A new design of copper-bearing non-quenched plastic mold steel is presented and explained. Two kinds of microstrueture can be obtained from this new type copper-bearing steel via cooling with different cooling rates, ...A new design of copper-bearing non-quenched plastic mold steel is presented and explained. Two kinds of microstrueture can be obtained from this new type copper-bearing steel via cooling with different cooling rates, bain- ite and a mixed microstructure consisting of ferrite and bainite. It is found that, after proper tempering process, the hardness will be increased. Moreover, the hardness difference between different microstructures will be reduced. For further investigation, the samples tempered at different temperatures were examined by XRD and 3PAP （three di- mensional atom probe） analysis. Results show that the improvement is contributed mainly by the precipitation of Cu phase and transformation of residual austenite.展开更多
The influence of austenitizing temperature on the microstructure and corrosion resistance of 55Cr18MolVN high-nitrogen plastic mould steel was investigated. The microstructure, elemental distribution and Cr-depleted z...The influence of austenitizing temperature on the microstructure and corrosion resistance of 55Cr18MolVN high-nitrogen plastic mould steel was investigated. The microstructure, elemental distribution and Cr-depleted zone of different heat-treated samples were investigated by X-ray diffraction, electron probe microanalyzer analysis, and trans- mission electron microscopy. The corrosion resistance was evaluated using electrochemical measurements, and the analysis of passive film was carded out by X-ray photoelectron spectroscopy. The results indicated that the volume fraction of precipitates decreased, and the homogeneity of elements was improved with increasing austenitizing temperature. The degree of Cr-depleted zone around coarse M23C6 was severer than that around M2N, and pitting corrosion initiated preferentially around M23C6. The corrosion resistance of the samples increased with the austenitizing temperature. With the increase in austenitizing temperature, the passive film was thickened and Cr（III）cr2O3 in the inner layer of passive film was enriched, which enhanced the corrosion resistance of the steel. The higher content of nitrogen in solid solution at higher austenitizing temperature contributed to the increased intensity of CrN and NH3, leading to the increase in pH value in the pit, and promoting the repassivation of 55Cr18Mo1N steel.展开更多
In order to meet the demand of prehardened steel for large section plastic mould and save energy, a nonquenched prehardened （NQP） steel is developed. The temperature field of a large block is researched by finite el...In order to meet the demand of prehardened steel for large section plastic mould and save energy, a nonquenched prehardened （NQP） steel is developed. The temperature field of a large block is researched by finite element method simulation and 9 test steels are designed in the laboratory. Their microstructures and hardness are investigated when they are air cooled and control cooled at cooling rate similar to the simulation. The result shows that the hardness uniformity through section is closely correlated to bainitic hardenability for the NQP steel, and the hardness of one test steel （0.27C-1.95Mn-1.04Cr-0.45Mo-0.1V） fluctuates between HRC 40 and 43 under both cooling conditions. The test steel has better machinability compared with C45 steel, and the NQP steel is produced successfully in the factory based on the laboratory results. Its microstructure is bainite, and it is distributed uniformly through the size of 460 mm×800 mm×3 200 mm.展开更多
The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional preha...The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.展开更多
基金Sponsored by National Key Technology Research and Development Program in 11th Five-Year Plan of China(2007BAE51B04)
文摘A new design of copper-bearing non-quenched plastic mold steel is presented and explained. Two kinds of microstrueture can be obtained from this new type copper-bearing steel via cooling with different cooling rates, bain- ite and a mixed microstructure consisting of ferrite and bainite. It is found that, after proper tempering process, the hardness will be increased. Moreover, the hardness difference between different microstructures will be reduced. For further investigation, the samples tempered at different temperatures were examined by XRD and 3PAP （three di- mensional atom probe） analysis. Results show that the improvement is contributed mainly by the precipitation of Cu phase and transformation of residual austenite.
基金financially supported by National Natural Science Foundation of China (Grant Nos.51304041, 51434004 and U1435205)Fundamental Research Funds for the Central Universities (Grant No. N150204007)
文摘The influence of austenitizing temperature on the microstructure and corrosion resistance of 55Cr18MolVN high-nitrogen plastic mould steel was investigated. The microstructure, elemental distribution and Cr-depleted zone of different heat-treated samples were investigated by X-ray diffraction, electron probe microanalyzer analysis, and trans- mission electron microscopy. The corrosion resistance was evaluated using electrochemical measurements, and the analysis of passive film was carded out by X-ray photoelectron spectroscopy. The results indicated that the volume fraction of precipitates decreased, and the homogeneity of elements was improved with increasing austenitizing temperature. The degree of Cr-depleted zone around coarse M23C6 was severer than that around M2N, and pitting corrosion initiated preferentially around M23C6. The corrosion resistance of the samples increased with the austenitizing temperature. With the increase in austenitizing temperature, the passive film was thickened and Cr（III）cr2O3 in the inner layer of passive film was enriched, which enhanced the corrosion resistance of the steel. The higher content of nitrogen in solid solution at higher austenitizing temperature contributed to the increased intensity of CrN and NH3, leading to the increase in pH value in the pit, and promoting the repassivation of 55Cr18Mo1N steel.
基金Item Sponsored by Shanghai Leading Academic Discipline Project (T0101)
文摘In order to meet the demand of prehardened steel for large section plastic mould and save energy, a nonquenched prehardened （NQP） steel is developed. The temperature field of a large block is researched by finite element method simulation and 9 test steels are designed in the laboratory. Their microstructures and hardness are investigated when they are air cooled and control cooled at cooling rate similar to the simulation. The result shows that the hardness uniformity through section is closely correlated to bainitic hardenability for the NQP steel, and the hardness of one test steel （0.27C-1.95Mn-1.04Cr-0.45Mo-0.1V） fluctuates between HRC 40 and 43 under both cooling conditions. The test steel has better machinability compared with C45 steel, and the NQP steel is produced successfully in the factory based on the laboratory results. Its microstructure is bainite, and it is distributed uniformly through the size of 460 mm×800 mm×3 200 mm.
文摘The improvement of machining behavior of prehardened-mould steel for plastic is realized by using computer-aided composition design in this work. The results showed that the matrix composition of large sectional prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the control of composition aided by Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition the modification of calcium is optimized in the light of composition design.
