METHOD FOR GREATLY IMPROVING SURFACE CORROSION RESISTANCE OF MECHANICAL STEEL PARTS BY PERFORMING PREHEATING AND NITRIDING STEPS ON WORKPIECE FOR MECHANICAL STEEL PARTS IN FURNACE

摘要

PURPOSE: To provide a method that improves surface hardness and greatly improves surface corrosion resistance of the workpiece, thereby greatly extends life of mechanical steel parts by performing gas nitriding on a workpiece using NH3 gas by a nitriding temperature of 580 deg.C and performing gas nitrocarburizing on the workpiece using a mixed gas of NH3, N2 and CO2 at the nitriding temperature. CONSTITUTION: In a method for nitriding the surface of mechanical steel parts formed of carbon steel that are objects to be treated, the method comprises a preheating step of charging a cleaned object to be treated into a heat treatment furnace, and nitriding the object using NH3 gas only by infusing the NH3 gas into the heat treatment furnace in a flow rate of 30 to 40 L/min while heating the heat treatment furnace to 580 deg.C; and a nitriding step of purging an atmospheric gas in the heat treatment furnace composed in the preheating step while maintaining temperature of the heat treatment furnace as it is, and continuously introducing a mixed gas consisting of 70 vol.% of NH3, 20 vol.% of N2 and 10 vol.% of CO2 into the heat treatment furnace in a flow rate of 80 to 90 L/min, thereby nitriding the object to be treated for 70 to 100 minutes so that a nitride layer is formed on the surface of the object to be treated.