RU2722952C1 - Method of rolling pipe workpieces - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metal forming and can be used for production of seamless tubes by rolling hollow tubular billets in helical rolling mill. Hollow tubular billet - sleeve is subjected to rolling in four-roll mill of helical rolling, all rolls of which are drive, with squeezing along the wall up to 60 % on cylindrical mandrel. Two rolls have the same dimensions and are arranged in the mill by a cup-like pattern; the other two rolls have the same dimensions and are placed in the mill by a mushroom-like pattern. Rolls are made so that ratio of diameter in contact of cup-like roll to diameter in height of mushroom roll is 1.1–1.4, rolls are arranged so that roll-out angle for bowl rolls ranges from -3° to -10°, rolling angle for mushroom rolls ranges from 3° to 10°, feed angle for all rolls is from 6° to 12°.

EFFECT: invention enables reducing variation in wall thickness and out-of-roundness of pipes.

1 cl, 2 tbl, 3 dwg

Description

The invention relates to the field of metal forming, and in particular to methods for producing seamless tubes by rolling in a screw rolling mill.

A known method of rolling sleeves (hollow tube billets) in a screw rolling mill (RU 2320433 C2, published 03/27/2008). The production of pipes by this method requires a complex, from the point of view of implementation, deformation mode and the scheme of the sleeve forming according to this method can lead to the appearance of additional and residual stresses in the finished pipe and to its destruction. It is proposed to roll out according to a three-roll scheme, as a result of which metal flow into the gap between the rolls is possible and, as a result, the accuracy of the products obtained, primarily in terms of ovality, will decrease.

A known method of cross-screw firmware-rolling of sleeve blanks (RU 2527582 C2, published 09/10/2014). To implement the method requires two mandrels, which complicates the process of implementing the method. During rolling according to the proposed method, the pipe moves from one mandrel to another, which can lead to a decrease in the accuracy of the resulting products.

A known method of profiling and rolling short sleeves (SU 1559536 A1, published on 10.04.2000). This method provides rolling only short sleeves, and also requires additional centering of the mandrel rod in front of each roll gauge. For the implementation of rolling, several stands are necessary, which significantly complicates the process of forming and leads to an increase in energy consumption for its implementation.

A known method of hot screw rolling (RU 2549022 C1, published on 04/20/2015). To implement the method requires a mandrel of complex design. Due to the design features of the mandrel, it is possible to reduce its stability, which will lead to a decrease in the quality of the resulting pipes. The presence of a large number of holes in the mandrel will significantly reduce its strength, will necessitate its frequent replacement and reduce production efficiency.

A known method of screw rolling pipes (RU 2146569 C1, published on March 20, 2000). The method requires constant movement of the rolling mandrel and careful, constant monitoring of its movement.

The technical result of the invention is to obtain seamless pipes, characterized by a smaller difference and ovality compared to pipes obtained using existing methods. The proposed method can be used when rolling blanks from difficult to deform materials more evenly than with existing methods to distribute energy over the surface of the rolled sleeve and reduce wear of the rolls.

The technical result is achieved by the fact that in the proposed method, the rolling is carried out in a four-roll mill of helical rolling. All four rolls are driven, two rolls are the main and two auxiliary, while the rolls are made in such a way that the ratio of their diameters in the pinch is 1.1-1.4, while the main rolls should be located in a mill in a cup-like pattern, and auxiliary rolls - mushroom-shaped. The cup-shaped scheme for the main rolls assumes a negative rolling angle and the rolls are positioned so that the rolling angle lies in the range from -3 ° to -10 °, the rolling angle for mushroom-shaped rolls is positive and ranges from 3 ° to 10 °, the feed angle for all rolls ranges from 6 ° to 12 °.

The ratio of the diameters of the working and auxiliary rolls in pinch within 1.1-1.4 and the cup-shaped arrangement of working rolls and mushroom-shaped for auxiliary rolls allow to obtain equal (or close to equal) diameters of all rolls at the exit from the deformation zone, which creates uniformity of deformation and increases the dimensional accuracy of the resulting pipes. The arrangement of auxiliary rolls according to the mushroom pattern will allow longer contact with the rolling sleeve, the length of the deformation zone will increase, the contact area of the rolls and the workpiece will increase, which will allow more even distribution of energy over the surface of the workpiece. Due to a more even distribution of energy over the surface of the workpiece, the wear of the rolls will be reduced. The range of rolling angles for cup-shaped rolls from -3 ° to -10 ° and from 3 ° to 10 ° for mushroom-shaped is selected based on the possibility of placing their main drive. It is known that with screw firmware, the roll feed angle is recommended to be set within 14-18 °, because this provides the most favorable stress-strain state diagram from the point of view of ductility of stitched blanks. The angle of supply of the rolls during rolling is set within 0.5-0.7 of the feed angle with firmware. With this in mind, to implement the proposed method, the feed angle of the rolls must be set in the range from 6 to 12 degrees. The presence of four rolls (in comparison with a three-roll or two-roll rolling) creates a more closed gauge, increases the stability of the cross section of the pipe and the accuracy of its dimensions: the ovality decreases and the difference in size decreases. The proposed method can be performed in comparison with the existing methods of rolling compression in the pinch, which makes it possible to carry out the rolling of hollow pipe billets of non-plastic materials.

The invention is illustrated by the drawings in FIG. 1. where is the 3D model created in SolidWorks and consisting of working (I) and auxiliary (2) rolls, a rolling mandrel (3) and a workpiece (4) for implementing the proposed rolling method, as well as computer simulation results of the existing three-roll rolling method: in FIG. Figure 2 shows how the shape of the workpiece (4) changes in the pinch with three rolls (5) during rolling on the mandrel (3); in FIG. 3 shows how, according to the proposed method, work rolls (1) and auxiliary rolls (2) deform the workpiece (4) when rolling on the mandrel (3) in pinch.

The implementation of the proposed method is a computer model of the rolling process, created using the computing environment of finite element analysis QForm. To demonstrate the advantages of the proposed method, we also modeled the rolling of the liner in a three-roll mill of helical rolling in QForm. During the simulation, it was specified that the material of the stitched blank was steel 45. The rolls and mandrels were considered absolutely rigid bodies made of 40X steel. the initial temperature of the billet (sleeve) was 1150 ° C. The dimensions of the sleeve and the finished pipe, as well as other parameters of rolling in a three-roll mill and according to the proposed method for modeling in QForm are shown in tables 1 and 2, respectively. Comparison of the cross sections in the pinch during the simulation (Fig. 2-3) showed that the metal of the pipe obtained in the three-roll scheme flows into the gaps formed by the rolls (Fig. 2). and the proposed method of rolling (Fig. 3) creates a more closed caliber, there is no flow into the gaps between the rolls, which will allow to obtain pipes with less ovality and difference.

Claims (1)

A method of rolling tube blanks in a four-roll helical rolling mill, all of whose rolls are driven, with a wall compression of up to 60% on a cylindrical mandrel, characterized in that the rolling is carried out by two rolls of the same size, arranged in a mill in a cup-shaped pattern, and two other rolls of the same sizes located in the mill according to the mushroom pattern, while the ratio of the diameter in the pinch of the bowl-shaped roller to the diameter in the clip of the mushroom-shaped roll is 1.1-1.4, the rolling angle for the cup-shaped rolls is from -3 ° to -10 °, the rolling angle for mushroom-shaped rolls is from 3 ° to 10 °, and the feed angle for all rolls is from 6 ° to 12 °.

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