sprayed onto the carrier element (1). A method according to claim 1 or 2, characterized in that at the beginning of the thermal spraying process, a flange-like layer (3) is sprayed onto the carrier element (1), so that due to a certain layer thickness of this layer (3) directed to the carrier element (1) Flank (9) forms. A method according to claim 3, characterized in that the flange-like layer (3) is sprayed with a spraying angle (8) of 90 °. Method according to claim 3 or 4, characterized in that an angle (6a) which is substantially perpendicular to the flank ( 9) of the flange-like layer (3). Method according to one of the preceding claims, characterized in that as a carrier element (1) a particular hollow mandrel is selected, the outer surface of which is coatable. A method according to claim 6, characterized in that for releasing the coating material (5) from the carrier element (1), a coolant (11) is passed into the hollow mandrel. A method according to claim 7, characterized in that as coolant (11) in particular liquid CO ₂ or N ₂ is used. Method according to one of the preceding claims, characterized in that a cold gas spraying method is used as the thermal spraying method. Method according to one of the preceding claims, characterized in that it is the coating material is titanium. Method according to one of the preceding claims, characterized in that the carrier element (1) is aluminum. Method according to one of the preceding claims, characterized thereby, that the carrier element (1) and a spraying device (2) move relative to each other during the coating process.

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