The effect of processing parameters on the propensity for central fracturing in piercing

Abstract

Successful competition in the seamless tubular products market demands improvements in surface and dimensional quality in products from seamless pipe mills. It is reported that pass design, piercer setup and operating parameters have critical effects on both dimensional and surface quality. Defects which form during the piercing process are the result of these mechanical parameters (which control the localized stress states) in combination with metallurgical factors (which determine the material’s resistance to fracture by aggravating stresses). Understanding the detrimental effects of inclusions led to the development of cleaner materials, but economically feasible operations in this direction have been exhausted. Because of this, attention is directed to improvement of deformation limits by control of mechanical processing factors, such as piercer setup and point/pass design. Control of these parameters leads to an optimum pass design that produces conditions favorable not only for enhanced deformation before fracture, but also for energy and power requirements.