Method for producing seamless tubes

Details Method for producing seamless tubes Method for producing seamless tubes

B - Operations, Transporting

21

C

B21C 23/08 (2006.01) C22C 38/00 (2006.01) C22C 38/58 (2006.01)

Patent

CA 2749576

Provided is a method for producing a seamless tube, in which after a starting material to be extruded has been heated to a heating temperature T [°C] satisfying the relationship of Formula (1) or Formula (2) depending on the outside diameter do [mm] thereof, the starting material is hot extruded by providing a solid lubricating glass between the starting material to be extruded and a die, whereby a transverse flaw on the outer surface in the top portion of tube can be prevented when hot extrusion is performed by using a starting material for extrusion having low deformability at high temperatures. When d0<200, T <= 1250+1.1487×A--7.838×1n(t0/t)-10.135×1n(d0/d) ... (1); when d0>=200, T <= 1219+1.1487×A--7.838×1n(t0/t)-10.135×1n(d0/d) ... (2), where A = L/V av × 1000 [msec], V av = (V0 + V0×p)/2 [mm/sec], .rho. = (t0×(d0-t0))/(t×(d-t)), t0: wall thickness of starting material to be extruded [mm], d: outside diameter of extruded tube [mm], t: wall thickness thereof [mm], L: length of approach portion of die along extrusion direction [mm], and V0: ram speed [mm/sec].

La présente invention concerne un procédé pour la production de tube sans soudure grâce auquel on peut empêcher la fissure de section transversale à la surface extérieure de la partie supérieure du tube lors d'une extrusion à chaud au moyen d'un matériau à extruder présentant une faible déformabilité à haute température par le chauffage du matériau à extruder à une température T [°C] qui satisfait la corrélation dans la formule (1) ou (2) selon de diamètre extérieur d0[mm] de celui-ci suivie d'une extrusion à chaud avec interposition d'un verre lubrifié solide entre le matériau et la matrice. Lorsque d0<200, T?1250+1.1487×A-7.838×ln(t0/t)-10.135×ln(d0/d)(1); when d0?200, T?1219+1.1487×A-7.838×ln(t0/t)-10.135×ln(d0/d)(2); A=L/Vav×1000[msec]; Vav=(V0+V0×?)/2[mm/sec]; ?=(t0×(d0-t0))/(t×(d-t)); t0 étant l'épaisseur du matériau à extruder [mm]; d étant le diamètre extérieur du tube extrudé [mm]; t étant l'épaisseur du tube extrudé [mm]; L étant la longueur dans la direction d'extrusion de la partie se rapprochant de la matrice[mm]; et V0 étant la vitesse de coulisseau[mm/sec].

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