Ultra-low carbon ferritic stainless steel cold-rolled plate process

Factors affecting cold-rolled sheet with a body-centered cubic crystal structure of texture formation are:

(1) chemical composition. Increasing the chromium content ferritic stainless steel can be formed in favor of forming properties of texture components in the plate rolling process, the stabilizing elements Nh will strengthen austenite deformation texture, which led to a transformation texture y strengthening;

(2) solid solution elements and two-phase particles. Solute C atom of rotation ferrite grains rolling great impediment exists a two-phase solid solution alloying elements and particles does not affect the ferrite rolling texture components, but a solid solution alloy elements and the presence of two-phase particles can affect the degree of ferrite grains in the rolling process to stabilize the orientation of rotating them. ri, Nl1 added to help ferritic rolling texture to stabilize the rotation orientation;

(3) thermal processing. Such as low carbon steel with finishing temperature lower when ferrite region rolling, {111} recrystallization texture will be significantly enhanced;

(4) cold rolling reduction;

(5) annealing process, including temperature and time.

1 Materials and methods

Experimental ultra-low carbon steel is Crl8 ferrite laboratory vacuum induction furnace and rolling of the three components of 409 stainless steel plate. Cast ingot was forged blank size is 30mm thick x240mm wide × (560 ~ 660) mm long, for three billets were six times rolled, the heating temperature 1070 ℃, finishing temperature 851 ℃, hot-rolled total pressure under 88%, the hot rolled sheet having a thickness of 3.5mm, and finally cold rolled to 1.0mm sheet.

Taking into 1mm thick cold-rolled sheet width x28mm x20mm long rectangular specimen, wherein the length direction is the rolling direction. With a salt bath furnace at 850 ℃ cold rolled specimens condition 0 ~ 15min isothermal annealing at different times, according to the reply recrystallization stage determine the degree of change in hardness curve complete recrystallization, select Done to continue holding 3min after recrystallization sample extend the cut direction 7mm, polished to 1500 grit grinding section, the final adoption FeC1: HC1: H, O mass ratio of 1:10:20 in etchant etching, optical microscope photographs, According to GB / T6394-2002 ~ determination of the average grain size of metal "in grain size rating.

2 Results and discussion





Cr18-3 with the other two different orientations of its fiber texture density strength of 12.247. The reason may be Nb leads to inhibition of recrystallization texture development is not sufficient, while the original {001} texture strong, disappeared in the subsequent stage of the annealing is slow, still leave a certain proportion of damage formability Cr18-1 {001} <110> orientation texture.

Mechanical properties of ultra-low carbon 304 stainless steel sheets Cr18 annealed cold rolled sheet and formability of experimental data, the yield strength of Nb single stable Cr18-1 annealed cold rolled sheet and the highest tensile strength, and Ti, Nb double stabilized Cr18-2 secondly, ] ri single stable Crl8-3 lowest strength.

3 Conclusions

(1) Nb single stabilized recrystallized grains Crl8 cold rolled sheet after annealing treatment was small, high yield and tensile strength, but poor formability, r value is low, reach deep drawing timber requirements.

(2) Although the ri single stabilized Crl8 recrystallized grain size of the largest cold-rolled sheet, the intensity is not high, but the plastic is best conducive to forming properties of the {111} plane texture orientation density higher strength, its r value can reach 1.55, in line with the requirements of deep-drawing timber.

(3) Ti, Nb double stabilized recrystallized grain size Crl8 moderate cold rolled sheet, the r value reached 1.48, in line with the requirements of deep-drawing timber.
Average grain diameter and grain size level are: 0.18Nb; (e) Crl8-3,0.21Ti add Crl8 ferritic stainless steel cold rolled sheet grain 0.29% Nb of most small and uniform, because Nb in steel solid solution existence and carbonitride precipitation and steel C, N phase formation of niobium, Nb atoms in solid solution enrichment at the grain boundaries, and the lower the grain, so niobium has strongly drag the grain boundary mobility, this effect is much higher than the solution of titanium. In addition, the small dispersed niobium carbonitride NbC, NbN, Nb (CN) can stop pinning dislocations and subgrain boundary migration of grain growth with a strong impediment.