CN109930064B - Corrosion-resistant heat-resistant steel for high-pressure boiler pipe and production method thereof - Google Patents
Corrosion-resistant heat-resistant steel for high-pressure boiler pipe and production method thereof Download PDFInfo
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Abstract
The invention discloses a heat-resistant steel for a corrosion-resistant high-pressure boiler pipe and a production method thereof, wherein the heat-resistant steel comprises the following chemical components in percentage by weight: c: 0.13% -0.15%, Si:0.25% -0.30%, Mn: 1.00-1.20%, Cr: 0.35% -0.45%, Mo:0.25% -0.30%, Ni: 1.00-1.10%, Cu: 0.50-0.55%, Nb:0.015% -0.030%, Al: 0.015-0.030 percent of P, less than or equal to 0.013 percent of S, less than 0.003 percent of S, less than or equal to 0.010 percent of As, less than or equal to 0.010 percent of Sn, less than or equal to 0.010 percent of Pb, less than or equal to 0.010 percent of Bi, less than or equal to 0.035 percent of As, Sn, Sb, Pb and Bi, less than or equal to 0.02 percent of V, and [ H ]]≤0.00015%，[O]≤0.0020%，[N]Less than or equal to 0.0070 percent and the balance of Fe. From the components, the corrosion-resistant high-pressure boiler disclosed by the inventionThe heat-resistant steel for pipe and its production method are characterized by that a small quantity of Cr element is added, and the Cu-Cr composite effect is used to raise high-temp. strength, creep resistance and H resistance of high-pressure boiler pipe2S corrosion ability.
Description
Technical Field
The invention relates to the technical field of heat-resistant steel for corrosion-resistant high-pressure boiler pipes, in particular to heat-resistant steel for corrosion-resistant high-pressure boiler pipes and a production method thereof.
Background
Energy is closely related to human production and life. With the development of the world economy, the energy consumption is rapidly increased, the environmental problems are more severe, and the greenhouse effect caused by atmospheric pollution and carbon dioxide emission is increased. Heat-resistant steel is a special steel in the field of energy, and its development is closely related to energy, power, mechanical industry, and the like. In the fields of thermal power generation, nuclear power, petrochemical industry, aerospace, applied chemistry and the like, the performance life of the heat-resistant steel is related to the development level of the industry.
The heat-resistant steel for the boiler pipe is mainly used for power stations, the working environment of the heat-resistant steel is very severe, and the heat-resistant steel can be graphitized and creep deformed after being used for a long time in the environment of high temperature, high pressure and steam corrosion, so that the high-temperature strength of the heat-resistant steel is reduced, and the safe use of the boiler is influenced. In order to improve the power generation efficiency of the boiler, the steam temperature and the critical pressure must be increased, and the requirement on the high-temperature performance of the material of the heat-resistant steel must be increased. Because the content of sulfide in the boiler fuel coal or natural gas is generally high, H2S can be generated under the high-temperature reducing atmosphere, stress corrosion is caused to boiler tubes, and the corrosion resistance of the high-pressure boiler tubes must be improved comprehensively.
Due to design limitation, the conventional steel grade 15Ni1MnMoNbCu has poor H2S corrosion resistance, and high-temperature strength and heat resistance can be improved, so that the development of the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe is needed. The corrosion resistance of the material is mainly related to the grain boundary strength of the material, so that alloy elements such as Cr, Mo, Nb, Ni, Cu and the like are often added to refine the original austenite grain size. After quenching the original austenite with ultra-fine crystal grains, ultra-fine crystal grain ferrite and well-distributed ultra-fine carbide structures are formed, which is the most effective way for developing high-strength steel with hydrogen sulfide stress corrosion resistance. Pure steel with low contents of harmful elements [ H ], [ O ], [ N ], As, Sn, Pb, Sb and Bi is adopted, and failure caused by pitting corrosion of non-metallic impurities is reduced As much As possible; a good uniform and fine tempering structure is designed, so that the product performance is stable; the S content in the steel is reduced as much as possible, sulfide inclusions are reduced, and H2S stress corrosion is prevented from the root.
The national standard seamless steel tube for high-pressure boilers (GB/T5310-2017) specifies the 15Ni1MnMoNbCu material as follows: 0.10-0.17% of C, 0.25-0.50% of Si, 0.80-1.20% of Mn, 0.25-0.50% of Mo, 1.00-1.30% of Ni, 0.50-0.80% of Cu, 0.015-0.045% of Nb, less than or equal to 0.050% of Al, less than or equal to 0.025% of P, less than or equal to 0.015% of S, less than or equal to 0.02% of V, and less than or equal to 0.0200% of N. The steel grade adopted in China at present is subjected to smelting, rolling, hot pipe penetration, 880-980 ℃ normalizing and rapid cooling and 610-680 ℃ tempering, so that the high-temperature yield strength of 450 ℃ is more than or equal to 304Mpa, the longitudinal A is more than or equal to 19 percent, and the transverse A is more than or equal to 17 percent; the non-metallic inclusion A is less than or equal to 1.5 grade in thickness, the B is less than or equal to 1.5 grade in thickness, the C is less than or equal to 1.0 grade in thickness, the D is less than or equal to 1.5 grade in thickness. The high-pressure boiler tube produced by the steel has the high-temperature strength improved by 80% compared with that of a common high-pressure boiler tube with the temperature of 20G, A106B, and the weight can be effectively reduced by 50% -60%. The heat-resistant steel for the corrosion-resistant high-pressure boiler pipe, which is produced by the invention, has the advantages that the S content is controlled, 0.30-0.35% of Cr is added, the high-temperature strength, the creep resistance and the H2S corrosion resistance of the high-pressure boiler pipe are improved through the Cu-Cr composite effect, the service life of the high-pressure boiler pipe is prolonged, and the comprehensive cost is obviously reduced.
Disclosure of Invention
The invention aims to: overcomes the defects of the prior art, provides the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, and the final product has higher high-temperature strength, creep resistance and H resistance than a 'seamless steel pipe for high-pressure boiler' (GB/T5310-2017) standard 15Ni1MnMoNbCu material2S corrosion ability. Has the following properties: the yield strength at 450 ℃ is more than or equal to 330Mpa, the longitudinal A is more than or equal to 25 percent, and the transverse A is more than or equal to 20 percent; the thickness of the nonmetallic inclusion A is less than or equal to 1.0 level, the thickness of B is less than or equal to 1.0 level, the thickness of C is less than or equal to 0 level, the thickness of D is less than or equal to 1.0 level, and Ds is less than or equal to 1.0 level; s is less than or equal to 0.002 percent and can pass the hydrogen embrittlement test required by SSC (stress ring method) and ISO 11114-4.
The technical scheme adopted by the invention is as follows:
a corrosion-resistant heat-resistant steel for a high-pressure boiler pipe comprises the following chemical components in percentage by weight: c: 0.13% -0.15%, Si:0.25% -0.30%, Mn: 1.00-1.20%, Cr: 0.35% -0.45%, Mo:0.25% -0.30%, Ni: 1.00-1.10%, Cu: 0.50-0.55%, Nb:0.015% -0.030%, Al: 0.015-0.030 percent of P, less than or equal to 0.013 percent of S, less than 0.003 percent of As, less than or equal to 0.010 percent of Sn, less than or equal to 0.010 percent of Pb, less than or equal to 0.010 percent of Sb, less than or equal to 0.010 percent of Bi, less than or equal to 0.035 percent of As, Sn, Sb, Pb and Bi, less than or equal to 0.02 percent of V, less than or equal to 0.00015 percent of H, less than or equal to 0.0020 percent of O, less than or equal to 0.0070 percent of N, and the balance of Fe.
In a further improvement of the invention, the chemical composition of As, Sn, Sb, Pb and Bi satisfies the following condition (wt%): as + Sn + Sb + Pb + Bi is less than or equal to 0.035%.
0.35-0.45% of Cr element is added, so that the high-temperature strength and creep resistance of the steel are effectively improved on the premise of not influencing the plasticity and toughness of the steel, and certain corrosion resistance is also improved.
The S content is limited, the S is required to be less than 0.003 percent, and the H resistance of the high-pressure boiler tube is improved2The S corrosion performance can be popularized and applied to CNG gas boiler pipelines and high-sulfur coal-fired steam boiler pipelines.
The reasons for the limitations of the chemical composition of the heat-resistant steel for a corrosion-resistant high-pressure boiler tube according to the present invention are explained in detail below:
c: c is one of the most effective elements for improving the strength and is an element which has the greatest influence on the welding performance, in order to ensure the toughness and the welding performance, the content of C in a common high-pressure boiler pipe is not more than 0.20 percent, the requirements on the hydrogen sulfide corrosion resistance and the toughness are considered at the same time, the Mn/C ratio is improved as much as possible, and the content of C is controlled between 0.13 percent and 0.15 percent in comprehensive consideration;
si: si can be dissolved in ferrite and austenite to improve the strength and hardness of steel, particularly the yield strength of the steel; silicon has the deoxidation effect, but the content of silicon is not favorable for resisting the corrosion of hydrogen sulfide when exceeding 0.30 percent, so the content of Si in the invention is controlled between 0.25 percent and 0.30 percent;
mn: mn has the effect of solid solution strengthening, can expand an austenite region, reduce the transformation temperature from austenite to ferrite, further refine ferrite grains, improve the strength and toughness of steel, and compensate the strength loss caused by low carbon, but the Mn content is too high, segregation is generated, MnS inclusion sensitive to HIC cracks is easily generated, and therefore, the Mn content is controlled to be 1.00-1.20%;
cr: cr can improve the high-temperature mechanical property of steel, improve the strength and the hardness, form a layer of passive film on the surface of the steel and have the capacities of oxidation resistance and corrosion resistance; cr can improve the carbon dioxide corrosion resistance and can inhibit the adsorption of S; cr can be combined with C, so that the dispersion strengthening effect is improved, and the graphitization tendency is improved; the welding of high-pressure boiler pipes is not facilitated due to the excessively high Cr content, the proportion of other alloy elements is comprehensively considered, and 0.35-0.45% of Cr is added into the steel;
mo: mo has a solid solution strengthening effect on ferrite, can improve the creep strength of steel, can improve the tempering stability of the steel, can form a compact passive film on the surface, has the capability of resisting hydrogen sulfide corrosion, and can improve pitting corrosion, but Mo is a precious alloy and a scarce resource, and the content of Mo is controlled to be 0.25-0.30%;
ni: ni can stabilize austenite in steel, and does not reduce plasticity and toughness while improving strength; ni also has certain corrosion resistance and can be combined with copper elements in steel, when Ni: when Cu is more than or equal to 2:1, a copper-nickel enrichment layer is formed on the surface of the steel, the enrichment of single copper element is inhibited, and copper-induced cracks are prevented. However, since Ni is a precious alloy and affects the production cost of steel, 1.00-1.10% of Ni is added into the steel.
Cu: cu is generally used as a harmful element in steel, when the Cu content exceeds 0.20 percent and the steel temperature exceeds 1100 ℃, the surface of the steel is oxidized and decarburized, and is easily enriched in a decarburized layer grain boundary to form copper brittleness and surface cracks, so that the quality of the steel is seriously influenced; but Cu is one of the best elements for improving the corrosion resistance of steel, and in the corrosion process of steel, the copper can play a role of activating a cathode, so that a steel anode is passivated to slow down corrosion, and meanwhile, the copper can be enriched on the surface of the steel to form a thin corrosion-resistant layer to slow down corrosion; the corrosion resistance of the steel containing 0.20% of copper is more than 20% higher than that of the steel containing no copper, and the copper can improve the corrosion of seawater and H2S environment; copper can refine austenite grains and improve the strength of steel; however, copper belongs to scarce resources in China, the use cost is high, the advantages and the disadvantages are combined, and the Cu content is limited to 0.50-0.55 percent.
Nb: nb can increase the recrystallization temperature of austenite in steel, enlarge the temperature range of a non-recrystallization region, promote the deformation of austenite grains and the accumulation of defects, refine ferrite grains, and only 0.020% of Nb needs to be added to play a role in refining grains and improve the toughness of the steel. Therefore, 0.015% -0.030% of Nb is added into the steel grade.
Al: al is used as a deoxidizer and a refined grain element, and can inhibit the aging of low-carbon steel; aluminum can also improve the H2S corrosion resistance, but the high Al content easily produces a large amount of non-metallic inclusions, which is not beneficial to the improvement of the fatigue life of steel, and the Al content of the steel is controlled to be 0.015-0.030%.
P: p is generally a harmful element in steel, and P can improve the strength of steel, but reduces the plasticity and toughness, and also causes severe microsegregation, easily causes the formation of microcracks in quenched martensite, and becomes a hydrogen aggregation source, so that the P content is controlled to be less than 0.013%;
s: the increase of the S content can obviously increase the sensitivity of HIC, and in order to achieve the ideal hydrogen sulfide corrosion resistance effect, the S content in the steel is controlled to be below 0.003 percent and as low as possible, so that the H2S corrosion resistance is improved fundamentally;
as, Sn, Pb, Sb, Bi: the five-harmful elements of As, Sn, Pb, Sb and Bi are positioned in the fourth and fifth main groups of the periodic table of elements, the oxidability is lower than that of iron, and the elements cannot be removed in the smelting link; the alloy has large atomic radius, is easy to enrich in crystal boundary and surface, is extremely uneven in distribution, increases the hot brittleness tendency of steel, causes low-temperature brittleness, reduces the thermoplasticity of the steel, leads to surface cracking of a casting blank, and reduces the corrosion resistance of steel. In this steel, As is controlled to be less than or equal to 0.010%, Sn is controlled to be less than or equal to 0.010%, Pb is controlled to be less than or equal to 0.010%, Sb is controlled to be less than or equal to 0.010%, Bi is controlled to be less than or equal to 0.010%, As + Sn + Sb + Pb + Bi is controlled to be less than or equal to 0.035%.
V: the V element can refine crystal grains at high temperature, improve the toughness of the steel, but obviously reduce the creep property, so the V content of the steel is controlled to be less than or equal to 0.02 percent.
H: the H element reduces the plasticity of the steel, generates 'hairlines' or forms stress areas in the steel, and the hairlines expand to form cracks when the steel is subjected to rolling processing, so that the mechanical property, particularly the plasticity of the steel is deteriorated, even the steel is broken, and 'white spots' appear on steel fractures. Meanwhile, hydrogen causes spot segregation, hydrogen embrittlement, cracks in a heat affected zone of a weld joint and the like. Therefore, the invention and the process control the H to be less than 0.00015%.
O: the O element does not greatly affect the strength of the steel at room temperature, but significantly reduces the elongation and the surface shrinkage of the steel. With the increase of the O content, the occurrence probability of oxide inclusions of the material is greatly increased, thereby reducing the fatigue life of the material. The invention and the production process can stably control the O content within 0.0020 percent.
N: the N element can strengthen the steel, but obviously reduces the plasticity and toughness of the steel, and increases the aging tendency and cold brittleness. The content of the national standard requirement is less than 0.0200%. The invention and the production process control the N content within 0.0070%.
A method of producing a corrosion-resistant heat-resistant steel for a high-pressure boiler pipe as described above, comprising the steps of:
1) transferring molten iron:
the ladle and the covered heat preservation device thereof are adopted to transport molten iron, so that the heat loss is reduced, the molten iron pretreatment is facilitated, and the smelting temperature condition is improved;
2) KR desulfurization:
stirring in a ladle by using a stirring head, adding a desulfurizer to enable the desulfurizer to fully react with sulfur in molten iron, removing desulfurization products by using a slag skimmer, reducing the content of S in the molten iron, and ensuring that the S content of the desulfurized molten iron is less than or equal to 0.003%;
3) smelting in a converter:
smelting in a top-bottom combined blowing type converter of more than 100 tons, and carrying out primary smelting by taking 85% molten iron and 15% high-quality scrap steel as raw materials to realize C removal and pre-P removal; the slag blocking cone and the sliding plate are adopted for carrying out composite slag blocking, so that slag-free steel tapping is ensured, and P return is prevented;
4) refining:
deep deoxidation and alloying of molten steel are carried out in an LF furnace with the weight of more than 100 tons, and the alkalinity R: 5.0-8.0 refining slag; argon is blown at the bottom for stirring in the whole refining process, the stirring is carried out greatly in the early stage of refining, the S is removed and the impurities are removed through the reaction of the steel slag, and the weak stirring is adopted in the later stage of refining to prevent the secondary oxidation of the molten steel and promote the floating of the impurities;
5) vacuum degassing:
after LF refining, RH circulation degassing equipment is adopted for vacuum degassing and inclusion removal treatment, the [ H ] is less than or equal to 0.00015%, the [ O ] is less than or equal to 0.0006%, the [ N ] is less than or equal to 0.0030%, and all components enter the required internal control range;
6) modifying inclusions and soft blowing:
feeding 100-150 m of calcium-silicon silk threads to denature the impurities after vacuum treatment and continuously performing soft blowing, wherein the soft blowing time is kept at 20-25 minutes, so as to ensure that the impurities are fully floated and removed;
7) continuous casting:
a large round billet continuous casting machine is adopted, a carbon-free tundish covering agent and special crystallizer covering slag are used, automatic baking and automatic adding devices for covering slag are adopted to ensure uniform and timely addition, and full-protection casting in the whole process is carried out to produce continuous casting round billets; an M-EMS + S-EMS + F-EMS three-section electromagnetic stirring device is adopted, so that the tissue is fully and uniformly organized, and the internal quality is improved;
8) slow cooling:
entering a pit for slow cooling, eliminating internal stress, reducing the hardness of steel, avoiding the annealing process and reducing the production cost;
9) and (3) finishing:
and the defects are eliminated by manual inspection and grinding, so that the surface quality of the continuous casting billet is ensured.
According to a further improvement scheme of the invention, in the step 2), molten iron is made to form a vortex through stirring, 450-900 Kg of desulfurizing agent is added to the center of the vortex at one time, and the molten iron is stirred for 12-15 minutes according to the sulfur content of the molten iron.
According to a further improvement scheme of the invention, in the step 3), ferronickel is added along with scrap steel to carry out converter alloying; lime, special refining slag for copper-containing steel and various high-purity alloys are added into the steel to carry out pre-deoxidation and preliminary component adjustment.
In a further development of the invention, the high-purity alloy comprises manganese metal and low-carbon ferrochrome.
According to a further improvement scheme of the invention, in the step 4), 100-300 Kg of lime is added into the furnace, the ratio of the lime to the refining slag is controlled to be 2:1, and less slag smelting is carried out.
In a further improvement of the invention, in the step 5), the vacuum degree is maintained for 20-25 minutes under the vacuum degree of <100 Pa.
According to a further improvement scheme of the invention, in the step 8), the material is clamped into a pit with a heat-insulating material on the inner wall at a high temperature of 600-650 ℃ for slow cooling.
In the further improvement scheme of the invention, in the slow cooling process, the surface temperature of the round steel is maintained at the temperature when entering the pit, and the temperature of the core part of the round steel is quickly close to the surface temperature of the round steel; when the temperature of the round steel core is equal to the temperature of the surface of the round steel, the round steel core and the surface are simultaneously and slowly cooled.
The invention further improves the scheme that only one slow-cooling round steel is placed in a pit for slow cooling of the round steel and is clamped and fixed at the center of the pit, so that the distance between the round steel and the inner wall of the pit is equal.
The heat-resistant steel for the corrosion-resistant high-pressure boiler pipe, which is produced according to the invention, has the advantages of high-temperature strength, creep resistance and H resistance2S corrosion capacity and the like, and the material performance can reach the following level: the yield strength at 450 ℃ is more than or equal to 330Mpa, the longitudinal A is more than or equal to 25 percent, and the transverse A is more than or equal to 20 percent; non-metallic inclusions of grade A less than or equal to 1.0, grade B less than or equal to 1.0 and grade C less than or equal toGrade 0, grade C less than or equal to grade 0, grade D less than or equal to grade 1.0, grade Ds less than or equal to grade 1.0; the grain size is more than or equal to 10 grade, S is less than or equal to 0.002 percent, and the hydrogen embrittlement test required by SSC (stress ring method) and ISO 11114-4 can be passed.
The invention has the beneficial effects that:
according to the corrosion-resistant heat-resistant steel for the high-pressure boiler pipe and the production method thereof, the high-temperature strength, the creep resistance and the H resistance of the high-pressure boiler pipe are improved by optimizing alloy elements such as C, Si, Mn, Mo, Ni, Cu, Nb and Al, adding a small amount of Cr element and utilizing the Cu-Cr composite effect2S corrosion ability.
Secondly, the corrosion-resistant high-pressure boiler pipe heat-resistant steel and the production method thereof strictly limit the S content, require the S to be less than 0.003 percent, improve the H2S corrosion resistance of the high-pressure boiler pipe, and can be popularized and applied to CNG gas boiler pipelines and high-sulfur coal-fired steam boiler pipelines.
Thirdly, the invention relates to a heat-resistant steel for corrosion-resistant high-pressure boiler tube and a production method thereof, for As, Sn, Pb, Sb, Bi, As + Sn + Sb + Pb + Bi less than or equal to 0.035%, and [ H ]]、[O]The harmful elements are strictly limited, and the high-temperature strength, the creep resistance and the H resistance are facilitated2And (4) improving the corrosion capability of S.
Fourthly, according to the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, when molten iron is transported, a novel ladle and a capping and heat-insulating device thereof are adopted to insulate the molten iron, so that the heat loss is reduced, and the smelting temperature condition is improved.
Fifthly, according to the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, 450-900 Kg of self-made desulfurizer is adopted to carry out KR pre-desulfurization according to the steel type characteristics and the use environment thereof, the KR pre-desulfurization is stirred for 12-15 minutes according to the sulfur content of molten iron, the S content of the desulfurized molten iron is ensured to be less than or equal to 0.003%, and favorable conditions are created for refining desulfurization.
Sixthly, the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof are characterized in that 85% of molten iron and 15% of high-quality scrap steel are used as raw materials for primary smelting, ferronickel is added along with the scrap steel, and converter alloying is carried out; lime, special refining slag for copper-containing steel and various high-purity alloys (metal manganese and low-carbon ferrochrome) are added into the steel for pre-deoxidation and initial component adjustment.
Seventhly, according to the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, 100-300 Kg/furnace lime and 50-150 Kg/furnace refining slag are used for low-slag smelting, so that the refining efficiency is improved, and the purity of the steel is improved.
Eighth, according to the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, the steel is kept for 20-25 minutes under the vacuum degree of less than 100Pa by adopting a BOF + LF + VD + CCM process, so that the lower contents of gas and harmful residual elements are ensured, and the material has excellent comprehensive mechanical properties.
Ninth, according to the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, the steel is clamped into a pit at a high temperature of 600-650 ℃ for slow cooling, so that internal stress is fully eliminated, the hardness of the steel is reduced, the annealing process is omitted, and the production cost is reduced.
Tenth, according to the heat-resistant steel for the corrosion-resistant high-pressure boiler pipe and the production method thereof, the round steel entering the pit for slow cooling adopts a single pit, so that slow cooling interference of other round steel entering the pit later on the round steel entering the pit firstly is eliminated; and the distance between the round steel and the inner wall of the slow cooling pit is equal through clamping, so that the round steel entering the pit and slowly cooled can be simultaneously and slowly cooled on the surface and the core part at the same temperature.
Eleventh, according to the heat-resistant steel for a corrosion-resistant high-pressure boiler pipe and the production method thereof, the temperature of the surface of the round steel is reduced and slowed down by the slow cooling pit due to the heat-insulating material on the inner wall of the slow cooling pit, so that the temperature of the core part can be close to the surface temperature, and further, the slow cooling is performed at the same time, and the elimination of the internal stress is further ensured.
Description of the drawings:
FIG. 1 is a table showing the composition (wt%) of a conventional 15Ni1MnMoNbCu high-pressure boiler tube steel in comparison with that of the present invention.
FIG. 2 is a comparative table of compositions (wt%) of examples of the present application.
FIG. 3 is a table comparing the gas contents of the steels for high-pressure boiler tubes of the present application with those of the prior art.
FIG. 4 is a table comparing the mechanical properties of the steels for high-pressure boiler tubes of the present application with those of the prior art.
FIG. 5 is a comparative table showing the control levels of nonmetallic inclusions in examples of the present application.
The specific implementation mode is as follows:
1) transferring molten iron: the novel ladle and the capping heat-insulating device thereof are adopted to transfer molten iron, so that the heat loss is reduced, the molten iron pretreatment is facilitated, and the smelting temperature condition is improved;
2) KR desulfurization: stirring clockwise in a ladle by using a stirring head to enable molten iron to form a vortex, adding 450-900 Kg of self-made desulfurizer into the vortex at one time, stirring for 12-15 minutes according to the sulfur content of the molten iron to enable the desulfurizer to fully react with sulfur in the molten iron, removing desulfurization products by using a slag skimmer, reducing the S content of the molten iron, and ensuring that the S content of the desulfurized molten iron is less than or equal to 0.003%;
3) smelting in a converter: smelting in a top-bottom combined blowing type converter of more than 100 tons, and carrying out primary smelting by taking 85% molten iron and 15% high-quality scrap steel as raw materials to realize C removal and pre-P removal; adding ferronickel along with the scrap steel, and carrying out converter alloying; lime, special refining slag for copper-containing steel and various high-purity alloys (manganese metal and low-carbon ferrochrome) are added into the steel to be pre-deoxidized and the components are primarily adjusted, a slag blocking cone and a sliding plate are adopted to carry out composite slag blocking, so that the steel is ensured to be tapped without slag, and the P return is prevented;
4) refining: deep deoxidation and alloying of molten steel are carried out in an LF furnace with the weight of more than 100 tons, and the alkalinity R: 5.0-8.0 refining slag; adding 100-300 Kg of lime into the furnace, controlling the ratio of the lime to the refining slag to be 2:1, and performing less-slag smelting; argon is blown at the bottom for stirring in the whole refining process, the stirring is carried out greatly in the early stage of refining, the S is removed and the impurities are removed through the reaction of the steel slag, and the weak stirring is adopted in the later stage of refining to prevent the secondary oxidation of the molten steel and promote the floating of the impurities;
5) vacuum degassing: after LF refining, RH circulation degassing equipment is adopted for vacuum degassing and inclusion removal treatment, the vacuum degree of less than 100Pa is kept for 20-25 minutes, the [ H ] is less than or equal to 0.00015%, the [ O ] is less than or equal to 0.0006%, the [ N ] is less than or equal to 0.0030%, and all components enter the required internal control range;
6) modifying inclusions and soft blowing: feeding 100-150 m of calcium-silicon silk threads to denature the impurities after vacuum treatment and continuously performing soft blowing, wherein the soft blowing time is kept at 20-25 minutes, so as to ensure that the impurities are fully floated and removed;
7) continuous casting: a large round billet continuous casting machine is adopted, a carbon-free tundish covering agent and special crystallizer covering slag are used, automatic baking and automatic adding devices for covering slag are adopted to ensure uniform and timely addition, and full-protection casting in the whole process is carried out to produce continuous casting round billets; an M-EMS + S-EMS + F-EMS three-section electromagnetic stirring device is adopted, so that the tissue is fully and uniformly organized, and the internal quality is improved;
8) slow cooling: clamping the steel into a pit at a high temperature of 600-650 ℃ for slow cooling, eliminating internal stress, reducing the hardness of the steel, avoiding an annealing process and reducing the production cost;
9) and (3) finishing: and the defects are eliminated by manual inspection and grinding, so that the surface quality of the continuous casting billet is ensured.
The process conditions not limited in the above preparation method can be referred to the conventional techniques in the art.
Examples 1 to 4 were prepared according to the above process, and the components of each example 1 to 4 are shown in FIG. 2.
The gas content ratio of each of examples 1 to 4 to the prior art is shown in FIG. 3.
The mechanical property comparison of each of examples 1 to 4 with the prior art is shown in FIG. 4.
The non-metallic inclusion control level of each example is shown in figure 5.
As can be seen from FIG. 5, the non-metallic inclusions in the invention are stably controlled to be less than or equal to 1.0 level, and the process control level of the invention reaches the international advanced level.
Claims (1)
1. The utility model provides a corrosion-resistant high pressure boiler pipe is with heat-resistant steel which characterized in that: the chemical composition wt% is composed of the following components: 0.13%, Si: 0.29%, Mn: 1.03%, Cr: 0.37%, Mo: 0.28%, Ni: 1.03%, Cu: 0.54%, Nb: 0.017%, Al: 0.027 percent, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.0071 percent of As, less than or equal to 0.0021 percent of Sn, less than or equal to 0.0002 percent of Pb, less than or equal to 0.0012 percent of Bi, less than or equal to 0.035 percent of As, Sn, Sb, Pb and Bi, less than or equal to 0.004 percent of V, less than or equal to 0.00015 percent of [ H ], less than or equal to 0.0020 percent of [ O ], [ N ] less than or equal to 0.0070 percent, and the balance; the preparation method comprises the following steps of,
1) transferring molten iron: the ladle and the covered heat preservation device thereof are adopted to transport the molten iron, so that the heat loss is reduced, the molten iron pretreatment is facilitated, and the smelting temperature condition is improved;
2) KR desulfurization: stirring clockwise in a ladle by using a stirring head to enable molten iron to form a vortex, adding 450-900 Kg of self-made desulfurizer into the vortex at one time, stirring for 12-15 minutes according to the sulfur content of the molten iron to enable the desulfurizer to fully react with sulfur in the molten iron, removing desulfurization products by using a slag skimmer, reducing the S content of the molten iron, and ensuring that the S content of the desulfurized molten iron is less than or equal to 0.003%;
3) smelting in a converter: smelting in a top-bottom combined blowing type converter of more than 100 tons, and carrying out primary smelting by taking 85% molten iron and 15% high-quality scrap steel as raw materials to realize C removal and pre-P removal; adding ferronickel along with the scrap steel, and carrying out converter alloying; lime, special refining slag for copper-containing steel and various high-purity alloys, namely metal manganese and low-carbon ferrochrome are added into the steel for pre-deoxidation and initial component adjustment, and a slag blocking cone and a sliding plate are adopted for composite slag blocking, so that slag-free steel tapping is ensured, and P return is prevented;
4) refining: deep deoxidation and alloying of molten steel are carried out in an LF furnace with the weight of more than 100 tons, and the alkalinity R: 5.0-8.0 refining slag;
adding 100-300 Kg of lime into the furnace, controlling the ratio of the lime to the refining slag to be 2:1, and performing less-slag smelting; argon is blown at the bottom for stirring in the whole refining process, the stirring is carried out greatly in the early stage of refining, the S is removed and the impurities are removed through the reaction of the steel slag, and the weak stirring is adopted in the later stage of refining to prevent the secondary oxidation of the molten steel and promote the floating of the impurities;
5) vacuum degassing: after LF refining, RH circulation degassing equipment is adopted for vacuum degassing and inclusion removal treatment, the vacuum degree of less than 100Pa is kept for 20-25 minutes, the [ H ] is less than or equal to 0.00015%, the [ O ] is less than or equal to 0.0006%, the [ N ] is less than or equal to 0.0030%, and all components enter the required internal control range;
6) modifying inclusions and soft blowing: feeding 100-150 m of calcium-silicon silk threads to denature the impurities after vacuum treatment and continuously performing soft blowing, wherein the soft blowing time is kept at 20-25 minutes, so as to ensure that the impurities are fully floated and removed;
7) continuous casting: a large round billet continuous casting machine is adopted, a carbon-free tundish covering agent and special crystallizer covering slag are used, automatic baking and automatic adding devices for covering slag are adopted to ensure uniform and timely addition, and full-protection casting in the whole process is carried out to produce continuous casting round billets; an M-EMS + S-EMS + F-EMS three-section electromagnetic stirring device is adopted, so that the tissue is fully and uniformly organized, and the internal quality is improved;
8) slow cooling: clamping the steel into a pit at a high temperature of 600-650 ℃ for slow cooling, eliminating internal stress, reducing the hardness of the steel, avoiding an annealing process and reducing the production cost;
9) and (3) finishing: and the defects are eliminated by manual inspection and grinding, so that the surface quality of the continuous casting billet is ensured.
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