Method for piercing titanium alloy solid billet

Abstract

A method for piercing a titanium alloy solid billet, the method including: 1) providing a Mannesmann rotary piercer including two rollers, a feed channel, a plurality of centering devices, and a mandril including a plug; fixing the mandril using the plurality of centering devices, where the Mannesmann rotary piercer has a feeding angle of 6-18°, a cross angle of 15°, and a roll speed of 30-90 rpm; 2) heating a titanium alloy solid billet to 930-990° C.; 3) transferring the titanium alloy solid billet to the feed channel of the Mannesmann rotary piercer; and 4) aligning the titanium alloy solid billet with the plug of the mandril, and driving the titanium alloy solid billet to pass through the plug of the mandril, thereby piercing the titanium alloy solid billet and yielding a titanium alloy tube.

What is claimed is: 
     
         1 . A method, comprising:
 1) providing a Mannesmann rotary piercer comprising two rollers, two guide plates, a feed channel, a plurality of centering devices, and a mandril comprising a plug; fixing the mandril using the plurality of centering devices; wherein the Mannesmann rotary piercer has a feeding angle of 6-18°, a cross angle of 15°, and a roll speed of 30-90 rpm, and a plug advance of 5-15 mm; the feeding angle refers to a projection of an included angle between an axis of one of the two rollers and an axis of a billet along a connection line of rotation centers of the two rollers, and the cross angle refers to a projection of an included angle between the axis of one of the two rollers and the axis of the billet on a plane formed by a connection line of the rotation centers of the two rollers and the axis of the billet; the plug advance refers to a distance between a front end of the plug and a roll gorge along the axis of the billet, the roll gorge refers to the position of a minimum distance between the two rollers; a diameter reduction ratio of the billet is set as 6-12%;   2) heating a titanium alloy solid billet to 930-990° C.;   3) transferring the titanium alloy solid billet to the feed channel of the Mannesmann rotary piercer; and   4) aligning the titanium alloy solid billet with the plug of the mandril, and driving the titanium alloy solid billet to pass through the plug of the mandril, thereby piercing the titanium alloy solid billet and yielding a titanium alloy tube.   
     
     
         2 . The method of  claim 1 , wherein the mandril comprises a free end and a fixed end, and the plug is disposed on the free end; the centering device is installed in batches; a distance between a first one of the plurality of centering devices and the fixed end is (⅔) n l, where n refers to batch of installation of the centering devices, and l refers to a length of the mandril; the plurality of centering devices is 2 n -1 in number, and the centering devices are exponentially added in each installation; a distance between a second one of the plurality of centering devices and the free end is ⅓×(⅖) n-1 l; when n is greater than 2, suppose a distance between two adjacent centering devices is a, additional centering devices are disposed between the two adjacent centering devices, and a distance between the additional centering devices and one of the two adjacent centering devices close to the free end is ⅖a. 
     
     
         3 . The method of  claim 1 , wherein a heating time of the titanium alloy solid billet is D×(1.2 to 2) min, where D is a diameter of the titanium alloy solid billet with a unit of millimeter. 
     
     
         4 . The method of  claim 1 , wherein the two rollers each are a conical roll with double helix. 
     
     
         5 . The method of  claim 1 , wherein the Mannesmann rotary piercer comprises three cams for each centering device; an included angle of each two of the three cams is 120°, and the mandril is disposed in a hole enclosed by the three cams for each centering device. 
     
     
         6 . The method of  claim 1 , wherein the Mannesmann rotary piercer comprises two guide plates disposed between the two rollers, and the distance between the two guide plates is 1.05-1.1 times that of the two rollers in a cross section perpendicular to the axis of the billet, and a minimum distance between the two rollers is D−(1−diameter reduction ratio), where D is the diameter of the titanium alloy solid billet with a unit of millimeter. 
     
     
         7 . The method of  claim 1 , further comprising cooling the titanium alloy tube in air. 
     
     
         8 . The method of  claim 1 , further comprising machining a head and a tail of the titanium alloy tube. 
     
     
         9 . The method of  claim 1 , wherein in 4), the titanium alloy solid billet is pierced in the Mannesmann rotary piercer at a temperature between 860 and 1000° C.