Research On Improving Impact Toughness Of 10Ni3MnCuAl Plastic Mould Steel Core

With the increasing application of plastic products in all aspects and the improvement of surface requirements,plastic mould steel has a higher requirement for polishing performance while having excellent comprehensive mechanical properties.10Ni3Mn CuAl steel is a kind of time hardening pre-hardening plastic mould steel which is used for reference of the characteristics of foreign steel.Because of its excellent mirror polishing,it has a wide application market.However,there is a gap between the 10Ni3MnCuAl steel produced in China and the foreign countries'.There are some problems such as poor mechanical properties of the heart,coarse grain and uneven distribution of tissue.The core preparation process of the steel is still needed to be further studied.In view of the existing problems,it is of great significance to study the quality upgrading technology of the time hardening mould steel 10Ni3MnCuAl.In this paper,on the basis of the research on the existing industrial production technology of the time hardening pre-hardening plastic mould steel 10Ni3MnCuAl,the grain size was effectively optimized and the impact energy had been improved by pre-hardening test,heat treatment refining grain and optimizing the forging process.The following main conclusions are obtained:1.When the solid solution temperature is 880?and 920?,the cooling mode is water cooling,oil cooling and furnace cooling,the aging mode of 40h,?20+20?h and 60h is applied to the industrial trial production of 10Ni3MnCuAl large module.It is found that the impact performance obtained by the fast cooling process?such as water cooling and oil cooling?is superior to the slow cooling process.The main structure is martensite,slate bainite and a small amount of granular bainite.In bainite,the carbides and retained austenite are distributed in bainite,and the impact toughness is more than 15J;the structure of the furnace cold process is mainly granular bainite,and the structure of M/A island is distributed on bainite,and the impact toughness is less than 10J.The grain size of the core is larger than that of the edge,which is the key factor to deteriorate the impact toughness.When the grain size of the core is too large,the effect of different solid solution aging process on mechanical properties is not obvious,and the best heat treatment process can not be obtained.2.The grain of the test steel can be effectively refine by positive heat treatment.By"normalizing+aging","normalizing+solid solution+aging","normalizing+tempering+solid solution+aging",the impact performance can be improved.The impact toughness can be increased to 25J and the hardness reaches 41.3HRC for 1h at 950?and 2h at 530?.It is an ideal"grain refinement+pre-hardening"process.3.From the point of view of optimizing grain refinement in the forging process,the study based on the thermal simulation results of the forging process shows that when the strain is 0.65,the thermal deformation temperature is 1150?,and the forging process with the strain rate of0.1s^-1 is smaller and the grain structure uniformity is better.