Analysis Of Process For Quenching Piston’s Piston Impactor Based On ANSYS And Process Optimization Design

Due to the rapid economic development and continuous improvement of science and technology,DTH has been widely used in petroleum,mining,construction and other industries.China’s government investment in infrastructure is also very large,which led to the development of DTH-related technology and equipment.Piston piston is one of the important components of the impactor,and is easy to wear parts.At present,many manufacturers rely on their experience to design and produce pistons.In practice,fractures often occur.However,60% to 80% of the fractures are caused by quenching,which causes huge losses to engineering applications.Moreover,the manufacturers eager to optimize the DTH puncher quenching process parameters.Therefore,the process parameters of piston quenching for DTH have very important practical significance.In this paper,the finite element software ANSYS was used to simulate the quenching process of the piston of the down-hole impactor(material 20Cr2Ni4A).The formation characteristics and variation of temperature field,stress and strain field of the piston of the downhole impactor were analyzed Finally,the quenching process parameters are optimized,the study shows that:(1)The initial quenching temperature is 800°C,840°C,880°C,the quenching medium is oil,and the medium temperature is 20°C.It is concluded that the stress from the largest to the smallest stress is 880°C.When the stress is> 840°C,the stress> 800 °C stress.Since the austenite transformation temperature is 850°C,if 800°C is selected,it cannot be austenitized completely,but in the actual heat treatment,840°C is usually selected for heat treatment.(2)When the initial temperature is 840°C,the residual stress is the minimum,the medium temperature is constant,and when the temperature is 20°C,the medium is changed.The medium is water,12% FEROQUENCH aqueous solution,15% sodium chloride solution,20 engine oil.The maximum residual stress is the medium is water,and the smallest is oil.Through analysis,it was concluded that the change in stress from small to large 20 oil> 12% FEROQUENCH aqueous solution> 15% sodium chloride solution> water.Therefore,the medium selection oil is more appropriate.(3)The initial temperature is 840°C,the medium is quenching oil,and the quenching oil temperature is changed to optimize the medium temperature.The quenching oil temperature is 20°C,35°C,50°C,and 65°C,respectively.As the temperature of the quench oil increases,the residual stress decreases.Contrasting the quenching oil temperature is 35°C and the quenching oil temperature is 65°C,the residual stress difference is about 10 MPa,but the cost for the oil temperature at the quenching oil temperature of 60°C is much higher than the quenching oil temperature of 35°C.The safety hazards in the process will also increase,so the quench oil temperature is chosen to be 35°C.(4)In actual production,the piston cools from 840°C to 500°C.The cooling rate needs to be faster and the hardenability is good.The quenching oil is cooled.Although the stress obtained is the smallest,but the high temperature heating of the austenitic The amount of carbon is too large and the crystal grains are large.After cooling,a large amount of residual austenite remains in the workpiece,so that the hardness of the workpiece decreases,and the internal stress increases.Water and salt water were taken below.The initial temperature was 840°C.The medium temperature was 35°C.When cooled to 500°C,the oil was used for cooling.With time,water-oil quenching liquid,brine-oil quenching liquid,oil quenching liquid,the residual stress of oil quenching is the minimum,and the residual stress of water-oil quenching liquid is the largest.The law that produces residual stress from big to small is oil> brine oil> water oil.Before the conversion of martensite,rapid cooling is required.Although the residual stress generated by oil quench cooling is minimal,it may not be hardenability.If good hardenability is required,two-liquid quenching is selected,so brine-oil is selected.(5)The brine concentration also has influence on the residual stress.The following is the initial temperature is 840°C,the medium temperature is 35°C,and the brine concentration is 10%,15%,20%.When cooled to 500°C,it is cooled by oil.Over time,the higher the salt water concentration,the smaller the residual stress generated.Through the above comparison,the higher the brine concentration,the smaller the final residual stress,but the difference is not very large,but the higher the brine concentration,the greater the corrosion of the parts,and easier to be oxidized,choose to use 10% brine oil also Can save costs.(6)The temperature at the secondary quenching will also have an effect on the residual stress.The martensite transformation will occur at 400°C to 500°C.The stress analysis of oil quenching at 400°C,450°C,and 500°C is made below.Over time,the smaller the resulting residual stress is when the secondary quenching temperature is between 450°C and 500°C.