METHOD FOR HEAT TREATMENT OF CAM AND THE PARTS FOR A LARGE SHIP

摘要

A method for heat treatment of a cam and its parts for a large ship is provided to improve productivity and improve surface hardness and internal hardness of the cam and its parts for the large ship by reducing a process of a spheroidizing annealing step. A method for heat treatment of a cam and its parts for a large ship comprises a carburizing step, a quenching step and a tempering step, wherein the carburizing step comprises: a temperature raising process(s1) of loading a workpiece to be heat treated into a furnace, and heating the workpiece from a temperature of 400 deg.C or less to 850 deg.C at a rate of 100 to 120 deg.C/hr; an isothermal process(s2) of holding the workpiece at 850 deg.C for two hours while injecting methanol onto the workpiece to transfer sufficient heat into the workpiece; a temperature raising process(s3) of raising temperature of the workpiece to 950 deg.C, and continuously injecting methanol onto the workpiece; a carburizing process(s4) of holding the workpiece at 950 deg.C for 18 hours; a diffusion process(s5) of holding the workpiece at 950 deg.C for 17 hours to diffuse carburized carbon; a temperature lowering process(s6) of lowering temperature of the workpiece to a range of 830 to 870 deg.C to prevent the workpiece from being deformed of cracked during cooling; an isothermal process(s7) of holding the workpiece for about one hour such that heat with a temperature of 830 to 870 deg.C is uniformly distributed in the workpiece; and an air cooling process(s8) of leaving the workpiece in the atmosphere at room temperature to cool the workpiece.