Method for manufacturing thin-specification high-ti wear-resistant steel nm450

A method for manufacturing thin-specification high-Ti wear-resistant steel NM450, comprising the steps of:

• (1) slagging off qualified melted iron with a temperature greater than 1250° C. and a [S] no more than 0.020%, and removing S by KR according to requirements on a temperature, a weight and a sulfur content at a desulfurization end of incoming melted iron, wherein [S] is no more than 0.0020%, a whole-course argon blowing technology is employed, and an alkalinity of final slags ranges from 3.0 to 4.0;
• (2) smelting the melted iron in a converter, using pellet as a coolant, and adding the pellet and oxidized scale according to relevant regulations;
• and adding fluorite in a small amount in batches according to slag situations in the converter, wherein no more than 4 kg of fluorite is added in each ton of steel and no more than 5.5 kg of fluorite is added in each ton of steel during double slag, adding the fluorite 2 min before a blowing end point is strictly forbidden, double slag cutoff tapping is performed by using a slag-blocking awl and a slag-blocking plug, a slag thickness is no more than 50 mm, and deoxidizing is performed by a step-by-step deoxidation technology in the course of converter tapping;
• (3) feeding the melted steel to a LF refining station, and after the melted steel enters the refining station, stirring the melted steel by argon at a flow rate of 300 NL/min to 800 NL/min for 1 min to 2 min to facilitate melting slag;
• inserting a graphite electrode into the melted steel, supplying power to raise a temperature, blowing argon into the melted steel at the same time at an argon blowing flow rate of 100 NL/min to 400 NL/min, and blowing the argon for 4 min to 10 min, wherein the argon blowing flow rate ranges from 100 NL/min to 450 NL/min when desulfurizing the melted steel, and the temperature is measured after blowing the argon for 4 min to 10 min;
• the argon blowing flow rate ranges from 100 NL/min to 400 NL/min during sampling;
• and an argon blowing pressure ranges from 1.2 MPa to 1.8 MPa, slagging materials are added into the melted steel for slagging while refining the melted steel, and desulfurization refining and inclusion removal are performed to control a binary alkalinity R(CaO/Si02) in the slag to range from 1.3 to 2.8, and make Fe0+Mn0 in the slag be less than 2.0%, and the melted steel leaving the station [S] be no more than 0.008%;
• (4) refining the melted steel in a RH furnace, and after the melted steel reaches the RH furnace, opening a steel ladle to a position to be processed, and measuring a clearance height, a slag thickness and a temperature of the steel ladle, wherein a clearance of the steel ladle is controlled to range from 300 mm to 700 mm, a top slag thickness of the melted steel is controlled to be less than 100 mm, and the temperature of the melted steel is 1615° C. to 1630° C.;
• lifting the steel ladle according to the clearance height and the slag thickness of the steel ladle to ensure that an insertion depth of a stinger into the melted steel is no less than 600 mm, and finely adjusting alloying components according to the temperature, an oxygen content and steel sample components, with an alloying sequence of adding AL alloy first, then adding SiFe, MnFe, CrFe, MoFe and NbFe, circulating the alloy for 3 min under a limit vacuum degree after the alloy is added, and performing temperature measurement, sampling and oxygen determination;
• wherein, an oxygen content [O] in the steel needs to be controlled below 3 ppm after alloying, the temperature needs to be controlled to range from 1590° C. to 1600° C., an aluminum wire and a titanium wire or Ti alloy is fed in turn before the melted steel refined in the RH furnance leaves the station, and components of Als and Ti are adjusted, and finally B is microalloyed;
• (5) performing conventional slab continuous casting for the melted steel, emplopying a double-layer covering agent on a surface of melted steel in a tundish, adding sufficient alkaline covering agent on a lower layer, adding a low-carbon acidic covering agent on an upper layer, and emplopying constant weight operation on the tundish;
• emplopying long nozzle casting and argon protection on the melted steel from a bale to the tundish, using a special medium carbon wear-resistant steel mould fluxes, controlling a degree of superheat to range from 15° C. to 30° C., putting in a mould for electromagnetic stirring during the continuous casting, and emplopying a continuous casting soft reduction technology in a sector section, wherein a continuous casting drawing speed is controlled to range from 1.0 m/min to 1.2 m/min, a thickness of the slab for continuous casting is controlled to be 220 mm, and chemical components of the slab obtained after conventional slab continuous casting and contents thereof are as follows:
• 0.16 wt % to 0.20 wt % of C, 0.2 wt % to 0.4 wt % of Si, 0.8 wt % to 1.5 wt % of Mn, 0.10 wt % to 0.20 wt % of Mo, 0.30 wt % to 0.50 wt % of Cr, 0.02 wt % to 0.05 wt % of Nb, 0.10 wt % to 0.15 wt % of Ti, 0.0005 wt % to 0.0010 wt % of B, less than 0.015 wt % of P, less than 0.010 wt % of S, and the remaining of Fe and inevitable impurities;
• and cooling the slab to a room temperature, inspecting a quality and a surface of the slab, and removing a layer of coat on the surface of the slab for continuous casting;
• (6) feeding the slab into a furnace for heating, wherein a heating time in the heating furnace is no less than 240 min, a heating temperature ranges from 1180° C. to 1260° C., a temperature of the slab leaving the heating furnace is no less than 1150° C., and two-stage controlled rolling is employed;
• (7) dephosphorizing the slab by high-pressure water after the slab leaves the heating furnace, wherein a dephosphorizing pressure is no less than 16 MPa;
• (8) performing rough rolling for 5 passes to 9 passes after dephosphorizing, performing Austenite finish rolling in a non-recrystallization zone after reducing the temperature of the steel to 900° C. to 950° C. after rough rolling to ensure that a total reduction rate of the non-recrystallization zone is greater than 45%, and appropriately increasing a pass reduction rate according to a rolling capacity, wherein a reduction rate of 3 passes before finish rolling is particularly controlled to be no less than 50%, a final rolling temperature is controlled to range from 820° C. to 860° C., and a reduction rate of the last pass is controlled to be no more than12%;
• (9) cooling rolled piece by an ultra fast cooling device after the rolled piece leaves a rolling mill, wherein a cooling rate ranges from 15° C./s to 30° C./s, and a quenching termination temperature ranges from 550° C. to 650° C.;
• (10) coiling the rolled piece by a coiler, and performing stacking and cooling;
• (11) feeding the rolled piece to a heat processing workshop for flattening;
• (12) performing shot blasting processing on the steel plates to remove oxidized scale on a surface;
• (13) heating the steel plate to 900° C. to 950° C. in a heat processing furnace after flattening, keeping a temperature for 1.5 h to 2 h, and quenching;
• (14) tempering after cooling the temperature to 300° C. to 400° C.;
• and
• (15) finishing and inspecting the steel plate in a finishing set.