Chromium-nickel-manganese-nitrogen austenitic heat-resistant steel and preparation method thereof

Abstract

The invention discloses chromium-nickel-manganese-nitrogen austenitic heat-resistant steel and a preparation method thereof, and relates to the field of casting austenitic heat-resistant steel. The chromium-nickel-manganese-nitrogen austenitic heat-resistant steel comprises the following components in percentage by weight: 0.4-0.5% of C; si: 1.0% to 2.5%; mn: 4.0% to 6.0%; p: less than or equal to 0.04%; s: less than or equal to 0.03%; 0.2% to 0.5% of Mo; 23%-25% of Cr; ni: 4.0%-7.0%; 0.3% to 0.7% of Nb; 0.1%-0.3% of N; 0.3% to 0.5% of Cu; and the balance of Fe and inevitable impurities. According to the invention, manganese and nitrogen elements with low price are adopted to replace part of nickel element, and the content of niobium element is reduced, so that the production cost is reduced; by adding the molybdenum element, grains of the heat-resistant steel are refined, and the high-temperature strength and creep resistance of the steel are improved; by adding the copper element, the processability of the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel is improved; the added niobium, molybdenum, carbon and nitrogen are utilized to form a carbide or nitride strengthening phase, so that the adverse effect caused by adding the nitrogen element is reduced, the high-temperature strength of the steel is improved, and the steel still has high tensile strength at the temperature of 1000 DEG C or above and can resist the high temperature of 1050 DEG C or above.

Description

Technical Field

[0001] The invention relates to the field of cast austenitic heat-resistant steel, and in particular to a chromium-nickel-manganese-nitrogen austenitic heat-resistant steel and a preparation method thereof. Background Art

[0002] As the country's emission standards and lightweight requirements for the automotive industry are improved, small-sized and high-power engines have become a trend, and the exhaust temperature of the engine has reached over 1000°C. The commonly used high-nickel austenitic ductile iron D-5S material can no longer meet such high exhaust temperature requirements, and needs to be replaced by heat-resistant steel materials with higher temperature resistance requirements.

[0003] In the current market, the materials of turbocharger housings at home and abroad are mainly austenitic heat-resistant steel 1.4848+Nb and 1.4837+Nb, but the nickel content of 1.4848+Nb and 1.4837+Nb is about 20% and 12% respectively. In recent years, the price of nickel plates has been rising, resulting in a significant increase in production costs. Therefore, the high production costs can no longer meet the development needs of key engine parts such as exhaust manifolds and turbocharger housings. A new material that can meet the high temperature resistance requirements of key engine parts such as exhaust manifolds and turbocharger housings of small-sized and high-power engines and can meet low-cost manufacturing is needed to adapt to current development.

[0004] CN202410575387.7 discloses a nickel-saving fully austenitic heat-resistant steel and its preparation method and application, which contains the following components by mass percentage: C: 0.33% to 0.55%, Si: 0.01% to 0.03%, Cr: 8% to 16%, Mn: 5.2% to 7%, N: 0.65% to 0.9%, Ni: 8% to 10%, Ti: 0.6% to 1.2%, Nb: 0.22% to 0.36%, W: 0.36% to 0.52%, Co: 2.1% to 2.6%, Ce+Sc: 0.05% to 0.24%, S: ≤0.035%, P: ≤0.035%, and the rest is Fe and unavoidable impurities. The preparation method is: batching, medium frequency induction melting, pouring, and cutting off the riser. Compared with ZG40Cr25Ni20Si2 steel, the steel of this technical solution has a 15% improvement in high temperature strength and high temperature friction and wear performance at 900°C, while the nickel and chromium content is significantly reduced, which greatly reduces the manufacturing cost. However, this technical solution is mainly used in high temperature conditions of 800-900°C, so it does not clearly state the performance of steel at temperatures above 1000°C, and the use of multiple alloy elements also increases the manufacturing cost and process complexity. Summary of the invention

[0005] Based on the above technical problems, the purpose of the present invention is to provide a chromium-nickel-manganese-nitrogen austenitic heat-resistant steel and a preparation method thereof, by adopting low-priced manganese and nitrogen elements to replace part of the nickel element, and reducing the niobium content, thereby reducing the production cost, and at the same time by adding a certain amount of trace alloy molybdenum element to refine the grain of the heat-resistant steel, improve the high-temperature strength and creep resistance of the steel, and by adding a certain amount of copper element, improve the easy cutting performance of the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel to meet high-precision quality requirements; using the added niobium and molybdenum to form carbide or nitride strengthening phases with carbon and nitrogen, it not only reduces the adverse effects of adding nitrogen elements, but also improves the high-temperature strength of the steel; at the same time, the composition ratio of the material is optimized and strictly controlled, and through the interaction of each material component, the inherent metallurgical mechanism of the material is improved, and the mechanical performance indicators of the material are improved to meet the high temperature resistance and strength performance requirements of the current small-scale high-power engine key components exhaust manifolds, turbocharger housings and other products.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The invention provides a chromium-nickel-manganese-nitrogen austenitic heat-resistant steel, which contains, by weight percentage, the following: C: 0.4%-0.5%; Si: 1.0%-2.5%; Mn: 4.0%-6.0%; P: ≤0.04%; S: ≤0.03%; Mo: 0.2%-0.5%; Cr: 23%-25%; Ni: 4.0%-7.0%; Nb: 0.3%-0.7%; N: 0.1%-0.3%; Cu: 0.3%-0.5%; the balance is Fe and unavoidable impurities.

[0007] Furthermore, a chromium-nickel-manganese-nitrogen austenitic heat-resistant steel contains, by weight percentage: C: 0.465%; Si: 1.65%; Mn: 4.72%; P: ≤0.029%; S: ≤0.008%; Mo: 0.33%; Cr: 23.82%; Ni: 4.56%; Nb: 0.33%; N: 0.29%; Cu: 0.408%; the remainder is Fe and unavoidable impurities.

[0008] The main functions and composition ratios of the chemical elements in the chromium, nickel, manganese and nitrogen austenitic heat-resistant steel of the present invention are as follows: C: 0.4%~0.5% Carbon is an indispensable element in steel. The strengthening effect of carbon in steel is closely related to the composition and structure of the carbide it forms. The increase in carbon content in steel will reduce the plasticity and weldability of the steel. Therefore, in the present invention, the carbon content in austenitic heat-resistant steel is controlled within the range of 0.4% to 0.5%. Preferably, the carbon content is 0.465%.

[0009] Si: 1.0%~2.5% Silicon is a beneficial element in heat-resistant steel that resists high-temperature oxidation and corrosion. Silicon can form a dense protective film of silicon dioxide (SiO2) on the surface of steel, thereby effectively preventing oxygen and other corrosive gases from further invading the interior of the steel and improving the steel's oxidation resistance. In addition, silicon helps to stabilize the austenite structure and prevent phase changes at high temperatures. Therefore, adding silicon to steel can maintain the stability of the steel and good high-temperature performance. Adding silicon to steel can also improve its performance at room temperature. However, too high a silicon content may cause the plasticity and toughness of the steel to decrease, affecting the comprehensive performance of the steel. Therefore, in the present invention, the silicon content in austenitic heat-resistant steel is controlled within the range of 1.0% to 2.5%. Preferably, the content of silicon is 1.65%.

[0010] Cr: 23%~25% Chromium is the main element for high temperature oxidation resistance and high temperature corrosion resistance in heat-resistant steel castings. Like silicon, chromium can form a continuous and stable protective film of chromium oxide (Cr2O3) on the surface of steel, effectively preventing oxygen and other corrosive gases from further invading the interior of the steel, thereby significantly improving the oxidation resistance of the steel. In addition, chromium can improve the high temperature strength of heat-resistant steel, enable it to maintain good mechanical properties under high temperature environment, and improve the thermal strength of heat-resistant steel. However, an increase in chromium content will also lead to an increase in cost and may affect other properties of steel, such as plasticity and weldability. Therefore, in the present invention, the chromium content in austenitic heat-resistant steel is controlled within the range of 23% to 25%. Preferably, the content of chromium is 23.82%.

[0011] Mo: 0.2%~0.5% Molybdenum is a refractory metal and has a good effect on improving the thermal strength of heat-resistant steel. In addition, molybdenum can work together with other elements in steel, such as chromium, to form a dense oxide protective film, which helps to improve the oxidation resistance of heat-resistant steel and reduce the oxidation rate of steel in high temperature environments. However, too high a molybdenum content may lead to increased costs and other performance problems. Therefore, in the present invention, the molybdenum content in austenitic heat-resistant steel is controlled within the range of 0.2% to 0.5%. Preferably, the content of molybdenum is 0.33%.

[0012] Nb: 0.3%~0.7% Niobium is a carbide-forming element. Niobium effectively prevents grain coarsening of steel during high-temperature processing by forming fine niobium carbonitride particles, which not only improves the yield strength of steel, but also enhances its low-temperature toughness. In addition, niobium carbides are very stable at high temperatures, and react with nitrogen to form niobium nitride, which improves the thermal strength of heat-resistant steel. However, excessive niobium may cause adverse effects such as segregation and processability problems. Therefore, in the present invention, the niobium content in austenitic heat-resistant steel is controlled within the range of 0.3% to 0.7%. Preferably, the content of niobium is 0.33%.

[0013] Ni: 4.0%~7.0% Nickel is an important alloying element in austenitic heat-resistant steel. Nickel can enhance the oxidation resistance of heat-resistant steel, and work together with chromium to form a dense protective film of chromium oxide and nickel oxide on the surface of the steel, effectively preventing further erosion of the steel by oxygen and other corrosive gases. In addition, nickel helps to maintain austenitic structure at high temperatures, promote and stabilize austenite, and improve the high-temperature strength of heat-resistant steel. However, nickel is an expensive element, and the balance between cost and performance needs to be considered when using it. Therefore, in the present invention, the nickel content in austenitic heat-resistant steel is controlled within the range of 4.0% to 7.0%. Preferably, the content of nickel is 4.56%.

[0014] Mn: 4.0%~6.0% Manganese is a good deoxidizer and desulfurizer. Its ability to form and stabilize austenite structure in steel is second only to nickel. Manganese can replace part of nickel to reduce production costs. In addition, manganese can improve the hardenability of steel, that is, steel can obtain a deeper hardened layer during quenching. This helps to improve the heat treatment performance of heat-resistant steel. Therefore, in the present invention, the manganese content in austenitic heat-resistant steel is controlled within the range of 4.0% to 6.0%. Preferably, the content of manganese is 4.72%.

[0015] N: 0.1%~0.3% Nitrogen is an effective solid solution strengthening element, which can increase the yield strength and tensile strength of austenitic heat-resistant steel. The solid solution of nitrogen atoms in austenite can effectively hinder the movement of dislocations, thereby improving the strength of the material. In addition, nitrogen, as an alloying element, promotes the formation of austenite phase in austenitic heat-resistant steel, and its austenitizing effect is about 30 times that of nickel, so it can replace part of the nickel element and reduce production costs. Nitrogen can also promote the formation of carbonitrides, and these particles play a role in precipitation strengthening in steel, further improving the strength of steel. However, nitrogen combines with certain elements in steel (such as chromium, etc.) to easily form coarse nitrides, and the precipitation of these nitrides may cause the plasticity and toughness of the steel to decrease, especially at low temperatures. Therefore, in the present invention, the nitrogen content in austenitic heat-resistant steel is controlled within the range of 0.1% to 0.3%. Preferably, the content of nitrogen is 0.29%.

[0016] Cu: 0.3%~0.5% The copper element can form a graphite-copper composite phase with graphite to form a solid lubricating film, thereby improving the machining and cutting performance of high-chromium and high-manganese heat-resistant steel. In addition, copper, as a solid solution element, can increase the yield strength and tensile strength of austenitic heat-resistant steel, and improve the overall strength of the material through solid solution strengthening. Copper can promote the precipitation of certain carbides or nitrides, and these tiny precipitated phases can play a strengthening role and further improve the strength of the steel. However, the segregation of copper in steel may cause the local copper content to be too high, affecting the structural uniformity and performance of the steel. Therefore, in the present invention, the copper content in austenitic heat-resistant steel is controlled within the range of 0.3% to 0.5%. Preferably, the content of copper element is 0.408%.

[0017] S, P: S: ≤0.03%; P: ≤0.04% Sulfur and phosphorus are harmful elements that easily form grain boundary inclusions in steel, increase the brittleness of low alloy steel, and increase the cracking tendency during heat treatment. Therefore, their content should be controlled as low as possible. Therefore, in the present invention, the phosphorus and sulfur content in austenitic heat-resistant steel is selected to be P: ≤0.04%; S: ≤0.03%. Preferably, P: ≤0.029%; S: ≤0.008%.

[0018] The present invention also provides a method for preparing chromium-nickel-manganese-nitrogen austenitic heat-resistant steel, comprising the following steps: S101 smelting: put the cast steel raw materials into the medium frequency induction furnace, then heat up and melt, blow argon into the molten steel after the charge is melted, and the argon supply pressure is 0.20-0.30 MPa; after the molten steel is melted, remove the slag, detect the composition of the original molten steel, and then add 0.1%-0.3% of silicon-barium-calcium-aluminum composite deoxidizer into the furnace for deoxidation; S102 refining: heating the molten steel meeting the above chemical composition to 1660-1680°C, reducing the power of the electric furnace, performing constant temperature refining and slag removal, and closing the argon gas after the refining is completed; S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% rare earth silicon and 0.1% to 0.3% silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed and castings are poured. The pouring temperature is controlled at 1620 to 1640°C and the pouring time is controlled within 3 minutes.

[0019] Further, the raw materials for the cast steel are 24.5% to 53% of 1.4826+Nb heat-resistant steel returns, 20% to 30% of 304 stainless steel, 0% to 23% of carbon scrap steel, 15.2% to 24% of ferrochrome, 3.1% to 4.9% of electrolytic manganese, 0.3% to 1.5% of manganese-nitrogen alloy, 0.18% to 0.3% of recarburizer, 0.5% to 2.03% of ferrosilicon, 0.38% to 0.9% of ferromolybdenum, 0.3% to 0.5% of copper and 0.6% of slag-forming agent, in each case based on the total weight of the raw materials for the cast steel.

[0020] Further, the raw materials for cast steel are 1.4826+Nb heat-resistant steel returns=25%, 304 stainless steel=28%, carbon scrap steel=16%, ferrochrome=23%, electrolytic manganese=3.2%, manganese-nitrogen alloy=1.5%, recarburizer=0.3%, ferrosilicon=1.4%, ferromolybdenum=0.6%, copper=0.4%, and slag-forming agent=0.6%, in each case based on the total weight of the raw materials for cast steel.

[0021] Furthermore, in step S102, the refining time is 5 min.

[0022] Further, in step S101, a medium frequency induction furnace is used for smelting, a slag-making agent is first spread on the furnace bottom, and then 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome are added, and the furnace is started. When melting, the furnace first supplies 50% power, and after the current impact stops, the power is gradually increased to full load. After part of the furnace charge is melted, a carburizer and a manganese-nitrogen alloy are first added; Then, if there is carbon scrap steel, 30% of carbon scrap steel is added, and the carburizer and manganese-nitrogen alloy are pressed into the bottom of the furnace, followed by adding 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome, and after the molten steel is melted, 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added, and after melting, ferrosilicon, ferromolybdenum, electrolytic manganese, copper and the remaining carbon scrap steel are added in sequence; If there is no carbon scrap steel, add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome, and add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome after the molten steel is melted, and then add ferrosilicon, ferromolybdenum, electrolytic manganese and copper in sequence after melting; After the charge is melted, argon is blown into the molten steel with an argon supply pressure of 0.20-0.30 MPa. After the molten steel is melted, the slag is removed and the composition of the original molten steel is tested. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes. Then, after the charge is melted, 0.1%-0.3% of silicon-barium-calcium-aluminum composite deoxidizer is added into the furnace for deoxidation.

[0023] Furthermore, in step S101, when the component ratio is unqualified, correction is continued and completed within 5-8 minutes.

[0024] The present invention also provides use of the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel for manufacturing a turbocharger housing.

[0025] The present invention has the following beneficial effects: (1) The chromium-nickel-manganese-nitrogen austenitic heat-resistant steel of the present invention uses a lower nickel content in its composition design. By increasing the nitrogen element and the manganese element content to replace part of the nickel element, a new austenitic structure is obtained by the composite effect of austenitic elements such as manganese, nickel, carbon, and nitrogen. Chromium and silicon are used to improve the thermal strength and oxidation resistance of the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel; the added niobium and molybdenum form carbide or nitride strengthening phases with carbon and nitrogen, which not only reduces the adverse effects of the addition of nitrogen elements, but also further improves the high-temperature strength of the steel; in addition, the copper element can form a graphite-copper composite phase with graphite inside the structure, that is, a solid lubricating film, thereby improving the processing and cutting performance and practical performance of the material.

[0026] (2) The high-end engine supporting heat-resistant products (turbocharger housing, exhaust manifold) made of the chromium-nickel-manganese-nitrogen cast austenitic heat-resistant steel material of the present invention still have high tensile strength (up to 96 MPa) above 1000°C and can withstand temperatures above 1050°C. Through the corresponding supporting products, the engine's fuel can be fully burned, the power can be effectively improved, and the emission of harmful substances can be reduced, effectively achieving the purpose of energy saving, consumption reduction and emission reduction.

[0027] (3) Through the optimization of material composition ratio, the addition of trace alloy elements, the implementation of smelting process and other innovative technologies, a new "chromium-nickel-manganese-nitrogen austenitic heat-resistant steel" material and manufacturing method are obtained, which greatly reduces the production cost of the corresponding products and meets the growing market demand. The market prospects are broad. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are examples of the present invention and are only used to provide further understanding of the present invention. They constitute a part of the specification and are used to explain the present invention together with the embodiments of the present invention, but do not constitute a limitation of the present invention.

[0029] Figure 1 This is a metallographic structure diagram of Example 4 of the present invention at a magnification of 100 times; Figure 2 This is a metallographic structure diagram of Example 4 of the present invention at a magnification of 500 times. DETAILED DESCRIPTION

[0030] In the present invention, unless otherwise limited, all percentages are by weight.

[0031] Unless otherwise specified, numerical ranges include the starting and ending values ​​of the range. For example, when describing the content of an element as "0.4% to 0.5%", it means that 0.4% and 0.5% are both valid values ​​of the content.

[0032] The present invention is described in detail below with reference to the accompanying drawings and embodiments: Example 1 Main ingredients: 1.4826+Nb heat-resistant steel recycled material = 48%, 304 stainless steel = 28%, ferrochrome = 15.2%, electrolytic manganese = 4.9%, manganese-nitrogen alloy = 0.3%, recarburizer = 0.27%, ferrosilicon = 1.63%, ferromolybdenum = 0.7%, copper = 0.4%, slag-forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0033] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then put in 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the charge is melted, add the carburizer and manganese-nitrogen alloy first, then add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome. After the molten steel is melted, add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome. After melting, add ferrosilicon, ferromolybdenum, electrolytic manganese and copper in turn. After the charge is melted, start blowing argon into the molten steel. The argon supply pressure is 0.20~0.30 MPa; after the molten steel is melted, the slag is removed and the original molten steel composition is tested. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes; then 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon-barium-calcium-aluminum composite deoxidizer is added into the furnace for deoxidation.

[0034] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0035] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0036] The chemical composition analysis results of the test blocks and castings are shown in Table 1 below: Table 1 Example 2 Main ingredients: 1.4826+Nb heat-resistant steel returns = 25%, 304 stainless steel = 30%, carbon scrap = 17%, ferrochrome = 21%, electrolytic manganese = 3.1%, manganese-nitrogen alloy = 1.2%, recarburizer = 0.2%, ferrosilicon = 0.82%, ferromolybdenum = 0.68%, copper = 0.4%, slag-forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0037] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then add 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the furnace charge is melted, add the carburizer and manganese-nitrogen alloy first, and then add 30% of carbon scrap steel. The alloy is pressed into the bottom of the furnace, and then 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After the molten steel is melted, 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After melting, ferrosilicon, ferromolybdenum, electrolytic manganese, copper and the remaining carbon scrap steel are added in sequence. After the charge is melted, argon gas is blown into the molten steel, and the argon supply pressure is 0.20-0.30 MPa; after the molten steel is melted, the slag is removed and the original molten steel composition is detected. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes; then 0.1%-0.3% (based on the total weight of the cast steel raw materials) of silicon-barium-calcium-aluminum composite deoxidizer is added to the furnace for deoxidation.

[0038] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0039] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0040] The chemical composition analysis results of the test blocks and castings are shown in Table 2 below: Table 2 Example 3 Main ingredients: 1.4826+Nb heat-resistant steel returns = 43%, 304 stainless steel = 20%, carbon scrap = 12%, ferrochrome = 18%, electrolytic manganese = 3.4%, manganese-nitrogen alloy = 0.78%, recarburizer = 0.18%, ferrosilicon = 0.86%, ferromolybdenum = 0.78%, copper = 0.4%, slag-forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0041] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then add 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the furnace charge is melted, add the carburizer and manganese-nitrogen alloy first, and then add 30% of carbon scrap steel. The alloy is pressed into the bottom of the furnace, and then 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After the molten steel is melted, 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After melting, ferrosilicon, ferromolybdenum, electrolytic manganese, copper and the remaining carbon scrap steel are added in sequence. After the charge is melted, argon gas is blown into the molten steel, and the argon supply pressure is 0.20-0.30 MPa; after the molten steel is melted, the slag is removed and the original molten steel composition is detected. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes; then 0.1%-0.3% (based on the total weight of the cast steel raw materials) of silicon-barium-calcium-aluminum composite deoxidizer is added to the furnace for deoxidation.

[0042] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0043] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0044] The chemical composition analysis results of the test blocks and castings are shown in Table 3 below: Table 3 Example 4 Main ingredients: 1.4826+Nb heat-resistant steel returns = 25%, 304 stainless steel = 28%, carbon scrap = 16%, ferrochrome = 23%, electrolytic manganese = 3.2%, manganese-nitrogen alloy = 1.5%, recarburizer = 0.3%, ferrosilicon = 1.4%, ferromolybdenum = 0.6%, copper = 0.4%, slag-forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0045] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then add 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the furnace charge is melted, add the carburizer and manganese-nitrogen alloy first, and then add 30% of carbon scrap steel. The alloy is pressed into the bottom of the furnace, and then 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After the molten steel is melted, 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After melting, ferrosilicon, ferromolybdenum, electrolytic manganese, copper and the remaining carbon scrap steel are added in sequence. After the charge is melted, argon gas is blown into the molten steel, and the argon supply pressure is 0.20-0.30 MPa; after the molten steel is melted, the slag is removed and the original molten steel composition is detected. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes; then 0.1%-0.3% (based on the total weight of the cast steel raw materials) of silicon-barium-calcium-aluminum composite deoxidizer is added to the furnace for deoxidation.

[0046] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0047] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0048] The chemical composition analysis results of the test blocks and castings are shown in Table 4 below: Table 4 element C Si Mn P S Mo Cr Ni Nb Cu N Analysis results (%) 0.465 1.65 4.72 0.029 0.008 0.33 23.82 4.56 0.33 0.408 0.29 Example 5 Main ingredients: 1.4826+Nb heat-resistant steel returns = 24.5%, 304 stainless steel = 23%, carbon scrap = 23%, ferrochrome = 24%, electrolytic manganese = 3.2%, manganese-nitrogen alloy = 0.3%, recarburizer = 0.22%, ferrosilicon = 0.5%, ferromolybdenum = 0.38%, copper = 0.3%, slag-forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0049] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then add 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the furnace charge is melted, add the carburizer and manganese-nitrogen alloy first, and then add 30% of carbon scrap steel. The alloy is pressed into the bottom of the furnace, and then 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After the molten steel is melted, 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added. After melting, ferrosilicon, ferromolybdenum, electrolytic manganese, copper and the remaining carbon scrap steel are added in sequence. After the charge is melted, argon gas is blown into the molten steel, and the argon supply pressure is 0.20-0.30 MPa; after the molten steel is melted, the slag is removed and the original molten steel composition is detected. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes; then 0.1%-0.3% (based on the total weight of the cast steel raw materials) of silicon-barium-calcium-aluminum composite deoxidizer is added to the furnace for deoxidation.

[0050] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0051] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0052] The chemical composition analysis results of the test blocks and castings are shown in Table 5 below: Table 5 element C Si Mn P S Mo Cr Ni Nb Cu N Analysis results (%) 0.401 1.00 4.00 0.025 0.01 0.22 23.03 4.00 0.31 0.32 0.10 Example 6 Main ingredients: 1.4826+Nb heat-resistant steel recycled material = 53%, 304 stainless steel = 20%, ferrochrome = 16.8%, electrolytic manganese = 4.4%, manganese-nitrogen alloy = 1.5%, recarburizer = 0.27%, ferrosilicon = 2.03%, ferromolybdenum = 0.9%, copper = 0.5%, slag-forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0053] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then add 40% of 1.4826+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome. Start the furnace. When melting, the furnace first supplies 50% power. After the current impact stops, gradually increase the power to full load. After part of the charge is melted, add the carburizer and manganese-nitrogen alloy first, then add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome. After the steel liquid is melted, Then add 30% 1.4826+Nb heat-resistant steel recycled materials, 30% 304 stainless steel and 30% ferrochrome. After melting, add ferrosilicon, ferromolybdenum, electrolytic manganese and copper in sequence. After the charge is melted, start blowing argon into the molten steel, and the argon supply pressure is 0.20-0.30MPa. After the molten steel is melted, remove the slag and detect the composition of the original molten steel. If the composition ratio is unqualified, continue to correct it and complete it within 5-8 minutes. Then add 0.1%-0.3% (based on the total weight of the cast steel raw materials) of silicon-barium-calcium-aluminum composite deoxidizer into the furnace for deoxidation.

[0054] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0055] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0056] The chemical composition analysis results of the test blocks and castings are shown in Table 6 below: Table 6 element C Si Mn P S Mo Cr Ni Nb Cu N Analysis results (%) 0.499 2.49 5.98 0.022 0.008 0.49 24.98 6.98 0.69 0.50 0.29 Comparative Example 1: 1.4848+Nb Main ingredients: 1.4848+Nb heat-resistant steel recycled material = 69.5%, 304 stainless steel = 17%, ferrochrome = 7%, nickel plate = 4.7%, carburizer = 0.14%, ferrosilicon = 0.4%, ferroniobium = 0.66%, slag forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0057] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then put in 40% of 1.4848+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the charge is melted, add the carburizer first, then add 30% of 1.4848+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel, 30% of ferrochrome and all of niobium. After the molten steel is melted, add 30% of 1.4848+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome. After melting, add ferrosilicon and start blowing argon into the molten steel. The argon supply pressure is 0.20-0.30 MPa, and finally add nickel plate to prevent the molten steel from absorbing hydrogen; after the molten steel is melted, the slag is removed and the original molten steel composition is tested. If the composition ratio is unqualified, continue to correct it and it should be completed within 5-8 minutes; then add 0.1% to 0.3% silicon, barium, calcium and aluminum deoxidizer (based on the total weight of the cast steel raw materials) into the furnace for deoxidation.

[0058] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0059] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0060] The chemical composition analysis results of the test blocks and castings are shown in Table 7 below: Table 7 element C Si Mn P S Mo Cr Ni Nb Analysis results (%) 0.436 1.72 0.436 0.029 0.011 0.082 24.62 19.98 1.36 Comparative Example 2: 1.4837+Nb Main ingredients: 1.4837+Nb heat-resistant steel recycled material = 72%, 304 stainless steel = 17.5%, ferrochrome = 6.55%, nickel plate = 2.4%, carburizer = 0.12%, ferrosilicon = 0.2%, ferroniobium = 0.63%, slag forming agent = 0.6%, in each case based on the total weight of the cast steel raw materials.

[0061] S101 smelting: Use a 1-ton medium-frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then put in 40% of 1.4837+Nb heat-resistant steel recycled materials, 40% of 304 stainless steel and 40% of ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the charge is melted, add the carburizer first, then add 30% of 1.4837+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel, 30% of ferrochrome and all of niobium. After the molten steel is melted, add 30% of 1.4837+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome. After melting, add ferrosilicon. After the charge is melted, start blowing argon into the molten steel. The argon supply pressure is 0.20-0.30 MPa, and finally add metal nickel plate to prevent the molten steel from absorbing hydrogen; after the molten steel is melted, the slag is removed and the original molten steel composition is tested. If the composition ratio is unqualified, continue to correct it and it should be completed within 5-8 minutes; then add 0.1% to 0.3% silicon, barium, calcium and aluminum deoxidizer (based on the total weight of the cast steel raw materials) into the furnace for deoxidation.

[0062] S102 refining: Heat the molten steel with qualified chemical composition to 1660-1680℃, lower the power of the electric furnace, carry out constant temperature refining and slag removal, and turn off the argon gas after refining for 5 minutes.

[0063] S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of rare earth silicon and 0.1% to 0.3% (based on the total weight of the cast steel raw materials) of silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed, and the test blocks and turbocharger housing castings are poured. The pouring temperature is 1620 to 1640°C, and the pouring time is controlled within 3 minutes.

[0064] The chemical composition analysis results of the test blocks and castings are shown in Table 8 below: Table 8 element C Si Mn P S Mo Cr Ni Nb Analysis results (%) 0.423 1.63 0.426 0.031 0.008 0.071 24.92 12.16 1.35 The high temperature performance test results of Examples 1 to 4 of the present invention and Comparative Examples 1 to 2 at 1050°C and 1100°C are shown in Table 9 below. 0.2 is the yield strength, and A is the elongation after fracture.

[0065] Table 9 It can be seen from the results in the table that the high temperature performance of the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel of the present invention at 1050°C and 1100°C is better than that of the 1.4848+Nb and 1.4837+Nb steels of the prior art, or is equivalent to that of the 1.4848+Nb and 1.4837+Nb steels of the prior art. Among them, the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel of Example 4 has the best performance. Under this condition, the steel contains by weight percentage: C: 0.465%; Si: 1.65%; Mn: 4.72%; P: ≤0.029%; S: ≤0.008%; Mo: 0.33%; Cr: 23.82%; Ni: 4.56%; Nb: 0.33%; N: 0.29%; Cu: 0.408%; the balance is Fe and unavoidable impurities. Figure 1 and Figure 2 The metallographic structure diagrams at 100 times magnification and 500 times magnification of this embodiment are shown, and it can be seen from the diagrams that a uniform austenite microstructure is obtained.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed in the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A chromium-nickel-manganese-nitrogen austenitic heat-resistant steel, characterized in that: Contains by weight: C: 0.4% to 0.5%; Si: 1.0%~2.5%; Mn: 4.0%~6.0%; P: ≤0.04%; S: ≤0.03%; Mo: 0.2% ~ 0.5%; Cr: 23% ~ 25%; Ni: 4.0% ~ 7.0%; Nb: 0.3% ~ 0.7%; N: 0.1%~0.3%; Cu: 0.3%~0.5%; the balance is Fe and inevitable impurities.

2. The chromium-nickel-manganese-nitrogen austenitic heat-resistant steel according to claim 1, characterized in that: Contains by weight: C: 0.465%; Si: 1.65%; Mn: 4.72%; P: ≤ 0.029%; S: ≤0.008%; Mo: 0.33%; Cr: 23.82%; Ni: 4.56%; Nb: 0.33%; N: 0.29%; Cu: 0.408%; the balance is Fe and unavoidable impurities.

3. A method for preparing the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel according to any one of claims 1 to 2, characterized in that: The following steps are involved: S101 smelting: put the cast steel raw materials into the medium frequency induction furnace, then heat up and melt, blow argon into the molten steel after the charge is melted, and the argon supply pressure is 0.20-0.30 MPa; after the molten steel is melted, remove the slag, detect the composition of the original molten steel, and then add 0.1%-0.3% of silicon-barium-calcium-aluminum composite deoxidizer into the furnace for deoxidation; S102 refining: heating the molten steel having the chemical composition as described in claim 1 to 1660-1680° C., reducing the power of the electric furnace, performing constant temperature refining and slag removal, and closing the argon gas after the refining is completed; S103 steel tapping and pouring: After refining, slag removal is carried out, and 0.1% to 0.3% rare earth silicon and 0.1% to 0.3% silicon zirconium alloy are added into the ladle for secondary deoxidation and modification, followed by steel tapping. After steel tapping, the slag on the surface of the molten steel is removed and castings are poured. The pouring temperature is controlled at 1620 to 1640°C and the pouring time is controlled within 3 minutes.

4. The preparation method according to claim 3, characterized in that: In step S101, the cast steel raw material is 24.5% to 53% of 1.4826+Nb heat-resistant steel recycled materials, 20% to 30% of 304 stainless steel, 0% to 23% of carbon scrap steel, 15.2% to 24% of ferrochrome, 3.1% to 4.9% of electrolytic manganese, 0.3% to 1.5% of manganese-nitrogen alloy, 0.18% to 0.3% of recarburizer, 0.5% to 2.03% of ferrosilicon, 0.38% to 0.9% of ferromolybdenum, 0.3% to 0.5% of copper and 0.6% of slag-forming agent, in each case based on the total weight of the cast steel raw materials.

5. The preparation method according to claim 4, characterized in that: The specific process of step S101 is: Use medium frequency induction furnace for smelting. First, spread the slag-making agent on the bottom of the furnace, then put in 40% 1.4826+Nb heat-resistant steel recycled materials, 40% 304 stainless steel and 40% ferrochrome, start the furnace, and supply 50% power at the beginning of melting. After the current impact stops, gradually increase the power to full load. After part of the furnace charge is melted, add the carburizer and manganese-nitrogen alloy first; Then, if there is carbon scrap steel, 30% of carbon scrap steel is added, and the carburizer and manganese-nitrogen alloy are pressed into the bottom of the furnace, followed by adding 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome, and after the molten steel is melted, 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome are added, and after melting, ferrosilicon, ferromolybdenum, electrolytic manganese, copper and the remaining carbon scrap steel are added in sequence; If there is no carbon scrap steel, add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome, and add 30% of 1.4826+Nb heat-resistant steel recycled materials, 30% of 304 stainless steel and 30% of ferrochrome after the molten steel is melted, and then add ferrosilicon, ferromolybdenum, electrolytic manganese and copper in sequence after melting; After the charge is melted, argon is blown into the molten steel with an argon supply pressure of 0.20-0.30 MPa. After the molten steel is melted, the slag is removed and the composition of the original molten steel is tested. If the composition ratio is unqualified, correction is continued and completed within 5-8 minutes. Then, after the charge is melted, 0.1%-0.3% of silicon-barium-calcium-aluminum composite deoxidizer is added into the furnace for deoxidation.

6. The preparation method according to claim 3, characterized in that: In step S102, the refining time is 5 minutes.

7. Use of the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel according to any one of claims 1 to 2 or the chromium-nickel-manganese-nitrogen austenitic heat-resistant steel prepared according to the preparation method according to any one of claims 3 to 6 for manufacturing a turbocharger housing.

Images