Influences Of Rolling Process On Microstructure And Property Of Carbon Steel/Strainless Steel Clad Plate

In this work,microstructure evolution and mechanical property of carbon steel(CS)/stainless steel(SS)clad plate of hot-rolling technology was systematically studied by modern microstructure analysis techniques and the corresponding theoretical calculation methods.Main content of hot-rolling clad plates are introduced below:The CS microstructure evolution of the CS/SS clad plate in the hot rolling process under certain deformation conditions was researched by different microscope.The results show that the pearlite quantity increase by Clapeyron equation,it becomes more uniform with the reduction rate(?)increasing.The quantity of proeutectoid ferrite simultaneous decreases with ? increasing because of carbon atom diffusion.The thickness of cementite decreases with ? increasing,which reaches the minimum when the total reduction ratio is 55%.The proportion of small angle grain boundary of 4-ply sample is 7.2% when ? is 20%.Furthermore,the number of small angle grain boundaries increases sharply to 5 times than the former when ? is 30%.When the total reduction rate was 44%,the number of small angle grain boundaries decreased slightly.2.The stainless steel microstructure evolution of carbon–stainless-clad steel plate was investigated during vacuum hot-rolling bonding under different deformation conditions.When ? is 20%,the number of small grain less than 5?m is about 10% in SS,the large grain number of 50?m is only 0.2%.The grain obvious refinement with ?increasing.The clear austenite at the side is adjacent to the non-bonding interface,and the black ribbons that are parallel to the rolling direction in the midst of SS layer are clear and dense.However,the austenite and ribbons of the bonding interface are all obscured.The carbide M2 C precipitates in the interior of stainless steel(SS)and carbon content increases with rising reduction ratio(?).Furthermore,the dislocation density of the midst is high where the high energy of carbide M2 C is concentrated for single-pass rolling,and the quantity of M2 C increases with reduction ratio.Moreover,carbide almost disappeared while being transformed into austenite,and only minimal granular carbides were formed after two-pass rolling.3.The rolling force have an important effect on the carbides precipitation of bonding interface,and the cooling gradient has little effect on the thickness of carbide layer.The ferrite region near the bonding interface thicken with ? increasing,stress changes phase transformation that the pearlite could not be precipitated from the smallaustenite grain formed due to hot rolling.The thin layer of carbide M7C3 forms at the bonding interface of carbon steel/stainless steel clad after single pass rolling.In addition,its thickness increase with the reduction rate increasing.However,the carbide layer disappears as the result of the diffusion again of carbon atom from the damaged grain after the second pass rolling.4.The tensile strength of 3-ply increases from 498.8MPa to 586.6MPa and that of4-ply increases from 470.2MPa to 561.0MPa when ? increases from 20% to 44%.The carbide particles in CS precipitated are uniform,which leads to the higher tensile strength of the clad plate.The carbide layer of the bonding interface consists of M7C3 flake,which is easy to produce stress concentration and form fibrous region during the subsequent tensile test.The carbide flake is actually irregular continuous strip that precipitates in CS surface,which can be sheared off to flat and independent slice under stress.As this force increases gradually,these slices mostly break down into small particles.These particles extend along the slip direction,rather than the tensile direction,resulting in an increased carbide thickness of the bonding interface.However,the carbide-M7C3 is difficult to enter into SS,but only extends into the soft ferrite area of CS surface.The carbide-M7C3 of the bonding interface decrease the shear strength of the clad plate.The shear strength of clad plates is only about 200 MPa when ? is 30%.However,the shear strength is reach to above 300 MPa after the two pass rolling.