RU2347631C1 - Method for production of billets with fine-grained structure by combined screw and lengthwise rolling - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method includes outer roller deformation of billet by twisted it between adjacent cages of screw and lengthwise rolling. Deformation accompanied by change of physical-mechanical properties of metal and generation of fine-grained structure is provided since processing is started with lengthwise rolling, afterwards helical rolling is carried out with circular drafting and rotation of billet, affecting the billet with compressing force due to upthrust force achieved due to difference of metal outflow rates in process of lengthwise and helical rolling. Upthrust force is adjusted by changing of size of drafting screw and lengthwise rolling.

EFFECT: improved mechanical properties in production of lengthy billets with fine-grained structure.

2 cl, 1 dwg, 1 ex, 1 tbl

Description

The invention relates to the processing of metals by pressure, and more particularly to rolling production, and can be used to obtain long billets with a fine-grained structure.

A known method of processing axisymmetric workpieces by torsion during rotation of the container parts, in which the workpiece is moved along the container so that each section crosses it at least once through the junction of the container parts (RF patent No. 2021064, IPC B21J 5/00, publ. April 9, 1991).

The known method allows to obtain a high degree of intense plastic deformation and, as a consequence, high mechanical properties along the length and cross section of the workpieces. The disadvantage is the limited length of the workpieces and the low productivity of the process.

A known method of combined continuous helical and longitudinal rolling, including extralock deformation of the workpiece by twisting in the gap between adjacent stands of helical and longitudinal rolling (RF patent No. 2184657, IPC B21B 19/02, published on July 10, 2002). The disadvantage of this method is the instability of the mechanical characteristics along the length of the workpiece.

Closest to the proposed one is a method of combined continuous helical and longitudinal rolling, including non-rolling deformation of the workpiece by twisting in the gap between adjacent stands of screw and longitudinal rolling, moreover, twisting deformation is performed in the helical rolling mill, stopping the rotation of the workpiece at the exit of the rolls by roller wiring and choosing the calculated value radial compression of the workpiece (RF patent No. 2278747, IPC B21B 19/02, publ. 10.06. 2005).

This method allows to obtain blanks of any length with high technological productivity with the same level of mechanical properties along the entire length. But small degrees of intense plastic deformation (ε <3) do not provide high mechanical properties. In addition, the method is suitable only for ductile materials, since it involves the extraction of the workpiece (tension) between the stands of helical and longitudinal rolling.

The proposed invention is aimed at obtaining long billets with a fine-grained structure in a wide range of materials with high mechanical properties and uniform structure over the entire length.

The problem is solved by the method of combined continuous screw and longitudinal rolling, including non-rolling deformation of the workpiece by twisting in the gap between adjacent stands of screw and longitudinal rolling, in which, unlike the prototype, the processing is started by longitudinal rolling, after which cross-helical rolling with circular compression and rotation of the workpiece, while providing an action of compressive stress on the workpiece due to the back-up force achieved due to the difference in the velocity of the metal in the longitudinal and helical rolling.

The back pressure is controlled by changing the compression ratio of the transverse and helical rolling.

In the proposed method for the formation of a nanocrystalline structure in order to achieve high mechanical properties, intense plastic deformation of the workpiece is carried out using compressive stresses. This prevents the destruction of the deformable body at low temperatures and high deforming forces that occur during the processing of nanostructured materials. A local deformation zone is created, which is controllably moved along the workpiece, and thanks to this, the structure in each microvolume is sequentially and repeatedly worked out. In this case, it is possible to obtain large values of the degree of intense plastic deformation (ε <30).

The invention is illustrated by the drawing, which shows the scheme of combined rolling. The diagram indicates: blank 1, rolls of longitudinal rolling 2, rolls of cross-helical rolling 3.

The method of combined continuous longitudinal and helical rolling is as follows. At the beginning, the workpiece 1 is rolled in rolls of the stands of longitudinal rolling 2, where it receives deformation in the transverse direction, then it enters the rolls of cross-helical rolling 3, where the workpiece is crimped in a circular manner, and it receives a rotational movement. Due to the fact that in the rolls 2 the workpiece metal moves only along the axis, and in the rolls 3 there is, in addition, a rotational movement, the workpiece is twisted in the gap between these rolls. The axial velocity of metal exit from the rolls 2 is greater than from the rolls 3, as a result of which a back-up force is created in the workpiece area between these rolls. The amount of back pressure depends on the mechanical properties of the material and the degree of shear deformation and is selected empirically. A backing force of up to 10 GPa can be achieved.

An example implementation of the method.

Experimental rolling was carried out. When working out the rolling mode, the settings of the longitudinal rolling mill were changed. Workpieces with a diameter of 35 were made from VT1-0 alloy at room temperature.

The rolling results are shown in the table.

Estimated reduction, mm 5 5 5 5 5 5 Set compression, mm four 5 5.5 6 7 8 Total accumulated strain, ε 3 four 5 7 13 Process characteristic norm norm norm norm norm Process stop

As can be seen from the table, when the compression values are more than 4 mm, the rolling process proceeds normally, while it is possible to increase the degree of intense plastic deformation, which means that the mechanical characteristics are increased along the entire length of the rolled product. When crimping 8 mm, rolling stops, the workpiece loses stability.

Thus, the proposed invention allows to obtain long workpieces with a fine-grained structure, with high mechanical properties.

Claims (2)

1. The method of combined continuous screw and longitudinal rolling, including extralock deformation of the workpiece by twisting in the gap between adjacent stands of screw and longitudinal rolling, characterized in that the treatment is started by longitudinal rolling, after which cross-helical rolling with circular compression and rotation of the workpiece is carried out, ensuring the impact on the workpiece of compressive stress by back-up force due to the difference in the velocities of the flow of metal in the process of longitudinal and helical rolling. 2. The method according to claim 1, characterized in that the back-up force is controlled by changing the compression ratio of the transverse and helical rolling.