PURPOSE: To improve the life of a plug and the steel pipe quality by fitting a common steel made protection cap to the tip of a plug for piercing in case of manufacturing a seamless steel pipe with its piercing for an alloy steel.
CONSTITUTION: A common steel protection cap 2 preworked in the shape of almost a plug 1 is fitted to the tip of the plug 1 just before piercing. Accordingly, the cap 2 of the common steel of the tip is uniformly extended, the direct contact o the plug 1 with the alloy steel is interrupted and also the transference of the scale formed on the common steel to the plug 1 is enabled to protect the plug 1. The early wear and seizure are prevented and also the load increase caused at a piercing initial time can be reduced as well. This protection cap 2 has no need for its fitting on each piercing rolling, there is enough scale transference effect with its use on each 6-10 pieces although depending upon the components and a drastic plug life extension can be realized similarly.
KOISHIHARA MASAHIRO
TAKAGUCHI MITSURU
