EP2959983A1 - Method of manufacturing seamless hollow ingot of steel - Google Patents

Abstract

The invention relates to a method for producing a seamless hollow block 4a, b from a solid round block 1 made of steel with a hollow block diameter, which is rolled smaller or larger by reducing or expanding rolling than the solid round block 1, in which by means of a three-roll Slanting mill via a held between the rollers 2, a hole portion 10 and at least one smoothing member 12 having piercer 3a, b of the hollow block 4a, b is generated, wherein using an identical set of rollers for the reducing and expanding rollers, the setting for the rollers and the piercer determined and performed by the following equations:

Description

The invention relates to a method for producing a seamless hollow block made of steel according to the preamble of claim 1.

Seamless pipes, especially of steel, are generally produced in three main forming steps, namely by punching, stretching and finish rolling. In this case, solid round blocks are often first punched in a cross-rolling mill to form a hollow block and later introduced into the so-called dimensional or Streckreduzierwalzwerk for finish rolling. For the intermediate route, various methods are known, e.g. the impact bench procedure.

From the Font tapes, sheets, tubes 6 (1965), No. 4, pp. 184-189 It is known to widen a hollow block already produced by means of a separate skew rolling process in order to be able to produce different magnifying glass diameters for the required different finished diameter tubes after the measure or stretch reduction rolls. However, nothing is said about how to perform the expansion in combination with the punching in a single skew rolling operation.

Is known from the EP 1 901 862 B1 in that massive round blocks with a two- or three-roll cross-rolling mill can be punched with the same roll calibration in a strongly reducing or slightly widening manner, in which case the hollow block diameter produced is smaller or larger than that of the round block used. For example, then a hollow block of 186 mm diameter can be produced in the case of highly reducing rolling from a round block with a diameter of 220 mm. The degree of reduction is therefore 16%.

By slightly widening rolling a hollow block with a diameter of 186 mm can be produced with the known method of a solid round block with a diameter of 180 mm diameter at a Aufweitegrad of 3.3%. In order to increase the producible rolling spectrum significantly, however, at least twice as large diameter magnifications or more would be required without having to change the rollers for this purpose.

While according to EP 901 862 B1 the punching and at the same time strongly reducing rolls or slightly expanding rolls can be carried out solely by means of modified roll settings with the "normal rolls", it has hitherto not been possible to realize this also for the punching in combination with very strongly expanding rolling of, for example, over 5% , Here, the inlet and outlet travel angle is 3.5 ° and the transport angle is 10 °.

The entry angle describes the angle between the roll axis and the generatrix of the roll body in the inlet region.

The outlet angle is the angle between the roll axis and the generatrix of the roll body in the outlet region.

At entry and exit angles, a distinction must be made between the entry and exit angles specified by the calibration of the rolls and the effective entry and exit angles at which the rolling stock enters the entry section of the rolls.

The entry angle of the rolls is formed by the angle between the roll longitudinal axis and the generatrix of the roll body in the inlet region of the roll. Accordingly, the outlet angle is formed by the angle between the roll longitudinal axis and the generatrix of the roll body in the outlet region of the roll.

The effective entry angle at which the rolling stock enters the inlet part of the rolls results from the set spread angle between the roll longitudinal axis and the longitudinal axis of the rolling stock or rolling mill center axis. At a spread angle of 0 ° then the entry angle of the rollers corresponds to the effective entry angle. The same applies to the effective outlet angle.

In the case of a transport angle of zero degrees and a spread angle of zero degrees effectively effective in the rolling mill inlet and outlet angle correspond to the calibrated in the roller angles. Changes in the spread angle lead to changes in the effective entry and exit angles. In the case of an equal inlet and outlet angle of 3.5 ° calibrated in the roller body, the reduction of the spread angle by 1 ° leads to the reduction of the effective inlet angle to 2.5 ° and to the increase of the effective outlet angle to 4.5 °.

The spread angle describes the angle between the roll and rolling stock at a transport angle of zero degrees. The two axes intersect in front of the inlet side of the Slanting mill, resulting in a positive spread angle. If the point of intersection is on the outlet side, the spread angle is negative.

The transport angle, which specifies the feed of the rolling stock relative to the punch mandrel in the rolling mill, describes the angle by which the rolls are pivoted about a pivot axis perpendicular to the mill axis.

If, according to the state of the art, for example, thick-walled hollow blocks with a diameter of 155 mm to 192 mm are to be produced from the same round block, it has hitherto been necessary to use two different sets of rolls. Hollow blocks with a wall thickness over 25 mm are considered to be thick-walled. However, a stable rolling process could not yet be achieved with these measures. In addition, expensive roller sets have to be maintained with two different calibrations and corresponding changeover times of up to eight hours for the cross-rolling mill can be accepted.

The object of the invention is to provide a method for producing a seamless hollow block made of steel from a solid round block by cross rolling by means of a three-roll cross rolling mill, in which by means of a single set of rolls equally hollow blocks can be perforated strongly reducing and greatly widening. The hollow block diameter produced with a block diameter should be variably adjustable and differ in diameter by up to 35%. Furthermore, with the method, the changeover times and thus storage costs for additionally calibrated rolls should be significantly reduced.

This object is achieved on the basis of the preamble in conjunction with the characterizing part of claim 1.

The teaching of the invention comprises a method for producing a seamless hollow block from a solid round block made of steel with a hollow block diameter, which is rolled by reducing or bulging rolling smaller or larger than the solid round block used, in which by means of a three-roll cross rolling mill via a held between the rollers, a hole part and at least one smoothing part having perforated mandrel, the hollow block is produced, wherein for the production of the hollow block with a reduced or increased compared to the inserted round block diameter, in particular the clearance of the rollers in the narrowest cross section ("high point ") in relation to the diameter of the inserted round block and the position of Mandrel tip with respect to the high point (mandrel template) and the effective entry angle, characterized in that, using an identical rolling and reducing roll set, the settings for the rolls and piercing mandrel are determined and made by the following equations: effective entry angle: 2 ° to 7 ° Diameter high point: 75 to 90% of the block diameter Dorn template: (0.05 to 0.4) x length of roll inlet where the rolling technical limits are as follows:
reducing rolling up to -30%: Max. effective entry angle: 7 ° Diameter high point: 75 to 85% of the block diameter Dorn template: (0.2 to 0.4) x length of roll inlet expanding rolling up to + 16%: minute effective entry angle: 2 ° Diameter high point: 85 to 90% of the Blocls diameter Dorn template: (0.05 to 0.15) x length of roll inlet and wherein a piercing mandrel is used for the expanding rolling, which has an additional expansion part between the hole part and the smoothing part.

The desired hollow block diameters in the range between the limits for the reducing and expanding rolls can then be realized without changing the roll calibration with adaptation of the mandrel template, the diameter at the high point and by varying the spread angle, resulting in other effective entry and exit angles.

For example, if the diameter of the hollow block should be equal to that of the solid round block, the spread angle would have to be chosen so that in the case of a same length of the inlet and outlet part on the roller and the same inlet and outlet angle of about 3.5 ° to 4 , 0 ° result. The diameter at the high point would be about 85%, the Dornvorlage about 0.25 x block diameter.

The principle is that the larger the desired hollow block diameter, the larger the spread angle, the smaller the effective entry angle, the larger the exit angle, the larger the diameter at the high point and the smaller the mandrel template.

Experiments have surprisingly shown that only by a combined change in the effective angle of entry, the Dornvorlage and the diameter at a high point, a wide range of hollow block diameters can be rolled.

If necessary, for large diameter variations of the hollow block, the piercer should be recalibrated accordingly.

A basic requirement for the application of the invention is a three-roll cross rolling mill, in which the spread angle of the rolls can be changed. This describes the angle between roll and rolling stock at a transport angle of zero degrees. If the two axes intersect in front of the inlet side of the cross rolling mill, the result is a positive spread angle. If the point of intersection is on the outlet side, the spread angle is negative.

All the above data on entry and exit angles refer to a theoretical transport angle of zero degrees, which describes the pivoting of the rollers about the vertical to the rolling axis. This results in three-dimensional space once again changed (larger) entry and exit angles, which are not separately identified due to the complexity.

The great advantage of the proposed method is that it can be perforated from strongly reducing to strongly expanding with the same roll calibration, whereby the hollow block diameters achieved can differ by up to 35% with a roll calibration. This involves considerable time savings for no longer required roll change and the provision of appropriate sets of rolls. In addition, the number of required round block formats for the hollow block diameter to be produced can be reduced, which considerably reduces the logistics effort.
For the strongly expanding rolling, in addition to the variation of the roll adjustment according to the invention, only one appropriately calibrated mandrel with an additional expansion part is to be used.

For example, can be made in this way from a round block with 180 mm diameter, a hollow block with a diameter of 155 mm or a hollow block with a diameter of 192 mm. This corresponds to a realized reduction rate of approx. 14% or an expansion factor of approx. 7%.

The degree of expansion is defined as the difference between the diameter of hollow block and round block divided by the diameter of the round block.

In the course of the tests carried out, it was recognized that with the rolls originally intended for reduction, it is possible to have a strongly widening roll with a widening degree of significantly more than 5% or even more than 15%, if the angle of spread between the roll longitudinal axis and the rolling mill center axis and the distance of the rolls in the high point is adjusted so that there is a significant reduction in the effective angle of entry.

When reducing rolls, make sure that the piercer is calibrated without a widening part so that the mandrel has only one hole and one flattening part.

When adjusting the spread angle, it must be ensured that a large effective entry angle and a maximum length in the inlet part of the roller can be used in order to realize a reduction in the diameter of the incoming ingot below that of the required hollow block diameter.

In the subsequent outlet part is only the required minimum expansion to safely transport the hollow block on the piercer.

When expanding rollers, the spread angle is adjusted so that there is a correspondingly smaller angle in the inlet and a corresponding larger angle in the outlet.

Own investigations showed that from the EP 1 901 862 B1 previously known limits in the choice of the effective inlet angle in the range between 3.5 ° to 5 ° can be significantly extended with the roll settings according to the invention and also a stable rolling operation in widening rolls with even smaller effective inlet angle of 2 ° is possible.

When adjusting the spread angle, make sure that a small inlet angle and the shortest possible length of the inlet part are used during rolling, so that the maximum reduction in the incoming ingot diameter does not drop below 85% at the high point.

The mandrel template is to be significantly reduced during expansion compared to reducing, so that the entire expansion process takes place in the outlet part of the cross rolling mill. Here the maximum possible length of the outlet part is to be used for the forming process.

In the case of a roller with an inlet length of 300 mm and an outlet length of 200 mm, the mandrel pattern for reducing rollers is therefore 60 to 120 mm and for expanding rollers 15 to 45 mm.

According to the invention, the piercer has an additional widening part during the widening rolling between the hole part and the smoothing part, which causes a particularly large decrease in wall thickness behind the high point, which in turn can be converted into a diameter widening.

Special requirements for the transport angle with respect to the application of the invention do not exist. This can be used according to the possibilities of the rolling mill in the range of 5.5 ° to 12 °.

The following Table 1 shows the possibilities of the method according to the invention on the example of a Rohblockdurchmessers of 180 mm. With SPW the spread angle is marked, with the initial puncture diameter of the round block, with DHP the diameter at the high point, with the end the diameter of the produced hollow block and with DM change the achieved diameter change. Not listed are the appropriately set mandrel templates for the reducing and expanding rollers.

The results impressively demonstrate the now very broad rolling spectrum which can be achieved in order to produce diameter changes of the hollow block of -30% to + 15% with a round block diameter. This results in work areas for one and the same roll set of -22% ... + 12%, -30% ... + 6 ° or -20 .. + 16% for the diameter change. Table 1: Results of rolling tests Inlet length [mm] Outlet length [mm] Entry angle roller [°] Outlet angle roller [°] SPW [°] Entry angle effective [°] Outlet angle effective [°] DM puncture [mm] DHP [mm] DM end [mm] DM change [%] 220 180 2.0 5.0 -4 6.0 1 180 134 140 -22.2% 140 180 2.0 5.0 0 2.0 5 180 170 202 12.1% 220 180 3.0 4.0 -4 7.0 0 180 126 126 -30.0% 140 ^. 180 310 4.0 0 3.0 4 180 165 190 5.8% 200 200 4.0 4.0 -2.5 6.5 1.5 180 134 145 -19.5% 200 200 4.0 4.0 2 2.0 6 180 166 208 15.6%

The inventive method will be explained in more detail with reference to schematic representations.

In FIG. 1 are a longitudinal section and a cross section through a three-roll cross-rolling mill shown in which a round block is perforated strongly reducing in the direction of the transport arrow.

The three-roll cross rolling mill consists of three rollers 2, with which the round block 1 is rolled over a piercer 3a to a hollow block 4a with a relation to the initial diameter of the round block 1 greatly reduced diameter. The narrowest cross section between the three rollers 2 identifies the high point 6 and indicates the diameter of the hollow block 4a produced.

The tip of the hole dome 3a is seen at a distance 7 in the rolling direction in front of the high point 6 of the rollers 2. The tip of the piercer 3a assumes a position that ensures that the round block 1 is perforated reducing error-free.

The distance 7 is also referred to as a mandrel template. The piercing mandrel 3a used according to the invention for reducing rolls shows FIG. 2 , The perforated mandrel 3 a consists of a hole part 10, a smoothing part 12 and a cylindrical part 13. Only the hole part 10 projects clearly beyond the high point 6 into the inlet area of the rollers 2. With 5 of the spreading angle of the rollers is designated, which indicates the angular position of the roller longitudinal axis 8 to the rolling mill axis 9.

For the strongly dilating punching shows FIG. 3 also on a longitudinal and cross section through a three-roll cross rolling mill, the plant configuration. In this case, the round block 1 is transported in the direction of the arrow through the cross-rolling mill and greatly widening perforated. Clearly visible on the one hand compared to the diameter of the round block 1 significantly enlarged diameter of the hollow block 4b produced, resulting in a significantly increased roll spacing at high point 6 and a significantly reduced spread angle 5 of the rollers 2 against the settings for reducing rolls according to FIG. 1 reflects.

According to the invention shows FIG. 3 also in the first example ( FIG. 1 ) otherwise unusual position of the piercing mandrel 3b, which is set back relative to the position for reducing punching clearly in the direction of high point 6. The mandrel template 7 is therefore significantly reduced in expanding rollers compared to the reducing rollers, so that only a small part of the hole part 10 protrudes into the inlet region of the rollers 2.

The piercing mandrel 3b used according to the invention for the strongly reducing punching shows FIG. 4 , Opposite the piercer 3a for reducing rolls according to FIG. 2 For example, the perforated mandrel 3b according to the invention has an additional expansion part 11 for expanding rolling between the hole part 10 and the smoothing part 12, which causes a particularly large decrease in wall thickness behind the high point, which in turn can be converted into a diameter expansion.

In FIG. 5 Once again the transport angle 14 is shown, which describes the angle by which the rollers 2 are pivoted about a pivot axis 17 perpendicular to the rolling mill center axis 9.

The calibrated entry and exit angle of the rollers 2 is in FIG. 6 shown schematically.

The entry angle 15 describes the angle between the roller axis 8 and the generatrix of the rollers 2 in the inlet region. Again, the arrow indicates the direction of entry of the round block in the rollers 2.

The outlet angle 16 is the angle between the roller axis 8 and the generatrix of the rollers 2 in the outlet region.

At a spread angle of 0 ° then corresponds to the calibrated entry and exit angle of the effective entry and exit angle at which the rolling stock, so the round block 1, in the rollers 2 and runs out. <B> LIST OF REFERENCES </ b> 1 massive round block 2 roll 3a, 3b piercer 4a, 4b hollow block 5 splay 6 high point 7 Distance (spine template) 8th roll axis 9 Rolling mill center axis 10 hole part 11 Aufweiteteil 12 smoothing part 13 cylindrical part 14 transport angle 15 calibrated entry angle 16 calibrated outlet angle 17 swivel axis 18 Effective entry angle

Claims (5)

A method for producing a seamless hollow block 4a, b of a solid round block 1 made of steel with a hollow block diameter, which is rolled by reducing or bulging rolling smaller or larger than the solid round block 1 , in which by means of a three-roll cross rolling mill on a between the roll 2 held, a hole portion 10 and at least one smoothing 12 having perforated mandrel 3a, b of the hollow block 4a, b is produced, wherein in particular for the production of a reduced or increased compared to the block diameter hollow block diameter, the distance of the rollers 2 in the narrowest cross section 6 (Fig. high point) in relation to the diameter of the inserted round block 1 and the distance 7 of the tip of the piercer 3a, b with respect to the high point 6 (mandrel template) and the effective entry angle 18 are set characterized
that , using an identical rolling and reducing roll set, the settings for the rolls and piercer are determined and made by the following equations: Effective entry angle: 2 ° to 7 ° Diameter high point: 75 to 90% of the block diameter Dorn template: (0.05 to 0.4) x length of roll inlet where the rolling technical limits are as follows:
reducing rolling up to -30%: Max. effective entry angle: 7 ° Diameter high point: 75 to 85% of the block diameter Dorn template: (0.2 to 0.4) x length of roll inlet Expanding rolling up to + 16%: minute effective entry angle: 2 ° Diameter high point: 85 to 90% of the block diameter Dorn template: (0.05 to 0.15) x length of roll inlet, wherein a piercing mandrel 3a, b is used for the expanding rolling, which additionally has a widening part 11 between the hole part 10 and the smoothing part 12 . Method according to claim 1,
characterized,
that, so seen in the reducing rolls of the hole portion 10 of the piercing mandrel 3a in the inlet part of the rolls 2 in the rolling direction, is located before the high point and the smoothing part 12 behind it. Method according to claim 1,
characterized,
that the mandrel template is set back relative to the mandrel 7 submission to the reducing rolls with respect to the high point in the widening rollers. Method according to one of claims 1 to 3,
characterized,
that for the reducing rolling of a hollow block 4a, which is smaller in diameter by up to 30% than the diameter of the round block 1, depending on the required degree of reduction, the spread angle 5 at a calibrated inlet angle 15 of 2 ° and 3 ° up to 4 ° and raised at an inlet angle 15 of 4 ° up to 2.5 °, with an effective inlet angle 18 of up to 6 ° at a calibrated inlet angle 15 of up to 2 °, an effective inlet angle 18 of 7 ° at an inlet angle 15 of up to 3 ° and an effective entry angle 18 of up to 6.5 ° at an entry angle 15 of 4 ° results. Method according to one of claims 1 to 4,
characterized,
that for the widening rolling a hollow block 4b, which is larger in diameter by up to 16% than the diameter of the round block 1 depending on the required Aufweitegrad, the spread angle 5 at a calibrated inlet angle 15 of 2 ° and 3 ° up to 0 ° and at an inlet angle 15 of 4 ° to be lowered to -2 °, with an effective inlet angle 18 of up to 2 ° at a calibrated inlet angle 15 of 2 °, an effective inlet angle 18 of up to 3 ° at an inlet angle 15 of 3 ° and an effective inlet angle 18 of up to 2 ° at an inlet angle 15 of 4 ° results.

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