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
  • C22C38/04—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
  • C21D8/0221—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
  • 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 invention relates to a hot strip which is at most 5 mm thick made of high strength steel and a process for its Production.
• Hot strip means hot rolled Tape.
• hot strip is only manufactured up to strengths of around 800 N / mm 2 . These are thermomechanically rolled micro-alloyed steels. For applications that require additional strengths, soft hot strip is used and the strength required on the component is set by a subsequent heat treatment. For the thickness range below 2.0 mm, additional cold rolling is usually required to set the desired thickness. The required strength is also set in this case by a suitable heat treatment.
• From GB 2 195 658 A1 are forgings from one Steel with 0.01 to 0.20% C, up to 1.0% Si, 0.5 to 2.25% Mn, up to 1.5% Cr, up to 0.05% Ti, up to 0.10% Nb, 0.005 to 0.015% N and up to 0.06% A1 are known.
• the cooling of the Steel from the austenite area is to be controlled that the structure is fully martensitic. Be revealed however only examples with carbon contents below 0.10% and silicon contents over 0.17%. The Sulfur contents are relatively high at over 0.01%.
• the hot strip has after a broken cooling a dual-phase structure made of polygonal ferrite and one Mixture of pearlite and bainite.
• the hot strip known from DE 30 07 560 A1 is also used after hot rolling at a cooling rate cooled from 1 K / s or faster to a dual phase structure to produce from ferrite and martensite.
• a cooling rate cooled from 1 K / s or faster to a dual phase structure to produce from ferrite and martensite.
• Respect for satisfactory ductility and Weldability properties are carbon content in the Range of 0.02 to 0.09% recommended.
• the preferred Silicon content is relatively high at 1.0%.
• EP 0 492 623 A1 describes a steel made from a silicon-calmed steel Hot strip known, the Si contents of 0.1 wt .-% and more and has a martensite content of 60 - 100%.
• the known Hot strip is used for the production of welded steel pipe without that special emphasis is placed on a good surface quality becomes. Lowering the Si content below a lower limit of 0.03 % By weight is advised against on the grounds that lower ones Si content no longer has the properties of the known hot strip let achieve.
• the invention has for its object to produce a hot strip with tensile strength values over 800 N / mm 2 and at the same time good cold formability in the thickness range ⁇ 5 mm. This would mean an expansion of the direct use of hot strip for cold forming purposes, such as cold pressing, with clear economic advantages that result from the elimination of cold rolling and heat treatment.
• Carbon can preferably be from 0.08 to 0.15%, manganese from 1.75 to 1.90%, chromium from 0.5 to 0.6% and Nitrogen from 0.005 to 0.009% may be included.
• the tensile strength of the hot strip is preferably set to a value in the range from 800 to 1400 N / mm 2 by appropriate selection of the reel temperature within the aforementioned temperature range.
• the hot strip can be hot-dip galvanized to to become more corrosion resistant.
• Well cold-formable high-strength galvanized sheets are preferred for mechanically highly stressed components in automotive engineering used, e.g. for side impact beams and bumpers.
• the steel according to the invention achieves high strength without expensive alloying elements and without annealing like this is the case with known steels.
• a steel with 0.15% C, 0.01% Si, 1.77% Mn, 0.014% P, 0.003% S, 0.028% Al, 0.0043% N, 0.526% Cr, 0.017% Cu, 0.003% Mo, 0.027% Ni, balance Fe became to shed a slab.
• the slab was reduced to approx. 1250 ° C warmed up, at approx. Pre-rolled at 1120 ° C and at 840 ° C Final temperature rolled to a final thickness of 2 mm, then cooled and coiled at 50 ° C. This creates a Structure with more than 95% martensite.
• the yield strength reached values of 1120 N / mm 2 and the tensile strength values of 1350 N / mm 2 with elongation values A 50 to 11.1%.
• Example 2 A steel with the same analysis as in Example 1 was processed into 3.5 mm thick hot strip. The data are given in Table 1. The strength values are significantly higher when reeling instead of over 400 ° C to 95 ° C. sample Final rolling temperature ° C Reel temperature ° C Rp0.2 N / mm 2 rm N / mm 2 1 845 95 940 1243 2 845 95 997 1305 3 845 95 983 1199 4 * 850 420 742 803 5 * 850 420 691 793 6 * 850 420 641 741 7 845 95 916 1089 8th 845 95 1037 1293 9 845 95 1073 1328 10 * 835 455 672 768 11 * 835 455 643 760 12 * 835 455 676 778
• the hot strip can be hot-dip galvanized into the final shape before cold forming. Through the heat treatment cycle at. The martensite is left galvanized. Starting from a hot strip with tensile strengths in the range of 1200 - 1400 N / mm 2 , depending on the heat treatment cycle, tensile strengths between 800 and 1100 N / mm 2 are established during galvanizing.
• a 2.0 and 1.6 mm thick hot strip was galvanized.
• the following table 2 compares the properties in the rolled state and after galvanizing: rolled condition after galvanizing thickness re rm A80 re rm A80 mm N / mm 2 % N / mm 2 % 1.6 1052 1393 5.7 1065 1095 7 1.6 1048 1387 7.6 1040 1082 5.5 2.0 1098 1361 6.6 1058 1082 5.9

Landscapes

• 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 Sheet Steel (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Coating With Molten Metal (AREA)
• Meat, Egg Or Seafood Products (AREA)

Applications Claiming Priority (5)

Publications (2)

Family

ID=26027441

Family Applications (1)

Country Status (12)

Families Citing this family (23)

Family Cites Families (13)

• 1997
  • 1997-07-04 HU HU9903306A patent/HU220900B1/hu not_active IP Right Cessation
  • 1997-07-04 CA CA002260231A patent/CA2260231A1/en not_active Abandoned
  • 1997-07-04 TR TR1999/00053T patent/TR199900053T2/xx unknown
  • 1997-07-04 CN CN97196345A patent/CN1089811C/zh not_active Expired - Lifetime
  • 1997-07-04 CZ CZ9969A patent/CZ6999A3/cs unknown
  • 1997-07-04 ES ES97931775T patent/ES2230613T3/es not_active Expired - Lifetime
  • 1997-07-04 BR BR9710285A patent/BR9710285A/pt not_active IP Right Cessation
  • 1997-07-04 WO PCT/EP1997/003541 patent/WO1998002589A1/de active IP Right Grant
  • 1997-07-04 AT AT97931775T patent/ATE278811T1/de not_active IP Right Cessation
  • 1997-07-04 PL PL97331212A patent/PL185228B1/pl unknown
  • 1997-07-04 EP EP97931775A patent/EP0910675B1/de not_active Expired - Lifetime
  • 1997-07-04 US US09/214,480 patent/US6284063B1/en not_active Expired - Lifetime

Also Published As

Similar Documents

Legal Events