KR20140038472A - Turbocharger and component therefor - Google Patents

Abstract

Particularly disclosed is a component for turbocharger applications in diesel engines, the component being made of an iron-based alloy having a ferrite base structure comprising carbide and nitride structures.

Description

Turbocharger and its components {TURBOCHARGER AND COMPONENT THEREFOR}

The present invention relates to an exhaust gas turbocharger comprising a component according to the preamble of claim 1, in particular for a turbocharger application in a diesel engine, and a component according to the preamble of claim 7.

An exhaust gas turbocharger is a system for increasing the power of a piston engine. In an exhaust gas turbocharger, the power of the exhaust gas is used to increase power. The increase in power is the result of increased throughput of the mixture per work stroke.

The turbocharger consists essentially of an exhaust gas turbine together with a shaft and a compressor, wherein the compressor disposed in the intake pipe of the engine is connected to the shaft and the blade wheels located in the exhaust turbine and the casing of the compressor rotate. In the case of a turbocharger with a variable turbine structure, the regulating blades are additionally rotatably mounted to the blade bearing ring and are moved by an adjustment ring disposed in the turbine casing of the turbocharger.

There are very high demands on the material of the turbocharger, and in particular the kinematics or wastegate components of the turbocharger, or in the case of a VTG turbocharger. The material of these components must be heat resistant. In other words, the material should still have sufficient strength and hence dimensional stability even at very high temperatures of up to about 900 ° C. In addition, the material must have high wear resistance and adequate oxidation resistance, thereby reducing corrosion or wear of the material even at high operating temperatures of several hundred degrees Celsius, thereby continuing to ensure the material's resistance even under extreme operating conditions.

DE 10 2004 062 564 A1 discloses a blade bearing ring for a turbocharger with low slip wear and good thermal stability. In this type of blade bearing ring, austenitic materials, iron-based alloys with high sulfur content are used to improve the lubrication of the components. Due to the specific composition, the creep resistance of the material increases, achieving an increase in the dimensional stability of the blade bearing ring at temperatures above 850 ° C.

In this respect, it is an object of the present invention to provide a component for a turbocharger application according to the preamble of claim 1 and a turbocharger according to the preamble of claim 7 which are improved It has temperature and oxidation resistance and therefore very good dimensional stability and high high temperature strength and corrosion resistance, is characterized by optimum friction properties and further exhibits reduced wear sensitivity.

This object is achieved by the features of claims 1 and 7.

By the embodiment according to the invention in the form of components for turbocharger applications, or in the form of exhaust gas turbochargers comprising such components, the improvement of the temperature resistance of the material and in particular of the sliding wear characteristics and the tendency of oxidation To achieve a reduction of, the component consists of an iron-based alloy having a ferrite base structure, including carbide and nitride structures. In the context of the present invention, a carbide structure or nitride structure is understood in this case to mean a microstructured carbide precipitated phase or nitride precipitated phase formed at the particles and grain boundaries of the iron-based alloy. The carbide structure is in particular dendritic microstructure, as a result also achieving very good deformation and wear resistance of the material and thus of the components. Therefore, there is provided a component for turbocharger applications, or an exhaust gas turbocharger comprising at least one component according to the invention, which has an optimum temperature resistance of up to 900 ° C, high high temperature strength, and high wear resistance and resistance. It is corrosive and is also characterized by very good sliding properties and low oxidation tendency, especially at high operating temperatures. In addition, the components according to the invention and therefore the exhaust gas turbocharger according to the invention are also diesel-water stable in long-term operation.

Without wishing to be bound by theory, it is believed that the presence of carbide precipitates and nitride precipitates in ferritic iron-based alloys significantly increases the stability of the alloying materials, and hence the stability of the components, and the high temperature strength, especially due to friction wear, .

By way of example, ferrous alloys according to the invention, i.e. ferritic ferrous materials with carbides and nitride structures forming the constituent elements, have a contact pressure of 20 MPa, a sliding speed of 0.0025 m / s, a component temperature of about 850 DEG C, Is given a maximum sliding wear rate of 0.08 mm per diameter, that is, excellent friction and wear resistance. In addition, high temperature strength, dimensional stability, and high temperature performance are improved.

The dependent claims relate to advantageous improvements of the invention.

Thus, in one embodiment, the wear characteristics of the component, i.e. specifically the wear and tear resistance, can be determined by comparing the tungsten (W), titanium (Ti) and niobium (Nb) elements in the ferritic iron- It can be significantly improved by at least one use. The W, Ti, Nb elements substantially form carbide forming parts in the iron-based alloy, which, in addition to very good wear performance, increase the corrosion resistance of the material and thus of the component according to the invention.

In another embodiment, the component according to the invention for a turbocharger application is characterized in that it comprises at least one of the elements selected from C, W, Cr, Mn, Ti, V, Nb, Si. The presence of at least one of these elements should be understood to mean that such an element or a combination of these elements is then used to produce an iron-based alloy which is then processed to form the component according to the invention. The elements added to the iron-based alloy are here in their original form, ie in elemental form, for example in the form of inclusions or precipitation phases, or in the form of derivatives thereof, i.e. during the production of iron-based alloys or for iron-based alloys. As a metal carbide or metal nitride formed when forming the component according to the present invention prepared in the form, it may exist in the form of a compound of the element. The presence of the elements in this case can be detected directly in the components according to the invention by conventional analytical methods.

The element (C) here serves primarily to form the carbide structure according to the invention, i.e. the carbide precipitated phase, so that the strength and high temperature strength of the material and thus the strength and high temperature of the components according to the invention for turbocharger applications. Improve strength. Tungsten element also increases the high temperature strength and wear resistance of the material, mainly as a result of carbide structure formation, and contributes to the toughness of the material. The combination of chromium and / or molybdenum and tungsten enables a significant improvement in the corrosion resistance and high temperature corrosion performance of the material, especially in acidic media. The use of chromium here increases the high temperature tensile strength and scaling resistance of the material. Since chromium is also a strong carbide former, it also optimizes the wear characteristics of the material and hence of the component according to the invention. The use of elemental chromium in the iron-based alloy forming components according to the invention for turbocharger applications has another advantage: Under the high exhaust gas temperatures acting on the component, chromium is the Cr ₂ O ₃ surface layer on the component. That is, it forms an oxide surface layer, which effectively promotes the component's resistance to sliding friction and frictional wear under thermal load. The use of manganese has a deoxidizing effect. This expands the gamma region of the iron-based alloy and increases the yield strength and tensile strength of the material. In addition, manganese promotes wear resistance of components, especially at high operating temperatures. Vanadium refines the major particles of the iron-based alloy during the production of the iron-based alloy, thereby purifying the cast structure of the iron-based alloy. This achieves high particle purity, which promotes homogeneity of the iron-based alloy and allows higher dynamic contact pressures of the material. In the iron-based alloy forming the component according to the present invention, the niobium element serves as a carbide former to promote the carbide structure at the grain and grain boundaries of the iron-based alloy. Niobium also increases the high temperature strength and fatigue strength of the material and thus the component according to the invention for turbocharger applications. In addition, niobium promotes ferrite formation and reduces the gamma area of the iron-based alloy, and thus can be used within a regulated capacity. Silicon promotes the casting properties of iron-based alloys by reducing the viscosity of the melt during casting. In addition, the silicon in the material according to the invention promotes deoxidation and, thus, the addition of such elements to the alloy decisively improves high temperature corrosion resistance. Therefore, by appropriately selecting and combining the elements, it is possible to control the properties of the iron-based alloy in a targeted manner, so that the components according to the invention for turbocharger applications and therefore the exhaust gas turbochargers according to the invention are particularly Have balanced profile properties. Additional elements and compounds may be introduced into the iron base alloy.

According to a further embodiment, the components according to the invention for turbocharger applications comprise from 0.1% to 0.5% by weight, in particular from 0.25% to 0.4% by weight of carbon (C), from 15% to 22% by weight, in particular 18% to 20% by weight of chromium (Cr), up to 1.3% by weight, in particular up to 1% by weight of manganese (Mn), 0.8% to 2.1% by weight, in particular 1% to 1.8% by weight of silicon (Si) (Ti), 1.8 to 3.0% (by weight) of titanium oxide, 0.4 to 1.3% by weight, especially 0.6 to 1.1% by weight of niobium (Nb), 0.2 to 0.6% In particular from 2 to 2.7% by weight of tungsten (W), from 0.3 to 1.0% by weight, in particular from 0.5 to 0.8% by weight of vanadium (V), up to 3% by weight, in particular up to 2% Nitrogen (N), and residual iron (Fe). Here, the indication of the quantity in each case relates to the total weight of the iron-based alloy forming the component according to the invention. As mentioned above, the presence of the elements means that the elements may exist in elemental form and also in the form of one of the compounds of the elements in the iron-based alloy and thus in the component according to the invention for turbocharger applications. It should be understood to do. In this embodiment, substantially the above-mentioned elements are present in the components according to the invention in the indicated amounts. This means that inevitable impurities may be present (but preferably occupy less than 2% by weight, in particular less than 1% by weight, based on the total weight of the iron-based alloy). In this case, unavoidable residues or impurities include, for example, aluminum (Al), nickel (Ni), zirconium (Zr), cerium (Ce), boron (B), phosphorus (P), sulfur (S). The amount of individual elements can in this case be detected directly in the component according to the invention by conventional elemental analysis methods.

Surprisingly, it has been found that the precisely described combination provides a material, i.e. an iron-based alloy, which gives the component particularly balanced profile properties when processed to form a component for a turbocharger application. This composition according to the invention provides a component which is characterized by a particularly high high temperature strength, a high temperature resistance of up to 900 DEG C and, therefore, dimensional stability at high temperatures, and an excellent sliding property and consequently a particularly low sliding wear . In addition, corrosion and oxidation resistance are maximized during the operation of the turbocharger on that component, especially at high operating temperatures.

Therefore, the material produced in this way and forming the component according to the invention has the following properties.

According to another embodiment of the invention, the components for the turbocharger application are substantially free of sigma. This applies in particular to the operation of the components according to the invention at up to 900 ° C. This effectively counteracts embrittlement of the material, and consequently increases the durability of the component. Sigma phase is a high hardness brittle intermetallic phase. These occur only when the body centered cubic metal and the face centered cubic metal having a matching atomic radius collide with each other with only slight differences. This type of sigma phase is undesirable because it has a brittleness effect and also because of the properties of the iron matrix to draw chromium. Therefore, to avoid the undesirable effects described herein, the iron-based alloy according to the invention and thus the component according to the invention are substantially free of sigma phases. The reduction or prevention of sigma phase formation is in particular controlled by the desired selection of the elements of the iron-based alloy, in particular the silicon content in the alloying material being in each case up to 2.1% by weight, preferably 1.8% based on the total weight of the iron-based alloy Achieved in terms of% or less

Therefore, components for turbocharger applications featuring excellent wear performance, high slip wear resistance, high temperature strength, and dimensional stability even at high temperatures of up to 900 DEG C, and further characterized by excellent oxidation resistance and corrosion resistance Will be described according to the present invention. These excellent properties make the component according to the invention particularly suitable for components for turbocharger applications which are exposed to high temperatures and / or high friction levels of up to 900 ° C. Exemplary components include dynamic components, waste gate components, and VTG components, particularly VTG components and flap mount components.

Iron-based alloys can be manufactured and processed to form components according to the invention for turbocharger applications by conventional processes. To ensure dimensional stability, age-annealing may be performed at 900 ° C. for about 2 hours, followed by air cooling, to produce secondary precipitates. The material may be welded by TIG, plasma, EB welding processes.

As an object that can be handled independently, claim 7 consists of an iron-based alloy with a ferrite base structure and comprises at least one component as described above, comprising a carbide and nitride structure. Define the turbocharger.

Advantageous embodiments of the component according to the invention are also applicable in embodiments of the exhaust gas turbocharger according to the invention.

1 shows a partially cutaway perspective view of an exhaust gas turbocharger according to the invention.

1 shows a partially cutaway perspective view of an exhaust gas turbocharger according to the invention. 1 shows a turbocharger 1 according to the invention with a turbine casing 2 and a compressor casing 3 connected to the turbine casing via a bearing casing 28. The casings 2, 3, 28 are arranged along the axis of rotation R. The turbine casing is shown in partial cross-sectional view to show the placement of the blade bearing ring 6 and the radially outer guide grating 18, which is formed by the ring and has a shaft of rotation 8 and is distributed circumferentially. A plurality of adjustment blades 7 are provided. In this way, nozzle cross sections which become larger or smaller depending on the position of the regulating blades 7 are formed, which are larger on the turbine rotor 4 which is located in the center of the axis of rotation R with the exhaust gas from the engine. Or smaller, the exhaust gas is supplied through a supply duct 9, discharged through a central connecting element 10, and the compressor rotor 17 seated on the same shaft using the turbine rotor 4. Drive.

A drive device 11 is provided for controlling the movement or position of the adjusting blades 7. It can be designed in any desired manner, but the preferred embodiment includes a control casing 12, which controls the control movement of the tappet member 14 fastened thereto, so that the rear of the blade bearing ring 6 is controlled. The movement of the tappet member relative to the control ring 5 located in the control ring 5 is converted into a small rotational movement of the control ring. Free space 13 for the regulating blades 7 is formed between the blade bearing ring 6 and the annular portion 15 of the turbine casing 2. To ensure this free space 13, the blade bearing ring 6 has spacers 16.

Example

Unless otherwise specified, the indication of the amount of individual elements is in each case related to the total weight of the iron-based alloy.

A plurality of components according to the invention for turbocharger applications, in particular iron-based alloys with flap shafts, flap plates, bushes, have been produced from the following elements by a general process. The chemical analysis yielded the following values for the elements: C: 0.25 wt% to 0.4 wt%, Cr: 18 wt% to 20 wt%, Mn: less than 1 wt%, Si: 1 wt% to 1.8 wt% : 0.6% to 1.1% by weight, Ti: 0.3% to 0.5% by weight, W: 2% to 2.7% by weight, V: 0.5% to 0.8% by weight, N: 3% by weight or less, and remaining portions Iron (Fe). In addition, trace amounts of unavoidable residues of Al, Ni, Zr, Ce, B, P and S were found in a ratio of less than 1% by weight.

The components produced according to this embodiment were characterized by the following characteristics:

The material went through a series of validation tests, including the following tests.

Outdoor weathering test

Climate change test

Thermal shock test / cycle test-300 hours

-Hot-gas corrosion test in cracking furnace

-Strauss test according to DIN EN ISO 3651-2

Vibration friction wear test of friction system: bush / shaft at operating temperature (900 ℃)

Each component was characterized by excellent resistance to effort in all tests. Therefore, the material has very high abrasion resistance and excellent oxidation resistance, thereby significantly reducing the corrosion and wear / abrasion of the material under the indicated conditions, and consequently the resistance of the material and of the components formed of the material to the long term Guaranteed throughout.

Heat cycle test:

The components (shaft / bush) according to the invention have been subjected to thermal cycle testing, where the thermal shock is implemented as follows:

1. use of stationary rotors;

2. 2-EGT operation;

3. Duration of test: 350 hours (about 2000 cycles);

4. Throughout the test, the exhaust flaps of the EGTs remain 15 ° open;

5. High temperature: rated power point T3 = 750 ° C., mass flow EGT at turbine side: 0.5 kg / s;

6. Low temperature: T3 = 100 占 폚, mass flow EGT on the turbine side: 0.5 kg / s;

7. Cycle duration: 2 × 5 minutes (10 minutes);

8. Three intermediate crack tests are performed.

Given the following load groups, each component (shaft / bush) according to the present invention was characterized by low high temperature oxidation, i.e. an oxidation rate of less than or equal to 40 [mu] m, especially less than or equal to 35 [mu] m at component temperatures of 900 [deg.] C.

The results presented here demonstrate that the components according to the invention are ideally suited for turbocharger applications in the temperature range up to 900 ° C.

List of reference marks

1 turbocharger

2 turbine casing

3 compressor casing

4 turbine rotor

5 adjustable ring

6 blade bearing ring

7 adjustable blades

8 pivot axis

9 supply duct

10 axial connection parts

11 drive unit

12 control casing

13 Free space for the adjustable blades (7)

14 tappet member

15 annular part of the turbine casing (2)

16 spacer / spacer cam

17 compressor rotor

18 guide grid

28 bearing casing

R axis of rotation

Claims (10)

Especially for turbocharged applications in diesel engines,
Wherein said component is made of an iron-based alloy having a ferrite base structure comprising carbide and nitride structures. The component of claim 1, wherein the component comprises at least one of elements selected from W, Ti, Nb. The component of claim 1 or 2, wherein the component comprises at least one of elements selected from C, W, Cr, Mn, Ti, V, Nb, Si. The component as claimed in claim 1, wherein the component comprises substantially the following elements.
C: 0.1% to 0.5% by weight, in particular 0.25% to 0.4% by weight,
Cr: 15% to 22% by weight, in particular 18% to 20% by weight,
Mn: 1.3 wt% or less, especially 1 wt% or less,
Si: 0.8% to 2.1% by weight, in particular 1% to 1.8% by weight,
Nb: 0.4% to 1.3% by weight, in particular 0.6% to 1.1% by weight,
Ti: 0.2% to 0.6% by weight, in particular 0.3% to 0.5% by weight,
W: 1.8% to 3.0% by weight, in particular 2% to 2.7% by weight,
V: 0.3% to 1.0% by weight, in particular 0.5% to 0.8% by weight,
N: 3 wt% or less, especially 2 wt% or less, and
Fe: up to 100% by weight. The component of claim 1, wherein the component is substantially free of sigma. 6. Turbocharger application according to any one of claims 1 to 5, wherein the component is a dynamic component and / or a waste gate component and / or a VTG component, in particular a VTG component and / Component for. Especially as exhaust turbocharger for diesel engine,
Wherein said turbocharger comprises at least one component of an iron-based alloy having a ferrite base structure comprising a carbide and nitride structure. 8. The device of claim 7, wherein the component comprises at least one of elements selected from W, Ti, Nb, and in particular at least one of elements selected from C, W, Cr, Mn, Ti, V, Nb, Si. Exhaust gas turbocharger. The exhaust gas turbocharger according to claim 7 or 8, wherein the component substantially comprises the following elements.
C: 0.1% to 0.5% by weight, in particular 0.25% to 0.4% by weight,
Cr: 15% to 22% by weight, in particular 18% to 20% by weight,
Mn: 1.3 wt% or less, especially 1 wt% or less,
Si: 0.8% to 2.1% by weight, in particular 1% to 1.8% by weight,
Nb: 0.4% to 1.3% by weight, in particular 0.6% to 1.1% by weight,
Ti: 0.2% to 0.6% by weight, in particular 0.3% to 0.5% by weight,
W: 1.8% to 3.0% by weight, in particular 2% to 2.7% by weight,
V: 0.3% to 1.0% by weight, in particular 0.5% to 0.8% by weight,
N: 3 wt% or less, especially 2 wt% or less, and
Fe: up to 100% by weight. 10. An exhaust gas turbocharger according to any one of claims 7 to 9, wherein the component is substantially sigma-phase.

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