EP3861145A1

EP3861145A1 - Turbocharger, having a steel material for high-temperature applications

Info

Publication number: EP3861145A1
Application number: EP19782583.9A
Authority: EP
Inventors: Marc Hiller; Martin Thomas; Achim Koch
Original assignee: Vitesco Technologies GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2018-10-05
Filing date: 2019-10-01
Publication date: 2021-08-11
Also published as: DE102018217057A1; WO2020070163A1; US20210388738A1; US11454132B2; CN112771192A

Abstract

The invention relates to a turbocharger (1), comprising a turbine housing (21), which has an accommodating region for a turbine rotor disk (12) of the turbocharger (1), which accommodating region is arranged centrally with respect to a turbine housing axis (2a), and at least one turbine spiral channel (22), which tapers helically toward the accommodating region for the turbine rotor disk (12), wherein a wastegate valve, having a spindle arm and a valve plate arranged on the spindle arm, or a variable exhaust-gas guiding device, having bearing disks and guide vanes, is arranged in the turbine housing, characterized in that at least one of the following components: turbine housing, spindle arm and valve plate, or bearing disks and guide vanes, has a steel material (21a) for high-temperature applications, the material composition of which comprises, in addition to iron, Fe, at least the following alloying constituents in amounts within the specified limits in weight percent: carbon, C: 0.4-0.5%; silicon, Si: 1.25-1.75%; manganese, Mn: 3.0-12.0%; chromium, Cr: 19.5-20.5%; nickel, Ni: 5.0-6.0%; niobium, Nb: 1.00-1.5%. Said material composition ensures sufficient temperature resistance of the components, while having a lower nickel content and being less expensive in comparison with other high-temperature materials.

Description

description

Exhaust gas turbocharger made of a steel material for high-temperature applications

The invention relates to an exhaust gas turbocharger, the one

Steel material for high-temperature applications, in particular a steel material that is suitable for use at high temperatures up to over 1000 ° C.

The development of new technologies as well as the further development of appropriate devices and processes towards higher performance and efficiency while reducing the use of resources very often go hand in hand with increased demands on the materials used in terms of strength, temperature resistance, corrosion resistance and machinability. Furthermore, price also plays an important role in industrial use.

Such a technological challenge, which places ever increasing demands, is traditionally subject to vehicle construction and in particular the development of the internal combustion engines used in it.

To reduce fuel consumption and pollutant emissions while maintaining or even increasing the performance of the internal combustion engine, small-volume engine concepts, so-called downsizing concepts, are increasingly being used, which are equipped with exhaust gas turbochargers to increase performance. The prevailing high exhaust gas temperatures up to over 1000 ° C represent a strong challenge for the materials used in the exhaust gas turbine, particularly in gasoline internal combustion engines. There is a tendency to further increase the operating temperatures in order to use the thermal energy generated during combustion more efficiently can. Furthermore, there is also a tendency towards lean operation with lambda close to 1 in Otto combustion engines, as a result of which the exhaust gas temperatures also increase. The thermal load on the materials used in the exhaust gas area, i.e. also in the turbocharger, increases.

The principle of operation of an exhaust gas turbocharger is to use the energy contained in the exhaust gas flow to increase the pressure in the intake tract of the internal combustion engine and thus to better fill the combustion chamber with air-oxygen and thus more fuel, gasoline or diesel, per combustion process to be able to implement, so to increase the performance of the internal combustion engine.

For this purpose, the exhaust gas turbocharger has an exhaust gas turbine arranged in the exhaust tract of the internal combustion engine, a fresh air compressor arranged in the intake tract and an intermediate rotor bearing. The exhaust gas turbine has a turbine housing and a turbine impeller arranged therein, driven by the exhaust gas flow. The fresh air compressor has a compressor housing and a compressor impeller which is arranged therein and builds up a boost pressure. The turbine impeller and the compressor impeller are rotatably arranged on the opposite ends of a common shaft, the so-called rotor shaft, and thus form the so-called turbocharger rotor. The rotor shaft extends axially between the turbine impeller and the compressor impeller through the rotor bearing arranged between the exhaust gas turbine and the fresh air compressor, and is axially and axially rotatably supported therein in relation to the rotor shaft. According to this construction, the turbine impeller driven by the exhaust gas mass flow drives the compressor impeller via the rotor shaft, as a result of which the pressure in the intake tract of the internal combustion engine, based on the

Fresh air mass flow behind the fresh air compressor, increased and thereby better filling of the combustion chamber with

Air-oxygen is effected.

Furthermore, a device is usually provided in the turbine housing in order to influence the gas mass flow flowing from the turbine impeller. Here is essentially two different facilities that are optionally provided. On the one hand, this is a so-called wastegate valve, on the other hand, a so-called variable turbine geometry (VTG).

If necessary, the exhaust gas mass flow can be directed past the turbine impeller directly into the exhaust tract downstream of the exhaust gas turbine via a wastegate valve, whereas the direction and the amount of the exhaust gas mass flow impinging on the turbine impeller can be influenced via the variable turbine geometry.

Depending on the speed and exhaust gas mass flow of the internal combustion engine, depending on the load requirements, the Wastega te valve or the variable turbine geometry is set so that the speed of the turbine and compressor impeller and the pressure ratio, in particular on the exhaust gas turbine, are kept within the desired working range of the exhaust gas turbocharger can be.

In order to be able to use the thermal energy generated during combustion in the internal combustion engine with higher degrees of efficiency by the exhaust gas turbocharger, as already mentioned, the exhaust gas temperatures are kept as high as possible. Due to the hot exhaust gases flowing through the turbine housing, this and the components arranged in the exhaust gas mass flow are subjected to a thermal alternating stress with temperatures of over 1000 ° C. Furthermore, there is a demand for high strength and dimensional stability of the components with the lowest possible weight, that is, a reduced use of materials.

In order to be able to meet these high requirements, steel materials with mostly partially austenitic structures and in particular a high nickel content of up to 40% have been used. Such materials are, for example, cast steel materials with the short designation 1.4848 (GX40CrNiSi25-20) and 1.4849

(GX40NiCrSiNb38-l 9). The material 1.4848 is characterized by the following material composition: 0.3-0.5% C; 1.0-2.5% Si; Max . 2.0% Mn; max.0.04% P; max 0.03% S; 24.0-27.0% Cr; max 0.5% Mo; 19, 0-22, 0% Ni; Rest of Fe.

The material 1.4849 shows the following work

fabric composition on: 0.3-0.5% C; 1.0-2.5% Si; Max . 2.0% Mn; max 0.03% S; 18.0-21.0% Cr; max 0.5% Mo; 36.0-39.0% Ni;

1.2-1.8% Nb; Rest of Fe.

The high nickel content increases the strength and durability of the materials, especially at operating temperatures up to 1050 ° C. However, nickel is a relatively expensive material, which is why cheaper alternatives are sought.

Another highly heat-resistant material with a very low nickel content, which is used in particular in pressure and steam boiler construction as well as in aerospace engineering and turbine construction, is material 1.4923 (X22CrMoV12-l), which has the following composition: 0.18-0.24% C; 11.0-12.5% Cr; 0.3-0.8% Ni; 0.8-1.2% V; Rest of Fe. With this material, the elongation and creep strength are increased by the vanadium content and the increased addition of molybdenum. However, the strength values already drop significantly at temperatures above 500 ° C, which considerably limits the use for exhaust gas turbine housings, as described above.

The present invention is therefore based on the object of specifying an exhaust gas turbocharger having a steel material for high-temperature applications, which is characterized by low material costs, in particular in the case of a low nickel content of the material, in a temperature range up to over 1050 ° C. by sufficient strength and creep resistance for distinguishes the use in connection with internal combustion engines.

This object is achieved by an exhaust gas turbocharger with the features according to claim 1. Advantageous training and further education, which individually or, if they are not mutually exclusive alternatives, in combination can be used together are the subject of the dependent claims.

According to the invention, an exhaust gas turbocharger with a turbine housing is provided with a receiving area for a turbine impeller of the gas turbocharger arranged centrally to a turbine housing axis and at least one turbine spiral channel tapering helically towards the receiving area for the turbine impeller, with a wastegate valve with a spindle arm in the turbine housing and a flap plate arranged thereon, or a variable exhaust gas guide device with bearing disks and guide vanes is arranged, at least one of the components: turbine housing, spindle arm and valve plate, or bearing disks and guide vane, comprising a steel material for high-temperature applications, the material composition of which, apart from iron, Fe has at least the following alloy components in amounts within the specified limits in percent by weight:

Carbon, C: 0.4-0.5%;

Silicon, Si: 1.25-1.75%;

Manganese, Mn: 3.0-12.0%;

Chromium, Cr: 19.5-20.5%;

Nickel, Ni: 5.0-0.0.0%;

Niobium, Nb: 1.00-1.5%.

In a further embodiment of the steel material used in the exhaust gas bolader according to the invention, in particular at least one of the quantitative proportions of the alloy components silicon and manganese can be set within narrow limits, so that at least one of these components is added at least in quantities within the following limits in percent by weight:

Silicon, Si: 1.35-1.65%;

Manganese, Mn: 7.0-12.0%.

The amount of manganese can in particular also be further limited to a proportion of 9.0-12%.

This enables the desired material properties to be achieved at a higher level with greater reliability. In the alloy compositions given above, compared to known steel materials for high temperatures

In particular, the increased proportions of manganese, chromium and niobium in combination with moderate addition of nickel are responsible for the material properties achieved. The ge called alloy is characterized by high heat resistance with simultaneous corrosion resistance, especially in the aggressive, hot exhaust gases of an internal combustion engine.

Furthermore, additional alloy components may be added to achieve certain properties. For example, the material composition according to the invention can be supplemented by adding at least one of the further alloy constituents mentioned below, in proportions up to a maximum of the amounts indicated in percent by weight:

Tungsten, W: up to 0.6%;

Vanadium, V: up to 0.12%;

Copper, Cu: up to 0.25%;

Cobalt, Co: up to 1.0%;

Sulfur, S: up to 0.03% and

Phosphorus, P: up to 0.04%.

This means that at least one of these elements is added in a measurable amount, but in an amount up to the specified limit. However, two, three, four, five or all of these elements can also be added in different combinations, but each only in an amount up to the respectively specified limit.

Depending on the combination, this can have a positive effect on various secondary material properties of the alloy, such as machinability, weldability, castability, etc.

In addition, unavoidable impurities can be contained in quantities that are negligible in terms of material properties.

In a further refined embodiment, the steel material used in the exhaust gas turbocharger according to the invention is shows that it has at least one of the above-mentioned further alloy components added to the alloy in proportions of at least the stated amounts in percent by weight:

Tungsten, W: at least 0.3%;

Vanadium, V: at least 0.06%;

Copper, Cu: at least 0.1%;

Cobalt, Co: at least 0.5%;

Sulfur, S: at least 0.013% and

Phosphorus, P: at least 0.02%.

In combination with the previously defined upper limits for the addition quantities of the other alloy components, this results in a quantity range:

for tungsten, W: between 0.3 to 0.6%;

for vanadium, V: between 0.06 to 0.12%;

for copper, Cu: between 0.1 to 0.25%;

for cobalt, Co: between 0.5 to 1.0%;

for sulfur, S: between 0.013 and 0.03% and

for phosphorus, P: between 0.02 to 0.04%.

The steel material has at least one of these further elements in a quantity within the specified quantity range. However, the steel material can also have two, three, four, five or all of the other elements mentioned in quantities within the specified limits.

The high manganese content as well as the further alloy components contribute to the further increase of the desired material properties and in particular cause a progressive conversion of ferrite to austenite at higher material temperatures. In addition, the corrosion resistance is increased.

A further characteristic of the steel material used in the exhaust gas bolader according to the invention is accordingly characterized in that the steel material has a completely austenitic structure. This leads to a significant reduction in the formation of sigma phases in the Material structure and contributes to achieving and stabilizing the desired material properties.

With the specified material composition of the steel material used in the exhaust gas turbocharger according to the invention, the material properties required for use in turbine housings for exhaust gas turbochargers with respect to the minimum plug-in limit, the tensile strength and the corrosion resistance are achieved, while at the same time the nickel is greatly reduced in comparison with conventional high-temperature materials. Share and thus reduced material costs.

This is achieved, among other things, by coordinating the alloy components in terms of composition and quantity and possibly defining them within narrow limits so that a high proportion of the austenitic structure is formed, ideally up to 100%.

The exhaust-gas turbocharger according to the invention has a turbine housing with a receiving area for a turbine impeller of the exhaust-gas turbocharger, which is arranged centrally to a turbine housing axis, and at least one exhaust-gas spiral channel that tapers towards the receiving area for the turbine-impeller. A wastegate valve with a spindle arm and a flap plate arranged thereon or a variable exhaust gas guide device VTG with bearing disks and guide vanes are arranged in the turbine housing. This essentially corresponds to an arrangement as already described in the introduction. The exhaust gas turbocharger according to the invention is characterized in that at least one of the components: turbine housing, spindle arm and flap plate, or bearing washers and guide vane, has a steel material according to the invention with an alloy composition, as described in one of the embodiments described above.

A corresponding exhaust gas turbocharger is characterized by an increased service life with increased operational reliability. This is achieved through materials optimized for the application Properties of the components mentioned, in particular with regard to the high temperature strength, at the same time, compared to conventional components made of high-alloy nickel alloys, reduced price.

The features and combinations of features of the embodiments of the subject matter according to the invention mentioned above in the description, insofar as they cannot be used alternatively or are mutually exclusive, can be used individually, in part or as a whole, also in a mutual combination or complement, in a further development of the subject matter, without leaving the scope of the invention.

Corresponding designs of exhaust gas turbochargers according to the invention are explained in more detail with the aid of the figures, in which:

Figure 1 is a schematic simplified representation of a

Exhaust gas turbocharger with wastegate valve, in half sectional view, and

Figure 2 is a three-dimensional representation of an exhaust gas charger with variable exhaust gas guide, in a quarter-sectional view.

Parts with the same function and designation are identified throughout in the figures with the same reference symbols.

Based on the figure, the basic structure of an exhaust gas bolader 1 with a wastegate valve, as already described roughly in the introduction, is in a schematically simplified half

Sectional representation shown.

As a rule, a conventional exhaust gas turbocharger 1, as shown in FIGS. 1 and 2, has a multi-part structure. There are one in the exhaust system of the internal combustion engine

Turbine housing 20 that can be arranged, a compressor housing 30 that can be arranged in the intake tract of the internal combustion engine, and a bearing housing 40 arranged one behind the other on a common turbocharger axis 2 between the turbine housing 20 and the compressor housing 30. organizes and connects with each other in terms of assembly. A further structural unit of the exhaust gas turbocharger 1 is the turbocharger rotor 10, which has a rotor shaft 14, a turbine impeller 12 arranged in the turbine housing 20 and a compressor impeller 13 arranged in the compressor housing 30. The turbine impeller 12 and the compressor impeller 13 are arranged on the opposite ends of the common rotor shaft 14 and rotatably connected to them. The rotor shaft 14 extends axially through the bearing housing 40 in the direction of the turbocharger axis 2 and is rotatably supported axially and radially about its longitudinal axis, the rotor axis of rotation 15, wherein the rotor axis of rotation 15 lies in the turbocharger axis 2, that is to say coincides therewith. The turbine housing axis 2a is also in line with the rotor axis of rotation 15 and the turbocharger axis 2. The exhaust gas mass flow AM through the turbine housing 20 and the fresh air mass flow FM through the compressor housing 30 are each shown with corresponding arrows.

The turbine housing 20 has a turbine spiral channel 22, a so-called exhaust gas flow, which is arranged in a ring around the turbocharger axis 2 and the receiving area of the turbine impeller 12, in a helical manner tapering towards the receiving area and the turbine impeller 12, a so-called exhaust gas flow. This exhaust gas flow has a tangentially outwardly directed exhaust gas supply channel 23 with a bend

mer connection piece 24 for connection to an exhaust manifold (not shown) of an internal combustion engine, through which the exhaust gas mass flow AM flows into the respective exhaust gas flow. The exhaust gas flow also has an at least part of the inner circumference annular gap opening, the so-called exhaust gas inlet gap 25, which extends in at least a proportionally radial direction towards the turbine impeller 12 and through which the exhaust gas mass flow AM flows onto the turbine impeller 12.

The turbine housing 20 furthermore has an exhaust gas discharge duct 26 which runs away from the axial end of the turbine impeller 12 in the direction of the turbocharger axis 2 and has an outlet puff connection piece 27 for connection to the exhaust system (not shown) of the internal combustion engine. The exhaust gas mass flow AM emerging from the turbine impeller 12 is discharged into the exhaust system of the internal combustion engine via this exhaust gas discharge duct 26. The steel material SWst according to the invention, which characterizes the turbine housing 20 and from which the turbine housing 20 is made, is symbolized by the cross hatching.

A wastegate valve 29 connects the exhaust gas supply duct 23 in the flow direction of the exhaust gas mass flow AM in front of the turbine impeller 12 to the exhaust gas discharge duct 26 in the flow direction of the exhaust gas mass flow AM behind the turbine impeller 12 via a wastegate duct 291 in the turbine housing 20. The wastegate valve 29 can be closed via a closing device, can be opened or closed. This locking device has a spindle arm 292 which is rotatably mounted in the turbine housing 20 and on which a flap plate 293 is arranged. Both spindle arm 292 and the Klap penteller 293 are made in this example from the steel material SWst according to the invention. By actuating the spin delarm 292 by means of an external actuator (not shown), the flap plate 293 is placed or closed to close or open the wastegate valve 29 in a sealing manner on the valve seat 294 of the wastegate channel 291.

FIG. 2, on the other hand, shows an embodiment of an exhaust gas turbocharger 1 with an exhaust gas guide device, here a variable turbine geometry 50, also referred to as VTG for short. The basic structure of the exhaust gas turbocharger 1 with the turbine housing 20, the compressor housing 30, the bearing housing 40 and the turbocharger rotor 10 essentially corresponds to the exhaust gas turbocharger 1 shown in FIG. Instead of a wastegate valve, however, a VTG 50 is provided here. This consists essentially of two annular bearing disks 51, 52, which are arranged at a certain distance from one another in the annular gap-shaped transition region between the turbine spiral duct 22 and the turbine impeller 12 and thus form the exhaust gas inlet gap 25. Between the bearing disks 51, 52 are arranged in the exhaust gas inlet gap 25, distributed over the circumference of the exhaust gas inlet gap, several guide vanes. These are accommodated in a rotatably mounted manner in at least one of the bearing disks and their rotational position can be set by means of an actuating mechanism 55 arranged on the rear side of this bearing disk and an external actuator (not shown). Both the turbine housing 20 and the bearing disks 51, 52 and the guide vanes 53 in this embodiment consist of the steel material SWst according to the invention.

Claims

1. Exhaust gas turbocharger (1) with a turbine housing (21) with a receiving area for a turbine wheel (12) of the exhaust gas turbocharger (1) arranged centrally to a turbine housing axis (2a) and at least one helical to the receiving area for the turbine wheel (12) tapered, turbine spiral channel (22),

being a wastegate valve with a

Spindle arm and a flap plate arranged thereon, or a variable exhaust gas guide device with bearing disks and guide vanes is arranged,

characterized in that at least one of the components: turbine housing, spindle arm and flap plate, or bearing washers and guide vane, has a steel material (21a) for high-temperature applications, the material of which, apart from iron, Fe, contains at least the following alloy components in quantities in the specified limits in percent by weight:

Carbon, C: 0.4-0.5%;

Silicon, Si: 1.25-1.75%;

Manganese, Mn: 3.0-12.0%;

Chromium, Cr: 19.5-20.5%;

Nickel, Ni: 5.0-0.0.0%;

Niobium, Nb: 1.00-1.5%.

2. Exhaust gas turbocharger according to claim 1, characterized in that the steel material has at least one of the specified alloying constituents at least in quantities within the following limits in percent by weight:

Silicon, Si: 1.35-1.65%;

Manganese, Mn: 7.0-12.0%, especially 9.0-12%.

3. Exhaust gas turbocharger according to claim 1 or 2, characterized in that the steel material contains at least one of the further alloy components in proportions up to a maximum of the stated amounts in percent by weight:

Tungsten, W: up to 0.6%; Vanadium, V: up to 0.12%;

Copper, Cu: up to 0.25%;

Cobalt, Co: up to 1.0%;

Sulfur, S: up to 0.03% and

Phosphorus, P: up to 0.04%.

4. Exhaust gas turbocharger according to claim 3, characterized in that the steel material contains the at least one of the other alloying constituents in proportions of at least the given amounts in percent by weight:

Tungsten, W: at least 0.3%;

Vanadium, V: at least 0.06%;

Copper, Cu: at least 0.1%;

Cobalt, Co: at least 0.5%;

Sulfur, S: at least 0.013% and

Phosphorus, P: at least 0.02%.

5. Exhaust gas turbocharger according to one of the preceding claims, characterized in that the steel material has a completely austenitic structure.