The pseudo-equilibrium phase diagram and continuous cooling transformation diagram of an N-containing 8％ Cr roller steel were investigated by using thermodynamic calculation,differential scanning calorimetry,Ⅹ-ray d...The pseudo-equilibrium phase diagram and continuous cooling transformation diagram of an N-containing 8％ Cr roller steel were investigated by using thermodynamic calculation,differential scanning calorimetry,Ⅹ-ray diffraction,expansion method,and so on.Under equilibrium conditions,the main carbonitrides are MX,M7C3,and M23C6 types.The measured Ac1,Ac3,start temperature of martensitic transformation,and M7C3 transformation temperatures are 811,855,324,and 1100 ℃,respectively.Bainite appears at cooling rates ranging from 0.5 to 5 ℃/s and ferrite forms at grain boundaries at a cooling rate lower than 0.5 ℃/s.Finally,the effects of adding N and lowering the C content on workability and mechanical properties of common 8％Cr steel were discussed.展开更多
The low Ni steel modified hy rare earth(3Cr24NiTSiN with an addition of 0.3% Ce)for furnace roller has been developed.Due to the RE(rare earth)addition,a dense oxide film is formed on the steel surface at high tempera...The low Ni steel modified hy rare earth(3Cr24NiTSiN with an addition of 0.3% Ce)for furnace roller has been developed.Due to the RE(rare earth)addition,a dense oxide film is formed on the steel surface at high temperature,and the oxidation rate is decreased.This film has so good adhesion to the matrix that it will not be peeled off easily.The RE modified steel has excellent oxidation resistance and thermal strength even if being used continuously for a long period at high temperature.This steel roller has a service life of about 4 years com- parable to high Ni steel ones,so the low Ni steel can replace high Ni steel to make furnace roller.The Ni content of this material can be reduced by 65% in comparison with Cr25Ni20Si2 steel,The low Ni steel has better pro- eessing properties including melting,casting and working properties than that of high Ni ones.展开更多
Cold-rolled high strength steel sheets for automobiles contain more Mn and Si based alloy elements, which, under the reducing atmosphere in the annealing furnace, will get enriched on the strip surface. Since the furn...Cold-rolled high strength steel sheets for automobiles contain more Mn and Si based alloy elements, which, under the reducing atmosphere in the annealing furnace, will get enriched on the strip surface. Since the furnace rollers and the strips contact frequently, alloy elements on the roller surface will form hard protuberance. We call this protuberance ＂pick-up＂. In addition, with the increase of the amount of dust in the furnace atmosphere, the occurrence of furnace roller pick-up will also increase. Through chemical reaction and physical accumulation analysis combined with practical experience, the causes of pick-up in different furnace sections were analyzed. Methods of preventing furnace roller pick-up in the high strength steel sheet processing line were discussed and solutions to improving the strip surface quality in the continous annealing furnace were provided.展开更多
The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investi...The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investigating the manufacturing process of inlet deflector rollers, the root cause of the scratches was found. By modifying the manufacturing process of the rollers, the scratches have been thoroughly eliminated, and quality steel sheets have been consistently produced in the recoiling line.展开更多
The effect of roller shapes on strip buckling in a continuous annealing furnace was focused on. The tensile stress distribution, the transverse compressive stress, and the critical buckling stress of the strip were st...The effect of roller shapes on strip buckling in a continuous annealing furnace was focused on. The tensile stress distribution, the transverse compressive stress, and the critical buckling stress of the strip were studied by the finite element method （FEM） when the flat roller, crown roller, single taper roller, and double taper roller were used, respectively. Simulation results show that strip buckling is most likely to occur with the crown roller, then the double taper roller, and finally the single taper roller. Also, strip buckling can not occur when the flat roller is used. Considering strip snaking, the single taper roller and double taper roller are suggested in the continuous annealing fur-nace. The double taper roller with a better strip snaking-prevention ability should be applied in the sections with high strip temperature, and the single taper roller with a better buckling-prevention ability should be used in the sections with low strip temperature.展开更多
基金Sponsored by the Natural Science Foundation of Hebei Province for Distinguished Young Scholars(Grant No.E2011203131)the Natural Science Foundation-Steel and Iron Foundation of Hebei Province(Grant No.E2013203110)
文摘The pseudo-equilibrium phase diagram and continuous cooling transformation diagram of an N-containing 8％ Cr roller steel were investigated by using thermodynamic calculation,differential scanning calorimetry,Ⅹ-ray diffraction,expansion method,and so on.Under equilibrium conditions,the main carbonitrides are MX,M7C3,and M23C6 types.The measured Ac1,Ac3,start temperature of martensitic transformation,and M7C3 transformation temperatures are 811,855,324,and 1100 ℃,respectively.Bainite appears at cooling rates ranging from 0.5 to 5 ℃/s and ferrite forms at grain boundaries at a cooling rate lower than 0.5 ℃/s.Finally,the effects of adding N and lowering the C content on workability and mechanical properties of common 8％Cr steel were discussed.
文摘The low Ni steel modified hy rare earth(3Cr24NiTSiN with an addition of 0.3% Ce)for furnace roller has been developed.Due to the RE(rare earth)addition,a dense oxide film is formed on the steel surface at high temperature,and the oxidation rate is decreased.This film has so good adhesion to the matrix that it will not be peeled off easily.The RE modified steel has excellent oxidation resistance and thermal strength even if being used continuously for a long period at high temperature.This steel roller has a service life of about 4 years com- parable to high Ni steel ones,so the low Ni steel can replace high Ni steel to make furnace roller.The Ni content of this material can be reduced by 65% in comparison with Cr25Ni20Si2 steel,The low Ni steel has better pro- eessing properties including melting,casting and working properties than that of high Ni ones.
文摘Cold-rolled high strength steel sheets for automobiles contain more Mn and Si based alloy elements, which, under the reducing atmosphere in the annealing furnace, will get enriched on the strip surface. Since the furnace rollers and the strips contact frequently, alloy elements on the roller surface will form hard protuberance. We call this protuberance ＂pick-up＂. In addition, with the increase of the amount of dust in the furnace atmosphere, the occurrence of furnace roller pick-up will also increase. Through chemical reaction and physical accumulation analysis combined with practical experience, the causes of pick-up in different furnace sections were analyzed. Methods of preventing furnace roller pick-up in the high strength steel sheet processing line were discussed and solutions to improving the strip surface quality in the continous annealing furnace were provided.
文摘The inlet deflector rollers of a recoiling line are sprayed rollers. Short scratch lines have been found on the surface of steel sheets during commissioning. By adjusting the control parameters of the line and investigating the manufacturing process of inlet deflector rollers, the root cause of the scratches was found. By modifying the manufacturing process of the rollers, the scratches have been thoroughly eliminated, and quality steel sheets have been consistently produced in the recoiling line.
文摘The effect of roller shapes on strip buckling in a continuous annealing furnace was focused on. The tensile stress distribution, the transverse compressive stress, and the critical buckling stress of the strip were studied by the finite element method （FEM） when the flat roller, crown roller, single taper roller, and double taper roller were used, respectively. Simulation results show that strip buckling is most likely to occur with the crown roller, then the double taper roller, and finally the single taper roller. Also, strip buckling can not occur when the flat roller is used. Considering strip snaking, the single taper roller and double taper roller are suggested in the continuous annealing fur-nace. The double taper roller with a better strip snaking-prevention ability should be applied in the sections with high strip temperature, and the single taper roller with a better buckling-prevention ability should be used in the sections with low strip temperature.
