Crankshaft is an important part of marine engine.Using 45#steel as raw material of marine crank-shaft forgings can greatly reduce cost and relieve market pressure.This paper introduces the production practice of 45#steel forgings of crankshaft for ship by 35t EAF+LF+VD→4.5t special-shaped ingot casting→forging→normal-izing→roughing.During the smelting process,scrap steel shall be made from 42CrMo scrap without rust on the sur-face,refined with SiC powder for diffusion and deoxidation,vacuum followed by addition of Ti(0.03%),aluminum feeding wire,soft blowing for 25～30 minutes,and argon filling into the central injection pipe and the Tang Dao brick twice before casting.Forging process isothermal to 950℃using fast forging machine blank,precision forging machine rapid finalization,final forging temperature 780～830℃.The heat treatment process is 865～875℃/2h normalization,air cooling;645～655℃/10h tempering.After testing and analysis,the chemical composition of the steel is stable,the purity of the molten steel is high,w(P)≤0.008%,w(S)≤0.005%;general porosity 1.0,central porosity 1.0,no ingot segregation and no dot segregation;the grain size of 1/2 radius is grade 6,the structure is P+F;banded structure grade 1.5,no Widmanstatten structure,verifying the rationality and feasibility of the manufacturing process.
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