Zirconium-containing austenitic heat-resistant steel and preparation method thereof
Technical Field
The invention relates to the technical field of steel materials, and particularly relates to zirconium-containing austenitic heat-resistant steel and a preparation method thereof.
Background
The austenitic stainless steel has excellent corrosion resistance, weldability and comprehensive mechanical properties, and is widely applied to the industries of aerospace, chemical engineering, atomic energy and the like. But the working temperature of the common heat-resistant steel exceeds 900 ℃, the strength begins to be obviously reduced, and the oxidation speed is also obviously accelerated. Due to the development of the technology, the temperature of the heat-resistant material is higher and higher, and the use condition is more complicated, so that the increase of working equipment under the ultra-high temperature condition and the problem of high-temperature oxidation become important factors for restricting the application of the heat-resistant material to the high-temperature environment. Therefore, the development of heat resistant steel materials suitable for operation under ultra high temperature conditions is becoming urgent. At present, a plurality of researches and explorations are carried out by domestic and foreign scholars and production enterprises for prolonging the service life of heat-resistant steel. In fact, the development of new heat-resistant steel materials at home and abroad has no substantial breakthrough in the aspects of high-temperature performance (mechanical performance and oxidation resistance).
In the high-temperature alloy, some trace elements can obviously influence the mechanical property of the high-temperature alloy at a very low content, and the high-temperature alloy becomes a research hotspot in the field of high-temperature alloys. However, the effects of trace elements on superalloys are often diverse, some elements are generally considered as harmful or beneficial elements, the effects can be greatly or even reversely converted under different conditions, and the effects, laws and mechanisms of the different trace elements on the alloys are different under different alloy systems. Therefore, the heat-resistant steel with good performance has important significance for the development of steel.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the austenitic heat-resistant steel containing zirconium, which has good high-temperature mechanical property and high-temperature oxidation resistance and is suitable for materials such as heat-resistant equipment serving in a high-temperature environment.
The invention also aims to provide a preparation method of the zirconium-containing austenitic heat-resistant steel, which is simple to operate, strong in controllability and easy for industrial production.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
The invention provides zirconium-containing austenitic heat-resistant steel which comprises the following components in percentage by mass: 0.06-0.2%, Si: 0.4 to 1.0%, Mn: 0.5-1.5%, Cr: 16-22%, Ni: 28-34%, Zr: 0.2-0.35%, and the balance of Fe and impurity elements.
The invention provides a preparation method of zirconium-containing austenitic heat-resistant steel, which comprises the following steps: the raw materials are mixed and melted according to the proportion, cast and formed, and then post-treatment is carried out.
The beneficial effects of the invention include:
by adding zirconium element and reasonably controlling the contents of carbon, silicon, manganese, chromium, nickel and zirconium, the austenitic heat-resistant steel with good high-temperature mechanical property and high-temperature oxidation resistance is obtained by the preparation method provided by the invention. The tensile strength and the elongation of the material at 700 ℃ are respectively more than 290MPa and more than 30 percent; the oxidation weight gain of the surface of the material is less than 28.3g/m after being oxidized for 150 hours at 1000 DEG C2. The material is suitable for heat-resisting equipment and the like in service in a high-temperature environment. The preparation method is simple to operate, strong in controllability and easy for industrial production.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Next, a zirconium-containing austenitic heat-resistant steel and a method for producing the same according to an embodiment of the present invention will be described in detail.
The embodiment of the invention provides zirconium-containing austenitic heat-resistant steel which comprises the following components in percentage by mass: 0.06-0.2%, Si: 0.4 to 1.0%, Mn: 0.5-1.5%, Cr: 16-22%, Ni: 28-34%, Zr: 0.2-0.35%, and the balance of Fe and impurity elements.
In the above chemical composition, carbon is a component effective for imparting suitable tensile strength and high-temperature permanent strength required for heat-resistant steel. However, if the carbon content is too high, the toughness of the alloy is lowered and weldability may be deteriorated. For this reason, the carbon content is limited to 0.06 to 0.2% in the present invention. The carbon content may be 0.07%, 0.08%, 0.09%. Preferably, the carbon content may be 0.1 to 0.2%, wherein the carbon content may be 0.11%, 0.13%, 0.15%, 0.16%, 0.19%.
Silicon is beneficial to improving the high-temperature oxidation resistance of the heat-resistant steel, but excessive silicon destroys the welding performance of the alloy, and sigma phase is easy to form to destroy the ductility and toughness of the alloy if exposed to high-temperature environment for a long time. For this purpose, the silicon content is limited to 0.4 to 1.0%, and the silicon content may be 0.42%, 0.45%, 0.48%, 0.71%, 0.77%, 0.79%, 0.81%, 0.82%, 0.84%, 0.88%, 0.90%, 0.94%, 0.97%. Preferably, the silicon content may be 0.5 to 0.7%, wherein the silicon content may be 0.51%, 0.53%, 0.58%, 0.62%, 0.67%, 0.69%.
Manganese stabilizes austenite and increases the solubility of nitrogen in austenite, and too high a manganese content can impair oxidation resistance and reduce the creep limit of the alloy. Therefore, the manganese content should not exceed 1.5%, and the manganese content in the invention is 0.5-1.5%. The manganese content may be 0.55%, 0.6%, 0.65%, 0.7%, 0.75%. Preferably, the manganese content is 0.8-1.5%. Wherein, the manganese content can be 0.85%, 0.9%, 1.0%, 1.05%, 1.1%, 1.3%.
Chromium can improve the oxidation resistance and corrosion resistance of the heat-resistant steel, can form a compact chromium-containing oxide film in an oxidized medium, and can organize the continuous damage of a metal matrix. In this respect, in order to achieve sufficient corrosion resistance, a chromium content of at least 20% is required. However, if the chromium content is too high, the content of nickel needs to be increased in order to stabilize austenite and suppress the formation of sigma phase, and the chromium content is limited to 16 to 22% based on these considerations. The chromium content may be 20.5%, 21%, 21.5%. Preferably, the content of chromium is 16.5-20%. Wherein, the chromium content can be 17%, 17.5%, 18%, 19%, 19.5%.
Nickel is an element that strongly forms and stabilizes austenite and enlarges the austenite phase region, and at a specific chromium content, increasing the nickel content suppresses the oxide growth rate and increases the tendency to form a continuous chromium oxide layer. Therefore, the nickel content is preferably 28 to 34%. The nickel content may be 28.5%, 29%, 33.5%. Preferably, the nickel content is 30-33%. Wherein, the content of nickel can be 30.5%, 31%, 31.5% and 32%.
The trace elements can not only purify molten steel, but also refine the solidification structure of the steel, and change the property, the form and the distribution of inclusions, thereby improving various performances of the steel. As a surface active element, the silicon-based composite material can increase the crystal boundary diffusion activation energy, not only can block the crystal boundary sliding, but also can increase the surface energy of crystal boundary cracks, and is very effective in improving the endurance strength; in addition, the growth speed of an oxide layer of the heat-resistant steel in a high-temperature state is inhibited by the micro-Yuan-Kao, the formed oxide layer is well combined with the matrix, and the matrix can be protected from further oxidation under the action of high-temperature circulation.
Zirconium is regarded as a cleaning element in some high-temperature alloys, forms carbide and carbon-sulfur compounds through combination with C and S, and reduces solid solution concentration of the elements in grain boundaries, so that the addition of zirconium is beneficial to purifying the grain boundaries and enhancing the bonding force of the grain boundaries, and further is beneficial to maintaining the high-temperature strength and the lasting plasticity of the alloy. The zirconium content of the invention is 0.2-0.35%. May be 0.33% or 0.34%. Preferably, the zirconium content is 0.2 to 0.32%. Wherein, the content of zirconium can be 0.21%, 0.22%, 0.23%, 0.26%, 0.27%, 0.29%.
Further, in the preferred embodiment of the present invention, the austenitic heat-resistant steel contains a small amount of sulfur and phosphorus, and it should be noted that S is 0.03% or less and P is 0.03% or less. The high content of sulfur and phosphorus affects the high-temperature mechanical property and the high-temperature oxidation resistance of the austenitic heat-resistant steel, so the content needs to be controlled.
The embodiment of the invention provides a preparation method of the zirconium-containing austenitic heat-resistant steel, which comprises the following steps: the raw materials are mixed and melted according to the proportion, cast and formed, and then post-treatment is carried out.
Specifically, the method takes scrap steel, ferromanganese, ferrosilicon, ferrochromium, ferronickel and ferrozirconium as raw materials, calculates and weighs each raw material according to the weight percentage of each component of the zirconium modified heat-resistant steel, and carries out batching.
Heating scrap steel in an electric furnace to 1440-1460 ℃ to melt into first molten steel, adding ferromanganese and ferrosilicon to melt down in sequence after the first molten steel is melted down to obtain second molten steel, leading the temperature to reach 1510-1530 ℃, and deoxidizing by adopting aluminum wires. Then sequentially adding ferronickel and ferrochrome, heating until the temperature of the third molten steel reaches 1600-1630 ℃, and deoxidizing by adopting aluminum wires again.
And after deslagging the liquid surface of the third molten steel, quickly discharging the third molten steel out of the furnace, pouring the third molten steel into a casting ladle with ferrozirconium placed at the bottom end, controlling the temperature of the fourth molten steel in the ladle to be 1560-1580 ℃, standing for a period of time to reduce the temperature of the fourth molten steel to 1530-1540 ℃, and pouring the fourth molten steel into a casting mold for casting and forming to obtain the as-cast heat-resistant steel part. And (5) after the pouring is finished for 10 hours, boxing and taking out the casting. The first molten steel, the second molten steel, the third molten steel and the fourth molten steel in the present invention are for clarifying the mixing order of the raw materials, and the names thereof are not strictly required in the specific examples. In the embodiment of the present invention, aluminum wire deoxidation is adopted, which is a general technique in the technical field, and in other embodiments of the present invention, other deoxidation methods may be adopted, which is not limited in the present invention.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides austenitic heat-resistant steel containing zirconium and a preparation method thereof, and the preparation method comprises the following steps:
the chemical composition (weight percentage) of the austenitic heat-resistant steel containing zirconium of the present example: 0.14 percent of C, 0.50 percent of Si, 0.82 percent of Mn, 19.8 percent of Cr, 33.6 percent of Ni, 0.2 percent of Zr, less than or equal to 0.03 percent of S, less than or equal to 0.03 percent of P, and the balance of Fe and inevitable impurity elements.
Calculating and weighing the raw materials required by the smelting: scrap steel, ferromanganese, ferrosilicon, ferrochromium, ferronickel and ferrozirconium are proportioned.
Heating scrap steel in an electric furnace to 1450 ℃ for melting, after molten steel is melted down, sequentially adding ferromanganese and ferrosilicon for melting down to enable the temperature to reach 1520 ℃, deoxidizing by adopting aluminum wires, sequentially adding ferronickel and ferrochrome to enable the temperature of the molten steel to reach 1610 ℃, deoxidizing by adopting aluminum wires again, deslagging on the liquid level of the molten steel, rapidly discharging the molten steel out of the furnace, pouring the molten steel into a casting ladle with ferrozirconium at the bottom end, controlling the temperature of the molten steel in the ladle to be 1570 ℃, standing for a period of time to enable the temperature of the molten steel to be reduced to 1538 ℃, pouring the molten steel into a casting mold for casting and forming, and obtaining the cast heat-resistant steel part.
After pouring is completed for 10 hours, boxing and taking out the casting; and after cooling, performing sand removal, polishing and other treatments to obtain the zirconium-containing austenitic heat-resistant steel casting. The test result of the oxidation resistance of the casting is as follows: the tensile strength and the elongation of the material at 700 ℃ are 348MPa and 36.7 percent respectively; oxidized weight gain of 28.3g/m in unit area of 150h at 1000 DEG C2。
Example 2
The embodiment provides austenitic heat-resistant steel containing zirconium and a preparation method thereof, and the preparation method comprises the following steps:
the chemical composition (weight percentage) of the austenitic heat-resistant steel containing zirconium of the present example: 0.16 percent of C, 0.62 percent of Si, 1.2 percent of Mn, 18.4 percent of Cr, 30.6 percent of Ni, 0.26 percent of Zr, less than or equal to 0.03 percent of S, less than or equal to 0.03 percent of P, and the balance of Fe and inevitable impurity elements.
Calculating and weighing the raw materials required by the smelting: scrap steel, ferromanganese, ferrosilicon, ferrochromium, ferronickel and ferrozirconium are proportioned.
Heating scrap steel in an electric furnace to 1455 ℃ for melting, after molten steel is melted down, sequentially adding ferromanganese and ferrosilicon for melting down to 1530 ℃, deoxidizing by adopting aluminum wires, sequentially adding ferronickel and ferrochrome to make the molten steel temperature reach 1620 ℃, deoxidizing by adopting aluminum wires again, deslagging on the liquid level of the molten steel, rapidly discharging the molten steel out of the furnace, pouring the molten steel into a casting ladle with ferrozirconium at the bottom end, controlling the temperature of the molten steel in the ladle to 1575 ℃, standing for a period of time to make the temperature of the molten steel reduce to 1525 ℃, pouring the molten steel into a casting mold for casting and forming, and obtaining the cast heat-resistant steel piece.
After pouring is completed for 10 hours, boxing and taking out the casting; and after cooling, performing sand removal, polishing and other treatments to obtain the zirconium-containing austenitic heat-resistant steel casting. The test result of the oxidation resistance of the casting is as follows: the tensile strength and the elongation of the material at 700 ℃ are 336MPa and 38.7 percent respectively; oxidation weight gain of 27.5g/m per unit area of 150h at 1000 deg.C2。
Example 3
The embodiment provides austenitic heat-resistant steel containing zirconium and a preparation method thereof, and the preparation method comprises the following steps:
the chemical composition (weight percentage) of the austenitic heat-resistant steel containing zirconium of the present example: 0.19 percent of C, 0.59 percent of Si, 1.48 percent of Mn, 20.4 percent of Cr, 32.3 percent of Ni, 0.32 percent of Zr, less than or equal to 0.03 percent of S, less than or equal to 0.03 percent of P, and the balance of Fe and inevitable impurity elements.
Calculating and weighing the raw materials required by the smelting: scrap steel, ferromanganese, ferrosilicon, ferrochromium, ferronickel and ferrozirconium are proportioned.
Heating scrap steel in an electric furnace to 1460 ℃ for melting, after molten steel is melted down, sequentially adding ferromanganese and ferrosilicon for melting down to 1530 ℃, deoxidizing by adopting aluminum wires, sequentially adding ferronickel and ferrochrome to make the molten steel temperature reach 1630 ℃, deoxidizing by adopting aluminum wires again, deslagging on the liquid level of the molten steel, rapidly discharging the molten steel out of the furnace, pouring the molten steel into a ladle with ferrozirconium at the bottom end, controlling the temperature of the molten steel in the ladle to 1575 ℃, standing for a period of time to make the temperature of the molten steel reduced to 1540 ℃, pouring the molten steel into a casting mold for casting and forming, and obtaining the cast heat-resistant steel piece.
After pouring is completed for 10 hours, boxing and taking out the casting; and after cooling, performing sand removal, polishing and other treatments to obtain the zirconium-containing austenitic heat-resistant steel casting. The test result of the oxidation resistance of the casting is as follows: the tensile strength and the elongation of the material at 700 ℃ are 296MPa and 30.8 percent respectively; oxidized weight gain of 21.3g/m in unit area of 150h at 1000 DEG C2。
Comparative example 1
The present comparative example provides an austenitic heat-resistant steel and a method for producing the same, comprising:
the chemical components (weight percentage) of the austenitic heat-resistant steel in the comparative example are as follows: 0.12 percent of C, 0.46 percent of Si, 0.51 percent of Mn, 17.5 percent of Cr, 29.8 percent of Ni, less than or equal to 0.03 percent of S, less than or equal to 0.03 percent of P, and the balance of Fe and inevitable impurity elements.
Calculating and weighing the raw materials required by the smelting: scrap steel, ferromanganese, ferrosilicon, ferrochromium and ferronickel are mixed.
Heating scrap steel in an electric furnace to 1440 ℃ for melting, after molten steel is melted down, sequentially adding ferromanganese and ferrosilicon for melting down, enabling the temperature to reach 1510 ℃, deoxidizing by adopting aluminum wires, sequentially adding ferronickel and ferrochrome, enabling the temperature of the molten steel to reach 1610 ℃, deoxidizing by adopting aluminum wires again, deslagging on the liquid level of the molten steel, rapidly discharging the molten steel out of the furnace, pouring the molten steel into a casting ladle, controlling the temperature of the molten steel in the ladle to be 1565 ℃, standing for a period of time, reducing the temperature of the molten steel to 1530 ℃, pouring the molten steel into a casting mold for casting and forming, and obtaining the cast heat-resistant steel part.
After pouring is completed for 10 hours, boxing and taking out the casting; and after cooling, performing sand removal, polishing and other treatments to obtain the austenitic heat-resistant steel casting. The test result of the oxidation resistance of the casting is as follows: the tensile strength and the elongation of the material at 700 ℃ are 265MPa and 25.6 percent respectively; oxidized weight gain of 34.2g/m at 1000 ℃ for 150h per unit area2。
Comparative example 2
The present comparative example provides a zirconium-containing austenitic heat-resistant steel and a method for producing the same, comprising:
the chemical composition (weight percentage) of the austenitic heat-resistant steel containing zirconium of the present example: 0.12 percent of C, 0.45 percent of Si, 0.5 percent of Mn, 16.5 percent of Cr, 28.9 percent of Ni, 0.15 percent of Zr, less than or equal to 0.03 percent of S, less than or equal to 0.03 percent of P, and the balance of Fe and inevitable impurity elements.
Calculating and weighing the raw materials required by the smelting: scrap steel, ferromanganese, ferrosilicon, ferrochromium, ferronickel and ferrozirconium are proportioned.
Heating scrap steel in an electric furnace to 1445 ℃ for melting, after molten steel is melted down, sequentially adding ferromanganese and ferrosilicon for melting down to reach 1515 ℃, deoxidizing by adopting aluminum wires, sequentially adding ferronickel and ferrochrome to reach 1610 ℃ at the moment, deoxidizing by adopting aluminum wires again, deslagging on the liquid level of the molten steel, rapidly discharging the molten steel out of the furnace, pouring the molten steel into a ladle with ferrozirconium at the bottom end, controlling the temperature of the molten steel in the ladle to be 1570 ℃, standing for a period of time to reduce the temperature of the molten steel to 1530 ℃, pouring the molten steel into a casting mold for casting and forming, and obtaining the cast heat-resistant steel piece.
After pouring is completed for 10 hours, boxing and taking out the casting; and after cooling, performing sand removal, polishing and other treatments to obtain the zirconium-containing austenitic heat-resistant steel casting. The test result of the oxidation resistance of the casting is as follows: the tensile strength and the elongation of the material at 700 ℃ are 273MPa and 26.6 percent respectively; oxidation weight gain of 32.8g/m per unit area of 150h at 1000 DEG C2。
Test examples
The performance tests of the austenitic heat-resistant steels prepared in examples 1-3 and comparative examples 1-2 are respectively carried out, and the test results show that compared with the comparative examples, the austenitic heat-resistant steels prepared in the examples have better high-temperature mechanical properties and high-temperature oxidation resistance, namely, the performance of the austenitic heat-resistant steels is influenced by no addition of zirconium element or a small amount of addition of zirconium element. The tensile strength of the heat-resistant steel prepared by the preparation method is more than 296MPa at 700 ℃, the highest tensile strength can reach 348MPa, the elongation is more than 30 percent, the highest tensile strength can reach 38.7 percent, the oxidation weight gain per unit area is less than 28.3g/m after the heat-resistant steel is oxidized for 150 hours at 1000 DEG C2The minimum can reach 21.3g/m2. The preparation method provided by the invention is scientific and reasonable, and the austenitic heat-resistant steel with good high-temperature mechanical property and high-temperature oxidation resistance can be prepared.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.