Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/02—Pretreatment of the material to be coated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
  • B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
  • B21C37/15—Making tubes of special shape; Making tube fittings
  • B21C37/20—Making helical or similar guides in or on tubes without removing material, e.g. by drawing same over mandrels, by pushing same through dies ; Making tubes with angled walls, ribbed tubes and tubes with decorated walls
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G75/00—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general
• • 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
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
  • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
  • C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
  • C21D7/06—Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like
• • 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
  • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
  • C21D9/14—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes wear-resistant or pressure-resistant pipes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/052—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 40%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/053—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 30% but less than 40%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/058—Alloys based on nickel or cobalt based on nickel with chromium without Mo and W
• • 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
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/10—Oxidising

Definitions

• the present invention relates to a method of manufacturing a metal tube having a scale layer at least on the inner surface.
• the present invention relates to a method for manufacturing a metal tube having high strength at high temperatures and excellent corrosion resistance.
• the metal pipe obtained by the present invention is a pipe used in a carburizing gas atmosphere containing hydrocarbon gas, CO gas or the like, for example, a cracking furnace pipe, a reforming furnace pipe, a heating furnace in an oil refinery, a petrochemical plant or the like. Suitable for use in tubes, heat exchanger tubes, etc.
• the inner surface of the metal tube is exposed to a carburizing atmosphere. For this reason, it is preferable to form a Cr-based oxide scale layer on the inner surface of the metal tube to prevent carburization.
• the oxide scale layer mainly composed of Cr has a high density and has an effect of shielding the penetration of carbon into the metal tube.
• the Cr-based oxide scale layer has a small catalytic action against coking (carbon deposition). For this reason, it also has an effect of suppressing coking on the surface of the metal tube. As a result, the thermal conductivity to the fluid introduced into the metal tube can be maintained for a long time. Therefore, for example, when such a metal tube is used as a decomposition reaction tube, the yield of reaction products such as olefins is stabilized.
• This Cr-based oxide scale layer is formed even in an environment where a metal tube is used.
• carbon since carbon simultaneously enters the metal tube, it is difficult to uniformly form a Cr-based oxide scale layer on the inner surface of the metal tube. Therefore, it is effective to previously form an oxide scale layer mainly composed of Cr on the inner surface of the metal tube.
• Patent Document 1 in order to prevent Ni from eluting from a steel pipe when a stainless steel pipe containing 12 to 20% by mass of Cr and 40% by mass or less of Ni is used in a high-temperature and high-pressure water environment, A method for forming a scale layer on the surface of a steel pipe by carrying out a heat treatment in which an atmosphere of 0.01 to 0.5% by volume of oxygen containing oxygen is heated to 800 to 1100 ° C. and held for 2 to 20 minutes Is disclosed.
• Patent Document 2 discloses that the austenitic stainless steel stainless steel containing 14% by mass or less of Cr is heat-treated at 1100 ° C. or more by controlling the CO concentration in the barrel furnace to 150 ppm or more, and An invention for preventing scale unevenness due to abnormal oxidation is disclosed.
• Patent Document 3 as a stainless steel used in a carburizing gas atmosphere, the Cr concentration in a Cr-deficient layer is 10% by mass or more on the surface of a base material containing 20 to 55% by mass of Cr, or further on the outside thereof.
• An invention relating to stainless steel having a Cr-based oxide scale layer having a Cr content of 50% by mass or more is disclosed.
• Patent Document 4 relates to a method for producing an ethylene cracking furnace tube excellent in coking resistance, in a tube containing 15 to 30% by mass of Cr and 15 to 50% by mass of Ni having a depth of at least 50 ⁇ m from the surface.
• An invention is disclosed in which a cold working is performed, and then the tube is heated to 1100 ° C. or higher in an atmosphere of less than 5 vol% oxygen and 20 vol% nitrogen.
• Stainless steel having an oxide scale layer as described in Patent Document 3 is excellent in carburization resistance and caulking resistance. However, in actual production, it is difficult to uniformly form a Cr-based oxide scale layer over the entire inner surface of the tube.
• the austenite grain size having a depth of at least 30 ⁇ m from the surface layer is set to No. by cold working and nitrogen infiltration heat treatment.
• 7 or more finely divided layers can improve the stability of the Cr 2 O 3 oxide film produced during use under actual operating conditions of 750 to 1100 ° C.
• the oxide scale generated by the nitrogen infiltration heat treatment is removed, and a stable Cr 2 O 3 oxide film is formed on the finely divided layer in actual operation.
• the present invention has been made to solve such problems of the prior art, and by forming a uniform Cr-based oxide scale layer on the inner surface of a metal tube, carburizing or coking from carburizing gas can be achieved.
• An object of the present invention is to provide a method of manufacturing a metal tube having excellent resistance to the above.
• the present invention has been made on the basis of such knowledge, and the gist thereof is a method for producing a metal tube as shown in the following (1) to (4).
• a method of manufacturing a metal tube comprising forming a Cr-based oxide scale layer on at least the inner surface of the metal tube.
• the metal tube is, by mass%, C: 0.01 to 0.6%, Si: 0.1 to 5%, Mn: 0.1 to 10%, P: 0.08% or less, S : 0.05% or less, Cr: 20 to 55%, Ni: 20 to 70%, N: 0.001 to 0.25% and O (oxygen): 0.02% or less,
• the present invention it is possible to manufacture a metal tube having a Cr-based oxide scale layer uniformly on the inner surface of the metal tube.
• the metal pipe obtained by the production method of the present invention is excellent in carburization resistance and coking resistance in a carburizing gas environment.
• a metal tube having a predetermined chemical composition is mechanically treated and then subjected to a heat treatment for 0.5 to 60 minutes in a temperature range of 1050 to 1270 ° C.
• a Cr-based oxide scale layer is formed on at least the inner surface of the film.
• the metal tube used for the production method of the present invention needs to contain 20 to 55% Cr and 20 to 70% Ni.
• the upper limit is made 55%.
• the upper limit is preferably 35%. A more preferred range is 22 to 33%.
• Ni is an element necessary for obtaining a stable austenite structure. Ni is contained in an appropriate amount according to the Cr content. Ni has a function of reducing the penetration rate of carbon into the metal material. These effects are exhibited when the content is 20% or more. However, these effects saturate even when Ni is added excessively, thus increasing the manufacturing cost. Excessive Ni makes tube manufacture difficult. Therefore, the Ni content is 20 to 70%. A preferred lower limit is 23% and a preferred upper limit is 60%. A more preferred upper limit is 50%.
• the material for the metal tube for ethylene production preferably contains Cr: 20 to 35% and Ni: 20 to 60%.
• the metal tube used in the production method of the present invention has the above-described chemical composition, and there are no particular restrictions on the other components.
• C 0.01 to 0.6%, Si: 0.1 -5%, Mn: 0.1-10%, P: 0.08% or less, S: 0.05% or less, Cr: 20-55%, Ni: 20-70%, N: 0.001-0 .25% and O (oxygen): 0.02% or less is preferable, and the remainder has a chemical composition composed of Fe and impurities.
• C 0.01 to 0.6%
• Si 0.1 -5%
• Mn 0.1-10%
• P 0.08% or less
• S 0.05% or less
• Cr 20-55%
• Ni 20-70%
• N 0.001-0 .25%
• O (oxygen): 0.02% or less is preferable
• the remainder has a chemical composition composed of Fe and impurities.
• O oxygen
• Impurity means a component mixed from ore, scrap and the like when industrially producing a metal tube, and is allowed within a range that does not adversely affect the present invention.
• C 0.01 to 0.6%
• C is an element effective for ensuring high temperature strength. This effect becomes remarkable when C is contained by 0.01% or more.
• the content exceeds 0.6%, the toughness may be extremely deteriorated. Therefore, the C content is preferably 0.01 to 0.6%.
• a more preferred lower limit is 0.02%.
• a more preferred upper limit is 0.45%.
• a more preferred upper limit is 0.3%.
• Si 0.1 to 5% Since Si has a strong affinity for oxygen, it has the effect of promoting uniform formation of a Cr-based oxide scale layer. This effect becomes significant when the content is 0.1% or more. However, if its content exceeds 5%, the weldability deteriorates and the structure may become unstable. Accordingly, the Si content is preferably 0.1 to 5%. A preferable upper limit is 3%, and a more preferable upper limit is 2%. A more preferred lower limit is 0.3%.
• Mn 0.1 to 10%
• Mn is an element effective for deoxidation and effective for improving workability. Further, since Mn is an austenite generating element, a part of Ni can be replaced with Mn. In order to acquire these effects, it is preferable to make it contain 0.1% or more. However, if excessively contained, the formation of a Cr-based oxide scale layer may be hindered. Accordingly, the Mn content is preferably 0.1 to 10%. A preferable upper limit is 5%, and a more preferable upper limit is 2%.
• P 0.08% or less
• S 0.05% or less
• P and S are preferably segregated at the crystal grain boundaries and deteriorated in hot workability.
• P is 0.08% or less and S is 0.05% or less.
• P is 0.05% or less and S is 0.03% or less.
• P is 0.04% or less, and S is 0.015% or less.
• N 0.001 to 0.25%
• N is an element effective for improving the high-temperature strength. This effect becomes remarkable when the content is 0.001% or more. However, excessive addition may greatly impair processability. Therefore, the N content is preferably 0.001 to 0.25%. A preferable upper limit is 0.2%.
• Oxygen (O) is an element present as an impurity.
• oxygen content exceeds 0.02%, a large amount of oxide inclusions are precipitated in the metal material, the workability is lowered, and the surface flaw of the tube is caused. Therefore, the oxygen content is preferably 0.02% or less.
• the metal tube may further contain one type selected from the elements listed in the following (a) to (g).
• Cu is an element that stabilizes the austenite phase. Cu is also an element effective for improving the high-temperature strength. Therefore, Cu may be contained in the metal tube. However, when the content is excessive, hot workability may be reduced. Therefore, when Cu is contained, the content is preferably 5% or less. A more preferred upper limit is 3%. Said effect becomes remarkable when it contains 0.1% or more.
• Co is an element that stabilizes the austenite phase. If Co is contained, a part of Ni can be substituted. Therefore, Co may be contained in the metal tube. However, when the content is excessive, hot workability may be reduced. Therefore, when Co is contained, the content is preferably 5% or less. A more preferred upper limit is 3%. Said effect becomes remarkable when it contains 0.1% or more.
• Mo 3% or less
• W 6% or less
• Ta 6% or less
• Mo, W, and Ta are all elements that contribute to solid solution strengthening and improve high-temperature strength. It is valid. Therefore, one or more selected from these elements may be contained in the metal tube. However, when the content is excessive, the workability is deteriorated and the tissue stability may be impaired. Therefore, when one or more of these elements are contained, Mo is preferably 3% and W and Ta are preferably 6% or less. A preferable upper limit of these elements is 2.5%. A more preferred upper limit is 2%. In any element, the above effect becomes remarkable when 0.01% or more is contained. Moreover, when these are compounded and contained, it is preferable to make the upper limit of the total amount into 10%.
• Ti and Nb have a great effect in improving high-temperature strength, ductility and toughness even if contained in a very small amount. Therefore, one or two selected from these elements may be contained in the metal tube. However, when these elements are contained excessively, workability and weldability may be deteriorated. Therefore, when one or two of these elements are contained, Ti is preferably 1% or less and Nb is preferably 2% or less. In any element, the above effect becomes remarkable when 0.01% or more is contained. Moreover, when these are compounded and contained, it is preferable to make the upper limit of the total amount into 2%.
• B 0.1% or less, Zr: 0.1% or less, and Hf: 0.5% or less
• B, Zr, and Hf all strengthen grain boundaries and are hot Since it is an effective element for improving workability and high-temperature strength characteristics, one or more selected from these elements may be contained in the metal tube. However, if the content of any element is excessive, the weldability may be deteriorated. Therefore, when one or more of these elements are contained, the B and Zr contents are preferably 0.1% or less, and the Hf content is preferably 0.5% or less. In any element, the above effect becomes remarkable when 0.001% or more is contained. Moreover, when these are compounded and contained, it is preferable to make the upper limit of the total amount into 0.3%.
• Mg: 0.1% or less, Ca: 0.1% or less, and Al: 1% or less Mg, Ca, and Al are all effective in improving hot workability Element. Therefore, you may make 1 or more types selected from these elements contain in said metal pipe. However, when the content of these elements is excessive, the weldability may be deteriorated. Therefore, when one or more of these elements are contained, the Mg content is preferably 0.1% or less, the Ca content is 0.1% or less, and the Al content is 1% or less. A more preferable upper limit is 0.05% for Mg and Ca, and 0.6% for Al. In addition, said effect becomes remarkable when it contains 0.001% or more in Mg and Ca, and 0.01% or more in Al. A more preferred lower limit is 0.002% for Mg and Ca. Moreover, when these are compounded and contained, it is preferable to make the upper limit of the total amount into 0.5%.
• Y and Ln group are effective elements for improving oxidation resistance. Therefore, you may make 1 or more types selected from these elements contain in said metal pipe. When the content of any element is excessive, workability is reduced. Therefore, when one or more of these elements are contained, the content is preferably 0.15% or less. In addition, said effect becomes remarkable when it contains 0.0005% or more in any element.
• the upper limit of the preferable content is 0.10% or less. Moreover, when these are compounded and contained, it is preferable to make the upper limit of the total amount into 0.15%.
• the Ln group means from La of element number 57 to Lu of element 71. Among Ln groups, it is particularly preferable to use one or more of La, Ce and Nd.
• a lubricant is used to reduce the friction between the metal tube and the processing tool.
• the lubricant is usually removed by degreasing and washing after processing. However, a part of the lubricant remains on the inner surface of the pipe.
• a mechanical treatment is performed to remove this.
• oxidized scale, dirt, etc. generated during hot pipe production may adhere and remain on the surface of the metal pipe. These residues are preferably removed because they inhibit the uniform formation of the Cr-based oxide scale layer.
• the mechanical treatment is a treatment for enhancing the surface cleanliness by physically removing deposits such as lubricant, dirt and oxide scale remaining on the surface of the metal tube.
• the mechanical treatment include a blasting treatment, a grinding treatment (or friction treatment) in which an abrasive is directly brought into contact with the inner surface of the metal tube and removed by rubbing, and a method in which high pressure water is sprayed and removed without the abrasive. It is done.
• the blast treatment for example, air blast for projecting a projection material with compressed air, sand blasting using sand as a projection material (a type of air blasting), and projection material is projected by centrifugal force of an impeller made of wear-resistant alloy.
• shot blasting shot peening (a kind of shot blasting) whose main purpose is to impart strain to the metal surface, wet blasting and the like. Shot peening can remove surface deposits at the same time as applying strain.
• wet blasting in which the projection material is projected with high-pressure water can also be applied.
• the abrasive used for the mechanical treatment is not particularly limited.
• abrasives which consist of metals, such as cast steel, stainless steel, metal glass (amorphous), and Cr.
• the average particle diameter is preferably 300 ⁇ m or less, and most preferably 150 ⁇ m or less.
• the abrasive on the inner surface of the pipe When spraying the abrasive on the inner surface of the pipe at high speed, it may be sprayed from one end or both ends of the metal pipe, or may be sprayed by inserting a spray nozzle into the metal pipe and moving in the pipe.
• the abrasive or the non-woven fabric to which the abrasive is fixed may be dried or wetted with a liquid to directly contact the inner surface of the metal tube and move while rubbing.
• the metal tube subjected to the mechanical treatment is subjected to heat treatment, and a Cr-based oxide scale layer is formed on the inner surface of the metal tube.
• the heat treatment temperature is less than 1050 ° C.
• the oxide scale layer formed on the surface of the metal tube is thin, and the shielding property against penetration of carbon into the metal material is not sufficient.
• the temperature exceeds 1270 ° C.
• pores and cracks are generated in the oxide scale layer, and as a result, the density decreases, and the carburization resistance decreases. Therefore, the heat treatment was performed in the temperature range of 1050 to 1270 ° C.
• a preferred lower limit is 1120 ° C, and more preferred is 1160 ° C.
• the holding time of the heat treatment is less than 0.5 minutes, a Cr-based oxide scale layer having excellent carburization resistance cannot be formed uniformly.
• the holding time exceeds 60 minutes, only the thickness of the oxide scale layer is increased, resulting in a decrease in productivity and an increase in energy cost.
• the density of the oxide scale layer is lowered. Therefore, the holding period in the above temperature range is set to 0.5 to 60 minutes.
• the preferred lower limit is 2 minutes, and more preferred is 5 minutes.
• the preferred upper limit is 30 minutes, and more preferred is 15 minutes.
• the gas atmosphere in the heat treatment may be any conditions that can form a Cr-based oxide scale layer.
• it is an atmosphere such as atmospheric gas, a gas obtained by burning hydrocarbon fuel (LNG, butane, etc.) and air.
• the atmosphere may be DX gas, NX gas, RX gas, COG (C gas), hydrogen gas with a controlled dew point, or the like.
• a gas atmosphere in which these gases are mixed at an arbitrary ratio may be used.
• Cr-based oxide scale layer The Cr-based oxide scale layer is very important from the viewpoint of carburization resistance and coking resistance.
• an oxide scale layer containing 50% or more of Cr has a high density and a high shielding property against penetration of carbon into the metal material. Since the Cr-based oxide scale layer has a small catalytic effect on coking, it suppresses coking on the surface of the metal material. As a result, the thermal conductivity to the fluid in the pipe is maintained for a long time. For example, when used as a decomposition reaction tube, the yield of reaction products such as olefins is stabilized.
• the Cr content in the oxide scale layer is preferably 80% or more.
• the oxide scale layer having a high Cr content is denser and exhibits a strong shielding effect against the penetration of carbon into the metal material.
• the element content in the oxide scale layer can be measured by EDX. The measurement may be performed from the surface of the oxide scale layer. The quantification of the element is determined by the fraction of the detection element excluding C (carbon), O (oxygen) and the like.
• the present invention is particularly useful when manufacturing a metal tube having rib-like projections on the inner surface.
• a metal tube having rib-like protrusions on its inner surface it is considered that it is easily attacked by a carburizing gas, and oxide scale peeling is likely to occur.
• a tube having a rib-like projection on the inner surface of the tube a tube with an inner projection, a finned tube, and the like can be given.
• the protrusions, fins, etc. may be formed integrally with the tube itself or may be formed by welding or the like.
• a metal material having the chemical composition shown in Table 1 was melted using an electric furnace or a vacuum melting furnace to form a billet.
• the obtained billet was hot forged and cold rolled to produce a metal tube having an outer diameter of 56 mm and a wall thickness of 6 mm.
• Mechanical treatment under the conditions shown in Table 2 was performed on the metal tubes of specimen numbers 1 to 10. Some omitted mechanical processing. These were heat-treated under the conditions described in Table 2 to form oxide scales. Some performed alumina blasting as a mechanical treatment and no heat treatment.
• a total of five locations are cut at a pitch of 2 m from the longitudinal direction of the tube, and a ring-shaped test piece having a width of 50 mm and an oxide scale observation test piece to be described later. (20 ⁇ 20 mm square) was collected.
• the ring-shaped test piece was held at 1000 ° C. for 300 hours in a gas atmosphere of 15% CH 4 -3% CO 2 -82% H 2 by volume to perform carburization and coking tests.
• the coking resistance the mass of the test piece before and after the test was measured, the increase due to the coke deposition was determined, and the amount of deposited coke per unit area (mg / cm 2 ) was determined.
• the carburization resistance was evaluated by the amount of C entering the base material.
• the numbers in Table 2 indicate the numbers satisfying each of the above (1), (2) and (3) for five test pieces for each condition. For example, 3/5 out of 5 passes.
• the entire length of the inner surface of the metal tube is intended to be excellent in carburization resistance and caulking resistance. Therefore, it was judged that the case where all five passed satisfied the standard of the present invention.
• the metal pipe obtained by the present invention is a pipe used in a carburizing gas atmosphere containing hydrocarbon gas, CO gas, etc., for example, a cracking furnace pipe in a petroleum refining, petrochemical plant, etc., reforming Suitable for use as furnace tube, heating furnace tube, heat exchanger tube and the like.

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• 2010
  • 2010-02-15 CA CA2750014A patent/CA2750014C/en not_active Expired - Fee Related
  • 2010-02-15 JP JP2010506734A patent/JP4586938B2/ja active Active
  • 2010-02-15 KR KR1020117019029A patent/KR20110107370A/ko active Search and Examination
  • 2010-02-15 CN CN2010800069933A patent/CN102308015A/zh active Pending
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