EP1215366A2 - Turbomachine blade - Google Patents

Abstract

Turbine blade has a tensile strength Rm of at least 700 N/mm<2>, a creep limit Rp0.2, an expansion A of at least 15% and a constriction Z of at least 10%. The blade is produced from a powder metallurgical feed material formed by pulverizing a melt by atomizing with nitrogen and hot isostatically pressing the powder; machining and thermally treating or tempering.

Description

The invention relates to a turbine blade for steam or gas turbines as well as compressors, which shovel made of primary material by cutting Machining is created and thermally treated or remunerated.

Turbine blades with one for the respective use in the turbines and Compressors required shape can be made according to the drop forging process by machining from a billet or by forging Raw form with a subsequent chip removal can be created. It will Pre-material from alloys solidified in forms by forging and / or Rolls produced and optionally heat-treated for further processing. It is known to use casting blocks, continuous casting booms or remelting blocks for the To use primary material production.

To increase the efficiency, turbines are built with high steam inlet temperatures of up to 600 ° C and above and small gaps between the deflection and rotor blades, so that the quality and properties of the blade material are of particular importance. It is extremely important here that when the turbine heats up to the operating state and subsequently during load running, the blades "stand", ie do not bend, and that, particularly in the case of the rotor blades, the material does not creep at the high operating temperature and such a centrifugal load , Turbines for two-phase generators have a number of revolutions of 3000 or 3600 min- ¹ , which results in considerable stresses on the rotor blades when the same is high.

The turbine blades produced by the method described at the beginning point across the cross-section and if necessary in axis or Longitudinal segregations that result from block solidification. At a Hot forming and heat treatment are these inhomogeneities stretched and partially diminished by diffusion, a perfect one However, material homogeneity cannot be achieved. Even when used of remelting blocks such as electro-slag remelting or Vacuum remelting blocks is usually not a complete isotropy of the Alloy material achievable.

Now shows a turbine blade anisotropy with eccentric over the cross section ongoing segregations, so it can when heating and / or stress the same for emigration of the blade ends from the intended position what the turbine manufacturer has to take into account. For example a stronger picture of segregation can be disclosed by the magnetic powder method.

In turbine construction, the high availability and safety of the Thermal engine turbine blades required the highest possible on the one hand Have material homogeneity and on the other hand a low tendency to creep Have material at operating temperature. The aim of the invention is To create turbine blades that cut at the flow surfaces are processed and meet the above requirements.

This goal is achieved in that a turbine blade with the material properties at room temperature: tensile strenght R _m = at least 700 N / mm ² yield strength R _p0.2 = at least 550 N / mm ² strain A = at least 15% constriction Z = at least 10% for steam turbines or gas turbines and compressors, formed from a powder metallurgy (PM), in the case of pulverizing a melt by gas atomization using nitrogen and hot isostatic pressing (HIP) of the powder, manufactured raw material, which is machined and the turbine blade thus created is thermally treated or tempered.

The advantages achieved with the invention are essentially that a, after the powder metallurgy (PM) process is essentially free of segregation and a high material homogeneity from it manufactured turbine blade ensures. Even with a high degree of deformation or a large longitudinal stretch of the material, the homogeneity remains, in particular obtained across the cross section, causing no tendency to a There is bending of the free blade ends.

In powder manufacture, it is essential to the invention that these are replaced by a Gas atomization by means of nitrogen takes place because one on the surface of the Powdered grains with a diameter of less than 0.2 mm Nitrogen content due to diffusion at the temperatures of the hot isostatic Presses are used, is evened out. A condensing of Metal powder takes place in a known manner in a container, the Residual cavities are evacuated before a HIP-en or filled with nitrogen.

It was quite surprising for the person skilled in the art that in comparison with the Manufacturing according to the prior art, a PM manufacturing such an essential Increased quality of the turbine blade. On the one hand, kick at one thermal treatment or when tempering the material no or only slight changes in shape of the PM blade on what is known as straightening largely unnecessary and avoids straightening tension, on the other hand can the significantly improved blade quality used in turbine construction and the Operational reliability of the heat engine can be increased.

If, as according to a development of the invention, the primary material after the hot isostatic presses (HIP-en), preferably in a near-final dimension Form, not deformed (as-HIP-ed) is machined can be a special one economic manufacture of the turbine blade can be achieved. Although loud Expert opinion an undeformed PM turbine blade, in the so-called " AS-HIPED "condition, the desired mechanical material properties are not may have, it has been found that such a blade partially even has improved quality features.

Special material advantages, especially with regard to increased homogeneity, can be achieved if the PM raw material is made of an iron-based alloy, which solidifies without ledeburit. Although the PM process is especially for Alloys were developed which solidify primary precipitates, for example carbides, and form this process in case of ledeburit freezing Steel cannot be effective in terms of quality, it has surprisingly been found that thus a significant increase in the quality of the blade alloy material is achievable.

A turbine blade for high thermal and mechanical, in particular dynamic loads and a lack of tendency towards end bending in practical use can be created if the PM primary material is made of a martensitic chrome steel with a composition of in% by weight. Chrome (Cr) to 29.0 Carbon (C) to 0.4 Nitrogen (N) up to 0.3 (C + N) 0.16 to 0.4 Molybdenum (Mo) to 2.0 Vanadium (V) to 1.0 Silicon (Si) to 0.6 Manganese (Mn) to 2.0 Sulfur (S) to 0.49 (Mn / S) MIN 2.0 Tungsten (W) to 2.5 Nickel (Ni) MAX 3.0 Niobium (Nb) to 0.12 Boron (B) up to 0.01 Iron (Fe) rest as well as production-related impurities and accompanying elements.

It was unexpectedly found that the material is comparatively a has less tendency to creep at operating temperature. The causes of this are scientifically not fully understood, but it is believed that some Elements, preferably through PM production, a certain Effect of dispersion hardness and retain shape at high temperatures are.

In terms of production technology, but also with regard to the long-term use properties, it can be preferred if the PM primary material for the turbine blade is made of a martensitic chromium steel with a composition of 1% by weight Cr = 8.0 to 22.0, preferably 9.0 to 16.0 C = 0.1 to 0.35, preferably 0.15 to 0.3 N = 0.005 to 0.28, preferably 0.1 to 0.24 (C + N) = 0.11 to 0.40, preferably 0.21 to 0.29 Mo = 0.5 to 2.0, preferably 0.8 to 1.8 V = 0.08 to 0.6, preferably 0.12 to 0.4 Si = 0.05 to 0.5, preferably 0.1 to 0.35 Mn = 0.05 to 2.0, preferably 0.5 to 0.95 S = 0.002 to 0.39, preferably 0.06 to 0.35 (Mn / S) = MIN 2.1, preferably MIN 2.5 Nl = MAX 2.4, preferably MAX 0.9 B = up to 0.01 Fe = Rest and production-related impurities is formed. The synergetic effect of the alloying elements of the PM material is beneficial for turbine blades in several ways. On the one hand, although sulfides with only a small diameter are present, the machinability of the material is significantly improved; on the other hand, if a certain Mn / S ratio is maintained, the mechanical properties remain unchanged at a high level even with frequent operating cycles.

It can also be provided according to the invention that the PM material is made of a soft martensitic or nickel martensitic steel with a composition of in% by weight. C = to 0.1 N = to 0.098 (C + N) = 0.05 to 0.12 Si = to 1.0 Mn = to 2.0 Cr = up to 20.0 S = to 0.49 Mn / S = MIN 1.9 Mo = to 3.0 V = up to 0.2 Ni = up to 8.0 Cu = to 4.5 B = up to 0.01 Al = to 0.08 Nb = to 0.6 Fe = Rest and production-related impurities is formed.

In these turbine blades made of alloys with a higher nickel content can have essentially the same improvements in material properties as can be achieved with the previously mentioned martensitic chrome steels, whereby the blade quality is significantly increased.

In order to optimize the manufacturing outlay and the usage properties of the turbine blade, it can be advantageous if the PM starting material is made of a martensitic steel with a composition in% by weight of C = 0.02 to 0.08, preferably 0.03 to 0.05 N = 0.001 to 0.05, preferably 0.0015 to 0.039 Si = 0.08 to 0.5, preferably 0.1 to 0.4 Mn = 0.1 to 1.9, preferably 0.2 to 1.6 S = 0.003 to 0.39, preferably 0.1 to 0.35 Cr = 9.0 to 20.0, preferably 9.0 to 13.0 Mo = to 2.0, preferably 0.6 to 1.8 Ni = 3.0 to 7.9, preferably 3.5 to 6.8 Cu = 1.0 to 4.4 al to 0.04 Fe = Rest and production-related impurities is formed.

Extensive tests and material tests have shown that in particular for use at the highest temperatures, for example in gas turbines or Engines, it can be advantageous if that for a production of the blade PM raw material made of a nickel-based or cobalt-based alloy or one Alloy with less than 29 wt .-% iron is formed.

However, a chromium content is metallurgical or manufacturing technology, which is at least 14% by weight to nitrogen, which has a beneficial effect on the Exercises material properties to bring in solution.

Fig. 1 eine Probenlage im Knüppel in Längsrichtung

Fig. 2 eine Probenlage im Querschnitt des Knüppels

Fig. 3 eine Erprobung schematisch

The invention is explained in more detail below on the basis of material tests and test results.
Show it

Fig. 1 shows a sample layer in the stick in the longitudinal direction

Fig. 2 shows a sample layer in cross section of the stick

Fig. 3 shows a test schematically

1 were made from billets 1 for turbine blades with a Side length of D = 35 mm and a height of C = 350 mm samples 2 such taken that at the end of a provided clamping piece 22, the sample 2nd one side touches a central axis of the cross section (FIG. 2) and one opposite or outer side of the sample at a distance of 1/3 of the half Side length D is. The width of the samples was 1/4 of the side length D of the Stick.

The specimens were so crooked over the height C of the stick taken that the clamping end opposite, the outer sample side with was a distance of 1/8 D from the cross-sectional axis. This Sample arrangement in the examined billets was chosen to have the effect of centric longitudinal segregations.

A test is shown schematically in FIG. 3. The sample fixture took place in a holder 3, with a clamping piece 22 of a sample 2 in this was fixed. A respective one was carried out with different heating speeds Heating sample 2, which is then at temperatures between 300 ° C and 550 ° C were kept. The deviation of the was measured Clamping opposite sample end.

The investigations have shown that in an inventive PM material no deviations from an axially aligned position of the free End of sample also developed at high heating and cooling speeds. On the other hand, test specimens made from conventional primary material, i.e. in blocks solidified steels and subsequent reshaping of the blocks Bends with higher rates of temperature change and increase larger ingot cross sections.

Based on the creep tests of the material at temperatures of 550 ° C it was found that a turbine blade according to the invention by at least Has 23% better creep values.

Claims (9)

Turbine blade with the material properties at room temperature: Tensile strength: R _m = at least 700 N / mm ² Yield strength: R _{p 0.2} = at least 550 N / mm ² Elongation: A = at least 15% Constriction: Z = at least 10% for steam turbines or gas turbines, formed from a powder metallurgy (PM), when pulverizing a melt by gas atomization using nitrogen and hot isostatic pressing (HIP) of the powder, manufactured raw material, which is machined and the turbine blade thus created is thermally treated or tempered. Turbine blade according to claim 1, characterized in that the primary material is machined after hot isostatic pressing (HIP-en) and after hot forming with a degree of deformation of at least 2.5 times. Turbine blade according to claim 1, characterized in that the primary material after the hot isostatic pressing (HIP-en), preferably in a shape close to the final dimension, is machined without being deformed (as HIP-ed). Turbine blade according to claims 1 to 3, characterized in that the PM primary material is formed from an iron-based alloy which solidifies without ledeburite. Turbine blade according to claim 1 to 4, characterized in that the PM material
from a martensitic chrome steel with a composition of in% by weight Chrome (Cr) to 29.0 Carbon (C) to 0.4 Nitrogen (N) up to 0.3 (C + N) 0.16 to 0.4 Molybdenum (Mo) to 2.0 Vanadium (V) to 1.0 Silicon (Si) to 0.6 Manganese (Mn) to 2.0 Sulfur (S) to 0.49 (Mn / S) MIN 2.0 Tungsten (W) to 2.5 Nickel (Ni) MAX 3.0 Niobium (Nb) to 0.12 Boron (B) up to 0.01 Iron rest as well as manufacturing-related impurities and accompanying elements. Turbine blade according to one of claims 1 to 5, characterized in that the PM raw material made of a martensitic chrome steel with a composition in wt .-% of Cr = 8.0 to 22.0, preferably 9.0 to 16.0 C = 0.1 to 0.35, preferably 0.15 to 0.3 N = 0.005 to 0.28, preferably 0.1 to 0.24 (C + N) = 0.11 to 0.40, preferably 0.21 to 0.29 Mo = 0.5 to 2.0, preferably 0.8 to 1.8 V = 0.08 to 0.6, preferably 0.12 to 0.4 Si = 0.05 to 0.5, preferably 0.1 to 0.35 Mn = 0.4 to 1.1, preferably 0.5 to 0.95 S = 0.002 to 0.39, preferably 0.06 to 0.35 (Mn / S) = MIN 2.0, preferably Min 2.5 Ni = MAX 2.4, preferably MAX 0.9 B = up to 0.01 F = Rest and production-related impurities is formed. Turbine blade according to claims 1 to 4, characterized in that the PM raw material made of a soft martensitic or nickel martensitic steel with a composition of wt.% Of C = to 0.1 N = to 0.098 (C + N) = 0.05 to 0.12 Si = to 1.0 Mn = to 2.0 Cr = up to 20.0 S = to 0.49 Mn / S = MIN 1.9 Mo = to 3.0 V = up to 0.2 Ni = up to 8.0 Cu = to 4.5 B = up to 0.01 Al = to 0.08 Nb = to 0.6 Fe = Rest and production-related impurities is formed. Turbine blade according to claims 1 to 4 and 7, characterized in that the PM raw material made of a martensitic steel with a composition in% by weight C = 0.02 to 0.08, preferably 0.03 to 0.05 N = 0.001 to 0.05, preferably 0.0015 to 0.039 Si = 0.08 to 0.5, preferably 0.1 to 0.4 Mn = 0.1 to 1.9, preferably 0.2 to 1.6 S = 0.003 to 0.39, preferably 0.1 to 0.35 Cr = 9.0 to 20.0, preferably 9.0 to 13.0 Mo = to 2.0, preferably 0.6 to 1.8 Ni = 3.0 to 7.9, preferably 3.5 to 6.8 Cu = 1.0 to 4.4 Al = to 0.04 Fe = Rest and manufacturing-related impurities. Turbine blade according to Claims 1 to 3, characterized in that the PM raw material is formed from a nickel-based or cobalt-based alloy or an alloy with less than 29% by weight of iron.

Images