CN107747041B - Normalized manganese gas cylinder steel and preparation method thereof - Google Patents

Normalized manganese gas cylinder steel and preparation method thereof Download PDF

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CN107747041B
CN107747041B CN201711059940.8A CN201711059940A CN107747041B CN 107747041 B CN107747041 B CN 107747041B CN 201711059940 A CN201711059940 A CN 201711059940A CN 107747041 B CN107747041 B CN 107747041B
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steel
gas cylinder
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molten steel
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CN107747041A (en
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李诗斌
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Chengde Jianlong Special Steel Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/12Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese

Abstract

The invention provides a method for preparing a normalized manganese gas cylinder steel machine, wherein the gas cylinder steel comprises the following components in percentage by mass: 0.36-0.40% of C, 0.17-0.37% of Si, 1.55-1.70% of Mn, less than or equal to 0.25% of Cr, less than or equal to 0.10% of Mo, less than or equal to 0.05% of V, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 40-100 ppm of N and the balance of Fe. The normalized manganese gas cylinder steel and the preparation method thereof use a production process of converter plus refining (LF plus VD) plus continuous casting, Cr, Mo, V and N elements are added into the gas cylinder steel, and the yield strength and impact toughness of the gas cylinder steel in the normalized state are remarkably improved and stabilized through a reasonable slagging system in the refining process, so that the subsequent heat treatment cost is saved.

Description

Normalized manganese gas cylinder steel and preparation method thereof
Technical Field
The invention belongs to the field of special steel manufacturing, relates to gas cylinder steel, and particularly relates to normalized manganese gas cylinder steel and a preparation method thereof.
Background
The most common steel grade of the Mn-series gas cylinder pipe is 37Mn, the total market demand of the gas cylinder made of the Mn-series gas cylinder pipe exceeds 80%, and the Mn-series gas cylinder pipe is mainly applied to industrial gas cylinders (including medical gas cylinders). In order to save cost, domestic gas cylinder production enterprises mainly adopt a normalizing heat treatment process. At present, the mechanical property of the gas cylinder made of the normalized 37Mn steel is unstable, and the phenomenon that the yield strength and the impact energy can not reach the indexes of the prior art is generated occasionally. At present, the steel varieties for gas cylinders are mainly manganese series (such as industrial gas cylinders) and Cr-Mo series (such as vehicle-mounted gas cylinders). Since the 60 s, the gas cylinders are manufactured by adopting seamless pipes in China, and the working pressure is generally 12.25-29.40 MPa. As the media filled in the gas cylinder are various and have the characteristics of inflammability, explosiveness, high toxicity or corrosion, and the gas cylinder is repeatedly filled and has high liquidity, once explosion or leakage occurs, fire disasters or poisoning often occur to cause disastrous accidents, so the mechanical property, the internal quality and the external quality of the gas cylinder are very important for the production safety.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides normalized manganese gas cylinder steel and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention aims to provide normalized manganese gas cylinder steel, which comprises the following components in percentage by mass: 0.36-0.40% of C, 0.17-0.37% of Si, 1.55-1.70% of Mn, less than or equal to 0.25% of Cr, less than or equal to 0.10% of Mo, less than or equal to 0.05% of V, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 40-100 ppm of N and the balance of Fe.
Wherein the mass% of C may be 0.36%, 0.365%, 0.37%, 0.375%, 0.38%, 0.385%, 0.39%, 0.395%, 0.40%, etc., the mass% of Si may be 0.17%, 0.18%, 0.19%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.37%, etc., the mass% of Mn may be 1.55%, 1.56%, 1.58%, 1.60%, 1.62%, 1.65%, 1.68%, 1.70%, etc., the mass% of Cr may be 0%, 0.01%, 0.02%, 0.05%, 0.08%, 0.10%, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, etc., the mass% of Mo may be 0%, 0.01%, 0.02%, 0.04%, 0.03%, 0.05%, 0.04%, 0.05%, 0.06%, 0.05%, 0.06%, 0.9, 0.003%, 0.004%, or 0.005%, P may be 0%, 0.001%, 0.002%, 0.005%, 0.008%, 0.010%, 0.011%, 0.012%, 0.013%, 0.014%, or 0.015%, and N may be 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm, or 100ppm, but is not limited to the recited values, and other values not recited in the above numerical ranges are also applicable.
As a preferable technical scheme of the invention, the gas cylinder steel comprises the following components in percentage by mass: 0.37-0.38% of C, 0.24-0.30% of Si, 1.63-1.68% of Mn, 0.10-0.18% of Cr, less than or equal to 0.08% of Mo, less than or equal to 0.03% of V, less than or equal to 0.003% of S, less than or equal to 0.013% of P, 60-90 ppm of N and the balance of Fe.
The reasons for limiting the mass percentage of each element in the normalized manganese gas cylinder steel provided by the invention are as follows:
c: the steel can obviously improve the strength of the steel, and simultaneously can improve the hardenability and the hardenability of the steel, but the plasticity of the steel is deteriorated, because the yield strength performance of the material is considered, the steel adopts the central line Si, if the content of C is too high, the yield strength and the tensile strength of the steel pipe are too high after the normalizing heat treatment process, and on the contrary, the low-temperature impact performance is lower, even the lower limit of the standard is not reached. Because national standard per se has a strict requirement on the component C of the gas cylinder pipe, the mass percentage content range of C in the gas cylinder steel provided by the invention is determined to be 0.36-0.40%, and is further preferably 0.37-0.38% in consideration of the comprehensive performance of the material.
Si: exists in ferrite and austenite in a solid-solution state, has extremely strong effect of improving the strength of solid solution in steel and the cold working deformation hardening rate, and is second to P; but also reduces the toughness and plasticity of the steel to some extent. When the content of Si is high, if the content of C is too high, the graphitization of C in the steel is easily caused due to the action of high Si in the heat preservation process after the normalization. When the Si-containing steel is heated, a layer of SiO2 film is formed on the surface of the steel, so that the high-temperature oxidation resistance of the steel is improved, and the oxidation resistance of the steel can be improved by adding higher Si into Cr steel and Mn steel. However, Si is an element which obviously improves the yield strength of the steel, so that the content of Si is too high, the yield ratio of the material can be reduced, the anti-seismic performance of the material is reduced, and the total requirements of the material are integrated, wherein the mass percentage content of Si in the gas cylinder steel provided by the invention is determined to be 0.17-0.37%, and the preferable content is 0.24-0.30%.
Mn: ferrite can be dissolved in steel to strengthen a matrix, pearlite can be refined when the steel is cooled after rolling, the pearlite content can be relatively increased, and therefore, the strength and the hardness can be improved, the heat treatment performance can be improved, and the influence on the plasticity of the material is small. Along with the increase of Mn content, in addition to the decrease of Ms point of steel, the residual austenite in the steel also increases rapidly, so that during heat treatment, low-temperature treatment is generally required to be carried out in time to eliminate the residual austenite in the steel, meanwhile, along with the increase of Mn content, the heat conductivity coefficient of the steel is reduced rapidly, and the linear expansion coefficient of the steel is increased, so that large internal stress is easily generated in the heating or cooling process of materials, and cracking of workpieces is caused seriously, so that the requirements of all aspects of materials are combined, and the mass percentage content of Mn in the gas cylinder steel provided by the invention is determined to be 1.55-1.70%, and more preferably 1.63-1.68%.
Cr: the addition of steel grades can obviously improve the antioxidation of the steel and increase the corrosion resistance of the steel. Cr forms a continuous solid solution with iron, forms a plurality of carbides with C, the complex carbide of Cr (Cr, Fe)7C3, and (Cr, Fe)23C6 have a significant effect on the properties of the steel, in particular the wear resistance of the steel. Cr can significantly increase the hardenability of the steel, but also increases the temper brittleness tendency of the steel. Cr is an element with a tendency to passivate. Therefore, Cr with a certain component is added into the steel, so that the steel has corrosion resistance tendency and oxidation resistance. When it is attacked by a medium, an oxide film, called passive film, is formed on the surface of the steel part, which is dense under favorable conditions, is not dissolved and, when it is destroyed, recovers itself. The passivation of a metal or steel is not fixed but, for a given medium or condition, if the medium condition changes, the passivation is destroyed. In the quenched and tempered structural steel, Cr has the main function of improving the hardenability of the steel, so that the steel has good comprehensive mechanical properties after quenching and tempering, and a special protective film can be formed on the surface of the steel, so that the wear resistance and the corrosion resistance of the steel are improved. The addition of Cr element can improve the strength of steel to a certain extent, and make up for the domestic current situation that the strength of the gas cylinder pipe is occasionally lower than the off-line strength caused by the low control of C element. Comprehensively, the mass percentage of Cr in the gas cylinder steel provided by the invention is determined to be less than or equal to 0.25%, and the preferable mass percentage is 0.10-0.18%.
N: the formation of A body can be promoted in ferrite, the coarsening tendency of crystal grains can be reduced due to the occurrence of gamma phase, so the toughness and the welding performance of steel can be improved, N element is artificially added into the steel, the impact toughness of the steel can be obviously improved by controlling the N element within a certain range, but the content of N is not too high, N can generate nitride with other alloy elements after exceeding a certain standard to form non-metal inclusion, so that the purity of molten steel is caused, the harm of the effect of other alloy elements is reduced, and the control of the content of nitrogen within a proper range is the most important factor. Comprehensively considering and testing for many times, the mass percentage content of N in the gas cylinder steel provided by the invention is controlled to be 40-100 ppm, and further preferably 60-90 ppm.
Residual element P: practice proves that P is subjected to segregation among crystals to cause grain boundary embrittlement, so that high-temperature tempering brittleness of the material can be caused, and meanwhile, when the P exceeds a certain content, the brittleness transition temperature of the steel is greatly improved, so that the low-temperature impact toughness of the material is low, and the comprehensive mechanical property of the steel is deteriorated. Therefore, the design P is less than or equal to 0.015 percent.
Residual elements S: since both ferrite and austenite have low solubility, S is concentrated in a liquid portion which is not yet solidified as molten steel is solidified during solidification of a cast slab, and as a result, a large amount of sulfide inclusions are contained in the last solidified portion (between the core portion of the cast slab and the dendritic structure) of the cast slab, resulting in non-uniform macroscopic structure of steel. Since a high S content impairs the corrosion resistance of the steel and causes pitting corrosion on the steel surface, the present invention sets the S content as follows: s is less than or equal to 0.005 percent.
The second purpose of the invention is to provide a preparation method of the gas cylinder steel, which comprises the following steps:
(1) molten iron and scrap steel are dephosphorized by converter smelting by a double-slag method;
(2) simultaneously, blowing and pre-desulfurizing the molten steel to ensure that the desulfurization rate reaches 30-40%, and then carrying out primary component adjustment by adopting low-carbon drawing to obtain blown molten steel;
(3) performing LF refining, desulfurization and deoxidation on the blown molten steel obtained in the step (2) and performing component fine adjustment to obtain refined molten steel;
(4) and (4) carrying out VD degassing on the refined molten steel obtained in the step (3), feeding the molten steel after the vacuum breaking, controlling the content of N to be 40-100 ppm, and continuously casting to obtain the gas cylinder steel blank.
The gas cylinder steel preparation method provided by the invention has the advantages of primary component adjustment and fine component adjustment. The initial adjustment of the components means that the first proportioning of the components of molten steel is carried out after the molten steel is discharged from a converter through deoxidation alloying, and the alloys such as silicon manganese, high chromium, V sheets and the like are sequentially packed to ensure that the components of the molten steel meet C after the molten steel is refined and electrified to a primary electrode: 0.32 to 0.35%, Si: 0.17-0.23%, Mn 1.50-1.60%, Cr: 0.15-0.20%, V: 0.02-0.05%; the component fine adjustment means that after the molten steel is subjected to VD deep vacuum treatment, the N content of the steel tapped from the converter is adjusted to be too low by feeding MnN lines, so that the N content in the molten steel is stabilized within the range of 45-95 ppm.
As a preferable technical scheme of the invention, the double-slag method in the step (1) is to carry out primary blowing on molten iron and scrap steel for 2-10 min, then pour slag, and carry out secondary blowing on discharged materials for 5-15 min.
The time of the first blowing may be 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min or 10min, etc., and the time of the second blowing may be 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min or 15min, etc., but is not limited to the values listed, and other values not listed in the above numerical ranges are also applicable.
Preferably, a sliding plate slag blocking and steel retaining tapping operation is used in the step (1).
As a preferable technical scheme of the invention, lime and dolomite are added before the pre-desulfurization in the step (2).
As a preferred embodiment of the present invention, in the step (2), the blowing is carried out using an oxygen lance.
Preferably, the oxygen lance has a blowing pressure of 0.5 to 1MPa, such as 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa or 1MPa, but not limited to the recited values, and other values not recited within the range of values are also applicable.
Preferably, the lance position is 0.8 to 1.5m, such as 0.8m, 0.9m, 1.0m, 1.1m, 1.2m, 1.3m, 1.4m, or 1.5m, but not limited to the recited values, and other values not recited in this range are equally applicable.
As a preferable technical scheme of the invention, lime and SiC are added in the LF refining in the step (3).
As a preferable technical scheme of the invention, the high-carbon ferrochrome is added in the LF refining in the step (3) and the mass fraction of Cr is controlled to be 0.15-0.20%.
As a preferable technical scheme of the invention, the VD degassing in the step (4) adopts double-station degassing.
Preferably, the deep vacuum degree of VD in the step (4) is less than or equal to 67Pa, such as 5Pa, 10Pa, 15Pa, 20Pa, 25Pa, 30Pa, 35Pa, 40Pa, 45Pa, 50Pa, 55Pa, 60Pa, 65Pa or 67Pa, etc., but the method is not limited to the recited values, and other non-recited values in the numerical range are also applicable.
Preferably, the vacuum time for VD degassing in step (4) is not less than 15min, such as 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, 90min or 120min, but is not limited to the recited values, and other non-recited values in the range of the values are also applicable.
As a preferable technical scheme of the invention, the blank-breaking wire feeding in the step (4) is a MnN wire fed after blank breaking.
In the preparation method of the gas cylinder steel, Mo and V elements generally come from residual elements of molten steel, wherein when the V element in the molten iron is insufficient, vanadium sheets are used for slightly supplementing during tapping.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the invention provides normalized manganese gas cylinder steel, wherein after a continuous casting billet of the gas cylinder steel is rolled into a pipe, the normalized manganese gas cylinder steel completely meets the standard of the existing gas cylinder, the average yield strength is more than or equal to 550MPa, and the impact energy is more than or equal to 35J;
(2) the invention provides normalized manganese gas cylinder steel, wherein Cr, Mo, V and N elements are added into the gas cylinder steel, so that the cost of a steel billet is increased, but the cost of the subsequent quenching and tempering heat treatment process is saved by about 600 yuan/ton steel;
(3) the invention provides a preparation method of normalized manganese gas cylinder steel, which has higher molten steel purity, adopts semi-molten steel smelting in a converter, adopts a steel tapping sliding plate to double-slide and block slag to avoid slag discharge, adopts a high-aluminum refining slag system in the refining process, and controls the contents of inclusions and P, S in steel.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
A preparation method of normalized manganese gas cylinder steel comprises the following steps:
(1) adopting a double-slag method for molten iron and scrap steel, deslagging after blowing for 4min for the first time, and blowing again for 8min for dephosphorization to obtain dephosphorized molten steel;
(2) carrying out blowing pre-desulfurization on the dephosphorized molten steel obtained in the step (1), adding lime 1t and light burned dolomite 0.5t before desulfurization, blowing by using an oxygen lance with the pressure of 0.8MPa and the blowing lance position of 1.2m to ensure that the desulfurization rate reaches 30-40%, and then carrying out primary component adjustment by using low-carbon withdrawal to obtain blown molten steel;
(3) performing LF refining on the blown molten steel obtained in the step (2), adding 50kg of lime and SiC into a primary electrode, refining by using three levels of current, desulfurizing and deoxidizing by using a tertiary electrode, performing component fine adjustment, adding high-carbon ferrochrome during refining, and controlling the mass fraction of Cr to be 0.15-0.20% to obtain refined molten steel;
(4) and (4) carrying out VD degassing on the refined molten steel obtained in the step (3), degassing by adopting double-station VD, ensuring the vacuum time to be 30min under the deep vacuum degree of 60pa, feeding a MnN wire after breaking the vacuum, controlling the N content to be 40-100 ppm, and continuously casting to obtain the gas cylinder steel.
Example 2
A preparation method of normalized manganese gas cylinder steel comprises the following steps:
(1) adopting a double-slag method for molten iron and scrap steel, deslagging after blowing for 2min for the first time, and blowing again for 15min for dephosphorization to obtain dephosphorized molten steel;
(2) carrying out blowing pre-desulfurization on the dephosphorized molten steel obtained in the step (1), adding lime 1t and light burned dolomite 0.5t before desulfurization, blowing by using an oxygen lance with the pressure of 0.5MPa and the blowing lance position of 1.5m to ensure that the desulfurization rate reaches 30-40%, and then carrying out primary component adjustment by using low-carbon withdrawal to obtain blown molten steel;
(3) performing LF refining on the blown molten steel obtained in the step (2), adding 50kg of lime and SiC into a primary electrode, refining by using three levels of current, desulfurizing and deoxidizing by using a tertiary electrode, performing component fine adjustment, adding high-carbon ferrochrome during refining, and controlling the mass fraction of Cr to be 0.15-0.20% to obtain refined molten steel;
(4) and (4) carrying out VD degassing on the refined molten steel obtained in the step (3), degassing by adopting double-station VD, ensuring the vacuum time to be 60min under the deep vacuum degree of 67pa, feeding a MnN wire after breaking the vacuum, controlling the N content to be 40-100 ppm, and continuously casting to obtain the gas cylinder steel.
Example 3
A preparation method of normalized manganese gas cylinder steel comprises the following steps:
(1) adopting a double-slag method for molten iron and scrap steel, deslagging after blowing for 10min for the first time, and blowing again for 5min for dephosphorization to obtain dephosphorized molten steel;
(2) carrying out blowing pre-desulfurization on the dephosphorized molten steel obtained in the step (1), adding lime 1t and light burned dolomite 0.5t before desulfurization, blowing by using an oxygen lance with the pressure of 1MPa and the position of a blowing lance of 0.8m to ensure that the desulfurization rate reaches 30-40%, and then carrying out primary component adjustment by using low-carbon withdrawal to obtain blown molten steel;
(3) performing LF refining on the blown molten steel obtained in the step (2), adding 50kg of lime and SiC into a primary electrode, refining by using three levels of current, desulfurizing and deoxidizing by using a tertiary electrode, performing component fine adjustment, adding high-carbon ferrochrome during refining, and controlling the mass fraction of Cr to be 0.15-0.20% to obtain refined molten steel;
(4) and (4) carrying out VD degassing on the refined molten steel obtained in the step (3), degassing by adopting double-station VD, ensuring the vacuum time to be 15min under the deep vacuum degree of 30pa, feeding a MnN wire after breaking the vacuum, controlling the N content to be 40-100 ppm, and continuously casting to obtain the gas cylinder steel.
Example 4
The normalized manganese gas cylinder steel prepared by the preparation method of example 1 comprises the following components in percentage by mass: 0.36% of C, 0.17% of Si, 1.55% of Mn, 0.25% of Cr, 0.05% of Mo, 0.05% of V, 0.001% of S, 0.015% of P, 40ppm of N and the balance of Fe.
Example 5
The normalized manganese gas cylinder steel prepared by the preparation method of example 1 comprises the following components in percentage by mass: 0.40% of C, 0.37% of Si, 1.70% of Mn, 0.10% of Cr, 0.10% of Mo, 0.01% of V, 0.005% of S, 0.010% of P, 100ppm of N and the balance of Fe.
Example 6
The normalized manganese gas cylinder steel prepared by the preparation method of example 1 comprises the following components in percentage by mass: 0.37% of C, 0.30% of Si, 1.63% of Mn, 0.18% of Cr, 0.05% of Mo, 0.03% of V, 0.001% of S, 0.013% of P, 60ppm of N and the balance of Fe.
Example 7
The normalized manganese gas cylinder steel prepared by the preparation method of example 1 comprises the following components in percentage by mass: 0.38% of C, 0.24% of Si, 1.68% of Mn, 0.10% of Cr, 0.08% of Mo, 0.01% of V, 0.003% of S, 0.010% of P, 90ppm of N and the balance of Fe.
Example 8
The normalized manganese gas cylinder steel prepared by the preparation method of example 1 comprises the following components in percentage by mass: 0.375% of C, 0.27% of Si, 1.65% of Mn, 0.15% of Cr, 0.06% of Mo, 0.02% of V, 0.002% of S, 0.012% of P, 80ppm of N and the balance of Fe.
Comparative example 1
The normalized manganese cylinder steel prepared by the method of example 1 had the same composition as in example 8 except that Cr was not added.
Comparative example 2
A normalized manganese-based gas cylinder steel prepared by the method of example 1 had the same composition as in example 8 except that Cr was 0.50% by mass.
Comparative example 3
A normalized manganese-based gas cylinder steel was prepared by the method of example 1 under the same conditions as in example 8 except that the composition of the gas cylinder steel was N10 ppm by mass.
Comparative example 4
A normalized manganese-based gas cylinder steel was prepared by the method of example 1 under the same conditions as in example 8 except that the composition of the gas cylinder steel was changed to 200ppm by mass.
Comparative example 5
A normalized manganese-based gas cylinder steel prepared by the method of example 1 was prepared under the same conditions as in example 8 except that Mo was not added.
Comparative example 6
A normalized manganese-based gas cylinder steel prepared by the method of example 1 had the same composition as in example 8 except that Mo was 0.20% by mass.
Comparative example 7
The normalized manganese-based gas cylinder steel prepared by the method of example 1 had the same composition as in example 8 except that V was not added.
Comparative example 8
A normalized manganese-based gas cylinder steel prepared by the method of example 1 had the same composition as in example 8 except that V was 0.10% by mass.
The cylinder steels obtained in examples 4 to 8 and comparative examples 1 to 8 were continuously rolled into seamless steel pipes, and the specifications of the steel pipes were as follows: phi 219mm x 6.4mm x 9m, tensile strength, yield strength and impact absorption work of the steel pipe were measured, and the results are shown in table 1.
TABLE 1
According to the table 1, it can be seen that the tensile strength of the gas cylinder steel continuous rolling seamless steel pipe obtained in the examples 4-8 can reach 792MPa, the yield strength can reach 581MPa, and the impact energy can reach 57J. Comparative example 1, in which Cr is not added, results in a decrease in the yield strength of the steel pipe, while comparative example 2, in which Cr is added in an excessive amount, results in a decrease in the impact absorption work of the steel pipe. The content of N in comparative example 3, which is 10ppm, results in a decrease in the impact absorption work of the steel pipe, while the content of N in comparative example 4, which is 200ppm, results in a decrease in the tensile strength of the steel pipe. Comparative example 5, in which Mo was not added, resulted in an overall decrease in mechanical properties of the steel pipe, while comparative example 6, in which the content of Mo was 0.20 wt%, resulted in a decrease in the impact absorption work of the steel pipe. Comparative example 7, in which no V was added, resulted in a decrease in the impact absorption work of the steel pipe, and comparative example 8, in which the content of V was 0.10 wt%, resulted in a decrease in the yield strength of the steel pipe.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (8)

1. The normalized manganese gas cylinder steel is characterized by comprising the following components in percentage by mass: 0.36-0.40% of C, 0.17-0.37% of Si, 1.55-1.70% of Mn, 0.01-0.25% of Cr, 0.01-0.10% of Mo, 0.01-0.05% of V, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 70-100 ppm of N and the balance of Fe;
the preparation method of the gas cylinder steel comprises the following steps:
(1) molten iron and scrap steel are dephosphorized by converter smelting by a double-slag method;
(2) simultaneously, blowing and pre-desulfurizing the molten steel to ensure that the desulfurization rate reaches 30-40%, and then carrying out primary component adjustment by adopting low-carbon drawing to obtain blown molten steel;
(3) performing LF refining on the blown molten steel obtained in the step (2), refining by using three-level current, performing electrode desulfurization and deoxidation for three times, and performing component fine adjustment to obtain refined molten steel;
(4) and (4) carrying out VD degassing on the refined molten steel obtained in the step (3), feeding the molten steel after the vacuum breaking, controlling the content of N to be 70-100 ppm, and continuously casting to obtain the gas cylinder steel blank.
2. The cylinder steel according to claim 1, wherein the composition of the cylinder steel comprises, in mass percent: 0.37-0.38% of C, 0.24-0.30% of Si, 1.63-1.68% of Mn, 0.10-0.18% of Cr, 0.01-0.08% of Mo, 0.01-0.03% of V, less than or equal to 0.003% of S, less than or equal to 0.013% of P, 70-90 ppm of N and the balance of Fe.
3. A method for preparing the cylinder steel of claim 1, which is characterized by comprising the following steps:
(1) the molten iron and the scrap steel are dephosphorized by converter smelting by adopting a double-slag method, wherein the double-slag method comprises the steps of carrying out primary blowing on the molten iron and the scrap steel for 2-10 min, then deslagging, carrying out secondary blowing on the molten iron and the scrap steel for 5-15 min, and carrying out slag blocking and steel retaining and tapping operations by using a sliding plate in the smelting process;
(2) simultaneously, blowing and pre-desulfurizing molten steel by using an oxygen lance, wherein the blowing pressure of the oxygen lance is 0.5-1 MPa, the blowing lance position is 0.8-1.5 m, the desulfurization rate is ensured to reach 30-40%, lime and dolomite are added before pre-desulfurization, and then low-carbon-pulling is adopted and the components are primarily adjusted to obtain blown molten steel;
(3) performing LF refining on the blown molten steel obtained in the step (2), refining by using three-level current, performing electrode desulfurization and deoxidation for three times, and performing component fine adjustment to obtain refined molten steel;
(4) and (4) carrying out VD degassing on the refined molten steel obtained in the step (3), feeding the molten steel after the vacuum breaking, controlling the content of N to be 70-100 ppm, and continuously casting to obtain the gas cylinder steel blank.
4. The method of claim 3, characterized in that lime and SiC are added in the LF refining in the step (3).
5. The method according to claim 3, wherein the VD degassing of step (4) employs a two-station degassing.
6. The preparation method of claim 3, wherein the deep vacuum degree of VD in step (4) is less than or equal to 67 pa.
7. The preparation method according to claim 3, wherein the vacuum time for VD degassing in step (4) is more than or equal to 15 min.
8. The manufacturing method according to claim 3, characterized in that the blank feeding wire of the step (4) is a MnN wire after blank feeding.
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CN101086203A (en) * 2007-07-19 2007-12-12 天津钢铁有限公司 Method for producing continuous casting round billet for petroleum bush using convertor process
CN105256235A (en) * 2015-11-19 2016-01-20 攀钢集团西昌钢钒有限公司 High-pressure gas cylinder steel and method for removing scale on surface of high-pressure gas cylinder steel
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CN1034761A (en) * 1988-02-06 1989-08-16 冶金工业部攀枝花钢铁公司 Steel alloy for high-pressure tank
CN101086203A (en) * 2007-07-19 2007-12-12 天津钢铁有限公司 Method for producing continuous casting round billet for petroleum bush using convertor process
CN105331885A (en) * 2015-10-09 2016-02-17 天津钢铁集团有限公司 Production method of 37 Mn round billets for air cylinders
CN105256235A (en) * 2015-11-19 2016-01-20 攀钢集团西昌钢钒有限公司 High-pressure gas cylinder steel and method for removing scale on surface of high-pressure gas cylinder steel

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