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Die Steel Vacuum Nitriding

Vacuum nitriding technology uses the characteristics of clean and non-oxidized workpiece surface during vacuum heating, and uses vacuum heat treatment to carry out nitriding under negative pressure; after nitriding, the workpiece surface has high hardness and low brittleness, and the uniform nitriding layer can meet the needs of sharp-edged tools and Technical requirements for cold stamping dies.

During vacuum nitriding, the vacuum furnace is exhausted to a higher vacuum degree (1×10^-1Pa), and then the workpiece in the vacuum furnace is raised to (530-560) ° C, and at the same time enters the ammonia-based, containing many active substances. A compound gas is used, and the feeding amount of various gases is precisely controlled. The furnace pressure is controlled at 665Pa, and the inert gas in the furnace is rapidly cooled after holding for (3-5) hours. According to different materials, a hardened layer with (20-80) μm hardness (600-1500) HV can be obtained after this treatment.

Influencing factors of vacuum pulse nitriding

Nitriding temperature: the vacuum nitriding temperature is too high, the alloy compound is coarse, the nitriding temperature is too low, the nitriding layer is shallow, the alloy compound is less, and the hardness is low;furnace pressure; the higher the upper limit of the furnace pressure, the better the depth and hardness of the infiltrated layer, the higher the vacuum degree, and the better the hardness and thickness of the infiltrated layer;oxidation time: time increases, hardness increases, and the hardness increases more obviously when there is a compound layer, and the penetration layer also deepens. If the pulse time is too long, the infiltrated layer will become thinner, and the exhaust gas will not be able to fully burn; if the pulse time is too short, the surface will be more brittle.

Nitrogen flow: the more the flow, the higher the hardness, and the deeper the infiltration layer.

4Cr5MnSiV1 Steel Hot Extrusion Die Vacuum Nitriding Process

Vacuum nitriding is a “vacuum exhaust nitrogen carburizing” treatment that generates active nitrogen atoms infiltrating and diffusing into steel under low pressure to achieve hardening; the general nitriding temperature is 530~560C, and the holding time is 3~5h; The thickness of the carburizing layer of carbonitriding only increases significantly in the first 3~4 hours of nitriding, and then slows down significantly. When the die-casting mold is working, due to the concentrated rapid cooling and rapid heating, the service conditions are too strict, and the surface is prone to thermal shock cracks, thermal adhesion, melting loss, corrosion and other defects. For die-casting cavity molds, it is mainly to improve thermal shock resistance to prevent cracks; for casting cores, gates, and ejector pins, it is mainly to improve anti-adhesion, melting loss, and corrosion.

Vacuum nitriding process

Vacuuming 2. Heating with nitrogen gas 3. Furnace loading 4. Heating with nitrogen and ammonia gas after vacuuming 5. Heat preservation and nitriding 6. Cooling with nitrogen gas after vacuuming

Vacuum nitriding results of 4Cr5MoSiV1 steel extrusion die

Basically eliminate the vein-like grain structure in the seepage layer, and adjust the structure of the seepage layer by changing the ammonia flow rate of the furnace pressure level, and improve the thickness of the seepage layer.

Quality, the microhardness distribution of the vacuum nitriding layer is relatively flat, and the hardness distribution of only the diffusion layer is more ideal; the process equipment is simple, and the main raw material ammonia gas consumption is saved.

Production of H13, 3Cr2W8V die steel by vacuum pulse nitriding

The structure of the nitriding layer is uniform and dense, without obvious pores or inclusions, which has great influence on the wear resistance and durability of the material.

Corrosion resistance, fatigue resistance and seizure resistance all have very good effects.

Microstructure of Nitriding Layer of H13, 3Cr2W8V Die Steel

Under vacuum conditions, gases have more opportunities for movement and diffuse more rapidly. During the vacuum pulse nitriding process, the ammonia gas in the furnace is continuously renewed by using the pulse feeding and pumping methods to avoid stagnant gas, so that the surfaces of the mold can often be in contact with fresh ammonia gas, so that a uniform infiltrated layer can be obtained.

Die steel vacuum nitriding

After die steel is nitrided by vacuum pulse, a nitrided layer with thin compound layer, no obvious porosity and low brittleness can be obtained.

The low brittleness of the nitriding layer is the characteristic of vacuum pulse nitriding, which can greatly improve the life of die-casting dies, cold stamping dies and plastic dies.

Vacuum furnace selection: The vacuum nitriding furnace produced by SIMUWU company has low temperature and small deformation of the workpiece. This process is suitable for many types of steel and has a wide range of applications.Steel types suitable for vacuum ion nitriding include alloy structural steel, stainless acid-resistant steel, heat-resistant steel, alloy tool steel, high-speed tool steel and ductile iron. Commonly used steel types are 38CrMoAl, 18Cr2Ni4W, 40Cr, 42CrMo, 35CrMo, 45#, 20Cr, 40CrNiMo, etc.