What Are the Precautions for Die Steel Nitriding?

In order to ensure the quality of die steel, we must strictly implement the nitriding process, analyze the causes of defects in die steel nitriding, and take corresponding measures to improve die nitriding. quality and prolong the life of die steel.

Ⅰ. What are the precautions for die steel nitriding?

Gas nitriding has been widely used in mold production. It can significantly improve the surface hardness, wear resistance, seizure resistance, corrosion resistance and fatigue performance of the mold. General hot work die steel (any alloy tool steel with a tempering temperature of 550650 ° C) can be nitrided after quenching and tempering in a temperature zone below the tempering temperature; general carbon steel and low alloy steel are used in the production of plastics. The mold can be nitrided at the tempering temperature after quenching and tempering; some cold work molds with special requirements can also be quenched and tempered after gas nitriding.

However, due to various reasons, after the mold gas is nitrided, the hardness of the nitrided layer is low, the nitrided layer is shallow, the hardness of the nitrided layer is uneven, the surface of the mold is oxidized after nitriding, the nitrided layer is not dense, and the nitrided layer is brittle. , Deformation of the nitriding mold, and defects such as mesh and needle-like nitrides on the surface of the mold, which seriously affect the service life of the mold.

Therefore, it is of great significance to study the defects of the nitriding layer of the mold, analyze the causes, and discuss the technological measures to reduce and prevent the gas nitriding defects, which are of great significance to improve the product quality of the mold and prolong the service life of the mold. Reasonable use of cooling lubricating fluid, play the three major roles of cooling, washing and lubrication, keep cooling and lubrication clean, so as to control the grinding heat within the allowable range to prevent thermal deformation of the workpiece. Improve the cooling conditions during grinding, such as using oil-immersed grinding wheels or internal cooling grinding wheels. The cutting fluid is introduced into the center of the grinding wheel, and the cutting fluid can directly enter the grinding area to play an effective cooling effect and prevent the surface of the workpiece from being burnt.

The quenching stress after heat treatment is reduced to a minimum, because the quenching stress and the reticulated carbonized structure under the action of grinding force, the phase transformation of the structure is very easy to cause cracks in the workpiece. For high-precision molds, in order to eliminate the residual stress of grinding, low-temperature aging treatment should be performed after grinding to improve toughness.

Ⅱ. Countermeasures for gas nitriding of die steel

1. Select the appropriate nitrided steel, and strictly check the material composition and metallographic structure of the hot die steel.

2. Strictly control the furnace temperature of the upper and lower zones in the nitriding furnace to keep it in the same temperature zone all the time.

3. Before nitriding, the pipeline should be checked and cleaned regularly to keep the pipeline unobstructed.

4. During the pretreatment of plastic molds, the temperature should be strictly controlled to ensure the normal temperature of quenching and tempering.

5. The mold needs to be degreased with gasoline or alcohol before being installed in the furnace. The surface of the cleaned mold should not have oil stains or other contaminants.

6. When the molds are installed in the basket, a certain distance should be kept between the molds to prevent the contact and overlap of the working surfaces of the molds.

7. The nitriding furnace should be well sealed, the atmosphere in the furnace should be fully circulated, and the leaking nitriding tank should be replaced in time.

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