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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/02—Hardening by precipitation
• • 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
  • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
  • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot 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
  • C21D2261/00—Machining or cutting being involved
• • 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

Definitions

• the invention relates to a method according to the preamble of claim 1.
• the aim is to use profiles with high strength values in the delivery state for use as construction parts when high component strengths are to be achieved with small weights, e.g. B. for vehicle parts, hydraulic cylinders, steel structural components or when high loads are inevitable in the design limitation of dimensions, such as. B. in oilfield pipes for drilling technology.
• small weights e.g. B. for vehicle parts, hydraulic cylinders, steel structural components or when high loads are inevitable in the design limitation of dimensions, such as. B. in oilfield pipes for drilling technology.
• the pipes to limit the yield strength of the profiles to about 500 N / mm 2 and the tensile strength to about 650 N / mm 2 . Accordingly, the pipes must be formed from strips or piercing soft grades with a yield strength of up to 500 N / mm 2 , welded and, if the demands on the yield strength are higher, liquid-hardened and tempered, ie tempered.
• the invention has for its object to provide a method of the type mentioned, by means of which the disadvantages of the known methods avoided and in a relatively simple and therefore cost-effective manner while avoiding costly remuneration a manufacture of high-strength profiles, in particular closed tube profiles with a yield strength of more than 500 N / mm 2 , a tensile strength of more than 600 N / mm 2 and high toughness including the required mechanical welding.
• a precipitation-hardenable fine-grained steel is preferably understood to mean a steel which has a composition of Remainder has iron and usual impurities and which has an ASTM grain size of finer 6 in the finished state.
• the überalternde artificial aging of the precipitation hardenable fine-grain steel is done in which no grain refinement during cooling of preferably carried out above the A I -temperature at 850 to 750 ° C into a coil gehaspelten steel strip.
• cooling is slowed down speed reached, through which finely divided excretions are avoided and coagulated excretions are achieved.
• a corresponding microstructure is achieved according to the invention in sheet metal by furnace cooling, by means of which radiation and convection are prevented, from the rolling heat. With both the coiled steel strip and the steel sheet, it is essential that the slowed down cooling is carried out up to a temperature of 400 ° C., while the subsequent cooling down to room temperature is carried out in any way.
• an open profile produced cold in this way is preferably welded to a closed tubular profile before further treatment.
• the open or closed profiles produced according to the invention are subsequently subjected to precipitation hardening, which is also referred to as particle hardening and fine grain hardening, to dissolve the coarse precipitates by solution annealing above the A C3 temperature with subsequent cooling.
• precipitation hardening which is also referred to as particle hardening and fine grain hardening
• the type of cooling should be used to achieve the formation of finely divided carbides, nitrides and carbonitrides with simultaneous fine grain formation.
• the temperature of the solution annealing is advantageously chosen to be the temperature at which the stretch reduction of the starting pipe is started, ie the piercing temperature. A separate solution annealing is then no longer required in these reduced-stretch pipes, since the cooling following the solution annealing takes place during the reduction in stretch or immediately afterwards.
• tempering at a temperature of 500 to 600 ° C.
• This tempering can advantageously also be carried out in such a way that the cooling following the solution annealing is interrupted and continued in the range from 500 to 600 ° C. at a reduced cooling rate.
• a steel with a chemical composition of The rest of the iron and unavoidable impurities are coiled after the hot rolling to a strip, preferably hot wide strip without intermediate cooling after the last rolling pass at a temperature of about 750 ° C. and cooled to 400 ° C. in still air.
• the natural heat storage capacity of the federal government is used for the aging hot aging, in which the precipitation and coagulation of the carbides, nitrides and carbonitrides take place largely completely, avoiding grain refinement. Further cooling to room temperature is done in any way.
• the hot wide strip has a yield strength of 455 N / mm 2 and a tensile strength of 650 N / mm 2 after it has completely cooled to room temperature or has aged.
• the hot wide strip is then cut into strips, trimmed as necessary and subsequently cold formed, in the present example in a continuous process formed into a slotted tube, which is welded to a tube with a diameter of 159 mm by means of a high-frequency welding device.
• This tube is heated to a temperature of about 1030 ° C and rolled with this temperature as the piercing temperature in a stretch reduction process to the desired diameter of 60.3 mm.
• the finished tube is cooled on a cooling bed in still air to room temperature.
• the coarse carbides, nitrides and carbonitrides are dissolved in the steel while the tube is being heated or held to the rolling temperature and are finely distributed during cooling or after the rolling with simultaneous formation of fine grains.
• the finished tube has a yield strength of 648 N / mm 2 and a tensile strength of 845 N / mm 2 .

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Forging (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6059969

Family Applications (1)

Country Status (11)

Families Citing this family (9)

Family Cites Families (27)

• 1979
  • 1979-01-02 DE DE2900022A patent/DE2900022C3/de not_active Expired
  • 1979-12-01 EP EP79104823A patent/EP0013331B1/de not_active Expired
  • 1979-12-03 GR GR60667A patent/GR66519B/el unknown
  • 1979-12-26 US US06/106,548 patent/US4414042A/en not_active Expired - Lifetime
  • 1979-12-26 SU SU792858051A patent/SU1087078A3/ru active
  • 1979-12-27 RO RO7999732A patent/RO80871A/ro unknown
  • 1979-12-27 JP JP16953379A patent/JPS5591941A/ja active Pending
  • 1979-12-27 CA CA342,651A patent/CA1125150A/en not_active Expired
  • 1979-12-28 NO NO794340A patent/NO151295C/no unknown
  • 1979-12-31 ES ES487392A patent/ES487392A1/es not_active Expired
• 1980
  • 1980-01-02 MX MX180650A patent/MX152698A/es unknown
• 1984
  • 1984-01-30 US US06/499,995 patent/US4732623A/en not_active Expired - Fee Related

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