KR20080108013A - A material on the basis of a crni alloy, a semi-finished product, components for a combustion engine, and also a method for the manufacture of the material and of the semi-finished product - Google Patents

Abstract

A manufacturing method of material and a semi-finished product is provided to obtain excellent chemical characteristic such as high temperature corrosion for corresponding to high load at a large diesel engine. As the starting material for forming the component of the large diesel engine, the material alloying the CrNi alloy used for the manufacture of the semi-finished product has below chemical composition. [CrxNiyAz]Nk, the x+y+z+k = 100% in here. The component Az is one or more elements selected from the group of the chemical element consisting of [La, Ce, Y, Hf, Sc, Si, C, S, P, Al, Zr, B, Mo, Fe, Mn, O and the rare earth], Cr- content of material is 50%0% to weight%, and the content of the component Az at material characterizes 0%<=z&<50% to weight%.

Description

Materials based on CrNi alloys, semifinished products, components for combustion engines, and methods for producing the materials and the semifinished products. ALSO A METHOD FOR THE MANUFACTURE OF THE MATERIAL AND OF THE SEMI-FINISHED PRODUCT}

The present invention relates to a material based on CrNi alloys used in the production of semifinished products as starting materials for forming components of combustion engines, in particular large diesel engines, semifinished products made of the material according to the invention, and A component for a combustion engine manufactured from a finished product. The present invention also relates to a process for the preparation of the material and to a process for the preparation of the semifinished product by the isostatic pressing method.

For example, semifinished products of starting materials for combustion engines, in particular components of diesel engines, can be produced from suitable materials using hot isostatic pressure (HIP). Examples of such diesel engine components include, among others, four-stroke engines, in particular diesel engines, especially prechambers for large diesel engines or fuel atomisers or fuel nozzle heads for all types of two-stroke and four-stroke engines. to be.

In this regard, using the HIP process described above, it is possible to produce alloys that cannot be produced by molten metallurgy or other methods, or which must be accompanied by high cost and complexity.

For example, in the case of large diesel engines used above all as drive aggregates for power generation in ships or stationary installations, the fuel (which is typically heavy oil or other diesel fuel) is the combustion chamber by means of fuel injection nozzles. Is introduced. Such injection nozzles normally comprise a nozzle head that partially protrudes into the combustion chamber, which is also referred to as a nebulizer. Nozzle heads are wear parts that are subjected to high thermal, mechanical and chemical loads. Depending on the degree of load, the nozzle head may have cracks that may lead to damage or even breakage, such as loss of material, for example as a result of corrosion, erosion and / or wear.

The mechanical load is also due to high injection pressures, which can exceed 1,000 bar. Material loss can occur inside the nozzle head through cavitation and / or erosion. The thermal load is due to the high temperature in the combustion chamber and the enormous temperature change between the combustion temperature and the temperature of the newly supplied scavenging air. Inside the nozzle head through which fuel is introduced, intermittent injection also results in a sharp change in temperature. The chemical load on the nozzle head is mainly due to high temperature corrosion, ie hot corrosion. Hot corrosion caused mainly by vanadium, sodium and sulfur contained in the fuel promotes material weakening. Corrosion in particular is the cause of the nozzle head being already unusable after only a few thousand hours of operation and must be replaced.

Today, steel or alloys based on nickel or cobalt, for example Stellite 6, are commonly used as materials for nozzle heads in large diesel engines. Acceptable component life associated with erosion, wear and cavitation (particularly in the bore of the nozzle head) can be achieved today using cobalt-based alloy Stellite 6.

In this regard, alloys with high chromium and nickel content, for example alloys with a content of about 50% by weight of chromium and nickel, among others, for example Cr / Ni 65/35 produced using one of the HIP processes described above It is evident that alloys with a chromium content of more than 50% by weight, such as alloys, have very good properties with regard to the above-mentioned problems of hot and hot corrosion. Materials having such a high chromium content and good chemical properties with respect to high temperature and hot corrosion are already disclosed and described in EP 1 353 061.

At the same time, however, these materials produced by the HIP process tend to have poor toughness properties, such that the materials themselves exhibit very low notch impact values, for example. That is, these known alloys are relatively fragile and lack ductility, which, as is well known, results in low notch impact values.

Thus, there is room for improvement over the aforementioned materials, in particular for brittleness or ductility. Especially in engine configurations, especially in the case of the two-stroke large diesel engines, the development of even more powerful engines, mechanical load requirements in the future, especially for high load parts such as nozzle heads or prechambers, may also be expected. This is because it enables the expectation of further increase. This means that more and more new or modified materials will be required, but at the same time it means maintaining the good chemical properties of the known materials described above with regard to hot or hot corrosion.

Accordingly, it is an object of the present invention to respond to a high overall load in a large diesel engine, in particular as a nozzle head or prechamber for the injection of one material and components made therefrom, in particular engine components, inter alia, fuels, and particularly high ductility. It is also to provide a component, which has a notch bar impact value which is significantly increased compared to the known material, and at the same time the material exhibits excellent chemical properties with respect to hot and hot corrosion.

The subject matter of the present invention that meets this object is characterized by the features of the independent claims in each category.

Thus, as a starting material for forming components of combustion engines, in particular large diesel engines, a material based on CrNi alloys used in the production of semifinished products is provided, which has the following chemical composition:

[Cr _x Ni _y A _z ] N _k , where x + y + z + k = 100%,

Component A _z is one selected from the group of chemical elements consisting of {La, Ce, Y, Hf, Sc, Si, C, S, P, Al, Zr, B, Mo, Fe, Mn, O, and rare earths} The above element. The Cr-content of the material is 50% <x <100% by weight, the Ni-content of the material is y> 0% by weight, and the content of component A _z in the material is 0% by weight. ≤ z <50%. According to the invention, the nitrogen content of the material is 0.01% ≦ k ≦ 0.1% by weight.

That is, surprisingly, in chromium-nickel alloys with a nitrogen content of less than about 0.1% by weight, the notch bar impact value of a semifinished product made from the material in the isostatic compression process, also known as the HIP method in the material or the subject matter, and thereby Ductility has increased enormously in the lower concentration of nitrogen. Therefore, in some cases, in the case of less than about 0.1% by weight, the experiment showed that the notch bar impact value increased substantially stepwise in the lower direction in the form of a power law as a function of the concentration of nitrogen. Could indicate.

The following notch bar impact values were determined depending on the nitrogen concentration of the NiCr material: 8.84 J / m 2 at 0.01 wt% nitrogen, 6.3 J / m 2 at 0.067 wt% nitrogen, 3.37 J / m 2 at 0.05 wt% nitrogen, 0.2 nitrogen 2.1 J / m 2 at weight% and 0.98 J / m 2 at 0.56 weight% nitrogen.

In this regard, in other cases, the notch bar impact value may follow another law as a function of the concentration of nitrogen falling definitively.

However, it is clear that the notch bar impact value always increases somewhat rapidly or semi-stepwise in the low direction in CrNi alloys having a chromium concentration of at least 50% by weight and a nitrogen concentration of less than about 0.1% by weight.

At a nitrogen concentration of about 0.1% by weight, the notch bar impact value only varies slightly with the nitrogen concentration, or in a technically unrelated amount, so that the smallest change in the low concentration range of less than 0.1% by weight of such nitrogen It is even more surprising that we could not think that a technically meaningful change in the notch bar impact could result.

Therefore, in the present invention, for example, starting from a material known from EP 1 353 061, the notch bar impact value and thus accordingly, without affecting the good physical-chemical properties with regard to hot and hot corrosion Certain reductions in nitrogen content with respect to ductility can be used to improve these very substantially.

In this regard, the present invention not only can be advantageously applied with the above-mentioned materials, but also similarly with other related materials has good results.

In fact, the nitrogen content of the material according to the invention is 0.01% by weight ≤ k ≤ 0.1% by weight, in particular 0.01% by weight ≤ k ≤ 0.05% by weight, the nitrogen content being in particular 0.02% by weight. Which nitrogen content is actually chosen depends in particular on the requirements for notch bar impact values and the ductility of the semifinished product and the components to be produced therefrom.

When the notch bar impact value or the requirement for ductility of the component to be manufactured is not too high, it will be understood that for economic reasons alone a not too low nitrogen concentration of less than 0.1% by weight is chosen, because the material with an extremely small concentration of nitrogen This is because the production of the correspondingly expensive.

Particularly advantageously, depending on the component or application to be produced, the chromium content of the material is 52% by weight x 100% by weight, in particular 52% by weight x 70% by weight, in particular about 65% by weight, Preferably 52 wt% <x <60 wt%, inter alia 54 wt% <x <58 wt%, and the nickel content is at least 20 wt%.

The respective proportions of Cr and Ni, which are the base materials, are related to this, in this particular case, among other things, the requirements for hot corrosion and temperature loading, as well as the chemicals that the components to be manufactured from these materials will be exposed to in operation. This depends on physical problems and other environmental factors.

In addition to nitrogen, the material according to the invention may also contain oxygen, for example, and the oxygen content of the material is preferably 0.01% by weight ≦ O ≦ 0.5% by weight, in particular 0.01% by weight ≦ O ≦ 0.2% by weight. And, among others, about 0.1% by weight.

In particular, the high chromium content of the material according to the invention is particularly important for combating intensive attacks by high temperature corrosion, such as that typically occurs in the combustion space of large diesel engines driven using heavy oil. Chromium forms a layer of chromium oxide that adheres densely and firmly, which gives the material good chemical resistance. Due to the high chromium content, chromium can moreover rapidly diffuse out of the interior of the nozzle head and eliminate damage to the oxide layer generated there.

The material preferably contains at least one reactive element selected from the group consisting of lanthanum (La), cerium (Ce), yttrium (Y), hafnium (Hf), scandium (Sc) and rare earths, The content is up to 5% by weight.

The function of the reactive element in the material is to affect the stability of the chromium oxide layer itself and its adhesion to the nozzle head in a positive way. Reactive elements such as these elements, even in small amounts, can significantly improve the adhesion of the oxide layer, even with regard to oxidation behavior and, in particular, stresses associated with temperature changes.

In view of the mechanical and technical characteristics, the nickel content is also preferably at least 20% by weight, in particular at least 30% by weight.

Typically it is sufficient if one of the reactive elements is present in the material of the present invention. However, depending on the application, it may be advantageous to prepare a material containing a plurality of reactive elements.

In another specific embodiment, the material contains at least one element selected from the group consisting of elements Si, C, S, P, Al, Zr, B, Mo, Fe and Mn, the content of Si being 1% by weight Up to, in particular, up to 0.6% by weight, content of C is up to 1% by weight, in particular up to 0.6% by weight, and contents of S, P, Al, Zr, B, Mo, Fe and Mn are each up to 1% by weight, in particular 0.1 wt% or less.

Indeed, it has proven advantageous for the content of each reactive element to be below 1% by weight, in particular below 0.2% by weight. In this connection, the content of carbon (C) is in a very special case up to 1% by weight, in particular up to 0.05% by weight, and the content of silicon (Si) is in particular up to 0.05% by weight.

In this regard, the material is a gas sprayed metallic powder, which metallic powder preferably has a primary grain size of 10 μm to 200 μm, in particular 45 μm to 150 μm. This means that most of the powder grains have a size of 10-200 μm, in particular 40-150 μm, in the grain size distribution.

The invention further relates to a semifinished product which is used as a starting material for the formation of a corresponding component from the material according to the invention, the semifinished product according to the invention being a high temperature isostatic compression process, also known as a HIP process. Is prepared by.

For example, fuel injectors, in particular but not limited thereto, are problematic as components that can be produced from the semifinished product according to the invention, and are used in particular in two-stroke or four-stroke engines, in particular in two-stroke large diesel engines. This includes nozzle heads for fuel injection nozzles. However, other components of the prechamber or combustion engine for four-stroke engines, in particular those that are exposed to high temperatures and / or hot corrosion in operation, can be produced very advantageously from the semifinished product according to the invention.

The nozzle heads for fuel injection nozzles in combustion engines, in particular large diesel engines, made from semifinished products according to the invention or materials according to the invention, are of particular importance for practical use.

As already mentioned, the chromium-based alloys claimed by the present invention prove to be particularly durable against corrosion, in particular hot corrosion, erosion, wear, material loss and cavitation. Nozzles made of this type of chromium-based alloy can very well withstand high load populations in large diesel engines. The mechanical stability of the nozzle, the resistance to the formation of cracks or ruptures, and the permanent resilience to pulsating loads meet the requirements.

In a preferred embodiment, the nozzle head bends one or more nozzle holes for introducing fuel into the combustion space, starting from the longitudinal holes and the longitudinal holes, the transition from the longitudinal holes being preferably electrical -It is chemically rounded (electrolytic polishing of hard metal). The rounding of the passage section eliminates sharp edges in the flow path of the fuel, thereby optimizing the flow conditions.

The nozzle head according to the invention is particularly suitable for fuel injection nozzles for combustion engines, in particular for diesel engines. The nozzle head according to the invention or the fuel injection nozzle provided therewith is suitable for large diesel engines, for example two-stroke large diesel engines or four-stroke large diesel engines which are exhausted in a longitudinal direction with a crosshead drive. Especially suitable.

The present invention further provides a process for the preparation of materials and semifinished products according to the invention, wherein the materials are prepared according to a gas spraying method, and noble gases, in particular argon and / or helium, are used as spraying gases, Semifinished products are manufactured by high temperature isostatic compression processes in process chambers.

Due to the fact that rare gases such as helium or ultrapure argon are used as spray gases in the preparation of powdered materials, in contrast to methods known in the art, in which nitrogen or air is generally used as the spray gas, the nitrogen content in the materials is reduced. Can be lowered to a concentration of less than 0.1% by weight.

In producing a semifinished product by a high temperature isostatic compression process in the process chamber, the pressure of the process gas in the process chamber is preferably higher than 800 bar, in particular higher than about 1,000 bar.

The temperature of the process gas in the process chamber is actually chosen to be higher than 800 ° C, preferably at least 1,100 ° C.

Typical process times for the preparation of the semifinished product are selected from 2 hours to 5 hours, preferably about 3 hours.

During the high temperature isostatic compression process in the process chamber, rare gas is also preferably used as the process gas, among which argon, in particular ultrapure argon, is used, which can subsequently prevent the transfer of nitrogen into the semifinished product during the HIP process. .

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

According to the present invention, particularly as an engine component, especially a nozzle head or prechamber for injection of fuel, it can cope with a high load group in a large diesel engine, has a particularly high ductility, and thus increases the notch bar impact value. Can simultaneously produce components that exhibit good chemical properties with respect to hot and hot corrosion.

In Fig. 1, the dependence of the notch bar impact value on the nitrogen content of the material is shown as an example in a semi-finished product made from CrNi material according to the invention. The circles in the diagram correspond to the measurements of the notch bar impact values for the various samples with respective nitrogen contents given on the abscissa. The notch bar impact value associated with it is recorded on the ordinate. The five samples corresponding to the five circles in the diagram are essentially different due to the value of the nitrogen concentration reproduced on the abscissa. Otherwise, the samples were almost identical with chromium content of over 50% by weight.

According to the behavior of the notch bar impact value higher than 0.1 wt% nitrogen which is known as a function of nitrogen content from the prior art, the dependence of the notch bar impact value on the nitrogen content corresponding to the straight line G is less than 0.1 wt% nitrogen content. It was expected at small concentrations of.

That is, at a nitrogen concentration of less than about 0.1 wt% nitrogen, the notch bar impact value was expected to increase only slightly, ie only slightly improved ductility.

Thus, it has been convinced that ever lowering the nitrogen content in the material will not result in a related improvement. Apart from the fact, the relationship between notch bar impact value and nitrogen concentration is not actually known.

The three dots on the left side of the diagram according to the figures represent samples according to the invention with a nitrogen content of less than 0.1% by weight, and other semi-finished products according to the invention start with known materials having a nitrogen content of more than 0.1% by weight. It is demonstrated that the notch bar impact value is much larger than expected, and the notch bar impact value follows approximately curve K in the direction of lowering the nitrogen concentration and does not follow straight line G as previously thought.

Thus, the increase in notch bar impact value at the nitrogen ratio of less than about 0.1% by weight in the sample according to the invention is surprisingly much stronger, following the power law according to the nitrogen concentration in the example of FIG. 1 and flat as previously estimated Do not follow a straight slope.

2 shows a cross-sectional view of a fuel injection nozzle of a large diesel engine, inter alia a two-stroke large diesel engine with a longitudinal exhaust. The fuel injection nozzle 2 comprises an example of the nozzle heads 1, 11 according to the invention, which are fixed to the nozzle body 5. As shown, the nozzle heads 1, 11 are preferably detachably connected to the nozzle body 5 so that the nozzle heads 1, 11 can be exchanged separately, ie the entire fuel injection nozzle 2. It can be exchanged without the need.

The nozzle heads 1, 11 have a plurality of, for example, five nozzle holes 4 together with the longitudinal holes 3, only two of which are shown in FIG. 1. Each of the nozzle holes 4 starts radially from the longitudinal hole and inclines slightly downward and extends in the radial direction. In operation, fuel, usually heavy oil or other diesel fuel, is intermittently injected under high pressure in the manner already known into the combustion space, not shown, through the longitudinal holes and nozzle holes 4, in accordance with the working cycle of large diesel engines. .

In this embodiment, the nozzle heads 1, 11 comprise a material which is a chromium-based alloy containing reactive elements, wherein the content of chromium in the material is more than 50% by weight and the content of nitrogen is about 0.02% by weight. As the reactive element, an element selected from the group of rare earth metals or similar metals is suitable. Particularly suitable elements are lanthanum (La), cerium (Ce), yttrium (Y), hafnium (Hf), and scandium (Sc). The material preferably has a high proportion of nickel by weight of 20% to 50% by weight in order to ensure better processability, among other things.

In this embodiment, the nickel content of the alloy is greater than 45% by weight, and lanthanum is contained in a proportion of less than 0.1% by weight as a reactive element. Except for common contaminants, the rest is chromium.

Naturally the material may comprise one or more reactive elements. Each reactive element is preferably contained in an amount of up to 1% by weight relative to the total weight, inter alia up to 0.2% by weight.

The semifinished or nozzle heads 1, 11 according to the invention are preferably produced by hot isostatic pressing (HIP).

In this preparation, the starting material, ie chromium, nickel and lanthanum as reactive elements here, is sprayed into the powder by ultrapure argon to reduce the nitrogen content in the material. The grain size of the powder is mostly between 45 μm and 150 μm in this example. From the metal powder, blank or semi-finished products, for example bars, are produced by hot isostatic compression. The nozzle heads 1, 11 are made from the blank by a mechanical treatment method, typically a chip-producing treatment method. The longitudinal hole 3 and the nozzle hole 4 are drilled. Subsequently, the switching area (edge) between the longitudinal hole 3 and the nozzle hole 4 is preferably rounded. These edges are preferably electrochemically rounded (electrolytic polishing of hard metals).

Process parameters for high temperature isostatic compression can be optimized for each application.

The material according to the invention or the nozzle heads 1 and 11 produced therefrom have excellent durability against hot corrosion and associated material losses, and due to the low nitrogen content the high notch bar impact value and the associated material Obviously increased ductility is obtained.

Thus, a tremendous working life which has never been achieved is obtained, which is naturally a great advantage from an economic point of view.

The nozzle head according to the invention is therefore particularly suitable for future generations of large diesel engines, which on the one hand are much more powerful and meet the much higher demands on the load of the nozzle head. On the other hand, engines already in operation can also be retrofitted with components made from the material or semifinished product of the invention.

1 is a chart showing the effect of nitrogen content on the notch bar impact value.

2 is a view showing a cross section of the fuel injection nozzle according to the embodiment of the nozzle head according to the present invention.

Claims (18)

As a starting material for forming the component 1 of a combustion engine, in particular a large diesel engine, a material based on CrNi alloys used for the production of semi-finished products, The material has the following chemical composition: [Cr _x Ni _y A _z ] N _k , where x + y + z + k = 100%, Component A _z is one selected from the group of chemical elements consisting of {La, Ce, Y, Hf, Sc, Si, C, S, P, Al, Zr, B, Mo, Fe, Mn, O, and rare earths} Element, wherein the Cr-content of the material is 50% <x <100% by weight, the Ni-content of the material is y> 0% by weight, and the content of component A _z in the material is weight %, 0% ≤z <50% The nitrogen content of the material is a weight percent of the material, characterized in that 0.01% ≤k≤0.1%. The method of claim 1, Subsequently, the nitrogen content of the material is 0.01% by weight k≤0.05%, in particular 0.02% by weight. The method according to claim 1 or 2, The chromium content of the material is 52% by weight x 100% by weight, in particular 52% by weight x 70% by weight, in particular about 65% by weight, preferably 52% by weight x 60% by weight, in particular 54 wt% ≦ x ≦ 58 wt%. The method according to any one of claims 1 to 3, A material characterized by a nickel content of at least 20% by weight. The method according to any one of claims 1 to 4, The oxygen content of the material is 0.01% by weight ≦ O ≦ 0.5% by weight, in particular 0.01% by weight ≦ O ≦ 0.2% by weight, in particular about 0.1% by weight. The method according to any one of claims 1 to 5, Containing at least one reactive element selected from the group consisting of elements La, Ce, Y, Hf, Sc and rare earth elements, the content of each reactive element being no greater than 5% by weight, in particular less than 1% by weight, in particular less than 0.1% by weight Material characterized in that. The method according to any one of claims 1 to 6, The material contains at least one element selected from the group consisting of elements Si, C, S, P, Al, Zr, B, Mo, Fe and Mn, the content of Si being 1% by weight or less, in particular 0.6% by weight or less The content of C is 1 wt% or less, in particular 0.6 wt% or less, and the contents of S, P, Al, Zr, B, Mo, Fe and Mn are each 1 wt% or less, in particular 0.1 wt% or less. Substance. The method according to any one of claims 1 to 7, The material is a gas atomized metallic powder, wherein the metallic powder preferably has a main grain size of 10 μm to 200 μm, in particular 45 μm to 150 μm. As a semi-finished product made of the material according to any one of claims 1 to 8, The semi-finished product is characterized in that it is manufactured by a hot isostatic pressing process (hot isostatic pressing process). Components for combustion engines, in particular large diesel engines, made from the semifinished product according to claim 9. The method of claim 10, The component 1 is for a nozzle head 11, a four-stroke engine of a fuel injection nozzle 2 used in a fuel atomizer 11, in particular a two-stroke engine or a four-stroke engine, in particular a two-stroke large diesel engine. A prechamber (1), or another component (1) of a combustion engine. A nozzle head according to claim 10 or 11, Longitudinal bore 3, and One or more nozzle holes 4 extending from the longitudinal holes 3 for introducing fuel into the combustion space, The passage from the longitudinal hole (3) to the nozzle hole (4) is rounded, preferably electro-chemically rounded. A method of preparing a substance according to any one of claims 1 to 8, The material is produced according to the gas spray method, characterized in that a noble gas, in particular argon and / or helium, is used as the spraying gas. A method for producing a semi-finished product from a material according to any one of claims 1 to 8, The semi-finished product is a method of manufacturing a semi-finished product, characterized in that the production by a high temperature isostatic compression process in the process chamber. The method of claim 14, Process pressure of the process gas in the process chamber, the manufacturing method of the semi-finished product, characterized in that selected higher than 800 bar, preferably higher than 1,000 bar. The method according to claim 14 or 15, The process temperature of the process gas in the said process chamber is selected so that it may be higher than 800 degreeC, Preferably it is about 1,100 degreeC. The method according to any one of claims 14 to 16, Process time for the production of the semi-finished product is selected from the range of 2 hours to 5 hours, preferably about 3 hours. The method according to any one of claims 14 to 17, A process for producing a semi-finished product characterized in that rare gases, in particular argon, in particular ultrapure argon, are used.

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