WO2021121109A1 - 一种lng储罐用耐-165℃低温钢筋机械连接套筒及生产方法 - Google Patents

一种lng储罐用耐-165℃低温钢筋机械连接套筒及生产方法 Download PDF

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WO2021121109A1
WO2021121109A1 PCT/CN2020/135058 CN2020135058W WO2021121109A1 WO 2021121109 A1 WO2021121109 A1 WO 2021121109A1 CN 2020135058 W CN2020135058 W CN 2020135058W WO 2021121109 A1 WO2021121109 A1 WO 2021121109A1
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production method
temperature
low
sleeve
lng storage
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PCT/CN2020/135058
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English (en)
French (fr)
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郭湛
汪开忠
于同仁
姜婷
张晓瑞
余良其
宋祖峰
尹德福
徐雁
黄社清
张步海
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马鞍山钢铁股份有限公司
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Publication of WO2021121109A1 publication Critical patent/WO2021121109A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention belongs to a low-temperature steel material and a preparation process thereof, and particularly relates to a -165°C low-temperature resistant steel bar mechanical connection sleeve for an LNG storage tank and a production method.
  • Steel bars are often used as the skeleton material of reinforced concrete structures to support and strengthen the building structure. Sometimes it is also used in a certain low temperature environment.
  • the typical building structure is a liquefied natural gas (LNG) storage tank.
  • LNG liquefied natural gas
  • the storage temperature of LNG is -165°C, and the properties of metal materials at low temperatures change greatly compared with normal temperature.
  • low-temperature resistant metal materials should be selected.
  • low-temperature steel bars need to be imported from abroad. At present, domestic production of low-temperature steel bars has been realized in domestic batches such as Maanshan Iron & Steel.
  • Low-temperature steel bars are delivered at a fixed length, and need to be used after being mechanically connected by sleeves during construction. Since the design temperature of the LNG storage tank is -165°C, not only the sleeve is required to have good room temperature performance, but also to ensure the safety of the storage tank when the LNG leaks, it is required to have good strength and toughness under the condition of -165°C. As the construction of LNG storage tanks in coastal port cities in my country continues to increase, the demand for low-temperature reinforced mechanical connection sleeves has increased. However, there are no public reports on the specific composition and preparation methods of the steel used for low-temperature reinforced mechanical connection sleeves in China.
  • the Chinese invention patent "A steel bar connecting sleeve, application number 201010209694.1”, discloses a steel bar connecting sleeve, which includes a cylindrical sleeve body, the inner surface of the sleeve body is provided with internal threads, and the outer surface of the sleeve body is longitudinally oriented.
  • a plurality of longitudinal ribs protruding outward are provided, which is characterized in that the ends of the longitudinal ribs are arranged in an oblique shape with a smoothly decreasing height.
  • the smooth reduction in height refers to a shape such as an oblique line or an oblique arc.
  • the rib strength can be effectively improved, thereby ensuring the reliability of the connection, and at the same time, the effect of saving forging materials and reducing costs can be achieved.
  • the Chinese invention patent "A steel bar connecting sleeve, application number 201010608926.0” provides a steel bar connecting sleeve, including an inner through hole, the outer surface of the sleeve is provided with a wrench clamping position, and the wrench clamping position is a prismatic tooth.
  • the number of the prismatic teeth is greater than or equal to 4
  • the inner through hole is cylindrical, the inner through hole is provided with a thread, and the thread provided in the inner through hole engages with the thread of the end of the steel bar.
  • the steel bar connecting sleeve has a polygonal tooth shape on its cross-sectional outer surface, which overcomes the defects that the existing steel bar connecting sleeve is not easy to tighten and slipping caused by the circular outer surface of the steel bar connecting sleeve. But none of them can be used for mechanical connection of low-temperature steel bars at a design temperature of -165°C.
  • the invention provides a -165°C low-temperature resistant steel bar mechanical connection sleeve for LNG storage tanks and a production method thereof.
  • the room temperature mechanical properties of the produced sleeve meet the 500MPa level in JG/J 107-2016 "Technical Regulations for Mechanical Connection of Steel Bars"
  • the requirements of grade I rebar sleeves, the mechanical properties of -165°C meet the requirements of steel breakage f O max ⁇ 635MPa or sleeve damage f O max ⁇ 700MPa , A sgt ⁇ 3.0%.
  • a production method of -165°C low temperature resistant steel bar mechanical connecting sleeve for LNG storage tank including the following steps:
  • the base material for the -165°C low temperature resistant steel bar mechanical connecting sleeve for LNG storage tank mentioned in step 1) includes the following components by weight percentage:
  • step 1) includes the following process flow:
  • Step 1) Specifically:
  • the end point C content is ⁇ 0.05%, and the temperature is 1620-1660°C;
  • the argon gas flow rate in the early stage of the LF furnace refining is 200-600NL/min, and the molten steel is not greatly turned over.
  • the argon gas flow rate in the later stage of the refining is 20-150NL/min to ensure that the molten steel surface is not exposed and the slag surface is slightly fluctuating.
  • the aluminum feeding line controls the O content in the steel, and the exit temperature of the LF furnace is 1635-1650°C;
  • the RH vacuum degassing the vacuum in the early stage of the RH furnace is less than or equal to 100 Pa, the holding time is greater than or equal to 10 minutes, and the gas flow rate is increased by 800-1200NL/min; the later period of retention time is greater than or equal to 10 minutes, and the gas flow rate is increased by 600NL/min; [H] ⁇ 1.5 When leaving the station at ppm, the exit temperature is 1575-1585°C; argon blowing and stirring are turned on, and the argon flow rate is 20-150 standard liters/min to ensure that the steel surface is not exposed and the slag surface fluctuates slightly;
  • the continuous casting billet is specifically: after the composition is qualified, it is continuously cast into a 150mm 2 billet, and the superheat (temperature) of the molten steel in the tundish is ⁇ 30°C;
  • the forged round steel is specifically: forged into round steel, used as a base material for sleeve production, forging heating temperature 1100-1300°C, initial forging temperature ⁇ 1100°C, and final forging temperature ⁇ 850°C.
  • Step 2) includes the following processes: car inner and outer circle ⁇ tapping machined inner teeth ⁇ quenching ⁇ tempering.
  • JG/T163-2013 "Sleeve for Mechanical Connection of Steel Bars", select the type of sleeve to be processed.
  • the outer circle is turned by a lathe, and the dimensional accuracy is IT7-IT6, and the roughness value is Ra6.3-0.8 ⁇ m;
  • the inner circle is turned by a CNC lathe, the dimensional accuracy is IT4-IT3, and the roughness value is Ra1.6-0.4 ⁇ m; tapping is used Machined internal teeth, the inclination of the teeth is 75 O , and the machining tolerance is less than 0.02P.
  • the quenching refers to heating to 880°C, holding for 1 hour, and adopting water quenching treatment
  • the tempering is heating to 550° C., holding for 2 hours, and then air cooling to room temperature.
  • step 2) in accordance with the BB5 sleeve model requirements in JG/T163-2013 "Sleeves for Mechanical Connection of Steel Bars", the sleeve base material is processed into sleeves, and quenched at 880°C ⁇ 1h to increase the strength, 550°C ⁇ 2h tempering heat treatment to improve low temperature toughness.
  • the C content of the general mechanical connecting sleeve is 0.42-0.47%. Taking into account the performance, especially the requirements of low temperature toughness, the C content in the application of the present invention is set to 0.06-0.12%. Reducing the C content is not only beneficial to improving the low temperature toughness of steel, but also beneficial to improving corrosion resistance and welding performance.
  • Si is cheap, can promote the precipitation of proeutectoid ferrite in steel, and has little effect on the formation of pearlite. It can increase the critical point of A 1 and A 3 and has a strong solid solution strengthening effect. However, Si Too high is detrimental to plastic toughness, and the Si content range is selected to be 0.30-0.50%.
  • Mn lowers the critical points of A 1 and A 3 , and delays the transformation of pearlite while also delaying the transformation of ferrite. Mn has the effect of solid solution strengthening and improving hardenability.
  • the Mn content range is selected to be 1.30-1.80%.
  • Nickel has the function of refining the grain of steel, improving the low temperature performance of steel, and has the effects of solid solution strengthening and improving hardenability, but it is expensive, and the Ni content range is selected to be 1.00-2.50%.
  • Vanadium The present invention uses V as a microalloying element. In order to improve the strength of steel and ensure the strength performance of steel, the addition of V is necessary. V is a rich resource in our country. V dissolved in austenite can significantly increase the hardenability of steel. Carbides or carbonitrides of V are precipitated in ferrite, which has a significant precipitation strengthening effect. The range of V content is selected to be 0.060-1.000%.
  • S and P are harmful elements in the steel for sleeves. The lower the requirement, the better.
  • the present invention is controlled by ⁇ 0.010%.
  • Hydrogen and oxygen are harmful gases, H can cause white spots and microcracks, and O forms oxide inclusions in steel, which will reduce the low-temperature toughness of the material.
  • the invention provides a -165°C low-temperature resistant steel bar mechanical connecting sleeve for an LNG storage tank, which is produced by the above-mentioned method.
  • the invention adopts a mechanical connection sleeve produced by a steel grade different from the prior art. By controlling the production method of the invention, it can meet the requirement of -165°C low temperature resistance for the reinforced concrete structure of low-temperature storage tanks such as LNG in China.
  • the room temperature mechanics of the sleeve The performance meets the requirements of the 500MPa grade I sleeve in the JG/J 107-2016 "Technical Specification for Mechanical Connection of Steel Bars", that is, the unidirectional tensile performance of the sleeve at room temperature f O max , the steel breakage ⁇ 550 MPa or the sleeve damage ⁇ 605 MPa ,U 0 ⁇ 0.1mm, A sgt ⁇ 6.0%; sleeve high-stress repeated tension and compression performance f O max , steel bar break ⁇ 550MPa or sleeve damage ⁇ 605MPa, u 20 ⁇ 0.3mm; sleeve large deformation repeated tension and compression Performance f O max , steel bar breaking ⁇ 550MPa or sleeve damage ⁇ 605MPa, u 4 ⁇ 0.3mm, u 8 ⁇ 0.6mm; sleeve -165°C unidirectional tensile mechanical properties f O
  • a production method of -165°C low temperature resistant steel bar mechanical connecting sleeve for LNG storage tank including the following steps:
  • Step 1) The preparation of the base material is specifically: electric arc furnace smelting, the end point C content is ⁇ 0.05%, the temperature is 1620-1660°C; the argon flow rate of the LF furnace is 200-600NL/min in the early stage of refining, and the molten steel is not greatly changed.
  • the flow rate of argon gas is 20-150NL/min to ensure that the steel liquid level is not exposed and the slag surface slightly fluctuates.
  • the aluminum feeding line in the late refining stage controls the O content in the steel.
  • the exit temperature of the LF furnace is 1635-1650°C; the vacuum degree of the RH furnace is ⁇ 100 Pa , Hold time ⁇ 10 minutes, increase gas flow rate 800 ⁇ 1200NL/min; later hold time ⁇ 10 minutes, increase gas flow rate 600NL/min; when [H] ⁇ 1.5ppm, exit station, exit temperature 1575-1585°C, turn on blowing Argon stirring, the argon flow rate is 20-150 standard liters/min, to ensure that the molten steel surface is not exposed and the slag surface fluctuates slightly.
  • the billet is continuously cast into a square billet, and the superheat (temperature) of the molten steel in the tundish is less than or equal to 30°C.
  • the steel for the mechanical connection sleeve of the -165°C low temperature resistant steel bar for the LNG storage tank of the present invention adopts specific chemical composition, and 6 furnaces of steel are smelted according to the above process.
  • the process control of electric arc furnace smelting, LF furnace, vacuum degassing and continuous casting is shown Table 1 to Table 2.
  • the billet is forged into round steel and used as the base material of the sleeve.
  • the forging heating temperature is 1100-1300°C
  • the initial forging temperature is ⁇ 1100°C
  • the final forging temperature is ⁇ 850°C.
  • the outer circle is turned by a lathe, and the dimensional accuracy is IT7-IT6, and the roughness value is Ra6.3-0.8 ⁇ m; the inner circle is turned by a CNC lathe, the dimensional accuracy is IT4-IT3, and the roughness value is Ra1.6-0.4 ⁇ m; tapping is used Machined internal teeth, the inclination of the teeth is 75 O , and the machining tolerance is less than 0.02P.
  • ReL is the yield strength
  • R m is the tensile strength
  • a gt is the total elongation under the maximum force.
  • f O max is the tensile strength
  • u 0 is the residual deformation
  • a sgt is the total elongation under the maximum force.
  • Table 7 shows the high-stress repeated tension and compression performance of sleeves in Examples 1-3 of the present invention.
  • f O max is the tensile strength
  • u 20 is the residual deformation
  • f O max is the tensile strength
  • u 4 and u 8 are residual deformations.
  • ReL is the yield strength
  • R m is the tensile strength
  • a gt is the total elongation under the maximum force.
  • f O max is the tensile strength
  • a gt is the total elongation under the maximum force

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Abstract

本发明提供了一种LNG储罐用耐-165℃低温钢筋机械连接套筒及生产方法，生产方法为：将套筒母材经车内外圆→攻丝机加工内牙→淬火→回火工艺制作为套筒；母材成分：C 0.06-0.12％，Si 0.30-0.50％，Mn 1.30-1.80％，Ni 1.00-2.50％，V 0.060-1.000％，P≤0.010％、S≤0.010％，H≤0.00015％，O≤0.0015％，其余为Fe和杂质元素。本发明采用与现有技术不同的钢种生产的机械连接套筒，控制生产方法，生产的套筒可满足我国LNG等低温储罐钢筋混凝土结构耐-165℃低温的要求。

Description

一种LNG储罐用耐-165℃低温钢筋机械连接套筒及生产方法 技术领域
本发明属于低温用钢材料及其制备工艺，尤其涉及一种LNG储罐用耐-165℃低温钢筋机械连接套筒及生产方法。
背景技术
钢筋常用作钢筋混凝土结构的骨架材料，对建筑结构起着支撑、加固的作用，有时还在一定的低温环境下使用，典型的建筑结构是液化天然气(简称LNG)储罐。通常LNG储存温度为-165℃，而低温下金属材料的性质与常温状态相比变化较大，为保证LNG储罐的安全,需选用耐低温性质的金属材料。长期以来，低温钢筋需要从国外进口，目前国内马钢等实现了低温钢筋的国产化批量应用。
低温钢筋采用定尺交货，在施工中需要采用套筒机械连接后使用。由于LNG储罐的设计温度为-165℃，不仅要求套筒有良好的室温性能，而且为保证当LNG发生泄漏事故时储罐的安全，要求在-165℃条件下具有良好的强韧性能。随着我国沿海港口城市LNG储罐的建设力度不断加大，对低温钢筋机械连接套筒的需求增加，但国内还没用低温钢筋机械连接套筒用钢的具体成分及制备方法的公开报道。
低温钢筋机械连接套筒的要求是：
(1)套筒的室温力学性能满足JG/J 107-2016《钢筋机械连接技术规程》中500MPa级钢筋Ⅰ级套筒的要求；
(2)套筒常温单向拉伸性能f O max，钢筋拉断≥550MPa或套筒破坏≥605MPa，u 0≤0.1mm，A sgt≥6.0％；套筒高应力反复拉压性能f O max，钢筋拉断≥550MPa或套筒破坏≥605MPa，u 20≤0.3mm；套筒大变形反复拉压性能f O max，钢筋拉断≥550MPa或套筒破坏≥605MPa，u 4≤0.3mm，u 8≤0.6mm。
(3)套筒-165℃单向拉伸力学性能f O max，钢筋拉断≥635MPa或套筒破坏≥700MPa，A sgt≥3.0％。
中国发明专利《一种钢筋连接套筒，申请号201010209694.1》，公开了一种钢筋连接套筒，包括圆筒状的套筒本体，套筒本体内表设置有内螺纹，套筒本体外表沿纵向设置有数根向外凸起的纵肋，其特点在于所述纵肋端头处为高度平滑降低的斜形设置。所述高度平滑降低是指呈斜线形或者斜向的弧形等形状。可有效地提高肋条强度，进而保证连接牢靠性，同时还可以达到节省锻件材料，降低成本的效果。中国发明专利《一种钢筋连接套筒，申请号 201010608926.0》，提供一种钢筋连接套筒，包括内通孔，所述套筒外表面设有扳手卡位，所述扳手卡位为棱齿，所述棱齿个数大于等于4个，所述内通孔为圆柱形，所述内通孔中设有螺纹，所述内通孔中所设螺纹与钢筋端头螺纹相啮合。该钢筋连接套筒，其横截外表面呈多棱齿形，克服了现有的钢筋连接套筒圆形外表面所带来的不易旋紧、易打滑的缺陷。但均不能用于-165℃设计温度下低温钢筋的机械连接。
发明内容
本发明提供的一种LNG储罐用耐-165℃低温钢筋机械连接套筒及其生产方法，生产的套筒的室温力学性能满足JG/J 107-2016《钢筋机械连接技术规程》中500MPa级钢筋Ⅰ级套筒的要求，-165℃力学性能满足钢筋拉断f O max≥635MPa或套筒破坏f O max≥700MPa，A sgt≥3.0％的要求。
本发明具体技术方案如下：
一种LNG储罐用耐-165℃低温钢筋机械连接套筒的生产方法，包括以下步骤：
1)LNG储罐用耐-165℃低温钢筋机械连接套筒用母材的制备；
2)将母材加工成套筒。
步骤1)中所述LNG储罐用耐-165℃低温钢筋机械连接套筒用母材，包括以下重量百分比的成分：
C 0.06-0.12％，Si 0.30-0.50％，Mn 1.30-1.80％，Ni 1.00-2.50％，V 0.060-1.000％，P≤0.010％、S≤0.010％，H≤0.00015％，O≤0.0015％，其余为Fe和杂质元素。
进一步的，步骤1)包括以下工艺流程：
电弧炉冶炼→LF炉精炼→RH真空脱气→连铸方坯→锻造圆钢。
步骤1)具体为：
所述电弧炉冶炼，终点C含量≤0.05％、温度1620-1660℃；
所述LF炉精炼，LF炉精炼前期氩气流量200-600NL/min，以钢水不大翻为宜，精炼后期氩气流量20-150NL/min，保证钢液面不裸露、渣面微微波动，精炼后期喂铝线控制钢中O含量，LF炉出站温度1635-1650℃；
所述RH真空脱气：RH炉前期真空度≤100帕，保持时间≥10分钟，提升气体流量800-1200NL/min；后期保持时间≥10分钟，提升气体流量600NL/min；[H]≤1.5ppm时出站，出站温度1575-1585℃；开启吹氩搅拌，氩气流量20-150标升/分钟，保证钢液面不裸露，渣面微微波动；
所述连铸方坯具体为：成分合格后，经连铸成150mm 2方坯，中间包钢水过热度(温度) ≤30℃；
所述锻造圆钢具体为：锻造为圆钢，作为套筒制作的母材，锻造加热温度1100-1300℃，始锻温度≥1100℃，终锻温度≥850℃。
步骤2)包括以下工艺：车内外圆→攻丝机加工内牙→淬火→回火。
根据JG/T163-2013《钢筋机械连接用套筒》选择需要加工的套筒型号。采用车床车外圆，尺寸精度为IT7-IT6，粗糙度值Ra6.3-0.8μm；采用数控车床车内圆，尺寸精度为IT4-IT3，粗糙度值Ra1.6-0.4μm；采用攻丝机加工内牙，牙倾角75 O，加工公差≤0.02P。
所述淬火是指加热到880℃、保温1h，采用水淬火处理；
所述回火为加热到550℃、保温2h、再空冷至室温。
步骤2)中，按照JG/T163-2013《钢筋机械连接用套筒》中BB5套筒型号要求，将套筒母材加工成套筒，并经880℃×1h淬火，提高强度，550℃×2h回火热处理，改善低温韧性。
本发明钢各元素的作用如下：
碳：目前一般机械连接套筒的C含量为0.42-0.47％，综合考虑性能、尤其是低温韧性的要求，本发明申请的C含量取0.06-0.12％。降低C含量不仅有利于改善钢的低温韧性，还有利于改善耐蚀性能、焊接性能等。
硅：Si价格便宜，在钢中能促进先共析铁素体析出，同时对珠光体的形成影响不大，并能提高A 1、A 3临界点并有强烈的固溶强化作用，但Si过高对塑韧性不利，Si含量范围选择为0.30-0.50％。
锰：Mn降低A 1、A 3临界点，在推迟珠光体转变的同时，也推迟铁素体转变，Mn具有固溶强化和提高淬透性作用，Mn含量范围选择为1.30-1.80％。
镍：Ni具有细化钢的晶粒、改善钢的低温性能的作用，并具有固溶强化、提高淬透性作用，但其价格昂贵，Ni含量范围选择为1.00-2.50％。
钒：本发明采用V作为微合金化元素，为了提高钢的强度，保证钢的强度性能，V的加入是必要的。V是我国的富有资源，溶于奥氏体中的V能显著增加钢的淬透性，在铁素体中析出V的碳化物或碳氮化物，具有显著的析出强化作用。V含量范围选择为0.060-1.000％。
硫、磷：S、P在套筒用钢中属于有害元素，要求越低越好，本发明均按≤0.010％控制。
氢、氧：H、O属于有害气体，H能造成白点微裂纹，O在钢中形成氧化物夹杂，将降低材料的低温韧性。
本发明提供的一种LNG储罐用耐-165℃低温钢筋机械连接套筒，采用上述方法生产得到。
本发明采用与现有技术不同的钢种生产的机械连接套筒，通过控制本发明的生产方法， 可满足我国LNG等低温储罐钢筋混凝土结构耐-165℃低温的要求，套筒的室温力学性能满足JG/J 107-2016《钢筋机械连接技术规程》中500MPa级钢筋Ⅰ级套筒的要求，即套筒常温单向拉伸性能f O max，钢筋拉断≥550MPa或套筒破坏≥605MPa，u 0≤0.1mm，A sgt≥6.0％；套筒高应力反复拉压性能f O max，钢筋拉断≥550MPa或套筒破坏≥605MPa，u 20≤0.3mm；套筒大变形反复拉压性能f O max，钢筋拉断≥550MPa或套筒破坏≥605MPa，u 4≤0.3mm，u 8≤0.6mm；套筒-165℃单向拉伸力学性能f O max，钢筋拉断≥635MPa或套筒破坏≥700MPa，A sgt≥3.0％。
具体实施方式
实施例1-实施例6
一种LNG储罐用耐-165℃低温钢筋机械连接套筒的生产方法，包括以下步骤：
1)LNG储罐用耐-165℃低温钢筋机械连接套筒用钢母材的制备；
2)将套筒母材加工成套筒。
具体工艺流程：电弧炉冶炼→LF炉精炼→RH真空脱气→连铸方坯→锻造圆钢→车内外圆→攻丝机加工内牙→淬火→回火。
步骤1)母材的制备具体为：电弧炉冶炼，终点C含量≤0.05％、温度1620-1660℃；LF炉精炼前期氩气流量200-600NL/min，以钢水不大翻为宜，精炼后期氩气流量20-150NL/min，保证钢液面不裸露、渣面微微波动，精炼后期喂铝线控制钢中O含量，LF炉出站温度1635-1650℃；RH炉前期真空度≤100帕，保持时间≥10分钟，提升气体流量800～1200NL/min；后期保持时间≥10分钟，提升气体流量600NL/min；[H]≤1.5ppm时出站，出站温度1575-1585℃，开启吹氩搅拌，氩气流量20-150标升/分钟，保证钢液面不裸露，渣面微微波动。成分合格后，经连铸成方坯，中间包钢水过热度(温度)≤30℃。
本发明LNG储罐用耐-165℃低温钢筋机械连接套筒用钢采用特定化学成分，按照上述工艺冶炼6炉钢，其中电弧炉冶炼、LF炉、真空脱气及连铸过程工艺控制情况见表1-表2所示。
表1本发明实施例1-6中冶炼、LF、RH工艺控制情况
Figure PCTCN2020135058-appb-000001
Figure PCTCN2020135058-appb-000002
方坯经锻造成圆钢，作为套筒制作的母材，锻造加热温度1100-1300℃，始锻温度≥1100℃，终锻温度≥850℃。
表2本发明实施例1-6中连铸、锻造工艺控制情况
Figure PCTCN2020135058-appb-000003
实施例1-6所用的LNG储罐用耐-165℃低温钢筋机械连接套筒用钢的化学成分件见表3，余量为铁和不可避免的杂质。
表3本发明实施例1-6的成分(单位：wt％)
Figure PCTCN2020135058-appb-000004
本发明实施例1-6上述钢加工套筒型号尺寸精度及公差见表4。采用车床车外圆，尺寸精度为IT7-IT6，粗糙度值Ra6.3-0.8μm；采用数控车床车内圆，尺寸精度为IT4-IT3，粗糙度值Ra1.6-0.4μm；采用攻丝机加工内牙，牙倾角75 O，加工公差≤0.02P。
表4本发明实施例1-6的外形尺寸及公差
Figure PCTCN2020135058-appb-000005
本发明实施例1-6上述钢的单向拉伸力学性能见表5。
表5本发明实施例1-6钢的单向拉伸力学性能
Figure PCTCN2020135058-appb-000006
其中，R eL为屈服强度，R m为抗拉强度，A gt为最大力下总伸长率。
本发明实施例1-6生产的套筒单向拉伸力学性能见表6。
表6本发明实施例1-6套筒单向拉伸力学性能
Figure PCTCN2020135058-appb-000007
Figure PCTCN2020135058-appb-000008
其中，f O max为抗拉强度，u 0为残余变形，A sgt为最大力下总伸长率。
本发明实施例1-3套筒高应力反复拉压性能见表7。
表7本发明实施例1-6套筒高应力反复拉压性能
Figure PCTCN2020135058-appb-000009
其中，f O max为抗拉强度，u 20为残余变形。
本发明实施例1-6套筒大变形反复拉压性能见表8。
表8本发明实施例1-6套筒大变形反复拉压性能
Figure PCTCN2020135058-appb-000010
Figure PCTCN2020135058-appb-000011
其中，f O max为抗拉强度，u 4、u 8为残余变形。
本发明实施例1-6套筒-165℃单向拉伸力学性能见表9。
表9本发明实施例1-6套筒单向拉伸力学性能
Figure PCTCN2020135058-appb-000012
其中，R eL为屈服强度，R m为抗拉强度，A gt为最大力下总伸长率。
本发明实施例1-6套筒-165℃单向拉伸性能见表10。
表10本发明实施例1-6套筒-165℃单向拉伸性能
Figure PCTCN2020135058-appb-000013
其中，f O max为抗拉强度，A gt为最大力下总伸长率。

Claims (10)

  1. 一种LNG储罐用耐-165℃低温钢筋机械连接套筒的生产方法，其特征在于，所述生产方法包括以下步骤：
    1)LNG储罐用耐-165℃低温钢筋机械连接套筒用母材的制备；
    2)将母材加工成套筒；
    步骤1)中所述LNG储罐用耐-165℃低温钢筋机械连接套筒用母材，包括以下重量百分比的成分：
    C 0.06-0.12％，Si 0.30-0.50％，Mn 1.30-1.80％，Ni 1.00-2.50％，V 0.060-1.000％，P≤0.010％、S≤0.010％，H≤0.00015％，O≤0.0015％，其余为Fe和杂质元素。
  2. 根据权利要求1所述的生产方法，其特征在于，步骤1)包括以下工艺流程：
    电弧炉冶炼→LF炉精炼→RH真空脱气→连铸方坯→锻造圆钢。
  3. 根据权利要求2所述的生产方法，其特征在于，所述电弧炉冶炼，终点C含量≤0.05％、温度1620-1660℃。
  4. 根据权利要求2所述的生产方法，其特征在于，所述LF炉精炼，LF炉精炼前期氩气流量200-600NL/min，精炼后期氩气流量20-150NL/min，LF炉出站温度1635-1650℃。
  5. 根据权利要求2所述的生产方法，其特征在于，所述RH真空脱气：RH炉前期真空度≤100帕，保持时间≥10分钟，提升气体流量800～1200NL/min；后期保持时间≥10分钟，提升气体流量600NL/min；[H]≤1.5ppm时出站，出站温度1575-1585℃；开启吹氩搅拌，氩气流量20-150标升/分钟。
  6. 根据权利要求2所述的生产方法，其特征在于，所述连铸方坯具体为：经连铸成方坯，中间包钢水过热度≤30℃。
  7. 根据权利要求2所述的生产方法，其特征在于，所述锻造圆钢具体为：锻造加热温度1100-1300℃，始锻温度≥1100℃，终锻温度≥850℃。
  8. 根据权利要求1所述的生产方法，其特征在于，步骤2)包括以下工艺：车内外圆→攻丝机加工内牙→淬火→回火；所述淬火是指加热到880℃、保温1h，采用水淬火处理。
  9. 根据权利要求8所述的生产方法，其特征在于，所述回火为加热到550℃、保温2h、再空冷至室温。
  10. 一种权利要求1-9任一项所述方法生产的LNG储罐用耐-165℃低温钢筋机械连接套筒。
PCT/CN2020/135058 2019-12-16 2020-12-10 一种lng储罐用耐-165℃低温钢筋机械连接套筒及生产方法 WO2021121109A1 (zh)

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