Classifications

• • 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
  • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
• • 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
  • 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
  • C22C38/44—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
  • 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
  • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
• • 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
• • 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
  • C21D2211/008—Martensite

Definitions

• the present invention relates to the manufacture of boilers intended to work under pressure under conditions of risk of cracking under stress caused by H 2 S.
• boiled enclosures are used to treat gases having high H 2 S contents. These enclosures which work under pressure and contain flammable gases pose significant safety problems which are resolved by applying codified construction rules.
• codified construction rules by different standards or building codes, in particular the NACE MR 0175-97 standard and the codes of the ASME code type.
• H 2 S in particular in the presence of moisture, creates risks of rupture by stress corrosion, and the NACE standard defines conditions for partial pressure of H 2 S for which specific construction rules must be observed to guarantee the safety of the installations. These construction rules are also defined by the standard and are binding on builders.
• the NACE MR 0175-97 standard requires that materials must give satisfactory results when tested for cracking in the presence of hydrogen defined by standard NACE TM 0177-90, and indicates very generally the materials and the conditions of implementation likely to give satisfaction.
• For boilers it is theoretically possible to use carbon or low alloy steels, too both in the normalized state and in the quenched quenched state, provided that these contain less than 1% nickel and they have a hardness less than or equal to 22 HRC. Yes the enclosures or their components have been tensioned, the stress relieving must have been executed above 595 ° C. In addition, after assembly by welding of the components, the enclosures must be subjected to a post-welding heat treatment at a temperature above 620 ° C so as to obtain a hardness less than or equal to 22 HRC at all points.
• pressure vessels working under the risk of cracking under stress caused by H 2 S are manufactured using carbon and manganese steels in the standardized state whose guaranteed tensile strength Rm does not exceed not 485 MPa. This results in significant wall thicknesses and therefore heavy weights for the equipment thus constructed. The high weight is an annoyance, especially for the equipment installed on marine platforms.
• micro low carbon steels alloyed with vanadium or niobium obtained by controlled rolling. These steels achieve a guaranteed tensile strength level of around 550 MPa and a limit level guaranteed elasticity of around 450 MPa. On the one hand, these steels are not usable for making hot formed parts, on the other hand, they are only applicable only to thicknesses less than 40 mm.
• suitable welding conditions must be chosen, characterized in particular by a minimum preheating temperature and a welding energy per unit of minimum length.
• These welding conditions can be synthesized in the form of a cooling time between 800 ° C and 500 ° C of the weld bead or the area affected by the heat of welding (as defined in standard NF A 36- 000).
• this cooling time must be greater than a critical value which they have called “trc 800/500” (which will be defined more fully below), and which is a function of the steel used and of the constraints imposed by the building codes. Welding is all the more difficult to perform with reliability as this value is high.
• Tempered steels used in boilermaking have a trc 800/500 (critical cooling time between 800 ° C and 500 ° C) greater than 10 s, which is too important to allow these steels to be used in satisfactory conditions for manufacturing H 2 S resistant pressure vessels
• the object of the present invention is to remedy these drawbacks by proposing a means for manufacturing boilers, working in H 2 S medium, lighter than known speakers, while also being safe.
• the chemical composition of the steel is such that Nb + V ⁇ 0.02%; preferably also, it is such that: 0.04% ⁇ C ⁇ 0.09% Cr ⁇ 0.6% 0.2% ⁇ Mo ⁇ 0.5%
• the invention also relates to a boiler enclosure intended to work under pressure between - 40 ° C and 200 ° C under the conditions of risk of cracking under stress generated by H 2 S as defined by the standard NACE MR 0175-97.
• the steel has a martensitic or martensito-bainitic tempered structure containing less than 10% ferrite, and preferably not containing ferrite, a tensile strength Rm greater than or equal to 550 MPa, a yield strength greater than or equal at 450 MPa, an elongation A% greater than 17%, and a resilience KCV at - 40 ° C greater than or equal to 40 Joules,
• the hardness at all points of the surface of the enclosure is less than 248 HV.
• the composition of the steel is such that Nb + V ⁇ 0.02%. It is also preferable that: 0.04% ⁇ C ⁇ 0.09% Cr ⁇ 0.6% 0.2% ⁇ Mo ⁇ 0.5%
• the thickness of the walls of the sheet metal enclosure can be between 50 mm and 300 mm.
• the chemical composition is such that Nb + V ⁇ 0.02%. It is also preferable that: 0.04% ⁇ C ⁇ 0.09% Cr ⁇ 0.6% 0.2% ⁇ Mo ⁇ 0.5%
• the steel is chosen so that the critical cooling time trc 800/500 is less than 10 s.
• the critical cooling time trc 800/500 is measured by a series B.O.P. (Bead On Plate) which consists of measuring the hardness under a bead on a 20 mm thick sample on which a weld bead was made by the submerged arc process, then a post-welding heat treatment consisting of holding at 620 ° C for 4 hours, this holding being preceded by a heating and followed by cooling both carried out at a speed less than 50 ° C / hour.
• B.O.P. Bead On Plate
• trc 800/500 we vary the energy of welding between 1 kJ / mm and 3 kJ / mm, which varies the cooling time tr 800/500 between 4s and 20s, then we draw the curve giving the hardness under bead as a function of the cooling time tr 800/500, and the time for determining cooling tr 800/500 for which the hardness under cord is 248 HV; this time is the critical cooling time trc 800/500.
• the hardness under cord is measured according to French standard NF A 81-460.
• the NACE standard refers to a lower hardness under cord at 22 HRC.
• HRC hardness measurement is often difficult to perform, more than in principle, it makes a local average of the hardness. It is better and more easy to carry out a Vickers hardness measurement, and because of the relationship between hardness Vickers and Rockwell C hardness, ensuring Vickers hardness less than or equal at 248 HV, a Rockwell C hardness of less than 22 HRC is guaranteed.
• the quenching is carried out after reheating above the AC 3 point of the steel by cooling with water, oil, blown air or air, depending on the thickness of the component.
• the heat treatment includes at least one tempering after quenching and carried out at a temperature generally greater than 550 ° C., and preferably less than 680 ° C.
• a tempering is carried out at a temperature above 680 ° C, it corresponds to an “intercritical” treatment. In this case, it can be necessary to control cooling as after quenching.
• the “post-welding” treatment is an income produced at a temperature greater than or equal to 595 ° C, and preferably greater than 620 ° C, but less than 680 ° C.
• the quenching treatment and income can be done before or after shaping, and income can be intended simply to facilitate shaping or on the contrary to impart to steel its final properties.
• the final properties of the steel itself are imparted by the post-welding treatment, and the pre-tempering temperature is lower than the post-welding treatment temperature.
• the post-welding treatment essentially serves to relax the enclosure and soften it areas affected by welding heat; the post-welding treatment must, then, be performed at a temperature below the tempering temperature.
• the temperature T PS of post-welding treatment making it possible to obtain a hardness under a bead of less than 248 HV (or 22 HRC) depends, in part on the parameter tr 800/500, it follows that it is preferable to simultaneously determine the conditions welding and post-welding treatment, which can be done by a few BOP tests on samples.
• steels having the following chemical compositions can be used: VS Yes Mn Or Cr Mo Cu V THIS AT 0.08 0.24 0.89 1.8 0.25 0.4 0.21 0.01 0.28 B 0.07 0.23 1.57 1.37 0.21 0.21 0.23 0.01 0.30 VS 0.06 0.23 1.72 1.77 0.11 0.21 0.24 0.01 0.31 D 0.06 0.23 1.32 1.6 0.26 0.25 0.2 0.01 0.28 E 0.06 0.16 0.9 1.87 0.25 0.4 0.21 0.01 0.25
• These steels can be quenched and then returned to 665 ° C to obtain a returned martensito-bainitic structure, free of ferrite having a hardness of between 195 and 210 HV.
• These steels have a critical cooling time trc 800/500 of less than 10 s, as shown by the following results, obtained using the method described above:
• a steel having the following composition can be used: VS Yes Mn Or Cr Mo Cu Al S P Sn Ace Sb THIS 0.04 0.14 1.20 0.85 0.18 0.29 0.72 0.02 0.002 0.006 0.015 0.014 0.001 0.26
• This steel has a critical cooling time trc 800/500 of less than 4 s.
• the pressure vessel should have been built with 106 mm thick sheets. We thus obtained a gain of weight of 12%.
• tempered steel which makes it possible to obtain on sheets approximately the same tensile characteristics as above, and which has the following chemical composition: VS Yes Mn Or Cr Mo Cu Al V S P Sn THIS 0.075 0.245 1.32 0.509 0.147 0.212 0.17 0.018 0.047 0.0007 0.0088 0.009 0.26
• this steel has the drawback of having a very high critical cooling time trc 800/500, since for a cooling time of 10.4 s, the hardness under a bead is 262 HV after a post-welding treatment of 4h at 620 ° C, which does not meet the conditions imposed by the NACE standard.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Articles (AREA)
• Arc Welding In General (AREA)
• Butt Welding And Welding Of Specific Article (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Catalysts (AREA)

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• 1998
  • 1998-07-21 FR FR9809271A patent/FR2781506B1/fr not_active Expired - Fee Related
• 1999
  • 1999-07-01 EP EP99401632A patent/EP0974678B1/de not_active Expired - Lifetime
  • 1999-07-01 AT AT99401632T patent/ATE265553T1/de not_active IP Right Cessation
  • 1999-07-01 DE DE69916717T patent/DE69916717T2/de not_active Expired - Fee Related
  • 1999-07-01 ES ES99401632T patent/ES2220020T3/es not_active Expired - Lifetime
  • 1999-07-16 KR KR1019990028899A patent/KR20000011781A/ko not_active Withdrawn
  • 1999-07-20 CA CA002278407A patent/CA2278407A1/fr not_active Abandoned
  • 1999-07-21 US US09/358,662 patent/US6322642B1/en not_active Expired - Fee Related
  • 1999-07-21 JP JP11206247A patent/JP2000054026A/ja not_active Abandoned

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