| With the rapid development of nuclear energy industry in China,the follow-up treatment of high radioactive spent fuel discharged from the reactor is becoming more and more important.In many shielding materials,high boron stainless steel can not only be used as shielding material,but also can be used as structural material,so it is widely used in intermediate storage.The common high boron stainless steel preparation process is powder metallurgy and traditional fused casting.Because it is difficult to avoid the formation of low-melting-point eutectic borides during hot working,the plasticity and toughness of the materials are drastically reduced.The problem of solving the difficult processing of high-boron stainless steels has become an imminent issue right now.In order to solve the above problems,this paper proposes a vacuum hot-rolling composite method with powder cladding to prepare a high boron stainless steel composite plate with both neutron shielding capability and excellent mechanical properties.In this paper,a vacuum pressure sintering device is designed,and the simulation experiment of powder sintering densification is carried out on the Gleeble-3500 thermal simulator.The effects of different reductions on densification and the influence of vacuum on the composite interface were studied at a temperature of 1100°C and a strain rate of10s-1.It was found that the relative density of the sintered body reached 98%when the deformation amount was 60%.The higher the vacuum,the less the composite interface oxidizes and the better the bond strength.When the vacuum degree is 5 Pa or more,the composite interface undergoes a good metallurgical bond and there are no defects such as inclusions in the pores.According to the simulated test data,a practical and feasible technological parameter of vacuum hot rolling for powder pack is worked out.In order to get the core layer thickness:the clad thickness=4:1 of the composite board,the reasonable size of the package is designed,and the actual result is close to the expected result after the later test.The vacuum brazing furnace was used to weld the package under the vacuum temperature of 2.2×10-2Pa at 1130 degrees centigrade.Afterwards,the jacket was forged into a thin plate with a thickness of 3 mm using a multi-pass small deformation method.The composite plate was subjected to a solution treatment at 1050°C for 1 hour.The composite interface of high boron stainless steel composite plate prepared by vacuum hot rolling of powder package is combined with metallurgical bonding,and the small size of boride is distributed evenly on the grain boundary,and the mechanical properties of the high boron stainless steel composite plate are greatly improved.The mechanical properties of the composite plate with 304B7A close to the core material are measured.The yield strength of the composite plate is more than the technical requirements of the ASTM A887-89 standard in the United States,and the elongation is1.7 times that of the 304B7A high boron stainless steel plate.This paper puts forward the idea of preparing high boron stainless steel composite plate by vacuum hot rolling with powder package,and carries out the research on process basis.It can provide theoretical basis and technical guidance for the design and production of high boron stainless steel in our country.It has important practical significance. |
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