EP1795274B1 - PROCÉDÉ DE FAÇONNAGE À CHAUD D' UN ACIER CONTENANT DU Cr - Google Patents

PROCÉDÉ DE FAÇONNAGE À CHAUD D' UN ACIER CONTENANT DU Cr Download PDF

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Publication number
EP1795274B1
EP1795274B1 EP04770813A EP04770813A EP1795274B1 EP 1795274 B1 EP1795274 B1 EP 1795274B1 EP 04770813 A EP04770813 A EP 04770813A EP 04770813 A EP04770813 A EP 04770813A EP 1795274 B1 EP1795274 B1 EP 1795274B1
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Prior art keywords
rolling
scale
hollow shell
steam
feo
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German (de)
English (en)
Japanese (ja)
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EP1795274A1 (fr
EP1795274A4 (fr
Inventor
Yasuyoshi Sumitomo Metal Industries Ltd HIDAKA
Sumio c/o SUMITOMO METAL INDUSTRIES LTD. IIDA
Toshiro Sumitomo Metal Industries Ltd. ANRAKU
Hirotsugu Sumitomo Metal Industries Ltd NAKAIKE
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B23/00—Tube-rolling not restricted to methods provided for in only one of groups B21B17/00, B21B19/00, B21B21/00, e.g. combined processes planetary tube rolling, auxiliary arrangements, e.g. lubricating, special tube blanks, continuous casting combined with tube rolling
    • 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
    • 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
    • C23C8/16—Oxidising using oxygen-containing compounds, e.g. water, carbon dioxide
    • C23C8/18—Oxidising of ferrous surfaces
    • 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
    • C23C8/80—After-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel

Definitions

  • the present invention relates to a method for decreasing surface defects as well as for extending a tool-life in hot-working of alloy steels containing 5-18% Cr (hereinafter, simply referred to as a Cr-containing steel).
  • a Cr-containing steel For instance, in a hot-rolling process where hollow shells being produced using a piercing-rolling mill represented by Mannesmann Piercer are subjected to an elongation-rolling process by an elongation-rolling mill such as Plug Mill and Mandrel Mill, further including Pilger Mill, Disher Mill and the like, to obtain seamless steel tubes or pipes (hereinafter, simply referred to as tubes), the invention relates to a method for hot-working of Cr-containing steels that pertains to extend a life of a tool such as a plug and mandrel bar employed in the elongation-rolling process, and also to suppress generation of surface defects.
  • Cr-containing steels exhibit excellent function in heat resistance and corrosion resistance
  • Cr-containing steels have less hot-workability in comparison with carbon steels, so surface defects are likely generated on surfaces of hot-worked products and also, a tool-life is likely shortened.
  • an oxide scale layer formed on the workpiece is dependent on oxidizing parameters such as heating temperatures and atmospheres, and further a Cr content.
  • an oxide scale layer composed of three layers: FeO / Fe 3 O 4 / Fe 2 O 3 , each of which is formed in written order on a metal surface and has a predetermined thickness respectively, is formed. Then, when Cr is added, FeCr 2 O 4 that is a spinel-type compound oxide is formed on the genuine metal surface or at the inner side of the parent metal, and the FeO layer becomes thinner, ending up disappearing.
  • Japanese Patent Application Publication No. 05-269507 discloses a method for adhering a scale layer of 10-100 ⁇ m in thickness on an outside surface of a steel blank or hollow shell, either of these being a workpiece to be rolled, wherein in manufacturing seamless steel tubes made of a steel containing Cr of 12 wt% or more, an atmosphere and/or temperature in a heating furnace is controlled to thereby adjust a thickness of an oxide scale layer on an outside surface of a primary billet or a hollow shell.
  • Japanese Patent Application Publication No. 10-60538 discloses a manufacturing method comprising: heating a Cr-containing steel to form a scale of 100 ⁇ m or more in gross thickness being composed of an inner layer and outer layer; and subsequently cooling by high-pressure jet water to thereby remove the outer layer scale.
  • Fig. 1 shows a result of the survey on the stress-strain curve for each type of oxide scale, whereas (a) depicts the stress-strain curve of a -Fe 2 O 3 , (b) for ⁇ -Fe 3 O 4 , and (c) for FeO respectively.
  • Figs. 1(a) and 1(b) teach: Fe 2 O 3 only can allow about 5 % in elongation, which is defined to have no deformability: Meanwhile, Fe 3 O 4 can be elongated when subjected to tensile deformation experimentally at an extremely slow rate at heating temperatures of not less than 900°C, so that it is impossible to be elongated at a deformation speed during hot rolling and thus cracking occurs to end up in exfoliation.
  • FeO deforms in a manner to keep pace with a deformation speed during rolling.
  • FeO has high deformability, and its failure such as cracking does not take place when even high reduction-stress is applied thereon: further, it has lower hardness at elevated temperatures than that of steels, so it can be expected that depression-type defects are unlikely generated.
  • FeO is perceived as the most suitable scale to reduce surface defects and to extend a tool-life, so the best scale structure in hot working can be an oxide scale in which FeO exists.
  • An object of the present invention is to provide a method for hot working of Cr-containing steels containing 5 to 18% Cr in which surface defects to be generated after hot working can be reduced, and a tool-life can dramatically be extended, the method being realized by applying a plain operational procedure and/or by employing a simple apparatus configuration.
  • the present inventors looked into a method for manufacturing seamless steel tubes and made detail investigations thereon. Besides, in elongation-rolling, a rolling method by the Mandrel Mill is targeted. Therefore, hereinafter, the description bases on the Mandrel Mill rolling method.
  • a billet as a starting material is heated to about 1200°C, subsequently formed into a hollow shell by a piercer mills, thus having a newly created surface inside. Then, a mandrel bar to be a tool for restraint of the inside surface is inserted into the inside of the hollow shell to perform rolling, the mandrel bar being coated over its outside surface with a hot rolling lubricant.
  • temperatures of the in-processing tubing material in a Mandrel Mill rolling process are in the range of 1100-1200°C at an entrance of the Mill, and in the range of 800-1000°C at its exit.
  • the tubing material in which the mandrel is withdrawn therefrom is reheated as it is to temperatures in the range of 850-1100°C by a reheating furnace, subsequently being subjected to finish-rolling into a tube having predetermined dimensions by a finish-rolling machine such as a stretch reducer. And then, in the case of a tube made of a Cr-containing steel, quenching is applied from temperatures of not less than 900°C, followed by tempering treatment at temperatures close to 700°C.
  • the tubing material in which the mandrel bar is withdrawn therefrom after the Mandrel Mill rolling can be referred to as a finish-roll tube blank.
  • the oxide scale on the inside surface of the hollow shell made by the piercer is hardly elongated even in Mandrel Mill rolling, so the oxide scale cracks and an exposed substrate metal is brought into direct contact with the mandrel bar surface.
  • an insulation effect that the oxide scale should inherently hold is not exerted, so the surface temperature of the mandrel bar abruptly rises to induce a severe thermal fatigue, whereby a thermal fatigue cracking occurs on the mandrel bar surface.
  • Fig. 2 shows a relationship between a steam concentration and an oxidizing rate constant (mg 2 / cm 4 ⁇ sec) when oxidizing is performed at a heating temperature of 1200°C with duration of 3600 seconds in each open air atmosphere where a steam concentration is varied.
  • Fig. 3 shows a relationship between a scale thickness ( ⁇ m) and an oxidation time (sec) when a steam concentration (volume %) in an atmosphere is varied to 10% and 0% if a parameter be taken as a heating temperature (°C).
  • Figs. 2 and 3 base on the results of a high temperature oxidation test using test specimens sampled from round billets made of a ferritic stainless steel containing 13 mass% Cr. From the results of Fig. 2 , it can be recognized that an oxide scale intensively grows when steam of 2.5-20 volume % is contained in the atmosphere. And from the results of Fig. 3 , it can be seen that heating at 1100°C or more in the steam atmosphere with the steam concentration of 10 volume % makes it possible to secure an oxide scale thickness.
  • Table 1 shows the results of collating the oxide scale structures that were obtained in the high temperature oxidation test.
  • Table 1 Steam in Atmosphere (%) Scale Structure Outer Layer Scale Inner Layer Scale 0 (no steam) Fe 2 O 3 FeCr 2 O 4 Fe 3 O 4 Fe 3 O 4 2.5-20 Fe 2 O 3 Fe 3 O 4 FeCr 2 O 4 FeO FeO
  • any of the scale structures constitutes a dual layer structure composed of an outer and inner layer.
  • the outer layer scale is the scale to be formed outwardly from the genuine surface of the Cr-containing steel
  • the inner layer scale is the one to be formed inwardly from the genuine surface of the Cr-containing steel.
  • the scale that is formed in the atmosphere with steam of 2.5% or more comprises: the outer layer scale composed of Fe 2 O 3 , Fe 3 O 4 and FeO; and the inner layer scale composed of FeCr 2 O 4 and FeO.
  • the scale that is formed in the atmosphere without steam comprises: the outer layer scale composed of Fe 2 O 3 and Fe 3 O 4 ; and the inner layer scale composed of FeCr 2 O 4 and Fe 3 O 4 .
  • FeO has an excellent deformability in hot-working in comparison with other iron oxides, and has superb following capability to parent metal of hollow shell during an elongation-rolling process. That is, the scale layer having FeO prevents the mandrel bar from directly contacting with the hollow shell, thereby allowing the thermal fatigue to be alleviated, while reducing the metallic seizure.
  • the foregoing FeO plays a role of solid lubricant during hot rolling to lower friction resistance during rolling.
  • a lubricant of boric acid type is concurrently applied as an auxiliary lubricant
  • the thickened oxide scale reacts with B 2 O 3 that is contained in the auxiliary lubricant to form B-Fe type compound (mainly oxide), resulting in enhancing the lubrication effect much more.
  • the present invention is accomplished based on the above findings and pertains to a method for hot-working of Cr-containing steels as described in the following (1).
  • a "Cr-containing steel” described in the present invention pertains to an alloy steel containing Cr of 5-18% which can additionally contain other alloy elements such as Ni and Mo where necessary.
  • a seamless steel tube described in the present invention shall include a seamless steel pipe.
  • Fig. 4 is the diagram illustrating the plan view of the layout of Mandrel Mill when it is adopted as the elongation-rolling machine.
  • Fig. 4 generally outlines that a billet B heated to a prescribed temperature (about 1200°C) at a rotary-hearth type furnace 1 moves through a traverse table 2 toward a piercer 3 to be formed into a hollow shell H, which is subsequently transferred to a traverse table 4.
  • a moisture supply device 5A and/or 5B to an inside of the hollow shell H transferred to the traverse table 4, the inside being in the state of high temperature (about 1200°C), to heighten a steam concentration of the inside, thereby enabling to grow an oxide scale of the inside surface of the hollow shell.
  • a boric acid type auxiliary lubricant by way of example, is supplied into the inside by an auxiliary lubricant supply device 6 to form a film of the auxiliary lubricant on the inside surface.
  • the hollow shell H having the oxide scale thus grown on its inside surface is transferred to a hollow shell charging device 7a where a mandrel bar M is inserted into the bore thereof by means of a mandrel bar inserting device 7b. At this time, a predetermined lubricant is coated over the surface of the mandrel bar M by a lubricant coating device 7c.
  • the hollow shell H having the mandrel bar M inserted into its bore is subjected to an elongation-rolling process in the Mandrel Mill 7 by the hollow shell charging device 7a and mandrel bar inserting device 7b, thus yielding a finish-roll tube blank.
  • the mandrel bar withdrawn from the finish-roll tube blank after the elongation-rolling process moves through a traverse table 8 to a bar circulation path 9, and passes through a bar cooling bath 10 to return to a mandrel bar inserting device 7b, thus enabling it to be used for a hollow shell next in line to be subjected to the elongation-rolling process.
  • a plurality of mandrel bars M are circulated and used.
  • the processing method by the present invention features that moisture is supplied into the inside of the hollow shell H made by the piercing-rolling process at the piercer 3 to grow the oxide scale of the inside surface thereof, and then the elongation-rolling process is applied.
  • the moisture to be supplied into the hollow shell inside can be steam or water itself. This is because even if water itself be supplied, it can be instantly vaporized to become steam since the temperature of the shell inside is very high (about 1200 deg. C).
  • the oxidizing rate can be markedly increased, thus resulting in enhancing its effect.
  • the higher the steam concentration the more its effect can be, but when the steam concentration exceeds 20 volume%, its effect tends to saturate. Accordingly, the steam concentration of the shell inside is set in the range of 2.5 to 20 volume%.
  • oxidizing time that is a holding time of the steam atmosphere becomes longer, it becomes much better to secure the oxide scale thickness.
  • oxidizing starts under the condition that an oxidizing temperature is 1150°C and a steam atmosphere with a steam concentration of 2.5 volume% is established, in other words, after a lapse of about 15 seconds from the completion of moisture supply into the shell inside, formation of FeO and thickening of the oxide scale are discerned, which confirms that oxidizing for at least 15 seconds can sufficiently secure an oxide scale thickness and an amount of FeO.
  • the temperatures at the inside surface of the hollow shell are set at 1150°C or more and the steam atmosphere is maintained for 15 seconds or more.
  • the temperature of the hollow shell just after pierced by the piercer is usually more or less about 1200°C, and there is a time lag of 30-40 seconds until it reaches the entrance of the following Mandrel Mill, in other words, until the mandrel bar is inserted into its inside.
  • the moisture supply into the shell inside by about 15 seconds ahead of the start of the Mandrel Mill rolling would be adequate, and more preferably, the moisture is supplied into the shell inside as soon as possible after piercing by the piercer.
  • 5A is preferably employed to supply the moisture.
  • the moisture supply into the shell inside by the moisture supply device 5A is not limited to be only once, and can be applied in several batches by the device 5A or an additional supply can be done by the device 5B, or alternatively, a plurality of the moisture supply devices can be disposed between 5A and 5B wherein by using these devices, the moisture supply can be intermittently performed. Such a moisture supply in several batches makes it possible to maintain a high steam concentration within the shell inside.
  • the similar oxidizing conditions can make an adequate improvement.
  • the moisture supply into the hollow shell inside is carried out as early as possible ahead of the introduction of the auxiliary lubricant into the hollow shell inside by the auxiliary lubricant supply device 6.
  • auxiliary lubricant of the boric acid type, etc.
  • a lubricant in common use composed of sodium borate 70% - metal soap 30% can be selected.
  • Mandrel Mill is employed as the elongation-rolling machine, but the above can likewise be applied in any case that Plug Mill, Assel Mill, Pilger Mill or Disher Mill be employed as the elongation-rolling machine.
  • Table 2 Four steel grades having chemical compositions shown in Table 2 are made to prepare round billets measuring 191 mm in outside diameter and 2500 mm in length, while mandrel bars made of SKD61 steel grade are prepared, the mandrel bars measuring 160 mm in outside diameter and 12 m in length, having 400 Vickers Hardness in surface hardness, and being subjected to an oxide scale deposition treatment onto their surfaces.
  • the conditions of the oxide scale deposition treatment are: heating in an open air: heating temperature of 630°C: 20 minutes in holding time.
  • the scale structure thus obtained is an afore-mentioned stacking layer structure composed of (FeCr) 3 O 4 , Fe 3 O 4 and Fe 2 O 3 , each of which is formed outwardly in written order from the genuine metal surface, and more precisely, a dual layer structure composed of an inner layer and outer layer scale, the inner layer scale comprising FeCr 2 O 4 and Fe 3 O 4 , the outer layer scale comprising Fe 3 O 4 and Fe 2 O 3 , wherein a thickness thereof is 7 ⁇ 10 ⁇ m.
  • the round billet thus prepared was charged into the rotary hearth furnace to be heated at temperatures in the range of 1200-1250°C, and was rolled by the Mannesmann Piercer to yield a hollow shell measuring 196 mm in outside diameter, 16 mm in thickness and 7500 mm in length.
  • Condition No. 1 As Condition No. 1 (Inventive Example), about 200-300 cm 3 of an industrial water at room temperature was immediately injected into the inside of the hollow shell, and then, by using the above mandrel bar, the elongation rolling was applied to produce a finish-roll tube blank measuring 151 mm in outside diameter, 6.25 mm in thickness and 25 m in length by the Mandrel Mill. Meanwhile, it was confirmed by a gas analysis that the injected water vaporized immediately to thereby create an oxidizing atmosphere having a steam concentration of 10-20 volume% inside the shell.
  • Condition No. 2 (Inventive Example), after injecting a similar industrial water as above, an auxiliary lubricant of boric acid type was supplied into the hollow shell inside to form its film just before inserting the mandrel bar while other parameters were exactly the same with that of Condition No. 1, and then, the elongation rolling was applied to produce the finish-roll tube blank measuring 151 mm in outside diameter, 6.25 mm in thickness and 25 m in length.
  • Condition No. 3 Comparative Example
  • the water was not supplied into the inside of the hollow shell while other parameters were exactly the same with that of Condition No. 1, and then, the elongation rolling was applied to produce the finish-roll tube blank measuring 151 mm in outside diameter, 6.25 mm in thickness and 25 m in length.
  • Condition No. 4 Comparative Example
  • the auxiliary lubricant of boric acid type was supplied into the inside of the hollow shell instead of the water supply while other parameters were exactly the same with that of Condition No. 1, and then, the elongation rolling was applied to produce the finish-roll tube blank measuring 151 mm in outside diameter, 6.25 mm in thickness and 25 m in length.
  • the timing of the water supply was set to be either just after piercing-rolling by the piercer or 15 seconds before the elongation rolling, or alternatively both.
  • a graphite type lubricant was coated over the mandrel bar so as to form the film thickness of 150 ⁇ m after being dried and solidified. Further, as for the auxiliary lubricant of boric acid type, the lubricant composed of sodium borate 70% - metal soap 30% was supplied to cover the shell inside surface with the rate of 150g/m 2 .
  • a "Normalized Life Ratio" of the mandrel bar was defined and adopted.
  • Fig. 5 is the diagram showing the evaluation result in terms of "Normalized Life Ratio" when the auxiliary lubricant is not supplied
  • Fig. 6 is the diagram showing the evaluation result in terms of "Normalized Life Ratio” when the auxiliary lubricant is supplied.
  • the hot-working method of Cr-containing steels in accordance with the present invention is characterized in that: a newly created surface of Cr-containing steel is held in a steam atmosphere to form an oxide scale including FeO; and then, hot-working next in line is applied. More specifically, in producing seamless steel tubes, moisture is supplied into the inside of the hollow shell being made by the piercing-rolling process to hold the newly created inside surface of the shell in the steam atmosphere, so that the oxide scale including FeO is formed on the shell inside surface: and then, the elongation-rolling process next in line is applied: as such, the above entails just a plain operational procedure and a simple apparatus configuration, thus enabling to decrease the surface defects generated in hot-working and to extend the tool life dramatically. Hence, this invention can greatly contribute to efficiently manufacture Cr-containing steels, 5-18% Cr, which are in growing demand.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
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Abstract

L’invention porte sur un procédé de façonnage à chaud d’un acier contenant du Cr, consistant à maintenir une surface nouvellement formée de l’acier contenant du Cr dans une atmosphère de vapeur, pour ainsi constituer une calamine oxydée contenant du FeO, avant de réaliser un façonnage à chaud. Plus spécifiquement, un procédé de fabrication d’un tuyau d’acier sans soudure consiste à humidifier l’intérieur d’un tuyau creux brut fabriqué par percement, pour maintenir la surface interne nouvellement formée du tuyau creux brut dans une atmosphère de vapeur et ainsi former une calamine oxydée contenant du FeO, avant de procéder à l’étirage ultérieur. Le procédé permet, grâce à une simple procédure d’utilisation et un simple dispositif, la réduction des défauts superficiels provoqués par un façonnage à chaud, avec pour conséquence un rallongement considérable de la vie d’un outil utilisé dans le cadre de ce procédé, qui contribue largement à la production efficace d’un acier contenant du Cr, avec 5 à 18 % de Cr, celui-ci étant en demande croissante.

Claims (2)

  1. Procédé de façonnage à chaud d'un acier au chrome, contenant 5 à 18 % de chrome, dans lequel on forme par façonnage à chaud un tube d'acier sans soudure en exécutant un processus de perçage et roulage, puis un processus d'allongement et roulage, caractérisé en ce que :
    - on apporte de l'humidité à l'intérieur d'un cylindre creux formé lors dudit processus de perçage et roulage ;
    - on maintient la surface interne, juste formée, de ce cylindre creux à une température de 1150 °C ou plus, dans une atmosphère chargée d'humidité, qui en contient de 2,5 à 20 % en volume, cet environnement chargé d'humidité étant maintenu pendant 15 secondes ou plus ;
    - il se forme sur cette surface interne une couche d'oxyde comprenant de l'oxyde de fer FeO ;
    - et ce n'est qu'ensuite que l'on exécute le processus d'allongement et roulage.
  2. Procédé de façonnage à chaud d'un acier au chrome, conforme à la revendication 1, caractérisé en ce que, dans le cas où l'on met un lubrifiant à l'intérieur dudit cylindre creux, on apporte ladite humidité avant de mettre ce lubrifiant.
EP04770813A 2004-07-20 2004-07-20 PROCÉDÉ DE FAÇONNAGE À CHAUD D' UN ACIER CONTENANT DU Cr Expired - Fee Related EP1795274B1 (fr)

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PCT/JP2004/010302 WO2006008804A1 (fr) 2004-07-20 2004-07-20 PROCÉDÉ DE FAÇONNAGE À CHAUD D’UN ACIER CONTENANT DU Cr

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EP1795274A1 EP1795274A1 (fr) 2007-06-13
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EP1795274B1 true EP1795274B1 (fr) 2012-02-15

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CN101426594B (zh) * 2006-04-28 2011-04-06 住友金属工业株式会社 不锈钢钢管的制造方法
DE102011078171A1 (de) * 2011-06-28 2013-01-03 Robert Bosch Gmbh Verfahren zum Aufbringen einer korrosionsfesten und verschleißfesten Schicht auf einem Metallteil
TWI450976B (zh) * 2012-01-02 2014-09-01 China Steel Corp 彈簧盤元之感應熱處理方法
JP6008066B2 (ja) * 2014-10-08 2016-10-19 新日鐵住金株式会社 高強度と優れた化成処理性を有する熱処理鋼製品及びその製造方法

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JPH0890043A (ja) * 1994-09-26 1996-04-09 Sumitomo Metal Ind Ltd ステンレス継目無鋼管の製造方法
JP4417634B2 (ja) * 2003-01-20 2010-02-17 住友金属工業株式会社 継目無鋼管の製造方法

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JPS6415356A (en) * 1987-07-08 1989-01-19 Kobe Steel Ltd Hot-rolled steel sheet excellent in adhesive strength of scale and its production

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EP1795274A1 (fr) 2007-06-13
CN100493746C (zh) 2009-06-03
WO2006008804A1 (fr) 2006-01-26
EP1795274A4 (fr) 2009-03-18

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