CN103589952A - Rare earth alloying TRIP steel - Google Patents

Abstract

The invention relates to a rare earth alloying TRIP steel, wherein the chemical components of the slab meet: 0.18-0.22% of C, less than or equal to 0.8% of Si, 1.4-2.4% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, less than or equal to 0.8% of Alt, more than or equal to 0.025% of Nb, more than or equal to 0.01% of La, and the balance of Fe and unavoidable impurities. According to the present invention, the aluminum deoxidation manner is adopted to smelt, such that the TRIP steel produced through the method has excellent mechanical properties, wherein a tensile strength achieves more than 600 MPa, a yield strength achieves more than 400 MPa, and an elongation achieves more than 20%; and the rear earth solid state reaction effect is adopted to balance the percentage content of the microstructure component of the material so as to make the mechanical properties of the TRIP steel achieve the reasonable match and eliminate zinc-plating surface quality problem caused by high Si element content.

Description

A kind of RE alloyed TRIP steel

Technical field

The invention belongs to material heat treatment field, particularly steel plate continuous cooling transformation technique.

Background technology

TRIP steel is a kind of AHSS, is to make detecting residual austenite in steel plate strain induced martensite forming core under viscous deformation effect by phase-change induced plastic effect, introduces phase transformation strengthening and plasticity growth mechanisms, improves intensity and the toughness of steel plate.TRIP steel has polyphase structure, and existing soft phase ferrite, also has hard phase bainite, also has metastable residual austenite, in deformation process, can progressively change into martensite.The countries such as Germany, Korea S, Japan, Belgium are walked in the prostatitis of TRIP steel research, and German Research goes out pot galvanize TRIP steel, and TRIP600, other steel grade of TRIP800 grade have commercially produced; Korea S's Pu item has been developed 800MPa, 1000MPa and other Cold-Rolled TRIP Steel of 1200MPa level, and hot rolling TRIP600, TRIP800 are also just in Industry trial-production; After Belgium cock Li.Sang boolean company adopts activated diffusion and the enrichment of cementite microtextured, apply bell-type annealing technique, succeed in developing the TRIP steel without silicon and aluminium.Japan has also developed the TRIP steel plate of 600～800MPa level and the ultrahigh-strength steel plates of 1000MPa level.Since 2000, domestic research institution conducts in-depth research TRIP steel, and has obtained very much progress.Although automobile high-strength cold continuous rolling TRIP steel national standard is promulgation also, Anshan iron and steel plant can have been produced cold rolling TRIP590 steel and TRIP780 steel plate strip in batches, and Baosteel is developed the steel such as cold rolling TRIP600 and pot galvanize TRIP600.

To TRIP steel, research concentrates on three aspects substantially, and the one, the rationalization of thermal treatment process is explored; The 2nd, the research of alloying element on the impact of microstructure and property; The 3rd, the research of stability of retained austenite.As DQ steel heat treatment process two-phase (α+γ) district's critical temperature (Ac3～Ac1) isothermal processes that can realize the requirement of TRIP steel at continuous annealing furnace with process after cooling fast.Zinc-plated zinc liquid temperature is about 460 ℃, and zinc-plated rear cooling section cooling temperature, lower than 50 ℃, can be realized thermal treatment process and the follow-up quick cooling requirement of warm austempering in TRIP steel.

From TRIP steel chemical composition, with manganese, the silicon of middle low-carbon (LC) be steel or manganese, aluminium be steel or manganese, silicon, aluminium compound be that steel etc. is comparatively common, the TRIP steel report of high-carbon is less.The effect result of study demonstration of rare earth element to steel, rare earth can make it form martensitic temperature (being Ms) reduction, and martensitic stucture is changed and has obvious impact.Effect of Rare Earth On Micro Alloying In Steel size depend on trace rare-earth element the interaction of solution strengthening, rare earth element and other solute elements, the existence of rare earth (atom, inclusion or compound), particularly in the segregation situation of crystal boundary, and the impact of RE Elements on Steel surface and matrix structure etc.In different rare earth steels, all observe structure refinement, change ferritic content and size, the phenomenons such as gathering alligatoring of inhibition Carbide Phases.

The present invention discloses a kind of RE alloyed TRIP steel, mainly by the mode of microalloying of rare earth, impels bainite transformation to aggravate, thereby the quantity of ferrite, bainite and residual austenite in balance TRIP steel has guaranteed the rational Match of TRIP steel plasticity and intensity.

Summary of the invention

The object of the invention is to disclose a kind of RE alloyed TRIP steel.

Technical scheme of the present invention is such, (weight percent) chemical composition content of RE alloyed TRIP plate slab should meet: C0.18%-0.22%, Si≤0.8%, Mn1.4%-2.4%, P≤0.020%, S≤0.010%, Alt≤0.8%, Nb >=0.025%, La >=0.01%, surplus is Fe and inevitable impurity.Adopt single rare earth lanthanum microalloy treatment, by Rare Earth Lanthanum single-element microalloy treatment method, change phase transition point temperature and solid-state reaction kinetics.Adopt aluminium deoxidation mode to smelt.

TRIP steel board has had excellent mechanical property, and more than tensile strength reaches 600MPa, more than yield strength reaches 400MPa, unit elongation reaches more than 20%.Main strengthening phase is meticulous martensite, ferrite and residual austenite.

Outstanding advantages of the present invention is by the effect of rare earth element solid state reaction, the percentage composition of the microtexture component of balance material, thus make the mechanical property of TRIP steel reach comparatively reasonably coupling, abandon the galvanizing surface quality problems that cause because of high-content Si element.

Embodiment

Below in conjunction with embodiment, the present invention is further detailed explanation.

Embodiment 1:

The chemical composition of steel ingot and content (weight percent) are: C0.20%, and Si0.37%, Mn1.58%, P0.0124%, S0.004%, Alt0.040%, Nb0.033%, La0.013%, surplus is Fe and inevitable impurity.1250 ℃ of the Heating temperatures of steel ingot, soaking time 2.5 hours, 1190 ℃ of roughing temperature, 980 ℃ of final rolling temperatures, 850 ℃ of finishing temperatures, two sections of rolling total reductions 95%, slab is treated temperature thickness 10mm.Average on-line cooling speed is 30 ℃/s, and production board thickness is 4mm.Sampling detects, and its mechanical property detected value is in Table 1.

Table 1 mechanical property detected value

Claims (4)

1. a RE alloyed TRIP steel, it is characterized in that chemical composition is by weight percentage: C0.18%-0.22%, Si≤0.8%, Mn1.4%-2.4%, P≤0.020%, S≤0.010%, Alt≤0.8%, Nb >=0.025%, La >=0.01%, surplus is Fe and inevitable impurity.

2. a kind of RE alloyed TRIP steel as claimed in claim 1, is characterized in that changing phase transition point temperature and solid-state reaction kinetics by Rare Earth Lanthanum single-element microalloy treatment method.

3. a kind of RE alloyed TRIP steel as claimed in claim 1, is characterized in that main strengthening phase is meticulous martensite, ferrite and residual austenite.

4. a kind of RE alloyed TRIP steel as claimed in claim 1, is characterized in that adopting aluminium deoxidation mode to smelt.