JP2009522452A5 - - Google Patents

Description

From European Patent No. 1,108,07 2 B1 (Patent Document 1), a two-phase structure consisting of 70-90% ferrite and 30-10% martensite after finishing roll processing with two-stage cooling. There are known methods for producing duplex stainless steels. The first (slow) cooling is carried out in one cooling section, in which the hot strip is passed through water cooling stages arranged one after the other at a cooling rate of 20-30 K / sec. Cools reliably. In this case, the cooling is adjusted so that a cooling curve having a temperature that is still high enough to allow ferrite formation to be performed rapidly enters the ferrite region. This first cooling lasts for a period such that at least 70% of the austenite is converted to ferrite before another (rapid) cooling is followed immediately or without a downtime.

From European Patent Application No. 1,396,549 A1 (Patent Document 2), iron and inevitable impurities are used to produce hot-rolled steel strips having TRIP properties and free of pearlite. In addition, at least one element of the elements Ti and Nb as an important component and optionally at least one element of up to 0.8 Cr, up to 0.8% Cu, up to 1.0% Ni. The molten steel contained is cast into a thin-walled slab that is annealed at 1000-1200 ° C. for 10-60 minutes in an annealing furnace with an inlet temperature of 850-1050 ° C. After removing the scale, the thin slab is finish hot rolled at 750-1000 ° C and then cooled in two stages to a coiling temperature of 300-530 ° C. In this case, the cooling under the control of the first stage is performed at a cooling rate of at least 150 K / s and a cooling down time of 4 to 8 seconds. In addition to the method operations described above, it is important that Ti and / or Nb be present. This is because these elements are dissolved until the start of hot rolling, and during subsequent precipitation, the fineness of the hot strip, the increase in residual austenite content and the stability of the hot strip are improved. Because.

[0009]
Furthermore, EP 1,394,279 B1 (Patent Document 3) discloses a method for producing steel with higher strength and higher ductility and less carbon content. This steel has a tensile strength greater than 800 MPa, a similar expansion greater than 5% and an elongation greater than 20%. Starting from a quenched and heat tempered semi-finished product, a steel having a mixture of 0.20% C, 1.60% Mn and boron and more than 90% martensitic phase components is fully rolled. After cold rolling more than 20%, an annealing treatment is performed at a temperature of 500 to 600 ° C. At that time, a structure having an ultrafine crystalline granular ferrite structure of 100 to 300 nm is obtained together with iron carbide precipitated in the ferrite.
[Patent Document 1] European Patent No. 1,108,07 2 B1 Pat Patent Document 2] EP-1,396,549A1 [Patent Document 3] European Patent No. 1,394,279B1 Description [Disclosure of the Invention]
[Problems to be solved by the invention]

1, 2, 3 Method process 10 Hot rolling 20 Cooling under control 30 Area annealing 40 Strip galvanization 50 Press forming of connecting element 60 Pipe production 70 Press forming of structural member 80 Post-processing to finished product

Claims (1)

Conventional hot rolling line, thin-walled slab casting and rolling plant or corresponding narrow strip production using standard analysis and standard method operations, where the composition of the multiphase steel contains at least 30% ferrite and up to 50% martensite In a method for adjusting the properties of the intended combination in the case of hot-rolled multi-phase steels, such as duplex steels and TRIP steels produced on line and intermediate strip production lines or wire production lines, Subsequent to a cooling or subsequent finishing step from 10), for example subsequent to the finishing of the structural member, a subsequent or intermediately connected annealing process (30, 30) using a variable annealing temperature and a variable annealing period. 35) adjusting the desired combination of strength and yield ratio of the multiphase steel according to 35).