In the high pressure extrusion stage, the material characteristics of air source ball valve vary with different extrusion methods .
In this stage, high pressure extrusion within air ball valve products, the general said internal and outer high pressure stamping, basically does not occur between the ingot billet outer air ball valve flow after the die is still in the outer layer of the extrusion products and will not flow to the center of the products, high pressure extrusion stage starts out air ball valve die until normal extrusion process is coming to an end. When the air source ball valve is extruded, the material particle on any section of the billet enters the compression cone in the deformation zone at the same speed or with a certain speed difference, and the edge near the corner of the gasket and mold is pressed under low pressure, forming the difficult deformation zone. As the length of billet decreases, the contact friction area between the product and the extrusion wall decreases, while the extrusion pressure decreases.
High pressure extrusion stage air valves high pressure stamping not always absolute uniformity, the first is due to the existence of external friction, air ball valve material in the axial and radial on the same section of exist obvious uneven uneven deformation and high pressure stamping, followed by ingot billet temperature distribution on cross section, due to the heating mode, thermal deformation in the process of deformation and heat transfer, etc. The comprehensive function because of tired, high pressure caused by uneven stamping. The distribution of deformation resistance along the radial direction is different during extrusion. For example: valve set external friction or billet outer temperature is low. The outer deformation resistance of the metal is higher than that of the center, which will result in the uneven stamping phenomenon that the internal stamping speed is higher than the external stamping speed. When the valve group billet heating time is not enough to cause the inner deformation, that is, the pressure forging is not in place, it will make the outer surface products have cracks.
With the control of extrusion conditions and time, the quality of valve sets in different product extrusion will be different. The holes in the compression cone are gradually standardized with the high-pressure stamping speed. According to the calculation of the experimental data of valve set material and mechanical high-pressure stamping, the high-layer pneumatic stamping speed on the material surface is 25 times of the extrusion speed. The center of the high pressure stamping speed is 1 of the extrusion speed. 35 -- 2.1 times, the difference in the high pressure stamping speed indicates that the plastic deformation of the valve set surface in the deformation zone is uneven, and the result will inevitably reflect the quality of the extrusion valve set.
Air ball valve with the processing technology of extrusion process, the product of the round hole distance is becoming more and more reach a certain standard, longitudinal much smaller metal supply, back-end metal ingot billet speed change the stress state, to overcome the extrusion of friction, forced by the edge of the outer valve group to the center of the violent transverse (radial) high pressure stamping, extrusion is also rising rapidly at this time .