WO2023143290A1 - 一种耐硫酸铝腐蚀的高强度管道及其制造方法 - Google Patents

一种耐硫酸铝腐蚀的高强度管道及其制造方法 Download PDF

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WO2023143290A1
WO2023143290A1 PCT/CN2023/072827 CN2023072827W WO2023143290A1 WO 2023143290 A1 WO2023143290 A1 WO 2023143290A1 CN 2023072827 W CN2023072827 W CN 2023072827W WO 2023143290 A1 WO2023143290 A1 WO 2023143290A1
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corrosion
pipeline
resistant layer
layer
slab
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PCT/CN2023/072827
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English (en)
French (fr)
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闫博
焦四海
王治宇
李占杰
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宝山钢铁股份有限公司
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Publication of WO2023143290A1 publication Critical patent/WO2023143290A1/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
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B1/00—Layered products having a non-planar shape
    • B32B1/08—Tubular products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
    • B32B15/011—Layered products comprising a layer of metal all layers being exclusively metallic all layers being formed of iron alloys or steels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/18—Layered products comprising a layer of metal comprising iron or steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/06—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the heating method
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/10—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/10—Interconnection of layers at least one layer having inter-reactive properties
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
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    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/714—Inert, i.e. inert to chemical degradation, corrosion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2597/00—Tubular articles, e.g. hoses, pipes
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/20—Controlling water pollution; Waste water treatment

Definitions

  • the invention relates to a pipeline and a manufacturing method thereof, in particular to a high-strength pipeline resistant to aluminum sulfate corrosion and a manufacturing method thereof.
  • UPVC and CPVC materials are usually used to manufacture the above-mentioned pipeline equipment for transporting aluminum sulfate.
  • UPVC and CPVC materials have the problems of high processing difficulty, large expansion coefficient during use, low strength and easy softening and deformation, and their practical application effect is not ideal.
  • 300 series austenitic stainless steel to prepare the above-mentioned equipment and pipelines.
  • the structural strength of 300 series austenitic stainless steel is lower and the thickness required is larger, which increases the amount of materials used; at the same time, the welding and machining of 300 series austenitic stainless steel are more difficult;
  • 300 series stainless steel itself contains more precious metal elements such as Cr, Ni, etc., and the cost of using pure stainless steel is relatively high in the process of production, fabrication and installation.
  • the present invention expects to obtain a new pipeline, which adopts a reasonable design, which can form a corrosion-resistant layer resistant to aluminum sulfate on the surface of the carbon steel base, and finally A pipeline with corrosion resistance to aluminum sulfate, good mechanical properties and high economy is formed, which has great economic and social benefits.
  • One of the objectives of the present invention is to provide a pipeline, which adopts a reasonable design, which can form a corrosion-resistant layer resistant to aluminum sulfate on the surface of the carbon steel base, and finally form a corrosion-resistant layer with aluminum sulfate corrosion resistance and good mechanical properties.
  • a pipeline which adopts a reasonable design, which can form a corrosion-resistant layer resistant to aluminum sulfate on the surface of the carbon steel base, and finally form a corrosion-resistant layer with aluminum sulfate corrosion resistance and good mechanical properties.
  • it has great economic and social benefits.
  • the pipeline described in the present invention can solve the problem of 300 series stainless steel or stainless steel used in the environment of aluminum sulfate corrosion medium in the water supply station.
  • the essential pain point of carbon steel; the pipeline can be effectively applied to the pipeline equipment used in the aluminum sulfate medium environment of the water supply station, and greatly improve the applicability, safety and durability of these pipeline equipment, while avoiding secondary damage to the water quality pollute.
  • the present invention provides a pipeline, the pipeline has a corrosion-resistant layer and a base layer in the thickness direction, the corrosion-resistant layer is at least located on the inner wall of the pipeline, and the corrosion-resistant layer contains Fe and unavoidable impurities In addition, it also contains the following chemical elements in wt%:
  • the corrosion-resistant layer contains the following chemical elements in wt %:
  • the balance is Fe and unavoidable impurities
  • the aluminum sulfate corrosion resistance of the corrosion-resistant layer In the pipeline of the present invention, in order to ensure the aluminum sulfate corrosion resistance of the pipeline, the aluminum sulfate corrosion resistance of the corrosion-resistant layer must first be ensured.
  • the working conditions of aluminum sulfate corrosion medium in water supply plants or water supply pipe networks are as follows: the mass concentration of aluminum sulfate is below 30%, and the working temperature is 0-40°C.
  • the inventors optimized the chemical element composition of the pipeline corrosion-resistant layer, especially A certain amount of Cu element is added, and a special corrosion resistance equivalent formula and requirements are designed to control Cr, Mo, N and Cu to meet the following inequality: Cr+3.3 ⁇ Mo+16 ⁇ N+10 ⁇ Cu ⁇ 26.0%.
  • Cu can further improve the corrosion resistance of steel, especially in reducing media such as sulfate ions.
  • reducing media such as sulfate ions.
  • the addition of copper will affect the hot workability of the material, but for the composite material pipe of the present invention, the proportion of the corrosion resistance layer is low, and the influence on the overall hot workability can be ignored.
  • the design principle of the chemical elements of the corrosion-resistant layer is as follows:
  • C is a strong austenite-forming element, which can replace nickel to a certain extent, promote the formation of austenite, stabilize the austenite structure, and increase the strength of stainless steel.
  • the content of C element should not be too high.
  • the carbon content is too high, the combination of carbon and chromium will form chromium-rich carbides at the grain boundaries, resulting in intergranular corrosion. Therefore, in order to exert the beneficial effects of the C element, in the corrosion-resistant layer of the present invention, the mass percentage of the C element is controlled to satisfy 0 ⁇ C ⁇ 0.08%.
  • Si element is mainly used for deoxidation during the smelting process, so generally a certain amount of silicon needs to be added. However, it should be noted that the Si element content should not be too high. When the Si content is too high, the solubility of nitrogen will be reduced. Therefore, in the corrosion-resistant layer of the present invention, the mass percentage of Si element is controlled between 0.3-0.6%.
  • the Mn element is a strong austenite stabilizing element, and can increase the solubility of nitrogen in steel.
  • manganese has a negative impact on the corrosion resistance of austenitic stainless steel. Therefore, considering the beneficial effects and adverse effects of the Mn element, in the corrosion-resistant layer of the present invention, the mass percentage of the Mn element is controlled at 0.5- Between 2.0%, preferably 1.10-2.0%.
  • Ni is the most important element for forming and stabilizing the austenite phase. Adding an appropriate amount of Ni element can ensure the formation of austenite structure of the steel at room temperature. However, the price of nickel is expensive, in order to ensure a relatively low cost, it is not appropriate to add excessive nickel to the steel. Therefore, in the corrosion-resistant layer of the present invention, the mass percentage of Ni element is controlled between 11.00-13.00%.
  • Cr In the corrosion-resistant layer of the present invention, Cr is the guarantee for the stainless steel and corrosion resistance. Generally, the minimum chromium content for corrosion resistance is 10.5%. Since chromium is an element that significantly enhances the corrosion resistance, in order to ensure good corrosion resistance, the chromium content in the steel of the present invention is controlled above 16.50%. However, it should be noted that Cr is also the main ferrite-forming element, and too high a content of chromium will make it difficult to ensure that the corrosion-resistant layer obtains austenite structure at room temperature. Therefore, in the corrosion-resistant layer of the present invention, the mass percentage of Cr element is controlled between 16.50-18.00%.
  • Mo is an important element to improve corrosion resistance, and its mechanism is to stabilize the passive
  • molybdenum can also act synergistically with nitrogen to further improve pitting corrosion resistance, so the main function of adding molybdenum is to improve corrosion resistance.
  • the Mo element content should not be too high, too high molybdenum content will increase the cost of the alloy, in order to ensure a relatively low cost, in the corrosion-resistant layer of the present invention, the mass percentage of Mo element is controlled at 2.00-3.00% between.
  • N is a very strong element that forms, stabilizes and expands the austenite zone. Adding an appropriate amount of N element can effectively improve the pitting corrosion resistance of stainless steel. However, when the nitrogen content in the steel is too high, it will increase the risk of nitrogen-containing intermetallic phase formation, and at the same time increase the difficulty of smelting and hot processing, making it difficult to produce. Therefore, in the corrosion-resistant layer of the present invention, the mass percentage of N element is controlled between 0.02-0.15%.
  • Cu In the corrosion-resistant layer of the present invention, adding an appropriate amount of Cu element can improve the corrosion resistance of the material. At the same time, Cu element can cooperate with molybdenum to stabilize the passivation film and promote the enrichment of chromium in the passivation film, thereby improving the pitting corrosion resistance. Therefore, in the corrosion-resistant layer of the present invention, the mass percentage of Cu element is controlled between 0.01-0.3%, preferably 0.12-0.3%, more preferably 0.12-0.22%.
  • the corrosion-resistant layer of the pipeline while controlling the mass percentage of a single chemical element, the elements Cr, Mo, N and Cu are further controlled to satisfy: Cr+3.3 ⁇ Mo+16 ⁇ N+10 ⁇ Cu ⁇ 26.0%. Each element in the formula is substituted into the mass percentage of the corresponding element. Through such control, it can be further ensured that the corrosion resistant layer has quite excellent corrosion resistance in the environment of aluminum sulfate.
  • unavoidable impurities include: S ⁇ 0.030%; P ⁇ 0.045%.
  • both P and S are unavoidable impurity elements.
  • the lower the content of the impurity elements in the steel the better, if conditions permit.
  • the base layer contains the following chemical elements in wt %:
  • the balance is Fe and unavoidable impurities.
  • the base layer also contains at least one of the following chemical elements:
  • the inventor also selected the chemical composition of the base carbon steel. Good machinability.
  • C is an austenite stabilizing element, which can play a role of solid solution strengthening in steel, and can obviously improve the strength of steel.
  • the content of C element in the steel should not be too high.
  • the mass percentage of the C element is controlled between 0.01-0.20%.
  • Controlling the mass percentage of the C element to 0.01-0.20% not only ensures that the steel plate can obtain a certain hardness and strength in the air-cooled condition after rolling, but also avoids deterioration of the welding performance of the base steel.
  • Si In the base layer of the present invention, adding Si element to the steel can effectively improve the purity and deoxidation of the steel. Si element can play solid solution strengthening effect in steel, but Si element is unfavorable for the weldability of material; In the present invention, control the silicon content of base carbon steel to be less than or equal to 0.50%, will not affect the corrosion resistance of corrosion-resistant layer There is no impact on the properties, and the base carbon steel has good welding performance. Therefore, in the base layer of the present invention, the mass percentage of Si element is controlled between 0.10-0.50%.
  • Mn In the base layer of the present invention, adding an appropriate amount of Mn element to the steel can delay the pearlite transformation, reduce the critical cooling rate, and improve the hardenability of the steel; at the same time, the Mn element also has the effect of solid solution strengthening, which is the The main solid solution strengthening elements in However, Mn element should not be added too much. When the content of Mn element in steel is too high, segregation zone and martensitic structure will easily appear, which will have an adverse effect on the toughness of steel, and the appearance of segregation zone will also affect the corrosion resistance of steel. will be reduced.
  • the manganese content in low-carbon micro-alloyed steel does not exceed 2.00%, and at this time, the Mn element contained in the base carbon steel will not have adverse effects on the corrosion-resistant layer. Based on this, in the base layer of the present invention, the mass percentage of Mn element is controlled between 0.50-2.00%.
  • Al is a strong deoxidizing element. Al is added to ensure that the oxygen content in the steel is as low as possible. After deoxidation, the excess Al and N elements in the steel can combine to form AlN precipitates, thereby improving the strength of the steel and refining the austenite grain size of the steel during heat treatment. However, if the Al content is too high, it is easy to produce inclusions of alumina. Based on this, in the base layer of the present invention, the mass percentage of Al element is controlled between 0.02-0.04%.
  • Ti is a strong carbide forming element. Adding a small amount of Ti in the steel is beneficial to fix the N in the steel, and the TiN formed by the combination of Ti and N can make the base layer austenite The grains do not grow too much, and the original austenite grain size is refined.
  • Ti can also be combined with carbon and sulfur in steel to form compounds such as TiC, TiS, Ti 4 C 2 S 2 , which can exist in the form of inclusions and second phase particles.
  • these carbonitride precipitates of Ti can also prevent grain growth in the heat-affected zone during welding and improve welding performance.
  • the mass percentage of Ti element is controlled between 0.005-0.014%.
  • Nb is a strong carbide forming element, and a small amount of niobium is added to the base carbon steel mainly to increase the recrystallization temperature to cooperate with the formation of the base slab and the corrosion-resistant layer slab.
  • the higher final rolling temperature of the composite plate in the subsequent rolling process makes the grain refinement of the base layer after rolling in the recrystallization and non-recrystallization regions, which is conducive to improving the low temperature impact toughness of the base layer.
  • excessively high Nb content will lead to large-sized Nb-rich precipitates and reduce the plasticity and toughness of the material. Based on this, in the base layer of the present invention, the mass percentage of Nb element is controlled between 0.005-0.020%.
  • element N In the base layer of the present invention, element N can form second-phase particles with titanium and aluminum to refine grains and improve strength. However, when the mass percentage of N element is too high, the amount of TiN produced is too large and the particles are too coarse, which will affect the plasticity of the base carbon plate of the composite material of the present invention. Based on this, in the base layer of the present invention, the mass percentage of N element is controlled to be N ⁇ 0.006%.
  • B can greatly improve the hardenability of steel.
  • the high corrosion-resistant composite plate corrosion-resistant layer slab + base slab
  • it is required to obtain ferrite + pearlescent as much as possible Body structure, inhibit the formation of bainite.
  • the B content is too high, it will easily cause segregation and form compounds with oxygen and nitrogen, which cannot achieve the corresponding purpose. Therefore, in the present invention, it is required to control the addition amount of B element in the base layer to satisfy 0 ⁇ B ⁇ 0.0003%.
  • Ni is an element that stabilizes austenite, and it has a certain effect on improving the strength of steel.
  • adding an appropriate amount of Ni to steel, especially adding an appropriate amount of Ni to quenched and tempered steel can greatly improve the low temperature impact toughness of steel.
  • the Ni content is too high, the carbon equivalent will be increased and the welding performance will be affected; at the same time, Ni is a rare metal, which will lead to resource waste and cost increase.
  • an appropriate amount of Ni can be added, and the amount of Ni element added can be controlled to satisfy 0 ⁇ Ni ⁇ 0.20%.
  • the segregation tendency of the Cr element is smaller than that of Mn.
  • Mn content of the base carbon steel is high, and when there are obvious segregation bands and banded structures in the steel, the Mn content can be appropriately reduced, and the insufficient part can be reduced by Cr substitution.
  • adding an appropriate amount of Cr element to the base carbon steel is also beneficial to inhibit the diffusion of Cr in the corrosion-resistant layer to the base.
  • too high Cr content will affect the phase transition temperature of the substrate and affect the mechanical properties of the substrate. Based on this, in the base layer of the present invention, 0 ⁇ Cr ⁇ 0.22% of Cr elements can be added.
  • Mo element can significantly refine grains and improve the strength and toughness of steel.
  • Mo can also reduce the temper brittleness of steel, and at the same time, very fine carbides can be precipitated during tempering, which can significantly strengthen the base layer of steel.
  • the addition of Mo element is also beneficial to suppress the self-temper brittleness of the steel plate that is easy to occur during the air cooling process.
  • the Mo content is too high, the carbon equivalent will be increased, which will affect the welding performance, resulting in resource waste and cost increase. Based on this, in the base layer of the present invention, an appropriate amount of Mo can be added, and the amount of added Mo element can be controlled to satisfy 0 ⁇ Mo ⁇ 0.12%.
  • the thickness of the single-layer corrosion-resistant layer accounts for 0.5-10% of the total thickness of the pipeline, and the base layer contains the following chemical elements in wt %:
  • the balance is Fe and unavoidable impurities.
  • unavoidable impurities include: S ⁇ 0.010%; P ⁇ 0.015%.
  • P and S are unavoidable impurity elements in the base layer, and S will combine with Mn in the steel to form plastic inclusion manganese sulfide, which is especially unfavorable to the lateral plasticity and toughness of the steel. Therefore, the S in the base layer
  • the content of elements should be as low as possible.
  • P is also a harmful element in steel, which will seriously damage the plasticity and toughness of the steel plate.
  • both S and P are unavoidable impurity elements, and the lower the better, considering the actual steelmaking level of the steel plant, in the base layer described in the present invention, the S and P elements are controlled to satisfy : S ⁇ 0.010%; P ⁇ 0.015%.
  • the thickness of the single-layer corrosion-resistant layer accounts for 0.5-50% of the total thickness of the pipeline, more preferably, the thickness of the single-layer corrosion-resistant layer accounts for 2.5-28.6% of the total thickness of the pipeline. That is to say, if both the inner surface and the outer surface of the pipeline have corrosion-resistant layers, the thickness of each corrosion-resistant layer accounts for 0.5-50% of the total thickness of the pipeline. If only the inner surface of the pipeline has a corrosion-resistant layer, the thickness of the corrosion-resistant layer accounts for 0.5-50% of the total thickness of the pipeline.
  • the selection of the thickness of the corrosion-resistant layer plays a crucial role in obtaining good corrosion resistance, mechanical properties and formability of the pipeline described in the present invention.
  • the corrosion-resistant layer is too thick, it will affect the mechanical properties and production cost of the material; and when the corrosion-resistant layer is too thin, the corrosion resistance and service life of the material will be reduced. Therefore, in the present invention, it is preferable to control the thickness of the single-layer corrosion-resistant layer to account for 0.5-50% of the total thickness of the pipeline, and more preferably to control the thickness of the single-layer corrosion-resistant layer to account for 2.5-28.6% of the total thickness of the pipeline.
  • the thickness of the single-layer corrosion-resistant layer accounts for 2.5-20% of the total thickness of the pipeline.
  • the microstructure of the base layer is ferrite+pearlite or ferrite+pearlite+bainite; the microstructure of the corrosion-resistant layer is austenite.
  • the thickness of the diffusion layer or transition layer is about 50 ⁇ m-120 ⁇ m.
  • the yield strength of the pipeline is ⁇ 426MPa
  • the tensile strength is ⁇ 580MPa
  • the elongation is ⁇ 31%
  • the uniform corrosion rate (that is, the average corrosion rate) ⁇ 0.05 in an environment with a temperature ⁇ 40°C and an aluminum sulfate concentration ⁇ 30wt% mm/year.
  • another object of the present invention is to provide a method for manufacturing the above-mentioned pipeline, which is simple and feasible, and can effectively prepare the above-mentioned pipeline.
  • the present invention proposes the method for manufacturing above-mentioned pipeline, and it comprises the steps:
  • the corrosion-resistant layer slab and the base slab are assembled to obtain a composite slab; wherein, the preferred single-layer corrosion-resistant layer thickness accounts for 0.5-50% of the total thickness of the composite slab, more preferably 2.5-28.6% (
  • the single-layer corrosion-resistant layer/total thickness ratio of the pipeline in the finished pipeline is basically the same as the thickness ratio in this step);
  • smelting and casting can be designed according to the chemical composition to prepare the corrosion-resistant layer slab and the base layer slab, and then the two can be assembled to obtain a high-corrosion-resistant composite plate (corrosion-resistant layer plate + base layer plate ).
  • the obtained high-corrosion-resistant composite plate is further heated, rolled, and coiled to obtain a hot-rolled coil with a composite interlayer structure, and the hot-rolled coil is subjected to surface treatment and then made into a tube to obtain the present invention. pipeline.
  • the inventor has optimized the heating and rolling process of step (3) to ensure that a transition layer structure of a certain thickness can be formed between the corrosion-resistant layer and the base layer through processes such as heating and rolling. Realize the complete metallurgical combination of the corrosion-resistant layer and the base layer, so as to ensure the corrosion resistance and mechanical properties of aluminum sulfate, while improving the applicability and economical efficiency of the material, which can solve the problem of current water supply stations in the environment of aluminum sulfate corrosion
  • the prepared corrosion-resistant layer slab and the base slab can be pretreated, and the slab bonding surface is welded and sealed around, and the joint surface after welding and sealing Vacuuming is carried out to complete the Formation.
  • step (5) surface treatment is carried out on the hot-rolled coil, and pickling or mechanical descaling can be used.
  • step (6) conventional spiral welded pipes or straight seam welded pipes can be used for forming and welding, and the welding methods can be submerged arc welding, gas metal arc welding Shielded welding, plasma arc welding, stick arc welding, high frequency welding or laser welding.
  • the finish rolling temperature is 920-1000°C.
  • a preheating step is further included between step (2) and step (3), wherein the preheating temperature is 1100-1250°C.
  • the composite slab obtained by assembling can be heated at a temperature of 1100-1250°C, so that the corrosion-resistant layer on the surface of the composite slab can obtain a uniform austenitized structure, and the original possible existing
  • the carbides are completely dissolved, and at the same time, all or part of the compounds of alloying elements such as niobium and titanium in the carbon steel are dissolved; the elements of the corrosion-resistant layer and the carbon steel base layer are diffused at the interface to form a stable transition layer, and then slowly cooled to room temperature .
  • cold rolling and annealing are also included between step (5) and step (6); preferably, the annealing temperature is 900-1000°C.
  • step (5) in the manufacturing method of the present invention, in the actual use process, if the target product before pipe making is cold-rolled coils instead of hot-rolled coils, further steps can be made between step (5) and step (6). Added are cold rolling and annealing steps, which can be achieved by cold rolling to the target thickness, followed by annealing.
  • the inventors designed the composition of the corrosion-resistant layer and the base layer, and the ratio design of the two, and formed a corrosion-resistant layer resistant to aluminum sulfate corrosion on the surface of the base carbon steel plate through a rolling process, and finally formed a corrosion-resistant layer with both Aluminum sulfate corrosion-resistant, good mechanical properties and high economic efficiency of the strip, the strip can be processed into pipes and can be effectively applied to the pipeline equipment used in the water supply station in the environment of aluminum sulfate corrosion medium.
  • composition design of the corrosion-resistant layer and the base layer needs to meet the comprehensive performance of the material.
  • the composition of the corrosion-resistant layer needs to be designed according to the characteristics of aluminum sulfate corrosion, so as to meet the requirements of corrosion resistance under the working conditions.
  • the composition design of base carbon steel should also consider: when the carbon content of the transition layer is high, there will be a lack of stabilizing elements, and there will be an obvious decarburization layer on the carbon steel side at the interface junction.
  • the structure of the base material is not uniform, and surface defects are prone to occur after processing, and the mechanical properties are also difficult to meet.
  • the ratio of the corrosion-resistant layer to the base metal and the difference in material properties will make it difficult to control the heating process, rolling process, and heat treatment process.
  • the temperature is not uniform during the heating process, causing deformation and swelling, resulting in failure to combine with the base layer.
  • the corrosion-resistant layer is designed by designing the composition of the corrosion-resistant layer and the base layer and the ratio of the two. Combined with the base layer to form a billet, and apply appropriate heating, rolling, coiling processes, and cooperate with the pipe making process, a pipe with both aluminum sulfate corrosion resistance, good mechanical properties and high economic efficiency can be obtained.
  • a transitional layer structure of a certain thickness is formed between the corrosion-resistant layer and the base layer through processes such as heating and rolling, which realizes the complete metallurgical combination of the corrosion-resistant layer and the base layer, so as to ensure the corrosion resistance of aluminum sulfate and While improving the mechanical properties, the applicability and economy of the material are improved.
  • the pipeline manufactured by adopting the above-mentioned composition design and process control method can solve the essential pain point of 300 series stainless steel or carbon steel used in the environment of aluminum sulfate corrosive medium in the water supply plant station; the pipeline can be effectively applied to the aluminum sulfate medium environment of the water supply plant station Among the pipeline equipment used below, such as: aluminum sulfate mixing tank, concentration tank and pool connection pipeline, aluminum sulfate addition pipeline, which can meet the needs of these pipelines and equipment for aluminum sulfate corrosion resistance and mechanical properties, and greatly improve these pipelines The applicability, safety, and durability of the equipment, while avoiding secondary pollution to water quality, have great economic and social benefits.
  • the pipeline of the present invention Compared with the 300 series stainless steel pipes that are tried to be used in the aluminum sulfate mixing tank, the concentration tank, the tank connecting pipes, and the aluminum sulfate adding pipes in the current water supply station, the pipeline of the present invention has higher strength and better corrosion resistance. Welding and machining are simpler and more economical. Compared with carbon steel pipes, the strip steel of the pipes in the present invention can avoid the pipeline corrosion-resistant coating process, and at the same time, it has the corrosion resistance and durability that carbon steel pipes cannot match, and is more energy-saving, environmentally friendly and maintenance-free.
  • Fig. 1 is a schematic diagram of the interlayer structure of the pipeline according to the present invention in an embodiment.
  • Fig. 2 is a schematic diagram of the interlayer structure of the pipeline according to the present invention in another embodiment.
  • Example 3 is a photo of the microstructure of the interface between the base layer and the corrosion-resistant layer of the pipeline in Example 4.
  • FIG. 4 is a photograph of the microstructure of the base layer of the pipeline of Example 4.
  • Table 1 lists the mass percentages of various chemical elements in the corrosion-resistant layer in the pipelines of Examples 1-8.
  • Table 2 lists the mass percentages of each chemical element in the base layer of the pipeline of Examples 1-8.
  • the pipeline of embodiment 1-8 of the present invention all adopts following steps to make:
  • Heating and rolling heat the composite slab at a temperature of 1150-1200 ° C, and then perform multiple passes within the austenite recrystallization and non-recrystallization temperature range of the base slab and the corrosion-resistant layer slab
  • the total reduction rate is not lower than 90%
  • the final rolling temperature is not lower than 920°C, preferably the final rolling temperature is between 920-1000°C.
  • Coiling after water cooling, coiling is performed at a temperature of 500-620° C. to obtain hot-rolled coils.
  • Pipe making use spiral welded pipe or straight seam welded pipe for forming and welding; welding methods can choose submerged arc welding, gas metal arc welding pipe, tungsten inert gas shielded welding, plasma arc welding, electrode arc welding , high frequency welding or laser welding for tube making.
  • the pipelines of the embodiments 1-8 of the present invention are all made by the above steps (1)-step (6) process flow, and its chemical composition and related process parameters all meet the requirements of the present invention. Invention design specification control requirements.
  • Table 3 lists the specific process parameters of the pipelines of Examples 1-8 in the steps of the above-mentioned manufacturing method.
  • the corresponding pipes are further prepared in the pipe-making process of the step (6).
  • Table 4 lists the test results of the microstructure and mechanical properties of the pipes of Examples 1-8.
  • Aluminum sulfate corrosion resistance performance test each embodiment 1-8 hanging piece aluminum sulfate solution (under the environment of temperature ⁇ 40 °C and aluminum sulfate concentration ⁇ 30wt%), take out after 3 months and observe the surface condition of the corrosion resistant layer, measure Whether there is corrosion phenomenon in weight loss at the beginning of corrosion, calculate the annual corrosion rate of each embodiment, thus obtain the aluminum sulfate corrosion resistance of the sample pipelines of Examples 1-8.
  • Table 5 lists the test results of the aluminum sulfate corrosion resistance of the pipelines of Examples 1-8.
  • E means the average corrosion rate ⁇ 0.01mm/year; E*: means the average corrosion rate is 0.01-0.025mm/year; S: means the average corrosion rate is 0.025-0.04mm/year; S*: means the average corrosion rate 0.04-0.05mm/year.
  • the yield strength of the pipelines of Examples 1-8 is between 426-508MPa, the tensile strength is between 580-650MPa, and the elongation is between 31.0-40.5%. Among them, it has very excellent mechanical properties. At the same time, Examples 1-8 also have good corrosion resistance to aluminum sulfate, and the annual corrosion rate of aluminum sulfate in the test environment is ⁇ 0.05mm/year.
  • the present invention obtains pipes with good corrosion resistance and mechanical properties through suitable material selection, composition design, rolling and heat treatment processes and pipe making, which can solve the problem of sulfuric acid in the current water supply plant.
  • the essential pain point of 300 series stainless steel or carbon steel used in the environment of aluminum corrosive medium can meet the needs of pipeline equipment used in the environment of aluminum sulfate corrosive medium in water supply plants, and has great economic and social benefits.
  • Fig. 1 is a schematic diagram of the interlayer structure of the pipeline according to the present invention in an embodiment.
  • the pipeline of the present invention includes: two corrosion-resistant layers on the inner and outer surfaces of the pipeline and a base layer in the middle.
  • Fig. 2 is a schematic diagram of the interlayer structure of the pipeline according to the present invention in another embodiment.
  • the pipeline of the present invention includes: a corrosion-resistant layer on the inner surface of the pipeline and a base layer on the outer surface of the pipeline.
  • Example 3 is a photo of the microstructure of the interface between the base layer and the corrosion-resistant layer of the pipeline in Example 4.
  • FIG. 4 is a photograph of the microstructure of the base layer of the pipeline of Example 4.
  • the total thickness of the pipeline is 12mm, and the thickness of its single corrosion-resistant layer is 2mm.
  • the microstructure of the base layer of the pipeline is ferrite+pearlite; the microstructure of the corrosion-resistant layer is austenite; correspondingly, in the present invention, each element of the corrosion-resistant layer and the base layer is in the Diffusion occurs at the binding interface, forming a stable
  • the diffusion distance ie transition layer thickness

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Abstract

本发明公开了一种管道，其在厚度方向上具有耐蚀层和基层，耐蚀层至少位于管道内壁，耐蚀层除了含有Fe和不可避免的杂质之外，还含有以wt％计的下述化学元素：0＜C≤0.08％；Si：0.3-0.6％；Mn：0.5-2.0％；Ni：11.00-13.00％；Cr：16.50-18.00％；Mo：2.00-3.00％；N：0.02-0.2％；Cu：0.01-0.3％；并且Cr、Mo、N和Cu满足如下不等式：Cr+3.3×Mo+16×N+10×Cu≥26.0％。相应地，本发明还公开了制造上述管道的方法，其包括步骤：（1）制备耐蚀层板坯和基层板坯；（2）对耐蚀层板坯和基层板坯进行组坯，获得复合板坯；（3）加热和轧制：在1150-1200℃的温度下对复合板坯进行加热，轧制总压下率不低于90％，终轧温度不低于920℃；（4）卷取：水冷后，在500-620℃的温度下进行卷取，获得热轧卷；（5）对热轧卷进行表面处理；（6）制管。

Description

一种耐硫酸铝腐蚀的高强度管道及其制造方法 技术领域
本发明涉及一种管道及其制造方法，尤其涉及一种耐硫酸铝腐蚀的高强度管道及其制造方法。
背景技术
目前，在给水厂站或供水管网中，通常需要在混合池、浓缩池前添加硫酸铝，以用于混凝。由此，为确保管道设备的使用寿命，在制备如硫酸铝混合池、浓缩池以及池体连接管道、硫酸铝添加管道等管道或设备时，均要求具有良好的耐硫酸铝腐蚀性能。
在现有技术中，为了防止这些设备、管道被腐蚀，当前通常使用UPVC、CPVC材质生产制造上述用于运输硫酸铝的管道设备。但是，UPVC、CPVC材质存在着加工难度大、使用时膨胀系数大、强度低以及易软化变形的问题，其实际应用效果并不理想。
当前，部分研究人员考虑使用碳钢制备上述设备及管道。然而，采用碳钢材料制备的混合池、浓缩池以及池体连接管道、硫酸铝添加管道的内壁碳钢，在实际使用时会难以避免的被硫酸铝腐蚀，其不仅会导致水质污染，还极有可能导致管道渗漏、爆管。
另外，也有部分研究人员尝试使用300系奥氏体不锈钢制备上述设备及管道。但是，相较于碳钢，300系奥氏体不锈钢的结构强度较低所需厚度较大，从而增加了材料的用量；同时，300系奥氏体不锈钢的焊接、机械加工等难度较大；再者，300系不锈钢本身含有较多Cr、Ni、等贵重的金属元素，在生产、制作、安装过程中，使用纯不锈钢成本相对较高。
由此，针对上述现有技术中的不足与缺陷，本发明期望获得一种新的管道，该管道采用了合理的设计，其能够在碳钢基层的表面形成耐硫酸铝的耐蚀层，最终形成兼具耐硫酸铝腐蚀、良好的力学性能以及较高的经济性的管道，其具备极大的经济和社会效益。
发明内容
本发明的目的之一在于提供一种管道，该管道采用了合理的设计，其能够在碳钢基层的表面形成耐硫酸铝的耐蚀层，最终形成兼具耐硫酸铝腐蚀、良好的力学性能以及较高的经济性的管道，其具备极大的经济和社会效益。
本发明所述的管道能够解决给水厂站在硫酸铝腐蚀介质环境下使用的300系不锈钢或 碳钢的本质痛点；该管道可有效应用于给水厂站在硫酸铝介质环境下使用的管道设备中，并大幅提升这些管道设备的适用性、安全性、耐久性，同时避免对水质造成二次污染。
为了实现上述目的，本发明提供了一种管道，所述管道在厚度方向上具有耐蚀层和基层，所述耐蚀层至少位于管道内壁，所述耐蚀层除了含有Fe和不可避免的杂质之外，还含有以wt％计的下述化学元素：
0＜C≤0.08％；
Si：0.3-0.6％；
Mn：0.5-2.0％；
Ni：11.00-13.00％；
Cr：16.50-18.00％；
Mo：2.00-3.00％；
N：0.02-0.15％；
Cu：0.01-0.3％；
并且Cr、Mo、N和Cu满足如下不等式：Cr+3.3×Mo+16×N+10×Cu≥26.0％。
优选地，所述耐蚀层含有以wt％计的下述化学元素：
0＜C≤0.08％；
Si：0.3-0.6％；
Mn：0.5-2.0％；
Ni：11.00-13.00％；
Cr：16.50-18.00％；
Mo：2.00-3.00％；
N：0.02-0.15％；
Cu：0.01-0.3％；
余量为Fe和不可避免的杂质；
并且Cr、Mo、N和Cu满足如下不等式：Cr+3.3×Mo+16×N+10×Cu≥26.0％。
在本发明所述的管道中，为了确保管道的耐硫酸铝腐蚀性能，首先要保证耐蚀层的耐硫酸铝腐蚀性能。
当前给水厂站或供水管网的硫酸铝腐蚀介质使用工况条件为：硫酸铝质量浓度在30％以下，工作温度0-40℃。
根据上述工况条件，发明人对管道耐蚀层的化学元素成分进行了优化设计，其中特别 添加了一定量的Cu元素，并设计了专用的耐蚀当量公式及要求，控制Cr、Mo、N和Cu满足如下不等式：Cr+3.3×Mo+16×N+10×Cu≥26.0％。
需要说明的是，Cu可以进一步提升钢材的耐蚀性，特别是在硫酸根离子等还原性介质中作用明显，当Cu和Mo同时加入时，效果更为明显。通常，铜的添加将影响材料的热加工性能，但是对于本发明所述复合材质的管道来说，耐蚀层所占比例较低，对于整体的热加工性能的影响可以忽略。
在本发明中，耐蚀层的化学元素的设计原理如下所述：
C：在本发明所述的耐蚀层中，C是强奥氏体形成元素，一定程度上可以取代镍，促进奥氏体形成，并稳定奥氏体组织，同时可以提高不锈钢的强度。但是，C元素含量不宜过高，当碳含量过高时，碳与铬结合后会在晶界形成富铬碳化物，导致晶间腐蚀。因此，为了发挥C元素的有益效果，在本发明所述的耐蚀层中，控制C元素的质量百分比满足0＜C≤0.08％。
Si：在本发明所述的耐蚀层中，Si元素主要在熔炼过程中用于脱氧，因此一般需要添加一定含量的硅。但需要注意的是，Si元素含量同样不宜过高，当硅含量过高时，将降低氮的溶解度。因此，在本发明所述的耐蚀层中，将Si元素的质量百分比控制在0.3-0.6％之间。
Mn：在本发明所述的耐蚀层中，Mn元素是强烈的奥氏体组织稳定元素，并能提高氮在钢中的溶解度。但锰同时对奥氏体不锈钢的耐蚀性有着负面影响，因此，考虑到Mn元素的有益效果以及不利影响，在本发明所述的耐蚀层中，将Mn元素的质量百分比控制在0.5-2.0％之间，优选1.10-2.0％。
Ni：在本发明所述的耐蚀层中，Ni是形成和稳定奥氏体相最重要的元素，添加适量的Ni元素可以确保钢在室温的奥氏体组织形成。但是镍的价格昂贵，为保证相对较低的成本，钢中不宜添加过量的镍。因此，在本发明所述的耐蚀层中，将Ni元素的质量百分比控制在11.00-13.00％之间。
Cr：在本发明所述的耐蚀层中，Cr是钢材获得不锈性和耐蚀性的保证，一般地获得耐腐蚀性的最低铬含量是10.5％。由于铬是显著增强耐腐蚀性能的元素，为保证良好的耐蚀性，本发明钢中铬含量控制在16.50％以上。但需要注意的是，Cr同时也是主要的铁素体形成元素，过高含量的铬将难以保证耐蚀层获得室温奥氏体组织。因此，在本发明所述的耐蚀层中，将Cr元素的质量百分比控制在16.50-18.00％之间。
Mo：在本发明所述的耐蚀层中，Mo是提高耐腐蚀性能的重要元素，其机理是稳定钝 化膜及促进铬元素在钝化膜中的富集；此外，钼还可以与氮协同作用，从而进一步提高耐点蚀性能，因此添加钼的主要作用是提高耐腐蚀性。但是，Mo元素含量同样不宜过高，钼含量过高将增加合金成本，为保证相对较低的成本，在本发明所述的耐蚀层中，将Mo元素的质量百分比控制在2.00-3.00％之间。
N：在本发明所述的耐蚀层中，N是非常强烈的形成、稳定和扩大奥氏体区的元素，添加适量的N元素能够有效提高不锈钢的耐点腐蚀性能。但是当钢中氮含量过高时，将增大含氮金属间相形成的风险，同时提高熔炼和热加工的难度，导致难以生产。因此，在本发明所述的耐蚀层中，将N元素的质量百分比控制在0.02-0.15％之间。
Cu：在本发明所述的耐蚀层中，添加适量的Cu元素可以提高材料的耐蚀性。同时，Cu元素可以与钼协同，稳定钝化膜，促进铬在钝化膜中的富集，从而提升耐点蚀性能。因此，在本发明所述的耐蚀层中，将Cu元素的质量百分比控制在0.01-0.3％之间，优选0.12-0.3％，更优选0.12-0.22％。
相应地，在本发明所述管道的耐蚀层中，在控制单一化学元素质量百分比的同时，还进一步地控制元素Cr、Mo、N和Cu满足：Cr+3.3×Mo+16×N+10×Cu≥26.0％。式中各元素均代入对应元素的质量百分比。通过这样的控制，可以进一步确保耐蚀层在硫酸铝环境中具有相当优异的耐腐蚀性能。
优选地，在所述耐蚀层中，不可避免的杂质包括：S≤0.030％；P≤0.045％。
在本发明所述管道的耐蚀层中，P和S均是不可避免的杂质元素，为了确保钢材的质量，在条件允许的前提下，钢中杂质元素的含量越低越好。
优选地，所述基层含有以wt％计的下述化学元素：
C：0.01-0.20％；
Si：0.10-0.50％；
Mn：0.50-2.00％；
Al：0.02-0.04％；
Ti：0.005-0.014％；
Nb：0.005-0.020％；
N≤0.006％；
余量为Fe和不可避免的杂质。
优选地，所述基层还含有下述化学元素中的至少一种：
0＜B≤0.0003％；
0＜Ni≤0.20％；
0＜Cr≤0.22％；
0＜Mo≤0.12％。
为了保证本发明所述的管道获得较高的力学性能，发明人还对基层碳钢的化学成分进行了选择，其基层碳钢的化学元素成分选择既需要保证较高的强度，又需要兼顾较好的可加工性能。
由此，在本发明中，基层碳钢各化学元素的设计原理如下所述：
C：在本发明所述的基层中，C是奥氏体稳定化元素，其在钢中能够起到固溶强化的作用，可明显提高钢材的强度。但是，钢中C元素含量不宜过高，当钢中C元素含量过高时，不仅不利于对材料的焊接性能和韧性，也容易增加珠光体组织及马奥岛等硬相组织，对钢材的耐腐蚀性能造成不利影响。因此，考虑到钢板的强韧性匹配以及对碳钢材料耐腐蚀性的要求，在本发明所述的基层钢材中，将C元素的质量百分比控制在0.01-0.20％之间。
控制C元素的质量百分比为0.01-0.20％，不仅可以保证钢板在轧制后空冷情况下能够获得一定的硬度和强度，还可以避免恶化基层钢材的焊接性能。
Si：在本发明所述的基层中，钢中加入Si元素能够有效提高钢质纯净度和脱氧。Si元素在钢中能够起到固溶强化作用，但Si元素不利于材料的焊接性能；在本发明中，控制基层碳钢的硅含量为小于等于0.50％，不会对耐蚀层的耐蚀性有任何影响，且基层碳钢具备良好的焊接性能。由此，在本发明所述的基层中，将Si元素的质量百分比控制在0.10-0.50％之间。
Mn：在本发明所述的基层中，钢中加入适量的Mn元素可以推迟珠光体转变，降低临界冷却速度，提高钢材的淬透性；同时Mn元素还具有固溶强化的作用，其是钢中的主要固溶强化元素。但是，Mn元素不宜过多添加，当钢中Mn元素含量太高时，容易出现偏析带以及马氏体组织，其对于钢材的韧性有不利影响，且偏析带的出现对钢的耐腐蚀性能也会有所降低。一般低碳微合金钢中锰含量不超过2.00％，此时基层碳钢中含有的Mn元素也不会对耐蚀层有不良影响。基于此，在本发明所述的基层中，将Mn元素的质量百分比控制在0.50-2.00％之间。
Al：在本发明所述的基层中，Al是强脱氧元素。添加Al以确保钢中的氧含量尽量地低。脱氧后多余的Al和钢中的N元素能够结合形成AlN析出物，从而提高钢材强度并且在热处理加热时能细化钢的元素奥氏体晶粒度。但是，Al含量过高易产生氧化铝的夹杂物。基于此，在本发明所述的基层中，将Al元素的质量百分比控制在0.02-0.04％之间。
Ti：在本发明所述的基层中，Ti是强碳化物形成元素，钢中加入微量的Ti有利于固定钢中的N，Ti与N结合形成的TiN能使基层坯料加热时基层奥氏体晶粒不过分长大，细化原始奥氏体晶粒度。此外，Ti在钢中还可分别与碳和硫化合生成TiC、TiS、Ti4C2S2等化合物，它们能够以夹杂物和第二相粒子的形式存在。另外，Ti的这些碳氮化物析出物在焊接时还可阻止热影响区晶粒长大，改善焊接性能。但是，Ti含量过高会导致碳化钛等碳化物偏多、偏聚富集，影响材料力学性能。基于此，在本发明所述的基层中，将Ti元素的质量百分比控制在0.005-0.014％之间。
Nb：在本发明所述的基层中，Nb是强碳化物形成元素，基层碳钢中加入少量的铌主要是为了提高再结晶温度，以配合基层板坯与耐蚀层板坯组坯形成的复合板材在后续轧制工艺过程中的较高终轧温度，使得该基层在再结晶及未再结晶区轧制结束后晶粒细化，有利于提高基层的低温冲击韧性。但是，Nb含量过高会导致大尺寸富Nb析出相，降低材料塑韧性。基于此，在本发明所述的基层中，将Nb元素的质量百分比控制在0.005-0.020％之间。
N：在本发明所述的基层中，N元素可以与钛、铝生成第二相粒子，细化晶粒，提高强度。然而，当N元素的质量百分比过高时，则生成的TiN量太大且颗粒过于粗大，会影响本发明复合材料基层碳板的塑性。基于此，在本发明所述的基层中，将N元素的质量百分比控制为N≤0.006％。
B：在本发明中，B能极大地提高钢的淬透性，针对高耐蚀复合板(耐蚀层板坯+基层板坯)生产轧后空冷情况，要求尽量全部得到铁素体+珠光体组织，抑制贝氏体的形成。但是，B含量过高易造成偏析，与氧、氮形成化合物，无法达到相应目的。因此，在本发明中，要求控制基层的B元素的添加量满足0＜B≤0.0003％。
Ni：在本发明中，Ni是稳定奥氏体的元素，其对提高钢材强度有一定的作用。此外，钢中添加适量的Ni，尤其是在调质钢中添加适量的Ni能够大幅提高钢的低温冲击韧性。但是，Ni含量过高会提高碳当量，影响焊接性能；同时Ni属于稀有金属，带来资源浪费与成本提升。基于此，在本发明所述的基层中，可以添加适量的Ni，并控制Ni元素的添加量满足0＜Ni≤0.20％。
Cr：在本发明中，Cr元素的偏析倾向较Mn小，在基层碳钢Mn含量较高的时候，钢中有明显的偏析带及带状组织的时候，可适当降低Mn含量，不足部分以Cr替代。其次，基层碳钢中添加适量的Cr元素也有利于抑制耐蚀层的Cr向基层的扩散。但是，Cr含量过高会影响基材的相变温度，并影响基材的力学性能。基于此，在本发明所述的基层中，可以添加0＜Cr≤0.22％的Cr元素。
Mo：在本发明中，Mo元素能够显著地细化晶粒，提高钢材的强度和韧性。此外，Mo还能减少钢的回火脆性，同时回火时还能析出非常细小的碳化物，显著强化钢的基层。另外，Mo元素的添加还有利于抑制钢板在空冷过程中容易产生的自回火脆性。但是，Mo含量太高会提高碳当量，影响焊接性能，带来资源浪费与成本提升。基于此，在本发明所述的基层中，可以添加适量的Mo，并控制Mo元素的添加量满足0＜Mo≤0.12％。
优选地，单层耐蚀层厚度占管道总厚度的0.5-10％，并且所述基层含有以wt％计的下述化学元素：
C：0.01-0.18％；
Si：0.10-0.30％；
Mn：0.50-1.50％；
Al：0.02-0.03％；
Ti：0.005-0.014％；
Nb：0.005-0.015％；
N≤0.006％；
余量为Fe和不可避免的杂质。
优选地，在所述基层中，不可避免的杂质包括：S≤0.010％；P≤0.015％。
在本发明上述技术方案中，P、S均属于基层中不可避免的杂质元素，S在钢中会与Mn化合形成塑性夹杂物硫化锰，尤其对钢的横向塑性和韧性不利，因此基层中S元素的含量应尽可能地低。此外，P也是钢中的有害元素，其会严重损害钢板的塑性和韧性。
因此，对于本发明而言，S和P均是不可避免的杂质元素，应该越低越好，考虑到钢厂实际的炼钢水平，在本发明所述的基层中，控制S、P元素满足：S≤0.010％；P≤0.015％。
优选地，单层耐蚀层厚度占管道总厚度的0.5-50％，更优选单层耐蚀层厚度占管道总厚度的2.5-28.6％。也就是说，如果管道的内表面和外表面均具有耐蚀层，则每一个耐蚀层的厚度均占管道总厚度的0.5-50％。如果管道只有内表面具有耐蚀层，则该耐蚀层的厚度占管道总厚度的0.5-50％。
在本发明中，根据使用工况，耐蚀层厚度选择对本发明所述的管道获得良好的耐蚀性能、力学性能、成形性能具有至关重要的作用。当耐蚀层太厚时，会影响材料的力学性能以及生产成本；而耐蚀层太薄时，则会降低材料的耐蚀性和使用寿命。为此，在本发明中，优选控制单层耐蚀层厚度占管道总厚度的0.5-50％，更优选单层耐蚀层厚度占管道总厚度的2.5-28.6％。
优选地，单层耐蚀层厚度占管道总厚度的2.5-20％。
优选地，所述基层的微观组织为铁素体+珠光体或者铁素体+珠光体+贝氏体；所述耐蚀层的微观组织为奥氏体。
优选地，所述耐蚀层和所述基层之间具有扩散层或过渡层，所述扩散层或过渡层的厚度为约50μm-120μm。
优选地，所述管道的屈服强度≥426MPa，抗拉强度≥580MPa，延伸率≥31％，在温度≤40℃且硫酸铝浓度≤30wt％的环境下均匀腐蚀速率(即平均腐蚀速率)≤0.05mm/年。
相应地，本发明的另一目的在于提供一种上述管道的制造方法，该制造方法其简便可行，其可以有效制备上述管道。
为了实现上述目的，本发明提出了制造上述管道的方法，其包括如下步骤：
(1)制备耐蚀层板坯和基层板坯；
(2)对耐蚀层板坯和基层板坯进行组坯，获得复合板坯；其中，优选单层耐蚀层厚度占复合板坯总厚度的0.5-50％、更优选2.5-28.6％(成品管道中单层耐蚀层/管道总厚度比率与该步骤中的厚度比基本相同)；
(3)加热和轧制：在1150-1200℃的温度下对复合板坯进行加热，然后进行道次轧制，总压下率不低于90％，终轧温度不低于920℃；
(4)卷取：水冷后，在500-620℃的温度下进行卷取，获得热轧卷；
(5)对热轧卷进行表面处理；
(6)制管。
在本发明上述制造方法中，可以根据化学成分设计冶炼和铸造制备耐蚀层板坯和基层板坯，而后将二者进行组坯即可获得高耐蚀复合板(耐蚀层板材+基层板材)。将获得的高耐蚀复合板进一步进行加热、轧制、卷取，即可获得具有复合层间结构的热轧卷，对热轧卷进行表面处理后进行制管，即可得到本发明所述的管道。
在本发明中，发明人对步骤(3)的加热和轧制工艺进行了优化设计，以确保耐蚀层与基层之间通过加热、轧制等过程能够形成一定厚度的过渡层组织，以此实现耐蚀层与基层的完全冶金结合，从而在保证耐硫酸铝腐蚀性和力学性能的同时，提升材料的适用性与经济性，其能够解决目前给水厂站在硫酸铝腐蚀介质环境下使用的300系不锈钢或碳钢的本质痛点。
在本发明所述制造方法的步骤(2)中，可以对制备的耐蚀层板坯和基层板坯进行预处理，并对板坯贴合面进行四周焊接密封，对焊接密封后的结合面进行抽真空处理，以完成 组坯。
相应地，在步骤(5)中对热轧卷进行表面处理，可以采用酸洗或机械法除鳞。此外，在步骤(6)的制管工艺中，可以采用常规的螺旋焊管、或直缝焊管方式进行成型、焊接，其焊接方式可选择埋弧焊、熔化极气体保护电弧焊管、钨极惰性气体保护焊、等离子弧焊、焊条电弧焊、高频焊或激光焊。
优选地，在步骤(3)中，终轧温度为920-1000℃。
优选地，在步骤(2)和步骤(3)之间还包括预加热步骤，其中预加热温度为1100-1250℃。
在本发明所述的制造方法中，根据成品性能要求，还可以在步骤(2)和步骤(3)之间确定是否选择预加热工艺。在预加热工艺中，组坯获得的复合板坯可以在1100-1250℃的温度下加热，以使复合板坯表面的耐蚀层能获得均匀的奥氏体化组织，尽量使原先可能存在的碳化物完全溶解，同时使碳钢中的铌、钛等合金元素的化合物全部或部分溶解；使耐蚀层与碳钢基层各元素在界面发生扩散，形成稳定的过渡层，之后缓冷至室温。
优选地，在步骤(5)和步骤(6)之间还包括冷轧和退火；优选地，退火温度为900-1000℃。
在本发明所述的制造方法中，在实际使用过程中，若制管前的目标产品为冷轧卷，而不是热轧卷，则在步骤(5)和步骤(6)之间还可以进一步添加有冷轧和退火步骤，其可以通过冷轧至目标厚度，之后进行退火。
由此可见，在本发明中，发明人通过耐蚀层与基层成分设计、两者配比设计，通过轧制工艺在基层碳钢板表面形成耐硫酸铝腐蚀的耐蚀层，最终可以形成兼具耐硫酸铝腐蚀、良好的力学性能以及较高的经济性的板带，板带再加工成管道即可有效应用于给水厂站在硫酸铝腐蚀介质环境下使用的管道设备。
需要说明的是，在本发明设计过程中，其难度包括：
1)耐蚀层、基层成分设计需要满足材料的综合性能。耐蚀层需要针对硫酸铝腐蚀的特点设计成分，满足使用工况下耐腐蚀的要求。基层碳钢成分设计，除考虑满足力学性能要求外，还要考虑：两者结合过渡层碳含量较高时，缺少稳定化元素，界面结合处碳钢一侧会存在明显脱碳层，碳钢基材组织不均匀，加工后容易产生表面缺陷，力学性能也难以满足。
2)耐蚀层与基层金属的比例、材料特性的差异将导致加热工序、轧制工序、热处理工序难以控制。比如加热过程温度不均匀，引起变形鼓包，导致与基层无法结合。比如，在轧制过程中容易与基体分离、开裂，厚度的均匀性难以保证。
3)对于给水厂站在硫酸铝腐蚀介质环境下使用的管道、设备，例如硫酸铝混合池、浓 缩池以及池体连接管道、硫酸铝添加管道等，如果前期的复合未完成，结合质量不佳，则经过后续酸洗、制管成型、焊接等加工后，成品的耐蚀层的连续性、均匀性无法保证，会对设备及管道的适用性、安全性、耐久性造成巨大隐患。
在本发明中，通过合理的设计，发明人成功地克服了上述难点，并制备获得了本发明所述的管道。
相较于现有技术，本发明所述的管道及其制造方法具有如下所述的优点以及有益效果：
在本发明中，发明人考虑到根据当前给水厂站的管道设备在硫酸铝腐蚀介质环境下的使用工况条件，通过对耐蚀层和基层成分设计、两者配比设计，将耐蚀层和基层结合组坯，并施以合适的加热、轧制、卷取工艺，配合制管工艺，即可得到兼具耐硫酸铝腐蚀、良好的力学性能以及较高的经济性的管道，其屈服强度≥426MPa，抗拉强度≥580MPa，延伸率≥31％，在温度≤40℃且硫酸铝浓度≤30wt％的环境下均匀腐蚀速率(即平均腐蚀速率)≤0.05mm/年。
在本发明中，其耐蚀层与基层之间通过加热、轧制等过程形成了一定厚度的过渡层组织，实现了耐蚀层与基层的完全冶金结合，以在保证耐硫酸铝腐蚀性能和力学性能的同时，提升材料的适用性与经济性。
采用上述成分设计和工艺控制方法制造的管道，能够解决给水厂站在硫酸铝腐蚀介质环境下使用的300系不锈钢或碳钢的本质痛点；该管道可有效应用于给水厂站在硫酸铝介质环境下使用的管道设备中，例如：硫酸铝混合池、浓缩池以及池体连接管道、硫酸铝添加管道，其能够满足这些管道及设备对于耐硫酸铝腐蚀性能和力学性能的需求，大幅提升这些管道设备的适用性、安全性、耐久性，同时避免对水质造成二次污染，具备极大的经济和社会效益。
相比于目前给水厂站的硫酸铝混合池、浓缩池以及池体连接管道、硫酸铝添加管道尝试使用的300系不锈钢管道，本发明所述的管道的强度更高，耐蚀性更好，焊接、机械加工更简单，且具有更高的经济性。相比于碳钢钢管，本发明所述的管道的板带钢可以免除管道耐蚀涂装工序，同时又具有碳钢管难以企及的耐蚀性和耐久性，且更加节能、环保、免维护。
附图说明
图1为本发明所述的管道在一种实施方式下的层间结构示意图。
图2为本发明所述的管道在另一种实施方式下的层间结构示意图。
图3为实施例4的管道的基层与耐蚀层结合界面的微观组织照片。
图4为实施例4的管道的基层微观组织照片。
具体实施方式
下面将结合具体的实施例对本发明所述的管道及其制造方法做进一步的解释和说明，然而该解释和说明并不对本发明的技术方案构成不当限定。
实施例1-8
表1列出了实施例1-8的管道中的耐蚀层各化学元素质量百分比。
表1(wt％，余量为Fe和除P、S以外的其他不可避免的杂质)
注：在表1中，式Cr+3.3×Mo+16×N+10×Cu中各元素均代入对应元素的质量百分比。
表2列出了实施例1-8的管道的基层中各化学元素质量百分比。
表2(wt％，余量为Fe和除P、S以外的其他不可避免的杂质)
本发明所述实施例1-8的管道均采用以下步骤制得：
(1)根据表1和表2所示的化学成分冶炼和铸造，以分别制备耐蚀层板坯和基层板坯。
(2)对耐蚀层板坯和基层板坯进行组坯，获得复合板坯：控制单层耐蚀层厚度占复合板坯总厚度的0.5-50％(成品管道中单层耐蚀层/管道总厚度比率与该步骤中的厚度比基本 相同)，对耐蚀层板坯、基层板坯进行预处理，并对板坯贴合面进行四周焊接密封，对焊接密封后的结合面进行抽真空处理；组坯后根据成品性能要求，确定是否选择预加热工序，若需要进行预加热，则控制坯料在1100-1250℃的预加热温度下进行预加热。
(3)加热和轧制：在1150-1200℃的温度下对复合板坯进行加热，然后在基层板坯和耐蚀层板坯的奥氏体再结晶及未再结晶温度范围内多道次轧制，总压下率不低于90％，终轧温度不低于920℃，优选终轧温度介于920-1000℃之间。
(4)卷取：水冷后，在500-620℃的温度下进行卷取，获得热轧卷。
(5)采用酸洗或机械法除磷，对热轧卷进行表面处理；若目标产品为冷轧卷，则还进一步进行冷轧和退火工艺，冷轧至目标厚度之后进行退火，退火温度为900-1000℃。
(6)制管：采用螺旋焊管、或直缝焊管方式，进行成型、焊接；焊接方式可选择埋弧焊、熔化极气体保护电弧焊管、钨极惰性气体保护焊、等离子弧焊、焊条电弧焊、高频焊或激光焊多种方式进行制管。
需要说明的是，在本发明中，本发明所述的实施例1-8的管道均采用以上步骤(1)-步骤(6)的工艺流程制得，其化学成分及相关工艺参数均满足本发明设计规范控制要求。
表3列出了实施例1-8的管道在上述制造方法的步骤流程中的具体工艺参数。
表3
需要注意的是，按照上述表3所示的工艺参数，实施例1和实施例3经步骤(5)热轧卷表面处理后，还进一步进行了冷轧和退火，获得冷轧板；而实施例2和实施例4至实施例8经由步骤(5)获得热轧板。
相应地，根据实施例1-8在步骤(5)中制备的板材，进一步在步骤(6)的制管工艺中，制备对应的管道。
将采用上述工艺制得的成品实施例1-8的管道分别取样，并进一步地对实施例1-8的样品管道的微观组织进行观察，观察获得各实施例管道的微观组织后，进一步对实施例1-8的样品管道进行力学性能测试，所得的测试结果列于下述表4之中。
相关力学性能测试手段，如下所述：按照GB/T 6396－2008复合钢板力学及工艺性能试验方法进行，由此得到实施例1-8的样品管道的屈服强度、抗拉强度以及延伸率。
表4列出了实施例1-8的管道的微观组织、力学性能的测试结果。
表4
相应地，为了验证本发明制得的实施例1-8的耐硫酸铝腐蚀性能，还需要将实施例1-8的管道再次采样，并对得到的实施例1-8的样品管道进行耐硫酸铝腐蚀性能测试，测试结果列于下述表5之中。
耐硫酸铝腐蚀性能测试：将各实施例1-8挂片硫酸铝溶液中(温度≤40℃且硫酸铝浓度≤30wt％的环境下)，3个月后取出观察耐蚀层表面情况，测量腐蚀始失重是否出现有腐蚀现象，计算各实施例的年腐蚀速率，由此得到实施例1-8样品管道的耐硫酸铝腐蚀性能。
表5列出了实施例1-8的管道的耐硫酸铝腐蚀性能的测试结果。
表5
注：E：表示平均腐蚀速率≤0.01mm/年；E*：表示平均腐蚀速率为0.01-0.025mm/年；S：表示平均腐蚀速率为0.025-0.04mm/年；S*：表示平均腐蚀速率为0.04-0.05mm/年。
结合上述表4和表5可以看出，在本发明中，实施例1-8的管道的屈服强度在426-508MPa之间，抗拉强度在580-650MPa之间，延伸率在31.0-40.5％之间，其具有十分优异的力学性能。同时，实施例1-8还具有良好的耐硫酸铝腐蚀性能，其在试验环境下硫酸铝年腐蚀速率≤0.05mm/年。
从以上实施例可以看出，本发明通过合适的选材、成分设计、轧制和热处理工艺并配合制管，获得了具有良好耐蚀性能以及力学性能的管道，其能够解决目前给水厂站在硫酸铝腐蚀介质环境下使用的300系不锈钢或碳钢的本质痛点，能够满足给水厂站在硫酸铝腐蚀介质环境下的管道设备使用需求，具备极大的经济和社会效益。
图1为本发明所述的管道在一种实施方式下的层间结构示意图。
如图1所示，在该实施方式中，本发明所述的管道包括：位于管道内表面和外表面的两个耐蚀层以及位于中间的基层。
图2为本发明所述的管道在另一种实施方式下的层间结构示意图。
如图2所示，在该实施方式中，本发明所述的管道包括：位于管道内表面的耐蚀层以及位于管道外表面的基层。
图3为实施例4的管道的基层与耐蚀层结合界面的微观组织照片。
图4为实施例4的管道的基层微观组织照片。
如图3和图4所示，在实施例4中，管道的总厚度为12mm，其单层耐蚀层厚度为2mm。
观察发现，在实施例4中，管道的基层的微观组织为铁素体+珠光体；耐蚀层的微观组织为奥氏体；相应地，在本发明中，耐蚀层与基层各元素在结合界面发生扩散，形成了稳 定的扩散层(即过渡层)，其扩散距离(即过渡层厚度)为约50μm-120μm。
需要说明的是，本发明的保护范围中现有技术部分并不局限于本申请文件所给出的实施例，所有不与本发明的方案相矛盾的现有技术，包括但不局限于在先专利文献、在先公开出版物，在先公开使用等等，都可纳入本发明的保护范围。
此外，本案中各技术特征的组合方式并不限本案权利要求中所记载的组合方式或是具体实施例所记载的组合方式，本案记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。
还需要注意的是，以上所列举的实施例仅为本发明的具体实施例。显然本发明不局限于以上实施例，随之做出的类似变化或变形是本领域技术人员能从本发明公开的内容直接得出或者很容易便联想到的，均应属于本发明的保护范围。

Claims (15)

  1. 一种管道，其特征在于，所述管道在厚度方向上具有耐蚀层和基层，所述耐蚀层至少位于管道内壁，所述耐蚀层除了含有Fe和不可避免的杂质之外，还含有以wt％计的下述化学元素：
    0＜C≤0.08％；
    Si：0.3-0.6％；
    Mn：0.5-2.0％；
    Ni：11.00-13.00％；
    Cr：16.50-18.00％；
    Mo：2.00-3.00％；
    N：0.02-0.15％；
    Cu：0.01-0.3％，优选Cu：0.12-0.3％，更优选Cu：0.12-0.22％；
    并且Cr、Mo、N和Cu满足如下不等式：Cr+3.3×Mo+16×N+10×Cu≥26.0％。
  2. 根据权利要求1所述的管道，其特征在于，所述耐蚀层含有以wt％计的下述化学元素：
    0＜C≤0.08％；
    Si：0.3-0.6％；
    Mn：0.5-2.0％；
    Ni：11.00-13.00％；
    Cr：16.50-18.00％；
    Mo：2.00-3.00％；
    N：0.02-0.15％；
    Cu：0.01-0.3％，优选Cu：0.12-0.3％，更优选Cu：0.12-0.22％；
    余量为Fe和不可避免的杂质；
    并且Cr、Mo、N和Cu满足如下不等式：Cr+3.3×Mo+16×N+10×Cu≥26.0％。
  3. 根据权利要求1或2所述的管道，其特征在于，在所述耐蚀层中，不可避免的杂质包括：S≤0.030％；P≤0.045％。
  4. 根据权利要求1或2所述的管道，其特征在于，所述基层含有以wt％计的下述化学元素：
    C：0.01-0.20％；
    Si：0.10-0.50％；
    Mn：0.50-2.00％；
    Al：0.02-0.04％；
    Ti：0.005-0.014％；
    Nb：0.005-0.020％；
    N≤0.006％；
    余量为Fe和不可避免的杂质。
  5. 根据权利要求4所述的管道，其特征在于，单层耐蚀层厚度占管道总厚度的0.5-10％，并且所述基层含有以wt％计的下述化学元素：
    C：0.01-0.18％；
    Si：0.10-0.30％；
    Mn：0.50-1.50％；
    Al：0.02-0.03％；
    Ti：0.005-0.014％；
    Nb：0.005-0.015％；
    N≤0.006％；
    余量为Fe和不可避免的杂质。
  6. 根据权利要求4所述的管道，其特征在于，所述基层还含有下述化学元素中的至少一种：
    0＜B≤0.0003％；
    0＜Ni≤0.20％；
    0＜Cr≤0.22％；
    0＜Mo≤0.12％。
  7. 根据权利要求4所述的管道，其特征在于，在所述基层中，不可避免的杂质包括：S≤0.010％；P≤0.015％。
  8. 根据权利要求1或2所述的管道，其特征在于，单层耐蚀层厚度占管道总厚度的0.5-50％，优选单层耐蚀层厚度占管道总厚度的2.5-28.6％。
  9. 根据权利要求8所述的管道，其特征在于，单层耐蚀层厚度占管道总厚度的2.5-20％。
  10. 根据权利要求1或2所述的管道，其特征在于，所述基层的微观组织为铁素体+珠光体或者铁素体+珠光体+贝氏体；所述耐蚀层的微观组织为奥氏体。
  11. 根据权利要求1或2所述的管道，其特征在于，所述管道的屈服强度≥426MPa，抗拉 强度≥580MPa，延伸率≥31％，在温度≤40℃且硫酸铝浓度≤30wt％的环境下平均腐蚀速率≤0.05mm/年。
  12. 制造权利要求1-11中任一项所述的管道的方法，其特征在于，所述方法包括如下步骤：
    (1)制备耐蚀层板坯和基层板坯；
    (2)对耐蚀层板坯和基层板坯进行组坯，获得复合板坯；其中，优选单层耐蚀层厚度占复合板坯总厚度的0.5-50％、更优选2.5-20％；
    (3)加热和轧制：在1150-1200℃的温度下对复合板坯进行加热，然后进行多道次轧制，总压下率不低于90％，终轧温度不低于920℃；
    (4)卷取：水冷后，在500-620℃的温度下进行卷取，获得热轧卷；
    (5)对热轧卷进行表面处理；
    (6)制管。
  13. 根据权利要求12所述的方法，其特征在于，在步骤(3)中，终轧温度为920-1000℃。
  14. 根据权利要求12所述的方法，其特征在于，在步骤(2)和步骤(3)之间还包括预加热步骤，其中预加热温度为1100-1250℃。
  15. 根据权利要求12所述的方法，其特征在于，在步骤(5)和步骤(6)之间还包括冷轧和退火，优选地，退火温度为900-1000℃。
PCT/CN2023/072827 2022-01-26 2023-01-18 一种耐硫酸铝腐蚀的高强度管道及其制造方法 WO2023143290A1 (zh)

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