Classifications

• • 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
  • 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
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • 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
  • 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
  • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
• • 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
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0231—Warm rolling

Definitions

• the invention relates generically to a method for producing fine-grained, weldable large tube sheets from a micro-alloyed steel by thermomechanical rolling, the steel with
• Balance iron and usual impurities is produced and continuous cast slabs having titanium nitride precipitates made of this steel are thermomechanically rolled at a temperature of at most 850 ° C. with a degree of deformation of at least 60% and then finish-rolled in a temperature range of 750 to 650 ° C.
• the percentages indicate percentages by weight.
• Calcium may also be included in the impurities within the scope of the invention.
• the titanium content of the steel is in the range of 0.008 to 0.025%. A vote of the titanium content on the nitrogen content is not carried out. Niobium is not a mandatory alloying element.
• the steels are TiN-controlled steels in terms of precipitation hardening and grain refinement. After continuous casting, one works at a high cooling rate in order to produce a large number of fine, as it were fine-grained TiN precipitates, the size of which does not exceed 0.05 pm. Thereafter, precautions are taken to ensure that the size of the fine TiN precipitates does not increase in the further process and that the very fine TiN precipitates are also present in the finished rolled heavy plate.
• niobium can also be added to the steel, up to a maximum of 0.08%. However, this addition is not mandatory.
• This addition of niobium which can be combined with a considerable addition of vanadium, nickel and chromium, is expected to improve the strength and toughness. At least without substantial addition of the expensive alloying elements vanadium and / or nickel and / or chromium can improve the strength and toughness of the however, a high content of fine TiN precipitates grown steels cannot be confirmed.
• the element niobium does not work as expected in the TiN-controlled steels, since the low annealing temperature of the continuous cast slabs does not sufficiently dissolve the niobium bonds. If the titanium content is low in the known measures, the niobium forms NbCN with the effect of reducing the strength properties. If there is too much titanium, the toughness is impaired, including TiC.
• the invention has for its object to perform the generic method for a steel containing niobium as a compulsory microalloying element so that the large tube sheets are not controlled by TiN, but are controlled by niobium in terms of precipitation hardening and grain refinement.
• the invention teaches that the steel with a titanium content corresponding to about 3.5 to 4 times the existing nitrogen content and with a niobium content of at least 0.02 to 0.06% is produced that the continuous cast slabs on a Temperature between 1120 and 1160 ° C are heated, the titanium nitride precipitations reach a size of 0.2 to 0.06 microns, and that the continuous cast slabs, starting from this temperature, pre-rolled with a degree of deformation of at least 55% and after an intermediate cooling be subjected to thermomechanical rolling and finally finish rolling.
• the continuous cooling is carried out at a high cooling rate, with TiN precipitates being formed.
• the invention is based on the knowledge that titanium can perform a completely different function in a microalloyed steel of the specified composition with niobium as a mandatory alloying element than in a TiN-controlled steel. Titanium only acts as a denitrification element and prevents the formation of NbCN, ie niobium carbonitride, when it cools down from the continuous casting temperature.
• the process is carried out in such a way that the enlargement of the TiN precipitates which is to be carefully avoided according to the prior art (DE-OS 30 12 139, DE-OS 31 46 950) occurs precisely because the specified higher heating is used.
• the temperature at which the described enlargement of the TiN precipitates and the dissolution of the Nb bonds take place can be set as the annealing temperature.
• the time required for the treatment can easily be determined experimentally, ensures that the niobium dissolves in the austenite and can be determined by the limits specified for the size of the TiN precipitates. In general, the effects described already occur when the continuous cast slabs are heated.
• both thermomechanical rolling and finish rolling are refined.
• the invention teaches that the thermomechanical rolling is carried out at a temperature between 820 and 790 ° C, the finish rolling at a temperature between 700 and 680 ° C. It is within the scope of the invention, after the finish rolling, the large tube sheet with water at a speed of more than 15 ° C per second cool on average to a temperature between 550 and 500 ° C and then in air to room temperature. As a result, the strength is increased again without a loss of toughness and without the need for special alloying elements.
• Ferritic-pearlitic structure with a grain size of 11 to 12 ASTM.
• Ferritic-bainitic structure that corresponds to a grain size of less than 12 ASTM.
• the large pipes formed from the sheets produced according to the invention are particularly suitable for use as line pipes in permafrost areas because of the outstanding technological values.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Mechanical Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Heat Treatment Of Steel (AREA)
• Rigid Pipes And Flexible Pipes (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Articles (AREA)
• Piles And Underground Anchors (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Radar Systems Or Details Thereof (AREA)
• Rod-Shaped Construction Members (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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ID=6168326

Family Applications (1)

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Cited By (4)

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Citations (6)

Family Cites Families (5)

• 1983
  • 1983-05-11 CS CS833307A patent/CS330783A2/cs unknown
  • 1983-05-23 JP JP58090569A patent/JPS5913023A/ja active Pending
  • 1983-06-23 AU AU16189/83A patent/AU1618983A/en not_active Abandoned
  • 1983-07-02 EP EP83106483A patent/EP0098564B1/fr not_active Expired
  • 1983-07-02 AT AT83106483T patent/ATE19099T1/de not_active IP Right Cessation
  • 1983-07-07 CZ CS835157A patent/CZ278612B6/cs not_active IP Right Cessation
  • 1983-07-07 SK SK5157-83A patent/SK515783A3/sk unknown
  • 1983-07-07 NO NO832485A patent/NO161507C/no unknown
  • 1983-07-07 AU AU16632/83A patent/AU551994B2/en not_active Ceased
  • 1983-07-08 JP JP58123524A patent/JPH0647695B2/ja not_active Expired - Lifetime
  • 1983-07-08 CA CA000432128A patent/CA1211343A/fr not_active Expired
  • 1983-07-08 MX MX197979A patent/MX159207A/es unknown
  • 1983-07-11 US US06/512,450 patent/US4494999A/en not_active Expired - Lifetime

Patent Citations (6)

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