Steel material for deep-sea oil valve body and production method

Abstract

The invention relates to a steel material for a deep-sea petroleum valve body and a production method thereof. The steel material for a deep-sea petroleum valve body comprises, by mass percentage, C 0.12-0.14%, Si 0.4-0.42%, Mn 0.53-0.57%, Cr2.42-2.47%, Mo 0.93-0.97%, Ni 0.22-0.23%, Al 0.25-0.35%, Nb 0.01-0.02%, V0.01-0.02%, P≤0.01%, S≤0.005%, and the balance is Fe and unavoidable impurities. By designing the composition of the steel material, increasing the content of Ni and Al elements, combining the composite strengthening of V+Nb, strengthening the low-temperature impact toughness, improving the corrosion resistance of the steel, and inspecting the performance of the product after forging heat treatment, the product fully meets the requirements of the latest standards, which is conducive to improving the performance of the steel material.

Description

Technical Field

[0001] The invention relates to the field of steel materials, and in particular to a steel material for a deep-sea oil valve body and a production method thereof. Background Art

[0002] At present, with the advancement of deep-sea oil exploitation, the exploitation environment is becoming increasingly severe, and new requirements are put forward for the performance of steel used in the exploitation process. The deep-sea oil valve body steel used in the existing technology can no longer meet the requirements.

[0003] For example, CN109207862A discloses a wear-resistant special steel deep-sea petroleum valve body and a manufacturing method thereof. The valve body has the following chemical composition in weight percentage: C 0.10-0.15wt%, Mn 0.40-0.60wt%, P≤0.025wt%, S≤0.025wt%, Si 0.30-0.50wt%, Cr 11.50-13.50wt%, Mo≤0.60wt%, Ni 0.40-0.50wt%, H≤1.5ppm, O≤15ppm, N≤50ppm, and the rest is Fe and inevitable impurities. The main phase of the structure of the valve body is martensite, the second phase is austenite with a volume ratio of 8% or more and within 12%, and the internal volume ratio is 0% or more (excluding 0) and within 3% pearlite. The valve body uses new technology and new formula to significantly improve the corrosion resistance and mechanical properties of the valve body. In the product casting and molding manufacturing process, rapid processing ladle air brick equipment is used.

[0004] In view of this, the present invention improves the existing solution to solve the problem of poor mechanical properties of existing steel materials used for deep-sea oil valve bodies. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a steel material for deep-sea oil valve bodies and a production method to solve the problem of poor mechanical properties of steel materials for deep-sea oil valve bodies.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a steel material for a deep-sea petroleum valve body, wherein the steel material for a deep-sea petroleum valve body comprises, by weight percentage:

[0008] C 0.12-0.14%, Si 0.4-0.42%, Mn 0.53-0.57%, Cr 2.42-2.47%, Mo 0.93-0.97%, Ni 0.22-0.23%, Al 0.25-0.35%, Nb 0.01-0.02%, V 0.01-0.02%, P ≤ 0.01%, S ≤ 0.005%, and the balance is Fe and unavoidable impurities.

[0009] The steel for deep-sea oil valve bodies provided by the present invention designs the composition of the steel, increases the content of Ni and Al elements, combines V+Nb composite strengthening, strengthens low-temperature impact toughness, and improves the corrosion resistance of the steel. The product is tested for performance after forging heat treatment, which fully meets the requirements of the latest standards and is beneficial to improving the performance of the steel.

[0010] In the present invention, the C content in the steel for deep-sea oil valve body is 0.12-0.14% by mass, for example, it can be 0.12%, 0.121%, 0.122%, 0.123%, 0.124%, 0.125%, 0.126%, 0.127%, 0.128%, 0.129%, 0.13%, 0.131%, 0.132%, 0.133%, 0.134%, 0.135%, 0.136%, 0.137%, 0.138%, 0.139% or 0.14%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0011] In the present invention, the mass percentage of Si in the steel for deep-sea oil valve body is 0.4-0.42%, for example, it can be 0.4%, 0.401%, 0.402%, 0.403%, 0.404%, 0.405%, 0.406%, 0.407%, 0.408%, 0.409%, 0.41%, 0.411%, 0.412%, 0.413%, 0.414%, 0.415%, 0.416%, 0.417%, 0.418%, 0.419% or 0.42%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0012] In the present invention, the mass percentage of Mn in the steel for deep-sea oil valve body is 0.53-0.57%, for example, it can be 0.53%, 0.532%, 0.534%, 0.536%, 0.538%, 0.54%, 0.542%, 0.544%, 0.546%, 0.548%, 0.55%, 0.552%, 0.554%, 0.556%, 0.558%, 0.56%, 0.562%, 0.564%, 0.566%, 0.568% or 0.57%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0013] In the present invention, the mass percentage of Cr in the steel for deep-sea oil valve body is 2.42-2.47%, for example, it can be 2.42%, 2.422%, 2.424%, 2.426%, 2.428%, 2.43%, 2.432%, 2.434%, 2.436%, 2.438%, 2.44%, 2.442%, 2.444%, 2.446%, 2.448%, 2.45%, 2.452%, 2.454%, 2.456%, 2.458%, 2.46%, 2.462%, 2.464%, 2.466%, 2.468% or 2.47%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0014] In the present invention, the mass percentage of Mo in the steel for deep-sea oil valve body is 0.93-0.97%, for example, it can be 0.93%, 0.932%, 0.934%, 0.936%, 0.938%, 0.94%, 0.942%, 0.944%, 0.946%, 0.948%, 0.95%, 0.952%, 0.954%, 0.956%, 0.958%, 0.96%, 0.962%, 0.964%, 0.966%, 0.968% or 0.97%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0015] In the present invention, the mass percentage of Ni in the steel for deep-sea oil valve body is 0.22-0.23%, for example, it can be 0.22%, 0.221%, 0.222%, 0.223%, 0.224%, 0.225%, 0.226%, 0.227%, 0.228%, 0.229% or 0.23%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0016] In the present invention, the mass percentage of Al in the steel for deep-sea oil valve body is 0.25-0.35%, for example, it can be 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34% or 0.35%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0017] In the present invention, the Nb content in the steel for deep-sea oil valve body is 0.01-0.02% by mass, for example, it can be 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019% or 0.02%, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0018] In the present invention, the mass percentage of V in the steel for deep-sea oil valve body is 0.01-0.02%, for example, it can be 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019% or 0.02%, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0019] In the present invention, the mass percentage of P in the steel for deep-sea oil valve body is ≤0.01%, for example, it can be 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002% or 0.001%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0020] In the present invention, the mass percentage of S in the steel for deep-sea oil valve body is ≤0.005%, for example, it can be 0.005%, 0.004%, 0.003%, 0.002%, 0.001%, 0.0008%, 0.0006%, 0.0004%, 0.0002% or 0.0001%, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0021] As a preferred technical solution of the present invention, the steel for deep-sea oil valve body includes, by mass percentage, C 0.12-0.13%, Si 0.41-0.42%, Mn 0.54-0.55%, Cr 2.42-2.44%, Mo 0.93-0.95%, Ni 0.22-0.23%, Al 0.28-0.32%, Nb 0.01-0.02%, V 0.01-0.02%, P≤0.01%, S≤0.005%, and the balance is Fe and unavoidable impurities.

[0022] In a second aspect, the present invention provides a method for producing the steel material for deep-sea petroleum valve body as described in the first aspect, the production method comprising:

[0023] The molten iron is provided, and KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging are carried out in sequence to obtain steel for deep-sea oil valve body.

[0024] As a preferred technical solution of the present invention, the KR pretreatment includes KR desulfurization;

[0025] Preferably, a desulfurizing agent is added during the KR pretreatment;

[0026] Preferably, the desulfurizing agent comprises calcium oxide, fluorite powder and aluminum powder;

[0027] In the present invention, the addition amount of calcium oxide in the desulfurizer is 10-12kg / t, the addition amount of fluorite powder is 0.7-1.2kg / t, the addition amount of aluminum powder is 0.5-1kg / t, etc.; the desulfurization process is accompanied by stirring, the stirring speed is 75-90r / min, and the time is 12-15min.

[0028] Preferably, the sulfur content in the molten iron obtained by the KR pretreatment is ≤0.001% by mass, for example, it can be 0.001%, 0.0009%, 0.0008%, 0.0007%, 0.0006%, 0.0005%, 0.0004%, 0.0003%, 0.0002% or 0.0001%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0029] As a preferred technical solution of the present invention, the steel tapping temperature of the converter smelting is 1600-1630°C, for example, it can be 1600°C, 1602°C, 1604°C, 1606°C, 1608°C, 1610°C, 1612°C, 1614°C, 1616°C, 1618°C, 1620°C, 1622°C, 1624°C, 1626°C, 1628°C or 1630°C, but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0030] Preferably, the endpoint C of the converter smelting is 0.03-0.05% by mass percentage, for example, it can be 0.03%, 0.031%, 0.032%, 0.033%, 0.034%, 0.035%, 0.036%, 0.037%, 0.038%, 0.039%, 0.04%, 0.041%, 0.042%, 0.043%, 0.044%, 0.045%, 0.046%, 0.047%, 0.048%, 0.049% or 0.05%, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0031] Preferably, the endpoint P of the converter smelting is ≤0.007% in terms of mass percentage, for example, it can be 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002% or 0.001%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] Preferably, an alloy containing Ni and Mn is added when tapping the converter.

[0033] In the present invention, the alloy containing Ni and Mn may be a commonly used intermediate alloy containing Ni and Mn in the art.

[0034] In the present invention, during the steel tapping process of converter steelmaking, the liquid level is controlled to be above the inner edge of the outlet, and a slide plate is used to block the slag to prevent slag from falling during steel tapping.

[0035] As a preferred technical solution of the present invention, the deoxidation alloying is to add aluminum material for deoxidation 10-18s after the converter taps the steel, and add the intermediate alloy 30-40s after the converter taps the steel.

[0036] In the present invention, the converter tapping time of 30-40s is calculated based on the initial tapping time, for example, it may be 30s, 31s, 32s, 33s, 34s, 35s, 36s, 37s, 38s, 39s or 40s, but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0037] In the present invention, the addition amount of aluminum material in the deoxidation alloying is 1.5-2.5 kg / t, for example, it can be 1.5 kg / t, 1.6 kg / t, 1.7 kg / t, 1.8 kg / t, 1.9 kg / t, 2 kg / t, 2.1 kg / t, 2.2 kg / t, 2.3 kg / t, 2.4 kg / t or 2.5 kg / t, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0038] In the present invention, the intermediate alloy is added in sequence according to ferromolybdenum, nickel plate, low carbon ferromanganese, low carbon ferrochrome and ferrosilicon, and the added amount is selected according to the steel for deep-sea oil valve body, and can also be determined according to the composition of molten iron refined by LF.

[0039] As a preferred technical solution of the present invention, the deoxidizer used in the LF refining includes aluminum and / or silicon carbide;

[0040] Preferably, the white slag retention time in the LF refining is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0041] Preferably, the sulfur content in the LF refining is ≤0.002% by mass percentage, for example, it can be 0.002%, 0.002%, 0.0019%, 0.0018%, 0.0017%, 0.0016%, 0.0015%, 0.0014%, 0.0013%, 0.0012%, 0.0011%, 0.001% or 0.0001%, etc., but is not limited to the listed values, and other values ​​not listed in this range are also applicable.

[0042] Preferably, the slag used in the LF refining comprises, by mass percentage, 48-52% CaO, 3-6% MgO, and 2-6% SiO 2 ≤8%, the balance is Al 2 O 3 .

[0043] Preferably, the tapping temperature of the LF refining is 1660-1680°C, for example, it can be 1660°C, 1661°C, 1662°C, 1663°C, 1664°C, 1665°C, 1666°C, 1667°C, 1668°C, 1669°C, 1670°C, 1671°C, 1672°C, 1673°C, 1674°C, 1675°C, 1676°C, 1677°C, 1678°C, 1679°C or 1680°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0044] Preferably, the LF refining time is ≥ 70 min, for example, it can be 70 min, 72 min, 74 min, 76 min, 78 min, 80 min, 82 min, 84 min, 86 min, 88 min, 90 min, 95 min, 100 min, 110 min or 120 min, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0045] In the present invention, illustratively, the composition of the molten iron obtained by LF refining includes, by mass percentage, C 0.1-0.12%, Si 0.41-0.43%, Mn 0.55-0.57%, Cr 2.44-2.46%, Ni 0.22-0.24%, Mo 0.94-0.96%, V 0.014-0.016%, Al 0.02-0.04%, Nb 0.014-0.016%, P≤0.012%, S≤0.005%, and the balance is Fe and unavoidable impurities.

[0046] As a preferred technical solution of the present invention, an alloy containing V and Nb is added to the VD vacuum before breaking the vacuum, and an aluminum alloy wire is added after breaking the vacuum.

[0047] In the present invention, the alloy containing V and Nb may be a commonly used intermediate alloy containing V and Nb in the art.

[0048] Preferably, the deep vacuum time in the VD vacuum is ≥18 min, for example, it can be 18 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0049] Preferably, the absolute vacuum degree in the VD vacuum is ≤67Pa, for example, it may be 67Pa, 65Pa, 60Pa, 55Pa, 50Pa, 45Pa, 40Pa, 35Pa, 30Pa, 25Pa, 20Pa, 15Pa, 10Pa or 5Pa, etc., but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0050] Preferably, a heat preservation agent is added to the VD vacuum after breaking the vacuum, and soft blowing is performed for ≥ 20 min, for example, it can be 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min or 40 min, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0051] Preferably, the VD vacuum station temperature is 1580-1600°C, for example, it can be 1580°C, 1581°C, 1582°C, 1583°C, 1584°C, 1585°C, 1586°C, 1587°C, 1588°C, 1589°C, 1590°C, 1591°C, 1592°C, 1593°C, 1594°C, 1595°C, 1596°C, 1597°C, 1598°C, 1599°C or 1600°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0052] Preferably, the superheat temperature of the continuous casting molten steel in the continuous casting is 15-30°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, but is not limited to the listed values, and other values ​​not listed in this range are also applicable.

[0053] In the present invention, the slow cooling time after continuous casting is ≥72h, and the exit temperature after slow cooling is ≤120°C.

[0054] In the present invention, the ingot can be finished before forging, the surface quality can be regulated and the appearance can be inspected.

[0055] Preferably, the forging furnace temperature is 1220-1240°C, for example, it can be 1220°C, 1221°C, 1222°C, 1223°C, 1224°C, 1225°C, 1226°C, 1227°C, 1228°C, 1229°C, 1230°C, 1231°C, 1232°C, 1233°C, 1234°C, 1235°C, 1236°C, 1237°C, 1238°C, 1239°C or 1240°C, but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0056] Preferably, the final forging temperature of the forging is 800-920°C, for example, it can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C or 920°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0057] As a preferred technical solution of the present invention, normalizing, quenching and tempering are performed in sequence after forging.

[0058] Preferably, the normalizing temperature is 945-965°C, for example, it can be 945°C, 946°C, 947°C, 948°C, 949°C, 950°C, 951°C, 952°C, 953°C, 954°C, 955°C, 956°C, 957°C, 958°C, 959°C, 960°C, 961°C, 962°C, 963°C, 964°C or 965°C, but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0059] Preferably, the holding time for normalizing is 90-120 min, for example, it can be 90 min, 92 min, 94 min, 96 min, 98 min, 100 min, 102 min, 104 min, 106 min, 108 min, 110 min, 112 min, 114 min, 116 min, 118 min or 120 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0060] Preferably, the quenching temperature is 917-937°C, for example, it may be 917°C, 918°C, 919°C, 920°C, 921°C, 922°C, 923°C, 924°C, 925°C, 926°C, 927°C, 928°C, 929°C, 930°C, 931°C, 932°C, 933°C, 934°C, 935°C, 936°C or 937°C, but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0061] Preferably, the holding time for quenching is 90-120 min, for example, it can be 90 min, 92 min, 94 min, 96 min, 98 min, 100 min, 102 min, 104 min, 106 min, 108 min, 110 min, 112 min, 114 min, 116 min, 118 min or 120 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0062] Preferably, the holding temperature of the tempering is 660-680°C, for example, it can be 660°C, 661°C, 662°C, 663°C, 664°C, 665°C, 666°C, 667°C, 668°C, 669°C, 670°C, 671°C, 672°C, 673°C, 674°C, 675°C, 676°C, 678°C, 679°C or 680°C, but is not limited to the listed values, and other values ​​not listed in the range are also applicable.

[0063] Preferably, the holding time for tempering is 90-120 min, for example, it can be 90 min, 92 min, 94 min, 96 min, 98 min, 100 min, 102 min, 104 min, 106 min, 108 min, 110 min, 112 min, 114 min, 116 min, 118 min or 120 min, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0064] As a preferred technical solution of the present invention, the production method comprises: providing molten iron, sequentially performing KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging to obtain steel for deep-sea oil valve body;

[0065] The KR pretreatment includes KR desulfurization; a desulfurizer is added in the KR pretreatment; the desulfurizer includes calcium oxide, fluorite powder and aluminum powder; the sulfur content in the molten iron obtained by the KR pretreatment is ≤0.001% by mass percentage;

[0066] The tapping temperature of the converter smelting is 1600-1630°C; the end point C of the converter smelting is 0.03-0.05% by mass percentage; the end point P of the converter smelting is ≤0.007% by mass percentage; an alloy containing Ni and Mn is added when the converter taps the steel;

[0067] The deoxidation alloying step is to add aluminum material for deoxidation 10-18 seconds after the converter taps the steel, and add the intermediate alloy 30-40 seconds after the converter taps the steel;

[0068] The deoxidizer used in the LF refining includes aluminum and / or silicon carbide; the white slag retention time in the LF refining is 20-30 minutes; the sulfur content in the LF refining is ≤0.002wt% by mass percentage; the slag used in the LF refining includes, by mass percentage, CaO 48-52%, MgO 3-6%, SiO 2 ≤8%, the balance is Al 2 O 3 ; The tapping temperature of the LF refining is 1660-1680°C; The LF refining time is ≥70min;

[0069] Before breaking the vacuum in the VD vacuum, an alloy containing V and Nb is added, and after breaking the vacuum, an aluminum alloy wire is added; the deep vacuum time in the VD vacuum is ≥18min; the absolute vacuum degree in the VD vacuum is ≤67Pa; after breaking the vacuum in the VD vacuum, a heat preservation agent is added, and soft blowing is performed for ≥20min; the leaving station temperature of the VD vacuum is 1580-1600℃; the overheating temperature of the continuous casting molten steel in the continuous casting is 15-30℃;

[0070] The forging furnace temperature is 1220-1240°C; the final forging temperature is 800-920°C; after forging, normalizing, quenching and tempering are carried out in sequence; the normalizing temperature is 945-965°C; the normalizing holding time is 90-120min; the quenching temperature is 917-937°C; the quenching holding time is 90-120min; the tempering holding temperature is 660-680°C; the tempering holding time is 90-120min.

[0071] In the present invention, t in the unit kg / t refers to the mass of molten steel.

[0072] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0073] The steel for deep-sea oil valve body provided by the present invention effectively improves the mechanical properties of the obtained steel by designing its composition and preparation process. The obtained steel has a tensile strength of ≥750.5MPa, a compressive strength Rp0.2 ≥590.3MPa, and an impact energy of ≥50.3J at -60°C. DETAILED DESCRIPTION

[0074] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0075] Example 1

[0076] This embodiment provides a steel material for a deep-sea petroleum valve body, and the steel material for a deep-sea petroleum valve body includes, by mass percentage:

[0077] C 0.13%, Si 0.41%, Mn 0.55%, Cr 2.44%, Mo 0.95%, Ni 0.225%, Al 0.3%, Nb 0.015%, V 0.01%, P 0.01%, S 0.005%, and the balance is Fe and inevitable impurities.

[0078] The following production process is adopted, including:

[0079] The molten iron is provided, and KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging are carried out in sequence to obtain steel for deep-sea oil valve body.

[0080] The KR pretreatment is KR desulfurization; a desulfurizer is added in the KR pretreatment; the desulfurizer is calcium oxide, fluorite powder and aluminum powder, the addition amount of calcium oxide in the desulfurizer is 11kg / t, the addition amount of fluorite powder is 1kg / t, the addition amount of aluminum powder is 0.75kg / t, etc.; the desulfurization process is accompanied by stirring, the stirring speed is 80r / min, and the time is 14min; the sulfur content in the molten iron obtained by the KR pretreatment is 0.001% by mass percentage;

[0081] The tapping temperature of the converter smelting is 1615°C; the end point C of the converter smelting is 0.04% by mass percentage; the end point P of the converter smelting is 0.007% by mass percentage; an alloy containing Ni and Mn is added when the converter taps the steel;

[0082] The deoxidation alloying step is to add aluminum material (2kg / t) for deoxidation 14s after the converter taps steel, and to add a master alloy 35s after the converter taps steel, and to add ferromolybdenum, nickel plate, low-carbon ferromanganese, low-carbon ferrochrome and ferrosilicon in sequence;

[0083] The deoxidizer used in the LF refining is silicon carbide; the white slag retention time in the LF refining is 25 minutes; the sulfur content in the LF refining is 0.002wt% by mass percentage; the slag used in the LF refining includes, by mass percentage, CaO 50%, MgO 5%, SiO 2 8%, the balance is Al 2 O 3 ; The tapping temperature of the LF refining is 1670°C; The LF refining time is 70min;

[0084] Before breaking the vacuum in the VD vacuum, an alloy containing V and Nb is added, and after breaking the vacuum, an aluminum alloy wire is added; the deep vacuum time in the VD vacuum is 18 minutes; the absolute vacuum degree in the VD vacuum is 67Pa; after breaking the vacuum in the VD vacuum, a heat preservation agent (carbonized rice husk) is added, and soft blowing is performed for 20 minutes; the leaving station temperature of the VD vacuum is 1590°C; the overheating temperature of the continuous casting molten steel in the continuous casting is 25°C;

[0085] The forging furnace temperature is 1230°C; the final forging temperature is 850°C; after forging, normalizing, quenching and tempering are carried out in sequence; the normalizing temperature is 955°C; the holding time of normalizing is 100min; the quenching temperature is 927°C; the holding time of quenching is 110min; the holding temperature of tempering is 670°C; and the holding time of tempering is 90min.

[0086] The properties of the obtained steel are shown in Table 1.

[0087] Example 2

[0088] This embodiment provides a steel material for a deep-sea petroleum valve body, and the steel material for a deep-sea petroleum valve body includes, by mass percentage:

[0089] C 0.12%, Si 0.42%, Mn 0.53%, Cr 2.42%, Mo 0.97%, Ni 0.22%, Al 0.35%, Nb 0.01%, V 0.02%, P 0.001%, S 0.001%, and the balance is Fe and inevitable impurities.

[0090] The following production process is adopted, including:

[0091] The molten iron is provided, and KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging are carried out in sequence to obtain steel for deep-sea oil valve body.

[0092] The KR pretreatment includes KR desulfurization; a desulfurizer is added in the KR pretreatment; the desulfurizer includes calcium oxide, fluorite powder and aluminum powder, the addition amount of calcium oxide in the desulfurizer is 10kg / t, the addition amount of fluorite powder is 0.7kg / t, the addition amount of aluminum powder is 0.5kg / t, etc.; the desulfurization process is accompanied by stirring, the stirring speed is 75r / min, and the time is 15min; the sulfur content in the molten iron obtained by the KR pretreatment is 0.0001% by mass percentage;

[0093] The tapping temperature of the converter smelting is 1600°C; the end point C of the converter smelting is 0.03% by mass percentage; the end point P of the converter smelting is 0.001% by mass percentage; an alloy containing Ni and Mn is added when the converter taps the steel;

[0094] The deoxidation alloying step is to add aluminum material (2.5 kg / t) for deoxidation 10 seconds after the converter is tapped, and to add a master alloy 30 seconds after the converter is tapped, and to add ferromolybdenum, nickel plate, low-carbon ferromanganese, low-carbon ferrochrome and ferrosilicon in sequence;

[0095] The deoxidizer used in the LF refining includes aluminum and / or silicon carbide; the white slag retention time in the LF refining is 20 minutes; the sulfur content in the LF refining is 0.001wt% by mass percentage; the slag used in the LF refining includes, by mass percentage, CaO 48%, MgO 6%, SiO 2 1%, the balance is Al 2 O 3 ; The tapping temperature of the LF refining is 1660°C; The LF refining time is 100min;

[0096] Before breaking the vacuum in the VD vacuum, an alloy containing V and Nb is added, and after breaking the vacuum, an aluminum alloy wire is added; the deep vacuum time in the VD vacuum is 38 minutes; the absolute vacuum degree in the VD vacuum is 27Pa; after breaking the vacuum in the VD vacuum, a heat preservation agent (carbonized rice husk) is added, and soft blowing is performed for 30 minutes; the leaving station temperature of the VD vacuum is 1600°C; the overheating temperature of the continuous casting molten steel in the continuous casting is 15°C;

[0097] The forging furnace temperature is 1240°C; the final forging temperature is 920°C; after forging, normalizing, quenching and tempering are carried out in sequence; the normalizing temperature is 945°C; the holding time of normalizing is 90min; the quenching temperature is 937°C; the holding time of quenching is 120min; the holding temperature of tempering is 680°C; and the holding time of tempering is 110min.

[0098] The properties of the obtained steel are shown in Table 1.

[0099] Example 3

[0100] This embodiment provides a steel material for a deep-sea petroleum valve body, and the steel material for a deep-sea petroleum valve body includes, by mass percentage:

[0101] C 0.14%, Si 0.4%, Mn 0.57%, Cr 2.47%, Mo 0.93%, Ni 0.23%, Al 0.25%, Nb 0.02%, V 0.01%, P 0.004%, S 0.0005%, and the balance is Fe and inevitable impurities.

[0102] The following production process is adopted, including:

[0103] The molten iron is provided, and KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging are carried out in sequence to obtain steel for deep-sea oil valve body.

[0104] The KR pretreatment includes KR desulfurization; a desulfurizer is added in the KR pretreatment; the desulfurizer includes calcium oxide, fluorite powder and aluminum powder, the addition amount of calcium oxide in the desulfurizer is 12kg / t, the addition amount of fluorite powder is 1.2kg / t, the addition amount of aluminum powder is 1kg / t, etc.; the desulfurization process is accompanied by stirring, the stirring speed is 90r / min, and the time is 12min; the sulfur content of the molten iron obtained by the KR pretreatment is 0.0004% by mass percentage;

[0105] The tapping temperature of the converter smelting is 1630°C; the end point C of the converter smelting is 0.05% by mass percentage; the end point P of the converter smelting is 0.003% by mass percentage; an alloy containing Ni and Mn is added when the converter taps the steel;

[0106] The deoxidation alloying step is to add aluminum material (1.5 kg / t) for deoxidation 18 seconds after the converter is tapped, and to add a master alloy 40 seconds after the converter is tapped, and to add ferromolybdenum, nickel plate, low-carbon ferromanganese, low-carbon ferrochrome and ferrosilicon in sequence;

[0107] The deoxidizer used in the LF refining includes aluminum and / or silicon carbide; the white slag retention time in the LF refining is 30 minutes; the sulfur content in the LF refining is 0.0002% by mass; the slag used in the LF refining includes, by mass percentage: CaO 52%, MgO 3%, SiO 2 3%, the balance is Al 2 O 3 ; The tapping temperature of the LF refining is 1680°C; The time of the LF refining is 120min;

[0108] Before breaking the vacuum in the VD vacuum, an alloy containing V and Nb is added, and after breaking the vacuum, an aluminum alloy wire is added; the deep vacuum time in the VD vacuum is 48 minutes; the absolute vacuum degree in the VD vacuum is 40Pa; after breaking the vacuum in the VD vacuum, a heat preservation agent (carbonized rice husk) is added, and soft blowing is performed for 40 minutes; the leaving station temperature of the VD vacuum is 1580°C; the overheating temperature of the continuous casting molten steel in the continuous casting is 30°C;

[0109] The forging furnace temperature is 1220°C; the final forging temperature is 800°C; after forging, normalizing, quenching and tempering are carried out in sequence; the normalizing temperature is 965°C; the holding time of normalizing is 120min; the quenching temperature is 917°C; the holding time of quenching is 90min; the holding temperature of tempering is 660°C; and the holding time of tempering is 120min.

[0110] The properties of the obtained steel are shown in Table 1.

[0111] Example 4

[0112] The only difference from Example 1 is that the content of Mn element is 0.3%, and the changed amount is replaced by an equal amount of Fe.

[0113] Example 5

[0114] The only difference from Example 1 is that the content of Ni element is 0.4%, and the changed amount is replaced by an equal amount of Fe.

[0115] Example 6

[0116] The only difference from Example 1 is that the content of Ni element is 0.1%, and the changed amount is replaced by an equal amount of Fe.

[0117] Example 7

[0118] The only difference from Example 1 is that the content of Al element is 0.1%, and the changed amount is replaced by an equal amount of Fe.

[0119] Example 8

[0120] The only difference from Example 1 is that the content of Al element is 0.5%, and the changed amount is replaced by an equal amount of Fe.

[0121] Example 9

[0122] The only difference from Example 1 is that the content of Nb element is 0.2%, and the changed amount is replaced by an equal amount of Fe.

[0123] Example 10

[0124] The only difference from Example 1 is that the Nb element is not contained, and the changed amount is replaced by an equal amount of Fe.

[0125] Embodiment 11

[0126] The only difference from Example 1 is that the content of V element is 0.2%, and the changed amount is replaced by an equal amount of Fe.

[0127] Example 12

[0128] The only difference from Example 1 is that the V element is not contained, and the changed amount is replaced by an equal amount of Fe.

[0129] The mechanical properties of the steel obtained in the above embodiment are tested according to API SPECIFICATION 6A-2018, 21st EDITION, and the sampling method is to forge a 200 mm circle and sample at a position 25 mm away from the edge.

[0130] Table 1

[0131] Tensile strength / Rm Compressive strength / Rp0.2 -60℃ impact energy / J Example 1 750.5 600.8 55.2 Example 2 760.6 590.3 50.3 Example 3 810.7 605.1 57.8 Example 4 680.1 550.3 45.3 Example 5 650.2 528.2 35.1 Example 6 662.3 531.1 32.4 Example 7 664.6 534.3 20.6 Example 8 653.5 342.2 30.2 Example 9 658.1 538.4 40.1 Example 10 667.3 521.1 37.3 Embodiment 11 671.4 533.3 35.4 Example 12 672.6 538.4 36.6

[0132] It can be seen from the results of the above embodiments that the steel for deep-sea oil valve bodies provided by the present invention designs the composition of the steel, increases the content of Ni and Al elements, combines the composite strengthening of V+Nb, enhances the low-temperature impact toughness, and improves the corrosion resistance of the steel. The performance of the product after forging heat treatment is tested and fully meets the requirements of the latest standards, which is beneficial to improving the performance of the steel.

[0133] It is stated that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0134] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0135] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0136] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A steel material for deep-sea oil valve body, characterized in that: The steel material for deep-sea petroleum valve body is composed of the following components by weight percentage: C 0.12-0.14%, Si 0.4-0.42%, Mn 0.53-0.57%, Cr 2.42-2.47%, Mo 0.93-0.97%, Ni 0.22-0.23%, Al 0.25-0.35%, Nb 0.01-0.02%, V 0.01-0.02%, P≤0.01%, S≤0.005%, the balance is Fe and unavoidable impurities; The steel material for deep-sea petroleum valve body is prepared by the following production method, which comprises the following steps: Provide molten iron, and carry out KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging in sequence, and after forging, carry out normalizing, quenching and tempering in sequence to obtain steel for deep-sea oil valve body; The normalizing temperature is 945-965°C; the normalizing holding time is 90-120min; the quenching temperature is 917-937°C; the quenching holding time is 90-120min; the tempering holding temperature is 660-680°C; the tempering holding time is 90-120min.

2. The steel material for deep-sea petroleum valve body according to claim 1, characterized in that: The steel material for deep-sea oil valve body is composed of the following components in terms of mass percentage: C 0.12-0.13%, Si 0.41-0.42%, Mn 0.54-0.55%, Cr2.42-2.44%, Mo 0.93-0.95%, Ni 0.22-0.23%, Al 0.28-0.32%, Nb 0.01-0.02%, V0.01-0.02%, P≤0.01%, S≤0.005%, and the balance is Fe and unavoidable impurities.

3. A method for producing steel for deep-sea petroleum valve bodies as claimed in claim 1 or 2, characterized in that: The production method comprises: Provide molten iron, and carry out KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging in sequence, and after forging, carry out normalizing, quenching and tempering in sequence to obtain steel for deep-sea oil valve body; The normalizing temperature is 945-965°C; the normalizing holding time is 90-120min; the quenching temperature is 917-937°C; the quenching holding time is 90-120min; the tempering holding temperature is 660-680°C; the tempering holding time is 90-120min.

4. The production method according to claim 3, characterized in that: The KR pretreatment includes KR desulfurization.

5. The production method according to claim 4, characterized in that: A desulfurizing agent is added during the KR pretreatment.

6. The production method according to claim 5, characterized in that: The desulfurizing agent includes calcium oxide, fluorite powder and aluminum powder.

7. The production method according to claim 3, characterized in that: The sulfur content in the molten iron obtained by the KR pretreatment is ≤0.001% by mass.

8. The production method according to claim 3, characterized in that: The tapping temperature of the converter smelting is 1600-1630°C.

9. The production method according to claim 3, characterized in that: The end point C of the converter smelting is 0.03-0.05% by mass percentage.

10. The production method according to claim 3, characterized in that: The endpoint P of the converter smelting is ≤0.007% by mass percentage.

11. The production method according to claim 3, characterized in that: The alloy containing Ni and Mn is added when the converter is tapping steel.

12. The production method according to claim 3, characterized in that: The deoxidation alloying is to add aluminum material for deoxidation 10-18 seconds after the converter taps the steel, and add the intermediate alloy 30-40 seconds after the converter taps the steel.

13. The production method according to claim 3, characterized in that: The deoxidizer used in the LF refining includes aluminum and / or silicon carbide.

14. The production method according to claim 3, characterized in that: The white slag retention time in the LF refining is 20-30 minutes.

15. The production method according to claim 3, characterized in that: The sulfur content in the LF refining is ≤0.002wt% by mass.

16. The production method according to claim 3, characterized in that: The slag used in the LF refining comprises, by mass percentage, 48-52% CaO, 3-6% MgO, ≤8% SiO2, and the balance Al2O3.

17. The production method according to claim 3, characterized in that: The tapping temperature of the LF refining is 1660-1680°C.

18. The production method according to claim 3, characterized in that: The LF refining time is ≥70 min.

19. The production method according to claim 3, characterized in that: In the VD vacuum, an alloy containing V and Nb is added before breaking the vacuum, and an aluminum alloy wire is added after breaking the vacuum.

20. The production method according to claim 3, characterized in that: The deep vacuum time in the VD vacuum is ≥18 min.

21. The production method according to claim 3, characterized in that: The absolute vacuum degree in the VD vacuum is ≤67Pa.

22. The production method according to claim 3, characterized in that: In the VD vacuum, a heat preservation agent is added after breaking the vacuum, and soft blowing is performed for ≥20 minutes.

23. The production method according to claim 3, characterized in that: The VD vacuum station temperature is 1580-1600°C.

24. The production method according to claim 3, characterized in that: The superheat temperature of the molten steel during continuous casting is 15-30°C.

25. The production method according to claim 3, characterized in that: The forging furnace temperature is 1220-1240°C.

26. The production method according to claim 3, characterized in that: The final forging temperature of the forging is 800-920°C.

27. The production method according to claim 3, characterized in that: The production method comprises: Provide molten iron, and carry out KR pretreatment, converter smelting, deoxidation alloying, LF refining, VD vacuum, continuous casting, slow cooling, heating and forging in sequence to obtain steel for deep-sea oil valve body; The KR pretreatment includes KR desulfurization; a desulfurizer is added in the KR pretreatment; the desulfurizer includes calcium oxide, fluorite powder and aluminum powder; the sulfur content in the molten iron obtained by the KR pretreatment is ≤0.001% by mass percentage; The tapping temperature of the converter smelting is 1600-1630°C; the end point C of the converter smelting is 0.03-0.05% by mass percentage; the end point P of the converter smelting is ≤0.007% by mass percentage; an alloy containing Ni and Mn is added when the converter taps the steel; The deoxidation alloying step is to add aluminum material for deoxidation 10-18 seconds after the converter taps the steel, and add the intermediate alloy 30-40 seconds after the converter taps the steel; The deoxidizer used in the LF refining includes aluminum and / or silicon carbide; the white slag retention time in the LF refining is 20-30 minutes; the sulfur content in the LF refining is ≤0.002wt% by mass percentage; the slag used in the LF refining includes, by mass percentage, CaO 48-52%, MgO 3-6%, SiO2≤8%, and the balance is Al2O3; the tapping temperature of the LF refining is 1660-1680°C; the LF refining time is ≥70 minutes; Before breaking the vacuum in the VD vacuum, an alloy containing V and Nb is added, and after breaking the vacuum, an aluminum alloy wire is added; the deep vacuum time in the VD vacuum is ≥18min; the absolute vacuum degree in the VD vacuum is ≤67Pa; after breaking the vacuum in the VD vacuum, a heat preservation agent is added, and soft blowing is performed for ≥20min; the leaving station temperature of the VD vacuum is 1580-1600℃; the overheating temperature of the continuous casting molten steel in the continuous casting is 15-30℃; The forging furnace temperature is 1220-1240°C; the final forging temperature is 800-920°C; after forging, normalizing, quenching and tempering are carried out in sequence; the normalizing temperature is 945-965°C; the normalizing holding time is 90-120min; the quenching temperature is 917-937°C; the quenching holding time is 90-120min; the tempering holding temperature is 660-680°C; the tempering holding time is 90-120min.