Development And Properties Of Fe-Based Alloys For New Rollers

Steel production in China has the world’s largest consecutive years,including hot rolling is the production of strip,sheet,wire,rod of various materials such as metal forming process.the core of the hot rolling process is the preparation of rollers of different types of materials,because of the roll is one of the main consumables in metal forming process,the steel rolling process in the high temperature of billet and roll the relative motion of roll wear failure.Therefore,it is of great significance to deeply understand the mechanism of friction and wear at high temperature to improve the service life,stability and reliability of rolls.In this subject,7V-8Cr-XMo（X=0,1,3,5）iron-based alloy and high-chromium cast iron（Cr26）,which is a comparative material,were prepared,and the high-temperature friction and wear characteristics of the roll were simulated under severe working conditions.The wear test parameters:temperature（400°C,500°C,600°C）,load（10 N,20 N）,systematically studied the high temperature friction friction and wear loss mechanism of the roll under different temperature and load conditions,and also studied at different temperatures and time conditions on high temperature oxidation resistance of iron-based alloys.The microstructures of 7V-8Cr and 7V-8Cr-1Mo alloys areα-Fe phase,γ-Fe phase,VC and Cr₇C₃carbides,The microstructures of 7V-8Cr-3Mo 7V-8Cr-5Mo-Ⅰand7V-8Cr-5Mo-Ⅱareα-Fe phase,γ-Fe phase,vanadium-rich（V,Mo）C,chromium-rich（Cr,Mo）₇C₃and molybdenum-rich（Mo,Cr）₂C carbide.The carbon content of 7V-8Cr-5Mo-I is about 2.4%,and petal-shaped,rod-shaped and worm-shaped vanadium carbides and rod-shaped chromium-vanadium-molybdenum composite carbides are precipitated in the tissue.The carbon content of other new iron-based alloys is about 2.8%,and the vanadium carbide is in the form of clumps and agglomerates.As the content of Mo element increases,the content of Mo₂C in the structure of the developed iron-based alloy also increases,and the macroscopic hardness of the alloy increases,but the impact toughness decreases.The impact toughness of the developed iron-based alloy is about 1.5 times that of Cr26.The high-temperature friction and wear test results show that:when the load is 10 N,the wear amount of the new iron-based alloy increases with the increase of temperature,and decreases when it reaches 600℃.The wear amount of Cr26 continues to increase with the increase of temperature.Under the three temperature conditions 7V-8Cr-3Mo has the best wear resistance,and the wear resistance of 7V-8Cr-3Mo is about 3 times that of Cr26.When the load is 20 N,the wear amount of the six iron alloys decreases with the increase of temperature.The wear resistance of 7V-8Cr-3Mo is the best under the three temperature conditions,and the wear resistance of 7V-8Cr-3Mo is about 2 times that of Cr26.The wear surface mainly contains wear debris,furrows and lamellae spalling.The vanadium carbide in the form of agglomerate on the wear tangential surface is relatively complete,and the petal-shaped vanadium carbide cracks and peels off.The wear mechanism at 400°C and500°C is abrasive wear and tear.Fatigue wear,the wear mechanism at 600℃is the combination of abrasive wear,fatigue wear and adhesive wear.At this temperature,the subsurface layer of alloy wear produces a plastic flow layer,and the depth of the plastic flow layer increases with the increase of load.The high temperature oxidation test shows that the oxidation speed of 7V-8Cr-3Mo and Cr26 increases with the increase of temperature.The oxidation speed of 7V-8Cr-3Mo is higher than that of Cr26 at three temperatures,so the Poor oxidation resistance.At 400℃and 500℃,7V-8Cr-3Mo has a lower oxidation rate and better oxidation resistance.At600℃,it oxidizes rapidly,mainly producing tetrahedral V₂O₃,and spore-like and flake-like Fe₂O₃.Cr26 has good oxidation resistance at all three temperatures.At 600°C,dense spinel oxide Fe Cr₂O₄is formed covering the surface of the alloy,which effectively prevents the diffusion of oxygen atoms into the alloy,and its oxidation resistance is relatively high.