DE102010047868A1 - Hollow block manufacturing method, involves driving solid block in transportation zone in axial direction on mandrel, and rolling material such that material is expanded in circumferential direction and/or in axial direction - Google Patents

Abstract

The method involves driving a solid block (2) in a transportation zone (4) in an axial direction (a) on a mandrel (3) by exertion of force acting in the axial direction. A metallic material is rolled by two rollers (5) arranged around circumference of the block, so that the metallic material is pressed against a radially external surface (6) of the mandrel. The material is rolled such that the material is expanded in a circumferential direction and/or in the axial direction. The solid block is rolled to a hollow block (1) using a three-roller cross rolling mill. An independent claim is also included for a device for manufacturing a hollow block from a solid block.

Description

The invention relates to a method for producing a hollow block from a block of metallic material for further processing into a seamless tube, wherein a rolling of the material takes place over a piercer. Furthermore, the invention relates to an apparatus for producing a hollow block.

In the production of seamless tubes made of metallic material, a cast or rolled steel block is first formed into a thick-walled hollow body (tube blank) in a piercing process. This first stage of the piercing process is followed by rolling in a cross rolling mill.

Such a rolling process in a planetary cross rolling mill, for example, from DE 101 07 567 A1 known. In this case, a tube blank is fed to the planetary cross rolling mill, which is rolled in a gap to the finished seamless tube; The gap is formed between a number of Planetenschrägwalzen and a mandrel-shaped inner tool.

For punching the metallic block, the pressing and the oblique rolling are known.

A disadvantage of the technique of hole pressing, the limitation of the length of the material used due to the increasing eccentricity. In addition, an additional stretch rolling process is required here.

The punching of blocks by means of oblique rolls also has disadvantages: this process is a rolling process which takes place between rolls which are inclined with respect to one another and have the same direction of rotation; Here, the skew of the rollers causes an axial movement of the hollow block. In order to reduce free rolling movement, for example, with the two-roll cross rolling method outside the forming zone, guide bars or slices are used in the obliquely rolling punching, which delimit the roll gap at the open sides.

However, the problem here is that - in order to be able to perforate damage-free - to the production of certain austenitic steels high demands in terms of metallurgy, the structure and the Seigerungsausbildung must be made, which are only consuming to meet. Outside the forming zones, the material flow in the circumferential direction of the rolling stock causes bending stress, which can lead to crack formation in these steel groups.

The invention is therefore based on the object to provide a method for producing a hollow block of a block and a corresponding device, with which or with which it is possible to carry out the hole process with less material stress, d. H. It should be prevented that it comes to a material-damaging free material movement during the piercing process.

• a) Treiben des Blocks in einer Transportzone in axiale Richtung auf den Lochdorn durch Ausübung einer in axiale Richtung wirkende Kraft;
• b) Walzen des Materials durch mindestens zwei um den Umfang des Blocks herum angeordnete Walzen, so dass das Material gegen die radial außenliegende Oberfläche des Lochdorns gepresst wird und diesen kontaktiert, wobei das Walzen so erfolgt, dass das Material in Umfangsrichtung und/oder in radiale Richtung aufgeweitet wird, jedoch in axiale Richtung nicht gestaucht wird.

The solution of this problem by the invention is characterized according to the method by the steps:

• a) driving the block in a transport zone in the axial direction of the piercer by exerting an axially acting force;
• b) rolling the material through at least two rollers arranged around the circumference of the block such that the material is pressed against and contacts the radially outer surface of the piercer, the rolling being such that the material is circumferential and / or radial Direction is widened, but is not compressed in the axial direction.

The steps a) and b) take place simultaneously during the production of a hollow block.

By rolling the material in the region of the piercer, an axial feed force is preferably exerted on the material.

During rolling of the material, a roll gap is advantageously maintained between the radially outer surface of the piercing mandrel and the rolls, which increases radially in the advancing axial direction with a simultaneously decreasing wall thickness of the rolling stock.

In the region of the perforated mandrel, the cross-section of the rolling stock in a section perpendicular to the axial direction can be the same size at different axial positions. It is thus preferably provided that in each case cross-sections perpendicular to the longitudinal axis of the hollow block in the region of the piercer same cross-sectional areas are present. The material to be rolled is then neither accelerated nor decelerated in the axial direction, whereby it can be achieved that the finished hollow block has the same axial length as the block before punching.

In the transport zone, the rolling stock can be rolled cylindrically over a predetermined axial extent.

A specific embodiment provides that the extent of triangulation or oval formation is measured, influencing at least one process parameter becomes when a given amount is exceeded. For example, this process parameter is preferably the feed rate of the block.

The device for producing a hollow block from a block of metallic material for further processing into a seamless tube having a piercer and at least two rollers on the circumference of the rolling stock, according to the invention provides means for applying an axial force to the block and pressing it against the block Piercing mandrel, wherein the piercing mandrel and the rollers are formed so that they are suitable for maintaining the contact between the rolling stock and the radially outer surface of the piercing mandrel.

Thus, it should always be present contact of the rolling stock on the radially outer surface of the piercing pin, so that it has a guiding function for the material to be rolled.

Three or four rollers may be arranged around the circumference of the rolling stock, the rollers being designed in particular as planetary rollers, their axes enclosing an angle to the longitudinal axis of the rolling stock.

The piercing mandrel and the rolls are preferably designed such that the roll gap between the radially outer surface of the piercing mandrel and the rolls increases radially in the advancing axial direction, with a simultaneously decreasing wall thickness of the rolling stock.

The rollers can be stored stationary and in communication with a drive.

The invention thus focuses on the perforation of a hollow block, preferably by the cross rolling method.

According to the invention, in order to prevent the mentioned free material movement, which results in the damaging bending cycle stress, the block in the production of the hollow block via the inner tool, d. H. the piercer, driven. This is preferably done with a over a transport zone causing the feed punch. It is further provided that the forming material (i.e., the block or the hollow block) is transformed by the rotational movement of two or more inclined rollers so that the rolling stock is transported in the axial direction and stretched in the circumferential direction, d. H. is widened.

The partially forced material flow in the circumferential direction due to the mandrel geometry prevents the free movement of material and the otherwise associated bending stress of the material. The entire deformation goes into the expansion of the hollow block, which has the length of the output block after punching, d. H. the block length and the hollow block length are the same.

It can be produced by hot rolling seamless tubes made of high alloy steel by means of oblique rollers, which can be controlled without damage even in ratios of the outer diameter to the wall thickness of more than 5 without movement of material outside the zone of direct rolling contact.

In the block core is advantageously effected substantially a compressive stress state, which counteracts tearing in the core. Due to the material movement impressed by the mandrel or its geometry, in the three-roll cross-rolling process for closing the forming space, no internals such as those used in the two-roll cross-rolling process are necessary.

In the drawing, an embodiment of the invention is shown schematically. Show it:

1 a radial section through a part of a three-roll cross rolling mill, with which a block is rolled into a hollow block;

2 the section A-B according to 1 ; and

3 the section C-D according to 1 ,

In 1 is a three-roll cross rolling mill indicated, which need not be described in more detail, since it is known as such. A piercer 3 at the axial end of a mandrel 8th is fixed, is arranged fixed in the axial direction a. A massive block 2 becomes a hollow block 1 processed by the block 2 over the piercer 3 is rolled. The rolling takes place with three rollers arranged uniformly around the circumference 5 of which only one is sketched. These are skew rollers, ie their axis b and the axial direction a are skewed (ie they are not parallel and they do not intersect).

It is essential that a means 7 for applying an axial force is present, namely a press ram, with its front end face on the block 2 presses and so with a force F against the piercer 3 suppressed. The block 2 is via a transport zone 4 which ends at the axial position at which the piercer 3 starts, through the press stamp 7 in the resulting nip between the rolls 5 and the radially outer surface 6 of the piercer 3 introduced. In the area of the transport zone 4 have the rollers 5 a roller section 9 who is the block 2 cylindrically rolls. Due to the inclination of the rolling axis to the axial Direction a, however, this has a promotion of the block 2 in the axial direction a result.

As can be seen, in the axial direction a, the nip grows between the roller 5 and the radially outer surface 6 of the piercing pin radially continuous, while the wall thickness s decreases continuously. The corresponding sections A-B and C-D are in 2 or in 3 shown.

The contouring of the roller 5 in the region of the roll gap and the radially outer surface 6 of the piercer 3 is expertly chosen so that the material to be rolled always on the piercer 3 is applied. Furthermore, the nip widened over the axial direction a but radially so that with a corresponding decrease in the wall thickness s neither a stretching nor a compression of the material takes place. This has the consequence that the length of the rolling stock in the axial direction a remains unchanged.

The forming process can be assisted by a measuring and control system that directly or indirectly measures the ovalization or triangulation of the rolling stock and controls the feed rate or other forming parameters so that maximum ovalization is not exceeded.

In addition, the forming process can be assisted by guidance between the rollers, which obstruct or obstruct ovalization.

The rolling stock is thus perforated in a known cross rolling mill between the inclined rollers on the piercer. From the the hole thorn 3 opposite side is the rolling stock from the punch 7 over the piercer 3 driven, wherein the punch the feed over the transport zone 4 effected with a reduction required for the transport. The rolling stock is only widened by the geometry of the mandrel in interaction with the rollers or only increasingly stretched in the circumferential direction, as shown in the sectional views 2 and 3 can be removed.

The proposed process thus reduces the deleterious loading of the material during punching by causing substantially a compressive stress state in the block core which counteracts tearing in the core. By imprinted from the mandrel geometry material movement can be dispensed with closing of the forming space by special internals, as they are known for two-roll process.

Advantageously, such a hollow block is produced, which has optimum material properties, since a very gentle material forming is possible.

LIST OF REFERENCE NUMBERS

1

hollow block

2

block

3

piercer

4

transportation zone

5

roller

6

radially outer surface

7

Means for applying an axial force (pressing punch)

8th

mandrel

9

roller section

a

axial direction

b

Axis of the roller

F

force

s

wall thickness

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10107567 A1 [0003]

Claims (10)

Method for producing a hollow block ( 1 ) from a block ( 2 ) of metallic material for further processing into a seamless tube, wherein rolling of the material over a piercer ( 3 ), characterized by the steps of: a) driving the block ( 2 ) in a transport zone ( 4 ) in the axial direction (a) on the piercer ( 3 ) by exerting a force (F) acting in the axial direction (a); b) rolling the material through at least two around the circumference of the block ( 2 ) arranged around ( 5 ), so that the material against the radially outer surface ( 6 ) of the piercer ( 3 ) is pressed and contacted, wherein the rolling takes place so that the material is widened in the circumferential direction and / or in the radial direction, but in the axial direction (a) is not compressed. A method according to claim 1, characterized in that by rolling the material in the region of the piercer ( 3 ) an axial feed force is exerted on the material. A method according to claim 1 or 2, characterized in that during rolling of the material, a roll gap between the radially outer surface of the piercing mandrel ( 3 ) and the rollers ( 5 ) is maintained, which increases radially in the advancing axial direction (a) and at the same time has a decreasing wall thickness (s) of the rolling result. Method according to one of claims 1 to 3, characterized in that in the region of the piercer ( 3 ) At different axial positions of the cross section of the rolling stock in a section perpendicular to the axial direction (a) is the same size. Method according to one of claims 1 to 4, characterized in that in the transport zone ( 4 ) the rolling stock is rolled cylindrically over a predetermined axial extent. Method according to one of claims 1 to 5, characterized in that the extent of a triangulation or an oval formation is measured, wherein at least one process parameter is influenced when a predetermined amount is exceeded, wherein in particular the feed rate of the block ( 2 ) Is influenced. Device for producing a hollow block ( 1 ) from a block ( 2 ) of metallic material for further processing into a seamless tube containing a piercer ( 3 ) and at least two on the circumference of the rolling stock attacking rollers ( 5 ), in particular for carrying out the method according to one of claims 1 to 6, characterized by means ( 7 ) for applying an axial force (F) to the block ( 2 ) and for pressing the same against the piercer ( 3 ), wherein the piercer ( 3 ) and the rollers ( 5 ) are designed so that they are used to maintain the contact between rolling stock and radially outer surface ( 6 ) of the piercer ( 3 ) are suitable. Apparatus according to claim 7, characterized in that around the circumference of the rolling stock three or four rolls ( 5 ) are arranged, whose axes form an angle to the longitudinal axis of the rolling stock. Apparatus according to claim 7 or 8, characterized in that the piercer ( 3 ) and the rollers ( 5 ) are formed so that the nip between the radially outer surface of the piercer ( 3 ) and the rollers ( 5 ) becomes radially larger in the advancing axial direction (a) with simultaneously decreasing wall thickness (s) of the rolling stock. Device according to one of claims 7 to 9, characterized in that the rollers ( 5 ) are stationary and are in communication with a drive.

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