CN113817954A - High-molybdenum high-nitrogen steel and slab continuous casting process thereof - Google Patents
High-molybdenum high-nitrogen steel and slab continuous casting process thereof Download PDFInfo
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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Abstract
The invention discloses high-molybdenum high-nitrogen steel which contains the following chemical elements in percentage by mass besides Fe: 0<C≤0.02％，0<Si≤1.0％，0<Mn is less than or equal to 4.0%, Cr: 18-25%, Ni: 21-28%, W is less than or equal to 1.0%, Mo + W: 4-10%, N: 0.2-1.2%, Cu: 0.01-4.0%, and refined grain elements, wherein the refined grain elements are at least one of the following two types: (a) at least one rare earth element of No. 57-71 in the periodic table of chemical elements, the total content of which is 0.001-0.2%; (b) at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr, the total content of which is 0.001-0.5%. Correspondingly, the invention also discloses a slab continuous casting production process of the high-molybdenum high-nitrogen steel. The high-molybdenum high-nitrogen steel disclosed by the invention adopts reasonable chemical components and process design, has excellent quality and performance, has the area shrinkage of 70-85% at 1000-1300 ℃, the tensile strength of 50-100 MPa at 1000-1300 ℃, and the corrosion rate of 2-20 g/(m) m in wet-process phosphoric acid with the temperature of 80 ℃ and the concentration of 38%2·h)。
Description
Technical Field
The invention relates to a metal material and a slab continuous casting process thereof, in particular to alloy steel and a slab continuous casting process thereof.
Background
The high-nitrogen high-molybdenum alloy contains elements such as nitrogen, molybdenum, nickel, copper and the like, and the smelting and processing process is difficult and easy to generate segregation and cracking. The high-nitrogen high-molybdenum alloy is the variety with the highest requirement and the greatest difficulty in the alloy steel production process, and correspondingly, the high-nitrogen high-molybdenum alloy is the centralized embodiment of the steel mill process technology level.
With the rapid increase of market demand in recent years, the demand for high-nitrogen high-molybdenum alloy steel products is also rapidly promoted, and particularly, the demand of the high-nitrogen high-molybdenum alloy products is more vigorous than that of the high-nitrogen high-molybdenum alloy products due to the concern of China in the fields of petroleum and petrochemical industry, nuclear power and thermal power, clean energy, ship manufacturing, ocean engineering, environmental protection and the like. At present, only a small amount of test products of the Tai steel are put on the market in China, and basically all the Tai steel depends on import, wherein the Tai steel mainly adopts Japan metallurgy, and Ottompp and American SMC are inferior. Ottokumpp is taken as an example in Europe and America, and the remarkable characteristic of high quality and high price is that.
With the gradual application of continuous casting technology to the production of high-alloy steel in world ferrous metallurgy production, foreign advanced enterprises have adopted slab caster to produce special alloy products with remarkable success. However, the melting point of the high-molybdenum high-nitrogen alloy is lower than 1400 ℃ and is about 100 ℃ lower than that of carbon steel, the alloy has poor plasticity, and an intermediate phase is precipitated in the continuous casting cooling process, so that cracks are easy to generate.
Based on the above, the high-molybdenum high-nitrogen alloy and the slab continuous casting process thereof are expected to be obtained, and by adopting the slab continuous casting process, the performance and the quality of the prepared high-molybdenum high-nitrogen alloy can be ensured, the production efficiency is greatly improved, and the production cost is greatly reduced.
Disclosure of Invention
An object of the present invention is to provide a high-molybdenum high-nitrogen steel having a reduction of area of 70 to 85% at 1000 to 1300 ℃ and a tensile strength of 50 to 100MPa at 1000 to 1300 ℃, wherein the corrosion rate in wet-process phosphoric acid of 80 ℃ and 38% is 2 to 20 g/(m) in a wet-process phosphoric acid2H) and therefore it has excellent properties and quality.
In order to achieve the purpose, the invention provides high-molybdenum high-nitrogen steel which contains the following chemical elements in percentage by mass in addition to Fe:
0< C < 0.02%, 0< Si < 1.0%, 0< Mn < 4.0%, Cr: 18-25%, Ni: 21-28%, W is less than or equal to 1.0%, Mo + W: 4-10%, N: 0.2-1.2%, Cu: 0.01-4.0%, and refined grain elements, wherein the refined grain elements are at least one of the following two types:
(a) at least one rare earth element of No. 57-71 in the periodic table of chemical elements, the total content of which is 0.001-0.2%;
(b) at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr, the total content of which is 0.001-0.5%.
Further, in the high-molybdenum high-nitrogen steel of the present invention, the chemical elements are, by mass:
0< C < 0.02%, 0< Si < 1.0%, 0< Mn < 4.0%, Cr: 18-25%, Ni: 21-28%, W is less than or equal to 1.0%, Mo + W: 4-10%, N: 0.2-1.2%, Cu: 0.01-4.0%, refined grain elements, and the balance of Fe and other inevitable impurities; wherein the refined crystal grain elements are at least one of the following two types:
(a) at least one rare earth element of No. 57-71 in the periodic table of chemical elements, the total content of which is 0.001-0.2%;
(b) at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr, the total content of which is 0.001-0.5%.
In the high-molybdenum high-nitrogen steel, the design principle of each chemical element is as follows:
c: in the high-molybdenum high-nitrogen steel, carbon belongs to an element for enlarging an austenite area, and because the carbon element has low solubility in the nickel-rich alloy, carbide is easily formed and the alloy performance is influenced, the lower the carbon content in the steel is, the better the steel is. Based on the above, the mass percent of C in the high-molybdenum high-nitrogen steel is controlled to be 0< C < 0.02%.
Si: in the high molybdenum and high nitrogen steel of the invention, silicon is generally brought in by raw materials and alloy materials. The silicon element has the function of stabilizing carbide and harmful intermetallic phases, the content of the silicon element in the steel is not required to be too high, and the content of the silicon element in the steel must be strictly controlled. Based on the above, the mass percent of Si in the high-molybdenum high-nitrogen steel is controlled to be 0< Si < 1.0%.
In some preferred embodiments, the mass percentage of Si may be controlled to 0< Si.ltoreq.0.8% for better practical effects.
Mn: in the high-molybdenum high-nitrogen steel, manganese can replace nickel in the steel, the critical quenching speed of the steel can be reduced, the stability of austenite is increased during cooling, the decomposition of the austenite is inhibited, and the austenite formed at high temperature is kept to normal temperature. However, it should be noted that manganese is not so effective in improving the corrosion resistance of steel, and the protective effect of the formed oxide film is also low. Based on the above, the mass percent of Mn in the high-molybdenum high-nitrogen steel is controlled to be 0< Mn is less than or equal to 4.0%.
Ni: in the high-molybdenum high-nitrogen steel of the invention, the main function of the nickel element is to form an austenite crystal structure, so that the properties such as plasticity, weldability and toughness can be effectively improved. Based on the method, in order to obtain a pure austenitic structure from the ultra-low carbon nickel-containing alloy, the mass percent of Ni in the high-molybdenum high-nitrogen steel is controlled to be 21-28%.
In some preferred embodiments, the mass percentage of Ni can be controlled between 22% and 26% for better implementation.
Cr: in the high-molybdenum high-nitrogen steel, the chromium element is the only alloy element which enables the nickel element to have good corrosion resistance in an oxidizing medium, and the proper amount of chromium element is added into the steel, so that the acid resistance, salt resistance and oxidation resistance of the alloy can be effectively improved, and the corrosion resistance of the alloy is increased along with the increase of the chromium content. Based on the above, the mass percent of Cr in the high-molybdenum high-nitrogen steel is controlled to be 18-25%.
In some preferred embodiments, the mass percentage of Cr may be controlled to be between 20% and 24% for better implementation.
Mo, W: in the high-molybdenum high-nitrogen steel, molybdenum can mainly improve the corrosion resistance of nickel element in a reducing medium, and molybdenum can strongly improve the pitting corrosion resistance and the crevice corrosion resistance of the nickel-containing alloy. Correspondingly, in the high-molybdenum high-nitrogen steel, the behavior of the tungsten element is similar to that of the molybdenum element, and the local corrosion resistance of the alloy, such as pitting corrosion resistance, gap resistance and the like, can be mainly and effectively improved. However, it should be noted that when the contents of molybdenum and tungsten elements in the alloy are too high, both hot and cold working become difficult, and scale formation and peracid are more likely to occur during descaling. Based on the above, the beneficial effects and adverse effects of molybdenum and tungsten on nickel-containing alloy are comprehensively considered, and the mass percent of W in the high-molybdenum high-nitrogen steel is controlled to be less than or equal to 1.0%. Correspondingly, the content of a single W element is controlled, and meanwhile, the mass percent of Mo and W is controlled to be 4-10%.
In some preferred embodiments, for better implementation, the mass percent of W can be controlled to be less than or equal to 0.8%, and the mass percent of Mo and W can be controlled to be between 5 and 8%.
N: in the high-molybdenum high-nitrogen steel, nitrogen can replace nickel in the steel, the nitrogen can obviously improve the pitting corrosion resistance and the crevice corrosion resistance of the alloy, and the mass percent of N in the high-molybdenum high-nitrogen steel is controlled to be 0.2-1.2% in consideration of the production difficulty of nitrogen alloying under normal pressure.
In some preferred embodiments, the mass percentage of N may be controlled between 0.2% and 1.0% for better implementation.
Cu: in the high-molybdenum high-nitrogen steel, a proper amount of copper element is added into the alloy, so that the strength and the hardness of the nickel-containing alloy can be effectively improved, and the heat conductivity coefficient and the corrosion resistance in a reducing medium are improved. However, it should be noted that if the content of copper element in the steel is too high, the corrosion resistance of the steel in an oxidizing medium and the oxidation resistance of the steel in air are reduced. Based on the above, the mass percent of Cu in the high-molybdenum high-nitrogen steel is controlled to be 0.01-4.0%.
In some preferred embodiments, the mass percentage of Cu may be controlled between 0.02 to 3.0% for better performance.
It should be noted that the high-molybdenum high-nitrogen steel of the present invention further contains refined grain elements, and the refined grain elements may be at least one of the following two types: (a) at least one of No. 57-71 rare earth elements in the periodic table of chemical elements; (b) at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr.
According to the technical scheme, the grains can be obviously refined by adding trace rare earth elements into the steel, and the processing performance is improved. The more the rare earth is added, the finer the crystal grains are. However, it is to be noted that, in actual production, the more the amount of rare earth added and the more the burnout, the more the possibility of increasing impurities and hydrogen absorption, and the less the amount of residual in the alloy. Therefore, at least one element in No. 57-71 rare earth elements in the periodic table of chemical elements can be added into the refined grain elements, and the total content of the elements is controlled to be 0.001-0.2%.
In addition, the refined grain element in the high-molybdenum high-nitrogen steel can be at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr. The addition of appropriate amounts of these elements to the steel can refine the grains. In addition, these elements can also act as deoxidizers. In addition, these elements can also make the alloy have aging strengthening reaction to achieve the purpose of improving the strength. The total content of these elements is between 0.001 and 0.5%.
In some embodiments, the grain refining elements of the above-mentioned two types (a) and (b) may be added simultaneously.
Further, in the high molybdenum high nitrogen steel of the present invention, among other unavoidable impurities: p is less than or equal to 0.040 percent and/or S is less than or equal to 0.030 percent.
Further, in the high molybdenum high nitrogen steel of the present invention, among other unavoidable impurities: p is less than or equal to 0.020% and/or S is less than or equal to 0.020%.
In the technical scheme, P, S in the high-molybdenum high-nitrogen steel is an inevitable impurity element in the steel, both the P element and the S element can generate brittle substances with low melting points, hot brittleness is easily caused, and the lower the content of the impurity elements in the steel is, the better the content is.
Further, in the high-molybdenum high-nitrogen steel provided by the invention, the mass percentage of each chemical element meets at least one of the following conditions:
0<Si≤0.8％；
Cr：20～24％；
Ni：22～26％；
W≤0.8％；
Mo+W：5～8％；
N：0.2～1.0％；
Cu：0.02～3.0％；
the total content of at least one of No. 57-71 rare earth elements in the periodic table of chemical elements is 0.002-0.15%;
the total content of at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr is 0.002-0.35%.
Further, in the high-molybdenum high-nitrogen steel of the present invention, the microstructure thereof is a fully austenitic structure.
Further, in the high-molybdenum high-nitrogen steel of the invention, the performance meets at least one of the following conditions:
the reduction of area at 1000-1300 ℃ is 70-85%;
the tensile strength is 50-100 MPa at 1000-1300 ℃;
the corrosion rate in wet-process phosphoric acid with the temperature of 80 ℃ and the concentration of 38 percent is 2-20 g/(m)2·h)。
Accordingly, another object of the present invention is to provide a slab continuous casting process for producing high molybdenum and high nitrogen steel, which can effectively improve the quality of a continuous casting slab of high molybdenum and high nitrogen steel, wherein the produced continuous casting slab has excellent characteristics of good quality of the surface and the center of the continuous casting slab, can fully exert the advantages of continuous casting production, can effectively inhibit the generation of pits and cracks of the casting slab, significantly improve the quality of the surface and the center of the casting slab, and can realize multi-furnace continuous casting.
In order to achieve the purpose, the invention provides the slab continuous casting production process of the high-molybdenum high-nitrogen steel, which controls the process parameters of the continuous casting process to meet at least one of the following conditions:
after casting, the target pulling speed is 0.6-1.6 m/min within 4 min;
the superheat degree of the molten steel in the tundish is 15-65 ℃;
controlling the insertion depth of a water gap of the continuous casting crystallizer to be 85-125 mm;
the secondary cooling water is used for weak cooling, and the specific water amount is controlled to be 0.46 +/-0.1L/kg;
the electromagnetic stirring current of the secondary cooling zone is 1000-2000A, and the stirring frequency is 2.5-3.5 Hz;
the pressing amount under light pressing is 3-10 mm;
the central solid phase rate fs of the casting blank corresponding to the reduction interval is 0.1-0.5;
the grinding amount of the single surface of the casting blank is 3-10 mm.
In the slab continuous casting production process, the high-molybdenum high-nitrogen alloy steel has a peritectic reaction zone at the temperature of about 1390 ℃ in continuous casting, the solubility of nitrogen in high-temperature ferrite is low, and nitrogen is easily separated out in the temperature zone, so that the defect of subcutaneous air holes of casting blanks can be caused. Therefore, it is necessary to control the steel to rapidly pass through the temperature range to avoid excessive precipitation of nitrogen. Therefore, in the slab continuous casting production process, the continuous casting is started quickly after casting, and the target drawing speed specified by the process needs to be controlled within 4 min. Accordingly, the target pull rate can be controlled between 0.6-1.6 m/min because: if the average drawing speed is higher than 1.60m/min, the primary blank shell is thin, the casting blank is cooled unevenly, and longitudinal cracks and even breakout are easy to generate; if the average pulling speed is lower than 0.60m/min, the cooling time of the casting blank in the crystallizer is too long, the molten steel at the meniscus is in a low-temperature state, the melting effect of the casting powder is poor, longitudinal cracking is easily caused, and the overall production capacity of the continuous casting machine is influenced. In some preferred embodiments, the target pulling speed can be controlled to be 0.8-1.2 m/min, and the target pulling speed can be 0.8-1.2 m/min within 4min after casting.
In addition, in the slab continuous casting production process, if the superheat degree of molten steel in the continuous casting process is lower than 15 ℃, the molten steel has poor fluidity, so that a crystallizer water gap is easy to freeze steel, the pouring is forced to be interrupted, and the melting effect of the casting powder is poor; if the superheat degree of the molten steel is higher than 65 ℃, the primary blank shell in the continuous casting crystallizer is thin, the crack tendency is large, the solidification time is long, the selective crystallization is sufficient, and the casting blank segregation and the looseness are aggravated. Therefore, in the slab continuous casting production process, the superheat degree of the molten steel in the tundish is controlled to be 15-65 ℃. In some preferred embodiments, the superheat degree of the molten steel in the tundish can be controlled to be between 25 and 50 ℃.
In addition, it should be noted that the insertion depth of the water gap of the crystallizer is not too deep or too shallow during the slab continuous casting production process. If the insertion depth of the water gap of the crystallizer is too shallow, the impact of the water gap stream on a steel slag interface is stronger, the reaction probability of molten steel and crystallizer casting powder can be increased, and the probability of meniscus slag entrapment can be increased; and if the water gap of the crystallizer is inserted too deeply, the casting blank is easy to crack. Therefore, in the slab continuous casting production process, the insertion depth of the water gap of the continuous casting crystallizer is controlled to be 85-125 mm. In some preferred embodiments, the insertion depth of the water gap of the continuous casting crystallizer can be controlled between 90 mm and 115 mm.
In the slab continuous casting production process, the surface of a casting blank which is discharged out of a crystallizer may have a depression or a fine crack, and in order to prevent the further expansion of the defects in the secondary cooling zone, a large number of numerical simulation calculations show that the weak cooling in the secondary cooling zone is suitable for high-molybdenum high-nitrogen alloy. Therefore, in the slab continuous casting production process, the secondary cooling water is weakly cooled, and the specific water amount is controlled to be 0.46 +/-0.1L/kg.
In the slab continuous casting production process, in order to solve the problem of segregation and porosity possibly caused by high superheat degree of molten steel in the continuous casting process, a secondary cooling zone electromagnetic stirring and dynamic soft reduction process is added in the slab continuous casting production process. When the secondary cooling zone electromagnetic stirring and dynamic soft reduction process is adopted, if the electromagnetic stirring current intensity is lower than 1000A and the soft reduction is lower than 3mm, the effect of improving the center quality of the casting blank cannot be achieved; if the electromagnetic stirring current intensity is higher than 2000A, the liquid level fluctuation of the crystallizer is large, and the casting blank is easy to generate negative segregation; if the reduction under light pressure is more than 10mm, the narrow surface of the casting blank is easy to bulge, and cracks are easy to generate on the surface of the casting blank; further, if the reduction is performed too late at a light reduction, the billet may be cracked. Therefore, in the slab continuous casting production process, the electromagnetic stirring current of the secondary cooling zone is controlled to be 1000-2000A, the stirring frequency is controlled to be 2.5-3.5 Hz, the reduction under light pressure is controlled to be 3-10 mm, and the central solid phase rate fs of the casting blank corresponding to the reduction zone is controlled to be 0.1-0.5. Of course, in some preferred embodiments, in order to obtain better implementation effect, the electromagnetic stirring current in the secondary cooling zone may be controlled to be 1200-1600A, the reduction amount under light reduction may be controlled to be 4-8 mm, and the central solid fraction fs of the casting blank corresponding to the reduction interval may be controlled to be 0.2-0.4.
Correspondingly, in the slab continuous casting production process, the surface of the high-molybdenum high-nitrogen alloy continuous casting billet has defects of local depressions, slag pits, deep vibration marks and the like with different degrees, and the defects can influence the surface quality of subsequent hot-rolled and cold-rolled products. Therefore, in order to alleviate the defects, a thinning process can be adopted for the casting blank. However, it should be noted that when the grinding amount of the single surface of the casting blank is less than 3mm, the defect may not be completely removed; if the single-side grinding amount of the casting blank is more than 10mm, the yield of the casting blank is influenced. Therefore, in the slab continuous casting production process, the grinding amount of the single surface of the casting blank can be controlled to be 3-10 mm. In some preferred embodiments, the casting blank single-side thinning amount can be controlled to be between 4 and 8 mm.
Further, in the slab continuous casting production process of the present invention, the process parameters for controlling the continuous casting process satisfy at least one of the following:
the target pulling speed is 0.8-1.2 m/min within 4min after casting
The superheat degree of the molten steel in the tundish is 25-50 ℃;
controlling the insertion depth of a water gap of the continuous casting crystallizer to be 90-115 mm;
the electromagnetic stirring current of the secondary cooling zone is 1200-1600A;
the pressing amount under light pressing is 4-8 mm;
the central solid phase rate fs of the casting blank corresponding to the reduction interval is 0.2-0.4;
the grinding amount of the single surface of the casting blank is 4-8 mm.
Compared with the prior art, the high-molybdenum high-nitrogen steel and the slab continuous casting process thereof have the advantages and beneficial effects as follows:
the high-molybdenum high-nitrogen steel has a reduction of area of 70-85% at 1000-1300 ℃, a tensile strength of 50-100 MPa at 1000-1300 ℃, and a corrosion rate of 2-20 g/(m) in 38% wet-process phosphoric acid at 80 ℃ of2H) with good quality and excellent properties.
In addition, the slab continuous casting production process of the high-molybdenum high-nitrogen steel can effectively improve the quality of a high-molybdenum high-nitrogen steel continuous casting blank, the produced continuous casting blank has the excellent characteristics of good quality of the surface and the center of the continuous casting blank and the like, the advantages of continuous casting production can be fully exerted, the generation of the depression and the crack of the casting blank can be effectively inhibited, the quality of the surface and the center of the casting blank is obviously improved, and multi-furnace continuous casting can be realized. The continuous casting production process of the high-molybdenum high-nitrogen steel plate blank is a key technology for realizing the continuous casting production and quality assurance of the high-molybdenum high-nitrogen alloy plate blank, has popularization and application values for developing high-molybdenum high-nitrogen alloy varieties and optimizing the process for enterprises which adopt continuous casting process flows to realize production and tests, improves the productivity, reduces the production cost and can greatly enhance the comprehensive competitiveness of the enterprises.
Detailed Description
The high molybdenum high nitrogen steel and the slab continuous casting process thereof according to the present invention will be further explained and illustrated with reference to specific examples, which, however, should not be construed to unduly limit the technical solutions of the present invention.
Examples 1 to 8
Table 1 shows the mass percentages of the chemical elements in the high-molybdenum high-nitrogen steels of examples 1 to 8.
Table 1 (wt%, balance Fe and other unavoidable impurities except P, S)
In Table 1, Re in example 1 represents the mass percentage of any one or more elements of 57 to 71 in the periodic Table of chemical elements.
The high-molybdenum high-nitrogen steel of the embodiments 1 to 8 of the invention is prepared by adopting the following continuous casting production process:
in the continuous casting process, the casting is controlled to reach the target drawing speed of 0.6-1.6 m/min within 4min, and the drawing speed is constant; controlling the superheat degree of the molten steel in the tundish to be 15-65 ℃; controlling the insertion depth of a water gap of the continuous casting crystallizer to be 85-125 mm; controlling the secondary cooling water to use weak cooling, and controlling the specific water amount to be 0.46 +/-0.1L/kg; controlling the electromagnetic stirring current of the secondary cooling area to be 1000-2000A, and the stirring frequency to be 2.5-3.5 Hz; controlling the pressing amount under light pressure to be 3-10 mm; controlling the central solid phase rate fs of the casting blank corresponding to the reduction interval to be 0.1-0.5; the single-side grinding amount of the casting blank is controlled to be 3-10 mm.
Tables 2-1 and 2-2 list specific process parameters for the methods of making the high molybdenum, high nitrogen steels of examples 1-8.
Table 2-1.
Table 2-2.
It should be noted that, in the actual operation process, the casting blank central solid phase rate fs corresponding to the reduction interval is changed with the process parameters such as the degree of superheat, the pulling speed, and the like, and is not stabilized at a fixed value, so the casting blank central solid phase rate fs corresponding to the reduction interval in table 2-2 is represented as a range value at one end instead of a point value in each embodiment.
The high molybdenum, high nitrogen steels of examples 1-8 were subjected to various performance tests and the results are shown in Table 3.
Table 3 shows the results of the performance tests on the high molybdenum, high nitrogen steels of examples 1-8.
Table 3.
As can be seen from Table 3, the casting blanks of the high-molybdenum high-nitrogen steels of the embodiments 1 to 8 of the invention have excellent quality, the reduction of area is 70 to 85% at 1000 to 1300 ℃, the tensile strength of the embodiments is 50 to 100MPa at 1000 to 1300 ℃, and the corrosion rate of the embodiments in wet-process phosphoric acid (static solution) of 80 ℃ and 38% (shown by the alloy corrosion resistance test result) is 2 to 20 g/(m)2H) excellent quality and performance.
In conclusion, it can be seen that the invention is describedThe high-molybdenum high-nitrogen steel has a reduction of area of 70-85% at 1000-1300 ℃, a tensile strength of 50-100 MPa at 1000-1300 ℃, and a corrosion rate of 2-20 g/(m) in wet-process phosphoric acid of 38% at 80 ℃ of2H) with good quality and excellent properties.
In addition, the slab continuous casting production process of the high-molybdenum high-nitrogen steel can effectively improve the quality of a high-molybdenum high-nitrogen steel continuous casting blank, the produced continuous casting blank has the excellent characteristics of good quality of the surface and the center of the continuous casting blank and the like, the advantages of continuous casting production can be fully exerted, the generation of the depression and the crack of the casting blank can be effectively inhibited, the quality of the surface and the center of the casting blank is obviously improved, and multi-furnace continuous casting can be realized.
The continuous casting production process of the high-molybdenum high-nitrogen steel plate blank is a key technology for realizing the continuous casting production and quality assurance of the high-molybdenum high-nitrogen alloy plate blank, has popularization and application values for developing high-molybdenum high-nitrogen alloy varieties and optimizing the process for enterprises which adopt continuous casting process flows to realize production and tests, improves the productivity, reduces the production cost and can greatly enhance the comprehensive competitiveness of the enterprises.
It should be noted that the prior art in the protection scope of the present invention is not limited to the examples given in the present application, and all the prior art which is not inconsistent with the technical scheme of the present invention, including but not limited to the prior patent documents, the prior publications and the like, can be included in the protection scope of the present invention.
In addition, the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradictory to each other.
It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.
Claims (9)
1. The high-molybdenum high-nitrogen steel is characterized by also comprising the following chemical elements in percentage by mass in addition to Fe:
0< C < 0.02%, 0< Si < 1.0%, 0< Mn < 4.0%, Cr: 18-25%, Ni: 21-28%, W is less than or equal to 1.0%, Mo + W: 4-10%, N: 0.2-1.2%, Cu: 0.01-4.0%, and refined grain elements, wherein the refined grain elements are at least one of the following two types:
(a) at least one rare earth element of No. 57-71 in the periodic table of chemical elements, the total content of which is 0.001-0.2%;
(b) at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr, the total content of which is 0.001-0.5%.
2. The high-molybdenum high-nitrogen steel as claimed in claim 1, wherein the chemical elements are, by mass:
0< C < 0.02%, 0< Si < 1.0%, 0< Mn < 4.0%, Cr: 18-25%, Ni: 21-28%, W is less than or equal to 1.0%, Mo + W: 4-10%, N: 0.2-1.2%, Cu: 0.01-4.0%, refined grain elements, and the balance of Fe and other inevitable impurities; wherein the refined crystal grain elements are at least one of the following two types:
(a) at least one rare earth element of No. 57-71 in the periodic table of chemical elements, the total content of which is 0.001-0.2%;
(b) at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr, the total content of which is 0.001-0.5%.
3. The high molybdenum, high nitrogen steel according to claim 2, characterized in that among other unavoidable impurities: p is less than or equal to 0.040 percent and/or S is less than or equal to 0.030 percent.
4. The high molybdenum, high nitrogen steel according to claim 3, characterized in that among other unavoidable impurities: p is less than or equal to 0.020% and/or S is less than or equal to 0.020%.
5. The high-molybdenum high-nitrogen steel as claimed in claim 1 or 2, wherein the chemical elements further satisfy at least one of the following contents by mass:
0<Si≤0.8％；
Cr：20～24％；
Ni：22～26％；
W≤0.8％；
Mo+W：5～8％；
N：0.2～1.0％；
Cu：0.02～3.0％；
the total content of at least one of No. 57-71 rare earth elements in the periodic table of chemical elements is 0.002-0.15%;
the total content of at least one of Al, B, Ca, Mg, Nb, Ti, V, Y and Zr is 0.002-0.35%.
6. The high molybdenum, high nitrogen steel according to claim 1 or 2, characterized in that its microstructure is a fully austenitic structure.
7. The high molybdenum, high nitrogen steel according to claim 1 or 2, characterized in that its properties meet at least one of the following:
the reduction of area at 1000-1300 ℃ is 70-85%;
the tensile strength is 50-100 MPa at 1000-1300 ℃;
the corrosion rate in wet-process phosphoric acid with the temperature of 80 ℃ and the concentration of 38 percent is 2-20 g/(m)2·h)。
8. A slab continuous casting production process of high molybdenum high nitrogen steel according to any one of claims 1 to 7, characterized in that the process parameters of the continuous casting process are controlled to meet at least one of the following conditions:
after casting, the target pulling speed is 0.6-1.6 m/min within 4 min;
the superheat degree of the molten steel in the tundish is 15-65 ℃;
controlling the insertion depth of a water gap of the continuous casting crystallizer to be 85-125 mm;
the secondary cooling water is used for weak cooling, and the specific water amount is controlled to be 0.46 +/-0.1L/kg;
the electromagnetic stirring current of the secondary cooling zone is 1000-2000A, and the stirring frequency is 2.5-3.5 Hz;
the pressing amount under light pressing is 3-10 mm;
the central solid phase rate fs of the casting blank corresponding to the reduction interval is 0.1-0.5;
the grinding amount of the single surface of the casting blank is 3-10 mm.
9. The slab continuous casting production process according to claim 8, wherein the process parameter controlling the continuous casting process satisfies at least one of:
the target pulling speed is 0.8-1.2 m/min within 4min after casting
The superheat degree of the molten steel in the tundish is 25-50 ℃;
controlling the insertion depth of a water gap of the continuous casting crystallizer to be 90-115 mm;
the electromagnetic stirring current of the secondary cooling zone is 1200-1600A;
the pressing amount under light pressing is 4-8 mm;
the central solid phase rate fs of the casting blank corresponding to the reduction interval is 0.2-0.4;
the grinding amount of the single surface of the casting blank is 4-8 mm.
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