Process for the manufacture of metal tubes

A method of making an elongated seamless metal tube of I.D. of 0.005 to 0.5 in (0.13-12.7 mm) and with wall thickness of 0.002-0.2 in (0.05-5 mm) of material selected from the group consisting of:

• (a) alloys comprising a metal selected from the class consisting of nickel and reactive metals (titanium, niobium, tantalum, zirconium and/or hafnium) as a principal alloy ingredient and one or more additional alloy ingredients selected from the class consisting of aluminum, vanadium, nickel, iron, copper and niobium,
• (b) nickel aluminide and titanium aluminide, and
• (c) one or more of the elements, titanium, zirconium, hafnium
• comprising steps of:
• (1) forming a tubular blank of the metal assembled into an assembly with a metal core surrounded and contacted by the tubular blank, the core metal being capable of stable elongation--elongation with uniform reduction of cross section area in relation to the degree of elongation--with a greater degree of reduction than the tube blank or the same degree of reduction depending on applied conditions, the metal of the core having an elongation capability as described at (3) below when worked as described in (2) and (3), below,
• (2) elongating the assembly by mechanical working until the tube is reduced in cross section area outer diameter compared to the original billet assembly and the tube wall thickness is correspondingly reduced compared to the original tubular blank, but in a way that avoids metallurgical or chemical bonding at the tubular blank/core interface, and then
• (3) further elongating the core by mechanical working, but in a way that causes its elongation and corresponding cross area reduction to a greater degree than any concomitant elongation and cross section area reduction of the tube with such elongation/reduction retained when stretching forces are withdrawn so that a clearance is developed between the tube and core enabling longitudinal core removal, and then removing the core.