Method for processing a metal processing member

Abstract

The present invention relates to a method for treating a metal processing member. The following known steps are provided, namely, a powdery auxiliary substance (2) is sprayed onto the processing member (20) using a spraying device (10), wherein the auxiliary substance is at least partially melted when it exits the spraying device before it collides with the surface of the processing member. In order to enable a scale-preventive coating to be applied onto the processing member in a simple and easily separable manner, the method according to the invention provides that the processing member (20) has a temperature lower than the melting point of the powdery auxiliary substance, in particular a temperature below 50 °C, before the auxiliary substance (2) is sprayed onto it, that the powdery auxiliary substance has an antioxidant action; and it is further contemplated that a uniform coating of the auxiliary substance is formed on the processing member by melting of the auxiliary substance during spraying.

Description

Technical Field

[0001] The present invention relates to a method for treating a metal processing member.

Background Art

[0002] In the production of steel, in many cases, processing members such as steel pieces from continuous casting or hollow blocks for secondary processing by extrusion presses or radial forging are temporarily manufactured and then, for the first time, introduced again into a hot deformation process. For this purpose, these processing members need to be heated in a furnace to the deformation temperature. This can take several hours, during which a very thick oxide layer often forms on the surface of the processing member. This oxide layer, also referred to as scale, means a loss of material. Depending on the material, this can amount to 1 to 3% by weight of the processing member.

[0003] In order to prevent the formation of such a thick oxide layer, in principle, it is known in the prior art, in particular, to apply a solid powdery auxiliary substance onto the surface of the processing member. The aforementioned known auxiliary substances are, for example, powdery and only exhibit their desired anti-oxidation effect when at least partially melted. Therefore, known methods for applying such a powdery auxiliary substance onto the surface of a processing member include heating the processing member to a temperature corresponding to the melting point of the auxiliary substance, at least on its surface. The melting temperature of the known auxiliary substances is above 400°C and up to 1,000°C. At this time, the auxiliary substance becomes liquid and wets the surface. At this time, the auxiliary substance forms a protective film on the surface, and this protective film protects the surface of the processing member from oxidation, i.e., scale formation. Typical applications of this method are the glazing of extruded steel pieces for extrusion presses or the deoxidation of hollow blocks in seamless tubes, etc.

[0004] The necessary heating of the processing member to the above high temperature is in any case cost- and time-intensive.

[0005] Another known use for applying a powdery auxiliary substance onto the surface of a metal workpiece is flame spraying, which includes, in particular, known powder flame spraying. See Wikipedia. In this case, the powdery auxiliary substance melts at least partially in the burner flame and is then sprayed onto the surface of the workpiece to be coated at a very high speed. At this time, the speed varies from 70 m / s to 800 m / s depending on the auxiliary substance and method applied. Due to such high speeds, the particles of the auxiliary substance deform when hitting the surface of the workpiece and are embedded in that surface. Thereby, a very strong bond is created between the layer of the auxiliary substance and the surface of the workpiece. The application rate of the auxiliary substance onto the surface of the workpiece, i.e., the resulting layer thickness, is very small, typically only a few micrometers per spray pass, and the surface needs to be pre-treated specially. Flame spraying is one of the typical methods for coating workpieces with metals or oxides.

[0006] However, this known powder flame spraying method is not suitable for applying an antioxidant auxiliary substance as contemplated by the method according to the invention. This is, on the one hand, because in the present invention such a strong bond between the layer of the auxiliary substance and the workpiece is not desired. Rather, the layer of the auxiliary substance applied in accordance with the present invention should be just a "single application" (Einmalauftrag) that should partially or completely wear away from the surface of the workpiece during subsequent deformation or preparation processes. On the other hand, the layer thickness achievable per spray pass using powder flame spraying is too thin for a particular planned subsequent processing step of the workpiece.

[0007] DE10 2018 208 815A (Patent Document 1) discloses the features of the premise part described in claim 1 of the present application.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention is based on the problem of applying an anti-scale coating on a processing member in a known method for processing a processing member so that it can be easily and readily separated.

Means for Solving the Problems

[0010] The above problem is solved by the method according to claim 1.

[0011] This method is characterized in that before the powdery auxiliary substance is sprayed, the processing member has a temperature lower than the melting point of the powdery auxiliary substance, particularly a temperature of less than 50°C; the powdery auxiliary substance has an antioxidant effect; and a uniform coating of the auxiliary substance is formed on the processing member by melting of the auxiliary substance during the spraying of the auxiliary substance.

[0012] For the use of the method according to the invention, the processing member to be coated advantageously does not need to be pre-heated and typically room temperature is sufficient. In particular, unlike other methods for applying an auxiliary substance on a processing member (especially a processing member made of metal), the processing member does not need to be heated to the melting point of the auxiliary substance to be applied. This first results in a considerable cost saving, since heating the processing member to the melting temperature of the auxiliary substance is usually considerably more energy-intensive compared to the corresponding heating of the auxiliary substance. The claimed method can also be used in installations that absolutely exclude the use of liquid auxiliary substances, for example in the coating of lances in converters for reducing deposits.

[0013] In the present invention, it is necessary for the auxiliary substance to be injected to have an antioxidant effect on the metal processing member. Thereby, advantageously, when heated to the deformation temperature for a subsequent hot deformation process in the furnace, essentially less scale is formed on the metal processing member compared to the case where the antioxidant layer according to the present invention is not provided on the processing member. This also means correspondingly less material loss, since the scale formed on the processing member during heating typically needs to be removed before further deformation, ultimately meaning material loss. Due to the applied antioxidant auxiliary substance, only a small amount of scale is generated, thus reducing the consumption of time for cleaning the processing member and for removing the remaining scale that is still formed.

[0014] According to one embodiment of the present invention, a gas mixture consisting of at least an auxiliary substance, ambient air, and a propellant gas is heated to at least the melting temperature of the auxiliary substance contained therein to at least partially melt the auxiliary substance contained therein. The heating of the gas mixture can be carried out using either a heat source that does not form a flame or a burner that involves the formation of a flame. For example, in the case of a heat source that does not form a flame in the form of an electric heating coil, the gas mixture stream does not necessarily receive additional translational energy in the conveying direction during heating. This is different especially when the heating is carried out using a burner that involves the formation of a flame; in this case, the acceleration of the gas mixture in the direction towards the outlet of the injection device can cause an explosion of the gas mixture. Therefore, the selected method for heating the gas mixture to the melting temperature of the auxiliary substance also affects its outlet velocity from the injection device. In the case of an explosion or flame formation, the outlet velocity is significantly faster compared to the case where no flame is formed.

[0015] The transport of the powder to the outlet of the injection device is carried out by a propellant gas. Therefore, the flow rate of the propellant gas needs to be adapted to the amount of the auxiliary substance in each case. Furthermore, when using a burner, the amount of burner gas needs to be adapted to the amount of propellant gas so that the gas mixture is maintained in an ignitable state.

[0016] According to yet another embodiment, the injection device is configured in the form of a Venturi nozzle. The use of a Venturi nozzle has the advantage that, in order to achieve a substantially greater volume flow rate of the gas mixture at the outlet of the Venturi nozzle, the accelerating gas need only be introduced into the Venturi nozzle with a substantially lower initial volume flow rate. Therefore, due to its configuration, the Venturi nozzle advantageously functions as an amplifier of the volume flow rate.

[0017] According to yet another embodiment of the present invention, at least partially molten auxiliary material from 10 g to 80 g per second can be applied onto the surface of the processing member, and / or the liquid or paste-like particles of the molten auxiliary material impinge on the surface of the processing member with a particle velocity from just 4 m / s to 20 m / s. The required application amount of the auxiliary material per second onto the surface, or the said particle velocity which is low compared to other application methods of the auxiliary material onto the metallic processing member, advantageously results in an increase in the application efficiency, firstly because there are fewer particles rebounding from the surface of the processing member, and secondly because the particles remain in the injection device for a longer heating time. Therefore, the said application amount or low particle velocity required per second enables the formation of a thicker layer of the auxiliary material on the processing member than was possible in the prior art.

[0018] In the method according to the invention, the distance between the outlet of the injection device and the surface of the processing member during the injection of the auxiliary material is between 15 cm and 60 cm. This distance depends on whether a heat source without flame formation or a burner with flame formation is selected for the heating of the auxiliary material, and in the latter case, also on the length of the flame and the amount of burner gas used.

[0019] Advantageously, the auxiliary material applied using the method according to the invention not only has the above-mentioned antioxidant effect, but also has the property of separating existing oxidation, especially existing scale, from the surface of the processing member, and / or a lubricating effect. Depending on which of the above-mentioned properties the auxiliary material used in each case has, the amount of the auxiliary material applied onto the surface of the processing member is from 15 g / m 2 to 400 g / m2 between them.

[0020] In principle, all technical deoxidizers or lubricants containing fusible substances can be used as auxiliary substances. The melting temperature typically ranges from 500°C to 1,200°C. The non-fusible components of the auxiliary substances are optionally contained in the melted particles. The usual basic materials in the auxiliary substances are phosphates, borates or silicates, which are optionally enriched with soaps and / or graphite, etc.

[0021] The cleaner the surface of the workpiece before the application of the auxiliary substance, the better the effect of the antioxidant auxiliary substance applied on the workpiece. Therefore, it is particularly recommended to remove the oxidation, especially the existing scale, present on the surface of the workpiece before applying the auxiliary substance according to the method of the present invention. Thereby, the effectiveness of scale avoidance by the antioxidant auxiliary substance in the post-heating furnace is improved.

[0022] Finally, it should be mentioned that the method according to the present invention can be advantageously used even if it has been necessary to heat the workpiece before the auxiliary substance can be applied, for example, in the case of an extrusion press where the extruded steel strip is coated with a glass layer.

[0023] Two drawings are attached to this specification.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

[0025] Hereinafter, the present invention will be described in detail in the form of examples with reference to the above-mentioned drawings. In both drawings, the same technical elements are designated by the same reference numerals.

[0026] Figure 1 shows an injection device 10 in the form of a Venturi nozzle 12 with a heat source 16'. The outlet of the Venturi nozzle 12 and the heat source 16' are connected to each other via a conveying line 14. In the heat source 16', the gas mixture is heated without the formation of a flame. The heat source 16' is configured, for example, in the form of an electrically heated coil. The heat source 16' forms the outlet of the injection device 10 for the heated gas mixture.

[0027] The method according to the invention is implemented as follows using this injection device 10.

[0028] First, the auxiliary substance 2 and the ambient air 3 are sucked into the injection device 10, where they are mixed with a propellant gas 5, such as compressed air, to form a gas mixture 7. Propelled by the kinetic energy of this propellant gas, the gas mixture 7 flows as a continuous gas mixture stream in the conveying direction FR towards the outlet of the injection device 10 and flows out of this outlet.

[0029] When the powdered auxiliary substance 2 is sucked into the injection device 10, although this is not necessarily the case, it typically has the temperature of the ambient air 3 sucked in together. In the injection device, and especially for the first time at its outlet, the gas mixture is heated by the heat source 16' without the formation of a flame to at least the melting temperature of the auxiliary substance 2 contained in this gas mixture, so that as a result, this auxiliary substance in the gas mixture melts at least partially. After this melting, the auxiliary substance 2 is contained in the gas mixture in the form of liquid or paste-like particles.

[0030] Using the injection device 10, the gas mixture 7 exiting from its outlet is injected onto the surface of the processing member 20 together with the particles of the molten auxiliary substance 2 contained therein. On the surface of the processing member 20, as shown in FIG. 1, the auxiliary substance 2 that has been at least partially melted in advance forms a uniform coating. In the method according to the present invention, the processing member 20 is not preheated to a specified temperature before the application of the auxiliary substance, but rather has a typical room temperature or ambient temperature, that is, generally a temperature below 50°C. In particular, the processing member does not need to be heated to a temperature exceeding the melting point of the powdered auxiliary substance to be applied, because the auxiliary substance has already been melted in the injection device 10 and does not melt for the first time on the processing member 20. Since the injected auxiliary substance has an antioxidant effect in the method of the present invention, oxidation on the coated surface of the processing member, particularly the formation of a scale layer, is effectively reduced even if it is not prevented during subsequent heating of the processing member.

[0031] During the injection of the auxiliary substance, the injection device typically has a spacing between 15 cm and 60 cm with respect to the surface of the processing member 20. When a Venturi nozzle 12 is used, the propellant gas is introduced into the Venturi nozzle at an initial volume flow rate, for example, from 150 L / min to 300 L / min. The Venturi nozzle amplifies this volume flow rate, and as a result, the gas mixture exits the Venturi nozzle with a volume flow rate from 800 L / min to 4,000 L / min. Using the said gas mixture flow, at least partially melted auxiliary substance from 10 g to 80 g per second is applied onto the surface of the processing member. In other words, the liquid or paste-like particles of the melted auxiliary substance 2 collide with the surface of the processing member 20 at a particle velocity from 4 m / s to 20 m / s. At this relatively low particle velocity compared to other application methods, advantageously, there are few particles rebounding from the processing member, and therefore, by using the method according to the present invention, a thicker layer thickness can be achieved on the processing member.

[0032] In addition to the above-mentioned antioxidant effect, the auxiliary substance 2 may also be suitable for separating the oxidation, particularly the existing scale, present on the surface of the processing member. Furthermore, this has, among other things, a lubricating effect.

[0033] In principle, the amount of the auxiliary substance applied onto the surface of the processing member 20 is between 20 g / m 2 and 400 g / m 2 . This specific amount of the auxiliary substance also represents the layer thickness applied onto the surface of the processing member using the auxiliary substance. The amount of the auxiliary substance applied ultimately depends on the action and characteristics of the auxiliary substance 2. Therefore, when the auxiliary substance has only an antioxidant action, the application amount of the auxiliary substance is from 15 g / m 2 to 60 g / m 2 . When the auxiliary substance 2 has, in addition to the antioxidant action, the characteristic of separating the already existing oxidation on the processing member 20, this is, in particular, sprayed onto the processing member in an amount from 60 g / m 2 to 120 g / m 2 . When the auxiliary substance 2 has, in addition to the antioxidant action and the characteristic of separating the scale existing on the processing member, the above-mentioned lubricating action as well, the method according to the invention recommends applying the auxiliary substance onto the surface of the processing member in an amount from 120 g / m 2 to 400 g / m 2 .

[0034] In order to apply the above amount of the auxiliary substance onto the surface of the processing member 20, at the outlet of the Venturi nozzle or the injection device 10, the above-described gas mixture volume flow rate of from 800 L / min to 4,000 L / min is required.

[0035] Therefore, the amount of the initial volume flow of the propelling gas required has to be adapted to the application amount of the auxiliary substance desired in each case. The amount or volume flow rate of the auxiliary substance introduced into the injection device 10, as well as the resulting layer thickness on the surface of the processing member, depend on the type of the auxiliary substance and the purpose to be achieved with the coating of the processing member. The propelling gas 5 is introduced into the injection device in the form of a continuous volume flow, in particular, in order to achieve a continuous volume flow of the gas mixture at the outlet of the injection device and thereby enable a uniform application of the auxiliary substance onto the processing member.

[0036] At least the antioxidant auxiliary substances used in accordance with the present invention are, for example, phosphates, borates or silicates, or mixtures thereof. Optionally, soap and / or graphite may be included in the auxiliary substances. The melting temperature of the auxiliary substances according to the invention is in the temperature range from 500 °C to 1,200 °C. Accordingly, in order to at least partially melt the auxiliary substance 2, it is necessary to heat the gas mixture to a temperature from said temperature range using a heat source.

[0037] The method according to the invention can in principle be carried out on its own, i.e., without the processing of the preceding workpiece being carried out in due time and without the post-processing of the workpiece being carried out in due time. However, in particular, the method is integrated into the overall processing process of the workpiece which can carry out the timely pre-processing of the workpiece and / or the timely post-processing of the workpiece. The timely post-processing of the coated workpiece can in particular include heating the coated workpiece to a predetermined deformation temperature in a post-heating furnace and then deforming it. In particular, in said heating of the workpiece, the layer to which the auxiliary substance is applied exerts its antioxidant action, i.e., scale formation during heating is reduced.

[0038] Figure 2 shows a second variant of the method according to the invention and of the injection device 10 according to the invention. The injection device according to Figure 2 differs from the first variant shown in Figure 1 in that the heating of the gas mixture at the outlet of the injection device 10 is carried out using a burner 16. For the burner 16 to be able to function, this requires fuel, in particular fuel gas 6. The fuel gas 6 is sucked into the injection device 10 together with the auxiliary substance 2 and the ambient air and thus becomes a component of the gas mixture 7 in the injection device. Instead or additionally, as shown in Figure 2, the fuel gas can also be supplied directly to the burner at its location, i.e., at the outlet of the injection device 10. In both cases, the fuel gas, which can be, for example, propane gas, natural gas or hydrogen, is ignited in the burner 16 to form a flame 8. The auxiliary substance 2 contained in the gas mixture 7 is melted in the flame 8 and sprayed onto the surface of the workpiece 20.

[0039] In both the first variant shown in FIG. 1 and the second variant shown in FIG. 2 for heating the auxiliary substance 2 in the gas mixture, the auxiliary substance 2 cools very rapidly on the surface of the processing member 20, so that no significant heating of the processing member occurs by virtue of said application of the auxiliary substance alone.

Explanation of reference numerals

[0040] 2 Auxiliary substance 3 Ambient air 5 Propellant gas, e.g. compressed air 6 Fuel gas 7 Gas mixture 10 Injector 12 Venturi nozzle 14 Conveyor line 16 Burner as heat source 16’ Heat source without formation of a flame 20 Processing member FR Conveying direction

Claims

1. A method of treating a metallic workpiece (20), the method comprising the step of spraying a powdery auxiliary substance (2) onto the workpiece (20) using a spraying device (10), wherein the auxiliary substance (2) is at least partially melted when it exits the spraying device (10) before it impinges on the surface of the workpiece (20). Before the auxiliary substance (2) is sprayed onto the workpiece (20), the workpiece (20) has a temperature lower than the melting point of the powdery auxiliary substance, in particular a temperature of less than 50 °C; The powdery auxiliary substance (2) has an antioxidant effect; and By melting the auxiliary substance (2) during the spraying of the auxiliary substance, a uniform coating of the auxiliary substance is formed on the workpiece. The method as claimed in the preceding claim, characterized in that.

2. At least the auxiliary substance (2) and the ambient air (3) are mixed in the spraying device (10) with a propellant gas (5), for example compressed air, to form a gas mixture (7); and The gas mixture is propelled by the propellant gas (5) as a continuous gas mixture stream and flows in a transport direction (FR) to the outlet of the spraying device (10). The method according to claim 1, characterized in that.

3. The gas mixture (7) is heated in the spraying device (10) to at least the melting temperature of the auxiliary substance (2) contained therein, as a result of which the auxiliary substance (2) contained therein is at least partially melted; The heating of the gas mixture stream is carried out using a heat source (16') without flame formation, for example a heat source (16') in the form of an electrically heated coil, and / or a burner (16) with flame formation; and The heat source (16') without flame formation and / or the burner (16) are arranged, in particular, at the outlet of the spraying device (10). The method according to claim 2, characterized in that.

4. that the injection device (10) includes a Venturi nozzle (12); and that the accelerating gas (5) is introduced into the Venturi nozzle at an initial volume flow rate of 150 to 300 liters per minute to generate a gas mixture volume flow rate of 800 liters per minute to 4000 liters per minute at the outlet of the Venturi nozzle; A method according to claim 2 or 3, characterized in that.

5. When using an injection device (10) having a burner (16) at the outlet, before the gas mixture stream reaches the burner (16) of the Venturi nozzle (12), the burner gas (6) is mixed with the propelling gas together with the auxiliary substance (2), and / or that the burner gas (6) is directly injected into the burner (16) at the outlet of the injection device (10), and in each case, especially when propane gas or natural gas is used as the burner gas, a burner gas volume flow rate of 4 kg / h to 50 kg / h is used, A method according to claim 3 or 4, characterized in that.

6. Using the gas mixture stream, at least partially melted auxiliary substance (2) of 10 to 80 g per second is applied onto the surface of the processing member (20); and / or The liquid or paste-like particles of the melted auxiliary substance (2) collide with the surface of the processing member (20) at a particle velocity of 4 m / s to 20 m / s; A method according to any one of claims 2 to 5, characterized in that.

7. A method according to any one of claims 1 to 6, characterized in that the distance between the outlet of the injection device (10) and the surface of the processing member (20) is between 15 cm and 60 cm during the injection of the auxiliary substance (2).

8. The auxiliary substance (2) has, in addition to its antioxidant action, the property of separating existing oxidation, in particular existing scale, from the surface of the processing member (20), and especially further has a lubricating action. A method according to any one of claims 1 to 7, characterized in that.

9. The amount of the auxiliary substance (2) applied onto the surface of the processing member (20) is between 15 g / m² when the auxiliary substance (2) has only an antioxidant action ２ and 400 g / m² ２ and, in particular, between 15 and 60 g / m² ２ up to, or when the auxiliary substance (2) has, in addition to its antioxidant action, the property of separating existing oxidation on the processing member (20), then, in particular, between 60 g / m² ２ and 120 g / m² ２ up to, or when the auxiliary substance (2) is configured to have antioxidant properties, and to separate existing oxidation on the processing member (20), and additionally has a lubricating action, then, in particular, between 120 g / m² ２ and 400 g / m² ２ up to. A method according to any one of claims 1 to 8, characterized in that.

10. The auxiliary substance (2) is, for example, a phosphate, borate, silicate or a mixture thereof, and optionally, soap and / or graphite are added. A method according to any one of claims 1 to 9, characterized in that.

11. The melting temperature of the auxiliary substance (2) is in a temperature range between 500 °C and 1200 °C. A method according to any one of claims 2 to 10, characterized in that.

12. The oxidation existing on the surface of the processing member (20), in particular the existing scale, is removed therefrom before applying the auxiliary substance (2). A method according to any one of claims 1 to 11, characterized in that.

13. - Optionally: heating the processing member (20) uniformly coated with the auxiliary substance to a predetermined deformation temperature, and - deforming the processed member coated with the auxiliary substance (2), A method according to any one of claims 1 to 12, characterized in that.

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