Heat-resistant steel with excellent ultrahigh-temperature toughness and manufacturing method of heat-resistant steel

Abstract

The invention relates to the technical field of metal materials, in particular to heat-resistant steel with excellent ultrahigh-temperature toughness and a manufacturing method of the heat-resistant steel. The heat-resistant steel comprises the following chemical components in percentage by weight: 0.04%-0.10% of C, 1.0%-1.5% of Si, 1.0%-1.5% of Mn, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 24.0%-26.0% of Cr, 21.0%-23.0% of Ni, 6.0%-7.0% of Mo, 0.14%-0.20% of N, 1.5%-4.0% of Alt and the balance of Fe and inevitable impurities. On the basis of components of high C, middle Si and middle Mn, harmful elements P and S are controlled, a large number of alloy elements of Cr, Ni, Mo, N and Al are compositely added, a manufacturing method is combined, an austenite and carbide organization structure is obtained, and it is guaranteed that the steel has the ultra-high temperature heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to a heat-resistant steel with excellent ultra-high temperature strength and toughness and a method for manufacturing the same. Background Art

[0002] High-temperature heat-resistant steel, as an alloy steel with good heat resistance under high temperature conditions, is increasingly used in aviation, energy, chemical and other fields.

[0003] In recent years, the rapid development of the industrial sector has placed higher demands on the high strength and heat resistance of key metal materials required for the manufacture of corresponding equipment. In particular, service temperatures above 800°C have become commonplace in many industrial fields. For example, aircraft turbine engines and turbines in the aviation industry; core materials in nuclear power plants; furnace tubes in thermal power plants; and high-temperature reactors and furnace walls in petrochemical processes all have service temperatures or localized temperatures reaching 800°C or higher. Consequently, heat-resistant steels are required to exhibit enhanced thermal strength, stability, oxidation resistance, and ductility when operating at 800°C for extended periods.

[0004] Patent CN116716545A discloses a martensitic heat-resistant steel, its preparation method, and its application. This invention is a martensitic heat-resistant steel with an operating temperature range of 600-650°C, and cannot meet higher operating temperatures. Patent CN116356200A discloses a heat-resistant steel for boiler tubes, its production method, and its application. The product made from this steel has an operating temperature of 625-650°C. Although a large number of solid solution and precipitation strengthening elements are added to the composition, it still cannot meet the requirements of equipment used at 1000°C and above.

[0005] Although the heat-resistant steel products covered by the aforementioned patents contain a certain amount of alloying elements that enhance thermal strength and oxidation resistance, resulting in good heat resistance, their service temperature is still limited, generally below 650°C. To meet the needs of higher-temperature service environments, it is necessary to develop heat-resistant steel plates with excellent thermal strength, oxidation resistance, and ductility suitable for applications at 800°C and above, in order to meet the rapid development of my country's industrial equipment sector. Summary of the Invention

[0006] The purpose of the present invention is to provide a heat-resistant steel with excellent ultra-high temperature strength and toughness and a manufacturing method thereof. By designing the chemical composition and adopting a specific production and manufacturing process, a heat-resistant steel plate with excellent performance in high-temperature service at 800°C and above is obtained to meet the manufacturing requirements of special equipment for ultra-high temperature service.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] On one hand, the present invention provides a heat-resistant steel with excellent ultra-high temperature strength and toughness, the chemical composition of which is as follows: C 0.04%-0.10%, Si 1.0%-1.5%, Mn 1.0%-1.5%, P≤0.010%, S≤0.005%, Cr 24.0%-26.0%, Ni 21.0%-23.0%, Mo 6.0%-7.0%, N 0.14%-0.20%, Alt 1.5%-4.0%, and the balance being Fe and unavoidable impurities.

[0009] The reasons for limiting the amounts of chemical elements in the steel of the present invention are detailed as follows:

[0010] C: C is an essential strengthening element in steel. Its strengthening effect in steel is closely related to the composition and structure of the carbides it forms, and its strengthening effect is also temperature-dependent. To ensure high-temperature strength and carbide ratio, a certain amount of carbon must be added. Therefore, the present invention incorporates a certain amount of carbon. However, increasing the carbon content in steel reduces its plasticity and weldability. Therefore, the present invention limits the C content to 0.04% to 0.10%.

[0011] Si: Si is a beneficial element in heat-resistant steel that protects against high-temperature oxidation. Adding a certain amount of silicon forms a highly protective, dense SiO2 film on the steel surface. However, a silicon content exceeding 3% can degrade the steel's mechanical properties. Therefore, the present invention limits the Si content to 1.0% to 1.5%.

[0012] Mn: Mn is an excellent deoxidizer and desulfurizer. Its ability to form and stabilize austenite in steel is second only to nickel. Heat-resistant steels that use manganese instead of nickel have a wide range of applications. While manganese improves the instantaneous strength of steel at high temperatures, it has no significant effect on its endurance strength and creep strength. Therefore, the present invention limits the Mn content to 1.0% to 1.5%.

[0013] Both P and S are harmful elements in steel, which increase the brittleness of steel. Therefore, the content of phosphorus and sulfur in steel should be reduced as much as possible, S≤0.005%, P≤0.010%.

[0014] Cr: As an alloying element that reduces the γ-Fe phase and expands the α-Fe phase, Cr is a strong carbide-forming element. These carbides are extremely stable and significantly contribute to maintaining the excellent thermal strength of heat-resistant steel, enhancing its long-lasting strength and creep resistance. Furthermore, a certain amount of Cr forms an oxide film at ultra-high temperatures, improving the matrix's oxidation resistance and preventing graphitization. Therefore, the present invention limits the Cr content to 24.0% to 26.0%.

[0015] Ni: The main role of Ni in heat-resistant steel is to expand the austenite region of iron and to form and stabilize austenite. Ni and Fe can be infinitely solid-solved, which means that they can dissolve each other to a large extent to form a uniform alloy. The addition of nickel helps to expand the austenite region of iron, that is, to increase the stability and existence range of the austenite phase in steel. Austenite is a face-centered cubic lattice structure with good toughness and plasticity, but relatively low hardness. By adding Ni, heat-resistant steel can maintain the austenite state at higher temperatures, thereby improving its heat resistance and mechanical properties. Therefore, the present invention limits the Ni content range to 21.0% to 23.0%.

[0016] Mo: Mo is a refractory metal with a high melting point. It has a significant effect on improving the thermal strength and recrystallization of heat-resistant steel. It can also reduce the hot brittleness of steel and improve its resistance to high-temperature corrosion. Therefore, the present invention limits the Mo content to 6.0% to 7.0%.

[0017] N: The main functions of N in the steel of the present invention are solid solution strengthening, aging precipitation strengthening and improving the macrostructure of high chromium steel, making it dense and solid and increasing its strength. Therefore, the present invention limits the N content to 0.14% to 0.20%.

[0018] Alt: Aluminum is primarily used in steel as a deoxidizer and grain refiner. Aluminum effectively removes oxygen from molten steel, improving the steel's purity. It also refines the steel's grain structure, enhancing its strength and toughness. However, exceeding 8% significantly reduces the steel's plasticity and weldability. Therefore, the present invention limits the Alt content to 1.5% to 4.0%.

[0019] In the above technical solution, further, the room temperature mechanical properties of the heat-resistant steel are: R el ≥550MPa, R m The high temperature mechanical properties are: R p0.2 R of 140~190Mpa, 900℃ p0.2 R of 100~155MPa and 1000℃ p0.2 The pressure is 65~105Mpa, and the KV2 at 200℃ is ≥300J.

[0020] In the above technical solution, further, the thickness of the heat-resistant steel is 10 to 50 mm.

[0021] Another aspect of the present invention provides a method for manufacturing the above-mentioned heat-resistant steel with excellent ultra-high temperature toughness, the process of the method comprising: smelting, continuous casting, heating, rolling, and heat treatment; wherein:

[0022] Heating: The billet heating temperature is 1220-1280℃, and the total heating time is 6.5-8.5h;

[0023] Rolling: Billet rolling temperature ≥ 1050℃, single pass deformation rate 5% to 15%, final rolling temperature ≥ 950℃;

[0024] Heat treatment: The temperature of the solution treatment is 1130-1180°C, the holding time is t*(1.0-2.0)min, t is the thickness of the finished product, mm, and then it is quickly cooled to room temperature, and then aging treatment is carried out. The temperature of the aging treatment is 730-800°C, the holding time is 2.0-4.0h, and then it is water-cooled to room temperature.

[0025] In the above technical solution, further, in the smelting process: electric arc furnace smelting + AOD furnace refining is adopted, the furnace charge includes molten iron, scrap steel and alloy, the total amount of scrap steel and alloy accounts for 60% to 80% of the furnace charge, the electric arc furnace smelting temperature is 1550 to 1600°C, and the AOD furnace temperature is 1620 to 1650°C.

[0026] In the above technical solution, further, in the continuous casting process: the pouring temperature is 1520-1550° C., and the casting speed is 1.2-1.5 m / min.

[0027] In the above technical solution, further, in the heat treatment process, the rapid cooling rate is 50 to 80° C. / s.

[0028] The beneficial effects of the present invention are:

[0029] (1) The present invention controls harmful elements P and S on the basis of high C, medium Si and medium Mn components, and obtains an austenite plus carbide structure by adding a large amount of Cr, Ni, Mo, N and Al alloy elements in combination with a manufacturing method, thereby ensuring that the steel has ultra-high temperature heat strength and its room temperature mechanical properties are: R el ≥550MPa, R m The high temperature mechanical properties are: R p0.2 R of 130~195Mpa, 900℃ p0.2 R of 90~155MPa, 1000℃ p0.2 The pressure is 55~105Mpa, and the KV2 at 200℃ is ≥300J.

[0030] (2) The present invention obtains a heat-resistant alloy steel plate with excellent ultra-high temperature strength and toughness and a thickness specification of 10 to 50 mm. DETAILED DESCRIPTION

[0031] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0032] Unless otherwise specified, the materials used in the examples of the present invention can be obtained from commercial sources or prepared according to conventional methods well known to those skilled in the art.

[0033] Examples 1-10

[0034] The chemical compositions of the heat-resistant steels of Examples 1-10 of the present invention are shown in Table 1.

[0035] Table 1 Chemical composition of Examples 1-10 (wt, %)

[0036] Example C Si Mn P S Cr Ni Mo N Alt 1 0.06 1.3 1.1 0.03 0.002 25.4 21.6 6.2 0.18 1.3 2 0.04 1.3 1.2 0.05 0.003 24.7 22.8 6.0 0.20 2.1 3 0.09 1.2 1.4 0.06 0.003 24.9 22.6 7.0 0.19 1.0 4 0.07 1.0 1.0 0.03 0.002 26.0 21.3 6.5 0.15 2.8 5 0.1 1.4 1.2 0.05 0.001 25.6 21.8 6.2 0.18 3.4 6 0.05 1.5 1.1 0.06 0.005 25.5 22.3 6.5 0.16 4.0 7 0.07 1.1 1.3 0.07 0.003 24.2 23.0 6.3 0.16 2.4 8 0.08 1.2 1.5 0.04 0.002 25.8 21.0 6.1 0.17 2.6 9 0.06 1.0 1.2 0.08 0.001 24.6 24.5 6.4 0.15 1.5 10 0.09 1.4 1.3 0.10 0.004 26.0 22.0 6.3 0.16 2.9

[0037] The method for manufacturing the heat-resistant steel comprises the following steps:

[0038] (1) Smelting: Electric arc furnace smelting + AOD furnace refining is adopted. The charge includes molten iron, scrap steel and alloy. The total amount of scrap steel and alloy accounts for 60% to 80% of the charge. The electric arc furnace smelting temperature is 1550-1600℃, and the AOD furnace temperature is 1620-1650℃.

[0039] (2) Continuous casting: pouring temperature 1520-1550°C, casting speed 1.2-1.5 m / min;

[0040] (3) Heating: The billet heating temperature is 1220-1280°C, and the total heating time is 6.5-8.5h. By controlling the billet heating process, it is ensured that the alloy elements are fully dissolved, the billet is heated evenly, and the growth of the original austenite grains is effectively suppressed;

[0041] (4) Rolling: The billet rolling temperature is ≥1050℃, the single-pass deformation rate is 5% to 15%, and the final rolling temperature is ≥950℃;

[0042] (5) Heat treatment: The temperature of the solution treatment is 1130-1180°C, the holding time is t*(1.0-2.0)min, t is the thickness of the finished product, mm, and it is rapidly cooled to room temperature at a rate of 50-80°C / s, and then aging treatment is performed. The aging treatment temperature is 730-800°C, the holding time is 2.0-4.0h, and then water-cooled to room temperature; a large amount of alloying elements such as Cr, Ni, and Mo are added to the heat-resistant steel of the present invention, the purpose is to utilize the solid solution strengthening effect of carbon and alloying elements, so a higher solution treatment temperature is required to fully dissolve them in the austenite matrix and eliminate the structural defects and internal stresses caused by the rolling and cooling process to obtain a fully austenitic structure. After the solution treatment, the aging temperature is 730-800°C. At this temperature, the precipitates are not easy to aggregate and grow, and are not easy to exchange with the metal-based alloying elements. The aging precipitation is dispersed, and at the same time, the precipitation of chromium carbides is prevented from destroying the grain boundary strengthening effect.

[0043] The smelting and continuous casting process parameters of the heat-resistant steel of Examples 1-10 are shown in Table 2.

[0044] Table 2 Smelting and continuous casting process parameters of Examples 1-10

[0045]

[0046] Table 3 Heating, rolling and heat treatment process parameters of Examples 1-10

[0047] Example 1 2 3 4 5 6 7 8 9 10 Heating temperature / ℃ 1220 1225 1240 1280 1235 1230 1265 1250 1245 1260 Total heating time / h 7.5 7.0 6.5 7.5 8.0 7.0 6.5 7.5 8.5 7.0 Rolling temperature / ℃ 1052 1063 1067 1051 1069 1077 1070 1068 1053 1063 Single pass deformation rate / % 15 8 5 10 13 9 14 5 9 15 Finish rolling temperature / ℃ 960 951 983 972 959 964 978 982 983 972 Finished product thickness / mm 50 20 10 30 40 25 45 12 25 48 Solution temperature / ℃ 1135 1140 1140 1170 1160 1150 1170 1555 1160 1180 Solution holding time / min 60 28 20 45 80 40 62 24 45 48 Aging temperature / ℃ 750 780 770 750 740 765 745 800 790 750 Aging insulation time / h 2.2 3.5 2.6 4.0 3.5 3.7 2.0 3.6 3.9 2.4

[0048] The room temperature and high temperature mechanical properties of the heat-resistant steels of Examples 1-10 are shown in Table 4.

[0049] Table 4: Tissue performance effects of Examples 1-10

[0050]

[0051] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A heat-resistant steel with excellent ultra-high temperature toughness, characterized in that: The chemical composition of the heat-resistant steel is: C 0.04%-0.10%, Si 1.0%-1.5%, Mn 1.0%-1.5%, P≤0.010%, S≤0.005%, Cr 24.0%-26.0%, Ni 21.0%-23.0%, Mo 6.0%-7.0%, N 0.14%-0.20%, Alt 1.5%-4.0%, and the balance is Fe and unavoidable impurities.

2. The heat-resistant steel with excellent ultra-high temperature toughness according to claim 1, characterized in that: The room temperature mechanical properties of the heat-resistant steel are: el ≥550MPa, R m The high temperature mechanical properties are: R p0.2 R of 140~190Mpa, 900℃ p0.2 R of 100~155MPa and 1000℃ p0.2 The pressure is 65~105Mpa, and the KV2 at 200℃ is ≥300J.

3. The heat-resistant steel with excellent ultra-high temperature toughness according to claim 1, characterized in that: The thickness of the heat-resistant steel is 10 to 50 mm.

4. A method for manufacturing heat-resistant steel according to any one of claims 1 to 3, characterized in that: The process of the method includes: smelting, continuous casting, heating, rolling, and heat treatment; wherein: Heating: The billet heating temperature is 1220-1280℃, and the total heating time is 6.5-8.5h; Rolling: Billet rolling temperature ≥ 1050℃, single pass deformation rate 5% to 15%, final rolling temperature ≥ 950℃; Heat treatment: The temperature of the solution treatment is 1130-1180°C, the holding time is t*(1.0-2.0)min, t is the thickness of the finished product, mm, and then it is quickly cooled to room temperature, and then aging treatment is carried out. The temperature of the aging treatment is 730-800°C, the holding time is 2.0-4.0h, and then it is water-cooled to room temperature.

5. The manufacturing method according to claim 4, characterized in that In the smelting process: electric arc furnace melting + AOD furnace refining is adopted, the furnace charge includes molten iron, scrap steel and alloy, the total amount of scrap steel and alloy accounts for 60% to 80% of the furnace charge, the electric arc furnace melting temperature is 1550-1600℃, and the AOD furnace temperature is 1620-1650℃.

6. The manufacturing method according to claim 4, characterized in that In the continuous casting process: pouring temperature is 1520~1550℃, and casting speed is 1.2~1.5m / min.

7. The manufacturing method according to claim 4, characterized in that In the heat treatment process, the rapid cooling rate is 50-80° C. / s.

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