DE102007021999A1 - Method for hot rolling seamless tubes on an inner tool and inner tool - Google Patents

Abstract

The mandrel (5) outer circumference includes tool segments (8) of highly wear-resistant material. Between them, tool inserts (10) intervene, without gaps. The tool segments are pre-stressed axially and tangentially. They are held down radially. Cooling-, lubricating- and parting fluid is led directly into the contact region between the mandrel and the workpiece (3), via a central longitudinal bore (6) of the mandrel and radial feed bores (15). A bush (11) sets up axial pre-stressing of the segments and inserts, through its wedge-shaped contact surfaces (14). The segments are ceramic, especially a cermet. An independent claim IS INCLUDED FOR the mandrel employed.

Description

The invention relates to a method for hot rolling seamless tubes with one or more consecutively arranged longitudinal or Schrägwalzgerüsten and an inner tool used in the interior of the rolling stock in the form of a mandrel or roll bar, as by the DE 21 31 713 A1 known.

The Inner tools / mandrel rods are in the transformation of seamless tubes Depending on the manufacturing process, high mechanical and thermal loads exposed. Accordingly, a high wear of the tool surface occurs, where there is abrasion, adhesion and disruption comes and with relatively little life to surface damage on the forming material as well as the failure of the tool. Therefore, an attempt is made Hard-wearing, wear-resistant materials in highly loaded tool areas use.

Usually come for Forming tools Hot working steels, but increasingly also special materials (eg hard metals, nickel-cobalt alloys, Cermets) and ceramics. Ceramics, cermet and other highly wear-resistant materials have the for these purposes particularly disadvantageous properties of low thermal shock resistance, low bending strength and high crack sensitivity when Occurrence of tensile stresses.

used one interior tools, z. As rolling rods, the rings or ring segments with or without axial preload, it comes under load through the rolling stock to local tensile stresses, the emergence of Cracks and failure of the tool result. For this Reason is the use of wear-resistant materials to the in Interior of the rolling stock used tools so far unsuccessful.

Of the Invention is therefore based on the object, a generic method and a generic interior tool to create a seamless tube production without the use of special materials for allow the internal tool described disadvantages.

These Task is procedurally with the in claim 1 and with respect to the inner tool with the in the claim 4 specified characteristics solved.

advantageous and appropriate embodiments of the invention are in the dependent claims contain.

To present invention, the occurrence of tensile stresses is avoided by using tool bits that are distributed around the circumference, with which Tool parts, z. B. segments of highly wear-resistant material, under high be biased tangential compressive stresses. This will work together with an axial bias a state of stress with high compressive stresses generated when loaded by the rolling stock to a three-dimensional Compressive state leads and thereby avoiding the occurrence of tensile stresses allows. This makes the use of wear-resistant but brittle materials on the internal tools in rolling mills of the seamless tube production allows.

The Number of tool parts or segments depends on the number the rollers so that the mandrel / roll bar, d. H. the inner tool has two, three or more segments each in between arranged tool inserts can have.

The Workpiece inserts are arranged so that this in case of load in the area without rolling stock contact or in the area only low mechanical and thermal stress. When longitudinal rolling the inner tool is aligned so that the workpiece inserts in the Are positioned areas between the rollers. When cross rolling the roll bar or the inner tool should also be positioned like this be and not rotate.

Also when using special materials, such as ceramics, which has a low affinity to steel, and wear-resistant up to operating temperatures of over 1,000 ° C, it is advantageous that a Cool-, Lubricating and separating agent introduced into the contact zone tube inner tool becomes. For this purpose, the tool body is with a central longitudinal bore as well as with radial, oblique supply bores provided by which the medium under pressure and adhering to the inner surface of the tube promoted to the contact zone becomes. When several successively arranged rolling stands is every rolling stand supplied in this way with the medium. Also with skew rolling mills the supply takes place in the same way.

Further Details and features of the invention will become apparent from the claims and the following description of a schematic in the drawings illustrated embodiment of the Invention. Show it:

1 in a longitudinal section as a detail of a section of an inner tool for producing seamless tubes, and that shown in the contact region of the tubular rolling stock with a roll of a rolling stand, and

2 as a detail a cross section of the Inner tool (rolling / mandrel bar) along the line II-II of 1 ,

In front of a known as such Kontiwalzanlage 1 time to make seamless pipes 1 excerpts an area in which one in the rolling direction 2 continuous rolling stock 3 in contact with a roller 4 located. The perforated, tubular rolling stock 3 is between, successive rolls 4 the Kontiwalzanlage 1 on an interior tool 5 , rolled out rolled or mandrel bar, wherein the Kontiwalzanlage 1 advantageous with held inner tool 5 can be operated so that the feed path is between minus 1 stand distance to plus 1 stand distance.

The interior tool 5 consists of a central longitudinal bore 6 having basic body 7 and on this arranged tool segments 8th Made of a highly wear-resistant, heat-resistant material and between them, as indicated by arrow 9 (see. 2 ) radially engageable tool inserts 10 , The tool segments 8th and inserts 10 become one of the main body 7 enclosing sleeve 11 added.

Through the sleeve 11 become the tool segments arranged therein 8th and inserts 10 axially biased, as in 1 with the arrows 12 indicated. Because the tool segments 8th due to the radial adjustability (arrows 9 in 2 ) of the tool inserts 10 simultaneously a tangential pressure or Vorspanndung according to the in 2 registered double arrows 13 subject, occurs in the tool segments 8th no tensile stress, which is especially in brittle material, such as ceramic, the tool segments 8th is very important. During rolling, an all-round compressive stress is achieved. For better effectiveness when introducing the tangential and axial compressive stresses are on the one hand, the sleeve 11 with the tool segments 8th and - inserts 10 and on the other hand the tool inserts 10 with the tool segments 8th with wedge surfaces 14 to each other.

From the longitudinal bore 6 of the interior tool 5 starting and going through the main body 7 and the sleeve 11 passing through are radially, obliquely formed a plurality of supply bores 15 intended. One in the longitudinal bore 6 From a supply source, not shown, introduced cooling, lubricating and separating agent via the supply holes 15 under pressure directly into the contact zone between the rolling stock 3 and the interior tool 5 brought in. There it comes to the desired adhesion to the inner circumferential surface of the rolling stock 3 ,

1

Kontiwalzanlage

2

rolling direction (Arrow)

3

rolling

4

roller

5

internal tool (Mandrel / roller bar)

6

longitudinal bore

7

body

8th

tool segments

9

arrow (Radialanstellbarkeit)

10

tool insert

11

shell

12

arrow (Axial prestressing)

13

double arrow (Tangential pressure Norspannung)

14

wedge surfaces

15

feed bore

Claims (9)

Method for hot rolling seamless tubes with one or more longitudinal or transverse rolling stands arranged one behind the other and one inside the rolling stock ( 3 ) used interior tool ( 5 ) in the form of a mandrel, characterized in that an inner tool ( 5 ) having at its outer periphery a plurality of tool segments ( 8th ) made of a wear-resistant material and therebetween gapless tool inserts ( 10 ) is used, wherein the tool segments ( 8th ) are biased under tangential and axial compressive stresses. Method according to claim 1, characterized in that the tool inserts ( 10 ) are radially adjustable. Method according to claim 1 or 2, characterized in that via a central longitudinal bore ( 6 ) of the inner tool ( 5 ) as well as radial feed bores ( 15 ) between the longitudinal bore ( 6 ) and the tool surface a cooling, lubricating and separating agent directly into the contact area of the inner tool ( 5 ) and rolling stock ( 3 ). Indoor tool ( 5 ), arranged in the interior of the rolling stock ( 3 ), preferably held with only a limited feed, for hot rolling seamless tubes in one or more consecutively arranged longitudinal or Schrägwalzgerüsten, in particular for carrying out the method according to claim 1, characterized in that on the base body ( 7 ) of the inner tool ( 5 ) several tool segments ( 8th ) made of a highly wear-resistant, heat-resistant material and between these radially adjustable tool inserts ( 10 ) are arranged. Inner tool according to claim 4, characterized by one of the tool segments ( 8th ) and Tool inserts ( 10 ) axially biasing sleeve ( 11 ). Inner tool according to claim 5, characterized in that on the one hand the tool segments ( 8th ) on the tool inserts ( 10 ) and on the other hand, the sleeve ( 11 ) on the tool segments ( 8th ) and tool inserts ( 10 ) with wedge surfaces ( 14 ) issue. Inner tool according to one of claims 4 to 6, characterized in that the tool segments ( 8th ) consist of ceramic. Inner tool according to one of claims 4 to 6, characterized in that the tool segments ( 8th ) consist of cermet. Inner tool according to one of claims 4 to 8, characterized in that it has a central longitudinal bore ( 6 ) and is formed from this starting to the tool surface with radial feed holes, which extend directly into the contact area of the inner tool ( 5 ) and rolling stock ( 3 ) and distribute a cooling, lubricating and separating agent.