LUO Yi
,
WU Xiaochun
,
MIN Yongan
,
ZHU Zhu
,
WANG Hongbin
钢铁研究学报(英文版)
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 (027C195Mn104Cr045Mo01V) 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.
关键词:
NQP steel;large section plastic mould;temperature estimation;chemical composition;microstructure;machinability
GENG Hongming
,
WU Xiaochun
,
WANG Hongbin
,
MIN Yongan
,
ZHANG Hongkui
钢铁研究学报(英文版)
The machinability of 4Cr13 steel was improved obviously by adding Cu and S. The effect of copper addition on the machinability of 4Cr13 was similar to that of sulphur addition. By means of SEM, EBSD, and HREM, the distribution and size of the free cutting phase in the steel 4Cr13Cu were studied. The results showed that the free cutting phase was copperrich phase. The copperrich phases dispersed in the steel and were determined to have about 10 nm in diameter. The content of copper in the copperrich phase was over 70%.
关键词:
machinability;copperrich phase;EBSD;HREM
XIE Haojie
,
WU Xiaochun
,
MIN Yongan
钢铁研究学报(英文版)
On the basis of the uniform design method, six kinds of martensitic hot work die steels were designed. The phase transformation temperatures including Ac1, Ac3, and Ms were measured by DIL805A quenching dilatometer. The influences of the main elements on phase transformation temperatures were analyzed by quadratic stepwise regression analysis, and three corresponding equations were obtained. These equations, in which the interactions of the elements were considered, showed more effectiveness than the traditional ones. In addition, the thermal expansion coefficients of these steels in annealed state and quenched state were also obtained during the tests. The influences of chemical composition and temperature on the thermal expansion coefficient were analyzed; the equations obtained were verified by using several kinds of steels. The predicted values were in accordance with the results of the experiments.
关键词:
phase transformation temperature;thermal expansion coefficient;hot work die steel;uniform design;quadratic stepwise regression analysis
