Deoxidation of cross-rolled hollow blocks

Abstract

The invention relates to a method for producing a tube (2) or tubular pre-product from a solid billet in a rolling mill, comprising at least one roll (5a, 5b) acting from the outside on the solid billet or tubular pre-product and a mandrel (4) carrying a piercing head (3) and engaging from the inside in the tube or tubular pre-product, wherein immediately after the solid billet has been completely pierced by the piercing head a fluidized deoxidation agent and/or an inert gas is supplied to the end of the tube or tubular pre-product facing the roll and is guided through the tube or tubular pre-product into the interior of the tube or tubular pre-product when the mandrel is withdrawn. The invention further relates to a rolling mill for performing the method according to the invention, comprising at least one roll acting from the outside onto the solid billet or tubular pre-product and a mandrel carrying a piercing head and engaging from the inside in the tube or tubular pre-product, wherein a device is provided for feeding and introducing a fluidized deoxidation agent and/or an inert gas to the end of the tube or tubular pre-product facing the at least one roll.

Claims

1. A method of making a tube from a solid billet extending along an axis, the method comprising the steps of sequentially: engaging a piercing head of a mandrel into a rear end of the solid billet while rotating the billet about the axis with at least one roller engaging a front end of the billet so as to push the piercing head forward through the billet and form an axially throughgoing passage in the billet until the piercing head exits the front end of the billet, whereby the solid billet is formed into a tube; after the piercing head exits from the front end of the tube feeding into the passage at the front end a fluidized deoxidizing agent and/or an inert gas; retracting the piercing head axially rearward in the passage so as to depressurize the passage between the piercing head and the front end and draw in the fluidized deoxidizing agent and/or the inert gas; and mixing a vehicle gas with the deoxidizing agent.

2. The method according to claim 1, wherein the feeding of the fluidized deoxidizing agent and/or inert gas begins before retraction of the piercing mandrel.

3. The method according to claim 1, wherein the feeding of fluidized deoxidizing agent and/or an inert gas takes place within 10 seconds after completely piercing the solid billet.

4. A method of making a tube from a solid billet extending along an axis, the method comprising the steps of sequentially: engaging a piercing head of a mandrel into a rear end of the solid billet while rotating the billet about the axis with at least one roller engaging a front end of the billet so as to push the piercing head forward through the billet and form an axially throughgoing passage in the billet until the piercing head exits the front end of the billet, whereby the solid billet is formed into a tube; and thereafter by a process controller starting feeding into the passage at the front end a fluidized deoxidizing agent and/or an inert gas while simultaneously retracting the piercing head axially rearward in the passage so as to simultaneously depressurize the passage between the piercing head and the front end and draw in the fluidized deoxidizing agent and/or the inert gas.

5. The method according to claim 4, further comprising the step of: blocking entry of air into the passage of the tube at least mostly, at least at the start of the feeding of fluidized deoxidizing agent and/or inert gas.

6. The method according to claim 4, wherein the fluidized deoxidizing agent and/or inert gas is fed at a superatmospheric pressure of no more than 1 bar.

7. The method according to claim 4, wherein the deoxidizing agent is fed pneumatically.

8. An apparatus for making a tube from a solid billet extending along an axis, the apparatus comprising: a mandrel carrying a piercing head displaceable along the axis; at least one cross roller engageable with a front end of the solid billet for rotating the solid billet while engaging the piercing head into a rear end of the solid billet so as to push the piercing head forward through the billet and form an axially throughgoing passage in the billet until the piercing head exits the front end of the billet, whereby the solid billet is formed into a tube; a supply including a first supply of an inert gas, a second supply of a deoxidizing agent, and valves connected to the first and second supplies for creating a fluidized deoxidizing agent and feeding the fluidized deoxidizing agent into the passage at the front; and a retracting device configured to retract the piercing head axially rearward in the passage so as to depressurize the passage between the piercing head and the front end and draw in the fluidized deoxidizing agent.

9. The method according to claim 1, further comprising the step of: sealing the tube on at least one end with respect to the ambient atmosphere.

10. The rolling apparatus according to claim 8, further comprising: a process control unit for controlling feeding of agent and/or inert gas and for controlling the piercing head.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in greater detail below with reference to three figures in which:

(2) FIG. 1 is a schematic view of the method of making a tube or tubular preproduct from a solid billet using a prior-art rolling apparatus,

(3) FIG. 2 is a schematic view of a rolling apparatus before the start of the method according to the invention, and

(4) FIG. 3 is a schematic view of an inventive rolling apparatus when carrying out the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows a schematic view of a rolling apparatus 1 for piercing a workpiece 2 using a mandrel rod 4 carrying a piercing head 3. Two external cross-rolls 5a and 5b rotate the workpiece 2 and at the same time move it in the direction of the arrow 6 to thereby continuously form a tube 2 or tubular preproduct having an inner surface 7 newly created by the piercing head 3 from a solid metal block.

(6) FIG. 2 shows a schematic view of a rolling apparatus 1 according to the invention in which a device 8 for supplying deoxidizing agent and inert gas is provided on the end of the tube 2 at the rolls 5a and 5b. The piercing head 3 has just advanced completely through the workpiece 2 and the device 8 is shifted in the direction indicated by the arrow 9. The device 8 comprises a cover 10 for closing the end of the tube 2 juxtaposed with the rolls as well as valves 11 and 12 for supplying deoxidizing agent and inert gas through the device 8 into the tube 2.

(7) Finally, FIG. 3 shows the rolling apparatus 1 while carrying out the method according to the invention. As the piercing head 3 together with the mandrel rod 4 is being extracted out of the tube 2 in the direction of arrow 13 by a retracting means shown schematically at 17, a deoxidizing agent and nitrogen as the inert gas are fed into the tube 2 through the device 8 from the respective supplies 14 and 15 and in fed into the internal cavity of the tube 2 formed by the mandrel rod 4 and onto its inside wall 7, where it is fluidized. The device 8 also comprises a valve 16 through which nitrogen is fed from the supply 15 into the supply 14 for deoxidizing powder in such a way as to fluidize the deoxidizing powder with the nitrogen from the supply 15. In this preferred embodiment, nitrogen from the supply 15 thus also serves as a vehicle gas for the deoxidizing powder from the supply 14.