The Study On Influence Of Thermomechanical Treatment For The Microstructure And Properties Of CLAM Steel

China Low Activation Martensitic steel was considered as the choice of structural material for the first wall of future fusion,served in a harsh environment,so it was meaningful to improve the mechanical properties.This article mainly combined with thermal simulation testing machine and double roller mill in China Low Activation Martensitic?CLAM?steel for thermomechanical treatment,to research thermomechanical treatment for microstructure and properties of CLAM steel.The strain rate,deformation temperature and deformation were the three main influencing factors,to study thermomechanical treatment process parameters on CLAM steel about the grain size,martensitic lath,M₂₃C₆ carbide and MX.In consideration of the change of microstructure,selecting the optimum thermomechanical treatment process parameter,and then conducted hot rolling experiment on double roller hot rolling mill,to test CLAM steel performance after thermomechanical treatment,including of microhardness,tensile strength and yield strength.The study of strain rate was from 0.001 s^-1 to 5s^-1,with the increase of strain rate,the refinement trend of the grain and martensitic lath,and the quantity of MX nanoscale particles significantly increased.When the strain rate was 5 s^-1,the average grain size was the smallest,about 6um with uniform distribution,and the martensitic lath obviously refined,the average size about 170nm,at the same time the density of MX nanoscale particle significantly increased,about 8.112um^-2 with high density dislocation.When the deformation temperature was from750?to 900?,with the increase of deformation temperature,the grain size and martensitic lath appeared a certain degree of refinement,the quantity of MX nanoscale particles increased significantly;while the deformation temperature was from 950?to 1150?,with the increase of deformation temperature,the grain and martensitic lath became to grow up,and the density of MX nanoscale particles significantly decreased.When the deformation temperature was 900?,the refinement of grain was the most obvious,the average size about 3um,the refinement of martensitic lath was obvious,the average size about 145nm,and the maximum density of MX nanoscale particles was11.988um^-2.The research of deformation scope was 15%?45%,with the increase of deformation,the grain and martensitic lath refined obviously,the density of MX nanoscale particle increased significantly,while the deformation was 45%?60%,the refinement of grain martensitic lath was not prominent,and the quantity of MX nanoscale particle increased slightly.Based on the experiment on the thermal simulation testing machine,the best thermomechanical treatment process parameters was achieved,and then conducted the test on hot rolling mill,to test the mechanical properties.The hot rolling test of CLAM steel was respectively at the deformation temperature of 900?,and the grain was obviously refined,with the quantity of precipitation increasing significantly,compared with the traditional heat treatment,finally the properties were significantly improved:tensile strength increased about 80.3%,at the same time yield strength increased about 49.6%,the microhardness increased about 57.7%,while the elongation changed indistinctively.Thermomechanical treatment could effectively refine the austenite grain of CLAM steels by,which played a significant role in grain strengthening,at the same time martensite lath also received a significant refinement,strengthening phase MX to increase the density of nanoscale particles obviously,high density dislocation martensite lath substrate,to promote the strengthening phase precipitation,precipitation strengthening and dislocation strengthening,significantly improving the CLAM microscopic hardness,tensile strength and yield strength,and the toughness changed slightly.