DE102012007379B4 - Process for the cross rolling of cylindrical products - Google Patents

Abstract

Method for cross-rolling cylindrical products, in which the blank with a reduced front part (21) is introduced into the rolling mill and rolled in a rolling caliber whose forming zones are formed from at least three obliquely mounted rolls (1) on which a draw-in part, in the rolling direction, a working part with a generatrix angle of inclination to the rolling axis which is greater than the value of the critical angle (αG), in which the conditions for the axial blank gripping are not met, and a calibration part are arranged, characterized in that the forming zones of the rolling caliber of rolls (1 ) are formed on which in the rolling direction first of the working part (11) whose generatrix inclination angle (α1) is selected in the range between 20 ° and 45 °, and then the pull-in part (12) whose generatrix inclination angle (α2) in the range between 2 ° and 10 ° is selected, here is the diameter (dR) of the reduced front partly (21) of the blank (2) by 0.6 to 0.95 times the diameter reduction value (Δd2) of the blanking zone (2) formed in the caliber drawing zone (K2) formed by the draw-in parts (12) of the rolls (1) ) is made larger than the caliber diameter (DK) set in the cross section of the high point, and the length (lR) of the reduced front part (21) is in the range of 0.7 to 1.2 times the length (LK2) of the caliber intake zone (DK). K2).

Description

The invention relates to a method for the oblique rolling of cylindrical products on a rolling mill whose rolling caliber is formed by three obliquely mounted, arranged circumferentially symmetrical to the roll axis rollers, each of which via a draw-in, as a so-called shoulder (calibration to Assel) executed working part , in which the essential transformation takes place, and has a calibration part. The invention presented here can be used for the oblique rolling of solid, preferably continuously cast and / or non-preformed blanks as well as for the rolling of hollow blocks.

The Schrägwalzverfahren developed by Walter Assel is well known and has prevailed in the production of rolling bearing and thick-walled rotary part tubes. In the Assel process, the metallic cylinder-shaped thick-wall hollow block heated to rolling temperature is fed to the cross-rolling mill by means of a feed device and deformed on the outer surface by three rolls offset by 120 ° from one another. The inclination of the rollers relative to the rolling axis causes an axial movement of the hollow block with a value which is determined by the feed angle of the rollers. Under the action of the rotating rollers, the hollow block traverses on a helical path various zones of the rolling caliber in which the forming conditions are determined by the calibration of the roller.

In the case of skew rolling, a roll calibration is used which, functionally, consists of the intake, the working and the calibration region. The forming of the rolling caliber formed from the individual parts of the roller differ from each other by the inclination angle of the generatrix of the respective roller part to the roller axis (conicity of the zone) and by the length of the zone. Characteristic of the Assel method is the use of the working part of the roller in the form of a shoulder, where in a limited part of the roller there is a considerable change in the roller diameter. Here, the main deformation of the hollow block is concentrated on the narrow zone of the rolling caliber, whereby a high yield factor is achieved.

In order to enable the required forming conditions, the inclination angle of the surface line of the roll working member to the rolling axis is made substantially larger than the critical angle α _G between the roll generating line and the rolling axis, in which the conditions for the axial gripping of the blank by the rolls are not to fulfill more. For this reason, the requirements for the axial intake are not met in the working part of the roller. In the classic Assel process, the primary gripping of the blank takes place through the rollers in the draw-in part, which is located in front of the working part. On the contact surface of the roll pull-in part, as a result of the deformation of the blank, frictional forces form and accumulate, the total axial component of which applies the push-in force which is both for ensuring the stability of the secondary grip which is associated with overcoming the frontal counterforce of the shoulder , as well as for passing through the stationary phase of the process is required. In addition, the projection of the frictional forces on the direction of rotation of the blank (tangential direction) ensures that the condition for the rotation of the blank being rolled is satisfied.

If the value of the radial deformation taking place in the working part of the roll is high, a substantial proportion of the metal being formed is flowing in the tangential direction, which in the rolling space increases the hollow block circumference, ie. H. an extension, and thickening of the hollow block wall causes. The calibration part of the roll usually consists of two sections: the section for the compensation of the wall thickness nonuniformity of the rolled hollow block and the section for the adjustment of its circumferential ovality.

The constant improvement of the Assel process is mainly aimed at eliminating the problem associated with the formation of triangular funnels. In the stationary phase of the process, the underlying unreduced tube material counteracts funnel formation. When rolling the rear part of hollow blocks, especially in thin-walled Luppen, the tendency for funneling, because there is not enough material to be reshaped in the inlet cone of the Assel mill.

In addition, as the metal leaves the draw-in portion of the roll, the total disappearance, length and contact area of the metal and, consequently, the value of frictional forces acting in that area are also reduced. Therefore, the further fulfillment of the conditions for axial movement and rotation of the rolled in the working part rear end of the hollow block is mainly ensured by the contact forces that occur in the calibration. The considerable increase in circumference of the rear hollow block end located in this stage leads to a considerable broadening of the contact surface in the working part or in the calibration part, which makes it difficult to fulfill the conditions for a rotation of the hollow block located in the rolling process. When a critical funnel size is reached, the conditions for the rotation are no longer met. It comes to a jam in the spaces between the three rollers, which can lead to blocking the longitudinal feed movement.

In this case, the billet can get stuck in the Assel mill, so that an opening of the rollers is required. This disadvantage is a limitation for the use of the Assel process in the production of thin-walled pipes.

With the aim of solving the problem described above has been within the scope of the invention DE 3823135 C3 made the proposal to pre-reduce the diameter and / or the wall thickness of the rear hollow block end, before the hollow block is fed to the rolling mill. The intention in the Vorreduzierung the rear Hohlblockendes is to reduce by reducing the diameter value and / or the wall thickness of the hollow block, the radial deformation in the working part of the roller, which yes ultimately represents the decisive cause for the funnel formation. Here, the pre-reduction of the rear end takes place as far as possible so that the disturbance of the process eliminated in the Assel mill and a significant reduction of the scrap metal at the rear end of the tubes located in the rolling process is achieved. With the aim of reducing or eliminating the possibility of funneling during rolling of the rear hollow block end, various methods and devices have been proposed in the above-mentioned invention for subjecting the rear hollow block end to pre-reduction: a measure at any time prior to rolling can be performed on the Assel mill by using known and suitable methods such as plastic deformation such as forging or rolling or cutting such as turning. In the context of the abovementioned invention, the possibility was also presented of installing on the input side on the Assel rolling mill a device for pre-reducing the rear hollow block end; a description of the construction and function of this device is attached.

Also is in the known invention FR 1 096 090 A the method and equipment for the constriction of the profile of both ends of a hollow block has been presented. The narrowing process is performed on a cross rolling mill when punching a block or elongating a hollow block. Such a hollow block is provided for subsequent rolling in a pilgering mill. The profile of the front end of the proposed hollow block is carried out according to the profile, which is formed in the initial phase after a number of work cycles when rolling the non-profiled hollow block end in the pilger rolling mill.

The use of the hollow block with the two reduced ends allows to substantially reduce the end losses of the metal, to increase the pilgrimage performance and to facilitate the work of the pilgrim rollers in the initial and final stages of the process.

It is a procedure ( DE 197 51 205 A1 ) for avoiding triangulations and losses at the rear end of the lollipop in an Assel rolling mill by the application of a tensile force during rolling of the rear Luppenendes known. The main claim of the invention is that the longitudinal speed of the mandrel bar in the rolling direction during rolling of the rear Luppenendes is increased to about the Walzgutauslaufgeschwindigkeit. In one of the additional claims has been proposed to apply a tensile force on the outlet side exiting tube blank during the rolling of the rear end of the Luppen. According to the description of the invention, such a longitudinal force could be achieved, for example, with a three-pulley guide provided on the outlet side of the roll stand and displaceable in the rolling direction. The implementation of the proposed method requires the use of additional complicated equipment, which are also severely limited in the possibility of ensuring the technologically necessary size of the traction. In applying this method for rolling the main part of the billet (the stationary phase of the process) great difficulties may arise.

In the known invention DE 1602 017 A a method for reducing thick-walled tubes at almost constant wall thickness by means of three conical rolls, without the use of a mandrel, proposed. The rollers have a guide zone for driving, a working zone for the main forming and a calibration zone. This method can be used for rolling a specific, very limited range. Finally, it is one of the application variants of the known Asselkalibrierung.

Next, the present invention, the known method of skew rolling (s. DE 3231110 C2 ) of continuously cast blanks on a three-roll mill, the nip of which is formed by obliquely mounted, set on the feed angle rollers. Each roller contains an entry zone, an adjacent compression zone and a calibration section, wherein in the compression zone the solid blank is deformed at a single decrease of 20% to 40% and in the entry zone the individual decrease is 0.2 to 0.5 times the individual decrease in the compression zone is. As a result of the intense radial decrease in the process, a sufficiently good deformation of the cast structure from the outer areas achieved in the core zone of the blank. The implementation of the proposed forming process takes place at a significantly high roll feed angle, which is set to 15 ° to 35 °. In this case, the vector curve of the friction forces on the contact surface increases in the axial direction, as a result of which the axial component of the friction forces increases, which ensures the advance of the metal through the forming zone of the compression part.

With the objective of eliminating the increased ovality of the cylindrical product in the rolling process, which arises under the action of large individual decreases and as a result of existing at large roll feed angles high metal axial feed in the compression part, is proposed in the known method, for the calibration of the roller a Length to be within the range (0.3 to 0.6) of the total length of the strain zone.

According to the accompanying drawings and patent specification, roll calibration is used for the implementation of the rolling process mentioned here, which in terms of its functional properties is equivalent to roll calibration in the Assel process.

The methods under consideration, as well as other known methods of cross roll rolling in the mill with shoulder calendering, have a significant procedural deficiency associated with the specific forming conditions in the cross rolling mill. The effect of the axial butting force, which arises in the draw-in part of the roll and is required to meet the conditions of primary and secondary gripping in rolling with shoulder calibration of the rolls, has the consequence that the deformation of the blank in the working part of the rolls under intense axial pressure and consequently under biaxial compressive stress: in the radial and axial directions. Such a forming state of the blank in the working part of the roller in combination with open caliber part in the rolling gap has the consequence that a considerable part of compressed metal flows in the tangential direction. When rolling a solid blank, this leads to an increased ovality of the blank cross-section in the working part of the roller, - when rolling a hollow block is an enlargement of the same, and there is an increased tendency for funneling. As a consequence, there is a reduction in the stretchability of the rolling mill and increased energy costs during rolling.

Another disadvantage of the cross rolling method in the rolling mill with shoulder calibration of the rollers is the constant height of the shoulder in the working part, in which the decrease in the outside diameter of the rough rolling stock in the rolling process is specified from the outset. This limits the range of products that can be rolled with a single roll calibration size. In order to expand the assortment of products to be rolled, one takes in practice blanks with different outer diameters, increases the number of sets of rollers with different shoulder heights, and when rolling hollow blocks, the tool park is also expanded with thorns of different diameters. This drawback severely restricts the millable range, limits the flexibility of the mill, and increases production costs.

The present invention is based on the intention of eliminating the above-mentioned disadvantages by developing a new cross-rolling process, which is characterized by a significant change in the forming conditions for the rolled stock during rolling in the rolling shoulder with shoulder calibration of the rolls.

The set goal can be achieved in that in the method for the oblique rolling of cylindrical products, in which the blank with a reduced front part ( 21 ) is introduced into the rolling mill and is rolled in a rolling caliber whose forming zones are formed from at least three obliquely mounted rolls on which in the rolling direction a draw-in part, a working part with a generatrix inclination angle to the rolling axis which is greater than the value of the critical angle α _G at in which the conditions for the axial blank gripping are not met, and a calibration part are arranged, according to the present invention, the forming zones of the rolling caliber of rolls (FIG. 1 ) are formed on which in the rolling direction first of the working part ( 11 ), whose generatrix inclination angle α _{1 is selected} in the range between 20 ° and 45 °, and then the draw-in part (FIG. 12 ) whose generatrix inclination angle (α ₂ ) is selected in the range between 2 ° and 10 °, in which case the diameter (d _R ) of the reduced front part ( 21 ) of the blank ( 2 ) by 0.6 to 0.95 times the diameter reduction value (Δd ₂ ) of the infeed parts ( 12 ) of the rolls ( 1 ) formed Kalibereinzugzone (K ₂ ) to be rolled blank ( 2 ) greater than the set in the cross section of the high point caliber diameter (D _K ), and the length (l _R ) of the reduced front part ( 21 ) is selected in the range of 0.7 to 1.2 times the length (L _K2 ) of the caliber drawing zone (K ₂ ).

The implementation of the here presented Schrägwalzverfahrens and serving to its extension claims is by means of the accompanying drawings and the subsequent description of the presented process engineering explained using the example of rolling solid blanks.

1 shows the position of the blank and the rollers (in all drawings, two out of three work rolls are symbolically represented) in the rolling caliber during the stationary process phase.

2 and 3 show the realization of the blank gripping during rolling according to claim 1 of the invention presented here.

Here is in 2 the position of the rollers and the blank to each other in the primary contact (point X ₁ ) of the reduced blank front part with the draw-in part of the roller shown, and in

3 the position of rollers and blank to each other during the first contact (secondary gripping, point X ₂ ) of the actual blank body with the working part of the roller is shown.

4 illustrates the forming process of the blank in the rolling caliber according to claim 2 of the invention, and

5 contains a schematic representation of the introduction of the blank into the rolling caliber according to claim 3 of the invention.

As in 1 is located at the beginning of each roller ( 1 ) the working part ( 11 ), in which the generatrix inclination angle to the rolling axis α _{1 is} greater than the critical angle α _G , wherein the conditions for the axial insertion of the blank are not met in the rolling mill. Following this is the feeder part ( 12 ), in which a generatrix inclination angle α ₂ to the rolling axis is selected which is smaller than the critical angle α _G , in order to ensure that the conditions for an axial intake of the blank into the rolling mill and a stable operation of the stationary process phase are ensured. Behind this is the calibration part on the roller. The beginning of the calibration part coincides with the cross-section of the high point, in which the minimum distance between the rolling axis and the work rolls is set, whereby the caliber diameter D _{K is defined} in the cross section of the high point. The caliber diameter is the diameter of the circle which hypothetically fits between the contours of the three rolls in the considered cross-section of the roll nip. In practice, the calibration part of the roller consists of two sections (s. 1 ): the section for calibrating the geometrical dimensions of the rolling stock, the generatrix of which is generally parallel to the rolling axis, and the outlet section, which represents the opening of the caliber, and ensures that the rolled product is freely fed out of the rolling mill. When rolling hollow blocks in the outlet section also the ovality of the hollow block outer diameter is compensated.

The rolling elements form the corresponding forming zones of the rolling caliber: the caliber working zone (K ₁ ) and the caliber drawing zone (K ₂ ), their position in 1 indicated by dotted lines.

The rolling process according to claim 1 of the invention proceeds as follows (s. 2 ). With the aid of a feed device ( 3 ) the blank ( 2 ) with its reduced front part ( 21 ) into that of the rollers ( 1 ) introduced rolling caliber. Under the influence of the external push-in force, the first contact point of the reduced front part results ( 21 ) of the blank ( 2 ) with the rollers ( 1 ).

As in 2 shown, is for the reduced front ( 21 ) of the blank ( 2 ) a diameter d _R chosen that is so much smaller than the diameter of its main part d ₂ , that the first contact between blank ( 2 ) and roller ( 1 ) in the intake part ( 12 ) of the roller (s. 2 , Point X ₁ ) takes place in the rolling direction behind the working part ( 11 ), in which the main forming of the blank takes place.

In the first stage of gripping, only the reduced front part ( 21 ) of the blank ( 2 ) deformed. If the conditions for the primary gripping are met, the blank is helically formed along the draw-in part by the action of the rotating inclined rollers ( 12 ). The other stages of the process are without involving the feed device. On the contact surface of the roller pull-in part is formed as a result of the decrease of the reduced front part ( 21 ) and accumulates with forward movement of the blank ( 2 ) a resulting frictional force whose axial component which has a tensile force F ₂ (s. 3 ) ensures that the blank is moved further through the forming zones of the rolling caliber in the rolling mill.

3 shows the location of blank ( 2 ) and roller ( 1 ) to each other in the second stage of the blank gripping. Thanks to the selected length l _{R of} the reduced front part ( 21 ) (s. 2 ) the initial contact between the main part of the blank ( 2 ) and the working part ( 11 ) of the roller ( 1 ) - (s. 3 , Point X ₂ ) at the time when in the draw-in part ( 12 ) of the roller ( 1 ) due to the deformation of the reduced front part ( 21 ) has accumulated a reserve of axial tensile force F ₂ required to overcome the frontal counterforce of the shoulder F ₁ . If the conditions for the secondary gripping are met, all the forming zones of the rolling mill caliber are filled with metal, and the stationary phase of the rolling process occurs, in which the rear end of the blank ( 2 ) with an axial velocity V ₂ (s. 1 ).

In contrast to the known production technology solutions come in the here presented Schrägwalzverfahren due to the arrangement of the roller working part ( 11 ) in front of the pull-in part ( 12 ) Substantially changed forming conditions for the blank in all process phases for execution.

Here, the essential transformation of the blank plays ( 2 ) of the working part ( 11 ), is not under the influence of an axial compressive force (which is characteristic of the known rolling process with shoulder calibration of the roll), but it is effected by means of Axialzugkraft, as in 1 illustrated. Such a concept of the action of forces in the zone of intensive deformation of the blank creates substantially more favorable conditions for the flow of the metal in the axial direction with great radial deformation of the blank. As a result, in the caliber working zone (K ₁ ), the width of the contact surface with the roller ( 1 ) in this area, resulting in a significant improvement in the rotation conditions for the blank in the rolling process. As a consequence of what has been described above, it is possible to increase the overall decrease of the blank in the rolling mill, ie to intensify the stretchability without jeopardizing the stability of the rolling process.

In the stationary process phase (s. 1 ) the blank ( 2 ) having a high cross-sectional oval originating in the caliber working zone (K ₁ ) into the caliber drawing zone (K ₂ ). In the final phase of the metal exit from the caliber working zone (K ₁ ), the degree of ovality of the rear end of the blank increases. As the metal advances in the caliber draw zone (K ₂ ), cyclic radial compression of the blank ( 2 ), whereby the ovality of the outer diameter drops significantly. In this way, the feeder part ( 12 ) of the roller ( 1 ), in addition to its main function of ensuring process stability, in part also the function of the calibration part of a roller. The mentioned forming conditions in the draw-in part ( 12 ) of the roller ( 1 ) have a positive effect on the course of the process, especially in the final phase of the metal outlet from the rolling mill caliber. Ultimately, this provides the opportunity to increase the geometric precision of the rolled product and to use rolls with a calibration part of lesser length.

This substantial change in forming conditions in an area where the main stock removal of the blank is made, opens up the possibility of significantly reducing the load on the work rolls, increasing their usability and reducing the energy cost of rolling.

In general, this can be used to roll a solid blank with greater elongation, and in the production of tubes on the rolling line with an Assel mill, the working range can be substantially increased by producing thin-walled, high-precision tubes.

With the arrangement of the roller working part in front of the draw-in part, the abovementioned shortcomings of the cross-rolling mill, which are related to the originally specified constant shoulder height, are eliminated. In the method presented here, both by changing the caliber diameter D _K in the cross section of the high point (s. 1 ) as well as by the rolling of blanks with different output diameter, the possibility of a change in the diameter decrease on the blank in the working part of the roll into action.

Due to the aforementioned possibility of influencing the process of blank forming, the opportunity arises to significantly increase the flexibility of the rolling mill, to expand the range of products to be rolled and to reduce the production costs by using a set of rolls with a single caliber.

The diameter reduction value Δd _{2 of} the blank to be rolled ( 2 ) over the length of the caliber intake zone (K ₂ ) is selected within the range of 0.12 to 0.35 times the maximum diameter reduction value for a blank in the mill provided in the rolling table, which is given in the rolling table for that using the concrete Rolling size to be rolled assortment is provided. This choice depends on the production conditions for metal forming. When rolling blanks of difficultly deformable steels and alloys, the choice of Δd ₂ shifts in the direction of the higher values. Since, as the diameter of the rolling stock increases, the relative degree of deformation and the corresponding speed, which are decisive for the value of the deformation resistance of the metal during rolling, reduce, lower values of said range can be used. The diameter reduction value Δd ₂ to be selected also depends on the forming conditions in the caliber working zone (K ₁ ). With reduction of the shoulder inclination angle α ₁ to the rolling axis, the choice of the diameter reduction value Δd ₂ in the caliber drawing zone (K ₂ ) shifts in favor of the smaller values. If a diameter reduction value Δd _{2 is} chosen in the caliber intake zone (K ₂ ), which is below the stated range, there is the danger of a process failure in the execution of the secondary blank gripping, but diameter reduction values are selected. which are above the upper limit, this results in no significant changes in the effectiveness of the solution presented here in unreasonable increase in the roll barrel length.

D_K

– der Kaliberdurchmesser des Walzwerkes, der für das zu walzenden Erzeugnis im Querschnitt des hohen Punktes einzustellen ist;

Δd₂

– der ursprünglich gewählte Durchmesserabnahmewert des zu walzende Erzeugnisses über die Länge der Kalibereinzugzone (K₂)

The cross rolling method presented here can be realized with a certain combination of the geometric dimensions of the reduced blank front part. The diameter of the reduced front part ( 21 ) depends on the setting of the rolling mill in the cross section of the high point and the selected value Δd ₂ and can be determined according to the invention according to the following formula: d _R = D _K + (0.6 ... 0.95) Δd ₂ , Here are:

D _K

- the caliber diameter of the rolling mill to be set for the product to be rolled in the cross section of the high point;

Δd ₂

The originally selected diameter reduction value of the product to be rolled over the length of the caliber intake zone (K ₂ )

Said area for the choice of the diameter of the reduced front section ( 21 ) - d _R ensures the primary gripping of the blank ( 2 ) in the intake part ( 12 ) of the roller ( 1 ). When selecting a diameter d _R exceeding the upper limit, due to deviations in the rolling mill setting, due to a misalignment of the blank ( 2 ) when introduced into the rolls ( 1 ) etc., the first contact of the blank ( 2 ) with the roller ( 1 ) in the working part ( 11 ) in which the conditions for an axial gripping of the blank ( 2 ) are not met, and as a result, the rolling process will not be feasible. With a choice of d _R below the limit, there is the danger that, in connection with overcoming the frontal counterforce of the shoulder, the conditions for the secondary axial gripping of the blank ( 2 ) are not met.

In the context of compliance with the conditions for the secondary axial gripping of the blank ( 2 ) is also the determination of the length l _{R of} the reduced front section ( 21 ), which according to the invention in the range of 0.7 to 1.2 times the length L _{K2 of} the Kalibereinzugzone (K ₂ ) (s. 2 ) is selected. As the length l _R is reduced, so does the value of the axial tensile force which decreases on the contact surface of the draw-in part (FIG. 12 ) of the roller ( 1 ) to the contact between blank ( 2 ) and working part ( 11 ) - (s. 3 , Point X ₂ ) has accumulated. If a value below the stated range is chosen for l _R , instability of the rolling process can occur. If a value above the upper limit is chosen for the length l _R , this does not practically lead to an improvement of the conditions for the secondary gripping of the blank ( 2 ). Moreover, such a step could lead to additional costs in the prereduction of the front end ( 21 ) of the blank ( 2 ) to lead.

Between the reduced front part ( 21 ) and the cylindrical main part of the blank ( 2 ) is the production technology relevant coupling part ( 22 ). This coupling part ( 22 ), as shown in the drawings, may have a conical shape, or it may be designed with a convex or concave curved generatrix. The shape of the side surface of the coupling part ( 22 ) depends primarily on the method according to which the front part ( 21 ) of the blank ( 2 ) and the shape of the technical tools used for this purpose. Shape and length of the coupling part ( 22 ) have an influence on the way in which the phase of secondary grasping takes place. In the working part ( 11 ) of the roller ( 1 ) arises at the touchpad at the first contact ( 3 , Point X ₂ ) with the surface of the coupling part ( 22 ) an opposing force that further intensifies and reaches its maximum value when the zone is completely filled with metal. The longer the coupling part ( 22 ) of the blank ( 2 ), the smoother the increase of the counterforce in the contact zone, which has a favorable effect on the dynamic course of the secondary gripping phase. When rolling hard-to-deformable blanks as well as increasing the flank angle α ₁ as the frontal counterforce of the shoulder - F ₁ becomes stronger, but also to provide more favorable conditions for secondary gripping, it makes sense to use the coupling part (FIG. 22 ) longer.

The choice of the coefficient of proportionality between 0.7 and 1.2 for the determination of the length of the reduced front end ( 21 ) also depends on the shape and length of the coupling part ( 22 ). In a convex shape of the generatrix of the coupling part ( 22 ) or in a conical shape with a cone angle which is smaller than the angle α ₁ , the proportionality coefficient considered here is chosen smaller than 1.0; in a concave shape or a conical shape with a cone angle greater than the generatrix inclination angle α ₁ (as in FIG 2 and 3 shown), this coefficient can be chosen larger than 1.0.

With a fundamental change of Metallumformkonzeptes, as is realized in the Schrägwalzverfahren shown here, the possibility is created by selecting the generatrix inclination angle α ₁ , depending on the physical properties of the metal to be rolled and the range of dimensions of the range, optimal Set forming conditions. With the same other conditions (physical and geometrical blank parameters, required decrease, heating temperature, etc.) changes as the angle α ₁ and the frontal opposing force of the shoulder - F ₁ , and the rolling process is carried out with an axial traction of a different size. If a surface line inclination angle α _{1 is selected} with a value greater than the upper limit of the range (from 20 ° to 45 °), this results in difficult conditions for the secondary axial gripping of the blank (FIG. 2 ) with the rollers ( 1 ), and the frontal counterforce of the shoulder grows - F ₁ . This can adversely affect the stability of the rolling process. If a surface line inclination angle α _{1 is} chosen which is below the lower limit of the range, the value of the tensile force acting in the rolling caliber drops markedly, and this leads to a reduction in the effectiveness of the technological action on the rolling process described and implemented in the invention.

For the choice of the angle α ₂ - generatrix inclination angle of the draw-in part ( 12 ) of the roller ( 1 ) to the rolling axis - a value is preferably proposed in the range between 2 ° and 10 °. The larger the angle α ₂ , the lower becomes, with the same other forming conditions, on the feed parts ( 12 ) of the rolls ( 1 ) acting axial tensile force F ₂ (s. 1 ). Therefore, when rolling blanks of difficultly deformable steel grades and alloys, as well as for an assortment for which a large decrease in blank diameter is provided in the rolling tables, the choice of the generatrix inclination angle α ₂ shifts to the lower limit of the range.

The scheme of the forces acting on the contact surface of the various roll parts, which is realized in the presented cross rolling process, results in that in the cross section of the blank to be formed ( 2 ) an axial tensile stress σ _z is produced whose value changes over the length of the roll gap. From the cross section of the blank entry into the caliber working zone (K ₁ ), the value σ _{z increases} , reaches its maximum at the boundary to the caliber intake zone (K ₂ ) and then decreases again in the direction of the exit cross section from the roll nip.

The technological advantage of the proposed Schrägwalzverfahrens can be extended in its utility nor by claim 2, according to which on each of the rollers ( 1 ) in front of the pull-in part ( 12 ) an upsetting section ( 13 ) is arranged (s. 4 ), for whose generatrix inclination angle α ₃ to the rolling axis, a value which is close to the critical angle α _G , in the range between 12 ° and 20 ° is selected.

The value of the limit angle α _G depends, inter alia, on the quality of the roll surface, the value of the roll feed angle, the number of rolls, the physical properties of the blank, the temperature control during rolling. When rolling on three-roll mills, the value of this angle is practically within the limits of 14 to 16 degrees, which is covered by the above range. With an equivalence α ₃ = α _G , the deformation of the blank takes place ( 2 ) in the Kaliberstauchzone (K ₃ ) at a constant axial tensile force and consequently at constant stress σ _z . If an angle α ₃ > α _G selected, the tensile stress σ _{z increases} over the length of the Kaliberstauchzone (K ₃ ), and an angle α ₃ <α _{G is} selected, it decreases accordingly. If a generatrix inclination angle α _{3 is selected} in the range between 12 and 20 degrees, the axial tensile stress changes relatively little over the length L _{K3 of} the caliber-crushing zone (K ₃ ).

When executing a Kaliberstauchzone (K ₃ ) reduces the diameter decrease of the blank ( 2 ) in the caliber working zone (K ₁ ), which causes the maximum traction force value to drop and thereby also the maximum value of the tensile stress σ _z , which during the forming of the blank ( 2 ) in the Kaliberstauchzone (K ₃ ) unfolds its effect, is less. By redistribution of the diameter decrease of the blank ( 2 ) in the caliber working zone (K ₁ ) and the caliber crushing zone (K ₃ ), extremely optimal conditions can be achieved when rolling the product range provided in the rolling table.

The diameter reduction value Δd _{3 of} the blank to be rolled ( 2 ) over the length of the caliber-crushing zone (K ₃ ) is preferably selected within the range of 0.2 to 0.6 times the minimum diameter reduction value for a blank in the rolling mill provided in the rolling table.

When the upper limit of the above-indicated range is exceeded, the level of the axial tensile stress σ _z coming into effect in the rolling caliber weakens, and this is detrimental to the technological effectiveness of the cross rolling process presented here. If the lower limit of the said range is exceeded, the execution of an additional compression portion loses its technological meaning, while at the same time making difficult roller calibration.

In an implementation of the skew rolling method in accordance with claims 1 and 2 of the invention presented here, all stages of the process (the phase in which the forming zones of the rolling caliber are filled with metal, the stationary phase of the rolling process and the phase in which the rolled product leaves the caliber) under the action of the rollers ( 1 ).

According to claim 3 of the invention, the phase of the metal filling of the rolling caliber by means of a hydraulic or electromechanical feed device ( 3 ), which is able, the blank ( 2 ) at the specified axial speed on the rolling mill (s. 5 ).

This ensures that the introduction of the blank ( 2 ) at an axial insertion speed V _E , the value of which is selected in the range of 0.4 to 0.9 times the axial velocity V _{2 of} the rear blank face during the stationary phase of the rolling process. If an implementation of this proposal is a blank ( 2 ), for the reduced part of which geometric parameters are selected according to claim 1 of the present invention, it is also possible to use a blank ( 2 ), in which the diameter d _{R of} the reduced front part ( 21 ) is greater than the caliber diameter D _K2 at the beginning of the caliber intake zone (K ₂ ).

In 5 is the stage of the introduction of the blank according to claim 3 ( 2 ) is shown schematically in the executed according to claim 2 rolling caliber. With the help of the feed device ( 3 ) the blank ( 2 ) at an axial insertion speed, for which a value V _{E is} set, which is below the axial velocity V _{2 of} the rear blank face during the stationary phase of the rolling process, introduced into the rolling mill. During the metal filling of the rolling caliber part located in front of the caliber drawing zone (K ₂ ), the feed device ( 3 ) an axial push-in force with changing values, which is necessary for the maintenance of the selected axial insertion speed V _{E of} the blank ( 2 ) is required. During forward movement of the front blank end face along the Kalibereinzugzone (K ₂ ) whose deformation begins by the draw-in parts ( 12 ) of the rolls ( 1 ). The resulting in the forming zone and increasing axial tensile force F _{2 in} turn causes a decrease in the required, developed by the feed force force value to zero. Subsequently, during the further filling of the caliber intake zone (K ₂ ) with metal, the blank ( 2 ), under the influence of the increasing axial tensile force F ₂ with an axial velocity, which is above the insertion speed V _{E of} the push rod of the feed device to move forward. The active action of the feed device ( 3 ) is terminated automatically, and then the rolling process is exclusively under the action of the rollers ( 1 ) (s. 4 ).

In an implementation of the Schrägwalzverfahrens according to claim 3 lower requirements for the precision of the geometric parameters of the reduced front part apply ( 21 ) of the blank ( 2 ) and in particular to the roundness of the profile in cross section. As a result, the device for reducing the front part ( 21 ) are simplified in their construction. In addition, the presented concept opens up the possibility to select for the specific assortment of products to be rolled the constructively and technologically optimal combination of the auxiliary equipment required for the application of the proposed cross rolling process. With corresponding technical properties of the feed device can also unprofiled cylindrical blanks ( 2 ) are rolled.

An important influence on the selection of the axial insertion speed V _E during the insertion of the blank ( 2 ) has the diameter value d _{R of} the reduced front part ( 21 ). As the value d _{R increases} , the axial thrust force developed by the advancing means increases to ensure a constant axial insertion speed V _E. In order to avoid an overload of the feed device, in particular in the introduction of unprofiled blanks ( 2 ), it makes sense with increasing diameter d _{R of} the front part ( 21 ) of the blank ( 2 ) when selecting the value V _E in the direction of the lower limit of said range. If a value above the limit of the said range is selected for V _E , there is a risk that the conditions for a rotation of the blank ( 2 ), and this may be wedging of the blank ( 2 ) in the rolls ( 1 ) have as a consequence.

The proposed cross rolling method can be used in cross rolling mills of various types: in rolling mills with barrel rollers, which are adjusted to the rolling axis only by the feed angle, and in rolling mills with tapered rollers, which are additionally inclined to the rolling axis at a spread angle, both a divergent and a allows convergent arrangement of the roll axis to the rolling axis.

The presented process can find effective application in a planetary cross rolling mill (PSW). An important technological advantage of this rolling mill is that a non-rotating blank is rolled. The high elongation of the products in the rolling process is achieved in the PSW by the use of rollers arranged convergently with the rolling axis and by a large spread angle. With such a setting, a significant reduction of the roll diameter in the rolling direction is observed, which results in extremely high wear of that roll part on which the calibrating section is made, which is responsible for the accuracy of the geometrical dimensions of the rolled product.

The increased wear of the PSW rolls is also related to the considerable change in peripheral speed along the length of the roll; this circumstance leads to a strong slippage of the forming metal on the contact surface and increases the energy intensity of the process. These disadvantages are the reason that a widespread use of the planetary cross rolling mill in metallurgy can not be determined. One area of application is the rolling of blanks made of easily melting non-ferrous metals and alloys, eg. B. of copper. The proposed method achieves the PSW's characteristic degree of stretching of the products in the rolling process by using work rolls in which the absolute value of the spread angle is determined according to the design alone and is chosen between 0 and 55 °. If the presented invention realized in a PSW, is also given the opportunity to roll cylindrical products from a blank whose cross-section is a polygonal profile, up to the square with rounded corners.

The presented cross-rolling method for the production of cylindrical products offers the possibility of significantly increasing the stretchability and maneuverability of a rolling mill by changing the deformation conditions for the blank during rolling, and this provides the technological basis for the use of such a rolling mill in the construction of casting and Rolling modules that combine steel and rolling production in existing companies.

The proposed technological solution can also be realized in a block rolling mill, which stands at the beginning of a tube rolling mill and from batches of continuously cast Rohwalzzeugnisse with limited outer diameter range cylindrical blanks with different diameters, as provided in the respective tube rolling tables, produces.

This opens up the possibility of reducing the dependency on external suppliers and market fluctuations in the production of pipes, improving the overview of production costs, taking over smaller batches and more difficult to produce assortments, the forming conditions on rolling mills belonging to the tube rolling aggregate, to optimize and ensure a high quality standard of the finished pipes.

LIST OF REFERENCE NUMBERS

1

roller

11

Working part of the roller ( 1 )

12

Pull-in part of the roller ( 1 )

13

Upset section of the roller ( 1 )

2

blank

21

reduced front part of the blank ( 2 )

22

Coupling part (between the reduced front part ( 21 ) and the main part of the blank ( 2 ))

3

Feed device (schematic representation)

K ₁

Caliber work zone

K ₂

Caliber feed zone

K ₃

Caliber compression zone

d ₂

Diameter of the blank ( 2 )

d _R

Diameter of the reduced front part ( 21 ) of the blank ( 2 )

l _R

Length of the reduced front part ( 21 ) of the blank ( 2 )

D _K

Caliber diameter to be set for the product to be rolled in the cross section of the high point

D _K2

Caliber diameter at the beginning of its from the feeder part ( 12 ) of the roller ( 1 ) formed caliber intake zone (K ₂ )

L _K2

Length of the caliber intake zone (K ₂ )

Δd ₂

Diameter removal value in the caliber intake zone (K ₂ )

D _K3

Caliber diameter at the beginning of its from the upsetting section ( 13 ) of the roller ( 1 ) formed Kaliberstauchzone (K ₃ )

L _K3

Length of the caliber compression zone (K ₃₎

Δd ₃

Diameter reduction value in the caliber compression zone (K ₃₎

α ₁ , α ₂ , α ₃

Mantellinenneigungswinkel to the rolling axis in the working part ( 11 ), in the feeder ( 12 ) or in the compression section ( 13 ) of the roller ( 1 )

α _G

critical angle

V _E

Insertion speed of the blank ( 2 )

V ₂

axial velocity of the rear blank face during the stationary phase of the rolling process

F ₁

frontal counterforce of the shoulders

F ₂

traction

σ _z

tension

Claims (4)

Method for the oblique rolling of cylindrical products, in which the blank is provided with a reduced front part ( 21 ) introduced into the rolling mill and is rolled in a rolling caliber whose forming zones consist of at least three obliquely mounted rollers ( 1 ) are formed on which a pull-in part, a working part with a generatrix angle of inclination to the rolling axis, which is greater than the value of the critical angle (α _G ), in which the conditions for the axial Rohlingsgreifen not met, and a calibration part are arranged in the rolling direction, characterized in that the forming zones of the rolling caliber of rolls ( 1 ) are formed on which in the rolling direction first of the working part ( 11 ), whose generatrix inclination angle (α ₁ ) is selected in the range between 20 ° and 45 °, and then the draw-in part (FIG. 12 ) whose generatrix inclination angle (α ₂ ) is selected in the range between 2 ° and 10 °, in which case the diameter (d _R ) of the reduced front part ( 21 ) of the blank ( 2 ) by 0.6 to 0.95 times the diameter reduction value (Δd ₂ ) of the infeed parts ( 12 ) of the rolls ( 1 ) formed Kalibereinzugzone (K ₂ ) to be rolled blank ( 2 ) greater than the set in the cross section of the high point caliber diameter (D _K ), and the length (l _R ) of the reduced front part ( 21 ) is selected in the range of 0.7 to 1.2 times the length (L _K2 ) of the caliber drawing zone (K ₂ ). Method according to claim 1, characterized in that on each of the rolls ( 1 ) in front of the pull-in part ( 12 ) an upsetting section ( 13 ), for the generatrix angle (α ₃ ) of which a value close to the critical angle (α _G ) in the range between 12 ° and 20 ° is selected. Method according to one of claims 1 and 2, characterized in that an introduction of the blank ( 2 ) at an axial insertion speed (V _E ) whose value is selected in the range of 0.4 to 0.9 times the axial velocity (V ₂ ) of the rear blank face during the stationary phase of the rolling process. Method according to one of claims 1, 2 and 3, characterized in that the rolling is carried out in a planetary cross rolling mill whose rolling caliber of rolls ( 1 ) whose angular spread absolute value is selected in the range between 0 and 55 °.

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