CN112430783A - Nickel-saving type air valve alloy and preparation method thereof - Google Patents
Nickel-saving type air valve alloy and preparation method thereof Download PDFInfo
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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Abstract
A nickel-saving type gas valve alloy and a preparation method thereof belong to the technical field of gas valve alloy and gas valve steel manufacturing. The gas valve alloy comprises the following chemical components in percentage by weight: c: 0.03-0.10%, Si: 0.10 to 0.40%, Mn: 0.20-1.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.015 percent, Cr: 21.00-26.50%, Ni: 24.50-32.00%, Al: 0.50-1.80%, Ti: 2.20-3.00%, Nb: 0.85-2.50%, V: 0.20-0.50%, and the balance of Fe and inevitable impurities. Adopting a medium frequency induction furnace and electroslag remelting smelting. The method has the advantage that the raw material cost of the gas valve alloy is reduced by reducing the content of the Ni element. By properly adding the strengthening elements, the gas valve alloy strengthened by compounding the intermetallic compound and the carbide is obtained. The produced air valve has higher strength and hardness by adopting a reasonable smelting method.
Description
Technical Field
The invention belongs to the technical field of valve alloy and valve steel manufacturing, and particularly relates to a nickel-saving valve alloy and a preparation method thereof, which are used for manufacturing intake valves and exhaust valves of diesel engines, gasoline engines and natural gas engines for ships, trains, automobiles and motorcycles.
Background
The air valve material is a raw material for manufacturing the air valve, also called as the air valve, and can be divided into air valve steel and air valve alloy. The air valve steel is further classified into martensite air valve steel and austenite air valve steel according to the structure. The martensite air valve steel is the air valve steel which is developed earliest in the world, the air valve steel which is introduced in the past Soviet Union is the first to be introduced domestically, and as in the fifties of the last century, 4Cr9Si2 and 4Cr10Si2Mo (mu 107) and the like are introduced. Austenitic gas valve steels and gas valve alloys have been developed with the continuing advancement of internal combustion engines and the increasing demand for gas valve materials. In the seventh and eighties of the last century, which is the gold period for the development and introduction of austenite valve steel and valve alloy in China, LF steel, 21-4N (5Cr21Mn9Ni4N), 21-2N, 21-4NWNb, 21-12N, 23-8N, ResisTEL, Incone751, Nimonic80A and the like are successively developed. At present, domestic martensite air valve steel is mainly used for manufacturing air inlet valves and exhaust valves of engines with low load and common working condition conditions, such as agricultural vehicles, motorcycles and the like. The austenitic air valve steel has better heat strength and corrosion resistance than the martensitic air valve steel, and therefore, the austenitic air valve steel is often used for manufacturing an intake valve and an exhaust valve of an engine with higher load and worse working conditions, such as a household car, a high-grade car or a part of commercial vehicles. The valve alloy is the material with the best high-temperature corrosion resistance and high-temperature long-term performance in valve materials, and therefore, the valve alloy is used for manufacturing exhaust valves of high-grade passenger vehicles and exhaust valves of part of commercial vehicles.
The valve alloy is developed along with the development of valve steel, mainly refers to nickel-based high-temperature alloy and iron-nickel-based high-temperature alloy, and the nickel-based high-temperature alloy is developed in the 40 th century. In 1941, Nimonic 75 nickel-base alloys were produced first in the United kingdom. By increasing the Ni content, a Nimonic80 nickel base alloy appears with improved creep strength. An Inconel751 air valve alloy was developed in the United states with an aluminum content added to that of the Inconel X-750 alloy. The uk first adopted Nimonic80A on premium cars and japan also used Nimonic 90 on some racing cars. Some new alloys were developed, such as titanium alloys used in intake valves and TiAl-based alloys used in exhaust valves, and compared to conventional titanium alloys and nickel-based alloys, the high temperature oxidation resistance of the TiAl-based alloys at 900 ℃ temperature of 800-. Due to the development of high-parameter internal combustion engines and other requirements, gas valve alloys are developed in all countries of the world, the grades comprise Inconel751, Nimonic80A, N-155, VMS-513, NiFe25Cr20NbTi, RS417, R914 and the like, most of the alloys are Al and Ti precipitation hardening type alloys, the alloy quantity is high, the production difficulty is high, and the alloys are expensive due to high Ni content, but have the advantages of excellent high-temperature performance and long service life. So far, the national air valve steel bar standard has only two marks, one is Inconel751, and the other is Nimonic 80A. The two gas valve alloys have excellent high-temperature strength and high-temperature corrosion resistance, so that the two gas valve alloys are used for manufacturing exhaust valves of high-grade cars or exhaust valves of high-power commercial vehicles. However, the content of the alloy element nickel in the two gas valve alloys exceeds 65%, so that the raw material cost is greatly increased, and the application of the gas valve alloys is limited.
The smelting method of the gas valve steel and the gas valve alloy generally adopts an electric arc furnace or an electric arc furnace and electroslag remelting smelting method, and a continuous casting and rolling method is also adopted at present in China for martensite gas valve steel, so that the cost of the gas valve steel is greatly reduced, but the austenite gas valve steel and the gas valve alloy generally adopt a die casting method to ensure the uniformity of the internal tissues of the gas valve steel and the gas valve alloy. Steelmaking is an essential process for manufacturing gas valve steel and alloys. The earliest method of liquid steel production was the crucible method appearing in 1740 years, in which pig iron and scrap iron were charged into a crucible made of graphite and clay, furnace charge was heated with a flame, and then the molten charge was cast into a steel ingot. Until 1899, an electric arc furnace steelmaking method using scrap steel as a raw material has appeared, and the steelmaking method is continuously developed since the coming out of the world and is one of the current main steelmaking methods, and steel smelted by an electric arc furnace currently accounts for 30-40% of the total steel production in the world. In the aspect of electric arc furnace steelmaking, advanced technologies such as an electric arc furnace molten iron charging efficient smelting process, intensified oxygen utilization, scrap steel preheating, ultrahigh power utilization, oxygen combustion fluxing and the like are developed at home and abroad in succession, so that the indexes of the electric arc furnace in China, such as smelting time, electrode consumption, power consumption and the like, reach the international advanced level. The smelting function of the electric arc furnace is also simplified into melting, decarburization and heating from the traditional melting, decarburization, dephosphorization, desulfurization, deoxidation and the like, and the smelting time is shortened to 40-60 minutes.
The electric arc furnace is usually large in tonnage and suitable for smelting steel products in large batches. For small-batch products, induction furnaces such as vacuum induction furnaces, power frequency induction furnaces, medium frequency induction furnaces or high frequency induction furnaces can be used for smelting. Induction furnaces are mainly characterized by different methods of inputting electric energy into the charge. When alternating current passes through the primary coil, an alternating current magnetic field is generated, induced electromotive force is generated in metal furnace burden, the metal is heated and melted by utilizing the induction current formed in the heated metal by the electromagnetic induction, and meanwhile, the electromagnetic force is also generated to play a role in stirring. Compared with other smelting tools, the induction furnace has the following advantages: an electrode is not used, and steel grades with low carbon content can be smelted; the molten steel in the furnace can make the chemical components of the molten steel more uniform under the action of electromagnetic stirring, accelerate the reaction between the molten steel and the slag and promote the removal of non-metallic inclusions; in the induction smelting process, the loss of the alloy is less, and the yield is high; no arc decomposition occurs during the smelting process, and steel with very low gas content can be obtained. The induction furnace is used for smelting, the power density is high, the melting speed is high, the practicability is high, and the use is flexible. Before mass production in a metallurgical plant, an induction furnace is usually adopted for small-batch trial production, and a large-tonnage furnace is adopted for smelting after a basic production process is determined, so that the cost is saved.
Disclosure of Invention
Compared with the existing gas valve alloy, the gas valve alloy has the advantages of greatly reduced nickel content, lower cost, higher strength and hardness after heat treatment, yield limit of more than or equal to 1000MPa, and hardness of more than or equal to HRC 38.
In order to achieve the above object, the present invention is realized by:
the gas valve alloy comprises the following components: c: 0.03-0.10%, Si: 0.10 to 0.40%, Mn: 0.20-1.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.015 percent, Cr: 21.00-26.50%, Ni: 24.50-32.00%, Al: 0.50-1.80%, Ti: 2.20-3.00%, Nb: 0.85-2.50%, V: 0.20-0.50%, and the balance of Fe and inevitable impurities.
The preparation process of the nickel-saving type gas valve alloy and the technical measures for controlling the same are as follows:
(1) smelting by adopting a medium-frequency induction furnace and electroslag remelting, wherein a crucible of the medium-frequency induction furnace is formed by mixing and firing fused magnesia, metallurgical magnesia and a bonding agent; wherein the fused magnesia accounts for 45 percent of the crucible raw material, the metallurgical magnesia accounts for 50 percent, and the adhesive accounts for 5 percent; the adhesive consists of water glass and clay, and the two materials respectively account for 50 percent; the two kinds of magnesite are composed of particles with different particle sizes, wherein the particles with the particle size of 10-20 mm account for 10% of the total weight of all magnesite, the particles with the particle size of 5-less than 10mm account for 30% of the total weight of all magnesite, the particles with the particle size of 2-less than 5mm account for 40% of the total weight of all magnesite, and the magnesite with the particle size of less than 2mm accounts for 20% of the total weight of all magnesite; when the crucible is manufactured, a steel plate mold core is knotted, and the crucible is fired by a low-temperature sintering method;
the alloy raw material is baked before smelting to remove oil stain and iron rust.
(2) When smelting in a medium-frequency induction furnace, firstly charging the reclaimed alloy, and charging other raw materials and the reclaimed alloy into the furnace together with metal nickel, pure iron, low-carbon ferrochrome, ferrosilicon, ferrovanadium, photoelectric carbon and aluminum powder; after the power is switched on, the power is gradually increased, the power is respectively kept for 15-20 minutes at 80KW and 120KW, and the alloy melting condition is observed; then, respectively staying for 20-25 minutes at the power of 180KW and 220K, and further melting the raw materials; finally, performing full melting smelting when the power is 280 KW; when the molten steel is strongly boiled or splashed due to too high melting speed, immediately reducing the power to 230-260 KW, reducing the temperature by 40-50 ℃, and slowing down the reaction; and adding metal aluminum, titanium sponge and niobium in the alloying refining process at the later stage of smelting, adding metal manganese after 20-25 minutes, and pouring within 5 minutes after adding the metal manganese.
And (3) hot charging and annealing the demoulded steel ingot, covering heat-preservation asbestos on the surface of the steel ingot when the steel ingot is transferred to a workshop for annealing, wherein the surface temperature of the steel ingot before charging is 500-650 ℃. The annealing temperature is 890-900 ℃, the temperature is raised along with the furnace, and the temperature raising speed is 60-80 ℃/h. And preserving heat for 16-18 hours after the temperature is reached, cooling the furnace to 550-600 ℃, and discharging and air cooling. And finishing the steel ingot to be used as an electrode for electroslag remelting.
The key points of the invention are as follows: firstly, through reasonable component optimization design, the content of an alloy element Ni is reduced in the alloy, and strengthening elements Al, Ti, Nb and V are added, so that the mechanical property of the gas valve alloy is improved while the raw material cost of the gas valve alloy is reduced. By adopting a method of medium-frequency induction and electroslag remelting smelting, the gas valve alloy with higher strength and hardness is prepared.
The air valve alloy contains a certain amount of Ni, Al and Ti elements, and after high-temperature solid solution, the three elements are subjected to the following aging processThe elements may form intermetallic strengthening phases gamma' -phase, i.e. Ni3(Al, Ti), which is the main strengthening phase in steel. Because the air valve steel is used at high temperature, the strengthening phase has higher strength at high temperature and excellent stability, and the strength of the strengthening phase rises along with the rise of the temperature within a certain temperature range, so the strengthening phase can be used at high temperature for a long time; nb and V are strong carbide forming elements, and are easy to form carbide with C in steel, fine NbC or VC precipitated in the aging process is a second strengthening phase in the steel, and the secondary carbide has stable structure at high temperature and plays a strengthening role because the size is fine and blocks dislocation movement; at present, the commonly used domestic air valve alloy Nimonic80A contains Al and Ti with the contents of 1.0-1.8% and 1.8-2.7%, which are not different from the components of the invention, but do not contain Nb and V, and the strengthening effect is weaker than that of the air valve alloy of the invention. The Inconel751 alloy contains Al, Ti and Nb with the contents of 0.9-1.5%, 2.0-2.6% and 0.7-1.2%, which are not different from the content of the Inconel751, but the air valve alloy also contains 0.20-0.50% of V, and the number of formed carbides is more than that of the Inconel751, so that the strength and hardness are higher than those of the Inconel751, and the manufactured air valve has better wear resistance and longer service life.
Compared with the prior art, the invention has the beneficial effects that:
by reducing the content of the Ni element, the raw material cost of the gas valve alloy is reduced. By properly adding the strengthening elements, the gas valve alloy strengthened by compounding the intermetallic compound and the carbide is obtained. The produced air valve has higher strength and hardness by adopting a reasonable smelting method.
Detailed Description
The invention will be further illustrated with reference to an exemplary embodiment.
In the present example, the 6 furnace gas valve alloy was co-smelted, and the composition of the 6 furnace gas valve alloy is shown in table 1. The raw material cost of the gas valve alloy and the raw material cost of two gas valve alloys which are generally used at home at present are shown in a table 2, the raw material price in the table is calculated according to the product of the price of various metal raw materials at the date of patent application and the content of the metal raw materials in the gas valve alloy, and the raw material price of the gas valve alloy is obviously lower than that of the other two gas valve alloys due to the large nickel content difference. Because the air valve alloy belongs to novel alloy, a novel crucible is adopted when medium-frequency induction smelting is adopted. The crucible is made of metallurgical magnesite, fused magnesite and a small amount of adhesive. Since the crucible plays a key role in induction smelting and is required to have high compactness, thermal stability, high-temperature strength, thermal conductivity and the like, the crucible also has higher requirements on the granularity of raw materials for manufacturing the crucible, and the finer the granularity is, the denser the manufactured crucible is and the better the surface quality is. Therefore, the granularity of the magnesite adopted in the invention is shown in table 3, and the magnesite with the granularity of less than 5mm accounts for 55 percent of the total weight, thereby ensuring that the crucible has good service performance.
The alloy raw material is baked before smelting to remove oil stain and iron rust. When loading, the lower part is compact and the upper part is loose, namely, the small material is loaded below the upper part, and the large material is loaded above the lower part. The reclaimed material of the alloy of the invention is firstly charged, and other raw materials and the reclaimed material are charged together with metal nickel, pure iron, low-carbon ferrochrome, ferrosilicon, ferrovanadium, photoelectric carbon and aluminum powder. After the power is switched on, the power is gradually increased, the power is respectively kept for 15 minutes at 80KW and 120KW, and the alloy melting condition is observed. The batch was then left for 20 minutes at a power of 180KW and 220K, respectively, to further melt the starting material. Finally, carrying out full melting smelting at the power of 280 KW. If the melting speed is too fast, the molten steel is strongly boiled or splashed, the power is immediately reduced, the temperature is properly reduced, and the reaction is slowed down. Adding metal aluminum, sponge titanium and metal niobium in the alloying refining process at the later stage of smelting, adding metal manganese after 20 minutes, pouring within 5 minutes after adding the metal manganese, wherein the pouring temperature is 1450-1470 ℃, and the demoulding time is 4-5 hours. The pouring temperature, the demoulding time and the steel ingot surface state of the gas valve alloy in the embodiment of the invention are shown in the table 4. When the pouring temperature is too high, the shrinkage cavity and shrinkage porosity defects of the steel ingot are serious, and the yield of the steel ingot is influenced; when the casting temperature is low, the molten steel is solidified before feeding, dendritic crystal structures are easily generated, feeding of the molten steel is further hindered, and the generated shrinkage porosity is large. Therefore, the casting temperature is very critical, and as can be seen from table 4, the embodiment of the invention adopts the casting temperature of 1450-1470 ℃, so that better steel ingot quality can be obtained, the temperature is too high, the shrinkage cavity is larger, the temperature is lower, the shrinkage porosity is larger, and the yield of the steel ingot is influenced. The demolding time determines the temperature of the steel ingot after demolding, the demolding time is short, the steel ingot is exposed in the air too early, the cooling speed is too fast, and the steel ingot is easy to crack in the subsequent cooling process; the demoulding time is long, on one hand, the equipment is occupied, on the other hand, the temperature of the steel ingot is low, the steel ingot is likely to crack, and the steel ingot is transferred to an annealing process as soon as possible. As can be seen from Table 4, the demolding time of the embodiment of the invention is 4-5 hours, and the obtained steel ingot has good surface quality.
And (3) hot charging and annealing the demoulded steel ingot, covering heat-preservation asbestos on the surface of the steel ingot when the steel ingot is transferred to a workshop for annealing, wherein the surface temperature of the steel ingot before charging is 500-650 ℃. The annealing temperature is 890-900 ℃, the temperature is raised along with the furnace, and the temperature raising speed is 60-80 ℃/h. And preserving heat for 16-18 hours after the temperature is reached, cooling the furnace to 550-600 ℃, and discharging and air cooling. The effect of the annealing process of the steel ingot on the surface quality of the steel ingot is shown in table 5. The hot charging annealing is used for preventing the steel ingot from cracking caused by thermal stress due to too low temperature, too large temperature difference between the core part and the outside. Too fast a temperature rise also leads to non-uniform temperatures inside and outside the ingot and cracking, as can be seen from table 5. The annealing temperature and the holding time are used for relieving the thermal stress and the structural stress of the steel ingot by enough energy. The tapping temperature also directly affects the internal stress of the steel ingot, the tapping temperature is high, the thermal stress is still large after tapping, the steel ingot can crack, the phenomenon often occurs when other steel grades are produced, and the tapping temperature is low and wastes energy.
And (3) cutting the head and the tail of the annealed steel ingot, removing the part with more impurities, polishing the surface, cleaning the surface, and forging and cogging. The mechanical properties of the 6-furnace example and the comparison with the properties of Nimonic80A and Inconel751 are shown in Table 6. It can be seen that, because the content of Al and Ti in the gas valve alloy is slightly higher than that of Nimonic80A and Inconel751, and a strong carbide forming element V is additionally added, the strengthening phases in the alloy not only have gamma ' but also have NbC and VC, and the comprehensive strengthening effect of the two is stronger than that of the Nimonic80A strengthened by only gamma ' and that of the Inconel751 strengthened by only gamma ' and NbC. The valve alloy in the embodiment of the invention has good strength and hardness, which shows that the valve alloy has better wear resistance in the use process, and has longer service life as a valve.
Table 1 chemical composition (wt%) of the inventive examples,
TABLE 2 comparison of inventive examples with gas valve alloy principal components (wt%) and raw material costs
Note: the cost of raw materials is calculated according to the middle limit of the content of each alloy element
TABLE 3 proportion of the particle size of the magnesia in the crucible
TABLE 4 influence of pouring temperature and demould time on the quality of the ingot
| Furnace number | Pouring temperature (. degree.C.) | Shrinkage and loosening | Demold time (hours) | Quality of steel ingot surface |
| 1 | 1475 | The shrinkage cavity is deeper | 4.4 | Good effect |
| 2 | 1461 | Is normal | 4.5 | Good effect |
| 3 | 1445 | Shrinkage porosity exceeding standard | 4.4 | Good effect |
| 4 | 1466 | Is normal | 5.0 | Good effect |
| 5 | 1458 | Is normal | 5.0 | Good effect |
| 6 | 1455 | Is normal | 4.3 | Good effect |
TABLE 5 influence of annealing process on ingot surface quality
TABLE 6 comparison of mechanical properties of the alloys of the present invention with conventional gas valve alloys
Claims (3)
1. The nickel-saving type gas valve alloy is characterized by comprising the following chemical components in percentage by weight: c: 0.03-0.10%, Si: 0.10 to 0.40%, Mn: 0.20-1.00%, P: less than or equal to 0.015 percent, S: less than or equal to 0.015 percent, Cr: 21.00-26.50%, Ni: 24.50-32.00%, Al: 0.50-1.80%, Ti: 2.20-3.00%, Nb: 0.85-2.50%, V: 0.20-0.50%, and the balance of Fe and inevitable impurities.
2. A method for preparing a gas valve alloy as claimed in claim 1, wherein the technical parameters of the process steps and control are as follows:
(1) smelting by adopting a medium-frequency induction furnace and electroslag remelting, wherein a crucible of the medium-frequency induction furnace is formed by mixing and firing fused magnesia, metallurgical magnesia and a bonding agent; wherein the fused magnesia accounts for 45 percent of the crucible raw material, the metallurgical magnesia accounts for 50 percent, and the adhesive accounts for 5 percent; the adhesive consists of water glass and clay, and the two materials respectively account for 50 percent; the two kinds of magnesite are composed of particles with different particle sizes, wherein the particles with the particle size of 10-20 mm account for 10% of the total weight of all magnesite, the particles with the particle size of 5-less than 10mm account for 30% of the total weight of all magnesite, the particles with the particle size of 2-less than 5mm account for 40% of the total weight of all magnesite, and the magnesite with the particle size of less than 2mm accounts for 20% of the total weight of all magnesite; when the crucible is manufactured, a steel plate mold core is knotted, and the crucible is fired by a low-temperature sintering method;
(2) when smelting in a medium-frequency induction furnace, firstly charging the reclaimed alloy, and charging other raw materials and the reclaimed alloy into the furnace together with metal nickel, pure iron, low-carbon ferrochrome, ferrosilicon, ferrovanadium, photoelectric carbon and aluminum powder; after the power is switched on, the power is gradually increased, the power is respectively kept for 15-20 minutes at 80KW and 120KW, and the alloy melting condition is observed; then, respectively staying for 20-25 minutes at the power of 180KW and 220K, and further melting the raw materials; finally, performing full melting smelting when the power is 280 KW; when the molten steel is strongly boiled or splashed due to too high melting speed, the power is immediately reduced to 230-260 KW, the temperature is reduced by 40-60 ℃ (the reaction is slowed down), metal aluminum, titanium sponge and metal niobium are added in the alloying refining process in the later stage of smelting, metal manganese is added after 20-25 minutes, and casting is carried out within 5 minutes after the metal manganese is added.
3. The preparation method according to claim 2, wherein the demolded steel ingot is subjected to hot charging annealing, heat-preservation asbestos is required to cover the surface of the steel ingot when the steel ingot is transferred to a workshop for annealing, and the temperature of the surface of the steel ingot before charging is 500-650 ℃; the annealing temperature is 890-900 ℃, the temperature is increased along with the furnace, and the temperature increasing speed is 60-80 ℃/h; and preserving heat for 16-18 hours after the temperature is reached, cooling the furnace to 550-600 ℃, and discharging and air cooling.
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| CN115896499A (en) * | 2022-11-29 | 2023-04-04 | 江西宝顺昌特种合金制造有限公司 | UNS N10276 alloy and preparation method thereof |
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