| Soft-contact electromagnetic continuous casting(SC-EMCC)technology has a wide prospect in practice due to its advantages such as producing non-cracks billet and improving the surface quality of slab.So it makes continuous casting and rolling process possible and also improves the productivity with saving energy and reducing costs.But the key to apply this technology on a industrial scale is the special soft-contact mold.The mold used in SC-EMCC has to achieve suitable magnetic penetrability and cooling ability.The slit-less soft-contact mold as a novel technology can meet the demands.It is divided into two parts,The upper part is made of copper alloy with good magnetic penetrability which allows high frequency magnetic fields to penetrate into the mold and the other one remains the traditional material for its good cooling effect.Additionally,a reasonable method is used to connect the two parts together.lt is clear that the key issues for industrial practice is the development of the high magnetic penetrability copper alloy and the enough strength of the connection section of crystallizer.On the basis of the previous research results of our group,this paper indicates the relationship of the resistivity,the magnetic penetrability,and the composition of the copper alloys,Through adding,removing,adjusting,alloy elements and characterizes the main influence factors of microstructure evolution and changes of properties have been determined.phases constitution,solid solubility of alloy elements have been characterized,and hardness,tensile strength have also been tested.Through the TIG welding of copper with basic copper alloy and High Mn copper alloy,the microstructure,elements distribution of weld zone and hardness change from copper alloy side to copper side were analyzed,and then the tensile strength of the weldments were tested.The main research results are as follows.(1)The results of microstructure analysis on Cu-10Mn-5Si-3Al-1Ti-1.2P which was the previous research results of our group show that four distinguished phases in the alloy can be observed including a-Cu solution of Cu-Al-Si-Mn and precipitates of Mn5Si3,Mn-P,Mn-P-Ti.(2)The result shows that the resistivity,hardness and strength of the alloy decreased when 3%As was added and P,Ti were excluded respectively;the resistivity and hardness of the alloy remain when 1%Bi was added.(3)The resistivity of the alloy firstly increased then decreased and increased finally with manganese content increasing.form 5%,15%to 20%.But the alloy with 20%Mn was the hot brittleness because of the precipitation of coarse Mn5Si3.(4)Based on these results,Cu-40Mn-2Al copper alloy has been developed successfully,whose resistivity is 1.73×10-6Ω·m,the tensile strength reaches 402 MPa and the Vickers hardness is 143HV.It also has good plasticity which could be further processed such as forging.(5)Welding results show that good shaped and good fusion welding could be got by TIG.Hardness test result show that the hardness of the both welds similarly reduced gradually from the copper alloy to the pure copper.(6)The results of tensile test show the fracture section of the two alloy samples were both located at the side of pure copper.The tensile strength was about 200MPa which was similar with the strength of annealed pure copper.This shows that weld strength of the two alloys were greater than the pure copper,TIG welding can meet the requirements.On the basis of the evolution law of microstructure and properties of alloys,the Cu-40Mn-2Al has been developed and connected with copper successfully.This study gives many useful conclusions for fabricating new copper matrix composites with low electrical conductivity,high strength and low susceptibility,which can be used in the soft-contact electromagnetic continuous casting process. |
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