Deformation Degree of Non-standard Seamless Steel Tubes

The degree of deformation is related to the selected extrusion ratio.

Reducing the die hole diameter or increasing the diameter of the extrusion tube can increase the extrusion ratio, thereby increasing the degree of deformation. It can be seen that when the degree of deformation is about 60%, the difference between the strength and the elongation of the inner and outer layers of the extruded product is the largest, but when the degree of deformation is increased to 90%, the shear deformation is deep into the center of the product, so that the extrusion on performance of the inner and outer layers on the cross section of the product tends to be uniform. Therefore, in the extrusion production, the degree of deformation of the non-standard seamless steel pipe is generally selected to be more than 90%, that is, the extrusion ratio is equal to or greater than 10, to ensure uniform mechanical properties of the product in the cross section. The above factors affecting metal flow are summarized as external factors such as external friction, temperature, tool shape and degree of deformation. The internal factors are alloy composition, high temperature strength of metal, thermal conductivity and phase change, etc. The change of the extrusion conditions, the mutual influence of each other, the friction between the metal ingot and the extrusion tool has the greatest influence.

Four modes of metal flow for squeezing bars. Mode A. The metal flows evenly and is only available in the reverse extrusion because there is no pattern B of sliding friction between the ingot and the extrusion barrel during reverse extrusion. In the case of forward extrusion, this mode is obtained if the frictional resistance between the wall of the extrusion cylinder and the ingot is small. The metal flow is relatively uniform, so it is not easy to produce a central shrinkage and a circular tail. Such as copper, H96, tin phosphor bronze belongs to this type. Mode C. This flow pattern is obtained when the extrusion tool has a large frictional resistance to metal flow. The metal flows unevenly and produces a less long squeeze tail at the end of the extrusion. Such as alpha brass, white copper, nickel alloy, etc. belong to this type. Mode D. When the extrusion tool has great frictional resistance to metal flow, the high temperature deformation resistance of the metal or non-standard seamless steel pipe is low, and the temperature difference between the inner and outer parts of the ingot is very obvious, the metal flow is very uneven, and the flow mode is obtained. Such as? +? brass (HPb59-1, H62), aluminum bronze, etc., belong to this type. In actual production, the determination of the length of the ingot should also take into account the margin of the cutting edge and the width of the material when the pipe is extruded. For indeterminate products, in order to improve the yield, according to the equipment capacity and product specifications, the conventional ingots that have been normalized can be selected, and the length of the ingot is generally not calculated. In principle, long ingots are used as far as possible under the premise of equipment capability approval and product quality assurance. The pressing force of a non-standard seamless steel pipe is the force that forces the metal out of the die hole through the extrusion shaft. Extrusion force is an important basis for formulating the extrusion process, selecting and checking the extruder's capabilities and testing tool strength. There are many calculation methods for simple extrusion force. There are simple empirical formulas for calculating the elastic deformation of the tension column and the calculation formula for measuring the liquid pressure of the master cylinder.

It's Daisy from China.I feel very happy to serve you so visit to my article.