Hot-rolled steel for enameling having enameling and firing strengthening property, and manufacturing method therefor

Abstract

Disclosed is a hot-rolled steel for enameling having an enameling and firing strengthening property, comprising, in addition to Fe and inevitable impurities, the following chemical elements in mass percent: C: 0.03-0.07%, Si≤0.05%, Mn: 1.5-2.5%, Al: 0.01-0.05%, Cr: 0.25-0.65%, Cu: 0.02-0.20%, Ti: 0.01-0.08%, V: 0.01-0.10%, and Mo: 0.01-0.10%. Accordingly, further disclosed is a manufacturing method for the hot-rolled steel for enameling, comprising the steps of: (1) smelting and casting; (2) heating; (3) hot rolling, the temperature of rough rolling being controlled to be greater than 850° C., the start temperature of finish rolling being controlled to be 900-1050° C., and the final temperature of finish rolling being controlled to be 840-900° C.; (4) laminar cooling, the cooling speed being controlled to be 10-35° C./s; and (5) coiling. The hot-rolled steel for enameling provided by the present invention has low strength and good formability in a hot-rolled state, and after high-temperature enameling and firing, the yield strength of the hot-rolled steel for enameling is not decreased but increased, such that the strength of a final enamel product can be effectively improved.

1 . A hot-rolled steel for enameling having enamel firing strengthening properties, wherein, in addition to Fe and unavoidable impurities, it further comprises the following chemical elements in mass percentages:
 C: 0.03˜0.07%, Si≤0.05%, Mn: 1.5˜2.5%, Al: 0.01˜0.05%, Cr: 0.25˜0.65%, Cu: 0.02˜0.20%, Ti: 0.01˜0.08%, V: 0.01˜0.10%, Mo: 0.01˜0.10%.   
     
     
         2 . The hot-rolled steel for enameling according to  claim 1 , wherein it comprises the following chemical elements in mass percentages:
 C: 0.03˜0.07%, Si≤0.05%, Mn: 1.5˜2.5%, Al: 0.01˜0.05%, Cr: 0.25˜0.65%, Cu: 0.02˜0.20%, Ti: 0.01˜0.08%, V: 0.01˜0.10%, Mo: 0.01˜0.10%, with a balance of Fe and other unavoidable impurities.   
     
     
         3 . The hot-rolled steel for enameling according to  claim 1 , wherein it further comprises B: 0.0006˜0.003%. 
     
     
         4 . The hot-rolled steel for enameling according to  claim 1 , wherein each chemical element satisfies: (C−Ti/4−V/4.25)×(Mn+Cr)>0.05; wherein each of C, Ti, V, Cr and Mn represents the value of mass percentage of the corresponding element. 
     
     
         5 . The hot-rolled steel for enameling according to  claim 1 , wherein it has a microstructure of ferrite+pearlite. 
     
     
         6 . The hot-rolled steel for enameling according to  claim 5 , wherein it has a ferrite grain size of Grade 8˜10. 
     
     
         7 . The hot-rolled steel for enameling according to  claim 1 , wherein it has a thickness of 1.5-3.5 mm. 
     
     
         8 . The hot-rolled steel for enameling according to  claim 1 , wherein it has a yield strength of 345˜389 MPa in a hot-rolled state, and a yield strength of 402˜439 Mpa after high temperature enamel firing at a temperature in a range of 870˜950° C. 
     
     
         9 . An enameled steel comprising a substrate and an enamel layer on one or two surfaces of the substrate, wherein the substrate is the hot-rolled steel for enameling according to  claim 1 . 
     
     
         10 . The enameled steel according to  claim 9 , wherein the enameled steel has a yield strength of 400˜450 MPa, a tensile strength of 610˜660 MPa, an elongation A 50  of ≥18%; and/or, the substrate has a microstructure of ferrite+bainite. 
     
     
         11 . A manufacturing method for the hot-rolled steel for enameling according to  claim 1 , comprising steps of:
 (1) smelting and casting;   (2) heating;   (3) hot-rolling: wherein a rough rolling temperature is controlled at more than 850° C., an initial finish rolling temperature is controlled at 900˜1050° C., and a final finish rolling temperature is controlled at 840˜900° C.;   (4) laminar flow cooling: wherein a cooling rate is controlled at 10˜35° C./s;   (5) coiling.   
     
     
         12 . The manufacturing method according to  claim 9 , wherein, in step (2), a heating temperature is 1150˜1260° C. 
     
     
         13 . The manufacturing method according to  claim 9 , wherein, in step (5), a coiling temperature is controlled at 550˜680° C. 
     
     
         14 . A manufacturing method for the enameled steel according to  claim 9 , comprising a step of manufacturing the hot-rolled steel for enameling by the method comprising: (1) smelting and casting;
 (2) heating:   (3) hot-rolling: wherein a rough rolling temperature is controlled at more than 850° C., an initial finish rolling temperature is controlled at 900˜1050° C., and a final finish rolling temperature is controlled at 840˜900° C.;   (4) laminar flow cooling: wherein a cooling rate is controlled at 10˜35° C./s;   (5) coiling, and a step of enamel firing the hot-rolled steel for enameling as a substrate.   
     
     
         15 . The manufacturing method according to  claim 14 , wherein, in the step of enamel firing, the steel is enamel-fired at 870˜950° C. for 5˜15 min. 
     
     
         16 . The hot-rolled steel for enameling according to  claim 2 , wherein it further comprises B: 0.0006˜0.003%. 
     
     
         17 . The hot-rolled steel for enameling according to  claim 2 , wherein each chemical element satisfies: (C−Ti/4−V/4.25)×(Mn+Cr)>0.05; wherein each of C, Ti, V, Cr and Mn represents the value of mass percentage of the corresponding element. 
     
     
         18 . The hot-rolled steel for enameling according to  claim 5 , wherein the proportion of pearlite is 10˜45% by area ratio. 
     
     
         19 . The enameled steel according to  claim 10 , wherein the proportion of bainite is 10˜40% by area ratio. 
     
     
         20 . The manufacturing method according to  claim 15 , wherein the method further comprises a shot blasting treatment for the hot-rolled steel for enameling before the step of enamel firing, and/or the enamel firing treatment is carried out by one enamel coating/one firing or two enamel coatings/two firings.