H13 Steel Surface Based On QPQ Technology Process Research

The concept of deep QPQ technology has been put forward for a long time,but different processes have been developed with different processing objects.For H13die steel,this process can improve the thermal fatigue resistance and corrosion resistance of the die.The main contents of this paper are as follows:Through the theoretical analysis and practical application of existing bath salts and new titanium infiltration methods,a new method is proposed to increase the thickness of the new H13 die steel surface infiltration layer and form a compact film on the die surface to improve the die life and corrosion resistance.By studying the chemical composition of the new H13 die steel,QPQ treatment process parameters and titanium plating methods,the effects of the above factors on the quality,thickness and corrosion resistance of the treated layer were analyzed.At the same time,the above effects were verified by surface microhardness test,cross-section hardness distribution,metallographic observation and wear resistance test.The concentration of CNO^-in the new type of nitrogen salts was 30%after 2hours at 620?.During the next 36 hours,the concentration of CNO^-decreased slowly,the bath liquid fluidity was better,and the surface loose layer of the treated die steel was thinner by measuring.Adding regenerated salt after a period of time can convert carbonate into cyanate in bath.This process is to restore CNO^-activity,reduce the concentration of CN^-and adjust the height of the liquid.The oxide film formed by treatment can protect the appearance of the die and improve the corrosion resistance of the die.After deep QPQ treatment,the outer layer of the structure is Fe₃O₄ oxide film,followed by the nitride layer of iron?about 10-35 um thickness?,which is named as a N-containing alpha-Fe solid solution.The quality and thickness of the infiltrated layer will also change after deep QPQ treatment because of the different trace element content of the die steel itself.Compared with conventional process,the quality of deep QPQ treatment after titanium catalysis has been greatly improved.At the same nitriding temperature difference,titanium plating time and CNO^-concentration,the higher the CNO^-concentration,the more active nitrogen atoms in the solution,the thicker the nitriding layer formed.