Hot rolled and steel sheet and a method of manufacturing thereof

Abstract

A hot rolled steel sheet having a composition including the following elements 0.38%≤Carbon≤0.5%, 1%≤Manganese≤2%, 0.1%≤Silicon≤0.7%, 0 01%≤Aluminum≤0.1%, 0.3%≤Chromium≤1%, 0.002%≤Boron≤0.05%, 0.002%≤Phosphorus≤0.02%, 0%≤Sulfur≤0.005%, 0%≤Nitrogen≤0.01%, 0%≤Molybdenum≤0.5%, 0%≤Vanadium≤0.5%, 0%≤Niobium≤0.05%, 0.001%≤Titanium≤0.1%, 0%≤Nickel≤1%, 0%≤Copper≤1%, 0%≤Tin≤0.1%, 0%≤Lead≤0.1%, 0%≤Antimony≤0.1%, 0.0001%≤Calcium≤0.01%, 0%≤Magnesium≤0.0010%, the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet including in area fraction, at least 94% Martensite, 0% to 5% Residual Austenite and carbides of Chromium, Niobium, Vanadium and Iron from 0% to 5%.

What is claimed is: 
     
         1 - 14 . (canceled) 
     
     
         15 . A hot rolled steel sheet having a composition comprising the following elements, expressed in percentage by weight:
 0.38%≤Carbon≤0.5%   1%≤Manganese≤2%   0.1%≤Silicon≤0.7%   0 01%≤Aluminum≤0.1%   0.3%≤Chromium≤1%   0.002%≤Boron≤0.05%   0.002%≤Phosphorus≤0.02%   0%≤Sulfur≤0.005%.   0%≤Nitrogen≤0.01%   and one or more of the following optional elements:   0%≤Molybdenum≤0.5%   0%≤Vanadium≤0.5%   0%≤Niobium≤0.05%   0.001%≤Titanium≤0.1%   0%≤Nickel≤1%   0%≤Antimony≤0.1%   0.0001%≤Calcium≤0.01%   0%≤Magnesium≤0.0010%   a remainder composition being composed of iron and unavoidable impurities caused by processing,   a microstructure of the steel sheet comprising in area fraction, at least 94% Martensite, 0% to 5% Residual Austenite and carbides of Chromium, Niobium, Vanadium and Iron from 0% to 5%.   
     
     
         16 . The hot rolled steel sheet as recited in  claim 15  wherein the composition includes 0.2% to 0.6% of Silicon. 
     
     
         17 . The hot rolled steel sheet as recited in  claim 15  wherein the composition includes 0.39% to 0.48% of Carbon. 
     
     
         18 . The hot rolled steel sheet as recited in  claim 15  wherein the composition includes 1.3% to 1.8% of Manganese. 
     
     
         19 . The hot rolled steel sheet as recited in  claim 15  wherein the composition includes 0.02% to 0.06% of Aluminum. 
     
     
         20 . The hot rolled steel sheet as recited in  claim 15  wherein the Martensite is from 95% to 99% 
     
     
         21 . The hot rolled steel sheet as recited in  claim 15  wherein the steel sheet has a hardness of 580 Hv or more, and a wear loss equal to or less than 0.085 mm 3 /s. 
     
     
         22 . The hot rolled steel sheet as recited in  claim 21  wherein the hardness is 600 Hv or more, and the wear loss equal to or less than 0.080 mm 3 /s. 
     
     
         23 . A method of production of a hot rolled steel sheet comprising the following successive steps:
 providing a semi-finished product comprising the following elements, expressed in percentage by weight:
 0.38%≤Carbon≤0.5% 
 1%≤Manganese≤2% 
 0.1%≤Silicon≤0.7% 
 0 01%≤Aluminum≤0.1% 
 0.3%≤Chromium≤1% 
 0.002%≤Boron≤0.05% 
 0.002%≤Phosphorus≤0.02% 
 0%≤Sulfur≤0.005%. 
 0%≤Nitrogen≤0.01% 
   and one or more of the following optional elements:
 0%≤Molybdenum≤0.5% 
 0%≤Vanadium≤0.5% 
 0%≤Niobium≤0.05% 
 0.001%≤Titanium≤0.1% 
 0%≤Nickel≤1% 
 0%≤Copper≤1% 
 0%≤Tin≤0.1% 
 0%≤Lead≤0.1% 
 0%≤Antimony≤0.1% 
 0.0001%≤Calcium≤0.01% 
 0%≤Magnesium≤0.0010% 
   a remainder composition being composed of iron and unavoidable impurities caused by processing;   reheating the semi-finished product to a temperature from 1100° C. to 1300° C.;   rolling the semi-finished product in the austenitic range wherein the hot rolling finishing temperature is from 850° C. to 975° C. to obtain a hot rolled steel strip;   then cooling the hot rolled strip from hot rolling finishing temperature to a coiling temperature from 750° C. to 550° C.;   thereafter coiling the hot rolled steel strip at a temperature range from 750° C. to 550° C.;   cooling the coiled hot rolled steel strip to room temperature;   annealing the hot rolled steel strip by heating from room temperature to an annealing temperature Tsoak from Ac3 to Ac3+100° C., with a heating rate HR1 from 1° C./s to 100° C./s;   then perform annealing from 10 seconds to 1000 seconds;   then cooling the hot rolled steel strip to a cooling stop temperature T1 from Ms-75° C. to 20° C. with a cooling rate CR1 from 1° C./s to 150° C./s; and   then heating the hot rolled steel strip to tempering temperature Ttemper range from 100° C. to 300° C. during 10 seconds to 10 hours; and   thereafter cooling the hot rolled steel strip to room temperature to obtain a hot rolled steel sheet.   
     
     
         24 . The method as recited in  claim 23  wherein the reheating temperature for semi-finished product is from 1200° C. to 1275° C. 
     
     
         25 . The method as recited in  claim 23  wherein the hot rolling finishing temperature is from 880° C. to 930° C. 
     
     
         26 . The method as recited in  claim 23  wherein the coiling temperature range is from 570° C. to 720° C. 
     
     
         27 . The method as recited in  claim 23  wherein the cooling stop temperature T1 is from Ms-100° C. to 20° C. 
     
     
         28 . A method for using the steel sheet produced according to the method as recited in  claim 23 , the method comprising manufacturing parts or ancillary for agriculture machinery, mining machinery or engineering machinery. 
     
     
         29 . A method for using the steel sheet as recited in  claim 15 , the method comprising using the steel sheet to manufacture parts or ancillary for agriculture machinery, mining machinery or engineering machinery.