A pipe cross-section processing device that reduces friction during processing and improves the degree of freedom regarding the rotation angle of the pipe cross section is provided. The pipe cross-section processing device may include a rotation drive source configured to rotate the base, a shaft secured to a front end portion of the base, a slide base capable of a sliding movement along the axis of the shaft, a roller guide member secured to the slide base, a slide-base drive member configured to convert the rotational motion of the base into a linear motion so as to drive the slide base together with the roller guide member in a sliding movement, and a roller configured to be adhered to an inner surface of a pipe cross section to rotationally process a cross section of the pipe outwardly in a radial direction of the pipe.

A pipe cross-section processing device that reduces friction during processing and improves the degree of freedom regarding the rotation angle of the pipe cross section is provided. The pipe cross-section processing device may include a rotation drive source configured to rotate the base, a shaft secured to a front end portion of the base, a slide base capable of a sliding movement along the axis of the shaft, a roller guide member secured to the slide base, a slide-base drive member configured to convert the rotational motion of the base into a linear motion so as to drive the slide base together with the roller guide member in a sliding movement, and a roller configured to be adhered to an inner surface of a pipe cross section to rotationally process a cross section of the pipe outwardly in a radial direction of the pipe.

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.

A piercing machine includes a plurality of skewed rolls, a plug, a mandrel bar and an outer surface cooling mechanism. The outer surface cooling mechanism is disposed around the mandrel bar at a position that is rearward of the plug, and with respect to an outer surface of a hollow shell advancing through a cooling zone which has a specific length in an axial direction of the mandrel bar and which is located rearward of the plug, as seen from an advancing direction of the hollow shell, the outer surface cooling mechanism ejects a cooling fluid toward an upper part of the outer surface, a lower part of the outer surface, a left part of the outer surface and a right part of the outer surface of the hollow shell to cool the hollow shell inside the cooling zone.

A piercing machine includes a plurality of skewed rolls, a plug, a mandrel bar and an outer surface cooling mechanism. The outer surface cooling mechanism is disposed around the mandrel bar at a position that is rearward of the plug, and with respect to an outer surface of a hollow shell advancing through a cooling zone which has a specific length in an axial direction of the mandrel bar and which is located rearward of the plug, as seen from an advancing direction of the hollow shell, the outer surface cooling mechanism ejects a cooling fluid toward an upper part of the outer surface, a lower part of the outer surface, a left part of the outer surface and a right part of the outer surface of the hollow shell to cool the hollow shell inside the cooling zone.

A process of producing a duplex stainless steel tube comprises the steps of: a) producing an ingot or a continuous casted billet of said duplex stainless steel; b) hot extruding the ingot or the billet obtained from step a) into a tube; and c) cold rolling the tube obtained from step b) to a final dimension thereof.
The outer diameter D and the wall thickness t of the cold rolled tube is 50-250 mm respectively is 5-25 mm, and, for the cold rolling step, R and Q are set such that the following formula is satisfied:
Rp0.2target=416.53+113.26.Math.log Q+4.0479.Math.R+2694.9.Math.C %82.750.Math.(log Q).sup.20.04279.Math.R.sup.22.2601.Math.log Q.Math.R+16.9.Math.Cr %+26.1.Math.Mo %+83.6.Math.N %+Z(1)
wherein Rp0.2target is targeted yield strength and is 800-1100 MPa and 0<Q<3.6.

A process of producing a duplex stainless steel tube comprises the steps of: a) producing an ingot or a continuous casted billet of said duplex stainless steel; b) hot extruding the ingot or the billet obtained from step a) into a tube; and c) cold rolling the tube obtained from step b) to a final dimension thereof.
The outer diameter D and the wall thickness t of the cold rolled tube is 50-250 mm respectively is 5-25 mm, and, for the cold rolling step, R and Q are set such that the following formula is satisfied:
Rp0.2target=416.53+113.26.Math.log Q+4.0479.Math.R+2694.9.Math.C %82.750.Math.(log Q).sup.20.04279.Math.R.sup.22.2601.Math.log Q.Math.R+16.9.Math.Cr %+26.1.Math.Mo %+83.6.Math.N %+Z(1)
wherein Rp0.2target is targeted yield strength and is 800-1100 MPa and 0<Q<3.6.

A method for producing hot-rolled, seamless pipes having at least one wall thickening which can be arranged at any positions over the length of the pipe, wherein by means of a multiple-stand mandrel bar rolling mill, the rolls roll a hollow shell on a mandrel bar as an inner tool to a required nominal wall thickness and produce at specified positions over the length of the pipe a required wall thickening on the outer side of the pipe by opening the rolls in the rolling stands. The thickened wall is produced and finish-rolled by two rolling stands that are consecutive as seen in the rolling direction, in which the deviations of the finished contour of the thickening from an ideal circular cross-section are minimised, wherein the rolling stands located upstream are likewise opened as to avoid any contact of the rolls of these rolling stands with the previously produced thickening.

A method for producing hot-rolled, seamless pipes having at least one wall thickening which can be arranged at any positions over the length of the pipe, wherein by means of a multiple-stand mandrel bar rolling mill, the rolls roll a hollow shell on a mandrel bar as an inner tool to a required nominal wall thickness and produce at specified positions over the length of the pipe a required wall thickening on the outer side of the pipe by opening the rolls in the rolling stands. The thickened wall is produced and finish-rolled by two rolling stands that are consecutive as seen in the rolling direction, in which the deviations of the finished contour of the thickening from an ideal circular cross-section are minimised, wherein the rolling stands located upstream are likewise opened as to avoid any contact of the rolls of these rolling stands with the previously produced thickening.

A method for producing a seamless metal pipe includes the steps of: preparing a billet having a diameter (B); heating the billet; forming, in a center part of a rear end of the heated billet, a hole including four grooves extending in an axial direction of the billet, the grooves each having a groove width (D) satisfying Formula (1), a groove height (H) satisfying Formula (2), and a groove depth (L1) satisfying Formula (3); and subjecting the billet provided with the hole to piercing-rolling from a front end thereof by means of a piercing machine. By this means, the generation of burrs and internal defects at the rear end of a hollow shell after piercing-rolling can be suppressed.

0.12D/B0.25 (1)

0.10H/B0.20 (2)

0.05L1/B0.10 (3)