KR20180108881A - Turbocharger and component therefor - Google Patents

Abstract

And more particularly to a component for turbocharger application in a diesel engine, wherein the component consists 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 invention relates to an exhaust gas turbocharger according to the preamble of claim 1, in particular a component for a turbocharger application in a diesel engine, and a component according to the preamble of claim 7.

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

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

There are very high demands on the components of the turbocharger, and especially the kinematics or wastegate components of the turbocharger, or the VTG components in the case of a VTG turbocharger. The materials of these components must have heat resistance. In other words, the material must still have sufficient strength and hence dimensional stability at very high temperatures up to about 900 ° C. In addition, the material must have high abrasion resistance and adequate oxidation resistance, thereby reducing corrosion or abrasion of the material even at high operating temperatures of hundreds of degrees Celsius, ensuring the resistance of the material under extreme operating conditions.

DE 10 2004 062 564 A1 discloses a blade bearing ring for a turbocharger with low sliding wear and good thermal stability. In this type of blade bearing ring, austenitic materials use an iron-based alloy with a high sulfur content to improve the lubrication of the component. Due to the particular 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 view of this, it is an object of the present invention to provide a turbocharger according to the preamble of claim 1 and components for turbocharger application according to the preamble of claim 1, High temperature strength and corrosion resistance, characterized by optimum friction characteristics, and additionally exhibiting a reduction in wear sensitivity.

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

By means of embodiments according to the invention in the form of components in the form of components for turbocharger applications or in the form of exhaust gas turbochargers comprising such components, the improvement of the internal temperature properties of the materials, and in particular the improvement of the sliding wear characteristics, , Wherein the component consists of an iron-based alloy having a ferrite base structure comprising carbide and nitride structures. In the context of the present invention, the carbide structure or nitride structure is understood to mean a microstructured carbide precipitate phase or a nitride precipitate phase formed in the grain and grain boundary of the iron-based alloy in this case. The carbide structure is in particular a dendritic microstructure and as a result also achieves very good deformation resistance and wear resistance of the material and consequently of the components. Therefore, there is provided an exhaust gas turbocharger comprising a component for a turbocharger application, or at least one component according to the present invention, which has an optimum temperature resistance of up to 900 DEG C, high high temperature strength, And is characterized by very good sliding properties and low oxidation tendencies, 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, dewater stability, and high temperature performance are improved.

The dependent claims relate to advantageous improvements of the present 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- Can be significantly improved by at least one use. The W, Ti, and Nb elements substantially form the carbide forming portions in the iron-based alloy, which in addition to very good wear performance increases the corrosion resistance of the material and hence the components according to the invention.

In another embodiment, the component according to the present 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 and 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 alloys may here be used in their original form, i.e. in elemental form, e.g. in the form of inclusions or precipitation phases, or in the form of derivatives thereof, for example during the production of iron- The metal carbide or metal nitride may be present in the form of a compound of the corresponding 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 carbon (C) element here serves primarily to form the carbide structure, i.e. carbide precipitation phase, according to the invention, so that the strength and high temperature strength of the material and therefore the strength of the component according to the invention for turbocharger applications, Improves strength. The tungsten element also increases the high temperature strength and abrasion 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 corrosion resistance and hot corrosion performance, especially of materials in acidic media. The use of chromium here increases the high temperature tensile strength and scaling resistance of the material. Chromium is also a strong carbide former, thus also optimizing the wear properties of the material and hence of the components according to the invention. The use of chromium elements in the iron-based alloys to form components according to the invention for turbocharger applications has another advantage: under the high exhaust gas temperatures that act on the components, chromium forms Cr ₂ O ₃ surface layers That is, an oxide surface layer, which effectively promotes the resistance of the component to sliding friction and abrasion wear under thermal load. The use of manganese has 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 main particles of the iron-based alloy during the production of the iron-based alloy, and refines the casting structure of the iron-based alloy accordingly. Thereby, a high grain refinement is achieved, which promotes the homogeneity of the iron-based alloy and allows a higher dynamic contact pressure of the material. In the iron-based alloy forming the component according to the present invention, the niobium element acts as a carbide-forming agent, thereby promoting the carbide structure at the grain boundary and grain boundary of the iron-based alloy. Niobium also increases the high temperature strength and fatigue strength of the material according to the present invention for and accordingly turbocharger applications. In addition, niobium promotes ferrite formation and reduces the gamma region of the iron-based alloy, so it can be used within regulatory capacity. Silicon promotes the casting properties of iron-based alloys by reducing the viscosity of the melt during casting. In addition, silicon in the material according to the present invention promotes deoxidation, and thus the addition of these elements to alloys improves crucial high temperature corrosion resistance. Therefore, by appropriately selecting and combining the elements, the properties of the iron-based alloys can be controlled in a targeted manner, so that the components according to the invention for turbocharger applications and accordingly the exhaust gas turbocharger according to the invention, Balanced profile characteristics. Additional elements and compounds can be incorporated into the iron-based alloy.

According to another 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% by weight to 22% by weight, (Mn), 0.8 to 2.1 wt.%, In particular 1 to 1.8 wt.% Of silicon (Si), in particular 18 wt.% To 20 wt.% Cr, 1.3 wt. (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 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 these elements means that the elements may be present in elemental form and also in the form of one of the compounds of the elements in the component according to the invention for the iron-based alloy and accordingly for the turbocharger application . 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 occupies less than 2% by weight, especially less than 1% by weight, based on the total weight of the iron-based alloy). In this case, the inevitable residues or impurities include, for example, aluminum (Al), nickel (Ni), zirconium (Zr), cerium (Ce), boron (B), phosphorus (P) and sulfur (S). The amount of individual elements can in this case be detected directly in the components according to the invention by conventional elemental analysis methods.

Surprisingly, it has been found that precisely the combination described above provides a material, i. E., An iron-based alloy, that provides particularly well-balanced profile characteristics to the component when machined to form components for turbocharger applications. 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 . Also, during operation of the turbocharger on the component, corrosion resistance and oxidation resistance are maximized, especially at high operating temperatures.

Therefore, the material which is manufactured in this way and which forms the component according to the invention has the following characteristics.

According to another embodiment of the present invention, the components for the turbocharger application are substantially sigma-phase. This applies in particular to the operation of the components according to the invention at a maximum of 900 ° C. This effectively counteracts the embrittlement of the material, and as a result increases the durability of the component. The sigma phase is a brittle metal phase with high hardness. These occur only when the bodily-centered cubic metal and the face-centered cubic metal with matching atomic radii collide with each other with a slight difference. 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, in order to avoid the undesirable effects described herein, the iron-based alloys according to the invention and therefore the components according to the invention are substantially non-sigma phase. The reduction or prevention of sigma phase formation is controlled in particular by the targeted choice of the elements of the iron-based alloy, and in particular the silicon content in the alloying material is in each case 2.1% by weight or less, preferably 1.8% by weight % ≪ / RTI >

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 According to the present invention. Due to these excellent properties, the components according to the invention are particularly suitable for components for turbocharger applications 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.

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

As an object that can be treated independently, claim 7 is characterized in that it comprises at least one component, as described above, comprising an iron-based alloy having a ferrite base structure and including a carbide and nitride structure, Defines a turbocharger.

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

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

1 shows a partial cutaway perspective view of an exhaust gas turbocharger according to the present invention. 1 shows a turbocharger 1 according to the present invention having a turbine casing 2 and a compressor casing 3 connected to a turbine casing via a bearing casing 28. Fig. The casings 2, 3, 28 are disposed along the rotation axis R. The turbine casing is shown in partial cross-section to show the arrangement of the blade bearing ring 6 and the radial outer guide grid 18, the guide grid being formed by the ring and having a rotational axis 8, And a plurality of regulating blades (7). In this way, nozzle cross-sections are formed which are larger or smaller depending on the position of the regulating blades 7 so that they are larger on the turbine rotor 4 located at the center of the rotation axis R together with the exhaust gas from the engine The exhaust gas is supplied through the supply duct 9 and discharged through the central connecting part 10 to be supplied to the compressor rotor 17 which is seated on the same shaft using the turbine rotor 4 .

A driving device 11 is provided for controlling the movement or the position of the adjusting blades 7. While this may be designed in any desired manner, the preferred embodiment comprises a control casing 12, which controls the control movement of the tappet member 14 fastened thereto and is located at the rear of the blade bearing ring 6 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. A 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. In order to ensure this free space 13, the blade bearing ring 6 has spacers 16.

Example

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

A plurality of components according to the present invention for turbocharger application, specifically an iron-based alloy having formed flap shafts, flap plates, and bushings, are manufactured by the following process with the following elements. 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 wt% Ti, 0.3 to 0.5 wt%, W: 2 to 2.7 wt%, V: 0.5 to 0.8 wt%, N: 3 wt% 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 manufactured according to this embodiment were characterized by the following characteristics:

The material was subjected to a series of validation tests including the following tests.

- Outdoor weathering test

- Climate change test

- Thermal shock test / cycle test - 300 hours

- high temperature in the cracking furnace - gas corrosion test

- 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 action 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 .

Thermal cycle test:

The components (shaft / bush) according to the present invention were subjected to a heat cycle test, where thermal shock was performed as follows:

1. Use of stationary rotors;

2. 2-EGT operation;

3. Test duration: 350 hours (about 2000 cycles);

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

5. High temperature: Rated power point T3 = 750 ℃, Turbine side mass flow EGT: 0.5kg / s;

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

7. Cycle duration: 2X5 minutes (10 minutes);

8. Three intermediate crack tests are carried out.

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 shown here demonstrate that the components according to the invention are ideally suited for turbocharger applications in the temperature range of up to 900 < 0 > C.

1 turbocharger
2 turbine casing
3 Compressor casing
4 turbine rotor
5 Adjusting ring
6 blade bearing ring
7 Adjustable blade
8 Pivot axis
9 Supply duct
10 Axial connection parts
11 drive
12 Control casing
13 Free space for adjusting blades (7)
14 tappet member
15 annular portion of the turbine casing (2)
16 spacer / spacer cam
17 compressor rotor
18 Guide grid
28 Bearing casing
R rotating shaft

Claims (10)

As a component for turbocharger applications in diesel engines in particular,
Wherein the component comprises an iron-based alloy having a ferrite base structure comprising a carbide and nitride structure. The component of claim 1, wherein the component comprises at least one of the elements selected from W, Ti, and Nb. The component of claim 1 or 2, wherein the component comprises at least one of the elements selected from C, W, Cr, Mn, Ti, V, Nb and Si. 4. A component for a turbocharger application as claimed in any one of claims 1 to 3, wherein said 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, especially 18% to 20%
Mn: 1.3% by weight or less, particularly 1% by weight or less,
Si: 0.8 wt.% To 2.1 wt.%, Especially 1 wt.% To 1.8 wt.%,
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, especially 0.3 to 0.5% by weight,
W: 1.8 wt.% To 3.0 wt.%, Especially 2 wt.% To 2.7 wt.%,
V: 0.3% by weight to 1.0% by weight, in particular 0.5% by weight to 0.8% by weight,
N: 3% by weight or less, especially 2% by weight or less, and
Fe: at most 100% by weight. 5. A component for a turbocharger application as claimed in any one of claims 1 to 4, wherein the component is substantially non-sigma phase. 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 / A component for. Especially for exhaust gas turbochargers for diesel engines,
Wherein the turbocharger comprises at least one component of an iron-based alloy having a ferrite base structure comprising a carbide and nitride structure. 8. The method of claim 7, wherein the component comprises at least one of the elements selected from W, Ti, Nb and in particular at least one of the elements selected from C, W, Cr, Mn, Ti, V, , Exhaust gas turbocharger. 9. An exhaust gas turbocharger according to claim 7 or 8, wherein said 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, especially 18% to 20%
Mn: 1.3% by weight or less, particularly 1% by weight or less,
Si: 0.8 wt.% To 2.1 wt.%, Especially 1 wt.% To 1.8 wt.%,
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, especially 0.3 to 0.5% by weight,
W: 1.8 wt.% To 3.0 wt.%, Especially 2 wt.% To 2.7 wt.%,
V: 0.3% by weight to 1.0% by weight, in particular 0.5% by weight to 0.8% by weight,
N: 3% by weight or less, especially 2% by weight or less, and
Fe: at most 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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