阅读说明：本技术 具有耐高温性的钴基合金、用于生产矿物纤维的包含该合金的旋转器以及使用该旋转器生产矿物纤维的方法 (Cobalt-based alloy having high temperature resistance, spinner for producing mineral fiber comprising the same, and method for producing mineral fiber using the spinner ) 是由 马尔科·拉格雷卡 罗伯托·马西尼 于 2018-11-06 设计创作，主要内容包括：本发明涉及一种金属合金,其特征在于,以合金总重量的重量百分比计,其包含1-4％的铌(Nb)、0-0.5％的铪(Hf)、27-29％的铬、1-5％的镍(Ni)、0.3-0.45％的碳(C)、0-2％的钽(Ta)、0-2％的钛、1-3％的铁、低于0.5％的锰(Mn)、低于0.3％的硅(Si)、低于0.2％的锆(Zr),其余为钴(Co)和不可避免的杂质。这种金属合金在高温下具有优异的机械强度特性,使得其适用于制造用于生产例如玻璃纤维、岩石纤维之类矿物纤维的制品,特别是旋转器。(The invention relates to a metal alloy, characterized in that it comprises, in weight percentages based on the total weight of the alloy, 1-4% niobium (Nb), 0-0.5% hafnium (Hf), 27-29% chromium (Cr), 1-5% nickel (Ni), 0.3-0.45% carbon (C), 0-2% tantalum (Ta), 0-2% titanium (Ti), 1-3% iron (Fe), less than 0.5% manganese (Mn), less than 0.3% silicon (Si), less than 0.2% zirconium (Zr), the remainder being cobalt (Co) and unavoidable impurities. Such metal alloys have excellent mechanical strength properties at high temperatures, making them suitable for the manufacture of articles for the production of mineral fibres, such as glass fibres, rock fibres and the like, in particular spinners.)

1. A metal alloy comprising, in weight percent based on the total weight of the alloy:

niobium (Nb): 1 to 4 percent

Hafnium (Hf): 0 to 0.5 percent

Chromium (Cr): 27 to 29 percent

Nickel (Ni): 1 to 5 percent

Carbon (C): 0.3 to 0.45 percent

Tantalum (Ta): 0 to 2 percent of

Titanium (Ti): 0 to 2 percent of

Iron (Fe): 1 to 3 percent of

Manganese (Mn): less than 0.5 percent

Silicon (Si): less than 0.3 percent

Zirconium (Zr): less than 0.2%

The balance of cobalt (Co) and inevitable impurities.

2. The metal alloy of claim 1, wherein the metal alloy comprises Hf, and the sum of the contents of Nb + Hf is 1-4 wt% of the total weight of the alloy.

3. The metal alloy according to claim 1 or 2, wherein the metal alloy comprises Ta and the sum of the contents of Nb + Ta is 1-4 wt% of the total weight of the alloy.

4. The metal alloy according to claim 1 or 3, comprising the following elements in weight percentages of the total alloy weight:

niobium (Nb): 3.5 percent

Chromium (Cr): 28 percent of

Nickel (Ni): 1.5 percent

Carbon (C): 0.4 percent

Tantalum (Ta): 0.5 percent

Titanium (Ti): 1.4 percent

Iron (Fe): 2 percent of

Manganese (Mn): less than 0.3 percent

Silicon (Si): less than 0.3 percent

Zirconium (Zr): less than 0.2 percent of the total weight of the composition,

the balance of cobalt (Co) and inevitable impurities.

5. An article for producing mineral fibers such as glass fibers, rock fibers and the like comprising the alloy according to any one of the preceding claims.

6. A spinner for producing mineral fibres such as glass fibres, rock fibres and the like, comprising an alloy according to any one of the preceding claims 1 to 4, the spinner having a peripheral wall, the peripheral wall or a part thereof being provided with a plurality of holes.

7. A method of producing an article, in particular a spinner for producing mineral fibres, comprising the steps of:

melting a mixture of the elements constituting the alloy according to any one of claims 1 to 4 under vacuum or in an at least partially modified atmosphere to obtain a melt and cooling said melt to a temperature allowing the formation of grains,

-casting the melt into a mould, obtaining a rough article,

-subjecting the rough article to a first heat treatment at a first temperature and for a first period of time to dissolve carbides, followed by a second heat treatment at a second temperature and for a second period of time lower than the first temperature to precipitate carbides,

-cooling the rough article subjected to said heat treatment to room temperature, obtaining said article, in particular a spinner.

8. The method according to claim 7, wherein the melting is performed at a temperature between 1700 ℃ and 1750 ℃, preferably at 1730 ℃, and the cooling of the melt is performed at a temperature between 1500 ℃ and 1550 ℃, preferably at 1500 ℃.

9. The method according to claim 7 or 8, wherein the first heat treatment is performed at a first temperature between 1200 ℃ and 1250 ℃, preferably at 1200 ℃ for a time between 1.5 hours and 2 hours, preferably 2 hours, and the second heat treatment is performed at a second temperature between 1000 ℃ and 1050 ℃, preferably at 1000 ℃ for a time between 10 hours and 12 hours, preferably 10 hours.

10. A method of producing mineral fibres such as glass fibres, rock fibres and the like, comprising the steps of:

-pouring a flow of molten mineral material into a spinner according to claim 6, spinning the spinner;

-drawing primary filaments of molten mineral material exiting from the holes of the peripheral wall of the spinner or a part thereof by the action of hot gas, wherein the temperature of the molten material inside the spinner is preferably at least 1200 ℃.

Technical Field

In a more general aspect, the present invention relates to a novel metal alloy having high mechanical strength at very high temperatures.

In particular, the invention relates to a cobalt-based alloy having a high mechanical strength at high temperatures, which makes it suitable for the production of mineral fibres, such as in particular glass fibres, rock fibres and the like.

The invention also relates to an article, such as a spinner, particularly suitable for mineral fiber production, and a method of producing the article.

The invention also relates to a method for producing mineral fibres such as, in particular, glass fibres, rock fibres and the like, using said spinner.

Background

It is known that the production of mineral fibres, such as glass fibres, rock fibres and the like, is generally carried out by internal centrifugation, which consists in pouring a melt of mineral material (for example molten glass) into a rotor, known as a "spinner" operating at high speed, provided with a peripheral band (or disc) provided with a plurality of small holes. Due to the effect of the centrifugal force, the melt is ejected onto a perforated peripheral belt from which primary filaments of molten mineral material are ejected through the holes, said primary filaments in turn being drawn to form fine fibres due to the effect of the high temperature gas supplied by the annular burners surrounding the disc.

Since the spinner operates under extremely harsh conditions, in particular high centrifugal forces and high temperatures up to or even exceeding 1200 ℃, the spinner is subjected to significant thermal stresses, such as thermal shock during process start-up and shut-down; great mechanical stresses (high centrifugal forces and erosion of mineral material flows); and large chemical stresses due to oxidation and corrosion of the molten material and high temperature gases discharged from the burners around the spinner.

The effect of such stresses causes progressive degradation of the spinner which may occur in various forms, such as thermal creep deformation of the vertical walls, formation of cracks and/or wear caused by erosion in the region of the holes, etc., eventually leading to replacement of damaged parts.

Therefore, the material forming the above-described rotator is required to have high mechanical strength characteristics at high temperatures as well as corrosion and oxidation resistance characteristics.

In this regard, cobalt-based metal alloys are known to have high mechanical strength at high temperatures and may be used to manufacture spinners for producing glass fibers.

For example, U.S. patent No. 6,068,814 describes a metal alloy having high mechanical strength at high temperatures, which contains 40-50% cobalt, 9-12% chromium, 9-12% nickel, 6-12% tungsten, 2.8-4.8% niobium, 0.1-0.3% zirconium, 0.6-1% carbon, 0.1-0.3% silicon, 0.1-0.3% manganese, 0.1-0.3% titanium, 0.1-0.8% vanadium, and the balance impurities that do not significantly affect mechanical properties.

Application No. WO 2009/071847 describes an alloy comprising 23-34% chromium, 0.2-5% titanium, 0.5-7% ditantalum, 0.2-1.2% carbon, less than 5% nickel, less than 3% iron, less than 1% silicon and less than 0.5% manganese. This alloy is characterized in particular by a much lower nickel content compared with the existing alloys, which is said to give the material improved mechanical strength, thus increasing the service life of the spinner made with this material.

Despite the advances made to date, there is still a need for mineral fiber-based products that are more and more resistant to high temperatures to meet market demands. This requires the use of mineral compositions, in particular glass compositions which can be converted into fibres at higher temperatures, and therefore the spinners used for this purpose must also have high mechanical strength at higher temperatures than conventional nickel and/or cobalt based alloys.

It is therefore a main object of the present invention to provide a new metal alloy which is suitable for the production of spinners for the production of mineral fibres, such as glass fibres and rock fibres, and which has improved mechanical strength and corrosion resistance at high temperatures to meet the above requirements.

It is another object of the invention to provide an article, such as a spinner, in particular for the manufacture of mineral fibres, having improved mechanical strength and corrosion resistance at high temperatures.

Disclosure of Invention

These results are achieved mainly by a metal alloy characterized by comprising, in percentages by weight of the total weight of the alloy, the following elements:

niobium (Nb): 1 to 4 percent

Hafnium (Hf): 0 to 0.5 percent

Chromium (Cr): 27 to 29 percent

Nickel (Ni): 1 to 5 percent

Carbon (C): 0.3 to 0.45 percent

Tantalum (Ta): 0 to 2 percent of

Titanium (Ti): 0 to 2 percent of

Iron (Fe): 1 to 3 percent of

Manganese (Mn): less than 0.5 percent

Silicon (Si): less than 0.3 percent

Zirconium (Zr): less than 0.2%

The balance of cobalt (Co) and inevitable impurities. According to an embodiment of the invention, the metal alloy comprises Hf and the sum of the contents of Nb + Hf is 1-4 wt% based on the total weight of the alloy.

According to another embodiment of the invention, the metal alloy comprises Ta, and the sum of the Nb + Ta contents is comprised between 1 and 4 wt% of the total weight of the alloy.

According to a preferred embodiment of the invention, the metal alloy comprises the following elements in weight percentages of the total weight of the alloy:

niobium (Nb): 3.5 percent

Chromium (Cr): 28 percent of

Nickel (Ni): 1.5 percent

Carbon (C): 0.4 percent

Tantalum (Ta): 0.5 percent

Titanium (Ti): 1.4 percent

Iron (Fe): 2 percent of

Manganese (Mn): less than 0.3 percent

Silicon (Si): less than 0.3 percent

Zirconium (Zr): less than 0.2%

The balance of cobalt (Co) and inevitable impurities.

Furthermore, the above object is achieved by an article, such as in particular a spinner, for producing mineral fibres comprising the above alloy. According to the invention, the article can be produced by a process comprising the following steps:

melting a mixture of the elements constituting the aforesaid alloy under vacuum or in an at least partially modified atmosphere to obtain a melt and cooling said melt to a temperature allowing the formation of grains,

-casting the melt into a mould, obtaining a rough article,

-subjecting the rough article to a first heat treatment at a first temperature and for a first period of time to dissolve carbides, followed by a second heat treatment at a second temperature and for a second period of time lower than the first temperature to precipitate carbides,

-cooling the rough article subjected to said heat treatment to room temperature, obtaining said article, in particular a spinner.

The invention also relates to a method for producing mineral fibres, such as glass fibres, rock fibres and the like, in particular, using a spinner produced as described above. The method comprises the following steps:

-pouring a flow of molten mineral material into a rotating spinner comprising an alloy as described above and having a peripheral wall, said peripheral wall or a part thereof being provided with a plurality of holes,

drawing the primary filaments of molten mineral material emerging from the holes of the peripheral wall of the spinner or of a portion thereof by the action of hot gases,

preferably, the temperature of the molten material in the spinner is at least 1200 ℃.

Further characteristics and advantages of the invention will become clear from the following detailed description, which is provided by way of non-limiting example.

Detailed Description

In this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, percentages, and so forth, are to be understood as being limited in all instances by the term "about". Further, each range includes any combination of the minimum and maximum specific values described, and includes any intermediate ranges therein, even if not specifically mentioned.

In the metal alloy according to the invention, cobalt represents the basic austenitic structure.

Chromium, present as a component of the austenite system, is necessary to ensure a high-temperature antioxidant effect. Generally, when the chromium content is less than 27%, this effect cannot be ensured. Meanwhile, when the chromium content is more than 29%, it causes rapid decrease in mechanical strength and hardness of the alloy. Thus, in the alloy according to the invention, the chromium content is kept in the range of 27-29%.

Nickel is present in small amounts in the alloy according to the invention and helps to stabilize the structure of the alloy and improve its machinability. The nickel content is preferably not more than 5% because higher contents significantly increase the production cost of the alloy.

Manganese and silicon are present in small amounts in the alloy and affect decarburization while controlling fluidity. The content of each of these elements is kept at a value lower than 0.3%, because the greater the amount of one or both of these elements, the greater the alloy brittleness and the possibility of causing cracks or fissures (fixturing) during cooling after casting.

In the alloy according to the invention, niobium and titanium form, together with the carbon present, carbides which have the further effect of stabilizing the alloy structure and of providing it with high mechanical strength at high temperatures, even under operating conditions above 1200 ℃.

As mentioned above, the alloy according to the invention also contains niobium and may optionally also contain tantalum, both in reduced amounts. The presence of niobium improves the machinability of the alloy, while tantalum increases the hardness of the alloy, so that the presence of both elements is recommended. Preferably, when tantalum is present, it partially replaces the niobium content, such that in this embodiment the sum of the niobium + tantalum content is included within the expected value range for niobium, i.e., 1-4%.

Furthermore, the alloy according to the invention may also contain hafnium in order to further improve the mechanical strength under hot conditions. Preferably, hafnium, when present, partially replaces the niobium content, such that in this embodiment, the sum of the niobium + hafnium contents is included within the expected value range for niobium, i.e., 1% to 4%.

The alloy according to the invention further comprises zirconium, which is added as a deoxidizer in small percentages, i.e. below 0.1%.

The alloy according to the invention also contains carbon, which is a very important element. In fact, carbon forms carbides with chromium, niobium and titanium, increasing the bonding force between the structural crystals, thereby improving the fracture strength and the high temperature resistance.

It has surprisingly been found that the alloy produced from the combination of the above mentioned respective amounts of elements according to the invention has a mechanical strength at high temperature properties, in particular at temperatures above 1200 ℃, which is superior to conventional nickel and/or cobalt based alloys, while also maintaining a high oxidation and corrosion resistance.

The alloy according to the invention is therefore particularly suitable for the high temperature applications and oxidizing and/or corrosive environments typical of the centrifugal processes currently used for the production of mineral fibres, in particular glass fibres, rock fibres and the like. In these applications, the alloy according to the invention can be used in particular for the manufacture of spinners which in turn advantageously have a longer service life, without suffering mechanical damages, such as deformations and/or cracks and damages due to oxidation and/or corrosion, which negatively affect the quality of the mineral fibres obtained and/or the production process thereof, all also under operating conditions at particularly high temperatures, for example temperatures higher than 1200 ℃ as required by the recent mineral fibre forming processes.

Without being bound by any particular scientific theory, it is believed that the formation of carbides with chromium, niobium and titanium, which increase the bonding forces between the crystals of the alloy structure and thus improve the fracture strength and the high temperature resistance, contributes significantly to the achievement of the excellent mechanical strength properties of the alloy according to the present invention. At the same time, it should be noted that the alloy according to the invention is essentially free of tungsten, i.e. it contains no tungsten, or, due to unavoidable impurities, it contains a very small amount of tungsten. Thus, unlike existing metal alloys, as described in US 6,068,014, where the presence of tungsten carbide contributes significantly to achieving mechanical strength at high temperatures, in the alloy according to the invention the presence of other carbides, in particular chromium, niobium and optionally titanium and tantalum carbides, contributes to obtaining excellent mechanical strength properties at high temperatures.

The alloy according to the invention can be prepared by melting a mixture of the above-mentioned proportional constituent elements at a temperature between 1700 ℃ and 1750 ℃, preferably at 1730 ℃, preferably under vacuum or in an at least partially modified atmosphere obtained by at least partially replacing the air by an inert gas such as argon, and then cooling the melt, for example by air, to a temperature between 1500 ℃ and 1550 ℃, preferably 1500 ℃, so that the grains are formed in the correct way and then cast.

The melting can be carried out using techniques which are conventional per se, for example by induction melting.

In particular, the alloy according to the invention can be used to produce any article having high mechanical strength characteristics at high temperatures, such as, in particular, spinners for the production of mineral fibres.

In this regard, a mixture of the constituent elements of the alloy is melted, followed by cooling as described above, and the resulting molten material is cast in a suitable mold having the shape of the desired article, preferably a mold of ceramic material, to produce a rough article, such as a rough spinner.

The casting can be carried out in a manner conventional per se, for example, preferably under vacuum, and the lost-wax casting can preferably be carried out in a mold of the aforementioned type. The rough article may then be subjected to at least one finishing heat treatment. Preferably, the rough article is subjected to a first heat treatment at a first temperature between 1200 ℃ and 1250 ℃ for between 1.5 hours and 2.5 hours to dissolve carbides, followed by a second heat treatment at a second temperature lower than said first temperature and between 1000 ℃ and 1050 ℃ for between 10 hours and 12 hours to precipitate carbides.

Preferably, the first heat treatment is performed at a temperature of 1200 ℃ for 2 hours, and the second heat treatment is performed at a temperature of 1000 ℃ for 10 hours.

At the end of the above-mentioned heat treatment, the rough article is cooled, for example in air, to room temperature, obtaining the finished product.

Depending on the particular application, the finished product may be subjected to successive machining operations using a machine tool.

In particular, in the case of the spinner for producing mineral fibres, such as glass fibres, rock fibres and the like, obtained as described above, the spinner may be subjected to a drilling operation on its peripheral wall or a portion thereof (for example an endless belt or a disc) to discharge the primary filaments of molten mineral material poured into the spinner.

These holes are usually of very small size, for example between 0.4mm and 1mm, and can be made, for example, by electron beam or electroerosion procedures using machine tools which are conventional per se.

In this regard, it has been found that a spinner made of the alloy according to the present invention can also be easily machined using a general machine tool used in the related art.

The invention also relates to a method for producing mineral fibres, such as, in particular, glass fibres, rock fibres and the like, using a spinner produced as described above. The method comprises pouring a stream of molten mineral material into a rotating spinner containing an alloy according to the invention and drawing primary filaments of molten mineral material emerging from holes in a peripheral wall of the spinner, or a portion thereof, by the action of hot gas supplied by an annular burner externally surrounding such peripheral wall.

Advantageously, the spinner comprising the alloy according to the invention can process molten mineral material that will be converted into fibres even at very high temperatures, in particular with a melting temperature inside the spinner higher than 1200 ℃, within an effective operating time equal to several hundred hours, without the spinner being subjected to any mechanical or chemical damage (oxidation and/or corrosion) that negatively affects the production process and/or the quality of the mineral fibres thus obtained.

The invention will now be described by way of examples of embodiments provided by way of non-limiting examples.

Examples

Using an induction melting technique in an inert atmosphere (argon), a melt was prepared having the following composition:

niobium (Nb): 3.5 percent

Chromium (Cr): 28 percent of

Nickel (Ni): 1.5 percent

Carbon (C): 0.4 percent

Tantalum (Ta): 0.5 percent

Titanium (Ti): 1.4 percent

Iron (Fe): 2 percent of

Manganese (Mn): less than 0.3 percent

Silicon (Si): less than 0.3 percent

Zirconium (Zr): less than 0.2%

The balance of cobalt (Co) and inevitable impurities.

A melt was obtained by melting a mixture having the above composition at a temperature of 1730 c, then cooling to a temperature of 1500 c, and then lost wax casting under vacuum in a mold of ceramic material to form a rough spinner.

The rough spinner was then subjected to a first heat treatment at a temperature of 1200 c for 2 hours to dissolve the carbides, followed by a second heat treatment at a temperature of 1000 c for 10 hours to precipitate the carbides.

At the end of the above heat treatment, the rough spinner is cooled in air to room temperature, obtaining the finished spinner, which is subsequently machined so as to form a plurality of holes with a diameter of 0.6mm to 0.9mm on a portion of its peripheral wall. The performance of the finished spinner thus obtained was evaluated during the production of glass fibers, wherein the temperature of the mineral composition introduced into the spinner was higher than 1200 ℃.

The test results show that the spinner can operate for hundreds of hours without adversely affecting the quality of the glass fibers obtained during the production process.