DE102016218688A1 - Process for producing a hydrogen-carrying steel component for use in motor vehicles, hydrogen-carrying steel component and motor vehicle with a hydrogen-carrying steel component - Google Patents

Abstract

The invention relates to a method for producing a hydrogen-carrying steel component (1) for use in motor vehicles. The method comprises the steps of: i) producing a base body (2) made of steel with a nickel content of less than 13.0 percent by weight based on the total weight of the base body (2), ii) coating the base body (2) with a copper layer (3) and iii) performing a heat treatment with alloying copper from the copper layer (3) in the base body (2) and alloying of at least one steel component from the base body (2) in the copper layer (3).

Description

The invention relates to a process for producing a hydrogen-carrying steel component for use in motor vehicles, in particular in fuel cell vehicles. Furthermore, a hydrogen-carrying steel component and a motor vehicle with a hydrogen-carrying steel component are specified.

In the prior art steels with a nickel content of at least 13 percent by mass are usually used for hydrogen-carrying steel components in order to ensure sufficiently good hydrogen resistance of the steel components. A disadvantage of these hydrogen-carrying steel components used in the prior art is that these steels are very expensive due to the high nickel content, especially since nickel is one of the most expensive main alloying elements.

It is therefore an object to solve a method for producing a hydrogen-carrying steel component for use in motor vehicles indicate that is inexpensive and produces a steel component with high hydrogen resistance. It is also an object to provide a hydrogen-carrying steel component and a motor vehicle with such a steel component, which are characterized by a high hydrogen resistance and thus by a low embrittlement tendency at low cost.

These objects are achieved by the subject matters according to the independent patent claims. Advantageous embodiments and further developments of the subject matter will be apparent from the dependent claims, the following description and from the drawings.

According to one aspect of the invention, therefore, a method for producing a hydrogen-carrying steel component is described, wherein the steel component is designed for use in motor vehicles and in particular represents a mechanically stressed steel component. The method provides, in a first step, for producing a base body made of steel with a nickel content of less than 13.0 percent by mass and in particular less than 12 percent by mass, based on the total weight of the main body. Specifically, the main body is not limited and is adapted to be capable of carrying hydrogen, which also includes storage of hydrogen in the hydrogen-carrying steel member.

The main body is formed in particular from a corrosion-resistant, austenitic steel. Preferably, the base body consists of a chromium-nickel steel. According to an alternative embodiment, the base body is formed from a ferritic or a martensitic steel. Furthermore, the base body may have a multi-phase structure with austenitic, ferritic and / or martensitic structural constituents. For example, the base body may consist of a duplex steel with a ferritic and an austenitic structural constituent. Furthermore, the steel body can have a carbon content of less than 0.2 mass percent.

In a further step, the base body is coated with a copper layer. In particular, the copper layer covers all portions of the body that come into contact with hydrogen, and more particularly the areas of mechanical stress, and serves as a protective layer of the steel component against embrittlement by hydrogen. The copper used for the copper layer is essentially pure copper, so pure copper except for technical impurities, the sum of the technical impurities is at most one mass percent, based on the total weight of copper.

According to one embodiment, the copper layer is applied directly to a surface of the base body, wherein the surface of the base body can be processed mechanically and / or thermally before the application of the copper layer to achieve good adhesion. The processing of the surface of the base body before the application of the copper layer can be carried out, for example, by means of a blasting process, such as, for example, by sandblasting, jets of water or laser beams, or by exciting machining, e.g. done by milling, grinding or turning.

The method for applying the copper layer is not limited in detail. The copper layer can be applied, for example, by plating or by electroplating. Furthermore, the copper layer may be e.g. be applied chemically, for example by means of chemical vapor deposition, by thermal spraying, for example by plasma spraying, or by physical vapor deposition.

According to a further embodiment, a further layer can be applied to the base body, which is then arranged between the base body and the copper layer. The layer may be, for example, an adhesion-promoting layer or a functional layer whose coefficient of thermal expansion is preferably between the thermal expansion coefficient of the main body and the thermal expansion coefficient of the copper layer.

Subsequently, the coated with a copper layer body is subjected to a heat treatment. The heat treatment is carried out with parameters such that alloying of copper from the copper layer into the base body and alloying of at least one steel component, in particular iron, but possibly also nickel and / or chromium, from the base body into the copper layer. In other words, this means that the temperature and the duration of the treatment are chosen such that part of the copper from the copper layer diffuses into the steel and, secondly, one or more constituents of the steel, and in particular iron, diffuse into the copper layer. As a result, areas are formed in the steel component, which indicate a copper-doped steel. The alloying of, for example, copper and / or nickel and / or iron, as well as the composition of the steel component in its sections, can be detected by means of energy-dispersive X-ray analysis (EDX). The EDX method can also be used to qualitatively analyze a sufficient alloying of the respective substances and, if appropriate, to adapt the reaction conditions to the heat treatment. The heat treatment permanently increases the adhesive strength of the copper layer on the steel body.

By the method according to the invention thus a steel component is produced, which is characterized by a high resistance to hydrogen or hydrogen resistance. The application of the copper layer and the subsequent heat treatment permanently prevent embrittlement of the steel component, so that no cracks occur in the steel component and this remains impermeable to hydrogen. In this case, the heat treatment serves to firmly anchor the copper layer to the steel base body, so that spalling, e.g. By abrasion of passing hydrogen or abrasion by mechanical stress is prevented. The method is simply applicable without high technical complexity and not least due to the low content of nickel in the body inexpensive. Due to the good resistance to hydrogen, the steel component can also be formed with a smaller wall thickness, which is not only a cost reduction but also a weight reduction.

An advantageous development of the method provides that the heat treatment of the entire component in an oven, or a partial heat treatment, in particular by means of an inductive heating or using a laser or electron beam (for example, GESA) is performed. Carrying out the heat treatment in an oven offers particular advantages if relatively large portions of the copper layer-coated base body are to be heated to alloy copper in the steel and at least one steel component into the copper layer. When using a local heat source targeted smaller sections of the steel component can be heated. The use of a laser or electron beam is particularly advantageous if locally high amounts of heat are to be applied for a short time in order to force alloying in. Time savings also result from the advantageous development that the heat treatment by means of GESA (pulsed electron beam system) is performed. This large amounts of energy are applied in the short term, which allow remelting and thus an alloying of copper into the surface of the steel body. As a result, the adhesion of the copper layer on the body is significantly increased.

According to a further advantageous development, the heat treatment is carried out at a temperature of 750 ° C to 1050 ° C, in particular from 800 ° C to 950 ° C. At the indicated temperatures, both the steel used and the copper have not yet melted, but are thermally activated in that diffusion reactions of copper into the steel structure and diffusion reactions of at least one component of the steel into the copper layer occur. In addition, by a temperature range between 800 ° C and 950 ° C, oxidation reactions during the heat treatment can be reduced.

For reasons of cost reduction of the method is provided according to a development that the heat treatment for 0.5 to 8.0 hours, especially for 2 to 6 hours is performed. The specified time intervals are sufficient to accelerate an effective alloying and to firmly connect the copper layer to the steel main body.

A particularly good permanently resistant copper protective layer can advantageously be achieved if the heat treatment is carried out with exclusion of oxygen and particularly preferably in a protective gas atmosphere, for example in nitrogen, argon, helium, hydrogen or mixtures thereof.

Suitable for the coating process are all processes which are capable of depositing a sufficiently thick copper layer. Particularly preferably, the copper layer is applied by means of electrodeposition. As a result, a copper layer with a very uniform layer thickness without defects can be formed.

According to a further embodiment, the base body has a wall thickness between 0.1 mm and 20.0 mm. The term "wall thickness" In this case, the spatial extent of the basic body may be perpendicular to a main extension plane of the basic body. Particularly preferably, the base body has a wall thickness between 0.1 mm and 20.0 mm, in particular between 0.1 and 10 mm.

Further advantageously, the copper layer has a layer thickness between 2 .mu.m and 500 .mu.m, in particular between 10 .mu.m and 150 .mu.m and in particular between 20 .mu.m and 80 .mu.m. In this case, the term "layer thickness" is understood to mean the spatial extent of the copper layer perpendicular to a surface of the base body on which the copper layer is arranged.

According to a further embodiment, the steel component has a first partial section and a second partial section, wherein the basic body of the steel component is covered by the copper layer in the first partial section and remains free of the copper layer in the second partial section. Preferably, the steel component is subjected to a higher component stress when used in a suitable manner in a hydrogen atmosphere in the first section, in which the base body is covered by the copper layer, than in the second section, in which the base body is not covered by the copper layer. The term "component stress" may be understood to mean mechanical and / or thermomechanical stresses of the base body on which the copper layer is arranged. The copper layer preferably has a thickness of between 10.0 μm and 150 μm, more preferably between 20.0 μm and 80.0 μm.

Also according to the invention, a hydrogen-carrying steel component for use in motor vehicles is described. The steel component is preferably a mechanically stressed component, that is to say a component which is exposed to mechanical and / or thermomechanical stresses when used as intended. These voltages can be caused for example by temperature differences, by pressure differences and / or by vibrations.

According to the invention, the steel component comprises a base body made of steel with a nickel content of less than 13.0 percent by mass and in particular less than 12 percent by mass, based on the total weight of the base body, and a copper layer disposed on at least a portion of the base body, wherein copper from the copper layer are alloyed into the base body and at least one steel component from the base body in the copper layer.

Furthermore, the steel body may have a carbon content less than 0.2 mass percent.

The copper layer may for example be applied directly to a surface of the base body. Alternatively, the copper layer may be applied to a further layer, which is arranged between the base body and the copper layer.

As already stated above for the method according to the invention, the base body may advantageously be formed from an austenitic, a ferritic or a martensitic steel. Furthermore, the base body may have a multi-phase structure with austenitic, ferritic and / or martensitic structural constituents. For example, the base body may consist of a duplex steel with a ferritic and an austenitic structural constituent.

In other words, the steel component according to the invention comprises a base body and a copper layer, which is provided at least in those sections of the steel component, which serve the hydrogen guide, wherein the copper layer is integrated into the steel of the base body. In other words, copper is diffused / alloyed into the steel and one or more constituents of the steel are diffused / alloyed into the copper layer. Such a structure can be achieved by a heat treatment as described with respect to the method according to the invention. By anchoring the copper layer to the base body, the steel component is permanently effectively protected against embrittlement by hydrogen. The copper layer acts as a protective layer which is adhesively bonded to the base body, which prevents both cracking and abrasion or erosion of the steel. Due to the reduced content of nickel, the steel component can be produced inexpensively with very good mechanical properties, high impermeability to hydrogen and permanent embrittlement resistance.

According to an advantageous embodiment of the steel component, the hydrogen-carrying steel component is part of a motor vehicle. The hydrogen-carrying steel component may eg be part of a fuel cell vehicle or part of a motor vehicle with an internal combustion engine, in particular with a hydrogen reciprocating engine. For example, the hydrogen-carrying steel component may be a hydrogen tank or a part of a hydrogen tank. Furthermore, the hydrogen-carrying steel component may, for example, be a part of a line system between a hydrogen tank and a fuel cell of a fuel cell vehicle or between a fuel cell vehicle Hydrogen tank and an internal combustion engine act. In addition, the hydrogen-carrying steel component may be part of a sensor system and / or a control system. In the application, the hydrogen-carrying steel component or the copper layer of the steel component is preferably in contact with hydrogen.

According to a further embodiment, the hydrogen-carrying steel component has a further material layer, which is arranged between the base body and the copper layer. Preferably, the further material layer is applied directly to the base body. The copper layer can for example be applied directly to the further material layer. The further material layer can be, for example, an adhesion-promoting layer or a functional layer whose coefficient of thermal expansion lies between the thermal expansion coefficient of the main body and the thermal expansion coefficient of the copper layer.

According to a further embodiment, the hydrogen-carrying steel component has a further material layer, which is applied on the surface of the copper layer facing away from the base body on the copper layer. The further material layer may be e.g. to trade a paint.

Furthermore, according to the invention, a motor vehicle is specified which has at least one hydrogen-carrying steel component as described above. The motor vehicle may be e.g. to a fuel cell vehicle, that is to say a motor vehicle with a fuel cell drive, or a motor vehicle with an internal combustion engine, in particular with a hydrogen reciprocating engine act. The fuel cell vehicle has e.g. a hydrogen tank, a fuel cell, and a piping system connecting the hydrogen tank to the fuel cell. The hydrogen-carrying steel component may, for example, be the hydrogen tank, a part of the hydrogen tank, the piping system between the hydrogen tank and the fuel cell and / or a part of the piping system. Furthermore, the hydrogen-carrying steel component may be part of a sensor system and / or a control system. The motor vehicle is characterized by a high hydrogen resistance and low embrittlement tendency by hydrogen.

The advantages, advantageous effects and further development set out above for the method according to the invention are also applied to the steel component according to the invention and to the motor vehicle according to the invention.

Further advantages and advantageous embodiments of the method according to the invention described here and of the hydrogen-carrying steel component according to the invention will become apparent from the following in connection with FIGS 1 to 3 described embodiments.

Show it:

1 a schematic representation of a hydrogen-carrying steel component according to an embodiment,

2 a schematic representation of a hydrogen-carrying steel component according to another embodiment, and

3 a schematic representation of a method for producing a hydrogen-carrying steel component according to another embodiment.

In the exemplary embodiments and figures, identical or identically acting components may each be provided with the same reference numerals. The illustrated elements and their proportions with each other are basically not to be considered as true to scale.

Rather, individual elements can be shown exaggeratedly thick or large in size for better representability and / or better understanding.

1 shows a hydrogen-carrying steel component 1 for use in motor vehicles, which is a basic body 2 and one directly on the body 2 applied copper layer 3 having. The main body is made of steel, which has a nickel content of less than 13.0 percent by mass. In the hydrogen-carrying steel component 1 it is part of a pipeline system of a fuel cell vehicle. Alternatively, it may be in the hydrogen-carrying steel component 1 for example, also act as part of a hydrogen tank or the sensor system of a fuel cell vehicle.

The copper layer 3 consists in the illustrated embodiment of pure copper, which has only technically related impurities with a total content of a maximum of 1 percent by mass. The main body 2 of the hydrogen-carrying steel component 1 has a wall thickness W between 0.1 mm and 20.0 mm. The copper layer 3 has a layer thickness S between 2 μm and 500 μm, in particular between 20.0 μm and 80.0 μm.

Copper from the copper layer is in the steel, ie in the steel structure of the body 2 alloyed, in particular by diffusion. In addition, at least one component of the steel of the body is 2 in the copper layer 3 alloyed, in particular by diffusion.

As an alternative to the embodiment shown, between the main body 2 and the copper layer 3 be arranged another layer.

The further layer may be, for example, an adhesion-promoting layer or a functional layer whose thermal expansion coefficient is applied to the copper layer 3 adapted to be.

Furthermore, as an alternative to the in 1 shown embodiment, a further layer on the base body 2 be applied to the opposite surface of the copper layer. This further layer may be, for example, a lacquer or the like.

In 2 is a hydrogen-carrying steel component 1 shown which is a basic body 2 having, wherein the main body 2 made of steel with a nickel content of less than 13.0% by mass. The steel component 1 has a first section 4 and a second subsection 5 on, with the main body 2 only in the first section 4 from the copper layer 3 is covered. In the second section 5 is the main body 2 free from the copper layer 3 , Preferably, the steel component 1 when used as intended in a hydrogen atmosphere in the first section 4 a higher component stress, for example, higher mechanical and / or thermo-mechanical stresses exposed than in the second section 5 ,

In the first section 4 is copper from the copper layer in the steel, ie in the steel structure of the body 2 alloyed, in particular by diffusion. In addition, at least one component of the steel of the body is 2 , ie in particular from the first section 4 in the copper layer 3 alloyed, in particular by diffusion.

3 shows a schematic representation of a method for producing a hydrogen-carrying steel component 1 according to an embodiment. In method step A becomes a basic body 2 made of steel with nickel content smaller than 13.0 mass%.

Thereafter, in process step B, a copper layer 3 on the main body 2 applied.

The copper layer 3 can be applied, for example, mechanically or galvanically. Furthermore, the copper layer can be applied, for example, chemically, for example by means of chemical vapor deposition, by thermal spraying, for example by plasma spraying, or by physical vapor deposition.

In an optional method step A2, an intermediate layer is applied directly to the base body 2 applied before the copper layer 3 is applied directly to the intermediate layer. The intermediate layer may be, for example, an adhesion-promoting layer or a functional layer.

In the illustrated method step C, a heat treatment is carried out. The heat treatment serves to anchor the copper layer 3 with the main body 2 , By the heat treatment, which can be carried out for example by means of a furnace, an inductive heating, by means of a laser or by means of an electron beam (eg GESA), alloys at least one component of the steel of the body 2 in the copper layer 3 one. Furthermore, copper alloyed from the copper layer in the steel of the body 2 one. Thus, there is a mutual diffusion of copper on one side and at least one component of the steel on the other side. The heat treatment turns the copper layer into the steel of the main body 2 integrated whereby a permanently good hydrogen resistance is achieved.

Alternatively or additionally, the embodiments shown in the figures may have further features according to the embodiments of the general description.

LIST OF REFERENCE NUMBERS

1

 steel component

2

 body

3

 metal layer

4

 first section

5

 second subsection

A, A2, B, C

 steps

Claims (12)

Method for producing a hydrogen-carrying steel component ( 1 ) for use in motor vehicles, in particular a mechanically stressed steel component, comprising the steps of: - producing a basic body ( 2 ) of steel with a nickel content of less than 13.0% by mass, relative to the total weight of the body ( 2 ), - coating the basic body ( 2 ) with a copper layer ( 3 ) and - performing a heat treatment while alloying copper from the copper layer ( 3 ) in the basic body ( 2 ) and alloying in at least one steel component from the basic body ( 2 ) in the copper layer ( 3 ). A method according to claim 1, characterized in that the heat treatment of the entire component in an oven, or that a partial heat treatment, in particular by means of inductive heating, is carried out by means of a laser or using an electron beam. A method according to claim 1 or 2, characterized in that the heat treatment at a temperature of 750 ° C to 1050 ° C, in particular from 800 ° C to 950 ° C is performed. Method according to one of the preceding claims, characterized in that the heat treatment is carried out for 0.5 to 8 hours, in particular for 2 to 6 hours. Method according to one of the preceding claims, characterized in that the heat treatment is carried out under exclusion of oxygen, in particular in a protective gas atmosphere, such as in nitrogen, argon, helium, hydrogen or mixtures thereof. Method according to one of the preceding claims, characterized in that the copper layer is applied by means of electrodeposition on the base body. Method according to one of the preceding claims, characterized in that the basic body ( 2 ) has a wall thickness (W) between 0.1 mm and 20.0 mm, in particular between 0.1 and 10.0 mm. Method according to one of the preceding claims, characterized in that the copper layer ( 3 ) has a layer thickness (S) between 2 .mu.m and 500 .mu.m, in particular between 10 .mu.m and 150 .mu.m and in particular between 20 .mu.m and 80 .mu.m. A method according to any one of the preceding claims, characterized in that the steel component ( 1 ) a first subsection ( 4 ) and a second subsection ( 5 ), and wherein the basic body ( 2 ) in the first subsection ( 4 ) of the copper layer ( 3 ) and in the second subsection ( 5 ) free of the copper layer ( 3 ) remains. Hydrogen-carrying steel component for use in motor vehicles, in particular a mechanically stressed steel component, comprising a main body ( 2 ) of steel with a nickel content of less than 13.0% by mass, relative to the total weight of the body ( 2 ), and a copper layer ( 3 ) on at least one subsection ( 4 ) of the basic body ( 2 ), wherein copper from the copper layer ( 3 ) in the basic body ( 2 ) and at least one steel component from the main body ( 2 ) in the copper layer ( 3 ) is alloyed. Hydrogen-carrying steel component according to claim 10, characterized in that the hydrogen-carrying steel component ( 1 ) Is part of a hydrogen tank and / or a conduit system and / or a sensor system and / or a control system of a motor vehicle. Motor vehicle, in particular fuel cell vehicle, comprising at least one hydrogen-carrying steel component ( 1 ) according to claim 10 or 11.

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