Heat Treatment Process For Obtaining High Strength And High Toughness Of Ultra-high Carbon Fe-C Alloy

High strength and high toughness steel has great application value in engineering,and the related research has attracted increasing attention.In recent years,it has been found that ultra-high carbon steel has great potential as a candidate for high strength and high toughness steel.Generally,the high strength and high toughness combination of the ultra-high carbon steel is achieved by the addition of some alloying elements or by the special processing,which obviously leads to higher costs and complicated technology.It is necessary to explore a simple and low-cost process for preparing high strength and high toughness steel.In this paper,the effect of heat treatment process on the microstructure and mechanical properties of experimental steels with carbon content approaching 2.11 wt.%was studied.There are two kinds of experimental steels:not adding alloy elements and adding alloy elements.The method of obtaining high strength and high toughness of materials was explored.For the experimental steel I without adding alloy elements,when heating at a higher temperature of 930?between Ac₁ and Ac_cm,the ledeburite structure is basically eliminated,and the austenite with the skeletal morphology disappears.The proeutectoid carbides with fine grains are precipitated in the matrix after the treatment at a slow cooling rate of 1-2?/min?furnace cooling?.Meanwhile,the sample has a superior strength and toughness combination,the impact toughness and the tensile strength are 30 J/cm² and 792 MPa,respectively.For the experimental steel II adding alloy elements,when heating at the temperature of960?between Ac₁ and Ac_cm,the ledeburite structure and the skeletal austenite are basically eliminated.The proeutectoid carbides are uniformly precipitated in small particles after the treatment at a cooling rate of 10?/min,but the amount of precipitation is small.The impact toughness value is 13.96 J/cm² and the tensile strength value can reach 792 MPa.Compared with the experimental steel II,the tensile strength and impact toughness value of the experimental steel I are higher,and the heating temperature for obtaining the corresponding properties is lower,furnace cooling is also easy to be applied in engineering.The experimental steel I without alloying elements has more advantages than the experimental steel II with alloying elements.